Brief communicationHypoglycemic effect of hot-water extract of adzuki (Vigna angularis) in spontaneously diabetic KK-Ay mice
Introduction
Recently, there has been an increase in the prevalence of type 2 diabetes because of the promotion of high-grade meals, rapidly changing lifestyles, and hereditary elements. Consequently, diabetes is becoming a serious health problem worldwide. The percentage of patients with type 2 diabetes is highest among 50 to 60 y olds.
Adzuki beans (Vigna angularis) are an ingredient known well in East Asia. In Japan, adzuki beans are used mainly for the production of confectioneries such as youkan, manjuu, amanatto, etc. In the case of food processing, heat treatment of adzuki beans results in a large amount of hot-water extracts (HWEs), which are usually discarded. However, HWEs are known to contain various polyphenols. In recent research, many extracts and natural products, such as polyphenols, have been reported to improve the symptoms of diabetes [1], [2], [3]. We also previously reported that HWEs of adzuki were fractionated using HP-20 column chromatography, and its 40% ethanol fraction (EtEx.40) was found to suppress the elevation of blood glucose and plasma insulin levels after oral administration in mice and rats with streptozotocin-induced diabetes [4]. The present study examined the antidiabetic effects of EtEx.40 in spontaneously diabetic KK-Ay mice, which are a model for type 2 diabetes.
Section snippets
Preparation of test materials
Adzuki beans harvested in Tokachi, Hokkaido, Japan, were boiled and the HWEs of adzuki (15 L) obtained. We concentrated the HWE to 100 times by a plate heat exchanger (Izumi Food Machinery Co. Ltd., Hyogo, Japan). Thirty milliliters of concentrated HWE was subjected to open-column chromatography on a Diaion HP-20 (Mitsubishi Chemical Co. Ltd., Tokyo, Japan, column size 5 φ × 300 mm, resin wet volume 400 g) and eluted stepwise with 5 L of distilled water and 40% ethanol. The respective fractions
Ingestion of EtEx.40 suppresses development of type 2 diabetes
The parameters of growth and food consumption in the first experiment are presented in Figure 1A and Table 2. There were no differences in body weights and food intakes of all groups. However, water intake was inclined to increase until the final day of the experiment in both groups, but that of the mice fed the EtEx.40 (Ex) diet was lower than that of the cellulose (CEL) group during the feeding period (Table 2). As shown in Figures 1B-1 and 1B-2, blood glucose levels of the diabetic mice fed
Discussion
We demonstrated for the first time that EtEx.40 suppresses the development of spontaneous diabetes in KK-Ay mice. In addition, this phenomenon was observed after only short-term administration of EtEx.40.
In mice fed a CEL diet, the blood glucose levels, serum insulin levels, water consumption, and urinary glucose concentrations gradually increased with increasing body weight and food intake. These observations were almost the same as those reported by Odaka et al. [10]. In this study, there
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