ABSTRACT
Objective:To investigate the role of liver X-activated receptor (LXRα)/sterol-regulatory element binding protein (SREBP-1c) in arsenic induced lipid metabolism disorders in rats, and to provide a basis for study the mechanism of arsenic induced lipid metabolism disorders.Methods:Twenty-four healthy clean grade Wistar rats, were randomly divided into 4 groups according to body weight (80 - 100 g) by the random number table method, with 6 rats in each group, half male and half female. Rats in control group were given deionized water by gavage. The low, medium and high arsenic dose groups were given 2.5, 5.0 and 10.0 mg·kg -1·d -1 sodium arsenite solution by gavage, respectively. They were exposed to arsenic for 6 days a week for 4 months. At the end of the experiment, blood and liver samples of rats in each group were collected. The hepatic arsenic content was determined by inductively coupled plasma mass spectrometry (ICP-MS); the serum levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured by automatic biochemical analyzer. The mRNA expression levels of LXRα and SREBP-1c in liver tissues were determined by real-time PCR; the protein expression levels of LXRα, SREBP-1c, acetyl CoA carboxylase (ACC) and phospho-ACC (pACC) in liver tissues were determined by Western blotting. Results:The hepatic arsenic contents of rats in low, medium and high arsenic dose groups were (61.04 ± 4.98), (62.66 ± 6.71) and (87.86 ± 13.89) μg/g, respectively, which were higher than that in control group [(2.43 ± 0.63) μg/g, P < 0.05], and the hepatic arsenic content of rats in high arsenic dose group was higher than those in low and medium arsenic dose groups ( P < 0.05). The serum TG levels of rats in low, medium and high arsenic dose groups were (0.90 ± 0.17), (1.28 ± 0.24) and (1.82 ± 0.18) mmol/L, respectively, which were higher than that in control group [(0.50 ± 0.12) mmol/L, P < 0.05]; the serum LDL-C levels of rats in low, medium and high arsenic dose groups were (0.54 ± 0.04), (0.63 ± 0.07) and (0.69 ± 0.08) mmol/L, respectively, which were higher than that in control group [(0.27 ± 0.05) mmol/L, P < 0.05]; the serum TC levels of rats in medium and high arsenic dose groups were (1.88 ± 0.23) and (2.10 ± 0.10) mmol/L, respectively, which were higher than that in control group [(1.51 ± 0.14) mmol/L, P < 0.05]; the serum HDL-C levels of rats in medium and high arsenic dose groups were (0.84 ± 0.11) and (0.71 ± 0.14) mmol/L, respectively, which were lower than that in control group [(1.15 ± 0.08) mmol/L, P < 0.05]; and the serum levels of TG and LDL-C in medium and high arsenic dose groups were higher than those in low arsenic dose group ( P < 0.05), and the serum level of TG in high arsenic dose group was higher than that in medium arsenic dose group ( P < 0.05). The mRNA expression level of hepatic LXRα of rats in high arsenic dose group was higher than those in control group and low arsenic dose group ( P < 0.05); there was no significant difference in mRNA expression levels of hepatic SREBP-1c of rats between low, medium and high arsenic dose groups and control group ( P > 0.05). The protein expression levels of hepatic LXRα of rats in medium and high arsenic dose groups were higher than that in control group ( P < 0.05), and high arsenic dose group was higher than low arsenic dose group ( P < 0.05); the protein expression levels of hepatic SREBP-1c and ACC of rats in high arsenic dose group were higher than that in control group ( P < 0.05). There was a positive correlation between hepatic arsenic content in arsenic-exposed rats and the serum levels of TG, TC, LDL-C, the mRNA expression level of hepatic LXRα, the protein expression levels of hepatic LXRα, SREBP-1c and ACC ( r = 0.84, 0.62, 0.89, 0.55, 0.54, 0.64, 0.70, P < 0.05), and the serum level of HDL-C was negatively correlated with the hepatic arsenic content in arsenic-exposed rats ( r = - 0.75, P < 0.001). Conclusion:Sodium arsenite can increase the serum levels of TG, TC and LDL-C, decrease the serum level of HDL-C and increase the protein expression levels of LXRα and SREBP-1c in liver tissues, suggesting that arsenic induced lipid metabolism disorders in rats may be related to the upstream regulation mechanism of LXRα/SREBP-1c.