Effect of electroacupuncture on SIRT1/NF-κB signaling pathway in adipose tissue of obese rats

Abstract

To explore the effect of electroacupuncture (EA) on insulin sensitivity, adipose tissue inflammatory reaction and silent information regulation factor 1(SIRT1)/nuclear factor kappa B (NF-κB) signaling pathway in obese rats. A total of 100 SPF-grade Wistar male rats were collected. Thirteen rats of them were selected randomly as the normal group and fed with common forage, and the rest rats were fed with high-fat forage. Eight weeks later, 39 rats that met the obesity criteria were randomized into a model group, an EA group and a sham-EA group, 13 rats in each one. In each group, 3 rats were collected randomly and the hyperinsulinemic-euglycemic clamp was exerted to record glucose infusion rate (GIR) so as to determine insulin sensitivity. Afterwards, in the EA group, EA was applied to "Zusanli" (ST 36), "Fenglong" (ST 40), "Zhongwan" (CV 12) and "Guanyuan" (CV 4), stimulated with continuous wave, 2 Hz in frequency, 1 mA in current intensity, for 15 min. The treatment was given once every 2 days, 3 times a week, for 8 weeks totally. In the sham-EA group, the needles were inserted shallowly at the sites, 5 mm lateral to each of the acupoints stimulated in the EA group, and the electrodes were attached to the needle handles, but without electric stimulation exerted. The rest management was the same as the EA group. Before and after intervention, the body mass and the insulin sensitivity were measured. After intervention, the white adipose tissue was collected from the kidney in the rats. Western blot was adopted to detect the relative protein expressions of SIRT1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and acetylated NF-κB (Ac-NFκB). The real-time fluorescence quantitative PCR was used to detect the mRNA expressions of SIRT1, IL-6 and TNF-α. The immunofluorescence double labeling method was applied to detect the co-expression of SIRT1 and Ac-NFκB in adipose tissue. After fed with high-fat forage for 8 weeks, the body mass was significantly increased and GIR decreased in the rats of the model group as compared with the normal group (P<0.01), suggesting that the model of obese rat with insulin resistance was successfully established. After 8-week intervention, compared with the model group, the body mass was reduced and GIR increased in the rats of the EA group (P<0.01). The differences were not significant statistically in comparison between the sham-EA group and the model group (P>0.05). Compared with the normal group, in the model group, the protein and mRNA expressions of SIRT1 in adipose tissue were decreased, and the protein expression of Ac-NFκB increased, the protein and mRNA expressions of IL-6 and TNF-α increased (P<0.05, P<0.01). Compared with the model group, in the EA group, the protein and mRNA expressions of SIRT1 in adipose tissue were increased significantly, the protein expression of Ac-NFκB decreased, and the protein and mRNA expressions of IL-6 and TNF-α significantly decreased (P<0.05, P<0.01). There was no significant difference in each index between the sham-EA group and the model group (P>0.05). The results of immunofluorescence double labeling showed that SIRT1 and Ac-NFκB were co-expressed in adipose tissue. Electroacupuncture significantly reduces the body mass, inflammatory reaction conditions of adipose tissue and improves insulin sensitivity in obese rats. Regarding the potential mechanism, after the activation of SIRT1/NF-κB signaling pathway by electroacupuncture, and down-regulates the transcription of downstream inflammatory factors.