Parathyroid Hormone-related Protein In Milk Research Articles

Dmp1Cre-directed knockdown of parathyroid hormone-related protein (PTHrP) in murine decidua is associated with a life-long increase in bone mass, width, and strength in male progeny.

Parathyroid hormone-related protein (PTHrP, gene name Pthlh) is a pleiotropic regulator of tissue homeostasis. In bone, Dmp1Cre-targeted PTHrP deletion in osteocytes causes osteopenia and impaired cortical strength. We report here that this outcome depends on parental genotype. In contrast to our previous report using mice bred from heterozygous (flox/wild type) Dmp1Cre.Pthlhf/w parents, adult (16-week-old and 26-week-old) flox/flox (f/f) Dmp1Cre.Pthlhf/f mice from homozygous parents (Dmp1Cre.Pthlhf/f(hom) ) have stronger bones, with 40% more trabecular bone mass and 30% greater femoral width than controls. This greater bone size was observed in Dmp1Cre.Pthlhf/f(hom) mice as early as 12 days of age, when greater bone width was also found in male and female Dmp1Cre.Pthlhf/f(hom) mice compared to controls, but not in gene-matched mice from heterozygous parents. This suggested a maternal influence on skeletal size prior to weaning. Although Dmp1Cre has previously been reported to cause gene recombination in mammary gland, milk PTHrP protein levels were normal. The wide-bone phenotype was also noted in utero: Dmp1Cre.Pthlhf/f(hom) embryonic femurs were more mineralized and wider than controls. Closer examination revealed that Dmp1Cre caused PTHrP recombination in placenta, and in the maternal-derived decidual layer that resides between the placenta and the uterus. Decidua from mothers of Dmp1Cre.Pthlhf/f(hom) mice also exhibited lower PTHrP levels by immunohistochemistry and were smaller than controls. We conclude that Dmp1Cre leads to gene recombination in decidua, and that decidual PTHrP might, through an influence on decidual cells, limit embryonic bone radial growth. This suggests a maternal-derived developmental origin of adult bone strength. © 2021 American Society for Bone and Mineral Research (ASBMR).

Changes in parathyroid hormone-related protein concentrations in bovine milk from the early stage of lactation

The concentration of parathyroid hormone-related protein (PTHrP) in the blood of healthy animals is extremely low. However, milk contains a relatively large amount of PTHrP, and the changes in its levels in the early stages of lactation in cows remain unclear. To understand the characteristics of parturient changes in milk PTHrP content and the biological implications thereof, changes in milk PTHrP concentrations were measured at 7 time intervals between parturition and 21 days postpartum in 8 primiparous and 8 multiparous Holstein cows. Based on these results, milk samples were collected from 47 primiparous and 66 multiparous Holstein cows at 3 days postpartum to investigate the relationship between milk PTHrP concentration and the variables of cow age, milk yield, and milk calcium concentration. Milk PTHrP concentration in both parity groups was found to be lowest on the day of parturition (primiparous, 3.1±0.5nM and multiparous, 1.6±0.3nM) but to significantly increase on day 14 of lactation in primiparous cows (6.2±0.8nM) and day 7 of lactation in multiparous cows (4.1±0.2nM). Comparison of the 2 groups revealed that milk PTHrP concentrations in primiparous cows were higher than those of multiparous cows in the first 3 days of lactation. Although a significant negative relationship was found between milk PTHrP concentration and both age (r=−0.65) and milk calcium concentration (r=−0.19) at 3 days postpartum, no significant correlation was found between milk PTHrP concentration and milk yield. The study thus identified 3 unique characteristics of milk PTHrP concentration in the early stages of lactation: milk PTHrP concentration is higher in primiparous than multiparous cows, milk PTHrP concentration is lower in colostrum than later milk, and the difference in milk PTHrP concentration between primiparous and multiparous cows at 3 days postpartum is more strongly influenced by age than milk yield.

Changes in Serum Parathyroid Hormone–Related Protein in Breastfed Preterm Infants

Parathyroid hormone-related protein (PTHrP) has the ability to activate parathyroid hormone receptors and cause hypercalcemia. In a previous study we have demonstrated high concentrations of PTHrP in both term and preterm human milk (HM). PTHrP intestinal absorption and its influence upon calcium homeostasis of the preterm infant have not been studied yet. This study assessed the correlation between PTHrP concentrations in preterm HM and PTHrP in maternal and neonatal serum. We collected samples of expressed HM obtained from 16 mothers of preterm infants (25-34 weeks of gestation) and drew blood samples from both mothers and infants on postpartum days 2 and 10. PTHrP concentrations were measured by two-site immunoradiometric assay. Blood calcium (Ca), phosphorus (P), and alkaline phosphatase (ALP) concentrations were also measured. Neither maternal nor neonatal PTHrP serum concentrations varied significantly after 10 days of breastfeeding. There was a correlation between PTHrP concentrations in maternal serum and HM concentrations (R² = 0.24, p = 0.04), but not between HM and neonatal serum concentrations or between PTHrP concentrations in HM and preterm serum concentrations of Ca, P, and ALP. Despite high concentrations of PTHrP in preterm HM, serum concentrations of PTHrP of breastfed preterm infants did not increase over time. There was no correlation between PTHrP concentrations in HM and neonatal serum Ca concentration.

1027 Parathyroid Hormone Related Protein (PTHRP) in Preterm Human Milk

Background:Parathyroid hormone-related protein (PTHrP) has the ability to activate parathyroid hormone receptors and cause hypercalcaemia. In a previous study we demonstrated high levels of PTHrP in both term and preterm human milk (HM) (Breastfeeding Medicine, 2009). PTHrP intestinal absorption and its influence upon calcium homeostasis of the preterm infant (PTI) has not been studied yet.Objective: To assess the correlation between PTHrP level in preterm HM and PTHrP in maternal and neonatal serum. Design/Methods: We collected samples of expressed HM obtained from 16 mothers of preterm infants (25-34 weeks' gestation). In addition, blood samples from both mothers and infants were drawn. All samples were collected at days 2 and 10 postpartum. PTHrP levels were measured by twosite immunoradiometric assay. Blood calcium (Ca), Phosphorus (P) and alkaline phosphatase (ALP) levels were also measured.Results: Both maternal and neonatal PTHrP serum levles did not vary after 10 days of breastfeeding. No correlation was found between PTHrP level in HM and serum PTHrP, Ca, P and ALP of the breastfed PTI.Conclusions: Despite high levels of PTHrP in preterm HM, serum levels of PTHrP of the breast fed PTI do not increase over time. We found no correlation between PTHrP in HM and neonatal Ca serum concentration. We speculate that PTHrP intestinal absorption in the PTI is not significant.

Modification of the analysis of parathyroid hormone-related protein in milk and concentrations of this protein in commercial milk and milk products in Japan

Parathyroid hormone-related protein (PTHrP), which causes hypercalcemia associated with malignant tumors, is known to be present in milk. Gene expression of PTHrP in the mammary gland increases markedly during parturition and with the onset of lactation. Even when circulating PTHrP levels are extremely low or below the detection limit, milk PTHrP levels are remarkably high. Parathyroid hormone-related protein derived from the mammary gland is assumed to play a role in maintaining the maternal calcium homeostasis and calcium transport from blood to milk. In previous studies that determined the PTHrP concentrations in milk, the pretreatments and diluent composition were not standardized. Here, we investigated the effect of various pretreatment procedures and diluent constitutions and the consequent PTHrP concentrations in commercial milk and milk products in Japan. Significant differences were found in PTHrP concentrations in raw milk samples subjected to different combinations of pretreatments (mixing, centrifugation, acidification, and heating) and diluents (0pM standard solution of PTHrP, plasma treated with protease inhibitors, and original diluent). We measured the PTHrP concentrations in normal liquid milk, processed milk, milk drinks, formulated milk powders, and skim milk powder by using the appropriate combination of pretreatment (acidification) and diluent (plasma treated with protease inhibitors). The PTHrP concentration in normal liquid milk, processed milk, and skim milk powder was as high as that in raw milk (>5nM), whereas that in milk drinks differed considerably. The PTHrP concentration in infant formulas (<2nM) was lower than that in the other milk products. These results indicate that a certain amount of PTHrP is ingested when milk and milk products are consumed.

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation.

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E1077-E1085, 1992.--Production of parathyroid hormone-related protein (PTHrP) by the mammary gland of Sprague-Dawley rats has been examined using immunohistochemistry and in situ hybridization to detect PTHrP and PTHrP mRNA, respectively. PTHrP and PTHrP mRNA could be demonstrated in nests of epithelial cells of the developing mammary gland at day 14 of pregnancy and in the epithelial secretory cells lining the alveoli during the latter stages of pregnancy and during lactation. A specific radioimmunoassay was also used to measure the concentration of PTHrP secreted in the milk throughout lactation. The concentration of PTHrP in milk was relatively low initially but increased during the latter stages of lactation, whereas calcium concentrations remained virtually constant throughout lactation. No correlation was found between the concentrations of calcium and PTHrP in rat milk. These results show that PTHrP is present in rat milk and also in mammary tissue before parturition, and therefore it may assist in the development of the mammary gland during pregnancy.

Parathyroid Hormone-Related Protein (PTHrP) and Ca Levels in the Milk of Lactating Cows

To investigate the roles of mammary PTHrP in calcium uptake and/or release in the mammary gland of cows, plasma PTHrP and Ca levels, and their arterial-venous differences were examined in a Jersey cow during the periparturient period. Levels of Ca in both abdominal aorta and abdominal subcutaneous vein blood slightly decreased around the parturition and at 24 days after the parturition, however, no remarkable arterial-venous differences were observed. Plasma PTHrP levels in both arterial and venous samples were below the detection limit (0.57 pmol/l) during the experimental period. Milk PTHrP and Ca levels were measured in 9 Holstein dairy cows. Although plasma PTHrP levels in all arterial and venous samples were also below the detection limit, milk PTHrP and Ca levels were remarkably high, ranging from 14,900 pmol/l to 41,200 pmol/l and from 772 mg/l to 1,200 mg/l, respectively. In addition, a significant positive correlation (P<0.01) was observed between milk PTHrP and Ca levels. These results suggested that mammary PTHrP is closely related to Ca concentration in the milk.

Mammary-specific deletion of parathyroid hormone-related protein preserves bone mass during lactation.

Large amounts of calcium are transferred to offspring by milk. This demand results in negative calcium balance in lactating mothers and is associated with rapid bone loss. The mechanisms of bone loss during lactation are only partly understood. Several studies have suggested that parathyroid hormone-related protein (PTHrP) might be secreted into the circulation by the lactating mammary gland and regulate bone turnover during lactation. Because mammary development fails in the absence of PTHrP, conventional PTHrP knockout mice cannot be used to address this possibility. To examine this hypothesis, we therefore used mice carrying a beta-lactoglobulin promoter-driven Cre transgene, one null PTHrP allele, and one floxed PTHrP allele. Expression of Cre specifically in mammary epithelial cells during late pregnancy and lactation resulted in efficient deletion of the PTHrP gene; mammary gland PTHrP mRNA and milk PTHrP protein were almost completely absent. Removal of PTHrP from the lactating mammary glands resulted in reductions in levels of circulating PTHrP and 1,25-dihydroxy vitamin D and urinary cAMP. In addition, bone turnover was reduced and bone loss during lactation was attenuated. We conclude that during lactation mammary epithelial cells are a source of circulating PTHrP that promotes bone loss by increasing rates of bone resorption.

Impaired mammary function and parathyroid hormone-related protein during lactation in growth-restricted spontaneously hypertensive rats.

Evidence implicates pivotal roles for parathyroid hormone-related protein (PTHrP) during lactation, including stimulation of mammary and pup growth. As spontaneously hypertensive rat (SHR) pups are growth restricted compared with the control Wistar Kyoto (WKY), we examined the relative roles of pup suckling and maternal lactational environment on pup growth, mammary PTHrP, and milk PTHrP and calcium concentrations. SHR pups were lighter compared with the control from 6 days. SHR mammary PTHrP content and milk PTHrP were lower but maternal plasma PTHrP was raised compared with WKY. SHR mammary morphological development was also impaired compared with control. Cross fostering growth-restricted pups onto WKY mothers increased pup weight in association with normal mammary function and higher milk PTHrP and calcium. Control pups suckling on an SHR mother had reduced body weight. Both cross fostering groups were associated with increased maternal and milk PTHrP concentrations, indicating the importance of suckling, together with a functional mammary gland. The results suggested that impaired SHR mammary function and milk PTHrP are associated with a reduced SHR postnatal growth. Our data also indicated that milk and mammary PTHrP are regulated by different mechanisms but that they are influenced by the maternal lactational environment and the suckling pup.

Cloning of bovine parathyroid hormone-related protein (PTHrP) cDNA and expression of PTHrP mRNA in the bovine mammary gland.

Parathyroid hormone-related protein (PTHrP) produced by the mammary gland has been postulated to have multiple functions in both the mother and neonate. In humans, alternative 3'-mRNA splicing and endoproteolytic processing result in multiple bioactive PTHrP peptides. Multiple PTHrP peptides also have been reported in bovine milk. To investigate the source of molecular heterogeneity of PTHrP in bovine milk, bovine PTHrP was cloned from a bovine brain cDNA library, sequenced and used to characterize the mammary PTHrP transcript. A 1065 bp clone (bP1) for bovine PTHrP was isolated from a brain cDNA library. The bP1 clone contained the entire coding sequence of PTHrP and 61 and 473 nucleotides of the 5'- and 3'-untranslated regions (UTRs) respectively. The predicted amino acid sequence of bovine PTHrP was 72-92% homologous to the sequences of chicken, rat, mouse, human, and canine PTHrP with the highest sequence divergence present in the C-terminal region of the peptide. The 5'- and 3'-UTRs of bovine brain PTHrP have a high degree of homology to exons 4 and 9 of human PTHrP respectively. PTHrP was expressed as a single 1200 nucleotide mRNA transcript in lactating bovine mammary tissue. RT-PCR using region-specific oligonucleotide primers derived from bP1 demonstrated that PTHrP mRNA transcripts in bovine brain and lactating mammary gland utilize the same 5'- and 3'-UTRs. Expression of PTHrP mRNA was localized to secretory and ductular epithelial cells within the lactating mammary gland, as detected using in situ hybridization. Expression of PTHrP mRNA was demonstrated in the mammary gland during late pregnancy and throughout lactation in cows.

Parathyroid hormone-related protein and calcium concentrations in milk and blood of ewes

Parathyroid hormone-related protein (PTHrP) and calcium (Ca) concentrations were measured 2 to 3 months postpartum in milk and plasma or serum of 22 ewes by the use of commercial radioimmunoassay kits for PTHrP concentration, colorimetry for serum total Ca concentration (Ca tot), and atomic absorption spectrophotometry for milk total Ca concentration. Scatter plots did not reveal dependency between milk Ca and Ca tot, Ca tot and plasma PTHrP, milk Ca and milk PTHrP, and milk PTHrP and plasma PTHrP. Thus, the systemic and mammary effects of PTHrP are not major determinants of the endocrine, paracrine, and autocrine regulation of Ca homeostasis during lactation in ewes.

Effect of Treatment of Dairy Cows with Slow-Release Bovine Somatotropin During the Periparturient Period on Minerals in Plasma and Milk and on Parathyroid Hormone-Related Protein in Milk

Slow-release bST was given to dairy cows as a single injection prior to calving to determine whether such treatment prevented parturient hypocalcemia or modified the concentrations of Ca and parathyroid hormone-related protein in milk during the periparturient period. Cows were treated about 1 wk prepartum, and serial blood and milk samples were taken from these and similar prepartum control cows over a 3-wk period. Plasma growth hormone concentrations in the bST-treated group reached a peak 2 d after administration and then declined linearly to control concentrations over a 14-d period. Plasma Ca was unaffected by bST treatment 1 d prior to parturition, on the day of parturition, and at 1 and 6 to 9 d postpartum. Plasma P was higher, and plasma Mg was lower, in the bST-treated group on the day of parturition and 1 d postpartum. Concentrations of Ca, P, Mg, and protein in milk were lower in bST-treated cows than in controls at parturition. Milk production of the bST-treated and control groups was similar when measured at d 6 to 9 postpartum. Concentrations of parathyroid hormone-related protein in milk were substantial at parturition and remained high thereafter, although at parturition the concentration in the milk of the bST-treated group was lower than that of the control group.

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E1077-E1085, 1992.--Production of parathyroid hormone-related protein (PTHrP) by the mammary gland of Sprague-Dawley rats has been examined using immunohistochemistry and in situ hybridization to detect PTHrP and PTHrP mRNA, respectively. PTHrP and PTHrP mRNA could be demonstrated in nests of epithelial cells of the developing mammary gland at day 14 of pregnancy and in the epithelial secretory cells lining the alveoli during the latter stages of pregnancy and during lactation. A specific radioimmunoassay was also used to measure the concentration of PTHrP secreted in the milk throughout lactation. The concentration of PTHrP in milk was relatively low initially but increased during the latter stages of lactation, whereas calcium concentrations remained virtually constant throughout lactation. No correlation was found between the concentrations of calcium and PTHrP in rat milk. These results show that PTHrP is present in rat milk and also in mammary tissue before parturition, and therefore it may assist in the development of the mammary gland during pregnancy.

Parathyroid hormone-related protein in milk and its correlation with bovine milk calcium

Parathyroid hormone-related protein (PTHrP) has been shown to be present in milk of various mammals. We have assayed PTHrP in milk of various species by radioimmunoassay and estimated the molecular weights by Western blot analysis. PTHrP concentrations in bovine, ovine and human milk were 59.2 +/- 18.5, 74.1 +/- 35.0 and 36.6 +/- 20.7 micrograms/l (mean +/- S.D.) respectively, in pooled samples collected at various stages of lactation. PTHrP in mammalian milk was found to exist in two forms with molecular weights of 17.5 kDa and 21.5 kDa approximating those of PTHrP(1-108) and (1-141) respectively. In comparison, marsupial milk PTHrP appeared as a single low molecular weight form of 14.4 kDa which approximated to that of PTHrP(1-84). We performed a longitudinal study measuring the concentration of PTHrP in milk throughout lactation in cows, and found it to increase with the duration of lactation (r = 0.669, n = 91). We further examined the relationship between the concentration of PTHrP and total calcium in bovine milk, and the differences between these constituents in milk from Friesian and Jersey cows. PTHrP concentrations correlated positively with total milk calcium (r = 0.346, n = 105). The mean milk concentration of PTHrP of the Jerseys was significantly higher than that of the Friesians (52.6 +/- 5.4 micrograms/l compared with 41.0 +/- 4.8 micrograms/l, P less than 0.01), as was the mean milk calcium concentration (30.5 +/- 3.0 mmol/l compared with 26.7 +/- 2.7 mmol/l, P less than 0.01). We therefore postulate that production of PTHrP by the mammary gland may be associated with calcium transport from blood to milk. Also PTHrP may play a role in the development of milk fever in Jerseys which are predisposed to this condition.

Characterization of the molecular forms of parathyroid hormone-related protein in milk

Characterization of the molecular forms of parathyroid hormone-related protein in milk