Acute plant-derived C18 fatty acid exposure was associated with changes in muscle 5-LOX protein abundance and volatile profiles in triploid rainbow trout (Oncorhynchus mykiss)

Driven by sustainability, plant oils are increasingly used to replace fish oil in aquafeeds, thereby altering muscle fatty acid composition and potentially affecting volatile profiles. Lipoxygenases (LOXs) participate in fatty-acid bioconversion, but the role of 5-lipoxygenase (5-LOX) in non-immune fish muscle remains unclear. We hypothesized that acute intragastric exposure to plant-derived C18 fatty acids would be associated with changes in muscle 5-LOX protein abundance and volatile profiles in triploid rainbow trout. Using an acute oral gavage model, trout received oleic, linoleic, or α-linolenic acid, alone or with the selective 5-LOX inhibitor zileuton. Muscle samples were analyzed for 5-LOX mRNA expression, detectable protein abundance, and volatile profiles. Detectable 5-LOX protein abundance was low under basal conditions and changed after fatty-acid administration, with linoleic acid showing the clearest increase. Several major volatiles also changed across treatments. Under acute fatty-acid exposure, zileuton reduced hexanal concentration by 85.7% (221.2 to 31.6 ng/g) and decreased the nonanal odor activity value by 34.4%. These results indicate that acute plant-derived C18 fatty acid exposure was associated with changes in detectable muscle 5-LOX protein abundance and volatile profiles in triploid rainbow trout. The inhibitor-associated volatile changes further support the possibility that multiple oxidative processes may be involved under these acute conditions.