Obesity and diabetes: the harm is obvious, but there should be benefits
Man acquired diabetes and obesity in the late stages of evolution
Nadezhda Markina, Infox.ru
Scientists have found a mutation unique to humans that weakens insulin production and is associated with the risk of diabetes. Now the authors of the discovery are trying to understand what benefits the mutated gene has brought to a person.
As recent studies by American scientists have shown, after the age of 40, people with obesity begin to degrade the brain. The conclusion was made after the subjects aged 40 to 60 years who performed the test tasks were examined using magnetic resonance imaging. In addition to the fact that obese subjects coped worse with the task, they had reduced activity of the lower parietal lobe, frontal lobe, anterior cingulate gyrus of the cerebral cortex, as well as the hippocampus. Functional insufficiency was accompanied by a decrease in the volume of gray matter – the cerebral cortex.
Another group of researchers from the University of California at San Diego (University of California, San Diego) came to the conclusion that the predisposition to obesity and diabetes arose in human evolution as a relatively late "acquisition". Such consequences were caused by the loss of the function of the CMAH gene due to a mutation that distinguishes humans from all other mammals.
The CMAH gene is associated with the formation of sialic acid, which is part of the glycoproteins of the cell membrane. A mutant gene cannot form a sialic acid molecule of the desired type. Scientists have tested its connection with diabetes and obesity in experiments on mice. They obtained mutant mice with a "human" mutation of the CMAH gene and compared them with normal mice. Both were fed high-fat foods, which is why the animals in both groups developed insulin resistance. But only in mutant mice, insulin production by beta cells of the pancreas sharply decreased, and they gained a lot of weight. Normal animals were not affected by a fatty diet to such an extent.
"Since this mutation is unique to humans, it can be assumed that it brought some advantages to our ancestors," says Gerald Weissmann, editor-in—chief of The Journal of the Federation of American Societies of Experimental Biology. – Perhaps it was useful for protection from germs or from stress. To answer this question, it is necessary to find out all the functions of the CMAH gene. Whatever it was, it is obvious that its advantages outweighed the disadvantages and ensured the survival of our ancestors."
Another conclusion from the data obtained is that animal models are not suitable for studying the patterns of obesity and diabetes in humans.
A report on the study of a group led by Jane J. Kim (Pancreatic β-cell failure in obese mice with human-like CMP-Neu5Ac hydroxylase deficiency) is published in the FASEB journal; a popular summary of the results of the work (Missing molecule raises diabetes risk in humans) is on the PhysOrg website
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