The Divergent Effect of Coffee Polyphenol and Hydroxyhydroquinone Ingestion on Postprandial Hyperglycemia and Vascular Function in Healthy Men

Abstract

Epidemiological studies indicate that coffee consumption reduces the risk of diabetes and cardiovascular diseases. However, interventional studies have failed to clarify the beneficial effects of coffee consumption on blood glucose and the cardiovascular system. We previously demonstrated that 1) coffee polyphenol (CPP) consumption improved postprandial hyperglycemia and vascular endothelial function in humans, and 2) improvement in vascular endothelial function due to CPP was impaired by hydroxyhydroquinone (HHQ) in rats. This study aimed to elucidate the impact of concomitant consumption of HHQ, a prooxidant in coffee, on the beneficial effects of CPP consumption on postprandial blood glucose and vascular function in humans. We conducted a single-blind, randomized, placebo-controlled, crossover intervention study in healthy male adults, measuring blood and urine parameters and flow-mediated dilation after ingestion of a meal with CPP with or without HHQ up to 180 min postprandially. Ten healthy male adults consumed a test meal with either a placebo, control (CPP with HHQ), or active (CPP without HHQ) beverage. The CPP-including active (without HHQ) beverage significantly blunted the postprandial increase in blood glucose and decline in flow-mediated dilation but not the control (with HHQ) beverage, compared with the placebo beverage. The active beverage reduced blood oxidative stress biomarker response compared with the control beverage. In conclusion, these results demonstrate that concomitant ingestion of HHQ, which increases oxidative stress, interferes with the improvement of postprandial blood glucose and vascular endothelial function after CPP consumption in healthy humans.