Reduced Leptin Secretion by Fucoidan-Added Kochujang and Anti-adipogenic Effect of Fucoidan in Mouse 3T3-L1 Adipocytes

In order to improve the antiobesity effect of Kochujang, 1% of sea tangle powder, alginic acid extract, and fucoidan extract were added to Kochujang. Sea tangle powder-added Kochujang decreased leptin secretion by only 12% compared to Kochujang, whereas alginic acid or fucoidan-added Kochujang significantly decreased leptin secretion by more than 60% in 3T3-L1 adipocytes. Fucoidan, one of the active components of sea tangle, decreased leptin secretion by 56%, 60%, and 60% compared to the control in the concentrations of $1{\mu}M,\;2.5{\mu}M,\;and\;5{\mu}M$, respectively. To see the effect of fucoidan on TG formation during adipocyte differentiation, 3T3-L1 cells were treated with $1{\mu}M\;and\;5{\mu}M$ concentrations of fucoidan during adipocyte differentiation (from 'day 0' to 'day 6'). Oil red O staining showed fucoidan decreased the amount of TG droplets and $5{\mu}M$ fucoidan potently inhibited TG formation. To see the effect of fucoidan on lipolysis, differentiated 3T3-L1 adipocytes were treated with fucoidan. The secretion of glycerol, which is used to measure lipolytic activity, was increased by 21%, 37%, and 53% compared to the control in the concentrations of $1{\mu}M,\;2.5{\mu}M,\;and\;5{\mu}M$, respectively. Oil red O staining showed fucoidan decreased TG amount at $1{\mu}M\;and\;5{\mu}M$ concentrations. These results suggest that fucoidan decreases leptin secretion and TG accumulation by inhibition of adipocyte differentiation and induction of lipolysis. Since fucoidan is reported to have various biological activities in addition to an anti-adipogenic effect, it seems valuable to develop fucoidan-added Kochujang as a multi-functional Kochujang.