Beta-endorphin-like and alpha-MSH-like immunoreactivities in human milk

Endorphins, Sexuality, and Reproduction

Beta-endorphin is secreted from the hypothalamus and pituitary in both mother and newborn. The placenta produces numerous pituitary hormones from the third month of pregnancy, one of which is βE. It has been suggested that βE has a role in the appetitive and precopulatory phase of sexual behavior in animals. An increase in endorphin levels during sexual activity in humans may contribute to attachment and bonding between partners, but contradictory reports in the literature question the association between sexuality and βE levels. The level of βE also increases during pregnancy, rises in early labor, peaks in late labor, and drops in the postpartum period. This fluctuation provides natural analgesia, raises the pain threshold, decreases the sensation of pain, or suppresses pain, and decreases fear levels during labor and birth. Beta-endorphin also protects the fetus from hypoxia during labor and birth and potential neural damage by aiding blood flow to the brain under hypoxic conditions. It has been suggested that a variety of pharmacologic and nonpharmacologic complementary therapies, when used in pregnancy, labor, and birth, activate the opioid receptors in the CNS and alter the sensation of pain during labor and birth, affect the mother-child attachment and affect sexual function. These studies report contradictory results that will be discussed in this chapter.

The role of breast milk beta-endorphin and relaxin-2 on infant colic

BACKGROUND

The relationship between infant colic and breast milk beta-endorphin (BE) and relaxin-2 (RLX-2) has not been studied before.

METHODS

Thirty colic infants and their mothers constituted the study group, and the same sex, similar age and healthy infants and their mothers formed the control group. Maternal predisposing factors were analysed with questionnaires.

RESULTS

The frequency of headache and myalgia in the mothers was significantly higher in the study group compared to the control group. Sleep quality of mothers in the study group was worse than in the control group (p = 0.028). While breast milk RLX-2 level in the study group was not different from the control group, breast milk BE level in the study group was significantly higher than the control group (p = 0.039). A positive correlation was found between breast milk BE levels and crying times, and between sleep quality scores and crying times. Headache, myalgia, sleep quality and breast milk BE levels were found to have a significant effect on infant colic.

CONCLUSIONS

Breast milk RLX-2 has no role on infant colic. Breast milk BE may act as a biological mediator in transmitting of maternal predisposing factors such as poor sleep quality, headache and myalgia from mother to infant.

IMPACT

The relationship between infant colic and breast milk beta-endorphin (BE) and elaxin-2 (RLX-2) has not been studied before. Maternal sleep quality, headache, and myalgia are predisposing factors associated with infant colic. Breast milk RLX-2 has no effect on infant colic. Breast milk BE may play a role as a biological mediator in transmitting the effects of predisposing factors from mother to infant. Breast milk BE may be a mediator in biological communication between mother and infant.

Beta endorphin concentrations in human milk

BACKGROUND

The source and regulatory mechanisms that elevate beta-endorphin (beta-EP) approximately twofold higher than circulating plasma levels in the colostrum of lactating mothers are still unknown, and no studies have examined beta-EP availability previously during maturation phases of human milk. Therefore, the aim of this study was to determine whether concentrations of beta-EP vary over time between colostrum, transitional, and mature breast-milk and to evaluate whether this depends on the method of delivery.

METHODS

Mothers of healthy full-term and pre-term newborn infants who planned to breast-feed their newborn infants were considered for this study. They were consecutively recruited in one of 3 groups of 14, according to delivery method: group 1, vaginal delivery at term (gestational age 40.2 +/- 0.3 weeks; birth weight, 3.48 +/- 0.09 kg); group 2, preterm vaginal delivery (gestational age, 35.6 +/- 0.3 weeks; birth weight, 2.49 +/- 0.08 kg); and group 3, at-term elective cesarean section (gestational age, 39.0 +/- 0.3 weeks; birth weight, 3.32 +/- 0.14 kg). Three consecutive breast milk samples were obtained on the fourth day after birth, before each mother's discharge, and thereafter on the 10th and 30th postpartum days, close to expression of the colostrum, transitional, and mature milk production phases, respectively, to test beta-EP concentrations (beta-Endorphin 125I RIA; INCSTAR Corporation, Stillwater, MN). Data are presented as mean +/- standard deviation. Statistical comparison of beta-EP concentration among the three lactating mother groups was performed using the Kruskal-Wallis nonparametric test. In addition, to test the hypothesis of a trend toward smaller values with time of beta-EP, the authors computed within each mother group a P value per trend (Kruskal-Wallis test) of beta-EP concentration averages on the 4th, 10th, and 30th days, respectively. Student's t test for independent samples was used for the analysis of the other data. The 0.05 significance level was used in the statistical analysis. All computations were made by computer.

RESULTS

Colostrum beta-EP concentrations on the fourth postpartum day of group 1 and group 2 mothers who were delivered of a neonate vaginally, at term, or prematurely were significantly higher (P < 0.01) than colostrum levels of group 3 mothers who underwent cesarean section. Group 2 mothers who were delivered of a neonate vaginally and prematurely presented the highest beta-EP concentrations (P < 0.05), lasting until the transitional milk phase (10th day). No significant differences were found across all 3 groups of lactating mothers in mature milk (30th day) beta-EP concentrations. In addition, the beta-EP trend toward smaller values with time within each of the three groups on days 4, 10, and 30 was statistically significant (P < 0.01 per trend).

CONCLUSIONS

It is hypothesized that elevated beta-EP concentrations in colostrum and transitional milk of mothers who were vaginally delivered of infants may contribute to postnatal fetal adaptation, to overcoming birth stress of natural labor and delivery, and at the same time to the postnatal development of several related biologic functions of breast-fed infants.

Labor pain effects on colostral milk beta-endorphin concentrations of lactating mothers

beta-Endorphin (beta-EP) levels of colostral milk are approximately two-fold higher than in plasma of lactating women, in who concentrations peak at term, after the first and second stages of labor. We investigated the effect of labor pain and vaginal parturition on colostral beta-EP concentrations (beta-endorphin (125)I RIA, Incstar Corp., Stillwater, Minn., USA) of at-term nursing mother, in comparison to those having undergone elective cesarean section. Our results show that colostral milk beta-EP concentrations of mothers who delivered vaginally are significantly higher on the 4th postpartum day (6.0 +/- 0.5 vs. 4.3 +/- 0.4 pmol/l, respectively; p < 0.01) than colostral levels of mothers who underwent cesarean section. These data indicate the important influence of the labor process on the colostral opioid galactopoiesis. It is suggested that labor and parturition pain may increase colostral milk beta-EP concentrations of lactating mothers in order to help the newborn overcome the stressful perinatal events of natural labor and delivery.

Alpha-melanocyte-stimulating hormone in normal human physiology and disease states

Over the past two decades, research in animal models has indicated that alpha-melanocyte-stimulating hormone (alpha-MSH) has potent anti-inflammatory properties. Furthermore, recent data show that the peptide has antimicrobial effects and probably contributes to innate immunity. alpha-MSH, which is produced by many extrapituitary human cells, should no longer be considered solely a pituitary hormone; rather, it should be viewed as a ubiquitous modulatory peptide.

Proopiomelanocortin expression in the skin during induced hair growth in mice

We demonstrate for the first time a hair cycle-dependent gene and protein expression of proopiomelanocortin in mouse skin in vivo. Northern blot detected POMC mRNA with an apparent size of 0.9 kb in anagen but not telogen skin. Western blot emphasized a specific protein of 30-33 kDa recognized by anti beta-endorphin in late but not early anagen or telogen skin. By immunocytochemistry, beta-endorphin antigen was localized in the sebaceous gland in a hair cycle dependent manner.