Atorvastatin alters the expression of genes related to bile acid metabolism and circadian clock in livers of mice

Abstract

Aim: Atorvastatin is a HMG-CoA reductase inhibitor used for hyperlipidemia. Atorvastatin is generally safe but may induce cholestasis. The present study aimed to examine the effects of atorvastatin on hepatic gene expression related to bile acid metabolism and homeostasis, as well as the expression of circadian clock genes in livers of mice.

Methods: Adult male mice were given atorvastatin (10, 30, and 100 mg/kg, po) daily for 30 days, and blood biochemistry, histopathology, and gene expression were examined.

Results: Repeated administration of atorvastatin did not affect animal body weight gain or liver weights. Serum enzyme activities were in the normal range. Histologically, the high dose of atorvastatin produced scattered swollen hepatocytes, foci of feathery-like degeneration, together with increased expression of Egr-1 and metallothionein-1. Atorvastatin increased the expression of Cyp7a1 in the liver, along with FXR and SHP. In contract, atorvastatin decreased the expression of bile acid transporters Ntcp, Bsep, Ostα, and Ostβ. The most dramatic change was the 30-fold induction of Cyp7a1. Because Cyp7a1 is a circadian clock-controlled gene, we further examined the effect of atorvastatin on clock gene expression. Atorvastatin increased the expression of clock core master genes Bmal1 and Npas2, decreased the expression of clock feedback genes Per2, Per3, and the clock targeted genes Dbp and Tef, whereas it had no effect on Cry1 and Nr1d1 expression.

Conclusion: Repeated administration of atorvastatin affects bile acid metabolism and markedly increases the expression of the bile acid synthesis rate-limiting enzyme gene Cyp7a1, together with alterations in the expression of circadian clock genes.

Keywords: Atorvastatin; Bile acid transporters; Cholestasis; Clock gene expression; Cyp7a1; Mouse liver.

Figure 1. Histopathology.

Mice received atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Representative H&E staining of liver sections showed spotted feathery-like degeneration (thin arrows), and spotted blood lakes (peliosishepatis) (thick arrows). Magnitude 200×.

Figure 2. Effects of atorvastatin treatment on mRNA expression of Egr-1 and MT-1 in mouse livers.

Mice were given atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Total liver RNA was extracted and subjected to RT-PCR analysis. Data represents the mean ± SE of n = 5. ^∗Significantly different from control mice, p < 0.05.

Figure 3. Effects of atorvastatin treatment on mRNA expression of genes related to bile acid metabolism.

Mice were given atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Total liver RNA was extracted and subjected to RT-PCR analysis. Data represent the mean ± SE of n = 5. ^∗Significantly different from control mice, p < 0.05.

Figure 4. Effects of atorvastatin treatment on mRNA expression of bile acid transporters.

Mice were given atorvastatin 10, 30 or 100 mg/kg, po for 30 days.Total liver RNA was extracted and subjected to RT-PCR analysis. Data represent the mean ± SE of n = 5. *Significantly different from control mice, p < 0.05.

Figure 5. Effects of atorvastatin treatment on mRNA expression of clock core master genes Bmal1 and Npas2.

Mice were administered atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Total liver RNA was extracted and subjected to RT-PCR analysis. Data represent the mean ± SE of 4–5 mice. *Significantly different from control mice, p < 0.05.

Figure 6. Effects of atorvastatin treatment on mRNA expression of clock feedback control genes Per2, Per3 and Cry1.

Mice were given atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Total liver RNA was extracted and subjected to RT-PCR analysis. Data represent the mean ± SE of n = 5. ^∗Significantly different from control mice, p < 0.05.

Figure 7. Effects of atorvastatin treatment on mRNA expression of clock targeted or driven genes Dbp, Tef, and Nr1d1.

Mice were given atorvastatin 10, 30 or 100 mg/kg, po for 30 days. Total liver RNA was extracted and subjected to RT-PCR analysis. Data represent the mean ± SE of n = 5. ^∗Significantly different from control mice, p < 0.05.