Molecular Nutritional Research for Effective Utilization of Marine Lipid-soluble Components

Marine organisms contain unique lipid-soluble components. Therefore, we focused on the health benefits of these lipid-soluble components and conducted molecular nutritional studies. Fucoxanthin (Fx) is a typical marine carotenoid, found in brown seaweeds, such as Undaria pinnatifida (Wakame) and Saccharina japonica (Makonbu), and we demonstrated its anti-obesity and anti-diabetic effects in animal models. As the molecular mechanism for anti-diabetic effect, dietary Fx has found to activate insulin signaling pathways and glucose transporter 4 (GLUT 4) in the skeletal muscles of diabetic/obese KK-A^y mice. Notably, Fx promoted GLUT4 translocation in the soleus muscle, up-regulated GLUT4 expression in the EDL muscle, and prevented and improved hyperglycemia through effective glucose uptake depending on the muscle types. On the other hand, n-3 docosapentaenoic acid (n-3 DPA), an n-3 poly unsaturated fatty acid found in salmon and trout, is converted to EPA and DHA in cultured cells. The intracellular conversion of n-3 DPA differed different among cells derived from macrophages, liver, and intestines. n-3 DPA markedly down-regulates the mRNA expression of pro-inflammatory factors in activated macrophages. The suppressive effect of n-3 DPA on IL-6 mRNA expression was similar to that of DHA, but stronger than that of EPA. In addition, we demonstrated that n-3 PUFA-binding phosphatidylglycerol (PG) exhibited anti-inflammatory effects against activated macrophages, and that the effect was stronger than that of n-3 PUFA-phosphatidylcholine (PC). Furthermore, n-3 PUFA-PG significantly increased the intracellular EPA and DHA content compared to n-3 PUFA-PC treatment and induced Nrf2 activation. n-3 PUFA-PG, which enhances intracellular PUFAs, is contained in several microalgae such as Phaeodactylum tricornutum. It can also be enzymatically prepared and is expected to be used as a new functional lipid.