Increasing plasma fatty acids elevates F2-isoprostanes in humans: implications for the cardiovascular risk factor cluster Milos P. Stojiljkovic a {, Heno F. Lopes a , Da Zhang a , Jason D. Morrow b , Theodore L. Goodfriend c and Brent M. Egan a Objective To determine whether raised concentrations of non-esterified fatty acids (NEFAs) may contribute to the cardiovascular risk factor cluster by increasing oxidative stress in vivo. Design and Methods Plasma and urine F2-isoprostanes, biomarkers of oxidative stress, were measured after an overnight fast and during a 4 h infusion of Intralipid and heparin to increase NEFAs in 10 obese hypertensive patients with and 12 healthy normotensive individuals without evidence of insulin resistance. A time-control group of nine healthy normotensive individuals received saline and heparin. Results Plasma F2-isoprostanes increased more in obese hypertensive individuals than in lean normotensive individuals after 2 h (14.9 6 2.8 ng/ml compared with 4.6 6 2.8 ng/ml; P < 0.05) but not after 4 h (10.3 6 2.5 ng/ ml compared with 8.1 6 4.1 ng/ml; NS) of the Intralipid and heparin infusion. When obese and lean individuals were combined, plasma ( 9.1 6 2.5 ng/ml; P < 0.05) and urine ( 0.7 6 0.3 ng/mg creatinine; P < 0.05) F2-isoprostanes increased by about 20% after 4 h of Intralipid and heparin, whereas plasma F2-isoprostanes decreased by approximately 20% (29.7 6 4.5 ng/ml; P < 0.05) after 4 h of saline and heparin. When individuals from both infusions were combined, the correlation between changes in plasma NEFAs and F2-isoprostanes after 4 h persisted after controlling for changes in triglyceride concentrations (partial r 0.49; P < 0.01), whereas the correlation between changes in triglycerides and F2-isoprostanes did not persist after controlling for changes in NEFA concentrations (partial r 0.33, NS). Conclusions The findings indicate that an acute increase in plasma lipids increases the concentration of F2- isoprostanes, biomarkers of oxidative stress, especially in obese hypertensive individuals. The observations raise the possibility that increased concentrations of NEFAs contribute to the cardiovascular risk factor cluster through oxidative-stress-sensitive mechanisms. J Hypertens 20:1215–1221 & 2002 Lippincott Williams & Wilkins. Journal of Hypertension 2002, 20:1215–1221 Keywords: insulin resistance, fatty acids, F2-isoprostanes, oxidative stress, blood pressure a Departments of Pharmacology and Medicine, Medical University of South Carolina, Charleston, South Carolina, b Vanderbilt University School of Medicine, Nashville, Tennessee and c William S. Middleton Veterans’ Memorial Hospital, University of Wisconsin, Madison, Wisconsin, USA. {Present address: Department of Pharmacology and Toxicology, Military Medical Academy, Belgrade, FR Yugoslavia. Note: Some data in this report have been published previously (Am J Physiol 2001; 280:R1674–R1679). Sponsorship: This research was supported by grants from the National Institutes of Health HL58794, HL04290, HL55782, GM42056, DK48831, DK26657, CA77839, and General Clinical Research Center RR-01070. H.F.L. was supported by FAPESP and Fundac ¸a ˜ o EJ Zerbini (InCor), Sa ˜ o Paulo, Brazil. J.D.M. is the recipient of a Burroughs Wellcome Fund Clinical Scientist Award in Translational Research. Correspondence and requests for reprints to Brent M. Egan MD, Division of Clinical Pharmacology, MUSC, 96 Jonathan Lucas Street, Suite 826, PO Box 250623, Charleston, SC 29425, USA. Tel: +1 843 792 1715; fax: +1 843 792 0816; e-mail: eganbm@musc.edu Received 19 September 2001 Revised 21 January 2002 Accepted 6 February 2002 Introduction The mechanisms by which insulin resistance is linked to increased blood pressure remain incompletely de- fined. Although attention has focused on resistance to insulin-mediated glucose disposal, non-esterified fatty acids (NEFAs) are also resistant to insulin action and may contribute to several facets of the cluster [1–3]. Systemic blood pressure increases when plasma NEFAs are increased experimentally [4,5]. In the Paris Prospec- tive Study, normotensive men with greater plasma NEFA concentrations were more likely to develop hypertension than were men with lower NEFA concen- trations [6]. NEFAs may increase blood pressure and contribute to hypertension by impairing nitric oxide synthase activity [7] and endothelium-dependent vasodilatation [8] while augmenting vascular Æ 1 -adrenergic reactivity [9]. Some NEFAs also increase the production of reactive oxygen species in leukocytes and vascular smooth muscle cells Original article 1215 0263-6352 & 2002 Lippincott Williams & Wilkins