Alteration in mitochondrial Ca(2+) uptake disrupts insulin signaling in hypertrophic cardiomyocytes.
BACKGROUND
Cardiac hypertrophy is characterized by alterations in both cardiac bioenergetics and insulin sensitivity. Insulin promotes glucose uptake by cardiomyocytes and its use as a substrate for glycolysis and mitochondrial oxidation in order to maintain the high cardiac energy demands. Insulin stimulates Ca(2+) release from the endoplasmic reticulum, however, how this translates to changes in mitochondrial metabolism in either healthy or hypertrophic cardiomyocytes is not fully understood.


RESULTS
In the present study we investigated insulin-dependent mitochondrial Ca(2+) signaling in normal and norepinephrine or insulin like growth factor-1-induced hypertrophic cardiomyocytes. Using mitochondrion-selective Ca(2+)-fluorescent probes we showed that insulin increases mitochondrial Ca(2+) levels. This signal was inhibited by the pharmacological blockade of either the inositol 1,4,5-triphosphate receptor or the mitochondrial Ca(2+) uniporter, as well as by siRNA-dependent mitochondrial Ca(2+) uniporter knockdown. Norepinephrine-stimulated cardiomyocytes showed a significant decrease in endoplasmic reticulum-mitochondrial contacts compared to either control or insulin like growth factor-1-stimulated cells. This resulted in a reduction in mitochondrial Ca(2+) uptake, Akt activation, glucose uptake and oxygen consumption in response to insulin. Blocking mitochondrial Ca(2+) uptake was sufficient to mimic the effect of norepinephrine-induced cardiomyocyte hypertrophy on insulin signaling.


CONCLUSIONS
Mitochondrial Ca(2+) uptake is a key event in insulin signaling and metabolism in cardiomyocytes.
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. tomasg@bq.uchile.cl.
Tomás
T
Gutiérrez
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. Valentina.Parra@utsouthwestern.edu.|Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, 75390-8573, USA. Valentina.Parra@utsouthwestern.edu.
Valentina
V
Parra
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. rtroncoso@inta.uchile.cl.|Instituto de Nutrición y Tecnología de los Alimentos (INTA), Universidad de Chile, Santiago, 7830490, Chile. rtroncoso@inta.uchile.cl.
Rodrigo
R
Troncoso
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. pennanen@ciq.uchile.cl.
Christian
C
Pennanen
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. acontreras@med.uchile.cl.|Institute for Research in Dental Science, Faculty of Dentistry, Universidad de Chile, Santiago, 838049, Chile. acontreras@med.uchile.cl.
Ariel
A
Contreras-Ferrat
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. Cesarvasquez@ug.uchile.cl.
César
C
Vasquez-Trincado
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. pablomc@um.uchile.cl.
Pablo E
PE
Morales
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. camilalc@ug.uchile.cl.
Camila
C
Lopez-Crisosto
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. cristiansotomayorf@yahoo.com.
Cristian
C
Sotomayor-Flores
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. mchiong@uchile.cl.|Centro de Estudios Moleculares de la Célula, Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. mchiong@uchile.cl.
Mario
M
Chiong
Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, 75390-8573, USA. Beverly.Rothermel@utsouthwestern.edu.
Beverly A
BA
Rothermel
Advanced Center for Chronic Disease (ACCDiS), Facultad de Ciencias Quimicas y Farmaceuticas & Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. slavander@uchile.cl.|Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, 75390-8573, USA. slavander@uchile.cl.|Centro de Estudios Moleculares de la Célula, Facultad de Medicina, Universidad de Chile, Santiago, 838049, Chile. slavander@uchile.cl.
Sergio
S
Lavandero
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D006332:Cardiomegaly / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010101:Oxygen Consumption; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
D053496:Inositol 1,4,5-Trisphosphate Receptors; D007328:Insulin; D005947:Glucose; D002118:Calcium