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Background and Aims: In obesity, oxidative stress is responsible for the aberrant production of adipokines such as adiponectin, plasminogen activator inhibitor (PAI)-1 and interleukin-6 (IL-6), which is causally associated with obesity-related inflammation, insulin resistance and cardiovascular disease. However, the signaling transduction pathways participating in adipokine dysregulation induced by oxidative stress are largely unknown. Thus, the aim of the present study was to identify possible involved signaling pathways. Methods: 3T3-L1 cells were differentiated into adipocytes and underwent oxidative stress by exposure to extraneous H2O2. Quantitative PCR and immunoassays were performed to determine mRNA and protein levels of adipokines (adiponectin, PAI-1 and IL-6), respectively. Possible signaling pathways involved were high-throughout identified by Bioplex phosphoprotein assays and subsequently confirmed by inhibition of the targeted protein kinases such as Akt, ERK1/2, JAK/STAT, JNK, and p70 S6K, respectively. Results: H2O2 markedly suppressed adiponectin mRNA expression as well as protein secretion; however, it enhanced PAI-1 and IL-6 production in mature adipocytes. Akt,JAK/STAT and ERK1/2 participated in the H2O2-induced increase of PAI-1 and IL-6 expression, whereas adiponectin expression was reduced by H2O2 via Akt and JAK/STAT. Conclusions: Akt and JAK/STAT are congenerous pathways through which oxidative stress downregulates adiponectin and upregulates PAI-1 and IL-6 expression. ERK1/2 participates not in H2O2-induced decrease of adiponectin expression, but in the increase of PAI-1 and IL-6. [Copyright &y& Elsevier]

Abstract: Low plasma levels of adiponectin (hypoadiponectinemia) and elevated circulating concentrations of plasminogen activator inhibitor (PAI)-1 are causally associated with obesity-related insulin resistance and cardiovascular disease. However, the mechanism that mediates the aberrant production of these two adipokines in obesity remains poorly understood. In this study, we investigated the effects of hypoxia and reactive oxygen species (ROS) on production of adiponectin and PAI-1 in 3T3-L1 adipocytes. Quantitative PCR and immunoassays showed that ambient hypoxia markedly suppressed adiponectin mRNA expression and its protein secretion, and increased PAI-1 production in mature adipocytes. Dimethyloxallyl glycine, a stabilizer of hypoxia-inducible factor 1α (HIF-1α), mimicked the hypoxia-mediated modulations of these two adipokines. Hypoxia caused a modest elevation of ROS in adipocytes. However, ablation of intracellular ROS by antioxidants failed to alleviate hypoxia-induced aberrant production of adiponectin and PAI-1. On the other hand, the antioxidants could reverse hydrogen peroxide (H2O2)-induced dysregulation of adiponectin and PAI-1 production. H2O2 treatment decreased the expression levels of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer binding protein (C/EBPα), but had no effect on HIF-1α, whereas hypoxia stabilized HIF-1α and decreased expression of C/EBPα, but not PPARγ. Taken together, these data suggest that hypoxia and ROS decrease adiponectin production and augment PAI-1 expression in adipocytes via distinct signaling pathways. These effects may contribute to hypoadiponectinemia and elevated PAI-1 levels in obesity, type 2 diabetes, and cardiovascular diseases. [Copyright &y& Elsevier]