296: Investigation of the Impact of Dietary Fiber and Calcium on Gastrointestinal Mucus Permeability Using a Dynamic Mucus Model

Introduction

Gastrointestinal (GI) mucus is the first barrier against exogenous substances. Its dynamic natures, including the diminishment by chyme flow and altered physicochemical properties during nutrient penetration, affect nutrient digestion and absorption; however, this role is often overlooked. Soluble dietary fiber and calcium are crucial for healthy digestion function, yet their effects on nutrient absorption through mucus modulation are underexplored.

Methods

This study investigated the impact of dietary fiber and calcium on mucus permeability using a dynamic mucus model, with D-glucose and phycocyanin as examples of small and large nutrient molecules. The model comprised three layers: a top layer with simulated intestinal fluid flow (1 mL/min), a middle layer with ex vivo porcine intestinal mucus, and a bottom layer with circulation of simulated mucosal fluid (1 mL/min). To evaluate the impact of the dietary fiber and calcium: Alginate, cellulose nanocrystals (CNC), and CaCl₂ were added into the simulated intestinal fluid for top layer circulation. The control group without these additions was conducted for comparison. The mucus permeability coefficient was calculated using Fick's first law, based on steady-state time and nutrient concentration in the bottom layer.

Results

10 mM CaCl₂ significantly decreased phycocyanin (large molecule) permeability, likely due to enhanced mucous gel network, consistent with mucus rheological findings of increased viscosity and elasticity after calcium addition. However, the impact of dietary calcium on small molecule (glucose) permeability was not significant. Additionally, 2% alginate and 7% CNC significantly decreased glucose permeability from 5.3 × 10⁻⁶ cm/s to 3.4 × 10⁻⁶ cm/s and 1.2 × 10⁻⁶ cm/s, respectively, likely due to interactions with mucus and an increased unstirred water layer. Additionally, 3% and 7% CNC significantly increased the mucus thinginess from 0.9 mm to 1.9 and 2.0 mm. Rheological studies showed that alginate and CNC improved mucus viscosity, indicating that these interactions promoted a denser mucus structure that hindered nutrient penetration.

Significance

The dynamic mucus model developed was useful for studying the dynamic interaction between mucus and luminal contents. Dietary fiber and calcium reduced the nutrients' mucous permeability, suggesting their potential application in weight management and formulation of functional foods.

Authors: Zijin Qin, Fanbin Kong