1
|
Bremner SK, Berends R, Kaupisch A, Roccisana J, Sutherland C, Bryant NJ, Gould GW. Phosphorylation of the N-terminus of Syntaxin-16 controls interaction with mVps45 and GLUT4 trafficking in adipocytes. PeerJ 2023; 11:e15630. [PMID: 37520260 PMCID: PMC10373645 DOI: 10.7717/peerj.15630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 06/02/2023] [Indexed: 08/01/2023] Open
Abstract
The ability of insulin to stimulate glucose transport in muscle and fat cells is mediated by the regulated delivery of intracellular vesicles containing glucose transporter-4 (GLUT4) to the plasma membrane, a process known to be defective in disease such as Type 2 diabetes. In the absence of insulin, GLUT4 is sequestered in tubules and vesicles within the cytosol, collectively known as the GLUT4 storage compartment. A subset of these vesicles, known as the 'insulin responsive vesicles' are selectively delivered to the cell surface in response to insulin. We have previously identified Syntaxin16 (Sx16) and its cognate Sec1/Munc18 protein family member mVps45 as key regulatory proteins involved in the delivery of GLUT4 into insulin responsive vesicles. Here we show that mutation of a key residue within the Sx16 N-terminus involved in mVps45 binding, and the mutation of the Sx16 binding site in mVps45 both perturb GLUT4 sorting, consistent with an important role of the interaction of these two proteins in GLUT4 trafficking. We identify Threonine-7 (T7) as a site of phosphorylation of Sx16 in vitro. Mutation of T7 to D impairs Sx16 binding to mVps45 in vitro and overexpression of T7D significantly impaired insulin-stimulated glucose transport in adipocytes. We show that both AMP-activated protein kinase (AMPK) and its relative SIK2 phosphorylate this site. Our data suggest that Sx16 T7 is a potentially important regulatory site for GLUT4 trafficking in adipocytes.
Collapse
Affiliation(s)
| | - Rebecca Berends
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Alexandra Kaupisch
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Jennifer Roccisana
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Calum Sutherland
- Department of Cellular Medicine, University of Dundee, Dundee, United Kingdom
| | - Nia J. Bryant
- Department of Biology, University of York, York, United Kingdom
| | - Gwyn W. Gould
- SIPBS, University of Strathclyde, Glasgow, United Kingdom
| |
Collapse
|
2
|
Gu SH, Chang CH, Lin PL. Bombyxin-stimulated ecdysteroidogenesis in relation to sugar transporter/trehalase expressions in Bombyx prothoracic glands. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 151:103864. [PMID: 36336193 DOI: 10.1016/j.ibmb.2022.103864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 10/22/2022] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
Our previous studies showed that bombyxin stimulated ecdysteroidogenesis in Bombyx mori prothoracic glands (PGs) during a long-term incubation period in a phosphatidylinositol 3-kinase (PI3K)/Akt-dependent manner. In the present study, we further investigated the downstream signaling cascade in bombyxin-stimulated PGs. Our results showed that upon treatment with bombyxin, expression levels of the sugar transport 1 (St1) and St4 genes and trehalase 1 (Treh1) gene, but not ecdysteroid biosynthesis genes were greatly enhanced compared to the controls. Treatment with LY294002 (an inhibitor of PI3K) reduced the enhanced St1 and Treh1 expression levels, clearly indicating the involvement of PI3K. Treatment with 1 mM of mpV(pic) (a potent inhibitor of protein phosphotyrosine phosphatase and activator of insulin receptor (InR) kinase) also stimulated expression levels of the St1 and Treh1 genes, thus further confirming the involvement of the InR. Determining Treh enzyme activity showed that bombyxin treatment stimulated Treh enzyme activity in time- and PI3K-dependent manners. Validamycin A (a Treh inhibitor) blocked bombyxin-stimulated Treh enzyme activity and partly decreased bombyxin-stimulated ecdysteroidogenesis. A specific sugar transport inhibitor (cytochalasin B) and a glycolysis inhibitor (2-deoxy-D-glucose (2-DG)) also reduced bombyxin-stimulated ecdysteroidogenesis. Taken together, these results indicated that increased expressions of Sts and Treh1 and enhanced Treh enzyme activity downstream of InR/PI3K are involved in bombyxin-stimulated ecdysteroidogenesis in B. mori PGs.
Collapse
Affiliation(s)
- Shi-Hong Gu
- Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung, 404, Taiwan, ROC.
| | - Chia-Hao Chang
- Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung, 404, Taiwan, ROC
| | - Pei-Ling Lin
- Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung, 404, Taiwan, ROC
| |
Collapse
|
3
|
Dai HB, Wang HY, Wang FZ, Qian P, Gao Q, Zhou H, Zhou YB. Adrenomedullin ameliorates palmitic acid-induced insulin resistance through PI3K/Akt pathway in adipocytes. Acta Diabetol 2022; 59:661-673. [PMID: 34978596 DOI: 10.1007/s00592-021-01840-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/15/2021] [Indexed: 12/12/2022]
Abstract
AIMS White adipose tissue (WAT) dysfunction has been associated with adipose tissue low-grade inflammation and oxidative stress leading to insulin resistance (IR). Adrenomedullin (ADM), an endogenous active peptide considered as an adipokine, is associated with adipocytes function. METHODS We evaluated the protective effects of ADM against IR in 3T3-L1 adipocytes treated by palmitic acid (PA) and in visceral white adipose tissue (vWAT) of obese rats fed with high-fat diet. RESULTS We found that endogenous protein expressions of ADM and its receptor in PA-treated adipocytes were markedly increased. PA significantly induced impaired insulin signaling by affecting phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) axis and glucose transporter-4 (GLUT-4) levels, whereas ADM pretreatment enhanced insulin signaling PI3K/Akt and GLUT-4 membrane protein levels, decreased pro-inflammatory cytokines tumor necrosis factor α (TNFα), interleukin-1β (IL-1β) and IL-6 levels, and improved oxidative stress accompanied with reduced reactive oxygen species (ROS) levels and increased anti-oxidant enzymes manganese superoxide dismutase 2 (SOD2), glutathione peroxidase (GPx1) and catalase (CAT) protein expressions. Furthermore, ADM treatment not only improved IR in obese rats, but also effectively restored insulin signaling, and reduced inflammation and oxidative stress in vWAT of obese rats. CONCLUSIONS This study demonstrates a prevention potential of ADM against obesity-related metabolic disorders, due to its protective effects against IR, inflammation and oxidative stress in adipocytes.
Collapse
Affiliation(s)
- Hang-Bing Dai
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Hong-Yu Wang
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Fang-Zheng Wang
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Pei Qian
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Qing Gao
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Hong Zhou
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China
| | - Ye-Bo Zhou
- Department of Physiology, Nanjing Medical University, 101 Longmian Road, Nanjing, 211166, Jiangsu, China.
| |
Collapse
|
4
|
Black HL, Livingstone R, Mastick CC, Al Tobi M, Taylor H, Geiser A, Stirrat L, Kioumourtzoglou D, Petrie JR, Boyle JG, Bryant NJ, Gould GW. Knockout of Syntaxin-4 in 3T3-L1 adipocytes reveals new insight into GLUT4 trafficking and adiponectin secretion. J Cell Sci 2021; 135:273617. [PMID: 34859814 PMCID: PMC8767277 DOI: 10.1242/jcs.258375] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 11/18/2021] [Indexed: 11/20/2022] Open
Abstract
Adipocytes are key to metabolic regulation, exhibiting insulin-stimulated glucose transport that is underpinned by the insulin-stimulated delivery of glucose transporter type 4 (SLC2A4, also known and hereafter referred to as GLUT4)-containing vesicles to the plasma membrane where they dock and fuse, and increase cell surface GLUT4 levels. Adipocytokines, such as adiponectin, are secreted via a similar mechanism. We used genome editing to knock out syntaxin-4, a protein reported to mediate fusion between GLUT4-containing vesicles and the plasma membrane in 3T3-L1 adipocytes. Syntaxin-4 knockout reduced insulin-stimulated glucose transport and adiponectin secretion by ∼50% and reduced GLUT4 levels. Ectopic expression of haemagglutinin (HA)-tagged GLUT4 conjugated to GFP showed that syntaxin-4-knockout cells retain significant GLUT4 translocation capacity, demonstrating that syntaxin-4 is dispensable for insulin-stimulated GLUT4 translocation. Analysis of recycling kinetics revealed only a modest reduction in the exocytic rate of GLUT4 in knockout cells, and little effect on endocytosis. These analyses demonstrate that syntaxin-4 is not always rate limiting for GLUT4 delivery to the cell surface. In sum, we show that syntaxin-4 knockout results in reduced insulin-stimulated glucose transport, depletion of cellular GLUT4 levels and inhibition of adiponectin secretion but has only modest effects on the translocation capacity of the cells. This article has an associated First Person interview with Hannah L. Black and Rachel Livingstone, joint first authors of the paper. Summary: Syntaxin-4 knockout reduces insulin-stimulated glucose transport, depletes levels of cellular GLUT4 and inhibits secretion of adiponectin but only modestly affects the translocation capacity of the cells.
Collapse
Affiliation(s)
- Hannah L Black
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Rachel Livingstone
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Cynthia C Mastick
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.,Department of Biology, University of Nevada Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
| | - Mohammed Al Tobi
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Holly Taylor
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Angéline Geiser
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Laura Stirrat
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Dimitrios Kioumourtzoglou
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - John R Petrie
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK
| | - James G Boyle
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK.,School of Medicine, Dentistry and Nursing, University of Glasgow. Glasgow G12 8QQ, UK
| | - Nia J Bryant
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Gwyn W Gould
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| |
Collapse
|
5
|
Morris S, Geoghegan ND, Sadler JBA, Koester AM, Black HL, Laub M, Miller L, Heffernan L, Simpson JC, Mastick CC, Cooper J, Gadegaard N, Bryant NJ, Gould GW. Characterisation of GLUT4 trafficking in HeLa cells: comparable kinetics and orthologous trafficking mechanisms to 3T3-L1 adipocytes. PeerJ 2020; 8:e8751. [PMID: 32185116 PMCID: PMC7060922 DOI: 10.7717/peerj.8751] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/14/2020] [Indexed: 12/18/2022] Open
Abstract
Insulin-stimulated glucose transport is a characteristic property of adipocytes and muscle cells and involves the regulated delivery of glucose transporter (GLUT4)-containing vesicles from intracellular stores to the cell surface. Fusion of these vesicles results in increased numbers of GLUT4 molecules at the cell surface. In an attempt to overcome some of the limitations associated with both primary and cultured adipocytes, we expressed an epitope- and GFP-tagged version of GLUT4 (HA–GLUT4–GFP) in HeLa cells. Here we report the characterisation of this system compared to 3T3-L1 adipocytes. We show that insulin promotes translocation of HA–GLUT4–GFP to the surface of both cell types with similar kinetics using orthologous trafficking machinery. While the magnitude of the insulin-stimulated translocation of GLUT4 is smaller than mouse 3T3-L1 adipocytes, HeLa cells offer a useful, experimentally tractable, human model system. Here, we exemplify their utility through a small-scale siRNA screen to identify GOSR1 and YKT6 as potential novel regulators of GLUT4 trafficking in human cells.
Collapse
Affiliation(s)
- Silke Morris
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | | | - Jessica B A Sadler
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Anna M Koester
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | | | - Marco Laub
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Lucy Miller
- Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, UK
| | - Linda Heffernan
- School of Biology & Environmental Science, University College Dublin, Dublin, Ireland
| | - Jeremy C Simpson
- School of Biology & Environmental Science, University College Dublin, Dublin, Ireland
| | | | - Jon Cooper
- School of Engineering, University of Glasgow, Glasgow, UK
| | | | - Nia J Bryant
- Department of Biology, University of York, York, UK
| | - Gwyn W Gould
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| |
Collapse
|
6
|
Shen Y, Liu Y, Zheng SQ, Han J, Pei EL, Li ZH, Xie XY, Li ZQ, Luo M. Effects of Left Gastric Artery Ligation Versus Sleeve Gastrectomy on Obesity-Induced Adipose Tissue Macrophage Infiltration and Inflammation in Diet-Induced Obese Rats. Med Sci Monit 2019; 25:6719-6726. [PMID: 31493329 PMCID: PMC6752093 DOI: 10.12659/msm.915532] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Background Bariatric procedures such as left gastric artery ligation (LGAL) and sleeve gastrectomy (SG) have emerged as important procedures for treating morbid obesity. In this study, we compared the effects of LGAL vs. SG on obesity-induced adipose tissue macrophage infiltration and inflammation in diet-induced obese rats. Material/Methods Sprague-Dawley (SD) rats were fed a high-fat diet (HFD) for 16 weeks to induce obesity. SG, GLAL, or corresponding sham surgeries were performed in anesthetized rats. Inflammatory factor expression in serum and epididymal and retroperitoneal adipose tissues were analyzed 4 weeks after surgery. Macrophage infiltration and phenotype transformation were also assessed with Western blot analysis and immunofluorescence. Results Both LGAL and SG strongly attenuated high-fat diet (HFD)-induced fat accumulation in retroperitoneal and epididymal tissues. The expressions of inflammatory cytokines such as tumor necrosis factor (TNF)-agr;, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1 were downregulated after LGAL and after SG by promoting activation of M2 macrophages, despite continued exposure to HFD. Furthermore, both LGAL and SG resulted in increased macrophage infiltration, but did not contribute to phenotype transformation of macrophages to M1. Conclusions LGAL and SG both reduced fat accumulation caused by HFD feeding. Therapies designed to ameliorate the inflammatory response by promoting activation of M2 macrophages may be valuable.
Collapse
Affiliation(s)
- Yi Shen
- Department of Geriatrics, Tongji Hospital, Tongji University, School of Medicine, Shanghai, China (mainland)
| | - Yang Liu
- Department of Geriatrics, Tongji Hospital, Tongji University, School of Medicine, Shanghai, China (mainland)
| | - Shao-Qiu Zheng
- Department of Interventional and Vascular Surgery, Shanghai Tenth People's Hospital, Tongji University, School of Medicine, Shanghai, China (mainland)
| | - Jiang Han
- Division of General Surgery, Pudong New Area District Zhoupu Hospital, Shanghai, China (mainland)
| | - Er-Li Pei
- Department of General Surgery, Yangpu Hospital Affiliated to Shanghai Tongji University School of Medicine, Shanghai, China (mainland)
| | - Zhi-Hong Li
- Division of General Surgery, Pudong New Area District Zhoupu Hospital, Shanghai, China (mainland)
| | - Xiao-Yun Xie
- Department of Interventional and Vascular Surgery, Shanghai Tenth People's Hospital, Tongji University, School of Medicine, Shanghai, China (mainland)
| | - Zhi-Qiang Li
- Department of Neurology, Shanxi Academy of Medical Sciences, Shanxi Dayi Hospital, Taiyuan, Shanxi, China (mainland)
| | - Ming Luo
- Department of Geriatrics, Tongji Hospital, Tongji University, School of Medicine, Shanghai, China (mainland)
| |
Collapse
|
7
|
Overweight Mice Show Coordinated Homeostatic and Hedonic Transcriptional Response across Brain. eNeuro 2019; 5:eN-NWR-0287-18. [PMID: 30637329 PMCID: PMC6327943 DOI: 10.1523/eneuro.0287-18.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/09/2018] [Accepted: 10/15/2018] [Indexed: 12/29/2022] Open
Abstract
Obesogenic diets lead to overeating and obesity by inducing the expression of genes involved in hedonic and homeostatic responses in specific brain regions. However, how the effects on gene expression are coordinated in the brain so far remains largely unknown. In our study, we provided mice with access to energy-dense diet, which induced overeating and overweight, and we explored the transcriptome changes across the main regions involved in feeding and energy balance: hypothalamus, frontal cortex, and striatum. Interestingly, we detected two regulatory processes: a switch-like regulation with differentially expressed (DE) genes changing over 1.5-fold and “fine-tuned” subtler changes of genes whose levels correlated with body weight and behavioral changes. We found that genes in both categories were positioned within specific topologically associated domains (TADs), which were often differently regulated across different brain regions. These TADs were enriched in genes relevant for the physiological and behavioral observed changes. Our results suggest that chromatin structure coordinates diet-dependent transcriptional regulation.
Collapse
|
8
|
Guan X, Chaffey PK, Wei X, Gulbranson DR, Ruan Y, Wang X, Li Y, Ouyang Y, Chen L, Zeng C, Koelsch TN, Tran AH, Liang W, Shen J, Tan Z. Chemically Precise Glycoengineering Improves Human Insulin. ACS Chem Biol 2018; 13:73-81. [PMID: 29090903 PMCID: PMC6287623 DOI: 10.1021/acschembio.7b00794] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Diabetes is a leading cause of death worldwide and results in over 3 million annual deaths. While insulin manages the disease well, many patients fail to comply with injection schedules, and despite significant investment, a more convenient oral formulation of insulin is still unavailable. Studies suggest that glycosylation may stabilize peptides for oral delivery, but the demanding production of homogeneously glycosylated peptides has hampered transition into the clinic. We report here the first total synthesis of homogeneously glycosylated insulin. After characterizing a series of insulin glycoforms with systematically varied O-glycosylation sites and structures, we demonstrate that O-mannosylation of insulin B-chain Thr27 reduces the peptide's susceptibility to proteases and self-association, both critical properties for oral dosing, while maintaining full activity. This work illustrates the promise of glycosylation as a general mechanism for regulating peptide activity and expanding its therapeutic use.
Collapse
Affiliation(s)
- Xiaoyang Guan
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Patrick K. Chaffey
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Xiuli Wei
- Protein and Peptide Pharmaceutical Laboratory, Institute of Biophysics Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, People’s Republic of China
| | - Daniel R Gulbranson
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80303, United States
| | - Yuan Ruan
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Xinfeng Wang
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Yaohao Li
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Yan Ouyang
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80303, United States
| | - Liqun Chen
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Chen Zeng
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Theo N. Koelsch
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Amy H. Tran
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| | - Wei Liang
- Protein and Peptide Pharmaceutical Laboratory, Institute of Biophysics Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, People’s Republic of China
| | - Jingshi Shen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80303, United States
| | - Zhongping Tan
- Department of Chemistry and Biochemistry and BioFrontiers Institute, University of Colorado, Boulder, Colorado 80303, United States
| |
Collapse
|
9
|
Rodríguez-Rodero S, Menéndez-Torre E, Fernández-Bayón G, Morales-Sánchez P, Sanz L, Turienzo E, González JJ, Martinez-Faedo C, Suarez-Gutiérrez L, Ares J, Díaz-Naya L, Martin-Nieto A, Fernández-Morera JL, Fraga MF, Delgado-Álvarez E. Altered intragenic DNA methylation of HOOK2 gene in adipose tissue from individuals with obesity and type 2 diabetes. PLoS One 2017; 12:e0189153. [PMID: 29228058 PMCID: PMC5724849 DOI: 10.1371/journal.pone.0189153] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 11/20/2017] [Indexed: 12/16/2022] Open
Abstract
Aims/Hypothesis Failure in glucose response to insulin is a common pathology associated with obesity. In this study, we analyzed the genome wide DNA methylation profile of visceral adipose tissue (VAT) samples in a population of individuals with obesity and assessed whether differential methylation profiles are associated with the presence of type 2 diabetes (T2D). Methods More than 485,000 CpG genome sites from VAT samples from women with obesity undergoing gastric bypass (n = 18), and classified as suffering from type 2 diabetes (T2D) or not (no type 2 diabetes, NT2D), were analyzed using DNA methylation arrays. Results We found significant differential methylation between T2D and NT2D samples in 24 CpGs that map with sixteen genes, one of which, HOOK2, demonstrated a significant correlation between differentially hypermethylated regions on the gene body and the presence of type 2 diabetes. This was validated by pyrosequencing in a population of 91 samples from both males and females with obesity. Furthermore, when these results were analyzed by gender, female T2D samples were found hypermethylated at the cg04657146-region and the cg 11738485-region of HOOK2 gene, whilst, interestingly, male samples were found hypomethylated in this latter region. Conclusion The differential methylation profile of the HOOK2 gene in individuals with T2D and obesity might be related to the attendant T2D, but further studies are required to identify the potential role of HOOK2 gene in T2D disease. The finding of gender differences in T2D methylation of HOOK2 also warrants further investigation.
Collapse
Affiliation(s)
- Sandra Rodríguez-Rodero
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA), HUCA, Universidad de Oviedo, Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Edelmiro Menéndez-Torre
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Gustavo Fernández-Bayón
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA), HUCA, Universidad de Oviedo, Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Paula Morales-Sánchez
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA), HUCA, Universidad de Oviedo, Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Lourdes Sanz
- Surgery Department, Hospital Universitario Central de Asturias, Asturias, Spain
| | - Estrella Turienzo
- Surgery Department, Hospital Universitario Central de Asturias, Asturias, Spain
| | - Juan José González
- Surgery Department, Hospital Universitario Central de Asturias, Asturias, Spain
| | - Ceferino Martinez-Faedo
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Lorena Suarez-Gutiérrez
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Jessica Ares
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Lucia Díaz-Naya
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Alicia Martin-Nieto
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Juan L. Fernández-Morera
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
| | - Mario F. Fraga
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
- Centro de Investigación en Nanomateriales y Nanotecnología (CINN), El Entrego, Asturias, Spain
| | - Elías Delgado-Álvarez
- Endocrinology and Nutrition Department, Hospital Universitario Central de Asturias (HUCA), Asturias, Spain
- Endocrinology, Nutrition, Diabetes and Obesity Unit, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Asturias, Spain
- Medicine Department, Universidad de Oviedo, Asturias, Spain
- * E-mail: ,
| |
Collapse
|
10
|
Bergqvist N, Nyman E, Cedersund G, Stenkula KG. A systems biology analysis connects insulin receptor signaling with glucose transporter translocation in rat adipocytes. J Biol Chem 2017; 292:11206-11217. [PMID: 28495883 DOI: 10.1074/jbc.m117.787515] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 05/03/2017] [Indexed: 12/26/2022] Open
Abstract
Type 2 diabetes is characterized by insulin resistance, which arises from malfunctions in the intracellular insulin signaling network. Knowledge of the insulin signaling network is fragmented, and because of the complexity of this network, little consensus has emerged for the structure and importance of the different branches of the network. To help overcome this complexity, systems biology mathematical models have been generated for predicting both the activation of the insulin receptor (IR) and the redistribution of glucose transporter 4 (GLUT4) to the plasma membrane. Although the insulin signal transduction between IR and GLUT4 has been thoroughly studied with modeling and time-resolved data in human cells, comparable analyses in cells from commonly used model organisms such as rats and mice are lacking. Here, we combined existing data and models for rat adipocytes with new data collected for the signaling network between IR and GLUT4 to create a model also for their interconnections. To describe all data (>140 data points), the model needed three distinct pathways from IR to GLUT4: (i) via protein kinase B (PKB) and Akt substrate of 160 kDa (AS160), (ii) via an AS160-independent pathway from PKB, and (iii) via an additional pathway from IR, e.g. affecting the membrane constitution. The developed combined model could describe data not used for training the model and was used to generate predictions of the relative contributions of the pathways from IR to translocation of GLUT4. The combined model provides a systems-level understanding of insulin signaling in rat adipocytes, which, when combined with corresponding models for human adipocytes, may contribute to model-based drug development for diabetes.
Collapse
Affiliation(s)
| | - Elin Nyman
- From the Departments of Biomedical Engineering and.,Cardiovascular and Metabolic Diseases Innovative Medicines and Early Development Biotech Unit, AstraZeneca R&D, SE431 83 Gothenburg, Sweden, and
| | - Gunnar Cedersund
- From the Departments of Biomedical Engineering and .,Clinical and Experimental Medicine and Biomedical Engineering, Linköping University, SE581 85 Linköping, Sweden
| | - Karin G Stenkula
- Glucose Transport and Protein Trafficking, Department of Experimental Medical Sciences, Biomedical Centre, Lund University, SE221 84 Lund, Sweden
| |
Collapse
|
11
|
You MK, Kim HJ, Rhyu J, Kim HA. Pear pomace ethanol extract improves insulin resistance through enhancement of insulin signaling pathway without lipid accumulation. Nutr Res Pract 2017; 11:198-205. [PMID: 28584576 PMCID: PMC5449376 DOI: 10.4162/nrp.2017.11.3.198] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 11/29/2016] [Accepted: 02/07/2017] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND/OBJECTIVES The anti-diabetic activity of pear through inhibition of α-glucosidase has been demonstrated. However, little has been reported about the effect of pear on insulin signaling pathway in obesity. The aims of this study are to establish pear pomace 50% ethanol extract (PPE)-induced improvement of insulin sensitivity and characterize its action mechanism in 3T3-L1 cells and high-fat diet (HFD)-fed C57BL/6 mice. MATERIALS/METHODS Lipid accumulation, monocyte chemoattractant protein-1 (MCP-1) secretion and glucose uptake were measure in 3T3-L1 cells. Mice were fed HFD (60% kcal from fat) and orally ingested PPE once daily for 8 weeks and body weight, homeostasis model assessment of insulin resistance (HOMA-IR), and serum lipids were measured. The expression of proteins involved in insulin signaling pathway was evaluated by western blot assay in 3T3-L1 cells and adipose tissue of mice. RESULTS In 3T3-L1 cells, without affecting cell viability and lipid accumulation, PPE inhibited MCP-1 secretion, improved glucose uptake, and increased protein expression of phosphorylated insulin receptor substrate 1 [p-IRS-1, (Tyr632)], p-Akt, and glucose transporter type 4 (GLUT4). Additionally, in HFD-fed mice, PPE reduced body weight, HOMA-IR, and serum lipids including triglyceride and LDL-cholesterol. Furthermore, in adipose tissue, PPE up-regulated GLUT4 expression and expression ratio of p-IRS-1 (Tyr632)/IRS, whereas, down-regulated p-IRS-1 (Ser307)/IRS. CONCLUSIONS Our results collectively show that PPE improves glucose uptake in 3T3-L1 cells and insulin sensitivity in mice fed a HFD through stimulation of the insulin signaling pathway. Furthermore, PPE-induced improvement of insulin sensitivity was not accompanied with lipid accumulation.
Collapse
Affiliation(s)
- Mi-Kyoung You
- Department of Food and Nutrition / Research Institute of Human Ecology, Mokpo National University, 1666, Yeongsan-ro, Cheonggye-myeon, Muan-gun, Jeonam 58554, Korea
| | - Hwa-Jin Kim
- Department of Food and Nutrition / Research Institute of Human Ecology, Mokpo National University, 1666, Yeongsan-ro, Cheonggye-myeon, Muan-gun, Jeonam 58554, Korea
| | - Jin Rhyu
- Department of Food and Nutrition / Research Institute of Human Ecology, Mokpo National University, 1666, Yeongsan-ro, Cheonggye-myeon, Muan-gun, Jeonam 58554, Korea
| | - Hyeon-A Kim
- Department of Food and Nutrition / Research Institute of Human Ecology, Mokpo National University, 1666, Yeongsan-ro, Cheonggye-myeon, Muan-gun, Jeonam 58554, Korea
| |
Collapse
|
12
|
Nakao Y, Yoshihara H, Fujimori K. Suppression of Very Early Stage Of Adipogenesis by Baicalein, a Plant-Derived Flavonoid through Reduced Akt-C/EBPα-GLUT4 Signaling-Mediated Glucose Uptake in 3T3-L1 Adipocytes. PLoS One 2016; 11:e0163640. [PMID: 27669565 PMCID: PMC5036867 DOI: 10.1371/journal.pone.0163640] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/12/2016] [Indexed: 01/06/2023] Open
Abstract
Baicalein has been used as a Chinese medicine, and is an abundant plant flavonoid present in fruits and vegetables. Here, we examined the effects of baicalein in adipogenesis and investigated its molecular mechanism in adipocytes. Baicalein lowered the intracellular lipid accumulation and decreased the transcription levels of the adipocyte-specific genes in mouse 3T3-L1 adipocytes. Glucose uptake mediated by glucose transporter 4 (GLUT4) was reduced, causing down-regulation of the intracellular lipid accumulation. These reductions were also observed even when baicalein was added in only early stage of adipogenesis (0-2 days) of 6-day-adipogenesis. Chromatin immunoprecipitation assay showed that baicalein decreased the binding level of C/EBPα protein to the promoter region of the GLUT4 gene. Phosphorylation of Akt at 1 h after the initiation of adipogenesis was inhibited by the treatment with baicalein. Inhibition during only the first 1.5 h after the initiation of adipogenesis by baicalein or an Akt inhibitor was enough to decrease the lipid contents in the cells undergoing adipocyte differentiation for 6 days. These results indicate that baicalein decreased the intracellular lipid accumulation by down-regulation of glucose uptake via repression of Akt-C/EBPα-GLUT4 signaling in the very early stage of adipogenesis of 3T3-L1 adipocytes.
Collapse
Affiliation(s)
- Yukari Nakao
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569–1094, Japan
| | - Hideto Yoshihara
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569–1094, Japan
| | - Ko Fujimori
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569–1094, Japan
- * E-mail:
| |
Collapse
|
13
|
Nagai S, Wakai E, Shibano M, Fujimori K. Anti-obesity effects of Asian dayflower, Commelina communis, in mice with high-fat diet-induced obesity and in 3T3-L1 cells. J Funct Foods 2016. [DOI: 10.1016/j.jff.2016.02.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
|
14
|
Rab14 limits the sorting of Glut4 from endosomes into insulin-sensitive regulated secretory compartments in adipocytes. Biochem J 2016; 473:1315-27. [PMID: 26936971 DOI: 10.1042/bcj20160020] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/01/2016] [Indexed: 12/31/2022]
Abstract
Insulin increases glucose uptake by increasing the rate of exocytosis of the facilitative glucose transporter isoform 4 (Glut4) relative to its endocytosis. Insulin also releases Glut4 from highly insulin-regulated secretory compartments (GSVs or Glut4 storage vesicles) into constitutively cycling endosomes. Previously it was shown that both overexpression and knockdown of the small GTP-binding protein Rab14 decreased Glut4 translocation to the plasma membrane (PM). To determine the mechanism of this perturbation, we measured the effects of Rab14 knockdown on the trafficking kinetics of Glut4 relative to two proteins that partially co-localize with Glut4, the transferrin (Tf) receptor and low-density-lipoprotein-receptor-related protein 1 (LRP1). Our data support the hypothesis that Rab14 limits sorting of proteins from sorting (or 'early') endosomes into the specialized GSV pathway, possibly through regulation of endosomal maturation. This hypothesis is consistent with known Rab14 effectors. Interestingly, the insulin-sensitive Rab GTPase-activating protein Akt substrate of 160 kDa (AS160) affects both sorting into and exocytosis from GSVs. It has previously been shown that exocytosis of GSVs is rate-limited by Rab10, and both Rab10 and Rab14 are in vitro substrates of AS160. Regulation of both entry into and exit from GSVs by AS160 through sequential Rab substrates would provide a mechanism for the finely tuned 'quantal' increases in cycling Glut4 observed in response to increasing concentrations of insulin.
Collapse
|
15
|
Brewer PD, Habtemichael EN, Romenskaia I, Mastick CC, Coster ACF. Glut4 Is Sorted from a Rab10 GTPase-independent Constitutive Recycling Pathway into a Highly Insulin-responsive Rab10 GTPase-dependent Sequestration Pathway after Adipocyte Differentiation. J Biol Chem 2015; 291:773-89. [PMID: 26527681 DOI: 10.1074/jbc.m115.694919] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 02/04/2023] Open
Abstract
The RabGAP AS160/TBC1D4 controls exocytosis of the insulin-sensitive glucose transporter Glut4 in adipocytes. Glut4 is internalized and recycled through a highly regulated secretory pathway in these cells. Glut4 also cycles through a slow constitutive endosomal pathway distinct from the fast transferrin (Tf) receptor recycling pathway. This slow constitutive pathway is the only Glut4 cycling pathway in undifferentiated fibroblasts. The α2-macroglobulin receptor LRP1 cycles with Glut4 and the Tf receptor through all three exocytic pathways. To further characterize these pathways, the effects of knockdown of AS160 substrates on the trafficking kinetics of Glut4, LRP1, and the Tf receptor were measured in adipocytes and fibroblasts. Rab10 knockdown decreased cell surface Glut4 in insulin-stimulated adipocytes by 65%, but not in basal adipocytes or in fibroblasts. This decrease was due primarily to a 62% decrease in the rate constant of Glut4 exocytosis (kex), although Rab10 knockdown also caused a 1.4-fold increase in the rate constant of Glut4 endocytosis (ken). Rab10 knockdown in adipocytes also decreased cell surface LRP1 by 30% by decreasing kex 30-40%. There was no effect on LRP1 trafficking in fibroblasts or on Tf receptor trafficking in either cell type. These data confirm that Rab10 is an AS160 substrate that limits exocytosis through the highly insulin-responsive specialized secretory pathway in adipocytes. They further show that the slow constitutive endosomal (fibroblast) recycling pathway is Rab10-independent. Thus, Rab10 is a marker for the specialized pathway in adipocytes. Interestingly, mathematical modeling shows that Glut4 traffics predominantly through the specialized Rab10-dependent pathway both before and after insulin stimulation.
Collapse
Affiliation(s)
- Paul Duffield Brewer
- From the Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557
| | - Estifanos N Habtemichael
- the Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and
| | - Irina Romenskaia
- From the Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557
| | - Cynthia Corley Mastick
- From the Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557,
| | - Adelle C F Coster
- the Department of Applied Mathematics, School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales 2052, Australia
| |
Collapse
|
16
|
Watanabe M, Hisatake M, Fujimori K. Fisetin Suppresses Lipid Accumulation in Mouse Adipocytic 3T3-L1 Cells by Repressing GLUT4-Mediated Glucose Uptake through Inhibition of mTOR-C/EBPα Signaling. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:4979-4987. [PMID: 25945786 DOI: 10.1021/acs.jafc.5b00821] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
3,7,3',4'-Tetrahydroxyflavone (fisetin) is a flavonoid found in vegetables and fruits having broad biological activities. Here the effects of fisetin on adipogenesis and its regulatory mechanism in mouse adipocytic 3T3-L1 cells are studied. Fisetin inhibited the accumulation of intracellular lipids and lowered the expression of adipogenic genes such as peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein (C/EBP) α and fatty acid-binding protein 4 (aP2) during adipogenesis. Moreover, the mRNA levels of genes such as acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase involved in the fatty acid biosynthesis (lipogenesis) were reduced by the treatment with fisetin. The expression level of the glucose transporter 4 (GLUT4) gene was also decreased by fisetin, resulting in down-regulation of glucose uptake. Furthermore, fisetin inhibited the phosphorylation of the mammalian target of rapamycin (mTOR) and that of p70 ribosomal S6 kinase, a target of the mTOR complex, the inhibition of which was followed by a decreased mRNA level of the C/EBPα gene. The results obtained from a chromatin immunoprecipitation assay demonstrated that the ability of C/EBPα to bind to the GLUT4 gene promoter was reduced by the treatment with fisetin, which agreed well with those obtained when 3T3-L1 cells were allowed to differentiate into adipocytes in medium in the presence of rapamycin, an inhibitor for mTOR. These results indicate that fisetin suppressed the accumulation of intracellular lipids by inhibiting GLUT4-mediated glucose uptake through inhibition of the mTOR-C/EBPα signaling in 3T3-L1 cells.
Collapse
Affiliation(s)
- Marina Watanabe
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Mitsuhiro Hisatake
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Ko Fujimori
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| |
Collapse
|
17
|
Hwang JW, Do HJ, Kim OY, Chung JH, Lee JY, Park YS, Hwang KY, Seong SI, Shin MJ. Fermented soy bean extract suppresses differentiation of 3T3-L1 preadipocytes and facilitates its glucose utilization. J Funct Foods 2015. [DOI: 10.1016/j.jff.2015.04.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
|
18
|
Abstract
Insulin plays a fundamental role in whole-body glucose homeostasis. Central to this is the hormone's ability to rapidly stimulate the rate of glucose transport into adipocytes and muscle cells [1]. Upon binding its receptor, insulin stimulates an intracellular signalling cascade that culminates in redistribution of glucose transporter proteins, specifically the GLUT4 isoform, from intracellular stores to the plasma membrane, a process termed ‘translocation’ [1,2]. This is an example of regulated membrane trafficking [3], a process that also underpins other aspects of physiology in a number of specialized cell types, for example neurotransmission in brain/neurons and release of hormone-containing vesicles from specialized secretory cells such as those found in pancreatic islets. These processes invoke a number of intriguing biological questions as follows. How is the machinery involved in these membrane trafficking events mobilized in response to a stimulus? How do the signalling pathways that detect the external stimulus interface with the trafficking machinery? Recent studies of insulin-stimulated GLUT4 translocation offer insight into such questions. In the present paper, we have reviewed these studies and draw parallels with other regulated trafficking systems.
Collapse
|
19
|
Brewer PD, Habtemichael EN, Romenskaia I, Mastick CC, Coster ACF. Insulin-regulated Glut4 translocation: membrane protein trafficking with six distinctive steps. J Biol Chem 2014; 289:17280-98. [PMID: 24778187 DOI: 10.1074/jbc.m114.555714] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The trafficking kinetics of Glut4, the transferrin (Tf) receptor, and LRP1 were quantified in adipocytes and undifferentiated fibroblasts. Six steps were identified that determine steady state cell surface Glut4: (i) endocytosis, (ii) degradation, (iii) sorting, (iv) sequestration, (v) release, and (vi) tethering/docking/fusion. Endocytosis of Glut4 is 3 times slower than the Tf receptor in fibroblasts (ken = 0.2 min(-1) versus 0.6 min(-1)). Differentiation decreases Glut4 ken 40% (ken = 0.12 min(-1)). Differentiation also decreases Glut4 degradation, increasing total and cell surface Glut4 3-fold. In fibroblasts, Glut4 is recycled from endosomes through a slow constitutive pathway (kex = 0.025-0.038 min(-1)), not through the fast Tf receptor pathway (kex = 0.2 min(-1)). The kex measured in adipocytes after insulin stimulation is similar (kex = 0.027 min(-1)). Differentiation decreases the rate constant for sorting into the Glut4 recycling pathway (ksort) 3-fold. In adipocytes, Glut4 is also sorted from endosomes into a second exocytic pathway through Glut4 storage vesicles (GSVs). Surprisingly, transfer from endosomes into GSVs is highly regulated; insulin increases the rate constant for sequestration (kseq) 8-fold. Release from sequestration in GSVs is rate-limiting for Glut4 exocytosis in basal adipocytes. AS160 regulates this step. Tethering/docking/fusion of GSVs to the plasma membrane is regulated through an AS160-independent process. Insulin increases the rate of release and fusion of GSVs (kfuseG) 40-fold. LRP1 cycles with the Tf receptor and Glut4 in fibroblasts but predominantly with Glut4 after differentiation. Surprisingly, AS160 knockdown accelerated LRP1 exocytosis in basal and insulin-stimulated adipocytes. These data indicate that AS160 may regulate trafficking into as well as release from GSVs.
Collapse
Affiliation(s)
- Paul Duffield Brewer
- From the Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada 89557
| | - Estifanos N Habtemichael
- the Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and
| | - Irina Romenskaia
- From the Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada 89557
| | - Cynthia Corley Mastick
- From the Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada 89557,
| | - Adelle C F Coster
- the School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales 2052, Australia
| |
Collapse
|
20
|
Abstract
Insulin regulates glucose uptake by controlling the subcellular location of GLUT4 glucose transporters. GLUT4 is sequestered within fat and muscle cells during low-insulin states, and is translocated to the cell surface upon insulin stimulation. The TUG protein is a functional tether that sequesters GLUT4 at the Golgi matrix. To stimulate glucose uptake, insulin triggers TUG endoproteolytic cleavage. Cleavage accounts for a large proportion of the acute effect of insulin to mobilize GLUT4 to the cell surface. During ongoing insulin exposure, endocytosed GLUT4 recycles to the plasma membrane directly from endosomes, and bypasses a TUG-regulated trafficking step. Insulin acts through the TC10α GTPase and its effector protein, PIST, to stimulate TUG cleavage. This action is coordinated with insulin signals through AS160/Tbc1D4 and Tbc1D1 to modulate Rab GTPases, and with other signals to direct overall GLUT4 targeting. Data support the idea that the N-terminal TUG cleavage product, TUGUL, functions as a novel ubiquitin-like protein modifier to facilitate GLUT4 movement to the cell surface. The C-terminal TUG cleavage product is extracted from the Golgi matrix, which vacates an "anchoring" site to permit subsequent cycles of GLUT4 retention and release. Together, GLUT4 vesicle translocation and TUG cleavage may coordinate glucose uptake with physiologic effects of other proteins present in the GLUT4-containing vesicles, and with potential additional effects of the TUG C-terminal product. Understanding this TUG pathway for GLUT4 retention and release will shed light on the regulation of glucose uptake and the pathogenesis of type 2 diabetes.
Collapse
Affiliation(s)
- Jonathan P Belman
- Section of Endocrinology and Metabolism, Department of Internal Medicine, and Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, Box 208020, New Haven, CT, 06520-8020, USA
| | | | | |
Collapse
|
21
|
Moon HS, Dalamaga M, Kim SY, Polyzos SA, Hamnvik OP, Magkos F, Paruthi J, Mantzoros CS. Leptin's role in lipodystrophic and nonlipodystrophic insulin-resistant and diabetic individuals. Endocr Rev 2013; 34:377-412. [PMID: 23475416 PMCID: PMC3660716 DOI: 10.1210/er.2012-1053] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Leptin is an adipocyte-secreted hormone that has been proposed to regulate energy homeostasis as well as metabolic, reproductive, neuroendocrine, and immune functions. In the context of open-label uncontrolled studies, leptin administration has demonstrated insulin-sensitizing effects in patients with congenital lipodystrophy associated with relative leptin deficiency. Leptin administration has also been shown to decrease central fat mass and improve insulin sensitivity and fasting insulin and glucose levels in HIV-infected patients with highly active antiretroviral therapy (HAART)-induced lipodystrophy, insulin resistance, and leptin deficiency. On the contrary, the effects of leptin treatment in leptin-replete or hyperleptinemic obese individuals with glucose intolerance and diabetes mellitus have been minimal or null, presumably due to leptin tolerance or resistance that impairs leptin action. Similarly, experimental evidence suggests a null or a possibly adverse role of leptin treatment in nonlipodystrophic patients with nonalcoholic fatty liver disease. In this review, we present a description of leptin biology and signaling; we summarize leptin's contribution to glucose metabolism in animals and humans in vitro, ex vivo, and in vivo; and we provide insights into the emerging clinical applications and therapeutic uses of leptin in humans with lipodystrophy and/or diabetes.
Collapse
Affiliation(s)
- Hyun-Seuk Moon
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Fujimori K, Shibano M. Avicularin, a plant flavonoid, suppresses lipid accumulation through repression of C/EBPα-activated GLUT4-mediated glucose uptake in 3T3-L1 cells. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:5139-5147. [PMID: 23647459 DOI: 10.1021/jf401154c] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Avicularin (quercetin-3-O-α-L-arabinofuranoside) is a plant flavonoid and a quercetin glycoside. In this study, we found that avicularin suppressed the accumulation of intracellular lipids through repression of glucose transporter 4 (GLUT4)-mediated glucose uptake in mouse adipocytic 3T3-L1 cells. Avicularin was highly purified (purity of more than at least 99%) from Taxillus kaempferi (DC.) Danser (Loranthaceae) by high-performance liquid chromatography, and its structure was determined by nuclear magnetic resonance and mass spectrometry. Avicularin decreased the intracellular triglyceride level along with a reduction in the expression of adipogenic genes such as peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, and aP2 (fatty acid-binding protein 4). In contrast, avicularin did not affect the expression of lipogenic and lipolytic genes. Interestingly, the expression of the GLUT4 gene was significantly suppressed in an avicularin-concentration-dependent manner. Moreover, the binding of C/EBPα to the promoter region of the GLUT4 gene was repressed by adding avicularin to the medium in 3T3-L1 cells, as demonstrated by the results of a chromatin immunoprecipitation assay. These results indicate that avicularin inhibited the accumulation of the intracellular lipids by decreasing C/EBPα-activated GLUT4-mediated glucose uptake in adipocytes.
Collapse
Affiliation(s)
- Ko Fujimori
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
| | | |
Collapse
|
23
|
Yang Y, Wolfram J, Boom K, Fang X, Shen H, Ferrari M. Hesperetin impairs glucose uptake and inhibits proliferation of breast cancer cells. Cell Biochem Funct 2012; 31:374-9. [PMID: 23042260 DOI: 10.1002/cbf.2905] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 09/02/2012] [Accepted: 09/06/2012] [Indexed: 01/05/2023]
Abstract
The flavanone hesperetin is known to decrease basal glucose uptake, although the inhibitory mechanism is largely unknown. Here, we used MDA-MB-231 breast cancer cells to investigate the molecular pathways affected by hesperetin. The results indicate that the suppression of glucose uptake is caused by the down-regulation of glucose transporter 1 (GLUT1). Hesperetin was also found to inhibit insulin-induced glucose uptake through impaired cell membrane translocation of glucose transporter 4 (GLUT4). In addition, the phosphorylation of the insulin receptor-beta subunit (IR-beta) and Akt was suppressed. Hesperetin also decreased cellular proliferation, which is likely due to the inhibition of glucose uptake. Cancer cells are highly dependent on glucose and hesperetin may, therefore, have potential application as an anticancer agent.
Collapse
Affiliation(s)
- Yong Yang
- Department of Nanomedicine, The Methodist Hospital Research Institute, Houston, TX, USA
| | | | | | | | | | | |
Collapse
|
24
|
Abstract
Liver X receptors (LXRs) are members of the nuclear receptor family and are present in two isoforms, α and β, encoded by two separate genes. Originally described in the liver, LXRs have in the last 15 years been implicated in central metabolic pathways, including bile acid synthesis, lipid and glucose homeostasis. Although the vast majority of studies have been performed in non-adipose cells/tissues, results in recent years suggest that LXRs may have important modulatory roles in adipose tissue and adipocytes. Although several authors have published reviews on LXR, there have been no attempts to summarize the effects reported specifically in adipose systems. This overview gives a brief introduction to LXR and describes the sometimes-contradictory results obtained in murine cell systems and in rodent adipose tissue. The so far very limited number of studies performed in human adipocytes and adipose tissue are also presented. It should be apparent that although LXR may impact on several different pathways in metabolism, the clinical role of LXR modulation in adipose tissue is still not clear.
Collapse
|
25
|
Lee YJ, Kim MO, Ryu JM, Han HJ. Regulation of SGLT expression and localization through Epac/PKA-dependent caveolin-1 and F-actin activation in renal proximal tubule cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:971-82. [PMID: 22230192 DOI: 10.1016/j.bbamcr.2011.12.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Revised: 12/07/2011] [Accepted: 12/21/2011] [Indexed: 11/29/2022]
Abstract
This study demonstrated that exchange proteins directly activated by cAMP (Epac) and protein kinase A (PKA) by 8-bromo (8-Br)-adenosine 3',5'-cyclic monophosphate (cAMP) stimulated [(14)C]-α-methyl-D-glucopyranoside (α-MG) uptake through increased sodium-glucose cotransporters (SGLTs) expression and translocation to lipid rafts in renal proximal tubule cells (PTCs). In PTCs, SGLTs were colocalized with lipid raft caveolin-1 (cav-1), disrupted by methyl-β-cyclodextrin (MβCD). Selective activators of Epac or PKA, 8-Br-cAMP, and forskolin stimulated expressions of SGLTs and α-MG uptake in PTCs. In addition, 8-Br-cAMP-induced PKA and Epac activation increased phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), and nuclear factor kappa B (NF-κB), which were involved in expressions of SGLTs. Furthermore, 8-Br-cAMP stimulated SGLTs translocation to lipid rafts via filamentous actin (F-actin) organization, which was blocked by cytochalasin D. In addition, cav-1 and SGLTs stimulated by 8-Br-cAMP were detected in lipid rafts, which were blocked by cytochalasin D. Furthermore, 8-Br-cAMP-induced SGLTs translocation and α-MG uptake were attenuated by inhibition of cav-1 activation with cav-1 small interfering RNA (siRNA) and inhibition of F-actin organization with TRIO and F-actin binding protein (TRIOBP). In conclusion, 8-Br-cAMP stimulated α-MG uptake via Epac and PKA-dependent SGLTs expression and trafficking through cav-1 and F-actin in PTCs.
Collapse
Affiliation(s)
- Yu Jin Lee
- Department of Veterinary Physiology, Chonnam National University, Gwangju, Republic of Korea
| | | | | | | |
Collapse
|
26
|
García-Escobar E, Rodríguez-Pacheco F, Haro-Mora JJ, Gomez-Zumaquero JM, Rubio-Martín E, Gutierrez-Repiso C, Soriguer F, Rojo-Martínez G. Effect of insulin analogues on 3t3-l1 adipogenesis and lipolysis. Eur J Clin Invest 2011; 41:979-86. [PMID: 21366560 DOI: 10.1111/j.1365-2362.2011.02492.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Insulin has several biological functions besides glycaemic control. We investigated and compared the effects of six different commercial insulins on adipocyte cell differentiation, the lipolytic activity of differentiated cells, and the expression levels of genes involved in adipogenesis and associated with insulin activity. MATERIALS AND METHODS 3T3-L1 cells were induced to differentiate with six commercial insulins: glargine, lispro, aspart, detemir, NPH and regular recombinant human insulin (used as control). Cell differentiation, lipolysis and gene expression were measured at day 7 (D7) and day 10 (D10) after induction of differentiation in these cells. RESULTS The highest values of cell differentiation and lipolysis were found at D10 for all the insulins used. Preadipocyte differentiation differed at both times depending on the insulin used, with detemir insulin being the least adipogenic. The PPARγ mRNA level varied according to the insulin and was a good genetic marker of adipogenesis at D7. Cells treated with glargine insulin showed the highest lipolysis and HSL expression on both days. Gene expression levels of InsR, SREBP-1c and SCD-1 differed depending on the insulin studied. CONCLUSIONS Detemir insulin was the least adipogenic of the insulins tested, whereas treatment with glargine insulin tended to produce the highest lipolysis levels. Under these experimental conditions, the modifications made in commercial insulins to improve glycaemic control also affect adipocyte differentiation, the lipolysis level of differentiated cells, and the expression of different genes that can modify metabolic pathways independently of glucose metabolism.
Collapse
Affiliation(s)
- Eva García-Escobar
- Servicio de Endocrinología y Nutrición, Hospital Universitario Carlos Haya (Fundación IMABIS), Malaga, Spain.
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Ezer M, Yıldırım LT, Bayro O, Verspohl EJ, Dundar OB. Synthesis and antidiabetic activity of morpholinothiazolyl-2,4-thiazolidindione derivatives. J Enzyme Inhib Med Chem 2011; 27:419-27. [PMID: 21740103 DOI: 10.3109/14756366.2011.594047] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We report the synthesis and the in vitro insulin releasing and glucose uptake activity of the morpholino thiazolyl-2,4-thiazolidinediones (1-15). Compounds 5, 11-15 (at lower concentration; 0.001 mg/ml) were able to increase insulin release in the presence of 5.6 mmol/l glucose. The compounds, except derivative 3 show an increase of glucose uptake. Various compounds are interesting potential antidiabetic leads showing pancreatic and extrapancreatic effects.
Collapse
Affiliation(s)
- Melis Ezer
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Ankara University, Tandogan, Ankara, Turkey
| | | | | | | | | |
Collapse
|
28
|
Huang H, Han Y, Wang X, Chen C, Yu C, He D, Wang H, Zhou L, Asico LD, Jose PA, Zeng C. Inhibitory effect of the D(3) dopamine receptor on insulin receptor expression and function in vascular smooth muscle cells. Am J Hypertens 2011; 24:654-60. [PMID: 21415841 DOI: 10.1038/ajh.2011.41] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Vascular smooth muscle cell (VSMC) proliferation is regulated by numerous hormones and humoral factors. Our previous study found that stimulation of D(1)-like dopamine receptors inhibited insulin receptor expression and function in VSMCs. We hypothesize that there is also an interaction between D(3) dopamine and insulin receptors, i.e., stimulation of the D(3) receptor inhibits insulin receptor expression and function. METHODS Receptor expression was determined by immunoblotting, immunohistochemisty, and reverse transcriptase-PCR; VSMC proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-diphenyl-tetrazolium bromide (MTT) assay and cell number. RESULTS Insulin receptor protein is increased in the aorta of D(3) receptor deficient mice. Stimulation of the D(3) receptor inhibited insulin receptor mRNA and protein expression and insulin-mediated VSMC proliferation, and increased protein kinase A (PKA) activity, insulin receptor phosphorylation, and degradation in immortalized aortic VSMCs (A10 cells). These effects were blocked by a PKA inhibitor, indicating that the D(3) receptor-mediated decrease in insulin receptor expression was related to a decrease in transcription/post-transcription and increased degradation, involving PKA signaling. CONCLUSIONS D(3) receptor stimulation may be a target to reduce the adverse effect of insulin in hypertension by inhibition of insulin receptor expression and function in arterial VSMCs.
Collapse
|
29
|
Brewer PD, Romenskaia I, Kanow MA, Mastick CC. Loss of AS160 Akt substrate causes Glut4 protein to accumulate in compartments that are primed for fusion in basal adipocytes. J Biol Chem 2011; 286:26287-97. [PMID: 21613213 DOI: 10.1074/jbc.m111.253880] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The Akt substrate AS160 (TCB1D4) regulates Glut4 exocytosis; shRNA knockdown of AS160 increases surface Glut4 in basal adipocytes. AS160 knockdown is only partially insulin-mimetic; insulin further stimulates Glut4 translocation in these cells. Insulin regulates translocation as follows: 1) by releasing Glut4 from retention in a slowly cycling/noncycling storage pool, increasing the actively cycling Glut4 pool, and 2) by increasing the intrinsic rate constant for exocytosis of the actively cycling pool (k(ex)). Kinetic studies were performed in 3T3-L1 adipocytes to measure the effects of AS160 knockdown on the rate constants of exocytosis (k(ex)), endocytosis (k(en)), and release from retention into the cycling pool. AS160 knockdown released Glut4 into the actively cycling pool without affecting k(ex) or k(en). Insulin increased k(ex) in the knockdown cells, further increasing cell surface Glut4. Inhibition of phosphatidylinositol 3-kinase or Akt affected both k(ex) and release from retention in control cells but only k(ex) in AS160 knockdown cells. Glut4 vesicles accumulate in a primed pre-fusion pool in basal AS160 knockdown cells. Akt regulates the rate of exocytosis of the primed vesicles through an AS160-independent mechanism. Therefore, there is an additional Akt substrate that regulates the fusion of Glut4 vesicles that remain to be identified. Mathematical modeling was used to test the hypothesis that this substrate regulates vesicle priming (release from retention), whereas AS160 regulates the reverse step by stimulating GTP turnover of a Rab protein required for vesicle tethering/docking/fusion. Our analysis indicates that fusion of the primed vesicles with the plasma membrane is an additional non-Akt-dependent insulin-regulated step.
Collapse
Affiliation(s)
- Paul Duffield Brewer
- Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
| | | | | | | |
Collapse
|
30
|
Xu Y, Rubin BR, Orme CM, Karpikov A, Yu C, Bogan JS, Toomre DK. Dual-mode of insulin action controls GLUT4 vesicle exocytosis. ACTA ACUST UNITED AC 2011; 193:643-53. [PMID: 21555461 PMCID: PMC3166865 DOI: 10.1083/jcb.201008135] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Insulin releases an intracellular brake and promotes fusion pore expansion to translocate GLUT4 vesicles, and switches vesicle trafficking between distinct exocytic circuits. Insulin stimulates translocation of GLUT4 storage vesicles (GSVs) to the surface of adipocytes, but precisely where insulin acts is controversial. Here we quantify the size, dynamics, and frequency of single vesicle exocytosis in 3T3-L1 adipocytes. We use a new GSV reporter, VAMP2-pHluorin, and bypass insulin signaling by disrupting the GLUT4-retention protein TUG. Remarkably, in unstimulated TUG-depleted cells, the exocytic rate is similar to that in insulin-stimulated control cells. In TUG-depleted cells, insulin triggers a transient, twofold burst of exocytosis. Surprisingly, insulin promotes fusion pore expansion, blocked by acute perturbation of phospholipase D, which reflects both properties intrinsic to the mobilized vesicles and a novel regulatory site at the fusion pore itself. Prolonged stimulation causes cargo to switch from ∼60 nm GSVs to larger exocytic vesicles characteristic of endosomes. Our results support a model whereby insulin promotes exocytic flux primarily by releasing an intracellular brake, but also by accelerating plasma membrane fusion and switching vesicle traffic between two distinct circuits.
Collapse
Affiliation(s)
- Yingke Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Khan AA, Quigley JG. Control of intracellular heme levels: heme transporters and heme oxygenases. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1813:668-82. [PMID: 21238504 PMCID: PMC3079059 DOI: 10.1016/j.bbamcr.2011.01.008] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Revised: 12/31/2010] [Accepted: 01/06/2011] [Indexed: 12/19/2022]
Abstract
Heme serves as a co-factor in proteins involved in fundamental biological processes including oxidative metabolism, oxygen storage and transport, signal transduction and drug metabolism. In addition, heme is important for systemic iron homeostasis in mammals. Heme has important regulatory roles in cell biology, yet excessive levels of intracellular heme are toxic; thus, mechanisms have evolved to control the acquisition, synthesis, catabolism and expulsion of cellular heme. Recently, a number of transporters of heme and heme synthesis intermediates have been described. Here we review aspects of heme metabolism and discuss our current understanding of heme transporters, with emphasis on the function of the cell-surface heme exporter, FLVCR. Knockdown of Flvcr in mice leads to both defective erythropoiesis and disturbed systemic iron homeostasis, underscoring the critical role of heme transporters in mammalian physiology. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
Collapse
Affiliation(s)
- Anwar A. Khan
- Department of Medicine, Section of Hematology/Oncology, University of Illinois College of Medicine, 909 South Wolcott Avenue, Chicago, IL-60612
| | - John G. Quigley
- Department of Medicine, Section of Hematology/Oncology, University of Illinois College of Medicine, 909 South Wolcott Avenue, Chicago, IL-60612
| |
Collapse
|
32
|
Habtemichael EN, Brewer PD, Romenskaia I, Mastick CC. Kinetic evidence that Glut4 follows different endocytic pathways than the receptors for transferrin and alpha2-macroglobulin. J Biol Chem 2011; 286:10115-25. [PMID: 21252237 DOI: 10.1074/jbc.m111.217935] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin regulates glucose uptake through effects on the trafficking of the glucose transporter Glut4. To investigate the degree of overlap between Glut4 and the general endocytic pathways, the kinetics of trafficking of Glut4 and the receptors for transferrin (Tf) and α(2)-macroglobulin (α-2-M; LRP-1) were compared using quantitative flow cytometric assays. Insulin increased the exocytic rate constant (k(ex)) for both Glut4 and Tf. However, the k(ex) of Glut4 was 5-15 times slower than Tf in both basal and insulin-stimulated cells. The endocytic rate constant (k(en)) of Glut4 was also five times slower than Tf. Insulin did not affect the k(en) of either protein. In basal cells, the k(en) for α-2-M/LRP-1 was similar to Glut4 but 5-fold slower than Tf. Insulin increased k(en) for α-2-M/LRP-1 by 30%. In contrast, the k(ex) for LRP-1 was five times faster than Glut4 in basal cells, and insulin did not increase this rate constant. Thus, although there is overlap in the protein machineries/compartments utilized, the differences in trafficking kinetics indicate that Glut4, the Tf receptor, and LRP-1 are differentially processed both within the cell and at the plasma membrane. It has been reported that insulin decreases the k(en) of Glut4 in adipocytes. However, the effect of exocytosis on the "internalization" assays was not considered. Because it is counterintuitive, the effect of exocytosis on these assays is often overlooked in endocytosis studies. Using mathematical modeling and simulation, we show that the reported decrease in Glut4 k(en) can be entirely accounted for by the well established increase in Glut4 k(ex).
Collapse
Affiliation(s)
- Estifanos N Habtemichael
- Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
| | | | | | | |
Collapse
|
33
|
Zoidis E, Ghirlanda-Keller C, Schmid C. Stimulation of glucose transport in osteoblastic cells by parathyroid hormone and insulin-like growth factor I. Mol Cell Biochem 2010; 348:33-42. [PMID: 21076856 DOI: 10.1007/s11010-010-0634-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 10/28/2010] [Indexed: 12/01/2022]
Abstract
Insulin and parathyroid hormone (PTH) regulate glucose metabolism in bone cells. In order to differentiate between the effects of these hormones and to compare the potency of insulin with that of insulin-like growth factor (IGF) I, we treated rat bone-derived osteoblastic (PyMS) cells for different time periods and at different concentrations with insulin, IGF I, or PTH, and measured [1-(14)C]-2-deoxy-D-glucose (2DG) uptake and incorporation of D-[U-(14)C] glucose into glycogen. 2DG uptake was Na-independent with an apparent affinity constant (K (M)) of ~2 mmol/l. Expression of the high affinity glucose transporters (GLUT), GLUT1 and GLUT3 but not of GLUT4, was found by Northern and Western analysis. Similar to the findings with primary rat osteoblasts, but distinct from those in rat fibroblasts, 2DG uptake and glycogen synthesis were increased in this cell line after exposure to low concentrations (0.1 nmol/l and above) of PTH. IGF I at low doses (0.3 nmol/l and above) or insulin at higher doses (1 nmol/l and above) stimulated 2DG uptake and [(3)H] thymidine incorporation into DNA. 2DG transport was enhanced already after 30 min of IGF I treatment whereas the effect of PTH became significant after 6 h. It is concluded that IGF I rather than insulin may be a physiological regulator of 2DG transport and glycogen synthesis in osteoblasts.
Collapse
Affiliation(s)
- E Zoidis
- Clinic for Endocrinology and Diabetes, University Hospital of Zurich, Zurich, Switzerland.
| | | | | |
Collapse
|
34
|
Markan KR, Jurczak MJ, Allison MB, Ye H, Sutanto MM, Cohen RN, Brady MJ. Enhanced glycogen metabolism in adipose tissue decreases triglyceride mobilization. Am J Physiol Endocrinol Metab 2010; 299:E117-25. [PMID: 20424138 PMCID: PMC2904045 DOI: 10.1152/ajpendo.00741.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Adipose tissue is a primary site for lipid storage containing trace amounts of glycogen. However, refeeding after a prolonged partial fast produces a marked transient spike in adipose glycogen, which dissipates in coordination with the initiation of lipid resynthesis. To further study the potential interplay between glycogen and lipid metabolism in adipose tissue, the aP2-PTG transgenic mouse line was utilized since it contains a 100- to 400-fold elevation of adipocyte glycogen levels that are mobilized upon fasting. To determine the fate of the released glucose 1-phosphate, a series of metabolic measurements were made. Basal and isoproterenol-stimulated lactate production in vitro was significantly increased in adipose tissue from transgenic animals. In parallel, basal and isoproterenol-induced release of nonesterified fatty acids (NEFAs) was significantly reduced in transgenic adipose tissue vs. control. Interestingly, glycerol release was unchanged between the genotypes, suggesting that enhanced triglyceride resynthesis was occurring in the transgenic tissue. Qualitatively similar results for NEFA and glycerol levels between wild-type and transgenic animals were obtained in vivo during fasting. Additionally, the physiological upregulation of the phosphoenolpyruvate carboxykinase cytosolic isoform (PEPCK-C) expression in adipose upon fasting was significantly blunted in transgenic mice. No changes in whole body metabolism were detected through indirect calorimetry. Yet weight loss following a weight gain/loss protocol was significantly impeded in the transgenic animals, indicating a further impairment in triglyceride mobilization. Cumulatively, these results support the notion that the adipocyte possesses a set point for glycogen, which is altered in response to nutritional cues, enabling the coordination of adipose glycogen turnover with lipid metabolism.
Collapse
Affiliation(s)
- Kathleen R Markan
- Department of Medicine, Section of Endocrinology, Diabetes, and Metabolism, University of Chicago, 900 East 57th St., Chicago, IL 60637, USA
| | | | | | | | | | | | | |
Collapse
|
35
|
GLUT4 molecules are recruited at random for insertion within the plasma membrane upon insulin stimulation. FEBS Lett 2009; 584:537-42. [DOI: 10.1016/j.febslet.2009.11.093] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 11/30/2009] [Accepted: 11/30/2009] [Indexed: 01/14/2023]
|