Corticosteroid-binding globulin: the clinical significance of altered levels and heritable mutations

Diagnostic and therapeutic value of human serpin family proteins

SERPIN (serine proteinase inhibitors) is an acronym for the superfamily of structurally similar proteins found in animals, plants, bacteria, viruses, and archaea. Over 1500 SERPINs are known in nature, while only 37 SERPINs are found in humans, which participate in inflammation, coagulation, angiogenesis, cell viability, and other pathophysiological processes. Both qualitative or quantitative deficiencies or overexpression and/or abnormal accumulation of SERPIN can lead to diseases commonly referred to as "serpinopathies". Hence, strategies involving SERPIN supplementation, elimination, or correction are utilized and/or under consideration. In this review, we discuss relationships between certain SERPINs and diseases as well as putative strategies for the clinical explorations of SERPINs.

Proteomic mapping reveals dysregulated angiogenesis in the cerebral arteries of rats with early-onset hypertension

Hypertension is associated with the presence of vascular abnormalities, including remodeling and rarefaction. These processes play an important role in cerebrovascular disease development; however, the mechanistic changes leading to these diseases are not well characterized. Using data-independent acquisition-based mass spectrometry analysis, here we determined the protein changes in cerebral arteries in pre- and early-onset hypertension from the spontaneously hypertensive rat (SHR), a model that resembles essential hypertension in humans. Our analysis identified 125 proteins with expression levels that were significantly upregulated or downregulated in 12-week-old spontaneously hypertensive rats compared to normotensive Wistar Kyoto rats. Using an angiogenesis enrichment analysis, we further identified a critical imbalance in angiogenic proteins that promoted an anti-angiogenic profile in cerebral arteries at early onset of hypertension. In a comparison to previously published data, we demonstrate that this angiogenic imbalance is not present in mesenteric and renal arteries from age-matched SHRs. Finally, we identified two proteins (Fbln5 and Cdh13), whose expression levels were critically altered in cerebral arteries compared to the other arterial beds. The observation of an angiogenic imbalance in cerebral arteries from the SHR reveals critical protein changes in the cerebrovasculature at the early onset of hypertension and provides novel insights into the early pathology of cerebrovascular disease.

Light and electron microscopic studies on the influence of stress on prolactin-immunoreactivity in rat anterior pituitary lobe

An increasing number of evidence suggests an important role of prolactin in the modulation of stress response. However, the mechanisms of its action on the HPA axis are not yet understood. Glucocorticoids, liberated from adrenal cortex due to hormonal signals from pituitary corticotrophs are known to play a key role in systemic stress response. Previously we found evidence that corticosteroid-binding globulin (CBG) is involved in rapid, membrane-mediated actions of adrenal steroids. Here we studied qualitatively immunostainings for prolactin and CBG in pituitaries of male rats that had been subjected to osmotic challenge. We also examined late pregnant, parturient and early lactating rats, assuming that parturition represents a strong physiological stress. We employed double immunofluorescencent staining of semithin sections and immunoelectron microscopy. In stressed males we found increased prolactin immunofluorescence associated with membranes while in controls this staining was predominantly cytoplasmatic. CBG immunofluorescence was found in almost all prolactin cells of stressed males while such double staining was only occasionally observed in controls. Similar observations were made in females: While parturient rats showed intense membrane associated double staining for both antigens, late pregnant and early lactating animals showed patterns similar to that of male controls. Immunoelectron microscopy revealed increased exocytosis of prolactin containing vesicles in lactating rats. CBG was localized on cell membranes and additionally within prolactin vesicles. Our observations suggest prolactin liberation from pituitary lactotrophs along with CBG upon systemic stress response. Membrane effects of glucocorticoids mediated by CBG may be linked to stimulus secretion of prolactin.

Onset of Addison Disease appeared during the first trimester of a twin pregnancy: A case report

Addison Disease is an uncommon, life‐threatening condition affecting people at any age, including women during pregnancy. If left untreated, the disease can be rapidly fatal, but the prognosis is good if promptly recognized and hormones are replaced.

Occult Adrenal Insufficiency in Renal Amyloidosis Patients

Objective

Systemic amyloidosis may affect many organs, and may cause endocrinologic problems which may result in adrenal insufficiency. However, assessment of adrenocortical reserve is challenging in amyloidosis patients with renal involvement. We aimed to evaluate adrenocortical reserve with various methods of cortisol measurement to determine any occult clinical condition.

Methods

Patients with renal amyloidosis and healthy subjects were evaluated in this cross-sectional study. Basal cortisol, corticosteroid-binding globulin (CBG), and albumin levels were measured. Serum free cortisol (cFC) level was calculated. Cortisol response tests performed after ACTH stimulation test (250 μg, intravenously) were evaluated, and free cortisol index (FCI) was calculated.

Results

Twenty renal amyloidosis patients, and 25 healthy control subjects were included in the study. Patients and control subjects had similar median serum baseline cortisol levels [258 (126-423) vs 350 (314-391) nmol/L, p=0.169)] whereas patients’ stimulated cortisol levels at the 60^th minute were lower [624 (497-685) vs 743 (674-781) nmol/L, p=0.011)]. The 60^th-minute total cortisol levels of 8 of the 20 (40%) amyloidosis patients were <500 nmol/L, but only three of these 8 patients had stimulated FCI <12 nmol/mg suggesting an adrenal insufficiency (15%).

Conclusion

ACTH stimulation test and cortisol measurements should be considered in renal amyloidosis patients with severe proteinuria to avoid false positive results if only ACTH stimulation test is used. It will be appropriate to evaluate this group of patients together with estimated measurements as FCI.

The Free Hormone Hypothesis: When, Why, and How to Measure the Free Hormone Levels to Assess Vitamin D, Thyroid, Sex Hormone, and Cortisol Status

The free hormone hypothesis postulates that only the nonbound fraction (the free fraction) of hormones that otherwise circulate in blood bound to their carrier proteins is able to enter cells and exert biologic effects. In this review, I will examine four hormone groups-vitamin D metabolites (especially 25OHD), thyroid hormones (especially thyroxine [T4]), sex steroids (especially testosterone), and glucocorticoids (especially cortisol)-that are bound to various degrees to their respective binding proteins-vitamin D-binding protein (DBP), thyroid-binding globulin (TBG), sex hormone-binding globulin (SHBG), and cortisol-binding globulin (CBG)-for which a strong case can be made that measurement of the free hormone level provides a better assessment of hormonal status than the measurement of total hormonal levels under conditions in which the binding proteins are affected in levels or affinities for the hormones to which they bind. I will discuss the rationale for this argument based on the free hormone hypothesis, discuss potential exceptions to the free hormone hypothesis, and review functions of the binding proteins that may be independent of their transport role. I will then review the complications involved with measuring the free hormone levels and the efforts to calculate those levels based on estimates of binding constants and levels of both total hormone and total binding protein. In this review, the major focus will be on DBP and free 25OHD, but the parallels and differences with the other binding proteins and hormones will be highlighted. Vitamin D and its metabolites, thyroid hormones, sex steroids, and glucocorticoids are transported in blood bound to serum proteins. The tightness of binding varies depending on the hormone and the binding protein such that the percent free varies from 0.03% for T4 and 25OHD to 4% for cortisol with testosterone at 2%. Although the major function of the primary carrier proteins (DBP, TBG, SHBG, and CBG) may be to transport their respective lipophilic hormones within the aqueous media that is plasma, these proteins may have other functions independent of their transport function. For most tissues, these hormones enter the cell as the free hormone presumably by diffusion (the free hormone hypothesis), although a few tissues such as the kidney and reproductive tissues express megalin/cubilin enabling by endocytosis protein-bound hormone to enter the cell. Measuring the free levels of these protein-bound hormones is likely to provide a better measure of the true hormone status than measuring the total levels in situations where the levels and/or affinities of the binding proteins are altered. Methods to measure free hormone levels are problematic as the free levels can be quite low, the methods require separation of bound and free that could disturb the steady state, and the means of separating bound and free are prone to error. Calculation of free levels using existing data for association constants between the hormone and its binding protein are likewise prone to error because of assumptions of linear binding models and invariant association constants, both of which are invalid. © 2020 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Comparison of liver gene expression by RNAseq and PCR analysis after 8 weeks of feeding soy protein isolate- or casein-based diets in an obese liver steatosis rat model

Differential expression of genes provides insight into fundamental mechanisms associated with the ability of soy protein isolate to attenuate liver steatosis in genetically obese rats.

The HPA Axis During the Perinatal Period: Implications for Perinatal Depression

The transition to motherhood is characterized by some of the most pronounced endocrine changes a woman will experience in her lifetime. Unfortunately, matrescence is also a time in a woman's life when she is most susceptible to mental illness such as perinatal depression. A growing body of research has aimed to determine how key endocrine systems, such as the hypothalamic-pituitary-adrenal (HPA) axis, are involved in the dysregulation of perinatal mental health. However, very little research has consistently linked perinatal changes in the HPA axis with maternal mental illness. Therefore, the aims of this mini review are to: (i) clearly summarize the normative changes in the HPA axis that occur during pregnancy and the postpartum period; (ii) summarize what we know about the HPA axis in perinatal depression, and (iii) propose key areas for future research. Understanding physiological biomarkers that can predict which women are at risk for perinatal mood disorders will lead to better tools for treating, and ultimately preventing, these debilitating disorders, improving the health of mother, child, and family.

Characterization of the serum and salivary cortisol response to the intravenous 250 µg ACTH1-24 stimulation test

PURPOSE

The ACTH_1-24 stimulation test is commonly used to assess the hypothalamic-pituitary-adrenal (HPA) axis. Given variations in CBG concentration and binding affinity, serum total cortisol may misclassify some patients. Salivary cortisol correlates well with serum free cortisol but is easier to measure and widely available in commercial laboratories. The aim of this study was to investigate the utility of measuring salivary cortisol during the ACTH_1-24 stimulation test.

DESIGN AND METHODS

Case-control study in a clinical research facility. Eighty-seven patients with suspected cortisol deficiency, twenty-four healthy controls, and ten healthy women on the oral contraceptive (OC) underwent an intravenous 250 µg ACTH_1-24 stimulation test. Concordance of ACTH_1-24 stimulated serum and salivary cortisol was evaluated.

RESULTS

There was a significant difference in serum cortisol between the healthy volunteers and the women on the OC (P < 0.001) but no difference in salivary cortisol. The lower limit of the reference interval for salivary cortisol at 60 min was 26 nmol/L. 27/89 (30%) of tests with suspected HPA axis disorder failed the 60 min serum cortisol cut-off of 500 nmol/L. Of these, 24/27 (89%) had a salivary cortisol of <26 nmol/L. In contrast, 12/19 (63%) tests and 5/43 (12%) tests where the 60 min serum cortisol was 500-599 and ≥600 nmol/L, respectively had a salivary cortisol of <26 nmol/L.

CONCLUSIONS

Salivary cortisol provides additional diagnostic value during the 250 µg ACTH_1-24 stimulation test in patients with proven or suspected alterations in CBG and potentially those with a borderline 60 min serum cortisol 500-599 nmol/L.

The role of corticosteroid-binding globulin in the evaluation of adrenal insufficiency

Cortisol is a hydrophobic molecule that is largely bound to corticosteroid-binding globulin (CBG) in the circulation. In the assessment of adrenal insufficiency, many clinicians measure a total serum cortisol level, which assumes that CBG is present in normal concentrations and with a normal binding affinity for cortisol. CBG concentration and affinity are affected by a number of common factors including oral contraceptive pills (OCPs), fever and infection, as well as rare mutations in the serine protease inhibitor A6 (SERPINA6) gene, and as such, total cortisol levels might not be the ideal way to assess adrenal function in all clinical circumstances. This paper reviews the limitations of immunoassay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the measurement of total cortisol, the challenges of measuring free serum cortisol directly as well as the difficulties in calculating an estimated free cortisol from total cortisol, CBG and albumin concentrations. Newer approaches to the evaluation of adrenal insufficiency, including the measurement of cortisol and cortisone in the saliva, are discussed and a possible future role for these tests is proposed.

Altered apolipoprotein C expression in association with cognition impairments and hippocampus volume in schizophrenia and bipolar disorder

Proteomic analyses facilitate the interpretation of molecular biomarker probes which are very helpful in diagnosing schizophrenia (SZ). In the current study, we attempt to test whether potential differences in plasma protein expressions in SZ and bipolar disorder (BD) are associated with cognitive deficits and their underlying brain structures. Forty-two plasma proteins of 29 SZ patients, 25 BD patients and 93 non-clinical controls were quantified and analysed using multiple reaction monitoring-based triple quadrupole mass spectrometry approach. We also computed group comparisons of protein expressions between patients and controls, and between SZ and BD patients, as well. Potential associations of protein levels with cognitive functioning (psychomotor speed, executive functioning, crystallised intelligence) as well as underlying brain volume in the hippocampus were explored, using bivariate correlation analyses. The main finding of this study was that apolipoprotein expression differed between patients and controls and that these alterations in both disease groups were putatively related to cognitive impairments as well as to hippocampus volumes. However, none of the protein level differences were related to clinical symptom severity. In summary, altered apolipoprotein expression in BD and SZ was linked to cognitive decline and underlying morphological changes in both disorders. Our results suggest that the detection of molecular patterns in association with cognitive performance and its underlying brain morphology is of great importance for understanding of the pathological mechanisms of SZ and BD, as well as for supporting the diagnosis and treatment of both disorders.

Corticosteroid-binding globulin is a biomarker of inflammation onset and severity in female rats

Plasma corticosteroid-binding globulin (CBG) plays a critical role in regulating glucocorticoid bioavailability and is an acute phase 'negative' protein during inflammation. In an adjuvant-induced arthritis model, plasma CBG levels decrease in rats that develop severe inflammation, and we have now determined when and how these reductions in CBG occur. After administering complete Freund's adjuvant or saline intra-dermally at the tail base, blood samples were taken periodically for 16days. In adjuvant-treated rats, decreases in plasma CBG levels matched the severity of inflammation, and decreases were observed 4days before any clinical signs of inflammation. Decreases in CBG levels coincided with an ~5kDa reduction in its apparent size, consistent with proteolytic cleavage, and cleaved CBG lacked steroid-binding activity. At the termination of the experimental period, hepatic Cbg mRNA levels were decreased in rats with severe inflammation. While plasma TNF-α increased in all adjuvant-treated rats, increases in Il-4, IL-6, IL-10, IL-13 and IFN-γ were only observed in rats with cleaved CBG. Rats with cleaved CBG also exhibited increased spleen weights, and strong negative correlations were observed among CBG, IL-6 and spleen weights, respectively. However, there were no differences in hepatic Cbg mRNA levels in relation to the apparent proteolysis of CBG, suggesting that CBG cleavage occurs before changes in hepatic Cbg expression. Our results indicate that the levels and integrity of plasma CBG are biomarkers of the onset and severity of inflammation. Dynamic changes in the levels and function of CBG likely modulate the tissue availability of corticosterone during inflammation.

Altered lipid partitioning and glucocorticoid availability in CBG-deficient male mice with diet-induced obesity

OBJECTIVE

To evaluate how deficiency in corticosteroid-binding globulin (CBG), the specific carrier of glucocorticoids, affects glucocorticoid availability and adipose tissue in obesity.

METHODS

C57BL/6 (WT) and CBG-deficient (KO) male mice were fed during 12 weeks with standard or hyperlipidic diet (HL). Glucocorticoid availability and metabolic parameters were assessed.

RESULTS

Body weight and food intake were increased in KO compared with WT mice fed a standard diet and were similar when fed a HL diet. Expression of CBG was found in white adipose tissue by immunochemistry, real-time PCR, and Western blot. In obesity, the subcutaneous depot developed less in KO mice compared with WT, which was associated with a minor adipocyte area and peroxisome proliferator-activated receptor-γ expression. Conversely, the epididymal depot displayed higher weight and adipocyte area in KO than in WT mice. CBG deficiency caused a fall of hepatic 11β-hydroxysteroid dehydrogenase type 2 expression and an increase in epidymal adipose tissue, particularly in HL mice.

CONCLUSIONS

Deficiency in CBG drives lipid partitioning from subcutaneous to visceral adipose depot under a context of lipid excess and differentially modulates 11β-hydroxysteroid dehydrogenase type 2 expression.

Effects of a non-synonymous CBG gene single nucleotide polymorphism (SNP) on meat-quality traits in Berkshire pigs

Corticosteroid-binding globulin (CBG) is a plasma transport protein that has glucocorticoid-binding activity. In the present study, we identified CBG gene expression in several tissues of four pig breeds: Berkshire, Duroc, Landrace, and Yorkshire. Expression of CBG mRNA was detected in the liver of all four breeds, and was the highest in Berkshire pigs. We also found single nucleotide polymorphisms (SNPs) in the CBG gene from Berkshire pigs, including SNP c.919G>A, which corresponds to 307G>R. We analyzed the relationships between this CBG variant and various meat-quality traits. The SNP was significantly associated with backfat thickness, post-mortem pH24h, meat color [CIE a* (redness), CIE b* (yellowness)], water-holding capacity, fat content, moisture content, protein content, cooking loss, and shear force. However, the effects differed by gender: the values were significantly associated with almost all traits in gilts, whereas only cooking loss and shear force were shown significantly in barrows. The variant G allele was associated with decreases in backfat thickness, post-mortem pH24h, CIE a*, fat content, and cooking loss, but with increases in CIE b*, water-holding capacity, moisture content, protein content, and shear force. Because the general correlation between meat-quality traits were not validated in the present study, we suggest that certain SNP might be used in the restrictive application to distinguish meat-quality traits.

Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

This clinical practice guideline addresses the diagnosis and treatment of primary adrenal insufficiency.

PARTICIPANTS

The Task Force included a chair, selected by The Clinical Guidelines Subcommittee of the Endocrine Society, eight additional clinicians experienced with the disease, a methodologist, and a medical writer. The co-sponsoring associations (European Society of Endocrinology and the American Association for Clinical Chemistry) had participating members. The Task Force received no corporate funding or remuneration in connection with this review.

EVIDENCE

This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to determine the strength of recommendations and the quality of evidence.

CONSENSUS PROCESS

The evidence used to formulate recommendations was derived from two commissioned systematic reviews as well as other published systematic reviews and studies identified by the Task Force. The guideline was reviewed and approved sequentially by the Endocrine Society's Clinical Guidelines Subcommittee and Clinical Affairs Core Committee, members responding to a web posting, and the Endocrine Society Council. At each stage, the Task Force incorporated changes in response to written comments.

CONCLUSIONS

We recommend diagnostic tests for the exclusion of primary adrenal insufficiency in all patients with indicative clinical symptoms or signs. In particular, we suggest a low diagnostic (and therapeutic) threshold in acutely ill patients, as well as in patients with predisposing factors. This is also recommended for pregnant women with unexplained persistent nausea, fatigue, and hypotension. We recommend a short corticotropin test (250 μg) as the "gold standard" diagnostic tool to establish the diagnosis. If a short corticotropin test is not possible in the first instance, we recommend an initial screening procedure comprising the measurement of morning plasma ACTH and cortisol levels. Diagnosis of the underlying cause should include a validated assay of autoantibodies against 21-hydroxylase. In autoantibody-negative individuals, other causes should be sought. We recommend once-daily fludrocortisone (median, 0.1 mg) and hydrocortisone (15-25 mg/d) or cortisone acetate replacement (20-35 mg/d) applied in two to three daily doses in adults. In children, hydrocortisone (∼8 mg/m(2)/d) is recommended. Patients should be educated about stress dosing and equipped with a steroid card and glucocorticoid preparation for parenteral emergency administration. Follow-up should aim at monitoring appropriate dosing of corticosteroids and associated autoimmune diseases, particularly autoimmune thyroid disease.

Steroids and endocrine disruptors--History, recent state of art and open questions

This introductory chapter provides an overview of the levels and sites at which endocrine disruptors (EDs) affect steroid actions. In contrast to the special issue of Journal of Steroid Biochemistry and Molecular Biology published three years ago and devoted to EDs as such, this paper focuses on steroids. We tried to point to more recent findings and opened questions. EDs interfere with steroid biosynthesis and metabolism either as inhibitors of relevant enzymes, or at the level of their expression. Particular attention was paid to enzymes metabolizing steroid hormones to biologically active products in target cells, such as aromatase, 5α-reductase and 3β-, 11β- and 17β-hydroxysteroid dehydrogenases. An important target for EDs is also steroid acute regulatory protein (StAR), responsible for steroid precursor trafficking to mitochondria. EDs influence receptor-mediated steroid actions at both genomic and non-genomic levels. The remarkable differences in response to various steroid-receptor ligands led to a more detailed investigation of events following steroid/disruptor binding to the receptors and to the mapping of the signaling cascades and nuclear factors involved. A virtual screening of a large array of EDs with steroid receptors, known as in silico methods (≡computer simulation), is another promising approach for studying quantitative structure activity relationships and docking. New data may be expected on the effect of EDs on steroid hormone binding to selective plasma transport proteins, namely transcortin and sex hormone-binding globulin. Little information is available so far on the effects of EDs on the major hypothalamo-pituitary-adrenal/gonadal axes, of which the kisspeptin/GPR54 system is of particular importance. Kisspeptins act as stimulators for hormone-induced gonadotropin secretion and their expression is regulated by sex steroids via a feed-back mechanism. Kisspeptin is now believed to be one of the key factors triggering puberty in mammals, and various EDs affect its expression and function. Finally, advances in analytics of EDs, especially those persisting in the environment, in various body fluids (plasma, urine, seminal fluid, and follicular fluid) are mentioned. Surprisingly, relatively scarce information is available on the simultaneous determination of EDs and steroids in the same biological material. This article is part of a Special Issue entitled 'Endocrine disruptors & steroids'.

Hypothalamic-pituitary-adrenal axis dysregulation and cortisol activity in obesity: A systematic review

BACKGROUND

Although there is substantial evidence of differential hypothalamic-pituitary-adrenal (HPA) axis activity in both generalized and abdominal obesity, consistent trends in obesity-related HPA axis perturbations have yet to be identified.

OBJECTIVES

To systematically review the existing literature on HPA activity in obesity, identify possible explanations for inconsistencies in the literature, and suggest methodological improvements for future study.

DATA SOURCES

Included papers used Pubmed, Google Scholar, and the University of California Library search engines with search terms body mass index (BMI), waist-to-hip ratio (WHR), waist circumference, sagittal diameter, abdominal versus peripheral body fat distribution, body fat percentage, DEXA, abdominal obesity, and cortisol with terms awakening response, slope, total daily output, reactivity, feedback sensitivity, long-term output, and 11β-HSD expression.

STUDY ELIGIBILITY CRITERIA

Empirical research papers were eligible provided that they included at least one type of obesity (general or abdominal), measured at least one relevant cortisol parameter, and a priori tested for a relationship between obesity and cortisol.

RESULTS

A general pattern of findings emerged where greater abdominal fat is associated with greater responsivity of the HPA axis, reflected in morning awakening and acute stress reactivity, but some studies did show underresponsiveness. When examined in adipocytes, there is a clear upregulation of cortisol output (due to greater expression of 11β-HSD1), but in hepatic tissue this cortisol is downregulated. Overall obesity (BMI) appears to also be related to a hyperresponsive HPA axis in many but not all studies, such as when acute reactivity is examined.

LIMITATIONS

The reviewed literature contains numerous inconsistencies and contradictions in research methodologies, sample characteristics, and results, which partially precluded the development of clear and reliable patterns of dysregulation in each investigated cortisol parameter.

CONCLUSIONS AND IMPLICATIONS

The literature to date is inconclusive, which may well arise from differential effects of generalized obesity vs. abdominal obesity or from modulators such as sex, sex hormones, and chronic stress. While the relationship between obesity and adipocyte cortisol seems to be clear, further research is warranted to understand how adipocyte cortisol metabolism influences circulating cortisol levels and to establish consistent patterns of perturbations in adrenal cortisol activity in both generalized and abdominal obesity.

Corticosteroid-binding globulin: modulating mechanisms of bioavailability of cortisol and its clinical implications

Corticosteroid-binding globulin (CBG) is the principal transport protein of glucocorticoids. Approximately 80-90% of serum cortisol binds to CBG with high affinity and only about 5% of cortisol remain unbound and is considered biologically active. CBG seems to modulate and influence the bioavailability of cortisol to local tissues. In this review, we will discuss physicochemical properties of CBG and structure of CBG in the mechanisms of binding and release of cortisol. This review describes several factors affecting CBG functions, such as genetic factors or temperature. Furthermore, clinical implications of CBG abnormalities and the measurement of CBG and its use for assessment of free cortisol levels are described in this review.

Evaluation and management of diabetic and non-diabetic hypoglycemia in end-stage renal disease

Patients with end-stage renal disease (ESRD) regardless of diabetes status are at increased risk of hypoglycemia with a resultant array of adverse clinical outcomes. Therefore, hypoglycemia should be thoroughly evaluated in ESRD patients. In diabetic dialysis patients, hypoglycemic agents and nutritional alterations can trigger hypoglycemia in the background of diminished gluconeogenesis, reduced insulin clearance by the kidney and improved insulin sensitivity following initiation of renal replacement therapy. Detailed evaluation of antidiabetic regimen and nutritional patterns, patient education on self-monitoring of blood glucose and/or referral to a diabetes specialist may reduce risk of subsequent hypoglycemia. In certain situations, it is important to recognize the possibility of non-diabetic causes of hypoglycemia in patients with diabetes and to avoid treating pseudo-hyperglycemia caused by glucose- non-specific glucometers in patients utilizing icodextrin-based solutions for peritoneal dialysis. Adrenal insufficiency, certain medications, malnutrition and/or infection are among the most common causes of hypoglycemia in non-diabetic ESRD patients, and they should be suspected after exclusion of inadvertent use of hypoglycemic agents. The goal of this review article is to summarize approaches and recommendations for the work up and treatment of hypoglycemia in ESRD.

Gender difference in adrenal sensitivity to ACTH is abolished in type 2 diabetes

OBJECTIVE

Dysfunction of the hypothalamus-pituitary-adrenal (HPA) axis has been implicated in type 2 diabetes (T2D). The aim of this study was to investigate the impact of T2D and gender on the HPA axis.

METHODS

Synthetic ACTH (1 μg) was administered to 21 subjects with T2D (age 62 (54-70) years, 11 men/ten women, HbA1c 49±2 mmol/mol, treated with diet or oral antidiabetic drugs) and 38 controls (age 58 (41-67) years, 20 men/18 women). Fasting basal B-glucose, serum cortisol, insulin, IGF1 and IGFBP1 concentrations were measured, and sampling for all but IGF1 was repeated 30, 60, and 90 min after ACTH injection. Patients took 0.25 mg dexamethasone at 2200-2300 h and returned the next morning for the measurement of serum cortisol concentration.

DESIGN

Cross-sectional study.

RESULTS

Patients with T2D had similar fasting serum cortisol, IGF1 and IGFBP1 concentrations; however, serum cortisol concentration after administration of dexamethasone did not differ between the groups. Healthy women exhibited higher peak cortisol levels compared with healthy men (675±26 vs 582±21 nmol/l, P=0.014), while the peak levels were equally high in men and women with T2D, resulting in a higher peak level in men with T2D compared with healthy men (691±42 vs 582±21 nmol/l, P=0.024). Serum cortisol concentration after administration of dexamethasone did not differ between the groups, nor did IGF1 and IGFBP1.

NOVELTY OF THE FINDINGS

Some studies have previously indicated disturbed regulation of the hypothalamus-pituitary-adrenal (HPA) axis in subjects with type 2 diabetes (T2D); however, much remains unknown in this area. To the best of our knowledge, this is the first study to show that the gender difference in the adrenal response to ACTH (with greater reactivity in women) is abolished in T2D. While the clinical implications cannot be determined by this paper, it is known that gender differences exist in the pathogenesis and complications of T2D. Thus, our findings suggest that further research into gender differences in the HPA axis is warranted.

CONCLUSIONS

Gender differences in adrenal response to ACTH were abolished in T2D. Men with T2D had a higher peak cortisol compared with controls. Further studies are needed to elucidate the clinical implications.

Measurement of free glucocorticoids: quantifying corticosteroid-binding globulin binding affinity and its variation within and among mammalian species

Plasma glucocorticoids (GCs) are commonly used as measures of stress in wildlife. A great deal of evidence indicates that only free GC (GC not bound by the specific binding protein, corticosteroid-binding globulin, CBG) leaves the circulation and exerts biological effects on GC-sensitive tissues. Free hormone concentrations are difficult to measure directly, so researchers estimate free GC using two measures: the binding affinity and the binding capacity in plasma. We provide an inexpensive saturation binding method for calculating the binding affinity (equilibrium dissociation constant, K d) of CBG that can be run without specialized laboratory equipment. Given that other plasma proteins, such as albumin, also bind GCs, the method compensates for this non-specific binding. Separation of bound GC from free GC was achieved with dextran-coated charcoal. The method provides repeatable estimates (12% coefficient of variation in the red squirrel, Tamiasciurus hudsonicus), and there is little evidence of inter-individual variation in K d (range 2.0-7.3 nM for 16 Richardson's ground squirrels, Urocitellus richardsonii). The K d values of 28 mammalian species we assessed were mostly clustered around a median of 4 nM, but five species had values between 13 and 61 nM. This pattern may be distinct from birds, for which published values are more tightly distributed (1.5-5.1 nM). The charcoal separation method provides a reliable and robust method for measuring the K d in a wide range of species. It uses basic laboratory equipment to provide rapid results at very low cost. Given the importance of CBG in regulating the biological activity of GCs, this method is a useful tool for physiological ecologists.

Role of corticosteroid binding globulin in emotional reactivity sex differences in mice

Sex differences exist for stress reactivity as well as for the prevalence of depression, which is more frequent in women of reproductive age and often precipitated by stressful events. In animals, the differential effect of stress on male's and female's emotional behavior has been well documented. Crosstalk between the gonadal and stress hormones, in particular between estrogens and glucocorticoids, underlie these sex differences on stress vulnerability. We have previously shown that corticosteroid binding globulin (CBG) deficiency in a mouse model (Cbg k.o.) leads, in males, to an increased despair-like behavior caused by suboptimal corticosterone stress response. Because CBG displays a sexual dimorphism and is regulated by estrogens, we have now investigated whether it plays a role in the sex differences observed for emotional reactivity in mice. By analyzing Cbg k.o. and wild-type (WT) animals of both sexes, we detected sex differences in despair-like behavior in WT mice but not in Cbg k.o. animals. We showed through ovariectomy and estradiol (E2) replacement that E2 levels explain the sex differences found in WT animals. However, the manipulation of E2 levels did not affect the emotional behavior of Cbg k.o. females. As Cbg k.o. males, Cbg k.o. females have markedly reduced corticosterone levels across the circadian cycle and also after stress. Plasma free corticosterone levels in Cbg k.o. mice measured immediately after stress were blunted in both sexes compared to WT mice. A trend for higher mean levels of ACTH in Cbg k.o. mice was found for both sexes. The turnover of a corticosterone bolus was increased in Cbg k.o. Finally, the glucocorticoid-regulated immediate early gene early growth response 1 (Egr1) showed a blunted mRNA expression in the hippocampus of Cbg k.o. mutants while mineralocorticoid and glucocorticoid receptors presented sex differences but equivalent mRNA expression between genotypes. Thus, in our experimental conditions, sex differences for despair-like behavior in WT mice are explained by estrogens levels. Also, in both sexes, the presence of CBG is required to attain optimal glucocorticoid concentrations and normal emotional reactivity, although in females this is apparent only under low E2 concentrations. These findings suggest a complex interaction of CBG and E2 on emotional reactivity in females.

Inhibitory effects of cortisone and hydrocortisone on human Kv1.5 channel currents

Glucocorticoids are the primary hormones that respond to stress and protect organisms from dangerous situations. The glucocorticoids hydrocortisone and its dormant form, cortisone, affect the cardiovascular system with changes such as increased blood pressure and cardioprotection. Kv1.5 channels play a critical role in the maintenance of cellular membrane potential and are widely expressed in pancreatic β-cells, neurons, myocytes, and smooth muscle cells of the pulmonary vasculature. We examined the electrophysiological effects of both cortisone and hydrocortisone on human Kv1.5 channels expressed in Xenopus oocytes using a two-microelectrode voltage clamp technique. Both cortisone and hydrocortisone rapidly and irreversibly suppressed the amplitude of Kv1.5 channel current with IC50 values of 50.2±4.2μM and 33.4±3.2μM, respectively, while sustained the current trace shape of Kv1.5 current. The inhibitory effect of cortisone on Kv1.5 decreased progressively from -10mV to +30mV, while hydrocortisone׳s inhibition of the channel did not change across the same voltage range. Both cortisone and hydrocortisone blocked Kv1.5 channel currents in a non-use-dependent manner and neither altered the channel׳s steady-state activation or inactivation curves. These results show that cortisone and hydrocortisone inhibited Kv1.5 channel currents differently, and that Kv1.5 channels were more sensitive to hydrocortisone than to cortisone.

Inhibition of corticosteroid-binding globulin gene expression by glucocorticoids involves C/EBPβ

Corticosteroid-binding globulin (CBG), a negative acute phase protein produced primarily in the liver, is responsible for the transport of glucocorticoids (GCs). It also modulates the bioavailability of GCs, as only free or unbound steroids are biologically active. Fluctuations in CBG levels therefore can directly affect GC bioavailability. This study investigates the molecular mechanism whereby GCs inhibit the expression of CBG. GCs regulate gene expression via the glucocorticoid receptor (GR), which either directly binds to DNA or acts indirectly via tethering to other DNA-bound transcription factors. Although no GC-response elements (GRE) are present in the Cbg promoter, putative binding sites for C/EBPβ, able to tether to the GR, as well as HNF3α involved in GR signaling, are present. C/EBPβ, but not HNF3α, was identified as an important mediator of DEX-mediated inhibition of Cbg promoter activity by using specific deletion and mutant promoter reporter constructs of Cbg. Furthermore, knockdown of C/EBPβ protein expression reduced DEX-induced repression of CBG mRNA, confirming C/EBPβ’s involvement in GC-mediated CBG repression. Chromatin immunoprecipitation (ChIP) after DEX treatment indicated increased co-recruitment of C/EBPβ and GR to the Cbg promoter, while C/EBPβ knockdown prevented GR recruitment. Together, the results suggest that DEX repression of CBG involves tethering of the GR to C/EBPβ.

Investigation of genetic variants, birthweight and hypothalamic-pituitary-adrenal axis function suggests a genetic variant in the SERPINA6 gene is associated with corticosteroid binding globulin in the western Australia pregnancy cohort (Raine) study

Background

The hypothalamic-pituitary-adrenal (HPA) axis regulates stress responses and HPA dysfunction has been associated with several chronic diseases. Low birthweight may be associated with HPA dysfunction in later life, yet human studies are inconclusive. The primary study aim was to identify genetic variants associated with HPA axis function. A secondary aim was to evaluate if these variants modify the association between birthweight and HPA axis function in adolescents.

Methods

Morning fasted blood samples were collected from children of the Western Australia Pregnancy Cohort (Raine) at age 17 (n = 1077). Basal HPA axis function was assessed by total cortisol, corticosteroid binding globulin (CBG), and adrenocorticotropic hormone (ACTH). The associations between 124 tag single nucleotide polymorphisms (SNPs) within 16 HPA pathway candidate genes and each hormone were evaluated using multivariate linear regression and penalized linear regression analysis using the HyperLasso method.

Results

The penalized regression analysis revealed one candidate gene SNP, rs11621961 in the CBG encoding gene (SERPINA6), significantly associated with total cortisol and CBG. No other candidate gene SNPs were significant after applying the penalty or adjusting for multiple comparisons; however, several SNPs approached significance. For example, rs907621 (p = 0.002) and rs3846326 (p = 0.003) in the mineralocorticoid receptor gene (NR3C2) were associated with ACTH and SERPINA6 SNPs rs941601 (p = 0.004) and rs11622665 (p = 0.008), were associated with CBG. To further investigate our findings for SERPINA6, rare and common SNPs in the gene were imputed from the 1,000 genomes data and 8 SNPs across the gene were significantly associated with CBG levels after adjustment for multiple comparisons. Birthweight was not associated with any HPA outcome, and none of the gene-birthweight interactions were significant after adjustment for multiple comparisons.

Conclusions

Our study suggests that genetic variation in the SERPINA6 gene may be associated with altered CBG levels during adolescence. Replication of these findings is required.

Factitious Cushing's syndrome masquerading as Cushing's disease

CONTEXT

Factitious Cushing's syndrome is extremely rare. The diagnosis is challenging as cross-reactivity of synthetic corticosteroids or their metabolites in immunoassay measurements of plasma or urinary cortisol can make distinguishing between true and factitious Cushing's syndrome difficult. Adrenocorticotropin (ACTH) is usually suppressed in factitious Cushing's syndrome.

PATIENT

A 54-year-old woman presented with clinical and biochemical features of Cushing's syndrome and an unsuppressed ACTH concentration. She denied recent exogenous corticosteroid use.

INVESTIGATIONS AND RESULTS

Initial investigations revealed a markedly elevated urinary free cortisol, mildly elevated midnight salivary cortisol and normal morning cortisol concentration. Plasma ACTH was not suppressed at 13 ng/l (RR 10-60 ng/l). A pituitary MRI was normal, but inferior petrosal sinus sampling (IPSS) revealed a post corticotrophin releasing hormone ACTH ratio >20:1 in the left petrosal sinus. Ketoconazole therapy amplified discordance between the urinary free and morning plasma cortisol concentrations. Further investigation of this discordance using high-pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) revealed a urinary free cortisol excretion of only 20 nmol/24 h, but prednisolone excretion of 16,200 nmol/24 h.

CONCLUSIONS

Factitious Cushing's syndrome can mimic endogenous ACTH-dependent hypercortisolism during initial investigations and IPSS. This case highlights the importance of (i) recognizing the significance of discordant results; (ii) using an ACTH assay capable of reliably differentiating ACTH-dependent from ACTH-independent Cushing's syndrome; and (iii) appreciating that IPSS is only useful to localize the source of ACTH in confirmed ACTH-dependent Cushing's syndrome. In this case, measurement of corticosteroids by HPLC-MS/MS was essential in reaching the correct diagnosis.

A role for homeostatic drive in the perpetuation of complex chronic illness: Gulf War Illness and chronic fatigue syndrome

A key component in the body's stress response, the hypothalamic-pituitary-adrenal (HPA) axis orchestrates changes across a broad range of major biological systems. Its dysfunction has been associated with numerous chronic diseases including Gulf War Illness (GWI) and chronic fatigue syndrome (CFS). Though tightly coupled with other components of endocrine and immune function, few models of HPA function account for these interactions. Here we extend conventional models of HPA function by including feed-forward and feedback interaction with sex hormone regulation and immune response. We use this multi-axis model to explore the role of homeostatic regulation in perpetuating chronic conditions, specifically GWI and CFS. An important obstacle in building these models across regulatory systems remains the scarcity of detailed human in vivo kinetic data as its collection can present significant health risks to subjects. We circumvented this using a discrete logic representation based solely on literature of physiological and biochemical connectivity to provide a qualitative description of system behavior. This connectivity model linked molecular variables across the HPA axis, hypothalamic-pituitary-gonadal (HPG) axis in men and women, as well as a simple immune network. Inclusion of these interactions produced multiple alternate homeostatic states and sexually dimorphic responses. Experimental data for endocrine-immune markers measured in male GWI subjects showed the greatest alignment with predictions of a naturally occurring alternate steady state presenting with hypercortisolism, low testosterone and a shift towards a Th1 immune response. In female CFS subjects, expression of these markers aligned with an alternate homeostatic state displaying hypocortisolism, high estradiol, and a shift towards an anti-inflammatory Th2 activation. These results support a role for homeostatic drive in perpetuating dysfunctional cortisol levels through persistent interaction with the immune system and HPG axis. Though coarse, these models may nonetheless support the design of robust treatments that might exploit these regulatory regimes.

Effects of gender and age on hypothalamic-pituitary-adrenal reactivity after pharmacological challenge with low-dose 1-μg ACTH test: a prospective study in healthy adults

OBJECTIVE

Τhe aim of this study was to observe cortisol responses to a pharmacological challenge with 1 μg ACTH as a function of age and gender.

PATIENTS

Twenty-one young (13 women and 8 men; mean age: 43∙48 ± 10∙52 years) and forty elderly (20 women and 20 men; mean age: 79 ± 6∙76 years) volunteers without overt acute or chronic disease participated in this study.

MEASUREMENTS

Basal serum cortisol levels were measured, and cortisol values were obtained at 30 and 60 min after administration of 1 μg ACTH. Free thyroxine, triiodothyronine, thyrotrophin, prolactin, dehydroepiandrosterone sulphate (DHEAS), insulin-like growth factor-1, follicle stimulating hormone, luteinizing hormone, oestradiol levels in women and total testosterone levels in men were also measured at baseline.

RESULTS

No differences were observed between the groups of older and younger individuals in baseline plasma cortisol levels and mean cortisol responses at 30 and 60 min postchallenge. In the elderly subjects, statistically lower cortisol responses were observed in men at 30 and 60 min after 1-μg ACTH challenge (540∙17 ± 112∙28 vs 670∙11 ± 146∙49 nmol/l in women, P = 0∙003 at 30 min, and 482∙24 ± 108∙14 vs 568∙04 ± 135∙73 nmol/l in women, P = 0∙03 at 60 min). Furthermore, significant lower values in PRL, IGF-1, DHEAS and T3 were detected in older subjects when compared to the younger age group. Interestingly, a higher incidence of individuals who did not achieve normal responses to 1-μg ACTH test (>497 nmol/l) was noted in the group of elderly male subjects.

CONCLUSION

This study documents a marked gender effect in the elderly, in the cortisol response levels to 1-μg ACTH stimulation. Elderly men demonstrate a decreased responsiveness compared to women in the same age range.

Glucocorticoids and their receptors: insights into specific roles in mitochondria

Glucocorticoids (GCs) affect most physiological systems and are the most frequently used drugs for multiple disorders and organ transplantation. GC functions depend on a balance between circulating GC and cytoplasmic glucocorticoid receptor II (GR). Mitochondria individually enclose circular, double-stranded DNA that is expressed and replicated in response to nuclear-encoded factors imported from the cytoplasm. Fine-tuning and response to cellular demands should be coordinately regulated by the nucleus and mitochondria; thus mitochondrial-nuclear interaction is vital to optimal mitochondrial function. Elucidation of the direct and indirect effects of steroids, including GCs, on mitochondria is an important and emerging field of research. Mitochondria may also be under GC control because GRs are present in mitochondria, and glucocorticoid response elements (GREs) reside in the mitochondrial genome. Therefore, mitochondrial gene expression can be regulated by GCs via at least two different mechanisms: direct action on mitochondrial DNA and oxidative phosphorylation (OXPHOS) genes, or by an indirect effect through interaction with nuclear genes. In this review, we outline possible mechanisms of regulation of mitochondrial genes in response to GCs in view of translocation of the GR into mitochondria and the possible regulation of OXPHOS genes by GREs in the mitochondrial genome.

High-end normal adrenocorticotropic hormone and cortisol levels are associated with specific cardiovascular risk factors in pediatric obesity: a cross-sectional study

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) axis, and in particular cortisol, has been reported to be involved in obesity-associated metabolic disturbances in adults and in selected populations of adolescents. The aim of this study was to investigate the association between morning adrenocorticotropic hormone (ACTH) and cortisol levels and cardiovascular risk factors in overweight or obese Caucasian children and adolescents.

METHODS

This cross-sectional study of 450 obese children and adolescents (aged 4 to 18 years) was performed in a tertiary referral center. ACTH, cortisol, cardiovascular risk factors (fasting and post-challenge glucose, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, triglycerides, and hypertension) and insulin resistance were evaluated. All analyses were corrected for confounding factors (sex, age, puberty, body mass index), and odds ratios were determined.

RESULTS

ACTH and cortisol levels were positively associated with systolic and diastolic blood pressure, triglycerides, fasting glucose and insulin resistance. Cortisol, but not ACTH, was also positively associated with LDL-cholesterol. When adjusted for confounding factors, an association between ACTH and 2 h post-oral glucose tolerance test glucose was revealed. After stratification according to cardiovascular risk factors and adjustment for possible confounding factors, ACTH levels were significantly higher in subjects with triglycerides ≥90th percentile (P <0.02) and impaired fasting glucose or glucose tolerance (P <0.001). Higher cortisol levels were found in subjects with blood pressure ≥95th percentile and LDL-cholesterol ≥90th percentile. Overall, the highest tertiles of ACTH (>5.92 pmol/l) and cortisol (>383.5 nmol/l) although within the normal range were associated with increases in cardiovascular risk factors in this population.

CONCLUSIONS

In obese children and adolescents, high morning ACTH and cortisol levels are associated with cardiovascular risk factors. High ACTH levels are associated with high triglyceride levels and hyperglycemia, while high cortisol is associated with hypertension and high LDL-cholesterol. These specific relationships suggest complex mechanisms through which the HPA axis may contribute to metabolic impairments in obesity, and merit further investigations.

Chronic exposure to stress predisposes to higher autoimmune susceptibility in C57BL/6 mice: glucocorticoids as a double-edged sword

Stress activates the hypothalamic-pituitary-adrenocortical axis to promote the release of corticosterone (CORT), which consequently suppresses pathogenic stimulation of the immune system. Paradoxically, however, stress often promotes autoimmunity through yet unknown mechanisms. Here we investigated how chronic variable stress (CVS), and the associated alterations in CORT levels, affect the susceptibility to experimental autoimmune encephalomyelitis (EAE) in female and male C57BL/6 mice. Under baseline (nonstressed) conditions, females exhibited substantially higher CORT levels and an attenuated EAE with less mortality than males. However, CVS induced a significantly worsened EAE in females, which was prevented if CORT signaling was blocked. In addition, females under CVS conditions showed a shift toward proinflammatory Th1/Th17 versus Th2 responses and a decreased proportion of CD4(+) CD25(+) Treg cells. This demonstrates that whereas C57BL/6 female mice generally exhibit higher CORT levels and an attenuated form of EAE than males, they become less responsive to the immunosuppressive effects of CORT under chronic stress and thereby prone to a higher risk of destructive autoimmunity.

Differences in colocalization of corticosteroid-binding globulin and glucocorticoid receptor immunoreactivity in the rat brain

Endocrine regulation of central and systemic stress response as well as learning and memory are in part controlled by systemic glucocorticoid levels. So far steroids have been thought to act on the brain predominantly through nuclear receptors. However, some brain systems known to respond to glucocorticoids seem to be devoid of the respective receptor proteins (GR). It is likely that known central actions of adrenal steroids may also be mediated by non-genomic actions involving intrinsic binding globulins. In recent studies we described the intrinsic expression of corticosteroid-binding globulin (CBG) in rat, mouse and human brains. Here we report an immunohistochemical mapping study on the colocalization of CBG and of GR in the rat brain. In the nucleus accumbens, septum, hippocampus, globus pallidus, medial and basolateral amygdale nuclei, magnocellular preoptic nuclei, diagonal band of Broca high intensity of CBG immunoreactivity was accompanied by weak or moderate GR staining, and vice versa. In the caudate putamen, bed nucleus of stria terminalis, septohypothalamic nucleus and parvocellular subdivision of the paraventricular nucleus strong GR immunoreactivity was observed, but CBG was almost undetectable. In contrast, throughout the supraoptic nucleus and magnocellular subdivision of the paraventricular nucleus numerous strongly CBG-positive cells were observed, devoid of specific GR immunoreactivity. It is most likely that CBG in the brain may be involved in the response to changing systemic glucocorticoid levels in addition to known nuclear and membrane corticosteroid receptors, or in glucocorticoid responsive regions devoid of these receptors.

Regulation of cortisol bioavailability--effects on hormone measurement and action

Routine assessment of the hypothalamic-pituitary-adrenal axis relies on the measurement of total serum cortisol levels. However, most cortisol in serum is bound to corticosteroid-binding globulin (CBG) and albumin, and changes in the structure or circulating levels of binding proteins markedly affect measured total serum cortisol levels. Furthermore, high-affinity binding to CBG is predicted to affect the availability of cortisol for the glucocorticoid receptor. CBG is a substrate for activated neutrophil elastase, which cleaves the binding protein and results in the release of cortisol at sites of inflammation, enhancing its tissue-specific anti-inflammatory effects. Further tissue-specific modulation of cortisol availability is conferred by corticosteroid 11β-dehydrogenase. Direct assessment of tissue levels of bioavailable cortisol is not clinically practicable and measurement of total serum cortisol levels is of limited value in clinical conditions that alter prereceptor glucocorticoid bioavailability. Bioavailable cortisol can, however, be measured indirectly at systemic, extracellular tissue and cell levels, using novel techniques that have provided new insight into the transport, metabolism and biological action of glucocorticoids. A more physiologically informative approach is, therefore, now possible in the assessment of the hypothalamic-pituitary-adrenal axis, which could prove useful in clinical practice.

Two different corticosteroid-binding globulin variants that lack cortisol-binding activity in a greek woman

BACKGROUND

Corticosteroid-binding globulin (CBG), encoded by SERPINA6, is the principal plasma binding protein for cortisol. Most nonsynonymous single-nucleotide polymorphisms that alter the production or function of CBG occur rarely, and their clinical significance remains obscure.

METHODS

Serum and DNA were obtained from a Greek woman with low morning cortisol levels and from family members. SERPINA6 exons were sequenced, and serum CBG was measured by ELISA and cortisol-binding capacity assay. Recombinant CBG variants were produced for detailed functional studies.

RESULTS

A novel heterozygous c.1282G>C transversion in exon 5 of SERPINA6, resulting in a p.Trp393Ser (W371S) substitution, was identified in the proband, who was also heterozygous for single-nucleotide polymorphisms encoding the CBG Lyon (D367N) and CBG A224S variants. The proband had no measurable plasma cortisol-binding activity despite a CBG level of 273 nm by ELISA. She inherited CBG W371S from her mother whose plasma cortisol-binding capacity was approximately 50% lower than the CBG measurements by ELISA (314 nm). The proband's father and four children were heterozygous for CBG D367N; their CBG levels by ELISA were normal, but corresponding cortisol-binding capacity measurements were 50% lower. Pedigree analysis revealed that W371S segregates with A224 and that D367N and W371S segregate separately. Recombinant CBG D367N and CBG W371S had no measureable cortisol-binding activity.

CONCLUSION

A new CBG Athens (W371S) variant that lacks cortisol-binding activity has been identified in a carrier of the cortisol-binding deficient CBG Lyon (D367N) variant. Analyses of CBG levels in this pedigree illustrate how immunoassays fail to accurately reflect cortisol-binding activity.

Unraveling the time domains of corticosteroid hormone influences on brain activity: rapid, slow, and chronic modes

Brain cells are continuously exposed to corticosteroid hormones, although the levels vary (e.g., after stress). Corticosteroids alter neural activity via two receptor types, mineralocorticoid (MR) and glucocorticoid receptors (GR). These receptors regulate gene transcription but also, as we now know, act nongenomically. Via nongenomic pathways, MRs enhance and GRs suppress neural activity. In the hypothalamus, inhibitory GR effects contribute to negative feedback regulation of the stress axis. Nongenomic MR actions are also important extrahypothalamically and help organisms to immediately select an appropriate response strategy. Via genomic mechanisms, corticosteroid actions in the basolateral amygdala and ventral-most part of the cornu ammonis 1 hippocampal area are generally excitatory, providing an extended window for encoding of emotional aspects of a stressful event. GRs in hippocampal and prefrontal pyramidal cells increase surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and strengthen glutamatergic signaling through pathways partly overlapping with those involved in long-term potentiation. This raises the threshold for subsequent induction of synaptic potentiation and promotes long-term depression. Synapses activated during stress are thus presumably strengthened but protected against excitatory inputs reaching the cells later. This restores higher cognitive control and promotes, for example, consolidation of stress-related contextual information. When an organism experiences stress early in life or repeatedly in adulthood, the ability to induce synaptic potentiation is strongly reduced and the likelihood to induce depression enhanced, even under rest. Treatment with antiglucocorticoids can ameliorate cellular effects after chronic stress and thus provide an interesting lead for treatment of stress-related disorders.

Critical role of plasma corticosteroid-binding-globulin during stress to promote glucocorticoid delivery to the brain: impact on memory retrieval

We aimed at demonstrating that corticosteroid binding globulin (CBG), a plasma glycoprotein binding glucocorticoids with high affinity in blood, endorses a major role under stress conditions by regulating free glucocorticoid access to the brain and thereby influences glucocorticoid-dependent behaviors. Hence, we compared CBG-deficient mice (Cbg-/-) and their controls (Cbg+/+) in a specific memory task, i.e. the delayed alternation behavior, requiring memory retrieval both under stress and nonstress conditions and previously shown to be dependent on hippocampal glucocorticoid levels. Our results evidence that Cbg-/- mice, unlike controls, remain insensitive to stress applied before memory retrieval. Furthermore, under stress conditions, we observed a blunted surge of corticosterone (CORT) in plasma and no free CORT rise in the hippocampus of Cbg-/-. Moreover, intrahippocampal infusion of CORT through implanted cannulae was used to mimic stress CORT rise before memory retrieval. This infusion of CORT reproduced memory retrieval impairments in Cbg-/- as in Cbg+/+ controls. Finally, we provide evidence that Cbg-/- mice exhibit a normal adrenal response to stress and ACTH. Given that CBG deficiency is known to markedly impact on CORT clearance from plasma, our current article demonstrates that Cbg-/- insensitivity in memory retrieval after stress results from the blunted CORT response due to increased CORT clearance. Overall, our data suggest that the impact of CBG genetic deficiency on various behavioral patterns reported previously stems from a smaller CORT reservoir in blood. Inasmuch as CBG discloses interindividual variations, such a parameter ought to be taken into account when studying stress-induced glucocorticoid action in brain.

Non-genomic effect of glucocorticoids on cardiovascular system

Glucocorticoids (GCs) are essential steroid hormones for homeostasis, development, metabolism, and cognition and possess anti-inflammatory and immunosuppressive actions. Since glucocorticoid receptor II (GR) is nearly ubiquitous, chronic activation or depletion of GCs leads to dysfunction of diverse organs, including the heart and blood vessels, resulting predominantly from changes in gene expression. Most studies, therefore, have focused on the genomic effects of GC to understand its related pathophysiological manifestations. The nongenomic effects of GCs clearly differ from well-known genomic effects, with the former responding within several minutes without the need for protein synthesis. There is increasing evidence that the nongenomic actions of GCs influence various physiological functions. To develop a GC-mediated therapeutic target for the treatment of cardiovascular disease, understanding the genomic and nongenomic effects of GC on the cardiovascular system is needed. This article reviews our current understanding of the underlying mechanisms of GCs on cardiovascular diseases and stress, as well as how nongenomic GC signaling contributes to these conditions. We suggest that manipulation of GC action based on both GC and GR metabolism, mitochondrial impact, and the action of serum- and glucocorticoid-dependent kinase 1 may provide new information with which to treat cardiovascular diseases.

Cortisol and the polycystic ovary syndrome

Adrenal steroidogenesis is under the control of the hypothalamic-pituitary-adrenal (HPA) axis. Furthermore, metabolic factors including insulin and obesity-related signals may play a role in the regulation of both enzymes involved in the steroidogenetic pathways, as well as in the regulation of the HPA axis. In women with the polycystic ovary syndrome (PCOS), cortisol production rate is probably normal, although adrenal androgens can be overproduced in a subset of affected women. Cortisol metabolism and regeneration from inactive glucocorticoids can also be disrupted in PCOS, thereby contributing to determining an adrenal hyperandrogenic state. Finally, overactivity of the HPA axis may be related to the high prevalence of psychopathological and eating disorders in women with PCOS, implying a maladaptive allostatic load in the adaptive mechanisms to chronic stress exposure.

A role for corticosteroid-binding globulin variants in stress-related disorders

Primary stress-related diseases such as chronic fatigue syndrome, fibromyalgia or chronic widespread pain have been associated with altered activity of the hypothalamic-pituitary-adrenal axis due to measured relative hyper- or hypo-cortisolism in basal or experimentally stimulated states. A hereditary risk to development of these diseases has been proposed. Corticosteroid-binding globulin (CBG), a plasma transport vehicle for cortisol, may play a more active role in the hypothalamic-pituitary-adrenal axis. Chronically altered hypothalamic-pituitary-adrenal axis has been associated with common medical problems. Hypocortisolism has been observed in kindred studies of rare mutations of the SERPIN A6 (CBG) gene and more common SERPIN A6 polymorphisms associated with reduced CBG levels or CBG:cortisol-binding affinity. Over the last decade, studies of five different CBG gene mutations in humans, human genetic associations and transgenic mouse models have suggested that CBG may have hitherto unexpected roles in modulation of the stress response. Naturally occurring CBG variants may alter susceptibility to disorders associated with chronic stress and relative hypocortisolism. On the other hand, hypercortisolism has been linked with Cushing's disease and metabolic syndrome and CBG gene polymorphisms have been linked to obesity in animal models. In this article, we look at the evidence suggesting a role for CBG in stress-related disorders, focusing particularly on CBG gene polymorphisms and chronic pain/fatigue syndromes.

Intrinsic expression of transcortin in neural cells of the mouse brain: a histochemical and molecular study

Corticosteroid binding globulin (CBG, transcortin) has been shown to be expressed in the brain of rat and human species. In this study we examined the CBG brain expression and cDNA structure in mice, comparing wild-type (Cbg+/+) and Cbg knockout mice (Cbg-/-, obtained by genetic disruption of the SerpinA6 alias Cbg gene). We used double immunofluorescence labelling with specific neuronal and glial markers to analyze the cellular localization of CBG in various regions of the mouse brain. In wild-type (Cbg+/+) mice we found CBG immunoreactivity in neuronal perikarya of the magnocellular hypothalamic nuclei, amygdala, hippocampus, cerebral cortex, cerebellum and pituitary. A portion of glial cells (astrocytes, oligodendrocytes) contained CBG immunoreactivity, including some of the ependymal cells and choroid plexus cells. No CBG immunoreactivity was detected in Cbg-/- brain tissues. We showed by RT-PCR that the full-length Cbg mRNA is present in those regions, indicating an intrinsic expression of the steroid-binding globulin. Furthermore, we found by sequencing analysis that Cbg cDNA obtained from the mouse hypothalamus was homologous to Cbg cDNA obtained from the liver. Finally, we have evaluated the relative levels of CBG expression by quantitative PCR in various brain regions and in the liver. We found that brain levels of Cbg mRNA are low compared to the liver but significantly higher than in CBG-deficient mice. Although derived from the same gene than liver CBG, brain CBG protein may play a specific or complementary role that requires the production and analysis of brain-specific Cbg knockout models.

Challenges for the endocrine laboratory in critical illness

The endocrine laboratory must provide accurate and timely results for the critically ill patient. A number of pathophysiological factors affect assay systems for adrenal, thyroid and gonadal function tests. The effects are primarily on estimates of 'free hormone' concentration through abnormal binding protein concentrations and the effects of drugs and metabolites on hormone-protein binding. The limitations of the principal analytical techniques (immunoassay and chromatography-mass spectrometry) include drug effects, endogenous antibody interference and ion suppression. These effects are not always easily identified. Analytical specificity and standardisation result in differences in bias between assays and thus a requirement for assay specific decision limits and reference ranges. Good communication between clinician and laboratory is needed to minimise these effects. Developments in mass spectrometry should lead to greater sensitivity and wider applicability of the technique. International efforts to develop higher order reference materials and reference method procedures should lead to greater comparability of results.