Coadministration of Atorvastatin Prevents Nitroglycerin-Induced Endothelial Dysfunction and Nitrate Tolerance in Healthy Humans

ObjectivesWe aimed to assess whether concurrent administration of atorvastatin would modify the development of tolerance and endothelial dysfunction associated with sustained nitroglycerin (GTN) therapy in humans.BackgroundAnimal studies have demonstrated that administration of 3-hydroxy-3 methylglutaryl coenzyme A reductase inhibitors can protect against GTN-induced endothelial dysfunction and tolerance, likely through an antioxidant mechanism.MethodsThirty-six healthy male volunteers were randomized to receive continuous transdermal GTN (0.6 mg/h) and placebo, atorvastatin (80 mg/day) alone, or continuous transdermal GTN (0.6 mg/h) with concurrent atorvastatin (80 mg/day), all for 7 days. On the second visit, forearm blood flow was measured with venous-occlusion strain gauge plethysmography in response to incremental infusions of acetylcholine (7.5, 15, and 30 μg/min). Acetylcholine infusions were coinfused first with saline, and repeated during the coinfusion of vitamin C (24 mg/min). Blood pressure responses to sublingual GTN (400 μg) were assessed on both visits.ResultsAcetylcholine responses in the GTN plus placebo group were significantly attenuated versus those in the GTN plus atorvastatin and atorvastatin groups (p < 0.01). Coinfusion of vitamin C completely restored acetylcholine responses in the GTN plus placebo group (p < 0.01 vs. saline coinfusion), but caused no change in either the atorvastatin or the GTN plus atorvastatin groups. Blood pressure responses to sublingual GTN did not significantly change between visits in subjects receiving GTN plus atorvastatin and atorvastatin alone, but were significantly blunted in the GTN plus placebo group (p < 0.05).ConclusionsThe present findings demonstrate, for the first time in humans, that atorvastatin prevents both GTN-induced endothelial dysfunction and nitrate tolerance, likely by counteracting the GTN-induced increase in oxidative stress

Assessment of Endothelial Function in Humans and the Endothelial-protective Effects of 3-hydroxy-3-methylglutaryl coenzyme A Reductase Inhibitors

The endothelium plays an essential role in the regulation of vascular homeostasis and a state of endothelial dysfunction, which develops in the presence of cardiovascular risk factors, may contribute to the development and progression of cardiovascular disease. As such, the measurement of endothelial function, beyond being an experimental tool, may serve as an important tool to complement current risk assessment algorithms in the identification of high-risk patients. Flow-mediated dilation (FMD) is a non-invasive measure of peripheral conduit artery endothelial function that holds great promise. Presently, FMD suffers from methodological heterogeneity and a poor understanding of the various biological components involved in eliciting the dilatory response to a given shear stimulus. We compared both traditional and alternative methods of arterial diameter characterization with regards to their repeatability, nitric oxide-dependency, and their sensitivity in distinguishing between normal and dysfunctional endothelial responses. Our findings emphasize the importance of continuous arterial diameter measurement and suggest that the time to peak FMD is not a useful adjunctive measure of the FMD response. Given that endothelial dysfunction may be of clinical importance, strategies to correct it or prevent it from occurring may be of benefit. The 3-hydroxy-3-methylglutaryl coenzyme A inhibitors are agents that have demonstrated marked cholesterol-independent, endothelial-protective effects. We investigated the ability of rosuvastatin and atorvastatin to protect against endothelial dysfunction associated with ischemia and reperfusion (IR) injury, and chronic nitrate therapy. Using the FMD technique, we demonstrated, for the first time in humans, that acute rosuvastatin administration protects against IR-induced conduit artery endothelial dysfunction. Additionally, we demonstrated that this effect likely occurred by a cyclooxygenase-2-dependent mechanism, which may provide mechanistic insight into the observed cardio-toxicity with cyclooxygenase-2 inhibitors. In contrast, we observed that this endothelial-protective effect was lost upon sustained rosuvastatin administration, which may have important implications regarding the generation of sustained cardioprotective phenotypes. Finally, we demonstrated that atorvastatin co-administration prevented the development of tolerance and endothelial dysfunction associated with continuous transdermal nitroglycerin therapy in humans, likely through an antioxidant mechanism. Future studies are needed in disease patients to determine whether the concept of nitrate tolerance needs reconsideration in the presence of vascular-protective agents.Ph

Effects of estradiol on measurements of conduit artery endothelial function after ischemia and reperfusion in premenopausal women

In premenopausal women ovarian steroids are felt to play a role in the prevention of cardiovascular disease. We aimed to assess whether menstrual cycle variations in estrogen can modify the response to ischemia/reperfusion (IR) injury in humans. In an investigator-blind crossover study in 10 healthy, pre-menopausal women with regular menstrual cycles. They had flow-mediated dilatation (FMD) measured by ultrasound in the radial artery before and after IR (15 minutes of brachial artery ischemia, 15 minutes of reperfusion) during both the early and late follicular phases of the menstrual cycle. The order of these visits was not randomized. IR significantly blunted FMD in the early follicular phase (pre-IR: 7.1±1.0%; post-IR: 3.6±1.0%, P=0.01) when estradiol levels were low (148.4±19.8 pmol/L). Conversely, FMD was preserved after IR during the late follicular phase (pre-IR: 7.2±0.9%; post-IR: 7.0±0.8%, P=NS, P=0.03 compared to early follicular) when estradiol levels were high (825.7±85.8 pmol/L, PThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author