Mitochondrial Disease Research Articles

Relationship between Cellular Oxygen Consumption and Atherosclerosis-Associated Mitochondrial Mutations (Variants of the Mitochondrial Genome).

Mitochondria are the main sites of cellular aerobic energy production through conjugation of respiration and oxidative phosphorylation. We have recently discovered mutations (genome variants) of mitochondrial DNA (mtDNA) associated with atherosclerosis. We have then investigated the possible mechanisms underlying such association and the role of mitochondrial mutations in atherogenesis. Mitochondrial dysfunction is a known component of the pathogenesis of chronic human diseases, including atherosclerosis. The aim of the study was to explore whether there is a relationship between cellular oxygen consumption and atherosclerosis-associated mitochondrial mutations. The study of mitochondrial respiration abnormalities can help to understand the role of mtDNA mutations in pathology. By using the polarographic method with Clark electrode, we tested the possibility of respiration impairment in permeabilized cells carrying the tested mtDNA variants using the cybrid (cytoplasmic hybrid) lines. Mitochondria introduced in the cybrid lines were obtained from atherosclerotic patients that differed in the profile of mtDNA mutations, which made it possible to compare the degree of mtDNA mutation load with the rate of oxygen consumption by cybrid cells. It was found that three of the studied mutations were individually associated with impaired respiration. Besides, some combinations of two specific mutations have a high probability of being associated with altered oxygen consumption. As a result, eight mutations were identified, individually or paired combinations of which were associated with high or low rates of cellular respiration, significantly different from control cells. The observed effect may be involved in the pathogenesis of atherosclerosis. The study of mtDNA mutations associated with atherosclerosis can help reveal pharmacological targets for the development of novel therapies.

Mitochondrial membrane synthesis, remodelling and cellular trafficking.

Mitochondria are dynamic cellular organelles with complex roles in metabolism and signalling. Primary mitochondrial disorders are a group of approximately 400 monogenic disorders arising from pathogenic genetic variants impacting mitochondrial structure, ultrastructure and/or function. Amongst these disorders, defects of complex lipid biosynthesis, especially of the unique mitochondrial membrane lipid cardiolipin, and membrane biology are an emerging group characterised by clinical heterogeneity, but with recurrent features including cardiomyopathy, encephalopathy, neurodegeneration, neuropathy and 3-methylglutaconic aciduria. This review discusses lipid synthesis in the mitochondrial membrane, the mitochondrial contact site and cristae organising system (MICOS), mitochondrial dynamics and trafficking, and the disorders associated with defects of each of these processes. We highlight overlapping functions of proteins involved in lipid biosynthesis and protein import into the mitochondria, pointing to an overarching coordination and synchronisation of mitochondrial functions. This review also focuses on membrane interactions between mitochondria and other organelles, namely the endoplasmic reticulum, peroxisomes, lysosomes and lipid droplets. We signpost disorders of these membrane interactions that may explain the observation of secondary mitochondrial dysfunction in heterogeneous pathological processes. Disruption of these organellar interactions ultimately impairs cellular homeostasis and organismal health, highlighting the central role of mitochondria in human health and disease.

Electron transport chain inhibition increases cellular dependence on purine transport and salvage

Mitochondria house many metabolic pathways required for homeostasis and growth. To explore how human cells respond to mitochondrial dysfunction, we performed metabolomics in fibroblasts from patients with various mitochondrial disorders and cancer cells with electron transport chain (ETC) blockade. These analyses revealed extensive perturbations in purine metabolism, and stable isotope tracing demonstrated that ETC defects suppress de novo purine synthesis while enhancing purine salvage. In human lung cancer, tumors with markers of low oxidative mitochondrial metabolism exhibit enhanced expression of the salvage enzyme hypoxanthine phosphoribosyl transferase 1 (HPRT1) and high levels of the HPRT1 product inosine monophosphate. Mechanistically, ETC blockade activates the pentose phosphate pathway, providing phosphoribosyl diphosphate to drive purine salvage supplied by uptake of extracellular bases. Blocking HPRT1 sensitizes cancer cells to ETC inhibition. These findings demonstrate how cells remodel purine metabolism upon ETC blockade and uncover a new metabolic vulnerability in tumors with low respiration.

The possible association of mitochondrial fusion and fission in copper deficiency-induced oxidative damage and mitochondrial dysfunction of the heart

IntroductionAs an essential trace element, Copper (Cu) participates in numerous physiological and biological reactions in the body. Cu is closely related to heart health, and an imbalance of Cu will cause cardiac dysfunction. The research aims to examine how Cu deficiency affects the heart, assess mitochondrial function in the hearts, and disclose possible mechanisms of its influence. MethodsWeaned mice were fed Cu-deficient diets and intraperitoneally given copper sulfate (CuSO4) to correct the Cu deficiency. The pathological change of the heart was assessed using histological inspection. Cardiac function and oxidative stress levels were evaluated by biochemical assay kits. ELISA and ATP detection kits were used to detect the levels of complexes I-IV in the mitochondrial respiratory chain (MRC) and ATP, respectively. Real time PCR was utilized to determine mRNA expressions, and Western blotting was adopted to determine protein expressions, of molecules related to mitochondrial fission and fusion. ResultsCu deficiency gave rise to elevated heart index, cardiac histological alterations and oxidation injury, increased serum levels of creatine kinase (CK), lactic dehydrogenase (LDH), and creatine kinase isoenzyme MB (CK-MB) together with increased malondialdehyde (MDA) production, decreased the glutathione (GSH), Superoxide Dismutase (SOD), and Catalase (CAT) activities or contents. Besides, Cu deficiency caused mitochondrial damage characterized by decreased contents of complexes I-IV in the MRC and ATP in the heart. In the meantime, Cu deficiency also reduced protein and mRNA expressions of factors associated with mitochondrial fusion, including Mfn1 and Mfn2, while significantly increased factors Drip1 and Fis1 related to mitochondrial fission. However, adding CuSO4 improved the above changes significantly. ConclusionAccording to research results, Cu deficiency can cause heart damage in mice, along with oxidative damage and mitochondrial dysfunction, which are closely related to mitochondrial fusion and fission disorders.

Exploration of dietary interventions to treat mitochondrial fatty acid disorders in a mouse model

Mitochondrial fatty acids synthesis (mtFAS) is a conserved metabolic pathway essential for mitochondrial respiration. The best characterized mtFAS product is the medium-chain fatty acid octanoate (C8) used as a substrate in the synthesis of lipoic acid (LA), a cofactor required by several mitochondrial enzyme complexes. In humans, mutations in the mtFAS component enoyl reductase MECR cause childhood-onset neurodegenerative disorder MEPAN. A complete deletion of Mecr in mice is embryonically lethal, while selective deletion of Mecr in cerebellar Purkinje cells causes neurodegeneration in these cells. A fundamental question in the research of mtFAS deficiency is if the defect is amenable to treatment by supplementation with known mtFAS products. Here we used the Purkinje-cell specific mtFAS deficiency neurodegeneration model mice to study if feeding the mice with a medium-chain triacylglycerol-rich formula supplemented with LA could slow down or prevent the neurodegeneration in Purkinje cell-specific Mecr KO mice. Feeding started at the age of 4 weeks and continued until the age of 9 months. The neurological status on the mice was assessed at the age of 3, 6, and 9 months with behavioral tests and the state of the Purkinje cell deterioration in the cerebellum was studied histologically. We showed that feeding the mice with medium chain triacylglycerols and LA affected fatty acid profiles in the cerebellum and plasma but did not prevent the development of neurodegeneration in these mice. Our results indicate that dietary supplementation with medium chain fatty acids and LA alone is not an efficient way to treat mtFAS disorders.

Exclusion of sulfide:quinone oxidoreductase from mitochondria causes Leigh-like disease in mice by impairing sulfide metabolism.

Leigh syndrome is the most common inherited mitochondrial disease in children and is often fatal within the first few years of life. In 2020, mutations in the gene encoding sulfide:quinone oxidoreductase (SQOR), a mitochondrial protein, were identified as a cause of Leigh syndrome. Here, we report that mice with a mutation in the gene encoding SQOR (SqorΔN/ΔN mice), which prevented SQOR from entering mitochondria, had clinical and pathological manifestations of Leigh syndrome. SqorΔN/ΔN mice had increased blood lactate levels that were associated with markedly decreased complex IV activity and increased hydrogen sulfide (H2S) levels. Because H2S is produced by both gut microbiota and host tissue, we tested whether metronidazole (a broad-spectrum antibiotic) or a sulfur-restricted diet rescues SqorΔN/ΔN mice from developing Leigh syndrome. Daily treatment with metronidazole alleviated increased H2S levels, normalized complex IV activity and blood lactate levels, and prolonged the survival of SqorΔN/ΔN mice. Similarly, a sulfur-restricted diet normalized blood lactate levels and inhibited the development of Leigh syndrome. Taken together, these observations suggest that mitochondrial SQOR is essential to prevent systemic accumulation of H2S. Metronidazole administration and a sulfur-restricted diet may be therapeutic approaches to treatment of patients with Leigh syndrome caused by mutations in SQOR.

Multiomics analysis reveals serine catabolism as a potential therapeutic target for MELAS.

Mitochondrial disease is a devastating genetic disorder, with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and m.3243A>G being the most common phenotype and genotype, respectively. The treatment for MELAS patients is still less effective. Here, we performed transcriptomic and proteomic analysis in muscle tissue of MELAS patients, and discovered that the expression of molecules involved in serine catabolism were significantly upregulated, and serine hydroxymethyltransferase 2 (SHMT2) increased significantly in both the mRNA and protein levels. The SHMT2 protein level was also increased in myoblasts with m.3243A>G mutation, which was transdifferentiated from patients derived fibroblasts, accompanying with the decreased nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) ratio and cell viability. After treating with SHMT2 inhibitor (SHIN1), the NAD+/NADH ratio and cell viability in MELAS myoblasts increased significantly. Taken together, our study indicates that enhanced serine catabolism plays an important role in the pathogenesis of MELAS and that SHIN1 can be a potential small molecule for the treatment of this disease.

Epigenetic reprogramming of mtDNA and its etiology in mitochondrial diseases.

Mitochondrial functionality and its regulation are tightly controlled through a balanced crosstalk between the nuclear and mitochondrial DNA interactions. Epigenetic signatures like methylation, hydroxymethylation and miRNAs have been reported in mitochondria. In addition, epigenetic signatures encoded by nuclear DNA are also imported to mitochondria and regulate the gene expression dynamics of the mitochondrial genome. Alteration in the interplay of these epigenetic modifications results in the pathogenesis of various disorders like neurodegenerative, cardiovascular, metabolic disorders, cancer, aging and senescence. These modifications result in higher ROS production, increased mitochondrial copy number and disruption in the replication process. In addition, various miRNAs are associated with regulating and expressing important mitochondrial gene families like COX, OXPHOS, ND and DNMT. Epigenetic changes are reversible and therefore therapeutic interventions like changing the target modifications can be utilized to repair or prevent mitochondrial insufficiency by reversing the changed gene expression. Identifying these mitochondrial-specific epigenetic signatures has the potential for early diagnosis and treatment responses for many diseases caused by mitochondrial dysfunction. In the present review, different mitoepigenetic modifications have been discussed in association with the development of various diseases by focusing on alteration in gene expression and dysregulation of specific signaling pathways. However, this area is still in its infancy and future research is warranted to draw better conclusions.

Spectrum of rare and common mitochondrial DNA variations from 1029 whole genomes of self-declared healthy individuals from India

Mitochondrial disorders are a class of heterogeneous disorders caused by genetic variations in the mitochondrial genome (mtDNA) as well as the nuclear genome. The spectrum of mtDNA variants remains unexplored in the Indian population. In the present study, we have cataloged 2689 high confidence single nucleotide variants, small insertions and deletions in mtDNA in 1029 healthy Indian individuals. We found a major proportion (76.5 %) of the variants being rare (AF<=0.005) in the studied population. Intriguingly, we found two ‘confirmed’ pathogenic variants (m.1555 A>G and m.14484 T>C) with a frequency of ∼1 in 250 individuals in our dataset. The high carrier frequency underscores the need for screening of the mtDNA pathogenic mutations in newborns in India. Interestingly, our analysis also revealed 202 variants in our dataset which have been ‘reported’ in disease cases as per the MITOMAP database. Additionally, we found the frequency of haplogroup M (52.2 %) to be the highest among all the 18 top-level haplogroups found in our dataset. In comparison to the global population datasets, 20 unique mtDNA variants are found in the Indian population. We hope the whole genome sequencing based compendium of mtDNA variants along with their allele frequencies and heteroplasmy levels in the Indian population will drive additional genome scale studies for mtDNA. Furthermore, the identification of clinically relevant variants in our dataset will aid in better clinical interpretation of the variants in mitochondrial disorders.

Evaluation of the Frequency of Blood Ammonia Test Requests in Pediatric Clinics Before and After the Establishment of the Pediatric Metabolism Department

Abstract Background/Aims: Hyperammonemia causes severe mortality and morbidity when left unnoticed. We aimed to compare the number of ammonia test requests before and after establishing the Pediatric Metabolism Department (PMD) in a pediatric clinic. Methods: The study was conducted retrospectively between 15/11/2022-16/11/2023. Study data were evaluated before (pre-group) and after (post-group) the establishment of PMD. Results: Two hundred eighty-five admissions were assessed in the study. There were 99 admissions in the pre-group and 186 in the post-group. There were 17 admissions for different reasons in the pre-group and 29 in the post-group. The most common reasons for admission were elevated transaminases, seizures, vomiting, and metabolic acidosis. Definitive diagnosis was made in 16 (17.6%) patients admitted in the pre-group and 39 (23.8%) in the post-group. The most common diagnoses were genetic syndromes, mitochondrial diseases, and organic acidemias. Twenty-one patients were diagnosed with inherited metabolic diseases (IMDs). Mitochondrial diseases were the most commonly diagnosed IMD (8(38%)). An ammonia test was requested from 8 of 15 pediatric subunits in the pre-group and 13 in the post-group. In the pre-group, the pediatric subunit where ammonia was requested the most was the Pediatric Neurology Polyclinic (n=25 (25.3%)). In the post-group, the subunit that required the highest number of ammonia tests was the PMD (68(23.9%)). In the ROC analysis conducted for the predictive power of the initial ammonia level in requesting a control ammonia test, the area under the curve is 0.927, and the p-value is 0.001. For the cut-off value of 60.3 µmol/l, the sensitivity was 90.9%, and the specificity was 88.6%. Conclusions: After the establishment of PMD, an increase in ammonia test requests, in the diversity of reasons for requesting ammonia testing from admissions, and in IMD diagnosis were detected, and the positive effect of PMD on pediatricians' awareness of hyperammonemia was found.

Hematologic Manifestations in Primary Mitochondrial Diseases.

Primary mitochondrial disorders (PMDs) are known for their pleiotropic manifestations in humans, affecting almost any organ or system at any time. Hematologic manifestations, such as cytopenias and sideroblastic anemia, occur in 10% to 30% of patients with confirmed PMDs. These can be the initial presenting features or complications that develop over time. Surveillance for these manifestations allows for prompt identification and treatment. This article provides an overview of the pathophysiology underpinning the hematologic effects of mitochondrial dysfunction, discussing the 3 key roles of the mitochondria in hematopoiesis: providing energy for cell differentiation and function, synthesizing heme, and generating iron-sulfur clusters. Subsequently, the diagnosis and management of mitochondrial disorders are discussed, focusing on hematologic manifestations and the specific conditions commonly associated with them. Through this, we aimed to provide a concise point of reference for those considering a mitochondrial cause for a patient's hematologic abnormality, or for those considering a hematologic manifestation in a patient with known or suspected mitochondrial disease.

Gastrointestinal involvement in neuromuscular disorders.

Although not often discussed, many of the neuromuscular disorders (NMDs) affect the gastrointestinal tract (GIT). Depending on the type of NMD, the prevalence of GIT involvement ranges from <5% (e.g. hereditary neuropathies, myofibrillar myopathies) to 100% (e.g. MNGIE, OPMD). Particularly in NMDs with multisystem affection, involvement of the GIT can dominate the clinical presentation or at least make up a significant part of the clinical picture. The most prominent representatives of NMDs with multisystem involvement are the mitochondrial disorders (MIDs) and the myotonic dystrophies. The best known syndromic MIDs with GIT involvement are MNGIE, MELAS, Leigh, and Pearson syndromes. Among neuropathies, GIT involvement is most commonly found in ALS and GBS. GIT involvement may also be a feature of myasthenia. The clinical manifestations of GIT involvement are diverse and can affect the entire GIT, from the teeth to the rectum, including the liver and pancreas. The most well-known clinical manifestations of GIT involvement are dysphagia, nausea, vomiting, reflux, hollow organ dysmotility, hepatopathy, diabetes, diarrhea, constipation, and fecal incontinence. Even if treatment can usually only be symptomatic, the therapeutic options are diverse, are often effective, and can significantly and beneficially influence the course of the underlying NMD.

Aberrant ER-mitochondria communication is a common pathomechanism in mitochondrial disease

Genetic mutations causing primary mitochondrial disease (i.e those compromising oxidative phosphorylation [OxPhos]) resulting in reduced bioenergetic output display great variability in their clinical features, but the reason for this is unknown. We hypothesized that disruption of the communication between endoplasmic reticulum (ER) and mitochondria at mitochondria-associated ER membranes (MAM) might play a role in this variability. To test this, we assayed MAM function and ER-mitochondrial communication in OxPhos-deficient cells, including cybrids from patients with selected pathogenic mtDNA mutations. Our results show that each of the various mutations studied indeed altered MAM functions, but notably, each disorder presented with a different MAM “signature”. We also found that mitochondrial membrane potential is a key driver of ER-mitochondrial connectivity. Moreover, our findings demonstrate that disruption in ER-mitochondrial communication has consequences for cell survivability that go well beyond that of reduced ATP output. The findings of a “MAM-OxPhos” axis, the role of mitochondrial membrane potential in controlling this process, and the contribution of MAM dysfunction to cell death, reveal a new relationship between mitochondria and the rest of the cell, as well as providing new insights into the diagnosis and treatment of these devastating disorders.

The Phenotypic Range of Mitochondrial Myopathies and Disorders is More Diverse Than Expected.

The Phenotypic Range of Mitochondrial Myopathies and Disorders is More Diverse Than Expected.

Toxicity mechanism of acrolein on energy metabolism disorder and apoptosis in human ovarian granulosa cells

Acrolein (ACR), an unsaturated, highly reactive aldehyde, is a widespread environmental toxin. ACR exerts permanent and irreversible side effects on ovarian functions. Granulosa cells play a crucial role in supporting ovarian function. Thus, in this study, we investigated the toxicity effects of granulosa cells induced by ACR. Following treatment with varying ACR concentrations (0, 12.5, 25, 50, and 100 μM), we observed that ACR exposure induced reactive oxygen species accumulation, mitochondrial energy metabolism disorder, and apoptosis in KGN cells (a human ovarian granulosa cell line) in a dose-dependent manner. In addition, mitochondrial biogenesis in KGN cells displayed biphasic changes after ACR exposure, with activation at a low ACR dose (12.5 μM), but inhibition at higher ACR doses (≥50 μM). SIRT1/PGC-1α-mediated mitochondrial biogenesis is crucial for maintaining intracellular mitochondrial homeostasis and cellular function. The inhibition/activation of the SIRT1/PGC-1α pathway in KGN cells validated its role in ACR-induced damage. The results indicated that the inhibition of the SIRT1/PGC-1α pathway aggravated ACR-induced cell damage, whereas its activation partially counteracted ACR-induced cell damage. This study attempted to uncover a novel mechanism of ACR-induced ovarian toxicity so as to provide an effective treatment option for safeguarding female reproductive health from the adverse effects of ACR.

Molecular findings in patients for whole exome sequencing and mitochondrial genome assessment

ObjectiveWhole exome sequencing (WES) is becoming more widely used as a diagnostic tool in the field of medicine. In this article, we reported the diagnostic yield of WES and mitochondrial genome assessment in 2226 consecutive cases in a single clinical laboratory. Materials and methodsWe retrospectively analyzed consecutive WES reports from 2226 patients with various genetic disorders. WES-process was focused exclusively on the probands and aimed at a higher diagnostic capacity. We determined the diagnostic rate of WES overall and by phenotypic category, mode of inheritance, mitochondrial genome variant, and copy number variants (CNVs). ResultsAmong the 2226 patients who had diagnostic WES proband-only, the overall diagnostic yield of WES was 34.59% (770/2226). The highest diagnostic yield was observed in autosomal dominant disorders, at 45.58% (351/770), followed by autosomal recessive at 31.95%(246/770), X-linked disorder at 9.61%(74/770), and mitochondrial diseases at a notably lower 0.65%(5/770). The 12.21% (94/770) diagnoses were based on a total of 94 copy number variants reported from WES data. CNVs in children accounted for 67.02% of the total CNVs. While majority of the molecular diagnoses were related to nuclear genes, the inclusion of mitochondrial genome sequencing in the WES test contributed to five diagnoses. all mitochondrial diseases were identified in adults. ConclusionsThe proband-only WES provided a definitive molecular diagnosis for 34.59% of a large cohort of patients while analysis of WES simultaneously analyzed the SNVs, exons, mitochondrial genome, and CNVs, thereby improving the diagnostic yield significantly compared to the single-detection WES method; and facilitating the identification of novel candidate genes.

Mechanism of mitochondrial oxidative phosphorylation disorder in male infertility

Abstract Male infertility has become a global concern, accounting for 20–70% of infertility. Dysfunctional spermatogenesis is the most common cause of male infertility; thus, treating abnormal spermatogenesis may improve male infertility and has attracted the attention of the medical community. Mitochondria are essential organelles that maintain cell homeostasis and normal physiological functions in various ways, such as mitochondrial oxidative phosphorylation (OXPHOS). Mitochondrial OXPHOS transmits electrons through the respiratory chain, synthesizes adenosine triphosphate (ATP), and produces reactive oxygen species (ROS). These mechanisms are vital for spermatogenesis, especially to maintain the normal function of testicular Sertoli cells and germ cells. The disruption of mitochondrial OXPHOS caused by external factors can result in inadequate cellular energy supply, oxidative stress, apoptosis, or ferroptosis, all inhibiting spermatogenesis and damaging the male reproductive system, leading to male infertility. This article summarizes the latest pathological mechanism of mitochondrial OXPHOS disorder in testicular Sertoli cells and germ cells, which disrupts spermatogenesis and results in male infertility. In addition, we also briefly outline the current treatment of spermatogenic malfunction caused by mitochondrial OXPHOS disorders. However, relevant treatments have not been fully elucidated. Therefore, targeting mitochondrial OXPHOS disorders in Sertoli cells and germ cells is a research direction worthy of attention. We believe this review will provide new and more accurate ideas for treating male infertility.

The rate and nature of mitochondrial DNA mutations in human pedigrees

We examined the rate and nature of mitochondrial DNA (mtDNA) mutations in humans using sequence data from 64,806 contemporary Icelanders from 2,548 matrilines. Based on 116,663 mother-child transmissions, 8,199 mutations were detected, providing robust rate estimates by nucleotide type, functional impact, position, and different alleles at the same position. We thoroughly document the true extent of hypermutability in mtDNA, mainly affecting the control region but also some coding-region variants. The results reveal the impact of negative selection on viable deleterious mutations, including rapidly mutating disease-associated 3243A>G and 1555A>G and pre-natal selection that most likely occurs during the development of oocytes. Finally, we show that the fate of new mutations is determined by a drastic germline bottleneck, amounting to an average of 3 mtDNA units effectively transmitted from mother to child.

Remimazolam for anesthesia and sedation in pediatric patients: a scoping review.

Anesthetic management of pediatric patients poses several challenges and the optimal anesthetic agent for use in this population is still a matter of debate. We systematically searched PubMed/MEDLINE and Google Scholar from their inception for studies that investigated the role and potential applications of remimazolam, a novel ultra-short-acting benzodiazepine, in pediatric patients. Furthermore, in March 2024, an update of the literature search along with an additional post-hoc search on the EMBASE database were performed. A total of fourteen pertinent studies which spanned the 2021-2023 period explored remimazolam as either the primary or adjuvant hypnotic agent for inducing and/or maintaining general anesthesia or sedation. Preliminary evidence derived from these studies highlighted that remimazolam is a safe and effective option for both sedation and general anesthesia in pediatric patients, particularly those with concurrent mitochondrial disorders, myopathic diseases, or at risk for malignant hyperthermia. Moreover, the current evidence suggested that remimazolam may contribute to reducing preoperative anxiety and postoperative delirium in children. Its favorable pharmacodynamic and pharmacokinetic profile demonstrated potential safety, effectiveness, and ease-of-use in various perioperative pediatric contexts, making it suitable for integration into specific protocols, such as intraoperative monitoring of evoked potentials and management of difficult intubation. Notwithstanding these promising findings, further research is essential to determine optimal dosages, establish conclusive evidence of its superiority over other benzodiazepines, and elucidate the impact of genetic factors on drug metabolism.

Ellipsoid Zone Reflectivity: Exploring its Potential as a Novel Non-Invasive Biomarker for Assessing Mitochondrial Function

ABSTRACT The ellipsoid zone (EZ) on macular optical coherence tomography (OCT) scans exhibits high intensity due to a high density of light-scattering mitochondria, making its reflectivity a potential marker for mitochondrial function. Here, we developed a reliable analysis tool for extracting relative EZ reflectivity and explore its potential as a biomarker in various diseases. We analysed OCT scans of patients with optic neuritis (ON), primary progressive optic neuropathy (PPON), chronic progressive external ophthalmoplegia (CPEO), dominant optic atrophy (DOA), and healthy controls. EZ reflectivity (normalised to the retina pigment epithelium (RPE) and outer nuclear layer (ONL)) was evaluated. Reliability was assessed using intraclass correlation coefficients (ICC), and group differences were analysed through multivariable linear regression, adjusting for relevant confounders. In total, 12 controls, 23 ON patients, 7 CPEO patients, 13 DOA patients, and 13 PPON patients were included. EZ/RPE20% and EZ/ONL ratios demonstrated good test–retest reliability with ICCs of 0.76 (p < .001) and 0.63 (p = .013), respectively. Multivariable regression analysis revealed that median EZ/RPE20% and EZ/ONL ratios were lower in CPEO (r = -0.12, p = .036, and r = -0.59, p = .011), DOA (r = -0.16, p = .049, and r = -0.55, p = .082), PPON (r = -0.17, p = .014, and r = -0.57, p = .037), and ON (r = -0.11, p = .013, and r = -0.42, p = .006) compared to controls, respectively. These data show that EZ reflectivity can be reliably determined from OCT scans and appears to be reduced in neuroinflammatory and mitochondrial disorders. Further validation in larger prospective cohorts is warranted, but our findings suggest that EZ reflectivity might serve as a non-invasive in-vivo biomarker for mitochondrial health.