Beneficial effects of cholesterol-lowering therapy on the coronary endothelium in patients with coronary artery disease

Lovastatin preserves renal function in experimental diabetes

Although hyperlipidemia has been associated with the progression of glomerulosclerosis, little attention has been directed toward the use of lipid-lowering agents in altering diabetic nephropathy. We tested the hypothesis that lovastatin and the combination of lovastatin and enalapril would preserve renal function in streptozotocin-induced diabetic Wistar rats. Five groups of animals were studied: group 1, nondiabetic (n = 10); group 2, diabetic, insulin only (n = 12); group 3, lovastatin, (15 mg/kg/day, n = 13); group 4, enalapril, (50 mg/L drinking water, n = 10) and group 5, lovastatin plus enalapril, (n = 14). After 8 weeks of treatment, glomerular filtration rate (GFR, insulin clearance) was measured in anesthetized animals. The diabetic group was characterized by a GFR of 0.18 +/- 0.03 ml/min/g of kidney weight (gKW), a blood glucose level of 441 +/- 36 mg/dL, plasma cholesterol and triglyceride levels of 64 +/- 6.0 and 103 +/- 26.0 mg/dL. Lovastatin preserved GFR, 0.52 +/- 0.06 ml/min/gKW compared with the diabetic control subjects (P < 0.05). Enalapril also maintained GFR (0.42 +/- 0.06 ml/min/gKW, P < 0.05). In the lovastatin plus enalapril group, GFR (0.62 +/- 0.05 ml/min/gKW) was greater than in the enalapril group (P < 0.05), but was not different from the lovastatin group. Plasma lipid levels were not altered in any of the groups. Assessment of the kidneys by histology after treatment showed that the mesangial matrix injury score was better in the lovastatin, enalapril, and lovastatin plus enalapril groups compared with the diabetic group (P < 0.05). Lovastatin, enalapril, and lovastatin plus enalapril abrogated the decline in GFR and glomerular injury in diabetic rats. Lovastatin's direct renal protective effect seems to be independent of its lipid-lowering properties.

Clinic-daytime blood pressure difference and cardiovascular damage

OBJECTIVE

To investigate whether the clinic-daytime blood pressure difference can provide information on vascular reactivity to stress comparable to that of simple noninvasive stimuli such as a cold pressor test and isometric exercise, and whether there is any relationship between this blood pressure difference and noninvasive measurements of the left ventricular mass and carotid arterial wall.

DESIGN

Patients with newly discovered, never-treated, sustained hypertension were included in the study after a 1 month run-in, during which time their blood pressure was measured three times at 2 week intervals.

METHODS

Blood pressure was measured by a noninvasive procedure at rest and during a cold pressor test and an isometric exercise. The difference was calculated for systolic, diastolic and mean blood pressure as resting minus daytime ambulatory blood pressure. Parameters of the posterior wall and septal thickness of the left ventricle, aortic root and left atrium were studied by M-mode echocardiography. Carotid wall thickness and diameter were measured using ultrasound.

RESULTS

The 90 patients enrolled in the study were divided into tertiles of clinic-daytime blood pressure difference. The composition of the groups differed in sex, since the majority of women were in the highest tertile, but was comparable for age, body mass index, renin-aldosterone axis and lipid and carbohydrate metabolism. Blood pressure responses to cold and isometric exercise were more pronounced in patients in the lowest tertile of blood pressure difference. No intergroup differences were detected in echocardiographic parameters of ventricular (left ventricular mass, tertiles I-III: 46.5 +/- 10, 42.3 +/- 8, 44.8 +/- 13 g/m2.7, respectively) and carotid (intima-media thickness, tertiles I-III 0.58 +/- 0.1, 0.54 +/- 0.1, 0.62 +/- 0.1 mm, respectively) structure.

CONCLUSIONS

The present study indicates that the clinic-daytime blood pressure difference provides different information on cardiovascular reactivity compared with that obtained from the cold pressor test and isometric exercise. Moreover, it does not seem to have any relationship with ventricular hypertrophy and/or carotid wall thickening.

Retinal and optic nerve head ischemic disorders and atherosclerosis: role of serotonin

Ischemic disorders of the retina and optic nerve head (OPH) constitute a common cause of visual loss in the middle-aged and elderly population. These disorders have a high association with atherosclerosis. This review has considered the various aspects of atherosclerosis and its role, as well as that of serotonin, in the development of ischemic disorders of the retina and ONH. It is known that when platelets aggregate on an atheromatous plaque, serotonin is one of the agents released. Studies in experimental atherosclerotic monkeys have shown that, although serotonin has no effect on ocular vasculature in normal monkeys, in atherosclerotic monkeys it produces vasopasm of the central retinal artery (CRA) and/or posterior ciliary artery (PCA) in various combinations but not vasopasm of the arterioles in the retina; vasospasm of the CRA and/or PCA(s) can consequently cause transient, complete occlusion or impaired blood flow in these arteries. It is postulated that in some atherosclerotic individuals this mechanism may play an important role in the development of ischemic disorders of the retina and ONH, including amaurosis fugax, (CRA) occlusion and anterior ischemic optic neuropathy, and possibly also glaucomatous optic neuropathy, particularly in normal tension glaucoma. Studies have also shown that dietary treatment of atherosclerosis abolishes or markedly improves the serotonin induced vasoconstriction within a few months. All these considerations may have important implications for our understanding of the pathogenesis and management of these blinding disorders.

Effects of lipid-lowering drugs on left ventricular function and exercise tolerance in dyslipidemic coronary patients

Previous studies suggested that certain lipid-lowering drugs such as statins suppress ubiquinone, affect mitochondrial function, and may have deleterious effect on skeletal or cardiac muscles with potentially serious clinical consequences, especially in patients with established coronary heart disease and left ventricular dysfunction. In this double-blind study, we assessed the effects of 20 mg simvastatin (S, n = 32) or 200 mg micronized fenofibrate (F, n = 32, control group) on rest and exercise left ventricular function in hypercholesterolemic survivors of a previous Q-wave acute myocardial infarction. Left ventricular radionuclide imaging was performed at rest and during submaximal exercise and global and segmental (nine segment regional wall-motion score) ejection fractions were measured before treatment and 12 weeks later. Serum ubiquinone was reduced after treatment (p = 0.03) in the S but not the F group, whereas total and low-density lipoprotein (LDL) cholesterol were significantly reduced in both groups. Before treatment, mean global ejection fraction was 52.1+/-12.2% and 49.3+/-11.8% at rest in F and S patients, respectively, and increased (56.0+/-13.7% in F and 52.1+/-12.9% in S) at peak exercise (no difference between groups). After treatment, the increase in ejection fraction tended to be lower in S (0) than in F (+3.8%) but not significantly. However, ejection fraction at rest increased after treatment in S (p = 0.009) but not in F. Subgroup analyses indicated that the improvement in rest ejection fraction in S was essentially observed in patients with ejection fraction <40% (n = 8, +6%), whereas it was stable in patients with ejection fraction >40% (+1.8%). Finally, the numbers of akinetic or hypokinetic segments at rest and during exercise were not different in the two groups before and after treatment. Mean maximal exercise load (113+/-23 watts in F vs. 104+/-27 W in S before treatment) was not modified by the treatment (111+/-21 and 104+/-27 W). Thus a 12-week lipid-lowering treatment with either S or F did not negatively alter left ventricular function during exercise in dyslipidemic patients with established coronary heart disease and did not affect their ability to exercise. The improvement in left ventricular function at rest after simvastatin in patients with left ventricular dysfunction warrants confirmation in further studies with large sample size.

Vitamin E ingestion does not improve arterial endothelial dysfunction in older adults

Endothelial dysfunction is thought to be an important early event in atherogenesis, related in part to reduced bioavailability of nitric oxide in the arterial wall. Endothelial function may be impaired in the presence of oxidised low density lipoprotein. The use of vitamin E as an anti-oxidant might enhance the bioavailability of nitric oxide in this situation. The effect of vitamin E 1000 IU/day on arterial endothelial physiology was studied in 20 asymptomatic older subjects, aged 45-70 years, who showed evidence of age-related endothelial dysfunction. Endothelial function was assessed non-invasively using brachial ultrasound and the primary outcome measure was flow-mediated endothelium-dependent dilatation (FMD) in response to reactive hyperaemia. A double-blind, placebo-controlled, randomised crossover design was employed. After 3 weeks of stabilisation on a standard fat-reduced diet, subjects received vitamin E or placebo for 10 weeks in random order, separated by a washout period of 8 weeks. There were no significant changes in blood pressure, plasma lipid or lipoprotein concentrations. Plasma alpha-tocopherol increased from 50+/-3 (mean+/-S.E.M.) to 91+/-6 micromol/l (P < 0.001) with vitamin E ingestion. Total plasma F2alpha-isoprostanes, a measure of free radical-induced lipid peroxidation, were not altered by vitamin E ingestion (0.86+/-0.26 versus 0.82+/-0.25 nmol/l, P > 0.6). FMD was not significantly different between the placebo and vitamin E periods (2.7+/-0.6% versus 2.4+/-0.4%). Variation in FMD was not correlated with change in plasma alpha-tocopherol (r = - 0.03, P > 0.8). The study was powered to detect a minimum change in FMD of 2%. Glyceryl trinitrate endothelium-independent dilatation was not significantly changed with vitamin E (13.7+/-1.3% versus 13.6+/-1.4%,). These results exclude a major impact of medium-term supplementation with vitamin E on arterial endothelial function when age-related dysfunction is already present.

Delayed response of myocardial flow reserve to lipid-lowering therapy with fluvastatin

BACKGROUND

Lipid-lowering therapy can improve endothelial function in patients with coronary artery disease (CAD) and hypercholesterolemia. Little is known about induced changes in myocardial microcirculation. This study prospectively investigated the temporal effects of lipid-lowering therapy with fluvastatin on coronary flow and flow reserve (CFR) in patients with CAD assessed by PET.

METHODS AND RESULTS

In an open clinical trial, CFR was studied in 15 patients with angiographically documented multivessel CAD and hypercholesterolemia (LDL >160 mg/dL). Dynamic 13N-labeled ammonia PET imaging in conjunction with adenosine was used to assess regional and global CFR at baseline as well as at 2 and 6 months during treatment with fluvastatin (60 to 80 mg/d). Despite a rapid decrease in total cholesterol (29+/-6%) and LDL (37+/-9%), myocardial blood flow at rest and during stress was unchanged after 2 months of treatment (2.7+/-0.9 versus 2.5+/-0.6 mL x g-1 x min-1). At 6 months, stress blood flow as well as CFR increased significantly (3.4+/-1.0 mL x g-1 x min-1). No change in hemodynamic parameters was noted during the entire study. Nine of 15 patients increased CFR by >20%. All responders demonstrated improvement in anginal symptoms, whereas nonresponders stated no change (n=4) or worsening of symptoms (n=2). The improvement in CFR was not related to the amount of lipid lowering and was independent of the severity of stenoses.

CONCLUSIONS

Improvement in stress blood flow and CFR is delayed compared with the lipid-lowering effect of fluvastatin, suggesting a slow recovery of the vasodilatory response to adenosine.

[Endothelial dysfunction--assessment of current status and approaches to therapy]

The vascular endothelium is the inner lining of all blood vessels and serves as an important autocrine and paracrine organ, that regulates vascular wall functions. Because of its strategic location between the circulating blood and the vascular wall, the endothelium interacts with cellular and neurohumoral mediators, thus controlling vascular contractile state and cellular composition. The vascular endothelium maintains vascular homeostasis by modulating blood vessel tone, by regulating local cellular growth and extracellular matrix deposition and by controlling hemostatic as well as inflammatory responses. One of the best characterized and most important substances released from the endothelium is nitric oxide (NO). NO is a soluble gas which is continuously synthesized from the amino acid L-arginine in endothelial cells by the constitutively expressed nitric oxide synthase. The most important stimuli represent physical factors such as shear stress and pulsatile stretching of the vessel wall as well as circulating and locally released vasoactive substances. The endothelium can be seen as a biosensor, reacting to a large variety of stimuli and therefore maintaining adequate NO release. A large number of risk factors for atherosclerosis including hypercholesterolemia, systemic hypertension, smoking and diabetes have been associated with impaired endothelial NO-mediated vasodilation. "Endothelial dysfunction" is an early marker of atherosclerosis and may be closely related to the disease process. In acute coronary syndromes dysfunctional endothelium may trigger the devastating event of plaque rupture by promoting adhesion of leukocytes, vasoconstriction, activation of platelets and thrombos formation. Atherosclerotic blood vessels are further characterized by activation through zytokines and expression of cellular adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and endothelial-leukocyte adhesion molecule-1 (E-Selectin). After adhesion to the endothelium mononuclear cells migrate to the subendothelial space to take up oxidized LDL, thus transforming into foam cells, a hall mark of early atherosclerotic lesions. A number of conditions including infection with Chlamydia pneumoniae may cause continuous activation of the endothelium and inflammation of the vessel wall. Continuous endothelial dysfunction and activation, caused by risk factors and infection, represent the basis for atherogenesis and acute coronary syndromes.

Relationship between myometrial resistance artery behavior and circulating lipid composition

OBJECTIVES

The study investigated whether an inducible alteration in endothelium-dependent relaxation in myometrial vessels could be correlated with plasma lipid composition.

STUDY DESIGN

Myometrial resistance vessels were obtained from 10 women with normal pregnancy undergoing elective cesarean delivery. Paired vessels were incubated with plasma samples from patients with preeclampsia or from women with normal pregnancy and mounted on a wire myograph. After contraction with vasopressin, the degree of relaxation in response to bradykinin was observed. Plasma samples were assayed for cholesterol, triglycerides, apolipoprotein A1, and apolipoprotein B.

RESULTS

A significant reduction in endothelium-dependent relaxation with respect to control values was observed in vessels incubated in plasma samples from patients with preeclampsia (P =.0001). Although no significant difference was noted between the lipid profiles of the 2 subgroups, a significant correlation was found between the vessel relaxation and the plasma content of apolipoprotein A1 (R2 = 0.36, P = .025).

CONCLUSION

Plasma samples from women with pregnancies complicated by preeclampsia are capable of altering endothelium-dependent myometrial vessel relaxation. A significant relationship between the apolipoprotein A1 concentration and endothelial behavior supports the suggestion that aberrant lipid metabolism may be involved in the endothelial dysfunction characteristic of preeclampsia.

[Therapy with CSE inhibitors--more than lipid lowering?]

An elevated plasma cholesterol concentration is an established risk factor for coronary heart disease. Dietary and drug interventions with fibrate, nicotinic acid and colestyramine have resulted in a decreased rate of major coronary events but failed to decrease mortality. Studies using the more potent lipid lowering statins have shown remarkable results in primary (WOSCOPS, AFCAPS, TexCAPS) and secondary prevention (4S, CARE, LIPID). The use of these drugs reduced the risk for coronary events as well as the need for interventions. Furthermore, improvement of angina has been shown in several studies. In high-risk patients coronary heart disease associated mortality and overall mortality was reduced. Lowering of cholesterol was shown to be effective in women, older people and diabetics. Lipid lowering improves prognosis after heart transplant and could be an alternative to PTCA. Furthermore it was also shown that cholesterol lowering reduces the incidence of stroke. New mechanisms are discussed to explain the rapid onset of clinical improvement. Among these are: influences on inflammatory processes in the plaque, on vascular smooth muscle activity, on coagulation and on endothelial dysfunction.

Gender differences in myocardial blood flow dynamics: lipid profile and hemodynamic effects

OBJECTIVES

The purpose of the study was to compare myocardial blood flow (MBF) in hyperlipidemic postmenopausal women and age-matched hyperlipidemic men, and to analyze the relationship between cholesterol subfractions and myocardial blood flow in men and women.

BACKGROUND

Women are protected from coronary artery disease (CAD) events until well after menopause, in part due to gender-specific differences in lipid profiles.

METHODS

To examine the effect of these influences on coronary microcirculation, MBF was quantitated with N-13 ammonia/PET (positron emission tomography) at rest and during adenosine hyperemia in 15 women and 15 men, all nondiabetic, who were matched for age and total cholesterol levels (53+/-4 vs. 50+/-8 years, p = NS, 6.44+/-1.1 vs. 6.31+/-0.85 mmol/liter, or 249+/-41 vs. 244+/-33 mg/dl, p = NS).

RESULTS

Women had significantly higher high density lipoprotein (HDL) and lower triglyceride (Tg) levels than did men, and they showed significantly higher resting MBF and stress MBF levels. Significant correlations were found between resting and hyperemic MBF and HDL and Tg levels (r = 0.44, p < 0.02 for stress MBF vs. HDL; r = 0.48, p < 0.007 for stress MBF vs. Tg). Gender was the strongest predictor of hyperemic MBF in multivariate analysis. Women responded to adenosine hyperemia with a significantly higher heart rate than did men, and hemodynamic factors correlated significantly with blood flow both at rest and during stress.

CONCLUSIONS

These data suggest that the favorable lipid profile seen in women may be associated with preserved maximal blood flow in the myocardium.

Effect of long-term exercise training on regional myocardial perfusion changes in patients with coronary artery disease

The cardiac rehabilitation of patients with coronary artery disease (CAD) promotes exercise tolerance, improves left ventricular function, and decreases the heart rate and systolic blood pressure at the same load intensity. Several studies have shown that cardiac rehabilitation improves myocardial perfusion in CAD patients. However, the long-term (> or = 1 year) effect of cardiac rehabilitation on myocardial perfusion is still controversial. The effect of long-term exercise training on myocardial perfusion in CAD patients was assessed using thallium-201 (201Tl) exercise studies at a baseline (4 months after the onset of CAD) and at a 1-year or more follow-up in 58 patients with stable CAD. The subjects had been divided into a training group (n=35) participating in supervised exercise 2 times per week for the follow-up period, and the control group (n=23). There was an improvement in the myocardial perfusion on stress 201Tl scintigraphy in 20 of the 35 (57.1%) trained patients and in 3 of the 23 (13.0%) of the control patients (p<0.001). The number of 201Tl stress myocardial perfusion defect segments was significantly decreased after the cardiac rehabilitation training (231 to 153 segments), but showed no change in the control group (158 to 156 segments) (p<0.01). In spite of no significant differences in the number of involved coronary arteries, it improved (12/17 patients: 70.6%) more in the patients who had trained for more than 2 years compared to the patients who had trained for less than 2 years. The exercise tolerance increased in 25 of the 35 training group patients (71.4%), and in only 3 of the 23 control group patients (13.0%). The peak double products increased from 20,131+/-6,010 to 28,370+/-5,600 (p<0.01) in the training group, and showed no change in the control group (20,567+/-5,112 to 20,964+/-7,728 (NS)). The results indicated that the long-term physical training increased exercise tolerance and the double products of CAD patients. In addition, the training resulted in improved cardiac perfusion as evidenced by 201Tl scintigraphy. The findings suggest that exercise training is an advisable and effective treatment for patients with CAD.

Pharmacological effects of HMG CoA reductase inhibitors other than lipoprotein modulation

The HMG CoA reductase inhibitors reduce levels of low-density lipoproteins, raise high-density lipoproteins, and lower triglycerides. However, there are other pharmacological effects derived from HMG CoA reductase inhibitor therapy. Certain HMG CoA reductase inhibitors affect atherosclerotic plaque composition, endothelial function, platelet and clotting factors, and immune functioning. The unique extrahepatic pharmacological profile of agents in this class has not been fully characterized. All of the HMG CoA reductase inhibitors studied have improved endothelium-dependent vasodilatation. Vascular smooth muscle proliferation is not significantly affected by pravastatin but is by the other agents. Of all the HMG CoA reductase inhibitors, cerivastatin is the most potent inhibitor of vascular smooth muscle proliferation. Pravastatin is the only agent proven to significantly reduce platelet-thrombus formation and fibrinogen levels. Simvastatin has no effect on platelet-thrombus formation or fibrinogen levels, while atorvastatin and lovastatin have been shown to increase fibrinogen in some studies. Plasminogen activator inhibitor-1 levels are decreased by pravastatin, are not affected by atorvastatin, and are significantly increased by lovastatin and simvastatin. Pravastatin also has clinical benefits in transplant medicine as a result of inhibiting natural killer cell function, an effect that has not been explored with other HMG CoA reductase inhibitors.

Distinct and combined vascular effects of ACE blockade and HMG-CoA reductase inhibition in hypertensive subjects

Hypercholesterolemia and hypertension are frequently associated with elevated sympathetic activity. Both are independent cardiovascular risk factors and both affect endothelium-mediated vasodilation. To identify the effects of cholesterol-lowering and antihypertensive treatments on vascular reactivity and vasodilative capacity, we studied 30 hypercholesterolemic hypertensive subjects. They received placebo for 4 weeks, either enalapril or simvastatin for 14 weeks, and, finally, both medications for an additional 14 weeks. Postischemic forearm blood flow (MFBF) and minimal vascular resistance (mFVR) were used as indices of vasodilative capacity and structural vascular damage, respectively. Total (resting-stress-recovery phases) cardiovascular (blood pressure [BP] and heart rate [HR]) and regional hemodynamic (FBF and FVR) reactivity to stressful stimuli were calculated as area-under-the-curve (auc) (valuextime). Compared with baseline levels, simvastatin reduced total (TOT-C) and LDL cholesterol (LDL-C) (1.27 mmol/L, P<0.001 and 1.33 mmol/L, P<0.001, respectively). Enalapril also reduced TOT-C and LDL-C (0.6 mmol/L, P<0.001 and 0.58 mmol/L, P<0.05, respectively). MFBF was increased substantially by both treatments (P<0.001). Enalapril had a greater effect (-1.7 arbitrary units (AU), P<0.001) than simvastatin (-0.6 AU, P<0.05) on mFVR. During stress, FBF increased more with enalapril (4.4 FBFxminutes, P<0.001) than with simvastatin (1.8 FBFxminutes, P<0.01). Conversely, FVR stress response was reduced more with enalapril (9.1 FVRxminutes, P<0.001) than with simvastatin (2.9 FVRxminutes, P<0.01). During combination treatment, a significant (0.001>P<0.05) additive effect on hypercholesterolemia, structural vascular damage, BP, and FVR was shown. The findings suggest that angiotensin-converting enzyme (ACE) inhibition induces a larger reduction than HMG-CoA reductase blockade in vascular reactivity and structural damage in hypercholesterolemic hypertensive subjects.

Vascular effects of estrogen and cholesterol-lowering therapies in hypercholesterolemic postmenopausal women

BACKGROUND

Lipoproteins affect endothelium-dependent vasomotor responsiveness. Because lipoprotein effects of estrogen and cholesterol-lowering therapies differ, we studied the vascular responses to these therapies in hypercholesterolemic postmenopausal women.

METHODS AND RESULTS

We randomly assigned 28 women to conjugated equine estrogen (CE) 0.625 mg, simvastatin 10 mg, and their combination daily for 6 weeks. Compared with respective baseline values, simvastatin alone and combined with CE reduced LDL cholesterol to a greater extent than CE alone (both P<0.05). CE alone and combined with simvastatin raised HDL cholesterol and lowered lipoprotein(a) to a greater extent than simvastatin alone (all P<0.05). Flow-mediated dilation of the brachial artery (by ultrasonography) improved (all P<0.001 versus baseline values) on CE (4.0+/-2.6% to 10.2+/-3.9%), simvastatin (4.3+/-2.4% to 10.0+/-3.9%), and CE combined with simvastatin (4.6+/-2.0% to 9.8+/-2.6%), but similarly among therapies (P=0.507 by ANOVA). None of the therapies improved the dilator response to nitroglycerin (all P>/=0.184). Only therapies including CE lowered levels of plasminogen activator inhibitor type 1 and the cell adhesion molecule E-selectin (all P<0. 05 versus simvastatin).

CONCLUSIONS

Although estrogen and statin therapies have differing effects on lipoprotein levels, specific improvement in endothelium-dependent vasodilator responsiveness is similar. However, only therapies including estrogen improved markers of fibrinolysis and vascular inflammation. Thus, estrogen therapy appears to have unique properties that may benefit the vasculature of hypercholesterolemic postmenopausal women, even if they are already on cholesterol-lowering therapy.

Lovastatin maintains nitric oxide--but not EDHF-mediated endothelium-dependent relaxation in the hypercholesterolemic rabbit carotid artery

The endothelium contributes to the regulation of vascular tone by producing nitric oxide (NO) and the endothelium-derived hyperpolarising factor (EDHF). In hypercholesterolemia, endothelium-dependent relaxation is impaired but can be restored by treatment with lovastatin (LOVAS). We investigated the effects of LOVAS on NO and EDHF-mediated relaxation. Rabbits were fed 1% cholesterol diet for 4 weeks and 0.5%) cholesterol for the following 12 weeks (CHOL-group). The LOVAS group additionally received 10 mg of lovastatin over the last 12-week period. Experiments were performed in carotid artery rings. Relaxant responses to acetylcholine (ACh) were recorded in the presence of indomethacin. Nitro-L-arginine (NOARG, 100 microM) and potassium chloride (KCl, 35 mM) were used to differentiate between NO- and EDHF-mediated relaxations. Cholesterol impaired ACh-induced relaxations and this effect was prevented by LOVAS (control 100+/-1%, CHOL 81+/-6%, LOVAS 98+/-1%). In the presence of NOARG, relaxations to ACh were not different between the LOVAS and CHOL groups (control 78+/-4%, CHOL 64+/-6%, LOVAS 64+/-5%). When KCl was used, ACh-induced relaxations were similar in the LOVAS and control group (control 75+/-5%, CHOL 49+/-6%, LOVAS 76+/-2%). In arteries treated with NOARG and KCl together, no relaxations were observed. Relaxations of arteries from the control group were not affected by 18 h preincubation with lovastatin (10 microM). Lovastatin selectively maintains nitric oxide-mediated endothelium-dependent relaxation in hypercholesterolemic rabbit carotid arteries.

Endothelial derived vasoactive factors and leukocyte derived inflammatory mediators in subjects with asymptomatic atherosclerosis

To clarify relationships between the (endothelial vasodilatory and vasoconstrictive function) and leukocyte inflammatory mediators in subjects with asymptomatic atherosclerosis, we measured (intraplatelet cyclic 3',5'-guanosine monophosphate [cGMP] and cyclic 3',5'-adenosine monophosphate [cAMP]), plasma endothelin (ET-1), and plasma neopterin in 197 subjects with asymptomatic atherosclerosis (median age 63 years, range 49-69 years). We measured neutrophil protease 4 (NP4), tumor necrosis factor (TNFmu), soluble tumor necrosis factor receptor-1 (sTNFR-1), and neutrophil gelatinase associated lipocalin (NGAL) in 152 of the 197 subjects. Intraplatelet cGMP correlated inversely with plasma ET-1 (r=-0.22; p=0.01), which confirms earlier in vitro data of the inhibitory effect of ET-1 on NO production and/or the cGMP mediated inhibitory effect of NO on ET-1 production. Plasma neopterin as well as NP4 correlated directly with intraplatelet cGMP (r=0.24; p<0.01 and r=0.33; p<0.001, respectively). Intraplatelet cAMP correlated directly with plasma TNFmu (r=0.17; p<0.05) and sTNFR-1 (r=0.20; p<0.05). The relationship between leukocyte derived inflammatory mediators and intraplatelet cyclic nucleotides suggest an antiaggregating effect of leukocytes upon platelets, which may constitute a negative feedback mechanism that inhibits platelet activation during the atherosclerotic inflammatory process.

Prevalence of coronary blood flow reserve abnormalities among patients with nonobstructive coronary artery disease and chest pain

OBJECTIVE

To determine the prevalence of abnormalities in endothelium-dependent and endothelium-independent coronary flow reserve among patients with non-obstructive coronary artery disease and chest pain.

MATERIAL AND METHODS

We studied endothelium-dependent (after infusion of 10(-6) M to 10(-4) M of acetylcholine) and endothelium-independent (after administration of 18 to 36 micrograms of adenosine) coronary flow reserve among patients with nonobstructive coronary artery disease and chest pain who were undergoing assessment at Mayo Clinic Rochester. Coronary blood flow was derived from coronary artery diameter assessed by quantitative angiography and Doppler flow velocities.

RESULTS

The cohort consisted of 203 patients (158 female and 45 male patients), who ranged in age from 17 to 78 years (mean, 51). Most patients (92%) had at least one risk factor for atherosclerosis; a substantial proportion had undergone extensive cardiac and noncardiac evaluation. Whereas 41.5% of the patients had normal coronary flow reserve, 58.5% had an abnormal response: 11.3% an impaired response to adenosine (flow velocity ratio of 2.5 or less), 29.2% an impaired response to acetylcholine (flow reserve ratio of 1.5 or less), and 18% a combined abnormality. No correlation (r2 = 0.03) was noted between endothelium-dependent and endothelium-independent flow reserve.

CONCLUSION

Most study patients with chest pain and nonobstructive coronary artery disease undergoing coronary vasomotor evaluation had risk factors for coronary artery disease and diverse abnormalities in endothelium-dependent or endothelium-independent coronary flow reserve (or both). These findings underscore the need for a comprehensive assessment.

Therapy with nitroglycerin increases coronary vasoconstriction in response to acetylcholine

OBJECTIVES

The purpose of this study was to investigate whether therapy with nitroglycerin (GTN) would lead to abnormal coronary artery responses to the endothelium-dependent vasodilator acetylcholine.

BACKGROUND

Nitroglycerin therapy is associated with specific biochemical changes in the vasculature that may lead to increased vascular sensitivity to vasoconstrictors.

METHODS

Patients were randomized to continuous transdermal GTN, 0.6 mg/h (n = 8), or no therapy (n = 7), for 5 days prior to a diagnostic catheterization. Patients had similar risk factors for endothelial dysfunction. Quantitative angiography was performed in the morning to measure the mean luminal diameter of the left anterior descending coronary artery (LAD) in response to intracoronary acetylcholine (peak concentration, 10(-4) mol/liter). The transdermal preparation was removed from the GTN group, and 3 h later experimental procedures were repeated.

RESULTS

In the morning, the GTN group experienced greater coronary constriction in response to acetylcholine infusion than those not receiving GTN (-19.6+/-4.2 vs. -3.8+/-3.0%; p = 0.01). Three hours later, the GTN group continued to display greater constriction to acetylcholine (-24.1+/-5.9%) as compared to the non-GTN group (-1.8+/-4.8%). When the morning and afternoon responses to acetylcholine were compared, the increase in coronary constriction in the GTN group was greater than the change observed in the non-GTN group (p < 0.05).

CONCLUSIONS

This study demonstrates that therapy with GTN causes abnormal coronary vasomotor responses to the endothelium-dependent vasodilator acetylcholine, changes that were persistent for up to 3 hours after GTN discontinuation. This nitrate-associated vasomotor dysfunction has implications with respect to the development of nitrate tolerance and the potential for adverse events during nitrate withdrawal.

Importance of endothelial function in mediating the benefits of lipid-lowering therapy

Trials of lipid lowering by various methods have clearly demonstrated the benefits, clinically and angiographically. Evidence of slowed arterial disease progression and even regression has been convincing but modest, at best. For example, among those treated intensively in the Familial Atherosclerosis Treatment Study (FATS), the mean improvement in proximal stenosis severity was <1% per patient, and only 12% of all lesions showed convincing regression. Despite these modest arterial benefits, the associated reductions in major cardiovascular events have been surprisingly great (24-35% in 3 recent large trials and > or =50% in angiographic trials using combination therapies). The process of plaque disruption helps explain this discrepancy. Disruption can be predicted by a large accumulation of core lipid in the plaque and a high density of lipid-laden macrophages in its thinned fibrous cap. Lesions with these characteristics comprise only 10-20% of the overall lesion population but account for 60-90% of the acute clinical events. Lipid-lowering therapy has beneficial effects on these "high-risk" features of plaque morphology. The composite of data presented here supports the hypothesis that lipid-lowering therapy selectively depletes lipids from this relatively small but dangerous subgroup of fatty lesions, effectively stabilizing them.

The new pathophysiology of coronary artery disease

Our understanding of coronary artery disease risk and the atherosclerotic process has changed greatly in recent years. For example, it is now known that angiographically apparent coronary artery plaque is not the major cause of myocardial infarction (MI). Rather, it is unstable, soft plaque that cannot be seen angiographically that is prone to rupture and result in infarction. Also important are changes in vascular reactivity resulting from diet. Cholesterol levels by themselves reveal little about a patient's coronary artery disease risk. Most infarctions occur in patients who have normal total cholesterol levels. At-risk patients can be identified using the ratio of total-to-high-density lipoprotein (HDL) cholesterol levels. The ratio of triglyceride to HDL cholesterol levels is also important. Simple steps to assess patients' risk in practice are outlined. Primary prevention trials demonstrate that coronary artery disease risk can be lowered dramatically with diet and drug therapy.

Atherothrombogenicity of lipoprotein(a): the debate

Although lipoprotein(a) (Lp[a]) has been recognized as an atherothrombogenic factor, the underlying mechanisms for this pathogenicity have not been clearly defined. Plasma levels have received most of the attention in this regard; however, discrepancies among population studies have surfaced. Particularly limited is the information on the fate of Lp(a) that enters the arterial wall, in terms of mechanisms of endothelial transport and interactions with cells and macromolecules of the extracellular matrix. A typical Lp(a) represents a low-density lipoprotein (LDL)-like particle having as a protein moiety apo B-100 linked by a single interchain disulfide bond to a unique multikringle glycoprotein, called apolipoprotein(a) (apo[a]). In vitro studies have shown that Lp(a) can be dissected into its constituents, LDL and apo(a). In turn, the latter can be cleaved by enzymes of the elastase and metalloproteinase families into fragments that exhibit a differential behavior in terms of binding to macromolecules of the extracellular matrix: fibrinogen, fibronectin, and proteoglycans. By immunochemical criteria, apo(a) predominantly localizes in areas of human arteries affected by the atherosclerotic process, where elastase and metalloproteinase enzymes operate and where apo(a) fragments are potentially generated. The accumulation of these fragments in the vessel wall is likely to depend on their affinity for the constituents of the extracellular matrix. Thus, factors that modulate inflammation and inflammation-mediated fragmentation of Lp(a)/apo(a) may play an important role in the cardiovascular pathogenicity of Lp(a). This pathogenicity may be attenuated by measures directed at preventing the activation of those vascular cells that secrete enzymes with a proteolytic potential for Lp(a)/apo(a), namely, leukocytes, macrophages, and T cells.

Serum lipid physiology and the influence of glaucoma medications

Understanding the effect of serum lipid levels on risk factors for coronary heart disease and how they are influenced by medical therapy may lead to overall better care of the glaucoma patient. Elevated low-density lipoprotein and total cholesterol levels are major risk factors for heart disease. In contrast, high-density lipoprotein (HDL) is protective for heart disease. beta-adrenergic blockers, a class of medicines used to treat glaucoma, may influence serum lipid levels. Oral nonselective beta-adrenergic blockers reduce HDL cholesterol by 19% and increase triglycerides by 20-40%. Furthermore, topical nonselective beta-adrenergic blockers also decrease serum HDL and worsen the total cholesterol/HDL ratio. However, beta-blockers with intrinsic sympathomimetic activity appear to be lipid neutral. At present, there is no clear clinical evidence to indicate that changes in serum lipids with use of topical beta-adrenergic blockers significantly affect the clinical course of the patient. Little information is available for other classes of medicines used topically to treat glaucoma. However, oral preparations of prostaglandins, alpha-adrenergic agonists, angiotensin-converting enzyme inhibitors, and calcium channel blockers do not adversely affect serum lipid levels. Further study is required on newer glaucoma preparations to determine their specific actions on lipid levels. Additionally, further work is required to understand the significance of not only the adverse effect of beta-adrenergic blockers on lipid levels, but their overall effect on long-term cardiac morbidity and mortality.

Clinical implications of endothelial dysfunction

Endothelial dysfunction is increasingly recognized as an early event in the pathogenesis of cardiovascular disease. This observation is consistent with the growing appreciation of the role of endothelium in maintaining cardiovascular health. Endothelial dysfunction and coronary artery disease are both linked to hypertension, hypercholesterolemia, diabetes mellitus, and cigarette smoking. Modification of these conditions improves both endothelial function and coronary artery disease outcomes. Dietary and lifestyle modifications and antioxidant vitamin supplementation have a beneficial effect on endothelial function, as do angiotensin-converting enzyme inhibitors and lipid-lowering agents. Future studies will determine whether interventions that specifically target endothelial dysfunction can reduce rates of clinical disease.

Dyslipoproteinaemia and hyperoxidative stress in the pathogenesis of endothelial dysfunction in non-insulin dependent diabetes mellitus: an hypothesis

Endothelial dysfunction in non-insulin dependent (Type 2) diabetes mellitus (NIDDM) has implications for the pathogenesis of the two major complications, macrovascular disease and microangiopathy. Endothelial dysfunction is a consequence of a disturbance in the L-arginine/nitric oxide pathway. Its occurrence in NIDDM is well supported by both in vitro and in vivo studies. NIDDM results in diverse abnormalities in lipoprotein metabolism, the most significant being hypertriglyceridaemia which is associated with increased plasma concentrations of small dense LDL and low levels of HDL. Dysglycaemia results in hyperoxidative stress and increased formation of advanced-glycosylation endproducts, both of which enhance the oxidative modification of lipoprotein particles. Based on extensive in vitro studies and on human data, we generate the hypothesis that the development of endothelial dysfunction in NIDDM is a consequence of the effect of dyslipoproteinaemia, in particular increased circulatory concentrations of modified small dense LDL and of hyperoxidative stress on the formation, action and disposal of nitric oxide, by diverse molecular mechanisms; HDL is proposed to have a protective effect on these processes through its enzymic antioxidant properties. The hypothesis proposed is simple, testable and consistent with wide sources of evidence. The practical implications of the hypothesis and the existing opportunities for the prevention and reversal of endothelial dysfunction in NIDDM are also reviewed and discussed.

Increasing levels of leukocyte-derived inflammatory mediators in plasma and cAMP in platelets during follow-up after acute cerebral ischemia

Inflammatory mediators secreted by activated leukocytes play a role in the pathogenesis of atherosclerosis. They may also affect the production of vasodilatory and platelet antiaggregatory factors such as nitric oxide (NO) and prostacyclin (PGI2) from the vascular endothelium. Production of NO and PGI2, the effecs of which are mediated by cyclic 3',5'-guanosine monophosphate (cGMP) and cyclic 3',5'-adenosine monophosphate (cAMP), respectively, is disturbed in atherosclerosis, whereas increased NO levels have been found in acute cerebral ischemia. To investigate leukocyte activation and its possible influence upon endothelial function in cerebral ischemia we measured plasma neutrophil gelatinase-associated lipocalin (NGAL) and soluble tumor necrosis factor receptor protein-1 (sTNFR-1) by ELISA, and intraplatelet cAMP and cGMP by radioimmunoassay in 59 patients with acute ischemic stroke or transient ischemic attack (mean age 71 years, 27 males) and after a 1-year follow-up in 57/59 (97%) patients. NGAL (152 +/- 58 vs. 126 +/- 48 microgram/l), sTNFR-1 (3.50 +/- 2.2 vs. 2.59 +/- 1.31 microgram/l), and cAMP (5.12 +/- 1.71 vs. 4.06 +/- 0.92 pmol/10(9) platelets) were higher (p < 0.001) after follow-up than in acute cerebral ischemia. At follow-up sTNFR-1 and cGMP partially correlated (r = 0.31; p < 0.05), controlling for age and platelet count. In conclusion, plasma NGAL and sTNFR-1 and intraplatelet AMP increase after acute cerebral ischemia, indicating chronic inflammatory activity and endothelial activation. Plasma sTNFR-1 levels are related to intraplatelet cGMP levels.

Metabolism and drug interactions of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors in transplant patients: are the statins mechanistically similar?

3-Hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.88) inhibitors are the most effective drugs to lower cholesterol in transplant patients. However, immunosuppressants and several other drugs used after organ transplantation are cytochrome P4503A (CYP3A, EC 1.14.14.1) substrates. Pharmacokinetic interaction with some of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, specifically lovastatin and simvastatin, leads to an increased incidence of muscle skeletal toxicity in transplant patients. It is our objective to review the role of drug metabolism and drug interactions of lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin, and cerivastatin. In the treatment of transplant patients, from a drug interaction perspective, pravastatin, which is not significantly metabolized by CYP enzymes, and fluvastatin, presumably a CYP2C9 substrate, compare favorably with the other statins for which the major metabolic pathways are catalyzed by CYP3A.

Effects of short-term treatment of hyperlipidemia on coronary vasodilator function and myocardial perfusion in regions having substantial impairment of baseline dilator reverse

BACKGROUND

We tested the hypothesis that correction of hyperlipidemia improves coronary vasodilator response and maximal perfusion in myocardial regions having substantial impairment of pretreatment vasodilator capacity.

METHODS AND RESULTS

Measurements of myocardial blood flow were made with PET [13N]ammonia in 12 patients with ischemic heart disease (11 men; age, 65+/-8 years [mean+/-SD]) at rest and during adenosine at 70 and then 140 microg . kg-1 . min-1 for 5 minutes each before and approximately 4 months after simvastatin treatment (40 mg daily). Simvastatin reduced LDL (171+/-13 before versus 99+/-18 mg/dL after simvastatin, P<0.001) and increased HDL (39+/-8 versus 45+/-9 mg/dL, P<0.05). Myocardial segments were classified on the basis of pretreatment blood flow response to 140 microg . kg-1 . min-1 adenosine as normal (flow >/=2 mL . min-1 . g-1) or abnormal (flow <2 mL . min-1 . g-1). In normal segments, baseline myocardial blood flow (0.95+/-0.32) increased (P<0.001) at both low- (1.62+/-0.81) and high- (2.63+/-0.41) dose adenosine and was unchanged both at rest and with adenosine after simvastatin. In abnormal segments, myocardial blood flow at rest (0. 73+/-0.19) increased at low- (1.06+/-0.59, P<0.02) and high- (1. 29+/-0.33, P<0.01) dose adenosine. After simvastatin, myocardial blood flow increased more compared with pretreatment at both low- (1. 37+/-0.66, P<0.05 versus pretreatment) and high- (1.89+/-0.79, P<0. 01 versus pretreatment) dose adenosine.

CONCLUSIONS

Short-term lipid-lowering therapy increases stenotic segment maximal myocardial blood flow by approximately 45%. The mechanism involves enhanced, flow-mediated dilation of stenotic epicardial conduit vessels and may account at least in part for the efficacy of lipid lowering in secondary prevention trials and in reducing ischemic episodes in ambulatory patients.

Estradiol therapy combined with progesterone and endothelium-dependent vasodilation in postmenopausal women

BACKGROUND

Epidemiological studies indicate that estrogen replacement therapy decreases the risk of cardiovascular events in postmenopausal women. Estrogen may confer cardiovascular protection by improving endothelial function because it increases endothelium-dependent vasodilation. It is not known whether progesterone attenuates the beneficial effects of estrogen on endothelial function.

METHODS AND RESULTS

Seventeen postmenopausal women with mild hypercholesterolemia were enrolled in a placebo-controlled, crossover trial to evaluate the effect of transdermal estradiol, with and without vaginal micronized progesterone, on endothelium-dependent vasodilation in a peripheral conduit artery. Brachial artery diameter was measured with high-resolution B-mode ultrasonography. To assess endothelium-dependent vasodilation, brachial artery diameter was determined at baseline and after a flow stimulus induced by reactive hyperemia. To assess endothelium-independent vasodilation, brachial artery diameter was measured after administration of sublingual nitroglycerin. During estradiol therapy, reactive hyperemia caused an 11.1+/-1.0% change in brachial artery diameter compared with 4. 7+/-0.6% during placebo therapy (P<0.001). Progesterone did not significantly attenuate this improvement. During combined estrogen and progesterone therapy, flow-mediated vasodilation of the brachial artery was 9.6+/-0.8% (P=NS versus estradiol alone). Endothelium-independent vasodilation was not altered by estradiol therapy, either with or without progesterone, compared with placebo. There was a modest decrease in total and LDL cholesterol during treatment both with estradiol alone and when estradiol was combined with progesterone (all P<0.001 versus placebo). In a multivariate analysis that included serum estradiol, progesterone, total and LDL cholesterol concentrations, blood pressure, and heart rate, only the estradiol level was a significant predictor of endothelium-dependent vasodilation.

CONCLUSIONS

The addition of micronized progesterone does not attenuate the favorable effect of estradiol on endothelium-dependent vasodilation. The vasoprotective effect of hormone replacement therapy may extend beyond its beneficial actions on lipids.

The role of lipid-lowering therapy in multiple risk factor management

Epidemiological studies have demonstrated that the risk of death from coronary heart disease (CHD) increases in parallel with increasing serum cholesterol levels. The risk is highest in patients with severely elevated cholesterol levels [i.e. > 6.2 mmol/L(240 mg/dl)]. However, even in patients with serum cholesterol levels of 4.7 to 5.7 mmol/L (180 to 220 mg/dl), mortality from CHD is 30 to 70% higher than in patients with cholesterol levels < 4.7 mmol/L (180 mg/dl). A number of factors other than serum total cholesterol levels affect CHD risk. It is increasingly accepted that dysfunction of the vascular endothelium contributes to the pathogenesis of atherosclerosis. Experimental evidence and clinical studies suggest that endothelium-derived nitric oxide (NO) plays an important role as an endogenous antiatherogenic molecule, and that reduced levels of NO may promote progression of atherosclerosis. Hypercholesterolaemia can hasten atherogenesis in part by reducing levels of NO. In humans, it is possible to evaluate the effects of hypercholesterolaemia by measuring the vasodilator response to pharmacological or physical stimuli that increase the synthesis and release of endothelium-derived NO. The use of high resolution external ultrasound to assess post-ischaemic brachial artery vasodilation in patients with cardiovascular risk factors has demonstrated that endothelial dysfunction exists, even in the absence of overt atherosclerotic plaques. Impaired endothelium-dependent vasodilation has been observed in asymptomatic individuals with hypercholesterolaemia, as well as in patients with other recognised risk factors. Dietary and pharmacological lipid lowering has been shown to produce improvements in endothelial-dependent vasodilation. Among normocholesterolaemic healthy young individuals without cardiac risk factors, endothelium-dependent vasodilation was more likely to be impaired in those with relatively higher total and low density lipoprotein-cholesterol levels (i.e. above versus below the 25th percentile). This suggests that an inverse and continuous relationship exists between the prevailing cholesterol level and endothelial function. The implication of these findings is that the treatment of hypercholesterolaemia remains, at present, an underutilised means of reducing CHD.

Post-transcriptional regulation of endothelial nitric oxide synthase mRNA stability by Rho GTPase

The mechanism by which 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors increase endothelial nitric oxide synthase (eNOS) expression is unknown. To determine whether changes in isoprenoid synthesis affects eNOS expression, human endothelial cells were treated with the HMG-CoA reductase inhibitor, mevastatin (1-10 microM), in the presence of L-mevalonate (200 microM), geranylgeranylpyrophosphate (GGPP, 1-10 microM), farnesylpyrophosphate (FPP, 5-10 microM), or low density lipoprotein (LDL, 1 mg/ml). Mevastatin increased eNOS mRNA and protein levels by 305 +/- 15% and 180 +/- 11%, respectively. Co-treatment with L-mevalonate or GGPP, but not FPP or LDL, reversed mevastatin's effects. Because Rho GTPases undergo geranylgeranyl modification, we investigated whether Rho regulates eNOS expression. Immunoblot analyses and [35S]GTPgammaS-binding assays revealed that mevastatin inhibited Rho membrane translocation and GTP binding activity by 60 +/- 5% and 78 +/- 6%, both of which were reversed by co-treatment with GGPP but not FPP. Furthermore, inhibition of Rho by Clostridium botulinum C3 transferase (50 microg/ml) or by overexpression of a dominant-negative N19RhoA mutant increased eNOS expression. In contrast, activation of Rho by Escherichia coli cytotoxic necrotizing factor-1 (200 ng/ml) decreased eNOS expression. These findings indicate that Rho negatively regulates eNOS expression and that HMG-CoA reductase inhibitors up-regulate eNOS expression by blocking Rho geranylgeranylation, which is necessary for its membrane-associated activity.

Vasodilatory capacity of forearm resistance vessels is augmented in hypercholesterolemic patients after treatment with fluvastatin

Atherosclerotic vessels are characterized by endothelial and structural abnormalities as indicated by an impaired vasodilation to metabolic requirements. To determine whether effective treatment of hypercholesterolemia may improve vasodilatory capacity of resistance vessels, the authors examined the impact of 12 and 24 weeks of lipid-lowering therapy with the hepatic hydroxymethylglutaryl coenzyme A (HMG-CoA)-reductase inhibitor fluvastatin (40 to 80 mg/day) on the increment in forearm blood flow during reactive hyperemia in 24 hypercholesterolemic patients (mean age: 56 +/- 11 years; 15 men/9 women). Changes in forearm blood flow in response to reactive hyperemia were measured by venous occlusion plethysmography. Serum low-density lipoprotein (LDL)-cholesterol fell from 213 +/- 32 to 125 +/- 27 mg/dL (P<0.001) after 12 weeks and remained stable at a level of 125 +/- 18 mg/dL after 24 weeks of treatment. Baseline forearm blood flow was similar before and after 12 and 24 weeks of therapy. In contrast, forearm blood flow at peak reactive hyperemia was greater at week 12 (37.0 +/- 22.9 mL/min/100 mL; P<0.05), and at week 24 (47.1 +/- 33.5 mL/min/100 mL; P<0.05) than at week 0 (30.5 +/- 18.1 mL/min/100 mL). Compared with week 0 (defined as 100%), the percent change in forearm blood flow in response to reactive hyperemia was augmented at week 12 (171 +/- 144%; P<0.05 vs week 0) and at week 24 (218 +/- 228%; P<0.05 vs week 0). Thus, the lowering of high serum LDL cholesterol after short-term treatment with fluvastatin increased the blood flow responses during reactive hyperemia in forearm resistance vessels. These data indicate a beneficial effect of HMG-CoA reductase inhibition on structural wall properties of peripheral arteries in human atherosclerosis.

Additional benefit of vitamin E supplementation to simvastatin therapy on vasoreactivity of the brachial artery of hypercholesterolemic men

OBJECTIVES

The aim of this study was to determine whether the combination of lipid-lowering therapy and vitamin E supplementation improves peripheral endothelial function and whether it is more effective than lipid-lowering therapy alone.

BACKGROUND

Endothelium-dependent vasodilation is impaired in coronary and peripheral arteries of patients with hypercholesterolemia. Coronary endothelial function has been shown to improve under lipid-lowering and antioxidant therapy, but the effect of additive vitamin E supplementation in the brachial artery is unknown.

METHODS

Seven patients with hypercholesterolemia (mean+/-SD; age 51+/-10 yr) were studied. Endothelium-dependent, flow-mediated dilation (FMD) and endothelium-independent nitroglycerin-induced dilation (NMD) were assessed in the brachial artery using high resolution ultrasound 1) at baseline (BL I), 2) after 8 weeks of simvastatin (20 mg) and vitamin E (300 IU) therapy (Comb I), 3) after withdrawal of vitamin E for 4 weeks (Statin), 4) after therapy as in #2 for 4 weeks (Comb II) and 5) after withdrawal of both drugs for 4 weeks (BL II).

RESULTS

Combined simvastatin and vitamin E therapy reduced total cholesterol (Comb I vs. BL I: 276+/-22 vs. 190+/-14 mg/dl, p < 0.0001) and low-density lipoprotein (LDL)-C (197+/-22 vs. 106+/-22 mg/dl, p < 0.00001), augmented alpha tocopherol levels normalized to LDL (12.2+/-4.1 vs. 4.9+/-0.9 microg alpha-T/100 mg% LDL-C, p < 0.01) and resulted in significant improvements in FMD (16.4+/-4.7 vs. 4.9+/-2.5%, p < 0.001) as well as NMD (17.9+/-4.3 vs. 11.2+/-2.8%, p < 0.01). The ratio of FMD to NMD (0.92+/-0.17 vs. 0.46+/-0.24%, p < 0.05) also increased under combination therapy, indicating a greater improvement of FMD than that of NMD. After withdrawal of vitamin E, both FMD (Comb I vs. Statin: 16.4+/-4.7 vs. 7.9+/-4.7%, p < 0.01) and NMD (17.9+/-4.3 vs. 10.9+/-4.5%, p < 0.05) decreased significantly such that simvastatin alone only tended to improve FMD and did not change NMD. Results under combination therapy (Comb II vs. BL II) were reproducible.

CONCLUSIONS

Combined vitamin E and simvastatin therapy leads to an improvement of FMD and NMD in the brachial artery of patients with hypercholesterolemia. The improvement of FMD is more pronounced after combination therapy than after lipid-lowering therapy alone, similar to previous findings in the coronary circulation.

Inflammation, pravastatin, and the risk of coronary events after myocardial infarction in patients with average cholesterol levels. Cholesterol and Recurrent Events (CARE) Investigators

BACKGROUND

We studied whether inflammation after myocardial infarction (MI) is a risk factor for recurrent coronary events and whether randomized treatment with pravastatin reduces that risk.

METHODS AND RESULTS

A nested case-control design was used to compare C-reactive protein (CRP) and serum amyloid A (SAA) levels in prerandomization blood samples from 391 participants in the Cholesterol and Recurrent Events (CARE) trial who subsequently developed recurrent nonfatal MI or a fatal coronary event (cases) and from an equal number of age- and sex-matched participants who remained free of these events during follow-up (control subjects). Overall, CRP and SAA were higher among cases than control subjects (for CRP P=0.05; for SAA P=0.006) such that those with levels in the highest quintile had a relative risk (RR) of recurrent events 75% higher than those with levels in the lowest quintile (for CRP RR= 1.77, P=0.02; for SAA RR= 1.74, P=0.02). The study group with the highest risk was that with consistent evidence of inflammation (elevation of both CRP and SAA) who were randomly assigned to placebo (RR=2.81, P=0.007); this risk estimate was greater than the product of the individual risks associated with inflammation or placebo assignment alone. In stratified analyses, the association between inflammation and risk was significant among those randomized to placebo (RR=2.11, P=0.048) but was attenuated and nonsignificant among those randomized to pravastatin (RR=1.29, P=0.5).

CONCLUSIONS

Evidence of inflammation after MI is associated with increased risk of recurrent coronary events. Therapy with pravastatin may decrease this risk, an observation consistent with a nonlipid effect of this agent.

Current and future treatment of hyperlipidemia: the role of statins

Hyperlipidemia is recognized as one of the major risk factors for the development of coronary artery disease and progression of atherosclerotic lesions. Dietary therapy together with hypolipidemic drugs are central to the management of hyperlipidemia, which aims to prevent atherosclerotic plaque progression, induce regression, and so decrease the risk of acute coronary events in patients with pre-existing coronary or peripheral vascular disease. In patients at high risk of coronary artery disease but without evidence of atherosclerosis, treatment is designed to prevent the premature development of coronary artery disease, whereas in those with hypertriglyceridemia, treatment aims to prevent the development of hepatomegaly, splenomegaly, and pancreatitis. The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, are the most potent lipid-lowering agents currently available, and their use in the treatment of hyperlipidemia provides the focus for this review. Particular emphasis is given to cerivastatin, a new HMG-CoA reductase inhibitor that combines potent cholesterol-lowering properties with significant triglyceride-reducing effects. Recently completed primary and secondary intervention trials have shown that the significant reductions in low-density lipoprotein (LDL) cholesterol achieved with statins result in significant reductions in morbidity and mortality associated with coronary artery disease as well as reductions in the incidence of stroke and total mortality. Such benefits occur early in the course of statin therapy and have led to suggestions that these drugs may possess antiatherogenic effects over and above their capacity to lower atherogenic lipids and lipoproteins. Experimental studies have also shown statin-induced improvements in endothelial function, decreased platelet thrombus formation, improvements in fibrinolytic activity, and reductions in the frequency of transient myocardial ischemia.

Effects of omega-3 fatty acids and/or antioxidants on endothelial cell markers

BACKGROUND

Increased expression of cell adhesion molecules and increased procoagulant activity of the vascular endothelium have been postulated to characterize dysfunctional endothelium. The cellular effects of n-3 fatty acids (n-3 FAs) and antioxidants are still not clarified.

METHODS

In a randomized, factorial two-by-two design study, we have investigated 41 male smokers with hyperlipidaemia before and after 6 weeks of supplementation with either n-3 FAs (4.8 g daily) or placebo with the addition of antioxidants (150 mg of vitamin C, 75 mg of vitamin E and 15 mg of beta-carotene daily) or placebo with regard to the effects on some endothelial cell markers: thrombomodulin (sTM), von Willebrand factor (vWF), tissue plasminogen activator antigen (tPAag) and soluble forms of the cell adhesion molecules E-selectin, P-selectin and vascular cell adhesion molecule 1 (VCAM-1).

RESULTS

In the n-3 FA group, significant reductions in the plasma levels of vWF (P = 0.034) and sTM (P < 0.001) were demonstrated compared with placebo, whereas increased levels were found for E-selectin (P = 0.001) and VCAM-1 (P = 0.010). In the antioxidant group, no differences in changes were noted for any of the variables.

CONCLUSION

The reduction in the levels of sTM and vWF with n-3 FA supplementation could indicate an improvement with regard to the haemostatic markers of endothelial dysfunction, whereas the simultaneous increase in the soluble forms of E-selectin and VCAM-1 may suggest an adverse effect on the inflammatory system. The antioxidants seem to be neutral in their effect on these endothelial cell markers in our study population of smokers. The interpretation of the soluble forms of these molecules are, however, still debatable.

Endothelium and acute coronary syndromes

The vascular endothelium is a dynamic endocrine organ that regulates contractile, secretory, and mitogenic activities in the vessel wall and hemostatic processes within the vascular lumen. Risk factors for atherosclerosis such as cigarette smoking, hypertension, and increased serum lipid concentrations impair endothelial function and lead to the development of atherosclerotic vessels, which cause acute coronary syndromes. Atherosclerotic vessels progress from scattered foam cells to complex lesions with a lipid core and fibrous cap. Factors that weaken and cause the rupture of the fibrous cap will expose circulating blood products to the procoagulant materials in the lipid core. Thrombosis and subsequent remodeling of the unstable plaque may be catastrophic or clinically silent depending on the degree of vascular occlusion and availability of collateral blood flow. Evidence is presented that supports the view that endothelial dysfunction is an early marker of atherosclerosis and an important contributor to the atherogenic process.

Role of nitric oxide in cardiovascular disease: focus on the endothelium

Nitric oxide is a soluble gas continuously synthesized by the endothelium. This substance has a wide range of biological properties that maintain vascular homeostasis, including modulation of vascular dilator tone, regulation of local cell growth, and protection of the vessel from injurious consequences of platelets and cells circulating in blood. A growing list of conditions, including those commonly associated as risk factors for atherosclerosis such as hypertension and hypercholesterolemia, are associated with diminished release of nitric oxide into the arterial wall either because of impaired synthesis or excessive oxidative degradation. Diminished nitric oxide bioactivity may cause constriction of coronary arteries during exercise or during mental stress and contribute to provocation of myocardial ischemia in patients with coronary artery disease. Additionally, diminished nitric oxide bioactivity may facilitate vascular inflammation that could lead to oxidation of lipoproteins and foam cell formation, the precursor of the atherosclerotic plaque. Numerous therapies have been investigated to assess the possibility of reversing endothelial dysfunction by enhancing the release of nitric oxide from the endothelium, either through stimulation of nitric oxide synthesis or protection of nitric oxide from oxidative inactivation and conversion to toxic molecules such as peroxynitrite. Accordingly, causal relationships between improved endothelial function and reduction in myocardial ischemia and acute coronary events can now be investigated.

Reactive hyperemic response of the brachial artery: comparison of proximal and distal occlusion

RATIONALE AND OBJECTIVES

The authors compared the postocclusion hyperemic responses of the brachial artery after occluding blood flow proximal to and distal to the studied area.

MATERIALS AND METHODS

Response of the brachial artery to hypoxia was evaluated with duplex Doppler ultrasound in 13 healthy subjects. A pneumatic tourniquet was first positioned 2-5 cm superior to the left elbow, proximal to the area of artery studied. Two hours later the response was remeasured with the tourniquet positioned 2-5 cm inferior to the elbow, distal to the artery studied. Arterial diameter, mean and peak flow velocities, and heart rate were assessed.

RESULTS

No significant differences were observed between measurements of baseline and postischemic arterial diameter, percentage diameter change, baseline mean arterial blood flow velocity, baseline peak arterial blood flow velocity, or postischemic heart rate obtained with proximal occlusion of the artery and those obtained with distal occlusion. In contrast, mean and peak postischemic arterial blood flow velocity and preocclusion heart rate were higher in measurements made during proximal artery occlusion. Significant correlation was found between measurements of percentage change in artery diameter obtained with proximal artery occlusion and those obtained with distal occlusion (r = 0.611, P < .05).

CONCLUSION

There are no major differences in postischemic changes in brachial artery diameter related to reactive hyperemia between blood flow occlusion applied proximal and distal to the studied area. However, there are significant differences in the mean and peak systolic velocities. Either occlusion site can be used for clinical studies if arterial diameter change is monitored, but if velocity measurements are being compared, a single occlusion site should be chosen.

Differential effects of lovastatin on the trafficking of endogenous and lipoprotein-derived cholesterol in human monocyte-derived macrophages

Lovastatin has been shown to reduce cholesterol esterification in cholesterol-loaded human macrophages. Surprisingly, in nonloaded macrophages, lovastatin produces the opposite effect, lowering free cholesterol and increasing cholesteryl ester levels, as measured by high-performance liquid chromatography. In cholesterol-loaded cells, lovastatin reduced the cholesteryl esters of unsaturated but not those of saturated fatty acids. In nonloaded cells, by contrast, the cholesteryl esters of unsaturated fatty acids tended to increase after lovastatin treatment. Total (free plus esterified) cellular cholesterol content in nonloaded cells fell by 18% with 12-micromol/L lovastatin treatment but did not change in cholesterol-loaded cells. Lovastatin had no effect on the binding or uptake of acetylated low density lipoprotein, acyl coenzyme A:cholesterol acyltransferase (ACAT) activity, the secretion of [3H]cholesterol into the medium, or lysosomal hydrolysis of cholesteryl esters. Apolipoprotein (apo) E mRNA levels increased but apoE secretion into the medium decreased with lovastatin treatment in both cholesterol-loaded and nonloaded cells. Cholesterol of exogenous origin has been shown to pass via the cell membrane before its esterification by ACAT. We postulate that this is not the case for endogenous cholesterol, which may have direct access to ACAT. Our findings therefore suggest that lovastatin hinders the delivery of intracellular cholesterol to the plasma membrane, resulting in increased free cholesterol and lower levels of cholesteryl ester in cholesterol-loaded cells. In nonloaded cells, virtually all cholesterol is of endogenous origin and is normally translocated to the cell membrane. Lovastatin prevents this process, thus shunting newly synthesized cholesterol toward esterification and leading to an increase in the concentration of cholesteryl esters, even in the face of a drop in total and free cholesterol levels. Intracellular apoE may play a role in this process.

Stroke protection by 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors mediated by endothelial nitric oxide synthase

The treatment of ischemic strokes is limited to prophylactic agents that block the coagulation cascade. Here, we show that cholesterol-lowering agents, 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors, protect against cerebral injury by a previously unidentified mechanism involving the selective up-regulation of endothelial NO synthase (eNOS). Prophylactic treatment with HMG-CoA reductase inhibitors augments cerebral blood flow, reduces cerebral infarct size, and improves neurological function in normocholesterolemic mice. The up-regulation of eNOS by HMG-CoA reductase inhibitors is not associated with changes in serum cholesterol levels, but is reversed by cotreatment with L-mevalonate and by the downstream isoprenoid, geranylgeranyl pyrophosphate and not by farnesyl pyrophosphate. The blood flow and neuroprotective effects of HMG-CoA reductase inhibitors are completely absent in eNOS-deficient mice, indicating that enhanced eNOS activity by HMG-CoA reductase inhibitors is the predominant if not the only mechanism by which these agents protect against cerebral injury. Our results suggest that HMG-CoA reductase inhibitors provide a prophylactic treatment strategy for increasing blood flow and reducing brain injury during cerebral ischemia.

Increased bioavailability of nitric oxide after lipid-lowering therapy in hypercholesterolemic patients: a randomized, placebo-controlled, double-blind study

BACKGROUND

Impaired endothelium-dependent vasodilation is an early sign of atherosclerosis in hypercholesterolemic patients. We hypothesized that lipid-lowering therapy can improve endothelial function and that this effect is mainly mediated by increased bioavailability of nitric oxide (NO).

METHODS AND RESULTS

In a randomized, double-blind, placebo-controlled trial, we studied 29 patients (age, 50+/-12 years) with hypercholesterolemia (LDL cholesterol > or = 160 mg/dL) randomly assigned to receive either fluvastatin (40 mg twice daily; 17 patients) or placebo (12 patients). Forearm blood flow was measured by plethysmography before and after 24 weeks of treatment. Endothelium-dependent vasodilation was assessed by intra-arterial infusion of acetylcholine (ACh; 3, 12, 24, and 48 microg/min) and basal NO synthesis rate by intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA; 1, 2, and 4 micromol/min). Simultaneous intra-arterial infusion of L-NMMA (4 micromol/min) and ACh (12, 24, and 48 microg/min) was used to test whether any increase in endothelium-dependent vasodilation after lipid-lowering therapy could be blocked by this NO synthase inhibitor. Endothelium-dependent vasodilation improved significantly after 24 weeks of lipid-lowering therapy compared with before therapy (ACh 24 microg/min: 240+/-34% before versus 347+/-50% after therapy; P< or =0.01) and placebo (changes between after and before therapy with ACh 24 microg/min: 108+/-39% for fluvastatin versus -26+/-32% for placebo; P< or =0.05). This improvement in endothelium-dependent vasodilation could be blocked by simultaneous administration of L-NMMA (ACh 24 microg/min plus L-NMMA 4 micromol/min: 170+/-69% before versus 219+/-47% after treatment; P=NS).

CONCLUSIONS

Lipid-lowering therapy with fluvastatin can improve disturbed endothelial function in hypercholesterolemic patients compared with placebo. This improvement is mediated by increased bioavailability of NO.

Role of angiotensin-converting enzyme inhibition in reversal of endothelial dysfunction in coronary artery disease

Angiotensin-converting enzyme (ACE) inhibitors have shown unexpected benefits in the prevention of ischemic events in patients with hypertension and congestive heart failure. In addition to these clinical observations, there is a growing body of knowledge about the molecular and cellular effects of ACE inhibitors. For example, ACE inhibition prevents stimulation of smooth muscle cell angiotensin II receptors, thereby blocking both contractile and proliferative actions. Angiotensin II blockade also diminishes the production of superoxide anion, which inactivates ambient nitric oxide. ACE inhibition of kininase II inhibits the breakdown of bradykinin, a direct stimulant of nitric oxide release from the intact endothelial cell. Thus, at the cellular level within the vasculature, ACE inhibition shifts the balance of ongoing mechanisms in favor of those promoting vasodilatory, antiaggregatory, antithrombotic, and antiproliferative effects. These effects underlie the potential benefits of ACE inhibition in the therapy of ischemia and atherosclerosis. Some data is available in humans to show that these effects can be sustained for months, thereby maintaining improved endothelial function and, presumably, allowing the initiation of steps that might alter the progression of atherosclerosis. Definitive information is not yet available in humans to show that ACE inhibition clearly alters the progression of atherosclerosis or diminishes coronary events in uncomplicated coronary disease. This promising area of investigation is, however, the subject of multiple clinical trials, which should provide clarification of this important question in coming years.

Endothelial function in health and disease: new insights into the genesis of cardiovascular disease

The vascular endothelium secretes factors that not only modulate blood vessel tone, but also participate in the development and progression of atherosclerosis through their effects on platelet adhesion and aggregation, thrombogenicity, and cell proliferation. Altered activities of these substances in patients with risk factors for cardiovascular disease (e.g., hypercholesterolemia, hypertension, diabetes, aging, postmenopausal status, smoking, and infections) appear to underlie the atherosclerotic process. There is increasing evidence from both preclinical studies and clinical trials that nitric oxide (NO) plays a pivotal role in the pathophysiology of arteriosclerosis. This review describes the role of NO in human health and disease and summarizes strategies currently being used to measure and improve endothelial dysfunction.

Long-term effect of low-density lipoprotein apheresis on plasma lipoproteins and coronary heart disease in native vessels and coronary bypass in severe heterozygous familial hypercholesterolemia

Low-density lipoprotein (LDL) apheresis is a potent treatment for patients with coronary heart disease and severe hereditary forms of LDL hypercholesterolemia not adequately responsive to drug treatment. Until now, the beneficial effect of aggressive reduction of LDL cholesterol by LDL apheresis on the course of coronary heart disease has been demonstrated in one 3-year study and several studies lasting 2 years. We now report on the clinical course, lipoprotein concentrations, coronary angiograms, and side effects in patients undergoing LDL apheresis for as long as 8.6 years. Thirty-four patients (21 men and 13 women) with coronary heart disease and heterozygous familial hypercholesterolemia (FH) not adequately responsive to lipid-lowering drugs received weekly (four patients biweekly) LDL apheresis for 4.6 +/- 2.6 years under diet and lipid-lowering drug therapy; after 0.5 to 3 years, simvastatin in the maximal tolerable dose was added. The baseline LDL cholesterol concentration was 6.9 +/- 1.6 mmol/L. Combined treatment in the steady state yielded a pretreatment and posttreatment LDL cholesterol concentration of 4.8 +/- 0.9 and 1.8 +/- 0.4 mmol/L, respectively. The calculated interval mean LDL cholesterol was 3.3 +/- 0.6 mmol/L. Evaluation of the coronary angiographies revealed a definite regression of coronary lesions in four patients (11.8%); in 19 patients, there was a cessation of progression. Two patients developed atheromatous lesions in bypass grafts (L.H., 60% stenosis; S.M., occlusion). Of 23 patients eligible for the scoring of anginal symptoms, five (21.7%) reported a reduction of the frequency and severity of angina pectoris. The mean coronary symptom score in 23 patients changed from 1.65 +/- 0.83 at baseline to 1.39 +/- 0.66 at the end of the study. During the whole observation period, we observed three sudden deaths, one nonfatal myocardial infarction, and five patients requiring hospital admission because of unstable angina pectoris, one of which was followed by a transluminal coronary angioplasty. Aggressive reduction of LDL cholesterol with combined LDL apheresis and drugs induced regression of coronary lesions in four of 34 patients and prevented progression in 29 patients for as long as 8.6 years. The effect on LDL and high-density lipoprotein (HDL) cholesterol and lipoprotein(a) [Lp(a)] was comparable with all three apheresis techniques. Therefore, no obvious difference between the three techniques was found regarding changes in coronary lesions.