Objective

2

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

2

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

2

After the intervention

compared with the blank group

the model group showed significantly increased FBG

FINS

and HOMA-IR (

P

<

0.01)

while serum GLP-1 level was significantly decreased (

P

<

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 (

P

<

0.01

P

<

0.05)

and the protein expression of GLP-1R

PKA

GLP-1

ZO-1

and Occludin was also significantly decreased (

P

<

0.05

P

<

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 (

P

<

0.01)

along with higher serum GLP-1 level (

P

<

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 (

P

<

0.01

P

<

0.05)

and the protein expression of GLP-1R

PKA

GLP-1

ZO-1

and Occludin was also significantly elevated (

P

<

0.05

P

<

0.01).

Conclusion

2

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.