Effects of a catechin-free fraction derived from green tea on gene expression of enzymes related to lipid metabolism in the mouse liver

Abstract

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.

Health-promoting effects of green tea

“…6). In accordance with the results for these changes in hepatic gene expression of lipogenic enzymes, the plasma levels of triglycerides and cholesterol of mice given a diet containing the EGCG-free fraction were significantly reduced 90) (Table 1). The plasma glucose levels were not altered significantly, but tended to be reduced (Table 1).…”

“…83) This fraction also reduced the hepatic gene expression of lipogenic enzymes such as fatty acid synthase, 4-hydroxymethylglutaryl CoA reductase, acetyl CoA carboxylase α, and ATP-citrate lyase in association with the reduced gene expression of sterol response element-binding factor (SREBF)-1 and SREBF-2, key transcription factors for the gene expression of lipogenic enzymes 90) (Fig. 6).…”

Decreased hepatic gluconeogenesis in transgenic rats with increased circulating angiotensin-(1-7)

“…Recently, it has been documented that HNF4␣ has been implicated in gluconeogenesis through transcriptional regulation of G6Pase and PEPCK, which are rate-limiting enzymes in this process as discussed previously [27]. The mRNA expression of HNF4␣ analysis by RT-PCR showed significantly decreased levels Western blotting gel from TGR and SD rats.…”

“…Levels of glucose-6phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK) and HNF4␣ mRNA were determined by real-time quantitative PCR using SYBR Green reagent (Applied Biosystems, CA, USA) in an ABI Prism 7000 platform (Applied Biosystems). The following primer pairs were used: glucose-6-phosphatase (G6Pase) forward 5 -aacgtctgtctgtcccggatctac-3 ; G6Pase reverse 5 -acctctggaggctggcattg-3 ; PEPCK forward 5 -tgcccatgcaaggcatca-3 ; PEPCK reverse 5 -tctcatggcagctcctacaaacac-3 ; hepatocyte nuclear factor 4 alpha (HNF4␣) forward 5 -tgagcacctgctgcttgga-3 ; HNF4␣ reverse 5 -tcgaggatgcgaatggacac-3 ; ␤-actin forward 5 -tgacaggatgcagaaggaga-3 ; ␤-actin reverse 5tagagccaccaatccacaca-3 [23,27].…”

“…The HNF-4␣ gene, a hepatocyte nuclear factor, regulates the expression of genes responsible for gluconeogenic enzymes. Thus it plays an important role in this pathway and is considered a marker of gluconeogenesis [27].…”