Biology subjects

Treebak, J. T.

Publications and source records attributed to Treebak, J. T..

10 recordsLinked to original sources

bioRxiv2025

Repeated Disuse Atrophy Imprints a Molecular Memory in Skeletal Muscle: Transcriptional Resilience in Young Adults and Susceptibility in Aged Muscle

Disuse-induced muscle atrophy is common after illness, injury, or falls and becomes increasingly frequent with ageing. Whether skeletal muscle retains a "memory" of repeated disuse remains unknown. We investigated repeated lower-limb immobilization in young adults and a refined aged rat model, integrating physiological, multi-omic, immunohistochemical, biochemical, and primary human muscle stem cell (MuSC) analyses. To enable robust age comparisons, we integrated published young rat data with newly generated aged rat data. In young human muscle, repeated disuse elicited attenuated transcriptional perturbations in oxidative and mitochondrial pathways, suggestive of a protective molecular memory, despite similar atrophy to initial disuse. In contrast, aged muscle exhibited a detrimental memory, characterised by greater atrophy, exaggerated suppression of aerobic metabolism genes despite recovery after initial disuse, NAD and mitochondrial DNA depletion, and activation of proteasomal, extracellular-matrix, and DNA-damage pathways. Whereas young rats recovered muscle mass after initial disuse, aged rats did not. Repeated disuse induced DNA hypermethylation and downregulation of aerobic metabolism and mitochondrial genes across species. NR4A1 remained suppressed into recovery, while AChR subunit genes (CHRNA1, CHRND) were epigenetically primed. NMRK2, an NAD biosynthesis gene, was among the most downregulated after both atrophy periods, and nicotinamide riboside improved myotube size in MuSCs post-atrophy. Repeated disuse atrophy imprints a molecular memory in skeletal muscle shaping transcriptional resilience in young adults and exaggerated susceptibility in aged muscle.

physiology↗

bioRxiv2025

Common and distinct roles of AMPKγ isoforms in small-molecule activator-stimulated glucose uptake in mouse skeletal muscle

ObjectiveSmall-molecule activators targeting the allosteric drug and metabolite (ADaM) site of AMPK enhance insulin-independent glucose uptake in skeletal muscle and lower glucose in preclinical models of hyperglycemia. The regulatory AMPK{gamma} subunit plays a central role in energy sensing. While the skeletal muscle-selective {gamma}3 isoform is essential for AMP/ZMP-induced glucose uptake, it is dispensable for ADaM site-binding activators. We hypothesized that the predominant {gamma}1 isoform is required for ADaM site activator-stimulated glucose uptake in skeletal muscle. MethodsSingle-nucleus RNA sequencing (snRNA-seq) was performed on mouse and human skeletal muscle mapping AMPK subunit isoform distribution across resident cell types. To determine {gamma} isoform-specific requirements for activator-stimulated glucose uptake, skeletal muscle-specific inducible AMPK{gamma}1/{gamma}3 double knockout (im{gamma}1-/-/{gamma}3-/-) and single knockout (im{gamma}1-/- and im{gamma}3-/-) mice were generated. Ex vivo glucose uptake was measured following treatment with AICAR (AMP-mimetic) or MK-8722 (ADaM site activator), and in vivo MK-8722-induced blood glucose lowering was assessed. ResultssnRNA-seq revealed distinct AMPK isoform distribution: {gamma}1 was ubiquitously expressed, whereas {gamma}3 was enriched in glycolytic myofibers in both mouse and human skeletal muscle. Ex vivo, glucose uptake stimulated by either AICAR or MK-8722 was abolished in im{gamma}1-/-/{gamma}3-/- muscle, and MK-8722-induced blood glucose lowering was significantly blunted in vivo. AICAR but not MK-8722-stimulated muscle glucose uptake was abolished in im{gamma}3-/-, whereas both activators fully retained effects on glucose uptake and glucose lowering in im{gamma}1-/- mice. ConclusionsWhile {gamma}1 predominates in stabilizing the AMPK2{beta}2{gamma}1 complex, it is dispensable for AMPK activator-stimulated glucose uptake in skeletal muscle, whether mediated via the nucleotide-binding or ADaM site.

biochemistry↗

bioRxiv2024

Housing temperature dictates the systemic and tissue specific molecular responses to cancer in mice

Cancer cachexia is a metabolic condition affecting up to 80% of patients with cancer. Cachexia is mediated by reduced muscle and fat mass and impaired function, and it lowers survival for patients. With no approved drugs to treat cachexia, preclinical efforts focus on understanding the molecular mechanisms underlying this condition to reveal treatment targets. Housing laboratory mice at ambient temperature imposes cold stress, leading to induced thermogenic activity and consequent whole-body metabolic adaptations. Yet, the impact of housing temperature in in vivo preclinical cachexia remains unknown. We found that thermoneutral (TN) housing in C26 carcinoma-bearing (C26) mice affected lean and fat mass, but not muscle weight or force. TN housing improved glucose tolerance in C26 mice, while enhancing circulating abundance of FGF21 and IL-6. Thermogenic tissues, especially brown adipose tissue, exhibited housing temperature-dependent molecular responses to cancer in oxygen consumption, ATP levels and SERCA ATPase activity, which are all crucial for cancer-induced whole-body metabolic adaptations. We conclude that molecular and systemic adaptations to cancer in mice critically depend on housing temperature, which should be considered in the design and interpretation of preclinical cancer studies.

physiology↗

bioRxiv2024

Sucrase isomaltase dysfunction influences dietary sucrose intake and preference

ObjectiveTo characterise the role of Sucrase-isomaltase (SI) in regulating dietary behaviours, such as sweet preference and food liking in Si knockout (Sis-KO) mice and in population-based cohorts from Greenland and the UK. DesignWe profiled the appetitive and post-ingestive response to dietary carbohydrates in SI knockout (Sis-KO) mice. Alongside this, we conducted detailed dietary analysis of 45 foods in two Greenlandic population-based cohorts (IHIT, n=2778 and 68 foods, and B2018, n=2203 and 45 foods) with the presence of a common (allele frequency = 14.3%) SI Loss of function (LoF) variant, c.273-274delAG. Finally, we explored the association between SI hypomorphic variants, liking of 140 foods, and sucrose content using data from 134,766 UKBB participants with exome sequencing and questionnaire data available. ResultsSucrose naive Sis-KO mice had a significantly reduced intake of dietary sucrose, and preference for 10% liquid sucrose, in two-bottle preference studies. Mechanistically, oral administration of the short-chain fatty acid acetate reduced sucrose-preference in wild-type mice. In Greenlandic LoF homozygous carriers we show that the previously reported reduction in sugar intake may primarily be explained by a lower intake of cake and pastries, and of candy and chocolate and that added sugar is the main factor explaining these associations. In the UKBB, a negative association with "cake icing", the food with the highest sucrose content per 100g, was detected in SI hypomorphic carriers, as well as in sensitivity analyses conducted only including carriers of known CSID LoF variants. Further, a negative linear relationship was also observed between the effect estimates of hypomorphic SI variants on food liking and the estimated sucrose content per 100g of 88 sucrose-containing foods, indicating that food dislike in SI carriers correlates with the amount of sucrose in food. ConclusionCollectively, we demonstrated that genetic variation in the SI gene is associated with significant changes in sucrose preference, characterised by a rapid avoidance of dietary sucrose in Sis-KO mice, as well as lower consumption and increased disliking of sucrose rich foods in Greenlanders and Europeans, respectively. This work demonstrates that genetic variation in the SI gene may impact physiology beyond the gastrointestinal tract and suggest the possibility to target SI to reduce the preference, and intake, of dietary sucrose with implications for digestive and metabolic health.

genetics↗

bioRxiv2023

Insulin and Exercise-induced Phosphoproteomics of Human Skeletal Muscle Identify REPS1 as a New Regulator of Muscle Glucose Uptake

Skeletal muscle regulates glucose uptake in response to insulin and exercise which is critical for maintaining metabolic health. We conducted a comprehensive phosphoproteomic analysis of skeletal muscle from healthy people in response to an acute bout of exercise or insulin stimulation by a hyperinsulinemic euglycemic clamp. Our analysis revealed 233 phosphosites regulated by both exercise and insulin of which most phosphosites were regulated in opposite directions. However, 71 phosphosites on 55 proteins displayed regulation in the same direction, indicating a potential convergence of signaling pathways. We identified the vesicle-associated protein, REPS1, to be phosphorylated at Ser709 in response to both insulin and exercise. REPS1 protein level and Ser709 phosphorylation were closely related to insulin-stimulated glucose uptake in skeletal muscle and required for maximal insulin-stimulated glucose uptake. Furthermore, we observed that insulin triggered phosphorylation of REPS1 Ser709 via P90S6 kinase (RSK) and is impaired in mice and humans with insulin resistance. Collectively, REPS1 is a convergence point for insulin and exercise signaling and a promising therapeutic target in insulin resistance.

biochemistry↗

bioRxiv2021

Compound- and fiber type-selective requirement of AMPKγ3 for insulin-independent glucose uptake in skeletal muscle

Objective: The metabolic master-switch AMP-activated protein kinase (AMPK) mediates insulin-independent glucose uptake in muscle and regulates the metabolic activity of brown and beige adipose tissue (BAT). The regulatory AMPK{gamma}3 isoform is uniquely expressed in skeletal muscle and also potentially in BAT. Here, we investigated the role that AMPK{gamma}3 plays in mediating skeletal muscle glucose uptake and whole-body glucose clearance in response to small-molecule activators that act on AMPK via distinct mechanisms. We also assessed if {gamma}3 plays a role in adipose thermogenesis and browning. Methods: Global AMPK{gamma}3 knockout (KO) mice were generated. A systematic whole-body, tissue and molecular phenotyping linked to glucose homeostasis was performed in {gamma}3 KO and wild type (WT) mice. Glucose uptake in glycolytic and oxidative skeletal muscle ex vivo, as well as blood glucose clearance in response to small molecule AMPK activators that target nucleotide-binding domain of {gamma} subunit (AICAR) and allosteric drug and metabolite (ADaM) site located at the interface of the and {beta} subunit (991, MK-8722) were assessed. Oxygen consumption, thermography, and molecular phenotyping with a {beta}3-adrenergic receptor agonist (CL-316,243) treatment were performed to assess BAT thermogenesis, characteristics and function. Results: Genetic ablation of {gamma}3 did not affect body weight, body composition, physical activity, and parameters associated with glucose homeostasis under chow or high fat diet. {gamma}3 deficiency had no effect on fiber-type composition, mitochondrial content and components, or insulin-stimulated glucose uptake in skeletal muscle. Glycolytic muscles in {gamma}3 KO mice showed a partial loss of AMPK2 activity, which was associated with reduced levels of AMPK2 and {beta}2 subunit isoforms. Notably, {gamma}3 deficiency resulted in a selective loss of AICAR-, but not MK-8722-induced blood glucose-lowering in vivo and glucose uptake specifically in glycolytic muscle ex vivo. We detected {gamma}3 in BAT and found that it preferentially interacts with 2 and {beta}2. We observed no differences in oxygen consumption, thermogenesis, morphology of BAT and inguinal white adipose tissue (iWAT), or markers of BAT activity between WT and {gamma}3 KO mice. Conclusions: These results demonstrate that {gamma}3 plays a key role in mediating AICAR- but not ADaM site binding drug-stimulated blood glucose clearance and glucose uptake specifically in glycolytic skeletal muscle. We also showed that {gamma}3 is dispensable for thermogenesis and browning of iWAT.

physiology↗

bioRxiv2021

Disrupted circadian core-clock oscillations in Type 2 Diabetes are linked to altered rhythmic mitochondrial metabolism

Circadian rhythms are generated by an auto-regulatory feedback loop composed of transcriptional activators and repressors. Disruption of circadian rhythms contributes to Type 2 diabetes (T2D) pathogenesis. We elucidated whether altered circadian rhythmicity of clock genes is associated with metabolic dysfunction in T2D. Transcriptional cycling of core clock genes ARNTL, CLOCK, CRY1 and NR1D1 was altered in skeletal muscle from individuals with T2D and this was coupled with reduced number and amplitude of cycling genes and disturbed circadian oxygen consumption. Mitochondrial associated genes were enriched for differential circadian amplitudes in T2D, and positively correlated with insulin sensitivity. ChIP- sequencing identified CLOCK and BMAL1 binding to circadian mitochondrial genes associated with insulin sensitivity, implicating regulation by the core clock. Mitochondria disruption altered core-clock gene expression and free-radical production, phenomena that were restored by resveratrol treatment. We identify bi-directional communication between mitochondrial function and rhythmic gene expression, processes which are disturbed in diabetes.

physiology↗

bioRxiv2019

Mass-spectrometry based proteomics reveals mitochondrial supercomplexome plasticity

Mitochondrial respiratory complex subunits assemble in supercomplexes. Studies of supercomplexes have typically relied upon antibody-based protein quantification, often limited to the analysis of a single subunit per respiratory complex. To provide a deeper insight into mitochondrial and supercomplex plasticity, we combined Blue Native Polyacrylamide Gel Electrophoresis (BN-PAGE) and mass spectrometry to determine the supercomplexome of skeletal muscle from sedentary and exercise-trained mice. We quantified 422 mitochondrial proteins within ten supercomplex bands, in which we showed the debated presence of complex II and V. Upon exercise-induced mitochondrial biogenesis, non-stoichiometric changes in subunits and incorporation into supercomplexes was apparent. We uncovered the dynamics of supercomplex-related assembly proteins and mtDNA-encoded subunits within supercomplexes, as well as the complexes of ubiquinone biosynthesis enzymes and Lactb, a mitochondrial-localized protein implicated in obesity. Our approach can be applied to broad biological systems. In this instance, comprehensively analyzing respiratory supercomplexes illuminates previously undetectable complexity in mitochondrial plasticity. HighlightsO_LIComprehensive quantification of respiratory subunits within supercomplexes C_LIO_LIComplex II and V assemble within supercomplexes C_LIO_LIMitochondrial-encoded subunits display elevated upregulation upon exercise training C_LIO_LIExercise increases ubiquinone biosynthesis enzyme complexes C_LI

molecular biology↗

bioRxiv2019

Lysates of Methylococcus capsulatus Bath induce a lean-like microbiota, intestinal FoxP3+RORγt+IL-17+ Tregs and improve metabolism

Interactions between host and gut microbial communities may be modulated by diets and play pivotal roles in securing immunological homeostasis and health. Here we show that intake of feed based on whole-cell lysates of the non-commensal bacterium Methylococcus capsulatus Bath (McB) as protein source reversed high fat high sucrose-induced changes in the gut microbiota to a state resembling that of lean, low fat diet-fed mice, both under mild thermal stress (T22{degrees}C) and at thermoneutrality (T30{degrees}C). McB feeding selectively upregulated triple positive (Foxp3+ROR{gamma}t+IL-17+) regulatory T cells in the small intestine and colon, and enhanced mucus production and glycosylation status suggesting improved gut health. Mice receiving McB lysates further exhibited improved glucose regulation, reduced body and liver fat along with diminished hepatic immune infiltration. Collectively, these data points towards profound whole-body effects elicited by the McB lysate suggesting that it may serve as a potent modulator of immunometabolic homeostasis.

immunology↗

bioRxiv2019

Exercise-stimulated muscle ROS production and glucose uptake requires NADPH oxidase 2

Reactive oxygen species (ROS) act as intracellular compartmentalized second messengers mediating metabolic stress-adaptation. In skeletal muscle fibers, ROS have been suggested to stimulate glucose transporter 4 (GLUT4)-dependent glucose transport during artificially evoked contraction ex vivo but whether myocellular ROS production is stimulated by in vivo exercise to control metabolism is unclear. Here, we combined exercise in humans and mice with fluorescent dyes, genetically-encoded biosensors, and NADPH oxidase 2 (NOX2) loss-of-function models to demonstrate that NOX2 is the main source of cytosolic ROS during moderate-intensity exercise in skeletal muscle. Furthermore, two NOX2 loss-of-function mouse models lacking either p47phox or Rac1 presented striking phenotypic similarities, including greatly reduced exercise-stimulated glucose uptake and GLUT4 translocation. These findings indicate that NOX2 is a major myocellular ROS source regulating glucose transport capacity during moderate-intensity exercise.

physiology↗