Biological mechanisms for the clinical success of lipid-lowering in coronary artery disease and the use of surrogate end-points

Regulation of peripheral blood flow in complex regional pain syndrome: clinical implication for symptomatic relief and pain management

BACKGROUND

During the chronic stage of Complex Regional Pain Syndrome (CRPS), impaired microcirculation is related to increased vasoconstriction, tissue hypoxia, and metabolic tissue acidosis in the affected limb. Several mechanisms may be responsible for the ischemia and pain in chronic cold CPRS.

DISCUSSION

The diminished blood flow may be caused by either sympathetic dysfunction, hypersensitivity to circulating catecholamines, or endothelial dysfunction. The pain may be of neuropathic, inflammatory, nociceptive, or functional nature, or of mixed origin.

SUMMARY

The origin of the pain should be the basis of the symptomatic therapy. Since the difference in temperature between both hands fluctuates over time in cold CRPS, when in doubt, the clinician should prioritize the patient's report of a persistent cold extremity over clinical tests that show no difference. Future research should focus on developing easily applied methods for clinical use to differentiate between central and peripheral blood flow regulation disorders in individual patients.

Simvastatin attenuates cisplatin-induced kidney and liver damage in rats

Statins have anti-inflammatory effects that are not directly related to their cholesterol-lowering activity. This study aimed to investigate the effect of simvastatin on the extent of tissue damage in cisplatin-induced nephrotoxicity and hepatotoxicity. The rats received a single intravenous injection of 2.5mgkg(-1) cisplatin. Other groups received either simvastatin (1mgkg(-1)) or the vehicle (ethanol:saline) intraperitoneally for 10 days beginning 5 days prior to cisplatin injection. All animals were decapitated 5 days after cisplatin administration. Trunk blood was collected and analyzed for blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), albumin, and total bilirubin levels. The urine samples were used for the calculation of creatinine clearance levels. The kidney and liver samples were stored for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content or were processed for histopathological examinations. Formation of reactive oxygen species in tissue samples was monitored by using chemiluminescence method. Simvastation reduced the extent of both kidney and liver damage and preserved both kidney and liver functions (p<0.01-0.001). Increase in liver MDA level with a concomitant reduction in GSH in the cisplatin group was attenuated by simvastatin treatment (p<0.05-0.01). Increase in tissue collagen content and chemiluminescence levels in the kidney and liver samples of the cisplatin group was also reversed by simvastatin (p<0.001). In conclusion, simvastatin is beneficial in cisplatin-induced kidney and liver dysfunction and organ damage in rats via prevention of lipid peroxidation and tissue fibrosis, preservation of antioxidant glutathione, and suppression of neutrophil infiltration.

Effects of statins on experimental colitis in normocholesterolemic rats

OBJECTIVE

The results of previous studies suggest that statins have a direct anti-inflammatory effect that is not directly related to their cholesterol-lowering activity. The aim of this study was to investigate the effect of simvastatin (SIM) and fluvastatin (FLU) on trinitrobenzene sulfonic acid (TNBS)-induced colonic inflammation in rats.

MATERIAL AND METHODS

The drugs were given for 3 days (0.1 and 1 mg/kg day-1; intraperitoneally) after induction of colitis. The lesions in the distal colon were scored at the macroscopic and microscopic level. Tissue malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content were assessed and formation of reactive oxygen species and peroxynitrite was monitored by chemiluminescence (CL) assay. Trunk blood was collected for the measurement of serum tumor necrosis factor (TNF)-alpha level.

RESULTS

Treatment with SIM reduced the lesion score of the colitis group at macroscopic level (p<0.05), but there was no effect of treatment with FLU. The increase in colonic MDA level of the colitis group was reduced by both drugs at all doses (p<0.05-0.001). The decrease in GSH and the an increase in MPO activity in the colitis group were reversed by SIM at all doses (p<0.01), but FLU had no effect. An increase in colonic lucigenin CL value in the colitis group was reduced by SIM and FLU at all doses (p<0.001) and an increase in peroxynitrite ratio in the colitis group showed a significant reduction in SIM-treated groups; FLU reduced this effect at a dose of 1 mg/kg (p<0.01). An increase in tissue collagen content and serum TNF-alpha level in the colitis group was reversed by both drugs at all doses (p<0.001).

CONCLUSIONS

SIM and FLU seemed to be beneficial in a TNBS-induced rat colitis model through the prevention of lipid peroxidation, superoxide generation, cytokine production and neutrophil accumulation.

Post-infarction treatment with simvastatin reduces myocardial no-reflow by opening of the KATP channel

Simvastatin can prevent cardiac remodelling after myocardial infarction, though the exact mechanisms are uncertain. Myocardial no-reflow is associated with progressive cardiac remodelling. However, it remains unknown whether post-infarction treatment with simvastatin can also reduce myocardial no-reflow for which suppression of adenosine triphosphate-sensitive K+ (K(ATP)) channel opening is an important mechanism.

METHODS

Area at risk and the area of no-reflow were determined by myocardial contrast echocardiography (MCE) and by pathology in 45 mini-swine randomised into 5 groups: 10 control, 9 simvastatin, 9 glibenclamide, 9 simvastatin plus glibenclamide and 8 sham-operated. A myocardial infarction and reperfusion model was created by 3-h occlusion of the coronary artery followed by 4 weeks of reperfusion.

RESULTS

Compared with the control group, simvastatin significantly increased coronary blood volume (P<0.01) and decreased the area of no-reflow measured by MCE (78.5+/-4.5% to 43.7+/-4.3%) and pathological evaluation (82.3+/-1.9% to 45.2+/-3.8%) of area at risk (P<0.01). Simvastatin also increased the levels of K(ATP) channel proteins (SUR2 and Kir6.2) (P<0.05), but had no effect on necrosis area. The combination of simvastatin and glibenclamide had no significant effect on the above parameters.

CONCLUSIONS

Post-infarction treatment with simvastatin can reduce myocardial no-reflow. This beneficial effect is due to activation of the K(ATP) channel.

The Role of Salicornia herbacea in Ovariectomy-Induced Oxidative Stress

Ovarian hormone deficiency increases the generation of reactive oxygen species. Their excess induces oxidative stress, which results in the cell damage or death. It causes the aging diseases-atherosclerosis, rheumatoid arthritis, osteoporosis, etc. Ovariectomized rats are used as oxidative stress models. We verified the effects of ovariectomy-induced oxidative stress on free radical production as evaluated by DPPH elimination, lipoperoxidation evaluated by malondialdehyde levels, and antioxidant activation of superoxide dismutase, catalase, glutathione peroxidase, and estradiol in the liver and sera. Ovariectomized rats were given Salicornia herbacea (SH) intraperitoneally at the dose of 100 mg/kg daily for 2 months. Free radical-scavenging activity of SH was measured in comparison with that of L-ascorbic acid. The histopathology of liver tissue was also investigated. Antioxidative values in the ovariectomized group decreased, but those in the SH-treated group increased due to the free radical-scavenging activity of SH. Moreover, inflammation and cirrhosis in the liver tissue of SH-treated rats decreased significantly. These results suggest that SH may be a potential candidate for an antioxidative reagent.

Potential vascular benefits of statins

Atherosclerosis is associated with a number of functional abnormalities that affect endothelium-dependent vasomotor function, inflammation, and thrombosis. The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have effects on many of these functions, likely explaining their benefit in reducing the incidence of clinical events in patients at high risk of cardiovascular disease. Statins may improve this vascular biology by lowering levels of low-density lipoprotein (LDL) or potentially by a number of non-LDL-related mechanisms. Cell culture and some animal studies have demonstrated LDL-independent effects of statins. The non-LDL mechanisms include effects on isoprenoid production and function, interactions between caveolin and nitric oxide synthase, and direct immunomodulatory effects. Although these mechanisms are clearly demonstrated in the experimental setting, their relevance to the clinical use of statins is unknown. From a purely pragmatic viewpoint, the debate of lipid versus nonlipid effects of statins matters little to clinical practice. Their proven effect on vascular biology and risk reduction justifies their important therapeutic role.

Strategies to Increase HMG-CoA Reductase Inhibitor Use After Acute Myocardial Infarction

Coronary artery disease with its accompanying complication of acute myocardial infarction (MI) is one of the major causes of death in the modern world. A variety of both primary and secondary prevention strategies have been developed for the treatment of acute MI. One of the more important of these strategies is the prescription of HMG-CoA reductase inhibitors. HMG-CoA reductase inhibitors have the potential to positively affect the outcome of acute MI in a variety of ways including the reduction of low-density lipoprotein-cholesterol levels and stabilisation of the atherosclerotic plaque. Multiple large randomised clinical trials have documented the potential of HMG-CoA reductase inhibitors to reduce both short- and long-term mortality after acute MI. This benefit exists regardless of age, gender, clinical presentation, or even baseline lipid levels. However, despite this overwhelming amount of evidence supporting the use of HMG-CoA reductase inhibitors in the post-MI setting, multiple studies have documented the presence of a significant 'treatment gap'. Indeed, often, less than half of acute MI patients who would benefit from HMG-CoA reductase inhibitor therapy actually receive it. The reasons for the low utilisation of HMG-CoA reductase inhibitors in the acute MI patient are many, but may include poor communication, the high cost of treatment, the lack of associated symptoms and confusion regarding appropriate lipid levels to target. One approach that has been tried to address these issues is the development of institutional programmes specifically targeted to increase the use of HMG-CoA reductase inhibitors in acute MI patients. These programmes, often managed by nurses or pharmacists, have been piloted in several institutions. They have been effectively implemented in both inpatient and outpatient settings. In most cases they have been implemented without a great increase in expense. They have often increased the use of HMG-CoA reductase inhibitors to >90%. Most importantly, they have documented a significant improvement in the long-term survival of acute MI patients. Based on these preliminary studies, it is recommended that the implementation of these strategies be considered by most healthcare institutions.

No effect of simvastatin treatment on insulin sensitivity in patients with primary hypercholesterolemia

OBJECTIVE

Statins, in addition to cholesterol lowering, have nonlipid effects on formation and progression of atheromatous plaque. Insulin resistance and hyperinsulinemia may have detrimental influences on the arterial wall. Statins (may also) inhibit insulin signal transferring in vascular smooth cell cultures. However, their effect on insulin sensitivity remains controversial. Therefore, we decided to investigate the effect of simvastatin on insulin sensitivity in hypercholesterolemic patients.

PATIENTS AND METHODS

Eighteen patients with primary hypercholesterolemia were divided into simvastatin group (n = 9; 4 females, 5 males; BMI 30.6 +/- 4 kg/m2; mean ages 57 +/- 6 years) and placebo group (n = 9; 4 females, 5 males; BMI 28 +/- 2.9 kg/m2; mean ages 49 +/- 10 years). Simvastatin (20 mg/day) or placebo were given for 2 months. Total and HDL cholesterol were measured and LDL cholesterol was calculated by Friedewald formula. Insulin sensitivity was determined by using euglycemic hyperinsulinemic clamp technique [40 microU/m2/min insulin infusion rate; glucose disposal rate (M)= mg/kg/min] before and after treatment.

RESULTS

Plasma levels of total, LDL and HDL cholesterol decreased significantly in simvastatin group after treatment (p = 0.000, p = 0.000, and p = 0.048, respectively). Plasma levels of total cholesterol decreased significantly (p = 0.032), whereas LDL and HDL levels remained unchanged in placebo group. M value (mg/kg/min) decreased insignificantly in simvastatin group (4.32 +/- 1.57 vs. 3.71 +/- 1.91) and increased in placebo group (3.55 +/- 1.91 vs. 3.95 +/- 0.95).

CONCLUSION

Short-term simvastatin treatment did not affect insulin sensitivity determined by "gold standard" euglycemic hyperinsulinemic clamp method in hypercholesterolemic patients in this research. Further studies with simvastatin using higher doses and longer duration should be performed.

The 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor pravastatin reduces disease activity and inflammation in dextran-sulfate induced colitis

The dextran sulfate (DSS) model of colitis causes intestinal injury sharing many characteristics with inflammatory bowel disease, e.g., leukocyte infiltration, loss of gut epithelial barrier, and cachexia. These symptoms are partly mediated by entrapped leukocytes binding to multiple endothelial adhesion molecules (MAdCAM-1, VCAM-1, ICAM-1, and E-selectin). Pravastatin, an 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor, has anti-inflammatory potency in certain inflammation models; therefore, in this study, we measured the effects of pravastatin in DSS-induced colitis. The administration of pravastatin (1 mg/kg) relieved DSS-induced cachexia, hematochezia, and intestinal epithelial permeability, with no effect on serum cholesterol. Histopathologically, pravastatin prevented leukocyte infiltration and gut injury. Pravastatin also blocked the mucosal expression of MAdCAM-1. DSS treatment promoted mucosal endothelial nitric-oxide synthase (eNOS) mRNA degradation, an effect that was blocked by pravastatin. Importantly, the protective effects of pravastatin in DSS-induced colitis were not found in eNOS-deficient mice. Our results demonstrate that HMG-CoA reductase inhibitors preserve intestinal integrity in colitis, most likely via increased eNOS expression and activity, independent of cholesterol metabolism.

Statin lipid-lowering therapy for acute myocardial infarction and unstable angina: efficacy and mechanism of benefit

The use of statin agents in patients with acute coronary syndromes (ACSs) remains an area of intense clinical interest. Statin therapy has an established secondary preventive benefit in patients with coronary artery disease, and its extension to ACS seems logical. A number of observational studies have shown an association between initiation of statin therapy early in ACS and improved clinical outcome. Additionally, 4 randomized controlled trials have examined the use of statin therapy for ACS: the Myocardial Ischemia Reduction with Aggressive Cholesterol Lowering (MIRACL) study, the Pravastatin Turkish Trial, the Fluvastatin on Risk Diminishing After Acute Myocardial Infarction (FLORIDA) study, and the Lipid-Coronary Artery Disease (L-CAD) study. Three of these trials showed a benefit with early initiation of statin therapy, whereas 1 trial demonstrated neither benefit nor harm. All the available trials lacked the power and design to sufficiently evaluate whether early initiation of statin therapy reduces mortality and reinfarction in patients with ACS. Four ongoing trials have been designed and sufficiently powered to determine whether statin therapy reduces the risk of death and reinfarction when initiated early in ACS treatment. A body of evidence suggests that the pleiotropic actions of statin agents might modulate benefit in ACS. This article summarizes the available data and provides a rationale for early initiation of statin therapy for patients with ACS.

Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy

A hypothesis is presented based on a coalescence of anthropological estimations of Homo sapiens' phenotypes in the Late Paleolithic era 10,000 years ago, with Darwinian natural selection synergized with Neel's idea of the so-called thrifty gene. It is proposed that humans inherited genes that were evolved to support a physically active lifestyle. It is further postulated that physical inactivity in sedentary societies directly contributes to multiple chronic health disorders. Therefore, it is imperative to identify the underlying genetic and cellular/biochemical bases of why sedentary living produces chronic health conditions. This will allow society to improve its ability to effect beneficial lifestyle changes and hence improve the overall quality of living. To win the war against physical inactivity and the myriad of chronic health conditions produced because of physical inactivity, a multifactorial approach is needed, which includes successful preventive medicine, drug development, optimal target selection, and efficacious clinical therapy. All of these approaches require a thorough understanding of fundamental biology and how the dysregulated molecular circuitry caused by physical inactivity produces clinically overt disease. The purpose of this review is to summarize the vast armamentarium at our disposal in the form of the extensive scientific basis underlying how physical inactivity affects at least 20 of the most deadly chronic disorders. We hope that this information will provide readers with a starting point for developing additional strategies of their own in the ongoing war against inactivity-induced chronic health conditions.

Endothelium-derived nitric oxide regulates arterial elasticity in human arteries in vivo

Arterial elasticity is determined by structural characteristics of the artery wall and by vascular smooth muscle tone. The identity of endogenous vasoactive substances that regulate elasticity has not been defined in humans. We hypothesized that NO, a vasodilator released constitutively by the endothelium, augments arterial elasticity. Seven healthy young men were studied. A 20-MHz intravascular ultrasound catheter was introduced through an arterial sheath to measure brachial artery cross-sectional area, wall thickness, and intra-arterial pressure. After control was established, indices of elasticity (pressure-area relationship, instantaneous compliance, and stress-strain, pressure-incremental elastic modulus (E(inc)), and pressure-pulse wave velocity relationships) were examined over 0 to 100 mm Hg transmural pressure obtained by inflation of an external cuff. Thereafter, the basal production of endothelium-derived NO was inhibited by N(G)-monomethyl-L-arginine (L-NMMA) (4 and 8 mg/min). Finally, nitroglycerin (2.5 and 12.5 microgram/min), an exogenous donor of NO, was given to relax the vascular smooth muscle. Elasticity was measured under all of these conditions. L-NMMA (8 mg/min) decreased brachial artery area (P=0.016) and compliance (P<0.0001) and increased E(inc) (P<0.01) and pulse wave velocity (P<0.0001). Nitroglycerin (12.5 microgram/min) increased brachial artery area (P<0.001) and compliance (P<0.001) and decreased pulse wave velocity (P=0.02). NO, an endothelium-derived vasodilator, augments arterial elasticity in the human brachial artery. Loss of constitutively released NO associated with cardiovascular risk factors may adversely affect arterial elasticity in humans.

The use of statins in acute coronary syndromes: the mechanisms behind the outcomes

Lipid-lowering drugs, in particular statin treatments, have been shown to reduce the incidence of initial and recurrent coronary heart disease (CHD) events within several years of initiating therapy. This effect can be clinically detected within the first 1 to 2 years in randomized trials. Recent observational and clinical trial data suggest that lipid-lowering therapy initiated at the time of an acute coronary event can reduce recurrent events, and possibly all-cause mortality, in a much shorter period of time. The possible mechanisms by which this benefit occurs include the effect of reduced lipoprotein levels, as well as an independent effect of statins on endothelial function. Statins improve endothelial-dependent flow-mediated vasodilation by increasing the bioavailability of nitric oxide. They stabilize the plaque by modulating the inflammatory response within the vessel wall. They also decrease clot formation by decreasing the adherence of platelets to the ruptured plaque and by acting on the extrinsic coagulation cascade pathway. This review examines these effects of statins and lipoproteins on vascular function, as well as the clinical evidence supporting early treatment in acute coronary syndromes.

Effectiveness of statins in acute coronary syndromes

Over the past several years, results of clinical trials of lipid lowering have increased our understanding of the pathophysiology of coronary atherosclerosis and ischemia. Evidence is accumulating that cholesterol lowering has potential anti-ischemic effects and may have immediate consequences that have a favorable impact on coronary events, possibly even acute coronary syndromes. Yet, less than one half of all patients hospitalized for acute coronary syndromes have their cardiovascular risks appropriately modified. The results of recent statin trials provide impetus for the implementation of aggressive risk-reduction strategies in patients with coronary atherosclerosis, including those with recent acute coronary syndromes. Prevention is now a viable therapeutic goal.

Endothelial function and coronary artery disease

The endothelium produces a number of vasodilator and vasoconstrictor substances that not only regulate vasomotor tone, but also the recruitment and activity of inflammatory cells and the propensity towards thrombosis. Endothelial vasomotor function is a convenient way to assess these other functions, and is related to the long-term risk of cardiovascular disease. Lipids (particularly low density lipoprotein cholesterol) and oxidant stress play a major role in impairing these functions, by reducing the bioavailability of nitric oxide and activating pro-inflammatory signalling pathways such as nuclear factor kappa B. Biomechanical forces on the endothelium, including low shear stress from disturbed blood flow, also activate the endothelium increasing vasomotor dysfunction and promoting inflammation by upregulating pro-atherogenic genes. In contrast, normal laminar shear stress promotes the expression of genes that may protect against atherosclerosis. The sub-cellular structure of endothelial cells includes caveolae that play an integral part in regulating the activity of endothelial nitric oxide synthase. Low density lipoprotein cholesterol and oxidant stress impair caveolae structure and function and adversely affect endothelial function. Lipid-independent pathways of endothelial cell activation are increasingly recognized, and may provide new therapeutic targets. Endothelial vasoconstrictors, such as endothelin, antagonize endothelium-derived vasodilators and contribute to endothelial dysfunction. Some but not all studies have linked certain genetic polymorphisms of the nitric oxide synthase enzyme to vascular disease and impaired endothelial function. Such genetic heterogeneity may nonetheless offer new insights into the variability of endothelial function.

Direct adsorption of lipoproteins from whole blood by DALI apheresis: technique and effects

Low-density lipoprotein (LDL) apheresis can drastically reduce atherogenic lipoproteins in coronary patients in whom LDL and lipoprotein (a) (Lp[a]) cannot be sufficiently reduced by conservative therapy. LDL and Lp(a) adsorption by polyacrylate/polyacrylamide (DALI) is the simplest procedure for clinical LDL apheresis to date. DALI was first applied in patients in 1994 and introduced into clinical routine in 1996. It is the first LDL-hemoperfusion system, i.e., it adsorbs LDL and Lp(a) directly from whole blood. This markedly simplifies the extracorporeal circuit, the handling of the system, and reduces significantly staff time and, especially at higher blood flow rates, treatment time. Its features are high selectivity and capacity of lipoprotein removal (maximum about 8 g low-density lipoprotein cholesterol per session). Using citrate anticoagulation, good biocompatibility is evidenced by the lack of cell losses, hemolysis, thrombotic events, and complement activation. Some clotting factors of the intrinsic system are also adsorbed. There is significant bradykinin activation that, however, does not cause problems in most patients if angiotensin converting enzyme inhibitor medication is avoided. In a first long-term study, 93% of sessions were uneventful. Major side effects were citrate-induced paresthesias (1.3%) and hypotension (0.8%). To date, more than 25,000 DALI sessions have been performed all over the world.

Prevention of a first myocardial infarction

Coronary heart disease is the leading cause of morbidity and mortality in men and women in the Western world. We now have significant evidence that prevention of the first coronary event using lifestyle and pharmacologic therapies is paramount. Events are caused by inflamed arteries leading to rupture of atherosclerotic plaques that induce potentially occlusive thrombi. Analysis of event reduction trials has revealed that LDL-C lowering is only one part of the therapy needed to stabilize plaque. HMG-Co-A-reductase inhibitors, fibrates, and statins all have differing mechanisms of action that provide not only lipid but also inflammatory, rheologic, and coagulation benefits. Concentration and sizes of lipoprotein subfractions have emerged as important new tools with small dense LDL particles having more atherogenicity, which has led to an increasing use of aggressive combination therapy for prevention of first myocardial infarction. Proper use of lipid-lowering therapies requires knowledge of drug metabolism drug-drug interactions.

Elderly patients at risk for coronary heart disease or stroke: selecting an ideal product for lipid lowering

Coronary heart disease is an affliction of the elderly: 84% of those who die from the disease are over 65 years of age. In patients over 55 years, the incidence of stroke more than doubles with each decade of life. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, have been shown to lower cholesterol and lipids in both middle-aged and elderly patients in large clinical trials. Some statins have been shown to improve endothelial function and vasodilation and to normalize thrombin formation, which may be among the mechanisms involved in both coronary event and stroke prevention.

Relation between endothelial dysfunction and the acute coronary syndrome: implications for therapy

Endothelial dysfunction is present in patients with atherosclerosis, even in the early stages of disease, before plaque formation. Thus, it is a useful marker for early cardiovascular disease. In recent studies, statin therapy has been shown to improve endothelial function by increasing production of nitric oxide, a key vasodilator, from the endothelium. The improvement in endothelial function occurs by lipid lowering as well as by nonlipid mechanisms. These effects begin early in treatment, supporting prompt initiation of statin therapy. The functional benefits that result from an improvement in endothelial dysfunction include enhanced myocardial perfusion, reduced duration and burden of transient myocardial ischemia, and reduced angina pectoris. As dysfunctional endothelium encourages the recruitment of leukocytes into the arterial wall and thereby predisposes to inflammation and plaque disruption, improvement in endothelial function leads to plaque stabilization.

Effects of HMG-CoA reductase inhibitor on hemostasis

Clinical trials of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) therapy have demonstrated improvement in coronary atherosclerosis progression and reduction in risk of cardiovascular events. However, improvement in cardiovascular end-points is incompletely explained by the baseline or treated LDL cholesterol level. The beneficial effects of statins on clinical events may involve nonlipid mechanisms that modify hemostasis. Local activation of platelets and thrombus formation adjacent to atheromatous plaques, especially where ruptured or eroded, are now recognized to be of pathophysiological importance in the acute and chronic clinical expression of coronary heart disease. Thus, favorable effects of statins on hemostasis may be relevant to decreasing or delaying the progression and clinical manifestations of atherosclerosis.

Implications of cardiovascular risk in patients with type 2 diabetes who have abnormal lipid profiles: is lower enough?

Patients with type 2 diabetes are at high risk for coronary heart disease (CHD); frequently, these patients have abnormal lipid profiles, placing them at even greater risk. A syndrome of insulin resistance, hyperinsulinaemia, hypertension, and high levels of fibrinogen and plasminogen activator inhibitor contributes to cardiovascular risk, which is not sufficiently decreased by glycaemic control alone. In several large interventional trials, CHD risk in patients with diabetes was substantially reduced by aggressive lipid-lowering therapy. In patients with diabetes, CHD, low high-density lipoprotein levels, and normal low-density lipoprotein levels, gemfibrozil reduced fatal and non-fatal CHD events. For lipid-lowering in patients with diabetes and CHD, pravastatin and simvastatin are the only HMG-CoA reductase inhibitors shown to reduce fatal and non-fatal CHD events. Of these, pravastatin has less potential for drug-drug interactions and may be safer to use, particularly for combination therapy with fibric acid derivatives, as may now be important for CHD prevention in mixed dyslipidaemias.

Lipid-lowering therapy after coronary revascularization

Atherosclerosis is often asymptomatic, unrecognized, and undertreated. Lumen irregularities are important angiographic findings that should be addressed aggressively through risk factor modification, medical therapy, and coronary revascularization. Both angiographic and clinical benefits have been demonstrated with lipid reduction therapy in randomized clinical trials. Coronary revascularization is indicated for symptom relief and improvement in quality of life in patients with acute coronary syndromes at "intermediate" and "high" risk of subsequent death or myocardial infarction. In patients following percutaneous coronary intervention (PCI), future cardiac events may be related to lumen renarrowing or to progression of atherosclerotic disease at sites remote from the site of coronary revascularization. The time course of restenosis is relatively self-limiting, generally occurring within 6-12 months after the procedure. Clinical events occurring > 1 year after PCI generally relate to new lesions or progression of existing atherosclerotic disease. Patients with diabetes mellitus may be at higher risk for late coronary events than nondiabetic patients. In post-coronary artery bypass surgery (CABG) patients, the majority of late events relate to degeneration of saphenous vein grafts. Lipid lowering therapy after coronary revascularization has been shown to prevent clinical events related to plaque instability and inhibit progression of saphenous vein graft disease. Thus, there are 2 goals in management of patients with symptomatic coronary artery disease: (1) to relieve the flow-limiting stenosis, and (2) to prevent future clinical events with aggressive lipid lowering and modification of other risk factors. Patients, specialists, and primary care physicians each need to take accountability for this risk-factor modification.

Atherogenic lipids and endothelial dysfunction: mechanisms in the genesis of ischemic syndromes

Atherogenic lipids, particularly oxidized low-density lipoprotein, are responsible for a wide range of cellular dysfunctions within the vessel wall. The effects on endothelial cells disrupt normal control of vasomotion, with a reduction of effective nitric oxide activity, the development of a procoagulant surface, chronic low-grade inflammation, and abnormal cell growth. These changes are central not only in the development of atherosclerosis but also in the evolution of both stable and unstable ischemic syndromes. There is growing evidence that these abnormal changes in cell function respond rapidly to changes in the atherogenic lipids. Certain cell functions can improve within hours or days of cholesterol lowering.

The apolipoprotein epsilon4 allele determines prognosis and the effect on prognosis of simvastatin in survivors of myocardial infarction : a substudy of the Scandinavian simvastatin survival study

BACKGROUND

Carriers of the epsilon4 allele of the apolipoprotein E gene are at a higher risk of coronary heart disease than individuals with other genotypes. We examined whether the risk of death or a major coronary event in survivors of myocardial infarction depended on apolipoprotein E genotype and whether the benefits of treatment with simvastatin differed between genotypes.

METHODS AND RESULTS

Cox proportional hazards models were used to analyze 5.5 years of follow-up data from 966 Danish and Finnish myocardial infarction survivors enrolled in the Scandinavian Simvastatin Survival Study. A total of 16% of the 166 epsilon4 carriers in the placebo group died compared with 9% of the 312 patients without the allele, which corresponds to a mortality risk ratio of 1.8 (95% confidence interval, 1.1 to 3.1). The risk ratio was unaffected by considerations of sex, age, concurrent angina, diabetes, smoking, and serum lipids in multivariate analyses. Simvastatin treatment reduced the mortality risk to 0.33 (95% confidence interval, 0.16 to 0.69) in epsilon4 carriers and to 0.66 (95% confidence interval, 0. 35 to 1.24) in other patients (P=0.23 for treatment by genotype interaction). Apolipoprotein E genotype did not predict the risk of a major coronary event. Baseline serum levels of lipoprotein(a) also predicted mortality risk and could be combined with epsilon4-carrier status to define 3 groups of patients with different prognoses and benefits from treatment.

CONCLUSIONS

Myocardial infarction survivors with the epsilon4 allele have a nearly 2-fold increased risk of dying compared with other patients, and the excess mortality can be abolished by treatment with simvastatin.

Both raloxifene and estrogen reduce major cardiovascular risk factors in healthy postmenopausal women: A 2-year, placebo-controlled study

Currently raloxifene, a selective estrogen receptor modulator, is being investigated as a potential alternative for postmenopausal hormone replacement to prevent osteoporosis and cardiovascular disease. We compared the 2-year effects of raloxifene on a wide range of cardiovascular risk factors with those of placebo and conjugated equine estrogens (CEEs). Analyses were based on 56 hysterectomized but otherwise healthy postmenopausal women aged 54. 8+/-3.5 (mean+/-SD) years who entered this double-blind study and who were randomly assigned to raloxifene hydrochloride 60 mg/d (n=15) or 150 mg/d (n=13), placebo (n=13), or CEEs 0.625 mg/d (n=15). At baseline and after 6, 12, and 24 months of treatment, we assessed serum lipids, blood pressure, glucose metabolism, C-reactive protein, and various hemostatic parameters. Compared with placebo, both raloxifene and CEEs lowered the level of low density lipoprotein cholesterol by 0.53 to 0.79 mmol/L (all P<0.04) and lowered, at 24 months, the level of fibrinogen by 0.71 to 0.86 g/L (all P<0.05). The effects of raloxifene and CEEs did not differ significantly. In contrast to raloxifene, from 6 months on CEEs increased high density lipoprotein cholesterol by 0.25 to 0.29 mmol/L and reduced plasminogen activator inhibitor-1 antigen by 30.6 to 48.6 ng/mL (all P<0.02 versus both placebo and raloxifene). CEEs transiently increased C-reactive protein by 1.0 mg/L at 6 months (P<0.05 versus placebo) and prothrombin-derived fragment F1+2 by 0. 79 nmol/L at 12 months (P<0.001 versus placebo). Finally, from 12 months on, CEEs increased triglycerides by 0.33 to 0.56 mmol/L (all P<0.05 versus both placebo and raloxifene). Our findings suggest that in healthy postmenopausal women, raloxifene and estrogen monotherapy have similar beneficial effects on low density lipoprotein cholesterol and fibrinogen levels. These treatments differ, however, in their effects on high density lipoprotein cholesterol, triglycerides, and plasminogen activator inhibitor-1 and possibly in their effects on prothrombin fragment F1+2 and C-reactive protein.

Simvastatin preserves the ischemic-reperfused myocardium in normocholesterolemic rat hearts

BACKGROUND

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction as well as cardiomyocyte injury. These deleterious effects are due in large part to endothelial dysfunction leading to the upregulation of cell adhesion molecules and subsequent neutrophil-endothelium interaction. At clinically relevant doses, simvastatin, an HMG-CoA reductase inhibitor, has been shown to lower serum cholesterol levels and normalize endothelial cell function. We wanted to test the effects of simvastatin on neutrophil-mediated cardiac dysfunction in a controlled model of myocardial ischemia-reperfusion.

METHODS AND RESULTS

This study examines the effects of simvastatin in a neutrophil-dependent isolated perfused rat heart model of ischemia (I) (20 minutes) and reperfusion (R) (45 minutes) injury. Administration of simvastatin 25 micrograms/rat improved coronary flow and preserved left ventricular developed pressure (LVDP) and dP/dtmax, indexes of cardiac contractile function. Final LVDP was 95+/-5 mm Hg in I/R hearts perfused with PMNs and simvastatin, compared with 49+/-4 mm Hg in PMN-perfused I/R hearts receiving only vehicle (P<0.001). In addition, simvastatin significantly reduced PMN accumulation in the ischemic myocardium (P<0.01). In PMN-perfused rat hearts after I/R, simvastatin also significantly attenuated P-selectin expression, CD18 upregulation in rat PMNs, and PMN adherence to rat vascular endothelium. Significant, although less potent, effects were obtained with pravastatin.

CONCLUSIONS

These results provide evidence that HMG-CoA reductase inhibitors are potent and effective cardioprotective agents that inhibit leukocyte-endothelial cell interactions and preserve cardiac contractile function and coronary perfusion after myocardial ischemia and reperfusion. Moreover, these effects are unrelated to the cholesterol-lowering action of this agent and appear to be mediated by enhanced endothelial release of NO.

Lipoprotein modification and atherosclerosis in aging

The development of extensive atherosclerosis of major arteries of the heart, brain, and lower extremities is a particularly frequent problem in elderly individuals and is responsible for the majority of the cardiovascular morbidity and mortality in this population. Although the frequency and severity of this problem is well recognized, there has been relatively little investigation of the effects of aging on the development of atherosclerosis. Work by a number of investigators over the last 10-15 years has demonstrated that modifications of lipoproteins, resulting from oxidative stress, glycoxidation, formation of AGE, or other processes may play an important role in atherosclerosis. As described in this review, the aging process may enhance lipoprotein modification and atherosclerosis in several ways. Conditions such as hypertension, diabetes, and menopause all increase in frequency with advancing age and may contribute both directly and indirectly to lipoprotein modification and vascular injury.Additionally, in some studies of older animals and humans, there seems to be evidence for greater in vivo oxidative stress. Whether this is a specific consequence of aging and associated medical conditions, or related to differences in dietary fatty acid or antioxidant content or other lifestyle differences is currently unknown. One important consequence of this may be enhanced susceptibility of lipoproteins to oxidation. Additional study of lipoprotein modifications associated with aging is clearly needed, and may provide new insight and solutions to the common problem of atherosclerosis in the elderly.

Lowering LDL cholesterol: questions from recent meta-analyses and subset analyses of clinical trial DataIssues from the Interdisciplinary Council on Reducing the Risk for Coronary Heart Disease, ninth Council meeting

The benefit of cholesterol-lowering therapy in the prevention of coronary heart disease (CHD) is well established. The secondary prevention Scandinavian Simvastatin Survival Study (4S) and the primary prevention West of Scotland Coronary Prevention Study (WOSCOPS) demonstrated that lipid lowering with a statin can dramatically and cost-effectively reduce CHD morbidity and mortality with no increase in noncardiovascular mortality. The Cholesterol and Recurrent Events (CARE) trial extended benefit to CHD patients without high cholesterol. Post hoc analyses of data from these large trials are contributing to speculation, driven by subset analyses and meta-analyses, about whether cholesterol intervention should be target based, as current guidelines recommend. Whereas CARE data support the importance of baseline LDL cholesterol (LDL-C), with greatest clinical event risk reduction in the upper part of the LDL-C range in the trial, 4S found no difference in outcome according to baseline LDL-C in a quartile analysis, and WOSCOPS found no linear relation between decrease in LDL-C and decrease in relative risk for CHD. Furthermore, WOSCOPS showed no additional clinical benefit with LDL-C lowering beyond approximately 24%. Questions raised by such analyses require answers from prospective, hypothesis-based data, and at present there is no compelling argument for moving away from LDL-C targets. The hypothesis-based findings of 4S, CARE, and WOSCOPS support current clinical guidelines, and lowering LDL-C may reduce risk more substantially than might have been predicted.

[Mechanisms of plaque stabilization]

Numerous angiographic control regression studies have demonstrated that aggressive reduction of plasma cholesterol significantly reduces the incidence of clinical overt cardiovascular complications, but has almost no effect on the angiographically determined luminal diameter of the coronary arteries. These, as well as other morphological and molecular studies have led to a new paradigm of coronary heart disease, i.e. clinical prognosis is not mainly determined by the extent of a single stenosis but by the number and biological nature of atherosclerotic plaque. Accordingly, stable plaques can be differentiated from instable or vulnerable plaques. The vulnerable or instable plaque is characterized by a large lipid-rich core with surrounding inflammation and a thin friable overlying fibrous cap susceptible to rupture or fissuring and thereby a high risk of thrombus formation. Rupture and thrombus formation can cause an acute coronary syndrome, such as unstable angina or myocardial infarction. There is increasing clinical and experimental evidence that statins do not only lower plasma cholesterol, but might also have direct effects on the vessel wall, possibly explaining early benefits in cardiovascular complications. Reduction of plasma cholesterol by lipid lowering therapy has been shown to significantly improve paradoxic vasoconstriction of cardiac vessels, a phenomenon indicating endothelial dysfunction. In addition, lipid lowering therapy can result in a diminution of the lipid-rich core, a reduction of inflammatory cells within the plaques, decreased macrophage activation as well as foam cell formation and events related to thickening of the fibrous cap. A clinical prospective should be to better clinically morphologically characterize the vulnerability of plaques in order to therapeutically and preventively reduced specific events leading to acute coronary syndromes, such as unstable angina or myocardial infarction.

Role of endothelial dysfunction in coronary artery disease and implications for therapy

Atherosclerosis is a complex process that is characterized by the accumulation of modified low-density lipoprotein (LDL), local inflammatory and immune responses, and reduced nitric oxide bioavailability within the arterial wall. These cellular changes lead to endothelial vasomotor dysfunction, plaque instability, and the development of clinical events such as stable angina and the acute coronary syndromes. The vascular endothelium plays a critical role in modulating both the inflammatory response and vasomotor abnormalities that occur in those with coronary artery disease or risk factors for disease. In these conditions, endothelial cells are activated by cytokines to express cellular adhesion molecules that facilitate the adhesion of leukocytes to the endothelium, and their migration into the subintimal space. Cytokines stimulate inflammatory and smooth muscle cells in the intima to produce degradative enzymes, including metalloproteinases that can weaken the fibrous cap of atherosclerotic lesions and make them vulnerable to rupture. Endothelial cells also regulate vascular tone by the synthesis of nitric oxide. Atherosclerosis and other conventional risk factors for coronary artery disease are associated with endothelial vasodilator dysfunction in the coronary epicardial and resistance vessels, which likely contributes to myocardial ischemia. Several studies have demonstrated that lowering serum total and LDL cholesterol reverses endothelial vasomotor dysfunction, reduces myocardial ischemia, and lowers the risk of the acute coronary syndromes or need for revascularization. Improving endothelial function, for example, by lowering blood cholesterol should now be regarded as a goal of therapy in the treatment of coronary artery disease.

Lipoproteins and coagulation

A broad range of molecular and cellular interactions contribute to various pathophysiological alterations in haemostasis. Recent studies have shown strong links between lipoproteins and coagulation factors. Findings suggest that lipoproteins play an important role in the fibrinolytic and thrombogenic mechanisms that influence the risks of patients in acute coronary syndromes. We will examine specific aspects of lipoproteins with reference to the effects of hyperlipidaemia on endothelial dysfunction and haemostasis, and its relevance in the patient presenting for revascularization.