Mitochondrial morphology is altered in atrophied skeletal muscle of aged mice

Abstract Skeletal muscle aging is associated with a progressive decline in muscle mass and strength, a process termed sarcopenia. Evidence suggests that accumulation of mitochondrial dysfunction plays a causal role in sarcopenia, which could be triggered by impaired mitophagy. Mitochondrial function, mitophagy and mitochondrial morphology are interconnected aspects of mitochondrial biology, and may coordinately be altered with aging. However, mitochondrial morphology has remained challenging to characterize in muscle, and whether sarcopenia is associated with abnormal mitochondrial morphology remains unknown. Therefore, we assessed the morphology of SubSarcolemmal (SS) and InterMyoFibrillar (IMF) mitochondria in skeletal muscle of young (8-12wk-old) and old (88-96wk-old) mice using a quantitative 2-dimensional transmission electron microscopy approach. We show that sarcopenia is associated with larger and less circular SS mitochondria. Likewise, aged IMF mitochondria were longer and more branched, suggesting increased fusion and/or decreased fission. Accordingly, although no difference in the content of proteins regulating mitochondrial dynamics (Mfn1, Mfn2, Opa1 and Drp1) was observed, a mitochondrial fusion index (Mfn2-to-Drp1 ratio) was significantly increased in aged muscles. Our results reveal that sarcopenia is associated with complex changes in mitochondrial morphology that could interfere with mitochondrial function and mitophagy, and thus contribute to aging-related accumulation of mitochondrial dysfunction and sarcopenia

Segregation of Virulent Influenza A(H1N1) Variants in the Lower Respiratory Tract of Critically Ill Patients during the 2010–2011 Seasonal Epidemic

BACKGROUND: Since its appearance in 2009, the pandemic influenza A(H1N1) virus circulated worldwide causing several severe infections. METHODS: Respiratory samples from patients with 2009 influenza A(H1N1) and acute respiratory distress attending 24 intensive care units (ICUs) as well as from patients with lower respiratory tract infections not requiring ICU admission and community upper respiratory tract infections in the Lombardy region (10 million inhabitants) of Italy during the 2010-2011 winter-spring season, were analyzed. RESULTS: In patients with severe ILI, the viral load was higher in bronchoalveolar lavage (BAL) with respect to nasal swab (NS), (p<0.001) suggesting a higher virus replication in the lower respiratory tract. Four distinct virus clusters (referred to as cluster A to D) circulated simultaneously. Most (72.7%, n = 48) of the 66 patients infected with viruses belonging to cluster A had a severe (n = 26) or moderate ILI (n = 22). Amino acid mutations (V26I, I116M, A186T, D187Y, D222G/N, M257I, S263F, I286L/M, and N473D) were observed only in patients with severe ILI. D222G/N variants were detected exclusively in BAL samples. CONCLUSIONS: Multiple virus clusters co-circulated during the 2010-2011 winter-spring season. Severe or moderate ILI were associated with specific 2009 influenza A(H1N1) variants, which replicated preferentially in the lower respiratory tract

The impact of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, mitochondrial content, and intramyocellular lipids in men

Abtract Background: The exact impact of ageing on skeletal muscle phenotype and mitochondrial and lipid content remains controversial, probably because physical activity, which greatly influences muscle physiology, is rarely accounted for. The present study was therefore designed to investigate the effects of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, and mitochondrial and intramyocellular lipid content in men. Methods: Recreationally active young adult (20–30 yo; YA); active (ACT) and sedentary (SED) middle-age (50–65 yo; MA-ACT and MA-SED); and older (65 + yo; 65 + ACT and 65 + SED) and pre-frail older (65 + PF) men were recruited. Muscle biopsies from the vastus lateralis were collected to assess, on muscle cross sections, muscle phenotype (using myosin heavy chain isoforms immunolabelling), the fibre type-specific content of mitochondria (by quantifying the succinate dehydrogenase stain intensity), and the fibre type-specific lipid content (by quantifying the Oil Red O stain intensity). Results: Only 65 + SED and 65 + PF displayed significantly lower overall and type IIa fibre sizes vs. YA. 65 + SED displayed a lower type IIa fibre proportion vs. YA. MA-SED and 65 + SED displayed a higher hybrid type IIa/IIx fibre proportion vs. YA. Sedentary and pre-frail, but not active, men displayed lower mitochondrial content irrespective of fibre type vs. YA. 65 + SED, but not 65 + ACT, displayed a higher lipid content in type I fibres vs. YA. Finally, mitochondrial content, but not lipid content, was positively correlated with indices of muscle function, functional capacity, and insulin sensitivity across all subjects. Conclusions: Taken altogether, our results indicate that ageing in sedentary men is associated with (i) complex changes in muscle phenotype preferentially affecting type IIa fibres; (ii) a decline in mitochondrial content affecting all fibre types; and (iii) an increase in lipid content in type I fibres. They also indicate that physical activity partially protects from the effects of ageing on muscle phenotype, mitochondrial content, and lipid accumulation. No skeletal specific muscle phenotype of pre-frailty was observed

On improving the accuracy of simple aerial towed-cable system models

We outline a novel procedure for improving the accuracy of a simple one-link aerial towed-cable system model. The primary objective of this work is to provide a systematic framework for matching the dynamical motion of a simple aerial towed-cable system model with that of a correspondingly more complex model. The final outcome is to achieve a compromise between a model's representativeness and the ease with which it can be used for control purposes. By modifying the cable length and the payload drag coefficient of the simple model, the equilibrium position of the cable tip may be matched analytically to that of the more complex model. The modified cable length and drag coefficient are then used in dynamic simulations and shown to dramatically improve the accuracy of the simple model

Remote payload transportation using an aircraft-towed flexible cable system

We demonstrate the concept of using a cable towed beneath an aircraft to transport payloads without landing. The cable is modelled using a lumped parameter approach and the equations of motion are derived using Kane's method. Full three-dimensional dynamic coupling is preserved between the aircraft dynamics and the motion of the cable and payload. The system is controlled via aircraft maneuvering and prescribing the reel acceleration of the cable. A simulated payload transportation operation is numerically represented as a nonlinear optimal control problem and solved using a direct transcription technique implemented in Matlab. Numerical results are presented for a typical payload transportation operation

Clinical use of virally inactived plasma. The experience of Blood Transfusion Unit in Mantova, Italy

Riassunto. Introduzione. Il plasma fresco congelato (PFC) è un emocomponente il cui utilizzo clinico è molto diffuso in tutto il mondo. La sicurezza trasfusionale di questo prodotto è assicurata da test, obbligatori per legge, che vengono eseguiti su ogni singola donazione, ma può essere ulteriormente incrementata tramite l’utilizzo di alcune procedure tra cui il blu di metilene e la tecnica di inattivazione virale con solvente-detergente. Il Dipartimento di Medicina Trasfusionale ed Ematologia di Mantova, dal 2007, ha introdotto l’utilizzo di plasma di grado farmaceutico virus-inattivato con metodica solvente-detergente (Plasmasafe, Kedrion) in sostituzione al PFC da singolo donatore. Le linee guida per l’utilizzo di entrambi i prodotti sono le medesime. Materiali e metodi. Con l’obiettivo primario di valutare l’efficacia terapeutica e la sicurezza di Plasmasafe, si è deciso di monitorare gli eventi trasfusionali con questo prodotto nei pazienti del reparto di Rianimazione e Terapia Intensiva dell’Ospedale Carlo Poma di Mantova, eseguendo dosaggi di alcuni parametri coagulativi (PT, aPTT, ATIII, fibrinogeno, PC, PS, FV, FVII, FVIII) prima dell’infusione di Plasmasafe e a distanza di 24 ore dalla trasfusione. Risultati. Da un punto di vista clinico è stata confermata l’efficacia di Plasmasafe poiché si è sempre avuto arresto o riduzione dei sanguinamenti in atto; inoltre, non si sono registrate reazioni avverse post-trasfusionali di nessuna entità. I risultati di laboratorio statisticamente più eloquenti riguardano i dosaggi valutati come attività (PC, PS, ATIII, FV, FVII, FVIII) per i quali si è osservato un deciso incremento successivo all’infusione di una dose terapeutica di Plasmasafe. Infine, i pazienti trasfusi con Plasmasafe hanno ricevuto un volume significativamente inferiore rispetto ad una coorte storica di pazienti trattati con il PFC (503 mL con Plasmasafe versus 1549 mL con il PFC, P<0,001). Conclusioni. I risultati del nostro studio hanno chiaramente documentato che il Plasmasafe, un prodotto virus inattivato con un contenuto standard dei fattori della coagulazione, è un prodotto sicuro efficace ed economicamente vantaggioso in grado di correggere rapidamente i difetti emostatici nei pazienti critici

Protective role of Parkin in skeletal muscle contractile and mitochondrial function

International audienceParkin is an E3 ubiquitin ligase encoded by the Park2 gene. Parkin has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are sequestered in autophagosomes and delivered to lysosomes for degradation. Although Parkin has been mainly studied for its implication in neuronal degeneration in Parkinson disease, its role in other tissues remains largely unknown. In the present study, we investigated the skeletal muscles of Park2 knockout (Park2-/- ) mice to test the hypothesis that Parkin plays a physiological role in mitochondrial quality control in normal skeletal muscle, a tissue highly reliant on mitochondrial content and function. We first show that the tibialis anterior (TA) of Park2-/- mice display a slight but significant decrease in its specific force. Park2-/- muscles also show a trend for type IIB fibre hypertrophy without alteration in muscle fibre type proportion. Compared to Park2+/+ muscles, the mitochondrial function of Park2-/- skeletal muscles was significantly impaired, as indicated by the significant decrease in ADP-stimulated mitochondrial respiratory rates, uncoupling, reduced activities of respiratory chain complexes containing mitochondrial DNA (mtDNA)-encoded subunits and increased susceptibility to opening of the permeability transition pore. Muscles of Park2-/- mice also displayed a decrease in the content of the mitochondrial pro-fusion protein Mfn2 and an increase in the pro-fission protein Drp1 suggesting an increase in mitochondrial fragmentation. Finally, Park2 ablation resulted in an increase in basal autophagic flux in skeletal muscles. Overall, the results of the present study demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in normal skeletal muscles

The Lipid Metabolism as Target and Modulator of BOLD‐100 Anticancer Activity: Crosstalk with Histone Acetylation

Abstract The leading first‐in‐class ruthenium‐complex BOLD‐100 currently undergoes clinical phase‐II anticancer evaluation. Recently, BOLD‐100 is identified as anti‐Warburg compound. The present study shows that also deregulated lipid metabolism parameters characterize acquired BOLD‐100‐resistant colon and pancreatic carcinoma cells. Acute BOLD‐100 treatment reduces lipid droplet contents of BOLD‐100‐sensitive but not ‐resistant cells. Despite enhanced glycolysis fueling lipid accumulation, BOLD‐100‐resistant cells reveal diminished lactate secretion based on monocarboxylate transporter 1 (MCT1) loss mediated by a frame‐shift mutation in the MCT1 chaperone basigin. Glycolysis and lipid catabolism converge in the production of protein/histone acetylation substrate acetyl‐coenzymeA (CoA). Mass spectrometric and nuclear magnetic resonance analyses uncover spontaneous cell‐free BOLD‐100‐CoA adduct formation suggesting acetyl‐CoA depletion as mechanism bridging BOLD‐100‐induced lipid metabolism alterations and histone acetylation‐mediated gene expression deregulation. Indeed, BOLD‐100 treatment decreases histone acetylation selectively in sensitive cells. Pharmacological targeting confirms histone de‐acetylation as central mode‐of‐action of BOLD‐100 and metabolic programs stabilizing histone acetylation as relevant Achilles’ heel of acquired BOLD‐100‐resistant cell and xenograft models. Accordingly, histone gene expression changes also predict intrinsic BOLD‐100 responsiveness. Summarizing, BOLD‐100 is identified as epigenetically active substance acting via targeting several onco‐metabolic pathways. Identification of the lipid metabolism as driver of acquired BOLD‐100 resistance opens novel strategies to tackle therapy failure

SLC25A46 is required for mitochondrial lipid homeostasis and cristae maintenance and is responsible for Leigh syndrome

Abstract Mitochondria form a dynamic network that responds to physiological signals and metabolic stresses by altering the balance between fusion and fission. Mitochondrial fusion is orchestrated by conserved GTPases MFN1/2 and OPA1, a process coordinated in yeast by Ugo1, a mitochondrial metabolite carrier family protein. We uncovered a homozygous missense mutation in SLC25A46, the mammalian orthologue of Ugo1, in a subject with Leigh syndrome. SLC25A46 is an integral outer membrane protein that interacts with MFN2, OPA1, and the mitochondrial contact site and cristae organizing system (MICOS) complex. The subject mutation destabilizes the protein, leading to mitochondrial hyperfusion, alterations in endoplasmic reticulum (ER) morphology, impaired cellular respiration, and premature cellular senescence. The MICOS complex is disrupted in subject fibroblasts, resulting in strikingly abnormal mitochondrial architecture, with markedly shortened cristae. SLC25A46 also interacts with the ER membrane protein complex EMC, and phospholipid composition is altered in subject mitochondria. These results show that SLC25A46 plays a role in a mitochondrial/ER pathway that facilitates lipid transfer, and link altered mitochondrial dynamics to early‐onset neurodegenerative disease and cell fate decisions

The leukodystrophy mutation Polr3b R103H causes homozygote mouse embryonic lethality and impairs RNA polymerase III biogenesis

Abstract Recessive mutations in the ubiquitously expressed POLR3A and POLR3B genes are the most common cause of POLR3-related hypomyelinating leukodystrophy (POLR3-HLD), a rare childhood-onset disorder characterized by deficient cerebral myelin formation and cerebellar atrophy. POLR3A and POLR3B encode the two catalytic subunits of RNA Polymerase III (Pol III), which synthesizes numerous small non-coding RNAs. We recently reported that mice homozygous for the Polr3a mutation c.2015G > A (p.Gly672Glu) have no neurological abnormalities and thus do not recapitulate the human POLR3-HLD phenotype. To determine if other POLR3-HLD mutations can cause a leukodystrophy phenotype in mouse, we characterized mice carrying the Polr3b mutation c.308G > A (p.Arg103His). Surprisingly, homozygosity for this mutation was embryonically lethal with only wild-type and heterozygous animals detected at embryonic day 9.5. Using proteomics in a human cell line, we found that the POLR3B R103H mutation severely impairs assembly of the Pol III complex. We next generated Polr3aG672E/G672E/Polr3b+/R103Hdouble mutant mice but observed that this additional mutation was insufficient to elicit a neurological or transcriptional phenotype. Taken together with our previous study on Polr3a G672E mice, our results indicate that missense mutations in Polr3a and Polr3b can variably impair mouse development and Pol III function. Developing a proper model of POLR3-HLD is crucial to gain insights into the pathophysiological mechanisms involved in this devastating neurodegenerative disease