A newly discovered hormone has been found to play an important role in the digestion of fat, cholesterol, and fat-soluble vitamins, such as vitamins A, E, and D. The hormone is found to control the production of bile acid by sending signals to the liver.
The bile acids play a very important role in the emulsification of fats that enables absorption. The hormone is called fibroblast growth factor (FGF 15), the secretion of which depends on the level of bile acid secretion. FGF15 in turn limits further production of bile acid by the liver by negative feedback mechanism.
Bile acids are powerful detergents; the concentrations must be tightly regulated for proper functioning of the human body. The body needs enough quantity of the bile acid to absorb fat and other nutrients. However, too much can damage tissues and organs. This new mechanism probably holds the key to protect the body from the effects of over production of the bile acid.
Researchers have identified a receptor that senses bile acid and responds by secreting FGF15. In the liver, the secreted intestinal protein limits the activity of an enzyme called cholesterol 7a-hydroxylase (CYP7A1) critical to bile acid production. Animal models lacking FGF15 were found to have increased CYP7A1 activity and excrete greater quantities of bile acid.
The results of the present study have valuable clinical implications. For example, the above mentioned feedback mechanism might be an explanation to the liver damage associated with intravenous infusion of nutrients.
The findings also raise additional questions about the role that the circulating hormone may play in other parts of the body. An additional insight into cholesterol-derived bile acids might also yield important clues regarding cholesterol control. However, further studies in human beings are needed at the moment.