Could high insulin make you fat? Mouse study says yes

When we eat too much, obesity may develop as a result of chronically high insulin levels, not the other way around. That's according to new evidence in mice reported in the December 4th Cell Metabolism, a Cell Press publication, which challenges the widespread view that rising insulin is a secondary consequence of obesity and insulin resistance. Credit: Mehran et al., Current Biology

When we eat too much, obesity may develop as a result of chronically high insulin levels, not the other way around. That's according to new evidence in mice reported in the December 4th Cell Metabolism, a Cell Press publication, which challenges the widespread view that rising insulin is a secondary consequence of obesity and insulin resistance.

The new study helps to solve this chicken-or-the-egg dilemma by showing that animals with persistently lower insulin stay trim even as they indulge themselves on a high-fat, all-you-can-eat buffet. The findings come as some of the first direct evidence in mammals that circulating insulin itself drives obesity, the researchers say.

The results are also consistent with clinical studies showing that long-term insulin use by people with diabetes tends to come with , says James Johnson of the University of British Columbia.

"We are very inclined to think of insulin as either good or bad, but it's neither," Johnson said. "This doesn't mean anyone should stop taking insulin; there are nuances and ranges at which insulin levels are optimal."

Johnson and his colleagues took advantage of a genetic quirk in mice: that they have two insulin genes. Insulin1 shows up primarily in the pancreas and insulin2 in the brain, in addition to the . By eliminating insulin2 altogether and varying the number of good copies of insulin1, the researchers produced mice that varied only in their fasting blood insulin levels. When presented with high-fat food, those with one copy and lower fasting insulin were completely protected from even without any loss of appetite. They also enjoyed lower levels of inflammation and less fat in their livers, too.

Those differences traced to a "reprogramming" of the animals' fat tissue to burn and waste more energy in the form of heat. In other words, the mice had white fat that looked and acted more like the coveted, calorie-burning brown fat most familiar for keeping babies warm.

Johnson says it isn't clear what the findings might mean in the clinic just yet, noting that drugs designed to block insulin have been shown to come with unwanted side effects. But, he added, "there are ways to eat and diets that keep insulin levels lower or that allow to return to a healthy baseline each day."

Unfortunately, constant snacking is probably not the answer.

More information: Mehran et al.: "Hyperinsulinemia drives diet-induced obesity independently of brain insulin production." Cell Metabolism, DOI: 10.1016/j.cmet.2012.10.019

Related Stories

Improving obesity-induced insulin sensitivity

Jun 01, 2012

In recent years, a growing body of evidence has linked inflammation to the development of insulin resistance. In insulin resistance, the hormone insulin is less effective in promoting glucose uptake from the bloodstream into ...

Apelin hormone injections powerfully lower blood sugar

Nov 04, 2008

By injecting a hormone produced by fat and other tissues into mice, researchers report in the November Cell Metabolism that they significantly lowered blood sugar levels in normal and obese mice. The findings suggest that t ...

Enzyme boosts metabolism, prevents weight gain in mice

Nov 14, 2011

In a new study, scientists report that they substantially curbed weight gain, improved metabolism, and improved the efficacy of insulin in mice by engineering them to express a specific human enzyme in their fat tissue. Although ...

Recommended for you

Immune response may cause harm in brain injuries, disorders

36 minutes ago

Could the body's own immune system play a role in memory impairment and cognitive dysfunction associated with conditions like chronic epilepsy, Alzheimer's dementia and concussions? Cleveland Clinic researchers believe so, ...

One route to malaria drug resistance found

4 hours ago

Researchers have uncovered a way the malaria parasite becomes resistant to an investigational drug. The discovery, at Washington University School of Medicine in St. Louis, also is relevant for other infectious ...

Protein therapy successful in treating injured lung cells

4 hours ago

Cardiovascular researchers at The Ohio State University Wexner Medical Center have successfully used a protein known as MG53 to treat acute and chronic lung cell injury. Additionally, application of this protein proved to ...

User comments