Modulation of the brain lipids after long-term exposure to diets varying in their ratio and content in omega-6 and omega-3 polyunsaturated fatty acids in mice.

Lipids are essential for brain physiology. Although dietary lipids, including polyunsaturated fatty acids (PUFAs), are known to influence brain lipid composition, few studies have been conducted under conditions that reflect realistic societal challenges and long-term dietary exposure patterns. The primary objective of this study was to assess the effect of long-term dietary exposure to two n-6/n-3 PUFA precursor ratios reflecting health recommendations versus a Western diet, on the lipid composition of different brain structures (cortex, cerebellum, striatum, hippocampus and hypothalamus) in mice, as well as on cortical oxidative stress and inflammation. For this purpose, we used diets containing 5% fat by weight with two n-6/n-3 PUFA precursor ratios: LA/ALA = 5:1 (recommended ratio) and LA/ALA = 15:1 (Western diet-like ratio). We also studied the impact of supplementing a Western diet with fish oil rich in DHA and EPA. Lipid classes, as well as the fatty acid composition -including PUFAs- of brain structures were differentially affected by the diets. At an equivalent dietary n-6/n-3 PUFA ratio (5:1), fish oil rich in EPA and DHA as the main source of dietary n-3 PUFAs did not increase brain DHA levels compared with intake derived solely from ALA in vegetable oils. Supplementation in EPA- and DHA-rich fish oil exerted a greater effect on cortical oxidative and inflammatory status than a high LA/ALA ratio. Further studies are needed to determine how these PUFA-associated alterations affect brain structure function and/or homeostasis.