Flax Lignans modulate the digestion and absorption of α-linolenic acid in sunflower phospholipid-stabilized nanoemulsions: In vitro digestion simulation and in vivo studies in mice

Dietary supplementation with plant-derived α-linolenic acid (ALA), relying on its metabolic conversion into n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs), has the potential to optimize the dietary fatty acid profile and alleviate the global issue of insufficient n-3 LCPUFAs intake. Current research investigates the effects of flax lignans, with varying doses and structures, on the intestinal digestion-absorption and lymph-blood transport of ALA in sunflower phospholipid-stabilized nanoemulsions. The results indicated that the incorporation of flax lignans at various doses did not significantly alter the physical properties of nanoemulsions. However, medium and high doses of flax lignans, especially those partitioned within the aqueous phase and interface, reduced the release of free fatty acids and ALA content in micelles by potentially inhibiting enzyme activity during in vitro digestion. Meanwhile, intragastric administration of medium- or high-dose flax lignan-nanoemulsions decreased serum triglyceride, total cholesterol, and ALA levels, suggesting an inhibition of lymph-blood transport of ALA-containing chylomicrons. In contrast, the co-delivery of low-dose lignan-nanoemulsions increased serum ALA levels, particularly in flax lignan macromolecule (FLM, +31.4 %) and secoisolariciresinol (SECO, +39.6 %) nanoemulsions groups. Further results revealed that low-dose lignans enhanced ALA bioavailability (14.6 %-45.9 %), acting in a “rate-decelerating but efficiency-enhancing” manner based on the area under the blood concentration-time curve, accompanied by significant effects of FLM and SECO. Therefore, regulating the intestinal digestion and absorption of ALA-containing nanoemulsions may be an effective strategy to improve ALA lymph-blood transport and potential substrate levels for hepatic metabolic conversion. This research supports designing precise dietary delivery systems to improve ALA bioavailability.