Predictors of plasma lipoprotein(a) concentration in the West of Scotland Coronary Prevention Study cohort

Lipid Parameters and Proprotein Convertase Subtilisin/Kexin Type 9 in Healthy Lebanese Adults

Background: High levels of non-HDL cholesterol (non-HDL-C), triglycerides (TG), lipoprotein (a) (Lp(a)), and Proprotein convertase subtilisin/kexin type 9 (PCSK9) as well as low levels of HDL-C are strongly associated with cardiovascular disease (CVD). Our study aims to estimate the prevalence of dyslipidemia and high Lp(a) in the Lebanese population and to study the relationship of these variables with gender, age, body mass index (BMI), and PCSK9. Methods: This cross-sectional study was carried out on a sample of healthy volunteers aged 18 to 65. Blood samples were drawn from volunteers for total cholesterol (TC), HDL-C, TG, PCSK9, and Lp(a) measurements. Non-HDL-C was calculated by subtracting HDL-C from TC. Results: In total, 303 volunteer subjects with an average age of 38.9 years were included in the study. Respectively, 44%, 29.8%, and 44% of men had high non-HDL-C and TG with low HDL-C versus 23.5%, 8%, and 37% in women. Non-HDL-C and TG were significantly higher in men than in women, while the reverse was observed for HDL-C (p < 0.0001 for the three comparisons). Non-HDL-C and TG were significantly correlated with age and BMI (p< 0.0001 for all correlations), while HDL-C was inversely correlated with BMI (p < 0.0001) but not with age. Abnormal Lp(a) levels (≥75 nmol/L) were found in 19.1% of the population, predominantly in women (24.1% versus 13.4% in men, p = 0.004). The median PCSK9 and its interquartile was 300 (254−382) ng/L with no gender difference (p = 0.18). None of the following factors: gender, age, BMI, non-HDL-C, HDL-C, or TG, were independently associated with Lp(a), while PCSK9 was significantly correlated with age, non-HDL-C, and TG in both men and women and inversely correlated with HDL-C in men. Dyslipidemia is very common in the Lebanese population and is associated with age, high BMI, and male sex. Lp(a) is higher in women without any correlation with the lipid profile, whereas PCSK9 is associated with non-HDL-C and TG. Further studies are needed to evaluate the potential role of Lp(a) and PCSK9 in predicting CVD in healthy populations.

Lipoprotein (a): impact by ethnicity and environmental and medical conditions

Levels of lipoprotein (a) [Lp(a)], a complex between an LDL-like lipid moiety containing one copy of apoB, and apo(a), a plasminogen-derived carbohydrate-rich hydrophilic protein, are primarily genetically regulated. Although stable intra-individually, Lp(a) levels have a skewed distribution inter-individually and are strongly impacted by a size polymorphism of the LPA gene, resulting in a variable number of kringle IV (KIV) units, a key motif of apo(a). The variation in KIV units is a strong predictor of plasma Lp(a) levels resulting in stable plasma levels across the lifespan. Studies have demonstrated pronounced differences across ethnicities with regard to Lp(a) levels and some of this difference, but not all of it, can be explained by genetic variations across ethnic groups. Increasing evidence suggests that age, sex, and hormonal impact may have a modest modulatory influence on Lp(a) levels. Among clinical conditions, Lp(a) levels are reported to be affected by kidney and liver diseases.

Significant associations between lipoprotein(a) and corrected apolipoprotein B-100 levels in African-Americans

OBJECTIVES

Lipoprotein(a), Lp(a), represents an apolipoprotein (apo) B-carrying lipoprotein, yet the relationship between Lp(a) and apoB levels has not been fully explored.

METHODS

We addressed the relationship between Lp(a) and apoB-containing lipoprotein levels in 336 Caucasians and 224 African-Americans. Our approach takes unique molecular properties of Lp(a) as well as contribution of Lp(a) to the levels of these lipoproteins into account.

RESULTS

Levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apoB and apoB/apoA-1 did not differ across ethnicity. African-Americans had higher levels of Lp(a) and high-density lipoprotein cholesterol and lower triglyceride levels compared to Caucasians. Lp(a) levels were correlated with levels of TC (p < 0.005), LDL-C (p < 0.001), apoB (p < 0.05) or apoB/apoA-1 (p < 0.05) in both ethnic groups. These associations remained significant only in African-Americans after adjustments for the contribution of Lp(a)-cholesterol or Lp(a)-apoB. Furthermore, taking Lp(a)-apoB into account, allele-specific apo(a) levels were significantly associated with apoB levels and the apoB/apoA-1 ratio in African-Americans. The latter associations in African-Americans remained significant for allele-specific apo(a) levels for smaller apo(a) sizes (<26 K4 repeats), after controlling for the effects of age, sex, and BMI.

CONCLUSIONS

Although TC, LDL-C, and apoB levels were comparable between African-Americans and Caucasians, the associations of these parameters with Lp(a) and allele specific apo(a) levels differed between these two ethnic groups. In African-Americans, apoB and apoB/apoA-1 remained consistently and positively associated with both Lp(a) and allele-specific apo(a) levels after adjustments for the contribution of Lp(a)-apoB. The findings suggest an interethnic difference with a closer relationship between Lp(a) and apoB among African-Americans.

Drinking patterns are associated with variations in atherosclerotic risk factors in French men

BACKGROUND

While a relationship between alcohol and cardiovascular risk factors is well established, data suggest that the type of alcoholic beverage could modulate this relationship.

AIM OF THE STUDY

To determine whether drinking patterns modulate the relationship between alcohol and cardiovascular risk factors.

METHODS

We tested the relationship between preference of alcoholic beverages and atherosclerotic risk factors in a cross-sectional study of 2,126 men. A hierarchical clustering method determined six drinking patterns, 'low drinkers', 'high quality wines', 'beer and cider', 'digestives', 'local wines', and 'table wines', according to the preferential intake of alcoholic beverages. Logistic models estimated the relative risk of abnormal markers in the drinking patterns compared with low drinkers. Unadjusted estimates investigated the relationship with the cluster as a group, while adjustment on alcohol, nutritional and socio-demographic factors investigated the relationship with the preference of alcoholic beverage in itself.

RESULTS

Abstainers had high total plasma homocysteine (tHcy), even after full adjustment (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.8). Drinkers of high quality wine had low lipoprotein( a), high tHcy and high body mass index; beer and cider drinkers had high tHcy and waist circumference. Drinkers of digestives had high triacylglycerol; after adjustment they were at risk of low apolipoprotein A-I (OR = 3.1, 95% CI: 1.2, 7.3), and high tHcy (OR = 4.9, 95% CI: 1.2, 33.3). Local wines drinkers were similar to low drinkers. Table wine drinkers had high apolipoprotein B, high triacylglycerol, and high waist-to-hip ratio.

CONCLUSION

Our data suggest that preference of alcoholic beverage could indicate groups at specific risks of atherosclerotic disease.

Alcohol and Atherosclerotic Vascular Disease Risk Factors in French Men: Relationships Are Linear, J-Shaped, and U-Shaped

BACKGROUND

Although it is well admitted that alcohol displays a U-shaped relationship with atherosclerotic vascular disease, individual relationships between alcohol and atherosclerosis risk factors may be different and have not been determined precisely for several of them.

METHODS

A cross-sectional study within the SU.VI.MAX French cohort study was performed to assess the curve of potential relationships between alcohol and atherosclerosis risk factors in 2126 healthy men. Mean daily alcohol intake was derived from 37 alcoholic beverages in twelve 24-hr dietary recalls. Logistic models were adjusted for age.

RESULTS

Apolipoprotein B (ApoB), fasting glucose, body mass index, waist-to-hip ratio, and waist circumference displayed a linear relationship with alcohol. The odds ratios and 95% confidence intervals associated with abnormal values of the markers for the highest quintile of alcohol intake were 1.45 (1.06-1.97) for ApoB, 1.98 (1.40-2.80) for fasting glucose, and 1.74 (1.30-2.34) for body mass index. An inverse J-shaped relationship was assumed for ApoA1 and ApoB/ApoA1 ratio, whereas a U-shaped relationship was observed for serum triglycerides and mixed hyperlipidemia. Only the highest quintile of alcohol was associated with hypertension, although the test for linearity was also significant. No association was observed for Lp(a) or homocysteine. Associations were unmodified by further adjustment for carbohydrates, fiber, lipids, tobacco, or exercise.

CONCLUSIONS

The aggregate of the disparate alcohol risk factor relationships suggests probable net benefit at 15 to 25 g of alcohol/day.

Study of apo(a) length polymorphism and lipoprotein(a) concentrations in subjects with single or double apo(a) isoforms

Cardiovascular risk is associated with high lipoprotein(a) (Lp(a)) concentrations and low molecular weight apolipoprotein(a) (apo(a)) isoforms. We studied the relationship between these two biological parameters, particularly in subjects expressing two apo(a) isoforms. Plasma Lp(a) was measured by immunonephelometry in 530 unrelated Caucasian patients at high cardiovascular risk, and apo(a) size determined by immunoblotting using a recombinant standard. Two, one, or no apo(a) isoforms were detected in 258, 270, and 2 subjects, respectively. Lp(a) concentrations showed a non-Gaussian distribution, being higher in the 'double band' than in the 'single band' group (median 0.42 vs. 0.11 g/l, p < 0.0005). Apo(a) size distribution was bimodal, with two frequency peaks at 18 kringles (K) and 27 K. Small size apo(a) isoforms were more frequently found in the 'double band' group, where major isoforms were of lower size than minor isoforms (median 20 vs. 27 K). Regression analysis showed that apo(a) gene length accounted for 33% of Lp(a) variation, with a threshold effect at 20 K, no correlation being found over this value. The minor apo(a) isoform did not significantly influence Lp(a) concentration. These data confirm the relationship between apo(a) size and Lp(a) concentration and suggest that the assessment of cardiovascular risk should take into account the threshold effect at 20 K and the absence of influence of the minor apo(a) isoform.

Does correction of the friedewald formula using lipoprotein(a) change our estimation of ischemic heart disease risk? The Quebec Cardiovascular Study

BACKGROUND

LDL-cholesterol is usually calculated using the Friedewald formula. This calculation method does not take into account the presence of Lp(a), which is associated with LDL-cholesterol. Dahlen has suggested that the Friedewald formula should be modified to account for Lp(a) associated cholesterol. This study was undertaken to determine if correction of the Friedewald formula would result in a better evaluation of ischemic heart disease (IHD) risk.

METHODS

2222 men free from IHD were prospectively followed for 5 years for the appearance of myocardial infarction, coronary insufficiency or coronary death. At the baseline evaluation all had a complete fasting lipid profile which included Lp(a) determinations. LDL-cholesterol levels were calculated from total cholesterol, total triglycerides and HDL-cholesterol using the Friedewald formula and also using the Dahlen modification of the Friedewald formula.

RESULTS

During the follow-up there were 89 first IHD events. Both types of LDL-cholesterol calculations showed that the last tertile of the LDL-cholesterol distribution in comparison to the first tertile, doubles the relative risk (RR: 2.15; 95% confidence limits: 1.23-3.75) using the Friedewald formula (RR: 2.18; 95% confidence limits: 1.25-3.81) using the Dahlen modification. Lp(a) levels were not an independent predictor of IHD risk.

CONCLUSION

Modification of the Friedewald formula to account for Lp(a) levels does not improve our evaluation of IHD risk.

Serum lipoprotein(a) concentrations and apolipoprotein(a) phenotypes in hemodialysis, chronic ambulatory peritoneal dialysis and post-transplant patients

Serum lipoprotein(a) [Lp(a)] concentrations and apolipoprotein(a) apo(a) phenotypes were determined in 81 hemodialysis (HD) patients, 37 chronic ambulatory peritoneal dialysis (CAPD) patients, 25 post-transplant patients and 99 healthy subjects as the reference group. The CAPD patients had significantly higher serum Lp(a) concentration than HD patients, but both had significantly increased Lp(a) levels as compared with the reference group and post-transplant patients. When all studied groups were divided into two subgroups with at least one low molecular weight (LMW) isoform and with only one high molecular weight (HMW) isoform, they presented a similar distribution. (Pearson's chi-squared = 2,78; df = 3; p = NS). The median serum Lp(a) levels were significantly increased with HMW class versus the reference group and post-transplant patients. In CAPD patients, the LMW phenotypes showed significantly increased median serum Lp(a) concentrations versus the reference group, but they were not statistically elevated in HD patients. In the post-transplant patients, LMW and HMW phenotypes did not differ as compared to the reference group. The elevated Lp(a) levels in HD and CAPD groups were explained by apo(a) type-specific, but not by differences in, isoform frequencies. We conclude that HD and CAPD patients had increased Lp(a) levels compared with the reference group, whereas elevated Lp(a) concentrations were observed mainly in patients with HMW apo(a) phenotypes. Patients after renal transplantation showed a correction of Lp(a) levels mainly in HMW phenotypes. The LMW status corresponding to high Lp(a) levels and apo(a) isoforms could be used together with Lp(a) levels with other risk factors to assess in uremic patients the predisposition to coronary artery disease.