Human adiponectin binds to bacterial lipopolysaccharide.

Adiponectin has anti-inflammatory and anti-atherogenic properties in addition to its acknowledged roles in insulin sensitivity and energy homeostasis. These properties include the suppression of lipopolysaccharide [LPS]-mediated inflammatory events. We demonstrated that both recombinant and native adiponectin directly bind LPS derived from three different bacteria. The interaction occurred at pH 5.0-6.0 and was inhibited by the presence of Ca(2+) and Mg(2+), but enhanced by the sequestration of these cations. Maximal binding occurred at pH 6.0 in the presence of ethylenediaminetetraacetic acid. Lipid A and C1q were not inhibitory, although LPS, heparin, zymosan, and individual sugars all inhibited the reaction. Periodate-mediated deglycosylation of adiponectin, and reduction and alkylation also inhibited binding. Since adiponectin infiltrates into [relatively] acidic sites of inflammation, it may act as a scavenging anti-inflammatory agent in atherosclerosis and vascular damage where LPS [and other pro-inflammatory molecules] are present.