American journal of physiology. Cell physiology最新文献

Cancer cachexia is a wasting condition, primarily affecting skeletal muscle, impairing patients' quality of life, prognosis, and survival. The molecular triggers are incompletely defined, but given prior evidence for epigenetic plasticity in muscle, we speculate that dysregulated DNA methylation plays a role in muscle transcriptional alterations mediating cachexia severity. We aimed to describe and integrate the cachexia methylome and transcriptome. We used a time course approach in a mild cachexia model (colon-26, C26) coupled with a severe cachexia genetic model (Apc^Min/+) in both biological sexes to assess the methylome across degrees of cachexia pathology. The muscle methylome and transcriptome were analyzed separately and subsequently integrated using a computational technique to infer epigenetic control of gene expression. Male mice exhibited widespread disruptions to the transcriptome across time points, whereas females were more protected; in severe pathophysiologic phenotypes, the magnitude of change was similar between sexes. A conserved set of inflammation-related genes was dysregulated across cachexia progression and sex, including Osmr, Stat3, and Serpina3n. Epigenetic alterations in both sexes emerged in promoter regions as early as 10 days post-tumor implant in C26, despite a lack of physiologic phenotype and before the transcriptome disruptions. Our integration analysis suggests methylome alterations as a mechanism of cachexia pathophysiology in severe phenotypes. A conserved feature across -omics layers, sexes, and conditions was dysregulated Runx1 and neurodegeneration-related pathways, which may indicate cachexia-mediated denervation. Overall, we provide evidence for the role of epigenetics in cachexia progression and severity and a valuable resource to the cachexia research communities.NEW & NOTEWORTHY Using multi-omics integration, we establish that DNA methylation status likely influences the muscle transcriptome during cancer cachexia, affecting pathways commonly disrupted in cachexia including those associated with neurodegeneration and metabolism. Epigenetic dysregulation occurs early and progresses during the onset and establishment of cancer cachexia, highlighting DNA methylation as a potential therapeutic target to slow or mitigate disease progression.

It remains unclear how excess adipose tissue in obesity leads to inflammation, insulin resistance, and other comorbidities. Extracellular nucleosides can induce inflammation through the activation of immune cell toll-like and purinergic receptors. The present study quantified nucleoside release from adipocytes and adipose tissue. Cultured mouse adipocytes released many nucleosides used in RNA/DNA. Adipose tissue from obese mice released more nucleosides than that from control nonobese mice ex vivo and had higher interstitial fluid concentrations in vivo. Consistent with the mouse study, human adipose tissue also showed significant release of adenosine/deoxyadenosine, guanosine/deoxyguanosine, and uridine ex vivo. Adipocytes release nucleosides in part through the equilibrative nucleoside transporter 1, though other pathways also appear to contribute to extracellular nucleoside concentrations. Extracellular nucleosides induce adipose tissue expression of inflammatory cytokines Tnfα, Il6, and Il1β. These data uncover a previously unknown phenomenon of adipocyte release of nucleosides, which contribute to adipose tissue inflammation in obesity.NEW & NOTEWORTHY Adipose tissue inflammation contributes to the morbidity and mortality of obesity. Adipocytes are known to release uridine and adenosine, but information on other nucleosides is lacking. As nucleosides can induce inflammation, we characterized nucleoside release from mouse and human adipose tissue. Adipose tissue released adenosine/deoxyadenosine, guanosine/deoxyguanosine, and uridine ex vivo. Nucleoside secretion was associated with adipose tissue expression of inflammatory cytokines. This represents a new mechanism by which obese adipose tissue may develop inflammation.

Transplantation of pancreatic islets, containing insulin-secreting beta cells, provides substantial benefits for individuals with type 1 diabetes. However, the low yield of the procedure limits its therapeutic potential, as many islets are lost during preparation and transplantation, primarily due to ischemia/reperfusion injuries and oxidative stress. N1-guanyl-1,7-diaminoheptane (GC7), an inhibitor of eIF5A hypusination, improves the resistance of various cells and organs to ischemia/reperfusion. Our study therefore explored whether GC7 treatment of beta cell models in vitro could serve as a strategy to enhance their resistance to ischemia/reperfusion injuries. We treated rat INS-1 or mouse MIN6 cells with GC7 and analyzed insulin secretion, energetic metabolism, mitochondrial function, and both cell survival and oxidative stress under anoxia/reoxygenation conditions. In beta cells, eIF5A inhibition by GC7 treatment repressed transiently the mitochondrial activity, ATP production, and insulin secretion in response to glucose, which was linked to a metabolic shift from oxidative phosphorylation to anaerobic glycolysis. Following anoxia/reoxygenation to mimic ischemia/reperfusion, GC7 treatment significantly reduced oxidative stress while significantly improving cell survival by >50%. Collectively, these findings are a proof of concept, demonstrating that GC7 treatment of beta cells enhances their resistance to ischemia-reperfusion injury. Hence, the use of GC7 appears as a promising strategy to improve pancreatic islet survival during transplantation.NEW & NOTEWORTHY Treatment of rodent beta cell line with GC7, an inhibitor of eIF5A hypusination, reversibly slows down mitochondrial activity and shifts the cells' energy metabolism toward anaerobic glycolysis. As a result, GC7 treatment transiently inhibits ATP production and insulin secretion in response to glucose. These changes enhance the resistance of pancreatic beta cell line to ischemia/reperfusion by reducing oxidative stress and improving cell survival, highlighting the potential anti-ischemic benefits of GC7 for pancreatic islet transplantation.

Acute exercise increases energy demand in skeletal muscle and releases metabolic intermediates into circulation, yet the serum kinetics of exercise-mobilized metabolites remain poorly characterized. By applying high-frequency serial blood sampling and targeted metabolomics in a longitudinal exercise trial with 12 young, healthy adults (6 females, 6 males), we assessed temporal alterations in energy-related metabolites during acute aerobic exercise and after 1 h of recovery. We provide evidence for 42 exercise-responsive metabolites, including end products of glycolysis, tricarboxylic acid cycle intermediates, ketone bodies, and amino acids. Overall, the observed metabolic alterations closely resembled skeletal muscle energy metabolism, thereby refining fundamental principles of exercise biochemistry through detailed serum kinetics, including novel, so far uncharacterized responses in systemic energy homeostasis and interorgan crosstalk.NEW & NOTEWORTHY In our study, we provide detailed serum kinetics of energy-related metabolites during acute aerobic exercise and after 1 h of recovery. Semantic interpretation of our results against the backdrop of fundamental principles of exercise biochemistry indicate that serum metabolites mirror skeletal muscle energy metabolism, thus providing new insights into systemic energy homeostasis and interorgan crosstalk.

Rest is generally required for full muscle regeneration after an injury; however, rehabilitative activity is often used after injury to attempt a faster recovery. Although rehabilitative activity can enhance muscle regeneration, there is also a risk that returning to vigorous muscle contractions too early after sustaining an injury, could reinjure the muscle and negatively impact full muscle regeneration. It is not known whether mitochondrial transplantation (MT) added to rehabilitative muscle activity would speed the regeneration of muscle morphology more rapidly than resting during the recovery period. Therefore, submaximal electrically evoked isometric contractions (ECs) were given to the injured muscles of MT-treated mice, to test the hypothesis that MT would attenuate the negative regenerative effects of EC and improve the restoration of muscle mass and morphology after muscle injury. Cardiotoxin (CTX) was injected into the tibialis anterior (TA) muscle of one limb of C57BL/6 mice at 8-12 wk of age to induce muscle injury. Systemic delivery of MT or PBS was administered to the mice 48 h after injury. The TA received EC at 40 Hz every other day for up to 14 days after CTX injury. Although EC-induced mechanical injury slowed muscle repair, muscle fiber regeneration and nuclear domain size were improved by MT. The percentage of collagen and other noncontractile tissue was elevated in CTX-injured and EC-treated muscles; however, MT reduced fibrosis/noncontractile tissue deposition in regenerating muscles. Our results provide evidence that systemic mitochondria delivery can improve muscle repair and can attenuate contraction-suppressed muscle fiber regeneration during recovery after injury.NEW & NOTEWORTHY Electrically evoked muscle contractions conducted every other day after muscle injury caused additional damage and slowed recovery of muscle regeneration; however, mitochondria transplantation attenuated the negative regenerative effects of rehabilitative contractions on muscle fiber regeneration. This suggests that optimizing mitochondrially regulated repair may improve muscle regeneration. Furthermore, injured muscles treated by mitochondrial transplantation had lower collagen content/fibrosis than those treated with PBS after injury. Mitochondrial transplantation blunts fibrosis and improves muscle fiber repair after injury.

This systematic review investigates the role of noncoding RNAs (ncRNAs), including miRNAs, long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and transfer RNAs, in regulating mitochondrial biogenesis, dynamics, oxidative phosphorylation, and mitophagy in skeletal muscle and the potential applications of these ncRNAs in exercise molecular physiology. We conducted a comprehensive search in PubMed, Scopus, and Web of Science databases, identifying 45 relevant studies out of 2,378 records. The main findings indicate that miRNAs such as miR-128, miR-133a, miR-696, and miR-499 are critical regulators of mitochondrial function. Moreover, lncRNAs (lncEDCH1 and lncRNA-H19) and circRNA (circ-PTPN4) significantly influence mitochondrial biogenesis and function. Exercise interventions were shown to modulate the expression of these ncRNAs, particularly miR-133a and miR-696, leading to enhanced mitochondrial biogenesis and function. The review highlights the potential of these ncRNAs as biomarkers and therapeutic targets for improving mitochondrial function and treating metabolic and mitochondrial disorders. Further research is needed to explore the muscle-specific and exercise-modality-specific effects of ncRNAs to develop personalized interventions. Understanding the complex regulatory mechanisms of ncRNAs in mitochondrial adaptations can pave the way for innovative therapeutic strategies in exercise molecular physiology and metabolic health.

Pancreatic cancer (PC) is characterized by extensive desmoplasia, with heterogeneous cancer-associated fibroblasts (CAFs) as a major component. However, the contribution of distinct precursor cells to CAF heterogeneity remains poorly defined. This study investigated the role of Muc5ac in modulating CAF heterogeneity by maturing precursor cells, including adipose-derived mesenchymal stem cells (AD-MSCs), bone marrow-derived MSCs (BM-MSCs), and pancreatic stellate cells (PSCs), into different CAF subsets. RNA sequencing of precursor cells treated with conditioned media from Muc5ac-proficient or -deficient cancer cells revealed distinct transcriptional profiles. Muc5ac significantly modulated the expression of Dnmts and Tets in AD-MSCs, promoting the acquisition of extracellular matrix production, cytokine signaling, and antigen presentation programs, characteristic of both inflammatory (iCAF) and myofibroblastic (myCAF) CAF phenotypes. In PSCs, Muc5ac increased H3K27 acetylation independent of its interactome, which was validated in autochthonous murine models. Transcriptome analysis demonstrated that AD-MSCs contributed 44.4% to the CAF population, followed by PSCs (31.5%) and BM-MSCs (21.6%). Gene Ontology (GO) and KEGG analyses revealed distinct functional programs for each precursor population contributing to CAF heterogeneity. An age-dependent signature in AD-MSC maturation was identified, with a significant positive correlation between serum INHBA and MUC5AC from younger (≤55 yr, n = 20) compared with older (≥75 yr, n = 20) patients.NEW & NOTEWORTHY Cancer-associated fibroblast (CAF) heterogeneity limits effective stromal targeting in pancreatic cancer (PC). This study shows that adipose- and bone marrow-derived mesenchymal stem cells and pancreatic stellate cells intrinsically mature into distinct CAF subtypes. Muc5ac modulates the expression of epigenetic regulators and drives adipose-derived cells to dominate the CAF population. Defining precursor cell-specific CAF programs provides a framework to selectively target tumor-promoting CAFs, offering a potential strategy to improve stroma-targeted therapies in PC.

Increased degradation of the endothelial glycocalyx (EGX) is associated with cardiovascular disease. However, whether EGX impairment drives endothelial dysfunction or reflects disease severity remains unclear. Prior studies investigating EGX function primarily used two-dimensional (2-D) endothelial cell cultures, which poorly mimic the endothelial microenvironment, particularly lacking luminal shear flow. To address these limitations, we leveraged a three-dimensional (3-D) human endothelium-on-a-chip to examine the roles of EGX components, namely heparan sulfate (HS) and sialic acid (SA), in regulating vascular permeability and monocyte adhesion. EGX expression was markedly higher in perfused 3-D human umbilical vein endothelial cells (HUVECs) cultures than in 2-D cultures. In 3-D HUVECs, tumor necrosis factor-alpha, a disruptor of endothelial function, did not reduce EGX expression, whereas dengue nonstructural protein 1 downregulated EGX. In 3-D HUVECs, HS degradation by heparinase III significantly increased endothelial permeability to 70-kDa fluorescein isothiocyanate-dextran without inducing cytotoxicity, whereas SA cleavage by neuraminidase reduced vascular permeability. Interestingly, neither HS nor SA cleavage affected 3-D human coronary artery endothelial cells (HCAECs) permeability. However, neuraminidase treatment significantly increased monocyte adhesion in both 3-D HUVECs and HCAECs, an effect not observed in heparinase III-treated 3-D endothelium from either vessel bed. These findings demonstrate that HS and SA play distinct roles in regulating endothelial barrier function and vascular inflammation in 3-D human endothelium.NEW & NOTEWORTHY Using a perfused 3-D human endothelium-on-a-chip, we investigated the endothelial glycocalyx (EGX) in vascular regulation. EGX degradation was linked to endothelial dysfunction induced by dengue NS1, but not by TNF-α. In HUVECs, heparan sulfate (HS) degradation increased permeability, whereas sialic acid (SA) cleavage had the opposite effect. SA degradation, but not HS, enhanced monocyte adhesion in HUVECs and human coronary ECs. This study highlights distinct, component-specific roles of HS and SA in regulating vascular function.

The cellular mechanisms for the age-related loss in skeletal muscle contractile function and increased fatigability are unresolved. We previously observed that the depressive effects of fatiguing levels of hydrogen (H⁺; pH 6.8, 6.6, and 6.2) and inorganic phosphate (P_i; 12, 20, and 30 mM) did not differ in myofibers from young compared with older adults. However, these studies used saturating Ca²⁺, while fatigue during high-intensity contractions in vivo also likely involves a decrease in myoplasmic free Ca²⁺. Thus, we compared the Ca²⁺ sensitivity of myofibers from 10 young (22.1 ± 3.6; 5 women) and 13 older (71.7 ± 5.5; 7 women) adults in conditions mimicking quiescent (pH 7 + 4 mM P_i) and fatigued (pH 6.2 + 30 mM P_i) muscle. Fast fiber cross-sectional area was ∼35% smaller in older (4,859 ± 2,116 µm²) compared with young (7,446 ± 2,399 µm², P = 0.002), which corresponded with lower maximal absolute force (P_o) in both quiescent (old = 0.75 ± 0.30 mN; young = 1.13 ± 0.32 mN; P = 0.002) and fatigue conditions (old = 0.35 ± 0.14 mN; young = 0.52 ± 0.16 mN; P = 0.002). There were no differences in fast fiber size-specific P_o, indicating the age-related decline in force was due to differences in fiber size. Elevated H⁺ and P_i shifted the force-pCa relationship to the right, confirming nonhuman studies that these metabolites contribute to fatigue by depressing the sensitivity of the myofilaments to Ca²⁺. However, Ca²⁺ sensitivity was not different with age or sex in either condition, and the metabolite-induced shift in the force-pCa relationship did not differ with age in either the slow (P = 0.507) or fast (P = 0.115) fibers. These data suggest the age-related increase in fatigability of limb muscles cannot be explained by an increased sensitivity of the myofibers to elevated H⁺ and P_i in maximal or submaximal Ca²⁺.NEW & NOTEWORTHY This study reports the effects of elevated H⁺ and P_i on Ca²⁺ sensitivity of human skeletal muscle fibers and determines whether the effects of these metabolites are altered by aging in submaximal Ca²⁺. The metabolites markedly depressed Ca²⁺ sensitivity in human muscle fibers, but there was no effect of age or sex. These data suggest that Ca²⁺ sensitivity is preserved with age in conditions that mimic both quiescent and fatigued muscle.

Extracellular glutamine (Gln) is essential for muscle progenitor cell (MPC) function and skeletal muscle regeneration/development, especially under physiological stress like aging or catabolic conditions. Gln availability regulates MPC proliferation by modulating intracellular metabolic and epigenetic states. Gln deficiency reduces cell viability, induces G0/G1 cell cycle arrest, and downregulates MyoD expression, collectively inhibiting myogenesis in human primary myoblasts (human skeletal muscle myoblast) and mouse C2C12 cells. Mechanistically, Gln deficiency enhances nuclear localization of tricarboxylic acid cycle enzyme, α-ketoglutarate dehydrogenase complex, components (i.e., DLST and OGDH), elevates histone succinylation, and reduces chromatin accessibility at the myogenic regulatory regions (Myod1 locus). These changes establish a direct link between Gln availability and an epigenetic-metabolic axis crucial for myogenic gene regulation. Thus, extracellular Gln acts as a key regulator of MPC proliferation through metabolic-mediated control of chromatin state.NEW & NOTEWORTHY This study revealed that extracellular Gln regulates MPC proliferation through metabolic-epigenetic axis. Gln deficiency impairs myogenesis, enhances the nuclear localization of TCA cycle enzyme, increases histone succinylation, and reduces chromatin accessibility at the myogenic regulatory regions. These findings establish Gln as a critical modulator of chromatin state via intermediary metabolic mediators during myogenesis.