title: Systematic review: microbial dysbiosis and nonalcoholic fatty liver disease.
abstract: BACKGROUND
  The human intestinal microbiota is a key regulator of host metabolic and immune functions and alterations in the microbiome ('dysbiosis') have been implicated in several human diseases. Because of the anatomical links between the intestines and the liver, dysbiosis may also disrupt hepatic function and thereby contribute to the pathogenesis of nonalcoholic fatty liver disease (NAFLD).
  
  
  OBJECTIVE
  To perform a comprehensive review of the medical literature investigating associations between intestinal dysbiosis and NAFLD, with a particular emphasis on studies that characterise the microbiome in NAFLD.
  
  
  METHODS
  We conducted a search of PubMed, Embase, and Web of Science using multiple search terms including: 'NAFLD, NASH, fatty liver, steatohepatitis' combined with 'metagenome, microbiom*, microbiota*, fecal flora, intestinal flora, gut bacteria'. Results were manually reviewed and studies selected based on relevance to intestinal microbiota and NAFLD. We also included studies that addressed potential mechanistic models of pathways linking the dysbiosis to NAFLD.
  
  
  RESULTS
  Nine studies (five human and four animal models) were identified in our search that assessed associations between specific intestinal microbiota composition and NAFLD. We reviewed and summarised the results of additional investigations that more broadly addressed the mechanisms by which the microbiome may impact NAFLD pathogenesis.
  
  
  CONCLUSIONS
  Investigations in humans and animals demonstrate associations between intestinal dysbiosis and NAFLD; however, causality has not been proven and mechanistic links require further delineation. As the field of microbiome research matures in techniques and study design, more detailed insights into NAFLD pathogenesis and its associations with the intestinal microbiota will be elucidated.
authors: Division of Gastroenterology and Hepatology, University of Colorado Denver, Aurora, CO, USA.
authors: A
authors: A
authors: Wieland
authors: Division of Infectious Diseases and Microbiome Research Consortium, University of Colorado Denver, Aurora, CO, USA.
authors: D N
authors: DN
authors: Frank
authors: University of Colorado Health Science Library, Aurora, CO, USA.
authors: B
authors: B
authors: Harnke
authors: Division of Gastroenterology and Hepatology, University of Colorado Denver, Aurora, CO, USA.
authors: K
authors: K
authors: Bambha
mesh_terms: D000818:Animals; D064806:Dysbiosis / Q000382:microbiology*; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D054892:Metagenome; D064307:Microbiota; D023421:Models, Animal; D065626:Non-alcoholic Fatty Liver Disease / Q000382:microbiology* / Q000503:physiopathology*