Article

Temporal Changes in Milk Proteomes Reveal Developing Milk Functions

Mead Johnson Nutrition Pediatric Nutrition Institute, 2400 West Lloyd Expressway, Evansville, Indiana 47721, USA.
Journal of Proteome Research (Impact Factor: 4.25). 06/2012; 11(7):3897-907. DOI: 10.1021/pr3004002
Source: PubMed

ABSTRACT

Human milk proteins provide essential nutrition for growth and development, and support a number of vital developmental processes in the neonate. A complete understanding of the possible functions of human milk proteins has been limited by incomplete knowledge of the human milk proteome. In this report, we have analyzed the proteomes of whey from human transitional and mature milk using ion-exchange and SDS-PAGE based protein fractionation methods. With a larger-than-normal sample loading approach, we are able to largely extend human milk proteome to 976 proteins. Among them, 152 proteins are found to render significant regulatory changes between transitional milk and mature milk. We further found that immunoglobulins sIgA and IgM are more abundant in transitional milk, whereas IgG is more abundant in mature milk, suggesting a transformation in defense mechanism from newborns to young infants. Additionally, we report a more comprehensive view of a complement system and associated regulatory apparatus in human milk, demonstrating the presence and function of a system similar to that found in the circulation but prevailed by alternative pathway in complement activation. Proteins involved in various aspects of carbohydrate metabolism are also described, revealing either a transition in milk functionality to accommodate carbohydrate-rich secretions as lactation progresses, or a potentially novel way of looking at the metabolic state of the mammary tissue. Lately, a number of extracellular matrix (ECM) proteins are found to be in higher abundance in transitional milk and may be relevant to the development of infants' gastrointestinal tract in early life. In contrast, the ECM protein fibronectin and several of the actin cytoskeleton proteins that it regulates are more abundant in mature milk, which may indicate the important functional role for milk in regulating reactive oxygen species.

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Available from: Qiang Zhang, Aug 11, 2014
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    • "Some milk proteins are up-regulated as part of the inflammatory response that occurs during infection of the mammary gland [5] [6] [7]. Some host defence proteins are also known to be altered in abundance with the stage of lactation [8] [9] [10] [11]. This variability in the protein composition of milk, at least in part, may reflect the changing need of the offspring during its growth and development. "

    Full-text · Dataset · May 2015
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    • "Some milk proteins are up-regulated as part of the inflammatory response that occurs during infection of the mammary gland [5] [6] [7]. Some host defence proteins are also known to be altered in abundance with the stage of lactation [8] [9] [10] [11]. This variability in the protein composition of milk, at least in part, may reflect the changing need of the offspring during its growth and development. "
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    ABSTRACT: Human milk contains a range of host defence proteins that appear to contribute to health and wellbeing, but their variability in abundance among individuals has not been very well characterised. Milk from mothers of premature infants has altered composition, but the effect of gestation length on the host-defence properties of milk is not known. A study was therefore undertaken to determine the variability and effect of gestation length on the abundance of five host-defence proteins in milk; lactoferrin, secretory IgA, IgG, secretory component, and complement C3.Methods Milk was obtained from 30 mothers at their second and fifth week of lactation. These were from three groups of ten mothers having had very premature (V; 28–32 weeks gestation), premature (P; 33–36 weeks) or full term deliveries (T; 37–41 weeks). The concentration of each of the five proteins was measured in each milk sample by either ELISA or quantitative western blotting.ResultsThe concentration of IgG, and complement C3 ranged 22- and 17-fold respectively between mothers, while lactoferrin, secretory IgA, and secretory component ranged 7-, 9-, and 4-fold, respectively. The V group had significantly lower concentrations of four of the five proteins, the exception being IgG. Levels of these four proteins also decreased between weeks 2 and 5 of lactation in the P and T groups. Significant correlation was found between the concentrations of the host defence proteins within individual mothers, indicating some degree of co-ordinate regulation.Conclusions Mothers vary widely in the levels of host defence proteins in milk. Very short gestation length results in decreased abundance of host-defence proteins in milk. This may have functional implications for very premature infants.
    Full-text · Article · Nov 2014 · Early Human Development
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    • "Other human milk components with antimicrobial properties include lactoperoxidase [43], polypeptides released from α-lactalbumin [44] and possibly N-acetyl-ß-D-glucosaminidase [45] may also play a role in reducing bacterial growth. Recently, an additional 700 proteins have been identified in human milk [46,47]. These proteins are low in concentration and approximately a quarter of them are considered to have an immune response function [47] although their potency and activity in respect of inhibition of bacterial multiplication are unknown. "
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    ABSTRACT: Human milk possesses bacteriostatic properties, largely due to the presence of immunological proteins. Heat treatments such as Holder pasteurization reduce the concentration of immunological proteins in human milk and consequently increase the bacterial growth rate. This study investigated the bacterial growth rate and the immunological protein concentration of ultraviolet (UV-C) irradiated, Holder pasteurized and untreated human milk. Samples (n=10) of untreated, Holder pasteurized and UV-C irradiated human milk were inoculated with E. coli and S. aureus and the growth rate over 2 hours incubation time at 37°C was observed. Additionally, the concentration of sIgA, lactoferrin and lysozyme of untreated and treated human milk was analyzed. The bacterial growth rate of untreated and UV-C irradiated human milk was not significantly different. The bacterial growth rate of Holder pasteurized human milk was double compared to untreated human milk (p<0.001). The retention of sIgA, lactoferrin and lysozyme after UV-C irradiation was 89%, 87%, and 75% respectively, which were higher than Holder treated with 49%, 9%, and 41% respectively. UV-C irradiation of human milk preserves significantly higher levels of immunological proteins than Holder pasteurization, resulting in bacteriostatic properties similar to those of untreated human milk.
    Full-text · Article · Dec 2013 · PLoS ONE
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