Overweight and obesity are at epidemic proportions in Australia, reflecting the pattern in the developed and developing world. The main cause appears to be an energy mismatch, with excessive caloric consumption. One response of the body to excessive nutrient supply is energy storage in fat tissue and to aid in this the body also generates new fat tissue, termed adipogenesis (also known in cells as fat cell differentiation). In many people who gain excess body weight, fat tissue is abnormal and d ....Overweight and obesity are at epidemic proportions in Australia, reflecting the pattern in the developed and developing world. The main cause appears to be an energy mismatch, with excessive caloric consumption. One response of the body to excessive nutrient supply is energy storage in fat tissue and to aid in this the body also generates new fat tissue, termed adipogenesis (also known in cells as fat cell differentiation). In many people who gain excess body weight, fat tissue is abnormal and does not respond well to the chemical insulin, thus causing insulin resistance. This insulin resistant fat tissue is especially present in a central body (visceral) site. Insulin resistance related to this visceral fat predisposes to both diabetes and premature death from cardiovascular disease. Understanding how fat tissue develops and how it might cause insulin resistance is thus important in human health. One of the factors in fat that prevents normal development of fat tissue and which induces insulin resistance is transforming growth factor- (TGF- ). We have generated new data showing that two proteins which are increased by TGF- , termed connective tissue growth factor (CTGF) and insulin like growth factor binding protein-3, (IGFBP-3), prevent adipogenesis. We have shown this in cultured cells, and have found that CTGF and IGFBP-3 are increased in visceral fat in animal models of obesity and insulin resistance. Our preliminary work has further indicated how CTGF and IGFBP-3 might each work in the fat cell to prevent adipogenesis. This proposal will determine if TGF- works through CTGF and IGFBP-3 to block adipogenesis, and it will define how CTGF and IGFBP-3 have their inhibitory effects on fat cell differentiation. Cells in culture will be utilised and an animal model of dietary induced obesity and insulin resistance will help to define whether CTGF and IGFBP-3 prevent adipogenesis in vivo, furthering our understanding in how abnormal fat tissue may develop.Read moreRead less
Pathogenesis Of Antiretroviral Induced Sub-cutaneous Fat Wasting
Funder
National Health and Medical Research Council
Funding Amount
$331,650.00
Summary
The use of potent antiretroviral therapy has resulted in great clinical and survival benefit in patients with HIV infection and has in most cases, outweighed the risk of short term side effects. However, not that survival of patients with AIDS has considerably improved the long-term complications of chronic therapy have become a critical issue. Lipodystrophy syndrome(s) is the name given to a set of changes to blood lipids, glucose levels and body habitus and typically occurs in those successful ....The use of potent antiretroviral therapy has resulted in great clinical and survival benefit in patients with HIV infection and has in most cases, outweighed the risk of short term side effects. However, not that survival of patients with AIDS has considerably improved the long-term complications of chronic therapy have become a critical issue. Lipodystrophy syndrome(s) is the name given to a set of changes to blood lipids, glucose levels and body habitus and typically occurs in those successfully treated with anti-HIV therapy. The facial and body habitus changes are common, progressive and are frequently disfiguring. Aside from the psychological and social effects of such changes, many patiens are not able to retain their anonymity as HIV infected individuals. In addition, changes to blood lipids may lead to atherosclerosis. Already there have been several case reports of premature coronary disease in young HIV infected patients. It is increasingly difficult for patients to remain strictly adherent to chronic therapy because of all these concerns. There is an urgent need to understand the exact biological cause(s) of lipodystrophy syndrome(s) in HIV infected patients in order to help identify which of our currently available antiretroviral therapies will offer the long term clinical and survival benefit of strong viral suppression without increasing risk of vascular disease. Based on results of our previous studies on lipodystrophy syndrome, we have proposed that lipodystrophy may be the result of antiviral drugs depleting the DNA content of mitochondria within fat cells. We propose to examine sequential fat biopsy specimens from HIV infected volunteers to determine whether antiretroviral therapy has had adverse effects on mitochondrial DNA content and-or function.Read moreRead less
The Regulation Of Gene Expression During Adipogenesis
Funder
National Health and Medical Research Council
Funding Amount
$549,446.00
Summary
The body stores energy acquired from ingested food as fat droplets within storage cells termed adipocytes. The amount of fat varies between individuals and may also vary during an individual's life. The variations reflect differences in physiology, diet, and behaviour and have been the focus of intense study. Excessive accumulation of fat is a serious health problem as it is associated with conditions such as heart disease and diabetes. This grant application primarily concerns using a new line ....The body stores energy acquired from ingested food as fat droplets within storage cells termed adipocytes. The amount of fat varies between individuals and may also vary during an individual's life. The variations reflect differences in physiology, diet, and behaviour and have been the focus of intense study. Excessive accumulation of fat is a serious health problem as it is associated with conditions such as heart disease and diabetes. This grant application primarily concerns using a new line of genetically modified mice that have reduced fat. These mice lack a key gene regulatory protein that is implicated in fat accummulation and adipocyte formation. It is expected that a knowledge of the genes regulating the formation and function of fat storage cells will contribute to new strategies for controlling fat formation and will help in the prevention of diseases such as diabetes and heart disease.Read moreRead less
Leptin And The Regulation Of Substrate Partitioning
Funder
National Health and Medical Research Council
Funding Amount
$349,876.00
Summary
The prevalence of obesity is increasing with currently 18% of adult Australians being classified as obese. Obesity, particularly abdominal obesity, is associated with high blood lipid levels and blood pressure, and type 2 diabetes. In Australia, the cost of obesity is estimated to be $830 million per year. The ultimate aim of any obesity treatment programme is to reduce body fatness by burning off fat and to prevent further fat storage and so studies which focus on developing strategies to achie ....The prevalence of obesity is increasing with currently 18% of adult Australians being classified as obese. Obesity, particularly abdominal obesity, is associated with high blood lipid levels and blood pressure, and type 2 diabetes. In Australia, the cost of obesity is estimated to be $830 million per year. The ultimate aim of any obesity treatment programme is to reduce body fatness by burning off fat and to prevent further fat storage and so studies which focus on developing strategies to achieve these goals are very important. We have found that subjects who fail to keep weight off after being on a weight-reducing diet are bad fat burners. These people also have low levels of leptin, a hormone made by fat cells which helps to regulate food intake. The first aim of this study is to show that leptin increases the burning of fat by regulating the production and activity of factors which decide whether fat is used for energy or is stored in the body. The second aim is to find ways in which leptin levels can be changed so that fat burning is increased. Some of the ways in which we will change leptin levels are by changing the fat content of the diet, or by drugs, or by giving leptin itself. These studies will be performed in animal models of obesity and will help us to develop strategies for the treatment and prevention of obesity in humans.Read moreRead less
MATERNAL UNDERNUTRITION, INFANT REFEEDING, ADIPOSITY AND DIABETES
Funder
National Health and Medical Research Council
Funding Amount
$297,323.00
Summary
Malnutrition is a major health problem throughout the world and one of the priority areas for the WHO. Refeeding program guidelines have been established and implemented when children are assessed as being malnourished. Recent studies on the effect of these important programs throughout the world have suggested they may not have been as successful as wished. Indeed, even though many of the subjects are the urban poor, it has been found that many are developing diabetes in their twenties. This is ....Malnutrition is a major health problem throughout the world and one of the priority areas for the WHO. Refeeding program guidelines have been established and implemented when children are assessed as being malnourished. Recent studies on the effect of these important programs throughout the world have suggested they may not have been as successful as wished. Indeed, even though many of the subjects are the urban poor, it has been found that many are developing diabetes in their twenties. This is associated with an increase in abdominal fatness, out of proportion to the rest of the body's size and shape. The increase in diabetes in this group is most worrying and a major public health problem. It is not known whether the diabetes and abdominal fatness are caused by the refeeding programs or whether they are due to the fact that the body's metabolism was programmed during pregnancy. Perhaps the infants were malnourished whilst they were developing during pregnancy and metabolism was changed so they could store fat easily and not use glucose as readily in the rest of the body. This study is designed to show whether there are metabolic changes which predispose to diabetes and fatness present at birth in those who are malnourished or whether the refeeeding program designed to help them grow is the cause of these later problems.Read moreRead less
Lipid Metabolism In The Aromatase Knock-out Mouse (ArKO)
Funder
National Health and Medical Research Council
Funding Amount
$408,055.00
Summary
Studies of humans with natural mutations in aromatase, the enzyme responsible for oestrogen biosynthesis, have revealed a number of unexpected roles for oestrogens in both males and females. These discoveries even challenge the definitions of oestrogens and androgens as we now know them. We have created a mouse model of oestrogen insufficiency by targetted disruption of the aromatase gene. These mice display a number of age dependent phenotypes including both male and female infertility, undermi ....Studies of humans with natural mutations in aromatase, the enzyme responsible for oestrogen biosynthesis, have revealed a number of unexpected roles for oestrogens in both males and females. These discoveries even challenge the definitions of oestrogens and androgens as we now know them. We have created a mouse model of oestrogen insufficiency by targetted disruption of the aromatase gene. These mice display a number of age dependent phenotypes including both male and female infertility, undermineralisation of the bones, intra-abdominal obesity, hypercholesterolaemia and insulin resistance. We are addressing the mechanisms of all of those phenotypes but in the present application we focus on the abnormalities in lipid metabolism. Thus we will seek to understand the increase in adiposity by examining the role of oestrogen in lipid synthesis, oxidation and breakdown in adipose tissue from intra-abdominal sites. We will also examine the role that oestrogen plays in cholesterol uptake, synthesis and catabolism by the liver as well as fatty acid synthesis and oxidation by the liver. These studies will be correlated with whole body parameters such as feeding behaviour, physical activity, energy expenditure, glucose and fat oxidation rates. We will also examine the effect of feeding a high cholesterol or a high fat diet on lipid metabolism in the oestrogen deficient animals, and we will determine the effect of oestradiol and isoflavone replacement on the phenotype. In this way we aim to reach a better understanding of the multiplicity of roles that oestrogens play in the regulation of lipid and cholesterol metabolism in both males and females. The results of such studies will be the development of better strategies to deal with pathologies resulting from disturbances in cholesterol and lipid metabolism.Read moreRead less