Published online Sep 7, 2019. doi: 10.3748/wjg.v25.i33.4814
Peer-review started: May 21, 2019
First decision: June 9, 2019
Revised: July 4, 2019
Accepted: July 19, 2019
Article in press: July 19, 2019
Published online: September 7, 2019
The intimate connection and the strict mutual cooperation between the gut and the liver realizes a functional entity called gut-liver axis. The integrity of intestinal barrier is crucial for the maintenance of liver homeostasis. In this mutual relationship, the liver acts as a second firewall towards potentially harmful substances translocated from the gut, and is, in turn, is implicated in the regulation of the barrier. Increasing evidence has highlighted the relevance of increased intestinal permeability and consequent bacterial translocation in the development of liver damage. In particular, in patients with non-alcoholic fatty liver disease recent hypotheses are considering intestinal permeability impairment, diet and gut dysbiosis as the primary pathogenic trigger. In advanced liver disease, intestinal permeability is enhanced by portal hypertension. The clinical consequence is an increased bacterial translocation that further worsens liver damage. Furthermore, this pathogenic mechanism is implicated in most of liver cirrhosis complications, such as spontaneous bacterial peritonitis, hepatorenal syndrome, portal vein thrombosis, hepatic encephalopathy, and hepatocellular carcinoma. After liver transplantation, the decrease in portal pressure should determine beneficial effects on the gut-liver axis, although are incompletely understood data on the modifications of the intestinal permeability and gut microbiota composition are still lacking. How the modulation of the intestinal permeability could prevent the initiation and progression of liver disease is still an uncovered area, which deserves further attention.
Core tip: The integrity of the gut-liver axis is crucial for the maintenance of the homestasis of the organism. The disruption of the intestinal barrier and consequent increased intestinal permeability has been recently associated with the development of liver damage. This review summarizes present evidence on the relevance of the derangement of the gut-liver axis in the pathogenesis of liver damage and non-alcoholic fatty liver disease, the development of the complications of liver cirrhosis and its modifications after liver transplantation.