An Examination Of The Contribution Of Visceral Adiposity To Insulin Resistance In Humans.
Funder
National Health and Medical Research Council
Funding Amount
$335,800.00
Summary
The worldwide epidemic of Type 2 diabetes is related to major nutritional and activity changes interacting with a genetic predisposition. The two key defects in Type 2 diabetes are a reduced response to insulin (insulin resistance) and relative failure of insulin production. Insulin resistance is the earliest defect and is closely associated with cardiovascular risk. Obesity generates insulin resistance, but intraabdominal (visceral) fat has particular importance. Visceral fat cells are differen ....The worldwide epidemic of Type 2 diabetes is related to major nutritional and activity changes interacting with a genetic predisposition. The two key defects in Type 2 diabetes are a reduced response to insulin (insulin resistance) and relative failure of insulin production. Insulin resistance is the earliest defect and is closely associated with cardiovascular risk. Obesity generates insulin resistance, but intraabdominal (visceral) fat has particular importance. Visceral fat cells are different to other fat cells; they are very metabolically active and 'spill out' fatty acids indiscriminately contributing to insulin resistance in liver and muscle; they also produce hormones which may modify the action of insulin. We will study people undergoing abdominal surgery. Participants will be (1) normal weight and sensitive to insulin, (2) abdominally overweight and insulin resistant, (3) insulin resistant with Type 2 diabetes. We will document abdominal fat, circulating lipid and hormone levels and insulin action. At surgery fat biopsies will be obtained from (a) inside the abdominal cavity, (b) the fat layer under the abdominal skin and (c) fat in the buttock. The activity of a large number of genes in the fat tissue will be assessed in 8 subjects using DNA array (4 each from Groups 1 and 2). Then a small number of genes will be selected on the basis of different activity in visceral fat from buttock fat, and between insulin sensitive and insulin resistant people. The activity of these genes will be determined in all subjects in the 3 groups. We anticipate identifying a few (perhaps 3) genes whose activity is closely associated with insulin resistance and will examine their capability to block insulin action in a series of animal and cellular studies. These studies should identify specific mechanisms by which visceral fat creates insulin resistance. This would be an important step towards prevention and improved medication for Type 2 diabetes.Read moreRead less
Short Term Effects Of Overfeeding On Metabolic Risk In Humans
Funder
National Health and Medical Research Council
Funding Amount
$380,558.00
Summary
Obesity is associated with increased risk of diabetes, heart disease and cancer. Obesity prevalence is rapidly increasing and consitutes one of the greatest threats to human health. The aim of this study is to determine mechanism-s underlying the close relationship between obesity and insulin resistance by inducing experimental weight gain in humans with and without a genetic predisposition to diabetes. This project will help identify new candidates for anti-diabetes drugs.
Gene Variants In Adiponectin And Its Receptors As Risk Factors For Metabolic And Cardiovascular Disease
Funder
National Health and Medical Research Council
Funding Amount
$534,107.00
Summary
Obesity has a major impact on the development of metabolic syndrome (MetS), type 2 diabetes (T2D), and cardiovascular disease (CVD). It is important to identify the molecular links between obesity and these conditions. Adiponectin, an adipocyte-specific hormone, is a likely molecular candidate because of its pleiotropic metabolic actions. We will investigate the role of adiponectin, the variants within its gene ADIPOQ, and that of its two receptors, in the development of MetS, T2D, and CVD.
Role Of Impaired Insulin Signalling In Fatty Acid-induced Muscle Insulin Resistance In Vivo
Funder
National Health and Medical Research Council
Funding Amount
$481,500.00
Summary
Type 2 diabetes represents an escalating global health problem. In Australia 7.5% of the population has diabetes and another 16% insulin resistance (impaired action of insulin in tissues). As well as diabetes, insulin resistance is closely associated with obesity, dyslipidaemia, hypertension and cardiovascular diseases (Syndrome X). While genetic factors play a role, a high caloric intake (particularly with a high fat content) and a sedentary lifestyle are extremely important environmental contr ....Type 2 diabetes represents an escalating global health problem. In Australia 7.5% of the population has diabetes and another 16% insulin resistance (impaired action of insulin in tissues). As well as diabetes, insulin resistance is closely associated with obesity, dyslipidaemia, hypertension and cardiovascular diseases (Syndrome X). While genetic factors play a role, a high caloric intake (particularly with a high fat content) and a sedentary lifestyle are extremely important environmental contributors to Syndrome X and diabetes. From evidence that we and others have obtained over the last few years it is now evident that an important mediator of insulin resistance is the quantity of fat molecules which accumulate in muscle and liver. This project examines mechanisms whereby this fat accumulation can disrupt the signalling mechanism normally causing increased glucose metabolism in response to insulin. While basic experiments in cell systems have identified some candidates, a need exists to demonstrate whether they actually cause the insulin resistance in the whole animal or human, or are merely associated with it. We will combine metabolic-physiological studies with a novel technique we have recently established in our laboratory for introducing DNA into skeletal muscle of laboratory animal models. We now aim to exploit this approach to obtain more definitive data about the importance of insulin signalling changes to insulin resistance. Two major steps in insulin signalling will be investigated, involving the insulin receptor substrate proteins and the kinase Akt-PKB, both strongly implicated in lipid-induced insulin resistance. This knowledge will be invaluable in improving strategies to lessen or prevent lipid-associated insulin resistance, a major contributor to the metabolic derangement in Type 2 diabetes and Syndrome X.Read moreRead less
IGF BINDING PROTEIN-2 A MODULATOR OF IGF ACTION IN DEVELOPING AND NEOPLASTIC NEURONAL CELLS.
Funder
National Health and Medical Research Council
Funding Amount
$436,980.00
Summary
In early life the brain undergoes rapid growth and remodelling, a process regulated by many factors including the insulin-like growth factor (IGF) system, which potently enhances nerve cell (neuron) survival. Similarly, this system is active in response to brain injury such a stroke, but it may also enhance tumor survival. The regulation of availability of IGFs to the neuron is critical in all these processes. IGF binding protein-2 (IGFBP-2), which is highly abundant in the developing or damaged ....In early life the brain undergoes rapid growth and remodelling, a process regulated by many factors including the insulin-like growth factor (IGF) system, which potently enhances nerve cell (neuron) survival. Similarly, this system is active in response to brain injury such a stroke, but it may also enhance tumor survival. The regulation of availability of IGFs to the neuron is critical in all these processes. IGF binding protein-2 (IGFBP-2), which is highly abundant in the developing or damaged brain, and in tumours, plays a key role on the surface of neurons in regulating IGF availability. We have shown that IGFBP-2 associates with a specialised protein on the nerve cells, where it is further processed to smaller fragments. We believe that these processes are reactivated following brain injury or in cancer states where IGFBP-2 is highly abundant. We propose to determine how IGFBP-2 influences IGF action on the nerve cell surface, and to further ascertain the function of each step in this process. We will achieve this by examining the effects of the mutated version of IGFBP-2, designed to either prevent its binding to the cell surface or its processing to smaller fragments. We will use various human and mouse nerve cell for these studies, which will not only provide greater understanding of the regulation of IGF availability to developing brain cell, but also point to how these processes may be involved in enhancement of recovery from injury or stroke, or possibly in acceleration of tumour growth. The finding of this study will offer the potential for new and exciting treatment designed to alter the function of the IGF system, to either make it more active in response to brain injury or stroke, or less active in brain tumours.Read moreRead less
The Regulation Of Insulin Action In Liver And Skeletal Muscle By Protein Kinase C Epsilon
Funder
National Health and Medical Research Council
Funding Amount
$647,604.00
Summary
We have identified an enzyme, protein kinase C epsilon, which has a major negative impact on the control of blood glucose levels. We will now examine the mechansisms by which it affects insulin action in liver and muscle, two major target tissues of the hormone responsible for glucose disposal. This work is expected to validate PKCepsilon or its downstream effectors as therapeutic targets in the treatment of the insulin resistance which accompanies obesity and Type 2 diabetes.
Understanding The Cause And Consequence Of Impaired Insulin Secretion In The NZO Mouse A Model Of Diabetes.
Funder
National Health and Medical Research Council
Funding Amount
$711,224.00
Summary
Type 2 diabetes is a major health problem affeting over 1 million Australians. A key feature of this disease is reduced secretion of the pancreratic hormone insulin which results in high blood sugar levels. We are using a naturally occurring animal model of diates called the NZO mouse to understand why the pancreas secretes less insulin and the consequences of this defect. This project has the potential of providing better therapeutic strategies for patients with Type 2 diabetes.