Jul 2026· Istanbul University Journal of Health Sciences Research· 0 citations· 21 references
TL;DR
These findings reveal pronounced tissue divergence in mitochondrial remodeling in DARS2-related cardioskeletal myopathy and underscore caution when interpreting colchicine-based autophagy flux assays in heart versus skeletal muscle.
Abstract
Objective: Mitochondrial translation defects are a major cause of cardioskeletal myopathies, yet how mitochondrial biogenesis and autophagic turnover diverge between striated muscles in vivo remains unclear.Material and Methods: Using a heart- and skeletal muscle–specific mitochondrial aspartyl-tRNA synthetase (DARS2) knockout mouse model, mitochondrial protein markers (TOM20, VDAC) and biogenesis-associated transcripts (Tfam, Pgc-1α) were compared between the heart and quadriceps, and autophagy markers (LC3B-I/II and P62/SQSTM1) were assessed at baseline and following colchicine administration.Results: Knockout hearts displayed strong biogenesis-associated remodeling; in contrast, quadriceps displayed no induction of these markers. Steady-state autophagy markers in knockout hearts demonstrated reduced LC3B-II (and LC3B-II/I ratio) alongside marked P62 accumulation, which is consistent with impaired autophagic degradation/cargo clearance. Notably, colchicine did not elicit the expected LC3B-II accumulation in the heart, complicating straightforward flux interpretation in the cardiomyopathic context. In the quadriceps, colchicine robustly increased LC3B-II levels and the LC3B-II/LC3B-I ratio in both control and knockout muscles, indicating measurable autophagic response and supporting the technical feasibility of colchicine-based flux assays in this tissue.Conclusion: Together, these findings reveal pronounced tissue divergence in mitochondrial remodeling in DARS2-related cardioskeletal myopathy and underscore caution when interpreting colchicine-based autophagy flux assays in heart versus skeletal muscle.
Cardiac mitochondrial remodelling is a hallmark of type 2 diabetes-linked heart failure (T2DM-HF). We previously reported that mitochondrial morphological changes occur in early-stage disease and identified down-regulation of the mitochondrial protein Miro1 (Rhot1). Neuronal Miro1 regulates mitochondrial movement but the role of cardiac Miro1 remains poorly understood. Therefore, we generated a cardiac-specific Miro1 knockout (Miro1cko) mouse model to investigate how cardiomyocyte-Miro1 deficiency affects cardiac and mitochondrial structure-function. Miro1cko mice compared to controls develop mild diastolic and systolic dysfunction and electrical abnormalities, cellular hypertrophy and fibrosis. Miro1cko leads to aberrant mitochondrial respiration and elevated H₂O₂ production, consistent with electron microscopy showing disrupted cristae morphology, with putative links to Myosin19 down-regulation. Three-dimensional electron microscopy identified mitochondrial remodelling with interfibrillar mitochondria (IFM) ~50% smaller with an increased surface complexity. Since fusion-fission protein expression was unchanged these data identify Miro1 as a regulator of mitochondrial morphology. Mitochondrial density increases (34% Miro1cko; 30% control), with abnormal IFM clustering, which we suggest is associated with impaired mitophagy since PINK1 and Parkin are down-regulated (~80% and ~ 60% respectively) and imaging flow cytometry of isolated primary cardiomyocytes identified an ~2-fold reduction to mitochondrial clearance indicative of blunted mitophagy. Heterozygous knockout mice, which display a milder cardiac phenotype, rapidly developed HF symptoms when given a high fat diet with L-NAME. In conclusion, loss of Miro1 drives multiple aberrant mitochondrial remodelling events culminating in cardiac dysfunction and predisposes towards accelerated metabolic-HF development. Loss of Miro1 may represent a critical mechanistic link in T2DM-HF pathogenesis and therefore a potential therapeutic target.
Sarah Kassab, Zainab Albalawi, Asim M Khojah et al.· Journal of Molecular and Cel...· 0 citations
The findings support mitophagy inefficiency due to pathway saturation as a key pathogenetic mechanism in trisomic cells and identify metformin as a pharmacological tool capable of relieving the proteostatic overload intrinsic to trisomy 21.
Nunzia Mollo, Rosalba Natale, M. D’Ariano et al.· Cellular and Molecular Life...· 0 citations
Age-related muscle atrophy is closely associated with mitochondrial dysfunction and ferroptosis. This study established a D-gal-induced sarcopenia model in aged mice and a C2C12/GM17940 cell myotube senescence model, with young/control, old/D-gal, and formononetin (FMN) intervention groups. After shSIRT1 transfection and mitochondrial-targeted antioxidant Mito-C intervention, the effects and mechanism of FMN were detected by measuring mouse phenotypic indicators (lean mass, hindlimb muscle mass, grip strength) and cell indicators (viability, mitochondrial membrane potential, ROS, ATP, ferroptosis-related proteins). Results showed that FMN improved lean mass, grip strength, mitochondrial membrane potential, and ATP production, while reducing ROS and ferroptosis by regulating ACSL4, GPX4, and SLC7A11. Mechanistically, FMN exerted protective effects via the SIRT1/PGC-1α pathway, which was partially attenuated by SIRT1 knockdown or Mito-C. Collectively, FMN alleviates age-related sarcopenia by targeting mitochondrial function and ferroptosis, providing potential targets for sarcopenia treatment.
Xiao Wang, Linhan Zhong, Jun Yang et al.· International Journal of Bio...· 0 citations
Sepsis-induced myopathy (SIM) is characterized by skeletal muscle dysfunction associated with mitochondrial calcium overload. The mitochondria-associated endoplasmic reticulum membrane (MAM) plays a crucial role in mediating mitochondrial calcium uptake. Although MFN2 and the IP3R–GRP75–VDAC1 complex have each been implicated in mitochondrial calcium regulation, their respective contributions and potential interplay in the pathogenesis of SIM remain poorly understood.
A murine sepsis model was established by cecal ligation and puncture (CLP). Skeletal muscle function was assessed by compound muscle action potential (CMAP) recording and forelimb grip strength testing. Gastrocnemius muscle histology was evaluated by H&E and WGA staining. Tibialis anterior muscles were analyzed by immunofluorescence and transmission electron microscopy (TEM) to characterize MAM ultrastructure. Protein expression was quantified by western blotting, and MFN2 mRNA levels were measured by qPCR. Co-immunoprecipitation was performed to assess GRP75–VDAC1 protein interaction. Mitochondrial and cytoplasmic calcium levels were monitored using Rhod-2 AM and Fluo-4 AM, respectively.
Sepsis induced skeletal muscle atrophy and dysfunction both in vivo and in vitro. IP3R-dependent calcium transfer at MAM was associated with pathological mitochondrial calcium overload, and pharmacological IP3R inhibition with 2-APB attenuated mitochondrial calcium uptake and ameliorated muscle atrophy. Concurrently, sepsis-induced MFN2 downregulation was associated with reduced ER-mitochondria distance, further promoting mitochondrial calcium overload. AAV-mediated MFN2 overexpression restored ER-mitochondria distance and was associated with reduced VDAC1 protein expression, attenuated GRP75–VDAC1 interaction, collectively contributing to mitigation of mitochondrial calcium overload and amelioration of skeletal muscle atrophy.
MFN2 attenuates sepsis-induced mitochondrial calcium overload through two complementary mechanisms: increasing ER-mitochondria distance and modulating GRP75–VDAC1 interaction and IP3R–GRP75–VDAC1 complex assembly. These findings identify MFN2 as a potential regulator of MAM-mediated mitochondrial calcium homeostasis in SIM and suggest it may represent a therapeutic target for sepsis-induced skeletal muscle dysfunction.
Xuexin Li, Fei He, Yun Wang et al.· Skeletal Muscle· 0 citations
Parkinson’s disease (PD) is widely regarded as a disorder of dopaminergic neurons that involves mitochondrial dysfunction, impaired mitophagy, and oxidative stress. However, the nature and significance of skeletal muscle pathology remain unclear. In this study, we used Caenorhabditis elegans, which lack muscle stem cells in adulthood, to examine the effects of PDR-1/Parkin deficiency on mitochondrial homeostasis and motor function under conditions where muscle regeneration does not occur. Silencing of pdr-1 attenuated age-related mitochondrial fragmentation in body-wall muscle cells but was associated with later impairments in locomotor activity and loss of nuclear GFP signals, suggesting progressive muscle cell damage. By day 2 of adulthood, mitochondrial reactive oxygen species (mtROS) levels were elevated in muscle cells subjected to pdr-1 RNAi, and in the pdr-1(gk448) mutant this mtROS elevation was accompanied by a reduction in mitochondrial membrane potential (ΔΨm). In vivo imaging further revealed elevated mitochondrial Ca2+ levels ([Ca2+]mito) in PDR-1-deficient muscle cells. Moreover, the mtROS increase associated with PDR-1 deficiency was suppressed in mcu-1 mutants. These findings support a model in which MCU-1-dependent elevation of [Ca2+]mito contributes to oxidative mitochondrial defects in PDR-1/Parkin-deficient muscle.
Masahiro Kawasumi, Mika Teranishi· Antioxidants· 0 citations
How aging of human neurons affects dynamics of essential organelle such as mitochondria and autophagosomes remains largely unknown. MicroRNA-induced directly reprogrammed neurons (miNs) derived from adult fibroblasts retain age-associated signatures of the donor, enabling the study of age-dependent features in human neurons, including longitudinal isogenic samples. Transcriptomic analysis revealed that neurons derived from elderly individuals are characterized by gene expression changes associated with the regulation of autophagosomes, lysosomes, and mitochondria, compared to young counterparts. To clarify these changes at the cellular level, we performed live-cell imaging of cellular organelles in miNs from donors of different ages. Older donor miNs exhibit decreased mitochondrial membrane potential, which surprisingly co-occurs with a significant increase in mitochondrial fission and fusion events. We posit that the increased fission and fusion of mitochondria may reflect age-dependent compensation for impaired mitochondrial turnover, perhaps due to changes in macroautophagy/autophagy. We subsequently identified a significant decrease in autophagosome acidification in neurons derived from individuals > 65 years compared to younger donors, and a corresponding age-dependent reduction in neuritic lysosomes resulting in fewer lysosomes available to acidify autophagosomes. This age-dependent deficit in autolysosome flux was rescued by promoting autophagosome generation through TFEB, which also reversed the age-dependent increase in mitochondrial fission and fusion and improved mitochondrial health. Partial organelle recovery occurred after inducing mitophagy or inhibiting mitochondrial fission. Together, this work reveals a mechanism by which aging reduces autophagic flux secondary to a loss of neuritic lysosomes, resulting in mitochondria-intrinsic mechanisms to avoid loss of energy production.
Eva Klinman, Ji-sun Kwon, Roland E. Dolle et al.· Autophagy· 0 citations
