Association Between Zonulin and Lipopolysaccharide-binding Protein as Biomarkers of Intestinal Permeability and Hepatic Steatosis in Patients With Ulcerative Colitis

Abstract: This cross-sectional, exploratory proof-of-concept study aims to investigate whether serum zonulin and lipopolysaccharide-binding protein (LBP) levels, biomarkers of intestinal permeability, are associated with the severity of hepatic steatosis and fibrosis in adult patients with ulcerative colitis (UC) and metabolic dysfunction-associated steatotic liver disease (MASLD). The study was intentionally designed as a proof-of-concept investigation; therefore, a relatively small sample size (approximately 100 participants, with 82 required according to the power analysis) was selected a priori to explore potential associations and generate hypotheses for future research.

Hypothesis: Among patients with UC and MASLD, higher serum concentrations of zonulin and/or LBP are expected to be associated with increased odds of significant liver fibrosis, defined as liver stiffness measurement (LSM) >8 kPa. Similar associations are anticipated for hepatic steatosis, defined by a controlled attenuation parameter (CAP) ≥274 dB/m, and for advanced fibrosis (LSM >12 kPa). Because the distribution of LSM and CAP values in this population is unknown, additional multiple linear regression analyses will evaluate these outcomes as continuous variables to explore the strength and direction of associations across their full spectrum.

Study Population and Eligibility Criteria: Approximately 100 adult patients with UC in both clinical remission (partial Mayo score <2) and biochemical remission (fecal calprotectin <100 μg/g) will be recruited from a single tertiary-care center. Inclusion will require reliable transient elastography measurements obtained using FibroScan.

Major exclusion criteria include excessive alcohol consumption; previous liver diseases of autoimmune, viral, alcoholic, or hereditary/metabolic etiology; decompensated cirrhosis; celiac disease; type 1 diabetes mellitus; hepatitis B or C infection; previous malignancy; marked transaminase elevation (>5 times the upper limit of normal); hepatic congestion; biliary obstruction; portal vein thrombosis; Budd-Chiari syndrome; pregnancy; age below 18 years; inability or refusal to provide informed consent; and ulcerative colitis limited to the rectum (ulcerative proctitis).

A sample size of 82 participants provides 80% statistical power to detect a clinically relevant difference in MASLD prevalence between groups with high and low biomarker levels. To account for missing data and potential exclusions, approximately 100 participants will be enrolled.