Modeling hypothalamic pathophysiology in vitro for metabolic, circadian, and sleep disorders.

The hypothalamus, a small and intricate brain structure, orchestrates numerous neuroendocrine functions through specialized neurons and nuclei. Disruption of this complex circuitry can result in various diseases, including metabolic, circadian, and sleep disorders. Advances in in vitro models and their integration with new technologies have significantly benefited research on hypothalamic function and pathophysiology. We explore existing in vitro hypothalamic models and address their challenges and limitations as well as translational findings. We also highlight how collaborative efforts among multidisciplinary teams are essential to develop relevant and translational experimental models capable of replicating intricate neural circuits and neuroendocrine pathways, thereby advancing our understanding of therapeutic targets and drug discovery in hypothalamus-related disorders.

Lipodystrophy as a target to delay premature aging.

Lipodystrophy syndromes are rare diseases characterized by low levels and an abnormal distribution of adipose tissue, caused by diverse genetic or acquired causes. These conditions commonly exhibit metabolic complications, including insulin resistance, diabetes, hypertriglyceridemia, nonalcoholic fatty liver disease, and adipose tissue dysfunction. Moreover, genetic lipodystrophic laminopathies exhibit a premature aging phenotype, emphasizing the importance of restoring adipose tissue distribution and function. In this opinion, we discuss the relevance of adipose tissue reestablishment as a potential approach to alleviate premature aging and age-related complications in genetic lipodystrophy syndromes.

Ghrelin delays premature aging in Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare and fatal genetic condition that arises from a single nucleotide alteration in the LMNA gene, leading to the production of a defective lamin A protein known as progerin. The accumulation of progerin accelerates the onset of a dramatic premature aging phenotype in children with HGPS, characterized by low body weight, lipodystrophy, metabolic dysfunction, skin, and musculoskeletal age-related dysfunctions. In most cases, these children die of age-related cardiovascular dysfunction by their early teenage years. The absence of effective treatments for HGPS underscores the critical need to explore novel safe therapeutic strategies. In this study, we show that treatment with the hormone ghrelin increases autophagy, decreases progerin levels, and alleviates other cellular hallmarks of premature aging in human HGPS fibroblasts. Additionally, using a HGPS mouse model (LmnaG609G/G609G mice), we demonstrate that ghrelin administration effectively rescues molecular and histopathological progeroid features, prevents progressive weight loss in later stages, reverses the lipodystrophic phenotype, and extends lifespan of these short-lived mice. Therefore, our findings uncover the potential of modulating ghrelin signaling offers new treatment targets and translational approaches that may improve outcomes and enhance the quality of life for patients with HGPS and other age-related pathologies.

Primary cilia shape hallmarks of health and aging.

Primary cilia are specialized organelles that sense changes in extracellular milieu, and their malfunction is responsible for several disorders (ciliopathies). Increasing evidence shows that primary cilia regulate tissue and cellular aging related features, which led us to review the evidence on their role in potentiating and/or accelerating the aging process. Primary cilia malfunction is associated with some age-related disorders, from cancer to neurodegenerative and metabolic disorders. However, there is limited understanding of molecular pathways underlying primary cilia dysfunction, resulting in scarce ciliary-targeted therapies available. Here, we discuss the findings on primary cilia dysfunction as modulators of the health and aging hallmarks, and the pertinence of ciliary pharmacological targeting to promote healthy aging or treat age-related diseases.

Cellular Senescence: From Mechanisms to Current Biomarkers and Senotherapies.

An increase in life expectancy in developed countries has led to a surge of chronic aging-related diseases. In the last few decades, several studies have provided evidence of the prominent role of cellular senescence in many of these pathologies. Key traits of senescent cells include cell cycle arrest, apoptosis resistance, and secretome shift to senescence-associated secretory phenotype resulting in increased secretion of various intermediate bioactive factors important for senescence pathophysiology. However, cellular senescence is a highly phenotypically heterogeneous process, hindering the discovery of totally specific and accurate biomarkers. Also, strategies to prevent the pathologic effect of senescent cell accumulation during aging by impairing senescence onset or promoting senescent cell clearance have shown great potential during in vivo studies, and some are already in early stages of clinical translation. The adaptability of these senotherapeutic approaches to human application has been questioned due to the lack of proper senescence targeting and senescence involvement in important physiologic functions. In this review, we explore the heterogeneous phenotype of senescent cells and its influence on the expression of biomarkers currently used for senescence detection. We also discuss the current evidence regarding the efficacy, reliability, development stage, and potential for human applicability of the main existing senotherapeutic strategies. SIGNIFICANCE STATEMENT: This paper is an extensive review of what is currently known about the complex process of cellular senescence and explores its most defining features. The main body of the discussion focuses on how the multifeature fluctuation of the senescence phenotype and the physiological role of cellular senescence have both caused a limitation in the search for truly reliable senescence biomarkers and the progression in the development of senotherapies.

Understanding neuron-glia crosstalk and biological clocks in insomnia.

According to the World Health Organization, about one-third of the population experiences insomnia symptoms, and about 10-15% suffer from chronic insomnia, the most common sleep disorder. Sleeping difficulties associated with insomnia are often linked to chronic sleep deprivation, which has a negative health impact partly due to disruption in the internal synchronisation of biological clocks. These are regulated by clock genes and modulate most biological processes. Most studies addressing circadian rhythm regulation have focused on the role of neurons, yet glial cells also impact circadian rhythms and sleep regulation. Chronic insomnia and sleep loss have been associated with glial cell activation, exacerbated neuroinflammation, oxidative stress, altered neuronal metabolism and synaptic plasticity, accelerated age-related processes and decreased lifespan. It is, therefore, essential to highlight the importance of glia-neuron interplay on sleep/circadian regulation and overall healthy brain function. Hence, in this review, we aim to address the main neurobiological mechanisms involved in neuron-glia crosstalk, with an emphasis on microglia and astrocytes, in both healthy sleep, chronic sleep deprivation and chronic insomnia.

Ataxin-2 in the hypothalamus at the crossroads between metabolism and clock genes.

ATXN2 gene, encoding for ataxin-2, is located in a trait locus for obesity. Atxn2 knockout (KO) mice are obese and insulin resistant; however, the cause for this phenotype is still unknown. Moreover, several findings suggest ataxin-2 as a metabolic regulator, but the role of this protein in the hypothalamus was never studied before. The aim of this work was to understand if ataxin-2 modulation in the hypothalamus could play a role in metabolic regulation. Ataxin-2 was overexpressed/re-established in the hypothalamus of C57Bl6/Atxn2 KO mice fed either a chow or a high-fat diet (HFD). This delivery was achieved through stereotaxic injection of lentiviral vectors encoding for ataxin-2. We show, for the first time, that HFD decreases ataxin-2 levels in mouse hypothalamus and liver. Specific hypothalamic ataxin-2 overexpression prevents HFD-induced obesity and insulin resistance. Ataxin-2 re-establishment in Atxn2 KO mice improved metabolic dysfunction without changing body weight. Furthermore, we observed altered clock gene expression in Atxn2 KO that might be causative of metabolic dysfunction. Interestingly, ataxin-2 hypothalamic re-establishment rescued these circadian alterations. Thus, ataxin-2 in the hypothalamus is a determinant for weight, insulin sensitivity and clock gene expression. Ataxin-2's potential role in the circadian clock, through the regulation of clock genes, might be a relevant mechanism to regulate metabolism. Overall, this work shows hypothalamic ataxin-2 as a new player in metabolism regulation, which might contribute to the development of new strategies for metabolic disorders.

The impact of insomnia on frailty and the hallmarks of aging.

Throughout the course of life, there are age-related changes in sleep. Despite these normal changes, there is a high percentage of older adults that report sleep dissatisfaction with a high pervasiveness of chronic insomnia, the most common sleep disorder worldwide, with its prevalence being expected to continuously increase due to the growing rates of aging and obesity. This can have different adverse health outcomes, especially by promoting both physical and cognitive decline, which ultimately may aggravate frailty in older adults. Moreover, age-related frailty and sleep dysfunction may have a common mechanism related to the hallmarks of cellular aging. Cellular aging was categorized into nine hallmarks, such as DNA damage, telomere attrition and epigenetic changes. In the context of geriatric and chronic insomnia research, this review aims at discussing the current evidence from both animal models and human cohorts addressing the link between chronic insomnia, the hallmarks of aging and their impact on frailty. Moreover, the most recent research about the putative effect of insomnia therapeutic approaches on hallmarks of aging will be also highlighted.

SIRT1 activation and its circadian clock control: a promising approach against (frailty in) neurodegenerative disorders.

With the increase in life expectancy, the incidence of neurodegenerative disorders and their impact worldwide has been increasing in recent years. Neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease, have complex and varied mechanisms of pathogenesis. Importantly, they share the common feature of disrupted circadian rhythms. This hallmark is believed to underlie the symptoms of such diseases and even potentially contribute to their onset. In addition, the association of physical frailty with dementia and neurodegenerative disorders has been demonstrated. In fact, frail persons are 8 times more likely to have some form of dementia and population studies report a significant prevalence for frailty in older patients with AD and PD. SIRT1 regulates the acetylation status of clock components and controls circadian amplitude of clock genes. However, the mechanisms responsible for this circadian clock control have been the subject of contradictory findings. Importantly, the activation of SIRT1 has been shown to have very relevant therapeutic potential against neurodegeneration. Nevertheless, few studies have attempted to connect the therapeutic reestablishing of SIRT1 as an approach against circadian disruption in neurodegenerative diseases. In this review, we address: circadian rhythms as an important early biomarker of neurodegenerative disorders; mechanisms for SIRT1 activation and the novel sirtuin-activating compounds (STACs); SIRT1 circadian paradox and subsequent studies in an unprecedented way in the literature; the beneficial role of SIRT1 activation in neurodegeneration; innovative proposals of how circadian-based interventions (e.g., SIRT1 activators) may become an important therapeutic approach against neurodegenerative disorders and how non-pharmacologic interventions (e.g., Mediterranean-style diet) might help in the prevention and/or treatment of these high-burden disorders, while tackling frailty and enhancing robustness.

Peripheral biomarkers to diagnose obstructive sleep apnea in adults: A systematic review and meta-analysis.

BACKGROUND: Obstructive Sleep Apnea (OSA) has been recognized as a major health concern worldwide, given its increasing prevalence, difficulties in diagnosis and treatment, and impact on health, economy, and society. Clinical guidelines highlight the need of biomarkers to guide OSA clinical decision-making, but so far, without success. In this systematic review and meta-analysis, registered on the International Prospective Register of Systematic Reviews database (ID CRD42020132556), we proposed to gather and further explore candidates identified in the literature as potential OSA biomarkers. METHODS: Search strategies for eight different databases (PubMed/Medline, Cochrane Library, Biblioteca Virtual da Saúde, Web of Science, EMBASE, World Intellectual Property Organization database, and bioRxiV and medRxiV Preprint Servers) were developed. We identified studies exploring potential biomarkers of OSA, in peripheral samples of adults, with and without OSA, with no comorbidities defined in study inclusion criteria, published after the last systematic review and meta-analysis conducted on OSA biomarkers, until May 31st, 2020. Risk of bias was assessed through the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies. Demographic, clinical, and candidate biomarkers' data were collected and analyzed via random effects meta-analyses. FINDINGS: Among the 1512 unique studies screened, 120 met the inclusion criteria and 16 studies with low risk of bias were selected for meta-analyses. The selected 16 studies enrolled a total of 2156 participants, from which 1369 were diagnosed with OSA and 787 were disease-free controls. The assessed variables showed high heterogeneity. From the 38 biomarker candidates evaluated, only two were evaluated in more than one study. Most studies pinpointed candidates with more potential for OSA prognosis. ADAM29, FLRT2 and SLC18A3 mRNA levels in PBMCs, Endocan and YKL-40 levels in serum, and IL-6 and Vimentin levels in plasma revealed the most promising candidates for OSA diagnosis. INTERPRETATION: Although the current systematic review and meta-analysis allowed us to identify candidates to further explore as potential biomarkers in future studies, it is evident that OSA biomarkers research is still at an early stage. Most findings derive from small-size single-center study cohorts and single-candidate studies. We point several gaps in current OSA biomarker research that may guide into new directions and approaches towards the identification of OSA biomarkers.

SIRT2 Deficiency Exacerbates Hepatic Steatosis via a Putative Role of the ER Stress Pathway.

Nonalcoholic fatty liver disease (NAFLD), a condition strongly associated with obesity and insulin resistance, is characterized by hepatic lipid accumulation and activation of the endoplasmic reticulum (ER) stress response. The sirtuin 2 (SIRT2) protein deacetylase is emerging as a new player in metabolic homeostasis, but its role in the development of hepatic steatosis and its link with ER stress activation remains unknown. SIRT2-knockout (SIRT2-KO) and wild-type mice were fed either a control or a high-fat diet (HFD) for 4 weeks. Genetic manipulation of SIRT2 levels was performed in human hepatic cells. Although apparently normal under a control diet, SIRT2-KO mice showed accelerated body weight gain and adiposity on a HFD, accompanied by severe insulin resistance. Importantly, SIRT2-KO mice exhibited worsened hepatic steatosis independently from diet, consistent with upregulated gene expression of lipogenic enzymes and increased expression of ER stress markers. Exposure of hepatic cells to palmitate induced lipid accumulation, increased ER stress, and decreased SIRT2 expression. Moreover, SIRT2-silenced cells showed enhanced lipid accumulation and ER stress activation under basal conditions, whereas SIRT2 overexpression abrogated palmitate-induced lipid deposition and ER stress activation. Our findings reveal a role for SIRT2 in the regulation of hepatic lipid homeostasis, potentially through the ER stress response, suggesting that SIRT2 activation might constitute a therapeutic strategy against obesity and its metabolic complications.

PET Imaging of the Neuropeptide Y System: A Systematic Review.

Neuropeptide Y (NPY) is a vastly studied biological peptide with numerous physiological functions that activate the NPY receptor family (Y1, Y2, Y4 and Y5). Moreover, these receptors are correlated with the pathophysiology of several diseases such as feeding disorders, anxiety, metabolic diseases, neurodegenerative diseases, some types of cancers and others. In order to deepen the knowledge of NPY receptors' functions and molecular mechanisms, neuroimaging techniques such as positron emission tomography (PET) have been used. The development of new radiotracers for the different NPY receptors and their subsequent PET studies have led to significant insights into molecular mechanisms involving NPY receptors. This article provides a systematic review of the imaging biomarkers that have been developed as PET tracers in order to study the NPY receptor family.

A look on food intake and satiety: from humans to rodent models.

Satiety is a complex state, influenced by numerous factors that go beyond food ingestion. Satiety influences food habits and behavior, thus affecting human health. This review provides an overview of physiological mechanisms involved in satiety and of methodologies to assess food intake and satiety in both animal models and humans. The following topics are highlighted: differences between satiety and satiation; how the central nervous system regulates food intake and satiety; the impact of different macronutrients on satiety; and how the manipulation of food composition might influence overall satiety. Bringing together knowledge on this myriad of satiety mechanisms and how we can study them is useful to better understand and control obesity and other eating disorders.

Skin senescence: mechanisms and impact on whole-body aging.

The skin is the largest organ and has a key protective role. Similar to any other tissue, the skin is influenced not only by intrinsic/chronological aging, but also by extrinsic aging, triggered by environmental factors that contribute to accelerating the skin aging process. Aged skin shows structural, cellular, and molecular changes and accumulation of senescent cells. These senescent cells can induce or accelerate the age-related dysfunction of other nearby cells from the skin, or from different origins. However, the extent and underlying mechanisms remain unknown. In this opinion, we discuss the possible relevant role of skin senescence in the induction of aging phenotypes to other organs/tissues, contributing to whole-body aging. Moreover, we suggest that topical administration of senolytics/senotherapeutics could counteract the overall whole-body aging phenotype.

Blueberry Counteracts Prediabetes in a Hypercaloric Diet-Induced Rat Model and Rescues Hepatic Mitochondrial Bioenergetics.

The paramount importance of a healthy diet in the prevention of type 2 diabetes is now well recognized. Blueberries (BBs) have been described as attractive functional fruits for this purpose. This study aimed to elucidate the cellular and molecular mechanisms pertaining to the protective impact of blueberry juice (BJ) on prediabetes. Using a hypercaloric diet-induced prediabetic rat model, we evaluated the effects of BJ on glucose, insulin, and lipid profiles; gut microbiota composition; intestinal barrier integrity; and metabolic endotoxemia, as well as on hepatic metabolic surrogates, including several related to mitochondria bioenergetics. BJ supplementation for 14 weeks counteracted diet-evoked metabolic deregulation, improving glucose tolerance, insulin sensitivity, and hypertriglyceridemia, along with systemic and hepatic antioxidant properties, without a significant impact on the gut microbiota composition and related mechanisms. In addition, BJ treatment effectively alleviated hepatic steatosis and mitochondrial dysfunction observed in the prediabetic animals, as suggested by the amelioration of bioenergetics parameters and key targets of inflammation, insulin signaling, ketogenesis, and fatty acids oxidation. In conclusion, the beneficial metabolic impact of BJ in prediabetes may be mainly explained by the rescue of hepatic mitochondrial bioenergetics. These findings pave the way to support the use of BJ in prediabetes to prevent diabetes and its complications.

PI3K/AKT/MTOR and ERK1/2-MAPK signaling pathways are involved in autophagy stimulation induced by caloric restriction or caloric restriction mimetics in cortical neurons.

Caloric restriction has been shown to robustly ameliorate age-related diseases and to prolong lifespan in several model organisms, and these beneficial effects are dependent on the stimulation of autophagy. Autophagy dysfunction contributes to the accumulation of altered macromolecules, and is a key mechanism of promoting aging and age-related disorders, as neurodegenerative ones. We have previously shown that caloric restriction (CR), and CR mimetics Neuropeptide Y (NPY) and ghrelin, stimulate autophagy in rat cortical neurons, however by unknown molecular mechanisms. Overall, we show that CR, NPY, and ghrelin stimulate autophagy through PI3K/AKT/MTOR inhibition and ERK1/2-MAPK activation. The knowledge of these kinases in autophagy regulation and the contribution to the understanding of molecular mechanism facilitates the discovery of more targeted therapeutic strategies to stimulate autophagy, which is relevant in the context of age-related disorders.

Long-term continuous positive airway pressure treatment ameliorates biological clock disruptions in obstructive sleep apnea.

BACKGROUND: Obstructive Sleep Apnea (OSA) is a highly prevalent and underdiagnosed sleep disorder. Recent studies suggest that OSA might disrupt the biological clock, potentially causing or worsening OSA-associated comorbidities. However, the effect of OSA treatment on clock disruption is not fully understood. METHODS: The impact of OSA and short- (four months) and long-term (two years) OSA treatment, with Continuous Positive Airway Pressure (CPAP), on the biological clock was investigated at four time points within 24 h, in OSA patients relative to controls subjects (no OSA) of the same sex and age group, in a case-control study. Plasma melatonin and cortisol, body temperature and the expression levels and rhythmicity of eleven clock genes in peripheral blood mononuclear cells (PBMCs) were assessed. Additional computational tools were used for a detailed data analysis. FINDINGS: OSA impacts on clock outputs and on the expression of several clock genes in PBMCs. Neither short- nor long-term treatment fully reverted OSA-induced alterations in the expression of clock genes. However, long-term treatment was able to re-establish levels of plasma melatonin and cortisol and body temperature. Machine learning methods could discriminate controls from untreated OSA patients. Following long-term treatment, the distinction between controls and patients disappeared, suggesting a closer similarity of the phenotypes. INTERPRETATION: OSA alters biological clock-related characteristics that differentially respond to short- and long-term CPAP treatment. Long-term CPAP was more efficient in counteracting OSA impact on the clock, but the obtained results suggest that it is not fully effective. A better understanding of the impact of OSA and OSA treatment on the clock may open new avenues to OSA diagnosis, monitoring and treatment.

Small-molecule modulators of the circadian clock: Pharmacological potentials in circadian-related diseases.

Disruption of circadian oscillations has a wide-ranging impact on health, with the potential to induce the development of clock-related diseases. Small-molecule modulators of the circadian clock (SMMCC) target core or noncore clock proteins, modulating physiological effects as a consequence of agonist, inverse agonist, or antagonist interference. These pharmacological modulators are usually identified using chemical screening of large libraries of active compounds. However, target-based screens, chemical optimization, and circadian crystallography have recently assisted in the identification of these compounds. In this review, we focus on established and novel SMMCCs targeting both core and noncore clock proteins, identifying their circadian targets, detailed circadian effects, and specific physiological effects. In addition, we discuss their therapeutic potential for the treatment of diverse clock-related disorders (such as metabolic-associated disorders, autoimmune diseases, mood disorders, and cancer) and as chronotherapeutics. Future perspectives are also considered, such as clinical trials, and potential safety hazards, including those in the absence of clinical trials.

Neuropeptide Y (NPY) intranasal delivery alleviates Machado-Joseph disease.

Machado-Joseph disease (MJD) is the most common dominantly-inherited ataxia worldwide with no effective treatment to prevent, stop or alleviate its progression. Neuropeptide Y (NPY) is a neuroprotective agent widely expressed in the mammalian brain. Our previous work showed that NPY overexpression mediated by stereotaxically-injected viral vectors mitigates motor deficits and neuropathology in MJD mouse models. To pursue a less invasive translational approach, we investigated whether intranasal administration of NPY would alleviate cerebellar neuropathology and motor and balance impairments in a severe MJD transgenic mouse model. For that, a NPY solution was administered into mice nostrils 5 days a week. Upon 8 weeks of treatment, we observed a mitigation of motor and balance impairments through the analysis of mice behavioral tests (rotarod, beam walking, pole and swimming tests). This was in line with a reduction of cerebellar pathology, evidenced by a preservation of cerebellar granular layer and of Purkinje cells and reduction of mutant ataxin-3 aggregate numbers. Furthermore, intranasal administration of NPY did not alter body weight gain, food intake, amount of body fat nor cholesterol or triglycerides levels. Our findings support the translational potential of intranasal infusion of NPY as a pharmacological intervention in MJD.

Common risk factors and therapeutic targets in obstructive sleep apnea and osteoarthritis: An unexpectable link?

Osteoarthritis (OA) and Obstructive Sleep Apnea (OSA) are two highly prevalent chronic diseases for which effective therapies are urgently needed. Recent epidemiologic studies, although scarce, suggest that the concomitant occurrence of OA and OSA is associated with more severe manifestations of both diseases. Moreover, OA and OSA share risk factors, such as aging and metabolic disturbances, and co-morbidities, including cardiovascular and metabolic diseases, sleep deprivation and depression. Whether this coincidental occurrence is fortuitous or involves cause-effect relationships is unknown. This review aims at collating and integrating present knowledge on both diseases by providing a brief overview of their epidemiology and pathophysiology, analyzing current evidences relating OA and OSA and discussing potential common mechanisms by which they can aggravate each other. Such mechanisms constitute potential therapeutic targets whose pharmacological modulation may provide more efficient ways of reducing the consequences of OA and OSA and, thus, lessen the huge individual and social burden that they impose.