Myosteatosis: an emerging biomarker of aging

Adipose tissue infiltration into skeletal muscle (i.e., myosteatosis) has emerged as an independent contributor to metabolic disorders and declines in skeletal muscle function with age. It remains unclear whether myosteatosis is a marker of aging or simply a consequence of disease or disuse. This review summarizes evidence from population-based epidemiologic studies that utilized non-invasive imaging to measure myosteatosis and to evaluate age-related changes among community-dwelling middle aged and older adults. Myosteatosis consistently increased with age, independent of weight change, and the burden of myosteatosis was greater among women, and non-White racial and Hispanic ethnic groups after accounting for physical activity levels, chronic disease burden, and overall body size. Myosteatosis accumulation is not uniform throughout the body and is differentially associated with clinically meaningful age-related outcomes, including changes to gait, balance, muscle strength, and physical function. Hormonal, cellular, genetic, and lifestyle differences comprise the biological pathways that may lead to age-related increases in myosteatosis. Future work in diverse populations using standardized imaging methodologies could include longitudinal measures of biological markers to better understand the biological precursors that accompany the phenotypic change. In conclusion, evidence from several well-characterized epidemiologic studies is consistent with myosteatosis an independent marker of aging.