Preliminary data on the dietary safety, tolerability and effects on lipid metabolism of the marine microalga Tisochrysis lutea

The marine microalga Tisochrysis lutea is an interesting source of nutrients and bioactive compounds such as fucoxanthin and docosahexaenoic acid, used so far mainly in aquaculture. To investigate its dietary safety and tolerability on mammals, male Sprague-Dowley rats were fed an AIN-76 diet containing 20% of T. lutea F&M-M36 biomass, for 1 month. T. lutea rich diet showed an apparent digestibility similar to that of the non enriched AIN-76 diet and did not affect growth or animal behavior, but was associated to higher water intake, urinary excretion and urinary sodium probably due to the high salt content of the algal biomass. However, blood pressure, creatinine and urea, kidney morphology and heart left ventricular wall thickness were not affected. T. lutea fed rats showed an increase in cholesterol high density lipoprotein, HDL (p < 0.05) and decreased plasma triglycerides (p = 0.06), together with an increased excretion of fecal lipids (p < 0.05). Up-regulation of PPARγ (p < 0.05) and UCP-1 (p < 0.05) and down-regulation of LPL genes (p < 0.05) in the liver of T. lutea fed rats were also observed. These preliminary data indicate that the T. lutea-rich diet was well tolerated in the short term and suggest that this marine microalga may represent a promising source of functional foods and bioactive compounds for the control of dyslipidemias. Its salt content, however, poses a safety issue, which must be overcome before proposing its use in humans.