Biology subjects

Kiens, B.

Publications and source records attributed to Kiens, B..

8 recordsLinked to original sources

bioRxiv2026

A quantitative redox proteome of the human muscle response to exercise

Reactive oxygen species (ROS) regulate protein function through reversible cysteine oxidation. In human skeletal muscle, exercise-induced ROS initiates adaptations such as mitochondrial biogenesis, increased insulin sensitivity, and hypertrophy. However, specific protein targets of ROS regulation during exercise remain unclear owing to longstanding challenges in analyzing redox proteomes in vivo. We applied cysteine derivatization and multiplexed proteomics to map muscle protein cysteine oxidation in humans during exercise. The OxiMuscle dataset quantifies reversible modifications across 9,177 unique cysteine sites on 2,782 proteins, comprising 17,492 individual cysteine site measurements in young men undergoing three types of exercise, providing the first comprehensive, site-resolved and quantitative analysis of the exercise-regulated redox cysteine proteome in humans. We systematically define cysteine oxidation targets regulated by at least one form of exercise, many of which reside in proteins with established roles in muscle physiology. Among these sites is a redox-regulated cysteine on the autophagy receptor protein p62. We demonstrate that reversible oxidation of this cysteine regulates p62-mediated autophagy upon myotube contraction and mouse muscle adaptation to exercise in vivo. Together, these results define a redox-driven mechanism linking exercise-induced autophagy to muscle adaptation. More broadly, our findings offer a comprehensive resource on redox-signaling networks in human muscle, accessible at http://oximuscle-alb-1899330623.us-east-1.elb.amazonaws.com/.

cell biology↗

bioRxiv2026

Rac1 deficiency reduces mitochondrial respiratory capacity, impairs fatty acid metabolism and causes muscle wasting

BackgroundThe age-related progressive decline in skeletal muscle function is characterised by declining mitochondrial quality control and perturbed fatty acid metabolism, contributing to frailty and increased mortality. The actin cytoskeleton, a key structural component of skeletal muscle, has recently been implicated in mitochondrial anchoring and dynamics. However, the role of actin-regulating proteins, including the Rho GTPase Rac1, in mitochondrial function and age-associated metabolic and functional muscle deterioration remains undefined. MethodsSkeletal muscle from mice with inducible muscle-specific deletion of Rac1 (Rac1 imKO) underwent unbiased mass spectrometry-based proteomic profiling. Mitochondrial morphology was assessed by transmission electron microscopy, and physiological parameters, including muscle mass and contraction-stimulated palmitate oxidation in isolated soleus muscle, were evaluated. Mitochondrial respiratory function was determined by high-resolution respirometry in permeabilised gastrocnemius skeletal muscle fibre bundles. Biochemically, muscular triacylglycerol (TG) content, mRNA (qPCR) and protein (immunoblotting) content were determined. In vastus lateralis muscle biopsies from healthy, untrained young (20-30 years) and old, sarcopenic (83-94 years) men, Rac1 and mitochondrial respiratory protein abundances were measured. A complementary human genetic association analysis was performed using the FinnGen dataset. ResultsRac1 deficiency triggered muscle wasting in middle-aged mice (Gastrocnemius: -10%; Quadriceps: -7%). Preceding muscle wasting, gene set enrichment analysis identified enrichment in fatty acid metabolism and oxidative phosphorylation pathways, consistent with increased mitochondrial volume density in Rac1 imKO muscle (subsarcolemmal: +467%; intermyofibrillar: +166%). Despite mitochondrial expansion at this stage, Rac1 deficiency attenuated the increase in palmitate oxidation in response to muscle contraction (-62%). At the muscle-wasting stage, Rac1 imKO muscle exhibited reduced mitochondrial respiratory capacity (-25-32%). Additionally, the mitochondrial dysfunction was associated with an accumulation of muscle TG (+78%, p = 0.096) and upregulation of fatty acid transporter, CD36 protein content (+25%), indicative of altered fatty acid handling. In humans, Rac1 muscle protein content was increased in old, sarcopenic subjects compared to young (+41%), and negatively correlated with quadriceps cross-sectional area (CSA) (r = -0.475) and type II fibre CSA (r = -0.466). In old, sarcopenic muscle, Rac1 protein content correlated negatively with protein content of multiple mitochondrial respiratory complexes (CI: r = -0.690, CIV: r = -0.938, CV: r = -0.704). GWAS further identified associations between Rac1 SNP variants and lipid metabolic and muscle-wasting diseases. ConclusionsMuscle Rac1 deficiency reduces mitochondrial respiratory capacity and metabolic flexibility through impaired fatty acid metabolism, leading to muscle wasting and highlighting a potential therapeutic target in age-related functional decline.

Molecular Biology↗

bioRxiv2023

The mitochondrial mRNA stabilizing protein, SLIRP, regulates skeletal muscle mitochondrial structure and respiration by exercise-recoverable mechanisms

Summary and graphical abstractDecline in mitochondrial function associates with decreased muscle mass and strength in multiple conditions, including sarcopenia and type 2 diabetes. Optimal treatment could include improving mitochondrial function, however, there are limited and equivocal data regarding the molecular cues controlling muscle mitochondrial plasticity. Here we uncover the mitochondrial-mRNA-stabilizing protein SLIRP, in complex with LRPPRC, as a PGC-1 target that regulates mitochondrial structure, respiration, and mitochondrially-encoded-mRNA pools in skeletal muscle. Exercise training effectively counteracted mitochondrial defects induced by loss of LRPPRC/SLIRP, despite sustained low mitochondrially-encoded-mRNA pools, via increased mitoribosome translation capacity. In humans, exercise training robustly increased muscle SLIRP and LRPPRC protein content across exercise modalities and sexes, yet this increase was less prominent in subjects with type 2 diabetes. Our work identifies a mechanism of post-transcriptional mitochondrial regulation in skeletal muscle through mitochondrial mRNA stabilization. It emphasizes exercise as an effective approach to alleviate mitochondrial defects by possibly increasing mitoribosome capacity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/564600v2_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@1cdc6c5org.highwire.dtl.DTLVardef@b4cb1borg.highwire.dtl.DTLVardef@182871corg.highwire.dtl.DTLVardef@7462ea_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

The Rho GTPase Rac1 mediates exercise training adaptations

Exercise training elicits tremendous health benefits; however, the molecular underpinnings are poorly understood. As one of the most regulated groups of proteins following acute exercise in human muscle, Rho GTPases are unexplored candidates for mediating the beneficial effects of exercise. The Rho GTPase Rac1 was activated during multiple exercise modalities and remained elevated hours after resistance exercise in human muscle. Inducible muscle-specific Rac1 knockout (Rac1 imKO) mice, displayed attenuated muscle protein synthesis, glycogen resynthesis and p38 MAPK signaling in recovery from contractions. Exercise training upregulated Rac1 protein content in human and mouse muscle. Overexpression of hyperactive Rac1 elevated reactive oxidant species production during exercise yet did not induce a trained muscle phenotype. In Rac1 imKO mice, the improvements in running capacity and muscle mass after exercise training were diminished. Using gain- and loss-of-function mouse models and human muscle biopsies, we identify Rac1 as a regulator of exercise training adaptions. HighlightsO_LIVarious exercise modalities activate Rac1 signaling in human skeletal muscle. C_LIO_LIHSP27, MNK1, and CREB are Rac1-dependent contraction-responsive targets in muscle. C_LIO_LIPost-contraction protein synthesis requires Rac1 but not NOX2. C_LIO_LIRac1-NOX2 signaling is necessary for post-contraction glycogen resynthesis. C_LIO_LIExercise training increases Rac1 protein content in human and mouse muscles. C_LIO_LIRac1 mediates critical adaptations to exercise training. C_LI

molecular biology↗

bioRxiv2023

Pantothenate Kinase 4 controls efficient skeletal muscle energy substrate metabolism via acetyl-CoA

Metabolic inflexibility in skeletal muscle (SkM) is closely linked to metabolic diseases. Exercise improves metabolic flexibility, rendering it a valuable discovery tool of mechanisms promoting efficient metabolism of glucose and lipids. We herein discover pantothenate kinase 4 (PanK4) as a conserved exercise target with high abundance in SkM. We go on to show that murine muscle Pank4 is dysregulated with high-fat diet feeding, and identify human PANK4 variants that associate with glycemic control and body mass index traits, indicating important roles of PanK4 in glucose metabolism and growth. Consistent with the latter, germline deletion of PanK4 reduces circulating IGF-1 and stunts growth in mice. Deletion specifically in mouse SkM reveals that PanK4 facilitates fatty acid oxidation by acting as a regulator of SkM acetyl-CoA, a key node in metabolism of both glucose and lipids. Consequently, without PanK4, elevated SkM acetyl-CoA levels allosterically gridlock key enzymes required for efficient lipid and glucose utilization, and these SkM metabolic perturbations manifest in whole-body insulin resistance. As proof of principle, we show that an increase in muscle PanK4 lowers SkM acetyl-CoA and increases SkM glucose utilization. Our findings identify PanK4 as a novel regulator of SkM energy substrate metabolism, warranting inclusion in comprehensive strategies against metabolic disease.

physiology↗

bioRxiv2020

Pharmacological but not physiological GDF15 suppresses feeding and the motivation to exercise

Growing evidence supports that pharmacological application of growth differentiation factor 15 (GDF15) suppresses appetite but also promotes sickness-like behaviors in rodents via GDNF family receptor -like (GFRAL)-dependent mechanisms1,2. Conversely, the endogenous regulation and secretion of GDF15 and its physiological effects on energy homeostasis and behavior remain elusive. Here we show, in four independent studies that prolonged, moderate- to high-intensity endurance exercise substantially increases circulating GDF15, in a time-dependent and reversible fashion, to peak levels otherwise only observed in pathophysiological conditions. This exercise-induced increase can be recapitulated in mice following forced treadmill running and is accompanied by increased Gdf15 expression in the liver, skeletal muscle, and heart muscle. Compared to other metabolic stressors, like fasting, acute high-fat diet feeding, severe caloric excess and temperature changes, exercise has a greater impact on circulating GDF15 levels. However, whereas pharmacological GDF15 inhibits appetite and suppresses wheel running activity via GFRAL, in response to exercise, the physiological induction of GDF15 does not. In summary, exercise-induced circulating GDF15 correlates with the duration of endurance exercise. However, higher GDF15 levels after exercise are not sufficient to evoke canonical pharmacological GDF15 effects on appetite or responsible for exercise aversion/fatigue. Thus, the physiological effects of GDF15 as an exerkine remain elusive.

physiology↗

bioRxiv2019

Restriction of essential amino acids dictates the systemic response to dietary protein dilution

Dietary protein dilution (DPD) promotes metabolic remodelling and health but the precise nutritional components driving this response remain elusive. Here we demonstrate that dietary amino acids (AA) are sufficient and necessary to drive the response to DPD. In particular, the restriction of dietary essential AA (EAA) supply, but not non-EAA, drives the systemic metabolic response to total AA deprivation. Furthermore, systemic deprivation of Thr and Trp, independent of total AA supply, are both adequate and necessary to confer the systemic metabolic response to both diet, and genetic AA-transport loss, driven AA restriction. Thr is also potentially limiting in low-protein diet fed humans, and dietary Thr restriction (DTR) retarded the development of obesity-associated metabolic dysfunction in mice. Liver-derived fibroblast growth factor 21 was required for the metabolic remodelling with DTR. Strikingly, hepatocyte-selective establishment of Thr biosynthetic capacity reversed the systemic response to DTR. Taken together, our studies demonstrate that the restriction of EAA are sufficient and necessary to confer the systemic metabolic effects of DPD.

physiology↗

bioRxiv2019

Tumor-bearing mice display reduced insulin-stimulated glucose uptake and microvascular perfusion and exhibit increased hepatic glucose production

BackgroundRedirecting glucose from skeletal muscle and adipose tissue, likely benefits the tumors energy demand to support tumor growth, as cancer patients with type 2 diabetes have 30% increased mortality rates. The aim of this study was to elucidate tissue-specific contributions and molecular mechanisms underlying cancer-induced metabolic perturbations. MethodsGlucose uptake in skeletal muscle and white adipose tissue (WAT), as well as hepatic glucose production, were determined in control and Lewis lung carcinoma (LLC) tumor-bearing C57BL/6 mice using isotopic tracers. Skeletal muscle microvascular perfusion was analyzed via a real-time contrast-enhanced ultrasound technique. Finally, the role of fatty acid turnover on glycemic control was determined by treating tumor-bearing insulin-resistant mice with nicotinic acid or etomoxir. ResultsLLC tumor-bearing mice displayed reduced insulin-induced blood-glucose-lowering and glucose intolerance, which was restored by etomoxir or nicotinic acid. Insulin-stimulated glucose uptake was 30-40% reduced in skeletal muscle and WAT of mice carrying large tumors. Despite compromised glucose uptake, tumor-bearing mice displayed upregulated insulin-stimulated phosphorylation of TBC1D4Thr642 (+18%), AKTSer474 (+65%), and AKTThr309 (+86%) in muscle. Insulin caused a 70% increase in muscle microvascular perfusion in control mice, which was abolished in tumor-bearing mice. Additionally, tumor-bearing mice displayed increased (+45%) basal (not insulin-stimulated) hepatic glucose production. ConclusionsCancer can result in marked perturbations on at least six metabolically essential functions; i) insulins blood-glucose-lowering effect, ii) glucose tolerance, iii) skeletal muscle and WAT insulin-stimulated glucose uptake, iv) intramyocellular insulin signaling, v) muscle microvascular perfusion, and vi) basal hepatic glucose production in mice. The mechanism causing cancer-induced insulin resistance may relate to fatty acid metabolism.

cancer biology↗