TY - JOUR T1 - Gut-derived lipopolysaccharide augments adipose macrophage accumulation but is not essential for impaired glucose or insulin tolerance in mice JF - Gut JO - Gut SP - 1701 LP - 1707 DO - 10.1136/gutjnl-2011-301689 VL - 61 IS - 12 AU - Robert Caesar AU - Christopher S Reigstad AU - Helene Kling Bäckhed AU - Christoph Reinhardt AU - Maria Ketonen AU - Gunnel Östergren Lundén AU - Patrice D Cani AU - Fredrik Bäckhed Y1 - 2012/12/01 UR - http://gut.bmj.com/content/61/12/1701.abstract N2 - Background Obesity is associated with accumulation of macrophages in white adipose tissue (WAT), which contribute to the development of insulin resistance. Germ-free (GF) mice have reduced adiposity and are protected against diet-induced obesity, Objective To investigate whether the gut microbiota and, specifically, gut-derived lipopolysaccharide (LPS) promote WAT inflammation and contribute to impaired glucose metabolism. Method Macrophage composition and expression of proinflammatory and anti-inflammatory markers were compared in WAT of GF, conventionally raised and Escherichia coli-monocolonised mice. Additionally, glucose and insulin tolerance in these mice was determined. Results The presence of a gut microbiota resulted in impaired glucose metabolism and increased macrophage accumulation and polarisation towards the proinflammatory M1 phenotype in WAT. Monocolonisation of GF mice for 4 weeks with E.coli W3110 or the isogenic strain MLK1067 (which expresses LPS with reduced immunogenicity) resulted in impaired glucose and insulin tolerance and promoted M1 polarisation of CD11b cells in WAT. However, colonisation with E.coli W3110 but not MLK1067 promoted macrophage accumulation and upregulation of proinflammatory and anti-inflammatory gene expression as well as JNK phosphorylation. Conclusion Gut microbiota induced LPS-dependent macrophage accumulation in WAT, whereas impairment of systemic glucose metabolism was not dependent on LPS. These results indicate that macrophage accumulation in WAT does not always correlate with impaired glucose metabolism. ER -