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World J Gastroenterol. Nov 28, 2014; 20(44): 16452-16463
Published online Nov 28, 2014. doi: 10.3748/wjg.v20.i44.16452
Obesity, fatty liver disease and intestinal microbiota
Nur Arslan
Nur Arslan, Department of Pediatrics, Division of Pediatric Gastroenterology, Nutrition and Metabolism, Dokuz Eylul University Faculty of Medicine, Izmir 35340, Turkey
Nur Arslan, Department of Molecular Medicine, Dokuz Eylul University Faculty of Medicine, Izmir 35340, Turkey
Author contributions: Arslan N designed and wrote the manuscript.
Correspondence to: Nur Arslan, MD, PhD, Department of Pediatrics, Division of Pediatric Gastroenterology, Nutrition and Metabolism, Dokuz Eylul University Faculty of Medicine, Cumhuriyet Blv 144, Izmir 35340, Turkey. nur.arslan@deu.edu.tr
Telephone: +90-232-4126107 Fax: +90-232-4126005
Received: February 23, 2014
Revised: May 14, 2014
Accepted: August 13, 2014
Published online: November 28, 2014
Processing time: 281 Days and 19.8 Hours
Abstract

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disorder that is increasing in prevalence with the worldwide epidemic of obesity. NAFLD is the hepatic manifestation of the metabolic syndrome. The term NAFLD describes a spectrum of liver pathology ranges from simple steatosis to steatosis with inflammation nonalcoholic steatohepatitis and even cirrhosis. Metabolic syndrome and NAFLD also predict hepatocellular carcinoma. Many genetic and environmental factors have been suggested to contribute to the development of obesity and NAFLD, but the exact mechanisms are not known. Intestinal ecosystem contains trillions of microorganisms including bacteria, Archaea, yeasts and viruses. Several studies support the relationship between the intestinal microbial changes and obesity and also its complications, including insulin resistance and NAFLD. Given that the gut and liver are connected by the portal venous system, it makes the liver more vulnerable to translocation of bacteria, bacterial products, endotoxins or secreted cytokines. Altered intestinal microbiota (dysbiosis) may stimulate hepatic fat deposition through several mechanisms: regulation of gut permeability, increasing low-grade inflammation, modulation of dietary choline metabolism, regulation of bile acid metabolism and producing endogenous ethanol. Regulation of intestinal microbial ecosystem by diet modifications or by using probiotics and prebiotics as a treatment for obesity and its complications might be the issue of further investigations.

Keywords: Intestinal microbiota; Dysbiosis, Nonalcoholic fatty liver disease; Obesity

Core tip: There is increasing evidence for the relation between dietary habits, gut microbiota and obesity. Nonalcoholic fatty liver disease is a common complication of obesity. This manuscript summarizes the relationship between intestinal microbial dysregulation and fatty liver disease related with obesity, and their proposed mechanisms.