Dietary n-6/ n-3 Ratio Influences Brain Fatty Acid Composition in Adult Rats

Abstract

There is mounting evidence that diets supplemented with polyunsaturated fatty acids (PUFA) can impact brain biology and functions. This study investigated whether moderately high-fat diets differing in n-6/n-3 fatty acid ratio could impact fatty acid composition in regions of the brain linked to various psychopathologies. Adult male Sprague Dawley rats consumed isocaloric diets (35% kcal from fat) containing different ratios of linoleic acid (n-6) and alpha-linolenic acid (n-3) for 2 months. It was found that the profiles of PUFA in the prefrontal cortex, hippocampus, and hypothalamus reflected the fatty acid composition of the diet. In addition, region-specific changes in saturated fatty acids and monounsaturated fatty acids were detected in the hypothalamus, but not in the hippocampus or prefrontal cortex. This study in adult rats demonstrates that fatty acid remodeling in the brain by diet can occur within months and provides additional evidence for the suggestion that diet could impact mental health.

Keywords: brain; diet; linoleic acid; polyunsaturated fatty acids; rat; α-linolenic acid.

Figure 1

Prefrontal Cortex (PFC), hippocampus (HPC), and hypothalamus (HYP) composition of (a) total saturated fatty acids (SFA); (b) total monounsaturated fatty acids (MUFA); (c) total n-3 polyunsaturated fatty acids (PUFA); (d) total n-6 PUFA; (e) n-3 PUFA:LC-PUFA ratio, which was calculated as the sum of EPA+DPAn-3+DHA/sum of all PUFA ≥ 20 carbons; and (f) DHA:AA ratio in rats fed experimental diets. Values correspond to % fatty acid ± standard error of the mean (n = 6–8 rats per diet group). The * denotes statistical difference between diet groups within brain regions (α ≤ 0.05). FD, flaxseed diet (low n-6/n-3 ratio); SD, safflower diet (high n-6/n-3 ratio).