151
|
Abstract
The chaperone GRP78 (glucose related protein 78), also called BiP (binding immunoglobulin protein) is a key regulator of endoplasmic reticulum (ER) stress. We recently described that over-expression of GRP78 specifically in the ventromedial nucleus of the hypothalamus (VMH) releases hypothalamic ER stress in rodent obese models leading to weight loss, reduced hepatic steatosis and improved insulin and leptin sensitivity. The action of GRP78 is mediated by a feeding-independent mechanism involving increased sympathetic tone, augmented brown adipose tissue (BAT) thermogenesis and induction browning of white adipose tissue (WAT).
Collapse
Affiliation(s)
- Cristina Contreras
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela, -Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - Marcos F. Fondevila
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela, -Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - Miguel López
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela, -Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| |
Collapse
|
152
|
Laperrousaz E, Denis RG, Kassis N, Contreras C, López M, Luquet S, Cruciani-Guglielmacci C, Magnan C. Lipoprotein Lipase Expression in Hypothalamus Is Involved in the Central Regulation of Thermogenesis and the Response to Cold Exposure. Front Endocrinol (Lausanne) 2018; 9:103. [PMID: 29593657 PMCID: PMC5861133 DOI: 10.3389/fendo.2018.00103] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/02/2018] [Indexed: 11/15/2022] Open
Abstract
Lipoprotein lipase (LPL) is expressed in different areas of the brain, including the hypothalamus and plays an important role in neural control of the energy balance, including feeding behavior and metabolic fluxes. This study tested the hypothesis that hypothalamic LPL participates in the control of body temperature. We first showed that cold exposure induces decreased activity and expression of LPL in the mouse hypothalamus. We then selectively deleted LPL in the mediobasal hypothalamus (MBH) through an adeno-associated virus approach in LPL-floxed mice and generated MBHΔ Lpl mice with 30-35% decrease in hypothalamic LPL activity. Results showed a decrease in body temperature in MBHΔ Lpl mice when compared with controls at 22°C. Exposure to cold (4°C for 4 h) decreased the body temperature of the control mice while that of the MBHΔ Lpl mice remained similar to that observed at 22°C. MBHΔ Lpl mice also showed increased energy expenditure during cold exposure, when compared to controls. Finally, the selective MBH deletion of LPL also increased the expression of the thermogenic PRMD16 and Dio2 in subcutaneous and perigonadal adipose tissues. Thus, the MBH LPL deletion seems to favor thermogenesis. These data demonstrate that for the first time hypothalamic LPL appears to function as a regulator of body temperature and cold-induced thermogenesis.
Collapse
Affiliation(s)
- Elise Laperrousaz
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| | - Raphaël G Denis
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| | - Nadim Kassis
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| | - Cristina Contreras
- NeurObesity Group, Department of Physiology, Centro de Investigación en Medicina Molecular y Enfermedades Crónicas (CiMUS), University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - Miguel López
- NeurObesity Group, Department of Physiology, Centro de Investigación en Medicina Molecular y Enfermedades Crónicas (CiMUS), University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - Serge Luquet
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| | - Céline Cruciani-Guglielmacci
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| | - Christophe Magnan
- Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, Sorbonne Paris Cité, Université Denis Diderot, Paris, France
| |
Collapse
|
153
|
Louzada RA, Carvalho DP. Similarities and Differences in the Peripheral Actions of Thyroid Hormones and Their Metabolites. Front Endocrinol (Lausanne) 2018; 9:394. [PMID: 30072951 PMCID: PMC6060242 DOI: 10.3389/fendo.2018.00394] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 06/26/2018] [Indexed: 01/16/2023] Open
Abstract
Thyroxine (T4) and 3,5,3'-triiodothyronine (T3) are secreted by the thyroid gland, while T3 is also generated from the peripheral metabolism of T4 by iodothyronine deiodinases types I and II. Several conditions like stress, diseases, and physical exercise can promote changes in local TH metabolism, leading to different target tissue effects that depend on the presence of tissue-specific enzymatic activities. The newly discovered physiological and pharmacological actions of T4 and T3 metabolites, such as 3,5-diiodothyronine (3,5-T2), and 3-iodothyronamine (T1AM) are of great interest. A classical thyroid hormone effect is the ability of T3 to increase oxygen consumption in almost all cell types studied. Approximately 30 years ago, a seminal report has shown that 3,5-T2 increased oxygen consumption more rapidly than T3 in hepatocytes. Other studies demonstrated that exogenous 3,5-T2 administration was able to increase whole body energy expenditure in rodents and humans. In fact, 3,5-T2 treatment prevents diabetic nephropathy, hepatic steatosis induced by high fat diet, insulin resistance, and weight gain during aging in Wistar male rats. The regulation of mitochondria is likely one of the most important actions of T3 and its metabolite 3,5-T2, which was able to restore the thermogenic program of brown adipose tissue (BAT) in hypothyroid rats, just as T3 does, while T1AM administration induced rapid hypothermia. T3 increases heart rate and cardiac contractility, which are hallmark effects of hyperthyroidism involved in cardiac arrhythmia. These deleterious cardiac effects were not observed with the use of 3,5-T2 pharmacological doses, and in contrast T1AM was shown to promote a negative inotropic and chronotropic action at micromolar concentrations in isolated hearts. Furthermore, T1AM has a cardioprotective effect in a model of ischemic/reperfusion injury in isolated hearts, such as occurs with T3 administration. Despite the encouraging possible therapeutic use of TH metabolites, further studies are needed to better understand their peripheral effects, when compared to T3 itself, in order to establish their risk and benefit. On this basis, the main peripheral effects of thyroid hormones and their metabolites in tissues, such as heart, liver, skeletal muscle, and BAT are discussed herein.
Collapse
|
154
|
Cioffi F, Gentile A, Silvestri E, Goglia F, Lombardi A. Effect of Iodothyronines on Thermogenesis: Focus on Brown Adipose Tissue. Front Endocrinol (Lausanne) 2018; 9:254. [PMID: 29875734 PMCID: PMC5974034 DOI: 10.3389/fendo.2018.00254] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/03/2018] [Indexed: 02/05/2023] Open
Abstract
Thyroid hormones significantly influence energy expenditure by affecting the activity of metabolic active tissues, among which, mammalian brown adipose tissue (BAT) plays a significant role. For a long time, the modulation of BAT activity by 3,3',5-triiodo-l-thyronine (T3) has been ascribed to its direct actions on this tissue; however, recent evidence indicates that T3, by stimulating specific brain centers, activates the metabolism of BAT via the sympathetic nervous system. These distinct mechanisms of action are not mutually exclusive. New evidence indicates that 3,5-diiodo-l-thyronine (3,5-T2), a thyroid hormone derivative, exerts thermogenic effects, by influencing mitochondrial activity in metabolically active tissues, such as liver, skeletal muscle, and BAT. At the moment, due to the absence of experiments finalized to render a clear cut discrimination between peripheral and central effects induced by 3,5-T2, it is not possible to exclude that some of the metabolic effects exerted by 3,5-T2 may be mediated centrally. Despite this, some evidence suggests that 3,5-T2 plays a role in adrenergic stimulation of thermogenesis in BAT. This mini-review provides an overview of the effects induced by T3 and 3,5-T2 on BAT thermogenesis, with a focus on data suggesting the involvement of central adrenergic stimulation. These aspects may reveal new perspectives in thyroid physiology and in the control of energy metabolism.
Collapse
Affiliation(s)
- Federica Cioffi
- Department of Sciences and Technologies, University of Sannio, Benevento, Italy
| | | | - Elena Silvestri
- Department of Sciences and Technologies, University of Sannio, Benevento, Italy
| | - Fernando Goglia
- Department of Sciences and Technologies, University of Sannio, Benevento, Italy
- *Correspondence: Fernando Goglia, ; Assunta Lombardi,
| | - Assunta Lombardi
- Department of Biology, University of Naples Federico II, Naples, Italy
- *Correspondence: Fernando Goglia, ; Assunta Lombardi,
| |
Collapse
|
155
|
Cunarro J, Casado S, Lugilde J, Tovar S. Hypothalamic Mitochondrial Dysfunction as a Target in Obesity and Metabolic Disease. Front Endocrinol (Lausanne) 2018; 9:283. [PMID: 29904371 PMCID: PMC5990598 DOI: 10.3389/fendo.2018.00283] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 05/14/2018] [Indexed: 01/06/2023] Open
Abstract
Mitochondria are important organelles for the adaptation to energy demand that play a central role in bioenergetics metabolism. The mitochondrial architecture and mitochondrial machinery exhibits a high degree of adaptation in relation to nutrient availability. On the other hand, its disruption markedly affects energy homeostasis. The brain, more specifically the hypothalamus, is the main hub that controls energy homeostasis. Nevertheless, until now, almost all studies in relation to mitochondrial dysfunction and energy metabolism have focused in peripheral tissues like brown adipose tissue, muscle, and pancreas. In this review, we highlight the relevance of the hypothalamus and the influence on mitochondrial machinery in its function as well as its consequences in terms of alterations in both energy and metabolic homeostasis.
Collapse
Affiliation(s)
- Juan Cunarro
- Departamento de Fisioloxía and Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela, Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Madrid, Spain
| | - Sabela Casado
- Departamento de Fisioloxía and Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela, Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), Santiago de Compostela, Spain
| | - Javier Lugilde
- Departamento de Fisioloxía and Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela, Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), Santiago de Compostela, Spain
| | - Sulay Tovar
- Departamento de Fisioloxía and Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela, Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Madrid, Spain
- *Correspondence: Sulay Tovar,
| |
Collapse
|
156
|
Abstract
Hypothalamic AMPK plays a key role in the control of energy homeostasis by regulating energy intake and energy expenditure, particularly modulating brown adipose tissue (BAT) thermogenesis. The function of AMPK can be assayed by analyzing its phosphorylated protein levels in tissues, since AMPK is activated when it is phosphorylated at Thr-172. Here, we describe a method to obtain hypothalamic (nuclei-specific) protein extracts and the suitable conditions to assay AMPK phosphorylation by Western blotting.
Collapse
|
157
|
Inhibition of central de novo ceramide synthesis restores insulin signaling in hypothalamus and enhances β-cell function of obese Zucker rats. Mol Metab 2017; 8:23-36. [PMID: 29233519 PMCID: PMC5985020 DOI: 10.1016/j.molmet.2017.10.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/17/2017] [Accepted: 10/27/2017] [Indexed: 12/29/2022] Open
Abstract
Objectives Hypothalamic lipotoxicity has been shown to induce central insulin resistance and dysregulation of glucose homeostasis; nevertheless, elucidation of the regulatory mechanisms remains incomplete. Here, we aimed to determine the role of de novo ceramide synthesis in hypothalamus on the onset of central insulin resistance and the dysregulation of glucose homeostasis induced by obesity. Methods Hypothalamic GT1-7 neuronal cells were treated with palmitate. De novo ceramide synthesis was inhibited either by pharmacological (myriocin) or molecular (si-Serine Palmitoyl Transferase 2, siSPT2) approaches. Obese Zucker rats (OZR) were intracerebroventricularly infused with myriocin to inhibit de novo ceramide synthesis. Insulin resistance was determined by quantification of Akt phosphorylation. Ceramide levels were quantified either by a radioactive kinase assay or by mass spectrometry analysis. Glucose homeostasis were evaluated in myriocin-treated OZR. Basal and glucose-stimulated parasympathetic tonus was recorded in OZR. Insulin secretion from islets and β-cell mass was also determined. Results We show that palmitate impaired insulin signaling and increased ceramide levels in hypothalamic neuronal GT1-7 cells. In addition, the use of deuterated palmitic acid demonstrated that palmitate activated several enzymes of the de novo ceramide synthesis pathway in hypothalamic cells. Importantly, myriocin and siSPT2 treatment restored insulin signaling in palmitate-treated GT1-7 cells. Protein kinase C (PKC) inhibitor or a dominant-negative PKCζ also counteracted palmitate-induced insulin resistance. Interestingly, attenuating the increase in levels of hypothalamic ceramides with intracerebroventricular infusion of myriocin in OZR improved their hypothalamic insulin-sensitivity. Importantly, central myriocin treatment partially restored glucose tolerance in OZR. This latter effect is related to the restoration of glucose-stimulated insulin secretion and an increase in β-cell mass of OZR. Electrophysiological recordings also showed an improvement of glucose-stimulated parasympathetic nerve activity in OZR centrally treated with myriocin. Conclusion Our results highlight a key role of hypothalamic de novo ceramide synthesis in central insulin resistance installation and glucose homeostasis dysregulation associated with obesity. de novo ceramide synthesis induces hypothalamic insulin resistance through PKCζ. Hypothalamic ceramides induce glucose homeostasis dysregulation seen with obesity. Hypothalamic ceramides mediate inhibition of insulin secretion induced by obesity. Hypothalamic ceramides decreases β cell mass in obese rats. Hypothalamic ceramides decreases parasympathetic tonus.
Collapse
|