Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 94, Issue 4, Pages 1479-1484Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.01061.2002
Keywords
aging; gene expression; mitochondrial transcription factor a; nuclear respiratory factor 1; cytochrome-c oxidase
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Funding
- NCRR NIH HHS [RR-00044] Funding Source: Medline
- NIA NIH HHS [AG-18254, AG-17891] Funding Source: Medline
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Muscle concentrations of mRNAs encoded by mitochondrial DNA (mtDNA) decline with aging. To determine whether this can be explained by diminished mtDNA levels, we measured the relative concentrations of mtDNA and a representative mtDNA transcript [encoding cytochrome-c oxidase, subunit 2 (COX-2)] in muscle of young (21-27 yr) and older subjects (65-75 yr). The amount of COX-2 mRNA (relative to 28S rRNA) was 22% lower (P = 0.04) in older muscle, and the amount of mtDNA (relative to nuclear DNA) was 38% lower (P = 0.0002). The average level of mitochondrial transcription factor A (Tfam), a protein essential for mtDNA replication, was similar in younger and older muscle. Warn mRNA, nuclear respiratory factor-1 mRNA, and several mRNAs encoding proteins required for mtDNA replication were expressed at similar levels in younger and older muscle. The mtDNA concentrations were only weakly related to age-adjusted aerobic fitness (maximal oxygen consumption) and self-reported physical activity levels. We conclude that the lower concentration of mitochondrial mRNAs in older muscle can be explained by a reduced concentration of mtDNA.
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