Muscles love sweets
Vittorio Sartorelli and Marcella Fulco from the US National Institutes of Health have demonstrated that glucose deficiency prevents stem cells from turning into mature muscle cells. This discovery provides new data to specialists studying the effects of calorie restriction on the physiology of the body and aging processes, and may also provide new opportunities for the treatment of muscle atrophy.
It is logical to assume that the intake of nutrients into the body, such as glucose, has a significant impact on the development of cells, but the reactions of cells to changes in the amount of incoming nutrients are poorly understood.
The authors found that glucose deficiency suppresses the differentiation of skeletal myoblasts and activates the enzyme adenosine monophosphate-activated protein kinase (AMPK). This indicates the existence of a signaling mechanism in which, in conditions of glucose deficiency, AMPK activation stimulates the expression of the Nampt enzyme that provides NAD+ biosynthesis. NAD+ is known as a cofactor of the SIRT1 protein, which plays an important role in many physiological processes, including the differentiation of skeletal muscle cells, and is also involved in the regulation of life expectancy and aging processes. Scientists emphasize the fact that suppressing the activity of AMPK, Nampt or SIRT1 leads to the fact that muscle cells begin to "ignore" the lack of nutrients and continue to differentiate in unsuitable conditions.
The researchers suggest that the AMPK-Nampt-SIRT1 signaling mechanism is a kind of "checkpoint" for the cell. Its activation in conditions of nutrient deficiency temporarily keeps cells from such energy-consuming processes as differentiation. With sufficient intake of nutrients, this mechanism is inactivated, resuming the physiological development of cells.
The results of the study are important not only for specialists studying the development of muscle tissue. The identified mechanism also functions in other tissues of the adult body and participates in reactions to calorie restriction of the diet. Moreover, the authors found that glucose deficiency and taking metformin, a drug used to treat type 2 diabetes and one of the potential geroprotectors, have the same effects and lead to the activation of SIRT1. This indicates that the positive effect of reducing the caloric content of the diet on diabetic patients may be due to the activation of the signal chain "AMPK-Nampt-SIRT1". The researchers also read that AMPK and SIRT1 are potential targets for preventing muscle tissue atrophy.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily15.05.2008