Metabolite accumulation in VLCAD deficiency markedly disrupts mitochondrial bioenergetics and Ca²⁺ homeostasis in the heart

Abstract

We studied the effects of the major long-chain fatty acids accumulating in very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, namely cis-5-tetradecenoic acid (Cis-5) and myristic acid (Myr), on important mitochondrial functions in isolated mitochondria from cardiac fibers and cardiomyocytes of juvenile rats. Cis-5 and Myr at pathological concentrations markedly reduced mitochondrial membrane potential (ΔΨ ), matrix NAD(P)H pool, Ca retention capacity, ADP- (state 3) and carbonyl cyanide 3-chlorophenyl hydrazine-stimulated (uncoupled) respiration, and ATP generation. By contrast, these fatty acids increased resting (state 4) respiration (uncoupling effect) with the involvement of the adenine nucleotide translocator because carboxyatractyloside significantly attenuated the increased state 4 respiration provoked by Cis-5 and Myr. Furthermore, the classical inhibitors of mitochondrial permeability transition (MPT) pore cyclosporin A plus ADP, as well as the Ca uptake blocker ruthenium red, fully prevented the Cis-5- and Myr-induced decrease in ΔΨ in Ca -loaded mitochondria, suggesting, respectively, the induction of MPT pore opening and the contribution of Ca toward these effects. The findings of the present study indicate that the major long-chain fatty acids that accumulate in VLCAD deficiency disrupt mitochondrial bioenergetics and Ca homeostasis, acting as uncouplers and metabolic inhibitors of oxidative phosphorylation, as well as inducers of MPT pore opening, in the heart at pathological relevant concentrations. It is therefore presumed that a disturbance of bioenergetics and Ca homeostasis may contribute to the cardiac manifestations observed in VLCAD deficiency.

Mitochondrial energetics is impaired in very long-chain acyl-CoA dehydrogenase deficiency and can be rescued by treatment with mitochondria-targeted electron scavengers

“…Regardless of mutation, VLCAD-deficient cells showed a marked decrease of mitochondrial RC function and ATP levels that tended to be exaggerated by growth in glucose-free media. Although the ACADVL gene mutations were heterogeneous in the examined fibroblasts, impairment in oxygen consumption was observed in all cultured cells, which is in line with observations showing that long-chain fatty acids accumulated in VLCADD impairs bioenergetics in mitochondria of rat brain (26). These findings are accompanied by increased ROS production measured with an in vivo probe and an in vitro technique.…”

“…Moreover, previous works have shown cellular toxicity induced by the major accumulated long-chain fatty acids and acylcarnitines in VLCADD. At high concentrations, these metabolites provoke mitochondrial dysfunction by different mechanisms, including calcium homeostasis disturbance, mitochondrial membrane potential dissipation, OXPHOS uncoupling and apoptosis (26,37).…”

Cardioprotection stimulated by resveratrol and grape products prevents lethal cardiac arrhythmias in an animal model of ischemia and reperfusion

“…Humans with very long chain acetyl-CoA dehydrogenase deficiency (VLCAD), an electron transfer flavoprotein-dependent enzyme located in the internal mitochondrial matrix, have a defect in the mitochondrial oxidation of long-chain fatty acids, leading to the development of hypertrophic heart disease and arrhythmias that can lead to death. The treatment of these patients involves the administration of glucose, a high caloric diet with medium chain triglycerides and supplementation with L-carnitine 46 . Using differentiated cardiomyocytes from pluripotent stem cells of a patient with VLCAD, it was found that resveratrol led to increased fatty acid oxidation by increasing mitochondrial biogenesis and control of cytosolic Ca 2+ concentration, which could lead to better control of arrhythmias in these patients by consuming food containing resveratrol 47 .…”

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

“…Induction of mPT pore opening was also demonstrated to be caused by Myr (Bodrova et al, 2003). Recent studies demonstrated that, apart from Myr, pathological concentrations of Cis-5 disturb mitochondrial bioenergetics and calcium homeostasis in the heart, liver, and skeletal muscle (Cecatto et al, 2018a(Cecatto et al, , 2019(Cecatto et al, , 2020. These results were obtained in different tissue preparations, such as isolated mitochondria, permeabilized cardiomyocytes and hepatocytes, and heart fibers.…”