Hypothalamus as an endocrine organ

AI-assisted quantification of hypothalamic atrophy in amyotrophic lateral sclerosis by convolutional neural network-based automatic segmentation

The hypothalamus is a small structure of the brain with an essential role in metabolic homeostasis, sleep regulation, and body temperature control. Some neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and dementia syndromes are reported to be related to hypothalamic volume alterations. Despite its crucial role in human body regulation, neuroimaging studies of this structure are rather scarce due to work-intensive operator-dependent manual delineations from MRI and lack of automated segmentation tools. In this study we present a fully automatic approach based on deep convolutional neural networks (CNN) for hypothalamic segmentation and volume quantification. We applied CNN of U-Net architecture with EfficientNetB0 backbone to allow for accurate automatic hypothalamic segmentation in seconds on a GPU. We further applied our approach for the quantification of the normalized hypothalamic volumes to a large neuroimaging dataset of 432 ALS patients and 112 healthy controls (without the ground truth labels). Using the automated volumetric analysis, we could reproduce hypothalamic atrophy findings associated with ALS by detecting significant volume differences between ALS patients and controls at the group level. In conclusion, a fast and unbiased AI-assisted hypothalamic quantification method is introduced in this study (whose acceptance rate based on the outlier removal strategy was estimated to be above 95%) and made publicly available for researchers interested in the conduction of hypothalamus studies at a large scale.

Zika virus infection leads to hormone deficiencies of the hypothalamic-pituitary-gonadal axis and diminished fertility in mice

IMPORTANCE

Zika virus (ZIKV) infection in pregnant women during the third trimester can cause neurodevelopmental delays and cryptorchidism in children without microcephaly. However, the consequences of congenital ZIKV infection on fertility in these children remain unclear. Here, using an immunocompetent mouse model, we reveal that congenital ZIKV infection can cause hormonal disorders of the hypothalamic-pituitary-gonadal axis, leading to reduced fertility and decreased sexual preference. Our study has for the first time linked the hypothalamus to the reproductive system and social behaviors after ZIKV infection. Although the extent to which these observations in mice translate to humans remains unclear, these findings did suggest that the reproductive health and hormone levels of ZIKV-exposed children should receive more attention to improve their living quality.

Development of circadian neurovascular function and its implications

The neurovascular system forms the interface between the tissue of the central nervous system (CNS) and circulating blood. It plays a critical role in regulating movement of ions, small molecules, and cellular regulators into and out of brain tissue and in sustaining brain health. The neurovascular unit (NVU), the cells that form the structural and functional link between cells of the brain and the vasculature, maintains the blood-brain interface (BBI), controls cerebral blood flow, and surveils for injury. The neurovascular system is dynamic; it undergoes tight regulation of biochemical and cellular interactions to balance and support brain function. Development of an intrinsic circadian clock enables the NVU to anticipate rhythmic changes in brain activity and body physiology that occur over the day-night cycle. The development of circadian neurovascular function involves multiple cell types. We address the functional aspects of the circadian clock in the components of the NVU and their effects in regulating neurovascular physiology, including BBI permeability, cerebral blood flow, and inflammation. Disrupting the circadian clock impairs a number of physiological processes associated with the NVU, many of which are correlated with an increased risk of dysfunction and disease. Consequently, understanding the cell biology and physiology of the NVU is critical to diminishing consequences of impaired neurovascular function, including cerebral bleeding and neurodegeneration.

Maternal obesity damages the median eminence blood-brain barrier structure and function in the progeny: the beneficial impact of cross-fostering by lean mothers

Maternal obesity is an important risk factor for obesity, cardiovascular, and metabolic diseases in the offspring. Studies have shown that it leads to hypothalamic inflammation in the progeny, affecting the function of neurons regulating food intake and energy expenditure. In adult mice fed a high-fat diet, one of the hypothalamic abnormalities that contribute to the development of obesity is the damage of the blood-brain barrier (BBB) at the median eminence-arcuate nucleus (ME-ARC) interface; however, how the hypothalamic BBB is affected in the offspring of obese mothers requires further investigation. Here, we used confocal and transmission electron microscopy, transcript expression analysis, glucose tolerance testing, and a cross-fostering intervention to determine the impact of maternal obesity and breastfeeding on BBB integrity at the ME-ARC interface. The offspring of obese mothers were born smaller; conversely, at weaning, they presented larger body mass and glucose intolerance. In addition, maternal obesity-induced structural and functional damage of the offspring's ME-ARC BBB. By a cross-fostering intervention, some of the defects in barrier integrity and metabolism seen during development in an obesogenic diet were recovered. The offspring of obese dams breastfed by lean dams presented a reduction of body mass and glucose intolerance as compared to the offspring continuously exposed to an obesogenic environment during intrauterine and perinatal life; this was accompanied by partial recovery of the anatomical structure of the ME-ARC interface, and by the normalization of transcript expression of genes coding for hypothalamic neurotransmitters involved in energy balance and BBB integrity. Thus, maternal obesity promotes structural and functional damage of the hypothalamic BBB, which is, in part, reverted by lactation by lean mothers.NEW & NOTEWORTHY Maternal dietary habits directly influence offspring health. In this study, we aimed at determining the impact of maternal obesity on BBB integrity. We show that DIO offspring presented a leakier ME-BBB, accompanied by changes in the expression of transcripts encoding for endothelial and tanycytic proteins, as well as of hypothalamic neuropeptides. Breastfeeding in lean dams was sufficient to protect the offspring from ME-BBB disruption, providing a preventive strategy of nutritional intervention during early life.

Involvement of the GABAergic system in PTSD and its therapeutic significance

The neurobiological mechanism of post-traumatic stress disorder (PTSD) is poorly understood. The inhibition of GABA neurons, especially in the amygdala, is crucial for the precise regulation of the consolidation, expression, and extinction of fear conditioning. The GABAergic system is involved in the pathophysiological process of PTSD, with several studies demonstrating that the function of the GABAergic system decreases in PTSD patients. This paper reviews the preclinical and clinical studies, neuroimaging techniques, and pharmacological studies of the GABAergic system in PTSD and summarizes the role of the GABAergic system in PTSD. Understanding the role of the GABAergic system in PTSD and searching for new drug targets will be helpful in the treatment of PTSD.

The Contribution of Cell Imaging to the Study of Anterior Pituitary Function and Its Regulation

Advances in the knowledge of the neuroendocrine system are closely related to the development of cellular imaging and labeling techniques. This synergy ranges from the staining techniques that allowed the first characterizations of the anterior pituitary gland, its relationship with the hypothalamus, and the birth of neuroendocrinology; through the development of fluorescence microscopy applications, specific labeling strategies, transgenic systems, and intracellular calcium sensors that enabled the study of processes and dynamics at the cellular and tissue level; until the advent of super-resolution microscopy, miniscopes, optogenetics, fiber photometry, and other imaging methods that allowed high spatiotemporal resolution and long-term three-dimensional cellular activity recordings in living systems in a conscious and freely moving condition. In this review, we briefly summarize the main contributions of cellular imaging techniques that have allowed relevant advances in the field of neuroendocrinology and paradigm shifts that have improved our understanding of the function of the hypothalamic-pituitary axes. The development of these methods and equipment is the result of the integration of knowledge achieved by the integration of several disciplines and effort to solve scientific questions and problems of high impact on health and society that this system entails.

Research progress on the role of hormones in ischemic stroke

Ischemic stroke is a major cause of death and disability around the world. However, ischemic stroke treatment is currently limited, with a narrow therapeutic window and unsatisfactory post-treatment outcomes. Therefore, it is critical to investigate the pathophysiological mechanisms following ischemic stroke brain injury. Changes in the immunometabolism and endocrine system after ischemic stroke are important in understanding the pathophysiological mechanisms of cerebral ischemic injury. Hormones are biologically active substances produced by endocrine glands or endocrine cells that play an important role in the organism's growth, development, metabolism, reproduction, and aging. Hormone research in ischemic stroke has made very promising progress. Hormone levels fluctuate during an ischemic stroke. Hormones regulate neuronal plasticity, promote neurotrophic factor formation, reduce cell death, apoptosis, inflammation, excitotoxicity, oxidative and nitrative stress, and brain edema in ischemic stroke. In recent years, many studies have been done on the role of thyroid hormone, growth hormone, testosterone, prolactin, oxytocin, glucocorticoid, parathyroid hormone, and dopamine in ischemic stroke, but comprehensive reviews are scarce. This review focuses on the role of hormones in the pathophysiology of ischemic stroke and discusses the mechanisms involved, intending to provide a reference value for ischemic stroke treatment and prevention.

The Impact of Intermittent Hypoxia on Metabolism and Cognition

Intermittent hypoxia (IH), one of the primary pathologies of sleep apnea syndrome (SAS), exposes cells throughout the body to repeated cycles of hypoxia/normoxia that result in oxidative stress and systemic inflammation. Since SAS is epidemiologically strongly correlated with type 2 diabetes/insulin resistance, obesity, hypertension, and dyslipidemia included in metabolic syndrome, the effects of IH on gene expression in the corresponding cells of each organ have been studied intensively to clarify the molecular mechanism of the association between SAS and metabolic syndrome. Dementia has recently been recognized as a serious health problem due to its increasing incidence, and a large body of evidence has shown its strong correlation with SAS and metabolic disorders. In this narrative review, we first outline the effects of IH on the expression of genes related to metabolism in neuronal cells, pancreatic β cells, hepatocytes, adipocytes, myocytes, and renal cells (mainly based on the results of our experiments). Next, we discuss the literature regarding the mechanisms by which metabolic disorders and IH develop dementia to understand how IH directly and indirectly leads to the development of dementia.

Kisspeptin Modulation of Reproductive Function

Kisspeptin is a peptide expressed mainly in the infundibular nucleus of the hypothalamus. Kisspeptin plays a crucial role in the regulation of reproductive functions. It is regarded as the most important factor responsible for the control of the hypothalamic–pituitary–gonadal axis, the onset of puberty, and the regulation of menstruation and fertility. Kisspeptin activity influences numerous processes such as steroidogenesis, follicular maturation, ovulation, and ovarian senescence. The identification of kisspeptin receptor mutations that cause hypogonadotropic hypogonadism has initiated studies on the role of kisspeptin in puberty. Pathologies affecting the neurons secreting kisspeptin play a major role in the development of PCOS, functional hypothalamic amenorrhea, and perimenopausal vasomotor symptoms. Kisspeptin analogs (both agonists and antagonists), therefore, may be beneficial as therapy in those afflicted with such pathologies. The aim of this review is to summarize the influence of kisspeptin in the physiology and pathology of the reproductive system in humans, as well as its potential use in therapy.

Integrative Hedonic and Homeostatic Food Intake Regulation by the Central Nervous System: Insights from Neuroimaging

Food intake regulation in humans is a complex process controlled by the dynamic interaction of homeostatic and hedonic systems. Homeostatic regulation is controlled by appetitive signals from the gut, adipose tissue, and the vagus nerve, while conscious and unconscious reward processes orchestrate hedonic regulation. On the one hand, sight, smell, taste, and texture perception deliver potent food-related feedback to the central nervous system (CNS) and influence brain areas related to food reward. On the other hand, macronutrient composition stimulates the release of appetite signals from the gut, which are translated in the CNS into unconscious reward processes. This multi-level regulation process of food intake shapes and regulates human ingestive behavior. Identifying the interface between hormones, neurotransmitters, and brain areas is critical to advance our understanding of conditions like obesity and develop better therapeutical interventions. Neuroimaging studies allow us to take a glance into the central nervous system (CNS) while these processes take place. This review focuses on the available neuroimaging evidence to describe this interaction between the homeostatic and hedonic components in human food intake regulation.

Anorexigenic Effects of Intermittent Hypoxia on the Gut-Brain Axis in Sleep Apnea Syndrome

Sleep apnea syndrome (SAS) is a breathing disorder characterized by recurrent episodes of upper-airway collapse, resulting in intermittent hypoxia (IH) during sleep. Experimental studies with animals and cellular models have indicated that IH leads to attenuation of glucose-induced insulin secretion from pancreatic β cells and to enhancement of insulin resistance in peripheral tissues and cells, such as the liver (hepatocytes), adipose tissue (adipocytes), and skeletal muscles (myocytes), both of which could lead to obesity. Although obesity is widely recognized as a major factor in SAS, it is controversial whether the development of SAS could contribute directly to obesity, and the effect of IH on the expression of appetite regulatory genes remains elusive. Appetite is regulated appropriately by both the hypothalamus and the gut as a gut-brain axis driven by differential neural and hormonal signals. In this review, we summarized the recent epidemiological findings on the relationship between SAS and feeding behavior and focused on the anorexigenic effects of IH on the gut-brain axis by the IH-induced up-regulation of proopiomelanocortin and cocaine- and amphetamine-regulated transcript in neuronal cells and the IH-induced up-regulation of peptide YY, glucagon-like peptide-1 and neurotensin in enteroendocrine cells and their molecular mechanisms.

Brain Imaging of the GLP-1 Receptor in Obesity Using 68Ga-NODAGA-Exendin-4 PET

Stimulation of glucagon-like peptide-1 (GLP-1) receptors increases the insulin release in the pancreas during high glucose levels, and also stimulates a feeling of satiety. Likewise, synthetic GLP-1 receptor agonists derived from exendin are used successfully in the treatment of type-2 diabetes mellitus and obesity. Interestingly, preclinical and clinical studies further suggest that GLP-1 receptor agonists may decrease motor, behavioral, and cognitive symptoms in (animal models) Parkinson’s disease and Alzheimer’s disease and may slow down neurodegeneration. These observations suggest stimulation of GLP-1 receptors in the brain. The GLP-1 positron emission tomography (PET) tracer ⁶⁸Ga-NODAGA-exendin-4 has been developed and successfully used for imaging in humans. In an ongoing study on the effects of bariatric surgery on GLP-1 receptor expression, we performed ⁶⁸Ga-NODAGA-exendin-4 PET in obese subjects. Here we evaluated whether GLP-1 receptor binding could be visualized in the central nervous system in 10 obese subjects (seven woman; body mass index: mean ± SD: 39 ± 4.4 kg/m²) before bariatric surgery. Although we observed clear uptake in the pituitary area (mean SUV_max 4.3 ± 2.3), we found no significant uptake in other parts of the brain. We conclude that ⁶⁸Ga-NODAGA-exendin-4 PET cannot be used to analyze GLP-1 receptors in the brain of obese subjects.

Hormonal Regulation of Oxidative Phosphorylation in the Brain in Health and Disease

The developing and adult brain is a target organ for the vast majority of hormones produced by the body, which are able to cross the blood–brain barrier and bind to their specific receptors on neurons and glial cells. Hormones ensure proper communication between the brain and the body by activating adaptive mechanisms necessary to withstand and react to changes in internal and external conditions by regulating neuronal and synaptic plasticity, neurogenesis and metabolic activity of the brain. The influence of hormones on energy metabolism and mitochondrial function in the brain has gained much attention since mitochondrial dysfunctions are observed in many different pathological conditions of the central nervous system. Moreover, excess or deficiency of hormones is associated with cell damage and loss of function in mitochondria. This review aims to expound on the impact of hormones (GLP-1, insulin, thyroid hormones, glucocorticoids) on metabolic processes in the brain with special emphasis on oxidative phosphorylation dysregulation, which may contribute to the formation of pathological changes. Since the brain concentrations of sex hormones and neurosteroids decrease with age as well as in neurodegenerative diseases, in parallel with the occurrence of mitochondrial dysfunction and the weakening of cognitive functions, their beneficial effects on oxidative phosphorylation and expression of antioxidant enzymes are also discussed.

Neural Circuits of Interoception

The present paper considers recent progress in our understanding of the afferent/ascending neural pathways and neural circuits of interoception. Of particular note is the extensive role of rostral neural systems, including cortical systems, in the recognition of internal body states, and the reciprocal role of efferent/descending systems in the regulation of those states. Together these reciprocal interacting networks entail interoceptive circuits that play an important role in a broad range of functions beyond the homeostatic maintenance of physiological steady-states. These include the regulation of behavioral, cognitive, and affective processes across conscious and nonconscious levels of processing. We highlight recent advances and knowledge gaps that are important for accelerating progress in the study of interoception.

Seasonal Regulation of Metabolism: The Effect of Wintertime Fasting and Autumnal Fattening on Key Central Regulators of Metabolism and the Metabolic Profile of the Raccoon Dog (Nyctereutes Procyonoides)

Investigations into the mechanisms regulating obesity are frantic and novel translational approaches are needed. The raccoon dog (Nyctereutes procyonoides) is a canid species representing a promising model to study metabolic regulation in a species undergoing cycles of seasonal obesity and fasting. To understand the molecular mechanisms of metabolic regulation in seasonal adaptation, we analyzed key central nervous system and peripheral signals regulating food intake and metabolism from raccoon dogs after autumnal fattening and winter fasting. Expressions of neuropeptide Y (NPY), orexin-2 receptor (OX2R), pro-opiomelanocortin (POMC) and leptin receptor (ObRb) were analyzed as examples of orexigenic and anorexigenic signals using qRT-PCR from raccoon dog hypothalamus samples. Plasma metabolic profiles were measured with ¹H NMR-spectroscopy and LC-MS. Circulating hormones and cytokines were determined with canine specific antibody assays. Surprisingly, NPY and POMC were not affected by the winter fasting nor autumn fattening and the metabolic profiles showed a remarkable equilibrium, indicating conserved homeostasis. However, OX2R and ObRb expression changes suggested seasonal regulation. Circulating cytokine levels were not increased, demonstrating that the autumn fattening did not induce subacute inflammation. Thus, the raccoon dog developed seasonal regulatory mechanisms to accommodate the autumnal fattening and prolonged fasting making the species unique in coping with the extreme environmental challenges.

Neuroendocrine control of appetite and metabolism

Body homeostasis is predominantly controlled by hormones secreted by endocrine organs. The central nervous system contains several important endocrine structures, including the hypothalamic-pituitary axis. Conventionally, neurohormones released by the hypothalamus and the pituitary gland (hypophysis) have received much attention owing to the unique functions of the end hormones released by their target peripheral organs (e.g., glucocorticoids released by the adrenal glands). Recent advances in mouse genetics have revealed several important metabolic functions of hypothalamic neurohormone-expressing cells, many of which are not readily explained by the action of the corresponding classical downstream hormones. Notably, the newly identified functions are better explained by the action of conventional neurotransmitters (e.g., glutamate and GABA) that constitute a neuronal circuit. In this review, we discuss the regulation of appetite and metabolism by hypothalamic neurohormone-expressing cells, with a focus on the distinct contributions of neurohormones and neurotransmitters released by these neurons.

Expression of genes for Kisspeptin (KISS1), Neurokinin B (TAC3), Prodynorphin (PDYN), and gonadotropin inhibitory hormone (RFRP) across natural puberty in ewes

Expression of particular genes in hypothami of ewes was measured across the natural pubertal transition by in situ hybridization. The ewes were allocated to three groups (n = 4); prepubertal, postpubertal and postpubertally gonadectomized (GDX). Prepubertal sheep were euthanized at 20 weeks of age and postpubertal animals at 32 weeks. GDX sheep were also euthanized at 32 weeks, 1 week after surgery. Expression of KISS1, TAC3, PDYN in the arcuate nucleus (ARC), RFRP in the dorsomedial hypothalamus and GNRH1 in the preoptic area was quantified on a cellular basis. KISS1R expression by GNRH1 cells was quantified by double-label in situ hybridization. Across puberty, detectable KISS1 cell number increased in the caudal ARC and whilst PDYN cell numbers were low, numbers increased in the rostral ARC. TAC3 expression did not change but RFRP expression/cell was reduced across puberty. There was no change across puberty in the number of GNRH1 cells that expressed the kisspeptin receptor (KISS1R). GDX shortly after puberty did not increase expression of any of the genes of interest. We conclude that KISS1 expression in the ARC increases during puberty in ewes and this may be a causative factor in the pubertal activation of the reproductive axis. A reduction in expression of RFRP may be a factor in the onset of puberty, removing negative tone on GNRH1 cells. The lack of changes in expression of genes following GDX suggest that the effects of gonadal hormones may differ in young and mature animals.

Endocrine-disrupting activity of mancozeb

The objective of the present study was to review the existing data on the mechanisms involved in the endocrine disrupting activity of mancozeb (MCZ) in its main targets, including thyroid and gonads, as well as other endocrine tissues that may be potentially affected by MCZ. MCZ exposure was shown to interfere with thyroid functioning through impairment of thyroid hormone synthesis due to inhibition of sodium-iodine symporter (NIS) and thyroid peroxidase (TPO) activity, as well as thyroglobulin expression. Direct thyrotoxic effect may also contribute to thyroid pathology upon MCZ exposure. Gonadal effects of MCZ involve inhibition of sex steroid synthesis due to inhibition of P450scc (CYP11A1), as well as 3β-HSD and 17β-HSD. In parallel with altered hormone synthesis, MCZ was shown to down-regulate androgen and estrogen receptor signaling. Taken together, these gonad-specific effects result in development of both male and female reproductive dysfunction. In parallel with clearly estimated targets for MCZ endocrine disturbing activity, namely thyroid and gonads, other endocrine tissues may be also involved. Specifically, the fungicide was shown to affect cortisol synthesis that may be mediated by modulation of CYP11B1 activity. Moreover, MCZ exposure was shown to interfere with PPARγ signaling, being a key regulator of adipogenesis. The existing data also propose that endocrine-disrupting effects of MCZ exposure may be mediated by modulation of hypothalamus-pituitary-target axis. It is proposed that MCZ neurotoxicity may at least partially affect central mechanisms of endocrine system functioning. However, further studies are required to unravel the mechanisms of MCZ endocrine disrupting activity and overall toxicity.

Automated segmentation of the hypothalamus and associated subunits in brain MRI

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A publicly available deep learning tool to segment the hypothalamus and its subunits.

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Our tool outperforms inter-rater accuracy and approaches intra-rater precision level.

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It can robustly generalise to unseen heterogeneous datasets.

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It yields a rejection rate of less than 1% in a QC analysis performed on 675 scans.

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It detects subtle subunit-specific hypothalamic atrophy in Alzheimer’s Disease.

Despite the crucial role of the hypothalamus in the regulation of the human body, neuroimaging studies of this structure and its nuclei are scarce. Such scarcity partially stems from the lack of automated segmentation tools, since manual delineation suffers from scalability and reproducibility issues. Due to the small size of the hypothalamus and the lack of image contrast in its vicinity, automated segmentation is difficult and has been long neglected by widespread neuroimaging packages like FreeSurfer or FSL. Nonetheless, recent advances in deep machine learning are enabling us to tackle difficult segmentation problems with high accuracy. In this paper we present a fully automated tool based on a deep convolutional neural network, for the segmentation of the whole hypothalamus and its subregions from T1-weighted MRI scans. We use aggressive data augmentation in order to make the model robust to T1-weighted MR scans from a wide array of different sources, without any need for preprocessing. We rigorously assess the performance of the presented tool through extensive analyses, including: inter- and intra-rater variability experiments between human observers; comparison of our tool with manual segmentation; comparison with an automated method based on multi-atlas segmentation; assessment of robustness by quality control analysis of a larger, heterogeneous dataset (ADNI); and indirect evaluation with a volumetric study performed on ADNI. The presented model outperforms multi-atlas segmentation scores as well as inter-rater accuracy level, and approaches intra-rater precision. Our method does not require any preprocessing and runs in less than a second on a GPU, and approximately 10 seconds on a CPU. The source code as well as the trained model are publicly available at https://github.com/BBillot/hypothalamus_seg, and will also be distributed with FreeSurfer.

Understanding the trade-off between the environment and fertility in cows and ewes

The environment contributes to production diseases that in turn badly affect cow performance, fertility and culling. Oestrus intensity is lower in lame cows, and in all cows 26% potential oestrus events are not expressed (to avoid getting pregnant). To understand these trade-offs, we need to know how animals react to their environment and how the environment influences hypothalamus-pituitary-adrenal axis (HPA) interactions with the hypothalamus-pituitary-ovarian axis (HPO). Neurotransmitters control secretion of GnRH into hypophyseal portal blood. GnRH/LH pulse amplitude and frequency drive oestradiol production, culminating in oestrus behaviour and a precisely-timed GnRH/LH surge, all of which are disrupted by poor environments. Responses to peripheral neuronal agents give clues about mechanisms, but do these drugs alter perception of stimuli, or suppress consequent responses? In vitro studies confirm some neuronal interactions between the HPA and HPO; and immuno-histochemistry clarifies the location and sequence of inter-neurone activity within the brain. In both species, exogenous corticoids, ACTH and/or CRH act at the pituitary (reduce LH release by GnRH), and hypothalamus (lower GnRH pulse frequency and delay surge release). This requires inter-neurones as GnRH cells do not have receptors for HPA compounds. There are two (simultaneous, therefore fail-safe?) pathways for CRH suppression of GnRH release via CRH-Receptors: one being the regulation of kisspeptin/dynorphin and other cell types in the hypothalamus, and the other being the direct contact between CRH and GnRH cell terminals in the median eminence. When we domesticate animals, we must provide the best possible environment otherwise animals trade-off with lower production, less intense oestrus behaviour, and impaired fertility. Avoiding life-time peri-parturient problems by managing persistent lactations in cows may be a worthy trade-off on both welfare and economic terms – better than the camouflage use of drugs/hormones/feed additives/intricate technologies? In the long term, getting animals and environment in a more harmonious balance is the ultimate strategy.

A Special Cranial Nucleus (CSF-Contacting Nucleus) in Primates

BACKGROUND

There is a unique nucleus (CSF-contacting nucleus) in the brain of rat. It has been demonstrated in our previous research. The extraordinary feature of this nucleus is that it is not connected to any parenchymal organ but to the CSF. In primates, however, the presence or absence of this nucleus has not been proven. Confirmation of the presence of this nucleus in primates will provide the structural basis for brain-CSF communication and help to understand the neurohumoral regulatory mechanisms in humans.

METHODS

The tracer cholera toxin B subunit conjugated to horseradish peroxidase (CB-HRP) was injected into the CSF in the lateral ventricle (LV) of primate rhesus monkeys. After 48 h, the monkeys were perfused and the brain was dissected out, and sectioned for CB-HRP staining. The CB-HRP positive structures were observed under confocal and electron microscopy. The three-dimensional (3D) structure of the CB-HRP positive neurons cluster was reconstructed by computer software.

RESULTS

(1) CB-HRP labeling is confined within the ventricle, but not leakage into the brain parenchyma. (2) From the midbrain inferior colliculus superior border plane ventral to the aqueduct to the upper part of the fourth ventricle (4V) floor, a large number of CB-HRP positive neurons are consistently located, form a cluster, and are symmetrically located on both sides of the midline. (3) 3D reconstruction shows that the CB-HRP positive neurons cluster in the monkey brain occupies certain space. The rostral part is large and caudal part is thin appearing a "rivet"-like shape. (4) Under electron microscopy, the CB-HRP positive neurons show different types of synaptic connections with the non-CSF-contacting structures in the brain. Some of the processes stretch directly into the ventricle cavity.

CONCLUSION

Same as we did in rats, the CSF-contacting nucleus is also existed in the primate brain parenchyma. We also recommend listing it as the XIII pair of cranial nucleus, which is specialized in the communications between the brain and the CSF. It is significant to the completing of innervation in the organism.

MCH Neurons Regulate Permeability of the Median Eminence Barrier

Melanin-concentrating hormone (MCH)-expressing neurons are key regulators of energy and glucose homeostasis. Here, we demonstrate that they provide dense projections to the median eminence (ME) in close proximity to tanycytes and fenestrated vessels. Chemogenetic activation of MCH neurons as well as optogenetic stimulation of their projections in the ME enhance permeability of the ME by increasing fenestrated vascular loops and enhance leptin action in the arcuate nucleus of the hypothalamus (ARC). Unbiased phosphoRiboTrap-based assessment of cell activation upon chemogenetic MCH neuron activation reveals MCH-neuron-dependent regulation of endothelial cells. MCH neurons express the vascular endothelial growth factor A (VEGFA), and blocking VEGF-R signaling attenuates the leptin-sensitizing effect of MCH neuron activation. Our experiments reveal that MCH neurons directly regulate permeability of the ME barrier, linking the activity of energy state and sleep regulatory neurons to the regulation of hormone accessibility to the ARC.

MCH neurons provide dense projections to the median eminence

MCH neuron activation promotes permeability of the median eminence barrier

MCH neuron activation enhances microvessel fenestration in the ME

MCH neuron activation enhances leptin action in the arcuate nucleus

Peripheral and central compensatory mechanisms for impaired vagus nerve function during peripheral immune activation

BACKGROUND

Determining the etiology and possible treatment strategies for numerous diseases requires a comprehensive understanding of compensatory mechanisms in physiological systems. The vagus nerve acts as a key interface between the brain and the peripheral internal organs. We set out to identify mechanisms compensating for a lack of neuronal communication between the immune and the central nervous system (CNS) during infection.

METHODS

We assessed biochemical and central neurotransmitter changes resulting from subdiaphragmatic vagotomy and whether they are modulated by intraperitoneal infection. We performed a series of subdiaphragmatic vagotomy or sham operations on male Wistar rats. Next, after full, 30-day recovery period, they were randomly assigned to receive an injection of Escherichia coli lipopolysaccharide or saline. Two hours later, animal were euthanized and we measured the plasma concentration of prostaglandin E2 (with HPLC-MS), interleukin-6 (ELISA), and corticosterone (RIA). We also had measured the concentration of monoaminergic neurotransmitters and their metabolites in the amygdala, brainstem, hippocampus, hypothalamus, motor cortex, periaqueductal gray, and prefrontal medial cortex using RP-HPLC-ED. A subset of the animals was evaluated in the elevated plus maze test immediately before euthanization.

RESULTS

The lack of immunosensory signaling of the vagus nerve stimulated increased activity of discrete inflammatory marker signals, which we confirmed by quantifying biochemical changes in blood plasma. Behavioral results, although preliminary, support the observed biochemical alterations. Many of the neurotransmitter changes observed after vagotomy indicated that the vagus nerve influences the activity of many brain areas involved in control of immune response and sickness behavior. Our studies show that these changes are largely eliminated during experimental infection.

CONCLUSIONS

Our results suggest that in vagotomized animals with blocked CNS, communication may transmit via a pathway independent of the vagus nerve to permit restoration of CNS activity for peripheral inflammation control.

The homotopic connectivity of the functional brain: a meta-analytic approach

Homotopic connectivity (HC) is the connectivity between mirror areas of the brain hemispheres. It can exhibit a marked and functionally relevant spatial variability, and can be perturbed by several pathological conditions. The voxel-mirrored homotopic connectivity (VMHC) is a technique devised to enquire this pattern of brain organization, based on resting state functional connectivity. Since functional connectivity can be revealed also in a meta-analytical fashion using co-activations, here we propose to calculate the meta-analytic homotopic connectivity (MHC) as the meta-analytic counterpart of the VMHC. The comparison between the two techniques reveals their general similarity, but also highlights regional differences associated with how HC varies from task to rest. Two main differences were found from rest to task: (i) regions known to be characterized by global hubness are more similar than regions displaying local hubness; and (ii) medial areas are characterized by a higher degree of homotopic connectivity, while lateral areas appear to decrease their degree of homotopic connectivity during task performance. These findings show that MHC can be an insightful tool to study how the hemispheres functionally interact during task and rest conditions.

Fluorescent blood-brain barrier tracing shows intact leptin transport in obese mice

Background/objectives

Individuals carrying loss-of-function gene mutations for the adipocyte hormone leptin are morbidly obese, but respond favorably to replacement therapy. Recombinant leptin is however largely ineffective for the vast majority of obese individuals due to leptin resistance. One theory underlying leptin resistance is impaired leptin transport across the blood–brain-barrier (BBB). Here, we aim to gain new insights into the mechanisms of leptin BBB transport, and its role in leptin resistance.

Methods

We developed a novel tool for visualizing leptin transport using infrared fluorescently labeled leptin, combined with tissue clearing and light-sheet fluorescence microscopy. We corroborated these data using western blotting.

Results

Using 3D whole brain imaging, we display comparable leptin accumulation in circumventricular organs of lean and obese mice, predominantly in the choroid plexus (CP). Protein quantification revealed comparable leptin levels in microdissected mediobasal hypothalami (MBH) of lean and obese mice (p = 0.99). We further found increased leptin receptor expression in the CP (p = 0.025, p = 0.0002) and a trend toward elevated leptin protein levels in the MBH (p = 0.17, p = 0.078) of obese mice undergoing weight loss interventions by calorie restriction or exendin-4 treatment.

Conclusions

Overall, our findings suggest a crucial role for the CP in controlling the transport of leptin into the cerebrospinal fluid and from there to target areas such as the MBH, potentially mediated via the leptin receptor. Similar leptin levels in circumventricular organs and the MBH of lean and obese mice further suggest intact leptin BBB transport in leptin resistant mice.

The origins of the circumventricular organs

The circumventricular organs (CVOs) are specialised neuroepithelial structures found in the midline of the brain, grouped around the third and fourth ventricles. They mediate the communication between the brain and the periphery by performing sensory and secretory roles, facilitated by increased vascularisation and the absence of a blood-brain barrier. Surprisingly little is known about the origins of the CVOs (both developmental and evolutionary), but their functional and organisational similarities raise the question of the extent of their relationship. Here, I review our current knowledge of the embryonic development of the seven major CVOs (area postrema, median eminence, neurohypophysis, organum vasculosum of the lamina terminalis, pineal organ, subcommissural organ, subfornical organ) in embryos of different vertebrate species. Although there are conspicuous similarities between subsets of CVOs, no unifying feature characteristic of their development has been identified. Cross-species comparisons suggest that CVOs also display a high degree of evolutionary flexibility. Thus, the term 'CVO' is merely a functional definition, and features shared by multiple CVOs may be the result of homoplasy rather than ontogenetic or phylogenetic relationships.