The Microbiome and the Liver: The Basics

Abstract

The relationships between the microbiota and other aspects of normal human biology continue to be explored. Indeed, the volume of information relating to the interplay between the host and the microbiota has grown exponentially-especially with the advent of ever-improving techniques for rapidly sequencing and identifying bacterial populations and their functions. The gut is initially sterile at birth and colonization and dynamic changes occur during infancy and early childhood in order to establish a mature microbiome. The mature microbiome has direct and important interactions with host metabolism. Bacterial translocation from the gut microbiome is thought to be a key driver of inflammation in liver disease and changes in tolerance to these bacteria drive inflammation in the liver and elsewhere in the host. As we are better able to describe the composition and functional properties of the microbiome, the range of its impact on the homeostatic functions of the human body and implications for disease continue to be extended.

The Gut-Brain Axis and the Microbiome: Clues to Pathophysiology and Opportunities for Novel Management Strategies in Irritable Bowel Syndrome (IBS)

“…Parenthetically, it must be noted that the concept of a microbiota-gut-brain axis (and, indeed, a microbiota-gut-liver-brain axis) is far from new and was well described over 50 years ago in seminal studies on the pathogenesis of hepatic encephalopathy (HE) which identified the centrality of the gut microbiota to the genesis of this syndrome and described the beneficial impact of an intervention that modified gut bacterial population; a poorly absorbed antibiotic, on the symptoms of this syndrome [ 26 , 27 ]. Indeed, the model developed to explain the pathophysiology of HE; namely, the convergence of small intestinal bacterial overgrowth (SIBO) and/or an abnormal microbiota, impaired gut barrier function, a pro-inflammatory state and the appearance in the systemic circulation of neuro-active molecules generated by bacterial metabolism has become virtually ubiquitous in relation to most disorders where a role for the microbiota-gut-brain axis has been invoked [ 28 ] ( Figure 1 ).…”

Secondary Sclerosing Cholangitis in Critically Ill Patients Alters the Gut–Liver Axis: A Case Control Study

“…Microbiological bile analysis from patients with SC-CIP and primary sclerosing cholangitis (PSC) showed an altered microbiological profile in these two groups, with predominance of drug-resistant organisms in the bile of SC-CIP [ 14 ]. Data on the gut microbiome in SC-CIP is not available to date, but other chronic liver diseases have distinct changes in microbiome composition with potential impact on inflammation (non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease, PSC and cirrhosis) [ 15 , 16 , 17 , 18 ]. Altered gut microbiome composition is thought to increase intestinal permeability [ 19 ].…”

“…It is most commonly seen in cirrhosis but was also described in alcohol-induced injury, NAFLD and hepatits C virus (HCV)-mediated liver injury [ 20 , 21 , 22 , 23 , 24 ]. When gut permeability is increased, bacteria from the intestinal lumen can translocate into extraintestinal locations of the body (lymph nodes, blood) and trigger inflammatory reactions, leading to disease progression [ 16 , 25 ].…”

The complement system in liver diseases: Evidence-based approach and therapeutic options

“…2 ). The mature microbiome might drive inflammation in liver disease and governs tolerance to these bacteria [ 53 ]. The gut associated lymphoid tissue [ 51 ] (GALT) scans microbiata composition:, portal blood reaching the liver will be processed at least in part, by immune recognition.…”