Effects of in vitro simulated digestion on the hypoglycaemic capacity of wheat bran-soluble dietary fibre.

Wheat bran-soluble dietary fibre (WB-SDF) is known for its hypoglycaemic properties and its potential to control postprandial blood glucose levels in individuals with hyperglycaemia. However, the digestive process may alter its glucose-lowering potential. This study investigated the effects of in vitro simulated digestion on the hypoglycaemic efficacy of WB-SDF. The hypoglycaemic effects of WB-SDF were determined by examining its glucose-binding capacity, glucose dialysis retardation index and ability to inhibit glucose uptake and transport in Caco-2 cells. Structural changes after digestion were analysed via polysaccharide conformation analysis, microstructure observation and particle size measurements to evaluate their impacts on hypoglycaemic efficacy. Results indicate that WB-SDF and digested wheat bran-dietary fibre significantly decreased glucose adsorption and α-glucosidase activity compared with the control group in Caco-2 cells. However, simulated digestion resulted in a relatively smaller reduction in α-glucosidase activity compared with the WB-SDF treatment group. The massive loss of surface laminar structure, reduction of -OH groups and partial glycosidic bond breakage in digested wheat bran-dietary fibre after digestion led to reduced glucose adsorption capacity and glucose dialysis retardation index. Moreover, the reduction in particle size after digestion enhanced the inhibition of glucose transport-related gene expression in Caco-2 cells. Thus, although digestion weakens the glucose adsorption of WB-SDF, it improves its ability to inhibit glucose transport, highlighting the intricate interplay between structural modifications and hypoglycaemic efficacy.