Hormonal regulation of the novel adipocytokine visfatin in 3T3-L1 adipocytes

Recently visfatin was characterized as a novel adipocytokine that is upregulated in obesity and exerts insulin-mimetic effects in various tissues. To clarify expression and regulation of this adipocytokine, visfatin mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction in 3T3-L1 adipocytes during adipogenesis and after treatment with various hormones known to alter insulin sensitivity. Visfatin expression was about 6-fold higher in 3T3-L1 adipocytes in vitro as compared with epididymal fat in vivo and increased during adipogenic conversion more than 3-fold. Interestingly, 100 nM dexamethasone significantly increased visfatin mRNA by almost 1(.)5-fold. In contrast, 500 ng/ml growth hormone (GH). 10 ng/ml tumor necrosis factor (TNF) alpha,and 10 mu M isoproterenol downregulated visfatin expression by 45%, 36 0, and 43% respectively. Insulin did not influence synthesis of this adipocytokine. The effects of dexamethasone, GH, TNF alpha and isoproterenol were time- and dose-dependent. Furthermore, activation of G(S)-protein-coupled pathways by forskolin and cholera toxin was sufficient to significantly downregulate visfatin mRNA. Taken together, our results show a differential regulation of visfatin mRNA by insulin resistance-inducing hormones, supporting the view that this adipocytokine might be an interesting novel candidate linking core components of the metabolic syndrome such as obesity and insulin resistance.