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Tzounakou AM, Stathori G, Paltoglou G, Valsamakis G, Mastorakos G, Vlahos NF, Charmandari E. Childhood Obesity, Hypothalamic Inflammation, and the Onset of Puberty: A Narrative Review. Nutrients 2024; 16:1720. [PMID: 38892653 PMCID: PMC11175006 DOI: 10.3390/nu16111720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
The onset of puberty, which is under the control of the hypothalamic-pituitary-gonadal (HPG) axis, is influenced by various factors, including obesity, which has been associated with the earlier onset of puberty. Obesity-induced hypothalamic inflammation may cause premature activation of gonadotropin-releasing hormone (GnRH) neurons, resulting in the development of precocious or early puberty. Mechanisms involving phoenixin action and hypothalamic microglial cells are implicated. Furthermore, obesity induces structural and cellular brain alterations, disrupting metabolic regulation. Imaging studies reveal neuroinflammatory changes in obese individuals, impacting pubertal timing. Magnetic resonance spectroscopy enables the assessment of the brain's neurochemical composition by measuring key metabolites, highlighting potential pathways involved in neurological changes associated with obesity. In this article, we present evidence indicating a potential association among obesity, hypothalamic inflammation, and precocious puberty.
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Affiliation(s)
- Anastasia-Maria Tzounakou
- Center for the Prevention and Management of Overweight and Obesity, Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ‘Aghia Sophia’ Children’s Hospital, 11527 Athens, Greece; (A.-M.T.); (G.S.)
| | - Galateia Stathori
- Center for the Prevention and Management of Overweight and Obesity, Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ‘Aghia Sophia’ Children’s Hospital, 11527 Athens, Greece; (A.-M.T.); (G.S.)
| | - George Paltoglou
- Diabetes Unit, Second Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ‘P. & A. Kyriakou’ Children’s Hospital, 11527 Athens, Greece;
| | - Georgios Valsamakis
- Second Department of Obstetrics and Gynecology, National and Kapodistrian University of Athens Medical School, ‘Aretaieion’ University Hospital, 11528 Athens, Greece; (G.V.); (G.M.); (N.F.V.)
| | - George Mastorakos
- Second Department of Obstetrics and Gynecology, National and Kapodistrian University of Athens Medical School, ‘Aretaieion’ University Hospital, 11528 Athens, Greece; (G.V.); (G.M.); (N.F.V.)
| | - Nikolaos F. Vlahos
- Second Department of Obstetrics and Gynecology, National and Kapodistrian University of Athens Medical School, ‘Aretaieion’ University Hospital, 11528 Athens, Greece; (G.V.); (G.M.); (N.F.V.)
| | - Evangelia Charmandari
- Center for the Prevention and Management of Overweight and Obesity, Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ‘Aghia Sophia’ Children’s Hospital, 11527 Athens, Greece; (A.-M.T.); (G.S.)
- Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, 11527 Athens, Greece
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Jetton TL, Galbraith OT, Peshavaria M, Bonney EA, Holmén BA, Fukagawa NK. Sex-specific metabolic adaptations from in utero exposure to particulate matter derived from combustion of petrodiesel and biodiesel fuels. CHEMOSPHERE 2024; 346:140480. [PMID: 37879369 PMCID: PMC10841900 DOI: 10.1016/j.chemosphere.2023.140480] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 10/15/2023] [Accepted: 10/17/2023] [Indexed: 10/27/2023]
Abstract
Maternal exposure to particulate matter derived from diesel exhaust has been shown to cause metabolic dysregulation, neurological problems, and increased susceptibility to diabetes in the offspring. Diesel exhaust is a major source of air pollution and the use of biodiesel (BD) and its blends have been progressively increasing throughout the world; however, studies on the health impact of BD vs. petrodiesel combustion-generated exhaust have been controversial in part, due to differences in the chemical and physical nature of the associated particulate matter (PM). To explore the long-term impact of prenatal exposure, pregnant mice were exposed to PM generated by combustion of petrodiesel (B0) and a 20% soy BD blend (B20) by intratracheal instillation during embryonic days 9-17 and allowed to deliver. Offspring were then followed for 52 weeks. We found that mother's exposure to B0 and B20 PM manifested in striking sex-specific phenotypes with respect to metabolic adaptation, maintenance of glucose homeostasis, and medial hypothalamic glial cell makeup in the offspring. The data suggest PM exposure limited to a narrower critical developmental window may be compensated for by the mother and/or the fetus by altered metabolic programming in a marked sex-specific and fuel-derived PM-specific manner, leading to sex-specific risk for diseases related to environmental exposure later in life.
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Affiliation(s)
- Thomas L Jetton
- From the Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, USA.
| | - Oban T Galbraith
- From the Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, USA
| | - Mina Peshavaria
- From the Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, USA; Department of Obstetrics, Gynecology and Reproductive Sciences, USA
| | | | - Britt A Holmén
- Larner College of Medicine, Department of Civil & Environmental Engineering, College of Engineering and Mathematical Sciences, USA
| | - Naomi K Fukagawa
- From the Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, USA; University of Vermont, Burlington, VT 05405, USA; USDA-ARS, Beltsville Human Nutrition Research Center, Beltsville, MD 20705-2350, USA
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Ruck L, Wiegand S, Kühnen P. Relevance and consequence of chronic inflammation for obesity development. Mol Cell Pediatr 2023; 10:16. [PMID: 37957462 PMCID: PMC10643747 DOI: 10.1186/s40348-023-00170-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Accepted: 10/26/2023] [Indexed: 11/15/2023] Open
Abstract
BACKGROUND Increasing prevalence of morbid obesity accompanied by comorbidities like type 2 diabetes mellitus (T2DM) led to a demand for improving therapeutic strategies and pharmacological intervention options. Apart from genetics, inflammation processes have been hypothesized to be of importance for the development of obesity and related aspects like insulin resistance. MAIN TEXT Within this review, we provide an overview of the intricate interplay between chronic inflammation of the adipose tissue and the hypothalamus and the development of obesity. Further understanding of this relationship might improve the understanding of the underlying mechanism and may be of relevance for the establishment of new treatment strategies.
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Affiliation(s)
- Lisa Ruck
- Klinik Für Pädiatrische Endokrinologie und Diabetologie, Charité Universitätsmedizin, Berlin, Germany.
- Berlin Institute of Health at Charité-Universitätsmedizin Berlin, BIH Biomedical Innovation Academy, BIH Charité Junior Clinician Scientist Program, Charitéplatz 1, 10117, Berlin, Germany.
| | - Susanna Wiegand
- Abteilung Interdisziplinär, Sozial-Pädiatrisches Zentrum, Charité Universitätsmedizin, Berlin, Germany
| | - Peter Kühnen
- Klinik Für Pädiatrische Endokrinologie und Diabetologie, Charité Universitätsmedizin, Berlin, Germany
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Sonnefeld L, Rohmann N, Geisler C, Laudes M. Is human obesity an inflammatory disease of the hypothalamus? Eur J Endocrinol 2023; 188:R37-R45. [PMID: 36883605 DOI: 10.1093/ejendo/lvad030] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/23/2023] [Accepted: 03/02/2023] [Indexed: 03/09/2023]
Abstract
Obesity and its comorbidities are long-standing, challenging global health problems. Lack of exercise, overnutrition, and especially the consumption of fat-rich foods are some of the most important factors leading to an increase in prevalence in modern society. The pathophysiology of obesity as a metabolic inflammatory disease has moved into focus since new therapeutic approaches are required. The hypothalamus, a brain area responsible for energy homeostasis, has recently received special attention in this regard. Hypothalamic inflammation was identified to be associated with diet-induced obesity and new evidence suggests that it may be, beyond that, a pathological mechanism of the disease. This inflammation impairs the local signaling of insulin and leptin leading to dysfunction of the regulation of energy balance and thus, weight gain. After a high-fat diet consumption, activation of inflammatory mediators such as the nuclear factor κB or c-Jun N-terminal kinase pathway can be observed, accompanied by elevated secretion of pro-inflammatory interleukins and cytokines. Brain resident glia cells, especially microglia and astrocytes, initiate this release in response to the flux of fatty acids. The gliosis occurs rapidly before the actual weight gain. Dysregulated hypothalamic circuits change the interaction between neuronal and non-neuronal cells, contributing to the establishment of inflammatory processes. Several studies have reported reactive gliosis in obese humans. Although there is evidence for a causative role of hypothalamic inflammation in the obesity development, data on underlying molecular pathways in humans are limited. This review discusses the current state of knowledge on the relationship between hypothalamic inflammation and obesity in humans.
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Affiliation(s)
- Lena Sonnefeld
- Institute of Diabetes and Clinical Metabolic Research, University Medical Centre Schleswig-Holstein, Kiel 24105, Germany
| | - Nathalie Rohmann
- Institute of Diabetes and Clinical Metabolic Research, University Medical Centre Schleswig-Holstein, Kiel 24105, Germany
| | - Corinna Geisler
- Institute of Diabetes and Clinical Metabolic Research, University Medical Centre Schleswig-Holstein, Kiel 24105, Germany
| | - Matthias Laudes
- Institute of Diabetes and Clinical Metabolic Research, University Medical Centre Schleswig-Holstein, Kiel 24105, Germany
- Division of Endocrinology, Diabetes and Clinical Nutrition, Department of Medicine 1, University Medical Centre Schleswig-Holstein, Kiel 24105, Germany
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Obesity-Related Neuroinflammation: Magnetic Resonance and Microscopy Imaging of the Brain. Int J Mol Sci 2022; 23:ijms23158790. [PMID: 35955925 PMCID: PMC9368789 DOI: 10.3390/ijms23158790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 08/03/2022] [Accepted: 08/06/2022] [Indexed: 12/01/2022] Open
Abstract
Obesity is a major risk factor of Alzheimer’s disease and related dementias. The principal feature of dementia is a loss of neurons and brain atrophy. The mechanistic links between obesity and the neurodegenerative processes of dementias are not fully understood, but recent research suggests that obesity-related systemic inflammation and subsequent neuroinflammation may be involved. Adipose tissues release multiple proinflammatory molecules (fatty acids and cytokines) that impact blood and vessel cells, inducing low-grade systemic inflammation that can transition to tissues, including the brain. Inflammation in the brain—neuroinflammation—is one of key elements of the pathobiology of neurodegenerative disorders; it is characterized by the activation of microglia, the resident immune cells in the brain, and by the structural and functional changes of other cells forming the brain parenchyma, including neurons. Such cellular changes have been shown in animal models with direct methods, such as confocal microscopy. In humans, cellular changes are less tangible, as only indirect methods such as magnetic resonance (MR) imaging are usually used. In these studies, obesity and low-grade systemic inflammation have been associated with lower volumes of the cerebral gray matter, cortex, and hippocampus, as well as altered tissue MR properties (suggesting microstructural variations in cellular and molecular composition). How these structural variations in the human brain observed using MR imaging relate to the cellular variations in the animal brain seen with microscopy is not well understood. This review describes the current understanding of neuroinflammation in the context of obesity-induced systemic inflammation, and it highlights need for the bridge between animal microscopy and human MR imaging studies.
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Near-infrared light reduces glia activation and modulates neuroinflammation in the brains of diet-induced obese mice. Sci Rep 2022; 12:10848. [PMID: 35761012 PMCID: PMC9237037 DOI: 10.1038/s41598-022-14812-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 06/13/2022] [Indexed: 12/06/2022] Open
Abstract
Neuroinflammation is a key event in neurodegenerative conditions such as Alzheimer's disease (AD) and characterizes metabolic pathologies like obesity and type 2 diabetes (T2D). Growing evidence in humans shows that obesity increases the risk of developing AD by threefold. Hippocampal neuroinflammation in rodents correlates with poor memory performance, suggesting that it contributes to cognitive decline. Here we propose that reducing obesity/T2D-driven neuroinflammation may prevent the progression of cognitive decline associated with AD-like neurodegenerative states. Near-infrared light (NIR) has attracted increasing attention as it was shown to improve learning and memory in both humans and animal models. We previously reported that transcranial NIR delivery reduced amyloid beta and Tau pathology and improved memory function in mouse models of AD. Here, we report the effects of NIR in preventing obesity-induced neuroinflammation in a diet-induced obese mouse model. Five-week-old wild-type mice were fed a high-fat diet (HFD) for 13 weeks to induce obesity prior to transcranial delivery of NIR for 4 weeks during 90-s sessions given 5 days a week. After sacrifice, brain slices were subjected to free-floating immunofluorescence for microglia and astrocyte markers to evaluate glial activation and quantitative real-time polymerase chain reaction (PCR) to evaluate expression levels of inflammatory cytokines and brain-derived neurotrophic factor (BDNF). The hippocampal and cortical regions of the HFD group had increased expression of the activated microglial marker CD68 and the astrocytic marker glial fibrillary acidic protein. NIR-treated HFD groups showed decreased levels of these markers. PCR revealed that hippocampal tissue from the HFD group had increased levels of pro-inflammatory interleukin (IL)-1β and tumor necrosis factor-α. Interestingly, the same samples showed increased levels of the anti-inflammatory IL-10. All these changes were attenuated by NIR treatment. Lastly, hippocampal levels of the neurotrophic factor BDNF were increased in NIR-treated HFD mice, compared to untreated HFD mice. The marked reductions in glial activation and pro-inflammatory cytokines along with elevated BDNF provide insights into how NIR could reduce neuroinflammation. These results support the use of NIR as a potential non-invasive and preventive therapeutic approach against chronic obesity-induced deficits that are known to occur with AD neuropathology.
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Szalanczy AM, Key CCC, Woods LCS. Genetic variation in satiety signaling and hypothalamic inflammation: merging fields for the study of obesity. J Nutr Biochem 2022; 101:108928. [PMID: 34936921 PMCID: PMC8959400 DOI: 10.1016/j.jnutbio.2021.108928] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 11/08/2021] [Accepted: 12/01/2021] [Indexed: 02/07/2023]
Abstract
Although obesity has been a longstanding health crisis, the genetic architecture of the disease remains poorly understood. Genome-wide association studies have identified many genomic loci associated with obesity, with genes being enriched in the brain, particularly in the hypothalamus. This points to the role of the central nervous system (CNS) in predisposition to obesity, and we emphasize here several key genes along the satiety signaling pathway involved in genetic susceptibility. Interest has also risen regarding the chronic, low-grade obesity-associated inflammation, with a growing concern toward inflammation in the hypothalamus as a precursor to obesity. Recent studies have found that genetic variation in inflammatory genes play a role in obesity susceptibility, and we highlight here several key genes. Despite the interest in the genetic variants of these pathways individually, there is a lack of research that investigates the relationship between the two. Understanding the interplay between genetic variation in obesity genes enriched in the CNS and inflammation genes will advance our understanding of obesity etiology and heterogeneity, improve genetic risk prediction analyses, and highlight new drug targets for the treatment of obesity. Additionally, this increased knowledge will assist in physician's ability to develop personalized nutrition and medication strategies for combating the obesity epidemic. Though it often seems to present universally, obesity is a highly individual disease, and there remains a need in the field to develop methods to treat at the individual level.
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Bhusal A, Rahman MH, Suk K. Hypothalamic inflammation in metabolic disorders and aging. Cell Mol Life Sci 2021; 79:32. [PMID: 34910246 PMCID: PMC11071926 DOI: 10.1007/s00018-021-04019-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/01/2021] [Accepted: 10/29/2021] [Indexed: 12/15/2022]
Abstract
The hypothalamus is a critical brain region for the regulation of energy homeostasis. Over the years, studies on energy metabolism primarily focused on the neuronal component of the hypothalamus. Studies have recently uncovered the vital role of glial cells as an additional player in energy balance regulation. However, their inflammatory activation under metabolic stress condition contributes to various metabolic diseases. The recruitment of monocytes and macrophages in the hypothalamus helps sustain such inflammation and worsens the disease state. Neurons were found to actively participate in hypothalamic inflammatory response by transmitting signals to the surrounding non-neuronal cells. This activation of different cell types in the hypothalamus leads to chronic, low-grade inflammation, impairing energy balance and contributing to defective feeding habits, thermogenesis, and insulin and leptin signaling, eventually leading to metabolic disorders (i.e., diabetes, obesity, and hypertension). The hypothalamus is also responsible for the causation of systemic aging under metabolic stress. A better understanding of the multiple factors contributing to hypothalamic inflammation, the role of the different hypothalamic cells, and their crosstalks may help identify new therapeutic targets. In this review, we focus on the role of glial cells in establishing a cause-effect relationship between hypothalamic inflammation and the development of metabolic diseases. We also cover the role of other cell types and discuss the possibilities and challenges of targeting hypothalamic inflammation as a valid therapeutic approach.
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Affiliation(s)
- Anup Bhusal
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
| | - Md Habibur Rahman
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- Division of Endocrinology, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Kyoungho Suk
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- Brain Science and Engineering Institute, Kyungpook National University, Daegu, 41944, Republic of Korea.
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Brain Volume Loss, Astrocyte Reduction, and Inflammation in Anorexia Nervosa. ADVANCES IN NEUROBIOLOGY 2021; 26:283-313. [PMID: 34888839 DOI: 10.1007/978-3-030-77375-5_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Anorexia nervosa is the third most common chronic disease in adolescence and is characterized by low body weight, body image distortion, weight phobia, and severe somatic consequences. Among the latter, marked brain volume reduction has been linked to astrocyte cell count reduction of about 50% in gray and white matter, while neuronal and other glial cell counts remain normal. Exact underlying mechanisms remain elusive; however, first results point to important roles of the catabolic state and the very low gonadal steroid hormones in these patients. They also appear to involve inflammatory states of "hungry astrocytes" and interactions with the gut microbiota. Functional impairments could affect the role of astrocytes in supporting neurons metabolically, neurotransmitter reuptake, and synapse formation, among others. These could be implicated in reduced learning, mood alterations, and sleep disturbances often seen in patients with AN and help explain their rigidity and difficulties in relearning processes in psychotherapy during starvation.
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Diet, body weight and pain susceptibility - A systematic review of preclinical studies. NEUROBIOLOGY OF PAIN 2021; 10:100066. [PMID: 34195483 PMCID: PMC8237587 DOI: 10.1016/j.ynpai.2021.100066] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/26/2021] [Accepted: 06/11/2021] [Indexed: 02/07/2023]
Abstract
Obesity has been associated with increased susceptibility to chronic pain. Dietary and genetic models of obesity have been used to study this association. Allodynia is a common finding but alterations in nociception were inconsistent across studies. In subacute/chronic models, nocifencive behaviors were increased and/or sustained. Reviewed studies are overall consonant with the clinical literature.
Obesity has been associated with increased chronic pain susceptibility but causes are unclear. In this review, we systematize and analyze pain outcomes in rodent models of obesity as these can be important tools for mechanistic studies. Studies were identified using MEDLINE/PubMed and Scopus databases using the following search query: (((pain) OR (nociception)) AND (obesity)) AND (rat OR (mouse) OR (rodent))). From each eligible record we extracted the following data: species, strain, sex, pain/obesity model and main behavioral readouts. Out of 695 records 33 were selected for inclusion. 27 studies assessed nociception/acute pain and 17 studies assessed subacute or chronic pain. Overall genetic and dietary models overlapped in pain-related outcomes. Most acute pain studies reported either decreased or unaltered responses to noxious painful stimuli. However, decreased thresholds to mechanical innocuous stimuli, i.e. allodynia, were frequently reported. In most studies using subacute and chronic pain models, namely of subcutaneous inflammation, arthritis and perineural inflammation, decreased thresholds and/or prolonged pain manifestations were reported in obesity models. Strain comparisons and longitudinal observations indicate that genetic factors and the time course of the pathology might account for some of the discrepancies observed across studies. Two studies reported increased pain in animals subjected to high fat diet in the absence of weight gain. Pain-related outcomes in experimental models and clinical obesity are aligned indicating that the rodent can be an useful tool to study the interplay between diet, obesity and pain. In both cases weight gain might represent only a minor contribution to abnormal pain manifestation.
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Hypothalamic Astrocytes as a Specialized and Responsive Cell Population in Obesity. Int J Mol Sci 2021; 22:ijms22126176. [PMID: 34201099 PMCID: PMC8228119 DOI: 10.3390/ijms22126176] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/03/2021] [Accepted: 06/04/2021] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are a type of glial cell anatomically and functionally integrated into the neuronal regulatory circuits for the neuroendocrine control of metabolism. Being functional integral compounds of synapses, astrocytes are actively involved in the physiological regulatory aspects of metabolic control, but also in the pathological processes that link neuronal dysfunction and obesity. Between brain areas, the hypothalamus harbors specialized functional circuits that seem selectively vulnerable to metabolic damage, undergoing early cellular rearrangements which are thought to be at the core of the pathogenesis of diet-induced obesity. Such changes in the hypothalamic brain region consist of a rise in proinflammatory cytokines, the presence of a reactive phenotype in astrocytes and microglia, alterations in the cytoarchitecture and synaptology of hypothalamic circuits, and angiogenesis, a phenomenon that cannot be found elsewhere in the brain. Increasing evidence points to the direct involvement of hypothalamic astrocytes in such early metabolic disturbances, thus moving the study of these glial cells to the forefront of obesity research. Here we provide a comprehensive review of the most relevant findings of molecular and pathophysiological mechanisms by which hypothalamic astrocytes might be involved in the pathogenesis of obesity.
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Hypothalamic Microglial Heterogeneity and Signature under High Fat Diet-Induced Inflammation. Int J Mol Sci 2021; 22:ijms22052256. [PMID: 33668314 PMCID: PMC7956484 DOI: 10.3390/ijms22052256] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/18/2021] [Accepted: 02/19/2021] [Indexed: 12/17/2022] Open
Abstract
Under high-fat feeding, the hypothalamus atypically undergoes pro-inflammatory signaling activation. Recent data from transcriptomic analysis of microglia from rodents and humans has allowed the identification of several microglial subpopulations throughout the brain. Numerous studies have clarified the roles of these cells in hypothalamic inflammation, but how each microglial subset plays its functions upon inflammatory stimuli remains unexplored. Fortunately, these data unveiling microglial heterogeneity have triggered the development of novel experimental models for studying the roles and characteristics of each microglial subtype. In this review, we explore microglial heterogeneity in the hypothalamus and their crosstalk with astrocytes under high fat diet-induced inflammation. We present novel currently available ex vivo and in vivo experimental models that can be useful when designing a new research project in this field of study. Last, we examine the transcriptomic data already published to identify how the hypothalamic microglial signature changes upon short-term and prolonged high-fat feeding.
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Rahman MH, Bhusal A, Kim JH, Jha MK, Song GJ, Go Y, Jang IS, Lee IK, Suk K. Astrocytic pyruvate dehydrogenase kinase-2 is involved in hypothalamic inflammation in mouse models of diabetes. Nat Commun 2020; 11:5906. [PMID: 33219201 PMCID: PMC7680139 DOI: 10.1038/s41467-020-19576-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 10/22/2020] [Indexed: 02/07/2023] Open
Abstract
Hypothalamic inflammation plays an important role in disrupting feeding behavior and energy homeostasis as well as in the pathogenesis of obesity and diabetes. Here, we show that pyruvate dehydrogenase kinase (PDK)-2 plays a role in hypothalamic inflammation and its sequelae in mouse models of diabetes. Cell type-specific genetic ablation and pharmacological inhibition of PDK2 in hypothalamic astrocytes suggest that hypothalamic astrocytes are involved in the diabetic phenotype. We also show that the PDK2-lactic acid axis plays a regulatory role in the observed metabolic imbalance and hypothalamic inflammation in mouse primary astrocyte and organotypic cultures, through the AMPK signaling pathway and neuropeptidergic circuitry governing feeding behavior. Our findings reveal that PDK2 ablation or inhibition in mouse astrocytes attenuates diabetes-induced hypothalamic inflammation and subsequent alterations in feeding behavior. Hypothalamic inflammation is involved in the pathogenesis of diabetes. The underlying mechanisms are unclear. Here, the authors show that astrocytic PDK2 ablation or inhibition attenuates hypothalamic inflammation in mouse models of diabetes.
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Affiliation(s)
- Md Habibur Rahman
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science and Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Anup Bhusal
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science and Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Jae-Hong Kim
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science and Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Mithilesh Kumar Jha
- Department of Neurology, Johns Hopkins University, Baltimore, MD, 21205, USA
| | - Gyun Jee Song
- Department of Medical Science, College of Medicine, Catholic Kwandong University, Gangneung-si, Republic of Korea.,Translational Brain Research Center, International St. Mary's Hospital, Catholic Kwandong University, Incheon, Republic of Korea
| | - Younghoon Go
- Korean Medicine Application Center, Korea Institute of Oriental Medicine, Daegu, 41062, Republic of Korea
| | - Il-Sung Jang
- Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea.,Brain Science and Engineering Institute, Kyungpook National University, Daegu, 41944, Republic of Korea
| | - In-Kyu Lee
- Department of Internal Medicine, School of Medicine, Kyungpook National University Hospital, Daegu, 700-721, Republic of Korea.,Research Institute of Aging and Metabolism, Kyungpook National University, Daegu, 700-721, Republic of Korea
| | - Kyoungho Suk
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science and Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea. .,Brain Science and Engineering Institute, Kyungpook National University, Daegu, 41944, Republic of Korea.
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14
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Obesity Drives Delayed Infarct Expansion, Inflammation, and Distinct Gene Networks in a Mouse Stroke Model. Transl Stroke Res 2020; 12:331-346. [PMID: 32588199 DOI: 10.1007/s12975-020-00826-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/11/2020] [Accepted: 06/03/2020] [Indexed: 01/11/2023]
Abstract
Obesity is associated with chronic peripheral inflammation, is a risk factor for stroke, and causes increased infarct sizes. To characterize how obesity increases infarct size, we fed a high-fat diet to wild-type C57BL/6J mice for either 6 weeks or 15 weeks and then induced distal middle cerebral artery strokes. We found that infarct expansion happened late after stroke. There were no differences in cortical neuroinflammation (astrogliosis, microgliosis, or pro-inflammatory cytokines) either prior to or 10 h after stroke, and also no differences in stroke size at 10 h. However, by 3 days after stroke, animals fed a high-fat diet had a dramatic increase in microgliosis and astrogliosis that was associated with larger strokes and worsened functional recovery. RNA sequencing revealed a dramatic increase in inflammatory genes in the high-fat diet-fed animals 3 days after stroke that were not present prior to stroke. Genetic pathways unique to diet-induced obesity were primarily related to adaptive immunity, extracellular matrix components, cell migration, and vasculogenesis. The late appearance of neuroinflammation and infarct expansion indicates that there may be a therapeutic window between 10 and 36 h after stroke where inflammation and obesity-specific transcriptional programs could be targeted to improve outcomes in people with obesity and stroke.
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Jin S, Kim KK, Park BS, Kim DH, Jeong B, Kang D, Lee TH, Park JW, Kim JG, Lee BJ. Function of astrocyte MyD88 in high-fat-diet-induced hypothalamic inflammation. J Neuroinflammation 2020; 17:195. [PMID: 32560726 PMCID: PMC7304177 DOI: 10.1186/s12974-020-01846-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/19/2020] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND A growing body of evidence shows that hypothalamic inflammation is an important factor in the initiation of obesity. In particular, reactive gliosis accompanied by inflammatory responses in the hypothalamus are pivotal cellular events that elicit metabolic abnormalities. In this study, we examined whether MyD88 signaling in hypothalamic astrocytes controls reactive gliosis and inflammatory responses, thereby contributing to the pathogenesis of obesity. METHODS To analyze the role of astrocyte MyD88 in obesity pathogenesis, we used astrocyte-specific Myd88 knockout (KO) mice fed a high-fat diet (HFD) for 16 weeks or injected with saturated free fatty acids. Astrocyte-specific gene expression in the hypothalamus was determined using real-time PCR with mRNA purified by the Ribo-Tag system. Immunohistochemistry was used to detect the expression of glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, phosphorylated signal transducer and activator of transcription 3, and α-melanocyte-stimulating hormone in the hypothalamus. Animals' energy expenditure was measured using an indirect calorimetry system. RESULTS The astrocyte-specific Myd88 KO mice displayed ameliorated hypothalamic reactive gliosis and inflammation induced by injections of saturated free fatty acids and a long-term HFD. Accordingly, the KO mice were resistant to long-term HFD-induced obesity and showed an improvement in HFD-induced leptin resistance. CONCLUSIONS These results suggest that MyD88 in hypothalamic astrocytes is a critical molecular unit for obesity pathogenesis that acts by mediating HFD signals for reactive gliosis and inflammation.
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Affiliation(s)
- Sungho Jin
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
- Present address: Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Kwang Kon Kim
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Byong Seo Park
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
- Division of Life Sciences, College of Life Sciences and Bioengineering, Incheon National University, Incheon, 22012, Republic of Korea
| | - Dong Hee Kim
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Bora Jeong
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Dasol Kang
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Tae Hwan Lee
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Jeong Woo Park
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea
| | - Jae Geun Kim
- Division of Life Sciences, College of Life Sciences and Bioengineering, Incheon National University, Incheon, 22012, Republic of Korea.
| | - Byung Ju Lee
- Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Republic of Korea.
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Cargnin-Carvalho A, de Mello AH, Bressan JB, Backes KM, Uberti MF, Fogaça JB, da Rosa Turatti C, Cavalheiro EKFF, Vilela TC, Rezin GT. Can fructose influence the development of obesity mediated through hypothalamic alterations? J Neurosci Res 2020; 98:1662-1668. [PMID: 32524664 DOI: 10.1002/jnr.24628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 03/16/2020] [Accepted: 03/30/2020] [Indexed: 12/13/2022]
Abstract
Epidemiological data from the last decades point to an exponential growth in the number of obese people. Different behavioral factors, mainly associated with food consumption, appear to contribute significantly to its development. Concomitant with increased obesity rates, an increase in the consumption of fructose has been observed; therefore, fructose consumption has been implicated as an important obesogenic factor. However, changes in brain activity due to fructose consumption are possible, especially in relation to hypothalamic satiety mechanisms. In addition, the obese state may provide an environment of chronic inflammation and further contribute to the discontinuation of satiety mechanisms in the hypothalamus. We briefly review the intrinsic alterations to the increased adipose tissue, its connections with the hypothalamus in the control of energy signaling mechanisms and, consequently, the participation of fructose as a co-adjuvant or trigger. Presenting the current context with clinical trials involving human and animal studies, we seek to contribute to a better understanding of the role of fructose in the progression of obesity.
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Affiliation(s)
- Anderson Cargnin-Carvalho
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Aline Haas de Mello
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Joice Benedet Bressan
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Kassiane Mathiola Backes
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Marcela Fornari Uberti
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Jéssica Benedet Fogaça
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Cristini da Rosa Turatti
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Eulla Keimili Fernandes Ferreira Cavalheiro
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Thais Ceresér Vilela
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
| | - Gislaine Tezza Rezin
- Laboratory of Neurobiology of Inflammatory and Metabolic Processes, Postgraduate Program in Health Sciences, University of Southern Santa Catarina at Tubarão, Santa Catarina, Brazil
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Lee WH, Seo D, Lim SG, Suk K. Reverse Signaling of Tumor Necrosis Factor Superfamily Proteins in Macrophages and Microglia: Superfamily Portrait in the Neuroimmune Interface. Front Immunol 2019; 10:262. [PMID: 30838001 PMCID: PMC6389649 DOI: 10.3389/fimmu.2019.00262] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 01/30/2019] [Indexed: 12/14/2022] Open
Abstract
The tumor necrosis factor (TNF) superfamily (TNFSF) is a protein superfamily of type II transmembrane proteins commonly containing the TNF homology domain. The superfamily contains more than 20 protein members, which can be released from the cell membrane by proteolytic cleavage. Members of the TNFSF function as cytokines and regulate diverse biological processes, including immune responses, proliferation, differentiation, apoptosis, and embryogenesis, by binding to TNFSF receptors. Many TNFSF proteins are also known to be responsible for the regulation of innate immunity and inflammation. Both receptor-mediated forward signaling and ligand-mediated reverse signaling play important roles in these processes. In this review, we discuss the functional expression and roles of various reverse signaling molecules and pathways of TNFSF members in macrophages and microglia in the central nervous system (CNS). A thorough understanding of the roles of TNFSF ligands and receptors in the activation of macrophages and microglia may improve the treatment of inflammatory diseases in the brain and periphery. In particular, TNFSF reverse signaling in microglia can be exploited to gain further insights into the functions of the neuroimmune interface in physiological and pathological processes in the CNS.
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Affiliation(s)
- Won-Ha Lee
- BK21 Plus KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu, South Korea
| | - Donggun Seo
- BK21 Plus KNU Biomedical Convergence Program, Department of Pharmacology, School of Medicine, Brain Science & Engineering Institute, Kyungpook National University, Daegu, South Korea
| | - Su-Geun Lim
- BK21 Plus KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu, South Korea
| | - Kyoungho Suk
- BK21 Plus KNU Biomedical Convergence Program, Department of Pharmacology, School of Medicine, Brain Science & Engineering Institute, Kyungpook National University, Daegu, South Korea
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