Project description:INTRODUCTION: Mild cold acclimation is known to increase brown adipose tissue (BAT) activity and cold-induced thermogenesis (CIT) in humans. We here tested the effect of a lifestyle with frequent exposure to extreme cold on BAT and CIT in a Dutch man known as 'the Iceman', who has multiple world records in withstanding extreme cold challenges. Furthermore, his monozygotic twin brother who has a 'normal' sedentary lifestyle without extreme cold exposures was measured. METHODS: The Iceman (subject A) and his brother (subject B) were studied during mild cold (13°C) and thermoneutral conditions (31°C). Measurements included BAT activity and respiratory muscle activity by [18F]FDG-PET/CT imaging and energy expenditure through indirect calorimetry. In addition, body temperatures, cardiovascular parameters, skin perfusion, and thermal sensation and comfort were measured. Finally, we determined polymorphisms for uncoupling protein-1 and ?3-adrenergic receptor. RESULTS: Subjects had comparable BAT activity (A: 1144 SUVtotal and B: 1325 SUVtotal), within the range previously observed in young adult men. They were genotyped with the polymorphism for uncoupling protein-1 (G/G). CIT was relatively high (A: 40.1% and B: 41.9%), but unlike during our previous cold exposure tests in young adult men, here both subjects practiced a g-Tummo like breathing technique, which involves vigorous respiratory muscle activity. This was confirmed by high [18F]FDG-uptake in respiratory muscle. CONCLUSION: No significant differences were found between the two subjects, indicating that a lifestyle with frequent exposures to extreme cold does not seem to affect BAT activity and CIT. In both subjects, BAT was not higher compared to earlier observations, whereas CIT was very high, suggesting that g-Tummo like breathing during cold exposure may cause additional heat production by vigorous isometric respiratory muscle contraction. The results must be interpreted with caution given the low subject number and the fact that both participants practised the g-Tummo like breathing technique.

Project description:Adipose tissues play a pivotal role in energy homeostasis. They are existent in two forms: white adipose tissue and brown adipose tissue (BAT). Being the primary source of non-shivering thermogenesis of mammals, BAT plays an irreplaceable role in maintaining body temperature . Damaged DNA binding protein 1 (DDB1) is usually recognized as a component of the CUL4-DDB1 E3 complex. We have previously shown that DDB1 functions independently of CUL4 to promote adipogenesis. In the thesis, we focus on the function of DDB1 in mature adipocytes. We crossed Ddb1f/f mice with Adipoq-Cre or Ucp1-Cre mice to generate adipose tissue or BAT-specific mice, designated Ddb1-AKO and Ddb1-BKO mice respectively. At 8-12 weeks, BAT in these mice was servely whitened with decreased mitochdiral content. The thermogenic genes were also significantly downregulated at both RNA and protein levels. To further characterize the effect of DDB1 on thermogenesis, we first examined the bdy temperature of the pulps on postnatal day 3, and found that depletion of DDB1 caused a significant decrease in surface temperature.When the adult mice were subjected to cold challenge, both Ddb1-AKO and Ddb1-BKO mice showed dramatically decreased body temperature compared with control mice. At the end of the experiment, Ddb1-AKO and Ddb1-BKO mice had higher contents in BAT triglycerides and lower blood glucose level. Furthermore, the oxygen comsumption in Ddb1-AKO and Ddb1-BKO mice failed to respond to epinephrine injection. . All these results above demonstrated that lacking of DDB1 in brown adipocytes leads to a destruction in thermogenesis of BAT. We have also examined the phenotypes of Ddb1-AKO and Ddb1-BKO mice on high-fat-diet feeding. Compared with control mice, these mice showed decreased body weight, but significantly glucose intolerance and increased triglycierde content in liver, indicating that these mice have partial lipodystrophy. To study whether the effect of DDB1 was dependent on CUL4, we generated adipose tissue-specific Cul4a or CUl4b knockout mice, and found that these mice have no visible defect in BAT morphology compared with control mice, indicating a CUL4-independent function of DDB1. RNA-Seq analysis revealed that DDB1 is required for cold-induced expression of around 900 genes. ChIP-Seq analysis revelaed that these genes were subjected to regulation of promoter-proximally paused RNA polymerase II (Pol II), and that DDB1 is required for the release of paused Pol II upon cold stimulation. Our findings have thus revealed that DDB1 plays an important role in maintaining the theremogenic function of BAT by regulating the expression of thermogenic genes upon cold stimulation. Our studies will shed insights into transcriptional regulation of thermogenic gene

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Brown Fat AKT2 Is a Cold-Induced Kinase that Stimulates ChREBP-Mediated De Novo Lipogenesis to Optimize Fuel Storage and Thermogenesis.

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Brown Fat AKT2 Is a Cold-Induced Kinase that Stimulates ChREBP-Mediated De Novo Lipogenesis to Optimize Fuel Storage and Thermogenesis.

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