Electroacupuncture at the Zusanli and Baihui acupoints ameliorates type-2 diabetes-induced reductions in proliferating cells and differentiated neuroblasts in the hippocampal dentate gyrus with increasing brain-derived neurotrophic factor levels

Abstract

In the current study, we investigated whether electroacupuncture (EA) can inhibit pathological reductions in neurogenesis. Zucker diabetic fatty (ZDF) rats at 7 weeks of age were anesthetized with zoletil, and sham-acupuncture or EA at the Zusanli (ST36) and Baihui (GV20) acupoints was administered once a day for 5 weeks. In the ZDF group that received sham-EA (ZDF-Sham group), the blood glucose level was significantly increased together with age as compared to the control littermates [Zucker lean control (ZLC) rat]. In contrast, proliferating cells and differentiated neuroblasts were significantly decreased in the ZDF-Sham group compared to the ZLC group. Although EA treatment decreased blood glucose levels, this was not statistically significant when compared to blood glucose levels changes in the ZDF-Sham group. However, proliferating cells and differentiated neuroblasts were significantly increased with EA in ZDF rats as compared to those in the ZDF-Sham group. Brain-derived neurotrophic factor (BDNF) levels were significantly decreased in hippocampal homogenates of ZDF-Sham group compared to those in the ZLC group. The EA treatment significantly increased the BDNF levels compared to those in the ZDF-Sham group, and BDNF levels in this group were similar to those in the ZLC group. These results suggest that EA at ST36 and GV20 can ameliorate the reductions in proliferating cells and differentiated neuroblasts in the dentate gyrus induced by type-2 diabetes without significantly reducing blood glucose levels with increasing BDNF levels.

Fig. 1.

Age-related changes in blood glucose levels in ZLC, ZDF-Sham and ZDF-EA rats. Blood glucose concentration levels are unchanged in the ZLC group. However, both the ZDF-Sham and ZDF-EA groups show significantly increasing blood glucose levels correlating with age. At 12 weeks of age, the blood glucose levels are low in the ZDF-EA group as compared to the ZDF-Sham group (n=9 per group; *P<0.05, significantly different from the ZLC group). There are no significant differences in blood glucose levels between ZDF-Sham and ZDF-EA groups at experimental ages. Bars indicate means ± SEM.

Fig. 2.

Immunohistochemistry for Ki67 in the dentate gyrus in ZLC (A), ZDF-Sham (B) and ZDF-EA (C) rats. In the ZLC group, Ki67-positive nuclei (arrows) are detected in the dentate gyrus. In the ZDF-Sham group, fewer Ki67-positive nuclei are observed in the dentate gyrus as compared to those in the ZLC group. In the ZDF-EA group, abundant Ki67-positive nuclei are detected in the dentate gyrus. GCL, granule cell layer; ML, molecular layer; PoL, polymorphic layer. Scale bar=100 µm. D: Quantitative analysis of Ki67-positive nuclei per section in the ZLC, ZDF-Sham and ZDF-EA rats using image analyzer (n=5 per group; *P<0.05, significantly different from the ZLC group, #P<0.05, significantly different from the ZDF-Sham group). Bars indicate means ± SEM.

Fig. 3.

Immunohistochemistry for DCX in the dentate gyrus in ZLC (A and B), ZDF-Sham (C and D) and ZDF-EA (E and F) rats. In the ZLC group, the somas of DCX-immunoreactive neuroblasts are detected in the subgranular zone of the dentate gyrus. Dendrites (arrows) are well developed and extended into the molecular layer (ML). In the ZDF-Sham group, DCX-immunoreactive neuroblasts are significantly decreased as compared to the ZLC group. In some neuroblasts (arrowheads), DCX-immunoreactive dendrites are particularly poorly developed. In the ZDF-EA group, DCX-immunoreactive neuroblasts with well-developed dendrites are abundant in the dentate gyrus. GCL, granule cell layer; PoL, polymorphic layer. Scale bar=100 µm (A, C and E) and 25 µm (B, D and F). G: Analysis of DCX-immunoreactive neuroblasts per section in the ZLC, ZDF-Sham and ZDF-EA rats (n=5 per group; *P<0.05, significantly different from the ZLC group, #P<0.05, significantly different from the ZDF-Sham group). Bars indicate means ± SEM.

Fig. 4.

BDNF levels in the hippocampi of ZLC, ZDF-Sham and ZDF-EA rats. Note that BDNF levels are significantly decreased in the ZDF-Sham group and reversed EA treatment (n=4 per group; *P<0.05, significantly different from the ZLC group, #P<0.05, significantly different from the ZDF-Sham group). Bars indicate means ± SEM.