Original Article J. Clin. Biochem. Nutr., 45, 202–206, September 2009 DtjJ01KOchoC098bryeu.18Bino3grS20N0tn1i-on9a605,cal-40iJl3o/e08aj6Atfcp96ybCratfniloci.0nrle9iFc-ra3el6eBhRioacbdhiceiamtlsiRsterIysneanrtcdehNsJuatptiraintnioanl α-Glucosidase and Suppresses -Psicose In i the Glycemic Response after Ingestion of Carbohydrates in Rats Tatsuhiro Matsuo* and Ken Izumori Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kita-gun, Kagawa 761-0795, Japan ;?92384R?05aec0cc9eeivpetedd31.46.240.200909 Received 3 April, 2009; Accepted 16 April, 2009 CopySriugmhtm©a2r0y0? DJ C-pBsNicose is one of the rare sugars present in small quantities in commercial carbohydrates and agricultural products. In this study, we investigated the effects of D-psicose on the activities of α-amylases and α-glucosidases in vitro, and evaluated the effects of D- psicose on the in vivo postprandial glycemic response using rats. In the in vitro study, D-psicose potently inhibited the intestinal sucrase and maltase, however, slightly inhibited the intestinal and salivary α-amylase activities. Male Wistar rats (6 months old) were administrated 2 g/kg of sucrose, maltose or soluble starch together with 0.2 g/kg of D-psicose or D-fructose. The D-psicose significantly inhibited the increment of plasma glucose concentration induced by sucrose or maltose. The starch-induced glycemic response tended to be suppressed by D- psicose, however the suppression was not significant. These results suggest that D-psicose inhibits intestinal sucrase and maltase activities and suppresses the plasma glucose increase the normally occurs after sucrose and maltose ingestion. Thus, D-psicose may be useful in preventing postprandial hyperglycemia in diabetic patients when foods containing sucrose and maltose are ingested. Key Words: D-psicose, sucrase, maltase, plasma glucose, rat Introduction D-psicose (D-ribo-2-hexulose), a C-3 epimer of D-fructose, is a “rare sugar” present in small quantities in commercial mixtures of D-glucose and D-fructose obtained from the hydrolysis of sucrose or isomerization of D-glucose [1]. Because of the very small amounts of D-psicose in natural products, few studies have examined D-psicose metabolism in animals. Recently, we developed a new method for producing D-psicose enzymatically on a large scale [2], making it possible to conduct such studies. We have since demonstrated that D-psicose is a sweet carbohydrate that provides no energy to growing rats [3–5] and that it causes little toxic effect in rats [6–7]. Thus, D-psicose may be useful as a sweetener for obese people seeking to lose weight. *To whom correspondence should be addressed. Tel/Fax: +81-87-891-3082 E-mail: matsuo@ag.kagawa-u.ac.jp 202 On the other hand, it has been proven that strict glycemic control is associated with a low incidence of microvascular and macrovascular complications in diabetes [8], and a delay or inhibition of carbohydrate digestion could be helpful for avoiding postprandial hyperglycemia in diabetic patients [9, 10]. Specific inhibitors of α-glucosidases have shown a definite therapeutic value in suppressing the postprandial glycemic increase by delaying carbohydrate digestion [9–11]. Acarbose [9–13] and L-arabinose [14–17] are known to be competitive and uncompetitive inhibitors of the intestinal α-glucosidases, ie, sucrase, and maltase. It has also been shown that pancreatic amylase is inhibited by acarbose [13]. Although the majority of dietary carbohydrates are starch, daily ingestion of sucrose is large in many advanced countries, however, agents that inhibit neither starch nor sucrose digestion have been used. Previously, we reported that a diet containing 5% D- psicose increased liver glycogen content in rats fed a high-fat or a low-fat diet for 16 weeks [18]. We also observed that D-psicose significantly suppressed the increment of plasma