PGC-1α regulates mitochondrial calcium homeostasis, SR stress and cell death to mitigate skeletal muscle aging
Age-related impairment of muscle function severely affects the health of an increasing elderly population. While causality and the underlying mechanisms remain poorly understood, exercise is an efficient intervention to blunt these aging effects. We thus investigated the role of the peroxisome proliferator-activated receptor {gamma} coactivator 1 (PGC-1), a potent regulator of mitochondrial function and exercise adaptation, in skeletal muscle during aging. We demonstrate that PGC-1 overexpression improves mitochondrial dynamics and calcium buffering in an estrogen-related receptor (ERR)-dependent manner. Moreover, we show that sarcoplasmic reticulum stress is attenuated by PGC-1. As a result, PGC-1 prevents tubular aggregate formation and fiber apoptosis in old muscle. Similarly, the pro-apoptotic effects of ceramide and thapsigargin were blunted by PGC-1 in muscle cells. Accordingly, mice with muscle-specific gain- and loss-of-function of PGC-1 exhibit a delayed and premature aging phenotype, respectively. Together, our data reveal a key protective effect of PGC-1 on muscle function and overall health span in aging.\n\nStatement of significanceThe loss of muscle function in aging results in a massive impairment in life quality, e.g. by reducing motor function, strength, endurance, the ability to perform daily tasks or social interactions. Unfortunately, the mechanistic aspects underlying age-related muscle disorders remain poorly understood and treatments improving the disease are extremely limited. We now show that PGC-1, a transcriptional coactivator, is a key regulator of mitochondrial calcium homeostasis, cellular stress and death, all of which are linked to muscle aging and dysfunction. As a result, inhibition of the age-related decline in muscle PGC-1 considerably reduces aging of muscle and constitutes a promising target to prevent and treat the deterioration of muscle function in the elderly.\n\nAbbreviationsBNIP3, BCL2/Adenovirus E1B 19kDa interacting protein 3; Cpt1b, carnitine palmitoyltransferase 1B; CSQ1, calsequestrin 1; Drp1, dynamin-related protein 1; ER stress, endoplasmic reticulum stress; ERR, estrogen-related receptor ; Fis1, fission 1; GRP75, Glucose-Regulated Protein 75; IGFBP5, insulin like growth factor binding protein 5; IP3, inositol 1,4,5-trisphosphate; IP3R1, inositol 1,4,5-trisphosphate receptor type 1; Letm1, leucine zipper and EF-hand containing transmembrane protein 1; MAMs, mitochondria-associated ER membranes; Mcad, medium-chain acyl-CoA dehydrogenase; Opa1, optic atrophy 1; OXPHOS, oxidative phosphorylation; PGC-1, peroxisome proliferator-activated receptor {gamma} coactivator 1; pH2AX, phospho-H2A Histone Family Member X; ppRB, phospho-preproretinoblastoma-associated protein; Puma, BCL2 Binding Component 3; ROS, reactive oxygen species; SR, sarcoplasmic reticulum; TA, tibialis anterior; TBP, TATA binding protein; TPG, thapsigargin; Ucp3, uncoupling protein 3; VDAC, voltage-dependent anion channel; XBP1, X-Box Binding Protein 1; Xiap, X-linked inhibitor of apoptosis protein