Stability of milk fat globule membrane proteins toward human enzymatic gastrointestinal digestion

Abstract

The milk fat globule membrane (MFGM) fraction refers to the thin film of polar lipids and membrane proteins that surrounds fat globules in milk. It is its unique biochemical composition that renders MFGM with some beneficial biological activities, such as anti-adhesive effects toward pathogens. However, a prerequisite for the putative bioactivity of MFGM is its stability during gastrointestinal digestion. We, therefore, subjected MFGM material, isolated from raw milk, to an in vitro enzymatic gastrointestinal digestion. Sodium dodecyl sulfate PAGE, in combination with 2 staining methods, Coomassie Blue and periodic acid Schiff staining, was used to evaluate polypeptide patterns of the digest, whereas mass spectrometry was used to confirm the presence of specific MFGM proteins. Generally, it was observed that glycoproteins showed higher resistance to endogenous proteases compared with non-glycosylated proteins. Mucin 1 displayed the highest resistance to digestion and a considerable part of this protein was still detected at its original molecular weight after gastric and small intestine digestion. Cluster of differentiation 36 was also quite resistant to pepsin. A significant part of periodic acid Schiff 6/7 survived the gastric digestion, provided that the lipid moiety was not removed from the MFGM material. Overall, MFGM glycoproteins are generally more resistant to gastrointestinal digestion than serum milk proteins and the presence of lipids, besides glycosylation, may protect MFGM glycoproteins from gastrointestinal digestion. This gastrointestinal stability makes MFGM glycoproteins amenable to further studies in which their putative health-promoting effects can be explored.

Exosomes from breast milk inhibit HIV-1 infection of dendritic cells and subsequent viral transfer to CD4+ T cells

“…Further investigation is also needed to conclude whether MUC1 levels or the degree of glycosylation of MUC1 on milk-derived exosomes impact viral infection. It has been shown that several of the molecules found on milk-derived exosomes, such as MUC1 and CD36, are more resistant to gastrointestinal digestion when associated with the membrane of milk fat globulins [30]. In addition, the higher gastric pH of the newborn relative to the adult [31], as well the finding that exosomes are longlasting in vivo [32], suggest that exosomes might be protected from degradation in the stomach and could potentially impact the immune system of the breastfed child.…”

Defatted bovine milk fat globule membrane inhibits association of enterohaemorrhagic Escherichia coli O157:H7 with human HT-29 cells

“…In fact, defatted bovine MFGM has previously been digested in vitro and SDS gels have been used to analyse the protein and glycoprotein composition post-digestion. Coomassie-stained gels demonstrated hydrolysis of MFGM proteins after 20 min of pepsin digestion; however, many bands corresponding to MFGM glycoproteins were observed on the PAS stained gel indicating incomplete hydrolysis and partial resistance to the action of pepsin (Le et al, 2012). In vitro intestinal digestion led to hydrolysis of all remaining MFGM glycoproteins with the exception of Muc1 (Le et al, 2012).…”

“…Coomassie-stained gels demonstrated hydrolysis of MFGM proteins after 20 min of pepsin digestion; however, many bands corresponding to MFGM glycoproteins were observed on the PAS stained gel indicating incomplete hydrolysis and partial resistance to the action of pepsin (Le et al, 2012). In vitro intestinal digestion led to hydrolysis of all remaining MFGM glycoproteins with the exception of Muc1 (Le et al, 2012). Similarly, PAS staining of whole MFGM indicated resistance of CD36 and Muc1 to in vivo gastric digestion (Gallier et al, 2013a) and potential resistance of Muc1 to in vivo intestinal digestion (Gallier et al, 2013b).…”

Technical difficulties and future challenges in isolating membrane material from milk fat globules in industrial settings – A critical review

“…After concentration (a volume reduction ratio of 20) and diafiltration (four diafiltration steps), the recovery of phospholipids was calculated to be between 95 and 99%. However, other studies showed that some membrane proteins were susceptible to enzymatic degradation (Corredig & Dalgleish, 1997b;Kobylka & Carraway, 1973;Le et al, 2012;Shimizu, Yamauchi, & Kanno, 1979;Vanderghem et al, 2011). Therefore, the simultaneous permeation of MFGM proteins during ultracentrifugation of hydrolysed buttermilk whey needs to be further explored.…”