Iron overload induces hypogonadism in male mice via extrahypothalamic mechanisms

High Concentration of Iron Ions Contributes to Ferroptosis-Mediated Testis Injury

In order to explore the effect of excessive iron supplementation on ferroptosis in mouse testes, Kunming mice received injections of varying concentrations of iron. The organ weight, sperm density, and malformation rate were measured. Observations of pathological and ultrastructural alterations in spermatogenic tubules were conducted using haematoxylin eosin (HE) staining and transmission electron microscopy(TEM). Transcript levels of related genes and serum biochemical indicators were measured in mouse testicular tissue. The results showed that higher iron concentration inhibited the growth of mice; reduced the organ coefficients of the testis, heart, and liver; and increased the rate of sperm malformation and mortality. Supplementation with high levels of iron ions can adversely affect the male reproductive system by reducing sperm count, damaging the structure of the seminiferous tubules and causing sperm cell abnormalities. In addition, the iron levels also affected the immune response and blood coagulation ability by affecting the red blood cells, white blood cells and platelets. The results showed that iron ions can affect mouse testicular tissue and induce ferroptosis by altering the expression of ferroptosis-related genes. However, the degree of effect was different for the different concentrations of iron ions. The study also revealed the potential role of deferoxamine in inhibiting the occurrence of ferroptosis. Nevertheless, the damage caused to the testis by deferoxamine supplementation suggests the need for further research in this direction. This study provides reference for reproductive toxicity induced by environmental iron exposure and clarifies the mechanism of reproductive toxicity caused by iron overload and the important role of iron in the male reproductive system.

Foxo1 is an iron-responsive transcriptional factor regulating systemic iron homeostasis

The liver plays a crucial role in maintaining systemic iron homeostasis by secreting hepcidin, which is essential for coordinating iron levels in the body. Imbalances in iron homeostasis are associated with various clinical disorders related to iron deficiency or iron overload. Despite the clinical significance, the mechanisms underlying how hepatocytes sense extracellular iron levels to regulate hepcidin synthesis and iron storage are not fully understood. In this study, we identified Foxo1, a well-known regulator of macronutrient metabolism, which translocates to the nucleus of hepatocytes in response to high-iron feeding, holo-transferrin, and bone morphogenetic protein 6 (BMP6) treatment. Furthermore, Foxo1 plays a crucial role in mediating hepcidin induction in response to both iron and BMP signals by directly interacting with evolutionally conserved Foxo binding sites within the hepcidin promoter region. These binding sites were found to colocalize with Smad-binding sites. To investigate the physiological relevance of Foxo1 in iron metabolism, we generated mice with hepatocyte-specific deletion of Foxo1. These mice exhibited reduced hepatic hepcidin expression and serum hepcidin levels, accompanied by elevated serum iron and liver nonheme iron concentrations. Moreover, high-iron diet further exacerbated these abnormalities in iron metabolism in mice lacking hepatic Foxo1. Conversely, hepatocyte-specific Foxo1 overexpression increased hepatic hepcidin expression and serum hepcidin levels, thereby ameliorating iron overload in a murine model of hereditary hemochromatosis (Hfe-/- mice). In summary, our study identifies Foxo1 as a critical regulator of hepcidin and systemic iron homeostasis. Targeting Foxo1 may offer therapeutic opportunities for managing conditions associated with aberrant iron metabolism.

Spotlight on iron overload and ferroptosis: Research progress in female infertility

Iron is an essential trace element for organisms. However, iron overload, which is common in haematological disorders (e.g. haemochromatosis, myelodysplastic syndromes, aplastic anaemia, and thalassaemia, blood transfusion-dependent or not), can promote reactive oxygen species generation and induce ferroptosis, a novel form of programmed cell death characterised by excess iron and lipid peroxidation, thus causing cell and tissue damage. Infertility is a global health concern. Recent evidence has indicated the emerging role of iron overload and ferroptosis in female infertility by inducing hypogonadism, causing ovary dysfunction, impairing preimplantation embryos, attenuating endometrial receptivity, and crosstalk between subfertility-related disorders, such as polycystic ovary syndrome and endometriosis. In addition, gut microbiota and their metabolites are involved in iron metabolism, ferroptosis, and female infertility. In this review, we systematically elaborate on the current research progress in female infertility with a novel focus on iron overload and ferroptosis and summarise promising therapies targeting iron overload and ferroptosis to recover fertility in women. In summary, our study provides new insights into female infertility and offers literature references for the clinical management of female infertility associated with iron overload and ferroptosis, which may be beneficial for females with haematopoietic disorders suffering from both iron overload and infertility.

Biomarkers of Iron Are Associated with Anterior-Pituitary-Produced Reproductive Hormones in Men with Infertility

Approximately 16% of North American couples are affected by infertility, with 30% of cases being attributable to male factor infertility. The regulation of reproductive hormones via the hypothalamic-pituitary-gonadal axis is important for spermatogenesis and subsequently male fertility. Maintaining iron homeostasis is critical to normal reproductive physiological function. This cross-sectional study's objective was to determine the association between serum biomarkers of iron and reproductive hormones. Men experiencing infertility (n = 303) were recruited from Mount Sinai Hospital, Toronto. Serum was analyzed for iron and ferritin as biomarkers of iron status and reproductive hormones (follicle-stimulating hormone, luteinizing hormone, testosterone, estradiol, and prolactin), which were the primary outcome. Associations were determined using non-parametric Spearman's rank correlation coefficient, linear regressions, and logistic regressions. A significant independent monotonic inverse relationship between serum iron and prolactin (p = 0.0002) was found. In linear regression analyses, iron was inversely associated with luteinizing hormone (unadjusted p = 0.03, adjusted p = 0.03) and prolactin (unadjusted p = 0.001 and adjusted p = 0.003). Serum ferritin was inversely associated with both gonadotropins, follicle-stimulating hormone (adjusted p = 0.03), and luteinizing hormone (adjusted p = 0.02). These findings suggest that biomarkers of iron are associated with pituitary-produced reproductive hormones, which play a role in the hypothalamic-pituitary-gonadal signaling pathway involved in spermatogenesis, testicular testosterone production, and male fertility.

Insulin-like Growth Factor 1, Growth Hormone, and Anti-Müllerian Hormone Receptors Are Differentially Expressed during GnRH Neuron Development

Gonadotropin-releasing hormone (GnRH) neurons are key neuroendocrine cells in the brain as they control reproduction by regulating hypothalamic-pituitary-gonadal axis function. In this context, anti-Müllerian hormone (AMH), growth hormone (GH), and insulin-like growth factor 1 (IGF1) were shown to improve GnRH neuron migration and function in vitro. Whether AMH, GH, and IGF1 signaling pathways participate in the development and function of GnRH neurons in vivo is, however, currently still unknown. To assess the role of AMH, GH, and IGF1 systems in the development of GnRH neuron, we evaluated the expression of AMH receptors (AMHR2), GH (GHR), and IGF1 (IGF1R) on sections of ex vivo mice at different development stages. The expression of AMHR2, GHR, and IGF1R was assessed by immunofluorescence using established protocols and commercial antibodies. The head sections of mice were analyzed at E12.5, E14.5, and E18.5. In particular, at E12.5, we focused on the neurogenic epithelium of the vomeronasal organ (VNO), where GnRH neurons, migratory mass cells, and the pioneering vomeronasal axon give rise. At E14.5, we focused on the VNO and nasal forebrain junction (NFJ), the two regions where GnRH neurons originate and migrate to the hypothalamus, respectively. At E18.5, the median eminence, which is the hypothalamic area where GnRH is released, was analyzed. At E12.5, double staining for the neuronal marker ß-tubulin III and AMHR2, GHR, or IGF1R revealed a signal in the neurogenic niches of the olfactory and VNO during early embryo development. Furthermore, IGF1R and GHR were expressed by VNO-emerging GnRH neurons. At E14.5, a similar expression pattern was found for the neuronal marker ß-tubulin III, while the expression of IGF1R and GHR began to decline, as also observed at E18.5. Of note, hypothalamic GnRH neurons labeled for PLXND1 tested positive for AMHR2 expression. Ex vivo experiments on mouse sections revealed differential protein expression patterns for AMHR2, GHR, and IGF1R at any time point in development between neurogenic areas and hypothalamic compartments. These findings suggest a differential functional role of related systems in the development of GnRH neurons.

Acetylated Oligopeptide and N-acetyl cysteine Protected Against Oxidative Stress, Inflammation, Testicular-Blood Barrier Damage, and Testicular Cell Death in Iron-Overload Rat Model

Multiple organs, including the testes, are damaged by iron overload. It has been shown that N-acetyl cysteine (NAC) influences oxidative stress in iron overload. The present study aimed to evaluate the roles of acetylated peptide (AOP) and NAC in the inhibition of iron-overload induced-testicular damage. At the beginning of the experiment, NAC (150 mg /kg) was given for a week to all 40 rats. Then, four groups were formed by dividing the animals (10 rats/group). Group I included healthy control rats. Group II (iron overload) was given intraperitoneal iron dextran (60 mg/kg/day) 5 days a week for 4 weeks. Group III (NAC) was given NAC orally at a dose of 150 mg/kg/day for 4 weeks in addition to iron dextran. Group IV (AOP) was given AOP orally at a dose of 150 mg/kg/day for 4 weeks besides iron dextran. When the experiment time was over, testosterone serum level, testicular B cell lymphoma-2 (BCL-2) and protein kinase B (PKB) protein levels, nuclear factor kappa-B (NF-κB), and Beclin1 mRNA expression levels, and malondialdehyde (MDA), and reduced glutathione (GSH) were determined by ELISA, quantitative reverse transcription-PCR, and chemical methods. Finally, histopathological examinations and immunohistochemical detection of claudin-1 and CD68 were performed. The iron overload group exhibited decreased testosterone, BCL-2, PKB, claudin-1, and GSH and increased MDA, NF-κB, Beclin1, and CD68, while both NAC and AOP treatments protected against the biochemical and histopathological disturbances occurring in the iron overload model. We concluded that NAC and AOP can protect against testes damage by iron overload via their antioxidant, anti-inflammatory, antiapoptotic, and ant-autophagic properties. The NAC and AOP may be used as preventative measures against iron overload-induced testicular damage.

Diversity within olfactory sensory derivatives revealed by the contribution of Dbx1 lineages

In vertebrates, the embryonic olfactory epithelium contains progenitors that will give rise to distinct classes of neurons, including olfactory sensory neurons (OSNs; involved in odor detection), vomeronasal sensory neurons (VSNs; responsible for pheromone sensing), and gonadotropin-releasing hormone (GnRH) neurons that control the hypothalamic-pituitary-gonadal axis. Currently, these three neuronal lineages are usually believed to emerge from uniform pools of progenitors. Here, we found that the homeodomain transcription factor Dbx1 is expressed by neurogenic progenitors in the developing and adult mouse olfactory epithelium. We demonstrate that Dbx1 itself is dispensable for neuronal fate specification and global organization of the olfactory sensory system. Using lineage tracing, we characterize the contribution of Dbx1 lineages to OSN, VSN, and GnRH neuron populations and reveal an unexpected degree of diversity. Furthermore, we demonstrate that Dbx1-expressing progenitors remain neurogenic in the absence of the proneural gene Ascl1. Our work therefore points to the existence of distinct neurogenic programs in Dbx1-derived and other olfactory lineages.

Effects of Ferroptosis on Male Reproduction

Ferroptosis is a relatively novel form of regulated cell death that was discovered in 2012. With the increasing research related to the mechanisms of ferroptosis, previous studies have demonstrated that the inactive of the intracellular antioxidant system and iron overload can result in the accumulation of reactive oxygen species (ROS), which can ultimately cause lipid peroxidation in the various cell types of the body. ROS accumulation can cause sperm damage by attacking the plasma membrane and damaging DNA. Acute ferroptosis causes oxidative damage to sperm DNA and testicular oxidative stress, thereby causing male reproductive dysfunction. This review aims to discuss the metabolic network of ferroptosis, summarize and analyze the relationship between male reproductive diseases caused by iron overload as well as lipid peroxidation, and provide a novel direction for the research and prevention of various male reproductive diseases.

A Novel Loss-of-Function SEMA3E Mutation in a Patient with Severe Intellectual Disability and Cognitive Regression

Intellectual disability (ID) is a neurological disorder arising from early neurodevelopmental defects. The underlying genetic and molecular mechanisms are complex, but are thought to involve, among others, alterations in genes implicated in axon guidance and/or neural circuit formation as demonstrated by studies on mouse models. Here, by combining exome sequencing with in silico analyses, we identified a patient affected by severe ID and cognitive regression, carrying a novel loss-of-function variant in the semaphorin 3E (SEMA3E) gene, which encodes for a key secreted cue that controls mouse brain development. By performing ad hoc in vitro and ex vivo experiments, we found that the identified variant impairs protein secretion and hampers the binding to both embryonic mouse neuronal cells and tissues. Further, we revealed SEMA3E expression during human brain development. Overall, our findings demonstrate the pathogenic impact of the identified SEMA3E variant and provide evidence that clinical neurological features of the patient might be due to a defective SEMA3E signaling in the brain.

p140Cap Controls Female Fertility in Mice Acting via Glutamatergic Afference on Hypothalamic Gonadotropin-Releasing Hormone Neurons

p140Cap, encoded by the gene SRCIN1 (SRC kinase signaling inhibitor 1), is an adaptor/scaffold protein highly expressed in the mouse brain, participating in several pre- and post-synaptic mechanisms. p140Cap knock-out (KO) female mice show severe hypofertility, delayed puberty onset, altered estrus cycle, reduced ovulation, and defective production of luteinizing hormone and estradiol during proestrus. We investigated the role of p140Cap in the development and maturation of the hypothalamic gonadotropic system. During embryonic development, migration of Gonadotropin-Releasing Hormone (GnRH) neurons from the nasal placode to the forebrain in p140Cap KO mice appeared normal, and young p140Cap KO animals showed a normal number of GnRH-immunoreactive (-ir) neurons. In contrast, adult p140Cap KO mice showed a significant loss of GnRH-ir neurons and a decreased density of GnRH-ir projections in the median eminence, accompanied by reduced levels of GnRH and LH mRNAs in the hypothalamus and pituitary gland, respectively. We examined the number of kisspeptin (KP) neurons in the rostral periventricular region of the third ventricle, the number of KP-ir fibers in the arcuate nucleus, and the number of KP-ir punctae on GnRH neurons but we found no significant changes. Consistently, the responsiveness to exogenous KP in vivo was unchanged, excluding a cell-autonomous defect on the GnRH neurons at the level of KP receptor or its signal transduction. Since glutamatergic signaling in the hypothalamus is critical for both puberty onset and modulation of GnRH secretion, we examined the density of glutamatergic synapses in p140Cap KO mice and observed a significant reduction in the density of VGLUT-ir punctae both in the preoptic area and on GnRH neurons. Our data suggest that the glutamatergic circuitry in the hypothalamus is altered in the absence of p140Cap and is required for female fertility.

BDNF Val66Met polymorphism alters food intake and hypothalamic BDNF expression in mice

Obesity, a rising public health burden, is a multifactorial disease with an increased risk for patients to develop several pathological conditions including type 2 diabetes mellitus, hypertension, and cardiovascular disease. Increasing evidence suggests a relationship between the human brain-derived neurotrophic factor (BDNF) Val66Met single-nucleotide polymorphism (SNP) and obesity, although the underlying mechanisms of this connection are still not completely understood. In the present study, we found that homozygous knock-in BDNF^Met/Met mice were overweight and hyperphagic compared to wildtype BDNF^Val/Val mice. Increased food intake was associated with reduction of total BDNF and BDNF1, BDNF4 and BDNF6 transcripts in the hypothalamus of BDNF^Met/Met mice. In contrast, in the white adipose tissue total BDNF and Glut4 expression levels were augmented, while sirtuin 1 and leptin receptor (Ob-R) expression levels were reduced in BDNF^Met/Met mice. Moreover, plasmatic leptin levels were decreased in BDNF^Met/Met mice. However, BDNF^Val/Val and BDNF^Met/Met mice showed a similar response to the insulin tolerance test and glucose tolerance test. Altogether, these results suggest that BDNF Val66Met SNP strongly contributes to adipose tissue pathophysiology, resulting in reduced circulating leptin levels and hypothalamic expression of BDNF, which, in turn, promote increased food intake and overweight in BDNF^Met/Met mice.

From Environment to Genome and Back: A Lesson from HFE Mutations

The environment and the human genome are closely entangled and many genetic variations that occur in human populations are the result of adaptive selection to ancestral environmental (mainly dietary) conditions. However, the selected mutations may become maladaptive when environmental conditions change, thus becoming candidates for diseases. Hereditary hemochromatosis (HH) is a potentially lethal disease leading to iron accumulation mostly due to mutations in the HFE gene. Indeed, homozygosity for the C282Y HFE mutation is associated with the primary iron overload phenotype. However, both penetrance of the C282Y variant and the clinical manifestation of the disease are extremely variable, suggesting that other genetic, epigenetic and environmental factors play a role in the development of HH, as well as, and in its progression to end-stage liver diseases. Alcohol consumption and dietary habits may impact on the phenotypic expression of HFE-related hemochromatosis. Indeed, dietary components and bioactive molecules can affect iron status both directly by modulating its absorption during digestion and indirectly by the epigenetic modification of genes involved in its uptake, storage and recycling. Thus, the premise of this review is to discuss how environmental pressures led to the selection of HFE mutations and whether nutritional and lifestyle interventions may exert beneficial effects on HH outcomes and comorbidities.

PLXNA1 and PLXNA3 cooperate to pattern the nasal axons that guide gonadotropin-releasing hormone neurons

Gonadotropin-releasing hormone (GnRH) neurons regulate puberty onset and sexual reproduction by secreting GnRH to activate and maintain the hypothalamic-pituitary-gonadal axis. During embryonic development, GnRH neurons migrate along olfactory and vomeronasal axons through the nose into the brain, where they project to the median eminence to release GnRH. The secreted glycoprotein SEMA3A binds its receptors neuropilin (NRP) 1 or NRP2 to position these axons for correct GnRH neuron migration, with an additional role for the NRP co-receptor PLXNA1. Accordingly, mutations in SEMA3A, NRP1, NRP2 and PLXNA1 have been linked to defective GnRH neuron development in mice and inherited GnRH deficiency in humans. Here, we show that only the combined loss of PLXNA1 and PLXNA3 phenocopied the full spectrum of nasal axon and GnRH neuron defects of SEMA3A knockout mice. Together with Plxna1, the human orthologue of Plxna3 should therefore be investigated as a candidate gene for inherited GnRH deficiency.

HS6ST1 Insufficiency Causes Self-Limited Delayed Puberty in Contrast With Other GnRH Deficiency Genes

CONTEXT

Self-limited delayed puberty (DP) segregates in an autosomal-dominant pattern, but the genetic basis is largely unknown. Although DP is sometimes seen in relatives of patients with hypogonadotropic hypogonadism (HH), mutations in genes known to cause HH that segregate with the trait of familial self-limited DP have not yet been identified.

OBJECTIVE

To assess the contribution of mutations in genes known to cause HH to the phenotype of self-limited DP.

DESIGN, PATIENTS, AND SETTING

We performed whole-exome sequencing in 67 probands and 93 relatives from a large cohort of familial self-limited DP, validated the pathogenicity of the identified gene variant in vitro, and examined the tissue expression and functional requirement of the mouse homolog in vivo.

RESULTS

A potentially pathogenic gene variant segregating with DP was identified in 1 of 28 known HH genes examined. This pathogenic variant occurred in HS6ST1 in one pedigree and segregated with the trait in the six affected members with heterozygous transmission (P = 3.01 × 10-5). Biochemical analysis showed that this mutation reduced sulfotransferase activity in vitro. Hs6st1 mRNA was expressed in peripubertal wild-type mouse hypothalamus. GnRH neuron counts were similar in Hs6st1+/- and Hs6st1+/+ mice, but vaginal opening was delayed in Hs6st1+/- mice despite normal postnatal growth.

CONCLUSIONS

We have linked a deleterious mutation in HS6ST1 to familial self-limited DP and show that heterozygous Hs6st1 loss causes DP in mice. In this study, the observed overlap in potentially pathogenic mutations contributing to the phenotypes of self-limited DP and HH was limited to this one gene.

Iron and a Man's Reproductive Health: the Good, the Bad, and the Ugly

PURPOSE OF REVIEW

To discuss the physiologic and pathologic effects of iron on men's reproductive health.

RECENT FINDINGS

Iron overload diseases are associated with hypogonadotropic hypogonadism, infertility, and sexual dysfunction in men. Recent findings have elucidated the roles by which iron may affect the male reproductive axis. Iron is requisite for life. Iron can also catalyze the production of reactive oxygen species. To maintain balance, the human body tightly regulates dietary iron absorption. Severe iron overload disorders-e.g., hereditary hemochromatosis and β-thalassemia-occur when these regulatory mechanisms are deficient. While iron is necessary, the male reproductive system is particularly sensitive to iron overload. Hypogonadotropic hypogonadism, infertility, and sexual dysfunction commonly occur if excess iron from iron overload disorders is not removed. The average male in the USA consumes significantly more iron than needed to replace daily losses. How this degree of iron loading may affect one's reproductive health remains less clear, but there is evidence it may have adverse effects.