Central regulation of food intake is not affected by inclusion of defatted Tenebrio molitor larvae meal in diets for European sea bass (Dicentrarchus labrax)

Abstract

The homeostatic regulation of food intake in fish has been thoroughly studied in the last years with dietary nutrient composition is one of the factors involved. Despite several studies addressed the impact of insect meal-based diets in food intake of fish, there is no knowledge about their impact in mechanisms of food intake regulation. This study aimed to explore underlying mechanisms through evaluation of dietary fishmeal (FM) replacement by defatted (d-) Tenebrio molitor (dTM) larvae meal in European sea bass. Fish (55 ± 2 g) fed a FM-based diet (CTRL) were compared with those fed two experimental diets containing increasing levels of dTM to replace 40 and 80% of FM (TM40 and TM80, respectively). After ten weeks of feeding, fish food intake was calculated; samples of plasma and different brain areas (hypothalamus and telencephalon) were collected at different post-prandial times (2, 6 and 24 h after feeding) to evaluate circulating metabolites and mRNA abundance in hypothalamus and telencephalon of neuropeptides involved in food intake regulation. No differences occurred in food intake and weight gain among diets. Plasma cholesterol levels decreased 24 h after feeding in fish fed TM40; fish fed dTM diets had higher cholesterol levels, 2 and 6 h after feeding, than those fed CTRL diet. Increased non-esterified fatty acids (NEFA) levels occurred in plasma of fish fed TM80, regardless of the sampling time. At central level, no changes occurred in the mRNA abundance of neuropeptide Y (npy), agouti-related protein 2 (agrp2), pro-opio melanocortin a (pomca) or cocaine- and amphetamine-related transcript 2 (cartpt2). The obtained results suggest that dietary FM replacement by dTM up to 80% in European sea bass does not affect food intake or its central homeostatic regulation, supporting the use of dTM as FM replacement in diets for European sea bass.