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(Circulation. 1997;95:1126-1131.)
© 1997 American Heart Association, Inc.

Articles

Simvastatin, an HMG–Coenzyme A Reductase Inhibitor, Improves Endothelial Function Within 1 Month

Gerard O'Driscoll, MB, BCh, BAO; Danny Green, PhD; Roger R. Taylor, MBBS, FRACP

the Department of Cardiology and Medicine, Royal Perth (Australia) Hospital and the Department of Human Movement, University of Western Australia, Perth (D.G.).

Correspondence to Gerard O'Driscoll, Department of Cardiology, Royal Perth Hospital, Wellington St, Perth, Western Australia 6000.

	Abstract

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Background Cholesterol-lowering therapy can improve cardiovascular morbidity and mortality in patients with atherosclerosis. Although the mechanisms responsible are unclear, these benefits precede macroscopic changes in the vasculature. Emerging evidence that improvement in endothelial function may occur requires substantiation; in particular, it is unclear how early any such improvement would be detectable after initiation of therapy.

Methods and Results This randomized, double-blind, placebo-controlled crossover study evaluated the effect of simvastatin (20 mg daily for 4 weeks) on endothelium-dependent and endothelium-independent vasodilation and on the response to the inhibitor of nitric oxide synthesis, N^G-monomethyl-L-arginine (L-NMMA), in the forearm vasculature of subjects with moderate elevation of total serum cholesterol (6.0 to 10.0 mmol/L) by use of strain-gauge plethysmography. Studies were repeated after 3 more months of open therapy. When the results are expressed as percentage changes in flow in the infused arm relative to the noninfused arm, the vasodilator response to acetylcholine was significantly increased after 4 weeks of treatment with simvastatin (P<.0005), and this improvement was further enhanced after 3 months (P<.005). Concurrently, simvastatin augmented the vasoconstrictor response to L-NMMA, an effect that was maintained at 3 months (P<.0005). The response to the endothelium-independent vasodilator sodium nitroprusside was unaltered.

Conclusions These observations indicate that within 1 month of treatment with simvastatin, both the stimulated and basal nitric oxide dilator functions of the endothelium are augmented, and the benefits of this HMG–coenzyme A reductase inhibitor persist with continued therapy.

Key Words: blood flow • cholesterol • endothelium • hypercholesterolemia

	Introduction

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Hypercholesterolemia is a risk factor for cardiovascular disease, particularly ischemic heart disease, and several recent studies have indicated that cholesterol reduction is associated with decreased cardiovascular morbidity and mortality in patients with established disease^{1 2} and in subjects with mild hypercholesterolemia.³ In other studies, clinical improvement has been documented in response to lipid-lowering therapy despite relatively minor angiographic changes, suggesting that benefits are not causally related only to regression of obstructive disease.^{4 5} It has been proposed that enhanced endothelial function might contribute to the improvement in clinical status.^{6 7 8}

Hypercholesterolemia is associated with impaired endothelial function,^{9 10 11 12} and animal^{13 14} and human^{7 15 16} studies indicate that endothelial function improves with lowering of serum cholesterol. In human large coronary arteries, NO-dependent, ACh-stimulated vasoconstriction was attenuated after 6 months.^{6 15} Although a recent report indicated that lipid lowering increased forearm vasodilation in response to serotonin after 3 months of treatment,¹⁶ a previous study found that despite significant reduction of serum cholesterol after 12 days of therapy, no difference in coronary vascular function was evident between patients treated with lovastatin and those given placebo.⁷ Thus, it remains unclear how early improvement in endothelial function might occur in response to lipid-lowering therapy.

In this study, we documented an effect on both basal NO-mediated dilatation and ACh-stimulated dilatation, largely NO dependent, in the forearm vasculature after 4 weeks of therapy with the HMG-CoA reductase inhibitor simvastatin.

	Methods

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Subjects
Subjects were eligible for entry if they had a total serum cholesterol of 6.0 to 10.0 mmol/L and were not receiving cholesterol-lowering therapy. All undertook a screening program consisting of a medical history and examination and full hematologic and biochemical profiles, including measurement of serum electrolytes, liver function, uric acid, creatine phosphokinase, and serum lipids. The following were excluded: cigarette smokers; premenopausal women; those with renal or hepatic impairment, hypertension, or diabetes mellitus; and patients taking vitamin supplements or vasoactive drugs such as nitrates, calcium channel antagonists, ß-blockers, or ACE inhibitors. The study protocol was approved by Royal Perth Hospital Ethics Committee, and subjects gave written informed consent.

Ten subjects (8 men, 2 women; age, 50±2 years [mean±SE]) with total serum cholesterol concentrations ranging from 6.2 to 7.5 mmol/L were enrolled. Medical histories and examinations were unremarkable except for 2 men, 1 of whom had undergone coronary artery bypass surgery and another who had surgically treated peripheral vascular disease several years earlier. Both were asymptomatic. Apart from 1 patient who was on aspirin 150 mg daily, no subject was taking medication before or for the duration of the experimental period.

Study Design
The effect of 4 weeks of simvastatin therapy was studied by use of a randomized, double-blind, placebo-controlled crossover protocol that was followed by 3 months of open therapy. Subjects were randomized in equal numbers to receive simvastatin 20 mg daily (Zocor, Merck Sharp & Dohme) or a similarly packaged placebo. After 4 weeks, each subject returned for a study of forearm vascular function. Then, after crossover, they were restudied 4 weeks later. Of the 10 subjects, 2 withdrew at this time, and the remainder continued on simvastatin 20 mg daily for 3 more months and returned for a final study. Subjects refrained from drinking alcohol or caffeine-containing beverages 12 hours before the procedure. At each visit, the biochemical and hematologic parameters were repeated. There were no adverse side effects.

Vascular Function Protocol
Investigations were conducted in a quiet, climate-controlled laboratory (24°C; relative humidity, 55%) with subjects lying supine and both forearms resting above heart level. A 20-gauge arterial cannula (Arrow) was introduced into the brachial artery of the nondominant arm under local anesthesia with <2 mL of 1% lidocaine (Astra Pharmaceuticals) to transduce pressure and infuse drugs or physiological saline. FBF (mL/100 mL forearm tissue per minute) was measured simultaneously in both arms by gallium/indium strain-gauge (SG24, Medasonics) plethysmography. Each wrist was connected to a flow-regulated source of compressed air, and the arm cuffs were connected to a rapid-inflation device (E20, D.E. Hokanson). Output from the strain gauges passed through an amplifier (SPG 16, Medasonics) and was sampled by an on-line microcomputer at 75 Hz before being displayed on a monitor in real time. A software program coordinated the acquisition, storage, and display of data, as well as inflation and deflation of the arm cuffs, ensuring that blood flow measures were synchronized with cuff inflation during recording periods. Intra-arterial pressure was measured continuously (Transpac, Abbot Laboratories) throughout the study. Drug infusions were administered with a constant-rate infusion pump (IVAC 770, IVAC Corp).

Baseline measurements started at least 20 minutes after cannulation of the brachial artery, when FBF had stabilized. Blood flow measurements were taken by inflating the wrist cuffs to 220 mm Hg to exclude the hands from the circulation and rapidly inflating the upper arm cuffs to 45 mm Hg for 10 of every 15 seconds throughout the baseline and drug infusion periods. Output from the strain gauges was stored, and the average of the last five flow measurements from each period was used for analysis. Between infusions, the cuffs were deflated, allowing at least 15 minutes for FBF to recover before further baseline measures.

All solutions were prepared aseptically from sterile stock solutions or ampoules immediately before infusion into the brachial artery. ACh (Miochol, Johnson & Johnson) was infused at 10, 20, and 40 µg/min, each for 3 minutes, to produce a cumulative dose-response curve. This was followed by SNP (David Bull Laboratories) infusion at 2, 4, and 8 µg/min, each for 3 minutes, and then L-NMMA (Clinalfa) at 2, 4, and 8 µmol/min, each for 5 minutes.

Statistical Analysis
Absolute measurements of FBF are subject to error due to the lack of precise standards for calibration purposes, so it is appropriate to describe induced changes relative to baseline measurements. Furthermore, although the low doses of drugs infused in the study produced negligible systemic effects and showed no effect on blood pressure or heart rate, it was necessary to exclude an alteration in overall hemodynamics as a cause of the flow changes seen in the infused forearm. Thus, FBF was measured simultaneously in both arms (although only one arm was infused), and the noninfused arm served as a control. As in previous articles,^{17 18 19 20} FBF in the infused arm is described as a ratio to that in the noninfused arm. Changes in these ratios during ACh, SNP, and L-NMMA infusions are expressed as percentage changes from the baseline immediately preceding each drug administration.

Results are expressed as mean±SE. Two-way ANOVA with repeated measures was used to compare simvastatin and placebo treatments at the three doses. When a significant difference was revealed by this analysis, comparisons at each drug infusion level were made by use of two-tailed t tests. A value of P<.05 was considered significant.

	Results

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Table 1 presents the serum lipid levels, heart rate, and blood pressure data at the time of the placebo study and after 4 weeks and 3 additional months of simvastatin therapy. After 4 weeks of therapy, total serum cholesterol was 19% lower than after placebo (P<.02), LDL cholesterol was 28% lower (P<.05), triglycerides were 21% lower (P=NS), and HDL cholesterol was not significantly different. The 3-month levels were similarly depressed relative to the placebo measures. Other biochemical and hematologic variables were unaltered.

View this table: [in this window] [in a new window]   Table 1. Lipid and Hemodynamic Values at Studies

The baseline FBF values preceding infusion of ACh, SNP, and L-NMMA were not different in either arm, indicating an adequate washout period between drug infusions. The responses to intra-arterial drug infusions in terms of measured absolute FBF (Table 2) were not different between simvastatin and placebo treatment periods. However, such direct comparisons are not the most appropriate. The percentage changes in flow, from the preceding baseline and relative to the noninfused arm, induced by the drug infusions are presented in Table 3 and graphically shown in Fig 1. The vasodilation induced by ACh increased significantly between placebo and 4 weeks (P<.0005, ANOVA) and between placebo and 3 months of simvastatin therapy (P<.0001). The ACh response was also significantly enhanced at 3 months relative to 4 weeks (P<.01). The decrease in FBF induced by L-NMMA was significantly greater after 4 weeks (P<.01) and 3 months (P<.0005) of therapy relative to placebo. The L-NMMA response at 3 months was slightly but not significantly greater than at 4 weeks. The results of paired t tests between placebo and treatment groups at each drug dose are listed in Table 3. Forearm vascular responses in each individual subject improved in individuals while on treatment relative to responses obtained from subjects on placebo (Fig 2). Fig 2 also shows that there was no relation between the percentage increase in blood flow ratio in response to ACh and the decrease in serum cholesterol in individuals at either 4 weeks or 3 months. Similarly, the change in response to L-NMMA was not related to the decrease in cholesterol. Responses to the endothelium-independent vasodilator SNP were not significantly altered by simvastatin therapy.

View this table: [in this window] [in a new window]   Table 2. FBFs in Infused and Noninfused Arms During Simvastatin and Placebo Administration

View this table: [in this window] [in a new window]   Table 3. Percentage Changes From Baseline in the Flow Ratio Induced by Drug Infusions During Simvastatin and Placebo Administration

View larger version (13K): [in this window] [in a new window]   Figure 1. Percentage changes in blood flow ratio (infused/noninfused arm) from the baseline preceding each drug infusion for three dose levels of ACh (A), SNP (B), and L-NMMA (C). Results are expressed as mean±SE. The response to ACh was significantly greater after 4 weeks of therapy (*P<.0005), and there was a significant increase with an additional 3 months of treatment (P<.005). The response to L-NMMA was significantly different after 4 weeks (P<.01), and the subsequent increase was not significant. There was no change in the response to SNP. indicates placebo; , 1 month of simvastatin; and , 3 months of simvastatin.

View larger version (13K): [in this window] [in a new window]   Figure 2. Relative increase in blood flow ratio induced by the highest dose of ACh vs the decrease in serum cholesterol at 4 weeks (top) and 3 months (bottom).

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
This study examined the effects of cholesterol-lowering therapy with the HMG-CoA reductase inhibitor simvastatin on the endothelial function of patients with moderately elevated serum cholesterol. After 4 weeks of treatment with simvastatin (20 mg daily), the vasodilator response to ACh was significantly increased, as was L-NMMA–induced vasoconstriction, indicating that both stimulated and basal vasodilator function of the endothelium were enhanced. By contrast, the response to the endothelium-independent vasodilator SNP was unchanged. Improvement in endothelial function increased with continued administration of simvastatin despite the absence of further reduction in serum cholesterol, and there was no relation between the decrease in cholesterol and the improvement in endothelial function. FBF responses to infused agents were analyzed by reference to the basal flow in the infused and noninfused arms, as in previous studies.^{17 18 19 20} This corrects first for inaccuracy in strain-gauge calibration in the absence of independent absolute flow measurements and second for any other changes occurring in hemodynamics. Examination of measured values of absolute FBF did not reveal the differences between simvastatin and placebo periods that did exist.

It is now known that abnormal function of the endothelium is detectable before the establishment of obvious intimal lesions in patients with risk factors for atherosclerosis.^{21 22 23} A number of studies performed in animals^{12 24} and in the coronary^{9 10 25} and peripheral^{11 26} vascular beds of humans indicate that hypercholesterolemia impairs endothelial function and that the degree of impairment is correlated with serum cholesterol concentration.¹⁵ In addition, cholesterol-lowering interventions can reverse endothelial dysfunction in both the coronary and peripheral vasculature.^{6 7 8 15 16 27} However, these studies were not randomized,^{6 15 27} were performed in patients with established atherosclerosis,^{7 8} or documented improvement after longer periods of treatment (6 months in the coronary circulation^{6 7 15} and 3 months¹⁶ or at least 8 weeks²⁷ in the peripheral circulation). We have demonstrated, after 4 weeks of therapy, improvement in endothelial function in the forearm vascular bed, one seldom prone to atherosclerosis, in previously untreated subjects with hypercholesterolemia using a randomized, double-blind, placebo-controlled crossover design.

The present study is the first to report that vascular changes occur rapidly and to indicate that L-NMMA–mediated vasoconstriction is enhanced after cholesterol-lowering therapy, indicative of an augmented basal effect of NO. The disparity between this finding and that of Stroes et al,¹⁶ who reported unchanged L-NMMA responses after 3 months of combined simvastatin and cholestyramine administration, may be attributable to differences in patient characteristics, study design, or analysis. Stroes et al¹⁶ recruited predominantly premenopausal women suffering from familial hypercholesterolemia who had higher cholesterol levels and had been treated previously with lipid-lowering therapy. The study was not placebo controlled and did not construct a dose-response curve to L-NMMA, although the single dose used was the same as our highest infusion level. That study, however, found a convincing difference in dose-response curves to the endothelium-dependent serotonin according to treatment status, the dose being the calculated plasma concentration of serotonin in the FBF and the response being expressed as the percentage decrease in vascular resistance induced.

Decreased availability of the NO substrate L-arginine or impaired activity of the NO synthase enzyme is not primarily responsible for the impaired endothelial function in hypercholesterolemia,²⁸ and although the effect of NO is impaired, its production is increased.²⁹ Excess endothelial-derived superoxide generation occurs in hypercholesterolemia, and these radicals can inactivate NO,³⁰ augment oxidation of LDL,³¹ and lead to increased endothelial cell membrane damage through generation of peroxynitrite and hydroxyl radicals. Oxidized LDL inhibits the production of NO from L-arginine,³² a finding that may explain the observation in both humans³³ and animals³⁴ that impaired endothelium-dependent relaxation in hypercholesterolemia can be reversed by the provision of excess substrate (L-arginine).^{33 35 36} This benefit of L-arginine is lost after lipid-lowering therapy.¹⁶ Further evidence that the oxidation state is important is provided by the observation that despite a similar reduction in serum cholesterol with lipid-lowering therapy alone or in combination with an antioxidant, endothelium-dependent coronary vasomotion was improved significantly more with the latter regimen.⁸ Subsequently, the coronary vascular response to ACh was found to vary inversely with the in vitro oxidizability of LDL.³⁷ However, Garcia et al³⁸ have shown that superoxide dismutase coinfusion had no effect on ACh responses in hypercholesterolemic subjects, failing to support the theory of extracellular destruction of NO by superoxide anions.

The relative potency of the HMG-CoA reductase inhibitors cannot be assessed from the literature concerning endothelial function, but simvastatin is more potent, perhaps as much as twice as potent, than pravastatin, fluvastatin, and lovastatin in lowering cholesterol. It was interesting that the improvement in endothelial function with simvastatin therapy did not correlate with the decrease in serum cholesterol. This may be due to the relatively small numbers, the relative consistency of the decrease in cholesterol, and the imprecision in measurements. In addition to these factors, a biological lag phase might explain why the improvement between 4 weeks and 3 months was not associated with a further decrease in serum cholesterol. However, there is the possibility that the improvement in endothelial function might not be due solely to a reduction in circulating cholesterol concentration. Administration of fish oils improved endothelial function without altering serum cholesterol.²⁷ Perhaps the effects of HMG-CoA reductase inhibitors, other than lipid lowering per se, such as inhibition of cholesterol synthesis or lowering oxidized LDL could improve endothelial function, whereas other effects such as reduced monocyte chemotaxis or smooth muscle cell migration and proliferation^{39 40} and reduced platelet thrombus formation recently demonstrated in vitro⁴¹ could contribute to cardiovascular benefit. It is also possible that simvastatin may be acting as an antioxidant, which is consistent with the observation that human monocyte-derived macrophages treated with simvastatin showed a dose-dependent decrease in superoxide formation.⁴² Whatever the precise mechanisms responsible for the damaging effect of hypercholesterolemia on the endothelium and for the beneficial effect of HMG-CoA reductase inhibition, the benefit is rapidly induced and continues without a further decrease in cholesterol levels.

	Selected Abbreviations and Acronyms

 

ACh = acetylcholine CoA = coenzyme A FBF = forearm blood flow L-NMMA = NG-monomethyl-L-arginine NO = nitric oxide SNP = sodium nitroprusside

	Acknowledgments

 
This study was supported by Healthway, W.A. We are grateful to Merck, Sharpe and Dohme for the supply of simvastatin.

Received July 15, 1996; revision received October 2, 1996; accepted October 13, 1996.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Scandinavian Simvastatin Survival Study Investigators. Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S). Lancet. 1994;344:1383-1389.[Medline] [Order article via Infotrieve]
   
2. Byington RP, Jukema JW, Salonen JT, Pitt B, Bruschke AV, Hoen H, Furberg CD, Mancini J. Reduction in cardiovascular events during pravastatin therapy. Circulation. 1995;92:2419-2425.[Abstract/Free Full Text]
   
3. Shepherd J, Cobbe S, Ford I, Isles CG, Lorimar AR, MacFarlane P, McKillop JH, Packard CJ. Prevention of coronary heart disease with pravastatin in men with hypercholesterolemia: West of Scotland Coronary Prevention Study. N Engl J Med. 1995;333:1301-1307. See comments.[Abstract/Free Full Text]
   
4. Brown BC, Zhao XQ, Sacco DE, Albers JJ. Lipid-lowering and plaque regression: new insights into prevention of plaque disruption and clinical events in coronary disease. Circulation. 1993;87:1781-1791.[Abstract/Free Full Text]
   
5. Brown G, Albers JJ, Fisher L, Schaefer SM, Lin JT, Kaplan C, Zhao XQ, Bisson BD, Fitzpatrick VF, Dodge HT. Regression of coronary artery disease as a result of intensive lipid lowering therapy in men with high levels of apolipoprotein B. N Engl J Med. 1990;323:1289-1298.[Abstract]
   
6. Egashira K, Hirooka Y, Kai H, Sugimachi M, Suzuki S, Inou T, Takeshita A. Reduction in serum cholesterol with pravastatin improves endothelium-dependent coronary vasomotion in patients with hypercholesterolemia. Circulation. 1994;89:2519-2524.[Abstract/Free Full Text]
   
7. Treasure CB, Klein JL, Weintraub WS, Talley JD, Stillabower ME, Kosinski AS, Zhang J, Boccuzzi SJ, Cedarholm JC, Alexander RW. Beneficial effects of cholesterol-lowering therapy on the coronary endothelium in patients with coronary artery disease. N Engl J Med. 1995;332:481-487.[Abstract/Free Full Text]
   
8. Anderson TJ, Meredith IT, Yeung AC, Frei B, Selwyn AP, Ganz P. The effect of cholesterol-lowering and antioxidant therapy on endothelium-dependent coronary vasomotion. N Engl J Med. 1995;332:488-493.[Abstract/Free Full Text]
   
9. Vita JA, Treasure CB, Yeung AC, Vekshtein VI, Fantasia GM, Fish RD, Ganz P, Selwyn AP. Patients with evidence of coronary endothelial dysfunction as assessed by acetylcholine infusion demonstrate marked increase in sensitivity to constrictor effects of catecholamines. Circulation. 1992;85:1390-1397.[Abstract/Free Full Text]
   
10. Zeiher AM, Drexler H, Saurbier B, Just H. Endothelium-mediated coronary blood flow modulation in humans: effects of age, atherosclerosis, hypercholesterolemia, and hypertension. J Clin Invest. 1993;92:652-662.
    
11. Chowienczyk PJ, Watts GF, Cockcroft JR, Ritter JM. Impaired endothelium-dependent vasodilation of forearm resistance vessels in hypercholesterolaemia. Lancet. 1992;340:1430-1432.[Medline] [Order article via Infotrieve]
    
12. Chappell SP, Lewis MJ, Henderson AH. Effect of lipid feeding on endothelium dependent relaxation in rabbit aortic preparations. Cardiovasc Res. 1987;21:34-38.[Medline] [Order article via Infotrieve]
    
13. Kroon AA, Stalenhoef AF, Buikema H, Demacker PN, de Wilde PC, Leijten PA, van Gilst WH. The effect of cholesterol reduction on the endothelial function and progression of atherosclerosis in WHHL rabbits. Atherosclerosis. 1993;103:221-230.[Medline] [Order article via Infotrieve]
    
14. Osborne JA, Siegman MJ, Sedar AW, Mooers SU, Lefer AM. Lack of endothelium-dependent relaxation in coronary resistance arteries of cholesterol-fed rabbits. Am J Physiol. 1989;256:C591-C597.[Abstract/Free Full Text]
    
15. Leung WH, Lau CP, Wong CK. Beneficial effect of cholesterol-lowering therapy on coronary endothelium-dependent relaxation in hypercholesterolaemic patients. Lancet. 1993;341:1496-1500.[Medline] [Order article via Infotrieve]
    
16. Stroes ES, Koomans HA, de Bruin TW, Rabelink TJ. Vascular function in the forearm of hypercholesterolaemic patients off and on lipid-lowering medication. Lancet. 1995;346:467-471.[Medline] [Order article via Infotrieve]
    
17. Calver A, Collier J, Moncada S, Vallance P. Effect of intra-arterial N^G-monomethyl-L-arginine in patients with hypertension: the nitric oxide dilator system appears impaired. J Hypertens. 1992;10:1025-1031.[Medline] [Order article via Infotrieve]
    
18. Green DJ, O'Driscoll JG, Blanksby BA, Taylor RR. Lack of effect of vitamin E administration on basal nitric oxide function in male smokers and non-smokers. Clin Sci. 1995;89:343-348.[Medline] [Order article via Infotrieve]
    
19. Benjamin N, Calver A, Collier J, Robinson B, Vallance P, Webb D. Measuring forearm blood flow and interpreting the responses to drugs and mediators. Hypertension. 1995;25:918-931.[Abstract/Free Full Text]
    
20. Calver A, Collier J, Vallance P. Inhibition and stimulation of nitric oxide synthesis in the human forearm arterial bed of patients with insulin-dependent diabetes. J Clin Invest. 1992;90:2548-2554.
    
21. Zeiher AM, Drexler H, Wollschlager H, Just H. Modulation of coronary vasomotor tone in humans: progressive endothelial dysfunction with different early stages of coronary atherosclerosis. Circulation. 1991;83:391-401.[Abstract/Free Full Text]
    
22. Celermajer DS, Sorensen KE, Gooch VM, Spiegelhalter DJ, Miller OI, Sullivan ID, Lloyd JK, Deanfield JE. Non-invasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet. 1992;340:1111-1115.[Medline] [Order article via Infotrieve]
    
23. Reddy KG, Nair R, Sheehan HM, Hodgson JM. Evidence that selective endothelial dysfunction may occur in the absence of angiographic or ultrasound atherosclerosis in patients with risk factors for atherosclerosis. J Am Coll Cardiol. 1994;23:833-843.[Abstract]
    
24. Sellke FW, Armstrong ML, Harrison DG. Endothelium-dependent vascular relaxation is abnormal in the coronary microcirculation of atherosclerotic primates. Circulation. 1990;81:1586-1593.[Abstract/Free Full Text]
    
25. Egashira K, Inou T, Yamada A, Hirooka Y, Maruoka Y, Takeshita A. Impaired coronary blood flow response to acetylcholine in patients with coronary risk factors and proximal atherosclerotic lesions. J Clin Invest. 1993;91:29-37.
    
26. Creager MA, Cooke JP, Mendelsohn ME, Gallagher SJ, Coleman SM, Loscalzo J, Dzau VJ. Impaired vasodilation of forearm resistance vessels in hypercholesterolemic humans. J Clin Invest. 1990;86:228-234.
    
27. Chin JP, Dart AM. Therapeutic restoration of endothelial function in hypercholesterolemic subjects: effect of fish oils. Clin Exp Pharmacol Physiol. 1994;21:749-755.[Medline] [Order article via Infotrieve]
    
28. Casino PR, Kilcoyne CM, Quyyumi AA, Hoeg JM, Panza JA. Investigation of decreased availability of nitric oxide precursor as the mechanism responsible for impaired endothelium-dependent vasodilation in hypercholesterolemic patients. J Am Coll Cardiol. 1994;23:844-850.[Abstract]
    
29. Minor RLJ, Myers PR, Guerra RJ, Bates JN, Harrison DG. Diet-induced atherosclerosis increases the release of nitrogen oxides from rabbit aorta. J Clin Invest. 1990;86:2109-2116.
    
30. Ohara Y, Peterson TE, Harrison DG. Hypercholesterolemia increases endothelial superoxide anion production. J Clin Invest. 1993;91:2546-2551.
    
31. Darley Usmar VM, Hogg N, O'Leary VJ, Wilson MT, Moncada S. The simultaneous generation of superoxide and nitric oxide can initiate lipid peroxidation in human low density lipoprotein. Free Radic Res. 1992;17:9-20.
    
32. Tanner FC, Noll G, Boulanger CM, Luscher TF. Oxidized low density lipoproteins inhibit relaxations of porcine coronary arteries: role of scavenger receptor and endothelium-derived nitric oxide. Circulation. 1991;83:2012-2020.[Abstract/Free Full Text]
    
33. Drexler H, Zeiher AM, Meinzer K, Just H. Correction of endothelial dysfunction in coronary microcirculation of hypercholesterolaemic patients by L-arginine. Lancet. 1991;338:1546-1550.[Medline] [Order article via Infotrieve]
    
34. Cooke JP, Dzau J, Creager A. Endothelial dysfunction in hypercholesterolemia is corrected by L-arginine. Basic Res Cardiol. 1991;86:173-181.
    
35. Creager MA, Gallagher SJ, Girerd XJ, Coleman SM, Dzau VJ, Cooke JP. L-Arginine improves endothelium-dependent vasodilation in hypercholesterolemic humans. J Clin Invest. 1992;90:1248-1253.
    
36. Casino PR, Kilcoyne CM, Quyyumi AA, Hoeg JM, Panza JA. The role of nitric oxide in endothelium-dependent vasodilation of hypercholesterolemic patients. Circulation. 1993;88:2541-2547.[Abstract/Free Full Text]
    
37. Anderson T, Meredith I, Charbonneau F, Yeung A, Frei B, Selwyn A, Ganz P. Endotheliun-dependent coronary vasomotion relates to the susceptibility of LDL to oxidation in humans. Circulation. 1996;93:1647-1650.[Abstract/Free Full Text]
    
38. Garcia CE, Kilcoyne CM, Cardillo C, Cannon RO, Quyyumi AA, Panza JA. Evidence that endothelial dysfunction in patients with hypercholesterolaemia is not due to increased extracellular nitric oxide breakdown by superoxide anions. Am J Cardiol. 1995;76:1157-1161.[Medline] [Order article via Infotrieve]
    
39. Corsini A, Raiteri M, Soma M, Fumagalli R, Paoletti R. Simvastatin but not pravastatin inhibits the proliferation of rat aorta myocytes. Pharmacol Res. 1991;23:173-180.[Medline] [Order article via Infotrieve]
    
40. Kobashigawa JA, Katznelson S, Laks H, Johnson JA, Yeatman L, Wang XM, Chia D, Terasaki PI, Sabad A, Cogert GA. Effect of pravastatin on outcomes after cardiac transplantation. N Engl J Med. 1995;333:621-627.[Abstract/Free Full Text]
    
41. Lacoste L, Lam J, Hung J, Letchacovski G, Solymoss C, Waters D. Hyperlipidemia and coronary disease: correction of the increased thrombogenic potential with cholesterol reduction. Circulation. 1995;92:3172-3177.[Abstract/Free Full Text]
    
42. Giroux LM, Davignon J, Naruszewicz M. Simvastatin inhibits the oxidation of low-density lipoproteins by activated human monocyte-derived macrophages. Biochim Biophys Acta. 1993;1165:335-338.[Medline] [Order article via Infotrieve]
    

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				K. M. Maki-Petaja, A. D. Booth, F. C. Hall, S. M.L. Wallace, J. Brown, C. M. McEniery, and I. B. Wilkinson Ezetimibe and Simvastatin Reduce Inflammation, Disease Activity, and Aortic Stiffness and Improve Endothelial Function in Rheumatoid Arthritis J. Am. Coll. Cardiol., August 28, 2007; 50(9): 852 - 858. [Abstract] [Full Text] [PDF]

				G. I. Boger, T. K. Rudolph, R. Maas, E. Schwedhelm, E. Dumbadze, A. Bierend, R. A. Benndorf, and R. H. Boger Asymmetric Dimethylarginine Determines the Improvement of Endothelium-Dependent Vasodilation by Simvastatin: Effect of Combination With Oral L-Arginine J. Am. Coll. Cardiol., June 12, 2007; 49(23): 2274 - 2282. [Abstract] [Full Text] [PDF]

				P. H. McNulty, B. J. Robertson, M. A. Tulli, J. Hess, L. A. Harach, S. Scott, and L. I. Sinoway Effect of hyperoxia and vitamin C on coronary blood flow in patients with ischemic heart disease J Appl Physiol, May 1, 2007; 102(5): 2040 - 2045. [Abstract] [Full Text] [PDF]

				P. Strazzullo, S. M. Kerry, A. Barbato, M. Versiero, L. D'Elia, and F. P. Cappuccio Do Statins Reduce Blood Pressure?: A Meta-Analysis of Randomized, Controlled Trials Hypertension, April 1, 2007; 49(4): 792 - 798. [Abstract] [Full Text] [PDF]

				C H Strey, J M Young, J H Lainchbury, C M Frampton, M G Nicholls, A M Richards, and R S Scott Short-term statin treatment improves endothelial function and neurohormonal imbalance in normocholesterolaemic patients with non-ischaemic heart failure Heart, November 1, 2006; 92(11): 1603 - 1609. [Abstract] [Full Text] [PDF]

				J. M. Zimmet and J. M. Hare Nitroso-Redox Interactions in the Cardiovascular System Circulation, October 3, 2006; 114(14): 1531 - 1544. [Full Text] [PDF]

				M. Tonelli Do Statins Protect the Kidney by Reducing Proteinuria? Ann Intern Med, July 18, 2006; 145(2): 147 - 149. [Full Text] [PDF]

				K. Groschel, U. Ernemann, J. B. Schulz, T. Nagele, C. Terborg, and A. Kastrup Statin Therapy at Carotid Angioplasty and Stent Placement: Effect on Procedure-related Stroke, Myocardial Infarction, and Death. Radiology, July 1, 2006; 240(1): 145 - 151. [Abstract] [Full Text] [PDF]

				S. Sandhu, N. Wiebe, L. F. Fried, and M. Tonelli Statins for Improving Renal Outcomes: A Meta-Analysis J. Am. Soc. Nephrol., July 1, 2006; 17(7): 2006 - 2016. [Abstract] [Full Text] [PDF]

				K. Sakoda, M. Yamamoto, Y. Negishi, J.K. Liao, K. Node, and Y. Izumi Simvastatin decreases IL-6 and IL-8 production in epithelial cells. J. Dent. Res., June 1, 2006; 85(6): 520 - 523. [Abstract] [Full Text] [PDF]

				S. Fichtlscherer, C. Schmidt-Lucke, S. Bojunga, L. Rossig, C. Heeschen, S. Dimmeler, and A. M. Zeiher Differential effects of short-term lipid lowering with ezetimibe and statins on endothelial function in patients with CAD: clinical evidence for 'pleiotropic' functions of statin therapy Eur. Heart J., May 2, 2006; 27(10): 1182 - 1190. [Abstract] [Full Text] [PDF]

				H. Sourij, R. Zweiker, and T. C. Wascher Effects of Pioglitazone on Endothelial Function, Insulin Sensitivity, and Glucose Control in Subjects With Coronary Artery Disease and New-Onset Type 2 Diabetes Diabetes Care, May 1, 2006; 29(5): 1039 - 1045. [Abstract] [Full Text] [PDF]

				M. A. Arias, J. Sanchez-Gila, and D. Amar Obesity As a Risk Factor for Developing Postoperative Atrial Fibrillation Chest, March 1, 2006; 129(3): 828 - 829. [Full Text] [PDF]

				A. Rashidi, M. Rahman, M. Tonelli, C. Isles, T. Craven, C. Furberg, A. Tonkin, M. A. Pfeffer, J. Shepherd, S. M. Cobbe, et al. Letter Regarding Article by Tonelli et al, "Effect of Pravastatin on Rate of Kidney Function Loss in People With or at Risk for Coronary Disease" * Response Circulation, January 31, 2006; 113(4): e59 - e60. [Full Text] [PDF]

				M. E. Alnaeb, F. Youssef, D. P. Mikhailidis, and G. Hamilton Short-term Lipid-Lowering Treatment with Atorvastatin Improves Renal Function But Not Renal Blood Flow Indices in Patients with Peripheral Arterial Disease Angiology, January 1, 2006; 57(1): 65 - 71. [Abstract] [PDF]

				Y. Rikitake and J. K. Liao Rho GTPases, Statins, and Nitric Oxide Circ. Res., December 9, 2005; 97(12): 1232 - 1235. [Abstract] [Full Text] [PDF]

				S. M. Kawut, E. M. Horn, K. K. Berekashvili, A. C. Widlitz, E. B. Rosenzweig, and R. J. Barst von Willebrand Factor Independently Predicts Long-term Survival in Patients With Pulmonary Arterial Hypertension Chest, October 1, 2005; 128(4): 2355 - 2362. [Abstract] [Full Text] [PDF]

				J. L. Martin-Ventura, L. M. Blanco-Colio, A. Gomez-Hernandez, B. Munoz-Garcia, M. Vega, J. Serrano, L. Ortega, G. Hernandez, J. Tunon, and J. Egido Intensive Treatment With Atorvastatin Reduces Inflammation in Mononuclear Cells and Human Atherosclerotic Lesions in One Month Stroke, August 1, 2005; 36(8): 1796 - 1800. [Abstract] [Full Text] [PDF]

				K. M. Parmar, V. Nambudiri, G. Dai, H. B. Larman, M. A. Gimbrone Jr., and G. Garcia-Cardena Statins Exert Endothelial Atheroprotective Effects via the KLF2 Transcription Factor J. Biol. Chem., July 22, 2005; 280(29): 26714 - 26719. [Abstract] [Full Text] [PDF]

				H. Lorenz, C. Junger, K. Seidl, A. Gitt, S. Schneider, R. Schiele, H. Wienbergen, R. Winkler, M. Gottwik, W. Delius, et al. Do statins influence the prognostic impact of non-sustained ventricular tachycardia after ST-elevation myocardial infarction? Eur. Heart J., June 1, 2005; 26(11): 1078 - 1085. [Abstract] [Full Text] [PDF]

				P. Di Napoli, A. A. Taccardi, A. Grilli, M. A. De Lutiis, A. Barsotti, M. Felaco, and R. De Caterina Chronic treatment with rosuvastatin modulates nitric oxide synthase expression and reduces ischemia-reperfusion injury in rat hearts Cardiovasc Res, June 1, 2005; 66(3): 462 - 471. [Abstract] [Full Text] [PDF]

J. R. Jacobson, J. W. Barnard, D. N. Grigoryev, S.-F. Ma, R. M. Tuder, and J. G. N. Garcia Simvastatin attenuates vascular leak and inflammation in murine inflammatory lung injury Am J Physiol Lung Cell Mol Physiol, June 1, 2005; 288(6): L1026 - L1032. [Abstract] [Full Text] [PDF]