1.Application of electrical impedance tomography-guided PEEP titration in acute respiratory distress syndrome patients with intra-abdominal hypertension
World Journal of Emergency Medicine 2026;17(1):70-75
BACKGROUND Individualized positive end-expiratory pressure (PEEP) titration is a crucial technique in mechanical ventilation therapy for acute respiratory distress syndrome (ARDS) patients with intra-abdominal hypertension (IAH). This study aimed to evaluate the effectiveness of electrical impedance tomography (EIT)-guided PEEP titration in this population.
METHODS: This prospective study enrolled 36 ARDS patients, including 22 patients with IAH and 14 without IAH. All the patients underwent EIT-guided PEEP titration at the intersection point between alveolar overdistension and collapse during a decremental PEEP trial. The changes in pulmonary ventilation distribution, respiratory mechanics and hemodynamics during the titration process were observed.
RESULTS: After EIT-guided PEEP titration was performed, the PEEP, peak inspiratory pressure and plateau pressure increased significantly (P<0.05). Furthermore, no significant differences were observed in respiratory system compliance, tidal volume, driving pressure, or the 4*DP+RR index between the two groups (P>0.05). The mechanical power increased in the non-IAH (NIAH) group after PEEP titration (P<0.05). Ventilation in gravity-dependent lung regions significantly increased (P<0.05), and the oxygenation index (PaO2/FiO2) improved significantly (P<0.05) in both groups. However, blood pressure, heart rate, respiratory rate, central venous pressure, and lactate levels did not significantly change. In the IAH group, the PaO2/FiO2 ratio improved less than that in the NIAH group did (P<0.05).
CONCLUSION: In our study, individualized PEEP titration guided by EIT improved oxygenation in ARDS patients with concomitant IAH without significantly affecting hemodynamics. The presence of IAH may limit the improvement of oxygenation during EIT-guided PEEP titration.
2.Analysis of specific risks and long-term toxicities of BCR-ABL1 TKIs in pediatric patients with hematological malignancies
Luping WEN ; Fan XIA ; Ziqiong LIAO ; Benjie ZHOU ; Hui CHEN
China Pharmacy 2026;37(8):1050-1055
OBJECTIVE To analyze the specific risks and long-term toxicities of four BCR-ABL1 tyrosine kinase inhibitors (TKIs)(imatinib, dasatinib, nilotinib, and bosutinib) in pediatric patients with hematological malignancies. METHODS Adverse drug event (ADE) reports submitted to the the United States FDA Adverse Event Reporting System (FAERS) from January 2012 to December 2024, with imatinib, dasatinib, nilotinib, and bosutinib as the primary suspect drugs, were collected. Data mining was performed using the reporting odds ratio method and proportional reporting ratio method. ADE terms were classified and summarized by system organ class (SOC) and preferred term (PT) according to the Medical Dictionary for Drug Regulatory Activities (MedDRA, version 26.0). Meanwhile, the ADE reports were divided by age into the adult group (≥18 years) and the pediatric group (<18 years) to compare the differences in ADE between the two groups. RESULTS A total of 1 512 pediatric ADE reports were included: 993 for imatinib, 391 for dasatinib, 112 for nilotinib, and 16 for bosutinib. Among the reported ADEs, the patients were mainly aged 12-<18 years; the reports mainly originated from the United States, France, and Japan; and the primary indications were chronic myeloid leukemia and acute lymphoblastic leukemia. A total of 5 256 ADE signals were mined, among which 235 were positive signals, involving 1 103 PT across 27 SOC. The top five PT ranked by the number of positive signals were nausea, febrile neutropenia, abdominal pain, neutropenia, and anemia. The top two SOC were general disorders and administration site conditions, and gastrointestinal disorders. Compared with the adult group, the pediatric group had relatively higher proportions of events related to infections and infestations as well as blood and lymphatic system disorders. Pediatric long-term toxicity signals primarily included growth retardation, accompanied by signals related to endocrine system abnormalities and bone metabolism abnormalities. Specific signals included imatinib-associated septic shock, dasatinib-associated chylothorax, and nilotinib-associated electrocardiographic QT interval prolongation. CONCLUSIONS When pediatric patients use BCR-ABL1 TKIs, priority monitoring of infection risk and hematologic parameters is required, along with long-term follow-up of height, endocrine, and bone metabolism parameters. Targeted screening and management of drug-specific signals should be performed to ensure the long-term safety of pediatric medication.
3.Fibroblast Growth Factors in Parkinson’s Disease: Multi-target Neuroprotective Mechanisms Involving Neuroinflammation, Cellular Stress, and Ferroptosis
Hui WANG ; Zi-Gui ZHOU ; Teng-Teng HAN ; Chang-Zhi YANG ; Xue-Wen TIAN
Progress in Biochemistry and Biophysics 2026;53(4):855-874
Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the selective loss of dopaminergic neurons in the substantia nigra pars compacta and the pathological accumulation ofα‑synuclein. Although extensive progress has been made in elucidating its pathogenesis, current therapeutic approaches remain largely symptomatic, and effective disease-modifying treatments are still unavailable. Increasing evidence indicates that PD is driven by the interaction of multiple pathological processes, including neuroinflammation, iron homeostasis dysregulation and ferroptosis, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, oxidative stress, and impaired protein homeostasis, which together contribute to neuronal vulnerability and degeneration. Fibroblast growth factors (FGFs) comprise a family of 22 ligands that play important roles in neural development, stress responses, metabolic regulation, and the maintenance of nervous system homeostasis. Recent studies have shown that several FGF family members, such as FGF1, FGF2, FGF9, and FGF21, exert neuroprotective effects in cellular and animal models of PD. These effects include the regulation of inflammatory responses, oxidative stress, iron homeostasis, cellular stress adaptation, and neuronal survival. Compared with therapeutic strategies targeting a single pathogenic pathway, FGFs appear to influence multiple disease-related processes, suggesting their potential relevance to the complex pathophysiology of PD. Experimental evidence indicates that altered FGF signaling may contribute to dopaminergic neuron dysfunction through the coordinated regulation of several interconnected mechanisms. FGFs have been reported to modulate neuroinflammation by affecting the activation of microglia and astrocytes, thereby influencing the inflammatory environment in the central nervous system. In addition, FGFs are involved in the regulation of iron homeostasis and ferroptosis, partly through antioxidant signaling pathways associated with NRF2, SLC7A11, and GPX4. Moreover, FGFs can alleviate ER stress and mitochondrial dysfunction by activating intracellular signaling pathways such as PI3K/AKT, AMPK-PGC-1α, as well as SIRT1-dependent programs, which support cellular energy metabolism and redox balance. Recent advances in single-cell and spatial transcriptomic studies further suggest that FGF signaling is not limited to neuron-intrinsic mechanisms but also involves interactions among different glial cell types. Altered FGF ligand-receptor communication between astrocytes and oligodendrocytes has been observed in PD models and is associated with increased susceptibility of dopaminergic neurons to oxidative stress and ferroptosis. These findings indicate that the biological effects of FGFs are influenced by cell type and disease stage and may vary under different pathological conditions. In this review, we summarize recent progress in understanding the roles of FGF family members in PD, with a focus on their involvement in iron homeostasis dysregulation and ferroptosis, neuroinflammation, cellular stress responses, and neuronal protection and regeneration. By integrating current evidence, this review aims to provide a clearer understanding of how FGFs participate in PD pathogenesis and to offer a theoretical basis for future studies exploring their potential value in disease-modifying therapeutic strategies.
4.The Structure and Function of The YopJ Family Effectors in The Bacterial Type III Secretion System
Ao-Ning LI ; Wen-Bo LI ; Yu-Ying LU ; Min-Hui ZHU ; Yu-Long QIN ; Yong ZHAO ; Zhao-Huan ZHANG
Progress in Biochemistry and Biophysics 2026;53(3):516-533
The Type III Secretion System (T3SS) serves as a pivotal virulence apparatus for numerous Gram-negative bacterial pathogens, enabling them to infect both animal and plant hosts. Functioning as a molecular syringe, the T3SS directly translocates bacterial effector proteins from the bacterial cytoplasm into the interior of eukaryotic host cells. These effectors are central weapons that precisely manipulate a wide spectrum of host cellular physiological processes, ranging from cytoskeletal dynamics to immune signaling, to establish a favorable niche for bacterial survival and proliferation. Among the diverse arsenal of T3SS effectors, the YopJ family constitutes a critical group of virulence factors. Members of this family are characterized by a conserved catalytic triad structure—a hallmark of the CE clan of cysteine proteases that has been evolutionarily repurposed to confer acetyltransferase activity. A defining and intriguing feature of these enzymes is their stringent dependence on a host-derived eukaryotic cofactor, inositol hexakisphosphate (IP6), for allosteric activation. This requirement acts as a sophisticated molecular safeguard, ensuring enzymatic activity only within the appropriate host environment, thereby preventing detrimental effects on the bacterium itself. While seminal studies on individual members such as Yersinia’s YopJ and Salmonella’s AvrA have provided deep mechanistic insights, a systematic and integrative understanding of the structure-function relationships across the entire family remains fragmented. Key questions persist regarding how a conserved catalytic core has diverged to recognize distinct host substrates in different kingdoms of life. To address this gap, this article provides a systematic review of the YopJ family, focusing on three interconnected aspects: their structural features, their catalytic mechanism, and their divergent immunosuppressive strategies in animal versus plant hosts. By conducting a comparative analysis of the sequences and resolved three-dimensional structures of three representative members (e.g., HopZ1a, PopP2, AvrA), we elucidate regions of significant variation embedded within the conserved core catalytic architecture. These variable regions, often involving surface loops and substrate-binding interfaces, are crucial determinants of target specificity and functional specialization. The functional divergence of this effector family is most apparent when comparing their modes of action in different hosts. In animal hosts, YopJ-family effectors primarily sabotage innate immune signaling pathways. They achieve this by acetylating key serine and threonine residues within the activation loops of critical kinases in the MAPK and NF‑κB pathways. This post-translational modification blocks the phosphorylation and subsequent activation of these kinases, leading to potent suppression of inflammatory cytokine production. Conversely, in plant hosts, the strategy broadens to dismantle the two-tiered plant immune system. YopJ homologs target a more diverse set of substrates, including immune-associated receptor-like cytoplasmic kinases (RLCKs), microtubule networks via tubulin acetylation (which disrupts cellular trafficking and signaling), and transcription factors central to defense gene regulation. This multi-target approach effectively suppresses both Pattern-Triggered Immunity (PTI) and Effector-Triggered Immunity (ETI). In conclusion, this synthesis aims to deepen the mechanistic understanding of YopJ family-mediated pathogenesis by integrating structural biology with cellular function across host kingdoms. Elucidating the precise molecular basis for substrate selection—how conserved platforms achieve target diversity—is a major frontier. Furthermore, this knowledge provides a vital theoretical foundation for developing novel anti-virulence strategies. Targeting the conserved IP6-binding pocket or the catalytic acetyltransferase activity itself represents a promising avenue for designing broad-spectrum inhibitors that could disarm this critical family of bacterial effectors, potentially offering new therapeutic approaches against a range of pathogenic bacteria.
5.The Regulatory Effects and Mechanisms of Piezo1 Channel on Chondrocytes and Bone Metabolic Dysregulation in Osteoarthritis
Yan LI ; Tao LIU ; Yu-Biao GU ; Hui-Qing TIAN ; Lei ZHANG ; Bi-Hui BAI ; Zhi-Jun HE ; Wen CHEN ; Jin-Peng LI ; Fei LI
Progress in Biochemistry and Biophysics 2026;53(3):564-576
Osteoarthritis (OA), a highly prevalent degenerative joint disease worldwide, is defined by articular cartilage degradation, abnormal bone remodeling, and persistent chronic inflammation. It severely compromises patients’ quality of life, and currently, there is no radical cure. Abnormal mechanical stress is widely regarded as a core driver of OA pathogenesis, and the exploration of mechanical signal perception and transduction mechanisms has become crucial for deciphering OA’s pathophysiological processes. Piezo1, a key mechanosensitive cation channel belonging to the Piezo protein family, has recently gained significant attention due to its pivotal role in mediating cellular responses to mechanical stimuli in joint tissues. This review systematically examines Piezo1’s expression patterns, regulatory mechanisms, and pathological functions in OA, with a particular focus on its dual roles in modulating chondrocyte homeostasis and bone metabolism disorders, while also delving into the underlying molecular signaling pathways and potential therapeutic implications. Piezo1, consisting of approximately 2 500 amino acids and forming a unique trimeric propeller-like structure, is widely expressed in chondrocytes, osteocytes, mesenchymal stem cells, and synovial cells. It exhibits permeability to cations such as Ca2+, K+, and Na+, and directly responds to membrane tension changes induced by mechanical stimuli like fluid shear stress and mechanical overload. In OA patients and animal models, Piezo1 expression is significantly upregulated, especially in cartilage regions subjected to abnormal mechanical stress (e.g., human temporomandibular joint cartilage). This overexpression is closely associated with aggravated cartilage degeneration, increased chondrocyte apoptosis, accelerated cellular senescence, and intensified inflammatory responses. Mechanical overload and pro-inflammatory cytokines (e.g., IL-1β) are key inducers of Piezo1 upregulation: IL-1β activates the PI3K/AKT/mTOR signaling pathway to enhance Piezo1 expression, forming a pathogenic positive feedback loop that inhibits chondrocyte autophagy, promotes apoptosis, and further accelerates joint degeneration. Mechanistically, Piezo1 mediates OA progression through multiple interconnected pathways. When activated by mechanical stress, Piezo1 triggers excessive Ca2+ influx, leading to endoplasmic reticulum stress (ERS) and mitochondrial dysfunction, which directly induce chondrocyte apoptosis. This process involves the activation of downstream signaling cascades such as cGAS-STING and YAP-MMP13/ADAMTS5. YAP, a transcriptional regulator, upregulates the expression of matrix metalloproteinase 13 (MMP13) and aggrecanase (ADAMTS5), thereby accelerating cartilage matrix degradation. Additionally, Piezo1-driven Ca2+ overload promotes the accumulation of reactive oxygen species (ROS) and upregulates senescence markers (p16 and p21), accelerating chondrocyte senescence via the p38MAPK and NF-κB pathways. Senescent chondrocytes secrete senescence-associated secretory phenotype (SASP) factors (e.g., IL-6, IL-1β), further amplifying joint inflammation. In terms of bone metabolism, Piezo1 maintains joint homeostasis by promoting the differentiation of fibrocartilage stem cells into chondrocytes and balancing bone formation and resorption through regulating the FoxC1/YAP axis and RANKL/OPG ratio. Therapeutically, targeting Piezo1 shows promising potential. Preclinical studies have demonstrated that Piezo1 inhibitors (e.g., GsMTx4) can reduce joint damage and alleviate pain in OA mice. Simultaneously, siRNA-mediated co-silencing of Piezo1 and TRPV4 (another mechanosensitive channel) decreases intracellular Ca2+ concentration, inhibits chondrocyte apoptosis, and promotes cartilage repair. Conditional knockout of Piezo1 using Gdf5-Cre transgenic mice alleviates cartilage degeneration in post-traumatic OA models by downregulating MMP13 and ADAMTS5 expression. Despite existing challenges, such as off-target effects of inhibitors, inefficient local drug delivery, and interindividual genetic variability, strategies like developing selective Piezo1 antagonists, optimizing targeted nanocarriers, and combining Piezo1-targeted therapy with physical therapy provide viable avenues for clinical translation. The authors propose that Piezo1 serves as a critical therapeutic target for OA, and future research should focus on deciphering its context-dependent regulatory networks, developing tissue-specific intervention strategies, and validating their efficacy and safety in clinical trials to address the unmet medical needs of OA patients.
6.Acute Inflammatory Pain Induces Sex-different Brain Alpha Activity in Anesthetized Rats Through Optically Pumped Magnetometer Magnetoencephalography
Meng-Meng MIAO ; Yu-Xuan REN ; Wen-Wei WU ; Yu ZHANG ; Chen PAN ; Xiang-Hong LIN ; Hui-Dan LIN ; Xiao-Wei CHEN
Progress in Biochemistry and Biophysics 2025;52(1):244-257
ObjectiveMagnetoencephalography (MEG), a non-invasive neuroimaging technique, meticulously captures the magnetic fields emanating from brain electrical activity. Compared with MEG based on superconducting quantum interference devices (SQUID), MEG based on optically pump magnetometer (OPM) has the advantages of higher sensitivity, better spatial resolution and lower cost. However, most of the current studies are clinical studies, and there is a lack of animal studies on MEG based on OPM technology. Pain, a multifaceted sensory and emotional phenomenon, induces intricate alterations in brain activity, exhibiting notable sex differences. Despite clinical revelations of pain-related neuronal activity through MEG, specific properties remain elusive, and comprehensive laboratory studies on pain-associated brain activity alterations are lacking. The aim of this study was to investigate the effects of inflammatory pain (induced by Complete Freund’s Adjuvant (CFA)) on brain activity in a rat model using the MEG technique, to analysis changes in brain activity during pain perception, and to explore sex differences in pain-related MEG signaling. MethodsThis study utilized adult male and female Sprague-Dawley rats. Inflammatory pain was induced via intraplantar injection of CFA (100 μl, 50% in saline) in the left hind paw, with control groups receiving saline. Pain behavior was assessed using von Frey filaments at baseline and 1 h post-injection. For MEG recording, anesthetized rats had an OPM positioned on their head within a magnetic shield, undergoing two 15-minute sessions: a 5-minute baseline followed by a 10-minute mechanical stimulation phase. Data analysis included artifact removal and time-frequency analysis of spontaneous brain activity using accumulated spectrograms, generating spectrograms focused on the 4-30 Hz frequency range. ResultsMEG recordings in anesthetized rats during resting states and hind paw mechanical stimulation were compared, before and after saline/CFA injections. Mechanical stimulation elevated alpha activity in both male and female rats pre- and post-saline/CFA injections. Saline/CFA injections augmented average power in both sexes compared to pre-injection states. Remarkably, female rats exhibited higher average spectral power 1 h after CFA injection than after saline injection during resting states. Furthermore, despite comparable pain thresholds measured by classical pain behavioral tests post-CFA treatment, female rats displayed higher average power than males in the resting state after CFA injection. ConclusionThese results imply an enhanced perception of inflammatory pain in female rats compared to their male counterparts. Our study exhibits sex differences in alpha activities following CFA injection, highlighting heightened brain alpha activity in female rats during acute inflammatory pain in the resting state. Our study provides a method for OPM-based MEG recordings to be used to study brain activity in anaesthetized animals. In addition, the findings of this study contribute to a deeper understanding of pain-related neural activity and pain sex differences.
7.Identification of core genes of osteoarthritis by bioinformatics
Xuekun ZHU ; Heng LIU ; Hui FENG ; Yunlong GAO ; Lei WEN ; Xiaosong CAI ; Ben ZHAO ; Min ZHONG
Chinese Journal of Tissue Engineering Research 2025;29(3):637-644
BACKGROUND:At present,osteoarthritis has become a major disease affecting the quality of life of the elderly,and the therapeutic effect is poor,often focusing on preventing the disease process,and the pathogenesis of osteoarthritis is still not fully understood.Bioinformatics analysis was carried out to explore the main pathogenesis of osteoarthritis and related mechanisms of gene coding regulation. OBJECTIVE:To screen core differential genes with a major role in osteoarthritis by gene expression profiling. METHODS:Datasets were downloaded from the Gene Expression Omnibus(GEO):GSE114007,GSE117999,and GSE129147.Differential genes in the GSE114007 and GSE117999 data collections were screened using R software,performing differential genes to weighted gene co-expression network analysis.The module genes most relevant to osteoarthritis were selected to perform protein interaction analysis.Candidate core genes were selected using the cytocape software.The candidate core genes were subsequently subjected to least absolute shrinkage and selection operator regression and COX analysis to identify the core genes with a key role in osteoarthritis.The accuracy of the core genes was validated using an external dataset,GSE129147. RESULTS AND CONCLUSION:(1)A total of 477 differential genes were identified,265 differential genes associated with osteoarthritis were obtained by weighted gene co-expression network analysis,and 8 candidate core genes were identified.The least absolute shrinkage and selection operator regression analysis finally yielded a differential gene ASPM with core value that was externally validated.(2)It is concluded that abnormal gene ASPM expression screened by bioinformatics plays a key central role in osteoarthritis.
8.Bioactive metabolites: A clue to the link between MASLD and CKD?
Wen-Ying CHEN ; Jia-Hui ZHANG ; Li-Li CHEN ; Christopher D. BYRNE ; Giovanni TARGHER ; Liang LUO ; Yan NI ; Ming-Hua ZHENG ; Dan-Qin SUN
Clinical and Molecular Hepatology 2025;31(1):56-73
Metabolites produced as intermediaries or end-products of microbial metabolism provide crucial signals for health and diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD). These metabolites include products of the bacterial metabolism of dietary substrates, modification of host molecules (such as bile acids [BAs], trimethylamine-N-oxide, and short-chain fatty acids), or products directly derived from bacteria. Recent studies have provided new insights into the association between MASLD and the risk of developing chronic kidney disease (CKD). Furthermore, alterations in microbiota composition and metabolite profiles, notably altered BAs, have been described in studies investigating the association between MASLD and the risk of CKD. This narrative review discusses alterations of specific classes of metabolites, BAs, fructose, vitamin D, and microbiota composition that may be implicated in the link between MASLD and CKD.
9.Local overexpression of miR-429 sponge in subcutaneous white adipose tissue improves obesity and related metabolic disorders.
Liu YAO ; Wen-Jing XIU ; Chen-Ji YE ; Xin-Yu JIA ; Wen-Hui DONG ; Chun-Jiong WANG
Acta Physiologica Sinica 2025;77(3):441-448
Obesity is a worldwide health problem. An imbalance in energy metabolism is an important cause of obesity and related metabolic diseases. Our previous studies showed that inhibition of miR-429 increased the protein level of uncoupling protein 1 (UCP1) in beige adipocytes; however, whether local inhibition of miR-429 in subcutaneous adipose tissue affects diet-induced obesity and related metabolic disorders remains unclear. The aim of this study was to investigate the effect of local overexpression of miR-429 sponge in subcutaneous adipose tissue on obesity and related metabolic disorders. The control adeno-associated virus (AAV) or AAV expressing the miR-429 sponge was injected into mouse inguinal white adipose tissue. Seven days later, the mice were fed a high-fat diet for 10 weeks to induce obesity. The effects of the miR-429 sponge on body weight, adipose tissue weight, plasma glucose and lipid levels, and hepatic lipid content were explored. The results showed that the overexpression of miR-429 sponge in subcutaneous white adipose tissue reduced body weight and fat mass, decreased fasting blood glucose and plasma cholesterol levels, improved glucose tolerance, and alleviated hepatic lipid deposition in mice. Mechanistic investigation showed that the inhibition of miR-429 significantly upregulated the expression of UCP1 in adipocytes and adipose tissue. These results suggest that local inhibition of miR-429 in subcutaneous white adipose tissue ameliorates obesity and related metabolic disorders potentially by upregulating UCP1, and miR-429 is a potential therapeutic target for the treatment of obesity and related metabolic disorders.
Animals
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MicroRNAs/physiology*
;
Obesity/metabolism*
;
Mice
;
Adipose Tissue, White/metabolism*
;
Metabolic Diseases
;
Subcutaneous Fat/metabolism*
;
Male
;
Uncoupling Protein 1/metabolism*
;
Diet, High-Fat
;
Mice, Inbred C57BL
10.Eccentric treadmill exercise promotes adaptive hypertrophy of gastrocnemius in rats.
Zhi-Qiang DAI ; Yu KE ; Yan ZHAO ; Ying YANG ; Hui-Wen WU ; Hua-Yu SHANG ; Zhi XIA
Acta Physiologica Sinica 2025;77(3):449-464
The present study aimed to investigate the effects of eccentric treadmill exercise on adaptive hypertrophy of skeletal muscle in rats. Thirty-two 3-month-old Sprague Dawley (SD) rats were selected and randomly assigned to one of the four groups based on their body weights: 2-week quiet control group (2C), 2-week downhill running exercise group (2E), 4-week quiet control group (4C), and 4-week downhill running exercise group (4E). The downhill running protocol for rats in the exercise groups involved slope of -16°, running speed of 16 m/min, training duration of 90 min, and 5 training sessions per week. Twenty-four hours after the final session of training, all the four groups of rats underwent an exhaustion treadmill exercise. After resting for 48 h, all the rats were euthanized and their gastrocnemius muscles were harvested for analysis. HE staining was used to measure the cross-sectional area (CSA) and diameter of muscle fibers. Transmission electron microscope was used to observe the ultrastructural changes in muscle fibers. Purithromycin surface labeling translation method was used to measure protein synthesis rate. Immunofluorescence double labeling was used to detect the colocalization levels of lysosomal-associated membrane protein 2 (Lamp2)-leucyl-tRNA synthetase (LARS) and Lamp2-mammalian target of rapamycin (mTOR). Western blot was used to measure the protein expression levels of myosin heavy chain (MHC) IIb and LARS, as well as the phosphorylation levels of mTOR, p70 ribosomal protein S6 kinase (p70S6K), and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). The results showed that, compared with the 2C group rats, the 2E group rats showed significant increases in wet weight of gastrocnemius muscle, wet weight/body weight ratio, running distance, running time, pre- and post-exercise blood lactate levels, myofibrillar protein content, colocalization levels of Lamp2-LARS and Lamp2-mTOR, and LARS protein expression. Besides these above changes, compared with the 4C group, the 4E group further exhibited significantly increased fiber CSA, fiber diameter, protein synthesis rate, and phosphorylation levels of mTOR, p70S6K, and 4E-BP1. Compared with the quiet control groups, the exercise groups exhibited ultrastructural damage of rat gastrocnemius muscle, which was more pronounced in the 4E group. These findings suggest that eccentric treadmill exercise may promote mTOR translocation to lysosomal membrane, activating mTOR signaling via up-regulating LARS expression. This, in turn, increases protein synthesis rate through the mTOR-p70S6K-4E-BP1 signaling pathway, promoting protein deposition and inducing adaptive skeletal muscle hypertrophy. Although the ultrastructural changes of skeletal muscle are more pronounced, the relatively long training cycles during short-term exercise periods have a more significant effect on promoting gastrocnemius muscle protein synthesis and adaptive hypertrophy.
Animals
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Rats, Sprague-Dawley
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Physical Conditioning, Animal/physiology*
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Rats
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Muscle, Skeletal/metabolism*
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TOR Serine-Threonine Kinases/metabolism*
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Male
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Hypertrophy
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Adaptation, Physiological/physiology*
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Adaptor Proteins, Signal Transducing/metabolism*
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Ribosomal Protein S6 Kinases, 70-kDa/metabolism*
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Intracellular Signaling Peptides and Proteins


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