Researchers at Montreal’s McGill University may have made a breakthrough, that could lead to new drugs with never-before-seen ability to control obesity, by identifying brain cells that control appetite.
The researchers say they have long been interested in a part of the brain called the median eminence, a section of the hypothalamus that releases regulatory hormones. They pinpointed NG2-glia cells, which send a signal to the brain that the body has had enough to eat.
“We developed an interest in NG2-glia cells in this specific part of the brain because unlike neurons, during much of our adult lives these cells are constantly dividing and they do so most actively in the median eminence,” says Tina Djogo, co-lead author of the study which was published this week in the journal Cell Metabolism. “But though these cells were first described about thirty years ago it has been difficult so far to pinpoint their exact functions in the adult brain.”
The researchers say a hormone called leptin, which is known to be a regulator of body fat mass, is the key.
“About twenty years ago there was a big step forward in our understanding of obesity when researchers discovered that our appetite is controlled by a key molecule called leptin. Leptin is a hormone which is produced by our fat cells, and is delivered by the blood to the brain to signal the brain that we are full and can stop eating,” explains researcher Dr. Maia Kokoeva. “But even though receptors for leptin were discovered soon after in the hypothalamus, a brain area that regulates food intake and body weight, it has remained unclear how exactly leptin is detected.”
The scientist say the resistance to leptin that causes obesity in mice can be circumvented through the prevention of NG2-glia loss in the median eminence. When they employed a drug to drug to kill the NG2-glia cells, a group of mice they tested immediately begam to gain weight. They say the potential exists for drugs that raise the population of NG2-glia could have the opposite effect.
In Canada, as in much of the developed world, obesity is a major problem because of its link to a myriad of chronic diseases. According to statistics from the Canadian government in 2008, 37 per cent of Canadian adults were overweight and 25 per cent of them were obese. Of G7 countries, Canada trailed only the United States and Germany in terms of obesity levels.
There was some recent good news, however. A report published earlier this week in the Canadian Medical Association Journal revealed that childhood obesity in Canada dropped from 30.7 per cent in 2004 to 27 per cent in 2013.
One expert approached the results cautiously.
“If this is a real trend, and not some manifestation of analytical or methodological limitation or selection bias, it may reflect a variety of things: increased public health awareness, reduced energy intake, increased energy expenditure, improved preventive health care — evidence that the many efforts being made by many groups and sectors over many years now may be finally taking root — let’s hope,” Mark Tremblay, director of the Healthy Active Living and Obesity Research program at the Children’s Hospital in Eastern Ontario in Ottawa, told the CBC.