Exploring effects of natural hyperoxic environment on liver lipid metabolism based on the bile acid-farnesoid X receptor pathway in sub-healthy rats

Abstract

Objective: To investigate the effect of natural hyperoxic environment on liver lipid metabolism and liver function based on the bile acid-farnesoid X receptor pathway in sub-healthy rats. Methods: Forty adult male Wistar rats were randomly divided into control group (n = 10) and sub-healthy model group (n = 30). The control group was fed a normal diet, and the model group was fed a high-fat-sugar diet with limited daily activities for 5 weeks. The sub-healthy model was successfully established and the feeding conditions were restored. The hyperoxic intervention group (healthy group) were placed in a natural hyperoxic environment for 7 days. The rats feeding status in the spontaneous recovery group were unchanged. The appearance and exhaustive swimming time were compared before and after in healthy rats. Peripheral blood was collected for biochemical measurement. The fluorescence intensity of FXR and peroxisome proliferator activated receptor α (PPAR α) in liver tissue was detected by fluorescence double staining. Real-time fluorescent semi-quantitative PCR and Western blot were used to detect the RNA and protein expression condition of bile acid-FXR signaling pathway related indicators (FXR, PPARα, and SREBP-1c) in liver tissues. Results: Compared with the control group, the model group had gained body weight, and the vitality was decreased, while triglycerides [TG, (1.18 ± 0.20) mmol/L vs. (0.65 ± 0.12) mmol/L] and total cholesterol [TC, (1.23 ± 0.29) mmol/L vs. (1.00 ± 0.25) mmol/L] level was increased, (P < 0.05), which suggests the presence of hepatic steatosis. TG and TC level in the healthy group and spontaneous recovery group were lower than the model group, and the differences between the healthy group and the model group were statistically significant (P < 0.05). Compared with the model group, the expression of FXR and PPARα in the liver of the healthy and the spontaneous recovery group was enhanced, while the expression of the sterol regulatory element binding protein 1c (SREBP-1c) was decreased. FXR and PPARα mRNA levels in the healthy group and the model group were (9.27 ± 0.26 vs. 6.77 ± 0.20), and (9.71 ± 0.21 vs. 7.09 ± 0.24), P < 0.01, respectively. Compared with the model group, spontaneous recovery group mRNA levels were 7.99 ± 0.30 and 8.44 ± 0.28, P < 0.05, respectively. FXR and SREBP-1c protein levels between the healthy group and the model group were (1.30 ± 0.19 vs.0.43 ± 0.28), and (1.56 ± 0.22 vs. 2.43 ± 0.19), P < 0.01, respectively. Compared with the model group, the FXR and SREBP-1c protein levels of the spontaneous recovery group were 0.81 ± 0.33 vs. 2.10 ± 0.38, P < 0.05, respectively. In addition, natural hyperoxic environment had enhanced liver lipid metabolism and improved lipid disorders. Conclusion: The natural hyperoxic environment have the ability to regulate liver lipid metabolism and can improve mild hyperlipidemia to a certain extent.