Genistein restricts leptin secretion from rat adipocytes

To determine the influence of genistein and daidzein on leptin release, adipocytes isolated from the epididymal fat tissue were incubated for 2 h in Krebs-Ringer buffer. Leptin secretion stimulated by glucose with insulin was significantly diminished by genistein (0.25-1 mM). This effect of genistein may arise from several aspects of its action in adipocytes documented in the literature such as the inhibition of glucose transport and metabolism, the attenuation of insulin signalling, the inhibition of cAMP phosphodiesterase and the stimulation of lipolysis. However, the bypassing of the restrictive action of genistein on glucose transport and glycolysis (by the use of alanine instead of glucose) and on insulin action (by the use of nicotinic acid) was not sufficient to restore leptin secretion from isolated adipocytes. It was also demonstrated that the restriction of the stimulatory influence of genistein on cAMP/protein kinase A (PKA) pathway (by the inhibition of PKA activity) did not improve leptin release. Results obtained in our experiments point at the restriction of glucose metabolism following formation of pyruvate as the pivotal reason of the inhibitory action of genistein on leptin release.