ORCID Profile
0000-0002-0154-8305
Current Organisations
Monash Institute of Pharmaceutical Sciences
,
Flinders University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Biochemistry and Cell Biology | Physiology | Animal Physiology - Cell | Medical Physiology | Signal Transduction | Cellular Nervous System | Gastroenterology and Hepatology | Analytical Biochemistry | Plant Biology not elsewhere classified | Agricultural Biotechnology not elsewhere classified | Cell Physiology | Nutritional Physiology | Systems Biology | Animal Physiology - Systems | Cellular Nervous System | Cell Physiology | Endocrinology | Cell Metabolism
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Wine Grapes | Beverages (excl. Fruit Juices) | Nervous System and Disorders | Nervous system and disorders | Endocrine organs and diseases (incl. diabetes) | National Security | Human Pharmaceutical Treatments (e.g. Antibiotics) | Cardiovascular System and Diseases | Diabetes | Digestive System Disorders | Endocrine Organs and Diseases (excl. Diabetes) |
Related Links
Publications
Current Therapies That Modify Glucagon Secretion: What Is the Therapeutic Effect of Such Modifications?
Publisher: Springer Science and Business Media LLC
Date: 28-10-2017
DOI: 10.1007/S11892-017-0967-Z
Abstract: Hyperglucagonemia contributes significantly to hyperglycemia in type 2 diabetes and suppressed glucagon levels may increase the risk of hypoglycemia. Here, we give a brief overview of glucagon physiology and the role of glucagon in the pathophysiology of type 2 diabetes and provide insights into how antidiabetic drugs influence glucagon secretion as well as a perspective on the future of glucagon-targeting drugs. Several older as well as recent investigations have evaluated the effect of antidiabetic agents on glucagon secretion to understand how glucagon may be involved in the drugs' efficacy and safety profiles. Based on these findings, modulation of glucagon secretion seems to play a hitherto underestimated role in the efficacy and safety of several glucose-lowering drugs. Numerous drugs currently available to diabetologists are capable of altering glucagon secretion: metformin, sulfonylurea compounds, insulin, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, sodium-glucose cotransporter 2 inhibitors and amylin mimetics. Their erse effects on glucagon secretion are of importance for their in idual efficacy and safety profiles. Understanding how these drugs interact with glucagon secretion may help to optimize treatment.
Aging Differentially Affects Multiple Aspects of Vesicle Fusion Kinetics
Publisher: Public Library of Science (PLoS)
Date: 18-11-2011
Alzheimer's disease and endocytic dysfunction: Clues from the Down syndrome-related proteins, DSCR1 and ITSN1
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.ARR.2005.11.001
Abstract: Down syndrome (DS) is a genetically-based disorder which results in multiple conditions for sufferers. Amongst these is a common early incidence of Alzheimer's disease (AD) which usually affects DS in iduals by their mid 40s. This fact provides a clue that one or more of the genes located on chromosome 21 may be involved in the onset of AD. Current evidence suggests that endosomal disorders may underlie the earliest pathology of AD, preceding the classical pathological markers of beta-amyloid plaque deposition and neurofibrillary tangles. Therefore, any genes involved in endocytosis and vesicle trafficking which are over-expressed in DS are novel candidates in the pathogenesis of AD. Intersectin-1 (ITSN1) and Down syndrome candidate region 1 (DSCR1) are two such genes. Extensive in vitro data and data from Drosophila indicates that the over-expression of either of these genes or their products results in inhibition or ablation of endocytosis in neuronal as well as non-neuronal cells. This review discusses in detail the known and potential roles of ITSN1 and DSCR1 in DS, AD, endocytosis and vesicle trafficking.
The nutrient-sensing repertoires of mouse enterochromaffin cells differ between duodenum and colon
Publisher: Wiley
Date: 02-03-2017
DOI: 10.1111/NMO.13046
Abstract: Enterochromaffin (EC) cells within the gastrointestinal (GI) tract provide almost all body serotonin (5-hydroxytryptamine [5-HT]). Peripheral 5-HT, released from EC cells lining the gut wall, serves erse physiological roles. These include modulating GI motility, bone formation, hepatic gluconeogenesis, thermogenesis, insulin resistance, and regulation of fat mass. Enterochromaffin cells are nutrient sensors, but which nutrients they are responsive to and how this changes in different parts of the GI tract are poorly understood. To accurately undertake such an examination, we undertook the first isolation and purification of primary mouse EC cells from both the duodenum and colon in the same animal. This allowed us to compare, in an internally controlled manner, regional differences in the expression of nutrient sensors in EC cells using real-time PCR. Both colonic and duodenal EC cells expressed G protein-coupled receptors and facilitative transporters for sugars, free fatty acids, amino acids, and lipid amides. We find differential expression of nutrient receptor and transporters in EC cells obtained from duodenal and colonic EC cells. Duodenal EC cells have higher expression of tryptophan hydroxylase-1, sugar transporters GLUT2, GLUT5, and free fatty acid receptors 1 and 3 (FFAR1 and FFAR3). Colonic EC cells express higher levels of GLUT1, FFAR2, and FFAR4. We highlight the ersity of EC cell physiology and identify differences in the regional sensing repertoire of EC cells to an assortment of nutrients. These data indicate that not all EC cells are similar and that differences in their physiological responses are likely dependent on their location within the GI tract.
The gut microbiome regulates host glucose homeostasis via peripheral serotonin
Publisher: Proceedings of the National Academy of Sciences
Date: 16-09-2019
Abstract: The gut microbiome is an established regulator of aspects of host metabolism, such as glucose handling. Despite the known impacts of the gut microbiota on host glucose homeostasis, the underlying mechanisms are unknown. The gut microbiome is also a potent mediator of gut-derived serotonin synthesis, and this peripheral source of serotonin is itself a regulator of glucose homeostasis. Here, we determined whether the gut microbiome influences glucose homeostasis through effects on gut-derived serotonin. Using both pharmacological inhibition and genetic deletion of gut-derived serotonin synthesis, we find that the improvements in host glucose handling caused by antibiotic-induced changes in microbiota composition are dependent on the synthesis of peripheral serotonin.
Huntingtin-associated protein-1 (HAP1) regulates endocytosis and interacts with multiple trafficking-related proteins
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.CELLSIG.2017.02.023
Abstract: Huntingtin-associated protein 1 (HAP1) was initially identified as a binding partner of huntingtin, mutations in which underlie Huntington's disease. Subcellular localization and protein interaction data indicate that HAP1 may be important in vesicle trafficking, cell signalling and receptor internalization. In this study, a proteomics approach was used for the identification of novel HAP1-interacting partners to attempt to shed light on the physiological function of HAP1. Using affinity chromatography with HAP1-GST protein fragments bound to Sepharose columns, this study identified a number of trafficking-related proteins that bind to HAP1. Interestingly, many of the proteins that were identified by mass spectrometry have trafficking-related functions and include the clathrin light chain B and Sec23A, an ER to Golgi trafficking vesicle coat component. Using co-immunoprecipitation and GST-binding assays the association between HAP1 and clathrin light chain B has been validated in vitro. This study also finds that HAP1 co-localizes with clathrin light chain B. In line with a physiological function of the HAP1-clathrin interaction this study detected a dramatic reduction in vesicle retrieval and endocytosis in adrenal chromaffin cells. Furthermore, through examination of transferrin endocytosis in HAP1
Adiponectin increases insulin content and cell proliferation in MIN6 cells via PPARγ-dependent and PPARγ-independent mechanisms
Publisher: Wiley
Date: 07-06-2012
DOI: 10.1111/J.1463-1326.2012.01626.X
Abstract: Adiponectin is an important adipokine whose levels are decreased in obesity despite increases in adipocyte mass. Studies in animal models implicate adiponectin as an insulin sensitizer in skeletal muscle and liver. Thiazolidinediones (TZDs) are insulin sensitizers and ligands for peroxisome proliferator-activated γ receptors (PPARγ) and these receptors are expressed in β cells where their activation promotes cell survival. We hypothesize that adiponectin promotes β cell survival by activating PPARγ. We used MIN6 cells to investigate the effect of adiponectin on PPARγ expression, β-cell proliferation, insulin synthesis and insulin secretion. We demonstrate that MIN6 cells contain adiponectin receptors and that adiponectin activates PPARγ mRNA and protein expression. This increase in PPARγ expression is blocked by the PPARγ antagonist, GW9662, indicating a transcriptional feedback loop involving PPARγ activation of itself. Adiponectin causes a significant increase in insulin content and secretion and this occurs also via PPARγ activation due to the inhibitory effect of GW9662. Adiponectin also promotes MIN6 cell proliferation, however, this effect is independent of PPARγ activation. Our results identify novel roles for the adipokine, adiponectin, in β-cells function. Adiponectin upregulates PPARγ expression, insulin content and insulin secretion through PPARγ-dependent mechanisms. Reductions in circulating adiponectin levels in obese in iduals could therefore result in negative effects on β-cell function and this may have direct relevance to β-cell dysfunction in type 2 diabetes.
Amperometry in Single Cells and Tissue
Publisher: Springer US
Date: 22-11-2021
Oxygen sensitivity in the sheep adrenal medulla: role of SK channels
Publisher: American Physiological Society
Date: 11-2001
DOI: 10.1152/AJPCELL.2001.281.5.C1434
Abstract: The hypoxia-evoked secretion of catecholamines from the noninnervated fetal adrenal gland is essential for surviving intrauterine hypoxemia. The ion channels responsible for the initial depolarization that leads to catecholamine secretion have not been identified. Patch-cl studies of adrenal chromaffin cells isolated from fetal and adult sheep revealed the presence of a Ca 2+ -dependent K + current that was reduced by hypoxia. Apamin, a blocker of small-conductance K + (SK) channels, reduced the Ca 2+ -dependent K + current, and the sensitivity of the channels to apamin indicated that the channels involved were of the SK2 subtype. In the presence of apamin, the hypoxia-evoked change in K + currents was largely eliminated. Both hypoxia and apamin blocked a K + current responsible for maintaining the resting potential of the cell, and the depolarization resulting from both led to an influx of Ca 2+ . Simultaneous application of hypoxia and apamin did not potentiate the increase in cytosolic Ca 2+ concentration beyond that seen with either agent alone. Similar results were seen with curare, another blocker of SK channels. These results indicate that closure of SK2 channels would be the initiating event in the hypoxia-evoked catecholamine secretion in the adrenal medulla.
The Regulation of Peripheral Metabolism by Gut-Derived Hormones
Publisher: Frontiers Media SA
Date: 04-01-2018
Regional differences in nutrient-induced secretion of gut serotonin
Publisher: Wiley
Date: 03-2017
DOI: 10.14814/PHY2.13199
Loss of K-Cl co-transporter KCC3 causes deafness, neurodegeneration and reduced seizure threshold
Publisher: Wiley
Date: 15-10-2003
DOI: 10.1093/EMBOJ/CDG519
Amyloid beta1-42 (Aβ42 ) up-regulates the expression of sortilin via the p75NTR/RhoA signaling pathway
Publisher: Wiley
Date: 22-08-2013
DOI: 10.1111/JNC.12383
Abstract: Sortilin, a Golgi sorting protein and a member of the VPS10P family, is the co-receptor for proneurotrophins, regulates protein trafficking, targets proteins to lysosomes, and regulates low density lipoprotein metabolism. The aim of this study was to investigate the expression and regulation of sortilin in Alzheimer's disease (AD). A significantly increased level of sortilin was found in human AD brain and in the brains of 6-month-old swedish-amyloid precursor protein/PS1dE9 transgenic mice. Aβ₄₂ enhanced the protein and mRNA expression levels of sortilin in a dose- and time-dependent manner in SH-SY5Y cells, but had no effect on sorLA. In addition, proBDNF also significantly increased the protein and mRNA expression of sortilin in these cells. The recombinant extracellular domain of p75(NTR) (P75ECD-FC), or the antibody against the extracellular domain of p75(NTR), blocked the up-regulation of sortilin induced by Amyloid-β protein (Aβ), suggesting that Aβ₄₂ increased the expression level of sortilin and mRNA in SH-SY5Y via the p75(NTR) receptor. Inhibition of ROCK, but not Jun N-terminal kinase, suppressed constitutive and Aβ₄₂-induced expression of sortilin. In conclusion, this study shows that sortilin expression is increased in the AD brain in human and mice and that Aβ₄₂ oligomer increases sortilin gene and protein expression through p75(NTR) and RhoA signaling pathways, suggesting a potential physiological interaction of Aβ₄₂ and sortilin in Alzheimer's disease.
Release of 5-Hydroxytryptamine From the Mucosa Is Not Required for the Generation or Propagation of Colonic Migrating Motor Complexes
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1053/J.GASTRO.2009.09.020
Abstract: The pacemaker mechanism that underlies the cyclic generation of colonic migrating motor complexes (CMMCs) is unknown, although studies have suggested that release of 5-hydroxytryptamine (5-HT) from enterochromaffin cells in the mucosa is essential. However, no recordings of 5-HT release from the colon have been made to support these suggestions. We used real-time erometry to record 5-HT release directly from the mucosa in mouse isolated colon to determine whether 5-HT release from enterochromaffin cells was required for CMMC generation. We found that 5-HT was released from mucosal enterochromaffin cells during many, but not all, CMMC contractions. However, spontaneous CMMCs still were recorded even after removal of the mucosa, and submucosa and submucosal plexus when all release of 5-HT had been abolished. CMMC pacemaker frequency was slower in the absence of the mucosa, an effect reversed by focal application of exogenous 5-HT onto the myenteric plexus. Despite the absence of the mucosa and all detectable release of 5-HT, ondansetron significantly reduced CMMC frequency, suggesting that 5-HT(3) receptor blockade slows the CMMC pacemaker via a mechanism independent of 5-HT release from enterochromaffin cells. Our results show that 5-HT can be released dynamically during CMMCs. However, the intrinsic pacemaker and pattern generator underlying CMMC generation lies within the myenteric plexus and/or muscularis externa and does not require any release of 5-HT from enterochromaffin cells. Endogenous release of 5-HT from enterochromaffin cells plays a modulatory role, not an essential role, in CMMC generation.
Activin A stimulates catecholamine secretion from rat adrenal chromaffin cells: a new physiological mechanism
Publisher: Bioscientifica
Date: 08-2005
DOI: 10.1677/JOE.1.06301
Abstract: Activin A is a member of the transforming growth factor-β family and has known roles in the adrenal cortex, from which activin A is secreted. We aimed to find whether activin A induces secretion of catecholamines from chromaffin cells of the adrenal medulla, which neighbours the adrenal cortex in vivo. Using carbon fibre erometry, we were able to measure catecholamine secretion in real-time from single chromaffin cells dissociated from the rat adrenal medulla. Activin A stimulated catecholamine secretion in a rapid and dose-dependent manner from chromaffin cells. This effect was fully reversible upon washout of activin A. The minimum dose at which activin A had a maximal effect was 2 nM, with an EC 50 of 1.1 nM. The degree of secretion induced by activin A (2 nM) was smaller than that due to membrane depolarization caused by an increase in the external K + concentration from 5 to 70 mM. No response to activin A was seen when Ca 2+ channels were blocked by Cd 2+ (200 μM). We conclude from these findings that activin A is capable of stimulating a robust level of catecholamine secretion from adrenal chromaffin cells in a concentration-dependent manner. This occurs via the opening of voltage-gated Ca 2+ channels, causing Ca 2+ entry, thereby triggering exocytosis. These findings illustrate a new physiological role of activin A and a new mechanism in the control of catecholamine secretion from the adrenal medulla.
Pharmacological and structure-activity relationship studies of oleoyl-lysophosphatidylinositol synthetic mimetics
Publisher: Elsevier BV
Date: 10-2021
Circulating cathepsin S improves glycemic control in mice
Publisher: Bioscientifica
Date: 02-2020
DOI: 10.1530/JOE-20-0408
Abstract: Cathepsin S (CTSS) is a cysteine protease that regulates many physiological processes and is increased in obesity and type 2 diabetes. While previous studies show that deletion of CTSS improves glycaemic control through suppression of hepatic glucose output, little is known about the role of circulating CTSS in regulating glucose and energy metabolism. We assessed the effects of recombinant CTSS on metabolism in cultured hepatocytes, myotubes and adipocytes, and in mice following acute CTSS administration. CTSS improved glucose tolerance in lean mice and this coincided with increased plasma insulin. CTSS reduced G6pc and Pck1 mRNA expression and glucose output from hepatocytes but did not affect glucose metabolism in myotubes or adipocytes. CTSS did not affect insulin secretion from pancreatic β-cells, rather CTSS stimulated glucagon-like peptide (GLP)-1 secretion from intestinal mucosal tissues. CTSS retained its positive effects on glycaemic control in mice injected with the GLP1 receptor antagonist Exendin (9–39) amide. The effects of CTSS on glycaemic control were not retained in high-fat-fed mice or db/db mice, despite the preservation of CTSS’ inhibitory actions on hepatic glucose output in isolated primary hepatocytes. In conclusion, we unveil a role for CTSS in the regulation of glycaemic control via direct effects on hepatocytes, and that these effects on glycaemic control are abrogated in insulin resistant states.
The 18th International Symposia on Chromaffin Cell Biology
Publisher: Wiley
Date: 06-2016
DOI: 10.1111/JNC.13631
Small molecules demonstrate the role of dynamin as a bi-directional regulator of the exocytosis fusion pore and vesicle release
Publisher: Springer Science and Business Media LLC
Date: 05-05-2015
DOI: 10.1038/MP.2015.56
Abstract: Hormones and neurotransmitters are stored in specialised vesicles and released from excitable cells through exocytosis. During vesicle fusion with the plasma membrane, a transient fusion pore is created that enables transmitter release. The protein dynamin is known to regulate fusion pore expansion (FPE). The mechanism is unknown, but requires its oligomerisation-stimulated GTPase activity. We used a palette of small molecule dynamin modulators to reveal bi-directional regulation of FPE by dynamin and vesicle release in chromaffin cells. The dynamin inhibitors Dynole 34-2 and Dyngo 4a and the dynamin activator Ryngo 1-23 reduced or increased catecholamine released from single vesicles, respectively. Total internal reflection fluorescence (TIRF) microscopy demonstrated that dynamin stimulation with Ryngo 1-23 reduced the number of neuropeptide Y (NPY) kiss-and-run events, but not full fusion events, and slowed full fusion release kinetics. Amperometric stand-alone foot signals, representing transient kiss-and-run events, were less frequent but were of longer duration, similarly to full erometric spikes and pre-spike foot signals. These effects are not due to alterations in vesicle size. Ryngo 1-23 action was blocked by inhibitors of actin polymerisation or myosin II. Therefore, we demonstrate using a novel pharmacological approach that dynamin not only controls FPE during exocytosis, but is a bi-directional modulator of the fusion pore that increases or decreases the amount released from a vesicle during exocytosis if it is activated or inhibited, respectively. As such, dynamin has the ability to exquisitely fine-tune transmitter release.
The composition of the gut microbiota following early-life antibiotic exposure affects host health and longevity in later life
Publisher: Elsevier BV
Date: 08-2021
DOI: 10.1016/J.CELREP.2021.109564
Abstract: Studies investigating whether there is a causative link between the gut microbiota and lifespan have largely been restricted to invertebrates or to mice with a reduced lifespan because of a genetic deficiency. We investigate the effect of early-life antibiotic exposure on otherwise healthy, normal chow-fed, wild-type mice, monitoring these mice for more than 700 days in comparison with untreated control mice. We demonstrate the emergence of two different low- ersity community types, post-antibiotic microbiota (PAM) I and PAM II, following antibiotic exposure. PAM II but not PAM I mice have impaired immunity, increased insulin resistance, and evidence of increased inflammaging in later life as well as a reduced lifespan. Our data suggest that differences in the composition of the gut microbiota following antibiotic exposure differentially affect host health and longevity in later life.
The β-cell/EC axis: How do islet cells talk to each other?
Publisher: American Diabetes Association
Date: 13-12-2014
DOI: 10.2337/DB13-0617
Abstract: Within the pancreatic islet, the β-cell represents the ultimate biosensor. Its central function is to accurately sense glucose levels in the blood and consequently release appropriate amounts of insulin. As the only cell type capable of insulin production, the β-cell must balance this crucial workload with self-preservation and, when required, regeneration. Evidence suggests that the β-cell has an important ally in intraislet endothelial cells (ECs). As well as providing a conduit for delivery of the primary input stimulus (glucose) and dissemination of its most important effector (insulin), intraislet blood vessels deliver oxygen to these dense clusters of metabolically active cells. Furthermore, it appears that ECs directly impact insulin gene expression and secretion and β-cell survival. This review discusses the molecules and pathways involved in the crosstalk between β-cells and intraislet ECs. The evidence supporting the intraislet EC as an important partner for β-cell function is examined to highlight the relevance of this axis in the context of type 1 and type 2 diabetes. Recent work that has established the potential of ECs or their progenitors to enhance the re-establishment of glycemic control following pancreatic islet transplantation in animal models is discussed.
p75 neurotrophin receptor interacts with and promotes BACE1 localization in endosomes aggravating amyloidogenesis.
Publisher: Wiley
Date: 27-09-2018
DOI: 10.1111/JNC.14206
Abstract: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive deposition of amyloid beta (Aβ) and dysregulation of neurotrophic signaling, causing synaptic dysfunction, loss of memory, and cell death. The expression of p75 neurotrophin receptor is elevated in the brain of AD patients, suggesting its involvement in this disease. However, the exact mechanism of its action is not yet clear. Here, we show that p75 interacts with beta-site amyloid precursor protein cleaving enzyme-1 (BACE1), and this interaction is enhanced in the presence of Aβ. Our results suggest that the colocalization of BACE1 and amyloid precursor protein (APP) is increased in the presence of both Aβ and p75 in cortical neurons. In addition, the localization of APP and BACE1 in early endosomes is increased in the presence of Aβ and p75. An increased phosphorylation of APP-Thr668 and BACE1-Ser498 by c-Jun N-terminal kinase (JNK) in the presence of Aβ and p75 could be responsible for this localization. In conclusion, our study proposes a potential involvement in amyloidogenesis for p75, which may represent a future therapeutic target for AD. Cover Image for this Issue: doi. 10.1111/jnc.14163.
Gut Serotonin Is a Regulator of Obesity and Metabolism
Publisher: Elsevier BV
Date: 07-2015
Engineering Fluorescent Gold Nanoclusters Using Xanthate-Functionalized Hydrophilic Polymers: Toward Enhanced Monodispersity and Stability
Publisher: American Chemical Society (ACS)
Date: 22-12-2020
The ever-changing roles of serotonin
Publisher: Elsevier BV
Date: 08-2020
Is There a Role for Endogenous 5-HT in Gastrointestinal Motility? How Recent Studies Have Changed Our Understanding.
Publisher: Springer International Publishing
Date: 2016
DOI: 10.1007/978-3-319-27592-5_11
Abstract: Over the past few years, there have been dramatic changes in our understanding of the role of endogenous 5-hydroxytryptamine (5-HT) in the generation of gastrointestinal (GI) motility patterns in the small and large intestine. The idea that endogenous 5-HT played a major role in the generation of peristalsis in the small intestine was first proposed in the mid 1950s, after it was discovered that endogenous 5-HT could be released from the mucosa at a similar time that peristalsis occurred and that exogenous 5-HT could potently stimulate peristalsis. The fact that exogenous 5-HT stimulated peristalsis and that there was a similarity in timing between the release of 5-HT from the mucosa and the onset of peristalsis led investigators to propose that release of endogenous 5-HT from the mucosa was causally related to the generation of peristalsis. In further support of this, other studies showed that selective 5-HT antagonists could inhibit or block peristalsis, and other motor patterns, such as the migrating motor complex. Taken together, based on these findings, some laboratories believed that endogenous 5-HT (synthesized in the gut wall) was an important mediator, or initiator, of different propulsive motor patterns in the lower GI tract. This notion changed dramatically in the past few years, however, after it was discovered that removal of the mucosa abolished all cyclical release of endogenous 5-HT, but did not block peristalsis, nor the cyclical migrating complex. Furthermore, other laboratories revealed that genetic deletion of the gene tryptophan hydroxylase 1 (TPH-1) (that synthesizes endogenous 5-HT in the mucosa) actually had no inhibitory effect on transit of intestinal contents in live animals. Then, perhaps one of the most startling of all observations was the discovery that selective 5-HT receptor antagonists actually have the same inhibitory effects on peristalsis and the migrating complex in segments of intestine that had been depleted of all endogenous 5-HT. Taken together, these recent findings have led to a major revision in our understanding of the functional role of endogenous 5-HT in the generation of propulsive motor patterns in the lower GI tract. This review will focus on how our understanding of endogenous 5-HT in the GI tract has changed substantially in recent times.
The presence of 5-HT in myenteric varicosities is not due to uptake of 5-HT released from the mucosa during dissection: use of a novel method for quantifying 5-HT immunoreactivity in myenteric ganglia
Publisher: Wiley
Date: 31-07-2013
DOI: 10.1111/NMO.12189
Abstract: Quantifying the relative abundance of different neurotransmitters in the myenteric plexus has proved challenging using conventional immunocytochemical approaches. Here, we present a new method of quantifying neurotransmitter content of an important enteric signalling molecule, serotonin (5-HT), in the myenteric plexus of guinea pig colon under different experimental conditions. Sections of guinea pig distal colon were exposed to different conditions including changes in temperature, dissection protocol, stimulation with faecal pellet distension and exogenous 5-HT. Sections were fixed and immuno-labelled for 5-HT. 5-HT staining density was quantified within myenteric plexus ganglia using defined settings and an analysis approach that uses threshold settings allowing for variances in background and tissue staining intensities and which calculates the area of tissue containing 5-HT above these thresholds. No differences were found in 5-HT immunoreactivity in the myenteric plexus when compared between tissues that were freshly fixed, undissected, or with mucosa and submucous plexus dissected away at either 4 or 37 °C. Increased myenteric plexus 5-HT density was observed in preparations repeatedly stimulated using faecal pellet stimulation prior to fixation. Furthermore, exogenous 5-HT also increased 5-HT density. We demonstrate that quantitative differences in 5-HT immunoreactivity can be characterized using immunohistochemistry. This approach may be applied to measuring other neurotransmitter(s) within the enteric nervous system. While 5-HT is present in the guinea-pig enteric ganglia, this is not due to accumulation via in vitro handling and release from the mucosa, and furthermore, repeated colonic stimulation via distension increases 5-HT in the myenteric plexus.
Diminished Piezo2-Dependent Tactile Sensitivity Occurs in Aging Human Gut and Slows Gastrointestinal Transit in Mice
Publisher: Elsevier BV
Date: 05-2022
The Suitability of Glioblastoma Cell Lines as Models for Primary Glioblastoma Cell Metabolism
Publisher: MDPI AG
Date: 11-12-2020
Abstract: In contrast to most non-malignant tissue, cells comprising the brain tumour glioblastoma (GBM) preferentially utilise glycolysis for metabolism via “the Warburg effect”. Research into therapeutics targeting the disease’s highly glycolytic state offer a promising avenue to improve patient survival. These studies often employ GBM cell lines for in vitro studies which translate poorly to the in vivo patient context. The metabolic traits of five of the most used GBM cell lines were assessed and compared to primary GBM and matched, healthy brain tissue. In patient-derived GBM cell lines, the basal mitochondrial rate (p = 0.043) and ATP-linked respiration (p 0.001) were lower than primary adjacent normal cells from the same patient, while reserve capacity (p = 0.037) and Krebs cycle capacity (p = 0.002) were higher. Three cell lines, U251MG, U373MG and D54, replicate the mitochondrial metabolism of primary GBM cells. Surprisingly, glycolytic capacity is not different between healthy and GBM tissue. The T98G cell line recapitulated glycolysis-related metabolic parameters of the primary GBM cells and is recommended for research relating to glycolysis. These findings can guide preclinical research into the development of novel therapeutics targeting metabolic pathways in GBM.
Role of the Vesicular Chloride Transporter ClC-3 in Neuroendocrine Tissue
Publisher: Society for Neuroscience
Date: 15-10-2008
DOI: 10.1523/JNEUROSCI.3750-08.2008
Abstract: ClC-3 is an intracellular chloride transport protein known to reside on endosomes and synaptic vesicles. The endogenous protein has been notoriously difficult to detect in immunohistological experiments because of the lack of reliable antibodies. Using newly generated antibodies, we now examine its expression pattern at the cellular and subcellular level. In all tissues examined, immunostaining indicated that ClC-3 is a vesicular protein, with a prominent expression in endocrine cells like adrenal chromaffin cells and pancreatic islet cells. In line with a possible function of ClC-3 in regulating vesicle trafficking or exocytosis in those secretory cells, capacitance measurements and erometry indicated that exocytosis of large dense-core vesicles (LDCVs) was decreased in chromaffin cells from ClC-3 knock-out mice. However, immunohistochemistry complemented with subcellular fractionation showed that ClC-3 is not detectable on LDCVs of endocrine cells, but localizes to endosomes and synaptic-like microvesicles in both adrenal chromaffin and pancreatic β cells. This observation points to an indirect influence of ClC-3 on LDCV exocytosis in chromaffin cells, possibly by affecting an intracellular trafficking step.
Distinguishing the contributions of neuronal and mucosal serotonin in the regulation of colonic motility
Publisher: Wiley
Date: 21-03-2022
DOI: 10.1111/NMO.14361
Abstract: Specialized enterochromaffin (EC) cells within the mucosal lining of the gut synthesize and secrete almost all serotonin (5‐hydroxytryptamine, 5‐HT) in the body. Significantly lower amounts of 5‐HT are made by other peripheral tissues and serotonergic neurons within the enteric nervous system (ENS). EC cells are in close proximity to 5‐HT receptors in the ENS, and the role of 5‐HT as a modulator of gut motility, particularly colonic motor complexes, has been well defined. However, the relative contribution of neuronal 5‐HT to this process under resting and stimulus‐evoked conditions is unclear. In this study, we combined the use of the selective serotonin transporter (SERT) inhibitor, fluoxetine, with two models of mucosal 5‐HT depletion—surgical removal of the mucosa and our Tph1 Cre/ERT2 Rosa26 DTA mouse line—to determine the relative contribution of neuronal and mucosal 5‐HT to resting and distension‐evoked colonic motility. Fluoxetine significantly reduced the frequency of colonic migrating complexes (CMCs) in flat‐sheet preparations with the mucosa present and in intact control Tph1‐DTA colons in which EC cells were present. No such effect was observed in mucosa‐free preparations or in intact Tph1‐DTA preparations lacking EC cell 5‐HT. We demonstrate that mucosal 5‐HT release plays an important role in distension‐evoked colonic motility, and that SERT inhibition no longer alters gut motility when EC cells are absent, thus demonstrating that ENS 5‐HT does not play a role in regulating gut motility.
Galanin receptor 3 - a potential target for acute pancreatitis therapy
Publisher: Wiley
Date: 08-02-2011
DOI: 10.1111/J.1365-2982.2010.01662.X
Abstract: Galanin participates in the pathogenesis of acute pancreatitis (AP). The galanin receptor (GALR) sub-types involved, however, are unclear. We aimed to determine GALRs messenger RNA (mRNA) expression in mouse pancreas, describe their localization, and ascertain if GALR2 and GALR3 are involved in AP. Galanin receptor expression in murine whole pancreas, acinar, and islet cells was quantified by polymerase chain reaction lification of reverse-transcribed RNA for mRNA, Western blot analysis for protein and in situ hybridization for GALR localization. Isolated acinar cells were used to determine galanin's effect on amylase secretion. Acute pancreatitis was induced in mice by caerulein injections. Mice, with and without AP, were treated with the highly selective GALR2 antagonist M871, or the specific GALR3 antagonist SNAP-37889. Indices of AP were measured at 12 h. Murine pancreas expresses mRNA for GALRs. In islets the expression of all GALR are comparable, whereas in acinar cells GALR3 is predominantly expressed. Western blot analysis confirmed that the GALR proteins are expressed by acinar cells. In situ hybridization analysis confirmed that GALR3 mRNA is present in islet and acinar cells, while mRNA for GALR1 and 2 is confined to islets. Galanin did not influence basal and caerulein-stimulated amylase release from acinar cells. M871 treatment reduced some, whereas SNAP-37889 treatment reduced all indices of AP (by 40-80%). Galanin receptor mRNA and protein are expressed in mouse pancreas, with GALR3 mRNA predominating. GALR3 antagonism reduced the severity of AP whereas GALR2 antagonism was less effective. GALR3 is a potential target for treatment of AP.
Somatostatin decreases voltage-gated Ca2+currents in GH3 cells through activation of somatostatin receptor 2
Publisher: American Physiological Society
Date: 06-2007
DOI: 10.1152/AJPENDO.00047.2007
Abstract: The secretion of growth hormone (GH) is inhibited by hypothalamic somatostatin (SRIF) in somatotropes through five subtypes of the somatostatin receptor (SSTR1–SSTR5). We aimed to characterize the subtype(s) of SSTRs involved in the Ca 2+ current reduction in GH3 somatotrope cells using specific SSTR subtype agonists. We used nystatin-perforated patch cl to record voltage-gated Ca 2+ currents, using a holding potential of −80 mV in the presence of K + and Na + channel blockers. We first established the presence of T-, L-, N-, and P/Q-type Ca 2+ currents in GH3 cells using a variety of channel blockers (Ni + , nifedipine, ω-conotoxin GVIA, and ω-agatoxin IVA). SRIF (200 nM) reduced L- and N-type but not T- or P/Q-type currents in GH3 cells. A range of concentrations of each specific SSTR agonist was tested on Ca 2+ currents to find the maximal effective concentration. Activation of SSTR2 with 10 −7 and 10 −8 M L-797,976 decreased the voltage-gated Ca 2+ current and abolished any further decrease by SRIF. SSTR1, SSTR3, SSTR4, and SSTR5 agonists at 10 −7 M did not modify the voltage-gated Ca 2+ current and did not affect the Ca 2+ current response to SRIF. These results indicate that SSTR2 is involved mainly in regulating voltage-gated Ca 2+ currents by SRIF, which contributes to the decrease in intracellular Ca 2+ concentration and GH secretion by SRIF.
The influence of the gut microbiome on host metabolism through the regulation of gut hormone release
Publisher: Frontiers Media SA
Date: 16-04-2019
Inhibition of Miro1 disturbs mitophagy and pancreatic β-cell function interfering insulin release via IRS-Akt-Foxo1 in diabetes
Publisher: Impact Journals, LLC
Date: 16-09-2017
Homozygous mutation of STXBP5L explains an autosomal recessive infantile-onset neurodegenerative disorder
Publisher: Oxford University Press (OUP)
Date: 11-12-2014
DOI: 10.1093/HMG/DDU614
Abstract: We report siblings of consanguineous parents with an infantile-onset neurodegenerative disorder manifesting a predominant sensorimotor axonal neuropathy, optic atrophy and cognitive deficit. We used homozygosity mapping to identify an ∼12-Mbp interval identical by descent (IBD) between the affected in iduals on chromosome 3q13.13-21.1 with an LOD score of 2.31. We combined family-based whole-exome and whole-genome sequencing of parents and affected siblings and, after filtering of likely non-pathogenic variants, identified a unique missense variant in syntaxin-binding protein 5-like (STXBP5L c.3127G>A, p.Val1043Ile [CCDS43137.1]) in the IBD interval. Considering other modes of inheritance, we also found compound heterozygous variants in FMNL3 (c.114G>C, p.Phe38Leu and c.1372T>G, p.Ile458Leu [CCDS44874.1]) located on chromosome 12. STXBP5L (or Tomosyn-2) is expressed in the central and peripheral nervous system and is known to inhibit neurotransmitter release through inhibition of the formation of the SNARE complexes between synaptic vesicles and the plasma membrane. FMNL3 is expressed more widely and is a formin family protein that is involved in the regulation of cell morphology and cytoskeletal organization. The STXBP5L p.Val1043Ile variant enhanced inhibition of exocytosis in comparison with wild-type (WT) STXBP5L. Furthermore, WT STXBP5L, but not variant STXBP5L, promoted axonal outgrowth in manipulated mouse primary hippoc al neurons. However, the FMNL3 p.Phe38Leu and p.Ile458Leu variants showed minimal effects in these cells. Collectively, our clinical, genetic and molecular data suggest that the IBD variant in STXBP5L is the likely cause of the disorder.
Serotonin Deficiency Is Associated With Delayed Gastric Emptying
Publisher: Elsevier BV
Date: 06-2021
Role of 5-HT in the enteric nervous system and enteroendocrine cells
Publisher: Wiley
Date: 17-08-2022
DOI: 10.1111/BPH.15930
Abstract: Since the 1950s, considerable circumstantial evidence had been presented that endogenous 5‐HT (serotonin) synthesized from within the wall of the gastrointestinal (GI) tract played an important role in GI motility and transit. However, identifying the precise functional role of gut‐derived 5‐HT has been difficult to ascertain, for a number of reasons. Over the past decade, as recording techniques have advanced significantly and access to new genetically modified animals improved, there have been major new insights and major changes in our understanding of the functional role of endogenous 5‐HT in the GI tract. Data from many different laboratories have shown that major patterns of GI motility and transit still occur with minor or no, change when all endogenous 5‐HT is pharmacologically or genetically ablated from the gut. Furthermore, antagonists of 5‐HT 3 receptors are equally, or more potent at inhibiting GI motility in segments of intestine that are completely depleted of endogenous 5‐HT. Here, the most recent findings are discussed with regard to the functional role of endogenous 5‐HT in enterochromaffin cells and enteric neurons in gut motility and more broadly in some major homeostatic pathways.
A Gut-Intrinsic Melanocortin Signaling Complex Augments L-Cell Secretion in Humans
Publisher: Elsevier BV
Date: 08-2021
DOI: 10.1053/J.GASTRO.2021.04.014
Abstract: Hypothalamic melanocortin 4 receptors (MC4R) are a key regulator of energy homeostasis. Brain-penetrant MC4R agonists have failed, as concentrations required to suppress food intake also increase blood pressure. However, peripherally located MC4R may also mediate metabolic benefits of MC4R activation. Mc4r transcript is enriched in mouse enteroendocrine L cells and peripheral administration of the endogenous MC4R agonist, α-melanocyte stimulating hormone (α-MSH), triggers the release of the anorectic hormones Glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) in mice. This study aimed to determine whether pathways linking MC4R and L-cell secretion exist in humans. GLP-1 and PYY levels were assessed in body mass index-matched in iduals with or without loss-of-function MC4R mutations following an oral glucose tolerance test. Immunohistochemistry was performed on human intestinal sections to characterize the mucosal MC4R system. Static incubations with MC4R agonists were carried out on human intestinal epithelia, GLP-1 and PYY contents of secretion supernatants were assayed. Fasting PYY levels and oral glucose-induced GLP-1 secretion were reduced in humans carrying a total loss-of-function MC4R mutation. MC4R was localized to L cells and regulates GLP-1 and PYY secretion from ex vivo human intestine. α-MSH immunoreactivity in the human intestinal epithelia was predominantly localized to L cells. Glucose-sensitive mucosal pro-opiomelanocortin cells provide a local source of α-MSH that is essential for glucose-induced GLP-1 secretion in small intestine. Our findings describe a previously unidentified signaling nexus in the human gastrointestinal tract involving α-MSH release and MC4R activation on L cells in an autocrine and paracrine fashion. Outcomes from this study have direct implications for targeting mucosal MC4R to treat human metabolic disorders.
Role of 5-Hydroxytryptamine in the control of gut motility
Publisher: Elsevier
Date: 2018
Bright Future of Gold Nanoclusters in Theranostics
Publisher: American Chemical Society (ACS)
Date: 12-10-2021
Abstract: Quantum-sized gold nanoclusters (AuNCs) are emerging as theranostic agents-those that combine diagnostics and therapeutic properties-given their ultrasmall size <3 nm, which makes them behave more like a molecule rather than a nanoparticle. This molecule-like behavior endows AuNCs with interesting properties including photoluminescence, catalytic activity, and paramagnetism-all without the presence of any toxic heavy metal. But despite these fundamental advances, scalable synthetic approaches to produce high-quality AuNCs with well-controlled and programmable properties for biological applications as well as methods to determine their structure-property relationships are not widely available. In this Perspective, we will discuss what is known so far about AuNCs as well as how to move forward to propel AuNCs as a theranostic agent of choice for many biomedical applications.
Metformin triggers PYY secretion in human gut mucosa
Publisher: The Endocrine Society
Date: 12-02-2019
Abstract: The antidiabetic drug metformin causes weight loss, but the underlying mechanisms are unclear. Recent clinical studies show that metformin increases plasma levels of the anorectic gut hormone, peptide YY (PYY), but whether this is through a direct effect on the gut is unknown. We hypothesized that exposure of human gut mucosal tissue to metformin would acutely trigger PYY secretion. Mucosal tissue was prepared from 46 human colonic and 9 ileal s les obtained after surgical resection and ex vivo secretion assays were performed. Tissue was exposed to metformin, as well as a series of other compounds as part of our mechanistic studies, in static incubations. Supernatant was s led after 15 minutes. PYY levels in supernatant, measured using ELISA. Metformin increased PYY secretion from both ileal (P < 0.05) and colonic (P < 0.001) epithelia. Both basal and metformin-induced PYY secretion were unchanged across body mass index or in tissues obtained from in iduals with type 2 diabetes. Metformin-dependent PYY secretion was blocked by inhibitors of the plasma membrane monoamine transporter (PMAT) and the serotonin reuptake transporter (SERT), as well as by an inhibitor of AMP kinase (AMPK). This is a report of a direct action of metformin on the gut epithelium to trigger PYY secretion in humans, occurring via cell internalization through PMAT and SERT and intracellular activation of AMPK. Our results provide further support that the role of metformin in the treatment of metabolic syndrome has a gut-based component.
Somatostatin Increases Voltage-Gated K+ Currents in GH3 Cells through Activation of Multiple Somatostatin Receptors
Publisher: The Endocrine Society
Date: 11-2005
DOI: 10.1210/EN.2005-0696
Abstract: The secretion of GH by somatotropes is inhibited by somatostatin (SRIF) through five specific membrane receptors (SSTRs). SRIF increases both transient outward (IA) and delayed rectifying (IK) K+ currents. We aim to clarify the subtype(s) of SSTRs involved in K+ current enhancement in GH3 somatotrope cells using specific SSTR subtype agonists. Expression of all five SSTRs was confirmed in GH3 cells by RT-PCR. Nystatin-perforated patch cl was used to record voltage-gated K+ currents. We first established the presence of IA and IK type K+ currents in GH3 cells using different holding potentials (−40 or −70 mV) and specific blockers (4-aminopirimidine and tetraethylammonium chloride). SRIF (200 nm) increased the litude of both IA and IK in a fully reversible manner. Various concentrations of each specific SRTR agonist were tested on K+ currents to find the maximal effective concentration. Activation of SSTR2 and SSTR4 by their respective agonists, L-779,976 and L-803,087 (10 nm), increased K+ current litude without preference to IA or IK, and abolished any further increase by SRIF. Activation of SSTR1 and SSTR5 by their respective agonists, L-797,591 or L-817,818 (10 nm), increased K+ current litude, but SRIF evoked a further increase. The SSTR3 agonist L-797,778 (10 nm) did not affect the K+ currents or the response to SRIF. These results indicate that SSTR1, -2, -4, and -5 may all be involved in the enhancement of K+ currents by SRIF but that only the activation of SSTR2 or -4 results in the full activation of K+ current caused by SRIF.
Mice deficient for the chromosome 21 ortholog Itsn1 exhibit vesicle-trafficking abnormalities
Publisher: Oxford University Press (OUP)
Date: 02-08-2008
DOI: 10.1093/HMG/DDN224
Abstract: Enlarged early endosomes in the neurons of young Down syndrome (DS) and pre-Alzheimer's disease (AD) brains suggest that a disturbance in endocytosis is one of the earliest hallmarks of AD pathogenesis in both conditions. We identified a chromosome 21 gene, Intersectin-1 (ITSN1) that is up-regulated in DS brains and has a putative function in endocytosis and vesicle trafficking. To elucidate the function of ITSN1 and assess its contribution to endocytic defects associated with DS and AD, we generated Itsn1 null mice. In knockout mice we found alterations in a number of parameters associated with endocytic and vesicle trafficking events. We found a reduced number of exocytosis events in chromaffin cells and a slowing of endocytosis in neurons. Endosome size was increased in neurons and NGF levels were reduced in the septal region of the brain. Our data is the first indication that Itsn1 has a role in endocytosis in an in vivo mammalian model, and that a disruption in Itsn1 expression causes a disturbance in vesicle trafficking and endocytic function in the brain. These results imply a role for ITSN1 in the early endocytic anomalies reported in DS brains which may have ramifications for the onset of AD.
DSCR1/RCAN1 regulates vesicle exocytosis and fusion pore kinetics: Implications for Down syndrome and Alzheimer's disease
Publisher: Oxford University Press (OUP)
Date: 07-01-2008
DOI: 10.1093/HMG/DDM374
Abstract: Genes located on chromosome 21, over-expressed in Down syndrome (DS) and Alzheimer's disease (AD) and which regulate vesicle trafficking, are strong candidates for involvement in AD neuropathology. Regulator of calcineurin activity 1 (RCAN1) is one such gene. We have generated mutant mice in which RCAN1 is either over-expressed (RCAN1(ox)) or ablated (Rcan1-/-) and examined whether exocytosis from chromaffin cells, a classic cellular model of neuronal exocytosis, is altered using carbon fibre erometry. We find that Rcan1 regulates the number of vesicles undergoing exocytosis and the speed at which the vesicle fusion pore opens and closes. Cells from both Rcan1-/- and RCAN1(ox) mice display reduced levels of exocytosis. Changes in single-vesicle fusion kinetics are also evident resulting in the less catecholamine released per vesicle with increasing Rcan1 expression. Acute calcineurin inhibition did not replicate the effect of RCAN1 overexpression. These changes are not due to alterations in Ca2+ entry or the readily releasable vesicle pool size. Thus, we illustrate a novel regulator of vesicle exocytosis, Rcan1, which influences both exocytotic rate and vesicle fusion kinetics. If Rcan1 functions similarly in neurons then overexpression of this protein, as occurs in DS and AD brains, will reduce both the number of synaptic vesicles undergoing exocytosis and the amount of neurotransmitter released per fusion event. This has direct implications for the pathogenesis of these diseases as sufficient levels of neurotransmission are required for synaptic maintenance and the prevention of neurodegeneration and vesicle trafficking defects are the earliest hallmark of AD neuropathology.
Opioid receptor stimulation suppresses the adrenal medulla hypoxic response in sheep by actions on Ca2+ and K+ channels
Publisher: Wiley
Date: 23-02-2004
NKCC1-Dependent GABAergic Excitation Drives Synaptic Network Maturation during Early Hippocampal Development
Publisher: Society for Neuroscience
Date: 18-03-2009
DOI: 10.1523/JNEUROSCI.1377-08.2009
Abstract: A high intracellular chloride concentration in immature neurons leads to a depolarizing action of GABA that is thought to shape the developing neuronal network. We show that GABA-triggered depolarization and Ca 2+ transients were attenuated in mice deficient for the Na–K–2Cl cotransporter NKCC1. Correlated Ca 2+ transients and giant depolarizing potentials (GDPs) were drastically reduced and the maturation of the glutamatergic and GABAergic transmission in CA1 delayed. Brain morphology, synaptic density, and expression levels of certain developmental marker genes were unchanged. The expression of lynx1, a protein known to d en network activity, was decreased. In mice deficient for the neuronal Cl − /HCO 3 − exchanger AE3, GDPs were also diminished. These data show that NKCC1-mediated Cl − accumulation contributes to GABAergic excitation and network activity during early postnatal development and thus facilitates the maturation of excitatory and inhibitory synapses.
Increased Expression of the Glucose-Responsive Gene, RCAN1, Causes Hypoinsulinemia, β-Cell Dysfunction, and Diabetes
Publisher: The Endocrine Society
Date: 11-2012
DOI: 10.1210/EN.2011-2149
Abstract: RCAN1 is a chromosome 21 gene that controls secretion in endocrine cells, regulates mitochondrial function, and is sensitive to oxidative stress. Regulator of calcineurin 1 (RCAN1) is also an endogenous inhibitor of the protein phosphatase calcineurin, the inhibition of which leads to hypoinsulinemia and diabetes in humans and mice. However, the presence or the role of RCAN1 in insulin-secreting β-cells and its potential role in the pathogenesis of diabetes is unknown. Hence, the aim of this study is to investigate the presence of RCAN1 in β-cells and identify its role in β-cell function. RCAN1 is expressed in mouse islets and in the cytosol of pancreatic β-cells. We find RCAN1 is a glucose-responsive gene with a 1.5-fold increase in expression observed in pancreatic islets in response to chronic hyperglycemia. The overexpression of the human RCAN1.1 isoform in mice under the regulation of its endogenous promoter causes diabetes, age-associated hyperglycemia, reduced glucose tolerance, hypoinsulinemia, loss of β-cells, reduced β-cell insulin secretion, aberrant mitochondrial reactive oxygen species production, and the down-regulation of key β-cell genes. Our data therefore identifies a novel molecular link between the overexpression of RCAN1 and β-cell dysfunction. The glucose-responsive nature of RCAN1 provides a potential mechanism of action associated with the β-cell dysfunction observed in diabetes.
Mechanisms underlying distension-evoked peristalsis in guinea pig distal colon: is there a role for enterochromaffin cells?
Publisher: American Physiological Society
Date: 09-2011
Abstract: The mechanisms underlying distension-evoked peristalsis in the colon are incompletely understood. It is well known that, following colonic distension, 5-hydroxytryptamine (5-HT) is released from enterochromaffin (EC) cells in the intestinal mucosa. It is also known that exogenous 5-HT can stimulate peristalsis. These observations have led some investigators to propose that endogenous 5-HT release from EC cells might be involved in the initiation of colonic peristalsis, following distension. However, because no direct evidence exists to support this hypothesis, the aim of this study was to determine directly whether release of 5-HT from EC cells was required for distension-evoked colonic peristalsis. Real-time erometric recordings of 5-HT release and video imaging of colonic wall movements were performed on isolated segments of guinea pig distal colon, during distension-evoked peristalsis. Amperometric recordings revealed basal and transient release of 5-HT from EC cells before and during the initiation of peristalsis, respectively. However, removal of mucosa (and submucosal plexus) abolished 5-HT release but did not inhibit the initiation of peristalsis nor prevent the propagation of fecal pellets or intraluminal fluid. Maintained colonic distension by fecal pellets induced repetitive peristaltic waves, whose intrinsic frequency was also unaffected by removal of the submucosal plexus and mucosa, although their propagation velocities were slower. In conclusion, the mechanoreceptors and sensory neurons activated by radial distension to initiate peristalsis lie in the myenteric plexus and/or muscularis externa, and their activation does not require the submucosal plexus, release of 5-HT from EC cells, nor the presence of the mucosa. The propagation of peristalsis and propulsion of liquid or solid content along the colon is entrained by activity within the myenteric plexus and/or muscularis externa and does not require sensory feedback from the mucosa, nor neural inputs arising from submucosal ganglia.
The contribution of voltage‐gated Ca2+ currents to K+ channel activation during ovine adrenal chromaffin cell development
Publisher: Wiley
Date: 13-03-2009
DOI: 10.1016/J.IJDEVNEU.2009.03.003
Abstract: Prior to the development of adrenal innervation, the adrenal medulla is capable of responding to low blood oxygen directly. However, this response is lost once adrenal innervation is established. Previous work by our group has outlined mechanisms involved in this direct hypoxic response and the means by which innervation causes the loss of the direct hypoxic response in the ovine adrenal. The current study further investigates mechanisms which may underlie the developmental loss of the direct hypoxic response by concentrating on two aspects of cell function which regulate catecholamine secretion: the contribution of different types of Ca2+ channels to the total Ca2+ current and the contribution of each Ca2+ channel type to K+ channel activation. We identified that Ca2+ current size at -40 to -10 mV is increased in litude in fetal chromaffin cells. This is not due to the increased prevalence or size of T-type Ca2+ currents present at these voltages. The relative contribution of L-, N- or P/Q-type Ca2+ channels to total Ca2+ current and to activation of the K+ current is unchanged during chromaffin cell development, however K+ current density increases with age. Our results indicate that there is a developmental shift in relative expression of T-type, but not L-, N- or P/Q-type, Ca2+ channels in ovine chromaffin cells. The increased K+ current density in adult cells may result in an altered response to an equal stimulus, while larger Ca2+ current at negative voltages in fetal cells may facilitate Ca2+ entry and catecholamine secretion in response to small depolarisations such as those induced by hypoxia.
Long-term inhibition of protein tyrosine kinase impairs electrophysiologic activity and a rapid component of exocytosis in pancreatic β-cells
Publisher: Bioscientifica
Date: 08-2005
DOI: 10.1677/JME.1.01779
Abstract: Dysfunction of pancreatic β-cells is a fundamental feature in the pathogenesis of type 2 diabetes. As insulin receptor signaling occurs via protein tyrosine kinase (PTK), we investigated the role of PTK activity in the etiology of β-cell dysfunction by inhibiting PTK activity in primary cultured mouse pancreatic β-cells and INS-1 cells with genistein treatment over 24 h. Electrophysiologic recordings showed genistein treatment significantly attenuated ATP-sensitive K + (K ATP ) and voltage-dependent Ca 2+ currents, and depolarized the resting membrane potential in primary β-cells. When stimulated by high glucose, genistein-treated β-cells exhibited a time delay of both depolarization and Ca 2+ influx, and were unable to fire action potentials, as well as displaying a reduced level of Ca 2+ influx and a loss of Ca 2+ oscillations. Semiquantitative PCR analysis revealed decreased expression of K ATP and L-type Ca 2+ channel mRNA in genistein-treated islets. PTK inhibition also significantly reduced the rapid component of secretory vesicle exocytosis, as indicated by membrane capacitance measurements, and this is likely to be due to the reduced Ca 2+ current litude in these cells. These results illustrate that compromised PTK activity contributes to pancreatic β-cell dysfunction and may be involved in the etiology of type 2 diabetes.
Treatment of type 2 diabetes with the designer cytokine IC7Fc
Publisher: Springer Science and Business Media LLC
Date: 25-09-2019
DOI: 10.1038/S41586-019-1601-9
Abstract: The gp130 receptor cytokines IL-6 and CNTF improve metabolic homeostasis but have limited therapeutic use for the treatment of type 2 diabetes. Accordingly, we engineered the gp130 ligand IC7Fc, in which one gp130-binding site is removed from IL-6 and replaced with the LIF-receptor-binding site from CNTF, fused with the Fc domain of immunoglobulin G, creating a cytokine with CNTF-like, but IL-6-receptor-dependent, signalling. Here we show that IC7Fc improves glucose tolerance and hyperglycaemia and prevents weight gain and liver steatosis in mice. In addition, IC7Fc either increases, or prevents the loss of, skeletal muscle mass by activation of the transcriptional regulator YAP1. In human-cell-based assays, and in non-human primates, IC7Fc treatment results in no signs of inflammation or immunogenicity. Thus, IC7Fc is a realistic next-generation biological agent for the treatment of type 2 diabetes and muscle atrophy, disorders that are currently pandemic.
Identification of unique release kinetics of serotonin from guinea-pig and human enterochromaffin cells
Publisher: Wiley
Date: 12-11-2013
Enteroendocrine cells sense bacterial tryptophan catabolites to activate enteric and vagal neuronal pathways
Publisher: Elsevier BV
Date: 02-2021
Mechanisms Controlling Glucose-Induced GLP-1 Secretion in Human Small Intestine
Publisher: American Diabetes Association
Date: 06-04-2017
DOI: 10.2337/DB17-0058
Abstract: Intestinal glucose stimulates secretion of the incretin hormone glucagon-like peptide 1 (GLP-1). The mechanisms underlying this pathway have not been fully investigated in humans. In this study, we showed that a 30-min intraduodenal glucose infusion activated half of all duodenal L cells in humans. This infusion was sufficient to increase plasma GLP-1 levels. With an ex vivo model using human gut tissue specimens, we showed a dose-responsive GLP-1 secretion in the ileum at ≥200 mmol/L glucose. In ex vivo tissue from the duodenum and ileum, but not the colon, 300 mmol/L glucose potently stimulated GLP-1 release. In the ileum, this response was independent of osmotic influences and required delivery of glucose via GLUT2 and mitochondrial metabolism. The requirement of voltage-gated Na+ and Ca2+ channel activation indicates that membrane depolarization occurs. KATP channels do not drive this, as tolbutamide did not trigger release. The sodium–glucose cotransporter 1 (SGLT1) substrate α-MG induced secretion, and the response was blocked by the SGLT1 inhibitor phlorizin or by replacement of extracellular Na+ with N-methyl-d-glucamine. This is the first report of the mechanisms underlying glucose-induced GLP-1 secretion from human small intestine. Our findings demonstrate a dominant role of SGLT1 in controlling glucose-stimulated GLP-1 release in human ileal L cells.
Islets and pancreatic ductal adenocarcinoma – An opportunity for translational research from the ‘Bench to the Bedside’
Publisher: Elsevier BV
Date: 04-2020
Evidence for Glucagon Secretion and Function Within the Human Gut
Publisher: The Endocrine Society
Date: 03-02-2021
Abstract: Glucagon is secreted by pancreatic α cells in response to hypoglycemia and increases hepatic glucose output through hepatic glucagon receptors (GCGRs). There is evidence supporting the notion of extrapancreatic glucagon but its source and physiological functions remain elusive. Intestinal tissue s les were obtained from patients undergoing surgical resection of cancer. Mass spectrometry analysis was used to detect glucagon from mucosal lysate. Static incubations of mucosal tissue were performed to assess glucagon secretory response. Glucagon concentration was quantitated using a highly specific sandwich enzyme-linked immunosorbent assay. A cholesterol uptake assay and an isolated murine colonic motility assay were used to assess the physiological functions of intestinal GCGRs. Fully processed glucagon was detected by mass spectrometry in human intestinal mucosal lysate. High glucose evoked significant glucagon secretion from human ileal tissue independent of sodium glucose cotransporter and KATP channels, contrasting glucose-induced glucagon-like peptide 1 (GLP-1) secretion. The GLP-1 receptor agonist Exendin-4 attenuated glucose-induced glucagon secretion from the human ileum. GCGR blockade significantly increased cholesterol uptake in human ileal crypt culture and markedly slowed ex vivo colonic motility. Our findings describe the human gut as a potential source of extrapancreatic glucagon and demonstrate a novel enteric glucagon/GCGR circuit with important physiological functions beyond glycemic regulation.
Reduction in Voltage-Gated K+ Currents in Primary Cultured Rat Pancreatic β-Cells by Linoleic Acids
Publisher: The Endocrine Society
Date: 02-2006
DOI: 10.1210/EN.2005-0225
Abstract: Free fatty acids (FFAs), in addition to glucose, have been shown to stimulate insulin release through the G protein-coupled receptor (GPCR)40 receptor in pancreatic β-cells. Intracellular free calcium concentration ([Ca2+]i) in β-cells is elevated by FFAs, although the mechanism underlying the [Ca2+]i increase is still unknown. In this study, we investigated the action of linoleic acid on voltage-gated K+ currents. Nystatin-perforated recordings were performed on identified rat β-cells. In the presence of nifedipine, tetrodotoxin, and tolbutamide, voltage-gated K+ currents were observed. The transient current represents less than 5%, whereas the delayed rectifier current comprises more than 95%, of the total K+ currents. A long-chain unsaturated FFA, linoleic acid (10 μm), reversibly decreased the litude of K+ currents (to less than 10%). This reduction was abolished by the cAMP rotein kinase A system inhibitors H89 (1 μm) and Rp-cAMP (10 μm) but was not affected by protein kinase C inhibitor. In addition, forskolin and 8′-bromo-cAMP induced a similar reduction in the K+ current as that evoked by linoleic acid. Insulin secretion and cAMP accumulation in β-cells were also increased by linoleic acid. Methyl linoleate, which has a similar structure to linoleic acid but no binding affinity to GPR40, did not change K+ currents. Treatment of cultured cells with GPR40-specific small interfering RNA significantly reduced the decrease in K+ current induced by linoleic acid, whereas the cAMP-induced reduction of K+ current was not affected. We conclude that linoleic acid reduces the voltage-gated K+ current in rat β-cells through GPR40 and the cAMP-protein kinase A system, leading to an increase in [Ca2+]i and insulin secretion.
Metformin-induced glucagon-like peptide-1 secretion contributes to the actions of metformin in type 2 diabetes
Publisher: American Society for Clinical Investigation
Date: 06-12-2018
RCAN1 Regulates Mitochondrial Function and Increases Susceptibility to Oxidative Stress in Mammalian Cells
Publisher: Hindawi Limited
Date: 2014
DOI: 10.1155/2014/520316
Abstract: Mitochondria are the primary site of cellular energy generation and reactive oxygen species (ROS) accumulation. Elevated ROS levels are detrimental to normal cell function and have been linked to the pathogenesis of neurodegenerative disorders such as Down's syndrome (DS) and Alzheimer’s disease (AD). RCAN1 is abundantly expressed in the brain and overexpressed in brain of DS and AD patients. Data from nonmammalian species indicates that increased RCAN1 expression results in altered mitochondrial function and that RCAN1 may itself regulate neuronal ROS production. In this study, we have utilized mice overexpressing RCAN1 R C A N 1 o x and demonstrate an increased susceptibility of neurons from these mice to oxidative stress. Mitochondria from these mice are more numerous and smaller, indicative of mitochondrial dysfunction, and mitochondrial membrane potential is altered under conditions of oxidative stress. We also generated a PC12 cell line overexpressing RCAN1 P C 12 R C A N 1 . Similar to R C A N 1 o x neurons, P C 12 R C A N 1 cells have an increased susceptibility to oxidative stress and produce more mitochondrial ROS. This study demonstrates that increasing RCAN1 expression alters mitochondrial function and increases the susceptibility of neurons to oxidative stress in mammalian cells. These findings further contribute to our understanding of RCAN1 and its potential role in the pathogenesis of neurodegenerative disorders such as AD and DS.
Carbon-Fiber Amperometry in the Study of Exocytosis
Publisher: Humana Press
Date: 03-10-2014
Ghrelin Reduces Voltage-Gated Potassium Currents in GH<SUB>3</SUB> Cells Via Cyclic GMP Pathways
Publisher: Springer Science and Business Media LLC
Date: 2005
Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)
Publisher: Informa UK Limited
Date: 02-01-2016
ClC-3—A Granular Anion Transporter Involved in Insulin Secretion?
Publisher: Elsevier BV
Date: 10-2010
Exocytosis is impaired in mucopolysaccharidosis IIIA mouse chromaffin cells
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.NEUROSCIENCE.2012.09.034
Abstract: Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disorder caused by a deficiency in the activity of the lysosomal hydrolase, sulphamidase, an enzyme involved in the degradation of heparan sulphate. MPS IIIA patients exhibit progressive mental retardation and behavioural disturbance. While neuropathology is the major clinical problem in MPS IIIA patients, there is little understanding of how lysosomal storage generates this phenotype. As reduced neuronal communication can underlie cognitive deficiencies, we investigated whether the secretion of neurotransmitters is altered in MPS IIIA mice utilising adrenal chromaffin cells, a classical model for studying secretion via exocytosis. MPS IIIA chromaffin cells displayed heparan sulphate storage and electron microscopy revealed large electron-lucent storage compartments. There were also increased numbers of large/elongated chromaffin granules, with a morphology that was similar to immature secretory granules. Carbon fibre erometry illustrated a significant decrease in the number of exocytotic events for MPS IIIA, when compared to control chromaffin cells. However, there were no changes in the kinetics of release, the amount of catecholamine released per exocytotic event, or the amount of Ca(2+) entry upon stimulation. The increased number of large/elongated granules and reduced number of exocytotic events suggests that either the biogenesis and/or the cell surface docking and fusion potential of these vesicles is impaired in MPS IIIA. If this also occurs in central nervous system neurons, the reduction in neurotransmitter release could help to explain the development of neuropathology in MPS IIIA.
The Impact of Long-Term Macrolide Exposure on the Gut Microbiome and Its Implications for Metabolic Control
Publisher: American Society for Microbiology
Date: 17-08-2023
DOI: 10.1128/SPECTRUM.00831-23
Abstract: Long-term macrolide therapy is widely used in chronic respiratory diseases although its antibacterial activity can also affect the gut microbiota, a key regulator of host physiology. Macrolide-associated studies on the gut microbiota have been limited to short antibiotic courses and have not examined its consequences for host immune and metabolic regulation.
Dynamin regulates L cell secretion in human gut
Publisher: Elsevier BV
Date: 09-2021
DOI: 10.1016/J.MCE.2021.111398
Abstract: The mechanochemical enzyme dynamin mediates endocytosis and regulates neuroendocrine cell exocytosis. Enteroendocrine L cells co-secrete the anorectic gut hormones glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) postprandially and is a potential therapeutic target for metabolic diseases. In the present study, we aimed to determine if dynamin is implicated in human L cell secretion. Western blot was performed on the murine L cell line GLUTag. Static incubation of human colonic mucosae with activators and inhibitors of dynamin was carried out. GLP-1 and PYY contents of the secretion supernatants were assayed using ELISA. s: Both dynamin I and II are expressed in GLUTag cells. The dynamin activator Ryngo 1-23 evoked significant GLP-1 and PYY release from human colonic mucosae while the dynamin inhibitor Dynole 3-42 significantly inhibited release triggered by known L cell secretagogues. Thus, the cell signaling regulator dynamin is able to bi-directionally regulate L cell hormone secretion in the human gut and may represent a novel target for gastrointestinal-targeted metabolic drug development.
Editorial: Gastrointestinal Hormones
Publisher: Frontiers Media SA
Date: 25-07-2019
The gut-brain axis: spatial relationship between spinal afferent nerves and 5-HT-containing enterochromaffin cells in mucosa of mouse colon
Publisher: American Physiological Society
Date: 05-2022
Abstract: We show an absence of close physical contact between spinal afferent nerves and 5-HT-containing EC cells in mouse colonic mucosa. Similar relative distances were observed between randomized EC cells and spinal afferents compared with actual data. This spatial relationship suggests that substances released from colonic 5-HT-containing EC cells are unlikely to act via synaptic transmission to neighboring spinal afferents that relay sensory information from the gut lumen to the brain.
Synaptic Activation of Putative Sensory Neurons by Hexamethonium-sensitive nerve pathways in mouse colon
Publisher: American Physiological Society
Date: 2018
Abstract: The gastrointestinal tract contains its own independent population of sensory neurons within the gut wall. These sensory neurons have been referred to as intrinsic primary afferent neurons (IPANs) and can be identified by immunoreactivity to calcitonin gene-related peptide (CGRP) in mice. A common feature of IPANs is a paucity of fast synaptic inputs observed during sharp microelectrode recordings. Whether this is observed using different recording techniques is of particular interest for understanding the physiology of these neurons and neural circuit modeling. Here, we imaged spontaneous and evoked activation of myenteric neurons in isolated whole preparations of mouse colon and correlated recordings with CGRP and nitric oxide synthase (NOS) immunoreactivity, post hoc. Calcium indicator fluo 4 was used for this purpose. Calcium responses were recorded in nerve cell bodies located 5–10 mm oral to transmural electrical nerve stimuli. A total of 618 recorded neurons were classified for CGRP or NOS immunoreactivity. Aboral electrical stimulation evoked short-latency calcium transients in the majority of myenteric neurons, including ~90% of CGRP-immunoreactive Dogiel type II neurons. Activation of Dogiel type II neurons had a time course consistent with fast synaptic transmission and was always abolished by hexamethonium (300 μM) and by low-calcium Krebs solution. The nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium iodide (during synaptic blockade) directly activated Dogiel type II neurons. The present study suggests that murine colonic Dogiel type II neurons receive prominent fast excitatory synaptic inputs from hexamethonium-sensitive neural pathways. NEW & NOTEWORTHY Myenteric neurons in isolated mouse colon were recorded using calcium imaging and then neurochemically defined. Short-latency calcium transients were detected in % of calcitonin gene-related peptide-immunoreactive neurons to electrical stimulation of hexamethonium-sensitive pathways. Putative sensory Dogiel type II calcitonin gene-related peptide-immunoreactive myenteric neurons may receive widespread fast synaptic inputs in mouse colon.
Copper modulates the large dense core vesicle secretory pathway in PC12 cells
Publisher: Oxford University Press (OUP)
Date: 2013
DOI: 10.1039/C3MT20231C
Abstract: Copper (Cu) is an essential biometal involved in a number of cell functions. Abnormal Cu homeostasis has been identified as a major factor in a number of neurodegenerative disorders. However, little is known about how cells of brain origin maintain Cu homeostasis and in particular, how they respond to an elevated Cu environment. Understanding these processes is essential to obtaining a greater insight into the pathological changes in neurodegeneration and ageing. Although previous studies have shown that Cu in neurons can be associated with synaptic function, there is little understanding of how Cu modulates the regulated secretory vesicle pathways in these cells. In this study, we examined the effect of elevated intracellular Cu on proteins associated with the regulated secretory vesicle pathway in NGF-differentiated PC12 cells that exhibit neuronal-like properties. Increasing intracellular Cu with a cell-permeable Cu-complex (Cu(II)(gtsm)) resulted in increased expression of synaptophysin and robust translocation of this and additional vesicular proteins from synaptic-like microvesicle (SLMV) fractions to chromogranin-containing putative large dense core vesicle (LDCV) fractions in density gradient preparations. The LDCV fractions also contained substantially elevated Cu levels upon treatment of cells with Cu(II)(gtsm). Expression of the H(+) pump, V-ATPase, which is essential for vesicle maturation, was increased in Cu-treated cells while inhibition of V-ATPase prevented translocation of synaptophysin to LDCV fractions. Cu treatment was found to inhibit release of LDCVs in chromaffin cells due to reduced Ca(2+)-mediated vesicle exocytosis. Our findings demonstrate that elevated Cu can modulate LDCV metabolism potentially resulting in sequestration of Cu in this vesicle pool.
From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways
Publisher: Springer Science and Business Media LLC
Date: 19-04-2016
DOI: 10.1038/MP.2016.50
Huntingtin-associated protein-1 is a synapsin I-binding protein regulating synaptic vesicle exocytosis and synapsin I trafficking.
Publisher: Wiley
Date: 18-07-2016
DOI: 10.1111/JNC.13703
Abstract: Huntingtin-associated protein-1 (HAP1) is involved in intracellular trafficking, vesicle transport, and membrane receptor endocytosis. However, despite such erse functions, the role of HAP1 in the synaptic vesicle (SV) cycle in nerve terminals remains unclear. Here, we report that HAP1 functions in SV exocytosis, controls total SV turnover and the speed of vesicle fusion in nerve terminals and regulates glutamate release in cortical brain slices. We found that HAP1 interacts with synapsin I, an abundant neuronal phosphoprotein that associates with SVs during neurotransmitter release and regulates synaptic plasticity and neuronal development. The interaction between HAP1 with synapsin I was confirmed by reciprocal co-immunoprecipitation of the endogenous proteins. Furthermore, HAP1 co-localizes with synapsin I in cortical neurons as discrete puncta. Interestingly, we find that synapsin I localization is specifically altered in Hap1(-/-) cortical neurons without an effect on the localization of other SV proteins. This effect on synapsin I localization was not because of changes in the levels of synapsin I or its phosphorylation status in Hap1(-/-) brains. Furthermore, fluorescence recovery after photobleaching in transfected neurons expressing enhanced green fluorescent protein-synapsin Ia demonstrates that loss of HAP1 protein inhibits synapsin I transport. Thus, we demonstrate that HAP1 regulates SV exocytosis and may do so through binding to synapsin I. The Proposed mechanism of synapsin I transport mediated by HAP1 in neurons. HAP1 interacts with synapsin I, regulating the trafficking of synapsin I containing vesicles and/or transport packets, possibly through its engagement of microtubule motors. The absence of HAP1 reduces synapsin I transport and neuronal exocytosis. These findings provide insights into the processes of neuronal trafficking and synaptic signaling.
Neuropeptides 2010 Conference: The 7th Joint Meeting of the European Neuropeptide Club and the American Summer Neuropeptide Conference 21–24 June 2010 Pécs, Hungary
Publisher: Elsevier BV
Date: 12-2010
Emerging Roles for Serotonin in Regulating Metabolism: New Implications for an Ancient Molecule
Publisher: The Endocrine Society
Date: 22-03-2019
Abstract: Serotonin is a phylogenetically ancient biogenic amine that has played an integral role in maintaining energy homeostasis for billions of years. In mammals, serotonin produced within the central nervous system regulates behavior, suppresses appetite, and promotes energy expenditure by increasing sympathetic drive to brown adipose tissue. In addition to these central circuits, emerging evidence also suggests an important role for peripheral serotonin as a factor that enhances nutrient absorption and storage. Specifically, glucose and fatty acids stimulate the release of serotonin from the duodenum, promoting gut peristalsis and nutrient absorption. Serotonin also enters the bloodstream and interacts with multiple organs, priming the body for energy storage by promoting insulin secretion and de novo lipogenesis in the liver and white adipose tissue, while reducing lipolysis and the metabolic activity of brown and beige adipose tissue. Collectively, peripheral serotonin acts as an endocrine factor to promote the efficient storage of energy by upregulating lipid anabolism. Pharmacological inhibition of serotonin synthesis or signaling in key metabolic tissues are potential drug targets for obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).
The neuronal and endocrine roles of RCAN1 in health and disease
Publisher: Wiley
Date: 29-11-2018
Abstract: The regulator of calcineurin 1 (RCAN1) was first discovered as a gene located on human chromosome 21, expressed in neurons and overexpressed in the brains of Down syndrome in iduals. Increased expression of RCAN1 has been linked with not only Down syndrome-associated pathology but also an associated neurological disorder, Alzheimer's Disease, in which neuronal RCAN1 expression is also increased. RCAN1 has additionally been demonstrated to affect other cell types including endocrine cells, with links to the pathogenesis of β-cell dysfunction in type 2 diabetes. The primary functions of RCAN1 relate to the inhibition of the phosphatase calcineurin, and to the regulation of mitochondrial function. Various forms of cellular stress such as reactive oxygen species and hyperglycaemia cause transient increases in RCAN1 expression. The short term (hours to days) induction of RCAN1 expression is generally thought to have a protective effect by regulating the expression of pro-survival genes in multiple cell types, many of which are mediated via the calcineurin/NFAT transcriptional pathway. However, strong evidence also supports the notion that chronic (weeks-years) overexpression of RCAN1 has a detrimental effect on cells and that this may drive pathophysiological changes in neurons and endocrine cells linked to Down syndrome, Alzheimer's Disease and type 2 diabetes. Here we review the evidence related to these roles of RCAN1 in neurons and endocrine cells and their relationship to these human health disorders.
CrossTalk opposing view: 5-HT is not necessary for peristalsis
Publisher: Wiley
Date: 31-07-2015
DOI: 10.1113/JP270183
Phosphatidylinositol(4,5)bisphosphate coordinates actin-mediated mobilization and translocation of secretory vesicles to the plasma membrane of chromaffin cells
Publisher: Springer Science and Business Media LLC
Date: 04-10-2011
DOI: 10.1038/NCOMMS1500
Abstract: Neurosecretory vesicles undergo docking and priming before Ca(2+)-dependent fusion with the plasma membrane. Although de novo synthesis of phosphatidylinositol(4,5)bisphosphate (PtdIns(4,5)P(2)) is required for exocytosis, its precise contribution is still unclear. Here we show that inhibition of the p110δ isoform of PI3-kinase by IC87114 promotes a transient increase in PtdIns(4,5)P(2), leading to a potentiation of exocytosis in chromaffin cells. We then exploit this pathway to examine the effect of a transient PtdIns(4,5)P(2) increase on neurosecretory vesicles behaviour, outside the context of a secretagogue stimulation. Our results demonstrate that a rise in PtdIns(4,5)P(2) is sufficient to promote the mobilization and recruitment of secretory vesicles to the plasma membrane via Cdc42-mediated actin reorganization. PtdIns(4,5)P(2), therefore, orchestrates the actin-based conveyance of secretory vesicles to the plasma membrane.
Endothelial Progenitor Cells Enhance Islet Engraftment, Influence β-Cell Function, and Modulate Islet Connexin 36 Expression
Publisher: SAGE Publications
Date: 2015
Abstract: The success of pancreatic islet transplantation is limited by delayed engraftment and suboptimal function in the longer term. Endothelial progenitor cells (EPCs) represent a potential cellular therapy that may improve the engraftment of transplanted pancreatic islets. In addition, EPCs may directly affect the function of pancreatic β-cells. The objective of this study was to examine the ability of EPCs to enhance pancreatic islet transplantation in a murine syngeneic marginal mass transplant model and to examine the mechanisms through which this occurs. We found that cotransplanted EPCs improved the cure rate and initial glycemic control of transplanted islets. Gene expression data indicate that EPCs, or their soluble products, modulate the expression of the β-cell surface molecule connexin 36 and affect glucose-stimulated insulin release in vitro. In conclusion, EPCs are a promising candidate for improving outcomes in islet transplantation, and their mechanisms of action warrant further study.
Myristyl Trimethyl Ammonium Bromide and Octadecyl Trimethyl Ammonium Bromide Are Surface-Active Small Molecule Dynamin Inhibitors that Block Endocytosis Mediated by Dynamin I or Dynamin II
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 16-08-2007
Abstract: Dynamin is a GTPase enzyme involved in membrane constriction and fission during endocytosis. Phospholipid binding via its pleckstrin homology domain maximally stimulates dynamin activity. We developed a series of surface-active small-molecule inhibitors, such as myristyl trimethyl ammonium bromide (MiTMAB) and octadecyltrimethyl ammonium bromide (OcTMAB), and we now show MiTMAB targets the dynamin-phospholipid interaction. MiTMAB inhibited dynamin GTPase activity, with a Ki of 940 +/- 25 nM. It potently inhibited receptor-mediated endocytosis (RME) of transferrin or epidermal growth factor (EGF) in a range of cells without blocking EGF binding, receptor number, or autophosphorylation. RME inhibition was rapidly reversed after washout. The rank order of potency for a variety of MiTMAB analogs on RME matched the rank order for dynamin inhibition, suggesting dynamin recruitment to the membrane is a primary cellular target. MiTMAB also inhibited synaptic vesicle endocytosis in rat brain nerve terminals (synaptosomes) without inducing depolarization or morphological defects. Therefore, the drug rapidly and reversibly blocks multiple forms of endocytosis with no acute cellular damage. The unique mechanism of action of MiTMAB provides an important tool to better understand dynamin-mediated membrane trafficking events in a variety of cells.
Oxygen-sensing pathway for SK channels in the ovine adrenal medulla
Publisher: Wiley
Date: 19-09-2005
DOI: 10.1111/J.1440-1681.2010.04279.X
Abstract: 1. The intracellular pathways that modulate the opening of oxygen-sensitive ion channels during periods of hypoxia are poorly understood. Different tissues appear to use either NADPH oxidase or a rotenone-sensitive mechanism as an oxygen sensor. The aim of the present study was to identify the oxygen-sensing pathway in the oxygen-sensitive sheep adrenal medullary chromaffin cell (AMCC). 2. The whole-cell patch-cl technique was used to measure K+ currents in dissociated adult ovine chromaffin cells as well as SK channel currents expressed in the H4IIE cell line. 3. Diphenyliodonium, an inhibitor of NADPH oxidase, had no effect on the hypoxia-evoked closure of K+ channels in primary AMCC, whereas the mitochondrial inhibitor rotenone abolished the hypoxia-evoked response. Both these compounds significantly reduced K+ current litude under normoxic conditions. 4. One possible mechanism through which the oxygen sensor may modulate K+ channel activity is by altering the redox state of the cell. In sheep AMCC, altering the redox state by the addition of H2O2 to the extracellular solution increased K+ conductance. 5. The oxygen-sensitive K+ (Ko2) channels in sheep chromaffin cells are from the SK family and the whole-cell conductance of cells expressing mouse SK2 or SK3, but not human SK1, was increased by H2O2 and decreased by the reducing agent dithiothreitol. 6. These studies show that, in sheep AMCC, Ko2 channels are modulated via a rotenone-sensitive mechanism and that alteration of the cellular redox state mimics the change produced by alterations in Po2. In a heterologous expression system, SK2 and SK3 channels, the channels that initiate hypoxia-evoked changes in AMCC function, are modulated appropriately by changes in cellular redox state.
Pyrimidyn Compounds: Dual-Action Small Molecule Pyrimidine-Based Dynamin Inhibitors
Publisher: American Chemical Society (ACS)
Date: 30-05-2013
DOI: 10.1021/CB400137P
Single-cell gene expression links SARS-CoV-2 infection and gut serotonin
Publisher: BMJ
Date: 23-08-2023
A Syntenic Cross Species Aneuploidy Genetic Screen Links RCAN1 Expression to β-Cell Mitochondrial Dysfunction in Type 2 Diabetes
Publisher: Public Library of Science (PLoS)
Date: 19-05-2016
HAP1 Is Required for Endocytosis and Signalling of BDNF and Its Receptors in Neurons.
Publisher: Springer Science and Business Media LLC
Date: 12-01-2017
Linoleic acid induces Ca2+-induced inactivation of voltage-dependent Ca2+ currents in rat pancreatic β-cells
Publisher: Bioscientifica
Date: 23-11-2007
DOI: 10.1677/JOE-07-0426
Abstract: Free fatty acids (FFAs) regulate insulin secretion in a complex pattern and induce pancreatic β-cell dysfunction in type 2 diabetes. Voltage-dependent Ca 2 + channels (VDCC) in β-cells play a major role in regulating insulin secretion. The aim of present study is to clarify the action of the FFA, linoleic acid, on VDCC in β-cells. The VDCC current in primary cultured rat β-cells were recorded under nystatin-perforated whole-cell recording configuration. The VDCC was identified as high-voltage-gated Ca 2 + channels due to there being no difference in current litude under holding potential between −70 and −40 mV. Linoleic acid (10 μM) significantly inhibited VDCC currents in β-cells, an effect which was fully reversible upon washout. Methyl-linoleic acid, which does not activate G protein coupled receptor (GPR)40, neither did alter VDCC current in rat β-cells nor did influence linoleic acid-induced inhibition of VDCC currents. Linoleic acid-induced inhibition of VDCC current was not blocked by preincubation of β-cells with either the specific protein kinase A (PKA) inhibitor, H89, or the PKC inhibitor, chelerythrine. However, pretreatment of β-cells with thapsigargin, which depletes intracellular Ca 2+ stores, completely abolished linoleic acid-induced decrease in VDCC current. Measurement of intracellular Ca 2+ concentration ([Ca 2+ ] i ) illustrated that linoleic acid induced an increase in [Ca 2+ ] i and that thapsigargin pretreatment inhibited this increase. Methyl-linoleic acid neither did induce increase in [Ca 2+ ] i nor did it block linoleic acid-induced increase in [Ca 2+ ] i . These results suggest that linoleic acid stimulates Ca 2+ release from intracellular Ca 2+ stores and inhibits VDCC currents in rat pancreatic β-cells via Ca 2+ -induced inactivation of VDCC.
Alterations in GLP-1 and PYY release with aging and body mass in the human gut
Publisher: Elsevier BV
Date: 12-2023
Serotonin-secreting enteroendocrine cells respond via diverse mechanisms to acute and chronic changes in glucose availability
Publisher: Springer Science and Business Media LLC
Date: 12-2015
Cellular regulation of peripheral serotonin
Publisher: Elsevier
Date: 2019
Exocytosis in non‐neuronal cells
Publisher: Wiley
Date: 02-05-2016
DOI: 10.1111/JNC.13602
Abstract: Exocytosis is the process by which stored neurotransmitters and hormones are released via the fusion of secretory vesicles with the plasma membrane. It is a dynamic, rapid and spatially restricted process involving multiple steps including vesicle trafficking, tethering, docking, priming and fusion. For many years great steps have been undertaken in our understanding of how exocytosis occurs in different cell types, with significant focus being placed on synaptic release and neurotransmission. However, this process of exocytosis is an essential component of cell signalling throughout the body and underpins a erse array of essential physiological pathways. Many similarities exist between different cell types with regard to key aspects of the exocytosis pathway, such as the need for Ca(2+) to trigger it or the involvement of members of the N-ethyl maleimide-sensitive fusion protein attachment protein receptor protein families. However, it is also equally clear that non-neuronal cells have acquired highly specialized mechanisms to control the release of their own unique chemical messengers. This review will focus on several important non-neuronal cell types and discuss what we know about the mechanisms they use to control exocytosis and how their specialized output is relevant to the physiological role of each in idual cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. Non-neuronal cells have acquired highly specialized mechanisms to control the release of unique chemical messengers, such as polarised fusion of insulin granules in pancreatic β cells targeted towards the vasculature (top). This review discusses mechanisms used in several important non-neuronal cell types to control exocytosis, and the relevance of intermediate vesicle fusion pore states (bottom) and their specialized output to the physiological role of each cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. This article is part of a mini review series on Chromaffin cells (ISCCB Meeting, 2015).
Diet differentially regulates enterochromaffin cell serotonin content, density and nutrient sensitivity in the mouse small and large intestine
Publisher: Wiley
Date: 07-05-2020
DOI: 10.1111/NMO.13869
Direct Reprogramming of Mouse Fibroblasts to Neural Stem Cells by Small Molecules
Publisher: Hindawi Limited
Date: 2016
DOI: 10.1155/2016/4304916
Abstract: Although it is possible to generate neural stem cells (NSC) from somatic cells by reprogramming technologies with transcription factors, clinical utilization of patient-specific NSC for the treatment of human diseases remains elusive. The risk hurdles are associated with viral transduction vectors induced mutagenesis, tumor formation from undifferentiated stem cells, and transcription factors-induced genomic instability. Here we describe a viral vector-free and more efficient method to induce mouse fibroblasts into NSC using small molecules. The small molecule-induced neural stem (SMINS) cells closely resemble NSC in morphology, gene expression patterns, self-renewal, excitability, and multipotency. Furthermore, the SMINS cells are able to differentiate into astrocytes, functional neurons, and oligodendrocytes in vitro and in vivo . Thus, we have established a novel way to efficiently induce neural stem cells (iNSC) from fibroblasts using only small molecules without altering the genome. Such chemical induction removes the risks associated with current techniques such as the use of viral vectors or the induction of oncogenic factors. This technique may, therefore, enable NSC to be utilized in various applications within clinical medicine.
Augmented capacity for peripheral serotonin release in human obesity
Publisher: Springer Science and Business Media LLC
Date: 03-2018
DOI: 10.1038/S41366-018-0047-8
Abstract: Evidence from animal studies highlights an important role for serotonin (5-HT), derived from gut enterochromaffin (EC) cells, in regulating hepatic glucose production, lipolysis and thermogenesis, and promoting obesity and dysglycemia. Evidence in humans is limited, although elevated plasma 5-HT concentrations are linked to obesity. We assessed (i) plasma 5-HT concentrations before and during intraduodenal glucose infusion (4 kcal/min for 30 min) in non-diabetic obese (BMI 44 ± 4 kg/m Plasma 5-HT was twofold higher in obese than control responders prior to (P = 0.025), and during (iAUC, P = 0.009), intraduodenal glucose infusion, and related positively to BMI (R Human obesity is characterized by an increased capacity to produce and release 5-HT from the proximal small intestine, which is strongly linked to higher body mass, and glycemic control. Gut-derived 5-HT is likely to be an important driver of pathogenesis in human obesity and dysglycemia.
Sugar Responses of Human Enterochromaffin Cells Depend on Gut Region, Sex, and Body Mass
Publisher: MDPI AG
Date: 22-01-2019
DOI: 10.3390/NU11020234
Abstract: Gut-derived serotonin (5-HT) is released from enterochromaffin (EC) cells in response to nutrient cues, and acts to slow gastric emptying and modulate gastric motility. Rodent studies also evidence a role for gut-derived 5-HT in the control of hepatic glucose production, lipolysis and thermogenesis, and in mediating diet-induced obesity. EC cell number and 5-HT content is increased in the small intestine of obese rodents and human, however, it is unknown whether EC cells respond directly to glucose in humans, and whether their capacity to release 5-HT is perturbed in obesity. We therefore investigated 5-HT release from human duodenal and colonic EC cells in response to glucose, sucrose, fructose and α-glucoside (αMG) in relation to body mass index (BMI). EC cells released 5-HT only in response to 100 and 300 mM glucose (duodenum) and 300 mM glucose (colon), independently of osmolarity. Duodenal, but not colonic, EC cells also released 5-HT in response to sucrose and αMG, but did not respond to fructose. 5-HT content was similar in all EC cells in males, and colonic EC cells in females, but 3 to 4-fold higher in duodenal EC cells from overweight females (p 0.05 compared to lean, obese). Glucose-evoked 5-HT release was 3-fold higher in the duodenum of overweight females (p 0.05, compared to obese), but absent here in overweight males. Our data demonstrate that primary human EC cells respond directly to dietary glucose cues, with regional differences in selectivity for other sugars. Augmented glucose-evoked 5-HT release from duodenal EC is a feature of overweight females, and may be an early determinant of obesity.
Regulator of Calcineurin 1 helps coordinate whole‐body metabolism and thermogenesis
Publisher: EMBO
Date: 02-11-2018
Activity-driven relaxation of the cortical actomyosin II network synchronizes Munc18-1-dependent neurosecretory vesicle docking
Publisher: Springer Science and Business Media LLC
Date: 24-02-2015
DOI: 10.1038/NCOMMS7297
Abstract: In neurosecretory cells, secretory vesicles (SVs) undergo Ca(2+)-dependent fusion with the plasma membrane to release neurotransmitters. How SVs cross the dense mesh of the cortical actin network to reach the plasma membrane remains unclear. Here we reveal that, in bovine chromaffin cells, SVs embedded in the cortical actin network undergo a highly synchronized transition towards the plasma membrane and Munc18-1-dependent docking in response to secretagogues. This movement coincides with a translocation of the cortical actin network in the same direction. Both effects are abolished by the knockdown or the pharmacological inhibition of myosin II, suggesting changes in actomyosin-generated forces across the cell cortex. Indeed, we report a reduction in cortical actin network tension elicited on secretagogue stimulation that is sensitive to myosin II inhibition. We reveal that the cortical actin network acts as a 'casting net' that undergoes activity-dependent relaxation, thereby driving tethered SVs towards the plasma membrane where they undergo Munc18-1-dependent docking.
Abundance of Synaptic Vesicle-Related Proteins in Alpha-Synuclein-Containing Protein Inclusions Suggests a Targeted Formation Mechanism.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2019
DOI: 10.1007/S12640-019-00014-0
Abstract: Proteinaceous α-synuclein-containing inclusions are found in affected brain regions in patients with Parkinson's disease (PD), Dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). These appear in neurons as Lewy bodies in both PD and DLB and as glial cytoplasmic inclusions (GCIs) in oligodendrocytes in MSA. The role they play in the pathology of the diseases is unknown, and relatively little is still known about their composition. By purifying the inclusions from the surrounding tissue and comprehensively analysing their protein composition, vital clues to the formation mechanism and role in the disease process may be found. In this study, Lewy bodies were purified from postmortem brain tissue from DLB cases (n = 2) and GCIs were purified from MSA cases (n = 5) using a recently improved purification method, and the purified inclusions were analysed by mass spectrometry. Twenty-one percent of the proteins found consistently in the GCIs and LBs were synaptic-vesicle related. Identified proteins included those associated with exosomes (CD9), clathrin-mediated endocytosis (clathrin, AP-2 complex, dynamin), retrograde transport (dynein, dynactin, spectrin) and synaptic vesicle fusion (synaptosomal-associated protein 25, vesicle-associated membrane protein 2, syntaxin-1). This suggests that the misfolded or excess α-synuclein may be targeted to inclusions via vesicle-mediated transport, which also explains the presence of the neuronal protein α-synuclein within GCIs.
Mitochondrial dysfunction, oxidative stress, regulation of exocytosis and their relevance to neurodegenerative diseases
Publisher: Wiley
Date: 24-09-2008
DOI: 10.1111/J.1471-4159.2007.04997.X
Abstract: A common feature in the early stages of many neurodegenerative diseases lies in mitochondrial dysfunction, oxidative stress, and reduced levels of synaptic transmission. Many genes associated with neurodegenerative diseases are now known to regulate either mitochondrial function, redox state, or the exocytosis of neurotransmitters. Mitochondria are the primary source of reactive oxygen species and ATP and control apoptosis. Mitochondria are concentrated in synapses and significant alterations to synaptic mitochondrial localization, number, morphology, or function can be detrimental to synaptic transmission. Mitochondrial by-products are capable of regulating various steps of neurotransmission and mitochondrial dysfunction and oxidative stress occur in the early stages of many neurodegenerative diseases. This mini-review will highlight the prospect that mitochondria regulates synaptic exocytosis by controlling synaptic ATP and reactive oxygen species levels and that dysfunctional exocytosis caused by mitochondrial abnormalities may be a common underlying phenomenon in the initial stages of some human neurodegenerative diseases.
Rebuttal from Nick J. Spencer, Tiong Cheng Sia, Simon J Brookes, Marcello Costa and Damien J. Keating
Publisher: Wiley
Date: 31-07-2015
DOI: 10.1113/JP270684
RCAN1 regulates vesicle recycling and quantal release kinetics via effects on calcineurin activity
Publisher: Wiley
Date: 07-01-2013
DOI: 10.1111/JNC.12086
Abstract: We have previously shown that Regulator of Calcineurin 1 (RCAN1) regulates multiple stages of vesicle exocytosis. However, the mechanisms by which RCAN1 affects secretory vesicle exocytosis and quantal release kinetics remain unknown. Here, we use carbon fibre erometry to detect exocytosis from chromaffin cells and identify these underlying mechanisms. We observe reduced exocytosis with repeated stimulations in chromaffin cells over-expressing RCAN1 (RCAN1(ox)), but not in wild-type (WT) cells, indicating a negative effect of RCAN1 on vesicle recycling and endocytosis. Acute exposure to calcineurin inhibitors, cyclosporine A and FK-506, replicates this effect in WT cells but has no additional effect in RCAN1(ox) cells. When we chronically expose WT cells to cyclosporine A and FK-506 we find that catecholamine release per vesicle and pre-spike foot (PSF) signal parameters are decreased, similar to that in RCAN1(ox) cells. Inhibiting calcineurin activity in RCAN1(ox) cells has no additional effect on the amount of catecholamine release per vesicle but further reduces PSF signal parameters. Although electron microscopy studies indicate these changes are not because of altered vesicle number or distribution in RCAN1(ox) cells, the smaller vesicle and dense core size we observe in RCAN1(ox) cells may underlie the reduced quantal release in these cells. Thus, our results indicate that RCAN1 most likely affects vesicle recycling and quantal release kinetics via the inhibition of calcineurin activity.
The gut microbiome and mental health: advances in research and emerging priorities
Publisher: Springer Science and Business Media LLC
Date: 02-03-2022
DOI: 10.1038/S41380-022-01479-W
Abstract: The gut microbiome exerts a considerable influence on human neurophysiology and mental health. Interactions between intestinal microbiology and host regulatory systems have now been implicated both in the development of psychiatric conditions and in the efficacy of many common therapies. With the growing acceptance of the role played by the gut microbiome in mental health outcomes, the focus of research is now beginning to shift from identifying relationships between intestinal microbiology and pathophysiology, and towards using this newfound insight to improve clinical outcomes. Here, we review recent advances in our understanding of gut microbiome-brain interactions, the mechanistic underpinnings of these relationships, and the ongoing challenge of distinguishing association and causation. We set out an overarching model of the evolution of microbiome-CNS interaction and examine how a growing knowledge of these complex systems can be used to determine disease susceptibility and reduce risk in a targeted manner.
Differentiation of the 50B11 dorsal root ganglion cells into NGF and GDNF responsive nociceptor subtypes
Publisher: SAGE Publications
Date: 2021
Abstract: The embryonic rat dorsal root ganglion (DRG) neuron-derived 50B11 cell line is a promising sensory neuron model expressing markers characteristic of NGF and GDNF-dependent C-fibre nociceptors. Whether these cells have the capacity to develop into distinct nociceptive subtypes based on NGF- or GDNF-dependence has not been investigated. Here we show that by augmenting forskolin (FSK) and growth factor supplementation with NGF or GDNF, 50B11 cultures can be driven to acquire differential functional responses to common nociceptive agonists capsaicin and ATP respectively. In addition, to previous studies, we also demonstrate that a differentiated neuronal phenotype can be maintained for up to 7 days. Western blot analysis of nociceptive marker proteins further demonstrates that the 50B11 cells partially recapitulate the functional phenotypes of classical NGF-dependent (peptidergic) and GDNF-dependent (non-peptidergic) neuronal subtypes described in DRGs. Further, 50B11 cells differentiated with NGF/FSK, but not GDNF/FSK, show sensitization to acute prostaglandin E2 treatment. Finally, RNA-Seq analysis confirms that differentiation with NGF/FSK or GDNF/FSK produces two 50B11 cell subtypes with distinct transcriptome expression profiles. Gene ontology comparison of the two subtypes of differentiated 50B11 cells to rodent DRG neurons studies shows significant overlap in matching or partially matching categories. This transcriptomic analysis will aid future suitability assessment of the 50B11 cells as a high-throughput nociceptor model for a broad range of experimental applications. In conclusion, this study shows that the 50B11 cell line is capable of partially recapitulating features of two distinct types of embryonic NGF and GDNF-dependent nociceptor-like cells.
Local Sphingosine Kinase 1 Activity Improves Islet Transplantation
Publisher: American Diabetes Association
Date: 07-02-2017
DOI: 10.2337/DB16-0837
Abstract: Pancreatic islet transplantation is a promising clinical treatment for type 1 diabetes, but success is limited by extensive β-cell death in the immediate posttransplant period and impaired islet function in the longer term. Following transplantation, appropriate vascular remodeling is crucial to ensure the survival and function of engrafted islets. The sphingosine kinase (SK) pathway is an important regulator of vascular beds, but its role in the survival and function of transplanted islets is unknown. We observed that donor islets from mice deficient in SK1 (Sphk1 knockout) contain a reduced number of resident intraislet vascular endothelial cells. Furthermore, we demonstrate that the main product of SK1, sphingosine-1-phosphate, controls the migration of intraislet endothelial cells in vitro. We reveal in vivo that Sphk1 knockout islets have an impaired ability to cure diabetes compared with wild-type controls. Thus, SK1-deficient islets not only contain fewer resident vascular cells that participate in revascularization, but likely also a reduced ability to recruit new vessels into the transplanted islet. Together, our data suggest that SK1 is important for islet revascularization following transplantation and represents a novel clinical target for improving transplant outcomes.
What is the role of endogenous gut serotonin in the control of gastrointestinal motility?
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.PHRS.2018.06.017
Abstract: In recent years, there have been dramatic changes in our understanding of the role of endogenous 5-Hydroxytryptamine (5-HT or serotonin) in the control of gastrointestinal (GI) motility. Whilst it is well accepted that there are numerous types of 5-HT receptors expressed on enteric neurons and that exogenous 5-HT potently stimulates GI-motility, understanding the role of endogenous 5-HT in GI-motility has been substantially more difficult to resolve. Recent studies found 5-HT
Erratum: Mice deficient for the chromosome 21 ortholog Itsn1 exhibit vesicle-trafficking abnormalities (Human Molecular Genetic (2008) vol. 17(21) (3281-3290) 10.1093/hmg/ddn224)
Publisher: Oxford University Press (OUP)
Date: 22-10-2009
DOI: 10.1093/HMG/DDN378
Exocytosis, Mitochondrial Injury and Oxidative Stress in Neurodegenerative Diseases
Publisher: Humana Press
Date: 2009
Huntingtin‐associated protein 1 regulates exocytosis, vesicle docking, readily releasable pool size and fusion pore stability in mouse chromaffin cells
Publisher: Wiley
Date: 17-02-2014
A new 'dual' in the crown for electrochemistry
Publisher: Wiley
Date: 14-11-2011
Huntingtin-associated protein 1: Eutherian adaptation from a TRAK-like protein, conserved gene promoter elements, and localization in the human intestine
Publisher: Springer Science and Business Media LLC
Date: 13-10-2016
The Diverse Metabolic Roles of Peripheral Serotonin
Publisher: The Endocrine Society
Date: 03-2017
DOI: 10.1210/EN.2016-1839
Abstract: Serotonin (5-hydroxytryptamine or 5-HT) is a multifunctional bioamine with important signaling roles in a range of physiological pathways. Almost all of the 5-HT in our bodies is synthesized in specialized enteroendocrine cells within the gastrointestinal (GI) mucosa called enterochromaffin (EC) cells. These cells provide all of our circulating 5-HT. We have long appreciated the important contributions of 5-HT within the gut, including its role in modulating GI motility. However, evidence of the physiological and clinical significance of gut-derived 5-HT outside of the gut has recently emerged, implicating 5-HT in regulation of glucose homeostasis, lipid metabolism, bone density, and diseases associated with metabolic syndrome, such as obesity and type 2 diabetes. Although a new picture has developed in the last decade regarding the various metabolic roles of peripheral serotonin, so too has our understanding of the physiology of EC cells. Given that they are scattered throughout the lining of the GI tract within the epithelial cell layer, these cells are typically difficult to study. Advances in isolation procedures now allow the study of pure EC-cell cultures and single cells, enabling studies of EC-cell physiology to occur. EC cells are sensory cells that are capable of integrating cues from ingested nutrients, the enteric nervous system, and the gut microbiome. Thus, levels of peripheral 5-HT can be modulated by a multitude of factors, resulting in both local and systemic effects for the regulation of a raft of physiological pathways related to metabolism and obesity.
ICAM-1-related long non-coding RNA: promoter analysis and expression in human retinal endothelial cells
Publisher: Springer Science and Business Media LLC
Date: 09-05-2018
Identification of a Rhythmic Firing Pattern in the Enteric Nervous System That Generates Rhythmic Electrical Activity in Smooth Muscle
Publisher: Society for Neuroscience
Date: 28-05-2018
Mechanisms controlling hormone secretion in human gut and its relevance to metabolism
Publisher: Bioscientifica
Date: 2019
DOI: 10.1530/JOE-19-0399
Abstract: The homoeostatic regulation of metabolism is highly complex and involves multiple inputs from both the nervous and endocrine systems. The gut is the largest endocrine organ in our body and synthesises and secretes over 20 different hormones from enteroendocrine cells that are dispersed throughout the gut epithelium. These hormones include GLP-1, PYY, GIP, serotonin, and CCK, each of which play pivotal roles in maintaining energy balance and glucose homeostasis. Some are now the basis of several clinically used glucose-lowering and weight loss therapies. The environment in which these enteroendocrine cells exist is also complex, as they are exposed to numerous physiological inputs including ingested nutrients, circulating factors and metabolites produced from neighbouring gut microbiome. In this review, we examine the erse means by which gut-derived hormones carry out their metabolic functions through their interactions with different metabolically important organs including the liver, pancreas, adipose tissue and brain. Furthermore, we discuss how nutrients and microbial metabolites affect gut hormone secretion and the mechanisms underlying these interactions.
Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles
Publisher: Wiley
Date: 10-12-2016
DOI: 10.1002/JCP.25256
Abstract: Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber erometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from in idual vesicles.
Purification of α-synuclein containing inclusions from human post mortem brain tissue
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.JNEUMETH.2016.03.016
Abstract: Comparison with existing methods. Neurodegenerative disorders affect a large proportion of the elderly population. A group of disorders, known as the α-synucleinopathies, are characterised by the presence of α-synuclein-containing protein inclusions, such as Lewy Bodies (LBs) found in neurons from Parkinson's Disease (PD) and Dementia with Lewy Bodies (DLB), and Glial Cytoplasmic Inclusions (GCIs) found in oligodendrocytes from Multiple System Atrophy (MSA). The analysis of the protein composition of inclusions has been hindered by limitations of methods for isolating the inclusions from the surrounding tissue. Four modifications were made to the published method for GCI purification by Gai et al. (1999) which were: collecting the entire inclusion-containing part of the Percoll gradient lysis of nuclei prior to DNAse digestion limited tryptic digestion to release inclusions from the cytoskeletal meshwork and increased antibody and magnetic bead concentrations/volumes to capture the larger amounts of inclusions. The optimised method gave a 28-fold increase in yield compared to the published method of Gai et al. (1999). A 2D-DIGE comparison revealed a 3.8-fold increase in α-synuclein enrichment and a corresponding 5.2-fold reduction in tubulin contamination. This method was also successfully adapted to the purification of LBs from DLB tissue. A 2D-DIGE comparison of purified GCIs (n=2) revealed that GCIs consist of 11.7% α-synuclein, 1.9% α-β-crystallin and 2.3% 14-3-3 proteins compared to 8.5%, 2.0% and 1.5% in LBs, respectively. This study has generated an improved method for the purification of α-synuclein-containing inclusions with a yield sufficient for multiple forms of analysis.
Related Organisations
Amrita University Amrita Centre For Nanosciences And Molecular Medicine
Location: India
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