title: Metabolic endotoxemia with obesity: Is it real and is it relevant?
abstract: Obesity is associated with metabolic derangements in multiple tissues, which contribute to the progression of insulin resistance and the metabolic syndrome. The underlying stimulus for these metabolic derangements in obesity are not fully elucidated, however recent evidence in rodents and humans suggests that systemic, low level elevations of gut derived endotoxin (lipopolysaccharide, LPS) may play an important role in obesity related, whole-body and tissue specific metabolic perturbations. LPS initiates a well-characterized signaling cascade that elicits many pro- and anti-inflammatory pathways when bound to its receptor, Toll-Like Receptor 4 (TLR4). Low-grade elevation in plasma LPS has been termed "metabolic endotoxemia" and this state is associated with a heightened pro-inflammatory and oxidant environment often observed in obesity. Given the role of inflammatory and oxidative stress in the etiology of obesity related cardio-metabolic disease risk, it has been suggested that metabolic endotoxemia may serve a key mediator of metabolic derangements observed in obesity. This review provides supporting evidence of mechanistic associations with cell and animal models, and provides complimentary evidence of the clinical relevance of metabolic endotoxemia in obesity as it relates to inflammation and metabolic derangements in humans. Discrepancies with endotoxin detection are considered, and an alternate method of reporting metabolic endotoxemia is recommended until a standardized measurement protocol is set forth.
authors.affiliation: The Department of Human Nutrition, Foods, and Exercise, 295 West Campus Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Fralin Translational Obesity Research Center, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Metabolic Phenotyping Core, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: nabilb@vt.edu.
authors.forename: Nabil E
authors.initials: NE
authors.lastname: Boutagy
authors.affiliation: The Department of Human Nutrition, Foods, and Exercise, 295 West Campus Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Fralin Translational Obesity Research Center, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Metabolic Phenotyping Core, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: mcmillr@vt.edu.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: McMillan
authors.affiliation: The Department of Human Nutrition, Foods, and Exercise, 295 West Campus Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Fralin Translational Obesity Research Center, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Metabolic Phenotyping Core, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: frisardm@vt.edu.
authors.forename: Madlyn I
authors.initials: MI
authors.lastname: Frisard
authors.affiliation: The Department of Human Nutrition, Foods, and Exercise, 295 West Campus Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Fralin Translational Obesity Research Center, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA; The Metabolic Phenotyping Core, 1981 Kraft Drive, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: hulvermw@vt.edu.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Hulver
mesh_terms: D000818:Animals; D019446:Endotoxemia / Q000097:blood* / Q000209:etiology / Q000473:pathology; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000097:blood*; D009765:Obesity / Q000097:blood* / Q000150:complications / Q000473:pathology; D018384:Oxidative Stress; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4
keywords: Endotoxin detection; Inflammation; Metabolic endotoxemia; Obesity; Substrate metabolism