Another "obesity gene"

Another gene was added to hereditary obesity

Kirill Stasevich, Science and Life (nkj.ru )

Overweight can appear not only because of an unhealthy diet and a sedentary lifestyle. Sometimes the cause of obesity lies in the genes: because of some mutation inherited, a person gets fatter, despite all efforts to eat right. Moreover, hereditary obesity begins early: a person gets extra pounds while still being a small child.

Usually, such obesity is easy to determine simply by the medical history of the family, since it is hereditary. But it is much more difficult to understand which genes are responsible for it. Actually, the obesity genes began to be actively "caught" in the last twenty years, when the methods of molecular biology finally made it possible to accurately read large amounts of DNA and compare huge arrays of genetic data.

One of these "obesity genes" is described in Nature Medicine by the staff of Bristol and Cambridge Universities (Wade et al., Loss-of-function mutations in the melanocortin 4 receptor in a UK birth cohort). This is the MC4R gene, or melanocortin receptor 4. Strictly speaking, its role in the development of obesity was first noticed earlier, and this study has specified the mechanisms of its association with obesity. 

Scientists analyzed the DNA of about 6 thousand people born in the early 90s in Bristol; genetic information was compared with their medical history. As a result, it was possible to identify mutations in MC4R, due to which young people become overweight. Moreover, obesity due to a broken MC4R can be so strong that by the age of 18 a person may already have 17 extra kilograms.

Melanocortin is one of the hormones that control eating behavior; the feeling of fullness depends on it. But, as for other hormones, the cells must have receptors for melanocortin, otherwise the cells will not feel it. The MC4R receptor is synthesized in the brain, and the neurons that synthesize it are connected to brain centers that affect appetite. If the receptor does not work, it seems to the brain that we have received little food, that our nutrient reserves are too small, and we need to eat more.

According to the authors of the work, about one person out of three hundred and forty has mutations in the MC4R gene; although, of course, this frequency may be different in different populations in different countries. Genetic analysis done in early childhood can detect damaged MC4R in time. The point is not only to confirm hereditary obesity, but also to take some measures that would allow you to restrain the accumulation of excess weight.

MC4R is far from the only gene associated with obesity. Most often, the FTO (fat mass and obesity-associated protein) gene is discussed here, but in general there are more than a hundred of them. It is worth adding that hereditary obesity is not always associated with changes in the genes themselves, sometimes it's all about epigenetic mechanisms – that is, inherited settings of genetic activity.

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