bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2023‒04‒23
thirty-one papers selected by
Dario Brunetti
Fondazione IRCCS Istituto Neurologico

  1. Science. 2023 Apr 21. 380(6642): eabj5559
      Cells respond to mitochondrial poisons with rapid activation of the adenosine monophosphate-activated protein kinase (AMPK), causing acute metabolic changes through phosphorylation and prolonged adaptation of metabolism through transcriptional effects. Transcription factor EB (TFEB) is a major effector of AMPK that increases expression of lysosome genes in response to energetic stress, but how AMPK activates TFEB remains unresolved. We demonstrate that AMPK directly phosphorylates five conserved serine residues in folliculin-interacting protein 1 (FNIP1), suppressing the function of the folliculin (FLCN)-FNIP1 complex. FNIP1 phosphorylation is required for AMPK to induce nuclear translocation of TFEB and TFEB-dependent increases of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and estrogen-related receptor alpha (ERRα) messenger RNAs. Thus, mitochondrial damage triggers AMPK-FNIP1-dependent nuclear translocation of TFEB, inducing sequential waves of lysosomal and mitochondrial biogenesis.
  2. bioRxiv. 2023 Apr 03. pii: 2023.04.02.535296. [Epub ahead of print]
      Healthy mitochondria are critical for reproduction. During aging, both reproductive fitness and mitochondrial homeostasis decline. Mitochondrial metabolism and dynamics are key factors in supporting mitochondrial homeostasis. However, how they are coupled to control reproductive health remains unclear. We report that mitochondrial GTP metabolism acts through mitochondrial dynamics factors to regulate reproductive aging. We discovered that germline-only inactivation of GTP- but not ATP-specific succinyl-CoA synthetase (SCS), promotes reproductive longevity in Caenorhabditis elegans. We further revealed an age-associated increase in mitochondrial clustering surrounding oocyte nuclei, which is attenuated by the GTP-specific SCS inactivation. Germline-only induction of mitochondrial fission factors sufficiently promotes mitochondrial dispersion and reproductive longevity. Moreover, we discovered that bacterial inputs affect mitochondrial GTP and dynamics factors to modulate reproductive aging. These results demonstrate the significance of mitochondrial GTP metabolism in regulating oocyte mitochondrial homeostasis and reproductive longevity and reveal mitochondrial fission induction as an effective strategy to improve reproductive health.
  3. Trends Mol Med. 2023 Apr 19. pii: S1471-4914(23)00070-9. [Epub ahead of print]
      Duchenne muscular dystrophy (DMD), myotonic dystrophy type 1 (DM1), and spinal muscular atrophy (SMA) are the most prevalent neuromuscular disorders (NMDs) in children and adults. Central to a healthy neuromuscular system are the processes that govern mitochondrial turnover and dynamics, which are regulated by AMP-activated protein kinase (AMPK). Here, we survey mitochondrial stresses that are common between, as well as unique to, DMD, DM1, and SMA, and which may serve as potential therapeutic targets to mitigate neuromuscular disease. We also highlight recent advances that leverage a mutation-agnostic strategy featuring physiological or pharmacological AMPK activation to enhance mitochondrial health in these conditions, as well as identify outstanding questions and opportunities for future pursuit.
    Keywords:  Duchenne muscular dystrophy; mitophagy; myotonic dystrophy type 1; skeletal muscle; spinal muscular atrophy
  4. Cell Rep. 2023 Apr 20. pii: S2211-1247(23)00383-2. [Epub ahead of print]42(5): 112372
      Autophagy is a homeostatic process critical for cellular survival, and its malfunction is implicated in human diseases including neurodegeneration. Loss of autophagy contributes to cytotoxicity and tissue degeneration, but the mechanistic understanding of this phenomenon remains elusive. Here, we generated autophagy-deficient (ATG5-/-) human embryonic stem cells (hESCs), from which we established a human neuronal platform to investigate how loss of autophagy affects neuronal survival. ATG5-/- neurons exhibit basal cytotoxicity accompanied by metabolic defects. Depletion of nicotinamide adenine dinucleotide (NAD) due to hyperactivation of NAD-consuming enzymes is found to trigger cell death via mitochondrial depolarization in ATG5-/- neurons. Boosting intracellular NAD levels improves cell viability by restoring mitochondrial bioenergetics and proteostasis in ATG5-/- neurons. Our findings elucidate a mechanistic link between autophagy deficiency and neuronal cell death that can be targeted for therapeutic interventions in neurodegenerative and lysosomal storage diseases associated with autophagic defect.
    Keywords:  CP: Cell biology; CP: Metabolism; NAD; NADases; NAM; NMN; NR; autophagy; cell death; cell survival, human embryonic stem cell-derived neurons; mitochondria; nicotinamide; nicotinamide adenine dinucleotide; nicotinamide mononucleotide; nicotinamide riboside
  5. Methods Mol Biol. 2023 ;2662 53-65
      Measuring the mitochondrial respiratory capacity of brown adipocytes ex vivo is an essential approach to understand the cell-autonomous regulators of mitochondrial uncoupling in brown adipose tissue. Here, we describe two protocols to isolate brown preadipocytes from mice, their ex vivo differentiation to mature brown adipocytes and the quantification of their mitochondrial uncoupling capacity by respirometry.
    Keywords:  Brown adipocytes; Mitochondria; Respirometry; Thermogenesis; Uncoupling
  6. Cerebellum. 2023 Apr 22.
      Different pathogenic variants in the DNA polymerase-gamma2 (POLG2) gene cause a rare, clinically heterogeneous mitochondrial disease. We detected a novel POLG2 variant (c.1270 T > C, p.Ser424Pro) in a family with adult-onset cerebellar ataxia and progressive ophthalmoplegia. We demonstrated altered mitochondrial integrity in patients' fibroblast cultures but no changes of the mitochondrial DNA were found when compared to controls. We consider this novel, segregating POLG2 variant as disease-causing in this family. Moreover, we systematically screened the literature for POLG2-linked phenotypes and re-evaluated all mutations published to date for pathogenicity according to current knowledge. Thereby, we identified twelve published, likely disease-causing variants in 19 patients only. The core features included progressive ophthalmoplegia and cerebellar ataxia; parkinsonism, neuropathy, cognitive decline, and seizures were also repeatedly found in adult-onset heterozygous POLG2-related disease. A severe phenotype relates to biallelic pathogenic variants in POLG2, i.e., newborn-onset liver failure, referred to as mitochondrial depletion syndrome. Our work underlines the broad clinical spectrum of POLG2-related disease and highlights the importance of functional characterization of variants of uncertain significance to enable meaningful genetic counseling.
    Keywords:  Adult-onset ataxia; Mitochondrial dysfunction; POLG2
  7. Clin Neurol Neurosurg. 2023 Apr 07. pii: S0303-8467(23)00128-2. [Epub ahead of print]229 107712
      Mitochondrial neurogastrointestinal encephalopathy (MNGIE) is a well-known mitochondrial depletion syndrome. Since Van Goethem et al. described MNGIE syndrome with pathogenic POLG1 mutations in 2003, POLG1 gene became a target for MNGIE patients. Cases with POLG1 mutations strikingly differ from classic MNGIE patients due to a lack of leukoencephalopathy. Here we present a female patient with very early onset disease and leukoencephalopathy compatible with classic MNGIE disease who turned out to have homozygous POLG1 mutation compatible with MNGIE-like syndrome, mitochondrial depletion syndrome type 4b.
    Keywords:  Gastroparesis; Inherited peripheral neuropathy; Leukoencephalopathy; MNGIE syndrome; Mitochondrial DNA Depletion Syndrome
  8. J Cell Sci. 2023 Apr 19. pii: jcs.260578. [Epub ahead of print]
      Mitochondria are essential organelles of eukaryotic cells that are characterized by their unique and complex membrane system. They are confined from the cytosol by an envelope consisting of two membranes. Signals, metabolites, proteins and lipids have to be transferred across these membranes via proteinaceous contact sites to keep mitochondria functional. In the present study we identified a novel mitochondrial contact site that is formed by the inner membrane protein Cqd1 and the outer membrane proteins Por1 and Om14. Similar to the mitochondrial porin, Por1, Cqd1 is highly conserved, suggesting that this complex is conserved in form and function from yeast to human. Cqd1 is a member of the UbiB protein kinase-like family (also called aarF domain containing kinases). It was recently shown that Cqd1 in cooperation with Cqd2 controls the cellular distribution of coenzyme Q by a yet unknown mechanism. Our data suggest that Cqd1 is additionally involved in phospholipid homeostasis. Moreover, overexpression of CQD1 and CQD2 causes tethering of mitochondria to the endoplasmic reticulum, which might explain the ability of Cqd2 to rescue ERMES deletion phenotypes.
    Keywords:  Contact sites; Mitochondria; Mitochondrial biogenesis; Mitochondrial morphology; Phospholipids; UbiB protein family
  9. Mol Syndromol. 2023 Apr;14(2): 171-174
      Introductıon: Succinate dehydrogenase deficiency, also known as mitochondrial complex II deficiency, is a rare inborn error of metabolism, accounting for approximately 2% of mitochondrial disease. Mutations in the four genes SDHA, B, C,and D have been reported resulting in diverse clinical presentations. The vast majority of clinically affected individuals reported in the literature harbor genetic variants within the SDHA gene and present with a Leigh syndrome phenotype, clinically defined as a subacute necrotizing encephalopathy.Case Report: Herein, we report the first case of a 7-year-old child who was diagnosed as having succinate dehydrogenase deficiency. The affected child presented at 1 year of age with encephalopathy and developmental regression following viral illnesses. MRI changes supported a clinical diagnosis of Leigh syndrome and c.1328C>Q and c.872A>C SDHA variants were identified as compound heterozygous. Mitochondrial cocktail treatment including L-carnitine, riboflavin, thiamine, biotin, and ubiquinone was started. Mild clinical improvement was observed after treatment. He is now unable to walk and speak. The second patient, a 21-year-old woman, presented with generalized muscle weakness, easy fatigability, and cardiomyopathy. Investigations revealed increased lactate level of 67.4 mg/dL (4.5-19.8) with repeatedly increased plasma alanine levels 1,272 µmol/L (200-579). We administered carnitine, coenzyme, riboflavin, and thiamine for empirical therapy with the suspicion of mitochondrial disease. Clinical exome sequencing revealed compound heterozygous variants NM_004168.4:c.1945_1946del (p.Leu649GlufsTer4) at exon 15 of the SDHA gene and NM_004168.4:c.1909-12_1909-11del at intron 14 of SDHA gene.
    Discussion and Conclusion: There are several very different presentations including Leigh syndrome, epileptic encephalopathy, and cardiomyopathy. Some cases present following viral illness; this feature is not specific to mitochondrial complex II deficiency and occurs in many other mitochondrial disease presentations. There is no cure for complex II deficiency, though some reported patients showed clinical improvement following riboflavin therapy. Riboflavin is not the only therapeutic intervention that is available to patients with an isolated complex II deficiency and various other compounds have shown promise in the treatment of symptoms, including L-carnitine and ubiquinone. Treatment alternatives such as parabenzoquinone EPI-743 and rapamycin are under study in the treatment of the disease.
    Keywords:  Leigh syndrome phenotype; Metabolic diseases; Mitochondrial disease; Succinate dehydrogenase deficiency; Whole-exome sequencing
  10. Mol Syndromol. 2023 Apr;14(2): 101-108
      Introduction: Antenatal presentation of hypertrophic cardiomyopathy (HCM) is rare. We describe familial recurrence of antenatal HCM associated with intrauterine growth restriction and the diagnostic process undertaken.Methods: Two pregnancies with antenatal HCM were followed up. Biological assessment including metabolic analyses, genetic analyses, and respiratory chain study was performed. We describe the clinical course of these two pregnancies, antenatal manifestations as well as specific histopathological findings, and review the literature.
    Results: The assessment revealed a deficiency in complex I of the respiratory chain and two likely pathogenic variations in the ACAD9 gene.
    Discussion and Conclusion: Antenatal HCM is rare and a diagnosis is not always made. In pregnancies presenting with cardiomyopathy and intrauterine growth restriction, ACAD9 deficiency should be considered as one of the potential underlying diagnoses, and ACAD9 molecular testing should be included among other prenatal investigations.
    Keywords:  ACAD9 mutations; Antenatal hypertrophic cardiomyopathy; Congenital disease; Fetal histopathology; Intrauterine growth restriction; Mitochondrial complex I deficiency
  11. Geroscience. 2023 Apr 22.
      Altered mitochondrial function is tightly linked to lifespan regulation, but underlying mechanisms remain unclear. Here, we report the chronological and replicative lifespan variation across 167 yeast knock-out strains, each lacking a single nuclear-coded mitochondrial gene, including 144 genes with human homologs, many associated with diseases. We dissected the signatures of observed lifespan differences by analyzing profiles of each strain's proteome, lipidome, and metabolome under fermentative and respiratory culture conditions, which correspond to the metabolic states of replicative and chronologically aging cells, respectively. Examination of the relationships among extended longevity phenotypes, protein, and metabolite levels revealed that although many of these nuclear-encoded mitochondrial genes carry out different functions, their inhibition attenuates a common mechanism that controls cytosolic ribosomal protein abundance, actin dynamics, and proteasome function to regulate lifespan. The principles of lifespan control learned through this work may be applicable to the regulation of lifespan in more complex organisms, since many aspects of mitochondrial function are highly conserved among eukaryotes.
    Keywords:  Aging; Metabolism; Mitochondrial proteins; Omics; Yeast
  12. Dis Model Mech. 2023 Apr 01. pii: dmm049783. [Epub ahead of print]16(4):
      The list of mitochondrial DNA (mtDNA) variants detected in individuals with neurodegenerative diseases is constantly growing. Evaluating their functional consequences and pathogenicity is not easy, especially when they are found in only a limited number of patients together with wild-type mtDNA (heteroplasmy). Owing to its amenability to mitochondrial genetic transformation and incapacity to stably maintain heteroplasmy, and the strong evolutionary conservation of the proteins encoded in mitochondria, Saccharomyces cerevisiae provides a convenient model to investigate the functional consequences of human mtDNA variants. We herein report the construction and energy-transducing properties of yeast models of eight MT-ATP6 gene variants identified in patients with various disorders: m.8843T>C, m.8950G>A, m.9016A>G, m.9025G>A, m.9029A>G, m.9058A>G, m.9139G>A and m.9160T>C. Significant defect in growth dependent on respiration and deficits in ATP production were observed in yeast models of m.8950G>A, m.9025G>A and m.9029A>G, providing evidence of pathogenicity for these variants. Yeast models of the five other variants showed very mild, if any, effect on mitochondrial function, suggesting that the variants do not have, at least alone, the potential to compromise human health.
    Keywords:   MT-ATP6 ; ATP synthase; LHON; MILS; Mitochondrial DNA mutation; Mitochondrial diseases; Yeast; mtDNA
  13. bioRxiv. 2023 Apr 04. pii: 2023.04.03.535431. [Epub ahead of print]
      Neurodevelopmental disorder genes are broadly expressed supporting the concept that these disorders are systemic diseases that impact neurodevelopment. We tested the systemic disease model focusing on Rett syndrome, which is caused by mutations in MECP2 . Transcriptomes and proteomes of organs and brain regions from Mecp2 -null mice and MECP2 -null human cells were assessed. Widespread changes in the transcriptome and proteome were identified in brain regions and organs of presymptomatic Mecp2 -null male mice and mutant cell lines. The extent of these transcriptome and proteome modifications was similar in cortex, liver, kidney, and skeletal muscle and more pronounced than in the hippocampus and striatum. In particular, Mecp2 - and MECP2 -sensitive proteomes were enriched in synaptic and metabolic annotated gene products, the latter encompassing lipid and mitochondrial pathways. MECP2 mutations altered pyruvate-dependent mitochondrial respiration while maintaining the capacity to use glutamine as a mitochondrial carbon source. We conclude that mutations in Mecp2 / MECP2 perturb lipid and mitochondrial metabolism systemically limiting cellular flexibility to utilize mitochondrial fuels.
  14. Methods Mol Biol. 2023 ;2662 67-75
      High-resolution respirometry is commonly used to quantify mitochondrial respiratory rates. In the respirometry chamber, a change in oxygen concentration is measured by a polarographic electrode to derive the rate of oxygen consumption (JO2). Here, we describe our adapted protocol to bioenergetically phenotype mitochondria from mouse brown adipose tissue (BAT). Given the presence of uncoupling protein 1 (UCP1), mitochondria from BAT provide unique challenges and opportunities in applying high-resolution respirometry to understand energy transduction through oxidative phosphorylation (OXPHOS).
    Keywords:  Bioenergetics; Mitochondria; Oroboros Oxygraph-2 K respirometry; Oxygen consumption rate; Respiration; Uncoupling protein 1
  15. Mol Metab. 2023 Apr 14. pii: S2212-8778(23)00061-3. [Epub ahead of print] 101727
      OBJECTIVE: Mitochondrial network dynamics may play role in metabolic homeostasis. Whether mitochondrial network dynamics are involved in adaptations to day-night fluctuations in energy supply and demand is unclear. Here we visualized and quantified the mitochondrial network morphology in human skeletal muscle of young healthy lean and older individuals with obesity over the course of 24 h METHODS: Muscle biopsies taken at 5 timepoints over a 24-hour period obtained from young healthy lean and older metabolically impaired obese males were analyzed for mitochondrial network integrity with confocal laser scanning microscopy. Variation of level of fragmentation over the course of the day were aligned with variation of mitochondrial respiration over the day RESULTS: Young healthy lean individuals displayed a day-night rhythmicity in mitochondrial network morphology, which aligned with the day-night rhythmicity of mitochondrial respiratory capacity, with a more fused network coinciding with higher mitochondrial respiratory capacity. In the older individuals with obesity, the mitochondrial network was more fragmented overall compared to young healthy lean individuals and completely lacked 24 h rhythmicity, which was also true for the mitochondrial respiratory capacity CONCLUSIONS: Our data shows a paralleled rhythmicity between mitochondrial network morphology and mitochondrial oxidative capacity, which oscillates over the course of a mimicked real-life day in human skeletal muscle of young, healthy lean individuals. In older individuals with obesity, the lack of a 24-hour rhythmicity in mitochondrial network connectivity was also aligned with a lack in respiratory capacity. This suggests that 24-hour rhythmicity in mitochondrial network connectivity is a determinant of rhythmicity in mitochondrial respiratory capacity. Thus, restoring mitochondrial network integrity may promote mitochondrial respiratory capacity and hence contribute to blunting the metabolic aberrations in individuals with a disturbed 24-hour rhythmicity in metabolism, like older individuals with obesity.
    Keywords:  Day-night rhythm; Mitochondrial function; Mitochondrial network integrity; Skeletal muscle
  16. Cell Rep. 2023 Apr 20. pii: S2211-1247(23)00431-X. [Epub ahead of print]42(5): 112420
      Sun et al. demonstrate that defects in autophagy cause nicotinamide adenine dinucleotide (NAD) depletion and neurotoxicity.1 Restoring NAD levels rescues cytotoxicity in autophagy-deficient neurons, providing a potential therapy for neurodegenerative and lysosomal storage diseases associated with autophagy defects.
  17. Cell Metab. 2023 Apr 11. pii: S1550-4131(23)00094-3. [Epub ahead of print]
      Even-chain acylcarnitine (AC) metabolites, most of which are generated as byproducts of incomplete fatty acid oxidation (FAO), are viewed as biomarkers of mitochondrial lipid stress attributable to one or more metabolic bottlenecks in the β-oxidation pathway. The origins and functional implications of FAO bottlenecks remain poorly understood. Here, we combined a sophisticated mitochondrial phenotyping platform with state-of-the-art molecular profiling tools and multiple two-state mouse models of respiratory function to uncover a mechanism that connects AC accumulation to lipid intolerance, metabolic inflexibility, and respiratory inefficiency in skeletal muscle mitochondria. These studies also identified a short-chain carbon circuit at the C4 node of FAO wherein reverse flux of glucose-derived acetyl CoA through medium-chain ketothiolase enhances lipid tolerance and redox stability in heart mitochondria by regenerating free CoA and NAD+. The findings help to explain why diminished FAO capacity, AC accumulation, and metabolic inflexibility are tightly linked to poor health outcomes.
    Keywords:  acylcarnitines; bioenergetics; exercise; fatty acid oxidation; heart; ketothiolase; metabolic flexibility; mitochondria; pyruvate; skeletal muscle
  18. Ann Transl Med. 2023 Mar 31. 11(6): 264
      Background and Objective: The mitochondrion is a crucial organelle for aerobic respiration and energy metabolism. It undergoes dynamic changes, including changes in its shape, function, and distribution through fission, fusion, and movement. Under normal conditions, mitochondrial dynamics are in homeostasis. However, once the balance is upset, the nervous system, which has high metabolic demands, will most likely be affected. Recent studies have shown that the imbalance of mitochondrial dynamics is involved in the occurrence and development of various neurological diseases. However, whether the regulation of mitochondrial dynamics can be used to treat neurological diseases is still unclear. We aimed to comprehensively analyze mitochondrial dynamics regulation and its potential role in the treatment of neurological diseases.Methods: A comprehensive literature review was carried out to understand the mechanisms and applications of mitochondrial dynamics in neurological diseases based on the literature available in PubMed, Web of Science, and Google Scholar.
    Key Content and Findings: This review discusses the molecular mechanisms related to mitochondrial dynamics and expounds upon the role of mitochondrial dynamics in the occurrence and development of neurodegenerative diseases, epilepsy, cerebrovascular disease, and brain tumors. Several clinically tested drugs with fewer side effects have been shown to improve the mitochondrial dynamics and nervous system function in neurological diseases.
    Conclusions: Disorders of mitochondrial dynamics can cause various neurological diseases. Elucidation of mechanisms and applications involved in mitochondrial dynamics will inform the development of new therapeutic targets and strategies for neurological diseases. Dynamin-related protein 1 (Drp1), as a highly relevant molecular for mitochondrial dynamics, might be a potential target for treating neurological diseases in the future.
    Keywords:  Alzeimer’s disease; Drp1; Parkinson’s disease; mitochondrial dynamics; mitochondrial fusion protein
  19. Brain. 2023 Apr 18. pii: awad127. [Epub ahead of print]
      Prolonged exposure to glucocorticoids, the main stress hormones, damages the brain and is a risk factor for depression and Alzheimer's disease. Two major drivers of glucocorticoid-related neurotoxicity are mitochondrial dysfunction and Tau pathology; however, the molecular/cellular mechanisms precipitating these events, and their causal relationship, remain unclear. Using cultured murine hippocampal neurons and 4-5-month-old mice treated with the synthetic glucocorticoid dexamethasone, we investigate the mechanisms underlying glucocorticoid-induced mitochondrial damage and Tau pathology. We find that glucocorticoids stimulate opening of the mitochondrial permeability transition pore via transcriptional upregulation of its activating component, Cyclophilin D. Inhibition of Cyclophilin D is protective against glucocorticoid-induced mitochondrial damage as well as Tau phosphorylation and oligomerization in cultured neurons. We further identify the mitochondrially-targeted compound mito-apocynin as an inhibitor of glucocorticoid-induced permeability transition pore opening, and show that this compound protects against mitochondrial dysfunction, Tau pathology, synaptic loss, and behavioral deficits induced by glucocorticoids in vivo. Finally, we demonstrate that mito-apocynin and the glucocorticoid receptor antagonist mifepristone rescue Tau pathology in cytoplasmic hybrid cells, an ex vivo Alzheimer's disease model wherein endogenous mitochondria are replaced with mitochondria from Alzheimer's subjects. These findings show that mitochondrial permeability transition pore opening is a precipitating factor in glucocorticoid-induced mitochondrial dysfunction, and that this event stimulates Tau pathogenesis. Our data also link glucocorticoids to mitochondrial dysfunction and Tau pathology in the context of Alzheimer's disease, and suggest that mitochondria are promising therapeutic targets for mitigating stress- and Tau-related brain damage.
    Keywords:  cyclophilin D; glucocorticoids; mPTP; mitochondria; stress; tau
  20. Brain. 2023 Apr 18. pii: awad131. [Epub ahead of print]
      Leber Hereditary Optic Neuropathy (LHON) is a primary inherited neurodegenerative disorder of the optic nerve. It has been ascribed to variants in the mitochondrial genome, mainly the m.3460G > A, m.11778G > A and m.14484T > C mutations in ND1, ND4 and ND6 respectively. Nonetheless, inconclusive molecular diagnosis is not uncommon. Recently, biallelic mutations in the NDUFS2, DNAJC30, MCAT and NDUFA12 nuclear genes have been identified in unresolved LHON cases, identifying an autosomal recessive LHON (arLHON, OMIM:619382). The clinical presentation of arLHON copies that of typical mtLHON, with an acute phase of sudden and severe vision loss, telangiectatic and tortuous vessels around the optic nerve, and swelling of the retinal nerve fiber layer (RNFL). This is followed by a chronic phase of RNFL loss, but eventually, affected individuals recovered partial or full visual acuity. Idebenone treatment significantly improved vision recovery in DNAJC30-associated patients. As mtLHON, arLHON predominantly affected male as compared to female carriers. The discovery of arLHON cases breaks with the dogma of exclusive maternal inheritance. It defines a new neuro-ophthalmo-genetic paradigm which should be considered in individuals manifesting a LHON phenotype, but inconclusive molecular diagnosis. NDUFS2, DNAJC30, MCAT and NDUFA12 should be investigated in these individuals, knowing that other arLHON genes might exist.
    Keywords:  Leber; autosomal; optic neuropathy; recessive
  21. Cell Stem Cell. 2023 Apr 14. pii: S1934-5909(23)00088-7. [Epub ahead of print]
      Cell-based therapies are being developed for various neurodegenerative diseases that affect the central nervous system (CNS). Concomitantly, the roles of individual cell types in neurodegenerative pathology are being uncovered by genetic and single-cell studies. With a greater understanding of cellular contributions to health and disease and with the arrival of promising approaches to modulate them, effective therapeutic cell products are now emerging. This review examines how the ability to generate diverse CNS cell types from stem cells, along with a deeper understanding of cell-type-specific functions and pathology, is advancing preclinical development of cell products for the treatment of neurodegenerative diseases.
    Keywords:  Alzheimer disease; GABAergic neurons; Parkinson disease; age-related macular degeneration; astrocytes; central nervous system; dopaminergic neurons; frontotemporal dementia; microglia; neurodegenerative disease; neurons; oligodendrocytes; organoids; photoreceptors; preclinical studies; progressive supranuclear palsy; retina; retinal pigment epithelium; stem cell therapy; transplantation
  22. Methods Mol Biol. 2023 ;2662 167-181
      Recombinant adeno-associated virus (AAV) vectors are attractive vehicles for gene therapy. Yet targeting adipose tissue is still a challenging task. We recently showed that a novel engineered hybrid serotype Rec2 displays high efficacy of gene transfer to both brown and white fat. Furthermore, the administration route influences the tropism and efficacy of Rec2 vector with oral administration transducing interscapular brown fat, while intraperitoneal injection preferentially targets visceral fat and liver. To restrict off-target transgene expression in the liver, we further develop a single rAAV vector harboring two expression cassettes: one using CBA promoter driving a transgene and another using a liver-specific albumin promoter driving a microRNA targeting the woodchuck posttranscriptional regulatory element (WPRE) sequence in this rAAV vector. In vivo studies by our lab and others have shown that the Rec2/dual-cassette vector system provides a powerful tool for gain-of-function and loss-of-function studies. Here we offer an updated protocol for AAV packaging and delivery to brown fat.
    Keywords:  Direct injection; Oral administration; rAAV serotype Rec2; rbown fat
  23. Mol Cells. 2023 Apr 20.
      Thermal stress induces dynamic changes in nuclear proteins and relevant physiology as a part of the heat shock response (HSR). However, how the nuclear HSR is fine-tuned for cellular homeostasis remains elusive. Here, we show that mitochondrial activity plays an important role in nuclear proteostasis and genome stability through two distinct HSR pathways. Mitochondrial ribosomal protein (MRP) depletion enhanced the nucleolar granule formation of HSP70 and ubiquitin during HSR while facilitating the recovery of damaged nuclear proteins and impaired nucleocytoplasmic transport. Treatment of the mitochondrial proton gradient uncoupler masked MRP-depletion effects, implicating oxidative phosphorylation in these nuclear HSRs. On the other hand, MRP depletion and a reactive oxygen species (ROS) scavenger non-additively decreased mitochondrial ROS generation during HSR, thereby protecting the nuclear genome from DNA damage. These results suggest that suboptimal mitochondrial activity sustains nuclear homeostasis under cellular stress, providing plausible evidence for optimal endosymbiotic evolution via mitochondria-to-nuclear communication.
    Keywords:  genome stability; heat shock response; mitohor­mesis; mitonuclear communication; nuclear proteostasis
  24. Brain. 2023 Apr 18. pii: awad128. [Epub ahead of print]
    European Spinocerebellar ataxia type 3/Machado-Joseph disease Initiative (ESMI) study group
      Transcriptional dysregulation has been described in spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD), an autosomal dominant ataxia caused by a polyglutamine expansion in the ataxin-3 protein. As ataxin-3 is ubiquitously expressed, transcriptional alterations in blood may reflect early changes that start before clinical onset and might serve as peripheral biomarkers in clinical and research settings. Our goal was to describe enriched pathways and report dysregulated genes which can track disease onset, severity, or progression in carriers of the ATXN3 mutation (pre-ataxic subjects and patients). Global dysregulation patterns were identified by RNA sequencing of blood samples from 40 carriers of ATXN3 mutation and 20 controls and further compared with transcriptomic data from post-mortem cerebellum samples of MJD patients and controls. Ten genes - ABCA1, CEP72, PTGDS, SAFB2, SFSWAP, CCDC88C, SH2B1, LTBP4, MEG3 and TSPOAP1 - whose expression in blood was altered in the pre-ataxic stage and simultaneously, correlated with ataxia severity in the overt disease stage, were analysed by quantitative real-time PCR in blood samples from an independent set of 170 SCA3/MJD subjects and 57 controls. Pathway enrichment analysis indicated the Gαi signalling and the oestrogen receptor signalling to be similarly affected in blood and cerebellum. SAFB2, SFSWAP and LTBP4 were consistently dysregulated in pre-ataxic subjects compared to controls, displaying a combined discriminatory ability of 79%. In patients, ataxia severity was associated with higher levels of MEG3 and TSPOAP1. We propose expression levels of SAFB2, SFSWAP and LTBP4 as well as MEG3 and TSPOAP1 as stratification markers of SCA3/MJD progression, deserving further validation in longitudinal studies and in independent cohorts.
    Keywords:   ATXN3 ; RNA-seq; ataxin-3; neurodegenerative disease; polyQ diseases
  25. Nat Commun. 2023 04 17. 14(1): 2194
      Mitochondria are hubs where bioenergetics, redox homeostasis, and anabolic metabolism pathways integrate through a tightly coordinated flux of metabolites. The contributions of mitochondrial metabolism to tumor growth and therapy resistance are evident, but drugs targeting mitochondrial metabolism have repeatedly failed in the clinic. Our study in pancreatic ductal adenocarcinoma (PDAC) finds that cellular and mitochondrial lipid composition influence cancer cell sensitivity to pharmacological inhibition of electron transport chain complex I. Profiling of patient-derived PDAC models revealed that monounsaturated fatty acids (MUFAs) and MUFA-linked ether phospholipids play a critical role in maintaining ROS homeostasis. We show that ether phospholipids support mitochondrial supercomplex assembly and ROS production; accordingly, blocking de novo ether phospholipid biosynthesis sensitized PDAC cells to complex I inhibition by inducing mitochondrial ROS and lipid peroxidation. These data identify ether phospholipids as a regulator of mitochondrial redox control that contributes to the sensitivity of PDAC cells to complex I inhibition.
  26. Ageing Res Rev. 2023 Apr 14. pii: S1568-1637(23)00094-6. [Epub ahead of print]87 101935
      Physical training is a potent therapeutic approach for improving mitochondrial health through peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) signaling pathways. However, comprehensive information regarding the physical training impact on PGC-1α in the different physiological systems with advancing age is not fully understood. This review sheds light on the frontier-of-knowledge data regarding the chronic effects of exercise on the PGC-1α signaling pathways in rodents and humans. We address the molecular mechanisms involved in the different tissues, clarifying the precise biological action of PGC-1α, restricted to the aged cell type. Distinct exercise protocols (short and long-term) and modalities (aerobic and resistance exercise) increase the transcriptional and translational PGC-1α levels in adipose tissue, brain, heart, liver, and skeletal muscle in animal models, suggesting that this versatile molecule induces pleiotropic responses. However, PGC-1α function in some human tissues (adipose tissue, heart, and brain) remains challenging for further investigations. PGC-1α is not a simple transcriptional coactivator but supports a biochemical environment of mitochondrial dynamics, controlling physiological processes (primary metabolism, tissue remodeling, autophagy, inflammation, and redox balance). Acting as an adaptive mechanism, the long-term effects of PGC-1α following exercise may reflect the energy demand to coordinate multiple organs and contribute to cellular longevity.
    Keywords:  Age; Metabolism; Mitochondria function; PGC-1α; Physical activity
  27. CNS Neurosci Ther. 2023 Apr 20.
      AIMS: Elamipretide (EPT), a novel mitochondria-targeted peptide, has been shown to be protective in a range of diseases. However, the effect of EPT in spinal cord injury (SCI) has yet to be elucidated. We aimed to investigate whether EPT would inhibit pyroptosis and protect against SCI.METHODS: After establishing the SCI model, we determined the biochemical and morphological changes associated with pyroptosis, including neuronal cell death, proinflammatory cytokine expression, and signal pathway levels. Furthermore, mitochondrial function was assessed with flow cytometry, quantitative real-time polymerase chain reaction, and western blot.
    RESULTS: Here, we demonstrate that EPT improved locomotor functional recovery following SCI as well as reduced neuronal loss. Moreover, EPT inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis occurrence and decreased pro-inflammatory cytokines levels following SCI. Furthermore, EPT alleviated mitochondrial dysfunction and reduced mitochondrial reactive oxygen species level.
    CONCLUSION: EPT treatment may protect against SCI via inhibition of pyroptosis.
    Keywords:  elamipretide; mitochondrial dysfunction; neuroinflammation; pyroptosis; spinal cord injury
  28. J Gerontol A Biol Sci Med Sci. 2023 Apr 17. pii: glad106. [Epub ahead of print]
      Advancing age and many disease states are associated with declines in nicotinamide adenine dinucleotide (NAD +) levels. Preclinical studies suggest that boosting NAD + abundance with precursor compounds, such as nicotinamide riboside or nicotinamide mononucleotide, has profound effects on physiological function in models of aging and disease. Translation of these compounds for oral supplementation in humans has been increasingly studied within the last ten years; however, the clinical evidence that raising NAD + concentrations can improve physiological function is unclear. The goal of this review was to synthesize the published literature on the effects of chronic oral supplementation with NAD + precursors on healthy aging and age-related chronic diseases. We identified nicotinamide riboside, nicotinamide riboside co-administered with pterostilbene, and nicotinamide mononucleotide as the most common candidates in investigations of NAD +-boosting compounds for improving physiological function in humans. Studies have been performed in generally healthy midlife and older adults, adults with cardiometabolic disease risk factors such as overweight and obesity, and numerous patient populations. Supplementation with these compounds is safe, tolerable, and can increase the abundance of NAD + and related metabolites in multiple tissues. Dosing regimens and study durations vary greatly across interventions, and small sample sizes limit data interpretation of physiological outcomes. Limitations are identified and future research directions are suggested to further our understanding of the potential efficacy of NAD +-boosting compounds for improving physiological function and extending human healthspan.
    Keywords:  Clinical Trials; Nicotinamide Riboside; Nutrition; Physiology; Successful Aging
  29. PLoS Biol. 2023 Apr;21(4): e3002058
      Genes associated with risk for brain disease exhibit characteristic expression patterns that reflect both anatomical and cell type relationships. Brain-wide transcriptomic patterns of disease risk genes provide a molecular-based signature, based on differential co-expression, that is often unique to that disease. Brain diseases can be compared and aggregated based on the similarity of their signatures which often associates diseases from diverse phenotypic classes. Analysis of 40 common human brain diseases identifies 5 major transcriptional patterns, representing tumor-related, neurodegenerative, psychiatric and substance abuse, and 2 mixed groups of diseases affecting basal ganglia and hypothalamus. Further, for diseases with enriched expression in cortex, single-nucleus data in the middle temporal gyrus (MTG) exhibits a cell type expression gradient separating neurodegenerative, psychiatric, and substance abuse diseases, with unique excitatory cell type expression differentiating psychiatric diseases. Through mapping of homologous cell types between mouse and human, most disease risk genes are found to act in common cell types, while having species-specific expression in those types and preserving similar phenotypic classification within species. These results describe structural and cellular transcriptomic relationships of disease risk genes in the adult brain and provide a molecular-based strategy for classifying and comparing diseases, potentially identifying novel disease relationships.
  30. Neuroscience. 2023 Apr 19. pii: S0306-4522(23)00164-1. [Epub ahead of print]
      Mitochondrial damage is a central mechanism involved in neurological disorders as Alzheimer's, and Parkinson's disease and amyotrophic lateral sclerosis. Energy production is the most studied mitochondrial function; however, mitochondria are also involved in processes like calcium buffering homeostasis, and cell death control during apoptosis and necrosis. Using transmission electron microscopy, in this in vivo study in males rats we describe ultrastructural mitochondrial alterations of spinal motor neurons along chronic AMPA-induced excitotoxicity, which has been described as one of the most relevant mechanisms in ALS disease. Mitochondrial alterations begin with a crest swelling, which progresses to a full mitochondrial swelling and crest disruption. Changes on the mitochondrial morphology from elongated to a circular shape also occur along the AMPA-excitotoxicity process. In addition, by combining the TUNEL assay and immunohistochemistry for mitochondrial enzymes, we show evidence of mitochondrial DNA damage. Evidence of mitochondrial alterations during an AMPA-excitotoxic event is relevant because resembles the mitochondrial alterations previously reported in ALS patients and in transgenic familial ALS models, suggesting that a chronic excitotoxic model can be related to sporadic ALS (as has been shown in recent papers), which represent more than the 90% of the ALS cases. Understanding the mechanisms involved in motor neuron degenerative process, such as the ultrastructural mitochondrial changes permits to design strategies for MN-degeneration treatments in ALS.
    Keywords:  Excitotoxicity; Mitochondria; Motor neurons; Spinal cord; Ultrastructure