Clostridium ramosum promotes high-fat diet-induced obesity in gnotobiotic mouse models.
Bottom Line: Clostridium ramosum, a member of the Erysipelotrichi, is associated with symptoms of the metabolic syndrome in humans.Clostridium ramosum, a member of the Erysipelotrichi, has been linked to symptoms of the metabolic syndrome.Identification of obesogenic bacteria and understanding their mode of action enable the development of novel strategies for the treatment of this epidemic disease.
Affiliation: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany.Show MeSH
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Mentions: Liver weight in obese SIHUMI mice was higher than that in less obese SIHUMIw/oCra mice or obese Cra mice (Fig. 3A). SIHUMI and Cra mice displayed higher liver triglyceride contents and a tendency for higher liver glycogen contents than SIHUMIw/oCra mice (Fig. 3B and C). To investigate the impact of C. ramosum on liver metabolism in SIHUMI mice in more detail, expression levels of genes involved in lipid transport (fatty acid translocase [Cd36]), lipid synthesis (acetyl coenzyme A [acetyl-CoA] carboxylase 1 [Acaca] and fatty acid synthase [Fasn]), triglyceride synthesis (glycerol-3-phosphate acyltransferase 1 [Gpat1], diacylglycerol acyltransferase 2 [Dgat2]), cholesterol synthesis (HMG-CoA reductase [Hmgcr]), and lipid catabolism (peroxisome proliferator-activated receptor alpha [Ppara] and carnitine palmitoyltransferase 1a [Cpt1a]) were analyzed (Fig. 4). The presence of C. ramosum in SIHUMI mice reduced the mRNA levels of Cd36, Ppara, and Cpt1a significantly and increased those of Fasn (3-fold, P = 0.074) compared with those in SIHUMIw/oCra mice (Fig. 4A, C, G, and H). The data imply reduced lipid uptake and lipid catabolism and elevated fatty acid synthesis in the livers of SIHUMI mice. In contrast to SIHUMI mice, the presence of C. ramosum in monoassociated mice increased the mRNA levels of Acaca and reduced those of Gpat1, indicating increased fatty acid synthesis in conjunction with a reduced triglyceride formation in Cra mice compared with SIHUMIw/oCra mice (Fig. 4B and D). The mRNA levels of Cd36, Gpat1, Ppara, and Cpt1a differed between SIHUMI and Cra mice, suggesting that the effects of C. ramosum on liver metabolism are modulated by the presence of other bacterial species.
Affiliation: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany.