Li, Eileena

Mitochondrial function declines with age but increases with caloric restriction (CR). Mitochondria and muscle fibers were prepared from young (8–11mo) and old (22–24mo) AL‐fed and old CR mice. State 3 respiration was lower in OAL vs. YAL, but preserved in OCR (). Normalizing to protein content eliminated the age‐effect in AL mice but amplified the effect of CR, indicating that CR enhances the intrinsic mito function. ROS production in isolated fibers increased with age in AL but not CR mice (). Coupling was reduced in OAL but not OCR. These results indicate that mito capacity declines with age in situ and in vitro, apparently driven largely by decreased mitochondrial protein content. CR increases mito capacity and efficiency independently of mito protein content. YAL OAL OCR Fibers (pmol/s/m g tiss) CI 54.0±4.1 38.9±1.6 50.8±3.0 CII 44.4±3.4 36.9±1.4 45.0±2.3 CI+II 63.4±5.5 51.8±2.5 67.0±3.4 Mito (pmol/s/m g tiss) CI 38.9±1.8 21.5±2.6 30.7±2.0 CII 30.6±0.9 19.6±1.2 24.7±1.4 CI+II 59.0±1.6 34.0±1.9 46.7±2.7 Mito (pmol/s/m g prot) CI 8350±635 7071±1082 10422±863 CII 6536±414 6309±506 8408±676 CI+II 12601±762 11063±1156 15949±1381 H 2 O 2 (pM/s/mg tiss) CI 10.0±1.8 30.8±3.7 15.0±2.0 CI+II 141.4±20.9 187.2±53.8 101.1±13.6 P:O State IV to III 2.94±0.03 2.71±0.02 2.92±0.05 Means±SEM. P<0.05 OAL vs YAL, P<0.05 OCR vs OAL, P<0.05 OCR vs. OAL & YAL.