Study Finds Insulin Link To Obesity Gene (340)

KNOXVILLE, Tenn. — The same gene which controls fur color in mice also may affect weight gain in humans as they grow older, a University of Tennessee researcher said Friday.

Dr. Michael Zemel said a study by UT, Oak Ridge National Laboratory and Glaxo-Wellcome pharmaceutical firm may help scientists understand why people gain weight as they age.

A report on their research appears in the current issue of Proceedings of the National Academy of Science.

Zemel said the agouti gene is found in skin cells of mice and controls their fur color. In humans, the same gene lies in fat tissue and is believed to regulate fat metabolism, said Zemel, head of the nutrition department at UT-Knoxville.

The gene does not exist naturally in the fat cells of mice, he said. In their study, the researchers inserted it into the fat tissue of mice. It did not affect their weight, Zemel said.

When mice with the added agouti gene in their fat cells were injected with insulin — a hormone that regulates blood sugar in humans — they gained weight at nearly twice the normal rate, Zemel said.

The results suggest that interaction of insulin and agouti genes may be a reason why humans gain weight as they age, Zemel said.

“As people get older, they develop insulin resistance, especially middle-aged and older men,” Zemel said. “As that happens, the body secretes more insulin to compensate.

“That increase in insulin, combined with the agouti gene already in their fat tissue, may be one of the mechanisms that triggers weight gain or obesity as we get older.”

The research team includes Dr. Erby Wilkinson, a pathologist at UT’s College of Veterinary Medicine; Dr. Randall Mynatt of Pennington Biomedical Research in Baton Rouge, La.; Dr. Rick Woychik, an ORNL geneticist and adjunct pathology professor at UT, and Dr. William Wilkison of Glaxo-Wellcome.

“This project demonstrates the synergy of the relationships between ORNL, UT and industry,” Woychik said. “It would not have been possible without the teamwork between geneticists, pathologists and physiologists at these institutions.”

—Contact: Dr. Michael Zemel (423-974-5445)