Lipoprotein (a) and stroke

Lipoprotein (a) and coronary heart disease among women: beyond a cholesterol carrier?

AIMS

With its homology with plasminogen, lipoprotein(a) [Lp(a)] may be related to thrombosis and inflammation. We assessed the role of Lp(a) in coronary heart diseases (CHD) by a recently developed assay that is not affected by the plasminogen-like Kringle-type-2 repeats.

METHODS AND RESULTS

Of 32 826 women from the Nurses' Health Study, who provided blood at baseline, we documented 228 CHD events during 8 years of follow-up. Each case was compared with two matched controls. In a multivariable model adjusted for body mass index, family history, hypertension, diabetes, post-menopausal hormone use, physical activity, blood drawing characteristics, and alcohol intake, the odd ratio (OR) for Lp(a) levels > or =30 mg/dL was 1.9(95% CI: 1.3-3.0) when compared with those with Lp(a)<30 mg/dL. Women with high levels of both Lp(a) (> or =30 mg/dL) and fibrinogen (> or =400 mg/dL) had an OR of 3.2(95% CI: 1.6-6.5) for CHD, when compared with the combination of low levels (P interaction=0.05). Women with high levels of both Lp(a) and C-reactive protein (> or =3 mg/L) had an OR of 3.67(95% CI: 2.03-6.64) for CHD, when compared with the combination of low levels (P interaction=0.06).

CONCLUSION

Lp(a) levels >30 mg/dL are associated with twice the risk of CHD events among women and may be related to thrombosis and inflammation.

Risk factors for first-ever acute ischemic non-embolic stroke in elderly individuals

BACKGROUND

Stroke is a leading cause of mortality and subsequent serious long-term physical and mental disability among survivors. In the elderly, ischemic stroke accounts for more than 80% of all strokes.

OBJECTIVES

To identify major risk factors for a first-ever acute ischemic/non-embolic stroke in individuals older than 70 years.

METHODS

A population-based case-control study of patients admitted to the University Hospital of Ioannina, Epirus, Greece, due to first-ever ischemic/non-embolic stroke from March 1997 to January 2002. All patients were subjected to brain CT and had their serum lipids and biochemical metabolic parameters determined within 24 h from the onset of symptoms.

RESULTS

A total of 163 (aged>70 years) consecutive stroke patients and 166 apparently healthy volunteers were studied. An atherogenic lipid profile and metabolic disturbances were more prevalent in the patient group than in stroke-free controls. Multivariate logistic regression analysis identified diabetes mellitus (odds ratio (OR), 1.92; 95% CI, 1.02-3.63), triglycerides (TG) (OR, 1.16; 95% CI, 1.09-1.22), HDL-cholesterol (OR, 0.57; 95% CI, 0.43-0.76), apo A-I (OR, 0.80; 95% CI, 0.70-0.92), lipoprotein(a) [LP(a)] (OR, 1.51; 95% CI, 1.25-1.79), uric acid (OR, 1.30; 95% CI, 1.06-1.59) albumin (OR, 0.38; 95% CI, 0.20-0.70) fibrinogen (OR, 1.10; 95% CI, 1.05-1.13) and the metabolic syndrome (OR 2.48, 95% CI, 1.16-5.29) as significantly associated with ischemic/non-embolic stroke.

CONCLUSION

Ischemic non-embolic stroke in the elderly is associated with dyslipidemia and several predictor metabolic factors, which could be substantially modified by lifestyle changes and therapeutic intervention.

Prevention and treatment of the metabolic syndrome

The prevalence of the metabolic syndrome is increasing owing to lifestyle changes leading to obesity. This syndrome is a complex association of several interrelated abnormalities that increase the risk for cardiovascular disease and progression to diabetes mellitus (DM). Insulin resistance is the key factor for the clustering of risk factors characterizing the metabolic syndrome. The National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III defined the criteria for the diagnosis of the metabolic syndrome and established the basic principles for its management. According to these guidelines, treatment involves the improvement of the underlying insulin resistance through lifestyle modification (eg, weight reduction and increased physical activity) and possibly by drugs. The coexistent risk factors (mainly dyslipidemia and hypertension) should also be addressed. Since the main goal of lipid-lowering treatment is to achieve the NCEP low-density lipoprotein cholesterol (LDL-C) target, statins are a good option. However, fibrates (as monotherapy or in combination with statins) are useful for the treatment of the metabolic syndrome that is commonly associated with hypertriglyceridemia and decreased high-density lipoprotein cholesterol (HDL-C) levels. The blood pressure target is < 140/90 mm Hg. The effect on carbohydrate homeostasis should possibly be taken into account in selecting an antihypertensive drug. Patients with the metabolic syndrome commonly have other less well-defined metabolic abnormalities (eg, hyperuricemia and raised C-reactive protein levels) that may also be associated with an increased cardiovascular risk. It seems appropriate to manage these abnormalities. Drugs that beneficially affect carbohydrate metabolism and delay or even prevent the onset of DM (eg, thiazolidinediones or acarbose) could be useful in patients with the metabolic syndrome. Furthermore, among the more speculative benefits of treatment are improved liver function in nonalcoholic fatty liver disease and a reduction in the risk of acute gout.

Plasma lipoprotein(a) levels: a comparison between diabetic and non-diabetic patients with acute ischemic stroke

OBJECTIVE: The aim of this study was to evaluate lipoprotein(a) (Lp(a)), total cholesterol, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), very low density lipoprotein cholesterol (VLDL ), triglycerides , apolipoprotein A (apo A) and B100 (apo B100), uric acid, glycaemic and insulin plasmatic concentrations in patients affected by acute stroke. In this group of patients, we have compared the variables between type 2 diabetic patients and non-diabetic patients. METHOD: We evaluate a total of 34 non-diabetic patients (22 males and 12 females; mean age 66.71 ± 10.83 years) and a group of 26 type 2 diabetic patients (15 males and 11 females; mean age 66.35 ± 9.92 years) in a cross-sectional study. RESULTS: Mean Lp(a) concentration did not significantly differ between type 2 diabetic patients and non-diabetic subjects (29.49 ± 23.09 vs 44.81 ± 44.34 mg/dl). The distribution of Lp(a)levels was highly skewed towards the higher levels in both groups, being over 30 mg/dl in 50%. Lp(a) concentration was positively correlated with abdominal adiposity, using waist-hip ratio(WHR)(p< 0.05). No association was found between Lp(a) and others risk factors like sex, age, other lipidic parameters and the presence of stroke. CONCLUSIONS: Our results showed that there were no significant differences between diabetic and non-diabetic patients' serum Lp(a) levels, which indicates that elevated Lp(a) levels were associated with ischemic stroke, irrespective of the presence of type 2 diabetes mellitus (type 2 DM).

Biomarkers of Alzheimer disease in plasma

Plasma and serum biochemical markers proposed for Alzheimer disease (AD) are based on pathophysiologic processes such as amyloid plaque formation [amyloid beta-protein (A beta), A beta autoantibodies, platelet amyloid precursor protein (APP) isoforms], inflammation (cytokines), oxidative stress (vitamin E, isoprostanes), lipid metabolism (apolipoprotein E, 24S-hydroxycholesterol), and vascular disease [homocysteine, lipoprotein (a)]. Most proteins or metabolites evaluated in plasma or serum thus far are, at best, biological correlates of AD: levels are statistically different in AD versus controls in some cohorts, but they lack sensitivity or specificity for diagnosis or for tracking response to therapy. Approaches combining panels of existing biomarkers or surveying the range of proteins in plasma (proteomics) show promise for discovering biomarker profiles that are characteristic of AD, yet distinct from nondemented patients or patients with other forms of dementia.

Long-Term Effects of Lipoprotein(a) on Carotid Atherosclerosis in Elderly Japanese

BACKGROUND

Serum level of lipoprotein(a) [Lp(a)] is hereditarily constant throughout life within an individual, but the relationship between Lp(a) and atherosclerosis in elderly people is still controversial.

METHODS

Serum Lp(a) levels were studied in 208 elderly Japanese participants aged 80 years with a variety of diseases, using carotid ultrasonography (US), brain computerized tomography (CT), electrocardiography (ECG), and ankle brachial pressure index (ABPI). Carotid plaque lesions were divided into 3 types based on the US echogenicity assessed by a computer-assisted system: L type (hypoechoic plaque), H type (hyperechoic plaque), and M type (heterogeneous plaque).

RESULTS

The frequency of the L type and occlusion was significantly higher in the high Lp(a) group (n = 38) than in the normal Lp(a) group (n = 170). The mean height of the plaque was also greater in the high Lp(a) group than in the normal Lp(a) group. There was no difference in CT findings between the two groups. Myocardial ischemia on ECG and low ABPI (<0.9) were both frequently, but not significantly, seen in the high Lp(a) group. Among factors influencing US findings, multiple regression analysis showed that high Lp(a) correlated markedly to L type and cigarette smoking correlated to M type.

CONCLUSIONS

These findings indicate that, in Japanese elderly patients aged 80, serum Lp(a) strongly correlates with hypoechoic carotid lesions, which correspond histologically to lipid-rich, unstable atherosclerosis. This suggested that Lp(a) could promote the formation of atherosclerosis throughout life, and play a role as an independent risk factor for circulatory disturbance of the organ later in life.

Lipoprotein (a) and acute-phase response in patients with vestibular neuronitis

BACKGROUND

Vestibular neuronitis (VN) is a relatively common condition characterized by the acute onset of vertigo, nausea and vomiting, in the absence of auditory or central nervous system involvement. The exact aetiology (inflammatory, viral or vascular?) remains obscure. Lipoprotein (a) [Lp(a)] is an atherogenic particle. Its serum levels are mainly genetically determined and vary widely between individuals. Whether Lp(a) is consistently a positive acute-phase reactant is controversial.

PURPOSE

We evaluated the alterations in lipidaemic parameters and serum biological markers (including acute-phase reactants) in adult patients presenting acutely with VN.

SUBJECTS AND METHODS

A total of 34 consecutive VN patients (24 men and 11 women) and 37 apparently healthy controls (25 men and 12 women) were studied. Laboratory evaluation was performed during the acute episode and 6 months later (stable state).

RESULTS

Serum Lp(a) concentrations were significantly lower at the time of presentation (median value 6.4 vs. 16.4 mg dL-1 in the stable state, P < 0.001), whereas fibrinogen levels were significantly higher during the acute episode than in the stable state (median value 293.0 vs. 202.0 mg dL-1, respectively, P < 0.0001). During the acute episode, plasma fibrinogen correlated with CRP levels (Spearman r = 0.84, P < 0.0001). By contrast, inverse correlations were noted between Lp(a) levels and CRP (Spearman r = -0.47, P = 0.007) as well as between Lp(a) and fibrinogen levels (Spearman r = -0.35, P = 0.05).

CONCLUSION

Vestibular neuronitis episodes are associated with evidence of an acute inflammatory response as reflected by significant elevations in plasma fibrinogen and CRP concentrations, whereas Lp(a) behaves as a negative acute-phase reactant.

Screening for hypercoagulable syndromes following stroke

Patients with ischemic stroke of unclear etiology are often screened for hypercoagulable syndromes or thrombophilias. These have been recognized to cause venous thrombosis, and include hereditary deficiencies of coagulation factors, genetic mutations, or acquired disorders. However, the majority of coagulation disorders are only rarely associated with ischemic stroke. The tests most commonly used to screen for thrombophilias comprise a complex array of assays that may be unreliable in various settings, including acute thrombosis, inflammation, and uses of medications such as anticoagulants. The diagnostic yield of thrombophilia tests in unselected stroke patients is very low, but may improve with careful selection of younger patients who have an otherwise undetermined cause of stroke or a history of venous thrombosis or multiple miscarriages. Various strategies have been developed that can guide the selection of patients (based on specific characteristics) and tests in the evaluation of thrombophilias. Although the diagnosis of thrombophilia aids in the potential explanation of stroke etiology, the best regimen for secondary prevention treatment for the majority of thrombophilias is still unknown.

The increasing impact of laboratory medicine on clinical cardiology

The practice of cardiology continues to evolve along with a better understanding of the pathophysiology of cardiovascular disease and the development of new therapeutic procedures. Consequently, new demands are being made on the in vitro diagnostics industry to improve the performance of existing cardiac markers and to develop novel markers for new cardiac disease indications. Indeed, in the last 20 years there has been a progressive increase in new laboratory tests for markers of cardiac diseases. Several highly sensitive and/or specific assays for the detection of myocardial ischemic damage as well as some immunoassays for cardiac natriuretic hormones, now considered a reliable marker of myocardial function, have become commercially available. In parallel, a growing number of some novel risk factors, which can be assessed and monitored by laboratory methods, have been added to the classical risk factors for cardiovascular disease. Finally, the recent explosion of genetic analysis may soon place at the clinical cardiologist's disposal many laboratory tests for defining the diagnosis at the molecular level, assessing new risk factors, and better targeting the pharmaceutical approaches in patients with cardiovascular disease. In the present article, after a brief description of the analytical tests included in these four groups, each group's impact on clinical cardiology is discussed in detail.

Fibrinolytic function and atrial fibrillation

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia, which is associated with a substantial risk of stroke and thromboembolism. A prothrombotic or hypercoagulable state has been observed in these patients, although previous studies have mainly focused on various clotting factors, endothelial damage or dysfunction markers and platelet activation. However, fibrinolytic function has been less frequently studied, despite the fibrinolytic system playing an important role in preventing intravascular thrombosis. Indeed, increasing evidence suggests that an imbalance between the fibrinolytic function is of great importance in cardiovascular disease. This review will begin by providing a brief approach to fibrinolytic function and examine previous studies about fibrinolytic activity and atrial fibrillation.

Lipoprotein(a): an emerging cardiovascular risk factor

Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.

Apolipoprotein E polymorphism and atherosclerosis

The relationship between apolipoprotein (apo) E and vascular disease has been the subject of a considerable amount of research. However, this relationship is far from clearly defined. This deficiency appears to be due to a multitude of factors. Among these are differences in ethnicity, age (and possibly gender), diagnostic criteria, and environmental factors (eg, diet and smoking) that have contributed to the contradictory findings. Several diseases and their treatment may also influence this relationship. There are also documented interactions between apo E genotypes and other genes or vascular risk factors. One possible clinically relevant application of identifying the apo E genotype could be to assess the response to a particular drug treatment. It may also be that apo E polymorphism will become a good predictor of vascular death (eg, from myocardial infarction or stroke) rather than an indicator of the risk of developing vascular disease but without an acute ischemic event. More research is required to define the place of apo E genotyping in the management of vascular disease in its various forms. Whatever the future brings, the evaluation of apo E genotypes will need to be rapid, cheap, and technically undemanding before this investigation becomes widely available and clinically relevant.

Antiphospholipid antibodies are common in patients referred for percutaneous patent foramen ovale closure

Very little is known about any interaction between patent foramen ovale (PFO) and various hypercoagulable disorders that have been associated with cryptogenic stroke. Percutaneous PFO closure for secondary prevention of paradoxical thromboembolization is receiving increasing attention. Hypercoagulability may affect the potential risks and expected benefits of percutaneous PFO closure. Consecutive patients undergoing percutaneous PFO closure at a single center were screened for the presence of antiphospholipid antibodies, elevated lipoprotein(a), hyperhomocysteinemia, and dysfibrinogenemia. Sixteen of 34 patients (47%) with complete arterial hypercoagulability screening had laboratory evidence of arterial hypercoagulability. Thirteen of these patients (38%) had antiphospholipid antibodies. Antiphospholipid antibodies appear to be common in patients referred for percutaneous PFO closure for secondary prevention of systemic thromboembolic events. Thorough testing based on established recommendations is warranted. Further studies are needed regarding the interaction between PFO and various hypercoagulable disorders that have been associated with cryptogenic stroke.

Prospective assessment of risk factors for recurrent stroke during childhood--a 5-year follow-up study

BACKGROUND

Risk factors for arterial stroke in children include congenital heart malformations, vasculopathies, infectious diseases, collagen tissue diseases, and metabolic disorders. Results of previous case-control studies have shown an association between ischaemic stroke and hereditary prothrombotic risk factors: factor V G1691A and factor II G20210A mutations, raised lipoprotein (a), and deficiencies in antithrombin, protein C, and protein S. The relevance of these factors to a second ischaemic stroke event is not known.

METHODS

We assessed the risk of a second arterial ischaemic stroke associated with these prothrombotic risk factors, with underlying diseases or stroke comorbidities, and with stroke subtypes (cardiac, vascular, infectious, idiopathic). 167 boys and 134 girls aged between 6 months and 18 years of age (median 7 years) with a first episode of ischaemic stroke were followed-up prospectively for a median of 44 months (range 20-56).

FINDINGS

Recurrent ischaemic stroke was diagnosed in 20 of 301 children who survived (6.6%) at a median of 5 months (range 1.5-36) after first stroke onset. The relative risk of having a second stroke was significantly increased in patients with raised lipoprotein (a) (relative risk 4.4, 95% CI 1.9-10.5) and in children with familial protein C deficiency (3.5, 1.1-10.9). Additionally, survival analysis showed that a first ischaemic stroke of vascular origin was significantly associated with having a second stroke (odds ratio 3.9, 95% CI 1.4-10.6).

INTERPRETATION

Raised lipoprotein (a), protein C deficiency, and stroke of vascular origin are risk factors for recurrent arterial ischaemic stroke in childhood.

Risk factors for cryptogenic ischaemic stroke

This case-control study was designed to identify risk factors for cryptogenic brain infarction. We assessed the frequency of prothrombotic states, homocysteine, lipoprotein (a) [Lp(a)] and other lipids and the apolipoprotein E phenotype together with conventional risk factors in 46 patients (19 women and 27 men) with cryptogenic brain infarction aged from 15 to 60 years and in 104 community-based controls. Multivariate odds ratios (ORs) for risk factors and 95% CIs were calculated by logistic regression. Hypertension (OR 4.5; 95% CI, 1.5-13.2; P = 0.006), current smoking (OR 2.9; 95% CI, 1.2-6.8; P = 0.012), low HDL cholesterol (HDL-C) (OR 5.4; 95% CI, 1.1-25.5; P = 0.035) and high clotting factor VIII activity (OR 3.6; 95% CI, 1.1-12.2; P = 0.041) were variables associated with cryptogenic brain infarction. These risk factors were not equally frequent in women and men. Low HDL-C and high factor VIII activity in the women, and hypertension, current smoking and a low level of plasma folate in the men were risk factors for cryptogenic stroke. Several of the observed risk factors for cryptogenic brain infarction were lifestyle-associated, which emphasizes the role of health education in addition to pharmacological treatment in the prevention of stroke.

Statins and renal function

Renal disease is often associated with an increased risk of vascular events. Moreover, an accelerated form of atherosclerosis commonly occurs in these patients. The reasons for these associations are not clearly defined but include the widespread presence of several established risk factors (eg, dyslipidemia, hypertension, and diabetes). Other predictors of atherosclerotic disease may also be abnormally elevated (eg, homocysteine, fibrinogen, and lipoprotein a). In addition, there is evidence that impaired renal function per se predicts vascular risk. Despite this high-risk background, the potential benefit of treatment with statins has not been widely investigated in these patients. The present review considers the evidence (experimental and clinical) that statins exert beneficial effects in patients with different types of renal disease. This includes improved renal function, decreased microalbuminuria, and a fall in blood pressure. Statins may also improve renal allograft survival. The potential mechanisms mediating these effects are considered. The interactions between statins and several risk factors that may be present in patients with impaired renal function are also considered. There is an urgent need to define the role of statins in these high-risk patients. Which is the statin of choice? This question is relevant because impaired renal function can interfere with statin pharmacokinetics. Furthermore, other drugs administered to these patients may cause serious interactions with statins.

Lipoprotein (a) does not participate in the early acute phase response to training or extreme physical activity and is unlikely to enhance any associated immediate cardiovascular risk

AIMS

To investigate the proposal that lipoprotein (a) (Lp(a)) contributes to the acute phase response and thus possibly to the acute cardiac risks associated with major physical effort.

METHODS/RESULTS

Fit, healthy, British army recruits were reviewed at the beginning and the end of a 10 week programme of basic training concluding with an intense 48 hour military exercise. Final recruit assessment was staggered over the last week of training, giving rise to six recruit groups, with determination of Lp(a), C reactive protein (CRP), fibrinogen, albumin, and total creatine kinase values from 12 hours to five days after the final exercise. A clear acute phase response was seen following the final exercise, marked by a significant increase in circulating concentrations of fibrinogen and a reduction of albumin, and a trend with non-significant increases in CRP.

CONCLUSION

Lp(a) did not behave as an early marker of the acute response. Previous reports may have been confounded by concurrent disease in older subjects and by late sampling. Lp(a) determination for cardiovascular risk profiling is not confounded by associated physical effort. It is also unlikely that the acute risks of major physical effort are enhanced by any process involving Lp(a).

Relation of Apo(a) size to carotid atherosclerosis in an elderly multiethnic population

Lipoprotein(a) [Lp(a)] is a novel risk factor for atherosclerosis, whose role in multiracial populations has been debated. We recently demonstrated a significant association of elevated levels of Lp(a) carried in particles containing small apolipoprotein(a) [apo(a)] isoforms with coronary artery disease in African American and white men. To extend these findings, we investigated the associations between Lp(a) levels, apo(a) size, and maximum internal carotid artery plaque thickness (MPT) in a randomly selected elderly multiethnic population (173 men and 253 women, consisting of 135 African Americans, 146 Hispanics, and 145 whites; mean age 70.5+/-11.4 years). Lp(a) levels were not associated with MPT. Among white men, MPT was associated with a small apo(a) isoform size (P=0.03) as well as with the amount of Lp(a) carrying the small apo(a) size (P=0.04), and the latter showed a borderline association in African American men (P=0.07). Among white women, but not in Hispanic or African American women, MPT was associated with the amount of Lp(a) carrying a small apo(a) isoform size (P<0.01). For all patients, the amount of Lp(a) carrying the small apo(a) size was associated with carotid atherosclerosis when there was control for age, sex, ethnicity, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, diabetes mellitus, hypertension, waist-to-hip ratio, and current smoking status (P=0.03). This association was significant for all men (P=0.03) and for white women (P=0.007). The results suggest that molecular properties of apo(a) are important in determining the atherogenicity of Lp(a).