Regulation of skeletal muscle protein synthetic and degradative signaling by alanyl-glutamine in piglets challenged with Escherichia coli lipopolysaccharide.

Bolin Zhang, Changning Yu, Meng Lin, Ya'nan Fu, Lin Zhang, Meijuan Meng, Shen Xing, Jiaolong Li, Hui Sun, Feng Gao, Guanghong Zhou

Nutrition (Burbank, Los Angeles County, Calif.) 2015 May

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The aim of this study was to investigate the effects of alanyl-glutamine (Ala-Gln) on skeletal muscle protein synthetic and degradative signaling in piglets challenged with Escherichia coli lipopolysaccharide (LPS). Piglets were arranged in a 2 × 2 factorial design and the main effects were LPS challenge (0 or 100 units) and diets (0.62% Ala or 0.5% Ala-Gln). After treatment with either Ala or Ala-Gln for 10 d, piglets were injected twice with either saline or LPS on days 11 and 15. During days 11 to 15 (postchallenge), LPS challenge affected the growth performance of piglets. Ala-Gln supplementation tended to alleviate the reduction of the average daily weight gain (P = 0.071) and the average daily feed intake (P = 0.087) of the LPS-challenged piglets. LPS challenge increased the concentrations of cytokines in plasma (P < 0.05), however, Ala-Gln supplementation prevented the elevation of cortisol induced by LPS challenge (P < 0.05). Moreover, Ala-Gln supplementation increased the mRNA expressions of insulin-like growth factor-1 signaling and Akt (P < 0.05). Ala-Gln supplementation also increased the phosphorylation abundance of the mammalian target of rapamycin, eIF-4 E binding protein 1 and ribosomal protein S6 kinase 1 (P < 0.05). Additionally, Ala-Gln supplementation down-regulated the mRNA abundances of toll-like receptor 4 (TLR4), muscle atrophy F-box, and muscle RING finger 1, which are associated with protein degradation induced by LPS challenge. Ala-Gln supplementation had beneficial effects in improving protein synthesis signaling of skeletal muscle, and reversed the deleterious changes of signaling molecules in muscle atrophy mainly through down-regulation of Akt/FOXO and TLR4 signaling pathways induced by LPS challenge. Copyright © 2015 Elsevier Inc. All rights reserved.

Citation

Bolin Zhang, Changning Yu, Meng Lin, Ya'nan Fu, Lin Zhang, Meijuan Meng, Shen Xing, Jiaolong Li, Hui Sun, Feng Gao, Guanghong Zhou. Regulation of skeletal muscle protein synthetic and degradative signaling by alanyl-glutamine in piglets challenged with Escherichia coli lipopolysaccharide. Nutrition (Burbank, Los Angeles County, Calif.). 2015 May;31(5):749-56