Summary As bioactive ingredients of functional foods, dietary fiber and wheat albumin (WA) are known to suppress hyperglycemia in patients with type 2 diabetes mellitus. The combined effects of these bioactive ingredients were examined using an animal model of type 2 diabetes mellitus. First, oral starch tolerance tests (OSTTs) with the simultaneous intake of a dietary fiber mixture (DF) and WA were performed as an acute study. Male GotoKakizaki rats received a soluble starch solution [700 mg/kg body weight (bw)] containing DF and/or WA (each 300 mg/kg bw). In these OSTTs, the combined intake of DF and WA suppressed hyperglycemia much more effectively than each separate intake. Second, in a chronic intake study, diets containing DF and/or WA were administered to male Zucker diabetic fatty rats over 84 d. The combined effects of DF and WA were not observed in glycosylated hemoglobin concentration levels or fasting blood glucose levels, but appeared as an improvement in liver lipid contents. Variations in the liver lipid contents were similarly reflected in those of the plasma lipid concentrations. In conclusion, this study found that the simultaneous intake of bioactive DF and WA improved the postprandial hyperglycemia and the chronic lipid metabolism disorders in rat models of type 2 diabetes mellitus. Key Words type 2 diabetes mellitus, dietary fiber, wheat albumin, combined effect, lipid metabolism disorderIn type 2 diabetes mellitus, postprandial hyperglycemia caused by a lack of prompt insulin secretion is closely associated with insulin resistance and thus hyperglycemia, which leads to a lipid metabolism disorder that results in arteriosclerosis (1-3). Some dietary fiber, such as water-soluble dietary fiber, physically retards the absorption of glucide and suppresses postprandial hyperglycemia (4). In Japan, therefore, the dietary fibers extracted mostly from various plants are used as functional ingredients of foods. On the other hand, wheat albumin (WA), based on the action of its principle component 0.19-albumin (termed by its electrophoretic mobility), inhibits mammalian amylase (5, 6), delays glucide digestion in vivo, and suppresses postprandial hyperglycemia (7). Thus, WA is widely distributed as a bioactive ingredient of food for specified health uses (FOSHU) in the market. Various consumers, intentionally or unintentionally take simultaneously more than two of these functional ingredients in foods. However, the combined effects of dietary fiber and WA on the postprandial hyperglycemia and also on chronic glucide and lipid metabolism are unknown. Here the simultaneous intake of these ingredients was examined using a rat model of type 2 diabetes mellitus.
MATERIALS AND METHODSApproval and feeding conditions. All rats were maintained under standard conditions of 2362˚C and 55615% humidity with a 12 h/12 h light/dark cycle. The rats were individually housed in clean cages with free access to water and basal diet (CLEA rodent diet CE-2; CLEA Japan, Inc., Tokyo, Japan) ad libitum during the acclimation p...