| 1. |
- Grankvist, Nina, et al.
(author)
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Global 13C tracing and metabolic flux analysis of intact human liver tissue ex vivo
- 2024
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In: Nature Metabolism. - : Springer Nature. - 2522-5812.
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Journal article (peer-reviewed)abstract
- Liver metabolism is central to human physiology and influences the pathogenesis of common metabolic diseases. Yet, our understanding of human liver metabolism remains incomplete, with much of current knowledge based on animal or cell culture models that do not fully recapitulate human physiology. Here, we perform in-depth measurement of metabolism in intact human liver tissue ex vivo using global 13C tracing, non-targeted mass spectrometry and model-based metabolic flux analysis. Isotope tracing allowed qualitative assessment of a wide range of metabolic pathways within a single experiment, confirming well-known features of liver metabolism but also revealing unexpected metabolic activities such as de novo creatine synthesis and branched-chain amino acid transamination, where human liver appears to differ from rodent models. Glucose production ex vivo correlated with donor plasma glucose, suggesting that cultured liver tissue retains individual metabolic phenotypes, and could be suppressed by postprandial levels of nutrients and insulin, and also by pharmacological inhibition of glycogen utilization. Isotope tracing ex vivo allows measuring human liver metabolism with great depth and resolution in an experimentally tractable system.
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| 2. |
- Sundqvist, Nicolas, 1993-
(author)
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Mathematical Modelling of Cerebral Metabolism : From Ion Channels to Metabolic Fluxes
- 2024
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Doctoral thesis (other academic/artistic)abstract
- The brain is the most metabolically active organ in the human body and therefore rely on a continuous supply of oxygen and glucose. Neuronal stimulation in specific regions of the leads to the firing of action potentials, a process facilitated by voltage-gated ion channels in the neurons’ cell membranes. This activation of the ion channels significantly elevates the brain’s metabolic energy demand, compelling neurons to ramp up their metabolic activity in response. Concurrently, this neuronal activation also initiates a signalling cascade that induces vasodilation and increases blood flow, thereby ensuring that regions with elevated neural activity are adequately supplied with oxygen and nutrients. This dynamic interplay between neuronal activity and cerebral blood flow (CBF) regulation constitutes the neurovascular coupling (NVC). The NVC is a cornerstone in interpreting functional Magnetic Resonance Imaging (fMRI) Blood Oxygen Level-Dependent (BOLD) responses. The BOLD response is an indirect, non-invasive, and highly sensitive indicator of neuronal activity, reflecting changes in blood oxygenation and flow associated with the neuronal and metabolic activity in the brain. By examining these responses, we can gain insights into the complex interactions between neuronal activity, energy metabolism, and CBF.Additionally, techniques such as 13C Metabolic Flux Analysis (13C MFA) makes it possible to gain further insight into the cerebral metabolism. This method enables a detailed examination of metabolic pathways and fluxes by tracking the incorporation of 13C-labelled substrates into various metabolites. By using 13C MFA, researchers can quantify the flow of substrates through metabolic networks, offering a deeper understanding of how cell such as neurons adapt their metabolism during different functional states and conditions.Central to exploring these multifaceted aspects of cerebral metabolism is the use of mathematical modelling and systems biology. These disciplines provide a framework for integrating diverse biological data, allowing for the simulation and prediction of complex neurovascular interactions under various physiological and pathological conditions. Mathematical models can encapsulate the dynamics of ion channel kinetics, metabolic pathways, and neurovascular coupling, offering a comprehensive view of the interplay between neuronal activity, metabolism, and cerebral blood flow. This approach is instrumental in bridging the gap between molecular-scale events and observable physiological phenomena, enhancing our understanding of cerebral metabolism and its critical role in the brain’s function.Paper I sets the foundation by developing a mechanistic model that integrates the mechanisms of the NVC with the metabolism. This model connects cerebral regulation of blood flow and metabolism, using small mechanistic model to represent the central metabolism. By integrating experimental data based on nuclear magnetic resonance spectroscopy (NMRS), the model successfully captures the dynamics of metabolites in response to neuronal stimuli, providing a crucial link between metabolic changes and NVC.Paper II extends the investigation to the realm of ion channel kinetics. By developing a generic model structure for voltage-gated ion channels, this paper explores how ion channel activity, a fundamental aspect of neuronal function, influences cerebral metabolism. The model, validated against experimental data and existing kinetic models, accurately predicts various channel behaviours and action potential characteristics. It includes mechanisms like voltage sensor movements and rate constants dependent on membrane voltage, offering a universal approach for studying all types of voltage-gated ion channels in neural networks and other applications.Paper III further explores the neurovascular relationship by examining the influence of inhibitory neurons on CBF and metabolism. This study introduces an expanded mathematical model that integrates the effects of γ-aminobutyric acid(GABA)ergic inhibitory neurons on vascular responses, aligning with new experimental evidence and enhancing understanding of neurovascular coupling (NVC). The model, validated with data from various studies, not only captures vascular changes triggered by inhibitory neuron activation but also reveals how these neurovascular responses vary with stimulation frequency, underscoring the important role of inhibitory neuron in the NVC.Paper IV tackles the critical aspect of accurately measuring metabolic fluxes in cells, focusing on 13C MFA. This study introduces a novel approach for model selection in MFA, ensuring that the chosen models accurately represent the underlying metabolic processes. This method enhances our ability to identify and understand key metabolic pathways and reactions, providing deeper insights into various metabolic conditions. Connecting back to the cerebral metabolism, application of 13C MFA to neuronal systems offers a powerful tool for studying metabolically linked neuropathology such as the development of Alzheimer’s disease.In Conclusion, this thesis establishes key components for understanding the mechanisms of the cerebral metabolism. The integration of mathematical modelling across different scales, from ion channels to cerebral blood flow, is used to provide a comprehensive perspective on how cerebral metabolism is regulated and how it interacts with other physiological processes. This work not only advances our basic scientific knowledge but also holds significant potential for improving our understanding of neurological disorders where metabolism and neurovascular function are impaired.
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| 3. |
- Sundqvist, Nicolas, et al.
(author)
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Validation-based model selection for C-13 metabolic flux analysis with uncertain measurement errors
- 2022
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In: PloS Computational Biology. - : Public Library of Science. - 1553-734X .- 1553-7358. ; 18:4
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Journal article (peer-reviewed)abstract
- Accurate measurements of metabolic fluxes in living cells are central to metabolism research and metabolic engineering. The gold standard method is model-based metabolic flux analysis (MFA), where fluxes are estimated indirectly from mass isotopomer data with the use of a mathematical model of the metabolic network. A critical step in MFA is model selection: choosing what compartments, metabolites, and reactions to include in the metabolic network model. Model selection is often done informally during the modelling process, based on the same data that is used for model fitting (estimation data). This can lead to either overly complex models (overfitting) or too simple ones (underfitting), in both cases resulting in poor flux estimates. Here, we propose a method for model selection based on independent validation data. We demonstrate in simulation studies that this method consistently chooses the correct model in a way that is independent on errors in measurement uncertainty. This independence is beneficial, since estimating the true magnitude of these errors can be difficult. In contrast, commonly used model selection methods based on the chi(2)-test choose different model structures depending on the believed measurement uncertainty; this can lead to errors in flux estimates, especially when the magnitude of the error is substantially off. We present a new approach for quantification of prediction uncertainty of mass isotopomer distributions in other labelling experiments, to check for problems with too much or too little novelty in the validation data. Finally, in an isotope tracing study on human mammary epithelial cells, the validation-based model selection method identified pyruvate carboxylase as a key model component. Our results argue that validation-based model selection should be an integral part of MFA model development.
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| 4. |
- Ruiz-Pérez, María Victoria, et al.
(author)
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Inhibition of fatty acid synthesis induces differentiation and reduces tumor burden in childhood neuroblastoma
- 2021
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In: iScience. - : Elsevier BV. - 2589-0042. ; 24:2
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Journal article (peer-reviewed)abstract
- Many metabolic pathways, including lipid metabolism, are rewired in tumors to support energy and biomass production and to allow adaptation to stressful environments. Neuroblastoma is the second deadliest solid tumor in children. Genetic aberrations, as the amplification of the MYCN-oncogene, correlate strongly with disease progression. Yet, there are only a few molecular targets successfully exploited in the clinic. Here we show that inhibition of fatty acid synthesis led to increased neural differentiation and reduced tumor burden in neuroblastoma xenograft experiments independently of MYCN-status. This was accompanied by reduced levels of the MYCN or c-MYC oncoproteins and activation of ERK signaling. Importantly, the expression levels of genes involved in de novo fatty acid synthesis showed prognostic value for neuroblastoma patients. Our findings demonstrate that inhibition of de novo fatty acid synthesis is a promising pharmacological intervention strategy for the treatment of neuroblastoma independently of MYCN-status.
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| 5. |
- Schober, Florian A., et al.
(author)
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The one-carbon pool controls mitochondrial energy metabolism via complex I and iron-sulfur clusters
- 2021
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:8
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Journal article (peer-reviewed)abstract
- Induction of the one-carbon cycle is an early hallmark of mitochondrial dysfunction and cancer metabolism. Vital intermediary steps are localized to mitochondria, but it remains unclear how one-carbon availability connects to mitochondrial function. Here, we show that the one-carbon metabolite and methyl group donor S-adenosylmethionine (SAM) is pivotal for energy metabolism. A gradual decline in mitochondrial SAM (mitoSAM) causes hierarchical defects in fly and mouse, comprising loss of mitoSAM-dependent metabolites and impaired assembly of the oxidative phosphorylation system. Complex I stability and iron-sulfur cluster biosynthesis are directly controlled by mitoSAM levels, while other protein targets are predominantly methylated outside of the organelle before import. The mitoSAM pool follows its cytosolic production, establishing mitochondria as responsive receivers of one-carbon units. Thus, we demonstrate that cellular methylation potential is required for energy metabolism, with direct relevance for pathophysiology, aging, and cancer.
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| 6. |
- Willman, Ania, et al.
(author)
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Evidensbaserad omvårdnad : en bro mellan forskning och klinisk verksamhe
- 2016. - 4., [rev.] uppl.
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Book (other academic/artistic)abstract
- Evidensbaserad omvårdnad definieras i denna bok som både ett förhållningssätt och en process. Förhållningssättet innebär en vilja att använda bästa tillgängliga vetenskapliga bevis som underlag för vårdbeslut. Processen består i hur man praktiskt går tillväga för att finna, sammanställa, kritiskt värdera och implementera detta underlag. Evidensbaserad omvårdnad handlar således om en strävan att bedriva omvårdnad på en god och säker grund och att tillgodose samhällets krav på att forskningsresultat utnyttjas på bästa sätt. Denna fjärde upplaga har förtydligats och alla länkar samt webbadresser har uppdaterats. Ett nytt avsnitt om ledarskapets betydelse för implementering av evidens har tillkommit. På bokens webbsida finns en film som visar evidensbaserad omvårdnad i klinisk verksamhet.
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| 7. |
- Sheppard, Nina Gustafsson, et al.
(author)
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The folate-coupled enzyme MTHFD2 is a nuclear protein and promotes cell proliferation
- 2015
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 5
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Journal article (peer-reviewed)abstract
- Folate metabolism is central to cell proliferation and a target of commonly used cancer chemotherapeutics. In particular, the mitochondrial folate-coupled metabolism is thought to be important for proliferating cancer cells. The enzyme MTHFD2 in this pathway is highly expressed in human tumors and broadly required for survival of cancer cells. Although the enzymatic activity of the MTHFD2 protein is well understood, little is known about its larger role in cancer cell biology. We here report that MTHFD2 is co-expressed with two distinct gene sets, representing amino acid metabolism and cell proliferation, respectively. Consistent with a role for MTHFD2 in cell proliferation, MTHFD2 expression was repressed in cells rendered quiescent by deprivation of growth signals (serum) and rapidly re-induced by serum stimulation. Overexpression of MTHFD2 alone was sufficient to promote cell proliferation independent of its dehydrogenase activity, even during growth restriction. In addition to its known mitochondrial localization, we found MTHFD2 to have a nuclear localization and co-localize with DNA replication sites. These findings suggest a previously unknown role for MTHFD2 in cancer cell proliferation, adding to its known function in mitochondrial folate metabolism.
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| 8. |
- Nilsson, Roland, et al.
(author)
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Metabolic enzyme expression highlights a key role for MTHFD2 and the mitochondrial folate pathway in cancer
- 2014
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5, s. 3128-
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Journal article (peer-reviewed)abstract
- Metabolic remodeling is now widely regarded as a hallmark of cancer, but it is not clear whether individual metabolic strategies are frequently exploited by many tumours. Here we compare messenger RNA profiles of 1,454 metabolic enzymes across 1,981 tumours spanning 19 cancer types to identify enzymes that are consistently differentially expressed. Our meta-analysis recovers established targets of some of the most widely used chemotherapeutics, including dihydrofolate reductase, thymidylate synthase and ribonucleotide reductase, while also spotlighting new enzymes, such as the mitochondrial proline biosynthetic enzyme PYCR1. The highest scoring pathway is mitochondrial one-carbon metabolism and is centred on MTHFD2. MTHFD2 RNA and protein are markedly elevated in many cancers and correlated with poor survival in breast cancer. MTHFD2 is expressed in the developing embryo, but is absent in most healthy adult tissues, even those that are proliferating. Our study highlights the importance of mitochondrial compartmentalization of one-carbon metabolism in cancer and raises important therapeutic hypotheses.
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| 9. |
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| 10. |
- Andersson, Elisabeth, et al.
(author)
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Aktuellt kunskapsläge vid kateterspolning : systematisk litteraturgranskning
- 2011
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In: Vård i Norden. - : Sykepleiernes Samarbeid i Norden (SSN). - 0107-4083 .- 1890-4238. ; 31:4, s. 27-31
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Journal article (peer-reviewed)abstract
- Aim: Reviewing the scientific literature with regards to urinary catheter washouts in order to prevent occlusion. Background: Patients with long-term indwelling urinary catheters often suffers from catheter blockage. Encrustations and the forming of biofilm on the catheter surface are among the most common causes of occlusion. It is unknown whether urinary catheter washout is the treatment of choice to prevent occlusion. Methods: A systematic review of the scientific literature regarding urinary catheter washouts. The study was conducted by two independent reviewers. The search used MeSH and freetext terms, in The Cochrane Database of Systematic Reviews, Academic Search Elite, CINAHL, MedLine and SweMed+, and an additional mapping of clinical guidelines in order to update praxis. Findings: The study shows that there is insufficient scientific evidence as to whether urinary catheter washouts prevent catheter blockage. Conclusion: There is insufficient evidence that urinary catheter washouts are beneficial. Individual care planning and evaluation of long-term indwelling catheter care is important in minimizing the risk of harmful side effects.
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