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.

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.