Défense de thèse en sciences biologiques

Influence of the content in dietary polyunsaturated fatty acids on lipid metabolisms and immune responses of common carp (Cyprinus carpio) - in vivo and in vitro approaches

Jury

• Frederik DE LAENDER (UNamur), President
• Patrick KESTEMONT (UNamur), Supervisor and Secretary
• TRAN NANG Thu (Vietnam National University of Agriculture)
• Robert MANDIKI (UNamur)
• Yvan LARONDELLE (UCLouvain)
• Daniel MONTERO (ULPGC, Las Palmas, Gran Canaria, Spain)
  

Summary

The common carp Cyprinus carpio is an important aquaculture species; it is the most cultured fish for human food consumption. As a freshwater fish, they are able to biosynthesise the long chain polyunsaturated fatty acids (LC-PUFAs) from PUFA precursors. LC-PUFAs play an important role in fish immune system in particular and in animals more generally, and their imbalance or inadequate supply could lead to negative effects on fish health. LC-PUFAs released from cell phospholipid membranes have participated in the metabolisms of some active molecules involved in immune responses such as inflammatory processes. However, information of the influences of LC-PUFA amount effects on fish immune system via these processes is still limited. In this context, this current thesis was conducted to determine the influence of dietary FA amounts from various plant oil sources on (1) growth performance, feed utilisation and survival; (2) FA compositions; (3) immune status and (4) pro and anti-inflammatory responses in common carp. To reach these objectives, four experiments were carried out during this thesis. First experiment was designed using six plant oil sources including cod liver oil (CLO), linseed oil (LO), sesame oil (SO), sunflower oil (SFO) and two blends of these plant oils – SLO (SO + LO, v:v, 1:1), SSFO (SO + SFO, v:v, 1:1). The second experiment was then carried out using three dietary lipid sources (CLO, LO and SFO) in combination with an immunostimulant (β-glucan). In third experiment, head kidney leucocytes (HKL) and peripheral blood mononuclear cells (PBMC) were isolated from common carp fed with different dietary lipid sources (CLO, SO, LO and SLO); cells were then exposed to E.coli LPS. The last experiment was performed using the same lipid sources in third experiment; moreover, two LC-PUFA-supplemented diets (LO + ARA, LOA and SO + DHA, SOD) were formed. Results showed that tested lipid sources did not influence the fish growth and survival but SLO induced a higher feed utilisation. FA tissue compositions were modified by oil sources. The common carp were able to biosynthesize LC-PUFA from PUFA precursors conducting to high level of EPA (from ALA) in LO-fed fish compared to SFO and SO-fed ones or ARA (from LA) in fish fed SO and SFO-based diet even if these LC-PUFAs were totally absent in plant oil-based diets. SLO diet induced the positive effects in terms of balance in synthesized LC-PUFAs compared to their pure plant oils. SFO-based diet induced some alterations of immunomodulatory action of β-glucan in lysozyme activity while this negative effect was exhibited in complement activity for LO-based diet. However, the overall immune status in plant oil-fed fish in normal condition as well as bacterial challenge did not alter compared to fish oil-fed ones. SLO induced the better immunomodulatory responses of fish cells to LPS via the higher eicosanoid metabolism processes. Time and LPS-dose dependences were observed for expression of inflammatory cytokines and other mediators involved in inflammatory processes. HKLs from fish fed plant oil diet more balanced in FA precursors (SLO) or supplemented with ARA (LOA) and DHA (SOD) were exhibited the comparable modulation in acute inflammatory processes with those in CLO leucocytes.

 

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