Study sheds new light on relationship between obesity and diabetes

Scientists at the Walter and Eliza Hall Institute (WEHI) have completed a study showing that cells which lead to inflammation in fat tissue may be a primary cause of insulin resistance in sufferers of diabetes.

Researchers at the institute as well as at Monash University’s Centre for Obesity Research and Education, analysed the fat tissue of more than 100 Victorians who had undergone lapband surgery.

Their research focussed on macrophages, white blood cells derived from the bone marrow which act as immune cells that normally respond to infections.

In people who are obese, macrophages move into the fat tissue where they lead to inflammation, but more importantly, release what are known as cytokines. Cytokines are chemical messenger molecules which immune cells uses to communicate and the researchers found that certain cytokines cause cells to become resistant to insulin, increasing the susceptibility of diabetes and heart disease.

“We have shown that insulin resistance in human obesity is closely related to the presence of inflammatory cells in fat tissue, in particular a population of macrophage cells,” said WEHI scientist and project leader Professor Len Harrison.

The findings were published this week in the journal Diabetes.

More than than 1 million Australians are affected by diabetes and it is hoped that this discovery will open the door for novel new anti-inflammatory treatments that mitigate against insulin resistance.

“The complications of obesity such as insulin resistance and diabetes, cardiovascular disease associated with hardening of the arteries, and liver problems are the result of inflammation that occurs in the fat tissue,” Professor Harrison said. “These complications could be prevented by developing drugs that target certain cytokines released by the macrophages.

“Encouragingly, our study also showed that when obese people lost weight the macrophages in the fat tissue disappeared, as did the risk of developing insulin resistance and diabetes.”

Funding for the research was provided by the Australian National Health and Medical Research Council, theVictorian Government, Diabetes Australia Research Trust and the Royal Australasian College of Physicians Research and Education Foundation.