Jun 2026· Frontiers in Cell and Developmental Biology· Vol 14· 1 citation· 24 references
Medicine
TL;DR
It is suggested that UA promotes mitochondrial functional adaptation during myogenic differentiation, with accompanying changes in myogenic phenotype, without clear evidence of altered steady-state mitophagy/autophagy markers or mitochondrial morphology.
Abstract
Introduction Skeletal muscle differentiation in the C2C12 myoblast model requires extensive mitochondrial remodeling to meet rising bioenergetic demands through coordinated changes in biogenesis, dynamics, and respiratory adaptation. Urolithin A (UA), a gut microbiota-derived metabolite of ellagitannins, improves mitochondrial health, but its role in late-stage myogenic differentiation remains unclear. Methods C2C12 myotubes were treated with UA (2 μM) for 72 h during late-stage differentiation (days 3–6). Mitochondrial signaling, respiratory capacity, myogenic morphology, and ultrastructure were assessed by Western blot, high-resolution respirometry, hematoxylin–eosin staining, and transmission electron microscopy. Results UA was non-cytotoxic and increased AMPKα phosphorylation and PGC-1α expression, whereas TOM20, MFN2, and OPA1 were unchanged. Mitophagy/autophagy-related markers (p-ULK1, p62, BNIP3L/NIX, LC3-II/I) were not altered, indicating no detectable changes in steady-state autophagy under the conditions tested. UA selectively increased OXPHOS Complex I and II abundance and enhanced maximal uncoupled respiration, and was associated with increased myotube diameter and myogenic marker abundance. No overt ultrastructural differences were observed by electron microscopy. Discussion These findings suggest that UA promotes mitochondrial functional adaptation during myogenic differentiation, with accompanying changes in myogenic phenotype, without clear evidence of altered steady-state mitophagy/autophagy markers or mitochondrial morphology.
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.
S. Dogan· Istanbul University Journal...· 0 citations
BACKGROUND
Palmitic acid (PA)-driven lipotoxicity in skeletal muscle is associated with excessive reactive oxygen species (ROS) and disturbed mitochondrial dynamics. This study aimed to characterize PA-induced alterations in oxidative status and fusion-fission balance in C2C12 skeletal muscle cells and to test whether N-acetylcysteine (NAC), dichloroacetate (DCA), or metformin mitigate these changes.
METHODS
Differentiated C2C12 myotubes were exposed to PA under conditions detailed in the Methods. Intracellular ROS was quantified, antioxidant defenses were assessed by activities of catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD), and mitochondrial dynamics were evaluated by expression of the fusion protein mitofusin 1 (MFN1) and the fission protein dynamin-related protein 1 (DRP1), together with morphological assessment of mitochondrial fragmentation.
RESULTS
PA exposure increased ROS and was accompanied by decreases in CAT, GPx, and SOD activities. PA shifted mitochondrial dynamics toward fission, with reduced MFN1, elevated DRP1, and increased mitochondrial fragmentation. Co-treatment with NAC, DCA, or metformin attenuated PA-induced ROS accumulation, improved antioxidant enzyme activities relative to PA alone, and partially normalized MFN1 and DRP1 expression, with reduced fragmentation.
CONCLUSIONS
In an in vitro C2C12 model, PA-induced lipotoxicity is associated with oxidative stress and a fusion-fission imbalance favoring mitochondrial fragmentation. NAC, DCA, and metformin mitigate these alterations and help preserve mitochondrial homeostasis. These findings support targeting oxidative stress and mitochondrial dynamics as a potential approach to counteract mitochondrial dysfunction under lipotoxic conditions.
Zhixing Cai, Yue Chen, Lili Chen et al.· Journal of Oleo Science· 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
BACKGROUND
Sertoli cells (SCs) provide essential metabolic support for spermatogenesis, including lactate production for developing germ cells. While insulin's role in SC glucose metabolism is well-established, its regulation of fatty acid (FA) uptake and oxidation-critical for germ cell support and residual body clearance-remains unknown. Insulin deficiency in diabetes mellitus (DM) impairs male fertility through mechanisms that may involve disrupted SC metabolism.
OBJECTIVES
To determine whether insulin regulates FA uptake and oxidation in SCs and to elucidate mechanistic links between insulin deficiency and impaired spermatogenesis.
MATERIALS AND METHODS
The TM4 mouse SC line was cultured under defined in vitro conditions in the presence of insulin (10 µg/mL) versus under insulin-deprived conditions for 18 h. FA metabolism was assessed using RT-qPCR (FAT/CD36, ACADL, and CPT1A), Western blotting, 1H-NMR spectroscopy, functional FA uptake assay, Oil Red O staining, JC-1 mitochondrial assessment, and Seahorse real-time metabolic analysis.
RESULTS
Insulin deprivation significantly reduced glucose consumption, glutamine consumption, and lactate production. FAT/CD36 expression and FA uptake capacity decreased markedly, with reduced intracellular lipid droplet accumulation. Conversely, FA oxidation enzyme expression (CPT1A, ACADL) remained unchanged, as did mitochondrial membrane potential and oxygen consumption rates with/without etomoxir.
DISCUSSION AND CONCLUSION
In the TM4 mouse SC line under defined in vitro conditions, insulin selectively regulates FA uptake while maintaining no control over downstream FA oxidation. This dissociation reveals that insulin modulates FA entry for storage and/or biosynthesis, while FA oxidation operates constitutively. Impaired FA uptake under insulin deficiency may compromise SC support for spermatogenesis, providing a mechanistic link to male infertility in DM that requires confirmation in primary SCs and in vivo diabetic models.
M. Llavanera, Ana D Martins, C. Santos et al.· Andrology· 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
PURPOSE: Sarcopenia is characterized by progressive skeletal muscle atrophy associated with impaired proteostasis, mitochondrial dysfunction, and chronic metabolic stress. Through transcriptomic analysis of aged skeletal muscle, CCL5 was identified as a stress-responsive immune-related factor consistently upregulated under sarcopenic conditions. This study aimed to investigate the role of CCL5 in a palmitate (PA)-induced in vitro model of sarcopenia. METHODS: Fully differentiated C2C12 myotubes were treated with PA to induce metabolic stress–associated atrophy. Morphological changes, myogenic signaling, protein turnover pathways, mitochondrial function, and apoptosis-related markers were analyzed. Candidate genes identified from transcriptomic analysis of aged skeletal muscle were validated in the PA-induced atrophy model, and the effects of exogenous recombinant CCL5 treatment were examined. RESULTS: PA treatment recapitulated key pathological features of muscle atrophy, including reduced myotube diameter, suppressed myogenic signaling, inhibition of the AKT–mTOR pathway, increased proteolysis, mitochondrial dysfunction, and activation of apoptosis. Among the candidate genes identified through transcriptomic analysis of aged skeletal muscle in our previous study, Ccl5 was markedly upregulated in PA-treated myotubes. Notably, exogenous CCL5 treatment partially restored myotube diameter under PA-induced stress. However, CCL5 did not significantly alter canonical regulatory pathways of muscle atrophy, including protein synthesis, protein degradation, or mitochondrial biogenesis. Instead, CCL5 selectively restored the expression of desmin, an intermediate filament protein critical for myofiber structural integrity. CONCLUSIONS: CCL5 may attenuate metabolic stress–induced myotube atrophy by preserving cytoskeletal stability rather than regulating classical proteostasis pathways, highlighting a potential CCL5–CCR5–mediated mechanism for maintaining skeletal muscle structural integrity.
Chan-Young So, Sujin Kim, Keren Esther Kristina Mantik et al.· Exercise Science· 0 citations
