Suppressive effect of ascophyllan HS on postprandial blood sugar level through the inhibition of α-glucosidase and stimulation of glucagon-like peptide-1 (GLP-1) secretion

Abstract A sulfated polysaccharide ascophyllan inhibited α- glucosidasein a concentration dependent manner, and >90% activity was inhibited at 1.0 mg/mL. The inhibitory activity was much higher than that of acarbose. No significant inhibitory effect of ascophyllan on α-amylase was observed up to 10.0 mg/mL. Ascophyllan HS, a commercially available ascophyllan preparation showed even higher inhibitory effect on α- glucosidasethan ascophyllan. Interestingly, ascophyllan and ascophyllan HS induced the secretion of glucagon-like peptide-1(GLP-1) from human intestinal NCI-H716 cell line in a concentration dependent manner (10–100 ng/mL). The oral glucose tolerance tests revealed that after continuous 8-week ingestionof ascophyllan HS at 100 mg/day, the glucose area under the curve values of the ascophyllan HS ingestedgroup were significantly lower than placebo ingestedgroup. Serum glycosylated hemoglobin (HbA1c) level in ascophyllan HS ingestedgroup tended to decrease after 8-week ingestion, whereas no significant change was observed in placebo ingestedgroup. This is the first report indicating that ascophyllan can induce the secretion of GLP-1 from human intestinal cell line (NCI-H716), besides the potent inhibitory effect on α- glucosidase. Furthermore, clinical trial suggested that ascophyllan HS may be a practically applicable blood glucose controlling agent in humans.