Biology subjects

Schoenfelder, M.

Publications and source records attributed to Schoenfelder, M..

6 recordsLinked to original sources

bioRxiv2026

Plasma metabolite responses to an oral protein tolerance test differ between young and sarcopenic participants and suggest altered anabolic sensitivity

BackgroundSarcopenia is associated with anabolic resistance, a blunted muscle protein synthesis response to protein ingestion. Here, we hypothesized that anabolic resistance may be associated with a delayed postprandial decline in circulating plasma amino acids following protein ingestion. We therefore wanted to investigate whether an oral protein tolerance test (OPTT) combined with untargeted plasma metabolomics can detect age-related or sarcopenia-related differences in amino acid time courses consistent with altered postprandial amino acid handling, which could potentially reflect reduced anabolic sensitivity. Moreover, we investigated whether metabolites other than amino acids reacted to the OPTT. MethodsTwelve young healthy adults (controls: 22-28 years) and 12 older adults with clinically diagnosed probable or confirmed sarcopenia (70-91 years) ingested 20 g of whey protein after an overnight fast. We collected venous blood at baseline, 1 h, and 2 h post-ingestion and analyzed the samples by untargeted LC-HRMS plasma metabolomics. Linear mixed-effects models were fitted for 2,968 metabolic features with Benjamini-Hochberg FDR correction. For each category (branched-chain amino acid, essential amino acid [EAA], total amino acid) we summed the within-subject log2 fold changes (FC) of the constituent amino acids. This composite is reported as the summed log2FC Results201 metabolites were structurally annotated including 58 amino acid-related metabolites and 97 lipids. Fourteen of 17 proteinogenic amino acids increased significantly after protein ingestion (FDR<0.05). In young controls, essential amino acids rose more steeply at 1 h than in sarcopenic individuals (+10.06 {+/-} 1.05 vs. +7.84 {+/-} 1.58 summed log2FC) and declined more between 1 and 2 h (-4.93 {+/-} 1.29 vs. -0.20 {+/-} 2.27 summed log2FC). Leucine exemplified this pattern best, rising 1.74 log2FC in controls and declining to 0.96 at 2 h, while remaining elevated at 1.61 log2FC in the sarcopenic group at 2 h (p=0.009). Beyond amino acids, whey protein lowered circulating free fatty acids in both groups (FA 18:2, FA 18:1, FA 16:0; all FDR<0.05). Medium- and long-chain acylcarnitines (Car 8:0, Car14:2) declined postprandially in controls but remained elevated in sarcopenic individuals (p<0.05), suggesting altered postprandial lipid metabolism. ConclusionIn this proof-of-concept study, an OPTT showed that plasma EAAs declined more slowly from their postprandial peak in older adults with sarcopenia than in young adults, consistent with altered postprandial amino acid handling that may reflect anabolic resistance. Whey protein ingestion additionally modulates lipid and acylcarnitine metabolism in an age-dependent manner, suggesting broader alterations in postprandial metabolic regulation in older adults with sarcopenia.

physiology↗

bioRxiv2026

Multi-platform plasma proteomics reveals orthogonal metabolic signatures distinguishing elite athletic phenotypes

Exercise confers profound health benefits, yet the molecular mechanisms linking physical activity to health and longevity are incompletely known. Here we applied three mass spectrometry (MS)-based and one aptamer-based proteomics workflows to elite athletes with contrasting metabolic phenotypes, sampled before and after maximal exhaustive exercise. MS detected larger effect sizes and resolved isoforms; aptamers extended proteome coverage but with unannotated proteoform biases. Acute exercise induced coordinated platelet degranulation, neutrophil activation, and extracellular matrix turnover, with peptide topology analysis providing direct evidence for vesicular release. Chronic adaptations organized along two orthogonal axes: a muscle mass gradient marked by hypertrophy signaling and attenuated systemic inflammation, and an oxidative capacity gradient characterized by metabolic health-associated proteins (APOA4, IGFBP2, ITLN1) and dampened IGF-I signaling. Exploratory biological age analysis suggested younger adipose age in athletes. The plasma proteome provides an integrated readout of exercise adaptation, linking cardiorespiratory fitness to metabolic health and healthy aging.

biochemistry↗

bioRxiv2025

Sample-multiplexed FACS-preprocessing of PBMCs enables scalable scRNA-seq without compromising transcriptomic or cellular integrity

Efficient preprocessing of peripheral blood mononuclear cells (PBMCs) for single-cell RNA-Sequencing (scRNA-seq) is crucial to ensure high sample throughput while maintaining sample integrity. In particular, when enrichment of rare immune cell populations is necessary to enable their representative profiling among more common PBMCs, sample preprocessing may become a detrimental bottleneck. Here, we present an optimized fluorescence-activated cell sorting (FACS)-based preprocessing workflow designed to enrich rare immune cells while conserving overall PBMC composition. The protocol integrates dead cell removal, targeted rare cell enrichment, channel splitting, and hash-based sample multiplexing together with a new powerful yet lightweight demultiplexing tool (YAHD), improving throughput and cell yield, reducing batch effects, and preserving biological context. Validation across cryopreserved human PBMCs obtained from different scientifically relevant sources (clinical routine and laboratory setting) demonstrated improved sample viability and representation of rare subsets in the final scRNA-seq data. Thorough transcriptomic assessment confirmed non-concerning levels of stress induction and T cell activation as well as low technical variability, removing concerns around FACS-processing, cross-donor multiplexing and channel splitting. The presented approach enables scalable and biologically faithful PBMC preprocessing for scRNA-seq, advancing the study of immune heterogeneity in health and disease.

genomics↗

bioRxiv2025

miR-196a-5p and miR-342-3p mediate skeletal muscle and thermogenic adipose tissue crosstalk through extracellular vesicles

Small extracellular vesicles (small EVs) are nanovesicles found in tissues and body fluids that contain regulatory molecules including microRNAs, termed exomiRs. Research in murine models has demonstrated that exercise can trigger the release of small EVs into the circulation. The aim of this study was to study exomiR release in humans pre and post exercise and to characterise the function of these microRNAs especially in relation to thermogenic fat. We found that exercise increased the release of exomiR-196a-5p in endurance athletes, a microRNA that induces UCP1 expression and browning of white adipocytes. We observed that myotubes specifically release miR-196a-5p within small EVs after in vitro exercise-mimicking conditions such as electrical pulse stimulation and cAMP treatment. Likewise, the expression at basal levels of the exercise-induced exomiR-342-3p negatively correlated with BMI and age. EV proteomics revealed a positive correlation between FABP4+ and miR-342-3p, suggesting an adipocyte cell origin. Overexpression of miR-342-3p increased Myogenin levels during skeletal muscle cell differentiation, indicating a positive role in muscle differentiation. Our results suggest that oxidative extreme metabolic capacities in endurance athletes contribute to the enhanced release of circulatory exomiRs after exercise mediating bi-directional crosstalk between skeletal muscle and thermogenic adipose tissue. Graphical abstractO_LISerum-EVs from endurance athletes increase UCP1 expression in white adipocytes. C_LIO_LImiR-196a and miR-342-3p are increased in serum-EVs from endurance athletes. C_LIO_LIMuscle cells release EVs enriched in miR-196a after electrical pulse stimulation. C_LIO_LImiR-196a and miR-342-3p have browning and myogenic potential, respectively. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/656129v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1bd9b25org.highwire.dtl.DTLVardef@114a549org.highwire.dtl.DTLVardef@6f863borg.highwire.dtl.DTLVardef@1d5c528_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Investigating Cell Viability under Shear Stress in Complex Microstreaming Flows Generated by Ultrasound-Driven Actuated Microbubbles

The analysis of rare or specialized cells is often a time-consuming process due to their low concentrations. In this study, we applied, for the first time, a method previously used on polymer particles to manipulate human cells. This technique enables the automatic direction and collection of target cells passing through a microchannel, significantly increasing their concentration for further analysis. The movement of the cells is controlled by an acoustically induced vortex flow generated by a microbubble. By modulating the activation of this microstreaming, the cells are shifted either to the upper or lower regions of the channel and directed into a side channel for collection downstream. The localized stress distribution, along with long-term testing that showed no cell damage, confirmed the biocompatibility of this method, making it a promising tool for lab-on-a-chip systems and biomedical diagnostics. Impact StatementThis study presents an innovative use of ultrasound-driven microbubble streaming for the precise manipulation and sorting of human cells in microfluidic environments, all while maintaining cell viability. The research shows that the localized shear stress near the microbubble is significantly below the damage threshold for cells, confirming the biocompatibility of this method. The potential impact of this work is considerable for lab-on-a-chip systems and biomedical diagnostics. It offers a reliable, non-invasive solution for the manipulation, sorting, and removal of compromised cells, thus streamlining research and diagnostic procedures. By ensuring the safe and efficient handling of rare or specialized cells, this technique can accelerate various biomedical applications. Additionally, the studys evidence of sustained cell viability under microstreaming conditions suggests broader applicability in biomedical devices, particularly in automated dead cell removal and selective cell positioning.

biophysics↗

bioRxiv2022

Skeletal muscle hypertrophy rewires glucose metabolism in mice: an experimental investigation and systematic review

BackgroundProliferating cancer cells shift their metabolism toward glycolysis even in the presence of oxygen to especially generate glycolytic intermediates as substrates for anabolic reactions. We hypothesize that a similar metabolic remodeling occurs during skeletal muscle hypertrophy. MethodsWe used mass spectrometry in hypertrophying C2C12 myotubes in vitro and plantaris mice muscle in vivo and assessed metabolomic changes and the incorporation of [U-13C6]glucose tracer. We performed enzyme inhibition of the key serine synthesis pathway enzyme phosphoglycerate dehydrogenase (Phgdh) for further mechanistic analysis and conducted a systematic review to align any changes in metabolomics during muscle growth with published findings. Finally, UK Biobank was used to link the findings to population level. ResultsThe metabolomics analysis in myotubes revealed IGF-1 induced altered metabolite concentrations in anabolic pathways such as in the pentose phosphate (ribose-5-phosphate/ribulose-5-phosphate: +40%; p=0.01) and serine synthesis pathway (serine: - 36.8%; p=0.009). Like the hypertrophy-stimulation with IGF-1 in myotubes in vitro, the concentration of the dipeptide L-carnosine was decreased by 26.6% (p=0.001) during skeletal muscle growth in vivo. However, phosphorylated sugar (glucose-6-phosphate, fructose-6-phosphate or glucose-1-phosphate) decreased by 32.2% (p=0.004) in the overloaded muscle in vivo, while increased in the IGF-1 stimulated myotubes in vitro. The systematic review revealed that 10 metabolites linked to muscle hypertrophy were directly associated with glycolysis and its interconnected anabolic pathways. We demonstrated that labelled carbon from [U-13C6]glucose is increasingly incorporated by [~]13% (p=0.001) into the non-essential amino acids in hypertrophying myotubes, which is accompanied by an increased depletion of media serine (p=0.006). The inhibition of Phgdh suppressed muscle protein synthesis in growing myotubes by 58.1% (p<0.001) highlighting the importance of the serine synthesis pathway for maintaining muscle size. Utilizing data from the UK Biobank (n=450,243), we then discerned genetic variations linked to the serine synthesis pathway (PHGDH and PSPH) and to its downstream enzyme (SHMT1), revealing their association with appendicular lean mass in humans (p<5.0e-8). ConclusionUnderstanding the mechanisms that regulates skeletal muscle mass will help in developing effective treatments against muscle weakness. Our results provide evidence for metabolic rewiring of glycolytic intermediates into anabolic pathways during muscle growth, such as in the serine synthesis.

molecular biology↗