The connection between metabolism and reproductive function is well recognized, and we hypothesized that the pituitary gonadotropes, which produce luteinizing hormone and follicle-stimulating hormone (FSH), mediate some of the effects directly via insulin-independent glucose transporters, which allow continued glucose metabolism during hyperglycemia. We found that glucose transporter 1 is the predominant glucose transporter in primary gonadotropes and a gonadotrope precursor-derived cell line, and both are responsive to culture in high glucose; moreover, metabolite levels were altered in the cell line. Several of the affected metabolites are cofactors for chromatin-modifying enzymes, and in the gonadotrope precursor-derived cell line, we recorded global changes in histone acetylation and methylation, decreased DNA methylation, and increased hydroxymethylation, some of which did not revert to basal levels after cells were returned to normal glucose. Despite this weakening of epigenetic-mediated repression seen in the model cell line, FSH β-subunit ( Fshb) mRNA levels in primary gonadotropes were significantly reduced, apparently due in part to increased autocrine/paracrine effects of inhibin. However, unlike thioredoxin interacting protein and inhibin subunit α, Fshb mRNA levels did not recover after the return of cells to normal glucose. The effect on Fshb expression was also seen in 2 hyperglycemic mouse models, and levels of circulating FSH, required for follicle growth and development, were reduced. Thus, hyperglycemia seems to target the pituitary gonadotropes directly, and the likely extensive epigenetic changes are sensed acutely by Fshb. This scenario would explain clinical findings in which, even after restoration of optimal blood glucose levels, fertility often remains adversely affected. However, the relative accessibility of the pituitary provides a possible target for treatment, particularly crucial in the young in which hyperglycemia is increasingly common and fertility most relevant.-Feldman, A., Saleh, A., Pnueli, L., Qiao, S., Shlomi, T., Boehm, U., Melamed, P. Sensitivity of pituitary gonadotropes to hyperglycemia leads to epigenetic aberrations and reduced follicle-stimulating hormone levels.
Keywords: DNA methylation; fertility; gonadotropin; histone acetylation; histone methylation.