Sex hormone binding globulin and corticosteroid binding globulin as major effectors of steroid action

Seasonal variation in gonadal hormones, spatial cognition, and hippocampal attributes: More questions than answers

A large body of research has been dedicated to understanding the factors that modulate spatial cognition and attributes of the hippocampus, a highly plastic brain region that underlies spatial processing abilities. Variation in gonadal hormones impacts spatial memory and hippocampal attributes in vertebrates, although the direction of the effect has not been entirely consistent. To add complexity, individuals in the field must optimize fitness by coordinating activities with the appropriate environmental cues, and many of these behaviors are correlated tightly with seasonal variation in gonadal hormone release. As such, it remains unclear if the relationship among systemic gonadal hormones, spatial cognition, and the hippocampus also exhibits seasonal variation. This review presents an overview of the relationship among gonadal hormones, the hippocampus, and spatial cognition, and how the seasonal release of gonadal hormones correlates with seasonal variation in spatial cognition and hippocampal attributes. Additionally, this review presents other neuroendocrine mechanisms that may be involved in modulating the relationship among seasonality, gonadal hormone release, and the hippocampus and spatial cognition, including seasonal rhythms of steroid hormone binding globulins, neurosteroids, sex steroid hormone receptor expression, and hormone interactions. Here, endocrinology, ecology, and behavioral neuroscience are brought together to present an overview of the research demonstrating the mechanistic effects of systemic gonadal hormones on spatial cognition and the hippocampus, while, at a functional level, superimposing seasonal effects to examine ecologically-relevant circannual changes in gonadal hormones and spatial behaviors.

Group-specific component exon 11 haplotypes (D432E and T436K) and risk of albuminuria in type 2 diabetes mellitus patients

BACKGROUND

Emerging evidence indicates group-specific component (GC) variants are associated with ethnicity. We aimed to investigate the association of GC variants and protein expression level with T2DM and diabetic nephropathy (DN) in Saudi patients.

SUBJECTS AND METHODS

A total of 200 participants (120 T2DM/80 controls) were genotyped for GC-rs7041/GC-rs4588 by real-time polymerase chain reaction. Serum GC was assessed by ELISA and in silico analysis was executed.

RESULTS

GC-rs7041 frequency distribution showed no difference between the study groups, while GC-rs4588 showed association with T2DM under all genetic models. rs4588*AA variant was correlated with higher serum GC globulin, albuminuria, and poor glycaemic control. A higher frequency of rs7041*TT and rs4588*AA was evident in macroalbuminuria vs. normoalbuminuria group. Carrying GC-2 haplotype was 2.5 more likely to develop diabetes and correlated with the levels of albuminuria.

CONCLUSIONS

GC variants could have independent effects on the risk of T2DM and DN in the study population.

Challenges for measuring oxytocin: The blind men and the elephant?

Since its discovery more than a century ago, oxytocin has become one of the most intensively studied molecules in behavioral biology. In the last five years, Psychoneuroendocrinology has published more than 500 articles with oxytocin in the title, with many of these articles including measures of endogenous oxytocin concentrations. Despite longstanding interest, methods of measuring endogenous oxytocin are still in active development. The widely varying oxytocin concentrations detected by different approaches to measurement - and lack of correlation among these techniques - has led to controversy and confusion. We identify features of oxytocin that may help to explain why various approaches may be differentially sensitive to diverse conformational states of the oxytocin molecule. We propose that discrepancies in data generated by different methods of measurement are not necessarily an indicator that some methods are valid whereas others are not. Rather, we propose that current challenges in the measurement of oxytocin may be analogous to the parable of the blind men and the elephant, with different methods of sample preparation and measurement being sensitive to different states in which the oxytocin molecule can exist.

Estrogen receptors and sex hormone binding globulin in neuronal cells and tissue

Estrogens exert a critical influence on neuronal tissues and cells. As demonstrated in many clinical studies, estrogens are neuroprotective to the extent that they improve prognosis for women with neurodegenerative diseases. Unfortunately, we still do not know exactly how these effects are mediated. Fifty years ago the first estrogen receptor was found, but since then many other new pathways of estrogen action have been identified. This review describes several of these pathways of estrogen effects and provides some conclusions and correlations about these as determined by recent studies with nerve growth factor differentiated rat pheochromocytoma cell line.

An active and selective molecular mechanism mediating the uptake of sex steroids by prostate cancer cells

Steroid hormones play important roles in normal physiological functions and diseases. Sex steroids hormones are important in the biology and treatment of sex hormone-related cancer such as prostate cancer and breast cancer. Cells may take up steroids using multiple mechanisms. The conventionally accepted hypothesis that steroids cross cell membrane through passive diffusion has not been tested rigorously. Experimental data suggested that cells may take up sex steroid using an active uptake mechanism. ³H-testosterone uptake by prostate cancer cells showed typical transporter-mediated uptake kinetic. Cells retained testosterone taken up from the medium. The uptake of testosterone was selective for certain steroid hormones but not others. Data also indicated that the active and selective uptake mechanism resided in cholesterol-rich membrane domains, and may involve ATP and membrane transporters. In summary, the present study provided strong evidence to support the existence of an active and selective molecular mechanism for sex steroid uptake.

Assessment of Vitamin D-Binding Protein and Early Prediction of Nephropathy in Type 2 Saudi Diabetic Patients

Early detection of diabetic nephropathy (DN) represents a great challenge in an attempt to reduce the burden of chronic kidney diseases in diabetic patients. This study aimed to investigate the potential early prediction role of urinary vitamin D-binding protein (uVDBP) for the diagnosis of DN and to examine the possible correlation to serum VDBP, high-sensitivity C-reactive protein (hs-CRP), and insulin resistance in these patients. Serum and urine samples were obtained from 40 healthy volunteers and 120 patients with type 2 diabetes divided into 3 groups: normoalbuminuria, microalbuminuria, and macroalbuminuria (urinary albumin excretion rate < 30, 30-300, and >300 μg/mg, resp.); n = 40/group. Serum and urinary VDBP levels were quantified by ELISA. Insulin resistance has been assessed by homeostasis model assessment index (HOMAI). Correction for urine creatinine concentration was applied for urinary quantitative measurements. uVDBP levels were significantly elevated in micro- and macroalbuminuria patient groups compared with those of the normoalbuminuria patient group and controls (820.4 ± 402.8 and 1458.1 ± 210.0 compared with 193.1 ± 141.0 and 127.7 ± 21.9 ng/mg, resp.) (P < 0.001). There was significant correlation between serum and urinary levels of VDBP in total patient group. Receiver operating characteristic analysis of uVDBP levels showed optimum cut-off value of 216.0 ng/mg corresponding to 98.8% sensitivity and 80.0% specificity and an area under the curve of 0.973 to discriminate the normoalbuminuria from the microalbuminuria groups. In multivariate analysis, ordination plot showed obvious demarcation between the study groups caused by the higher levels of uVDBP and albumin/creatinine ratio among other variables. The study findings suggested a possible clinical application of uVDPB as an early and a good marker for the detection of early renal disease in type 2 DM Saudi patients. Large-scale validation studies are warranted to confirm the results before including uVDBP with the available list of other conventional biomarkers.

SCRAMBLE'N'GAMBLE: a tool for fast and facile generation of random data for statistical evaluation of QSAR models

A common practice in modern QSAR modelling is to derive models by variable selection methods working on large descriptor pools. As pointed out previously, this is intrinsically burdened with the risk of finding random correlations. Therefore it is desirable to perform tests showing the performance of models built on random data. In this contribution, we introduce a simple and freely available software tool SCRAMBLE’N’GAMBLE that is aimed at facilitating data preparation for y-randomization and pseudo-descriptors tests. Then, four close-to-real-world modelling situations are analysed. The tests indicate what the quality of obtained QSAR models is like in comparison to chance models derived from random data. The non-randomness is not the only requirement for a good QSAR model, however, it is a good practice to consider it together with internal statistical parameters and possible physical interpretations of a model.

Phospholipase C-related but catalytically inactive proteins regulate ovarian follicle development

Phospholipase C-related but catalytically inactive proteins PRIP-1 and -2 are inositol-1,4,5-trisphosphate binding proteins that are encoded by independent genes. Ablation of the Prip genes in mice impairs female fertility, which is manifested by fewer pregnancies, a decreased number of pups, and the decreased and increased secretion of gonadal steroids and gonadotropins, respectively. We investigated the involvement of the PRIPs in fertility, focusing on the ovaries of Prip-1 and -2 double-knock-out (DKO) mice. Multiple cystic follicles were observed in DKO ovaries, and a superovulation assay showed a markedly decreased number of ovulated oocytes. Cumulus-oocyte complexes showed normal expansion, and artificial gonadotropin stimulation regulated the ovulation-related genes in a normal fashion, suggesting that the ovulation itself was probably normal. A histological analysis showed atresia in fewer follicles of the DKO ovaries, particularly in the secondary follicle stages. The expression of luteinizing hormone receptor (LHR) was aberrantly higher in developing follicles, and the phosphorylation of extracellular signal-regulated protein kinase, a downstream target of LH-LHR signaling, was higher in DKO granulosa cells. This suggests that the up-regulation of LH-LHR signaling is the cause of impaired follicle development. The serum estradiol level was lower, but estradiol production was unchanged in the DKO ovaries. These results suggest that PRIPs are positively involved in the development of follicles via their regulation of LH-LHR signaling and estradiol secretion. Female DKO mice had higher serum levels of insulin, testosterone, and uncarboxylated osteocalcin, which, together with reduced fertility, are reminiscent of polycystic ovary syndrome in humans.

How serpins transport hormones and regulate their release

The adaptation of the serpin framework and its mechanism to perform diverse functions is epitomised in the hormone carriers of the blood. Thyroxine and the corticosteroids are transported bound in a 1:1 ratio on almost identical sites in the two homologous binding-globulins, TBG and CBG. Recent structural findings show an equilibrated, rather than on-and-off, release of the hormones from the carriers, reflecting small reversible movements of the hinge region of the reactive loop that modify the conformational flexibility of the underlying hormone-binding site. Consequently, contrary to previous concepts, the binding affinities of TBG and CBG are not fixed but can be allosterically modified to allow differential hormone delivery. Notably, the two carriers function like protein thermocouples with a surge in hormone release as body temperatures rise in fevers, and conversely a large diminution in free hormone levels at hibernation temperatures. By comparison angiotensinogen, the source of the angiotensin peptides that control blood pressure, does not appear to utilise the serpin mechanism. It has instead evolved a 63 residue terminal extension containing the buried angiotensin cleavage site, which on interaction moves into the active cleft of the renin. The conformational shift involved is critically linked by a labile disulphide bridge. The observation of changes in the redox status of this S-S bridge, in the hypertensive complication of pregnancy, pre-eclampsia, has opened an unexpected level of regulation at what is the initial stage in the control of blood pressure.

New Roles for Corticosteroid Binding Globulin and Opposite Expression Profiles in Lung and Liver

Corticosteroid-binding globulin (CBG) is the specific plasma transport glycoprotein for glucocorticoids. Circulating CBG is mainly synthesized in liver but, its synthesis has been located also in other organs as placenta, kidney and adipose tissue with unknown role. Using an experimental model of acute pancreatitis in cbg^-/- mice we investigated whether changes in CBG affect the progression of the disease as well as the metabolism of glucocorticoids in the lung. Lack of CBG does not modify the progression of inflammation associated to pancreatitis but resulted in the loss of gender differences in corticosterone serum levels. In the lung, CBG expression and protein level were detected, and it is noteworthy that these showed a sexual dimorphism opposite to the liver, i.e. with higher levels in males. Reduced expression of 11β-HSD2, the enzyme involved in the deactivation of corticosterone, was also observed. Our results indicate that, in addition to glucocorticoids transporter, CBG is involved in the gender differences observed in corticosteroids circulating levels and plays a role in the local regulation of corticosteroids availability in organs like lung.

Sex Hormone Binding Globulin Modifies Testosterone Action and Metabolism in Prostate Cancer Cells

Sex Hormone Binding Globulin (SHBG) is the major serum carrier of sex hormones. However, growing evidence suggests that SHBG is internalised and plays a role in regulating intracellular hormone action. This study was to determine whether SHBG plays a role in testosterone uptake, metabolism, and action in the androgen sensitive LNCaP prostate cancer cell line. Internalisation of SHBG and testosterone, the effects of SHBG on testosterone uptake, metabolism, regulation of androgen responsive genes, and cell growth were assessed. LNCaP cells internalised SHBG by a testosterone independent process. Testosterone was rapidly taken up and effluxed as testosterone-glucuronide; however this effect was reduced by the presence of SHBG. Addition of SHBG, rather than reducing testosterone bioavailability, further increased testosterone-induced expression of prostate specific antigen and enhanced testosterone-induced reduction of androgen receptor mRNA expression. Following 38 hours of testosterone treatment cell morphology changed and growth declined; however, cotreatment with SHBG abrogated these inhibitory effects. These findings clearly demonstrate that internalised SHBG plays an important regulatory and intracellular role in modifying testosterone action and this has important implications for the role of SHBG in health and disease.

Evaluation of seasonal changes of serum and plasma estradiol-17β, progesterone and testosterone in dolphins (Tursiops truncatus) by chemiluminescence

Aim:

The purpose of the research was to test and validate an innovative and safe chemiluminescence method to evaluate sexual hormones in serum and plasma samples of Tursiops truncatus.

Materials and Methods:

The research was performed on 9 bottlenose dolphins entertained in Oltremare and in Zoomarine aquatic parks, sampled by the tail vein or from the ventral one and an ultrasound monitoring, throughout a 6 months period. Blood samples were analyzed using a chemiluminescence method. Data obtained were compared to radioimmunoassay and enzyme immuno assay reference data, with the purpose to test and validate this method, through the calculation of the coefficient of variability, and its reliability on serum and plasma samples. A one-way analysis of variance was applied to test the effect of time on serum and plasma hormonal changes.

Results:

Mean concentrations of estradiol-17β in serum were equal to 149.07±6.82 pmol/L, and in plasma equal to 159.14±12.99 pmol/L; mean values of progesterone in serum were equal to 0.69±0.05 pmol/L, and in plasma equal to 0.64±0.05 pmol/L; mean values of testosterone in serum were equal to 44.43±14.42 nmol/L, and in plasma equal to 48.99±11.20 nmol/L.

Conclusion:

It would be interesting to widen the investigations on a larger number of subjects, in which the relationship between the concentrations of free and binding steroid hormones, with the dosing of binding proteins, would define the physiological ranges of reference in the T. truncatus.

Sex differences in the long-lasting effects of a single exposure to immobilization stress in rats

In male rats, a single exposure to a severe stressor such as immobilization (IMO) results in marked activation of the HPA axis and reduction of body weight gain. In addition, the HPA response to the same (homotypic) stressor is reduced, whereas the response to a different (heterotypic) stressor is enhanced for days. Although sex differences in the responsiveness of the HPA axis have been described, there are few studies about the influence of sex on long-lasting effects of stress. Thus, we have compared the consequences of a single exposure to IMO in male and female rats. Females showed a similar ACTH response to the first IMO associated with higher corticosterone, but they were more resistant than males to stress-induced loss of body weight. Unstressed females showed higher resting levels of ACTH and corticosterone, but they did not show the increase in the resting levels of HPA hormones observed in males on the day after IMO. During exposure to a different stressor (open-field) two days after IMO, enhanced corticosterone response and hypoactivity was observed in males, but not in females. Finally, a second exposure to IMO 8 days after the first one resulted in a reduction of the HPA response and of the negative impact on body weight as compared to the first exposure, and this protective effect was greater in females. In sum, IMO-exposed females showed a greater reduction of the response to a second IMO and appear to be more resistant than males to some of the negative impacts of IMO.

The causal effect of vitamin D binding protein (DBP) levels on calcemic and cardiometabolic diseases: a Mendelian randomization study

BACKGROUND

Observational studies have shown that vitamin D binding protein (DBP) levels, a key determinant of 25-hydroxy-vitamin D (25OHD) levels, and 25OHD levels themselves both associate with risk of disease. If 25OHD levels have a causal influence on disease, and DBP lies in this causal pathway, then DBP levels should likewise be causally associated with disease. We undertook a Mendelian randomization study to determine whether DBP levels have causal effects on common calcemic and cardiometabolic disease.

METHODS AND FINDINGS

We measured DBP and 25OHD levels in 2,254 individuals, followed for up to 10 y, in the Canadian Multicentre Osteoporosis Study (CaMos). Using the single nucleotide polymorphism rs2282679 as an instrumental variable, we applied Mendelian randomization methods to determine the causal effect of DBP on calcemic (osteoporosis and hyperparathyroidism) and cardiometabolic diseases (hypertension, type 2 diabetes, coronary artery disease, and stroke) and related traits, first in CaMos and then in large-scale genome-wide association study consortia. The effect allele was associated with an age- and sex-adjusted decrease in DBP level of 27.4 mg/l (95% CI 24.7, 30.0; n = 2,254). DBP had a strong observational and causal association with 25OHD levels (p = 3.2 × 10(-19)). While DBP levels were observationally associated with calcium and body mass index (BMI), these associations were not supported by causal analyses. Despite well-powered sample sizes from consortia, there were no associations of rs2282679 with any other traits and diseases: fasting glucose (0.00 mmol/l [95% CI -0.01, 0.01]; p = 1.00; n = 46,186); fasting insulin (0.01 pmol/l [95% CI -0.00, 0.01,]; p = 0.22; n = 46,186); BMI (0.00 kg/m(2) [95% CI -0.01, 0.01]; p = 0.80; n = 127,587); bone mineral density (0.01 g/cm(2) [95% CI -0.01, 0.03]; p = 0.36; n = 32,961); mean arterial pressure (-0.06 mm Hg [95% CI -0.19, 0.07]); p = 0.36; n = 28,775); ischemic stroke (odds ratio [OR]  = 1.00 [95% CI 0.97, 1.04]; p = 0.92; n = 12,389/62,004 cases/controls); coronary artery disease (OR = 1.02 [95% CI 0.99, 1.05]; p = 0.31; n = 22,233/64,762); or type 2 diabetes (OR = 1.01 [95% CI 0.97, 1.05]; p = 0.76; n = 9,580/53,810).

CONCLUSIONS

DBP has no demonstrable causal effect on any of the diseases or traits investigated here, except 25OHD levels. It remains to be determined whether 25OHD has a causal effect on these outcomes independent of DBP. Please see later in the article for the Editors' Summary.

Establishing regional specificity of neuroestrogen action

The specificity of estrogen signaling in brain is defined at one level by the types and distributions of receptor molecules that are activated by estrogens. At another level, as our understanding of the neurobiology of the estrogen synthetic enzyme aromatase has grown, questions have emerged as to how neuroactive estrogens reach specific target receptors in functionally relevant concentrations. Here we explore the spatial specificity of neuroestrogen signaling with a focus on studies of songbirds to provide perspective on some as-yet unresolved questions. Studies conducted in both male and female songbirds have helped to clarify these interesting facets of neuroestrogen physiology.

Localization of sex hormone binding globulin in the rat vomeronasal organ

Volatile and non-volatile derivates of gonadal steroids are known to act as pheromones in many mammalian species. Pheromones have multiple effects on the brain via the olfactory system. Their primary port of entry seems to be the vomeronasal organ (VNO) but the underlying cellular and molecular mechanisms are unclear so far. Recently we localized sex hormone binding globulin (SHBG) in both the main and the accessory olfactory system of rat with immunocytochemistry and RT-PCR. The accessory olfactory system consisting of VNO and accessory olfactory bulb showed high expression of SHBG. In the present paper we studied SHBG expression in the VNO in greater detail. In semithin sections we found SHBG immunostaining in the perinuclear cytoplasm of some of the sensory neurons, in sensory cilia and in their axons. A portion of the basal cells and some of the goblet cells in the non-sensory epithelium showed intense SHBG staining. SHBG was abundant in exocrine cells of the vomeronasal glands, perhaps compartimentalized in secretory vesicles. In situ hybridization revealed specific signals in sensory and non-sensory cells of the VNO. Our findings indicate that SHBG expressed in the VNO may be liberated into nasal secretions to bind aerosolic steroids. SHBG in sensory cells may be involved in signaling actions of pheromones.

Sex hormone binding globulin in the rat olfactory system

Ovarian steroids are known to act on the olfactory system. Their mode of action, however, is mostly unclear to date since nuclear receptors are lacking in sensory neurons. Here we used immunocytochemistry and RT-PCR to study expression and distribution of sex hormone binding globulin (SHBG) in the rat olfactory system. Single sensory cells in the olfactory mucosa and their projections in the olfactory bulb showed specific SHBG immunostaining as determined by double immunofluorescence with olfactory marker protein OMP. Larger groups of SHBG stained sensory cells occurred in the vomeronasal organ (VNO). A portion of the olfactory glomeruli in the accessory olfactory bulb showed large networks of SHBG positive nerve fibres. Some of the mitral cells showed SHBG immune fluorescence. RT-PCR revealed SHBG encoding mRNA in the olfactory mucosa, in the VNO and in the olfactory bulbs indicating intrinsic expression of the binding globulin. The VNO and its related projections within the limbic system are known to be sensitive to gonadal steroid hormones. We conclude that SHBG may be of functional importance for rapid effects of olfactory steroids on limbic functions including the control of reproductive behaviours through pheromones.