SMALL INTESTINAL BACTERIAL OVERGROWTH IN THE INTESTINE AND MICROBIOME ALTERATIONS AS A RISK FACTOR FOR LIPID METABOLISM DISORDERS IN PATIENTS WITH NONALCOHOLIC FATTY LIVER DISEASE
Authors: Kvit Kh. B. , Kharchenko N. V. 
Published: January 2025

Dysbiosis, or microbial imbalance, can lead to diseases like obesity, insulin resistance, lipid metabolism disorders, and non-alcoholic fatty liver disease (NAFLD). NAFLD, a leading chronic liver disease globally associated with metabolic syndrome, highlights the significance of gut health. Small intestinal bacterial overgrowth (SIBO) is an example of microbiota imbalance, characterized by excessive bacterial growth in the upper intestine, causing nutrient absorption disruption and bile acid imbalance.
Recent studies show a strong association between SIBO and lipid metabolic disorders in NAFLD patients, where gut-liver interactions enable bacterial toxins and products to impact liver function through a weakened gut barrier. Current studies show gut microbiota alterations significantly influence NAFLD and related metabolic disorders. Key bacterial groups like Firmicutes, Bacteroidetes, and Actinobacteria, and the Firmicutes/Bacteroidetes index are of particular interest. Patients with NAFLD show elevated Firmicutes and lower Bacteroidetes. An increased Firmicutes/Bacteroidetes index is a marker of NAFLD, correlating with obesity and hypercholesterolemia progression.
This study aims to assess gut microbiome composition and SIBO prevalence in NAFLD patients, determining their role as risk factors in disease progression.
A total of 342 patients with dyslipidemia from St. Panteleimon Hospital, Truskavetskurort LLC, and Intersono Medical Center were included, aged 21-69 (mean 45.03±0.67). The inclusion criteria were confirmed hyperlipidemia by clinical lab tests and family history. 150 control patients without dyslipidemia (mean age 45.98±0.43) were also included, matched in age, gender, and comorbidities. NAFLD diagnosis was based on ultrasound or liver steatometry, with stages (S1-S3) established by parenchymal echogenicity and hepato-renal index. Diagnostic criteria included ultrasound, steatometry, and cardiometabolic risk factors (waist circumference, blood pressure, triglyceride, HDL levels, fasting glucose, HOMA-IR, and C-reactive protein). Exclusion criteria included significant alcohol consumption, hepatitis B/C, autoimmune liver diseases, cirrhosis, and prior antibiotic use. All patients underwent biochemical tests, stool sample DNA extraction, and qPCR for Firmicutes, Actinobacteria, and Bacteroidetes. SIBO was assessed using hydrogen breath tests, with a positive result being hydrogen levels above 20 ppm.
Gut microbiome analysis showed significant differences between dyslipidemia patients and controls, with lower Bacteroidetes and higher Other bacteria. SIBO was found in 53.4% of dyslipidemia and 52.2% of NAFLD patients, but only 34% of controls. The Firmicutes/Bacteroidetes ratio increased in NAFLD patients and correlated with higher triglycerides and TNF-α levels. Actinobacteria levels correlated with C-reactive protein and TNF-α, indicating that Firmicutes growth influences lipid metabolism disruption.
This study confirms gut microbiome’s critical role in dyslipidemia and NAFLD, with SIBO prevalent in NAFLD, particularly in steatosis and type IIb dyslipidemia. Key findings show the increased Firmicutes/Bacteroidetes ratio and Firmicutes’ role in lipid metabolism disorders, highlighting SIBO's impact on NAFLD progression. Further research is needed to determine microbiome changes as predictive markers for NAFLD and dyslipidemia and explore SIBO treatment as a potential treatment strategy.