Uncoupling, metabolic inhibition and induction of mitochondrial permeability transition in rat liver mitochondria caused by the major long-chain hydroxyl monocarboxylic fatty acids accumulating in LCHAD deficiency

Abstract

Patients with long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) deficiency commonly present liver dysfunction whose pathogenesis is unknown. We studied the effects of long-chain 3-hydroxylated fatty acids (LCHFA) that accumulate in LCHAD deficiency on liver bioenergetics using mitochondrial preparations from young rats. We provide strong evidence that 3-hydroxytetradecanoic (3HTA) and 3-hydroxypalmitic (3HPA) acids, the monocarboxylic acids that are found at the highest tissue concentrations in this disorder, act as metabolic inhibitors and uncouplers of oxidative phosphorylation. These conclusions are based on the findings that these fatty acids decreased ADP-stimulated (state 3) and uncoupled respiration, mitochondrial membrane potential and NAD(P)H content, and, in contrast, increased resting (state 4) respiration. We also verified that 3HTA and 3HPA markedly reduced Ca2+ retention capacity and induced swelling in Ca2+-loaded mitochondria. These effects were mediated by mitochondrial permeability transition (MPT) induction since they were totally prevented by the classical MPT inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca2+ uptake blocker. Taken together, our data demonstrate that the major monocarboxylic LCHFA accumulating in LCHAD deficiency disrupt energy mitochondrial homeostasis in the liver. It is proposed that this pathomechanism may explain at least in part the hepatic alterations characteristic of the affected patients.

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

“…Noteworthy, morphological mitochondrial alterations in skeletal muscle detected by magnetic resonance imaging, as well as increased blood levels of creatine phosphokinase and lactic acid associated with episodic rhabdomyolysis, were found in VLCAD-deficient patients [23,24], suggesting a disturbance of mitochondrial energy homeostasis, although, to the best of our knowledge, ATP production was not measured in these patients. In addition, we previously demonstrated that long-chain hydroxylated fatty acids accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency strongly disturb mitochondrial functions in various tissues [27][28][29]. In addition, we previously demonstrated that long-chain hydroxylated fatty acids accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency strongly disturb mitochondrial functions in various tissues [27][28][29].…”

Deregulation of mitochondrial functions provoked by long‐chain fatty acid accumulating in long‐chain 3‐hydroxyacyl‐CoA dehydrogenase and mitochondrial permeability transition deficiencies in rat heart – mitochondrial permeability transition pore opening as a potential contributing pathomechanism of cardiac alterations in these disorders

“…Their final concentrations in the incubation medium were in the range 10–60 μ m , whereas the EtOH concentration was always 1%. The chosen doses were previously used in other studies investigating the effects of the long‐chain fatty acids on biochemical parameters and are similar to those found in plasma of the affected patients . The same percentage of EtOH was present in controls and was found not to alter per se the parameters evaluated.…”

“…These findings are probably related to the marked decrease of ATP formation caused by 3HTA and 3HPA in the heart. On the other hand, we cannot rule out the possibility that the decrease of mitochondrial reducing equivalents and ΔΨm provoked by of 3HTA and 3HPA in the absence of exogenous Ca 2+ were at least partly a result of the uncoupling behavior of these fatty acids .…”

“…With regard to the mechanisms underlying LCHFA‐induced mPT opening in Ca 2+ ‐loaded mitochondria, these may be provoked by oxidative stress, as well as by oxidative phosphorylation uncouplers that lead to NADH oxidation and secondarily nonselective permeabilization . In this scenario, LCHFAs were demonstrated to provoke oxidative stress and uncouple the oxidative phosphorylation .…”

Cyclophilin inhibition as a potential treatment for nonalcoholic steatohepatitis (NASH)

“…In vitro studies with CsA have reinforced findings from genetic knockout/knockdown by showing that cyclophilin inhibition can protect mitochondria from the kinds of metabolic disturbances that occur in NASH. For example, CsA blocked mPT in liver mitochondria following application of short-, medium-, and long-chain fatty acids or lysophosphatidylcholine [118][119][120][121]; blocked mPT and significantly reduced mitochondrial ROS, ATP depletion, and death of preadipocytes induced by high fatty acid concentrations [122]; blocked mPT and significantly reduced fructose-induced or high glucose-induced death of INS-1 pancreatic islet cells [123]; blocked mPT and restored the ATP deficit induced by long-chain fatty acids or palmitoyl-L-carnitine in cardiac mitochondria [124][125][126][127][128]; blocked mPT and prevented palmitate-induced insulin resistance in muscle mitochondria [107]; blocked hepatocyte death resulting from high glucose and hydrogen peroxide [129]; and alleviated fatty acid-induced ER stress gene induction, ROS elevation, and death of LO2 hepatocytes [60,130]. Düfer et al (2001), in contrast, found that CsA diminished glucose-induced insulin secretion of mouse pancreatic islets in vitro by inhibiting glucose-stimulated oscillations of the cytoplasmic free calcium concentration [131].…”