ENHANCEMENT OF THE VANADATE-STIMULATED RELEASE OF LIPOPROTEIN-LIPASE ACTIVITY BY ASTILBIN FROM THE LEAVES OF ENGELHARDTIA-CHRYSOLEPIS

Astilbin, a dihydroflavonol rhamnoside isolated from the leaves of Eng elhardtia chrysolepis, enhanced the vanadate-stimulated release of lip oprotein lipase (LPL) activity from rat isolated fat pads. N-[2-(Methy lamino)ethyl]-5-isoquinolinesulfonamide (H-8), a potent inhibitor of c AMP-dependent protein kinase (PKA), markedly inhibited the enhancement by astilbin. Lipolysis in the fat pads was stimulated by astilbin alo ne in a dose-dependent manner and this stimulation was suppressed in t he presence of vanadate, probably due to its antilipolytic action. A s ignificant enhancement by astilbin was observed with increasing effect s of vanadate on cAMP content in the fat pads and on cAMP phosphodiest erase (PDE) activity in the particulate fraction although astilbin alo ne showed only a slight increase in the cellular cAMP content and PDE activity. Astilbin may enhance the vanadate-stimulated release of LPL activity through a synergistic effect on an increase in the cellular c AMP content produced by vanadate accompanied by more potent activation of PKA.