Objective: To analyze content of human milk osteopontin(OPN) and to explore associated factors in Chinese populations.
Methods: The samples and data were extracted from the database for human milk composition in China between 2011 and 2013. A sub-sample of 459 mothers was randomly selected after stratification according to lactation stage, and human milk OPN concentrations were determined by ultra performance liquid chromatography-tandem mass spectrometer(UPLC/MS).
Results: The average OPN concentration(M(P25, P75)) in breast milk was 44.0(30.1-72.0) mg/L within 0-330 days postpartum. OPN concentrations were independent of lactation stage, which were 45.6(31.8, 80.7) mg/L in colostrum, 41.3(29.2, 70.0) mg/L in transitional milk and 46.9(30.2, 71.9) mg/L in mature milk, corresponding to 0.40%、0.42% and 0.65% of the total milk protein content(OPN/protein%). The percentage of OPN to total protein in milk showed an increasing trend with lactation progression(r=0.21, P<0.001). Multivariate analysis showed that sleep quality of mothers within one week prior to milk collection was correlated with the breast milk OPN level(P=0.04). The OPN level in breast milk from mothers with good sleep quality was significantly higher than that from mothers with poor sleep quality(46.5 mg/L vs.34.7 mg/L). The median level of milk OPN concentration in mothers from Yunnan was higher than mothers from Beijing(50.5 mg/L vs.36.1 mg/L, P=0.03). Maternal age, mode of delivery, prepregnancy body mass index, weight gain during pregnancy, passive smoking and outdoor activities 24 hours prior to milk collection were not correlated with milk OPN concentration. OPN concentration in breast milk was not related to preterm birth. Also, milk OPN concentration did not correlate with diarrhoea, respiratory disease, or allergic disease in infants during two weeks before milk collection.
Conclusion: The concentration of OPN in breast milk of Chinese woman may be similar among different lactation stages. Geographic region and sleep quality of mothers may be related to the milk OPN concentration.
Keywords: human milk; influential factors; osteopontin.