The size and interfacial composition of milk fat globules are key factors controlling triglycerides bioavailability in simulated human gastro-duodenal digestion
Résumé
Lipids organisation might modulate fatty acid bioavailability leading to health implications. We determined
whether the size and the interfacial composition of cow milk fat globules could affect triglycerides
digestibility. Native fat globules of various sizes covered by their biological membrane (4.2 mm, large LFG
6.6 mm, small SFG 1.7 mm) or homogenised heat-treated (0.3 mm) were digested in gastric and duodenal
conditions simulating human physiology. Lipolysis extents were calculated from the amount of free fatty
acids generated, and the fatty acid composition of the products of lipolysis was determined by GC
analysis. SFG were more efficiently hydrolysed than LFG by gastric (13.3 versus 5.6%), gastric plus
pancreatic (62.9 versus 48.7%) and pancreatic (79.6 versus 54.7%) lipases. A higher lipid interface area
with native SFG, that might increase lipases binding sites, can explain these results. However, the homogenisation, which markedly decreases fat globule size increasing consequently the lipid/water
interface area, did not improve gastric (9%) or duodenal (64.5%) lipolysis probably due to an important
change in globule surface composition (proteins versus phospholipids). Interestingly, the size of the milk
globule (SFG and HM versus NM and LFG) controls the type of the free fatty acids generated by the
human gastric lipase, palmitic versus oleic acid, suggesting a different orientation of the accessible mixed
triglycerides. Moreover, the type of monoglycerides produced from SFG digestion could be less atherogenic
compared to LFG. The size of fat globules governs gastric and duodenal lipolysis extent when the
composition of the interfacial layer is appropriate. It might further control fatty acid bioavailability
impacting on gastric emptying rate via the preferential release of oleic acid, a strong stimulator of CCK.