Impact of human milk pasteurization on digestive kinetics and intestinal lipid absorption using a combination of in vitro models

IntroductionHuman milk is a complex biological fluid recognized as the gold standard in neonatal nutrition,especially for preterm infants since it supports growth and brain development. Donor human milk,pasteurized for safety reasons, is the first option to feed preterm infants when mothers’ own milk isnot available.ObjectiveThe aim of the present study was to determine the impact of breastmilk pasteurization on pretermgastrointestinal digestion and to evaluate its effect on lipid absorption.MethodologyKinetics of digestion and structural desintegration of pasteurized human milk (PHM) and raw humanmilk (RHM) were evaluated using a static in vitro digestion model that we adapted to simulatepreterm digestion ability. Caco-2 /TC7 cells, an intestinal absorption model, were subsequently incubatedwith diluted PHM vs RHM-digestion media.Main findingsDuring in vitro digestion, proteolysis was evaluated by SDS-PAGE followed by densitometry. Lactoferrinproteolysis was significantly (p<0.05) higher in PHM than in RHM in the gastric and intestinalphases with 26±4 % and 53±18% of intact lactoferrin remaining at 60 min of intestinal digestion forPHM and RHM, respectively. β-casein was less susceptible to pepsinolysis in PHM, with 78±3 %remaining at 60 min of gastric digestion vs. 37±4% for RHM, but less than 5% remained at 60 min ofintestinal digestion for both milks. The lipolysis kinetics, determined by thin layer chromatography,was not significantly different between RHM and PHM. In Caco-2 cells after 16h of incubation, cellmonolayer integrity assesses by occludine immunostaining was unaffected and intracellular lipiddroplets could be visible using Oil Red O staining. Triglyceride secretion measured in the basolateralmedium seems to be higher for RHM than PHM, supporting further exploration of the gene expressioninvolved in intestinal lipid absorption.