| 1. |
- Ryden, Mikael, et al.
(författare)
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Transplanted Bone Marrow-Derived Cells Contribute to Human Adipogenesis
- 2015
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 22:3, s. 408-417
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Tidskriftsartikel (refereegranskat)abstract
- Because human white adipocytes display a high turnover throughout adulthood, a continuous supply of precursor cells is required to maintain adipogenesis. Bone marrow (BM)-derived progenitor cells may contribute to mammalian adipogenesis; however, results in animal models are conflicting. Here we demonstrate in 65 subjects who underwent allogeneic BM or peripheral blood stem cell (PBSC) transplantation that, over the entire lifespan, BM/PBSC-derived progenitor cells contribute similar to 10% to the subcutaneous adipocyte population. While this is independent of gender, age, and different transplantation-related parameters, body fat mass exerts a strong influence, with up to 2.5-fold increased donor cell contribution in obese individuals. Exome and whole-genome sequencing of single adipocytes suggests that BM/PBSC-derived progenitors contribute to adipose tissue via both differentiation and cell fusion. Thus, at least in the setting of transplantation, BM serves as a reservoir for adipocyte progenitors, particularly in obese subjects.
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| 2. |
- Arner, Erik, et al.
(författare)
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Adipocyte Turnover : Relevance to Human Adipose Tissue Morphology
- 2010
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 59:1, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE-Adipose tissue may contain few large adipocytes (hypertrophy) or many small adipocytes (hyperplasia). We investigated factors of putative importance for adipose tissue morphology. RESEARCH DESIGN AND METHODS-Subcutaneous adipocyte size and total fat mass were compared in 764 subjects with BMI 18-60 kg/m(2). A morphology value was defined as tire difference between the measured adipocyte volume and the expected volume given by a curved-line fit for a given body fat mass and was related to insulin values. In 35 subjects, in vivo adipocyte turnover was measured by exploiting incorporation of atmospheric C-14 into DNA. RESULTS-Occurrence of hyperplasia (negative morphology value) or hypertrophy (positive morphology value) was independent of sex and body weight but con-elated with fasting plasma insulin levels and insulin sensitivity, independent of adipocyte volume (beta-coefficient = 0.3, P < 0.0001). Total adipocyte number and morphology were negatively related (r = -0.66); i.e., the total adipocyte number was greatest in pronounced hyperplasia and smallest in pronounced hypertrophy. The absolute number of new adipocytes generated each year was 70% lower (P < 0.001) in hypertrophy than in hyperplasia, and individual values for adipocyte generation and morphology were strongly related (r = 0.7, P < 0.001). The relative death rate (similar to 10% per year) or mean age of adipocytes (similar to 10 years) was not correlated with morphology. CONCLUSIONS-Adipose tissue morphology correlates with insulin measures and is linked to the total adipocyte number independently of sex and body fat level. Low generation rates of adipocytes associate with adipose tissue hypertrophy, whereas high generation rates associate with adipose hyperplasia. Diabetes 59:105-109, 2010
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| 3. |
- Arner, Peter, et al.
(författare)
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Dynamics of human adipose lipid turnover in health and metabolic disease
- 2011
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 478:7367, s. 110-113
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Tidskriftsartikel (refereegranskat)abstract
- Adipose tissue mass is determined by the storage and removal of triglycerides in adipocytes(1). Little is known, however, about adipose lipid turnover in humans in health and pathology. To study this in vivo, here we determined lipid age by measuring (14)C derived from above ground nuclear bomb tests in adipocyte lipids. We report that during the average ten-year lifespan of human adipocytes, triglycerides are renewed six times. Lipid age is independent of adipocyte size, is very stable across a wide range of adult ages and does not differ between genders. Adipocyte lipid turnover, however, is strongly related to conditions with disturbed lipid metabolism. In obesity, triglyceride removal rate (lipolysis followed by oxidation) is decreased and the amount of triglycerides stored each year is increased. In contrast, both lipid removal and storage rates are decreased in non-obese patients diagnosed with the most common hereditary form of dyslipidaemia, familial combined hyperlipidaemia. Lipid removal rate is positively correlated with the capacity of adipocytes to break down triglycerides, as assessed through lipolysis, and is inversely related to insulin resistance. Our data support a mechanism in which adipocyte lipid storage and removal have different roles in health and pathology. High storage but low triglyceride removal promotes fat tissue accumulation and obesity. Reduction of both triglyceride storage and removal decreases lipid shunting through adipose tissue and thus promotes dyslipidaemia. We identify adipocyte lipid turnover as a novel target for prevention and treatment of metabolic disease.
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| 4. |
- Castillejo-Lopez, Casimiro, et al.
(författare)
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Detailed Functional Characterization of a Waist-Hip Ratio Locus in 7p15.2 Defines an Enhancer Controlling Adipocyte Differentiation
- 2019
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Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 20, s. 42-59
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Tidskriftsartikel (refereegranskat)abstract
- We combined CAGE sequencing in human adipocytes during differentiation with data from genome-wide association studies to identify an enhancer in the SNX10 locus on chromosome 7, presumably involved in body fat distribution. Using reporter assays and CRISPR-Cas9 gene editing in human cell lines, we characterized the role of the enhancer in adipogenesis. The enhancer was active during adipogenesis and responded strongly to insulin and isoprenaline. The allele associated with increased waist-hip ratio in human genetic studies was associated with higher enhancer activity. Mutations of the enhancer resulted in less adipocyte differentiation. RNA sequencing of cells with disrupted enhancer showed reduced expression of established adipocyte markers, such as ADIPOQ and LPL, and identified CHI3L1 on chromosome 1 as a potential gene involved in adipocyte differentiation. In conclusion, we identified and characterized an enhancer in the SNX10 locus and outlined its plausible mechanisms of action and downstream targets.
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| 5. |
- Ehrlund, A, et al.
(författare)
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Transcriptional Dynamics During Human Adipogenesis and Its Link to Adipose Morphology and Distribution
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 66:1, s. 218-230
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Tidskriftsartikel (refereegranskat)abstract
- White adipose tissue (WAT) can develop into several phenotypes with different pathophysiological impact on type 2 diabetes. To better understand the adipogenic process, the transcriptional events that occur during in vitro differentiation of human adipocytes were investigated and the findings linked to WAT phenotypes. Single-molecule transcriptional profiling provided a detailed map of the expressional changes of genes, enhancers, and long noncoding RNAs, where different types of transcripts share common dynamics during differentiation. Common signatures include early downregulated, transient, and late induced transcripts, all of which are linked to distinct developmental processes during adipogenesis. Enhancers expressed during adipogenesis overlap significantly with genetic variants associated with WAT distribution. Transiently expressed and late induced genes are associated with hypertrophic WAT (few but large fat cells), a phenotype closely linked to insulin resistance and type 2 diabetes. Transcription factors that are expressed early or transiently affect differentiation and adipocyte function and are controlled by several well-known upstream regulators such as glucocorticosteroids, insulin, cAMP, and thyroid hormones. Taken together, our results suggest a complex but highly coordinated regulation of adipogenesis.
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| 6. |
- Rydén, Mikael, et al.
(författare)
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Lipolysis defect in people with obesity who undergo metabolic surgery
- 2022
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Ingår i: Journal of Internal Medicine. - : Wiley-Blackwell Publishing Inc.. - 0954-6820 .- 1365-2796. ; 292:4, s. 667-678
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Cross-sectional studies demonstrate that catecholamine stimulation of fat cell lipolysis is blunted in obesity. We investigated whether this defect persists after substantial weight loss has been induced by metabolic surgery, and whether it is related to the outcome.DESIGN/METHODS: Patients with obesity not able to successfully reduce body weight by conventional means (n = 126) were investigated before and 5 years after Roux-en-Y gastric bypass surgery (RYGB). They were compared with propensity-score matched subjects selected from a control group (n = 1017), and with the entire group after adjustment for age, sex, body mass index (BMI), fat cell volume and other clinical parameters. Catecholamine-stimulated lipolysis (glycerol release) was investigated in isolated fat cells using noradrenaline (natural hormone) or isoprenaline (synthetic beta-adrenoceptor agonist).RESULTS: Following RYGB, BMI was reduced from 39.9 (37.5-43.5) (median and interquartile range) to 29.5 (26.7-31.9) kg/m2 (p < 0.0001). The post-RYGB patients had about 50% lower lipolysis rates compared with the matched and total series of controls (p < 0.0005). Nordrenaline activation of lipolysis at baseline was associated with the RYGB effect; those with high lipolysis activation (upper tertile) lost 30%-45% more in body weight, BMI or fat mass than those with low (bottom tertile) initial lipolysis activation (p < 0.0007).CONCLUSION: Patients with obesity requiring metabolic surgery have impaired ability of catecholamines to stimulate lipolysis, which remains despite long-term normalization of body weight by RYGB. Furthermore, preoperative variations in the ability of catecholamines to activate lipolysis may predict the long-term reduction in body weight and fat mass.
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| 7. |
- Andersson, Daniel P., et al.
(författare)
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Omentectomy in addition to gastric bypass surgery and influence on insulin sensitivity : A randomized double blind controlled trial
- 2014
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Ingår i: Clinical Nutrition. - : Elsevier BV. - 0261-5614 .- 1532-1983. ; 33:6, s. 991-996
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Tidskriftsartikel (refereegranskat)abstract
- Background & aims: Accumulation of visceral adipose tissue is associated with insulin resistance and cardio-vascular disease. The aim of this study was to elucidate whether removal of a large amount of visceral fat by omentectomy in conjunction with Roux en-Y gastric bypass operation (RYGB) results in enhanced improvement of insulin sensitivity compared to gastric bypass surgery alone. Methods: Eighty-one obese women scheduled for RYGB were included in the study. They were randomized to RYGB or RYGB in conjunction with omentectomy. Insulin sensitivity was measured by hyperinsulinemic euglycemic clamp before operation and sixty-two women were also reexamined 2 years post-operatively. The primary outcome measure was insulin sensitivity and secondary outcome measures included cardio-metabolic risk factors. Results: Two-year weight loss was profound but unaffected by omentectomy. Before intervention, there were no clinical or metabolic differences between the two groups. The difference in primary outcome measure, insulin sensitivity, was not significant between the non-omentectomy (6.7 +/- 1.6 mg/kg body weight/minute) and omentectomy groups (6.6 +/- 1.5 mg/kg body weight/minute) after 2 years. Nor did any of the cardio-metabolic risk factors that were secondary outcome measures differ significantly. Conclusion: Addition of omentectomy to gastric bypass operation does not give an incremental effect on long term insulin sensitivity or cardio-metabolic risk factors. The clinical usefulness of omentectomy in addition to gastric bypass operation is highly questionable.
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| 8. |
- Andersson, Karl-Erik, et al.
(författare)
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Urinary bladder contraction and relaxation: Physiology and pathophysiology
- 2004
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Ingår i: Physiological Reviews. - : American Physiological Society. - 1522-1210 .- 0031-9333. ; 84:3, s. 935-986
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Forskningsöversikt (refereegranskat)abstract
- The detrusor smooth muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and micturition. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signaling pathways. Functional changes of the detrusor can be found in several clinically important conditions, e.g., lower urinary tract symptoms (LUTS) and bladder outlet obstruction. The aim of this review is to summarize and synthesize basic information and recent advances in the understanding of the properties of the detrusor smooth muscle, its contractile system, cellular signaling, membrane properties, and cellular receptors. Alterations in these systems in pathological conditions of the bladder wall are described, and some areas for future research are suggested.
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| 9. |
- Arner, Erik
(författare)
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Solving repeat problems in shotgun sequencing
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shotgun sequencing is the most powerful strategy for large scale sequencing. Two main approaches exist: clone-by-clone and whole genome shotgun (WGS). In the clone-by-clone strategy, overlapping clones are amplified and then sheared in a random fashion. In the WGS approach, a sufficient amount of cells from the target organism are obtained, and the random shearing is performed on extracted DNA. In both approaches, the resulting fragments are cloned and the fragment ends are subsequently sequenced, producing sequence reads. If a sufficient amount of sequence has been obtained, the reads will overlap in a way that makes it possible to deduce their correct order. A number of computer programs have been developed for this task. However, none of these programs are capable of producing correct assemblies if the target sequence contains repeats. This is because assembly algorithms in general are greedy, which means that when faced with different alternatives for the positioning of a read, the algorithm will fit the read at the first available position meeting the criteria for inclusion into the assembly. The resulting assemblies typically have the repeat regions degenerated, truncating the regions into a few copies with abnormally high shotgun coverage. This phenomenon occurs even when the repeat copies differ from each other, since the assembly programs are unable to distinguish the subtle differences between repeat elements from the sequencing errors produced by the sequencing apparatus. The work presented here is aimed at solving the repeat problem by detecting and utilizing single base differences between nearly identical repeats. In paper I, a statistical method for detecting repeat differences in the presence of sequencing errors was developed, implemented, and tested on simulated data. We showed that it is possible to obtain high specificity as well as sensitivity compared to other methods, by evaluating coinciding deviations from consensus in pairs of columns in multiple alignments. In paper II, a finishing tool (DNPTrapper) that visualizes the differences and enables manual and semi-automatic resolution of repeat regions was constructed and tested with simulated data as well as real data from the Trypanosoma cruzi WGS project. Results showed that using DNPTrapper, it is possible to resolve and analyze complicated repeat regions previously considered difficult or even impossible to resolve. Finally in paper III, five repeated genes in T. cruzi were analyzed using DNPTrapper. Different repeat characteristics in the parasite were described, and it was shown that thorough analysis of repeat regions is required for correcting erroneous consensus sequences of repeated genes in the assembly.
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| 10. |
- Arner, Peter, et al.
(författare)
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Variations in the size of the major omentum are primarily determined by fat cell number
- 2013
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 98:5, s. E897-E901
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Accumulation of visceral adipose tissue (VAT) is strongly linked to insulin resistance. Variations in the size of any adipose depot are determined by alterations in adipocyte volume and/or number. The individual contribution of each of the latter factors was determined in the major omentum, a fully resectable VAT depot.SUBJECTS: Total removal of the major omentum (omentectomy) was performed in conjunction with bariatric surgery in 55 obese patients. Tissue weight as well as mean adipocyte size and number in the omentum were determined. In subgroups, total VAT was estimated by computerized tomography (n = 17) or dual-energy x-ray absorptiometry (n = 34).RESULTS: The weight of the major omentum (on average 0.6 kg) correlated significantly with total VAT mass estimated by computerized tomography or dual-energy x-ray absorptiometry (r = 0.48-0.7; P < .01). Omental weight in relation to total body fat correlated with several features of the metabolic syndrome and inversely with serum-leptin (P < .001). Mean adipocyte size and total adipocyte number correlated strongly with omental weight (r = 0.6-0.8; P < .0001), irrespective of body mass index and total body fat mass, and accounted almost in total for interindividual variations in omental size. However, stepwise regression analysis demonstrated that adipocyte number was significantly (P < .0001) more important (62%) than adipocyte size (35%).CONCLUSION: The size of the major omentum is representative for VAT mass and correlates with a pernicious metabolic profile. Variations in omental weight are primarily determined by adipocyte number and to a lesser degree by adipocyte size, suggesting that increased VAT mass in obesity is predominantly dependent on adipocyte proliferation.
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