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Dolab N, Kamkar MZ, Amiriani T, Yuzugulen J, Marjani M, Marjani A. The association between leptin and adiponectin, and metabolic syndrome components and serum levels of lipid peroxidation in bipolar disorder patients treated with lithium and valproic acid. Heliyon 2020; 6:e04553. [PMID: 32760840 PMCID: PMC7393417 DOI: 10.1016/j.heliyon.2020.e04553] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 07/04/2020] [Accepted: 07/22/2020] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The aim of study is to assess a relation between the adiponectin and leptin levels, and metabolic syndrome components and lipid peroxidation treated with Li and VPA in bipolar disorder patients and compared with controls. MATERIALS AND METHODS 56 patients and 31 healthy controls were enrolled. The ATP III criteria were used to determine metabolic syndrome components. Leptin, adiponectin, lipid peroxidation and lipid profiles were measured. RESULTS Malondialdehyde in Li patients was higher than VPA patients. BMI, waist circumference (WC), triglyceride, malondialdehyde and adiponectin levels were increased, whereas HDL-cholesterol (VPA treated patients) and leptin were decreased in patients compared with controls. Leptin and adiponectin were correlated with WC, triglyceride and malondialdehyde in both groups. Adiponectin was correlated with HDL-cholesterol in VPA patients. CONCLUSION Patients should be checked metabolic syndrome components, serum leptin and adiponectin level occasionally to prevent possible deficiency or pathologic increase of these parameters.
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Affiliation(s)
- Neda Dolab
- Student Research Committee, Metabolic Disorders Research Center, Department of Biochemistry and Biophysics, Gorgan Faculty of Medicine, Golestan University Medical Sciences, Gorgan, Iran
| | - Mohammad Zaman Kamkar
- Department of Psychiatry, Golestan Research Center of Psychiatry, Golestan University of Medical Sciences, Gorgan, Golestan Province, Iran
| | - Taghi Amiriani
- Golestan Research Center of Gastroenterology and Hepatology, Golestan University of Medical Sciences, Gorgan, Iran
| | - Jale Yuzugulen
- Faculty of Pharmacy, Eastern Mediterranean University, Mersin 10, Famagusta, North Cyprus, Turkey
| | - Majid Marjani
- Faculty of Pharmacy, Eastern Mediterranean University, Mersin 10, Famagusta, North Cyprus, Turkey
| | - Abdoljalal Marjani
- Metabolic Disorders Research Center, Department of Biochemistry and Biophysics, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Golestan province, Iran
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Kim SH, Huh CS, Choi ID, Jeong JW, Ku HK, Ra JH, Kim TY, Kim GB, Sim JH, Ahn YT. The anti-diabetic activity of Bifidobacterium lactis HY8101 in vitro and in vivo. J Appl Microbiol 2014; 117:834-45. [PMID: 24925305 DOI: 10.1111/jam.12573] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/13/2014] [Accepted: 06/08/2014] [Indexed: 01/19/2023]
Abstract
AIMS The aim of this study was to evaluate the effects of Bifidobacterium lactis HY8101 on insulin resistance induced using tumour necrosis factor-α (TNF-α) in rat L6 skeletal muscle cells and on the KK-A(Y) mouse noninsulin-dependent diabetes mellitus (NIDDM) model. METHODS AND RESULTS The treatment using HY8101 improved the insulin-stimulated glucose uptake and translocation of GLUT4 via the insulin signalling pathways AKT and IRS-1(Tyr) in TNF-α-treated L6 cells. HY8101 increased the mRNA levels of GLUT4 and several insulin sensitivity-related genes (PPAR-γ) in TNF-α-treated L6 cells. In KK-A(Y) mice, HY8101 decreased fasting insulin and blood glucose and significantly improved insulin tolerance. HY8101 improved diabetes-induced plasma total cholesterol and triglyceride (TG) levels and increased the muscle glycogen content. We observed concurrent transcriptional changes in the skeletal muscle tissue and the liver. In the skeletal muscle tissue, the glycogen synthesis-related gene pp-1 and GLUT4 were up-regulated in mice receiving HY8101 treatment. In the liver, the hepatic gluconeogenesis-regulated genes (PCK1 and G6PC) were down-regulated in mice receiving HY8101 treatment. CONCLUSIONS Bifidobacterium lactis HY8101 can be used to moderate glucose metabolism, lipid metabolism and insulin sensitivity in mice and in cells. SIGNIFICANCE AND IMPACT OF THE STUDY Bifidobacterium lactis HY8101 might have potential as a probiotic candidate for alleviating metabolic syndromes such as diabetes.
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Affiliation(s)
- S-H Kim
- R&BD Center, Korea Yakult Co. Ltd., Yongin, Korea
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Fan TWM, Yuan P, Lane AN, Higashi RM, Wang Y, Hamidi AB, Zhou R, Guitart X, Chen G, Manji HK, Kaddurah-Daouk R. Stable isotope-resolved metabolomic analysis of lithium effects on glial-neuronal metabolism and interactions. Metabolomics 2010; 6:165-179. [PMID: 20631920 PMCID: PMC2903070 DOI: 10.1007/s11306-010-0208-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Despite the long-established therapeutic efficacy of lithium in the treatment of bipolar disorder (BPD), its molecular mechanism of action remains elusive. Newly developed stable isotope-resolved metabolomics (SIRM) is a powerful approach that can be used to elucidate systematically how lithium impacts glial and neuronal metabolic pathways and activities, leading ultimately to deciphering its molecular mechanism of action. The effect of lithium on the metabolism of three different (13)C-labeled precursors ([U-(13)C]-glucose, (13)C-3-lactate or (13)C-2,3-alanine) was analyzed in cultured rat astrocytes and neurons by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography mass spectrometry (GC-MS). Using [U-(13)C]-glucose, lithium was shown to enhance glycolytic activity and part of the Krebs cycle activity in both astrocytes and neurons, particularly the anaplerotic pyruvate carboxylation (PC). The PC pathway was previously thought to be active in astrocytes but absent in neurons. Lithium also stimulated the extracellular release of (13)C labeled-lactate, -alanine (Ala), -citrate, and -glutamine (Gln) by astrocytes. Interrogation of neuronal pathways using (13)C-3-lactate or (13)C-2,3-Ala as tracers indicated a high capacity of neurons to utilize lactate and Ala in the Krebs cycle, particularly in the production of labeled Asp and Glu via PC and normal cycle activity. Prolonged lithium treatment enhanced lactate metabolism via PC but inhibited lactate oxidation via the normal Krebs cycle in neurons. Such lithium modulation of glycolytic, PC and Krebs cycle activity in astrocytes and neurons as well as release of fuel substrates by astrocytes should help replenish Krebs cycle substrates for Glu synthesis while meeting neuronal demands for energy. Further investigations into the molecular regulation of these metabolic traits should provide new insights into the pathophysiology of mood disorders and early diagnostic markers, as well as new target(s) for effective therapies.
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Affiliation(s)
- Teresa W.-M. Fan
- Department of Chemistry, Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40292, USA
- Department of Medicine, Structural Biology Program, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research Building, Louisville, KY 40208, USA,
| | - Peixiong Yuan
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Andrew N. Lane
- Department of Chemistry, Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40292, USA
- Department of Medicine, Structural Biology Program, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Richard M. Higashi
- Department of Chemistry, Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40292, USA
- Department of Medicine, Structural Biology Program, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Yun Wang
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Anahita B. Hamidi
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Rulun Zhou
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Xavier Guitart
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Guang Chen
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Husseini K. Manji
- Biomarker Laboratory, Laboratory of Molecular Pathophysiology, Mood and Anxiety Disorder Program, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
- Johnson & Johnson, Titusville, NJ, USA
| | - Rima Kaddurah-Daouk
- Department of Psychiatry, Duke University Medical Center, Box 3950, Durham, NC 27710, USA,
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Yin J, Zuberi A, Gao Z, Liu D, Liu Z, Ye J. Shilianhua extract inhibits GSK-3beta and promotes glucose metabolism. Am J Physiol Endocrinol Metab 2009; 296:E1275-80. [PMID: 19351808 PMCID: PMC2692393 DOI: 10.1152/ajpendo.00092.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The extract of plant Shilianhua (SLH; Sinocrassula indica Berge) is a component in a commercial product for control of blood glucose. However, it remains to be investigated whether the SLH extract enhances insulin sensitivity in a model of type 2 diabetes. To address this question, the SLH crude extract was fractionated into four parts on the basis of polarity, and bioactivities of each part were tested in cells. One of the fractions, F100, exhibited a strong activity in the stimulation of glucose consumption in vitro. Glucose consumption was induced significantly by F100 in 3T3-L1 adipocytes, L6 myotubes, and H4IIE hepatocytes in the absence of insulin. F100 also increased insulin-stimulated glucose consumption in L6 myotubes and H4IIE hepatocytes. It increased insulin-independent glucose uptake in 3T3-L1 adipocytes and insulin-dependent glucose uptake in L6 cells. The glucose transporter-1 (GLUT1) protein was induced in 3T3-L1 cells, and the GLUT4 protein was induced in L6 cells by F100. Mechanism study indicated that F100 induced GSK-3beta phosphorylation, which was comparable with that induced by insulin. Additionally, the transcriptional activity of NF-kappaB was inhibited by F100. In RAW 264.7 macrophages, mRNA expression of NF-kappaB target genes (TNFalpha and MCP-1) was suppressed by F100. In KK.Cg-A(y)/+ mice, F100 decreased fasting insulin and blood glucose and improved insulin tolerance significantly. We conclude that the F100 may be a bioactive component in the SLH plant. It promotes glucose metabolism in vitro and in vivo. Inhibition of GSK-3beta and NF-kappaB may be the potential mechanism.
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Affiliation(s)
- Jun Yin
- Pennington Biomedical Research Center, Louisiana State University System, 6400 Perkins Rd., Baton Rouge, LA 70808, USA
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5
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Vasudevan SM. Lithium may play a positive role in controlling drug induced metabolic syndrome in some psychiatric patients. Asian J Psychiatr 2008; 1:63-4. [PMID: 23051002 DOI: 10.1016/j.ajp.2008.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 09/25/2008] [Indexed: 11/26/2022]
Affiliation(s)
- S M Vasudevan
- Community Mental Health Center, Circles of care, Inc., 400 East Sheridan Road, Melbourne, FL 32901, United States
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Finlay D, Patel S, Dickson LM, Shpiro N, Marquez R, Rhodes CJ, Sutherland C. Glycogen synthase kinase-3 regulates IGFBP-1 gene transcription through the thymine-rich insulin response element. BMC Mol Biol 2004; 5:15. [PMID: 15350195 PMCID: PMC517930 DOI: 10.1186/1471-2199-5-15] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 09/06/2004] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Hepatic expression of several gene products involved in glucose metabolism, including phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase) and insulin-like growth factor binding protein-1 (IGFBP-1), is rapidly and completely inhibited by insulin. This inhibition is mediated through the regulation of a DNA element present in each of these gene promoters, that we call the Thymine-rich Insulin Response Element (TIRE). The insulin signalling pathway that results in the inhibition of these gene promoters requires the activation of phosphatidylinositol 3-kinase (PI 3-kinase). However, the molecules that connect PI 3-kinase to these gene promoters are not yet fully defined. Glycogen Synthase Kinase 3 (GSK-3) is inhibited following activation of PI 3-kinase. We have shown previously that inhibitors of GSK-3 reduce the activity of two TIRE-containing gene promoters (PEPCK and G6Pase), whose products are required for gluconeogenesis. RESULTS In this report we demonstrate that in H4IIE-C3 cells, four distinct classes of GSK-3 inhibitor mimic the effect of insulin on a third TIRE-containing gene, IGFBP-1. We identify the TIRE as the minimum requirement for inhibition by these agents, and demonstrate that the target of GSK-3 is unlikely to be the postulated TIRE-binding protein FOXO-1. Importantly, overexpression of GSK-3 in cells reduces the insulin regulation of TIRE activity as well as endogenous IGFBP-1 expression. CONCLUSIONS These results implicate GSK-3 as an intermediate in the pathway from the insulin receptor to the TIRE. Indeed, this is the first demonstration of an absolute requirement for GSK-3 inhibition in insulin regulation of gene transcription. These data support the potential use of GSK-3 inhibitors in the treatment of insulin resistant states such as Type 2 diabetes mellitus, but suggest that it will be important to identify all TIRE-containing genes to assess potential side effects of these agents.
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Affiliation(s)
- David Finlay
- Department of Pathology and Neurosciences, University of Dundee, Ninewells Medical School and Hospital, Dundee, DD1 9SY United Kingdom
| | - Satish Patel
- Department of Pathology and Neurosciences, University of Dundee, Ninewells Medical School and Hospital, Dundee, DD1 9SY United Kingdom
- Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, Ontario M5G 2M9 Canada
| | - Lorna M Dickson
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA
| | - Natalia Shpiro
- Division of Biological Chemistry, School of Life Sciences, University of Dundee, DD1 4EH, United Kingdom
| | - Rodolfo Marquez
- Division of Biological Chemistry, School of Life Sciences, University of Dundee, DD1 4EH, United Kingdom
| | - Chris J Rhodes
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA
| | - Calum Sutherland
- Department of Pathology and Neurosciences, University of Dundee, Ninewells Medical School and Hospital, Dundee, DD1 9SY United Kingdom
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Ring DB, Johnson KW, Henriksen EJ, Nuss JM, Goff D, Kinnick TR, Ma ST, Reeder JW, Samuels I, Slabiak T, Wagman AS, Hammond MEW, Harrison SD. Selective glycogen synthase kinase 3 inhibitors potentiate insulin activation of glucose transport and utilization in vitro and in vivo. Diabetes 2003; 52:588-95. [PMID: 12606497 DOI: 10.2337/diabetes.52.3.588] [Citation(s) in RCA: 382] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin resistance plays a central role in the development of type 2 diabetes, but the precise defects in insulin action remain to be elucidated. Glycogen synthase kinase 3 (GSK-3) can negatively regulate several aspects of insulin signaling, and elevated levels of GSK-3 have been reported in skeletal muscle from diabetic rodents and humans. A limited amount of information is available regarding the utility of highly selective inhibitors of GSK-3 for the modification of insulin action under conditions of insulin resistance. In the present investigation, we describe novel substituted aminopyrimidine derivatives that inhibit human GSK-3 potently (K(i) < 10 nmol/l) with at least 500-fold selectivity against 20 other protein kinases. These low molecular weight compounds activated glycogen synthase at approximately 100 nmol/l in cultured CHO cells transfected with the insulin receptor and in primary hepatocytes isolated from Sprague-Dawley rats, and at 500 nmol/l in isolated type 1 skeletal muscle of both lean Zucker and ZDF rats. It is interesting that these GSK-3 inhibitors enhanced insulin-stimulated glucose transport in type 1 skeletal muscle from the insulin-resistant ZDF rats but not from insulin-sensitive lean Zucker rats. Single oral or subcutaneous doses of the inhibitors (30-48 mg/kg) rapidly lowered blood glucose levels and improved glucose disposal after oral or intravenous glucose challenges in ZDF rats and db/db mice, without causing hypoglycemia or markedly elevating insulin. Collectively, our results suggest that these selective GSK-3 inhibitors may be useful as acute-acting therapeutics for the treatment of the insulin resistance of type 2 diabetes.
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Nikoulina SE, Ciaraldi TP, Mudaliar S, Carter L, Johnson K, Henry RR. Inhibition of glycogen synthase kinase 3 improves insulin action and glucose metabolism in human skeletal muscle. Diabetes 2002; 51:2190-8. [PMID: 12086949 DOI: 10.2337/diabetes.51.7.2190] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glycogen synthase kinase (GSK)-3 has been implicated in the regulation of multiple cellular physiological processes in skeletal muscle. Selective cell-permeable reversible inhibitors (INHs) of GSK-3 (CT98014 and CHIR98023 [Chiron, Emeryville, CA] and LiCl) were used to evaluate the role of GSK-3 in controlling glucose metabolism. Acute treatment (30 min) of cultured human skeletal muscle cells with either INH resulted in a dose-dependent activation of glycogen synthase (GS) with a maximally effective concentration of approximately 2 micromol/l. The maximal acute effect of either INH on GS (103 +/- 25% stimulation over basal) was greater than the maximal insulin response (48 +/- 9%, P < 0.05 vs. INH); LiCl was as effective as insulin. The GSK-3 inhibitor effect, like that of insulin, was on the activation state (fractional velocity [FV]) of GS. Cotreatment of muscle cells with submaximal doses of INH and insulin resulted in an additive effect on GS FV (103 +/- 10% stimulation, P < 0.05 vs. either agent alone). Glucose incorporation into glycogen was also acutely stimulated by INH. While prolonged (6-24 h) insulin exposure led to desensitization of GS, INH continued to activate GS FV for at least 24 h. Insulin and LiCl acutely activated glucose uptake, whereas INH stimulation of glucose uptake required more prolonged exposure, starting at 6 h and continuing to 24 h. Chronic (4-day) treatment with INH increased both basal (154 +/- 32% of control) and insulin-stimulated (219 +/- 74%) glucose uptake. Upregulation of uptake activity occurred without any change in total cellular GLUT1 or GLUT4 protein content. Yet the same chronic treatment resulted in a 65 +/- 6% decrease in GSK-3 protein and a parallel decrease (61 +/- 11%) in GSK-3 total activity. Together with the INH-induced increase in insulin-stimulated glucose uptake, there was an approximately 3.5-fold increase (P < 0.05) in insulin receptor substrate (IRS)-1 protein abundance. Despite upregulation of IRS-1, maximal insulin stimulation of Akt phosphorylation was unaltered by INH treatment. The results suggest that selective inhibition of GSK-3 has an impact on both GS and glucose uptake, including effects on insulin action, using mechanisms that differ from and are additive to those of insulin.
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Affiliation(s)
- Svetlana E Nikoulina
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
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Fisher JS, Nolte LA, Kawanaka K, Han DH, Jones TE, Holloszy JO. Glucose transport rate and glycogen synthase activity both limit skeletal muscle glycogen accumulation. Am J Physiol Endocrinol Metab 2002; 282:E1214-21. [PMID: 12006350 DOI: 10.1152/ajpendo.00254.2001] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We varied rates of glucose transport and glycogen synthase I (GS-I) activity (%GS-I) in isolated rat epitrochlearis muscle to examine the role of each process in determining the rate of glycogen accumulation. %GS-I was maintained at or above the fasting basal range during 3 h of incubation with 36 mM glucose and 60 microU/ml insulin. Lithium (2 mM LiCl) added to insulin increased glucose transport rate and muscle glycogen content compared with insulin alone. The glycogen synthase kinase-3beta inhibitor GF-109203 x (GF; 10 microM) maintained %GS-I about twofold higher than insulin with or without lithium but did not increase glycogen accumulation. When %GS-I was lowered below the fasting range by prolonged incubation with 36 mM glucose and 2 mU/ml insulin, raising rates of glucose transport with bpV(phen) or of %GS-I with GF produced additive increases in glycogen concentration. Phosphorylase activity was unaffected by GF or bpV(phen). In muscles of fed animals, %GS-I was approximately 30% lower than in those of fasted rats, and insulin-stimulated glycogen accumulation did not occur unless %GS-I was raised with GF. We conclude that the rate of glucose transport is rate limiting for glycogen accumulation unless %GS-I is below the fasting range, in which case both glucose transport rate and GS activity can limit glycogen accumulation.
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Affiliation(s)
- Jonathan S Fisher
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Abstract
Identified originally as a regulator of glycogen metabolism, glycogen synthase kinase-3 (GSK3) is now a well-established component of the Wnt signalling pathway, which is essential for setting up the entire body pattern during embryonic development. It may also play important roles in protein synthesis, cell proliferation, cell differentiation, microtubule dynamics and cell motility by phosphorylating initiation factors, components of the cell-division cycle, transcription factors and proteins involved in microtubule function and cell adhesion. Generation of the mouse knockout of GSK3beta, as well as studies in neurons, also suggest an important role in apoptosis. The substrate specificity of GSK3 is unusual in that efficient phosphorylation of many of its substrates requires the presence of another phosphorylated residue optimally located four amino acids C-terminal to the site of GSK3 phosphorylation. Recent experiments, including the elucidation of its three-dimensional structure, have enhanced our understanding of the molecular basis for the unique substrate specificity of GSK3. Insulin and growth factors inhibit GSK3 by triggering its phosphorylation, turning the N-terminus into a pseudosubstrate inhibitor that competes for binding with the 'priming phosphate' of substrates. In contrast, Wnt proteins inhibit GSK3 in a completely different way, by disrupting a multiprotein complex comprising GSK3 and its substrates in the Wnt signalling pathway, which do not appear to require a 'priming phosphate'. These latest findings have generated an enormous amount of interest in the development of drugs that inhibit GSK3 and which may have therapeutic potential for the treatment of diabetes, stroke and Alzheimer's disease.
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Affiliation(s)
- S Frame
- Division of Signal Transduction Therapy, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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