Various kinds of N-substituted valiolamine derivatives, including compounds 23a, 24a, and 34a, which are structurally analogous to the key pseudodisaccharides (25a and 26a) of naturally occurring oligosaccharide alpha-D-glucosidase inhibitors, have been synthesized and estimated by the measure of inhibitory activity against porcine sucrase and maltase. The N-substituted valiolamine derivatives evaluated in this study have been found to be more potent than the corresponding N-substituted valienamine derivatives as well as the parent valiolamine. It is noteworthy that even simple N-substituted valiolamine derivatives such as N-[2-hydroxy-1-(hydroxymethyl)ethyl]-, N-[(1R,2R)-2-hydroxycyclohexyl]-, and N-[(R)-(-)-beta-hydroxyphenethyl]valiolamine (6, 8a, and 9a) have the stronger alpha-D-glucosidase inhibitory activity against porcine intestinal maltase and sucrase than naturally occurring oligosaccharide alpha-D-glucosidase inhibitors.
The fa-gene was transferred from the Zucker rat (13 M strain) to the Wistar Kyoto (WKY) rat. The survey, performed at the 10th generation of backcrossing, showed that Wistar fatty rats (fa/fa), a congenic strain of WKY, developed obesity and obesity-related features, such as hyperinsulinemia and hyperlipemia, in the same manner as Zucker fatty rats. Males, but not females, showed hyperglycemia, glucosuria, and polyuria as early as 8 wk of age. Tolerance and insulin response to oral glucose were decreased with advancing age in males. The diabetic changes appeared to be caused by an interaction between predisposition to develop diabetes in the WKY rat and fa-induced obesity. This is because WKY rats were found to be less sensitive to insulin than Zucker rats by both the glucose tolerance test and the steady-state blood glucose method which estimates overall insulin sensitivity.
A new disaccharidase inhibitor, AO-128, showed 190-3900-fold more potent inhibition of purified rat small intestine sucrase-isomaltase (S-1) complex and 23-33-fold more potent inhibition of semipurified porcine small intestine disaccharidases than acarbose. AO-128 suppressed elevation of the blood glucose concentration after oral sucrose, maltose, and starch, but not after oral glucose, fructose, and lactose. The chronic addition of AO-128 to the diet produced antiobesity and antidiabetic actions in obese and/or diabetic animals. Undesirable side effects, such as diarrhea and soft feces, were observed only for the first 5-7 d and suppression of intestinal disaccharidase activities was observed even at the end of the experiment, suggesting that the suppressive or delaying effect of AO-128 on elevation of the postprandial blood glucose concentrations is involved in reduction in body weight gain and prevention and/or amelioration of the diabetic state. Thus, AO-128 is useful as an adjunct to the dietary management of obesity and diabetes.
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