Lipolysis Triggers a Systemic Insulin Response Essential for Efficient Energy Replenishment of Activated Brown Adipose Tissue in Mice

Transcription factor E3 (TFE3) is a transcription factor that binds to E-box motifs and promotes energy metabolism-related genes. We previously reported that TFE3 directly binds to the insulin receptor substrate-2 promoter in the liver, resulting in increased insulin response. However, the role of TFE3 in other tissues remains unclear. In this study, we generated adipose-specific TFE3 transgenic (aP2-TFE3 Tg) mice. These mice had a higher weight of white adipose tissue (WAT) and brown adipose tissue than wild-type (WT) mice under fasting conditions. Lipase activity in the WAT in these mice was lower than that in the WT mice. The mRNA level of adipose triglyceride lipase (ATGL), the rate-limiting enzyme for adipocyte lipolysis, was significantly decreased in aP2-TFE3 Tg mice. The expression of Foxo1, which directly activates ATGL expression, was also suppressed in transgenic mice. Promoter analysis confirmed that TFE3 suppressed promoter activities of the ATGL gene. In contrast, G0S2 and Perilipin1, which attenuate ATGL activity, were higher in transgenic mice than in WT mice. These results indicated that the decrease in lipase activity in adipose tissues was due to a decrease in ATGL expression and suppression of ATGL activity. We also showed that thermogenesis was suppressed in aP2-TFE3 Tg mice. The decrease in lipolysis in WAT of aP2-TFE3 Tg mice inhibited the supply of fatty acids to brown adipose tissue, resulting in the inhibition of the expression of thermogenesis-related genes such as UCP1. Our data provide new evidence that TFE3 regulates lipid metabolism by controlling the gene expression related to lipolysis and thermogenesis in adipose tissue.

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Comprehensive transcriptional profiling and mouse phenotyping reveals dispensable role for adipose tissue selective long noncoding RNA Gm15551

10.1101/2021.12.17.473160 ◽

2021 ◽

Author(s):

Christoph Andreas Engelhard ◽

Chien Huang ◽

Sajjad Khani ◽

Petr Kasparek ◽

Jan Prochazka ◽

...

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Noncoding Rna ◽

Insulin Response ◽

Fine Tuning ◽

Loss Of Function ◽

Specific Expression ◽

Interscapular Brown Adipose Tissue ◽

Brown Adipose

Cold and nutrient activated brown adipose tissue (BAT) is capable of increasing systemic energy expenditure via uncoupled respiration and secretion of endocrine factors thereby protecting mice against diet-induced obesity and improving insulin response and glucose tolerance in men. Long non-coding RNAs (lncRNAs) have recently been identified as fine tuning regulators of cellular function. While certain lncRNAs have been functionally characterised in adipose tissue, their overall contribution in the activation of BAT remains elusive. We identified lncRNAs correlating to interscapular brown adipose tissue (iBAT) function in high fat diet (HFD) and cold stressed mice. We focused on Gm15551 which has an adipose tissue specific expression profile, is highly upregulated during adipogenesis and downregulated by β-adrenergic activation in mature adipocytes. Albeit we performed comprehensive transcriptional and adipocyte physiology profiling in vitro and in vivo, we could not detect an effect of gain or loss of function of Gm15551.

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Functional characterization of human brown adipose tissue metabolism

Biochemical Journal ◽

10.1042/bcj20190464 ◽

2020 ◽

Vol 477 (7) ◽

pp. 1261-1286 ◽

Cited By ~ 3

Author(s):

Marie Anne Richard ◽

Hannah Pallubinsky ◽

Denis P. Blondin

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Functional Characterization ◽

Human Infants ◽

Positron Emission ◽

Brown Adipose ◽

Treatment Of Obesity ◽

And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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