Abstracts
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Sunday 3 September
Monday 4 September
- Symposium: Stress - New frontiers, 9am
- Mortyn Jones Lecture, 11am
- Symposium: Metabolism - Beyond the hypothalamus, 4pm
Tuesday 5 September
- Symposium: Rhythms of life, 9am
- Alison Douglas lecture, 11am
- Symposium: Neuroendocrine adaptations during pregnancy & development, 2pm
Wednesday 6 September
- Symposium: Reproductive Neuroendocrinology, 9am
- Julia Buckingham and Michael Harbuz Prize lectures, 11am
Sunday 3 September 2023
Public Lecture
Anna Murray - Decoding the Biological Clock: Exploring the Genetics of Human Reproductive Ageing
As women age, their ability to conceive and carry a pregnancy to term declines, a process known as reproductive ageing. This phenomenon is governed by a complex interplay of genetic and environmental factors, and recent advances in genomics have shed new light on the underlying mechanisms.
Our research uses large scale genomics data to identify the genes and biological processes that govern reproductive ageing. Humans are born with all the eggs that they will produce in life and this pool reduces across the lifespan. Genetic variation influences the process of ovarian decline mostly by affecting how the ovary repairs damage to DNA, which could occur through environmental effects or be part of the normal way eggs are generated. Some genes when not expressed cause earlier entry into menopause, which could cause infertility. Reduced expression of other genes can extend reproductive lifespan and provide potential targets for extending fertility, through improved assisted conception technologies.
Understanding the genetics of reproductive ageing is not only important for fertility and family planning, but also has implications for broader health outcomes. For example, early menopause has been linked to an increased risk of certain diseases, including osteoporosis and cardiovascular disease. The genomics of human reproductive ageing represents a fascinating and rapidly evolving field of research with broad implications for human health.
Monday 4 September 2023
Symposium: Stress - New frontiers, 9am
Eder Zavala - Quantitative analysis of high-resolution daily profiles of HPA axis hormones
The Hypothalamic-Pituitary-Adrenal (HPA) axis is the key regulatory pathway responsible for maintaining homeostasis under conditions of real or perceived stress. Endocrine responses to stressors are mediated by adrenocorticotrophic hormone (ACTH) and corticosteroid (CORT) hormones. In healthy, non-stressed conditions, ACTH and CORT exhibit highly correlated ultradian pulsatility with an amplitude modulated by circadian processes. Disruption of these hormonal rhythms can occur as a result of stressors or in the very early stages of disease. Despite the fact that misaligned endocrine rhythms are associated with increased morbidity, a quantitative understanding of their mechanistic origin and pathogenicity is missing. Mathematically, the HPA axis can be understood as a dynamical system that is optimised to respond and adapt to perturbations. Normally, the body copes well with minor disruptions, but finds it difficult to withstand severe, repeated or long-lasting perturbations. Whilst a healthy HPA axis maintains a certain degree of robustness to stressors, its fragility in diseased states is largely unknown, and this understanding constitutes a critical step toward the development of digital tools to support clinical decision-making. This talk will explore how these challenges are being addressed by combining high-resolution biosampling techniques with mathematical and computational analysis methods. This interdisciplinary approach is helping us quantify the inter-individual variability of daily hormone profiles and develop novel “dynamic biomarkers” that serve as a normative reference and to signal endocrine dysfunction. By shifting from a qualitative to a quantitative description of the HPA axis, these insights bring us a step closer to personalised clinical interventions for which timing is key.
Naresh Hanchate - Mapping brain circuitry of stress using new single-cell genomic tools
The mammalian brain contains millions to billions of neurons highly interconnected in a vast array of neural circuits. The molecular identities and functions of individual neuronal components within specific circuits are yet undefined. Previously, we developed a new method, termed “Connect-seq”, by combining retrograde viral tracing and single-cell transcriptomics to uncover the molecular identities of upstream neurons in a specific circuit. Application of Connect-seq to hypothalamic neurons controlling physiological responses to fear and stress revealed subsets of upstream neurons that express diverse constellations of signaling molecules and can be distinguished by their anatomical locations. However, it is still unable to reconstruct a molecular map of the entire circuit, largely due to the insufficiency of data. To overcome these limitations, we developed a significantly improved method, termed ‘nuc-Connect-seq’, by combining single-nucleus transcriptomics and retrograde viral tracing and employing droplet-based microfluidics. Due to its rapid tissue dissociation and barcoding strategy, nuc-Connect-seq enables rapid profiling of thousands of single-neuron transcriptomes in a specific circuit in a massively parallel fashion. Moreover, nuc-Connect-seq has added advantage over Connect-seq in reducing methodology-induced transcription of activity-regulated genes, enabling its application to investigate neuronal activation of individual neuronal components within specific circuits.
Michael Emmerson - Acute thermal stress upregulates transcript expression of genes involved in cellular stress in the hypothalamus of nestling zebra finches depending on embryo acoustic experience
Michael G. Emmerson1*, Mylene M. Mariette2, David F. Clayton3, Elisabetta Versace1, Kate L. Buchanan2, Julia M. George4
Embryos detect and respond to parent vocalisations, with different parent vocalisations shifting individuals onto alternative developmental trajectories and constructing different later-life phenotypes. For example, zebra finches exposed to parent heat calls (produced at temperatures >26°C) as embryos develop into adults with greater thermal tolerance than those exposed to control calls. What mechanisms underpin this is unclear, but differences in stress physiology are plausible. Vertebrates have similar neuroendocrine stress responses, like hypothalamic-pituitary-adrenal axis activation and secretion of stress coping hormones (e.g., catecholamines, glucocorticoids). Hypothalamic nuclei regulate stress and temperature responses, with heat calls possibly shaping hypothalamic gene expression to enhance later-life thermal tolerance. Zebra finch eggs (n = 68) were therefore exposed to parent heat or control calls during incubation, and twelve days after hatching birds were subject to an acute thermal challenge (40°C). Brains were collected before or after the acute thermal challenge. Hypothalamus samples were then collected and whole genome transcript abundance quantification was conducted via QuantSeq. An acute thermal challenge upregulated transcript expression of six genes, including a stress responsive transcription factor (ZBTB16), glucocorticoid receptor co-chaperone (FKBP5), and a marker of DNA damage (DDIT4). Embryo heat call exposure blunted the rise in FKBP5, but not DDIT4 or ZBTB16, and resulted in greater transcript expression of a gene inhibiting cell death (FAIM2) compared to tet call exposure. Heat calls therefore improve thermal tolerance by altering stress-responsive gene transcription in glucocorticoid and cell survival pathways, revealing that parent vocalisations shape the neurodevelopmental trajectories of their offspring to improve stress resilience.
1. Queen Mary University of London, School of Behavioural & Biological Sciences
2. Deakin University, School of Life & Environmental Sciences, Centre for Integrative Ecology
3. Clemson University, Department of Genetics and Biochemistry
4. Clemson University, Department of Biological Sciences
Lora Martucci - The endolysosomal cation channel TPC regulates social behaviour by controlling oxytocin secretion
L. Martucci1, J.-M. Launay2, C. Grimm3, A. Galione1, J.-M. Cancela4;
Oxytocin (OT) is a prominent regulator of many aspects of mammalian social behaviour and stored in large dense-cored vesicles (LDCVs) in hypothalamic neurons. It is released in response to activity-dependent Ca2+influx, but is mainly dependent on Ca2+ release from intracellular stores, which primes LDCVs for exocytosis. Despite its importance, critical aspects of the Ca2+-dependent mechanisms of its secretion remain to be identified. In a recently published paper, using immunostaining, we showed that lysosomes are in close proximity with the OT LDCVs, and that the direct activation of endolysosomal two-pore channels (TPCs)provides the critical Ca2+ signals to prime OT release by increasing the releasable LDCV pool without directly stimulating exocytosis. Using radioimmunoassays, we observed a dramatic reduction in plasma OT levels in TPC knockout mice, and impaired secretion of OT from the hypothalamus demonstrating the importance of neuropeptide vesicles priming for activity-dependent release. Furthermore, we showed that activation of type 1metabotropic glutamate receptors sustains somatodendritic OT release by recruiting TPCs. The priming effect could be mimicked by a direct application of NAADP, the endogenous agonist of TPCs, or a selective TPC2agonist, TPC2-A1-N. Confocal calcium imaging revealed reduced aspects of Ca2+ responses evoked by glutamatergic stimulation in presence of pharmacological inhibitors of TPCs or TPC deletion. Finally, behavioural experiments revealed that mice lacking TPCs exhibit impaired maternal and social behaviour, which is restored by direct OT administration. This study demonstrates an unexpected role for lysosomes and TPCs in controlling neuropeptide secretion, and in regulating social behaviour.
LL Martucci et al., PNAS, 2023
1. University of Oxford, Department of Pharmacology, Oxford, United Kingdom,
2I. NSERM UMR-S 942, Hôpital Lariboisière, Paris, France,
3. Ludwig-Maximilians- Munich University, Walther Straub Institute of Pharmacology and Toxicology, Munich, Germany,
4. Neuroscience Paris-Saclay Institute, CNRS UMR 9197, Saclay, France
Mortyn Jones lecture, 11am
Valerie Simonneaux - Neuroendocrine mechanisms of seasonal adaptation
The annual change in the nocturnal production of the pineal hormone melatonin has long been known to be pivotal for the seasonal adaptation of biological functions in mammals. The discovery that melatonin acts on the pars tuberalis cells to control the synthesis of TSH, which in turn acts on the hypothalamic tanycytes to modulate local thyroid hormone metabolism, has been a breakthrough in our understanding of the neuroendocrine mechanisms underlying seasonal adaptation. In this lecture, I will discuss how this melatonin/TSH/T3 signal impacts hypothalamic circuits to synchronize various biological functions with the seasons.
Symposium: Metabolism - Beyond the hypothalamus, 4pm
Jenni Harvey - Food for thought: Exploring the cognitive enhancing and therapeutic potential of leptin
Evidence is accumulating that the endocrine hormone leptin is a potent regulator of hippocampal synaptic function. Indeed, recent studies have highlighted the cognitive enhancing actions of leptin as this hormone regulates many aspects of synaptic function including glutamate receptor trafficking, neuronal morphology and activity dependent synaptic plasticity. Furthermore, leptin-insensitivity is associated with impairments in hippocampal-dependent memory tasks and activity-dependent synaptic plasticity. However, there is significant decline in the ability of leptin to regulate hippocampal synaptic function with age and leptin dysfunction has been linked to neurodegenerative disorders like Alzheimer's disease. Here, we will review the impact of leptin-driven changes on hippocampal excitatory synaptic function, and how this is providing valuable insight into leptin’s role in higher cognitive functions in health and disease.
Dan Brierley - Mapping GLP-1 signalling pathways in the gut-brain axis reveals novel strategies for obesity pharmacotherapy
Centre for Cardiovascular & Metabolic Neuroscience; Department of Neuroscience, Physiology & Pharmacology; University College London; UK
The anorexigenic peptide glucagon-like peptide-1 (GLP-1) is secreted from gut enteroendocrine cells and brain preproglucagon (PPG) neurons, which respectively define the peripheral and central GLP-1 systems. PPG neurons in the nucleus tractus solitarii (NTS) have been assumed to link the peripheral and central GLP-1 systems in a unified gut-brain satiation circuit, in which GLP-1 released from the gut in response to meals acts via vagal and/or hormonal gut-brain pathways to trigger central release of GLP-1 from PPGNTS neurons to suppress further eating. However, direct evidence for this hypothesis is lacking, and the gut-brain connectivity necessary for this circuit has not been demonstrated.
We tested this hypothesis using complementary circuit mapping and behavioural approaches in transgenic mouse models which allowed selective manipulation of neuronal populations within the peripheral and central GLP-1 systems. Contrary to the unified GLP-1 circuit hypothesis, we determined that PPGNTS neurons are not a major target of either vagal or hormonal signalling pathways from the peripheral GLP-1 system. Furthermore, PPGNTS neurons are not activated by or required for the anorectic effects of the GLP-1RA drugs semaglutide or liraglutide. Consistent with the alternative hypothesis that peripheral and central GLP-1 systems are anatomically and functionally distinct entities, we demonstrated that chemogenetic activation of PPGNTS neurons, concurrent with peripheral semaglutide administration, suppressed eating more potently than either manipulation alone. Furthermore, this apparently additive effect could be replicated pharmacologically, as the 5-HT2CR agonist anti-obesity drug lorcaserin required PPGNTS neurons for its anorectic effect, and individually anorexigenic doses of lorcaserin and liraglutide suppressed eating to a greater extent when administered concurrently than either monotherapy alone.
We therefore conclude that central and peripheral GLP-1 systems suppress eating via apparently independent gut-brain circuits, providing a rationale for investigation of strategies for additive pharmacological manipulation of these systems for the treatment of obesity.
Astrid Van Irsen - Activation of Drd1 MSNs in the medial shell of the nucleus accumbens projecting to the lateral hypothalamic area improves glucose homeostasis
Astrid A. S. van Irsen(*)1-4, Tess Kool1-4, Anouk M. Corstens1-4, Margo Slomp1-4, Andries Kalsbeek1-4, Susanne E. la Fleur1-4.
The nucleus accumbens (NAc) plays a critical role in reward and food-motivated behavior. It contains a core that is surrounded by a medial and lateral shell. The majority of accumbal neurons consists of medium spiny neurons (MSNs), which nearly all either express dopamine D1 receptors (Drd1) or dopamine D2 (Drd2) receptors. Previous findings showed that in rats deep brain stimulation of the NAc medial shell (mshNAc) increased blood glucose and plasma glucagon concentrations compared to sham or core stimulation. Moreover, infusion of vanoxerine, a dopamine reuptake inhibitor, into the mshNAc of rats decreased endogenous glucose production, blood glucose and plasma glucagon concentrations compared to vehicle. These effects may seem contradictory, however, this can likely be explained by the opposing effects of Drd1 and Drd2 activation under different conditions and their distinctive projections. Based on previous viral tracer experiments in rats (unpublished), we know mshNAc MSNsDrd1 mainly project to the lateral hypothalamic area (LHA).
To determine the role of this mshNAcDrd1>LHA connection in glucose metabolism, we employed chemogenetics in Drd1-Cre transgenic male rats to target MSNsDrd1 in the mshNAc. We compared overall activation of MSNsDrd1 in the mshNAc to specific activation of the mshNAcDrd1>LHA connection, on glucose tolerance. Activation of the mshNAcDrd1>LHA connection improved glucose tolerance (drug effect p<0.05 and interaction effect drug x time p<0.01, n=9), whereas overall mshNAc MSNDrd1 activation did not result in a significant effect. Overall, these results increase our understanding of neural circuitry underlying glucose metabolism. Currently we are replicating this experiment in female rats.
1. Amsterdam UMC location University of Amsterdam, Endocrinology Laboratory, Dept Clin Chemistry, Meibergdreef 9, Amsterdam, The Netherlands
2. Amsterdam Neuroscience, Cellular and Molecular Mechanisms, Amsterdam, The Netherlands
3. Amsterdam Gastroenterology Endocrinology & Metabolism, Amsterdam, The Netherlands
4. Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
Sophie Buller - Oligodendrocyte plasticity contributes towards the regulation of glucose homeostasis in adult mice
Sophie Buller1,*, Emily Staricoff1, Christine Riches1, Anthony Tsang1, Kentaro Ikemura2, Sara Kohnke1, Sam Virtue1, Antonio Vidal-Puig1, Satoshi Hirohata2, William Richardson3, Michael Schwartz4, Mark Evans1, Clemence Blouet1
Unlike what occurs in other brain regions, new oligodendrocytes (OL) and myelin are continuously produced and replaced in the adult median eminence (ME). While ME oligodendrocyte progenitor cell (OPC) proliferation, differentiation and myelin turnover are regulated by nutritional cues, detailed understanding of the physiological and functional significance of ME OL plasticity is lacking. Here, we demonstrate that manipulation of blood glucose levels rapidly alter ME OL lineage progression. To test the role of OL plasticity in the regulation of glucose homeostasis, we used Pdgfra-CreERT2;R26R-GFP;Myrffl/fl (Myrffl/fl) mice to blunt new OL production. Myrffl/fl mice rapidly become glucose intolerant and insulin resistant, show an exacerbated counter-regulatory response (CRR) to neuroglycopenia and exhibit significant hypercorticosteronaemia compared to controls. To disentangle the role of OPC differentiation vs. myelination in this phenotype, we used Pdgfra-CreERT2;R26R-GFP;Mbpfl/fl (Mbpfl/fl) mice to prevent new compact myelin generation. Glucose tolerance, insulin sensitivity and the CRR are unaffected by Mbp deletion despite profound hypocorticosteronaemia in this model, suggesting that compact myelin in the ME is not essential for glucose homeostasis, and new OLs contribute towards the regulation of glucose homeostasis through myelin-independent mechanisms. We identified ADAMTS4, an aggrecanase exclusively expressed by myelinating OLs as a potential candidate mediating these effects. ADAMTS4 administration to the ME acutely decreased food intake, increased plasma corticosterone and reduced insulin sensitivity compared to vehicle in C57BL/6J mice. Collectively these data indicate a role for adult-born OLs, independent of new compact myelin generation, in the regulation of glucose homeostasis and the hypothalamic-pituitary-adrenal axis.
1. Wellcome Trust-MRC Institute of Metabolic Science-Metabolic Research Laboratories, University of Cambridge, Cambridge, UK
2. Department of Medical Technology, Graduate School of Health Sciences, Okayama University, Okayama, Japan
3. Wolfson Institute for Biomedical Research, University College London, London, UK
4. Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA
Tuesday 5 September 2023
Symposium: Rhythms of life, 9am
Lukasz Chrobok - Circadian timekeeping in the brainstem satiety centre
Lukasz Chrobok, Charlotte Muir, Tanya Kaur, Jake Ahern, Hugh D. Piggins
Feeding is critical for survival and is orchestrated through the interplay of brain and gut signals. A subset of brain structures localised in the hypothalamus and brainstem coordinate both the amount and circadian times of day that food is consumed. Although the master circadian clock is localised in the suprachiasmatic nuclei of the hypothalamus (SCN), local extra-SCN timekeeping mechanisms are important for circadian physiology including the daily patterning of feeding.
Daily timekeeping mechanisms in the hypothalamus are much researched, but circadian rhythms in the brainstem are under-explored. Thus, we are evaluating potential local clock control over the brainstem’s dorsal vagal complex (DVC). Real-time bioluminescence recording of clock gene expression (PER2::LUC) ex vivo reveals that in developing and adult DVC, PER2 rhythms can be sustained for days to weeks, even when isolated from the SCN. Assessing neuronal activity in DVC brain slices on a multielectrode array recording platform, shows that the PER2 rhythms are accompanied by electrophysiological rhythms with peak neuronal firing at late day. Manipulating the rodent diet reveals that this temporal variation in DVC neurophysiological activity is notably dampened by consumption of a high-fat food. Importantly, assessment of gene expression in vivo by qPCR and RNAscope in situ hybridisation reveals that core clock genes are rhythmically expressed in the DVC with their expression present in neurochemically diverse cellular populations. This suggests that the potential for circadian timekeeping in the DVC is not due to a distinct subpopulation of cells, but rather arises from multiple different neuronal and non-neuronal groups.
Collectively, these studies point to how circadian mechanisms alter molecular and cellular activity in the DVC. Future research determining how diet and circadian signals interact to influence DVC function are necessary. Our research adds to a growing literature on the importance of understanding local extra-SCN clocks in the daily patterning of physiology and behaviour.
Beatriz Baño-Otálora - Brighten up your circadian clock: Impact of daytime light intensity on behaviour and brain clock function in a diurnal mammal
Centre for Biological Timing | Division of Diabetes, Endocrinology, & Gastroenterology | School of Medical Sciences | Faculty of Biology, Medicine & Health | The University of Manchester | Manchester
Circadian or ~24h rhythms constitute a fundamental feature of mammalian physiology and behaviour. These rhythms are orchestrated by a brain master clock, the suprachiasmatic nucleus of the hypothalamus (SCN), which is synchronized with the external world mainly by light. Circadian rhythms evolved under conditions in which there was a large difference in light intensity between day and night. However, the advent of artificial lighting has allowed humans unprecedented freedom to choose when to be active and exposed to light. So, we now live in a society in which we experience artificial light at night, but also, we deprive ourselves from exposure to bright light during the day by spending most of the waking hours in relatively dimly lit indoor environments. Over the past years, there has been a growing understanding of the potential negative effects that exposure to light-at-night can have on human health. However, our knowledge of the impact of exposure to low light intensity during the day is much more limited.
In this talk, I will present our work using a recently established diurnal rodent model, Rhabdomys pumilio to understand the impact of daytime light intensity and self-selected light exposure on daily rhythms in physiology and behaviour, and clock function. Our results show that bright daytime light enhances the robustness of behavioural and physiological rhythms and increases the amplitude of circadian rhythms in electrical activity in the SCN and gene expression in central and peripheral tissues. These findings reveal an impact of light on circadian amplitude and highlight the potential importance of daytime light exposure for circadian health.
Jarne Jermei - The impact of time-restricted feeding on microglial function
Jarne Jermei*1, Han Jiao1, Chun-Xia Yi1
Microglia are the resident brain immune cells, initiating local immune responses. It is well established that an obesogenic high-fat diet (HFD) causes brain inflammation. HFD consumption stimulates microglial activity also in the hypothalamus, resulting in decreased numbers of the appetite-curbing pro-opiomelanocortin (POMC) neurons, which eventually leads to obesity. Previously, we observed that in rats fed a HFD, hypothalamic microglial cells are constantly activated, instead of showing daily rhythmicity, probably due to their constantly elevated 24-hour food consuming behaviour. The goal of this study was to investigate whether indeed eating at the wrong time of the day affects microglial activity. To answer this research question, a time-restricted feeding (TRF) experiment was performed. Specifically, Wistar rats fed with a chow diet or HFD were divided into three groups, i.e. ad libitum, only light-phase feeding or only dark-phase feeding. After 4 weeks of TRF, rats were sacrificed every 4 hours along the light/dark cycle to study the daily rhythm in microglial activity and immunometabolism. HFD dark-fed rats showed a reduction in adiposity compared to the light-fed and ad libitum-fed rats. Interestingly, first analyses of the RNA sequencing data showed that the amplitude of the daily rhythm of microglial clock genes was altered in light-fed rats, compared to the dark- and ad libitum-fed rats, especially in the HFD groups. In conclusion, our data suggest that HFD food intake restricted to the active period has beneficial metabolic outcomes, preventing obesity. Importantly, the microglial clock is clearly affected by the timing of food intake.
1. Laboratory of Endocrinology, Amsterdam University Medical Center, Amsterdam Gastroenterology & Metabolism, University of Amsterdam, Amsterdam, The Netherlands.
Callum Stewart - The Molecular Architecture of a Circannual Timer in a Seasonal Rodent
Calum Stewart* – University of Glasgow
Timothy A. Liddle – University of Glasgow
Gaurav Majumdar - University of Allahabad
Christopher J. Marshall – University of Bristol
Tyler J. Stevenson – University of Glasgow
Seasonal alterations in energy balance, reproduction and behaviour allow animals to survive harsh seasonal conditions. The neuroendocrine mechanisms allowing for the precise timing of the seasonal response are not fully elucidated. To date, there have been no in-depth studies into the molecular changes in hypothalamic nuclei over the entirety of the seasonal waveform. This study aimed to generate high frequency transcriptomic data from individual hypothalamic nuclei across the seasonal waveform. Siberian hasmters (N = 54) were held under constant short photoperiod (8L:16D) for up to 32 weeks. At 4-week intervals, groups of animals were culled (n = 6), and physiological measurements were taken. Body mass, adipose mass and testes mass were recorded. Physiological factors showed previously reported seasonal changes, initial reduction followed by spontaneous recovery (P < 0.05). Individual hypothalamic nuclei were then dissected, and the molecular programme was assessed by Oxford Nanopore sequencing. This revealed several hundred transcripts differentially expressed by exposure to short photoperiod (FDR < 0.1). The transcripts and patterns of expression were unique to individual nuclei. Many of these transcripts showed dynamic changes throughout the seasonal waveform, indicating a complex relationship between central expression and the seasonal phenotype. This study is the first to generate a high dimensionality and high frequency seasonal transcriptome and uncovers the neuroendocrine mechanisms which may underlie the seasonal response.
Alison Douglas lecture, 11am
Manuel Tena-Sempere - Exploring the neuroendocrine basis of puberty and reproduction: Kisspeptins and beyond
Instituto Maimónides de Investigación Biomédica de Cordoba (IMIBIC); Department of Cell Biology, Physiology and Immunology, University of Cordoba; Hospital Universitario Reina Sofia; and CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, 14004 Cordoba, Spain
Pubertal maturation and reproductive function are intimately related phenomena, controlled by sophisticated developmental programs and regulatory circuits, centered around the hypothalamic-pituitary-gonadal axis. In this highly-hierarchical neuroendocrine system, hypothalamic neurons, producing gonadotropin-releasing hormone (GnRH), are masterpiece for timed pubertal onset and fertility, operating under the control of a wide variety of central transmitters and peripheral hormones, whose nature and mode of action have been partially exposed over the last decades. In this context, a major breakthrough was the identification, back in 2003, of the reproductive roles of kisspeptins, as major stimulators of GnRH neurons, responsible for their dynamic regulation along the lifespan. Of note, this seminal finding not only transformed our understanding of the mechanisms controlling puberty and reproduction, but boosted also a New Age in reproductive neuroendocrinology, which has led to the discovery of additional novel signals, neuroendocrine pathways and molecular regulatory mechanisms responsible for the precise control of puberty and fertility, and their interplay with other essential body functions, such as energy homeostasis and metabolism. In this lecture, I will discuss examples of major developments and recent findings in this area, aiming also to highlight new pathways for further progress of this very active domain of neuroendocrine research.
Symposium: Neuroendocrine adaptations during pregnancy & development, 2pm
Sharon Ladyman - Neuroendocrine control of body temperature and physical activity during pregnancy
Centre for Neuroendocrinology, University of Otago, Dunedin New Zealand
Numerous changes in physiology and behaviour are required during pregnancy as the maternal body adapts to met the demands of providing the fetus with the optimal nutrients and environment for healthy growth and development. A particularly striking behavioural change is a profound reduction in voluntary running wheel activity (RWA) that occurs as soon as mice become pregnant. The hormone prolactin increases due to mating and our recent work demonstrated that prolactin action in the preoptic area of the hypothalamus (POA) drives this pregnancy-induced suppression of voluntary physical activity. The POA is a brain region associated with multiple homeostatic and behavioural roles, including maternal behaviour, but another POA function of considerable interest is the control of thermoregulation. Pregnancy represents a significant challenge to maternal thermoregulation, as the thermogenic effects of the pregnancy hormone progesterone and the metabolic heat generated from fetal development must be dissipated to prevent teratogenic effects of hyperthermia. We have demonstrated a role of prolactin, acting in the POA, in influencing thermoregulatory responses in pregnancy. Firstly, AAV-Cre-mediated deletion of Prlr in the POA resulted in significant hyperthermia throughout pregnancy. Secondly, mice lacking Prlr in glutamatergic neurons (including heat-sensitive POA neurons) have poor pregnancy outcomes specifically when housed at elevated environmental temperature (30°C) while control pregnant mice are unaffected. We hypothesize that during pregnancy prolactin acts on thermoregulatory circuits in the POA to sensitise them to increases in temperature and more rapidly engage counter-regulatory actions to lower body temperature. Moreover, we predict that these thermoregulatory actions of prolactin may underlie the suppressive effect of prolactin on voluntary physical activity, such that pregnant mice terminate engagement in voluntary physical activity sooner to protect against activity-induced elevations in body temperature. These adaptive changes provide resilience to the thermal challenge of pregnancy, enabling mothers to cope with increases in environmental temperatures.
Laura Dearden - Early life programming of obesity via a hypothalamic miRNA involved in fatty acid sensing
In utero exposure to maternal obesity programs an increased risk of obesity. Animal models have shown that offspring obesity is often preceded by increased food intake, however, the mechanisms that mediate these changes are not understood. Using a mouse model of maternal diet-induced obesity we observed increased intake specifically of a high-fat pellet in adult offspring of obese mothers. Through small RNA sequencing, we identified programmed overexpression of miR-505-5p in the hypothalamus of offspring of obese mothers that is established in the fetus and remains to adulthood, and confirmed in vitro that fatty acid exposure increases expression of miR-505-5p in hypothalamic neurons. Pulsed SILAC analysis demonstrated protein targets of miR-505-5p are enriched in pathways involved in fatty acid metabolism. These include key components of neuronal fatty acid sensing pathways that we find to be associated with BMI in human genetic studies. Over-expression of miR-505-5p decreased neuronal fatty acid uptake and metabolism in neurons in vitro. Importantly, intra-cerebroventricular injection of a miR-505-5p mimic in mice resulted in increased intake specifically of a high-fat pellet. Collectively these data suggest that maternal obesity induces over-expression of miR-505-5p in offspring hypothalamus, resulting in altered fatty acid sensing and increased intake of high-fat diet. This represents a novel mechanism by which exposure to obesity in pregnancy programs obesity in offspring.
Helen Eachus - Elevated glucocorticoid: from adaptive plasticity to allostatic overload
Glucocorticoids (GC) are thought to be implicated in stress-related psychiatric disorders. Acute stress triggers adaptive responses allowing animals to respond appropriately to threat, however, exposure to chronic GC is associated with negative effects on the brain and behaviour in later life. This apparent dichotomy of effects exposes the question of whether the effects of GC might be temporally dynamic. It is known that environmental stress can increase organism growth rates but at a cost to fitness in later life. However the developmental trajectory of GC-induced effects on the brain is unclear. In an optogenetic zebrafish model, our recent work describes how elevated GC causes precocious hypothalamic development followed by failed maturation. In GC-exposed animals, hypothalamic proliferation is initially increased, the hypothalamus is larger, and one of its associated behavioural functions, feeding, develops early. However, precocious development is followed by a rapid decline. In GC-exposed animals, excess hypothalamic progenitor cells fail to differentiate and proliferative radial glia are lost from the hypothalamus. This correlates with altered numbers of differentiated neurons, which are known to regulate food intake, plus suppressed feeding and growth. Our data highlight the developmental dynamics of hypothalamic neurogenesis following GC exposure and indicate that the hypothalamus is a GC-sensitive brain region. Alteration of hypothalamic neurogenesis is likely a mechanism through which GC exerts its effects on behaviour and its associated pathologies. Further understanding of how stress and GC exposure can alter development trajectories at the molecular and cellular level is of critical importance to reduce the burden of mental and physical ill health across the life-course.
Wednesday 6 September
Symposium: Reproductive Neuroendocrinology, 9am
Allan Herbison - Recording the GnRH pulse and surge generators in vivo
Allan E. Herbison
Department of Physiology Development and Neuroscience, University of Cambridge, UK
Fertility in mammals is critically dependent upon episodic gonadotropin hormone secretion. It is now clear that kisspeptin neurons located in the arcuate nucleus (ARN) represent the gonadotropin-releasing hormone (GnRH) pulse generator in both males and females. In rodents, these kisspeptin neurons target GnRH neuron processes termed dendrons in the ventrolateral ARN to drive pulsatile gonadotropin secretion. In females, a second episode generator operates once per cycle to drive the preovulatory luteinizing hormone surge. This appears to involve a population of kisspeptin neurons located in the rostral periventricular area that integrate endocrine and circadian signals and project to nearby GnRH neuron cell bodies. A clear understanding of these episode generators requires their activity patterns to be established in vivo. We have used GCaMP-based fibre photometry approaches combined with in vivo CRISPR gene editing and local neurotransmitter receptor modulation to determine the activity patterns of kisspeptin and GnRH neurons in freely behaving male and female mice. This has generated predictable as well as surprising observations and, together, enable the construction of a simple model explaining the cyclical control of fertility in females.
Elodie Desroziers - Unusual suspect: role of microglia in the neuroendocrine disorder polycystic ovary syndrome
Aisha Sati1,2, Mel Prescott1, Kay Potapov1, Rebecca Campbell1, Elodie Desroziers1,3.
1. Center for Neuroendocrinology, Department of Physiology, School of biomedical sciences, University of Otago, Dunedin, New Zealand
2. GIGA-Neurosciences, Université de Liège, Liège Belgium
3. Sorbonne Université, Institut de Biologie Paris Seine, Neuroscience Paris Seine, Paris, France
Infertility disorders currently affect 1 in 6 couples worldwide. Polycystic Ovary Syndrome (PCOS) is the most common infertility disorder in women of reproductive age worldwide. PCOS is characterised by an elevated blood level of androgens, menstrual dysfunction and multiple cyst-like follicles in the ovary. Although commonly considered an ovarian disorder, the brain is now a prime suspect in both the development and maintenance of PCOS. Recent animal-based studies demonstrate that androgen excess in early life and adulthood contribute to the pathological neuronal wiring associated with infertility. To date, the mechanisms underlying this altered brain wiring remain unknown. Microglia, the immune cells of the brain, are active sculptors of neuronal wiring across development, mediating both the formation and removal of neuronal inputs. Therefore, we hypothesized that microglia may contribute to the PCOS phenotype responsible for infertility. To this aim, we assessed whether microglia phenotype and function are altered in the brain of the PNA mouse model of PCOS across development. In PNA mice, changes in the number and morphology of microglia have been only observed in the vicinity of the GnRH neurons where the neuronal wiring is detected and in time-specific manner. In addition, an altered refinement of GABA inputs onto the GnRH neurons has been observed prior to the remodelling of the circuitry in PCOS. To conclude, this study is the first to characterize microglia in a mouse model of PCOS and suggest a role of microglia in the brain wiring abnormalities associated with PCOS.
Deyana Ivanova - The amygdala, a key upstream regulator of the hypothalamic GnRH pulse generator
Stress profoundly impedes pubertal development, disrupts reproduction and suppresses pulsatile luteinizing hormone (LH) secretion in mammals. The amygdala is the integrative centre for processing emotions, regulating the stress response and controlling anxiety. The amygdala also sends inhibitory signals to reproductive centres where previous findings have shown an inhibitory influence of the amygdala on the timing of puberty as well as on pulsatile LH secretion in adults. Stress alters neuronal activity within the posterodorsal medial amygdala (MePD), increasing the expression of Urocortin3 (Ucn3) and its receptor while enhancing the inhibitory output from the MePD to key hypothalamic reproductive centres. In this work we investigate the function of the stress neuronal circuitry within the MePD, which is involved in modulating pubertal timing, pulsatile LH secretion and dynamic corticosterone secretion in the presence of stress in mice. We find a functional role for MePD Ucn3 neurons and efferents to the hypothalamic paraventricular nucleus in modulating the activity of the hypothalamus pituitary gonadal and the hypothalamus pituitary adrenal axes, thus the MePD may act as a central hub integrating anxiogenic cues with the stress and reproductive axis. We also employ mathematical modelling to dissect the involvement of neurokinin 3 receptor signalling within the MePD in mediating stress-induced suppression of pulsatile LH secretion in mice.
Julia Buckingham Award and Michael Harbuz Prize lectures, 11am
Julia Buckingham Award winner: Simon J. Guillot - Hypothalamus-driven sleep alterations in a neurodegenerative disease: Amyotrophic Lateral Sclerosis
ALS is a progressive motor neuron disease inexorably leading to a premature death. Sleep disturbances have been ascribed to respiratory insufficiency, muscle cramps, spasticity, or restless legs syndrome, all leading to increased wakefulness. However, a recent neuropathological study in ALS patients described a loss of orexin-producing neurons, a neuropeptide involved in sleep and metabolic regulation, undermining the idea that sleep alterations are linked to central and peripheral changes. Yet, sleep changes are poorly characterized in ALS, and their relationships to motor symptom onset, disease progression and orexin neurons remain unknown. Here, we used electroencephalography coupled with indirect calorimetry recordings to characterize sleep and energy metabolism in two mouse models of ALS -Superoxide Dismutase 1 G86R (Sod1G86R) and Fused in Sarcoma (FusΔNLS).
In both Sod1G86R and FusΔNLS mice, electroencephalograms showed an increase in wakefulness and a decrease in rapid eye movement (REM) as well as non-rapid eye movement (NREM) episodes before the onset of major motor troubles. We did not observe an altered number of Orexin-positive neurons in the lateral hypothalamus of these mice.
Moreover, Suvorexant®, a drug antagonizing both orexin receptors, induced an increase in REM sleep and a decrease in wake quantities compared to control in both mouse lines. Interestingly, Sod1G86R and FusΔNLS mice displayed an increase in body temperature, energy expenditure and locomotor activity, as well as a lower respiratory quotient that were successfully rescued in both mouse models by the drug.
Sleep analysis in presymptomatic gene carriers and ALS patients matched with healthy controls is ongoing. Hence, preliminary results tend to point at sleep impairments in ALS patients and presymptomatic gene carriers, following our previous results in mice.
Thus, our results show that two mouse models of ALS display sleep and metabolic impairments and provide pharmacological evidence for the involvement of the lateral hypothalamus in these defects.
Michael Harbuz Prize winner: Teodora Georgescu - Suppression of fever, but not sickness behaviours in late pregnancy in mice
Teodora Georgescu1,3, Zin Khant Aung1, David R. Grattan1,2, Rosemary S. E. Brown3
Introduction
Postpartum aggression in females is conserved across many species and enables a mother to guard her young from danger and potential threats. This protective behaviour is typically exhibited by mothers and not virgin females, but it is unknown how hormones act to induce this behaviour after birth of offspring. We have previously identified a population of prolactin sensitive neurones in the hypothalamic ventromedial nucleus (VMN), a region known to direct aggressive behaviours. As prolactin is high during pregnancy and lactation, we hypothesised that prolactin acts in the VMN to regulate maternal aggression.
Results
By using c-fos immunoreactivity in a prolactin receptor (Prlr)-reporter mouse line, we found that VMN Prlr-expressing neurones increased their activity following exposure to a juvenile male intruder. These neurones were predominantly glutamatergic. Next, we used a conditional knockout model to delete Prlr from glutamatergic neurones (Prlrlox/lox/VGlut2-Cre). Surprisingly, in the absence of prolactin signalling in glutamatergic neurones, maternal mice display heightened aggression towards intruders. Lactating Prlrlox/lox/VGlut2-Cre mice showed significantly reduced latencies to attack, increased episodes of attacking and a greater time spent attacking. To specifically knockout Prlr from the VMN, we bilaterally administered an AAV-Cre into the VMN of adult Prlrlox/lox mice. As seen with the vGlut2-knockout mice, these mice showed significantly heightened maternal aggression compared to control mice. To understand how prolactin regulates maternal aggression, we pharmacologically blocked prolactin action during lactation but saw no changes in maternal aggression. Utilising calcium imaging, we similarly found that the majority of the neurones that express the Prlr in the VMN (74.07%) did not respond to prolactin with changes in intracellular calcium. This suggests prolactin is not acutely acting in the VMN to regulate behaviour, but is likely to be acting through a transcriptional pathway to change responsiveness of these neurones to other inputs.
Conclusion
Together, these data demonstrate a novel role for prolactin in aggressive behaviour, with prolactin being important in moderating the level of aggression in a lactating mouse.
1. Department of Anatomy and Centre for Neuroendocrinology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
2. Maurice Wilkins Centre for Molecular Biodiscovery, New Zealand.
3. Department of Physiology and Centre for Neuroendocrinology, School of
Biomedical Sciences, University of Otago, Dunedin, New Zealand.
