In another publication Maeda and his colleagues reported tha

In another publication, Maeda and his colleagues [43] reported that abdominal white adipose tissue weights of rats and mice fed fucoxanthin were markedly reduced compared to those fed a control diet. The daily consumption of fucoxanthin in mice also significantly decreased body weight. Again clear signals of uncoupling protein-1 and its mRNA were found in abdominal white adipose tissue in mice fed fucoxanthin, although there is little expression of uncoupling protein-1 in white adipose tissue in mice fed a control diet. These findings suggest that the seaweed carotenoid, fucoxanthin, upregulates the expression of uncoupling protein-1 in white adipose tissue and is an active component for the anti-obesity effect of Undaria lipids [40,43]. Maeda et al. [44] also investigated the anti-obesity effects of fucoxanthin-rich wakame lipids on high fat diet-induced obesity in mice. A diet of both high fat and wakame lipids rich in fucoxanthin markedly suppressed body weight and white adipose tissue weight gain induced by a high fat diet. These results suggest that dietary wakame lipids may ameliorate changes in lipid metabolism induced by a high fat diet. The administration of fucoxanthin-rich wakame lipids as a functional food may therefore provide a biochemical and nutritional basis for the prevention of obesity. In order to understand the mechanisms underlying the anti-obesity effects of fucoxanthin and its metabolite fucoxanthinol, Matsumoto and her colleagues [45] investigated the effects of these carotenoids on the carboxypeptidase of triglycerides in conscious rats implanted with cannulae into a lymph duct and the portal or jugular vein. A duodenal infusion of test oil emulsion with or without 2mg of fucoxanthin or fucoxanthinol was administered in the lymph duct and the portal or the jugular vein. The inhibitory activities of fucoxanthin and fucoxanthinol on pancreatic lipase activity were assessed in vitro. Increases in lymphatic and blood triglyceride levels were much lower in the two carotenoid-treated groups than in the carotenoid-free group, indicating that these marine carotenoids inhibit both lipase activity in the gastrointestinal lumen and triglyceride absorption [45]. Jeon et al. [46] assessed an ethanol extract of fucoxanthin-rich seaweed in mice in regard to potential anti-obesity effects. Groups of mice received a high-fat diet supplemented with 0.2% conjugated linoleic acid as the positive control or 1.43% or 5.72% fucoxanthin-rich seaweed ethanol extract for six weeks. The study showed that supplementation with two doses of fucoxanthin-rich seaweed reduced body and abdominal white adipose tissue weights, plasma and hepatic triglyceride, and/or cholesterol concentrations compared to a high-fat control group. Activities of adipocytic fatty acid synthesis, hepatic fatty acid and triglyceride synthesis, and cholesterol-regulating enzyme were also reduced by fucoxanthin-rich seaweed ethanol extract. These results indicate that fucoxanthin affects the plasma and hepatic lipid profile and body fat mass [46]. Maeda et al. [47] showed that both fucoxanthin and fucoxanthinol inhibited intercellular lipid accumulation during adipocyte differentiation of 3T3-L1 cells. The suppressive effect of fucoxanthinol on the differentiation in mice of preadipocytes to adipocytes was stronger than that of fucoxanthin [47], and the suppressive effect of amarouciaxanthin A, a dominant metabolite of fucoxanthin in white adipose tissue, was stronger than that of fucoxanthinol [48]. Kang et al. [49] reported that fucoxanthin inhibited 3T3-L1 adipocyte differentiation at intermediate and late stages, while it enhanced adipocyte differentiation at an early stage by affecting the expression of key adipogenic transcriptional regulators and inhibited glucose uptake. These findings suggest that fucoxanthin exerts anti-obesity effects by inhibiting the expression of key transcriptional regulators and glucose uptake in mature adipocytes. The unique suppressive effect of fucoxanthin on adipocyte differentiation appears to be linked to its structural properties, since an allenic bond is essential for the expression of this activity, and carotenoids without this bond show no activity [50]. A more detailed account of anti-obesity effects of fucoxanthin and its metabolites has been provided by Peng and co-authors [51].