Bile Acid Detoxification By Nuclear Receptor-mediated CYP3A Regulation
Funder
National Health and Medical Research Council
Funding Amount
$196,527.00
Summary
Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that many of these adverse effects of obstructed bile flow are due to the retention of a component of bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic ....Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that many of these adverse effects of obstructed bile flow are due to the retention of a component of bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic and cause the death of cells in the liver if their concentration becomes too high. Evidence has emerged that the body has control mechanisms to try and combat rising levels of bile acids in cholestatic liver diseases. One such mechanism, which is the subject of this application, is the metabolism of bile acids to less toxic forms, by a process called hydroxylation. A particular class of liver enzymes, known as cytochromes P450 CYP3As, appear to mediate these hydroxylation reactions. Liver cytochrome P450 enzymes are important to medicine in areas as broad as drug breakdown, steroid hormone regulation and the formation or elimination of cancer causing chemicals. These enzymes are present in high concentration in the human liver, but the factors governing how much of these enzymes are produced have been poorly understood. The present projects builds on discoveries concerning the regulation of cytochrome P450 enzymes made by our group over the last few years, including an in-depth understanding of the way the production of CYP3As are increased by some drugs. We intend to determine the mechanism by which bile acids increase the level of CYP3A enzymes are how effective these enzymes are in hydroxylating bile acids. An understanding of these issues will allow us to better manage patents with cholestatic liver diseases and develop new strategies for treating these diseases, for example, development of novel drugs that increase bile acid hydroxylation in the liver.Read moreRead less
Hepatic Fibrogenesis In Paediatric Cholestatic Liver Disease.
Funder
National Health and Medical Research Council
Funding Amount
$254,250.00
Summary
Liver disease in children causes a significant impact on lifespan and quality of life. The commonest causes of liver disease in children are cholestatic, or diseases related to obstruction of bile flow out of the liver. In ways we are only beginning to understand, obstruction of bile flow stimulates liver scar formation which, if untreated, leads to replacement of normal liver tissue and ultimately to failure of the liver. In infants, the most common and serious cholestatic liver disease is bili ....Liver disease in children causes a significant impact on lifespan and quality of life. The commonest causes of liver disease in children are cholestatic, or diseases related to obstruction of bile flow out of the liver. In ways we are only beginning to understand, obstruction of bile flow stimulates liver scar formation which, if untreated, leads to replacement of normal liver tissue and ultimately to failure of the liver. In infants, the most common and serious cholestatic liver disease is biliary atresia. It develops at, or shortly after birth with progressive destruction of the bile ducts, responsible for transporting bile out of the liver. Without early diagnosis and surgery these infants develop progressive liver scarring leading to liver failure and death or liver transplantation within 1-2 years. It is the commonest reason for liver transplantation in children (55-60%) in the Western world. Even with successful surgery, most, if not all patients will come to liver transplantation over the subsequent 25 years because of ongoing, but slower, scar formation. In older children, diseases like cystic fibrosis cause bile duct blockages leading to progressive liver scarring that is slower and unpredictable, contributing to ill health in up to 20% of patients and death from end stage liver disease or liver transplantation in 5%. Using liver tissue from children with these two disorders we have been able to identify the key cells that control the liver scar process, the Hepatic Stellate Cell. We now need to investigate the role of bile constituents on the scar-forming process in these two diseases. We will utilise a well characterised animal model to investigate the influence of bile constituents on cells isolated from this model and apply these findings back to patient samples to determine their role in paediatric cholestatic liver disease. This will help us to better understand the disease process and importantly, develop more effective and earlier treatment.Read moreRead less
Molecular Mechanisms Of Feed-forward Regulation Of Bile Acid Detoxification And Elimination In Cholestasis
Funder
National Health and Medical Research Council
Funding Amount
$334,500.00
Summary
Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that may of these adverse effects of obstructed bile flow are due to the retention of a component or bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic ....Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that may of these adverse effects of obstructed bile flow are due to the retention of a component or bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic and cause the death of cells within the liver if their concentration becomes too high. Evidence has emerged that the body has control mechanisms to try and combat rising levels of bile acids in cholestatic liver diseases. These control mechanisms are complex and include enzymes from the cytochrome P450 family as well as several specialized transport molecules. In cholestasis these mechanisms promote the removal of bile acids through the urine as well as converting very toxic bile acids to less toxic forms. The present projects builds on discoveries concerning the regulation of cytochrome P450 enzymes made by our group over the last few years, including an in-depth understanding of the way the production of CYP3As is increased by some drugs. We intend to determine in detail how defense mechanisms against toxic bile acids are engaged. In particular, we wish to identify the receptor molecules that 'sense' the rising levels of bile acids that occur in cholestatic liver diseases. An understanding of these issues will allow us to better manage patents with these diseases and develop new strategies for treating cholestatic disorders, for example, development of novel drugs that can influence bile acid detoxification in the liver and other organs.Read moreRead less
Exploiting The Pharmacokinetic And Pharmacodynamic Properties Of Bile Acid Receptor Agonists To Treat Liver Disease
Funder
National Health and Medical Research Council
Funding Amount
$653,952.00
Summary
We have generated preliminary data suggesting that chemicals made by the liver, called bile acids, act on fat cells to release a hormone called adiponectin. In liver disease adiponectin has favorable effects, including reducing liver inflammation and fibrosis (scarring). By using drugs that mimic the action of bile acids we expect that adiponectin production by fat cells can be increased, creating a new way to treat patients with chronic liver diseases.
Function Of The Vitamin D Receptor In Hepatic Non-Parenchymal Cells
Funder
National Health and Medical Research Council
Funding Amount
$509,304.00
Summary
Nuclear receptors are sensors that control many aspects of metabolism, including responses to injury. Our work and has suggested that the Vitamin D Receptor (VDR) may play a vital role in how the liver responds to damage and whether the liver will the scar and move on to cirrhosis. Our experiments will determine if this is so, and in which cells VDR has this role. This work will provide a basis for future treatments to improve or prevent severe liver diseases.
The sphincter of Oddi is a valve-like structure, which regulates the flow of bile and pancreatic juice into the gut. The sphincter of Oddi is under complex control involving nerves and hormones. We know that abnormal sphincter of Oddi function (sphincter of Oddi dysfunction) is associated with a number of human diseases including acute pancreatitis. We are able to recognise abnormal sphincter activity, but we do not know what causes it. One possible reason may be that the nerves going to the sph ....The sphincter of Oddi is a valve-like structure, which regulates the flow of bile and pancreatic juice into the gut. The sphincter of Oddi is under complex control involving nerves and hormones. We know that abnormal sphincter of Oddi function (sphincter of Oddi dysfunction) is associated with a number of human diseases including acute pancreatitis. We are able to recognise abnormal sphincter activity, but we do not know what causes it. One possible reason may be that the nerves going to the sphincter along the bile duct (which carries bile from the liver and gallbladder) may be damaged due to the passage of gallstones or during surgery on the bile ducts or gallbladder. We know that the main bile duct is able to sense pressure changes within and communicate this information (via nerves) to the sphincter which inturn alters its activity to relieve the pressure. Where these nerves are located and the chemical messages they use, are unknown. The aim of this project is to gain some of this information. This knowledge may allow us to design different surgical procedures or develop drugs to prevent or manage the abnormal sphincter of Oddi.Read moreRead less
How Does Dietary Cholesterol Induce Non-alcoholic Steatohepatitis?
Funder
National Health and Medical Research Council
Funding Amount
$802,600.00
Summary
Non-alcoholic fatty liver disease is the most common liver disease that can progress to non-alcoholic steatohepatitis (NASH), cirrhosis and liver cancer. Dietary cholesterol is a major risk factor for NASH. We can demonstrate that cholesterol changes the gut bacteria. These bacteria generate toxic chemicals (bile acids) that signal to the liver and induce NASH. In this project, we use novel ways to clarify the mechanisms of liver inflammation and test novel therapeutic approaches to reverse it.