INTERACTION OF SESAMIN AND EICOSAPENTAENOIC ACID AGAINST DELTA-5 DESATURATION AND N-6 N-3 RATIO OF ESSENTIAL FATTY-ACIDS IN RAT/

Sesamin is a specific inhibitor of Delta 5 desaturation, the conversio n from dihomo-gamma-linolenic acid (20:3, n-6 to arachidonic acid (AA, 20:4, n-6), Previously, we reported that sesamin inhibited Delta 5 de saturation of n-6 fatty acids in rat hepatocytes but not that of n-3 f atty acids, from 20:4 (n-3) to eicosapentaenoic acid (EPA, 20:5, n-3), In this study, we investigated the interaction of sesamin and EPA on Delta 5 desaturation of both series and the n-6/n-3 fatty acids ratio by measuring actural. fatty acid contents in vivo. Rats were fed three types of dietary oils; 1) linoleic acid (LA, 18:2, n-6): linolenic ac id (LLA, 18:3, n-3) = 3:1, n-6/n-3 ratio of 3:1 (LA group), 2) LA:LLA = 1:3, n-6/n-3 ratio of 1:3 (LLA group), 3) LA:LLA:EPA = 1:0.5:3, n-6/ n-3 ratio of 1:3.5 (EPA group) with or without sesamin (0.5% w/w) for 4 weeks, In all groups, sesamin administration increased the content o f dihomo-gamma-linolenic acid (20:3, n-6) in the liver and decreased t he Delta 5 desaturation index of n-6 fatty acid, the ratio of 20:4/20: 3 (n-6), On the contrary, the Delta 5 desaturation index of n-3 fatty acid, the ratio of 20:5 + 22:5 + 22:6/20:4 (n-3), was increased by the administration of sesamin, These results suggest that sesamin inhibit s the Delta 5 desaturation of n-6 fatty acid, but not that of n-3 fatt y acid in rat livers, Sesamin administration decreased incorporation o f EPA (n-3) and simultaneously increased the AA (n-6) content in the l iver, The n-6/n-3 ratio in the liver was increased by administering se samin under n-3 rich conditions, i.e., the LLA and EPA groups.