Antidiabetic effect of polyphenols from brown alga Ecklonia kurome in genetically diabetic KK-Ay mice

Context: Prevalence of diabetes mellitus type 2 (DM-II) is increasing in Japan. Brown alga Ecklonia kurome Okamura (Laminariaceae) (kurome in Japanese) is rich in phlorotannins, a kind of polyphenol. Phlorotannins have been reported to possess various bioactivities; however, few studies have reported its effect on DM-II. Objective: The present study was conducted to investigate the antidiabetic effect of polyphenols from E. kurome (KPP) on KK-A(y) mice, the animal model for human DM-II. Materials and methods: Inhibitory activities of KPP against alpha-amylase and alpha-glucosidase in vitro, and effects on oral carbohydrate tolerance test in vivo were investigated. KK-A(y) mice were fed with 0.1% KPP containing water for 5 weeks. A glucose tolerance test was conducted at week 4 of the 5-week period. At the end of experiment, blood biochemical parameters, including blood glucose, insulin, glycoalbumin, and fructosamine were determined. Furthermore, the kidneys and pancreatic islets were histologically examined. Results: KPP showed inhibitory activities on carbohydrate-hydrolyzing enzymes and decreased postprandial blood glucose levels. The body weight gain and blood glucose levels in the KPP group were lower than the control group during the experimental period. KPP improved glucose tolerance and decreased the fasting blood glucose and insulin levels, fructosamine and glycoalbumin levels compared with the control group. Furthermore, KPP contracted the pancreatic islet size and decreased renal mesangial matrix in KK-A(y) mice. Discussion and conclusion: These results suggest that KPP is effective against DM-II and might provide a source of therapeutic agents for DM-II.