| 1. |
- Bader, Erik, et al.
(författare)
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Identification of proliferative and mature beta-cells in the islets of Langerhans
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 535:7612, s. 430-
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of beta-cells. Pancreatic beta-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential(1-5); understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches. Here we show that Fltp (also known as Flattop and Cfap126), a Wnt/planar cell polarity (PCP) effector and reporter gene(6), acts as a marker gene that subdivides endocrine cells into two subpopulations and distinguishes proliferation-competent from mature beta-cells with distinct molecular, physiological and ultrastructural features. Genetic lineage tracing revealed that endocrine subpopulations from Fltp-negative and -positive lineages react differently to physiological and pathological changes. The expression of Fltp increases when endocrine cells cluster together to form polarized and mature 3D islet mini-organs(7-9). We show that 3D architecture and Wnt/PCP ligands are sufficient to trigger beta-cell maturation. By contrast, the Wnt/PCP effector Fltp is not necessary for beta-cell development, proliferation or maturation. We conclude that 3D architecture and Wnt/PCP signalling underlie functional beta-cell heterogeneity and induce beta-cell maturation. The identification of Fltp as a marker for endocrine subpopulations sheds light on the molecular underpinnings of islet cell heterogeneity and plasticity and might enable targeting of endocrine subpopulations for the regeneration of functional beta-cell mass in diabetic patients.
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| 2. |
- Fischer, Katrin, et al.
(författare)
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The scaffold protein p62 regulates adaptive thermogenesis through ATF2 nuclear target activation
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- During beta -adrenergic stimulation of brown adipose tissue (BAT), p38 phosphorylates the activating transcription factor 2 (ATF2) which then translocates to the nucleus to activate the expression of Ucp1 and Pgc-1 alpha. The mechanisms underlying ATF2 target activation are unknown. Here we demonstrate that p62 (Sqstm1) binds to ATF2 to orchestrate activation of the Ucp1 enhancer and Pgc-1 alpha promoter. P62(Delta 69-251) mice show reduced expression of Ucp1 and Pgc-1 alpha with impaired ATF2 genomic binding. Modulation of Ucp1 and Pgc-1 alpha expression through p62 regulation of ATF2 signaling is demonstrated in vitro and in vivo in p62(Delta 69-251) mice, global p62(-/-) and Ucp1-Cre p62(flx/flx) mice. BAT dysfunction resulting from p62 deficiency is manifest after birth and obesity subsequently develops despite normal food intake, intestinal nutrient absorption and locomotor activity. In summary, our data identify p62 as a master regulator of BAT function in that it controls the Ucp1 pathway through regulation of ATF2 genomic binding. Beta-adrenergic stimulation of brown adipose tissue leads to thermogenesis via the activating transcription factor 2 (ATF2) mediated expression of the thermogenic genes Ucp1 and Pgc-1 alpha. Here, the authors show that the scaffold protein p62 regulates brown adipose tissue function through modifying ATF2 genomic binding and subsequent Ucp1 and Pgc-1 alpha induction.
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| 3. |
- Schmidt, Sebastian, et al.
(författare)
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A reversible state of hypometabolism in a human cellular model of sporadic Parkinson's disease
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Sporadic Parkinson's Disease (sPD) is a progressive neurodegenerative disorder caused by multiple genetic and environmental factors. Mitochondrial dysfunction is one contributing factor, but its role at different stages of disease progression is not fully understood. Here, we showed that neural precursor cells and dopaminergic neurons derived from induced pluripotent stem cells (hiPSCs) from sPD patients exhibited a hypometabolism. Further analysis based on transcriptomics, proteomics, and metabolomics identified the citric acid cycle, specifically the alpha-ketoglutarate dehydrogenase complex (OGDHC), as bottleneck in sPD metabolism. A follow-up study of the patients approximately 10 years after initial biopsy demonstrated a correlation between OGDHC activity in our cellular model and the disease progression. In addition, the alterations in cellular metabolism observed in our cellular model were restored by interfering with the enhanced SHH signal transduction in sPD. Thus, inhibiting overactive SHH signaling may have potential as neuroprotective therapy during early stages of sPD. Mitochondrial dysfunction is a contributing factor in Parkinson's disease. Here the authors carry out a multilayered omics analysis of Parkinson's disease patient-derived neuronal cells, which reveals a reversible hypometabolism mediated by alpha-ketoglutarate dehydrogenase deficiency, which is correlated with disease progression in the donating patients.
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| 4. |
- Ai, Jiaoyu, et al.
(författare)
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Bcl3 Couples Cancer Stem Cell Enrichment With Pancreatic Cancer Molecular Subtypes
- 2021
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Ingår i: Gastroenterology. - : Elsevier BV. - 0016-5085 .- 1528-0012. ; 161:1, s. 318-332
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: The existence of different subtypes of pancreatic ductal adenocarcinoma (PDAC) and their correlation with patient outcome have shifted the emphasis on patient classification for better decision-making algorithms and personalized therapy. The contribution of mechanisms regulating the cancer stem cell (CSC) population in different subtypes remains unknown.Methods: Using RNA-seq, we identified B-cell CLL/lymphoma 3 (BCL3), an atypical nf-κb signaling member, as differing in pancreatic CSCs. To determine the biological consequences of BCL3 silencing in vivo and in vitro, we generated bcl3-deficient preclinical mouse models as well as murine cell lines and correlated our findings with human cell lines, PDX models, and 2 independent patient cohorts. We assessed the correlation of bcl3 expression pattern with clinical parameters and subtypes.Results: Bcl3 was significantly down-regulated in human CSCs. Recapitulating this phenotype in preclinical mouse models of PDAC via BCL3 genetic knockout enhanced tumor burden, metastasis, epithelial to mesenchymal transition, and reduced overall survival. Fluorescence-activated cell sorting analyses, together with oxygen consumption, sphere formation, and tumorigenicity assays, all indicated that BCL3 loss resulted in CSC compartment expansion promoting cellular dedifferentiation. Overexpression of BCL3 in human PDXs diminished tumor growth by significantly reducing the CSC population and promoting differentiation. Human PDACs with low BCL3 expression correlated with increased metastasis, and BCL3-negative tumors correlated with lower survival and nonclassical subtypes.Conclusions: We demonstrate that bcl3 impacts pancreatic carcinogenesis by restraining CSC expansion and by curtailing an aggressive and metastatic tumor burden in PDAC across species. Levels of BCL3 expression are a useful stratification marker for predicting subtype characterization in PDAC, thereby allowing for personalized therapeutic approaches.
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| 5. |
- Cavalieri, Riccardo, et al.
(författare)
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Activating ligands of Uncoupling protein 1 identified by rapid membrane protein thermostability shift analysis
- 2022
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Ingår i: Molecular Metabolism. - : Elsevier BV. - 2212-8778. ; 62
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Uncoupling protein 1 (UCP1) catalyses mitochondrial proton leak in brown adipose tissue to facilitate nutrient oxidation for heat production, and may combat metabolic disease if activated in humans. During the adrenergic stimulation of brown adipocytes, free fatty acids generated from lipolysis activate UCP1 via an unclear interaction. Here, we set out to characterise activator binding to purified UCP1 to clarify the activation process, discern novel activators and the potential to target UCP1.Methods: We assessed ligand binding to purified UCP1 by protein thermostability shift analysis, which unlike many conventional approaches can inform on the binding of hydrophobic ligands to membrane proteins. A detailed activator interaction analysis and screening approach was carried out, supported by investigations of UCP1 activity in liposomes, isolated brown fat mitochondria and UCP1 expression-controlled cell lines.Results: We reveal that fatty acids and other activators influence UCP1 through a specific destabilising interaction, behaving as transport substrates that shift the protein to a less stable conformation of a transport cycle. Through the detection of specific stability shifts in screens, we identify novel activators, including the over-the-counter drug ibuprofen, where ligand analysis indicates that UCP1 has a relatively wide structural specificity for interacting molecules. Ibuprofen successfully induced UCP1 activity in liposomes, isolated brown fat mitochondria and UCP1-expressing HEK293 cells but not in cultured brown adipocytes, suggesting drug delivery differs in each cell type.Conclusions: These findings clarify the nature of the activator-UCP1 interaction and demonstrate that the targeting of UCP1 in cells by approved drugs is in principle achievable as a therapeutic avenue, but requires variants with more effective delivery in brown adipocytes.
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| 6. |
- Divakaruni, Ajit S., et al.
(författare)
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A practical guide for the analysis, standardization and interpretation of oxygen consumption measurements
- 2022
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Ingår i: Nature Metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 4:8, s. 978-994
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Tidskriftsartikel (refereegranskat)abstract
- Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following pharmacologic and genetic interventions, and characterize energy metabolism in physiology and disease. The conceptual and practical benefits of respirometry have made it a frontline technique to understand how mitochondrial function can interface with—and in some cases control—cell physiology. Nonetheless, an appreciation of the complexity and challenges involved with such measurements is required to avoid common experimental and analytical pitfalls. Here we provide a practical guide to oxygen consumption measurements covering the selection of experimental models and instrumentation, as well as recommendations for the collection, interpretation and normalization of data. These guidelines are provided with the intention of aiding experimental design and enhancing the overall reputability, transparency and reliability of oxygen consumption measurements.
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| 7. |
- Dludla, Phiwayinkosi V., et al.
(författare)
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Uncoupling proteins as a therapeutic target to protect the diabetic heart
- 2018
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Ingår i: Pharmacological Research. - : Elsevier BV. - 1043-6618 .- 1096-1186. ; 137, s. 11-24
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Forskningsöversikt (refereegranskat)abstract
- Myocardial remodeling and dysfunction caused by accelerated oxidative damage is a widely reported phenomenon within a diabetic state. Altered myocardial substrate preference appears to be the major cause of enhanced oxidative stress-mediated cell injury within a diabetic heart. During this process, exacerbated free fatty acid flux causes an abnormal increase in mitochondrial membrane potential leading to the overproduction of free radical species and subsequent cell damage. Uncoupling proteins (UCPs) are expressed within the myocardium and can protect against free radical damage by modulating mitochondrial respiration, leading to reduced production of reactive oxygen species. Moreover, transgenic animals lacking UCPs have been shown to be more susceptible to oxidative damage and display reduced cardiac function when compared to wild type animals. This suggests that tight regulation of UCPs is necessary for normal cardiac function and in the prevention of diabetes-induced oxidative damage. This review aims to enhance our understanding of the pathophysiological mechanisms relating to the role of UCPs in a diabetic heart, and further discuss known pharmacological compounds and hormones that can protect a diabetic heart through the modulation of UCPs.
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| 8. |
- Elhag, Sara, et al.
(författare)
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Differences in Cell-Intrinsic Inflammatory Programs of Yolk Sac and Bone Marrow Macrophages
- 2021
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Ingår i: Cells. - : MDPI AG. - 2073-4409. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Tissue-resident macrophages have mixed developmental origins. They derive in variable extent from yolk sac (YS) hematopoiesis during embryonic development. Bone marrow (BM) hematopoietic progenitors give rise to tissue macrophages in postnatal life, and their contribution increases upon organ injury. Since the phenotype and functions of macrophages are modulated by the tissue of residence, the impact of their origin and developmental paths has remained incompletely understood. Methods: In order to decipher cell-intrinsic macrophage programs, we immortalized hematopoietic progenitors from YS and BM using conditional HoxB8, and carried out an in-depth functional and molecular analysis of differentiated macrophages. Results: While YS and BM macrophages demonstrate close similarities in terms of cellular growth, differentiation, cell death susceptibility and phagocytic properties, they display differences in cell metabolism, expression of inflammatory markers and inflammasome activation. Reduced abundance of PYCARD (ASC) and CASPASE-1 proteins in YS macrophages abrogated interleukin-1 beta production in response to canonical and non-canonical inflammasome activation. Conclusions: Macrophage ontogeny is associated with distinct cellular programs and immune response. Our findings contribute to the understanding of the regulation and programming of macrophage functions.
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| 9. |
- Fischer, Katrin, et al.
(författare)
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Alternatively activated macrophages do not synthesize catecholamines or contribute to adipose tissue adaptive thermogenesis
- 2017
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 23:5, s. 623-630
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Tidskriftsartikel (refereegranskat)abstract
- Adaptive thermogenesis is the process of heat generation in response to cold stimulation. It is under the control of the sympathetic nervous system, whose chief effector is the catecholamine norepinephrine (NE). NE enhances thermogenesis through beta 3-adrenergic receptors to activate brown adipose tissue and by 'browning' white adipose tissue. Recent studies have reported that alternative activation of macrophages in response to interleukin (IL)-4 stimulation induces the expression of tyrosine hydroxylase (TH), a key enzyme in the catecholamine synthesis pathway, and that this activation provides an alternative source of locally produced catecholamines during the thermogenic process. Here we report that the deletion of Th in hematopoietic cells of adult mice neither alters energy expenditure upon cold exposure nor reduces browning in inguinal adipose tissue. Bone marrow-derived macrophages did not release NE in response to stimulation with IL-4, and conditioned media from IL-4-stimulated macrophages failed to induce expression of thermogenic genes, such as uncoupling protein 1 (Ucp1), in adipocytes cultured with the conditioned media. Furthermore, chronic treatment with IL-4 failed to increase energy expenditure in wild-type, Ucp1(-/-) and interleukin-4 receptor-alpha double-negative (Il4ra(-/-)) mice. In agreement with these findings, adipose-tissue-resident macrophages did not express TH. Thus, we conclude that alternatively activated macrophages do not synthesize relevant amounts of catecholamines, and hence, are not likely to have a direct role in adipocyte metabolism or adaptive thermogenesis.
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| 10. |
- Fyda, Thomas Jacob, et al.
(författare)
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Disruption of thermogenic UCP1 predated the divergence of pigs and peccaries
- 2020
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:15
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Tidskriftsartikel (refereegranskat)abstract
- Uncoupling protein 1 (UCP1) governs non-shivering thermogenesis in brown adipose tissue. It has been estimated that pigs lost UCP1 similar to 20 million years ago (MYA), dictating cold intolerance among piglets. Our current understanding of the root causes of UCP1 loss are, however, incomplete. Thus, examination of additional species can shed light on these fundamental evolutionary questions. Here, we investigated UCP1 in the Chacoan peccary (Catagonus wagneri), a member of the Tayassuid lineage that diverged from pigs during the late Eocene-mid Oligocene. Exons 1 and 2 have been deleted in peccary UCP1 and the remaining exons display additional inactivating mutations. A common nonsense mutation in exon 6 revealed that UCP1 was pseudogenized in a shared ancestor of pigs and peccaries. Our selection pressure analyses indicate that the inactivation occurred 36.2-44.3 MYA during the mid-late Eocene, which is much earlier than previously thought. Importantly, pseudogenized UCP1 provides the molecular rationale for cold sensitivity and current tropical biogeography of extant peccaries.
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