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Lagou MK, Karagiannis GS. Obesity-induced thymic involution and cancer risk. Semin Cancer Biol 2023; 93:3-19. [PMID: 37088128 DOI: 10.1016/j.semcancer.2023.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 04/25/2023]
Abstract
Declining thymic functions associated either with old age (i.e., age-related thymic involution), or with acute involution as a result of stress, infectious disease, or cytoreductive therapies (e.g., chemotherapy/radiotherapy), have been associated with cancer development. A key mechanism underlying such increased cancer risk is the thymus-dependent debilitation of adaptive immunity, which is responsible for orchestrating immunoediting mechanisms and tumor immune surveillance. In the past few years, a blooming set of evidence has intriguingly linked obesity with cancer development and progression. The majority of such studies has focused on obesity-driven chronic inflammation, steroid/sex hormone and adipokine production, and hyperinsulinemia, as principal factors affecting the tumor microenvironment and driving the development of primary malignancy. However, experimental observations about the negative impact of obesity on T cell development and maturation have existed for more than half a century. Here, we critically discuss the molecular and cellular mechanisms of obesity-driven thymic involution as a previously underrepresented intermediary pathology leading to cancer development and progression. This knowledge could be especially relevant in the context of childhood obesity, because impaired thymic function in young individuals leads to immune system abnormalities, and predisposes to various pediatric cancers. A thorough understanding behind the molecular and cellular circuitries governing obesity-induced thymic involution could therefore help towards the rationalized development of targeted thymic regeneration strategies for obese individuals at high risk of cancer development.
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Affiliation(s)
- Maria K Lagou
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA; Tumor Microenvironment of Metastasis Program, Albert Einstein Cancer Center, Bronx, NY, USA
| | - George S Karagiannis
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA; Tumor Microenvironment of Metastasis Program, Albert Einstein Cancer Center, Bronx, NY, USA; Cancer Dormancy and Tumor Microenvironment Institute, Albert Einstein College of Medicine, Bronx, NY, USA; Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY, USA; Integrated Imaging Program for Cancer Research, Albert Einstein College of Medicine, Bronx, NY, USA.
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2
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Gotlieb N, Moeller J, Kriegsfeld LJ. Circadian Control of Neuroendocrine Function: Implications for Health and Disease. CURRENT OPINION IN PHYSIOLOGY 2018; 5:133-140. [PMID: 30957055 DOI: 10.1016/j.cophys.2018.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The circadian timing system orchestrates daily rhythms in physiology and behavior via the suprachiasmatic nucleus (SCN), the master brain clock. Because endocrine secretions have far-reaching influence on the brain and periphery, circadian regulation of hormones is essential for normal functioning and disruptions to circadian timing (e.g., irregular sleep patterns, limited exposure to sunlight, jet lag, nighttime light exposure) have detrimental health consequences. Herein, we provide an overview of circadian timing in three major endocrine axes, the hypothalamo-pituitary-gonadal (HPG), hypothalamo-pituitary-adrenal (HPA) and hypothalamo-pituitary-thyroid (HPT) axes, and then consider the negative health consequences of circadian disruptions in each of these systems. For example, disruptions to HPG axis circadian timing lead to a host of negative reproductive outcomes such as irregular menstrual cycles, low sperm density and increased rates of miscarriages and infertility. Dysregulation of HPA axis timing is associated with obesity and metabolic disease, whereas disruptions to the HPT axis are associated with dysregulated metabolic gene rhythms in the heart. Together, this overview underscores the significance of circadian endocrine rhythms in normal health and disease prevention.
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Affiliation(s)
- Neta Gotlieb
- Department of Psychology, University of California, Berkeley, CA, 94720
| | - Jacob Moeller
- Graduate Group in Endocrinology, University of California, Berkeley, CA 94720
| | - Lance J Kriegsfeld
- Department of Psychology, University of California, Berkeley, CA, 94720.,Graduate Group in Endocrinology, University of California, Berkeley, CA 94720.,The Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720
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Gilloteaux J, Subramanian K, Solomon N, Nicaise C. The leptin receptor mutation of the obese Zucker rat causes sciatic nerve demyelination with a centripetal pattern defect. Ultrastruct Pathol 2018; 42:377-408. [PMID: 30339059 DOI: 10.1080/01913123.2018.1522405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Young male Zucker rats with a leptin receptor mutation are obese, have a non-insulin-dependent diabetes mellitus (NIDDM), and other endocrinopathies. Tibial branches of the sciatic nerve reveal a progressive demyelination that progresses out of the Schwann cells (SCs) where electron-contrast deposits are accumulated while the minor lines or intermembranous SC contacts display exaggerated spacings. Cajal bands contain diversely contrasted vesicles adjacent to the abaxonal myelin layer with blemishes; they appear dispatched centripetally out of many narrow electron densities, regularly spaced around the myelin annulus. These anomalies widen and yield into sectors across the stacked myelin layers. Throughout the worse degradations, the adaxonal membrane remains along the axonal neuroplasm. This peripheral neuropathy with irresponsive leptin cannot modulate hypothalamic-pituitary-adrenal axis and SC neurosteroids, thus exacerbates NIDDM condition. Additionally, the ultrastructure of the progressive myelin alterations may have unraveled a peculiar, centripetal mode of trafficking maintenance of the peripheral nervous system myelin, while some adhesive glycoproteins remain between myelin layers, somewhat hindering the axon mutilation. Heading title: Peripheral neuropathy and myelin.
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Affiliation(s)
- Jacques Gilloteaux
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK.,b Unité de Recherche en Physiologie Moléculaire (URPhyM), Laboratoire de Neurodégénérescence et Régénération, Département de Médecine , Université de Namur , Namur , Belgium
| | - Kritika Subramanian
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK.,c Department of Clinical and Epidemiological Virology , Rega Institute of Medical Research, Katholiele Universiteit Leuven , Leuven , Belgium
| | - Nadia Solomon
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK
| | - Charles Nicaise
- b Unité de Recherche en Physiologie Moléculaire (URPhyM), Laboratoire de Neurodégénérescence et Régénération, Département de Médecine , Université de Namur , Namur , Belgium
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Nicolaides NC, Charmandari E, Kino T, Chrousos GP. Stress-Related and Circadian Secretion and Target Tissue Actions of Glucocorticoids: Impact on Health. Front Endocrinol (Lausanne) 2017; 8:70. [PMID: 28503165 PMCID: PMC5408025 DOI: 10.3389/fendo.2017.00070] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 03/24/2017] [Indexed: 12/13/2022] Open
Abstract
Living organisms are highly complex systems that must maintain a dynamic equilibrium or homeostasis that requires energy to be sustained. Stress is a state in which several extrinsic or intrinsic disturbing stimuli, the stressors, threaten, or are perceived as threatening, homeostasis. To achieve homeostasis against the stressors, organisms have developed a highly sophisticated system, the stress system, which provides neuroendocrine adaptive responses, to restore homeostasis. These responses must be appropriate in terms of size and/or duration; otherwise, they may sustain life but be associated with detrimental effects on numerous physiologic functions of the organism, leading to a state of disease-causing disturbed homeostasis or cacostasis. In addition to facing a broad spectrum of external and/or internal stressors, organisms are subject to recurring environmental changes associated with the rotation of the planet around itself and its revolution around the sun. To adjust their homeostasis and to synchronize their activities to day/night cycles, organisms have developed an evolutionarily conserved biologic system, the "clock" system, which influences several physiologic functions in a circadian fashion. Accumulating evidence suggests that the stress system is intimately related to the circadian clock system, with dysfunction of the former resulting in dysregulation of the latter and vice versa. In this review, we describe the functional components of the two systems, we discuss their multilevel interactions, and we present how excessive or prolonged activity of the stress system affects the circadian rhythm of glucocorticoid secretion and target tissue effects.
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Affiliation(s)
- Nicolas C. Nicolaides
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ’Aghia Sophia’ Children’s Hospital, Athens, Greece
- Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
- *Correspondence: Nicolas C. Nicolaides,
| | - Evangelia Charmandari
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ’Aghia Sophia’ Children’s Hospital, Athens, Greece
- Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Tomoshige Kino
- Division of Experimental Genetics, Sidra Medical and Research Center, Doha, Qatar
| | - George P. Chrousos
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, ’Aghia Sophia’ Children’s Hospital, Athens, Greece
- Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
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Kolbe I, Dumbell R, Oster H. Circadian Clocks and the Interaction between Stress Axis and Adipose Function. Int J Endocrinol 2015; 2015:693204. [PMID: 26000016 PMCID: PMC4426660 DOI: 10.1155/2015/693204] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 04/03/2015] [Accepted: 04/03/2015] [Indexed: 01/21/2023] Open
Abstract
Many physiological processes and most endocrine functions show fluctuations over the course of the day. These so-called circadian rhythms are governed by an endogenous network of cellular clocks and serve as an adaptation to daily and, thus, predictable changes in the organism's environment. Circadian clocks have been described in several tissues of the stress axis and in adipose cells where they regulate the rhythmic and stimulated release of stress hormones, such as glucocorticoids, and various adipokine factors. Recent work suggests that both adipose and stress axis clock systems reciprocally influence each other and adrenal-adipose rhythms may be key players in the development and therapy of metabolic disorders. In this review, we summarize our current understanding of adrenal and adipose tissue rhythms and clocks and how they might interact to regulate energy homoeostasis and stress responses under physiological conditions. Potential chronotherapeutic strategies for the treatment of metabolic and stress disorders are discussed.
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Affiliation(s)
- Isa Kolbe
- Chronophysiology Group, Medical Department I, University of Lübeck, 23538 Lübeck, Germany
| | - Rebecca Dumbell
- Chronophysiology Group, Medical Department I, University of Lübeck, 23538 Lübeck, Germany
| | - Henrik Oster
- Chronophysiology Group, Medical Department I, University of Lübeck, 23538 Lübeck, Germany
- *Henrik Oster:
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Leliavski A, Dumbell R, Ott V, Oster H. Adrenal Clocks and the Role of Adrenal Hormones in the Regulation of Circadian Physiology. J Biol Rhythms 2014; 30:20-34. [DOI: 10.1177/0748730414553971] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) and subordinate clocks that disseminate time information to various central and peripheral tissues. While the function of the SCN in circadian rhythm regulation has been extensively studied, we still have limited understanding of how peripheral tissue clock function contributes to the regulation of physiological processes. The adrenal gland plays a special role in this context as adrenal hormones show strong circadian secretion rhythms affecting downstream physiological processes. At the same time, they have been shown to affect clock gene expression in various other tissues, thus mediating systemic entrainment to external zeitgebers and promoting internal circadian alignment. In this review, we discuss the function of circadian clocks in the adrenal gland, how they are reset by the SCN and may further relay time-of-day information to other tissues. Focusing on glucocorticoids, we conclude by outlining the impact of adrenal rhythm disruption on neuropsychiatric, metabolic, immune, and malignant disorders.
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Affiliation(s)
- Alexei Leliavski
- Chronophysiology Group, Medical Department, University of Lübeck, Germany
| | - Rebecca Dumbell
- Chronophysiology Group, Medical Department, University of Lübeck, Germany
| | - Volker Ott
- Institute of Neuroendocrinology, University of Lübeck, Germany
| | - Henrik Oster
- Chronophysiology Group, Medical Department, University of Lübeck, Germany
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Alzoubi KH, Aleisa AM, Alkadhi KA. Expression of gLTP in sympathetic ganglia of obese Zucker rats in vivo: molecular evidence. J Mol Neurosci 2008; 35:297-306. [PMID: 18563301 DOI: 10.1007/s12031-008-9110-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 05/21/2008] [Indexed: 12/20/2022]
Abstract
Long-term potentiation in sympathetic ganglia (gLTP) is similar to LTP of the hippocampal area CA1 in that its expression involves similar changes in signaling molecules. We have shown previously that the stress-prone, hypertensive obese Zucker rats (OZR) expressed gLTP in sympathetic ganglia and that high blood pressure was reduced by treatment with 5-HT(3) receptor antagonists. In the present study, we present additional electrophysiological evidence for the pre-expression of gLTP in sympathetic ganglia from OZR indicated by failure of repetitive stimulation to express gLTP in isolated superior cervical ganglia (SCG) and inhibition of baseline ganglionic transmission by a 5-HT(3) receptor antagonist. We have also investigated the role of key signaling molecules in the expression of gLTP in the hypertensive OZR. Immunoblot analysis showed a significant increase in the levels of phosphorylated (P-)CaMKII and protein kinase C gamma (PKCgamma) in SCG from OZR. The ratio of P-CaMKII to the total CaMKII was markedly increased in OZR ganglia, suggesting increased phosphorylation of this molecule. Additionally, there was a significant decrease in the levels of calcineurin in ganglia. Furthermore, the neural nitric oxide synthase and hemeoxygenase II, which are essential for the expression of gLTP, were significantly elevated in OZR ganglia. The present findings confirm that ganglia from OZR have expressed gLTP and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade similar to that of LTP of the brain hippocampal area CA1.
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Affiliation(s)
- K H Alzoubi
- Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
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Dysfunctional nurturing behavior in rat dams with limited access to nesting material: a clinically relevant model for early-life stress. Neuroscience 2008; 154:1132-42. [PMID: 18501521 DOI: 10.1016/j.neuroscience.2008.04.019] [Citation(s) in RCA: 288] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 03/06/2008] [Accepted: 04/04/2008] [Indexed: 01/05/2023]
Abstract
BACKGROUND Early-life emotional stress may be associated with affective and cognitive disorders later in life, yet satisfactory animal models for studying the underlying mechanisms are limited. Because maternal presence and behavior critically influence molecular and behavioral stress responses in offspring, we sought to create a model of dysfunctional, fragmented maternal nurturing behavior that would, in turn, provoke chronic early-life stress in the offspring. METHODS Sprague-Dawley rat dams' nursing and nurturing behaviors were altered by limiting their ability to create satisfactory nests during postpartum days 2-9. Maternal behavior was observed throughout the diurnal cycle, and the frequency and duration of nurturing behaviors were scored. In addition, potential stress and anxiety of the dams were assessed using behavioral, molecular and hormonal measures. RESULTS Both the quantity and the quality of dams' care of their pups were profoundly influenced by restriction of nesting materials in their cages: licking/grooming activities decreased and the frequency of leaving the pups increased, resulting in fragmented interactions between the dams and pups. The abnormal activity patterns of the dams were accompanied by increased anxiety-like behavior in the open field, but not in the elevated plus maze tests. Additionally, dams' plasma corticosterone levels and adrenal weights were augmented, suggesting chronic stress of these dams. By the end of the limited-nesting, stress-inducing period, hypothalamic corticotropin releasing hormone (CRH) mRNA expression was reduced in the limited-nesting dams, while arginine-vasopressin (AVP) mRNA levels were not significantly affected. CONCLUSION Limiting dams' ability to construct a nest for their pups leads to an abnormal repertoire of nurturing behaviors, possibly as a result of chronic stress and mild anxiety of the dams. Because the fragmented and aberrant maternal behavior provoked chronic stress in the pups, the limited-nesting paradigm provides a useful tool for studying the mechanisms and consequences of such early-life stress experience in the offspring.
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Jöhren O, Dendorfer A, Dominiak P, Raasch W. Gene expression of mineralocorticoid and glucocorticoid receptors in the limbic system is related to type-2 like diabetes in leptin-resistant rats. Brain Res 2007; 1184:160-7. [PMID: 17945204 DOI: 10.1016/j.brainres.2007.09.036] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 09/13/2007] [Accepted: 09/18/2007] [Indexed: 11/28/2022]
Abstract
Diabetes is often accompanied by a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis which is regulated centrally via glucocorticoid (GR) and mineralocorticoid receptors (MR). Here, we compared the expression of both receptor subtypes in the brain of Zucker fatty and Zucker diabetic fatty (ZDF) rats together with their respective control rats. Both strains are primarily leptin resistant due to a mutated leptin receptor; ZDF rats, however, develop type-2 like diabetes. Using quantitative real-time PCR (qPCR) we found increased hypothalamic corticotrophin releasing hormone (CRH) levels in rats with the genetic ZDF background independently from leptin resistance. This was accompanied by elevated plasma corticosterone levels and by a higher reactivity of the HPA axis in response to CRH. Rats with the genetic ZDF background showed increased mRNA levels of GR in the amygdala and hypothalamus and increased mRNA levels of MR in the hippocampus and hypothalamus compared to rats with the Zucker fatty background. In leptin resistant ZDF rats but not in Zucker fatty rats, the mRNA levels of MR were selectively increased in the amygdala compared to nondiabetic control rats. No differences in the GR mRNA levels were found between leptin resistant Zucker fatty rats and lean control rats. Thus, an increased drive of the HPA axis in rats with ZDF background is associated with a differential expression of GR and MR in the limbic system. This dysregulation of the HPA axis may eventually lead, in combination with leptin resistance, to the development of diabetes in ZDF rats.
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Affiliation(s)
- Olaf Jöhren
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Ratzeburger Allee 160, D-23538, Lübeck, Germany.
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Alkadhi K, Alzoubi K. Role of long-term potentiation of sympathetic ganglia (gLTP) in hypertension. Clin Exp Hypertens 2007; 29:267-86. [PMID: 17653963 DOI: 10.1080/10641960701500356] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ganglionic long-term potentiation (gLTP) is an activity-dependent sustained increase in the synaptic efficacy of the nicotinic pathway that has been demonstrated in autonomic ganglia. Sustained enhancement in ganglionic transmission as in chronic mental stress may affect the activity of autonomic functions, including blood pressure and heart rate. An increase in sympathetic activity associated with psychosocial stress and stress-prone conditions such as obesity and aging could result in in vivo expression of gLTP leading to hypertension of a neural origin. Recent reports indicated that the prevention of the expression of gLTP in animal models of hypertension prevented or reduced high blood pressure. Although stress-induced hypertension normalizes within a few days of stress relief, prolonged mild-moderate hypertension may contribute to atherosclerotic cardiovascular diseases. The relation between hypertension and enhanced ganglionic transmission as a result of in vivo expression of gLTP is discussed in this review.
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Affiliation(s)
- Karim Alkadhi
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204-5515, USA.
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Müller H, Schweitzer N, Jöhren O, Dominiak P, Raasch W. Angiotensin II stimulates the reactivity of the pituitary-adrenal axis in leptin-resistant Zucker rats, thereby influencing the glucose utilization. Am J Physiol Endocrinol Metab 2007; 293:E802-10. [PMID: 17595220 DOI: 10.1152/ajpendo.00650.2006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The HPA axis is hyperactive under conditions of leptin and insulin resistance as well as after ANG II administration. We hypothesized that a hyperreactivity of the HPA axis to ANG contributes to an impaired glucose utilization in obesity, since leptin resistance and an overactive renin-angiotensin-aldosterone system are features of obesity. Zucker rats were treated with ANG via subcutaneous minipumps (0, 0.9, and 9.0 mug/h; 4 wk). PA axis reactivity and glucose homeostasis were characterized after CRH treatment and during an oral glucose tolerance test (OGTT). The elevated plasma profile of corticosterone after CRH stimulation in saline-treated OZR compared with LZR confirmed that the sensitization of the PA axis depended on leptin resistance. Irrespective of the rat strain, circulating ANG levels and blood pressure were selectively increased after administration of 9 mug/h ANG (high ANG). Only high ANG induced an elevation of the corticosterone and glucose response after CRH stimulation in OZR but did not affect the ACTH secretion. During OGTT, corticosterone and consequently glucose increased in OZR after high ANG, whereas the insulin secretion was decreased. In the adrenal glands of OZR, AT(1A) receptor mRNA levels increased after high ANG. We conclude that the impairment of glucose utilization after ANG stimulation is potentiated in leptin-resistant rats as a result of a hyperreactive PA axis, thereby confirming the functional importance of a dysregulation within the HPA axis in metabolic syndrome or obesity. The ACTH-independent stimulation of corticosterone release and the selective increase of AT(1A) receptor mRNA in the adrenals of OZR indicated a sensitization of adrenals toward ANG, causing a stimulation of the PA axis.
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Affiliation(s)
- Helge Müller
- Institute of Experimental and Clinical Pharmacology and Toxicology, University Clinic of Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
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Burén J, Bergström SA, Loh E, Söderström I, Olsson T, Mattsson C. Hippocampal 11beta-hydroxysteroid dehydrogenase type 1 messenger ribonucleic acid expression has a diurnal variability that is lost in the obese Zucker rat. Endocrinology 2007; 148:2716-22. [PMID: 17332068 DOI: 10.1210/en.2006-0897] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Circulating levels of glucocorticoids show a circadian rhythm. Obesity is associated with a flattening of the diurnal rhythm; plasma cortisol levels are slightly increased during the trough, although they are normal or low in the morning. Studies in humans and in leptin-resistant Zucker rats suggest that tissue-specific alterations in glucocorticoid exposure might play a key role for development of obesity and obesity-associated dysregulation of the hypothalamic-pituitary-adrenal axis. We hypothesized that there is a circadian rhythm in prereceptor metabolism of glucocorticoids exerted by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in brain and/or peripheral tissues (liver, fat, and muscle) that might be abrogated in obesity. The present study demonstrates a circadian rhythm in 11beta-HSD1 mRNA expression (35-45% increase at morning vs. evening, P < 0.05) in dentate gyrus granular layer and CA1 subregions of the hippocampus in lean Zucker rats that was lost in the obese rats. Sprague Dawley rats also revealed a diurnal rhythm in hippocampal 11beta-HSD1 mRNA expression. There was no circadian variation in 11beta-HSD enzyme activity in peripheral tissues, although obese Zucker rats had a decreased enzyme activity in liver and epididymal fat (by approximately 40%, P < 0.05) compared with lean rats. In Sprague Dawley rats, 11beta-HSD activity in adipose tissue was higher in retroperitoneal and epididymal vs. sc fat (P < 0.001). In summary, obese Zucker rats lack a circadian rhythm of 11beta-HSD1 gene expression in the hippocampus, which may contribute to increased activity of the hypothalamic-pituitary-adrenal axis and altered diurnal variation of circulating corticosterone levels.
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Affiliation(s)
- Jonas Burén
- Department of Public Health and Clinical Medicine, Umeå University Hospital, SE-901 85 Umeå, Sweden.
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Duclos M, Timofeeva E, Michel C, Richard D. Corticosterone-dependent metabolic and neuroendocrine abnormalities in obese Zucker rats in relation to feeding. Am J Physiol Endocrinol Metab 2005; 288:E254-66. [PMID: 15383369 DOI: 10.1152/ajpendo.00087.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The obese Zucker (fa/fa) rat is characterized by hyperphagia, hyperinsulinemia, an increase in fat deposition, and a hyperactivity in the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis in fa/fa rats is hypersensitive to stressful experimental conditions. Food deprivation even leads to a stress reaction in obese fa/fa rats. The present study was conducted to investigate the role of corticosterone in obese rats on the basal, fasting, and postprandial metabolic rate as well as on the central expression of the thyrotropin-releasing hormone (TRH) in these conditions. In addition, the study was aimed at clarifying whether the high levels of corticosterone in obese rats are responsible for the induction of the stress reaction to food deprivation in these animals. The present results demonstrate that whole body fat oxidation and postprandial metabolic responses in obese Zucker rats were improved by adrenalectomy (ADX). At the level of the central nervous system, ADX reversed a decrease in TRH mRNA expression in the paraventricular hypothalamus (PVH) detected in fasting animals. Considering all feeding conditions, the obese rats demonstrated lower TRH mRNA levels compared with lean animals. ADX resulted in an enhanced postprandial activation of the parvocellular PVH. In contrast, the magnocellular part of the PVH was less responsive to refeeding in ADX animals. Finally, ADX failed to prevent the stress response of obese rats to food deprivation. The present results provide evidence that the removal of adrenals resolve some of the metabolic defects encountered in obese Zucker rats. They also demonstrate that not all the abnormalities of the obese Zucker rats are attributable to the hyperactivity of the HPA axis.
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Affiliation(s)
- Martine Duclos
- Laboratoire Neurogénétique, Université Laval, Quebec, Canada
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Asensio C, Muzzin P, Rohner-Jeanrenaud F. Role of glucocorticoids in the physiopathology of excessive fat deposition and insulin resistance. Int J Obes (Lond) 2004; 28 Suppl 4:S45-52. [PMID: 15592486 DOI: 10.1038/sj.ijo.0802856] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Glucocorticoids are important hormones in the regulation of metabolic homeostasis. We infused normal rats with dexamethasone given intracerebroventricularly (i.c.v.) for 3 days. This resulted in hyperphagia, hyperinsulinemia, and marked insulin resistance. Similar metabolic defects were observed following i.c.v. infusion of neuropeptide Y (NPY) in normal rats. As central dexamethasone infusion enhanced NPY content in the arcuate nucleus, it suggested that its metabolic effects are mediated by NPY. Moreover, due to the lack of effects observed in vagotomized animals, activation of the parasympathetic nervous system by central dexamethasone infusion is proposed. Glucocorticoid action is known to involve prereceptor metabolism by enzymes such as 11beta-HSD-1 that converts inactive into active glucocorticoids. Mice overexpressing 11beta-HSD-1 in adipose tissue were shown to be obese and insulin resistant. We recently observed that adipose tissue 11beta-HSD-1 mRNA expression is increased at the onset of high-fat diet-induced obesity and positively correlated with the degree of hyperglycemia. In human obesity, increased adipose tissue 11beta-HSD-1 expression and activity were also reported. Resistin is a new adipose tissue-secreted hormone shown to play a role in glucose homeostasis by increasing hepatic glucose production and inhibiting muscle and adipose tissue glucose utilization. We observed increased adipose tissue resistin expression in the early phase of high-fat diet-induced obesity as well as decreased resistin expression in response to leptin. A positive correlation between glycemia and adipose tissue resistin expression further suggested a role of this hormone in the development of insulin resistance. The melanocortin system is another important player in the regulation of energy balance. Peripheral administration of a melanocortin agonist decreased food intake and body weight and favored lipid oxidation, effects that were more marked in obese than in lean rats. It is proposed that both resistin and melanocortin agonists may influence adipose tissue 11beta-HSD-1, thereby decreasing or enhancing glucose metabolism.
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Affiliation(s)
- C Asensio
- Laboratory of Metabolism, Department of Internal Medicine, Department of Cell Biology and Metabolism, Faculty of Medicine, University of Geneva, Switzerland
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Mattsson C, Lai M, Noble J, McKinney E, Yau JL, Seckl JR, Walker BR. Obese Zucker rats have reduced mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type 1 expression in hippocampus-implications for dysregulation of the hypothalamic-pituitary-adrenal axis in obesity. Endocrinology 2003; 144:2997-3003. [PMID: 12810555 DOI: 10.1210/en.2002-221015] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Obese Zucker rats have elevated basal corticosterone levels and an increased stress response suggestive of an increased activity of the hypothalamic-pituitary-adrenal (HPA) axis. We hypothesized that altered central expression of glucocorticoid receptors (GR), mineralocorticoid receptors (MR), and/or 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) contribute to these changes. In brains from young adult male rats, in situ hybridization and Western blotting showed that obese rats had normal hippocampal GR mRNA and protein levels. In contrast, in obese rats, 11betaHSD1 mRNA levels were reduced in a subpopulation of hippocampal cells in the main neuronal layers (by 37-47%, P < 0.05), whereas 11betaHSD1 levels in sparse high-expressing cells did not differ. MR mRNA was decreased in all regions of the hippocampus (by 37-49%, P < 0.05 for CA1-2 and P < 0.01 for dentate gyrus) and in frontal cortex (by 16%, P < 0.05) in obese rats. In whole hippocampal homogenates, however, neither the protein concentration of MR by Western blot nor activity of 11betaHSD1 was measurably different between the phenotypes. To test the functional importance of lower central MR expression, groups of lean and obese rats were given spironolactone before restraint stress. In vehicle-treated animals, obese rats had higher plasma corticosterone levels than lean rats after stress (by ANOVA, P < 0.05). Spironolactone markedly increased the corticosterone response in both groups, but the incremental rise was smaller in the obese rats, so that spironolactone abolished the differences between groups. We conclude that lower levels of MR, but not GR, contribute to the increased HPA activity in the obese Zucker rats and that this seems more influential during stress than in the basal state. This may be exacerbated by impaired local regeneration of corticosterone by 11betaHSD1. These abnormalities could contribute to the subtle changes in the HPA axis in rodent and human obesity.
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Affiliation(s)
- Cecilia Mattsson
- Endocrinology Unit, Department of Medical Sciences, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, Scotland, United Kingdom
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Vicennati V, Ceroni L, Gagliardi L, Gambineri A, Pasquali R. Comment: response of the hypothalamic-pituitary-adrenocortical axis to high-protein/fat and high-carbohydrate meals in women with different obesity phenotypes. J Clin Endocrinol Metab 2002; 87:3984-8. [PMID: 12161547 DOI: 10.1210/jcem.87.8.8718] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Subjects with abdominal obesity are characterized by hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis. Food intake, particularly at noon, is a well-known inducer of HPA axis activation. Whether obese subjects present an abnormal response to meals containing different macronutrient proportions is at present unknown. Therefore, this study was carried out to investigate the effect of a high-lipid/protein meal (HLP-meal) and a high-carbohydrate meal (HCHO-meal) on the HPA axis activity in women with different obesity phenotypes. Nondepressed, noncomplicated obese (body mass index greater than 28 kg/m(2)) women with abdominal (A-BFD) (n = 10) and peripheral body fat distribution (P-BFD) (n = 9) and a group of 11 normal-weight controls were investigated in the follicular phase of the menstrual cycle. They were randomly given an 800-kcal HCHO-meal (containing 89% carbohydrates, 11% proteins, 0% lipids), and an 800-kcal HLP-meal (containing 53% lipids, 43% proteins, 4% carbohydrates), which were eaten within 15 min at noon, with an interval of 2 d between each meal. Blood samples for ACTH, cortisol, glucose, and insulin were obtained at 15-min intervals before and after each meal. Baseline hormone and glucose concentrations in the three groups were similar. After the HLP-meal, ACTH tended to similarly but insignificantly increase in all groups, whereas cortisol increased significantly (P < 0.05) in the P-BFD group and insignificantly in the other groups. Conversely, both ACTH and cortisol significantly (P < 0.05) increased only in the A-BFD group, without any significant changes in both controls and P-BFD women. The analysis of the interaction between meals and groups clearly indicated that the cortisol response to the HLP-meal and the HCHO-meal was significantly different (P < 0.025) between the two obese groups, the A-BFD group being characterized by a significantly lower response to the HLP-meal and a significantly higher response to the HCHO-meal, compared with the P-BFD group. Considering all groups together and after adjusting for body mass index, a highly significant relationship was found between cortisol-area under the curve and ACTH-area under the curve after each meal test. However, no relationships were found between changes in ACTH and cortisol and those of glucose, insulin, and the glucose:insulin ratio after each meal. Therefore, our data demonstrate that the response of the HPA axis to meals containing different macronutrient proportions may depend on the pattern of body fat distribution. We also suggest that the activation of the HPA axis following the ingestion of large amounts of carbohydrates may have some pathophysiological relevance, specifically in women with the abdominal obesity phenotype.
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Affiliation(s)
- Valentina Vicennati
- Endocrine Unit, Department of Internal Medicine and Gastroenterology, S. Orsola-Malpighi Hospital, University Alma Mater of Bologna, 40138 Bologna, Italy
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del Mar Grasa M, Cabot C, Adán C, de Matteis R, Esteve M, Cinti S, Fernández JA, Remesar X, Alemany A. Corticosteroid-binding globulin synthesis and distribution in rat white adipose tissue. Mol Cell Biochem 2001; 228:25-31. [PMID: 11855738 DOI: 10.1023/a:1013304223967] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Corticosterone binding (CB) capacity was determined in visceral and subcutaneous white adipose tissue (WAT), as well as in plasma of lean Zucker rats. Perfusion of rats with saline eliminated most liver and kidney corticosterone binding but did not affect CB in WAT. The cytosol extracts of isolated cells, however, did not bind corticosterone in detectable amounts. By means of a RT-PCR procedure it was found that corticosterone-binding globulin (CBG) was expressed in WAT. By immunohistochemical detection in WAT sections, CBG was seen in a thin layer surrounding the cells near the plasma membrane. These data suggest that the CBG layer surrounding the cells may act as a protective barrier limiting the access of glucocorticoids to adipocytes.
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Affiliation(s)
- M del Mar Grasa
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Spain
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Pasquali R, Vicennati V, Calzoni F, Gnudi U, Gambineri A, Ceroni L, Cortelli P, Menozzi R, Sinisi R, Rio GD. alpha2-adrenoceptor regulation of the hypothalamic-pituitary-adrenocortical axis in obesity. Clin Endocrinol (Oxf) 2000; 52:413-21. [PMID: 10762283 DOI: 10.1046/j.1365-2265.2000.00871.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Abdominal obesity is associated with hyper-responsiveness of the hypothalamic-pituitary-adrenocortical (HPA) axis to stimulatory neuropeptides and to stress. Catecholamines are involved in the regulation of the HPA axis, particularly during stress, via alpha-adrenoceptor modulation. DESIGN In this study, we investigated the effects of pre-treatment with an alpha2-adrenoceptor agonist, clonidine (2 microg/kg over 10 minutes) and antagonist, yohimbine (0.125 mg/kg bolus, followed by 0. 001 mg/kg/minutes per 90 minutes infusion) on the HPA axis, measured by ACTH and cortisol response to combined CRH (human, 100 microg) plus AVP (0.3 IU) administration, and on noradrenalin (NA) and adrenalin (A) blood levels, in a group of obese women with abdominal (A-BFD) or peripheral (P-BFD) body fat distribution and in nonobese controls. RESULTS During the control CRH + AVP test the ACTH but not the cortisol response was higher (P < 0.05) in obese A-BFD women than in controls, with minor and transient variations of NA levels. Neither the control test nor clonidine or yohimbine influenced basal or post CRH + AVP A concentrations. Clonidine pretreatment similarly and significantly decreased NA levels in all women and, compared to the control test, marginally influenced the ACTH response to CRH + AVP. Conversely, during yohimbine infusion NA levels steadily and similarly increased to values more or less double baseline values in all groups. Compared to the control test, however, the ACTH response to the CRH + AVP test performed during yohimbine infusion significantly decreased in the control subjects whereas a tendency to a further increase occurred in the obese groups and, specifically, in the A-BFD group significantly (P < 0.05) more than in the P-BFD group. CONCLUSIONS This study shows that alpha2-adrenoceptor regulation of the HPA axis is different in obese and nonobese women, particularly in stressed conditions. We suggest that the abnormal ACTH response to CRH + AVP challenge with increased noradrenergic tone may represent a specific pathophysiological aspect of the abnormal response to stress or to other specific stimulatory factors in obese women, particularly those with abdominal body fat distribution.
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Affiliation(s)
- R Pasquali
- Endocrinology Section, Department of Internal Medicine & Gastroenterology, S. Orsola-Malpighi Hospital, Bologna, Italy.
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Livingstone DE, Jones GC, Smith K, Jamieson PM, Andrew R, Kenyon CJ, Walker BR. Understanding the role of glucocorticoids in obesity: tissue-specific alterations of corticosterone metabolism in obese Zucker rats. Endocrinology 2000; 141:560-3. [PMID: 10650936 DOI: 10.1210/endo.141.2.7297] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The role of glucocorticoids in obesity is poorly understood. Observations in obese men suggest enhanced inactivation of cortisol by 5alpha-reductase and altered reactivation of cortisone to cortisol by 11betahydroxysteroid dehydrogenase type 1 (11betaHSD1). These changes in glucocorticoid metabolism may influence corticosteroid receptor activation and feedback regulation of the hypothalamic-pituitary-adrenal axis (HPA). We have compared corticosterone metabolism in vivo and in vitro in male obese and lean Zucker rats, aged 9 weeks (n = 8/group). Steroids were measured in 72-h urine and 0900 h trunk blood samples. 5alpha-Reductase type 1 and 11betaHSD activities were assessed in dissected tissues. Obese animals were hypercorticosteronemic and excreted more total corticosterone metabolites (2264+/-623 vs. 388+/-144 ng/72 h; P = 0.003), with a greater proportion being 5alpha-reduced or 11-oxidized. 11-Dehydrocorticosterone was also elevated in plasma (73+/-9 vs. 18+/-2 nM; P = 0.001) and urine (408+/-111 vs. <28 ng/72 h; P = 0.01). In liver of obese rats, 5alpha-reductase type 1 activity was greater (20.6+/-2.7% vs. 14.1+/-1.5%; P<0.04), but 11betaHSD1 activity (maximum velocity, 3.43+/-0.56 vs. 6.57+/-1.13 nmol/min/mg protein; P = 0.01) and messenger RNA levels (0.56+/-0.08 vs. 1.03+/-0.15; P = 0.02) were lower. In contrast, in obese rats, 11betaHSD1 activity was not different in skeletal muscle and sc fat and was higher in omental fat(36.4+/-6.2 vs. 19.2+/-6.6; P = 0.01), whereas 11betaHSD2 activity was higher in kidney (16.7+/-0.6% vs. 11.3+/-1.5%; p = 0.01). We conclude that greater inactivation of glucocorticoids by 5alpha-reductase in liver and 11betaHSD2 in kidney combined with impaired reactivation of glucocorticoids by 11betaHSD1 in liver may increase the MCR of glucocorticoids and decrease local glucocorticoid concentrations at these sites. By contrast, enhanced 11betaHSD1 in omental adipose tissue may increase local glucocorticoid receptor activation and promote obesity.
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Affiliation(s)
- D E Livingstone
- Department of Medical Sciences, University of Edinburgh, Western General Hospital, United Kingdom
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Abstract
The postnatal limbic-hypothalamic-pituitary-adrenal (LHPA) axis in the rodent is remarkably different from the adult, both in structure and function. The first 2 weeks postnatally are characterized by a 'silent period' during which the developing animal is hyporesponsive to stress (stress hyporesponsive period-SHRP), followed by a new and unique phase of stress responsiveness when the animal fails to swiftly terminate glucocorticoid secretion. In this review, we summarize our work which focuses on the regulatory biology of the components of the LHPA system and the consequences of its disruption on the adaptive responses of the developing organism. We find that the animal during the first 2 weeks of life responds to an intermittent chronic challenge increasing anterior pituitary POMC post-translational events, while the adult increases genomic events. The result for both the mature and the developing animal is the same, an increase in corticosterone (CS) levels. In addition, we have found evidence of impaired rate sensitive feedback in the weanling animal, as well as changes in ACTH clearance. Similar to the young animal emerging from SHRP, maternally deprived pups during the first week of life exhibit a substantial and sustained ACTH and CS response to stress. In the deprived animal these changes are accompanied by decreases in mineralocorticoid receptor gene expression in the hippocampus, suggesting that changes in mineralocorticoid to glucocorticoid receptor ratios may be important in this phenomena. What has become evident from our studies is that mechanisms underlying normal LHPA development are dynamic, age dependent and distinct to the strategies used by the mature organism to cope with stress.
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Affiliation(s)
- D M Vázquez
- Mental Health Research Institute, University of Michigan, Ann Arbor 48109-0646, USA.
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Arvaniti K, Deshaies Y, Richard D. Effect of leptin on energy balance does not require the presence of intact adrenals. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:R105-11. [PMID: 9688967 DOI: 10.1152/ajpregu.1998.275.1.r105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The present study was conducted to assess the effects of leptin on food intake and energy balance in the presence or absence of corticosterone. Three cohorts of C57BL/6 mice differing in their corticosterone status [nonadrenalectomized (intact), adrenalectomized (ADX), and ADX with corticosterone replacement] were infused with either saline or leptin at a dose of 150 microg . kg-1 . day-1. Throughout the study, mice had free access to both a high-starch and a high-fat diet. At the end of the experimental period, mice were decapitated and their carcasses were processed for the determination of energy, protein, and lipid contents. Leptin significantly reduced body gains in weight, fat, and energy, whereas corticosterone therapy significantly promoted all of these gains. Leptin and ADX significantly reduced food intake and gross energetic efficiency, whereas corticosterone therapy significantly increased these variables. The effects of leptin, ADX, and corticosterone on food intake were accounted for by changes in the intake of the high-fat diet. Leptin also attenuated the preference for fat that developed quickly in mice simultaneously exposed to the high-starch and high-fat regimen. Altogether, the results of this study 1) emphasize the abilities of leptin and corticosterone to, respectively, decrease and increase energy deposition and ingestion of fat, 2) do not substantiate any leptin-corticosterone interaction in the regulation of energy balance, and 3) demonstrate that leptin can produce its effect on energy and fat gains in the absence of an intact hypothalamic-pituitary-adrenal axis.
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Affiliation(s)
- K Arvaniti
- Département de Physiologie, Faculté de Médecine, Université Laval, Quebec, Canada G1K 7P4
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Leal AM, Moreira AC. Food and the circadian activity of the hypothalamic-pituitary-adrenal axis. Braz J Med Biol Res 1997; 30:1391-405. [PMID: 9686157 DOI: 10.1590/s0100-879x1997001200003] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Temporal organization is an important feature of biological systems and its main function is to facilitate adaptation of the organism to the environment. The daily variation of biological variables arises from an internal time-keeping system. The major action of the environment is to synchronize the internal clock to a period of exactly 24 h. The light-dark cycle, food ingestion, barometric pressure, acoustic stimuli, scents and social cues have been mentioned as synchronizers or "zeitgebers". The circadian rhythmicity of plasma corticosteroids has been well characterized in man and in rats and evidence has been accumulated showing daily rhythmicity at every level of the hypothalamic-pituitary-adrenal (HPA) axis. Studies of restricted feeding in rats are of considerable importance because they reveal feeding as a major synchronizer of rhythms in HPA axis activity. The daily variation of the HPA axis stress response appears to be closely related to food intake as well as to basal activity. In humans, the association of feeding and HPA axis activity has been studied under physiological and pathological conditions such as anorexia nervosa, bulimia, malnutrition, obesity, diabetes mellitus and Cushing's syndrome. Complex neuroanatomical pathways and neurochemical circuitry are involved in feeding-associated HPA axis modulation. In the present review we focus on the interaction among HPA axis rhythmicity, food ingestion, and different nutritional and endocrine states.
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Affiliation(s)
- A M Leal
- Divisão de Endocrinologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brasil
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Vázquez DM, Van Oers H, Levine S, Akil H. Regulation of glucocorticoid and mineralocorticoid receptor mRNAs in the hippocampus of the maternally deprived infant rat. Brain Res 1996; 731:79-90. [PMID: 8883857 DOI: 10.1016/0006-8993(96)00465-9] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The hypothalamic-pituitary-adrenal (HPA) axis in the developing rat has a limited response to acute challenges between days 3 and 14 of life. Several hypotheses have been proposed to explain this quiescent state. Immaturity of brain, pituitary and adrenal elements or excessive feedback inhibition are common explanations. Recently, a series of studies by Levine and co-workers has shown that prolonged maternal deprivation (24 h) results in increased basal and stress induced corticosterone (CS) levels. An increased adrenal response to ACTH along with an enhanced and sustained ACTH response have been implicated in this phenomenon. A brain structure that appears to be important for normal HPA function is the hippocampus, a structure rich in corticosteroid receptors, which has been hypothesized to play a role in the basal tone of the HPA and in the magnitude and duration of stress responses. Thus, to study further the possible mechanisms leading to an enhanced and sustained ACTH response that is seen in maternally deprived pups, we used in situ hybridization to investigate hippocampal mineralocorticoid (MR) and glucocorticoid receptor (GR) gene expression in 12 groups of animals: six groups involved 24 h maternally deprived (DEP) and non-deprived (NDEP) rat pups at three ages (6-, 9-, and 12-days-old); the other six groups included pups similarly treated, but challenged with an exposure to a mild stressor (saline injection) and sacrificed 1 h thereafter. We found: (1) an age effect for almost every hippocampal subfield for both MR and GR mRNAs: MR increases with age, while GR decreases: (2) down-regulation of MR mRNA in CA1 region in the DEP animals; and (3) down-regulation of GR mRNA, also in CA1, in the saline-injected DEP and NDEP animals. Our results indicate that corticoid receptors in the developing CA1 hippocampal region appear to be sensitive to circulating CS. They also suggest that the relative ratio of GR and MR in the CA1 region may contribute to the enhanced and sustained CS response seen after a mild stressor in deprived animals.
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Affiliation(s)
- D M Vázquez
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109-0720, USA
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Mistry AM, Helferich W, Romsos DR. Elevated neuronal c-Fos-like immunoreactivity and messenger ribonucleic acid (mRNA) in genetically obese (ob/ob) mice. Brain Res 1994; 666:53-60. [PMID: 7889367 DOI: 10.1016/0006-8993(94)90281-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Adult genetically obese (ob/ob) mice display a number of metabolic alterations, the primary cause of which may be a defect in their central nervous system (CNS). The protein encoded by the protooncogene c-fos, c-Fos, functions as a nuclear transcription factor, and also serves as a marker of neuronal activity. The specific objectives of this study were (1) to use c-Fos immunohistochemistry to identify regions with altered neuronal activity in 6-7 week old male lean and ob/ob mice; (2) to examine c-fos relative mRNA abundance by northern blot analysis in brains of these mice and compare it with that of neuropeptide Y (NPY), a peptide well known to alter feeding and (3) determine changes in c-Fos immunoreactivity and mRNA caused by food deprivation. Fos-like immunoreactivity (FLI) tended to be higher in ad libitum fed ob/ob mice than in lean controls in most brain regions examined. The most prominent and consistent differences were in the paraventricular nuclei (PVN) where the numbers of Fos-positive nuclei were approximately 3 fold higher in ob/ob mice. Food deprivation for 24 h increased FLI in the PVN in lean mice but did not further augment FLI in the PVN of ob/ob mice. Arcuate nuclei of lean and ob/ob mice showed minimal FLI staining under ad libitum fed conditions. Food deprivation however, induced FLI in arcuate nuclei of both lean and ob/ob mice. The abundance of c-fos mRNA in whole brain of ob/ob mice averaged several fold higher than in leans under both fed and fasted conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A M Mistry
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing 48824-1224
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