CINCINNATINew research led by the University of Cincinnati (UC) suggests that the hunger hormone ghrelin is activated by fats from the foods we eatnot those made in the bodyin order to optimize nutrient metabolism and promote the storage of body fat.
The findings, the study's author says, turn the current model about ghrelin on its head and point to a novel stomach enzyme (GOAT) responsible for the ghrelin activation process that could be targeted in future treatments for metabolic diseases.
The laboratory study, led by Matthias Tschp, MD, UC associate professor of psychiatry and internal medicine, is published online ahead of print Friday, June 5, 2009, in the journal Nature Medicine.
Ghrelin is a hormone that was believed to accumulate during periods of fasting and is found in the body in high concentrations just before meals. It is dubbed the "hunger hormone" because it has been shown that administration of pharmacological doses acts in the brain to stimulate hunger and increase food intake in animal models and humans.
The ghrelin hormone is unique in that it requires acylation (the addition of a fatty acid) by a specific enzyme (ghrelin O-acyl transferase, or GOAT) for activation. Originally it was assumed that the fatty acids attached to ghrelin by GOAT were produced by the body during fasting.
The new data by Tschp and his team suggests that the fatty acids needed for ghrelin activation actually come directly from ingested dietary fats. In a departure from an earlier model that was upheld for nearly a decade, Tschp says, it appears that the ghrelin system is a lipid sensor in the stomach that informs the brain when calories are availablegiving the green light to other calorie-consuming processes such as growing.
Tschp and his team used mouse models to test the effects of over expressing the GOAT enzyme, or "knocking it out." They found that, when exposed to a lipid-rich diet, mice without GO
|Contact: Dama Kimmon|
University of Cincinnati Academic Health Center