Effects of Siwei Yuganzi decoction on LXRα and CYP7A1 in hyperlipidemic rats

Background: Hyperlipidemia (HLP) is a disorder in which lipids in the blood are disturbed due to abnormal lipid metabolism. Statins and fibrates lipid-regulating drugs prevent the generation of lipids and improves HLP, thereby reducing the likelihood of developing cardiovascular and cerebrovascular diseases. However, their adverse reactions and side effects limit a wide range of clinical applications. Tibetan medicine compound preparation Siwei Yuganzi decoction (SYD) is an adaptation of a classical prescription of the Tibetan medicine Sanguo decoction, that has been proved to have the effect of improving lipid metabolism; however, its possible mechanism remains unknown. Methods: Sixty specificpathogen free grade Sprague Dawley rats were randomly divided into the blank control group, the HLP group, the Chinese patent medicine Xuezhikang positive control group, and the treatment groups with Tibetan SYD high, middle, and lowdosages respectively. Ten rats were assigned to each group. Every rat in these groups was fed with a highfat emulsion to establish the hyperlipidemic animal model, except for those in the blank control group. Then the rats in the blank control and HLP groups were fed with 0.9% normal saline, those in Xuezhikang group were fed with Xuezhikang suspension at the dose of 0.11 g/kg/d, and those in SYD groups were fed with the SYD suspension at the dosage of 16.2 g/kg/d (high dosage), 10.8 g/kg/d (middle dosage), and 5.4 g/kg/d (low dosage), respectively. After 8 weeks, the levels of serum total cholesterol (TC), triglyceride (TG), lowdensity lipoprotein cholesterol (LDLC), and highdensity lipoprotein cholesterol (HDLC) were detected by the ELISA. The mRNA and protein expression levels of liver X receptor α (LXRα) and cholesterol 7αhydroxylase 1 (CYP7A1) were detected using RTPCR, western blotting, and immunohistochemistry. Results: The serum levels of TC, TG, and LDLC in the HLP group were higher than those in the blank control group (P 0.05), whereas the serum levels of HDLC and the expression levels of both LXRα and CYP7A1 mRNA and proteins in the liver in the HLP group were lower than those in the control group (P 0.05). After the treatment of the Xuezhikang and SYD, the serum levels of TG, TC, and LDLC significantly decreased (P 0.05), whereas the serum levels of HDLC and the expression levels of both LXRα and CYP7A1 mRNA and proteins in the liver significantly increased compared with those in the HLP group (P 0.05). Furthermore, The serum levels of TC, TG, and LDLC in the SYD group at high dosage were lower (P 0.05), the serum level of HDLC was higher, and the expression levels of both LXRα and CYP7A1 mRNA and proteins in the liver tissue were higher than those in the Xuezhikang group (P 0.05). Conclusion: SYD can improve the serum levels of TC, TG, and LDLC in the hyperlipidemic animal model via increasing the expression of both LXRα and CYP7A1 mRNA and proteins in the liver tissue.