Effect Of Epigallocatechin Gallate (EGCG) On Growth Performance And Antioxidant Capacity In Heat-stressed Broilers

Heat stress induces oxidative stress,which seriously affects the growth performance and health of broilers.EGCG is an important component of tea polyphenols,it has biological effects such as antioxidant,antiinflamatory,antiapoptotic.The study were conducted to investigate whether EGCG could alleviates heat stress suffered by broiler,and to research the mechanisms from both in virto and in vivo,which provided the theoretical basis for undstand heat stress.Exp.1 Effect of epigallocatechin gallate(EGCG)on growth performance and antioxidant capacity in heat-stressed broilers.192 2-week old Arbor Acres broilers chickens were divided into 4 groups with 6 replicates per group and 8 chickens per replicate: one thermoneutral control group(28°C,TN group),which was fed the basal diet;and three cyclic high-temperature groups(35°C from 7:00 to 19:00 h;28°C from19:00 h to 7:00 h,heat stress(HS)group),which were fed the basal diet with added EGCG at doses of 0 mg/kg(HS0 group),300 mg/kg(HS300 group),and 600 mg/kg(HS600 group).The growth performance,hepatic oxidative stress indicators[superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),catalase(CAT),and malondialdehyde(MDA)],blood biochemical as well as AMPK/SIRT1 pathway-related proteins expression levels were analyzed.The results showed that compared to TN group,heat stress in HS0 group chickens significantly decreased final body weight(BW),average daily gain(ADG),and average daily feed intake(ADFI),,and reduced significantly the activities of GSH-Px at 35 d and SOD at 21,28,35 d and CAT at 28 d,serum glucose levels,serum alkaline phosphatase activity at 35 d,and the protein expression levels of p-AMPK?,Sirt1,PGC-1?,UCP3 and Nrf2,but increased significantly the CAT activity at 21 d and MDA content at 21,28,35 d,the levels of serum uric acid,cholesterol,triglyceride content,,as were the activities of creatine kinase,lactate dehydrogenase,aspartate aminotransferase,and the protein expression levels of HSF1,NOX2 in the HS0 group(P<0.05).After the heat-stressed broilers were supplemented with 300 mg/kg and 600 mg/kg EGCG,there were significant increase in final BW,ADG,ADFI at 35 d,and the activities of GSH-Px,SOD and CAT at 21,28,35 d,serum glucose content,the activities of serum alkaline phosphatase,and the protein expression levels of p-AMPK?,Sirt1,PGC-1?,UCP3,Nrf2,but significant reduce in MDA content,the activities of lactate dehydrogenase,creatine kinase,and aspartate aminotransferase(P < 0.05)as were the protein expression levels of HSF1,NOX2 in HS300 and HS600 group compared with HS0 group(P<0.05).In conclusion,EGCG increased activities of antioxidant enzymes(SOD,GSH-Px,and CAT)and regulated antioxidant-related protein expression(Nrf2,NOX,UCP3,and HSF1)via affecting AMPK/Sirt1-PGC-1? pathway,which alleviates the heat stress response and improves the overall performance of broilers.Exp.2 Effect of EGCG and heat stress on antioxidant activity of myoblasts.To investigate whether EGCG has protective effect on myoblasts treated by heat stress.Cell viability was measured by CCK-8 assay after myoblasts were treated with various concentrations of EGCG(0?10?20?30 ?50umol/L)and/or heat stress for 12 hours in vitro,and the best protective concentrations of EGCG(25?mol/L)were subsequently screened by CCK-8 assay.The cells were randomly divided into four groups:(1)Normal temperature group(TN,37?),(2)Heat stress group(HS,41?),(3)EGCG 25?mol/L protection group,(4)EGCG 25?mol / L add inhibitor group[HS25(-)],The expression of PGC-1,Nrf2,SOD1 and GPx1 mRNA was detected by RT-PCR.After heat stress for 12 hours,The myoblasts viability decreased to 74.41%,which reached the significant difference(P<0.05)compared with the normal temperature group.After adding different concentrations of EGCG,the viability of myoblasts increased,25 ?mol/L EGCG is the best protective concentration against heat stress damage.The expression of PGC-1,Nrf2,SOD1 and GPx1 mRNA in HS group and HS25 group increased significantly when compared with TN group(P < 0.05),the expression of all genes decreased significantly after adding 10?mol/L Compound C into HS25 group.EGCG can alleviate heat stress and improve cell survival by regulating the expression of antioxidant genes.These results demonstrated that heat stress reduce growth performance,liver antioxidant enzyme activity and the change of serum metabolites,finally impair tissue structure integrity of broilder.The addition of EGCG in the diet could improve the heat stress effect.EGCG had beneficial effects in broilder induced by heat stress thtoughting the expression of AMPK?Sirt1?PGC-1? and antioxidant gene in liver.