Regulation Mechanism Of Tannic Acid Alleviating Intestinal Oxidative Damage In Weaned Piglets

During the weaning period,piglets has reduced feed intake,intestinal dysfunction,diarrhea,and decreases the growth performance,seriously affecting the production efficiency of pig industry.A large number of antibiotics have been used in pig industry to treat diarrhea and promote growth performance of weaned piglets,which leading to the production of super bacteria,environmental pollution,residues of livestock products,and threats to human health.In many countries,with the prohibition of adding antibiotics in diets,it is a focus of finding antibiotics alternative in animal nutrition research,which can promote the growth performance of livestock.Tannic acid(TA),as a plant polyphenol,has many functions of anti-bacterial,anti-inflammation,and anti-oxidation,which is considered as a potential antibiotic substitute.However,it seriously affects the application in monogastric animals that tannic acid has the poor palatability and supplementation of high dose tannic acid in diet has the negative effect of anti-nutrition.In this study,we will investigate that the effects of proper dose of microencapsulated TA in the diet on the growth performance and feed intake of weaned piglets,and clarified the effect of TA on the intestinal function in weaned piglets.Afterwards,we will explore that the effects of TA on intestinal anti-oxidation in mice induced by diquat,and at last examine that the mechanism of TA alleviating the intestinal oxidative damage induced by tertbutyl hydrogen peroxide(TBH).The main findings are described in the following section:1.A total of 45 healthy piglets(Duroc × [Landrace × Yorkshire],weaned at21d)with similar body weight,which were randomly divided to 5 groups and the experiment period was 14 days.The control group were raised on a basal diet,the antibiotics group were raised on the control group with three antibiotics(375 mg/kg Chlortetracycline 20%,500 mg/kg Enramycin 4%,1500 mg/kg Oxytetracycline calcium 20%),three doses of microencapsulated TA were fed on the control group with 500 mg/kg,1000 mg/kg 1500 mg/kg TA,with 30%effective concentration after micro-encapsulation.(1)The results showed that three doses TA groups have no adverse effects on growth performance,organ weight and the p H value of gastrointestinal content,and the method of microencapsulation have resolved the poor palatability of TA.We chose the TA2(1000 mg/kg)for the next investigation due to TA2 have the similar growth performance with the control group.(2)TA2 significantly decreased the duodenal crypt depth and the activity of maltase in ileum,enhanced the duodenal ratio of villus height to crypt depth and the jejunal m RNA expression of nutrient carrier SLC5A1,and these effects of TA2 were similar with AB group,which compared with control group.(3)Compared with control group,TA2 significantly inhibited the MDA content in serum,the m RNA and protein expression of Kelch Like ECH Associated Protein 1(Keap1),increased the activity of Glutathione peroxidase in jejunum and the protein expression of tight junction(Zonula Occludens-1,ZO-1).(4)Compared with control group,TA2 significantly modified the colonic bacteria composition,improved the relative abundance of Bacteroidetes,and decreased the relative abundance of Clostridium and Firmicutes,it is better of the effect of TA2 to colonic bacteria than AB group.2.In the first section,we found that supplementation the microencapsulated TA have reduced the intestinal oxidative stress and improved the intestinal barrier in weaning piglets,we will investigate the effect of TA on intestine oxidative injury in diquat-induced mouse model in the second section.A total of50 adult male C57BL/6J mice with similar body weight,were divided into control group,diquat group,diquat + 2.5 mg/kg TA(LTA),diquat + 5 mg/kg(MTA),diquat + 10 mg/kg(HTA).LTA,MTA and HTA groups were oral gavaged corresponding concentration every day,the control group and diquat group were treated with same volume.Except for the control group,other groups were intraperitoneally injected with 24 mg/kg diquat,the control group were intraperitoneally injected the same volume of saline.The dose of 2.5 to 10mg/kg TA have no adverse effect on body weight,this result is same as the effect of TA on the growth performance in weaning piglets.LTA group could alleviate the morphological damage in jejunum by increasing the villus height and crypt depth,but MTA and HTA groups did not alleviate the morphological damage in the jejunum.LTA,MTA and HTA groups improved the length of colon,MTA and HTA groups decreased crypt depth of the colon.LTA could activate Nrf2 pathway and promote the m RNA expression of tight junction protein(ZO-1).3.In the first and second section,we found that the proper concentration of TA could alleviate the oxidative injury in weaned piglets and diquat-induced mice model,but the mechanism is still unclear,then we will investigate the mechanism of antioxidative role of TA in IPEC-J2 cells induced oxidative injury by TBH.(1)Build the IPEC-J2 cell oxidative damage model was performed with 200 μM TBH,and the treated dose of TA in cells was 0.1 to 25 μM.The pretreated concentration of TA(0.5-25 μM)could ameliorate the reduction of cell viability induced by TBH,the pretreated concentration of TA with 2.5 μM and 5 μM were the best concentration to alleviate oxidative injury in IPEC-J2 cells.(2)5 μM TA treated group accelerated the wound healing and wound width of monolayer cells,2.5 μM and 5 μM pretreated TA groups relieved the decline of TER values in IPEC-J2 monolayer cells caused by TBH,and improved the m RNA and protein expression of intestinal tight junction.(3)2.5μM and 5 μM pretreated TA groups ameliorated the increase of reactive oxygen species(ROS)and MDA content,activated Nrf2 pathway in cells,inhibited the m RNA expression of IL-6 and TNF-α,and declined the autophagy in cells.In conclusion,supplementation the microcapsulated TA in the dietary have no negative effects,solves the palatability of TA,and alleviates the intestinal oxidative injury of weaning piglets.Its mechanism might be associated with promoted the function of intestinal barrier and intestinal antioxidant capacity,which alleviating the intestinal oxidative damage of weaned piglets.This study may provide the basal data for applying TA in the dietary of weaned piglets,and provide the new insights into replacing antibiotics in livestock.