Dissecting the Molecular and Cellular Pathophysiology of Sarcopenic Obesity in the Elderly

Ageing is characterised by a change in body composition with a parallel decrease in muscle mass and an increase and central redistribution of fat. When drastically exacerbated, these two processes culminate in a condition known as sarcopenic obesity (SO). SO is characterised by the coexistence of obesity and sarcopenia (i.e. reduced muscle mass and function) and is a growing public health problem in the elderly. The health risks of obesity and sarcopenia act synergistically, maximising the risk of disability of OS. The molecular mechanisms underlying OS are largely unknown. Increased fat mass induces chronic systemic inflammation and alters the profiles of adipokines and hormones, promoting the development of sarcopenia. On the other hand, the reduction in muscle tissue (SM) typical of sarcopenia is characterised by an alteration in the metabolic properties of skeletal muscle with an increase in insulin resistance and a reduction in energy expenditure that favours the accumulation and dysfunction of adipose tissue (AT). The cellular alterations that would seem to underlie OS are: altered autophagy, cellular senescence, epigenetic and mitochondrial alterations and maladaptive activation of intra- and intercellular inflammatory circuits (e.g. cytokines, extracellular vesicles, dysfunctional circulating leukocytes). However, the interconnections between these mechanisms are still unclear. The impact of OS can be dramatic on the health and quality of life of those affected. Therefore, the identification of early biomarkers that can recognise overweight and obese individuals at risk of developing SO is of paramount importance. This would shed light on the heterogeneity of an otherwise homogeneous clinical condition, opening new horizons towards the conscious design of more personalised therapeutic strategies, allowing a more rational use of the limited resources available for the growing elderly population. The study design designed to achieve this aim is a cross-sectional observational study with an additional multicentre procedure lasting two years.