Stereospecific effects of (+)- and (-)-catechin on glycogen metabolism in isolated rat hepatocytes.
(+)- and (-)-catechin showed opposite effects on glycogen metabolism in isolated rat hepatocytes. Addition of 0.5 mM catechin to hepatocytes from fasted rats resulted in the case of the (+)-isomer in a 90% stimulation and the case of the (-)-isomer in a 90% inhibition of net glycogen production. When 0.5 mM of the two isomers were added to hepatocytes from fed rats, (+)-catechin inhibited glycogenolysis by 33%, whereas the (-)-isomer stimulated the same process by 42%. At equal concentrations, the effects of (-)-catechin were stronger than those of the (+)-isomer. (-)-Epicatechin acted in a manner similar to (+)-catechin; however, the effect was less pronounced. (+)-Catechin antagonized the inhibitory action of suboptimal doses of glucagon on glycogen production whereby no change in basal or glucagon-elevated cyclic AMP level was observed. The activities of glycogen synthase a and glycogen phosphorylase a were changed by (+)- and (-)-catechin in a way corresponding to the changes in glycogen production and breakdown. (-)-Catechin, however, stimulated the activities of both glycogen synthase a and glycogen phosphorylase a in hepatocytes from fed rats. A possible interaction of the flavonoids or of their metabolites with glycogen phosphorylase is discussed.
D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology*; D002392:Catechin / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000187:drug effects*; D008112:Liver Glycogen / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D001578:Benzopyrans; D008112:Liver Glycogen; D002392:Catechin