SARCOPENIA IN FRAIL ELDERLY OBESE PARTICIPANTS

Abstract

Purpose/Hypothesis: To quantify skeletal muscle lipid accumulation in sarcopenic skeletal muscle of obese older adults with mild to moderate physical frailty and to assess its impact on strength and function. Subjects: Eighteen physically-frail, obese elderly participants (13 women, 5 men; mean age=69 ± 4, BMI=36.7 ± 5,PPT= 29 ± 2). Materials/Methods: Intra-myocellular (IMCL) and extra-myocellular (EMCL) lipid content in the soleus (SOL) and medial gastrocnemius (MG) muscles were quantified by non-invasive magnetic resonance spectroscopy (1H MRS) using a 3T whole-body imaging system. Thigh and calf muscle and fat volumes were quantified using magnetic resonance imaging. Muscle strength (peak torque) of the lower extremities was quantified using a Biodex Isokinetic dynamometer. The nine item physical performance test (PPT) was used to provide an objective assessment of physical function. T-tests were used to compared IMCL and EMCL values between muscles. Pearson correlation coefficients were calculated to assess impact of lipid content on strength and function. Results: IMCL content was 2.9% ± 1.5 and 3.5% ± 1.8 in the MG and SOL, respectively. EMCL content was 12.4% ± 8.4 and 9.2% ± 8.1 in the MG and SOL, respectively. IMCL and EMCL contents in the predominately slow twitch SOL were not significantly different (p > .05) compared to MG. MG IMCL content correlates negatively with LE strength (r = −0.16 to −0.42) and function (r = −0.46), whereas EMCL accumulation in both LE muscles (predominately MG) was inversely associated with LE strength. EMCL accumulation in the SOL negatively impacts function (r = −0.42). Conclusions: Obese older adults with mild to moderate physical frailty have an excessive amount of IMCL present in MG and SOL. Excess lipid accumulation in predominately type II muscle fibers negatively impacts strength and function to a greater degree than excess lipid accumulation in slow twitch fibers. Clinical Relevance: Skeletal muscle lipid content is elevated in elderly obese individuals. Increased lipid accumulation in the muscle with aging may be a critical component of sarcopenia. Further studies aimed at improving our understanding of the role of therapeutic interventions for ameliorating impairments in sarcopenia will assist physical therapists in the design of optimal exercise prescriptions to improve physical function. Supported by: New Investigator Fellowship Training Initiative (NIFTI), Foundation for Physical Therapy & NIH R01 AG 025501.