[Electroacupuncture preconditioning alleviates podocyte injury via PTEN/PI3K pathway in type 2 diabetes rats]

To observe the effect of electroacupuncture (EA) preconditioning on podocytes and phosphatase and tension homologous protein (PTEN)/phosphoinositide-3-kinase (PI3K) signaling pathway in rats with type 2 diabetic kidney injury, so as to explore its potential mechanisms.

Fifty male Wistar rats were randomly divided into control, model, EA, inhibitor, and sham EA groups, with 10 rats in each group. Diabetes model was established by high-fat and high-sugar diet and intraperitoneal injection of streptozotocin (40 mg/kg). For rats in the EA group, EA (2 Hz, 1 mA) preconditioning was applied to "Guanyuan" (CV4), "Zhongwan" (CV12), and bilateral "Zusanli" (ST36), "Fenglong" (ST40) for 15 min, once every other day for 8 weeks. And rats in the sham EA group were given acupuncture at the subcutaneous areas of the same acupoints without EA stimulation. Rats of the inhibitor group were given intraperitoneal injection of BPV (HOpic, 0.6 mg/kg, 0.5 mg/mL) combined with the same EA stimulation as EA group once a week for 8 weeks. The blood glucose level of rats was recorded. Urinary albumin (ALB) content in rats was detected by ELISA. The contents of serum urea (Urea), creatinine (Crea), total cholesterol (TC) and triglyceride (TG) were detected by automatic biochemical analyzer. HE staining, PAS staining and Masson staining were used to observe the pathological changes of renal tissues. The ultrastructural changes of podocytes were observed by transmission electron microscopy. The relative expression levels of Synaptopodin, microtubule-associated protein light chain 3 Ⅱ(LC3-Ⅱ), PTEN and PI3K proteins in kidney were detected by Western blot.

Compared with the control group, the blood glucose, content of serum ALB, Urea, Crea, TC, TG and renal PI3K protein expression in the model group were significantly increased (P<0.01), while the expression levels of renal Synaptopodin, LC3-Ⅱ and PTEN proteins were decreased (P<0.01). Compared with the model group, the blood glucose, content of serum ALB, Urea, Crea, TC, TG and renal PI3K protein expression in the EA group decreased (P<0.01, P<0.05), while the expression levels of renal Synaptopodin, LC3-Ⅱ and PTEN proteins increased (P<0.01). In comparison with the EA group, the blood glucose, ALB, Urea, Crea, TC, TG content and PI3K protein expression level were increased (P<0.05, P<0.01), while the expression levels of Synaptopodin, LC3-Ⅱ and PTEN proteins were decreased (P<0.01) in the inhibitor group；whereas, the blood glucose, ALB, Urea, TC, TG content and PI3K protein expression level were increased (P<0.05, P<0.01), while the expression levels of Synaptopodin, LC3-Ⅱ and PTEN proteins were decreased (P<0.01) in the sham EA group. HE staining and PAS staining showed glomerular hypertrophy and glomerular glycogen deposition；and Masson staining displayed an enhancement of glomerular fibrosis；and electron microscope revealed foot process fusion, basement membrane thickening and autophagosomes reduction in the rat' s kidney of the model, inhibitor and sham EA groups, which were relatively milder in the EA group.

EA promotes the expression of PTEN gene-encoded protein in the kidneys of type 2 diabetic rats, thereby inhibiting the activation of PI3K, increasing the autophagy level and protecting the podocytes.