Yarnall, Alison J., Granic, Antoneta, Waite, Samantha, Hollingsworth, Kieren G., Warren, Charlotte, Vincent, Amy E., Turnbull, Doug M., Taylor, Robert W., Dodds, Richard M., and Sayer, Avan A.
There has been little work on the relationship between sarcopenia, a progressive skeletal muscle disorder, and age-related neurodegenerative diseases such as Parkinson's disease (PD). We aimed to determine: 1) the feasibility of characterizing skeletal muscle across a range of cognitive function in PD; 2) if muscle mitochondrial respiratory chain (MRC) function and content are preserved in older adults with PD. Sarcopenia was defined using handgrip strength, chair rise and bioimpedance analysis. MRC function was assessed using phosphorous magnetic resonance spectroscopy (MRS) by estimating τ 1/2 PCr (s) (phosphocreatine half-time recovery) in the calf muscles following a bout of aerobic exercise. Biopsy of the vastus lateralis muscle was performed, and MRC content assessed by fluorescent immunohistochemistry for porin and components of MRC Complexes I and IV. Nine participants (78% male; mean age 79.9; PD duration 3.3 years) were recruited. Four had cognitive impairment. Six participants had probable sarcopenia. Eight participants completed MRS and had mean (SD) τ 1/2 PCr of 37.8 (7.6) seconds, suggesting preserved mitochondrial function. Muscle biopsies were obtained in all and the procedure was well tolerated. Porin Z-score, a proxy for mitochondrial mass, was lower than expected compared to controls (0–89% of fibres with low porin). There was a small amount of Complex I (0.16–4.59%) and Complex IV (0–3.79%) deficiency. Detailed phenotyping, muscle biopsy and imaging was feasible and acceptable across a spectrum of cognitive function in PD. Sarcopenia was relatively common and may be associated with lower mitochondrial mass and low levels of MRC deficiency. • MRS estimated τ 1/2 PCr(s) in calf muscles following a bout of aerobic exercise. • Fluorescent immunohistochemistry assessed porin & components of MRC Complexes I/IV. • Muscle biopsies were obtained in all patients and the procedure was well tolerated. • This study represents the first comprehensive muscle phenotyping in PD. • Sarcopenia was relatively common across the cognitive spectrum in PD. [ABSTRACT FROM AUTHOR]