Obesity-related metabolic disorders are characterized by mild chronic inflammation, leukocyte infiltration, and tissue fibrosis as a result of adipocytokine production from the expanding white adipose tissue. Annexin A1 (AnxA1) is an endogenous glucocorticoid regulated protein, which modulates systemic anti-inflammatory processes and, therefore, may be altered with increasing adiposity in humans. Paradoxically, we found that plasma AnxA1 concentrations inversely correlated with BMI, total percentage body fat, and waist-to-hip ratio in human subjects. Plasma AnxA1 was also inversely correlated with plasma concentrations of the acute-phase protein, C-reactive protein (CRP), and the adipocytokine leptin, suggesting that as systemic inflammation increases, anti-inflammatory AnxA1 is reduced. In addition, AnxA1 gene expression and protein were significantly up-regulated during adipogenesis in a human adipocyte cell line compared to vehicle alone, demonstrating for the first time that AnxA1 is expressed and excreted from human adipocytes. These data demonstrate a failure in the endogenous anti-inflammatory system to respond to increasing systemic inflammation resulting from expanding adipose tissue, a condition strongly linked to the development of type 2 diabetes and cardiovascular disease. These data raise the possibility that a reduction in plasma AnxA1 may contribute to the chronic inflammatory phenotype observed in human obesity.
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