Bile acid flux through portal but not peripheral veins inhibits CYP7A1 expression without involvement of ileal FGF19 in rabbits

INT-767 prevents NASH and promotes visceral fat brown adipogenesis and mitochondrial function

The bile acid receptors, farnesoid X receptor (FXR) and Takeda G-protein-coupled receptor 5 (TGR5), regulate multiple pathways, including glucose and lipid metabolism. In a rabbit model of high-fat diet (HFD)-induced metabolic syndrome, long-term treatment with the dual FXR/TGR5 agonist INT-767 reduces visceral adipose tissue accumulation, hypercholesterolemia and nonalcoholic steatohepatitis. INT-767 significantly improves the hallmarks of insulin resistance in visceral adipose tissue (VAT) and induces mitochondrial and brown fat-specific markers. VAT preadipocytes isolated from INT-767-treated rabbits, compared to preadipocytes from HFD, show increased mRNA expression of brown adipogenesis markers. In addition, INT-767 induces improved mitochondrial ultrastructure and dynamic, reduced superoxide production and improved insulin signaling and lipid handling in preadipocytes. Both in vivo and in vitro treatments with INT-767 counteract, in preadipocytes, the HFD-induced alterations by upregulating genes related to mitochondrial biogenesis and function. In preadipocytes, INT-767 behaves mainly as a TGR5 agonist, directly activating dose dependently the cAMP/PKA pathway. However, in vitro experiments also suggest that FXR activation by INT-767 contributes to the insulin signaling improvement. INT-767 treatment counteracts HFD-induced liver histological alterations and normalizes the increased pro-inflammatory genes. INT-767 also induces a significant reduction of fatty acid synthesis and fibrosis markers, while increasing lipid handling, insulin signaling and mitochondrial markers. In conclusion, INT-767 significantly counteracts HFD-induced liver and fat alterations, restoring insulin sensitivity and prompting preadipocytes differentiation toward a metabolically healthy phenotype.

Effect of obeticholic acid on liver regeneration following portal vein embolization in an experimental model

Background

The bile salt-activated transcription factor farnesoid X receptor (FXR) is a key mediator of proliferative bile salt signalling, which is assumed to play a role in the early phase of compensatory liver growth. The aim of this study was to evaluate the effect of a potent FXR agonist (obeticholic acid, OCA) on liver growth following portal vein embolization (PVE).

Methods

Rabbits were allocated to receive daily oral gavage with OCA (10 mg/kg) or vehicle (control group) starting 7 days before PVE (n = 18 per group), and continued until 7 days after PVE. PVE of the cranial liver lobes was performed using polyvinyl alcohol particles and coils on day 0. Caudal liver volume (CLV) was analysed by CT volumetry on days –7, –1, +3 and +7. Liver function was determined by measuring mebrofenin uptake using hepatobiliary scintigraphy. Additional parameters analysed were plasma aminotransferase levels, and histological scoring of haematoxylin and eosin- and Ki-67-stained liver sections.

Results

Three days after PVE of the cranial lobes, the increase in CLV was 2·2-fold greater in the OCA group than in controls (mean(s.d.) 56·1(20·3) versus 26·1(15·4) per cent respectively; P < 0·001). This increase remained greater 7 days after PVE (+1·5-fold; P = 0·020). The increase in caudal liver function at day +3 was greater in OCA-treated animals (+1·2-fold; P = 0·017). The number of Ki-67-positive hepatocytes was 1·6-fold higher in OCA-treated animals 3 days after PVE (P = 0·045). Plasma aminotransferase levels and histology did not differ significantly between groups.

Conclusion

OCA accelerated liver regeneration after PVE in a rabbit model. OCA treatment might increase the efficacy of PVE and, thereby, resectability.