Dietary linoleic acid elevates endogenous 2-arachidonoylglycerol and anandamide in Atlantic salmon (Salmo salarL.) and mice, and induces weight gain and inflammation in mice

Abstract

Dietary intake of linoleic acid (LA) has increased dramatically during the twentieth century and is associated with a greater prevalence of obesity. Vegetable oils are recognised as suitable alternatives to fish oil (FO) in feed for Atlantic salmon (Salmo salar L.) but introduce high amounts of LA in the salmon fillet. The effect on fish consumers of such a replacement remains to be elucidated. Here, we investigate the effect of excessive dietary LA from soyabean oil (SO) on endocannabinoid levels in Atlantic salmon and mice, and study the metabolic effects in mice when SO replaces FO in feed for Atlantic salmon. Atlantic salmon were fed FO and SO for 6 months, and the salmon fillet was used to produce feed for mice. Male C57BL/6J mice were fed diets of 35 % of energy as fat based on FO- and SO-enriched salmon for 16 weeks. We found that replacing FO with SO in feed for Atlantic salmon increased LA, arachidonic acid (AA), decreased EPA and DHA, elevated the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (AEA), and increased TAG accumulation in the salmon liver. In mice, the SO salmon diet increased LA and AA and decreased EPA and DHA in the liver and erythrocyte phospholipids, and elevated 2-AG and AEA associated with increased feed efficiency, weight gain and adipose tissue inflammation compared with mice fed the FO salmon diet. In conclusion, excessive dietary LA elevates endocannabinoids in the liver of salmon and mice, and increases weight gain and counteracts the anti-inflammatory properties of EPA and DHA in mice.

Early Low-Fat Diet Enriched With Linolenic Acid Reduces Liver Endocannabinoid Tone and Improves Late Glycemic Control After a High-Fat Diet Challenge in Mice

“…Evidence has accumulated indicating a tonic overactivation of ECS after HFD-induced obesity (14,35,47). Nevertheless, data from the literature (12,14,48) also suggest that the effect of HFD feeding on peripheral EC levels may depend on the FA composition of the diet. In the current study, we consistently observed that tissue EC contents were generally higher after long-term administration of an HFD, whatever the early LFD.…”

“…AA is endogenously biosynthesized from the essential FA (10) linoleic acid (LA [or C18:2n-6]). As a consequence, a dietary supplementation in LA (11,12) or AA itself (13) is able to elevate the tissue contents of EC. Conversely, diets enriched with n-3 polyunsaturated FAs, such as eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (DHA [or C22:6n-3]), cause a decrease in 2-AG and AEA levels because of the replacement of AA in phospholipids with such FAs (13,14).…”

Modulation of plasma N-acylethanolamine levels and physiological parameters by dietary fatty acid composition in humans

“…Furthermore, a similar trend was exhibited with DHEA/OEA and percent android fat, indicating that OEA levels have less affi nity for android fat distribution when compared with both AEA and DHEA. It has been identifi ed that the effect of AEA on weight gain can be reduced with the inclusion of dietary EPA and DHA and can reduce visceral fat mass in rats ( 15,30,31 ), thus the observation that DHEA, the NAE-analog of DHA, was correlated with android fat deposition more so than OEA suggests that circulating OEA levels may contribute to a more desirable regional body fat deposition profi le than do other NAEs. Moreover, it was also observed that plasma NAE levels exhibited a moderate direct correlation with carbohydrate oxidation but were inversely correlated with fat oxidation, both resting and postprandial, of which plasma AEA levels showed the strongest correlation.…”

Fish Nutrition and Current Issues in Aquaculture: The Balance in Providing Safe and Nutritious Seafood, in an Environmentally Sustainable Manner

“…From a human health standpoint, increases in ω6 fatty acids in salmon fillets are a concern. When mice were fed farmed salmon raised on diets with 100% soybean oil, the excessive dietary LA elevated endocannabinoids in the liver, increased weight gain and counteracted the anti-inflammatory properties of EPA and DHA [69] and also exaggerated insulin resistance and increased accumulation of fat in the liver in rats [34]. The typical "Western" diet is already dangerously high in ω6 fatty acids, which is why it is so important to consume fish that are high in ω3 fatty acids to balance this ratio.…”