Main phylotypes of gut microbiota and their connection with the degree of obesity and the stage of liver fibrosis in patients with non-alcoholic fatty liver disease
Authors: Chereliuk N. I. , Gridnyev O. E. 
Published: March 2023

Objective — to analyse the state of the relative composition of gut microbiota (GM) at the level of the main phylotypes in patients with non‑alcoholic fatty liver disease (NAFLD) with different body mass index and degree of liver fibrosis.

Materials and methods. The study involved 105 people. The main group consisted of 85 patients with NAFLD with obesity of 36.50 [32.00; 40.60] kg/m2, who were divided into three subgroups depending on the degree of obesity. Subgroup I included 38 patients who were diagnosed with the first degree of obesity. Subgroup II included 23 patients diagnosed with the second degree. Subgroup III consisted of 24 patients with the third degree of obesity. The control group consisted of 20 practically healthy individuals 23.50 [21.35; 25.78] kg/m2. Determination of the degree of fibrosis according to METAVIR scale by measuring the average stiffness of the liver parenchyma in the mode of shear wave elastography. The composition of GM at the level of the main phylotypes was studied by identifying total bacterial DNA and DNA of Bacteroidetes, Firmicutes, as well as Firmicutes/Bacteroidetes ratio by quantitative real‑time polymerase chain reaction using universal primers for the 16S rRNA gene and taxon‑specific primers. Statistical processing was performed using Statistica 13.1.

Results. In the comorbid course of NAFLD and the first degree of obesity, 47.37 % of patients had no signs of fibrosis and the same number were diagnosed with F1 fibrosis, two patients (5.26 %) had F2 fibrosis, and F3 fibrosis was not diagnosed in any patient. In subgroup II, two‑thirds actually had liver fibrosis, but F3 fibrosis was not detected in any patient. In patients of subgroup III, only 20.83 % of patients had no signs of liver fibrosis, while 37.50 % were diagnosed with F1 fibrosis, 33.33 % with F2 fibrosis, and 8.33 % with F3 fibrosis. In other words, the most severe F3 fibrosis was observed in patients with the third degree of obesity. In patients of the subgroup I, the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes was found compared to the control group: 3.07 times (p < 0.01) in the absence of fibrosis and already in the presence of the 1st stage of fibrosis this indicator increased to 3.21 (p < 0.01), while in the 2nd stage it increased almost 4 times (p < 0.01). However, when comparing this indicator in the first subgroup between the stages of fibrosis, no statistically significant deviations were found (p > 0.05), i.e., the changes were only tendency‑like. In patients of the subgroup II, the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes was also found compared to the control group: 3.25 times (p < 0.01) in the absence of fibrosis, 3.81 times (p < 0.01) in the 1st stage of fibrosis, 5.08 times (p < 0.01) in the 2nd stage of fibrosis, which was the maximum value. Also, the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes by 1.57 times (p < 0.01) was found at F2 compared to F0, while between other stages of fibrosis, the changes were trending and had no statistically significant differences. In patients of subgroup III in the absence of fibrosis, the relative ratio of Firmicutes/Bacteroidetes also exceeded that of the control group and progressively increased with increasing fibrosis. It should be noted that the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes between F2 and F0 by 1.28 times (p < 0.01) and between F3 and F0 by 1.35 times (p < 0.01) was found.

Conclusions. When analysing the relative composition of GM in the studied subgroups depending on the stage of fibrosis, it was found that the increase in the stage of liver fibrosis is associated with certain disorders of Firmicutes/Bacteroidetes ratio, the relative content of Firmicutes and Bacteroidetes. Thus, in the subgroup I, the relative composition of GM significantly differed only from the control group, while in patients of the subgroup II with F2 fibrosis there was the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes by more than one and a half times compared to patients without signs of fibrosis. At the same time, in patients of the subgroup III with fibrosis, not only F2, but also F3, the statistically significant increase in the relative ratio of Firmicutes/Bacteroidetes was found.