Insulin-like protein points to new diabetes drugs

Japanese investigators have isolated a new compound produced by fat tissue that shares properties with insulin and may lead to the development of new diabetes drugs. They call the protein visfatin.

Visfatin is produced in abdominal visceral fat of both humans and mice. The blood level of the protein "increases during the development of obesity," the team reports in the journal Science, published online Thursday at the ScienceExpress Web site.

"Surprisingly," Dr. Iichiro Shimomura, from Osaka University and colleagues write, "visfatin binds to and activates the insulin receptor."

There are, however, "important differences" between visfatin and insulin, the team notes. For example, visfatin levels do not change markedly with fasting or feeding, as is the case with insulin.

It's known that obesity, and specifically the accumulation of fat in the abdomen around the visceral organs, is linked to the development of insulin resistance that can lead to overt diabetes. Shimomura explained how visfatin may play into this scenario.

Chronically high levels of visfatin resulting from visceral fat obesity, he said, "may underlie insulin resistance by continuously stimulating insulin receptors."

Alternatively, "as visfatin activates insulin receptor in a different manner from insulin, visfatin may be useful to treat insulin resistance," the researcher commented.

Indeed, the researchers found that visfatin displays beneficial insulin-like effects in mice. High doses of synthetic visfatin lowered blood glucose levels in insulin-resistant or insulin-deficient animals.

But as the two authors of a related editorial point out, much remains to be discovered about how visfatin, insulin and glucose are related.

SOURCE: Science, online December 16, 2004.