Biology subjects

Krook, A.

Publications and source records attributed to Krook, A..

12 recordsLinked to original sources

bioRxiv2025

Exercise intensity modulates the human plasma secretome and interorgan communication

Exercise is recognized as first-line therapy for many cardiometabolic diseases, including obesity, type 2 diabetes, and hypertension. Despite the abundant health-promoting effects of exercise, in-depth characterization of circulatory factors that mediate these benefits in humans remains incomplete. Moreover, how different modes and intensities of exercise uniquely regulate these processes is unclear. Here, we address these questions by conducting a multi-cohort human exercise intervention, incorporating sprint-interval exercise (SIE) and moderate-intensity exercise (MIE) to analyze intensity-dependent regulation of interorgan crosstalk. We find that exercise intensity distinctly influences the plasma proteome and metabolome in both untrained and trained participants. SIE led to immediate and robust changes to the plasma proteome, whereas MIE resulted in delayed secretory kinetics. By leveraging large, multi-organ gene and protein expression datasets, in combination with in vitro and in vivo tissue sampling, we map the differentially regulated proteins to their predicted tissue of origin and destination. We find that adipocytes are particularly sensitive to exercise intensity, undergoing broad transcriptomic remodeling following in vitro incubation with SIE as compared to MIE plasma. These findings underscore the integrated whole-body response following acute exercise and highlight exercise intensity as a key factor influencing interorgan communication.

physiology↗

bioRxiv2024

Human-specific lncRNA TMEM9B-AS1 is downregulated in skeletal muscle of individuals with type 2 diabetes and regulates ribosomal biogenesis

Long non-coding RNAs (lncRNAs) are important regulators of skeletal muscle physiology, with altered expression noted in several human diseases including type 2 diabetes. Here we report TMEM9B-AS1, a previously uncharacterized lncRNA, is downregulated in skeletal muscle of men with type 2 diabetes. Silencing of TMEM9B-AS1 in primary human myotubes attenuated protein synthesis, concomitant with reduced phosphorylation of ribosomal protein S6, a downstream target of ERK and mTOR pathways. Moreover, we provide evidence that TMEM9B-AS1 plays a pivotal role in the regulation of ribosomal biogenesis by facilitating mRNA stabilization of the transcription factor MYC through a direct physical interaction with the RNA-binding protein IGF2BP1. Disrupted ribosomal biogenesis resulting from TMEM9B-AS1 silencing is linked reduced skeletal muscle mass in type 2 diabetes, elucidating molecular mechanisms contributing to skeletal muscle loss in metabolic disease.

cell biology↗

bioRxiv2024

miR-29a-3p, a new myokine orchestrating resistance exercise via coordinated metabolic responses

It remains unclear whether the adaptive response to different exercise models is mediated by EV miRNAs released from skeletal muscle and their functional metabolic role. We sequenced miRNA-loaded plasma EVs obtained from resting mice after 4-weeks endurance or resistance training. Resistance exercise increased the expression of a 11-miRNA profile grouped into two functional clusters. Using both genetically modified animal models and in vitro approaches, we have identified miR-29a-3p as a novel myokine secreted into the bloodstream as EV cargo by contracting skeletal muscle. It is a cornerstone in the adaptation to resistance training by mediating the coordinated expression and secretion of other miRNAs and affecting muscle mass development and energy metabolism in muscle and liver. Taken together, our study suggests a coordinating and determinant role of miR-29a-3p in the response and adaptation to resistance training, possibly due to its role as a myokine through its regulatory role in energy metabolism.

molecular biology↗

bioRxiv2024

Downregulation of NR4A3 During Inactivity Alters Glucose Metabolism and Impairs Translation in Human Skeletal Muscle

The transcription factor NR4A3 is regulated by exercise and a potent modulator of skeletal muscle metabolism. We report here that physical inactivity decreased skeletal muscle NR4A3 levels, concomitant with mitochondrial function and proteostasis pathways. Silencing of NR4A3 in myotubes decreased glucose oxidation and increased lactate production. This coincided with greater signalling downstream of AMPK and elevated rates of fatty acid oxidation. While NR4A3 silencing reduced protein synthesis, mTORC1 signalling, and ribosomal transcription, overexpression of the canonical NR4A3 protein isoform augmented translation and cellular protein content. Moreover, restoration of NR4A3 levels rescued glucose oxidation in NR4A3-silenced myotubes and restored phosphorylation of mTORC1 substrates. NR4A3 depletion reduced myotube area and altered the abundance of contractile elements. Thus, downregulation of NR4A3 has adverse effects on skeletal muscle metabolism, myotube size, and contractile apparatus by directing mTORC1 signalling and ribosomal biogenesis. Our data demonstrate that NR4A3 controls skeletal muscle atrophy associated with physical inactivity.

physiology↗

bioRxiv2024

Personalized Molecular Signatures of Insulin Resistance and Type 2 Diabetes

HighlightsO_LIAdvanced proteomics analysis reveals personalized signatures of insulin resistance C_LIO_LIFasting muscle proteome and phosphoproteome predicts whole-body insulin sensitivity C_LIO_LIInsulin-stimulated phosphoproteome reveals selective insulin resistance signatures C_LIO_LIPhosphoproteome and proteome atlas explains sex-specific muscle metabolism C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/578994v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@a83000org.highwire.dtl.DTLVardef@1e77336org.highwire.dtl.DTLVardef@3d1ecdorg.highwire.dtl.DTLVardef@b1592b_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Insulin resistance is a hallmark of type 2 diabetes, which is a highly heterogeneous disease with diverse pathology. Understanding the molecular signatures of insulin resistance and its association with individual phenotypic traits is crucial for advancing precision medicine in type 2 diabetes. Utilizing cutting-edge proteomics technology, we mapped the proteome and phosphoproteome of skeletal muscle from >120 men and women with normal glucose tolerance or type 2 diabetes, with varying degrees of insulin sensitivity. Leveraging deep in vivo phenotyping, we reveal that fasting proteome and phosphoproteome signatures strongly predict insulin sensitivity. Furthermore, the insulin-stimulated phosphoproteome revealed both dysregulated and preserved signaling nodes - even in individuals with severe insulin resistance. While substantial sex-specific differences in the proteome and phosphoproteome were identified, molecular signatures of insulin resistance remained largely similar between men and women. These findings underscore the need for precision medicine approaches in type 2 diabetes care, acknowledging disease heterogeneity.

biochemistry↗

bioRxiv2024

Decreased sarcomeric mitochondrial creatine kinase 2 impairs skeletal muscle mitochondrial function independently of insulin action in type 2 diabetes

Plasma creatine levels are associated with risk of type 2 diabetes. Since skeletal muscle is the main disposal site of both creatine and glucose, we investigated the role of intramuscular creatine metabolism in the pathophysiology of insulin resistance in type 2 diabetes. We report in men with type 2 diabetes, plasma creatine levels are increased, while intramuscular phosphocreatine content is reduced. These alterations are coupled to reduced expression of sarcomeric mitochondrial creatine kinase 2 (CKMT2). In C2C12 myotubes, Ckmt2 silencing reduced mitochondrial respiration, membrane potential, and glucose oxidation. Electroporation-mediated overexpression of Ckmt2 in skeletal muscle of high-fat diet-fed male mice increased mitochondrial respiration, independent of creatine availability. Thus, beyond the canonical role of CKMT2 on creatine phosphorylation, we reveal a previously underappreciated role of CKMT2 on mitochondrial homeostasis, independent of insulin action. Collectively, our data provides functional evidence into how CKMT2 mediates mitochondrial dysfunction associated with type 2 diabetes.

physiology↗

bioRxiv2023

Inhibition of mammalian mtDNA transcription paradoxically activates liver fatty acid oxidation to reverse diet-induced hepatosteatosis and obesity

The oxidative phosphorylation (OXPHOS) system in mammalian mitochondria plays a key role in harvesting energy from ingested nutrients1, 2. Mitochondrial metabolism is very dynamic and can be reprogrammed to support both catabolic and anabolic reactions, depending on physiological demands or disease states3, 4. Rewiring of mitochondrial metabolism is intricately linked to metabolic diseases5, 6 and is also necessary to promote tumour growth7-11. Here, we demonstrate that per oral treatment with an inhibitor of mitochondrial transcription (IMT)11 shifts whole animal metabolism towards fatty acid oxidation, which, in turn, leads to rapid normalization of body weight, reversal of hepatosteatosis and restoration of glucose tolerance in mice on high-fat diet. Paradoxically, the IMT treatment causes a severe reduction of OXPHOS capacity concomitant with a marked upregulation of fatty acid oxidation in the liver, as determined by proteomics and non-targeted metabolomics analyses. The IMT treatment leads to a marked reduction of complex I, the main dehydrogenase that feeds electrons into the ubiquinone (Q) pool, whereas the levels of electron transfer flavoprotein dehydrogenase (ETF-DH) and other dehydrogenases connected to the Q pool are increased. This rewiring of metabolism caused by reduced mtDNA expression in the liver provides a novel principle for drug treatment of obesity and obesity-related pathology.

physiology↗

bioRxiv2023

The nuclear receptor Nr2f6 represses skeletal muscle oxidative metabolism and force production.

ObjectiveThe maintenance of skeletal muscle plasticity upon changes in the environment, nutrient supply, and exercise depends on regulatory mechanisms that couple structural and metabolic adaptations. However, the mechanisms that interconnect both processes at the transcriptional level remain underexplored. Nr2f6, a nuclear receptor, regulates metabolism and cell differentiation in peripheral tissues. However, its role in the skeletal muscle is still elusive. Here, we aimed to investigate, for the first time, the effects of Nr2f6 modulation on muscle biology in vivo and in vitro. MethodsGlobal RNA-seq was performed in Nr2f6-knockdown C2C12 myocytes (N=4-5). Molecular and metabolic assays and proliferation experiments were performed using stable Nr2f6 knockdown and overexpression C2C12 cell lines (N=3-6). Nr2f6 content was evaluated in in vitro and in vivo lipid overload models (N=3-6). In vivo experiments included Nr2f6 overexpression in mouse tibialis anterior muscle, followed by gene array transcriptomics and molecular assays (N=4), ex vivo contractility experiments (N=5), and histological analysis (N=7). The conservation of Nr2f6 depletion effects was confirmed in primary human and mouse skeletal muscle cells. ResultsNr2f6 knockdown upregulated genes associated with muscle differentiation, metabolism, and contraction, while cell cycle-related genes were downregulated. In human skeletal muscle cells, Nr2f6 overexpression significantly increased the expression of myosin heavy chain genes (2-3-fold). Nr2f6 content in skeletal muscle decreased by 40% in lipid-overloaded myotubes and by 50% in mice fed a high-fat diet. Depletion of Nr2f6 increased myocyte lipid oxidative capacity by 75% and protected against lipid-induced cell death. This protection was associated with direct repression of uncoupling protein 3 (20%) and PGC-1 (30%) promoter activity following Nr2f6 overexpression. Nr2f6 overexpression in mice resulted in an atrophic and hypoplastic state, characterized by a significant reduction in muscle mass (15%) and myofiber content (18%), accompanied by an impairment (50%) in force production. These functional phenotypes were accompanied by the establishment of an immune response molecular signature and a decrease in genes involved in oxidative metabolism and muscle contractility. Additionally, Nr2f6 regulated core components of the cell division machinery, effectively decoupling muscle cell proliferation from differentiation. ConclusionIn summary, our findings reveal a novel role for Nr2f6 as a molecular transducer that plays a crucial role in maintaining the balance between skeletal muscle contractile function and oxidative capacity. These findings have significant implications for the development of potential therapeutic strategies for metabolic diseases and myopathies.

biochemistry↗

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↗

bioRxiv2021

Circadian Transcriptomic and Epigenomic Remodeling in Response to Lipid Overload and Human Obesity

Obesity and elevated circulating lipids may impair metabolism by disrupting the molecular circadian clock. We tested the hypothesis that lipid-overload may interact with the circadian clock and alter the rhythmicity of gene expression through epigenomic mechanisms in skeletal muscle. Palmitate reprogrammed the circadian transcriptome in myotubes without altering the rhythmic mRNA expression of core clock genes. Genes with enhanced cycling in response to palmitate were associated with post-translational modification of histones. Cycling of histone 3 lysine 27 acetylation (H3K27ac), a marker of active gene enhancers, was modified by palmitate treatment. Chromatin immunoprecipitation and sequencing confirmed that palmitate exposure altered the cycling of DNA regions associated with H3K27ac. Overlap of mRNA and DNA regions associated with H3K27ac and pharmacological inhibition of histone acetyl transferases revealed novel cycling genes associated with lipid exposure of primary human myotubes. Palmitate exposure disrupts transcriptomic rhythmicity and modifies enhancers through changes in histone H3K27 acetylation in a circadian manner. Thus, histone acetylation is responsive to lipid-overload and redirects the circadian chromatin landscape leading to reprogramming of circadian genes in skeletal muscle.

physiology↗

bioRxiv2020

Branched-Chain Amino Acid Metabolism is Regulated by ERRα and is Further Impaired by Glucose Loading in Type 2 Diabetes

Aims/hypothesisIncreased levels of branched-chain amino acids (BCAAs) are associated with type 2 diabetes pathogenesis. However, most metabolomic studies are limited to an analysis of plasma metabolites under fasting conditions, rather than the dynamic shift in response to a metabolic challenge. Moreover, metabolomic profiles of peripheral tissues involved in glucose homeostasis are scarce and the transcriptomic regulation of genes involved in BCAA catabolism is partially unknown. This study aimed to identify differences in circulating and skeletal muscle BCAA levels in response to an OGTT in individuals with normal glucose tolerance (NGT) or type 2 diabetes. Additionally, transcription factors involved in the regulation of the BCAA gene set were identified. MethodsPlasma and vastus lateralis muscle biopsies were obtained from individuals with NGT or type 2 diabetes before and after an OGTT. Plasma and quadriceps muscles were harvested from skeletal muscle-specific PGC-1 knockout and transgenic mice. BCAA-related metabolites and genes were assessed by LC-MS/MS and RT-PCR, respectively. Small interfering RNA and adenovirus-mediated overexpression techniques were used in primary human skeletal muscle cells to study the role of PGC-1A and ESRRA in the expression of the BCAA gene set. Radiolabeled leucine was used to analyze the impact of ERR knockdown on leucine oxidation. ResultsImpairments in BCAA catabolism in people with type 2 diabetes under fasting conditions were exacerbated after a glucose load. Branched-chain keto acids were reduced 37-56% after an OGTT in the NGT group, whereas no changes were detected in individuals with T2D. These changes were concomitant with a stronger correlation with glucose homeostasis biomarkers and downregulated expression of BCAT2, BCKDH complex subunits and 69% of downstream BCAA-related genes in skeletal muscle. In primary human myotubes overexpressing PGC-1, 61% of the analyzed BCAA genes were upregulated, while 67% were downregulated in the quadriceps of skeletal muscle-specific PGC-1 knockout mice. ESRRA (encoding estrogen-related receptor , ERR) silencing completely abrogated the PGC-1-induced upregulation of BCAA-related genes in primary human myotubes. Conclusions/interpretationMetabolic inflexibility in type 2 diabetes impacts BCAA homeostasis and attenuates the decrease of circulating and skeletal muscle BCAA-related metabolites after a glucose challenge. Transcriptional regulation of BCAA genes in primary human myotubes via a PGC-1 is ERR-dependent. Research in contextO_ST_ABSWhat is already known about this subject?C_ST_ABSO_LICirculating levels of BCAA are elevated in type 2 diabetes. C_LIO_LIPGC-1 is involved in the transcription of the BCAA gene set. C_LI What is the key question?O_LIDoes metabolic inflexibility associated with type 2 diabetes encompass BCAA homeostasis and PGC-1 mediated transcription of the BCAA gene set? C_LI What are the new findings?O_LIBCAA homeostasis is further compromised by a glucose challenge in type 2 diabetes. C_LIO_LIAn OGTT reveals coordinated regulation between BCAA metabolites, blood glucose, and HbA1c levels. C_LIO_LIERR is essential for PGC-1-mediated BCAA gene expression in primary human myotubes. C_LI How might this impact on clinical practice in the foreseeable future?O_LIAn OGTT can be used to underscore impairments in BCAA metabolism. These findings suggest that interventions targeting the PGC-1/ ERR axis may improve BCAA homeostasis. C_LI

physiology↗

bioRxiv2019

Transcriptomic Profiling of Skeletal Muscle Adaptations to Exercise and Inactivity

The molecular mechanisms underlying the response to exercise and inactivity are not fully understood. We propose an innovative approach to profile the skeletal muscle transcriptome to exercise and inactivity using 66 published datasets. Data collected from human studies of aerobic and resistance exercise, including acute and chronic exercise training, were integrated using meta-analysis methods (www.metamex.eu). Gene ontology and pathway analyses reveal selective pathways activated by inactivity, aerobic versus resistance and acute versus chronic exercise training. We identified NR4A3 as one of the most exercise- and inactivity-responsive genes, and established a role for this nuclear receptor in mediating the metabolic responses to exercise-like stimuli in vitro. The meta-analysis (MetaMEx) also highlights the differential response to exercise in individuals with metabolic impairments. MetaMEx provides the most extensive dataset of skeletal muscle transcriptional responses to different modes of exercise and an online interface to readily interrogate the database.

physiology↗