Lisa Kolden Midtbø:
Background: Due to a growing global aquaculture production, fish oil (FO) and fish meal (FM) are partly replaced with vegetable ingredients in aqua feed for Atlantic salmon. These replacements in the feed lead to an altered fatty acid composition in the salmon fillet. We aimed to investigate how these changes affects obesity development and insulin sensitivity in mice eating the salmon.
In addition, we wanted to investigate how the background diet affects the antiobesity effect of FO.
Results: Western diets (WDs) were produced containing salmon fed either FO (WD-FO), or with partly replacement (80%) of FO with different vegetable oils (VOs); rape seed oil (WDRO), olive oil (WD-OO) or soybean oil (WD-SO). These diets were given to C57BL/6J mice, and mice had higher hepatic lipid accumulation and lower insulin sensitivity when given WD-SO compared with WD-FO. Mice given WD-SO had higher hepatic levels of diacylglycerol (DAG), ceramides and arachidonic acid (AA)-derived oxylipins compared with mice fed WD-FO. In addition, C57BL/6J mice were fed fish oil-enriched diets with different carbohydrate sources, and we observed that sucrose dose-dependently abrogate the antiobesity effect of fish oil. High-GI starch had a stronger effect on reducing the antiobesity effect of FO compared with low-GI starch.
Conclusions: In summary, our results demonstrate that the background diet affects the antiobesity effect of FO and that replacement of FO with SO in aqua feed increased hepatic lipid accumulation and reduces insulin sensitivity. Elevated hepatic levels of DAG, ceramides and AA-derived oxylipins might be a link between the observed hepatic lipid accumulation and the reduced insulin sensitivity.