Advanced Glycation End Products Upregulate Insulin Receptor Substrate-1 (IRS-1) in Human Cumulus Granulosa Cells

Women with polycystic ovary syndrome (PCOS) and insulin resistance (IR) commonly have elevated serum advanced glycation end-products (AGEs) that accumulate in their ovaries, potentially altering ovarian function. AGEs have been shown to interfere with insulin signaling in granulosa cells (GCs) by suppressing the translocation of glucose transporters. Additionally, PCOS has been associated with insulin receptor substrate (IRS)-1 polymorphisms and upregulation in IRS-1 gene expression in GCs. We hypothesize that AGEs are partly responsible for ovarian IR by altering IRS-1 in human GCs. Cumulus granulosa cells from women undergoing IVF were cultured in control media or media containing human glycated albumin (HGA) as a source of AGEs. The quantification of mRNA expression was compared using RT-PCR for receptors for AGEs (RAGE), IRS-1, IRS-2, Glucose Transporter Type (GLUT)-1, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). In addition, IRS-1 protein intensity was assessed by immunofluorescence. Compared to the control group, HGA-treated GCs showed a statistically significant upregulation in RAGE mRNA by 314% and in IRS-1 mRNA by 423%. Even though there was a 183% increase in GLUT-1 mRNA, it did not reach statistical significance. There was no change in IRS-2 or NF-κB mRNA expression levels. Immunofluorescence showed that IRS-1 deposition was visualized in GCs, and the addition of HGA resulted in a significant increase in the intensity of IRS-1 protein compared to control cells. The AGE-induced upregulation in IRS-1, the primary insulin receptor substrate, in GCs could indicate compensation for insulin action deficiency and potentially IR. Additionally, immunofluorescence analysis of GLUT-4 revealed a statistically significant reduction in cytoplasmic GLUT-4 signal in HGA-treated GCs compared to controls (2.10 ± 0.21 vs. 3.81 ± 0.22 arbitrary units; p = 0.010), consistent with AGE-mediated disruption of glucose transporter localization. These results suggest that AGE exposure may initiate early molecular changes consistent with altered insulin signaling, but do not establish insulin resistance per se.