| Intrauterine growth retardation(IUGR)was defined as the impairment of the growth and development of the embryo and its organs during pregnancy.Liver is one of the most important organs of human body,which plays an important role in the metabolism and transformation of nutrients.Studies have shown that IUGR can damage the hepatic development,antioxidant and immune functions,and lead to the disorder of lipid metabolism in weaned piglets.Dihydroartemisinin(DHA)is an antimalarial drug produced by the reduction of artemisinin(a major active substance in Artemisia annua)by sodium borohydride.It is the main metabolite of artemisinin in vivo.In addition,it has the functions of antioxidation,reducing fat content,anticancer,antifungal and immunoregulation.Therefore,DHA was applied to IUGR weaned piglets for the first time in this study.The objective of the present study was to investigate whether dietary DHA supplementation can alleviate the negative effects of IUGR on hepatic function.It provides a new method to improve the liver damage of the offspring of IUGR and a scientific basis for the application of DHA.Trial 1 was conducted to investigate the effect of DHA on antioxidative function in the liver of IUGR-affected weaned piglets.The piglets were selected from 10 litters of newborn piglets.According to the statistics of pig farms,two IUGR-affected piglets and one normal birth weight(NBW)piglet were selected for each litter.All piglets were allowed to suckle naturally until weaning age(21 d old).At weaning,the piglets were divided into 3 experimental groups(n=10),as follows:NBW(normal birth weight group given a basal diet),IUGR(intrauterine growth retardation group given the basal diet),and IUGR-DHA(IUGR group given the basal diet+80 mg/kg DHA).There were 10 piglets in each group,half of which were male and half female.At the end of the experiment,the piglets were slaughtered after blood collection,and the liver tissues were separated.The results showed that:(1)Compared with NBW group,IUGR group significantly increased(P<0.05)serum content of malondialdehyde(MDA),and decreased(P<0.05)the serum activities of total superoxide dismutase(T-SOD),glutathione peroxidase(GSH-Px)and catalase(CAT).The activities of antioxidant capacity(T-AOC),T-SOD and GSH-Px and the content of GSH were decreased(P<0.05)in the liver of IUGR-affected weaned piglets,the content of protein carbonyl(PC),8-hydroxy-2 deoxyguanosine(8-OHdG)and oxidized glutathione(GSSG)and the GSSG/GSH ratio were increased(P<0.05).DHA supplementation significantly decreased(P<0.05)the serum content of MDA in IUGR-affected weaned piglets,and increased(P<0.05)the serum activities of T-AOC,T-SOD,GSH-Px and CAT.And increased(P<0.05)the activity of T-SOD and the content of GSH in the liver of IUGR-affected weaned piglets,and significantly decreased(P<0.05)the content of MDA,PC,8-OHdG and GSSG and the ratio of GSSG/GSH.(2)Compared with the NBW group,IUGR significantly decreased(P<0.05)the mRNA expression levels of nuclear erythroid 2-related factor 2(Nrf2),heme oxygenase 1(HO-1)and CAT in the liver of weaned piglets.And decreased(P<0.05)the protein expression of Nrf2.DHA supplementation significantly increased(P<0.05)the mRNA expression of Nrf2,HO-1,CAT and GPx1 in the liver of IUGR-affected weaned piglets.And increased(P<0.05)the protein expression of Nrf2 and HO-1.Conclusions:DHA may alleviate oxidative stress of weaned piglets caused by IUGR through Nrf2/ARE signaling pathway.Trial 2 was conducted to investigate the effect of DHA on insulin level and lipid metabolism in the liver of IUGR-affected weaned piglets.The present study design shared the same details of the experiment design as that of trial 1.The results showed that:(1)Compared with the NBW group,the serum glucose,insulin growth factor 1(IGF-1)and high-density lipoprotein cholesterol(HDL-C)in the IUGR-affected weaned piglets were significantly decreased(P<0.05),the serum insulin level,total cholesterol(TC),very-low-density lipoprotein cholesterol(VLDL-C)and non-esterified fatty acid(NEFA)and homeostasis model assessment of insulin resistance(HOMA-IR)value significantly increased(P<0.05).DHA supplementation significantly decreased(P<0.05)the serum insulin,TC,VLDL-C and NEFA levels and HOMA-IR value of IUGR-affected weaned piglets,and increased(P<0.05)the IGF-1 and HDL-C content.(2)Compared with NBW group,triglycerides(TG)and NEFA contents in the liver of IUGR-affected weaned piglets were significantly increased(P<0.05),hepatic lipase(HL)and total lipase(TL)activities were significantly decreased(P<0.05).Dietary DHA supplementation significantly reduced(P<0.05)the TG and NEFA content and fatty acid synthase(FAS)activity in the liver of IUGR-affected weaned piglets,and significantly increased(P<0.05)the activities of lipoprotein lipase(LPL),HL and TL.(3)Compared with NBW group,the mRNA expression of IGF-1,insulin receptor substrate 1(IRS1),phosphatidylinositol 3-kinase(PI3K),protein kinase B(AKT2),stearoyl-CoA desaturase(SCD),adenosine monophosphate activated protein kinase α(AMPKα)and silence information regulator 1(SIRT1)in the liver of IUGR-affected weaned piglets were significantly decreased(P<0.05),and the mRNA expression of acetyl-CoA carboxylase β(ACCβ)and sterol regulatory element-binding protein-1(SREBP-1)were significantly increased(P<0.05).DHA supplementation significantly increased(P<0.05)the mRNA expression of IRS1,AKT2,AMPKα,CPT-1 and SIRT1 in the liver of IUGR-affected weaned piglets.The mRNA expression of ACCβ,FAS and SREBP-1 were significantly decreased(P<0.05).Conclusions:Dietary supplementation of 80 mg/kg DHA can effectively alleviate insulin resistance,and DHA can alleviate IUGR induced lipid metabolism and liver lipid accumulation through the activation of AMPK/SIRT1 signaling pathway.Trial 3 was conducted to investigate the effect of DHA on the development of liver and immune function in IUGR-affected piglets.The present study shared the same details of the experiment design as that of trial 1.The results showed that:(1)Compared with the NBW group,IUGR significantly reduced(P<0.05)the liver weight of weaned piglets and increased(P<0.05)the liver index,activities of aspartate aminotransferase(AST)and alanine aminotransferase(ALT)and the AST/ALT ratio in serum.Dietary supplementation with DHA significantly increased(P<0.05)the liver weight and reduced(P<0.05)the serum activities of AST and ALT and the AST/ALT ratio.(2)In NBW group,the morphology and structure of liver tissue were normal.The ultrastructure of hepatocytes in NBW group was normal.Compared with NBW group,the hepatocytes in IUGR group were disorganized,and the intercellular space was loose.The hepatocytes in IUGR group showed degeneration.Mitochondrion and endoplasmic reticulum were obviously swollen,nuclei were seriously deformed,and gaps appeared around nuclei and cytoplasm.Dietary supplementation with DHA effectively improve lesions and ultrastructural abnormalities in the liver of IUGR-affected piglets.3)Compared with NBW group,the contents of tumor necrosis factor alpha(TNF-α)and interleukin 1beta(IL-1β)in the liver of IUGR-affected weaned piglets were significantly higher(P<0.05).Dietary supplementation with DHA significantly reduced the levels of TNF-α,IL-1β,and interleukin 6(IL-6)in the liver of IUGR-affected weaned piglets(P<0.05).(4)Compared with the NBW group,the IUGR significantly increased(P<0.05)the mRNA expression of interferon gamma(IFN-γ),TNF-α,IL-1β and IL-6 mRNA in the liver.Dietary supplementation with DHA significantly reduced(P<0.05)the mRNA expression of IFN-y,TNF-α,IL-1β and IL-6 in the liver of IUGR-affected weaned piglets.Conclusions:Dietary supplementation with 80 mg/kg DHA can significantly reduce the serum transaminase activity of IUGR-affected weaned piglets and the content of TNF-α,IL-1β and IL-6 in the liver.Moreover,the damage of hepatic tissue morphology and structure induced by IUGR were repaired.In summary:IUGR not only caused the damage of the hepatic development and insulin resistance,increased the serum transaminase activity in weaned piglets,but also impaired the antioxidant function and immune function in the liver of weaned piglets,resulting in the disorder of lipid metabolism and hepatic lipid accumulation.Dietary supplementation with 80 mg/kg DHA could improve the serum antioxidant capacity in IUGR-affected weaned piglets,and repair the oxidative stress in the liver of IUGR-affected weaned piglets through Nrf2/ARE signaling pathway.Dietary supplementation with 80 mg/kg DHA could effectively alleviate the insulin resistance caused by IUGR,and repair the abnormal lipid metabolism and hepatic lipid accumulation caused by IUGR through the AMPK/SIRT1 signaling pathway.Dietary supplementation with 80 mg/kg DHA could significantly reduce the serum transaminase activity and the levels of TNF-α,IL-1β and IL-6 in the liver of IUGR-affected weaned piglets.And alleviate the damage of hepatic tissue structure caused by IUGR and improved the immune function in the liver of IUGR-affected weaned piglets. |
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