Physiopathological mechanism of sarcopenia
The aetiology of sarcopenia is multifactorial but still poorly understood while the sequelae of this phenomenon, i.e. loss of independence and metabolic complications, represent a major public health. The most evident metabolic explanation for muscle decline in elderly people is an imbalance between protein synthesis abd breakdown rates but other causes like neurodegenerative processes, reduction in anabolic hormone productions or sensitivity such as insulin, growth and sex hormones, dysregulation of cytokine secretions, modification in the response to inflammatory events, inadequate nutritional intakes and sedentarity lifestyle are involved. Consequently, the age-related loss of muscle mass could be counteracted by adequate metabolic interventions including nutritional intakes or exercise training. Recent observations clearly show that changes in quantitative as well as qualitative intakes of dietary protein are able to counteract some pathophysiological processes related to muscle loss progression. Other strategies including changes in daily protein pattern, the speed of protein digestion or specific amino acids supplementation may be beneficial to improve short term muscle anabolic response in elderly people. The beneficial impact of resistance or endurance training on muscle mass and function is highlighted in many studies suggesting that the potential anabolic response to exercise still remains despite a lesser metabolic response to nutrients. Thus a multimodal approach combining nutrition, exercise, hormones, specific anabolic drugs may an innovative treatment for limiting the development of sarcopenia with aging.