Fig. 1.

Aging promotes loss of both peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α) and Pgc-1β in skeletal muscle. Relative mRNA expression of Pgc-1α (A) or Pgc-1β (B) in tissues from young wild-type (WT) or muscle-specific Pgc-1α knockout (MKO) mice (6 mo; n = 8). Expression is normalized to levels in tissues of age-matched WT mice. C: expression of Pgc-1 coactivators in young (6 mo; n = 8) vs. aged quadriceps muscle (24 mo; n = 5) in WT and MKO mice expressed relative to mRNA levels in young WT mice. Data are means ± SE (*P < 0.05 WT vs. MKO of similar age; #P < 0.05 young vs. old mice of similar genotype).