Obesity Research Update: Genes Affiliated with Severe Obesity

They were all fed the same diet…but only one is overweight.

A couple of papers regarding obesity research have come out in the past week that may be of interest if you are a science nerd like me.

Researchers at Boston Children’s Hospital have identified a gene affiliated with severe obesity.  It appears that the MRAP2 gene has a role in metabolism regulation.  Mice with a mutant MRAP2 gene were fed equal quantities of food as their normal counterparts, but gained weight.  From the BCH press release:

The protein created by the Mrap2 gene appears to facilitate signaling to a receptor in the brain called Mc4r, which helps increase metabolism and decrease appetite as part of a larger signaling chain involved in energy regulation. Fat cells produce the hormone leptin, prompting receptors in the brain to instigate production of a second hormone, αMSH. Mc4r detects this hormone with the aid of Mrap2, leading to a decrease in appetite and weight. Mutations in this signaling chain, including mutations in Mc4r, are known to increase the likelihood of obesity.

Another study done by researchers in the UK illustrates that a gene involved in the development of the hypothalamus (which has a role in regulating hunger) contributes to severe obesity as well.  The SIM1 gene, when found in the heterozygous condition (SIM1 +/-) in mammals causes them to gain weight even when fed equally as mice who are homozygous for the SIM1 gene (SIM1 +/+).  It is thought that an altered signaling pathway involving the mutant SIM1 protein during hypothalamic development is what causes the weight gain in heterozygote mammals.

Both of these studies provide further proof that the process of losing weight is not as simple as “eat less, move more.”  Personally, I have always thought there were genetic components and until recently, those thoughts were not supported by evidence.  Reading studies like these validates what I’ve thought all along and demonstrates that obesity is a multi-factorial disease process whose complexity is yet to be fully understood.