Lipoprotein(a) and apolipoprotein(a) in polycystic ovary syndrome

OBJECTIVE

Levels of lipoprotein(a), Lp(a), an independent risk factor for cardiovascular disease (CVD), are affected by sex hormones. Women with polycystic ovary syndrome (PCOS) have elevated androgen levels and are at increased CVD risk. We investigated the impact of PCOS-related hormonal imbalance on Lp(a) levels in relation to apo(a) gene size polymorphism, a major regulator of Lp(a) level.

DESIGN

Cross-sectional.

PATIENTS

Forty-one Caucasian women with PCOS based on the NIH criteria.

MEASUREMENTS

(1) Apo(a) gene size polymorphism measured as Kringle (K) 4 repeat number; (2) total plasma Lp(a) level; (3) allele-specific apo(a) level assessing the amount of Lp(a) carried by an individual apo(a) allele/isoform; and (4) sex hormone levels.

RESULTS

The mean age was 32 ± 6 years, and the mean BMI was 35 ± 8 with 66% of women classified as obese (BMI >30 kg/m² ). LDL cholesterol was borderline high (3·37 mmol/l), and HDL cholesterol was low (1·06 mmol/l). The distribution of Lp(a) level was skewed towards lower levels with a median level of 22·1 nmol/l (IQR: 6·2-66·5 nmol/l). Lp(a) levels were not correlated with age, body weight or BMI. The median allele-specific apo(a) level was 10·6 nmol/l (IQR: 3·1-31·2 nmol/l), and the median apo(a) size was 27 (IQR: 23-30) K4 repeats. Allele-specific apo(a) levels were significantly and inversely correlated with K4 repeats (r = -0·298, P = 0·007). Neither Lp(a) nor allele-specific apo(a) levels were significantly associated with testosterone or dehydroepiandrosterone sulphate levels.

CONCLUSIONS

The apo(a) genetic variability remains the major regulator of plasma Lp(a) levels in women with PCOS.

Rhesus monkey (Macaca mulatta) lipoprotein(a) and apolipoprotein(a): high frequency of small size apolipoprotein(a) isoforms

BACKGROUND

Levels of lipoprotein(a), Lp(a), a genetically regulated independent cardiovascular risk factor present in humans and Old World monkeys, are impacted by the apolipoprotein(a), apo(a), gene. Allele-specific apo(a) levels, taking both the apo(a) genotypic and phenotypic characteristics into account, are useful markers to determine atherosclerotic cardiovascular risk.

METHODS

We determined (i) the genetic variability of apo(a), (ii) Lp(a) levels, and (iii) allele-specific apo(a) levels in rhesus monkeys (n = 95).

RESULTS

Lp(a) levels differed substantially between animals (range: 4-247 nmol/l) with a skewed distribution toward lower levels. Lp(a) and allele-specific apo(a) levels were inversely related to the number of apo(a) Kringle 4 (K4) repeats. The median apo(a) size was 23 K4 repeats, and the prevalence of a small size apo(a) (≤22 K4) was 43%.

CONCLUSIONS

Distribution of Lp(a) and allele-specific apo(a) levels in rhesus monkeys reflected the corresponding human patterns, but with a high prevalence of smaller apo(a) sizes.

Abstract 446: Divergent Trajectory Patterns of Systemic Versus Vascular Inflammation over Age in Healthy Caucasian and African-American Families

Objectives: Age and inflammation both are risk factors for cardiovascular disease. The association between these two risk factors across lifespan and ethnicity in the general population is poorly understood.

Methods: We assessed the relationship of systemic (C-reactive protein, serum amyloid A, fibrinogen, haptoglobin and α-acid glycoprotein) and vascular (pentraxin-3, soluble intercellular adhesion molecule-1 and soluble vascular adhesion molecule-1) inflammatory burden with age in healthy Caucasian and African-American families with members aged 6 to 74 years (n=267). To collectively assess systemic and vascular risk factors across the age spectrum, a composite z-score for each category of inflammatory markers was calculated based on individual levels.

Results: We observed a contrasting pattern in systemic vs. vascular inflammatory burden over age with an increase in systemic but a decrease in vascular inflammatory markers in both ethnic groups (p<0.05 for all). There were no significant differences in trends between the two ethnic groups. These observations remained significant after taking the correlations of siblings and parents from the same family into account. In multivariate analyses adjusting for covariates (BMI, blood pressure, total, LDL and HDL cholesterol, triglyceride and glucose), the trajectory patterns of fibrinogen and α-acid glycoprotein levels were no longer regulated with age in either ethnic group, whereas the results for vascular inflammation remained unchanged. The results based on the composite z-score for each marker category confirmed the findings of individual markers as the composite z-score for systemic inflammation increased with age (p=0.005), while the composite z-score for vascular inflammation declined with age (p=0.0002) regardless of ethnicity.

Conclusions: There was a diverging pattern in systemic vs. vascular inflammatory burden as function of age, which was independent of ethnicity, family correlation and individuals’ metabolic burden. The findings illustrate the complex relationship between age and inflammation, and suggest that a perceived elevation of vascular markers among the very young may be an indication of dynamic growth rather than a disease process.

HIV disease activity as a modulator of lipoprotein(a) and allele-specific apolipoprotein(a) levels

OBJECTIVE

Mechanisms underlying the cardiovascular risk of lipoprotein(a) are poorly understood. We investigated the relationship of apolipoprotein(a) (apo(a)) size, lipoprotein(a), and allele-specific apo(a) levels with HIV disease activity parameters in a biethnic population.

METHODS AND RESULTS

Lipoprotein(a) and allele-specific apo(a) levels were determined in 139 white and 168 black HIV-positive patients. Plasma HIV RNA viral load and CD4+ T-cell count were used as surrogates for disease activity. Lipoprotein(a) and allele-specific apo(a) levels were higher in blacks than whites (for both P<0.001). Apo(a) allele size distribution was similar between the 2 ethnic groups, with a median apo(a) size of 28 kringle 4 repeats. Allele-specific apo(a) levels were positively associated with CD4+ T-cell count (P=0.027) and negatively with plasma HIV RNA viral load (P<0.001). Further, allele-specific apo(a) levels associated with smaller (<28 kringle 4) atherogenic apo(a) sizes were higher in subjects with CD4+ T-cell counts of ≥350 (P=0.002).

CONCLUSIONS

Allele-specific apo(a) levels were higher in subjects with high CD4+ T-cell count or low plasma HIV RNA viral load. The findings suggest that HIV disease activity reduced allele-specific apo(a) levels. Higher allele-specific apo(a) levels associated with atherogenic small apo(a) sizes might contribute to increased cardiovascular risk in HIV-positive subjects with improved disease status.