Vitamin C, diclophenac, and l-arginine protect endothelium-dependent vasodilation against elevated circulating fatty acid levels in humans

Abstract 

An acute elevation of circulating non-esterified fatty acids (NEFAs) has previously been shown to impair endothelium-dependent vasodilation (EDV). In this study, we investigated if local administration of vitamin C (n=8, 18 mg/min), l-arginine (n=8, 12.5 mg/min), or the cyclooxygenase (COX) inhibitor diclophenac (n=8, 0.5 mg/min) can counteract the endothelial dysfunction seen during infusion of Intralipid® plus heparin (n=10). EDV and endothelium-independent vasodilation (EIDV) were studied in the forearm after local administration of methacholine chloride (Mch; 2 and 4 μg/min) and sodium nitroprusside (SNP; 5 and 10 μg/min). Forearm blood flow (FBF) was determined with venous occlusion plethysmography. Intralipid® and heparin increased circulating NEFA levels sevenfold and impaired EDV (P<0.001 vs baseline). Concomitant administration of l-arginine or diclophenac abolished the NEFA-induced impairment in EDV. Concomitant vitamin C administration actually improved EDV (P<0.05 vs baseline). NEFA elevation increased EIDV (P<0.01), but this effect was not significant after l-arginine or diclophenac infusions. In conclusion, an acute elevation of circulating NEFAs led to impaired EDV. Administration of l-arginine, vitamin C or COX inhibition abolished this effect, suggesting that NEFAs might interact with endothelial vasodilatory function through multiple mechanisms.

Keywords:  Nitric oxide, Cyclooxygenase, Lipid peroxidation, Triglyceride and endothelium, Vasodilation, Fatty acid

Abbreviations:  ADMA, asymmetrical dimethylarginine, COX, cyclooxygenase, EDV, endothelium-dependent vasodilation, EIDV, endothelium-independent vasodilation, FBF, forearm blood flow, Mch, methacholine chloride, NEFA, non-esterified fatty acid, NO, nitric oxide, SNP, sodium nitroprusside, VSMC, vascular smooth muscle cell