Figure 2. Mitochondrial biogenesis and COX activity are impaired in frail old.

(A) PGC-1α, CS, COX subunits- I, II, and IV, and phospho-GSK3β (Ser⁹) protein content, (B) citrate synthase and (C) mitochondrial complex IV activity (nmol.min⁻¹.mg of protein⁻¹) in the vastus lateralis of young, AO, and SO subjects (N = 10/group; ♀  =  ♂). (D) Mitochondrial complex IV activity (nmol.min⁻¹.mg of protein⁻¹) positively correlates (r = 0.77) with maximal isometric torque (N.m). Asterisk denotes significant changes vs. young, dagger denotes significant changes vs. AO, and double dagger denotes significant changes vs. both young and AO (P≤0.05).