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Hristov M, Nankova A, Andreeva-Gateva P. Alterations of the glutamatergic system in diabetes mellitus. Metab Brain Dis 2024; 39:321-333. [PMID: 37747631 DOI: 10.1007/s11011-023-01299-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 09/17/2023] [Indexed: 09/26/2023]
Abstract
Diabetes mellitus (DM) is a chronic disease characterized by elevated blood glucose levels caused by a lack of insulin production (type 1 diabetes) or insulin resistance (type 2 diabetes). It is well known that DM is associated with cognitive deficits and metabolic and neurophysiological changes in the brain. Glutamate is the main excitatory neurotransmitter in the central nervous system that plays a key role in synaptic plasticity, learning, and memory processes. An increasing number of studies have suggested that abnormal activity of the glutamatergic system is implicated in the pathophysiology of DM. Dysfunction of glutamatergic neurotransmission in the central nervous system can provide an important neurobiological substrate for many disorders. Magnetic resonance spectroscopy (MRS) is a non-invasive technique that allows a better understanding of the central nervous system factors by measuring in vivo the concentrations of brain metabolites within the area of interest. Here, we briefly review the MRS studies that have examined glutamate levels in the brain of patients with DM. The present article also summarizes the available data on abnormalities in glutamatergic neurotransmission observed in different animal models of DM. In addition, the role of gut microbiota in the development of glutamatergic alterations in DM is addressed. We speculate that therapeutic strategies targeting the glutamatergic system may be beneficial in the treatment of central nervous system-related changes in diabetic patients.
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Affiliation(s)
- Milen Hristov
- Department of Pharmacology and Toxicology, Faculty of Medicine, Medical University of Sofia, 2 "Zdrave" St, Sofia, 1431, Bulgaria.
| | - Anelia Nankova
- Department of Endocrinology, Faculty of Medicine, Medical University of Sofia, Sofia, 1431, Bulgaria
| | - Pavlina Andreeva-Gateva
- Department of Pharmacology and Toxicology, Faculty of Medicine, Medical University of Sofia, 2 "Zdrave" St, Sofia, 1431, Bulgaria
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Insulin-Induced Recurrent Hypoglycemia Up-Regulates Glucose Metabolism in the Brain Cortex of Chemically Induced Diabetic Rats. Int J Mol Sci 2021; 22:ijms222413470. [PMID: 34948265 PMCID: PMC8708764 DOI: 10.3390/ijms222413470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 12/20/2022] Open
Abstract
Diabetes is a chronic metabolic disease that seriously compromises human well-being. Various studies highlight the importance of maintaining a sufficient glucose supply to the brain and subsequently safeguarding cerebral glucose metabolism. The goal of the present work is to clarify and disclose the metabolic alterations induced by recurrent hypoglycemia in the context of long-term hyperglycemia to further comprehend the effects beyond brain harm. To this end, chemically induced diabetic rats underwent a protocol of repeatedly insulin-induced hypoglycemic episodes. The activity of key enzymes of glycolysis, the pentose phosphate pathway and the Krebs cycle was measured by spectrophotometry in extracts or isolated mitochondria from brain cortical tissue. Western blot analysis was used to determine the protein content of glucose and monocarboxylate transporters, players in the insulin signaling pathway and mitochondrial biogenesis and dynamics. We observed that recurrent hypoglycemia up-regulates the activity of mitochondrial hexokinase and Krebs cycle enzymes (namely, pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and succinate dehydrogenase) and the protein levels of mitochondrial transcription factor A (TFAM). Both insults increased the nuclear factor erythroid 2–related factor 2 (NRF2) protein content and induced divergent effects in mitochondrial dynamics. Insulin-signaling downstream pathways were found to be down-regulated, and glycogen synthase kinase 3 beta (GSK3β) was found to be activated through both decreased phosphorylation at Ser9 and increased phosphorylation at Y216. Interestingly, no changes in the levels of cAMP response element-binding protein (CREB), which plays a key role in neuronal plasticity and memory, were caused by hypoglycemia and/or hyperglycemia. These findings provide experimental evidence that recurrent hypoglycemia, in the context of chronic hyperglycemia, has the capacity to evoke coordinated adaptive responses in the brain cortex that will ultimately contribute to sustaining brain cell health.
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Horak T, Horakova M, Svatkova A, Kadanka Z, Kudlicka P, Valosek J, Rohan T, Kerkovsky M, Vlckova E, Kadanka Z, Deelchand DK, Henry PG, Bednarik J, Bednarik P. In vivo Molecular Signatures of Cervical Spinal Cord Pathology in Degenerative Compression. J Neurotrauma 2021; 38:2999-3010. [PMID: 34428934 PMCID: PMC8917902 DOI: 10.1089/neu.2021.0151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Degenerative cervical myelopathy (DCM) is a severe consequence of degenerative cervical spinal cord (CSC) compression. The non-myelopathic stage of compression (NMDC) is highly prevalent and often progresses to disabling DCM. This study aims to disclose markers of progressive neurochemical alterations in NMDC and DCM by utilizing an approach based on state-of-the-art proton magnetic resonance spectroscopy (1H-MRS). Proton-MRS data were prospectively acquired from 73 participants with CSC compression and 47 healthy controls (HCs). The MRS voxel was centered at the C2 level. Compression-affected participants were clinically categorized as NMDC and DCM, radiologically as mild (MC) or severe (SC) compression. CSC volumes and neurochemical concentrations were compared between cohorts (HC vs. NMDC vs. DCM and HC vs. MC vs. SC) with general linear models adjusted for age and height (pFWE < 0.05) and correlated to stenosis severity, electrophysiology, and myelopathy symptoms (p < 0.05). Whereas the ratio of total creatine (tCr) to total N-acetylaspartate (tNAA) increased in NMDC (+11%) and in DCM (+26%) and SC (+21%), myo-inositol/tNAA, glutamate + glutamine/tNAA, and volumes changed only in DCM (+20%, +73%, and −14%) and SC (+12%, +46%, and −8%, respectively) relative to HCs. Both tCr/tNAA and myo-inositol/tNAA correlated with compression severity and volume (−0.376 < r < −0.259). Myo-inositol/tNAA correlated with myelopathy symptoms (r = −0.670), whereas CSC volume did not. Short-echo 1H-MRS provided neurochemical signatures of CSC impairment that reflected compression severity and clinical significance. Whereas volumetry only reflected clinically manifest myelopathy (DCM), MRS detected neurochemical changes already before the onset of myelopathy symptoms.
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Affiliation(s)
- Tomas Horak
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Department of Neurology, University Hospital Brno, Brno, Czechia.,Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia
| | - Magda Horakova
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Department of Neurology, University Hospital Brno, Brno, Czechia.,Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia
| | - Alena Svatkova
- Department of Medicine III, Clinical Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.,Department of Imaging Methods, Faculty of Medicine, University of Ostrava, Czechia
| | - Zdenek Kadanka
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Department of Neurology, University Hospital Brno, Brno, Czechia
| | - Petr Kudlicka
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia
| | - Jan Valosek
- Department of Neurology, Faculty of Medicine and Dentistry, Palacky University, Olomouc, Czechia.,Department of Biomedical Engineering, University Hospital, Olomouc, Czechia
| | - Tomas Rohan
- Department of Radiology, University Hospital Brno, Brno, Czechia
| | - Milos Kerkovsky
- Department of Radiology, University Hospital Brno, Brno, Czechia
| | - Eva Vlckova
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Department of Neurology, University Hospital Brno, Brno, Czechia.,Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia
| | - Zdenek Kadanka
- Department of Neurology, University Hospital Brno, Brno, Czechia
| | - Dinesh K Deelchand
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Pierre-Gilles Henry
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Josef Bednarik
- Faculty of Medicine, Masaryk University, Brno, Czechia.,Department of Neurology, University Hospital Brno, Brno, Czechia.,Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia
| | - Petr Bednarik
- Multimodal and Functional Imaging Laboratory, Central European Institute of Technology, Brno, Czechia.,Department of Biomedical Imaging and Image-guided Therapy, High Field MR Centre, Medical University of Vienna, Vienna, Austria
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Bednarik P, Spurny B, Silberbauer LR, Svatkova A, Handschuh PA, Reiter B, Konadu ME, Stimpfl T, Spies M, Bogner W, Lanzenberger R. Effect of Ketamine on Human Neurochemistry in Posterior Cingulate Cortex: A Pilot Magnetic Resonance Spectroscopy Study at 3 Tesla. Front Neurosci 2021; 15:609485. [PMID: 33841073 PMCID: PMC8024494 DOI: 10.3389/fnins.2021.609485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 02/23/2021] [Indexed: 12/28/2022] Open
Abstract
Ketamine is a powerful glutamatergic long-lasting antidepressant, efficient in intractable major depression. Whereas ketamine's immediate psychomimetic side-effects were linked to glutamate changes, proton MRS (1H-MRS) showed an association between the ratio of glutamate and glutamine and delayed antidepressant effect emerging ∼2 h after ketamine administration. While most 1H-MRS studies focused on anterior cingulate, recent functional MRI connectivity studies revealed an association between ketamine's antidepressant effect and disturbed connectivity patterns to the posterior cingulate cortex (PCC), and related PCC dysfunction to rumination and memory impairment involved in depressive pathophysiology. The current study utilized the state-of-the-art single-voxel 3T sLASER 1H-MRS methodology optimized for reproducible measurements. Ketamine's effects on neurochemicals were assessed before and ∼3 h after intravenous ketamine challenge in PCC. Concentrations of 11 neurochemicals, including glutamate (CRLB ∼ 4%) and glutamine (CRLB ∼ 13%), were reliably quantified with the LCModel in 12 healthy young men with between-session coefficients of variation (SD/mean) <8%. Also, ratios of glutamate/glutamine and glutamate/aspartate were assessed as markers of synaptic function and activated glucose metabolism, respectively. Pairwise comparison of metabolite profiles at baseline and 193 ± 4 min after ketamine challenge yielded no differences. Minimal detectable concentration differences estimated with post hoc power analysis (power = 80%, alpha = 0.05) were below 0.5 μmol/g, namely 0.39 μmol/g (∼4%) for glutamate, 0.28 μmol/g (∼10%) for Gln, ∼14% for glutamate/glutamine and ∼8% for glutamate/aspartate. Despite the high sensitivity to detect between-session differences in glutamate and glutamine concentrations, our study did not detect delayed glutamatergic responses to subanesthetic ketamine doses in PCC.
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Affiliation(s)
- Petr Bednarik
- High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
- Institute for Clinical Molecular MRI in Musculoskeletal System, Karl Landsteiner Society, Vienna, Austria
| | - Benjamin Spurny
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Leo R. Silberbauer
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Alena Svatkova
- Department of Medicine III, Clinical Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria
| | - Patricia A. Handschuh
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Birgit Reiter
- Clinical Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Melisande E. Konadu
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Thomas Stimpfl
- Clinical Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Marie Spies
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - Wolfgang Bogner
- High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
- Institute for Clinical Molecular MRI in Musculoskeletal System, Karl Landsteiner Society, Vienna, Austria
| | - Rupert Lanzenberger
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
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Bednařík P, Henry PG, Khowaja A, Rubin N, Kumar A, Deelchand D, Eberly LE, Seaquist E, Öz G, Moheet A. Hippocampal Neurochemical Profile and Glucose Transport Kinetics in Patients With Type 1 Diabetes. J Clin Endocrinol Metab 2020; 105:5601935. [PMID: 31637440 PMCID: PMC7046023 DOI: 10.1210/clinem/dgz062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 09/27/2019] [Indexed: 01/28/2023]
Abstract
CONTEXT Longstanding type 1 diabetes (T1D) may lead to alterations in hippocampal neurochemical profile. Upregulation of hippocampal glucose transport as a result of recurrent exposure to hypoglycemia may preserve cognitive function during future hypoglycemia in subjects with T1D and impaired awareness of hypoglycemia (IAH). The effect of T1D on hippocampal neurochemical profile and glucose transport is unknown. OBJECTIVE To test the hypothesis that hippocampal neurochemical composition is altered in T1D and glucose transport is upregulated in T1D with IAH. DESIGN AND PARTICIPANTS Hippocampal neurochemical profile was measured with single-voxel magnetic resonance spectroscopy at 3T during euglycemia in 18 healthy controls (HC), 10 T1D with IAH, and 12 T1D with normal awareness to hypoglycemia (NAH). Additionally, 12 HC, 8 T1D-IAH, and 6 T1D-NAH were scanned during hyperglycemia to assess hippocampal glucose transport with metabolic modeling. SETTING University medical center. MAIN OUTCOME MEASURES Concentrations of hippocampal neurochemicals measured during euglycemia and ratios of maximal transport rate to cerebral metabolic rate of glucose (Tmax/CMRGlc), derived from magnetic resonance spectroscopy-measured hippocampal glucose as a function of plasma glucose. RESULTS Comparison of hippocampal neurochemical profile revealed no group differences (HC, T1D, T1D-IAH, and T1D-NAH). The ratio Tmax/CMRGlc was not significantly different between the groups, T1D-IAH (1.58 ± 0.09) and HC (1.65 ± 0.07, P = 0.54), between T1D-NAH (1.50 ± 0.09) and HC (P = 0.19), and between T1D-IAH and T1D-NAH (P = 0.53). CONCLUSIONS Subjects with T1D with sufficient exposure to recurrent hypoglycemia to create IAH did not have alteration of Tmax/CMRglc or neurochemical profile compared with participants with T1D-NAH or HC.
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Affiliation(s)
- Petr Bednařík
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, Minneapolis, Minnesota
- High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria
- Department of Imaging Methods, Faculty of Medicine, University of Ostrava, Ostrava, Czech Republic
| | - Pierre-Gilles Henry
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota
| | - Amir Khowaja
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Nathan Rubin
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota
| | - Anjali Kumar
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Dinesh Deelchand
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota
| | - Lynn E Eberly
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota
| | - Elizabeth Seaquist
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, Minneapolis, Minnesota
| | - Gülin Öz
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota
| | - Amir Moheet
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, Minneapolis, Minnesota
- Correspondence and Reprint Requests: Amir Moheet, MBBS, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, MMC 101, 420 Delaware St. SE, Minneapolis, MN 55455. E-mail:
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