Impact Of Iron Overload On Reproductive Axis Impairment: Pathophysiological Insights From In Vitro And In Vivo Studies

Introduction: Iron is an essential micronutrient for proper brain development in the fetal/early neonatal period. Conversely, iron overload is the most important factor afflicting the hypothalamus-pituitary axis leading to hypogonadotropic hypogonadism. Methods: Male C57Bl6/J mice, GN-11 cells (immature/migratory GnRH neurons), qPCR/Western blotting analyses, Boyden’s chamber assay (chemomigration), Ferric Ammonium Citrate (FAC, source of ferric iron). Results: Dietary-iron overload (IED) significantly increased mice testis iron content (+49% vs. Control, CTR) and reduced testicular weight and length. Hypothalamic GnRH gene expression was increased in IED mice (+34% vs. CTR, p< 0.01), leaving Kiss1 and GPR54 unchanged. IED promoted reduction of pituitary LHβ mRNA levels. Treatment of GN-11 cells with 200 µM FAC: a) induced a significant increment of intracellular iron content (24 h; +10 fold vs. CTR); b) modulated transferrin receptor and ferritin H mRNA levels (24 h); c) inhibited FBS-induced chemomigration in dose- (200-1000 µM) and time- (24-72 h) dependent; d) modulated pERK1/2, pAkt and pAMPK protein levels (5-180 min; 5 fold, +95% and -50% vs. CTR, respectively; all p<0.05); e) inhibited GN-11 chemomigration via AKT modulation (as assessed by using a specific Akt inhibitor; 90 min). Conclusions: The impairment of the adult reproductive axis by iron overload, leading to hypogonadotropic hypogonadism, may include specific hypothalamic derangements, in addition to the known pituitary and gonadal changes. Moreover, iron overload appears to negatively affect in vitro GnRH neuron migratory ability, thereby possibly impairing GnRH cell migration from foetal olfactory placode into forebrain and hypothalamus, where these neurons subsequently promote the reproductive competence.