An interactomics overview of the human and bovine milk proteome over lactation.
BACKGROUND
Milk is the most important food for growth and development of the neonate, because of its nutrient composition and presence of many bioactive proteins. Differences between human and bovine milk in low abundant proteins have not been extensively studied. To better understand the differences between human and bovine milk, the qualitative and quantitative differences in the milk proteome as well as their changes over lactation were compared using both label-free and labelled proteomics techniques. These datasets were analysed and compared, to better understand the role of milk proteins in development of the newborn.


METHODS
Human and bovine milk samples were prepared by using filter-aided sample preparation (FASP) combined with dimethyl labelling and analysed by nano LC LTQ-Orbitrap XL mass spectrometry.


RESULTS
The human and bovine milk proteome show similarities with regard to the distribution over biological functions, especially the dominant presence of enzymes, transport and immune-related proteins. At a quantitative level, the human and bovine milk proteome differed not only between species but also over lactation within species. Dominant enzymes that differed between species were those assisting in nutrient digestion, with bile salt-activated lipase being abundant in human milk and pancreatic ribonuclease being abundant in bovine milk. As lactation advances, immune-related proteins decreased slower in human milk compared to bovine milk. Notwithstanding these quantitative differences, analysis of human and bovine co-expression networks and protein-protein interaction networks indicated that a subset of milk proteins displayed highly similar interactions in each of the different networks, which may be related to the general importance of milk in nutrition and healthy development of the newborn.


CONCLUSIONS
Our findings promote a better understanding of the differences and similarities in dynamics of human and bovine milk proteins, thereby also providing guidance for further improvement of infant formula.
Dairy Science and Technology, Food Quality and Design Group, Wageningen University, Postbox 8129, 6700EV Wageningen, The Netherlands.
Lina
L
Zhang
Biometris, Wageningen University and Research Centre, P.O. Box 16, 6700 AA Wageningen, The Netherlands.|Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.|Bioscience, cluster Applied Bioinformatics, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
Aalt D J
ADJ
van Dijk
Dairy Science and Technology, Food Quality and Design Group, Wageningen University, Postbox 8129, 6700EV Wageningen, The Netherlands.
Kasper
0000-0002-9017-4447
K
Hettinga
Bovine milk; Human milk; Lactation; Protein interaction networks; Proteomics