Arginine Supplementation in MELAS Syndrome: What Do We Know about the Mechanisms?

MELAS syndrome, characterized by mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes, represents a devastating mitochondrial disease, with the stroke-like episodes being its primary manifestation. Arginine supplementation has been used and recommended as a treatment for these acute attacks; however, insufficient evidence exists to support this treatment for MELAS. The mechanisms underlying the effect of arginine on MELAS pathophysiology remain unclear, although it is hypothesized that arginine could increase nitric oxide availability and, consequently, enhance blood supply to the brain. A more comprehensive understanding of these mechanisms is necessary to improve treatment strategies, such as dose and regimen adjustments; identify which patients could benefit the most; and establish potential markers for follow-up. This review aims to analyze the existing evidence concerning the mechanisms through which arginine supplementation impacts MELAS pathophysiology and provide the current scenario and perspectives for future investigations.

Magnetic resonance spectroscopy in MELAS syndrome: correlation with CSF and plasma metabolite levels and change after glutamine supplementation.

PURPOSE: MELAS syndrome is a genetic disorder caused by mitochondrial DNA mutations. We previously described that MELAS patients had increased CSF glutamate and decreased CSF glutamine levels and that oral glutamine supplementation restores these values. Proton magnetic resonance spectroscopy (1H-MRS) allows the in vivo evaluation of brain metabolism. We aimed to compare 1H-MRS of MELAS patients with controls, the 1H-MRS after glutamine supplementation in the MELAS group, and investigate the association between 1H-MRS and CSF lactate, glutamate, and glutamine levels. METHODS: We conducted an observational case-control study and an open-label, single-cohort study with single-voxel MRS (TE 144/35 ms). We assessed the brain metabolism changes in the prefrontal (PFC) and parieto-occipital) cortex (POC) after oral glutamine supplementation in MELAS patients. MR spectra were analyzed with jMRUI software. RESULTS: Nine patients with MELAS syndrome (35.8 ± 3.2 years) and nine sex- and age-matched controls were recruited. Lactate/creatine levels were increased in MELAS patients in both PFC and POC (0.40 ± 0.05 vs. 0, p < 0.001; 0.32 ± 0.03 vs. 0, p < 0.001, respectively). No differences were observed between groups in glutamate and glutamine (Glx/creatine), either in PFC (p = 0.930) or POC (p = 0.310). No differences were observed after glutamine supplementation. A positive correlation was found between CSF lactate and lactate/creatine only in POC (0.85, p = 0.003). CONCLUSION: No significant metabolite changes were observed in the brains of MELAS patients after glutamine supplementation. While we found a positive correlation between lactate levels in CSF and 1H-MRS in MELAS patients, we could not monitor treatment response over short periods with this tool. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04948138; initial release 24/06/2021; first patient enrolled on 1/07/2021. https://clinicaltrials.gov/ct2/show/NCT04948138.

Glutamine metabolism in diseases associated with mitochondrial dysfunction.

Mitochondrial dysfunction can arise from genetic defects or environmental exposures and impact a wide range of biological processes. Among these are metabolic pathways involved in glutamine catabolism, anabolism, and glutamine-glutamate cycling. In recent years, altered glutamine metabolism has been found to play important roles in the pathologic consequences of mitochondrial dysfunction. Glutamine is a pleiotropic molecule, not only providing an alternate carbon source to glucose in certain conditions, but also playing unique roles in cellular communication in neurons and astrocytes. Glutamine consumption and catabolic flux can be significantly altered in settings of genetic mitochondrial defects or exposure to mitochondrial toxins, and alterations to glutamine metabolism appears to play a particularly significant role in neurodegenerative diseases. These include primary mitochondrial diseases like Leigh syndrome (subacute necrotizing encephalopathy) and MELAS (mitochondrial myopathy with encephalopathy, lactic acidosis, and stroke-like episodes), as well as complex age-related neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Pharmacologic interventions targeting glutamine metabolizing and catabolizing pathways appear to provide some benefits in cell and animal models of these diseases, indicating glutamine metabolism may be a clinically relevant target. In this review, we discuss glutamine metabolism, mitochondrial disease, the impact of mitochondrial dysfunction on glutamine metabolic processes, glutamine in neurodegeneration, and candidate targets for therapeutic intervention.

[Therapeutics for Mitochondrial Encephalomyopathy].

In MELAS, taurine modification defect in the anticodon of mitochondrial leucine tRNA causes codon translation failure. An investigator-started clinical trials of high-dose taurine therapy, that showed its efficacy in preventing stroke-like episodes, and improving the taurine modification rate. The drug was found to be safe. Taurine has been approved as a drug covered by public insurance for prevention of stroke-like episodes since 2019. Recently, L-arginine hydrochloride has also been approved for off-label use as a treatment for both acute and intermittent stages of stroke-like episodes.

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes diagnosed after metformin-triggered stroke-like episodes.

A 40-year-old man with sensorineural hearing loss and diabetes mellitus was hospitalized with acute-onset impaired consciousness and clumsiness in his left hand. He had been taking metformin for 4 months. A neurological examination revealed confusion and weakness in the left upper limb. Increased lactate levels were detected in the serum and cerebrospinal fluid. Magnetic resonance imaging revealed lesions in the right parietal and bilateral temporal lobes with a lactate peak in magnetic resonance spectroscopy. Finally, we made a genetic diagnosis of mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes based on the detection of m.3243A>G. It is well-known that metformin should not be administered in patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes because metformin inhibits mitochondrial function and triggers stroke-like episodes. However, our patient was diagnosed with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes after metformin administration. Thus, we encourage physicians to exercise caution in the prescription of metformin in patients with short stature, sensorineural hearing loss, or young-onset diabetes mellitus because these patients may have undiagnosed mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes.

High-dose oral glutamine supplementation reduces elevated glutamate levels in cerebrospinal fluid in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome.

BACKGROUND AND PURPOSE: Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is a genetically heterogeneous disorder caused by mitochondrial DNA mutations. There are no disease-modifying therapies, and treatment remains mainly supportive. It has been shown previously that patients with MELAS syndrome have significantly increased cerebrospinal fluid (CSF) glutamate and significantly decreased CSF glutamine levels compared to controls. Glutamine has many metabolic fates in neurons and astrocytes, and the glutamate-glutamine cycle couples with many metabolic pathways depending on cellular requirements. The aim was to compare CSF glutamate and glutamine levels before and after dietary glutamine supplementation. It is postulated that high-dose oral glutamine supplementation could reduce the increase in glutamate levels. METHOD: This open-label, single-cohort study determined the safety and changes in glutamate and glutamine levels in CSF after 12 weeks of oral glutamine supplementation. RESULTS: Nine adult patients with MELAS syndrome (66.7% females, mean age 35.8 ± 3.2 years) were included. After glutamine supplementation, CSF glutamate levels were significantly reduced (9.77 ± 1.21 vs. 18.48 ± 1.34 µmol/l, p < 0.001) and CSF glutamine levels were significantly increased (433.66 ± 15.31 vs. 336.31 ± 12.92 µmol/l, p = 0.002). A side effect observed in four of nine patients was a mild sensation of satiety. One patient developed mild and transient elevation of transaminases, and another patient was admitted for an epileptic status without stroke-like episode. DISCUSSION: This study demonstrates that high-dose oral glutamine supplementation significantly reduces CSF glutamate and increases CSF glutamine levels in patients with MELAS syndrome. These findings may have potential therapeutic implications in these patients. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov Identifier: NCT04948138. Initial release 24 June 2021, first patient enrolled 1 July 2021. https://clinicaltrials.gov/ct2/show/NCT04948138.

Mitochondrial stroke-like episodes: The search for new therapies.

A mitochondrial stroke-like event is an evolving subacute neurological syndrome linked to seizure activity and focal metabolic brain derangement in a genetically determined mitochondrial disorder. The acronym "MELAS" (mitochondrial encephalopathy associated with lactic acidosis and stroke-like lesions) identifies subjects with molecular, biochemical and/or histological evidence of mitochondrial disorder who experience stroke-like lesions. MELAS is a rare inherited mitochondrial disease linked to severe multiorgan involvement and stress-induced episodes of metabolic decompensation and lactic acidosis. Unfortunately, there are no etiopathogenetic therapies for stroke-like episodes to date, and the treatment is mainly based on anti-epileptic drugs and supportive therapies. This perspective opinion article discusses the current care standards for MELAS patients and revises current and innovative emerging therapies for mitochondrial stroke-like episodes.

Current perspectives on mitochondrial dysfunction in migraine.

Mitochondria are an autonomous organelle that plays a crucial role in the metabolic aspects of a cell. Cortical spreading depression (CSD) and fluctuations in the cerebral blood flow have for long been mechanisms underlying migraine. It is a neurovascular disorder with a unilateral manifestation of disturbing, throbbing and pulsating head pain. Migraine affects 2.6% and 21.7% of the general population and is the major cause of partial disability in the age group 15-49. Higher mutation rates, imbalance in concentration of physiologically relevant molecules and oxidative stress biomarkers have been the main themes of discussion in determining the role of mitochondrial disability in migraine. The correlation of migraine with other disorders like hemiplegic migraine; mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes [MELAS]; tension-type headache (TTH); cyclic vomiting syndrome (CVS), ischaemic stroke; and hypertension has helped in the assessment of the physiological and morphogenetic basis of migraine. Here, we have reviewed the different nuances of mitochondrial dysfunction and migraine. The different mtDNA polymorphisms that can affect the generation and transmission of nerve impulse has been highlighted and supported with research findings. In addition to this, the genetic basis of migraine pathogenesis as a consequence of mutations in nuclear DNA that can, in turn, affect the synthesis of defective mitochondrial proteins is discussed along with a brief overview of epigenetic profile. This review gives an overview of the pathophysiology of migraine and explores mitochondrial dysfunction as a potential underlying mechanism. Also, therapeutic supplements for managing migraine have been discussed at different junctures in this paper.

MELAS syndrome: an acute stroke-like episode complicated by renal tubular acidosis.

MELAS, a mitochondrially inherited multisystem disorder, can present with acute stroke-like episodes. The literature thus far supports the use of L-arginine therapy in acute MELAS flares to alleviate and shorten the duration of symptoms. This is the case of a patient who presented with ataxia and worsening confusion on a background of genetically confirmed MELAS syndrome. In this instance, intravenous L-arginine therapy, along with corticosteroids, was administered in keeping with best practice. However, in a metabolically vulnerable patient, L-arginine therapy resulted in a further deterioration in his clinical status and the development of a non-anion gap metabolic acidosis.

Endocrine disorders in a patient with a suspicion of a mitochondrial disease, MELAS syndrome - a case report and literature review.

MELAS syndrome (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) is a genetically determined disease caused by mutations in mitochondrial DNA. We present a girl who was suspected of MELAS syndrome during the diagnostic evaluation of short stature. The patient suffered from symptoms potentially indicating mitochondrial disease, such as muscular weakness, cranial nerve VI palsy, headaches, retinitis pigmentosa, sensory-neural hearing loss, and elevated lactic acid. T2-weighted brain MRI showed hyperintense lesions in the white matter. Muscular biopsy revealed ragged red fibres. Genetic evaluation did not detect the most common mutations in the MT-TL1 gene and MT-ND5 gene. Endocrine tests led to the confirmation of growth hormone deficiency, and so replacement treatment was started. After 1 year of recombinant growth hormone therapy the patient was diagnosed with diabetes. At the age of 14 years the LH-RH test showed prepubertal values. Endocrine disorders may be one of the first manifestations of MELAS syndrome. In differential diagnosis of short stature, less common causes, such as mitochondrial diseases, should be taken into consideration.

Effect of rapamycin on mitochondria and lysosomes in fibroblasts from patients with mtDNA mutations.

Maintaining mitochondrial function and dynamics is crucial for cellular health. In muscle, defects in mitochondria result in severe myopathies where accumulation of damaged mitochondria causes deterioration and dysfunction. Importantly, understanding the role of mitochondria in disease is a necessity to determine future therapeutics. One of the most common myopathies is mitochondrial encephalopathy lactic acidosis stroke-like episodes (MELAS), which has no current treatment. Recently, patients with MELAS treated with rapamycin exhibited improved clinical outcomes. However, the cellular mechanisms of rapamycin effects in patients with MELAS are currently unknown. In this study, we used cultured skin fibroblasts as a window into the mitochondrial dysfunction evident in MELAS cells, as well as to study the mechanisms of rapamycin action, compared with control, healthy individuals. We observed that mitochondria from patients were fragmented, had a threefold decline in the average speed of motility, a twofold reduced mitochondrial membrane potential, and a 1.5- to 2-fold decline in basal respiration. Despite the reduction in mitochondrial function, mitochondrial import protein Tim23 was elevated in patient cell lines. MELAS fibroblasts exhibited increased MnSOD levels and lysosomal function when compared with healthy controls. Treatment of MELAS fibroblasts with rapamycin for 24 h resulted in increased mitochondrial respiration compared with control cells, a higher lysosome content, and a greater localization of mitochondria to lysosomes. Our studies suggest that rapamycin has the potential to improve cellular health even in the presence of mtDNA defects, primarily via an increase in lysosomal content.

L-arginine effects on cerebrovascular reactivity, perfusion and neurovascular coupling in MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) syndrome.

OBJECTIVE: We previously showed that MELAS patients have decreased cerebrovascular reactivity (CVR) (p≤ 0.002) and increased cerebral blood flow (CBF) (p<0.0026); changes correlated with disease severity and % mutant mtDNA (inversely for CVR; directly for CBF). We ran a prospective pilot in 3 MELAS sibs (m.3243A>G tRNALeu(UUR)) with variable % mutant blood mtDNA to assess effects of L-Arginine (L-Arg) (single dose and 6-wk steady-state trial) on regional CBF, arterial CVR and neurovascular coupling. METHODS: Patients were studied with 3T MRI using arterial spin labeling (ASL) to measure CBF and changes in % Blood Oxygen Level Dependent (BOLD) signal to changes in arterial partial pressure of CO2 to measure CVR. Task fMRI consisted of an alternating black and white checkerboard to evaluate visual cortex response in MELAS and controls. RESULTS: Following L-Arg, there was restoration of serum Arg (76-230 µM) in MELAS sibs and a trend towards increasing CVR in frontal and corresponding decrease in occipital cortex; CVR was unchanged globally. There was a 29-37% reduction in baseline CBF in one patient following 6 wks of L-Arg. Pre-treatment fMRI activation in response to visual cortex stimulus was markedly decreased in the same patient compared to controls in primary visual striate cortex V1 and extrastriate regions V2 to V5 with a marked increase toward control values following a single dose and 6 wks of L-Arg. CONCLUSION: Proposed "healing" effect may be due to more efficient utilization of energy substrates with increased cellular energy balances and ensuing reduction in signalling pathways that augment flow in the untreated state. CLASSIFICATION OF EVIDENCE: This prospective pilot study provides Class III evidence that oral L-Arginine (100 mg/kg single dose or 100 mg/kg three times daily po X 6 weeks) normalizes resting blood flow from elevated pre-treatment levels in patients with MELAS syndrome, selectively increases their CVR from reduced pre-treatment levels in regions most impaired at the expense of less abnormal regions, and normalizes reduced BOLD fMRI activation in response to visual cortex stimulus. CLINICAL TRIALS.GOV (NIH): NCT01603446.

Afectación encefálica global y uso de L-arginina en un paciente con síndrome de MELAS / Global cerebral involvement and L-arginine use in a patient with MELAS síndrome

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Mitochondrial DNA 10158T>C mutation in a patient with mitochondrial encephalomyopathy with lactic acidosis, and stroke-like episodes syndrome: A case-report and literature review (CARE-complaint).

RATIONALE: Mitochondrial encephalomyopathy with lactic acidosis and stroke- like episodes (MELAS) syndrome is caused by mitochondrial respiratory chain dysfunction and oxidative phosphorylation disorder. It is a rare clinical metabolic disease involved with multiple systems. PATIENT CONCERNS: A 22-year-old patient presented with limb convulsion accompanied by loss of consciousness, headache, partial blindness, blurred vision, and so on. DIAGNOSES: Brain magnetic resonance imaging showed a high-intensity area in bilateral occipital cortex, left parietal lobe and cerebellum on diffusion-weighted imaging. These focus did not distribute as vascular territory. The pathological examination of skeletal muscle revealed several succinate dehydrogenase reactive vessels with overreaction and increased content of lipid droplets in some muscle fibers. Genetic testing showed that the patient carried m.10158T>C mutation. INTERVENTIONS: She was provided with traditional arginine hydrochloride therapy and orally medication of coenzyme Q (10 mg). OUTCOMES: Mitochondrial DNA of blood and hair follicle of patient carried m.10158T>C mutation LESSONS:: For the suspected patients of MELAS syndrome, if the hot-spot mutation test is negative, more detection sites should be selected.

Therapeutic management of stroke-like episodes varies from that of encephalitis.

INTRODUCTION: Stroke-like episodes (SLEs) are typical cerebral manifestations of certain mitochondrial disorders (MIDs). They are characterised by a vasogenic edema in a non-vascular distribution. PATIENTS CONCERNS:: none DIAGNOSIS:: SLEs show up on cerebral MRI as stroke-like lesions (SLLs), characterised by vasogenic edema in a non-vascular distribution. SLLs expand in the acute stage and regress during the chronic stage. They show hyperperfusion in the acute stage and hypoperfusion in the chronic stage. INTERVENTIONS: SLLs respond favorably to antiseizure drugs, to No-precursors, steroids, the ketogenic diet, and antioxidants. OUTCOME: SLLs end up as normal tissue, white matter lesion, grey matter lesion, cyst, laminar cortical necrosis, or the toenail sign. CONCLUSIONS: SLLs are a frequent manifestation of MIDs. They undergo dynamic changes in the acute and chronic stage. They need to be differentiated from ischemic stroke as they are differentially treated.

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.