Electroacupuncture alleviates type 2 diabetes mellitus by promoting plasma-derived exosomal circular RNA of enhancer of zeste homolog 1 expression.

OBJECTIVE

To investigate the effect of electroacupuncture (EA) on regulatory functions of one specific exosomal circRNA of Enhancer of Zeste Homolog (CircEZH) and its potential mechanisms of action in type 2 diabetes (T2DM).

METHODS

Mice were fed a high-fat diet (HFD) and intraperitoneally injected with streptozotocin to create the T2DM model and then were used for two experiments involving the following groups: experiment 1 (control group, T2DM group, T2DM+EA group, 10 mice per group) and experiment 2 [control group, T2DM group, T2DM+ CircEZH1-siRNA (20 nmol/20 g) group, 10 mice per group]. Exosomal size, distribution, and morphology were evaluated via transmission electron microscopy and nanoparticle tracking analysis. The expression of CircEZH1 and CircEZH2 in exosomes was assessed by quantitative real-time polymerase chain reaction. Insulin expression was assessed by enzyme-linked immunosorbent assay, immunofluorescence, and western blotting. The effects of exosomal CircEZH1 knockout and overexpression in Min6 cells were assessed by cell counting kit-8 and flow cytometry. Meanwhile, the effect of CircEZH1 knockout on insulin sensitivity was assessed by glucose tolerance test (GTT) and insulin tolerance test (ITT) in vivo.

RESULTS

EA treatment significantly reduced the serum insulin level and cell apoptosis in pancreatic tissue in a T2DM model. EA treatment markedly upregulated CircEZH1 expression in the exosomes of T2DM mice. Further study showed that CircEZH1 overexpression resulted in increased Min6 cell viability and decreased Min6 cell apoptosis when compared with the levels in an overexpression control group. In Min6 cells with CircEZH1 knockout, the opposite trends were identified. CircEZH1-knockout Min6 cells also showed reduced insulin expression. In vivo, CircEZH1-knockout T2DM mice displayed damaged insulin sensitivity, which was demonstrated by elevated levels of fasting blood glucose and decreased glucose tolerance in the GTT and insulin sensitivity in the ITT.

CONCLUSIONS

EA can affect CircEZH1 expression specifically in the exosomes in β cells in the pancreatic islets to improve T2DM. Exosomal CircEZH1 is a potential therapeutic candidate to treat T2DM.