Similarities Between the Lipid Profiles of Skin and Liver of European Sea Bass (Dicentrarchus labrax) Fed Diets With Different Lipid Content.

Abstract

The fatty acid composition of fish is influenced by species, age, diet, and tissues, which respond differently to dietary lipids. This study examined how two commercial diets with contrasting polyunsaturated fatty acid (PUFA) profiles, affecting eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), alter the fatty acid composition in European sea bass (Dicentrarchus labrax) tissues and tested whether skin or mucus sampling can indicate hepatic lipid status. Twenty-four sea bass were reared under controlled conditions and fed Optima Plus T3 (diet A) or Protect D4 (diet B) for 30 days, and six fish were sampled at baseline. After feeding, skin mucus, skin, flesh, and liver were collected, lipids were extracted, and fatty acid methyl esters were quantified by gas chromatography. ANOVA and multivariate analyses were used to assess diet- and tissue-dependent shifts. Despite isoenergetic diets and no growth differences, the tissue lipid profiles changed significantly, indicating rapid dietary imprinting. Diet B reduced total n-3 PUFA levels in skin mucus, whereas livers from fish fed diet B showed higher total PUFA, n-6 PUFA, and monounsaturated fatty acid levels than those fed diet A, with altered arachidonic (ARA)/EPA and n-3/n-6 ratios in the liver and mucus. The key fatty acids driving these differences included docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in the mucus and linoleic and oleic acids in the liver. Muscle and skin showed fewer class-level changes but specific shifts (e.g., EPA and α-linolenic acid were higher with diet A; ARA and linoleic acids were higher with diet B). Multivariate ordination revealed close clustering and low dissimilarity between the liver and skin, with linoleic acid as the principal contributor. These findings support the use of small skin biopsies to infer hepatic lipid profile changes, offering a practical tool for monitoring liver conditions and diet-related pathologies in aquaculture.