New tolls and strategies for the metabolic phenotyping at molecular level of Mediterranean farmed fish

Abstract

Clinical haematology and basic blood biochemistry are common diagnostic tools to assess health and welfare in humans and most livestock production systems, but the use of such analyses as diagnostic tools is poorly established in fish farming due to the paucity of reliable information on reference values. Thus, several attempts have been conducted within the ARRAINA project to compile and generate new data for all fish species in the project, and gilthead sea bream in particular (Ballester-Lozano et al., 2015). Similarly, clinical signs of liver steatosis, accumulation of intestinal lipid droplets or intestine submucosa inflammation are arising from lipid-related metabolic disorders, but a direct link with a specific nutrient or group of nutrients is often lacking for the histopathological scoring. This also applies to molecular approaches and important research efforts were done over the course of the last years to construct and continuously update the sea bream and sea bass CSIC-transcriptomic databases (www.nutrigroup-iats.org/) on actively transcribed genes of larvae, and intestine and immune-relevant tissues of juvenile fish (Calduch-Giner et al., 2013). Examples of use of these on-line searchable databases includes: i) definition of molecular identity and extensive searches of new genes exclusive of fish lineages, ii) reference libraries in proteomics and next generation sequencing studies, and iii) design of specific microarray and PCR-arrays for wide- and pathway-focused gene expression profiling and fingerprinting. The aim of the present overview is to underline how these new molecular tools have contributed to identify and validate new biomarkers and approaches that have specificity, sensitivity and diagnostic/predictive value for the assessment and improvement of nutritional condition in Mediterranean farmed fish.