Fenofibrate and extended-release niacin improve the endothelial protective effects of HDL in patients with metabolic syndrome

Background: Fibrates and niacin are at present the most effective therapies to increase plasma levels of high density lipoprotein-cholesterol (HDL-C); to date, limited data are available on their effects on HDL protective functions. Methods and results: Within a multicenter, randomized, open-label, cross-over study, 37 patients with metabolic syndrome received 6 weeks' treatment with fenofibrate or extended-release niacin (ER niacin), with a 4 weeks' wash-out period. HDL ability to preserve endothelial cell homeostasis was assessed by incubating cultured endothelial cells with HDL isolated from patients at baseline and after each treatment. HDL isolated from patients at baseline were as effective as control HDL in inhibiting vascular cell adhesion molecule-1 (VCAM-1) expression, but less efficient in promoting endothelial cell nitric oxide (NO) release. Both fenofibrate and ER niacin increased HDL ability to inhibit TNFα-induced VCAM-1 expression (+. 7% and +. 11%, respectively). Fenofibrate and ER niacin also improved the impaired HDL ability to induce the expression of endothelial nitric oxide synthase and NO production (+. 10% and +. 8%, respectively). Interestingly, HDL isolated after treatment showed an ability to promote endothelial NO release similar to HDL isolated from controls. No differences were observed between the two drugs. With both drugs, HDL function was improved irrespective of baseline HDL-C levels. Conclusion: Treatment with fenofibrate or ER niacin in patients with metabolic syndrome not only increased HDL-C levels but also improved the endothelial protective effects of HDL.