Zonulin — effective biomarker for the diagnosis of intestinal lesions in patients with nonalcoholic fatty liver disease in COVID‑19
Authors: Stehura A. V. , Sirchak Y. S. 
Published: October 2024

The SARS‑CoV‑2 virus mainly attacks the respiratory system, but can also affect several organs, in particular, causing gastrointestinal symptoms such as vomiting, diarrhea or abdominal pain in the early stages of the disease. Intestinal dysfunction leads to a change in intestinal microorganisms and an increase in the content of inflammatory cytokines. Liver dysfunction is also relatively common in patients with coronavirus disease 2019 (COVID19).
Objective — to investigate the efficacy of zonulin in determining intestinal damage in patients with nonalcoholic fatty liver disease with COVID‑19.
Materials and methods. The study included 76 patients with non‑alcoholic fatty liver disease (NAFLD) who had complaints indicating intestinal disorders during the outpatient stage of follow‑up after ­COVID‑19. From the anamnesis, it was found that all examined patients had a confirmed diagnosis of infection with SARS‑CoV‑2 virus. All patients had a mostly mild course of COVID‑19, which did not require hospitalization. Patients with NAFLD were divided into two groups depending on defecation violation: group I — 36 patients who, after an acute respiratory infection caused by the SARS‑CoV‑2 virus, developed periodic diarrhea (on average, in (38.7±5.2) days after a negative PCR result for SARS‑CoV‑2 virus); group II — 40 patients with constipation, which began to bother on average in (86.9±7.4) days after a negative PCR result. The control group included 20 practically healthy individuals. The level of zonulin was determined in blood serum and faeces by enzyme‑linked immunosorbent assay. Patients underwent faecal culture to assess the quantitative and qualitative composition of the colon microflora.
Results. During the anthropometric examination, overweight and first‑degree obesity were detected more frequently in patients of both groups: overweight was diagnosed most frequently in patients of group I (38.9%) and first‑degree obesity in patients of group II (35.0%). The microbiological examination of faeces in both groups of patients revealed a decrease in the number of bifidus and lactobacilli, as well as Enterococcus and E. coli with normal enzymatic properties. In group I patients, Citrobacter and Staphylococcus were statistically significantly (p <0.05) more often detected in increased concentrations in faeces, whereas in group II patients Enterobacter, Klebsiella and Clostridium were detected (p <0.05). Significant changes were found in the analysis of zonulin levels in both serum and faeces in patients with NAFLD after COVID‑19. Serum zonulin levels in patients of group I increased 6.5‑fold, and in patients of group II—8.6‑fold (p <0.001). An increase in the concentration of zonulin in the faeces was also detected — by 7.5 and 9.7 times, respectively (p <0.001). A correlation was established between the level of zonulin in both blood serum and faeces and a decrease in the number of bifidus and lactobacilli in faeces in patients of both groups. Also, a strong correlation was found between the number of Enterobacter, Klebsiella and Clostridium and a medium intensity correlation between the number of Staphylococcus in the faeces in patients of group ІІ. In patients of group І, a correlation was found between the number of Staphylococcus and Citrobacter. The level of zonulin (both in blood serum and faeces) directly depended on changes in body mass index in the patients we examined, namely, overweight in patients of group І and obesity of the first degree in patients of group ІІ.
Conclusions. In patients with NAFLD after COVID19, changes in the quantitative and qualitative composition of the colon microflora were found in the intestinal lesions, including a decrease in the number of bifidobacteria and lactobacilli, as well as an increase in the content of Staphylococcus and Citrobacter in the faeces in patients with predominant diarrhoea and Enterobacter, Klebsiella and Clostridium in patients with predominant constipation. An increase in the level of zonulin in the blood serum and faeces in patients with NAFLD after ­COVID‑19 was detected. A more pronounced deviation from the norm was found in patients of group ІІ (with complaints of constipation). A direct correlation was established between the level of zonulin in the blood serum and faeces and changes in the quantitative and qualitative composition of the colon microflora, as well as an increase in body mass index in patients with NAFLD after ­COVID‑19.