Biodisponibilité et devenir métabolique de l’ALA en fonction du niveau alimentaire chez les rongeurs
Intervention orale de Leslie Couëdelo, Responsable Projet Nutrition-Santé & Biochimie des Lipides, au 17ème Congrès Euro Fed Lipid, 22 octobre 2019 : « Bioavailability and metabolic fate of ALA according to its food level in rodents ».
Omega-3 (n-3) polyunsaturated fatty acids (PUFA) are essential for the organism and are associated with positive health effects for the prevention of several diseases. However, the n-3 PUFA intakes, and especially in alpha-linolenic acid (ALA), the metabolic precursor of n-3 long-chain (LC) PUFA (EPA and DHA), are twice lower than the national advises. Because of its high susceptibility towards B-oxidation, in which way could we improve the ALA bioavailability and its bioconversion in n-3 LC-PUFA without generating lipid oxydation and oxydative stress?
The impact of ALA dietary level on its bioavailability, and its bioconversion in n-3 LC-PUFA, were followed in rats on a 60-day kinetics (D0, D15, D30 and D60) without occulting their impact on lipid peroxidation and oxidative stress. Four lipid formulas were designed so that only the ALA proportions were variables (0, 0.3, 1 and 2.5% TEI) in the experimental diets.
This nutritional study showed that when the diet is devoid in n-3 PUFAs, ALA levels but also those of EPA and DHA decrease in all lipid fractions of the liver and plasma. Considering DHA, its level is more slowly lowered in the PLs, suggesting that it is preserved as much as possible to limit its deficiency. However as soon as the diet provides ALA, its bioavailability and its bioconversion in EPA is linearly correlated with the ALA intake (R2=0.98). From 0.3 to 2.5% of ALA in the diet, ALA and EPA are mostly packaged in all lipid fractions (TG, CE and FFA) of the blood and the liver. But only 0.3% of ALA promotes the maximal bioconversion in DHA, wich preserve its levels in PL and TG in the liver and plasma. Moreover, the improvement ALA bioconversion in EPA and DHA has not shown any impact on the oxidative stress and lipid peroxidation in plasma and liver. Our study demonstrate that 15 days of 1% ALA intake in the diet is sufficient to promote its bioavailability and its bioconversion in EPA and DHA, to maintain their higest levels in all lipid fractions of the plasma and liver. These n-3 PUFA enrichments in plasma and hepatic lipids could impact the quality of lipoproteins synthesized by the liver (HDL, LDL) and their metabolic fate in the peripheral cells.
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