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Cardiorespiratory fitness and mitochondrial oxidative capacity are associated with reduced walking speed in older adults, but their impact on walking speed in older adults with diabetes has not been clearly defined. We examined differences in cardiorespiratory fitness and skeletal muscle mitochondrial oxidative capacity between older adults with and without diabetes, as well as determined their relative contribution to slower walking speed in older adults with diabetes. Participants with diabetes (n = 159) had lower cardiorespiratory fitness and mitochondrial respiration in permeabilized fiber bundles compared with those without diabetes (n = 717), following adjustments for covariates including BMI, chronic comorbid health conditions, and physical activity. Four-meter and 400-m walking speeds were slower in those with diabetes. Mitochondrial oxidative capacity alone or combined with cardiorespiratory fitness mediated ∼20–70% of the difference in walking speed between older adults with and without diabetes. Additional adjustments for BMI and comorbidities further explained the group differences in walking speed. Cardiorespiratory fitness and skeletal muscle mitochondrial oxidative capacity contribute to slower walking speeds in older adults with diabetes. Article Highlights: The contributors to slower walking speed in older adults with diabetes remain unclear. This study was conducted to answer the question of how mitochondrial oxidative capacity and cardiorespiratory fitness impact walking speed in older adults with diabetes. We found that mitochondrial oxidative capacity, cardiorespiratory fitness, and walking speed were lower in older adults with diabetes compared with those without diabetes. In addition, mitochondrial oxidative capacity and cardiorespiratory fitness contributed to slower walking speed in those with diabetes. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial energetics are an important property of aging muscle, as generation of energy is pivotal to the execution of muscle contraction. However, its association with functional outcomes, including leg power and cardiorespiratory fitness is largely understudied.Methods: In the Study of Muscle, Mobility, and Aging (SOMMA), we collected vastus lateralis biopsies from older adults (n=879,70-94 years,59.2% women). Maximal state 3 respiration (Max OXPHOS) was assessed in permeabilized fiber bundles by high-resolution respirometry. Capacity for maximal adenosine triphosphate production (ATPmax) was measured in vivo by 31P magnetic resonance spectroscopy. Leg extension power was measured with a Keiser press system, and VO2 peak was determined using a standardized cardiopulmonary exercise test. Gender-stratified multivariate linear regression models were adjusted for age, race, technician/site, adiposity, and physical activity with beta-coefficients expressed per 1 SD increment in the independent variable.Results: Max OXPHOS was associated with leg power for both women (β=0.12Watts/kg,p<0.001) and men (β=0.11Watts/kg,p<0.050). ATPmax was associated with leg power for men (β=0.09Watts/kg p<0.05) but was not significant for women (β=0.03Watts/kg,p=0.11). Max OXPHOS and ATPmax were associated with VO2 peak in women and men (Max OXPHOS, βwomen=1.03mL/kg/min, βmen=1.32 mL/kg/min; ATPmax βwomen=0.87mL/kg/min, βmen=1.50mL/kg/min;all p<0.001).Conclusions: Higher muscle mitochondrial energetics measures were associated with both better cardiorespiratory fitness and greater leg power in older adults. Muscle mitochondrial energetics explained a greater degree of variance in VO2 peak compared to leg power. [ABSTRACT FROM AUTHOR]