No evidence that the PLA1/PLA2 polymorphism of platelet glycoprotein IIIa is implicated in angiographically characterized coronary atherosclerosis and premature myocardial infarction

Platelet membrane glycoprotein IIb/IIIa plays an important role in platelet aggregation. A polymorphism of the gene encoding the IIIa subunit, with the two allele forms PLA1 and PLA2, has been identified. Some, but not all, studies suggest that the PLA2 allele confers an increased risk of suffering a myocardial infarction. Conversely, a recent study suggests that the PLA1 allele may contribute to early atherosclerosis and more rapid progression of stable coronary artery disease. To test whether these associations could be reproduced in a well-characterized sample of survivors of premature myocardial infarction, we examined 369 patients admitted to coronary care units in the Stockholm area who suffered a first myocardial infarction before the age of 60 years. There were no significant differences in extent of coronary artery disease according to PLA genotype group (based on quantitative coronary angiography). In addition, the frequencies of PLA1 and PLA2 alleles did not differ from those of 388 well-matched control subjects without coronary artery disease. These results suggest that the PLA1/PLA2 polymorphism of the platelet glycoprotein IIIa gene does not substantially contribute to the development of coronary atherosclerosis or the genetic susceptibility to premature myocardial infarction.

Genetic Predisposition of the Interleukin-6 Response to Inflammation: Implications for a Variety of Major Diseases?

Background: A single-nucleotide polymorphism (SNP) in the promoter region of the interleukin-6 (IL-6) gene at position −174 (G>C) has been reported to be associated with a variety of major diseases, such as Alzheimer disease, atherosclerosis, and cardiovascular disease, cancer, non-insulin-dependent diabetes mellitus, osteoporosis, sepsis, and systemic-onset juvenile chronic arthritis. However, authors of previous in vitro and in vivo studies have reported conflicting results regarding the functionality of this polymorphism. We therefore aimed to clarify the role of the −174 SNP for the induction of IL-6 in vivo.

Methods: We vaccinated 20 and 18 healthy individuals homozygous for the −174 C and G alleles, respectively, with 1 mL of Salmonella typhii vaccine. IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured in the blood at baseline and up to 24 h after vaccination.

Results: Individuals with the G genotype had significantly higher plasma IL-6 values at 6, 8, and 10 h after vaccination than did individuals with the C genotype (P <0.005). There were no differences between the two genotypes regarding serum concentrations of IL-1β and TNF-α before or after vaccination.

Conclusions: The −174 G>C SNP in the promoter region of the IL-6 gene is functional in vivo with an increased inflammatory response associated with the G allele. Considering the central role of IL-6 in a variety of major diseases, the present finding might be of major relevance.

Prognostic value of plasma interleukin-6 concentrations and the -174 G > C and -572 G > C promoter polymorphisms of the interleukin-6 gene in patients with acute myocardial infarction treated with thrombolysis

The present study was performed to investigate the prognostic value of plasma interleukin-6 (IL-6) concentrations and promoter polymorphisms of the IL-6 gene in patients with acute myocardial infarction treated with thrombolysis. Two hundred and eight patients with myocardial infarction treated with thrombolysis were included and followed for 2-5 years. Plasma concentrations of IL-6 were measured at admission and 48 h after admission. Genotyping for the -174 G > C and -572 G > C IL-6 polymorphisms was performed. Patients who died of cardiovascular causes or suffered a new myocardial infarction during follow-up had increased plasma concentrations of IL-6 at admission (P < 0.002) and at 48 h after admission (P < 0.05) compared with patients who had an uneventful course. IL-6 levels above the median at admission were independently associated with a worse prognosis. No associations were found between IL-6 levels and the promoter polymorphisms. The -174 G > C polymorphism was not associated with cardiovascular death or a new myocardial infarction, whereas the -572 G > C polymorphism showed a borderline significant increase in risk (P = 0.05) in univariate analysis. In conclusion, the early IL-6 response during myocardial infarction is associated with prognosis in patients with Q-wave myocardial infarction, whereas no associations were found between IL-6 genotype and phenotype.

Human Evidence That the Cystatin C Gene Is Implicated in Focal Progression of Coronary Artery Disease

OBJECTIVE

Overexpression of elastolytic cysteine and aspartic proteases, known as cathepsins, is implicated in atherogenesis. The potential significance of imbalance in expression between cathepsins and their inhibitor cystatin C in cardiovascular disease has been highlighted by the demonstration of cystatin C deficiency in human atherosclerosis and abdominal aortic aneurysms.

METHODS AND RESULTS

We identified and characterized physiologically relevant polymorphisms in the promoter region of the cystatin C gene that influence cystatin C production and used these polymorphisms as a tool to examine the significance of cystatin C in coronary atherosclerosis in vivo in humans. Seven polymorphisms, all in strong-linkage disequilibrium, were identified in the cystatin C gene, of which 2 promoter polymorphisms (-82G/C and -78T/G) were functional in vitro in electromobility shift and transient transfection assays. Genotyping of 1105 individuals (237 survivors of a first myocardial infarction before age 60 and 2 independent groups comprising a total of 868 healthy individuals) revealed that the plasma cystatin C concentration was significantly lower in carriers of the mutant haplotype. Furthermore, the mutant haplotype was associated with a higher average number of stenoses per coronary artery segment in unselected postinfarction patients (N=237) undergoing routine coronary angiography.

CONCLUSIONS

These results provide human evidence for an important role of cystatin C in coronary artery disease.

C-reactive protein and myocardial infarction during percutaneous coronary intervention

OBJECTIVE

To evaluate the prognostic information of preprocedural C-reactive protein (CRP) levels in serum to predict myocardial infarction during percutaneous coronary interventions (PCI).

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

A total of 400 consecutive patients with normal serum troponin T levels (</=0.03 microg L-1) presenting with stable or unstable angina pectoris.

INTERVENTIONS

PCI.

MAIN OUTCOME MEASURES

C-reactive protein levels in serum measured by a high sensitive method. Myocardial infarction defined as a serum troponin T elevation the day after PCI to a level >0.05 microg L-1.

RESULTS

Eighty-three patients (21%) experienced a myocardial infarction during PCI. The median value of CRP before the procedure was 1.83 (0.12-99.7) mg L-1. No difference was seen in CRP levels before PCI between patients without or with myocardial infarction during PCI. Multivariate analysis identified stent implantation (OR 2.68, 95% CI 1.18-7.28, P = 0.03), procedure time (OR 2.15, 95% CI 1.28-3.67, P < 0.005) and complications during the procedure (OR 3.62, 95% CI 1.72-7.58, P < 0.001) as independent predictors of myocardial infarction during PCI.

CONCLUSION

Increased CRP levels in serum before PCI were not associated with myocardial infarction during the procedure. Furthermore, patients with an expected long procedure and a high probability of stent implantation have an increased risk of developing myocardial infarction during PCI. This finding may be useful to help the operator to decide the antithrombotic regime before, during and after the procedure and the need for observation after the procedure.

The plasminogen activator inhibitor-1 -675 4G/5G genotype influences the risk of myocardial infarction associated with elevated plasma proinsulin and insulin concentrations in men from Europe: the HIFMECH study

Although the potential role of plasminogen activator inhibitor-1 (PAI-1) in the development of coronary artery disease is strongly supported by its biological characteristics, results of clinical studies remain controversial.

OBJECTIVES

To investigate whether plasma PAI-1 concentrations and the -675 4G/5G polymorphism located in the PAI-1 gene could constitute risk markers for myocardial infarction (MI).

PATIENTS AND METHODS

We used a European case-control study, the HIFMECH study, comparing 598 men with MI and 653 age-matched controls.

RESULTS

Insulin resistance explained a major part of the variation in PAI-1 (24%) whereas inflammation had only a minor contribution (0.01%). For both cases and controls plasma PAI-1 concentrations were significantly higher in the North than the South, and in both regions were higher in individuals with MI compared with control subjects [overall odds ratio (OR) for a 1 SD increase=1.54, 95% confidence interval (CI) 1.34, 1.77]. This difference was observed in all the centers studied. Overall, the difference between cases and control subjects remained significant after controlling for inflammation variables (OR=1.30, 95% CI 1.08, 1.57), but lost significance after controlling for insulin resistance variables (OR=1.17, 95% CI 0.98, 1.40). The 4G allele was associated with significantly higher PAI-1 levels in cases but not controls and, taken independently, did not modify the risk of MI (P=0.9). However, a significant interaction was observed with both insulin or proinsulin and the risk of MI (P=0.05 and 0.02, respectively), but not with triglycerides or body mass index (BMI). The insulin or proinsulin effect on risk was observed only in the carriers of the 4G/4G genotype. This interaction appeared not to be mediated by plasma PAI-1 antigen concentrations (P=0.01 and 0.02 after adjustment for PAI-1 plasma levels). The interaction with proinsulin but not insulin remained statistically significant after further adjustment for other factors associated with insulin resistance (triglycerides and BMI) and C-reactive protein (P=0.01).

CONCLUSION

This study suggests that PAI-1 has a role in risk of MI in the presence of underlying insulin resistance. A significant interaction between insulin or proinsulin and the -675 4G/5G polymorphism was observed in risk for MI. The mechanisms for these interactions remain to be determined.

Prognostic value of plasma C-reactive protein and fibrinogen determinations in patients with acute myocardial infarction treated with thrombolysis

OBJECTIVES

To investigate the prognostic value of plasma C-reactive protein (CRP) and fibrinogen determinations in patients with acute myocardial infarction treated with thrombolysis.

DESIGN

Longitudinal study of morbidity and mortality.

SETTING

Coronary care unit at Danderyd Hospital, Stockholm, Sweden.

SUBJECTS

A total of 222 patients aged 75 years or below, treated with thrombolysis because of typical symptoms of myocardial infarction and electrocardiogram showing ST-segment elevation or bundle branch block were included in the study. The patients were followed for 24-60 months (mean 40 +/- 16 months).

MAIN OUTCOME MEASURES

Cardiovascular death or new myocardial infarction.

RESULTS

Concentrations of CRP were significantly higher at 48 h than at 3 months, whilst the levels of fibrinogen were similar. CRP and fibrinogen concentrations measured during the acute phase of myocardial infarction were associated with cardiovascular death or a new myocardial infarction during follow-up in univariate analysis. CRP levels measured 3 months after the acute event were not associated with subsequent events whereas fibrinogen concentrations showed a borderline prognostic significance (P = 0.05). When CRP and fibrinogen were entered into multivariate analysis together with the previously established prognostic factors in the patient group (age, diabetes mellitus and left ventricular function), these markers of inflammation did not add further prognostic information.

CONCLUSION

C-reactive protein and fibrinogen do not carry the same independent prognostic information after acute myocardial infarction treated with thrombolysis as in studies previously reported for patients with unstable angina or non-Q-wave myocardial infarction.

[C-reactive protein potential risk factor for cardiovascular disease]

C-reactive protein (CRP) is a protein produced mainly in the liver upon stimulation by interleukin-6. CRP is part of the acute phase response to inflammation and plasma concentrations rise 100-1000 times in patients with for example bacterial infections. High sensitive methods have made it possible to measure and compare low CRP levels in plasma. Prospective studies have shown that increased but comparatively low plasma CRP concentrations are associated with future coronary heart disease (CHD) in healthy individuals and in patients with known CHD. Further support for an important role for CRP comes from in vitro studies that have suggested that the CRP protein is intimately and actively involved in the atherosclerotic process. This has stimulated the interest for clinical evaluation and treatment of increased plasma CRP levels.

Comparison of effects of a thrombin-based femoral artery closure device with those of a mechanical compression device on serum C-reactive protein and amyloid A after percutaneous coronary intervention

The present study evaluates whether the closing procedure of the femoral artery after percutaneous coronary intervention influences the degree of inflammation related to the procedure as measured by C-reactive protein (CRP) and serum amyloid A (SAA). A thrombin-based device (Duett sealing device) was compared with a mechanical compression device (FemoStop).

Under utilisation of evidence-based treatment partially explains for the unfavourable prognosis in diabetic patients with acute myocardial infarction

AIMS

The prognosis after an acute myocardial infarction is worse for patients with diabetes mellitus than for those without. We investigated whether differences in the use of evidence-based treatment may contribute to the differences in 1-year survival in a large cohort of consecutive acute myocardial infarction patients with and without diabetes mellitus.

METHODS

We included patients below the age of 80 years from the Register of Information and Knowledge about Swedish Heart Intensive care Admissions (RIKS-HIA), which included all patients admitted to coronary care units at 58 hospitals during 1995-1998. In all 5193 patients had the combination of acute myocardial infarction and diabetes mellitus while 20440 had myocardial infarction but no diabetes diagnosed. Multivariate logistical regression analyses were performed to evaluate the influence of diabetes mellitus on the use of evidence-based treatment and its association with survival during the first year after the index hospitalisation.

RESULTS

The prevalence of diabetes mellitus was 20.3% (males 18.5%; females 24.4%). The 1-year mortality was substantially higher among diabetic patients compared with those without diabetes mellitus (13.0 vs. 22.3% for males and 14.4 vs. 26.1% for female patients, respectively) with an odds ratio (OR) (95% confidence interval (CI)) in three different age groups: <65 years 2.65 (2.23-3.16); 65-74 years 1.81 (1.61-2.04) and >75 years 1.71 (1.50-1.93). During hospital stay patients with diabetes mellitus received significantly less treatment with heparins (37 vs. 43%; p<0.001), intravenous beta blockade (29 vs. 33%; p<0.001), thrombolysis (31 vs. 41%; p<0.001) and acute revascularisation (4 vs. 5%; p<0.003). A similar pattern was apparent at hospital discharge. After multiple adjustments for dissimilarities in baseline characteristics between the two groups, patients with diabetes were significantly less likely to be treated with reperfusion therapy (OR 0.83), heparins (OR 0.88), statins (OR 0.88) or to be revascularised within 14 days from hospital discharge procedures (OR 0.86) while the use of ACE-inhibitors was more prevalent among diabetic patients compared to non-diabetic patients (OR 1.45). The mortality reducing effects of evidence-based treatment like reperfusion, heparins, aspirin, beta-blockers, lipid-lowering treatment and revascularisation were, in multivariate analyses, of equal benefit in diabetic and non-diabetic patients.

INTERPRETATION

Diabetes mellitus continues to be a major independent predictor of 1-year mortality following an acute myocardial infarction, especially in younger age groups. This may partly be explained by less use of evidence-based treatment although treatment benefits are similar in both patients with and without diabetes mellitus. Thus a more extensive use of established treatment has a potential to improve the poor prognosis among patients with acute myocardial infarction and diabetes mellitus.

Autoantibodies against modified low-density lipoproteins in coronary artery disease

OBJECTIVES

To evaluate the importance of different autoantibodies against modified low-density lipoprotein (LDL) in patients with coronary artery disease (CAD).

BACKGROUND

Previous studies of autoantibodies against LDL have shown that patients with CAD have increased titers of autoantibodies against LDL modified by copper and malondialdehyde (MDA), whereas there is a lack of information about autoantibody titers against LDL modified by hypochlorite (HOCl). Studies of autoantibodies in relation to severity of atherosclerosis are few and have reached divergent results. Furthermore, no data exist on the relationship between autoantibody titers and prognosis.

METHODS

Titers of autoantibodies against copper-, MDA- and HOCl-modified LDL were determined in serum by ELISA. Autoantibody titers in young male survivors of a first myocardial infarction were compared with those of healthy controls and related to coronary angiographic findings and to prognosis during 11 years of follow-up.

RESULTS

Patients had higher titers of autoantibodies against LDL modified by copper and MDA than controls. In contrast, no consistent associations were found between autoantibody titers and global severity of coronary atherosclerosis or number and severity of coronary stenoses and prognosis.

CONCLUSIONS

The prognostic value of autoantibodies against modified LDL is limited in young postinfarction patients despite the fact that autoantibody titers against copper- and MDA-modified LDL are raised compared with healthy controls. Furthermore, the results indicate that autoantibodies against modified LDL are not protective in later stages of coronary atherosclerosis.

In vitro and in vivo lipolysis of plasma triglycerides increases the resistance to oxidative modification of low-density lipoproteins

BACKGROUND

The majority of studies on low-density lipoprotein (LDL) particle size and susceptibility to oxidative modification have been either descriptive or interventional, but there are few mechanistic studies.

MATERIALS AND METHODS

Effects of exhaustive in vitro and in vivo lipolysis of serum and plasma triglycerides, respectively, by lipoprotein lipase (LPL) were investigated in healthy normotriglyceridemic men. The LDL end-product of lipolysis of very low-density lipoprotein (VLDL) underwent compositional analysis, gradient gel electrophoresis and an assessment of resistance to copper-induced oxidative modification.

RESULTS

The LDL particle contents of free fatty acid and alpha-tocopherol increased, whereas the contents of free and esterified cholesterol, alpha-carotene and coenzyme Q10 decreased upon incubation of serum with LPL in vitro. The LDL particle size decreased and the resistance to the oxidative modification of LDL increased. Lipolysis of plasma triglycerides in vivo, achieved by intravenous injection of heparin, did not alter the LDL particle size but increased the resistance to the oxidative modification of LDL. This change was accompanied by an increase in the LDL particle content of alpha-tocopherol, whereas the free fatty acid content was unaltered.

CONCLUSIONS

The results show that the increased resistance to oxidative modification of LDL after lipolysis of plasma triglycerides was concomitant with an increased LDL particle content of alpha-tocopherol, and that free fatty acids did not seem to contribute to the increased resistance to oxidative modification of LDL in vivo. Furthermore, our data indicate that the resistance of LDL to oxidative modification is not dependent on particle size.

[Treatment of coronary artery stenosis. Considerable improvement of the catheter-based technique]

The technique to treat coronary artery stenoses by percutaneous coronary intervention (PCI) was introduced in 1977 and has since undergone considerable improvement. Important developments have been: 1. The use of stents, which minimize the risk of acute occlusions and reduce the incidence of restenosis. 2. Improvement in antiplatelet therapy, which decrease the risk of thromboembolic complications during and after PCI. 3. Specific treatment against restenosis by drug-eluting stents. PCI treatment with stents and reinforced antiplatelet therapy is well established today. If the initial encouraging results with PCI using drug-eluting stents without restenosis hold their promise, the vast majority of coronary revascularisations will be performed by PCI in the future.

Platelet function and myocardial injury during percutaneous coronary intervention

BACKGROUND

Several studies have shown that inhibition of the glycoprotein IIb/IIIa receptor can reduce myocardial injury during percutaneous coronary intervention (PCI). The present study was performed to investigate platelet function, using a bedside diagnostic system, to test the hypothesis that patients with activated platelets have an increased risk for myocardial injury during PCI. Such information would be valuable to guide the PCI operator to whom he or she should give a glycoprotein IIb/IIIa inhibitor during and after the procedure.

METHODS

155 consecutive patients undergoing PCI were included in the study. 94 of the patients had stable angina pectoris and the remaining patients had unstable angina pectoris or ongoing myocardial infarction. Troponin T levels were measured in serum before PCI and at 6 am the day after PCI by an immunoassay. Platelet function was analyzed in arterial blood before PCI using the platelet function analyzer PFA-100(R) by Dade Behring.

RESULTS

The platelet function analyzer PFA-100(R) could not discriminate between patients with or without myocardial injury during the procedure but between patients with or without acetyl salicylic acid.

CONCLUSION

The platelet function analyzer PFA-100(R) cannot be used to guide the PCI operator to whom he or she should give a glycoprotein IIb/IIIa inhibitor but the results indicate that PFA-100(R) can be used to monitor platelet effects of ASA therapy.

A triglyceride-rich fat emulsion and free fatty acids but not very low density lipoproteins impair endothelium-dependent vasorelaxation

OBJECTIVE

To investigate the effects of triglycerides and free fatty acids on endothelium-dependent and endothelium-independent vasorelaxation.

METHODS

Femoral arterial rings from rats were studied in organ baths. The vascular segments were constricted with phenylephrine after 20 min of preincubation with the triglyceride-rich fat emulsion Intralipid, free fatty acids (16:0, 18:1, 18:3) bound to bovine serum albumin, or very low density lipoproteins. Endothelium-dependent and endothelium-independent relaxations were determined after administration of acetylcholine and nitric oxide donors, respectively.

RESULTS

Preincubation with Intralipid caused a concentration-dependent impairment of endothelium-dependent but not endothelium-independent relaxation. Very low density lipoproteins did not affect vascular function. All free fatty acids impaired endothelium-dependent relaxation, whereas endothelium-independent relaxation was unaffected. Administration of the antioxidant vitamin C partly reversed the impairment of the endothelium-dependent relaxation induced by Intralipid and free fatty acids.

CONCLUSIONS

The present study demonstrates that the triglyceride-rich fat emulsion Intralipid and individual FFAs impair endothelium-dependent relaxation of arterial rings from rat, whereas triglycerides in the form of VLDL do not affect endothelial function. The finding that the antioxidant vitamin C partly reverses this impairment indicates the involvement of oxidative mechanisms.

[A controlled trial with prolonged follow up: percutaneous intervention in acute myocardial infarction is equivalent to thrombolytic therapy]

Previous studies comparing percutaneous coronary intervention (PCI) with thrombolysis for treatment of myocardial infarction with ST-elevation have in meta-analyses but not in randomized trials shown that PCI is more effective. Despite a large volume of primary PCI performed in Sweden no controlled trials have been carried out. The present study included 96 patients with myocardial infarction with ST-segment elevation treated with primary PCI 1995-1998. The main indications were shock (15 cases), contraindication to thrombolysis (24 cases), as an alternative to thrombolysis (57 cases), with a mortality in the respective groups of 67, 25 and 10 percent. Controls matched for age and infarct location and treated with thrombolysis could be identified for 55 of the patients treated with PCI. After four years 40 percent and 52 percent of the patients treated with PCI and thrombolysis respectively reached the combined endpoint of death/myocardial infarction/revascularization/angina pectoris (not significant). In conclusion, the study shows that primary PCI in patients with myocardial infarction with ST-segment elevation can be performed safely also in Sweden.

Mild-to-moderate hypertriglyceridemia in young men is associated with endothelial dysfunction and increased plasma concentrations of asymmetric dimethylarginine

OBJECTIVES

The aim of this study was to investigate endothelial function and common carotid intima-media thickness (IMT) in healthy young men with mild-to-moderate hypertriglyceridemia. Plasma asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, was measured to further elucidate the mechanisms involved.

BACKGROUND

Hypertriglyceridemia is a risk factor for coronary heart disease although the mechanisms behind the increased risk remain to be defined. Acute elevation of plasma triglycerides induced by an intravenous fat load is associated with impaired endothelial function. The results of studies examining acute effects induced by a high-fat meal or effects of chronic hypertriglyceridemia on endothelial function are more inconsistent.

METHODS

Flow-mediated vasodilation and nitroglycerin-induced vasodilation of the brachial artery and common carotid IMT were measured noninvasively by ultrasound technique in 15 hypertriglyceridemic (HTG) subjects and 15 matched controls, mean age 34 years. Plasma concentrations of ADMA were measured by high-performance liquid chromatography.

RESULTS

Flow-mediated vasodilation was decreased in the HTG group (p < 0.0001), whereas nitroglycerin-induced vasodilation and carotid IMT did not differ significantly. Asymmetric dimethylarginine concentrations were higher in the HTG group (p < 0.05).

CONCLUSIONS

Hypertriglyceridemia in young men is associated with endothelial dysfunction and increased plasma concentration of ADMA but not with increased IMT of the common carotid artery. The corollary is that chronic hypertriglyceridemia results in endothelial dysfunction, possibly due to increased ADMA concentration, and that endothelial dysfunction might precede increased IMT among the early manifestations of atherosclerosis.