Lipid metabolism modulation by five different food types in the monogonont marine rotifer Brachionus koreanus

To investigate the effects of five different foods on fatty acid metabolism in the monogonont marine rotifer Brachionus koreanus, we measured life cycle parameters, analyzed the area of Nile red staining, fatty acid composition, and mRNA expression of fatty acid desaturase (Fads) and elongation of very long chain fatty acid (Elovl) genes. Among the five different foods (Tetraselmis suecica, Chlorella sp., Isochrysis galbana, Chaetoceros sp., and Nannochloropsis oculata), life span of L galbana-fed group was significantly increased compared to the other groups. However, the reproduction parameters (cumulative offspring and daily reproduction) were the highest in T. suecica-fed group, and the lowest in Chlorella sp.-fed group. The area of Nile red staining analysis showed similar trends, in respect to the content of total fatty acid. The single fatty acid analysis result clearly indicated that not only the most of the content of fatty acid was highly dependent on the food types, especially in omega-6 fatty acids group, but also, B. koreanus could newly synthesize some specific fatty acids by themselves (e.g. omega-3 and -9 families). Lastly, the mRNA expression of Elovl and Fads genes were modulated by food types indicating the lipid metabolism could be controlled by food in B. koreanus and probably very small amount of 18:3n-3 fatty acids was utilized and synthesized omega-3 fatty acids through the increase in Elovl and Fads gene expression in Chaetoceros sp. and N. oculata-fed groups. In conclusion, this study revealed that although B. koreanus could modulate fatty acid metabolism by itself, some nutrient values (e.g. omega-6 fatty acids) should be considered, therefore, it is important to understand the essential nutrient through both the molecular and quantitative analysis.