Human milk adiponectin is associated with infant growth in two independent cohorts

Abstract

Background: Adiponectin, a circulating adipocyte protein, is associated with lower obesity. We have previously shown that adiponectin is present in human milk. This study determined whether higher milk adiponectin is associated with infant growth and investigated milk adiponectin's oligomeric form.

Design and methods: This is a study of two parallel longitudinal cohorts of breastfed infants born between 1998 and 2005. Forty-five mother-infant pairs from Cincinnati, OH and 277 mother-infant pairs from Mexico City, Mexico were analyzed. All participants were healthy, term infants breastfed at least 1 month who completed 6 months of follow-up. Monthly milk samples (n = 1,379) up to 6 months were assayed for adiponectin by radioimmunoassay. Infant weight-for-age, length-for-age, and weight-for-length Z-scores up to 6 months of age were calculated using World Health Organization standards. Repeated-measures analysis was conducted. The structural form of human milk adiponectin was assessed by western blot.

Results: In the population studies, initial milk adiponectin was 24.0 +/- 8.6 microg/L and did not differ by cohort. Over the first 6 months, higher milk adiponectin was associated with lower infant weight-for-age Z-score (-0.20 +/- 0.04, p < 0.0001) and weight-for-length Z-score (-0.29 +/- 0.08, p = 0.0002) but not length-for-age Z-score, adjusted for covariates, with no difference by cohort. By western blot, human milk adiponectin was predominantly in the biologically active high-molecular-weight form.

Conclusions: Our data suggest milk adiponectin may play a role in the early growth and development of breastfed infants.

Figures

FIG. 1.

Milk adiponectin concentrations by month and cohort. Data presented are unadjusted mean ± SE values. *p = 0.03.

FIG. 2.

(A) Predicted WA Z-score (±95% confidence limits [CL]) from combined model, presented in Table 3. Milk adiponectin was modeled using natural log transformation and then back-transformed to original units. (B) Predicted WA Z-scores from cohort-specific models including the same covariates as the combined model.

FIG. 3.

Western blots of human milk adiponectin. (A) In native PAGE, 13 μL (13) or 10.4 μL (10) of milk (M) or serum (S) (13 μL of a 1:60 dilution) was applied to each well of a native PAGE 3–12% Bis-Tris gel. Bands were blotted and incubated with anti-adiponectin antibody and anti-rabbit secondary antibody, and overlaid photographic film was developed to visualize adiponectin bands. Human milk adiponectin is found as the 18mer, a form associated with highest activity for controlling many metabolic processes. (B) In SDS-PAGE, milk (M) or serum (S; 1:60) was applied to each well of a 4–12% gel; molecular weight markers are Multimark (Invitrogen). Both human serum adiponectin and human milk adiponectin reduce to a single band whose weight is consistent with a stable monomer.