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Zhang L, Koller J, Gopalasingam G, Qi Y, Herzog H. Central NPFF signalling is critical in the regulation of glucose homeostasis. Mol Metab 2022; 62:101525. [PMID: 35691527 PMCID: PMC9234230 DOI: 10.1016/j.molmet.2022.101525] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 06/03/2022] [Indexed: 11/01/2022] Open
Abstract
OBJECTIVE Neuropeptide FF (NPFF) group peptides belong to the evolutionary conserved RF-amide peptide family. While they have been assigned a role as pain modulators, their roles in other aspects of physiology have received much less attention. NPFF peptides and their receptor NPFFR2 have strong and localized expression within the dorsal vagal complex that has emerged as the key centre for regulating glucose homeostasis. Therefore, we investigated the role of the NPFF system in the control of glucose metabolism and the histochemical and molecular identities of NPFF and NPFFR2 neurons. METHODS We examined glucose metabolism in Npff-/- and wild type (WT) mice using intraperitoneal (i.p.) glucose tolerance and insulin tolerance tests. Body composition and glucose tolerance was further examined in mice after 1-week and 3-week of high-fat diet (HFD). Using RNAScope double ISH, we investigated the neurochemical identity of NPFF and NPFFR2 neurons in the caudal brainstem, and the expression of receptors for peripheral factors in NPFF neurons. RESULTS Lack of NPFF signalling in mice leads to improved glucose tolerance without significant impact on insulin excursion after the i.p. glucose challenge. In response to an i.p. bolus of insulin, Npff-/- mice have lower glucose excursions than WT mice, indicating an enhanced insulin action. Moreover, while HFD has rapid and potent detrimental effects on glucose tolerance, this diet-induced glucose intolerance is ameliorated in mice lacking NPFF signalling. This occurs in the absence of any significant impact of NPFF deletion on lean or fat masses, suggesting a direct effect of NPFF signalling on glucose metabolism. We further reveal that NPFF neurons in the subpostrema area (SubP) co-express receptors for peripheral factors involved in glucose homeostasis regulation such as insulin and GLP1. Furthermore, Npffr2 is expressed in the glutamatergic NPFF neurons in the SubP, and in cholinergic neurons of the dorsal motor nucleus of the vagus (DMV), indicating that central NPFF signalling is likely modulating vagal output to innervated peripheral tissues including those important for glucose metabolic control. CONCLUSIONS NPFF signalling plays an important role in the regulation of glucose metabolism. NPFF neurons in the SubP are likely to receive peripheral signals and mediate the control of whole-body glucose homeostasis via centrally vagal pathways. Targeting NPFF and NPFFR2 signalling may provide a new avenue for treating type 2 diabetes and obesity.
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Affiliation(s)
- Lei Zhang
- Neuroscience Division, Garvan Institute of Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia; St. Vincent's Clinical Campus, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, NSW Australia.
| | - Julia Koller
- Neuroscience Division, Garvan Institute of Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia; St. Vincent's Clinical Campus, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, NSW Australia
| | - Gopana Gopalasingam
- Neuroscience Division, Garvan Institute of Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia
| | - Yue Qi
- Neuroscience Division, Garvan Institute of Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia
| | - Herbert Herzog
- Neuroscience Division, Garvan Institute of Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia; St. Vincent's Clinical Campus, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, NSW Australia
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Mukherjee S, Skrede S, Milbank E, Andriantsitohaina R, López M, Fernø J. Understanding the Effects of Antipsychotics on Appetite Control. Front Nutr 2022; 8:815456. [PMID: 35047549 PMCID: PMC8762106 DOI: 10.3389/fnut.2021.815456] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/10/2021] [Indexed: 12/16/2022] Open
Abstract
Antipsychotic drugs (APDs) represent a cornerstone in the treatment of schizophrenia and other psychoses. The effectiveness of the first generation (typical) APDs are hampered by so-called extrapyramidal side effects, and they have gradually been replaced by second (atypical) and third-generation APDs, with less extrapyramidal side effects and, in some cases, improved efficacy. However, the use of many of the current APDs has been limited due to their propensity to stimulate appetite, weight gain, and increased risk for developing type 2 diabetes and cardiovascular disease in this patient group. The mechanisms behind the appetite-stimulating effects of the various APDs are not fully elucidated, partly because their diverse receptor binding profiles may affect different downstream pathways. It is critical to identify the molecular mechanisms underlying drug-induced hyperphagia, both because this may lead to the development of new APDs, with lower appetite-stimulating effects but also because such insight may provide new knowledge about appetite regulation in general. Hence, in this review, we discuss the receptor binding profile of various APDs in relation to the potential mechanisms by which they affect appetite.
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Affiliation(s)
- Sayani Mukherjee
- Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
| | - Silje Skrede
- Department of Clinical Science, University of Bergen, Bergen, Norway.,Section of Clinical Pharmacology, Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Norway
| | - Edward Milbank
- NeurObesity Group, Department of Physiology, Center for Research in Molecular Medicine and Chronic Diseases, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Centro de Investigación Biomédica en Red de la Fisiopatología de la Obesidad y Nutrición, Madrid, Spain.,SOPAM, U1063, INSERM, University of Angers, SFR ICAT, Bat IRIS-IBS, Angers, France
| | | | - Miguel López
- NeurObesity Group, Department of Physiology, Center for Research in Molecular Medicine and Chronic Diseases, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición, Centro de Investigación Biomédica en Red de la Fisiopatología de la Obesidad y Nutrición, Madrid, Spain
| | - Johan Fernø
- Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
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Dos Santos KM, Moraes DJDA, da Silva MP, Antunes VR. Exercise training rescues the electrical activity of liver-projecting DMNV neurones in response to oxytocin in spontaneously hypertensive rats. J Neuroendocrinol 2021; 33:e12977. [PMID: 33942389 DOI: 10.1111/jne.12977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 03/30/2021] [Accepted: 04/02/2021] [Indexed: 12/15/2022]
Abstract
A neural circuit between the paraventricular nucleus of the hypothalamus (PVN) and the dorsal motor nucleus of the vagus (DMNV) constitutes part of an important parasympathetic autonomic pathway that controls hepatic glucose production. Intracerebroventricular injection of insulin activates oxytocinergic neurones in the PVN and elicits the release of oxytocin into the circulation, which plays an important role in the metabolism of glucose. Moreover, the central action of insulin can reduce the concentration of glucose in blood taken from the hepatic vein of Wistar rats via activation of vagal efferent nerves to the liver. This mechanism is impaired in sedentary spontaneously hypertensive rats (SHR). Because aerobic exercise increases vagal tone, partly mediated by increasing the oxytocinergic connections between the PVN and DMNV, we hypothesised that oxytocin (OT) might alter the excitability of liver-projecting DMNV neurones. Thus, we investigated the effects of OT on electrical properties of the liver-projecting DMNV neurones from Wistar, SHR subjected to 4 weeks of exercise training, as well sedentary controls, using whole cell patch-clamping. The results show that OT increased the resting membrane potential of DMNV neurones in Wistar rats, as well as the firing frequency of these cells, but not in sedentary SHR. However, in SHR subjected to 4 weeks of exercise training, the effects of OT on liver-projecting DMNV neurones of were similar to those seen in Wistar rats. These findings show that OT elicits similar changes in the electrophysiological properties of liver-projecting DMNV neurones of Wistar and exercise-trained but not sedentary SHR. These results indicate that exercise training can restore the sensitivity of liver-projecting DMNV neurones of exercise-trained SHR to OT.
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Affiliation(s)
- Karoline Martins Dos Santos
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Davi José de Almeida Moraes
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Brazil
| | - Melina Pires da Silva
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Brazil
| | - Vagner Roberto Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
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Pitra S, Smith BN. Musings on the wanderer: What's new in our understanding of vago-vagal reflexes? VI. Central vagal circuits that control glucose metabolism. Am J Physiol Gastrointest Liver Physiol 2021; 320:G175-G182. [PMID: 33205998 PMCID: PMC7938771 DOI: 10.1152/ajpgi.00368.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Neurons in the brain stem dorsal vagal complex (DVC) take part in a continuous bidirectional crosstalk, in which they receive and respond to a vast array of signaling molecules, including glucose. Importantly, chronic dysregulation of blood glucose concentration, a hallmark of high prevalence pathologies, such as diabetes and metabolic syndrome, can induce neuroplasticity in DVC neural networks, which is hypothesized to either contribute to or compensate for the glycemic or insulinemic dysregulation observed in these conditions. Here, we revisit the topic of vagal reflexes to review recent research on the importance of DVC function in regulating systemic glucose homeostasis and the neuroplastic changes in this brain region that are associated with systemic glucose alterations. We also discuss the critical connection between these nuclei and the gut and the role of central vagal circuits in the favorable outcomes associated with bariatric surgical procedures for metabolic disorders.
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Affiliation(s)
- Soledad Pitra
- 1Department of Neuroscience, University of Kentucky, Lexington, Kentucky
| | - Bret N. Smith
- 1Department of Neuroscience, University of Kentucky, Lexington, Kentucky,2Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
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Wean JB, Smith BN. Fibroblast Growth Factor 19 Increases the Excitability of Pre-Motor Glutamatergic Dorsal Vagal Complex Neurons From Hyperglycemic Mice. Front Endocrinol (Lausanne) 2021; 12:765359. [PMID: 34858337 PMCID: PMC8632226 DOI: 10.3389/fendo.2021.765359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/26/2021] [Indexed: 01/14/2023] Open
Abstract
Intracerebroventricular administration of the protein hormone fibroblast growth factor 19 (FGF19) to the hindbrain produces potent antidiabetic effects in hyperglycemic mice that are likely mediated through a vagal parasympathetic mechanism. FGF19 increases the synaptic excitability of parasympathetic motor neurons in the dorsal motor nucleus of the vagus (DMV) from hyperglycemic, but not normoglycemic, mice but the source of this synaptic input is unknown. Neurons in the area postrema (AP) and nucleus tractus solitarius (NTS) express high levels of FGF receptors and exert glutamatergic control over the DMV. This study tested the hypothesis that FGF19 increases glutamate release in the DMV by increasing the activity of glutamatergic AP and NTS neurons in hyperglycemic mice. Glutamate photoactivation experiments confirmed that FGF19 increases synaptic glutamate release from AP and NTS neurons that connect to the DMV in hyperglycemic, but not normoglycemic mice. Contrary to expectations, FGF19 produced a mixed effect on intrinsic membrane properties in the NTS with a trend towards inhibition, suggesting that another mechanism was responsible for the observed effects on glutamate release in the DMV. Consistent with the hypothesis, FGF19 increased action potential-dependent glutamate release in the NTS in hyperglycemic mice only. Finally, glutamate photoactivation experiments confirmed that FGF19 increases the activity of glutamatergic AP neurons that project to the NTS in hyperglycemic mice. Together, these results support the hypothesis that FGF19 increases glutamate release from AP and NTS neurons that project to the DMV in hyperglycemic mice. FGF19 therefore modifies the local vago-vagal reflex circuitry at several points. Additionally, since the AP and NTS communicate with several other metabolic regulatory nuclei in the brain, FGF19 in the hindbrain may alter neuroendocrine and behavioral aspects of metabolism, in addition to changes in parasympathetic output.
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Affiliation(s)
- Jordan B. Wean
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY, United States
| | - Bret N. Smith
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY, United States
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, United States
- *Correspondence: Bret N. Smith,
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Saki K, Mansouri V, Abdi S, Fathi M, Razzaghi Z, Haghazali M. Assessment of common and differentially expressed proteins between diabetes mellitus and fatty liver disease: a network analysis. GASTROENTEROLOGY AND HEPATOLOGY FROM BED TO BENCH 2021; 14:S94-S101. [PMID: 35154608 PMCID: PMC8817743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/11/2021] [Indexed: 12/03/2022]
Abstract
AIM This study aimed to introduce the main biomarkers related to NFLD and diabetes II to determine common pathogenic and metabolite factors linking NFLD to diabetes II. BACKGROUND Nonalcoholic fatty liver disease (NFLD) is chronic hepatic failure with a broad range of hepatic disorders. NFLD and diabetes type 2 coexist regularly to drive adverse outcomes such as hepatocellular carcinoma and vascular complications. METHODS The proteins related to NFDL and diabetes mellitus were extracted from String database. Proteins related to each disease were included in protein-protein interaction networks in Cytoscape software. Obtained networks were analyzed using Cytoscape network analyzer. The central nodes were determined as top hubs based on degree value. The top hubs related to NFLD and diabetes mellites were compared. RESULTS In total, 200 proteins related to NFDL and diabetes mellitus were found separately in String database and connected through undirected edges in individual networks. Central nodes based on degree value were determined for each disease. Ten percent of top nodes were selected based on degree value as the 20 top hubs for each disease. Target common hub proteins between NFDL and diabetes mellitus comprised INS, AKT1, ALB, PPARG, IL6, GPDPH, LEP, TNF, ADIPOQ, IGF1, TP53, MAPK3, and SIRT1. CONCLUSION According to the results, 13 common and 14 discriminatory central dysregulated proteins were determined for NAFLD and diabetes mellitus.
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Affiliation(s)
- Kourosh Saki
- Proteomics Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Vahid Mansouri
- Proteomics Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Saeed Abdi
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Fathi
- Critical Care Quality Improvement Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Zahra Razzaghi
- Laser Application in Medical Sciences Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Mehrdad Haghazali
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
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Effects of metabolic state on the regulation of melanocortin circuits. Physiol Behav 2020; 224:113039. [PMID: 32610101 PMCID: PMC7387173 DOI: 10.1016/j.physbeh.2020.113039] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 06/01/2020] [Accepted: 06/26/2020] [Indexed: 12/14/2022]
Abstract
Dysfunction in neurophysiological systems that regulate food intake and metabolism are at least partly responsible for obesity and related comorbidities. An important component of this process is the hypothalamic melanocortin system, where an imbalance can result in severe obesity and deficits in glucose metabolism. Exercise offers many health benefits related to cardiovascular improvements, hunger control, and blood glucose homeostasis. However, the molecular mechanism underlying the exercise-induced improvements to the melanocortin system remain undefined. Here, we review the role of the melanocortin system to sense hormonal, nutrient, and neuronal signals of energy status. This information is then relayed onto secondary neurons in order to regulate physiological parameters, which promote proper energy and glucose balance. We also provide an overview on the effects of physical exercise to induce biophysical changes in the melanocortin circuit which may regulate food intake, glucose metabolism and improve overall metabolic health.
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Cowen N, Bhatnagar A. The Potential Role of Activating the ATP-Sensitive Potassium Channel in the Treatment of Hyperphagic Obesity. Genes (Basel) 2020; 11:genes11040450. [PMID: 32326226 PMCID: PMC7230375 DOI: 10.3390/genes11040450] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 04/16/2020] [Indexed: 02/06/2023] Open
Abstract
To evaluate the potential role of ATP-sensitive potassium (KATP) channel activation in the treatment of hyperphagic obesity, a PubMed search was conducted focused on the expression of genes encoding the KATP channel, the response to activating the KATP channel in tissues regulating appetite and the establishment and maintenance of obesity, the evaluation of KATP activators in obese hyperphagic animal models, and clinical studies on syndromic obesity. KATP channel activation is mechanistically involved in the regulation of appetite in the arcuate nucleus; the regulation of hyperinsulinemia, glycemic control, appetite and satiety in the dorsal motor nucleus of vagus; insulin secretion by β-cells; and the synthesis and β-oxidation of fatty acids in adipocytes. KATP channel activators have been evaluated in hyperphagic obese animal models and were shown to reduce hyperphagia, induce fat loss and weight loss in older animals, reduce the accumulation of excess body fat in growing animals, reduce circulating and hepatic lipids, and improve glycemic control. Recent experience with a KATP channel activator in Prader-Willi syndrome is consistent with the therapeutic responses observed in animal models. KATP channel activation, given the breadth of impact and animal model and clinical results, is a viable target in hyperphagic obesity.
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A hindbrain inhibitory microcircuit mediates vagally-coordinated glucose regulation. Sci Rep 2019; 9:2722. [PMID: 30804396 PMCID: PMC6389891 DOI: 10.1038/s41598-019-39490-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 12/14/2018] [Indexed: 02/07/2023] Open
Abstract
Neurons in the brainstem dorsal vagal complex integrate neural and humoral signals to coordinate autonomic output to viscera that regulate a variety of physiological functions, but how this circuitry regulates metabolism is murky. We tested the hypothesis that premotor, GABAergic neurons in the nucleus tractus solitarius (NTS) form a hindbrain micro-circuit with preganglionic parasympathetic motorneurons of the dorsal motor nucleus of the vagus (DMV) that is capable of modulating systemic blood glucose concentration. In vitro, neuronal activation or inhibition using either excitatory or inhibitory designer receptor exclusively activated by designer drugs (DREADDs) constructs expressed in GABAergic NTS neurons increased or decreased, respectively, action potential firing of GABAergic NTS neurons and downstream synaptic inhibition of the DMV. In vivo, DREADD-mediated activation of GABAergic NTS neurons increased systemic blood glucose concentration, whereas DREADD-mediated silencing of these neurons was without effect. The DREADD-induced hyperglycemia was abolished by blocking peripheral muscarinic receptors, consistent with the hypothesis that altered parasympathetic drive mediated the response. This effect was paralleled by elevated serum glucagon and hepatic phosphoenolpyruvate carboxykinase 1 (PEPCK1) expression, without affecting insulin levels or muscle metabolism. Activity in a hindbrain inhibitory microcircuit is sufficient to modulate systemic glucose concentration, independent of insulin secretion or utilization.
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Functional Neuroplasticity in the Nucleus Tractus Solitarius and Increased Risk of Sudden Death in Mice with Acquired Temporal Lobe Epilepsy. eNeuro 2017; 4:eN-NWR-0319-17. [PMID: 29085908 PMCID: PMC5661358 DOI: 10.1523/eneuro.0319-17.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/13/2017] [Accepted: 10/16/2017] [Indexed: 12/23/2022] Open
Abstract
Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in individuals with refractory acquired epilepsy. Cardiorespiratory failure is the most likely cause in most cases, and central autonomic dysfunction has been implicated as a contributing factor to SUDEP. Neurons of the nucleus tractus solitarius (NTS) in the brainstem vagal complex receive and integrate vagally mediated information regarding cardiorespiratory and other autonomic functions, and GABAergic inhibitory NTS neurons play an essential role in modulating autonomic output. We assessed the activity of GABAergic NTS neurons as a function of epilepsy development in the pilocarpine-induced status epilepticus (SE) model of temporal lobe epilepsy (TLE). Compared with age-matched controls, mice that survived SE had significantly lower survival rates by 150 d post-SE. GABAergic NTS neurons from mice that survived SE displayed a glutamate-dependent increase in spontaneous action potential firing rate by 12 wks post-SE. Increased spontaneous EPSC frequency was also detected, but vagal afferent synaptic release properties were unaltered, suggesting that an increase in glutamate release from central neurons developed in the NTS after SE. Our results indicate that long-term changes in glutamate release and activity of GABAergic neurons emerge in the NTS in association with epileptogenesis. These changes might contribute to increased risk of cardiorespiratory dysfunction and sudden death in this model of TLE.
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Boychuk CR, Smith KC, Smith BN. Functional and molecular plasticity of γ and α1 GABA A receptor subunits in the dorsal motor nucleus of the vagus after experimentally induced diabetes. J Neurophysiol 2017; 118:2833-2841. [PMID: 28835522 DOI: 10.1152/jn.00085.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 08/17/2017] [Accepted: 08/17/2017] [Indexed: 12/13/2022] Open
Abstract
Chronic experimentally induced hyperglycemia augments subunit-specific γ-aminobutyric acid A (GABAA) receptor-mediated inhibition of parasympathetic preganglionic motor neurons in the dorsal motor nucleus of the vagus (DMV). However, the contribution of α1 or γ GABAA receptor subunits, which are ubiquitously expressed on central nervous system neurons, to this elevation in inhibitory tone have not been determined. This study investigated the effect of chronic hyperglycemia/hypoinsulinemia on α1- and γ-subunit-specific GABAA receptor-mediated inhibition using electrophysiological recordings in vitro and quantitative RT-PCR. DMV neurons from streptozotocin-treated mice demonstrated enhancement of both phasic and tonic inhibitory currents in response to application of the α1-subunit-selective GABAA receptor-positive allosteric modulator zolpidem. Responses to low concentrations of the GABAA receptor antagonist gabazine suggested an additional increased contribution of γ-subunit-containing receptors to tonic currents in DMV neurons. Consistent with the functional elevation in α1- and γ-subunit-dependent activity, transcription of both the α1- and γ2-subunits was increased in the dorsal vagal complex of streptozotocin-treated mice. Overall, these findings suggest an increased sensitivity to both zolpidem and gabazine after several days of hyperglycemia/hypoinsulinemia, which could contribute to altered parasympathetic output from DMV neurons in diabetes.NEW & NOTEWORTHY Glutamate and GABA signaling in the dorsal vagal complex is elevated after several days of chronic hyperglycemia in a mouse model of type 1 diabetes. We report persistently enhanced GABAA receptor-mediated responses to the somnolescent zolpidem in preganglionic vagal motor neurons. These results imply a broader impact of chronic hyperglycemia on central vagal function than previously appreciated and reinforce the hypothesis that diabetes effects in the brain can impact regulation of metabolic homeostasis.
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Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Katalin C Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
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Han C, Rice MW, Cai D. Neuroinflammatory and autonomic mechanisms in diabetes and hypertension. Am J Physiol Endocrinol Metab 2016; 311:E32-41. [PMID: 27166279 PMCID: PMC4967151 DOI: 10.1152/ajpendo.00012.2016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 05/03/2016] [Indexed: 02/07/2023]
Abstract
Interdisciplinary studies in the research fields of endocrinology and immunology show that obesity-associated overnutrition leads to neuroinflammatory molecular changes, in particular in the hypothalamus, chronically causing various disorders known as elements of metabolic syndrome. In this process, neural or hypothalamic inflammation impairs the neuroendocrine and autonomic regulation of the brain over blood pressure and glucose homeostasis as well as insulin secretion, and elevated sympathetic activation has been appreciated as a critical mediator. This review describes the involved physiology and mechanisms, with a focus on glucose and blood pressure balance, and suggests that neuroinflammation employs the autonomic nervous system to mediate the development of diabetes and hypertension.
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Affiliation(s)
- Cheng Han
- Department of Molecular Pharmacology, Diabetes Research Center, Institute of Aging, Albert Einstein College of Medicine, Bronx, New York
| | - Matthew W Rice
- Department of Molecular Pharmacology, Diabetes Research Center, Institute of Aging, Albert Einstein College of Medicine, Bronx, New York
| | - Dongsheng Cai
- Department of Molecular Pharmacology, Diabetes Research Center, Institute of Aging, Albert Einstein College of Medicine, Bronx, New York
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Derbenev AV, Zsombok A. Potential therapeutic value of TRPV1 and TRPA1 in diabetes mellitus and obesity. Semin Immunopathol 2016; 38:397-406. [PMID: 26403087 PMCID: PMC4808497 DOI: 10.1007/s00281-015-0529-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022]
Abstract
Diabetes mellitus and obesity, which is a major risk factor in the development of type 2 diabetes mellitus, have reached epidemic proportions worldwide including the USA. The current statistics and forecasts, both short- and long-term, are alarming and predict severe problems in the near future. Therefore, there is a race for developing new compounds, discovering new receptors, or finding alternative solutions to prevent and/or treat the symptoms and complications related to obesity and diabetes mellitus. It is well demonstrated that members of the transient receptor potential (TRP) superfamily play a crucial role in a variety of biological functions both in health and disease. In the recent years, transient receptor potential vanilloid type 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) were shown to have beneficial effects on whole body metabolism including glucose homeostasis. TRPV1 and TRPA1 have been associated with control of weight, pancreatic function, hormone secretion, thermogenesis, and neuronal function, which suggest a potential therapeutic value of these channels. This review summarizes recent findings regarding TRPV1 and TRPA1 in association with whole body metabolism with emphasis on obese and diabetic conditions.
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Affiliation(s)
- Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA.
- Department of Medicine, Endocrinology Section, School of Medicine, Tulane University, 1430 Tulane Ave., New Orleans, LA, 70112, USA.
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O'Hare JD, Zsombok A. Brain-liver connections: role of the preautonomic PVN neurons. Am J Physiol Endocrinol Metab 2016; 310:E183-9. [PMID: 26646097 PMCID: PMC4838125 DOI: 10.1152/ajpendo.00302.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 12/01/2015] [Indexed: 12/28/2022]
Abstract
Diabetes mellitus and the coexisting conditions and complications, including hypo- and hyperglycemic events, obesity, high cholesterol levels, and many more, are devastating problems. Undoubtedly, there is a huge demand for treatment and prevention of these conditions that justifies the search for new approaches and concepts for better management of whole body metabolism. Emerging evidence demonstrates that the autonomic nervous system is largely involved in the regulation of glucose homeostasis; however, the underlying mechanisms are still under investigation. Within the hypothalamus, the paraventricular nucleus (PVN) is in a unique position to integrate neural and hormonal signals to command both the autonomic and neuroendocrine outflow. This minireview will provide a brief overview on the role of preautonomic PVN neurons and the importance of the PVN-liver pathway in the regulation of glucose homeostasis.
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Affiliation(s)
- James D O'Hare
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
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Anwar IJ, Miyata K, Zsombok A. Brain stem as a target site for the metabolic side effects of olanzapine. J Neurophysiol 2015; 115:1389-98. [PMID: 26719086 DOI: 10.1152/jn.00387.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 12/30/2015] [Indexed: 01/27/2023] Open
Abstract
Olanzapine, an atypical antipsychotic, is widely prescribed for the treatment of schizophrenia and bipolar disorder despite causing undesirable metabolic side effects. A variety of mechanisms and brain sites have been proposed as contributors to the side effects; however, the role of the dorsal motor nucleus of the vagus nerve (DMV), which plays a crucial role in the regulation of subdiaphragmatic organs and thus governs energy and glucose homeostasis, is largely unknown. Identifying the effect of olanzapine on the excitability of DMV neurons in both sexes is thus crucial to understanding possible underlying mechanisms. Whole cell patch-clamp electrophysiological recordings were conducted in stomach- and liver-related DMV neurons identified with retrograde viral tracers and in random DMV neurons. The effect of olanzapine on the neuronal excitability of DMV neurons both in male and female mice was established. Our data demonstrate that olanzapine hyperpolarizes the DMV neurons in both sexes and this effect is reversible. The hyperpolarization is associated with decreased firing rate and input resistance. Olanzapine also decreases the excitability of a subset of stomach- and liver-related DMV neurons. Our study demonstrates that olanzapine has a powerful effect on DMV neurons in both sexes, indicating its ability to reduce vagal output to the subdiaphragmatic organs, which likely contributes to the metabolic side effects observed in both humans and experimental models. These findings suggest that the metabolic side effects of olanzapine may partially originate in the DMV.
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Affiliation(s)
- Imran J Anwar
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Kayoko Miyata
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
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Halmos KC, Gyarmati P, Xu H, Maimaiti S, Jancsó G, Benedek G, Smith BN. Molecular and functional changes in glucokinase expression in the brainstem dorsal vagal complex in a murine model of type 1 diabetes. Neuroscience 2015; 306:115-22. [PMID: 26297899 PMCID: PMC4575893 DOI: 10.1016/j.neuroscience.2015.08.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/24/2015] [Accepted: 08/12/2015] [Indexed: 11/27/2022]
Abstract
Glucose concentration changes in the nucleus tractus solitarius (NTS) affect visceral function and metabolism by influencing central vagal circuits, especially inhibitory, GABAergic NTS neurons. Acutely elevated glucose can alter NTS neuron activity, and prolonged hyperglycemia and hypoinsulemia in animal models of type 1 diabetes results in plasticity of neural responses in the NTS. NTS neurons contributing to metabolic regulation therefore act as central glucose sensors and are functionally altered in type 1 diabetes. Glucokinase (GCK) mediates cellular utilization of glucose, linking increased glucose concentration to excitability changes mediated by ATP-sensitive K(+) channels (KATP). Using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, and in vitro electrophysiology, we tested the hypothesis that changes in GCK expression in the NTS accompany the development of diabetes symptoms in the streptozotocin (STZ)-treated mouse model of type 1 diabetes. After several days of hyperglycemia in STZ-treated mice, RNA expression of GCK, but not Kir6.2 or SUR1, was decreased versus controls in the dorsal vagal complex. Electrophysiological recordings in vitro indicated that neural responses to acute hyperglycemia, and synaptic responsiveness to blockade of GCK with glucosamine, were attenuated in GABAergic NTS neurons from STZ-treated mice, consistent with reduced molecular and functional expression of GCK in the vagal complex of hyperglycemic, STZ-treated mice. Altered autonomic responses to glucose in type 1 diabetes may therefore involve reduced functional GCK expression in the dorsal vagal complex.
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Affiliation(s)
- K C Halmos
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, United States; Department of Physiology, University of Szeged, Dom ter 10 H-6720, Szeged, Hungary
| | - P Gyarmati
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, United States
| | - H Xu
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, United States
| | - S Maimaiti
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, United States
| | - G Jancsó
- Department of Physiology, University of Szeged, Dom ter 10 H-6720, Szeged, Hungary
| | - G Benedek
- Department of Physiology, University of Szeged, Dom ter 10 H-6720, Szeged, Hungary
| | - B N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, United States.
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The Wanderer Falters: Central Vagal Dysregulation Triggers SUDEP. Epilepsy Curr 2015; 15:269-70. [PMID: 26445937 DOI: 10.5698/1535-7511-15.5.269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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18
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Browning KN, Travagli RA. Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions. Compr Physiol 2015; 4:1339-68. [PMID: 25428846 DOI: 10.1002/cphy.c130055] [Citation(s) in RCA: 322] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Although the gastrointestinal (GI) tract possesses intrinsic neural plexuses that allow a significant degree of autonomy over GI functions, the central nervous system (CNS) provides extrinsic neural inputs that regulate, modulate, and control these functions. While the intestines are capable of functioning in the absence of extrinsic inputs, the stomach and esophagus are much more dependent upon extrinsic neural inputs, particularly from parasympathetic and sympathetic pathways. The sympathetic nervous system exerts a predominantly inhibitory effect upon GI muscle and provides a tonic inhibitory influence over mucosal secretion while, at the same time, regulates GI blood flow via neurally mediated vasoconstriction. The parasympathetic nervous system, in contrast, exerts both excitatory and inhibitory control over gastric and intestinal tone and motility. Although GI functions are controlled by the autonomic nervous system and occur, by and large, independently of conscious perception, it is clear that the higher CNS centers influence homeostatic control as well as cognitive and behavioral functions. This review will describe the basic neural circuitry of extrinsic inputs to the GI tract as well as the major CNS nuclei that innervate and modulate the activity of these pathways. The role of CNS-centered reflexes in the regulation of GI functions will be discussed as will modulation of these reflexes under both physiological and pathophysiological conditions. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide these answers.
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Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania
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Boychuk CR, Gyarmati P, Xu H, Smith BN. Glucose sensing by GABAergic neurons in the mouse nucleus tractus solitarii. J Neurophysiol 2015; 114:999-1007. [PMID: 26084907 DOI: 10.1152/jn.00310.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/15/2015] [Indexed: 12/23/2022] Open
Abstract
Changes in blood glucose concentration alter autonomic function in a manner consistent with altered neural activity in brain regions controlling digestive processes, including neurons in the brain stem nucleus tractus solitarii (NTS), which process viscerosensory information. With whole cell or on-cell patch-clamp recordings, responses to elevating glucose concentration from 2.5 to 15 mM were assessed in identified GABAergic NTS neurons in slices from transgenic mice that express EGFP in a subset of GABA neurons. Single-cell real-time RT-PCR was also performed to detect glutamic acid decarboxylase (GAD67) in recorded neurons. In most identified GABA neurons (73%), elevating glucose concentration from 2.5 to 15 mM resulted in either increased (40%) or decreased (33%) neuronal excitability, reflected by altered membrane potential and/or action potential firing. Effects on membrane potential were maintained when action potentials or fast synaptic inputs were blocked, suggesting direct glucose sensing by GABA neurons. Glucose-inhibited GABA neurons were found predominantly in the lateral NTS, whereas glucose-excited cells were mainly in the medial NTS, suggesting regional segregation of responses. Responses were prevented in the presence of glucosamine, a glucokinase (GCK) inhibitor. Depolarizing responses were prevented when KATP channel activity was blocked with tolbutamide. Whereas effects on synaptic input to identified GABAergic neurons were variable in GABA neurons, elevating glucose increased glutamate release subsequent to stimulation of tractus solitarius in unlabeled, unidentified neurons. These results indicate that GABAergic NTS neurons act as GCK-dependent glucose sensors in the vagal complex, providing a means of modulating central autonomic signals when glucose is elevated.
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Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Peter Gyarmati
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Hong Xu
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
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Zsombok A, Jiang Y, Gao H, Anwar IJ, Rezai-Zadeh K, Enix CL, Münzberg H, Derbenev AV. Regulation of leptin receptor-expressing neurons in the brainstem by TRPV1. Physiol Rep 2014; 2:2/9/e12160. [PMID: 25263209 PMCID: PMC4270226 DOI: 10.14814/phy2.12160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The central nervous system plays a critical role in the regulation of feeding behavior and whole‐body metabolism via controlling the autonomic output to the visceral organs. Activity of the parasympathetic neurons in the dorsal motor nucleus of the vagus (DMV) determines the vagal tone and thereby modulates the function of the subdiaphragmatic organs. Leptin is highly involved in the regulation of food intake and alters neuronal excitability of brainstem neurons. Transient receptor potential vanilloid type 1 (TRPV1) has also been shown to increase neurotransmission in the brainstem and we tested the hypothesis that TRPV1 regulates presynaptic neurotransmitter release to leptin receptor‐expressing (LepRbEGFP) DMV neurons. Whole‐cell patch‐clamp recordings were performed to determine the effect of TRPV1 activation on excitatory and inhibitory postsynaptic currents (EPSC, IPSC) of LepRbEGFP neurons in the DMV. Capsaicin, a TRPV1 agonist increased the frequency of miniature EPSCs in 50% of LepRbEGFP neurons without altering the frequency of miniature IPSCs in the DMV. Stomach‐projecting LepRbEGFP neurons were identified in the DMV using the transsynaptic retrograde viral tracer PRV‐614. Activation of TRPV1 increased the frequency of mEPSC in ~50% of stomach‐related LepRbEGFP DMV neurons. These data demonstrate that TRPV1 increases excitatory neurotransmission to a subpopulation of LepRbEGFP DMV neurons via presynaptic mechanisms and suggest a potential interaction between TRPV1 and leptin signaling in the DMV. e12160 Our data demonstrate that TRPV1 is involved in the regulation of a subpopulation of leptin receptor‐expressing neurons in the dorsal motor nucleus of the vagus via presynaptic mechanisms.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
| | - Yanyan Jiang
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
| | - Hong Gao
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Imran J Anwar
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Kavon Rezai-Zadeh
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana
| | - Courtney L Enix
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Heike Münzberg
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana
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Guan X. The CNS glucagon-like peptide-2 receptor in the control of energy balance and glucose homeostasis. Am J Physiol Regul Integr Comp Physiol 2014; 307:R585-96. [PMID: 24990862 DOI: 10.1152/ajpregu.00096.2014] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The gut-brain axis plays a key role in the control of energy balance and glucose homeostasis. In response to luminal stimulation of macronutrients and microbiota-derived metabolites (secondary bile acids and short chain fatty acids), glucagon-like peptides (GLP-1 and -2) are cosecreted from endocrine L cells in the gut and coreleased from preproglucagonergic neurons in the brain stem. Glucagon-like peptides are proposed as key mediators for bariatric surgery-improved glycemic control and energy balance. Little is known about the GLP-2 receptor (Glp2r)-mediated physiological roles in the control of food intake and glucose homeostasis, yet Glp1r has been studied extensively. This review will highlight the physiological relevance of the central nervous system (CNS) Glp2r in the control of energy balance and glucose homeostasis and focuses on cellular mechanisms underlying the CNS Glp2r-mediated neural circuitry and intracellular PI3K signaling pathway. New evidence (obtained from Glp2r tissue-specific KO mice) indicates that the Glp2r in POMC neurons is essential for suppressing feeding behavior, gastrointestinal motility, and hepatic glucose production. Mice with Glp2r deletion selectively in POMC neurons exhibit hyperphagic behavior, accelerated gastric emptying, glucose intolerance, and hepatic insulin resistance. GLP-2 differentially modulates postsynaptic membrane excitability of hypothalamic POMC neurons in Glp2r- and PI3K-dependent manners. GLP-2 activates the PI3K-Akt-FoxO1 signaling pathway in POMC neurons by Glp2r-p85α interaction. Intracerebroventricular GLP-2 augments glucose tolerance, suppresses glucose production, and enhances insulin sensitivity, which require PI3K (p110α) activation in POMC neurons. Thus, the CNS Glp2r plays a physiological role in the control of food intake and glucose homeostasis. This review will also discuss key questions for future studies.
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Affiliation(s)
- Xinfu Guan
- U.S. Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics; and Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas
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22
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Jiang Y, Zsombok A. Regulation of neurons in the dorsal motor nucleus of the vagus by SIRT1. Front Neurosci 2014; 7:270. [PMID: 24454277 PMCID: PMC3887315 DOI: 10.3389/fnins.2013.00270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 12/20/2013] [Indexed: 12/29/2022] Open
Abstract
Neurons in the dorsal motor nucleus of the vagus (DMV) play a critical role in the regulation of autonomic functions. Previous studies indicated that central activation of sirtuin 1 (SIRT1) has beneficial effects on homeostasis, most likely via modulation of the autonomic output. Sirtuins are NAD+-dependent deacetylases and have been associated with longevity. SIRT1 is one of the best-characterized sirtuins expressed in mammals, and may be involved in the regulation of metabolism. Resveratrol, a SIRT1 activator reduced hyperglycemia likely through activation of vagal output; however, the cellular mechanisms of action have not been determined. In this study, whole-cell patch-clamp electrophysiology on acute brainstem slices was used to test the hypothesis that activation of SIRT1 with resveratrol enhances neurotransmission in DMV neurons. Application of resveratrol increased the frequency of spontaneous excitatory postsynaptic currents (sEPSC). This effect was KATP channel-dependent and was prevented with pre-application of SIRT1 inhibitor, EX527. Resveratrol also increased miniature EPSC (mEPSC) frequency without change in amplitude. Furthermore, our data demonstrated that resveratrol regulates excitatory neurotransmission in a PI3 kinase-dependent manner, since wortmannin, a PI3K inhibitor prevented the increase of mEPSC frequency caused by resveratrol. In conclusion, our data demonstrate that resveratrol via SIRT1 increases excitatory neurotransmission to DMV neurons. These observations suggest that activation of SIRT1 may regulate the function of subdiaphragmatic organs through controlling the activity of parasympathetic DMV neurons.
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Affiliation(s)
- Yanyan Jiang
- Neuroscience Program, School of Science and Engineering, Tulane University New Orleans, LA, USA ; Department of Physiology, School of Medicine, Tulane University New Orleans, LA, USA
| | - Andrea Zsombok
- Neuroscience Program, School of Science and Engineering, Tulane University New Orleans, LA, USA ; Department of Physiology, School of Medicine, Tulane University New Orleans, LA, USA
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Diepenbroek C, van der Plasse G, Eggels L, Rijnsburger M, Feenstra MGP, Kalsbeek A, Denys D, Fliers E, Serlie MJ, la Fleur SE. Alterations in blood glucose and plasma glucagon concentrations during deep brain stimulation in the shell region of the nucleus accumbens in rats. Front Neurosci 2013; 7:226. [PMID: 24339800 PMCID: PMC3857552 DOI: 10.3389/fnins.2013.00226] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 11/06/2013] [Indexed: 12/24/2022] Open
Abstract
Deep brain stimulation (DBS) of the nucleus accumbens (NAc) is an effective therapy for obsessive compulsive disorder (OCD) and is currently under investigation as a treatment for eating disorders. DBS of this area is associated with altered food intake and pharmacological treatment of OCD is associated with the risk of developing type 2 diabetes. Therefore we examined if DBS of the NAc-shell (sNAc) influences glucose metabolism. Male Wistar rats were subjected to DBS, or sham stimulation, for a period of 1 h. To assess the effects of stimulation on blood glucose and glucoregulatory hormones, blood samples were drawn before, during and after stimulation. Subsequently, all animals were used for quantitative assessment of Fos immunoreactivity in the lateral hypothalamic area (LHA) using computerized image analysis. DBS of the sNAc rapidly increased plasma concentrations of glucagon and glucose while sham stimulation and DBS outside the sNAc were ineffective. In addition, the increase in glucose was dependent on DBS intensity. In contrast, the DBS-induced increase in plasma corticosterone concentrations was independent of intensity and region, indicating that the observed DBS-induced metabolic changes were not due to corticosterone release. Stimulation of the sNAc with 200 μA increased Fos immunoreactivity in the LHA compared to sham or 100 μA stimulated animals. These data show that DBS of the sNAc alters glucose metabolism in a region- and intensity- dependent manner in association with neuronal activation in the LHA. Moreover, these data illustrate the need to monitor changes in glucose metabolism during DBS-treatment of OCD patients.
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Affiliation(s)
- Charlene Diepenbroek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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Decreased Efferents of Mesencephalic Raphe Nuclei to Striatum in Animal Model of Streptozocin-Induced Diabetes. ARCHIVES OF NEUROSCIENCE 2013. [DOI: 10.5812/archneurosci.11055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Breivik T, Gundersen Y, Gjermo P, Opstad PK. Chronic treatment with the glucocorticoid receptor antagonist RU486 inhibits diabetes-induced enhancement of experimental periodontitis. J Periodontal Res 2013; 49:36-44. [PMID: 23586673 DOI: 10.1111/jre.12076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2013] [Indexed: 01/11/2023]
Abstract
BACKGROUND AND OBJECTIVE Chronic hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and excessive glucocorticoid hormone release have been associated with diabetes, altered immune responses and increased susceptibility to periodontitis. In the present study we tested the impact of streptozotocin (STZ)-induced diabetes on ligature-induced periodontitis and the effect of subsequent treatment with the glucocorticoid receptor (GR) antagonist, RU486. MATERIAL AND METHODS A single dose of STZ [45 mg/kg, intraperitoneally (i.p.)] or vehicle was given 10 d before induction of ligature-induced periodontitis and implantation subcutaneously of a drug pellet containing the GR antagonist, RU486, or a placebo pellet. Periodontitis was assessed when the ligatures had been in place for 21 d. Two hours before decapitation all rats received gram-negative bacterial lipopolysaccharide (LPS) (150 μg/kg, i.p.) to induce a robust immune and stress response. RESULTS Compared with control rats, STZ-treated rats developed significantly more periodontal bone loss, and RU486 treatment of STZ -treated rats significantly inhibited this effect. STZ-treated rats also showed significantly higher levels of the HPA axis-derived hormone, corticosterone, as well as of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-α), but lower levels of the anti-inflammatory cytokines interleukin-10 (IL-10) and transforming growth factor-1beta (TGF-1β) after LPS stimulation. GR blockade had no statistically significant effects on these measurements in diabetic rats, but tended to enhance the levels of TNF-α and TGF-1β, and reduce the levels of IL-10 and blood glucose. CONCLUSION In diabetic subjects, excessive GR activation as a result of chronic high levels of glucocorticoid hormones may alter immune-system responses in a manner that may increase the susceptibility to periodontitis.
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Affiliation(s)
- T Breivik
- Faculty of Dentistry, Department of Periodontology, University of Oslo, Oslo, Norway; Division of Protection, Norwegian Defence Research Establishment, Kjeller, Norway
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Zsombok A. Autonomic control and bariatric procedures. Auton Neurosci 2013; 177:81-6. [PMID: 23538033 DOI: 10.1016/j.autneu.2013.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 10/10/2012] [Accepted: 03/01/2013] [Indexed: 12/12/2022]
Abstract
The sudden improvement of metabolic profile and the remission of type 2 diabetes after bariatric surgery, well before weight loss, raise important new questions regarding glycemic control. Currently, various types of bariatric procedures target type 2 diabetes in obese and non-obese patients. Nevertheless, the origin of the dramatic metabolic improvements, including glucose homeostasis, is poorly understood, and the role of the gastrointestinal (GI) tract remains relatively speculative, as well as why these procedures are variably effective. One neglected explanation is that such interventions disrupt neural networks mediating GI-brain communication and could alter the autonomic output to the visceral organs, including the liver. Incretins, e.g., glucagon-like peptide 1 (GLP-1), have major influence on the central nervous system. Moreover, the level of GLP-1 is observed to significantly increase after bariatric surgery and could be a key factor in the weight-independent, anti-diabetic effect. Therefore, this review will evaluate the effect of GLP-1 on the central nervous system, with emphasis on the cellular effects of GLP-1, and will provide an overview of the autonomic control of the liver.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, Endocrinology Section, Tulane University, School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112, United States; Department of Medicine, Endocrinology Section, Tulane University, School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112, United States.
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Williams KH, Shackel NA, Gorrell MD, McLennan SV, Twigg SM. Diabetes and nonalcoholic Fatty liver disease: a pathogenic duo. Endocr Rev 2013; 34:84-129. [PMID: 23238855 DOI: 10.1210/er.2012-1009] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent data increasingly support a complex interplay between the metabolic condition diabetes mellitus and the pathologically defined nonalcoholic fatty liver disease (NAFLD). NAFLD predicts the development of type 2 diabetes and vice versa, and each condition may serve as a progression factor for the other. Although the association of diabetes and NAFLD is likely to be partly the result of a "common soil," it is also probable that diabetes interacts with NAFLD through specific pathogenic mechanisms. In particular, through interrelated metabolic pathways currently only partly understood, diabetes appears to accelerate the progression of NAFLD to nonalcoholic steatohepatitis, defined by the presence of necroinflammation, with varying degrees of liver fibrosis. In the research setting, obstacles that have made the identification of clinically significant NAFLD, and particularly nonalcoholic steatohepatitis, difficult are being addressed with the use of new imaging techniques combined with risk algorithms derived from peripheral blood profiling. These techniques are likely to be used in the diabetes population in the near future. This review examines the pathogenic links between NAFLD and diabetes by exploring the epidemiological evidence in humans and also through newer animal models. Emerging technology to help screen noninvasively for differing pathological forms of NAFLD and the potential role of preventive and therapeutic approaches for NAFLD in the setting of diabetes are also examined.
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Affiliation(s)
- K H Williams
- Sydney Medical School and the Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
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Tamaddonfard E, Farshid AA, Asri-Rezaee S, Javadi S, Khosravi V, Rahman B, Mirfakhraee Z. Crocin improved learning and memory impairments in streptozotocin-induced diabetic rats. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2013; 16:91-100. [PMID: 23638297 PMCID: PMC3637909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 12/08/2012] [Indexed: 11/30/2022]
Abstract
OBJECTIVE(S) Crocin influences many biological functions including memory and learning. The present study was aimed to investigate the effects of crocin on learning and memory impairments in streptozotocine-induced diabetic rats. MATERIALS AND METHODS Diabetes was induced by intraperitoneal (IP) injection of streptozotocin (STZ, 45 mg/kg). Transfer latency (TL) paradigm in elevated plus-maze (EPM) was used as an index of learning and memory. Plasma levels of total antioxidant capacity (TAC) and malondialdehyde (MDA), blood levels of glucose, and serum concentrations of insulin were measured. The number of hippocampal neurons was also counted. RESULTS STZ increased acquisition transfer latency (TL1) and retention transfer latency (TL2), and MDA, decreased transfer latency shortening (TLs) and TCA, produced hyperglycemia and hypoinsulinemia, and reduced the number of neurons in the hippocampus. Learning and memory impairments and blood TCA, MDA, glucose, and insulin changes induced by streptozotocin were improved with long-term IP injection of crocin at doses of 15 and 30 mg/kg. Crocin prevented hippocampal neurons number loss in diabetic rats. CONCLUSION The results indicate that oxidative stress, hyperglycemia, hypoinsulinemia, and reduction of hippocampal neurons may be involved in learning and memory impairments in STZ-induced diabetic rats. Antioxidant, antihyperglycemic, antihypoinsulinemic, and neuroprotective activities of crocin might be involved in improving learning and memory impairments.
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Affiliation(s)
- Esmaeal Tamaddonfard
- Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran,Corresponding author: Esmaeal Tamaddonfard, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran. Tel: +98-441-2770508; Fax: +984412771926;
| | - Amir Abbas Farshid
- Department of Pathobiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Siamak Asri-Rezaee
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Shahram Javadi
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Voria Khosravi
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Bentolhoda Rahman
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
| | - Zahra Mirfakhraee
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
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29
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Ahrén B. Islet nerves in focus--defining their neurobiological and clinical role. Diabetologia 2012; 55:3152-4. [PMID: 23001378 DOI: 10.1007/s00125-012-2727-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 08/30/2012] [Indexed: 01/28/2023]
Abstract
Although it is well established that the pancreatic islets are innervated by autonomic nerves, the detailed islet innervation pattern is still unclear. In this issue of Diabetologia (DOI: 10.1007/s00125-012-2699-6 ) novel details of the islet neuroanatomy and its plasticity in experimental diabetes are described. By using a 3-dimensional (3-D) imaging technique, it has been shown that, in islets from normal mice, sympathetic nerves mainly form a neurovascular complex in addition to innervating peripherally located islet alpha cells. There are also pronounced changes in islet neuroanatomy in experimental diabetes. These findings suggest novel neural-islet regulatory mechanisms as well as neural involvement in the development of diabetes, and therefore advance both basic and clinical knowledge of islet neurobiology.
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Affiliation(s)
- B Ahrén
- Department of Clinical Sciences, Lund University, Lund, Sweden.
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30
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Gao H, Miyata K, Bhaskaran MD, Derbenev AV, Zsombok A. Transient receptor potential vanilloid type 1-dependent regulation of liver-related neurons in the paraventricular nucleus of the hypothalamus diminished in the type 1 diabetic mouse. Diabetes 2012; 61:1381-90. [PMID: 22492526 PMCID: PMC3357291 DOI: 10.2337/db11-0820] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The paraventricular nucleus (PVN) of the hypothalamus controls the autonomic neural output to the liver, thereby participating in the regulation of hepatic glucose production (HGP); nevertheless, mechanisms controlling the activity of liver-related PVN neurons are not known. Transient receptor potential vanilloid type 1 (TRPV1) is involved in glucose homeostasis and colocalizes with liver-related PVN neurons; however, the functional role of TRPV1 regarding liver-related PVN neurons has to be elucidated. A retrograde viral tracer was used to identify liver-related neurons within the brain-liver circuit in control, type 1 diabetic, and insulin-treated mice. Our data indicate that TRPV1 regulates liver-related PVN neurons. This TRPV1-dependent excitation diminished in type 1 diabetic mice. In vivo and in vitro insulin restored TRPV1 activity in a phosphatidylinositol 3-kinase/protein kinase C-dependent manner and stimulated TRPV1 receptor trafficking to the plasma membrane. There was no difference in total TRPV1 protein expression; however, increased phosphorylation of TRPV1 receptors was observed in type 1 diabetic mice. Our data demonstrate that TRPV1 plays a pivotal role in the regulation of liver-related PVN neurons. Moreover, TRPV1-dependent excitation of liver-related PVN neurons diminishes in type 1 diabetes, thus indicating that the brain-liver autonomic circuitry is altered in type 1 diabetes and may contribute to the autonomic dysfunction of HGP.
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Affiliation(s)
- Hong Gao
- Department of Physiology, Tulane University, School of Medicine, New Orleans, Louisiana, USA.
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31
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Farooqui AA, Farooqui T, Panza F, Frisardi V. Metabolic syndrome as a risk factor for neurological disorders. Cell Mol Life Sci 2012; 69:741-62. [PMID: 21997383 PMCID: PMC11115054 DOI: 10.1007/s00018-011-0840-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 09/08/2011] [Accepted: 09/15/2011] [Indexed: 02/07/2023]
Abstract
The metabolic syndrome is a cluster of common pathologies: abdominal obesity linked to an excess of visceral fat, insulin resistance, dyslipidemia and hypertension. At the molecular level, metabolic syndrome is accompanied not only by dysregulation in the expression of adipokines (cytokines and chemokines), but also by alterations in levels of leptin, a peptide hormone released by white adipose tissue. These changes modulate immune response and inflammation that lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point,' resulting in the initiation and development of metabolic syndrome. Metabolic syndrome is a risk factor for neurological disorders such as stroke, depression and Alzheimer's disease. The molecular mechanism underlying the mirror relationship between metabolic syndrome and neurological disorders is not fully understood. However, it is becoming increasingly evident that all cellular and biochemical alterations observed in metabolic syndrome like impairment of endothelial cell function, abnormality in essential fatty acid metabolism and alterations in lipid mediators along with abnormal insulin/leptin signaling may represent a pathological bridge between metabolic syndrome and neurological disorders such as stroke, Alzheimer's disease and depression. The purpose of this review is not only to describe the involvement of brain in the pathogenesis of metabolic syndrome, but also to link the pathogenesis of metabolic syndrome with neurochemical changes in stroke, Alzheimer's disease and depression to a wider audience of neuroscientists with the hope that this discussion will initiate more studies on the relationship between metabolic syndrome and neurological disorders.
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Affiliation(s)
- Akhlaq A Farooqui
- Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, OH 43221, USA.
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32
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Functional plasticity of central TRPV1 receptors in brainstem dorsal vagal complex circuits of streptozotocin-treated hyperglycemic mice. J Neurosci 2011; 31:14024-31. [PMID: 21957263 DOI: 10.1523/jneurosci.2081-11.2011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Emerging data indicate that central neurons participate in diabetic processes by modulating autonomic output from neurons in the dorsal motor nucleus of the vagus (DMV). We tested the hypothesis that synaptic modulation by transient receptor potential vanilloid type 1 (TRPV1) receptors is reduced in the DMV in slices from a murine model of type 1 diabetes. The TRPV1 agonist capsaicin robustly enhanced glutamate release onto DMV neurons by acting at preterminal receptors in slices from intact mice, but failed to do so in slices from diabetic mice. TRPV1 receptor protein expression in the vagal complex was unaltered. Brief insulin preapplication restored TRPV1-dependent modulation of glutamate release in a PKC- and PI3K-dependent manner. The restorative effect of insulin was prevented by brefeldin A, suggesting that insulin induced TRPV1 receptor trafficking to the terminal membrane. Central vagal circuits critical to the autonomic regulation of metabolism undergo insulin-dependent synaptic plasticity involving TRPV1 receptor modulation in diabetic mice after several days of chronic hyperglycemia.
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33
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Levi J, Gray SL, Speck M, Huynh FK, Babich SL, Gibson WT, Kieffer TJ. Acute disruption of leptin signaling in vivo leads to increased insulin levels and insulin resistance. Endocrinology 2011; 152:3385-95. [PMID: 21750049 DOI: 10.1210/en.2011-0185] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Leptin, an adipocyte-derived hormone, plays an essential role in the maintenance of normal body weight and energy expenditure, as well as glucose homeostasis. Indeed, leptin-deficient ob/ob mice are obese with profound hyperinsulinemia, insulin resistance, and often hyperglycemia. Interestingly, low doses of exogenous leptin can reverse the hyperinsulinemia and hyperglycemia in these animals without altering body weight. The hyperinsulinemia in ob/ob mice may result directly from the absence of leptin signaling in pancreatic β-cells and, in turn, contribute to both obesity and insulin resistance. Here, we acutely attenuated endogenous leptin signaling in normal mice with a polyethylene glycol (PEG)ylated mouse leptin antagonist (PEG-MLA) to determine the contribution of leptin signaling in the regulation of glucose homeostasis. PEG-MLA was either injected or continuously administered via osmotic minipumps for several days, and various metabolic parameters were assessed. PEG-MLA-treated mice had increased fasting and glucose-stimulated plasma insulin levels, decreased whole-body insulin sensitivity, elevated hepatic glucose production, and impaired insulin-mediated suppression of hepatic glucose production. Moreover, PEG-MLA treatment resulted in increased food intake and increased respiratory quotient without significantly altering energy expenditure or body composition as assessed by the lean:lipid ratio. Our findings indicate that alterations in insulin sensitivity occur before changes in the lean:lipid ratio and energy expenditure during the acute disruption of endogenous leptin signaling.
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Affiliation(s)
- Jasna Levi
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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34
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Zsombok A, Gao H, Miyata K, Issa A, Derbenev AV. Immunohistochemical localization of transient receptor potential vanilloid type 1 and insulin receptor substrate 2 and their co-localization with liver-related neurons in the hypothalamus and brainstem. Brain Res 2011; 1398:30-9. [PMID: 21620379 DOI: 10.1016/j.brainres.2011.04.048] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 04/29/2011] [Accepted: 04/29/2011] [Indexed: 02/05/2023]
Abstract
The central nervous system plays an important role in the regulation of energy balance and glucose homeostasis mainly via controlling the autonomic output to the visceral organs. The autonomic output is regulated by hormones and nutrients to maintain adequate energy and glucose homeostasis. Insulin action is mediated via insulin receptors (IR) resulting in phosphorylation of insulin receptor substrates (IRS) inducing activation of downstream pathways. Furthermore, insulin enhances transient receptor potential vanilloid type 1 (TRPV1) mediated currents. Activation of the TRPV1 receptor increases excitatory neurotransmitter release in autonomic centers of the brain, thereby impacting energy and glucose homeostasis. The aim of this study is to determine co-expression of IRS2 and TRPV1 receptors in the paraventricular nucleus of the hypothalamus (PVN) and dorsal motor nucleus of the vagus (DMV) in the mouse brain as well as expression of IRS2 and TRPV1 receptors at liver-related preautonomic neurons pre-labeled with a trans-neural, viral tracer (PRV-152). The data indicate that IRS2 and TRPV1 receptors are present and co-express in the PVN and the DMV. A large portion (over 50%) of the liver-related preautonomic DMV and PVN neurons expresses IRS2. Moreover, the majority of liver-related DMV and PVN neurons also express TRPV1 receptors, suggesting that insulin and TRPV1 actions may affect liver-related preautonomic neurons.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, Tulane University Health Science Center, New Orleans, LA 70112, USA.
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35
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Gray SL, Donald C, Jetha A, Covey SD, Kieffer TJ. Hyperinsulinemia precedes insulin resistance in mice lacking pancreatic beta-cell leptin signaling. Endocrinology 2010; 151:4178-86. [PMID: 20631001 DOI: 10.1210/en.2010-0102] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The adipocyte hormone leptin acts centrally and peripherally to regulate body weight and glucose homeostasis. The pancreatic beta-cell has been shown to be a key peripheral target of leptin, with leptin suppressing insulin synthesis and secretion from beta-cells both in vitro and in vivo. Mice with disrupted leptin signaling in beta-cells (lepr(flox/flox) RIPcre tg+ mice) display hyperinsulinemia, insulin resistance, glucose intolerance, obesity, and reduced fasting blood glucose. We hypothesized that hyperinsulinemia precedes the development of insulin resistance and increased adiposity in these mice with a defective adipoinsular axis. To determine the primary defect after impaired beta-cell leptin signaling, we treated lepr(flox/flox) RIPcre tg+ mice with the insulin sensitizer metformin or the insulin-lowering agent diazoxide with the rationale that pharmacological improvement of the primary defect would alleviate the secondary symptoms. We show that improving insulin sensitivity with metformin does not normalize hyperinsulinemia, whereas lowering insulin levels with diazoxide improves insulin sensitivity. Taken together, these results suggest that hyperinsulinemia precedes insulin resistance in beta-cell leptin receptor-deficient mice, with insulin resistance developing as a secondary consequence of excessive insulin secretion. Therefore, pancreatic beta-cell leptin receptor-deficient mice may represent a model of obesity-associated insulin resistance that is initiated by hyperinsulinemia.
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Affiliation(s)
- Sarah L Gray
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, 2350 Health Sciences Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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Nagaya T, Yoshida H, Takahashi H, Kawai M. Heart rate-corrected QT interval in resting ECG predicts the risk for development of type-2 diabetes mellitus. Eur J Epidemiol 2010; 25:195-202. [PMID: 20066475 DOI: 10.1007/s10654-009-9423-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/31/2009] [Indexed: 02/05/2023]
Abstract
Chronic and subclinical sympathetic over-activity may underlie development of type-2 diabetes mellitus (DM). Since longer heart rate-corrected QT interval (QTc) represents predominance of sympathetic activity within autonomic balance, we investigated influences of QTc on the incidence of DM in a follow-up study. The subjects were 12,530 men and 7,163 women aged 30-59 years and apparently healthy at baseline. QTc in resting ECG was obtained using Bazett's formula (QTcB), Fridericia's formula (QTcF) and the linear regression technique (QTcLR). Incident DM was identified by 'fasting serum glucose > or =7.00 mmol l(-1) (126 mg dl(-1))' or/and 'on medication for DM'. Using Cox proportional hazard models, hazard ratio (HR) for incident DM was estimated according to the quartiles (Q1-Q4) of QTcB, QTcF or QTcLR, and its linear trends across the quartiles were checked. Baseline age, BMI, smoking, drinking, exercise and education were computed as conventional confounders. During the follow-up of 93,337 person-years for men and 51,517 person-years for women, 637 men and 192 women developed DM. The multivariate-adjusted HRs(95% confidence interval) for Q4 of QTcB, QTcF and QTcLR against corresponding Q1 were 1.85(1.46, 2.34), 1.31(1.04, 1.65) and 1.58(1.26, 1.99), respectively, for men, and 2.03(1.31, 3.16), 1.34(0.91, 2.00) and 1.58(1.04, 2.38), respectively, for women. Both sexes showed increasing trends in the HRs across the quartiles of QTcB, QTcF and QTcLR. In conclusion, QTc in resting ECG moderately but proportionally predicts the risk for development of DM in middle-aged healthy men and women. Moreover, the adverse effects of prolonged QTc are independent of those of conventional risk factors.
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Affiliation(s)
- Teruo Nagaya
- Department of Public Health, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Nagoya, Japan.
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