Insulin receptors in the brains of mice are involved in appetite, weight gain and fertility, new research has shown.
When researchers "knocked out" insulin receptors in the brains of genetically altered mice, they discovered that the animals ate more, put on fat, had fertility problems, and developed insulin resistance throughout the body -- a precursor to diabetes in humans.
Insulin is a key hormone in metabolism, and its levels rise as levels of body fat rise.
Although obese people often have chronically high insulin levels, they often become or are already resistant to the hormone and eventually develop diabetes.
While it is well known that tissue such as muscle and fat can become insulin resistant, it had been assumed previously that the brain is not sensitive to insulin.
This study, however, confirms earlier evidence that insulin receptors in the brain help control food intake and body weight.
The fact that knocking out the brain's insulin receptors triggered
infertility in the mice was something of a surprise finding to many.
The mice showed increased levels of the "obesity hormone" leptin, as well. Leptin is believed to help the body regulate fat, perhaps through triggering feelings of satiety.
Leptin resistance has also been linked to obesity, as noted in another article this week. One researcher proposed that it is possible that insulin resistance and leptin resistance act together in the onset of obesity and diabetes.
Science September 22, 2000;289:2122-2125.
More evidence from one of the top science periodicals in the world 'Science' documenting the importance of insulin in obesity and chronic disease. Of the traditional medical paradigm will use this information to develop drugs to work on the brain insulin receptors. I imagine that there will be a certain (small) subset of individuals who will have a genetic receptor defect problem and this will be a miracle.
This is not too different from what we currently have today with elevated cholesterol levels. When I was in medical school 20 years ago, we did not understand much about LDL receptor defects. Now we have medications that counteract these genetic problems that occur in about one in 1000 people that result in cholesterol levels above 350.
Obviously, this is a very small subset of the population, as most everyone with elevated cholesterol levels will respond just like individuals with impaired insulin receptor sensitivities, to diet and exercise.