| 1. |
- Betz, Mattias J., et al.
(författare)
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Presence of Brown Adipocytes in Retroperitoneal Fat From Patients With Benign Adrenal Tumors: Relationship With Outdoor Temperature
- 2013
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Ingår i: Journal of Clinical Endocrinology & Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 98:10, s. 4097-4104
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Tidskriftsartikel (refereegranskat)abstract
- Context: Brown adipose tissue (BAT) is a metabolically highly active organ with increased thermogenic activity in rodents exposed to cold temperature. Recently its presence in the cervical adipose tissue of human adults and its association with a favorable metabolic phenotype have been reported. Objective: The objective of the study was to determine the prevalence of retroperitoneal BAT in human adults. Patients: Fifty-seven patients who underwent surgery for benign adrenal tumors were included in this study. Main Outcome Measures: Prevalence of retroperitoneal BAT adjacent to the removed adrenal tumor as determined by uncoupling protein 1 (UCP1) protein and mRNA expression was measured. Results: Using protein and mRNA expression analysis, we detected UCP1 protein in 26 of 57 patients (45.6%) as well as high mRNA expression of genes characteristic for brown adipocytes, independent of the adrenal tumor type. The presence of brown adipocytes within the retroperitoneal fat was associated with a significantly lower outdoor temperature during the month prior to surgery. Importantly, UCP1 expression on both mRNA and protein level was inversely correlated to outdoor temperature, whereas body mass index, sex, age, and diabetes status were not. Conclusions: These findings suggest that human retroperitoneal adipose tissue can acquire a BAT phenotype, thereby adapting to environmental challenges. These adaptive processes might provide a valuable therapeutic target in the treatment of obesity and insulin resistance.
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| 2. |
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| 3. |
- Lidell, Martin, 1970, et al.
(författare)
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Evidence for two types of brown adipose tissue in humans
- 2013
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 19:5, s. 631-634
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Tidskriftsartikel (refereegranskat)abstract
- The previously observed supraclavicular depot of brown adipose tissue (BAT) in adult humans was
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| 4. |
- Orava, J., et al.
(författare)
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Blunted Metabolic Responses to Cold and Insulin Stimulation in Brown Adipose Tissue of Obese Humans
- 2013
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Ingår i: Obesity. - : Wiley. - 1930-7381. ; 21:11, s. 2279-2287
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Inactive brown adipose tissue (BAT) may predispose to weight gain. This study was designed to measure metabolism in the BAT of obese humans, and to compare it to that in lean subjects. The impact of weight loss on BAT and the association of detectable BAT with various metabolic characteristics were also assessed. Design and Methods: Using positron emission tomography (PET), cold-and insulin-stimulated glucose uptake and blood flow in the BAT of obese and lean humans were quantified. Further, cold-induced glucose uptake was measured in obese subjects before and after a 5-month conventional weight loss. Results: Mean responses in BAT glucose uptake rate to both cold and insulin stimulation were twice as large in lean as in obese subjects. Blood flow in BAT was also lower in obese subjects under cold conditions. The increase in cold-induced BAT glucose uptake rate after weight loss was not statistically significant. Subjects with cold-activated detectable BAT were leaner and had higher whole-body insulin sensitivity than BAT-negative subjects, irrespective of age and gender. Conclusions: The effects of cold and insulin on BAT activity are severely blunted in obesity, and the presence of detectable BAT may contribute to a metabolically healthy status.
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| 5. |
- Rahman, S., et al.
(författare)
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Inducible Brown Adipose Tissue, or Beige Fat, Is Anabolic for the Skeleton
- 2013
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 154:8, s. 2687-2701
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Tidskriftsartikel (refereegranskat)abstract
- It is known that insulin resistance and type 2 diabetes mellitus are associated with increased fractures and that brown adipose tissue (BAT) counteracts many if not all of the symptoms associated with type 2 diabetes. By the use of FoxC2(AD)(+/Tg) mice, a well-established model for induction of BAT, or beige fat, we present data extending the beneficial action of beige fat to also include a positive effect on bone. FoxC2(AD)(+/Tg) mice are lean and insulin-sensitive and have high bone mass due to increased bone formation associated with high bone turnover. Inducible BAT is linked to activation of endosteal osteoblasts whereas osteocytes have decreased expression of the Sost transcript encoding sclerostin and elevated expression of Rankl. Conditioned media (CM) collected from forkhead box c2 (FOXC2)-induced beige adipocytes activated the osteoblast phenotype and increased levels of phospho-AKT and beta-catenin in recipient cells. In osteocytes, the same media decreased Sost expression. Immunodepletion of CM with antibodies against wingless related MMTV integration site 10b (WNT10b) and insulin-like growth factor binding protein 2 (IGFBP2) resulted in the loss of pro-osteoblastic activity, and the loss of increase in the levels of phospho-AKT and beta-catenin. Conversely, CM derived from cells overexpressing IGFBP2 or WNT10b restored osteoblastic activity in recipient cells. In conclusion, beige fat secretes endocrine/paracrine activity that is beneficial for the skeleton.
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