Background: High-density lipoprotein (HDL) is the sole lipoprotein present in follicular fluid (FF). The objectives of this study were to examine HDL lipid composition and associated enzyme activities in FF and serum and to relate these levels to embryo morphology parameters in women undergoing in vitro fertilization (IVF).
Methods: Serum and FF were prospectively obtained from 60 women undergoing IVF. HDL lipids, apolipoprotein AI (ApoAI), paraoxonase 1 (PON1) and paraoxonase 3 (PON3) activities were determined. Bivariate analysis and ordinal logistic regression models were employed to examine the associations between biochemical measures and embryo morphology parameters [embryo cell number (ECN) and embryo fragmentation score (EFS)] as surrogate markers of oocyte health.
Results: All biochemical parameters were significantly (P < 0.05) lower in FF than serum except PON3 levels which were significantly higher. FF-HDL cholesterol (OR 0.66, 95%CI 0.46-0.96) and ApoAI (OR 0.13, 95%CI 0.03-0.97) levels were negative predictors for EFS; however, their effects were not independent and the level of one moderated the effect of the other. Limited to Day 3 embryo transfers, FF-PON1-arylesterase activity was a significant positive predictor for ECN (OR 1.09, 95%CI 1.01-1.17).
Conclusions: In this pilot study, our data suggests that HDL and its component proteins within FF may play protective roles in the health of the human oocyte and subsequent early embryo development. We describe for the first time the activities of PON1 and PON3 in FF. We suspect that PON3 activity may be locally generated due to higher activities in FF compared with serum.