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      GABA induces a hormonal counter-regulatory response in subjects with long-standing type 1 diabetes

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          Abstract

          Introduction

          Experimentally, gamma-aminobutyric acid (GABA) has been found to exert immune-modulatory effects and induce beta-cell regeneration, which make it a highly interesting substance candidate for the treatment of type 1 diabetes (T1D). In many countries, including those in the European Union, GABA is considered a pharmaceutical drug. We have therefore conducted a safety and dose escalation trial with the first controlled-release formulation of GABA, Remygen (Diamyd Medical).

          Research design and methods

          Six adult male subjects with long-standing T1D (age 24.8±1.5 years, disease duration 14.7±2.2 years) were enrolled in an 11-day dose escalation trial with a controlled-release formulation of GABA, Remygen. Pharmacokinetics, glucose control and hormonal counter-regulatory response during hypoglycemic clamps were evaluated at every dose increase (200 mg, 600 mg and 1200 mg).

          Results

          During the trial there were no serious and only a few, transient, adverse events reported. Without treatment, the counter-regulatory hormone response to hypoglycemia was severely blunted. Intake of 600 mg GABA more than doubled the glucagon, epinephrine, growth hormone and cortisol responses to hypoglycemia.

          Conclusions

          We find that the GABA treatment was well tolerated and established a counter-regulatory response to hypoglycemia in long-standing T1D. Further studies regarding not only the clinical potential of Remygen for beta-cell regeneration but also its potential use as hypoglycemic prophylaxis are warranted.

          Trail registration number

          NCT03635437 and EudraCT2018-001115-73.

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          Most cited references17

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          Identification of the 64K autoantigen in insulin-dependent diabetes as the GABA-synthesizing enzyme glutamic acid decarboxylase.

          The pancreatic islet beta-cell autoantigen of relative molecular mass 64,000 (64K), which is a major target of autoantibodies associated with the development of insulin-dependent diabetes mellitus (IDDM) has been identified as glutamic acid decarboxylase, the biosynthesizing enzyme of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid). Pancreatic beta cells and a subpopulation of central nervous system neurons express high levels of this enzyme. Autoantibodies against glutamic acid decarboxylase with a higher titre and increased epitope recognition compared with those usually associated with IDDM are found in stiff-man syndrome, a rare neurological disorder characterized by a high coincidence with IDDM.
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            Long-Term GABA Administration Induces Alpha Cell-Mediated Beta-like Cell Neogenesis

            The recent discovery that genetically modified α cells can regenerate and convert into β-like cells in vivo holds great promise for diabetes research. However, to eventually translate these findings to human, it is crucial to discover compounds with similar activities. Herein, we report the identification of GABA as an inducer of α-to-β-like cell conversion in vivo. This conversion induces α cell replacement mechanisms through the mobilization of duct-lining precursor cells that adopt an α cell identity prior to being converted into β-like cells, solely upon sustained GABA exposure. Importantly, these neo-generated β-like cells are functional and can repeatedly reverse chemically induced diabetes in vivo. Similarly, the treatment of transplanted human islets with GABA results in a loss of α cells and a concomitant increase in β-like cell counts, suggestive of α-to-β-like cell conversion processes also in humans. This newly discovered GABA-induced α cell-mediated β-like cell neogenesis could therefore represent an unprecedented hope toward improved therapies for diabetes.
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              GABA is an effective immunomodulatory molecule

              In recent years, it has become clear that there is an extensive cross-talk between the nervous and the immune system. Somewhat surprisingly, the immune cells themselves do express components of the neuronal neurotransmitters systems. What role the neurotransmitters, their ion channels, receptors and transporters have in immune function and regulation is an emerging field of study. Several recent studies have shown that the immune system is capable of synthesizing and releasing the classical neurotransmitter GABA (γ-aminobutyric acid). GABA has a number of effects on the immune cells such as activation or suppression of cytokine secretion, modification of cell proliferation and GABA can even affect migration of the cells. The immune cells encounter GABA when released by the immune cells themselves or when the immune cells enter the brain. In addition, GABA can also be found in tissues like the lymph nodes, the islets of Langerhans and GABA is in high enough concentration in blood to activate, e.g., GABA-A channels. GABA appears to have a role in autoimmune diseases like multiple sclerosis, type 1 diabetes, and rheumatoid arthritis and may modulate the immune response to infections. In the near future, it will be important to work out what specific effects GABA has on the function of the different types of immune cells and determine the underlying mechanisms. In this review, we discuss some of the recent findings revealing the role of GABA as an immunomodulator.
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                Author and article information

                Journal
                BMJ Open Diabetes Res Care
                BMJ Open Diabetes Res Care
                bmjdrc
                bmjdrc
                BMJ Open Diabetes Research & Care
                BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )
                2052-4897
                2021
                11 October 2021
                : 9
                : 1
                : e002442
                Affiliations
                [1 ]departmentDepartment of Medical Cell Biology, Science for Life Laboratory , Uppsala University , Uppsala, Sweden
                [2 ]departmentDepartment of Medical Sciences, Science for Life Laboratory , Uppsala University , Uppsala, Sweden
                [3 ]departmentDepartment of Medical Cell Biology , Uppsala University , Uppsala, Sweden
                [4 ]departmentDepartment of Medical Sciences , Uppsala University , Uppsala, Sweden
                [5 ]departmentDepartment of Women’s and Children’s Health , Uppsala University , Uppsala, Sweden
                Author notes
                [Correspondence to ] Professor Per-Ola Carlsson; per-ola.carlsson@ 123456mcb.uu.se

                DE and HL are joint first authors.

                Author information
                http://orcid.org/0000-0001-8843-7941
                Article
                bmjdrc-2021-002442
                10.1136/bmjdrc-2021-002442
                8506884
                34635547
                bf1b9b8e-d8cd-4e48-92d3-c4086db9614c
                © Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

                This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:  http://creativecommons.org/licenses/by-nc/4.0/.

                History
                : 22 June 2021
                : 29 September 2021
                Funding
                Funded by: http://dx.doi.org/10.13039/501100003748, Svenska Sällskapet för Medicinsk Forskning;
                Award ID: N/A
                Funded by: http://dx.doi.org/10.13039/501100008550, Diabetesfonden;
                Award ID: N/A
                Funded by: http://dx.doi.org/10.13039/501100004973, Barndiabetesfonden;
                Award ID: N/A
                Funded by: http://dx.doi.org/10.13039/501100004359, Vetenskapsrådet;
                Award ID: N/A
                Funded by: Exodiab;
                Categories
                Emerging Technologies, Pharmacology and Therapeutics
                1506
                Custom metadata
                unlocked

                diabetes mellitus,type 1,hypoglycemia,receptors,gaba-a
                diabetes mellitus, type 1, hypoglycemia, receptors, gaba-a

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