The Association Between Body Composition, Mitochondrial Function and Fatigability and Physical Function in Older Adults

[摘要] The 39 million Americans over the age of 65 accounted for 13% of the United States population in 2008. The absolute and relative number of older adults (age ≥65 years) is starting to rise rapidly as the baby boomers begin to turn 65. The prevalence of mobility disability in older (30%) adults is high and is a large public health concern as disability is associated with lower quality of life, higher health care costs, and mortality. There are many reasons for age-related disability, however; the role of changes to skeletal muscle remains unclear. Fatigue is also an independent risk factor for physical disability and is common among older adults. This dissertation aimed to provide novel insight into the association between skeletal muscle energetics, changes in regional body composition and physical function and fatigability in older adults. First, decreases in visceral and intermuscular adipose tissue as well as an increase in muscle density, a marker of intramyocellular fat, following a weight-loss and physical activity intervention, were shown to be related to improved physical performance. Next, mitochondrial function, measured by phosphocreatine recovery (mM ATP/s)in the quadriceps following an exercise-bout using 31P magnetic resonance spectroscopy, was examined in relation to walking performance (time to walk 400m) and perceived performance fatigability (perceived exertion following a 0.67ms treadmill-walk). Mitochondrial function was related to walking performance in higher functioning older adults and older adults who were functionally impaired but able to ambulate 400m without discomfort. Mitochondrial function was also significantly lower in those with high compared to low fatigability. This research provides novel evidence that function can be improved by targeting specific fat depots and mitochondrial function may impact overall function and fatigability. These findings could have large public health implications, as the etiology of age-related disability in regard to skeletal muscle is unclear. The prevalence of disability among older adults is quite high and is associated with increased health care costs and mortality. Clinicians, public health professionals and researchers can use this information to design interventions, treatments and future research studies focused on skeletal muscle to improve function in older adults.

[发布机构] the University of Pittsburgh