(-)-Epigallocatechin-3-gallate blocks 3T3-L1 adipose conversion by inhibition of cell proliferation and suppression of adipose phenotype expression

Aims: A major objective in the treatment of obese individuals is the development of agents that reduce body fat and improve metabolic homeostasis. Among a variety of biological effects, green tea exerts an anti-obesity effect; however, the mechanisms behind its activity on adipose tissue are uncertain. Tea contains high levels of (-)-epigallocatechin-3-gallate (EGCG), which is one of its main bioactive substances. Therefore, we studied the effects of EGCG on mouse embryonic fibroblast-adipose like cell line (3T3-L1) preadipocyte proliferation and differentiation. Main methods: 3T3-L1 cells were incubated with physiologically attainable (0.1-1 mu M) and pharmacological (5 mu M, 10 mu M) concentrations of EGCG for various lengths of time. Cell proliferation was assessed by cell counting and cell cycle analysis. Adipose conversion was evaluated by lipid accumulation and expression of CCAAT/enhancer binding protein alpha (C/EBP alpha) and peroxisome proliferator-activated receptor gamma (PPAR gamma) transcription factors. Key findings: A dose dependent suppressive effect on preadipocyte proliferation was observed, with the highest reduction in cell number at 10 mu M EGCG. On the other hand, adipose conversion was fully inhibited with 10 mu M EGCG. Flow-cytometric analysis showed that 3T3-L1 cells treated with EGCG underwent an arrest of cell cycle at G2/M. The inhibition of the expression of C/EBP alpha and PPAR gamma was accompanied by the inhibitory effect of EGCG. Microscopic observation showed that 3T3-L1 cells treated with EGCG maintained the fibroblastic shape and failed to accumulate cytoplasmic fat droplets even after the induction of differentiation. Significance: Our results suggest that EGCG reduces adipogenesis through an arrest of cell cycle and a blockage of adipose phenotype expression. These results also suggest that the anti-obesity activity of green tea may be partially attributed to its suppressive effects in adipogenesis. (C) 2011 Elsevier Inc. All rights reserved.