Advanced glycation end products alter steroidogenic gene expression by granulosa cells: an effect partially reversible by vitamin D

STUDY QUESTION: Does vitamin D attenuate the adverse effects of advanced glycation end products (AGEs) on steroidogenesis by human granulosa cells (GCs)? SUMMARY ANSWER: AGEs alter the expression of genes important in steroidogenesis while 1,25-dihydroxyvitamin D3 (vit D3) in vitro attenuates some of the actions of AGEs on steroidogenic gene expression, possibly by downregulating the expression of the pro-inflammatory cell membrane receptor for AGEs (RAGE). WHAT IS KNOWN ALREADY: Vitamin D attenuates the pro-inflammatory effects of AGEs in non-ovarian tissues. STUDY DESIGN, SIZE, DURATION: Women who were undergoing IVF were enrolled. Follicular fluid samples (n = 71) were collected and cumulus GCs (n = 12) were treated in culture. PARTICIPANTS/MATERIALS, SETTING, METHODS: Follicular fluid levels of the anti-inflammatory soluble RAGE (sRAGE), AGEs and 25-hydroxyvitamin D (25-OHD) were quantified for possible correlations. GCs of each participant were split equally and treated with either media alone (control) or with human glycated albumin (HGA as a precursor for AGEs) with or without vit D3 after which RT-PCR and immunofluorescence were performed and cell culture media estradiol (E2) levels were compared. MAIN RESULTS AND THE ROLE OF CHANCE: In follicular fluid, sRAGE levels were positively correlated with 25-OHD levels. HGA treatment (i) increased CYP11A1 (by 48%), 3 beta-HSD (by 38%), StAR (by 42%), CYP17A1 (by 30%) and LHR (by 37%) mRNA expression levels (P < 0.05 for all) but did not alter CYP19A1 or FSHR mRNA expression levels; and (ii) increased E2 release in cell culture media (P = 0.02). Vit D3 treatment (i) downregulated RAGE mRNA expression by 33% and RAGE protein levels by 44% (P < 0.05); (ii) inhibited the HGA-induced increase in CYP11A1, StAR, CYP17A1 and LHR mRNA levels, but not the increase in 3 beta-HSD mRNA levels; and (iii) did not inhibit the HGA-induced E2 release in cell culture media. LIMITATIONS REASONS FOR CAUTION: This study used luteinized GCs that were collected from women who received gonadotropins thus the results obtained may not fully extrapolate to non-luteinized GCs in vivo. WIDER IMPLICATIONS OF THE FINDINGS: This study suggests that there is a relationship between AGEs and their receptors (RAGE and sRAGE) with vitamin D. Understanding the interaction between AGEs and vitamin D in ovarian physiology could lead to a more targeted therapy for the treatment of ovarian dysfunction.