| 1. |
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| 2. |
- Sweeney, M. D., et al.
(författare)
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Vascular dysfunction-The disregarded partner of Alzheimer's disease
- 2019
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Ingår i: Alzheimers & Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 15:1, s. 158-167
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Tidskriftsartikel (refereegranskat)abstract
- Increasing evidence recognizes Alzheimer's disease (AD) as a multifactorial and heterogeneous disease with multiple contributors to its pathophysiology, including vascular dysfunction. The recently updated AD Research Framework put forth by the National Institute on Aging-Alzheimer's Association describes a biomarker-based pathologic definition of AD focused on amyloid, tau, and neuronal injury. In response to this article, here we first discussed evidence that vascular dysfunction is an important early event in AD pathophysiology. Next, we examined various imaging sequences that could be easily implemented to evaluate different types of vascular dysfunction associated with, and/or contributing to, AD pathophysiology, including changes in blood-brain barrier integrity and cerebral blood flow. Vascular imaging biomarkers of small vessel disease of the brain, which is responsible for >50% of dementia worldwide, including AD, are already established, well characterized, and easy to recognize. We suggest that these vascular biomarkers should be incorporated into the AD Research Framework to gain a better understanding of AD pathophysiology and aid in treatment efforts. (C) 2018 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.
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| 5. |
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| 7. |
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| 10. |
- Mestre, Humberto, et al.
(författare)
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Aquaporin-4-dependent glymphatic solute transport in the rodent brain
- 2018
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Ingår i: eLife. - 2050-084X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The glymphatic system is a brain-wide clearance pathway; its impairment contributes to the accumulation of amyloid-β. Influx of cerebrospinal fluid (CSF) depends upon the expression and perivascular localization of the astroglial water channel aquaporin-4 (AQP4). Prompted by a recent failure to find an effect of Aqp4 knock-out (KO) on CSF and interstitial fluid (ISF) tracer transport, five groups re-examined the importance of AQP4 in glymphatic transport. We concur that CSF influx is higher in wild-type mice than in four different Aqp4 KO lines and in one line that lacks perivascular AQP4 (Snta1 KO). Meta-analysis of all studies demonstrated a significant decrease in tracer transport in KO mice and rats compared to controls. Meta-regression indicated that anesthesia, age, and tracer delivery explain the opposing results. We also report that intrastriatal injections suppress glymphatic function. This validates the role of AQP4 and shows that glymphatic studies must avoid the use of invasive procedures.
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| 11. |
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| 12. |
- Raizen, David M., et al.
(författare)
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Beyond the symptom : the biology of fatigue
- 2023
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Ingår i: Sleep. - : Oxford University Press. - 0161-8105 .- 1550-9109. ; 46:9
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Tidskriftsartikel (refereegranskat)abstract
- A workshop titled “Beyond the Symptom: The Biology of Fatigue” was held virtually September 27–28, 2021. It was jointly organized by the Sleep Research Society and the Neurobiology of Fatigue Working Group of the NIH Blueprint Neuroscience Research Program. For access to the presentations and video recordings, see: https://neuroscienceblueprint.nih.gov/about/event/beyond-symptom-biology-fatigue.The goals of this workshop were to bring together clinicians and scientists who use a variety of research approaches to understand fatigue in multiple conditions and to identify key gaps in our understanding of the biology of fatigue. This workshop summary distills key issues discussed in this workshop and provides a list of promising directions for future research on this topic. We do not attempt to provide a comprehensive review of the state of our understanding of fatigue, nor to provide a comprehensive reprise of the many excellent presentations. Rather, our goal is to highlight key advances and to focus on questions and future approaches to answering them.
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| 13. |
- Dahlman, I, et al.
(författare)
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Adipose tissue pathways involved in weight loss of cancer cachexia
- 2010
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Ingår i: British Journal of Cancer. - : Springer Science and Business Media LLC. - 0007-0920 .- 1532-1827. ; 102:10, s. 1541-8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The regulatory gene pathways that accompany loss of adipose tissue in cancer cachexia are unknown and were explored using pangenomic transcriptome profiling. METHODS: Global gene expression profiles of abdominal subcutaneous adipose tissue were studied in gastrointestinal cancer patients with (n=13) or without (n=14) cachexia. RESULTS: Cachexia was accompanied by preferential loss of adipose tissue and decreased fat cell volume, but not number. Adipose tissue pathways regulating energy turnover were upregulated, whereas genes in pathways related to cell and tissue structure (cellular adhesion, extracellular matrix and actin cytoskeleton) were downregulated in cachectic patients. Transcriptional response elements for hepatic nuclear factor-4 (HNF4) were overrepresented in the promoters of extracellular matrix and adhesion molecule genes, and adipose HNF4 mRNA was downregulated in cachexia. CONCLUSIONS: Cancer cachexia is characterised by preferential loss of adipose tissue; muscle mass is less affected. Loss of adipose tissue is secondary to a decrease in adipocyte lipid content and associates with changes in the expression of genes that regulate energy turnover, cytoskeleton and extracellular matrix, which suggest high tissue remodelling. Changes in gene expression in cachexia are reciprocal to those observed in obesity, suggesting that regulation of fat mass at least partly corresponds to two sides of the same coin.
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| 14. |
- Hagberg, C. E., et al.
(författare)
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Flow Cytometry of Mouse and Human Adipocytes for the Analysis of Browning and Cellular Heterogeneity
- 2018
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 24:10
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Tidskriftsartikel (refereegranskat)abstract
- Adipocytes, once considered simple lipid-storing cells, are rapidly emerging as complex cells with many biologically diverse functions. A powerful high-throughput method for analyzing single cells is flow cytometry. Several groups have attempted to analyze and sort freshly isolated adipocytes; however, using an adipocyte-specific reporter mouse, we demonstrate that these studies fail to detect the majority of white adipocytes. We define critical settings required for adipocyte flow cytometry and provide a rigid strategy for analyzing and sorting white and brown adipocyte populations. The applicability of our protocol is shown by sorting mouse adipocytes based on size or UCP1 expression and demonstrating that a subset of human adipocytes lacks the beta(2)-adrenergic receptor, particularly in the insulin-resistant state. In conclusion, the present study confers key technological insights for analyzing and sorting mature adipocytes, opening up numerous downstream research applications.
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| 15. |
- Madsen, Lise, et al.
(författare)
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UCP1 induction during recruitment of brown adipocytes in white adipose tissue is dependent on cyclooxygenase activity.
- 2010
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 5:6, s. e11391-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The uncoupling protein 1 (UCP1) is a hallmark of brown adipocytes and pivotal for cold- and diet-induced thermogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that cyclooxygenase (COX) activity and prostaglandin E(2) (PGE(2)) are crucially involved in induction of UCP1 expression in inguinal white adipocytes, but not in classic interscapular brown adipocytes. Cold-induced expression of UCP1 in inguinal white adipocytes was repressed in COX2 knockout (KO) mice and by administration of the COX inhibitor indomethacin in wild-type mice. Indomethacin repressed beta-adrenergic induction of UCP1 expression in primary inguinal adipocytes. The use of PGE(2) receptor antagonists implicated EP(4) as a main PGE(2) receptor, and injection of the stable PGE(2) analog (EP(3/4) agonist) 16,16 dm PGE(2) induced UCP1 expression in inguinal white adipose tissue. Inhibition of COX activity attenuated diet-induced UCP1 expression and increased energy efficiency and adipose tissue mass in obesity-resistant mice kept at thermoneutrality. CONCLUSIONS/SIGNIFICANCE: Our findings provide evidence that induction of UCP1 expression in white adipose tissue, but not in classic interscapular brown adipose tissue is dependent on cyclooxygenase activity. Our results indicate that cyclooxygenase-dependent induction of UCP1 expression in white adipose tissues is important for diet-induced thermogenesis providing support for a surprising role of COX activity in the control of energy balance and obesity development.
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| 16. |
- Nordstrom, EA, et al.
(författare)
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A human-specific role of cell death-inducing DFFA (DNA fragmentation factor-alpha)-like effector A (CIDEA) in adipocyte lipolysis and obesity
- 2005
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 54:6, s. 1726-1734
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Tidskriftsartikel (refereegranskat)abstract
- Elevated circulating fatty acid concentration is a hallmark of insulin resistance and is at least in part attributed to the action of adipose tissue-derived tumor necrosis factor-α (TNF-α) on lipolysis. Cell death-inducing DFFA (DNA fragmentation factor-α)-like effector A (CIDEA) belongs to a family of proapoptotic proteins that has five known members in humans and mice. The action of CIDEA is unknown, but CIDEA-null mice are resistant to obesity and diabetes. We investigated CIDEA in adipose tissue of obese and lean humans and mice. The mRNA was expressed in white human fat cells and in brown mouse adipocytes. The adipose mRNA expression of CIDEA in mice was not influenced by obesity. However, CIDEA expression was decreased twofold in obese humans and normalized after weight reduction. Low adipose CIDEA expression was associated with several features of the metabolic syndrome. Human adipocyte depletion of CIDEA by RNA interference stimulated lipolysis and increased TNF-α secretion by a posttranscriptional effect. Conversely, TNF-α treatment decreased adipocyte CIDEA expression via the mitogen-activated protein kinase c-Jun NH2-terminal kinase. We propose an important and human-specific role for CIDEA in lipolysis regulation and metabolic complications of obesity, which is at least in part mediated by cross-talk between CIDEA and TNF-α.
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| 17. |
- van den Broek, Sara Lopes, et al.
(författare)
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Pretargeted Imaging beyond the Blood-Brain Barrier-Utopia or Feasible?
- 2022
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Ingår i: Pharmaceuticals. - : MDPI. - 1424-8247. ; 15:10
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Tidskriftsartikel (refereegranskat)abstract
- Pretargeting is a promising nuclear imaging technique that allows for the usage of antibodies (Abs) with enhanced imaging contrast and reduced patient radiation burden. It is based on bioorthogonal chemistry with the tetrazine ligation-a reaction between trans-cyclooctenes (TCOs) and tetrazines (Tzs)-currently being the most popular reaction due to its high selectivity and reactivity. As Abs can be designed to bind specifically to currently 'undruggable' targets such as protein isoforms or oligomers, which play a crucial role in neurodegenerative diseases, pretargeted imaging beyond the BBB is highly sought after, but has not been achieved yet. A challenge in this respect is that large molecules such as Abs show poor brain uptake. Uptake can be increased by receptor mediated transcytosis; however, it is largely unknown if the achieved brain concentrations are sufficient for pretargeted imaging. In this study, we investigated whether the required concentrations are feasible to reach. As a model Ab, we used the bispecific anti-amyloid beta (A beta) anti-transferrin receptor (TfR) Ab 3D6scFv8D3 and conjugated it to a different amount of TCOs per Ab and tested different concentrations in vitro. With this model in hand, we estimated the minimum required TCO concentration to achieve a suitable contrast between the high and low binding regions. The estimation was carried out using pretargeted autoradiography on brain sections of an Alzheimer's disease mouse model. Biodistribution studies in wild-type (WT) mice were used to correlate how different TCO/Ab ratios alter the brain uptake. Pretargeted autoradiography showed that increasing the number of TCOs as well as increasing the TCO-Ab concentration increased the imaging contrast. A minimum brain concentration of TCOs for pretargeting purposes was determined to be 10.7 pmol/g in vitro. Biodistribution studies in WT mice showed a brain uptake of 1.1% ID/g using TCO-3D6scFv8D3 with 6.8 TCO/Ab. According to our estimations using the optimal parameters, pretargeted imaging beyond the BBB is not a utopia. Necessary brain TCO concentrations can be reached and are in the same order of magnitude as required to achieve sufficient contrast. This work gives a first estimate that pretargeted imaging is indeed possible with antibodies. This could allow the imaging of currently 'undruggable' targets and therefore be crucial to monitor (e.g., therapies for intractable neurodegenerative diseases).
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| 18. |
- 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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| 19. |
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| 20. |
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| 21. |
- Cannon, Barbara, et al.
(författare)
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Human brown adipose tissue : Classical brown rather than brite/beige?
- 2020
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Ingår i: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 105:8, s. 1191-1200
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Tidskriftsartikel (refereegranskat)abstract
- New Findings What is the topic of this review? It has been suggested that human brown adipose tissue (BAT) is more similar to the brite/beige adipose tissue of mice than to classical BAT of mice. The basis of this is discussed in relationship to the physiological conditions of standard experimental mice.
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| 22. |
- Cheung, L., et al.
(författare)
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Human mediastinal adipose tissue displays certain characteristics of brown fat
- 2013
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Ingår i: Nutrition & Diabetes. - : Springer Science and Business Media LLC. - 2044-4052. ; 3:UNSP e66
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The amount of intra-thoracic fat, of which mediastinal adipose tissue comprises the major depot, is related to various cardiometabolic risk factors. Autopsy and imaging studies indicate that the mediastinal depot in adult humans could contain brown adipose tissue (BAT). To gain a better understanding of this intra-thoracic fat depot, we examined possible BAT characteristics of human mediastinal in comparison with subcutaneous adipose tissue. MATERIALS AND METHODS: Adipose tissue biopsies from thoracic subcutaneous and mediastinal depots were obtained during open-heart surgery from 33 subjects (26 male, 63.7 +/- 13.8 years, body mass index 29.3 +/- 5.1 kg m(-2)). Microarray analysis was performed on 10 patients and genes of interest confirmed by quantitative PCR (qPCR) in samples from another group of 23 patients. Adipocyte size was determined and uncoupling protein 1 (UCP1) protein expression investigated with immunohistochemistry. RESULTS: The microarray data showed that a number of BAT-specific genes had significantly higher expression in the mediastinal depot than in the subcutaneous depot. Higher expression of UCP1 (24-fold, P < 0.001) and PPARGC1A (1.7-fold, P = 0.0047), and lower expression of SHOX2 (0.12-fold, P < 0.001) and HOXC8 (0.14-fold, P < 0.001) in the mediastinal depot was confirmed by qPCR. Gene set enrichment analysis identified two gene sets related to mitochondria, which were significantly more highly expressed in the mediastinal than in the subcutaneous depot (P < 0.01). No significant changes in UCP1 gene expression were observed in the subcutaneous or mediastinal depots following lowering of body temperature during surgery. UCP1 messenger RNA levels in the mediastinal depot were lower than those in murine BAT and white adipose tissue. In some mediastinal adipose tissue biopsies, a small number of multilocular adipocytes that stained positively for UCP1 were observed. Adipocytes were significantly smaller in the mediastinal than the subcutaneous depot (cross-sectional area 2400 +/- 810 versus 3260 +/- 980 mu m(2), P < 0.001). CONCLUSIONS: Human mediastinal adipose tissue displays some characteristics of BAT when compared with the subcutaneous depot at microscopic and molecular levels.
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| 23. |
- de Jong, Jasper M. A., et al.
(författare)
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A stringent validation of mouse adipose tissue identity markers
- 2015
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 308:12, s. E1085-E1105
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Tidskriftsartikel (refereegranskat)abstract
- The nature of brown adipose tissue in humans is presently debated: whether it is classical brown or of brite/beige nature. The dissimilar developmental origins and proposed distinct functions of the brown and brite/beige tissues make it essential to ascertain the identity of human depots with the perspective of recruiting and activating them for the treatment of obesity and type 2 diabetes. For identification of the tissues, a number of marker genes have been proposed, but the validity of the markers has not been well documented. We used established brown (interscapular), brite (inguinal), and white (epididymal) mouse adipose tissues and corresponding primary cell cultures as validators and examined the informative value of a series of suggested markers earlier used in the discussion considering the nature of human brown adipose tissue. Most of these markers unexpectedly turned out to be noninformative concerning tissue classification (Car4, Cited1, Ebf3, Eva1, Fbxo31, Fgf21, Lhx8, Hoxc8, and Hoxc9). Only Zic1 (brown), Cd137, Epsti1, Tbx1, Tmem26 (brite), and Tcf21 (white) proved to be informative in these three tissues. However, the expression of the brite markers was not maintained in cell culture. In a more extensive set of adipose depots, these validated markers provide new information about depot identity. Principal component analysis supported our single-gene conclusions. Furthermore, Zic1, Hoxc8, Hoxc9, and Tcf21 displayed anteroposterior expression patterns, indicating a relationship between anatomic localization and adipose tissue identity (and possibly function). Together, the observed expression patterns of these validated marker genes necessitates reconsideration of adipose depot identity in mice and humans.
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| 24. |
- de Jong, Jasper M. A., et al.
(författare)
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Human brown adipose tissue is phenocopied by classical brown adipose tissue in physiologically humanized mice
- 2019
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Ingår i: Nature Metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 1:8, s. 830-843
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Tidskriftsartikel (refereegranskat)abstract
- Human and rodent brown adipose tissues (BAT) appear morphologically and molecularly different. Here we compare human BAT with both classical brown and brite/beige adipose tissues of 'physiologically humanized' mice: middle-aged mice living under conditions approaching human thermal and nutritional conditions, that is, prolonged exposure to thermoneutral temperature (approximately 30 degrees C) and to an energy-rich (high-fat, high-sugar) diet. We find that the morphological, cellular and molecular characteristics (both marker and adipose-selective gene expression) of classical brown fat, but not of brite/beige fat, of these physiologically humanized mice are notably similar to human BAT. We also demonstrate, both in silico and experimentally, that in physiologically humanized mice only classical BAT possesses a high thermogenic potential. These observations suggest that classical rodent BAT is the tissue of choice for translational studies aimed at recruiting human BAT to counteract the development of obesity and its comorbidities.
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| 25. |
- de Jong, Jasper M. A., et al.
(författare)
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Promotion of lipid storage rather than of thermogenic competence by fetal versus newborn calf serum in primary cultures of brown adipocytes
- 2018
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Ingår i: Adipocyte. - : Informa UK Limited. - 2162-3945 .- 2162-397X. ; 7:3, s. 166-179
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Tidskriftsartikel (refereegranskat)abstract
- Much current understanding of brown adipocyte development comes from in-vitro cell models. Serum type may affect the behavior of cultured cells and thus conclusions drawn. Here, we investigate effects of serum type (fetal bovine versus newborn calf) on responses to differentiation inducers (the PPAR agonist rosiglitazone or the neurotransmitter norepinephrine) in cultured primary brown adipocytes. Lipid storage was enhanced by fetal versus newborn serum. However, molecular adipose conversion (Pparg2 and Fabp4 expression) was not affected by serum type. Rosiglitazone-induced (7-days) expression of thermogenic genes (i.e. Ucp1, Pgc1a, Dio2 and Elovl3) was not systematically affected by serum type. However, importantly, acute (2h) norepinephrine-induced thermogenic gene expression was overall markedly higher (and adipose genes somewhat lower) in cells cultured in newborn serum. Thus, newborn serum promotes thermogenic competence, and the use of fetal serum in brown adipocyte cultures (as is often routine) counteracts adequate differentiation. Agents that counteract this inhibition may therefore confoundingly be ascribed genuine thermogenic competence-inducing properties.
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| 26. |
- de Jong, Jasper M. A., et al.
(författare)
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The β3-adrenergic receptor is dispensable for browning of adipose tissues
- 2017
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 312:6, s. E508-E518
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Tidskriftsartikel (refereegranskat)abstract
- Brown and brite/beige adipocytes are attractive therapeutic targets to treat metabolic diseases. To maximally utilize their functional potential, further understanding is required about their identities and their functional differences. Recent studies with β3-adrenergic receptor knockout mice reported that brite/beige adipocytes, but not classical brown adipocytes, require the β3-adrenergic receptor for cold-induced transcriptional activation of thermogenic genes. We aimed to further characterize this requirement of the β3-adrenergic receptor as a functional distinction between classical brown and brite/beige adipocytes. However, when comparing wild-type and β3-adrenergic receptor knockout mice, we observed no differences in cold-induced thermogenic gene expression (Ucp1, Pgc1a, Dio2 and Cidea) in brown or white (brite/beige) adipose tissues. Irrespective of the duration of the cold exposure or the sex of the mice, we observed no effect of the absence of the β3-adrenergic receptor. Experiments with the β3-adrenergic receptor agonist CL-316,243 verified the functional absence of β3-adrenergic signaling in these knockout mice. The β3-adrenergic receptor knockout model in the present study was maintained on a FVB/N background, whereas earlier reports used C57BL/6 and 129Sv mice. Thus, our data imply background-dependent differences in adrenergic signaling mechanisms in response to cold exposure. Nonetheless, the present data indicate that the β3-adrenergic receptor is dispensable for cold-induced transcriptional activation in both classical brown and, as opposed to earlier studies, brite/beige cells. This should be taken into account in the increasing number of studies on the induction of browning and their extrapolation to human physiology.
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| 27. |
- Dixen, Karen, et al.
(författare)
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ERR gamma Enhances UCP1 Expression and Fatty Acid Oxidation in Brown Adipocytes
- 2013
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Ingår i: Obesity. - : Wiley. - 1930-7381 .- 1930-739X. ; 21:3, s. 516-524
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Estrogen-related receptors (ERRs) are important regulators of energy metabolism. Here we investigated the hypothesis that ERR gamma impacts on differentiation and function of brown adipocytes. Design and Methods: We characterize the expression of ERR gamma in adipose tissues and cell models and investigate the effects of modulating ERR? activity on UCP1 gene expression and metabolic features of brown and white adipocytes. Results: ERR gamma was preferentially expressed in brown compared to white fat depots, and ERR gamma was induced during cold-induced browning of subcutaneous white adipose tissue and brown adipogenesis. Overexpression of ERR gamma positively regulated uncoupling protein 1 (UCP1) expression levels during brown adipogenesis. This ERR gamma-induced augmentation of UCP1 expression was independent of the presence of peroxisome proliferator-activated receptor coactivator-1 (PGC-1 alpha) but was associated with increased rates of fatty acid oxidation in adrenergically stimulated cells. ERR? did not influence mitochondrial biogenesis, and its reduced expression in white adipocytes could not explain their low expression level of UCP1. Conclusions: Through its augmenting effect on expression of UCP1, ERR gamma may physiologically be involved in increasing the potential for energy expenditure in brown adipocytes, a function that is becoming of therapeutic interest.
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| 28. |
- Du, Ting, et al.
(författare)
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Cerebrospinal fluid is a significant fluid source for anoxic cerebral oedema
- 2022
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Ingår i: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 145:2, s. 787-797
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Tidskriftsartikel (refereegranskat)abstract
- Cerebral oedema develops after anoxic brain injury. In two models of asphyxial and asystolic cardiac arrest without resuscitation, we found that oedema develops shortly after anoxia secondary to terminal depolarizations and the abnormal entry of CSF. Oedema severity correlated with the availability of CSF with the age-dependent increase in CSF volume worsening the severity of oedema. Oedema was identified primarily in brain regions bordering CSF compartments in mice and humans. The degree of ex vivo tissue swelling was predicted by an osmotic model suggesting that anoxic brain tissue possesses a high intrinsic osmotic potential. This osmotic process was temperature-dependent, proposing an additional mechanism for the beneficial effect of therapeutic hypothermia. These observations show that CSF is a primary source of oedema fluid in anoxic brain. This novel insight offers a mechanistic basis for the future development of alternative strategies to prevent cerebral oedema formation after cardiac arrest.
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| 29. |
- Feldmann, Helena M., et al.
(författare)
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UCP1 ablation induces obesity and abolishes diet-induced thermogenesis in mice exempt from thermal stress by living at thermoneutrality.
- 2009
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Ingår i: Cell metabolism. - : Elsevier BV. - 1932-7420 .- 1550-4131. ; 9:2, s. 203-9
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Tidskriftsartikel (refereegranskat)abstract
- As original studies of UCP1-ablated mice failed to demonstrate an obesogenic effect, alternative mechanisms for adaptive adrenergic thermogenesis have been sought. However, we demonstrate here that in C57Bl6 mice exempt from thermal stress (i.e., kept at thermoneutrality), UCP1 ablation in itself induced obesity, even in mice fed control diet, and vastly augmented diet-induced obesity (high-fat diet); i.e., the mice exhibited increased metabolic efficiency. In wild-type mice, high-fat diet increased norepinephrine-induced thermogenesis; i.e., diet-induced thermogenesis was observed, but no such effect was observed in UCP1-ablated mice, demonstrating that diet-induced thermogenesis fully emanates from UCP1 activity. We conclude that ambient temperature is qualitatively determinative for the outcome of metabolic studies, that no other protein and no other mechanism can substitute for UCP1 in mediating diet-induced adrenergic thermogenesis, and that UCP1 activity can be determinative for obesity development in mice and possibly in humans.
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| 30. |
- Fischer, Alexander W., et al.
(författare)
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Leptin Raises Defended Body Temperature without Activating Thermogenesis
- 2016
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 14:7, s. 1621-1631
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Tidskriftsartikel (refereegranskat)abstract
- Leptin has been believed to exert its weight-reducing action not only by inducing hypophagia but also by increasing energy expenditure/thermogenesis. Leptin-deficient ob/ob mice have correspondingly been thought to be thermogenically limited and to show hypothermia, mainly due to atrophied brown adipose tissue (BAT). In contrast to these established views, we found that BAT is fully functional and that leptin treatment did not increase thermogenesis in wildtype or in ob/ob mice. Rather, ob/ob mice showed a decreased but defended body temperature (i. e., were anapyrexic, not hypothermic) that was normalized to wild-type levels after leptin treatment. This was not accompanied by increased energy expenditure or BAT recruitment but, instead, was mediated by decreased tail heat loss. The weight-reducing hypophagic effects of leptin are, therefore, not augmented through a thermogenic effect of leptin; leptin is, however, pyrexic, i. e., it alters centrally regulated thresholds of thermoregulatory mechanisms, in parallel to effects of other cytokines.
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| 31. |
- Hansen, Ida R., et al.
(författare)
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Contrasting effects of cold acclimation versus obesogenic diets on chemerin gene expression in brown and brite adipose tissues
- 2014
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1841:12, s. 1691-1699
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Tidskriftsartikel (refereegranskat)abstract
- Based on results from a signal sequence trap, we investigated chemerin gene expression in brown adipose tissue. Male NMRI mice were exposed to 30, 22 or 4 degrees C for 3 weeks, or were fed control (chow) diet, cafeteria diet or high-fat diet at thermoneutrality for the same time. In brown adipose tissue, cold acclimation strongly diminished chemerin gene expression, whereas obesogenic diets augmented expression. Qualitatively, changes in expression were paralleled in brite/beige adipose tissues (e.g. inguinal), whereas white adipose tissue (epididymal) and muscle did not react to these cues. Changes in tissue expression were not directly paralleled by alterations in plasma levels. Both these intact animal studies and brown adipocyte cell culture studies indicated that the gene expression regulation was not congruent with a sympathetic/adrenergic control. The data are discussed in relation to suggested endocrine, paracrine and autocrine effects of chemerin.
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| 32. |
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| 33. |
- Isidor, Marie S., et al.
(författare)
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An siRNA-based method for efficient silencing of gene expression in mature brown adipocytes
- 2016
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Ingår i: Adipocyte. - : Informa UK Limited. - 2162-3945 .- 2162-397X. ; 5:2, s. 175-185
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Tidskriftsartikel (refereegranskat)abstract
- Brown adipose tissue is a promising therapeutic target for opposing obesity, glucose intolerance and insulin resistance. The ability to modulate gene expression in mature brown adipocytes is important to understand brown adipocyte function and delineate novel regulatory mechanisms of non-shivering thermogenesis. The aim of this study was to optimize a lipofection-based small interfering RNA (siRNA) transfection protocol for efficient silencing of gene expression in mature brown adipocytes. We determined that a critical parameter was to deliver the siRNA to mature adipocytes by reverse transfection, i.e. transfection of non-adherent cells. Using this protocol, we effectively knocked down both high-and low-abundance transcripts in a model of mature brown adipocytes (WT-1) as well as in primary mature mouse brown adipocytes. A functional consequence of the knockdown was confirmed by an attenuated increase in uncoupled respiration (thermogenesis) in response to beta-adrenergic stimulation of mature WT-1 brown adipocytes transfected with uncoupling protein 1 siRNA. Efficient gene silencing was also obtained in various mouse and human white adipocyte models (3T3-L1, primary mouse white adipocytes, hMADS) with the ability to undergo browning. In summary, we report an easy and versatile reverse siRNA transfection protocol to achieve specific silencing of gene expression in various models of mature brown and browning-competent white adipocytes, including primary cells.
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| 34. |
- Kalinovich, Anastasia V., et al.
(författare)
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UCP1 in adipose tissues: two steps to full browning
- 2017
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Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 134, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- The possibility that brown adipose tissue thermogenesis can be recruited in order to combat the development of obesity has led to a high interest in the identification of "browning agents", i.e. agents that increase the amount and activity of UCP1 in brown and brite/beige adipose tissues. However, functional analysis of the browning process yields confusingly different results when the analysis is performed in one of two alternative steps. Thus, in one of the steps, using cold acclimation as a potent model browning agent, we find that if the browning process is followed in mice initially housed at 21 °C (the most common procedure), there is only weak molecular evidence for increases in UCP1 gene expression or UCP1 protein abundance in classical brown adipose tissue; however, in brite/beige adipose depots, there are large increases, apparently associating functional browning with events only in the brite/beige tissues. Contrastingly, in another step, if the process is followed starting with mice initially housed at 30 °C (thermoneutrality for mice, thus similar to normal human conditions), large increases in UCP1 gene expression and UCP1 protein abundance are observed in the classical brown adipose tissue depots; there is then practically no observable UCP1 gene expression in brite/beige tissues. This apparent conundrum can be resolved when it is realized that the classical brown adipose tissue at 21 °C is already essentially fully differentiated and thus expands extensively through proliferation upon further browning induction, rather than by further enhancing cellular differentiation. When the limiting factor for thermogenesis, i.e. the total amount of UCP1 protein per depot, is analyzed, classical brown adipose tissue is by far the predominant site for the browning process, irrespective of which of the two steps is analyzed. There are to date no published data demonstrating that alternative browning agents would selectively promote brite/beige tissues versus classical brown tissue to a higher degree than does cold acclimation. Thus, to restrict investigations to examine adipose tissue depots where only a limited part of the adaptation process occurs (i.e. the brite/beige tissues) and to use initial conditions different from the thermoneutrality normally experienced by adult humans may seriously hamper the identification of therapeutically valid browning agents. The data presented here have therefore important implications for the analysis of the potential of browning agents and the nature of human brown adipose tissue.
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| 35. |
- Luijten, Ineke H. N., et al.
(författare)
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In the absence of UCP1-mediated diet-induced thermogenesis, obesity is augmented even in the obesity-resistant 129S mouse strain
- 2019
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 316:5, s. E729-E740
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Tidskriftsartikel (refereegranskat)abstract
- The attractive tenet that recruitment and activation of brown adipose tissue (BAT) and uncoupling protein 1 (UCP1) could counteract the development of obesity and its comorbidities in humans has been experimentally corroborated mainly by experiments demonstrating that UCP1-ablated mice on a C57B1/6 background (exempt from thermal stress) become more obese when fed a high-fat diet. However, concerns may be raised that this outcome of UCP1 ablation is restricted to this very special inbred and particularly obesity-prone mouse strain. Therefore, we have examined to which degree UCP1 ablation has similar metabolic effects in a mouse strain known to be obesity resistant: the 129S strain. For this, male 129S2/sv or 129SV/Pas mice and corresponding UCP1-knockout mice were fed chow or a high-fat or a cafeteria diet for 4 w.k. The absence of UCP1 augmented obesity (weight gain, body fat mass, %body fat, fat depot size) in high-fat diet- and cafeteria-fed mice, with a similar or lower food intake, indicating that, when present, UCP1 indeed decreases metabolic efficiency. The increased obesity was due to a decrease in energy expenditure. The consumption of a high-fat or cafeteria diet increased total BAT UCP1 protein levels in wild-type mice, and correspondingly. high-fat diet and cafeteria diet-fed mice demonstrated increased norepinephrine-induced oxygen consumption. There was a positive correlation between body fat and total BAT UCP1 protein content. No evidence for diet-induced adrenergic thermogenesis was found in UCP1-ablated mice. Thus, the obesity-reducing effect of UCP1 is not restricted to a particular, and perhaps not representative, mouse strain.
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| 36. |
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| 37. |
- Martikainen, Maria-Viola, et al.
(författare)
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TUBE project: Transport-derived ultrafines and the brain effects
- 2022
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 19:1
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Tidskriftsartikel (refereegranskat)abstract
- The adverse effects of air pollutants on the respiratory and cardiovascular systems are unquestionable. However, in recent years, indications of effects beyond these organ systems have become more evident. Traffic-related air pollution has been linked with neurological diseases, exacerbated cognitive dysfunction, and Alzheimer’s disease. However, the exact air pollutant compositions and exposure scenarios leading to these adverse health effects are not known. Although several components of air pollution may be at play, recent experimental studies point to a key role of ultrafine particles (UFPs). While the importance of UFPs has been recognized, almost nothing is known about the smallest fraction of UFPs, and only >23 nm emissions are regulated in the EU. Moreover, the role of the semivolatile fraction of the emissions has been neglected. The Transport-Derived Ultrafines and the Brain Effects (TUBE) project will increase knowledge on harmful ultrafine air pollutants, as well as semivolatile compounds related to adverse health effects. By including all the major current combustion and emission control technologies, the TUBE project aims to provide new information on the adverse health effects of current traffic, as well as information for decision makers to develop more effective emission legislation. Most importantly, the TUBE project will include adverse health effects beyond the respiratory system; TUBE will assess how air pollution affects the brain and how air pollution particles might be removed from the brain. The purpose of this report is to describe the TUBE project, its background, and its goals.
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| 38. |
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| 39. |
- Munk, Anne Sofie, et al.
(författare)
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PDGF-B Is Required for Development of the Glymphatic System
- 2019
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; , s. 3-2969
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Tidskriftsartikel (refereegranskat)abstract
- The glymphatic system is a highly polarized cerebrospinal fluid (CSF) transport system that facilitates the clearance of neurotoxic molecules through a brain-wide network of perivascular pathways. Herein we have mapped the development of the glymphatic system in mice. Perivascular CSF transport first emerges in hippocampus in newborn mice, and a mature glymphatic system is established in the cortex at 2 weeks of age. Formation of astrocytic endfeet and polarized expression of aquaporin 4 (AQP4) consistently coincided with the appearance of perivascular CSF transport. Deficiency of platelet-derived growth factor B (PDGF-B) function in the PDGF retention motif knockout mouse line Pdgfb ret/ret suppressed the development of the glymphatic system, whose functions remained suppressed in adulthood compared with wild-type mice. These experiments map the natural development of the glymphatic system in mice and define a critical role of PDGF-B in the development of perivascular CSF transport.
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| 40. |
- Olsen, Hanne T., et al.
(författare)
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Nonsedation or Light Sedation in Critically Ill, Mechanically Ventilated Patients
- 2020
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Ingår i: New England Journal of Medicine. - : MASSACHUSETTS MEDICAL SOC. - 0028-4793 .- 1533-4406. ; 382:12, s. 1103-1111
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Tidskriftsartikel (refereegranskat)abstract
- Background In critically ill, mechanically ventilated patients, daily interruption of sedation has been shown to reduce the time on ventilation and the length of stay in the intensive care unit (ICU). Data on whether a plan of no sedation, as compared with a plan of light sedation, has an effect on mortality are lacking. Methods In a multicenter, randomized, controlled trial, we assigned, in a 1:1 ratio, mechanically ventilated ICU patients to a plan of no sedation (nonsedation group) or to a plan of light sedation (i.e., to a level at which the patient was arousable, defined as a score of -2 to -3 on the Richmond Agitation and Sedation Scale [RASS], on which scores range from -5 [unresponsive] to +4 [combative]) (sedation group) with daily interruption. The primary outcome was mortality at 90 days. Secondary outcomes were the number of major thromboembolic events, the number of days free from coma or delirium, acute kidney injury according to severity, the number of ICU-free days, and the number of ventilator-free days. Between-group differences were calculated as the value in the nonsedation group minus the value in the sedation group. Results A total of 710 patients underwent randomization, and 700 were included in the modified intention-to-treat analysis. The characteristics of the patients at baseline were similar in the two trial groups, except for the score on the Acute Physiology and Chronic Health Evaluation (APACHE) II, which was 1 point higher in the nonsedation group than in the sedation group, indicating a greater chance of in-hospital death. The mean RASS score in the nonsedation group increased from -1.3 on day 1 to -0.8 on day 7 and, in the sedation group, from -2.3 on day 1 to -1.8 on day 7. Mortality at 90 days was 42.4% in the nonsedation group and 37.0% in the sedated group (difference, 5.4 percentage points; 95% confidence interval [CI], -2.2 to 12.2; P=0.65). The number of ICU-free days and of ventilator-free days did not differ significantly between the trial groups. The patients in the nonsedation group had a median of 27 days free from coma or delirium, and those in the sedation group had a median of 26 days free from coma or delirium. A major thromboembolic event occurred in 1 patient (0.3%) in the nonsedation group and in 10 patients (2.8%) in the sedation group (difference, -2.5 percentage points; 95% CI, -4.8 to -0.7 [unadjusted for multiple comparisons]). Conclusions Among mechanically ventilated ICU patients, mortality at 90 days did not differ significantly between those assigned to a plan of no sedation and those assigned to a plan of light sedation with daily interruption. (Funded by the Danish Medical Research Council and others; NONSEDA ClinicalTrials.gov number, NCT01967680.)
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| 41. |
- Olsen, Jessica M., et al.
(författare)
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β3-Adrenergically induced glucose uptake in brown adipose tissue is independent of UCP1 presence or activity : Mediation through the mTOR pathway
- 2017
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Ingår i: Molecular Metabolism. - : Elsevier BV. - 2212-8778. ; 6:6, s. 611-619
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveToday, the presence and activity of brown adipose tissue (BAT) in adult humans is generally equated with the induced accumulation of [2-18F]2-fluoro-2-deoxy-d-glucose([18F]FDG) in adipose tissues, as investigated by positron emission tomography (PET) scanning. In reality, PET-FDG is currently the only method available for in vivoquantification of BAT activity in adult humans. The underlying assumption is that the glucose uptake reflects the thermogenic activity of the tissue.MethodsTo examine this basic assumption, we here followed [18F]FDG uptake by PET and by tissue [3H]-2-deoxy-d-glucose uptake in wildtype and UCP1(−/−) mice, i.e. in mice that do or do not possess the unique thermogenic and calorie-consuming ability of BAT.ResultsUnexpectedly, we found that β3-adrenergically induced (by CL-316,243) glucose uptake was UCP1-independent. Thus, whereas PET-FDG scans adequately reflect glucose uptake, this acute glucose uptake is not secondary to thermogenesis but is governed by an independent cellular signalling, here demonstrated to be mediated via the previously described KU-0063794-sensitive mTOR pathway.ConclusionsThus, PET-FDG scans do not exclusively reveal active BAT deposits but rather any tissue possessing an adrenergically-mediated glucose uptake pathway. In contrast, we found that the marked glucose uptake-ameliorating effect of prolonged β3-adrenergictreatment was UCP1 dependent. Thus, therapeutically, UCP1 activity is required for any anti-diabetic effect of BAT activation.
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| 42. |
- Shabalina, Irina G., et al.
(författare)
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UCP1 in Brite/Beige Adipose Tissue Mitochondria Is Functionally Thermogenic
- 2013
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 5:5, s. 1196-1203
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Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of white fat browning, in which certain white adipose tissue depots significantly increase gene expression for the uncoupling protein UCP1 and thus supposedly acquire thermogenic, fat-burning properties, has attracted considerable attention. Because the mRNA increases are from very low initial levels, the metabolic relevance of the change is unclear: is the UCP1 protein thermogenically competent in these brite/beige-fat mitochondria? We found that, in mitochondria isolated from the inguinal white adipose depot of cold-acclimated mice, UCP1 protein levels almost reached those in brown-fat mitochondria. The UCP1 was thermogenically functional, in that these mitochondria exhibited UCP1-dependent thermogenesis with lipid or carbohydrate substrates with canonical guanosine diphosphate (GDP) sensitivity and loss of thermogenesis in UCP1 knockout (KO) mice. Obesogenic mouse strains had a lower thermogenic potential than obesity-resistant strains. The thermogenic density (UCP1-dependent oxygen consumption per g tissue) of inguinal white adipose tissue was maximally one-fifth of interscapular brown adipose tissue, and the total quantitative contribution of all inguinal mitochondria was maximally one-third of all interscapular brown-fat mitochondria, indicating that the classical brown adipose tissue depots would still predominate in thermogenesis.
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| 43. |
- Shinoda, Kosaku, et al.
(författare)
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Genetic and functional characterization of clonally derived adult human brown adipocytes
- 2015
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 21:4, s. 389-394
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Tidskriftsartikel (refereegranskat)abstract
- Brown adipose tissue (BAT) acts in mammals as a natural defense system against hypothermia, and its activation to a state of increased energy expenditure is believed to protect against the development of obesity. Even though the existence of BAT in adult humans has been widely appreciated(1-8), its cellular origin and molecular identity remain elusive largely because of high cellular heterogeneity within various adipose tissue depots. To understand the nature of adult human brown adipocytes at single cell resolution, we isolated clonally derived adipocytes from stromal vascular fractions of adult human BAT from two individuals and globally analyzed their molecular signatures. We used RNA sequencing followed by unbiased genome-wide expression analyses and found that a population of uncoupling protein 1 (UCP1)-positive human adipocytes possessed molecular signatures resembling those of a recruitable form of thermogenic adipocytes (that is, beige adipocytes). In addition, we identified molecular markers that were highly enriched in UCP1-positive human adipocytes, a set that included potassium channel K3 (KCNK3) and mitochondrial tumor suppressor 1 (MTUS1). Further, we functionally characterized these two markers using a loss-of-function approach and found that KCNK3 and MTUS1 were required for beige adipocyte differentiation and thermogenic function. The results of this study present new opportunities for human BAT research, such as facilitating cell-based disease modeling and unbiased screens for thermogenic regulators.
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| 44. |
- Siersbaek, Majken S., et al.
(författare)
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Genome-Wide Profiling of Peroxisome Proliferator-Activated Receptor gamma in Primary Epididymal, Inguinal, and Brown Adipocytes Reveals Depot-Selective Binding Correlated with Gene Expression
- 2012
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Ingår i: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 32:17, s. 3452-3463
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Tidskriftsartikel (refereegranskat)abstract
- Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a master regulator of adipocyte differentiation and function. We and others have previously mapped PPAR gamma binding at a genome-wide level in murine and human adipocyte cell lines and in primary human adipocytes. However, little is known about how binding patterns of PPAR gamma differ between brown and white adipocytes and among different types of white adipocytes. Here we have employed chromatin immunoprecipitation combined with deep sequencing to map and compare PPAR gamma binding in in vitro differentiated primary mouse adipocytes isolated from epididymal, inguinal, and brown adipose tissues. While these PPAR gamma binding profiles are overall similar, there are clear depot-selective binding sites. Most PPAR gamma binding sites previously mapped in 3T3-L1 adipocytes can also be detected in primary adipocytes, but there are a large number of PPAR gamma binding sites that are specific to the primary cells, and these tend to be located in closed chromatin regions in 3T3-L1 adipocytes. The depot-selective binding of PPAR gamma is associated with highly depot-specific gene expression. This indicates that PPAR gamma plays a role in the induction of genes characteristic of different adipocyte lineages and that preadipocytes from different depots are differentially preprogrammed to permit PPAR gamma lineage-specific recruitment even when differentiated in vitro.
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| 45. |
- Wang, Yanling, et al.
(författare)
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In brown adipocytes, adrenergically induced beta(1)-/beta(3)-(G(s))-, alpha(2)-(G(i))- and alpha(1)-(G(q))-signalling to Erk1/2 activation is not mediated via EGF receptor transactivation
- 2013
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 319:17, s. 2718-2727
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Tidskriftsartikel (refereegranskat)abstract
- Brown adipose tissue is unusual in that the neurotransmitter norepinephrine influences cell destiny in ways generally associated with effects of classical growth factors: regulation of cell proliferation, of apoptosis, and progression of differentiation. The norepinephrine effects are mediated through G-protein-coupled receptors; further mediation of such stimulation to e.g. Erk1/2 activation is in cell biology in general accepted to occur through transactivation of the EGF receptor (by external or internal pathways). We have examined here the significance of such transactivation in brown adipocytes. Stimulation of mature brown adipocytes with cirazoline (alpha(1)-adrenoceptor coupled via G(q)), clonidine (alpha(2) via G(i)) or CL316243 (beta(3) via G(s)) or via beta(1)-receptors significantly activated Erk1/2. Pretreatment with the EGF receptor kinase inhibitor AG1478 had, remarkably, no significant effect on Erk1/2 activation induced by any of these adrenergic agonists (although it fully abolished EGF-induced Erk1/2 activation), demonstrating absence of EGF receptor-mediated transactivation. Results with brown preadipocytes (cells in more proliferative states) were not qualitatively different. Joint stimulation of all adrenoceptors with norepinephrine did not result in synergism on Erk1/2 activation. AG1478 action on EGF-stimulated Erk1/2 phosphorylation showed a sharp concentration response relationship (IC50 0.3 mu M); a minor apparent effect of AG1478 on norepinephrine-stimulated Erk1/2 phosphorylation showed nonspecific kinetics, implying caution in interpretation of partial effects of AG1478 as reported in other systems. Transactivation of the EGF receptor is clearly not a universal prerequisite for coupling of G-protein coupled receptors to Erk1/2 signalling cascades.
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| 46. |
- Wang, Yanling, 1982-, et al.
(författare)
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In brown adipocytes, adrenergically induced β1-/β3-(Gs)-, α2-(Gi)- and α1-(Gq)-mediated Erk1/2 activation is not mediated via EGF receptor transactivation
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Brown adipose tissue is unusual in utilising the neurotransmitter norepineph- rine to influence cell destiny in ways generally associated with classical growth factors: regulation of cell proliferation, apoptosis, progression of differentiation. These effects are thus mediated through G-protein-coupled receptors; mediation of such stimulation to e.g. Erk1/2 activation is generally accepted to occur through transactivation of the EGF receptor (by external or internal pathways). We have examined here the significance of such transac- tivation in brown adipocytes. Stimulation of mature brown adipocytes with cirazoline (α1-adrenoceptor coupled via Gq), clonidine (α2 via Gi) or CL316243 (β3 via Gs) significantly activated Erk1/2. Pretreatment with the EGF receptor kinase inhibitor AG1478 had, remarkably, no significant effect on Erk1/2 activation induced by any of the adrenergic agonists (although it fully abolished EGF-induced Erk1/2 activation), demonstrating absence of transactivation. Results with brown adipocytes in more proliferative states were not qualitatively different. Joint stimulation of all adrenoceptors with norepinephrine did not result in synergism on Erk1/2 activation or in occur- rence of transactivation. AG1478 action on EGF-stimulated Erk1/2 phos- phorylation showed a sharp concentration-response relationship with an IC50 of approx. 0.3 μM; a minor effect of AG1478 on norepinephrine- stimulated Erk1/2 phosphorylation was clearly nonspecific, occurring suc- cessively and only partially over 3 decades of AG1478 concentrations; cau- tion may therefore be required in interpretation of effects of AG1478 at higher concentrations. Transactivation of the EGF receptor is clearly not a universal prerequisite for coupling of G-protein coupled receptors to Erk1/2 signaling cascades.
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| 47. |
- Xue, Yuan, et al.
(författare)
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Hypoxia-independent angiogenesis in adipose tissues during cold acclimation.
- 2009
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 9:1, s. 99-109
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Tidskriftsartikel (refereegranskat)abstract
- The molecular mechanisms of angiogenesis in relation to adipose tissue metabolism remain poorly understood. Here, we show that exposure of mice to cold led to activation of angiogenesis in both white and brown adipose tissues. In the inguinal depot, cold exposure resulted in elevated expression levels of brown-fat-associated proteins, including uncoupling protein-1 (UCP1) and PGC-1alpha. Proangiogenic factors such as VEGF were upregulated, and endogenous angiogenesis inhibitors, including thrombospondin, were downregulated. In wild-type mice, the adipose tissues became hypoxic during cold exposure; in UCP1(-/-) mice, hypoxia did not occur, but, remarkably, the augmented angiogenesis was unaltered and was thus hypoxia independent. Intriguingly, VEGFR2 blockage abolished the cold-induced angiogenesis and significantly impaired nonshivering thermogenesis capacity. Unexpectedly, VEGFR1 blockage resulted in the opposite effects: increased adipose vascularity and nonshivering thermogenesis capacity. Our findings have conceptual implications concerning application of angiogenesis modulators for treatment of obesity and metabolic disorders.
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