Age-related variations in follicular apolipoproteins may influence human oocyte maturation and fertility potential.

OBJECTIVE To investigate involvement of specific apolipoproteins in the process of human oocyte maturation and age-related infertility as molecular constituents of follicular fluid. DESIGN Laboratory-based observational study. SETTING Basic science laboratory at a large academic institution. PATIENT(S) Follicular fluid obtained from healthy women aged 18 to 45 years undergoing in vitro fertilization for unexplained infertility, ovulatory dysfunction, tubal disease, male factor infertility, or oocyte donation. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Specific concentration of apolipoproteins and content of lipoprotein particles in follicular fluid and blood plasma as related to reproductive aging. RESULT(S) We registered a decline of follicular apolipoprotein A1 (Apo A1) and apolipoprotein CII (Apo CII) and an increase of the apolipoprotein E (Apo E) with age, which parallels a lower number of retrieved mature oocytes in older women. Follicular apolipoprotein A1, apolipoprotein B (Apo B), apolipoprotein E, and apolipoprotein C II are present in diverse heterogeneous complexes including very-low-density lipoproteins (VLDL), intermediate-low-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL) that vary with patient age and differ from the blood plasma lipoprotein complexes. CONCLUSION(S) Age-related variation in follicular apolipoprotein content and distribution in the cholesterol particles may be associated with the decrease in production of mature oocytes and the age-related decline in fertility potential.