Altered glutamine metabolism of cultured fibroblasts predicts severity of cardiac dysfunction in the dilated cardiomyopathy with ataxia syndrome (DCMA), a mitochondrial cardiomyopathy

Dilated cardiomyopathy with ataxia (DCMA) syndrome is a rare mitochondrial disorder caused by mutations in the poorly understood DNAJC19 gene. The clinical presentation of DCMA is very diverse with symptoms ranging from mild cardiac dysfunction to intractable heart failure leading to death in early childhood. Although several lines of evidence indicate that DCMA symptoms are linked to mitochondrial function, the molecular underpinnings of this disease are unclear and there is no way to predict which patients are at risk for developing life-threatening symptoms. To address this we developed a metabolic flux assay for assessing the metabolic function of mitochondria in dermal fibroblasts derived from DCMA patients. Using this approach we discovered that fibroblasts from patients with DCMA showed elevated glutamine uptake, increased glutamate and ammonium secretion, and elevated lactate production when compared to controls. Moreover, the magnitude of these metabolic perturbations was closely correlated with patient cardiac dysfunction. This clinical/metabolic correlation was confirmed in a second blinded cohort of DCMA fibroblasts. Moreover, our metabolic flux diagnostic strategy correctly differentiated severe from mild DCMA cases with only one incorrect patient classification (positive predictive value 1.0 and negative predictive value 0.83). These findings suggest that glutamine catabolism is abnormal in DCMA and may serve as an early biomarker for predicting clinical progression. One Sentence SummaryAlterations in glutamine and lactate metabolism in patient-derived dermal fibroblasts are associated with the severity of cardiomyopathy in DCMA.