15 research outputs found

    NRF2 and RIP140 as new therapeutic targets for X-linked adrenoleukodystrophy (X-ALD): Control of redox/metabolic homeostasis and inflammation

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    [eng] X-linked adrenoleukodystrophy (X-ALD) is a rare neurometabolic disease characterized by the loss of function of the peroxisomal transporter ABCD1, which leads to an accumulation of very long-chain fatty acids, inducing mitochondrial reactive oxygen species. Clinical phenotypes in humans range from adrenal insufficiency to fatal inflammatory cerebral demyelination. Abcd1-null mice (Abcd1- mice) develop late onset axonal degeneration in the spinal cord and locomotor disability resembling the most common phenotype in humans, adrenomyeloneuropathy (AMN). Oxidative stress and mitochondrial dysfunction are key common features in X-ALD patients as well as in Abcd1- mouse. In this thesis, we sought to explore novel therapeutic targets that would contribute to better understand the pathophysiology of the disease, based on the existing knowledge on these hallmarks of X-ALD. First, we studied the nuclear factor erythroid-derived 2, like 2 (NFE2L2, also known as NRF2), in X-ALD mouse models (Abcd1- and Abcd1-/Abcd2-/- mice) and in fibroblasts derived from healthy subjects and X-ALD patients. Here, we identify that NRF2, the master regulator of endogenous antioxidant response, and its target genes are impaired in X-ALD due to an aberrant activity of the AKT/GSK-3β axis. Moreover, GSK-3β inhibitors reactivated the blunted NRF2-dependent response upon oxidative stress in X-ALD fibroblasts (Chapter I). In a second study, we sought to determine the role of RIP140 (receptor interacting protein 140), a transcriptional coregulator essential for metabolic homeostasis and inflammatory response, in X-ALD pathophysiology. To address this objective we studied RIP140 in Abcd1- mouse, organotypic spinal cord slice cultures (OSCSC) from mice and normal appearing white matter (NAWM) from healthy subjects and cerebral X-ALD patients. We found out a redox-dependent increase of RIP140 in the spinal cord and OSCSC from Abcd1- mice, as well as an induction of RIP140 in the NAWM of childhood cerebral ALD (ccALD) patients (Chapter II). Finally, we explored the therapeutic potential of targeting NRF2 and RIP140, independently, in X-ALD mice (Abcd1- and Abcd1-/Abcd2-/- mice). Regarding NRF2, we followed a pharmacologic approach, by treating Abcd1- and Abcd1-/Abcd2-/- mice with dimethyl fumarate, an FDA-approved NRF2 activator (Chapter I). In the case of RIP140, we followed a genetic approach, by crossing RIP140-deficient mice with X-ALD mouse models (Chapter II). In both cases, the therapeutic intervention led to an amelioration of i) mitochondrial dysfunction, ii) bioenergetic failure, iii) oxidative damage and iv) dysregulated inflammatory profile, and most importantly, halted axonal degeneration and behavioural abnormalities in X-ALD mice (Chapters I and II). Collectively, these findings reveal an impairment of the AKT/GSK-3β/NRF2 axis that controls endogenous response against oxidative stress, as well as point to RIP140 as a candidate for the impaired mitochondrial biogenesis and induction of proinflammatory response in X-ALD. Finally, the results of this doctoral thesis indicate that therapies based on NRF2 activation and RIP140 inhibition may be valuable strategies to treat X-ALD and other neurodegenerative disorders which share impaired redox homeostasis, mitochondrial dysfunction and neuroinflammation among their hallmarks.[spa] La adrenoleuocodistrofia ligada al cromosoma X (X-ALD) es una enfermedad neurometabólica rara, que se caracteriza por la pérdida de función del transportador peroxisomal ABCD1. Como consecuencia se acumulan ácidos grasos de cadena muy larga, que inducen la producción de especies reactivas de oxígeno en la mitocondria. El cuadro clínico de X-ALD en humanos es variable, desde la insuficiencia adrenal hasta una desmielinización inflamatoria cerebral que suele ser fatal. Los ratones nulos para el gen Abcd1 (ratones Abcd1-) desarrollan una degeneración axonal de aparición tardía en la médula espinal, además de presentar incapacidad locomotora, un fenotipo similar al más común en humanos, la adrenomieloneuropatía (AMN). El estrés oxidativo y la disfunción mitocondrial son unas características claves de X-ALD, tanto en el modelo de ratón como en humanos. En esta tesis, hemos decidido explorar nuevas dianas terapéuticas que contribuyan a una mejor comprensión de la fisiopatología de esta enfermedad, basándonos en el conocimiento existente sobre estas alteraciones en X-ALD. En primer lugar, estudiamos el factor nuclear NRF2 (nuclear factor, erythroid-derived 2, like 2; también NFE2L2) en los modelos animales de X-ALD (ratones Abcd1- y Abcd1-/Abcd2-/-) y en fibroblastos de pacientes con X-ALD y sujetos sanos. Así, identificamos que NRF2, el regulador maestro de la respuesta antioxidante endógena, así como sus genes diana, están inhibidos en X-ALD, debido a una actividad aberrante del eje AKT/GSK-3β. Además, inhibidores de GSK-3β reactivaron la respuesta frente al estrés oxidativo dependiente de NRF2, que estaba bloqueada en los fibroblastos de pacientes con X-ALD (Capítulo I). En el segundo estudio, pretendemos determinar el papel de RIP140 (receptor interacting protein 140) en la fisiopatología de X-ALD. RIP140 es un coregulador transcripcional esencial para la homeostasis metabólica y la respuesta inflamatoria. Para lograr este objetivo, primero estudiamos RIP140 en los ratones Abcd1-, en cultivos organotípicos de láminas de médula espinal (OSCSC) de ratón, y en sustancia blanca cerebral de apariencia normal (NAWM) de pacientes X-ALD. De este modo, encontramos una inducción mediada por estrés oxidativo de RIP140 en la médula espinal y en OSCSC de los ratones Abcd1-, además de una activación de RIP140 en NAWM de pacientes con ALD cerebral infantil (ccALD) (Capítulo II). Por último, investigamos el potencial terapéutico de estas vías para tratar X-ALD, mediante la administración en la dieta de dimetil fumarato, un activador de NRF2 aprobado por la FDA, a los ratones X-ALD (Capítulo I); y a través de la deleción del gen Rip140 en los ratones X-ALD (Capítulo II). En ambos casos, la intervención terapéutica conllevó una mejora de i) la disfunción mitocondrial, ii) el fallo bioenergético, iii) el daño oxidativo, iv) la alteración del perfil inflamatorio, y sobre todo, detuvo la degeneración axonal y previno las alteraciones en el comportamiento en los ratones X-ALD (Capítulos I y II). En conjunto, estos resultados muestran una disfunción del eje AKT/GSK-3β/NRF2, que controla la respuesta antioxidante endógena, así como apuntan a RIP140 como responsable de la disminuida biogenesis mitocondrial y la inducción de la respuesta pro-inflamatoria que observamos en X-ALD. Finalmente, los resultados derivados de esta tesis doctoral indican que terapias basadas en la activación de NRF2 o la inhibición de RIP140 tienen un valor potencial como estrategias terapéuticas para tratar pacientes con X-ALD u otras enfermedades neurodegenerativas, que compartan como sello distintivo, un fallo en la homeostasis redox, disfunción mitocondrial y neuroinflamación.[cat] L’adrenoleuocodistròfia lligada al cromosoma X (X-ALD) és una malaltia neurometabòlica rara, que es caracteritza per la pèrdua de funció del transportador peroxisomal ABCD1. Com a conseqüència s'acumulen àcids grassos de cadena molt llarga, que indueixen la producció d'espècies reactives d'oxigen en el mitocondri. El quadre clínic de X-ALD en humans és variable, des de la insuficiència adrenal fins a una desmielinització inflamatòria cerebral que sol ser fatal. Els ratolins nuls per al gen Abcd1 (ratolins Abcd1-) desenvolupen una degeneració axonal d'aparició tardana en la medul·la espinal, a més de presentar incapacitat locomotora, un fenotip similar al més comú en humans, l’adrenomieloneuropatia (AMN). L'estrès oxidatiu i la disfunció mitocondrial són unes característiques claus de X-ALD, tant en el model de ratolí com en humans. En aquesta tesi, hem decidit explorar noves dianes terapèutiques que contribueixin a una millor comprensió de la fisiopatologia d'aquesta malaltia, basant-nos en el coneixement existent sobre aquestes alteracions en X-ALD. En primer lloc, hem estudiat el factor nuclear NRF2 (nuclear factor, erythroid-derived 2, like 2; també NFE2L2) en els models animals de X-ALD (ratolins Abcd1- i Abcd1-/ Abcd2-/-) i en fibroblasts de pacients amb X-ALD i subjectes sans. Així, hem identificat que NRF2, el regulador mestre de la resposta antioxidant endògena, així com els seus gens diana, estan inhibits en X-ALD, a causa d'una activitat aberrant de l'eix AKT/GSK-3β. A més, inhibidors de GSK-3β van reactivar la resposta enfront de l'estrès oxidatiu dependent de NRF2, que estava bloquejada en els fibroblasts de pacients amb X-ALD (Capítol I). En el segon estudi, pretenem determinar el paper de RIP140 (receptor interacting protein 140) en la fisiopatologia de X-ALD. RIP140 és un coregulador transcripcional essencial per a l'homeòstasi metabòlica i la resposta inflamatòria. Per aconseguir aquest objectiu, primer hem estudiat RIP140 en els ratolins Abcd1-, en cultius organotípics de làmines de medul·la espinal (OSCSC) de ratolí, i en substància blanca cerebral d'aparença normal (NAWM) de pacients X-ALD. D'aquesta manera, hem trobat una inducció de RIP140 intervinguda per estrès oxidatiu en la medul·la espinal i en OSCSC dels ratolins Abcd1-, a més d'una activació de RIP140 en NAWM de pacients amb ALD cerebral infantil (ccALD) (Capítol II). Finalment, hem investigat el potencial terapèutic d'aquestes vies per tractar X-ALD, mitjançant l'administració en la dieta de dimetil fumarat, un activador de NRF2 aprovat per la FDA, als ratolins X-ALD (Capítol I); i a través de la deleció del gen Rip140 en els ratolins X-ALD (Capítol II). En tots dos casos, la intervenció terapèutica va comportar una millora de i) la disfunció mitocondrial, ii) la fallada bioenergètica, iii) el dany oxidatiu, iv) l'alteració del perfil inflamatori i, sobretot, va aturar la degeneració axonal i va prevenir les alteracions en el comportament en els ratolins X-ALD (Capítols I i II). En conjunt, aquests resultats mostren una disfunció de l'eix AKT/GSK-3β/NRF2, que controla la resposta antioxidant endògena, així com senyalen a RIP140 com a responsable de la disminuïda biogènesis mitocondrial i la inducció de la resposta pro- inflamatòria que observem en X-ALD. Finalment, els resultats derivats d'aquesta tesi doctoral indiquen que teràpies basades en l'activació de NRF2 o la inhibició de RIP140 tenen un valor potencial com a estratègies terapèutiques per tractar pacients amb X-ALD o altres malalties neurodegeneratives, que comparteixin com a segell distintiu, una fallada en l'homeòstasi redox, disfunció mitocondrial i neuroinflamació

    Oxidative stress and mitochondrial dynamics malfunction are linked in Pelizaeus-Merzbacher disease

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    Pelizaeus-Merzbacher disease (PMD) is a fatal hypomyelinating disorder characterized by early impairment of motor development, nystagmus, choreoathetotic movements, ataxia and progressive spasticity. PMD is caused by variations in the proteolipid protein gene PLP1, which encodes the two major myelin proteins of the central nervous system, PLP and its spliced isoform DM20, in oligodendrocytes. Large duplications including the entire PLP1 gene are the most frequent causative mutation leading to the classical form of PMD. The Plp1 overexpressing mouse model (PLP-tg66/66 ) develops a phenotype very similar to human PMD, with early and severe motor dysfunction and a dramatic decrease in lifespan. The sequence of cellular events that cause neurodegeneration and ultimately death is poorly understood. In this work, we analyzed patient-derived fibroblasts and spinal cords of the PLP-tg66/66 mouse model, and identified redox imbalance, with altered antioxidant defense and oxidative damage to several enzymes involved in ATP production, such as glycolytic enzymes, creatine kinase and mitochondrial proteins from the Krebs cycle and oxidative phosphorylation. We also evidenced malfunction of the mitochondria compartment with increased ROS production and depolarization in PMD patient's fibroblasts, which was prevented by the antioxidant N-acetyl-cysteine. Finally, we uncovered an impairment of mitochondrial dynamics in patient's fibroblasts which may help explain the ultrastructural abnormalities of mitochondria morphology detected in spinal cords from PLP-tg66/66 mice. Altogether, these results underscore the link between redox and metabolic homeostasis in myelin diseases, provide insight into the pathophysiology of PMD, and may bear implications for tailored pharmacological intervention

    Aberrant regulation of the GSK-3β/NRF2 axis unveils a novel therapy for adrenoleukodystrophy

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    The nuclear factor erythroid 2‐like 2 (NRF2) is the master regulator of endogenous antioxidant responses. Oxidative damage is a shared and early‐appearing feature in X‐linked adrenoleukodystrophy (X‐ALD) patients and the mouse model (Abcd1 null mouse). This rare neurometabolic disease is caused by the loss of function of the peroxisomal transporter ABCD1, leading to an accumulation of very long‐chain fatty acids and the induction of reactive oxygen species of mitochondrial origin. Here, we identify an impaired NRF2 response caused by aberrant activity of GSK‐3β. We find that GSK‐3β inhibitors can significantly reactivate the blunted NRF2 response in patients' fibroblasts. In the mouse models (Abcd1 − and Abcd1 −/Abcd2 −/− mice), oral administration of dimethyl fumarate (DMF/BG12/Tecfidera), an NRF2 activator in use for multiple sclerosis, normalized (i) mitochondrial depletion, (ii) bioenergetic failure, (iii) oxidative damage, and (iv) inflammation, highlighting an intricate cross‐talk governing energetic and redox homeostasis in X‐ALD. Importantly, DMF halted axonal degeneration and locomotor disability suggesting that therapies activating NRF2 hold therapeutic potential for X‐ALD and other axonopathies with impaired GSK‐3β/NRF2 axis. Keywords: adrenoleukodystrophy, dimethyl fumarate, GSK‐3, NRF2, oxidative stress Subject Categories: Genetics, Gene Therapy & Genetic Disease, Metabolism, Neuroscienc

    PREreview of "GLUD1 dictates muscle stem cell differentiation by controlling mitochondrial glutamate levels"

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    <p><strong>This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at <a href="https://prereview.org/reviews/10066121">https://prereview.org/reviews/10066121</a>.</strong></p> <p>This review reflects comments and contributions from Marina Schernthanner and Pablo Ranea-Robles. Review synthesized by Pablo Ranea-Robles.</p><p>In this study, the authors studied the role of GLUD1 in satellite cells in the muscle. These cells are responsible for dynamic changes in muscular cells upon different signals, such as exercise. It is well known that metabolic changes play an important role in the fate decision of these cells toward proliferation or differentiation. Here, they found that GLUD1 and glutamine anaplerosis are decreased in differentiation, in contrast to what happens during proliferation. Using inducible KO cells and mice, they show how GLUD1 deficiency induces differentiation to myotubes and imbalance fusion of fibers. This phenotype was associated with an accumulation of glutamate only in mitochondria together with decreased levels of mitochondrial aspartate. In consequence, the malate-aspartate shuttle was inhibited, disturbing the NAD/NADH ratio between the cytosolic and mitochondrial compartments. In conclusion, they establish the role of GLUD1 in muscle satellite cells as a brake on differentiation, allowing proper proliferation using glutamine to feed the TCA cycle. Overall, we found this an excellent study, highly relevant, easy to read, and with multiple techniques and models to sustain their conclusions. Therefore, we would like to congratulate the authors on such a high-impact study. Below, a few comments we think could improve the manuscript and its understanding by the broad scientific community.</p><p>Major comments:</p><ul><li><p>We had no major comments</p></li></ul><p>Minor comments:</p><ul><li><p>Could authors expand on how they know/tested that the custom media they used worked fine on the protocols of differentiation/proliferation? Was it possible to control for the amount of FBS in proliferation vs differentiation media (there appears to be a big difference between 30% and 0.2% FBS) without affecting the maintenance/differentiation of cells? FBS per se contains a number of growth factors, which could influence metabolomic analyses?</p></li><li><p>I would recommend adding some implications/impact of these results more on a big picture over muscular function.</p></li><li><p>The graphical abstract is excellent. I would just recommend to make the changes in NAD/NADH more clear, and indicate better the status of WT cell (quiescent vs prolif)</p></li><li><p>Are there more number of cells after 48h in fig 2?</p></li><li><p>What is the ratio Glu/alpha-kg in the cytosol?</p></li><li><p>Metabolic changes were done with proliferation media, as I understand it, why did the authors not perform metabolomic analysis with the differentiation media?</p></li><li><p>Figure 5D - can the authors show the metabolite levels of the cytosolic fraction as well (maybe in a supplementary figure)? Given that few differences were observed in whole cell lysates, as shown in B, one would expect that mitochondrial and cytosolic metabolite levels display opposite trends that balance each other out, correct?</p></li><li><p>Figure 4 - aren't these minimal differences in transcription upon loss of Glud1 surprising, given the strong phenotypic difference in figure 1? What mediates precocious differentiation if not transcriptional changes? Could it be that the authors are dealing with somewhat heterogeneous populations here and thus relative enrichment of MuSC vs differentiated cell populations might not be readily picked up by bulk RNA-seq?</p></li><li><p>Figure 3C-D - couldn't a reduction in GFP+ cells in theory also be due to increased cell death of GFP+ PAX7+ MuSC? Have the authors excluded this possibility by f.e. showing that there is no difference in TUNEL+(general cell death, DNA damage marker) and Caspase-3+ (apoptotic) cells between KO and WT MuSCs? For D) addition of nuclear signals to indicate cell fusion as expected in muscle fibers/myotubes would be helpful.</p></li></ul><p>Suggestions for future studies:</p><ul><li><p> It would be extremely interesting to evaluate a possible rescue of the phenotype in vivo. Perhaps with alanine supplementation?</p></li></ul> <h2>Competing interests</h2> <p> The author declares that they have no competing interests. </p&gt

    PREreview of "A kidney-hypothalamus axis promotes compensatory glucose production in response to glycosuria"

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    This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/8431146. This review reflects comments and contributions from Marina Schernthanner, Femi Arogundade and Pablo Ranea-Robles. Review synthesized by Jonny Coates. The study leverages the phenotype presented by the renal Glut2 KO mice (glycosuria with normal glycemia) to investigate how the body senses this glucose loss and the mechanisms behind metabolic homeostasis processes that lead to enhanced glucose production so glycemia remains stable. The use of a genetically modified mouse model with renal Glut2 knockout provides a controlled system for studying the specific role of renal glucose transporters in glucose homeostasis. The study involves various methods, including measurements of glucose production, metabolomics, gene expression related to the hypothalamic-pituitary-adrenal axis, afferent renal nerve ablation, and analysis of secreted proteins. The authors point to a kidney/hypothalamus axis and suggest the involvement of different acute phase proteins in this homeostatic response. The limitations of the study are acknowledged, and further research is suggested to delve deeper into the role of secretory proteins and the specific source of endogenous glucose production after afferent renal denervation. The manuscript is well written and the results are potentially of interest. The study's findings have potential implications for the field of diabetes treatment, as they suggest a mechanism that may explain why SGLT2 inhibitors don't achieve their full potential in lowering blood glucose levels. However, we think that some of the conclusions are merely based on descriptive assessments of changes occurring in the renal Glut2 KO mice. There are a lack of details in the reporting of some of the results and, in particular, in the discussion section, that would also require a bit more explanation from the authors. Right now, it could be hard for the reader to place this research in context. We have summarized our comments below Major comments: The study mentions the use of male and female mice, but it's important to know the sample sizes for each experimental group and how gender might influence the results. Additionally, the authors should provide more details about the control groups and their matching criteria to ensure the validity of comparisons. Moreover, the exact genetic information for the knockout mice i.e. what is the CreER driver that makes it kidney-specific? Is missing. It is currently inconsistent in terms of sex and age of mice used for different experiments. Minor comments: While the metabolomics analysis is described, more information is needed about the biological significance of the changes observed in the metabolites. How do these changes relate to the compensatory glucose production, and are they causally linked? The paper would benefit from improved organization and clarity, particularly in the results and discussion sections. Crh+ cells in control image of fig 2 are not clear. The authors could consider highlighting the are where these cells are present, or add an inset showing a zoomed image of some positive cells How specific is the use of capsaicin to selectively suppress afferent renal nerve activity? Does this impact other neurons? Either citations or experimental data should be included here. The conditions of mice in Sup Fig. 1 are not clear and should be stated clearly in this part of the text and in the figure legend. The study is transparent about its limitations and raises important questions for future research. This acknowledgment of limitations contributes to the scientific rigor of the work. While control groups are mentioned, it's not clear how these controls were chosen or matched to the experimental group. Further information is needed on how these controls were used to make valid comparisons. While the study describes the experimental procedures in detail, it's essential to provide information on how many times these experiments were replicated to assess the reproducibility of the results. This is especially crucial given the complex methods used. Blocking the HPA axis and assessing responses in KO and WT mice would strengthen the data in Fig 2 Investigating or showing the levels of glucagon and adrenaline to delineate mechanisms of tissue-specific glucose production would further strengthen the data presented. Is it possible to measure glucose production under denervation conditions? That would support the conclusion if the increased glucose production is blunted Not everyone might be familiar with the abbreviation 2D-DIGE. Explaining this before first use would be beneficial. Supp fig 2 could be fused with Fig 4 to make the argument more convincing. The authors state that "It is possible that afferent renal denervation in the present study attenuated only hepatic glucose production through the hypothalamus without affecting the compensatory increase in renal (local) glucose production". Addressing this would significantly strengthen the manuscript, particularly given that the title includes "hypothalamus-kidney axis". Comments on reporting: The paper mentions the use of statistical tests but lacks information on the specific statistical tests performed for each analysis. It's crucial to provide details on the tests used, assumptions made, and how p-values were adjusted for multiple comparisons, if applicable. Suggestions for future studies: Extend the research to human subjects, particularly individuals with diabetes treated with SGLT2 inhibitors. Investigate whether similar mechanisms and pathways are at play in humans, and whether these findings have clinical relevance. Investigate the specific roles of secreted proteins, such as acute phase proteins and major urinary proteins, in glucose regulation and potential interactions with the kidney-hypothalamus axis. Explore how the kidney-hypothalamus axis integrates with other nervous system and endocrine signals involved in glucose regulation, such as insulin and glucagon. Conduct in-depth studies on the impact of afferent renal nerve activity on glucose homeostasis and the signaling pathways involved. Investigate the role of sensory nerves in detecting glycosuria and triggering compensatory responses. Competing interests The author declares that they have no competing interests

    Metabolic interactions between peroxisomes and mitochondria with a special focus on acylcarnitine metabolism

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    Carnitine plays an essential role in mitochondrial fatty acid β-oxidation as a part of a cycle that transfers long-chain fatty acids across the mitochondrial membrane and involves two carnitine palmitoyltransferases (CPT1 and CPT2). Two distinct carnitine acyltransferases, carnitine octanoyltransferase (COT) and carnitine acetyltransferase (CAT), are peroxisomal enzymes, which indicates that carnitine is not only important for mitochondrial, but also for peroxisomal metabolism. It has been demonstrated that after peroxisomal metabolism, specific intermediates can be exported as acylcarnitines for subsequent and final mitochondrial metabolism. There is also evidence that peroxisomes are able to degrade fatty acids that are typically handled by mitochondria possibly after transport as acylcarnitines. Here we review the biochemistry and physiological functions of metabolite exchange between peroxisomes and mitochondria with a special focus on acylcarnitines

    Slc22a5 haploinsufficiency does not aggravate the phenotype of the long-chain acyl-CoA dehydrogenase KO mouse

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    Secondary carnitine deficiency is commonly observed in inherited metabolic diseases characterised by the accumulation of acylcarnitines such as mitochondrial fatty acid oxidation (FAO) disorders. It is currently unclear if carnitine deficiency and/or acylcarnitine accumulation play a role in the pathophysiology of FAO disorders. The long-chain acyl-CoA dehydrogenase (LCAD) KO mouse is a model for long-chain FAO disorders and is characterised by decreased levels of tissue and plasma free carnitine. Tissue levels of carnitine are controlled by SLC22A5, the plasmalemmal carnitine transporter. Here, we have further decreased carnitine availability in the LCAD KO mouse through a genetic intervention by introducing one defective Slc22a5 allele (jvs). Slc22a5 haploinsufficiency decreased free carnitine levels in liver, kidney, and heart of LCAD KO animals. The resulting decrease in the tissue long-chain acylcarnitines levels had a similar magnitude as the decrease in free carnitine. Levels of cardiac deoxycarnitine, a carnitine biosynthesis intermediate, were elevated due to Slc22a5 haploinsufficiency in LCAD KO mice. A similar increase in heart and muscle deoxycarnitine was observed in an independent experiment using Slc22a5jvs/jvs mice. Cardiac hypertrophy, fasting-induced hypoglycemia and increased liver weight, the major phenotypes of the LCAD KO mouse, were not affected by Slc22a5 haploinsufficiency. This may suggest that secondary carnitine deficiency does not play a major role in the pathophysiology of these phenotypes. Similarly, our data do not support a major role for toxicity of long-chain acylcarnitines in the phenotype of the LCAD KO mouse

    Aberrant regulation of the GSK‐3β/NRF2 axis unveils a novel therapy for adrenoleukodystrophy

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    Abstract The nuclear factor erythroid 2‐like 2 (NRF2) is the master regulator of endogenous antioxidant responses. Oxidative damage is a shared and early‐appearing feature in X‐linked adrenoleukodystrophy (X‐ALD) patients and the mouse model (Abcd1 null mouse). This rare neurometabolic disease is caused by the loss of function of the peroxisomal transporter ABCD1, leading to an accumulation of very long‐chain fatty acids and the induction of reactive oxygen species of mitochondrial origin. Here, we identify an impaired NRF2 response caused by aberrant activity of GSK‐3β. We find that GSK‐3β inhibitors can significantly reactivate the blunted NRF2 response in patients’ fibroblasts. In the mouse models (Abcd1− and Abcd1−/Abcd2−/− mice), oral administration of dimethyl fumarate (DMF/BG12/Tecfidera), an NRF2 activator in use for multiple sclerosis, normalized (i) mitochondrial depletion, (ii) bioenergetic failure, (iii) oxidative damage, and (iv) inflammation, highlighting an intricate cross‐talk governing energetic and redox homeostasis in X‐ALD. Importantly, DMF halted axonal degeneration and locomotor disability suggesting that therapies activating NRF2 hold therapeutic potential for X‐ALD and other axonopathies with impaired GSK‐3β/NRF2 axis

    Dietary restriction in the long-chain acyl-CoA dehydrogenase knockout mouse

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    Patients with a disorder of mitochondrial long-chain fatty acid β-oxidation (FAO) have reduced fasting tolerance and may present with hypoketotic hypoglycemia, hepatomegaly, (cardio)myopathy and rhabdomyolysis. Patients should avoid a catabolic state because it increases reliance on FAO as energy source. It is currently unclear whether weight loss through a reduction of caloric intake is safe in patients with a FAO disorder. We used the long-chain acyl-CoA dehydrogenase knockout (LCAD KO) mouse model to study the impact of dietary restriction (DR) on the plasma metabolite profile and cardiac function. For this, LCAD KO and wild type (WT) mice were subjected to DR (70% of ad libitum chow intake) for 4 weeks and compared to ad libitum chow fed mice. We found that DR had a relatively small impact on the plasma metabolite profile of WT and LCAD KO mice. Echocardiography revealed a small decrease in left ventricular systolic function of LCAD KO mice, which was most noticeable after DR, but there was no evidence of DR-induced cardiac remodeling. Our results suggest that weight loss through DR does not have acute and detrimental consequences in a mouse model for FAO disorders

    Protection against overfeeding-induced weight gain is preserved in obesity but does not require FGF21 or MC4R

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    Abstract Overfeeding triggers homeostatic compensatory mechanisms that counteract weight gain. Here, we show that both lean and diet-induced obese (DIO) male mice exhibit a potent and prolonged inhibition of voluntary food intake following overfeeding-induced weight gain. We reveal that FGF21 is dispensable for this defense against weight gain. Targeted proteomics unveiled novel circulating factors linked to overfeeding, including the protease  legumain (LGMN). Administration of recombinant LGMN lowers body weight and food intake in DIO mice. The protection against weight gain is also associated with reduced vascularization in the hypothalamus and sustained reductions in the expression of the orexigenic neuropeptide genes, Npy and Agrp, suggesting a role for hypothalamic signaling in this homeostatic recovery from overfeeding. Overfeeding of melanocortin 4 receptor (MC4R) KO mice shows that these mice can suppress voluntary food intake and counteract the enforced weight gain, although their rate of weight recovery is impaired. Collectively, these findings demonstrate that the defense against overfeeding-induced weight gain remains intact in obesity and involves mechanisms independent of both FGF21 and MC4R
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