Review of recent clinical trials of lipid lowering in coronary artery disease

Triacetyl-3-hydroxyphenyladenosine, a derivative of cordycepin, attenuates atherosclerosis in apolipoprotein E-knockout mice

The cholesterol-modulating, immune-regulating and anti-inflammatory properties of cordycepin are well documented. Here we examined the effects of triacetyl-3-hydroxyphenyladenosine (THPA), a derivative of cordycepin, on the development of atherosclerosis (AS) in apolipoprotein E-knockout (apoE-/-) mice. The atherosclerotic lesion formation displayed by the oil red O staining-positive area was reduced significantly in either the aortic root section or the whole aorta en face in THPA-administrated apoE-/- mice. Plasma analysis by enzymatic method or enzyme-linked immunosorbent assay (ELISA) showed that high-density lipoprotein-cholesterol (HDL-C) was decreased, whereas apolipoprotein A-I (apoA-I) levels were markedly increased by THPA. In addition, ELISA and spectrophotometric measurement showed that plasma levels of tumor necrosis factor-α, interleukin-1 and malondialdehyde were decreased in mice treated with THPA. Realtime polymerase chain reaction detection disclosed that the expression of several transporters involved in reverse cholesterol transport was induced by THPA, and the expression of hepatic ABCA1 and apoA-I, which play roles in the maturation of HDL-C, was also elevated in the THPA-treated groups. Moreover, THPA enhanced the expression of endothelial nitric oxide synthase (NOS), and reduced the expression of inducible NOS and lectin-like oxidized LDL receptor-1 in the aorta, suggesting that THPA can exert endothelial protection effects. In addition, the expression or activation of several proinflammatory factors in the aorta was suppressed by THPA. In conclusion, our results reveal the inhibitory effects of THPA on AS in apoE-/- mice.

Omega-3 fatty acids and atorvastatin affect connexin 43 expression in the aorta of hereditary hypertriglyceridemic rats

Statins and omega-3 polyunsaturated fatty acids (n-3 PUFA) reduce cardiovascular disease incidence during hypertriglyceridemia (HTG). To elucidate possible cardioprotective mechanisms, we focused on gap junction protein connexin 43 (Cx43). Its expression is disturbed during atherogenesis, but little information is available on its expression during HTG. Experiments were performed on adult male hereditary HTG (hHTG) rats treated with n-3 PUFA (30 mg/day) and atorvastatin (0.5 mg/100 g body weight per day) for 2 months. Cx43 expression and distribution in the aorta were investigated by using Western blotting and immunolabeling, followed by quantitative analysis. Transmission electronmicroscopy was used to study ultrastructure of endothelial contact sites. In contrast to age-matched Wistar, Cx43 expression in aorta of hHTG rats was significantly higher (p < 0.05), and prominent Cx43 immunospots were seen in tunica media and less in endothelium of hHTG rats. Changes in Cx43 expression were accompanied by local qualitative subcellular alterations of interendothelial connections. Treatment of hHTG rats with n-3 PUFA and atorvastatin markedly lowered Cx43 expression in aorta and modified connexin distribution in endothelium and media (p < 0.05 vs. untreated hHTG). The protective effect of treatment of HTG was observed on the structural integrity of the endothelium and was readily visible at the molecular level. Results indicate the involvement of altered Cx43 expression in vascular pathophysiology during HTG and during HTG treatment.

Decrease in density of INa is in the common final pathway to heart block in murine hearts overexpressing calcineurin

Overexpression of calcineurin in transgenic mouse heart results in massive cardiac hypertrophy followed by sudden death. Sudden deaths are caused by abrupt transitions from sinus rhythm to heart block (asystole) in calcineurin-overexpressing (CN) mice. Preliminary studies showed decreased maximum change in potential over time (d V/d tmax) of phase 0 of the action potential. Accordingly, the hypothesis was tested that decreased activity of the sodium channel contributes to heart block. Profound decreases in activity of sodium currents ( INa) paralleled the changes in action potential characteristics. Progressive age-dependent decreases were observed such that at 42–50 days of life little sodium channel function existed. However, this was not paralleled by decreased protein expression as assessed by immunocytochemistry or by Western blot. Since calcineurin can interact with the ryanodine receptor, we assessed whether chronic in vitro treatment with BAPTA-AM, thapsigargin, and ryanodine could rescue the decrease of INa. All of these treatments rescued INa to levels indistinguishable from wild type. The nonspecific PKC inhibitor bisindolylmaleimide I also rescued the decrease of INa. To assess whether decreased sodium channel activity contributes to sudden death in vivo, the response to encainide (20 mg/kg) was assessed: 6 of 10 young CN mice died because of asystole, whereas 0 of 10 wild-type mice died ( P < 0.01). Moreover, encainide produced exaggerated prolongation of the QRS width in sinus beats before the heart block. Catecholamine tone appears necessary to support life in older CN mice because propranolol (1 mg/kg) triggered asystolic death in five of six CN mice. We conclude that decrease in sodium channel activity is in the common final pathway to asystole in CN mice.

Statins reduce connexin40 and connexin43 expression in atherosclerotic aorta of rabbits

BACKGROUND

Gap junction protein connexin43 (Cx43) expression was enhanced in proliferating smooth muscle cells (SMCs) in the neointima of atherosclerotic lesions. HMG-CoA Reductase Inhibitors (statins) can reduce Cx43 expression in vivo and in vitro. Connexin40 (Cx40) is also a very important connexin in SMCs of arterial wall.

METHODS

We observed the expression of Cx40 and Cx43 in a rabbit model of a high-cholesterol diet and investigated the effect of lovastatin (10 mg.kg-1.d-1, 2 weeks) or fluvastatin (10 mg.kg-1.d-1, 2 weeks) on these changes by the methods of western blotting, RT-PCR, immunohistochemistry, and transmission electron microscope.

RESULTS

There was abundant expression of Cx40 mRNA and protein in SMCs of rabbit aorta. Besides Cx43, Cx40 expression was also obviously upregulated in atherosclerotic plaques. Treatment with statins reduced the over-expression of Cx43 and Cx40 in atherosclerotic lesion. Cx40 and Cx43 gap junction quantity from each of the arteries obtained at the different drug treatment levels revealed no significant difference. Neointimal SMCs had abundant, large gap junctions, whereas normal SMCs had smaller, less frequent junctions. Statins also normalized the enlarged gap junctions.

CONCLUSIONS

These results provide novel in vivo evidence for the key role of gap junctions in atherogenesis and the possible mechanism in antiatherogenic effect of statins.

Basic mechanisms of cardiac impulse propagation and associated arrhythmias

Propagation of excitation in the heart involves action potential (AP) generation by cardiac cells and its propagation in the multicellular tissue. AP conduction is the outcome of complex interactions between cellular electrical activity, electrical cell-to-cell communication, and the cardiac tissue structure. As shown in this review, strong interactions occur among these determinants of electrical impulse propagation. A special form of conduction that underlies many cardiac arrhythmias involves circulating excitation. In this situation, the curvature of the propagating excitation wavefront and the interaction of the wavefront with the repolarization tail of the preceding wave are additional important determinants of impulse propagation. This review attempts to synthesize results from computer simulations and experimental preparations to define mechanisms and biophysical principles that govern normal and abnormal conduction in the heart.

Statins and secondary prevention of coronary heart disease

A mini-review (Griffiths, 2002) of double-blind randomized controlled trials (RCTs) was undertaken to assess the long-term effect of lipid lowering treatments (statins versus placebo) in secondary prevention of myocardial infarction (MI). The population sample was adult patients with a history of MI, documented coronary heart disease or coronary artery disease. The Cochrane Library and the database Medline were searched and three RCTs appeared to possess all of the stipulated inclusion and exclusion criteria. The trials all compared statins against a placebo; one trial was of simvastatin--the Scandinavian Simvastatin Survival Study (1994)--and the other two were of pravastatin--the Cholesterol and Recurrent Events Trial (CARE) (Sacks et al, 1996) and Long Term Intervention with Pravastatin Ischaemic Disease (LIPID) (Anon, 1998). The trials demonstrated that statins had a clear and consistent effect in significantly reducing the risk of MI. Overall an approximate decline of 30% in MI was produced from the three trials.

From membrane differential filtration to lipidfiltration: technological progress in low-density lipoprotein apheresis

Extracorporeal low-density lipoprotein (LDL) apheresis is an established and highly effective therapy for patients with familial hypercholesterolemia (FH) not adequately responding to diet and drug therapy alone. Based on different methodology, five treatment options of LDL apheresis are available and in widespread practical use in Germany. All methods are safe and demonstrate equivalent efficacy of reducing LDL cholesterol with respect to the single apheresis session as well as during long-term treatment. Owing to methodological properties all methods also exhibit characteristics of additional plasma protein elimination, which do not impair, but in part, increase the beneficial therapeutic effect of LDL apheresis. Fibrinogen reduction has to be mentioned as an example. The lipidfiltration system is based on plasmafiltration previously named membrane differential filtration (MDF), synonymous with double filtration plasmapheresis (DFPP). The new term lipidfiltration was the result of technological progress leading to a significant improvement of the efficiency. The system consists of a novel lipid filter with enhanced sieving characteristics and capacity, and is completed by an enhanced therapy machine with an optimized heating unit.

α-Heterosubstituted Aldehydes in Organic Synthesis. Enantioselective Approaches to New Analogues of Mevinic Acids

Various aldol approaches towards the asymmetric synthesis of the lactone moiety of HMG-CoA-reductase inhibitors are described. Auxiliary controlled as well as catalytic aldol reactions resulted only in modest to low selectivities, whereas 1,2-additions to readily available highly enantiomerically enriched α-heterosubstituted aldehydes yielded δ-hydroxy-β-ketoesters with a high degree of diastereocontrol and in good chemical yields. The novel mevinic acid analogues could then be obtained bysyn-reduction of the addition products.

Isotopomer spectral analysis of intermediates of cholesterol synthesis in human subjects and hepatic cells

Steroid intermediates of the cholesterol synthesis pathway are characterized by rapid turnover rates relative to cholesterol due to their small pool size. Because the small pools will label rapidly, these intermediates may provide valuable information about the incorporation of isotopes in de novo synthesis of cholesterol and related compounds. The labeling of cholesterol synthesis intermediates from [1-(13)C]acetate was investigated in human subjects and in liver cell models by means of isotopomer spectral analysis (ISA). In human subjects, infusing [1-(13)C]acetate into the duodenum for 12 h demonstrated that approximately 50% of the plasma lathosterol pool was derived from de novo synthesis during this interval. The lipogenic acetyl-CoA precursor pool enrichment reached a constant value within 3 h of the start of the infusion. In vitro studies indicated that liver cell models decrease de novo lathosterol synthesis when cholesterol synthesis is inhibited by statins or cholesterol-containing serum. We propose a new calculation to increase the accuracy and precision of cholesterol synthesis estimates in vivo combining the ISA of lathosterol and cholesterol.

Weak effect of hypertension and other classic risk factors in the elderly who have already paid their toll

The aim of the CASTEL, a population-based (n=3282) prospective study which began 14 years ago, was to identify those items which had a prognostic impact in the elderly, and to evaluate whether the typical cardiovascular risk factors, particularly arterial hypertension, play a role after the age of 65 years. Initial screening, final follow-up and annual detection of mortality were performed. Mantel-Hanszel approach and multivariate Cox model were used for statistics. Cardiovascular mortality was 23.3% in normotensive, 23.3% in borderline, and 25% in the sustained hypertensive subjects (insignificant difference). In women, the incidence of stroke and coronary artery disease weakly depended on pulse pressure. Historical stroke and myocardial infarction predicted cardiovascular mortality in women; diabetes, uricaemia and high heart rate in men. In the very old, the predictors were less numerous, and blood pressure was not a predictor whatsoever; pulse blood pressure and murmurs at the neck were especially predictive in women, historical heart failure, proteinuria and tachycardia in men, historical stroke and myocardial infarction, pulmonary disease, left ventricular hypertrophy, diabetes and uricaemia in both genders. The elderly have a different cardiovascular risk pattern compared to younger people. Hypertension is not a predictor of coronary and stroke mortality. Prognosis depends on pulse pressure rather than on the label 'hypertension'. Hypercholesterolaemia is not a risk factor. This could simply indicate that elderly persons are the survivors in a population where significant mortality has already made its mark, eliminating those with the worst risk pattern. The two genders have a different risk profile due to sex-specific susceptibility to risk factors.

Pravastatin reduces restenosis two years after percutaneous transluminal coronary angioplasty (REGRESS trial)

The Regression Growth Evaluation Statin Study (REGRESS) is a placebo-controlled multicenter study designed to assess the effect of 2-year treatment with pravastatin on the progression and regression of angiographically documented coronary artery disease. One of the secondary end points was the occurrence of 2-year restenosis in the percutaneous transluminal coronary angioplasty (PTCA) block. We randomly assigned eligible patients to receive pravastatin 40 mg once daily or placebo. The end point was the percent diameter stenosis of the target lesion at 24 months, as assessed by (semi)quantitative coronary angiography. Two hundred twenty-one patients underwent scheduled PTCA, which was considered successful in 201 patients. One hundred seventy-eight patients underwent angiographic restudy (89%). The patients in the pravastatin group (n = 109) and placebo group (n = 112) were similar at baseline. Percent diameter stenosis before angioplasty was 78 +/- 14% (mean +/- SD) in the pravastatin group and 80 +/- 14% in the placebo group (p = 0.46). At follow-up, the percent diameter stenosis was 32 +/- 23% in the pravastatin group and 45 +/- 29% in the placebo group (p < 0.001). Clinical restenosis was significantly lower in the pravastatin group (7%) compared with the placebo group (29%) (p < 0.001). Risk reduction for all events was 58%. We conclude that treatment with pravastatin reduces 2-year clinical and angiographic restenosis.

Fluvastatin: effects beyond cholesterol lowering

Coronary heart disease (CHD) remains a major therapeutic challenge in the Western world, and strategies aimed at cholesterol lowering form the mainstay of treatment. Fluvastatin is an established 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor ("statin") for the treatment of hypercholesterolemia. Its efficacy and safety have been established in numerous clinical trials. Emerging evidence now indicates that treatment with fluvastatin slows the progression of atherosclerotic CHD and reduces the incidence of cardiovascular morbimortality in the secondary prevention setting. This effect of fluvastatin cannot be explained by cholesterol lowering alone; nonlipid-related mechanisms (so-called "pleiotropic effects") undoubtedly contribute to a certain extent, and are probably linked to modulation of the mevalonate pathway. This review discusses the experimental evidence regarding the antiatherosclerotic and antithrombotic effects of fluvastatin that may contribute to its beneficial action on disease progression and clinical events. Such effects include decreased expression of adhesion molecules in monocytes and leucocyte-endothelium adherence responses, immunomodulation, prevention of low-density lipoprotein oxidation, inhibition of cholesterol esterification and accumulation, along with effects on smooth muscle cell proliferation and migration. Pleiotropic actions aimed at plaque stabilization (eg, decreased secretion of matrix metalloproteinases by macrophages), together with effects on platelet activity, tissue factor expression, and endothelial function, may contribute to an antithrombotic effect of fluvastatin. Taken together, the results of these studies indicate that the effects of fluvastatin, at therapeutic doses, may extend beyond cholesterol lowering.

Synthesis of the fatty sterol bound protein for a new sterol antibody

For the purpose of applying the particular antibodies as a new diagnostic procedure for atherosclerosis and related diseases, we successfully achieved the synthesis of the fatty sterol with a linker, then linked the target protein to this sterol. Synthesis was started from pregnenolone and achieved by the Grignard reaction with pentenyl magnesium bromide, regioselective photoaddition of thiolacetic acid toward the 25-double bond, esterification of 3-OH with linoleic anhydride, in situ conjunction of the cross-linker (MBS) to the thiol group after selective deprotection from its acetyl ester, and finally by the reaction with protein such as KLH or albumin through this linker.

A novel human hepatic organic anion transporting polypeptide (OATP2). Identification of a liver-specific human organic anion transporting polypeptide and identification of rat and human hydroxymethylglutaryl-CoA reductase inhibitor transporters

A novel human organic transporter, OATP2, has been identified that transports taurocholic acid, the adrenal androgen dehydroepiandrosterone sulfate, and thyroid hormone, as well as the hydroxymethylglutaryl-CoA reductase inhibitor, pravastatin. OATP2 is expressed exclusively in liver in contrast to all other known transporter subtypes that are found in both hepatic and nonhepatic tissues. OATP2 is considerably diverged from other family members, sharing only 42% sequence identity with the four other subtypes. Furthermore, unlike other subtypes, OATP2 did not transport digoxin or aldosterone. The rat isoform oatp1 was also shown to transport pravastatin, whereas other members of the OATP family, i.e. rat oatp2, human OATP, and the prostaglandin transporter, did not. Cis-inhibition studies indicate that both OATP2 and roatp1 also transport other statins including lovastatin, simvastatin, and atorvastatin. In summary, OATP2 is a novel organic anion transport protein that has overlapping but not identical substrate specificities with each of the other subtypes and, with its liver-specific expression, represents a functionally distinct OATP isoform. Furthermore, the identification of oatp1 and OATP2 as pravastatin transporters suggests that they are responsible for the hepatic uptake of this liver-specific hydroxymethylglutaryl-CoA reductase inhibitor in rat and man.

Changes in cholesterol levels in women after coronary artery bypass surgery

OBJECTIVE

To examine the predictors of change in cholesterol levels in a cohort of women between the time of surgery and 1 year after coronary artery bypass graft surgery (CABG).

DESIGN AND SETTING

This study was a prospective, descriptive study held at a Mid-Atlantic tertiary care medical center.

METHODS

Lipid profiles, lifestyle behaviors, and other major coronary risk factors were measured at the time of surgery and again 12 months later from a consecutive convenience sample of 130 women who underwent first-time, isolated CABG.

RESULTS

The sample population was 24% black and 76% white and had a mean age of 65 years and an average of 11 years of education. Although no statistically significant changes in cholesterol levels were observed, a majority (55%) of women had increases in total cholesterol level, whereas 45% had decreased total cholesterol level between baseline and 1 year of follow-up. After controlling for preoperative cholesterol values, a change in cholesterol level was independently predicted by ejection fraction, smoking status, and body mass index. At 1 year, plasma lipoprotein levels were not optimally managed, with high proportions of values exceeding national guidelines for secondary prevention.

CONCLUSIONS

Women continue to have high cholesterol levels after CABG, putting them at high risk for future coronary heart disease events. Effective secondary prevention programs targeting multiple lifestyle behaviors and adequate pharmacotherapy are needed.