The Effects of Glutamine Supplementation on Liver Inflammatory Response and Protein Metabolism in Muscle of Lipopolysaccharide-Challenged Broilers.

Simple Summary: Our previous study suggested that glutamine (Gln), defined as a conditionally essential amino acid, contributed to improving growth performance, alleviating inflammatory responses and intestinal permeability, as well as rescuing the destroyed intestinal mucosa induced by LPS exposure. In addition, it was demonstrated that LPS-induced immune stress led to a severe loss of muscle mass. Here, Gln was proven to function in regulating inflammatory responses, protein synthesis, and degradation during sepsis. Our results showed that Gln administration attenuated liver inflammatory reactions, elevated protein synthesis, and inhibited protein degradation of broilers subjected to LPS challenge. The aim of our present study was to investigate the effects of Gln supplementation on liver inflammatory responses as well as protein synthesis and degradation in the muscle of LPS-challenged broilers. A total of 120 one-day-old male broiler chickens (Arbor Acres Plus) were randomly arranged in a 2 × 2 factorial design with five replicates per treatment and six broilers per replicate, containing two main factors: immune challenge (injected with LPS in a dose of 0 or 500 µg/kg of body weight) and dietary treatments (supplemented with 1.22% alanine or 1% Gln). After feeding with an alanine or Gln diet for 15 days, broilers were administrated an LPS or a saline injection at 16 and 21 days. The results showed that Gln supplementation alleviated the increased mRNA expressions of interleukin-6, interleukin-1β, and tumor necrosis factor-α induced by LPS in liver. Moreover, the increased activity of aspartate aminotransferase combined with the decreased expression of glutaminase in muscle were observed following Gln addition. In addition, in comparison with the saline treatment, LPS challenge altered the signaling molecules' mRNA expressions associated with protein synthesis and degradation. However, Gln supplementation reversed the negative effects on protein synthesis and degradation in muscle of LPS-challenged broilers. Taken together, Gln supplementation had beneficial effects: alleviating inflammatory responses, promoting protein synthesis, and inhibiting protein degradation of LPS-challenged broilers. [ABSTRACT FROM AUTHOR]