Lipoprotein (a): structure, properties and possible involvement in thrombogenesis and atherogenesis

Lipoprotein(a): Just an Innocent Bystander in Arterial Hypertension?

Elevated plasma lipoprotein(a) [Lp(a)] is a relatively common and highly heritable trait conferring individuals time-dependent risk of developing atherosclerotic cardiovascular disease (CVD). Following its first description, Lp(a) triggered enormous scientific interest in the late 1980s, subsequently dampened in the mid-1990s by controversial findings of some prospective studies. It was only in the last decade that a large body of evidence has provided strong arguments for a causal and independent association between elevated Lp(a) levels and CVD, causing renewed interest in this lipoprotein as an emerging risk factor with a likely contribution to cardiovascular residual risk. Accordingly, the 2022 consensus statement of the European Atherosclerosis Society has suggested inclusion of Lp(a) measurement in global risk estimation. The development of highly effective Lp(a)-lowering drugs (e.g., antisense oligonucleotides and small interfering RNA, both blocking LPA gene expression) which are still under assessment in phase 3 trials, will provide a unique opportunity to reduce "residual cardiovascular risk" in high-risk populations, including patients with arterial hypertension. The current evidence in support of a specific role of Lp(a) in hypertension is somehow controversial and this narrative review aims to overview the general mechanisms relating Lp(a) to blood pressure regulation and hypertension-related cardiovascular and renal damage.

Administration of insulin like growth factor I (IGFI) lowers serum lipoprotein(a)-impact on atherosclerotic cardiovascular disease

Insulin like growth factor I (IGFI) secreted by the liver upon stimulation by pituitary growth hormone (GH) acts as the most important growth stimulating hormone in children. The present review presents evidence that among its additional metabolic effects, IGF-I suppresses the synthesis of lipoprotein(a) [Lp(a)], an independent risk factor for atherosclerotic cardiovascular disease. In view of this property, it is suggested that the addition of IGF-I to the armamentarium of hyperlipoproteinemia treatment should be considered.

Lipoprotein(a), family history of cardiovascular disease, and incidence of heart failure

Lipoprotein(a) (Lp(a)) is a largely genetically determined biomarker for cardiovascular disease (CVD), while its potential interplay with family history (FHx) of CVD, a measure of both genetic and environmental exposures, remains unclear. We examined the associations of Lp(a) in terms of circulating concentration or polygenetic risk score (PRS), and FHx of CVD with risk of incident heart failure (HF). Included were 299,158 adults from the UK Biobank without known HF and CVD at baseline. Hazards ratios (HRs) and 95% Cls were estimated by Cox regression models adjusted for traditional risk factors defined by the Atherosclerosis Risk in Communities study HF risk score. During the 11.8-year follow-up, 5,502 incidents of HF occurred. Higher levels of circulating Lp(a), Lp(a) PRS, and positive FHx of CVD were associated with higher risks of HF. Compared with individuals who had lower circulating Lp(a) and no FHx, HRs (95% CIs) of HF were 1.36 (1.25, 1.49), 1.31 (1.19, 1.43), and 1.42 (1.22, 1.67) for those with higher Lp(a) and a positive history of CVD for all family members, parents, and siblings, respectively; similar results were observed by using Lp(a) PRS. The risk estimates for HF associated with elevated Lp(a) and positive FHx were attenuated after excluding those with incident myocardial infarction (MI) during follow-up. Lp(a) and FHx of CVD were independent risk factors for incident HF, and the highest risk of HF was observed among individuals with both risk factors. The association may be partly mediated by myocardial infarction.

Impact of lipoprotein(a) levels on primary patency after endovascular therapy for femoropopliteal lesions

Lipoprotein(a) [Lp(a)] is a risk factor for peripheral artery disease (PAD). However, the relationship between Lp(a) levels and clinical events after endovascular therapy (EVT) for the femoropopliteal artery in PAD patients remains unclear. Thus, this study aimed to assess the impact of Lp(a) levels on primary patency after EVT for de novo femoropopliteal lesions in PAD patients. A retrospective analysis was conducted on 109 patients who underwent EVT for de novo femoropopliteal lesions, and Lp(a) levels were measured before EVT between June 2016 and December 2019. Patients were divided into low Lp(a) [Lp(a) < 30 mg/dL; 78 patients] and high Lp(a) [Lp(a) ≥ 30 mg/dL; 31 patients] groups. The main outcome was primary patency following EVT. Loss of primary patency was defined as a peak systolic velocity ratio > 2.4 on a duplex scan or > 50% stenosis on angiography. Cox proportional hazards analysis was performed to determine whether high Lp(a) levels were independently associated with loss of primary patency. The mean follow-up duration was 28 months. The rates of primary patency were 83 and 76% at 1 year and 75 and 58% at 2 years in the low and high Lp(a) groups, respectively (P = 0.02). After multivariate analysis, High Lp(a)[Lp(a) ≥ 30 mg/dL] (hazard ratio 2.44; 95% CI 1.10-5.44; P = 0.03) and female sex (hazard ratio 2.65; 95% CI 1.27-5.51; P < 0.01) were independent predictors of loss of primary patency. Lp(a) levels might be associated with primary patency after EVT for de novo femoropopliteal lesions.

Increase of serum lipoprotein (a), an adverse effect of growth hormone treatment

A number of reports show that high endogenous, or therapeutic administration of human growth hormone (hGH) cause an increase of serum lipoprotein a, Lp(a). Being thrombogenic Lp(a) is an independent risk factor of atherosclerotic cardiovascular disease (ASCVD). Hence, it is hypothesized that the recently reported association between childhood hGH treatment and cardiovascular morbidity is probably due to the GH effect on Lp(a) synthesis. It is therefore suggested to determine serum Lp(a) levels before and during hGH treatment in children and adults.

Impact of Lipoprotein(a) Levels on Perioperative Outcomes in Cardiac Surgery

Altered lipid metabolism has been shown to be of major importance in a range of metabolic diseases, with particular importance in cardiovascular disease (CVD). As a key metabolic product, altered lipoprotein(a) (Lp(a)) levels may be associated with adverse clinical outcomes in high-risk cardiovascular patients undergoing cardiac surgery. We aimed to investigate the impact of the important metabolite Lp(a) on complications and clinical outcomes in high-risk patients. A prospective observational cohort study was performed. Data were derived from the Bern Perioperative Biobank (ClinicalTrials.gov NCT04767685), and included 192 adult patients undergoing elective cardiac surgery. Blood samples were collected at 24 h preoperatively, before induction of general anaesthesia, upon weaning from cardiopulmonary bypass (CPB), and the first morning after surgery. Clinical endpoints included stroke, myocardial infarction, and mortality within 30 days after surgery or within 1 year. Patients were grouped according to their preoperative Lp(a) levels: <30 mg/dL (n = 121; 63%) or >30 mg/dL (n = 71, 37%). The groups with increased vs. normal Lp(a) levels were comparable with regard to preoperative demographics and comorbidities. Median age was 67 years (interquartile range (IQR) 60.0, 73.0), with median body mass index (BMI) of 23.1 kg/m² (23.7, 30.4), and the majority of patients being males (75.5%). Over the observational interval, Lp(a) levels decreased in all types of cardiac surgery after CPB (mean decline of approximately -5 mg/dL). While Lp(a) levels decreased in all patients following CPB, this observation was considerably pronounced in patients undergoing deep hypothermic circulatory arrest (DHCA) (decrease to preoperative Lp(a) levels by -35% (95% CI -68, -1.7), p = 0.039). Increased Lp(a) levels were neither associated with increased rates of perioperative stroke or major adverse events in patients undergoing cardiac surgery, nor with overall mortality in the perioperative period, or at one year after surgery. Other than for cohorts in neurology and cardiology, elevated Lp(a) might not be a risk factor for perioperative events in cardiac surgery.

Relationship Between Lipoprotein(a) and Angiographic Severity of Femoropopliteal Lesions

AIM

High levels of lipoprotein(a) [Lp(a)] are a risk factor for peripheral artery disease (PAD). However, the relationship between Lp(a) levels and the severity of femoropopliteal lesions in patients with PAD has not been systematically studied. This study aimed to assess the impact of Lp(a) levels on angiographic severity of femoropopliteal lesions in patients with PAD.

METHODS

We retrospectively analyzed a single-center database including 108 patients who underwent endovascular therapy for de novo femoropopliteal lesions and measured the Lp(a) levels before therapy between June 2016 and September 2019. Patients were divided into low Lp(a) [Lp(a) ＜30 mg/dL; 77 patients] and high Lp(a) [Lp(a) ≥ 30 mg/dL; 31 patients] groups. Trans-Atlantic Inter-Society Consensus (TASC) II classification, calcification [referring to the peripheral arterial calcium scoring system (PACSS) classification], and lesion length were compared between the groups.

RESULTS

The prevalence of TASC II class D (13% vs 38%, P＜0.01) and severe calcification (PACSS 4) (6% vs 23%, P=0.02) was significantly higher and the lesion length longer (123±88 mm vs 175±102 mm, P＜0.01) in the high Lp(a) group than in the low Lp(a) group. In multivariate analysis, Lp(a) ≥ 30 was an independent predictor for the prevalence of TASC II class D (HR=3.67, 95% CI 1.27-10.6, P=0.02) and PACSS 4 (HR=4.97, 95% CI 1.27-19.4, P=0.02).

CONCLUSION

The prevalence of TASC II class D and severe calcification of femoropopliteal lesions was higher in patients with high Lp(a) than those with low Lp(a).

The association between lipoprotein (a) and carotid atherosclerosis in patients with type 2 diabetes without pre-existing cardiovascular disease: A cross-sectional study

AIMS

Lipoprotein (a) [Lp(a)] has been considered a determinant of residual cardiovascular risk. We aimed to investigate associations between serum Lp(a) levels and carotid atherosclerosis.

METHODS

This cross-sectional study included 662 type 2 diabetic patients without cardiovascular disease. The mean value of three right and left measurements was used to indentify increased carotid intima-media thickness (CIMT). A carotid plaque was defined as a focal wall thickening >50% of the surrounding IMT or its CIMT ≥1.5 mm. The presence of carotid atherosclerosis was defined as having CIMT ≥1.0 mm or carotid plaque.

RESULTS

A total of 34.3% of patients had carotid atherosclerosis. The median Lp(a) level was significantly higher in subjects with carotid atherosclerosis (14.6 vs. 10.2 mg/dL, P < 0.001). The log-transformed Lp(a) level per 1-standard deviation increase was significantly associated with higher risk of the presence of carotid atherosclerosis (odds ratio [OR] 1.46; 95% confidence interval [CI] 1.16 - 1.84, P = 0.001) after adjusting other parameters. The log Lp(a) level was still significantly associated with the risk of carotid atherosclerosis in subjects with optimal low-density lipoprotein cholesterol (LDL-C) <100 mg/dL (OR 1.48; 95% CI 1.16 - 1.88, P = 0.001). Higher Lp(a) and LDL-C had an additive effect on the presence of carotid atherosclerosis.

CONCLUSION

Elevated Lp(a) was significantly associated with the presence of carotid atherosclerosis in patients with type 2 diabetes, independent of conventional cardiometabolic risk factors.

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.

Lipoprotein(a) levels are associated with coronary severity but not with outcomes in Chinese patients underwent percutaneous coronary intervention

BACKGROUND AND AIMS

The association between lipoprotein(a) [Lp(a)] levels and the risk of cardiovascular disease is of great interest but still controversial. This study sought to investigate the impact of Lp(a) on coronary severity and long-term outcomes of patients who undergo percutaneous coronary intervention (PCI).

METHODS AND RESULTS

A total of 6714 consecutive patients who received PCI were enrolled to analyze the association between Lp(a) and coronary severity and major adverse cardiovascular and cerebrovascular events (MACCE). Patients were divided into tertiles according to Lp(a) levels on admission. Coronary severity was evaluated by SYNTAX scoring system. The MACCE included recurrent myocardial infarction, unplanned target vessel revascularization, stent thrombosis, ischemic stroke and all-cause mortality. Significantly, Lp(a) levels were positively associated with coronary severity (p < 0.001). Multivariate logistic regression analyses showed Lp(a) was an independent predictor of intermediate to high SYNTAX score. During an average of 874 days follow-up, 755 patients presented with MACCE (11.25%) were reported. The incidence rates of MACCE, all-cause mortality, cardiac death, target vessel revascularization, recurrent myocardial infarction, stent thrombosis, stroke and bleeding were not statistically different among the Lp(a) tertile groups. Furthermore, both Kaplan-Meier and Cox regression analyses found no relationship between Lp(a) and cardiovascular outcomes (p > 0.05).

CONCLUSION

Lp(a) is an independent predictor of the prevalence of more complex coronary artery lesions (SYNTAX score ≥ 23) in patients with PCI. In addition, our study has shown that Lp(a) has no relationship with long-term cardiovascular outcomes in Chinese patients with PCI.

Comparison of Different Ldl-Apheresis Techniques

LDL-apheresis is an extracorporeal technique which removes all apo B100-containing lipoproteins (VLDL, LDL, Lp(a)) from plasma, in patients whith homozygous, and double heterozygous, familial hypercholesterolemia (FH). One of the most significant technical characteristics of LDL-apheresis is the selectivity in the removal of atherogenic lipoproteins, namely LDLs, which has been improved in the most recently developed techniques. The oldest system for therapeutic plasmapheresis in the treatment of severe hyperlipoproteinemias, is plasma-exchange, where all plasma components are unselectively removed. More recently, the systems (dextransulphate cellulose LDL-apheresis [DSC/LDL-A], heparin induced LDL precipitation-apheresis [HELP/LDL-A], immunoadsorption LDL-apheresis [IMA/LDL-A], direct adsorption of lipids [DALI]) have permitted a selective removal of LDL and of other apo B100-containing lipoproteins. The higher selectivity, thus the higher efficacy and safety, has also allowed the treatment of high risk patients with severe cardiovascular conditions, and pediatric patients. Therefore, it is currently possible to begin treatment with LDL-apheresis, even at a very early age. The most recent system for LDL-apheresis (DALI: Direct Adsorption of Lipids) even permits the removal of LDL from whole blood, without previous cell/plasma separation. This system is promising for further progress in the technology related to LDL-apheresis.

High performance affinity chromatography and related separation methods for the analysis of biological and pharmaceutical agents

The last few decades have witnessed the development of many high-performance separation methods that use biologically related binding agents. The combination of HPLC with these binding agents results in a technique known as high performance affinity chromatography (HPAC). This review will discuss the general principles of HPAC and related techniques, with an emphasis on their use for the analysis of biological compounds and pharmaceutical agents. Various types of binding agents for these methods will be considered, including antibodies, immunoglobulin-binding proteins, aptamers, enzymes, lectins, transport proteins, lipids, and carbohydrates. Formats that will be discussed for these methods range from the direct detection of an analyte to indirect detection based on chromatographic immunoassays, as well as schemes based on analyte extraction or depletion, post-column detection, and multi-column systems. The use of biological agents in HPLC for chiral separations will also be considered, along with the use of HPAC as a tool to screen or study biological interactions. Various examples will be presented to illustrate these approaches and their applications in fields such as biochemistry, clinical chemistry, and pharmaceutical research.

Lipoprotein(a) and the risk of cardiovascular disease in the European population: results from the BiomarCaRE consortium

AIMS

As promising compounds to lower Lipoprotein(a) (Lp(a)) are emerging, the need for a precise characterization and comparability of the Lp(a)-associated cardiovascular risk is increasing. Therefore, we aimed to evaluate the distribution of Lp(a) concentrations across the European population, to characterize the association with cardiovascular outcomes and to provide high comparability of the Lp(a)-associated cardiovascular risk by use of centrally determined Lp(a) concentrations.

METHODS AND RESULTS

Based on the Biomarkers for Cardiovascular Risk Assessment in Europe (BiomarCaRE)-project, we analysed data of 56 804 participants from 7 prospective population-based cohorts across Europe with a maximum follow-up of 24 years. All Lp(a) measurements were performed in the central BiomarCaRE laboratory (Biokit Quantia Lp(a)-Test; Abbott Diagnostics). The three endpoints considered were incident major coronary events (MCE), incident cardiovascular disease (CVD) events, and total mortality. We found lower Lp(a) levels in Northern European cohorts (median 4.9 mg/dL) compared to central (median 7.9 mg/dL) and Southern European cohorts (10.9 mg/dL) (Jonckheere-Terpstra test P < 0.001). Kaplan-Meier curves showed the highest event rate of MCE and CVD events for Lp(a) levels ≥90th percentile (log-rank test: P < 0.001 for MCE and CVD). Cox regression models adjusted for age, sex, and cardiovascular risk factors revealed a significant association of Lp(a) levels with MCE and CVD with a hazard ratio (HR) of 1.30 for MCE [95% confidence interval (CI) 1.15‒1.46] and of 1.25 for CVD (95% CI 1.12‒1.39) for Lp(a) levels in the 67‒89th percentile and a HR of 1.49 for MCE (95% CI 1.29‒1.73) and of 1.44 for CVD (95% CI 1.25‒1.65) for Lp(a) levels ≥ 90th percentile vs. Lp(a) levels in the lowest third (P < 0.001 for all). There was no significant association between Lp(a) levels and total mortality. Subgroup analysis for a continuous version of cube root transformed Lp(a) identified the highest Lp(a)-associated risk in individuals with diabetes [HR for MCE 1.31 (95% CI 1.15‒1.50)] and for CVD 1.22 (95% CI 1.08‒1.38) compared to those without diabetes [HR for MCE 1.15 (95% CI 1.08‒1.21; HR for CVD 1.13 (1.07-1.19)] while no difference of the Lp(a)- associated risk were seen for other cardiovascular high risk states. The addition of Lp(a) levels to a prognostic model for MCE and CVD revealed only a marginal but significant C-index discrimination measure increase (0.001 for MCE and CVD; P < 0.05) and net reclassification improvement (0.010 for MCE and 0.011 for CVD).

CONCLUSION

In this large dataset on harmonized Lp(a) determination, we observed regional differences within the European population. Elevated Lp(a) was robustly associated with an increased risk for MCE and CVD in particular among individuals with diabetes. These results may lead to better identification of target populations who might benefit from future Lp(a)-lowering therapies.

Lipoprotein (a) as a cause of cardiovascular disease: insights from epidemiology, genetics, and biology

Human epidemiologic and genetic evidence using the Mendelian randomization approach in large-scale studies now strongly supports that elevated lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular disease, that is, for myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis. The Mendelian randomization approach used to infer causality is generally not affected by confounding and reverse causation, the major problems of observational epidemiology. This approach is particularly valuable to study causality of Lp(a), as single genetic variants exist that explain 27-28% of all variation in plasma Lp(a). The most important genetic variant likely is the kringle IV type 2 (KIV-2) copy number variant, as the apo(a) product of this variant influences fibrinolysis and thereby thrombosis, as opposed to the Lp(a) particle per se. We speculate that the physiological role of KIV-2 in Lp(a) could be through wound healing during childbirth, infections, and injury, a role that, in addition, could lead to more blood clots promoting stenosis of arteries and the aortic valve, and myocardial infarction. Randomized placebo-controlled trials of Lp(a) reduction in individuals with very high concentrations to reduce cardiovascular disease are awaited. Recent genetic evidence documents elevated Lp(a) as a cause of myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis.

Outcome Analysis for Treatment in 100 Patients with Deep Vein Thrombosis

The treatment of acute deep vein thrombosis has been the subject of much research aimed at delineat ing the safest and most effective approach to diagnosis and treatment. Studies regarding long-term treatment have been limited by the narrow scope of laboratory and clinical analyses of many patients. In this study of 100 patients with a history of deep vein thrombosis, treated on an outpatient basis by a diverse group of clinicians, follow-up data were retrieved in order to determine the outcomes of various approaches to acute and long-term care. Among individuals followed for > 1 year, in only two patients (2%) was death attributable to a thrombotic event related to the etiology of the first episode of deep vein thrombosis. Most deceased patients succumbed to unrelated causes (11%). Among the 77 survivors, most (52%) received long-term antiplatelet therapy. All individ uals with a plasma coagulation defect, whether inherited or acquired, received anticoagulation with either heparin or warfarin. Since the long-term clinical outcome of most patients with deep vein thrombosis is dependent upon the underlying factor predisposing to thrombosis, the most important treatment decision is to select the therapy most likely to provide benefit without causing hemorrhage. An tiplatelet therapy, heparin, or warfarin may be chosen as appropriate for the individual patient.

High-Performance Affinity Chromatography: Applications in Drug-Protein Binding Studies and Personalized Medicine

The binding of drugs with proteins and other agents in serum is of interest in personalized medicine because this process can affect the dosage and action of drugs. The extent of this binding may also vary with a given disease state. These interactions may involve serum proteins, such as human serum albumin or α1-acid glycoprotein, or other agents, such as lipoproteins. High-performance affinity chromatography (HPAC) is a tool that has received increasing interest as a means for studying these interactions. This review discusses the general principles of HPAC and the various approaches that have been used in this technique to examine drug-protein binding and in work related to personalized medicine. These approaches include frontal analysis and zonal elution, as well as peak decay analysis, ultrafast affinity extraction, and chromatographic immunoassays. The operation of each method is described and examples of applications for these techniques are provided. The type of information that can be obtained by these methods is also discussed, as related to the analysis of drug-protein binding and the study of clinical or pharmaceutical samples.

Analysis of drug interactions with very low density lipoprotein by high-performance affinity chromatography

High-performance affinity chromatography (HPAC) was utilized to examine the binding of very low density lipoprotein (VLDL) with drugs, using R/S-propranolol as a model. These studies indicated that two mechanisms existed for the binding of R- and S-propranolol with VLDL. The first mechanism involved non-saturable partitioning of these drugs with VLDL, which probably occurred with the lipoprotein's non-polar core. This partitioning was described by overall affinity constants of 1.2 (±0.3) × 10(6) M(-1) for R-propranolol and 2.4 (±0.6) × 10(6) M(-1) for S-propranolol at pH 7.4 and 37 °C. The second mechanism occurred through saturable binding by these drugs at fixed sites on VLDL, such as represented by apolipoproteins on the surface of the lipoprotein. The association equilibrium constants for this saturable binding at 37 °C were 7.0 (±2.3) × 10(4) M(-1) for R-propranolol and 9.6 (±2.2) × 10(4) M(-1) for S-propranolol. Comparable results were obtained at 20 and 27 °C for the propranolol enantiomers. This work provided fundamental information on the processes involved in the binding of R- and S-propranolol to VLDL, while also illustrating how HPAC can be used to evaluate relatively complex interactions between agents such as VLDL and drugs or other solutes.

[Effect of biliary obstruction on lipoprotein(a) concentration]

OBJECTIVES

This study was appointed to determine the correlation between the concentration of lipoprotein(a) [Lp(a)], apolipoproteins and lipids with biochemical parameters of liver function in a group of patients with reversible cholestasis. We have also determined the concentration of these parameters once solved the biliary obstruction process.

MATERIAL AND METHODS

Eighteen adults over 17 years with extrahepatic cholestasis were included in the study on a prospective basis, and we determined in them biochemical liver function parameters and lipoprotein metabolism parameters, particularly Lp(a) before and after unblocking.

RESULTS

The concentration of Lp(a) prior to desobstruction was inverse and statistically significantly correlated with the concentration of gamma glutamyl transpeptidase (correlation coefficient [r] = -0.757, P = .018). The concentration of Lp(a) (median = 2.66 mg/dL, interquartile range = 5,62) showed a statistically significant increase (median = 9.72 mg/dL, interquartile range = 28.76, P < .001), once the unblocking was performed. Concentrations of total cholesterol and triglycerides had a statistically significant decrease, and HDL cholesterol and apolipoprotein A-1 showed a statistically significant increase once the unblocking was carried out.

CONCLUSIONS

The concentration of Lp(a) is decreased during cholestasis, although there is a significant simultaneous hypercholesterolemia. Cholestasis has a causal role in lowering Lp(a), because the unblocking of bile duct recovers Lp(a) concentration. Our study supports the concept that bile acids exert a controlling effect on the synthesis of Lp(a) and open a mechanism for the treatment of hyper Lp(a).

Identification and analysis of stereoselective drug interactions with low-density lipoprotein by high-performance affinity chromatography

Columns containing immobilized low-density lipoprotein (LDL) were prepared for the analysis of drug interactions with this agent by high-performance affinity chromatography (HPAC). R/S-Propranolol was used as a model drug for this study. The LDL columns gave reproducible binding to propranolol over 60 h of continuous use in the presence of pH 7.4 0.067 M potassium phosphate buffer. Experiments conducted with this type of column through frontal analysis indicated that two types of interactions were occurring between R-propranolol and LDL, while only a single type of interaction was observed between S-propranolol and LDL. The first type of interaction, which was seen for both enantiomers, involved non-saturable binding; this interaction had an overall affinity (nK(a)) of 1.9 (±0.1) × 10(5) M(-1) for R-propranolol and 2.7 (±0.2) × 10(5) M(-1) for S-propranolol at 37 °C. The second type of interaction was observed only for R-propranolol and involved saturable binding that had an association equilibrium constant (K(a)) of 5.2 (±2.3) × 10(5) M(-1) at 37 °C. Similar differences in binding behavior were found for the two enantiomers at 20 °C and 27 °C. This is the first known example of stereoselective binding of drugs by LDL or other lipoproteins. This work also illustrates the ability of HPAC to be used as a tool for characterizing mixed-mode interactions that involve LDL and related binding agents.

Treatment of symptomatic HyperLp(a)lipoproteinemia with LDL-apheresis: a multicentre study

LDL-apheresis (LDLa) efficacy in the treatment of symptomatic HyperLp(a)lipoproteinemia -HyperLp(a)- has been studied in a multicentre trial. After 3.1+/-2.7 years of weekly and biweekly treatment, the data from 19 patients (males:12; females:7; aged 53.8+/-9.3 years; mean body mass index: 24.6+/-2.3 Kg/m²) were evaluated. Data were collected using the same questionnaire shared by 5 participating centres. A total of 2331 procedures were performed. A mean of 3593.7+/-800.3 ml of plasma or 8115.3+/-2150.1 ml of blood, depending upon the technique used (H.E.L.P., D.A.LI., Dextransulphate, Lipocollect 200), was regularly treated on average every 10.1+/-2.6 days. Baseline mean Lp(a) levels were 172.3+/-153.8 mg/dL. The mean pre-/post-apheresis Lp(a) levels decreased from 124.5+/-107.2 mg/dL (p<0.001 vs baseline) to 34.2+/-40.6 mg/dL (p<0.001 vs pre-). Baseline mean LDL-cholesterol (LDLC) levels were 152.3+/-74.6 mg/dL. The mean pre-/post-apheresis LDLC levels decreased from 130.4+/-61.1 mg/dL (p<0.004 vs baseline) to 41.2+/-25.1 mg/dL (p<0.001 vs pre-). The hypolipidemic drugs given to the patients during LDLa were: ezetimibe+simvastatin, atorvastatin, rosuvastatin, pravastatin, acipimox, and omega-3 fatty acids. 58% of the patients had arterial hypertension. Cigarette smokers were 5.3%. Alcohol intake was present in 21%. 52.6% were physically active. Patients with coronary artery disease (CAD) submitted to coronary catheterization before LDLa were 95%. In 5.5% (#1) CAD recurred despite treatment with LDLa. 79% were submitted to coronary revascularization before LDLa. CAD was: monovasal in 8 patients (42.1%), bivasal in 5 (26.4%), trivasal in 4 (21%), plurivasal in 2 (10.5%). In 94.5% of the sample the lesions were stable (< 0% deviation) over 3.1+/-2.7 years. 37% had both CAD and extra-coronary artery disease. This multicentre study confirmed that long-term treatment with LDLa was at least able to stabilize CAD in the majority of the individuals with symptomatic HyperLp(a).

Lipoprotein(a) levels in centenarians

In elderly subjects (above 65 years), cardio- and cerebrovascular diseases are known to contribute to the death rate. Serum lipoprotein(a) = Lp(a), a low density lipoprotein, is involved in the atherogenic processes, as confirmed by several clinical trials. We evaluated serum Lp(a) levels in a group of centenarians (15 females and 7 males, mean age 102.81 +/- 2.5 years) compared to 25 healthy control subjects (10 males and 15 females, mean age 51.12 +/- 15.34 years). In all subjects Lp(a) serum levels were determined by ELISA method (EIA mod. 2550 reader). Statistical analysis of the results was performed by using the Student's t test. In centenarians the mean Lp(a) level increased (39.6 +/- 23.53 mg/dl) compared to that of the control group (16.78 +/- 16.24 mg/dl) (p < 0.005). The elevated Lp(a) values observed in centenarians may be attributed to the presence of low molecular weight lipoprotein isoforms which are known to be associated with cardio-cerebrovascular risk. Therefore, it seems that elevated Lp(a) levels alone are not risk factors for the onset of acute acute vascular accidents and do not influence longevity.

Analysis of drug interactions with high-density lipoprotein by high-performance affinity chromatography

Columns containing immobilized lipoproteins were prepared for the analysis of drug interactions with these particles by high-performance affinity chromatography (HPAC). This approach was evaluated by using it to examine the binding of high-density lipoprotein (HDL) to the drugs propranolol and verapamil. HDL was immobilized by the Schiff base method onto silica and gave HPAC columns with reproducible binding to propranolol over 4-5days of continuous operation at pH 7.4. Frontal analysis experiments indicated that two types of interaction were occurring between R- or S-propranolol and HDL at 37 degrees C: saturable binding with an association equilibrium constant (K(a)) of 1.1-1.9x10(5)M(-1) and nonsaturable binding with an overall affinity constant (n K(a)) of 3.7-4.1x10(4)M(-1). Similar results were found at 4 and 27 degrees C. Verapamil also gave similar behavior, with a K(a) of 6.0x10(4) M(-1) at 37 degrees C for the saturable sites and an n K(a) for the nonsaturable sites of 2.5x10(4)M(-1). These measured affinities gave good agreement with solution phase values. The results indicated that HPAC can be used to study drug interactions with HDL, providing information that should be valuable in obtaining a better description of how drugs are transported within the body.

Characterization of drug-protein interactions in blood using high-performance affinity chromatography

The binding of drugs with proteins in blood, serum, or plasma is an important process in determining the activity, distribution, rate of excretion, and toxicity of drugs in the body. High-performance affinity chromatography (HPAC) has received a great deal of interest as a means for studying these interactions. This review examines the various techniques that have been used in HPAC to examine drug-protein binding and discusses the types of information that can be obtained through this approach. A comparison of these techniques with traditional methods for binding studies (e.g., equilibrium dialysis and ultrafiltration) will also be presented. The use of HPAC with specific serum proteins and binding agents will then be discussed, including HSA and alpha(1)-acid glycoprotein (AGP). Several examples from the literature are provided to illustrate the applications of such research. Recent developments in this field are also described, such as the use of improved immobilization techniques, new data analysis methods, techniques for working directly with complex biological samples, and work with immobilized lipoproteins. The relative advantages and limitations of the methods that are described will be considered and the possible use of these techniques in the high-throughput screening or characterization of drug-protein binding will be discussed.

Lipoprotein(a) is related to the extent of lesions in the coronary vasculature and to unstable coronary syndromes

BACKGROUND

Lp(a) is a highly atherogenic particle with a prothrombotic effect. Until now its relation to the extent and severity of the atheromatic lesions had not been established by standard procedures.

HYPOTHESIS

This study examined the correlation of Lp(a) to the extent and severity of coronary artery disease (CAD) and its relation to unstable clinical events (not including sudden death).

METHODS

In 202 patients undergoing coronary angiography, plasma lipids were measured with the usual procedures and Lp(a) with the enzyme-linked immunosorbent assay. The extent of CAD was expressed in the number of diseased vessels and its severity in terms of the severity coefficient and the obstruction coefficient.

RESULTS

A very strong relationship between LP(a) and the number of diseased vessels (p = 0.0007) signifying diffuse atherosclerosis, but no relation with the severity of the lesions. was found. However, it was the only lipid that correlated significantly with the number of totally occluded vessels (p = 0.0003). The thrombogenic ability of Lp(a) was manifested by increased incidence of myocardial infarction and unstable angina episodes in patients with elevated Lp(a) (p = 0.0157).

CONCLUSION

Elevated Lp(a) predisposes to the extent of CAD and total occlusions but not to the severity of lesions. Patients with increased Lp(a) levels and unstable angina are at increased danger of suffering myocardial infarction. Thus, Lp(a) may predispose to plaque destabilization and thrombosis of noncritical lesions.

Atherosclerosis pathophysiology and the role of novel risk factors: a clinicobiochemical perspective

Atherosclerosis is the root cause of the biggest killer of the 21st century. Mechanisms contributing to atherogenesis are multiple and complex. A number of theories-including the role of dyslipidemia, hypercoagulability, oxidative stress, endothelial dysfunction, and inflammation and infection by certain pathogens-have been propounded from time to time explain this complex phenomenon. Recently it has been suggested that atherosclerosis is a multifactorial, multistep disease that involves chronic inflammation at every step, from initiation to progression, and that all the risk factors contribute to pathogenesis by aggravating the underlying inflammatory process. A better understanding of the pathogenesis of atherosclerosis will aid in devising pharmaceutical and lifestyle modifications for reducing mortality resulting from coronary artery disease (CAD).A comprehensive literature search was conducted using the Web sites of the National Library of Medicine (http:// www.ncbl.nlm.nih.gov/) and PubMed Central, the US National Library of Medicine's digital archive of life sciences literature (http:// www.pubmedcentral.nih.gov/). The data were accessed from books and journals in which relevant articles in this field were published. The whole spectrum of coronary artery disease evolves through various events that lead to the formation and progression of atherosclerotic plaque and finally its complications. Atherosclerosis is the culprit behind coronary artery disease, cerebral vascular disease, and peripheral vascular disease. The pathogenic mechanisms are varied and complex. Of late, the role of lipoprotein (a), homocysteine, and inflammation and infection as prime culprits in pathogenesis of CAD is the subject of intense research and debate. The appreciation of the role of inflammation in atherosclerosis provides a mechanistic framework to understand the clinical benefits of newer therapeutic strategies, and a better understanding of pathogenesis aids in formulating preventive and therapeutic strategies in reducing mortality resulting from CAD.An in-depth knowledge of the various pathogenic mechanisms involved in atherosclerosis can help in substantiating the current existing knowledge about the CAD epidemic. This knowledge will help clinicians to better manage the disease, which affects Indians in its most severe form.

Effects of non-oral postmenopausal hormone therapy on markers of cardiovascular risk: a systematic review

OBJECTIVE

To review the effects of non-oral administration of postmenopausal hormone therapy (HT) on risk markers for atherosclerotic and venous thromboembolic disease.Non-oral postmenopausal HT appears not to increase venous thromboembolic risk, whereas the effect on coronary heart disease risk is less clear.

DESIGN

Systematic review of literature obtained from MEDLINE, EMBASE, and CENTRAL databases from 1980 until and including April 2006. Terms for "postmenopausal hormone therapy" and for "non-oral administration" were combined in the search.

SETTING

Randomized clinical trials.

PATIENT(S)

Postmenopausal women, both healthy and with established cardiovascular disease or specified cardiovascular risk factors

INTERVENTION(S)

Non-oral HT (e.g., transdermal or intranasal) compared with oral HT or no treatment/placebo.

MAIN OUTCOME MEASURE(S)

Lipoprotein(a), homocysteine, C-reactive protein (CRP), cell adhesion molecules, markers of endothelial dysfunction, coagulation, and fibrinolysis.

RESULT(S)

Seventy-two studies investigating either transdermal or intranasal administration were included. For non-oral HT, decreases in lipoprotein(a), cell adhesion molecules, and factor VII generally were significant, resistance to activated protein C (APCr) was slightly increased, and other markers including CRP and homocysteine did not change. Compared with oral HT, changes in CRP and APCr were smaller, changes in cell adhesion molecules and some fibrinolytic parameters tended to be smaller, whereas changes in other factors including lipoprotein(a) and homocysteine did not differ.

CONCLUSION(S)

Potentially unfavorable changes seen with oral HT on two important markers, CRP and APCr, are substantially smaller with non-oral HT. Non-oral HT has minor effects on the other cardiovascular risk markers studied. Therefore, compared with oral HT, non-oral HT appears be safer with respect to atherosclerotic and venous thromboembolic disease risk.

Serum leptin, oxidized low density lipoprotein and plasma asymmetric dimethylarginine levels and their relationship with dyslipidaemia in adolescent girls with polycystic ovary syndrome

OBJECTIVE

The aim of this study was to investigate serum leptin, oxidized low density lipoprotein (ox-LDL) and asymmetric dimethylarginine (ADMA) levels and their interaction with dyslipidaemia in adolescents with polycystic ovary syndrome (PCOS).

PATIENTS AND DESIGN

The study group consisted of 23 obese (obPCOS) and 21 nonobese girls with PCOS (nPCOS), and 31 lean healthy controls. PCOS was defined by the National Institutes of Health (NIH) criteria as the presence of chronic oligoanovulation and hyperandrogenism. Fasting leptin, ox-LDL, ADMA and detailed lipid-lipoprotein profile were determined. Atherogenic index (AI) was calculated as [Total cholesterol - HDL cholesterol/HDL cholesterol]. Logarithmic transformations were made for ox-LDL.

RESULTS

Total cholesterol, triglycerides, LDL cholesterol, very low density lipoprotein (VLDL) cholesterol, apolipoprotein B, lipoprotein A levels and AI were higher and apolipoprotein AI was lower in obPCOS compared to those in controls (P < 0.05). LDL cholesterol, apolipoprotein B and lipoprotein A levels were higher in nPCOS compared to controls (P < 0.05). ADMA and ox-LDL levels did not differ in the three groups. Leptin was significantly higher in obPCOS compared with that in the other two groups (P < 0.001) and it was correlated with triglycerides (r = 0.62), VLDL cholesterol (r = 0.45), lipoprotein A (r = 0.38) and AI (r = 0.43) in the PCOS group (P < 0.05).

CONCLUSION

Our data demonstrate that ADMA and ox-LDL levels in adolescent PCOS subjects were not different than those in controls. Abnormal lipid profile was shown in obese and nonobese girls with PCOS and leptin was related with these lipid abnormalities in the PCOS subjects.

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.

Role of Phospholipid Transfer Protein on the Plasma Distribution of Amphotericin B Following the Incubation of Different Amphotericin B Formulations

PURPOSE

The purpose of this study was to investigate the role of phospholipid transfer protein (PLTP) on the plasma distribution of amphotericin B (AmpB) following incubation with different AmpB formulations in human plasmas with varying lipid profiles.

METHODS

In a first set of experiments, plasma distribution profiles of AmpB were determined following the incubation of Fungizone and lipid-based formulations (Abelcet and AmBisome) at a concentration of 20 microg AmpB/mL for 5-120 min at 37 degrees C in the plasma obtained from six different individuals (total cholesterol concentrations range between 62 and 332 mg/dL). In a second set of experiments, Abelcet, and AmBisome at a concentration of 20 microg AmpB/mL were incubated for 5 min at 37 degrees C in human plasma (total cholesterol = 163 mg/dL) that had been pretreated with an antibody raised up against PLTP (1:400 v/v dilution from stock solution) for 20 min at 37 degrees C. Following incubation, the human plasma was separated into its lipoprotein and lipoprotein-deficient fractions by density gradient ultracentrifugation and analyzed for AmpB content by high-performance liquid chromatography.

RESULTS

The majority of AmpB was covered in the lipoprotein-deficient plasma and high-density lipoprotein (HDL) fractions following incubation of Fungizone in human plasma. The majority of AmpB (48.7-87.2%) was recovered in the HDL fraction following incubation of Abelcet and AmBisome in human plasma. The presence of the PLTP antibody resulted in a 20% decrease in the percentage AmpB recovered in the HDL fraction following the incubation of Abelcet. However, the plasma distribution of AmpB remained unchanged following the incubation of AmBisome in plasma containing the PLTP antibody.

CONCLUSIONS

Taken together, these findings suggest indirect evidence that PLTP may play an important role in the plasma distribution profile of AmpB following the incubation of Abelcet and may be one of the factors responsible for the preferential association of AmpB with HDL when administered as Abelcet.

Intranasal continuous combined 17β-estradiol/norethisterone therapy improves the lipid profile in healthy postmenopausal women

OBJECTIVE

To compare the effects of continuous combined 17beta-estradiol (E2) plus norethisterone (acetate) [NET(A)] therapy by either intranasal or oral administration on the lipid profile in postmenopausal women.

DESIGN

Randomized, double-blind, multicenter trial.

SETTING

Gynecologic outpatient department.

PATIENT(S)

Two-hundred thirty-three healthy postmenopausal women.

INTERVENTION(S)

Women received continuous combined hormone therapy, either intranasal E2/NET (175 microg/275 microg) as a spray (n = 117) or oral E2/NETA (1 mg/0.5 mg) as a capsule (n = 116), for 1 year.

MAIN OUTCOME MEASURE(S)

Fasting plasma concentrations of lipids and (apo)lipoproteins; and atherogenic indices at baseline and after 12, 24, and 52 weeks of treatment.

RESULT(S)

We found a significant (P < .001) decrease from baseline in both treatment groups in total, low-density lipoprotein- (LDL), high-density lipoprotein- (HDL), and HDL2-cholesterol, in triglycerides, apolipoprotein B (apoB), and lipoprotein(a). Levels of HDL3-cholesterol and apolipoprotein A1 (apoA1) were transiently decreased in the intranasal group. In the oral group, compared with the intranasal group, the decrease was larger for ratio total and LDL-cholesterol and lipoprotein(a) and smaller for triglycerides and apoA1. In the oral group, the ratios total/HDL cholesterol and LDL/HDL cholesterol were lowered, and the ratio apoB/LDL was increased, more than in the intranasal group.

CONCLUSION(S)

Both intranasal and oral E2/NET(A) therapy improved the lipid profile of healthy postmenopausal women, with some effects being more pronounced after oral administration.

Association of serum lipoprotein(a) with ultrasonographically determined early atherosclerotic changes in the carotid and femoral arteries in kidney transplanted patients

OBJECTIVES

To evaluate the association of serum lipoprotein(a) [Lp(a)] with carotid intimal media thickness (IMT) and carotid femoral plaque occurrence in kidney transplant patients.

PATIENTS AND METHODS

Fifty-four subjects included 29 group 1 normal healthy persons and 25 group 2 kidney transplant patients underwent carotid IMT measurements and carotid femoral plaque assessment by B-mode ultrasonography. Also we measured cholesterol, triglyceride, HDL-C, LDL-C and Lp(a) as well as BUN and creatinine.

RESULTS

There was a significant difference between Lp(a) in the two groups (P = .016). There was a significant difference between carotid IMT of the two groups (P < .001). Moreover there was a significant difference between the plaque scores of kidney transplant patients and the normal group (P = .05). There were no correlations between carotid IMT and plaque score in normal subjects or in kidney transplant patients (P > .05). There was a significant correlation between carotid IMT with age in Group 1 (P = .035). No correlation between carotid IMT and serum Lp(a) was seen in the two groups. No significant correlations between plaque score and serum Lp(a) were observed. There was no correlation between duration of transplant and thickening of intimal media complex in this group. In this group a positive correlation was demonstrated between carotid IMT with serum LDL-C (P < .001).

CONCLUSIONS

Age was the most important factor associated with thickening of intimal media complex in normal subjects and in plaque formation in the renal transplant group. Serum LDL-C may be associated with thickening of intimal media complex in kidney transplant patients. Serum Lp(a) may not be a significant factor in thickening of the intimal media complex or plaque occurrence in kidney transplant patients.

Effects of androgenic-anabolic steroids on apolipoproteins and lipoprotein (a)

OBJECTIVES

To investigate the effects of two different regimens of androgenic-anabolic steroid (AAS) administration on serum lipid and lipoproteins, and recovery of these variables after drug cessation, as indicators of the risk for cardiovascular disease in healthy male strength athletes.

METHODS

In a non-blinded study (study 1) serum lipoproteins and lipids were assessed in 19 subjects who self administered AASs for eight or 14 weeks, and in 16 non-using volunteers. In a randomised double blind, placebo controlled design, the effects of intramuscular administration of nandrolone decanoate (200 mg/week) for eight weeks on the same variables in 16 bodybuilders were studied (study 2). Fasting serum concentrations of total cholesterol, triglycerides, HDL-cholesterol (HDL-C), HDL2-cholesterol (HDL2-C), HDL3-cholesterol (HDL3-C), apolipoprotein A1 (Apo-A1), apolipoprotein B (Apo-B), and lipoprotein (a) (Lp(a)) were determined.

RESULTS

In study 1 AAS administration led to decreases in serum concentrations of HDL-C (from 1.08 (0.30) to 0.43 (0.22) mmol/l), HDL2-C (from 0.21 (0.18) to 0.05 (0.03) mmol/l), HDL3-C (from 0.87 (0.24) to 0.40 (0.20) mmol/l, and Apo-A1 (from 1.41 (0.27) to 0.71 (0.34) g/l), whereas Apo-B increased from 0.96 (0.13) to 1.32 (0.28) g/l. Serum Lp(a) declined from 189 (315) to 32 (63) U/l. Total cholesterol and triglycerides did not change significantly. Alterations after eight and 14 weeks of AAS administration were comparable. No changes occurred in the controls. Six weeks after AAS cessation, serum HDL-C, HDL2-C, Apo-A1, Apo-B, and Lp(a) had still not returned to baseline concentrations. Administration of AAS for 14 weeks was associated with slower recovery to pretreatment concentrations than administration for eight weeks. In study 2, nandrolone decanoate did not influence serum triglycerides, total cholesterol, HDL-C, HDL2-C, HDL3-C, Apo-A1, and Apo-B concentrations after four and eight weeks of intervention, nor six weeks after withdrawal. However, Lp(a) concentrations decreased significantly from 103 (68) to 65 (44) U/l in the nandrolone decanoate group, and in the placebo group a smaller reduction from 245 (245) to 201 (194) U/l was observed. Six weeks after the intervention period, Lp(a) concentrations had returned to baseline values in both groups.

CONCLUSIONS

Self administration of several AASs simultaneously for eight or 14 weeks produces comparable profound unfavourable effects on lipids and lipoproteins, leading to an increased atherogenic lipid profile, despite a beneficial effect on Lp(a) concentration. The changes persist after AAS withdrawal, and normalisation depends on the duration of the drug abuse. Eight weeks of administration of nandrolone decanoate does not affect lipid and lipoprotein concentrations, although it may selectively reduce Lp(a) concentrations. The effect of this on atherogenesis remains to be established.

Lipoprotein(a) in patients who have non-insulin-dependent diabetes with and without coronary artery disease

OBJECTIVE

To determine whether the level of lipoprotein(a) [Lp(a)] contributes to an increased risk of coronary artery disease (CAD) in patients with non-insulin-dependent diabetes mellitus (NIDDM).

METHODS

We prospectively evaluated established cardiovascular risk factors, metabolic control, and Lp(a) levels in 53 men with NIDDM and CAD and compared these variables in 42 male patients with NIDDM but without CAD.

RESULTS

The groups were comparable for age, diabetes control, treatment and duration of diabetes, obesity, and other cardiac risk factors. Lp(a) levels did not differ between the groups (12.2 versus 12.4 mg/dL in those with and without CAD, respectively) and were unrelated to age, duration of diabetes, diabetes control, obesity, smoking, hypertension, urinary albumin, cholesterol, triglycerides, or high-density lipoprotein cholesterol. Patients with retinopathy had a higher Lp(a) concentration than did those without retinopathy (24.9 +/- 6.0 versus 10.1 +/- 1.5 mg/dL; P = 0.01). A significant correlation existed between Lp(a) and low-density lipoprotein cholesterol concentrations (P = 0.01).

CONCLUSION

Routine measurement of Lp(a) level in patients with NIDDM does not seem warranted because no association was found between Lp(a) concentration and CAD in this study population.

Effect of Nandrolone Decanoate on serum lipoprotein (a) and its isoforms in hemodialysis patients

Malnutrition, anemia and increased atherosclerosis are the main causes of mortality in hemodialysis patients. Therapies designed to improve the disorders might therefore be expected to improve outcome. The effects of Nandrolone Decanoate (ND), in 64 stable hemodialysis patients, were studied with respect to the following parameters: nutritional status, hematological indexes, lipid profiles including serum levels of lipoprotein(a) [Lp(a)] in terms of differences in apolipoprotein(a) [apo(a)]. The patients were treated with ND at dose of 100 mg/I.M./week for 4 months. After 2 and 4 months of treatment the elevations in the serum levels of albumin (p < 0.0001), creatinine (p < 0.009), hemoglobin (p < 0.03), hematocrit (p < 0.03), cholesterol (p = 0.007) and triglyceride (p < 0.04) were noticed. Marked decrease in the concentration of high-density lipoprotein cholesterol (p = 0.007) and Lp(a) (p < 0.0001) were also found. These effects after 2 months of treatment withdrawal were relatively constant. By dividing patients according to the baseline Lp(a) levels and molecular weight of apo(a) isoform, it was noticed that the decrease in serum Lp(a) was significant in patients with high Lp(a) (>30 mg/dl) than those of with low Lp(a) (<30 mg/dl), irrespective of apo(a) molecular weight. It may be suggested that, ND has beneficial effect on nutritional status and treatment of anemia in hemodialysis patients. In spite the adverse effect of ND on lipid profile, it decreases Lp(a) mostly in patients with high serum Lp(a) preferently by the effect on apo(a) gene transcriptional activity.

Oral, more than transdermal, estrogen therapy improves lipids and lipoprotein(a) in postmenopausal women: a randomized, placebo-controlled study

OBJECTIVE

To assess the effects of low-dose oral and transdermal estrogen therapy on the lipid profile and lipoprotein(a) [Lp(a)] levels in healthy, postmenopausal women and to study the additional influence of gestodene administration.

DESIGN

In a multicenter, randomized, double-blind, placebo-controlled study, 152 healthy, hysterectomized, postmenopausal women received daily either placebo (n = 49), 50 microg transdermal 17beta-estradiol (tE2, n = 33), 1 mg oral 17beta-estradiol (oE2, n = 37), or 1 mg oE2 combined with 25 microg gestodene (oE2 + G, n = 33) for 13 cycles of 28 days, followed by 4 cycles of placebo in each group. Fasting serum concentrations of total, high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol, triglycerides, and Lp(a) were measured at baseline and in cycles 4, 13, and 17.

RESULTS

In cycle 13, a significant mean percentage decrease from baseline was found in all treatment groups compared with placebo in total cholesterol (tE2, -4.7%; oE2, -6.9%; oE2 + G, -10.5%) and LDL cholesterol (tE2, -5.8%; oE2, -12.6%; oE2 + G, -13.6%). For both oral groups, the reductions were already significant in cycle 4. None of the treatment groups showed a significant change in HDL cholesterol or triglycerides. In cycle 13, Lp(a) was decreased compared with placebo in the oE2 group (-6.6%) and the oE2 + G group (-8.2%). After washout, all observed changes had returned to baseline level, except for the decreases in total and LDL cholesterol in the oE2 + G group.

CONCLUSIONS

Oral E2 and E2 + G, and to a lesser extent transdermal E2, decreased total and LDL cholesterol. Lp(a) was lowered only by the oral treatments.

Modifications in lipoprotein surface charge alter cyclosporine A association with low-density lipoproteins

PURPOSE

The purpose of this study was to examine the influence of lipoprotein surface charge on the plasma distribution of cyclosporine A (CSA).

METHODS

Phosphatidylinositol (PI; 40 micromol) was administered intravenously to rabbits. Blood was removed 10 min after injection and plasma was retrieved. Radiolabeled CSA ([3H] CSA) at a concentration of 1000 ng/mL was incubated for 60 min at 37 degrees C in control and PI-treated rabbit plasma. After incubation, plasma was separated into its lipoprotein and lipoprotein-deficient plasma (LPDP) fractions by density gradient ultracentrifugation, and the percentage of [3H]CSA recovered in each fraction was determined by radioactivity. To determine lipoprotein surface charge within control and PI-treated plasma, the zeta potential of each lipoprotein fraction was measured. The effect of PI on lipoprotein surface charge was further confirmed by gel electrophoresis.

RESULTS

PI treatment caused low-density lipoprotein (LDL) fraction to migrate further on the agarose gel, indicative of an increased negative surface charge. Zeta potential analysis further showed that LDL particles had a surface potential of -11.4 +/- 1.9 mV and -17.4 +/- 3 mV in control and PI-treated groups, respectively. A greater percentage of [3H]CSA was recovered within the LDL (16.4 +/-1.1% vs. 7.7 +/- 2.1%; n = 3; p < 0.05) fraction after incubation in PI treated than in control plasma, respectively.

CONCLUSION

These findings suggest that modifications in lipoprotein surface charge alter CSA distribution within the LDL plasma fraction.

Association between plasma lipoprotein(a) and endothelial dysfunction in normocholesterolemic and non-diabetic patients with angiographically normal coronary arteries

The present study was designed to examine whether elevated levels of lipoprotein(a) (Lp(a)) are related to the impairment of the endothelium-dependent vasoresponse to acetylcholine (ACh) in normocholesterolemic and non-diabetic human normal coronary arteries. ACh (30 microg) was injected into the left main coronary artery of 31 patients (serum low-density cholesterol <160mg/dl and fasting plasma glucose <126mg/dl) with angiographically normal coronary arteries, and the relation between diameter change and lipid levels was analyzed. The mean diameter change of all coronary segments examined (segments 6, 8, 11 and 13) was reduced by 14.6+/-26.5% in response to ACh, but increased by 23.3+/-6.0% in response to nitroglycerin, suggesting endothelial dysfunction in those arteries. The mean diameter change of the left anterior descending artery or left circumflex artery in each patient was negatively correlated only with the level of Lp(a). Stepwise multiple regression analysis also revealed that only Lp(a) among the lipids showed significant correlation with impaired vasodilation (p=0.033). These findings suggest that elevated levels of plasma Lp(a) might be a strong predictor of endothelial dysfunction in normocholesterolemic and non-diabetic subjects.

Impact of glycemic control on serum lipoprotein (a) in Arab children with type 1 diabetes

BACKGROUND

Lipoprotein (a) (Lp (a)) is an independent risk factor for coronary artery disease (CAD), a major cause of death in patients with type 1 diabetes mellitus. Both type 1 diabetes and CAD represent major problems in Kuwait. Data on the effect of metabolic control on Lp (a) in diabetic children are limited and this is particularly true for Arab children. The objectives of the present study were to analyze serum Lp (a) levels in patients with type 1 diabetes compared with non-diabetic children, taking into account the effect of glycemic control.

METHODS

Circulating lipids, including Lp (a), were measured in serum samples from 60 prepubertal non-diabetic children and 58 prepubertal children with type 1 diabetes. Comparisons of Lp (a) concentrations were made between the non-diabetic and diabetic children with good to fair control (glycosylated hemoglobin (GHb) <11%) and a group of diabetic children with poor control (GHb > or = 11%).

RESULTS

The mean serum Lp (a) level in all diabetic children was 187.62+160.43 mg/L, compared with 162.88+156.06 mg/L in the control group. The group of children with poor glycemic control had higher median Lp (a) levels (147.50 mg/L) than either the group of diabetic children with good to fair control (95 mg/L; P<0.028) or the group of non-diabetic children (125 mg/L; P<0.04). Moreover, 38.3% of poorly controlled diabetic children had elevated Lp (a) levels > or = 250 mg/L, compared with 12.5% of diabetic children with good to fair control and 16.7% of non-diabetic children (P<0.025 and P<0.039, respectively). No association was found between Lp (a), diabetes duration and insulin dose.

CONCLUSIONS

In Arab children, highest Lp (a) levels are associated with poorest metabolic control. The prevalence of Lp (a) levels associated with cardiovascular risk is higher in poorly controlled diabetic children. Increased levels of Lp (a) may be another contributing factor to the high risk for CAD in diabetic patients.

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).

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.

High level of lipoprotein(a) is a strong predictor for progression of coronary artery disease

Elevated levels of serum lipoprotein(a) [Lp(a)] are reported to be associated with risk of atherosclerosis and thrombosis. Little is known about the influence of Lp(a) on the progression of coronary artery disease. We evaluated the association of serum Lp(a) and the long-term changes of angiographic severity in patients who underwent repeated coronary angiography at intervals of more than 2 years. We evaluated 70 patients, and divided them into 3 groups by angiographic findings. Median Lp(a) concentration was significantly higher in the progression group (N=36) than in the no-change group (N=23) or the regression group (N=11) (32.4 vs 22, 19.3 mg/dl, p<0.05). Furthermore, the progression group had more patients whose Lp(a) levels were greater than 30 mg/dl (p=0.006), while in the regression group all patients were under 30 mg/dl. Stepwise logistic regression analysis for progression of lesions showed that Lp(a) > or =30 mg/dl remained significant, giving an estimated odds ratio (OR) of 2.46 (p= 0.005). In the subgroup analysis, OR in patients with mild lesions was reduced to 2.05 (p<0.05) while in patients with severe lesions OR was increased to 3.39 (p=0.003). The serum Lp(a) level has a close correlation with angiographic progression, and may be an important predictor for progression.

Lipoprotein (a) and the risk of ischemic stroke in young women

BACKGROUND AND PURPOSE

lipoprotein (a) (lp (a)) is a lipid-containing particle similar to LDL which has been found in atherosclerotic plaque. The role of lp (a) in ischemic stroke remains controversial, but some studies suggest lp (a) is particularly important as a risk factor for stroke in young adults. We investigated the role of lp (a) as a risk factor for stroke in young women enrolled in the Stroke Prevention in Young Women Study.

METHODS

subjects were participants in a population-based, case-control study of risk factors for ischemic stroke in young women. Cases were derived from surveillance of 59 regional hospitals in the central Maryland, Washington DC, Pennsylvania and Delaware area. Lp (a) was measured in 110 cases and 216 age-matched controls. Demographics, risk factors, and stroke subtype were determined by interview and review of medical records.

RESULTS

lp (a) values were higher in blacks than whites, but within racial groups, the distribution of lp (a) values was similar between cases and controls. After adjustment for age, race, hypertension, diabetes, cigarette smoking, coronary artery disease, total cholesterol and HDL cholesterol, the odds ratio for an association of lp (a) and stroke was 1.36 (95% CI 0.80-2.29). There was no dose-response relationship between lp (a) quintile and stroke risk. Among stroke subtypes, only lacunar stroke patients had significantly elevated lp (a) values compared to controls.

CONCLUSIONS

we found no association of lp (a) with stroke in a population of young women with ischemic stroke. Small numbers of patients limit conclusions regarding risk in ischemic stroke subtypes, but we could not confirm previous suggestions of an association of lp (a) with atherosclerotic stroke in young adults.

Are lipid-dependent indicators of cardiovascular risk affected by renal transplantation?

Hyperlipoproteinemia has been reported to frequently occur in kidney transplanted patients, thus possibly explaining, at least in part, the increased incidence of cardiovascular disease in this population. To evaluate the impact of renal transplantation (Tx), and related immunosuppressive therapy, on plasma lipoprotein and Lp(a) profile, we selected a cohort of kidney transplanted patients (36 M/14 F; age 33.8 + 12.0 yr, range 13-62) lacking significant causes of hyperlipidemia. All patients received a triple immunosuppressive regimen and showed a stable renal function after Tx (plasma creatinine: 1.36 +/- 0.35 mg/dL). One year after Tx, we found a significant increase of total cholesterol (TC), LDL, HDL, ApoB and ApoA-I (p < 0.005), while plasma triglyceride levels remained unmodified. Lp(a) plasma levels after Tx were within the normal range and displayed a significant inverse relationship with apo(a) size. Noteworthy, LDL/HDL ratio and ApoB/ ApoA-I ratio in kidney transplanted patients were almost superimposable with those of normal controls. Specifically, LDL/HDL ratio significantly decreased in 64% of patients after Tx, due to a prevalent increase of HDL, and was associated with a moderate amelioration of plasma TG. In a multiple linear regression model, post-Tx HDL level was significantly related to recipient's age, gender, BMI and cyclosporine (CyA) trough levels (Adj-R2 = 0.35, p = 0.0002), with gender and CyA trough levels being the better predictors of HDL. In conclusion, immunosuppressive regimens, in themselves, do not appear to significantly increase the atherogenic risk related to lipoproteins. Rather, other factors can affect the lipoprotein profile and its vascular effects in renal transplant recipients.

Effects of misoprostol on lipoprotein (a) levels of ovariectomized rats

OBJECTIVE

To determine the effects of misoprostol on plasma lipoprotein (a) concentrations of ovariectomized rats.

DESIGN

Controlled prospective study.

SETTING

Animal research laboratory.

ANIMAL(S)

Four-month-old female Sprague-Dawley rats.

INTERVENTION(S)

Blood samples were obtained before and 60 days after ovariectomy, and the rats were divided into three groups. Group I (five rats) was treated with vehicle (water); groups II and III (nine and eight rats, respectively) were treated with oral misoprostol at 100 and 200 microg/kg/d, respectively, for 60 days, after which blood was drawn again.

MAIN OUTCOME MEASURE(S)

Serum lipoprotein (a) levels.

RESULT(S)

The median lipoprotein (a) level before ovariectomy was 10.8 mg/dL (range, 10.6-46.5 mg/dL). Sixty days after ovariectomy, the level increased significantly to 15.9 mg/dL (range, 10.6-36.9 mg/dL). After treatment, there was no change in lipoprotein (a) levels in the vehicle-treated group (range, 16.3-21.1 mg/dL); however, the lipoprotein (a) levels decreased significantly in the group treated with 100 microg/kg/d of misoprostol, from 15.4 mg/dL to 10.8 mg/dL, and in the group treated with 200 microg/kg/d of misoprostol, from 17.1 mg/dL to 10.6 mg/dL.

CONCLUSION(S)

Misoprostol caused a significant decrease in lipoprotein (a) levels.

Associations among serum lipoprotein(a) levels, apolipoprotein(a) phenotypes, and myocardial infarction in patients with extremely low and high levels of serum lipoprotein(a)

A high serum lipoprotein(a) [Lp(a)] level, which is genetically determined by apolipoprotein(a) [apo(a)] size polymorphism, is an independent risk factor for coronary atherosclerosis. However, the associations among Lp(a) levels, apo(a) phenotypes, and myocardial infarction (MI) have not been studied. Patients with MI (cases, n = 101, M/F: 86/15, age: 62+/-10y) and control subjects (n = 92, M/F: 53/39, age: 58+/-14y) were classified into quintile groups (Groups I to V) according to Lp(a) levels. Apo(a) isoform phenotyping was performed by a sensitive, high-resolution technique using sodium dodecyl sulfate-agarose/gradient polyacrylamide gel electrophoresis (3-6%), which identified 26 different apo(a) phenotypes, including a null type. Groups with higher Lp(a) levels (Groups II, III, and V) had higher percentages of MI patients than that with the lowest Lp(a) levels (Group I) (54%, 56%, or 75% vs. 32%, p<0.05). Groups with different Lp(a) levels had different frequency distributions of apo(a) isoprotein phenotypes: Groups II, III, IV, and V, which had increasing Lp(a) levels, had increasingly higher percentages of smaller isoforms (A1-A4, A5-A9) and decreasingly lower percentages of large isoforms (A10-A20, A21-A25) compared to Group I. An apparent inverse relationship existed between Lp(a) and the apo(a) phenotype. Subjects with the highest Lp(a) levels (Group V) had significantly (p<0.05) higher serum levels of total cholesterol, apo B, and Lp(a). Patients with MI and the controls had different distributions of apo(a) phenotypes: i.e., more small isoforms and more large size isoforms, respectively (A1-A4/A5-A9/A10-A20/A21-A25: 35.7%/27.7%/20.8%/15.8% and 22.8%/23.9%/29.4%/23.9%, respectively). Lp(a) (parameter estimate +/- standard error: 0.70+/-0.20, Wald chi2 = 12.4, p = 0.0004), apo(a) phenotype (-0.43+/-0.15, Wald chi2 = 8.17, p = 0.004), High-density lipoprotein-cholesterol, apo A-I, and apo B were significantly associated with MI after adjusting for age, gender, and conventional risk factors, as assessed by a univariate logistic regression analysis. The association between Lp(a) and MI was independent of the apo(a) phenotype, but the association between the apo(a) phenotype and MI was not independent of Lp(a), as assessed by a multivariate logistic regression analysis. This association was not influenced by other MI- or Lp(a)-related lipid variables. These results suggest that apo(a) phenotype contributes to, but does not completely explain, the increased Lp(a) levels in MI. A stepwise logistic regression analysis with and without Lp(a) in the model identified Lp(a) and the apo(a) phenotype as significant predictors for MI, respectively.

Effect of Lp(a) on the early functional and structural changes of atherosclerosis

Epidemiologic studies have shown a significant relationship between elevated plasma levels of Lp(a) and increased risk of cardiovascular events; however, the mechanisms by which elevated Lp(a) levels produce this increased risk are not known. To test the hypothesis that high Lp(a) levels might contribute to the development of subclinical atherosclerosis, we examined the influence of Lp(a) levels on early functional and structural atherosclerotic vascular changes. Flow-mediated (endothelium-dependent) and nitrate-mediated (smooth muscle-dependent) arterial dilations were measured by high-resolution ultrasound in 241 normal healthy subjects (aged 15 to 69 years; 116 men). In addition, carotid artery intima-media thickness was measured by ultrasound in 71 subjects. Plasma Lp(a) was measured using a 2-sided immunoradiometric assay (cohort median, 10 mg/dL; interquartile range, 3.9 to 24.4 mg/dL). In these subjects, there were no significant relationships between Lp(a) and arterial endothelial function, smooth muscle responses, or carotid wall thickness (P>0.25). By contrast, other lipid risk factors, such as LDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratio, were significantly correlated with abnormal arterial function and structure (P</=0.01). These data suggest that elevated Lp(a) levels do not confer cardiovascular risk by contributing to the early functional or structural changes of atherosclerosis.