Visfatin is one of the latest proteins to be identified in the adipose tissue. Visfatin is similar to a previously described protein- pre-B cell colony-enhancing factor (PBEF)- which is expressed in lymphocytes. Science. 2005 Jan 21;307(5708):426-30    Plasma levels of visfatin seem to correlate with obesity. Visfatin binds to and activates the insulin receptor with lowering of plasma glucose levels in mice. On the other hand, heterozygous mutations of the visfatin gene results in hyperglycemia in mice. Insulin does not seem to regulate visfatin production, while Dexamethasone increased visfatin mRNA expression (studied in 3T3-L1 adipocytes in vitro).   J Endocrinol. 2005 Jun;185(3):R1-8.  TNF alpha, and growth hormone seem to down-regulate visfatin expression. Regulation by these insulin-resistance inducing hormones suggest a link between visfatin and the metabolic syndrome. Yet, the Wistar Ottawa Karlsburg W (RT1u) rats (WOKW) which develop the classic metabolic syndrome with obesity, moderate hypertension, dyslipidaemia, hyperinsulinaemia, and impaired glucose tolerance Int J Obes Relat Metab Disord. 2002 Apr;26(4):573-6.  did not show any changes in Visfatin gene expression in its adipocytes     Biochem Biophys Res Commun. 2005 Jul 15;332(4):1070-2     but further studies to determine the physiological role of visfatin in glucose homeostasis and obesity in other rodents and man is awaited.
 

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