Back in the 1970s and 1980s, Stanford's Gerald Reaven, MD, had the darndest time convincing others that type 2 diabetes wasn't caused by a lack of insulin. No one would believe him that, as we now know, type 2 diabetics are insulin resistant -- their cells no longer respond to insulin's cue to take in glucose.
Fast-forward a few years. Insulin resistance has been implicated in a slew of symptoms such as high blood pressure and heart troubles known as metabolic syndrome — it isn't just a problem for diabetes. Scientists knew that about half of insulin resistance was governed by weight, exercise and diet. But the heredity half was a mystery — until now.
Thanks to an international collaboration and many months of work, a team of researchers led by Joshua Knowles, MD, PhD, and Thomas Quertermous, MD, have found the first gene known to contribute to insulin resistance. It's called NAT2, and when mutated, it leads to a greater chance for carriers to become insulin resistant.
From the release:
"It's still early days," Knowles said. "We're just scratching the surface with the handful of variants that are related to insulin resistance that have been found."
Researchers found NAT2 by compiling data from about 5,600 individuals for whom they had both genetic information and a direct test of insulin sensitivity. Measuring insulin sensitivity takes several hours and is usually done in research settings. No genes met the high standards demanded by genome-wide association studies. Yet NAT2 appeared promising, so researchers followed up with experiments using mice.
When they knocked out the analogous gene in mice, the mice's cells took up less glucose in response to insulin. These mice also had higher fasting-glucose, insulin and triglyceride levels.
"Our goal was to try to get a better understanding of the foundation of insulin resistance," Knowles said. "Ultimately, we hope this effort will lead to new drugs, new therapies and new diagnostic tests."
Previously: New insulin-decreasing hormone discovered, named for goddess of starvation, Stanford researchers identify a new pathway governing growth of insulin-producing cells and Faulty fat cells may help explain how type 2 diabetes begins
Image by Andy Leppard