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Kanemoto N, Okamoto T, Tanabe K, Shimada T, Minoshima H, Hidoh Y, Aoyama M, Ban T, Kobayashi Y, Ando H, Inoue Y, Itotani M, Sato S. Antidiabetic and cardiovascular beneficial effects of a liver-localized mitochondrial uncoupler. Nat Commun 2019; 10:2172. [PMID: 31092829 PMCID: PMC6520346 DOI: 10.1038/s41467-019-09911-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Accepted: 04/08/2019] [Indexed: 12/11/2022] Open
Abstract
Inducing mitochondrial uncoupling (mUncoupling) is an attractive therapeutic strategy for treating metabolic diseases because it leads to calorie-wasting by reducing the efficiency of oxidative phosphorylation (OXPHOS) in mitochondria. Here we report a safe mUncoupler, OPC-163493, which has unique pharmacokinetic characteristics. OPC-163493 shows a good bioavailability upon oral administration and primarily distributed to specific organs: the liver and kidneys, avoiding systemic toxicities. It exhibits insulin-independent antidiabetic effects in multiple animal models of type I and type II diabetes and antisteatotic effects in fatty liver models. These beneficial effects can be explained by the improvement of glucose metabolism and enhancement of energy expenditure by OPC-163493 in the liver. Moreover, OPC-163493 treatment lowered blood pressure, extended survival, and improved renal function in the rat model of stroke/hypertension, possibly by enhancing NO bioavailability in blood vessels and reducing mitochondrial ROS production. OPC-163493 is a liver-localized/targeted mUncoupler that ameliorates various complications of diabetes.
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Affiliation(s)
- Naohide Kanemoto
- Department of Lead Discovery Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan.
| | - Takashi Okamoto
- Department of Lead Discovery Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Koji Tanabe
- Department of CNS Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Takahiro Shimada
- Department of Drug Metabolism and Pharmacokinetics, Nonclinical Research Center, Tokushima Research Institute, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Hitomi Minoshima
- Pharmaceutical Planning Group, Otsuka Pharmaceutical Co., Ltd., 2-16-4 Shinagawa Grand Central Tower Minatominami Minato-ku, Tokyo, 108-8242, Japan
| | - Yuya Hidoh
- Department of Drug Metabolism and Pharmacokinetics, Nonclinical Research Center, Tokushima Research Institute, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Masashi Aoyama
- Biology and Translational Research Unit, Department of Medical Innovations, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Takashi Ban
- Department of Renal and Cardiovascular Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Yusuke Kobayashi
- Department of Lead Discovery Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Hikaru Ando
- Department of Lead Discovery Research, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Yuki Inoue
- Department of Drug Safety Research, Nonclinical Research Center, Tokushima Research Institute, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
| | - Motohiro Itotani
- Quality Assurance Section (Tokushima Wajiki Factory), Quality Assurance Department, Headquarters for Product Safety and Quality Assurance, Otsuka Pharmaceutical Co., Ltd., 306-2 Otsubo Koniu aza Naka-cho Naka-gun, Tokushima, 771-5209, Japan
| | - Seiji Sato
- Medicinal Chemistry Research Laboratories, New Drug Research Division, Otsuka Pharmaceutical Co., Ltd., 463-10 Kagasuno Kawauchi-cho, Tokushima, 771-0192, Japan
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Kowalski GM, Bruce CR. The regulation of glucose metabolism: implications and considerations for the assessment of glucose homeostasis in rodents. Am J Physiol Endocrinol Metab 2014; 307:E859-71. [PMID: 25205823 DOI: 10.1152/ajpendo.00165.2014] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The incidence of insulin resistance and type 2 diabetes (T2D) is increasing at alarming rates. In the quest to understand the underlying causes of and to identify novel therapeutic targets to treat T2D, scientists have become increasingly reliant on the use of rodent models. Here, we provide a discussion on the regulation of rodent glucose metabolism, highlighting key differences and similarities that exist between rodents and humans. In addition, some of the issues and considerations associated with assessing glucose homeostasis and insulin action are outlined. We also discuss the role of the liver vs. skeletal muscle in regulating whole body glucose metabolism in rodents, emphasizing the importance of defective hepatic glucose metabolism in the development of impaired glucose tolerance, insulin resistance, and T2D.
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Affiliation(s)
- Greg M Kowalski
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia
| | - Clinton R Bruce
- Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia
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3
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Baker DJ, Atkinson AM, Wilkinson GP, Coope GJ, Charles AD, Leighton B. Characterization of the heterozygous glucokinase knockout mouse as a translational disease model for glucose control in type 2 diabetes. Br J Pharmacol 2014; 171:1629-41. [PMID: 24772483 DOI: 10.1111/bph.12498] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE The global heterozygous glucokinase (GK) knockout (gk(wt/del)) male mouse, fed on a high-fat (60% by energy) diet, has provided a robust and reproducible model of hyperglycaemia. This model could be highly relevant to some facets of human type 2 diabetes (T2D). We aimed to investigate the ability of standard therapeutic agents to lower blood glucose at translational doses, and to explore the glucose-lowering potential of novel glucokinase activators (GKAs) in this model. EXPERIMENTAL APPROACH We measured the ability of insulin, metformin, glipizide, exendin-4 and sitagliptin, after acute or repeat dose administration, to lower free-feeding glucose levels in gk(wt/del) mice. Further, we measured the ability of novel GKAs, GKA23, GKA71 and AZD6370 to control glucose either alone or in combination with some standard agents. KEY RESULTS A single dose of insulin (1 unit·kg(-1)), metformin (150, 300 mg·kg(-1)), glipizide (0.1, 0.3 mg·kg(-1)), exendin-4 (2, 20 μg·kg(-1)) and GKAs reduced free-feeding glucose levels. Sitagliptin (10 mg·kg(-1)), metformin (300 mg·kg(-1)) and AZD6370 (30, 400 mg·kg(-1)) reduced glucose excursions on repeat dosing. At a supra-therapeutic dose (400 mg·kg(-1)), AZD6370 also lowered basal levels of glucose without inducing hypoglycaemia. CONCLUSION AND IMPLICATIONS Standard glucose-lowering therapeutic agents demonstrated significant acute glucose lowering in male gk(wt/del) mice at doses corresponding to therapeutic free drug levels in man, suggesting the potential of these mice as a translatable model of human T2D. Novel GKAs also lowered glucose in this mouse model.
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Giménez-Cassina A, Garcia-Haro L, Choi CS, Osundiji MA, Lane EA, Huang H, Yildirim MA, Szlyk B, Fisher JK, Polak K, Patton E, Wiwczar J, Godes M, Lee DH, Robertson K, Kim S, Kulkarni A, Distefano A, Samuel V, Cline G, Kim YB, Shulman GI, Danial NN. Regulation of hepatic energy metabolism and gluconeogenesis by BAD. Cell Metab 2014; 19:272-84. [PMID: 24506868 PMCID: PMC3971904 DOI: 10.1016/j.cmet.2013.12.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 10/07/2013] [Accepted: 12/05/2013] [Indexed: 01/01/2023]
Abstract
The homeostatic balance of hepatic glucose utilization, storage, and production is exquisitely controlled by hormonal signals and hepatic carbon metabolism during fed and fasted states. How the liver senses extracellular glucose to cue glucose utilization versus production is not fully understood. We show that the physiologic balance of hepatic glycolysis and gluconeogenesis is regulated by Bcl-2-associated agonist of cell death (BAD), a protein with roles in apoptosis and metabolism. BAD deficiency reprograms hepatic substrate and energy metabolism toward diminished glycolysis, excess fatty acid oxidation, and exaggerated glucose production that escapes suppression by insulin. Genetic and biochemical evidence suggests that BAD's suppression of gluconeogenesis is actuated by phosphorylation of its BCL-2 homology (BH)-3 domain and subsequent activation of glucokinase. The physiologic relevance of these findings is evident from the ability of a BAD phosphomimic variant to counteract unrestrained gluconeogenesis and improve glycemia in leptin-resistant and high-fat diet models of diabetes and insulin resistance.
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Affiliation(s)
- Alfredo Giménez-Cassina
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Luisa Garcia-Haro
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Cheol Soo Choi
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA; Division of Endocrinology, Lee Gil Ya Cancer and Diabetes Institute, Gil Medical Center, Gachon University, Incheon 405-760, Korea
| | - Mayowa A Osundiji
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Elizabeth A Lane
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Hu Huang
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
| | - Muhammed A Yildirim
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Benjamin Szlyk
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Jill K Fisher
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Klaudia Polak
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Elaura Patton
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Jessica Wiwczar
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Marina Godes
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Dae Ho Lee
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
| | - Kirsten Robertson
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Sheene Kim
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Ameya Kulkarni
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Alberto Distefano
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Varman Samuel
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Gary Cline
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Young-Bum Kim
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
| | - Gerald I Shulman
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Nika N Danial
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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Cao H, Sekiya M, Ertunc ME, Burak MF, Mayers JR, White A, Inouye K, Rickey LM, Ercal BC, Furuhashi M, Tuncman G, Hotamisligil GS. Adipocyte lipid chaperone AP2 is a secreted adipokine regulating hepatic glucose production. Cell Metab 2013; 17:768-78. [PMID: 23663740 PMCID: PMC3755450 DOI: 10.1016/j.cmet.2013.04.012] [Citation(s) in RCA: 192] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 03/19/2013] [Accepted: 04/17/2013] [Indexed: 11/30/2022]
Abstract
Proper control of hepatic glucose production is central to whole-body glucose homeostasis, and its disruption plays a major role in diabetes. Here, we demonstrate that although established as an intracellular lipid chaperone, aP2 is in fact actively secreted from adipocytes to control liver glucose metabolism. Secretion of aP2 from adipocytes is regulated by fasting- and lipolysis-related signals, and circulating aP2 levels are markedly elevated in mouse and human obesity. Recombinant aP2 stimulates glucose production and gluconeogenic activity in primary hepatocytes in vitro and in lean mice in vivo. In contrast, neutralization of secreted aP2 reduces glucose production and corrects the diabetic phenotype of obese mice. Hyperinsulinemic-euglycemic and pancreatic clamp studies upon aP2 administration or neutralization demonstrated actions of aP2 in liver. We conclude that aP2 is an adipokine linking adipocytes to hepatic glucose production and that neutralizing secreted aP2 may represent an effective therapeutic strategy against diabetes.
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Affiliation(s)
- Haiming Cao
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115, USA
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Kehlenbrink S, Koppaka S, Martin M, Relwani R, Cui MH, Hwang JH, Li Y, Basu R, Hawkins M, Kishore P. Elevated NEFA levels impair glucose effectiveness by increasing net hepatic glycogenolysis. Diabetologia 2012; 55:3021-8. [PMID: 22847060 PMCID: PMC6317075 DOI: 10.1007/s00125-012-2662-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 06/29/2012] [Indexed: 01/13/2023]
Abstract
AIMS/HYPOTHESIS Acute hyperglycaemia rapidly suppresses endogenous glucose production (EGP) in non-diabetic individuals, mainly by inhibiting glycogenolysis. Loss of this 'glucose effectiveness' contributes to fasting hyperglycaemia in type 2 diabetes. Elevated NEFA levels characteristic of type 2 diabetes impair glucose effectiveness, although the mechanism is not fully understood. Therefore we examined the impact of increasing NEFA levels on the ability of hyperglycaemia to regulate pathways of EGP. METHODS We performed 4 h 'pancreatic clamp' studies (somatostatin; basal glucagon/growth hormone/insulin) in seven non-diabetic individuals. Glucose fluxes (D-[6,6-(2)H(2)]glucose) and hepatic glycogen concentrations ((13)C magnetic resonance spectroscopy) were quantified under three conditions: euglycaemia, hyperglycaemia and hyperglycaemia with elevated NEFA (HY-NEFA). RESULTS EGP was suppressed by hyperglycaemia, but not by HY-NEFA. Hepatic glycogen concentration decreased ~14% with prolonged fasting during euglycaemia and increased by ~12% with hyperglycaemia. In contrast, raising NEFA levels in HY-NEFA caused a substantial ~23% reduction in hepatic glycogen concentration. Moreover, rates of gluconeogenesis were decreased with hyperglycaemia, but increased with HY-NEFA. CONCLUSIONS/INTERPRETATION Increased NEFA appear to profoundly blunt the ability of hyperglycaemia to inhibit net glycogenolysis under basal hormonal conditions.
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Affiliation(s)
- S Kehlenbrink
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Cummins TD, Barati MT, Coventry SC, Salyer SA, Klein JB, Powell DW. Quantitative mass spectrometry of diabetic kidney tubules identifies GRAP as a novel regulator of TGF-beta signaling. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:653-61. [PMID: 19836472 DOI: 10.1016/j.bbapap.2009.09.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 09/22/2009] [Accepted: 09/29/2009] [Indexed: 01/13/2023]
Abstract
The aim of this study was to define novel mediators of tubule injury in diabetic kidney disease. For this, we used state-of-the-art proteomic methods combined with a label-free quantitative strategy to define protein expression differences in kidney tubules from transgenic OVE26 type 1 diabetic and control mice. The analysis was performed with diabetic samples that displayed a pro-fibrotic phenotype. We have identified 476 differentially expressed proteins. Bioinformatic analysis indicated several clusters of regulated proteins in relevant functional groups such as TGF-beta signaling, tight junction maintenance, oxidative stress, and glucose metabolism. Mass spectrometry detected expression changes of four physiologically relevant proteins were confirmed by immunoblot analysis. Of these, the Grb2-related adaptor protein (GRAP) was up-regulated in kidney tubules from diabetic mice and fibrotic kidneys from diabetic patients, and subsequently confirmed as a novel component of TGF-beta signaling in cultured human renal tubule cells. Thus, indicating a potential novel role for GRAP in TGF-beta-induced tubule injury in diabetic kidney disease. Although we targeted a specific disease, this approach offers a robust, high-sensitivity methodology that can be applied to the discovery of novel mediators for any experimental or disease condition.
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Affiliation(s)
- Timothy D Cummins
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY, USA
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Kehlenbrink S, Tonelli J, Koppaka S, Chandramouli V, Hawkins M, Kishore P. Inhibiting gluconeogenesis prevents fatty acid-induced increases in endogenous glucose production. Am J Physiol Endocrinol Metab 2009; 297:E165-73. [PMID: 19417129 PMCID: PMC2711655 DOI: 10.1152/ajpendo.00001.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucose effectiveness, the ability of glucose per se to suppress endogenous glucose production (EGP), is lost in type 2 diabetes mellitus (T2DM). Free fatty acids (FFA) may contribute to this loss of glucose effectiveness in T2DM by increasing gluconeogenesis (GNG) and impairing the response to hyperglycemia. Thus, we first examined the effects of increasing plasma FFA levels for 3, 6, or 16 h on glucose effectiveness in nondiabetic subjects. Under fixed hormonal conditions, hyperglycemia suppressed EGP by 61% in nondiabetic subjects. Raising FFA levels with Liposyn infusion for > or =3 h reduced the normal suppressive effect of glucose by one-half. Second, we hypothesized that inhibiting GNG would prevent the negative impact of FFA on glucose effectiveness. Raising plasma FFA levels increased gluconeogenesis by approximately 52% during euglycemia and blunted the suppression of EGP by hyperglycemia. Infusion of ethanol rapidly inhibited GNG and doubled the suppression of EGP by hyperglycemia, thereby restoring glucose effectiveness. In conclusion, elevated FFA levels rapidly increased GNG and impaired hepatic glucose effectiveness in nondiabetic subjects. Inhibiting GNG could have therapeutic potential in restoring the regulation of glucose production in type 2 diabetes mellitus.
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Affiliation(s)
- Sylvia Kehlenbrink
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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Abstract
The glucokinase (GCK) gene was one of the first candidate genes to be identified as a human “diabetes gene". Subsequently, important advances were made in understanding the impact of GCK in the regulation of glucose metabolism. Structure elucidation by crystallography provided insight into the kinetic properties of GCK. Protein interaction partners of GCK were discovered. Gene expression studies revealed new facets of the tissue distribution of GCK, including in the brain, and its regulation by insulin in the liver. Metabolic control analysis coupled to gene overexpression and knockout experiments highlighted the unique impact of GCK as a regulator of glucose metabolism. Human GCK mutants were studied biochemically to understand disease mechanisms. Drug development programs identified small molecule activators of GCK as potential antidiabetics. These advances are summarized here, with the aim of offering an integrated view of the role of GCK in the molecular physiology and medicine of glucose homeostasis.
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Affiliation(s)
- P B Iynedjian
- Department of Cell Physiolgy and Metabolism, University of Geneva School of Medicine, CMU 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland.
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Kaiser JP, Beier JI, Zhang J, David Hoetker J, von Montfort C, Guo L, Zheng Y, Monia BP, Bhatnagar A, Arteel GE. PKCepsilon plays a causal role in acute ethanol-induced steatosis. Arch Biochem Biophys 2008; 482:104-11. [PMID: 19022218 DOI: 10.1016/j.abb.2008.11.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 10/27/2008] [Accepted: 11/03/2008] [Indexed: 12/17/2022]
Abstract
Steatosis is a critical stage in the pathology of alcoholic liver disease (ALD), and preventing steatosis could protect against later stages of ALD. PKCepsilon has been shown to contribute to hepatic steatosis in experimental non-alcoholic fatty liver disease (NAFLD); however, the role of PKCepsilon in ethanol-induced steatosis has not been determined. The purpose of this study was to therefore test the hypothesis that PKCepsilon contributes to ethanol-induced steatosis. Accordingly, the effect of acute ethanol on indices of hepatic steatosis and insulin signaling were determined in PKCepsilon knockout mice and in wild-type mice that received an anti-sense oligonucleotide (ASO) to knockdown PKCepsilon expression. Acute ethanol (6g/kg i.g.) caused a robust increase in hepatic non-esterified free fatty acids (NEFA), which peaked 1h after ethanol exposure. This increase in NEFA was followed by elevated diacylglycerols (DAG), as well as by the concomitant activation of PKCepsilon. Acute ethanol also changed the expression of insulin-responsive genes (i.e. increased G6Pase, downregulated GK), in a pattern indicative of impaired insulin signaling. Acute ethanol exposure subsequently caused a robust increase in hepatic triglycerides. The accumulation of triglycerides caused by ethanol was blunted in ASO-treated or in PKCepsilon(-/-) mice. Taken together, these data suggest that the increase in NEFA caused by hepatic ethanol metabolism leads to an increase in DAG production via the triacylglycerol pathway. DAG then subsequently activates PKCepsilon, which then exacerbates hepatic lipid accumulation by inducing insulin resistance. These data also suggest that PKCepsilon plays a causal role in at least the early phases of ethanol-induced liver injury.
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Affiliation(s)
- J Phillip Kaiser
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY 40292, USA
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Johnson D, Shepherd RM, Gill D, Gorman T, Smith DM, Dunne MJ. Glucose-dependent modulation of insulin secretion and intracellular calcium ions by GKA50, a glucokinase activator. Diabetes 2007; 56:1694-702. [PMID: 17360975 DOI: 10.2337/db07-0026] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Because glucokinase is a metabolic sensor involved in the regulated release of insulin, we have investigated the acute actions of novel glucokinase activator compound 50 (GKA50) on islet function. Insulin secretion was determined by enzyme-linked immunosorbent assay, and microfluorimetry with fura-2 was used to examine intracellular Ca(2+) homeostasis ([Ca(2+)](i)) in isolated mouse, rat, and human islets of Langerhans and in the MIN6 insulin-secreting mouse cell line. In rodent islets and MIN6 cells, 1 micromol/l GKA50 was found to stimulate insulin secretion and raise [Ca(2+)](i) in the presence of glucose (2-10 mmol/l). Similar effects on insulin release were also seen in isolated human islets. GKA50 (1 micromol/l) caused a leftward shift in the glucose-concentration response profiles, and the half-maximal effective concentration (EC(50)) values for glucose were shifted by 3 mmol/l in rat islets and approximately 10 mmol/l in MIN6 cells. There was no significant effect of GKA50 on the maximal rates of glucose-stimulated insulin secretion. In the absence of glucose, GKA50 failed to elevate [Ca(2+)](i) (1 micromol/l GKA50) or to stimulate insulin release (30 nmol/l-10 micromol/l GKA50). At 5 mmol/l glucose, the EC(50) for GKA50 in MIN6 cells was approximately 0.3 micromol/l. Inhibition of glucokinase with mannoheptulose or 5-thioglucose selectively inhibited the action of GKA50 on insulin release but not the effects of tolbutamide. Similarly, 3-methoxyglucose prevented GKA50-induced rises in [Ca(2+)](i) but not the actions of tolbutamide. Finally, the ATP-sensitive K(+) channel agonist diazoxide (200 micromol/l) inhibited GKA50-induced insulin release and its elevation of [Ca(2+)](i.) We show that GKA50 is a glucose-like activator of beta-cell metabolism in rodent and human islets and a Ca(2+)-dependent modulator of insulin secretion.
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Affiliation(s)
- Daniel Johnson
- Faculty of Life Sciences, Core Technology Facility, University of Manchester, Manchester, UK
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Qu S, Altomonte J, Perdomo G, He J, Fan Y, Kamagate A, Meseck M, Dong HH. Aberrant Forkhead box O1 function is associated with impaired hepatic metabolism. Endocrinology 2006; 147:5641-52. [PMID: 16997836 PMCID: PMC2665253 DOI: 10.1210/en.2006-0541] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
FoxO1 plays an important role in mediating the effect of insulin on hepatic metabolism. Increased FoxO1 activity is associated with reduced ability of insulin to regulate hepatic glucose production. However, the underlying mechanism and physiology remain unknown. We studied the effect of FoxO1 on the ability of insulin to regulate hepatic metabolism in normal vs. insulin-resistant liver under fed and fasting conditions. FoxO1 gain of function, as a result of adenovirus-mediated or transgenic expression, augmented hepatic gluconeogenesis, accompanied by decreased glycogen content and increased fat deposition in liver. Mice with excessive FoxO1 activity exhibited impaired glucose tolerance. Conversely, FoxO1 loss of function, caused by hepatic production of its dominant-negative variant, suppressed hepatic gluconeogenesis, resulting in enhanced glucose disposal and improved insulin sensitivity in db/db mice. FoxO1 expression becomes deregulated, culminating in increased nuclear localization and accounting for its increased transcription activity in livers of both high fat-induced obese mice and diabetic db/db mice. Increased FoxO1 activity resulted in up-regulation of hepatic peroxisome proliferator-activated receptor-gamma coactivator-1beta, fatty acid synthase, and acetyl CoA carboxylase expression, accounting for increased hepatic fat infiltration. These data indicate that hepatic FoxO1 deregulation impairs the ability of insulin to regulate hepatic metabolism, contributing to the development of hepatic steatosis and abnormal metabolism in diabetes.
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Affiliation(s)
- Shen Qu
- Rangos Research Center, Children's Hospital of Pittsburgh, Department of Pediatrics, University of Pittsburgh School of Medicine, 3460 5th Avenue, Room 5140, Pittsburgh, Pennsylvania 15213, USA
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Okamoto H, Obici S, Accili D, Rossetti L. Restoration of liver insulin signaling in Insr knockout mice fails to normalize hepatic insulin action. J Clin Invest 2005; 115:1314-22. [PMID: 15864351 PMCID: PMC1087162 DOI: 10.1172/jci23096] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Accepted: 02/07/2005] [Indexed: 12/22/2022] Open
Abstract
Partial restoration of insulin receptor Insr expression in brain, liver, and pancreatic beta cells is sufficient for rescuing Insr knockout mice from neonatal death, preventing diabetes ketoacidosis, and normalizing life span and reproductive function. However, the transgenically rescued mice (referred to as L1) have marked hyperinsulinemia, and approximately 30% develop late-onset type 2 diabetes. Analyses of protein expression indicated that L1 mice had modestly reduced Insr content but normal insulin-stimulated Akt phosphorylation in the liver. Conversely, L1 mice had a near complete ablation of Insr protein product in the arcuate and paraventricular nuclei of the hypothalamus, which was associated with a failure to undergo insulin-dependent Akt phosphorylation in the hypothalamus. To test whether reconstitution of insulin signaling in the liver is sufficient for restoring in vivo hepatic insulin action, we performed euglycemic hyperinsulinemic clamp studies in conscious L1 and WT mice. During the clamp, L1 mice required an approximately 50% lower rate of glucose infusion than did WT controls, while the rate of glucose disappearance was not significantly altered. Conversely, the rate of glucose production was increased approximately 2-fold in L1 mice. Thus, restoration of hepatic insulin signaling in Insr knockout mice fails to normalize the in vivo response to insulin.
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Affiliation(s)
- Haruka Okamoto
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA
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Song K, Zhang X, Zhao C, Ang NT, Ma ZA. Inhibition of Ca2+-independent phospholipase A2 results in insufficient insulin secretion and impaired glucose tolerance. Mol Endocrinol 2004; 19:504-15. [PMID: 15471944 PMCID: PMC2917620 DOI: 10.1210/me.2004-0169] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Islet Ca2+-independent phospholipase A2 (iPLA2) is postulated to mediate insulin secretion by releasing arachidonic acid in response to insulin secretagogues. However, the significance of iPLA2 signaling in insulin secretion in vivo remains unexplored. Here we investigated the physiological role of iPLA2 in beta-cell lines, isolated islets, and mice. We showed that small interfering RNA-specific silencing of iPLA2 expression in INS-1 cells significantly reduced insulin-secretory responses of INS-1 cells to glucose. Immunohistochemical analysis revealed that mouse islet cells expressed significantly higher levels of iPLA2 than pancreatic exocrine acinar cells. Bromoenol lactone (BEL), a selective inhibitor of iPLA2, inhibited glucose-stimulated insulin secretion from isolated mouse islets; this inhibition was overcome by exogenous arachidonic acid. We also showed that iv BEL administration to mice resulted in sustained hyperglycemia and reduced insulin levels during glucose tolerance tests. Clamp experiments demonstrated that the impaired glucose tolerance was due to insufficient insulin secretion rather than decreased insulin sensitivity. Short-term administration of BEL to mice had no effect on fasting glucose levels and caused no apparent pathological changes of islets in pancreas sections. These results unambiguously demonstrate that iPLA2 signaling plays an important role in glucose-stimulated insulin secretion under physiological conditions.
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Affiliation(s)
- Keying Song
- Division of Experimental Diabetes and Aging, Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, New York, New York 10029, USA
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Peterside IE, Selak MA, Simmons RA. Impaired oxidative phosphorylation in hepatic mitochondria in growth-retarded rats. Am J Physiol Endocrinol Metab 2003; 285:E1258-66. [PMID: 14607783 DOI: 10.1152/ajpendo.00437.2002] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intrauterine growth retardation (IUGR) has been linked to the development of type 2 diabetes in adulthood. We have developed an IUGR model in the rat whereby the animals develop diabetes between 3 and 6 mo of age that is associated with insulin resistance. Alterations in hepatic glucose metabolism are known to contribute to the hyperglycemia of diabetes; however, the mechanisms underlying this phenomenon have not been fully explained. To address this issue, intact liver mitochondria were isolated from IUGR and control offspring at different ages to examine the nature and time course of possible defects in oxidative metabolism. Phosphoenolpyruvate carboxykinase (PEPCK) expression was also measured in livers of IUGR and control offspring. Rates of ADP-stimulated (state 3) oxygen consumption were increased for succinate in the fetus and for alpha-ketoglutarate and glutamate at day 1, reflecting possible compensatory metabolic adaptations to acute hypoxia and acidosis in IUGR rats. By day 14, oxidation of glutamate and alpha-ketoglutarate had returned to normal, and by day 28, oxidation rates of pyruvate, glutamate, succinate, and alpha-ketoglutarate were significantly lower than those of controls. Rotenone-sensitive NADH-O2 oxidoreductase activity was similar in control and IUGR mitochondria at all ages, showing that the defect responsible for decreased pyruvate, glutamate, and alpha-ketoglutarate oxidation in IUGR liver precedes the electron transport chain and involves pyruvate and alpha-ketoglutarate dehydrogenases. Increased levels of manganese superoxide dismutase suggest that an antioxidant response has been mounted, and hydroxynonenal (HNE) modification of pyruvate dehydrogenase E2-(catalytic) and E3-binding protein subunits suggests that HNE-induced inactivation of this key enzyme may play a role in the mechanism of injury. The level of PEPCK mRNA was increased 250% in day 28 IUGR liver, indicating altered gene expression of the gluconeogenic enzyme that precedes overt hyperglycemia. These results indicate that uteroplacental insufficiency impairs mitochondrial oxidative phosphorylation in the liver and that this derangement predisposes the IUGR rat to increased hepatic glucose production by suppressing pyruvate oxidation and increasing gluconeogenesis.
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Affiliation(s)
- Iyalla E Peterside
- Department of Pediatrics, Children's Hospital and University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Hawkins M, Tonelli J, Kishore P, Stein D, Ragucci E, Gitig A, Reddy K. Contribution of elevated free fatty acid levels to the lack of glucose effectiveness in type 2 diabetes. Diabetes 2003; 52:2748-58. [PMID: 14578293 DOI: 10.2337/diabetes.52.11.2748] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Increased circulating free fatty acids (FFAs) inhibit both hepatic and peripheral insulin action. Because the loss of effectiveness of glucose to suppress endogenous glucose production and stimulate glucose uptake contributes importantly to fasting hyperglycemia in type 2 diabetes, we examined whether the approximate twofold elevations in FFA characteristic of poorly controlled type 2 diabetes contribute to this defect. Glucose levels were raised from 5 to 10 mmol/l while maintaining fixed hormonal conditions by infusing somatostatin with basal insulin, glucagon, and growth hormone. Each individual was studied at two FFA levels: with (NA+) and without (NA-) infusion of nicotinic acid in nine individuals with poorly controlled type 2 diabetes (HbA(1c) = 10.1 +/- 0.7%) and with (LIP+) and without (LIP-) infusion of lipid emulsion in nine nondiabetic individuals. Elevating FFA to approximately 500 micro mol/l blunted the ability of glucose to suppress endogenous glucose production (LIP- = -48% vs. LIP+ = -28%; P < 0.01) and increased glucose uptake (LIP- = 97% vs. LIP+ = 51%; P < 0.01) in nondiabetic individuals. Raising FFA also blunted the endogenous glucose production response in 10 individuals with type 2 diabetes in good control (HbA(1c) = 6.3 +/- 0.3%). Conversely, normalizing FFA nearly restored the endogenous glucose production (NA- = -7% vs. NA+ = -41%; P < 0.001) and glucose uptake (NA- = 26% vs. NA+ = 64%; P < 0.001) responses to hyperglycemia in individuals with poorly controlled type 2 diabetes. Thus, increased FFA levels contribute substantially to the loss of glucose effectiveness in poorly controlled type 2 diabetes.
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Affiliation(s)
- Meredith Hawkins
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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Murphy HC, Regan G, Bogdarina IG, Clark AJL, Iles RA, Cohen RD, Hitman GA, Berry CL, Coade Z, Petry CJ, Burns SP. Fetal programming of perivenous glucose uptake reveals a regulatory mechanism governing hepatic glucose output during refeeding. Diabetes 2003; 52:1326-32. [PMID: 12765940 DOI: 10.2337/diabetes.52.6.1326] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Increased hepatic gluconeogenesis maintains glycemia during fasting and has been considered responsible for elevated hepatic glucose output in type 2 diabetes. Glucose derived periportally via gluconeogenesis is partially taken up perivenously in perfused liver but not in adult rats whose mothers were protein-restricted during gestation (MLP rats)-an environmental model of fetal programming of adult glucose intolerance exhibiting diminished perivenous glucokinase (GK) activity. We now show that perivenous glucose uptake rises with increasing glucose concentration (0-8 mmol/l) in control but not MLP liver, indicating that GK is flux-generating. The data demonstrate that acute control of hepatic glucose output is principally achieved by increasing perivenous glucose uptake, with rising glucose concentration during refeeding, rather than by downregulation of gluconeogenesis, which occurs in different hepatocytes. Consistent with these observations, glycogen synthesis in vivo commenced in the perivenous cells during refeeding, MLP livers accumulating less glycogen than controls. GK gene transcription was unchanged in MLP liver, the data supporting a recently proposed posttranscriptional model of GK regulation involving nuclear-cytoplasmic transport. The results are pertinent to impaired regulation of hepatic glucose output in type 2 diabetes, which could arise from diminished GK-mediated glucose uptake rather than increased gluconeogenesis.
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Affiliation(s)
- Helena C Murphy
- Department of Diabetes and Metabolic Medicine, St. Bart's and the London School of Medicine and Dentistry, Queen Mary University of London, Mile End, London E1 4NS, U.K
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18
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Hawkins M, Gabriely I, Wozniak R, Reddy K, Rossetti L, Shamoon H. Glycemic control determines hepatic and peripheral glucose effectiveness in type 2 diabetic subjects. Diabetes 2002; 51:2179-89. [PMID: 12086948 DOI: 10.2337/diabetes.51.7.2179] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucose effectiveness is impaired in type 2 diabetes. We hypothesize that chronic hyperglycemia and hyperlipidemia contribute importantly to this defect. To test this hypothesis, we compared the effect of acute hyperglycemia on glucose turnover in type 2 diabetic subjects in good control (GC) (n = 14, age 51.7 +/- 3.7 years, BMI 28.4 +/- 1.0 kg/ m(2), HbA(1c) 5.9 +/- 0.2%) and poor control (PC) (n = 10, age 50.0 +/- 2.5 years, BMI 27.9 +/- 1.5 kg/m(2), HbA(1c) 9.9 +/- 0.6%) with age- and weight-matched nondiabetic subjects (ND) (n = 11, age 47.0 +/- 4.4 years, BMI 28.5 +/- 1.0 kg/m(2), HbA(1c) 5.1 +/- 0.2%). Fixed hormonal conditions were attained by infusing somatostatin for 6 h with replacement of basal insulin, glucagon, and growth hormone. Glucose fluxes ([3-(3)H]glucose) were compared during euglycemic (5 mmol/l, t = 180-240 min) and hyperglycemic (Hy) (10 mmol/l, t = 300-360 min, variable glucose infusion) clamp intervals. Acute hyperglycemia suppressed hepatic glucose production (GP) by 43% and increased peripheral glucose uptake (GU) by 86% in the ND subjects. Conversely, GP failed to suppress (-7%) and GU was suboptimally increased (+34%) in response to Hy in the PC group. However, optimal glycemic control was associated with normal glucose effectiveness in GC subjects (GP -38%, GU +72%; P > 0.05 for GC vs. ND). To determine whether short-term correction of hyperglycemia and/or hyperlipidemia is sufficient to reverse the impairment in glucose effectiveness, five PC subjects were restudied after 72 h of normoglycemia ( approximately 100 mg/dl; variable insulin infusions). These subjects regained normal effectiveness of glucose to suppress GP and stimulate GU and in response to Hy (GP -47%, GU + 71%; P > 0.05 vs. baseline studies). Thus, chronic hyperglycemia and/or hyperlipidemia contribute to impaired effectiveness of glucose in regulating glucose fluxes in type 2 diabetes and hence to worsening of the overall metabolic condition. Short-term normalization of plasma glucose might break the vicious cycle of impaired glucose effectiveness in type 2 diabetes.
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Affiliation(s)
- Meredith Hawkins
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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Hawkins M, Gabriely I, Wozniak R, Vilcu C, Shamoon H, Rossetti L. Fructose improves the ability of hyperglycemia per se to regulate glucose production in type 2 diabetes. Diabetes 2002; 51:606-14. [PMID: 11872657 DOI: 10.2337/diabetes.51.3.606] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The ability of hyperglycemia per se to suppress endogenous glucose production (GP) is blunted in type 2 diabetes. This could be due in part to decreased glucose-induced flux through glucokinase (GK). Because fructose activates hepatic GK, we examined whether catalytic amounts of fructose could restore inhibition of GP by hyperglycemia in humans with type 2 diabetes. Glucose fluxes ([3-(3)H]glucose) were measured during euglycemia (5 mmol/l) and after abrupt onset of hyperglycemia (10 mmol/l; variable dextrose infusion) under fixed hormonal conditions (somatostatin infusion for 6 h with basal insulin/glucagon/growth hormone replacement). A total of 10 subjects with moderately controlled type 2 diabetes and 7 age- and BMI-matched nondiabetic subjects were studied on up to three separate occasions under the following conditions: without fructose (F(-)) or with infusion of fructose at two dosages: 0.6 mg/kg center dot min (low F) and 1.8 mg/kg center dot min (high F). Although GP failed to decrease in response to hyperglycemia in type 2 diabetes, the coinfusion of both doses of fructose was associated with comparable decreases in GP in response to hyperglycemia (low F = -27%, high F = -33%; P < 0.01 vs. F(-) at both dosages), which approached the 44% decline in GP observed without fructose in the nondiabetic subjects. GP responses to hyperglycemia were not altered by the addition of fructose in the nondiabetic group (low F = -47%, high F = -42%; P > 0.05 vs. F(-)). Thus, the administration of small amounts of fructose to type 2 diabetic subjects partially corrected the regulation of GP by hyperglycemia per se, yet did not affect this regulation in the nondiabetic subjects. This suggests that the liver's inability to respond to hyperglycemia in type 2 diabetes, likely caused by impaired GK activity, contributes substantially to the increased GP in these individuals.
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Affiliation(s)
- Meredith Hawkins
- Division of Endocrinology and Diabetes Research and Training Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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Combs TP, Berg AH, Obici S, Scherer PE, Rossetti L. Endogenous glucose production is inhibited by the adipose-derived protein Acrp30. J Clin Invest 2001; 108:1875-81. [PMID: 11748271 PMCID: PMC209474 DOI: 10.1172/jci14120] [Citation(s) in RCA: 630] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Intraperitoneal injection of purified recombinant Acrp30 lowers glucose levels in mice. To gain insight into the mechanism(s) of this hypoglycemic effect, purified recombinant Acrp30 was infused in conscious mice during a pancreatic euglycemic clamp. In the presence of physiological hyperinsulinemia, this treatment increased circulating Acrp30 levels by approximately twofold and stimulated glucose metabolism. The effect of Acrp30 on in vivo insulin action was completely accounted for by a 65% reduction in the rate of glucose production. Similarly, glucose flux through glucose-6-phosphatase (G6Pase) decreased with Acrp30, whereas the activity of the direct pathway of glucose-6-phosphate biosynthesis, an index of hepatic glucose phosphorylation, increased significantly. Acrp30 did not affect the rates of glucose uptake, glycolysis, or glycogen synthesis. These results indicate that an acute increase in circulating Acrp30 levels lowers hepatic glucose production without affecting peripheral glucose uptake. Hepatic expression of the gluconeogenic enzymes phosphoenolpyruvate carboxykinase and G6Pase mRNAs was reduced by more than 50% following Acrp30 infusion compared with vehicle infusion. Thus, a moderate rise in circulating levels of the adipose-derived protein Acrp30 inhibits both the expression of hepatic gluconeogenic enzymes and the rate of endogenous glucose production.
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Affiliation(s)
- T P Combs
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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21
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Desai UJ, Slosberg ED, Boettcher BR, Caplan SL, Fanelli B, Stephan Z, Gunther VJ, Kaleko M, Connelly S. Phenotypic correction of diabetic mice by adenovirus-mediated glucokinase expression. Diabetes 2001; 50:2287-95. [PMID: 11574410 DOI: 10.2337/diabetes.50.10.2287] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hyperglycemia of diabetes is caused in part by perturbation of hepatic glucose metabolism. Hepatic glucokinase (GK) is an important regulator of glucose storage and disposal in the liver. GK levels are lowered in patients with maturity-onset diabetes of the young and in some diabetic animal models. Here, we explored the adenoviral vector-mediated overexpression of GK in a diet-induced murine model of type 2 diabetes as a treatment for diabetes. Diabetic mice were treated by intravenous administration with an E1/E2a/E3-deleted adenoviral vector encoding human hepatic GK (Av3hGK). Two weeks posttreatment, the Av3hGK-treated diabetic mice displayed normalized fasting blood glucose levels (95 +/- 4.8 mg/dl; P < 0.001) when compared with Av3Null (135 +/- 5.9 mg/dl), an analogous vector lacking a transgene, and vehicle-treated diabetic mice (134 +/- 8 mg/dl). GK treatment also resulted in lowered insulin levels (632 +/- 399 pg/ml; P < 0.01) compared with the control groups (Av3Null, 1,803 +/- 291 pg/ml; vehicle, 1,861 +/- 392 pg/ml), and the glucose tolerance of the Av3hGK-treated diabetic mice was normalized. No significant increase in plasma or hepatic triglycerides, or plasma free fatty acids was observed in the Av3hGK-treated mice. These data suggest that overexpression of GK may have a therapeutic potential for the treatment of type 2 diabetes.
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Affiliation(s)
- U J Desai
- Genetic Therapy, Inc., Gaithersburg, Maryland. Novartis Institute for Biomedical Research, Summit, New Jersey, USA
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Shiota M, Postic C, Fujimoto Y, Jetton TL, Dixon K, Pan D, Grimsby J, Grippo JF, Magnuson MA, Cherrington AD. Glucokinase gene locus transgenic mice are resistant to the development of obesity-induced type 2 diabetes. Diabetes 2001; 50:622-9. [PMID: 11246883 DOI: 10.2337/diabetes.50.3.622] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Transgenic mice that overexpress the entire glucokinase (GK) gene locus have been previously shown to be mildly hypoglycemic and to have improved tolerance to glucose. To determine whether increased GK might also prevent or diminish diabetes in diet-induced obese animals, we examined the effect of feeding these mice a high-fat high-simple carbohydrate low-fiber diet (HF diet) for 30 weeks. In response to this diet, both normal and transgenic mice became obese and had similar BMIs (5.3 +/- 0.1 and 5.0 +/- 0.1 kg/m2 in transgenic and non-transgenic mice, respectively). The blood glucose concentration of the control mice increased linearly with time and reached 17.0 +/- 1.3 mmol/l at the 30th week. In contrast, the blood glucose of GK transgenic mice rose to only 9.7 +/- 1.2 mmol/l at the 15th week, after which it returned to 7.6 +/- 1.0 mmol/l by the 30th week. The plasma insulin concentration was also lower in the GK transgenic animals (232 +/- 79 pmol/l) than in the controls (595 +/- 77 pmol/l), but there was no difference in plasma glucagon concentrations. Together, these data indicate that increased GK levels dramatically lessen the development of both hyperglycemia and hyperinsulinemia associated with the feeding of an HF diet.
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Affiliation(s)
- M Shiota
- Department of Molecular Physiology and Biophysics, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-0615, USA.
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Mevorach M, Giacca A, Aharon Y, Hawkins M, Shamoon H, Rossetti L. Regulation of endogenous glucose production by glucose per se is impaired in type 2 diabetes mellitus. J Clin Invest 1998; 102:744-53. [PMID: 9710443 PMCID: PMC508937 DOI: 10.1172/jci2720] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We examined the ability of an equivalent increase in circulating glucose concentrations to inhibit endogenous glucose production (EGP) and to stimulate glucose metabolism in patients with Type 2 diabetes mellitus (DM2). Somatostatin was infused in the presence of basal replacements of glucoregulatory hormones and plasma glucose was maintained either at 90 or 180 mg/dl. Overnight low-dose insulin was used to normalize the plasma glucose levels in DM2 before initiation of the study protocol. In the presence of identical and constant plasma insulin, glucagon, and growth hormone concentrations, a doubling of the plasma glucose levels inhibited EGP by 42% and stimulated peripheral glucose uptake by 69% in nondiabetic subjects. However, the same increment in the plasma glucose concentrations failed to lower EGP, and stimulated glucose uptake by only 49% in patients with DM2. The rate of glucose infusion required to maintain the same hyperglycemic plateau was 58% lower in DM2 than in nondiabetic individuals. Despite diminished rates of total glucose uptake during hyperglycemia, the ability of glucose per se (at basal insulin) to stimulate whole body glycogen synthesis (glucose uptake minus glycolysis) was comparable in DM2 and in nondiabetic subjects. To examine the mechanisms responsible for the lack of inhibition of EGP by hyperglycemia in DM2 we also assessed the rates of total glucose output (TGO), i.e., flux through glucose-6-phosphatase, and the rate of glucose cycling in a subgroup of the study subjects. In the nondiabetic group, hyperglycemia inhibited TGO by 35%, while glucose cycling did not change significantly. In DM2, neither TGO or glucose cycling was affected by hyperglycemia. The lack of increase in glucose cycling in the face of a doubling in circulating glucose concentrations suggested that hyperglycemia at basal insulin inhibits glucose-6-phosphatase activity in vivo. Conversely, the lack of increase in glucose cycling in the presence of hyperglycemia and unchanged TGO suggest that the increase in the plasma glucose concentration failed to enhance the flux through glucokinase in DM2. In summary, both lack of inhibition of EGP and diminished stimulation of glucose uptake contribute to impaired glucose effectiveness in DM2. The abilities of glucose at basal insulin to both increase the flux through glucokinase and to inhibit the flux through glucose-6-phosphatase are impaired in DM2. Conversely, glycogen synthesis is exquisitely sensitive to changes in plasma glucose in patients with DM2.
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Affiliation(s)
- M Mevorach
- Department of Medicine, Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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