New Horizons: Gonadotropin-Releasing Hormone and Cognition

Association of neurodegeneration, cognitive impairment, and short stature in Down syndrome; Could proinflammatory cytokines be the common factor?

Down syndrome (DS), caused by an extra copy of chromosome 21, is the most prevalent chromosomal disorder. It leads to various complications including, cardiac and endocrine dysfunctions, impairment of the immune system, growth retardation, and certain neurological conditions. Stunted growth in this population might be linked to an increased risk of a variety of co-occurring conditions, particularly neurological disorders. Studies indicate that the levels of neurodegeneration and neuroinflammation markers are higher in shorter children with DS. The disruption of insulin-like growth factor 1 (IGF1) signalling pathway due to the overexpression of proinflammatory cytokine genes could help establish a connection between short stature and neurodegeneration in DS. These cytokines disrupt the production of IGF1 in the liver, thereby inhibiting IGF1 from promoting bone and brain growth. Additionally, elevated cytokines levels impair the production of sex hormones by affecting the gonadal axis, further exacerbating the aforementioned conditions. The group of GnRH neurons responsible for cognitive functions is also impaired in DS, and treatment with GnRH agonists has demonstrated improvements in cognition. Although GnRH agonists can delay the fusion of growth plates by inhibiting pulsatile GnRH secretion, they may also lead to cognitive impairments. Hypothyroidism, the most prevalent endocrine complication of DS, can also contribute to both cognitive impairment and short stature. In conclusion, the increase of proinflammatory cytokines, through various mechanisms, can play a significant role in the development of both cognitive impairments and short stature in DS.

GnRH and Cognition

GnRH is traditionally recognized as the central regulator of reproduction through its pulsatile secretion, which governs the hypothalamic-pituitary-gonadal axis. However, recent evidence has highlighted its broader role in brain development and function, including in cognitive and higher intellectual processes. GnRH production follows distinct phases, from its early activation during minipuberty-the first postnatal activation of GnRH neurons during the infantile period-, its reactivation and stabilization starting at puberty, and its eventual decline with age and the loss of gonadal steroid feedback. This evolution depends on the establishment, maturation and activation of GnRH neurons, a complex process regulated by the cellular and molecular environment of these neurons, including multiple neuronal and glial types as well as a minipubertal "switch" in gene expression, the perturbation of which may have long-term or delayed consequences for both reproductive and cognitive function. The cognitive role of GnRH may be related to its recently revealed involvement in maintaining myelination and synaptic plasticity, whereas disruptions in its finely tuned rhythmic secretion, either age-related or pathological, are associated with cognitive decline and neurodegenerative disorders. Restoring physiological GnRH levels and pulsatility can reverse age-related cognitive decline and improve sensory functions even in adulthood, suggesting a mobilization of the "cognitive reserve" in both animal models and human patients. This review highlights recent advances in our understanding of the GnRH system and the therapeutic potential of pulsatile GnRH therapy to mitigate age-related cognitive decline and neurodegenerative processes.

Genetics and Epigenetics of Human Pubertal Timing: The Contribution of Genes Associated With Central Precocious Puberty

Human puberty is a dynamic biological process determined by the increase in the pulsatile secretion of GnRH triggered by distinct factors not fully understood. Current knowledge reveals fine tuning between an increase in stimulatory factors and a decrease in inhibitory factors, where genetic and epigenetic factors have been indicated as key players in the regulation of puberty onset by distinct lines of evidence. Central precocious puberty (CPP) results from the premature reactivation of pulsatile secretion of GnRH. In the past decade, the identification of genetic causes of CPP has largely expanded, revealing hypothalamic regulatory factors of pubertal timing. Among them, 3 genes associated with CPP are linked to mechanisms involving DNA methylation, reinforcing the strong role of epigenetics underlying this disorder. Loss-of-function mutations in Makorin Ring-Finger Protein 3 (MKRN3) and Delta-Like Non-Canonical Notch Ligand 1 (DLK1), 2 autosomal maternally imprinted genes, have been described as relevant monogenic causes of CPP with the phenotype exclusively associated with paternal transmission. MKRN3 has proven to be a key component of the hypothalamic inhibitory input on GnRH neurons through different mechanisms. Additionally, rare heterozygous variants in the Methyl-CpG-Binding Protein 2 (MECP2), an X-linked gene that is a key factor of DNA methylation machinery, were identified in girls with sporadic CPP with or without neurodevelopmental disorders. In this mini-review, we focus on how the identification of genetic causes of CPP has revealed epigenetic regulators of human pubertal timing, summarizing the latest knowledge on the associations of puberty with MKRN3, DLK1, and MECP2.

An update on the role of sex hormones in the function of the cardiorenal mitochondria

Multiple studies have highlighted the crucial role of mitochondrial bioenergetics in understanding the progression of cardiorenal diseases, revealing new potential treatment targets related to mitochondrial metabolism. There are well-established sexual dimorphisms in cardiac and renal physiology, with premenopausal females being generally protected from pathology compared with males. The mechanisms of this protection remain to be fully elucidated, however, they clearly depend, at least in part, on sex hormones. Sex hormones contribute to regulating mitochondrial function, and vice versa, highlighting the existence of a bidirectional relationship pivotal for cellular energy metabolism; however, there are still large gaps in knowledge when the sex differences in mitochondrial bioenergetics in health and disease are concerned. This manuscript provides an overview of the new evidence that has been accumulated regarding the role of sex hormones in renal and cardiac mitochondria-dependent cellular energetics, metabolism, and signaling, mainly focusing on the data obtained within the last 3-5 years. We briefly discuss mitochondrial function and different types of sex hormones for the reader and then focus on novel research underscoring the emerging mitochondrial pathways regulated by sex hormones, which might be of interest for the development of novel therapeutic strategies for cardiorenal conditions.

Disorders of puberty and neurodevelopment: A shared etiology?

The neuroendocrine control of puberty and reproduction is fascinatingly complex, with up- and down-regulation of key reproductive hormones during fetal, infantile, and later childhood periods that determine the correct function of the hypothalamic-pituitary-gonadal axis and the timing of puberty. Neuronal development is a vital element of these processes, and multiple conditions of disordered puberty and reproduction have their etiology in abnormal neuronal migration or function. Although there are numerous documented cases across multiple conditions wherein patients have both neurodevelopmental disorders and pubertal abnormalities, this has mostly been described ad hoc and the associations are not clearly documented. In this review, we aim to describe the overlap between these two groups of conditions and to increase awareness to ensure that puberty and reproductive function are carefully monitored in patients with neurodevelopmental conditions, and vice versa. Moreover, this commonality can be explored for clues about the disease mechanisms in these patient groups and provide new avenues for therapeutic interventions for affected individuals.

Novel insights into minipuberty and GnRH: Implications on neurodevelopment, cognition, and COVID-19 therapeutics

In humans, the first 1000 days of life are pivotal for brain and organism development. Shortly after birth, gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus are activated, a phenomenon known as minipuberty. This phenomenon, observed in all mammals studied, influences the postnatal development of the hypothalamic-pituitary-gonadal (HPG) axis and reproductive function. This review will put into perspective the results of recent studies showing that the impact of minipuberty extends beyond reproductive function, influencing sensory and cognitive maturation. Studies in mice have revealed the role of nitric oxide (NO) in regulating minipuberty amplitude, with NO deficiency linked to cognitive and olfactory deficits. Additionally, findings indicate that cognitive and sensory defects in adulthood in a mouse model of Down syndrome are associated with an age-dependent decline of GnRH production, whose origin can be traced back to minipuberty, and point to the potential therapeutic role of pulsatile GnRH administration in cognitive disorders. Furthermore, this review delves into the repercussions of COVID-19 on GnRH production, emphasizing potential consequences for neurodevelopment and cognitive function in infected individuals. Notably, GnRH neurons appear susceptible to SARS-CoV-2 infection, raising concerns about potential long-term effects on brain development and function. In conclusion, the intricate interplay between GnRH neurons, GnRH release, and the activity of various extrahypothalamic brain circuits reveals an unexpected role for these neuroendocrine neurons in the development and maintenance of sensory and cognitive functions, supplementing their established function in reproduction. Therapeutic interventions targeting the HPG axis, such as inhaled NO therapy in infancy and pulsatile GnRH administration in adults, emerge as promising approaches for addressing neurodevelopmental cognitive disorders and pathological aging.

Key mRNAs and lncRNAs of pituitary that affect the reproduction of FecB + + small tail han sheep

BACKGROUND

The pituitary directly regulates the reproductive process through follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Transcriptomic research on the pituitaries of ewes with different FecB (fecundity Booroola) genotypes has shown that some key genes and lncRNAs play an important role in pituitary function and sheep fecundity. Our previous study found that ewes with FecB + + genotypes (without FecB mutation) still had individuals with more than one offspring per birth. It is hoped to analyze this phenomenon from the perspective of the pituitary transcriptome.

RESULTS

The 12 Small Tail Han Sheep were equally divided into polytocous sheep in the follicular phase (PF), polytocous sheep in the luteal phase (PL), monotocous sheep in the follicular phase (MF), and monotocous sheep in the luteal phase (ML). Pituitary tissues were collected after estrus synchronous treatment for transcriptomic analysis. A total of 384 differentially expressed genes (DEGs) (182 in PF vs. MF and 202 in PL vs. ML) and 844 differentially expressed lncRNAs (DELs) (427 in PF vs. MF and 417 in PL vs. ML) were obtained from the polytocous-monotocous comparison groups in the two phases. Functional enrichment analysis showed that the DEGs in the two phases were enriched in signaling pathways known to play an important role in sheep fecundity, such as calcium ion binding and cAMP signaling pathways. A total of 1322 target relationship pairs (551 pairs in PF vs. MF and 771 pairs in PL vs. ML) were obtained for the target genes prediction of DELs, of which 29 DEL-DEG target relationship pairs (nine pairs in PF vs. MF and twenty pairs in PL vs. ML). In addition, the competing endogenous RNA (ceRNA) networks were constructed to explore the regulatory relationships of DEGs, and some important regulatory relationship pairs were obtained.

CONCLUSION

According to the analysis results, we hypothesized that the pituitary first receives steroid hormone signals from the ovary and uterus and that VAV3 (Vav Guanine Nucleotide Exchange Factor 3), GABRG1 (Gamma-Aminobutyric Acid A Receptor, Gamma 1), and FNDC1 (Fibronectin Type III Domain Containing 1) played an important role in this process. Subsequently, the reproductive process was regulated by gonadotropins, and IGFBP1 (Insulin-like Growth Factor Binding Protein 1) was directly involved in this process, ultimately affecting litter size. In addition, TGIF1 (Transforming Growth Factor-Beta-Induced Factor 1) and TMEFF2 (Transmembrane Protein With EGF Like And Two Follistatin Like Domains 2) compensated for the effect of the FecB mutation and function by acting on TGF-β/SMAD signaling pathway, an important pathway for sheep reproduction. These results provided a reference for understanding the mechanism of multiple births in Small Tail Han Sheep without FecB mutation.

Functional GnRH receptor signaling regulates striatal cholinergic neurons in neonatal but not in adult mice

Reproduction in mammals is controlled by hypothalamic gonadotropin-releasing hormone (GnRH) neurons. Recent studies from our laboratory established that the basal ganglia of the human brain contain additional large populations of GnRH synthesizing neurons which are absent in adult mice. Such extrahypothalamic GnRH neurons mostly occur in the putamen where they correspond to subsets of the striatal cholinergic interneurons (ChINs) and express GnRHR autoreceptors. In an effort to establish a mouse model for functional studies of striatal GnRH/GnRHR signaling, we carried out electrophysiological experiments on acute brain slices from male transgenic mice. Using PN4-7 neonatal mice, half of striatal ChINs responded with transient hyperpolarization and decreased firing rate to 1.2 µM GnRH, whereas medium spiny projection neurons remained unaffected. GnRH acted on its specific receptor because no response was observed in the presence of the GnRHR antagonist Antide. Addition of the membrane-impermeable G protein-coupled receptor inhibitor GDP-β-S to the internal electrode solution eliminated the effect of GnRH. Further, GnRH was able to inhibit ChINs in presence of tetrodotoxin which blocked action potential mediated events. Collectively, these data indicated that the receptor underlying the effects of GnRH in neonatal mice is localized within ChINs. GnRH responsiveness of ChINs was transient and entirely disappeared in adult mice. These results raise the possibility to use neonatal transgenic mice as a functional model to investigate the role of GnRH/GnRHR signaling discovered earlier in adult human ChINs.

Androgen Deprivation Therapy for Prostate Cancer: Focus on Cognitive Function and Mood

Prostate cancer is the second leading cause of cancer death in men in the United States. Androgen deprivation therapy (ADT) is currently the primary treatment for metastatic prostate cancer, and some studies have shown that the use of anti-androgen drugs is related to a reduction in cognitive function, mood changes, diminished quality of life, dementia, and possibly Alzheimer's disease. ADT has potential physiological effects such as a reduction in white matter integrity and a negative impact on hypothalamic functions due to the lowering of testosterone levels or the blockade of downstream androgen receptor signaling by first- and second-generation anti-androgen drugs. A comparative analysis of prostate cancer patients undergoing ADT and Alzheimer patients identified over 30 shared genes, illustrating common ground for the mechanistic underpinning of the symptomatology. The purpose of this review was to investigate the effects of ADT on cognitive function, mood, and quality of life, as well as to analyze the relationship between ADT and Alzheimer's disease. The evaluation of prostate cancer patient cognitive ability via neurocognitive testing is described. Future studies should further explore the connection among cognitive deficits, mood disturbances, and the physiological changes that occur when hormonal balance is altered.

Long-COVID cognitive impairments and reproductive hormone deficits in men may stem from GnRH neuronal death

BACKGROUND

We have recently demonstrated a causal link between loss of gonadotropin-releasing hormone (GnRH), the master molecule regulating reproduction, and cognitive deficits during pathological aging, including Down syndrome and Alzheimer's disease. Olfactory and cognitive alterations, which persist in some COVID-19 patients, and long-term hypotestosteronaemia in SARS-CoV-2-infected men are also reminiscent of the consequences of deficient GnRH, suggesting that GnRH system neuroinvasion could underlie certain post-COVID symptoms and thus lead to accelerated or exacerbated cognitive decline.

METHODS

We explored the hormonal profile of COVID-19 patients and targets of SARS-CoV-2 infection in post-mortem patient brains and human fetal tissue.

FINDINGS

We found that persistent hypotestosteronaemia in some men could indeed be of hypothalamic origin, favouring post-COVID cognitive or neurological symptoms, and that changes in testosterone levels and body weight over time were inversely correlated. Infection of olfactory sensory neurons and multifunctional hypothalamic glia called tanycytes highlighted at least two viable neuroinvasion routes. Furthermore, GnRH neurons themselves were dying in all patient brains studied, dramatically reducing GnRH expression. Human fetal olfactory and vomeronasal epithelia, from which GnRH neurons arise, and fetal GnRH neurons also appeared susceptible to infection.

INTERPRETATION

Putative GnRH neuron and tanycyte dysfunction following SARS-CoV-2 neuroinvasion could be responsible for serious reproductive, metabolic, and mental health consequences in long-COVID and lead to an increased risk of neurodevelopmental and neurodegenerative pathologies over time in all age groups.

FUNDING

European Research Council (ERC) grant agreements No 810331, No 725149, No 804236, the European Union Horizon 2020 research and innovation program No 847941, the Fondation pour la Recherche Médicale (FRM) and the Agence Nationale de la Recherche en Santé (ANRS) No ECTZ200878 Long Covid 2021 ANRS0167 SIGNAL, Agence Nationale de la recherche (ANR) grant agreements No ANR-19-CE16-0021-02, No ANR-11-LABEX-0009, No. ANR-10-LABEX-0046, No. ANR-16-IDEX-0004, Inserm Cross-Cutting Scientific Program HuDeCA, the CHU Lille Bonus H, the UK Medical Research Council (MRC) and National Institute of Health and care Research (NIHR).

A role for GnRH in olfaction and cognition: Implications for veterinary medicine

Pulsatile secretion of gonadotropin-releasing hormone (GnRH) is essential for the activation and maintenance of the function of the hypothalamic-pituitary-gonadal (HPG) axis, which controls the onset of puberty and fertility. Two provocative recent studies suggest that, in addition to control reproduction, the neurons in the brain that produce GnRH are also involved in the control postnatal brain maturation, odour discrimination and adult cognition. Long-acting GnRH antagonists and agonists are commonly used to control fertility and behaviour in veterinary medicine, primarily in males. This review puts into perspective the potential risks of these androgen deprivation therapies and immunization on olfactory and cognitive performances and well-aging in domestic animals, including pets. We will also discuss the results reporting beneficial effects of pharmacological interventions restoring physiological GnRH levels on olfactory and cognitive alterations in preclinical models of Alzheimer's disease, which shares many pathophysiological and behavioural hallmarks with canine cognitive dysfunction. These novel findings raise the intriguing possibility that pulsatile GnRH therapy holds therapeutic potential for the management of this behavioural syndrome affecting older dogs.