[Effects of free fatty acids on nitric oxide synthase activity and mRNA expression in endothelial cell of SD rat aorta]

Abstract

Objective: To test the hypothesis that free fatty acids (FFA) induced endothelial dysfunction might relate with the inhibitions of endothelial nitric oxide synthase (eNOS) mRNA expression and activity, and to explore the possible pathogenic mechanisms.

Methods: Male SD rats underwent 6 h infusion in two groups: Normal control (NC, n=20) infused with saline; FFA group (n=20) infused with 20% intralipid + heparin. Blood samples were collected at the end of infusion so as to measure the concentrations of FFA, nitrogen oxides (NOx), reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH) and high sensitivity C-reactive protein (hs-CRP). The eNOS activity and mRNA expression were analyzed with aortic endothelial homogenate.

Results: In FFA group, the plasma FFA concentration was higher [(1146.4+/-336.6) micromol/L vs (345.5+/-113.6) micromol/L, P<0.01] while the NOx level was lower [(14.3+/-1.9) micromol/L vs (19.3+/-2.9) micromol/L, P<0.01]. The serum concentrations of ROS, MDA, hs-CRP were elevated in FFA group when compared with controls [ROS: (864.3+/-135.4) mmol/L vs (452.4+/-90.5) mmol/L, P<0.05; MDA: (8.05+/-1.69) nmol/L vs (5.53+/-0.43) noml/L, P<0. 05; hs-CRP: (0.35+/-0.04) mg/L vs (0.21+/-0.03) mg/L, P<0.053] while GSH level was significantly declined in FFA group [(153.1+/-55.9) mg/L vs (171.9+/-60.5) mg/L, P<0.05]. Both the eNOS mRNA level and eNOS activity in endothelial homogenate were decreased in FFA group [eNOS mRNA/beta-actin: 1.42 vs 2.12, P<0.01; eNOS activity: (1.15+/-0.42) pmol/(min x mg) vs (2.43+/-0.56) pmol/(min x mg), P<0.01].

Conclusion: The eNOS mRNA expression and activity may be inhibited by elevated circulating FFAs concentration, of which mechanisms may be related to the increased oxidative stress and moderate inflammation.