An emerging concept in the fi eld of innate immunology is that of metabolic endotoxemia, which is defi ned as a subclinical elevation in circulating endotoxin levels. This elevation is not overtly apparent in a clinical setting but is being investigated as a signifi cant potential etiology for several chronic diseases. Diseases including type II diabetes mellitus, atherosclerosis, Parkinson’s disease and cancer metastasis arise in the context of chronic low-grade infl ammation, of which the source has not clearly been defi ned. Interestingly, several recent studies have demonstrated signifi cant correlations between
disease development and plasma endotoxin levels. However, most information on LPS signaling has been obtained using high doses of LPS (10-200 ng/ml) while little to no studies have been published regarding the effects of very low doses of LPS (1 pg-100 pg/ml) on infl ammatory and metabolic alterations. Thus, much information has yet to be acquired
on the phenotype of metabolic endotoxemia. However, there is a small but substantial pool of evidence for metabolic endotoxemia as a critical infl uence on the development of chronic disease. This pool of evidence is reviewed here, including sources of metabolic endotoxemia, current understanding in endotoxin signaling (namely lipopolysaccharide), and contributions to disease pathology.