Disturbance of energy and calcium homeostasis and permeability transition induction provoked by fatty acids accumulated in VLCAD deficiency in rat skeletal muscle mitochondria

Alexandre Umpierrez Amaral PhD1*, Cristiane Cecatto MSc2, Alessandro Wajner PhD2, Janaína Camacho da Silva PhD2, Kaleb Pinto Spannenberger2, Moacir Wajner MD, PhD2,3

1Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Erechim, RS, Brazil

2Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade

Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil

3Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil

* e-mail: alexandreuamaral@gmail.com; Tel: +55 51 998378489

Cis-5-tetradecenoic (Cis-5) and myristic (Myr) acids are accumulated in tissues of very long-chain acyl-CoA dehydrogenase (VLCAD) deficient patients who usually manifest recurrent rhabdomyolysis, cardiomyopathy and hepatopathy. Symptomatology is usually worsen during episodes of metabolic decompensation, in which the body concentrations of the accumulating metabolites rapidly increase, suggesting toxicity of these fatty acids. Therefore, the present work investigated the effects of Cis-5 and Myr (10-30 µM) on energy and calcium homeostasis in mitochondrial preparations from skeletal muscle from 30-day-old Wistar rats supplemented with exogenous calcium (30

µM). Our data showed that Cis-5 and Myr significantly decreased mitochondrial membrane potential (ΔΨm) in the absence of calcium in glutamate/malate-supported mitochondria. Furthermore, this effect was more intense after calcium supplementation. On the other hand, Cis-5 and Myr-induced ΔΨm dissipation was less evident in pyruvate/malate supported mitochondria. We also observed that Cis-5 and Myr-induced collapse of ΔΨm in calcium-loaded mitochondria was prevented by cyclosporine A (CsA) plus ADP (inhibitors of mitochondrial permeability transition, mPT) and by ruthenium red (RR – inhibitor of mitochondrial calcium uniporter), indicating the involvement of mPT pore opening and the importance of calcium in this effect. Cis-5 and Myr also markedly decreased mitochondrial NAD(P)H content and calcium retention capacity, which were prevented by CsA, confirming mPT pore opening induction. Taken together, our data indicate that the major fatty acids accumulating in VLCAD deficiency severely disturb mitochondrial energy and calcium homeostasis in

skeletal muscle probably due to mPT induction. It is postulated that our present data may contribute to further explain the pathogenesis of the rhabdomyolysis presented by VLCAD deficient patients especially during metabolic decompensation.

Financial support: PROPESQ/UFRGS, FAPERGS and CNPq.

Keywords: very-long-chain acyl-CoA dehydrogenase deficiency; rhabdomyolysis; mitochondrial energy homeostasis; mitochondrial calcium homeostasis; mitochondrial permeability transition.