PKB signaling and atrogene expression in skeletal muscle of aged mice

First published May 5, 2011; doi:10.1152/japplphysiol.00175.2011.— The purpose of this study was to determine if PKB signaling is decreased and contractile protein degradation is increased in extensor digitorum longus (EDL) and soleus (SOL) muscles from middle-aged (MA) and aged (AG) mice. We also examined the effect of age on atrogene expression in quadriceps muscle. PKB activity, as assessed by Thr308 and Ser473 phosphorylation, was significantly higher in EDL and SOL muscles from AG than MA mice. The age-related increase in PKB activity appears to be due to an increase in expression of the kinase, as PKB- and PKB- levels were significantly higher in EDL and SOL muscles from AG than MA mice. The phosphory-lation of forkhead box 3a (FOXO3a) on Thr32, a PKB target, was significantly higher in EDL muscles from AG than MA mice. The rate of contractile protein degradation was similar in EDL and SOL muscles from AG and MA mice. Atrogin-1 and muscle-specific RIN