Bile Acids and Gut Microbiome in the Pathogenesis of Inflammation in Cirrhosis

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DESCRIPTION (provided by applicant): Alcoholic liver disease and cirrhosis are one of the leading causes of morbidity and mortality in the US, as well as in the VA Health System. However, despite several programs to prevent and treat alcohol abuse, a significant proportion of affected Veterans continue to drink, even in the setting of cirrhosis. This can lead to a substantial burden that stems from an unchecked inflammatory milieu and endotoxemia due to bacterial translocation that precipitates infections, multi-organ failure and death. These patients are poor candidates for abstinence pharmacological therapy, are often non-adherent and cannot be offered liver transplant due to their continued drinking. Therefore prevention of this unchecked inflammation and bacterial translocation is critical; however, the exact mechanisms behind these are unclear, which is a major gap in our knowledge. Bile acids (BAs) and gut microbiota are key components of the intestinal milieu, whose interaction impacts bacterial translocation and inflammation. Our group has focused on delineating the role of microbiota, using culture- independent analyses, with inflammation and their modulation by BAs, especially the membrane-destabilizing secondary BAs in cirrhosis. We also discovered that actively drinking cirrhotics have a highly significant increase in fecal secondary BAs and intestinal inflammatory cytokine expression that may mediate intestinal injury and potentiate inflammation in these patients. Therefore, the study of the role of secondary BAs in the pathogenesis of intestinal and systemic inflammation in the context of altered gut microbiota or dysbiosis, in actively drinking cirrhotics compared to abstinent alcoholic cirrhotics and cirrhotics with non-alcoholic liver disease is critical in delineating the role of the intestinal milieu in the progression of liver disease. Our central hypothesis: Patients with cirrhosis, especially alcoholic cirrhotic patients who continue to drink, develop enhanced intestinal and systemic inflammation due to an increase in secondary bile acids associated with altered gut microbiota. This central hypothesis will be tested using these two specific aims: Specific aim 1: To define the effect of secondary bile acids on systemic and gut inflammation, gut microbiome and endotoxemia in cirrhotic patients with continued alcohol abuse compared to abstinent alcoholic cirrhotics and non-alcoholic cirrhotics using a systems biology approach. We will study the interaction of BAs with microbiome of the duodenal, ileal, colonic and fecal origin with systemic and intestinal wall inflammation in age- and cirrhosis-severity matched actively drinking cirrhotics compared to abstinent alcoholic cirrhotics, cirrhotic with NAFLD and healthy controls using a systems biology approach in 100 subjects. Specific Aim 2: To define the role of bile acids and gut microbiota in the pathogenesis of the increased intestinal and systemic inflammation, endotoxemia and bacterial translocation in a germ-free mouse model after colonization with stool from alcoholic cirrhotic patients. We will be utilizing germ-free mice to elucidate the individual contributions of bile acids and microbiota on endotoxemia, inflammation and bacterial translocation. Six groups of germ-free mice will be used: 1) without intervention 2) fed deoxycholic acid alone 3) colonized with healthy human stool 4) colonized with alcoholic cirrhotic stool. Each group will be evaluated for intestinal and systemic inflammation, endotoxemia, BA profile (serum, gallbladder, liver, fecal, intestinal contents) and microbiome changes (Groups 3-4) will be performed after colonization and compared between groups. The studies will provide a novel integrative platform to study the role of secondary bile acids and gut microbiota in the development of intestinal and systemic inflammation in all cirrhotic patients using cutting-edge translational and systems biology approaches. We expect the results of this proposal to increase our insight into the development of focused therapeutic approaches that benefit this underserved population of Veterans.