Monogenetic inborn errors of metabolism cause a wide phenotypic heterogeneity that may even differ between family members carrying the same genetic variant. Computational modelling of metabolic ...networks may identify putative sources of this inter-patient heterogeneity. Here, we mainly focus on medium-chain acyl-CoA dehydrogenase deficiency (MCADD), the most common inborn error of the mitochondrial fatty acid oxidation (mFAO). It is an enigma why some MCADD patients--if untreated--are at risk to develop severe metabolic decompensations, whereas others remain asymptomatic throughout life. We hypothesised that an ability to maintain an increased free mitochondrial CoA (CoASH) and pathway flux might distinguish asymptomatic from symptomatic patients. We built and experimentally validated, for the first time, a kinetic model of the human liver mFAO. Metabolites were partitioned according to their water solubility between the bulk aqueous matrix and the inner membrane. Enzymes are also either membrane-bound or in the matrix. This metabolite partitioning is a novel model attribute and improved predictions. MCADD substantially reduced pathway flux and CoASH, the latter due to the sequestration of CoA as medium-chain acyl-CoA esters. Analysis of urine from MCADD patients obtained during a metabolic decompensation showed an accumulation of medium- and short-chain acylcarnitines, just like the acyl-CoA pool in the MCADD model. The model suggested some rescues that increased flux and CoASH, notably increasing short-chain acyl-CoA dehydrogenase (SCAD) levels. Proteome analysis of MCADD patient-derived fibroblasts indeed revealed elevated levels of SCAD in a patient with a clinically asymptomatic state. This is a rescue for MCADD that has not been explored before. Personalised models based on these proteomics data confirmed an increased pathway flux and CoASH in the model of an asymptomatic patient compared to those of symptomatic MCADD patients. We present a detailed, validated kinetic model of mFAO in human liver, with solubility-dependent metabolite partitioning. Personalised modelling of individual patients provides a novel explanation for phenotypic heterogeneity among MCADD patients. Further development of personalised metabolic models is a promising direction to improve individualised risk assessment, management and monitoring for inborn errors of metabolism.
Abstract
Background and Aims
Developing novel therapies to battle the global public health burden of heart failure remains challenging. This study investigates the underlying mechanisms and potential ...treatment for 4-hydroxynonenal (4-HNE) deleterious effects in heart failure.
Methods
Biochemical, functional, and histochemical measurements were applied to identify 4-HNE adducts in rat and human failing hearts. In vitro studies were performed to validate 4-HNE targets.
Results
4-HNE, a reactive aldehyde by-product of mitochondrial dysfunction in heart failure, covalently inhibits Dicer, an RNase III endonuclease essential for microRNA (miRNA) biogenesis. 4-HNE inhibition of Dicer impairs miRNA processing. Mechanistically, 4-HNE binds to recombinant human Dicer through an intermolecular interaction that disrupts both activity and stability of Dicer in a concentration- and time-dependent manner. Dithiothreitol neutralization of 4-HNE or replacing 4-HNE-targeted residues in Dicer prevents 4-HNE inhibition of Dicer in vitro. Interestingly, end-stage human failing hearts from three different heart failure aetiologies display defective 4-HNE clearance, decreased Dicer activity, and miRNA biogenesis impairment. Notably, boosting 4-HNE clearance through pharmacological re-activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) using Alda-1 or its improved orally bioavailable derivative AD-9308 restores Dicer activity. ALDH2 is a major enzyme responsible for 4-HNE removal. Importantly, this response is accompanied by improved miRNA maturation and cardiac function/remodelling in a pre-clinical model of heart failure.
Conclusions
4-HNE inhibition of Dicer directly impairs miRNA biogenesis in heart failure. Strikingly, decreasing cardiac 4-HNE levels through pharmacological ALDH2 activation is sufficient to re-establish Dicer activity and miRNA biogenesis; thereby representing potential treatment for patients with heart failure.
Mitochondrial dysfunction characterized by impaired bioenergetics, oxidative stress and aldehydic load is a hallmark of heart failure. Recently, different research groups have provided evidence that ...selective activation of mitochondrial detoxifying systems that counteract excessive accumulation of ROS, RNS and reactive aldehydes is sufficient to stop cardiac degeneration upon chronic stress, such as heart failure. Therefore, pharmacological and non-pharmacological approaches targeting mitochondria detoxification may play a critical role in the prevention or treatment of heart failure. In this review we discuss the most recent findings on the central role of mitochondrial dysfunction, oxidative stress and aldehydic load in heart failure, highlighting the most recent preclinical and clinical studies using mitochondria-targeted molecules and exercise training as effective tools against heart failure.
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•Heart failure affects over 25 million people worldwide.•Heart failure therapies target mainly neurohumoral over-activation.•Mitochondrial dysfunction and oxidative stress are hallmarks of heart failure.•Mitochondrial-derived aldehydes accumulate in failing hearts.•Therapies targeting mitochondrial detoxification improves heart failure outcome.
•HILIC-MS/MS method covers free CoA and acyl-CoAs (short to long-chain) in one run.•The method employing a zwitterionic HILIC column was characterized.•Limit of detection is in the range of ...(1.3–12.4) pmol mL−1 in the targeted method.•Application in HepG2 cells shows high acyl-CoAs and low free CoA in starved state.
Acyl-CoAs play a significant role in numerous physiological and metabolic processes making it important to assess their concentration levels for evaluating metabolic health. Considering the important role of acyl-CoAs, it is crucial to develop an analytical method that can analyze these compounds. Due to the structural variations of acyl-CoAs, multiple analytical methods are often required for comprehensive analysis of these compounds, which increases complexity and the analysis time. In this study, we have developed a method using a zwitterionic HILIC column that enables the coverage of free CoA and short- to long-chain acyl-CoA species in one analytical run. Initially, we developed the method using an LC-QTOF instrument for the identification of acyl-CoA species and optimizing their chromatography. Later, a targeted HILIC-MS/MS method was created in scheduled multiple reaction monitoring mode using a QTRAP MS detector. The performance of the method was evaluated based on various parameters such as linearity, precision, recovery and matrix effect. This method was applied to identify the difference in acyl-CoA profiles in HepG2 cells cultured in different conditions. Our findings revealed an increase in levels of acetyl-CoA, medium- and long-chain acyl-CoA while a decrease in the profiles of free CoA in the starved state, indicating a clear alteration in the fatty acid oxidation process.
O 4-hidroxi-2-nonenal (4-HNE) é um dos principais produtos da peroxidação lipídica, processo exacerbado no quadro de estresse oxidativo. Em função de sua alta reatividade com biomoléculas, seu ...acúmulo tem sido relacionado ao estabalecimento e progressão de inúmeras doenças, incluindo as cardiovasculares. Recentemente, nosso grupo identificou a interação entre 4-HNE e a proteína Dicer em coração de ratos com insuficiência cardíaca (dados não publicados). Dicer é uma RNAse importante na biogênese de microRNAs (miRNA), com papel na regulação gênica póstranscricional, de modo que alterações em sua função poderiam afetar diversos processos celulares. Tanto a interação entre o aldeído e Dicer, quanto o efeito sobre a mesma não foram descritos na literatura. Nesse contexto, o presente estudo tem como objetivo avaliar o efeito do 4-HNE na atividade e a expressão da Dicer. Nossa hipótese é que o 4-HNE afete negativamente o perfil de atividade e expressão da Dicer. Para testar essa hipótese, utilizamos o modelo animal de disfunção cardíaca induzida cirurgicamente e avaliamos: a formação de adutos de 4-HNE-proteínas, atividade e expressão de Dicer, e os níveis de miRNAs cardíacos. Em cultura celular (H9C2, MEF e HEK293), por sua vez, avaliamos o efeito agudo de 4-HNE sobre as mesmas variáveis após sua adição no meio de cultura. E, por último, utilizando a proteína recombinante, analisamos o efeito direto do aldeído sobre a estabilidade e atividade da enzima in vitro. Como esperado, em ensaios com a proteína isolada, observamos que o 4-HNE interage diretamente com a RNAse Dicer, e a formação de conjugados Dicer-4-HNE é responsável pela inibição e perda de estabilidade da proteína de forma tempo- e concentração-dependentes. No modelo animal, demonstramos um prejuízo na atividade de Dicer no coração de animais com disfunção cardíaca induzida por infarto do miocárdio, sem alteração em sua expressão, acompanhado de diminuição dos níveis da maioria dos miomiRs analisados. Notavelmente, ambos os parâmetros, assim como os níveis de adutos de 4-HNE-proteínas, foram melhorados no grupo tratado com Alda-1, agonista alostérico da enzima ALDH2 (responsável pela remoção do 4-HNE). Dessa forma, sugerimos a existência de associação entre os níveis de 4-HNE, atividade de Dicer e alteração na expressão de miRNAs no quadro de disfunção cardíaca. Consistente com os dados observados in vivo, em modelos celulares, a exposição aguda ao 4-HNE demonstrou reduzir a atividade de Dicer e afetar a via de biossíntese de miRNAs. Porém, não observamos proteção por Alda nesse modelo. Conjuntamente, nossos dados sugerem que a atividade de Dicer é modulada por 4-HNE em quadros de estresse agudo e crônico de aldeídos. Contudo, mais estudos são necessários a fim de elucidar o mecanismo pelo qual essa modulação ocorre. Visto que o acúmulo de 4-HNE e a desregulação na biogênese de miRNAs tem sido associados ao desenvolvimento de patologias, o estudo da interação entre Dicer e o aldeído é importante na compreensão dessas doenças e planejamento de novas estratégias terapêuticas.
4-hydroxy-2-nonenal (4-HNE) is a major by-product of lipid peroxidation, a process that is exacerbated under oxidative stress conditions. This aldehyde is a very reactive molecule associated with the establishment and progression of many diseases, including cardiovascular diseases. We recently found using proteomics that 4-HNE directly targets Dicer in failing hearts, a critical enzyme for miRNA biology (unpublished data). Neither the aldehyde-Dicer adduction, nor its effect on protein stability and activity has been previously reported. Therefore, this study aimed to fill this gap by further investigating 4-HNE-Dicer interaction and characterizing its effect on Dicer profile. We hypothesize that 4-HNE will make adducts with Dicer and compromise its function and levels. Using an animal model of cardiac dysfunction, we evaluated the following parameters: levels of 4-HNE adducted proteins, Dicer levels and activity, and the levels of heart specific miRNAs (myomiRs). The same variables were analyzed in distinct cellular models (H9C2, MEF, HEK293) after acute exposure to 4-HNE. Additionally, we synthetized recombinant Dicer, and protein function and stability were assessed in vitro. As expected, the experiments with recombinant protein revealed that 4-HNE directly interacts with Dicer, and the formation of 4-HNE-DICER adduct causes loss of Dicer cleavage activity and stability in a time- and concentration-dependent manner. Regarding the animal model, Dicer activity, but not protein levels, dropped in failing hearts, which was paralleled by a reduction of mature miRNA levels. Of interest, animals with cardiac dysfunction chronically treated with a small molecule activator of aldehyde dehydrogenase 2 (ALDH2), termed Alda-1, displayed an elevated cardiac Dicer activity and mature miRNA levels compared with vehicle-treated animals. ALDH2 is the mains enzyme responsible for 4-HNE clearance. In this context, this study points out a potential connection among 4-HNE levels, Dicer activity and myomiR levels in cardiac dysfunction. Consistent with our in vivo data, cells acutely exposed to 4-HNE showed an increase in 4-HNE-protein adducts followed by a reduction in Dicer activity and changes in miRNA biosynthesis. However, Alda showed no protective effect in the latter model. Taken together, our findings using animal and cellular models suggest that Dicer activity is impaired in chronic (cardiac dysfunction) and acute aldehyde stress conditions. However, the molecular mechanisms involved in this response are still unclear. As both 4-HNE accumulation and microRNAs have been linked to innumerous pathologies, clarifying the modulation of Dicer activity under such conditions will certainly contribute to a better understanding the diseases and future therapeutic strategies.
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