London, June 6 (ANI): Defying all previous studies, researchers have found that fatty foods, and not the fat made in the body, activate the hunger hormone ghrelin to optimise nutrient metabolism and promote the storage of body fat.
The study, led by Dr. Matthias Tschop, University of Cincinnati (UC) associate professor of psychiatry and internal medicine, has instead pointed to a novel stomach enzyme (GOAT) responsible for the ghrelin activation process and could be targeted in future treatments for metabolic diseases.
Ghrelin, a hormone believed to accumulate during periods of fasting, 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 as it gets activated via acylation (the addition of a fatty acid) by a specific enzyme (ghrelin O-acyl transferase, or GOAT).
Originally, scientists believed that the body produced the fatty acids attached to ghrelin via GOAT during fasting.
However, the new data has indicated that the fatty acids needed for ghrelin activation actually come directly from ingested dietary fats.
Tschop said that the ghrelin system is apparently a lipid sensor in the stomach that informs the brain when calories are available-giving the green light to other calorie-consuming processes such as growing.
The researchers made use of mouse models to test the effects of over expressing the GOAT enzyme, or "knocking it out."
It was found that, when exposed to a lipid-rich diet, mice without GOAT accumulated less fat than their normal counterparts, while those with over-expressed GOAT accumulated more fat mass than normal mice.
"When exposed to certain fatty foods, mice with more GOAT gain more fat. Mice without GOAT gain less fat since their brain does not receive the 'fats are here, store them' signal," Nature magazine quoted Tschop as saying.
"Our GOAT studies in mice offer an explanation of what could have been happening during the longer fasting periods in these human studies. Without dietary fats, ghrelin peaks remain inactive and don't affect storage of fat," Tschop added.
The study has been published in the journal Nature Medicine. (ANI)