Postprandial pattern of digestive enzymes and protein turnover in meagre (Argyrosomus regius) juveniles

After a meal, a sequence of physiological changes occurs in animals in response to digestion, absorption and assimilation of the ingested nutrients. These processes are very important for the aquaculture sector since they will define the efficiency by which food is converted into growth, thus contributing to reduce the production costs and also undigested food in the effluents. Here we investigated the activity of digestive enzymes in the midgut and the protein degradation systems following a single meal to define postprandial patterns of action in hepatic and muscle tissues of meagre juveniles. Fish were fed with a single meal followed by a period of 24 h without feed. The activity of several digestive enzymes (α-amylase, trypsin, aminopeptidase, alkaline and acid phosphatases) plus the analysis of key players of the ubiquitin-proteasome (UPS) and autophagy-lysosomal (ALS) systems were examined just before feeding (0 h, basal point) and 2, 4, 6, 8 and 24 h after food ingestion. Digestion was activated around 4 h after food ingestion and nutrients available for protein degradation 2 h later. This work provided information about the short-term physiological effects induced by a single meal to support scientists' decision when planning a specific study involving digestion and protein degradation, and also to fish farmers on how to better manage feeding protocols when producing A. regius juveniles. Our results suggested that meagre juveniles, under the experimental conditions used, can be fed every 4 h, time when digestion starts, however further studies should be addressed to find the optimal feeding regime for this juvenile species. [Display omitted] •Digestive enzymes and protein turnover exhibit a diel pattern in meagre juveniles after feeding.•The digestion process is activated 4 h after food ingestion.•Digested nutrients are available for protein degradation 2 h after food digestion.•Meagre juveniles fed a single meal showed poor stimulation of digestive enzymes in the midgut and protein turnover in the muscle and liver.