Antiatherosclerotic effects of beta-blockers

Inhibition of differentiation of monocyte-derived macrophages toward an M2-Like phenotype May Be a neglected mechanism of β-AR receptor blocker therapy for atherosclerosis

The clinical efficacy of adrenergic β-receptor (β-AR) blockers in significantly stabilizing atherosclerotic plaques has been extensively supported by evidence-based medical research; however, the underlying mechanism remains unclear. Recent findings have highlighted the impact of lipid-induced aberrant polarization of macrophages during normal inflammatory-repair and regenerative processes on atherosclerosis formation and progression. In this review, we explore the relationship between macrophage polarization and atherosclerosis, as well as the influence of β-AR blockers on macrophage polarization. Based on the robust evidence supporting the use of β-AR blockers for treating atherosclerosis, we propose that their main mechanism involves inhibiting monocyte-derived macrophage differentiation towards an M2-like phenotype.

Pharmacological interventions for asymptomatic carotid stenosis

BACKGROUND

Carotid artery stenosis is narrowing of the carotid arteries. Asymptomatic carotid stenosis is when this narrowing occurs in people without a history or symptoms of this disease. It is caused by atherosclerosis; that is, the build-up of fats, cholesterol, and other substances in and on the artery walls. Atherosclerosis is more likely to occur in people with several risk factors, such as diabetes, hypertension, hyperlipidaemia, and smoking. As this damage can develop without symptoms, the first symptom can be a fatal or disabling stroke, known as ischaemic stroke. Carotid stenosis leading to ischaemic stroke is most common in men older than 70 years. Ischaemic stroke is a worldwide public health problem.

OBJECTIVES

To assess the effects of pharmacological interventions for the treatment of asymptomatic carotid stenosis in preventing neurological impairment, ipsilateral major or disabling stroke, death, major bleeding, and other outcomes.

SEARCH METHODS

We searched the Cochrane Stroke Group trials register, CENTRAL, MEDLINE, Embase, two other databases, and three trials registers from their inception to 9 August 2022. We also checked the reference lists of any relevant systematic reviews identified and contacted specialists in the field for additional references to trials.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs), irrespective of publication status and language, comparing a pharmacological intervention to placebo, no treatment, or another pharmacological intervention for asymptomatic carotid stenosis.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. Two review authors independently extracted the data and assessed the risk of bias of the trials. A third author resolved disagreements when necessary. We assessed the evidence certainty for key outcomes using GRADE.

MAIN RESULTS

We included 34 RCTs with 11,571 participants. Data for meta-analysis were available from only 22 studies with 6887 participants. The mean follow-up period was 2.5 years. None of the 34 included studies assessed neurological impairment and quality of life. Antiplatelet agent (acetylsalicylic acid) versus placebo Acetylsalicylic acid (1 study, 372 participants) may result in little to no difference in ipsilateral major or disabling stroke (risk ratio (RR) 1.08, 95% confidence interval (CI) 0.47 to 2.47), stroke-related mortality (RR 1.40, 95% CI 0.54 to 3.59), progression of carotid stenosis (RR 1.16, 95% CI 0.79 to 1.71), and adverse events (RR 0.81, 95% CI 0.41 to 1.59), compared to placebo (all low-certainty evidence). The effect of acetylsalicylic acid on major bleeding is very uncertain (RR 0.98, 95% CI 0.06 to 15.53; very low-certainty evidence). The study did not measure neurological impairment or quality of life. Antihypertensive agents (metoprolol and chlorthalidone) versus placebo The antihypertensive agent, metoprolol, may result in no difference in ipsilateral major or disabling stroke (RR 0.14, 95% CI 0.02 to1.16; 1 study, 793 participants) and stroke-related mortality (RR 0.57, 95% CI 0.17 to 1.94; 1 study, 793 participants) compared to placebo (both low-certainty evidence). However, chlorthalidone may slow the progression of carotid stenosis (RR 0.45, 95% CI 0.23 to 0.91; 1 study, 129 participants; low-certainty evidence) compared to placebo. Neither study measured neurological impairment, major bleeding, adverse events, or quality of life. Anticoagulant agent (warfarin) versus placebo The evidence is very uncertain about the effects of warfarin (1 study, 919 participants) on major bleeding (RR 1.19, 95% CI 0.97 to 1.46; very low-certainty evidence), but it may reduce adverse events (RR 0.89, 95% CI 0.81 to 0.99; low-certainty evidence) compared to placebo. The study did not measure neurological impairment, ipsilateral major or disabling stroke, stroke-related mortality, progression of carotid stenosis, or quality of life. Lipid-lowering agents (atorvastatin, fluvastatin, lovastatin, pravastatin, probucol, and rosuvastatin) versus placebo or no treatment Lipid-lowering agents may result in little to no difference in ipsilateral major or disabling stroke (atorvastatin, lovastatin, pravastatin, and rosuvastatin; RR 0.36, 95% CI 0.09 to 1.53; 5 studies, 2235 participants) stroke-related mortality (lovastatin and pravastatin; RR 0.25, 95% CI 0.03 to 2.29; 2 studies, 1366 participants), and adverse events (fluvastatin, lovastatin, pravastatin, probucol, and rosuvastatin; RR 0.76, 95% CI 0.53 to1.10; 7 studies, 3726 participants) compared to placebo or no treatment (all low-certainty evidence). The studies did not measure neurological impairment, major bleeding, progression of carotid stenosis, or quality of life.

AUTHORS' CONCLUSIONS

Although there is no high-certainty evidence to support pharmacological intervention, this does not mean that pharmacological treatments are ineffective in preventing ischaemic cerebral events, morbidity, and mortality. High-quality RCTs are needed to better inform the best medical treatment that may reduce the burden of carotid stenosis. In the interim, clinicians will have to use other sources of information.

Modifiable risk factors for carotid atherosclerosis: a meta-analysis and systematic review

Background

Carotid atherosclerosis is a major cause of stroke, but the conclusion about risk factors for carotid atherosclerosis is still controversial. The aim of our present meta-analysis and systematic review was to explore the modifiable risk factors for carotid atherosclerosis.

Methods

We searched PubMed from January 1962 to October 2018 to include longitudinal and cross-sectional studies. The results were pooled using random effects model. Heterogeneity was measured by I² statistic and publication bias was assessed by funnel plots.

Results

A total of 14,700 articles were screened, of which 76 with 27 factors were eligible. Our meta-analysis of cross-sectional studies indicated nine factors (hyperlipidemia, hyperhomocysteinemia, hypertension, hyperuricemia, smoking, metabolic syndrome, hypertriglyceridemia, diabetes, and higher low density lipoprotein) were significantly associated with the presence of carotid plaque, among which four (hyperlipidemia, hyperhomocysteinemia, hypertension, and hyperuricemia) could elevate the risk of atherosclerosis by at least 50%; and one factor (hypertension) was associated with increased carotid intima-media thickness. In the systematic review, another five factors [negative emotion, socioeconomic strain, alcohol, air pollution, and obstructive sleep apnea syndrome (OSAS)] were also related to the presence of atherosclerosis. The cross-sectional associations with most of the above 14 factors were further confirmed by longitudinal studies. Among them, the managements of 4 factors (hypertension, hyperlipidemia, diabetes and OSAS) were indicated to prevent carotid atherosclerosis by cohort studies.

Conclusions

Effective interventions targeting pre-existing disease, negative emotion, lifestyle and diet may reduce the risk of carotid atherosclerosis. Further good-quality prospective studies are needed to confirm these findings.

Pathophisiology of abdominal aortic aneurysm: biomarkers and novel therapeutic targets

Abdominal aortic aneurysm (AAA) is a vascular pathology with a high rate of morbidity and mortality and a prevalence that, in men over 65 years, can reach around 8%. In this disease, usually asymptomatic, there is a progressive dilatation of the vascular wall that can lead to its rupture, a fatal phenomenon in more than 80% of cases. The treatment of patients with asymptomatic aneurysms is limited to periodic monitoring with imaging tests, control of cardiovascular risk factors and treatment with statins and antiplatelet therapy. There is no effective pharmacological treatment capable of limiting AAA progression or avoiding their rupture. At present, the aortic diameter is the only marker of risk of rupture and determines the need for surgical repair when it reaches values greater than 5.5cm. This review addresses the main aspects related to epidemiology, risk factors, diagnosis and clinical management of AAA, exposes the difficulties to have good biomarkers of this pathology and describes the strategies for the identification of new therapeutic targets and biomarkers in AAA.

Metoprolol reduces proinflammatory cytokines and atherosclerosis in ApoE-/- mice

A few studies in animals and humans suggest that metoprolol (β1-selective adrenoceptor antagonist) may have a direct antiatherosclerotic effect. However, the mechanism behind this protective effect has not been established. The aim of the present study was to evaluate the effect of metoprolol on development of atherosclerosis in ApoE^−/− mice and investigate its effect on the release of proinflammatory cytokines. Male ApoE^−/− mice were treated with metoprolol (2.5 mg/kg/h) or saline for 11 weeks via osmotic minipumps. Atherosclerosis was assessed in thoracic aorta and aortic root. Total cholesterol levels and Th1/Th2 cytokines were analyzed in serum and macrophage content in lesions by immunohistochemistry. Metoprolol significantly reduced atherosclerotic plaque area in thoracic aorta (P < 0.05 versus Control). Further, metoprolol reduced serum TNFα and the chemokine CXCL1 (P < 0.01 versus Control for both) as well as decreasing the macrophage content in the plaques (P < 0.01 versus Control). Total cholesterol levels were not affected. In this study we found that a moderate dose of metoprolol significantly reduced atherosclerotic plaque area in thoracic aorta of ApoE^−/− mice. Metoprolol also decreased serum levels of proinflammatory cytokines TNFα and CXCL1 and macrophage content in the plaques, showing that metoprolol has an anti-inflammatory effect.

Conventional treatment after myocardial infarction in routine clinical practice results in regression of left common carotid intima-media thickness

This study aimed to evaluate the effect of standard medical treatment on the progression of atherosclerosis after a myocardial infarction, in an ordinary clinical setting, by measuring the right and left common carotid intima-media thickness (IMT). The first investigation took place 3-12 months after the index event; the second took place 3·3-8·2 years after the first. In both investigations, the right and left carotid arteries of 102 patients were examined with an ultrasound duplex scanner. Common carotid IMT and calculated cross-sectional intima-media area (cIMa) were measured on both sides. More than 90% of the patients were treated with aspirin, beta-blockers and statins. In the first investigation, IMT and cIMa were significantly greater on the left side compared to the right (IMT: 0·83 ± 0·22 and 0·74 ± 0·18 mm, P<0·001; cIMa: 18·2 ± 5·2 and 16·3 ± 5·1 mm(2) , P<0·001). In the second investigation, IMT on the left side was significantly reduced compared to the first investigation (0·79 ± 0·22 and 0·83 ± 0·22 mm, P<0·05) with a corresponding tendency towards a decrease in cIMa on the same side. In our study, conventional medical treatment after a myocardial infarction in ordinary clinical routines resulted in regression of the common carotid IMT on the left side. The significant side difference in IMT emphasizes the importance of where and how the carotid IMT is measured in studies using this surrogate end point.

[Cardioprotection]

The demographic change is associated with an increasing number of elderly patients with serious comorbidities. The prevalence of coronary heart disease in particular increases with age and raises the risk of perioperative myocardial ischemia. In the last few years various interventions have been evaluated to lower the perioperative risk for serious cardiovascular events. This includes cardioprotective medical interventions, for example with β-receptor blockers and statins. Current guidelines recommend that patients who are on β-receptor blockers or statins for chronic treatment of cardiovascular diseases should continue this medication throughout the perioperative period. Myocardial conditioning has been assessed to be effective under numerous experimental conditions and clinical trials have also provided evidence for myocardial protection by conditioning. Besides ischemic and anesthetic-induced preconditioning the noninvasive technique of remote preconditioning offers interesting possibilities, especially for patients with serious comorbidities; however, large scale randomized clinical multicentre trials are still needed. Regarding cardioprotective effectiveness, the clinical data for regional anesthesia are very heterogeneous; nevertheless regional anesthesia is very effective in postoperative pain therapy. Therefore regional anesthesia should be used as a part of multimodal therapy concepts to lower the risk of perioperative cardiovascular events.

Ivabradine: recent and potential applications in clinical practice

INTRODUCTION

published data indicate that heart rate is an independent strong predictor of cardiovascular and all-cause mortality in men and women of all ages, with and without cardiovascular disease, including atherosclerosis, ventricular arrhythmias, and left ventricular dysfunction. Ivabradine is a pure heart-rate-lowering agent with well-documented antianginal and anti-ischemic properties comparable to well-established anti-anginal agents.

AREAS COVERED

this short review explores recent results with ivabradine, a new medication that lowers heart rate by selectively inhibiting the I (f) current. This review also describes future potential applications.

EXPERT OPINION

measurement of heart rate represents an important component of the assessment of patients with coronary artery disease and chronic heart failure, and should be viewed in the same light as other risk factors, because a high heart rate has direct detrimental effects not only on myocardial ischemia but also on the progression of atherosclerosis, ventricular arrhythmias and left ventricular function. Ivabradine has anti-ischemic and antianginal efficacy equivalent to that of β-blockers and calcium channel antagonists in the treatment of chronic stable angina pectoris. Recently ivabradine has been shown to improve cardiac outcomes in stable coronary artery disease and left ventricular systolic dysfunction in patients who have heart rates of ≥ 70 bpm and in patients with stable angina.

Slightly Elevated High-Sensitivity C-Reactive Protein (hsCRP) Concentrations Are Associated With Carotid Atherosclerosis in Women With Varying Degrees of Glucose Tolerance

We examined whether high-sensitivity C-reactive protein (hsCRP) ≥2.0 mg/L was associated with increased intima-media thickness (IMT), plaque burden, and plaque echolucency in carotid arteries. Women (n = 635) from a population sample of 64-year-old females with varying degrees of glucose tolerance underwent risk factor assessment, measurement of hsCRP, and ultrasound examinations of the carotid arteries. Participants with hsCRP levels ≥2.0 mg/L had elevated carotid bulb IMT independently of other cardiovascular risk factors compared with those with hsCRP <2.0 mg/L. The participants with plaques in the highhsCRP group had larger total plaque area compared to those with plaque in the lower hsCRP group. Plaque echolucency did not differ between groups. High-sensitivity CRP levels ≥2.0 mg/L were accompanied by elevated IMT in the carotid bulbs independently of other cardiovascular risk factors. Total plaque area was larger among women with plaques in the high hsCRP group versus the lower hsCRP group.

Heart Rate Control in an Unselected Consecutive Population of Outpatients With Stable Coronary Artery Disease: Analysis of the CARDIf Study Cohort

Background: Despite increasing pharmacological and mechanical treatment options, coronary artery disease (CAD) continues to be associated with considerable mortality and morbidity. The detrimental effects of elevated heart rate (HR) on cardiac morbidity and mortality are well established. Although β-blockers represent the mainstay of treatment of patients with CAD and heart failure (HF), according to current guidelines, these drugs are most often undertitrated for various reasons despite the lack of real contraindications. This observational, cross-sectional, multicenter survey was designed to assess which clinical variables influence HR and whether HR is adequately controlled; and the rate of administration of β-blockers in patients with chronic CAD attending outpatient clinics. Methods: Over 6 months 2226 (of 2362 screened) outpatients with stable CAD and resting HR > 60 beats/min (bpm) were enrolled. Left ventricular systolic function was not a criterion of inclusion. Each patient had a full clinical examination and the past medical history, angina, or HF-related symptoms were evaluated. In each patient, the demographics and cardiovascular risk factors were assessed; weight, height, and body mass index (BMI) was calculated; sitting blood pressure and a HR by a 12-lead electrocardiogram was obtained. Results: Overall, 45.4% of patients with CAD were not under β-blocker therapy. Male patients featured a significantly lower HR than females, corrected from β-blockers use. In multiple regression analysis, which also included the use/nonuse of β-blockers as independent variable, not using β-blockers, female sex (OR 2.55), New York Heart Association (NYHA) classes I and II (OR 1.62 vs classes III-IV), smoking (OR 0.89), and increased BMI (OR 0.14) were all independent determinants of resting HR, with the lack of β-blockade therapy (OR 3.35) being the main determinant of the magnitude of HR increase. Heart rate in patients under β-blocker therapy was significantly less than in untreated patients (73.6 10.0 vs 77.1 10.4, P < .0001), although it often did not reach target values of <70 bpm. Among patients with HF symptoms, 56.6% were under β-blocker therapy. In patients free of symptoms of HF, HR was significantly less in those receiving a β-blocker (72.3 10 vs 76.7 11 bpm, P < .0001). Conclusion: This survey demonstrates that HR is poorly controlled in a broadly representative cohort of outpatients with CAD, even in those on β-blocker therapy, mainly because of undertitration of therapy—almost half of the patients with CAD and elevated resting HR are not on β-blockers. This might be related to absolute or relative controindications and to haemodynamic and chronotropic intolerance to beta-blockers.

Effect of metoprolol on vulnerable plaque in rabbits by changing shear stress around plaque and reducing inflammation

The beta-adrenoceptor antagonists are known to reduce cardiovascular events, but less is known about their effects on vulnerable plaque. The purpose of this study is to explore the role of metoprolol on vulnerable plaque and the possible mechanism. Vulnerable plaque model was established by local transfection with p53 gene in New Zealand Rabbits. Metoprolol treatment attenuated vessel positive remodeling and reduced vulnerability index (1.61+/-0.58 vs. 2.33+/-0.12, P<0.01). Although the difference did not reach statistical significance, the rate of rupture of atherosclerotic plaque (31% vs. 75%) and intima-media thickness (0.05+/-0.01 vs. 0.08+/-0.01 cm) were less in the metoprolol group than in the control group. The level of shear stress-related inflammatory cytokines such as intercellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), matrix metalloproteinase 1 (MMP-1), were lower in the metoprolol group than in the control group (P<0.01). Compared with control group, total cholesterol and low-density lipoprotein cholesterol were lower (P<0.01) in the metoprolol group. After metoprolol treatment, shear stress increased, and was not different to baseline (physiological shear stress, P>0.05). Shear stress and vulnerability index showed a negative correlation. These findings suggest that metoprolol could inhibit the development of atherosclerosis and stabilize vulnerable plaque by regulation of lipid and reduction of inflammation, in which the change from low shear stress to physiological shear stress around plaque may play an important role.

Ivabradine: beyond heart rate control

Chronic stable angina pectoris (CSAP) usually occurs in patients with coronary artery disease (CAD) that affects one or more large epicardial arteries. It results when myocardial perfusion is insufficient to meet cardiac metabolic demand. Elevated heart rate (HR) is an important factor in the development of myocardial ischemia and angina pectoris. The pharmacologic agents most commonly administered in the treatment of CSAP are beta-blockers and calcium channel blockers (CCBs). However, the use of beta-blockers is limited by poor compliance related to contraindications and comorbidities, especially in elderly patients. Ivabradine is a new selective HR-lowering agent that selectively inhibits the pacemaker current I (f) in the sinus atrial node. In several randomized controlled trials, ivabradine 5-10 mg twice daily has demonstrated equivalent anti-ischemic and anti-anginal activity to beta-blockers and CCBs, with a good safety and tolerability profile. Although ivabradine has been shown not to improve cardiac outcomes in patients with stable CAD and left ventricular systolic dysfunction, it may be used to reduce the incidence of CAD outcomes in a subgroup of patients with HR > or =70 bpm. The aim of this short review is to summarize the use of ivabradine in the treatment of CSAP, and its potential utility in atherosclerosis, primitive and dilatative cardiomyopathy, and arrhythmias, such as postural tachycardia syndrome and inappropriate sinus tachycardia, where exclusive lowering of elevated HR may prove beneficial.

Early use of beta-blockers attenuates systemic inflammatory response and lung oxygenation impairment after distal type acute aortic dissection

We have reported that serum C-reactive protein (CRP) elevation is an independent predictor of lung oxygenation impairment (LOI) after distal type acute aortic dissection (AAD). Systemic activation of the inflammatory system after aortic injury may play a role in the development of LOI. The aim of this study is to clarify the effect of beta-blockers on systemic inflammation and the development of LOI after distal type AAD. A total of 49 patients, who were admitted with distal type AAD and treated conservatively, were examined. White blood cell (WBC) count, serum CRP level, and arterial blood gases were measured serially. Forty patients received beta-blocker treatment within 24 h of the onset, while 9 patients received no beta-blocker treatment. Maximum WBC count, maximum CRP level, lowest PaO₂/FiO₂ (P/F) ratio, and patient background were compared between the two groups. There was no difference between the groups according to age, sex, coronary risk factors, blood pressure, serum level of CRP, WBC count, and oxygenation index on admission. Beta-blocker treatment was associated with lower maximum WBC count (P = 0.0028) and lower maximum serum CRP level (P = 0.0004). The minimum P/F ratio was higher in patients with beta-blocker treatment than in those without (P = 0.0076). Multivariate analysis revealed that administration of a beta-blocker was an independent negative determinant of LOI (P/F ratio ≤200 mmHg). In conclusion, early use of beta-blockers prevented excessive inflammation and LOI after distal type AAD, suggesting a pleiotropic effect of beta-blockers on the inflammatory response after AAD.

Comparative evaluation of atenolol and metoprolol on cardiovascular complications associated with streptozotocin-induced diabetic rats

Recently, various clinical studies have indicated that lipophilic β-blockers reduce the coronary mortality in diabetic patients; however, systematic studies have not been reported. The objective of the present investigation was to compare the effects of chronic treatment with metoprolol and atenolol on cardiovascular complications in streptozotocin (STZ)-induced diabetic rats. Injection of STZ produced hyperglycemia, hypoinsulinemia, hyperlipidemia, increased blood pressure, cardiac hypertrophy, reduction in heart rate, and structural alterations in cardiac tissues. Metoprolol and atenolol effectively prevented the development of hypertension in diabetic rats. Metoprolol treatment produced a slight but significant reduction in serum glucose levels with elevation in serum insulin levels, while atenolol produced a slight increase in glucose levels but no effect on insulin levels. Moreover, neither metoprolol nor atenolol treatment reduced the elevated cholesterol levels in diabetic rats. Metoprolol treatment significantly prevented STZ-induced increase in triglyceride levels, but atenolol failed to produce this effect. Metoprolol exhibited a minimal improvement in STZ-induced bradycardia, whereas atenolol produced a further reduction in heart rate. Histological examination showed metoprolol treatment also prevented STZ-induced hypertrophy and some of the alterations in cardiomyocytes. In conclusion, our data suggest that metoprolol has some beneficial effects over atenolol with respect to cardiovascular complications associated with diabetes mellitus.

Determination of stability constants of the inclusion complexes of β-blockers in heptakis (2,3-dimethyl-6-sulfato)-β-cyclodextrin

The beta-blockers possess at least one chiral center and the S(-)-enantiomer shows higher affinity for binding to the beta-adrenergic receptors than antipode. The stability constants of acebutolol, celiprolol, propranolol and terbutaline in the inclusion complexes with single-isomer heptakis (2,3-dimethyl-6-sulfato)-beta-cyclodextrin (HDMS-beta-CD) were determined by capillary electrophoresis. The approximation and linear double reciprocal methods were adapted with comparable results. Among the beta-blockers studied, propranolol had the lowest stability constant but the highest enantioselectivity, indicating that the magnitudes of the stability constants carried little information about enantioseparation. The magnitudes of enantioselectivities between the enantiomer pair were in the order of propranolol > celiprolol > terbutaline > acebutolol.

The severe cardiorenal syndrome: 'Guyton revisited'

The incidence of cardiac failure and chronic renal failure is increasing and it has now become clear that the co-existence of the two problems has an extremely bad prognosis. We propose the severe cardiorenal syndrome (SCRS), a pathophysiological condition in which combined cardiac and renal dysfunction amplifies progression of failure of the individual organ, so that cardiovascular morbidity and mortality in this patient group is at least an order of magnitude higher than in the general population. Guyton has provided an excellent framework describing the physiological relationships between cardiac output, extracellular fluid volume control, and blood pressure. While this model is also sufficient to understand systemic haemodynamics in combined cardiac and renal failure, not all aspects of the observed accelerated atherosclerosis, structural myocardial changes, and further decline of renal function can be explained. Since increased activity of the renin-angiotensin system, oxidative stress, inflammation, and increased activity of the sympathetic nervous system seem to be cornerstones of the pathophysiology in combined chronic renal disease and heart failure, we have explored the potential interactions between these cardiorenal connectors. As such, the cardiorenal connection is an interactive network with positive feedback loops, which, in our view, forms the basis for the SCRS.

Selenoproteins, Cholesterol-Lowering Drugs, and the Consequences Revisiting of the Mevalonate Pathway

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and peroxisome proliferator-activated receptor alpha activators (fibrates) are the backbone of pharmacologic hypercholesterolemia and dyslipidemia treatment. Many of their clinical effects, however, are still enigmatic. This article describes how a side road of the mevalonate pathway, characterized in recent years, can rationalize a major fraction of these unexplained observations. This side road is the enzymatic isopentenylation of selenocysteine-tRNA([Ser]Sec) (Sec-tRNA), the singular tRNA to decode the unusual amino acid selenocysteine. The functionally indispensable isopentenylation of Sec-tRNA requires a unique intermediate from the mevalonate pathway, isopentenyl pyrophosphate, which concomitantly constitutes the central building block for cholesterol biosynthesis, and whose formation is suppressed by statins and fibrates. The resultant inhibition of Sec-tRNA isopentenylation profoundly decreases selenoprotein expression. This effect might seamlessly explain the immunosuppressive, redox, endothelial, sympatholytic, and thyroidal effects of statins and fibrates as well as their common side effects and drug interactions.

Noninvasive atherosclerosis imaging for predicting cardiovascular events and assessing therapeutic interventions

Noninvasive assessment of atherosclerosis offers an opportunity to provide individual cardiovascular risk management and an opportunity to monitor the efficacy of therapy targeted toward atherosclerosis. The three imaging modalities that currently hold the most promise at the clinical and research levels are ultrasound for carotid intima-media thickness, computed tomography for coronary artery calcification, and magnetic resonance imaging for carotid and aortic plaque imaging. The following review describes the evidence that validates each technique as a surrogate marker of atherosclerosis, with an emphasis on cardiovascular events and the progression of disease. Both the particular strengths and limitations of each imaging modality are discussed.