Contents lists available at ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox Plasma biochemistry, gene expression and liver histomorphology in common carp (Cyprinus carpio) fed with different dietary fat sources P. Eljasik a,∗ , R. Panicz a , M. Sobczak a , J. Sadowski b , V. Barbosa c , A. Marques c , J. Dias d a Department of Meat Science, Faculty of Food Science and Fisheries, West Pomeranian University of Technology, 71-550, Szczecin, 4 Kazimierza Królewicza Street, Poland b Department of Aquatic Bioengineering and Aquaculture, Faculty of Food Science and Fisheries, West Pomeranian University of Technology, 71-550, Szczecin, 4 Kazimierza Królewicza Street, Poland c Divisão de Aquacultura, Valorização e Bioprospecção. Instituto Português do Mar e da Atmosfera, I.P. Lisboa. Portugal, Avenida Professor Doutor Alfredo Magalhães Ramalho 6, 1495-165, Algés, Portugal d Sparos Lda, Área Empresarial de Marim, Lote C, 8700-221, Olhão, Portugal ARTICLE INFO Keywords: EPA and DHA Fat metabolism Fish fortification Hepatocyte histomorphology Lipid-dependent genes Schizochytrium ABSTRACT Demand for omega-3 long chain polyunsaturated fatty acids has become global challenge for aquaculture and different components have been used to increase nutritional value of fillets. The aim of this study was to evaluate influences of feeds on zootechnical parameters, biochemical plasma parameters, expression of lipid-dependent genes, hepatocyte histomorphologies, and fatty acid profiles in common carp fillets. We compared a control diet (CTRL), mimicking a commercial feed formulation for common carp, with three diets containing blends of vegetable oils and a DHA-rich alga (Schizochytrium sp.) included at 3.125% (CB1) or 1.563% (CB2), and 2.1% salmon oil (CB3). The study revealed no differences in final body weight of fish fed CB1-3 diets in comparison with significantly lower CTRL. Concentrations of all biochemical parameters in plasma increased gradually in fish fed CB1-3 diets when compared to CTRL diet, with exception of triacylglycerol levels. Expression of hepatic fas, elovl-5a and pparα genes increased significantly in fish fed CB1 and CB2. Additionally, eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) accumulation in muscle tissue was directly proportional to the amounts supplied in the diets. Our study revealed that carp fillet profiles can be manipulated for DHA and EPA-contents using enriched diets, depending on the source of fat. 1. Introduction The essential role of omega-3 polyunsaturated fatty acids (n-3 PUFAs) in human nutrition has been studied widely in recent years (EFSA, 2014). The n-3 PUFAs functions in neurogenesis, neuro- transmission, protection against oxidative stress, and are particularly important during brain development (Innis, 2007). Moreover, they are components of cell walls, determining fluidity, elasticity and perme- ability, and have beneficial effects against development of various human conditions, such as inflammation and autoimmune, cardiovas- cular and neurodegenerative diseases (Arts and Kohler, 2009; Liu and Ma, 2014; Zhang et al., 2019). The recommended daily intakes for ei- cosapentaenoic (EPA) and docosahexaenoic (DHA) acids (re- commended by national and international authorities – 250mg/day) is achieved by only 26% of Europeans (Sioen et al., 2017). A good source of n-3 fatty acids in human diets is fish, specifically marine fish. Generally, EFA (essential fatty acid) contents of freshwater fish is lower, and dependent on physico-chemical parameters of their habitat, season and geographical location as well as physiology (Williams et al., 2017). Freshwater fish fillets are more susceptible to changes in dietary fatty acid (FA) profile, i.e. ingredients in new feed blends. For example, fillets from Nile tilapia (Oreochromis niloticus) fed increased proportions of fish oil (FO) in an experimental diet had contained more DHA and EPA compared with fish fed a control diet (Özlüer Hunt et al., 2018). A comparable observation has been de- scribed for Atlantic salmon (Salmo salar)(Sissener, 2018). This supports the rational of utilizing sustainable raw materials rich in PUFAs for feed production. Decreasing availability and growing costs associated with animal ingredients rich in PUFAs has forced producers to consider plant-based ingredients (e.g. rapeseed oil, sunflower oil), insects (e.g. black soldier fly larvae meal), microalgae (e.g. Schizochytrium sp. meal) and by-products from fish processing (e.g. salmon meal). However, new implemented ingredients are potentially hazardous, because may in- clude a range of contaminants, like heavy metals, mycotoxins, pesticide https://doi.org/10.1016/j.fct.2020.111300 Received 30 January 2020; Received in revised form 5 March 2020; Accepted 20 March 2020 ∗ Corresponding author. Department of Meat Science, Faculty of Food Science and Fisheries, West Pomeranian University of Technology, Kazimierza Królewicza 4, 71-550, Szczecin, Poland. E-mail address: peljasik@zut.edu.pl (P. Eljasik). Food and Chemical Toxicology 140 (2020) 111300 Available online 26 March 2020 0278-6915/ © 2020 Elsevier Ltd. All rights reserved. T