qRT-PCR analysis of transcript levels of metabolic genes in skeletal muscle of wild-type and TWEAK-KO mice. TA muscle from 4.5-month-old wild-type and TWEAK-KO mice were isolated and processed to measure mRNA levels of PGC-1α, PPARδ, HK II, PGAM2, PDK4, and mCPT1. Data are represented as mean ± SD. N = 4 in each group. *P <0.05. values vary significantly from wild-type mice. HK II, hexokinase-2; KO, knockout; mCPT1, mitochondrial carnitine palmitoyltransferase 1; PDK4, pyruvate dehydrogenase kinase-4; PGAM2, phosphoglycerate mutase 2; PGC-1α, PPAR coactivator 1α; PPAR, peroxisome proliferator-activated receptor; TA, tibial anterior; TWEAK, TNF-like weak inducer of apoptosis.