ObjectiveTo investigate the effect and mechanism of Sishenwan in restoring the intestinal barrier function in the rat model of diarrhea-predominant irritable bowel syndrome （IBS-D） due to spleen-kidney Yang deficiency based on intestinal flora and short-chain fatty acids. MethodsAfter the delivery of 10 SPF-grade pregnant rats， 4 male suckling rats were kept in each litter for the experiment. The male suckling rats were randomly allocated into blank， model， low-dose （3.51 g·kg^-1） Sishenwan， high-dose （7.02 g·kg^-1） Sishenwan， and Peifeikang （0.54 g·kg^-1） groups， with 8 rats in each group. The blank group was fed conventionally， and the other groups were subjected to mother-child separation and Sennae Folium gavage （1 g·mL^-1， 10 mL·kg^-1） for the modeling of IBS-D due to spleen-kidney Yang deficiency. After the modeling was completed， the rats in Sishenwan groups were administrated with the corresponding dose of Sishenwan decoction by gavage， and the Peifeikang group with bifidobacterium triple live powder+normal saline suspension. The blank and model groups were treated with an equal volume of normal saline by gavage. The general conditions and fecal characteristics of rats were observed. After 2 weeks of administration， the rats were anesthetized for sample collection. The pathological changes of the colon tissue in rats were observed by hematoxylin-eosin staining. Enzyme-linked immunosorbent assay was employed to measure the levels of transforming growth factor-beta （TGF-β）， interleukin-10 （IL-10）， and interleukin-22 （IL-22）. Immumohistochemical staining （IHC） was performed to detect the positive expression of zonula occludens-1 （ZO-1） and occludin in the colon tissue. Western blot was employed to determine the protein levels of ZO-1 and occludin in the colon tissue of rats， and 16S rRNA gene sequencing was performed for intestinal flora. Gas chromatography-mass spectrometry was employed to determine the content of short-chain fatty acids （SCFAs） in the cecum contents of rats. ResultsThe colon tissue in the blank group presented a clear structure， neat glands， and no inflammatory cell infiltration. In the model group， the colon tissue showcased a disorganized structure， irregular arrangement of glands， and inflammatory cell infiltration. Compared with the model group， the low-dose and high-dose Sishenwan groups and the Peifeikang group exhibited an intact colon tissue structure， regular arrangement of glands， and reduced inflammatory cell infiltration. Compared with the blank group， the modeling lowered the levels of TGF-β， IL-10， and IL-22 in the serum （P<0.01）， down-regulated the protein levels of ZO-1 and occludin in the colon tissue （P<0.01）， and decreased the content of acetic acid and propionic acid and increased the content of butyric acid in cecum contents （P<0.05）. Compared with the model group， low-dose and high-dose Sishenwan raised the levels of TGF-β， IL-10， and IL-22 in the serum （P<0.05， P<0.01）， and Peifeikang elevated the levels of TGF-β and IL-10 in the serum （P<0.01）. High-dose Sishenwan and Peifeikang up-regulated the protein levels of ZO-1 and occludin （P<0.05， P<0.01）， increased the content of acetic acid and propionic acid in cecum contents （P<0.05）， and decreased the content of butyric acid （P<0.05）. The 16S rRNA gene sequencing results showed that the intestinal flora structure of the model group changed compared with that of the blank group. Compared with the model group， Sishenwan and Peifeikang increased the relative abundance of Lachnospiraceae， Muribaculaceae， Akkermansiaceae， Ligilactobacillus， UBA3282， Akkermansia， and Corynebacterium while reducing the relative abundance of Oscillospiraceae， Desulfovibrionaceae， Lactobacillus， Romboutsia， and Desulfovibrio. They can restore the intestinal flora structure similar to that in the blank group. ConclusionSishenwan can alleviate diarrhea symptoms and colonic mucosal inflammation， increase the expression of tight junction proteins in the colonic mucosa， and strengthen the intestinal barrier in IBS-D rats with the syndrome of spleen-kidney Yang deficiency. The mechanism of action may be related to optimizing the structure and balance of intestinal flora and regulating the SCFAs， and the effect of high-dose Sishenwan is obvious.

ObjectiveTo investigate the effect and mechanism of Sishenwan in restoring the intestinal barrier function in the rat model of diarrhea-predominant irritable bowel syndrome （IBS-D） due to spleen-kidney Yang deficiency based on intestinal flora and short-chain fatty acids. MethodsAfter the delivery of 10 SPF-grade pregnant rats， 4 male suckling rats were kept in each litter for the experiment. The male suckling rats were randomly allocated into blank， model， low-dose （3.51 g·kg^-1） Sishenwan， high-dose （7.02 g·kg^-1） Sishenwan， and Peifeikang （0.54 g·kg^-1） groups， with 8 rats in each group. The blank group was fed conventionally， and the other groups were subjected to mother-child separation and Sennae Folium gavage （1 g·mL^-1， 10 mL·kg^-1） for the modeling of IBS-D due to spleen-kidney Yang deficiency. After the modeling was completed， the rats in Sishenwan groups were administrated with the corresponding dose of Sishenwan decoction by gavage， and the Peifeikang group with bifidobacterium triple live powder+normal saline suspension. The blank and model groups were treated with an equal volume of normal saline by gavage. The general conditions and fecal characteristics of rats were observed. After 2 weeks of administration， the rats were anesthetized for sample collection. The pathological changes of the colon tissue in rats were observed by hematoxylin-eosin staining. Enzyme-linked immunosorbent assay was employed to measure the levels of transforming growth factor-beta （TGF-β）， interleukin-10 （IL-10）， and interleukin-22 （IL-22）. Immumohistochemical staining （IHC） was performed to detect the positive expression of zonula occludens-1 （ZO-1） and occludin in the colon tissue. Western blot was employed to determine the protein levels of ZO-1 and occludin in the colon tissue of rats， and 16S rRNA gene sequencing was performed for intestinal flora. Gas chromatography-mass spectrometry was employed to determine the content of short-chain fatty acids （SCFAs） in the cecum contents of rats. ResultsThe colon tissue in the blank group presented a clear structure， neat glands， and no inflammatory cell infiltration. In the model group， the colon tissue showcased a disorganized structure， irregular arrangement of glands， and inflammatory cell infiltration. Compared with the model group， the low-dose and high-dose Sishenwan groups and the Peifeikang group exhibited an intact colon tissue structure， regular arrangement of glands， and reduced inflammatory cell infiltration. Compared with the blank group， the modeling lowered the levels of TGF-β， IL-10， and IL-22 in the serum （P<0.01）， down-regulated the protein levels of ZO-1 and occludin in the colon tissue （P<0.01）， and decreased the content of acetic acid and propionic acid and increased the content of butyric acid in cecum contents （P<0.05）. Compared with the model group， low-dose and high-dose Sishenwan raised the levels of TGF-β， IL-10， and IL-22 in the serum （P<0.05， P<0.01）， and Peifeikang elevated the levels of TGF-β and IL-10 in the serum （P<0.01）. High-dose Sishenwan and Peifeikang up-regulated the protein levels of ZO-1 and occludin （P<0.05， P<0.01）， increased the content of acetic acid and propionic acid in cecum contents （P<0.05）， and decreased the content of butyric acid （P<0.05）. The 16S rRNA gene sequencing results showed that the intestinal flora structure of the model group changed compared with that of the blank group. Compared with the model group， Sishenwan and Peifeikang increased the relative abundance of Lachnospiraceae， Muribaculaceae， Akkermansiaceae， Ligilactobacillus， UBA3282， Akkermansia， and Corynebacterium while reducing the relative abundance of Oscillospiraceae， Desulfovibrionaceae， Lactobacillus， Romboutsia， and Desulfovibrio. They can restore the intestinal flora structure similar to that in the blank group. ConclusionSishenwan can alleviate diarrhea symptoms and colonic mucosal inflammation， increase the expression of tight junction proteins in the colonic mucosa， and strengthen the intestinal barrier in IBS-D rats with the syndrome of spleen-kidney Yang deficiency. The mechanism of action may be related to optimizing the structure and balance of intestinal flora and regulating the SCFAs， and the effect of high-dose Sishenwan is obvious.