Effect of quercetin on traits of the metabolic syndrome, endothelial function and inflammation in men with different APOE isoforms

Abstract Background and aims The polyphenol quercetin may prevent cardiovascular diseases due to its vasorelaxant and anti-oxidative properties. We investigated the effects of quercetin on risk factors of atherosclerosis, biomarkers of inflammation and oxidative stress, depending on the apolipoprotein E ( APOE ) genotype. Methods and results In a double-blind crossover study 49 healthy male subjects with APOE genotype 3 / 3 ( n  = 19), 3 / 4 ( n  = 22) and 4 / 4 ( n  = 8) consumed 150 mg/d quercetin or placebo for 8 weeks each, intermitted by a three-week washout phase. After each intervention, endothelial function, anthropometry, metabolic and inflammatory parameters were measured in the fasting and postprandial state following a standardized lipid-rich meal. Endothelial function was not changed. In all subjects combined, quercetin significantly decreased waist circumference ( P  = 0.004) and postprandial systolic blood pressure ( P  = 0.044). Postprandial triacylglycerol concentrations were significantly decreased and HDL-cholesterol concentrations increased after quercetin as compared to placebo consumption ( P  = 0.025). Quercetin also moderately increased levels of TNFα ( P  = 0.024). There was a significant gene–diet interaction for waist circumference and for body mass index (BMI). Conclusions Quercetin supplementation improved some risk factors of cardiovascular disease, yet exerted slightly pro-inflammatory effects. Genotype-dependent effects were seen only on waist circumference and BMI.