Soybean oil prevents hypothalamic N3 fatty acid composition but does not prevent peripheral tissue fatty acid disturbance in rats

Linoleic (LA) and alpha-linolenic (ALA) acids are the only truly essential N6 and N3
polyunsaturated fatty acids (PUFAs), and the precursors of arachidonicand
docosahexaenoic (DHA) acids, the most prevalent PUFAs in the mammalian brain.
Whilst main dietary sources of N6 are plant oils and red meat, the main sources of DHA
include seawater fish. This issue becomes apparent when considering typical
westernised diets. Furthermore, marine sources are currently threatened due to
overfishing and no sustainability. Here we investigated the serum, hypothalamus, liver
and white adipose tissues (WAT) fatty acid (FA) composition of rats fed a diet enriched
with either fish oil (FO) or soybean oil (SO). Whilst FO contains abundant DHA, SO
provides small amounts of ALA, alongside its important LAcontent. Fifteen 35-day old
Wistar rats were fed a control chow, or a diet enriched with FO (FOD) or SO (SOD) for
8 weeks. Rats were sacrificed, trunk blood collected, hypothalamus, liver and WAT
dissected, and their FA composition analysed by gas chromatography. FOD increased
N3 content and SOD increased N6 content in all tissues. However, SOD significantly
increased DHAin hypothalamus and serum, a result not observed in other SOD tissues.
Whilst the SOD rats developed obesity, the FOD did not. SOD rats developed obesity
and imbalanced N6/N3 peripherally, but their hypothalamic N3 content was increased.
Such results further corroborate biomagnification and the preferential FAuptake by the
brain. Additional studies are necessary to investigate how nutrient-unbalanced diets
further affect brain metabolism.