Dysbiosis and liver diseases (Review)

Dysbiosis, a qualitative and quantitative aberrancy of gut microbiota, has attracted marked attention. At present, advances in molecular biological techniques have made it possible to analyze gut microbiota at the DNA and RNA levels without culturing, and methods such as 16S ribosomal RNA targeting analysis and metagenomic analysis using next‑generation sequencers have been developed. The relationship between gut microbiota and various diseases has been extensively examined. Gut microbiota are essential for the immune system, energy intake and fat storage, and humans use them to build complex immune regulatory mechanisms and to obtain energy from food. The liver is the first organ to be nourished by the portal blood flow of intestinal origin, and liver diseases can be strongly influenced by various factors of intestinal origin, such as intestinal bacteria, bacterial components, and intestinal bacterial metabolites. Rigorous research has revealed that the composition of the gut microbiota is altered and the diversity of bacteria is reduced in liver diseases. Significance of various factors transported to the liver by portal vein blood flow from the intestine has been extensively investigated. Gut microbiota in liver disease can be associated with disease progression regardless of disease etiology and even with carcinogenesis. The relationship between gut microbiota and liver diseases (hepatitis virus‑related diseases, autoimmune liver diseases, alcoholic liver disease, non‑alcoholic fatty liver disease, non‑alcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma) and the treatments of dysbiosis (antibiotics, prebiotics, probiotics and fecal microbiota transplantation) in liver disease are outlined based on the current evidence.