Lipid class and nonesterified fatty acid profiles in plasma of North Atlantic cod (Gadus morhua)

Abstract

Metabolic energy status is a critical metric for the evaluation of fish condition and health. Thus, we (i) conducted comprehensive and comparative measurements of nonesterified fatty acids (NEFAs) and other plasma lipids in fed and food-deprived (10 weeks) Atlantic cod (Gadus morhua) and (ii) compared three common methods for measuring total plasma NEFAs (Folch extraction/Iatroscan, Wako ® enzymatic, and acetyl chloride extraction/GC). Plasma total lipid, phospholipid, triacylglycerol, and NEFA levels were 83%-95% lower in food-deprived fish. In contrast, the concentration of a previously unidentified lipid class (ethyl ketone) was only 60% lower and was in fact almost threefold higher when expressed as a percentage of total lipid. Considerable differences in the NEFA profile were also observed, for example, 22:1ω11 (dominant NEFA in fed fish) was not detected, 20:1ω9 was 97% lower, and monounsaturated fatty acids were selectively reduced. Importantly, the acetyl chloride/GC method resulted in an eightfold overestimation of NEFA in fed fish. These results (i) suggest that plasma lipids reflect the energetic/nutritional status of wild gadids and can be used to monitor their responses to changing environmental conditions and (ii) caution against using the acetyl chloride/GC method of NEFA measurement without prior separation of plasma lipids by solid-phase chromatography. Résumé :Le niveau d'énergie métabolique est une métrique importante pour l'évaluation de la condition et de la santé des poissons. Nous avons donc (i) procédé à des dosages complets et comparatifs des acides gras non estérifiés (NEFA) et des autres acides gras du plasma chez des morues franches (Gadus morhua) nourries ou privées de nourriture pendant 10 semaines et (ii) comparé trois méthodes communes de dosage des NEFA totaux du plasma (extraction Folch/Iatroscan, analyse enzymatique Wako ® , extraction au chlorure d'acétyle/chromatographie en phase gazeuse (GC)). Les concentrations de lipides plasmatiques totaux, de phospholipides, de triacylglycérol (TAG) et de NEFA sont toutes plus basses de 83-95 % chez les poissons qui jeûnent. En revanche, la concentration d'une classe encore inédite de lipides (l'éthyl-cétone) est réduite de seulement 60 % et, en fait, elle est presque trois fois plus grande lorsqu'elle est exprimée en pourcent des lipides totaux. Il existe aussi des différences considérables dans les profils des NEFA : par exemple, le 22:1T11 (NEFA dominant chez les poissons nourris) n'est mesurable, le 20:1T9 est réduit de 97 % et les acides gras non saturés subissent une réduction sélective. Fait important à noter, la méthode du chlorure d'acétyle/GC surestime les NEFA chez les poissons nourris par un facteur de huit. Ces résultats (i) indiquent que les lipides plasmatiques reflètent le statut énergétique/nutritionnel des gadidés sauvages et peuvent servir à suivre leurs réactions aux conditions changeantes du milieu et (ii) mettent en garde contre l'utilisation de la méthode du chlorure d'acétyle/GC de dosage des NEFA sans séparation p...

Accumulation of Hydroxyl Lipids and 4‐Hydroxy‐2‐Hexenal in Live Fish Infected with Fish Diseases

“…The change in the liver TAG level was related to the change in the total lipid level; therefore, TAG are a major component of total lipids in fish liver. When fish suffer from disease, they must mobilize energy reserves to maintain cellular homeostasis and provide energy for swimming muscle contraction, central nervous system functioning, and gonad development [37,38]. In particular, lipids, which mainly consist of TAG, are an important source of energy for fish [39].…”

Influence of the timing of weaning on growth and survival of juvenile winter flounder (Pseudopleuronectesamericanus)

“…The observed ketone proportion (20% of total lipids) in the juveniles represents a much higher value than what has been previously found for winter flounder larvae (maximum of 5% in pelagic larvae; Vagner et al 2014) and juveniles (maximum of 10% from settlement to 45 days post-settlement; Fraboulet et al 2010;Vagner et al 2014), supporting the possible use of the commercial inert food by W3 juveniles. The function of ketones in fish metabolism is still unknown (Alkanani et al 2005), but it could provide an alternative lipid-based energy source (Ballantyne 2004). Elasmobranch fishes use ketone bodies as an energy source (Zammit and Newsholme 1979), but marine teleost fishes generally show no enhanced capacity for ketone body metabolism, even during food deprivation (Zammit and Newsholme 1979;Segner et al 1997).…”

Contributions from metabolomics to fish research

“…Another study is looking into monitoring the energetic and nutritional status of fed and food-deprived North Atlantic cod (Gadus morhua) by measuring the plasma profile of non-esterified fatty acids (NEFAs) by GC-MS. 36 Large differences in plasma NEFA concentrations were found, primarily attributable to differences in monounsaturated fatty acids (MUFAs). In addition, a pre-viously unidentified class of lipids was found.…”