Altered Fibroblast Glutamine Metabolism Is Linked to the Severity of Cardiac Dysfunction in <scp>DCMA</scp> , a Mitochondrial Cardiomyopathy

The dilated cardiomyopathy with ataxia (DCMA) syndrome is a rare mitochondrial disorder caused by mutations in the poorly understood DNAJC19 gene. Cardiac involvement in DCMA ranges from mild conduction abnormalities to early severe myocardial dysfunction. Although evidence suggests that DCMA is linked to abnormalities in mitochondrial function, the molecular underpinnings of this condition are unclear, and there is no way to predict which patients will develop life-threatening disease. To address this, we developed a metabolic flux assay for assessing the metabolic function of mitochondria in fibroblasts derived from DCMA patients. Using this approach, we discovered that DCMA fibroblasts have elevated glutamine uptake, increased glutamate and ammonium secretion, and elevated lactate production. Moreover, we observed that these cellular perturbations were closely correlated with cardiac dysfunction in a blinded cohort of patient cell lines. These findings suggest that glutamine catabolism is abnormal in DCMA and may serve as a predictor of clinical progression.