Abstract 938: Circulating biomarkers of gut barrier function: Correlates and responses to calcium supplementation among sporadic colorectal adenoma patients in a dose-response randomized controlled trial

Gut barrier dysfunction contributes to several gastrointestinal disorders, including inflammatory bowel diseases and colorectal cancer, but factors associated with intestinal hyperpermeability have rarely been assessed in human populations, and there is very limited clinical trial evidence on whether gut barrier function may be modified by dietary factors. To address these gaps, we 1) evaluated factors associated with baseline circulating biomarkers of gut barrier function, and 2) tested the effect of calcium on these biomarkers over a 4-month treatment period among patients with previous colorectal adenoma in a randomized, double-blinded, placebo-controlled clinical trial (n = 193). Patients were randomized to placebo (n = 66), 1.0 g calcium (n = 64), or 2.0 g calcium (n = 63) daily. Circulating levels of anti-flagellin and anti-lipopolysaccharide (LPS) immunoglobulins (Igs) as markers of colonic hyperpermeability were measured at baseline and at 4-month follow-up via ELISA. At baseline, mean levels of anti-flagellin and anti-LPS IgA but not IgG were higher among men and those with a larger body mass index (BMI), a larger waist circumference, and higher levels of plasma C-reactive protein. Mean anti-flagellin IgG levels were higher among those with higher proinflammatory cytokine scores. We did not observe effects of calcium on anti-flagellin or anti-LPS Igs: the relative change of a combined permeability score (defined as the sum of the optical densities of all biomarkers) from baseline to follow-up was 0.07 (95% confidence interval [CI] -0.13, 0.27) for each treatment group relative to the placebo group (p-values ≥ 0.5). Our results suggest that 1) men and those with a larger BMI or waist circumference may have greater gut permeability, 2) markers of gut permeability and systemic inflammation may be directly associated with one another, and 3) supplemental calcium administered for 4 months may not modify circulating levels of biomarkers of gut barrier function. Citation Format: Baiyu Yang, Roberd M. Bostick, Andrew T. Gewirtz, Hao Quang Tran, Veronika Fedirko. Circulating biomarkers of gut barrier function: Correlates and responses to calcium supplementation among sporadic colorectal adenoma patients in a dose-response randomized controlled trial. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 938. doi:10.1158/1538-7445.AM2015-938