Apical sodium-dependent bile acid transporter inhibition with volixibat improves metabolic aspects and components of non-alcoholic steatohepatitis in Ldlr-/-.Leiden mice

Abstract: Interruption of bile acid recirculation through inhibition of the apical sodium-dependent bile acid transporter (ASBT) is a promising strategy to alleviate hepatic cholesterol accumulation in non-alcoholic steatohepatitis, and improve the metabolic aspects of the disease. Putative disease-attenuating effects of the ASBT inhibitor volixibat (5, 15, and 30 mg/kg) were investigated in high-fat diet (HFD)-fed Ldlr-/-.Leiden mice over 24 weeks. Plasma and fecal bile acid levels, plasma insulin, lipids, and liver enzymes were monitored. Final analyses included liver histology, intrahepatic lipids, mesenteric white adipose tissue mass, and liver gene profiling. Consistent with its mechanism of action, volixibat significantly increased total bile acid excretion. At the highest dose, volixibat significantly attenuated the HFD-induced increase in hepatocyte hypertrophy, hepatic triglyceride and cholesteryl ester levels, and mesenteric white adipose tissue deposition, while total plasma bile acid levels remained constant. Non-alcoholic fatty liver disease activity score was significantly lower in volixibat-treated mice than in the HFD controls. Gene profiling showed that volixibat reversed the inhibitory effect of the HFD on metabolic master regulators, including peroxisome proliferator-activated receptor-γ coactivator-1β, insulin receptor, and sterol regulatory element-binding transcription factor 2. Volixibat may have beneficial effects on physiological and metabolic aspects of non-alcoholic steatohepatitis pathophysiology. Experimental design: Mice (N = 75, between 16-18 weeks old) were matched by body weight and plasma cholesterol, triglyceride, and blood glucose levels were divided into five study groups, and maintained on either a chow diet (n = 10), a HFD (n = 20), or a HFD supplemented with volixibat 5, 15, or 30 mg/kg (n = 15 in each dose group) for 24 weeks (Fig 2). Food intake and body weight were monitored throughout the study to ensure accurate volixibat dosing. The schedule of assessments over the 24 weeks is shown in Fig 2, and included measurements of plasma cholesterol triglycerides, insulin, and liver enzymes, and determination of the lipoprotein profile. Bile acid species were measured in plasma and feces. Plasma samples (collected at weeks 0, 4, 8, 12, 16, 20, and 24) were obtained via a tail bleed after 5 hours of fasting (Fig 2). The mice were sacrificed at week 24 and the livers were isolated for histological evaluation of NASH parameters (as described above) [40] and lipid analysis. White adipose tissue depots were also collected and weighed. Gene expression analysis was carried out on liver tissue from eight mice in each group, selected as being representative of the group based on mean values of NASH parameters. All analyses were performed blindly.