American journal of physiology. Cell physiology最新文献

{"title":"Umbilical cord mesenchymal stem cells-derived extracellular vesicles improve excessive autophagy of granulosa cells through METTL3.","authors":"Weiqin Zhou, Ju Zhang, Xuanping Lu, Ziwei Zhao, Yujing Weng, Chunrong Zhu","doi":"10.1152/ajpcell.00785.2024","DOIUrl":"https://doi.org/10.1152/ajpcell.00785.2024","url":null,"abstract":"<p><p><b>Objective:</b> Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder impacting women's fertility. We assessed the effect of umbilical cord mesenchymal stem cell-derived extracellular vesicles (UC-MSC-EVs) on PTEN-induced kinase 1 (PINK1)/Parkin-mediated excessive autophagy of ovarian granulosa cells (GCs) through methyltransferase-like 3 (METTL3). <b>Methods:</b> Human ovarian GC line KGN was cultured and treated with dehydroepiandrosterone (DHEA) and UC-MSC-EVs. Cell apoptosis and viability, autophagy-related protein levels, adenosine triphosphate (ATP) and mitochondrial membrane potential (MMP) level, and microtubule-associated protein 1 light chain 3 beta (LC3B) and translocase of outer mitochondrial membrane 20 (TOMM20) co-localization were assessed by flow cytometry, CCK-8, western blot, kit, and immunofluorescence. PINK1 N6-methyladenosine (m6A) modification, METTL3 levels, and PINK1 mRNA stability were determined by Me-RIP, RT-qPCR and western blot. The PCOS mouse model was established and treated with UC-MSC-EVs. Serum hormone and ovarian tissue autophagy-related protein levels were determined by ELISA. <b>Results:</b> DHEA decreased KGN cell viability and p62 level, increased PINK1, Parkin, LC3BII/I and Beclin-1 protein levels, ATP content, MMP level, TOMM20⁺LC3B⁺ cell number and apoptosis, which were partly abrogated by UC-MSC-EVs treatment. PINK1 had m6A modification sites. METTL3 was a PINK1 m6A-modified Writer protein. After DHEA treatment, KGN cells showed elevated METTL3 and PINK1 m6A modification levels and mRNA stability, while UC-MSC-EV treatment caused the opposite results. METTL3 overexpression partly averted UC-MSC-EVs-improved PINK1/Parkin-mediated mitophagy. UC-MSC-EVs curbed PINK1/Parkin-mediated excessive autophagy through METTL3 and improved ovarian function in PCOS mice. <b>Conclusions:</b> UC-MSC-EVs suppressed PINK1/Parkin-mediated mitophagy of ovarian GCs through METTL3, thereby improving PCOS.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143662035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enteroendocrine Cells Regulate Intestinal Barrier Permeability.","authors":"Jennifer G Nwako, Sparsh D Patel, Taevon J Roach, Saanvi R Gupte, Samara G Williams, Anne Marie Riedman, Heather A McCauley","doi":"10.1152/ajpcell.01077.2024","DOIUrl":"10.1152/ajpcell.01077.2024","url":null,"abstract":"<p><p>The intestinal epithelial barrier is essential for nutrient absorption and protection against ingested pathogens and foreign substances. Barrier integrity is maintained by tight junctions which are sensitive to inflammatory signals, thus creating a feed-forward loop with an increasingly permeable barrier that further drives inflammation and is the hallmark of inflammatory bowel disease. There are currently no therapeutic strategies to improve the intestinal epithelial barrier. We hypothesized that enteroendocrine cells may play an unappreciated role in maintaining barrier integrity. To test this hypothesis, we seeded human intestinal enteroids with genetic loss of enteroendocrine cells on Transwell filters and evaluated transepithelial electrical resistance, paracellular permeability, and the localization and abundance of junctional proteins. We found that enteroendocrine cells were required to maintain a healthy barrier in crypt-like \"stem\" and villus-like differentiated cultures. Additionally, exogenous supplementation of enteroendocrine-deficient cultures with the hormones peptide tyrosine tyrosine (PYY) and the somatostatin analog octreotide was sufficient to rescue many aspects of this barrier defect both at baseline and in the presence of the inflammatory cytokine tumor necrosis factor (TNF). Surprisingly, these improvements in barrier function occurred largely independently of changes in protein abundance of junctional proteins zona-occludens 1, occludin, and claudin-2. These findings support a novel role for enteroendocrine cells in augmenting epithelial barrier function in the presence of inflammatory stimuli and present an opportunity for developing therapies to improve the intestinal barrier.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143646946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Blocking dopamine receptor 2 decreases gastrin levels in <i>H. pylori</i>-infected mice through increasing gastric somatostatin content.","authors":"Qianying Shen, Yue-Yue Zhou, Yan-Lin Wang, Yao Qi, Dong-Bo Lian, Zhe-Hong Li, Meng-Fei Chen, Xiao-Li Zhang, Yue Zhang, Jin Song, Li-Fei Zheng, Jin-Xia Zhu","doi":"10.1152/ajpcell.00993.2024","DOIUrl":"https://doi.org/10.1152/ajpcell.00993.2024","url":null,"abstract":"<p><p>Long-term infection with <i>Helicobacter pylori</i> (<i>H. pylori</i>) leads to elevated serum gastrin levels, which are closely related to gastric cancer. Eradication of <i>H</i><i>.</i> <i>pylori</i> to treat the high gastrin levels is increasingly challenged by antibiotic resistance. Dopamine (DA) receptor 1 (D₁R) is expressed on G cells in the gastric antrum. Parietal cells produce DA, which inhibits somatostatin (SOM) release through D₂R on D cells in the gastric mucosa. Whether targeted intervention in DRs can improve high gastrin levels after <i>H. pylori</i> infection remains to be explored. In this study, human gastric tissue, <i>H. pylori</i>-infected mice, D₁R and D₂R knockout mice, RT‒qPCR, ELISA, IHC, Western Blot, HE staining and <i>ex vivo</i> incubation of gastric mucosae were used. We found that <i>H. pylori</i> infection destroyed the mitochondria of parietal cells and reduced DA content in the gastric mucosa at 10 weeks after infection. Moreover, gastrin-positive cell numbers and serum gastrin levels were increased. D₁R, but not D₂R, was observed in G cells. DA promoted gastric gastrin secretion. Interestingly, both D1- and D2-like agonists mimicked the effect of DA on the gastrin secretion, which was antagonized by their antagonists. Blocking D₂R with domperidone or knocking out D₂R resulted in decreased gastrin-positive cell numbers and gastrin levels but increased SOM levels at 10 weeks after <i>H. pylori</i> infection. Our findings highlight the key regulatory effect of D₂R on gastrin secretion and elucidate the role of domperidone in reducing the elevated gastrin level associated with <i>H. pylori</i> infection.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143646891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diurnal differences in postprandial glucose and triglyceride metabolism reveal metabolic flexibility and resilience.","authors":"Rebecca Dörner, Franziska A Hägele, Shauna D O'Donovan, Jennifer L Miles-Chan, Manfred J Müller, Anja Bosy-Westphal","doi":"10.1152/ajpcell.00102.2025","DOIUrl":"https://doi.org/10.1152/ajpcell.00102.2025","url":null,"abstract":"<p><p>Objective The study investigated the diurnal variance in metabolic resilience (i.e., the robustness, the recovery and re-orientation of metabolism) and metabolic flexibility in glucose and fat oxidation rates to three identical test meals. Methods Eight young, healthy subjects consumed identical liquid mixed meals three times a day (33 % of energy requirement each), followed by a defined bout of physical activity conducted in a whole-room indirect calorimeter to continuously assess energy expenditure and postprandial changes in substrate oxidation rates, as a measure of metabolic flexibility. A mathematical metabolic resilience model was used to analyze the postprandial blood parameters. Results Throughout the day, postprandial glucose area under the curve (AUC) increased (breakfast mean ±SD 17.3 ±2.4 vs. dinner 20.8 ±2.0 g/180min; p<0.001) while triglyceride AUC decreased (breakfast 434 ±158 vs. dinner 365 ±104 mg/180min; p=0.039) at identical insulin AUC and energy balance. Fat oxidation increased from breakfast 24.8 ±8.7 to dinner 28.0 ±8.7 g/180min (p=0.029), while respiratory exchange ratio declined from 0.035 ±0.026 to 0.012 ±0.029 (p=0.005). Metabolic resilience model reveals a diurnal increased rate of lipolysis of circulating triglycerides at a concomitant decrease in the rate of exogenous and endogenous triglyceride appearance. Conclusion Meal-to-meal changes in glucose AUC indicate rising insulin resistance during the day. However, this reflects a resilient metabolism that shifts to triglyceride metabolism in the evening while maintaining insulin AUC and energy balance.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143646945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physiological Function of Cyclic Nucleotide Phosphodiesterases in Atrial Myocytes and their Potential as Targets in Atrial Fibrillation.","authors":"Matthew John Read, Andreas Koschinski, Samuel Jitu Bose, Rebecca Ab Burton","doi":"10.1152/ajpcell.00782.2024","DOIUrl":"https://doi.org/10.1152/ajpcell.00782.2024","url":null,"abstract":"<p><p>Cyclic nucleotide hy drolysing phosphodiesterases (PDEs) are key regulators of cyclic nucleotide (e.g. cAMP and cGMP) signalling. Here we examine the role of PDEs in the physiology of atrial myocytes (AMs), the pathogenesis of atrial fibrillation (AF) and the potential of PDEs as therapeutic targets for AF. PDE1-5 and 8 are present and functional in AMs. PDE2-4 are important regulators of AM contraction but their role beyond atrial contractility is unclear. The role of PDE1,5 and 8 in healthy AMs is unknown but of interest because of their roles in ventricular myocytes. We propose that PDE2-5 and PDE8 are potential targets to prevent the triggering of AF considering their effects on Ca²⁺ handling and /or electrical activity. PDE1-5 are possible targets to treat patients with paroxysmal or persistent AF caused by pulmonary vein automaticity. PDE8B2 is a possible target for patients with persistent AF due to its altered expression. Research should aim to identify the presence, localisation, and function of specific PDE isoforms in human atria. Ultimately, the paucity of PDE isoform-specific small molecule modulators and the difficulty of delivering PDE-targeted medications or therapies to particular cell types limit current research and its application.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143584307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intestinal Luminal Anion Transporters and their Interplay with Gut Microbiome and Inflammation.","authors":"Nazim Husain, Anoop Kumar, Arivarasu N Anbazhagan, Ravinder K Gill, Pradeep K Dudeja","doi":"10.1152/ajpcell.00026.2025","DOIUrl":"https://doi.org/10.1152/ajpcell.00026.2025","url":null,"abstract":"<p><p>The intestine, as a critical interface between the external environment and the internal body, plays a central role in nutrient absorption, immune regulation, and maintaining homeostasis. The intestinal epithelium, composed of specialized epithelial cells, hosts apical anion transporters that primarily mediate the transport of chloride and bicarbonate ions, essential for maintaining electrolyte balance, pH homeostasis, and fluid absorption/secretion. Additionally, the intestine hosts a diverse population of gut microbiota that plays a pivotal role in various physiological processes including nutrient metabolism, immune regulation and maintenance of intestinal barrier integrity, all of which are critical for host gut homeostasis and health. The anion transporters and gut microbiome are intricately interconnected, where alterations in one can trigger changes in the other leading to compromised barrier integrity and increasing susceptibility to pathophysiological states including gut inflammation. This review focuses on the interplay of key apical anion transporters including Down Regulated in Adenoma (DRA, SLC26A3), Putative Anion Transporter-1 (PAT1, SLC26A6) and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR, ABCC7) with the gut microbiome, barrier integrity and their relationship to gut inflammation.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143565777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extracellular matrix matters: matrix-based bioscaffolds in advancing translational cancer research and targeted therapy.","authors":"Nikos K Karamanos, Zoi Piperigkou, Chrisavgi Gourdoupi, Sylvia Mangani, Maria dM Vivanco","doi":"10.1152/ajpcell.00050.2025","DOIUrl":"https://doi.org/10.1152/ajpcell.00050.2025","url":null,"abstract":"<p><p>The onset, development and progression of cancer are greatly influenced by the microenvironmental cues originating from diverse elements within the tumor niche. Extracellular matrix (ECM), the complex and dynamic macromolecular 3D network, governs cell functionality and play key roles in tumor growth and spreading. This article highlights the significance of ECM-based bioscaffolds in providing a relevant microenvironment not only for studying tumor behavior and drug efficacy but also for narrowing the gap between translational cancer research and targeted cancer treatment. The development of novel and user-friendly platforms that resemble the human tumor microenvironment in early and advanced cancer stages, may help to predict treatment response, thus facilitating the development and testing of new drugs, bridging the gap between <i>in vitro</i> and <i>in vivo</i> models. Additionally, we present innovative strategies leveraging ECM bioscaffolds for personalized cancer treatment, including drug delivery systems and tissue engineering approaches. Specific case studies as well as ethical concerns related to the use of ECM bioscaffolds in research and therapy are also presented and critically discussed. By elucidating the intricate interplay between ECM and cancer biology, this article underscores the potential of ECM bioscaffolds as novel platforms for shaping future therapeutic interventions and advancing precision oncology.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143539881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Body composition alterations in patients with lung cancer.","authors":"Deena B Snoke, Gary S Atwood, Emma R Bellefleur, Alice M Stokes, Michael J Toth","doi":"10.1152/ajpcell.01048.2024","DOIUrl":"10.1152/ajpcell.01048.2024","url":null,"abstract":"<p><p>Most patients with lung cancer experience cancer cachexia (CC), a syndrome of skeletal muscle and adipose tissue wasting. Knowledge of body composition changes in patients is limited, however, because most studies have been cross-sectional, comparing patients with noncancer controls or patients with and without CC. Few studies, in contrast, have evaluated body composition in patients with lung cancer over time. This review examines our current understanding of longitudinal body composition changes in patients with lung cancer and identifies modifying factors contributing to variation in muscle and adipose tissue wasting, focusing on biological sex. We identified 32 studies conducting longitudinal measurements of body composition by computed tomography, bioelectrical impedance, dual X-ray absorptiometry, or total body nitrogen, with a total of <i>n</i> = 3,951 patients (35% female). All studies evaluated changes following diagnosis while patients were receiving treatment. Most studies reporting muscle-specific outcomes show decreased skeletal muscle mass, with more pronounced muscle wasting in males and male-enriched populations. In a small number of studies reporting muscle density, the majority show increased myosteatosis. Adiposity changes are less frequently reported, although wasting appears more prevalent in late-stage disease. Further studies are needed to define adipose changes along the lung cancer continuum. Our review emphasizes the need for balanced recruitment based on biological sex and sex-based analyses. In addition, consensus reporting of relevant patient data and outcomes in future studies will allow for meta-analysis and assist in the development of effective treatments for lung CC.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C872-C886"},"PeriodicalIF":5.0,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143062983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transmission of peripheral blood α-synuclein fibrils exacerbates synucleinopathy and neurodegeneration in Parkinson's disease by endothelial Lag3 endocytosis.","authors":"Qingrui Duan, Qingxi Zhang, ShuoLin Jiang, Kun Nie, Shujun Feng, Yihui Qiu, Peikun He, Yuxuan Xing, Jiaxuan Liu, Guixian Ma, Yuhu Zhang, Yuyuan Gao, Lijuan Wang","doi":"10.1152/ajpcell.00639.2024","DOIUrl":"10.1152/ajpcell.00639.2024","url":null,"abstract":"<p><p>Parkinson's disease (PD) is an age-related neurodegenerative disorder. The pathological feature of PD is abnormal α-synuclein (α-syn) formation and transmission. Recent evidence demonstrates that α-syn preformed fibrils (α-syn PFFs) can be detected in the serum of patients with PD. The peripheral blood α-syn PFF can cross the blood-brain barrier (BBB) and aggravate neuronal damage, but the mechanism remains to be elucidated. We constructed the PD mouse models of different severity: the mild pathology (A53T ONLY) and the severe pathology (A53T + Brain FIB); this was followed by α-syn PFFs intravenous injection. Then, we used endothelium-specific Lag3 knockout mice (Lag3-ECs-CKO) to decrease the blood α-syn PFFs spreading. We observed that intravenous transmission of α-syn PFFs significantly aggravated motor deficits, dopaminergic neuron loss, neuroinflammation, and pathologic α-syn deposition in A53T ONLY, but not in A53T + Brain FIB. Blocking endothelial Lag3 endocytosis by Lag3-ECs-CKO decreased the blood α-syn PFFs spreading and improved the symptoms and pathogenesis of PD mice. Our findings reveal the role of peripheral blood α-syn PFFs transmission in the mild pathology or early-stage PD and the mechanism of endothelial Lag3 endocytosis in the pathology of α-syn transmission. Targeting endothelial Lag3 to prevent α-syn from spreading from the blood to the brain may be a disease-modifying therapy in early-stage PD.<b>NEW & NOTEWORTHY</b> This study highlights the transmission mechanism of peripheral blood α-synuclein preformed fibrils (α-syn PFFs) through endothelial Lag3 endocytosis in the mild pathology or early-stage Parkinson's disease (PD). Targeting endothelial Lag3 as a perspective of decreasing peripheral blood α-syn PFFs transmission may be a disease-modifying therapy in early-stage PD.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C836-C855"},"PeriodicalIF":5.0,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142798696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cellular mechanisms underlying overreaching in skeletal muscle following excessive high-intensity interval training.","authors":"Daiki Watanabe, Masanobu Wada","doi":"10.1152/ajpcell.00623.2024","DOIUrl":"10.1152/ajpcell.00623.2024","url":null,"abstract":"<p><p>Overreaching (OR) can be defined as a decline in physical performance resulting from excessive exercise training, necessitating days to weeks recovery. Impairments in the contractile function of skeletal muscle are believed to be a primary factor contributing to OR. However, the cellular mechanism triggering OR remains unclear. The purpose of this study was to elucidate the mechanisms underlying OR. Rats' plantar flexor muscles were subjected to repeated electrical stimulations mimicking excessive high-intensity interval training (HIIT) daily for 13 consecutive days, and isometric torques were monitored. The torque was measured one day after HIIT, and subsequently, the physiological function of type II fibers was analyzed by using mechanically skinned-fiber technique. Eleven of 17 rats exhibited torque decline, whereas others did not. Thus, the rats were divided into OR and nonoverreaching (NOR) groups. Skinned fibers from the gastrocnemius (GAS) muscles of both groups showed decreased depolarization-induced force and increased myofibrillar Ca²⁺ sensitivity. However, the fibers from the OR group, but not the NOR group, exhibited a decrease in myofibrillar maximal force. Biochemical analyses of a superficial region of GAS muscle revealed that α-actinin 2 content was increased in the NOR group, but not in the OR group, whereas calpain-3 autolysis was increased in the OR group, but not in the NOR group. These findings shed light on the cellular mechanism underlying OR: OR following excessive HIIT was induced by a decreased myofibrillar maximal force, whereas Ca²⁺ sensitivity was increased.<b>NEW & NOTEWORTHY</b> An early sign of overtraining is a performance impairment known as overreaching (OR). This study revealed the cellular mechanism underlying OR by combining in vivo fatiguing contractions with mechanically skinned-fiber technique. Thirteen consecutive days of intense training result in myofibrillar force depression in OR. This study provides valuable insights not only for athletes and coaches but also for nonathletes who incorporate exercise into their daily activity.</p>","PeriodicalId":7585,"journal":{"name":"American journal of physiology. Cell physiology","volume":" ","pages":"C921-C938"},"PeriodicalIF":5.0,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143187660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}