Effects of Qiwei Baizhu San on intestinal barrier and TLR4/NF-κB signaling pathway in diabetic rats

Abstract:

[Background] Qiwei Baizhu San can be used to treat diabetes caused by deficiency of both qi and yin. Especially in recent years, it has been widely used in improving insulin resistance of diabetes mellitus. [Objective] To observe the effects of Qiwei Baizhu San on intestinal barrier and inflammatory factors in diabetic rats and to explore its mechanism. [Methods] Sixty SD male rats in specific pathogen free (SPF) grade were randomly divided into a normal control group, a model group, a metformin group, and high, medium, and low-dose Qiwei Baizhu San groups, with 10 rats in each group. The diabetic rat model was established by intraperitoneal injection of streptozotocin (STZ). Rats in the normal control group were given a normal diet, and rats in the model group, the metformin group, and the high, medium, and low-dose Qiwei Baizhu San groups were all given high-sugar and high-fat diets. After successful modeling, the metformin group and the Qiwei Baizhu San groups were treated with metformin and Qiwei Baizhu San by gavage, respectively. Normal saline was given by gavage in the normal control group and the model group. The general living status of rats before and after treatment was observed. After 4 weeks of drug intervention, fasting blood glucose (FBG), fasting insulin (FINS), and lipopolysaccharide (LPS) were detected by an automatic biochemical analyzer. Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in rat serum were measured by enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin (HE) staining was used to observe the pathological changes in colon tissues of rats in each group, and immunohistochemistry was used to observe the expression position and level of occludin protein in colon tissues. Western blotting assay was used to determine the protein expressions of zonula occludens-1 (ZO-1), occludin, toll-like receptor 4 (TLR4), and nuclear factor kappa B (NF-κ B). [Results] As compared with the normal control group, the FBG of rats after modeling in each group was ≥11.1 mmol/L (P <0.01). As compared with the model group, the FBG of rats in the low and medium-dose Qiwei Baizhu San groups decreased, but the difference was statistically insignificant (P >0.05). The FBG of rats in the high-dose Qiwei Baizhu San group and the metformin group decreased as compared with the model group (P <0.05). As compared with the model group, the levels of FINS, LPS, IL-6, and TNF-α in the metformin group and high, medium, and low-dose Qiwei Baizhu San groups decreased (P <0.01). As compared with the blank group, the intestinal cells in the model group were disorderly arranged, the intestinal villi were incompletely broken and sparsely spaced, the goblet cells were significantly reduced and unevenly distributed, accompanied by neutrophil exudation, and the average optical density of occludin protein was reduced (P <0.01). As compared with the model group, the intestinal villi of the rats in the high-dose Qiwei Baizhu San group and the metformin group were more arranged neatly and completely, the number of colonic goblet cells was restored to varying degrees, the neutrophil exudation was reduced, and the average optical density of occludin protein was increased to varying degrees (P <0.01). The results of Western blot showed that as compared with the model group, the protein expressions of ZO-1 and occludin in the ileum tissues of rats in the high-dose Qiwei Baizhu San group and the metformin group increased (P <0.01), and the protein expressions of toll-like receptor 4 (TLR4) and nuclear factor kappa B (NF-κ B) decreased (P <0.01). [Conclusion] Qiwei Baizhu San can up-regulate the expression of tight junction protein in the intestine, promote the repair of intestinal mucosal mechanical barrier, maintain the integrity of tight junctions, reduce the level of serum LPS, inhibit the TLR4/NF-κ B pathway, and reduce the release of IL-6, TNF-α, and other inflammatory factors, thus reducing the inflammatory reaction and improving insulin resistance of the body.