Human aging is characterized by skeletal muscle wasting, a debilitating condition which sets the susceptibility for diseases that directly affect the quality of life and often limit life span. Sarcopenia, i.e, the reduction of muscle mass and/or function, is the consequence of a reduction of protein synthesis and an increase in muscle protein degradation. In addition, the capacity for muscle regeneration is severely impaired in aging and this can lead to disability, particularly in patients with other concomitant diseases or organ impairment. Immobility and lack of exercise, increased levels of proinflammatory cytokines, increased production of oxygen free radicals or impaired detoxification, low anabolic hormone output, malnutrition and reduced neurological drive have been advocated as being responsible for sarcopenia. It is intriguing to notice that multiple pathways converge on skeletal muscle dysfunction, but the factors involved sometimes diverge to different pathways, thus intersecting at critical points. It is reasonable to argue that the activity of these nodes results from the net balance of regulating mechanisms, as in the case of the GH/IGF-l axis, the testosterone and cortisol functions, the pro-and anti-inflammatory cytokines and receptors. Both genetic and epigenetic mechanisms operate in regulating the final phenotype, the extent of muscle atrophy and reduction in strength and force generation. It is widely accepted that intervention on lifestyle habits represents an affordable and practical way to modify on a large scale some detrimental outcomes of aging, and particularly sarcopenia. The identification of the molecular chain able to reverse sarcopenia is a major goal of studies on human aging. Sarcopenia (i.e. loss ofmuscle mass and strength) is a highly prevalent condition in older people.Several cross-sectional and longitudinal studies have shown a relationship between sarcopenia and physical disability which, in turn, carries on the risk of more severe health outcomes, such as hospitalisation, nursing home admission and mortality. The definition of sarcopenia as a pathological entity is still a matter of debate, and its pathogenesis is also far from being completely elucidated. In recent years, several contributions have been produced on sarcopenia, and therefore, in this paper, we attempt to critically review the more recent observations in this important field of clinical research.
