Abstract | AIMS: The insulin-sensitive glucose transporter protein GLUT4 (solute carrier family 2 member 4 (Slc2a4) gene) plays a key role in glycemic homeostasis. Decreased GLUT4 expression is a current feature in insulin resistant conditions such as diabetes, and the restoration of GLUT4 content improves glycemic control. This study investigated the effect of insulin upon Slc2a4/GLUT4 expression, focusing on the AT-rich element, E-box and nuclear factor NF-kappa-B (NFKB) site. MAIN METHODS: Rat soleus muscles were incubated during 180 min with insulin, added or not with wortmannin ( phosphatidylinositol-4,5-bisphosphate 3- kinase catalytic subunit gamma isoform (PI3K)-inhibitor), ML9 ( serine/threonine protein kinase (AKT) inhibitor) and tumor necrosis factor (TNF, GLUT4 repressor), and processed for analysis of GLUT4 protein (Western blotting); Slc2a4, myocyte enhancer factor 2a/d (Mef2a/d), hypoxia inducible factor 1a (Hif1a), myogenic differentiation 1 (Myod1) and nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1) messenger ribonucleic acids (mRNAs) (polymerase chain reaction (PCR)); and AT-rich- ( myocyte-specific enhancer factor 2 (MEF2)-binding site), E-box- ( hypoxia inducible factor 1 alpha (HIF1A)- and myoblast determination protein 1 (MYOD1)-binding site), and NFKB-binding activity (electrophoretic mobility assay). KEY FINDINGS:
Insulin increased Slc2a4 mRNA expression (140%) and nuclear proteins binding to AT-rich and E-box elements (~90%), all effects were prevented by wortmannin and ML9. Insulin also increased Mef2a/d and Myod1 mRNA expression, suggesting the participation of these transcriptional factors in the Slc2a4 enhancing effect. Conversely, insulin decreased Nfkb1 mRNA expression and protein binding to the NFKB-site (~50%). Furthermore, TNF-induced inhibition of GLUT4 expression (~40%) was prevented by insulin in an NFKB-binding repressing mechanism. GLUT4 protein paralleled the Slc2a4 mRNA regulations. SIGNIFICANCE:
Insulin enhances the Slc2a4/GLUT4 expression in the skeletal muscle by activating AT-rich and E-box elements, in a PI3K/AKT-dependent mechanism, and repressing NFKB-site activity as well. These results unravel how post-prandial increase of insulin may guarantee GLUT4 expression, and how the insulin signaling impairment can participate in insulin resistance-induced repression of GLUT4.
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Authors | Paulo Alexandre Moraes, Caio Yogi Yonamine, Danilo Correa Pinto Junior, João Victor DelConti Esteves, Ubiratan Fabres Machado, Rosana Cristina Mori |
Journal | Life sciences
(Life Sci)
Vol. 114
Issue 1
Pg. 36-44
(Sep 26 2014)
ISSN: 1879-0631 [Electronic] Netherlands |
PMID | 25123536
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Copyright | Copyright © 2014 Elsevier Inc. All rights reserved. |
Chemical References |
- Glucose Transporter Type 4
- Insulin
- NF-kappa B
- RNA, Messenger
- Slc2a4 protein, rat
- Transcription Factors
- Phosphatidylinositol 3-Kinases
- Proto-Oncogene Proteins c-akt
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Topics |
- AT Rich Sequence
(genetics)
- Animals
- B-Lymphocytes
(metabolism)
- Binding Sites
- Blotting, Western
- E-Box Elements
(genetics)
- Gene Expression Regulation
(drug effects)
- Glucose Transporter Type 4
(genetics)
- Insulin
(pharmacology)
- Insulin Resistance
- Male
- Muscle, Skeletal
(metabolism)
- NF-kappa B
(metabolism)
- Phosphatidylinositol 3-Kinases
(metabolism)
- Proto-Oncogene Proteins c-akt
(metabolism)
- RNA, Messenger
(metabolism)
- Rats
- Rats, Wistar
- Transcription Factors
(genetics)
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