- 著者
- Kensuke Yasui Noriyuki Miyoshi Hiroki Tanabe Yoko Ishigami Ryuuta Fukutomi Shinjiro Imai Mamoru Isemura
- 出版者
- Biomedical Research Press
- 雑誌
- Biomedical Research (ISSN:03886107)
- 巻号頁・発行日
- vol.32, no.2, pp.119-125, 2011 (Released:2011-05-03)
- 参考文献数
- 15
- 被引用文献数
- 2 3
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.
- 著者
- Kensuke Yasui Noriko Paeng Noriyuki Miyoshi Takuji Suzuki Kyoko Taguchi Yoko Ishigami Ryuuta Fukutomi Shinjiro Imai Mamoru Isemura Tsutomu Nakayama
- 出版者
- Biomedical Research Press
- 雑誌
- Biomedical Research (ISSN:03886107)
- 巻号頁・発行日
- vol.33, no.1, pp.9-13, 2012 (Released:2012-02-24)
- 参考文献数
- 18
- 被引用文献数
- 14 18
Many biological activities of green tea have been attributed to a major constituent, (minus;)-epigallocatechin gallate (EGCG). We previously reported that EGCG and an EGCG-free fraction derived from green tea modulated the gene expression of gluconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, in the mouse liver. EGCG is also known to affect the gene expression of enzymes related to lipid metabolism. 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 prepared an EGCG-free water-soluble fraction (GT-W), and examined its effects on the hepatic gene expression of lipogenic enzymes in mice. The results of quantitative real-time PCR assays indicated that the dietary administration of GT-W for 4 weeks reduced the hepatic gene expression of lipogenic enzymes: fatty acid synthase, hydroxymethylglutaryl coenzyme A reductase, and acetyl-coenzyme A carboxylase alpha. Also, the gene expression of sterol regulatory element-binding transcription factor (Srebf)1 and/or Srebf2 was reduced, suggesting that the reduction of Srebfs contributed to the down-regulation of the lipogenic enzymes, since these transcription factors bind the promoter region to enhance their expression. The plasma levels of triglycerides and cholesterol were reduced with statistical significance in the group given a diet containing GT-W. These results suggest that in addition to EGCG, green tea contains some component(s) which may help to prevent arteriosclerosis and obesity.