Dietary L-arginine supplementation influences the muscle fiber characteristics and meat quality of Mongolian sheep through the NO/AMPK/PGC-1α pathway

Abstract

L-arginine serves as a substrate for the production of nitric oxide (NO) in animals, and it can also impact muscle fiber characteristics and meat quality in these animals. The present study was designed to explore the effects of adding 1% L-arginine to a basal diet regimen on the muscle fiber characteristics and meat quality of Mongolian sheep. Dietary L-arginine supplementation reduced shear force in the longissimus thoracis (LT) and increased a* in biceps femoris (BF) muscles (p < 0.05). L-arginine supplementation also increased the proportion of type IIA muscle fiber in the LT (p < 0.05) and type I muscle fiber in the BF (p < 0.05) while reducing both the diameter and CSA of type IIB muscle fiber in both the LT and BF (CSA in LT, p < 0.01; all others, p < 0.05). L-arginine treatment was also associated with the upregulation of MyHC IIa (LT), MyHC I (BF), nNOS (LT & BF), AMPKα1 (BF), PGC-1α (LT & BF) (PGC-1α in BF, p < 0.01; all others, p < 0.05), together with an increase in nNOS content (LT, p < 0.01; BF, p < 0.05). Dietary L-arginine supplementation was associated with a significant increase in the post-slaughter tenderness of lamb meat, which is related to transitions in muscle fiber types. The gene expression and nNOS analysis results generated herein further indicate that this effect is mediated by the NO/AMPK/PGC-1α pathway. Further studies are thus warranted to provide further insight into the role that NO signaling plays in controlling the associations between L-arginine, muscle fiber characteristics, and meat quality.