Biology subjects

Karlstaedt, A.

Publications and source records attributed to Karlstaedt, A..

10 recordsLinked to original sources

bioRxiv2026

Metabolic niches: MALDI imaging reveals lipidomic heterogeneity in the human heart

The human heart is characterized by aberrant lipid accumulation and remodeling during periods of stress and disease, yet spatially resolved lipidomic profiling of the human heart remains unreported. Here, we employ matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to map lipid distributions across five anatomical regions of healthy human donor hearts (left and right atrium, left and right ventricle, and interventricular septum). Cryosections of donor hearts from healthy subjects were thaw-mounted onto indium tin oxide slides, coated with 2,5-dihydroxyacetophenone, and analyzed on a Bruker timsTOF fleX mass spectrometer in positive and negative ionization modes (50-1850 m/z; 20 m raster). Serial sections were stained with hematoxylin and eosin to enable histological co-registration with lipid distributions. We identified 150 unique lipid species with acyl-chain resolution across four glycerophospholipid classes -- phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylserine (PS) -- with abundances and spatial distributions differing significantly between regions. H&E co-registration further resolved epicardial and myocardial compartments, enabling tissue-specific lipid mapping. These findings establish the first spatially resolved lipidomic atlas of the human heart and provide a framework for identifying region-specific lipid biomarkers of cardiovascular disease.

Molecular Biology↗

bioRxiv2026

Reductive carboxylation via isocitrate dehydrogenase 1 supports cardiac metabolic adaptation during oncometabolic stress.

BackgroundCardiovascular disease and cancer are the two leading causes of morbidity and mortality worldwide. Metabolic dysregulation of cancer cells extends beyond the tumor microenvironment and increases the risk for cardiovascular diseases. One common somatic mutation in cancer cells affects isocitrate dehydrogenase (IDH) 1 and 2, which catalyzes the oxidative decarboxylation of isocitrate to alpha-ketoglutarate in the cytosol and mitochondria, respectively. IDH1 and 2 mutations cause the production of the oncometabolite D-2-hydroxyglutarate (D2-HG), which allosterically inhibits -ketoglutarate dehydrogenase (-KGDH) and is associated with reduced cardiac contractile function. MethodsWe combined stable isotope tracer studies with computational modeling to investigate the fundamental role of IDH isoforms in cardiac adaptation under oncometabolic stress. ResultsWe uncovered an unexpected cardiac phenotype that expands the role of IDH1 in the heart beyond oxidative metabolism. We quantified the stable isotopomer distributions from glucose and glutamine in perfused working rat hearts and isolated adult ventricular cardiomyocytes using mass spectrometry-based metabolomics. Our analysis revealed that defective mitochondrial metabolism causes the redirection of carbon flux from oxidative towards reductive pathways. Reductive carboxylation of -KGDH increases glutamine uptake and glutamine-derived citrate formation in working rat heart perfusions and cultured adult mouse ventricular cardiomyocytes. To identify which IDH isoform is responsible for redirecting carbon flux, we developed knockout models of IDH1, IDH2, and IDH3 in adult mouse ventricular cardiomyocytes. Loss of IDH1 expression impaired the reductive formation of citrate and caused functional defects in cardiomyocytes. Lastly, epigenetic analyses of histone marks revealed that IDH1 induces widespread alterations in histone acetylation and tri-methylation. ConclusionOur results highlight a novel role for IDH1 in cardiac metabolism and transcriptional control of metabolic adaptation to tumor-mediated stress and provide evidence that reductive-citrate formation may induce epigenetic modifications in the heart.

systems biology↗

bioRxiv2026

Capturing Cardiomyocyte Cell-to-Cell Heterogeneity via Shotgun Single Cell Top-Down Proteomics

Individual cells exhibit distinct molecular landscapes shaped by proteins and the diverse functional repertoire of their corresponding proteoforms. These structurally diverse variants (e.g., post-translationally modified including truncated proteolyzed forms) collectively orchestrate cellular functions. However, resolving proteoform heterogeneity at single-cell (SC) resolution remains a significant analytical challenge. Here, we present a shotgun SC top-down proteomics (SC-TDP) strategy that enables direct, unbiased proteoform profiling from single cardiomyocytes. Across 13 individual cardiomyocytes isolated from mouse heart, we identified a total of 57 proteins represented by 165 distinct proteoforms, including phosphorylated, succinylated, trimethylated, truncated, amongst others. Notably, proteoform composition varied substantially among cells, revealing a previously unrecognized level of molecular heterogeneity among cardiomyocytes. Together, these findings establish SC-TDP as a powerful tool for uncovering the proteoform diversity at the SC level. Our strategy paves the way for defining functional heterogeneity in cardiac tissue with unprecedented molecular resolution, enabling direct examination of the proteoform landscape that underlies cellular identity and physiology.

cell biology↗

bioRxiv2025

Interferon gamma signaling drives cardiac metabolic rewiring

BackgroundIFN-gamma (IFN-{gamma}) signaling influences myocardial inflammation and fibrosis across a wide range of conditions, including ischemic and non-ischemic heart failure (HF). However, the direct effects of IFN-{gamma} on cardiomyocytes remain poorly understood. Here, we developed a novel in vivo model to investigate how IFN-{gamma} impacts myocardial metabolism and function. MethodsMale C57BL/6J mice were injected intravenously with hepatotropic adeno-associated virus (AAV2/8) carrying Ifng and nLuc reporter under the albumin promoter (AAV- Ifng) or empty vector control virus (AAV-ctrl). Cardiac alterations were monitored on day 28 through flow cytometry, bulk RNA sequencing, targeted metabolomics, isolated mitochondrial activity, echocardiography, and in vivo imaging using [18F]fluordeoxyglucose ([18F]FDG) and [18F]fluoro-6-thia-heptadecanoic acid. Additionally, mice lacking IFN-{gamma} receptor expression in cardiomyocytes (Myh6Cre Ifngr1fl/fl) were used to further dissect the cell-intrinsic roles of IFN-{gamma} signaling in cardiomyocyte metabolic reprograming. ResultsAfter confirming liver-specific viral transfection and elevated serum IFN-{gamma} production at physiological levels, we observed cardiac metabolic adaptation and rewiring in animals treated with AAV-Ifng compared to control animals. Myocardial bulk RNA sequencing and gene set enrichment analysis identified an IFN-{gamma} response signature accompanied by marked down-regulations of oxidative phosphorylation and fatty acid oxidation pathways. Functional assessment of isolated cardiac mitochondria showed decreased oxygen consumption, and targeted metabolomics confirmed metabolic shifts toward glycolysis in mice overexpressing IFN-{gamma}. In vivo imaging confirmed increased cardiac glucose uptake following AAV-Ifng treatment. Notably, these metabolic alterations were abrogated in mice with cardiomyocyte-specific deletion of IFN-{gamma} receptors (IFNGR). ConclusionsSystemic IFN-{gamma} induces pronounced metabolic reprogramming in the heart, characterized by increased glucose uptake and reduced oxidative phosphorylation, via direct signaling through cardiomyocyte IFNGR. These alterations mirror those observed in aging and some forms of HF, thereby highlighting that, beyond classical inflammation, this cytokine regulates cardiac metabolism. Novelty and significanceO_ST_ABSWhat is known?C_ST_ABSO_LIImmunological mechanisms can impact myocardial disease progression through complex context-dependent mechanisms. C_LIO_LIIFN-{gamma}, a cytokine primarily secreted by natural killer and T cells, promotes myocardial inflammation and fibrosis in the context of autoimmune myocarditis, pressure-overload-induced heart failure, and Chagas cardiomyopathy. C_LIO_LICytokines exert pleiotropic effects and can influence inflammatory responses through mechanisms involving control of energy metabolism. C_LI What new information does this article contribute?O_LIA novel adeno-associated virus model of systemic IFN-{gamma} elevation allows assessment of cardio-immune-metabolic crosstalk without confounding factors. C_LIO_LIIFN-{gamma} drives cardiac metabolic reprogramming in inflammatory contexts, characterized by enhanced glucose uptake and glycolysis with mitochondrial dysfunction, ultimately altering cardiac metabolic fluxes and function. C_LIO_LIThe IFN-{gamma}-induced cardiac metabolic reprogramming is, at least in part, mediated through direct signaling via receptors on cardiomyocytes. C_LI

immunology↗

bioRxiv2025

Bat power-metabolic profiling of the Egyptian fruit bat Rousettus aegyptiacus reveals distinctive cardiac adaptations

AimThe present study aimed to elucidate which pathways contribute to cardiometabolic adaptation in Egyptian fruit bats. MethodsUtilising cardiac tissues from Egyptian fruit bats (Rousettus aegyptiacus) and C57BL/6J mice, we combined liquid chromatography-mass spectrometry metabolic profiling, non-targeted 1H NMR spectroscopy, and in silicocomputational modelling using the genome-scale mammalian network CardioNet. Main FindingsOur analyses revealed that bat hearts exhibit a distinct metabolic profile characterised by depleted glycogen reserves and increased reliance on lipid oxidation to meet energy demands. Notably, bat hearts displayed elevated fluxes in oxidative phosphorylation, {beta}-oxidation of long-chain fatty acids, and the Krebs cycle, alongside reduced amino acid catabolism. These findings suggest that bats have evolved unique metabolic strategies to support the high-energy demands of flight, maintaining cardiac function without succumbing to pathological remodelling. ConclusionsThis study provides the first comprehensive insight into the metabolic adaptations in the cardiac tissue of a bat species, contributing to our understanding of how these mammals endure extreme physiological stresses. Integrating metabolomics with computational modelling offers a powerful approach to studying metabolic adaptations in non-model species, potentially informing therapeutic strategies for human cardiac conditions.

systems biology↗

bioRxiv2025

Immunomodulation by AZD1656 reverses cardiac dysfunction, metabolic remodelling and reduces infarct size in type 2 diabetic cardiomyopathy

Type 2 diabetes (T2D) precipitates diabetic cardiomyopathy (dbCM), a condition characterized by chronic inflammation, metabolic dysregulation and impaired cardiac performance. Here we show that the glucokinase activator AZD1656, originally developed for glycaemic control but later identified to have immunomodulatory effects, reverses cardiac dysfunction and metabolic remodelling in dbCM. In obese, hyperglycaemic db/db mice with diastolic dysfunction, six weeks of AZD1656 treatment improved myocardial performance, reduced infarct size and enhanced post-ischaemic recovery. Integrated metabolic, functional and histological analyses revealed restoration of mitochondrial metabolism and attenuation of fibrosis. Mechanistically, AZD1656 remodelled the cardiac immune landscape by promoting regulatory T-cell infiltration. These findings demonstrate a link between cardiac inflammation and metabolic remodelling in dbCM and highlight that modulation of immune cells and metabolism can protect the diabetic heart. Targeting immunometabolic pathways may therefore offer a therapeutic strategy to alleviate cardiac dysfunction and reduce infarct vulnerability in T2D

physiology↗

bioRxiv2024

ATP-dependent citrate lyase Drives Left Ventricular Dysfunction by Metabolic Remodeling of the Heart

BackgroundMetabolic remodeling is a hallmark of the failing heart. Oncometabolic stress during cancer increases the activity and abundance of the ATP-dependent citrate lyase (ACL, Acly), which promotes histone acetylation and cardiac adaptation. ACL is critical for the de novo synthesis of lipids, but how these metabolic alterations contribute to cardiac structural and functional changes remains unclear. MethodsWe utilized human heart tissue samples from healthy donor hearts and patients with hypertrophic cardiomyopathy. Further, we used CRISPR/Cas9 gene editing to inactivate Acly in cardiomyocytes of MyH6-Cas9 mice. In vivo, positron emission tomography and ex vivo stable isotope tracer labeling were used to quantify metabolic flux changes in response to the loss of ACL. We conducted a multi-omics analysis using RNA-sequencing and mass spectrometry-based metabolomics and proteomics. Experimental data were integrated into computational modeling using the metabolic network CardioNet to identify significantly dysregulated metabolic processes at a systems level. ResultsHere, we show that in mice, ACL drives metabolic adaptation in the heart to sustain contractile function, histone acetylation, and lipid modulation. Notably, we show that loss of ACL increases glucose oxidation while maintaining fatty acid oxidation. Ex vivo isotope tracing experiments revealed a reduced efflux of glucose-derived citrate from the mitochondria into the cytosol, confirming that citrate is required for reductive metabolism in the heart. We demonstrate that YAP inactivation facilitates ACL deficiency. Computational flux analysis and integrative multi-omics analysis indicate that loss of ACL induces alternative isocitrate dehydrogenase 1 flux to compensate. ConclusionsThis study mechanistically delineates how cardiac metabolism compensates for suppressed citrate metabolism in response to ACL loss and uncovers metabolic vulnerabilities in the heart.

molecular biology↗

bioRxiv2023

Lipid metabolism drives allele-specific early-stage hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) results from pathogenic variants in sarcomeric protein genes, that increase myocyte energy demand and lead to cardiac hypertrophy. But it is unknown whether a common metabolic trait underlies the cardiac phenotype at early disease stage. This study characterized two HCM mouse models (R92W-TnT, R403Q-MyHC) that demonstrate differences in mitochondrial function at early disease stage. Using a combination of cardiac phenotyping, transcriptomics, mass spectrometry-based metabolomics and computational modeling, we discovered allele-specific differences in cardiac structure/function and metabolic changes. TnT-mutant hearts had impaired energy substrate metabolism and increased phospholipid remodeling compared to MyHC-mutants. TnT-mutants showed increased incorporation of saturated fatty acid residues into ceramides, cardiolipin, and increased lipid peroxidation, that could underlie allele-specific differences in mitochondrial function and cardiomyopathy. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=172 HEIGHT=200 SRC="FIGDIR/small/564562v1_ufig1.gif" ALT="Figure 1"> O_LINKSMALLFIG WIDTH=185 HEIGHT=200 SRC="FIGDIR/small/564562v1_ufig2.gif" ALT="Figure 1"> O_LINKSMALLFIG WIDTH=200 HEIGHT=74 SRC="FIGDIR/small/564562v1_ufig3.gif" ALT="Figure 1"> View larger version (90K): org.highwire.dtl.DTLVardef@195b1d7org.highwire.dtl.DTLVardef@cead88org.highwire.dtl.DTLVardef@e2bf35org.highwire.dtl.DTLVardef@776765_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2023

Mitochondrial citrate carrier SLC25A1 is a dosage-dependent regulator of metabolic reprogramming and morphogenesis in the developing heart

The developing mammalian heart undergoes an important metabolic shift from glycolysis toward mitochondrial oxidation, such that oxidative phosphorylation defects may present with cardiac abnormalities. Here, we describe a new mechanistic link between mitochondria and cardiac morphogenesis, uncovered by studying mice with systemic loss of the mitochondrial citrate carrier SLC25A1. Slc25a1 null embryos displayed impaired growth, cardiac malformations, and aberrant mitochondrial function. Importantly, Slc25a1 heterozygous embryos, which are overtly indistinguishable from wild type, exhibited an increased frequency of these defects, suggesting Slc25a1 haploinsuffiency and dose-dependent effects. Supporting clinical relevance, we found a near-significant association between ultrarare human pathogenic SLC25A1 variants and pediatric congenital heart disease. Mechanistically, SLC25A1 may link mitochondria to transcriptional regulation of metabolism through epigenetic control of gene expression to promote metabolic remodeling in the developing heart. Collectively, this work positions SLC25A1 as a novel mitochondrial regulator of ventricular morphogenesis and cardiac metabolic maturation and suggests a role in congenital heart disease.

developmental biology↗

bioRxiv2020

Oncometabolism Drives Autophagy Activation in Skeletal Muscle

About 20-30% of cancer-associated deaths are due to complications from cachexia which is characterized by skeletal muscle atrophy. Metabolic reprogramming in cancer cells causes body-wide metabolic and proteomic remodeling, which remain poorly understood. Here, we present evidence that the oncometabolite D-2-hydroxylgutarate (D2-HG) impairs NAD+ redox homeostasis in skeletal myotubes, causing atrophy via deacetylation of LC3-II by the nuclear deacetylase Sirt1. Overexpression of p300 or silencing of Sirt1 abrogate its interaction with LC3, and subsequently reduced levels of LC3 lipidation. Using RNA-sequencing and mass spectrometry-based metabolomics and proteomics, we demonstrate that prolonged treatment with the oncometabolite D2-HG in mice promotes cachexia in vivo and increases the abundance of proteins and metabolites, which are involved in energy substrate metabolism, chromatin acetylation and autophagy regulation. We further show that D2-HG promotes a sex-dependent adaptation in skeletal muscle using network modeling and machine learning algorithms. Our multi-omics approach exposes new metabolic vulnerabilities in response to D2-HG in skeletal muscle and provides a conceptual framework for identifying therapeutic targets in cachexia.

systems biology↗