Effect of dietary leucine supplementation on skeletal muscle fiber type transformation in weaning piglets

To investigate the effects of dietary leucine supplementation on muscle fiber type transformation in weaning piglets, 54 21-day-old male DLY (Duroc × Landrace × Yorkshire) weaned piglets were randomly divided into control, 0.25% and 0.5% leucine groups. The experiment lasted for 42 d. The results showed that dietary supplementation of 0.25% leucine significantly increased the protein expressions of slow MyHC, myoglobin and Troponin I-SS and the mRNA expressions of MyHC I, MyHC IIa, Tnni1, Tnnc1, Tnnt1 and myoglobin, while decreased the protein level of fast MyHC and the mRNA level of MyHC IIb in longissimus dorsi (LD) muscle. Furthermore, 0.25% leucine significantly increased succinic dehydrogenase (SDH) activity and decreased lactate dehydrogenase (LDH) activity. In addition, our data found that 0.25% leucine significantly increased serum adiponectin (AdipoQ) concentration, and the protein levels of AdipoQ, adiponectin receptor 1 (AdipoR1), phosphorylated AMP-activated protein kinase (p-AMPK) and PPAR-γ coactivator-1α (PGC-1α) and the mRNA levels of AdipoQ, AdipoR1 and AMPKα2. Together, our findings indicate that leucine promotes porcine skeletal muscle fiber type transformation from fast-twitch to slow-twitch, and the effect may be mediated by AdipoQ-AMPK-PGC-1α signaling pathway.