Ghrelin, a hormone produced in the stomach, induces food intake and operates through a brain region that controls cravings for food and other energy sources, researchers at Yale School of Medicine report in the October 19 online issue of The Journal of Clinical Investigation.
Ghrelin was previously associated with growth hormone release, appetite, learning, and memory and has now been linked with the reward circuitry of the brain that regulates food cravings.
According to lead author Tamas Horvath, components of the reward circuitry of the ventral tegmental area (VTA), may be responsible for overeating and addiction. "Targeting this region pharmacologically is an interesting tool to explore," said Horvath, chair of the Section of Comparative Medicine at Yale School of Medicine and professor of comparative medicine, neurobiology and obstetrics, gynecology & reproductive sciences.
In this study, Horvath and colleagues found that ghrelin could signal directly in the VTA region and activate dopamine neuronal activity, which controls reward-associated behavior to promote interest in food as a reward. As a default, ghrelin's action may also alter seeking of drugs and substances that work through the same pathways.
"We found that if we selectively block ghrelin in this part of the brain, we can suppress feeding or the need to seek out food and energy," said Horvath. "It also suggests that perhaps it could interfere with the need to seek out drugs as well."
Horvath said ghrelin, which was originally found to signal in the hypothalamus, has now been shown to have a broad influence on various brain functions. "This makes sense because the major driving force of life is seeking energy to survive," he said. "Future studies will explore the relationships between ghrelin and cocaine addiction."
The National Institute of Diabetes and Digestive and Kidney Disease of the National Institutes of Health funded the study.
Other authors on the study include first author Alfonso Abizaid, Zhong-Wu Liu, Zane B. Andrews, Marya Shanabrough, Erzsebet Borok, John Elsworth, Robert Roth, Mark Sleeman, Marina Picciotto, Matthias Tschop, and Xiao-Bing Gao.
Citation: Journal of Clinical Investigation, 116, 12 (Online: October 19; Print: December 2006)