Effects of flavonol-rich green tea (Camellia sinensis L. cv. Sofu) on blood glucose and insulin levels in diabetic mice

Findings from epidemiological studies and intervention trials seem to suggest that green tea consumption prevents type 2 diabetes. The anti-diabetic effects are most commonly attributed to the polyphenolic fraction of green tea. Green teas contain catechins; however, they also contain flavonols and their glycosides. Here, we compared between a common and a flavonol-rich tea cultivar, with regard to the anti-diabetic effects, in a type 2 diabetes mouse model using NSY (Nagoya-ShibataYasuda) mice. Water or a tea infusion, made from a common (control tea, TeaC) or a flavonol-rich (flavonol-rich tea, TeaF) cultivar, was given to the NSY mice as the solo drinking fluid from 4 until 13 weeks of age. At 12 weeks of age, fasting plasma insulin concentration was significantly lower in mice drinking TeaF than in mice drinking water. Relative to water, TeaC had no significant effect on plasma insulin levels. Thus, there were significant differences in efficacy with regard to maintenance of glucose homeostasis between a common and a flavonol-rich tea cultivars; therefore, tea flavonols are likely to have benefits with regard to preventing diabetes.