Effects of Antidiabetic Medications on the Postprandial State in Prediabetes

It is a paradox that medical efforts to control blood glucose in type 2 diabetes mellitus have not decreased the risk of cardiovascular disease. Postprandial lipid concentrations are a strong predictor of cardiovascular risk, independent of traditional cardiovascular risk factors. The new classes of antidiabetic medications - GLP-1 agonists and DPP-IV inhibitors - affect lipid as well as glucose metabolism. This study will investigate the efficacy of these medications in reducing postprandial hyperlipidemia, disrupting the concurrent proinflammatory free fatty acid signaling, and ameliorating endothelial dysfunction in individuals with prediabetes. This will consist of a single center, randomized, crossover, placebo-controlled double-blinded prospective trial involving three study arms representing the aforementioned medications: exenatide (GLP-1 agonist), saxagliptin (DPP-IV inhibitor), and placebo (control arm). Each subject will participate in each of the three arms, which are three separate, daylong outpatient studies. For each study arm, subjects will eat a standardized atherogenic high-fat test lunch. Venous blood draws and measurements of forearm blood flow will be done prior to the meal and periodically during a 6-hour period after the meal. Forearm blood flow measurements will assess for changes in endothelial function. The blood will be analyzed for multiple markers of hyperlipidemia and free fatty acid signaling. After completing the three randomized study visits, subjects are invited to participate in an optional, nonrandomized extension study. For the extension study, subjects will take exenatide ER (extended-release exenatide) weekly for total of six weeks. Then subjects return to eat a standardized atherogenic high-fat test lunch. Venous blood draws and measurements of forearm blood flow will be done prior to the meal and periodically during a 4-hour period after the meal, for the same analyses described before. The results will provide new insights into the anti-inflammatory effects of multiple antidiabetic medications via the mechanisms of postprandial hyperlipidemia, free fatty acid signaling, and endothelial function in prediabetic individuals.