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At least 973 records · Page 54Linked to original sources
PubMed2004

Detection of a CBG-like protein in human Fallopian tube tissue.

The acrosome reaction (AR), a modified exocytotic process, is prerequisite for successful mammalian fertilization. The protein component that is responsible for the AR-inducing activity of human follicular fluid, has been found to be immunologically identical with corticosteroid-binding globulin (CBG), which is well characterized and serves as a transport protein for progesterone and cortisol in the plasma. Our findings have shown that the CBG-like protein is expressed by endothelial cells of the Fallopian tube depending on the hormonal cycle. In the culture medium of human epithelial tubal cells, the CBG-like protein was detected by Western blot analysis. The protein was also found in biologically active form in human tubular fluid. Our investigations strongly indicate that human Fallopian tube cells actively express and secrete a CBG-like progesterone-binding protein, which might play a role in the in vivo modulation of human sperm AR.

Acrosome Reaction↗
PubMed2003

Effects of prenatal stress on corticosteroid receptors and monoamine concentrations in limbic areas of suckling piglets (Sus scrofa) at different ages.

The present study was conducted in order to reveal the effects of prenatal stress on the central stress regulation in domestic pigs by measuring changes in corticosteroid receptor binding and monoamine concentrations in different limbic brain regions. Pregnant sows were subjected to a restraint stress for 5 min daily during the last 5 weeks of gestation. Maternal stress resulted in a significantly higher number of glucocorticoid receptors in the hippocampus, but decreased glucocorticoid receptors in the hypothalamus of the offspring at the first postnatal day. No alterations of hippocampal mineralocorticoid receptors were found. There was also no significant effect of prenatal stress on the brain monoamine concentrations. Prenatally stressed piglets showed lower basal plasma cortisol and increased corticosteroid binding globulin concentrations at the third postnatal day indicating decreased free cortisol concentrations after birth. Morbidity and mortality during the suckling period were significantly increased in prenatally stressed litters, as shown by a higher frequency of diseased and died piglets per litter. In conclusion, the results indicate that in pigs restraint stress during late gestation affects the ontogeny of the foetal neuroendocrine feedback system with consequences for the regulation of the hypothalamo-pituitary-adrenal function and the vitality of the offspring.

Adrenocorticotropic Hormone↗
PubMed1985

The regulation of glucocorticosteroid secretion during the perinatal period.

The regulation of adrenal activity during the perinatal period raises different experimental problems; studies are often limited and their conclusions vary with the species studied. During the perinatal period, the profile of the ratio of adrenal weight to body weight reaches a minimum earlier the more mature is the species; this minimum occurs before birth in sheep, at birth in guinea-pigs and 10 days after birth in mice. In mature species, fetal plasma cortisol is higher than that of the mother; it rises sharply near term. In other species, maternal plasma cortisol remains higher than that of the fetus which also rises during the days before birth. In all species, the fetal adrenal is activated concomitantly with a sharp increase of the action of corticosteroid binding globulin on fetal plasma. The origins of this protein in the fetal plasma and the regulation of its concentration are topics of actual research. Before birth, placental transfer of cortisol increases regularly and slowly. During the perinatal period it is demonstrated that fetal catabolism of cortisol augments up to the adult level independently of changes in hormone secretion around birth.

Adrenal Glands↗
PubMed1995

Levels of sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) messenger ribonucleic acid (mRNAs) in ovarian endometriosis.

Recently, much evidence has indicated that sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) play a role in the intracellular action of sex steroids in target cells. In the present work, expression of SHBG mRNA and CBG mRNA was demonstrated in tissues of human normal endometrium and pelvic endometriosis, using the reverse transcription-polymerase chain reaction (RT-PCR). SHBG mRNA levels were higher in pelvic endometriosis than in normal endometrium (P < 0.02), while CBG mRNA levels were lower than in normal endometrium (P < 0.05). The SHBG mRNA/CBG mRNA ratio was significantly higher in pelvic endometriosis than in normal endometrium (P < 0.01). These findings suggest that overexpression of intercellular SHBG in endometriotic tissues results in the formation of the estrogen-predominant milieu, since SHBG-bound estrogen is considered to be protected from the metabolism in liver and available in endometrial cells, thereby assisting the development of the pelvic endometriosis.

Adult↗
PubMed2001

Study of the effect of changing glucose, insulin, and insulin-like growth factor-I levels on serum corticosteroid binding globulin in lean, obese, and obese subjects with glucose intolerance.

We have previously described that serum corticosteroid binding globulin (CBG) concentrations are associated with insulin secretion. The present study was designed to evaluate the effects of changing insulin concentrations, both endogenous and after exogenous insulin administration, on circulating CBG levels in vivo. Serum CBG concentrations were measured during an insulin-modified frequently sampled intravenous (IV) glucose tolerance test (FSIVGT) in 14 lean and 19 obese otherwise healthy subjects with varying degrees of glucose tolerance. Acute insulin response to glucose (AIRg) correlated significantly with serum CBG concentrations at time 0 (r = -.38, P =.029), 22 minutes (r = -.41, P =.01), 50 minutes (r = -.41, P =.01), and 180 minutes (r = -.39, P =.02). Insulin sensitivity (S(I)) was not associated with serum CBG concentration at time 0 (r = -.16, P = not significant [NS]), but correlated significantly with CBG concentration at 22 minutes (r = -.41, P =.02) and 50 minutes (r = -.35, P =.048) of the FSIVGT. In lean subjects, serum CBG concentration decreased significantly after IV insulin from 37.9 +/- 5.4 to 35.4 +/- 3 mg/L (P =.02) and returned to basal levels thereafter. In contrast, obese, glucose-tolerant subjects had lower CBG levels than lean and obese glucose intolerant subjects (33.8 +/- 3.0 v 37.9 +/- 5.4 and 39.8 +/- 4.4 mg/L, respectively), and their serum CBG concentrations remained unchanged during FSIVGT. Mean serum-free insulin-like growth factor-I (IGF-I) concentrations steadily declined from 1.21 +/- 0.81 to 0.8 +/- 0.36 microg/L during the FSIVGT, and this effect was restricted to lean subjects. Basal serum-free IGF-I did not correlate with CBG levels at time 0, but correlated inversely with the serum CBG concentrations at 22 minutes (r = -.36, P =.04). Stepwise multivariant analysis showed that AIRg (P =.035) and S(I) (P =.046), but not free IGF-I levels, independently contributed to 28% of CBG variance at 22 minutes. These results suggest that insulin, but not IGF-I, constitutes an important negative regulator of CBG liver synthesis. Endogenous and exogenous insulin do not affect serum CBG concentrations in insulin-resistant obese subjects with preserved or decreased insulin secretion. Obese glucose-tolerant subjects are hypothesized to exhibit tonically inhibited serum CBG levels. In contrast, in lean subjects, the higher the insulin secretion the lower the serum CBG concentration. The mechanisms of this CBG inhibitory effect exerted by insulin and its implication on cortisol homeostasis and fat distribution in humans await further investigations.

Adult↗
PubMed2001

Modulation of corticosterone availability to white adipose tissue of lean and obese Zucker rats by corticosteroid-binding globulin.

Corticosterone-binding (CB) capacity was determined in periovarian and subcutaneous white adipose tissue (WAT), as well as in plasma of lean and obese Zucker rats. In lean rats, plasma CB was twice the level of obese rats. In lean rat WAT, dexamethasone binding accounted for only 0.05-0.09% of corticosterone binding, and aldosterone bound even less; in the obese rats, dexamethasone accounted for 0.2 - 0.3 % of corticosterone binding. Scatchard plots showed that KD for corticosterone was 3.1 nM (WAT) or 3.4 nM (plasma) in lean rats and 1.8 nM (WAT) or 1.5 nM (plasma) in obese rats. The total CB capacity in WAT was lower in the obese than in lean rats (47-50%). Plasma non-esterified fatty acid levels were higher in obese rats. The results suggest that CBG may limit the access of glucocorticoids to adipocytes more weakly in obese rats because of the lower CBG. Fatty acids may increase the affinity of CBG for corticosterone, which would make WAT cells less accessible to circulating glucocorticoids. The modulation of CBG by fatty acids may protect fat reserves by decreasing the sensitivity of WAT to glucocorticoids.

Adipose Tissue↗
PubMed2004

Pregnancy-associated corticosteroid-binding globulin: high resolution separation of glycan isoforms.

Corticosteroid-binding globulin (CBG) is a glycoprotein that functions as a specific carrier of cortisol in the circulation. CBG contains six sites for N-glycosylation with, on average, five sites occupied by a mixture of biantennary and triantennary oligosaccharides with variable additional terminal sialic acid residues leading to glycoforms with significant heterogeneity in mass and isoelectric points. During pregnancy, a form of CBG possessing only triantennary oligosaccharides comprising approximately 10 % of total CBG appears specifically. We describe the first application of two-dimensional gel electrophoresis to the separation of human CBG glycoforms. This technique resolved a greater degree of charge heterogeneity than previous studies, and allowed simultaneous visualization of changes to the size and isoelectric points of CBG during pregnancy. Profiles of CBG glycoforms during pregnancy showed a general increase in size followed by a shift to lower pI in a large proportion of the glycoprotein. This may result from the enhancement of triantennary glycosylation, with the extent of incorporation of sialic acid increasing with the number of available sites for its addition. The pregnancy-specific CBG previously defined probably represents a subset of the acidic and high molecular weight glycoforms we have resolved by two-dimensional electrophoresis and now describe as pregnancy-associated CBG.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2006

Effects on the male endocrine system of long-term treatment with gonadotropin-releasing hormone agonists and estrogens in male-to-female transsexuals.

We studied hormonal changes resulting from long-term treatment with gonadotropin-releasing hormone agonist and 17beta estradiol valerate in 40 healthy middle-aged male-to-female transsexuals over a period of two years. All of the participants received injections of 3.8 mg goserelin acetate every four weeks in combination with 6 mg oral 17beta estradiol valerate per day for cross-sex hormone treatment for male-to-female transsexuals. There was a significant reduction in the levels of serum luteinizing hormone and follicle-stimulating hormone to the hypogonadal stage. Mean testosterone levels decreased by 97% to 0.52 and 0.59 nmol/l after 12 months and 24 months, respectively. There was a significant reduction in dehydroepiandrosterone sulfate by 37% after 12 months and 43% after 24 months, and androstendione by 29% after 12 months and 27% after 24 months, respectively. Cortisol levels were reduced by 43% and 50%, respectively. Estrogen levels were significantly increased from 77.51 to 677 after 12 months and 661 pmol/l after 24 months. Sex hormone-binding globulin and corticoid-binding globulin levels were significantly increased after 12 and 24 months. There was a significant decrease in all measured androgen fractions and cortisol during long-term treatment with gonadotropin-releasing hormone agonist and 17beta estradiol valerate. Apart from suppression of testicular hormone production, one possible interpretation is that treatment with long-term gonadotropin-releasing hormone agonist and 17beta estradiol valerate influences adrenal hormone levels in healthy middle-aged male-to-female transsexuals. Cortisol serum levels may be decreased due to estrogen-induced increase in corticoid-binding globulin.

Adolescent↗
PubMed2006

Plasma variation of corticosteroid-binding globulin and sex hormone-binding globulin.

Sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) circulate in plasma and bind their cognate ligands with high affinity, offering a steroid delivery system to target tissues by a variety of mechanisms. Analysis of these steroid-binding proteins is gaining importance in the clinical setting, although more information is warranted on their diurnal and biological variation. This study shows that plasma SHBG (in normal subjects) exhibits little diurnal or biological variation over the 30 day period studied, in contrast to CBG, where plasma levels peak in the early afternoon. This leads to attenuation of the diurnal free cortisol level rhythm compared to total cortisol. We also show that plasma CBG is significantly lower in male subjects with the metabolic syndrome compared to age-matched lean counterparts, and may therefore act as a surrogate marker of insulin resistance. The consequence of lower levels of CBG in these obese male subjects is reflected by higher levels of circulating free cortisol, potentially offering a more favourable environment for adipogenesis.

Adult↗
PubMed2006

Expression of corticosterone-binding globulin in the rat hypothalamus.

We observed coexistence of corticosteroid-binding globulin (CBG) with vasopressin (VP) and oxytocin (OT) in magnocellular neurons in rat hypothalamus by combined immunoperoxidase staining and immunofluorescence. A portion of the supraoptic and of the paraventricular neurons showed double immunostaining of CBG with either VP or with OT. CBG staining was intensified by pretreating animals with colchicine to block axonal transport. CBG was also observed in widespread axonal projections throughout the lateral hypothalamus, the median eminence and the posterior pituitary lobe. Single ependymal cells and some of the endocrine cells in the anterior lobe contained specific CBG immunoreactivity. IN SITU hybridization of semithin sections with a synthetic oligonucleotide probe to CBG mRNA provided staining of magnocellular hypothalamic neurons, but not ependymal cells or anterior lobe cells. Western blots of CBG extracted by affinity chromatography from hypothalamus homogenates showed a band at approximately 50 kDa. Our observations indicate the intrinsic expression of CBG in peptidergic hypothalamus neurons in rat. The multiple locations of CBG-expressing neurons indicate multiple functional properties, probably exceeding the role of a mere steroid transporter. CBG is likely to be subject to axonal transport and secretion in a neuropeptide-like fashion, perhaps involved in neuroendocrine regulation, which may include stress responses.

Animals↗
PubMed2006

Expression of corticosteroid-binding protein in the human hypothalamus, co-localization with oxytocin and vasopressin.

Corticosteroid-binding globulin, a specific steroid carrier in serum with high binding affinity for glucocorticoids, is expressed in various tissues. In the present study, we describe the immunocytochemical distribution of this protein in neurons and nerve fibers in the human hypothalamus. CBG immunoreactive perikarya and fibers were observed in the paraventricular, supraoptic, and sexual dimorphic nuclei in the perifornical region, as well as in the lateral hypothalamic and medial preoptic areas, the region of the diagonal band, suprachiasmatic and ventromedial nuclei, bed nucleus of the stria terminalis and some epithelial cells from the choroid plexus and ependymal cells. Stained fibers occurred in the median eminence and infundibulum. Double immunostaining revealed a partial co-localization of corticosteroid-binding globulin with oxytocin and, to a lesser extent, with vasopressin in the paraventricular and the supraoptic nuclei. Double immunofluorescence staining showed coexistence of these substances in axonal varicosities in the median eminence. We conclude that neurons of the human hypothalamus are capable of expressing corticosteroid-binding globulin, in part co-localized with the classical neurohypophyseal hormones. The distribution of CBG immunoreactive neurons, which is widespread but limited to specific nuclei, indicates that CBG has many physiological functions that may include neuroendocrine regulation and stress response.

Aged↗
PubMed2006

Plasma-binding globulins and acute stress response.

Within studies of acute stress physiology an increase in glucocorticoid secretion is thought to be the primary mediator of tissue response to stress. Corticosteroid-binding globulin may regulate tissue availability of steroids, but has not been considered a dynamic component of the acute stress response. Here, we examined CBG level over the common 60-minute time frame in an acute capture and handling protocol to investigate whether CBG capacity is dynamic or static over short stressors. Using a comparative approach, we measured CBG response to capture and handling stress in nine species of birds, representing five orders and nine families. CBG capacity significantly declined within 30 - 60 minutes of capture in five of the nine species examined. This decline may serve to significantly increase the level of corticosterone reaching tissues during acute stress.

Acute-Phase Reaction↗
PubMed1993

Corticosteroid-binding globulin levels in the rat serum under conditions of starvation and restriction of motions.

Serum corticosteroid-binding globulin (CBG) concentrations were measured by a radioligand method in rats under the action of some factors influencing activity of pituitary-adrenal system. Basal CBG levels were about 2-fold higher in females than in males. In females only starvation resulted in a significant lowering of CBG activity, while in males CBG was affected only by restriction of motions for 5h Ether treatment in both sexes, pregnancy in females and adrenalectomy in males did not influence CBG levels.

Adrenalectomy↗