Glutamine Improves Oxidation Resistance Of Skeletal Muscle And Serum In Heat-stressed Broliler

High temperature environment is easy to cause oxidative damage of broiler,and then decreases economic of broiler production.How to improve the negative effects of high temperature environment has become a research hotspot in animal nutrition.In the present work,the effects of glutamine(Gln)on oxidative damage of skeletal muscle in heatstressed broilers were studied from two aspects including acute heat stress and chronic heat stress.Furthermore,Broiler skeletal muscle satellite cells(SCs)were also used to study the role of Gln in enhancing the antioxidant function of skeletal muscle cells in broilers.1.Effect of glutamine on meat quality and oxidation state of breast and thigh muscle in broilers under acute heat stress300 42-day-old broilers were randomly divided into five groups:a control group(23℃),which was fed basal diet,and four experimental groups(34 C),supplemented with 0,0.5%,1.0%,and 2.0%Gln of basal diet.The time of acute heat stress is 24 h.Results showed that acute heat stress markedly decreased(P<0.05)body weight gain,feed intake,breast and thigh muscle pH,WHC,hardness and gumminess,but markedly increased(P<0.05)breast and thigh muscle CL,L*and malondialdehyde(MDA)in broilers.Dietary 2.0%markedly increased(P<0.05)feed intake,breast and thigh muscle pH,WHC,hardness,gumminess,glutathione(GSH)and GSH-Px,but markedly decreased(P<0.05)breast and thigh muscle CL and MDA in acute heat-stressed broilers.2.Effect of glutamine on serum biochemical profile,oxidation state and antioxidant capacity in broilers under chronic heat stress300 22-day-old broilers were randomly divided into five groups:a control group(23℃),which was fed basal diet,and four experimental groups(34℃ 8 h/day),supplemented with 0,0.5%,1.0%,and 1.5%Gln of basal diet.The time of chronic heat stress is 22-42 day.Results showed that chronic heat stress markedly decreased(P<0.05)serum total peotein(TP),GSH,T-SOD,and total antioxidant capacity(T-AOC),but markedly increased(P<0.05)serum glucose and MDA in 35-and 42-day-old broiler.Dietary 1.5%markedly increased(P<0.05)serum TP,GSH,T-SOD,and T-AOC,but markedly decreased(P<0.05)erum glucose and MDA in chronic-heat-stressed broilers.3.Effect of glutamine on breast and thigh muscle Nrf2 pathway and antioxidase gene expression in broilers under chronic heat stressOn day 42,the breast and thigh muscle were used to detect Nrf2 pathway and antioxidase gene expression.Results showed that chronic heat stress markedly decreased(P<0.05)breast GSH-Px and Nrf2 mRNA expression levels.Furthermore,chronic heat stress markedly decreased(P<0.05)thigh SOD,CAT,GSH-Px and Nrf2 mRNA expression levels,but markedly increased(P<0.05)thigh Keap1 mRNA expression level.Dietary 1.5%markedly increased(P<0.05)breast GSH-Px and Nrf2 mRNA expression levels;dietary 1.5%markedly increased(P<0.05)thigh SOD、CAT、GSH-Px,and Nrf2 mRNA expression levels,but markedly decreased(P<0.05)thigh Keapl mRNA expression levels.4.Effect of glutamine on oxidation state,antioxidase gene expression and Nrf2 pathway in broiler skeletal muscle satellite cells(SCs)under heat stressThe groups of broiler SCs included:I group:37℃、3 h(the medium without glutamine);Ⅱ group:45℃、3 h(the medium without glutamine);Ⅲ 45℃ 3 h(the medium with 15 mM glutamine).After heat stress 3 h,the oxidation state,antioxidase gene expression and Nrf2 pathway were detected in broiler SCs.Results showed that heat stress markedly increased(P<0.05)SCs MDA levelr,but markedly decreased(P<0.05)SOD,GSH,T-AOC,and Nrf2 protein expression levels.Heat stress also markedly decreased(P<0.05)SOD,GSH-Px,and Nrf2 mRNA expression levels.The addition of 15 mM Gln in the medium markedly decreased(P<0.05)MDA,but markedly increased(P<0.05)SOD,GSH,T-AOC,and Nrf2 protein expression levels in heat-stressed broiler SCs.The addition of 15 mM Gln also markedly increased(P<0,05)SOD,GSH-Px,and Nrf2 mRNA expression levels in heat-stressed broiler SCs.From the above results,it can be seen that heat stress can cause oxidative damage to the body,and Gln has a protective effect on it.This study indicated that Gln might enhance the antioxidant capacity of skeletal muscle in the heat-stresssed broiler by the Nrf2 signaling pathway.