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Continuum (Minneapolis, Minn.) Dec 2022Metabolic myopathies are disorders that affect skeletal muscle substrate oxidation. Although some drugs and hormones can affect metabolism in skeletal muscle, this... (Review)
Review
PURPOSE OF REVIEW
Metabolic myopathies are disorders that affect skeletal muscle substrate oxidation. Although some drugs and hormones can affect metabolism in skeletal muscle, this review will focus on the genetic metabolic myopathies.
RECENT FINDINGS
Impairments in glycogenolysis/glycolysis (glycogen storage disease), fatty acid transport/oxidation (fatty acid oxidation defects), and mitochondrial metabolism (mitochondrial myopathies) represent most metabolic myopathies; however, they often overlap clinically with structural genetic myopathies, referred to as pseudometabolic myopathies. Although metabolic myopathies can present in the neonatal period with hypotonia, hypoglycemia, and encephalopathy, most cases present clinically in children or young adults with exercise intolerance, rhabdomyolysis, and weakness. In general, the glycogen storage diseases manifest during brief bouts of high-intensity exercise; in contrast, fatty acid oxidation defects and mitochondrial myopathies usually manifest during longer-duration endurance-type activities, often with fasting or other metabolic stressors (eg, surgery, fever). The neurologic examination is often normal between events (except in the pseudometabolic myopathies) and evaluation requires one or more of the following tests: exercise stress testing, blood (eg, creatine kinase, acylcarnitine profile, lactate, amino acids), urine (eg, organic acids, myoglobin), muscle biopsy (eg, histology, ultrastructure, enzyme testing), and targeted (specific gene) or untargeted (myopathy panels) genetic tests.
SUMMARY
Definitive identification of a specific metabolic myopathy often leads to specific interventions, including lifestyle, exercise, and nutritional modifications; cofactor treatments; accurate genetic counseling; avoidance of specific triggers; and rapid treatment of rhabdomyolysis.
Topics: Young Adult; Infant, Newborn; Child; Humans; Muscular Diseases; Metabolism, Inborn Errors; Mitochondrial Myopathies; Rhabdomyolysis; Glycogen Storage Disease; Fatty Acids
PubMed: 36537979
DOI: 10.1212/CON.0000000000001182 -
Neurotherapeutics : the Journal of the... Oct 2018Mitochondrial myopathies are progressive muscle conditions caused primarily by the impairment of oxidative phosphorylation (OXPHOS) in the mitochondria. This causes a... (Review)
Review
Mitochondrial myopathies are progressive muscle conditions caused primarily by the impairment of oxidative phosphorylation (OXPHOS) in the mitochondria. This causes a deficit in energy production in the form of adenosine triphosphate (ATP), particularly in skeletal muscle. The diagnosis of mitochondrial myopathy is reliant on the combination of numerous techniques including traditional histochemical, immunohistochemical, and biochemical testing combined with the fast-emerging molecular genetic techniques, namely next-generation sequencing (NGS). This has allowed for the diagnosis to become more effective in terms of determining causative or novel genes. However, there are currently no effective or disease-modifying treatments available for the vast majority of patients with mitochondrial myopathies. Existing therapeutic options focus on the symptomatic management of disease manifestations. An increasing number of clinical trials have investigated the therapeutic effects of various vitamins, cofactors, and small molecules, though these trials have failed to show definitive outcome measures for clinical practice thus far. In addition, new molecular strategies, specifically mtZFNs and mtTALENs, that cause beneficial heteroplasmic shifts in cell lines harboring varying pathogenic mtDNA mutations offer hope for the future. Moreover, recent developments in the reproductive options for patients with mitochondrial myopathies mean that for some families, the possibility of preventing transmission of the mutation to the next generation is now possible.
Topics: Adenosine Triphosphate; Humans; Mitochondrial Myopathies; Muscle, Skeletal
PubMed: 30406383
DOI: 10.1007/s13311-018-00674-4 -
Arquivos de Neuro-psiquiatria Nov 2015Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is a rare mitochondrial disorder. Diagnostic criteria for MELAS include typical... (Review)
Review
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.
Topics: Biopsy; Diagnosis, Differential; Humans; MELAS Syndrome; Magnetic Resonance Imaging; Mutation
PubMed: 26517220
DOI: 10.1590/0004-282X20150154 -
Handbook of Clinical Neurology 2023Mitochondrial dysfunction, especially perturbation of oxidative phosphorylation and adenosine triphosphate (ATP) generation, disrupts cellular homeostasis and is a... (Review)
Review
Mitochondrial dysfunction, especially perturbation of oxidative phosphorylation and adenosine triphosphate (ATP) generation, disrupts cellular homeostasis and is a surprisingly frequent cause of central and peripheral nervous system pathology. Mitochondrial disease is an umbrella term that encompasses a host of clinical syndromes and features caused by in excess of 300 different genetic defects affecting the mitochondrial and nuclear genomes. Patients with mitochondrial disease can present at any age, ranging from neonatal onset to late adult life, with variable organ involvement and neurological manifestations including neurodevelopmental delay, seizures, stroke-like episodes, movement disorders, optic neuropathy, myopathy, and neuropathy. Until relatively recently, analysis of skeletal muscle biopsy was the focus of diagnostic algorithms, but step-changes in the scope and availability of next-generation sequencing technology and multiomics analysis have revolutionized mitochondrial disease diagnosis. Currently, there is no specific therapy for most types of mitochondrial disease, although clinical trials research in the field is gathering momentum. In that context, active management of epilepsy, stroke-like episodes, dystonia, brainstem dysfunction, and Parkinsonism are all the more important in improving patient quality of life and reducing mortality.
Topics: Adult; Infant, Newborn; Humans; Mitochondrial Encephalomyopathies; DNA, Mitochondrial; Quality of Life; Mitochondrial Diseases; Stroke
PubMed: 37562887
DOI: 10.1016/B978-0-323-98818-6.00025-X -
Nature Reviews. Cardiology Apr 2017Heart failure is a pressing worldwide public-health problem with millions of patients having worsening heart failure. Despite all the available therapies, the condition... (Review)
Review
Heart failure is a pressing worldwide public-health problem with millions of patients having worsening heart failure. Despite all the available therapies, the condition carries a very poor prognosis. Existing therapies provide symptomatic and clinical benefit, but do not fully address molecular abnormalities that occur in cardiomyocytes. This shortcoming is particularly important given that most patients with heart failure have viable dysfunctional myocardium, in which an improvement or normalization of function might be possible. Although the pathophysiology of heart failure is complex, mitochondrial dysfunction seems to be an important target for therapy to improve cardiac function directly. Mitochondrial abnormalities include impaired mitochondrial electron transport chain activity, increased formation of reactive oxygen species, shifted metabolic substrate utilization, aberrant mitochondrial dynamics, and altered ion homeostasis. In this Consensus Statement, insights into the mechanisms of mitochondrial dysfunction in heart failure are presented, along with an overview of emerging treatments with the potential to improve the function of the failing heart by targeting mitochondria.
Topics: Consensus; Drug Discovery; Electron Transport; Heart Failure; Humans; Kearns-Sayre Syndrome; Mitochondria, Heart; Mitochondrial Myopathies; Prognosis
PubMed: 28004807
DOI: 10.1038/nrcardio.2016.203 -
Neurology Jul 2023Primary mitochondrial myopathies (PMMs) encompass a group of genetic disorders that impair mitochondrial oxidative phosphorylation, adversely affecting physical... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND AND OBJECTIVES
Primary mitochondrial myopathies (PMMs) encompass a group of genetic disorders that impair mitochondrial oxidative phosphorylation, adversely affecting physical function, exercise capacity, and quality of life (QoL). Current PMM standards of care address symptoms, with limited clinical impact, constituting a significant therapeutic unmet need. We present data from MMPOWER-3, a pivotal, phase-3, randomized, double-blind, placebo-controlled clinical trial that evaluated the efficacy and safety of elamipretide in participants with genetically confirmed PMM.
METHODS
After screening, eligible participants were randomized 1:1 to receive either 24 weeks of elamipretide at a dose of 40 mg/d or placebo subcutaneously. Primary efficacy endpoints included change from baseline to week 24 on the distance walked on the 6-minute walk test (6MWT) and total fatigue on the Primary Mitochondrial Myopathy Symptom Assessment (PMMSA). Secondary endpoints included most bothersome symptom score on the PMMSA, NeuroQoL Fatigue Short-Form scores, and the patient global impression and clinician global impression of PMM symptoms.
RESULTS
Participants (N = 218) were randomized (n = 109 elamipretide; n = 109 placebo). The m0ean age was 45.6 years (64% women; 94% White). Most of the participants (n = 162 [74%]) had mitochondrial DNA (mtDNA) alteration, with the remainder having nuclear DNA (nDNA) defects. At screening, the most frequent bothersome PMM symptom on the PMMSA was tiredness during activities (28.9%). At baseline, the mean distance walked on the 6MWT was 336.7 ± 81.2 meters, the mean score for total fatigue on the PMMSA was 10.6 ± 2.5, and the mean T score for the Neuro-QoL Fatigue Short-Form was 54.7 ± 7.5. The study did not meet its primary endpoints assessing changes in the 6MWT and PMMSA total fatigue score (TFS). Between the participants receiving elamipretide and those receiving placebo, the difference in the least squares mean (SE) from baseline to week 24 on distance walked on the 6MWT was -3.2 (95% CI -18.7 to 12.3; = 0.69) meters, and on the PMMSA, the total fatigue score was -0.07 (95% CI -0.10 to 0.26; = 0.37). Elamipretide treatment was well-tolerated with most adverse events being mild to moderate in severity.
DISCUSSION
Subcutaneous elamipretide treatment did not improve outcomes in the 6MWT and PMMSA TFS in patients with PMM. However, this phase-3 study demonstrated that subcutaneous elamipretide is well-tolerated.
TRIAL REGISTRATION INFORMATION
Trial registered with clinicaltrials.gov, Clinical Trials Identifier: NCT03323749; submitted on October 12, 2017; first patient enrolled October 9, 2017.
CLINICALTRIALS
gov/ct2/show/NCT03323749?term = elamipretide&draw = 2&rank = 9.
CLASSIFICATION OF EVIDENCE
This study provides Class I evidence that elamipretide does not improve the 6MWT or fatigue at 24 weeks compared with placebo in patients with primary mitochondrial myopathy.
Topics: Humans; Female; Middle Aged; Male; Quality of Life; Merozoite Surface Protein 1; Mitochondrial Myopathies; Fatigue; Double-Blind Method; Treatment Outcome
PubMed: 37268435
DOI: 10.1212/WNL.0000000000207402 -
Cell Metabolism Jun 2020NAD is a redox-active metabolite, the depletion of which has been proposed to promote aging and degenerative diseases in rodents. However, whether NAD depletion occurs...
NAD is a redox-active metabolite, the depletion of which has been proposed to promote aging and degenerative diseases in rodents. However, whether NAD depletion occurs in patients with degenerative disorders and whether NAD repletion improves their symptoms has remained open. Here, we report systemic NAD deficiency in adult-onset mitochondrial myopathy patients. We administered an increasing dose of NAD-booster niacin, a vitamin B3 form (to 750-1,000 mg/day; clinicaltrials.govNCT03973203) for patients and their matched controls for 10 or 4 months, respectively. Blood NAD increased in all subjects, up to 8-fold, and muscle NAD of patients reached the level of their controls. Some patients showed anemia tendency, while muscle strength and mitochondrial biogenesis increased in all subjects. In patients, muscle metabolome shifted toward controls and liver fat decreased even 50%. Our evidence indicates that blood analysis is useful in identifying NAD deficiency and points niacin to be an efficient NAD booster for treating mitochondrial myopathy.
Topics: Adolescent; Adult; Aged; Female; Humans; Male; Middle Aged; Mitochondrial Myopathies; Muscles; NAD; Niacin; Young Adult
PubMed: 32386566
DOI: 10.1016/j.cmet.2020.04.008 -
Neurologic Clinics Aug 2020Healthy muscle relies on a complex and interdependent network that includes, but is not limited to, proteins, ion channels, and the production and utilization of ATP.... (Review)
Review
Healthy muscle relies on a complex and interdependent network that includes, but is not limited to, proteins, ion channels, and the production and utilization of ATP. Disruptions to the system can occur for a number of reasons (genetic mutations, toxins, systemic disease, inflammation), yet they clinically present with symptoms that are nonspecific and common to myopathies: weakness, muscle pain, cramping, hypotonia. This article uses a case-based format to review the clinical reasoning and diagnostic tools that guide the accurate diagnosis of myopathies. We specifically focus on toxic, metabolic, mitochondrial, and late-onset congenital myopathies.
Topics: Adult; Female; Humans; Male; Middle Aged; Mitochondrial Myopathies; Muscle Weakness; Muscular Diseases; Mutation; Myalgia
PubMed: 32703473
DOI: 10.1016/j.ncl.2020.04.002 -
Current Neurology and Neuroscience... Jun 2016Progressive external ophthalmoplegia (PEO), marked by progressive bilateral ptosis and diffuse reduction in ocular motility, represents a finding of mitochondrial... (Review)
Review
Progressive external ophthalmoplegia (PEO), marked by progressive bilateral ptosis and diffuse reduction in ocular motility, represents a finding of mitochondrial myopathy rather than a true diagnosis. PEO often occurs with other systemic features of mitochondrial dysfunction that can cause significant morbidity and mortality. Accurate and early recognition of PEO is paramount for the optimal care of these patients. We present an evidence-based review of the presenting neuro-ophthalmic features, differential diagnosis, diagnostic tools, systemic implications, and treatment options for isolated PEO and other PEO-associated mitochondrial syndromes.
Topics: Biopsy; Diagnosis, Differential; Disease Progression; Genetic Testing; Humans; Ophthalmoplegia, Chronic Progressive External; Treatment Outcome
PubMed: 27072953
DOI: 10.1007/s11910-016-0652-7 -
Current Rheumatology Reports Oct 2015Patients with autoimmune myositis typically present with muscle weakness, elevated serum levels of muscle enzymes, and abnormal muscle biopsies. However, patients with... (Review)
Review
Patients with autoimmune myositis typically present with muscle weakness, elevated serum levels of muscle enzymes, and abnormal muscle biopsies. However, patients with other acquired myopathies or genetic muscle diseases may have remarkably similar presentations. Making the correct diagnosis of another muscle disease can prevent these patients from being exposed to the risks of immunosuppressive medications, which benefit those with myositis, but not those with other types of muscle disease. Here, we review some of the most common acquired and inherited muscle diseases that can mimic autoimmune myositis, including inclusion body myositis, limb girdle muscular dystrophies, metabolic myopathies, mitochondrial myopathies, and endocrine myopathies. We emphasize aspects of the medical history, physical exam, laboratory evaluation, and muscle biopsy analysis that can help clinicians distinguish myositis mimics from true autoimmune myositis.
Topics: Autoimmune Diseases; Diagnosis, Differential; Endocrine System Diseases; Glycogen Storage Disease Type II; Glycogen Storage Disease Type V; Humans; Mitochondrial Myopathies; Muscular Dystrophies; Muscular Dystrophies, Limb-Girdle; Myositis; Myositis, Inclusion Body
PubMed: 26290112
DOI: 10.1007/s11926-015-0541-0