In Australia over 7% of the population have type 2 diabetes. This epidemic represents a major health problem. The majority of overweight individuals do not develop diabetes because their insulin-secreting pancreatic beta-cells adequately compensate with over-secretion. It is the failure of this so called, beta-cell compensation, that is fundamental to the development of diabetes. We propose that in susceptible individuals, a gradual rise in blood glucose levels resulting from obesity and insulin ....In Australia over 7% of the population have type 2 diabetes. This epidemic represents a major health problem. The majority of overweight individuals do not develop diabetes because their insulin-secreting pancreatic beta-cells adequately compensate with over-secretion. It is the failure of this so called, beta-cell compensation, that is fundamental to the development of diabetes. We propose that in susceptible individuals, a gradual rise in blood glucose levels resulting from obesity and insulin resistance leads to beta-cell failure and overt diabetes. This project will investigate the mechanisms responsible for beta-cell failure in a mouse model with a similar time-dependent progression to obesity and type 2 diabetes as that seen in humans. C57BL-KsJ db-db mice progress from a pre-diabetic phase of insulin over-secretion, obesity and insulin resistance to a diabetic state characterised by the appearance of high blood glucose and lipid levels and the loss of insulin secretory capacity. With age, there are also a reduced number of beta-cells because of increased cell death. db-db mice will be studied at different stages in their natural progression to diabetes to fully characterise the secretory dysfunction and the changes in beta-cell phenotype over the time-course of diabetes development. The use of laser capture microdissection will allow us to study selectively the actual beta-cells without contamination from the other cells of the pancreas. The mice will also be treated with an agent that lowers blood glucose levels without affecting lipids to test the influence of hyperglycaemia itself in the development of beta-cell dysfunction. We will also test if the changes observed in the mice are regulated independently by high glucose levels in cell culture systems. The role of one candidate protein called ID-1 will be investigated as a potential link between hyperglycaemia and the development of beta-cell dysfunction.Read moreRead less
The current epidemic of type 2 diabetes represents a major global health problem, with over 7% of the Australians suffering the disease. While there is a well-established relationship between obesity and insulin resistance, the majority of overweight individuals do not develop type 2 diabetes because their pancreatic beta-cells compensate with enhanced insulin secretion. It is the failure of beta-cell compensation that is fundamental to the development of diabetes. The beta-cell is a highly spec ....The current epidemic of type 2 diabetes represents a major global health problem, with over 7% of the Australians suffering the disease. While there is a well-established relationship between obesity and insulin resistance, the majority of overweight individuals do not develop type 2 diabetes because their pancreatic beta-cells compensate with enhanced insulin secretion. It is the failure of beta-cell compensation that is fundamental to the development of diabetes. The beta-cell is a highly specialised cell with a unique metabolic profile and differentiation specifically geared towards making these cells able to sense fluctuations in circulating glucose levels and secrete insulin accordingly. We propose that in susceptible individuals, a gradual rise in blood glucose (hyperglycaemia) and lipid levels resulting from increasing obesity and insulin resistance leads to a loss of the unique expression pattern of genes necessary for appropriate insulin secretion. This exacerbates hyperglycaemia, which causes further beta-cell dedifferentiation and eventually the death of beta-cells by apoptosis. We have recently found evidence in several models of diabetes that supports this hypothesis. We propose to use animal studies and cell culture systems to investigate the following hypotheses important for our understanding of beta-cell failure and progression to diabetes: 1) The loss of beta-cell phenotype (dedifferentiation) underlies the loss of insulin secretory function in failing beta-cells. 2) Hyperglycaemia plays a critical role regulating the progression to beta-cell dedifferentiation. 3) The overexpression of key candidate gene products play an integral role linking hyperglycaemia to the loss of beta-cell secretion. 4) Endoplasmic reticulum stress is necessary for beta-cell death in diabetes. Our studies will make a major contribution to our understanding of why beta-cells fail in diabetes and aim to provide novel therapeutic targets in the treatment of diabetes.Read moreRead less
Investigation Of The Roles Of Protein Kinase C Epsilon In Insulin Secretion And Insulin Clearance
Funder
National Health and Medical Research Council
Funding Amount
$627,148.00
Summary
The rise in blood insulin levels after a meal normally reduces blood sugar levels by increasing glucose uptake and storage in certain tissues, especially muscle. Type 2 diabetes is characterized in part by a failure of the pancreas to produce adequate insulin in response to increases in blood sugar. This loss of insulin secretion has been strongly linked to increases in the availability of fat, although the reasons for this are not clear. We have recently found that mice lacking a specific enzym ....The rise in blood insulin levels after a meal normally reduces blood sugar levels by increasing glucose uptake and storage in certain tissues, especially muscle. Type 2 diabetes is characterized in part by a failure of the pancreas to produce adequate insulin in response to increases in blood sugar. This loss of insulin secretion has been strongly linked to increases in the availability of fat, although the reasons for this are not clear. We have recently found that mice lacking a specific enzyme (protein kinase C epsilon) are much less susceptible to the problems in dealing with blood sugar that are caused by a high fat diet. We showed that this is due partly to improved insulin secretion, and also to a slower breakdown of insulin by the liver, which increases its availability to target tissues. The aim of this project is to investigate the mechanisms occurring in the liver and in the pancreas by which this enzyme contributes to improved insulin action. Firstly, we will examine insulin uptake in liver cells, to investigate how the enzyme controls this process. Secondly, we will determine the mechanism through which the activation of the enzyme, upon increased fat supply to pancreatic beta-cells, reduces insulin secretion in response to glucose. Finally, will assess the relative importance of these two actions of the enzyme in improving the control of blood sugar levels. This work will lead to a better understanding of the mechanisms by which fat oversupply, and hence obesity, can play a role in the development of Type 2 diabetes, so that they can be targeted both for the development of new and more effective treatments for the disorder and for prevention of its onset.Read moreRead less
Therapeutic Strategies And Screening Methods For PKC Epsilon Antagonists In The Treatment Of Type 2 Diabetes
Funder
National Health and Medical Research Council
Funding Amount
$157,375.00
Summary
Type 2 diabetes is a chronic disease affecting over a million Australians and hundreds of millions of people worldwide. Its prevalence is rising due to several factors such as an increase in caloric intake, the aging of the population, and the common sedentary lifestyle of Western civilization. Type 2 diabetes occurs when the pancreas is unable to produce enough insulin for the body to cope with rising blood glucose levels after a meal, and has been strongly linked to obesity. We have now shown ....Type 2 diabetes is a chronic disease affecting over a million Australians and hundreds of millions of people worldwide. Its prevalence is rising due to several factors such as an increase in caloric intake, the aging of the population, and the common sedentary lifestyle of Western civilization. Type 2 diabetes occurs when the pancreas is unable to produce enough insulin for the body to cope with rising blood glucose levels after a meal, and has been strongly linked to obesity. We have now shown that an enzyme found in the pancreas becomes inappropriately activated under conditions of fat oversupply, and plays an important role in the development of defects in insulin release from the pancreas in response to glucose. Excitingly, we have also shown that inhibition of this enzyme can partly reverse these defects once they have been established. We now intend to further validate this enzyme as a drug target by determining the optimum dosing regimen for the treatment of type 2 diabetes in a mouse model, and testing whether this approach can be used in conjunction with previously-developed drugs which promote insulin action, to improve bood glucose handling better than either treatment alone. This would promote the enzyme as a therapeutic strategy in the treatment of Type 2 diabetes. We also plan to develop a high throuhput screen to identify novel inhibitors of the enzyme, which will further increase the attractiveness of the project to pharmaceutical companies, who are better able to implent full commercialization of our findings.Read moreRead less
Targeting RCAN1 To Treat Type 2 Diabetes And Obesity
Funder
National Health and Medical Research Council
Funding Amount
$814,468.00
Summary
Obesity and impaired insulin secretion are significant contributors to Type 2 diabetes. In this project we demonstrate that a protein called RCAN1 contributes to both fat mass and insulin secretion and that this contribution is exacerbated in obesity and in Type 2 diabetes. We will identify how RCAN1 controls these major metabolic pathways with outcomes including the development of new therapeutics for obesity and Type 2 diabetes.
Investigation Of Pancreatic Insulin-secreting Cell Function And Survival
Funder
National Health and Medical Research Council
Funding Amount
$375,750.00
Summary
Diabetes remains a major health problem in Australia. Both type 1 and type 2 diabetes is eventually due to pancreatic insulin-producing beta-cell destruction, which is caused mainly by the cell death, so called 'apoptosis' or programmed suicide of the cells. Thus, attempting to protect beta-cells against death and rescue their insulin secretory function is emerging as a strategy for the treatment of diabetes. However, how the beta-cells undergo death and how to protect the cell death are still n ....Diabetes remains a major health problem in Australia. Both type 1 and type 2 diabetes is eventually due to pancreatic insulin-producing beta-cell destruction, which is caused mainly by the cell death, so called 'apoptosis' or programmed suicide of the cells. Thus, attempting to protect beta-cells against death and rescue their insulin secretory function is emerging as a strategy for the treatment of diabetes. However, how the beta-cells undergo death and how to protect the cell death are still not completely understood. We have recently discovered a new protein, named sphingosine kinase, that is a strong protector against cell death. We also found that this enzyme is involved in process of insulin secretion. Thus, this application seeks to establish a dual role of this enzyme in protecting beta-cells from death and promoting insulin secretion by the cells. This will ultimately allow us to create new therapeutic strategy to target this protein for the management of diabetes.Read moreRead less
Type 2 diabetes is caused by multiple genetic defects, resulting in high blood sugar levels. These high sugar levels are primarily due to a decrease in the concentration of insulin, a hormone produced by the pancreas. A number of recent studies have aimed to identify which genes are regulated under conditions that mimic diabetes. One gene shown to have altered expression levels under these conditions is an enzyme called fructose-1,6-bisphosphatase (or FBPase). This enzyme is involved in the meta ....Type 2 diabetes is caused by multiple genetic defects, resulting in high blood sugar levels. These high sugar levels are primarily due to a decrease in the concentration of insulin, a hormone produced by the pancreas. A number of recent studies have aimed to identify which genes are regulated under conditions that mimic diabetes. One gene shown to have altered expression levels under these conditions is an enzyme called fructose-1,6-bisphosphatase (or FBPase). This enzyme is involved in the metabolism of sugar and is usually expressed at undetectable levels in the pancreas, but when blood sugar levels are high, the amount of FBPase in the pancreas increases considerably. We hypothesise that this increase in FBPase may contribute to the decrease in insulin secretion by the pancreas, seen in the diabetic state. The aim of this proposal therefore is to study mice that we have modified to express increased FBPase specifically in the pancreas, in order to determine whether this will lead to a decrease in insulin release and to diabetes. If this is the case, then FBPase could be targeted for the development of drugs that would improve the control of blood sugar levels in diabetes.Read moreRead less
Mechanisms Of PKCepsilon-dependent Regulation Of Beta-cell Lipid Metabolism And Insulin Secretion
Funder
National Health and Medical Research Council
Funding Amount
$555,892.00
Summary
Lipid loading of the insulin-producing beta cells of the pancreas contributes to the onset of Type 2 diabetes, but the mechanisms are poorly understood. We have recently established that inhibiting the enzyme PKCe helps restore insulin secretion. By better defining the cellular role of PKCe we will clarify how insulin secretion is disrupted by fatty acids and cholesterol.
Molecular Determinants Of Amino Acid-dependent Signalling By The Calcium-sensing Receptor
Funder
National Health and Medical Research Council
Funding Amount
$566,035.00
Summary
Amino acids are the building blocks of proteins and an alternative energy source to carbohydrate and fat. Proteins are major structural components of our bodies. They also fulfil an amazing diversity of cellular and bodily functions acting, for example, as enzymes (biological catalysts), receptors, molecular chaperones and biological machines. Thus, amino acids are key nutrients and the human body has developed mechanisms for tightly regulating cellular responses depending upon their levels in b ....Amino acids are the building blocks of proteins and an alternative energy source to carbohydrate and fat. Proteins are major structural components of our bodies. They also fulfil an amazing diversity of cellular and bodily functions acting, for example, as enzymes (biological catalysts), receptors, molecular chaperones and biological machines. Thus, amino acids are key nutrients and the human body has developed mechanisms for tightly regulating cellular responses depending upon their levels in blood. Identifying amino acid sensing molecules and identifying the mechanisms they use to control cellular responses is thus a key issue in human biology. The applicant identified the calcium-sensing receptor as an amino acid sensor and has shown that this receptor provides a means by which fluctuations in amino acid levels regulate the secretion of the key calcium-regulating hormone, PTH. In the current proposal, the mechanisms that link amino acid activation of the calcium-sensing receptor to its key cellular responses will be determined.Read moreRead less
Type 2 diabetes is a health crisis in Australia. In this project, we will investigate the mechanisms whereby high glucose and fat impair pancreatic beta-cell function leading to type 2 diabetes. We will establish how endoplasmic reticulum stress and the protein Id1 are linked with loss of beta-cell gene expression and function. The information gained will further our understanding of the basic mechanisms regulating insulin secretion and provide new therapeutic targets for diabetes treatment.