PGC-1ss Down-Regulation Is Associated With Reduced ERR Activity and MCAD Expression in Skeletal Muscle of Senescence-Accelerated Mice

Abstract
Mitochondrial dysfunction is involved in the development of aging. Here, we examined the effect of aging on the skeletal muscle expression of two isoforms of the transcriptional peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1 (PGC-1) in an experimental murine model of accelerated aging, the senescence-accelerated mouse (SAM). The senescence-accelerated prone mice (SAM-P8) showed no changes in PGC-1α, but a decrease in PGC-1β expression (52% reduction, p <.001) was observed compared to the senescence-accelerated resistant mice (SAM-R1). In agreement with the proposed role of PGC-1β as an estrogen-related receptor (ERR) protein ligand, the expression of the ERRα target gene medium-chain acyl-coenzyme A dehydrogenase was strongly suppressed (85%, p <.001) in SAM-P8. The decrease in the expression of medium-chain acyl-coenzyme A dehydrogenase was consistent with the reduction in ERRα DNA-binding activity of SAM-P8. These findings indicate that the age-mediated decrease in PGC-1β expression in SAM-P8 skeletal muscle affects the expression of genes involved in mitochondrial fatty acid oxidation.