Teamwork makes the dream work: functional collaborations between families, scientists, and healthcare providers to drive progress in the treatment of Leigh Syndrome.

BACKGROUND: Leigh syndrome, an inherited neurometabolic disorder, is estimated to be the most common pediatric manifestation of mitochondrial disease. No treatments are currently available for Leigh syndrome due to many hurdles in drug discovery efforts. Leigh syndrome causal variants span over 110 different genes and likely lead to both unique and shared biochemical alterations, often resulting in overlapping phenotypic features. The mechanisms by which pathogenic variants in mitochondrial genes alter cellular phenotype to promote disease remain poorly understood. The rarity of cases of specific causal variants creates barriers to drug discovery and adequately sized clinical trials. BODY: To address the current challenges in drug discovery and facilitate communication between researchers, healthcare providers, patients, and families, the Boston University integrative Cardiovascular Metabolism and Pathophysiology (iCAMP) Lab and Cure Mito Foundation hosted a Leigh Syndrome Symposium. This symposium brought together expert scientists and providers to highlight the current successes in drug discovery and novel models of mitochondrial disease, and to connect patients to providers and scientists to foster community and communication. CONCLUSION: In this symposium review, we describe the research presented, the hurdles ahead, and strategies to better connect the Leigh syndrome community members to advance treatments for Leigh syndrome.

Acarbose suppresses symptoms of mitochondrial disease in a mouse model of Leigh syndrome.

Mitochondrial diseases represent a spectrum of disorders caused by impaired mitochondrial function, ranging in severity from mortality during infancy to progressive adult-onset disease. Mitochondrial dysfunction is also recognized as a molecular hallmark of the biological ageing process. Rapamycin, a drug that increases lifespan and health during normative ageing, also increases survival and reduces neurological symptoms in a mouse model of the severe mitochondrial disease Leigh syndrome. The Ndufs4 knockout (Ndufs4-/-) mouse lacks the complex I subunit NDUFS4 and shows rapid onset and progression of neurodegeneration mimicking patients with Leigh syndrome. Here we show that another drug that extends lifespan and delays normative ageing in mice, acarbose, also suppresses symptoms of disease and improves survival of Ndufs4-/- mice. Unlike rapamycin, acarbose rescues disease phenotypes independently of inhibition of the mechanistic target of rapamycin. Furthermore, rapamycin and acarbose have additive effects in delaying neurological symptoms and increasing maximum lifespan in Ndufs4-/- mice. We find that acarbose remodels the intestinal microbiome and alters the production of short-chain fatty acids. Supplementation with tributyrin, a source of butyric acid, recapitulates some effects of acarbose on lifespan and disease progression, while depletion of the endogenous microbiome in Ndufs4-/- mice appears to fully recapitulate the effects of acarbose on healthspan and lifespan in these animals. To our knowledge, this study provides the first evidence that alteration of the gut microbiome plays a significant role in severe mitochondrial disease and provides further support for the model that biological ageing and severe mitochondrial disorders share underlying common mechanisms.

N-acetylcysteine and cysteamine bitartrate prevent azide-induced neuromuscular decompensation by restoring glutathione balance in two novel surf1-/- zebrafish deletion models of Leigh syndrome.

SURF1 deficiency (OMIM # 220110) causes Leigh syndrome (LS, OMIM # 256000), a mitochondrial disorder typified by stress-induced metabolic strokes, neurodevelopmental regression and progressive multisystem dysfunction. Here, we describe two novel surf1-/- zebrafish knockout models generated by CRISPR/Cas9 technology. While gross larval morphology, fertility, and survival into adulthood appeared unaffected, surf1-/- mutants manifested adult-onset ocular anomalies and decreased swimming activity, as well as classical biochemical hallmarks of human SURF1 disease, including reduced complex IV expression and enzymatic activity and increased tissue lactate. surf1-/- larvae also demonstrated oxidative stress and stressor hypersensitivity to the complex IV inhibitor, azide, which exacerbated their complex IV deficiency, reduced supercomplex formation, and induced acute neurodegeneration typical of LS including brain death, impaired neuromuscular responses, reduced swimming activity, and absent heartrate. Remarkably, prophylactic treatment of surf1-/- larvae with either cysteamine bitartrate or N-acetylcysteine, but not other antioxidants, significantly improved animal resiliency to stressor-induced brain death, swimming and neuromuscular dysfunction, and loss of heartbeat. Mechanistic analyses demonstrated cysteamine bitartrate pretreatment did not improve complex IV deficiency, ATP deficiency, or increased tissue lactate but did reduce oxidative stress and restore glutathione balance in surf1-/- animals. Overall, two novel surf1-/- zebrafish models recapitulate the gross neurodegenerative and biochemical hallmarks of LS, including azide stressor hypersensitivity that was associated with glutathione deficiency and ameliorated by cysteamine bitartrate or N-acetylcysteine therapy.

ACTH for epileptic spasms in Leigh syndrome with SLC19A3 mutation can induce status dystonicus.

Patients with Leigh syndrome (LS) sometimes develop epileptic spasms (ES). ACTH treatment for ES may be effective without serious adverse events in some patients with LS. Status dystonicus is a life-threatening disorder characterized by an acute exacerbation of generalized dystonia and often develops as a triggered event. The underlying pathophysiology of status dystonicus remains unclear. To our knowledge, there has been no reported case of status dystonicus associated with ACTH treatment. Here, we describe the first reported patient with LS, harbouring compound heterozygous mutations in SLC19A3 gene, who developed status dystonicus following initial intramuscular injection of a course of ACTH treatment for ES. Stressors can precipitate acute exacerbation in SLC19A3-related disorders. Interestingly, in this patient, external discomfort stimuli tended to induce transient hypertonia with opisthotonos. This report suggests that attention should be paid to acute exacerbation of generalized dystonia when ACTH treatment for ES is started in patients with LS, who have dystonia tend to exacerbate transiently by external discomfort stimuli.

Differential effects of mTOR inhibition and dietary ketosis in a mouse model of subacute necrotizing encephalomyelopathy.

Genetic mitochondrial diseases are the most frequent cause of inherited metabolic disorders and one of the most prevalent causes of heritable neurological disease. Leigh syndrome is the most common clinical presentation of pediatric mitochondrial disease, typically appearing in the first few years of life, and involving severe multisystem pathologies. Clinical care for Leigh syndrome patients is difficult, complicated by the wide range of symptoms including characteristic progressive CNS lesion, metabolic sequelae, and epileptic seizures, which can be intractable to standard management. While no proven therapies yet exist for the underlying mitochondrial disease, a ketogenic diet has led to some reports of success in managing mitochondrial epilepsies, with ketosis reducing seizure risk and severity. The impact of ketosis on other aspects of disease progression in Leigh syndrome has not been studied, however, and a rigorous study of the impact of ketosis on seizures in mitochondrial disease is lacking. Conversely, preclinical efforts have identified the intracellular nutrient signaling regulator mTOR as a promising therapeutic target, with data suggesting the benefits are mediated by metabolic changes. mTOR inhibition alleviates epilepsies arising from defects in TSC, an mTOR regulator, but the therapeutic potential of mTOR inhibition in seizures related to primary mitochondrial dysfunction is unknown. Given that ketogenic diet is used clinically in the setting of mitochondrial disease, and mTOR inhibition is in clinical trials for intractable pediatric epilepsies of diverse causal origins, a direct experimental assessment of their effects is imperative. Here, we define the impact of dietary ketosis on survival and CNS disease in the Ndufs4(KO) mouse model of Leigh syndrome and the therapeutic potential of both dietary ketosis and mTOR inhibition on seizures in this model. These data provide timely insight into two important clinical interventions.

Cell-Permeable Succinate Increases Mitochondrial Membrane Potential and Glycolysis in Leigh Syndrome Patient Fibroblasts.

Mitochondrial disorders represent a large group of severe genetic disorders mainly impacting organ systems with high energy requirements. Leigh syndrome (LS) is a classic example of a mitochondrial disorder resulting from pathogenic mutations that disrupt oxidative phosphorylation capacities. Currently, evidence-based therapy directed towards treating LS is sparse. Recently, the cell-permeant substrates responsible for regulating the electron transport chain have gained attention as therapeutic agents for mitochondrial diseases. We explored the therapeutic effects of introducing tricarboxylic acid cycle (TCA) intermediate substrate, succinate, as a cell-permeable prodrug NV118, to alleviate some of the mitochondrial dysfunction in LS. The results suggest that a 24-hour treatment with prodrug NV118 elicited an upregulation of glycolysis and mitochondrial membrane potential while inhibiting intracellular reactive oxygen species in LS cells. The results from this study suggest an important role for TCA intermediates for treating mitochondrial dysfunction in LS. We show, here, that NV118 could serve as a therapeutic agent for LS resulting from mutations in mtDNA in complex I and complex V dysfunctions.

Targeted Therapies for Leigh Syndrome: Systematic Review and Steps Towards a 'Treatabolome'.

BACKGROUND: Leigh syndrome (LS) is the most frequent paediatric clinical presentation of mitochondrial disease. The clinical phenotype of LS is highly heterogeneous. Though historically the treatment for LS is largely supportive, new treatments are on the horizon. Due to the rarity of LS, large-scale interventional studies are scarce, limiting dissemination of information of therapeutic options to the wider scientific and clinical community. OBJECTIVE: We conducted a systematic review of pharmacological therapies of LS following the guidelines for FAIR-compliant datasets. METHODS: We searched for interventional studies within Clincialtrials.gov and European Clinical trials databases. Randomised controlled trials, observational studies, case reports and case series formed part of a wider MEDLINE search. RESULTS: Of the 1,193 studies initially identified, 157 met our inclusion criteria, of which 104 were carried over into our final analysis. Treatments for LS included very few interventional trials using EPI-743 and cysteamine bitartrate. Wider literature searches identified case series and reports of treatments repleting glutathione stores, reduction of oxidative stress and restoration of oxidative phosphorylation. CONCLUSIONS: Though interventional randomised controlled trials have begun for LS, the majority of evidence remains in case reports and case series for a number of treatable genes, encoding cofactors or transporter proteins of the mitochondria. Our findings will form part of the international expert-led Solve-RD efforts to assist clinicians initiating treatments in patients with treatable variants of LS.

Lithium for Leigh syndrome – damage, benefit, or both?

With interest we read the article by Basterreche et al. about a 23yo female with Leigh syndrome diagnosed at age 4y and manifesting with severe psychomotor impairment, severe self-harm, hetero-aggressions, bilateral hypodensities of the basal ganglia, and cerebellar atrophy.

Paradoxical reaction to increased doses of intrathecal baclofen in a patient with Leigh syndrome.

In clinical practice, intrathecal baclofen (ITB) therapy is used to control spasticity. After initial placement of the ITB pump, clinicians incrementally increase the dose until effectiveness in alleviating spasms and spasticity is optimized. However, this case describes a 4-year-old male with Leigh syndrome who developed a paradoxical worsening of spasticity and pain with incremental increase of his ITB pump. In this rare genetic disease with a poor prognosis, an ITB pump was trialed and implanted and titrated upwards with initial improvement. However, his spasticity and pain then began to worsen with each dosage increase. Subsequently, his symptoms improved significantly when the dose was weaned. This is the first case that describes this paradoxical reaction in a pediatric population and discusses recommendations about how clinicians should safely titrate the pump for patient care.

Clinical exome sequencing reveals a mutation in PDHA1 in Leigh syndrome: A case of a Chinese boy with lethal neuropathy.

BACKGROUND: Leigh syndrome, the most common mitochondrial syndrome in pediatrics, has diverse clinical manifestations and is genetically heterogeneous. Pathogenic mutations in more than 75 genes of two genomes (mitochondrial and nuclear) have been identified. PDHA1 encoding the E1 alpha subunit is an X-chromosome gene whose mutations cause pyruvate dehydrogenase complex deficiency. METHODS: Here, we have described a 12-year-old boy with lethal neuropathy who almost died of a sudden loss of breathing and successive cardiac arrest. Extracorporeal membrane oxygenation rescued his life. His diagnosis was corrected from Guillain-Barré syndrome to Leigh syndrome 1 month later by clinical exome sequencing. Furthermore, we used software to predict the protein structure caused by frameshift mutations. We treated the boy with vitamin B1, coenzyme Q10, and a ketogenic diet. RESULTS: A PDHA1 mutation (NM_000284.4:c.1167_1170del) was identified as the underlying cause. The amino acid mutation was p.Ser390LysfsTer33. Moreover, the protein structure prediction results suggested that the protein structure has changed. The parents of the child were negative, so the mutation was de novo. The comprehensive assessment of the mutation was pathogenic. His condition gradually improved after receiving treatment. CONCLUSION: This case suggests that gene detection should be popularized to improve diagnosis accuracy, especially in developing countries such as China.

Tetracyclines promote survival and fitness in mitochondrial disease models.

Mitochondrial diseases (MDs) are a heterogeneous group of disorders resulting from mutations in nuclear or mitochondrial DNA genes encoding mitochondrial proteins1,2. MDs cause pathologies with severe tissue damage and ultimately death3,4. There are no cures for MDs and current treatments are only palliative5-7. Here we show that tetracyclines improve fitness of cultured MD cells and ameliorate disease in a mouse model of Leigh syndrome. To identify small molecules that prevent cellular damage and death under nutrient stress conditions, we conduct a chemical high-throughput screen with cells carrying human MD mutations and discover a series of antibiotics that maintain survival of various MD cells. We subsequently show that a sub-library of tetracycline analogues, including doxycycline, rescues cell death and inflammatory signatures in mutant cells through partial and selective inhibition of mitochondrial translation, resulting in an ATF4-independent mitohormetic response. Doxycycline treatment strongly promotes fitness and survival of Ndufs4-/- mice, a preclinical Leigh syndrome mouse model8. A proteomic analysis of brain tissue reveals that doxycycline treatment largely prevents neuronal death and the accumulation of neuroimmune and inflammatory proteins in Ndufs4-/- mice, indicating a potential causal role for these proteins in the brain pathology. Our findings suggest that tetracyclines deserve further evaluation as potential drugs for the treatment of MDs.

Efficacy of perampanel for epileptic seizures and daily behavior in a patient with Leigh syndrome: A case report.

BACKGROUND: Leigh syndrome (LS) is a mitochondrial disorder that shows abnormal basal ganglia lesion and psychomotor regression. Although vitamins have been used for LS, we have not found any effective drug. CASE PRESENTATION: A 26-year-old man who showed psychomotor delay and short stature at the age of 1 year was diagnosed with LS according to the results of cerebrospinal fluid and high signal intensity in the bilateral striatum on T2-weighted magnetic resonance imaging. He demonstrated psychomotor delay and breathing disorders, but the progression was very slow. His symptoms suddenly worsened at the age of 24 years after acute epididymitis. He showed epileptic seizures simultaneously and his activities of daily living (ADL) significantly worsened. Several antiepileptic drugs were ineffective, but his seizures were suppressed by a low dose of perampanel and his ADL improved. CONCLUSION AND DISCUSSION: Our case showed that low-dose perampanel could be a drug for epileptic seizures and improvement of ADL in patients with LS.

PKC downregulation upon rapamycin treatment attenuates mitochondrial disease.

Leigh syndrome is a fatal neurometabolic disorder caused by defects in mitochondrial function. Mechanistic target of rapamycin (mTOR) inhibition with rapamycin attenuates disease progression in a mouse model of Leigh syndrome (Ndufs4 knock-out (KO) mouse); however, the mechanism of rescue is unknown. Here we identify protein kinase C (PKC) downregulation as a key event mediating the beneficial effects of rapamycin treatment of Ndufs4 KO mice. Assessing the impact of rapamycin on the brain proteome and phosphoproteome of Ndufs4 KO mice, we find that rapamycin restores mitochondrial protein levels, inhibits signalling through both mTOR complexes and reduces the abundance and activity of multiple PKC isoforms. Administration of PKC inhibitors increases survival, delays neurological deficits, prevents hair loss and decreases inflammation in Ndufs4 KO mice. Thus, PKC may be a viable therapeutic target for treating severe mitochondrial disease.

Effects of clofibrate and KH176 on life span and motor function in mitochondrial complex I-deficient mice.

Mitochondrial complex I (CI), the first multiprotein enzyme complex of the OXPHOS system, executes a major role in cellular ATP generation. Consequently, dysfunction of this complex has been linked to inherited metabolic disorders, including Leigh disease (LD), an often fatal disease in early life. Development of clinical effective treatments for LD remains challenging due to the complex pathophysiological nature. Treatment with the peroxisome proliferation-activated receptor (PPAR) agonist bezafibrate improved disease phenotype in several mitochondrial disease mouse models mediated via enhanced mitochondrial biogenesis and fatty acid ß-oxidation. However, the therapeutic potential of this mixed PPAR (α, δ/ß, γ) agonist is severely hampered by hepatotoxicity, which is possibly caused by activation of PPARγ. Here, we aimed to investigate the effects of the PPARα-specific fibrate clofibrate in mitochondrial CI-deficient (Ndufs4-/-) mice. Clofibrate increased lifespan and motor function of Ndufs4-/- mice, while only marginal hepatotoxic effects were observed. Due to the complex clinical and cellular phenotype of CI-deficiency, we also aimed to investigate the therapeutic potential of clofibrate combined with the redox modulator KH176. As described previously, single treatment with KH176 was beneficial, however, combining clofibrate with KH176 did not result in an additive effect on disease phenotype in Ndufs4-/- mice. Overall, both drugs have promising, but independent and nonadditive, properties for the pharmacological treatment of CI-deficiency-related mitochondrial diseases.

Clinical, biochemical and metabolic characterization of patients with short-chain enoyl-CoA hydratase(ECHS1) deficiency: two case reports and the review of the literature.

BACKGROUND: Short-chain enoyl-CoA hydratase (SCEH or ECHS1) deficiency is a rare congenital metabolic disorder caused by biallelic mutations in the ECHS gene. Clinical phenotype includes severe developmental delay, regression, dystonia, seizures, elevated lactate, and brain MRI abnormalities consistent with Leigh syndrome (LS). SCEH is most notably involved in valine catabolism. There is no effective treatment for the disease, patients may respond to dietary restriction of valine and supplementation of N-acetylcysteine . CASE PRESENTATION: We describe two patients who presented in infancy or early childhood with SCEH deficiency. Both patients were shown to harbor heterozygous or homozygous variants in the ECHS1 gene, and developmental retardation or regression as the onset manifestation. Brain MRI showed abnormal signals of bilateral pallidus. Urine metabolic examination showed increased levels of 2,3-dihydroxy-2-methylbutyric acid and S-(2-carboxypropyl) cysteamine S-(2-carboxypropoxypropyl) cysteamine (SCPCM). A valine restricted diet and combined of N-acetylcysteine supplementation were utilized in the two patients. CONCLUSIONS: In clinical practice, The elevated urinary 2,3-dihydroxy-2-methylbutyrate, S-(2-carboxypropyl) cysteine, S-(2-carboxypropyl) cysteine and N-acetyl-S-(2-carboxypropyl) cysteine levels might be clues for diagnosis of SCEH deficiency which can be confirmed throughGenetic sequencing of ECHS1 gene. Early cocktail therapy, valine restrictied diet and N-acetylcysteine supplementation could improve the prognosis of patients.

Exploring mTOR inhibition as treatment for mitochondrial disease.

Leigh syndrome and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) are two of the most frequent pediatric mitochondrial diseases. Both cause severe morbidity and neither have effective treatment. Inhibiting the mammalian target of rapamycin (mTOR) pathway has been shown in model mice of Leigh syndrome to extend lifespan and attenuate both the clinical and pathological progression of disease. Based on this observation, we treated two children with everolimus, a rapamycin analogue. The child with Leigh syndrome showed sustained benefit, while the child with MELAS failed to respond and died of progressive disease. We discuss possible mechanisms underlying these disparate responses to mTOR inhibition.