The composition of the diet changes the expression of the gene that regulates carbohydrate metabolism

German scientists from the Karlsruhe Research Center (Forschungszentrum Karlsruhe) have identified a gene in the genome of a fruit fly whose activity increases and decreases depending on the amount of proteins and carbohydrates in the insect's diet. This discovery will help to understand the mechanisms by which the insect body, and possibly the human body, copes with extreme dietary regimes, including diets with low carbohydrates and high protein, such as, for example, the Kremlin diet, which has been very popular lately. In addition, the discovery provides new data on the relationship between diet and life expectancy.

The gene, called tobi (from the English "target of brain insulin" – the target of brain insulin), encodes the enzyme alpha-glucosidase, which converts stored "animal starch" – glycogen – into glucose. The consumption of a large amount of proteins increases, and carbohydrates – suppresses the activity of this gene. Scientists have asked the question: why does the body need a similar mechanism that releases glucose under certain nutritional conditions?

One of the answers emerges when considering the processes that occur when consuming protein-rich foods. For example, if a person adheres to a low-carb protein diet, insulin is released in the body, which stimulates the absorption of glucose contained in the blood by cells. (For most people, insulin is associated with carbohydrates, but it is also released in response to the intake of amino acids into the body.) An increase in insulin levels with a low concentration of glucose in the blood leads to the development of hypoglycemia (a decrease in glucose levels below the permissible blood level). The inclusion of the mechanism of conversion of glycogen into glucose compensates for the absence of carbohydrates in food. The authors believe that it is this function that the tobi gene performs in the drosophila body.

In the animal body, one of the most important metabolic control systems is the antagonistic action of the hormones insulin and glucagon. In response to the consumption of large amounts of carbohydrates, the cells of the pancreas begin to synthesize insulin, which normalizes the level of glucose in the blood. With a decrease in blood glucose, another type of pancreatic cell secretes glucagon, which provides the breakdown of stored glycogen to glucose. The authors note that the antagonism between these two hormones is not absolute, because amino acids stimulate the secretion of both insulin and glucagon.

Previously, scientists identified insulin- and glucagon-like peptides in the body of drosophila, but the functions of these compounds were not completely clear. The new work, in which the authors analyzed changes in gene activity in flies that do not have insulin-producing cells, led to the discovery of tobi. The activity of this gene increased when drosophila were fed protein-rich yeast paste and decreased when fed sweet syrup. The tobi gene expression model is similar to the action of glucagon in the mammalian body, which suggests the existence of a similar hormone in flies that regulates the activity of tobi.

Earlier experiments also showed that fruit flies without insulin-producing cells (which are also characterized by low expression of tobi) live longer than normal individuals. The latest work confirmed these data, however, only in the case of keeping insects on a protein diet.

The results suggest that proteins may have a much more pronounced effect on carbohydrate metabolism and insulin secretion than previously thought. They also provide new evidence in favor of the fact that not only the quantity, but also the quality of calories consumed affects life expectancy. In the future, they plan to study in detail the role of the tobi gene in the processes of metabolism and life expectancy.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily 

10.04.2008