Obesity Causes Diabetes? Maybe not.
By
Miranda Hitti
WebMD Medical News
Reviewed by
Louise Chang, MD
Aug. 23, 2007 -- Scientists may have found a loophole in the link between obesity and diabetes.
A new study shows that some extremely obese mice metabolically resemble much skinnier mice.
The key is a hormone called adiponectin, according to the researchers, who included Philipp Scherer, PhD, of the University of Texas Southwestern Medical Center in Dallas.
Scherer's team studied genetically engineered mice that lacked leptin, a hormone that helps regulate appetite. Without leptin, the mice binged on chow; packing on extra weight.
But despite what you might expect, the mice that gained the most weight actually had the best metabolism and were least likely to develop type 2 diabetes.
"The message isn't that it's good to be obese, but that expanded fat mass, when stored in the right places, can help prevent diabetes and reduce the risk of heart disease," Scherer says in a news release.
The findings appear in today's online edition of
The Journal of Clinical Investigation.
Obesity Experiment
Some of the mice also had higher-than-normal levels of the hormone adiponectin, which controls sensitivity to insulin.
The mice with extra adiponectin gained the most weight. They became morbidly obese, even though they didn't eat more than mice with normal adiponectin levels.
However, the mice with extra adiponectin were more sensitive to insulin than the other mice, lowering their odds of developing type 2 diabetes. They also had better cholesterol and triglyceride levels.
In short, the mice with extra adiponectin were beyond obese, but their extreme obesity didn't bog down their metabolism.
Why? It may be a chain reaction from extra adiponectin, according to the study.
Hormone Help
Scherer's team took a close look at how the mice stored their fat.
The mice with extra adiponectin added lots of little fat cells to their fatty tissue. But the mice with normal adiponectin levels expanded the size of their fat cells.
Creating many small fat cells may be healthier than making bloated fat cells, the researchers suggest.
Obviously, mice are different from people -- and the mice in this study weren't normal mice. They were genetically engineered to have their leptin and adiponectin levels altered.
But the researchers point out that not all extremely obese people have insulin resistance (a risk factor for type 2 diabetes), and higher levels of adiponectin often accompany favorable metabolic profiles.
Of course, reams of research show that extra weight makes diabetes and a host of other health problems more likely. The adiponectin study doesn’t change that.
Scherer cautions that until scientists figure out how to put the findings to work in humans, "exercise and reduction of food intake are the best ways to stay healthy."
SOURCES: Kim, J.
The Journal of Clinical Investigation, Aug. 23, 2007; online edition. News release, University of Texas Southwestern Medical Center.
Obesity Causes Diabetes