Lipids and lipoprotein subfractions in women with PCOS: relationship to metabolic and endocrine parameters

OBJECTIVE

Women with polycystic ovary syndrome (PCOS) exhibit an abnormal lipoprotein profile, characterized by raised concentrations of plasma triglyceride, marginally elevated low density lipoprotein (LDL)-cholesterol, and reduced high density lipoprotein (HDL)-cholesterol. However, a normal LDL-cholesterol level may be misleading since LDL exists as subpopulations of particles differing in size and atherogenic potential. Smaller LDL particles are more atherogenic and high concentrations often occur in association with elevated circulating triglyceride concentrations (but frequently normal total LDL-cholesterol), increased hepatic lipase activity (HL) and insulin resistance. Information on LDL subclasses and HL activity in women with PCOS is sparse. The aim of this study was to determine the concentrations of small, dense LDL (LDL-III) in women with PCOS relative to body mass index (BMI)-matched controls. We also examined the association of lipoprotein subfraction concentrations with endogenous sex hormone concentrations, since existing literature suggested that androgens up-regulate and oestrogens down-regulate HL activity, a key determinant of LDL subfraction distribution.

DESIGN

Cross sectional study.

PATIENTS

Fifty-two women with oligomenorrhoea and polycystic ovaries determined by ultrasound and BMI matched women with normal menstrual rhythm (NMR) and normal ovarian appearances (n = 14) were recruited from gynaecology clinics. Anthropometric data and fasting blood samples were obtained for metabolic, hormonal and LDL subfraction estimation and a heparin provocation test was used to estimate HL activity.

RESULTS SUBJECTS

with PCOS demonstrated higher waist:hip ratio (WHR), testosterone, triglyceride, VLDL-cholesterol concentrations, and HL activity (P < 0·05), whereas SHBG concentrations were significantly lower than controls. PCOS women had higher concentrations (38.0 vs. 25.0 mg/l; P = 0·026) and proportions (12·8 vs. 8·2%; P = 0·006) of small, dense LDL (LDL III), relative to controls. Within the PCOS group, plasma triglyceride and HL activity were the strongest univariate predictors of LDL III mass. They remained as independent predictors in multivariate analysis, and together accounted for 37% of its variability (P = 0·0002). Independent predictors of plasma triglyceride and HL in turn, were measures of fat distribution (waist circumference or WHR) and fasting insulin concentration. Serum testosterone concentration was not associated either in univariate or multivariate analysis with any of the measured lipid, lipoprotein or subfraction parameters, nor with HL activity in the women with PCOS.

CONCLUSION

We conclude that women with polycystic ovary syndrome have increased hepatic lipase activity and mass and percentage of small, dense low density lipoprotein relative to body mass index-matched controls with normal menstrual rhythm and normal ovaries. Further, these metabolic perturbances appear related more closely to adiposity/insulin metabolism than to circulating androgen levels.