Intestinal barrier in chronic gut and liver diseases: Pathogenesis and therapeutic targets

The intestinal barrier is the primary defense that separates the host from the external environment, possessing several crucial physiological functions, including nutrient digestion, absorption, and protection against potentially harmful dietary antigens and pathogenic microorganisms. Nevertheless, various factors, such as diet, medications, circadian rhythm disturbances, gut microbiota, microbial metabolites, and genetic predisposition, can disrupt the intestinal barrier. Such disruption may lead to bacterial translocation, subsequently triggering enterohepatic and systemic inflammation. Impaired intestinal barrier has been implicated in the pathogenesis of numerous diseases, particularly chronic gut and liver diseases. In this review, we will summarize the fundamental functions of intestinal barrier and discuss clinical correlations between intestinal barrier dysfunction and diseases such as colitis, colorectal cancer, and chronic liver diseases including metabolic dysfunction-associated steatohepatitis, alcohol-associated liver disease, and primary sclerosing cholangitis. Additionally, we will also highlight some potential therapeutic strategies aimed at restoring barrier integrity to improve disease management.