[Electroacupuncture improves inflammatory reaction and insulin sensitivity in insulin-resistant obese rats]

Abstract

Objective: To observe the effect of electroacupuncture (EA) on inflammatory reaction and insulin sensitivity in insulin-resistant obese (OIR) rats.

Methods: Thirteen male Wistar rats were randomly selected as the control group and fed with common diet. The other 39 rats were fed with high-fat diet for 8 weeks to establish OIR model and then randomized into model, EA and sham EA groups. EA (2 Hz, 1 mA) was applied to unilateral "Zusanli" (ST36), "Fenglong" (ST40), "Zhongwan" (CV12) and "Guanyuan" (CV4) for 15 min, once every other day for 8 weeks, and sham EA was applied to unilateral 4 control spots about 5 mm lateral to the aforementioned 4 acupoints after shallowly inserting acupuncture needles, but without electric current output. After 8 weeks' intervention, the body weight was recorded and the glucose infusion rate (GIR) measured using hyperinsulinemic-euglycemic clamp technique. At the 6^th week of intervention, glucose contents of intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tole-rance test (IPITT) were measured. The levels of serum insulin (INS) and inflammatory factors as C-reactive protein (CRP), IL-6 and TNF-α were measured by using ELISA at the end of the treatment. The expression levels of IL-6, TNF-α, monocyte chemoattractant protein-1(MCP-1), IL-10 and IL-1β proteins and mRNAs in the abdominal adipose tissues were detected by Western blot and quantitative real time-PCR, separately. The CD68 expression (displaying infiltration of macrophages) of adipose tissue was detected using immunohistochemistry.

Results: After modeling, the contents of glucose of IPGTT at 30, 60 and 120 min and those of IPITT at 15, 30, 60 and 120 min, serum INS, CRP, IL-6 and TNF-α, as well as the expression levels of IL-6, TNF-α, IL-1β and MCP-1 proteins and mRNAs and CD68 protein were significantly increased (P<0.01, P<0.05), while the levels of GIR and IL-10 protein and mRNA were obviously decreased in the model group in comparison with those of the control group (P<0.01), suggesting an increase of inflammation and a decline of INS sensitivity. Following the interventions, the increased contents of glucose of IPGTT and IPITT, serum INS, CRP, IL-6 and TNF-α, expression levels of IL-6, TNF-α, IL-1β and MCP-1 proteins and mRNAs and CD68 protein, and the decreased levels of GIR and IL-10 protein and mRNA were evidently reversed in the EA group compared with the model group (P<0.01, P<0.05) rather than those in the sham EA group (P>0.05).

Conclusion: EA can reduce the level of inflammation and improve insulin sensitivity in OIR rats.

Keywords: Acupuncture; Adipose tissue; Inflammatory reaction; Insulin resistance; Obesity.