OBJECTIVE: To observe the effect of electroacupuncture (EA) on the glucagon-like peptide-1 receptor (GLP-1R)/protein kinase A (PKA) signaling pathway in the colon tissue of type 2 diabetes mellitus (T2DM) rats and explore the mechanisms underlying EA's improvement of insulin resistance and intestinal mucosal barrier injury.
METHODS: Among 24 SPF-grade male Wistar rats, 6 rats were randomly assigned to a blank group, and the remaining 18 rats were used to establish the T2DM model through a combination of high-sucrose/high-fat diet feeding and intraperitoneal injection of streptozotocin. Successfully modeled rats were randomly assigned to a model group, an EA group, and an EA+inhibitor group, with 6 rats per group. The EA group received EA at bilateral "Tianshu" (ST25), "Shangjuxu" (ST37), "Pishu" (BL20), and "Weiwanxiashu" (EX-B3); EA was applied to ipsilateral "Shangjuxu" (ST37) and "Weiwanxiashu" (EX-B3) using disperse-dense wave (2 Hz/50 Hz, 1-3 mA) for 20 min per session. The EA+inhibitor group received the same EA treatment combined with intraperitoneal injection of the GLP-1 receptor inhibitor Exenatide. All treatments were administered once daily, six times per week, for 6 weeks. Fasting blood glucose (FBG) was measured before modeling and before/after intervention. After the intervention, serum fasting insulin (FINS) and GLP-1 levels were measured by ELISA, and the homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Colon morphology was observed using HE staining. Positive expression of zonula occludens-1 (ZO-1) and Occludin in colon tissue was detected by immunohistochemistry. Protein expression of GLP-1R, PKA, GLP-1, ZO-1, and Occludin in colon tissue was analyzed by Western blot.
RESULTS: After the intervention, compared with the blank group, the model group showed significantly increased FBG, FINS, and HOMA-IR (<0.01), while serum GLP-1 level was significantly decreased (<0.01); histologically, the colonic mucosal epithelial cells exhibited shedding, crypt atrophy was observed, the number of goblet cells was markedly reduced, and inflammatory cell infiltration was evident in the lamina propria; the positive expression of ZO-1 and Occludin in colon tissue was significantly reduced (<0.01,<0.05), and the protein expression of GLP-1R, PKA, GLP-1, ZO-1, and Occludin was also significantly decreased (<0.05,<0.01). Compared with the model group and the EA+inhibitor group, the EA group showed significantly lower levels of FBG, FINS, and HOMA-IR (<0.01), along with higher serum GLP-1 level (<0.01); the inflammatory cell infiltration in the colon was reduced, the number of goblet cells was increased, and the structure of the mucosal epithelium and crypts was more normalized; the positive expression of ZO-1 and Occludin in colon tissue was significantly increased (<0.01,<0.05), and the protein expression of GLP-1R, PKA, GLP-1, ZO-1, and Occludin was also significantly elevated (<0.05,<0.01). P P P P P P P P P P P P
CONCLUSION: EA could reduce blood glucose levels, improve insulin resistance, and repair intestinal mucosal barrier injury in T2DM rats. The underlying mechanism may be related to the activation of the GLP-1R/PKA signaling pathway.
