Vanadium-binding protein from vanadium-enriched sea cucumber Apostichopus japonicus inhibits adipocyte differentiation through activating WNT/β-catenin pathway

A vanadium-binding protein (VBP) was isolated from the intestine of edible sea cucumber using a procedure which involved precipitating the extract by the addition of (NH4)2SO4, ion exchange chromatography on DEAE-Sepharose Fast Flow, and gel filtration chromatography on Sephacryl S-300 HR. The inhibitory effect of VBP on adipocyte differentiation was then examined. VBP up-regulated the mRNA expression of WNT/β-catenin related factors, namely FZ1, LRP5 and LRP6, while it had no effect on Wnt10b and GSK3β. qRT-PCR and western blotting results showed that VBP enhanced the level of total β-catenin, nuclear β-catenin and exhibited marked inhibitory effect on adipocyte differentiation. The lipid accumulation of cells treated with VBP was decreased by 24.07%. VBP decreased the expression of PPARγ and C/EBPα, further indicating the inhibitory effect on adipocyte differentiation. These findings suggest that VBP exhibits marked inhibitory effect on adipocyte differentiation and this effect is mediated by activating the WNT/β-catenin pathway.