Findings indicate that TWEAK suppression may represent a promising strategy for preserving muscle mass and metabolic homeostasis during aging, though its capacity to fully restore functional capacity requires further investigation.
Abstract
Mitochondrial dysfunction is an important cause of sarcopenia, and TWEAK/Fn14, as one of the major muscle wasting cytokines, its role in the development of sarcopenia by regulating mitochondrial biogenesis remains unclear. Expression of TWEAK in old and young mice was both detected. TWEAK was silenced in C2C12 myocytes using lentiviral vectors. Immunofluorescence, western blot, real-time polymerase chain reaction (RT-PCR), and ELISA were enrolled to analyze the effects of TWEAK on myotube size, mitochondrial content, mitochondrial ROS, and inflammatory factors. Additionally, aged mice received two injections of AAV9 vectors at 15 and 17 months of age. Upon reaching 18 months of age, the effects of TWEAK knockdown on grip strength, muscle mass, and gastrocnemius muscle indices were evaluated. TWEAK/Fn14 expression was significantly increased in old mice (
p
< 0.001). Compared with young controls, old mice exhibited a significant decrease in grip strength (
p
< 0.001) and a significant increase in lean mass (
p
< 0.05), whereas no significant difference was observed in fat content. In DEX-treated C2C12 myotubes, TWEAK knockdown significantly increased myotube diameter, enhanced ATP content and mitochondrial quantity, upregulated protein expression of SIRT1, PGC-1α, and p-AMPK, and inhibited mitochondrial ROS, Ca
2+
levels, p-p38 expression, and the secretion of inflammatory cytokines (TNF-α, IL-1β, IL-6, and iNOS). In aged mice, TWEAK knockdown did not significantly alter forelimb grip strength or lean mass, but significantly increased fat mass (
p
< 0.05). Mechanistically, TWEAK knockdown promoted AMPK signaling, inhibited p38 MAPK activation, enhanced mitochondrial biogenesis, and reduced serum levels of IL-1β, IL-6, and iNOS (
p
< 0.05), whereas serum TNF-α levels showed no significant difference. TWEAK knockdown attenuates age-related skeletal muscle mass loss and improves mitochondrial biogenesis in skeletal muscle, accompanied by modulated inflammatory factor release and altered AMPK-p38 MAPK signaling activity. However, no significant improvement in forelimb grip strength was observed in the in vivo experiment. These findings indicate that TWEAK suppression may represent a promising strategy for preserving muscle mass and metabolic homeostasis during aging, though its capacity to fully restore functional capacity requires further investigation.
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
Sarcopenia is characterized by the progressive loss of skeletal muscle mass and strength, accompanied by impaired regenerative capacity. This study examined age-related changes in skeletal muscle regeneration and the associated expression of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and myogenin (MyoG). Male C57BL/6 mice aged 3, 13, and 23 months were subjected to barium chloride (BaCl2)-induced tibialis anterior muscle injury. In parallel, C2C12 cells were exposed to repeated low-dose hydrogen peroxide (H2O2) to induce senescence-associated changes under oxidative stress, and the effect of the TWEAK inhibitor L524 was evaluated. Muscle mass and grip strength showed age-dependent declines. Following BaCl2 injury, MyoD expression was induced similarly across age groups, whereas MyoG and embryonic myosin heavy chain expression significantly decreased with advancing age. TWEAK expression increased in injured muscle with age, while p-4E-BP1 showed no clear age-dependent change. In C2C12 cells, repeated H2O2 exposure at 100 μM, which maintained cell viability above 90%, induced senescence-associated changes, reduced myotube formation, increased TWEAK expression, and decreased MyoG expression, whereas treatment with the TWEAK inhibitor L524 attenuated the H2O2-associated reduction in MyoG expression. Collectively, these findings suggest that TWEAK signaling may be associated with oxidative stress and age-related impairments in muscle regeneration.
Jin-Hwa Kim, Hyun-Tae Kim, Jeong-won Kim et al.· Experimental Gerontology· 0 citations
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
ABSTRACT Background Sarcopenia is a major contributor to frailty and mortality in ageing and obesity and is tightly linked to metabolic dysfunction. Imeglimin is a first‐in‐class oral hypoglycaemic agent targeting mitochondrial function; however, despite the central role of mitochondria in skeletal muscle homeostasis, its effects on skeletal muscle under sarcopenia‐relevant conditions remain unclear. Methods Imeglimin was administered to male C57BL/6 mice with high‐fat diet (HFD)–induced obesity for 6 weeks and to naturally aged (18 months old) male mice for 12 weeks. Skeletal muscle fibre morphology and transcriptomic profiles were analysed in fast‐ and slow‐twitch muscles. In parallel, C2C12 myotubes were exposed to palmitate with or without imeglimin, and inflammatory gene expression and reactive oxygen species (ROS) generation were assessed. Results Imeglimin significantly increased the cross‐sectional area (CSA) of Type II fibres in the extensor digitorum longus (EDL) muscle of HFD‐fed mice (+66%, p < 0.01 vs. controls). Transcriptomic analyses revealed suppression of conserved molecular signatures of muscle atrophy, including activation of immediate‐early genes and inflammatory pathways (−62% to −79%, p < 0.05 vs. HFD‐fed mice). In palmitate‐treated C2C12 myotubes, imeglimin attenuated lipotoxicity‐induced inflammatory gene expression (−28% to −72%, p < 0.05 vs. controls) with reduced ROS generation, consistent with its cell‐autonomous effect on myocytes. Notably, in naturally aged mice, 12‐week imeglimin treatment preserved EDL muscle fibre size (+14%, p < 0.05 vs. controls) without altering systemic glucose tolerance, accompanied by transcriptomic changes overlapping with those observed in the HFD model (−27% to −82%, p < 0.05 vs. aged controls). Conclusions Imeglimin attenuates skeletal muscle atrophy in obesity and ageing, accompanied by coordinated suppression of stress‐ and inflammation‐associated transcriptional programmes. These findings indicate that pharmacological regulation of mitochondrial stress responses influences skeletal muscle vulnerability under chronic metabolic stress and identify skeletal muscle as a previously underappreciated target of imeglimin action.
Yangli Ye, Diandian Qian, Ikumi Nomura et al.· Journal of Cachexia, Sarcope...· 0 citations
OBJECTIVE
The aim of this study was to explore the potential role of microRNA (miR)-133a, the nucleotide-binding oligomerization domain, leucine-rich repeat family pyrin domain-containing 3 (NLRP3) inflammasome and Sirtuin1 (SIRT1) in the effects of electroacupuncture (EA) on disuse muscular atrophy in mice.
METHODS
C2C12 cells were analyzed for protein expression of NLRP3, SIRT1, myogenin (MyoG) and myosin heavy chain protein (MyHC) after being transfected with a miR-133a-1 mimetic or miR-133a-3p inhibitor. Disuse muscular atrophy was induced in mice by tail suspension, and the mice either remained untreated (DA group) or received EA (frequency 20 Hz, intensity 1 mA, 15 min per day). The morphology of skeletal muscle was measured by muscle/body weight ratios, muscle fiber cross-sectional area (CSA) and expression of Atrogin-1 and Muscle RING finger-1 (MuRF1). miR-133a, NLRP3, apoptosis-associated speck-like protein (ASC), caspase-1 and SIRT1 were detected sequentially. Differentiation of skeletal muscle was examined by measurement of MyoG and MyHC.
RESULTS
In our in vitro experiments, overexpression of miR-133a downregulated the expression of NLRP3 and SIRT1, and upregulated the expression of MyoG and MyHC. In our in vivo experiments, EA effectively ameliorated muscle wet weight and fiber CSA in the mouse model of disuse muscular atrophy, and decreased Atrogin-1 and MuRF1. EA also significantly increased the expression of miR-133a, inhibited the expression of NLRP3, ASC, caspase-1 and SIRT1, and increased the expression of MyoG and MyHC.
CONCLUSIONS
These results indicate that EA-induced reductions of disuse muscular atrophy may be related to miR-133a. First, miR-133a may inhibit NLRP3 inflammasome activation to reduce muscle loss. Second, miR-133a may regulate SIRT1 expression to induce skeletal muscle differentiation and potentially promote muscle tissue recovery.
Xing Cai, Yalian Zhang, Zhong Yang et al.· Acupuncture in Medicine· 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