Evidence for inefficient contraction and abnormal mitochondrial activity in sarcopenia using magnetic resonance spectroscopy

BackgroundMitochondrial dysfunction has been implicated in sarcopenia. P-31 magnetic resonance spectroscopy (MRS) enables non-invasive measurement of adenosine triphosphate (ATP) synthesis rates to probe mitochondrial function. Here, we assessed muscle energetics in older sarcopenic and non-sarcopenic men and compared with muscle biopsy-derived markers of mitochondrial function. MethodsTwenty Chinese men with sarcopenia (SARC, age = 73.1 +/- 4.1 years) and 19 healthy aged and sex-matched controls (CON, age = 70.3 +/- 4.2 years) underwent assessment of strength, physical performance, and magnetic resonance imaging. Concentrations of phosphocreatine (PCr), ATP and inorganic phosphate (Pi) as well as muscle pH were measured at rest and during an interleaved rest-exercise protocol to probe muscle mitochondrial function. Results were compared to biopsy-derived mitochondrial complex activity and expression to understand underlying metabolic perturbations. ResultsDespite matched muscle contractile power (strength/cross-sectional area), the ATP contractile cost was higher in SARC compared with CON (low-intensity exercise: 1.06 +/- 0.59 vs. 0.57 +/- 0.22, moderate: 0.93 +/- 0.43 vs. 0.58 +/- 0.68, high: 0.70 +/- 0.57 vs. 0.43 +/- 0.51 mmol L-1 min(-1) bar(-1) cm(-2), P = 0.003,