Insulin potentiates TRPC3-mediated cation currents in normal but not in insulin-resistant mouse cardiomyocytes.
OBJECTIVE
Recent studies show that bioactive lipids alter intracellular Ca(2+) handling of cardiac cells differently in normal and insulin-resistant cardiomyocytes. In the present study we measured non-selective cation currents (NSCC) focusing on the interaction between insulin, the bioactive lipid diacylglycerol (DAG) and canonical transient receptor potential 3 (TRPC3) channels.


METHODS
Whole cell patch-clamp was used to measure NSCC in ventricular cardiomyocytes isolated from adult wild-type (WT) and insulin resistant, obese ob/ob mice. Western blot, immunoprecipitation and immunofluorescence staining were used to study the concentration and cellular distribution of TRPC3 channels.


RESULTS
Application of the membrane permeable DAG analogue (OAG, 30 microM) induced an NSCC, which was approximately 40% smaller in ob/ob than in WT cardiomyocytes. Insulin induced a small NSCC with similar amplitude in ob/ob and WT cells. Pretreatment with insulin (60 nM) increased the OAG-induced NSCC in WT (by approximately 50%) but not in ob/ob cells. OAG-induced currents were inhibited by adding anti-TRPC3 antibodies to the patch pipette solution. The expression of TRPC3 was lower in ob/ob than in WT cardiomyocytes. TRPC3 was detected in glucose transporter 4 (GLUT4) immunoprecipitates. Insulin exposure resulted in a translocation of TRPC3 to the plasma membrane in WT but not in ob/ob cardiomyocytes.


CONCLUSIONS
Insulin-resistant ob/ob cardiomyocytes showed decreases in DAG-mediated NSCC, which were accompanied by decreased TRPC3 expression and defective insulin-mediated trafficking of this protein.
Fauconnier
Jérémy
J
Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Lanner
Johanna T
JT
Sultan
Ariane
A
Zhang
Shi-Jin
SJ
Katz
Abram
A
Bruton
Joseph D
JD
Westerblad
Håkan
H
D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology; D051275:Glucose Transporter Type 4 / Q000032:analysis / Q000378:metabolism; D047468:Immunoprecipitation; D007328:Insulin / Q000494:pharmacology*; D007333:Insulin Resistance; D007473:Ion Channels / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism; D018408:Patch-Clamp Techniques; D050052:TRPC Cation Channels / Q000032:analysis / Q000378:metabolism*
D004075:Diglycerides; D051275:Glucose Transporter Type 4; D007328:Insulin; D007473:Ion Channels; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C038237:1-oleoyl-2-acetylglycerol