Researchers at the Joslin Diabetes Center found that a neuropeptide, melanin concentrating hormone (MCH), plays a role in the growth of insulin-producing beta cells and the secretion of insulin.
"It's a very logical connection," states Rohit N. Kulkarni, M.D., Ph.D., investigator at Joslin Diabetes Center and assistant professor of medicine at Harvard Medical School, who led the study. "Whenever you eat food, your body needs more insulin. When MCH induces appetite, it simultaneously increases insulin secretion from beta cells and enhances growth of beta cells. If the proteins that mediate the growth mechanism can be identified, it could lead to the development of new drugs that would enhance beta cell growth to treat type 1 and type 2 diabetes."
An earlier Joslin-led study examined the connection between obesity and MCH. Dr. Kulkarni and his colleagues observed changes in beta cell mass that wsere out of proportion with the degree of obesity, suggesting that MCH had a direct effect on islets.
The investigators went on to first confirm that MCH and its receptors are indeed expressed in islet cells of mice and humans. After treating human donor or mouse pancreatic islet cells with MCH, they found that it increased insulin secretion. In the next phase, the researchers examined genetically engineered mice that did not produce MCH and consequently had abnormally small islets. "This indicated to us that MCH is important for growth of islets," explains Dr. Kulkarni.
The next step in the research process is to pinpoint exactly how MCH is regulating the growth of beta cells and identify which proteins are involved in this growth process. "We know MCH is having an effect on both growth and function likely by recruiting different proteins. It will be worth exploring which proteins are being activated by MCH to cause the growth effect," Dr. Kulkarni explains.
The follow-up study will look at how MCH interacts with glucagon-like peptide 1 (GLP-1), a hormone involved in beta cell growth.
The research, conducted with scientists at Beth Israel Deaconess Medical Center in Boston and other institutions, will appear in the February 2007 issue of Diabetes.