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García AP, Gaydou L, Pérez E, Barrantes FJ. Insulin resistance induced by long-term hyperinsulinemia abolishes the effects of acute insulin exposure on cell-surface nicotinic acetylcholine receptor levels and actin cytoskeleton morphology. Biochem Biophys Res Commun 2023; 685:149165. [PMID: 37922786 DOI: 10.1016/j.bbrc.2023.149165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 10/26/2023] [Indexed: 11/07/2023]
Abstract
Using CHO-K1/A5 cells, a clonal cell line that robustly expresses adult muscle-type nicotinic acetylcholine receptor (nAChR), we explored whether insulin resistance in these mammalian cells affects cell-surface expression of the nAChR, its endocytic internalization, and actin cytoskeleton integrity. Acute nanomolar insulin stimulation resulted in a slow increase in nAChR cell-surface levels, reaching maximum levels at ∼1 h. Long periods of insulin incubation caused CHO-K1/A5 cells to become insulin resistant, as previously observed with several other cell types. Furthermore, long-term insulin treatment abolished the effects of short-term insulin exposure on cell-surface nAChR levels, suggestive of a desensitization phenomenon. It also affected the kinetics of ligand-induced nAChR internalization. Since the integrity of the cortical actin cytoskeleton affects nAChR endocytosis, we also studied the effects of long-term insulin treatment on this meshwork. We found that it significantly affected the cortical actin morphology of CHO-K1/A5 cells and the response of the actin cytoskeleton to a subsequent short-term insulin stimulus. Overall, the present results show for the first time the effects of insulin signaling on cell-surface nAChR expression and actin cytoskeleton-associated internalization.
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Affiliation(s)
- Ana Paula García
- Laboratorio de Neurobiología Molecular, Instituto de Investigaciones Biomédicas (BIOMED) UCA-CONICET, Facultad de Ciencias Médicas, Universidad Católica de Argentina, Buenos Aires, Argentina; Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral-CONICET, Santa Fe, Argentina
| | - Luisa Gaydou
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral-CONICET, Santa Fe, Argentina; Departamento de Bioquímica Clínica y Cuantitativa, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Eugenia Pérez
- Laboratorio de Neurobiología Molecular, Instituto de Investigaciones Biomédicas (BIOMED) UCA-CONICET, Facultad de Ciencias Médicas, Universidad Católica de Argentina, Buenos Aires, Argentina
| | - Francisco J Barrantes
- Laboratorio de Neurobiología Molecular, Instituto de Investigaciones Biomédicas (BIOMED) UCA-CONICET, Facultad de Ciencias Médicas, Universidad Católica de Argentina, Buenos Aires, Argentina.
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Tekin H, Frøbert O, Græsli AR, Kindberg J, Bilgin M, Buschard K. Hibernation and plasma lipids in free-ranging brown bears-implications for diabetes. PLoS One 2023; 18:e0291063. [PMID: 37669305 PMCID: PMC10479895 DOI: 10.1371/journal.pone.0291063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Accepted: 08/18/2023] [Indexed: 09/07/2023] Open
Abstract
Brown bears (Ursus arctos) prepare for winter by overeating and increasing adipose stores, before hibernating for up to six months without eating, drinking, and with minimal movement. In spring, the bears exit the den without any damage to organs or physiology. Recent clinical research has shown that specific lipids and lipid profiles are of special interest for diseases such as diabetes type 1 and 2. Furthermore, rodent experiments show that lipids such as sulfatide protects rodents against diabetes. As free-ranging bears experience fat accumulation and month-long physical inactivity without developing diabetes, they could possibly be affected by similar protective measures. In this study, we investigated whether lipid profiles of brown bears are related to protection against hibernation-induced damage. We sampled plasma from 10 free-ranging Scandinavian brown bears during winter hibernation and repeated sampling during active state in the summer period. With quantitative shotgun lipidomics and liquid chromatography-mass spectrometry, we profiled 314 lipid species from 26 lipid classes. A principal component analysis revealed that active and hibernation samples could be distinguished from each other based on their lipid profiles. Six lipid classes were significantly altered when comparing plasma from active state and hibernation: Hexosylceramide, phosphatidylglycerol, and lysophosphatidylglycerol were higher during hibernation, while phosphatidylcholine ether, phosphatidylethanolamine ether, and phosphatidylinositol were lower. Additionally, sulfatide species with shorter chain lengths were lower, while longer chain length sulfatides were higher during hibernation. Lipids that are altered in bears are described by others as relevant for and associated with diabetes, which strengthens their position as potential effectors during hibernation. From this analysis, a range of lipids are suggested as potential protectors of bear physiology, and of potential importance in diabetes.
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Affiliation(s)
- Hasim Tekin
- Bartholin Instituttet, Rigshospitalet, Copenhagen, Denmark
| | - Ole Frøbert
- Department of Cardiology, Faculty of Health, Örebro University Hospital, Örebro, Sweden
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark
- Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark
| | - Anne Randi Græsli
- Department of Forestry and Wildlife Management, Inland Norway University of Applied Sciences, Koppang, Norway
| | - Jonas Kindberg
- Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden
- Norwegian Institute for Nature Research, Trondheim, Norway
| | - Mesut Bilgin
- Lipidomics Core Facility, Danish Cancer Institute, Copenhagen, Denmark
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Xiao D, Chang W. Phosphatidylserine in Diabetes Research. Mol Pharm 2023; 20:82-89. [PMID: 36480277 DOI: 10.1021/acs.molpharmaceut.2c00707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phospholipids are lipids that constitute the basic structure of cell membranes. In-depth research has shown that in addition to supporting cell structures, phospholipids participate in multiple cellular processes, including promoting cell signal transduction, guiding protein translocation, activating enzymatic activity, and eliminating dysfunctional/redundant organelles/cells. Diabetes is a chronic metabolic disease with a complicated etiology and pathology. Studies have shown that the level of certain phospholipids, for example, the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in liver tissue, is negatively associated with insulin sensitivity. In addition, PS is a phospholipid exhibiting extensive cellular functions in diabetes. For this review, we analyzed many PS studies focusing on diabetes and insulin sensitivity in recent years and found that PS participates in controlling insulin secretion, regulating insulin signaling transduction, and participating in the progression of diabetic complications by mediating coagulation disorders in the microvasculature or targeting mitochondria. Moreover, PS supplements in food and PS-containing liposomes have been shown to protect against type 1 and type 2 diabetes (T1D and T2D, respectively) in animal studies. Therefore, by summarizing the regulatory roles played by PS in diabetes and the potential of successfully using PS or PS-containing liposomes for diabetic therapy, we hope to provide new ideas for further research into the mechanisms of diabetes and for drug development for treating diabetes and its complications.
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Affiliation(s)
- Dandan Xiao
- Institute for Translational Medicine, The Affiliated Hospital, College of Medicine, Qingdao University, Qingdao 266071, China.,School of Basic Medical Sciences, College of Medicine, Qingdao University, Qingdao 266071, China
| | - Wenguang Chang
- Institute for Translational Medicine, The Affiliated Hospital, College of Medicine, Qingdao University, Qingdao 266071, China
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Incorporation of Oxidized Phenylalanine Derivatives into Insulin Signaling Relevant Proteins May Link Oxidative Stress to Signaling Conditions Underlying Chronic Insulin Resistance. Biomedicines 2022; 10:biomedicines10050975. [PMID: 35625712 PMCID: PMC9138545 DOI: 10.3390/biomedicines10050975] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 12/12/2022] Open
Abstract
A link between oxidative stress and insulin resistance has been suggested. Hydroxyl free radicals are known to be able to convert phenylalanine (Phe) into the non-physiological tyrosine isoforms ortho- and meta-tyrosine (o-Tyr, m-Tyr). The aim of our study was to examine the role of o-Tyr and m-Tyr in the development of insulin resistance. We found that insulin-induced uptake of glucose was blunted in cultures of 3T3-L1 grown on media containing o- or m-Tyr. We show that these modified amino acids are incorporated into cellular proteins. We focused on insulin receptor substrate 1 (IRS-1), which plays a role in insulin signaling. The activating phosphorylation of IRS-1 was increased by insulin, the effect of which was abolished in cells grown in m-Tyr or o-Tyr media. We found that phosphorylation of m- or o-Tyr containing IRS-1 segments by insulin receptor (IR) kinase was greatly reduced, PTP-1B phosphatase was incapable of dephosphorylating phosphorylated m- or o-Tyr IRS-1 peptides, and the SH2 domains of phosphoinositide 3-kinase (PI3K) bound the o-Tyr IRS-1 peptides with greatly reduced affinity. According to our data, m- or o-Tyr incorporation into IRS-1 modifies its protein–protein interactions with regulating enzymes and effectors, thus IRS-1 eventually loses its capacity to play its role in insulin signaling, leading to insulin resistance.
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Dual Function of PI(4,5)P2 in Insulin-Regulated Exocytic Trafficking of GLUT4 in Adipocytes. J Mol Biol 2020; 432:4341-4357. [DOI: 10.1016/j.jmb.2020.06.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 06/15/2020] [Accepted: 06/18/2020] [Indexed: 11/17/2022]
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Zaulkffali AS, Md Razip NN, Syed Alwi SS, Abd Jalil A, Abd Mutalib MS, Gopalsamy B, Chang SK, Zainal Z, Ibrahim NN, Zakaria ZA, Khaza'ai H. Vitamins D and E Stimulate the PI3K-AKT Signalling Pathway in Insulin-Resistant SK-N-SH Neuronal Cells. Nutrients 2019; 11:nu11102525. [PMID: 31635074 PMCID: PMC6836113 DOI: 10.3390/nu11102525] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 09/20/2019] [Accepted: 09/27/2019] [Indexed: 01/06/2023] Open
Abstract
This study investigated the effects of vitamins D and E on an insulin-resistant model and hypothesized that this treatment would reverse the effects of Alzheimer’s disease (AD) and improves insulin signalling. An insulin-resistant model was induced in SK-N-SH neuronal cells with a treatment of 250 nM insulin and re-challenged with 100 nM at two different incubation time (16 h and 24 h). The effects of vitamin D (10 and 20 ng/mL), vitamin E in the form of tocotrienol-rich fraction (TRF) (200 ng/mL) and the combination of vitamins D and E on insulin signalling markers (IR, PI3K, GLUT3, GLUT4, and p-AKT), glucose uptake and AD markers (GSK3β and TAU) were determined using quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). The results demonstrated an improvement of the insulin signalling pathway upon treatment with vitamin D alone, with significant increases in IR, PI3K, GLUT3, GLUT4 expression levels, as well as AKT phosphorylation and glucose uptake, while GSK3β and TAU expression levels was decreased significantly. On the contrary, vitamin E alone, increased p-AKT, reduced the ROS as well as GSK3β and TAU but had no effect on the insulin signalling expression levels. The combination of vitamins D and E only showed significant increase in GLUT4, p-AKT, reduced ROS as well as GSK3β and TAU. Thus, the universal role of vitamin D, E alone and in combinations could be the potential nutritional agents in restoring the sensitivity of neuronal cells towards insulin and delaying the pathophysiological progression of AD.
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Affiliation(s)
- Amirah Salwani Zaulkffali
- Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Nurliyana Najwa Md Razip
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Sharifah Sakinah Syed Alwi
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Afifah Abd Jalil
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Mohd Sokhini Abd Mutalib
- Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Banulata Gopalsamy
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Sui Kiat Chang
- Department of Nutrition and Dietetics, School of Health Sciences, International Medical University, Kuala Lumpur 57000, Malaysia.
| | - Zaida Zainal
- Nutrition Unit, Product Development and Advisory Services Division, Malaysian Palm Oil Board, Bandar Baru Bangi 43000, Malaysia.
| | - Nafissa Nadia Ibrahim
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Zainul Amiruddin Zakaria
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
| | - Huzwah Khaza'ai
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang 43400, Malaysia.
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Grice BA, Barton KJ, Covert JD, Kreilach AM, Tackett L, Brozinick JT, Elmendorf JS. Excess membrane cholesterol is an early contributing reversible aspect of skeletal muscle insulin resistance in C57BL/6NJ mice fed a Western-style high-fat diet. Am J Physiol Endocrinol Metab 2019; 317:E362-E373. [PMID: 31237447 PMCID: PMC6732462 DOI: 10.1152/ajpendo.00396.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Skeletal muscle insulin resistance manifests shortly after high-fat feeding, yet mechanisms are not known. Here we set out to determine whether excess skeletal muscle membrane cholesterol and cytoskeletal derangement known to compromise glucose transporter (GLUT)4 regulation occurs early after high-fat feeding. We fed 6-wk-old male C57BL/6NJ mice either a low-fat (LF, 10% kcal) or a high-fat (HF, 45% kcal) diet for 1 wk. This HF feeding challenge was associated with an increase, albeit slight, in body mass, glucose intolerance, and hyperinsulinemia. Liver analyses did not reveal signs of hepatic insulin resistance; however, skeletal muscle immunoblots of triad-enriched regions containing transverse tubule membrane showed a marked loss of stimulated GLUT4 recruitment. An increase in cholesterol was also found in these fractions from HF-fed mice. These derangements were associated with a marked loss of cortical filamentous actin (F-actin) that is essential for GLUT4 regulation and known to be compromised by increases in membrane cholesterol. Both the withdrawal of the HF diet and two subcutaneous injections of the cholesterol-lowering agent methyl-β-cyclodextrin at 3 and 6 days during the 1-wk HF feeding intervention completely mitigated cholesterol accumulation, cortical F-actin loss, and GLUT4 dysregulation. Moreover, these beneficial membrane/cytoskeletal changes occurred concomitant with a full restoration of metabolic responses. These results identify skeletal muscle membrane cholesterol accumulation as an early, reversible, feature of insulin resistance and suggest cortical F-actin loss as an early derangement of skeletal muscle insulin resistance.
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Affiliation(s)
- Brian A Grice
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Kelly J Barton
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Jacob D Covert
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Alec M Kreilach
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Lixuan Tackett
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Joseph T Brozinick
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
- Eli Lilly and Company, Indianapolis, Indiana
| | - Jeffrey S Elmendorf
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
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Zhang J, Oh E, Merz KE, Aslamy A, Veluthakal R, Salunkhe VA, Ahn M, Tunduguru R, Thurmond DC. DOC2B promotes insulin sensitivity in mice via a novel KLC1-dependent mechanism in skeletal muscle. Diabetologia 2019; 62:845-859. [PMID: 30707251 PMCID: PMC6451670 DOI: 10.1007/s00125-019-4824-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 12/14/2018] [Indexed: 12/11/2022]
Abstract
AIMS/HYPOTHESIS Skeletal muscle accounts for >80% of insulin-stimulated glucose uptake; dysfunction of this process underlies insulin resistance and type 2 diabetes. Insulin sensitivity is impaired in mice deficient in the double C2 domain β (DOC2B) protein, while whole-body overexpression of DOC2B enhances insulin sensitivity. Whether insulin sensitivity in the skeletal muscle is affected directly by DOC2B or is secondary to an effect on other tissues is unknown; the underlying molecular mechanisms also remain unclear. METHODS Human skeletal muscle samples from non-diabetic or type 2 diabetic donors were evaluated for loss of DOC2B during diabetes development. For in vivo analysis, new doxycycline-inducible skeletal-muscle-specific Doc2b-overexpressing mice fed standard or high-fat diets were evaluated for insulin and glucose tolerance, and insulin-stimulated GLUT4 accumulation at the plasma membrane (PM). For in vitro analyses, a DOC2B-overexpressing L6-GLUT4-myc myoblast/myotube culture system was coupled with an insulin resistance paradigm. Biochemical and molecular biology methods such as site-directed mutagenesis, co-immunoprecipitation and mass spectrometry were used to identify the molecular mechanisms linking insulin stimulation to DOC2B. RESULTS We identified loss of DOC2B (55% reduction in RNA and 40% reduction in protein) in the skeletal muscle of human donors with type 2 diabetes. Furthermore, inducible enrichment of DOC2B in skeletal muscle of transgenic mice enhanced whole-body glucose tolerance (AUC decreased by 25% for female mice) and peripheral insulin sensitivity (area over the curve increased by 20% and 26% for female and male mice, respectively) in vivo, underpinned by enhanced insulin-stimulated GLUT4 accumulation at the PM. Moreover, DOC2B enrichment in skeletal muscle protected mice from high-fat-diet-induced peripheral insulin resistance, despite the persistence of obesity. In L6-GLUT4-myc myoblasts, DOC2B enrichment was sufficient to preserve normal insulin-stimulated GLUT4 accumulation at the PM in cells exposed to diabetogenic stimuli. We further identified that DOC2B is phosphorylated on insulin stimulation, enhancing its interaction with a microtubule motor protein, kinesin light chain 1 (KLC1). Mutation of Y301 in DOC2B blocked the insulin-stimulated phosphorylation of DOC2B and interaction with KLC1, and it blunted the ability of DOC2B to enhance insulin-stimulated GLUT4 accumulation at the PM. CONCLUSIONS/INTERPRETATION These results suggest that DOC2B collaborates with KLC1 to regulate insulin-stimulated GLUT4 accumulation at the PM and regulates insulin sensitivity. Our observation provides a basis for pursuing DOC2B as a novel drug target in the muscle to prevent/treat type 2 diabetes.
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Affiliation(s)
- Jing Zhang
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
- Anwita Biosciences Inc, San Carlos, CA, USA
| | - Eunjin Oh
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Karla E Merz
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Arianne Aslamy
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Rajakrishnan Veluthakal
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Vishal A Salunkhe
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Miwon Ahn
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Ragadeepthi Tunduguru
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, USA
| | - Debbie C Thurmond
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA.
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Chang W, Hatch GM, Wang Y, Yu F, Wang M. The relationship between phospholipids and insulin resistance: From clinical to experimental studies. J Cell Mol Med 2018; 23:702-710. [PMID: 30402908 PMCID: PMC6349352 DOI: 10.1111/jcmm.13984] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 10/02/2018] [Indexed: 01/21/2023] Open
Abstract
Insulin resistance induced by high‐fat diet and impropriate life style is a major contributor to the pathogenesis of metabolic disease. However, the underlying molecular mechanisms remain unclear. Recent studies in metabolic dysfunction have extended this beyond simply elevated cholesterol and triglycerides levels and have identified a key role for lipid metabolism. For example, altered phospholipid metabolism has now become central in the pathogenesis of metabolic disease. In this review, we discuss the association between insulin sensitivity and phospholipid metabolism and highlight the most significant discoveries generated over the last several decades. Finally, we summarize the current knowledge surrounding the molecular mechanisms related to phospholipids and insulin resistance and provide new insight for future research into their relationship.
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Affiliation(s)
- Wenguang Chang
- Center for Regenerative Medicine, Institute for Translational Medicine, Qingdao University, Qingdao, China
| | - Grant M Hatch
- Departments of Pharmacology and Therapeutics, Biochemistry and Medical Genetics, Center for Research and Treatment of Atherosclerosis, DREAM Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada
| | - Yu Wang
- Center for Regenerative Medicine, Institute for Translational Medicine, Qingdao University, Qingdao, China
| | - Fei Yu
- Center for Regenerative Medicine, Institute for Translational Medicine, Qingdao University, Qingdao, China
| | - Man Wang
- Center for Regenerative Medicine, Institute for Translational Medicine, Qingdao University, Qingdao, China
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Stringer DM, Zahradka P, Taylor CG. Glucose transporters: cellular links to hyperglycemia in insulin resistance and diabetes. Nutr Rev 2016; 73:140-54. [PMID: 26024537 DOI: 10.1093/nutrit/nuu012] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Abnormal expression and/or function of mammalian hexose transporters contribute to the hallmark hyperglycemia of diabetes. Due to different roles in glucose handling, various organ systems possess specific transporters that may be affected during the diabetic state. Diabetes has been associated with higher rates of intestinal glucose transport, paralleled by increased expression of both active and facilitative transporters and a shift in the location of transporters within the enterocyte, events that occur independent of intestinal hyperplasia and hyperglycemia. Peripheral tissues also exhibit deregulated glucose transport in the diabetic state, most notably defective translocation of transporters to the plasma membrane and reduced capacity to clear glucose from the bloodstream. Expression of renal active and facilitative glucose transporters increases as a result of diabetes, leading to elevated rates of glucose reabsorption. However, this may be a natural response designed to combat elevated blood glucose concentrations and not necessarily a direct effect of insulin deficiency. Functional foods and nutraceuticals, by modulation of glucose transporter activity, represent a potential dietary tool to aid in the management of hyperglycemia and diabetes.
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Affiliation(s)
- Danielle M Stringer
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada.
| | - Peter Zahradka
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada
| | - Carla G Taylor
- D.M. Stringer was with the Department of Human Nutritional Sciences, University of Manitoba, and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada at the time of manuscript preparation. C.G. Taylor is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada. P. Zahradka is with the Department of Human Nutritional Sciences, University of Manitoba; the Department of Physiology, University of Manitoba; and the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Manitoba, Canada
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11
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n-3 polyunsaturated fatty acids suppress CD4(+) T cell proliferation by altering phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:85-96. [PMID: 26476105 DOI: 10.1016/j.bbamem.2015.10.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 10/12/2015] [Accepted: 10/13/2015] [Indexed: 02/07/2023]
Abstract
The mechanisms by which n-3 polyunsaturated fatty acids (n-3 PUFA), abundant in fish oil, exert their anti-inflammatory effects have not been rigorously defined. We have previously demonstrated that n-3 PUFA decrease the amount of phosphatidylinositol-(4,5)-bisphosphate, [PI(4,5)P2], in CD4(+) T cells, leading to suppressed actin remodeling upon activation. Since discrete pools of PI(4,5)P2 exist in the plasma membrane, we determined whether n-3 PUFA modulate spatial organization of PI(4,5)P2 relative to raft and non-raft domains. We used Förster resonance energy transfer (FRET) to demonstrate that lipid raft mesodomains in the plasma membrane of CD4(+) T cells enriched in n-3 PUFA display increased co-clustering of Lck(N10) and LAT(ΔCP), markers of lipid rafts. CD4(+) T cells enriched in n-3 PUFA also exhibited a depleted plasma membrane non-raft PI(4,5)P2 pool as detected by decreased co-clustering of Src(N15), a non-raft marker, and PH(PLC-δ), a PI(4,5)P2 reporter. Incubation with exogenous PI(4,5)P2 rescued the effects on the non-raft PI(4,5)P2 pool, and reversed the suppression of T cell proliferation in CD4(+) T cells enriched with n-3 PUFA. Furthermore, CD4(+) T cells isolated from mice fed a 4% docosahexaenoic acid (DHA)-enriched diet exhibited a decrease in the non-raft pool of PI(4,5)P2, and exogenous PI(4,5)P2 reversed the suppression of T cell proliferation. Finally, these effects were not due to changes to post-translational lipidation, since n-3 PUFA did not alter the palmitoylation status of signaling proteins. These data demonstrate that n-3 PUFA suppress T cell proliferation by altering plasma membrane topography and the spatial organization of PI(4,5)P2.
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Fang L, Kojima K, Zhou L, Crossman DK, Mobley JA, Grams J. Analysis of the Human Proteome in Subcutaneous and Visceral Fat Depots in Diabetic and Non-diabetic Patients with Morbid Obesity. ACTA ACUST UNITED AC 2015; 8:133-141. [PMID: 26472921 PMCID: PMC4603752 DOI: 10.4172/jpb.1000361] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
No longer regarded as simply a storage depot, fat is a dynamic organ acting locally and systemically to modulate energy homeostasis, glucose sensitivity, insulin resistance, and inflammatory pathways. Here, mass spectrometry was used to survey the proteome of patient matched subcutaneous fat and visceral fat in 20 diabetic vs 22 nondiabetic patients with morbid obesity. A similar number of proteins (~600) were identified in each tissue type. When stratified by diabetic status, 19 and 41 proteins were found to be differentially abundant in subcutaneous fat and omentum, respectively. These proteins represent pathways known to be involved in metabolism. Five of these proteins were differentially abundant in both fat depots: moesin, 78 kDa glucose-regulated protein, protein cordon-bleu, zinc finger protein 611, and cytochrome c oxidase subunit 6B1. Three proteins, decorin, cytochrome c oxidase subunit 6B1, and 78 kDa glucose-regulated protein, were further tested for validation by western blot analysis. Investigation of the proteins reported here is expected to expand on the current knowledge of adipose tissue driven biochemistry in diabetes and obesity, with the ultimate goal of identifying clinical targets for the development of novel therapeutic interventions in the treatment of type 2 diabetes mellitus. To our knowledge, this study is the first to survey the global proteome derived from each subcutaneous and visceral adipose tissue obtained from the same patient in the clinical setting of morbid obesity, with and without diabetes. It is also the largest study of diabetic vs nondiabetic patients with 42 patients surveyed.
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Affiliation(s)
- Lingling Fang
- Ningbo Lihuili Hospital; Ningbo, Zhejiang, China ; Department of Surgery, University of Alabama at Birmingham; Birmingham, AL, USA
| | - Kyoko Kojima
- Comprehensive Cancer Center, University of Alabama at Birmingham; Birmingham, AL, USA
| | - Lihua Zhou
- Department of Surgery, University of Alabama at Birmingham; Birmingham, AL, USA
| | - David K Crossman
- Heflin Center for Genomic Science, University of Alabama at Birmingham; Birmingham, AL, USA ; Department of Genetics, University of Alabama at Birmingham; Birmingham, AL, USA
| | - James A Mobley
- Department of Surgery, University of Alabama at Birmingham; Birmingham, AL, USA ; Comprehensive Cancer Center, University of Alabama at Birmingham; Birmingham, AL, USA ; Heflin Center for Genomic Science, University of Alabama at Birmingham; Birmingham, AL, USA
| | - Jayleen Grams
- Department of Surgery, University of Alabama at Birmingham; Birmingham, AL, USA ; Department of Surgery, Birmingham Veterans Administration Medical Center, Birmingham, AL, USA
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Abstract
Extensive actin cytoskeleton remodelling occurs during adipocyte development. We have previously shown that disruption of stress fibres by the actin-severing protein cofilin is a requisite step in adipogenesis. However, it remains unclear whether actin nucleation and assembly into the cortical structure are essential for adipocyte development. In the present study we investigated the role of cortical actin assembly and of actin nucleation by the actin-related protein 2/3 (Arp2/3) complex in adipogenesis. Cortical actin structure formation started with accumulation of filamentous actin (F-actin) patches near the plasma membrane during adipogenesis. Depletion of Arp2/3 by knockdown of its subunits Arp3 or ARPC3 strongly impaired adipocyte differentiation, although adipogenesis-initiating factors were unaffected. Moreover, the assembly of F-actin-rich structures at the plasma membrane was suppressed and the cortical actin structure poorly developed after adipogenic induction in Arp2/3-deficient cells. Finally, we provide evidence that the cortical actin cytoskeleton is essential for efficient glucose transporter 4 (GLUT4) vesicle exocytosis and insulin signal transduction. These results show that the Arp2/3 complex is an essential regulator of adipocyte development through control of the formation of cortical actin structures, which may facilitate nutrient uptake and signalling events.
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Hoffman NJ, Penque BA, Habegger KM, Sealls W, Tackett L, Elmendorf JS. Chromium enhances insulin responsiveness via AMPK. J Nutr Biochem 2014; 25:565-72. [PMID: 24725432 DOI: 10.1016/j.jnutbio.2014.01.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 01/02/2014] [Accepted: 01/24/2014] [Indexed: 12/19/2022]
Abstract
Trivalent chromium (Cr(3+)) is known to improve glucose homeostasis. Cr(3+) has been shown to improve plasma membrane-based aspects of glucose transporter GLUT4 regulation and increase activity of the cellular energy sensor 5' AMP-activated protein kinase (AMPK). However, the mechanism(s) by which Cr(3+) improves insulin responsiveness and whether AMPK mediates this action is not known. In this study we tested if Cr(3+) protected against physiological hyperinsulinemia-induced plasma membrane cholesterol accumulation, cortical filamentous actin (F-actin) loss and insulin resistance in L6 skeletal muscle myotubes. In addition, we performed mechanistic studies to test our hypothesis that AMPK mediates the effects of Cr(3+) on GLUT4 and glucose transport regulation. Hyperinsulinemia-induced insulin-resistant L6 myotubes displayed excess membrane cholesterol and diminished cortical F-actin essential for effective glucose transport regulation. These membrane and cytoskeletal abnormalities were associated with defects in insulin-stimulated GLUT4 translocation and glucose transport. Supplementing the culture medium with pharmacologically relevant doses of Cr(3+) in the picolinate form (CrPic) protected against membrane cholesterol accumulation, F-actin loss, GLUT4 dysregulation and glucose transport dysfunction. Insulin signaling was neither impaired by hyperinsulinemic conditions nor enhanced by CrPic, whereas CrPic increased AMPK signaling. Mechanistically, siRNA-mediated depletion of AMPK abolished the protective effects of CrPic against GLUT4 and glucose transport dysregulation. Together these findings suggest that the micronutrient Cr(3+), via increasing AMPK activity, positively impacts skeletal muscle cell insulin sensitivity and glucose transport regulation.
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Affiliation(s)
- Nolan J Hoffman
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Brent A Penque
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Kirk M Habegger
- Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Medicine - Endocrinology, Diabetes & Metabolism University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Whitney Sealls
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Lixuan Tackett
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Jeffrey S Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Penque BA, Hoggatt AM, Herring BP, Elmendorf JS. Hexosamine biosynthesis impairs insulin action via a cholesterolgenic response. Mol Endocrinol 2013; 27:536-47. [PMID: 23315940 DOI: 10.1210/me.2012-1213] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Plasma membrane cholesterol accumulation has been implicated in cellular insulin resistance. Given the role of the hexosamine biosynthesis pathway (HBP) as a sensor of nutrient excess, coupled to its involvement in the development of insulin resistance, we delineated whether excess glucose flux through this pathway provokes a cholesterolgenic response induced by hyperinsulinemia. Exposing 3T3-L1 adipocytes to physiologically relevant doses of hyperinsulinemia (250pM-5000pM) induced a dose-dependent gain in the mRNA/protein levels of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR). These elevations were associated with elevated plasma membrane cholesterol. Mechanistically, hyperinsulinemia increased glucose flux through the HBP and O-linked β-N-acetylglucosamine (O-GlcNAc) modification of specificity protein 1 (Sp1), known to activate cholesterolgenic gene products such as the sterol response element-binding protein (SREBP1) and HMGR. Chromatin immunoprecipitation demonstrated that increased O-GlcNAc modification of Sp1 resulted in a higher binding affinity of Sp1 to the promoter regions of SREBP1 and HMGR. Luciferase assays confirmed that HMGR promoter activity was elevated under these conditions and that inhibition of the HBP with 6-diazo-5-oxo-l-norleucine (DON) prevented hyperinsulinemia-induced activation of the HMGR promoter. In addition, both DON and the Sp1 DNA-binding inhibitor mithramycin prevented the hyperinsulinemia-induced increases in HMGR mRNA/protein and plasma membrane cholesterol. In these mithramycin-treated cells, both cortical filamentous actin structure and insulin-stimulated glucose transport were restored. Together, these data suggest a novel mechanism whereby increased HBP activity increases Sp1 transcriptional activation of a cholesterolgenic program, thereby elevating plasma membrane cholesterol and compromising cytoskeletal structure essential for insulin action.
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Affiliation(s)
- Brent A Penque
- Departments of Cellular and Integrative Physiology, Indiana UniversitySchool of Medicine, Indianapolis, IN 46202, USA
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Penque BA, Tackett L, Elmendorf JS. Trivalent Chromium Modulates Hexosamine Biosynthesis Pathway Transcriptional Activation of Cholesterol Synthesis and Insulin Resistance. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/ojemd.2013.34a1001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Habegger KM, Hoffman NJ, Ridenour CM, Brozinick JT, Elmendorf JS. AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol. Endocrinology 2012; 153:2130-41. [PMID: 22434076 PMCID: PMC3339638 DOI: 10.1210/en.2011-2099] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AMP-activated protein kinase (AMPK) enhances glucose transporter GLUT4 regulation. AMPK also suppresses energy-consuming pathways such as cholesterol synthesis. Interestingly, recent in vitro and in vivo data suggest that excess membrane cholesterol impairs GLUT4 regulation. Therefore, this study tested whether a beneficial, GLUT4-regulatory aspect of AMPK stimulation involved cholesterol lowering. Using L6 myotubes stably expressing an exofacial myc-epitope-tagged-GLUT4, AMPK stimulation by 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR; 45 min, 1 mm) or 2,4-dinitrophenol (DNP; 30 min, 200 μm) increased cell surface GLUT4myc labeling by approximately ≈ 25% (P < 0.05). Insulin (20 min, 100 nm) also increased GLUT4myc labeling by about 50% (P < 0.05), which was further enhanced (≈ 25%, P < 0.05) by AICAR or DNP. Consistent with AMPK-mediated suppression of cholesterol synthesis, AICAR and DNP decreased membrane cholesterol by 20-25% (P < 0.05). Whereas AMPK knockdown prevented the enhanced basal and insulin-stimulated GLUT4myc labeling by AICAR and DNP, cholesterol replenishment only blocked the AMPK-associated enhancement in insulin action. Cells cultured in a hyperinsulinemic milieu, resembling conditions in vivo that promote the progression/worsening of insulin resistance, displayed an increase in membrane cholesterol. This occurred concomitantly with a loss of cortical filamentous actin (F-actin) and defects in GLUT4 regulation by insulin. These derangements were prevented by AMPK stimulation. Examination of skeletal muscle from insulin-resistant Zucker rats revealed a similar elevation in membrane cholesterol and loss of F-actin. Lowering cholesterol to control levels restored F-actin structure and insulin sensitivity. In conclusion, these data suggest a novel aspect of GLUT4 regulation by AMPK involves membrane cholesterol lowering. Moreover, this AMPK-mediated process protected against hyperinsulinemia-induced insulin resistance.
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Affiliation(s)
- Kirk M Habegger
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Aqueous Extract of Paeonia suffruticosa Inhibits Migration and Metastasis of Renal Cell Carcinoma Cells via Suppressing VEGFR-3 Pathway. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:409823. [PMID: 22454663 PMCID: PMC3291499 DOI: 10.1155/2012/409823] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 11/02/2011] [Indexed: 12/19/2022]
Abstract
Renal cell carcinoma (RCC) cells are characterized by strong drug resistance and high metastatic incidence. In this study, the effects of ten kinds of Chinese herbs on RCC cell migration and proliferation were examined. Aqueous extract of Paeonia suffruticosa (PS-A) exerted strong inhibitory effects on cancer cell migration, mobility, and invasion. The results of mouse xenograft experiments showed that the treatment of PS-A significantly suppressed tumor growth and pulmonary metastasis. We further found that PS-A markedly decreased expression of VEGF receptor-3 (VEGFR-3) and phosphorylation of FAK in RCC cells. Moreover, the activation of Rac-1, a modulator of cytoskeletal dynamics, was remarkably reduced by PS-A. Additionally, PS-A suppressed polymerization of actin filament as demonstrated by confocal microscopy analysis and decreased the ratio of F-actin to G-actin in RCC cells, suggesting that PS-A inhibits RCC cell migration through modulating VEGFR-3/FAK/Rac-1 pathway to disrupt actin filament polymerization. In conclusion, this research elucidates the effects and molecular mechanism for antimigration of PS-A on RCC cells and suggests PS-A to be a therapeutic or adjuvant strategy for the patients with aggressive RCC.
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Habegger KM, Penque BA, Sealls W, Tackett L, Bell LN, Blue EK, Gallagher PJ, Sturek M, Alloosh MA, Steinberg HO, Considine RV, Elmendorf JS. Fat-induced membrane cholesterol accrual provokes cortical filamentous actin destabilisation and glucose transport dysfunction in skeletal muscle. Diabetologia 2012; 55:457-67. [PMID: 22002007 PMCID: PMC3245823 DOI: 10.1007/s00125-011-2334-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 09/19/2011] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Diminished cortical filamentous actin (F-actin) has been implicated in skeletal muscle insulin resistance, yet the mechanism(s) is unknown. Here we tested the hypothesis that changes in membrane cholesterol could be a causative factor, as organised F-actin structure emanates from cholesterol-enriched raft microdomains at the plasma membrane. METHODS Skeletal muscle samples from high-fat-fed animals and insulin-sensitive and insulin-resistant human participants were evaluated. The study also used L6 myotubes to directly determine the impact of fatty acids (FAs) on membrane/cytoskeletal variables and insulin action. RESULTS High-fat-fed insulin-resistant animals displayed elevated levels of membrane cholesterol and reduced F-actin structure compared with normal chow-fed animals. Moreover, human muscle biopsies revealed an inverse correlation between membrane cholesterol and whole-body glucose disposal. Palmitate-induced insulin-resistant myotubes displayed membrane cholesterol accrual and F-actin loss. Cholesterol lowering protected against the palmitate-induced defects, whereas characteristically measured defects in insulin signalling were not corrected. Conversely, cholesterol loading of L6 myotube membranes provoked a palmitate-like cytoskeletal/GLUT4 derangement. Mechanistically, we observed a palmitate-induced increase in O-linked glycosylation, an end-product of the hexosamine biosynthesis pathway (HBP). Consistent with HBP activity affecting the transcription of various genes, we observed an increase in Hmgcr, a gene that encodes 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. In line with increased HBP activity transcriptionally provoking a membrane cholesterol-based insulin-resistant state, HBP inhibition attenuated Hmgcr expression and prevented membrane cholesterol accrual, F-actin loss and GLUT4/glucose transport dysfunction. CONCLUSIONS/INTERPRETATION Our results suggest a novel cholesterolgenic-based mechanism of FA-induced membrane/cytoskeletal disorder and insulin resistance.
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Affiliation(s)
- K. M. Habegger
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
| | - B. A. Penque
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
| | - W. Sealls
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | - L. Tackett
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
| | - L. N. Bell
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Department of Medicine, Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, IN USA
| | - E. K. Blue
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
| | - P. J. Gallagher
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
| | - M. Sturek
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | - M. A. Alloosh
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | | | - R. V. Considine
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Department of Medicine, Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, IN USA
| | - J. S. Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
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Bhonagiri P, Pattar GR, Habegger KM, McCarthy AM, Tackett L, Elmendorf JS. Evidence coupling increased hexosamine biosynthesis pathway activity to membrane cholesterol toxicity and cortical filamentous actin derangement contributing to cellular insulin resistance. Endocrinology 2011; 152:3373-84. [PMID: 21712361 PMCID: PMC3159786 DOI: 10.1210/en.2011-1295] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hyperinsulinemia is known to promote the progression/worsening of insulin resistance. Evidence reveals a hidden cost of hyperinsulinemia on plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP(2))-regulated filamentous actin (F-actin) structure, components critical to the normal operation of the insulin-regulated glucose transport system. Here we delineated whether increased glucose flux through the hexosamine biosynthesis pathway (HBP) causes PIP(2)/F-actin dysregulation and subsequent insulin resistance. Increased glycosylation events were detected in 3T3-L1 adipocytes cultured under conditions closely resembling physiological hyperinsulinemia (5 nm insulin; 12 h) and in cells in which HBP activity was amplified by 2 mm glucosamine (GlcN). Both the physiological hyperinsulinemia and experimental GlcN challenge induced comparable losses of PIP(2) and F-actin. In addition to protecting against the insulin-induced membrane/cytoskeletal abnormality and insulin-resistant state, exogenous PIP(2) corrected the GlcN-induced insult on these parameters. Moreover, in accordance with HBP flux directly weakening PIP(2)/F-actin structure, pharmacological inhibition of the rate-limiting HBP enzyme [glutamine-fructose-6-phosphate amidotransferase (GFAT)] restored PIP(2)-regulated F-actin structure and insulin responsiveness. Conversely, overexpression of GFAT was associated with a loss of detectable PM PIP(2) and insulin sensitivity. Even less invasive challenges with glucose, in the absence of insulin, also led to PIP(2)/F-actin dysregulation. Mechanistically we found that increased HBP activity increased PM cholesterol, the removal of which normalized PIP(2)/F-actin levels. Accordingly, these data suggest that glucose transporter-4 functionality, dependent on PIP(2) and/or F-actin status, can be critically compromised by inappropriate HBP activity. Furthermore, these data are consistent with the PM cholesterol accrual/toxicity as a mechanistic basis of the HBP-induced defects in PIP(2)/F-actin structure and impaired glucose transporter-4 regulation.
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Affiliation(s)
- Padma Bhonagiri
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Hoffman NJ, Elmendorf JS. Signaling, cytoskeletal and membrane mechanisms regulating GLUT4 exocytosis. Trends Endocrinol Metab 2011; 22:110-6. [PMID: 21216617 PMCID: PMC3049829 DOI: 10.1016/j.tem.2010.12.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/03/2010] [Accepted: 12/06/2010] [Indexed: 10/25/2022]
Abstract
Solving how insulin regulates glucose transport into skeletal muscle and adipose tissue remains a fundamental challenge in biology and a significant issue in medicine. A central feature of this process is the coordinated accumulation of the glucose transporter GLUT4 into the plasma membrane. New signaling and cytoskeletal mechanisms of insulin-stimulated GLUT4 exocytosis are of emerging interest, particularly those at or just beneath the plasma membrane. This review examines signals that functionally engage GLUT4 exocytosis, considers cytoskeletal regulation of the stimulated GLUT4 itinerary, and appraises the involvement of plasma membrane parameters in GLUT4 control. We also explore how these newly-defined signaling, cytoskeletal and membrane mechanisms could be of therapeutic interest in the treatment and/or prevention of GLUT4 dysregulation in disease.
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Affiliation(s)
- Nolan J Hoffman
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Centers for Diabetes Research, Membrane Biosciences, and Vascular Biology and Medicine, VanNuys Medical Science Building Room 308A, Indianapolis, IN 46202, USA
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Sealls W, Penque BA, Elmendorf JS. Evidence that chromium modulates cellular cholesterol homeostasis and ABCA1 functionality impaired by hyperinsulinemia--brief report. Arterioscler Thromb Vasc Biol 2011; 31:1139-40. [PMID: 21311039 DOI: 10.1161/atvbaha.110.222158] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Trivalent chromium (Cr3+) is an essential micronutrient. Findings since the 1950s suggest that Cr3+ might benefit cholesterol homeostasis. Here we present mechanistic evidence in support of this role of Cr3+. METHODS AND RESULTS High-density lipoprotein cholesterol generation in 3T3-L1 adipocytes, which are rendered ineffective by the hyperinsulinemia that is known to accompany disorders of lipid metabolism, was corrected by Cr3+. Mechanistically, Cr3+ reversed hyperinsulinemia-induced cellular cholesterol accrual and associated defects in cholesterol transporter ATP-binding cassette transporter-A1 trafficking and apolipoprotein A1-mediated cholesterol efflux. Moreover, direct activation of AMP-activated protein kinase, which is known to be activated by Cr3+, or inhibition of hexosamine biosynthesis pathway activity, which is known to be elevated by hyperinsulinemia, mimics Cr3+ action. CONCLUSIONS These findings suggest a mechanism of Cr3+ action that fits with long-standing claims of its role in cholesterol homeostasis. Furthermore, these data imply a mechanistic basis for the coexistence of dyslipidemia with hyperinsulinemia.
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Affiliation(s)
- Whitney Sealls
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Bldg, Rm 308A, Indianapolis, IN 46260, USA
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Chien Y, Lai YH, Kwok CF, Ho LT. Endothelin-1 suppresses long-chain fatty acid uptake and glucose uptake via distinct mechanisms in 3T3-L1 adipocytes. Obesity (Silver Spring) 2011; 19:6-12. [PMID: 20559307 DOI: 10.1038/oby.2010.124] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Endothelin-1 (ET-1) has been demonstrated to induce insulin resistance (IR) and lipolysis, raising the possibility that ET-1 may also contribute to the elevated fatty acid levels in IR-associated comorbidities. We attempted to evaluate whether ET-1 also affects the long-chain fatty acid (LCFA) utilization in 3T3-L1 adipocytes. The effects of chronic ET-1 exposure on basal and insulin-stimulated LCFA uptake, and LCFA uptake kinetics were examined in 3T3-L1 adipocytes. Chronic exposure to ET-1 induced IR and suppressed basal and insulin-stimulated LCFA uptake. Given that insulin acutely stimulates LCFA uptake, there was dramatically similar trend of dose-response curves for ET-1-suppressed LCFA uptake, and also similar corresponding IC₅₀ values, between basal and insulin-stimulated states, reflecting that ET-1 predominantly suppresses basal LCFA uptake. Results of LCFA kinetics, western blots, and CD36 inhibition using sulfosuccinimidyl oleate (SSO) revealed that suppression of LCFA uptake by ET-1 is associated with downregulation of CD36. ET type A receptor (ET(A)R) antagonist BQ-610 reversed the IR induction and the ET-1-suppressed LCFA uptake. Exogenous replenishment of phosphatidylinositol (PI) 4, 5-bisphosphate (PIP₂) prevented IR induction, but not the suppression of LCFA uptake by ET-1. Pharmacological inhibition of the activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) completely blocked the ET-1-suppressed LCFA uptake. Serving as an inducer of IR, ET-1 also chronically suppresses LCFA uptake via PIP₂-independent and ERK-dependent pathway. The interplay between impaired glucose disposal and diminished LCFA utilization, induced by ET-1, could worsen the dysregulation of adipose metabolism and energy homeostasis in insulin-resistant states.
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Affiliation(s)
- Yueh Chien
- Institutes of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan
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Lai YH, Chien Y, Kwok CF, Ho LT. Enhanced long-chain fatty acid uptake contributes to overaccumulation of triglyceride in hyperinsulinemic insulin-resistant 3T3-L1 adipocytes. Metabolism 2010; 59:1784-93. [PMID: 20580042 DOI: 10.1016/j.metabol.2010.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 04/21/2010] [Accepted: 05/11/2010] [Indexed: 11/21/2022]
Abstract
The precise pathogenesis of obesity remains controversial. In obesity, diminished adipose glucose utilization suggests that some other substrates may be responsible for the adipose triglyceride (TG) overaccumulation. Here we attempted to evaluate if long-chain fatty acid (LCFA) flux was modulated by a physiologically relevant condition of hyperinsulinemia in 3T3-L1 adipocytes and if the altered LCFA influx might eventually contribute to the TG overaccumulation in obesity. The effects of prolonged insulin exposure to adipocytes on basal, insulin-stimulated LCFA uptake as well as intracellular LCFA metabolism were measured. Prolonged insulin exposure was found to induce insulin resistance (IR) yet enhance basal and insulin-stimulated LCFA uptake in normoglycemic condition, and the addition of high glucose exacerbated these abnormalities of both glucose and LCFA influx. Along with the enhanced LCFA uptake was an increase in the rates of intracellular LCFA deposition and incorporation into TG; but a decrease was found in basal and insulin-suppressive LCFA oxidation, as well as in isoproterenol-induced fatty acid efflux. Inhibition of either phosphatidylinositol 3-kinase or mitogen-activated protein kinase (MAPK) pathway did not prevent the induction of IR, whereas the enhanced basal and insulin-stimulated LCFA uptake was abrogated by inhibition of MAPK pathway. In hyperinsulinemic insulin-resistant 3T3-L1 adipocytes, basal and insulin-stimulated LCFA uptake tends to increase via a MAPK-dependent mechanism. The increment of LCFA influx predominantly accounts for TG overaccumulation, but not for mitochondrial oxidation, and is prone to retain within adipocytes. These findings may interpret the plausible mechanism of pathogenesis for obesity in hyperinsulinemia-associated IR.
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Affiliation(s)
- Ying-Hsiu Lai
- Institute of Physiology, National Yang-Ming University, Taipei 11221, Taiwan
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Polymorphisms in the tropomyosin TPM1 short isoform promoter alter gene expression and are associated with increased risk of metabolic syndrome. Am J Hypertens 2010; 23:399-404. [PMID: 20075843 DOI: 10.1038/ajh.2009.278] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Inflammation contributes to the development of atherosclerotic lesions in the metabolic syndrome. Tropomyosin isoform expression is altered in this disease and has a role in inflammatory cell plasticity, motility, and insulin sensitivity. We determined the frequency of haplotype carriage of three single-nucleotide polymorphisms (SNPs) in the short isoform promoter of the TPM1 gene in 300 normal controls and 500 metabolic syndrome patients. The effect of each haplotype on tropomyosin gene expression was assessed. METHODS PCR-restriction fragment length polymorphism assays were developed for each polymorphism. Promoter activity was measured using luciferase assays in the insulin-sensitive human embryonic kidney (HEK) 293 and the monocyte THP-1 lines. RESULTS The SNPs -111(T/C), -426(T/C), and -491(A/G), relative to the TPM1 short isoform transcription start site, occurred in haplotypes ATT, GCT, GTT, and GTC, and were in strong linkage disequilibrium. ATT had a frequency of 66%. The presence of -491G, which conforms to a predicted binding site for transcription factor AML-1, caused a decrease in gene expression of 24% in the HEK 293 cells. In the THP-1 cells, haplotypes GTC and GTT gave 24% lower expression, whereas haplotype GCT gave expression at wild-type levels. The carriage of a -491G allele gave an odds ratio of 1.4 (95% CI 1.02-1.8) for the metabolic syndrome (P < 0.03). CONCLUSIONS A polymorphism in the TPM1 short isoform promoter region is predicted to alter transcription factor binding, alters gene expression and is associated with the metabolic syndrome. This could affect inflammatory cells and cytoskeleton-mediated insulin signaling.
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Xiong W, Jordens I, Gonzalez E, McGraw TE. GLUT4 is sorted to vesicles whose accumulation beneath and insertion into the plasma membrane are differentially regulated by insulin and selectively affected by insulin resistance. Mol Biol Cell 2010; 21:1375-86. [PMID: 20181829 PMCID: PMC2854095 DOI: 10.1091/mbc.e09-08-0751] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
GLUT4 is sorted to vesicles whose accumulation beneath and insertion into the plasma membrane are differentially regulated by insulin and selectively affected by insulin resistance. Insulin stimulates glucose transport by recruiting the GLUT4 glucose transporter to the plasma membrane. Here we use total internal reflection fluorescence microscopy to show that two trafficking motifs of GLUT4, a FQQI motif and a TELE-based motif, target GLUT4 to specialized vesicles that accumulate adjacent to the plasma membrane of unstimulated adipocytes. Mutations of these motifs redistributed GLUT4 to transferrin-containing recycling vesicles adjacent to the plasma membrane, and the degree of redistribution correlated with the increases of the GLUT4 mutants in the plasma membrane of basal adipocytes. These results establish that GLUT4 defaults to recycling endosomes when trafficking to specialized vesicles is disrupted, supporting the hypothesis that the specialized vesicles are derived from an endosomal compartment. Insulin stimulates both the accumulation of GLUT4 in the evanescent field and the fraction of this GLUT4 that is inserted into the plasma membrane. Unexpectedly, these two steps are differentially affected by the development of insulin resistance. We ascribe this selective insulin resistance to inherent differences in the sensitivities of GLUT4 vesicle accumulation and insertion into the plasma membrane to insulin. Differences in insulin sensitivities of various processes may be a general mechanism for the development of the physiologically important phenomenon of selective insulin resistance.
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Affiliation(s)
- Wenyong Xiong
- Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10065, USA
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Mayer CM, Belsham DD. Central insulin signaling is attenuated by long-term insulin exposure via insulin receptor substrate-1 serine phosphorylation, proteasomal degradation, and lysosomal insulin receptor degradation. Endocrinology 2010; 151:75-84. [PMID: 19887566 DOI: 10.1210/en.2009-0838] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Central insulin signaling is critical for the prevention of insulin resistance. Hyperinsulinemia contributes to insulin resistance, but it is not yet clear whether neurons are subject to cellular insulin resistance. We used an immortalized, hypothalamic, clonal cell line, mHypoE-46, which exemplifies neuronal function and expresses the components of the insulin signaling pathway, to determine how hyperinsulinemia modifies neuronal function. Western blot analysis indicated that prolonged insulin treatment of mHypoE-46 cells attenuated insulin signaling through phospho-Akt. To understand the mechanisms involved, time-course analysis was performed. Insulin exposure for 4 and 8 h phosphorylated Akt and p70-S6 kinase (S6K1), whereas 8 and 24 h treatment decreased insulin receptor (IR) and IR substrate 1 (IRS-1) protein levels. Insulin phosphorylation of S6K1 correlated with IRS-1 ser1101 phosphorylation and the mTOR-S6K1 pathway inhibitor rapamycin prevented IRS-1 serine phosphorylation. The proteasomal inhibitor epoxomicin and the lysosomal pathway inhibitor 3-methyladenine prevented the degradation of IRS-1 and IR by insulin, respectively, and pretreatment with rapamycin, epoxomicin, or 3-methyladenine prevented attenuation of insulin signaling by long-term insulin exposure. Thus, a sustained elevation of insulin levels diminishes neuronal insulin signaling through mTOR-S6K1-mediated IRS-1 serine phosphorylation, proteasomal degradation of IRS-1 and lysosomal degradation of the IR.
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Ng Y, Ramm G, James DE. Dissecting the mechanism of insulin resistance using a novel heterodimerization strategy to activate Akt. J Biol Chem 2009; 285:5232-9. [PMID: 20022950 DOI: 10.1074/jbc.m109.060632] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Insulin resistance can occur in response to many different external insults, including chronic exposure to insulin itself as well as other agonists such as dexamethasone. It is generally thought that such defects arise due to a defect(s) at an early stage in the insulin signaling cascade. One model suggests that this involves activation of the mammalian target of rapamycin/S6 kinase pathway, which inactivates insulin receptor substrate via Ser/Thr phosphorylation. However, we have recently shown that insulin receptor substrate is not a major node for insulin resistance defects. To explore the mechanism of insulin resistance, we have developed a novel system to activate Akt independently of its upstream effectors as well as other insulin-responsive pathways such as mitogen-activated protein kinase. 3T3-L1 adipocytes were rendered insulin-resistant either with chronic insulin or dexamethasone treatment, but conditional activation of Akt2 stimulated hemagglutinin-tagged glucose transporter 4 translocation to the same extent in these insulin-resistant and control cells. However, addition of insulin to cells in which Akt was conditionally activated resulted in a reversion to the insulin-resistant state, indicating a feedforward inhibitory mechanism activated by insulin itself. This effect was overcome with wortmannin, implicating a role for phosphatidylinositol 3-kinase in this inhibitory process. We conclude that in chronic insulin- and dexamethasone-treated cells, acute activation with insulin itself is required to activate a feedforward inhibitory pathway likely emanating from phosphatidylinositol 3-kinase that converges on a target downstream of Akt to cause insulin resistance.
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Affiliation(s)
- Yvonne Ng
- Diabetes and Obesity Research Program, The Garvan Institute of Medical Research, Sydney, New South Wales 2010
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Compartmentalization and regulation of insulin signaling to GLUT4 by the cytoskeleton. VITAMINS AND HORMONES 2009; 80:193-215. [PMID: 19251039 DOI: 10.1016/s0083-6729(08)00608-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
One of the early events in the development of Type 2 diabetes appears to be an inhibition of insulin-mediated GLUT4 redistribution to the cell surface in tissues that express GLUT4. Understanding this process, and how it begins to breakdown in the development of insulin resistance is quite important as we face treatment and prevention of metabolic diseases. Over the past few years, and increasing number of laboratories have produced compelling data to demonstrate a role for both the actin and microtubule networks in the regulation of insulin-mediated GLUT4 redistribution to the cell surface. In this review, we explore this process from insulin-signal transduction to fusion of GLUT4 membrane vesicles, focusing on studies that have implicated a role for the cytoskeleton. We see from this body of work that both the actin network and the microtubule cytoskeleton play roles as targets of insulin action and effectors of insulin signaling leading to changes in GLUT4 redistribution to the cell surface and insulin-mediated glucose uptake.
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Bhonagiri P, Pattar GR, Horvath EM, Habegger KM, McCarthy AM, Elmendorf JS. Hexosamine biosynthesis pathway flux contributes to insulin resistance via altering membrane phosphatidylinositol 4,5-bisphosphate and cortical filamentous actin. Endocrinology 2009; 150:1636-45. [PMID: 19036880 PMCID: PMC2659275 DOI: 10.1210/en.2008-1102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We recently found that plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP(2))-regulated filamentous actin (F-actin) polymerization was diminished in hyperinsulinemic cell culture models of insulin resistance. Here we delineated whether increased glucose flux through the hexosamine biosynthesis pathway (HBP) causes the PIP(2)/F-actin dysregulation and insulin resistance induced by hyperinsulinemia. Increased HBP activity was detected in 3T3-L1 adipocytes cultured under conditions closely resembling physiological hyperinsulinemia (5 nm insulin for 12 h) and in cells where HBP activity was amplified by 2 mm glucosamine (GlcN). Both the physiological hyperinsulinemia and experimental GlcN challenge induced comparable losses of PIP(2) and F-actin. In addition to protecting against the insulin-induced membrane/cytoskeletal abnormality and insulin-resistant state, exogenous PIP(2) corrected the GlcN-induced insult on these parameters. Moreover, in accordance with HBP flux directly weakening PIP(2)/F-actin structure, inhibition of the rate-limiting HBP enzyme (glutamine:fructose-6-phosphate amidotransferase) restored PIP(2)-regulated F-actin structure and insulin responsiveness. Conversely, overexpression of glutamine:fructose-6-phosphate amidotransferase was associated with a loss of detectable plasma membrane PIP(2) and insulin sensitivity. A slight decrease in intracellular ATP resulted from amplifying HBP by hyperinsulinemia and GlcN. However, experimental maintenance of the intracellular ATP pool under both conditions with inosine did not reverse the PIP(2)/F-actin-based insulin-resistant state. Furthermore, less invasive challenges with glucose, in the absence of insulin, also led to PIP(2)/F-actin dysregulation. Accordingly, we suggest that the functionality of cell systems dependent on PIP(2) and/or F-actin status, such as the glucose transport system, can be critically compromised by inappropriate HBP activity.
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Affiliation(s)
- Padma Bhonagiri
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Room 308A, Indianapolis, Indiana 46202.
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Abstract
Accumulated evidence over the last several years indicates that insulin regulates multiple steps in the overall translocation of GLUT4 vesicles to the fat/muscle cell surface, including formation of an intracellular storage pool of GLUT4 vesicles, its movement to the proximity of the cell surface, and the subsequent docking/fusion with the plasma membrane. Insulin-stimulated formation of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3); and in some cases, of its catabolite PtdIns(3,4)P(2)] plays a pivotal role in this process. PtdIns(3,4,5)P(3) is synthesized by the activated wortmannin-sensitive class IA phosphoinositide (PI) 3-kinase and controls the rate-limiting cell surface terminal stages of the GLUT4 journey. However, recent research is consistent with the conclusion that signals by each of the remaining five PIs, i.e., PtdIns(3)P, PtdIns(4)P, PtdIns(5)P, PtdIns(3,5)P(2), and PtdIns(4,5)P(2), may act in concert with that of PtdIns(3,4,5)P(3) in integrating the insulin receptor-issued signals with GLUT4 surface translocation and glucose transport activation. This review summarizes the experimental evidence supporting the complementary function of these PIs in insulin responsiveness of fat and muscle cells, with particular reference to mechanistic insights and functional significance in the regulation of overall GLUT4 vesicle dynamics.
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Affiliation(s)
- Assia Shisheva
- Wayne State University School of Medicine, Detroit, MI 48201, USA.
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Insulin action on glucose transporters through molecular switches, tracks and tethers. Biochem J 2008; 413:201-15. [DOI: 10.1042/bj20080723] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Glucose entry into muscle cells is precisely regulated by insulin, through recruitment of GLUT4 (glucose transporter-4) to the membrane of muscle and fat cells. Work done over more than two decades has contributed to mapping the insulin signalling and GLUT4 vesicle trafficking events underpinning this response. In spite of this intensive scientific research, there are outstanding questions that continue to challenge us today. The present review summarizes the knowledge in the field, with emphasis on the latest breakthroughs in insulin signalling at the level of AS160 (Akt substrate of 160 kDa), TBC1D1 (tre-2/USP6, BUB2, cdc16 domain family member 1) and their target Rab proteins; in vesicle trafficking at the level of vesicle mobilization, tethering, docking and fusion with the membrane; and in the participation of the cytoskeleton to achieve optimal temporal and spatial location of insulin-derived signals and GLUT4 vesicles.
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Horvath EM, Tackett L, Elmendorf JS. A novel membrane-based anti-diabetic action of atorvastatin. Biochem Biophys Res Commun 2008; 372:639-43. [PMID: 18514061 DOI: 10.1016/j.bbrc.2008.05.095] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 05/16/2008] [Indexed: 12/25/2022]
Abstract
We recently found that chromium picolinate (CrPic), a nutritional supplement thought to improve insulin sensitivity in individuals with impaired glucose tolerance, enhances insulin action by lowering plasma membrane (PM) cholesterol. Recent in vivo studies suggest that cholesterol-lowering statin drugs benefit insulin sensitivity in insulin-resistant patients, yet a mechanism is unknown. We report here that atorvastatin (ATV) diminished PM cholesterol by 22% (P<0.05) in 3T3-L1 adipocytes. As documented for CrPic, this small reduction in PM cholesterol enhanced insulin action. Replenishment of cholesterol mitigated the positive effects of ATV on insulin sensitivity. Co-treatment with CrPic and ATV did not amplify the extent of PM cholesterol loss or insulin sensitivity gain. In addition, analyses of insulin signal transduction suggest a non-signaling basis of both therapies. Our data reveal an unappreciated beneficial non-hepatic effect of statin action and highlight a novel mechanistic similarity between two recently recognized therapies of impaired glucose tolerance.
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Affiliation(s)
- Emily M Horvath
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, VanNuys Medical Science, Building Rm 308A, Indianapolis, IN 46202, USA
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Robinson KA, Buse MG. Mechanisms of high-glucose/insulin-mediated desensitization of acute insulin-stimulated glucose transport and Akt activation. Am J Physiol Endocrinol Metab 2008; 294:E870-81. [PMID: 18303120 PMCID: PMC2703196 DOI: 10.1152/ajpendo.00644.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High-glucose/low-dose insulin-mediated insulin resistance of glucose transport was studied in 3T3-L1 adipocytes. In this model, proximal insulin signaling, including insulin receptor substrate (IRS)-1-bound phosphatidylinositol 3-kinase (PI 3-kinase) activation, is preserved, but insulin-stimulated protein kinase B (Akt) activation is markedly impaired. To assess a difference in acute insulin-stimulated production of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3], cells were labeled with [32P]orthophosphate, and glycerophosphoinositides were quantified by HPLC. Although basal PtdIns(3,4,5)P3 was similar, insulin stimulated its production 33.6% more in controls (P < 0.03) than in insulin-resistant cells. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) protein, a lipid phosphatase that dephosphorylates PtdIns(3,4,5)P3 in the 3-position, was significantly and specifically increased in insulin-resistant cells. Treatment with rapamycin [a specific inhibitor of mammalian target of rapamycin complex 1 (mTORC1)] inhibited the increased PTEN expression and partially restored insulin-stimulated glucose transport and Akt activation to insulin-resistant cells. Acute insulin markedly stimulated Ser(636/639) phosphorylation of IRS-1; this was rapamycin inhibited but was significantly decreased in cells that had been preexposed to insulin, whereas total IRS-1 was unaffected. These findings were essentially paralleled by changes in the activation of p70 S6 kinase and S6-ribosomal protein. Overexpression of uncoupling protein-1 or manganese superoxide dismutase did not prevent the development of insulin-resistant glucose transport and impaired Akt activation in high-glucose/low-insulin-pretreated cells. The insulin resistance associated with glucotoxicity in our model reflects in part decreased availability of PtdIns(3,4,5)P3, which correlates with increased PTEN protein expression. Chronic activation of mTORC1 plays a role in stimulating PTEN expression and possibly in activation or induction of a phosphoprotein phosphatase. No evidence was found for a role for increased mitochondrial superoxide production in this model.
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Affiliation(s)
- Katherine A Robinson
- Division of Endocrinology, Department of Medicine, Medical University of South Carolina, Charleston, SC, USA
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Horvath EM, Tackett L, McCarthy AM, Raman P, Brozinick JT, Elmendorf JS. Antidiabetogenic effects of chromium mitigate hyperinsulinemia-induced cellular insulin resistance via correction of plasma membrane cholesterol imbalance. Mol Endocrinol 2007; 22:937-50. [PMID: 18165437 DOI: 10.1210/me.2007-0410] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Previously, we found that a loss of plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure contributes to insulin-induced insulin resistance. Interestingly, we also demonstrated that chromium picolinate (CrPic), a dietary supplement thought to improve glycemic status in insulin-resistant individuals, augments insulin-regulated glucose transport in insulin-sensitive 3T3-L1 adipocytes by lowering PM cholesterol. Here, to gain mechanistic understanding of these separate observations, we tested the prediction that CrPic would protect against insulin-induced insulin resistance by improving PM features important in cytoskeletal structure and insulin sensitivity. We found that insulin-induced insulin-resistant adipocytes display elevated PM cholesterol with a reciprocal decrease in PM PIP2. This lipid imbalance and insulin resistance was corrected by the cholesterol-lowering action of CrPic. The PM lipid imbalance did not impair insulin signaling, nor did CrPic amplify insulin signal transduction. In contrast, PM analyses corroborated cholesterol and PIP2 interactions influencing cytoskeletal structure. Because extensive in vitro study documents an essential role for cytoskeletal capacity in insulin-regulated glucose transport, we next evaluated intact skeletal muscle from obese, insulin-resistant Zucker (fa/fa) rats. Because insulin resistance in these animals likely involves multiple mechanisms, findings that cholesterol-lowering restored F-actin cytoskeletal structure and insulin sensitivity to that witnessed in lean control muscle were striking. Also, experiments using methyl-beta-cyclodextrin to shuttle cholesterol into or out of membranes respectively recapitulated the insulin-induced insulin-resistance and protective effects of CrPic on membrane/cytoskeletal interactions and insulin sensitivity. These data predict a PM cholesterol basis for hyperinsulinemia-associated insulin resistance and importantly highlight the reversible nature of this abnormality.
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Affiliation(s)
- Emily M Horvath
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202, USA
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Etkovitz N, Rubinstein S, Daniel L, Breitbart H. Role of PI3-kinase and PI4-kinase in actin polymerization during bovine sperm capacitation. Biol Reprod 2007; 77:263-73. [PMID: 17494916 DOI: 10.1095/biolreprod.106.056705] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
We have recently demonstrated the involvement of phospholipase D (PLD) in actin polymerization during mammalian sperm capacitation. In the present study, we investigated the involvement of phosphatidylinositol 3- and 4-kinases (PI3K and PI4K) in actin polymerization, as well as the production of PIP(2(4,5)), which is a known cofactor for PLD activation, during bovine sperm capacitation. PIK3R1 (p85 alpha regulatory subunit of PI3K) and PIKCB (PI4K beta) in bovine sperm were detected by Western blotting and immunocytochemistry. Wortmannin (WT) inhibited PI3K and PI4K type III at concentrations of 10 nM and 10 microM, respectively. PI4K activity and PIP(2(4,5)) production were blocked by 10 microM WT but not by 10 nM WT, whereas PI3K activity and PIP(3(3,4,5)) production were blocked by 10 nM WT. Moreover, spermine, which is a known PI4K activator and a component of semen, activated sperm PI4K, resulting in increased cellular PIP(2(4,5)) and F-actin formation. The increases in PIP(2(4,5)) and F-actin intracellular levels during sperm capacitation were mediated by PI4K but not by PI3K activity. Activation of protein kinase A (PKA) by dibutyryl cAMP enhanced PIP(2(4,5)), PIP(3(3,4,5)), and F-actin formation, and these effects were mediated through PI3K. On the other hand, activation of PKC by phorbol myristate acetate enhanced PIP(2(4,5)) and F-actin formation mediated by PI4K activity, while the PI3K activity and intracellular PIP(3(3,4,5)) levels were reduced. These results suggest that two alternative pathways lead to PI4K activation: indirect activation by PKA, which is mediated by PI3K; and activation by PKC, which is independent of PI3K activity. Our results also suggest that spermine, which is present in the ejaculate, regulates PI4K activity during the capacitation process in vivo.
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Affiliation(s)
- Nir Etkovitz
- The Mina & Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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Abstract
The dissection of mechanisms that regulate glucose transport by insulin has revealed an intricate network of signaling molecules scattered from the insulin receptor to the intracellular glucose transporter GLUT4. It is also appreciated that some insulin receptor signals jaunt in different directions to regulate events essential for the efficient redistribution of GLUT4 to the plasma membrane. Moreover key assists in the process appear to be arranged by membrane lipids and cytoskeletal proteins. Following current considerations of insulin signals regulating GLUT4, this review will focus on in vitro and in vivo evidence that supports an essential role for phosphoinositides and actin filaments in the control of glucose transport. The discussion will visit recent cell culture, whole animal, and human data highlighting membrane and cytoskeletal aspects of insulin resistance.
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Affiliation(s)
- Joseph T Brozinick
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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Min J, Kyung Kim Y, Cipriani PG, Kang M, Khersonsky SM, Walsh DP, Lee JY, Niessen S, Yates JR, Gunsalus K, Piano F, Chang YT. Forward chemical genetic approach identifies new role for GAPDH in insulin signaling. Nat Chem Biol 2006; 3:55-9. [PMID: 17115034 DOI: 10.1038/nchembio833] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Accepted: 09/11/2006] [Indexed: 11/09/2022]
Abstract
Insulin and insulin-like growth factor have an essential role in growth, development and the maintenance of metabolic homeostasis, including glucose uptake from the bloodstream. Researchers have identified mutations in insulin receptors that cause severe insulin resistance, and a temperature-sensitive daf-2 (a gene encoding an insulin receptor-like protein) mutant in Caenorhabditis elegans has served as an insulin resistance model. Here we report a forward chemical genetic approach with a tagged library that we used to identify a small molecule, GAPDH segregator (GAPDS), that suppresses the dauer formation induced by the daf-2 mutant. Like insulin, GAPDS increased both glucose uptake and the concentration of phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) in mammalian preadipocytes. Using affinity matrices and RNA interference, we identified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a GAPDS target. We discovered that GAPDH stimulates phosphatase activity against not only PtdIns(3,4,5)P(3) but also PtdIns(4,5)P(2). These results suggest that GAPDH is both an active regulator in the phosphoinositide-mediated signaling pathway and a potential new target for insulin resistance treatment.
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Affiliation(s)
- Jaeki Min
- Department of Chemistry, New York University, New York, New York 10003, USA
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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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Sheetz MP, Sable JE, Döbereiner HG. Continuous membrane-cytoskeleton adhesion requires continuous accommodation to lipid and cytoskeleton dynamics. ACTA ACUST UNITED AC 2006; 35:417-34. [PMID: 16689643 DOI: 10.1146/annurev.biophys.35.040405.102017] [Citation(s) in RCA: 232] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The plasma membrane of most animal cells conforms to the cytoskeleton and only occasionally separates to form blebs. Previous studies indicated that many weak interactions between cytoskeleton and the lipid bilayer kept the surfaces together to counteract the normal outward pressure of cytoplasm. Either the loss of adhesion strength or the formation of gaps in the cytoskeleton enables the pressure to form blebs. Membrane-associated cytoskeleton proteins, such as spectrin and filamin, can control the movement and aggregation of membrane proteins and lipids, e.g., phosphoinositol phospholipids (PIPs), as well as blebbing. At the same time, lipids (particularly PIPs) and membrane proteins affect cytoskeleton and signaling dynamics. We consider here the roles of the major phosphatidylinositol-4,5-diphosphate (PIP2) binding protein, MARCKS, and PIP2 levels in controlling cytoskeleton dynamics. Further understanding of dynamics will provide important clues about how membrane-cytoskeleton adhesion rapidly adjusts to cytoskeleton and membrane dynamics.
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Affiliation(s)
- Michael P Sheetz
- Biological Sciences Department, Columbia University, New York, NY, 10027, USA.
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McCarthy AM, Spisak KO, Brozinick JT, Elmendorf JS. Loss of cortical actin filaments in insulin-resistant skeletal muscle cells impairs GLUT4 vesicle trafficking and glucose transport. Am J Physiol Cell Physiol 2006; 291:C860-8. [PMID: 16774991 PMCID: PMC2424226 DOI: 10.1152/ajpcell.00107.2006] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Study has demonstrated an essential role of cortical filamentous actin (F-actin) in insulin-regulated glucose uptake by skeletal muscle. Here, we tested whether perturbations in F-actin contributed to impaired insulin responsiveness provoked by hyperinsulinemia. In L6 myotubes stably expressing GLUT4 that carries an exofacial myc-epitope tag, acute insulin stimulation (20 min, 100 nM) increased GLUT4myc translocation and glucose uptake by approximately 2-fold. In contrast, a hyperinsulinemic state, induced by inclusion of 5 nM insulin in the medium for 12 h decreased the ability of insulin to stimulate these processes. Defects in insulin signaling did not readily account for the observed disruption. In contrast, hyperinsulinemia reduced cortical F-actin. This occurred concomitant with a loss of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)), a lipid involved in cytoskeletal regulation. Restoration of plasma membrane PIP(2) in hyperinsulinemic cells restored F-actin and insulin responsiveness. Consistent with these in vitro observations suggesting that the hyperinsulinemic state negatively affects cortical F-actin structure, epitrochlearis skeletal muscle from insulin-resistant hyperinsulinemic Zucker fatty rats displayed a similar loss of F-actin structure compared with that in muscle from lean insulin-sensitive littermates. We propose that a component of insulin-induced insulin resistance in skeletal muscle involves defects in PIP(2)/F-actin structure essential for insulin-regulated glucose transport.
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Affiliation(s)
- Alicia M McCarthy
- Dept. of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Abstract
In skeletal muscle and adipose tissue, insulin-stimulated glucose uptake is dependent upon translocation of the insulin-responsive glucose transporter GLUT4 from intracellular storage compartments to the plasma membrane. This insulin-induced redistribution of GLUT4 protein is achieved through a series of highly organized membrane trafficking events, orchestrated by insulin receptor signals. Recently, several key molecules linking insulin receptor signals and membrane trafficking have been identified, and emerging evidence supports the importance of subcellular compartmentalization of signaling components at the right time and in the right place. In addition, the translocation of GLUT4 in adipocytes requires insulin stimulation of dynamic actin remodeling at the inner surface of the plasma membrane (cortical actin) and in the perinuclear region. This results from at least two independent insulin receptor signals, one leading to the activation of phosphatidylinositol (PI) 3-kinase and the other to the activation of the Rho family small GTP-binding protein TC10. Thus, both spatial and temporal regulations of actin dynamics, both beneath the plasma membrane and around endomembranes, by insulin receptor signals are also involved in the process of GLUT4 translocation.
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Affiliation(s)
- Makoto Kanzaki
- TUBERO/Tohoku University Biomedical Engineering Research Organization, Tohoku University, Sendai, Japan
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Funaki M, DiFransico L, Janmey PA. PI 4,5-P2 stimulates glucose transport activity of GLUT4 in the plasma membrane of 3T3-L1 adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:889-99. [PMID: 16828894 PMCID: PMC3118463 DOI: 10.1016/j.bbamcr.2006.05.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 05/08/2006] [Accepted: 05/09/2006] [Indexed: 12/16/2022]
Abstract
Insulin-stimulated glucose uptake through GLUT4 plays a pivotal role in maintaining normal blood glucose levels. Glucose transport through GLUT4 requires both GLUT4 translocation to the plasma membrane and GLUT4 activation at the plasma membrane. Here we report that a cell-permeable phosphoinositide-binding peptide, which induces GLUT4 translocation without activation, sequestered PI 4,5-P2 in the plasma membrane from its binding partners. Restoring PI 4,5-P2 to the plasma membrane after the peptide treatment increased glucose uptake. No additional glucose transporters were recruited to the plasma membrane, suggesting that the increased glucose uptake was attributable to GLUT4 activation. Cells overexpressing phosphatidylinositol-4-phosphate 5-kinase treated with the peptide followed by its removal exhibited a higher level of glucose transport than cells stimulated with a submaximal level of insulin. However, only cells treated with submaximal insulin exhibited translocation of the PH-domains of the general receptor for phosphoinositides (GRP1) to the plasma membrane. Thus, PI 4,5-P2, but not PI 3,4,5-P3 converted from PI 4,5-P2, induced GLUT4 activation. Inhibiting F-actin remodeling after the peptide treatment significantly impaired GLUT4 activation induced either by PI 4,5-P2 or by insulin. These results suggest that PI 4,5-P2 in the plasma membrane acts as a second messenger to activate GLUT4, possibly through F-actin remodeling.
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Affiliation(s)
- Makoto Funaki
- Department of Physiology, Institute for Medicine and Engineering, University of Pennsylvania, 1080 Vagelos Research Laboratories, 3340 Smith Walk, Philadelphia, 19104, USA.
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Bedi D, Clarke KJ, Dennis JC, Zhong Q, Brunson BL, Morrison EE, Judd RL. Endothelin-1 inhibits adiponectin secretion through a phosphatidylinositol 4,5-bisphosphate/actin-dependent mechanism. Biochem Biophys Res Commun 2006; 345:332-9. [PMID: 16682005 DOI: 10.1016/j.bbrc.2006.04.098] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 04/19/2006] [Indexed: 11/28/2022]
Abstract
Adiponectin is an adipokine with profound insulin-sensitizing, anti-inflammatory, and anti-atherogenic properties. Plasma levels of adiponectin are reduced in insulin resistant states such as obesity, type 2 diabetes and cardiovascular disease. However, the mechanism(s) by which adiponectin concentrations are decreased during disease development is unclear. Studies have shown that endothelin-1 (ET-1), a vasoconstrictor peptide, affects adipocyte glucose metabolism and secretion of adipokines such as leptin, resistin, and adiponectin. The goal of our study was to determine the mechanism by which ET-1 decreases adiponectin secretion. 3T3-L1 adipocytes were treated for 24h with ET-1 (10nM) and then stimulated with vehicle or insulin (100 nM) for a period of 1-2h. Chronic ET-1 (24h) treatment significantly decreased basal and insulin-stimulated adiponectin secretion by 66% and 47%, respectively. Inhibition of phosphatidylinositol 4,5-bisphosphate (PIP(2)) hydrolysis by the PLCbeta inhibitor, U73122, or exogenous addition of PIP(2):histone carrier complex (1.25:0.625 microM) ameliorated the decrease in basal and insulin-stimulated adiponectin secretion observed with ET-1. However, treatment with exogenous PIP(2):histone carrier complex and the actin depolymerizing agent latrunculin B (20 microM) did not reverse the ET-1-mediated decrease in adiponectin secretion. In conclusion, we demonstrate that ET-1 inhibits basal and insulin-stimulated adiponectin secretion through PIP(2) modulation of the actin cytoskeleton.
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Affiliation(s)
- Deepa Bedi
- Boshell Diabetes and Metabolic Diseases Research Program, Department of Anatomy, Physiology and Pharmacology, Auburn University, USA
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Chae KS, Dryer SE. The p38 mitogen-activated protein kinase pathway negatively regulates Ca2+-activated K+ channel trafficking in developing parasympathetic neurons. J Neurochem 2005; 94:367-79. [PMID: 15998288 DOI: 10.1111/j.1471-4159.2005.03201.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The trafficking of large-conductance Ca2+-activated K+ channels (K(Ca)) in chick ciliary ganglion neurons is regulated by growth factors. Here we show that a canonical p38 cascade inhibits K(Ca) trafficking in ciliary ganglion neurons. Two different p38 inhibitors (SB202190 or SB203580) or over-expression of dominant-negative forms of several components of the p38 cascade increased K(Ca) in ciliary neurons. Inhibition of protein synthesis or Golgi processing had no effect on this phenomenon, suggesting that p38 is acting at a distal step of the trafficking pathway. Depolymerization of filamentous actin (F-actin) increased functional expression of K(Ca), whereas stabilization of F-actin inhibited the effect of SB202190 on K(Ca) trafficking. SB202190 also caused an immunochemically detectable increase in K(Ca) on the plasma membrane. Inhibition of p38 decreased the extent of cortical F-actin in ciliary neurons. Macroscopic K(Ca) is suppressed by transforming growth factor (TGF) beta3. Application of TGFbeta3 increased the phosphorylation of p38 in ciliary neurons and increased cortical F-actin. Thus, the p38 signaling cascade endogenously suppresses development of functional K(Ca), in part by stabilizing an F-actin barrier that prevents plasma membrane insertion of functional channel complexes. This cascade also appears to mediate inhibitory effects of TGFbeta3 on the expression of K(Ca).
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Affiliation(s)
- Kwon-Seok Chae
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5513, USA
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Bijian K, Takano T, Papillon J, Le Berre L, Michaud JL, Kennedy CRJ, Cybulsky AV. Actin cytoskeleton regulates extracellular matrix-dependent survival signals in glomerular epithelial cells. Am J Physiol Renal Physiol 2005; 289:F1313-23. [PMID: 16014575 DOI: 10.1152/ajprenal.00106.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Adhesion of rat glomerular epithelial cells (GEC) to collagen activates focal adhesion kinase (FAK) and the Ras-extracellular signal-regulated kinase (ERK) pathway and supports survival (prevents apoptosis). The present study addresses the relationship between actin organization and the survival phenotype. Parental GEC (adherent to collagen) and GEC stably transfected with constitutively active mutants of mitogen-activated protein kinase kinase (R4F-MEK) or FAK (CD2-FAK) (on plastic) showed ERK activation, low levels of apoptosis, and a cortical distribution of F-actin. Parental GEC adherent to plastic showed increased apoptosis, disorganization of cortical F-actin, and formation of prominent stress fibers. Assembly of cortical F-actin was, at least in part, mediated via ERK. However, disruption of the actin cytoskeleton with cytochalasin D or latrunculin B in parental GEC (on collagen) and in GEC that express R4F-MEK or CD2-FAK (on plastic) decreased ERK activation and increased apoptosis. Expression of a constitutively active RhoA (L(63)RhoA) induced assembly of cortical F-actin, promoted ERK activation, and supplanted the requirement of collagen for survival. Adhesion of GEC to collagen increased phosphatidylinositol-4,5-bisphosphate (PIP(2)). Downregulation or sequestration of PIP(2) by transfection with an inositol 5'-phosphatase or the plextrin-homology domain of phospholipase C-delta1 decreased F-actin content and survival. Moreover, overexpression of wild-type or K256E mutant alpha-actinin-4 with increased affinity for F-actin increased apoptosis. These results demonstrate a reciprocal relationship between collagen-induced cortical F-actin assembly and collagen-dependent survival signaling, including ERK activation. Appropriate remodeling of the actin cytoskeleton may be necessary for facilitating survival, as both disassembly and excessive crosslinking affect survival adversely.
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Affiliation(s)
- Krikor Bijian
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
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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: 38] [Impact Index Per Article: 2.0] [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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