Altered expression and insulin-induced trafficking of Na+-K+-ATPase in rat skeletal muscle: effects of high-fat diet and exercise.
Skeletal muscle Na(+)-K(+)-ATPase plays a central role in the clearance of K(+) from the extracellular fluid, therefore maintaining blood [K(+)]. Na(+)-K(+)-ATPase activity in peripheral tissue is impaired in insulin resistant states. We determined effects of high-fat diet (HFD) and exercise training (ET) on skeletal muscle Na(+)-K(+)-ATPase subunit expression and insulin-stimulated translocation. Skeletal muscle expression of Na(+)-K(+)-ATPase isoforms and transcription factor DNA binding was determined before or after 5 days of swim training in Wistar rats fed chow or HFD for 4 or 12 wk. Skeletal muscle insulin resistance was observed after 12 wk of HFD. Na(+)-K(+)-ATPase alpha(1)-subunit protein expression was increased 1.6-fold (P < 0.05), whereas alpha(2)- and beta(1)-subunits and protein expression were decreased twofold (P < 0.01) in parallel with decrease in plasma membrane Na(+)-K(+)-ATPase activity after 4 wk of HFD. Exercise training restored alpha(1)-, alpha(2)-, and beta(1)-subunit expression and Na(+)-K(+)-ATPase activity to control levels and reduced beta(2)-subunit expression 2.2-fold (P < 0.05). DNA binding activity of the alpha(1)-subunit-regulating transcription factor ZEB (AREB6) and alpha(1) mRNA expression were increased after HFD and restored by ET. DNA binding activity of Sp-1, a transcription factor involved in the regulation of alpha(2)- and beta(1)-subunit expression, was decreased after HFD. ET increased phosphorylation of the Na(+)-K(+)-ATPase regulatory protein phospholemman. Phospholemman mRNA and protein expression were increased after HFD and restored to control levels after ET. Insulin-stimulated translocation of the alpha(2)-subunit to plasma membrane was impaired by HFD, whereas alpha(1)-subunit translocation remained unchanged. Alterations in sodium pump function precede the development of skeletal muscle insulin resistance. Disturbances in skeletal muscle Na(+)-K(+)-ATPase regulation, particularly the alpha(2)-subunit, may contribute to impaired ion homeostasis in insulin-resistant states such as obesity and type 2 diabetes.
Galuska
Dana
D
Departments of Physiology, Karolinska Institutet, von Eulers väg 4a, 4 tr, SE-171 77, Stockholm, Sweden.
Kotova
Olga
O
Barrès
Romain
R
Chibalina
Daria
D
Benziane
Boubacar
B
Chibalin
Alexander V
AV
D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000235:genetics / Q000378:metabolism; D004036:Diet, Atherogenic; D004041:Dietary Fats / Q000494:pharmacology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D007333:Insulin Resistance / Q000235:genetics; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009765:Obesity / Q000150:complications / Q000235:genetics / Q000378:metabolism; D010042:Ouabain / Q000493:pharmacokinetics; D010805:Physical Conditioning, Animal / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism*; D013550:Swimming; D014316:Tritium / Q000493:pharmacokinetics
D004041:Dietary Fats; D007328:Insulin; D014316:Tritium; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase