Dietary LA and sex effects on oxylipin profiles in rat kidney, liver, and serum differ from their effects on PUFAs

Abstract

A vast literature on fatty acids in mammals exists, but comparable compositional data on oxylipins is lacking. Weanling Sprague-Dawley rats were therefore provided control diets or diets with higher linoleic acid (LA) or with higher LA and α-linolenic acid (LA+ALA) for 6 weeks. Kidneys, livers, and serum were analyzed for oxylipins and fatty acids. The proportion of tissue oxylipins derived from LA was greater than the relative proportion of LA itself, whereas arachidonic acid (AA) oxylipins were overrepresented in serum. Higher dietary LA increased kidney LA and AA oxylipins, despite not altering LA or AA. In liver, both LA and AA and their oxylipins were higher, whereas in serum only LA oxylipins were higher with higher dietary LA. Higher LA resulted in a higher ratio of n-6/n-3 PUFA-derived oxylipins; adding ALA to the LA diet mitigated this and many, but not all, effects of the LA diet. Approximately 40% of oxylipins detected were influenced by sex and, unlike their PUFA precursors, most (>90%) of these were higher in males. These differences in dietary LA and sex on oxylipin and fatty acid profiles further our understanding of the effects of fatty acids and may have implications for dietary LA recommendations.

The Brain Oxylipin Profile Is Resistant to Modulation by Dietary n‐6 and n‐3 Polyunsaturated Fatty Acids in Male and Female Rats

“…In kidneys, adipose (Leng et al, ; Mendonça et al, ), and heart (unpublished data), oxylipins derived from LNA have the highest mass, and in liver the ARA oxylipins have the greatest mass, but only make up approximately 40% of the total (Leng et al, ). Interestingly, serum has similarly high levels of ARA oxylipins, but very low levels of DHA oxylipins (Leng et al, , ). The rat whole brain oxylipin profile reported herein was similar to the female mouse whole brain profile (Ostermann et al, ).…”

“… All ingredients were from Dyets (Bethlehem, PA, USA), except EPA fish oil (95.3% EPA) and DHA fish oil (95.1% DHA) that were from Larodan (Solna, Sweden), and TBHQ was from Sigma‐Aldrich (Oakville, ON, Canada). Adapted from Leng et al, , , and Mendonça et al, . ALA, α‐linolenic acid; ARA, arachidonic acid; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; LNA, linoleic acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acids. …”

“…All ingredients were from Dyets (Bethlehem, PA, USA), except EPA fish oil (95.3% EPA) and DHA fish oil (95.1% DHA) that were from Larodan (Solna, Sweden), and TBHQ was from Sigma‐Aldrich (Oakville, ON, Canada). Adapted from Leng et al, , , and Mendonça et al, .…”

“…Increased dietary n‐6 PUFA (LNA) feeding results in increased LNA and ARA oxylipins and decreased EPA oxylipins in the cerebral cortex of rat brain (Taha et al, ), while limiting dietary LNA reduces lipopolysaccharide (LPS)‐induced increases in the brain PGE 2 concentration (Taha et al, ). However, while the effects of dietary PUFA on brain fatty acid composition have been well characterized, oxylipin profiles do not necessarily reflect tissue precursor PUFA composition (Leng et al, , ; Mendonça et al, ). Thus, while there is more DHA than ARA in the brain (Innis, ; Sun et al, ), for example, whether DHA oxylipins constitute the majority of brain oxylipins is not clear.…”

“…For example, 17‐β‐estradiol treatment in ovariectomized rats increases basal PGI 2 synthesis in cerebral blood vessels compared to untreated control rats (Ospina et al, ). There are also few studies of sex differences on the oxylipin profile in other tissues, but these indicate that oxylipins are generally higher in males in kidneys, liver, and serum (Leng et al, , ), and higher in females in heart (unpublished data) and adipose tissues (Mendonça et al, ). Furthermore, in these latter tissues, diet can influence the sex differences—for example, adipose oxylipins are higher in male rats provided a DHA‐rich diet but higher in female rats provided diets enriched in either α‐linolenic acid (ALA) or EPA (Mendonça et al, ).…”