On the Utilization of Dietary Glycerol in Carnivorous Fish—Part II: Insights Into Lipid Metabolism of Rainbow Trout (Oncorhynchus mykiss) and European Seabass (Dicentrarchus labrax)

Glycerol is the by-product of biodiesel production and its utilisation in fish feed has recently gained relevance. As an important metabolic intermediate structural component triacylglycerol (TAG), it still unclear whether supplementation affects lipid and/or deposition different tissues. Accordingly, a set studies was aimed to evaluate how increasing levels dietary glycerol (0, 2.5 5%) affect synthesis liver, muscle adipose tissue. After growth trial with rainbow trout (8 weeks) European seabass (6 were sampled at 6 24 h assess mRNA metabolism-related enzymes. The remaining subjected consisting 6-day residence deuterated water ( 2 H O) for flux calculations. This study stands as second part broader experiment that also evaluating carbohydrate metabolism Viegas et al., 2022 ). Dietary 5% significantly increased plasma TAG both species liver seabass, no repercussions on perivisceral fat index. Despite responding expected postprandial setting, only fas Δ6-fad responded by glycerol. In trout, observed differences regulation these enzymes not reflected de novo lipogenic fluxes. fractional synthetic rates (FSR) overall low all tissues average 0.04, 0.02 0.01% d –1 , fat, respectively. other hand, despite Δ6-fad, profile higher MUFA expense lower PUFA. Moreover, altered capacity hepatic TAG-bound FA (0.32 ± 0.18, 0.57 0.82 0.24 0%, 2.5% supplementation, respectively). findings present suggest up did severely impact nor potential accumulation.