O2 Long-term albumin infusion reduces the mortality of cirrhosis and ACLF animal models by modulating the gut-liver axis and hepatic TLR4 signalling

<h3></h3> Long-term albumin infusion has been shown to reduce mortality in cirrhosis, but the mechanism of its beneficial effect remains unknown. The aims of this study were to understand the role of albumin in modulating the gut-liver-axis by studying models of cirrhosis and ACLF. Models: Rats: 34 Analbuminaemic (NAR) and 36 wild-type (WT); 4-week bile duct ligation (BDL ± LPS (ACLF) (0.025 mg/kg ip) ± Human albumin 20% (1.5 g/kg ip; 2-week). Mice: 39 C57Bl mice 12-week carbon tetrachloride (CCL4) (orally ± 2 mg/kg LPS) (ACLF) ± albumin injections (1.5 g/kg ip; 2-week). Plasma biochemistry and hepatic TUNEL staining. Liver qPCR and RT2 PCR profiler for TLR4 genes. Plasma cytokines analysed with Luminex, TLR4 reporter cells assay and plasma cell death ELISA. Gut permeability assessed with plasma D-lactate. Western blot and RT2 PCR Profiler of tight junction proteins. Survival: Coma-free survival was reduced in both WT and NAR ACLF animals, which was significantly increased in the ACLF treated with albumin (p=0.027). Liver injury: 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&lt;0.001 respectively]. Gut permeability: In both cirrhosis and ACLF models, increased gut permeability and reduced abundance of tight junction proteins, ZO-1, claudin-4 and occludin was observed, which were restored by albumin infusions (NAR ACLF p=0.011). Cytokines, PAMPs and DAMPs: Albumin infusions decreased circulating cytokines (IL-1beta [WT ACLF 659.2-&gt;522.8 pg/mL, NAR ACLF 123.5-&gt;8.8 pg/mL], IL-10 [NAR ACLF 110.1-&gt;12 pg/mL], IL-6 [WT ACLF 13696.7-&gt;10310.0 pg/mL, NAR ACLF 4915.8-&gt;237.1 pg/mL] and TNFalpha [NAR ACLF 2519.4-&gt;97.7]), pathogen and damage associated molecular patterns (measured by plasma TLR4 activation and plasma markers of cell death respectively) in cirrhosis models and ACLF models significantly (TLR4 reporter NAR ACLF [p&lt;0.001], Cell death WT ACLF [p&lt;0.001], NAR ACLF [p=0.012]). Gene expression: The absence of endogenous albumin was associated with greater hepatic TLR4 expression and related genes (TLR4, TNFalpha, and IL-1beta), with a significant reduction of expression in all disease groups with the addition of albumin injections (p&lt;0.05). Long-term albumin infusions significantly reduce mortality of ACLF animals by impacting on hepatic TLR4 related pathways that significantly reduce endotoxin sensitivity. This is manifested by significant reduction in the severity of inflammation, hepatocyte cell death and further endotoxemia. The data show for the first time that these beneficial effects are likely due to the effect of albumin on the integrity of the gut tight junctions and permeability.