Inhibitory Effects of Vanadium-Binding Proteins Purified from the Sea Squirt Halocynthia roretzi on Adipogenesis in 3T3-L1 Adipocytes

The inhibitory effects of vanadium-binding proteins (VBPs) from the blood plasma and the intestine of sea squirt on adipogenesis in 3T3-L1 adipocytes were examined. 3T3L-1 cells treated with VBP (blood plasma) decreased markedly the lipid content in maturing pre-adipocytes in a dose-dependent manner, whereas VBP (intestine) did not show significant effects on lipid accumulation. Both VBPs did not have significant effect on cell viability. In order to demonstrate the anti-adipogenic effects of VBP (blood plasma), the expressions of several adipogenic transcription factors and enzymes were investigated by Reverse Transcriptase-Polymerase Chain Reaction. VBP (blood plasma) down-regulated the expressions of transcription factors; PPAR-gamma, C/EBP-alpha, SREBP1, and FAS, but did not have significant effects on the expressions of lipolytic enzymes; HSL and LPL. Both the crude and purified VBPs significantly increased the mRNA levels of Wnt10b, FZ1, LRP6, and beta-catenin, while decreased the expression of GSK-3 beta. Hence, VBP (blood plasma) inhibited adipogenesis by activating WNT/beta-catenin pathway via the activation of Wnt10b. Based on the findings, VBP (blood plasma) decreased lipid accumulation which was mediated by decreasing adipogenesis, not by lipolysis. Therefore, VBP (blood plasma) could be used to treat obesity.