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Beyond fatty acid composition of milk fat that can impact the health of consumers, interest is growing regarding the importance of the supramolecular structure of milk lipids on their nutritional properties. Indeed, milk fat is found naturally under the form of an emulsion of lipid droplets called the milk fat globule (MFG) composed of a triglyceride core stabilized by a complex trilayered membrane called the MFG membrane. Recent researches have highlighted that this unique structure and the presence of bioactive lipids such as sphingomyelin could have a beneficial metabolic impact on lipid metabolism and contribute to intestinal and systemic health. The purpose of this chapter is to provide a focused overview on the composition of milk lipids, their organization as MFG and, their impact on lipid digestion and postprandial lipemia. In addition, the long-term effect on lipid metabolism and related metabolic players such as inflammation and gut microbiota are discussed.

Metabolic diseases are characterized by an altered lipid metabolism and metabolic inflammation. Numerous food products contain polar lipid (PL) emulsifiers that could impact these risk factors. We evaluated the impact of using PL from milk (MPL) (i) acutely on lipid digestion and postprandial lipemia and (ii) in the longer term in addition to a high fat diet on adiposity and adipose tissue inflammation. We compared MPL to soybean PL (SPL) that is currently the main commercial source of PL.In mice, an emulsion stabilized by MPL results in a more rapid postprandial lipemia than an emulsion stabilized by SPL, with an early increase in lipemia and a faster clearance. Differences in lipemia can originate from differential kinetics of lipid hydrolysis in the mouse gut, as an increase intestinal TG hydrolysis is observed in vitro. Moreover, early MPL-derived chylomicrons are smaller than SPL-derived chylomicrons. In the longer term, compared with HF diet, HF-SPL diet increases hepatic lipids, white adipose tissue (WAT) mass, with larger and more numerous adipocytes and increases expression of pro-inflammatory adipokines. This is not observed with HF-MPL diet despite similar dietary intakes. HFP-MPL mice have a lower expression in WAT of marker of macrophage infiltration and more numerous goblet cells in the colon, suggesting an improved gut barrier function with this diet.Postprandial lipemia in mice can be modulated by emulsifying with MPL compared with SPL, partly through differences in chylomicron assembly, and intestinal TG hydrolysis rate. Moreover unlike SPL, MPL in a high fat diet do not induce WAT hypertrophy and inflammation, Les maladies métaboliques d’origine nutritionnelle sont caractérisées par un métabolisme des lipides perturbé et une inflammation métabolique. Les lipides polaires (LP) sont des agents émulsifiants utilisés dans l’industrie agroalimentaire. Le but de notre étude a été d’évaluer l’impact de l’utilisation de nouveaux LP issus du lait sur (i) la digestion et le métabolisme postprandial des lipides, et (ii) à plus long terme sur l’adiposité et l’inflammation dans le tissu adipeux (TA), en comparaison avec les LP de soja, actuellement les plus consommés.Chez la souris, les LP laitiers induisent une cinétique de lipémie postprandiale plus précoce en comparaison avec les LP de soja, associée à une augmentation de la lipolyse intestinale in vitro. De plus, les chylomicrons sécrétés durant le pic de lipémie sont plus petits avec les LP laitiers. D’autre part, la substitution d’une partie des lipides d’un régime hyper-lipidique par des LP laitiers ne modifie pas le stockage des lipides dans le foie et le TA contrairement aux LP de soja qui induisent une augmentation des lipides hépatiques, des adipocytes et des marqueurs inflammatoires dans le TA. Par ailleurs, Les LP laitiers induisent une diminution de l’expression génique de marqueurs de l’infiltration macrophagique dans le TA et du nombre de cellules à gobelet dans le côlon, suggérant une barrière intestinale renforcée.Ces travaux démontrent que les LP laitiers, par rapport aux LP de soja, stimulent la digestion des lipides et induisent une cinétique plus rapide de lipémie postprandiale. A long terme ils n’induisent pas les altérations métaboliques du TA observées en présence de LP de soja dans un régime hyper-lipidique

Metabolic diseases of nutritional origin, such as obesity and type 2 diabetes, are characterized by disordered lipid metabolism including postprandial hyperlipemia. Recent works suggest that the composition of dietary fat can modulate the kinetics of postprandial lipemia. In this context, polar lipids (PL) are of utmost importance in food formulation because of their multifunctionality and excellent emulsifying properties. Recently, interest has developed on potential beneficial metabolic effect of dietary PL, among which is improved lipid metabolism. In the present study, we hypothesized that (i) PL from different sources (vegetal vs animal) could have a different impact on postprandial lipemia and (ii) this could be linked to different digestive lipolysis due to emulsion interface. For this purpose, mice were administrated an oral gavage of triacylglycerols (TAG) emulsified with soybean PL or milk PL. The two emulsions presented similar initial lipid phase surface area (i.e. ~24m 2/g of lipid). After gavage, blood samples were collected. We observed higher plasma TAG and Free Fatty Acids (FFA) concentration s at 1 h in mice fed with the milk PL emulsion. Noteworthy, at 4 h plasma TAG and FFA concentrations were significantly lower for these mice suggesting that the kinetics of TAG-rich lipoproteins in plasma depends on the type of emulsifier. Additionally, the two emulsions were digestedin vitro using a static model of human digestion (gastric a nd intestinal phases of 60 minutes using simulated digestive fluids and porcine enzymes mainly). In the gastric phase, the hydrolysis kinetics of TAG were comparable however in the intestinal phase, the kinetics of lipolysis of the milk PL emulsion were faster than thesoybean PL emulsion. All together, these data suggest that the quality of PL have an impact on digestivelipolysis and postprandial lipemia