14 July 2015

Two mutations causing diabetes and obesity have been found

According to data presented in the Journal of Clinical Investigation (Lorenzo et al., Ankyrin-B metabolic syndrome combines age-dependent adiposity with pancreatic beta cell insufficiency – VM), one of the mutations – R1788W – is found in the genome of about a million Americans. The second, less dangerous mutation, known as L1622I, is present in 7% of the genomes of the African-American population.

The authors of the study studied the effect of mutations on the body during preclinical studies. It turned out that the presence of two copies of R1788W mutations in the genome of mice was accompanied by a decrease in the production of insulin by cells – the hormone responsible for reducing the concentration of glucose in the blood. Despite this, the level of glucose in the blood of animals remained within the normal range. In this regard, scientists decided to conduct a glucose tolerance test for mice.

"We thought that the main problem in mutant mice would be related to insulin-producing cells, but it turned out that it was the target cells in which the glucose concentration was significantly increased," the scientists explained. It is known that a molecular transporter, GLUT4, is required for glucose to enter cells and tissues. Normally, this compound is located inside the cell, letting in incoming glucose in the event that insulin is present in the blood. If the hormone is not released, then GLUT4 blocks the "entry" for glucose.

The authors of the study found that in mutant mice GLUT4 was located not only inside the cells of muscle and adipose tissue, but also on their surface. Thus, glucose can enter cells independently without the help of the GLUT4 transporter. According to scientists, after some time, the mutant mice developed obesity, as well as insulin resistance.

"The obesity epidemic began in the 1980s, when sugary sodas and French fries became popular. We were able to detect genetic factors that, combined with such a diet, aggravated the situation. We believe that the data obtained is just the beginning, and many more similar genes will be found," said study co–author George Barth Geller.

In the picture from the Duke University press release, on the left is a normal adipocyte, on the right – with the R1788W mutation. The nuclei of cells are highlighted in blue, the fatty inclusions are highlighted in green.

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