Sarco/Endoplasmic Reticulum Ca2+ ATPase Activation Shifts Cardiac Fuel Preference Without Impairing Cardiac Function in Obese Mice.

BACKGROUND

Activity of SERCA (sarco/endoplasmic reticulum Ca2+ ATPase) affects cardiac metabolism and function and is under investigation in clinical trials. SERCA function also regulates glucose metabolism in multiple tissues, but it is unknown how these effects extend to the heart. Pressure overload-induced cardiac hypertrophy corresponds to increased cardiac glucose oxidation in obesity. We hypothesized that SERCA activation by the compound CDN1163 would increase ATP demand due to Ca2+ cycling, leading to increased fat oxidation to maintain cardiac energy homeostasis.

METHODS

In vivo [U-13C3]lactate tracer experiments were performed to assess fasting cardiac metabolic fluxes in Mc4r-/- mice fed a Western diet and treated with CDN1163. Fluxes were estimated by fitting a mathematical model of cardiac metabolism to 13C enrichment measurements of plasma and tissue metabolites taken at the end of the isotope infusion. Metabolic flux measurements were combined with echocardiography, gene expression, and enzymatic assays to assess the effects of SERCA activation on heart function and metabolism following 8 weeks of CDN1163 treatment.

RESULTS

CDN1163 increased cardiac ATPase activity, decreased cytosolic Ca2+ signaling, and decreased cardiac glucose uptake and glycolysis in obese mice. A greater fraction of mitochondrial acetyl-coenzyme A was obtained from nonglycolytic sources, such as fat, to sustain citric acid cycle flux, corresponding to an increase in mitochondrial activity. CDN1163 treatment upregulated gene expression of enzymes in β-oxidation and lipid handling. No changes in basal cardiac function or compensatory left ventricular remodeling were observed.

CONCLUSIONS

SERCA activation promotes flux from nonglucose substrates to fuel cardiac mitochondrial metabolism in obese mice.