Effect of TWEAK on expression of PGC-1α and mitochondria oxidative metabolism genes in cultured primary myotubes. Primary myotubes prepared from wild-type mice were treated with soluble TWEAK protein (10 ng/ml or 100 ng/ml) for 72 hours followed by RNA isolation and performing qRT-PCR to study transcript levels of PGC-1α, Tfam, Tfam2m, Cyt-c, Cox I, Cox IV, Cox 7b, and MCAD. Data are presented as mean ± SD. *P <0.05; values vary significantly from untreated myotubes. Cox, cytochroms c oxidase; Cyt c, cytochrome c; MCAD, medium-chain acyl-coenzyme A dehydrogenase; PGC-1α, PPAR coactivator 1α; PPAR, peroxisome proliferator-activated receptor; Tfam, transcription factor A mitochondrial; TWEAK, TNF-like weak inducer of apoptosis.