Polycystic ovary syndrome (PCOS) is characterised by hyperandrogenism
and insulin resistance. Granulosa cells in PCOS demonstrate impaired
insulin-induced glucose uptake and lactate accumulation, suggesting a post
receptor, signalling pathway-specific impairment of insulin action.
Gonadotrophins are also important in the regulation of glucose metabolism by
of granulosa cells.
The first objective of this project was to use KK1 cells an immortalised mouse
granulosa cell line, to characterise insulin, androgen and FSH signalling as
well as glucose metabolism. Cell lysates were subjected to western
immunoblotting for key proteins in the insulin signalling pathways. Glucose
metabolism of KK1 cells was also measured. Surprisingly, androgen alone
stimulated glucose uptake and lactate production and augmented insulin-induced
glucose metabolism. This suggests that the insulin resistance
observed in granulosa cells from women with PCOS is not a direct effect of
exposure to androgen.
The main part of the thesis was examination of insulin action on human
primary ovarian granulosa-lutein (GL) cells to investigate the mechanism of
insulin resistance in PCOS. Insulin and FSH signalling in GL cells from
women with anovulatory PCOS (anovPCO, n=11) was compared to that in GL
cells from ovulatory women with (ovPCO, n=8) and without polycystic ovaries
(controls n=12). Primary GL cells were incubated with insulin or FSH and
analysed for glucose metabolism and progesterone production. Cell lysates
were prepared for identification of signalling pathways, using western
immunoblotting.
The results confirmed selective impairment of glucose metabolism in cells
from anovulatory PCOS. No significant impairment of insulin stimulated PI3K
signalling was observed. However there was a reduction of p42/44ERK
phosphorylation in the ovulatory PCOS group compared to controls. The
significance of this finding with respect to impaired glucose metabolism in
granulosa cells remains to be determined. We also showed FSH induced
glucose metabolism, but without clear evidence of activation of the PI3-kinase
pathway
