Aldosterone Mediated Cardiac Pathophysiology:The Role Of Corticosteroid Receptors And 11 HSD Isoforms
Funder
National Health and Medical Research Council
Funding Amount
$481,500.00
Summary
Aldosterone a hormone that circulates in blood and is associated with cardiovascular disease. Recently, two clinical trials (RALES, EPHUSUS) demonstrate that if you stop this hormone from acting by giving drugs that inhibit it from binding to the receptor that mediates its response, there is an improvement in the health of heart failure patients. How aldosterone mediates its detrimental effects on heart is largely unknown. Glucocorticoids are another hormone that circulates in blood and can bind ....Aldosterone a hormone that circulates in blood and is associated with cardiovascular disease. Recently, two clinical trials (RALES, EPHUSUS) demonstrate that if you stop this hormone from acting by giving drugs that inhibit it from binding to the receptor that mediates its response, there is an improvement in the health of heart failure patients. How aldosterone mediates its detrimental effects on heart is largely unknown. Glucocorticoids are another hormone that circulates in blood and can bind to the same receptor as aldosterone. In contrast to aldosterone glucocorticoids appear to play a basic maintenance role in heart. Our central hypothesis is that in the healthy heart aldosterone has minimal effects , however, in the diseased heart aldosterone associated pathophysiology is a result of both an increase in the ability of aldosterone to signal to cells and disruption of glucocorticoid signalling. This grant proposal will address how aldosterone and glucocorticoids may directly signal within cardiac cells and how this signalling changes in the diseased heart. In addition, we investigate if enzymes that metabolize glucocortioids and thus render them non-functional play a role in cardiac disease, and if we can reverse the detrimental effects of aldosterone by artificially increasing the production of glucocorticoids in heart. By understanding the mechanisms by which aldosterone promotes cardiac disease, and the role of glucocorticoids and their metabolism in this process will lead to a better understanding of aldosterone induced pathology and thus lead to novel therapeutic targets.Read moreRead less
Molecular Characterisation Of The Ligand-binding Domain Of The Mineralocorticoid Receptor
Funder
National Health and Medical Research Council
Funding Amount
$215,183.00
Summary
The steroid hormone aldosterone regulates blood pressure by controlling sodium retention. The important role of this hormone in blood pressure control is underlined by the fact that all known monogenetic hypertensive conditions involve aldosterone or sodium reabsorption. Aldosterone works by activating an intracellular 'receptor' protein that in turn switches on specific genes. The products of these genes act to produce sodium retention. Antagonists (blockers) of this receptor are used in the tr ....The steroid hormone aldosterone regulates blood pressure by controlling sodium retention. The important role of this hormone in blood pressure control is underlined by the fact that all known monogenetic hypertensive conditions involve aldosterone or sodium reabsorption. Aldosterone works by activating an intracellular 'receptor' protein that in turn switches on specific genes. The products of these genes act to produce sodium retention. Antagonists (blockers) of this receptor are used in the treatment of hypertension but have undesirable side effects. The design of new, more specific, antagonists has been slow because we do not understand how these drugs bind to the receptor and what effect they have on the protein. How the aldosterone receptor functions is poorly understood. This project aims to investigate the receptor in detail. We are in the process of determining regions of the receptor structure important for hormone binding. This information is vital for the design of new antagonists. The aldosterone receptor is unusual in that it is also activated by cortisol, a steroid hormone involved in stress and inflammation. By examining hormone binding it may be possible to determine if the two steroids activate the receptor in the same way. An understanding of how both natural hormones and synthetic antagonists function is impossible without thorough study of the receptor itself. We intend to examine fundamental aspects of aldosterone receptor function. In particular we wish to identify proteins that interact with the receptor. These proteins either enhance or inhibit the ability of the receptor to switch on genes and are vital to explaining the actions of both natural hormones and synthetic antagonists. Results from these experiments should advance our understanding of the basic biology of aldosterone action and its role in cardiovascular biology, and lead to the design of better receptor antagonists for use in the treatment of hypertension and cardiac fibrosis.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.
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
Defining The Insulin-signalling Defect In Human Insulin Resistance And Type 2 Diabetes
Funder
National Health and Medical Research Council
Funding Amount
$94,280.00
Summary
Problems with the way insulin removes glucose from the circulation contribute to developing type 2 diabetes. Despite research to date, controversy remains regarding the nature of known defects in insulin action and their relevance to humans. We plan to measure molecules involved in insulin action in muscle of people with insulin resistance, which is linked to diabetes. These studies will define new defects that cause insulin resistance and type 2 diabetes in humans.
A Transgenic Analysis Of The Physiologic Roles Of Signalling Domains In The Growth Hormone Receptor
Funder
National Health and Medical Research Council
Funding Amount
$262,500.00
Summary
The key hormone promoting growth postnatally is growth hormone (GH), and it acts through the growth hormone receptor to initiate a variety of signals which regulate gene expression. In addition to its role in growth, GH is an importnat metabolic regulator in starvation. It also appears to play a significant role in the ageing process, since mice lacking the GH receptor live 50% longer than normal mice. Although the signalling systems used by the GH receptor are reasonably well defined in vitro, ....The key hormone promoting growth postnatally is growth hormone (GH), and it acts through the growth hormone receptor to initiate a variety of signals which regulate gene expression. In addition to its role in growth, GH is an importnat metabolic regulator in starvation. It also appears to play a significant role in the ageing process, since mice lacking the GH receptor live 50% longer than normal mice. Although the signalling systems used by the GH receptor are reasonably well defined in vitro, we have no idea which signals are used to control postnatal growth, metabolism and ageing in the live animal. With NHMRC support, we have been creating mice with individual signalling domains of the GH receptor deleted. This proposal aims to use these mice to determine how the GH receptor brings about its actions of promoting postnatal growth, regulating metabolism and altering lifespan. In particular, through the use of gene arrays, we intend to define the key genes regulated in these processes. This would provide potential therapeutic targets for drug development to individually alter these key processes.Read moreRead less
Growth hormone is responsible for normal postnatal growth, is an important metabolic regulator in starvation, and has many useful therapeutic applications, including forms of cardiac insufficiency, Crohns disease and, it is thought, amelioration of ageing. The means whereby GH brings about these changes are not known, although we do know a considerable amount about how the individual domains within the GH receptor signal. What we do not know is which genes are regulated by GH in these processes, ....Growth hormone is responsible for normal postnatal growth, is an important metabolic regulator in starvation, and has many useful therapeutic applications, including forms of cardiac insufficiency, Crohns disease and, it is thought, amelioration of ageing. The means whereby GH brings about these changes are not known, although we do know a considerable amount about how the individual domains within the GH receptor signal. What we do not know is which genes are regulated by GH in these processes, and how this will change the state of the cell. We propose here to use the new technique of gene arrays to uncover the programs, or groups of genes, which GH regulates to change important cellular processes. When used in conjunction with cells expressing GH receptor mutants which are unable to signal to defined pathways, we will be able to know which functional families genes are regulated, and how they are regulated. This information will enable us to know how GH regulates cell growth and metabolism, and therfore to understand what goes wrong when GH or its mediator, IGF-1 , are abnormal. We can also use this information to validate small molecules designed to mimic GH through activating its receptor, to be certain that they are acting in the same way as GH.Read moreRead less