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Galley JC, Singh S, Awata WMC, Alves JV, Bruder-Nascimento T. Adipokines: Deciphering the cardiovascular signature of adipose tissue. Biochem Pharmacol 2022; 206:115324. [PMID: 36309078 PMCID: PMC10509780 DOI: 10.1016/j.bcp.2022.115324] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/19/2022] [Accepted: 10/20/2022] [Indexed: 11/02/2022]
Abstract
Obesity and hypertension are intimately linked due to the various ways that the important cell types such as vascular smooth muscle cells (VSMC), endothelial cells (EC), immune cells, and adipocytes, communicate with one another to contribute to these two pathologies. Adipose tissue is a very dynamic organ comprised primarily of adipocytes, which are well known for their role in energy storage. More recently adipose tissue has been recognized as the largest endocrine organ because of its ability to produce a vast number of signaling molecules called adipokines. These signaling molecules stimulate specific types of cells or tissues with many adipokines acting as indicators of adipocyte healthy function, such as adiponectin, omentin, and FGF21, which show anti-inflammatory or cardioprotective effects, acting as regulators of healthy physiological function. Others, like visfatin, chemerin, resistin, and leptin are often altered during pathophysiological circumstances like obesity and lipodystrophy, demonstrating negative cardiovascular outcomes when produced in excess. This review aims to explore the role of adipocytes and their derived products as well as the impacts of these adipokines on blood pressure regulation and cardiovascular homeostasis.
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Affiliation(s)
- Joseph C. Galley
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Pediatrics Research in Obesity and Metabolism (CPROM), University of Pittsburgh, Pittsburgh, PA, USA
| | - Shubhnita Singh
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Pediatrics Research in Obesity and Metabolism (CPROM), University of Pittsburgh, Pittsburgh, PA, USA
| | - Wanessa M. C. Awata
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Pediatrics Research in Obesity and Metabolism (CPROM), University of Pittsburgh, Pittsburgh, PA, USA
| | - Juliano V. Alves
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Pediatrics Research in Obesity and Metabolism (CPROM), University of Pittsburgh, Pittsburgh, PA, USA
| | - Thiago Bruder-Nascimento
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Pediatrics Research in Obesity and Metabolism (CPROM), University of Pittsburgh, Pittsburgh, PA, USA
- Endocrinology Division at UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, PA, USA
- Vascular Medicine Institute (VMI), University of Pittsburgh, Pittsburgh, PA, USA
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Gauda EB, Conde S, Bassi M, Zoccal DB, Almeida Colombari DS, Colombari E, Despotovic N. Leptin: Master Regulator of Biological Functions that Affects Breathing. Compr Physiol 2020; 10:1047-1083. [PMID: 32941688 DOI: 10.1002/cphy.c190031] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Obesity is a global epidemic in developed countries accounting for many of the metabolic and cardiorespiratory morbidities that occur in adults. These morbidities include type 2 diabetes, sleep-disordered breathing (SDB), obstructive sleep apnea, chronic intermittent hypoxia, and hypertension. Leptin, produced by adipocytes, is a master regulator of metabolism and of many other biological functions including central and peripheral circuits that control breathing. By binding to receptors on cells and neurons in the brainstem, hypothalamus, and carotid body, leptin links energy and metabolism to breathing. In this comprehensive article, we review the central and peripheral locations of leptin's actions that affect cardiorespiratory responses during health and disease, with a particular focus on obesity, SDB, and its effects during early development. Obesity-induced hyperleptinemia is associated with centrally mediated hypoventilation with decrease CO2 sensitivity. On the other hand, hyperleptinemia augments peripheral chemoreflexes to hypoxia and induces sympathoexcitation. Thus, "leptin resistance" in obesity is relative. We delineate the circuits responsible for these divergent effects, including signaling pathways. We review the unique effects of leptin during development on organogenesis, feeding behavior, and cardiorespiratory responses, and how undernutrition and overnutrition during critical periods of development can lead to cardiorespiratory comorbidities in adulthood. We conclude with suggestions for future directions to improve our understanding of leptin dysregulation and associated clinical diseases and possible therapeutic targets. Lastly, we briefly discuss the yin and the yang, specifically the contribution of relative adiponectin deficiency in adults with hyperleptinemia to the development of metabolic and cardiovascular disease. © 2020 American Physiological Society. Compr Physiol 10:1047-1083, 2020.
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Affiliation(s)
- Estelle B Gauda
- Division of Neonatology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Silvia Conde
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Lisboa, Portugal
| | - Mirian Bassi
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Debora Simoes Almeida Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, São Paulo, Brazil
| | - Nikola Despotovic
- Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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Suyama S, Lei W, Kubota N, Kadowaki T, Yada T. Adiponectin at physiological level glucose-independently enhances inhibitory postsynaptic current onto NPY neurons in the hypothalamic arcuate nucleus. Neuropeptides 2017; 65:1-9. [PMID: 28606559 DOI: 10.1016/j.npep.2017.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/17/2017] [Accepted: 03/17/2017] [Indexed: 12/13/2022]
Abstract
Adiponectin regulates glucose and lipid metabolism, acting against atherosclerosis and metabolic syndrome. Accumulating evidences suggest that adiponectin acts on the brain including the arcuate nucleus of hypothalamus (ARC). The ARC contains orexigenic neuropeptide Y (NPY)/agouti related peptide (AgRP) neurons and anorexigenic proopiomelanocortin (POMC) neurons, the first order neurons for feeding regulation. We recently reported that intracerebroventricular injection of adiponectin at low glucose level suppressed food intake, while at elevated glucose level it promoted food intake, exhibiting glucose-dependent reciprocal effects. As an underlying neuronal mechanism, physiological level of adiponectin at low glucose activated ARC POMC neurons and at high glucose inactivated them. Now, whether physiological level of adiponectin also affects NPY/AgRP neurons is essential for fully understanding the adiponectin action, but it remains to be clarified. We here report that a physiological dose of adiponectin, in both high and low glucose conditions, attenuated action potential firing without altering resting membrane potential in ARC NPY neurons. This adiponectin effect was abolished by GABAA receptor blockade. Adiponectin enhanced amplitude but not frequency of inhibitory postsynaptic current (IPSC) onto NPY neurons. These results demonstrate that adiponectin enhances IPSC onto NPY neurons to attenuate action potential firing in NPY neurons in a glucose-independent manner, being contrasted to its glucose-dependent effect on POMC neurons.
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Affiliation(s)
- Shigetomo Suyama
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi 320-0498, Japan
| | - Wang Lei
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi 320-0498, Japan
| | - Naoto Kubota
- Department of Diabetes and Metabolic Diseases, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Takashi Kadowaki
- Department of Diabetes and Metabolic Diseases, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Toshihiko Yada
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi 320-0498, Japan.
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Loewen SP, Paterson AR, Loh SY, Rogers MF, Hindmarch CCT, Murphy D, Ferguson AV. Sex-specific differences in cardiovascular and metabolic hormones with integrated signalling in the paraventricular nucleus of the hypothalamus. Exp Physiol 2017; 102:1373-1379. [PMID: 28762571 DOI: 10.1113/ep086436] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 07/20/2017] [Indexed: 12/29/2022]
Abstract
NEW FINDINGS What is the topic of this review? We describe roles of crucial signalling molecules in the paraventricular nucleus of the hypothalamus and highlight recent data suggesting sex-specific changes in the expression of crucial signalling molecules and their receptors, which may underlie sex differences in both cardiovascular and metabolic function. What advances does it highlight? This review highlights the integrative capacity of the paraventricular nucleus in mediating cardiovascular and metabolic effects by integrating information from multiple signalling molecules. It also proposes that these signalling molecules have sex-specific differential gene expression, indicating the importance of considering these differences in our ongoing search to understand the female-male differences in the regulation of crucial autonomic systems. Many traditional cardiovascular hormones have been implicated in metabolic function. Conversely, many hormones traditionally involved in metabolic regulation have an effect on cardiovascular function. Many of these signalling molecules exert such effects through specific actions in the paraventricular nucleus, an integrative autonomic control centre located in the hypothalamus. Here, we focus on four cardiovascular/metabolic peptide hormones that signal within the paraventricular nucleus, namely angiotensin II, orexin, adiponectin and nesfatin-1. Each of these hormones has specific electrophysiological effects on paraventricular nucleus neurons that can be related to its physiological actions. In addition, we introduce preliminary transcriptomic data indicating that the genes for some of these hormones and their receptors have sex-specific differential expression.
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Affiliation(s)
- Spencer P Loewen
- Centre for Neuroscience, Queen's University, Kingston, Ontario, Canada
| | - Alex R Paterson
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Dorothy Hodgkin Building, University of Bristol, Bristol, BS1 3NY, UK
| | - Su Yi Loh
- Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Mark F Rogers
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Dorothy Hodgkin Building, University of Bristol, Bristol, BS1 3NY, UK
| | - Charles C T Hindmarch
- Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.,Queen's Cardiopulmonary Unit (QCPU), Translational Institute of Medicine (TIME), Department of Medicine, Queen's University, Kingston, Ontario, Canada
| | - David Murphy
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Dorothy Hodgkin Building, University of Bristol, Bristol, BS1 3NY, UK.,Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Licursi M, Alberto CO, Dias A, Hirasawa K, Hirasawa M. High-fat diet-induced downregulation of anorexic leukemia inhibitory factor in the brain stem. Obesity (Silver Spring) 2016; 24:2361-2367. [PMID: 27663886 DOI: 10.1002/oby.21647] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/06/2016] [Accepted: 07/21/2016] [Indexed: 12/14/2022]
Abstract
OBJECTIVE High-fat diet (HFD) is known to induce low-grade hypothalamic inflammation. Whether inflammation occurs in other brain areas remains unknown. This study tested the effect of short-term HFD on cytokine gene expression and identified leukemia inhibitory factor (LIF) as a responsive cytokine in the brain stem. Thus, functional and cellular effects of LIF in the brain stem were investigated. METHODS Male rats were fed chow or HFD for 3 days, and then gene expression was analyzed in different brain regions for IL-1β, IL-6, TNF-α, and LIF. The effect of intracerebroventricular injection of LIF on chow intake and body weight was also tested. Patch clamp recording was performed in the nucleus tractus solitarius (NTS). RESULTS HFD increased pontine TNF-α mRNA while downregulating LIF in all major parts of the brain stem, but not in the hypothalamus or hippocampus. LIF injection into the cerebral aqueduct suppressed food intake without conditioned taste aversion, suggesting that LIF can induce anorexia via lower brain regions without causing malaise. In the NTS, a key brain stem nucleus for food intake regulation, LIF induced acute changes in neuronal excitability. CONCLUSIONS HFD-induced downregulation of anorexic LIF in the brain stem may provide a permissive condition for HFD overconsumption. This may be at least partially mediated by the NTS.
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Affiliation(s)
- Maria Licursi
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University St. John's, Newfoundland, Canada
| | - Christian O Alberto
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University St. John's, Newfoundland, Canada
| | - Alex Dias
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University St. John's, Newfoundland, Canada
| | - Kensuke Hirasawa
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University St. John's, Newfoundland, Canada
| | - Michiru Hirasawa
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University St. John's, Newfoundland, Canada.
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Glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding. Sci Rep 2016; 6:30796. [PMID: 27503800 PMCID: PMC4977585 DOI: 10.1038/srep30796] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 07/11/2016] [Indexed: 12/22/2022] Open
Abstract
Adiponectin regulates glucose and lipid metabolism, acting against metabolic syndrome and atherosclerosis. Accumulating evidence suggest that adiponectin acts on the brain including hypothalamic arcuate nucleus (ARC), where proopiomelanocortin (POMC) neurons play key roles in feeding regulation. Several studies have examined intracerebroventricular (ICV) injection of adiponectin and reported opposite effects, increase or decrease of food intake. These reports used different nutritional states. The present study aimed to clarify whether adiponectin exerts distinct effects on food intake and ARC POMC neurons depending on the glucose concentration. Adiponectin was ICV injected with or without glucose for feeding experiments and administered to ARC slices with high or low glucose for patch clamp experiments. We found that adiponectin at high glucose inhibited POMC neurons and increased food intake while at low glucose it exerted opposite effects. The results demonstrate that glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding.
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Chabry J, Nicolas S, Cazareth J, Murris E, Guyon A, Glaichenhaus N, Heurteaux C, Petit-Paitel A. Enriched environment decreases microglia and brain macrophages inflammatory phenotypes through adiponectin-dependent mechanisms: Relevance to depressive-like behavior. Brain Behav Immun 2015. [PMID: 26209808 DOI: 10.1016/j.bbi.2015.07.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Regulation of neuroinflammation by glial cells plays a major role in the pathophysiology of major depression. While astrocyte involvement has been well described, the role of microglia is still elusive. Recently, we have shown that Adiponectin (ApN) plays a crucial role in the anxiolytic/antidepressant neurogenesis-independent effects of enriched environment (EE) in mice; however its mechanisms of action within the brain remain unknown. Here, we show that in a murine model of depression induced by chronic corticosterone administration, the hippocampus and the hypothalamus display increased levels of inflammatory cytokines mRNA, which is reversed by EE housing. By combining flow cytometry, cell sorting and q-PCR, we show that microglia from depressive-like mice adopt a pro-inflammatory phenotype characterized by higher expression levels of IL-1β, IL-6, TNF-α and IκB-α mRNAs. EE housing blocks pro-inflammatory cytokine gene induction and promotes arginase 1 mRNA expression in brain-sorted microglia, indicating that EE favors an anti-inflammatory activation state. We show that microglia and brain-macrophages from corticosterone-treated mice adopt differential expression profiles for CCR2, MHC class II and IL-4recα surface markers depending on whether the mice are kept in standard environment or EE. Interestingly, the effects of EE were abolished when cells are isolated from ApN knock-out mouse brains. When injected intra-cerebroventricularly, ApN, whose level is specifically increased in cerebrospinal fluid of depressive mice raised in EE, rescues microglia phenotype, reduces pro-inflammatory cytokine production by microglia and blocks depressive-like behavior in corticosterone-treated mice. Our data suggest that EE-induced ApN increase within the brain regulates microglia and brain macrophages phenotype and activation state, thus reducing neuroinflammation and depressive-like behaviors in mice.
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Affiliation(s)
- Joëlle Chabry
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Sarah Nicolas
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Julie Cazareth
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Emilie Murris
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Alice Guyon
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Nicolas Glaichenhaus
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Catherine Heurteaux
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France
| | - Agnès Petit-Paitel
- Université de Nice Sophia Antipolis, 06103 Nice, France; Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 06560 Valbonne, France.
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Adiponectin-Mediated Analgesia and Anti-Inflammatory Effects in Rat. PLoS One 2015; 10:e0136819. [PMID: 26352808 PMCID: PMC4564279 DOI: 10.1371/journal.pone.0136819] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 08/10/2015] [Indexed: 02/02/2023] Open
Abstract
The adipose tissue-derived protein, adiponectin, has significant anti-inflammatory properties in a variety of disease conditions. Recent evidence that adiponectin and its receptors (AdipoR1 and AdipoR2) are expressed in central nervous system, suggests that it may also have a central modulatory role in pain and inflammation. This study set out to investigate the effects of exogenously applied recombinant adiponectin (via intrathecal and intraplantar routes; 10–5000 ng) on the development of peripheral inflammation (paw oedema) and pain hypersensitivity in the rat carrageenan model of inflammation. Expression of adiponectin, AdipoR1 and AdipoR2 mRNA and protein was characterised in dorsal spinal cord using real-time polymerase chain reaction (PCR) and Western blotting. AdipoR1 and AdipoR2 mRNA and protein were found to be constitutively expressed in dorsal spinal cord, but no change in mRNA expression levels was detected in response to carrageenan-induced inflammation. Adiponectin mRNA, but not protein, was detected in dorsal spinal cord, although levels were very low. Intrathecal administration of adiponectin, both pre- and 3 hours post-carrageenan, significantly attenuated thermal hyperalgesia and mechanical hypersensitivity. Intrathecal administration of adiponectin post-carrageenan also reduced peripheral inflammation. Intraplantar administration of adiponectin pre-carrageenan dose-dependently reduced thermal hyperalgesia but had no effect on mechanical hypersensitivity and peripheral inflammation. These results show that adiponectin functions both peripherally and centrally at the spinal cord level, likely through activation of AdipoRs to modulate pain and peripheral inflammation. These data suggest that adiponectin receptors may be a novel therapeutic target for pain modulation.
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Rohde K, Keller M, Horstmann A, Liu X, Eichelmann F, Stumvoll M, Villringer A, Kovacs P, Tönjes A, Böttcher Y. Role of genetic variants in ADIPOQ in human eating behavior. GENES AND NUTRITION 2014; 10:449. [PMID: 25542302 DOI: 10.1007/s12263-014-0449-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 11/29/2014] [Indexed: 12/12/2022]
Abstract
The beneficial effects of adiponectin and its negative correlation with BMI are well described. Adiponectin serum levels are altered in eating disorders such as anorexia nervosa, bulimia nervosa or binge eating. Here, we tested the hypothesis that (1) adiponectin serum levels correlate with human eating behavior factors and (2) that genetic variants of the ADIPOQ locus influence both serum levels and eating behavior. We analyzed 11 SNPs within ADIPOQ and in the 5' UTR and measured serum adiponectin levels in 1,036 individuals from the German Sorbs population. The German version of the three-factor eating questionnaire (FEV) was completed by 548 Sorbs. For replication purposes, we included an independent replication cohort from Germany (N = 350). In the Sorbs, we observed positive correlations of restraint with adiponectin serum levels (P = 0.001; r = 0.148) which, however, did not withstand adjustment for covariates (P = 0.083; r = 0.077). In addition, four SNPs were nominally associated with serum adiponectin levels (all P < 0.05). Of these, two variants (rs3774261; rs1501229, all P < 0.05) were also related to disinhibition. Furthermore, three variants were exclusively associated with hunger (rs2036373, P = 0.049) and disinhibition (rs822396; rs864265, all P < 0.05). However, none of these associations withstood Bonferroni corrections for multiple testing (all P > 9.3 × 10(-4)). In our replication cohort, we observed similar effect directions at rs1501229 for disinhibition and hunger. A meta-analysis resulted in nominal statistical significance P = 0.036 (Z score 2.086) and P = 0.017 (Z score 2.366), respectively. Given the observed relationship of the SNPs with adiponectin levels and eating behavior, our data support a potential role of adiponectin in human eating behavior. Whether the relationship with eating behavior is mediated by the effects of circulating adiponectin warrants further investigations.
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Affiliation(s)
- Kerstin Rohde
- IFB Adiposity Diseases, University of Leipzig, Liebigstraße 21, 04103, Leipzig, Germany,
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Penumarti A, Abdel-Rahman AA. Neuronal nitric oxide synthase-dependent elevation in adiponectin in the rostral ventrolateral medulla underlies g protein-coupled receptor 18-mediated hypotension in conscious rats. J Pharmacol Exp Ther 2014; 351:44-53. [PMID: 25100751 DOI: 10.1124/jpet.114.216036] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Direct activation of the endocannabinoid receptor G protein-coupled receptor 18 (GPR18) in the rostral ventrolateral medulla (RVLM) of conscious rats by abnormal cannabidiol (Abn CBD; trans-4-[3-methyl-6-(1-methylethenyl)-2-cyclohexen-1-yl]-5-pentyl-1,3-benzenediol) elevates local nitric oxide (NO) and adiponectin (ADN) levels and reduces oxidative stress and blood pressure (BP). However, the molecular mechanisms for GPR18-mediated neurochemical responses, including the nitric oxide synthase isoform that generates NO, and their potential causal link to the BP reduction are not known. We hypothesized that GPR18-mediated enhancement of Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), and neuronal nitric oxide synthase (nNOS) phosphorylation, triggered by a reduction in cAMP, accounts for the NO/ADN-dependent reductions in RVLM oxidative stress and BP. Intra-RVLM GPR18 activation (Abn CBD; 0.4 μg) enhanced RVLM Akt, ERK1/2, and nNOS phosphorylation as well as ADN levels during the hypotensive response. Prior GPR18 blockade with O-1918 (1,3-dimethoxy-5-methyl-2-[(1R,6R)-3-methyl-6-(1-methylethenyl)-2-cyclohexen-1-yl]benzene) produced the opposite effects and abrogated Abn CBD-evoked neurochemical and BP responses. Pharmacological inhibition of RVLM phosphoinositide 3-kinase (PI3K)/Akt (wortmannin), ERK1/2 (PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one]), or nNOS (N(ω)-propyl-l-arginine), or activation of adenylyl cyclase (forskolin) virtually abolished intra-RVLM Abn CBD-evoked hypotension and the increases in Akt, ERK1/2, and nNOS phosphorylation and in ADN levels in the RVLM. Our pharmacological and neurochemical findings support a pivotal role for PI3K, Akt, ERK1/2, nNOS, and adenylyl cyclase, via modulation of NO, ADN, and cAMP levels, in GPR18 regulation of the RVLM redox state and BP in conscious rats.
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Affiliation(s)
- Anusha Penumarti
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Abdel A Abdel-Rahman
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, North Carolina
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Mimee A, Kuksis M, Ferguson AV. α-MSH exerts direct postsynaptic excitatory effects on NTS neurons and enhances GABAergic signaling in the NTS. Neuroscience 2013; 262:70-82. [PMID: 24370637 DOI: 10.1016/j.neuroscience.2013.12.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/06/2013] [Accepted: 12/18/2013] [Indexed: 11/27/2022]
Abstract
The central melanocortin system plays an essential role in the regulation of energy balance. While anorexigenic effects of α-melanocyte-stimulating hormone (α-MSH) acting in the nucleus of the solitary tract (NTS), a critical medullary autonomic control center, have been established, the cellular events underlying these effects are less well characterized. In this study, we used whole-cell patch-clamp electrophysiology to examine firstly whether α-MSH exerts direct postsynaptic effects on the membrane potential of rat NTS neurons in slice preparation, and secondly whether α-MSH influences GABAergic signaling in the NTS. In normal artificial cerebrospinal fluid, perfusion of α-MSH (500 nM) resulted in a depolarization in 39% of cells (n=16, mean 6.14±0.54 mV), and a hyperpolarization in 22% of cells (n=9, -6.79±1.02 mV). Studies using tetrodotoxin to block neuronal communication revealed α-MSH exerts direct depolarizing effects on some NTS neurons, and indirect inhibitory effects on others. A third subset of neurons is simultaneously directly depolarized and indirectly hyperpolarized by α-MSH, resulting in a net lack of effect on membrane potential. The inhibitory inputs influenced by α-MSH were identified as GABAergic, as α-MSH increased the frequency, but not amplitude, of inhibitory postsynaptic currents (IPSCs) in 50% of NTS neurons. α-MSH had no effect on the frequency or amplitude of miniature IPSCs. Furthermore, pharmacological blockade of GABAA and GABAB receptors, and physical removal of all synaptic inputs via cellular dissociation, abolished hyperpolarizations induced by α-MSH. We conclude α-MSH exerts direct, postsynaptic excitatory effects on a subset of NTS neurons. By exciting GABAergic NTS neurons and presynaptically enhancing GABAergic signaling, α-MSH also indirectly inhibits other NTS cells. These findings provide critical insight into the cellular events underlying medullary melanocortin anorexigenic effects, and expand the understanding of the circuitries involved in central melanocortin signaling.
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Affiliation(s)
- A Mimee
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada
| | - M Kuksis
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada
| | - A V Ferguson
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada.
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The complex interaction between overweight, hypertension, and sympathetic overactivity. ACTA ACUST UNITED AC 2012; 3:353-65. [PMID: 20409978 DOI: 10.1016/j.jash.2009.10.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 09/29/2009] [Accepted: 10/01/2009] [Indexed: 11/22/2022]
Abstract
There is ample evidence in the epidemiological and clinical literature that hypertension and overweight are closely and causally interrelated. Sympathetic nervous system (SNS) overactivity has been well documented in both hypertension and overweight, but it is not clear whether this is a coincidental finding or whether the association reflects a mechanistic role of SNS in these two interrelated clinical conditions. Whereas in this review we focus on the evidence for a primary role of SNS in the development of hypertension and overweight, it is clear that the process can be initiated from other starting points such as primary overeating or sleep apnea. After overweight evolves, hormones secreted by fat cells further accelerate SNS overactivity, weight gain, and blood pressure increase. The main thesis of this article is that regardless of where the process started, the same clinical picture of hypertension, overweight, and SNS overactivity will emerge. There is good evidence that in genetically prone individuals, prolonged SNS stimulation elicits a down regulation of beta-adrenergic receptors. This in turn decreases the ability to dissipate calories and diminishes the beta-adrenoceptor-mediated vasodilatation. We hypothesize that beta-adrenoceptor downregulation is the linchpin in the association of SNS with overweight and hypertension.
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14
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Bassi M, do Carmo JM, Hall JE, da Silva AA. Chronic effects of centrally administered adiponectin on appetite, metabolism and blood pressure regulation in normotensive and hypertensive rats. Peptides 2012; 37:1-5. [PMID: 22749987 PMCID: PMC3427463 DOI: 10.1016/j.peptides.2012.06.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/20/2012] [Accepted: 06/20/2012] [Indexed: 11/23/2022]
Abstract
Acute studies suggest that adiponectin may reduce sympathetic activity and blood pressure (BP) via actions on the central nervous system (CNS). However, the chronic effects of adiponectin on energy expenditure and cardiovascular function are still poorly understood. We tested if chronic intracerebroventricular (ICV) infusion of adiponectin (1 or 7μg/day) in Sprague-Dawley rats fed a high fat diet (HFD) for 8 weeks and at the high dose (7μg/day) in spontaneously hypertensive rats (SHRs), a hypertensive model associated with sympathetic overactivity, evoked chronic reductions in BP and heart rate (HR). We also determined if chronic ICV adiponectin infusion alters appetite, whole body oxygen consumption (VO(2)), and insulin and leptin levels. Neither dose of adiponectin infused for 7 days significantly altered BP or HR in the HFD group (115±2 to 112±2mmHg and 384±6 to 379±6bpm at 1μg/day; 109±3 to 111±3mmHg and 366±5 and 367±5bpm at 7μg/day). The higher dose slightly reduced food intake (14±1 to 11±1g/day), whereas VO(2), insulin and leptin levels were not affected by the treatment. In SHRs, ICV adiponectin infusion reduced appetite (22±2 to 12±2g/day) and insulin levels (∼55%), but did not alter BP (162±4 to 164±3mmHg) or HR (312±5 to 322±8bpm). These results suggest that adiponectin, acting via its direct actions on the CNS, has a small effect to reduce appetite and insulin levels, but it has no long-term action to reduce BP or HR, or to alter whole body metabolic rate.
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Affiliation(s)
- Mirian Bassi
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA
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15
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Mimee A, Smith PM, Ferguson AV. Nesfatin-1 influences the excitability of neurons in the nucleus of the solitary tract and regulates cardiovascular function. Am J Physiol Regul Integr Comp Physiol 2012; 302:R1297-304. [DOI: 10.1152/ajpregu.00266.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Nesfatin-1 has been identified as one of the most potent centrally acting anorexigenic peptides, and it has also been shown to play important roles in the control of cardiovascular function. In situ hybridization and immunohistochemical studies have revealed the expression of nesfatin-1 throughout the brain and, in particular, in the medullary autonomic gateway known as the nucleus of the solitary tract (NTS). The present study was thus undertaken to explore the cellular correlates and functional roles of nesfatin-1 actions in the medial NTS (mNTS). Using current-clamp electrophysiology recordings from mNTS neurons in slice preparation, we show that bath-applied nesfatin-1 directly influences the excitability of the majority of mNTS neurons by eliciting either depolarizing (42%, mean: 7.8 ± 0.8 mV) or hyperpolarizing (21%, mean: −8. 2 ± 1.0 mV) responses. These responses were observed in all electrophysiologically defined cell types in the NTS and were site specific and concentration dependent. Furthermore, post hoc single cell reverse transcriptase polymerase reaction revealed a depolarizing action of nesfatin-1 on NPY and nucleobindin-2-expressing mNTS neurons. We have also correlated these actions of nesfatin-1 on neuronal membrane potential with physiological outcomes, using in vivo microinjection techniques to demonstrate that nesfatin-1 microinjected into the mNTS induces significant increases in both blood pressure (mean AUC = 3354.1 ± 750.7 mmHg·s, n = 6) and heart rate (mean AUC = 164.8 ± 78.5 beats, n = 6) in rats. Our results provide critical insight into the circuitry and physiology involved in the profound effects of nesfatin-1 and highlight the NTS as a key structure mediating these autonomic actions.
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Affiliation(s)
- Andrea Mimee
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
| | - Pauline M. Smith
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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16
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Iannitti T, Graham A, Dolan S. Increased central and peripheral inflammation and inflammatory hyperalgesia in Zucker rat model of leptin receptor deficiency and genetic obesity. Exp Physiol 2012; 97:1236-45. [PMID: 22523380 DOI: 10.1113/expphysiol.2011.064220] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study investigated whether sensitivity to nociceptive stimuli is altered in obese rats using established models of inflammatory pain, and using real-time PCR, profiled alterations in expression of key adipokine and inflammatory mediator mRNA (adiponectin, tumor necrosis factor-α, interleukin-1β, cyclooxygenase-2, inducible nitric oxide synthase (iNOS)) in spinal cord with obesity. Responses to thermal and mechanical stimulation of the hindpaw and paw oedema were assessed in adult male Zucker fatty rats (fa/fa) and their lean littermates (fa/-; n = 6-9 per group) in the absence of inflammation (acute nociception), then in response to intradermal hindpaw injection of carrageenan (3%; 50 μl) or capsaicin (10 μg; 50 μl) or hindpaw incision. The analgesic potency of morphine (1, 2.5 or 5 mg kg(-1) or vehicle; s.c.) was also assessed. Acute nociception was unaltered in obese animals, but following carrageenan-induced inflammation the obese rats were significantly more sensitive to mechanical and thermal stimulation of the inflamed paw, and displayed greater paw oedema. No difference in the capsaicin- or paw-incision-induced pain sensitivity or in the analgesic potency of morphine was observed between groups. Levels of adiponectin and inducible nitric oxide synthase mRNA were downregulated in spinal cord from obese rats, whereas tumour necrosis factor-α mRNA was upregulated; interleukin-1β and cyclo-oxygenase were unchanged. The increased pain sensitivity and inflammatory response together with changes in spinal adipokine expression in obese rats fit well with the hypothesis that obesity is a chronic low-grade inflammatory disorder, producing a state where responses to subsequent inflammatory challenge are potentiated.
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Affiliation(s)
- Tommaso Iannitti
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK
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17
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Abstract
Obesity-related hypertension is increasingly recognized as a distinct hypertensive phenotype requiring a modified approach to diagnosis and management. In this review rapidly evolving insights into the complex and interdependent mechanisms linking obesity to hypertension are discussed. Overweight and obesity are associated with adipose tissue dysfunction, characterized by enlarged hypertrophied adipocytes, increased infiltration by macrophages and marked changes in secretion of adipokines and free fatty acids. This results in chronic vascular inflammation, oxidative stress, activation of the renin-angiotensin-aldosterone system and sympathetic overdrive, eventually leading to hypertension. These mechanisms may provide novel targets for anti-hypertensive drug treatment. Recognition of obesity-related hypertension as a distinct diagnosis enables tailored therapy in clinical practice. This includes lifestyle modification and accommodated choice of blood pressure-lowering drugs.
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Affiliation(s)
- J A N Dorresteijn
- Department of Vascular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
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18
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Dadson K, Liu Y, Sweeney G. Adiponectin action: a combination of endocrine and autocrine/paracrine effects. Front Endocrinol (Lausanne) 2011; 2:62. [PMID: 22649379 PMCID: PMC3355882 DOI: 10.3389/fendo.2011.00062] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 10/10/2011] [Indexed: 12/15/2022] Open
Abstract
The widespread physiological actions of adiponectin have now been well characterized as clinical studies and works in animal models have established strong correlations between circulating adiponectin level and various disease-related outcomes. Thus, conventional thinking attributes many of adiponectin's beneficial effects to endocrine actions of adipose-derived adiponectin. However, it is now clear that several tissues can themselves produce adiponectin and there is growing evidence that locally produced adiponectin can mediate functionally important autocrine or paracrine effects. In this review article we discuss regulation of adiponectin production, its mechanism of action via receptor isoforms and signaling pathways, and its principal physiological effects (i.e., metabolic and cardiovascular). The role of endocrine actions of adiponectin and changes in local production of adiponectin or its receptors in whole body physiology is discussed.
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Affiliation(s)
- Keith Dadson
- Department of Biology, York UniversityToronto, ON, Canada
| | - Ying Liu
- Department of Biology, York UniversityToronto, ON, Canada
| | - Gary Sweeney
- Department of Biology, York UniversityToronto, ON, Canada
- Institut Pasteur KoreaSeoul, South Korea
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19
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Mercer RE, Chee MJS, Colmers WF. The role of NPY in hypothalamic mediated food intake. Front Neuroendocrinol 2011; 32:398-415. [PMID: 21726573 DOI: 10.1016/j.yfrne.2011.06.001] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 05/17/2011] [Accepted: 06/13/2011] [Indexed: 12/29/2022]
Abstract
Neuropeptide Y (NPY) is a highly conserved neuropeptide with orexigenic actions in discrete hypothalamic nuclei that plays a role in regulating energy homeostasis. NPY signals via a family of high affinity receptors that mediate the widespread actions of NPY in all hypothalamic nuclei. These actions are also subject to tight, intricate regulation by numerous peripheral and central energy balance signals. The NPY system is embedded within a densely-redundant network designed to ensure stable energy homeostasis. This redundancy may underlie compensation for the loss of NPY or its receptors in germline knockouts, explaining why conventional knockouts of NPY or its receptors rarely yield a marked phenotypic change. We discuss insights into the hypothalamic role of NPY from studies of its physiological actions, responses to genetic manipulations and interactions with other energy balance signals. We conclude that numerous approaches must be employed to effectively study different aspects of NPY action.
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Affiliation(s)
- Rebecca E Mercer
- Department of Medical Genetics, University of Alberta, Edmonton, AB, Canada T6G 2H7
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20
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Li FYL, Cheng KKY, Lam KSL, Vanhoutte PM, Xu A. Cross-talk between adipose tissue and vasculature: role of adiponectin. Acta Physiol (Oxf) 2011; 203:167-80. [PMID: 21062420 DOI: 10.1111/j.1748-1716.2010.02216.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Adipose tissue is a highly dynamic endocrine organ, secreting a number of bioactive substances (adipokines) regulating insulin sensitivity, energy metabolism and vascular homeostasis. Dysfunctional adipose tissue is a key mediator that links obesity with insulin resistance, hypertension and cardiovascular disease. Obese adipose tissue is characterized by adipocyte hypertrophy and infiltration of inflammatory macrophages and lymphocytes, leading to the augmented production of pro-inflammatory adipokines and vasoconstrictors that induce endothelial dysfunction and vascular inflammation through their paracrine and endocrine actions. By contrast, the secretion of adiponectin, an adipokine with insulin sensitizing and anti-inflammatory activities, is decreased in obesity and its related pathologies. Emerging evidence suggests that adiponectin is protective against vascular dysfunction induced by obesity and diabetes, through its multiple favourable effects on glucose and lipid metabolism as well as on vascular function. Adiponectin improves insulin sensitivity and metabolic profiles, thus reducing the classical risk factors for cardiovascular disease. Furthermore, adiponectin protects the vasculature through its pleiotropic actions on endothelial cells, endothelial progenitor cells, smooth muscle cells and macrophages. Data from both animal and human investigations demonstrate that adiponectin is an important component of the adipo-vascular axis that mediates the cross-talk between adipose tissue and vasculature. This review highlights recent work on the vascular protective activities of adiponectin and discusses the molecular pathways underlying the vascular actions of this adipokine.
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Affiliation(s)
- F Y L Li
- Department of Medicine, University of Hong Kong, Hong Kong
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21
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Abstract
It has long been recognized that cardiac autonomic neuropathy increases morbidity and mortality in diabetes and may have greater predictive power than traditional risk factors for cardiovascular events. Significant morbidity and mortality can now be attributable to autonomic imbalance between the sympathetic and parasympathetic nervous system regulation of cardiovascular function. New and emerging syndromes include orthostatic tachycardia, orthostatic bradycardia and an inability to use heart rate as a guide to exercise intensity because of the resting tachycardia. Recent studies have shown that autonomic imbalance may be a predictor of risk of sudden death with intensification of glycaemic control. This review examines an association of autonomic dysregulation and the role of inflammatory cytokines and adipocytokines that promote cardiovascular risk. In addition, conditions of autonomic imbalance associated with cardiovascular risk are discussed. Potential treatment for restoration of autonomic balance is outlined.
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Affiliation(s)
- A I Vinik
- Eastern Virginia Medical School, Strelitz Diabetes Research Center and Neuroendocrine Unit, 855 W Brambleton Avenue, Norfolk, VA 23510, USA.
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22
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Vlasova M, Purhonen AK, Jarvelin MR, Rodilla E, Pascual J, Herzig KH. Role of adipokines in obesity-associated hypertension. Acta Physiol (Oxf) 2010; 200:107-27. [PMID: 20653609 DOI: 10.1111/j.1748-1716.2010.02171.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
It has been well documented that obesity is a major risk factor for the development of the hypertensive state. The correlation between body mass index and blood pressure level is well established. Nevertheless, the exact mechanisms which contribute to obesity-related hypertension remain poorly understood. In the last years, we have realized that the white adipose tissue is not just an inert organ for nutrient storage and isolation but rather depending on the body mass index the biggest endocrinological organ. Thus, the possible contribution of adipokines to the blood pressure elevation becomes an attractive hypothesis to explain the hypertensive state that often occurs in obesity. In this review, we consider direct and indirect effects of main adipokines on structural and functional changes in the cardiovascular system.
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Affiliation(s)
- M Vlasova
- Department of Pharmaceutics, University of Kuopio, Kuopio, Finland
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23
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Hoyda TD, Ferguson AV. Adiponectin modulates excitability of rat paraventricular nucleus neurons by differential modulation of potassium currents. Endocrinology 2010; 151:3154-62. [PMID: 20444939 DOI: 10.1210/en.2009-1390] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The adipocyte-derived hormone adiponectin acts at two seven-transmembrane domain receptors, adiponectin receptor 1 and adiponectin receptor 2, present in the paraventricular nucleus of the hypothalamus to regulate neuronal excitability and endocrine function. Adiponectin depolarizes rat parvocellular preautonomic neurons that secrete either thyrotropin releasing hormone or oxytocin and parvocellular neuroendocrine corticotropin releasing hormone neurons, leading to an increase in plasma adrenocorticotropin hormone concentrations while also hyperpolarizing a subgroup of neurons. In the present study, we investigate the ionic mechanisms responsible for these changes in excitability in parvocellular paraventricular nucleus neurons. Patch clamp recordings of currents elicited from slow voltage ramps and voltage steps indicate that adiponectin inhibits noninactivating delayed rectifier potassium current (I(K)) in a majority of neurons. This inhibition produced a broadening of the action potential in cells that depolarized in the presence of adiponectin. The depolarizing effects of adiponectin were abolished in cells pretreated with tetraethyl ammonium (0/15 cells depolarize). Slow voltage ramps performed during adiponectin-induced hyperpolarization indicate the activation of voltage-independent potassium current. These hyperpolarizing responses were abolished in the presence of glibenclamide [an ATP-sensitive potassium (K(ATP)) channel blocker] (0/12 cells hyperpolarize). The results presented in this study suggest that adiponectin controls neuronal excitability through the modulation of different potassium conductances, effects which contribute to changes in excitability and action potential profiles responsible for peptidergic release into the circulation.
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Affiliation(s)
- Ted D Hoyda
- Department of Physiology, Queen's University, 4th Floor Botterell Hall, Kingston, Ontario, Canada K7L 3N6
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24
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Alim I, Fry WM, Walsh MH, Ferguson AV. Actions of adiponectin on the excitability of subfornical organ neurons are altered by food deprivation. Brain Res 2010; 1330:72-82. [PMID: 20206611 DOI: 10.1016/j.brainres.2010.02.076] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/22/2010] [Accepted: 02/25/2010] [Indexed: 12/13/2022]
Abstract
Adiponectin (ADP) is a peptide produced by adipose tissue, which acts as an insulin sensitizing hormone. Recent studies have shown that adiponectin receptors (AdipoR1 and AdipoR2) are present in the CNS, and although adiponectin does appear in both circulation and the cerebrospinal fluid there is still some debate as to whether or not ADP crosses the blood brain barrier (BBB). Circumventricular organs (CVO) are CNS sites which lack normal BBB, and thus represent sites at which circulating adiponectin may act to directly influence the CNS. The subfornical organ (SFO) is a CVO that has been implicated in the regulation of energy balance as a consequence of the ability of SFO neurons to respond to a number of different circulating satiety signals including amylin, CCK, PYY and ghrelin. Our recent microarray analysis suggested the presence of adiponectin receptors in the SFO. We report here that the SFO shows a high density of mRNA for both adiponectin receptors (AdipoR1 and AdipoR2), and that ADP influences the excitability of dissociated SFO neurons. Separate subpopulations of SFO neurons were either depolarized (8.9+/-0.9 mV, 21 of 97 cells), or hyperpolarized (-8.0+/-0.5 mV, 34 of 97 cells), by bath application of 10nM ADP, effects which were concentration dependent and reversible. Our microarray analysis also suggested that 48 h of food deprivation resulted in specific increases in AdipoR2 mRNA expression (no effect on AdipoR1 mRNA), observations which we confirm here using real-time PCR techniques. The effects of food deprivation also resulted in a change in the responsiveness of SFO neurons to adiponectin with 77% (8/11) of cells tested responding to adiponectin with depolarization, while no hyperpolarizations were observed. These observations support the concept that the SFO may be a key player in sensing circulating ADP and transmitting such information to critical CNS sites involved in the regulation of energy balance.
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Affiliation(s)
- Ishraq Alim
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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