Study On The Effect Of Oat β-glucan On Starch Digestion, Glucose Adsorption And Blood Sugar

Oat β-glucan(OBG) consists of linear cell wall homopolysaccharides of d-glucopyranose that are arranged as blocks of consecutive(1→4)-linked β-d-glucose residues separated by single(1→3)-linkages. There have been some publications that report the hypoglycemic effect of oat β-glucan. However, few studies have focused on the effect of OBG on the starch digestion, glucose adsorption in the small intestine and hypoglycemic effect of non-obese diabetes.Therefore, the objective of this study was to investigate the influence mechanism of OBG on starch digestibility in vitro and non-obese diabetic model mice. This study provides valuable information for future research on the hypoglycaemic properties of OBG and hypoglycemic food.The effects of baking, boiling, steaming, and microwave treatment on the molecular weight of OBG were investigated, the results showed that the change of the molecular weight of OBG was affected by food processing and the OBGs degraded by steaming, boiling, microwave treatment, and baking in order of degradation degree from high to low.Oat β-glucan has a strong effect in delaying the digestion of starch, which is related to its solution viscosity. As molecular weight and concentration of OBG increased, the effect on delaying starch digestion was better: the glycemic index reduced, slowly digestible starch increased. When the concentration of undegraded oat β-glucan ≥ 30 mg/m L, resistant starch fragment increased to 70.21%.When the concentration of OBG was below 7.5 mg/m L, the inhibition rate of OBG on porcine pancreatic α-amylase inhibition was below 15.87%; As the concentration of OBG increased to 10 mg/m L or more, the inhibition rate of α-amylase was also increasing rapidly due to the rapid increase in solution viscosity; When the concentration of OBG was 30 mg/m L, the inhibition rate was up to 54.33%. The way of fluorescence quenching between porcine α-amylase and OBG is static quenching. Circular dichroism(CD) spectrum showed that α-helix increased and β-fold reduced when the concentration of OBG decreased.The result of CD illustrates spectrum that OBG was able to changed the secondary structure of α-amylase. Molecular docking simulations(Autodock Vina) revealed that: OBG was able to lie in the hydrophobic pocket of porcine α-amylase in form of the minimum energy conformations.ASP 300, TRP 58 and TRP 59 was the potential binding sites of the α-amylase.This study examined how the molecular weight(MW) and concentration of OBG affects in vitro glucose diffusion. The effect of OBG on in vitro glucose transportation and Na+/K+-ATPase activity in the everted small intestines of normal rats was also examined. All of the OBG samples could adsorb glucose molecules, hinder glucose diffusion and decrease in vitro starch digestion. Furthermore, when the molecular weights and concentrations of OBG were higher, their effects on glucose diffusion and glucose adsorption were more evident. The transport of glucose via glucose transporters and Na+/K+-ATPase activity in the rat small intestinal mucosa were significantly lower in the OBG group than in the group without OBG. However, as the concentration of OBG in the solution increased, the Na+/K+-ATPase activity in the small intestine increased due to stronger gastrointestinal motility. OBG could significantly inhibit intestinal disaccharidase activity. The greatest effect was observed in high-MW OBG, with an inhibition of 23.15%(sucrase activity) and 10.40%(maltase activity). The smallest effect was seen in low-MW OBG, with an inhibition of 2.47%(sucrase activity) and 3.94%(maltase activity).The study also investigates how OBG control blood sugar levels and improve insulin sensitivity in streptozotocin-nicotinamide-induced non-obese diabetic mice. After oral gavage administration of different concentration and molecular weight of oat β-glucan for 28 days, the body weight, fasting blood glucose, serum insulin, hepatic antioxidant enzyme, hepatic glycogen, glucose kinase and G-6-phosphatase activity of diabetic mice were measured in the corresponding time. In comparison with negative model group, OBG, especially medium or high doses of high-MW oat β-glucan, has a strong hypoglycemic effect on non-obese diabetic mice, which may be related to high viscosity of solution, improvement in hepatogenic glycometabolism, increasing hepatic antioxidant enzyme activity, increasing insulin secretion, and decline in insulin resistance.