Fig 1.
Comparison of bile acid (BA) metabolism between human and mouse.
CA and CDCA are end products in the human liver, but the mouse liver further metabolizes CDCA to MCAs by CYP2C70. In addition, the mouse liver can convert secondary BAs, DCA and LCA, into CA and CDCA by CYP2A12. Because of the low intestinal re-absorption rate (human and mouse) and small CDCA pool (wild-type mouse), the enterohepatic circulation of LCA is usually less (thin arrows) than those of other BAs (thick arrows). Knockout of the Cyp2a12 and Cyp2c70 genes results in mice with a human-like hydrophobic BA composition. Cyp2a12 and Cyp2c70 are genes responsible for hepatic BA 7α-hydroxylation and CDCA 6β-hydroxylation, respectively.
Table 1.
Effects of UDCA administration on the fertility of DKO mice.
Fig 2.
Effects of UDCA treatment on liver injury.
DKO mice were bred under UDCA administration, and offspring in both sexes were divided into two groups: one stopped receiving UDCA at six weeks of age while the other continued UDCA until 20 weeks. (A) Serum activities of AST, ALT, and ALP in mice at 20 weeks with (+) or without (discontinued) (-) UDCA treatment. The blue shaded areas indicate the normal ranges. (B) Representative histopathologic features of the livers at the age of 20 weeks with or without UDCA treatment. Hematoxylin/eosin stain. Scale bars, 100 μm. Arrows indicate ductular reaction (black), infiltration of immune cells (red), and focal necrosis of hepatocytes (blue). (C) Hepatic mRNA expression levels of inflammatory cytokines in mice at 20 weeks with or without UDCA treatment. Each column and error bar represents the mean and SEM. *P < 0.05, **P < 0.01, and ***P < 0.001 were considered statistically significantly different by the Tukey-Kramer test.
Fig 3.
Effects of UDCA treatment on BA pool and fecal BA excretion.
DKO mice at 20 weeks of age, with (+) or without (-) UDCA treatment, were compared. (A) Composition of BAs in the total BA pool and feces. The total BA pool in the enterohepatic circulation was calculated by adding total BAs in the liver, gallbladder, and small intestine. The broken line indicates the boundary between conjugated and unconjugated BAs. (B) BA amounts in the total pool and feces. Each column and error bar represents the mean and SEM. *P < 0.05 and **P < 0.01 were considered statistically significantly different by the Tukey-Kramer test.
Fig 4.
Comparison of BA compositions, concentrations, and hydrophobicity indices among serum, liver, and bile.
DKO mice at 20 weeks of age, with (+) or without (-) UDCA treatment, were compared. (A) BA compositions in serum, liver, and bile. The broken lines indicate the boundary between conjugated and unconjugated BAs. (B) BA concentrations in serum, liver, and bile. *P < 0.05 was considered statistically significantly different from UDCA treated male mice by the Tukey-Kramer test. (C) Hydrophobicity indices of total BAs in serum, liver, and bile. Each column and error bar represents the mean and SEM. **P < 0.01, ***P < 0.001, and ****P < 0.0001 were considered statistically significantly different by the Tukey-Kramer test.
Fig 5.
Comparison of LCA detoxification activities.
DKO mice at 20 weeks of age, with (+) or without (-) UDCA treatment, were compared. (A) Proposed metabolic pathways for LCA in mice. (B) Hepatic concentrations of LCA-3S and TLCA-3S and mRNA expression levels of Sult2a1. (C) Hepatic concentrations of HDCAs (HDCA + THDCA) and MDCAs (MDCA + TMDCA) and mRNA expression levels of Cyp3a11. (D) Hepatic microsomal enzyme activities that catalyze 6α-, 6β-, and 7α-hydroxylations of TLCA. Each column and error bar represents the mean and SEM. *P < 0.05 and **P < 0.01 were considered statistically significantly different by the Tukey-Kramer test.
Fig 6.
Effects of UDCA treatment on hepatic cholesterol and BA metabolism.
DKO mice at 20 weeks of age, with (+) or without (-) UDCA treatment were compared. (A) Hepatic mRNA expression levels of nuclear receptors and their target genes. (B) Hepatic concentrations of cholesterol and oxysterols. CHOL, cholesterol; HC, hydroxycholesterol; EC, epoxycholesterol. (C) Hepatic mRNA expression levels of the key enzyme in the cholesterol biosynthetic pathway and serum sterol concentrations associated with cholesterol metabolism. (D) Hepatic activities and mRNA expression levels of key enzymes in the BA biosynthetic pathways and serum concentrations of FGF15. Each column and error bar represents the mean and SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 were considered statistically significantly different by the Tukey-Kramer test.