Electroacupuncture improving obesity-induced insulin resistance via regulating intestinal SIRT1/TLR4 signaling pathway.

Objectives: To observe the effect of electroacupuncture (EA) in obese rats with insulin resistance (IR) through regulating intestinal silent information regulator 1 (SIRT1)/Toll-like receptor 4 (TLR4) signaling pathway, so as to explore the underlying mechanism of EA in improving obesity-induced IR.

Methods: A total of 40 Wistar rats were randomly divided into 4 groups, i.e. normal group, model group, EA group and EA combined with inhibitor group, with 10 rats in each group. The obesity-induced IR model was induced by feeding high-fat diet for 8 weeks. EA (2 Hz, 1mA) was applied at "Zhongwan"(CV12), "Guanyuan"(CV4), "Zusanli"(ST36) and "Fenglong" (ST40) for 10 min, 3 times a week for 8 weeks in both EA and EA combined with inhibitor groups. Sirtinol, an inhibitor of SIRT1 was injected into the tail vein (1 mg/kg), 3 times a week for 8 weeks in EA combined with inhibitor group. The body weight, glucose infusion rate (GIR) of rats in each group were recorded. The contents of serum C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and lipopolysaccharide (LPS) were detected by ELISA. Mucosal morphological changes in the small intestine was observed by HE staining and was graded using Chiu's score. The protein relative expression levels of SIRT1 and TLR4 and the co-labeling of SIRT1 with TLR4 in the small intestine was detected by Western blot and double immunofluorescence staining, separately.

Results: Compared with the normal group, the body weight, serum contents of CRP, TNF-α, IL-6, LPS, Chiu's score, TLR4 protein relative expression level and percentage of TLR4 positive expression area were increased (<0.01, <0.05), while the GIR, SIRT1 protein expression, percentage of SIRT1 positive expression area and SIRT1/TLR4 were decreased (<0.01) in the model group. The pathological injury of small intestine mucosa was severe, accompanied with inflammatory cell infiltration in the model group. Following interventions, the body weight, serum contents of CRP, TNF-α and LPS, Chiu's score, TLR4 protein relative expression level and percentage of TLR4 positive expression area were decreased(<0.01, <0.05), and the GIR was increased (<0.01), the pathological injury and inflammatory cell infiltration of small intestine mucosa were reduced in both EA and EA combined with inhibitor groups in contrast to the model group. Compared with the model group, the serum IL-6 content was significantly decreased (<0.01), and the SIRT1 protein relative expression level and percentage of positive expression area, SIRT1/TLR4 were increased (<0.01, <0.05) in the EA group. Compared with the EA group, EA combined with inhibitor group showed the body weight, serum CRP, IL-6, LPS, Chiu's score, TLR4 protein relative expression level and TLR4 positive expression area were increased (<0.01, <0.05), and the GIR level , SIRT1 relative expression level, SIRT1/TLR4 ratio were decreased (<0.05, <0.01).

Conclusions: EA can reduce the body weight and ameliorate peripheral insulin sensitivity in IR obese rats, which may be related with its function in regulating intestinal SIRT1/TLR4 signaling pathway to reduce inflammatory response.