Leucine‐induced promotion of post‐absorptive EAA utilization and hepatic gluconeogenesis contributes to protein synthesis in skeletal muscle of dairy calves

Abstract

The high rate of protein synthesis in skeletal muscle of dairy calves can benefit their first lactation even lifetime milk yield. Since the rate of protein synthesis is relatively low in the post‐absorptive state, the aim of this research was to determine whether leucine supplementation could increase the post‐absorptive essential amino acid (EAA) utilization and protein synthesis in the skeletal muscle. Ten male neonatal dairy calves (38 ± 3 kg) were randomly assigned to either the control (CON, no leucine supplementation, n = 5) or supplementation with 1.435 g leucine/L milk (LEU, n = 5). Results showed that leucine significantly increased the length and protein concentration in longissimus dorsi (LD) muscle, whereas it decreased creatinine concentration and glutamic‐oxalacetic transaminase (GOT) activity. Compared to the control group, leucine supplementation also reduced the glutamic‐pyruvic transaminase (GPT) activity. Supplementation of leucine improved the phosphorylation of mammalian target of rapamycin (mTOR), eukaryotic initiation factor 4E‐binding protein 1 (4EBP1) and substrates ribosomal protein S6 kinase 1 (p70S6K). Supplementation of leucine resulted in increased concentrations of glucose, methionine, threonine, histidine and EAAs and decreased concentration of arginine in serum. Liver glucose concentration was higher and pyranic acid was lower in LEU compared to CON. In conclusion, leucine supplementation can promote post‐absorptive EAA utilization and hepatic gluconeogenesis, which contributes to protein synthesis in skeletal muscle of dairy calves.

Dietary Concentrate Supplementation Alters Serum Metabolic Profiles Related to Energy and Amino Acid Metabolism in Grazing Simmental Heifers

“…Leucine mainly serves as a substrate for protein synthesis and is widely used in the estimation of protein synthesis in heifers ( 36 ). Furthermore, a recent study demonstrated that leucine could also act as a signal to increase the rate of protein synthesis in the skeletal muscle of calves ( 37 ). In this study, concentrate supplementation increased the concentrations of glutamine and leucine, indicating that supply feeding can influence protein metabolism.…”

Effects of Different Dietary Starch Sources and Digestible Lysine Levels on Carcass Traits, Serum Metabolites, Liver Lipid and Breast Muscle Protein Metabolism in Broiler Chickens

“…Li et al [ 38 ] found that leucine stimulated mTOR signal passage and affected skeletal muscle protein synthesis. Similarly, Zheng et al [ 39 ] also found that leucine could activate the mTOR signaling pathway, thereby enhancing the phosphorylation expression of its downstream signaling molecules S6K1 and Eif4E and finally promoting protein synthesis in dairy cow skeletal muscle. S6K1 mainly accelerates protein synthesis by enhancing translation initiation factors [ 40 ], while Eif4E promotes protein synthesis by stimulating the translation of a subset of mRNAs with 5`-terminal pyrimidine motifs [ 41 ].…”

Functional Amino Acids and Autophagy: Diverse Signal Transduction and Application

“…Leucine can strongly stimulate skeletal muscle anabolism and overcome the anabolism resistance of aging [ 134 ]. In addition, leucine can promote the protein synthesis of skeletal muscle and the transformation of muscle fiber types from fast muscle to slow muscle [ 136 ].…”