Lipin-1 is a multifunctional metabolic regulator, involving in triacylglycerol and bioactive glycerolipids synthesis as an enzyme, transcriptional regulation as a coactivator, and adipogenesis. In obesity, adipose lipin-1 expression is decreased. Although lipin-1 is implicated in the pathogenesis of obesity, the mechanism is still not clear. Since TNF-alpha is deeply involved in the pathogenesis of obesity, insulin resistance, and diabetes, here we investigated the role of TNF-alpha on lipin-1 expression in adipocytes. Quantitative PCR studies showed that TNF-alpha, suppressed both lipin-1A and -1B isoform, expression in time- and close-dependent manners in mature 3T3-L1 adpocytes. A Jak2 inhibitor, AG490, reversed the suppressive effect of TNF-alpha on both lipin-1 A and -1 beta. In contrast, NF-kappa B, MAPKs, ceramide, and beta-catenin pathway tested were not involved in the mechanism. These results suggest that TNF-alpha could be involved in obesity-induced lipin-1 Suppression in adipocytes and Jak2 may play an important role in the mechanism. (C) 2009 Elsevier Inc. All rights reserved.