Effect of Grape Seed Proanthocyanidins on Colon Epithelial Barrier of Sheep Fed a High-Concentrate Diet and Its Mechanism
[Objective]This study was conducted to investigate the effects of grape seed proanthocyanidins(GSPs)on colon epithelial barrier of sheep fed a high-concentrate diet and the mechanism of alleviating colon epithelial injury through Nrf2/ARE pathway.[Method]A total of forty-eight 4-month-old 1/2 Dorper × 1/2 thin-tailed Han crossed ram lambs with similar body weight(22.75 kg±1.20 kg)were randomly assigned into four experimental treatment groups,with 12 lambs in each group.Lambs in each group were supplemented with the basal diets of 0(CON group),10(10GSPs group),20(20GSPs group)and 40 mg/kg BW GSPs(40GSPs group),respectively.The feeding experiment lasted for 60 days,including 15 days adaptation period and 45 days experimental period.On the morning after the trial period ended,6 sheep in each group were slaughtered and colon tissues were collected for morphological and inflammatory cell infiltration analysis.The levels of interleukin-2(IL-2),IL-4,prostaglandin E2(PGE2)and other inflammatory factors,and the expression levels of nuclear factor-like-2 factor(Nrf2),heme oxygenase-1(HO-1),glutathione peroxidase 4(GPx4)and other related genes and proteins were detected in colon tissues.[Result](DIn CON group,colon mucosal epithelial cells were seriously missing,lamina propria was exposed,intestinal gland arrangement was loose,spaces were widened,tight junction protein was missing and damaged.Whereas,the colonic morphological structure and tight junction protein distribution was normal in 20GSPs and 40GSPs groups.②The enzyme activities of myeloperoxidase(MPO)and inducible nitric oxide synthase(iNOS),and the concentrations of nitric oxide(NO),IL-2 in colon tissues were linearly decreased with the increase of GSPs supplementation(P＜0.05).③Compared with CON group,the gene and protein expression of Nrf2 and HO-1 in colon tissues in 20GSPs and 40GSPs groups were significantly increased(P＜0.05),and the expression of GPx4 gene in colon tissues in 40GSPs group was significantly increased(P＜0.05).④Compared with CON group,the gene and protein expression of Toll-like receptor 4(TLR4)in colon tissues of lambs in 20GSPs and 40GSPs groups were significantly decreased,and the gene and nuclear protein expression of nuclear factor kappa B(NF-κB)p65 in colon tissues of lambs in 40GSPs group were significantly decreased(P＜0.05).The gene and protein expression of tumor necrosis factor α(TNF-α)and protein expression levels of IL-1 β in colon tissues of lambs in 20GSPs and 40GSPs groups were also significantly lower than those in CON group(P＜0.05).[Conclusion]GSPs could reduce local inflammation of colon tissue and alleviate colon epithelial tissue damage by activating Nrf2 pathway and inhibiting the activation of NF-κB inflammatory signaling pathway in sheep fed high-concentrate diet.
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