title: Effects of a catechin-free fraction derived from green tea on gene expression of gluconeogenic enzymes in rat hepatoma H4IIE cells and in the mouse liver.
abstract: Many biological activities of green tea have been attributed to a major constituent, (-)-epigallocatechin gallate (EGCG). We previously reported that EGCG and a catechin-rich green tea beverage modulated the gene expression of gluconeogenic enzymes, glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), in the mouse liver. However, it remains to be examined whether or not a constituent other than EGCG contributes to the change in gene expression of these enzymes. In this study, we separated the hot water infusion of green tea leaves (GT) into an ethanol-soluble fraction (GT-E) and an EGCG-free water-soluble fraction (GT-W), and examined their effects using rat hepatoma H4IIE cells. The inclusion of GT, GT-E, and GT-W in the culture medium reduced the gene expression of G6Pase and PEPCK. GT-W caused a decrease in expression of the transcription factor HNF4α. Reduced levels of PEPCK and HNF4α proteins were demonstrated in the cells treated with GT-W. GT-W showed an activity similar to insulin, but different from EGCG. Administration of GT-W to mice for 4 weeks reduced the hepatic expression of G6Pase, PEPCK, and HNF4α. These results suggest that green tea contains some component(s) with insulin-like activity distinguishable from EGCG and that drinking green tea may help to prevent diabetes.
authors.affiliation: Health Care Research Center, Nisshin Pharma Inc., Fujimino, Saitama, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Yasui
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Miyoshi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Tanabe
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ishigami
authors.forename: Ryuuta
authors.initials: R
authors.lastname: Fukutomi
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Imai
authors.forename: Mamoru
authors.initials: M
authors.lastname: Isemura
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000235:genetics; D002392:Catechin / Q000494:pharmacology; D045744:Cell Line, Tumor; D003924:Diabetes Mellitus, Type 2 / Q000517:prevention & control; D015870:Gene Expression; D005943:Gluconeogenesis / Q000187:drug effects* / Q000235:genetics; D005952:Glucose-6-Phosphatase / Q000235:genetics / Q000378:metabolism*; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism*; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013662:Tea / Q000737:chemistry
chemical_list: D000975:Antioxidants; D051557:Hepatocyte Nuclear Factor 4; C496594:Hnf4a protein, rat; D007328:Insulin; D010936:Plant Extracts; D012333:RNA, Messenger; D013662:Tea; D002392:Catechin; D005952:Glucose-6-Phosphatase; D019764:Phosphoenolpyruvate Carboxykinase (ATP)