The human hypothalamus in metabolic and episodic disorders

Hypothalamic volume and asymmetry in the pediatric population: a retrospective MRI study

This study investigated age- and sex-related changes in the volumetric development and asymmetry of the normal hypothalamus from birth to 18. Individuals aged 0-18 with MRI from 2012 to 2020 were selected for this retrospective study. Seven hundred individuals (369 [52.7%] Males) who had 3D-T1 sequences and were radiologically normal were included in the study. Hypothalamus volume was calculated using MRICloud automated segmentation pipelines. Hypothalamus asymmetry was calculated as the difference between right and left volumes divided by the mean (in percent). The measurement results of 23 age groups were analyzed with SPSS (ver.23). The mean hypothalamic volume in the first year of life reached 69% of the mean hypothalamic volume between 0 and 18 years (1119.01 ± 196.09 mm³), 88% in the second year. The mean volume of the hypothalamus without mammillary body increased in the five-age segment, while it increased in the six-age segment with mammillary body. Although the hypothalamus volumes of males were larger than females in all age groups, a significant difference was found between the age groups of 3-8 and 12-18 years (p < 0.05). In the pediatric brain, the hypothalamus was right-lateralized between 2.39% and 14.02%. The first 2 years of life were critical in the volumetric development of the hypothalamus. A segmental and logarithmic increase in the hypothalamus volume was demonstrated. In the pediatric brain, asymmetry and sexual dimorphism were detected in the hypothalamus. Information on normal hypothalamus structure and development facilitates the recognition of abnormal developmental trajectories.

Hypothalamus and neuroendocrine diseases: The use of human-induced pluripotent stem cells for disease modeling

The hypothalamus, which is part of the brain of all vertebrate animals, is considered the link between the central nervous system (CNS) and (i) the endocrine system via the pituitary gland and (ii) with our organs via the autonomic nervous system. It synthesizes and releases neurohormones, which in turn stimulate or inhibit the secretion of other hormones within the CNS, and sends and receives signals to and from the peripheral nervous and endocrine systems. As the brain region responsible for energy homeostasis, the hypothalamus is the key regulator of thermoregulation, hunger and satiety, circadian rhythms, sleep and fatigue, memory and learning, arousal and reproductive cycling, blood pressure, and heart rate and thus orchestrates complex physiological responses in order to maintain metabolic homeostasis. These critical roles implicate the hypothalamus in neuroendocrine disorders such as obesity, diabetes, anorexia nervosa, bulimia, and others. In this chapter, we focus on the use of human-induced pluripotent stem cells (hiPSCs) and their differentiation into hypothalamic neurons in order to model neuroendocrine disorders such as extreme obesity in a dish. To do so, we discuss important steps of human hypothalamus development, neuroendocrine diseases related to the hypothalamus, multiple protocols to differentiate hiPSCs into hypothalamic neurons, and severe obesity modeling in vitro using hiPSCs-derived hypothalamic neurons.

Neurogenesis in the adult hypothalamus: A distinct form of structural plasticity involved in metabolic and circadian regulation, with potential relevance for human pathophysiology

The adult brain harbors specific niches where stem cells undergo substantial plasticity and, in some regions, generate new neurons throughout life. This phenomenon is well known in the subventricular zone of the lateral ventricles and the subgranular zone of the hippocampus and has recently also been described in the hypothalamus of several rodent and primate species. After a brief overview of preclinical studies illustrating the pathophysiologic significance of hypothalamic neurogenesis in the control of energy metabolism, reproduction, thermoregulation, sleep, and aging, we review current literature on the neurogenic niche of the human hypothalamus. A comparison of the organization of the niche between humans and rodents highlights some common features, but also substantial differences, e.g., in the distribution and extent of the hypothalamic neural stem cells. Exploring the full dynamics of hypothalamic neurogenesis in humans raises a formidable challenge however, given among others, inherent technical limitations. We close with discussing possible functional role(s) of the human hypothalamic niche, and how gaining more insights into this form of plasticity could be relevant for a better understanding of pathologies associated with disturbed hypothalamic function.

Generation of neuropeptidergic hypothalamic neurons from human pluripotent stem cells

Hypothalamic neurons orchestrate many essential physiological and behavioral processes via secreted neuropeptides, and are relevant to human diseases such as obesity, narcolepsy and infertility. We report the differentiation of human pluripotent stem cells into many of the major types of neuropeptidergic hypothalamic neurons, including those producing pro-opiolemelanocortin, agouti-related peptide, hypocretin/orexin, melanin-concentrating hormone, oxytocin, arginine vasopressin, corticotropin-releasing hormone (CRH) or thyrotropin-releasing hormone. Hypothalamic neurons can be generated using a 'self-patterning' strategy that yields a broad array of cell types, or via a more reproducible directed differentiation approach. Stem cell-derived human hypothalamic neurons share characteristic morphological properties and gene expression patterns with their counterparts in vivo, and are able to integrate into the mouse brain. These neurons could form the basis of cellular models, chemical screens or cellular therapies to study and treat common human diseases.

Interleukin-6 receptor α is co-localised with melanin-concentrating hormone in human and mouse hypothalamus

Interleukin (IL)-6 deficient mice develop mature-onset obesity. Furthermore, i.c.v. administration of IL-6 increases energy expenditure, suggesting that IL-6 centrally regulates energy homeostasis. To investigate whether it would be possible for IL-6 to directly influence the energy homeostasis via hypothalamic regulation in humans and rodents, we mapped the distribution of the ligand binding IL-6 receptor α (IL-6Rα) in this brain region. In the human hypothalamus, IL-6Rα-immunoreactivity was detected in perikarya and first-order dendrites of neurones. The IL-6Rα-immunoreactive (-IR) neurones were observed posterior to the level of the interventricular foramen. There, IL-6Rα-IR neurones were located in the lateral hypothalamic, perifornical, dorsal and posterior hypothalamic areas, the hypothalamic dorsomedial nucleus and in the zona incerta. In the caudal part of the hypothalamus, the density of the IL-6Rα-IR neurones gradually increased. Double-labelling immunofluorescent studies demonstrated that IL-6Rα immunoreactivity was localised in the same neurones as the orexigenic neuropeptide, melanin-concentrating hormone (MCH). By contrast, IL-6Rα-immunoreactivity was not observed in the orexin B-IR neurones. To determine whether the observed expression of IL-6Rα is evolutionary conserved, we studied the co-localisation of IL-6Rα with MCH and orexin in the mouse hypothalamus, where IL-6Rα-immunoreactivity was present in numerous MCH-IR and orexin-IR neurones. Our data demonstrate that the MCH neurones of the human hypothalamus, as well as the MCH and orexin neurones of the mouse hypothalamus, contain IL-6Rα. This opens up the possibility that IL-6 influences the energy balance through the MCH neurones in humans, and both MCH and orexin neurones in mice.

MRI atlas of the human hypothalamus

Gaining new insights into the anatomy of the human hypothalamus is crucial for the development of new treatment strategies involving functional stereotactic neurosurgery. Here, using anatomical comparisons between histology and magnetic resonance images of the human hypothalamus in the coronal plane, we show that discrete gray and white hypothalamic structures are consistently identifiable by MRI. Macroscopic and microscopic images were used to precisely annotate the MRI sequences realized in the coronal plane in twenty healthy volunteers. MRI was performed on a 1.5 T scanner, using a protocol including T1-weighted 3D fast field echo, T1-weighted inversion-recovery, turbo spin echo and T2-weighted 2D fast field echo imaging. For each gray matter structure as well as for white matter bundles, the different MRI sequences were analyzed in comparison to each other. The anterior commissure and the fornix were often identifiable, while the mammillothalamic tract was more difficult to spot. Qualitative analyses showed that MRI could also highlight finer structures such as the paraventricular nucleus, the ventromedial nucleus of the hypothalamus and the infundibular (arcuate) nucleus, brain nuclei that play key roles in the regulation of food intake and energy homeostasis. The posterior hypothalamic area, a target for deep brain stimulation in the treatment of cluster headaches, was readily identified, as was the lateral hypothalamic area, which similar to the aforementioned hypothalamic nuclei, could be a putative target for deep brain stimulation in the treatment of obesity. Finally, each of the identified structures was mapped to Montreal Neurological Institute (MNI) space.

Hypothalamic involvement assessed by T1 relaxation time in patients with relapsing—remitting multiple sclerosis

Recent work in multiple sclerosis, focusing on neuropathological abnormalities, found a frequent and severe hypothalamic involvement. The possible clinical implications are disturbances in sleep and sexual activity, depression, memory impairment and fatigue. Despite this there are no magnetic resonance imaging studies focusing on in vivo hypothalamic pathology in multiple sclerosis. Our objective was to investigate magnetic resonance imaging-detectable abnormalities related to pathological changes in the hypothalamus of patients with multiple sclerosis, and to subsequently explore the relationship with fatigue. We used T1 relaxation time as a sensitive measure of pathology. Using region of interest analysis, median T1 values in the hypothalamus were measured in 44 relapsing—remitting multiple sclerosis patients and in 13 healthy controls. Fatigue was assessed using the Fatigue Severity Scale, and patients were divided in two subgroups, fatigued and non-fatigued, according to Fatigue Severity Scale scores. We found a significantly higher T1 relaxation time in the hypothalamus of multiple sclerosis patients compared with controls ( p = 0.027). There was a significant correlation between T1 values and fatigue severity (rho 0.437, p = 0.008), and median T1 values were different among the study groups. Our results show that pathological involvement of the hypothalamus in relapsing—remitting multiple sclerosis is detectable using magnetic resonance imaging, and that the pathology measured by quantitative T1 might reflect fatigue.

Kleine-Levin syndrome: a systematic study of 108 patients

OBJECTIVE

Kleine-Levin syndrome is a rare disorder characterized by relapsing-remitting episodes of hypersomnia, cognitive disturbances, and behavioral disturbances, such as hyperphagia and hypersexuality.

METHODS

We collected detailed clinical data and blood samples on 108 patients, 79 parent pairs, and 108 matched control subjects. We measured biological markers and typed human leukocyte antigen genes DR and DQ.

RESULTS

Novel predisposing factors were identified including increased birth and developmental problems (odds ratio, 6.5). Jewish heritage was overrepresented, and five multiplex families were identified. Human leukocyte antigen typing was unremarkable. Patients were 78% male (mean age at onset, 15.7 +/- 6.0 years), averaged 19 episodes of 13 days, and were incapacitated 8 months over 14 years. The disease course was longer in men, in patients with hypersexuality, and when onset was after age 20. During episodes, all patients had hypersomnia, cognitive impairment, and derealization; 66% had megaphagia; 53% reported hypersexuality (principally men); and 53% reported a depressed mood (predominantly women). Patients were remarkably similar to control subjects between episodes regarding sleep, mood, and eating attitude, but had increased body mass index. We found marginal efficacy for amantadine and mood stabilizers, but found no increased family history for neuropsychiatric disorders.

INTERPRETATION

The similarity of the clinical and demographic features across studies strongly suggests that Kleine-Levin syndrome is a genuine disease entity. Familial clustering and increased prevalence in the Jewish population support a role for a major genetic susceptibility factor. Considering the inefficacy of available treatments, we propose that disease management should primarily be supportive and educational.