Acta Physiol (Oxf)
· 2026 May · PMID 41998837
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AIM: Mito Thermo Yellow (MTY) is a mitochondrially targeted fluorophore that shows marked fluorescence quenching with increasing temperature, allowing for interrogating temperature dynamics in the mitochondria of live ce...AIM: Mito Thermo Yellow (MTY) is a mitochondrially targeted fluorophore that shows marked fluorescence quenching with increasing temperature, allowing for interrogating temperature dynamics in the mitochondria of live cells. Here we re-evaluate published MTY fluorescence responses used to argue in favor of the 'hot mitochondria' concept; the assertion that mitochondria operate while maintaining substantial (> 10°C) apparent temperature gradients (ΔT) between themselves and their cellular environment. RESULTS: We find that MTY fluorescence kinetics are incompatible with the expected dynamics of mitochondrial heat production and diffusion. We further explore the published effects of mitochondrial inhibitors on MTY, and related evidence for ΔT of > 10°C, again concluding results are inconsistent with the expected heat production dynamics. Thus, assertions of ΔT > 10°C between mitochondria and their cellular environment based on MTY fluorescence intensity changes are unlikely to be reporting a signal that is uniquely intramitochondrial temperature. In addition to these analyses, we further argue that the inference mitochondria can operate at an internal temperature of > 48°C, as reported using MTY, is improbable as these internal temperatures would cause protein denaturation and aggregation and induction of the heat shock (HSR), unfolded protein (UPR), and integrated (ISR) stress responses. CONCLUSION: Taken as a whole, we conclude MTY and similar tools must be re-evaluated in regard to if they are providing solely information on local temperature and thus are so far inadequate, unto themselves, to demonstrate the existence of hot mitochondria.
Edwards A, Reilly TM, Ralph DL
… +6 more, Tajdini M, Finch AM, Patel A, McFarlin BE, Koepsell H, McDonough AA
Acta Physiol (Oxf)
· 2026 May · PMID 41998818
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AIM: Pre-translational studies of mechanisms underlying chronic diseases in adult humans should ideally use animal models corresponding to mature adult rather than young animals. In this study, we examined the impact of...AIM: Pre-translational studies of mechanisms underlying chronic diseases in adult humans should ideally use animal models corresponding to mature adult rather than young animals. In this study, we examined the impact of age and past pregnancy on renal function in Sprague Dawley female rats. METHODS: In 4.5 month virgins and 12 month breeders, rates of glomerular filtration, urinary excretion, responses to diuretic and electrolyte challenges, and relative abundance of renal tubule transporters (per mg protein) were compared and simulations performed to determine the impact of age on tubular transport and energetics. RESULTS: Twelve month versus 4.5 month females exhibited ~25% higher GFR, lower abundance of key Na transporters, higher AQP2 abundance, and comparable urinary excretion rates. Twelve month rats excreted a saline bolus slower than 4.5 month, yet excreted more Na following furosemide and hydrochlorothiazide challenges. In response to a 3% K-rich meal, both age groups exhibited similar excretion profiles. With age, SGLT1 abundance rose while SGLT2 was unchanged. Sodium pump activity and Electron Transport Chain complex abundance were lower in 12 month versus 4.5 month rats. Model simulations suggest that as female rats age and breed, their kidneys adapt to larger filtration rates by expanding surface area and reabsorption capacity predominantly along the proximal nephron, where transport is most energetically efficient. The decrease in Na transporter abundance acts to counteract the effects of increased tubular size. CONCLUSION: Our findings suggest a greater propensity for sodium retention in females with age, which warrants consideration for hypertension and kidney disease studies.
INTRODUCTION: In physoclist fish, that is, in fish with a closed swimbladder, oxygen has been shown to be the main gas in the swimbladder. Gas gland cells, crucial for the filling of the swimbladder, produce and secrete...INTRODUCTION: In physoclist fish, that is, in fish with a closed swimbladder, oxygen has been shown to be the main gas in the swimbladder. Gas gland cells, crucial for the filling of the swimbladder, produce and secrete lactic acid. The resulting acidification of the blood releases oxygen from the hemoglobin via the Root effect, generating high oxygen partial pressures required for the diffusion of oxygen into the swimbladder. CO in swimbladder gas was believed mainly to result from a wash out of HCO from the plasma due to acidification, but this reaction would diminish blood acidification. This study therefore attempted to revisit our current information about CO production and also about CO and HCO movements in swimbladder tissue to elucidate the role of CO for swimbladder function. METHODS: Targeted literature search has been conducted to search for relevant publications. RESULTS: The data reveal that European eel Anguilla anguilla gas gland cells produce most of the CO in the pentose phosphate shunt. CO diffuses into the swimbladder lumen and into the blood, facilitated by aquaporin 1. Membrane-bound carbonic anhydrase together with HCO transporters allow for CO and HCO cycling across the basolateral gas gland cell membrane, supporting proton secretion and blood acidification. Countercurrent concentration of CO, HCO and protons in the rete mirabile results in a significant acidification of arterial blood in the rete. CONCLUSIONS: CO production together with CO and HCO movements in swimbladder tissue significantly support blood acidification and the generation of high oxygen as well as CO partial pressures.
AIM: Loss-of-function mutations in KCNJ10, encoding Kir4.1, cause EAST/SeSAME syndrome, with renal salt-wasting tubulopathy and hypokalemia. We hypothesized that Kir4.1 deletion specifically in the distal convoluted tubu...AIM: Loss-of-function mutations in KCNJ10, encoding Kir4.1, cause EAST/SeSAME syndrome, with renal salt-wasting tubulopathy and hypokalemia. We hypothesized that Kir4.1 deletion specifically in the distal convoluted tubule (DCT) stimulates ENaC activity via the mammalian target of rapamycin (mTOR)-dependent mechanisms, contributing to hypokalemia. METHODS: Metabolic cages, electrophysiology, immunoblotting, immunostaining, and in vivo diuretic response experiments were used to examine biochemical parameters, Kir4.1/Kir5.1 activity, NCC and ENaC function in the DCT-specific Kir4.1 knockout (DCT-Kir4.1 KO) mice under normal or K restriction conditions. RESULTS: DCT-Kir4.1 KO mice exhibited impaired basolateral K channel and NCC activity, enhanced ENaC activity, and mild hypokalemia. Amiloride treatment induced similar natriuresis and kaliuresis in DCT-Kir4.1 KO and kidney-specific Kir4.1 KO mice, but had minimal effects in collecting system Kir4.1 KO mice, suggesting high ENaC activity following Kir4.1 deletion in the DCT. Notably, severe hypokalemia, along with upregulated ENaC expression and activity, was observed in DCT-Kir4.1 KO mice under dietary K restriction. Patch-clamp experiments further revealed elevated ENaC currents in the DCT2 of KO mice on a low-K diet, independent of aldosterone levels. Inhibition of mTOR with AZD8055 reduced SGK1/Nedd4-2 phosphorylation, cleaved α-ENaC expression, and DCT2 ENaC currents, suggesting a role for mTOR in ENaC hyperactivity in K-restricted DCT-Kir4.1 KO mice. This notion was also supported by the upregulated Rictor expression observed in the isolated DCT of these KO mice. CONCLUSION: We conclude that Kir4.1 deletion drives ENaC hyperactivity in the DCT via the mTORC2-dependent SGK1/Nedd4-2 signaling pathway, promoting low potassium diet-induced hypokalemia.
BACKGROUND: The tandem pore domain halothane-inhibited potassium (THIK-1) channel is a member of the two-pore domain potassium (K2P) channel family and plays a critical role in maintaining the resting membrane potential....BACKGROUND: The tandem pore domain halothane-inhibited potassium (THIK-1) channel is a member of the two-pore domain potassium (K2P) channel family and plays a critical role in maintaining the resting membrane potential. THIK-1 has emerged as a key regulator of microglial physiology and neuroimmune signaling. With the rapid accumulation of structural, electrophysiological, and functional evidence, there is an increasing need for an integrated understanding of THIK-1 in the context of microglial biology and disease. AIMS: This review provides a comprehensive synthesis of the structural, regulatory, and functional properties of THIK-1, with a particular focus on its roles in microglial physiology, neuroimmune signaling, and central nervous system (CNS) pathologies. MATERIALS AND METHODS: We conducted a comprehensive review of recent literature, including electrophysiological, molecular, and structural studies, with particular emphasis on cryo-electron microscopy findings, pharmacological modulation, and disease-associated functional analyses. RESULTS: THIK-1 is selectively enriched in microglia and contributes to essential cellular processes, including surveillance motility, synaptic pruning, and inflammasome activation. Its high constitutive activity makes it a dominant determinant of the microglial membrane potential. Structural studies have identified key features, including a lipid-interacting pocket and a cytoplasmic gate, which underlie lipid- and anesthetic-mediated regulation. Functionally, THIK-1-mediated K⁺ efflux is required for NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation and pyroptosis. Accumulating evidence links THIK-1 to major CNS disorders, including neuroinflammation, neurodegeneration (e.g., Alzheimer's and Parkinson's diseases), and psychiatric disorders. DISCUSSION: The convergence of structural, electrophysiological, and immunological findings positions THIK-1 as a central regulator of neuroimmune signaling. Integration of these findings provides new insights into how ion channel activity shapes microglial function and disease processes. CONCLUSION: THIK-1 represents a critical nexus between ion channel biophysics and neuroimmune dysfunction. A comprehensive understanding of its regulation and function supports its potential as a microglia-specific therapeutic target in neuroinflammatory and neurodegenerative disorders.
AIMS: Phospholamban (PLN) is a key regulator of sarco-endoplasmic reticulum calcium ATPase (SERCA) activity and myocardial contractility, but its expression control remains incompletely understood. This study seeks to cl...AIMS: Phospholamban (PLN) is a key regulator of sarco-endoplasmic reticulum calcium ATPase (SERCA) activity and myocardial contractility, but its expression control remains incompletely understood. This study seeks to clarify the molecular mechanism of PLN regulation and its functional relevance in cardiac physiology. METHODS AND RESULTS: Using cardiomyocyte-specific ZBTB20 knockout (CZB20KO) mice and primary cardiomyocytes, we demonstrated that ZBTB20 deficiency significantly reduced PLN protein at a higher magnitude than its mRNA levels, accompanied by a marked increase in the expression levels of miR-221 and miR-222 derived from the same gene cluster. Cardiomyocyte-specific deletion of miR-221/222 alone did not affect cardiac PLN expression in the mice, but fully restored the expression of PLN protein and the basal cardiac contractility in the context of ZBTB20 deficiency, as evidenced by normal left ventricular ejection fraction and fractional shortening compared to control mice. Through luciferase reporter assays with 3'UTR binding site mutagenesis and gain/loss-of-function experiments, we identified miR-221 but not its paralog miR-222 as a direct regulator of PLN by targeting its 3'UTR of mRNA. Moreover, cardiomyocyte-specific overexpression of miR-221 in mice led to a reduction in cardiac PLN protein levels. ChIP assay did not reveal significant binding of ZBTB20 to the miR-221/222 gene cluster. CONCLUSIONS: Our study identifies miR-221 as a novel regulator of cardiac PLN expression and a mediator of the regulation of PLN by ZBTB20. Thus this work provides insights into the regulation of basal contractility and functional reserve of the heart.
Sassi A, Chassot A, Jellali S
… +6 more, Liaudet N, Polat A, Baier F, Stroka D, Furuse M, Feraille E
Acta Physiol (Oxf)
· 2026 May · PMID 41930611
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AIM: Renal sodium reabsorption occurs through both transcellular and paracellular pathways. Tight junction proteins play a key role in mediating paracellular transport. The collecting duct is critical for the fine tuning...AIM: Renal sodium reabsorption occurs through both transcellular and paracellular pathways. Tight junction proteins play a key role in mediating paracellular transport. The collecting duct is critical for the fine tuning of sodium balance and is highly responsive to changes in dietary salt intake. This study aimed to determine whether a low-sodium diet modulates paracellular sodium permeability by regulating the expression or localization of claudin-3, a major tight junction protein in the collecting duct. METHODS: Wild-type and claudin-3 knockout male mice were fed low (0.01%) or normal (0.18%) sodium diets for 7 days, with or without treatment with spironolactone, a mineralocorticoid receptor antagonist. The expression of tight junction proteins was analyzed by immunoblotting and immunofluorescence. Functional effects of claudin-3 on ion permeability were evaluated in cultured mouse collecting duct principal cells using chamber recordings after claudin-3 overexpression or gene silencing. RESULTS: Low-sodium diet increases claudin-3 expression in mouse kidneys. In cultured cells, aldosterone enhanced claudin-3 abundance and its plasma membrane localization. Claudin-3 overexpression reduced, while its silencing increased paracellular permeability to sodium and chloride. Claudin-3 knockout mice on a low-sodium diet compensated by upregulating epithelial sodium channel subunits, claudin-4, claudin-8, and claudin-10. This adaptive response persisted under mineralocorticoid receptor blockade. CONCLUSIONS: Our findings demonstrate that aldosterone strengthens the paracellular sodium barrier in the collecting duct by inducing claudin-3. In the absence of claudin-3, compensatory regulation of other claudins and sodium transporters preserves sodium homeostasis under low-salt conditions, thus revealing adaptive mechanisms in renal sodium handling.
AIM: Neuronal activity drives increases in cerebral blood flow to match metabolic demands, with capillary dilation critical for blood-brain exchange. However, the molecular mechanisms coupling neuronal activity to capill...AIM: Neuronal activity drives increases in cerebral blood flow to match metabolic demands, with capillary dilation critical for blood-brain exchange. However, the molecular mechanisms coupling neuronal activity to capillary diameter adjustments remain unclear. We examined the contribution of pericyte pannexin1 channels to capillary responses during increased neuronal excitability and investigated the underlying signaling pathway. METHODS: To induce neuronal excitability, we administered picrotoxin, a GABAA receptor antagonist, to acute hippocampal slices and in vivo, which induces epileptiform activity. Pericyte pannexin1 activity and capillary responses were monitored via dye uptake and capillary diameter measurements in slices from wild-type and pannexin1-deficient mice. Pharmacological blockade of adenosine A1 receptors and exogenous adenosine application were used to identify the signaling pathway. RESULTS: In vivo picrotoxin administration inhibited pericyte pannexin1 channel activity in the hippocampus. Equivalent suppression was observed in picrotoxin-treated acute hippocampal slices, where neuronal excitability led to pericyte pannexin1 inhibition and capillary dilation. Both responses were abolished by tetrodotoxin and absent in pannexin1-deficient mice, confirming dependence on neuronal activity and pannexin1 expression. Pharmacological blockade of adenosine A1 receptors prevented pannexin1 inhibition and the associated vasodilatory response, whereas exogenous adenosine recapitulated these effects, demonstrating that adenosine signaling is required for neuronal activity-dependent modulation of pericyte pannexin1. CONCLUSION: We identify a previously uncharacterized adenosine-pannexin1 signaling axis in pericytes linking neuronal excitability to capillary relaxation. This mechanism provides a molecular substrate for activity-dependent capillary regulation and supports a role for pericyte pannexin1 in adenosine-mediated neurovascular responses during states of elevated metabolic demand.
Vieira-da-Silva AL, Esteca MV, Silva FA
… +5 more, Divino IA, Carneiro FS, Ropelle ER, Torsoni AS, Baptista IL
Acta Physiol (Oxf)
· 2026 May · PMID 41906200
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AIM: The liver exhibits a remarkable regenerative capacity, enabling this organ to maintain homeostasis even after significant injury. However, hepatic regeneration requires sufficient energy to sustain cellular hypertro...AIM: The liver exhibits a remarkable regenerative capacity, enabling this organ to maintain homeostasis even after significant injury. However, hepatic regeneration requires sufficient energy to sustain cellular hypertrophy and proliferation, thus ensuring efficient tissue repair. Therefore, dietary modulation of pathways regulating mitochondrial quality may enhance liver regeneration. This study aimed to investigate the effects of preoperative beta-hydroxy-beta-methylbutyrate (HMB) supplementation on mitochondrial quality control pathways and its impact on the liver regeneration process in mice undergoing partial hepatectomy (PHx). METHODS: Male C57BL/6J mice were supplemented with 600 mg/kg HMB via gavage for 10 days. On the 10th day, supplementation was discontinued, and the mice underwent a ⅔ liver resection. The subsequent 7 days have constituted the liver regeneration period. For a second injury induction, at the end of the 7th day of regeneration, acetaminophen (APAP) overdose was administered via gavage. We then analyzed several markers of mitochondrial quality and liver function. RESULTS: Our results indicate that preoperative HMB supplementation modulates cell cycle progression, preventing excessive hepatic mass accumulation. Additionally, HMB regulates mitochondrial dynamics by decreasing Parkin, Mfn2, and DRP1 protein levels while increasing the mitochondrial markers VDAC2 and Tom20. Following a second injury from an APAP overdose, the HMB-supplemented group demonstrated increased mtDNA content and enhanced mitochondrial capacity, both critical for effective tissue recovery. CONCLUSION: Our findings suggest that preoperative HMB supplementation preserves hepatic mitochondrial capacity after PHx.
Nolze A, Rabe S, Ruhs S
… +4 more, Strätz N, Quarch K, Köhler C, Grossmann C
Acta Physiol (Oxf)
· 2026 May · PMID 41895823
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AIM: Cardiovascular diseases display strong sex differences. Angiotensin II (AngII) is implicated in this process. The ubiquitously expressed enzymatic beta subunit of calcineurin (PPP3CB), a serine/threonine phosphatase...AIM: Cardiovascular diseases display strong sex differences. Angiotensin II (AngII) is implicated in this process. The ubiquitously expressed enzymatic beta subunit of calcineurin (PPP3CB), a serine/threonine phosphatase, can mediate pathological effects of AngII in the heart. Our aim was to explore the role of calcineurin in sex-dependent AngII-mediated vascular changes. METHODS: We used female and male mice with a global PPP3CB knockout that were treated with AngII for 4 weeks as an in vivo model. For validation experiments and investigation of signaling pathways, primary aortic vascular smooth muscle cells (aVSMCs) isolated from respective female and male WT mice were utilized. RESULTS: AngII-induced increase in blood pressure was less pronounced and not calcineurin-dependent in female compared to male mice with no changes in media thickness or lumen area. Wire and pressure myography showed an AngII-induced calcineurin-dependent endothelial dysfunction in males but not in females. In aVSMCs from female mice, AngII did not influence wound closure or cell proliferation as was detectable in aVSMCs of male mice. As an underlying mechanism for these sex differences in long-term AngII effects, RNA-seq data and IPA revealed differentially regulated genes and pathways, involving extracellular matrix components, calcineurin, Ctgf, Egfr, and Tgfb1. Downstream of Egfr, we identified sex-dependent activation of PKC signaling in male and ERK/MAPK signaling in female as mediators of Ctgf expression. CONCLUSION: Overall, the relevance of AngII-calcineurin signaling for pathophysiological effects in the vasculature differs between female and male mice, suggesting both sexes require customized prevention and treatment strategies for cardiovascular disorders.
Wang X, Guo F, Wang X
… +4 more, Guo Y, Fan S, Hong L, Jin H
Acta Physiol (Oxf)
· 2026 Apr · PMID 41886752
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AIM: The aim of this study is to determine whether Angiotensin-(1-7) [Ang-(1-7)] alleviates isoproterenol (ISO)-induced cardiac hypertrophy by suppressing excessive autophagy and apoptosis through coordinated Mas recepto...AIM: The aim of this study is to determine whether Angiotensin-(1-7) [Ang-(1-7)] alleviates isoproterenol (ISO)-induced cardiac hypertrophy by suppressing excessive autophagy and apoptosis through coordinated Mas receptor (MasR) and angiotensin II type-2 receptor (ATR) signaling, and to elucidate the underlying mechanisms. METHODS: ISO-induced hypertrophy was established in mice and assessed by echocardiography, histology, and hypertrophic markers. H9c2 cardiomyocytes were exposed to ISO and treated separately with A-779 (MasR antagonist), PD123319 (ATR antagonist), and a combination of both receptor antagonists. Receptor interplay was examined using pharmacological blockade and co-immunoprecipitation. Autophagy and apoptosis were evaluated by transmission electron microscopy and TUNEL. RESULTS: Ang-(1-7) attenuated ventricular dysfunction, myocardial enlargement, and upregulation of hypertrophic markers in mice with ISO-induced hypertrophy. Pharmacological inhibition with A-779 and PD123319 revealed that Ang-(1-7) actions require reciprocal regulation between MasR and ATR. Both receptors synergistically contributed to the anti-apoptotic effect, while the anti-autophagic response was mediated predominantly by MasR. Transmission electron microscopy and TUNEL staining confirmed that Ang-(1-7) treatment alleviated excessive autophagy and apoptosis in cardiomyocytes. Furthermore, experiments with dual receptor antagonists and co-immunoprecipitation showed an interaction between MasR and ATR, supporting their coordinated signaling role in cardiac protection. CONCLUSION: Ang-(1-7) ameliorates ISO-induced cardiac hypertrophy by suppressing excessive autophagy and apoptosis via synergistic MasR-ATR signaling. Receptor crosstalk may represent a therapeutic entry point for pathological hypertrophy.
Acta Physiol (Oxf)
· 2026 Apr · PMID 41862191
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Thyroid hormones (THs) are under negative feedback regulation via the hypothalamic-pituitary-thyroid (HPT) axis. How this axis operates to keep the circulating THs within a narrow physiological range is not well understo...Thyroid hormones (THs) are under negative feedback regulation via the hypothalamic-pituitary-thyroid (HPT) axis. How this axis operates to keep the circulating THs within a narrow physiological range is not well understood quantitatively. Led by the design principle of robust homeostatic feedback control, here we review and synthesize the literature under a unifying theme of signal amplification in the HPT axis, providing evidence for its existence, location, functional significance, and potential molecular mechanisms. Drawing on human studies of the circulating TSH-T4 relationship, we assert that a signal amplifier exists in the brain, where the TH feedback signal is amplified to inhibit TRH and TSH. With mathematical models we illustrate that placing the signal amplifier of the HPT feedback loop in the brain, not in the thyroid, provides an evolutionary advantage, which minimizes the disruption of operating TH levels by possible perturbations. We review the molecular neuroendocrine literature to reveal how signal amplification (ultrasensitivity) is likely achieved mechanically in the hypothalamus and anterior pituitary. We identify multiple signaling pathways in the TRH neurons, β2-tanycytes, and thyrotropes that mediate the feedback action of THs, including transcriptional and posttranslational regulations of the synthesis, maturation, degradation, and release of TRH and TSH. Collectively, these multistep regulations amplify T3 signal, providing a high feedback loop gain for robust TH homeostatic control. The nature's design principle revealed here enhances our cross-scale understanding of the systems biology of the HPT axis as a dynamical control system, which can promote precision thyroid medicine and risk assessment of thyroid-disrupting chemicals.
Sanchez-Gomez J, Ruiz-Campos S, Chica-Perez A
… +6 more, Baena-Raya A, Acosta FM, Wolfrum C, Rensen PCN, Romacho T, Martinez-Tellez B
Acta Physiol (Oxf)
· 2026 Apr · PMID 41849245
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Brown adipose tissue (BAT) is increasingly recognized as a metabolically active tissue in humans, although its physiological relevance remains incompletely understood. In rodents, BAT is well characterized, with intersca...Brown adipose tissue (BAT) is increasingly recognized as a metabolically active tissue in humans, although its physiological relevance remains incompletely understood. In rodents, BAT is well characterized, with interscapular BAT (iBAT) representing the main thermogenic depot. In contrast, the existence and persistence of iBAT in adult humans have long been overlooked. In this review, we synthesize anatomical, histological, imaging, and molecular evidence supporting the presence of a potentially active iBAT depot within the dorsocervical subcutaneous adipose tissue in humans. Gene expression and histological studies have conclusively identified dorsocervical subcutaneous adipose tissue as iBAT in human neonates. In adults, the persistence of this depot has been suggested by early histological observations, although definitive molecular confirmation is still lacking. More recent data from HIV-1-infected individuals report increased expression of BAT-related markers in the dorsocervical region; however, histological analyses have not consistently confirmed the presence of iBAT in this population. In parallel, two independent cold-induced F-FDG-PET/CT studies have reported elevated glucose uptake in this area, with a higher prevalence in women. Taken together, these findings suggest that a dorsocervical subcutaneous adipose depot with BAT-like characteristics may persist into adulthood, particularly in women. Nevertheless, targeted biopsy studies combined with molecular and cellular analyses, together with advanced PET-CT imaging using tracers capable of assessing thermogenic activity in vivo, are required to clarify whether this tissue represents classical BAT, a beige adipose depot, or a developmentally retained adipose niche. Defining the identity and function of this depot would advance current concepts of human adipose tissue heterogeneity.
AIM: Sarcopenia is associated with metabolic dysregulation, yet the molecular mediators remain poorly defined. This study aimed to identify relevant regulators of muscle mass and to elucidate the role and underlying mech...AIM: Sarcopenia is associated with metabolic dysregulation, yet the molecular mediators remain poorly defined. This study aimed to identify relevant regulators of muscle mass and to elucidate the role and underlying mechanism of progranulin in skeletal muscle protein synthesis. METHODS: We combined transcriptomic profiling of muscles from high-fat diet-fed mice with human genetic data from the HugeAMP Type 2 Diabetes Knowledge Portal to identify potential regulators. Clinically, 172 participants were stratified into low muscle mass (LMM) and normal muscle mass (NMM) groups according to the Asian Working Group for Sarcopenia criteria, and serum progranulin was measured. In vitro, recombinant progranulin was applied to L6 myoblasts to assess proliferation and differentiation and to differentiated L6 myotubes to evaluate protein synthesis and mTOR/S6K/S6 signaling. We performed shRNA-mediated knockdown of Ephrin type-A receptor 2 (EphA2), a functional progranulin receptor, to determine its impact on progranulin-induced effects in L6 myotubes. RESULTS: Transcriptomics identified Grn as a top downregulated gene in metabolically stressed muscle. Clinically, serum progranulin levels were significantly lower in the LMM group than the NMM group (280.71 ± 148.09 vs. 378.96 ± 139.65 ng/mL, p < 0.001). In vitro, progranulin did not affect the proliferation or differentiation of L6 myoblasts. However, it dose-dependently enhanced protein synthesis and increased phosphorylation of mTOR, S6K, and S6 in L6 myotubes. Furthermore, EphA2 knockdown attenuated progranulin-induced protein synthesis and phosphorylation of mTOR, S6K, and S6. CONCLUSION: Progranulin acts as a novel regulator of skeletal muscle metabolism, which enhances protein synthesis through EphA2-mediated activation of the mTOR signaling cascade.