Dietary n-6 PUFA deprivation for 15 weeks reduces arachidonic acid concentrations while increasing n-3 PUFA concentrations in organs of post-weaning male rats

Abstract

Few studies have examined effects of feeding animals a diet deficient in n-6 polyunsaturated fatty acids (PUFAs) but with an adequate amount of n-3 PUFAs. To do this, we fed post-weaning male rats a control n-6 and n-3 PUFA adequate diet and an n-6 deficient diet for 15 weeks, and measured stable lipid and fatty acid concentrations in different organs. The deficient diet contained nutritionally essential linoleic acid (LA,18:2n-6) as 2.3% of total fatty acids (10% of the recommended minimum LA requirement for rodents) but no arachidonic acid (AA, 20:4n-6), and an adequate amount (4.8% of total fatty acids) of alpha-linolenic acid (18:3n-3). The deficient compared with adequate diet did not significantly affect body weight, but decreased testis weight by 10%. AA concentration was decreased significantly in serum (-86%), brain (-27%), liver (-68%), heart (-39%), testis (-25%), and epididymal adipose tissue (-77%). Eicosapentaenoic (20:5n-3) and docosahexaenoic acid (22:6n-3) concentrations were increased in all but adipose tissue, and the total monounsaturated fatty acid concentration was increased in all organs. The concentration of 20:3n-9, a marker of LA deficiency, was increased by the deficient diet, and serum concentrations of triacylglycerol, total cholesterol and total phospholipid were reduced. In summary, 15 weeks of dietary n-6 PUFA deficiency with n-3 PUFA adequacy significantly reduced n-6 PUFA concentrations in different organs of male rats, while increasing n-3 PUFA and monounsaturated fatty acid concentrations. This rat model could be used to study metabolic, functional and behavioral effects of dietary n-6 PUFA deficiency.

Fig. 1

Body weights of rats fed n-6 PUFA adequate (○) and deficient diets (•) over 15 weeks after weaning. Values are mean ± SD (n=10 for both dietary groups).

Fig. 2

Fatty acid concentrations in serum total lipids of rat fed n-6 PUFA adequate (○) and deficient (•) diets over 15 weeks. (A) LA, (B) AA, (C) 20:3n-9, (D) α-LNA, (E) EPA, (F) DHA. Values are mean ± SD (n=4–5 for both dietary groups). * p<0.05, **p<0.01, and ***p<0.001 differs significantly from mean in the adequate group.