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Over a hundred billion bacteria are found in human intestines. This has emerged as an environmental factor in metabolic diseases, such as obesity and related diseases. The majority of these bacteria belong to two dominant phyla,
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Obesity has become one of the most serious issues threatening the health of humankind, and we conducted this study to examine whether and how celastrol protects against obesity.
We fed male Sprague-Dawley rats a high-fat diet and administered celastrol to obese rats for 3 weeks. By recording body weight (BW) and other measures, we identified the effective dose of celastrol for obesity treatment. Feces were collected to perform 16S rRNA sequencing, and hypothalami were extracted for transcriptome sequencing. We then treated leptin knockout rats with celastrol and explored the changes in energy metabolism. Male Institute of Cancer Research (ICR) mice were used to test the acute toxicity of celastrol.
We observed that celastrol reduced BW and promoted energy expenditure at a dose of 500 µg/kg BW but that food intake was not changed after administration. The diversity of the gut microbiota was improved, with an increased ratio of
Our study revealed that celastrol decreased the BW of obese rats by enhancing energy expenditure but not by suppressing food intake and that this effect was mediated by the improvement of the gut microbiota and the activation of the hypothalamic leptin signaling pathway.
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Cyclic adenosine monophosphate (cAMP) signaling is critical for regulating metabolic homeostasis in mammals. In particular, transcriptional regulation by cAMP response element-binding protein (CREB) and its coactivator, CREB-regulated transcription coactivator (CRTC), is essential for controlling the expression of critical enzymes in the metabolic process, leading to more chronic changes in metabolic flux. Among the CRTC isoforms, CRTC2 is predominantly expressed in peripheral tissues and has been shown to be associated with various metabolic pathways in tissue-specific manners. While initial reports showed the physiological role of CRTC2 in regulating gluconeogenesis in the liver, recent studies have further delineated the role of this transcriptional coactivator in the regulation of glucose and lipid metabolism in various tissues, including the liver, pancreatic islets, endocrine tissues of the small intestines, and adipose tissues. In this review, we discuss recent studies that have utilized knockout mouse models to delineate the role of CRTC2 in the regulation of metabolic homeostasis.
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Chronic energy surplus increases body fat, leading to obesity. Since obesity is closely associated with most metabolic complications, pathophysiological roles of adipose tissue in obesity have been intensively studied. White adipose tissue is largely divided into subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). These two white adipose tissues are similar in their appearance and lipid storage functions. Nonetheless, emerging evidence has suggested that SAT and VAT have different characteristics and functional roles in metabolic regulation. It is likely that there are intrinsic differences between VAT and SAT. In diet-induced obese animal models, it has been reported that adipogenic progenitors in VAT rapidly proliferate and differentiate into adipocytes. In obesity, VAT exhibits elevated inflammatory responses, which are less prevalent in SAT. On the other hand, SAT has metabolically beneficial effects. In this review, we introduce recent studies that focus on cellular and molecular components modulating adipogenesis and immune responses in SAT and VAT. Given that these two fat depots show different functions and characteristics depending on the nutritional status, it is feasible to postulate that SAT and VAT have different developmental origins with distinct adipogenic progenitors, which would be a key determining factor for the response and accommodation to metabolic input for energy homeostasis.
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