Exploration of mechanisms underlying the beneficial effect of long-term albumin in models of cirrhosis and aclf

Chronic albumin infusions have been shown to reduce mortality in cirrhosis, but the mechanism of its beneficial effect remains unknown. We aim to understand the role of albumin in modulating the gut-liver-axis by studying rodent models of cirrhosis and ACLF in analbuminaemic rats and the administration of chronic albumin infusions in these models. 10 rodent groups: Naïve, cirrhosis (4-wk; bile-duct ligation (BDL)) and acute-on-chronic liver failure (ACLF) models (induced by lipopolysaccharide (LPS) 0.025 mg/kg intraperitoneal (i.p.) to BDL) ± albumin infusion (1.5 g/kg ip; 2-wk) of analbuminaemic (NAR) and wild-type (SD) rats. Plasma biochemistry and hepatic TUNEL staining. Liver qPCR and RT2 PCR profiler for TLR4 genes. Plasma cytokines analysed with Luminex, TLR4 reporter cells for PAMPs and cell death ELISA analysis of DAMPs. Gut permeability assessed with plasma D-lactate. Western blot and RT2 PCR Profiler of tight junction proteins. Coma-free survival was reduced in analbuminaemic cirrhotic animals, and ACLF animals of both species, which was significantly improved in the cirrhosis and ACLF models treated with albumin (p=0.027). In models of cirrhosis and ACLF, an increase in gut permeability (measured using plasma D-lactate) and reduced abundance of tight junction proteins, ZO-1, claudin-4 and occludin was observed, which were restored by albumin infusion. Increased gut permeability was associated with increased systemic inflammation, as measured by plasma cytokines (IL-1beta, IL-10, IL-6 and TNFalpha), in addition to increased circulation of pathogen and damage associated molecular patterns (measured by plasma TLR4 activation and plasma markers of cell death respectively). The absence of endogenous albumin was associated with greater hepatic TLR4 expression, with a significant reduction in expression in all disease groups with the addition of albumin injections. Liver injury (assessed by plasma ALT and hepatic TUNEL staining) improved following albumin injection, with significant reduction seen in WT ACLF animals [p=0.01; p<0.001 respectively]. The results of this study provide novel insights into the mechanism of improved survival observed in cirrhosis and ACLF with long term albumin infusion pointing to its effects on reducing gut translocation and permeability through effects on the tight junctions. This results in improvement of gut integrity and decreased hepatic TLR4 pathway activation, which impacts on severity of inflammation, liver injury and mortality.