Regulation of Serum Amyloid A3 SAA3 in Mouse Colonic Epithelium and Adipose Tissue by the Intestinal MicrobiotaReport as inadecuate




Regulation of Serum Amyloid A3 SAA3 in Mouse Colonic Epithelium and Adipose Tissue by the Intestinal Microbiota - Download this document for free, or read online. Document in PDF available to download.

The gut microbiota has been proposed as an environmental factor that affects the development of metabolic and inflammatory diseases in mammals. Recent reports indicate that gut bacteria-derived lipopolysaccharide LPS can initiate obesity and insulin resistance in mice; however, the molecular interactions responsible for microbial regulation of host metabolism and mediators of inflammation have not been studied in detail. Hepatic serum amyloid A SAA proteins are markers and proposed mediators of inflammation that exhibit increased levels in serum of insulin-resistant mice. Adipose tissue-derived SAA3 displays monocyte chemotactic activity and may play a role in metabolic inflammation associated with obesity and insulin resistance. To investigate a potential mechanistic link between the intestinal microbiota and induction of proinflammatory host factors, we performed molecular analyses of germ-free, conventionally raised and genetically modified Myd88−-− mouse models. SAA3 expression was determined to be significantly augmented in adipose 9.9±1.9-fold; P<0.001 and colonic tissue 7.0±2.3-fold; P<0.05 by the presence of intestinal microbes. In the colon, we provided evidence that SAA3 is partially regulated through the Toll-like receptor TLR-MyD88-NF-kappaB signaling axis. We identified epithelial cells and macrophages as cellular sources of SAA3 in the colon and found that colonic epithelial expression of SAA3 may be part of an NF-kappaB-dependent response to LPS from gut bacteria. In vitro experiments showed that LPS treatments of both epithelial cells and macrophages induced SAA3 expression 27.1±2.5-fold vs. 1.6±0.1-fold, respectively. Our data suggest that LPS, and potentially other products of the indigenous gut microbiota, might elevate cytokine expression in tissues and thus exacerbate chronic low-grade inflammation observed in obesity.



Author: Christopher S. Reigstad, Gunnel Östergren Lundén, Jenny Felin, Fredrik Bäckhed

Source: http://plos.srce.hr/



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