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Exercise efficiency is reduced by mitochondrial uncoupling in the elderly.
MedLine Citation:
PMID:  23085769     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Reduced exercise efficiency accompanies aging in humans. Here we evaluated the impact of changes in the contractile-coupling and mitochondrial-coupling efficiencies on the reduction in exercise efficiency in the elderly. Nine adult (mean: 38.8 yrs) and 40 elderly subjects (mean: 68.8 yrs) performed a cycle ergometer test to measure O2 uptake and leg power output up to the aerobic limit (O2max). Reduced leg power output per O2 uptake was reflected in a drop in delta efficiency (εD) from 0.27±0.01 (mean±SEM) in adults to 0.22±0.01 in the elderly group. Similar declines with age were apparent for both leg power output at O2max (Pmax) and ATP generation capacity (ATPmax) determined in vivo using 31P magnetic resonance spectroscopy. These similar declines resulted in unchanged contractile-coupling efficiency values (εC) in adult (0.50±0.05) vs. elderly (0.58±0.04) groups and agreed with independent measures of muscle contractile-coupling efficiency in human quadriceps (0.5). The mitochondrial-coupling efficiency calculated from the ratio of delta to contractile-coupling efficiencies in the adults (εD/εC = 0.58±0.08) corresponded with values for well-coupled mitochondria (0.6). However, εD/εC was significantly lower in the elderly (0.44±0.03). Conversion of ATPmax per mitochondrial volume (ATPmax/Vv[mt,f]) reported in these groups into thermodynamic units confirmed this drop in mitochondrial-coupling efficiency from 0.57±0.08 in adults to 0.41±0.03 in elderly. Thus, two independent methods revealed that reduced mitochondrial-coupling efficiency was a key part of the drop in exercise efficiency in these elderly subjects and may be an important part of the loss of exercise performance with age.
Authors:
Kevin Conley; Sharon Jubrias; M Elaine Cress; Peter Esselman
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-19
Journal Detail:
Title:  Experimental physiology     Volume:  -     ISSN:  1469-445X     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1 University of Washington;
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