Cardiac MRI reveals myocardial fibrosis and systolic dysfunction in mitochondrial trifunctional protein–deficient mice

Cardiomyopathy is an important manifestation in patients with fatty acid oxidation disorders and represents a major cause of morbidity and early mortality in mitochondrial trifunctional protein (TFP) deficiency. Although a mouse model carrying the TFP β-subunit p.Met404Lys mutation (βTFP-deficient) has been described, cardiac involvement in this model has not been systematically characterized. Here, we combined cardiac histology and multiparametric cardiac MRI (CMR) to define myocardial structure, function, and tissue characteristics in this mouse model. Histological analysis with automated whole-slide collagen quantification revealed myocardial fibrosis with collagen deposition in mutant hearts, and CMR demonstrated increased myocardial extracellular volume in both male and female homozygous mutants. Homozygous males showed reduced ejection fraction, impaired systolic strain, and increased left ventricular end-systolic volume, indicating systolic dysfunction. Male mice were more severely affected than females and exhibited reduced survival. Together, these findings demonstrate that βTFP-deficient mice develop fibrotic cardiomyopathy with systolic dysfunction, reproducing important cardiac features observed in human TFP deficiency. This work establishes the model as a relevant platform for investigating disease mechanisms and therapeutic strategies for cardiomyopathy in TFP deficiency.