Apo Phenotypes Research Articles

Relation of Apolipoprotein(a) Size to Alzheimer’s Disease and Vascular Dementia

Lipoprotein(a) [Lp(a)] level is a newly established vascular risk factor which has been suggested to play a role in dementia. However, the majority of Lp(a) cell-to-cell interactions are mediated by its specific apolipoprotein(a) [apo(a)] moiety. This suggests that the size polymorphism of apo(a) may be of importance in conveying the Lp(a)-related risk. Specifically, we postulated that variation in apo(a) isoform size may lead to increased risk of vascular dementia (VaD), Alzheimer’s disease (AD), stroke, or all three of them. Under a case-control design we compared Lp(a) plasma levels and the distribution of apo(a) phenotypes in groups of subjects consisting of 50 VaD patients, 162 sporadic AD patients, 95 non-demented stroke patients (NDS), and 105 normal controls. The prevalence of small-sized apo(a) isoforms in the VaD group was significantly higher than that in the stroke and normal control groups, with an odds ratio of 5.29 (95% CI 2.24–12.49, p = 0.0001) for the development of VaD for individuals with at least one apo(a) isoform of low molecular weight (LMW). Furthermore, the possession of at least one small-sized apo(a) isoform significantly increased the risk of AD to 1.92 (95% CI 1.02–3.61, p = 0.0434). Our results demonstrate that possession of at least one LMW apo(a) isoform is significantly associated with dementia and specifically offer new evidence of a strong association between the lipoprotein system and post-stroke dementia.

Apolipoprotein(a) size polymorphism is associated with coronary heart disease in polygenic hypercholesterolemia

In addition to high serum cholesterol levels, various cardiovascular risk factors may be involved in the development of coronary heart disease (CHD) in hypercholesterolemic subjects. As the levels of lipoprotein(a) [Lp(a)], an important and independent cardiovascular risk factor, are high in polygenic hypercholesterolemia (PH), we investigated plasma Lp(a) levels and apolipoprotein(a) [apo(a)] phenotypes in relation to occurrence of CHD events in PH patients. Lp(a) levels and apo(a) isoforms were determined in 191 PH patients, 83 normocholesterolemic subjects with CHD, and 94 normocholesterolemic controls without CHD. Lp(a) levels were similar in the hypercholesterolemic subjects with (n=100) or without CHD (n=91): 21.4 (range 6.6-59.23) vs 18.5 (range 5.25-57.25) mg/dL (p=NS). Low molecular weight apo(a) isoforms were more prevalent (55%) in the PH patients with CHD, whereas high molecular weight apo(a) isoforms were more prevalent (62.6%) in those without CHD: this difference was significant (p<0.05). A stepwise multiple-discriminant analysis made in order to determine the independence of common cardiovascular risk factors, Lp(a) levels and low molecular weight apo(a) isoforms in predicting CHD among hypercholesterolemic subjects showed that the presence of a positive family history of CHD, smoking, age, and the presence of at least one apo(a) isoform of low molecular weight were independently associated with CHD. Despite high Lp(a) levels, our findings do not support the hypothesis that Lp(a) plays an independent role in determining clinical CHD in PH subjects. However, the presence of at least one low molecular weight apo(a) isoform is an independent genetic predictor of CHD in hypercholesterolemic subjects. Together with other cardiovascular risk factors, apo(a) phenotypes should be assessed to evaluate the overall CHD risk status of all subjects with high serum cholesterol levels.

Lipoprotein(a)- and low-density lipoprotein–derived cholesterol in nephrotic syndrome: Impact on lipid-lowering therapy?

Patients with nephrotic syndrome have the highest lipoprotein(a) [Lp(a)] concentrations known. Lp(a) is an low-density lipoprotein (LDL)-like particle consisting of 45% cholesterol. The usual methods to determine LDL cholesterol do not distinguish between cholesterol derived from LDL and Lp(a) and are thus the net result of cholesterol levels from both lipoproteins. High Lp(a) concentrations therefore significantly contribute to the measured or calculated LDL cholesterol levels. Since statins have no influence on Lp(a) levels, it can be expected that the LDL cholesterol-lowering effect of statins may be diminished in patients who have a pronounced elevation of Lp(a) levels accompanied by only moderate elevations of LDL cholesterol. We investigated 207 patients with nondiabetic nephrotic syndrome in whom Lp(a) concentrations were strikingly elevated when compared to 274 controls (60.4 +/- 85.4 mg/dL vs. 20.0 +/- 32.8 mg/dL, P < 0.0001). According to National Kidney Foundation Dialysis Outcomes Quality Initiative (K/DOQI) Clinical Practice Guidelines for Managing Dyslipidemias, almost 95% of these patients are candidates for a therapeutic intervention to lower LDL cholesterol. LDL cholesterol levels corrected for Lp(a)-derived cholesterol, however, were 27 mg/dL lower than uncorrected concentrations (compared to only 9 mg/dL in controls). If Lp(a)-corrected levels instead of total LDL cholesterol levels were used, 25.7% of patients with low-molecular-weight (LMW) apolipoprotein(a) [apo(a)] isoforms were classified no longer to be in need of LDL cholesterol-lowering therapeutic intervention compared to only 2.3% of patients with high-molecular-weight (HMW) apo(a) phenotypes (P < 0.00001). This ("pseudo") pharmacogenetic effect results in incorrect determination of LDL cholesterol. Our observation has an impact on the indication for, and assessment of efficacy of intervention. This potential artifact should be investigated in ongoing large trials in renal patients as well as in nonrenal African American subjects who have on average markedly higher Lp(a) levels. In nonrenal Caucasian subjects with much lower Lp(a) concentrations, this issue will be less relevant.

Lipoprotein(a)-Associated Atherothrombotic Risk in Hemodialysis Patients

Background: Hemodialysis patients show a considerably higher risk of atherothrombotic disease than the general population. We investigated both lipoprotein(a) [Lp(a)] plasma levels and apolipoprotein(a) [apo(a)] phenotypes in relation to occurrence of atherothrombotic events in hemodialysis patients compared with subjects showing a normal kidney function. Methods: Lp(a) levels and apo(a) isoforms were determined in 118 hemodialysis patients, including 59 with prior atherothrombotic events, and in 182 subjects with normal creatinine clearance, including 82 who experienced a prior atherothrombotic event. Results: Lp(a) levels in hemodialysis patients (median; 20 mg/dl) were higher (p < 0.01) than in age- and sex-matched subjects with normal renal function without a history of atherothrombosis (11.3 mg/dl). Among hemodialysis patients, median Lp(a) levels were higher in subjects with than in those without prior atherothrombosis (34 vs. 15 mg/dl, p < 0.05). In hemodialysis patients and in subjects without nephropathy, the percentage of low-molecular-weight apo(a) phenotypes were significantly higher in patients with than in those without a history of prior atherothrombotic events (56.9% vs. 33.9%, p < 0.05; 62.2% vs. 25%, p < 0.00001,respectively). Stepwise regression analysis indicated that the presence of at least one apo(a) isoform of low molecular weight was an independent predictor of atherothrombosis in hemodialysis patients (p < 0.05). Conclusions: Elevated Lp(a) plasma levels appear to be associated with atherothrombosis, independent of their origin due to genetic factors or related to the impaired kidney function. Low-molecular-weight apo(a) isoforms are reliable genetic markers of atherothrombosis both in patients with impaired kidney function and in subjects without nephropathy.

Apolipoprotein(a) phenotypes are reliable biomarkers for familial aggregation of coronary heart disease

Lipoprotein(a) [Lp(a)] is an atherogenic and prothrombotic molecule formed by the covalent binding of the highly polymorphic apolipoprotein(a) [apo(a)] to apoprotein B-100 of LDL. High Lp(a) concentrations are a recognized genetic risk factor for coronary heart disease (CHD) and have been shown to be related with a familial clustering of ischemic cardiac events. Nevertheless, the association between apolipoprotein(a) isoforms and a positive familial history of CHD has received far less attention. In this report, we explored the distribution of apo(a) phenotypes in 127 CHD subjects with a family history of coronary events and in 92 CHD patients without such a history. Twenty-two apo(a) isoforms were detected by a high-resolution immunoblotting method. In univariate analysis, the percentage of subjects with at least one small sized apo(a) isoform was significantly higher in CHD patients with a positive family history than in those without (P<0.01). Multivariate analysis showed that apo(a) isoforms of low molecular weight were the best predictors of familial aggregation of cardiac ischemia. We conclude that apo(a) size polymorphism is strongly associated with a familial history of CHD and is more efficient than Lp(a) plasma concentrations in predicting the familial clustering of coronary disease. When detected by high-resolution techniques, apo(a) phenotypes are objective laboratory markers that can substitute for a knowledge of a positive family history of CHD and should be used, together with Lp(a) levels, to better assess the familial predisposition to coronary events.

The apolipoprotein(a) size polymorphism is associated with nephrotic syndrome

The atherogenic serum lipoprotein(a) [Lp(a)] is significantly elevated in patients with nephrotic syndrome. The underlying mechanism for this elevation is poorly understood. We investigated in 207 patients with nondiabetic nephrotic syndrome and 274 controls whether the apolipoprotein(a) [apo(a)] kringle-IV repeat polymorphism explains the elevated Lp(a) levels in these patients. Patients showed a tremendous elevation of Lp(a) concentrations when compared to controls (mean 60.4 vs. 20.0 mg/dL and median 29.8 vs. 6.4 mg/dL, P < 0.0001). Primary and secondary causes contributed to this elevation. The primary causes became apparent by a markedly elevated number of low-molecular-weight apo(a) phenotypes which are usually associated with high Lp(a) levels. This frequency was 35.7% in patients compared to only 24.8% in controls (P= 0.009). In addition, secondary causes by the pathogenetic mechanisms of the nephrotic syndrome itself resulted in a different increase of Lp(a) in the various apo(a) isoform groups. Based on the measured Lp(a) concentrations in each subject, we calculated separately the Lp(a) concentrations arising from the two expressed isoforms by estimating the relative proportion of the two serum isoforms in the sodium dodecyl sulfate (SDS) agarose gel electrophoresis. Low-molecular-weight isoforms were associated with 40% to 75% elevated Lp(a) concentrations when compared to matched isoforms from controls. High-molecular-weight apo(a) isoforms showed 100% to 500% elevated Lp(a) levels compared to matched isoforms from controls. The severity of the nephrotic syndrome as well as the degree of renal impairment did not influence the Lp(a) concentrations. The tremendously increased Lp(a) levels in nephrotic syndrome ar caused by primary genetic as well as disease-related mechanisms.

Relationship between plasma lipoprotein (a), apolipoprotein (a) phenotypes, and other coronary heart disease risk factors in a Melbourne South Asian population

Background: High plasma lipoprotein(a) [Lp(a)] level is a strong and important risk factor for cardiovascular disease (CVD). Small-sized apolipoprotein(a) [apo(a)] isoforms (F, B, S1, and S2) are inversely correlated with the high levels of Lp(a) in plasma and significantly associated with CVD. Although the effects of apo(a) phenotypes and various risk factors on Lp(a) status in South Asian population may have been studied in other countries, there are no reports involving these risk factors in Australia. Methods and results: Factors contributing to variation in Lp(a) were surveyed in 402 (216 males and 186 females) South Asian Melburnians. There was a negative relationship between low alcohol beer per day and Lp(a) in men ( P < 0.05). Approximately 21% of the variance of Lp(a) concentration in men and 6% in women were explained by age. Age was positively associated with Lp(a) concentrations in men but negatively in women. The most commonly occurring phenotype was apo(a) S3. In this phenotype, Lp(a) concentrations ranged from non-detectable to 811 mg/l. After adjusting for age, an inverse correlation was observed between Lp(a) concentration and apo(a) phenotypes ( P < 0.01). Conclusions: Although Lp(a) has been reported to be genetically determined, there are clearly other factors contributing to variations in Lp(a) concentrations in a South Asian population.

In vitro inhibition of fibrinolysis by apolipoprotein(a) and lipoprotein(a) is size- and concentration-dependent

Lipoprotein(a) (Lp(a)) is considered an independent risk factor for atherosclerotic heart and circulatory diseases. The unique, polymorphic character of Lp(a) is based on its apolipoprotein(a) (apo(a)), which has remarkable structural analogies with plasminogen, an important protein for fibrinolysis. The formation of plasmin from plasminogen is a fundamental step in the dissolution of fibrin. Repression of this step may lead to a deceleration of fibrinolysis. It has been suggested that Lp(a) has antifibrinolytic properties through apo(a) and that the apo(a)-size polymorphism has a distinct influence on the prothrombotic properties of Lp(a). However, the results on this topic are controversial. Therefore we used a standardized in vitro fibrinolysis model to provide further information on the influence of Lp(a) on plasmin formation. Monitoring the time-course of plasmin formation, we investigated the inhibition of plasmin formation through dependence on Lp(a), respectively, free apo(a) concentration. Furthermore, we investigated the influence of three Lp(a)/apo(a) phenotypes ((22K)Lp(a), 22 kringle-4 repeats; (30K)Lp(a), 30 kringle-4 repeats; (35K)Lp(a), 35 kringle-4 repeats). Adding varying amounts of Lp(a) to our model, we observed that the rate of plasmin formation was inversely related to the Lp(a) concentration. At 0.1 micromol/l (30K)Lp(a), for example, the plasmin formation was reduced by 12.7% and decreased further by 40.7% at 0.25 micromol/l Lp(a). A similar but more distinct effect was observed when free (30K)apo(a) was added to the model (25.3% at 0.1 micromol/l vs. 59.3% at 0.25 micromol/l). Comparing the antifibrinolytic influence of different apo(a) phenotypes we found that the reduction of plasmin generation advanced with the size of apo(a). At 0.1 micromol/l Lp(a) the reduction of the plasmin formation increased in the order (22K)Lp(a), (30K)Lp(a) and (35K)Lp(a) from 3.7% to 10.7% and 22.3%, respectively. Experiments with different phenotypes of free apo(a) showed similar results (0.5 micromol/l: (22K)apo(a), 56.4% vs. (30K)Lp(a), 80.4%). Summarizing these results, our study indicates a distinct interrelation of Lp(a)/apo(a) phenotype and concentration with the formation of plasmin. From the antifibrinolytic Lp(a)/apo(a) effect in vitro it may be hypothesized that Lp(a)/apo(a) also has an inhibitory influence on in vivo fibrinolysis.

Time-dependent lipid response on fluvastatin therapy of patients with hypercholesterolemia sensitive to apoE phenotype

Sixty-seven male patients with hypercholesterolemia, divided into three groups according to apolipoprotein E phenotype (33 with apoE3/3 phenotype, E3 group; 23 with 2/2 or 2/3, E2+ group; 11 with 4/4 or 4/3, E4+ group), received daily 20–40 mg of fluvastatin for 12 weeks. The levels of triglyceride (TG), cholesterol (Chol), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured after 0, 4, 8 and 12 weeks on fluvastatin and after 4 weeks washout period. Lipid percentage changes (Δ) were not associated with apoE phenotype for any treatment time. Cholesterol decreased by 14% after 12 weeks and HDL-C increased by 14–16% after 12 weeks for three phenotype groups. ΔTG, ΔChol, ΔLDL-C were associated positively, while negatively for ΔHDL-C, with the corresponding basal lipid values for the three groups. The positive ΔTG values occurred at a low basal TG 0 level and became negative at TG 0 >1.6–1.9 mM. For E3 and E4+ groups, only a single parameter contributed significantly into a variation of lipid percentage changes. For the E2+ group, TG 0 and Chol 0 contributed in a reciprocal manner into ΔTG 12/0, both positively into ΔChol 8/0; Chol 0 and HDL-C 0 both negatively contributed into ΔHDL-C 12/0. HDL-C 0 contributed reciprocally into LDL-C variability for E2+ and E4+ groups. Three effects seem to contribute differently into lipid response among patients with different apoE phenotype: the inhibition of hepatic and lipoprotein lipase activities, the competition between TG-rich and low-density lipoproteins for LDL-receptor and the accumulation of intermediate-density lipoproteins in patients bearing E2 isoform.

Relationship between apolipoprotein(a) size polymorphism and coronary heart disease in overweight subjects.

BackgroundOverweight is associated with an increased cardiovascular risk which is only partially explained by conventional risk factors. The objective of this study was to evaluate lipoprotein(a) [Lp(a)] plasma levels and apolipoprotein(a) [apo(a)] phenotypes in relation to coronary heart disease (CHD) in overweight subjects.MethodsA total of 275 overweight (BMI ≥ 27 kg/m2) subjects, of which 155 had experienced a CHD event, 337 normal weight subjects with prior CHD and 103 CHD-free normal weight subjects were enrolled in the study. Lp(a) levels were determined by an ELISA technique and apo(a) isoforms were detected by a high-resolution immunoblotting method.ResultsLp(a) levels were similar in the three study groups. Overweight subjects with CHD had Lp(a) concentrations significantly higher than those without [median (interquartile range): 20 (5–50.3) versus 12.6 (2.6–38.6) mg/dl, P < 0.05]. Furthermore, overweight subjects with CHD showed a higher prevalence of low molecular weight apo(a) isoforms than those without (55.5% versus 40.8%, P < 0.05) and with respect to the control group (55.5% versus 39.8%, P < 0.05). Stepwise regression analysis showed that apo(a) phenotypes, but not Lp(a) levels, entered the model as significant independent predictors of CHD in overweight subjects.ConclusionsOur data indicate that small-sized apo(a) isoforms are associated with CHD in overweight subjects. The characterization of apo(a) phenotypes might serve as a reliable biomarker to better assess the overall CHD risk of each subject with elevated BMI, leading to more intensive treatment of modifiable cardiovascular risk factors.

Association between small apolipoprotein(a) isoforms and frontotemporal dementia in humans

Apolipoprotein(a) [apo(a)] is a genetically polymorphic glycoprotein that has several similarities to apolipoprotein E. However, its role as a risk factor for frontotemporal dementia (FTD) remains to be elucidated. We therefore investigated the effect of an apo(a) polymorphism on the incidence of FTD in a sample of Caucasian Italian patients. From the entire group of FTD patients ( n=54), 55.6% of the subjects had at least one apo(a) low molecular weight (MW) isoform, compared to 29.9% of non-demented controls ( n=77). The difference between the two groups was statistically significant (odds ratio 2.93, 95% confidence interval 1.42–6.06, P=0.003). The FTD group was further divided into sporadic ( n=26) and familial ( n=28) cases. Even after such dichotomization, both sporadic and familial FTD patients showed a significantly higher prevalence of low MW apo(a) isoforms than the cognitively healthy controls ( P=0.011 and P=0.025, respectively). Our data suggest a role of apo(a) phenotypes of low MW in mediating susceptibility to FTD.

Antibody phenotyping test for the human apolipoprotein E2 isoform.

Numerous methods have been described to determine the apolipoprotein E (apoE) phenotype or genotype of individuals (1)(2). These techniques are relatively time-consuming, and interpretation of the results can be difficult. Here, we report the development of a rapid and specific antibody-based test for the identification of the apoE2 isoform. Previously, we characterized the binding properties of a panel of anti-human apoE monoclonal antibodies (mAbs) (3)(4)(5). The locations of epitopes of selected mAbs from the panel are presented in Fig. 1A⇓ . Although neither mAb 6C5 nor 3H1 showed apoE isoform specificity, mAb 2E8 recognized an epitope that includes the apoE LDL receptor-binding site and resembles the LDL receptor in terms of its fine specificity. Several apoE variants that are defective in their ability to mediate binding of lipoproteins to the LDL receptor and are associated with type III hyperlipoproteinemia are poorly recognized by mAb 2E8. These include the relatively common apoE2 (Arg158-Cys) isoform as well as many, but not all, of the rare variants, including apoE2 (Arg136-Ser). Thus, similar to DNA-based phenotyping assays, our immunoassay is designed to detect the most common apoE2 isoforms. When mixtures of purified apoE2 and apoE3 were prepared and tested in a sandwich ELISA format using mAb 6C5 for capture and the 2E8-horseradish peroxidase (HRP) conjugate for the identification, there was selective identification of the apoE3 isoform (Fig. 1D⇓ ). Similarly, there was selective identification of apoE2 in mixtures …

ApoE phenotype influences plasma ASP in hyperapoB subjects

Acylation stimulating protein (ASP) is increased in cardiovascular patients who often present with dyslipidemias. The aim of the present study was to examine the influence of apolipoprotein E (apoE) phenotype and lipids on ASP. Plasma ASP, lipids and apoE phenotype were measured in 407 subjects and separated according to the 75th percentile of apolipoprotein B (apoB) into a HyperapoB (HB) group (apoB=152±34 mg/dl, 117 men, 80 women) and a normal apoB (NB) group (apoB=88±19 mg/dl, 126 men, 84 women). Triglyceride (TG), cholesterol and LDL cholesterol were significantly increased in HB versus NB but there was no difference in age or body mass index (BMI). HB had increased ASP (42%>75th percentile, median=48.4 nM, P<0.001) versus NB (36.5 nM). There was no difference in ASP in NB with any apoE3 variant (E3/3=41 nM, n=98; E3/4=46 nM, n=55; E3/2=50 nM, n=41), but ASP was increased in E2/2 (126 nM, n=9), and E4/4 (186 nM, n=5, P<0.001 ANOVA). In HB, ASP was increased in three apoE phenotypes: E2/4 (209 nM, n=6), E2/2 (135 nM, n=6) and E4/4 (189 nM, n=26), P<0.001 ANOVA relative to the other apoE phenotypes (E3/3=50 nM, n=102; E3/4=41 nM, n=40; E3/2=87 nM, n=17) with a wide range of values. By stepwise regression analysis, the best model that predicted ASP was: [plasma non-esterified fatty acid (NEFA)+TG+cholesterol], where r=0.407, P=0.001. These data suggest that apoE phenotype may potentially influence ASP, although primarily in rare apoE phenotypes.

Oxidized LDL Autoantibodies Are Related to Apolipoprotein E Phenotype, Independently of Postprandial Change in Plasma Triglycerides and LDL Size, among Patients with Angiographically Verified Coronary Artery Disease and Healthy Controls

Objective: Oxidized low-density lipoprotein (LDL) autoantibodies (oxLDLab), apolipoprotein E (apoE) phenotype, postprandial triglyceride changes and LDL size are suggested to be risk factors for coronary artery disease (CAD). Our aim was to study the interaction between these new risk factors among patients with CAD and healthy controls. Methods: oxLDLab from 31 men with angiographically verified CAD and 31 healthy men were analyzed by enzyme-linked immunosorbent assay. Isoelectric focusing and immunoblotting were used for apoE phenotyping. Triglyceride level was measured after 12 h of fasting and 3, 5 and 7 h after a high-fat meal. Nondenaturing gradient gel electrophoresis was used to separate LDL particles according to size. Results: oxLD- Lab levels increased according to apoE phenotype in the following order: E2 < E3 < E4 (p = 0.004, ANOVA). The postprandial response of triglycerides, the size of LDL particles and the concentration of LDL and high-density lipoprotein (HDL) cholesterol did not differ between apoE phenotypes, and the use of these variables as covariates did not change the statistically significant difference in oxLDLab levels between apoE phenotypes (p = 0.01, ANCOVA). oxLDLab levels did not differ between the patient and control groups. Conclusion: We found an association between apoE allele Ε2 and decreased levels of oxLDLab, which was independent of the postprandial response of triglycerides, the size of LDL particles and plasma LDL and HDL cholesterol levels. The mechanism by which apoE affects oxidation of LDL remains unknown.

Lipoprotein (a) levels and apolipoprotein (a) isoform size in patients with subclinical hypothyroidism: effect of treatment with levothyroxine.

The increased risk for ischemic heart disease (IHD) associated with subclinical hypothyroidism (SH) has been partly attributed to dyslipidemia. There is limited information on the effect of SH on lipoprotein (a) [Lp(a)], which is considered a significant predictor of IHD. Serum Lp(a) levels are predominantly regulated by apolipoprotein [apo(a)] gene polymorphisms. The aim of our study was to evaluate the Lp(a) levels and apo(a) phenotypes in patients with SH compared to healthy controls as well as the influence of levothyroxine substitution therapy on Lp(a) values in relation to the apo(a) isoform size. Lp(a) levels were measured in 69 patients with SH before and after restoration of a euthyroid state and in 83 age- and gender-matched healthy controls. Apo(a) isoform size was determined by sodium dodecyl sulfate (SDS) agarose gel electrophoresis followed by immunoblotting and development via chemiluminescence. Patients with SH exhibited increased Lp(a) levels compared to controls (median value 10.6 mg/dL vs. 6.0 mg/dL, p = 0.003]), but this was not because of differences in the frequencies of apo(a) phenotypes. There was no association between thyrotropin (TSH) and Lp(a) levels in patients with SH. In subjects with either low (LMW; 25 patients and 28 controls) or high (HMW; 44 patients and 55 controls) molecular weight apo(a) isoforms, Lp(a) concentrations were higher in patients than in the control group (median values 26.9 mg/dL vs. 21.8 mg/dL, p = 0.02 for LMW, and 6.0 mg/dL versus 3.3 mg/dL, p < 0.001 for HMW). Levothyroxine treatment resulted in an overall reduction of Lp(a) levels (10.6 mg/dL baseline vs. 8.9 mg/dL posttreatment, p = 0.008]). This effect was mainly evident in patients with LMW apo(a) isoforms associated with high baseline Lp(a) concentrations (median values 26.9 mg/dL vs. 23.2 mg/dL pretreatment and posttreatment, respectively; p = 0.03). In conclusion, even though a causal effect of thyroid dysfunction on Lp(a) was not clearly demonstrated in patients with SH, levothyroxine treatment is beneficial, especially in patients with increased baseline Lp(a) levels and LMW apo(a) isoforms.

Novel mass spectrometric immunoassays for the rapid structural characterization of plasma apolipoproteins

Novel mass spectrometric immunoassays (MSIAs) for the isolation and structural characterization of plasma apolipoprotein A-I (apoA-I), apoA-II, and apoE have been developed. The assays combine selective isolation of apolipoprotein species via affinity capture with mass-specific detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In application, plasma (from 50 microl of whole blood drawn from individuals, using finger lancet) was addressed with affinity pipette tips derivatized with antibodies toward the specific apolipoprotein. The time required for each assay was approximately 15 min, less if assays on multiple individuals were performed in parallel. In a brief study of five individuals, several recently reported apoA-II variants were identified and observed consistently in all individuals. Additionally, the apoE phenotype of E3/E3 was observed in three of the individuals, and E2/E3 and E3/E4 observed in the remaining two individuals, the latter of whom suffers from Alzheimer's disease. Overall, the MSIA approach offers a rapid, sensitive, and highly accurate means of profiling apolipoproteins from small volumes of plasma.

Efficiency of intestinal cholesterol absorption in humans is not related to apoE phenotype

The present study investigated the role of apolipoprotein E (apoE) phenotype on intestinal cholesterol absorption and cholesterol synthesis. Studies were carried out in eight subjects homozygous for the apoE4 and 12 subjects homozygous for the E2 allele (six normocholesterolemic volunteers and six patients with type III hyperlipoproteinemia). Cholesterol absorption did not differ between the three groups of subjects and averaged 38 +/- 2% (mean +/- SEM) in normolipemic E2/2, 37 +/- 4% in type III hyperlipemic E2/2, and 41 +/- 3% in E4/4 subjects, respectively. Dietary intake of fat and cholesterol had no influence on cholesterol absorption efficiency. A positive correlation between efficiency of cholesterol absorption and the ratio of campesterol to cholesterol in plasma, an indirect marker for cholesterol absorption, was observed after combining the results of the three groups (r = 0.504; P < 0.02). Bile acid and total cholesterol synthesis were also not affected by the different apoE alleles, but the well-known relationship between body weight and cholesterol synthesis was noticed (r = 0.574; P < 0.01). Thus, the present study provides evidence that the efficiency of intestinal absorption and synthesis of cholesterol in humans are not related to the apoE phenotype.

Abstract: Neurological Development and Serum Lipids and Lipoproteins in aCoronary Heart Disease Prevention Trial in Childhood. The STRIP Project

Neurological Development and Serum Lipids and Lipoproteins in a Coronary Heart Disease Prevention Trial in Childhood. The STRIP Project LEENA RASK-NISSILA, M.D., M.Sc. The winner of the Vaino Kannisto Fund Award in 2002 The Department of Pediatrics, the Department of Medicine and the Research Center of Applied and Preventive Cardiovascular Medicine, University of Turku, and the Research and Development Center of the Social Insurance Institution, Turku, Finland. Annales of Universitatis Turkuensis, University ofTurku, Turku, Finland 2002. In the prospective randomized STRIP project, a low-saturated fat, low-cholesterol diet was introduced to the intervention families of7-month-old infants (n=540). Control infants (n=522) consumed an unrestricted diet. Nutrient intakes, serum lipid values and growth were studied frequently. Five-year-old children (n=496) participated in the neurodevelopmental tests. The fat, saturated fat and cholesterol intakes of the intervention children were continuously less than those of the control children. The neurological development of 5year-old intervention children was at least as good as that of the control children. Total fat and saturated fat intakes, serum cholesterol concentrations and apolipoprotein (apo) E phenotype did not associate with the children's neurodevelopment. In boys, high intakes of protein, polyunsaturated fatty acids and cholesterol predicted a favorable outcome in the neurodevelopmental tests. Serum cholesterol concentrations were continuously 3-5% lower in the intervention children than in the control children. Five-year-old intervention boys had 9% lower mean serum LDL cholesterol concentrations than the control boys, whereas no difference was seen in girls. Serum triglyceride concentrations were similar in the two groups. Dietary intervention did not influence the tracking of serum lipids and lipoproteins, which remained strong during the follow-up. The tracking of non-HDL cholesterol and apoB in children with apoE phenotypes 2/3 or 3/3 was stronger than that in the other children, and the tracking of HDL cholesterol was stronger in the boys than in the girls. The results of the STRIP study show that saturated fat and cholesterol restrictions <lue to repeated, individualized dietary counseling during the first 5 years of a child's life reduce age-associated increases in children's serum cholesterol concentrations without any adverse impact on their neurological development.

Effects of gender, apolipoprotein E phenotype and cholesterol‐lowering by plant stanol esters in children: The STRIP study

Aim: To evaluate the effects of gender, apolipoprotein E phenotype and cholesterol absorption and synthesis (estimated as serum plant sterol and cholesterol precursor sterol concentrations) on the cholesterol‐lowering effect of plant stanol esters in children. Methods: Eighty‐one healthy, normocholesterolaemic 6‐y‐old children (45 boys) were recruited from the Special Turku Coronary Risk Factor Intervention Project (STRIP), a randomized prospective trial aiming at atherosclerosis prevention in childhood. This placebo‐controlled, double‐blind, cross‐over study comprised two 3‐mo study periods and a 6‐wk wash‐out period. During the study periods, 20 g of the children's daily dietary fat intake was replaced with plant stanol ester margarine or control margarine. Results: In boys, plant stanol esters reduced serum total and low‐density lipoprotein cholesterol concentrations by 6% (0.09 to 0.42mmol/L) and 9% (0.09 to 0.36mmol/L), respectively (p &gt; 0.01 for both). In girls, the decreases in concentrations were 4% (0.03 to 0.38 mmol/L) and 6% (0.02 to 0.32 mmol/1) (p &gt; 0.05 for both). The response rate did not differ between the genders. Serum total and low‐density lipoprotein cholesterol concentrations decreased by 6% and 8% (p &gt; 0.01 for both), respectively, in both children with the apolipoprotein E 3/4 or 4/4 (apoE4+) phenotype and the apolipoprotein E 2/3 or 3/3 (apoE4—) phenotype. Cholesterol absorption decreased both in the apoE4+ children and in the apoE4— children, but cholesterol synthesis consistently increased in the apoE4+ children only. Conclusion: Plant stanol esters reduce serum cholesterol concentration in healthy children irrespective of their gender or apoE4 phenotype.

Differential contribution of testosterone and estradiol in the determination of cholesterol and lipoprotein profile in healthy middle-aged men

The role of endogenous sex steroids in the association between male gender and cardiovascular risk remains unclear. We performed a cross-sectional analysis of the role of endogenous testosterone (T) and estradiol (E 2), as well as their respective biologically active fractions, in the determination of lipids and lipoproteins in an occupation-based cohort of 715 healthy middle-aged men. Serum T, sex hormone binding globulin (SHBG) and E 2 were measured by immunoassays; free T (FT) and free E 2 (FE 2) were calculated using a validated equation. Serum total cholesterol (Chol), HDL-cholesterol (HDL-Chol), apolipoproteins A1 (ApoA1), B (ApoB), E (ApoE), ApoE phenotype, lipoprotein a (Lpa), fibrinogen, C-reactive protein (CRP), systolic (SBP) and diastolic blood pressure (DBP) were assessed. Serum levels of T and FT, correlated positively with HDL-Chol and ApoA1 with Spearman correlation coefficients, partialised for age and body mass index (BMI), ranging between 0.14 and 0.17 ( P<0.001); FT was associated with total Chol and ApoB levels ( r=0.12 for both T and FT; P<0.01). After adjustment for age and BMI, both serum E 2 and FE 2 levels correlated significantly with ApoE ( r=0.25 and r=0.26 for E 2 and FE 2, respectively; P<0.001). Free and total E 2 were associated with both SBP and DBP with correlation coefficients partialised for age and BMI ranging between 0.11 and 0.13 ( P<0.01). No correlation was found between any of the studied sex steroids, fibrinogen, Lpa or CRP. In multiple linear regression analyses, T was the most important independent hormonal determinant of HDL-Chol levels, when E 2, SHBG and exogenous factors were considered in the model ( P<0.01), whereas E 2 contributed mostly in the determination of ApoE levels ( P<0.001) and SBP ( P<0.01). When FT and FE 2 were considered in multivariate analyses as independent hormonal variables, FT was the most significant predictor of HDL-Chol ( P<0.01) and ApoB ( P<0.01) concentrations. Moreover, in the same multivariate model, ApoE ( P<0.001) concentration as well as SBP ( P<0.001) was most affected by FE 2 levels in comparison with FT. In conclusion, our findings do suggest a differential role of T and E 2 in the determination of traditional cardiovascular risk factors in healthy middle-aged men. In the determination of both HDL-Chol and ApoB levels endogenous (F)T may be involved, whereas (F)E 2 may contribute to the determination of ApoE levels in this study group of 715 healthy middle-aged men. Regarding the observational design of the study, the physiological relationship of the observed associations between sex steroids and cardiovascular risk factors remains to be unravelled.