The intake of the essential fatty acid precursor α-linolenic acid (ALA) contributes to ensure adequate n-3 long-chain polyunsaturated fatty acid (LC-PUFA) bioavailability. Conversely, linoleic acid (LA) intake may compromise tissue n-3 PUFA status as its conversion to n-6 LC-PUFA shares a common enzymatic pathway with the n-3 family. This study aimed to measure dietary ALA and LA contribution to LC-PUFA biosynthesis and tissue composition. Rats were fed with control or experimental diets moderately enriched in ALA or LA for 8 weeks. Liver Δ6- and Δ5-desaturases were analyzed and FA composition was determined in tissues (red blood cells, liver, brain and heart). Hepatic Δ6-desaturase activity was activated with both diets, and Δ5-desaturase activity only with the ALA diet. The ALA diet led to higher n-3 LC-PUFA composition, including DHA in brain and heart. The LA diet reduced n-3 content in blood, liver and heart, without impacting n-6 LC-PUFA composition. At levels relevant with human nutrition, increasing dietary ALA and reducing LA intake were both beneficial in increasing n-3 LC-PUFA bioavailability in tissues.
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