Toxic effects of dietary hydrolysed lipids: an in vivo study on fish larvae.

We have previously described that fish larvae absorb a larger fraction of dietary monoacylglycerol than TAG. To investigate how dietary hydrolysed lipids affect a vertebrate at early life stages over time, we fed Atlantic cod (Gadus morhua) larvae six diets with different degrees of hydrolysed lipids for 30 d. The different diets had no effect on growth, but there was a positive correlation between the level of hydrolysed lipids in the diets and mortality. Important genes in lipid metabolism, such as PPAR, farnesoid X receptor (FXR) and stearoyl-CoA desaturase (SCD), were regulated by the different diets. Genes involved in the oxidative stress response did not respond to the increased lipid hydrolysation in the diets. However, enterocyte damage was observed in animals fed diets with 2.7 % NEFA (diet 3) or more. It is thus possible that mortality was due to infections and/or osmotic stress due to the exposure of the subepithelial tissue. In contrast to earlier experiments showing a positive effect of dietary hydrolysed lipids, we have demonstrated a toxic effect of dietary NEFA on Atlantic cod larvae. Toxicity is not acute but needs time to accumulate.