Cerebral lactic acidosis correlates with neurological impairment in MELAS

Psychobiological regulation of plasma and saliva GDF15 dynamics in health and mitochondrial diseases

GDF15 (growth differentiation factor 15) is a marker of cellular energetic stress linked to physical-mental illness, aging, and mortality. However, questions remain about its dynamic properties and measurability in human biofluids other than blood. Here, we examine the natural dynamics and psychobiological regulation of plasma and saliva GDF15 in four human studies representing 4,749 samples from 188 individuals. We show that GDF15 protein is detectable in saliva (8% of plasma concentration), likely produced by salivary glands secretory duct cells. Using a brief laboratory socio-evaluative stressor paradigm, we find that psychosocial stress increases plasma (+3.5-5.9%) and saliva GDF15 (+43%) with distinct kinetics, within minutes. Moreover, saliva GDF15 exhibits a robust awakening response, declining by ~40-89% within 30-45 minutes from its peak level at the time of waking up. Clinically, individuals with genetic mitochondrial OxPhos diseases show elevated baseline plasma and saliva GDF15, and post-stress GDF15 levels in both biofluids correlate with multi-system disease severity, exercise intolerance, and the subjective experience of fatigue. Taken together, our data establish that saliva GDF15 is dynamic, sensitive to psychological states, a clinically relevant endocrine marker of mitochondrial diseases. These findings also point to a shared psychobiological pathway integrating metabolic and mental stress.

Mitochondrial complex I density is associated with IQ and cognition in cognitively healthy adults: an in vivo [18F]BCPP-EF PET study

BACKGROUND

Mitochondrial function plays a key role in regulating neurotransmission and may contribute to general intelligence. Mitochondrial complex I (MC-I) is the largest enzyme of the respiratory chain. Recently, it has become possible to measure MC-I distribution in vivo, using a novel positron emission tomography tracer [18F]BCPP-EF, thus, we set out to investigate the association between MC-I distribution and measures of cognitive function in the living healthy brain.

RESULTS

Analyses were performed in a voxel-wise manner and identified significant associations between [18F]BCPP-EF DVRCS-1 in the precentral gyrus and parietal lobes and WAIS-IV predicted IQ, WAIS-IV arithmetic and WAIS-IV symbol-digit substitution scores (voxel-wise Pearson's correlation coefficients transformed to Z-scores, thresholded at Z = 2.3 family-wise cluster correction at p < 0.05, n = 16). Arithmetic scores were associated with middle frontal and post-central gyri tracer uptake, symbol-digit substitution scores were associated with precentral gyrus tracer uptake. RAVLT recognition scores were associated with [18F]BCPP-EF DVRCS-1 in the middle frontal gyrus, post-central gyrus, occipital and parietal regions (n = 20).

CONCLUSIONS

Taken together, our findings support the theory that mitochondrial function may contribute to general intelligence and indicate that interindividual differences in MC-I should be a key consideration for research into mitochondrial dysfunction in conditions with cognitive impairment.

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.

Perceived association of mood and symptom severity in adults with mitochondrial diseases

Individuals with genetic mitochondrial diseases suffer from multisystemic symptoms that vary in severity from day-to-day and week-to-week, but the underlying causes of symptomatic fluctuations are not understood. Based upon observations that: i) patients and their families frequently report that stressful life events either trigger exacerbations of existing symptoms or the onset of new symptoms, ii) psychological states and stress hormones influence mitochondrial energy production capacity, and iii) epidemiological reports document a robust connection between traumatic/stressful life events and various neurologic disorders, we hypothesized that mitochondrial disease symptom severity may vary according to participant's mood. To investigate this we administered the Stress, Health and Emotion Survey (SHES) in 70 adults (majority white (84%) cisgender women (83%), ages 18-74) with self-reported mitochondrial diseases (MELAS, 18%; CPEO, 17%; Complex I deficiency, 13%). Participants rated the severity of each of their symptom(s) over the past year on either good or bad days. On days marked by more stress, sadness and other negative emotions, some but not all symptoms were reported to be worse, including fatigue, exercise intolerance, brain fog, and fine motor coordination. By contrast, on days marked by happiness and calmness, participants reported these and other symptoms to be better, or less severe. Other symptoms including diminished sweating, hearing problems, and dystonia were in general unrelated to mood. Thus, some individuals living with mitochondrial diseases, at times perceive a connection between their mood and symptom severity. These preliminary associative results constitute an initial step towards developing more comprehensive models of the factors that influence the clinical course of mitochondrial diseases.

Clinical and radiological description of 120 pediatric stroke-like episodes

BACKGROUND AND PURPOSE

Stroke-like episodes (SLEs) are defined as acute onset of neurological symptoms mimicking a stroke and radiological lesions non-congruent to vascular territory. We aimed to analyze the acute clinical and radiological features of SLEs to determine their pathophysiology.

METHODS

We performed a monocenter retrospective analysis of 120 SLEs in 60 children over a 20-year period. Inclusion criteria were compatible clinical symptoms and stroke-like lesions on brain magnetic resonance imaging (MRI; performed for all 120 events) with focal hyperintensity on diffusion-weighted imaging in a non-vascular territory.

RESULTS

Three groups were identified: children with mitochondrial diseases (n = 22) involving mitochondrial DNA mutations (55%) or nuclear DNA mutations (45%); those with other metabolic diseases or epilepsy disorders (n = 22); and those in whom no etiology was found despite extensive investigations (n = 16). Age at first SLE was younger in the group with metabolic or epilepsy disorders (18 months vs. 128 months; p < 0.0001) and an infectious trigger was more frequent (69% vs. 20%; p = 0.0001). Seizures occurred in 75% of episodes, revealing 50% episodes of SLEs and mainly leading to status epilepticus (90%). Of the 120 MRI scans confirming the diagnosis, 28 were performed within a short and strict 48-h period and were further analyzed to better understand the underlying mechanisms. The scans showed primary cortical hyperintensity (n = 28/28) with decreased apparent diffusion coefficient in 52% of cases. Systematic hyperperfusion was found on spin labeling sequences when available (n = 18/18).

CONCLUSION

Clinical and radiological results support the existence of a vicious circle based on two main mechanisms: energy deficit and neuronal hyperexcitability at the origin of SLE.

Identifying encephalopathies from acute metabolic derangements

Metabolic derangements, when acute and severe, affect brain function. This presents mostly with a marked decline in the level of consciousness, resulting in impaired responsiveness, abnormal receptivity, impaired content, and loss of memory retention. The term metabolic encephalopathy has been used but is conjecture that can be challenged in the age of modern neuroimaging. We now recognize that many metabolic encephalopathies may involve structural lesions and at an early stage. Common clinical conundrums are the evaluation of the degree of brain injury and its recoverability. This review discusses the appropriate terminology for these conditions, the diagnostic approach, therapy recommendations, and prediction of recovery potential. In evaluating a presumed metabolic cause for encephalopathy, we must (1) search for and rule out structural injury to the brain despite an obvious explanatory metabolic derangement, (2) recognize that several confounding conditions often co-exist, and (3) acknowledge that resolution of brain dysfunction may be protracted despite normalization of laboratory values.

Time to harmonize mitochondrial syndrome nomenclature and classification: A consensus from the North American Mitochondrial Disease Consortium (NAMDC)

OBJECTIVE

To harmonize terminology in mitochondrial medicine, we propose revised clinical criteria for primary mitochondrial syndromes.

METHODS

The North American Mitochondrial Disease Consortium (NAMDC) established a Diagnostic Criteria Committee comprised of members with diverse expertise. It included clinicians, researchers, diagnostic laboratory directors, statisticians, and data managers. The Committee conducted a comprehensive literature review, an evaluation of current clinical practices and diagnostic modalities, surveys, and teleconferences to reach consensus on syndrome definitions for mitochondrial diseases. The criteria were refined after manual application to patients enrolled in the NAMDC Registry.

RESULTS

By building upon published diagnostic criteria and integrating recent advances, NAMDC has generated updated consensus criteria for the clinical definition of classical mitochondrial syndromes.

CONCLUSIONS

Mitochondrial diseases are clinically, biochemically, and genetically heterogeneous and therefore challenging to classify and diagnose. To harmonize terminology, we propose revised criteria for the clinical definition of mitochondrial disorders. These criteria are expected to standardize the diagnosis and categorization of mitochondrial diseases, which will facilitate future natural history studies and clinical trials.

Visual memory failure presages conversion to MELAS phenotype

OBJECTIVE

To examine the correlation between verbal and visual memory function and correlation with brain metabolites (lactate and N-Acetylaspartate, NAA) in individuals with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).

METHODS

Memory performance and brain metabolites (ventricular lactate, occipital lactate, and occipital NAA) were examined in 18 MELAS, 58 m.3243A > G carriers, and 20 familial controls. Measures included the Selective Reminding Test (verbal memory), Benton Visuospatial Retention Test (visual memory), and MR Spectroscopy (NAA, Lactate). ANOVA, chi-squared/Fisher's exact tests, paired t-tests, Pearson correlations, and Spearman correlations were used.

RESULTS

When compared to carriers and controls, MELAS patients had the: (1) most impaired memory functions (Visual: p = 0.0003; Verbal: p = 0.02), (2) greatest visual than verbal memory impairment, (3) highest brain lactate levels (p < 0.0001), and (4) lowest brain NAA levels (p = 0.0003). Occipital and ventricular lactate to NAA ratios correlated significantly with visual memory performance (p ≤ 0.001). Higher lactate levels (p ≤ 0.01) and lower NAA levels (p = 0.0009) correlated specifically with greater visual memory dysfunction in MELAS. There was little or no correlation with verbal memory.

INTERPRETATION

Individuals with MELAS are at increased risk for impaired memory. Although verbal and visual memory are both affected, visual memory is preferentially affected and more clearly associated with brain metabolite levels. Preferential involvement of posterior brain regions is a distinctive clinical signature of MELAS. We now report a distinctive cognitive phenotype that targets visual memory more prominently and earlier than verbal memory. We speculate that this finding in carriers presages a conversion to the MELAS phenotype.

CURRENT PERSPECTIVES ON MITOCHONDRIAL DYSFUNCTION IN MIGRAINE

Mitochondria is 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, 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, MELAS, TTH, CVS, ischemic 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.

Lactate-Dependent Cross-Talk Between Astrocyte and GnRH-I Neurons in Hypothalamus of Aged Brain: Decreased GnRH-I Transcription

GnRH-I produced by hypothalamic neurosecretory cells is considered a master regulator of mammalian reproduction. Although GnRH-I transcription is well studied, the effect of ageing on transcriptional regulation of GnRH-I has not yet been explored. Here, we elucidate the effects of ageing on the metabolic environment like lactate level and TNF-α and how these affect GnRH-I transcription. Using pathway analysis of transcriptomic data, we found that lactate is upregulated in ageing astrocytes due to the downregulation of cellular respiration pathways possibly resulting in greater pyruvate concentration for lactate production. This lactate could then be shuttled into neurons where it would affect GnRH-I transcription. We showed that supra-physiological level of lactate in young mouse brain can mimic metabolic disturbances in the old brain and cause downregulation in GnRH-I transcription at a young age. In particular, we found upregulation of GnRH-I repressors in the young brain treated with high levels of lactate similar to old brain. Hence, this confirmed that aged metabolic environment can affect GnRH-I transcription even in the young brain. Further downstream analysis using the TRUST database showed NF-Kb signalling which lies downstream of both lactate and TNF-α as being capable of upregulating GnRH-I repressors. Since NF-Kb signalling has been shown in our study as well as others to be induced by TNF-α during ageing, it is likely that GnRH-I transcriptional regulation is mediated through these pathways. Thus, we formed a model for explaining the downregulation of GnRH-I transcription during ageing through differential expression of its TFs in an aged metabolic environment.

Clinical Characteristics of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, a maternally inherited mitochondrial disorder, is characterized by its genetic, biochemical and clinical complexity. The most common mutation associated with MELAS syndrome is the mtDNA A3243G mutation in the MT-TL1 gene encoding the mitochondrial tRNA-leu(UUR), which results in impaired mitochondrial translation and protein synthesis involving the mitochondrial electron transport chain complex subunits, leading to impaired mitochondrial energy production. Angiopathy, either alone or in combination with nitric oxide (NO) deficiency, further contributes to multi-organ involvement in MELAS syndrome. Management for MELAS syndrome is amostly symptomatic multidisciplinary approach. In this article, we review the clinical presentations, pathogenic mechanisms and options for management of MELAS syndrome.

Circulating markers of NADH-reductive stress correlate with mitochondrial disease severity

Mitochondrial disorders represent a large collection of rare syndromes that are difficult to manage both because we do not fully understand biochemical pathogenesis and because we currently lack facile markers of severity. The m.3243A>G variant is the most common heteroplasmic mitochondrial DNA mutation and underlies a spectrum of diseases, notably mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes (MELAS). To identify robust circulating markers of m.3243A>G disease, we first performed discovery proteomics, targeted metabolomics, and untargeted metabolomics on plasma from a deeply phenotyped cohort (102 patients, 32 controls). In a validation phase, we measured concentrations of prioritized metabolites in an independent cohort using distinct methods. We validated 20 analytes (1 protein, 19 metabolites) that distinguish patients with MELAS from controls. The collection includes classic (lactate, alanine) and more recently identified (GDF-15, α-hydroxybutyrate) mitochondrial markers. By mining untargeted mass-spectra we uncovered 3 less well-studied metabolite families: N-lactoyl-amino acids, β-hydroxy acylcarnitines, and β-hydroxy fatty acids. Many of these 20 analytes correlate strongly with established measures of severity, including Karnofsky status, and mechanistically, nearly all markers are attributable to an elevated NADH/NAD+ ratio, or NADH-reductive stress. Our work defines a panel of organelle function tests related to NADH-reductive stress that should enable classification and monitoring of mitochondrial disease.

Brain MRS correlates with mitochondrial dysfunction biomarkers in MELAS-associated mtDNA mutations

Objective

The purpose of this study was to investigate correlations between brain proton magnetic resonance spectroscopy (¹H‐MRS) findings with serum biomarkers and heteroplasmy of mitochondrial DNA (mtDNA) mutations. This study enrolled patients carrying mtDNA mutations associated with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke‐like episodes (MELAS), and MELAS‐Spectrum Syndrome (MSS).

Methods

Consecutive patients carrying mtDNA mutations associated with MELAS and MSS were recruited and their serum concentrations of lactate, alanine, and heteroplasmic mtDNA mutant load were evaluated. The brain protocol included single‐voxel ¹H‐MRS (1.5T) in the medial parieto‐occipital cortex (MPOC), left cerebellar hemisphere, parieto‐occipital white matter (POWM), and lateral ventricles. Relative metabolite concentrations of N‐acetyl‐aspartate (NAA), choline (Cho), and myo‐inositol (mI) were estimated relative to creatine (Cr), using LCModel 6.3.

Results

Six patients with MELAS (age 28 ± 13 years, 3 [50%] female) and 17 with MSS (age 45 ± 11 years, 7 [41%] female) and 39 sex‐ and age‐matched healthy controls (HC) were enrolled. These patients demonstrated a lower NAA/Cr ratio in MPOC compared to HC (p = 0.006), which inversely correlated with serum lactate (p = 0.021, rho = −0.68) and muscle mtDNA heteroplasmy (p < 0.001, rho = −0.80). Similarly, in the cerebellum patients had lower NAA/Cr (p < 0.001), Cho/Cr (p = 0.002), and NAA/mI (p = 0.001) ratios, which negatively correlated with mtDNA blood heteroplasmy (p = 0.001, rho = −0.81) and with alanine (p = 0.050, rho = −0.67). Ventricular lactate was present in 78.3% (18/23) of patients, correlating with serum lactate (p = 0.024, rho = 0.58).

Conclusion

Correlations were found between the peripheral and biochemical markers of mitochondrial dysfunction and brain in vivo markers of neurodegeneration, supporting the use of both biomarkers as signatures of MELAS and MSS disease, to evaluate the efficacy of potential treatments.

Exploring triheptanoin as treatment for short chain enoyl CoA hydratase deficiency

We explored the benefits of triheptanoin as a treatment for Short Chain Enoyl Co‐A Hydratase (SCEH) deficiency. One child with early onset, severe SCEH Deficiency was treated with triheptanoin, an odd chain oil with anapleurotic properties, for 37 months. Blood and urine chemistry safety measures, motor skills assessment, physical exam, and neurological assessment were monitored over a 27 month period. Modest sustained gains in motor skills, attention, muscle bulk, and strength were observed without any significant adverse effects. Triheptanoin appears to be a promising effective treatment for SCEH Deficiency.

Advanced magnetic resonance spectroscopic neuroimaging: Experts' consensus recommendations

Magnetic resonance spectroscopic imaging (MRSI) offers considerable promise for monitoring metabolic alterations associated with disease or injury; however, to date, these methods have not had a significant impact on clinical care, and their use remains largely confined to the research community and a limited number of clinical sites. The MRSI methods currently implemented on clinical MRI instruments have remained essentially unchanged for two decades, with only incremental improvements in sequence implementation. During this time, a number of technological developments have taken place that have already greatly benefited the quality of MRSI measurements within the research community and which promise to bring advanced MRSI studies to the point where the technique becomes a true imaging modality, while making the traditional review of individual spectra a secondary requirement. Furthermore, the increasing use of biomedical MR spectroscopy studies has indicated clinical areas where advanced MRSI methods can provide valuable information for clinical care. In light of this rapidly changing technological environment and growing understanding of the value of MRSI studies for biomedical studies, this article presents a consensus from a group of experts in the field that reviews the state-of-the-art for clinical proton MRSI studies of the human brain, recommends minimal standards for further development of vendor-provided MRSI implementations, and identifies areas which need further technical development.

Cognitive functioning and mental health in mitochondrial disease: A systematic scoping review

Mitochondrial diseases (MDs) are rare, heterogeneous, hereditary and progressive in nature. In addition to the serious somatic symptoms, patients with MD also experience problems regarding their cognitive functioning and mental health. We provide an overview of all published studies reporting on any aspect of cognitive functioning and/or mental health in patients with MD and their relatives. A total of 58 research articles and 45 case studies were included and critically reviewed. Cognitive impairments in multiple domains were reported. Mental disorders were frequently reported, especially depression and anxiety. Furthermore, most studies showed impairments in self-reported psychological functioning and high prevalence of mental health problems in (matrilineal) relatives. The included studies showed heterogeneity regarding patient samples, measurement instruments and reference groups, making comparisons cautious. Results highlight a high prevalence of cognitive impairments and mental disorders in patients with MD. Recommendations for further research as well as tailored patientcare with standardized follow-up are provided. Key gaps in the literature are identified, of which studies on natural history are of highest importance.

Mitochondrial Medicine: Genetic Underpinnings and Disease Modeling Using Induced Pluripotent Stem Cell Technology

Mitochondrial medicine is an exciting and rapidly evolving field. While the mitochondrial genome is small and differs from the nuclear genome in that it is circular and free of histones, it has been implicated in neurodegenerative diseases, type 2 diabetes, aging and cardiovascular disorders. Currently, there is a lack of efficient treatments for mitochondrial diseases. This has promoted the need for developing an appropriate platform to investigate and target the mitochondrial genome. However, developing these therapeutics requires a model system that enables rapid and effective studying of potential candidate therapeutics. In the past decade, induced pluripotent stem cells (iPSCs) have become a promising technology for applications in basic science and clinical trials, and have the potential to be transformative for mitochondrial drug development. Engineered iPSC-derived cardiomyocytes (iPSC-CM) offer a unique tool to model mitochondrial disorders. Additionally, these cellular models enable the discovery and testing of novel therapeutics and their impact on pathogenic mtDNA variants and dysfunctional mitochondria. Herein, we review recent advances in iPSC-CM models focused on mitochondrial dysfunction often causing cardiovascular diseases. The importance of mitochondrial disease systems biology coupled with genetically encoded NAD⁺/NADH sensors is addressed toward developing an in vitro translational approach to establish effective therapies.

Measuring transverse relaxation rates of the major brain metabolites from single-voxel PRESS acquisitions at a single TE

PURPOSE

To compare transverse relaxation rates of brain metabolites estimated from single-TE PRESS acquisitions with more conventionally derived rates estimated from multiple-TE PRESS acquisitions.

METHODS

Single-voxel (8 mL) PRESS data within white matter from 6 subjects were acquired at five different TEs. Transverse relaxation rates R₂ of N-acetylaspartate, creatine, and choline were estimated from a single TE using full versus right-side-only sampling of the echo. These R₂ values were compared with R_2Hahn values obtained from the multiple-TE PRESS acquisitions.

RESULTS

Following baseline subtraction and RMS weighting, interindividual mean R₂ values from TE = 288 ms magnitude spectra for choline, creatine, and N-acetylaspartate were highly correlated with respective R_2Hahn values (r² = 0.99). Paired individual measurements at this TE showed less correlation (r² = 0.48), primarily due to the N-acetylaspartate resonance. Using TE = 360 ms data for N-acetylaspartate and 288 ms for choline and creatine resulted in an improved correlation coefficient (r² = 0.80). The average absolute intra-individual differences in the estimated R₂ s between single-TE and Hahn method was 9.6 ± 7.7%.

CONCLUSION

For the major brain metabolite singlets, R_2Hahn values showed correlations with more fragile measurements of R₂ from a single TE that are worthy of interest. Because the left side of long-TE spin echoes is available "for free" from an acquisition perspective, and although the single-TE method for estimating R₂ values is associated with lower precision, the reduction in scan time may be clinically helpful.

Sex-specific metabolic alterations in the type 1 diabetic brain of mice revealed by an integrated method of metabolomics and mixed-model

Type 1 diabetes (T1D) can cause brain region-specific metabolic disorders, but whether gender influences T1D-related brain metabolic changes is rarely reported. Therefore, here we examined metabolic changes in six different brain regions of male and female mice under normal and T1D conditions using an integrated method of NMR-based metabolomics and linear mixed-model, and aimed to explore sex-specific metabolic changes from normal to T1D. The results demonstrate that metabolic differences occurred in all brain regions between two genders, while the hippocampal metabolism is more likely to be affected by T1D. At the 4th week after streptozotocin treatment, brain metabolic disorders mainly occurred in the cortex and hippocampus in female T1D mice, but the striatum and hippocampus in male T1D mice. In addition, anaerobic glycolysis was significantly altered in male mice, mainly in the striatum, midbrain, hypothalamus and hippocampus, but not in female mice. We also found that female mice exhibited a hypometabolism status relative to male mice from normal to T1D. Collectively, this study suggests that T1D affected brain region-specific metabolic alterations in a sex-specific manner, and may provide a metabolic view on diabetic brain diseases between genders.

Systematic review of cognitive deficits in adult mitochondrial disease

The profile and trajectory of cognitive impairment in mitochondrial disease are poorly defined. This systematic review sought to evaluate the current literature on cognition in mitochondrial disease, and to determine future research directions. A systematic review was conducted, employing PubMed, Medline, Psycinfo, Embase and Web of Science, and 360‐degree citation methods. English language papers on adult patients were included. The literature search yielded 2421 articles, of which 167 met inclusion criteria. Case reports and reviews of medical reports of patients yielded broad diagnoses of dementia, cognitive impairment and cognitive decline. In contrast, systematic investigations of cognitive functioning using detailed cognitive batteries identified focal cognitive rather than global deficits. Results were variable, but included visuospatial functioning, memory, attention, processing speed and executive functions. Conclusions from studies have been hampered by small sample sizes, variation in genotype and the breadth and depth of assessments undertaken. Comprehensive cognitive research with concurrent functional neuroimaging and physical correlates of mitochondrial disease in larger samples of well‐characterized patients may discern the aetiology and progression of cognitive deficits. These data provide insights into the pattern and trajectory of cognitive impairments, which are invaluable for clinical monitoring, health planning and clinical trial readiness.

Cognitive deficits in adult m.3243A>G- and m.8344A>G-related mitochondrial disease: importance of correcting for baseline intellectual ability

Objective

To determine the cognitive profile of adult patients with mitochondrial disease, and the effect of disease severity on cognition.

Methods

Using a prospective case-control design, we compared cognition of patients to normative data and to matched controls, assessed three times over 18 months. Forty-nine patients with m.3243A>G (N = 36) and m.8344A>G (N = 13) mtDNA mutations and 32 controls, matched by age (±5 years) and premorbid cognition (±10 WTAR FSIQ points), participated. Participants completed neuropsychological assessments of general cognition (WAIS-IV), executive function (D-KEFS), and memory (WMS-IV). Potential predictors of cognition were explored.

Results

Patients show mild-to-moderate premorbid cognitive impairment, but substantial impairment in current general cognition and distinct domains, including verbal comprehension, perceptual reasoning, working memory, processing speed, and memory retrieval. Executive dysfunction may be caused by slower decision-making. Patients performed worse than controls, except on memory tasks, indicating intact memory, when premorbid cognition is controlled for. Premorbid cognition and disease severity were consistent predictors of cognition in patients; however, cognitive decline appears slow and is unlikely in the short-term, when other disease-specific factors remain stable.

Interpretation

Patients should be monitored to facilitate early identification of a complex profile of cognitive deficits and individuals with higher disease burden should be followed up more closely. On development of cognitive difficulties, appropriate compensatory strategies should be determined through in-depth assessment. Using strategies such as slower presentation of information, multiple modes of presentation, active discussion to aid understanding and decision-making, and use of memory aids, may ameliorate difficulties.

Synaptic energy metabolism and neuronal excitability, in sickness and health

Most of the energy produced in the brain is dedicated to supporting synaptic transmission. Glucose is the main fuel, providing energy and carbon skeletons to the cells that execute and support synaptic function: neurons and astrocytes, respectively. It is unclear, however, how glucose is provided to and used by these cells under different levels of synaptic activity. It is even more unclear how diseases that impair glucose uptake and oxidation in the brain alter metabolism in neurons and astrocytes, disrupt synaptic activity, and cause neurological dysfunction, of which seizures are one of the most common clinical manifestations. Poor mechanistic understanding of diseases involving synaptic energy metabolism has prevented the expansion of therapeutic options, which, in most cases, are limited to symptomatic treatments. To shed light on the intersections between metabolism, synaptic transmission, and neuronal excitability, we briefly review current knowledge of compartmentalized metabolism in neurons and astrocytes, the biochemical pathways that fuel synaptic transmission at resting and active states, and the mechanisms by which disorders of brain glucose metabolism disrupt neuronal excitability and synaptic function and cause neurological disease in the form of epilepsy.

[Genetic causes of stroke in young patients]

The paper addresses genetic causes of stroke: MELAS, antiphospholipid syndrome, CADASIL, Fabry disease. The etiology and pathogenesis, symptoms, diagnosis, treatment methods of these diseases are described.

MELAS: Monitoring treatment with magnetic resonance spectroscopy

BACKGROUND

To assess the utility of Magnetic Resonance Spectroscopy (MRS) as a biomarker of response to L-arginine in mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS).

AIMS

To describe a case of MELAS treated with L-arginine that showed improvement clinically and on serial MRS METHODS: MRS was performed on a 1.5-Tesla scanner to evaluate a MELAS patient before, during, and after intravenous (IV) L-arginine therapy for the treatment of stroke-like episodes. L-arginine was infused at a dose of 500 mg/kg daily for 7 days followed by oral arginine therapy.

RESULTS

The patient had clinical improvement after treatment with IV L-arginine. MRS performed before, during, and after treatment with IV L-arginine showed significant improvement in brain lactate and increase in the N-acetylaspartate/Choline (NAA/Cho) ratio compared to pre-treatment baseline.

CONCLUSION

Serial MRS imaging showed significant improvement in lactate peaks and NAA/Cho ratios that corresponded with clinical improvement after L-arginine therapy. Given this correlation between radiologic and clinical improvement, MRS may be a useful biomarker assessing response to treatment in MELAS.

Cerebral imaging in paediatric mitochondrial disorders

OBJECTIVES

Because the central nervous system (CNS) is the second most frequently affected organ in mitochondrial disorders (MIDs) and since paediatric MIDs are increasingly recognised, it is important to know about the morphological CNS abnormalities on imaging in these patients. This review aims at summarising and discussing current knowledge and recent advances concerning CNS imaging abnormalities in paediatric MIDs.

METHODS

A systematic literature review was conducted.

RESULTS

The most relevant CNS abnormalities in paediatric MIDs on imaging include white and grey matter lesions, stroke-like lesions as the morphological equivalent of stroke-like episodes, cerebral atrophy, calcifications, optic atrophy, and lactacidosis. Because these CNS lesions may be seen with or without clinical manifestations, it is important to screen all MID patients for cerebral involvement. Some of these lesions may remain unchanged for years whereas others may be dynamic, either in the sense of progression or regression. Typical dynamic lesions are stroke-like lesions and grey matter lesions. Clinically relevant imaging techniques for visualisation of CNS abnormalities in paediatric MIDs are computed tomography, magnetic resonance (MR) imaging, MR spectroscopy, single-photon emission computed tomography, positron-emission tomography, and angiography.

CONCLUSIONS

CNS imaging in paediatric MIDs is important for diagnosing and monitoring CNS involvement. It also contributes to the understanding of the underlying pathomechanisms that lead to CNS involvement in MIDs.

Early detection of elevated lactate levels in a mitochondrial disease model using chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) at 7T-MRI

This study aimed to use chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) at 7T-MRI for early detection of intracerebral lactate in a mitochondrial disease model without brain lesions. We considered Ndufs4-knockout (KO) mice as Leigh syndrome models and wild-type (WT) mice as control mice. Brain MRI and ¹H-MRS were performed. T₂WI data acquired with the Rapid Acquisition with Refocused Echoes (RARE) sequence were used for evaluation of brain lesions. CEST imaging of mice brains was performed using RARE with a magnetization transfer (MT) pulse. The MT ratio (MTR) asymmetry curves and five MTR asymmetry maps at 0.5, 1.0, 2.0, 3.0, and 3.5 ppm were calculated using these CEST images. Metabolite concentrations were measured by MRS. T₂WI MRI revealed no obvious abnormal findings in KO and WT mice brains at 6 weeks of age. The MTR asymmetry maps at 0.5 ppm, 1.0 ppm, and 2.0 ppm of the KO mice were higher than those of the control mice. Brain ¹H MRS revealed a significant increase in lactate levels in all KO mice in comparison with those in the control mice. Additionally, creatine levels in the KO mice were slightly higher than those in the control mice. The levels of the other four metabolites-mIns, NAA + NAAG, GPC + PCh, and Glu + Gln-did not change significantly. We propose that CEST imaging can be used as a biomarker of intracerebral elevated lactate levels in mitochondrial disease.

Cognitive characteristics of mitochondrial diseases in children

INTRODUCTION

This retrospective descriptive study was undertaken to further define the intelligence profiles of children with mitochondrial disorders, in the context of seizures and age of symptom onset.

METHODS

We retrospectively identified forty-nine pediatric patients with definitive mitochondrial disease diagnoses and complete intelligence or adaptive functioning testing data. Patients were 0-216 months at onset of symptoms and 61-250 months of age at testing. Twenty-four of 49 patients had seizures. Twenty-one of the 24 patients with seizures had medically intractable seizures. All patients had Wechsler Intellectual Quotient (IQ) testing, except nine patients with seizures who were unable to engage in IQ testing and were assessed with a structured parent interview measure, the Vineland Adaptive Behavior Scales. We used descriptive and exploratory data analysis methods to characterize test results.

RESULTS

Distribution of ages for patients with the Vineland assessment was younger than those given the Wechsler. The median overall score (combining Wechsler and Vineland summary scores) for all patients was 85 (interquartile range [IQR]: 50, 102), with the group without seizures obtaining a higher median Full Scale IQ (FSIQ) of 100 (IQR: 86, 109), compared to the group with seizures with a median FSIQ of 67 (IQR: 49.5, 89), a difference that is both statistically and clinically different (Δ = 33; 95% CI: 9, 52). The adaptive function measure was composed of patients only with intractable epilepsy and yielded the lowest overall median summary score of 43 (IQR: 37, 50). This general trend in differences between the FSIQ scores of the groups with and without seizures was also seen across all subscale measures analyzed-IQ index scores and two subtest scores, Digit Span and Coding-though differences were not always statistically different. Vargha-Delaney's A effect sizes ranged between 0.68 and 0.90, trends that mirrored those of distributional and median differences. Groups without versus with seizures differed most distinctly in Performance IQ (PIQ), with the group without seizures' median PIQ being 100 (IQR 94, 112) versus the group with seizures' median PIQ being 63 (IQR 54, 84), a difference of 37 points (95% CI).

DISCUSSION

Results suggest that patients with mitochondrial diseases with seizures and early onset disease represent a worse cognitive phenotype, as compared with those with no seizures, who can have average intelligence. Results are discussed in the context of current literature.

Correlation of Serum Biomarkers and Magnetic Resonance Spectroscopy in Monitoring Disease Progression in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes Due to mtDNA A3243G Mutation

Background: Analysis of serum biomarkers and magnetic resonance spectroscopy (MRS) are useful for monitoring disease progression in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). We evaluated the correlation of serum biomarkers and MRS parameters during changes associated with stroke-like episodes. Methods: In 13 symptomatic MELAS patients carrying the A3243G mutation, we retrospectively obtained 207 voxels from 41 MRS studies, which were divided into three groups according to the temporal association with stroke-like episodes. The MRS NAA/Cr, Cho/Cr, NAA/Cho ratios, the presence of a lactate peak, serum biomarkers, serum lactate level and the pyruvate (Lac/Pyr) ratio were determined. Results: In regions with acute infarcts, the severity of serum Lac/Pyr and that of the MRS lactate peak (P = 0.0007) correlated; serum lactate (P = 0.02), severity of elevated serum lactate (P = 0.04), and serum Lac/Pyr (P = 0.02) correlated weakly. In previously infarcted regions, the severity of the MRS lactate peak and serum Lac/Pyr (P = 0.03), as well as the severity of serum Lac/Pyr (P = 0.02) were weakly correlated. In structurally normal regions, we found a weak to moderate negative correlation between serum lactate and MRS NAA/Cr (P = 0.008), and between the severity of elevated serum lactate and MRS NAA/Cr (P = 0.002) as well as MRS NAA/Cho (P = 0.02). Conclusions: MRS parameters correlate with specific serum biomarkers, and are useful for monitoring changes in brain metabolites, particularly as related to stroke-like episodes.

Cognitive impairment in neuromuscular diseases: A systematic review

Neuromuscular diseases are multifactorial pathologies characterized by extensive muscle fiber damage that leads to the activation of satellite cells and to the exhaustion of their pool, with consequent impairment of neurobiological aspects, such as cognition and motor control. To review the knowledge and obtain a broad view of the cognitive impairment on Neuromuscular Diseases. Cognitive impairment in neuromuscular disease was explored; a literature search up to October 2017 was conducted, including experimental studies, case reports and reviews written in English. Keywords included Cognitive Impairment, Neuromuscular Diseases, Motor Neuron Diseases, Dystrophinopathies and Mitochondrial Disorders. Several cognitive evaluation scales, neuroimaging scans, genetic analysis and laboratory applications in neuromuscular diseases, especially when it comes to the Motor Neuron Diseases, Dystrophinopathies and Mitochondrial Disorders. In addition, organisms model using rats in the genetic analysis and laboratory applications to verify the cognitive and neuromuscular impacts. Several studies indicate that congenital molecular alterations in neuromuscular diseases promote cognitive dysfunctions. Understanding these mechanisms may in the future guide the proper management of the patient, evaluation, establishment of prognosis, choice of treatment and development of innovative interventions such as gene therapy.

Mitochondrial function in individuals at clinical high risk for psychosis

Alterations in mitochondrial function have been implicated in the etiology of schizophrenia. Most studies have investigated alterations in mitochondrial function in patients in which the disorder is already established; however, whether mitochondrial dysfunction predates the onset of psychosis remains unknown. We measured peripheral mitochondrial complex (I–V) function and lactate/pyruvate levels in 27 antipsychotic-naïve individuals at clinical high risk for psychosis (CHR) and 16 healthy controls. We also explored the association between mitochondrial function and brain microglial activation and glutathione levels using a translocator protein 18 kDa [¹⁸F]FEPPA PET scan and ¹H-MRS scan, respectively. There were no significant differences in mitochondrial complex function and lactate/pyruvate levels between CHR and healthy controls. In the CHR group, mitochondrial complex III function (r = −0.51, p = 0.008) and lactate levels (r = 0.61, p = 0.004) were associated with prodromal negative symptoms. As previously reported, there were no significant differences in microglial activation and glutathione levels between groups, however, mitochondrial complex IV function was inversely related to microglial activation in the hippocampus in CHR (r = −0.42, p = 0.04), but not in healthy controls. In conclusion, alterations in mitochondrial function are not yet evident in CHR, but may relate to the severity of prodromal symptoms, particularly negative symptoms.

Monitoring clinical progression with mitochondrial disease biomarkers

Mitochondrial disorders are genetically determined metabolic diseases due to a biochemical deficiency of the respiratory chain. Given that multi-system involvement and disease progression are common features of mitochondrial disorders they carry substantial morbidity and mortality. Despite this, no disease-modifying treatments exist with clear clinical benefits, and the current best management of mitochondrial disease is supportive. Several therapeutic strategies for mitochondrial disorders are now at a mature preclinical stage. Some are making the transition into early-phase patient trials, but the lack of validated biomarkers of disease progression presents a challenge when developing new therapies for patients. This update discusses current biomarkers of mitochondrial disease progression including metabolomics, circulating serum markers, exercise physiology, and both structural and functional imaging. We discuss the advantages and disadvantages of each approach, and consider emerging techniques with a potential role in trials of new therapies.

Mitochondrial dysfunction and cerebral metabolic abnormalities in patients with mitochondrial encephalomyopathy subtypes: Evidence from proton MR spectroscopy and muscle biopsy

AIMS

Accumulated evidence indicates that cerebral metabolic features, evaluated by proton magnetic resonance spectroscopy (¹ H-MRS), are sensitive to early mitochondrion dysfunction associated with mitochondrial encephalomyopathy (ME). The metabolite ratios of lactate (lac)/Cr, N-acetyl aspartate (NAA)/creatine (Cr), total choline (tCho)/Cr, and myoinositol (mI)/Cr are measured in the infarct-like lesions by ¹ H-MRS and may reveal metabolic changes associated with ME. However, the application of this molecular imaging technique in the investigation of the pathology of ME subtypes is unknown.

METHODS

In this study, cerebral metabolic features of pathologically diagnosed ME cases, that is, 19 mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); nine chronic progressive external ophthalmoplegia (CPEO); and 23 healthy controls, were investigated using ¹ H-MRS. Receiver operating characteristics (ROC) analysis was used to evaluate the diagnostic power of the cerebral metabolites. Histochemical evaluation was carried out on muscle tissues derived from biopsy to assess the abnormal mitochondrial proliferation. The association between cerebral metabolic and mitochondrial cytopathy was examined by correlation analysis.

RESULTS

Patients with MELAS or CPEO exhibited a significantly higher Lac/Cr ratio and a lower NAA/Cr ratio compared with controls. The ROC curve of Lac/Cr ratio indicated prominent discrimination between MELAS or CPEO and healthy control subjects, whereas the NAA/Cr ratio may present diagnostic power in the distinction of MELAS from CPEO. Lower NAA/Cr ratio was associated with higher Lac/Cr in MELAS, but not in CPEO. Furthermore, higher ragged-red fibers (RRFs) percentages were associated with elevated Lac/Cr and reduced NAA/Cr ratios, notably in MELAS. This association was not noted in the case of mI/Cr ratio.

CONCLUSIONS

Mitochondrial cytopathy (lactic acidosis and RRFs on muscle biopsy) was associated with neuronal viability but not glial proliferation, notably in MELAS. Mitochondrial neuronopathy and neuronal vulnerability are considered significant causes in the pathogenesis of MELAS, particularly with regard to stroke-like episodes.

Elevations of Ventricular Lactate Levels Occur in Both Chronic Fatigue Syndrome and Fibromyalgia

Background

Chronic fatigue syndrome (CFS) and fibromyalgia (FM) frequently have overlapping symptoms, leading to the suggestion that the same disease processes may underpin the two disorders - the unitary hypothesis. However, studies investigating the two disorders have reported substantial clinical and/or biological differences between them, suggesting distinct pathophysiological underpinnings.

Purpose

The purpose of this study was to further add to the body of evidence favoring different disease processes in CFS and FM by comparing ventricular cerebrospinal fluid lactate levels among patients with CFS alone, FM alone, overlapping CFS and FM symptoms, and healthy control subjects.

Methods

Ventricular lactate was assessed in vivo with proton magnetic resonance spectroscopic imaging (¹H MRSI) with the results normed across the 2 studies in which the data were collected.

Results

Mean CSF lactate levels in CFS, FM and CFS+FM did not differ among the three groups, but were all significantly higher than the mean values for control subjects.

Conclusion

While patients with CFS, FM and comorbid CFS and FM can be differentiated from healthy subjects based on measures of CFS lactate, this neuroimaging outcome measure is not a viable biomarker for differentiating CFS from FM or from patients in whom symptoms of the two disorders overlap.

Analysis of Gait Disturbance in Glut 1 Deficiency Syndrome

Anticipating potential therapies for Glut 1 deficiency syndrome (Glut1DS) emphasizes the need for effective clinical outcome measures. The 6-minute walk test is a well-established outcome measure that evaluates walking ability in neurological diseases. Twenty-one children with Glut 1 deficiency syndrome and 21 controls performed the 6-minute walk test. Fatigue was determined by comparing distance walked in the first and sixth minutes. Gait was analyzed by stride length, velocity, cadence, base of support, and percentage time in double support. Independent sample t-tests examined differences between group. Repeated-measures analysis of variance evaluated gait parameters over time. Glut 1 deficiency syndrome patients walked less (P < .05), had slower velocities (P < .0001), had shorter stride lengths (P < .0001), spent more time in double support (P < .001), and had increasing variability in base of support (P = .009). Glut 1 deficiency syndrome patients have impaired motor performance, walk more slowly, and have poor balance. The 6-minute walk test with gait analysis may serve as a useful outcome measure in clinical trials in Glut 1 deficiency syndrome.

Review: Central nervous system involvement in mitochondrial disease

Mitochondrial respiratory chain defects are an important cause of inherited disorders affecting approximately 1 in 5000 people in the UK population. Collectively these disorders are termed ‘mitochondrial diseases’ and they result from either mitochondrial DNA mutations or defects in nuclear DNA. Although they are frequently multisystem disorders, neurological deficits are particularly common, wide‐ranging and disabling for patients. This review details the manifold neurological impairments associated with mitochondrial disease, and describes the efforts to understand how they arise and progressively worsen in patients with mitochondrial disease. We describe advances in our understanding of disease pathogenesis through detailed neuropathological studies and how this has spurred the development of cellular and animal models of disease. We underscore the importance of continued clinical, molecular genetic, neuropathological and animal model studies to fully characterize mitochondrial diseases and understand mechanisms of neurodegeneration. These studies are instrumental for the next phase of mitochondrial research that has a particular emphasis on finding novel ways to treat mitochondrial disease to improve patient care and quality of life.

MELAS: A Multigenerational Impact of the MTTL1 A3243G MELAS Mutation

BACKGROUND

the maternally inherited MTTL1 A3243G mutation in the mitochondrial genome causes MelaS (Mitochondrial encephalopathy lactic acidosis with Stroke-like episodes), a condition that is multisystemic but affects primarily the nervous system. Significant intra-familial variation in phenotype and severity of disease is well recognized.

METHODS

retrospective and ongoing study of an extended family carrying the MTTL1 A3243G mutation with multiple symptomatic individuals. tissue heteroplasmy is reviewed based on the clinical presentations, imaging studies, laboratory findings in affected individuals and pathological material obtained at autopsy in two of the family members.

RESULTS

there were seven affected individuals out of thirteen members in this three generation family who each carried the MTTL1 A3243G mutation. the clinical presentations were varied with symptoms ranging from hearing loss, migraines, dementia, seizures, diabetes, visual manifestations, and stroke like episodes. three of the family members are deceased from MelaS or to complications related to MelaS.

CONCLUSIONS

the results of the clinical, pathological and radiological findings in this family provide strong support to the current concepts of maternal inheritance, tissue heteroplasmy and molecular pathogenesis in MelaS. neurologists (both adult and paediatric) are the most likely to encounter patients with MelaS in their practice. genetic counselling is complex in view of maternal inheritance and heteroplasmy. newer therapeutic options such as arginine are being used for acute and preventative management of stroke like episodes.

Diagnosing Glucose Transporter 1 Deficiency at Initial Presentation Facilitates Early Treatment

OBJECTIVE

To profile the initial clinical events of glucose transporter 1 deficiency syndrome (Glut1 DS) in order to facilitate the earliest possible diagnosis.

STUDY DESIGN

We retrospectively reviewed 133 patients with Glut1 DS from a single institution. Family interviews and medical record reviews identified the first clinical event(s) reported by the caregivers.

RESULTS

Average age of the first event was 8.15 ± 11.9 months (range: 0.01-81). Ninety-one patients experienced the first symptom before age 6 months (68%). Thirty-three additional patients (25%) presented before age 2 years. Only 9 patients (7%), reported the first event after age 2 years. Seizures were the most common first event (n = 81, 61%), followed by eye movement abnormalities (n = 51, 38%) and changes in muscle strength and tone (n = 30, 22%). Eye movement abnormalities, lower cerebrospinal fluid glucose values, and lower Columbia Neurological Scores correlated with earlier onset of the first event (r: -0.17, 0.22, and 0.25 respectively, P < .05). There was no correlation with age of first event and red blood cell glucose uptake or mutation type.

CONCLUSIONS

Glut1 DS is a treatable cause of infantile onset encephalopathy. Health care providers should recognize the wide spectrum of paroxysmal events that herald the clinical onset of Glut1 DS in early infancy to facilitate prompt diagnosis, immediate treatment, and improved long-term outcome.

When should MELAS (Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes) be the diagnosis?

Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is a rare mitochondrial disorder. Diagnostic criteria for MELAS include typical manifestations of the disease: stroke-like episodes, encephalopathy, evidence of mitochondrial dysfunction (laboratorial or histological) and known mitochondrial DNA gene mutations. Clinical features of MELAS are not necessarily uniform in the early stages of the disease, and correlations between clinical manifestations and physiopathology have not been fully elucidated. It is estimated that point mutations in the tRNALeu(UUR) gene of the DNAmt, mainly A3243G, are responsible for more of 80% of MELAS cases. Morphological changes seen upon muscle biopsy in MELAS include a substantive proportion of ragged red fibers (RRF) and the presence of vessels with a strong reaction for succinate dehydrogenase. In this review, we discuss mainly diagnostic criterion, clinical and laboratory manifestations, brain images, histology and molecular findings as well as some differential diagnoses and current treatments.

Mitochondrial Encephalomyopathy Lactic Acidosis and Stroke-Like Episodes (MELAS): A Case Report and Critical Reappraisal of Treatment Options

IMPORTANCE

Stroke-like episodes signal progression and significant disability in the mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes syndrome. Arginine is widely used as a treatment for stroke-like episode, although there is little evidence for this intervention. We discuss the management of a patient with mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes who presented with a stroke-like episode.

OBSERVATION

During a seizure, which triggers the stroke-like episode, neurons are forced to utilize glycolysis as a source of adenosine triphosphate. Glycolytic by-products are damaging to the neuron. Breakdown of the blood-brain barrier leads to vasogenic edema.

CONCLUSION

Treatment of stroke-like episode should include anticonvulsants interictally to prevent seizures and dexamethasone ictally to help repair the blood-brain barrier.

Increased ventricular cerebrospinal fluid lactate in depressed adolescents

BACKGROUND

Mitochondrial dysfunction has been increasingly examined as a potential pathogenic event in psychiatric disorders, although its role early in the course of major depressive disorder (MDD) is unclear. Therefore, the purpose of this study was to investigate mitochondrial dysfunction in medication-free adolescents with MDD through in vivo measurements of neurometabolites using high-spatial resolution multislice/multivoxel proton magnetic resonance spectroscopy.

METHODS

Twenty-three adolescents with MDD and 29 healthy controls, ages 12-20, were scanned at 3T and concentrations of ventricular cerebrospinal fluid lactate, as well as N-acetyl-aspartate (NAA), total creatine (tCr), and total choline (tCho) in the bilateral caudate, putamen, and thalamus were reported.

RESULTS

Adolescents with MDD exhibited increased ventricular lactate compared to healthy controls [F(1,41)=6.98, P=0.01]. However, there were no group differences in the other neurometabolites. Dimensional analyses in the depressed group showed no relation between any of the neurometabolites and symptomatology, including anhedonia and fatigue.

CONCLUSIONS

Increased ventricular lactate in depressed adolescents suggests mitochondrial dysfunction may be present early in the course of MDD; however it is still not known whether the presence of mitochondrial dysfunction is a trait vulnerability of individuals predisposed to psychopathology or a state feature of the disorder. Therefore, there is a need for larger multimodal studies to clarify these chemical findings in the context of network function.

Lactate and its many faces

BACKGROUND

Lactate is traditionally seen as a marker of ischemia and a waste product of anaerobic glycolysis. In the last thirty years a more beneficial side of lactate as an alternative 'glucose sparing' fuel has been demonstrated. However, the translation of these growing insights to clinical practice seems to appear with great delay.

METHODS

A review of the literature was performed, focusing on glucose and lactate in relation to cerebral energy metabolism, in the context of four typical clinical situations, namely (transient states of) low glucose availability for the brain due to hypoglycemia, combined with high blood lactate concentrations; permanent neuroglycopenia; lactic acidosis in mitochondrial disorders; and ischemic as well as traumatic brain injury.

RESULTS

Lactate is thought to be an alternative fuel in the brain of patients with glucose transporter type 1 deficiency syndrome and glycogen storage disease, and it has been demonstrated that lactate might have a protective role in ischemic and traumatic brain injury.

CONCLUSION

Lactate has an apparently largely ignored, but potential beneficial role in the clinical management of several neurologic disorders.

Effect of Milnacipran Treatment on Ventricular Lactate in Fibromyalgia: A Randomized, Double-Blind, Placebo-Controlled Trial

Milnacipran, a serotonin/norepinephrine reuptake inhibitor, has been approved by the US Food and Drug Administration for the treatment of fibromyalgia (FM). This report presents the results of a randomized, double-blind, placebo-controlled trial of milnacipran conducted to test the hypotheses that a) similar to patients with chronic fatigue syndrome, patients with FM have increased ventricular lactate levels at baseline; b) 8 weeks of treatment with milnacipran will lower ventricular lactate levels compared with baseline levels and with ventricular lactate levels after placebo; and c) treatment with milnacipran will improve attention and executive function in the Attention Network Test compared with placebo. In addition, we examined the results for potential associations between ventricular lactate and pain. Baseline ventricular lactate measured by proton magnetic resonance spectroscopic imaging was found to be higher in patients with FM than in healthy controls (F1,37 = 22.11, P < .0001, partial η(2) = .37). Milnacipran reduced pain in patients with FM relative to placebo but had no effect on cognitive processing. At the end of the study, ventricular lactate levels in the milnacipran-treated group had decreased significantly compared with baseline and after placebo (F1,18 = 8.18, P = .01, partial η(2) = .31). A significantly larger proportion of patients treated with milnacipran showed decreases in both ventricular lactate and pain than those treated with placebo (P = .03). These results suggest that proton magnetic resonance spectroscopic imaging measurements of lactate may serve as a potential biomarker for a therapeutic response in FM and that milnacipran may act, at least in part, by targeting the brain response to glial activation and neuroinflammation.

PERSPECTIVE

Patients treated with milnacipran showed decreases in both pain and ventricular lactate levels compared with those treated with placebo, but, even after treatment, levels of ventricular lactate remained higher than in controls. The hypothesized mechanism for these decreases is via drug-induced reductions of a central inflammatory state.