Fat cells in fact aids insulin secretion

Author:  Shrestha Suvash
Date:  November 2007

Fat cells produce an enzyme which triggers pancreatic beta cells to secret more insulin, concludes a study conducted at Washington University School of Medicine, St Louis and published in the November issue of Cell Metabolism. Shin-ichiro Imai, the lead researcher, asserts this finding could provide a better therapy for Diabetes Mellitus Type 2, which more than 7 million people are living with in the USA alone.

The enzyme, discovered in 2004, was named Visfatin and believed to be similar to insulin. But this new study revealed that the fat derivative is not an insulin-like hormone, but rather an enzyme that affects the level of insulin. It's now called Nampt.

Because Nampt levels are low in pancreatic cells, the pancreas depends on fat cells for Nampt and the compound Nampt produces, NMN. Researchers found NMN in the bloodstream of laboratory mice in a concentration sufficient enough to enhance insulin secretion from pancreatic beta cells. They claim no one previously knew that NMN circulated in blood.

"We think this secretion process allows fat cells to communicate with the pancreas and aid its function," says Imai. "I suspect this process could be critical for compensating pancreatic beta cell function in the face of increasing insulin resistance."

But then how come obese people are more often diabetic? Well, it might be because the enzyme-induced enhancement of pancreatic function has a limit and beyond that limit, the mechanism does not provide any protection, explains Imai.

In their study of mice, they found mice with one instead of two copies of the Nampt gene had impaired ability to metabolize glucose and had defective insulin secretion, which was restored by the injection of NMN.

Now, Imai and his group seem interested in NMN and are working to find out how much NMN is present in the blood of normal and diabetic patients. They hope to initiate clinical trials to test NMN as a therapeutic agent in patients with type 2 diabetes. In addition, they want to identify factors that cause secretion of Nampt from the fat cells and determine the exact mechanism of action of NMN.

Written by Suvash Shrestha

Reviewed by Lisa Merolla

Published by Pooja Ghatalia.