Dietary Tryptophan Supplementation Ameliorates Intestinal Injury In Lipopolysaccharide-challenged Piglets

A total of 40 crossbred healthy male weaned piglets(Yorkshire x Landrance,weaned at 28 day of age)was used to investigate weather dietary Tryptophan(Trp)supplementation attenuate the intestine injury in lipopolysaccharides(LPS)challenged weaned pigs.The animals were randomly assigned into 1 of 5 groups:(1)basic diet group(CON);(2)LPS group;(3)0.2% Trp group;(4)LPS + 0.2% Trp group;(5)LPS + 0.4% Trp group.Piglets in the CON and LPS groups were fed a basic diet,and those in the 0.2% Trp and LPS+0.2% Trp group were fed a basic diet with 0.2% Trp supplementation,and those in the LPS + 0.4% Trp group were fed the basal diet with 0.4% Trp supplementation.On days 10,20,and 29 of the trial,piglets in the LPS,LPS+0.2% Trp,and LPS+0.4% Trp groups were challenged with LPS(80 μg/kg body weight),whereas those in the CON and 0.2% Trp groups received the sterile saline(80 μg/kg body weight).All piglets were observed for 30 days and then sacrificed for analysis.The results are as follows.(1)The final body weight,average daily gain,and average daily feed intake in the LPS group were decreased than that in the CON group(P < 0.05),whereas no differeces were observed compared those in the LPS+0.2%Trp and LPS+0.4%Trp groups(P > 0.05).(2)The diarrhea rate in the LPS group was increased than that in the CON,LPS+0.2%Trp,and LPS+0.4%Trp groups(P < 0.05).(3)Compared with the CON group,serum glucose concentration in the LPS group and serum MDA in the 0.2%Trp group were decreased(P < 0.05),whereas liver CAT and serum GSH-Px concentrations in the 0.2%Trp group were increased(P < 0.05).The liver CAT and T-AOC concentrations in the LPS+0.2%Trp group were increased than those in the LPS group(P < 0.05),whereas liver CAT and T-SOD concentrations in the LPS+0.4%Trp were increased than those in the LPS group(P < 0.05).(4)Lower villus height,crypt depth,V:C ratio and muscle thickness in duodenum and jejunum in the LPS group were observed(P < 0.05)relative to those in the CON group.Compared with the CON group,decrease(P ? 0.05)in the ileal villus height and crypt depth,and increase(P ? 0.05)in the V:C and muscle thickness in ileum were observed in LPS group.The crypt depth in the jejunum and ileum in the 0.2%Trp was increased with respect to that in the CON group(P < 0.05).Compared with the LPS group,the villus height and crypt depth in the duodenum,jejunum and ileum were significantly higher in LPS+0.2%Trp and LPS+0.4%Trp groups(P < 0.05).A decrease in muscle thickness in the duodenum,jejunum and ileum was observed in LPS+0.4%Trp group relative to the LPS group(P < 0.05).The microvillus in LPS-treatment piglets were shorter and more sparse than those in CON group piglets.(5)The jejunum microvilli were disordered and contorted with different lengths.Dietary Trp treatment attenuated the negative changes induced by LPS injection.The tight junctions of jejunal epithelial cells were destroyed by LPS treatment,but were reversed following the Trp treatment.(6)Compared with the CON group,the duodenal occludin and jejunal ZO-1 mRNA expression levels were decreased in the LPS group(P < 0.05),whereas jejunal and ileal Occludin mRNA expression levels were increased in the 0.2%Trp group(P < 0.05).The duodenal Occludin and jejunal ZO-1 mRNA expression levels were increased in the LPS+0.2%Trp than those in the LPS group(P < 0.05).In conclusion,LPS treatment impairs small intestine morphology,whereas dietary supplementation with Trp attenuates the intestine injury in lipopolysaccharides(LPS)challenged weaned piglets via improving intestinal morphology,and the expression of Occludin and ZO-1 mRNA in the intestine.The results provide experimental evidence for further understanding of tryptophan’s alleviation of intestinal barrier injury,and also provide a theoretical basis for promoting animal growth and intestinal health.