Respirometric Profiling of Muscle Mitochondria and Blood Cells Are Associated With Differences in Gait Speed Among Community-Dwelling Older Adults

Background. Gait speed provides an integrated measure of physical ability that is predictive of morbidity, disability, and mortality in older adults. Energy demands associated with walking suggest that mitochondrial bioenergetics may play a role in gait speed. Here, we examined the relationship between gait speed and skeletal muscle mitochondrial bioenergetics, and further evaluated whether blood-based bioenergetic profiling might have similar associations with gait speed. Methods. Participants in this study were comprised of two subsets ( n = 17 per subset) and were overweight/obese ( body mass index, 30.9 +/- 2.37), well-functioning, community-dwelling older adults ( 69.1 +/- 3.69 years) without major comorbidity. Gait speeds were calculated from a fast-paced 400 m walk test. Respiratory control ratios were measured from mitochondria isolated from leg skeletal muscle biopsies from one subset. Maximal respiration and spare respiratory capacity were measured from peripheral blood mononuclear cells from the other subset. Results. Individual differences in gait speed correlated directly with respiratory control ratio of mitochondria isolated from skeletal muscle ( r =.536, p =.027) and with both maximal respiration and spare respiratory capacity of peripheral blood mononuclear cells ( r =.585 and p =.014; r =.609 and p =.009, respectively). Conclusions. The bioenergetic profile of mitochondria isolated from skeletal muscle is associated with gait speed in older adults. Blood- based bioenergetic profiling is also associated with gait speed and may provide an alternative measure of mitochondrial function.