Secondary prevention of coronary heart disease: the role of fibric acids

The Role of High-Density Lipoprotein Cholesterol in 2022

PURPOSE OF THE REVIEW

High-density lipoproteins (HDL) are responsible for the transport in plasma of a large fraction of circulating lipids, in part from tissue mobilization. The evaluation of HDL-associated cholesterol (HDL-C) has provided a standard method for assessing cardiovascular (CV) risk, as supported by many contributions on the mechanism of this arterial benefit. The present review article will attempt to investigate novel findings on the role and mechanism of HDL in CV risk determination.

RECENT FINDINGS

The most recent research has been aimed to the understanding of how a raised functional capacity of HDL, rather than elevated levels per se, may be responsible for the postulated CV protection. Markedly elevated HDL-C levels appear instead to be associated to a raised coronary risk, indicative of a U-shaped relationship. While HDL-C reduction is definitely related to a raised CV risk, HDL-C elevations may be linked to non-vascular diseases, such as age-related macular disease. The description of anti-inflammatory, anti-oxidative and anti-infectious properties has indicated potential newer areas for diagnostic and therapeutic approaches. In the last two decades inconclusive data have arisen from clinical trials attempting to increase HDL-C pharmacologically or by way of recombinant protein infusions (most frequently with the mutant A-I Milano); prevention of stent occlusion or heart failure treatment have shown instead significant promise. Targeted clinical studies are still ongoing.

Supplementation of hydrogen-rich water improves lipid and glucose metabolism in patients with type 2 diabetes or impaired glucose tolerance

Oxidative stress is recognized widely as being associated with various disorders including diabetes, hypertension, and atherosclerosis. It is well established that hydrogen has a reducing action. We therefore investigated the effects of hydrogen-rich water intake on lipid and glucose metabolism in patients with either type 2 diabetes mellitus (T2DM) or impaired glucose tolerance (IGT). We performed a randomized, double-blind, placebo-controlled, crossover study in 30 patients with T2DM controlled by diet and exercise therapy and 6 patients with IGT. The patients consumed either 900 mL/d of hydrogen-rich pure water or 900 mL of placebo pure water for 8 weeks, with a 12-week washout period. Several biomarkers of oxidative stress, insulin resistance, and glucose metabolism, assessed by an oral glucose tolerance test, were evaluated at baseline and at 8 weeks. Intake of hydrogen-rich water was associated with significant decreases in the levels of modified low-density lipoprotein (LDL) cholesterol (ie, modifications that increase the net negative charge of LDL), small dense LDL, and urinary 8-isoprostanes by 15.5% (P < .01), 5.7% (P < .05), and 6.6% (P < .05), respectively. Hydrogen-rich water intake was also associated with a trend of decreased serum concentrations of oxidized LDL and free fatty acids, and increased plasma levels of adiponectin and extracellular-superoxide dismutase. In 4 of 6 patients with IGT, intake of hydrogen-rich water normalized the oral glucose tolerance test. In conclusion, these results suggest that supplementation with hydrogen-rich water may have a beneficial role in prevention of T2DM and insulin resistance.

Avoiding and Managing Bleeding Complications in Patients with Non-ST-Segment Elevation Acute Coronary Syndromes

Antithrombotic therapy coupled with early use of cardiac catheterization and revascularization have decreased morbidity and mortality rates in patients who have acute ischemic heart disease but who carry a risk for bleeding. Bleeding complications in patients with acute coronary syndromes are associated with worse clinical outcomes, including recurrent ischemic events and death. Determining the appropriate balance between preventing ischemic events and causing bleeding in patients with acute coronary syndromes present a challenging problem for clinicians. Antithrombotics studied in recent clinical trials that have focused on bleeding reduction include bivalirudin and fondaparinux. In this review, the incidence, predictors, and clinical outcomes associated with bleeding are discussed. Furthermore, the association between antithrombotic agents and bleeding and propose strategies to prevent bleeding complications are also discussed.

A Comparison between Ranolazine and CVT-4325, a Novel Inhibitor of Fatty Acid Oxidation, on Cardiac Metabolism and Left Ventricular Function in Rat Isolated Perfused Heart during Ischemia and Reperfusion

Inhibition of fatty acid oxidation has been reported to be cardioprotective against myocardial ischemic injury; however, recent studies have questioned whether the cardioprotection associated with putative fatty acid oxidation inhibitors, such as ranolazine and trimetazidine, are due to changes in substrate oxidation. Therefore, the goals of this study were to compare the effects of ranolazine with a new fatty acid oxidation inhibitor, CVT-4325 [(R)-1-(2-methylbenzo[d]thiazol-5-yloxy)-3-(4-((5-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-3-yl)methyl)-piperazin-1-yl)propan-2-ol], on carbohydrate and fatty acid oxidation and on left ventricular (LV) function in the response to ischemia/reperfusion in rat isolated perfused hearts. Metabolic fluxes were determined in hearts perfused in an isovolumic Langendorff mode using 13C nuclear magnetic resonance isotopomer analysis or in isolated working hearts using [14C]glucose and [3H]palmitate, with and without 10 microM ranolazine or 3 microM CVT-4325. Isovolumic perfused hearts were also subjected to 30 min of low-flow ischemia (0.3 ml/min) and 60 min of reperfusion, and working hearts were subjected to 15 min of zero-flow ischemia and 60 min of reperfusion. Regardless of the experimental protocol, ranolazine had no effect on carbohydrate or fatty acid oxidation, whereas CVT-4325 significantly reduced fatty acid oxidation up to approximately 7-fold with a concomitant increase in carbohydrate oxidation. At these same concentrations, although ranolazine significantly improved LV functional recovery following ischemia/reperfusion, CVT-4325 had no significant protective effect. These results demonstrate that at pharmacologically relevant concentrations, ischemic protection by ranolazine was not mediated by inhibition of fatty acid oxidation and conversely that inhibition of fatty acid oxidation with CVT-4325 was not associated with improved LV functional recovery.

Hypertriglyceridemia—why, when and how should it be treated?

The relationship between serum triglyceride levels and cardiovascular disease has remained enigmatic despite four decades of research. The majority of the available evidence tends to support the role of hypertriglyceridemia as an independent risk factor for cardiovascular disease. However, there are no guidelines recommending a target triglyceride level for prevention of cardiovascular disease. The focus of lipid lowering therapy still remains the reduction of global cardiovascular risk by optimizing LDL cholesterol levels. Therapeutic options for triglyceride-lowering include lifestyle modification and pharmacological agents, such as fibrates, omega 3 fatty acids and niacin. Post-hoc analyses of the Helsinki Heart Study, Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial and Bezafibrate Infarction Prevention Study suggest a beneficial effect of the treatment of hypertriglyceridemia with fibrates, mainly in obese subjects with insulin resistance. However, in order to establish the actual clinical relevance of lowering triglyceride levels, prospective trials need to be conducted with the specific purpose of studying the effects of triglyceride reduction on clinical end points, i. e. coronary events and stroke.

[First responder defibrillation in the LAGO-die Therme--results and experiences]

The use of automated external defibrillator (AED) by persons other than paramedics and emergency medical technicians is advocated by several US- and European organizations. However, at the present time it is still unclear to identify public places with a high incidence of out-of-hospital cardiac arrest. There are few data on the potential impact of public access defibrillators on survival after out-of-hospital cardiac arrest in sporting arenas or water parks. Therefore, we studied prospectively incidence of out-of-hospital cardiac arrest in the LAGO-die Therme in Herne. This is one of the most important swimming parks in Europe and member of the European Waterpark Association EWA. Eight AEDs were placed in the waterpark LAGO-die Therme. The locations where the defibrillators were stored were chosen to make possible a target interval of 60 seconds from collapse to first defibrillation. Twenty waterpark officers were instructed in cardiopulmonary resuscitation and in the use of the AED. During November 16, 2001 and December 31, 2004, 2.05 Mio. visitors were counted in the LAGO. Out-of-hospital cardiac arrest occurred in none of them. AED were used in two visitors with non arrhythmogenic syncope, no shock was delivered. Questionaires were done in 588 visitors (336 males, 252 females, mean age 38+21 years) in 2002 and in 579 visitors (322 males, 257 females, mean age 37+/-25 years) in 2004. In 2002, 77% of the visitors noticed the AED and, therefore, 49% performed more sporting activities. In addition, in 2004, AED was noticed by 480 visitors (83%) and 277 visitors (48%) did more sporting activities. There were no significant differences between 2002 and 2004 (p=ns). Despite no out-of-hospital cardiac arrest in the waterpark during the 3 year follow- up, it seems reasonable to install AED in sporting places with thousands of visitors per year.

Bezafibrates Cause Moderate, Reversible Impairment in Renal Function in Patients without Prior Renal Disease

BACKGROUND/AIMS

To determine whether bezafibrates have adverse effects on renal function.

METHODS

(1) A 3-year retrospective survey of 526 patients who were on bezafibrate for a while and 614 controls following fluctuations of serum creatinine levels. (2) A prospective study on 33 patients with previous evidence of bezafibrate-induced elevation in serum creatinine. The patients were examined after 3 months on bezafibrate 400 mg/day and then after 3 months without bezafibrate. Eight patients repeated the tests after 3 months on bezafibrate 200 mg/day.

RESULTS

Retrospective: 295 bezafibrate-treated patients (56%) and 67 controls (11%) demonstrated fluctuations > or = 0.2 mg/dl in serum creatinine levels (p < 0.001); 113 patients (21%) and 16 controls (3%) showed fluctuations > or = 0.3 mg/dl (p < 0.001). Prospective: bezafibrate 400 mg/dl increased serum creatinine from 1.16 +/- 0.19 to 1.42 +/- 0.2 mg/dl (p < 0.001) and urea from 37 +/- 8 to 44 +/- 8 mg/dl (p < 0.001); creatinine clearance (Ccr) decreased from 104 +/- 23 to 82 +/- 27 ml/min (p < 0.001). CPK increased from 82 +/- 32 to 130 +/-58 mg/dl (p < 0.0001) and urinary myoglobin increased from 95.4 +/- 21 to 199 +/- 99 mg/dl (p < 0.0001). The 8 patients given bezafibrate 200 mg/dl experienced similar dose-dependent changes.

CONCLUSIONS

Bezafibrate causes quiet common, dose-dependent and reversible changes in serum creatinine in patients with normal renal function, associated with a significant increase in serum CPK and urine myoglobin, suggestive of drug-induced mild subclinical skeletal muscle injury compromising renal function.

WITHDRAWAL OF INTRAVENOUS GLYCERYL TRINITRATE: ABSENCE OF REBOUND PHENOMENA WITH TRANSITION TO ORAL ISOSORBIDE DINITRATE

1. Glyceryl trinitrate (GTN) is frequently infused intravenously as a component of the management of acute coronary syndromes (ACS). Abrupt cessation of GTN infusion after periods of more than 24 h administration often induces rebound vasoconstriction reflecting 'pseudotolerance'; this is also the basis of the 'zero hour phenomenon' during chronic nitrate therapy. The efficacy of oral nitrate regimens to prevent vasoconstriction following cessation of intravenous GTN has not been previously examined. Therefore, we investigated the effects of transition from intravenous GTN to oral isosorbide dinitrate (ISDN) on a parameter of apparent arterial stiffness in patients with ACS. 2. The effects of GTN infusion at 5 microg/min on augmentation index (AIx) were quantified in patients (n = 10) with stable angina pectoris in order to establish the magnitude of effect on apparent arterial stiffness. 3. This infusion rate of GTN reduced AIx from 23 +/- 10% (SD) to 3 +/- 14% (SD) (P < 0.01). The effect of transition from GTN infusion of greater than 24 h duration to ISDN (10 mg tds) were examined in patients (n = 16) with ACS (unstable angina/non-Q-wave myocardial infarction). No patient developed recurrent angina during the 24 h following cessation of GTN infusion. The level of AIx was 8 +/- 4% (SD) prior to GTN cessation and fell to 5 +/- 6% (SD) on ISDN (P = 0.05). 4. Thus, in patients treated for ACS, transition from intravenous GTN to low dose oral ISDN is associated with an incremental vasodilatation and no evidence of 'rebound' ischaemia.

["Meet the AIX-PERTs." Emergency medical care at the beginning of the medical reform curriculum in Aachen]

BACKGROUND

Extensive knowledge and skills in the basics of emergency medical care are of paramount importance for every physician and should therefore be an integral part of medical education.

METHODS

Regulations for medical licensure in Germany were revised by the administrative authorities in 2002 and as a consequence the Medical Faculty of the University of Aachen (Germany) decided to start the Medical Reform Curriculum Aachen. A multidisciplinary, problem-oriented and organ-related approach to medical education replaces the classical discrimination between basic and clinical sciences.

RESULTS

With AIX-PERT (AIX-la-Chapelle Program for Emergency medical care and Resuscitation Training), a program consisting of problem-based learning sessions was developed for introduction to the first year students. Defined teaching objectives in emergency medicine are now incorporated in undergraduate medical education.

CONCLUSION

The extremely positive evaluation of the new approach encouraged us to promote AIX-PERT further. In the future the effects of success of this approach will be assessed by longitudinal studies of skills and knowledge during the continuing curriculum.

Guinea pigs as models to study the hypocholesterolemic effects of drugs

Guinea pigs are useful models to investigate the mechanisms of the hypocholesterolemic effects of drugs. Like humans, guinea pigs are one of the few species that carry the majority of cholesterol in LDL. This animal model has also been shown to develop atherosclerosis when challenged with hypercholesterolemic diets. In addition, plasma lipid profiles in males, females and ovariectomized guinea pigs, a model for menopause, follow similar patterns to those observed in humans. In this report, drugs aimed at lowering plasma cholesterol and triglycerides in hyperlipidemic individuals are reviewed. Studies analyzing the hypolipidemic effect of HMG-CoA reductase inhibitors, acyl CoA cholesterol acyltransferase inhibitors, fibrates, bile acid resins, apical sodium bile acid transporter inhibitors, and others show that guinea pigs and humans have comparable responses to drug therapy. In addition, results from the limited clinical reports addressing specific effects of drugs on LDL catabolism or VLDL synthesis are in agreement with observations in guinea pigs. From the review of these studies, it is apparent that the guinea pig is a useful animal model to further explore the mechanisms of action of lipid lowering drugs including effects on specific receptors and regulatory enzymes involved in cholesterol metabolism and on early atherosclerosis development.

ABBREVIATIONS

ACAT, acyl-CoA:cholesterol acyltransferase; ASBT, apical sodium co-dependent bile acid transporter; ApoB, apolipoprotein B; CHD, coronary heart disease; CYP7, cholesterol 7alpha-hydroxylase; HDL, high density lipoprotein; HMG-CoA, 3-hydroxy-3-methylglutaryl coenzyme A; FCR, free catabolic rate; LDL, low density lipoprotein; PPAR, peroxisome proliferators-activated receptor; TC, total cholesterol; TG, triglycerides; VLDL, very low density lipoprotein.

Impact of low-flow ischemia on substrate oxidation and glycolysis in the isolated perfused rat heart

Interventions that stimulate carbohydrate oxidation appear to be beneficial in the setting of myocardial ischemia or infarction. However, the mechanisms underlying this protective effect have not been defined, in part because of our limited understanding of substrate utilization under ischemic conditions. Therefore, we used (1)H and (13)C NMR spectroscopy to investigate substrate oxidation and glycolytic rates in a global low-flow model of myocardial ischemia. Isolated male Sprague-Dawley rat hearts were perfused for 30 min under conditions of normal flow (control) and low-flow ischemia (LFI, 0.3 ml/min) with insulin and (13)C-labeled lactate, pyruvate, palmitate, and glucose at concentrations representative of the physiological fed state. Despite a approximately 50-fold reduction in substrate delivery and oxygen consumption, oxidation of all exogenous substrates plus glycogen occurred during LFI. Oxidative metabolism accounted for 97% of total calculated ATP production in the control group and approximately 30% in the LFI group. For controls, lactate oxidation was the major source of ATP; however, in LFI, this shifted to a combination of oxidative and nonoxidative glycogen metabolism. Interestingly, in the LFI group, anaplerosis relative to citrate synthase increased sevenfold compared with controls. These results demonstrate the importance of oxidative energy metabolism for ATP production, even during very-low-flow ischemia. We believe that the approach described here will be valuable for future investigations into the underlying mechanisms related to the protective effect of increasing cardiac carbohydrate utilization and may ultimately lead to identification of new therapeutic targets for treatment of myocardial ischemia.

TxA2-mediated myocardial ischemia as a consequence of an acute lung inflammatory reaction in the rabbit

Epidemiological studies link acute infection of the respiratory tract to a transient increased risk of acute myocardial infarction. The underlying mechanisms remain unknown. We hypothesized that vasoactive mediators produced by inflammatory cells in the lungs and drained in the coronary circulation may trigger acute myocardial ischemia. To test this hypothesis we used an experimental model in the rabbit. Injection of the bacterial-derived peptide N-formyl-Met-Leu-Phe (or N-formyl-Methionyl-Leucyl-Phenylalanine)(fMLP) in the jugular vein induced massive recruitment of both polymorphonuclear leukocytes (PMN) and platelets in the microcirculation of the lungs, accompanied by rapid and marked increase of leukotriene B4, cysteinyl leukotrienes and thromboxane (Tx) A2 in the aortic blood. In all animals, fMLP evoked ischemic electrocardiographic changes: within the first minute of infusion a profound depression of the ST segment and inversion of the T wave were observed. Mean aortic pressure and heart rate fell to 64.0 +/- 6.9 and 83.5 +/- 3.1% of the basal levels at 3 and 10 min, respectively. All these alterations were transient. Aspirin, prevented electrocardiographic ischemic changes, reverted bradycardia and hypotension but did not significantly modify either PMN or platelet recruitment nor leukotriene synthesis. Ridogrel, a Tx-synthase and receptor inhibitor, prevented ECG alterations and bradycardia, but did not prevent and even worsened hypotension; it blocked platelet, but not PMN, sequestration. Pretreatment of animals with intravenous high dose of aspirin prevented ridogrel-dependent hypotension and platelet inhibition, suggesting that PGI2 contributes to the effects of Tx-synthase and receptor inhibitor. In hypercholesterolemic rabbits, ECG alterations persisted longer than in normal controls. In summary, our results indicate that acute activation of PMN and platelets in the lungs provokes transient myocardial ischemia, in normal animals that is exacerbated in hypercholesterolemic rabbits. TxA2 appears to be the major mediator of this phenomenon. Moreover the data suggest that a balance between TxA2 and PGI2 plays a pivotal role in platelet activation and recruitment in our model.

Pathophysiologic role of myocardial apoptosis in post-infarction left ventricular remodeling

Left ventricular (LV) remodeling and heart failure (HF) complicate acute myocardial infarction (AMI) even weeks to months after the initial insult. Apoptosis may represent an important pathophysiologic mechanism causing progressive myocardiocyte loss and LV dilatation even late after AMI. This review will discuss the role of apoptosis according to findings in animal experimental data and observational studies in humans in order to assess clinical relevance, determinants, and mechanisms of myocardial apoptosis and potential therapeutic implications. More complete definition of the impact of myocardiocyte loss on prognosis and of the mechanisms involved may lead to improved understanding of cardiac remodeling and possibly improved patients' care. Mitochondrial damage and bcl-2 to bax balance play a central role in ischemia-dependent apoptosis while angiotensin II and beta(1)-adrenergic-stimulation may be major causes of receptor-mediated apoptosis. Benefits due to treatment with ACE-inhibitors and beta-blockers appear to be in part due to reduced myocardial apoptosis. Moreover, infarct-related artery patency late after AMI may be a major determinant of myocardial apoptosis and clinical benefits deriving from an open artery late post AMI (the "open artery hypothesis") may be, at least in part, due to reduced myocardiocyte loss.

ApoC-III gene polymorphisms and risk of coronary artery disease

Several polymorphisms in the apolipoprotein C-III (apoC-III) gene have been associated with hypertriglyceridemia, but the link with coronary artery disease risk is still controversial. In particular, apoC-III promoter sequence variants in the insulin responsive element (IRE), constitutively resistant to downregulation by insulin, have never been investigated in this connection. We studied a total of 800 patients, 549 of whom had angiographically documented coronary atherosclerosis, whereas 251 had normal coronary arteriograms. We measured plasma lipids, insulin, apoA-I, apoB, and apoC-III and assessed three polymorphisms in the apoC-III gene, namely, T-455C in the IRE promoter region, C1100T in exon 3, and Sst1 polymorphic site (S1/S2) in the 3' untranslated region. Each variant influenced triglyceride levels, but only the T-455C (in homozygosity) and S2 alleles influenced apoC-III levels. In coronary artery disease (CAD) patients, 18.6% were homozygous for the -455C variant compared with only 9.2% in CAD-free group (P < 0.001). In logistic regression models, homozygosity for -455C variant was associated with a significantly increased risk of CAD (OR = 2.5 and 2.18 for unadjusted and adjusted models, respectively) suggesting that it represents an independent genetic susceptibility factor for CAD.

Lipid-lowering trials in diabetes

Type 2 diabetes is increasingly recognized as a major risk factor for coronary heart disease (CHD). The recent Adult Treatment Panel III of the National Cholesterol Education Program makes special mention of diabetes and the metabolic syndrome and proposes a secondary goal of therapy following achievement of the LDL goal, namely non-HDL cholesterol (the sum of VLDL and LDL cholesterol, i.e. total cholesterol-HDL cholesterol). In addition diabetes is recognized as a CHD risk equivalent. Much information is available from subgroup analysis of the major CHD secondary prevention trials of lipid-lowering with regard to the benefits for diabetic patients. However little information is available from clinical trials in primary prevention. Ongoing trials will help fill this gap. Recently the first report of a large lipid-lowering trial addressing coronary atherosclerosis in a specific diabetic population has been published-the Diabetes Atherosclerosis Intervention Study (DAIS). In this study fenofibrate therapy was associated with reduced progression of coronary atherosclerosis assessed by quantitative coronary angiography.

Triglycerides: risk factor or fellow traveler?

An unresolved issue in preventive cardiology is whether the serum triglyceride level is an independent risk factor for coronary heart disease and, as a direct practical consequence, whether it has value as a diagnostic test. Evidence published in the past year has contributed substantially to clarifying these issues. In this review, we discuss the data that bears upon the importance of triglycerides as a risk factor and the implications of recent clinical trials directed at lipid lowering. We then discuss the alternatives for triglyceride lowering therapy in the light of this new knowledge.

Hypertriglyceridemia and the fibrate trials

Epidemiological studies published since 1996 have established that hypertriglyceridemia can predict risk of cardiovascular disease in a manner statistically independent of HDL cholesterol. Nevertheless, the relationship of concentrations of plasma triglycerides to risk of cardiovascular disease remains less than straightforward, partly because triglycerides are carried in lipoproteins of different atherogenicity, partly because hypertriglyceridemia is associated with non-lipid atherogenic and thrombogenic processes. For example, the association of highest risk of cardiovascular disease to moderate rather than to severe hypertriglyceridemia can be understood in terms of the distribution of triglycerides between different classes of plasma lipoproteins. It is counter-intuitive to most clinicians, however, and hence it can result in the misdirection of clinical efforts including drug therapy. Fibrates lower plasma triglycerides, and raise HDL, efficiently and with few immediate side-effects. Central to their mode of action is activation of certain nuclear receptors in cells. There is no necessary connection, however, between that fascinating biochemistry and clinical benefit as defined by reductions in rates of death by coronary artery disease. A review of trials of cholesterol-lowering by diet and drugs, published between 1966 and 1996, included 12 trials of therapy with fibrates or placebo in more than 21000 patients. Overall, these trials indicated no benefit in terms of reduction in risk of coronary deaths. The period since 1996 has seen the publication of four additional trials of treatment of 6144 patients with fibrates or placebo. Two of them were major trials. The VA-HIT was very encouraging, because treatment with gemfibrozil produced a signficant reduction in the combined incidence of fatal and non-fatal coronary events. There was no significant reduction in coronary deaths, however. The results of BIP were frankly disappointing, because they demonstrated no significant effect of treatment with bezafibrate on either the primary end-point of the trial or on rates of coronary death. Clinical indications for the use of fibrates can obviously not be based on biochemical insights, however intriguing in their own right, but they have also not been satisfactorily defined by the randomized clinical trials published to date. Hope remains, however, that some clarification will result from ongoing trials of fibrate treatment of patients with type II diabetes.