[Electroacupuncture mitigates hyperlipidemia via improving cholesterol metabolism mediated by SCAP/SREBP-2 signaling in liver tissue in rats].

Objective: To explore the effect of electroacupuncture (EA) on sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP)/ SREBP-2 signaling and the expressions of its downstream cholesterol metabolism related molecules 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), proprotein convertase subtilisin/kexin type 9 (PCSK9), and low-density lipoprotein receptor (LDLR) in the liver tissue in rats with hyperlipidemia (HLP), so as to reveal its mechanisms underlying improvement of HLP.

Methods: Male SD rats were randomly divided into normal control, HLP model and EA groups (n=10/group). The HLP model was established by feeding the rats with high-fat diet for 28 d. Rats in the EA group received EA stimulation (2 Hz/100 Hz, 2 mA) at "Fenglong" (ST40) and "Yinlingquan"(SP9) for 30 min, once daily for 28 d. The contents of total cholesterol (TC), triglyceride (TG), high density lipoprotein-cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) in the serum, the activity of glutamic oxaloacetic transaminase (AST) and glutamic pyruvic transaminase (ALT) were detected by automatic biochemical analysis. The content of TC in the liver tissue was detected using high performance liquid chromatography. The mRNA and protein expression levels of SCAP, SREBP-2, HMGCR, PCSK9 and LDLR in the liver tissue were measured by using quantitative real-time PCR and Western blot, respectively. The immunofluorescence density of liver SCAP was determined by using immunofluorescence histochemistry.

Results: Compared with the normal control group, the contents of liver TC, serum TC, LDL-C, the activities of AST and ALT, and the mRNA and protein expression levels of SCAP, SREBP-2, HMGCR, PCSK9 as well as SCAP immunoactivity were significantly increased (P<0.01), while the LDLR mRNA and protein levels were markedly decreased (P<0.01) in the model group. In comparison with the model group, the contents of liver TC， serum TC, LDL-C, the activities of AST and ALT and the expression of SCAP, SREBP-2, HMGCR, PCSK9 mRNAs and proteins and SCAP immunoactivity were considerably decreased in the EA group (P<0.01), while the LDLR protein level was evidently increased in the EA group (P<0.05).

Conclusion: EA intervention can inhibit the synthesis of cholesterol in the liver and thus improve hyperlipidemia in HLP rats, which may be realized by down-regulating the protein and mRNA expressions of hepatic SCAP/SREBP-2, HMGCR and PCSK9, and up-regulating LDLR protein.