LIPID MEDIATORS OF INFLAMMATION RESOLUTION IN GILTHEAD SEABREAM Sparus aurata: EFFECTS OF INSECT OIL INCLUSION UNDER ACUTE STRESS

Introduction and Methodology

Inflammation is a natural biological process that eliminates harmful stimuli and promotes tissue repair. Under normal conditions, inflammation resolution is actively mediated by specialized pro-resolving lipid mediators (SPMs) derived from the n-3 long-chain polyunsaturated fatty acids, EPA and DHA. However, disruption of this process under stressful conditions may impair immune homeostasis and compromise health. While SPMs have been studied in mammals, their role in teleost fish remains poorly understood. In aquaculture, the increasing use of alternative lipid sources, such as insect oils, raises questions about their impact on lipid-mediated pathways involved in stress and inflammation, particularly under routine practices such as confinement and handling. The present study evaluated the response of juvenile gilthead seabream (Sparus aurata) to an acute stress event after 56 days of feeding with one of two experimental diets: a control diet containing fish oil and poultry oil, or a BSFLO diet in which Hermetia illucens oil fully replaced poultry oil (5.2% inclusion). Fish were then subjected to 1 min of air exposure followed by confinement. Blood samples were collected at the end of the feeding trial (before stress exposure) and 90 min after stress exposure to quantify resolvin-E1 and maresin-1 in plasma. These plasma SPMs were measured by ELISA (n=9) and analysed by two-way ANOVA (diet and stress as fixed factors).

Results

Acute stress significantly reduced plasma resolvin-E1 levels (p = 0.009), with higher values in non-stressed fish regardless of diet, while maresin-1 remained unchanged. Diet did not affect resolvin-E1, but BSFLO-fed fish tended to show higher maresin-1 levels (p = 0.069). These findings suggest a rapid utilization of resolvin-E1 during the early phase of inflammation resolution, whereas maresin-1 may contribute to later stages of the process. Further research is required to better elucidate the temporal dynamics of inflammation resolution in gilthead seabream.

Acknowledgment

This work has been supported by InsectERA Mobilizing Agenda (PRR - InsectERA - The ERA of the insect industry), funded by Portugal and European Union - NextGenerationEU, with the identifier C644917393-00000032. S. Moutinho was supported by FCT (2024.12176.CEECIND).