Endocrine Abstracts

Introduction: AGEs have been shown to be accumulated in granulosa cell layer from human ovaries in normal and in women with polycystic ovarian syndrome (PCOS) and insulin resistance. AGEs interfere with insulin signaling pathways of several target tissues and are implicated in insulin resistance mechanisms. There is evidence that within the ovary these pathways are also important for glucose metabolism and normal folliculogenesis. The effect of human glycated albumin (HGA) either alone or in combination with insulin was investigated in human ovarian granulosa cells (KGN) relative to Akt activation and glucose transporter 4 (Glut-4) translocation.

Method: KGN cells were cultured with insulin (100 ng/ml) or HGA (0.2 mg/ml) and insulin combined with HGA for 1 h. Activation of Akt was assessed in all conditions followed by the analysis of Glut-4 translocation from the cytoplasm to the membrane compartments of KGN cells. LY294002, a specific PI3K inhibitor was applied to define PI3K-mediated phosphorylation of Akt.

Results: Insulin treatment induced a six-fold increase in p-Akt levels in human granulosa cells compared to basal levels (P<0.001) but the combined treatment of insulin and HGA inhibited the insulin-mediated Akt phosphorylation. PI3K inhibitor was able to attenuate Akt phosphorylation indicating that insulin-stimulated Akt activation was PI3K-dependent.

In addition, insulin increased glycosylated Glut-4 variants in both cytosolic and membrane compartments compared to basal levels (P<0.001). Moreover, HGA increased Glut-4 in the cytosolic fraction while it severely reduced Glut-4 presence in membrane fraction (P<0.001). Combined treatment of insulin and HGA increased cytosolic fraction even further and remarkably reduced Glut-4 translocation to the membrane (P<0.001).

Conclusions: AGEs presence in the ovary associated to reduced glucose uptake by granulosa cells potentially affects follicular growth and contributes to the ovarian dysfunction observed in insulin-resistance states such as PCOS.