BACKGROUND: Glucose transporter 4 (GLUT4) is highly expressed in muscle and fat tissue, where triiodothyronine (T(3)) induces solute carrier family 2 facilitated glucose transporter member 4 (SLC2A4) gene transcription. T(3) was also shown to rapidly increase glucose uptake in myocytes exposed to cycloheximide, indicating that it might act nongenomically to regulate GLUT4 availability. We tested this hypothesis by evaluating, in thyroidectomized rats (Tx rats), the acute and/or chronic T(3) effects on GLUT4 mRNA expression and polyadenylation, protein content, and trafficking to the plasma membrane (PM) in skeletal muscle, as well as on blood glucose disappearance rate (kITT) after insulin administration. METHODS: Rats were surgically thyroidectomized and treated with T(3) (0.3 to 100 μg/100 g body weight) from 10 minutes to 5 days, and killed thereafter. Sham-operated (SO) rats were used as controls. Total RNA was extracted from the skeletal muscles (soleus [SOL] and extensorum digitalis longus [EDL]) and subjected to Northern blotting analysis using rat GLUT4 cDNA probe. Total protein was extracted and subjected to specific centrifugations for subcellular fractionation, and PM as well as microsomal (M) fractions were subjected to Western blotting analysis, using anti-GLUT4 antiserum as a probe. GLUT4 mRNA polyadenylation was examined by a rapid amplification of cDNA ends-poly(A) test (RACE-PAT). RESULTS: Thyroidectomy reduced skeletal muscle GLUT4 mRNA, mRNA poly(A) tail length, protein content, and trafficking to the PM, as well as the kITT. The acute T(3) treatment rapidly (30 minutes) increased all these parameters compared with Tx rats. The 5-day T(3) treatment increased GLUT4 mRNA and protein expression, and restored GLUT4 trafficking to the PM and kITT to SO values. CONCLUSIONS: The results presented here show for the first time that, in parallel to its transcriptional action on the SLC2A4 gene, T(3) exerts a rapid post-transcriptional effect on GLUT4 mRNA polyadenylation, which might increase transcript stability and translation efficiency, leading to the increased GLUT4 content and availability to skeletal muscle, as well as on GLUT4 translocation to the PM, improving the insulin sensitivity, as shown by the kITT.
BACKGROUND:Glucose transporter 4 (GLUT4) is highly expressed in muscle and fat tissue, where triiodothyronine (T(3)) induces solute carrier family 2 facilitated glucose transporter member 4 (SLC2A4) gene transcription. T(3) was also shown to rapidly increase glucose uptake in myocytes exposed to cycloheximide, indicating that it might act nongenomically to regulate GLUT4 availability. We tested this hypothesis by evaluating, in thyroidectomized rats (Tx rats), the acute and/or chronic T(3) effects on GLUT4 mRNA expression and polyadenylation, protein content, and trafficking to the plasma membrane (PM) in skeletal muscle, as well as on blood glucose disappearance rate (kITT) after insulin administration. METHODS:Rats were surgically thyroidectomized and treated with T(3) (0.3 to 100 μg/100 g body weight) from 10 minutes to 5 days, and killed thereafter. Sham-operated (SO) rats were used as controls. Total RNA was extracted from the skeletal muscles (soleus [SOL] and extensorum digitalis longus [EDL]) and subjected to Northern blotting analysis using ratGLUT4 cDNA probe. Total protein was extracted and subjected to specific centrifugations for subcellular fractionation, and PM as well as microsomal (M) fractions were subjected to Western blotting analysis, using anti-GLUT4 antiserum as a probe. GLUT4 mRNA polyadenylation was examined by a rapid amplification of cDNA ends-poly(A) test (RACE-PAT). RESULTS: Thyroidectomy reduced skeletal muscle GLUT4 mRNA, mRNA poly(A) tail length, protein content, and trafficking to the PM, as well as the kITT. The acute T(3) treatment rapidly (30 minutes) increased all these parameters compared with Tx rats. The 5-day T(3) treatment increased GLUT4 mRNA and protein expression, and restored GLUT4 trafficking to the PM and kITT to SO values. CONCLUSIONS: The results presented here show for the first time that, in parallel to its transcriptional action on the SLC2A4 gene, T(3) exerts a rapid post-transcriptional effect on GLUT4 mRNA polyadenylation, which might increase transcript stability and translation efficiency, leading to the increased GLUT4 content and availability to skeletal muscle, as well as on GLUT4 translocation to the PM, improving the insulin sensitivity, as shown by the kITT.
Authors: G Sebastian Hönes; Helena Rakov; John Logan; Xiao-Hui Liao; Eugenie Werbenko; Andrea S Pollard; Stine M Præstholm; Majken S Siersbæk; Eddy Rijntjes; Janina Gassen; Sören Latteyer; Kathrin Engels; Karl-Heinz Strucksberg; Petra Kleinbongard; Denise Zwanziger; Jan Rozman; Valerie Gailus-Durner; Helmut Fuchs; Martin Hrabe de Angelis; Ludger Klein-Hitpass; Josef Köhrle; David L Armstrong; Lars Grøntved; J H Duncan Bassett; Graham R Williams; Samuel Refetoff; Dagmar Führer; Lars C Moeller Journal: Proc Natl Acad Sci U S A Date: 2017-12-11 Impact factor: 11.205
Authors: Eun-Gyoung Hong; Brian W Kim; Dae Young Jung; Jong Hun Kim; Tim Yu; Wagner Seixas Da Silva; Randall H Friedline; Suzy D Bianco; Stephen P Seslar; Hiroko Wakimoto; Charles I Berul; Kerry S Russell; Ki Won Lee; P Reed Larsen; Antonio C Bianco; Jason K Kim Journal: Endocrinology Date: 2013-07-16 Impact factor: 4.736
Authors: Silvania da Silva Teixeira; Ana C Panveloski-Costa; Aline Carvalho; Fabiana P Monteiro Schiavon; Any de Castro Ruiz Marque; Raquel S Campello; Roberto B Bazotte; Maria T Nunes Journal: Physiol Rep Date: 2016-09