Oxidized phospholipids are present on plasminogen, affect fibrinolysis, and increase following acute myocardial infarction

Prognostic value of elevated lipoprotein (a) in patients with acute coronary syndromes: a systematic review and meta-analysis

Background

Elevated lipoprotein (a) level was recognized as an independent risk factor for significant adverse cardiovascular events in acute coronary syndrome (ACS) patients. Despite this recognition, the consensus in the literature regarding the prognostic significance of elevated lipoprotein (a) in ACS was also limited. Consequently, we conducted a thorough systematic review and meta-analysis to evaluate the prognostic relevance of elevated lipoprotein (a) level in individuals diagnosed with ACS.

Methods and results

A thorough literature review was conducted by systematically searching PubMed, Embase, and Cochrane databases until September 2023. This review specifically examined cohort studies exploring the prognostic implications of elevated lipoprotein (a) level in relation to major adverse cardiovascular events (MACE), including death, stroke, non-fatal myocardial infarction (MI), and coronary revascularization, in patients with ACS. The meta-analysis utilized aggregated multivariable hazard ratios (HR) and their respective 95% confidence intervals (CI) to evaluate prognostic implications between high and low lipoprotein (a) levels [the cut-off of high lipoprotein (a) level varies from 12.5 to 60 mg/dl]. Among 18,168 patients in the identified studies, elevated lipoprotein (a) was independently associated with increased MACE risk (HR 1.26; 95% CI: 1.17-1.35, P < 0.00001) and all-cause mortality (HR 1.36; 95% CI: 1.05-1.76, P = 0.02) in ACS patients. In summary, elevated lipoprotein (a) levels independently forecast MACE and all-cause mortality in ACS patients. Assessing lipoprotein (a) levels appears promising for risk stratification in ACS, offering valuable insights for tailoring secondary prevention strategies.

Systematic Review Registration

PROSPERO (CRD42023476543).

Lipoprotein(a), platelet function and cardiovascular disease

Lipoprotein(a) (Lp(a)) is associated with atherothrombosis through several mechanisms, including putative antifibrinolytic properties. However, genetic association studies have not demonstrated an association between high plasma levels of Lp(a) and the risk of venous thromboembolism, and studies in patients with highly elevated Lp(a) levels have shown that Lp(a) lowering does not modify the clotting properties of plasma ex vivo. Lp(a) can interact with several platelet receptors, providing biological plausibility for a pro-aggregatory effect. Observational clinical studies suggest that elevated plasma Lp(a) concentrations are associated with worse long-term outcomes in patients undergoing revascularization. Furthermore, in these patients, those with elevated plasma Lp(a) levels derive more benefit from prolonged dual antiplatelet therapy than those with normal Lp(a) levels. The ASPREE trial in healthy older individuals treated with aspirin showed a reduction in ischaemic events in those who had a single-nucleotide polymorphism in LPA that is associated with elevated Lp(a) levels in plasma, without an increase in bleeding events. In this Review, we re-examine the role of Lp(a) in the regulation of platelet function and suggest areas of research to define further the clinical relevance to cardiovascular disease of the observed associations between Lp(a) and platelet function.

Oxidized phospholipids in cardiovascular disease

Prolonged or excessive exposure to oxidized phospholipids (OxPLs) generates chronic inflammation. OxPLs are present in atherosclerotic lesions and can be detected in plasma on apolipoprotein B (apoB)-containing lipoproteins. When initially conceptualized, OxPL-apoB measurement in plasma was expected to reflect the concentration of minimally oxidized LDL, but, surprisingly, it correlated more strongly with plasma lipoprotein(a) (Lp(a)) levels. Indeed, experimental and clinical studies show that Lp(a) particles carry the largest fraction of OxPLs among apoB-containing lipoproteins. Plasma OxPL-apoB levels provide diagnostic information on the presence and extent of atherosclerosis and improve the prognostication of peripheral artery disease and first and recurrent myocardial infarction and stroke. The addition of OxPL-apoB measurements to traditional cardiovascular risk factors improves risk reclassification, particularly in patients in intermediate risk categories, for whom improving decision-making is most impactful. Moreover, plasma OxPL-apoB levels predict cardiovascular events with similar or greater accuracy than plasma Lp(a) levels, probably because this measurement reflects both the genetics of elevated Lp(a) levels and the generalized or localized oxidation that modifies apoB-containing lipoproteins and leads to inflammation. Plasma OxPL-apoB levels are reduced by Lp(a)-lowering therapy with antisense oligonucleotides and by lipoprotein apheresis, niacin therapy and bariatric surgery. In this Review, we discuss the role of role OxPLs in the pathophysiology of atherosclerosis and Lp(a) atherogenicity, and the use of OxPL-apoB measurement for improving prognosis, risk reclassification and therapeutic interventions.

Atherothrombotic and thrombolytic biomarkers in incident stroke and atrial fibrillation-related stroke: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND AIMS

Although several biomarkers have been studied in thromboembolic stroke, measuring the balance between thrombus formation and thrombolysis and data on its role in predicting stroke and atrial fibrillation (AF)-related stroke is limited. We sought to assess atherothrombotic biomarkers grouped into composite factors that reflect thrombotic and thrombolytic potential, and the balance between these factors as it relates to incident stroke or transient ischemic attack (TIA) and stroke/TIA in AF.

METHODS

A Thrombotic Factor, derived from fibrinogen, plasmin-antiplasmin complex, factor VIII, D-dimer, and lipoprotein(a); and a Thrombolytic Factor, derived from plasminogen and oxidized phospholipids on plasminogen, were evaluated at baseline in 5,764 Multi-Ethnic Study of Atherosclerosis (MESA) participants. We evaluated the association between these two factors representative of thrombotic and thrombolytic potential and incident stroke/TIA (n = 402), and AF-related stroke/TIA (n = 82) over a median of 13.9 and 3.7 years, respectively. Cox proportional hazard models adjusted for medication use, cardiovascular risk factors and CHA2DS2-VASc score were utilized. Harrell's C-index was estimated to evaluate model performance.

RESULTS

In models including both factors, Thrombotic Factor was positively while Thrombolytic Factor was inversely associated with incident stroke/TIA and AF-related stroke/TIA. Incorporating these factors along with the CHA2DS2-VASc in adjusted models resulted in a small improvement in risk prediction of incident stroke/TIA and AF-related stroke/TIA compared to models without the factors (C-index from 0.697 to 0.704, and from 0.657 to 0.675, respectively).

CONCLUSIONS

Composite biomarker factors, representative of the balance between thrombotic and thrombolytic propensity, provided an improvement in predicting stroke/TIA beyond CHA2DS2-VASc score.

Lipoprotein(a) is a new prognostic factor in patients with psoriasis and coronary artery disease: a retrospective cohort study

BACKGROUND

The prognostic value of lipoprotein (Lp) (a) in patients who have suffered from coronary artery disease (CAD) has not been fully studied, and the results are inconsistent. This study was conducted to evaluate whether increased Lp(a) concentrations cause differences in clinical adverse outcomes in patients with psoriasis who have already suffered from CAD.

METHODS

This retrospective cohort study included consecutive patients with psoriasis and CAD between January 2017 and May 2022 in our hospital. The clinical records were collected, and comparisons were made between patients in the low Lp(a) and high Lp(a) groups. Cox proportional hazard analysis and log-rank tests were used to evaluate the association between variables.

RESULTS

Among 295 patients, 148 patients were in the low Lp(a) group, and 147 were in the high Lp(a) group. These two groups did not differ significantly in age, gender or body mass index. Compared with the low Lp(a) group, the levels of platelet counts (P = 0.038) and high sensitivity C reactive protein (P = 0.012) were higher in the high Lp(a) group. Patients in the high Lp(a) group had higher total cholesterol levels (P = 0.029) and lower triglyceride levels (P = 0.037). Among the whole cohort, clinical adverse events were not correlated with Lp(a) concentrations after a median follow-up of 3 years. However, in the subgroup analysis, there were significant differences in all-cause death (log rank P = 0.036) and rehospitalization (log rank P = 0.037) between the two groups in patients with diabetes; a difference in rehospitalization (log rank P = 0.042) was also found between the two groups in men.

CONCLUSIONS

In patients with psoriasis and CAD, high levels of Lp(a) were related to a poor prognosis, especially in patients with diabetes and in men. These results will provide valuable information for the risk stratification of patients with psoriasis and CAD.

Combined effect of D-dimer, hs-CRP, and Lp(a) on 5-year clinical outcomes after percutaneous coronary intervention: A large real-world study in China

To reduce cardiovascular risk in patients with established coronary heart disease, the present study investigated the combined effect of D-dimer, high-sensitivity C-reactive protein (hs-CRP), and lipoprotein(a) [Lp(a)] on long-term cardiovascular outcomes from the perspectives of thrombosis, inflammation, and lipid risk simultaneously. Consecutive 10,724 patients with percutaneous coronary intervention (PCI) were enrolled throughout 2013. Over a median follow-up of 5.1 years, each individual elevation of D-dimer, hs-CRP, and Lp(a) was associated with poor ischemic outcomes but not bleeding. Concurrent high D-dimer, hs-CRP, and Lp(a) had even greater risks of all-cause death (hazard ratio [HR] 2.714, 95% confidence interval [CI] 1.742-4.231) and cardiac death (HR 4.152, 95% CI 2.207-7.812) and had incremental value beyond the traditional risk factors model. Concurrent high D-dimer, hs-CRP, and Lp(a) levels had a synergistic effect on adverse 5-year ischemic outcomes, highlighting that the potential utility of simultaneous assessment of multiple cardiovascular risk biomarkers may help to identify high-risk patients after PCI.

Novel Aspects Targeting Platelets in Atherosclerotic Cardiovascular Disease—A Translational Perspective

Platelets are important cellular targets in cardiovascular disease. Based on insights from basic science, translational approaches and clinical studies, a distinguished anti-platelet drug treatment regimen for cardiovascular patients could be established. Furthermore, platelets are increasingly considered as cells mediating effects “beyond thrombosis”, including vascular inflammation, tissue remodeling and healing of vascular and tissue lesions. This review has its focus on the functions and interactions of platelets with potential translational and clinical relevance. The role of platelets for the development of atherosclerosis and therapeutic modalities for primary and secondary prevention of atherosclerotic disease are addressed. Furthermore, novel therapeutic options for inhibiting platelet function and the use of platelets in regenerative medicine are considered.

Oxidized phospholipids and lipoprotein-associated phospholipase A2 (Lp-PLA2 ) in atherosclerotic cardiovascular disease: An update

Inflammation and oxidative stress conditions lead to a variety of oxidative modifications of lipoprotein phospholipids implicated in the occurrence and development of atherosclerotic lesions. Lipoprotein-associated phospholipase A2 (Lp-PLA₂ ) is established as an independent risk biomarker of atherosclerosis-related cardiovascular disease (ASCVD) and mediates vascular inflammation through the regulation of lipid metabolism in the blood and in atherosclerotic lesions. Lp-PLA₂ is associated with low- and high-density lipoproteins and Lipoprotein (a) in human plasma and specifically hydrolyzes oxidized phospholipids involved in oxidative stress modification. Several oxidized phospholipids (OxPLs) subspecies can be detoxified through enzymatic degradation by Lp-PLA₂ activation, forming lysophospholipids and oxidized non-esterified fatty acids (OxNEFAs). Lysophospholipids promote the expression of adhesion molecules, stimulate cytokines production (TNF-α, IL-6), and attract macrophages to the arterial intima. The present review article discusses new data on the functional roles of OxPLs and Lp-PLA₂ associated with lipoproteins.

Ancestry, Lipoprotein(a), and Cardiovascular Risk Thresholds: JACC Review Topic of the Week

This study reviews ancestral differences in the genetics of the LPA gene, risk categories of elevated lipoprotein(a) [Lp(a)] as defined by guidelines, ancestry-specific Lp(a) risk, absolute and proportional risk, predictive value of risk thresholds among different ancestries, and differences between laboratory vs clinical accuracy in Lp(a) assays. For clinical decision-making, the preponderance of evidence suggests that the predictive value of Lp(a) does not vary sufficiently to mandate the use of ancestry-specific risk thresholds. This paper interprets the literature on Lp(a) and ancestral risk to support: 1) clinicians on understanding cardiovascular disease risk in different ancestral groups; 2) trialists for the design of clinical trials to ensure adequate ancestral diversity to support broad conclusions of drug effects; 3) regulators in the evaluation of the design and interpretation of results of Lp(a)-lowering trials with different Lp(a) inclusion thresholds; and 4) clinical laboratories to measure Lp(a) by assays that discriminate risk thresholds appropriately.

Oxidized phospholipids on apolipoprotein B-100 versus plasminogen and risk of coronary heart disease in the PROCARDIS study

BACKGROUND AND AIMS

Oxidized phospholipids carried on the apolipoprotein B-100 (OxPL-apoB) component of Lp(a) are predictive of coronary heart disease (CHD), but the role of oxidized phospholipids carried on plasminogen (OxPL-PLG) is unknown. We examined the independent effects of OxPL-apoB and OxPL-PLG for risk of CHD before and after adjustment for Lp(a).

METHODS

Plasma levels of OxPL-apoB, OxPL-PLG, plasminogen and Lp(a) were measured in the PROCARDIS study of early-onset CHD (906 cases/858 controls). Multivariable logistic regression was used to estimate the odds ratios (OR) for each biomarker with CHD after adjustment for established risk factors.

RESULTS

Mean levels of OxPL-apoB were higher in cases than controls, but levels of OxPL-PLG and plasminogen were similar. For OxPL-apoB, individuals in the top vs bottom fifth had 2-fold higher age and sex-adjusted OR of CHD (OR = 2.61 [95%CI: 1.91, 3.55]), which were partially attenuated after adjustment for established risk factors. The findings for OxPL-apoB and CHD in PROCARDIS were comparable with those of a meta-analysis of all such studies. However, the associations of OxPL-apoB with CHD were fully attenuated by additional adjustment for Lp(a) (OR = 0.93 [0.54,1.60]). Neither OxPL-PLG nor plasminogen were associated with CHD. Overall, there were no differences in the predictive value for CHD of high vs normal levels (<20th or >80th percentile) of OxPL-apoB, OxPL-PLG, plasminogen or Lp(a) after stratifying for each other.

CONCLUSIONS

These results highlight the context-dependency of OxPL in plasma and suggest that their associated risk of CHD is chiefly mediated by their carriage on Lp(a).

Oxidized phospholipids and lipoprotein(a): An update

Over the past few years, there has been an undiminished interest in lipoprotein(a) [Lp(a)] and oxidized phospholipids (OxPLs), mainly carried on this lipoprotein. Elevated Lp(a) has been established as an independent causal risk factor for cardiovascular disease. OxPLs play an important role in atherosclerosis. The main questions that remain to be answered, however, is to what extent OxPLs contribute to the atherogenicity of Lp(a), what effect hypolipidaemic medications may have on their levels and the potential clinical benefit of their reduction. This narrative review aimed to summarize currently available data on OxPLs and cardiovascular risk, as well as the effect of established and emerging hypolipidaemic medications on Lp(a)-OxPLs.

Atherothrombotic factors and atherosclerotic cardiovascular events: the multi-ethnic study of atherosclerosis

AIMS

Traditional atherosclerotic cardiovascular disease (ASCVD) risk factors fail to address the full spectrum of the complex interplay of atherosclerotic and atherothrombotic factors integral to ASCVD events. This study sought to examine the association between atherothrombotic biomarkers and ASCVD events.

METHODS AND RESULTS

The association between atherothrombotic biomarkers and 877 ASCVD events with and without adjustment for traditional risk factors was evaluated via Cox proportional hazards models and factor analysis in 5789 Multi-Ethnic Study of Atherosclerosis participants over a median follow-up of 14.7 years. Factor analysis accounted for multidimensional relationship and shared variance among study biomarkers, which identified two new variables: a thrombotic factor (Factor 1), principally defined by shared variance in fibrinogen, plasmin-antiplasmin complex, factor VIII, D-dimer, and lipoprotein(a), and a fibrinolytic factor (Factor 2), principally defined by shared variance of plasminogen and oxidized phospholipids on plasminogen. In a model including both factors, the thrombotic factor was associated with the higher risk of ASCVD events [hazard ratio (HR) 1.57, 95% confidence interval (CI) 1.45, 1.70], while the fibrinolytic factor was associated with the lower risk of ASCVD events (HR 0.76, 95% CI 0.70, 0.82), with estimated ASCVD free survival highest for low atherothrombotic Factor 1 and high atherothrombotic Factor 2.

CONCLUSION

Two atherothrombotic factors, one representative of thrombotic propensity and the other representative of fibrinolytic propensity, were significantly and complementarily associated with incident ASCVD events, remained significantly associated with incident ASCVD after controlling for traditional risk factors, and have promise for identifying patients at high ASCVD event risk specifically due to their atherothrombotic profile.

The changing landscape of atherosclerosis

Emerging evidence has spurred a considerable evolution of concepts relating to atherosclerosis, and has called into question many previous notions. Here I review this evidence, and discuss its implications for understanding of atherosclerosis. The risk of developing atherosclerosis is no longer concentrated in Western countries, and it is instead involved in the majority of deaths worldwide. Atherosclerosis now affects younger people, and more women and individuals from a diverse range of ethnic backgrounds, than was formerly the case. The risk factor profile has shifted as levels of low-density lipoprotein (LDL) cholesterol, blood pressure and smoking have decreased. Recent research has challenged the protective effects of high-density lipoprotein, and now focuses on triglyceride-rich lipoproteins in addition to low-density lipoprotein as causal in atherosclerosis. Non-traditional drivers of atherosclerosis-such as disturbed sleep, physical inactivity, the microbiome, air pollution and environmental stress-have also gained attention. Inflammatory pathways and leukocytes link traditional and emerging risk factors alike to the altered behaviour of arterial wall cells. Probing the pathogenesis of atherosclerosis has highlighted the role of the bone marrow: somatic mutations in stem cells can cause clonal haematopoiesis, which represents a previously unrecognized but common and potent age-related contributor to the risk of developing cardiovascular disease. Characterizations of the mechanisms that underpin thrombotic complications of atherosclerosis have evolved beyond the 'vulnerable plaque' concept. These advances in our understanding of the biology of atherosclerosis have opened avenues to therapeutic interventions that promise to improve the prevention and treatment of now-ubiquitous atherosclerotic diseases.

Effect of bariatric surgery on plasma levels of oxidised phospholipids, biomarkers of oxidised LDL and lipoprotein(a)

BACKGROUND

Obesity is associated with adverse cardiovascular outcomes and this is improved following bariatric surgery. Oxidised phospholipids (OxPL) are thought to reflect the pro-inflammatory effects of lipoprotein(a) [Lp(a)], and both are independent predictors of cardiovascular disease.

OBJECTIVE

Our study sought to determine the impact of bariatric surgery on OxPL, biomarkers of oxidised LDL (OxLDL) and Lp(a).

METHODS

This is a prospective, observational study of 59 patients with severe obesity undergoing bariatric surgery. Blood samples were obtained prior to surgery and at 6 and 12 months after. Sixteen patients attending the tertiary medical weight management clinic at the same centre were also recruited for comparison. Lipid and metabolic blood parameters, OxLDL, OxPL on apolipoprotein B-100 (OxPL-apoB), IgG and IgM autoantibodies to MDA-LDL, IgG and IgM apoB-immune complexes and Lp(a) were measured.

RESULTS

Reduction in body mass index (BMI) was significant following bariatric surgery, from median 48 kg/m² at baseline to 37 kg/m² at 6 months and 33 kg/m² at 12 months. OxPL-apoB levels decreased significantly at 12 months following surgery [5.0 (3.2-7.4) to 3.8 (3.0-5.5) nM, p = 0.001], while contrastingly, Lp(a) increased significantly [10.2 (3.8-31.9) to 16.9 (4.9-38.6) mg/dl, p = 0.002]. There were significant post-surgical decreases in IgG and IgM biomarkers, particularly at 12 months, while OxLDL remained unchanged.

CONCLUSIONS

Bariatric surgery results in a significant increase in Lp(a) but reductions in OxPL-apoB and other biomarkers of oxidised lipoproteins, suggesting increased synthetic capacity and reduced oxidative stress. These biomarkers might be clinically useful to monitor physiological effects of weight loss interventions.

A critical role for plasminogen in inflammation

Plasminogen and its active form, plasmin, have diverse functions related to the inflammatory response in mammals. Due to these roles in inflammation, plasminogen has been implicated in the progression of a wide range of diseases with an inflammatory component. In this review, we discuss the functions of plasminogen in inflammatory regulation and how this system plays a role in the pathogenesis of diseases spanning organ systems throughout the body.

The role of oxidized phospholipids in the development of disease

Oxidized phospholipids (OxPLs), complex mixtures of phospholipid oxidation products generated during normal or pathological processes, are increasingly recognized to show bioactive effects on many cellular signalling pathways. There is a growing body of evidence showing that OxPLs play an important role in many diseases, so it is essential to define the specific role of OxPLs in different diseases for the design of disease therapies. In vastly diverse pathological processes, OxPLs act as pro-inflammatory agents and contribute to the progression of many diseases; in addition, they play a role in anti-inflammatory processes, promoting the dissipation of inflammation and inhibiting the progression of some diseases. In addition to participating in the regulation of inflammatory responses, OxPLs affect the occurrence and development of diseases through other pathways, such as apoptosis promotion. In this review, the different and even opposite effects of different OxPL molecular species are discussed. Furthermore, the specific effects of OxPLs in various diseases, as well as the receptor and cellular mechanisms involved, are summarized.

Impact of Lipoprotein(a) on Long-Term (Mean 6.2 Years) Outcomes in Patients With Three-Vessel Coronary Artery Disease

The aim of the cohort study was to investigate the relation between plasma lipoprotein(a) (Lp[a]) and long-term clinical outcomes in patients with three-vessel disease (TVD) after the following treatment strategies, including medical therapy alone, percutaneous coronary intervention, and coronary artery bypass grafting. A total of 6,175 consecutive patients with angiographically confirmed TVD and available baseline Lp(a) data were included in this study. Based on the median level of Lp(a) at admission, the patient was divided into 2 subgroups. Primary endpoint was major adverse cardiovascular events (MACE), of which all-cause death, myocardial infarction, and unplanned revascularization were all included. In general, the median value of Lp(a) reached 13.76 mg/dl for all patients. The median follow-up time of all patients was 6.2 years. For MACE, a total of 1,433 cases were generated, accounting for 23.2%, including 804 (13.0%) all-cause death, 302 (4.9 %) myocardial infarction, and 494 (8.0%) unplanned revascularization. For the incidence of MACE, the high Lp (a) and low Lp (a) groups were 24.3% to 22.1% (p = 0.015), respectively. When the risk factors were adjusted, the multivariate analysis showed that high Lp(a) levels was an independent predictor of primary outcome (adjusted hazard ratio 1.169, 95% confidence interval 1.046 to 1.306, p = 0.006). Except for gender group, there is a relatively consistent correlation in the various subgroups. In conclusion, plasma Lp(a) is a potential biomarker for risk stratification and prognosis in patients diagnosed with TVD.

Familial hypercholesterolemia and elevated lipoprotein(a): double heritable risk and new therapeutic opportunities

There is compelling evidence that the elevated plasma lipoprotein(a) [Lp(a)] levels increase the risk of atherosclerotic cardiovascular disease (ASCVD) in the general population. Like low-density lipoprotein (LDL) particles, Lp(a) particles contain cholesterol and promote atherosclerosis. In addition, Lp(a) particles contain strongly proinflammatory oxidized phospholipids and a unique apoprotein, apo(a), which promotes the growth of an arterial thrombus. At least one in 250 individuals worldwide suffer from the heterozygous form of familial hypercholesterolemia (HeFH), a condition in which LDL-cholesterol (LDL-C) is significantly elevated since birth. FH-causing mutations in the LDL receptor gene demonstrate a clear gene-dosage effect on Lp(a) plasma concentrations and elevated Lp(a) levels are present in 30-50% of patients with HeFH. The cumulative burden of two genetically determined pro-atherogenic lipoproteins, LDL and Lp(a), is a potent driver of ASCVD in HeFH patients. Statins are the cornerstone of treatment of HeFH, but they do not lower the plasma concentrations of Lp(a). Emerging therapies effectively lower Lp(a) by as much as 90% using RNA-based approaches that target the transcriptional product of the LPA gene. We are now approaching the dawn of an era, in which permanent and significant lowering of the high cholesterol burden of HeFH patients can be achieved. If outcome trials of novel Lp(a)-lowering therapies prove to be safe and cost-effective, they will provide additional risk reduction needed to effectively treat HeFH and potentially lower the CVD risk in these high-risk patients even more than currently achieved with LDL-C lowering alone.

An update on lipid oxidation and inflammation in cardiovascular diseases

Cardiovascular diseases (CVD), including ischemic heart diseases and cerebrovascular diseases, are the leading causes of morbidity and mortality worldwide. Atherosclerosis is the major underlying factor for most CVD. It is well-established that oxidative stress and inflammation are two major mechanisms leading to atherosclerosis. Under oxidative stress, polyunsaturated fatty acids (PUFA)-containing phospholipids and cholesterol esters in cellular membrane and lipoproteins can be readily oxidized through a free radical-induced lipid peroxidation (LPO) process to form a complex mixture of oxidation products. Overwhelming evidence demonstrates that these oxidized lipids are actively involved in the inflammatory responses in atherosclerosis by interacting with immune cells (such as macrophages) and endothelial cells. In addition to lipid lowering in the prevention and treatment of atherosclerotic CVD, targeting chronic inflammation has been entering the medical realm. Clinical trials are under way to lower the lipoprotein (a) (Lp(a)) and its associated oxidized phospholipids, which will provide clinical evidence that targeting inflammation caused by oxidized lipids is a viable approach for CVD. In this review, we aim to give an update on our understanding of the free radical oxidation of LPO, analytical technique to analyze the oxidation products, especially the oxidized phospholipids and cholesterol esters in low density lipoproteins (LDL), and focusing on the experimental and clinical evidence on the role of lipid oxidation in the inflammatory responses associated with CVD, including myocardial infarction and calcific aortic valve stenosis. The challenges and future directions in understanding the role of LPO in CVD will also be discussed.

Potent reduction of plasma lipoprotein (a) with an antisense oligonucleotide in human subjects does not affect ex vivo fibrinolysis

It is postulated that lipoprotein (a) [Lp(a)] inhibits fibrinolysis, but this hypothesis has not been tested in humans due to the lack of specific Lp(a) lowering agents. Patients with elevated Lp(a) were randomized to antisense oligonucleotide [IONIS-APO(a)_Rx] directed to apo(a) (n = 7) or placebo (n = 10). Ex vivo plasma lysis times and antigen concentrations of plasminogen, factor XI, plasminogen activator inhibitor 1, thrombin activatable fibrinolysis inhibitor, and fibrinogen at baseline, day 85/92/99 (peak drug effect), and day 190 (3 months off drug) were measured. The mean ± SD baseline Lp(a) levels were 477.3 ± 55.9 nmol/l in IONIS-APO(a)_Rx and 362.1 ± 89.9 nmol/l in placebo. The mean± SD percentage change in Lp(a) for IONIS-APO(a)_Rx was -69.3 ± 12.2% versus -5.4 ± 6.9% placebo (P < 0.0010) at day 85/92/99 and -15.6 ± 8.9% versus 3.2 ± 12.2% (P = 0.003) at day 190. Clot lysis times and coagulation/fibrinolysis-related biomarkers showed no significant differences between IONIS-APO(a)_Rx and placebo at all time points. Clot lysis times were not affected by exogenously added Lp(a) at concentrations up to 200 nmol/l to plasma with very low (12.5 nmol/l) Lp(a) levels, whereas recombinant apo(a) had a potent antifibrinolytic effect. In conclusion, potent reductions of Lp(a) in patients with highly elevated Lp(a) levels do not affect ex vivo measures of fibrinolysis; the relevance of any putative antifibrinolytic effects of Lp(a) in vivo needs further study.

Assessment and Treatment of Patients With Type 2 Myocardial Infarction and Acute Nonischemic Myocardial Injury

Although coronary thrombus overlying a disrupted atherosclerotic plaque has long been considered the hallmark and the primary therapeutic target for acute myocardial infarction (MI), multiple other mechanisms are now known to cause or contribute to MI. It is further recognized that an MI is just one of many types of acute myocardial injury. The Fourth Universal Definition of Myocardial Infarction provides a taxonomy for acute myocardial injury, including 5 subtypes of MI and nonischemic myocardial injury. The diagnosis of MI is reserved for patients with myocardial ischemia as the cause of myocardial injury, whether attributable to acute atherothrombosis (type 1 MI) or supply/demand mismatch without acute atherothrombosis (type 2 MI). Myocardial injury in the absence of ischemia is categorized as acute or chronic nonischemic myocardial injury. However, optimal evaluation and treatment strategies for these etiologically distinct diagnoses have yet to be defined. Herein, we review the epidemiology, risk factor associations, and diagnostic tools that may assist in differentiating between nonischemic myocardial injury, type 1 MI, and type 2 MI. We identify limitations, review new research, and propose a framework for the diagnostic and therapeutic approach for patients who have suspected MI or other causes of myocardial injury.

Prognostic value of lipoprotein (a) level in patients with coronary artery disease: a meta-analysis

Background

Elevated lipoprotein (a) is recognized as a risk factor for incident cardiovascular events in the general population and established cardiovascular disease patients. However, there are conflicting findings on the prognostic utility of elevated lipoprotein (a) level in patients with coronary artery disease (CAD).Thus, we performed a meta-analysis to evaluate the prognostic value of elevated lipoprotein (a) level in CAD patients.

Methods and results

A systematic literature search of PubMed and Embase databases was conducted until April 16, 2019. Observational studies reporting the prognostic value of elevated lipoprotein (a) level for cardiac events (cardiac death and acute coronary syndrome), cardiovascular events (death, stroke, acute coronary syndrome or coronary revascularisation), cardiovascular death, and all-cause mortality in CAD patients were included. Pooled multivariable adjusted risk ratio (RR) and 95% confidence interval (CI) for the highest vs. the lowest lipoprotein (a) level were utilized to calculate the prognostic value. Seventeen studies enrolling 283,328 patients were identified. Meta-analysis indicated that elevated lipoprotein (a) level was independently associated with an increased risk of cardiac events (RR 1.78; 95% CI 1.31–2.42) and cardiovascular events (RR 1.29; 95% CI 1.17–1.42) in CAD patients. However, elevated lipoprotein (a) level was not significantly associated with an increased risk of cardiovascular mortality (RR 1.43; 95% CI 0.94–2.18) and all-cause mortality (RR 1.35; 95% CI 0.93–1.95).

Conclusions

Elevated lipoprotein (a) level is an independent predictor of cardiac and cardiovascular events in CAD patients. Measurement of lipoprotein (a) level has potential to improve the risk stratification among patients with CAD.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1092-6) contains supplementary material, which is available to authorized users.

Integrated Lipidomics and Proteomics Point to Early Blood-Based Changes in Childhood Preceding Later Development of Psychotic Experiences: Evidence From the Avon Longitudinal Study of Parents and Children

BACKGROUND

The identification of early biomarkers of psychotic experiences (PEs) is of interest because early diagnosis and treatment of those at risk of future disorder is associated with improved outcomes. The current study investigated early lipidomic and coagulation pathway protein signatures of later PEs in subjects from the Avon Longitudinal Study of Parents and Children cohort.

METHODS

Plasma of 115 children (12 years of age) who were first identified as experiencing PEs at 18 years of age (48 cases and 67 controls) were assessed through integrated and targeted lipidomics and semitargeted proteomics approaches. We assessed the lipids, lysophosphatidylcholines (n = 11) and phosphatidylcholines (n = 61), and the protein members of the coagulation pathway (n = 22) and integrated these data with complement pathway protein data already available on these subjects.

RESULTS

Twelve phosphatidylcholines, four lysophosphatidylcholines, and the coagulation protein plasminogen were altered between the control and PEs groups after correction for multiple comparisons. Lipidomic and proteomic datasets were integrated into a multivariate network displaying a strong relationship between most lipids that were significantly associated with PEs and plasminogen. Finally, an unsupervised clustering approach identified four different clusters, with one of the clusters presenting the highest case-control ratio (p < .01) and associated with a higher concentration of smaller low-density lipoprotein cholesterol particles.

CONCLUSIONS

Our findings indicate that the lipidome and proteome of subjects who report PEs at 18 years of age are already altered at 12 years of age, indicating that metabolic dysregulation may contribute to an early vulnerability to PEs and suggesting crosstalk between these lysophosphatidylcholines, phosphatidylcholines, and coagulation and complement proteins.

Association of Plasma Lipoprotein(a) With Long-Term Adverse Events in Patients With Chronic Kidney Disease Who Underwent Percutaneous Coronary Intervention

We aimed to determine the association of plasma lipoprotein(a) (Lp[a]) with long-term clinical outcomes in patients with chronic kidney disease (CKD) after percutaneous coronary intervention (PCI) in an observational cohort study. Four hundred and twenty-seven consecutive patients with CKD who underwent PCI from January 2013 to December 2013 were included in this study. Patients were divided into 2 groups according to median levels of Lp(a). Outcomes included 2-year risk of major adverse cardiovascular and cerebrovascular events (MACCEs) and bleeding according to Bleeding Academic Research Consortium definitions. Overall, median of Lp(a) in all the patients was 217.8 mg/L. The 2-year MACCE rate across the high Lp(a) and low Lp(a) group was 23.0% versus 15.4% (p = 0.047) and bleeding event rate of the two groups 8.9% versus 4.2% (p = 0.049). The Lp(a) was significantly and positively correlated with high-sensitivity C-reactive protein levels (r² = 0.03, p < 0.001). Kaplan-Meier curves revealed that high Lp(a) had higher incidence of bleeding than low Lp(a) (p = 0.043) and had higher risk of MACCE (p = 0.049). Multivariable Cox regression analysis indicated that high Lp(a) was an independent predictor of Bleeding Academic Research Consortium bleeding compared with low Lp(a) (hazard ratios 2.29, 95% confidence intervals 1.01 to 5.15, p = 0.046). In conclusion, a high Lp(a) value may be associated with a poor prognosis after PCI for patients with CKD.

Lipoprotein(a) and oxidized phospholipids in calcific aortic valve stenosis

PURPOSE OF REVIEW

As the incidence of calcific aortic valve stenosis increases with the aging of the population, improved understanding and novel therapies to reduce its progression and need for aortic valve replacement are urgently needed.

RECENT FINDINGS

Lipoprotein(a) is the only monogenetic risk factor for calcific aortic stenosis. Elevated levels are a strong, causal, independent risk factor, as demonstrated in epidemiological, genome-wide association studies and Mendelian randomization studies. Lipoprotein(a) is the major lipoprotein carrier of oxidized phospholipids, which are proinflammatory and promote calcification of vascular cells, two key pathophysiological drivers of aortic stenosis. Elevated plasma lipoprotein(a) and oxidized phospholipids predict progression of pre-existing aortic stenosis and need for aortic valve replacement. The failure of statin trials in pre-existing aortic stenosis may be partially due to an increase in lipoprotein(a) and oxidized phospholipid levels caused by statins. Antisense oligonucleotides targeted to apo(a) are in Phase 2 clinical development and shown to lower both lipoprotein(a) and oxidized phospholipids.

SUMMARY

Lipoprotein(a) and oxidized phospholipids are key therapeutic targets in calcific aortic stenosis. Strategies aimed at potent lipoprotein(a) lowering to normalize levels and/or to suppress the proinflammatory effects of oxidized phospholipids may prevent progression of this disease.

Association of D-dimer with Plaque Characteristics and Plasma Biomarkers of Oxidation-Specific Epitopes in Stable Subjects with Coronary Artery Disease

D-dimer has emerged as a biomarker of cardiovascular event risk, yet pathophysiological factors associated with plasma D-dimer levels in stable coronary artery disease (CAD) subjects are poorly understood. In 106 stable CAD subjects undergoing intravascular ultrasound with virtual histology (IVUS-VH), we measured D-dimer, lipoprotein(a) (Lp(a)), plasminogen, biomarkers reflecting oxidation-specific epitopes (OSE) such as oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB), OxPL on plasminogen (OxPL-PLG), and autoantibodies to phosphorylcholine-BSA [PC-BSA] and a malondialdehyde [MDA] mimotope. In univariate analysis, D-dimer was positively associated with Lp(a), OxPL-apoB, OxPL-PLG, and coronary artery calcium, and inversely associated with autoantibodies to OSE and plaque fibrosis. D-dimer levels > 500 ng/ml also showed positive association with plaque necrosis. After multivariate analysis, D-dimer remained significantly associated with Lp(a) and plaque calcium. While further studies are needed, results provide evidence that plasma D-dimer levels are associated with levels of OxPLs and IVUS-VH indices linked to plaque erosion and rupture.

Impaired plasminogen binding in patients with venous thromboembolism: Association with protein carbonylation

INTRODUCTION

Venous thromboembolism (VTE) is associated with hypofibrinolysis. Its mechanisms are poorly understood. We investigated plasminogen-fibrin interaction and its association with fibrinolytic capacity and protein oxidation/carbonylation in VTE patients.

MATERIALS AND METHODS

Plasma-purified plasminogen conversion to plasmin and surface plasmon resonance employed for plasminogen-fibrin interactions were individually evaluated in all healthy controls and non-anticoagulated patients following VTE, 10-23months since the event. We also assessed plasma fibrin clot permeability (K_s), clot lysis time (LT), activators and inhibitors of fibrinolysis together with oxidation/carbonylation markers.

RESULTS

VTE patients had impaired plasminogen binding to fibrin (apparent Kd, +290%, p=0.002), reduced rate of plasmin generation (-4.7%, p=0.001), and longer LT (+18.6%, p<0.001) compared with controls. Fibrinogen and K_s were similar in both groups. Apparent Kd correlated with LT (r=0.43, p=0.037), tissue plasminogen activator-plasminogen activator inhibitor 1 (tPA-PAI-1) complexes (r=0.63, p=0.012), and active PAI-1 (r=0.49, p=0.03). Compared with controls, VTE patients had higher thiobarbituric acid reactive substances (TBARS), total protein carbonyl content (PC), and lower total antioxidant capacity (all p<0.001), that all were associated with LT (r=0.61, r=0.56, and r=-0.47, respectively, all p<0.05). Impaired plasminogen binding to fibrin reflected by apparent Kd positively correlated with TBARS (r=0.48, p=0.032) and PC (r=0.54, p=0.013) in the whole group.

CONCLUSIONS

Plasminogen-fibrin interactions are altered in young and middle-aged VTE patients, without known thrombophilias, except increased factor VIII. The mechanisms underlying these phenomena remain to be established.

Modified risk associations of lipoproteins and apolipoproteins by chronic low-grade inflammation

INTRODUCTION

Lipoproteins and the apolipoproteins (apo) that they carry are major determinants of cardiovascular diseases (CVD) as well as metabolic, renal and inflammatory chronic disorders either directly or through mediation of risk factors. The notion that elevated low-density lipoprotein cholesterol (LDL-C) and apoB levels are related to the acquisition of CVD and, high-density lipoprotein cholesterol (HDL-C) and apoA-I indicate protection against CVD has been challenged in the past decade. Advanced age, adiposity, ethnicity or impaired glucose intolerance rendered autoimmune activation in an environment of pro-inflammatory state/oxidative stress and may disrupt the linear risk association between lipoproteins. Areas covered: This review summarizes the modified risk associations of lipoproteins and apolipoprotein by an environment of chronic systemic low-grade inflammation with special emphasis on the non-linear relationship of lipoprotein(a) [Lp(a)], a biomarker of renewed interest in cardiometabolic risk. Expert commentary: It seems that autoimmune activation in an environment of pro-inflammatory state/oxidative stress not only disrupts the linear risk association between lipoproteins, but also may cause interference in immunoassays. Hence, methodological improvement in immunoassays and much further research focusing on population segments susceptible to a pro-inflammatory state is necessary for further advances in knowledge.

Pleiotropic effects of oxidized phospholipids

Oxidized phospholipids (OxPLs) are increasingly recognized to play a role in a variety of normal and pathological states. OxPLs were implicated in regulation of inflammation, thrombosis, angiogenesis, endothelial barrier function, immune tolerance and other important processes. Rapidly accumulating evidence suggests that OxPLs are biomarkers of atherosclerosis and other pathologies. In addition, successful application of experimental drugs based on structural scaffold of OxPLs in animal models of inflammation was recently reported. This review briefly summarizes current knowledge on generation, methods of quantification and biological activities of OxPLs. Furthermore, receptor and cellular mechanisms of these effects are discussed. The goal of the review is to give a broad overview of this class of lipid mediators inducing pleiotropic biological effects.

Association of lipoprotein(a) with long-term mortality following coronary angiography or percutaneous coronary intervention

BACKGROUND

There is no consistent evidence to suggest the association of plasma lipoprotein(a) (Lp[a]) with long-term mortality in patients undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI).

HYPOTHESIS

Level of Lp(a) is associated with long-term mortality following CAG or PCI.

METHODS

We enrolled 1684 patients with plasma Lp(a) data undergoing CAG or PCI between April 2009 and December 2013. The patients were divided into 2 groups: a low-Lp(a) group (Lp[a] <16.0 mg/dL; n = 842) and a high-Lp(a) group (Lp[a] ≥16.0 mg/dL; n = 842).

RESULTS

In-hospital mortality was not significantly different between the high and low Lp(a) groups (0.8% vs 0.5%, respectively; P = 0.364). During the median follow-up period of 1.95 years, the high-Lp(a) group had a higher long-term mortality than did the low-Lp(a) group (5.8% vs 2.5%, respectively; P = 0.003). After adjustment of confounders, multivariate Cox regression analysis revealed that a higher Lp(a) level was an independent predictor of long-term mortality (hazard ratio: 1.96, 95% confidence interval: 1.07-3.59, P = 0.029).

CONCLUSIONS

Our data suggested that an elevated Lp(a) level was significantly associated with long-term mortality following CAG or PCI. However, additional larger multicenter studies will be required to investigate the predictive value of Lp(a) levels and evaluate the benefit of controlling Lp(a) levels for patients undergoing CAG or PCI.

Circulating levels of plasminogen and oxidized phospholipids bound to plasminogen distinguish between atherothrombotic and non-atherothrombotic myocardial infarction

Oxidized phospholipids (OxPL) are abundant in atherosclerotic plaques. They are also bound to circulating plasminogen after myocardial infarction (MI), and their binding to plasminogen may accentuate fibrinolysis. We sought to assess whether circulating levels of plasminogen and OxPL bound to plasminogen (OxPL-PLG) increase following acute MI and whether this increase differs between atherothrombotic (Type 1) and non-atherothrombotic (Type 2) MI. We measured circulating levels of plasminogen and OxPL-PLG at 0, 6, 24, 48 h, and >3 months (stable state) following acute MI and following an angiogram for stable coronary artery disease (CAD). Forty-nine subjects met the criteria for acute MI, of whom 34 had clearly defined atherothrombotic (n = 22) or non-atherothrombotic (n = 12) MI; 15 patients met the criteria for stable CAD. Mean baseline levels of plasminogen and OxPL-PLG were lower in the acute MI group than in the stable CAD group (9.75 vs 20.2, p < 0.0001 for plasminogen and 165.5 vs 275.1, p = 0.0002 for OxPL-PLG) and did not change over time or between time points, including the 3-month follow-up. Mean baseline levels of plasminogen and OxPL-PLG were also lower in atherothrombotic (Type 1) than in non-atherothrombotic (Type 2) MI subjects (8.65 vs 12.1, p < 0.03 for plasminogen and 164.5 vs 245.7, p = 0.02 for OxPL-PLG), and this relationship did not change over time or between time points. Plasminogen and OxPL-PLG were lower in patients presenting with an acute MI than in those with stable CAD and also in those with atherothrombotic MI (Type 1) vs. those with non-atherothrombotic MI (Type 2). These findings persisted at a median follow-up of 3 months post-MI. The association of plasminogen and OxPL-PLG with acute MI, particularly atherothrombotic MI (Type 1), could reflect a reduced fibrinolytic capacity, associated with an increased risk of atherothrombotic events differentiating stable CAD from unstable CAD and atherothrombotic MI (Type 1) from non-atherothrombotic MI (Type 2). Additional study with a larger sample size is warranted.

Senescent cells expose and secrete an oxidized form of membrane-bound vimentin as revealed by a natural polyreactive antibody

Studying the phenomenon of cellular senescence has been hindered by the lack of senescence-specific markers. As such, detection of proteins informally associated with senescence accompanies the use of senescence-associated β-galactosidase as a collection of semiselective markers to monitor the presence of senescent cells. To identify novel biomarkers of senescence, we immunized BALB/c mice with senescent mouse lung fibroblasts and screened for antibodies that recognized senescence-associated cell-surface antigens by FACS analysis and a newly developed cell-based ELISA. The majority of antibodies that we isolated, cloned, and sequenced belonged to the IgM isotype of the innate immune system. In-depth characterization of one of these monoclonal, polyreactive natural antibodies, the IgM clone 9H4, revealed its ability to recognize the intermediate filament vimentin. By using 9H4, we observed that senescent primary human fibroblasts express vimentin on their cell surface, and MS analysis revealed a posttranslational modification on cysteine 328 (C328) by the oxidative adduct malondialdehyde (MDA). Moreover, elevated levels of secreted MDA-modified vimentin were detected in the plasma of aged senescence-accelerated mouse prone 8 mice, which are known to have deregulated reactive oxygen species metabolism and accelerated aging. Based on these findings, we hypothesize that humoral innate immunity may recognize senescent cells by the presence of membrane-bound MDA-vimentin, presumably as part of a senescence eradication mechanism that may become impaired with age and result in senescent cell accumulation.

Acute and long-term effect of percutaneous coronary intervention on serially-measured oxidative, inflammatory, and coagulation biomarkers in patients with stable angina

To derive insights into the temporal changes in oxidative, inflammatory and coagulation biomarkers in patients with stable angina undergoing percutaneous coronary intervention (PCI). PCI is associated with a variety of biochemical and mechanical stresses to the vessel wall. Oxidized phospholipids are present on plasminogen (OxPL-PLG) and potentiate fibrinolysis in vitro. We recently showed that OxPL-PLG increase following acute myocardial infarction, suggesting that they are involved in atherothrombosis. Plasma samples were collected before, immediately after, 6 and 24 h, 3 and 7 days, and 1, 3, and 6 months after PCI in 125 patients with stable angina undergoing uncomplicated PCI. Plasminogen levels, OxPL-PLG, and an array of 16 oxidative, inflammatory and coagulation biomarkers were measured with established assays. OxPL-PLG and plasminogen declined significantly immediately post-PCI, rebounded to baseline, peaked at 3 days and slowly returned to baseline by 6 months (p < 0.0001 by ANOVA). The temporal trends to maximal peak in biomarkers were as follows: immediately post PCI: OxPL-apoB and lipoprotein (a); Day 1-the inflammatory biomarker IL-6; Day 3-CRP and coagulation biomarkers OxPL-PLG, plasminogen and tissue plasminogen activity; Day 3 to 7-plasminogen activator inhibitor activity, and complement factor H binding to malondialdehyde-LDL and MDA-LDL IgG; Day 7-30 MDA-LDL IgM, CuOxLDL IgM, and ApoB-IC IgM and IgG; >30 days uPA activity, uPA antigen, CuOxLDL IgG and peptide mimotope to MDA-LDL. Most of the biomarkers trended to baseline by 6 months. PCI results in a specific, temporal sequence of changes in plasma biomarkers. These observations provide insights into the effects of iatrogenic barotrauma and plaque disruption during PCI and suggest avenues of investigation to explain complications of PCI and development of targeted therapies to enhance procedural success.

Lp(a) and cardiovascular risk: Investigating the hidden side of the moon

AIMS

This article reports current evidence on the association between Lp(a) and cardiovascular (CV) disease and on pathophysiological mechanisms. The available information on therapy for reduction of lipoprotein(a) is also discussed.

DATA SYNTHESIS

Although some evidence is conflicting, Lp(a) seems to increase CV risk through stimulation of platelet aggregation, inhibition of tissue factor pathway inhibitor, alteration of fibrin clot structure and promotion of endothelial dysfunction and phospholipid oxidation. Lp(a) 3.5-fold higher than normal increases the risk of coronary heart disease and general CV events, particularly in those with LDL cholesterol ≥ 130 mg/dl. High Lp(a) values represent also an independent risk factor for ischemic stroke (more relevant in young stroke patients), peripheral artery disease (PAD) and aortic and mitral stenosis. Furthermore, high Lp(a) levels seem to be associated with increased risk of cardiovascular events in patients with chronic kidney disease, particularly in those undergoing percutaneous coronary intervention.

CONCLUSIONS

Lipoprotein (a) (Lp[a]) seems to significantly influence the risk of cardiovascular events. The effects of statins and fibrates on Lp(a) are limited and extremely variable. Nicotinic acid was shown effective in reducing Lp(a) but, due to its side effects and serious adverse events during clinical trials, it is no longer considered a possible option for treatment. To date, the treatment of choice for high levels of Lp(a) in high CV risk patients is represented by LDL-Apheresis. Thanks to innovative technologies, new selectively inhibiting LPA drugs are being developed and tested.

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.

Advances in understanding gender difference in cardiometabolic disease risk

Gender differences exist in cardiovascular or metabolic disease risk, beyond the protective effect of estrogens, mostly burdening the postmenopausal female. We aimed to review herein sex differences in pro-inflammatory states, the independence of inflammation from insulin resistance, differences in high-density lipoprotein dysfunction, in gene-environment interactions, and in the influence of current and former smoking on cardiometabolic risk. Sex differences in absorption of long-chain fatty acids are highlighted. Differences exist in the first manifestation of cardiovascular disease, men being more likely to develop coronary heart disease as a first event, compared to women who have cerebrovascular disease or heart failure as a first event. Autoimmune activation resulting from pro-inflammatory states, a fundamental mechanism for numerous chronic diseases in people prone to metabolic syndrome, is much more common in women, and these constitute major determinants. Therapeutic approaches to aspects related to sex difference are briefly reviewed.

Lipoprotein (a): truly a direct prothrombotic factor in cardiovascular disease?

Elevated plasma concentrations of lipoprotein (a) [Lp(a)] have been determined to be a causal risk factor for coronary heart disease, and may similarly play a role in other atherothrombotic disorders. Lp(a) consists of a lipoprotein moiety indistinguishable from LDL, as well as the plasminogen-related glycoprotein, apo(a). Therefore, the pathogenic role for Lp(a) has traditionally been considered to reflect a dual function of its similarity to LDL, causing atherosclerosis, and its similarity to plasminogen, causing thrombosis through inhibition of fibrinolysis. This postulate remains highly speculative, however, because it has been difficult to separate the prothrombotic/antifibrinolytic functions of Lp(a) from its proatherosclerotic functions. This review surveys the current landscape surrounding these issues: the biochemical basis for procoagulant and antifibrinolytic effects of Lp(a) is summarized and the evidence addressing the role of Lp(a) in both arterial and venous thrombosis is discussed. While elevated Lp(a) appears to be primarily predisposing to thrombotic events in the arterial tree, the fact that most of these are precipitated by underlying atherosclerosis continues to confound our understanding of the true pathogenic roles of Lp(a) and, therefore, the most appropriate therapeutic target through which to mitigate the harmful effects of this lipoprotein.

Antisense therapy targeting apolipoprotein(a): a randomised, double-blind, placebo-controlled phase 1 study

BACKGROUND

Lipoprotein(a) (Lp[a]) is a risk factor for cardiovascular disease and calcific aortic valve stenosis. No effective therapies to lower plasma Lp(a) concentrations exist. We have assessed the safety, pharmacokinetics, and pharmacodynamics of ISIS-APO(a)Rx, a second-generation antisense drug designed to reduce the synthesis of apolipoprotein(a) (apo[a]) in the liver.

METHODS

In this randomised, double-blind, placebo-controlled, phase 1 study at the PAREXEL Clinical Pharmacology Research Unit (Harrow, Middlesex, UK), we screened for healthy adults aged 18-65 years, with a body-mass index less than 32·0 kg/m(2), and Lp(a) concentration of 25 nmol/L (100 mg/L) or more. Via a randomisation technique, we randomly assigned participants to receive a single subcutaneous injection of ISIS-APO(a)Rx (50 mg, 100 mg, 200 mg, or 400 mg) or placebo (3:1) in the single-dose part of the study or to receive six subcutaneous injections of ISIS-APO(a)Rx (100 mg, 200 mg, or 300 mg, for a total dose exposure of 600 mg, 1200 mg, or 1800 mg) or placebo (4:1) during a 4 week period in the multi-dose part of the study. Participants, investigators, and study staff were masked to the treatment assignment, except for the pharmacist who prepared the ISIS-APO(a)Rx or placebo. The primary efficacy endpoint was the percentage change from baseline in Lp(a) concentration at 30 days in the single-dose cohorts and at 36 days for the multi-dose cohorts. Safety and tolerability was assessed 1 week after last dose and included determination of the incidence, severity, and dose relation of adverse events and changes in laboratory variables, including lipid panel, routine haematology, blood chemistry, urinalysis, coagulation, and complement variables. Other assessments included vital signs, a physical examination, and 12-lead electrocardiograph. This trial is registered with European Clinical Trials Database, number 2012-004909-27.

FINDINGS

Between Feb 27, 2013, and July 15, 2013, 47 (23%) of 206 screened volunteers were randomly assigned to receive ISIS-APO(a)Rx as a single-dose or multi-dose of ascending concentrations or placebo. In the single-dose study, we assigned three participants to receive 50 mg ISIS-APO(a)Rx, three participants to receive 100 mg ISIS-APO(a)Rx, three participants to receive 200 mg ISIS-APO(a)Rx, three participants to receive 400 mg ISIS-APO(a)Rx, and four participants to receive placebo. All 16 participants completed treatment and follow-up and were included in the pharmacodynamics, pharmacokinetics, and safety analyses. For the multi-dose study, we assigned eight participants to receive six doses of 100 mg ISIS-APO(a)Rx, nine participants to receive six doses of 200 mg ISIS-APO(a)Rx, eight participants to receive six doses of 300 mg ISIS-APO(a)Rx, and six participants to receive six doses of placebo. Whereas single doses of ISIS-APO(a)Rx (50-400 mg) did not decrease Lp(a) concentrations at day 30, six doses of ISIS-APO(a)Rx (100-300 mg) resulted in dose-dependent, mean percentage decreases in plasma Lp(a) concentration of 39·6% from baseline in the 100 mg group (p=0·005), 59·0% in the 200 mg group (p=0·001), and 77·8% in the 300 mg group (p=0·001). Similar reductions were observed in the amount of oxidized phospholipids associated with apolipoprotein B-100 and apolipoprotein(a). Mild injection site reactions were the most common adverse events.

INTERPRETATION

ISIS-APO(a)Rx results in potent, dose-dependent, selective reductions of plasma Lp(a). The safety and tolerability support continued clinical development of ISIS-APO(a)Rx as a potential therapeutic drug to reduce the risk of cardiovascular disease and calcific aortic valve stenosis in patients with elevated Lp(a) concentration.

FUNDING

Isis Pharmaceuticals.

The mechanism by which moderate alcohol consumption influences coronary heart disease

Background

Moderate alcohol consumption is associated with a lower risk for coronary heart disease (CHD). A suitably integrated view of the CHD pathogenesis pathway will help to elucidate how moderate alcohol consumption could reduce CHD risk.

Methods

A comprehensive literature review was conducted focusing on the pathogenesis of CHD. Biomarker data were further systematically analysed from 294 cohort studies, comprising 1 161 560 subjects. From the above a suitably integrated CHD pathogenetic system for the purpose of this study was developed.

Results

The resulting integrated system now provides insight into the integrated higher-order interactions underlying CHD and moderate alcohol consumption. A novel ‘connection graph’ further simplifies these interactions by illustrating the relationship between moderate alcohol consumption and the relative risks (RR) attributed to various measureable CHD serological biomarkers. Thus, the possible reasons for the reduced RR for CHD with moderate alcohol consumption become clear at a glance.

Conclusions

An integrated high-level model of CHD, its pathogenesis, biomarkers, and moderate alcohol consumption provides a summary of the evidence that a causal relationship between CHD risk and moderate alcohol consumption may exist. It also shows the importance of each CHD pathway that moderate alcohol consumption influences.

How do high glycemic load diets influence coronary heart disease?

Background

Diet has a significant relationship with the risk of coronary heart disease (CHD). Traditionally the effect of diet on CHD was measured with the biomarker for low-density lipoprotein (LDL) cholesterol. However, LDL is not the only or even the most important biomarker for CHD risk. A suitably integrated view of the mechanism by which diet influences the detailed CHD pathogenetic pathways is therefore needed in order to better understand CHD risk factors and help with better holistic CHD prevention and treatment decisions.

Methods

A systematic review of the existing literature was conducted. From this an integrated CHD pathogenetic pathway system was constructed. CHD biomarkers, which are found on these pathways, are the only measurable data to link diet with these CHD pathways. They were thus used to simplify the link between diet and the CHD mechanism. Data were systematically analysed from 294 cohort studies of CHD biomarkers constituting 1 187 350 patients.

Results and discussion

The resulting integrated analysis provides insight into the higher-order interactions underlying CHD and high-glycemic load (HGL) diets. A novel “connection graph” illustrates the measurable relationship between HGL diets and the relative risks attributed to the important CHD serological biomarkers.

The “connection graph” vividly shows that HGL diets not only influence the lipid and metabolic biomarkers, but also the inflammation, coagulation and vascular function biomarkers in an important way.

Conclusion

A focus primarily on the low density lipoprotein cholesterol biomarker for CHD risk has led to the traditional guidelines of CHD dietary recommendations. This has however inadvertently led to HGL diets. The influence of HGL diets on the other CHD biomarkers is not always fully appreciated. Thus, new diets or other interventions which address the full integrated CHD impact, as shown in this paper, are required.

Pro-inflammatory interleukin-1 genotypes potentiate the risk of coronary artery disease and cardiovascular events mediated by oxidized phospholipids and lipoprotein(a)

OBJECTIVES

The aim of this study was to assess the influence of pro-inflammatory interleukin (IL)-1 genotype status on the risk for coronary artery disease (CAD), defined as >50% diameter stenosis, and cardiovascular events mediated by oxidized phospholipids (OxPLs) and lipoprotein (Lp) (a).

BACKGROUND

OxPLs are pro-inflammatory, circulate on Lp(a), and mediate CAD. Genetic variations in the IL-1 region are associated with increased inflammatory mediators.

METHODS

IL-1 genotypes, OxPL on apolipoprotein B-100 (OxPL/apoB), and Lp(a) levels were measured in 499 patients undergoing coronary angiography. The composite genotype termed IL-1(+) was defined by 3 single-nucleotide polymorphisms in the IL-1 gene cluster associated with higher levels of pro-inflammatory cytokines. All other IL-1 genotypes were termed IL-1(-).

RESULTS

Among IL-1(+) patients, the highest quartile of OxPL/apoB was significantly associated with a higher risk for CAD compared with the lowest quartile (odds ratio [OR]: 2.84; p = 0.001). This effect was accentuated in patients age ≤60 years (OR: 7.03; p < 0.001). In IL-1(-) patients, OxPL/apoB levels showed no association with CAD. The interaction was significant for OxPL/apoB (OR: 1.99; p = 0.004) and Lp(a) (OR: 1.96; p < 0.001) in the IL-1(+) group versus the IL-1(-) group in patients age ≤60 years but not in those age >60 years. In IL-1(+) patients age ≤60 years, after adjustment for established risk factors, high-sensitivity C-reactive protein, and Lp(a), OxPL/apoB remained an independent predictor of CAD. IL-1(+) patients above the median OxPL/apoB presented to the cardiac catheterization laboratory a mean of 3.9 years earlier (p = 0.002) and had worse 4-year event-free survival (death, myocardial infarction, stroke, and need for revascularization) compared with other groups (p = 0.006).

CONCLUSIONS

Our study suggests that IL-1 genotype status can stratify population risk for CAD and cardiovascular events mediated by OxPL. These data suggest a clinically relevant biological link between pro-inflammatory IL-1 genotype, oxidation of phospholipids, Lp(a), and genetic predisposition to CAD and cardiovascular events.