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Understanding the Mechanism Underlie the Antidiabetic Activity of Oleuropein Using Ex-Vivo Approach. Rep Biochem Mol Biol 2022; 11:146-156. [PMID: 35765534 PMCID: PMC9208562 DOI: 10.52547/rbmb.11.1.146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 12/25/2021] [Indexed: 01/11/2023]
Abstract
Background Oleuropein, the main constituent of olive fruit and leaves, has been reported to protect against insulin resistance and diabetes. While many experimental investigations have examined the mechanisms by which oleuropein improves insulin resistance and diabetes, much of these investigations have been carried out in either muscle cell lines or in vivo models two scenarios with many drawbacks. Accordingly, to simplify identification of mechanisms by which oleuropein regulates specific cellular processes, we resort, in the present study, to isolated muscle preparation which enables better metabolic milieu control and permit more detailed analyses. Methods For this purpose, soleus muscles were incubated for 12 h without or with palmitate (1.5 mM) in the presence or absence of oleuropein (1.5 mM), and compound C. Insulin-stimulated glucose transport, glucose transporter type 4 (GLUT4) translocation, Akt substrate of 160 kDa (AS160) phosphorylation and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation were examined. Results Palmitate treatment reduced insulin-stimulated glucose transport, GLUT4 translocation and AS160 phosphorylation, but AMPK phosphorylation was not changed. Oleuropein administration (12 h) fully rescued insulin-stimulated glucose transport, but partially restored GLUT4 translocation. However, it fully restored AS160 phosphorylation, raising the possibility that oleuropein may also have contributed to the restoration of glucose transport by increased GLUT4 intrinsic activity. Inhibition of AMPK phosphorylation with compound C (50 µM) prevented oleuropein -induced improvements in insulin-stimulated glucose transport, GLUT4 translocation, and AS160 phosphorylation. Conclusion Our results clearly indicate that oleuropein alleviates palmitate-induced insulin resistance appears to occur via an AMPK-dependent mechanism involving improvements in the functionality of the AS160-GLUT4 signaling system.
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Heber MF, Ferreira SR, Abruzzese GA, Raices T, Pignataro OP, Vega M, Motta AB. Metformin improves ovarian insulin signaling alterations caused by fetal programming. J Endocrinol 2019; 240:JOE-18-0520.R1. [PMID: 30620715 DOI: 10.1530/joe-18-0520] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 01/08/2019] [Indexed: 01/12/2023]
Abstract
Insulin resistance is the decreased ability of insulin to mediate metabolic actions. In the ovary, insulin controls ovulation and oocyte quality. Alterations in ovarian insulin signaling pathway could compromise ovarian physiology. Here, we aimed to investigate the effects of fetal programming on ovarian insulin signaling and evaluate the effect of metformin treatment. Pregnant rats were hyperandrogenized with testosterone and female offspring born to those dams were employed; at adulthood, prenatally hyperandrogenized (PH) offspring presented two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Half of each group was orally treated with metformin. Metformin treatment improved the estrous cyclicity in both PH groups. Both PH groups showed low mRNA levels of IR, IRS1 and Glut4. IRS2 was decreased only in PHanov. Metformin upregulated the mRNA levels of some of the mediators studied. Protein expression of IR, IRS1/2 and GLUT4 was decreased in both PH groups. In PHiov, metformin restored the expression of all the mediators, whereas, in PHanov, metformin restored only that of IR and IRS1/2. IRS1 phosphorylation was measured in tyrosine residues, which activates the pathway, and in serine residues, which impairs insulin action. PHiov presented high IRS1 phosphorylation on tyrosine and serine residues, whereas PHanov showed high serine phosphorylation and low tyrosine phosphorylation. Metformin treatment lowered serine phosphorylation only in PHanov rats. Our results suggest that PHanov rats have a defective insulin action, partially restored with metformin. PHiov rats had less severe alterations, and metformin treatment was more effective in this phenotype.
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Affiliation(s)
- Maria F Heber
- M Heber, Laboratorio de Fisio-patologia Ovarica, CEFYBO, Ciudad Autónoma de Buenos Aires, C1121ABG, Argentina
| | - Silvana R Ferreira
- S Ferreira, Laboratorio de Fisio-patologia Ovarica, Centro de Estudios Farmacologicos y Botanicos, Buenos Aires, Argentina
| | | | - Trinidad Raices
- T Raices, Laboratorio de Endocrinología Molecular y Transducción de Señales, Instituto de Biologia y Medicina Experimental, Buenos Aires, Argentina
| | - Omar Pedro Pignataro
- O Pignataro, Laboratorio de Endocrinología Molecular y Transducción de Señales, Instituto de Biologia y Medicina Experimental, Buenos Aires, Argentina
| | - Margarita Vega
- M Vega, Department of Obstetrics and Gynecology, University of Chile Clinical Hospital, Santiago, Chile
| | - Alicia B Motta
- A Motta, Laboratorio de Fisio-patologia Ovarica, CEFYBO, Buenos Aires, 1121, Argentina
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Zhao M, Gong D, Gao T, Zhang L, Li J, Lv P, Yu L, Zhou G, Gao F. In Ovo Feeding of Creatine Pyruvate Increases the Glycolysis Pathway, Glucose Transporter Gene Expression, and AMPK Phosphorylation in Breast Muscle of Neonatal Broilers. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:7684-7691. [PMID: 29974734 DOI: 10.1021/acs.jafc.8b02557] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This study aims to investigate in ovo feeding (IOF) of creatine pyruvate (CrPyr) on glucose metabolism, hormone concentration, and the 5'-AMP-activated protein kinase (AMPK) pathway in breast muscle of embryos and neonatal broilers. The three treatments were noninjected control, 0.75% NaCl treatment, and 12 mg CrPyr/egg treatment. The solution was injected on the 17.5 day of incubation. At hatch, 120 male broilers from each treatment were chosen for a 7 day feeding trial. Compared with other treatments, CrPyr treated broilers enhanced insulin and thyroxine levels in plasma, adenosine triphosphate (ATP) concentration, hexokinase and pyruvate kinase activities, glucose transporter protein mRNA expressions, as well as protein abundances of phosphor-liver kinase B1 and phosphor-AMPK in breast muscle at hatch. In conclusion, IOF of CrPyr improved the energy status, increased the gene expression of glucose transporter proteins, and facilitated glycolysis in breast muscle, which may be associated with the activated AMPK pathway.
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Affiliation(s)
- Minmeng Zhao
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
- College of Animal Science and Technology , Yangzhou University , Yangzhou 225009 , P. R. China
| | - Daoqing Gong
- College of Animal Science and Technology , Yangzhou University , Yangzhou 225009 , P. R. China
| | - Tian Gao
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Lin Zhang
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Jiaolong Li
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Peng'an Lv
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Lanlin Yu
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Guanghong Zhou
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
| | - Feng Gao
- College of Animal Science and Technology, Jiangsu Key Laboratory of Animal Origin Food Production and Safety Guarantee, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control , Nanjing Agricultural University , Nanjing 210095 , P. R. China
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Campello RS, Fátima LA, Barreto-Andrade JN, Lucas TF, Mori RC, Porto CS, Machado UF. Estradiol-induced regulation of GLUT4 in 3T3-L1 cells: involvement of ESR1 and AKT activation. J Mol Endocrinol 2017; 59:257-268. [PMID: 28729437 DOI: 10.1530/jme-17-0041] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/20/2017] [Indexed: 12/11/2022]
Abstract
Impaired insulin-stimulated glucose uptake involves reduced expression of the GLUT4 (solute carrier family 2 facilitated glucose transporter member 4, SLC2A4 gene). 17β-estradiol (E2) modulates SLC2A4/GLUT4 expression, but the involved mechanisms are unclear. Although E2 exerts biological effects by binding to estrogen receptors 1/2 (ESR1/2), which are nuclear transcriptional factors; extranuclear effects have also been proposed. We hypothesize that E2 regulates GLUT4 through an extranuclear ESR1 mechanism. Thus, we investigated the effects of E2 upon (1) subcellular distribution of ESRs and the proto-oncogene tyrosine-protein kinases (SRC) involvement; (2) serine/threonine-protein kinase (AKT) activation; (3) Slc2a4/GLUT4 expression and (4) GLUT4 subcellular distribution and glucose uptake in 3T3-L1 adipocytes. Differentiated 3T3-L1 adipocytes were cultivated or not with E2 for 24 h, and additionally treated or not with ESR1-selective agonist (PPT), ESR1-selective antagonist (MPP) or selective SRC inhibitor (PP2). Subcellular distribution of ESR1, ESR2 and GLUT4 was analyzed by immunocytochemistry; Slc2a4 mRNA and GLUT4 were quantified by qPCR and Western blotting, respectively; plasma membrane GLUT4 translocation and glucose uptake were analyzed under insulin stimulus for 20 min or not. E2 induced (1) translocation of ESR1, but not of ESR2, from nucleus to plasma membrane and AKT phosphorylation, effects mimicked by PPT and blocked by MPP and PP2; (2) increased Slc2a4/GLUT4 expression and (3) increased insulin-stimulated GLUT4 translocation and glucose uptake. In conclusion, E2 treatment promoted a SRC-mediated nucleus-plasma membrane shuttle of ESR1, and increased AKT phosphorylation, Slc2a4/GLUT4 expression and plasma membrane GLUT4 translocation; consequently, improving insulin-stimulated glucose uptake. These results unravel mechanisms through which estrogen improves insulin sensitivity.
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Affiliation(s)
- Raquel S Campello
- Department of Physiology and BiophysicsInstitute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Luciana A Fátima
- Department of Physiology and BiophysicsInstitute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - João Nilton Barreto-Andrade
- Department of Physiology and BiophysicsInstitute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Thais F Lucas
- Section of Experimental EndocrinologyDepartment of Pharmacology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Rosana C Mori
- Department of Physiology and BiophysicsInstitute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Catarina S Porto
- Section of Experimental EndocrinologyDepartment of Pharmacology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Ubiratan F Machado
- Department of Physiology and BiophysicsInstitute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Säll J, Pettersson AML, Björk C, Henriksson E, Wasserstrom S, Linder W, Zhou Y, Hansson O, Andersson DP, Ekelund M, Degerman E, Stenkula KG, Laurencikiene J, Göransson O. Salt-inducible kinase 2 and -3 are downregulated in adipose tissue from obese or insulin-resistant individuals: implications for insulin signalling and glucose uptake in human adipocytes. Diabetologia 2017; 60:314-323. [PMID: 27807598 PMCID: PMC6518086 DOI: 10.1007/s00125-016-4141-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 09/30/2016] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Salt-inducible kinases (SIKs) are related to the metabolic regulator AMP-activated protein kinase (AMPK). SIK2 is abundant in adipose tissue. The aims of this study were to investigate the expression of SIKs in relation to human obesity and insulin resistance, and to evaluate whether changes in the expression of SIKs might play a causal role in the development of disturbed glucose uptake in human adipocytes. METHODS SIK mRNA and protein was determined in human adipose tissue or adipocytes, and correlated to clinical variables. SIK2 and SIK3 expression and phosphorylation were analysed in adipocytes treated with TNF-α. Glucose uptake, GLUT protein levels and localisation, phosphorylation of protein kinase B (PKB/Akt) and the SIK substrate histone deacetylase 4 (HDAC4) were analysed after the SIKs had been silenced using small interfering RNA (siRNA) or inhibited using a pan-SIK-inhibitor (HG-9-91-01). RESULTS We demonstrate that SIK2 and SIK3 mRNA are downregulated in adipose tissue from obese individuals and that the expression is regulated by weight change. SIK2 is also negatively associated with in vivo insulin resistance (HOMA-IR), independently of BMI and age. Moreover, SIK2 protein levels and specific kinase activity display a negative correlation to BMI in human adipocytes. Furthermore, SIK2 and SIK3 are downregulated by TNF-α in adipocytes. Silencing or inhibiting SIK1-3 in adipocytes results in reduced phosphorylation of HDAC4 and PKB/Akt, less GLUT4 at the plasma membrane, and lower basal and insulin-stimulated glucose uptake in adipocytes. CONCLUSION/INTERPRETATION This is the first study to describe the expression and function of SIKs in human adipocytes. Our data suggest that SIKs might be protective in the development of obesity-induced insulin resistance, with implications for future treatment strategies.
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Affiliation(s)
- Johanna Säll
- Protein Phosphorylation Research Group, Department of Experimental Medical Science, Lund University, BMC C11, Klinikgatan 28, 22242, Lund, Sweden
| | - Annie M L Pettersson
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Christel Björk
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Emma Henriksson
- Protein Phosphorylation Research Group, Department of Experimental Medical Science, Lund University, BMC C11, Klinikgatan 28, 22242, Lund, Sweden
| | - Sebastian Wasserstrom
- Glucose Transport and Protein Trafficking, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Wilhelm Linder
- Protein Phosphorylation Research Group, Department of Experimental Medical Science, Lund University, BMC C11, Klinikgatan 28, 22242, Lund, Sweden
| | - Yuedan Zhou
- Diabetes and Endocrinology, Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | - Ola Hansson
- Diabetes and Endocrinology, Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden
| | - Daniel P Andersson
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Mikael Ekelund
- Surgery, Department of Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Eva Degerman
- Insulin Signal Transduction, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Karin G Stenkula
- Glucose Transport and Protein Trafficking, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Jurga Laurencikiene
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Olga Göransson
- Protein Phosphorylation Research Group, Department of Experimental Medical Science, Lund University, BMC C11, Klinikgatan 28, 22242, Lund, Sweden.
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6
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Martin JH, Nixon B, Lord T, Bromfield EG, Aitken RJ. Identification of a key role for permeability glycoprotein in enhancing the cellular defense mechanisms of fertilized oocytes. Dev Biol 2016; 417:63-76. [DOI: 10.1016/j.ydbio.2016.06.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 06/16/2016] [Accepted: 06/24/2016] [Indexed: 01/15/2023]
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7
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Cross-talk between signaling and metabolism in the vasculature. Vascul Pharmacol 2016; 83:4-9. [PMID: 27291139 DOI: 10.1016/j.vph.2016.06.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/01/2016] [Accepted: 06/04/2016] [Indexed: 12/16/2022]
Abstract
The link between signaling and metabolism was first recognized with insulin signal transduction. Efficient glucose uptake by the endothelium requires insulin receptor activation to deliver GLUT receptors to the cell surface. More recently however, additional evidence has emerged for a broader crosstalk as signaling events have been shown to regulate a large number of metabolic enzymes. Changes in the metabolic status of endothelial and smooth muscle cells are observed at times of increased proliferative activity and these coincide with activation of cell surface receptors. Intriguingly, a rise in glycolysis appears to be associated with remodeling of the actin cytoskeleton during migration and angiogenesis. Overall, understanding how do signaling and metabolic pathways intersect and cross-regulate each other has become an important question and an emerging cornerstone in vascular biology.
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8
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Oliveira AC, Andreotti S, Chimin P, Sertié RAL, Farias TDSM, Torres-Leal FL, de Proença ARG, Campaña AB, D'Avila LSP, Oliveira KA, Lima FB. Neonatal streptozotocin-induced diabetes in mothers promotes metabolic programming of adipose tissue in male rat offspring. Life Sci 2015; 136:151-6. [PMID: 26144624 DOI: 10.1016/j.lfs.2015.06.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 06/02/2015] [Accepted: 06/30/2015] [Indexed: 12/26/2022]
Abstract
AIMS Maternal hyperglycemia during pregnancy can lead to fetal changes, like macrosomia or obesity in adultlife. Experimentalmodels of diabetes have been studied to evaluate the consequences of offspring lipidmetabolism. This study aimed to investigate the metabolic changes in adipose tissue of offspring of streptozotocininduced diabetic mothers during neonatal period. MAIN METHODS Diabetes was induced in female rats by streptozotocin administration on 5th day of life. In adulthood, female rats were bred with control male rats. Male puppies were sacrificed on 12th week of life and epididymal (EP) and subcutaneous (SC) adipose fat pads were excised and weighted. Adipocytes were isolated and evaluated for basal and insulin-stimulated 2-deoxyglucose uptake, oxidation of glucose into CO2, and incorporationof glucose into lipids and lipolytic capacity. KEY FINDINGS Bodyweight, EP fat padweight and diameter of adipocytes fromoffspring of diabeticmothers were increased in comparison to offspring of control mothers. EP adipocytes from offspring of diabetic mothers presented increased basal and insulin stimulated glucose uptake in comparison to control ones. Similar pattern was observed for glucose oxidation into CO2 and incorporation into lipids. However, significant difference in lipolytic capacity in vitrowas not observed. Protein content of GLUT4, insulin receptor and acetyl-CoA carboxylase was significantly increased in EP fat pad of offspring of diabetic mothers in relation to control group. SIGNIFICANCE Metabolic programming occurred in the adipose tissue of offspring of diabetic mothers, increasing its capacity to store lipids with no changes in lipolytic capacity.
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Affiliation(s)
- Ariclécio C Oliveira
- Superior Institute of Biomedical Sciences, State University of Ceará, Brazil; Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil.
| | - Sandra Andreotti
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | - Patricia Chimin
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | - Rogério A L Sertié
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | - Talita da S M Farias
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | - Francisco L Torres-Leal
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil; Department of Biophysics and Physiology, Federal University of Piauí, Brazil
| | - André R G de Proença
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | - Amanda B Campaña
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
| | | | - Keciany A Oliveira
- Superior Institute of Biomedical Sciences, State University of Ceará, Brazil
| | - Fábio B Lima
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil
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Hu S, Chang Y, He M, Wang J, Wang Y, Xue C. Fucosylated chondroitin sulfate from sea cucumber improves insulin sensitivity via activation of PI3K/PKB pathway. J Food Sci 2015; 79:H1424-9. [PMID: 25041539 DOI: 10.1111/1750-3841.12465] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 01/22/2014] [Indexed: 12/23/2022]
Abstract
This study was to investigate the effects of fucosylated chondroitin sulfate (CHS) from sea cucumber on insulin sensitivity in skeletal muscle of type 2 diabetic mice induced by a high-fat high-sucrose diet (HFSD). CHS supplementation for 19 wk significantly improved insulin sensitivity by 20%, and reduced blood glucose and insulin levels. Western blotting assay showed that CHS significantly increased insulin-stimulated glucose transporter 4 (GLUT4) translocation to 1.7-fold, phosphorylation of phosphoinositide 3-kinase (PI3K) at p85 to 5.0-fold, protein kinase B (PKB) at Ser473 to 1.5-fold, and Thr308 to 1.6-fold in skeletal muscle. However, PI3K, PKB, and GLUT4 total proteins expression were unchangeable. In addition, qRT-PCR analysis proved that the insulin signaling was activated by CHS treatment, showing the increased mRNA expressions of glucose uptake-related key genes. It indicated that CHS improved insulin sensitivity by activation of PI3K/PKB signaling in skeletal muscle of type 2 diabetic mice. Identification of potential mechanism by which CHS increased insulin sensitivity might provide a new functional food or pharmaceutical application of sea cucumber.
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Affiliation(s)
- Shiwei Hu
- Authors are with College of Food Science and Engineering, Ocean Univ. of China, No.5, Yu Shan Rd., Qingdao, Shandong Province 266003, China
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Llanos P, Contreras-Ferrat A, Georgiev T, Osorio-Fuentealba C, Espinosa A, Hidalgo J, Hidalgo C, Jaimovich E. The cholesterol-lowering agent methyl-β-cyclodextrin promotes glucose uptake via GLUT4 in adult muscle fibers and reduces insulin resistance in obese mice. Am J Physiol Endocrinol Metab 2015; 308:E294-305. [PMID: 25491723 DOI: 10.1152/ajpendo.00189.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Insulin stimulates glucose uptake in adult skeletal muscle by promoting the translocation of GLUT4 glucose transporters to the transverse tubule (T-tubule) membranes, which have particularly high cholesterol levels. We investigated whether T-tubule cholesterol content affects insulin-induced glucose transport. Feeding mice a high-fat diet (HFD) for 8 wk increased by 30% the T-tubule cholesterol content of triad-enriched vesicular fractions from muscle tissue compared with triads from control mice. Additionally, isolated muscle fibers (flexor digitorum brevis) from HFD-fed mice showed a 40% decrease in insulin-stimulated glucose uptake rates compared with fibers from control mice. In HFD-fed mice, four subcutaneous injections of MβCD, an agent reported to extract membrane cholesterol, improved their defective glucose tolerance test and normalized their high fasting glucose levels. The preincubation of isolated muscle fibers with relatively low concentrations of MβCD increased both basal and insulin-induced glucose uptake in fibers from controls or HFD-fed mice and decreased Akt phosphorylation without altering AMPK-mediated signaling. In fibers from HFD-fed mice, MβCD improved insulin sensitivity even after Akt or CaMK II inhibition and increased membrane GLUT4 content. Indinavir, a GLUT4 antagonist, prevented the stimulatory effects of MβCD on glucose uptake. Addition of MβCD elicited ryanodine receptor-mediated calcium signals in isolated fibers, which were essential for glucose uptake. Our findings suggest that T-tubule cholesterol content exerts a critical regulatory role on insulin-stimulated GLUT4 translocation and glucose transport and that partial cholesterol removal from muscle fibers may represent a useful strategy to counteract insulin resistance.
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Affiliation(s)
- Paola Llanos
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile;
| | - Ariel Contreras-Ferrat
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile
| | - Tihomir Georgiev
- Medical Biophysics, Institute of Physiology und Pathophysiology, Ruprecht Karls Universität, Heidelberg, Germany
| | | | - Alejandra Espinosa
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Jorge Hidalgo
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Physiology and Biophysics Program, Institute of Biomedical Sciences (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Cecilia Hidalgo
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Physiology and Biophysics Program, Institute of Biomedical Sciences (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile; Biomedical Neuroscience Institute, Facultad de Medicina, Universidad de Chile, Santiago, Chile; and
| | - Enrique Jaimovich
- Center for Molecular Studies of the Cell, Facultad de Medicina, Universidad de Chile, Santiago, Chile; Cell and Molecular Biology Program, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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11
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Al Koborssy D, Palouzier-Paulignan B, Salem R, Thevenet M, Romestaing C, Julliard AK. Cellular and molecular cues of glucose sensing in the rat olfactory bulb. Front Neurosci 2014; 8:333. [PMID: 25400540 PMCID: PMC4212682 DOI: 10.3389/fnins.2014.00333] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 10/03/2014] [Indexed: 11/13/2022] Open
Abstract
In the brain, glucose homeostasis of extracellular fluid is crucial to the point that systems specifically dedicated to glucose sensing are found in areas involved in energy regulation and feeding behavior. Olfaction is a major sensory modality regulating food consumption. Nutritional status in turn modulates olfactory detection. Recently it has been proposed that some olfactory bulb (OB) neurons respond to glucose similarly to hypothalamic neurons. However, the precise molecular cues governing glucose sensing in the OB are largely unknown. To decrypt these molecular mechanisms, we first used immunostaining to demonstrate a strong expression of two neuronal markers of glucose-sensitivity, insulin-dependent glucose transporter type 4 (GLUT4), and sodium glucose co-transporter type 1 (SGLT1) in specific OB layers. We showed that expression and mapping of GLUT4 but not SGLT1 were feeding state-dependent. In order to investigate the impact of metabolic status on the delivery of blood-borne glucose to the OB, we measured extracellular fluid glucose concentration using glucose biosensors simultaneously in the OB and cortex of anesthetized rats. We showed that glucose concentration in the OB is higher than in the cortex, that metabolic steady-state glucose concentration is independent of feeding state in the two brain areas, and that acute changes in glycemic conditions affect bulbar glucose concentration alone. These data provide new evidence of a direct relationship between the OB and peripheral metabolism, and emphasize the importance of glucose for the OB network, providing strong arguments toward establishing the OB as a glucose-sensing organ.
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Affiliation(s)
- Dolly Al Koborssy
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Brigitte Palouzier-Paulignan
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Rita Salem
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Marc Thevenet
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Caroline Romestaing
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés CNRS 5023, University Lyon 1, Bâtiments Darwin C and Forel Villeurbanne, France
| | - A Karyn Julliard
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
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12
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Zhao K, Liu HY, Zhao FQ, Liu JX. Short communication: Protein kinase C regulates glucose uptake and mRNA expression of glucose transporter (GLUT) 1 and GLUT8 in lactating bovine mammary epithelial cells. J Dairy Sci 2014; 97:4329-32. [DOI: 10.3168/jds.2013-7848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/20/2014] [Indexed: 01/18/2023]
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13
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Eicosapentaenoic acid-enriched phosphatidylcholine isolated from Cucumaria frondosa exhibits anti-hyperglycemic effects via activating phosphoinositide 3-kinase/protein kinase B signal pathway. J Biosci Bioeng 2014; 117:457-63. [DOI: 10.1016/j.jbiosc.2013.09.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 09/10/2013] [Accepted: 09/10/2013] [Indexed: 12/20/2022]
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14
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Jensen VFH, Bøgh IB, Lykkesfeldt J. Effect of insulin-induced hypoglycaemia on the central nervous system: evidence from experimental studies. J Neuroendocrinol 2014; 26:123-50. [PMID: 24428753 DOI: 10.1111/jne.12133] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 12/13/2013] [Accepted: 01/08/2014] [Indexed: 12/12/2022]
Abstract
Insulin-induced hypoglycaemia (IIH) is a major acute complication in type 1 as well as in type 2 diabetes, particularly during intensive insulin therapy. The brain plays a central role in the counter-regulatory response by eliciting parasympathetic and sympathetic hormone responses to restore normoglycaemia. Brain glucose concentrations, being approximately 15-20% of the blood glucose concentration in humans, are rigorously maintained during hypoglycaemia through adaptions such as increased cerebral glucose transport, decreased cerebral glucose utilisation and, possibly, by using central nervous system glycogen as a glucose reserve. However, during sustained hypoglycaemia, the brain cannot maintain a sufficient glucose influx and, as the cerebral hypoglycaemia becomes severe, electroencephalogram changes, oxidative stress and regional neuronal death ensues. With particular focus on evidence from experimental studies on nondiabetic IIH, this review outlines the central mechanisms behind the counter-regulatory response to IIH, as well as cerebral adaption to avoid sequelae of cerebral neuroglycopaenia, including seizures and coma.
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Affiliation(s)
- V F H Jensen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Diabetes Toxicology and Safety Pharmacology, Novo Nordisk A/S, Maaloev, Denmark
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15
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Liu W, Zhao J. Insights into the molecular mechanism of glucose metabolism regulation under stress in chicken skeletal muscle tissues. Saudi J Biol Sci 2014; 21:197-203. [PMID: 24955006 DOI: 10.1016/j.sjbs.2014.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/23/2014] [Accepted: 01/26/2014] [Indexed: 12/28/2022] Open
Abstract
As substantial progress has been achieved in modern poultry production with large-scale and intensive feeding and farming in recent years, stress becomes a vital factor affecting chicken growth, development, and production yield, especially the quality and quantity of skeletal muscle mass. The review was aimed to outline and understand the stress-related genetic regulatory mechanism, which significantly affects glucose metabolism regulation in chicken skeletal muscle tissues. Progress in current studies was summarized relevant to the molecular mechanism and regulatory pathways of glucose metabolism regulation under stress in chicken skeletal muscle tissues. Particularly, the elucidation of those concerned pathways promoted by insulin and insulin receptors would give key clues to the understanding of biological processes of stress response and glucose metabolism regulation under stress, as well as their later effects on chicken muscle development.
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Affiliation(s)
- Wuyi Liu
- Department of Biology Sciences, Fuyang Normal College, China ; Department of Science and Technology Research, Fuyang Normal College, China
| | - Jingpeng Zhao
- Department of Animal Sciences, Shandong Agricultural University, China
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16
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Saito T, Okada S, Nohara A, Tagaya Y, Osaki A, Oh-I S, Takahashi H, Tsuchiya T, Hashimoto K, Satoh T, Yamada M, Pessin JE, Mori M. Syntaxin4 interacting protein (Synip) binds phosphatidylinositol (3,4,5) triphosphate. PLoS One 2012; 7:e42782. [PMID: 22880106 PMCID: PMC3411842 DOI: 10.1371/journal.pone.0042782] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022] Open
Abstract
The insulin responsive Glut4 transport vesicles contain the v-SNARE protein Vamp2 that associate with the plasma membrane t-SNARE protein Syntaxin 4 to drive insulin-stimulated Glut4 translocation in skeletal muscle and adipocytes. The syntaxin 4 interacting protein (Synip) binds to syntaxin 4 in the basal state and dissociates in the insulin-stimulated state allowing for the subsequent binding of Vamp2 containing Glut4 vesicles and fusion with the plasma membrane. In this study, we have found that Synip binds phosphatidylinositol 3,4,5-triphosphate (PIP3), but not phosphatidylinositol 3 phosphate (PIP) or phosphatidylinositol 3,4-biphosphate (PIP2) through the Synip WW domain as deletion of this domain (Synip ΔWW) failed to bind PIP3. Over-expressed Synip ΔWW in 3T3L1 adipocytes reduced the basal levels of Glut4 at the plasma membrane with no effect on the binding to syntaxin 4 in vitro. Subcellular fractionation demonstrated that the amount of Synip ΔWW at the PM was decreased in response to insulin in 3T3L1 adipocytes whereas the amount of Synip WT increased. These data suggest that in the presence of insulin, the dissociated Synip remains anchored to the plasma membrane by binding to PIP3.
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Affiliation(s)
- Tsugumichi Saito
- Department of Medicine and Molecular science, Gunma University School of Medicine, Maebashi, Gunma, Japan.
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17
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Caliceti C, Zambonin L, Prata C, Vieceli Dalla Sega F, Hakim G, Hrelia S, Fiorentini D. Effect of plasma membrane cholesterol depletion on glucose transport regulation in leukemia cells. PLoS One 2012; 7:e41246. [PMID: 22859971 PMCID: PMC3408441 DOI: 10.1371/journal.pone.0041246] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 06/22/2012] [Indexed: 11/19/2022] Open
Abstract
GLUT1 is the predominant glucose transporter in leukemia cells, and the modulation of glucose transport activity by cytokines, oncogenes or metabolic stresses is essential for their survival and proliferation. However, the molecular mechanisms allowing to control GLUT1 trafficking and degradation are still under debate. In this study we investigated whether plasma membrane cholesterol depletion plays a role in glucose transport activity in M07e cells, a human megakaryocytic leukemia line. To this purpose, the effect of cholesterol depletion by methyl-β-cyclodextrin (MBCD) on both GLUT1 activity and trafficking was compared to that of the cytokine Stem Cell Factor (SCF). Results show that, like SCF, MBCD led to an increased glucose transport rate and caused a subcellular redistribution of GLUT1, recruiting intracellular transporter molecules to the plasma membrane. Due to the role of caveolae/lipid rafts in GLUT1 stimulation in response to many stimuli, we have also investigated the GLUT1 distribution along the fractions obtained after non ionic detergent treatment and density gradient centrifugation, which was only slightly changed upon MBCD treatment. The data suggest that MBCD exerts its action via a cholesterol-dependent mechanism that ultimately results in augmented GLUT1 translocation. Moreover, cholesterol depletion triggers GLUT1 translocation without the involvement of c-kit signalling pathway, in fact MBCD effect does not involve Akt and PLCγ phosphorylation. These data, together with the observation that the combined MBCD/SCF cell treatment caused an additive effect on glucose uptake, suggest that the action of SCF and MBCD may proceed through two distinct mechanisms, the former following a signalling pathway, and the latter possibly involving a novel cholesterol dependent mechanism.
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Affiliation(s)
- Cristiana Caliceti
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Laura Zambonin
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Cecilia Prata
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | | | - Gabriele Hakim
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Silvana Hrelia
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Diana Fiorentini
- Biochemistry Department “G. Moruzzi”, Alma Mater Studiorum-University of Bologna, Bologna, Italy
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18
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de Oliveira AC, Andreotti S, Farias TDSM, Torres-Leal FL, de Proença ARG, Campaña AB, de Souza AH, Sertié RAL, Carpinelli AR, Cipolla-Neto J, Lima FB. Metabolic disorders and adipose tissue insulin responsiveness in neonatally STZ-induced diabetic rats are improved by long-term melatonin treatment. Endocrinology 2012; 153:2178-88. [PMID: 22374967 DOI: 10.1210/en.2011-1675] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Diabetes mellitus is a product of low insulin sensibility and pancreatic β-cell insufficiency. Rats with streptozotocin-induced diabetes during the neonatal period by the fifth day of age develop the classic diabetic picture of hyperglycemia, hypoinsulinemia, polyuria, and polydipsia aggravated by insulin resistance in adulthood. In this study, we investigated whether the effect of long-term treatment with melatonin can improve insulin resistance and other metabolic disorders in these animals. At the fourth week of age, diabetic animals started an 8-wk treatment with melatonin (1 mg/kg body weight) in the drinking water at night. Animals were then killing, and the sc, epididymal (EP), and retroperitoneal (RP) fat pads were excised, weighed, and processed for adipocyte isolation for morphometric analysis as well as for measuring glucose uptake, oxidation, and incorporation of glucose into lipids. Blood samples were collected for biochemical assays. Melatonin treatment reduced hyperglycemia, polydipsia, and polyphagia as well as improved insulin resistance as demonstrated by constant glucose disappearance rate and homeostasis model of assessment-insulin resistance. However, melatonin treatment was unable to recover body weight deficiency, fat mass, and adipocyte size of diabetic animals. Adiponectin and fructosamine levels were completely recovered by melatonin, whereas neither plasma insulin level nor insulin secretion capacity was improved in diabetic animals. Furthermore, melatonin caused a marked delay in the sexual development, leaving genital structures smaller than those of nontreated diabetic animals. Melatonin treatment improved the responsiveness of adipocytes to insulin in diabetic animals measured by tests of glucose uptake (sc, EP, and RP), glucose oxidation, and incorporation of glucose into lipids (EP and RP), an effect that seems partially related to an increased expression of insulin receptor substrate 1, acetyl-coenzyme A carboxylase and fatty acid synthase. In conclusion, melatonin treatment was capable of ameliorating the metabolic abnormalities in this particular diabetes model, including insulin resistance and promoting a better long-term glycemic control.
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Affiliation(s)
- Ariclécio C de Oliveira
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará 60135-420, Brazil
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Subcellular trafficking of the substrate transporters GLUT4 and CD36 in cardiomyocytes. Cell Mol Life Sci 2011; 68:2525-38. [PMID: 21547502 PMCID: PMC3134709 DOI: 10.1007/s00018-011-0690-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 04/01/2011] [Accepted: 04/12/2011] [Indexed: 12/16/2022]
Abstract
Cardiomyocytes use glucose as well as fatty acids for ATP production. These substrates are transported into the cell by glucose transporter 4 (GLUT4) and the fatty acid transporter CD36. Besides being located at the sarcolemma, GLUT4 and CD36 are stored in intracellular compartments. Raised plasma insulin concentrations and increased cardiac work will stimulate GLUT4 as well as CD36 to translocate to the sarcolemma. As so far studied, signaling pathways that regulate GLUT4 translocation similarly affect CD36 translocation. During the development of insulin resistance and type 2 diabetes, CD36 becomes permanently localized at the sarcolemma, whereas GLUT4 internalizes. This juxtaposed positioning of GLUT4 and CD36 is important for aberrant substrate uptake in the diabetic heart: chronically increased fatty acid uptake at the expense of glucose. To explain the differences in subcellular localization of GLUT4 and CD36 in type 2 diabetes, recent research has focused on the role of proteins involved in trafficking of cargo between subcellular compartments. Several of these proteins appear to be similarly involved in both GLUT4 and CD36 translocation. Others, however, have different roles in either GLUT4 or CD36 translocation. These trafficking components, which are differently involved in GLUT4 or CD36 translocation, may be considered novel targets for the development of therapies to restore the imbalanced substrate utilization that occurs in obesity, insulin resistance and diabetic cardiomyopathy.
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20
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Nomura T, Horikawa M, Shimamura S, Hashimoto T, Sakamoto K. Fat accumulation in Caenorhabditis elegans is mediated by SREBP homolog SBP-1. GENES AND NUTRITION 2009; 5:17-27. [PMID: 19936816 DOI: 10.1007/s12263-009-0157-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 10/22/2009] [Indexed: 11/30/2022]
Abstract
Research into the metabolism of fats may reveal potential targets for developing pharmaceutical approaches to obesity and related disorders. Such research may be limited, however, by the cost and time involved in using mammalian subjects or developing suitable cell lines. To determine whether invertebrates could be used to carry out such research more efficiently, we investigated the ability of Caenorhabditis elegans (C. elegans) to accumulate body fat following the consumption of excess calories and the mechanisms it uses to metabolize fat. C. elegans worms were grown on media containing various sugars and monitored for changes in body fat and expression of sbp-1, a homolog of the mammalian transcription factor SREBP-1c, which facilitates fat storage in mammals. The fat content increased markedly in worms exposed to glucose. In situ analysis of gene expression in transgenic worms carrying the GFP-labeled promoter region of sbp-1 revealed that sbp-1 mRNA was strongly expressed in the intestine. An sbp-1 knockdown caused a reduction in body size, fat storage, and egg-laying activity. RT-PCR analysis revealed a considerable decrease in the expression of fatty acid synthetic genes (including elo-2, fat-2, and fat-5) and a considerable increase of starvation-inducible gene acs-2. Normal egg-laying activity and acs-2 expression were restored on exposure to a polyunsaturated fatty acid. These findings suggest that SBP-1 and SREBP regulate the amount and composition of fat and response to starvation in a similar manner. Thus, C. elegans may be an appropriate subject for studying the metabolism of fats.
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Affiliation(s)
- Toshihisa Nomura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki Japan
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21
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Cook SA, Varela-Carver A, Mongillo M, Kleinert C, Khan MT, Leccisotti L, Strickland N, Matsui T, Das S, Rosenzweig A, Punjabi P, Camici PG. Abnormal myocardial insulin signalling in type 2 diabetes and left-ventricular dysfunction. Eur Heart J 2009; 31:100-11. [PMID: 19797329 DOI: 10.1093/eurheartj/ehp396] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
AIMS Whole body and myocardial insulin resistance are features of non-insulin-dependent diabetes mellitus (NIDDM) and left-ventricular dysfunction (LVD). We determined whether abnormalities of insulin receptor substrate-1 (IRS1), IRS1-associated PI3K (IRS1-PI3K), and glucose transporter 4 (GLUT4) contribute to tissue-specific insulin resistance. METHODS AND RESULTS We collected skeletal muscle (n = 27) and myocardial biopsies (n = 24) from control patients (n = 7), patients with NIDDM (n = 9) and patients with LVD (n = 8), who were characterized by euglycaemic-hyperinsulinaemic clamp and positron emission tomography. Comparative studies were carried out in three mouse models. We demonstrate an unrecognized reduction of IRS1 in skeletal muscle of LVD patients and an unexpected increase in cardiac IRS1-PI3K activity in NIDDM and LVD patients. In NIDDM, there was a concomitant reduction in sarcolemmal GLUT4, whereas in patients with LVD sarcolemmal GLUT4 was increased. We confirm activation of IRS1-PI3K and reduction in sarcolemmal GLUT4 in the insulin resistant ob/ob mouse heart where we also demonstrate perturbation of GLUT4 docking and fusion. A direct relationship between PI3K and GLUT4 was demonstrated in mice expressing activated PI3K in the heart and increased GLUT4 at the sarcolemma was confirmed in a mouse model of LVD. CONCLUSION Our data show that the mechanisms of myocardial insulin resistance are different between NIDDM and LVD.
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Affiliation(s)
- Stuart A Cook
- Medical Research Council Clinical Sciences Centre, Imperial College, Hammersmith Hospital Campus, London W12 0NN, UK
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22
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Bernhardt U, Carlotti F, Hoeben RC, Joost HG, Al-Hasani H. A dual role of the N-terminal FQQI motif in GLUT4 trafficking. Biol Chem 2009; 390:883-92. [DOI: 10.1515/bc.2009.095] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
AbstractIn adipocytes, the glucose transporter GLUT4 recycles between intracellular storage vesicles and the plasma membrane. GLUT4 is internalized by a clathrin- and dynamin-dependent mechanism, and sorted into an insulin-sensitive storage compartment. Insulin stimulation leads to GLUT4 accumulation on the cell surface. The N-terminal F5QQI motif in GLUT4 has been shown previously to be required for sorting of the protein in the basal state. Here, we show that the FQQI motif is a binding site for the medium chain adaptin μ1, a subunit of the AP-1 adaptor complex that plays a role in post-Golgi/endosomal trafficking events. In order to investigate the role of AP-1 and AP-2 in GLUT4 trafficking, we generated 3T3-L1 adipocytes expressing HA-GLUT4-GFP and knocked down the AP-1 and AP-2 complex by RNAi, respectively. In AP-1 and AP-2 knockdown adipocytes, GLUT4 accumulates at the cell surface in the basal state, consistent with a role of AP-1 in post-endosomal sorting of GLUT4 to the insulin-sensitive storage compartment, and of AP-2 in clathrin-mediated endocytosis. Our data demonstrate a dual role of the F5QQI motif and support the conclusion that the AP complexes direct GLUT4 trafficking and endocytosis.
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23
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Hou JC, Williams D, Vicogne J, Pessin JE. The glucose transporter 2 undergoes plasma membrane endocytosis and lysosomal degradation in a secretagogue-dependent manner. Endocrinology 2009; 150:4056-64. [PMID: 19477941 PMCID: PMC2736072 DOI: 10.1210/en.2008-1685] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In beta-cells of the pancreas, the glucose transporter (GLUT)-2 facilitative glucose transporter protein is localized to the plasma membrane and functions as part of the glucose sensing mechanism for the stimulation of insulin secretion. We observed that expressed GLUT2 protein in the cultured Min6B1 cell line undergoes enhanced endocytosis at high extracellular glucose concentrations that stimulate insulin secretion. Moreover, the internalized GLUT2 protein undergoes rapid degradation induced by chronic high-glucose or arginine stimulation but does not undergo plasma membrane recycling or accumulation in any microscopically apparent intracellular membrane compartment. The rapid degradation of GLUT2 was prevented by lysosomal inhibition (chloroquine) concomitant with the accumulation of GLUT2 in endomembrane structures. In contrast, neither endocytosis nor the lack of internal membrane localized GLUT2 remained completely unaffected by proteosomal inhibition (lactacystin) or an heat shock protein-90 inhibitor (geldanamycin). Moreover, the endocytosis and degradation of GLUT2 was specific for beta-cells because expression of GLUT2 in 3T3L1 adipocytes remained cell surface localized and did not display a rapid rate of degradation. Together, these data demonstrate that hyperglycemia directly affects beta-cell function and activates a trafficking pathway that results in the rapid endocytosis and degradation of the cell surface GLUT2 glucose transporter.
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Phospholipase D1 regulates lymphocyte adhesion via upregulation of Rap1 at the plasma membrane. Mol Cell Biol 2009; 29:3297-306. [PMID: 19332557 DOI: 10.1128/mcb.00366-09] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rap1 is a small GTPase that modulates adhesion of T cells by regulating inside-out signaling through LFA-1. The bulk of Rap1 is expressed in a GDP-bound state on intracellular vesicles. Exocytosis of these vesicles delivers Rap1 to the plasma membrane, where it becomes activated. We report here that phospholipase D1 (PLD1) is expressed on the same vesicular compartment in T cells as Rap1 and is translocated to the plasma membrane along with Rap1. Moreover, PLD activity is required for both translocation and activation of Rap1. Increased T-cell adhesion in response to stimulation of the antigen receptor depended on PLD1. C3G, a Rap1 guanine nucleotide exchange factor located in the cytosol of resting cells, translocated to the plasma membranes of stimulated T cells. Our data support a model whereby PLD1 regulates Rap1 activity by controlling exocytosis of a stored, vesicular pool of Rap1 that can be activated by C3G upon delivery to the plasma membrane.
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Hommelberg PPH, Plat J, Langen RCJ, Schols AMWJ, Mensink RP. Fatty acid-induced NF-kappaB activation and insulin resistance in skeletal muscle are chain length dependent. Am J Physiol Endocrinol Metab 2009; 296:E114-20. [PMID: 18957619 DOI: 10.1152/ajpendo.00436.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The saturated fatty acid (SFA) palmitate induces insulin resistance in cultured skeletal muscle cells, which may be related to NF-kappaB activation. The aim of this study was to evaluate whether other SFAs also exert these effects on skeletal muscle and whether these relate to chain length. Therefore, we incubated L6 and C(2)C(12) skeletal muscle cells with four different fatty acids, caprylate (C8:0), laurate (C12:0), palmitate (C16:0), and stearate (C18:0), to study effects on GLUT4 translocation, deoxyglucose uptake, and NF-kappaB activation. Incubation of L6 cells with the long-chain FAs C16:0 and C18:0 reduced insulin-stimulated GLUT4 translocation and deoxyglucose uptake, whereas L6 cells incubated with the medium-chain FAs C8:0 and C12:0 remained insulin sensitive. Besides increasing NF-kappaB DNA binding activity in both L6 and C(2)C(12) cells, C16:0 also induced NF-kappaB transcriptional activity. C18:0 showed comparable effects, whereas the SFAs with shorter chain lengths were not able to elevate NF-kappaB transcriptional activity. Collectively, these results demonstrate that SFA-induced NF-kappaB activation coincides with insulin resistance and depends on FA chain length.
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Affiliation(s)
- Pascal P H Hommelberg
- Maastricht University, Dept. of Human Biology, P. O. Box 616, 6200 MD, Maastricht, The Netherlands
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26
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Kwon S, Kim YJ, Kim MK. Effect of fructose or sucrose feeding with different levels on oral glucose tolerance test in normal and type 2 diabetic rats. Nutr Res Pract 2008; 2:252-8. [PMID: 20016727 PMCID: PMC2788191 DOI: 10.4162/nrp.2008.2.4.252] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 11/24/2008] [Accepted: 12/08/2008] [Indexed: 01/09/2023] Open
Abstract
This study was designed to determine whether acute fructose or sucrose administration at different levels (0.05 g/kg, 0.1 g/kg or 0.4 g/kg body weight) might affect oral glucose tolerance test (OGTT) in normal and type 2 diabetic rats. In OGTT, there were no significant differences in glucose responses between acute fructose- and sucrose-administered groups. However, in normal rats, the AUCs of the blood glucose response for the fructose-administered groups tended to be lower than those of the control and sucrose-administered groups. The AUCs of the lower levels fructoseor sucrose-administered groups tended to be smaller than those of higher levels fructose- or sucrose-administered groups. In type 2 diabetic rats, only the AUC of the lowest level of fructose-administered (0.05 g/kg body weight) group was slightly smaller than that of the control group. The AUCs of fructose-administered groups tended to be smaller than those of the sucrose-administered groups, and the AUCs of lower levels fructose-administered groups tended to be smaller than those fed higher levels of fructose. We concluded from this experiment that fructose has tendency to be more effective in blood glucose regulation than sucrose, and moreover, that smaller amount of fructose is preferred to larger amount. Specifically, our experiments indicated that the fructose level of 0.05 g/kg body weight as dietary supplement was the most effective amount for blood glucose regulation from the pool of 0.05 g/kg, 0.1 g/kg and 0.4 g/kg body weights. Therefore, our results suggest the use of fructose as the substitute sweetener for sucrose, which may be beneficial for blood glucose regulation.
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Affiliation(s)
- Sanghee Kwon
- Department of Food and Nutritional Sciences, Ewha Womans University, 11-1 Daehyung-dong, Seodaemun-gu, Seoul 120-750, Korea
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27
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Garcia-Souza EP, da Silva SV, Félix GB, Rodrigues AL, de Freitas MS, Moura AS, Barja-Fidalgo C. Maternal protein restriction during early lactation induces GLUT4 translocation and mTOR/Akt activation in adipocytes of adult rats. Am J Physiol Endocrinol Metab 2008; 295:E626-36. [PMID: 18559980 DOI: 10.1152/ajpendo.00439.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epidemiological and experimental studies have demonstrated that early postnatal nutrition has been associated with long-term effects on glucose homeostasis in adulthood. Recently, our group demonstrated that undernutrition during early lactation affects the expression and activation of key proteins of the insulin signaling cascade in rat skeletal muscle during postnatal development. To elucidate the molecular mechanisms by which undernutrition during early life leads to changes in insulin sensitivity in peripheral tissues, we investigated the insulin signaling in adipose tissue. Adipocytes were isolated from epididymal fat pads of adult male rats that were the offspring of dams fed either a normal or a protein-free diet during the first 10 days of lactation. The cells were incubated with 100 nM insulin before the assays for immunoblotting analysis, 2-deoxyglucose uptake, immunocytochemistry for GLUT4, and/or actin filaments. Following insulin stimulation, adipocytes isolated from undernourished rats presented reduced tyrosine phosphorylation of IR and IRS-1 and increased basal phosphorylation of IRS-2, Akt, and mTOR compared with controls. Basal glucose uptake was increased in adipocytes from the undernourished group, and the treatment with LY294002 induced only a partial inhibition both in basal and in insulin-stimulated glucose uptake, suggesting an involvement of phosphoinositide 3-kinase activity. These alterations were accompanied by higher GLUT4 content in the plasma membrane and alterations in the actin cytoskeleton dynamics. These data suggest that early postnatal undernutrition impairs insulin sensitivity in adulthood by promoting changes in critical steps of insulin signaling in adipose tissue, which may contribute to permanent changes in glucose homeostasis.
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Affiliation(s)
- Erica Patrícia Garcia-Souza
- Departament of Pharmacology, Institute of Biology, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, 20551-030, Brasil
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Wang PH, Tsai MJ, Hsu CY, Wang CY, Hsu HK, Weng CF. Toona sinensis Roem (Meliaceae) leaf extract alleviates hyperglycemia via altering adipose glucose transporter 4. Food Chem Toxicol 2008; 46:2554-60. [DOI: 10.1016/j.fct.2008.04.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 02/12/2008] [Accepted: 04/09/2008] [Indexed: 11/25/2022]
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Glucose regulation in birds. Comp Biochem Physiol B Biochem Mol Biol 2008; 151:1-9. [PMID: 18571448 DOI: 10.1016/j.cbpb.2008.05.007] [Citation(s) in RCA: 201] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 11/20/2022]
Abstract
Birds maintain higher plasma glucose concentrations (P(Glu)) than other vertebrates of similar body mass and, in most cases, appear to store comparatively very little glucose intracellularly as glycogen. In general, birds are insensitive to the regulation of P(Glu) by insulin. However, there appears to be no phylogenetic or dietary pattern in the avian response to exogenous insulin. Moreover, the high levels of P(Glu) do not appear to lead to significant oxidative stress as birds are longer-lived compared to mammals. Glucose is absorbed by the avian gastrointestinal tract by sodium-glucose co-transporters (SGLTs; apical side of cells) and glucose transport proteins (GLUTs; basolateral side of cells). In the kidney, both types of glucose transporters appear to be upregulated as no glucose appears in the urine. Data also indicate that the avian nervous system utilizes glucose as a metabolic substrate. In this review, we have attempted to bring together information from a variety of sources to portray how glucose serves as a metabolic substrate for birds by considering each organ system involved in glucose homeostasis.
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Diamanti-Kandarakis E, Argyrakopoulou G, Economou F, Kandaraki E, Koutsilieris M. Defects in insulin signaling pathways in ovarian steroidogenesis and other tissues in polycystic ovary syndrome (PCOS). J Steroid Biochem Mol Biol 2008; 109:242-6. [PMID: 18440223 DOI: 10.1016/j.jsbmb.2008.03.014] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age today. Women with PCOS often demonstrate defective ovarian steroid biosynthesis and present with hyperandrogenemia. Moreover, 50-70% of PCOS women are insulin resistant and hyperinsulinemic. Insulin acts on the ovary via its own receptor and interacts with gonadotrophins, modulating steroidogenesis. The precise role of insulin and the molecular mechanisms that take place are not yet completely explicated. This review will be focused on insulin's action on the ovary and other target tissues, describing the intracellular signaling pathways implicated in steroidogenesis and their defects in women with PCOS.
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Affiliation(s)
- Evanthia Diamanti-Kandarakis
- Endocrine Section, First Department of Internal Medicine, University of Athens Medical School, 17 Ag. Thoma, Goudi 11527, Athens, Greece.
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31
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Yuan T, Hong S, Yao Y, Liao K. Glut-4 is translocated to both caveolae and non-caveolar lipid rafts, but is partially internalized through caveolae in insulin-stimulated adipocytes. Cell Res 2008; 17:772-82. [PMID: 17846641 DOI: 10.1038/cr.2007.73] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Caveolae and non-caveolar lipid rafts are two types of membrane lipid microdomains that play important roles in insulin-stimulated glucose uptake in adipocytes. In order to ascertain their specific functions in this process, caveolae were ablated by caveolin-1 RNA interference. In Cav-1 RNAi adipocytes, neither insulin-stimulated glucose uptake nor Glut-4 (glucose transporter 4) translocation to membrane lipid microdomains was affected by the ablation of caveolae. With a modified sucrose density gradient, caveolae and non-caveolar lipid rafts could be separated. In the wild-type 3T3-L1 adipocytes, Glut-4 was found to be translocated into both caveolae and non-caveolar lipid rafts. However, in Cav-1 RNAi adipocytes, Glut-4 was localized predominantly in non-caveolar lipid rafts. After the removal of insulin, caveolae-localized Glut-4 was internalized faster than non-caveolar lipid raft-associated Glut-4. The internalization of Glut-4 from plasma membrane was significantly decreased in Cav-1 RNAi adipocytes. These results suggest that insulin-stimulated Glut-4 translocation and glucose uptake are caveolae-independent events. Caveolae play a role in the internalization of Glut-4 from plasma membrane after the removal of insulin.
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Affiliation(s)
- Taichang Yuan
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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32
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Abstract
One of the most important actions of insulin is the stimulation of the uptake of glucose into fat and muscle cells. Crucial to this response is the translocation of GLUT4 (glucose transporter-4) to the plasma membrane. The insulin-stimulated GLUT4 vesicle docking at the plasma membrane requires an interaction between VAMP-2 (vesicle-associated membrane protein-2) on the GLUT4 vesicle and syntaxin-4 in the plasma membrane. In the basal state, munc18c is thought to preclude GLUT4 vesicle docking by inhibiting this interaction. Here, we have used FCS (fluorescence correlation spectroscopy) in single living cells to show that munc18c binds to syntaxin-4 in both the basal and insulin-stimulated states. We show that munc18c contains two binding sites for syntaxin-4, one of which is disrupted by insulin, while the other is activated by insulin. Insulin-triggered repositioning of munc18c on syntaxin-4 in this way in turn allows syntaxin-4 to adopt its 'open' conformation and bind VAMP-2, resulting in the docking of the GLUT4 vesicle at the cell surface. The results also demonstrate the utility of using FCS in intact single living cells to elucidate cell signalling events.
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Lorenzo M, Fernández-Veledo S, Vila-Bedmar R, Garcia-Guerra L, De Alvaro C, Nieto-Vazquez I. Insulin resistance induced by tumor necrosis factor-alpha in myocytes and brown adipocytes. J Anim Sci 2007; 86:E94-104. [PMID: 17940160 DOI: 10.2527/jas.2007-0462] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Insulin resistance is an important contributor to the pathogenesis of type 2 diabetes, and obesity is a risk factor for its development, in part because adipose tissue secretes proteins, called adipokines, that may influence insulin sensitivity. Among these molecules, tumor necrosis factor (TNF)-alpha has been proposed as a link between obesity and insulin resistance because TNF-alpha is overexpressed in adipose tissues of obese animals and humans, and obese mice lacking either TNF-alpha or its receptor show protection against developing insulin resistance. Direct exposure to TNF-alpha induces a state of insulin resistance in terms of glucose uptake in myocytes and brown adipocytes because of the activation of proinflammatory pathways that impair insulin signaling at the level of the insulin receptor substrate (IRS) proteins. In this regard, the Ser(307) residue in IRS-1 has been identified as a site for the inhibitory effects of TNF-alpha in myotubes, with p38 mitogen-activated protein kinase and inhibitor kB kinase being involved in the phosphorylation of this residue. Conversely, Ser phosphorylation of IRS-2 mediated by TNF-alpha activation of mitogen-activated protein kinase was the mechanism found in brown adipocytes. Protein-Tyr phosphatase (PTP)1B acts as a physiological, negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of the insulin receptor and IRS-1, and PTP1B expression is increased in muscle and white adipose tissue of obese and diabetic humans and rodents. Moreover, up-regulation of PTP1B expression was recently found in cells treated with TNF-alpha Accordingly, myocytes and primary brown adipocytes deficient in PTP1B are protected against insulin resistance induced by this cytokine. Furthermore, down-regulation of PTP1B activity is possible by the use of pharmacological agonists of nuclear receptors that restore insulin sensitivity in the presence of TNF-alpha. In conclusion, the lack of PTP1B in muscle and brown adipocytes increases insulin sensitivity and glucose uptake and could confer protection against insulin resistance induced by adipokines.
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Affiliation(s)
- M Lorenzo
- Departamento de Bioquimica y Biologia Molecular II, Facultad de Farmacia, Universidad Complutense, 28040-Madrid, Spain.
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Roepke TA, Hamdoun AM, Cherr GN. Increase in multidrug transport activity is associated with oocyte maturation in sea stars. Dev Growth Differ 2007; 48:559-73. [PMID: 17118011 PMCID: PMC3159419 DOI: 10.1111/j.1440-169x.2006.00893.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we report on the presence of efflux transporter activity before oocyte maturation in sea stars and its upregulation after maturation. This activity is similar to the multidrug resistance (MDR) activity mediated by ATP binding cassette (ABC) efflux transporters. In sea star oocytes the efflux activity, as measured by exclusion of calcein-am, increased two-fold 3 h post-maturation. Experiments using specific and non-specific dyes and inhibitors demonstrated that the increase in transporter activity involves an ABCB protein, P-glycoprotein (P-gp), and an ABCC protein similar to the MDR-associated protein (MRP)-like transporters. Western blots using an antibody directed against mammalian P-gp recognized a 45 kDa protein in sea star oocytes that increased in abundance during maturation. An antibody directed against sea urchin ABCC proteins (MRP) recognized three proteins in immature oocytes and two in mature oocytes. Experiments using inhibitors suggest that translation and microtubule function are both required for post-maturation increases in transporter activity. Immunolabeling revealed translocation of stored ABCB proteins to the plasma cell membrane during maturation, and this translocation coincided with increased transport activity. These MDR transporters serve protective roles in oocytes and eggs, as demonstrated by sensitization of the oocytes to the maturation inhibitor, vinblastine, by MRP and PGP-specific transporter inhibitors.
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Affiliation(s)
- Troy A. Roepke
- Bodega Marine Laboratory, University of California Davis, Bodega Bay, California 94923, USA
| | - Amro M. Hamdoun
- Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, USA
| | - Gary N. Cherr
- Bodega Marine Laboratory, University of California Davis, Bodega Bay, California 94923, USA
- Departments of Environmental Toxicology and Nutrition, University of California Davis, Davis, California 95616, USA
- Author to whom all correspondence should be addressed.
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35
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Luiken JJFP, Momken I, Habets DDJ, El Hasnaoui M, Coumans WA, Koonen DPY, Glatz JFC, Bonen A. Arsenite modulates cardiac substrate preference by translocation of GLUT4, but not CD36, independent of mitogen-activated protein kinase signaling. Endocrinology 2006; 147:5205-16. [PMID: 17038550 DOI: 10.1210/en.2006-0849] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The protein thiol-modifying agent arsenite, a potent activator of stress signaling, was used to examine the involvement of MAPKs in the regulation of cardiac substrate uptake. Arsenite strongly induced p38 MAPK phosphorylation in isolated rat cardiac myocytes but also moderately enhanced phosphorylation of p42/44 ERK and p70 S6K. At the level of cardiomyocytic substrate use, arsenite enhanced glucose uptake dose dependently up to 5.1-fold but failed to stimulate long-chain fatty acid uptake. At the substrate transporter level, arsenite stimulated the translocation of GLUT4 to the sarcolemma but failed to recruit CD36 or FABPpm. Because arsenite did not influence the intrinsic activity of glucose transporters, GLUT4 translocation is entirely responsible for the selective increase in glucose uptake by arsenite. Moreover, the nonadditivity of arsenite-induced glucose uptake and insulin-induced glucose uptake indicates that arsenite recruits GLUT4 from insulin-responsive intracellular stores. Inhibitor studies with SB203580/SB202190, PD98059, and rapamycin indicate that activation of p38 MAPK, p42/44 ERK, and p70 S6K, respectively, are not involved in arsenite-induced glucose uptake. In addition, all these kinases do not play a role in regulation of cardiac glucose and long-chain fatty acid uptake by insulin. Hence, arsenite's selective stimulation of glucose uptake appears unrelated to its signaling actions, suggesting that arsenite acts via thiol modification of a putative intracellular protein target of arsenite within insulin-responsive GLUT4-containing stores. Because of arsenite's selective stimulation of cardiac glucose uptake, identification of this putative target of arsenite within the GLUT4-storage compartment may indicate whether it is a target for future strategies in prevention of diabetic cardiomyopathy.
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Affiliation(s)
- Joost J F P Luiken
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, P.O. Box 616, NL-6200 MD Maastricht, The Netherlands.
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36
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Strawbridge AB, Elmendorf JS. Endothelin-1 impairs glucose transporter trafficking via a membrane-based mechanism. J Cell Biochem 2006; 97:849-56. [PMID: 16240321 PMCID: PMC2409058 DOI: 10.1002/jcb.20687] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Endothelin-1 (ET-1) disrupts insulin-regulated glucose transporter GLUT4 trafficking. Since the negative consequence of chronic ET-1 exposure appears to be independent of signal disturbance along the insulin receptor substrate-1/phosphatidylinositol (PI) 3-kinase (PI3K)/Akt-2 pathway of insulin action, we tested if ET-1 altered GLUT4 regulation engaged by osmotic shock, a PI3K-independent stimulus that mimics insulin action. Regulation of GLUT4 by hyperosmotic stress was impaired by ET-1. Because of the mutual disruption of both insulin- and hyperosmolarity-stimulated GLUT4 translocation, we tested whether shared signaling and/or key phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated cytoskeletal events of GLUT4 trafficking were targets of ET-1. Both insulin and hyperosmotic stress signaling to Cbl were impaired by ET-1. Also, plasma membrane PIP2 and cortical actin levels were reduced in cells exposed to ET-1. Exogenous PIP2, but not PI 3,4,5-bisphosphate, restored actin structure, Cbl activation, and GLUT4 translocation. These data show that ET-1-induced PIP2/actin disruption impairs GLUT4 trafficking elicited by insulin and hyperosmolarity. In addition to showing for the first time the important role of PIP2-regulated cytoskeletal events in GLUT4 regulation by stimuli other than insulin, these studies reveal a novel function of PIP2/actin structure in signal transduction.
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Affiliation(s)
- Andrew B. Strawbridge
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
| | - Jeffrey S. Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
- *Correspondence to: Jeffrey S. Elmendorf, 635 Barnhill Drive, MS308A, Indianapolis, Indiana 46202., E-mail:
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37
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Inoue M, Chiang SH, Chang L, Chen XW, Saltiel AR. Compartmentalization of the exocyst complex in lipid rafts controls Glut4 vesicle tethering. Mol Biol Cell 2006; 17:2303-11. [PMID: 16525015 PMCID: PMC1446102 DOI: 10.1091/mbc.e06-01-0030] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Lipid raft microdomains act as organizing centers for signal transduction. We report here that the exocyst complex, consisting of Exo70, Sec6, and Sec8, regulates the compartmentalization of Glut4-containing vesicles at lipid raft domains in adipocytes. Exo70 is recruited by the G protein TC10 after activation by insulin and brings with it Sec6 and Sec8. Knockdowns of these proteins block insulin-stimulated glucose uptake. Moreover, their targeting to lipid rafts is required for glucose uptake and Glut4 docking at the plasma membrane. The assembly of this complex also requires the PDZ domain protein SAP97, a member of the MAGUKs family, which binds to Sec8 upon its translocation to the lipid raft. Exocyst assembly at lipid rafts sets up targeting sites for Glut4 vesicles, which transiently associate with these microdomains upon stimulation of cells with insulin. These results suggest that the TC10/exocyst complex/SAP97 axis plays an important role in the tethering of Glut4 vesicles to the plasma membrane in adipocytes.
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Affiliation(s)
- Mayumi Inoue
- Life Sciences Institute, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
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38
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Bernard JR, Reeder DW, Herr HJ, Rivas DA, Yaspelkis BB. High-fat feeding effects on components of the CAP/Cbl signaling cascade in Sprague-Dawley rat skeletal muscle. Metabolism 2006; 55:203-12. [PMID: 16423627 DOI: 10.1016/j.metabol.2005.08.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 08/21/2005] [Indexed: 10/25/2022]
Abstract
The aim of this investigation was to determine whether the CAP (Cbl-associated protein)/Cbl signaling cascade is present and responsive to insulin in skeletal muscle and if high-fat feeding impairs insulin-stimulated activation of this signaling cascade. Sprague-Dawley rats were assigned to either control (n = 16) or high fat-fed (n = 16) dietary groups. After a 12-week dietary period, animals were subjected to hind limb perfusions in the presence (n = 8 per group) or absence (n = 8 per group) of insulin. High-fat feeding reduced rates of insulin-stimulated skeletal muscle phosphatidylinositol 3-kinase activity and 3-O-methylglucose transport. In plasma membrane fractions, neither the high-fat diet nor insulin altered the insulin receptor beta subunit (IR-beta), APS (adaptor protein containing PH and SH2 domains), c-Cbl, or TC10 protein concentration, but high-fat feeding did decrease CAP protein concentration. APS, c-Cbl, CAP, and TC10 messenger RNA were present in the skeletal muscle and reflected the protein concentration of experimental groups. Despite insulin-stimulated plasma membrane IR-beta tyrosine phosphorylation being unaffected by high-fat feeding, c-Cbl tyrosine phosphorylation, the kinase activity of IR-beta toward APS, and glucose transporter 4 protein concentration were all significantly reduced in insulin-stimulated plasma membrane prepared from the skeletal muscle of high fat-fed animals. These findings suggest that the CAP/Cbl signaling cascade is present in skeletal muscle, activated by insulin, and impaired by high-fat feeding.
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Affiliation(s)
- Jeffrey R Bernard
- Department of Kinesiology, College of Health and Human Development, California State University Northridge, Northridge, CA 91330-8287, USA
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39
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Bryan BA, Mitchell DC, Zhao L, Ma W, Stafford LJ, Teng BB, Liu M. Modulation of muscle regeneration, myogenesis, and adipogenesis by the Rho family guanine nucleotide exchange factor GEFT. Mol Cell Biol 2006; 25:11089-101. [PMID: 16314529 PMCID: PMC1316953 DOI: 10.1128/mcb.25.24.11089-11101.2005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rho family guanine nucleotide exchange factors (GEFs) regulate diverse cellular processes including cytoskeletal reorganization, cell adhesion, and differentiation via activation of the Rho GTPases. However, no studies have yet implicated Rho-GEFs as molecular regulators of the mesenchymal cell fate decisions which occur during development and repair of tissue damage. In this study, we demonstrate that the steady-state protein level of the Rho-specific GEF GEFT is modulated during skeletal muscle regeneration and that gene transfer of GEFT into cardiotoxin-injured mouse tibialis anterior muscle exerts a powerful promotion of skeletal muscle regeneration in vivo. In order to molecularly characterize this regenerative effect, we extrapolate the mechanism of action by examining the consequence of GEFT expression in multipotent cell lines capable of differentiating into a number of cell types, including muscle and adipocyte lineages. Our data demonstrate that endogenous GEFT is transcriptionally upregulated during myogenic differentiation and downregulated during adipogenic differentiation. Exogenous expression of GEFT promotes myogenesis of C2C12 cells via activation of RhoA, Rac1, and Cdc42 and their downstream effector proteins, while a dominant-negative mutant of GEFT inhibits this process. Moreover, we show that GEFT inhibits insulin-induced adipogenesis in 3T3L1 preadipocytes. In summary, we provide the first evidence that the Rho family signaling pathways act as potential regulators of skeletal muscle regeneration and provide the first reported molecular mechanism illustrating how a mammalian Rho family GEF controls this process by modulating mesenchymal cell fate decisions.
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Affiliation(s)
- Brad A Bryan
- The Institute of Biosciences and Technology and Department of Medical Biochemistry and Genetics, University of Texas Health Science Center at Houston, 77030, USA
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40
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Abstract
Insulin stimulates glucose uptake in insulin-responsive tissues by means of the translocation of the glucose transporter GLUT4 from intracellular sites to the plasma membrane. Two pathways are required, one involving activation of a phosphatidylinositol 3-kinase (PI 3-kinase) and downstream protein kinases, and one involving activation of the Rho-family GTPase TC10. TC10 activation by insulin is catalyzed by the exchange factor C3G, which is translocated to lipid rafts along with its binding partner CrkII as a consequence of Cbl tyrosine phosphorylation by the insulin receptor. This activation of TC10 is dependent on localization of TC10 in the lipid raft subdomains of the plasma membrane. We describe experimental approaches using the insulin-responsive cell line 3T3-L1 adipocytes to study the role of TC10 in insulin-stimulated glucose transport.
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41
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Powelka AM, Seth A, Virbasius JV, Kiskinis E, Nicoloro SM, Guilherme A, Tang X, Straubhaar J, Cherniack AD, Parker MG, Czech MP. Suppression of oxidative metabolism and mitochondrial biogenesis by the transcriptional corepressor RIP140 in mouse adipocytes. J Clin Invest 2005; 116:125-36. [PMID: 16374519 PMCID: PMC1319222 DOI: 10.1172/jci26040] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Accepted: 10/25/2005] [Indexed: 01/06/2023] Open
Abstract
Using an siRNA-based screen, we identified the transcriptional corepressor RIP140 as a negative regulator of insulin-responsive hexose uptake and oxidative metabolism in 3T3-L1 adipocytes. Affymetrix GeneChip profiling revealed that RIP140 depletion upregulates the expression of clusters of genes in the pathways of glucose uptake, glycolysis, TCA cycle, fatty acid oxidation, mitochondrial biogenesis, and oxidative phosphorylation in these cells. Conversely, we show that reexpression of RIP140 in mouse embryonic fibroblasts derived from RIP140-null mice downregulates expression of many of these same genes. Consistent with these microarray data, RIP140 gene silencing in cultured adipocytes increased both conversion of [14C]glucose to CO2 and mitochondrial oxygen consumption. RIP140-null mice, previously reported to resist weight gain on a high-fat diet, are shown here to display enhanced glucose tolerance and enhanced responsiveness to insulin compared with matched wild-type mice upon high-fat feeding. Mechanistically, RIP140 was found to require the nuclear receptor ERRalpha to regulate hexose uptake and mitochondrial proteins SDHB and CoxVb, although it likely acts through other nuclear receptors as well. We conclude that RIP140 is a major suppressor of adipocyte oxidative metabolism and mitochondrial biogenesis, as well as a negative regulator of whole-body glucose tolerance and energy expenditure in mice.
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Affiliation(s)
- Aimee M. Powelka
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Asha Seth
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Joseph V. Virbasius
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Evangelos Kiskinis
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Sarah M. Nicoloro
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Adilson Guilherme
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Xiaoqing Tang
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Juerg Straubhaar
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Andrew D. Cherniack
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Malcolm G. Parker
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Michael P. Czech
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
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Alonso A, Fernández Y, Fernández R, Ordóñez P, Moreno M, Díaz F, Patterson AM, González C. Effect of food restriction on the insulin signalling pathway in rat skeletal muscle and adipose tissue. J Nutr Biochem 2005; 16:602-9. [PMID: 16081266 DOI: 10.1016/j.jnutbio.2005.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 03/02/2005] [Accepted: 03/04/2005] [Indexed: 11/17/2022]
Abstract
We tried to elucidate the effects of a brief and severe model of food restriction on insulin sensitivity in female rats, focusing on key proteins involved in the insulin signalling pathway in skeletal muscle and adipose tissue after 5, 10 and 15 days of food restriction. Using euglycemic clamp, we detected that food-restricted rats are significantly less sensitive to insulin action than control rats. However, the time of restriction promotes a progressive increase on insulin sensitivity. The analysis of the insulin signalling pathway showed a tissue-specific regulation of several proteins involved in insulin signalling. In skeletal muscle, insulin receptor substrate 1 and Glut4 are up-regulated at the end of the food restriction period, just the opposite of what we found in adipose tissue. In conclusion, a 50% reduction of food intake modulates insulin sensitivity through a tissue-specific regulation of the insulin signalling pathway in the main target tissues for this hormone.
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Affiliation(s)
- Ana Alonso
- Department of Functional Biology, Physiology Area, University of Oviedo, Oviedo, 33006 Spain
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43
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Nguyen MTA, Satoh H, Favelyukis S, Babendure JL, Imamura T, Sbodio JI, Zalevsky J, Dahiyat BI, Chi NW, Olefsky JM. JNK and tumor necrosis factor-alpha mediate free fatty acid-induced insulin resistance in 3T3-L1 adipocytes. J Biol Chem 2005; 280:35361-71. [PMID: 16085647 DOI: 10.1074/jbc.m504611200] [Citation(s) in RCA: 282] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Lipid infusion and high fat feeding are established causes of systemic and adipose tissue insulin resistance. In this study, we treated 3T3-L1 adipocytes with a mixture of free fatty acids (FFAs) to investigate the molecular mechanisms underlying fat-induced insulin resistance. FFA treatment impaired insulin receptor-mediated signal transduction and decreased insulin-stimulated GLUT4 translocation and glucose transport. FFAs activated the stress/inflammatory kinases c-Jun N-terminal kinase (JNK) and IKKbeta, and the suppressor of cytokine signaling protein 3, increased secretion of the inflammatory cytokine tumor necrosis factor (TNF)-alpha, and decreased secretion of adiponectin into the medium. RNA interference-mediated down-regulation of JNK blocked JNK activation and prevented most of the FFA-induced defects in insulin action. Blockade of TNF-alpha signaling with neutralizing antibodies to TNF-alpha or its receptors or with a dominant negative TNF-alpha peptide had a partial effect to inhibit FFA-induced cellular insulin resistance. We found that JNK activation by FFAs was not inhibited by blocking TNF-alpha signaling, whereas the FFA-induced increase in TNF-alpha secretion was inhibited by RNA interference-mediated JNK knockdown. Together, these results indicate that 1) JNK can be activated by FFAs through TNF-alpha-independent mechanisms, 2) activated JNK is a major contributor to FFA-induced cellular insulin resistance, and 3) TNF-alpha is an autocrine/paracrine downstream effector of activated JNK that can also mediate insulin resistance.
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Affiliation(s)
- M T Audrey Nguyen
- Division of Endocrinology-Metabolism, University of California, San Diego, La Jolla, California 92093-0673, USA
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Vulin AI, Jacob KK, Stanley FM. Integrin activates receptor-like protein tyrosine phosphatase alpha, Src, and Rho to increase prolactin gene expression through a final phosphatidylinositol 3-kinase/cytoskeletal pathway that is additive with insulin. Endocrinology 2005; 146:3535-46. [PMID: 15878970 DOI: 10.1210/en.2004-1386] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We previously showed that receptor-like protein tyrosine phosphatase (RPTP)-alpha inhibited insulin-increased prolactin gene transcription. Others suggested that RPTPalpha was a key intermediary between integrins and activation of Src. We present evidence that inhibition of insulin-increased prolactin gene transcription was secondary to RPTPalpha activation of Src, reflecting its role as mediator of integrin responses. Src kinase activity was increased in GH4 cells transiently or stably expressing RPTPalpha and cells plated on the integrin-alpha5beta1 ligand fibronectin. C-terminal Src kinase inactivated Src and blocked RPTPalpha inhibition of insulin-increased prolactin gene transcription. Expression of dominant-negative Src also prevented the RPTPalpha-mediated inhibition of insulin-increased prolactin gene expression. Low levels of a constitutively active Src mutant (SrcY/F) stimulated whereas higher expression levels of Src Y/F inhibited prolactin gene expression. Src-increased prolactin gene transcription was inhibited by expression of a blocking Rho-mutant (RhoN19), suggesting that Src acted through or required active Rho. Experiments with an activated Rho-mutant (RhoL63) demonstrated a biphasic activation/repression of prolactin gene transcription that was similar to the effect of Src. The effects of both Src and Rho were phosphatidylinositol 3-kinase dependent. Expression of SrcY/F or RhoL63 altered the actin cytoskeleton and morphology of GH4 cells. Taken together, these data suggest a physiological pathway from the cell matrix to increased prolactin gene transcription mediated by RPTPalpha/Src/Rho/phosphatidylinositol 3-kinase and cytoskeletal change that is additive with effects of insulin. Over activation of this pathway, however, caused extreme alteration of the cytoskeleton that blocked activation of the prolactin gene.
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Affiliation(s)
- Anthony I Vulin
- Department of Pharmacology, New York University Medical Center, New York, New York 10016, USA
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Strawbridge AB, Elmendorf JS. Phosphatidylinositol 4,5-bisphosphate reverses endothelin-1-induced insulin resistance via an actin-dependent mechanism. Diabetes 2005; 54:1698-705. [PMID: 15919791 PMCID: PMC2409056 DOI: 10.2337/diabetes.54.6.1698] [Citation(s) in RCA: 36] [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: 01/10/2023]
Abstract
Phosphatidylinositol (PI) 4,5-bisphosphate (PIP(2)) plays a pivotal role in insulin-stimulated glucose transport as an important precursor to PI 3,4,5-trisphosphate (PIP(3)) and a key regulator of actin polymerization. Since endothelin (ET)-1 impairs insulin sensitivity and PIP(2) is a target of ET-1-induced signaling, we tested whether a change in insulin-stimulated PIP(3) generation and signaling, PIP(2)-regulated actin polymerization, or a combination of both accounted for ET-1-induced insulin resistance. Concomitant with a time-dependent loss of insulin sensitivity, ET-1 caused a parallel reduction in plasma membrane PIP(2). Despite decreased insulin-stimulated PI 3-kinase activity and PIP(3) generation, ET-1 did not diminish downstream signaling to Akt-2. Furthermore, addition of exogenous PIP(2), but not PIP(3), restored insulin-regulated GLUT4 translocation and glucose transport impaired by ET-1. Microscopic and biochemical analyses revealed a PIP(2)-dependent loss of cortical filamentous actin (F-actin) in ET-1-treated cells. Restoration of insulin sensitivity by PIP(2) add-back occurred concomitant with a reestablishment of cortical F-actin. The corrective effect of exogenous PIP(2) in ET-1-induced insulin-resistant cells was not present in cells where cortical F-actin remained experimentally depolymerized. These data suggest that ET-1-induced insulin resistance results from reversible changes in PIP(2)-regulated actin polymerization and not PIP(2)-dependent signaling.
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Affiliation(s)
- Andrew B. Strawbridge
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
| | - Jeffrey S. Elmendorf
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana
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Tokushima Y, Takahashi K, Sato K, Akiba Y. Glucose uptake in vivo in skeletal muscles of insulin-injected chicks. Comp Biochem Physiol B Biochem Mol Biol 2005; 141:43-8. [PMID: 15820133 DOI: 10.1016/j.cbpc.2005.01.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2004] [Revised: 12/29/2004] [Accepted: 01/05/2005] [Indexed: 11/21/2022]
Abstract
Glucose uptake across the plasma membrane in animal cells plays a crucial role in whole-body glucose homeostasis. Insulin-stimulated glucose transport activity in vivo in several tissues was estimated using the 2-deoxy-D-[1-(3)H]glucose ([(3)H]2DG) uptake determination method. A tracer dose of [(3)H]2DG was injected intravenously into 8-day-old chicks (Gallus gallus) administered simultaneously or previously with porcine insulin (40 microg/kg BW). After 10 or 20 min, several major tissues, including skeletal and cardiac muscle, were sampled and their 2-deoxy-D-[1-(3)H]glucose 6-phosphate content analyzed. Plasma glucose concentration and [(3)H]2DG radioactivity were lowered by insulin within 20 min of [(3)H]2DG administration, while the plasma [(3)H]2DG/glucose ratio was not significantly different between chicks injected with insulin and their control counterparts. A marked uptake of 2DG was observed in cardiac tissue and brain, followed by kidney and skeletal muscles. In skeletal muscles, insulin increased the 2DG uptake in soleus, extensor digitorum longus and pectoralis superficialis muscles. On the other hand, no significant increases in insulin-induced 2DG uptake were detected in cardiac muscle or adipose tissue compared to controls. The results show that glucose transport across the plasma membrane in vivo in most skeletal muscles tested, but not cardiac muscle, was increased by insulin administration to chicks. These findings suggest that an insulin-responsive glucose transport mechanism is present in chickens, even though they intrinsically lack GLUT4 homologous gene, the insulin-responsive glucose transporter in mammals.
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Affiliation(s)
- Y Tokushima
- Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
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Takada T, Suzuki H, Gotoh Y, Sugiyama Y. Regulation of the cell surface expression of human BCRP/ABCG2 by the phosphorylation state of Akt in polarized cells. Drug Metab Dispos 2005; 33:905-9. [PMID: 15843490 DOI: 10.1124/dmd.104.003228] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human breast cancer resistance protein (BCRP/ABCG2) is believed to act as an efflux pump to protect the body from drugs and toxins. BCRP is known to accept many kinds of endogenous and exogenous compounds as substrates and to be localized on the apical membrane of various tissues. Expression of BCRP is also reported on the side population cells, and a recent report suggested involvement of Akt in the modulation of the side population phenotype. In the present study, we have characterized the effect of Akt on the polarized expression of BCRP using LLC-PK1 cells. After treatment with phosphatidylinositol 3-kinase (PI3K) inhibitors, internalization of stably transfected BCRP from the apical surface was observed after immunohistochemical staining, and the relative expression level of BCRP on the cell surface decreased to 49 +/- 14 and 51 +/- 8% of the control for LY294002 [2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride] and wortmannin treatment, respectively. This phenomenon was supported by the observation of internalized BCRP in presence of dominant negative-Akt. When the cells were treated with epidermal growth factor, the cell surface expression of BCRP was increased to 228 +/- 43% of the control accompanied by Akt stimulation. These results suggest that the relative expression of BCRP on the cell surface is regulated by the PI3K-Akt signaling pathway with a positive correlation in polarized cells. Alteration in Akt activities may influence the cellular extrusion of BCRP substrates by modifying epithelial BCRP localization.
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Affiliation(s)
- Tappei Takada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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Tejero ME, Proffitt JM, Cole SA, Freeland-Graves JH, Cai G, Peebles KW, Cox LA, Mahaney MC, Rogers J, Vandeberg JL, Blangero J, Comuzzie AG. Quantitative genetic analysis of glucose transporter 4 mRNA levels in baboon adipose. ACTA ACUST UNITED AC 2005; 12:1652-7. [PMID: 15536229 DOI: 10.1038/oby.2004.205] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Glucose transporter 4 (GLUT4) is an insulin-responsive glucose transporter expressed in adipose tissue. A decrease of the mRNA abundance of GLUT4 in adipose tissue has been observed in conditions of insulin resistance. The objective was to conduct quantitative genetic analyses using GLUT4 mRNA levels in omental adipose tissue of baboons as a novel phenotype. RESEARCH METHODS AND PROCEDURES A blood sample and a biopsy of omental adipose tissue were collected from 418 adult, pedigreed baboons. Total RNA was isolated from adipose tissue biopsies, and GLUT4 mRNA abundance was assayed by quantitative, real-time reverse transcription-polymerase chain reaction. Insulin and glucose were determined in fasting plasma by standard methods. Quantitative genetic analyses were conducted using GLUT4 mRNA, insulin, and glucose as quantitative traits. RESULTS GLUT4 mRNA expression in omental adipose tissue was heritable (h(2) = 0.23, p = 0.001). Bivariate genetic analyses revealed a significant genetic correlation (rho(G)) between GLUT4 mRNA abundance and both body weight (rho(G) = 0.63, p = 0.007), BMI (rho(G) = 0.59, p = 0.02) and insulin (rho(G) = 0.72, p = 0.04). A genome scan was conducted, and a quantitative trait locus was detected on chromosome 10p12 with a logarithm of the odds ratio score of 1.1. DISCUSSION GLUT4 mRNA abundance in omental adipose tissue has a significant genetic component. These findings suggest that expression of GLUT4 mRNA, plasma insulin levels, and body weight may be regulated by common genes.
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Affiliation(s)
- M Elizabeth Tejero
- Department of Genetics, Southwest Foundation for Biomedical Research, 7620 NW Loop 410, San Antonio, TX 78227-5301, USA
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Sweazea KL, Braun EJ. Glucose transport by English sparrow (Passer domesticus) skeletal muscle: have we been chirping up the wrong tree? ACTA ACUST UNITED AC 2005; 303:143-53. [PMID: 15662664 DOI: 10.1002/jez.a.131] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Glucose uptake by mammalian skeletal muscle has been extensively covered in the literature, whereas the uptake of glucose by avian skeletal muscle has yet to be examined. As skeletal muscle provides the majority of postprandial glucose uptake in mammals, this study was designed to characterize the glucose transport mechanisms and glycogen content of avian skeletal muscle. In addition, plasma glucose levels were measured. English sparrow extensor digitorum communis (EDC) skeletal muscles were used for this study to quantify in vitro radiolabeled-glucose uptake. Uptake of labeled glucose was shown to decrease in the presence of increasing unlabeled glucose and was maximal by 60 minutes of incubation. Various agents known to increase glucose transport in mammalian tissues, via the insulin and contraction-responsive pathways, were used to manipulate and characterize in vitro transport in birds. The typical effectors of the mammalian insulin pathway, insulin (2 ng/ml) and insulin-like growth factor-1 (48 ng/ml), did not increase skeletal muscle glucose transport. Likewise, inducers of the mammalian contraction-responsive pathway had no effect on glucose transport by in vitro avian skeletal muscle (5 mM caffeine, 2 mM AICAR (5'-aminoimidazole-4-carboxamide-1-b-D-ribofuranoside). Interestingly, 200 microM phloretin, an agent used to block glucose transport proteins, significantly inhibited its uptake (P<0.001). These results suggest that a glucose transporter is responsible for glucose uptake by avian skeletal muscle, albeit at unexpectedly low levels, considering the high plasma glucose concentrations (265.9+/-53.5 mg/dl) and low skeletal muscle glycogen content (9.1+/-4.11 nM glucose/mg) of English sparrows.
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Affiliation(s)
- Karen L Sweazea
- Department of Physiology, Arizona Health Sciences Center, University of Arizona, Tucson, Arizona, 85724-5051, USA
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Navarrete Santos A, Tonack S, Kirstein M, Kietz S, Fischer B. Two insulin-responsive glucose transporter isoforms and the insulin receptor are developmentally expressed in rabbit preimplantation embryos. Reproduction 2005; 128:503-16. [PMID: 15509696 DOI: 10.1530/rep.1.00203] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Glucose is the most important energy substrate for mammalian blastocysts. Its uptake is mediated by glucose transporters (GLUT). In muscle and adipocyte cells insulin stimulates glucose uptake by activation of the insulin receptor (IR) pathway and translocation of GLUT4. GLUT4 is expressed in bovine preimplantation embryos. A new insulin-responsive isoform, GLUT8, was recently described in mouse blastocysts. Thus, potentially, two insulin-responsive isoforms are expressed in early embryos. The mechanism of insulin action on embryonic cells, however, is still not clear. In the present study expression of IR, GLUT1, 2, 3, 4, 5 and 8 was studied in rabbit preimplantation embryos using RT-PCR, Western blotting and immunohistochemistry. The rabbit mRNA sequences for the complete coding region of IR, GLUT4 and a partial GLUT8 sequence were determined by RACE-PCR and sequencing. GLUT4 was expressed in 3-day-old morulae and in 4- and 6-day-old blastocysts. IR and GLUT8 transcripts were detectable only in blastocysts. Blastocysts also expressed GLUT1 and 3, but not GLUT2 and 5. Transcript numbers of GLUT4 and 8 were higher in trophoblast than in embryoblast cells. Translation of IR, GLUT4 and 8 proteins in blastocysts was confirmed by Western blotting. GLUT4 was localized mainly in the membrane and in the perinuclear region in trophoblast cells while in embryoblast cells its localization was predominantly in the perinuclear cytoplasm. The possible function(s) of two insulin-responsive isoforms, GLUT4 and GLUT8, in rabbit preimplantation embryos needs further investigation. It may not necessarily be linked to insulin-stimulated glucose transport.
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Affiliation(s)
- Anne Navarrete Santos
- Department of Anatomy and Cell Biology, Martin Luther University Faculty of Medicine, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany
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