Abstract
IntroductionThe loss of mitochondrial function and content have been implicated in sarcopenia although they have been little studied in the very old, the group in which sarcopenia is most common. In this pilot study, our aim was to determine if mitochondrial respiratory chain function and content are preserved among healthy 85-year-olds.MethodsWe recruited 19 participants (11 female) through their general practitioner and assessed their medical history, functional status and self-reported physical activity. We identified sarcopenia using grip strength, Timed Up-and-Go and bioimpedance analysis. We assessed mitochondrial respiratory chain function using phosphorous magnetic resonance spectroscopy, estimating τ1/2 PCr, the recovery half-time of phosphocreatine in the calf muscles following a bout of aerobic exercise. We performed a biopsy of the vastus lateralis muscle and assessed mitochondrial respiratory chain content by measuring levels of subunits of complex I and IV of the respiratory chain, expressed as Z-scores relative to that in young controls.ResultsParticipants had a median (IQR) of 2 (1,3) long-term conditions, reported regular aerobic physical activity, and one participant (5.3%) had sarcopenia. Sixteen participants completed the magnetic resonance protocol and the mean (SD) τ1/2 PCr of 35.6 (11.3) seconds was in keeping with preserved mitochondrial function. Seven participants underwent muscle biopsy and the mean fibre Z-scores were −0.7 (0.7) and −0.2 (0.4) for complexes I and IV, respectively, suggesting preserved content of mitochondrial respiratory chain enzymes.ConclusionMuscle mitochondrial respiratory chain function and content are preserved in a sample of active, well-functioning 85-year-olds, among whom sarcopenia was uncommon. The results from this study will help inform future work examining the association between muscle mitochondrial deficiency and sarcopenia.
Highlights
The loss of mitochondrial function and content have been implicated in sarcopenia they have been little studied in the very old, the group in which sarcopenia is most common
Impairments in skeletal muscle mitochondrial function and content have been implicated in the development of sarcopenia, the age-related loss of muscle mass and performance (Brierley et al, 1996; St-JeanPelletier et al, 2017; Joseph et al, 2012)
They had a median of two diseases and high levels of selfreported physical function and general health, especially among the women in the sample and when compared to normative data for the same age group (Bowling et al, 1999). They regularly engaged in aerobic physical activity with a mean rapid assessment of physical activity (RAPA) score of 4.8 (1.4)
Summary
The loss of mitochondrial function and content have been implicated in sarcopenia they have been little studied in the very old, the group in which sarcopenia is most common. In this pilot study, our aim was to determine if mitochondrial respiratory chain function and content are preserved among healthy 85year-olds. We assessed mitochondrial respiratory chain function using phosphorous magnetic resonance spectroscopy, estimating τ1/2 PCr, the recovery half-time of phosphocreatine in the calf muscles following a bout of aerobic exercise. Conclusion: Muscle mitochondrial respiratory chain function and content are preserved in a sample of active, well-functioning 85-year-olds, among whom sarcopenia was uncommon. Older patients with hip fracture are recognised to have high levels of sarcopenia and disability and multimorbidity (Di Monaco et al, 2011; Krishnan et al, 2014); in this setting, the influences of ageing per se and those of acute illness and overall frailty may be difficult to disentangle
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