Abstract
Dear Editor:
A
In total, 185 breastfeeding women participated in the study. They were enrolled in the first 3 days after giving birth (expressing colostrum, n=67), Days 6–14 (expressing transitional milk, n=47), or Days 28–178 (expressing mature milk, n=71) postpartum. Written informed consents were obtained from all subjects before participating in the study. The study protocol was approved by the Ethical Committee of Uludag University Medical School (Bursa, Turkey).
Foremilk samples were collected by hand expression 3 hours after breakfast and prior to the midday feeding, right after collection of blood samples. Choline compounds were extracted from whole milk and assayed as described previously. 1 Serum hormones were measured by using either the Architect 8200® (Abbott, North Chicago, IL) or the Immulite 2000® (Diagnostic Products Corp., a division of Siemens Healthcare, Los Angeles, CA) autoanalyzer. Commercially available assay kits were used to measure serum leptin, resistin (DSL, Webster, TX), and adiponectin (Linco Research, St. Charles, MO).
Relationships between concentrations of choline compounds in milk and hormones in serum were determined by Pearson's correlation analysis. Values of p<0.05 were considered significant.
Concentrations and content of choline compounds in breastmilk varied in a wide range at all lactation stages and among breastfeeding women (Fig. 1).
Concentrations in colostrum, translational milk (T milk), and mature milk (M Milk) of the choline compounds
Colostrum free choline concentrations correlated positively with serum prolactin (r=0.688) and adiponectin (r=0.297) and negatively with serum progesterone (r=−0.336), cortisol (r=−0.390), and leptin (r=−0.353). Phosphocholine concentrations in colostrum correlated positively with serum prolactin (r=0.636), adiponectin (r=0.333), and resistin (r=0.248) and negatively with serum cortisol (r=−0.467) and leptin (r=−0.264). Colostrum glycerophosphocholine concentrations correlated positively with serum prolactin (r=0.843) and adiponectin (r=0.264) and negatively with serum progesterone (r=−0.339), cortisol (r=−0.459), and leptin (r=−0.279). Phospholipid-bound choline concentration in colostrum showed weak positive association with serum estradiol (r=0.240) and cortisol (r=0.240) and negative association with adiponectin (r=−0.257). Total choline content correlated positively with serum prolactin (r=0.845) and adiponectin (r=0.278) and negatively with serum progesterone (r=−0.299), cortisol (r=−0.462), and leptin (r=−0.337).
Transitional milk free choline concentrations correlated positively with serum prolactin (r=0.474) and negatively with serum cortisol (r=−0.653) concentrations. Phosphocholine concentrations in transitional milk correlated negatively with serum prolactin (r=−0.334), progesterone (r=−0.311), and cortisol (r=−0.653) concentrations. Transitional milk glycerophosphocholine concentrations correlated negatively with serum prolactin (r=−0.369), progesterone (r=−0.336), and cortisol (r=−0.546) concentrations. Total choline contents in transitional milk correlated negatively with serum prolactin (r=−0.315), progesterone (r=−0.350), and cortisol (r=−0.672) concentrations. No significant correlation was found between concentrations of choline compounds in transitional milk and serum concentrations of estradiol, insulin, thyroid hormones, leptin, adiponectin, resistin, or ghrelin.
Mature milk free choline concentrations correlated positively with serum prolactin (r=0.643) and negatively with serum estradiol (r=−0.254) and cortisol (r=−0.565) concentrations. Phosphocholine concentrations in mature milk correlated negatively with maternal serum estradiol (r=−0.443), progesterone (r=−0.269), cortisol (r=−0332), and insulin (r=−0.406) concentrations. Mature milk glycerophosphocholine concentrations correlated negatively with maternal serum estradiol (r=−0.465), progesterone (r=−0.255), cortisol (r=−0.531), and insulin (r=−0.505) concentrations. Mature milk phospholipid-bound choline concentrations showed negative correlation with serum insulin (r=−0.434) and triiodothyronine (r=−0.310) concentrations. Mature milk total choline concentrations correlated negatively with maternal serum estradiol (r=−0.477), progesterone (r=−0.332), cortisol (r=−0.571), and insulin (r=−0.462) concentrations. No significant correlation was found between concentrations of choline compounds in mature milk and maternal serum concentrations of leptin, adiponectin, resistin, or ghrelin.
These data confirm and extend the findings in our previous studies3,4 that breastmilk contents of important bioactive compounds were associated with hormonal status of the breastfeeding women. It is apparent that prolactin, a reproductive and metabolic hormone, has positive association with choline content in breastmilk expressed during early lactation periods. In contrast, cortisol, a glucocorticoid hormone, has negative association with choline contents in breastmilk expressed throughout the first 6 months of lactation. Associations between milk content of choline compounds and maternal serum levels of other reproductive or metabolic hormones are weak, and, if they exist, they vary among the lactation periods. It is therefore possible that various maternal hormones (e.g., prolactin, cortisol, etc.) may influence milk choline content by altering synthesis and/or uptake of choline compounds from circulation by the mammary gland. Future studies with a longitudinal design may help us understand the mechanisms and causality of these relations.