3-hydroxypalmitic-acid and Mitochondrial-Myopathies

The pathogenesis of the muscular symptoms and recurrent rhabdomyolysis that are commonly manifested in patients with mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) deficiencies is still unknown. In this study we investigated the effects of the major long-chain monocarboxylic 3-hydroxylated fatty acids (LCHFA) accumulating in these disorders, namely 3-hydroxytetradecanoic (3HTA) and 3-hydroxypalmitic (3HPA) acids, on important mitochondrial functions in rat skeletal muscle mitochondria. 3HTA and 3HPA markedly increased resting (state 4) and decreased ADP-stimulated (state 3) and CCCP-stimulated (uncoupled) respiration. 3HPA provoked similar effects in permeabilized skeletal muscle fibers, validating the results obtained in purified mitochondria. Furthermore, 3HTA and 3HPA markedly diminished mitochondrial membrane potential, NAD(P)H content and Ca(2+) retention capacity in Ca(2+)-loaded mitochondria. Mitochondrial permeability transition (mPT) induction probably underlie these effects since they were totally prevented by cyclosporin A and ADP. In contrast, the dicarboxylic analogue of 3HTA did not alter the tested parameters. Our data strongly indicate that 3HTA and 3HPA behave as metabolic inhibitors, uncouplers of oxidative phosphorylation and mPT inducers in skeletal muscle. It is proposed that these pathomechanisms disrupting mitochondrial homeostasis may be involved in the muscle alterations characteristic of MTP and LCHAD deficiencies.

Topics: Animals; Calcium; Cardiomyopathies; Lipid Metabolism, Inborn Errors; Membrane Potential, Mitochondrial; Mitochondria, Muscle; Mitochondrial Myopathies; Mitochondrial Trifunctional Protein; Muscle, Skeletal; Myristic Acids; NADP; Nervous System Diseases; Oxygen Consumption; Palmitic Acids; Rats, Wistar; Rhabdomyolysis

Mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies are fatty acid oxidation disorders biochemically characterized by tissue accumulation of long-chain fatty acids and derivatives, including the monocarboxylic long-chain 3-hydroxy fatty acids (LCHFAs) 3-hydroxytetradecanoic acid (3HTA) and 3-hydroxypalmitic acid (3HPA). Patients commonly present severe cardiomyopathy for which the pathogenesis is still poorly established. We investigated the effects of 3HTA and 3HPA, the major metabolites accumulating in these disorders, on important parameters of mitochondrial homeostasis in Ca(2+) -loaded heart mitochondria. 3HTA and 3HPA significantly decreased mitochondrial membrane potential, the matrix NAD(P)H pool and Ca(2+) retention capacity, and also induced mitochondrial swelling. These fatty acids also provoked a marked decrease of ATP production reflecting severe energy dysfunction. Furthermore, 3HTA-induced mitochondrial alterations were completely prevented by the classical mitochondrial permeability transition (mPT) inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca(2+) uptake blocker, indicating that LCHFAs induced Ca(2+)-dependent mPT pore opening. Milder effects only achieved at higher doses of LCHFAs were observed in brain mitochondria, implying a higher vulnerability of heart to these fatty acids. By contrast, 3HTA and docosanoic acids did not change mitochondrial homeostasis, indicating selective effects for monocarboxylic LCHFAs. The present data indicate that the major LCHFAs accumulating in mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies induce mPT pore opening, compromising Ca(2+) homeostasis and oxidative phosphorylation more intensely in the heart. It is proposed that these pathomechanisms may contribute at least in part to the severe cardiac alterations characteristic of patients affected by these diseases.

Topics: Adenosine Triphosphate; Animals; Calcium Channel Blockers; Calcium Signaling; Cardiomyopathies; Cell Membrane Permeability; Enzyme Inhibitors; Humans; Lipid Metabolism, Inborn Errors; Long-Chain-3-Hydroxyacyl-CoA Dehydrogenase; Membrane Potential, Mitochondrial; Mitochondria, Heart; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Myopathies; Mitochondrial Permeability Transition Pore; Mitochondrial Swelling; Mitochondrial Trifunctional Protein; Myristic Acids; NADP; Nervous System Diseases; Organ Specificity; Oxidative Phosphorylation; Palmitic Acids; Rats, Wistar; Rhabdomyolysis

Long-chain 3-hydroxylated fatty acids (LCHFA) accumulate in long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiencies. Affected patients usually present severe neonatal symptoms involving cardiac and hepatic functions, although long-term neurological abnormalities are also commonly observed. Since the underlying mechanisms of brain damage are practically unknown and have not been properly investigated, we studied the effects of LCHFA on important parameters of mitochondrial homeostasis in isolated mitochondria from cerebral cortex of developing rats. 3-Hydroxytetradecanoic acid (3 HTA) reduced mitochondrial membrane potential, NAD(P)H levels, Ca(2+) retention capacity and ATP content, besides inducing swelling, cytochrome c release and H2O2 production in Ca(2+)-loaded mitochondrial preparations. We also found that cyclosporine A plus ADP, as well as ruthenium red, a Ca(2+) uptake blocker, prevented these effects, suggesting the involvement of the mitochondrial permeability transition pore (mPTP) and an important role for Ca(2+), respectively. 3-Hydroxydodecanoic and 3-hydroxypalmitic acids, that also accumulate in LCHAD and MTP deficiencies, similarly induced mitochondrial swelling and decreased ATP content, but to a variable degree pending on the size of their carbon chain. It is proposed that mPTP opening induced by LCHFA disrupts brain bioenergetics and may contribute at least partly to explain the neurologic dysfunction observed in patients affected by LCHAD and MTP deficiencies.

Topics: 3-Hydroxyacyl CoA Dehydrogenases; Acyl-CoA Dehydrogenase, Long-Chain; Adenosine Triphosphate; Animals; Calcium; Cardiomyopathies; Cerebral Cortex; Cytochromes c; Energy Metabolism; Homeostasis; Hydrogen Peroxide; Lauric Acids; Lipid Metabolism, Inborn Errors; Membrane Potential, Mitochondrial; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Myopathies; Mitochondrial Permeability Transition Pore; Mitochondrial Swelling; Mitochondrial Trifunctional Protein; Myristic Acids; NADP; Nervous System Diseases; Oxidants; Palmitic Acids; Rats; Rats, Wistar; Rhabdomyolysis