Intestinal bioavailability of n-3 long-chain polyunsaturated fatty acids influenced by the supramolecular form of phospholipids.

The aim of this work was to study the bioavailability of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), carried by marine phospholipids (PL) and formulated in different supramolecular forms. Marine PL were administrated in rats either (1) in bulk form, or (2) as an oil-in-water emulsion, or (3) as liposomes. Each dietary formulation was characterized by a similar fatty acid (FA) profile and provided the same n-3 LC-PUFA amount. Intestinal bioavailability of n-3 LC-PUFA was monitored in the lymph compartment in a duct fistula model. On the one hand, the emulsification of plant oils with PL increased the overall intestinal absorption of dietary FA by 84% without affecting the lymph FA profile compared with the bulk form, suggesting that emulsification favoured the absorption of the total dietary FA derived from both triglycerides (TG) and PL. On the other hand, the liposome form did not modify the lymph lipid amount compared with the bulk form, but specifically increased the n-3 LC-PUFA levels. The dietary forms of PL influenced the position of some FA on the glycerol backbone of lymph TG and PL. In conclusion, using marine PL as an emulsifier promoted total FA absorption independently of the dietary lipid carrier (TG or PL) and the FA type. Structuring PL as liposomes specifically increased the intestinal bioavailability of FA esterifed in this lipid class, such as DHA, resulting in a higher incorporation into lymph lipids. Thus, using specific PL supramolecular forms would guide n-3 LC-PUFA towards total lipid absorption or specific FA absorption, according to the dietary needs.

In vitro lipolysis and lymphatic absorption of n-3 long-chain PUFA in the rat: influence of the molecular lipid species as carrier.

The aim of this work was to study the bioavailability of fatty acids (FA), focusing on n-3 long-chain (LC) PUFA, carried by different molecular lipid species, that is, phospholipids (PL) or TAG, with three formulations based on fish oils or marine PL, providing a similar n-3 LC PUFA amount. The digestive lipolysis was first assessed using an in vitro enzymatic model. Then, intestinal absorption and enterocyte metabolism were investigated in vivo, on male Wistar rats through lymph lipid analysis. The in vitro results showed that the release of n-3 LC PUFA from lipolysis was increased by 48 % when FA were provided as PL rather than TAG. The in vivo results demonstrated that EPA and DHA from both TAG and PL were similarly absorbed and incorporated into lymph lipids. However, DHA was mainly distributed at the sn-1/3 positions of lymph TAG when provided as marine PL, whereas it was equally distributed at the three positions with marine TAG. On the whole, even if the molecular lipid species of n-3 LC PUFA did not greatly modify the in vivo digestion and absorption steps, it modulated the rearrangement of DHA on the glyceride positions of the lymph TAG, which may further impact the DHA metabolic fate and tissue accretion. Consequently, the present study has provided data which may be used to formulate lipid diets rich in DHA in the context of an insufficient consumption of n-3 PUFA in Western countries.

A critical assessment of transmethylation procedures for n-3 long-chain polyunsaturated fatty acid quantification of lipid classes.

Lipid transmethylation methods described in the literature are not always evaluated with care so to insure that the methods are effective, especially on food matrix or biological samples containing polyunsaturated fatty acid (PUFA). The aim of the present study was to select a method suitable for all lipid species rich in long chain n-3 PUFA. Three published methods were adapted and applied on individual lipid classes. Lipid (trans)methylation efficiency was characterized in terms of reaction yield and gas chromatography (GC) analysis. The acid-catalyzed method was unable to convert triglycerides and sterol esters, while the method using an incubation at a moderate temperature was ineffective on phospholipids and sterol esters. On the whole only the method using sodium methoxide and sulfuric acid was effective on lipid classes taken individually or in a complex medium. This study highlighted the use of an appropriate (trans)methylation method for insuring an accurate fatty acid composition.