Biology subjects

Esser, K. A.

Publications and source records attributed to Esser, K. A..

At least 19 recordsLinked to original sources

bioRxiv2026

A multi-organ spatial metabolomic atlas of exercising mice reveals neuronal Complex I as a convergent and sufficient axis for tau pathology reduction in PS19

We constructed a spatially resolved metabolomic atlas of long-term exercise across six major organs in wild-type mice: brain, heart, lung, liver, kidney, and skeletal muscle, cataloguing 224 metabolic features and revealing coordinated inter-organ remodeling. Surprisingly, the brain showed particularly pronounced region-specific adaptation. Because pathological tau associates with synaptic mitochondria from early stages of tauopathy, we extended this multi-organ spatial metabolomic approach to PS19 mice and found that exercise reduced over 70% of observable tau pathology in PS19 hippocampus and restored the mitochondrial-related metabolome. Integrated proteomic and spatial metabolomic analyses identified NADH dehydrogenase Complex I as the convergent node. To test this finding biologically, we expressed the yeast NADH dehydrogenase, Ndi1, in PS19 neurons in the absence of exercise. This increased cerebral antioxidants, restored shuttle-linked metabolites, and reduced tau pathology. Increasing NADH dehydrogenase activity through NDI1 reproduces the core anti-tau and metabolic effects of exercise. These findings provide a molecular mechanism for how exercise may prevent or slow tau pathology accumulation, complementing the human-cohort literature linking exercise to delayed cognitive decline.

neuroscience↗

bioRxiv2026

FBXL21 regulates diurnal proteostasis and stress response by targeting DNAJB6 and client proteins

Circadian regulation of proteostasis, a key determinant of muscle health, remains poorly understood. Here, we identified DNAJB6, an Hsp40 (DnaJ) co-chaperone, as a substrate of the circadian E3 ligase FBXL21. FBXL21 mediated the ubiquitination-dependent proteasomal degradation of both DNAJB6 and its client proteins including Desmin; causative mutations of DNAJB6 in myopathies, however, rendered resistance to FBXL21-directed degradation. Fbxl21 KO C2C12 cells displayed aberrant accumulation of Desmin, and showed aggravated cytoplasmic accumulation of TDP-43, another DNAJB6 client protein, in heat shock response. Under timed exercise as a physiological stressor, WT mice displayed robust diurnal rhythms in the levels of stress granule markers (G3BP1 and FUS) and TDP-43 as a function of exercise timing. In contrast, the Fbxl21 hypomorph Psttm mutant mice showed elevated expression of these proteins without exercise, which was exacerbated under exercise-induced stress conditions; importantly, these abnormalities were rescued by skeletal muscle-specific FBXL21 expression. Our study elucidates a novel diurnal regulatory mechanism of skeletal muscle proteostasis via FBXL21 as a chaperone-linked E3 ligase, highlighting the FBXL21-DNAJB6 axis as a potential therapeutic target for myopathies.

cell biology↗

bioRxiv2026

Housing Mice in Thermoneutrality Causes Tissue-specific Changes in Number, Identity, and Phase of Circadian-expressed mRNA Transcripts

Most laboratory mice are housed at room temperature (20-25{degrees}C), which exposes them to chronic mild cold stress because it is below their thermoneutral temperature (30{degrees}C). We hypothesized that mild cold stress suppresses circadian gene expression in peripheral tissues. We performed RNA sequencing on hearts, livers, and diaphragms collected every 4 hours over 48 hours in constant darkness from male mice to identify transcripts with approximately 24-hour rhythms. Thermoneutral housing produced tissue-specific changes in the number, identity, and timing of rhythmic transcripts without altering the expression of core circadian clock genes. In the heart, the number of rhythmic transcripts increased fourfold, whereas the diaphragm showed a 1.5-fold increase. In the liver, the overall number of rhythmic transcripts showed little change, but their identity changed by 30%. Gene Ontology analysis revealed coordinated changes in the temporal organization of metabolic pathways in the heart and liver. Together, these findings demonstrate that ambient housing temperature is a major determinant of tissue-specific circadian gene expression, altering the abundance, identity, and timing of rhythmic transcripts independently of the core circadian clock. SignificanceScientists typically house laboratory mice at room temperature, below their thermoneutrality, forcing them to increase their metabolic rate to maintain core body temperature. Since ambient temperature plays an important role in metabolism, cold stress could disrupt circadian gene expression. Comparing mice housed at room temperature with a warmer, thermoneutral temperature, we found that housing temperature causes tissue-specific differences in rhythmically expressed genes in the heart, liver, and diaphragm, without altering core clock genes. The heart was especially sensitive, with rhythmic genes peaking at the transition between subjective light and dark cycles, increasing fourfold. These results identify ambient housing temperature as an underrecognized variable that biases circadian gene expression in cardio-metabolic tissues, affecting interpretation of preclinical studies of metabolism and disease.

physiology↗

bioRxiv2026

Multi-omic responses to acute exercise in abdominal subcutaneous adipose tissue of sedentary adults: findings from MoTrPAC

Exercise induces widespread health benefits across multiple tissues, yet the acute molecular responses in human adipose tissue remain poorly defined. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) profiled temporal molecular changes in abdominal subcutaneous adipose tissue (ASAT) following a single bout of exercise. Healthy sedentary adults were randomized to endurance (EE), resistance (RE), or control (CON) groups. ASAT biopsies were collected pre-exercise and at 45min, 4hr, and 24hr post-exercise, followed by transcriptomic, proteomic, phosphoproteomic, and metabolomic analyses. EE and RE elicited distinct, time-resolved molecular programs involving angiogenesis, extracellular matrix remodeling, mitochondrial metabolism, substrate utilization, and circadian regulation. Phosphoproteomics revealed acute changes in cytoskeletal and branched-chain amino acid metabolism proteins associated with glycemic control. Temporal metabolomic shifts were cell-type-specific. Finally, we identified candidate adipose-derived exerkines with predicted endocrine actions. This multi-omic map of acute ASAT responses offers insight into adipose-specific mechanisms by which exercise promotes metabolic health.

systems biology↗

bioRxiv2025

Temporal Multi-Omic Analysis Uncovers Sex-Biased Molecular Programs Underlying Skeletal Muscle Adaptation to Endurance Training

BackgroundExercise training is known to benefit health and reduce disease risk. While skeletal muscle adaptations are fundamental to many of the health benefits of exercise training, the common and sex-specific molecular regulators that mediate these adaptations remain to be fully elucidated. MethodsTo this end, we leveraged skeletal muscle multi-omics data generated by the Molecular Transducers of Physical Activity Consortium (MoTrPAC), where 6 month-old male and female rats endurance trained for 1, 2, 4, or 8 weeks. Our objective was to identify shared and sex-specific multi-omic molecular responses to endurance training in skeletal muscle, and relate them to phenotypic adaptations. ResultsWe identified largely sexually-conserved transcriptomic and proteomic pathway enrichments in the gastrocnemius, which correlated with skeletal muscle responses from a published exercise study in humans. We uncovered sex-consistent post-translational modifications, including decreased oxidation of MYH2 and deacetylation of the {beta}-oxidation enzyme HADHA. Pathway enrichment analyses revealed sex-specific remodeling across the acetylome, redox proteome, and phosphoproteome; females decreased mitochondrial protein cysteine oxidation and increased mitochondrial cristae proteins, indicative of enhanced redox buffering and mitochondrial efficiency. Despite decreases in cysteine oxidation of key mitochondrial proteins, females displayed increases in the cysteine oxidation of proteins involved in glucose catabolism relative to males after 8 weeks of training, suggestive of sex-biased subcellular reactive oxygen species generation. Males demonstrated earlier induction of mitochondrial transcripts and predicted activation of mTOR. Although the increase in mitochondrial protein abundance was more modest in males, there was greater oxidation of mitochondrial proteins in response to training compared to females. ConclusionsThis work shows a large portion of the adaptive response to endurance training in skeletal muscle is shared between females and males, while there are distinct and nuanced sex-specific adaptations that are evident, particularly at the level of post-translational regulation.

physiology↗

bioRxiv2025

Hepatocyte FAM210A deficiency disrupts mitochondrial function and triggers juvenile steatosis with compensatory repair in adulthood

Mitochondrial dynamics are central to maintaining liver metabolic homeostasis, yet the mechanisms that safeguarding mitochondrial integrity during development and metabolic dysfunction remain poorly defined. Here, we identify Family with sequence similarity 210 member A (FAM210A) as a hepatocyte-enriched mitochondrial regulator essential for postnatal liver maturation. Hepatocyte-specific deletion of Fam210a (Fam210aHKO) in mice caused early growth restriction, reduced body and liver mass, and pronounced hepatic steatosis with glycogen depletion. These defects were accompanied by lower postprandial glucose levels in the fasted-refeeding state, impaired oxidative phosphorylation, reduced mtDNA content, and abnormal cristae architecture. Transcriptomic and proteomic profiling revealed broad suppression of fatty acid, sterol, and bile acid metabolism, with concomitant glutathione stress responses. Mechanistically, FAM210A deficiency disrupted the YME1L-OPA1 axis, driving excessive OPA1 cleavage and cristae destabilization. Strikingly, these juvenile defects were transient and resolved by adulthood, underpinned by enhanced hepatocyte proliferation and mitochondrial biogenesis, consistent with a compensatory stress-adaptive response via the activation of ISR signaling. Together, these findings uncover FAM210A as a developmental safeguard of mitochondrial remodeling in hepatocytes and indicate compensatory programs with therapeutic relevance for chronic liver disease.

physiology↗

bioRxiv2025

Exercise training remodels inter-organ endocrine networks

Exercise induces organism-wide molecular adaptations, partly mediated by humoral factors released in response to acute and chronic physical activity. However, the extent and specificity of endocrine effects from training-induced secreted factors remain unclear. Here, we applied systems genetics approaches to quantify inter-organ endocrine networks using multi-tissue transcriptomics and proteomics data collected from endurance-trained rats in The Molecular Transducers of Physical Activity Consortium (MoTrPAC). Eight weeks of endurance training significantly altered both the magnitude and specificity of endocrine effects across multiple origin-target tissue pairs. Subcutaneous white adipose tissue emerged as a key endocrine regulator impacted by training, while extracellular matrix-derived factors were identified as globally regulated secretory features in trained vs sedentary animals. Notably, secretory Wnt signaling factors were identified as key mediators of exercise-induced endocrine adaptations in multiple tissues. Our systems genetics framework provides an unprecedented atlas of inter-organ communication significantly remodeled by endurance exercise, serving as a valuable resource for novel exerkine discovery.

physiology↗

bioRxiv2025

Sexually distinct multi omic responses to progressive endurance exercise training in the rat lung. Findings from MoTrPAC

Despite the lungs being essential for ventilation and aerobic exercise capacity, conventionally the lungs are not thought to adapt to exercise training. Endurance exercise is key to pulmonary rehabilitation programs, which also displays sex-specific differences in therapeutic efficacy. Given the molecular underpinnings of sex-specific lung adaptations to endurance exercise are uncharacterized, we used a multi-omics approach to study sex differences in the lungs of 6-month-old Fischer 344 rats in response to an 8 week progressive endurance treadmill training protocol. This was accomplished by reannotating publicly accessible data from the Molecular Transducers of Physical Activity Consortium (MoTrPAC) and integrating newly-analyzed acetylome data to assess multi-omic sex differences in sedentary and progressively trained states. Female rats displayed enrichment in immune-related features and pathways at the transcriptome and proteome level that were maintained with training. Conversely, in the male rat lung there was an overall decrease in immune pathways following 8 weeks of training. Sexually conserved responses to training included increased enrichment in transcriptomic pathways related to type I alveoli and proteomic pathways related to cilia, and decreased mitochondrial protein acetylation. In both sexes, features known to be enriched in lung diseases were attenuated with training. Together our findings provide novel insight into sex specific responses to endurance exercise training in the rat lung and may offer translational insight into sex-specific differences in lung disease pathogenesis and treatment.

physiology↗

bioRxiv2025

Conditional Dystrophin ablation causes profound effects on muscle development, neurobehavior, and extracellular matrix pathways

Duchenne muscular dystrophy (DMD) patients suffer from skeletal and cardiopulmonary weakness, and interestingly up to one third are diagnosed on the autism spectrum. Dystrophin is an essential protein for regulating the transmission of intracellular force to the extracellular matrix within the skeletal muscle, but also plays key roles in neurobehavior and cognitive function. The mouse dystrophin gene (also abbreviated Dmd) is X-linked and has several isoforms with tissue-specific expression, including the large Dp427m muscle transcript found in heart and skeletal muscle, and the Dp427c transcript that encodes the brain-specific dystrophin cerebellar protein. Understanding the functional requirements and pathways that are affected by dystrophin loss will impact dystrophin replacement gene therapy and exon-skipping correction strategies. We generated conditional Dystrophin knockout mice by targeting exon 52 of the mouse Dystrophin (Dmdflox52) locus. We generated dystrophin constitutive and inducible myofiber knockout (Dmd mKO) mice to evaluate the tissue-specific function of the large skeletal muscle dystrophin isoform. Constitutive embryonic deletion of the Dystrophin gene exclusively in skeletal myofibers resulted in a severe skeletal muscle myopathy, dystrophic histopathology, and functional deficits compared to the mdx mouse. Transcriptomic analysis of skeletal myofibers of the Dmd mKO mice revealed the dysregulation of key extracellular matrix and cytokine signaling pathways. Separately, we generated Purkinje neuron cerebellar dystrophin knockout (Dmd:Pcp2 KO) mice that displayed neurobehavioral deficits in social approach, social memory, and spatial navigation and working memory. These studies reveal the essential requirement for dystrophin expression in both the skeletal muscle and brain for normal physiological and neurobehavioral function. Significance StatementDuchenne muscular dystrophy is caused by the lack of a functional dystrophin protein in muscle. The large dystrophin (Dp427m) isoform is expressed in skeletal, cardiac, and smooth muscle, but its tissue-specific requirements remain unknown. We generated and characterized a conditional skeletal muscle knockout mouse (Dmd mKO). Constitutive embryonic genetic ablation of skeletal muscle Dystrophin resulted in muscle histopathologies similar to the mdx mouse, while postnatal muscle Dystrophin ablation resulted in milder pathologies. Ablating cerebellar Dystrophin Dp427c using a Pcp2/L7-Cre driver resulted in sociobehavioral defects. Transcriptomic analysis of the Dmd mKO mice showed a severe reduction of extracellular matrix and cytokine signaling pathways. Our study reveals an essential role for skeletal muscle dystrophin and identifies essential pathways for modulation using dystrophin-replacement therapies.

genetics↗

bioRxiv2024

CosinorTest: An R Shiny App for Cosinor-model-based circadian and differential analysis in transcriptomic applications

Summary CosinorTest application is an interactive R Shiny tool designed to facilitate circadian and differential circadian analysis with transcriptomic data using Cosinor-model-based methods. This novel application integrates multiple major statistical algorithms to identify circadian rhythmicity in gene expression data and enables the comparison of differential circadian patterns between two experimental conditions. Key features of the CosinorTest app include circadian rhythmicity detection, differential patterns assessment, circadian and differential analyses with repeated measurement, and interactive data visualization, all contributing to a comprehensive understanding of underlying biological mechanisms. As the application doing all comprehensive circadian analysis using the Cosinor model, the CosinorTest app fills a crucial gap in the field of circadian biology and transcriptomics, providing a powerful and user-friendly platform for researchers, especially those without profound programming skills to explore the circadian gene expression regulation, and further advance circadian research. Availability and implementationCosinorTest is freely available at https://circadiananalysis.shinyapps.io/circadianapp/. Contacthading@augusta.edu Supplementary informationSupplementary files are available at bioR{chi}iv online.

bioinformatics↗

bioRxiv2024

A Bayesian Framework for Genome-wide Circadian Rhythmicity Biomarker Detection

Circadian rhythms are endogenous [~]24-hour cycles that significantly influence physiological and behavioral processes. These rhythms are governed by a transcriptional-translational feedback loop of core circadian genes and are essential for maintaining overall health. The study of circadian rhythms has expanded into various omics datasets, necessitating accurate analytical methodology for circadian biomarker detection. Here, we introduce a novel Bayesian framework for the genome-wide detection of circadian rhythms that is capable of incorporating prior biological knowledge and adjusting for multiple testing issue via a false discovery rate approach. Our framework leverages a Bayesian hierarchical model and employs a reverse jump Markov chain Monte Carlo (rjMCMC) technique for model selection. Through extensive simulations, our method, BayesCircRhy, demonstrated superior false discovery rate control over competing methods, robustness against heavier-tailed error distributions, and better performance compared to existing approaches. The methods efficacy was further validated in two RNA-Sequencing data, including a human resitrcted feeding data and a mouse aging data, where it successfully identified known and novel circadian genes. R package "BayesianCircadian" for the method is publicly available on GitHub https://github.com/jxncdhc/BayesianCircadian.

bioinformatics↗

bioRxiv2024

Alterations of the skeletal muscle nuclear proteome after acute exercise reveals a post-transcriptional influence.

Exercise is firmly established as a key contributor to overall well-being and is frequently employed as a therapeutic approach to mitigate various health conditions. One pivotal aspect of the impact of exercise lies in the systemic transcriptional response, which underpins its beneficial adaptations. While extensive research has been devoted to understanding the transcriptional response to exercise, our knowledge of the protein constituents of nuclear processes that accompany gene expression in skeletal muscle remains largely elusive. We hypothesize that alterations in the nuclear proteome following exercise hold vital clues for comprehending the transcriptional regulation and other related nuclear functions. We isolated skeletal muscle nuclei from C57BL/6 mice both sedentary control and one-hour post 30-minute treadmill running, to gain insights into the nuclear proteome after exercise. A substantial number of the 2,323 proteins identified, were related to nuclear functions. For instance, we found 59 proteins linked to nucleocytoplasmic transport were higher in sedentary mice compared to exercise, hinting at an exercise-induced modulation to nuclear trafficking. Furthermore, 135 proteins exhibited increased abundance after exercise (FDR < 0.1) while 89 proteins decreased, with the most prominent changes in proteins linked to mRNA processing and splicing. Super resolution microscopy further highlights potential localization change in mRNA processing proteins post-exercise, further suggesting changes in nuclear transport dynamics. Nonetheless, our data provide important considerations for the study of the nuclear proteome and supports a paradigm through which exercise downregulated mRNA processing and splicing, offering valuable insights into the broader landscape of the impact from acute exercise. New & NoteworthyExercise plays a crucial role in promoting muscle health, but our understanding of nuclear proteins orchestrating exercise responses is limited. Isolation of skeletal muscle nuclei coupled with mass spectrometry enhanced the identification of nuclear proteins. This approach was used to investigate the effects of acute exercise, revealing changes in the muscle nuclear proteome 1-hour post-exercise, including proteins linked to post-transcriptional processing and splicing. Our findings offer insights into the exercise-induced changes within muscle nuclear proteins.

physiology↗

bioRxiv2024

New role of cardiomyocyte Bmal1 in the regulation of sex-specific heart transcriptomes

It has been well established that cardiovascular diseases exhibit significant differences between sexes in both preclinical models and humans. In addition, there is growing recognition that disrupted circadian rhythms can contribute to the onset and progression of cardiovascular diseases. However little is known about sex differences between the cardiac circadian clock and circadian transcriptomes in mice. Here, we show that the the core clock genes are expressed in common in both sexes but the circadian transcriptome of the mouse heart is very sex-specific. Hearts from female mice expressed significantly more rhythmically expressed genes (REGs) than male hearts and the temporal pattern of REGs was distinctly different between sexes. We next used a cardiomyocyte-specific knock out of the core clock gene, Bmal1, to investigate its role in sex-specific gene expression in the heart. All sex differences in the circadian transcriptomes were significantly diminished with cardiomyocyte-specific loss of Bmal1. Surprisingly, loss of cardiomyocyte Bmal1 also resulted in a roughly 8-fold reduction in the number of all the differentially expressed genes between male and female hearts. We conclude that cardiomyocyte-specific Bmal1, and potentially the core clock mechanism, is vital in conferring sex-specific gene expression in the adult mouse heart.

physiology↗

bioRxiv2023

Targeted brain-specific tauopathy compromises peripheral skeletal muscle integrity and function

Tauopathies are neurodegenerative disorders in which the pathological intracellular aggregation of the protein tau causes cognitive deficits. Additionally, clinical studies report muscle weakness in populations with tauopathy. However, whether neuronal pathological tau species confer muscle weakness, and whether skeletal muscle maintains contractile capacity in primary tauopathy remains unknown. Here, we identified skeletal muscle abnormalities in a mouse model of primary tauopathy, expressing human mutant P301L-tau using adeno-associated virus serotype 8 (AAV8). AAV8-P301L mice showed grip strength deficits, hyperactivity, and abnormal histological features of skeletal muscle. Additionally, spatially resolved gene expression of muscle cross sections were altered in AAV8-P301L myofibers. Transcriptional changes showed alterations of genes encoding sarcomeric proteins, proposing a weakness phenotype. Strikingly, specific force of the soleus muscle was blunted in AAV8-P301L tau male mice. Our findings suggest tauopathy has peripheral consequences in skeletal muscle that contribute to weakness in tauopathy.

neuroscience↗

bioRxiv2023

Feeding Behavior Modifies Daily Rhythms in Autonomic Signaling and Core Body Temperature to Shape 24-hour Rhythms in Cardiac Electrophysiology

Rhythmic feeding behavior is critical for regulating the phase and amplitude in the {asymp}24-hour variation of the heart rate (RR intervals), ventricular repolarization (QT intervals), and core body temperature in mice. We hypothesized the changes in cardiac electrophysiology associated with feeding behavior were secondary to changes in core body temperature. Telemetry was used to record electrocardiograms and core body temperature in mice during ad libitum-fed conditions and after inverting normal feeding behavior by restricting food access to the light cycle. Light cycle-restricted feeding quickly modified the phase and amplitude of the 24-hour rhythms in RR intervals, QT intervals, and core body temperature to realign with the new feeding time. Heart rate variability analysis and inhibiting {beta}-adrenergic and muscarinic receptors suggested that the changes in the phase and amplitude of the 24-hour rhythms in RR intervals were secondary to changes in autonomic signaling. In contrast, the changes in the QT intervals closely mirrored changes in core body temperature. Studies at thermoneutrality confirmed the daily variation in the QT interval, but not the RR interval, and reflected daily changes in core body temperature (even in ad libitum-fed conditions). Correcting the QT interval for differences in core body temperature helped to unmask QT interval prolongation after starting light cycle-restricted feeding and in a mouse model of long QT syndrome. We conclude feeding behavior alters autonomic signaling and core body temperature to regulate the phase and amplitude in RR and QT intervals, respectively.

physiology↗

bioRxiv2023

Muscle Bmal1 is necessary for normal transcriptomic and metabolomic adaptation to endurance exercise training.

ObjectivesIn this investigation, we addressed the contribution of the core circadian clock factor, BMAL1, in skeletal muscle to both acute transcriptional responses to exercise and transcriptional remodelling in response to exercise training. Additionally, we adopted a systems biology approach to investigate how loss of skeletal muscle BMAL1 altered peripheral tissue homeostasis as well as exercise training adaptations in iWAT, liver, heart, and lung of male mice. MethodsCombining inducible skeletal muscle specific BMAL1 knockout mice, physiological testing and standardized exercise protocols, we performed a multi-omic analysis (transcriptomics, chromatin accessibility and metabolomics) to explore loss of muscle BMAL1 on muscle and peripheral tissue responses to exercise. ResultsMuscle-specific BMAL1 knockout mice demonstrated a blunted transcriptional response to acute exercise, characterized by the lack of upregulation of well-established exercise responsive transcription factors including Nr4a3 and Ppargc1a. Six weeks of exercise training in muscle-specific BMAL1 knockout mice induced significantly greater and divergent transcriptomic and metabolomic changes in muscle. Surprisingly, liver, lung, inguinal white adipose and heart showed divergent exercise training transcriptomes with less than 5% of exercise-training responsive genes shared for each tissue between genotypes. ConclusionOur investigation has uncovered the critical role that BMAL1 plays in skeletal muscle as a key regulator of gene expression programs for both acute exercise and training adaptations. In addition, our work has uncovered the significant impact that altered exercise response in muscle plays in the peripheral tissue adaptation to exercise training. We also note that the transcriptome adaptations to steady state training suggest that without BMAL1, skeletal muscle does not achieve the expected homeostatic program. Our work also demonstrates that if the muscle adaptations diverge to a more maladaptive state this is linked to increased inflammation across many tissues. Understanding the molecular targets and pathways contributing to health vs. maladaptive exercise adaptations will be critical for the next stage of therapeutic design for exercise mimetics.

physiology↗

bioRxiv2023

Early morning run-training results in enhanced endurance performance adaptations in mice.

Endurance performance exhibits time-of-day variation in both humans and rodents, peaking in the late active-phase. However, whether the timing of endurance training influences performance adaptations remains unclear. To investigate, female mice were trained 5-d/week for 6-weeks at either ZT13 or ZT22, using treadmill running at 70% of each animals maximal capacity. Endurance performance was assessed at baseline, week-3, and week-6. Secondary outcomes included blood glucose and lactate, cage activity, body composition, liver and skeletal muscle glycogen content, mitochondrial and contractile protein expression. At baseline, late-active phase (ZT22)-tested mice exhibited significantly higher endurance capacity than early-active phase (ZT13)-tested mice (P<0.05). Following 6 weeks of training, ZT13-trained mice demonstrated a greater rate of improvement, with endurance increasing by 132% (P<0.05), compared to 45% in afternoon ZT22-trained mice. By week 6, performance improved but was similar between groups (P>0.05), despite lower absolute training volumes in the ZT13 group. Both training groups reduced fat-mass (ZT13: -31%,ZT22: -32%; P<0.05 vs. control), with no differences in lean mass, food intake or muscle and liver glycogen content (P>0.05). In skeletal muscle, ZT13-trained mice were associated with increased (P<0.05) COXIV protein expression, citrate synthase activity, and shifts in MyHC isoform expression, without changes (P>0.05) in mitochondrial content. ZT13-training elicited superior performance adaptations despite lower absolute workloads, indicating enhanced training efficiency. These findings identify exercise timing as a biologically relevant factor influencing endurance adaptation and variability in exercise responses. NEW & NOTEWORTHYThis study demonstrates that endurance training in the early active phase induces greater performance adaptations than late active phase training in mice, resulting in overcoming diurnal differences in exercise performance, despite lower absolute training volumes. These findings reveal exercise timing influences training efficiency, likely via circadian regulation of skeletal muscle metabolism. This work identifies time-of-day as a biologically relevant and underappreciated variable contributing to the heterogeneity of exercise responses, even in tightly controlled preclinical models.

physiology↗

bioRxiv2023

Multiomic identification of key transcriptional regulatory programs during endurance exercise training

Transcription factors (TFs) play a key role in regulating gene expression. We conducted an integrated analysis of chromatin accessibility, DNA methylation, mRNA expression, protein abundance and phosphorylation across eight tissues in fifty rats of equally represented sexes following endurance exercise training (EET) to identify coordinated epigenomic and transcriptional changes and determine key TFs involved. We uncovered tissue-specific EET associated changes and TF motif enrichment across differentially expressed genes (DEGs), accessible regions (DARs), and methylated regions (DMRs). We discovered distinct routes of EET-induced regulation through either epigenomic alterations providing better access for TFs to affect target genes, or via changes in TF expression or activity enabling target gene responses. We identified TF motifs enriched among correlated epigenomic and transcriptomic alterations, DEGs correlated with exercise-related phenotypic and cell type composition changes, and EET-induced activity changes of TFs whose target genes are enriched for DEGs. This analysis elucidates the unique gene regulatory mechanisms mediating diverse transcriptional responses to EET across tissues.

genomics↗