Effects of Supplementation of Branched-Chain Amino Acids to Reduced-Protein Diet on Skeletal Muscle Protein Synthesis and Degradation in the Fed and Fasted States in a Piglet Model

Abstract

Supplementation of branched-chain amino acids (BCAA) has been demonstrated to promote skeletal muscle mass gain, but the mechanisms underlying this observation are still unknown. Since the regulation of muscle mass depends on a dynamic equilibrium (fasted losses–fed gains) in protein turnover, the aim of this study was to investigate the effects of BCAA supplementation on muscle protein synthesis and degradation in fed/fasted states and the related mechanisms. Fourteen 26- (Experiment 1) and 28-day-old (Experiment 2) piglets were fed reduced-protein diets without or with supplemental BCAA. After a four-week acclimation period, skeletal muscle mass and components of anabolic and catabolic signaling in muscle samples after overnight fasting were determined in Experiment 1. Pigs in Experiment 2 were implanted with carotid arterial, jugular venous, femoral arterial and venous catheters, and fed once hourly along with the intravenous infusion of NaH13CO3 for 2 h, followed by a 6-h infusion of [1-13C]leucine. Muscle leucine kinetics were measured using arteriovenous difference technique. The mass of most muscles was increased by BCAA supplementation. During feeding, BCAA supplementation increased leucine uptake, protein synthesis, protein degradation and net transamination. The greater increase in protein synthesis than in protein degradation resulted in elevated protein deposition. Protein synthesis was strongly and positively correlated with the intramuscular net production of α-ketoisocaproate (KIC) and protein degradation. Moreover, BCAA supplementation enhanced the fasted-state phosphorylation of protein translation initiation factors and inhibited the protein-degradation signaling of ubiquitin-proteasome and autophagy-lysosome systems. In conclusion, supplementation of BCAA to reduced-protein diet increases fed-state protein synthesis and inhibits fasted-state protein degradation, both of which could contribute to the elevation of skeletal muscle mass in piglets. The effect of BCAA supplementation on muscle protein synthesis is associated with the increase in protein degradation and KIC production in the fed state.

Dietary supplementation of branched-chain amino acids increases muscle net amino acid fluxes through elevating their substrate availability and intramuscular catabolism in young pigs

“…The feeding-induced stimulation of muscle protein synthesis in pigs is independently regulated by the increase of insulin and AA (54) . Our previous study has shown that the level of plasma insulin is not affected by BCAA supplementation (55) , which is consistent with results of other studies obtained by the infusion of individual BCAA or mixed EAA (4,56) . Thus, it seems that the anabolic effect of BCAA is unlikely mediated by insulin.…”

Advances in low-protein diets for swine

“…Muscle growth reflects protein accretion which is a balance between the rates of protein synthesis and degradation [ 104 ]. The mammalian target of rapamycin complex 1 (mTORC1) pathway plays a decisive role in controlling protein synthesis [ 105 ].…”

By-product Originating from Artisan Distillers of Rice Alcohol in Northern Vietnam: Production, Use and Nutrient Value for Smallholder Pig Raising

“…The result of this work indicated that sulphur amino acids levels in RDP were higher than that of ideal protein of previous studies [16,17,18]. The relative levels of the three branched chain amino acids (Leu, Ile, Val) were high, especially for Ile which could be considered as profitable for meat production and pig immunity owing to specific roles of these amino acids in that metabolisms [27]. Finally, high crude protein and amino acid levels in RDP could thus help to replace expensive protein sources as fishmeal or soybean meal for swine.…”