Grant Abstract: Novel action of grape skin components on postprandial hyperglycemia

Grant Number: 5R01AT007566-05
PI Name: Zhou
Project Title: Novel action of grape skin components on postprandial hyperglycemia

Abstract: Diabetes has become a major public health problem and is emerging as a pandemic. There is a strong need for developing novel complementary and alternative strategies for controlling diabetes. Our long-term goal is to develop a safe and effective nutritional intervention to support diabetes prevention and treatment. The objective of this application is to identify novel unique ?-glucosidase-inhibiting components in GSE, to elucidate the role of these components in lowering postprandial hyperglycemia, and to further assess the safety and efficacy of the GSE components in preclinical models for preventing and treating type-2 diabetes. GSE is a nutritional antioxidant supplement used frequently by the American public. We have recently found that that GSE intake exerts a novel inhibitory activity on postprandial hyperglycemia in diabetic mice, which is related to its specific inhibition of intestinal ?-glucosidases. Furthermore, we showed that dietary supplementation of GSE significantly reduced blood glucose in diet-induced obese mice independent of its effects on food intake, weight gain, or antioxidant activity. More recently, we demonstrated that oral intake of GSE significantly reduced postprandial blood glucose in humans. We therefore hypothesize that the novel inhibitory action of GSE on postprandial hyperglycemia is primarily mediated by specific inhibition of intestinal ?-glucosidases, and GSE and its active components could be developed and used as a safe and targeted nutritional intervention to support diabetes prevention and treatment. To test our hypothesis, we will pursue three aims: Aim 1 is to identify active ?-glucosidase-inhibiting components in GSE and further determine their inhibitory mechanisms. We will employ an activity-driven approach to isolate and identify active components in GSE. We will then determine their specificity, inhibitory mode, and possible additive/synergistic effects on specific ?- glucosidases. Aim 2 is to determine mechanisms underlying the novel inhibitory action of GSE on postprandial hyperglycemia. We will use a type-2 diabetic model to determine whether active ?-glucosidase-inhibiting components are responsible for lowering postprandial hyperglycemia; and whether these components primarily act on ?-glucosidases to ameliorate postprandial hyperglycemia. Aim 3 is to determine the efficacy and safety of GSE components in preclinical models for preventing and treating type-2 diabetes. We will perform three studies: Study 1 is an acute intake study to determine the most effective GSE preparation for treating postprandial hyperglycemia in db/db mice; Study 2 is to determine whether dietary supplementation of our GSE preparation can prevent the onset of diet-induced diabetes in diet-induced obese mice; and Study 3 is to determine whether our GSE preparation, following the onset of diabetes, can improve glycemic control in db/db mice. This transitional study will provide important preclinical data regarding the antidiabetic mechanisms, biological efficacy, and safety of GSE that should facilitate eventual translation into future clinical studies to assess GSE and its components as a safe, low cost, and evidence-based nutritional intervention for diabetes.

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