Effect of Physicochemical Properties of Carboxymethyl Cellulose on Diffusion of Glucose

Soluble dietary fibers (SDF) are known to reduce the post-prandial plasma glucose levels. However, the detailed mechanisms of this reduced glucose release in the human gut still remain unclear. The aim of our study was to systematically investigate the effect of different types of SDF on glucose release in an in vitro model as a prerequisite for the selection of fibers suitable for application in humans. Three types of carboxymethyl cellulose (CMC) were used to investigate the correlations between fiber concentration, molecular weight (M(W)), and viscosity on diffusion of glucose using a side-by-side system. CMC solutions below the coil overlap (c*) influenced the glucose diffusivity only marginally, whereas at concentrations above c* the diffusion of glucose was significantly decreased. Solutions of lower M(W) exhibited a lower viscosity with lower glucose diffusion compared to solutions with higher M(W) CMC, attributed to the higher density of the solutions. All CMC solutions showed a systematic positive deviation from Stokes-Einstein behavior indicating a greater rise in viscosity than reduction in diffusion. Therefore, our results pave the way for a new approach for assessing glucose diffusion in solutions comprising dietary fibers and may contribute to further elucidating the mechanisms of post-prandial plasma glucose level reduction.