Human milk adiponectin affects infant weight trajectory during the second year of life.

Objective: Serum adiponectin (APN) is associated with lower childhood obesity, and APN concentration in human milk is associated with slower growth during active breast-feeding. We examined infant weight gain in the second year of life after exposure to high or low levels of mother's milk APN.

Methods: Breast-feeding mother-infant pairs were recruited in Mexico City and studied for 2 years; 192 infants with at least 12 months' follow-up were analyzed. Monthly milk samples were assayed for APN; mothers were classified as producing high or low levels of milk APN. Infant and maternal serum APN were assessed during year 1. Infant anthropometry was measured monthly (year 1) or bimonthly (year 2), and World Health Organization z scores were calculated. Longitudinal adjusted models assessed weight-for-age and weight-for-length z score trajectories from 1 to 2 years.

Results: Maternal serum APN modestly correlated with milk APN (r=0.37, P<0.0001) and infant serum APN (r=0.29, P=0.01). Infants exposed to high milk APN experienced increasing weight-for-age and weight-for-length z scores between age 1 and 2 years in contrast to low milk APN exposure (P for group × time=0.02 and 0.054, respectively), adjusting for growth in the first 6 months and other covariates. In contrast, infant serum APN in year 1 was not associated with the rate of weight gain in year 2.

Conclusions: High human milk APN exposure was associated with accelerated weight trajectory during the second year of life, suggesting its role in catch-up growth after slower weight gain during the first year of life.