THE ROLE OF SKELETAL MUSCLE MYOSTATIN IN SARCOPENIA IN OLDER ADULTS

Abstract

Myostatin is a key negative regulator of muscle mass in humans and animals, having direct and indirect influences on molecular regulators of atrophy and hypertrophy, thus may impact fitness and physical function. We have shown that myostatin is elevated in conditions of chronic disability (e.g. paretic limb of stroke). Our hypothesis is that myostatin would be elevated in older adults with sarcopenia The purpose of this study was to examine the role of skeletal muscle myostatin in sarcopenia. Thirty-eight normal-weight to obese (BMI: 33 ± 5 kg/m2, X±SEM, range 21–45 kg/m2) men (n=21) and women (n=17) aged 45–81 years underwent a VO2max test, DXA scan to determine appendicular lean tissue (ALM), and vastus lateralis muscle biopsy. Quantitative real time PCR (Q-RT-PCR) was performed using Taqman probes with 36B4 as a reference to determine myostatin mRNA expression. Rates of sarcopenia were determined using (ALM/BMI) and sarcopenia was defined as < 0.789 in men and < 0.512 in women. Subjects had low fitness (VO2max: 24 ± 1 ml/kg/min) and on average 41 ± 1% body fat. The prevalence of sarcopenia in this cohort was 16%. Myostatin mRNA expression tended to be lower (29%) in those without sarcopenia than those with sarcopenia (68 ± 6 vs. 96 ± 18 AU, P=0.09). Myostatin expression was not related to age or VO2max. While myostatin may be important in muscle atrophy and sarcopenia, further work could address it’s implication in other aging cohorts of disability and chronic disease.