Acute elevations of medium- and long-chain fatty acid have different impacts on endothelium-dependent vasodilation in humans.

It has previously been shown that acute elevation of long-chain fatty acids (LCFA) impairs endothelium-dependent vasodilation (EDV) in humans. In this study, we tested the hypothesis that an elevation of both medium-chain fatty acids (MCFA) and LCFA affects the endothelium differently from LCFA elevation alone. Ten healthy volunteers received an intravenous infusion of Structolipid (structured TG, MCFA/LCFA ratio 1:1) and heparin for 2 h, while another 10 subjects received an infusion of Intralipid (LCFA only) and heparin. EDV and endothelium-independent vasodilation (EIDV) were studied in the forearm after local administration of methacholine chloride (2 and 4 microg/min) and sodium nitroprusside (5 and 10 microg/min). Forearm blood flow was determined by venous occlusion plethysmography. Intralipid and heparin increased circulating FA levels from 0.2 +/- 0.1 to 1.4 +/- 0.5 mmol/L (P < 0.001) and reduced EDV by 20% (P < 0.01). Although Structolipid and heparin increased circulating FA levels to a similar extent (from 0.4 +/- 0.1 to 1.8 +/- 0.4 mmol/L after 2 h), EDV was not significantly changed. EIDV increased slightly during both interventions (P < 0.05). In conclusion, an acute elevation of LCFA attenuated EDV, whereas an elevation of both MCFA and LCFA did not influence EDV. Thus, FA composition seems to be of importance for EDV in healthy humans.