Gonadotrophic control of human granulosa cell glycolysis

Follicular fluid lactate levels were measured in women undergoing infertility surgery during the follicular phase or oocyte recovery for in-vitro fertilization (IVF). In the largest ovulatory follicle lactate levels were low in the mid-follicular phase (group 1), 1.6-fold higher just prior to the onset of the luteinizing hormone (LH) surge (group 2) and a further 2.5-fold higher after the onset of the LH surge (group 3). In IVF patients mean lactate levels in all aspirated follicles were similar to those in group 3 subjects, but the levels within each patient were variable and were positively correlated with follicular volume. Basal granulosa cell lactate accumulation in vitro was 3-fold higher in group 3 compared with group 2 subjects, but stimulation by FSH or HCG was higher in group 2 (2- to 3-fold) compared with group 3 (1.4- to 2-fold). These results demonstrate that human follicular fluid lactate levels increase as a function of the maturity and size of the developing follicle. Granulosa cell lactate accumulation in vitro is under gonadotrophic control, which suggests that the effects observed in vivo reflect changes in granulosa cell glycolysis in response to gonadotrophic stimulation. Our findings support the concept that low molecular weight energy metabolites transduce gonadotrophin signals that regulate oocyte maturation.