Corticosteroid-binding proteins in human colostrum and milk and rat milk

Metabolic Conditions Including Obesity, Diabetes, and Polycystic Ovary Syndrome: Implications for Breastfeeding and Breastmilk Composition

Breastfeeding is internationally recognized as the recommended standard for infant nutrition, informed by evidence of its multiple benefits for both mother and baby. In the context of common metabolic conditions such as polycystic ovary syndrome, diabetes (type 1, type 2, and gestational), and obesity, breastfeeding may be particularly beneficial for both mother and infant. However, there is evidence of delayed lactogenesis and reduced breastfeeding rates and duration in women with these conditions, and the effects of altered maternal metabolic environments on breastmilk composition (and potentially infant outcomes) are incompletely understood. In this review, we explore the relationships between maternal metabolic conditions, lactogenesis, breastfeeding, and breastmilk composition. We examine relevant potential mechanisms, including the central role of insulin both in lactogenesis and as a milk-borne hormone. We also describe the bioactive and hormonal components of breastmilk and how these may link maternal and infant health.

The Association between Breastmilk Glucocorticoid Concentrations and Macronutrient Contents Throughout the Day

Background: Glucocorticoids (GCs) in breastmilk follow the maternal hypothalamus–pituitary–adrenal axis activity and may affect the offspring’s growth and neurodevelopment. There is some evidence suggesting that macronutrients in breastmilk also fluctuate throughout the day. We aimed to research whether GCs and macronutrients are correlated in multiple breastmilk samples obtained over a 24-h period. Methods: A total of 10 mothers provided 45 breastmilk samples collected over a 24-h period. Cortisol and cortisone levels were determined by LC–MS/MS, and macronutrients were measured with mid-infrared spectroscopy. Correlations between breastmilk GCs and macronutrients were assessed with Pearson correlations and linear mixed models. Results: No associations were found between breastmilk GCs and macronutrients (cortisol: β-0.1 (95% confidence interval: −1.0 to 0.7), −4.9 (−12.9 to 3.1) for fat, protein, and carbohydrates, respectively; and −0.3 (−5.6 to 5.0) and cortisone: 0.0 (−2.5 to 2.5), −17.4 (−39.8 to 5.0), and −2.7 (−17.7 to 12.3)) for fat, protein, and carbohydrates, respectively. Adjusting for the time of collection to account for GC rhythmicity did not change the results. Conclusion: We found no associations between GCs and macronutrients in human breastmilk. The excretion of GCs in breastmilk and the effects of breastmilk GCs on offspring are, therefore, likely independent of the excretion and effects of the macronutrients.

Soy protein supplementation is not androgenic or estrogenic in college-aged men when combined with resistance exercise training

It is currently unclear as to whether sex hormones are significantly affected by soy or whey protein consumption. Additionally, estrogenic signaling may be potentiated via soy protein supplementation due to the presence of phytoestrogenic isoflavones. Limited also evidence suggests that whey protein supplementation may increase androgenic signaling. Therefore, the purpose of this study was to examine the effects of soy protein concentrate (SPC), whey protein concentrate (WPC), or placebo (PLA) supplementation on serum sex hormones, androgen signaling markers in muscle tissue, and estrogen signaling markers in subcutaneous (SQ) adipose tissue of previously untrained, college-aged men (n = 47, 20 ± 1 yrs) that resistance trained for 12 weeks. Fasting serum total testosterone increased pre- to post-training, but more so in subjects consuming WPC (p < 0.05), whereas serum 17β-estradiol remained unaltered. SQ estrogen receptor alpha (ERα) protein expression and hormone-sensitive lipase mRNA increased with training regardless of supplementation. Muscle androgen receptor (AR) mRNA increased while ornithine decarboxylase mRNA (a gene target indicative of androgen signaling) decreased with training regardless of supplementation (p < 0.05). No significant interactions of supplement and time were observed for adipose tissue ERα/β protein levels, muscle tissue AR protein levels, or mRNAs in either tissue indicative of altered estrogenic or androgenic activity. Interestingly, WPC had the largest effect on increasing type II muscle fiber cross sectional area values (Cohen's d = 1.30), whereas SPC had the largest effect on increasing this metric in type I fibers (Cohen's d = 0.84). These data suggest that, while isoflavones were detected in SPC, chronic WPC or SPC supplementation did not appreciably affect biomarkers related to muscle androgenic signaling or SQ estrogenic signaling. The noted fiber type-specific responses to WPC and SPC supplementation warrant future research.

Nutritional programming by glucocorticoids in breast milk: Targets, mechanisms and possible implications

Vertical transmission of glucocorticoids via breast milk might pose a mechanism through which lactating women could prepare their infants for the postnatal environment. The primary source of breast-milk glucocorticoids is probably the systemic circulation. Research from our group showed that milk cortisol and cortisone concentrations follow the diurnal rhythm of maternal hypothalamus-pituitary-adrenal axis activity, with a higher abundance of cortisone compared to cortisol. Measurement of breast-milk glucocorticoid concentrations is challenging due to possible cross-reactivity with progestagens and sex steroids, which are severely elevated during pregnancy and after parturition. This requires precise methods that are not hindered by cross reactivity, such as LC-MS/MS. There are some data suggesting that breast-milk glucocorticoids could promote intestinal maturation, either locally or after absorption into the systemic circulation. Breast-milk glucocorticoids might also have an effect on the intestinal microbiome, although this has not been studied thus far. Findings from studies investigating the systemic effects of breast-milk glucocorticoids are difficult to interpret, since none took the diurnal rhythm of glucocorticoids in breast milk into consideration, and various analytical methods were used. Nevertheless, glucocorticoids in breast milk might offer a novel potential pathway for signal transmission from mothers to their infants.

Glucocorticoid receptor from lactating goat mammary tissue comparison of native and activated forms in a cell free system

Physicochemical properties of native and activated (DNA-binding) forms of the glucocorticoid receptor in cytosol prepared from lactating goat mammary tissue have been examined. Under hypotonic conditions the cytosolic receptor sediments at 8.4 S or 9.9 S in the absence or presence of 10 mM molybdate, respectively. The receptor in cytosol, either with or without molybdate elutes from DEAE-cellulose at approximately 200 mM potassium phosphate concentration. Isoelectric focusing reveals that this form of the receptor focuses at pH 5.5. Further, the cytosolic form of the receptor exhibits minimal binding affinity for polyanions such as DNA-cellulose. Its Stokes radius is 77 A and the mol. wt is approximately 331,000. Following exposure to in vitro activating conditions (including elevated ionic strength or temperature), the liganded receptor exhibits much lower affinity for DEAE-cellulose (elution at 35-55 mM potassium phosphate concentration). Other alterations in properties of the activated receptor, after partial purification, include sedimentation at 3.9 S in hypotonic sucrose gradients, binding to polyanions (DNA-cellulose), and an isoelectric point at pH 7.2. This receptor has a Stokes radius of 58 A and a mol wt of 98,000. A degraded form, with a mol. wt of approximately 57,000 and high affinity for polyanions, was the major form of the receptor obtained if appropriate precautions to prevent or remove proteolytic activity were not observed during purification and/or characterization of the activated receptor.

Concentrations of serum cortisol, progesterone, estradiol-17 beta, cholesterol and cholesterol ester in the doe during the reproductive stadium, in the fetal serum, in the amniotic fluid and in the milk of rabbits, as well as correlations between these parameters

1. Serum progesterone, estradiol-17 beta and cortisol, as well as cholesterol and cholesterol ester concentrations in pregnant and lactating rabbits (New Zealand white hybrids, n = 9), were measured. These parameters were also studied in the amniotic fluid, the milk and the fetal serum (28-day old fetuses). 2. Serum progesterone and estradiol-17 beta were significantly enhanced during gestation, while the content of cortisol showed a marked elevation at the end of pregnancy. The concentrations of these hormones decreased before parturition. 3. Serum cholesterol and cholesterol ester concentrations markedly decreased in the second half of gestation (74 and 76%, respectively) and elevated after parturition and in the first week of lactation.

Hormones in milk

Protein hormones (especially prolactin) and steroid hormones (gestagens, estrogens, corticoids, and androgens) can be detected by bioassay and radioimmunoassay in milk in a variety of species. In addition, milk contains vitamin D and beta-casomorphins (opiate-like peptides). It has been assumed that most of the hormones are transferred into milk by diffusion. However, evidence is available for active mechanisms like those for progesterone in goats and prolactin in cows. Most of the hormone profiles in milk are similar to the ones in blood plasma. Hormone concentrations in milk seem to be a good estimate of the average hormone content in plasma, especially for the measurement of longer-lasting secretory activities like progesterone and estrogen release during the estrous cycle or seasonal changes of prolactin in ruminants. Determination of progesterone and estrone sulfate in milk serves as a diagnostic tool in fertility control, especially in cows. Enzyme immunoassay kits are available for this monitoring purpose. Exogenously administered hormones are also transferred into milk. Residue studies have shown that the dilution is so great that it may be assumed that there is no potential risk for the consumer.

Controversies in neonatal nutrition

The assessment of growth parameters remains one of the most practical and valuable tools to estimate nutritional status in neonates. Growth assessment in full-term infants is performed by using charts developed by the National Center for Health and Statistics. The assessment of post-natal growth in premature infants is controversial and can be performed by using either intrauterine or extrauterine standards. The selection of appropriate growth charts should be based on clinical, demographic, ethnic, and socioeconomic similarities of the population used for reference. Daily energy intakes ranging from 100 to 120 kcal/kg/day have been recommended for full-term infants, while higher intakes ranging from 114 to 181 kcal/kg/day have been recommended for premature neonates. Full-term infants should be nursed or nipple fed on demand; however, premature infants should ideally be tube fed by intermittent gastric feeding (gavage). Continuous gastric and transpyloric feedings are indicated in selected infants. Human milk is a preferred food for full-term infants during the first six months of life; however, this precept does not suggest that all infants who are exclusively breast-fed will grow adequately. Preterm human milk is also a preferred food for the low birthweight infant, provided nutritional supplements are used. It is unclear whether the supplementation of vitamin D, iron, and fluoride in full-term breast-fed infants should be started at birth, at the time of initiation of solid foods, or at the age of six months. The routine supplementation of multivitamins, folic acid, and vitamin E to all low birthweight infants is controversial. Most investigators suggest vitamin supplementation be given until the intake of formula or breast milk is sufficient to meet daily requirements. Vitamin E appears to exert a protective effect in premature infants against the development of severe retinopathy. The supplementation of vitamin E should be dependent upon the serum vitamin E concentration. It is controversial whether iron supplementation for premature infants should be initiated soon after birth or at two months of age, or whether higher doses of iron should be given to very low birthweight infants. If iron supplementation is started at birth, vitamin E status should be closely monitored. Although the optimal intakes of calcium and phosphorus in infant feedings have not been firmly established, the levels of calcium and phosphorus in human milk appear to be inadequate for the growing low birthweight infant.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of total and free cortisol in bovine serum and milk or colostrum

Total (free plus protein-bound) and free cortisol concentrations in paired samples of serum and skim milk or colostrum were determined by specific radioimmunoassay after extraction or ultrafiltration. For 11 cows in established lactation mean total cortisol concentrations +/- SE in serum and milk were 4.5 +/- .7 ng/ml and .35 +/- .06 ng/ml, respectively. Concentrations of free cortisol in serum and milk were about .3 ng/ml, which is at the lower limit of the present assay. Following 200 IU Synacthen injection to 5 cows, total cortisol in serum and milk rose to 67 +/- 6.0 ng/ml and 11.4 +/- 1.5 ng/ml by 8 h postinjection, while free concentrations increased to 4.3 +/- .7 ng/ml and 6.5 +/- .8 ng/ml in serum and milk, respectively. Eight additional cows were sampled at 1 to 2 d after parturition, and total cortisol in serum and colostrum was 16.6 +/- 1.6 ng/ml and 4.4 +/- 1.3 ng/ml, and free cortisol was 2.4 +/- .4 ng/ml and 1.8 +/- .5 ng/ml, respectively. Free cortisol concentrations in colostrum or in milk from cows in established lactation, before or after adrenal stimulation, are directly related to free cortisol concentrations in the blood, while the bound cortisol in milk is more related to these two stages of lactation rather than the bound hormone in the blood. Measurement of free cortisol in milk should allow the monitoring of changes in plasma free cortisol in studies of stress in dairy cows.

Evidence for a transcortin-like component in human breast cyst fluid

The occurrence of a specific glucocorticoid binding activity was investigated in breast cyst fluid (BCF) samples aspirated from 481 women under treatment for breast cystic disease. [3H]cortisol was incubated with BCF at 4 degrees C with and without 100-fold molar excess of non-radioactive steroid in order to account for non-specific binding. Corticosterone, progesterone and dexamethasone-binding activities were also investigated in about 50% of the specimens. Consistent amounts of a specific cortisol-, corticosterone- and progesterone-binding component were observed in about 30% of samples. Apparent binding values ranged from 4.31 to 80.78 nmol/l for cortisol, from 3.94 to 75.72 nmol/l for corticosterone, and from 1.18 to 16.45 nmol/l for progesterone. No specific binding for dexamethasone was detected. Scatchard analyses for [3H]cortisol and [3H]progesterone were made in pools of 'positive' BCF, human serum and whey of human milk, respectively. The mean values of the apparent equilibrium association constant (Ka) were compatible with the existence of high affinity protein-hormone interactions in each considered medium. Data obtained in ligand competition experiments for different steroid molecules suggest the similarity of the glucocorticoid- and progesterone-binding component found in 30% of BCF samples examined with the plasma corticosteroid-binding globulin (CBG, transcortin) and especially with the transcortin-like component detected in the whey of the human milk. It is suggested that the transcortin-like component may play an important role in controlling kinetics of transport and in regulating the effective levels of cortisol and progesterone in numerous breast cyst fluids.

Cortisol and its possible role in regulation of sodium and potassium in human milk

Cortisol (F), Na, and K were measured in human milk samples taken every 4 h during 28 24-h cycles in 19 subjects. F in milk, measured by radioimmunoassay of unchromatographed extracts, demonstrated a circadian variation similar to that of plasma F and was dexamethasone-suppressible. Values ranged from 220 +/- 41 (SE) ng/dl at 2300 h to 1,214 +/- 210 at 0700 h. When milk extracts were chromatographed, a similar circadian variation was seen, and F ranged from 87 +/- 27 (SE) ng/dl at 2300 h to 784 +/- 164 at 700 h. The morning values of F exceeded previous estimates of corticosteroid binding capacity in milk, indicating the possibility of significant levels of unbound F. The subjects were divided into three groups according to time postpartum: I, 3.5-6 wk; II, 8-18 wk, and III, 20-32 wk. In milk, normalized values of F (unchromatographed) and electrolytes (x/means) were compared, with x the value at time t and means the mean value for a 24-h cycle. A significant circadian variation was seen in milk for (x/means)Na, (x/means)K, (x/means)Na/K, and x/means)F. Correlation of (x/means)F with (x/means)Na 4 h later was negative in all three groups (r = -0.36 to -0.56, P less than 0.10-0.001) as was (x/means)F vs. (x/means)Na/K (r = -0.33 to -0.61, P less than 0.10-0.001); (x/means)F vs. (x/means)K 4 h later was positive (r = 0.38 to 0.52, P less than 0.05-0.001). Dexamethasone administration caused a significant decrease in milk means Na and an increase in meansK in all five subjects (P less than 0.01). Thus, milk Na and K concentrations appeared regulated by adrenal corticosteroids.

A comparative study of vitamin D binding globulins in milk

1. The occurrence of 25-hydroxy vitamin D binding protein in human, bovine, monkey and porcine milk was investigated. 2. Sucrose gradient ultracentrifugation revealed the presence of 4.2 S and 5.7 S binding globulins in the whey of human, monkey and porcine milk. 3. Although bovine plasma also contains a 4.2 S globulin only a 5.7 S protein was found in bovine milk. 4. The 4.2 S and 5.7 S globulins in milk could not be resolved by polyacrylamide gel electrophoresis or by isoelectric focusing. 5. Plasma and whey binding proteins of any one species had the same isoelectric point but there were small differences among species (4.5-4.8). 6. Competitive displacement studies showed that the binding proteins in milk have high affinity for 25-hydroxy-cholecalciferol and 24,25-dihydroxycholecalciferol.

Glucocorticoids in mammary secretions and blood serum during reproduction and lactation and distributions of glucocorticoids, progesterone, and estrogens in fractions of milk

Concentrations of glucocorticoids were measured in milk and blood serum during the estrous cycle, prepartum, parturition, postpartum, and early and late lactation. Glucocorticoids in milk did not change during the estrous cycle, averaging .35 ng/ml whereas they averaged .50 ng/ml prepartum, 3.08 ng/ml at parturition, and .50 ng/ml 1 wk postpartum. Glucocorticoids in milk declined from .59 ng/ml to .25 ng/ml as lactation advanced from 1 to 10 mo. Concentrations of glucocorticoids in blood serum were approximately 8 to 10 ng/ml during all reproductive states. There was no positive relationship between percentage of milk fat and concentrations of glucocorticoids in milk. Cortisol was the predominant glucocorticoid in serum; in milk corticosterone concentrations exceeded those of cortisol. Glucocorticoids, being more polar, had higher affinity for the nonlipid portion of milk; in contrast, progesterone, estradiol 17beta, and estrone were located predominantly in the lipid fraction of milk.

Maternal and fetal serum levels of total cortisol and cortisone, unbound cortisol, and corticosteroid-binding globulin in vaginal delivery and cesarean section

The levels of corticosteroid-binding globulin (CBG, transcortin), total cortisol, and unbound cortisol were measured in maternal and fetal serum at the time of cesarean section or vaginal delivery. While the total cortisol levels in maternal serum do not differ significantly in vaginal delivery as compared to cesarean section, cord serum cortisol levels are significantly higher after vaginal delivery. There are no differences associated with the route of delivery between the mean levels of CBG in cord and maternal blood. However, after the vaginal delivery the unbound cortisol level in maternal serum is more than twice as high as that at cesarean section and in cord serum it is seven times as high. These changes reflect changes in total cortisol and may represent a prelabor surge of fetal cortisol production, or a stress response associated with labor, or a combination of both.