[Variation of maternal milk adiponectin and its correlation with infant growth]

To investigate the variation of human breast milk adiponectin (APN) concentration during lactation, analyze the relationship of APN concentrations in human breast milk with APN in infant serum, determine the association between maternal milk APN and infant body proportionality in the first year of life, and the period of greatest human milk exposure.

Subjects included 73 mother-infant pairs from Shanghai International Peace Maternity & Child Health Hospital. Maternal milk was collected at 2, 4, 13, 26 weeks and infant serum was collected at 26 weeks. The concentration of APN in maternal milk and infant serum were measured with commercially available ELISAs (R&D Systems). Weight-for-age Z-scores (WAZ), length-for-age Z-scores (LAZ), weight-for-length Z-scores (WLZ) and body mass index Z-scores (zBMI) of infants up to 1 year of age were calculated using World Health Organization (WHO) standards. Then the variation of maternal milk APN was investigated, the correlation between maternal milk APN and infant serum APN was analyzed; multivariate regression analysis was used to analyze covariates correlated with infant body proportionality, meanwhile determined the association between maternal milk APN and infant anthropometrics.

The concentration of APN in maternal milk at 2, 4, 13, 26 weeks was respectively (14.62 µg/L, 5.93 - 140.40 µg/L), (7.32 µg/L, 2.04 - 29.35 µg/L), (6.84 µg/L, 2.72 - 15.65 µg/L) and (4.88 µg/L, 1.12 - 13.38 µg/L). Higher milk APN in postpartum 2 weeks was associated with lower infant WAZ at 13, 26 and 52 weeks (P < 0.05). Milk APN in postpartum 4 weeks was inversely related to infant WAZ, WLZ, zBMI at 13, 26 and 52 weeks (all P < 0.05). Meanwhile, milk APN in postpartum 13 weeks had significantly negative correlation with infant WAZ, WLZ, zBMI at 13, 26 and 52 weeks (P < 0.01). Milk APN in postpartum 26 weeks also was inversely associated with infant WAZ, WLZ and zBMI at 52 weeks (P < 0.05). After adjusting covariates like birth weight using multivariate regression analysis, milk APN level is the most important influence factor to infant WAZ, WLZ, zBMI at 13, 26 and 52 weeks. There was a positive correlation between maternal milk APN and infant serum APN at 13, 26 weeks.

Milk APN concentration declines throughout lactation. Maternal milk APN may play a vital role in the growth and development of breastfed infants, particularly closely associated with infant weight. Infant serum APN clearly correlated with maternal milk APN.