Lp(a) lipoprotein is a major risk factor for cardiovascular disease: pathogenic mechanisms and clinical significance

Review of Isoflavones and Their Potential Clinical Impacts on Cardiovascular and Bone Metabolism Markers in Peritoneal Dialysis Patients

Cardiovascular disease is the most important cause of mortality in patients with chronic kidney disease, including patients undergoing peritoneal dialysis. Oxidative stress, systemic and vascular inflammation, and lipid abnormalities are important causes of cardiovascular disease in these patients. Bone disorders are also a common complication in dialysis patients and can lead to bone fractures, decreased quality of life, vascular calcification, cardiovascular disease, and increased mortality. Studies in non-uremic populations have shown that soy isoflavones have beneficial effects on oxidative stress, inflammation, lipid abnormalities, and markers of bone metabolism; however, very few studies in this field have been conducted with peritoneal dialysis patients. This paper reviews the key data regarding the effects of soy isoflavones on cardiovascular disease and bone markers and discusses the role of this nutraceutical in preventing and managing the complications of peritoneal dialysis.

A Case-Control Study of the Relationship Between SLC22A3-LPAL2-LPA Gene Cluster Polymorphism and Coronary Artery Disease in the Han Chinese Population

Background

Mutations in the solute carrier family 22 member 3 (SLC22A3), lipoprotein (a)-like 2 (LPAL2), and the lipoprotein (a) (LPA) gene cluster, which encodes apolipoprotein (a) [apo (a)] of the lipoprotein (a) [Lp (a)] lipoprotein particle, have been suggested to contribute to the risk of coronary artery disease (CAD), but the precise variants of this gene cluster have not yet been identified in Chinese populations.

Objectives

We sought to investigate the association between SLC22A3-LPAL2-LPA gene cluster polymorphisms and the risk of CAD in the Han Chinese population.

Patients and Methods

We recruited 551 CAD patients and 544 healthy controls for this case-control study. Four SNPs (rs9346816, rs2221750, rs3127596, and rs9364559) were genotyped in real time using the MassARRAY system (Sequenom; USA) in the SLC22A3-LPAL2-LPA gene cluster. All subjects were Chinese and of Han descent, and were recruited from the First Hospital of Jilin University based on convenience sampling from June 2009 to September 2012.

Results

The frequency of the minor allele G (34.8%) in rs9364559 was significantly higher in the CAD patients than in the healthy controls (29.4%) (P = 0.006). There was genotypic association between rs9364559 and CAD (P = 0.022), and these results still remained significant after adjustment for the conventional CAD risk factors through forward logistic regression analysis (P = 0.020, P = 0.019). Haplotype analyses from different blocks indicated that 11 haplotypes were associated with the risk of CAD. Seven haplotypes were associated with a reduced risk of CAD, whereas four haplotypes were associated with an increased risk of CAD.

Conclusions

Rs9364559 in the LPA gene may contribute to the risk of CAD in the Han Chinese population; haplotypes which contain rs9346816-G were all associated with an increased risk of CAD in this study.

Effects of Ginger on Serum Lipids and Lipoproteins in Peritoneal Dialysis Patients: A Randomized Controlled Trial

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BACKGROUND

In peritoneal dialysis (PD) patients, one of the major risk factors for cardiovascular disease is lipid abnormalities. This study was designed to investigate the effects of ginger supplementation on serum lipids and lipoproteins in PD patients. ♦

METHODS

In this randomized, double-blind, placebo-controlled trial, 36 PD patients were randomly assigned to either the ginger or the placebo group. The patients in the ginger group received 1,000 mg ginger daily for 10 weeks, while the placebo group received corresponding placebos. At baseline and at the end of week 10, 7 mL of blood were obtained from each patient after a 12- to 14-hour fast, and serum concentrations of triglyceride, total cholesterol, low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), and lipoprotein (a) [Lp (a)] were measured. ♦

RESULTS

Serum triglyceride concentration decreased significantly up to 15% in the ginger group at the end of week 10 compared with baseline (p < 0.01), and the reduction was significant in comparison with the placebo group (p < 0.05). There were no significant differences between the 2 groups in mean changes of serum total cholesterol, LDL-C, HDL-C, and Lp (a). ♦

CONCLUSION

This study indicates that daily administration of 1,000 mg ginger reduces serum triglyceride concentration, which is a risk factor for cardiovascular disease, in PD patients.

The association between the LPA gene polymorphism and coronary artery disease in Chinese Han population

Lp(a) has been well known as an independent risk factor for coronary artery disease (CAD). The LPA gene, as it encodes apo(a) of the Lp(a) lipoprotein particle, was associated with increased risk of CAD. The purpose of this study was to analyze the relationship between the polymorphisms of LPA gene and CAD in Chinese Han population. Five SNPs (rs1367211, rs3127596, rs6415085, rs9347438, and rs9364559) in the LPA gene were genotyped using Sequenom MassARRAY time-of-flight mass spectrometer (TOF) in 560 CAD patients as case group and 531 non-CAD subjects as control group. The numbers of these two groups were from Chinese Han ancestry. The results showed that allele (P = 0.046) and genotype (P = 0.026) of rs9364559 in the LPA gene was associated with CAD. The frequency of rs9364559 minor allele (G) in case group was obviously higher than that in control group. Results of haplotype analysis showed that 4 haplotypes which contained rs9364559-G were associated with increased risk of CAD in this population. This study explored rs9364559 in the LPA gene may be associated with the pathogenesis of CAD; and the risk of CAD might be higher in the population carrying 4 haplotypes of different blocks in the LPA gene.

Lack of association between four SNPs in the SLC22A3-LPAL2-LPA gene cluster and coronary artery disease in a Chinese Han population: a case control study

Background

Lipoprotein (a) (Lp [a]) is known being correlated with coronary artery disease (CAD). The SLC22A3-LPAL2-LPA gene cluster, relating with modulating the level of plasma Lp (a), has recently been reported to be associated with CAD in Caucasians. The purpose of this study was to verify whether this finding can be expanded to the Chinese Han population.

Methods and Results

Using a Chinese Han sample, which consisted of 1012 well-characterized CAD patients and 889 healthy controls, we tested the associations of four SNPs (rs2048327, rs3127599, rs7767084 and rs10755578) in the SLC22A3-LPAL2-LPA gene cluster, and their inferred haplotypes with the risk of CAD. Allelic, genotypic and haplotype association analyses all showed that the gene cluster was not associated with CAD in this Chinese Han sample.

Conclusions

We for the first time explored the association of the four SNPs in the SLC22A3-LPAL2-LPA gene cluster with CAD in a large Chinese Han sample. Nevertheless, this study did not reveal any significant evidence of this gene cluster to increase the risk of CAD in this population.

'Maintaining balance and harmony': Javanese perceptions of health and cardiovascular disease

Community intervention programmes to reduce cardiovascular disease (CVD) risk factors within urban communities in developing countries are rare. One possible explanation is the difficulty of designing an intervention that corresponds to the local context and culture.

OBJECTIVES

To understand people's perceptions of health and CVD, and how people prevent CVD in an urban setting in Yogyakarta, Indonesia.

METHODS

A qualitative study was performed through focus group discussions and individual research interviews. Participants were selected purposively in terms of socio-economic status (SES), lay people, community leaders and government officers. Data were analysed by using content analysis.

RESULTS

SEVEN CATEGORIES WERE IDENTIFIED: (1) heart disease is dangerous, (2) the cause of heart disease, (3) men have no time for health, (4) women are caretakers for health, (5) different information-seeking patterns, (6) the role of community leaders and (7) patterns of lay people's action. Each category consists of sub-categories according to the SES of participants. The main theme that emerged was one of balance and harmony, indicating the necessity of assuring a balance between 'good' and 'bad' habits.

CONCLUSIONS

The basic concepts of balance and harmony, which differ between low and high SES groups, must be understood when tailoring community interventions to reduce CVD risk factors.

Lipoprotein (a) as an acute phase reactant in patients on chronic hemodialysis

Lipoprotein (a) [Lp(a)], is an independent risk factor for atherosclerotic cardiovascular disease in patients on chronic hemodialysis. A low concentration of high density lipoprotein cholesterol (HDL-C) and serum albumin are another potential risk factors. The purpose of this study was to explore in patients on chronic hemodialysis, whether Lp(a) elevated levels are influenced by activated acute phase response (APR) and the correlation of Lp(a) with HDL-C and serum albumin. In 69 hemodialysis patients with C-reactive protein (CRP) levels over than 10 mg/L and 101 hemodialysis patients with CRP levels in the normal range, Lp(a), HDL-C and serum albumin were determined in relation to CRP, as a sensitive marker of an APR. Results showed that serum concentration of CRP in 69 hemodialysis patients was significantly higher than in controls (44,62 mg/L versus 8,75 mg/L, p<0,01).Patients with elevated CRP had significantly higher serum levels of Lp(a) and lower serum levels of HDL-C and albumin, than patients with CRP in the normal range ( 35,39 mg/dl versus 28,6 mg/dl, p<0,01, 0,91 mmol/L versus 1,29 mmol/L, p<0,01 and 33,56 g/L versus 35,86 g/L, p<0,01). Lp(a) levels correlated positively with CRP and negatively with HDL-C and serum albumin, in patients with elevated CRP, but not in healthy controls. According to the results Lp(a) reacts as an acute phase protein, in patients with APR.

Effects of Soy Consumption on Serum Lipids and Apoproteins in Peritoneal Dialysis Patients: A Randomized Controlled Trial

Background

Lipid abnormalities, particularly high serum concentration of lipoprotein(a) [Lp(a)], are one of the major risk factors for cardiovascular disease (CVD) in peritoneal dialysis (PD) patients. The present study was designed to investigate the effects of soy consumption on serum lipids and apoproteins, especially Lp(a), in PD patients.

Methods

This study was a randomized clinical trial in which 40 PD patients (20 males, 20 females) were randomly assigned to either the soy or the control group. Patients in the soy group received 28 g/day textured soy flour (containing 14 g of soy protein) for 8 weeks, whereas patients in the control group received their usual diet, without any soy. At baseline and the end of week 8 of the study, 5 mL of blood was collected from each patient after a 12- to 14-hour fast and serum triglyceride, total cholesterol, low density lipoprotein-cholesterol (LDL-C), high density lipoprote-incholesterol (HDL-C), apoprotein B100 (apo B100), apoprotein AI (apo AI), and Lp(a) were measured.

Results

In the present study, serum Lp(a) concentrations were above the normal range in 86% of the PD patients. Mean serum Lp(a) concentration was reduced significantly, by 41%, in the soy group at the end of week 8 compared to baseline ( p < 0.01); the reduction was also significant compared to the control group ( p < 0.05). During the study, mean serum Lp(a) concentration did not change significantly in the control group. There were no significant differences between the two groups in mean changes in serum triglyceride, total cholesterol, HDL-C, LDL-C, apo B100, or apoAI.

Conclusion

The results of our study indicate that soy consumption reduces serum Lp(a) concentration, which is a risk factor for cardiovascular disease in peritoneal dialysis patients.

Ethnicity and peripheral artery disease

Peripheral arterial disease (PAD) is an important healthcare problem and is an indicator of widespread atherosclerosis in other vascular territories, such as the cerebral and coronary circulations. PAD is associated with considerable morbidity and mortality. Most population-based studies investigating PAD prevalence and risk factors for its development and progression have been based on predominantly White ethnic groups. Much less is known about the characteristics of this disease in other ethnic groups. Understanding the epidemiology of PAD amongst ethnic minority groups is relevant, given that the population of minority ethnic groups in countries such as the United Kingdom rose by 53% between 1991 and 2001 and is expected to rise further in the future. This article aims to provide an overview of possible pathophysiological differences between ethnic groups for PAD, focussing predominantly on South Asians (people originating from India, Bangladesh and Pakistan) and Blacks (people of Black Caribbean and Black African descent) as these groups comprise the majority of all ethnic minorities in the United Kingdom.

Raloxifene has favourable effects on metabolic parameters but has no effect on left ventricular function in postmenopausal women

In this prospective randomized study, we investigated the effect of raloxifene on the echocardiographic parameters of left ventricular diastolic and systolic function and on blood levels of lipids, homocysteine, and lipoprotein (a) in postmenopausal osteoporotic patients and compared the results with those treated with risedronate. A total of 44 women were included in the study. Patients were randomized into two groups. Twenty-two patients received raloxifene 60 mg/day (group 1), and 22 patients received risedronate 5mg/day (group 2; the control group). All patients underwent quantitative two-dimensional pulsed wave Doppler and tissue Doppler echocardiography. Levels of fasting total-C, HDL-C, LDL-C, triglycerides, homocysteine, and lipoprotein (a) were measured. All echocardiographic and biochemical parameters were assessed at the beginning of the study and after the 6-month follow-up. Demographic characteristics and baseline metabolic and echocardiographic parameters were similar in the two groups. After 6 months of the therapy, serum levels of total-C, LDL-C, and homocysteine decreased significantly (P=.04, P=.02, P=.008, respectively) in the treated group when compared with the control group. All echocardiographic measurements except a wave from level of basal interventricular septum were similar in the two groups both before and after 6 month of therapy. In the control group, a wave from level of basal interventricular septum increased significantly (P=.019). In conclusions raloxifene may decrease serum levels of total-C, LDL-C, and homocysteine in postmenopausal osteoporotic patients and raloxifene therapy seems to have no significant effect on left ventricular systolic and diastolic function.

Ethnicity and cardiovascular disease prevention in the United Kingdom: a practical approach to management

The United Kingdom is a diverse society with 7.9% of the population from black and minority ethnic groups (BMEGs). The causes of the excess cardiovascular disease (CVD) and stroke morbidity and mortality in BMEGs are incompletely understood though socio-economic factors are important. However, the role of classical cardiovascular (CV) risk factors is clearly important despite the patterns of these risk factors varying significantly by ethnic group. Despite the major burden of CVD and stroke among BMEGs in the UK, the majority of the evidence on the management of such conditions has been based on predominantly white European populations. Moreover, the CV epidemiology of African Americans does not represent well the morbidity and mortality experience seen in black Africans and black Caribbeans, both in Britain and in their native African countries. In particular, atherosclerotic disease and coronary heart disease are still relatively rare in the latter groups. This is unlike the South Asian diaspora, who have prevalence rates of CVD in epidemic proportions both in the diaspora and on the subcontinent. As the BMEGs have been under-represented in research, a multitude of guidelines exists for the 'general population.' However, specific reference and recommendation on primary and secondary prevention guidelines in relation to ethnic groups is extremely limited. This document provides an overview of ethnicity and CVD in the United Kingdom, with management recommendations based on a roundtable discussion of a multidisciplinary ethnicity and CVD consensus group, all of whom have an academic interest and clinical practice in a multiethnic community.

Arginyl-glycyl-aspartyl (RGD) epitope of human apolipoprotein (a) inhibits platelet aggregation by antagonizing the IIb subunit of the fibrinogen (GPIIb/IIIa) receptor

An unknown epitope of apolipoprotein (a) antagonizes fibrinogen binding to agonist-stimulated platelet's fibrinogen (GPIIb/IIIa) receptor yielding lipoprotein (a) mediated decreased platelet aggregation. The purpose of this study was to test the hypothesis that human apolipoprotein (a)'s single arginyl-glycyl-aspartyl (RGD) epitope, unique to apolipoprotein (a) in lipoprotein (a) binds to the RGD binding motif on the IIb subunit of the GPIIb/IIIa receptor thus reducing platelet-bound fibrinogen and consequently decreasing agonist-stimulated platelet aggregation. Platelets (N=30 subjects) were prepared from fresh plasma, washed three times in Tyrode's buffer and stimulated using 10 microM ADP or 2 microg/ml collagen. Lipoprotein (a) was isolated from plasma using lectin affinity chromatography followed by ultracentrifugation. The peptide RGDS inhibited (125)I-labelled lipoprotein (a) binding to autologous platelets with IC-50's of 25.1+/-2.2 (mean+/-SEM) and 15.4+/-1.3 microM for collagen- and ADP-stimulation respectively. Further, RGDS reduced platelet binding of (125)I-labelled fibrinogen IC-50's of 35.5+/-3.2 (mean+/-SEM) and 20.7+/-2.2 microM for collagen- and ADP-stimulation respectively. The monoclonal antibody PAC-1, uniquely directed at the RGD binding motif on the IIb subunit on collagen- and ADP-stimulated platelets, inhibited binding of (125)I-labelled lipoprotein (a) with IC-50's of 6.4+/-0.7 and 2.5+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. Additionally, PAC-1 reduced platelet bound of (125)I-labelled fibrinogen with IC-50's of 9.0+/-1.4 and 4.1+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. In a dose-related fashion, a polyclonal antibody, specific for the RGD epitope on apolipoprotein (a), restored platelet aggregation to control levels, inhibited (125)I-labelled lipoprotein (a) binding, and increased (125)I-labelled fibrinogen by displacing lipoprotein (a) from the GPIIb/IIIa receptor. Thus a never before demonstrated aspect of the mechanism of lipoprotein (a)'s suggested novel role as an endogenous regulator of fibrinogen binding to collagen- and ADP-stimulated platelets has been shown. In conclusion, lipoprotein (a), via apolipoprotein (a)'s RGD epitope, binds to the RGD binding motif on the IIb protein of the GPIIb/IIIa receptor consequently reducing platelet-bound fibrinogen which results in decreased platelet aggregation.

Quo vadis haemapheresis. Current developments in haemapheresis

The techniques of haemapheresis originated in the development of centrifugal devices separating cells from plasma and later on plasma from cells. Subsequently membrane filtration was developed allowing for plasma-cell separation. The unspecificity of therapeutic plasma exchange led to the development of secondary plasma separation technologies being specific, semi-selective or selective such as adsorption, filtration or precipitation. In contrast on-line differential separation of cells is still under development. Whereas erythrocytapheresis, granulocytapheresis, lymphocytapheresis and stem cell apheresis are technically advanced, monocytapheresis may need further improvement. Also, indications such as erythrocytapheresis for the treatment of polycythaemia vera or photopheresis though being clinically effective and of considerable importance for an appropriate disease control are to some extent under debate as being either too costly or without sufficient understanding of the mechanism. Other forms of cell therapy are under development. Rheohaemapheresis as the most advanced technology of extracorporeal haemorheotherapy is a rapidly developing approach contributing to the treatment of microcirculatory diseases and tissue repair. Whereas the control of a considerable number of (auto-) antibody mediated diseases is beyond discussion, the indication of apheresis therapy for immune complex mediated diseases is quite often still under debate. Detoxification for artificial liver support advanced considerably during the last years, whereas conclusions on the efficacy of septicaemia treatment are debatable indeed. LDL-apheresis initiated in 1981 as immune apheresis is well established since 24 years, other semi-selective or unspecific procedures, allowing for the elimination of LDL-cholesterol among other plasma components are also being used. Correspondingly Lp(a) apheresis is available as a specific, highly efficient elimination procedure superior to techniques which also eliminate Lp(a). Quality control systems, more economical technologies as for instance by increasing automation, influencing the over-interpretation of evidence based medicine especially in patients with rare diseases without treatment alternative, more insight into the need of controlled clinical trials or alternatively improved diagnostic procedures are among others tools ways to expand the application of haemapheresis so far applied in cardiology, dermatology, haematology, immunology, nephrology, neurology, ophthalmology, otology, paediatrics, rheumatology, surgery and transfusion medicine.

Cardiovascular effects of raloxifene: the arterial and venous systems

BACKGROUND

Cardiovascular disease caused by atherosclerosis is the largest single killer of women. Prior observational data had suggested that hormone therapy may have cardioprotective effects.

METHODS

Data from clinical trials and basic science studies were evaluated to assess the cardiovascular effects of hormone therapy and selective estrogen replacement modulators.

RESULTS

Hormone therapy does not appear to lower the risk of cardiovascular events in older postmenopausal women. Selective estrogen receptor modulators (SERMS) have been approved for human use; tamoxifen is used for treatment and prevention of breast cancer and raloxifene is used for the treatment and prevention of osteoporosis. Raloxifene is the only SERM being specifically studied for its effects on coronary heart disease events in a prospective, randomized, controlled trial.

CONCLUSIONS

Although raloxifene does increase venous thromboembolic events, there is suggestive data that it may have favorable effects on the arterial systems in women. Only compelling positive data from the Raloxifene Use for The Heart (RUTH) trial will lead to greater use of SERMS to potentially lower the risk of atherosclerotic vascular disease.

A more detailed fatty acid composition of human lipoprotein(a)--a comparison with low density lipoprotein

Lipoprotein(a)'s (Lp(a)'s) fatty acid composition is partially known for the cholesteryl ester (CE), triglyceride (TG) and total phospholipid (PL) fractions. Individual PLs' fatty acids are unknown. This study sought to confirm and extend existing data and elucidate the individual PLs of Lp(a). For Lp(a) versus LDL, the mole percentage saturated fatty acids comprised 11.3+/-1.3 versus 16.8+/-1.2 (CE) (P<0.05), 43.4+/-5.2 versus 39.2+/-4.0 (TG) (P<0.05), 55.7+/-6.3 versus 54.7+/-5.9 (PL) (P>0.05), 51.9+/-3.5 versus 50.2+/-4.2 (choline-containing phospholipids (PC)) (P>0.05), 40.2+/-4.6 versus 43.1+/-3.9 (ethanolamine-containing phospholipids (PE)) (P>0.05), 73.2+/-7.6 versus 81.2+/-8.2 (sphingomyelin (SPH)) (P<0.05). Linoleic acid was CE's major fatty acid and while palmitic acid was the major fatty acid in all other fractions except PE.

Functional approach to investigate Lp(a) in ischaemic heart and cerebral diseases

BACKGROUND

Lp(a), a major cardiovascular risk factor, contains a specific apolipoprotein, apo(a), which by virtue of structural homology with plasminogen inhibits the formation of plasmin, the fibrinolytic enzyme. A number of clinical reports support the role of Lp(a) as a cardiovascular or cerebral risk factor, and experimental data suggest that it may contribute to atherothrombosis by inhibiting fibrinolysis.

DESIGN

A well-characterized model of a fibrin surface and an apo(a)-specific monoclonal antibody were used to develop a functional approach to detect pathogenic Lp(a). The assay is based on the competitive binding of Lp(a) and plasminogen for fibrin, and quantifies fibrin-bound Lp(a). High Lp(a) binding to fibrin is correlated with decreased plasmin formation. In a transversal case-control study we studied 248 individuals: 105 had a history of ischaemic cardiopathy (IC), 52 had cerebro-vascular disease (CVD) of thrombotic origin, and 91 were controls.

RESULTS

The remarkably high apo(a) fibrin-binding in CVD (0.268 +/- 0.15 nmol L-1) compared with IC (0.155 +/- 0.12 nmol L-1) suggests the existence of peculiar and poorly understood differences in pro- or anti-thrombotic mechanisms in either cerebral and/or coronary arteries.

CONCLUSIONS

Our results demonstrated that Lp(a) fibrin-binding and small Apo(a) isoforms are associated with athero-thrombotic disease.

Lipoprotein(a) in American Indians is low and not independently associated with cardiovascular disease. The Strong Heart Study

PURPOSE

To evaluate the distribution of lipoprotein(a) (Lp(a)) and assess its association to cardiovascular disease (CVD) in American Indians.

METHODS

Lp(a) was measured in 3991 American Indians (aged 45-74 years with no prior history of CVD at baseline) from 13 communities in Arizona, Oklahoma, and South/North Dakota. They were followed prospectively from 1989 to 1997 for CVD. The distribution of Lp(a) was examined by center, sex, and diabetic status. Spearman correlation coefficients and Cox regression models were used to evaluate the association of Lp(a) to CVD.

RESULTS

A total of 388 participants subsequently developed CVD. Median Lp(a) concentration in American Indians was 3.0 mg/dl. This was almost half of that in whites and one sixth in blacks from the CARDIA study measured by the same method. Nondiabetic participants had significantly higher Lp(a) levels than diabetic participants for both genders. Lp(a) levels were higher in women than in men for nondiabetic participants, but there was no gender difference for diabetic participants. Correlation analysis showed Lp(a) was significantly negatively correlated with the degree of Indian heritage, insulin, triglycerides (TG), fasting plasma glucose (FPG), and 2-hour plasma glucose (2hPG), and positively with low-density lipoproteins (LDL), apoprotein B (apoB), and fibrinogen (FIB). In Cox regression models, adjusting for other risk factors, Lp(a) was no longer a significant predictor of CVD in either diabetic or nondiabetic participants.

CONCLUSIONS

The lower concentration of Lp(a) in American Indians and the high correlation with Indian heritage confirm the concept that Lp(a) concentration is in large part genetically determined. Lp(a) concentration is not an independent predictor of CVD among American Indians; it is higher in those who develop CVD because of its positive correlation with LDL, apoB, and FIB.

Effects of raloxifene and hormone replacement therapy on markers of serum atherogenicity in healthy postmenopausal women

OBJECTIVE

To determine the effect of raloxifene (RLX) and hormone replacement therapy (HRT) on non-high density lipoprotein cholesterol (non-HDL-C) levels and the apolipoprotein-B/apolipoprotein-A1 (apo-B/apo-A1) concentration ratio, markers of serum atherogenicity, in postmenopausal women.

METHODS

Three hundred and ninety healthy postmenopausal women aged 45-72 years were enrolled in a double-blind, randomized, placebo-controlled, parallel trial at eight outpatient sites in the United States. Women were randomly assigned to receive continuous combined HRT (0.625 mg/day conjugated equine estrogen and 2.5 mg/day medroxyprogesterone acetate), 60 or 120 mg/day raloxifene, or placebo for 6 months. Serum concentrations of non-HDL cholesterol and the apo-B/apo-A1 concentration ratio were measured in serum samples obtained at baseline and at 6 months of treatment.

RESULTS

At 6 months, non-HDL-C and apo-B/apo-A1 were significantly reduced by 60 mg/day RLX (10 and 11%, respectively), 120 mg/day RLX (9 and 12%, respectively) and HRT (10 and 12%, respectively), compared with placebo. The effect of all treatments to lower non-HDL-C and apo-B/apo-A1 was greatest in women with hypercholesterolemia (total-C>240 mg/dl) at baseline. Among women with undesirable (>160 mg/dl) non-HDL cholesterol at baseline, RLX and HRT lowered the percentage of these women remaining above this threshold after 6 months (placebo, 89%; 60 mg/day RLX, 61%; 120 mg/day RLX, 74%; HRT, 58%). Similar results were observed for women with high (>190 mg/dl) non-HDL cholesterol at baseline.

CONCLUSION

In healthy postmenopausal women, RLX and HRT lower serum non-HDL-C and apo-B/apo-A1, indicators of serum atherogenicity, to a similar extent.

Lipoprotein(a) changes during natural menstrual cycle and ovarian stimulation with recombinant and highly purified urinary FSH

This prospective, randomized, controlled study compared the effects of recombinant human FSH (r-hFSH) and highly purified urinary FSH (u-hFSH HP) on lipoprotein(a) [Lp(a)] concentrations in women undergoing ovarian stimulation. Fifty infertile women were randomly allocated into two equally sized treatment groups (n = 25 per group). Thirty normal ovulation women were recruited as controls. The infertile women received u-hFSH or r-hFSH 150 IU/day starting on cycle day 2. From cycle day 6 the dose was adjusted according to ovarian response. Human chorionic gonadotrophin 10,000 IU was administered once there was at least one follicle > or =18 mm in diameter. The luteal phase was supported with progesterone 50 mg/day for at least 15 days. Repeated measurements of Lp(a) concentrations were performed during both stimulated and natural cycles. A significant increase in luteal phase Lp(a) concentrations was detected in the stimulated cycles, whereas no significant changes in serum Lp(a) concentrations were observed during natural cycles. There were no significant differences between the urinary and recombinant FSH effects on serum Lp(a). The luteal Lp(a) increase was transitory because after 1 month Lp(a) concentrations returned to baseline values if pregnancy failed to occur; in pregnant women persistent increased Lp(a) concentrations were found at the 8th week. The percentage changes in serum Lp(a) were positively correlated with the luteal progesterone increase (r = 0.40, P < 0.05), but not with follicular or luteal oestradiol increase. The women with low baseline Lp(a) (< or =5 mg/dl) had a greater increase of the Lp(a) concentrations at midluteal phase than women with baseline Lp(a) >5 mg/dl. In conclusion, the recombinant or urinary hFSH administration does not directly influence Lp(a) concentrations. The luteal Lp(a) increase in stimulated cycles is not related to gonadotrophin treatment per se, but appears to be related to the high luteal progesterone concentrations, physiologically or pharmacologically determined. Our results also suggest that the sensitivity to the progesterone changes could be related to apolipoprotein(a) phenotype.

Production and characterization of monoclonal antibodies directed to the kringle V and protease domains of human apolipoprotein(a)

Production and use of anti-apolipoprotein(a) monoclonal antibodies (MAbs) specific to single copy regions in the polymorphic lipoprotein(a) (Lp(a)) has been emphasized to be important for the standardization of measurements of the coronary heart disease risk factor, Lp(a). Here, mouse MAbs were prepared against the kringle V (V) and protease (P) domains of human apolipoprotein(a) (apo(a)), which domains are present in single copy in the apo(a) molecule. The cDNA for apo(a)VP was cloned from human liver cDNA library, and the V-P recombinant protein overexpressed in Escherichia coli was used as an antigen for the antibody production. Two antibodies named as MAb(a)20 and MAb(a)23 were finally produced, and they were characterized for their binding specificity and epitopes. The specificity of the antibodies was confirmed by an immunoblotting procedure and an enzyme-linked immunoassay (ELISA). It was shown that the antibodies had little, if any, cross-reactivity with human plasminogen, which is relatively abundant in human serum and is highly homologous (85%) with apo(a) in amino acid (aa) sequence. For epitope analysis, 3'-deletional series of apo(a)VP cDNA were constructed, and expression products of them were analyzed for the binding MAb(a)20 and MAb(a)23 do. It has been revealed that distinct epitopes were recognized by the two MAbs: MAb(a)23 (gamma2b, kappa) bound to the V region about 60 aa downstream from the N-terminal, and MAb(a)20 (gamma1, kappa) bound to the P region close to the C-terminal. A one step-sandwich ELISA system for Lp(a) was developed using MAb(a)20 as a capturing antibody and horseradish peroxidase (HRP)-coupled MAb(a)23 as a detecting antibody. The assay was found to be sensitive and useful for detecting Lp(a) in the range of 4-150 microg/dL (80 pM-3 nM).

Cardiovascular risk factors of migrants in Port Moresby from the highlands and island villages, Papua New Guinea

This study examined cardiovascular disease (CVD) risk factors, i.e., obesity, blood pressures, and serum lipoproteins and apoproteins, in relation to sociocultural characteristics in two rural-urban migrant populations (n = 173 adult males and females) in Port Moresby, the capital of Papua New Guinea. Tari migrants from the highlands and Balopa migrants from the islands differ genetically. More importantly, the lifestyle of the latter is more Westernized than that of the former in both Port Moresby and their homelands. The results demonstrate that CVD risk factors vary markedly among the origin/sex groups and that the length of stay in Port Moresby on CVD risk factors was significant only in Balopa males, most of whom had professional or skilled full-time jobs and were considered to have more stress. This study identified different CVD risk factors in the migrant groups: obesity or fatness for the Balopa migrants, and serum lipoproteins and apoproteins, particularly lipoprotein(a), for the Tari migrants. Am. J. Hum. Biol. 12:655-664, 2000. Copyright 2000 Wiley-Liss, Inc.

Lipoprotein Lp(a) and atherothrombotic disease

High plasma concentrations of lipoprotein (a) [Lp(a)] are now considered a major risk factor for atherosclerosis and cardiovascular disease. This effect of Lp(a) may be related to its composite structure, a plasminogen-like inactive serine-proteinase, apoprotein (a) [apo(a)], which is disulfide-linked to the apoprotein B100 of an atherogenic low-density lipoprotein (LDL) particle. Apo(a) contains, in addition to the protease region and a copy of kringle 5 of plasminogen, a variable number of copies of plasminogen-like kringle 4, giving rise to a series of isoforms. This structural homology endows Lp(a) with the capacity to bind to fibrin and to membrane proteins of endothelial cells and monocytes, and thereby inhibits binding of plasminogen and plasmin formation. This mechanism favors fibrin and cholesterol deposition at sites of vascular injury and impairs activation of transforming growth factor-beta (TGF-beta) that may result in migration and proliferation of smooth muscle cells into the vascular intima. It is currently accepted that this effect of Lp(a) is linked to its concentration in plasma, and an inverse relationship between apo(a) isoform size and Lp(a) concentrations that is under genetic control has been documented. Recently, it has been shown that inhibition of plasminogen binding to fibrin by apo(a) from homozygous subjects is also inversely associated with isoform size. These findings suggest that the structural polymorphism of apo(a) is not only inversely related to the plasma concentration of Lp(a), but also to a functional heterogeneity of apo(a) isoforms. Based on these pathophysiological findings, it can be proposed that the predictive value of Lp(a) as a risk factor for vascular occlusive disease in heterozygous subjects would depend on the relative concentration of the isoform with the highest affinity for fibrin.

Lp(a) and conventional risk profiles predict the severity of coronary stenosis in high-risk hospital-based patients

AIMS

To explore predictive power of Lp(a), of conventional lipoprotein profiles and their carrier proteins, and of biometric measurements, for the presence and severity of angiographically documented coronary disease in high-risk patients, and to compare risk profiles in men and women.

METHODS

We determined coronary artery disease (CAD) risk factors in 1308 Australian Caucasian patients (313 women and 995 men) aged < or =65 years who consecutively underwent coronary angiography.

RESULTS

In univariate analyses of the risk factors, lipid profiles, Lp(a), cigarette smoking, diabetes, hypertension and obesity were all higher in men and women with CAD and changed significantly with the number of significantly diseased vessels (> or =50% luminal obstruction). When stepwise logistic regression analysis was applied, age (OR 1.06, 95% CI: 1.04-1.09), TC/HDL-C (OR 1.29, 95% CI: 1.15-1.45), male gender (OR 2.64, 95% CI: 1.67-4.16), hyperLp(a) (> or =300 mg/L) (OR 2.09, 95% CI: 1.42-3.07), lifetime smoking dose (OR 1.02, 95% CI: 1.01-1.03), diabetes (OR 2.19, 95% CI: 1.14-4.18) and waist/hip ratio (OR 14.53, 95% CI: 1.21-174.90) were predictive of the disease. Both Lp(a) levels and percentage of hyperLp(a) increased linearly with the number of significantly diseased vessels. When the analyses were conducted in men and women separately, hyperLp(a), TC/HDL-C, lifetime smoking dose and age remained as significant predictors in both groups but the waist/hip ratio was only predictive in women.

CONCLUSIONS

As Lp(a) is an independent predictor of the occurrence and extent of coronary stenosis and relevant to treatment options, we suggest that it should be measured routinely in the coronary risk profile assessment of high-risk patients.

The Potential of SERMs for Reducing the Risk of Coronary Heart Disease

Selective estrogen receptor modulators (SERMs) represent a growing class of compounds that act as either estrogen receptor agonists or antagonists in a tissue-selective manner. Preclinical and clinical studies have shown that estrogen has favorable effects on serum lipids and might affect processes at the blood vessel wall to inhibit atherosclerosis. SERMs with the appropriate selectivity profile offer the opportunity to dissociate these favorable cardiovascular effects of estrogen from its unfavorable stimulatory effects on the breast and uterus. This article reviews the data from both animal and human studies that document the cardiovascular effects of SERMs and discusses the clinical implications of these results.

The relation between bone mineral density, insulin-like growth factor I, lipoprotein (a), body composition, and muscle strength in adolescent males

Osteoporosis is the most common metabolic bone disease. A low peak bone mass is regarded a risk factor for osteoporosis. Heredity, physical activity, and nutrition are regarded important measures for the observed variance in peak bone mass. Lp(a) lipoprotein is a well-known risk factor for atherosclerosis. Serum insulin-like growth factor I (IGF-I) has been found to be increased in males with early cardiovascular disease. In this study, we evaluated the association between bone mass, body constitution, muscle strength, Lp(a), and IGF-I in 47 Caucasian male adolescents (mean age, 16.9 yr). Bone mineral density (BMD) and body composition were measured by dual x-ray absorptiometry, muscle strength of thigh using an isokinetic dynamometer, IGF-I by RIA, and Lp(a) by enzyme-linked immunosorbent assay. IGF-I was only associated with Lp(a) (r = 0.38, P < 0.01). Lp(a) was related to total body (r = 0.40, P < 0.01), skull (r = 0.45, P < 0.01), and femoral neck BMD (r = 0.44, P < 0.01). Lp(a) was also related to fat mass (r = 0.34, P < 0.05) and muscle strength (r = 0.30-0.42, P < 0.05). After multiple regression and principal component (PC) analysis, the so-called PC body size (weight, fat mass, lean body mass, and muscle strength) was the most significant predictor of BMD (beta = 0.28-0.51, P < 0.05-0.01), followed by the so-called PC physical activity (beta = 0.28-0.38, P < 0.05-0.01, weight-bearing locations). However, the PC analysis confirmed that Lp(a) was an independent predictor of total body, skull, and femoral neck BMD (beta = 0.33-0.36, P < 0.01). The present investigation confirms that BMD, body size, and muscle strength are closely related and that the level of physical activity is a major determinant of BMD. However, the positive relation of Lp(a), a major risk factor for cardiovascular disease, to BMD has not previously been described. The importance of this observation has to be further investigated.

Lipoprotein(a), homocysteine, and remnantlike particles: emerging risk factors

Although lipoprotein(a) [Lp(a)] was first described more than 35 years ago, adequate prospective data have only recently supported Lp(a) as an independent risk factor for coronary heart disease (CHD). In vitro studies suggest that Lp(a) contributes to atherogenesis directly by cholesterol uptake and indirectly by the inhibition of fibrinolysis. In patients with CHD or a significant risk for CHD, Lp(a) should be measured and treated with either niacin or estrogen if the patient has Lp(a) cholesterol levels of more than 10 mg/dL or an Lp(a) mass of more than 30 mg/dL. In addition, homocysteine and remnantlike lipoprotein cholesterol are strongly supported by prospective or population-based prevalence data as independent risk factors for CHD. Homocysteine levels of more than 14 mumol/L should be treated with vitamin supplements of folate, B6, and B12. Remnantlike lipoprotein cholesterol is the product of a novel immunoassay that separates the partially hydrolyzed triglyceride-rich remnant particles. The association of these particles with CHD risk in women may explain the small independent CHD risk that triglycerides have in women in the Framingham Heart Study. A clear therapeutic intervention has not been documented but may include diet, fibric acid derivatives, or hydroxymethylglutamyl coenzyme A reductase inhibitors.

The atherogenic effects of chlamydia are dependent on serum cholesterol and specific to Chlamydia pneumoniae

Epidemiological investigations have linked Chlamydia pneumoniae infection to atherosclerosis. It is not clear, however, whether C. pneumoniae infection plays a causal role in the development of atherosclerosis. Mice with low-density lipoprotein receptor deficiency were induced to develop atherosclerotic lesions in aorta with a cholesterol-enriched diet that increased serum cholesterol by two- to threefold. Using this mouse model, we found that the chlamydial infection alone with either the C. pneumoniae AR39 or the C. trachomatis MoPn strain failed to induce any significant atherosclerotic lesions in aorta over a period of nine months. However, in the presence of a high-cholesterol diet, infection with the C. pneumoniae AR39 strain significantly exacerbated the hypercholesterolemia-induced atherosclerosis, demonstrating that a hypercholesterolemic condition is required for the C. pneumoniae to aggravate the development of atherosclerosis. Although both AR39 and MoPn antigens were detected in aorta of mice infected with the corresponding strains, only mice infected with the C. pneumoniae strain AR39 displayed enhanced atherosclerotic lesions, suggesting that the C. pneumoniae species may possess a unique atherogenic property. This study may provide a model for further understanding the mechanisms of C. pneumoniae atherogenesis and evaluating chlamydial intervention strategies for preventing the advancement of atherosclerotic lesions enhanced by C. pneumoniae infection.

Atherothrombogenicity of lipoprotein(a): the debate

Although lipoprotein(a) (Lp[a]) has been recognized as an atherothrombogenic factor, the underlying mechanisms for this pathogenicity have not been clearly defined. Plasma levels have received most of the attention in this regard; however, discrepancies among population studies have surfaced. Particularly limited is the information on the fate of Lp(a) that enters the arterial wall, in terms of mechanisms of endothelial transport and interactions with cells and macromolecules of the extracellular matrix. A typical Lp(a) represents a low-density lipoprotein (LDL)-like particle having as a protein moiety apo B-100 linked by a single interchain disulfide bond to a unique multikringle glycoprotein, called apolipoprotein(a) (apo[a]). In vitro studies have shown that Lp(a) can be dissected into its constituents, LDL and apo(a). In turn, the latter can be cleaved by enzymes of the elastase and metalloproteinase families into fragments that exhibit a differential behavior in terms of binding to macromolecules of the extracellular matrix: fibrinogen, fibronectin, and proteoglycans. By immunochemical criteria, apo(a) predominantly localizes in areas of human arteries affected by the atherosclerotic process, where elastase and metalloproteinase enzymes operate and where apo(a) fragments are potentially generated. The accumulation of these fragments in the vessel wall is likely to depend on their affinity for the constituents of the extracellular matrix. Thus, factors that modulate inflammation and inflammation-mediated fragmentation of Lp(a)/apo(a) may play an important role in the cardiovascular pathogenicity of Lp(a). This pathogenicity may be attenuated by measures directed at preventing the activation of those vascular cells that secrete enzymes with a proteolytic potential for Lp(a)/apo(a), namely, leukocytes, macrophages, and T cells.