Dietary linoleic acid (LA) does not alter renal phospholipid arachidonic acid (ARA) but does significantly alter oxylipins in renal tissue of obese rats

Concerns have been raised regarding the potential of dietary LA to elevate inflammation by increasing the production of n6 derived oxylipins. To examine the effect of dietary LA on ARA and oxylipin concentrations, renal phospholipid fatty acid and oxylipin concentrations were examined in obese rats provided diets varying only in oil content for 8 weeks. The oils and alpha linolenic acid (ALA) to LA (g per 100 g oil) content were as follows: canola to flax (20 to 18), canola (8 to 18), soy (9 to 53), high oleic canola to canola (5 to 16), high oleic canola (2 to 15), lard to soy (1 to 8), and safflower (0.2 to 73). Renal phospholipid fatty acids were analyzed by TLC and GC, and oxylipins were determined using HPLC/MS/MS. Thirty oxylipins were quantified in renal tissue. LA and ALA oxylipins were present at significant levels, with LA oxylipins being approximately twice the concentration of ARA oxylipins. Increasing the LA level in the diet did not change renal ARA concentrations but did alter ARA derived oxylipin levels. However, the differences were only observed with large variations in dietary LA. For example, dihydroxyeicosatrienoic acids and hydroxyeicosatetraenoic acids were 77 and 42 percent  higher, respectively, in kidneys from rats provided the safflower diet versus lard to soy diet. On the other hand, the levels of renal LA derived oxylipins were increased by as much as 7 fold when provided the safflower diet. Similarly, dietary ALA did not alter renal docosahexaenoic acid (DHA) levels or DHA oxylipins except when compared to the safflower diet that was almost devoid of ALA. Dietary ALA significantly altered renal ALA, EPA, and oxylipins derived from these fatty acids. Since LA oxylipins have demonstrated biological effects and are present in high quantities in tissue, these data indicate that increased dietary LA has important physiological effects that are not evident by examination of ARA concentrations alone. (Authors abstract)