Long-chain 3-hydroxy fatty acids accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase and mitochondrial trifunctional protein deficiencies uncouple oxidative phosphorylation in heart mitochondria

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Cardiomyopathy is a common clinical feature of some inherited disorders of mitochondrial fatty acid beta-oxidation including mitochondrial trifunctional protein (MTP) and isolated long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiencies. Since individuals affected by these disorders present tissue accumulation of various fatty acids, including long-chain 3-hydroxy fatty acids, in the present study we investigated the effect of 3-hydroxydecanoic (3 HDCA), 3-hydroxydodecanoic (3 HDDA), 3-hydroxytetradecanoic (3 HTA) and 3-hydroxypalmitic (3 HPA) acids on mitochondrial oxidative metabolism, estimated by oximetry, NAD(P)H content, hydrogen peroxide production, membrane potential (Delta I) and swelling in rat heart mitochondrial preparations. We observed that 3 HTA and 3 HPA increased resting respiration and diminished the respiratory control and ADP/O ratios using glutamate/malate or succinate as substrates. Furthermore, 3 HDDA, 3 HTA and 3 HPA decreased Delta I, the matrix NAD(P)H pool and hydrogen peroxide production. These data indicate that these fatty acids behave as uncouplers of oxidative phosphorylation. We also verified that 3 HTA-induced uncoupling-effect was not mediated by the adenine nucleotide translocator and that this fatty acid induced the mitochondrial permeability transition pore opening in calcium-loaded organelles since cyclosporin A prevented the reduction of mitochondrial Delta I and swelling provoked by 3 HTA. The present data indicate that major 3-hydroxylated fatty acids accumulating in MTP and LCHAD deficiencies behave as strong uncouplers of oxidative phosphorylation potentially impairing heart energy homeostasis.45416714757Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PRONEX IIFAPERGSFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROPESQ/UFRGSFINEP Rede Instituto Brasileiro de Neurociencia (IBN-Net) [01.06.0842-00]Instituto Nacional de Ciencia e Tecnologia, Excitotoxicidade e Neuroprotecao (INCT-EN)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FINEP Rede Instituto Brasileiro de Neurociencia (IBN-Net) [01.06.0842-00

Ethylmalonic acid impairs brain mitochondrial succinate and malate transport

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Tissue accumulation and high urinary excretion of ethylmalonic acid (EMA) occur in ethylmalonic encephalopathy (EE) and short chain acyl-CoA dehydrogenase deficiency (SCADD). Although these autosomal recessive disorders are clinically characterized by neurological abnormalities, the mechanisms underlying the brain damage are poorly known. Considering that little is known about the neurotoxicity of EMA and that hyperlacticacidemia occurs in EE and SCADD, we evaluated the effects of this metabolite on important parameters of oxidative metabolism in isolated rat brain mitochondria. EMA inhibited either ADP-stimulated or uncoupled mitochondrial respiration supported by succinate and malate, but not by glutamate plus malate. In addition, EMA mildly stimulated oxygen consumption by succinate-respiring mitochondria in resting state. Methylmalonic acid (MMA), malonic acid (MA) and butylmalonic acid (BtMA) had a similar effect on ADP-stimulated or uncoupled respiration. Furthermore, EMA-, MMA- and BtMA-induced inhibitory effects on succinate oxidation were significantly minimized by nonselective permeabilization of the mitochondrial membranes by alamethicin, whereas MA inhibitory effect was not altered. In addition, MA was the only tested compound that reduced succinate dehydrogenase activity. We also observed that EMA markedly inhibited succinate and malate transport through the mitochondrial dicarboxylate carrier. Mitochondrial membrane potential was also reduced by EMA and MA, but not by MMA, using succinate as electron donor, whereas none of these compounds was able to alter the membrane potential using glutamate plus malate as electron donors. Taken together, our results strongly indicate that EMA impairs succinate and malate uptake through the mitochondrial dicarboxylate carrier. (C) 2011 Elsevier Inc. All rights reserved.10518490Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PRONEX IIFAPERGSFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROPESQ/UFRGSFINEP, Rede Institut Brasileiro de Neurociencia (IBN-Net) [01.06.0842-00]Instiuto Nacional de Ciencia e Tecnologia Excitotoxicidade e Neuroprotecao (INCT-EN)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FINEP, Rede Institut Brasileiro de Neurociencia (IBN-Net) [01.06.0842-00