THE METABOLISM AND N-6 N-3 RATIO OF ESSENTIAL FATTY-ACIDS IN RATS - EFFECT OF DIETARY ARACHIDONIC-ACID AND A MIXTURE OF SESAME LIGNANS (SESAMIN AND EPISESAMIN)/

In this study, we examined the effect of dietary arachidonic acid (AA) and sesame lignans on the content and n-6/n-3 ratio oi polyunsaturate d fatty acid (PUFA) in rat liver and the concentrations of triglycerid e (TC) and ketone bodies in serum. For 4 wk, rats were fed two types o f dietary oils: (i) the control oil diet groups (CO and COS): soybean oil/perilla oil = 5:1, and (ii) the AA-rich oil group (AO and AOS): AA ethyl esters/palm oil/perilla oil = 2:2:1, with (COS and AOS) or with out (CO and AO) 0.5% (w/w) of sesame lignans. Dietary AA and sesame li gnans significantly affected hepatic PUFA metabolism. AA content and n -6/n-3 ratio in the liver were significantly increased in the AO group , despite the dietary total of n-6 PUFA being the same in all groups, while AOS diet reduced AA content and n-6/n-3 ratio to a level similar to the CO and COS groups. These results suggest that (i) dietary AA c onsiderably affects the hepatic profile and n-6/n-3 ratio of PUFA, and (ii) dietary sesame lignans reduce AA content and n-6/n-3 ratio in th e liver. In the AO group, the concentration of acetoacetate was signif icantly increased, but the ratio of beta-hydroxybutyrate/acetoacetate was decreased. On the other hand, the AO diet increased the concentrat ion of TG in serum by almost twofold as compared to other groups, Howe ver, the AOS diet significantly reduced serum TG level as compared to the AO group. In addition, the AOS diet significantly increased the ac etoacetate level, but reduced the beta-hydroxybutyrate/acetoacetate ra tio. These results suggest that dietary sesame lignans promote ketogen esis and reduce PUFA esterification into TG. This study resulted in tw o findings: (i) sesame lignans inhibited extreme changes of the n-6/n- 3 ratio by reducing hepatic PUFA content, and (ii) the reduction of he patic PUFA content may have occurred because of the effects of sesame lignans on PUFA degradation (oxidation) and esterification.