Sarcopenia: characteristics, genesis, remedies

Abstract

The term sarcopenia is defined as the loss of mass and muscular function with age. It is characterized by a metabolic status in which the muscles present a reduced ability to produce and use energy. Thus, in humans between 20 and 80 years of age, muscle mass decreases about 40%, with negative effects on mobility, strength production, metabolic rate and respiratory function. A continuous reparative process is also present in skeletal muscle due to the presence of quiescent adult stem cells, called satellite cells, which are able to change their phenotype when appropriate conditions are present. Sarcopenia is considered an event with a multifactorial etiology: (1) mitochondrial deletion, i.e., replication errors in mitochondrial DNA that lead to an energetic deficit and fiber atrophy; (2) protein synthesis alterations, with an imbalance between protein degradation and the ability of the fibers to synthesize protein; (3) loss of repair ability of the satellite cells, caused by an alteration in the proteic growth factors (mainly IGF–1, mIGF–1, HGF) and hormones (growth hormone, testosterone and estrogens), or by an imbalance of the antioxidant system. We are still far from a complete understanding of the causes and characteristics of the sarcopenic process, and from a solution to the problem. However, a suitable lifestyle (programmed physical training) and a suitable diet (caloric restriction) seem to be the most effective therapeutic approaches in order to control at least the more alarming symptoms of sarcopenia.