Inhibition of hepatic glucose 6-phosphatase system by the green tea flavanol epigallocatechin gallate.
Effect of 5-100 microM epigallocatechin gallate (EGCG) on hepatic glucose 6-phosphatase (G6Pase) system was investigated. EGCG inhibited G6Pase in intact but not in permeabilized rat liver microsomes, suggesting the interference with the transport. However, EGCG did not hinder microsomal glucose 6-phosphate (G6P) uptake. Instead, it increased the accumulation of radioactivity after the addition of [(14)C]G6P, presumably due to a slower release of [(14)C]glucose, the product of luminal hydrolysis. Indeed, EGCG was found to inhibit microsomal glucose efflux. Since G6Pase activity is depressed by glucose in a concentration-dependent manner, we concluded that EGCG inhibits G6Pase through an elevated luminal glucose level.
Csala
Miklós
M
Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Pathobiochemistry Research Group of The Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary. csala@puskin.sote.hu <csala@puskin.sote.hu>
Margittai
Eva
E
Senesi
Silvia
S
Gamberucci
Alessandra
A
Bánhegyi
Gábor
G
Mandl
József
J
Benedetti
Angelo
A
D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D044948:Flavonols / Q000302:isolation & purification / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000032:analysis / Q000037:antagonists & inhibitors*; D019298:Glucose-6-Phosphate / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D013662:Tea / Q000737:chemistry*
D044948:Flavonols; D013662:Tea; D019298:Glucose-6-Phosphate; D002392:Catechin; C045651:epigallocatechin gallate; D005952:Glucose-6-Phosphatase; D005947:Glucose