Background: Insulin resistance and hyperinsulinaemia are well-recognized characteristics of anovulatory women with polycystic ovary syndrome (PCOS) but, paradoxically, steroidogenesis by PCOS granulosa cells remains responsive to insulin. The hypothesis to be tested in this study is that insulin resistance in the ovary is confined to the metabolic effects of insulin (i.e. glucose uptake and metabolism), whereas the steroidogenic action of insulin remains intact.
Methods: Granulosa-lutein cells were obtained during IVF cycles from seven women with normal ovaries, six ovulatory women with PCO (ovPCO) and seven anovulatory women with PCO (anovPCO). Mean body mass index was in the normal range in all three groups. Granulosa-lutein cells were cultured with insulin (1, 10, 100 and 1000 ng/ml) and LH (1, 2.5 and 5 ng/ml). Media were sampled at 24 and 48 h and analysed for glucose uptake, lactate production and (48 h only) progesterone production.
Results: Insulin-stimulated glucose uptake by cells from anovPCO was attenuated at higher doses of insulin (100 and 1000 ng/ml) compared with that by cells from either ovPCO (P=0.02) or controls (P=0.02). Insulin and LH stimulated lactate production in a dose-dependent manner, but insulin-dependent lactate production was markedly impaired in granulosa-lutein cells from anovPCO compared with either normal (P=0.002) or ovPCO (P<0.0001). By contrast, there was no difference in insulin-stimulated progesterone production between granulosa-lutein cells from the three ovarian types.
Conclusions: Granulosa-lutein cells from women with anovPCOS are relatively resistant to the effects of insulin-stimulated glucose uptake and utilization compared with those from normal and ovPCO, whilst maintaining normal steroidogenic output in response to physiological doses of insulin. These studies support the probability of a post-receptor, signalling pathway-specific impairment of insulin action in PCOS.