(-)-Epigallocatechin gallate enhances the expression of genes related to insulin sensitivity and adipocyte differentiation in 3T3-L1 adipocytes at an early stage of differentiation
Received 9 October 2008; accepted 16 February 2009. published online 17 June 2009.
Abstract
Objective
(-)-Epigallocatechin gallate (EGCG) is thought to enhance insulin sensitivity in adipocytes, although doses used in in vitro experiments have been shown to promote apoptosis. To explore the effects of EGCG on insulin sensitivity in adipocytes, the expression of genes related to insulin sensitivity and adipocyte differentiation in 3T3-L1 adipocytes were measured in response to low doses of EGCG.
Methods
Increasing concentrations of low-dose EGCG were administered for 8 d to differentiating 3T3 adipocytes, either at days 0–8 (early stage) or at days 8–16 (late stage). Fat accumulation and cell activity were measured by Oil Red O staining and 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan assay, respectively. The expression of genes related to insulin sensitivity and adipocyte differentiation was measured by real-time reverse transcriptase–polymerase chain reaction.
Results
Fat accumulation and cell activity in 3T3-L1 cells at the early and late stages were reduced at EGCG concentrations ≥50μM. However, EGCG doses of 5–10μM reduced fat accumulation and induced the expression of genes related to insulin sensitivity (including Fabp4, Cd36, Lpl, Pck1, Acox1, Lypla3, and Ucp2) and adipocyte differentiation (Pparg1, Pparg2, Cebps, and Ppargc1a). These increases were only seen at the early, and not late, stages of differentiation.
Conclusion
These data indicate that low doses of EGCG, despite reducing triacylglycerol accumulation, induce the expression of genes related to insulin sensitivity in the early stage of differentiation.
Laboratory of Nutritional Physiology, Graduate School of Nutritional and Environmental Sciences, Global Center of Excellence Program, The University of Shizuoka, Shizuoka, Japan
This work was supported by a grant from Ministry of Health, Labor and Welfare of Japan, and by the global Center of Excellence Program for Evolutionary Human Health Sciences from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
ABSTRACT