High Glucose, High Insulin, and Their Combination Rapidly Induce Laminin-β1 Synthesis by Regulation of mRNA Translation in Renal Epithelial Cells

• Published in: Diabetes (New York, N.Y.) Vol. 56; no. 2; pp. 476 - 485
• Main Authors: MARIAPPAN, Meenalakshmi M, FELIERS, Denis, MUMMIDI, Srinivas, CHOUDHURY, Goutam Ghosh, KASINATH, Balakuntalam S
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.02.2007
• Subjects: Biological and medical sciences; Diabetes; Diabetes. Impaired glucose tolerance; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Epithelial cells; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Genetic aspects; Laminin; Medical sciences; Type 2 diabetes; Endocrinopathy; Pancreatic hormone; Laminin; Diabetes mellitus; Epithelial cell; Biosynthesis; Glucose; Insulin
• ISSN: 0012-1797; 1939-327X
• DOI: 10.2337/db05-1334

High Glucose, High Insulin, and Their Combination Rapidly Induce Laminin-β1 Synthesis by Regulation of mRNA Translation in Renal Epithelial Cells Meenalakshmi M. Mariappan 1 , Denis Feliers 1 , Srinivas Mummidi 2 , Goutam Ghosh Choudhury 1 3 and Balakuntalam S. Kasinath 1 3 1 O’Brien Kidney Research Center, Department of Medicine, University of Texas Health Science Center, South Texas Veterans Health Care System, GRECC San Antonio, Texas 2 Division of Infectious Diseases, Department of Medicine, University of Texas Health Science Center, South Texas Veterans Health Care System, GRECC San Antonio, Texas 3 South Texas Veterans Health Care System, GRECC San Antonio, Texas Address correspondence and reprint requests to Balakuntalam S. Kasinath, MD, Department of Medicine, MC7882, University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78229. E-mail: kasinath{at}uthscsa.edu Abstract Laminin is a glycoprotein that contributes to renal extracellular matrix expansion in diabetes. We investigated regulation of laminin-β1 synthesis in murine renal proximal tubular epithelial cells by 30 mmol/l glucose (high glucose), 1 nmol/l insulin (high insulin), and their combination (high glucose+high insulin), simulating conditions observed during progression of type 2 diabetes. Compared with 5 mmol/l glucose and no insulin (control), high glucose alone, high insulin alone, or high glucose+high insulin together increased laminin-β1 chain protein synthesis within 5 min, lasting for up to 60 min with no change in laminin-β1 mRNA levels. Cycloheximide, but not actinomycin-D, abrogated increased laminin-β1 synthesis. High glucose, high insulin, and high glucose+high insulin stimulated phosphorylation of 4E-BP1, a repressor binding protein for eukaryotic initiation factor 4E (eIF4E), that was dependent on activation of phosphatidylinositol 3-kinase, Akt, and mammalian target of rapamycin. High glucose, high insulin, and high glucose+high insulin also promoted release of eIF4E from 4E-BP1, phosphorylation of eIF4E, and increase in eIF4E association with eIF4G, critical events in the initiation phase of mRNA translation. High glucose, high insulin, and high glucose+high insulin increased Erk phosphorylation, which is an upstream regulator of eIF4E phosphorylation, and PD098059, which is a MEK inhibitor that blocks Erk activation, abolished laminin-β1 synthesis. This is the first demonstration of rapid increment in laminin-β1 synthesis by regulation of its mRNA translation by cells exposed to high glucose, high insulin, or high glucose+high insulin. AMPK, AMP-activated protein kinase DMEM, Dulbecco’s modified Eagle’s medium ECM, extracellular matrix eIF4E, eukaryotic initiation factor 4E GAPDH, glyceraldehyde-3-phosphate dehydrogenase MAP, mitogen-activated protein MCT, mouse cortical tubule mTOR, mammalian target of rapamycin PI 3-kinase, phosphatidylinositol 3-kinase PI3P, phosphatidylinositol 3 phosphate TCA, trichloroacetic acid VEGF, vascular endothelial growth factor Footnotes Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/db05-1334 . The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Accepted October 4, 2006. Received October 12, 2005. DIABETES