Effects Of Dietary Glutathione Supplementation On Growth Performance,Antioxidant Capacity And Intestinal Barrier In Weaned Piglets

The purpose of this study was to investigate the effects of dietary glutathione（GSH）supplementation on growth performance,antioxidant capacity and intestinal barrier of weaned piglets.Furthermore,the protective effect of GSH on oxidative stress induced by diquat and the underlying mechanism in weaned piglets were studied.Exp.1 Effects of Dietary Supplementation of Graded Levels of Glutathione on Growth Performance,Antioxidant Capacity and Intestinal Barrier of Weaned PigletsThis study aimed to investigate the effects of different levels of GSH on growth performance,antioxidant capacity and intestinal barrier of weaned piglets.A total of 180（Duroc×Landrace×Yorkshire,weighted 7.31±0.14 kg）piglets at 26±1 days of age were randomly assigned to five dietary treatments,with six replicates of six piglets per replicate.The treatments were basal diet（control）,and basal diet supplemented with GSH at the dose of 20,35,50 and 65 mg/kg diet.The trial lasted for 35 days.（1）GSH had no significant effect on growth performance of piglets（P>0.05）.（2）The contents of serum 8-hydroxy-2’-deoxyguanosine（8-OHd G）on 15^th day and protein carbonyl（PCO）on 36^th day were linearly（P<0.05）decreased as GSH supplemented increased,while the activities of glutathione peroxidase（GPX）on 15^th day and total superoxide dismutase（T-SOD）on 36^th day,and the total antioxidant capacity（T-AOC）were linearly improved（P<0.05）with the increasing doses of GSH.Supplementation with 35,50 and 65 mg/kg GSH increased serum T-SOD activity,and 50mg/kg GSH tended to improve serum T-AOC（P=0.09）.（3）In liver,dietary supplementation of GSH linearly increased the levels of catalase（CAT）and GSH（P<0.05）,while linearly decreased the content of malondialdehyde（MDA）（P<0.05）.CAT activity in 50 mg/kg GSH groups was significantly increased（P<0.05）.While 65 mg/kg GSH increased the activity of CAT（P<0.05）,tended to improve GSH content（P=0.09）,and decreased MDA content（P=0.09）.（4）GSH had no significant effect on serum cytokines,immunoglobulin and complement protein contents of piglets（P>0.05）.（5）With increasing GSH levels,the CAT activity,GSH content and T-AOC in jejunum were linearly improve（P<0.05）,while MDA content decreased linearly（P<0.05）.Supplementation with 50 mg/kg GSH significantly increased T-AOC,tended to improve the GSH content（P=0.08）and decreased the MDA content（P=0.09）.CAT activitity tended to improve in all GSH groups（P=0.07）.（6）Occludin and Claudin-1 m RNA expression levels in jejunum increased first and then decreased with the increasing doses of dietary GSH（P<0.05）.The Occludin m RNA expression levels in 20 and 35 mg/kg GSH groups were significantly increased（P<0.05）,and Claudin-1 m RNA expression levels in 35 and 50 mg/kg GSH groups were significantly increased（P<0.05）.These results showed that dietary GSH supplementation had no significant effects on growth performance and immune function of piglets.However,GSH supplementation increased the activities of antioxidases in serum,liver and jejunum,reduced the contents of oxidative damage products,and improved the function of the intestinal barrier.Exp.2 Ameliorative Effect of Glutathione on Oxidative Stress induced by Diquat in Weaned PigletsThis study was to investigate the protective effect of GSH on oxidative stress induced by diquat challenge and the underlying mechanism in weaned piglets.A total of 24（Duroc×Landrace×Yorkshire,weighted 6.51±0.08 kg）piglets at 26±1 days of age were randomly assigned to four dietary treatments,each treatment consisted of six replicates with one piglet per replicate.The positive control group and negative control group were fed with the same basal diet,and the experimental groups were fed with basal diets supplemented with 50 or 100 mg/kg GSH.15^th day of the trial,piglets in challenged groups（negative control group,50 mg/kg GSH group and 100 mg/kg GSH group）were received an intraperitoneal injection with diquat at 10 mg/kg BW,and the positive control group received with the same volumes of sterile saline.The trial lasted for 18 days.（1）Under normal condition（frist two weeks）,GSH had no significant effect on growth performance of piglets（P>0.05）.50 and 100 mg/kg GSH significantly decreased the contents of MDA,8-OHd G,PCO and diamine oxidase（DAO）in serum（P<0.05）.Supplementation with 100 mg/kg GSH tended to improve serum GPX（P=0.09）and T-SOD（P=0.08）activities.（2）Diquat injection significantly decreased the final weight,average daily gain（ADG）and average daily feed intake（ADFI）of piglets（P<0.05）.Compared with the negative control group,ADFI in 50 and 100 mg/kg GSH groups were significantly increased（P<0.05）,ADG in 100 mg/kg GSH group was aslo significantly increased（P<0.05）.（3）Diquat challenge significantly decreased T-AOC and the activity of T-SOD in serum（P<0.05）,and GSH content,activities of GPX and T-SOD in jejunum（P<0.05）,increased MDA and 8-OHd G contents（P<0.05）in serum and jejunum.Compared with the negative control group,50 and 100 mg/kg GSH significantly increased serum GSH contents and T-SOD activities（P<0.05）,jejunum GSH contents and GPX activities（P<0.05）,decreased serum 8-OHd G contents（P<0.05）.100 mg/kg GSH significantly increased serum T-AOC（P<0.05）,and decreased the content of 8-OHd G（P<0.05）.（4）Diquat injection significantly increased the levels of serum D-lactic acid（DLA）,DAO（P<0.05）,and jejunum IL-6 m RNA expression（P<0.05）,decreased jejunum ZO-1,Occludin and Claudin-1 m RNA expression levels（P<0.05）.Compared with the negative control group,50 and 100 mg/kg GSH significantly decreased the activities of DAO（P<0.05）in serum,increased jejunum ZO-1 m RNA expression levels（P<0.05）.Claudin-1m RNA expression level in 50 mg/kg GSH group was significantly increased（P<0.05）.DLA level in 100 mg/kg GSH group was significantly decreased（P<0.05）.（5）Diquat significantly increased the levels of Nrf2,GCLC and GPX1 m RNA expression in jejunum（P<0.05）,decreased the level of Keap1 m RNA expression（P<0.05）.Compared with the negative control group,jejunum Keap1 m RNA levels in 50 and100 mg/kg GSH groups were significantly increased（P<0.05）,GCLC m RNA level in 100mg/kg GSH group was significantly decreased（P<0.05）.（6）Diquat significantly decreased the levels of PGC-1α,SIRT-1,ATPS and Cyt c m RNA expression in jejunum（P<0.05）.Compared with the negative control group,in jejunum,TFAM m RNA levels in 50 and 100 mg/kg GSH groups were significantly increased（P<0.05）,PGC-1αm RNA level in 50 mg/kg GSH group and Cyt c m RNA level in 100 mg/kg GSH group were also significantly increased（P<0.05）.These results indicated that diquat challenge significantly decreased the growth performance and antioxidant capacity,damaged the structure and function of the intestine barrier of piglet.Dietary GSH supplementation could enhance the antioxidant capacity,and protect the normal function of mitochondria,relieve oxidative stress in weaned piglets.100mg/kg GSH had better protection aganist oxidative stress in piglets.In conclusion,dietary GSH supplementation can improve the antioxidant capacity and intestinal barrier function of weaned piglets.Furthermore,GSH can effectively ameliorate the oxidative damage and the inhibition of growth performance of piglets induced by diquat challenge.