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Dietary arachidonate (ARA) and its eicosanoid derivatives are major regulators of intestinal homeostasis and repair following injury, it was evaluated the effects of dietary ARA on desaturation and elongation of 13C-18:2(n-6) and mRNA abundance of Δ-6-desaturase (FADS2), elongase (ELOVL5), and Δ-5-desaturase (FADS1) in liver and intestine in piglets. Colostrum fed piglets (n=96) were acquired at 12–24 h of age and individually caged. Piglets were randomly allocated to 0, 0.5, 2.5, or 5% ARA or 5% eicosapentaenoid diets (EPA) diets differing in fatty acid composition. Pigs were euthanized after 0, 4, 8, and 16 d of treatment (n = 6). Liver and ileal mucosal samples were immediately frozen in liquid nitrogen and stored at -80ºC for subsequent mRNA quantification. Fresh liver and tissue homogenates were processed immediately for 13C-18:2(n-6) flux analyses.
In liver, the desaturation rate [nmol/(g tissue x h)] of 13C-18:2(n-6) to 13C-18:3(n-6) decreased 56% between 4 and 16 d but was not affected by diet. Whereas accumulation in 13C-20:3(n-6) also decreased with age by 67%, it increased linearly with increasing dietary ARA (P < 0.06). In comparison, intestinal flux was ~50% less than liver flux and was unaffected by age, but desaturation to 13C-18:3(n-6) increased linearly (by 57%) in pigs fed ARA diets (P < 0.001), equaling the rate observed in sow-fed controls. In both liver and intestine, alternate elongation to 13C-20:2(n-6) (via Δ-8-desaturase) was markedly elevated in pigs fed the 0% ARA diet compared with all other dietary treatments (P < 0.01). Transcript abundance of FADS2, ELOVL5, and FADS1 was not affected in liver by diet (P > 0.05) but decreased precipitously between birth and d 4 (~70%; P < 0.05). In contrast, intestinal abundance of FADS2 and FADS1 increased 60% from d 4 to 16.
In conclusion, dietary ARA regulated the desaturase-elongase pathway in a tissue-specific manner. In liver, ARA had modest effects on (n-6) fatty acid flux, and intestinal FADS2 activity and mRNA increased. Additionally, hepatic flux decreased with postnatal age, whereas intestinal flux did not change.
SK Jacobi, X Lin, BA Corl, HA Hess, RJ Harrell, J Odle. 2011. Dietary arachidonate differentially alters desaturase-elongase pathway flux and gene expression in liver and intestine of suckling pigs. The Journal of Nutrition, 141: 548–553. doi:10.3945/jn.110.127118.