Suppressive effect of hot water extract of wasabi (Wasabia japonica Matsum.) leaves on the differentiation of 3T3-L1 preadipocytes

This study investigated the effect of hot water extract of wasabi (Wasabia japonica Matsum.) leaves (WLE), without its specific pungent constituents, such as allyl isothiocyanate, on the differentiation of 3T3-L1 preadipocytes. WLE suppressed the increase in glycerol-3-phosphate dehydrogenase (GPDH) activity and triglyceride (TG) accumulation, markers of adipogenesis, in a dose-dependent manner. Quantitative real time RT-PCR results showed that WLE significantly reduced the mRNA expression levels of peroxisome proliferator-activated receptor (PPAR) gamma and CCAAT/enhancer-binding protein (C/EBP) alpha, both key adipogenic transcription factors, as subsequently were the mRNA expression levels of their target genes, such as adipocyte fatty acid binding protein 2 (aP2). Western blot analysis results showed that the protein expression levels of both PPAR gamma and C/EBP alpha were also inhibited by WLE. Thus, WLE suppressed the differentiation of 3T3-L1 preadipocytes, and the suppressive effect was mediated, in part, through the altered regulation of PPAR gamma, C/EBP alpha, and other specific genes, such as aP2. These results suggest that WLE may prevent obesity and insulin resistance by inhibiting the differentiation of preadipocytes. (C) 2009 Elsevier Ltd. All rights reserved.