INTRODUCTION. The human gut microbiota is a set of microorganisms that are in symbiosis with the host organism. The predominance of bacteria of Bacteroidetes, Firmicutes, Actinobacteria types is a characteristic feature of human gut microbiota. However, the composition of the gut microbiota is subject to change under the influence of a number of factors. The influence of the gut-liver axis on the pathogenesis of many chronic liver diseases of various etiologies, both infectious and metabolic, has been proven. At the same time, in the analyzed literature, the data on the relationship between the nature of GM changes and the stage of liver damage are quite controversial.
OBJECTIVE. Updating and systematization of ideas about the nature of changes in the composition of intestinal microbiota in chronic hepatitis C (CHC) and non-alcoholic fatty liver disease (NAFLD) at different stages of the disease.
MATERIALS AND METHODS. We analyzed the scientific literature on GM changes in chronic liver diseases with regard to their etiology and disease stage, in particular in chronic viral hepatitis C and NAFLD. The search was conducted in PubMed, Google Scholar, and eLIBRARY databases for 2000-2023 using the following keywords: gut microbiota; microbiota in hepatitis C; microbiota in NAFLD; microbiota in liver fibrosis; liver fibrosis progression. Sixty scientific articles were analyzed and 42 sources were selected, of which more than 60% were published within the last five years.
RESULTS. This review presents the results of original studies describing the main taxonomic differences between the microbiomes of healthy individuals and patients with CHC complicated by the formation of liver cirrhosis and hepatocellular carcinoma (HCC). Thus, patients with viral cirrhosis showed impoverishment of intestinal commensals Lachnospiraceae and Ruminococcaceae and significant enrichment of Streptococcaceae, Lactobacillaceae and Enterobacteriaceae. In patients with non-alcoholic steatohepatitis (NASH) and FII, enrichment of GM Phylum Bacteroides and Proteobacteria, Families Lachnospiraceae and Enterobacteriaceae, Genera Blautia and Escherichia, with a concomitant decrease of Prevotella was detected.
DISCUSSION. The analysis of GM taxonomic units in the previously described studies did not reveal significant differences depending on the etiology of the underlying disease. However, a decrease in the representative of the phylum Firmicutes - Ruminococcaceae was observed in CHC in contrast to NAFLD. A more distinct relationship can be observed in the changes of intestinal microbiota in F(III-IV) irrespective of etiology. Thus, in advanced liver fibrosis and cirrhosis of both CHC and NAFLD etiologies, enrichment of GM has been described due to an increase in phylum Proteobacteria, in particular the genus Escherichia and phylum Firmicutes (Blautia, Veillonellaceae). In the studies analyzed, at F(III-IV), an enrichment of the microbiota is observed due to an increase in the phylum Bacteroidetes. Regarding the genus Prevotella, contradictory results were found. In addition, there are ambiguous data regarding the genera Lactobacillus, Ruminococcaceae and Bifidobacteria.
CONCLUSION. Based on the results of the literature review, we obtained contradictory data on GM composition in patients with CHC and NAFLD. This may be due to the size of samples, heterogeneity of initial data during the selection of patients in the study. The relationship between the composition of microbiota and persistent inflammatory process, expressed liver fibrosis is observed. GM reflects not only functional disorders in chronic liver diseases of various etiologies, but can also serve as a diagnostic indicator of their progression.
