Electrophysiological Abnormalities in VLCAD Deficient hiPSC-Cardiomyocytes Can Be Improved by Lowering Accumulation of Fatty Acid Oxidation Intermediates

Abstract

Patients with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) can present with life-threatening cardiac arrhythmias. The pathophysiological mechanism is unknown. We reprogrammed fibroblasts from one mildly and one severely affected VLCADD patient, into human induced pluripotent stem cells (hiPSCs) and differentiated these into cardiomyocytes (VLCADD-CMs). VLCADD-CMs displayed shorter action potentials (APs), more delayed afterdepolarizations (DADs) and higher systolic and diastolic intracellular Ca2+ concentration ([Ca2+]i) than control CMs. The mitochondrial booster resveratrol mitigated the biochemical, electrophysiological and [Ca2+]i changes in the mild but not in the severe VLCADD-CMs. Accumulation of potentially toxic intermediates of fatty acid oxidation was blocked by substrate reduction with etomoxir. Incubation with etomoxir led to marked prolongation of AP duration and reduced DADs and [Ca2+]i in both VLCADD-CMs. These results provide compelling evidence that reduced accumulation of fatty acid oxidation intermediates, either by enhanced fatty acid oxidation flux through increased mitochondria biogenesis (resveratrol) or by inhibition of fatty acid transport into the mitochondria (etomoxir), rescues pro-arrhythmia defects in VLCADD-CMs and open doors for new treatments.

Recent Advances in the Pathophysiology of Fatty Acid Oxidation Defects: Secondary Alterations of Bioenergetics and Mitochondrial Calcium Homeostasis Caused by the Accumulating Fatty Acids

“…These fibroblasts revealed elevated mitochondrial mass and fusion, as well as an increased expression of MFN1, indicating alterations of mitochondrial dynamics besides the disruption of the endoplasmic reticulum-mitochondria crosstalk that is involved in cytosolic calcium homeostasis (Seminotti et al, 2019). This is in line with the observations of increased intracellular calcium concentrations that were correlated with fatty acid intermediate accumulation in fibroblasts from VLCAD-deficient patients differentiated into cardiomyocytes (Knottnerus et al, 2020). Furthermore, results obtained in the genetic mice model of VLCAD deficiency showed bioenergetics disruption.…”

Mitochondrial Fatty Acid Oxidation Disorders: Laboratory Diagnosis, Pathogenesis, and the Complicated Route to Treatment

“…In order to try and find a solution to this problem, we have recently performed electrophysiological studies in cardiomyocytes derived from induced pluripotent stem cells generated from skin fibroblasts from 2 different VLCADD patients. 68 The mitochondrial booster resveratrol was found to mitigate the biochemical, electrophysiological, and intracellular calcium changes in cardiomyocytes from the mildly affected patients, but not in those from the severe patient. Importantly, the electrophysiological abnormalities in cardiomyocytes from both the severely and mildly affected patient were markedly corrected by etomoxir, which is a powerful inhibitor of CPT1.…”

Diagnosis, genetic characterization and clinical follow up of mitochondrial fatty acid oxidation disorders in the new era of expanded newborn screening: A single centre experience

“…Even if the pathophysiological mechanism is still unknown, two putative pathophysiological mechanisms have been proposed for explain the muscular involvement in these patients. Both the energy shortage due to reduced ATP production and the toxic accumulation of acylcarnitines intermediates could play a role in the derangement of cellular metabolism [ 7 , 8 ]. Late onset forms of FAODs may present in the adolescence or adulthood and are mainly characterised by muscular signs and symptoms, such as fatigue, muscular pain, reduced exercise tolerance, and even a fatty liver disease [ 1 , 4 ].…”