Linoleic and α-linolenic acid as precursor and inhibitor for the synthesis of long-chain polyunsaturated fatty acids in liver and brain of growing pigs.
Level 5 - mechanism / opinion, no new human data
Animal study (growing pigs)
PubMed 22436184 · doi:10.1017/S1751731111001479
What was done
In a 2 × 2 factorial arrangement, 32 growing gilts from eight litters received one of four diets varying in linoleic acid (LA) and α-linolenic acid (ALA) intake. Low and high ALA intakes were 0.15 and 1.48 g/kg BW^0.75 per day, while low and high LA intakes were 1.31 and 2.65 g/kg BW^0.75 per day. Authors evaluated fatty acid composition and mRNA expression of Δ5-desaturase, Δ6-desaturase, elongase-2, and elongase-5 in liver and brain tissues.
What was found
Dietary LA increased arachidonic acid (ARA) in the liver. High ALA intake increased hepatic eicosapentaenoic acid (EPA) but decreased docosahexaenoic acid (DHA) (all P < 0.01) and reduced ARA by >40%. High LA intake decreased hepatic EPA by >35% and DHA by >20% (all P < 0.001). Liver mRNA levels of Δ5- and Δ6-desaturase increased with LA intake, and elongase-2 mRNA increased with both ALA and LA intakes. Brain DHA levels were virtually unaffected by dietary LA and ALA.
Why it matters
This study provides mechanistic evidence that dietary linoleic acid competitively suppresses hepatic long-chain n-3 fatty acid synthesis. It also indicates that brain DHA concentrations are buffered against dietary fluctuations in precursor fatty acids in growing pigs.
Limits
The study was conducted exclusively in growing female pigs, which limits direct extrapolation to human metabolism. The abstract does not report absolute baseline or final fatty acid concentrations, study duration, or functional neurological outcomes.
Cited by
- supports High levels of omega-6 fatty acids compete for shared enzymes and reduce the conversion of plant-based ALA to EPA and DHA.