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Sapkota S, Briski KP. Sex-Dimorphic Effects of Hypoglycemia on Metabolic Sensor mRNA Expression in Ventromedial Hypothalamic Nucleus-Dorsomedial Division (VMNdm) Growth Hormone-Releasing Hormone Neurons. ACS Chem Neurosci 2024; 15:2350-2358. [PMID: 38757688 DOI: 10.1021/acschemneuro.4c00206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024] Open
Abstract
Growth hormone-releasing hormone (Ghrh) neurons in the dorsomedial ventromedial hypothalamic nucleus (VMNdm) express the metabolic transcription factor steroidogenic factor-1 and hypoglycemia-sensitive neurochemicals of diverse chemical structures, transmission modes, and temporal signaling profiles. Ghrh imposes neuromodulatory control of coexpressed transmitters. Multiple metabolic sensory mechanisms are employed in the brain, including screening of the critical nutrient glucose or the energy currency ATP. Here, combinatory laser-catapult-microdissection/single-cell multiplex qPCR tools were used to investigate whether these neurons possess molecular machinery for monitoring cellular metabolic status and if these biomarkers exhibit sex-specific sensitivity to insulin-induced hypoglycemia. Data show that hypoglycemia up- (male) or downregulated (female) Ghrh neuron glucokinase (Gck) mRNA; Ghrh gene silencing decreased baseline and hypoglycemic patterns of Gck gene expression in each sex. Ghrh neuron glucokinase regulatory protein (Gckr) transcript levels were respectively diminished or augmented in hypoglycemic male vs female rats; this mRNA profile was decreased by Ghrh siRNA in both sexes. Gene transcripts encoding catalytic alpha subunits of the energy monitor 5-AMP-activated protein kinase (AMPK), i.e., Prkaa1 and 2, were increased by hypoglycemia in males, yet only the former mRNA was hypoglycemia-sensitive in females. Ghrh siRNA downregulated baseline and hypoglycemia-associated Prkaa subunit mRNAs in males but elicited divergent changes in Prkaa2 transcripts in eu- vs hypoglycemic females. Results provide unique evidence that VMNdm Ghrh neurons express the characterized metabolic sensor biomarkers glucokinase and AMPK and that the corresponding gene profiles exhibit distinctive sex-dimorphic transcriptional responses to hypoglycemia. Data further document Ghrh neuromodulation of baseline and hypoglycemic transcription patterns of these metabolic gene profiles.
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Affiliation(s)
- Subash Sapkota
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, University of Louisiana Monroe, Monroe, Louisiana 71201, United States
| | - Karen P Briski
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, University of Louisiana Monroe, Monroe, Louisiana 71201, United States
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2
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Su G, Farhat R, Laxman AK, Chapman-Natewa K, Nelson IE, Chan O. Astrocyte Glycogen Is a Major Source of Hypothalamic Lactate in Rats With Recurrent Hypoglycemia. Diabetes 2023; 72:1154-1160. [PMID: 37216640 PMCID: PMC10382650 DOI: 10.2337/db22-0902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 05/13/2023] [Indexed: 05/24/2023]
Abstract
Lactate is an important metabolic substrate for sustaining brain energy requirements when glucose supplies are limited. Recurring exposure to hypoglycemia (RH) raises lactate levels in the ventromedial hypothalamus (VMH), which contributes to counterregulatory failure. However, the source of this lactate remains unclear. The current study investigates whether astrocytic glycogen serves as the major source of lactate in the VMH of RH rats. By decreasing the expression of a key lactate transporter in VMH astrocytes of RH rats, we reduced extracellular lactate concentrations, suggesting excess lactate was locally produced from astrocytes. To determine whether astrocytic glycogen serves as the major source of lactate, we chronically delivered either artificial extracellular fluid or 1,4-dideoxy-1,4-imino-d-arabinitol to inhibit glycogen turnover in the VMH of RH animals. Inhibiting glycogen turnover in RH animals prevented the rise in VMH lactate and the development of counterregulatory failure. Lastly, we noted that RH led to an increase in glycogen shunt activity in response to hypoglycemia and elevated glycogen phosphorylase activity in the hours following a bout of hypoglycemia. Our data suggest that dysregulation of astrocytic glycogen metabolism following RH may be responsible, at least in part, for the rise in VMH lactate levels. ARTICLE HIGHLIGHTS Astrocytic glycogen serves as the major source of elevated lactate levels in the ventromedial hypothalamus (VMH) of animals exposed to recurring episodes of hypoglycemia. Antecedent hypoglycemia alters VMH glycogen turnover. Antecedent exposure to hypoglycemia enhances glycogen shunt activity in the VMH during subsequent bouts of hypoglycemia. In the immediate hours following a bout of hypoglycemia, sustained elevations in glycogen phosphorylase activity in the VMH of recurrently hypoglycemic animals contribute to sustained elevations in local lactate levels.
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Affiliation(s)
- Gong Su
- Cardiac Department, Aerospace Center Hospital, Peking University Aerospace School of Clinical Medicine, Beijing, China
| | - Rawad Farhat
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Utah, Salt Lake City, UT
| | - Anil K. Laxman
- University of Utah Health Sciences Metabolic Phenotyping Core, University of Utah, Salt Lake City, UT
| | | | - Irvane E. Nelson
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Utah, Salt Lake City, UT
| | - Owen Chan
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Utah, Salt Lake City, UT
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3
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de Bartolomeis A, De Simone G, De Prisco M, Barone A, Napoli R, Beguinot F, Billeci M, Fornaro M. Insulin effects on core neurotransmitter pathways involved in schizophrenia neurobiology: a meta-analysis of preclinical studies. Implications for the treatment. Mol Psychiatry 2023; 28:2811-2825. [PMID: 37085712 PMCID: PMC10615753 DOI: 10.1038/s41380-023-02065-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/23/2023]
Abstract
Impairment of insulin action and metabolic dysregulation have traditionally been associated with schizophrenia, although the molecular basis of such association remains still elusive. The present meta-analysis aims to assess the impact of insulin action manipulations (i.e., hyperinsulinemia, hypoinsulinemia, systemic or brain insulin resistance) on glutamatergic, dopaminergic, γ-aminobutyric acid (GABA)ergic, and serotonergic pathways in the central nervous system. More than one hundred outcomes, including transcript or protein levels, kinetic parameters, and other components of the neurotransmitter pathways, were collected from cultured cells, animals, or humans, and meta-analyzed by applying a random-effects model and adopting Hedges'g to compare means. Two hundred fifteen studies met the inclusion criteria, of which 180 entered the quantitative synthesis. Significant impairments in key regulators of synaptic plasticity processes were detected as the result of insulin handlings. Specifically, protein levels of N-methyl-D-aspartate receptor (NMDAR) subunits including type 2A (NR2A) (Hedges' g = -0.95, 95%C.I. = -1.50, -0.39; p = 0.001; I2 = 47.46%) and 2B (NR2B) (Hedges'g = -0.69, 95%C.I. = -1.35, -0.02; p = 0.043; I2 = 62.09%), and Postsynaptic density protein 95 (PSD-95) (Hedges'g = -0.91, 95%C.I. = -1.51, -0.32; p = 0.003; I2 = 77.81%) were found reduced in insulin-resistant animal models. Moreover, insulin-resistant animals showed significantly impaired dopamine transporter activity, whereas the dopamine D2 receptor mRNA expression (Hedges'g = 3.259; 95%C.I. = 0.497, 6.020; p = 0.021; I2 = 90.61%) increased under insulin deficiency conditions. Insulin action modulated glutamate and GABA release, as well as several enzymes involved in GABA and serotonin synthesis. These results suggest that brain neurotransmitter systems are susceptible to insulin signaling abnormalities, resembling the discrete psychotic disorders' neurobiology and possibly contributing to the development of neurobiological hallmarks of treatment-resistant schizophrenia.
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Affiliation(s)
- Andrea de Bartolomeis
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy.
| | - Giuseppe De Simone
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy
| | - Michele De Prisco
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy
- Bipolar and Depressive Disorders Unit, Institute of Neuroscience, Hospital Clinic, University of Barcelona, IDIBAPS, CIBERSAM, 170 Villarroel st, 12-0, 08036, Barcelona, Catalonia, Spain
| | - Annarita Barone
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy
| | - Raffaele Napoli
- Department of Translational Medical Sciences, University of Naples "Federico II", Via S. Pansini 5, 80131, Naples, Italy
- URT Genomic of Diabetes, Institute of Experimental Endocrinology and Oncology, National Research Council, Naples, Italy
| | - Francesco Beguinot
- Department of Translational Medical Sciences, University of Naples "Federico II", Via S. Pansini 5, 80131, Naples, Italy
- URT Genomic of Diabetes, Institute of Experimental Endocrinology and Oncology, National Research Council, Naples, Italy
| | - Martina Billeci
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy
| | - Michele Fornaro
- Section of Psychiatry, Laboratory of Molecular and Translational Psychiatry, Unit of Treatment-Resistant Psychiatric Disorders, Department of Neuroscience, Reproductive Sciences and Odontostomatology University of Naples "Federico II", School of Medicine, Via Pansini 5, 80131, Naples, Italy
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4
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Farhadi A, Totonchi M, Nabavi SM, Baharvand H, Pakdaman H, Hajizadeh-Saffar E, Mousavi SA, Hadi F, Al-Sinawi H, Li Q, Zhang JS, Tahamtani Y, Shahpasand K. P38 Initiates Degeneration of midbrain GABAergic and Glutamatergic Neurons in Diabetes Models. Eur J Neurosci 2022; 56:3755-3778. [PMID: 35513862 DOI: 10.1111/ejn.15686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 04/04/2022] [Accepted: 04/25/2022] [Indexed: 11/30/2022]
Abstract
Diabetes mellitus may cause tau protein hyperphosphorylation and neurodegeneration, but the exact mechanism by which diabetic conditions induce tau pathology remains unclear. Tau protein hyperphosphorylation is considered a major pathological hallmark of neurodegeneration and can be triggered by diabetes. Various tau-directed kinases, including P38, can be activated upon diabetic stress and induce tau hyperphosphorylation. Despite extensive research efforts the exact tau specie(s) and kinases driving neurodegeneration in diabetes mellitus have not been clearly elucidated. We herein employed different techniques to determine the exact molecular mechanism of tau pathology triggered by diabetes in in vivo and in vitro models. We showed that diabetes-related stresses and glucose metabolism deficiency could induce cis P-tau (an early driver of the tau pathology) accumulation in the midbrain and corpus callosum of the diabetic mice models and cells treated with 2-deoxy-D-glucose, respectively. We found that the active phosphorylated level of P38 was increased in the treated cells and diabetic mice models. We observed that oxidative stress activated P38, which directly and indirectly drove tau pathology in the GABAergic and Glutamatergic neurons of the midbrain of the diabetic mice after 96 hours, which accumulated in the other neighboring brain areas after two months. Notably, P38 inhibition suppressed tau pathogenicity and risk-taking behaviors in the animal models after 96 hours. The data establish P38 as a central mediator of diabetes mellitus induced tau pathology. Our findings provide mechanistic insight into the consequences of this metabolic disorder on the nervous system.
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Affiliation(s)
- Aisan Farhadi
- Department of Developmental Biology, Faculty of Basic Sciences and Advanced Technologies in Biology, University of Science and Culture, ACECR, Tehran, Iran.,Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.,Department of Brain and Cognitive Sciences, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Mehdi Totonchi
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.,Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Seyed Masood Nabavi
- Department of Brain and Cognitive Sciences, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Hossein Baharvand
- Department of Developmental Biology, Faculty of Basic Sciences and Advanced Technologies in Biology, University of Science and Culture, ACECR, Tehran, Iran.,Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.,Department of Brain and Cognitive Sciences, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Hossein Pakdaman
- Brain Mapping Research Center, Department of Neurology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ensiyeh Hajizadeh-Saffar
- Department of Regenerative medicine, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Seyed Ahmad Mousavi
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Fatemeh Hadi
- Department of Brain and Cognitive Sciences, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Hamed Al-Sinawi
- Department of Behavioral Medicine, Sultan Qaboos University Hospital, Muscat, Oman
| | - Quan Li
- Institute of Life Sciences, Wenzhou University, Wenzhou, Zhejiang, China
| | - Jin-San Zhang
- Institute of Life Sciences, Wenzhou University, Wenzhou, Zhejiang, China.,Division of Oncology Research, Mayo Clinic, Rochester, MN, USA
| | - Yaser Tahamtani
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.,Reproductive Epidemiology Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Koorosh Shahpasand
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran.,Department of Brain and Cognitive Sciences, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
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5
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The Case for Clinical Trials with Novel GABAergic Drugs in Diabetes Mellitus and Obesity. Life (Basel) 2022; 12:life12020322. [PMID: 35207609 PMCID: PMC8876029 DOI: 10.3390/life12020322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 02/09/2022] [Accepted: 02/16/2022] [Indexed: 11/17/2022] Open
Abstract
Obesity and diabetes mellitus have become the surprising menaces of relative economic well-being worldwide. Gamma amino butyric acid (GABA) has a prominent role in the control of blood glucose, energy homeostasis as well as food intake at several levels of regulation. The effects of GABA in the body are exerted through ionotropic GABAA and metabotropic GABAB receptors. This treatise will focus on the pharmacologic targeting of GABAA receptors to reap beneficial therapeutic effects in diabetes mellitus and obesity. A new crop of drugs selectively targeting GABAA receptors has been under investigation for efficacy in stroke recovery and cognitive deficits associated with schizophrenia. Although these trials have produced mixed outcomes the compounds are safe to use in humans. Preclinical evidence is summarized here to support the rationale of testing some of these compounds in diabetic patients receiving insulin in order to achieve better control of blood glucose levels and to combat the decline of cognitive performance. Potential therapeutic benefits could be achieved (i) By resetting the hypoglycemic counter-regulatory response; (ii) Through trophic actions on pancreatic islets, (iii) By the mobilization of antioxidant defence mechanisms in the brain. Furthermore, preclinical proof-of-concept work, as well as clinical trials that apply the novel GABAA compounds in eating disorders, e.g., olanzapine-induced weight-gain, also appear warranted.
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Hoffman EG, Jahangiriesmaili M, Mandel ER, Greenberg C, Aiken J, D’Souza NC, Pasieka A, Teich T, Chan O, Liggins R, Riddell MC. Somatostatin Receptor Antagonism Reverses Glucagon Counterregulatory Failure in Recurrently Hypoglycemic Male Rats. Endocrinology 2021; 162:6363563. [PMID: 34477204 PMCID: PMC8482965 DOI: 10.1210/endocr/bqab189] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Indexed: 12/12/2022]
Abstract
Recent antecedent hypoglycemia is a known source of defective glucose counter-regulation in diabetes; the mechanisms perpetuating the cycle of progressive α-cell failure and recurrent hypoglycemia remain unknown. Somatostatin has been shown to suppress the glucagon response to acute hypoglycemia in rodent models of type 1 diabetes. We hypothesized that somatostatin receptor 2 antagonism (SSTR2a) would restore glucagon counterregulation and delay the onset of insulin-induced hypoglycemia in recurrently hypoglycemic, nondiabetic male rats. Healthy, male, Sprague-Dawley rats (n = 39) received bolus injections of insulin (10 U/kg, 8 U/kg, 5 U/kg) on 3 consecutive days to induce hypoglycemia. On day 4, animals were then treated with SSTR2a (10 mg/kg; n = 17) or vehicle (n = 12) 1 hour prior to the induction of hypoglycemia using insulin (5 U/kg). Plasma glucagon level during hypoglycemia was ~30% lower on day 3 (150 ± 75 pg/mL; P < .01), and 68% lower on day 4 in the vehicle group (70 ± 52 pg/mL; P < .001) compared with day 1 (219 ± 99 pg/mL). On day 4, SSTR2a prolonged euglycemia by 25 ± 5 minutes (P < .05) and restored the plasma glucagon response to hypoglycemia. Hepatic glycogen content of SSTR2a-treated rats was 35% lower than vehicle controls after hypoglycemia induction on day 4 (vehicle: 20 ± 7.0 vs SSTR2a: 13 ± 4.4 µmol/g; P < .01). SSTR2a treatment reverses the cumulative glucagon deficit resulting from 3 days of antecedent hypoglycemia in healthy rats. This reversal is associated with decreased hepatic glycogen content and delayed time to hypoglycemic onset. We conclude that recurrent hypoglycemia produces glucagon counterregulatory deficiency in healthy male rats, which can be improved by SSTR2a.
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Affiliation(s)
- Emily G Hoffman
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Mahsa Jahangiriesmaili
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Erin R Mandel
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Caylee Greenberg
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Julian Aiken
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Ninoschka C D’Souza
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Aoibhe Pasieka
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Trevor Teich
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
| | - Owen Chan
- Department of Internal Medicine—Division of Endocrinology, Metabolism and Diabetes, University of Utah, Salt Lake City, UT 84112, USA
| | | | - Michael C Riddell
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON M3J 1P3, Canada
- Correspondence: Michael C. Riddell, PhD, School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto, ON, Canada, M3J 1P3.
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7
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Uddin MM, Ibrahim MMH, Briski KP. Glycogen Phosphorylase Isoform Regulation of Ventromedial Hypothalamic Nucleus Gluco-Regulatory Neuron 5'-AMP-Activated Protein Kinase and Transmitter Marker Protein Expression. ASN Neuro 2021; 13:17590914211035020. [PMID: 34596459 PMCID: PMC8495507 DOI: 10.1177/17590914211035020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Brain glycogen is remodeled during metabolic homeostasis and provides oxidizable
L-lactate equivalents. Brain glycogen phosphorylase (GP)-brain (GPbb;
AMP-sensitive) and -muscle (GPmm; norepinephrine-sensitive) type isoforms
facilitate stimulus-specific control of glycogen disassembly. Here, a whole
animal model involving stereotactic-targeted delivery of GPmm or GPbb siRNA to
the ventromedial hypothalamic nucleus (VMN) was used to investigate the premise
that these variants impose differential control of gluco-regulatory
transmission. Intra-VMN GPmm or GPbb siRNA administration inhibited glutamate
decarboxylate65/67 (GAD), a protein marker for the
gluco-inhibitory transmitter γ--aminobutyric acid (GABA), in the caudal VMN.
GPbb knockdown, respectively overturned or exacerbated hypoglycemia-associated
GAD suppression in rostral and caudal VMN. GPmm siRNA caused a segment-specific
reversal of hypoglycemic augmentation of the gluco-stimulatory transmitter
indicator, neuronal nitric oxide synthase (nNOS). In both cell types, GP siRNA
down-regulated 5′-AMP-activated protein kinase (AMPK) during euglycemia, but
hypoglycemic suppression of AMPK was reversed by GPmm targeting. GP knockdown
elevated baseline GABA neuron phosphoAMPK (pAMKP) content, and amplified
hypoglycemic augmentation of pAMPK expression in each neuron type. GPbb
knockdown increased corticosterone secretion in eu- and hypoglycemic rats.
Outcomes validate efficacy of GP siRNA delivery for manipulation of glycogen
breakdown in discrete brain structures in vivo, and document VMN GPbb control of
local GPmm expression. Results document GPmm and/or -bb regulation of GABAergic
and nitrergic transmission in discrete rostro-caudal VMN segments. Contrary
effects of glycogenolysis on metabolic-sensory AMPK protein during eu- versus
hypoglycemia may reflect energy state-specific astrocyte signaling. Amplifying
effects of GPbb knockdown on hypoglycemic stimulation of pAMPK infer that
glycogen mobilization by GPbb limits neuronal energy instability during
hypoglycemia.
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Affiliation(s)
- Md Main Uddin
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, 15512University of Louisiana Monroe, Monroe, LA, USA
| | - Mostafa M H Ibrahim
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, 15512University of Louisiana Monroe, Monroe, LA, USA
| | - Karen P Briski
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, 15512University of Louisiana Monroe, Monroe, LA, USA
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Abstract
The endogenous timekeeping system evolved to anticipate the time of the day through the 24 hours cycle of the Earth's rotation. In mammals, the circadian clock governs rhythmic physiological and behavioral processes, including the daily oscillation in glucose metabolism, food intake, energy expenditure, and whole-body insulin sensitivity. The results from a series of studies have demonstrated that environmental or genetic alterations of the circadian cycle in humans and rodents are strongly associated with metabolic diseases such as obesity and type 2 diabetes. Emerging evidence suggests that astrocyte clocks have a crucial role in regulating molecular, physiological, and behavioral circadian rhythms such as glucose metabolism and insulin sensitivity. Given the concurrent high prevalence of type 2 diabetes and circadian disruption, understanding the mechanisms underlying glucose homeostasis regulation by the circadian clock and its dysregulation may improve glycemic control. In this review, we summarize the current knowledge on the tight interconnection between the timekeeping system, glucose homeostasis, and insulin sensitivity. We focus specifically on the involvement of astrocyte clocks, at the organism, cellular, and molecular levels, in the regulation of glucose metabolism.
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Affiliation(s)
- Olga Barca-Mayo
- Circadian and Glial Biology Lab, Physiology Department, Molecular Medicine and Chronic Diseases Research Centre (CiMUS), University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Miguel López
- NeurObesity Lab, Physiology Department, Molecular Medicine and Chronic Diseases Research Centre (CiMUS), University of Santiago de Compostela, Santiago de Compostela, Spain
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9
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Weightman Potter PG, Washer SJ, Jeffries AR, Holley JE, Gutowski NJ, Dempster EL, Beall C. Attenuated Induction of the Unfolded Protein Response in Adult Human Primary Astrocytes in Response to Recurrent Low Glucose. Front Endocrinol (Lausanne) 2021; 12:671724. [PMID: 34122346 PMCID: PMC8187939 DOI: 10.3389/fendo.2021.671724] [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: 02/24/2021] [Accepted: 05/03/2021] [Indexed: 12/14/2022] Open
Abstract
AIMS/HYPOTHESIS Recurrent hypoglycaemia (RH) is a major side-effect of intensive insulin therapy for people with diabetes. Changes in hypoglycaemia sensing by the brain contribute to the development of impaired counterregulatory responses to and awareness of hypoglycaemia. Little is known about the intrinsic changes in human astrocytes in response to acute and recurrent low glucose (RLG) exposure. METHODS Human primary astrocytes (HPA) were exposed to zero, one, three or four bouts of low glucose (0.1 mmol/l) for three hours per day for four days to mimic RH. On the fourth day, DNA and RNA were collected. Differential gene expression and ontology analyses were performed using DESeq2 and GOseq, respectively. DNA methylation was assessed using the Infinium MethylationEPIC BeadChip platform. RESULTS 24 differentially expressed genes (DEGs) were detected (after correction for multiple comparisons). One bout of low glucose exposure had the largest effect on gene expression. Pathway analyses revealed that endoplasmic-reticulum (ER) stress-related genes such as HSPA5, XBP1, and MANF, involved in the unfolded protein response (UPR), were all significantly increased following low glucose (LG) exposure, which was diminished following RLG. There was little correlation between differentially methylated positions and changes in gene expression yet the number of bouts of LG exposure produced distinct methylation signatures. CONCLUSIONS/INTERPRETATION These data suggest that exposure of human astrocytes to transient LG triggers activation of genes involved in the UPR linked to endoplasmic reticulum (ER) stress. Following RLG, the activation of UPR related genes was diminished, suggesting attenuated ER stress. This may be a consequence of a successful metabolic adaptation, as previously reported, that better preserves intracellular energy levels and a reduced necessity for the UPR.
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Affiliation(s)
- Paul G. Weightman Potter
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
| | - Sam J. Washer
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
| | - Aaron R. Jeffries
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
| | - Janet E. Holley
- Royal Devon and Exeter Hospital, University of Exeter Medical School and the Department of Neurology, Exeter, United Kingdom
| | - Nick J. Gutowski
- Royal Devon and Exeter Hospital, University of Exeter Medical School and the Department of Neurology, Exeter, United Kingdom
| | - Emma L. Dempster
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
- *Correspondence: Emma L. Dempster, ; Craig Beall,
| | - Craig Beall
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
- *Correspondence: Emma L. Dempster, ; Craig Beall,
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10
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Alonge KM, D'Alessio DA, Schwartz MW. Brain control of blood glucose levels: implications for the pathogenesis of type 2 diabetes. Diabetologia 2021; 64:5-14. [PMID: 33043401 PMCID: PMC7718404 DOI: 10.1007/s00125-020-05293-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/10/2020] [Indexed: 12/22/2022]
Abstract
Despite a rapidly growing literature, the role played by the brain in both normal glucose homeostasis and in type 2 diabetes pathogenesis remains poorly understood. In this review, we introduce a framework for understanding the brain's essential role in these processes based on evidence that the brain, like the pancreas, is equipped to sense and respond to changes in the circulating glucose level. Further, we review evidence that glucose sensing by the brain plays a fundamental role in establishing the defended level of blood glucose, and that defects in this control system contribute to type 2 diabetes pathogenesis. We also consider the possibility that the close association between obesity and type 2 diabetes arises from a shared defect in the highly integrated neurocircuitry governing energy homeostasis and glucose homeostasis. Thus, whereas obesity is characterised by an increase in the defended level of the body's fuel stores (e.g. adipose mass), type 2 diabetes is characterised by an increase in the defended level of the body's available fuel (e.g. circulating glucose), with the underlying pathogenesis in each case involving impaired sensing of (or responsiveness to) relevant humoral negative feedback signals. This perspective is strengthened by growing preclinical evidence that in type 2 diabetes the defended level of blood glucose can be restored to normal by therapies that restore the brain's ability to properly sense the circulating glucose level. Graphical abstract.
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Affiliation(s)
- Kimberly M Alonge
- UW Medicine Diabetes Institute, University of Washington, Seattle, WA, USA
| | - David A D'Alessio
- Duke Division of Endocrinology, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Michael W Schwartz
- UW Medicine Diabetes Institute, University of Washington, Seattle, WA, USA.
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11
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Robb JL, Morrissey NA, Weightman Potter PG, Smithers HE, Beall C, Ellacott KLJ. Immunometabolic Changes in Glia - A Potential Role in the Pathophysiology of Obesity and Diabetes. Neuroscience 2020; 447:167-181. [PMID: 31765625 PMCID: PMC7567742 DOI: 10.1016/j.neuroscience.2019.10.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/10/2019] [Accepted: 10/11/2019] [Indexed: 12/15/2022]
Abstract
Chronic low-grade inflammation is a feature of the pathophysiology of obesity and diabetes in the CNS as well as peripheral tissues. Glial cells are critical mediators of the response to inflammation in the brain. Key features of glia include their metabolic flexibility, sensitivity to changes in the CNS microenvironment, and ability to rapidly adapt their function accordingly. They are specialised cells which cooperate to promote and preserve neuronal health, playing important roles in regulating the activity of neuronal networks across the brain during different life stages. Increasing evidence points to a role of glia, most notably astrocytes and microglia, in the systemic regulation of energy and glucose homeostasis in the course of normal physiological control and during disease. Inflammation is an energetically expensive process that requires adaptive changes in cellular metabolism and, in turn, metabolic intermediates can also have immunomodulatory actions. Such "immunometabolic" changes in peripheral immune cells have been implicated in contributing to disease pathology in obesity and diabetes. This review will discuss the evidence for a role of immunometabolic changes in glial cells in the systemic regulation of energy and glucose homeostasis, and how this changes in the context of obesity and diabetes.
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Affiliation(s)
- Josephine L Robb
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Nicole A Morrissey
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Paul G Weightman Potter
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Hannah E Smithers
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Craig Beall
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Kate L J Ellacott
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK.
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12
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The Role of Ventromedial Hypothalamus Receptors in the Central Regulation of Food Intake. Int J Pept Res Ther 2020. [DOI: 10.1007/s10989-020-10120-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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13
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Glendining KA, Fisher LC, Jasoni CL. Maternal Obesity Modulates Expression of Satb2 in Hypothalamic VMN of Female Offspring. Life (Basel) 2020; 10:life10040048. [PMID: 32344561 PMCID: PMC7235991 DOI: 10.3390/life10040048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/16/2020] [Accepted: 04/21/2020] [Indexed: 01/24/2023] Open
Abstract
Maternal obesity during pregnancy is associated with a greater risk of poor health outcomes in offspring, including obesity, metabolic disorders, and anxiety, however the incidence of these diseases differs for males and females. Similarly, animal models of maternal obesity have reported sex differences in offspring, for both metabolic outcomes and anxiety-like behaviors. The ventromedial nucleus of the hypothalamus (VMN) is a brain region known to be involved in the regulation of both metabolism and anxiety, and is well documented to be sexually dimorphic. As the VMN is largely composed of glutamatergic neurons, which are important for its functions in modulating metabolism and anxiety, we hypothesized that maternal obesity may alter the number of glutamatergic neurons in the offspring VMN. We used a mouse model of a maternal high-fat diet (mHFD), to examine mRNA expression of the glutamatergic neuronal marker Satb2 in the mediobasal hypothalamus of control and mHFD offspring at GD17.5. We found sex differences in Satb2 expression, with mHFD-induced upregulation of Satb2 mRNA in the mediobasal hypothalamus of female offspring, compared to controls, but not males. Using immunohistochemistry, we found an increase in the number of SATB2-positive cells in female mHFD offspring VMN, compared to controls, which was localized to the rostral region of the nucleus. These data provide evidence that maternal nutrition during gestation alters the developing VMN, possibly increasing its glutamatergic drive of offspring in a sex-specific manner, which may contribute to sexual dimorphism in offspring health outcomes later in life.
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MacGregor DJ, Leng G. Emergent decision-making behaviour and rhythm generation in a computational model of the ventromedial nucleus of the hypothalamus. PLoS Comput Biol 2019; 15:e1007092. [PMID: 31158265 PMCID: PMC6564049 DOI: 10.1371/journal.pcbi.1007092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 06/13/2019] [Accepted: 05/13/2019] [Indexed: 12/18/2022] Open
Abstract
The ventromedial nucleus of the hypothalamus (VMN) has an important role in diverse behaviours. The common involvement in these of sex steroids, nutritionally-related signals, and emotional inputs from other brain areas, suggests that, at any given time, its output is in one of a discrete number of possible states corresponding to discrete motivational drives. Here we explored how networks of VMN neurons might generate such a decision-making architecture. We began with minimalist assumptions about the intrinsic properties of VMN neurons inferred from electrophysiological recordings of these neurons in rats in vivo, using an integrate-and-fire based model modified to simulate activity-dependent post-spike changes in neuronal excitability. We used a genetic algorithm based method to fit model parameters to the statistical features of spike patterning in each cell. The spike patterns in both recorded cells and model cells were assessed by analysis of interspike interval distributions and of the index of dispersion of firing rate over different binwidths. Simpler patterned cells could be closely matched by single neuron models incorporating a hyperpolarising afterpotential and either a slow afterhyperpolarisation or a depolarising afterpotential, but many others could not. We then constructed network models with the challenge of explaining the more complex patterns. We assumed that neurons of a given type (with heterogeneity introduced by independently random patterns of external input) were mutually interconnected at random by excitatory synaptic connections (with a variable delay and a random chance of failure). Simple network models of one or two cell types were able to explain the more complex patterns. We then explored the information processing features of such networks that might be relevant for a decision-making network. We concluded that rhythm generation (in the slow theta range) and bistability arise as emergent properties of networks of heterogeneous VMN neurons.
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Affiliation(s)
- Duncan J. MacGregor
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
| | - Gareth Leng
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
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15
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MacDonald AJ, Robb JL, Morrissey NA, Beall C, Ellacott KLJ. Astrocytes in neuroendocrine systems: An overview. J Neuroendocrinol 2019; 31:e12726. [PMID: 31050045 DOI: 10.1111/jne.12726] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/26/2019] [Accepted: 04/28/2019] [Indexed: 12/11/2022]
Abstract
A class of glial cell, astrocytes, is highly abundant in the central nervous system (CNS). In addition to maintaining tissue homeostasis, astrocytes regulate neuronal communication and synaptic plasticity. There is an ever-increasing appreciation that astrocytes are involved in the regulation of physiology and behaviour in normal and pathological states, including within neuroendocrine systems. Indeed, astrocytes are direct targets of hormone action in the CNS, via receptors expressed on their surface, and are also a source of regulatory neuropeptides, neurotransmitters and gliotransmitters. Furthermore, as part of the neurovascular unit, astrocytes can regulate hormone entry into the CNS. This review is intended to provide an overview of how astrocytes are impacted by and contribute to the regulation of a diverse range of neuroendocrine systems: energy homeostasis and metabolism, reproduction, fluid homeostasis, the stress response and circadian rhythms.
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Affiliation(s)
- Alastair J MacDonald
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Josephine L Robb
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Nicole A Morrissey
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Craig Beall
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Kate L J Ellacott
- Neuroendocrine Research Group, Institute of Biomedical & Clinical Sciences, University of Exeter Medical School, Exeter, UK
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Weightman Potter PG, Vlachaki Walker JM, Robb JL, Chilton JK, Williamson R, Randall AD, Ellacott KLJ, Beall C. Basal fatty acid oxidation increases after recurrent low glucose in human primary astrocytes. Diabetologia 2019; 62:187-198. [PMID: 30293112 PMCID: PMC6290858 DOI: 10.1007/s00125-018-4744-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 08/22/2018] [Indexed: 12/20/2022]
Abstract
AIMS/HYPOTHESIS Hypoglycaemia is a major barrier to good glucose control in type 1 diabetes. Frequent hypoglycaemic episodes impair awareness of subsequent hypoglycaemic bouts. Neural changes underpinning awareness of hypoglycaemia are poorly defined and molecular mechanisms by which glial cells contribute to hypoglycaemia sensing and glucose counterregulation require further investigation. The aim of the current study was to examine whether, and by what mechanism, human primary astrocyte (HPA) function was altered by acute and recurrent low glucose (RLG). METHODS To test whether glia, specifically astrocytes, could detect changes in glucose, we utilised HPA and U373 astrocytoma cells and exposed them to RLG in vitro. This allowed measurement, with high specificity and sensitivity, of RLG-associated changes in cellular metabolism. We examined changes in protein phosphorylation/expression using western blotting. Metabolic function was assessed using a Seahorse extracellular flux analyser. Immunofluorescent imaging was used to examine cell morphology and enzymatic assays were used to measure lactate release, glycogen content, intracellular ATP and nucleotide ratios. RESULTS AMP-activated protein kinase (AMPK) was activated over a pathophysiologically relevant glucose concentration range. RLG produced an increased dependency on fatty acid oxidation for basal mitochondrial metabolism and exhibited hallmarks of mitochondrial stress, including increased proton leak and reduced coupling efficiency. Relative to glucose availability, lactate release increased during low glucose but this was not modified by RLG. Basal glucose uptake was not modified by RLG and glycogen levels were similar in control and RLG-treated cells. Mitochondrial adaptations to RLG were partially recovered by maintaining euglycaemic levels of glucose following RLG exposure. CONCLUSIONS/INTERPRETATION Taken together, these data indicate that HPA mitochondria are altered following RLG, with a metabolic switch towards increased fatty acid oxidation, suggesting glial adaptations to RLG involve altered mitochondrial metabolism that could contribute to defective glucose counterregulation to hypoglycaemia in diabetes.
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Affiliation(s)
- Paul G Weightman Potter
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK
| | - Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK
| | - Josephine L Robb
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK
| | - John K Chilton
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK
| | - Ritchie Williamson
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, UK
| | - Andrew D Randall
- Hatherly Laboratories, Prince of Wales Road, University of Exeter, Exeter, UK
| | - Kate L J Ellacott
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK
| | - Craig Beall
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter, EX2 5DW, UK.
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Güemes A, Georgiou P. Review of the role of the nervous system in glucose homoeostasis and future perspectives towards the management of diabetes. Bioelectron Med 2018; 4:9. [PMID: 32232085 PMCID: PMC7098234 DOI: 10.1186/s42234-018-0009-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/10/2018] [Indexed: 12/16/2022] Open
Abstract
Diabetes is a disease caused by a breakdown in the glucose metabolic process resulting in abnormal blood glucose fluctuations. Traditionally, control has involved external insulin injection in response to elevated blood glucose to substitute the role of the beta cells in the pancreas which would otherwise perform this function in a healthy individual. The central nervous system (CNS), however, also plays a vital role in glucose homoeostasis through the control of pancreatic secretion and insulin sensitivity which could potentially be used as a pathway for enhancing glucose control. In this review, we present an overview of the brain regions, peripheral nerves and molecular mechanisms by which the CNS regulates glucose metabolism and the potential benefits of modulating them for diabetes management. Development of technologies to interface to the nervous system will soon become a reality through bioelectronic medicine and we present the emerging opportunities for the treatment of type 1 and type 2 diabetes.
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Affiliation(s)
- Amparo Güemes
- Centre for Bio-Inspired Technology, Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London, UK
| | - Pantelis Georgiou
- Centre for Bio-Inspired Technology, Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London, UK
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