| 1. |
- Abreu-Vieira, Gustavo, et al.
(författare)
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Cidea improves the metabolic profile through expansion of adipose tissue
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- In humans, Cidea (cell death-inducing DNA fragmentation factor alpha-like effector A) is highly but variably expressed in white fat, and expression correlates with metabolic health. Here we generate transgenic mice expressing human Cidea in adipose tissues (aP2-hCidea mice) and show that Cidea is mechanistically associated with a robust increase in adipose tissue expandability. Under humanized conditions (thermoneutrality, mature age and prolonged exposure to high-fat diet), aP2-hCidea mice develop a much more pronounced obesity than their wild-type littermates. Remarkably, the malfunctioning of visceral fat normally caused by massive obesity is fully overcome-perilipin 1 and Akt expression are preserved, tissue degradation is prevented, macrophage accumulation is decreased and adiponectin expression remains high. Importantly, the aP2-hCidea mice display enhanced insulin sensitivity. Our data establish a functional role for Cidea and suggest that, in humans, the association between Cidea levels in white fat and metabolic health is not only correlative but also causative.
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| 2. |
- Assadi, Ghazaleh, et al.
(författare)
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Functional Analyses of the Crohn's Disease Risk Gene LACC1
- 2016
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Ingår i: PLOS ONE. - San Francisco, USA : Public Library of Science. - 1932-6203. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Genetic variation in the Laccase (multicopper oxidoreductase) domain-containing 1 (LACC1) gene has been shown to affect the risk of Crohn's disease, leprosy and, more recently, ulcerative colitis and juvenile idiopathic arthritis. LACC1 function appears to promote fatty-acid oxidation, with concomitant inflammasome activation, reactive oxygen species production, and anti-bacterial responses in macrophages. We sought to contribute to elucidating LACC1 biological function by extensive characterization of its expression in human tissues and cells, and through preliminary analyses of the regulatory mechanisms driving such expression.Methods: We implemented Western blot, quantitative real-time PCR, immunofluorescence microscopy, and flow cytometry analyses to investigate fatty acid metabolism-immune nexus (FAMIN; the LACC1 encoded protein) expression in subcellular compartments, cell lines and relevant human tissues. Gene-set enrichment analyses were performed to initially investigate modulatory mechanisms of LACC1 expression. A small-interference RNA knockdown in vitro model system was used to study the effect of FAMIN depletion on peroxisome function.Results: FAMIN expression was detected in macrophage-differentiated THP-1 cells and several human tissues, being highest in neutrophils, monocytes/macrophages, myeloid and plasmacytoid dendritic cells among peripheral blood cells. Subcellular co-localization was exclusively confined to peroxisomes, with some additional positivity for organelle endomembrane structures. LACC1 co-expression signatures were enriched for genes involved in peroxisome proliferator-activated receptors (PPAR) signaling pathways, and PPAR ligands downregulated FAMIN expression in in vitro model systems.Conclusion: FAMIN is a peroxisome-associated protein with primary role(s) in macrophages and other immune cells, where its metabolic functions may be modulated by PPAR signaling events. However, the precise molecular mechanisms through which FAMIN exerts its biological effects in immune cells remain to be elucidated.
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| 3. |
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| 4. |
- Laurencikiene, Jurga
(författare)
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Regulation of germline transcription in the immunoglobulin heavy chain locus
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During an immune response, activated B cells develop into high rate immunoglobulin (Ig) secreting plasma cells. They also switch from production of IgM to IgG, IgA or IgE. Specific isotypes of antibodies have functional and structural features that make them particularly well suited to defend against different types of pathogens. IgM is changed to another isotype via class switch recombination (CSR) - a non-homologous DNA recombination process. CSR is at least in part regulated at the transcriptional level. The external stimuli (cytokines or cell-to-cell contact) induce CSR to a particular constant heavy chain (CH) gene via their ability to modulate germline (GL) transcription of a given CH gene. The GL transcription is driven by GL promoters located upstream of each CH region. The GL promoters contain multiple transcription-factor binding sites and are tightly regulated during B cell differentiation. In addition, several enhancer elements with developmentally regulated activities are located in the IgH locus. The mouse 3' enhancers span a region of more than thirty kilobases and consist of four DNAse hypersensitivity sites - HS3a, HSI,2, HS3b and HS4. One possible function of the 3' enhancers could be regulation of CSR. We aimed to clarify the role of different IgH locus regulatory elements and transcription factors in regulation of GL transcription. Much evidence indicated that T cell-dependent activation of B lymphocytes is generated through the interaction of CD40 (on B cells) with CD40 ligand (on activated T cells). Therefore, using agonistic rat anti-mouse CD40 monoclonal antibody, we investigated the role of CD40 signalling in CSR. We found that stimulation of murine cells through CD40 induced GL y 1, y2b and low levels of e transcripts. However, cells were expressing only IgG2b, but not IgG1 or IgE. CD40, but not lipopolysaccharide (LPS), could induce GL y I transcripts, although both CD40 and LPS signalling involve NF-kB family proteins. We showed that LPS and CD40 stimulation induce different NF-kB complexes binding to GL y I promoter. The increased levels of IgE in atopic individuals could be associated with upregulation of GL e transcription. The transcription factor STAT6 is an important activator of the GL e promoter, induced by interleukin 4 (IL-4). We investigated whether increased levels of IgE in allergic individuals may be associated with alterations in the level or activation of STAT6. Our results demonstrated for the first time that upon IL-4 signalling, STAT6 activation and basal GL E promoter activity differ in B cells from different individuals. Although we did not find any association between STAT6 activation and allergy, we do not exclude the possibility that stronger activation of this transcription factor is associated with the atopic phenotype. Next, we investigated regulation of GL transcription by the IgH locus 3' enhancers. Previous studies have shown that the activity of the HS1,2 enhancer was induced in B cells approximately at the same differentiation stage when GL transcription is activated and CSR occurs. Therefore, we evaluated if HS 1,2 could regulate murine GL e and y2b promoters. We cloned GL promoters with or without HS1,2 in the luciferase expression vector and transiently transfected B cell lines or activated primary B cells. Both GL e and y2b promoters were strongly enhanced by HS1,2 in activated primary B cells. The main activity of the HS1,2 enhancer was found in a fragment being 90% homologous to the human HS1,2. By mutating transcription factor binding sites in HS1,2, we found that NF-AB (Nuclear Factor of Activated B cells) and NF-kB are differently important for interaction between the enhancer and the promoters. Our data imply that specific sites in HSI,2 selectively interact with different GL promoters. We further investigated interaction of the GL e promoter with 3' enhancers in chromatin environment. Transgenic mice containing GL e promoter, switch (Se) region and Cc region were generated. The GL e transgene was expressed in stimulated B cells. The expression was induced by the same stimuli that activated the endogenous GL e promoter (by LPS plus IL-4 or anti-CD40 plus IL-4). This finding indicates that expression of the GL e promoter does not absolutely require presence of the 3' enhancers in the transgenic system. It was shown by others that deletion of HS3a or HSI,2 enhancers has no effect on GL transcription and CSR, while the deletion of HS3bHS4 enhancers causes inhibition of CSR to most isotypes. We aimed at comparing the ability of these enhancer pairs to regulate GL transcription in transgenic mice. Therefore, either HS3a-HSI,2 or HS3b-HS4 were linked to the GL e transgenic construct. The GL e promoter was strongly up-regulated by both parts of the 3' enhancer complex. Expression of the enhancer-containing transgenes was B cell specific. Although, the transgenes were expressed in non-stimulated B cells, the expression could be further enhanced by stimuli. None of the constructs showed properties of a locus control region. We have also analyzed mutation rate in the S region of GL e transgenic mice. These mutations are known to be a sign of recruited recombination machinery. However, we did not find strong evidence for induction of mutations in any of the transgenic constructs, suggesting that other regulatory elements are needed for the recruitment of the recombination machinery.
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| 5. |
- Massier, Lucas, et al.
(författare)
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An integrated single cell and spatial transcriptomic map of human white adipose tissue
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Single-cell studies of human white adipose tissue (WAT) provide insights into the specialized cell types in the tissue. Here the authors combine publicly available and newly generated high-resolution and bulk transcriptomic results from multiple human datasets to provide a comprehensive cellular map of white adipose tissue. To date, single-cell studies of human white adipose tissue (WAT) have been based on small cohort sizes and no cellular consensus nomenclature exists. Herein, we performed a comprehensive meta-analysis of publicly available and newly generated single-cell, single-nucleus, and spatial transcriptomic results from human subcutaneous, omental, and perivascular WAT. Our high-resolution map is built on data from ten studies and allowed us to robustly identify >60 subpopulations of adipocytes, fibroblast and adipogenic progenitors, vascular, and immune cells. Using these results, we deconvolved spatial and bulk transcriptomic data from nine additional cohorts to provide spatial and clinical dimensions to the map. This identified cell-cell interactions as well as relationships between specific cell subtypes and insulin resistance, dyslipidemia, adipocyte volume, and lipolysis upon long-term weight changes. Altogether, our meta-map provides a rich resource defining the cellular and microarchitectural landscape of human WAT and describes the associations between specific cell types and metabolic states.
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| 6. |
- Negoita, Florentina, et al.
(författare)
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JUP/plakoglobin is regulated by salt-inducible kinase 2, and is required for insulin-induced signalling and glucose uptake in adipocytes
- 2020
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Ingår i: Cellular Signalling. - : Elsevier BV. - 1873-3913 .- 0898-6568. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Salt-inducible kinase 2 (SIK2) is abundant in adipocytes, but downregulated in adipose tissue from individuals with obesity and insulin resistance. Moreover, SIK isoforms are required for normal insulin signalling and glucose uptake in adipocytes, but the underlying molecular mechanisms are currently not known. The adherens junction protein JUP, also termed plakoglobin or γ-catenin, has recently been reported to promote insulin signalling in muscle cells.OBJECTIVE: The objective of this study was to analyse if JUP is required for insulin signalling in adipocytes and the underlying molecular mechanisms of this regulation.METHODS: Co-expression of SIK2 and JUP mRNA levels in adipose tissue from a human cohort was analysed. siRNA silencing and/or pharmacological inhibition of SIK2, JUP, class IIa HDACs and CRTC2 was employed in 3T3-L1- and primary rat adipocytes. JUP protein expression was analysed by western blot and mRNA levels by qPCR. Insulin signalling was evaluated by western blot as levels of phosphorylated PKB/Akt and AS160, and by monitoring the uptake of 3H-2-deoxyglucose.RESULTS: mRNA expression of SIK2 correlated with that of JUP in human adipose tissue. SIK2 inhibition or silencing resulted in downregulation of JUP mRNA and protein expression in 3T3-L1- and in primary rat adipocytes. Moreover, JUP silencing reduced the expression of PKB and the downstream substrate AS160, and consequently attenuated activity in the insulin signalling pathway, including insulin-induced glucose uptake. The known SIK2 substrates CRTC2 and class IIa HDACs were found to play a role in the SIK-mediated regulation of JUP expression.CONCLUSIONS: These findings identify JUP as a novel player in the regulation of insulin sensitivity in adipocytes, and suggest that changes in JUP expression could contribute to the effect of SIK2 on insulin signalling in these cells.
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| 7. |
- Pettersson, Amanda T, et al.
(författare)
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Twist1 in human white adipose tissue and obesity.
- 2011
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 96:1, s. 133-41
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Tidskriftsartikel (refereegranskat)abstract
- Twist1 is a transcription factor implicated in the regulation of TNFα signaling and was recently shown to be highly expressed in both human and murine adipose tissue, but its role in obesity is unknown.
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| 8. |
- Sütt, Silva, et al.
(författare)
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STK25 regulates oxidative capacity and metabolic efficiency in adipose tissue
- 2018
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Ingår i: Journal of Endocrinology. - 1479-6805 .- 0022-0795. ; 238:3, s. 187-202
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Tidskriftsartikel (refereegranskat)abstract
- Whole-body energy homeostasis at over-nutrition critically depends on how well adipose tissue remodels in response to excess calories. We recently identified serine/ threonine protein kinase (STK)25 as a critical regulator of ectopic lipid storage in non-adipose tissue and systemic insulin resistance in the context of nutritional stress. Here, we investigated the role of STK25 in regulation of adipose tissue dysfunction in mice challenged with a high-fat diet. We found that overexpression of STK25 in high-fat-fed mice resulted in impaired mitochondrial function and aggravated hypertrophy, inflammatory infiltration and fibrosis in adipose depots. Reciprocally, Stk25-knockout mice displayed improved mitochondrial function and were protected against diet-induced excessive fat storage, meta-inflammation and fibrosis in brown and white adipose tissues. Furthermore, in rodent HIB-1B cell line, STK25 depletion resulted in enhanced mitochondrial activity and consequently, reduced lipid droplet size, demonstrating an autonomous action for STK25 within adipocytes. In summary, we provide the first evidence for a key function of STK25 in controlling the metabolic balance of lipid utilization vs lipid storage in brown and white adipose depots, suggesting that repression of STK25 activity offers a potential strategy for establishing healthier adipose tissue in the context of chronic exposure to dietary lipids.
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| 9. |
- Säll, Johanna, et al.
(författare)
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Insulin induces Thr484 phosphorylation and stabilization of SIK2 in adipocytes
- 2019
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Ingår i: Cellular Signalling. - : Elsevier BV. - 1873-3913 .- 0898-6568. ; 55, s. 73-80
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: Salt-inducible kinase 2 (SIK2) is downregulated in adipose tissue from obese or insulin-resistant individuals and inhibition of SIK isoforms results in reduced glucose uptake and insulin signalling in adipocytes. However, the regulation of SIK2 itself in response to insulin in adipocytes has not been studied in detail. The aim of our work was to investigate effects of insulin on various aspects of SIK2 function in adipocytes.METHODS: Primary adipocytes were isolated from human subcutaneous and rat epididymal adipose tissue. Insulin-induced phosphorylation of SIK2 and HDAC4 was analyzed using phosphospecific antibodies and changes in the catalytic activity of SIK2 with in vitro kinase assay. SIK2 protein levels were analyzed in primary adipocytes treated with the proteasome inhibitor MG132.RESULTS: We have identified a novel regulatory pathway of SIK2 in adipocytes, which involves insulin-induced phosphorylation at Thr484. This phosphorylation is impaired in individuals with a reduced insulin action. Insulin stimulation does not affect SIK2 catalytic activity or cellular activity towards HDAC4, but is associated with increased SIK2 protein levels in adipocytes.CONCLUSION/INTERPRETATION: Our data suggest that downregulation of SIK2 in the adipose tissue of insulin-resistant individuals can partially be caused by impaired insulin signalling, which might result in defects in SIK2 expression and function.
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| 10. |
- Säll, Johanna, et al.
(författare)
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Salt-inducible kinase 2 and -3 are downregulated in adipose tissue from obese or insulin-resistant individuals : implications for insulin signalling and glucose uptake in human adipocytes
- 2017
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 60:2, s. 314-323
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: Salt-inducible kinases (SIKs) are related to the metabolic regulator AMP-activated protein kinase (AMPK). SIK2 is abundant in adipose tissue. The aims of this study were to investigate the expression of SIKs in relation to human obesity and insulin resistance, and to evaluate whether changes in the expression of SIKs might play a causal role in the development of disturbed glucose uptake in human adipocytes.METHODS: SIK mRNA and protein was determined in human adipose tissue or adipocytes, and correlated to clinical variables. SIK2 and SIK3 expression and phosphorylation were analysed in adipocytes treated with TNF-α. Glucose uptake, GLUT protein levels and localisation, phosphorylation of protein kinase B (PKB/Akt) and the SIK substrate histone deacetylase 4 (HDAC4) were analysed after the SIKs had been silenced using small interfering RNA (siRNA) or inhibited using a pan-SIK-inhibitor (HG-9-91-01).RESULTS: We demonstrate that SIK2 and SIK3 mRNA are downregulated in adipose tissue from obese individuals and that the expression is regulated by weight change. SIK2 is also negatively associated with in vivo insulin resistance (HOMA-IR), independently of BMI and age. Moreover, SIK2 protein levels and specific kinase activity display a negative correlation to BMI in human adipocytes. Furthermore, SIK2 and SIK3 are downregulated by TNF-α in adipocytes. Silencing or inhibiting SIK1-3 in adipocytes results in reduced phosphorylation of HDAC4 and PKB/Akt, less GLUT4 at the plasma membrane, and lower basal and insulin-stimulated glucose uptake in adipocytes.CONCLUSION/INTERPRETATION: This is the first study to describe the expression and function of SIKs in human adipocytes. Our data suggest that SIKs might be protective in the development of obesity-induced insulin resistance, with implications for future treatment strategies.
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