Endothelial dysfunction induced by postprandial lipemia is neutralized by addition of proteins to the fatty meal

Background Postprandial lipemia is known to reduce endothelium-dependent flow-mediated vasodilation (FMD). Because postprandial lipemia can be acutely mitigated when proteins are added to the fatty meal, we investigated whether this mitigation could neutralize the lipemia-induced endothelial dysfunction. Design Sixteen healthy students (aged 19–23, eight males and eight females) received three different test meals at intervals of 1 week between successive tests. Each meal contained whipping cream alone or whipping cream together with either caseinate or soy protein. The whipping cream contained 33% fat, and 3 ml (= 1 g fat) was given per kg body weight. The proteins added were either 50 g sodium caseinate or 50 g soy protein. FMD was assessed by two-dimensional ultrasonography of the brachial artery in the fasting state and 1, 2, 3, 4, 5, 6, 7, and 8 h after the fatty meal. Blood was withdrawn at the same time-points from the other arm. Triglycerides, free fatty acids, and insulin were determined using routine methods, and both l-arginine and asymmetric dimethylarginine (ADMA) were determined by LC-MS. Results Postprandial lipemia reduced FMD, the reduction reaching a maximum of 58% after 3 h. This impairment of endothelial function was not observed when either of the test proteins had been added to the fatty meal (p < 0.01 for caseinate and p < 0.001 for soy protein). The effects of the protein addition were decreases in triglycerides and free fatty acids, increased insulin concentrations at all time-points, and an increased arginine/ADMA ratio between 1 and 5 h after the meal, particularly in the case of the soy protein. Conclusion We suggest that the neutralization of the lipemia-induced endothelial dysfunction is caused by direct and indirect effects of the proteins insulinotropy and, secondly, by an increased supply of l-arginine.