Generation of Tetracosahexaenoic Acid in Benthic Marine Organisms

Tetracosahexaenoic acid (THA, 24:6n-3) has been shown to have the strongest ability to suppress accumulation of lipids in HepG2 cells among well-known n-3 highly unsaturated fatty acids, such as EPA and DHA. In this study, a method for mass production of THA was investigated using distributions of THA and DHA in thirty-two marine organisms, such as starfishes, right-eyed flounders, shellfishes, and sharks. The fatty acid composition of the marine organisms was analyzed using GC-FID and THA was detected in starfish, right-eyed flounder, and shark. Furthermore, the ratio of DHA and THA (DHA/THA) in each sample was calculated using chromatogram peak area of GC-FID, and the value was found to be lower than 1 in some starfishes. As a result, THA was thought to be synthesized in the starfishes. In contrast, the value of DHA/THA for right-eyed flounder and sharks was greater than 1. The THA accumulation in right-eyed flounder was considered to be because of the starfishes that the flounder consumes as part of its diet. DHA is synthesized from THA by beta-oxidation in peroxisomes, in the Sprecher's shunt. The high accumulation of THA observed in the flounder would be caused by the decreasing enzyme activation due to beta-oxidation in the peroxisomes of the starfishes. Understanding the differences in THA between aquatic species could also potentially allow us to understand why THA is generated in marine animals.