Organisation structurale et moléculaire des lipides dans les aliments : impacts possibles sur leur digestion et leur assimilation par l’Homme

Abstract

From the nutrition point of view, lipids are primarily considered as energy suppliers, their dietary intake having to be limited. In fact, lipids are sources of various fatty acids, and dietary recommendations include the required daily intakes in different fatty acids (fatty acid profile). Beyond these quantitative aspects, fatty acids are part of larger molecules, mainly triacylglycerols (TAG), that are organized in supramolecular structures as for example fat crystals and lipid droplets. Recent advances in nutrition research have demonstrated that these structures, and lipid organization in food matrices, influence digestibility and metabolism of fatty acids. Therefore, the members of the technological network Listral propose a synthesis of the knowledge about the influence of molecular and supramolecular structures of lipids on digestion and metabolic fate of dietary fatty acids originating from for the main food industry sectors. Fatty acids are mainly provided in the diet in the form of TAG, or phospholipids (PL) where they are esterified in external (sn-1, sn-3) or internal (sn-2) position of the glycerol backbone. They can also be found as ethyl esters (EE) in specific formulations. These molecular characteristics of the lipid molecules affect their hydrolysis and their absorption rate but also their metabolism in indifferent organs, as assessed in studies often using inter esterified fat sources. The results depend on the types of fatty acids (saturated or polyunsaturated fatty acids) but also on the model used for the studies: in vitro or in vivo studies ; animal model, human newborn or adult, either healthy or exhibiting some diseases. Among others, it was found that the crystal form and fat melting point as affected by the fatty acid profiles and the lipid molecular structures directly impact fatty acid absorption kinetics through modifications of lipolytic enzyme activities. However, in these studies, the relative effect of the thermal properties of lipids and the proportion of saturated fatty acids chains in sn-2 position were hardly distinguished. Supramolecular structures, namely type and size of the fat droplets and their interfacial composition, of lipids, either in their native forms or obtained after food processes, also affect the digestibility and absorption of lipids. This aspect is reviewed with specific focus on dairy, marine, meat, oil plant and egg products. The impact of other nutritional components present in these food matrices on the absorption of lipids is also discussed.

Molecular and structural organization of lipids in foods: their fate during digestion and impact in nutrition

“…Common characteristics are a TAG core surrounded by an interface or a membrane varying in composition, organization and complexity. In raw milk, the lipid globule is stabilized by a complex trilayer membrane made of phospho-and sphingo-lipids, cholesterol and proteins (Lopez, 2011;Raynal-Ljutovac et al, 2011). In egg yolk, the TAG core is stabilized by a monolayer interface containing phospholipids, proteins and cholesterol.…”

“…Since then, the interest of emulsion as carrier or delivery systems for nutrients, lipophilic bioactive compounds or drugs is booming (Velikov and Pelan, 2008;Raynal-Ljutovac et al, 2011;Yao et al, 2014;Livney, 2015;Mao and Miao, 2015;Norton et al, 2015;Singh et al, 2015;Joyce et al, 2016;Zhang et al, 2016). Some schematic structures of these delivery structures are presented in Figure 3.…”

Shiga Toxin-Producing Escherichia coli and Milk Fat Globules

“…Complex fat supramolecular organizations are also found in egg yolk or oilseeds in the form of oleosomes [ 64 ]. The MFGM is made of phospho- and sphingolipids, cholesterol, and proteins [ 65 , 66 ]. As a consequence of the mechanism of milk fat secretion from mammary epithelial cells, the MFGM is a complex trilayered structure, comprising a monolayer of polar lipids derived from the endoplasmic reticulum and a bilayer of polar lipids originating from the apical plasma membrane of the mammary secretory cells [ 67 , 68 , 69 ].…”

Impact of Rapeseed and Soy Lecithin on Postprandial Lipid Metabolism, Bile Acid Profile, and Gut Bacteria in Mice

“…Indeed, the FA composition of vegetable oils, as well the distribution of the FA within TAG molecules, has been shown to modulate their digestion rates and extent. [53,54] The observed difference between the two lecithins on plasma ALA abundance may also arise from a synergistic effect of ALA with other FA. In a combination of in vitro and in vivo studies, the digestion and absorption of ALA was greater when it was incorporated in rapeseed oil, rich in oleic acid and ALA, than that in sunflower oil, rich in n-6 PUFA.…”