Mitochondrial dysfunction caused by fatty acids accumulating in VLCAD deficiency

Alexandre Umpierrez Amaral PhD1,3*, Cristiane Cecatto MSc1, Kálita dos Santos Godoy1, Lucas Henrique Rodrigues da Silva1, Kaleb Pinto Spannenberger1, Janaína Camacho da Silva PhD1, Roger Frigério Castilho MD, PhD2, Moacir Wajner MD, PhD1

1Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil

2Departamento de Patologia Clínica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brazil

3Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto

Uruguai e das Missões, Erechim, RS, Brazil

* email: alexandreuamaral@gmail.com; Tel: +55 51 998378489

Very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is clinically characterized by episodes of metabolic decompensation, hypoketotic  hypoglycemia, liver dysfunction and cardiomyopathy, whose pathophysiology is  poorly understood. We investigated the effects of the major fatty acids accumulating in biological fluids of the affected patients (myristic – Myr and cis-5-tetradecenoic – Cis-5 acids) on important mitochondrial functions in heart, liver and brain mitochondria from young rats. Myr markedly decreased mitochondrial membrane potential (Δψm) in all tissues, whereas Cis-5 mildly dissipated Δψm. Furthermore, Myr and Cis-5 severely  decreased NAD(P)H content in the heart, and to a lesser degree in liver and brain. These effects

were enhanced after Ca2+ addition, particularly in the heart. In addition, Ca2+-induced brain mitochondrial swelling was elicited by Myr but not by Cis-5. Noteworthy, Myr- induced decrease of Δψm and swelling was abolished by cyclosporine A (CsA) plus ADP or ruthenium red (RR) in heart, liver and brain implying the involvement of mitochondrial permeability transition (mPT). Cis-5 induced decrease of Δψm was also prevented by CsA plus ADP and RR in the heart, implying mPT induction. Finally, we found that Ca2+ retention capacity was reduced by Myr and Cis-5 in heart and liver mitochondria, but not in the brain. These data suggest that predominant fatty acids accumulating in VLCAD deficiency, especially Myr, disturb mitochondrial functions with a higher toxicity directed towards the heart and liver. It is proposed that disturbance of mitochondrial homeostasis may be involved in the liver dysfunction and

cardiomyopathy characteristic of VLCAD deficient patients.

Financial support: We thank PROPESQ/UFRGS, FAPERGS and CNPq.

Keywords: very-long-chain acyl-CoA dehydrogenase deficiency; cardiomyopathy; hepatopathy; mitochondrial functions.