Development and pathomechanisms of cardiomyopathy in very long-chain acyl-CoA dehydrogenase deficient (VLCAD(-/-)) mice.

ABSTRACT

Hypertrophic cardiomyopathy is a typical manifestation of very long-chain acyl-CoA dehydrogenase deficiency (VLCADD), the most common long-chain ß-oxidation defects in humans; however in some patients cardiac function is fully compensated. Cardiomyopathy may also be reversed by supplementation of medium-chain triglycerides (MCT). We here characterize cardiac function of VLCAD-deficient (VLCAD(-/-)) mice over one year. Furthermore, we investigate the long-term effect of a continuous MCT diet on the cardiac phenotype. We assessed cardiac morphology and function in VLCAD(-/-) mice by in vivo MRI. Cardiac energetics were measured by (31)P-MRS and myocardial glucose uptake was quantified by positron-emission-tomography (PET). Metabolic adaptations were identified by the expression of genes regulating glucose and lipid metabolism using real-time-PCR. VLCAD(-/-) mice showed a progressive decrease in heart function over 12 months accompanied by a reduced phosphocreatine-to-ATP-ratio indicative of chronic energy deficiency. Long-term MCT supplementation aggravated the cardiac phenotype into dilated cardiomyopathy with features similar to diabetic heart disease. Cardiac energy production and function in mice with a ß-oxidation defect cannot be maintained with age. Compensatory mechanisms are insufficient to preserve the cardiac energy state over time. However, energy deficiency by impaired ß-oxidation and long-term MCT induce cardiomyopathy by different mechanisms. Cardiac MRI and MRS may be excellent tools to assess minor changes in cardiac function and energetics in patients with ß-oxidation defects for preventive therapy.