Fig. 6: Myonectin supplementation restores denervation-induced muscle atrophy through the AMPK/PGC1α pathway.

a–c WT mice at the age of 8–10 weeks were subjected to sciatic denervation-induced muscle atrophy operation. Gelatin hydrogel impregnated with recombinant myonectin (12 µg) or vehicle was injected into the fascia of the denervated gastrocnemius muscle just before denervation. At 5 days after sciatic nerve denervation, the denervated and non-denervated gastrocnemius muscles of myonectin- or vehicle-treated WT mice were used for analysis. a Gastrocnemius muscle weight/body weight ratio of myonectin- or vehicle-treated WT mice. N = 5 in each group. b Left panels show representative cross sectional muscle fiber images of myonectin- or vehicle-treated WT mice. Scale bars show 100 μm. Right panels show quantitative analyses of mean cross sectional area (CSA) and CSA distribution of gastrocnemius muscle in myonectin- or vehicle-treated WT mice. N = 5 in each group. c Left panels show representative Western blot analyses of pAMPK, AMPK, PGC1α, PGC1α4 and tubulin. Right panels show quantitative analyses of the PGC1α, PGC1α4 and pAMPK signals normalized to tubulin signal. N = 5 in each group. d, e WT and DN-AMPK Tg mice at 8–10 weeks were subjected to sciatic denervation-induced atrophy operation. Gelatin hydrogel impregnated with recombinant myonectin (12 µg) or vehicle was injected into the fascia of the denervated gastrocnemius muscle just before denervation. At 5 days after sciatic nerve denervation, WT and DN-AMPK Tg mice were sacrificed, and denervated and non-denervated gastrocnemius muscles were used for analysis. d Left panels show representative Western blot analyses of PGC1α, PGC1α4, IGF1 and tubulin. Right panel shows quantitative analyses of the PGC1α, PGC1α4 and IGF1 signals normalized to tubulin signal. N = 6 in each group. e The ratio of gastrocnemius muscle to body weight in myonectin- or vehicle-treated WT and DN-AMPK Tg mice. N = 6 in each group. Data are presented as means ± SEM. Two-tailed unpaired Student’s t-test (c) and one-way ANOVA with a post-hoc analysis (a, b, d, e) were performed. Gastroc. gastrocnemius muscle, BW body weight, V vehicle, M myonectin, DN-AMPK Tg transgenic mice overexpressing dominant negative mutant form of AMPK by a control of skeletal muscle specific human α-skeletal actin (HSA) promoter.