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Kopp KO, Li Y, Glotfelty EJ, Tweedie D, Greig NH. Incretin-Based Multi-Agonist Peptides Are Neuroprotective and Anti-Inflammatory in Cellular Models of Neurodegeneration. Biomolecules 2024; 14:872. [PMID: 39062586 PMCID: PMC11275108 DOI: 10.3390/biom14070872] [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] [Received: 05/29/2024] [Revised: 07/03/2024] [Accepted: 07/15/2024] [Indexed: 07/28/2024] Open
Abstract
Glucagon-like peptide-1 (GLP-1)-based drugs have been approved by the United States Food and Drug Administration (FDA) and are widely used to treat type 2 diabetes mellitus (T2DM) and obesity. More recent developments of unimolecular peptides targeting multiple incretin-related receptors ("multi-agonists"), including the glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) and the glucagon (Gcg) receptor (GcgR), have emerged with the aim of enhancing drug benefits. In this study, we utilized human and mouse microglial cell lines, HMC3 and IMG, respectively, together with the human neuroblastoma SH-SY5Y cell line as cellular models of neurodegeneration. Using these cell lines, we studied the neuroprotective and anti-inflammatory capacity of several multi-agonists in comparison with a single GLP-1 receptor (GLP-1R) agonist, exendin-4. Our data demonstrate that the two selected GLP-1R/GIPR dual agonists and a GLP-1R/GIPR/GcgR triple agonist not only have neurotrophic and neuroprotective effects but also have anti-neuroinflammatory properties, as indicated by the decreased microglial cyclooxygenase 2 (COX2) expression, nitrite production, and pro-inflammatory cytokine release. In addition, our results indicate that these multi-agonists have the potential to outperform commercially available single GLP-1R agonists in neurodegenerative disease treatment.
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Affiliation(s)
- Katherine O. Kopp
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA; (K.O.K.); (Y.L.); (D.T.)
| | - Yazhou Li
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA; (K.O.K.); (Y.L.); (D.T.)
| | - Elliot J. Glotfelty
- Cellular Stress and Inflammation Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA;
| | - David Tweedie
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA; (K.O.K.); (Y.L.); (D.T.)
| | - Nigel H. Greig
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA; (K.O.K.); (Y.L.); (D.T.)
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2
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Kononova S, Kashparov M, Xue W, Bobkova N, Leonov S, Zagorodny N. Gut Microbiome Dysbiosis as a Potential Risk Factor for Idiopathic Toe-Walking in Children: A Review. Int J Mol Sci 2023; 24:13204. [PMID: 37686011 PMCID: PMC10488280 DOI: 10.3390/ijms241713204] [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] [Received: 07/29/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023] Open
Abstract
Idiopathic toe walking (ITW) occurs in about 5% of children. Orthopedic treatment of ITW is complicated by the lack of a known etiology. Only half of the conservative and surgical methods of treatment give a stable positive result of normalizing gait. Available data indicate that the disease is heterogeneous and multifactorial. Recently, some children with ITW have been found to have genetic variants of mutations that can lead to the development of toe walking. At the same time, some children show sensorimotor impairment, but these studies are very limited. Sensorimotor dysfunction could potentially arise from an imbalanced production of neurotransmitters that play a crucial role in motor control. Using the data obtained in the studies of several pathologies manifested by the association of sensory-motor dysfunction and intestinal dysbiosis, we attempt to substantiate the notion that malfunction of neurotransmitter production is caused by the imbalance of gut microbiota metabolites as a result of dysbiosis. This review delves into the exciting possibility of a connection between variations in the microbiome and ITW. The purpose of this review is to establish a strong theoretical foundation and highlight the benefits of further exploring the possible connection between alterations in the microbiome and TW for further studies of ITW etiology.
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Affiliation(s)
- Svetlana Kononova
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Russia
| | - Mikhail Kashparov
- Department of Traumatology and Orthopedics, Peoples’ Friendship University of Russia, 117198 Moscow, Russia; (M.K.); (N.Z.)
- Scientific and Practical Center for Child Psychoneurology, 119602 Moscow, Russia
| | - Wenyu Xue
- School of Biological and Medical Physics, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (W.X.); (S.L.)
| | - Natalia Bobkova
- Institute of Cell Biophysics, Russian Academy of Sciences, 142290 Pushchino, Russia;
| | - Sergey Leonov
- School of Biological and Medical Physics, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (W.X.); (S.L.)
- Institute of Cell Biophysics, Russian Academy of Sciences, 142290 Pushchino, Russia;
| | - Nikolaj Zagorodny
- Department of Traumatology and Orthopedics, Peoples’ Friendship University of Russia, 117198 Moscow, Russia; (M.K.); (N.Z.)
- N.N. Priorov Central Research Institute of Traumatology and Orthopedics, 127299 Moscow, Russia
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3
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Mizukami H, Osonoi S. Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy. Int J Mol Sci 2020; 22:ijms22010094. [PMID: 33374137 PMCID: PMC7796340 DOI: 10.3390/ijms22010094] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 12/16/2020] [Accepted: 12/18/2020] [Indexed: 12/11/2022] Open
Abstract
Diabetic polyneuropathy (DPN) is the most common neuropathy manifested in diabetes. Symptoms include allodynia, pain, paralysis, and ulcer formation. There is currently no established radical treatment, although new mechanisms of DPN are being vigorously explored. A pathophysiological feature of DPN is abnormal glucose metabolism induced by chronic hyperglycemia in the peripheral nerves. Particularly, activation of collateral glucose-utilizing pathways such as the polyol pathway, protein kinase C, advanced glycation end-product formation, hexosamine biosynthetic pathway, pentose phosphate pathway, and anaerobic glycolytic pathway are reported to contribute to the onset and progression of DPN. Inhibitors of aldose reductase, a rate-limiting enzyme involved in the polyol pathway, are the only compounds clinically permitted for DPN treatment in Japan, although their efficacies are limited. This may indicate that multiple pathways can contribute to the pathophysiology of DPN. Comprehensive metabolic analysis may help to elucidate global changes in the collateral glucose-utilizing pathways during the development of DPN, and highlight therapeutic targets in these pathways.
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Affiliation(s)
- Hiroki Mizukami
- Department Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan;
- Correspondence: ; Tel.: +81-172-39-5025
| | - Sho Osonoi
- Department Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan;
- Department of Endocrinology and Metabolism, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan
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Mizukami H, Osonoi S, Takaku S, Yamagishi SI, Ogasawara S, Sango K, Chung S, Yagihashi S. Role of glucosamine in development of diabetic neuropathy independent of the aldose reductase pathway. Brain Commun 2020; 2:fcaa168. [PMID: 33305258 PMCID: PMC7713992 DOI: 10.1093/braincomms/fcaa168] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 08/04/2020] [Accepted: 08/24/2020] [Indexed: 12/30/2022] Open
Abstract
Long-term metabolic aberrations contribute to the development of diabetic neuropathy but the precise mechanism or mechanisms remains elusive. We have previously shown that aldose reductase-deficient mice exhibit delayed onset and progression of neuropathy following induction of diabetes, suggesting a role both for downstream metabolites of this enzyme and also for other unrelated pathways. In this study, we have utilized comprehensive metabolomics analyses to identify potential neurotoxic metabolites in nerve of diabetic mice and explored the mechanism of peripheral nerve injury. Aldose reductase knockout and control C57Bl/6J mice were made diabetic by injection of streptozotocin and followed for 8–16 weeks. Diabetic aldose reductase knockout mice exhibited delayed onset of nerve conduction slowing compared to diabetic wild-type mice. The sciatic nerves from aldose reductase knockout mice exposed to 12 weeks of diabetes were used for metabolomics analysis and compared with analyses of nerves from age-matched diabetic wild-type mice as well as non-diabetic aldose reductase knockout and wild-type mice. Neurotoxicity of candidate metabolites was evaluated using cultured Schwann cells and dorsal root ganglion neurons, and further confirmed in vivo. Metabolomics analysis identified elevated glucosamine levels in both diabetic aldose reductase knockout and diabetic wild mice. Exposure to glucosamine reduced survival of cultured Schwann cells and neurons accompanied by increased expression of cleaved caspase 3, CCAT-enhancer-binding homologous protein and mitochondrial hexokinase-I, along with ATP depletion. These changes were suppressed by siRNA to hexokinase-I or the ATP donor, inosine, but not by the antioxidant N-acetylcysteine or the endoplasmic reticulum-stress inhibitor 4-phenylbutyrate. The O-GlcNAcylation enhancer, O-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino N-phenylcarbamate, did not augment glucosamine neurotoxicity. Single dose glucosamine injection into mice caused a reduction of sciatic nerve Na, K-ATPase activity, ATP content and augmented expression of hexokinase-I, which were suppressed by pretreatment with inosine but not with 4-phenylbutyrate. Mice implanted with a subcutaneous pump to infuse glucosamine for 12 weeks developed nerve conduction slowing and intraepidermal nerve fibre loss, recapitulating prominent indices of diabetic neuropathy. While acute glucosamine neurotoxicity is unlikely to contribute substantially to the slowly developing neuropathy phenotype in humans, sustained energy deprivation induced by glucosamine may well contribute to the pathogenesis of diabetic neuropathy. Our data thus identifies a novel pathway for diabetic neuropathy that may offer a potential new therapeutic target.
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Affiliation(s)
- Hiroki Mizukami
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Sho Osonoi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Shizuka Takaku
- Diabetic Neuropathy Project, Tokyo Metropolitan Institute of Medical Science, Tokyo
| | - Shin-Ichiro Yamagishi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Saori Ogasawara
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Kazunori Sango
- Diabetic Neuropathy Project, Tokyo Metropolitan Institute of Medical Science, Tokyo
| | - Sookja Chung
- Faculty of Medicine, Macau University of Science and Technology, Taipa, Macau
| | - Soroku Yagihashi
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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Zhang D, Ma M, Liu Y. Protective Effects of Incretin Against Age-Related Diseases. Curr Drug Deliv 2019; 16:793-806. [PMID: 31622202 DOI: 10.2174/1567201816666191010145029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/01/2019] [Accepted: 09/19/2019] [Indexed: 12/11/2022]
Abstract
Incretin contains two peptides named glucagon-like peptide-1(GLP-1) and glucose-dependent
insulinotropic polypeptide (GIP). Drug therapy using incretin has become a new strategy for diabetic
treatments due to its significant effects on improving insulin receptors and promoting insulinotropic
secretion. Considering the fact that diabetes millitus is a key risk factor for almost all age-related diseases,
the extensive protective roles of incretin in chronic diseases have received great attention. Based
on the evidence from animal experiments, where incretin can protect against the pathophysiological
processes of neurodegenerative diseases, clinical trials for the treatments of Alzheimer’s disease (AD)
and Parkinson’s disease (PD) patients are currently ongoing. Moreover, the protective effect of incretin
on heart has been observed in cardiac myocytes, smooth muscle cells and endothelial cells of vessels.
Meanwhile, incretin can also inhibit the proliferation of aortic vascular smooth muscle cells, which can
induce atherosclerogenesis. Incretin is also beneficial for diabetic microvascular complications, including
nephropathy, retinopathy and gastric ulcer, as well as the hepatic-related diseases such as NAFLD
and NASH. Besides, the anti-tumor properties of incretin have been proven in diverse cancers including
ovarian cancer, pancreas cancer, prostate cancer and breast cancer.
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Affiliation(s)
- Di Zhang
- Chemistry Department, Shanxi Medical University, Taiyuan, Shanxi, China
| | - Mingzhu Ma
- Second Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
| | - Yueze Liu
- Second Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
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6
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Abstract
The regulation of glycemia is under a tight neuronal detection of glucose levels performed by the gut-brain axis and an efficient efferent neuronal message sent to the peripheral organs, as the pancreas to induce insulin and inhibit glucagon secretions. The neuronal detection of glucose levels is performed by the autonomic nervous system including the enteric nervous system and the vagus nerve innervating the gastro-intestinal tractus, from the mouth to the anus. A dysregulation of this detection leads to the one of the most important current health issue around the world i.e. diabetes mellitus. Furthemore, the consequences of diabetes mellitus on neuronal homeostasis and activities participate to the aggravation of the disease establishing a viscious circle. Prokaryotic cells as bacteria, reside in our gut. The strong relationship between prokaryotic cells and our eukaryotic cells has been established long ago, and prokaryotic and eukaryotic cells in our body have evolved synbiotically. For the last decades, studies demonstrated the critical role of the gut microbiota on the metabolic control and how its shift can induce diseases such as diabetes. Despite an important increase of knowledge, few is known about 1) how the gut microbiota influences the neuronal detection of glucose and 2) how the diabetes mellitus-induced gut microbiota shift observed participates to the alterations of autonomic nervous system and the gut-brain axis activity.
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Affiliation(s)
- Estelle Grasset
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, University of Gothenburg, 41345, Gothenburg, Sweden.
| | - Remy Burcelin
- Institut National de la Santé et de la Recherche Médicale (INSERM), Toulouse, France
- Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2 : 'Intestinal Risk Factors, Diabetes, Université Paul Sabatier (UPS), Dyslipidemia', F-31432, Toulouse, Cedex 4, France
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7
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Knudsen LB. Inventing Liraglutide, a Glucagon-Like Peptide-1 Analogue, for the Treatment of Diabetes and Obesity. ACS Pharmacol Transl Sci 2019; 2:468-484. [PMID: 32259078 DOI: 10.1021/acsptsci.9b00048] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Indexed: 01/08/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) has been in focus since the early 1980s as a long looked for incretin hormone, released from the gastrointestinal tract and with an important effect on glucose-dependent insulin secretion, providing efficient glucose lowering, with little risk for hypoglycemia. The enzyme dipeptidyl peptidase-4 (DPP-4) degrades GLP-1 very fast, and the remaining metabolite is cleared rapidly by the kidneys. Liraglutide is a fatty acid acylated analogue of GLP-1 that provides efficacy for 24 h/day. The mechanism of action for liraglutide is reviewed in detail with focus on pancreatic efficacy and safety, thyroid safety, and weight loss mechanism. Evolving science hypothesizes that GLP-1 has important effects on atherosclerosis, relevant for the cardiovascular benefit seen in the treatment of diabetes and obesity. Also, GLP-1 may be relevant in neurodegenerative diseases.
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Affiliation(s)
- Lotte Bjerre Knudsen
- Global Drug Discovery, Novo Nordisk, Novo Nordisk Park, DK-2760 Maaloev, Denmark
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8
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Li Y, Li L, Hölscher C. Incretin-based therapy for type 2 diabetes mellitus is promising for treating neurodegenerative diseases. Rev Neurosci 2018; 27:689-711. [PMID: 27276528 DOI: 10.1515/revneuro-2016-0018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 05/02/2016] [Indexed: 12/13/2022]
Abstract
Incretin hormones include glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Due to their promising action on insulinotropic secretion and improving insulin resistance (IR), incretin-based therapies have become a new class of antidiabetic agents for the treatment of type 2 diabetes mellitus (T2DM). Recently, the links between neurodegenerative diseases and T2DM have been identified in a number of studies, which suggested that shared mechanisms, such as insulin dysregulation or IR, may underlie these conditions. Therefore, the effects of incretins in neurodegenerative diseases have been extensively investigated. Protease-resistant long-lasting GLP-1 mimetics such as lixisenatide, liraglutide, and exenatide not only have demonstrated promising effects for treating neurodegenerative diseases in preclinical studies but also have shown first positive results in Alzheimer's disease (AD) and Parkinson's disease (PD) patients in clinical trials. Furthermore, the effects of other related incretin-based therapies such as GIP agonists, dipeptidyl peptidase-IV (DPP-IV) inhibitors, oxyntomodulin (OXM), dual GLP-1/GIP, and triple GLP-1/GIP/glucagon receptor agonists on neurodegenerative diseases have been tested in preclinical studies. Incretin-based therapies are a promising approach for treating neurodegenerative diseases.
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Nilsson M, Gjedde A, Brock B, Gejl M, Rungby J. The effects of incretin hormones on cerebral glucose metabolism in health and disease. Neuropharmacology 2017; 136:243-250. [PMID: 29274367 DOI: 10.1016/j.neuropharm.2017.12.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 12/14/2017] [Accepted: 12/18/2017] [Indexed: 12/25/2022]
Abstract
Incretin hormones, notably glucagon-like peptide-1 (GLP-1), are gluco-regulatory hormones with pleiotropic effects also in the central nervous system. Apart from a local production of GLP-1, systemic administration of the hormone has been shown to influence a number of cerebral pathologies, including neuroinflammation. Given the brains massive dependence on glucose as its major fuel, we here review the mechanistics of cerebral glucose transport and metabolism, focusing on the deleterious effects of both hypo- and hyperglycaemia. GLP-1, when administered as long-acting analogues or intravenously, appears to decrease transport of glucose in normoglycaemic conditions, without affecting the total cerebral glucose content. During hypoglycaemia this effect seems abated, whereas during hyperglycaemia GLP-1 regulates cerebral glucose metabolism towards stable levels resembling normoglycaemia. In Alzheimer's disease, a 6-month intervention with GLP-1 maintained cerebral glucose levels at baseline levels, contrasting the decline otherwise seen in Alzheimer's. Kinetic studies suggest blood-brain barrier (BBB) glucose transport as the key player in GLP-1 mediated effects on cerebral glucose metabolism. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'
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Affiliation(s)
- Malin Nilsson
- Department of Endocrinology, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Albert Gjedde
- Department of Neuroscience, Panum Institute, University of Copenhagen, Copenhagen, Denmark; Departments of Clinical Research, and Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
| | | | - Michael Gejl
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Jørgen Rungby
- Department of Endocrinology, Bispebjerg University Hospital, Copenhagen, Denmark.
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10
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Yagihashi S. Glucotoxic Mechanisms and Related Therapeutic Approaches. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 127:121-49. [PMID: 27133148 DOI: 10.1016/bs.irn.2016.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neuropathy is the earliest and commonest complication of diabetes. With increasing duration of diabetes, frequency and severity of neuropathy are worsened. Long-term hyperglycemia is therefore implicated in the development of this disorder. Nerve tissues require glucose energy to function and survive. Upon excessive glucose entry into the peripheral nerve, the glycolytic pathway and collateral glucose-utilizing pathways are overactivated and initiate adverse effects on nerve tissues. During hyperglycemia, flux through the polyol pathway, formation of advanced glycation end-products, production of free radicals, flux into the glucosamine pathway, and protein kinase C activity are all enhanced to negatively influence nerve function and structure. Suppression of these aberrant metabolic pathways has succeeded in prevention and inhibition of the development of neuropathy in animal models with diabetes. Satisfactory results were not attained, however, in patients with diabetes and further clinical trials are required. In this review, the author summarizes the hitherto proposed theories on the pathogenesis of diabetic neuropathy related to glucose metabolism and future prospects for the effective treatment of neuropathy.
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Affiliation(s)
- S Yagihashi
- Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
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11
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Gejl M, Rungby J, Brock B, Gjedde A. At the centennial of Michaelis and Menten, competing Michaelis-Menten steps explain effect of GLP-1 on blood-brain transfer and metabolism of glucose. Basic Clin Pharmacol Toxicol 2014; 115:162-71. [PMID: 24684709 DOI: 10.1111/bcpt.12240] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 03/17/2014] [Indexed: 12/16/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) is a potent insulinotropic incretin hormone with both pancreatic and extrapancreatic effects. Studies of GLP-1 reveal significant effects in regions of brain tissue that regulate appetite and satiety. GLP-1 mimetics are used for the treatment of type 2 diabetes mellitus. GLP-1 interacts with peripheral functions in which the autonomic nervous system plays an important role, and emerging pre-clinical findings indicate a potential neuroprotective role of the peptide, for example in models of stroke and in neurodegenerative disorders. A century ago, Leonor Michaelis and Maud Menten described the steady-state enzyme kinetics that still apply to the multiple receptors, transporters and enzymes that define the biochemical reactions of the brain, including the glucose-dependent impact of GLP-1 on blood-brain glucose transfer and metabolism. This MiniReview examines the potential of GLP-1 as a molecule of interest for the understanding of brain energy metabolism and with reference to the impact on brain metabolism related to appetite and satiety regulation, stroke and neurodegenerative disorders. These effects can be understood only by reference to the original formulation of the Michaelis-Menten equation as applied to a chain of kinetically controlled steps. Indeed, the effects of GLP-1 receptor activation on blood-brain glucose transfer and brain metabolism of glucose depend on the glucose concentration and relative affinities of the steps both in vitro and in vivo, as in the pancreas.
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Affiliation(s)
- Michael Gejl
- Department of Biomedicine - Pharmacology, Aarhus University, Aarhus, Denmark; Centre for Advanced Imaging, The University of Queensland, Brisbane, Qld, Australia
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12
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Greig NH, Tweedie D, Rachmany L, Li Y, Rubovitch V, Schreiber S, Chiang YH, Hoffer BJ, Miller J, Lahiri DK, Sambamurti K, Becker RE, Pick CG. Incretin mimetics as pharmacologic tools to elucidate and as a new drug strategy to treat traumatic brain injury. Alzheimers Dement 2014; 10:S62-75. [PMID: 24529527 PMCID: PMC4201593 DOI: 10.1016/j.jalz.2013.12.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 12/05/2013] [Indexed: 01/12/2023]
Abstract
Traumatic brain injury (TBI), either as an isolated injury or in conjunction with other injuries, is an increasingly common event. An estimated 1.7 million injuries occur within the USA each year and 10 million people are affected annually worldwide. Indeed, nearly one third (30.5%) of all injury-related deaths in the USA are associated with TBI, which will soon outpace many common diseases as the major cause of death and disability. Associated with a high morbidity and mortality and no specific therapeutic treatment, TBI has become a pressing public health and medical problem. The highest incidence of TBI occurs in young adults (15-24 years age) and in the elderly (≥75 years of age). Older individuals are particularly vulnerable to these types of injury, often associated with falls, and have shown increased mortality and worse functional outcome after lower initial injury severity. In addition, a new and growing form of TBI, blast injury, associated with the detonation of improvised explosive devices in the war theaters of Iraq and Afghanistan, are inflicting a wave of unique casualties of immediate impact to both military personnel and civilians, for which long-term consequences remain unknown and may potentially be catastrophic. The neuropathology underpinning head injury is becoming increasingly better understood. Depending on severity, TBI induces immediate neuropathologic effects that, for the mildest form, may be transient; however, with increasing severity, these injuries cause cumulative neural damage and degeneration. Even with mild TBI, which represents the majority of cases, a broad spectrum of neurologic deficits, including cognitive impairments, can manifest that may significantly influence quality of life. Further, TBI can act as a conduit to longer term neurodegenerative disorders. Prior studies of glucagon-like peptide-1 (GLP-1) and long-acting GLP-1 receptor agonists have demonstrated neurotrophic/neuroprotective activities across a broad spectrum of cellular and animal models of chronic neurodegenerative (Alzheimer's and Parkinson's diseases) and acute cerebrovascular (stroke) disorders. In view of the mechanisms underpinning these disorders as well as TBI, we review the literature and recent studies assessing GLP-1 receptor agonists as a potential treatment strategy for mild to moderate TBI.
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Affiliation(s)
- Nigel H Greig
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
| | - David Tweedie
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Lital Rachmany
- Department of Anatomy & Anthropology, Sackler School of Medicine and Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
| | - Yazhou Li
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Vardit Rubovitch
- Department of Anatomy & Anthropology, Sackler School of Medicine and Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
| | - Shaul Schreiber
- Department of Psychiatry, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Yung-Hsiao Chiang
- Department of Neurosurgery, Taipei Medical University Hospital, Taipei City, Taiwan, ROC; Graduate Institute of Neural Regenerative Medicine, Taipei Medical University, Taipei City, Taiwan, ROC
| | - Barry J Hoffer
- Department of Neurosurgery, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Jonathan Miller
- Department of Neurosurgery, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Debomoy K Lahiri
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kumar Sambamurti
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA
| | - Robert E Becker
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA; Aristea Translational Medicine, Park City, UT, USA
| | - Chaim G Pick
- Department of Anatomy & Anthropology, Sackler School of Medicine and Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
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Daniel B, Green O, Viskind O, Gruzman A. Riluzole increases the rate of glucose transport in L6 myotubes and NSC-34 motor neuron-like cells via AMPK pathway activation. Amyotroph Lateral Scler Frontotemporal Degener 2013; 14:434-43. [DOI: 10.3109/21678421.2013.808226] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Zhou J, Keenan MJ, Fernandez-Kim SO, Pistell PJ, Ingram DK, Li B, Raggio AM, Shen L, Zhang H, McCutcheon KL, Tulley RT, Blackman MR, Keller JN, Martin RJ. Dietary resistant starch improves selected brain and behavioral functions in adult and aged rodents. Mol Nutr Food Res 2013; 57:2071-4. [PMID: 23818307 DOI: 10.1002/mnfr.201300135] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 04/09/2013] [Accepted: 04/10/2013] [Indexed: 11/12/2022]
Abstract
Resistant starch (RS) is a dietary fiber that exerts multiple beneficial effects. The current study explored the effects of dietary RS on selected brain and behavioral functions in adult and aged rodents. Because glucokinase (GK) expression in hypothalamic arcuate nucleus and area postrema of the brainstem is important for brain glucose sensing, GK mRNA was measured by brain nuclei microdissection and PCR. Adult RS-fed rats had a higher GK mRNA than controls in both brain nuclei, an indicator of improved brain glucose sensing. Next, we tested whether dietary RS improve selected behaviors in aged mice. RS-fed aged mice exhibited (i) an increased eating responses to fasting, a behavioral indicator of improvement in aged brain glucose sensing; (ii) a longer latency to fall from an accelerating rotarod, a behavioral indicator of improved motor coordination; and (iii) a higher serum active glucagon-like peptide-1 (GLP-1). Then, GLP-1 receptor null (GLP-1RKO) mice were used to test the role of GLP-1 in brain glucose sensing, and they exhibited impaired eating responses to fasting. We conclude that in rodents (i) dietary RS improves two important indicators of brain function: glucose sensing and motor coordination, and (ii) GLP-1 is important in the optimal feeding response to a fast.
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Affiliation(s)
- June Zhou
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA, USA; Research Service, Veterans Affairs Medical Center, Washington, DC, USA
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15
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Burmeister MA, Ayala J, Drucker DJ, Ayala JE. Central glucagon-like peptide 1 receptor-induced anorexia requires glucose metabolism-mediated suppression of AMPK and is impaired by central fructose. Am J Physiol Endocrinol Metab 2013; 304:E677-85. [PMID: 23341495 DOI: 10.1152/ajpendo.00446.2012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) suppresses food intake via activation of a central (i.e., brain) GLP-1 receptor (GLP-1R). Central AMP-activated protein kinase (AMPK) is a nutrient-sensitive regulator of food intake that is inhibited by anorectic signals. The anorectic effect elicited by hindbrain GLP-1R activation is attenuated by the AMPK stimulator AICAR. This suggests that central GLP-1R activation suppresses food intake via inhibition of central AMPK. The present studies examined the mechanism(s) by which central GLP-1R activation inhibits AMPK. Supporting previous findings, AICAR attenuated the anorectic effect elicited by intracerebroventricular (icv) administration of the GLP-1R agonist exendin-4 (Ex-4). We demonstrate that Ex-4 stimulates glycolysis and suppresses AMPK phosphorylation in a glucose-dependent manner in hypothalamic GT1-7 cells. This suggests that inhibition of AMPK and food intake by Ex-4 requires central glucose metabolism. Supporting this, the glycolytic inhibitor 2-deoxyglucose (2-DG) attenuated the anorectic effect of Ex-4. However, icv glucose did not enhance the suppression of food intake by Ex-4. AICAR had no effect on Ex-4-mediated reduction in locomotor activity. We also tested whether other carbohydrates affect the anorectic response to Ex-4. Intracerebroventricular pretreatment with the sucrose metabolite fructose, an AMPK activator, attenuated the anorectic effect of Ex-4. This potentially explains the increased food intake observed in sucrose-fed mice. In summary, we propose a model whereby activation of the central GLP-1R reduces food intake via glucose metabolism-dependent inhibition of central AMPK. We also suggest that fructose stimulates food intake by impairing central GLP-1R action. This has significant implications given the correlation between sugar consumption and obesity.
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Affiliation(s)
- Melissa A Burmeister
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute at Lake Nona, Orlando, FL 32827, USA
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16
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Duarte AI, Candeias E, Correia SC, Santos RX, Carvalho C, Cardoso S, Plácido A, Santos MS, Oliveira CR, Moreira PI. Crosstalk between diabetes and brain: glucagon-like peptide-1 mimetics as a promising therapy against neurodegeneration. Biochim Biophys Acta Mol Basis Dis 2013; 1832:527-41. [PMID: 23314196 DOI: 10.1016/j.bbadis.2013.01.008] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/18/2012] [Accepted: 01/06/2013] [Indexed: 12/14/2022]
Abstract
According to World Health Organization estimates, type 2 diabetes (T2D) is an epidemic (particularly in under development countries) and a socio-economic challenge. This is even more relevant since increasing evidence points T2D as a risk factor for Alzheimer's disease (AD), supporting the hypothesis that AD is a "type 3 diabetes" or "brain insulin resistant state". Despite the limited knowledge on the molecular mechanisms and the etiological complexity of both pathologies, evidence suggests that neurodegeneration/death underlying cognitive dysfunction (and ultimately dementia) upon long-term T2D may arise from a complex interplay between T2D and brain aging. Additionally, decreased brain insulin levels/signaling and glucose metabolism in both pathologies further suggests that an effective treatment strategy for one disorder may be also beneficial in the other. In this regard, one such promising strategy is a novel successful anti-T2D class of drugs, the glucagon-like peptide-1 (GLP-1) mimetics (e.g. exendin-4 or liraglutide), whose potential neuroprotective effects have been increasingly shown in the last years. In fact, several studies showed that, besides improving peripheral (and probably brain) insulin signaling, GLP-1 analogs minimize cell loss and possibly rescue cognitive decline in models of AD, Parkinson's (PD) or Huntington's disease. Interestingly, exendin-4 is undergoing clinical trials to test its potential as an anti-PD therapy. Herewith, we aim to integrate the available data on the metabolic and neuroprotective effects of GLP-1 mimetics in the central nervous system (CNS) with the complex crosstalk between T2D-AD, as well as their potential therapeutic value against T2D-associated cognitive dysfunction.
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Affiliation(s)
- A I Duarte
- Life Sciences Department, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal.
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17
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Salcedo I, Tweedie D, Li Y, Greig NH. Neuroprotective and neurotrophic actions of glucagon-like peptide-1: an emerging opportunity to treat neurodegenerative and cerebrovascular disorders. Br J Pharmacol 2012; 166:1586-99. [PMID: 22519295 DOI: 10.1111/j.1476-5381.2012.01971.x] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Like type-2 diabetes mellitus (T2DM), neurodegenerative disorders and stroke are an ever increasing, health, social and economic burden for developed Westernized countries. Age is an important risk factor in all of these; due to the rapidly increasing rise in the elderly population T2DM and neurodegenerative disorders, both represent a looming threat to healthcare systems. Whereas several efficacious drugs are currently available to ameliorate T2DM, effective treatments to counteract pathogenic processes of neurodegenerative disorders are lacking and represent a major scientific and pharmaceutical challenge. Epidemiological data indicate an association between T2DM and most major neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. Likewise, there is an association between T2DM and stroke incidence. Studies have revealed that common pathophysiological features, including oxidative stress, insulin resistance, abnormal protein processing and cognitive decline, occur across these. Based on the presence of shared mechanisms and signalling pathways in these seemingly distinct diseases, one could hypothesize that an effective treatment for one disorder could prove beneficial in the others. Glucagon-like peptide-1 (GLP-1)-based anti-diabetic drugs have drawn particular attention as an effective new strategy to not only regulate blood glucose but also to reduce apoptotic cell death of pancreatic beta cells in T2DM. Evidence supports a neurotrophic and neuroprotective role of GLP-1 receptor (R) stimulation in an increasing array of cellular and animal neurodegeneration models as well as in neurogenesis. Herein, we review the physiological role of GLP-1 in the nervous system, focused towards the potential benefit of GLP-1R stimulation as an immediately translatable treatment strategy for acute and chronic neurological disorders.
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Affiliation(s)
- Isidro Salcedo
- Drug Design & Development Section, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
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18
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McGovern SF, Hunter K, Hölscher C. Effects of the glucagon-like polypeptide-1 analogue (Val8)GLP-1 on learning, progenitor cell proliferation and neurogenesis in the C57B/16 mouse brain. Brain Res 2012; 1473:204-13. [DOI: 10.1016/j.brainres.2012.07.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 07/12/2012] [Accepted: 07/16/2012] [Indexed: 12/16/2022]
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19
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Li Y, Chigurupati S, Holloway HW, Mughal M, Tweedie D, Bruestle DA, Mattson MP, Wang Y, Harvey BK, Ray B, Lahiri DK, Greig NH. Exendin-4 ameliorates motor neuron degeneration in cellular and animal models of amyotrophic lateral sclerosis. PLoS One 2012; 7:e32008. [PMID: 22384126 PMCID: PMC3285661 DOI: 10.1371/journal.pone.0032008] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 01/17/2012] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by a progressive loss of lower motor neurons in the spinal cord. The incretin hormone, glucagon-like peptide-1 (GLP-1), facilitates insulin signaling, and the long acting GLP-1 receptor agonist exendin-4 (Ex-4) is currently used as an anti-diabetic drug. GLP-1 receptors are widely expressed in the brain and spinal cord, and our prior studies have shown that Ex-4 is neuroprotective in several neurodegenerative disease rodent models, including stroke, Parkinson's disease and Alzheimer's disease. Here we hypothesized that Ex-4 may provide neuroprotective activity in ALS, and hence characterized Ex-4 actions in both cell culture (NSC-19 neuroblastoma cells) and in vivo (SOD1 G93A mutant mice) models of ALS. Ex-4 proved to be neurotrophic in NSC-19 cells, elevating choline acetyltransferase (ChAT) activity, as well as neuroprotective, protecting cells from hydrogen peroxide-induced oxidative stress and staurosporine-induced apoptosis. Additionally, in both wild-type SOD1 and mutant SOD1 (G37R) stably transfected NSC-19 cell lines, Ex-4 protected against trophic factor withdrawal-induced toxicity. To assess in vivo translation, SOD1 mutant mice were administered vehicle or Ex-4 at 6-weeks of age onwards to end-stage disease via subcutaneous osmotic pump to provide steady-state infusion. ALS mice treated with Ex-4 showed improved glucose tolerance and normalization of behavior, as assessed by running wheel, compared to control ALS mice. Furthermore, Ex-4 treatment attenuated neuronal cell death in the lumbar spinal cord; immunohistochemical analysis demonstrated the rescue of neuronal markers, such as ChAT, associated with motor neurons. Together, our results suggest that GLP-1 receptor agonists warrant further evaluation to assess whether their neuroprotective potential is of therapeutic relevance in ALS.
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Affiliation(s)
- Yazhou Li
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Srinivasulu Chigurupati
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Harold W. Holloway
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Mohamed Mughal
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - David Tweedie
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Daniel A. Bruestle
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Mark P. Mattson
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Yun Wang
- Molecular Neuropsychiatry Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Brandon K. Harvey
- Molecular Neuropsychiatry Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Balmiki Ray
- Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Debomoy K. Lahiri
- Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Nigel H. Greig
- Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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Park JH, Kim SJ, Park SH, Son DG, Bae JH, Kim HK, Han J, Song DK. Glucagon-like peptide-1 enhances glucokinase activity in pancreatic β-cells through the association of Epac2 with Rim2 and Rab3A. Endocrinology 2012; 153:574-82. [PMID: 22147008 DOI: 10.1210/en.2011-0259] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Glucokinase (GK), which phosphorylates D-glucose, is a major glucose sensor in β-cells for glucose-stimulated insulin secretion (GSIS) and is a promising new drug target for type 2 diabetes (T2D). In T2D, pancreatic β-cells exhibit defective glucose sensitivity, which leads to impaired GSIS. Although glucagon-like peptide-1-(7-36)-amide (GLP-1) is known to enhance β-cell glucose sensitivity, the effect of GLP-1 on GK activity is still unknown. The present study demonstrated that GLP-1 pretreatment for 30 min significantly enhanced GK activity in a glucose-dependent manner, with a lower Michaelis-Menten constant (K(m)) but unchanged maximal velocity (V(max)). Thus, GLP-1 acutely enhanced cellular glucose uptake, mitochondrial membrane potential, and cellular ATP levels in response to glucose in rat INS-1 and native β-cells. This effect of GLP-1 occurred via its G protein-coupled receptor pathway in a cAMP-dependent but protein kinase A-independent manner with evidence of exchange protein activated by cAMP (Epac) involvement. Silencing Epac2, interacting molecule of the small G protein Rab3 (Rim2), or Ras-associated protein Rab3A (Rab3A) significantly blocked the effect of GLP-1. These results suggested that GLP-1 can further potentiate GSIS by enhancing GK activity through the signaling of Epac2 to Rim2 and Rab3A, which is the similar pathway for GLP-1 to potentiate Ca(2+)-dependent insulin granule exocytosis. The present finding may also be an important mechanism of GLP-1 for recovery of GSIS in T2D.
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Affiliation(s)
- Jae-Hyung Park
- Department of Physiology, Keimyung University School of Medicine, Daegu 704-701, Korea
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21
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Park JH, Earm YE, Song DK. Cellular glucose availability and glucagon-like peptide-1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:286-92. [PMID: 21907232 DOI: 10.1016/j.pbiomolbio.2011.08.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 08/22/2011] [Accepted: 08/25/2011] [Indexed: 12/25/2022]
Abstract
Glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide (GIP, glucose-dependent insulinotropic polypeptide) are produced in enteroendocrine L-cells and K-cells, respectively. They are known as incretins because they potentiate postprandial insulin secretion. Although unresponsiveness of type 2 diabetes (T2D) patients to GIP has now been reconsidered, GLP-1 mimetics and inhibitors of the GLP-1 degradation enzyme dipeptidyl peptidase (DPP)-4 have now been launched as drugs against T2D. The major roles of GLP-1 in T2D are reduction of appetite, gastric motility, glucagon secretion, enhancement of insulin secretion and β-cell survival. For insulin secretion and peripheral insulin function, GLP-1 and its mimetics sensitise β-cells to glucose; accelerate blood glucose withdrawal, in-cell glucose utilisation and glycogen synthesis in insulin-sensitive tissues; and assist in the function and survival of neurons mainly using glucose as an energy source. Taken together, GLP-1 acts to potentiate glucose availability of various cells or tissues to assist with their essential functions and/or survival. Herein, we review the signalling pathways and clinical relevance of GLP-1 in enhancing cellular glucose availability. On the basis of our recent research results, we also describe a mechanism that regulates GLP-1 for glucokinase activity. Because diabetic tissues including β-cells resist glucose, GLP-1 may be useful for treating T2D.
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Affiliation(s)
- Jae-Hyung Park
- Department of Physiology, Keimyung University School of Medicine, 2800 Dalgubeoldae-Ro, Dalseo-Gu, Daegu 704-701, Republic of Korea
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