Glucocorticoids increase vasopressin V1b receptor coupling to phospholipase C

High salt intake activates the hypothalamic-pituitary-adrenal axis, amplifies the stress response, and alters tissue glucocorticoid exposure in mice

AIMS

High salt intake is common and contributes to poor cardiovascular health. Urinary sodium excretion correlates directly with glucocorticoid excretion in humans and experimental animals. We hypothesized that high salt intake activates the hypothalamic-pituitary-adrenal axis activation and leads to sustained glucocorticoid excess.

METHODS AND RESULTS

In male C57BL/6 mice, high salt intake for 2-8 weeks caused an increase in diurnal peak levels of plasma corticosterone. After 2 weeks, high salt increased Crh and Pomc mRNA abundance in the hypothalamus and anterior pituitary, consistent with basal hypothalamic-pituitary-adrenal axis activation. Additionally, high salt intake amplified glucocorticoid response to restraint stress, indicative of enhanced axis sensitivity. The binding capacity of Corticosteroid-Binding Globulin was reduced and its encoding mRNA downregulated in the liver. In the hippocampus and anterior pituitary, Fkbp5 mRNA levels were increased, indicating increased glucocorticoid exposure. The mRNA expression of the glucocorticoid-regenerating enzyme, 11β-hydroxysteroid dehydrogenase Type 1, was increased in these brain areas and in the liver. Sustained high salt intake activated a water conservation response by the kidney, increasing plasma levels of the vasopressin surrogate, copeptin. Increased mRNA abundance of Tonebp and Avpr1b in the anterior pituitary suggested that vasopressin signalling contributes to hypothalamic-pituitary-adrenal axis activation by high salt diet.

CONCLUSION

Chronic high salt intake amplifies basal and stress-induced glucocorticoid levels and resets glucocorticoid biology centrally, peripherally and within cells.

Investigation of possible underlying mechanisms behind water-induced glucose reduction in adults with high copeptin

Elevated copeptin, a surrogate marker of vasopressin, is linked to low water intake and increased diabetes risk. Water supplementation in habitual low-drinkers with high copeptin significantly lowers both fasting plasma (fp) copeptin and glucose. This study aims at investigating possible underlying mechanisms. Thirty-one healthy adults with high copeptin (> 10.7 pmol·L⁻¹ (men), > 6.1 pmol⁻¹ (women)) and 24-h urine volume of < 1.5L and osmolality of > 600 mOsm·kg⁻¹ were included. The intervention consisted of addition of 1.5 L water daily for 6 weeks. Fp-adrenocorticotropic hormone (ACTH), fp-cortisol, 24-h urine cortisol, fasting and 2 h (post oral glucose) insulin and glucagon were not significantly affected by the water intervention. However, decreased (Δ baseline-6 weeks) fp-copeptin was significantly associated with Δfp-ACTH (r = 0.76, p < 0.001) and Δfp-glucagon (r = 0.39, p = 0.03), respectively. When dividing our participants according to baseline copeptin, median fp-ACTH was reduced from 13.0 (interquartile range 9.2–34.5) to 7.7 (5.3–9.9) pmol L⁻¹, p = 0.007 in the top tertile of copeptin, while no reduction was observed in the other tertiles. The glucose lowering effect from water may partly be attributable to decreased activity in the hypothalamic–pituitary–adrenal axis.

ClinicalTrials.gov: NCT03574688.

Copeptin as a marker of atherosclerosis and arteriosclerosis

Background and aims

The precursor peptide of vasopressin, copeptin, has previously been linked to increased risk of developing diabetes mellitus, coronary artery disease and cardiovascular mortality. Whether elevated copeptin is associated with markers of atherosclerosis and arteriosclerosis in the general population is not known.

Methods

In this population-based, cross-sectional study, coronary artery calcium score (CACS), carotid-femoral pulse wave velocity (c-f PWV) and fasting plasma copeptin were measured in 5303 individuals in the Swedish cardiopulmonary bioimage study (SCAPIS). Multivariable logistic regression models were used to analyze the associations between copeptin and high CACS (>100) and high c-f PWV (>10 m/s), respectively.

Results

The number of individuals with high CACS and c-f PWV increased across increasing tertile of copeptin (11.7%, 13.3% and 16.3% for CACS and 6.9%, 8.5% and 10.6% for c-f PWV). The top tertile of copeptin was, compared with reference tertile 1, significantly associated with both high CACS and high c-f PWV after adjustment for age, sex, hypertension, diabetes mellitus, HDL, triglycerides, BMI, smoking status, creatinine and high sensitive CRP with an odds ratio (OR) of 1.260 (95% confidence interval (CI): 1.022–1.555) for CACS and OR 1.389 (95% CI: 1.069–1.807) for PWV.

Conclusions

Copeptin is associated with both coronary atherosclerosis and increased arterial stiffness in the general population. Our data indicates that copeptin may be a useful marker in the assessment of cardiovascular risk.

Possible roles of brain derived neurotrophic factor and corticotropin releasing hormone neurons in the nucleus of hippocampal commissure functioning within the avian neuroendocrine regulation of stress

Corticotropin releasing hormone (CRH) neurons located in the nucleus of hippocampal commissure (NHpC) have been proposed to be involved in the avian neuroendocrine regulation of stress and appeared to respond prior to CRH neurons in the hypothalamic paraventricular nucleus (PVN) when food deprivation stress was applied. Since the response of the NHpC was rapid and short-lived, was it regulated differentially from CRH neurons in the PVN? We, therefore, applied immobilization stress to test whether the NHpC response was stressor specific. Gene expression of CRH and stress-related genes in the NHpC, PVN, anterior pituitary (APit) as well as plasma corticosterone (CORT) were determined. Furthermore, brain derived neurotrophic factor (BDNF) and glucocorticoid receptor (GR) were examined regarding their possible roles in the regulation of CRH neurons. Data showed that rapid activation of CRH mRNA in the NHpC occurred and preceded a slower gene activation in the PVN, upregulation of proopiomelanocortin (POMC) transcripts in the APit and significant increases of CORT concentrations. Results suggested BDNF's role in negative feedback between CRH and CRHR1 in the NHpC and positive feedback between CRH and CRHR1 in the PVN. In the APit, V1bR activation appeared responsible for sustaining CORT release when stress persisted. Overall, data suggest that the NHpC functions as part of the HPA axis of birds and perhaps a comparable extra-hypothalamic structure occurs in other vertebrates.Lay SummaryThe nucleus of the hippocampal commissure, a structure outside of the hypothalamus, shows rapidly increased neural gene expression that appears to contribute to the early activation of the traditional hypothalamic-pituitary-adrenal (HPA) axis responsible for the production of stress hormones.

Is PTSD-Phenotype Associated with HPA-Axis Sensitivity? Feedback Inhibition and Other Modulating Factors of Glucocorticoid Signaling Dynamics

Previously, we found that basal corticosterone pulsatility significantly impacts the vulnerability for developing post-traumatic stress disorder (PTSD). Rats that exhibited PTSD-phenotype were characterized by blunted basal corticosterone pulsatility amplitude and a blunted corticosterone response to a stressor. This study sought to identify the mechanisms underlining both the loss of pulsatility and differences in downstream responses. Serial blood samples were collected manually via jugular vein cannula at 10-min intervals to evaluate suppression of corticosterone following methylprednisolone administration. The rats were exposed to predator scent stress (PSS) after 24 h, and behavioral responses were assessed 7 days post-exposure for retrospective classification into behavioral response groups. Brains were harvested for measurements of the glucocorticoid receptor, mineralocorticoid receptor, FK506-binding protein-51 and arginine vasopressin in specific brain regions to assess changes in hypothalamus–pituitary–adrenal axis (HPA) regulating factors. Methylprednisolone produced greater suppression of corticosterone in the PTSD-phenotype group. During the suppression, the PTSD-phenotype rats showed a significantly more pronounced pulsatile activity. In addition, the PTSD-phenotype group showed distinct changes in the ventral and dorsal CA1, dentate gyrus as well as in the paraventricular nucleus and supra-optic nucleus. These results demonstrate a pre-trauma vulnerability state that is characterized by an over-reactivity of the HPA and changes in its regulating factors.

A case of neonatal diabetes insipidus following dexamethasone for bronchopulmonary dysplasia

BACKGROUND

Diabetes insipidus (DI) is a disease resulting from defects in the arginine vasopressin system responsible for regulating body water homeostasis. It is characterized by polyuria with increased serum osmolality and sodium and can result from congenital or acquired disorders.

CLINICAL PRESENTATION

A baby was admitted to NICU for extreme prematurity (25 weeks gestation), extreme low birth weight (900 grams) and respiratory distress. He received one dose of Surfactant and was ventilated using high frequency jet ventilation for development of pulmonary interstitial emphysema. After nine days, he still required high settings with development of early chronic lung changes in the form of atelectasis. Therefore, he was started on a course of dexamethasone following the DART study protocol (Dexamethasone: A Randomized Trial). However, after six days (cumulative dose of 0.75 mg/kg/day) he developed polyuria (7.4 ml/kg/h) with increased serum sodium (150 mmol/L) and osmolality (348 mmol/L). He lost 85 grams of his weight in 24 hours, which represented a 9.8 %weight loss. The findings were suggestive of DI and given there were no apparent causes other than dexamethasone, it was discontinued. Over the following 48 hours, polyuria and hypernatremia gradually resolved, reaching 3.5 ml/kg/h, and 140 mmol/L respectively.

CONCLUSION

The use of dexamethasone is not an uncommon practice in tertiary care neonatal units. To our knowledge, our case is the first report of neonatal DI secondary to the use of dexamethasone. We recommend closely monitoring urine output and serum electrolytes in preterm infants receiving dexamethasone.

Plasma copeptin as a predictor of kidney disease

Background

Plasma copeptin, a marker of vasopressin, is associated with renal function decline in the general population. Our aim was to study the links between elevated copeptin and future risk of kidney disease.

Methods

Copeptin was measured in a sample of the Malmö Preventive Project (MPP) Reinvestigation (n = 5158) and in the Malmö Diet and Cancer Cardiovascular Cohort (MDC-CC) (n = 5162). According to national registers, 89 subjects in MPP and 180 in MDC-CC developed chronic kidney disease (CKD) during follow-up (8.7 and 19.6 years, respectively).

Results

After multivariate adjustment (gender, age, body mass index, smoking status, estimated glomerular filtration rate, prevalent diabetes, systolic blood pressure and prevalent antihypertensive treatment), copeptin (beta-coefficient per 1 standard deviation increment of ln copeptin) was independently associated with increased risk of CKD during follow-up in both cohorts (MPP: (HR) 1.46, 95% confidence interval (CI) 1.18–1.80, P < 0.001; MDC-CC: HR 1.25, 95% CI 1.02–1.54, P = 0.03) among subjects free from prevalent kidney disease at baseline. Furthermore, in MPP, elevated copeptin predicted a specified diagnosis of kidney disease other than CKD (HR 1.31, 95% CI 1.08–1.59, P = 0.006) after multivariate adjustment. In a corresponding analysis in MDC-CC, copeptin was associated with a 10% increased risk, which, however, was non-significant (P = 0.25). A meta-analysis of the MPP and MDC-CC data showed significant association between elevated copeptin and a specified diagnosis of kidney disease other than CKD (HR 1.18, 95% CI 1.05–1.34, P = 0.008).

Conclusion

An increased level of copeptin independently predicts development of both CKD and other specified kidney diseases, suggesting that copeptin can be used to identify individuals at risk for kidney disease development.

Copeptin relates to a fatty liver and measures of obesity in a South African population with mixed ethnicities

PURPOSE

Elevated copeptin, a vasopressin marker, is linked to metabolic disease, and obese rats with low-vasopressin concentration had a decreased risk of liver steatosis. We here investigated the association between copeptin and nonalcoholic fatty liver disease (NAFLD) and possible differences in copeptin concentration between ethnicities.

METHODS

In this cross-sectional study of 361 South Africans (n = 172 African black, 189 = Caucasian) with a mean age of 45 years and 45% men, plasma copeptin was measured and associated with NAFLD according to a validated fatty liver index accounting for measures of BMI, waist, triglycerides, and gamma-glutamyltransferase.

RESULTS

There was no significant difference in copeptin concentrations between ethnicities after age and gender adjustment (p = 0.24). Increasing copeptin tertile levels were significantly associated with obesity, overweight, and abdominal obesity, respectively, after multivariate adjustment for age, gender, ethnicity, and high HOMA-IR (p = 0.02 for all). Individuals in the second and third copeptin tertile had an increased odds (95% CI) of NAFLD of 1.77 (1.04-3.02) and 2.97 (1.74-5.06), respectively, compared to the bottom tertile (p < 0.001). The association between increasing copeptin tertile and NAFLD remained significant after adjustment for age, gender, ethnicity, high HOMA-IR, self-reported current alcohol intake, and statin treatment (p = 0.01).

CONCLUSIONS

Elevated plasma copeptin is independently associated with NAFLD in a population with mixed ethnicities, pointing at the pharmacologically modifiable vasopressin system as a new mechanism behind NAFLD.

Water intake keeps type 2 diabetes away? Focus on copeptin

INTRODUCTION

In both diabetic subjects and animal models high levels of vasopressin (AVP) have beendetected. The relationship between AVP and glucose metabolism is mediated through several direct andindirect effects and most of them are still unknown.

METHODS

We have reviewed 100 manuscripts retrieved from Cochrane Library, Embase and Pubmeddatabases in order to highlight a possible relationship between copeptin and type 2 diabetes and to provideinsights on the molecular mechanism that could explain this association.

RESULTS AND CONCLUSIONS

AVP potentiates CRH action at pituitary level resulting in an increased ACTH secretion and in turn in an increased cortisol secretion that escapes the negative feedback loop. Further, AVP regulates insulin and glucagon secretion through V1b receptor and promotes hepatic glycogenolysis and gluconeogenesis through V1a receptor. In addition to worsen glucose metabolism, AVP has been reported to have a role in the pathogenesis of diabetic complications such as cardiovascular diseases, kidney and ocular complications. Due to the very low concentration of AVP in the blood, the small size and poor stability, the assay of AVP is very difficult to perform. Thus, copeptin, the stable C-terminal portion of the prepro-vasopressin peptide has been identified as an easier assay to be measured and that mirrors AVP activity. Although there are promising evidence that copeptin could be involved in the pathogenesis of type 2 diabetes, further studies need to demonstrate the importance of copeptin as clinical marker to predict glucose metabolism derangements.

Evaluation of the value of plasma concentration of copeptin in the first prenatal visit to diagnose gestational diabetes mellitus

AIMS

Gestational diabetes mellitus (GDM) is increasing worldwide. The aim of this study was to investigate whether copeptin concentrations, measured at the first prenatal visit, are associated with risk of GDM.

METHODS

From July 2015 to June 2016, consecutive women who admitted to the obstetrics center of our hospital were included. Data for fasting plasma glucose and copeptin concentrations at the first prenatal visit and one-step GDM screening with 75-g oral glucose tolerance test performed between 24 and 28 weeks of gestation were collected and analyzed. The relationship between levels of copeptin and GDM were evaluated using univariate and multivariate regression analysis.

RESULTS

In this study, 101 out of the 827 women developed GDM (12.2%). The GDM distribution across the copeptin quartiles ranged between 4.4% (first quartile) and 25.1% (fourth quartile). For each 1 log-unit increase in plasma concentration of copeptin, the unadjusted and adjusted risk of GDM increased by 1442% (odds ratio 15.42 [95% CI 3.35-54.25], P < 0.001) and 642% (7.42 [2.69-16.02], P < 0.001), respectively. In a multivariate model using the fourth quartiles of copeptin versus quartiles 1 through 3 together with the clinical variables, the marker displayed prognostic information (GDM: OR for fourth quartile, 3.11 [95% CI 1.95-5.24; P = 0.001]). The net reclassification improvement statistic showed that the addition of copeptin to established risk factors significantly increased the correct reclassification of GDM (P = 0.02). The integrated discrimination improvement statistic found that the copeptin level significantly increased discrimination between women with GDM and without GDM (P = 0.01).

CONCLUSIONS

High copeptin concentrations at the first prenatal visit were associated with increased risk of GDM and might be useful in identifying women at risk of GDM for early prevention strategies.

Plasma copeptin and functional outcome in patients with ischemic stroke and type 2 diabetes

BACKGROUND

The activation of the arginine vasopressin system may be involved in the pathology of stroke and diabetes. In this study, we therefore evaluated the short-term prognostic value of early measurement of plasma copeptin levels in Chinese patients with type 2 diabetes mellitus (T2DM) and acute ischemic stroke (AIS).

METHODS

From July 2014 to June 2015, all T2DM patients with first-ever AIS were included. Plasma levels of copeptin were tested at admission. The prognostic value of copeptin to predict the functional outcome and mortality 3months after stroke was compared with the National Institutes of Health Stroke Scale score and with other known outcome predictors.

RESULTS

We recorded 247 stroke patients with T2DM. The copeptin levels were obtained in those patients with a median value of 14.3pmol/L (IQR, 9.5-17.1pmol/L). At 3-month follow-up, a favorable functional outcome was found in 86 patients (34.8%). Plasma copeptin levels in patients with an unfavorable outcome were significantly greater than those in patients with a favorable outcome (16.2 [IQR, 12.2-20.3] vs. 12.4 [IQR, 8.6-15.2] pmol/L; Z=5.399; P<0.0001). In univariate logistic regression analysis, with an unadjusted OR of 1.123 (95% CI, 1.072-1.177, P<0.001), copeptin had a strong association with unfavorable functional outcome. In multivariate analyses, a copeptin level in the highest inter-quartile (>17.1pmol/L) was associated with a higher risk of unfavorable functional outcome (OR=4.62; 95% CI=2.63-9.21; P<0.001). After adjusting for other outcome predictors, a copeptin level in the highest inter-quartile (>17.1pmol/L) was associated with a higher risk of mortality (OR=5.12; 95% CI=2.20-11.38; P<0.001).

CONCLUSION

Our study suggested that copeptin levels may reliably predict short-term stroke prognosis at its onset in Chinese patients with T2DM and stroke.

Serum levels of copeptin are associated with type 2 diabetes and diabetic complications in Chinese population

PURPOSE

The aim of this study was to investigate copeptin levels in serum, and assess their associations with type 2 diabetes (T2DM) and diabetic complications.

METHODS

In this post hoc analysis, serum levels of copeptin were tested in 306 patients with T2DM. Clinical information including diabetic retinopathy (DR) and diabetic nephropathy (DN) were collected. The relation of serum copeptin with DR and DN were investigated with the use of logistic regression models according to equal quartiles of the distributions of serum copeptin.

RESULTS

We found that serum copeptin levels were significantly higher in diabetes as compared to normal controls [9.4(IQR, 7.4-12.5) pmol/L vs. 4.1(IQR, 2.5-6.2) pmol/L; P<0.0001]. In multivariate analysis, there was an increased risk of T2DM associated with copeptin levels (OR 1.312, 95% CI: 1.204-1.403; P<0.0001) after adjusting for possible confounders. After adjustment for possible confounders, serum copeptin levels were positively associated with the DR (odds ratio [OR], 1.117; 95% confidence interval [CI], 1.072-1.241; P<0.001) and DN (OR, 1.259; 95% CI, 1.198-1.323; P<0.001). Compared with the first quartile of serum copeptin levels, the ORs for DR and DN were as follows: second quartile, 1.19 (95% CI, 0.94-1.51, P=0.12) and 1.37 (95% CI, 0.78-2.37, P=0.28); third quartile, 1.61 (95% CI, 1.18-2.43, P=0.005) and 2.12 (95% CI, 1.32-3.27, P=0.003); fourth quartile, 2.83 (95% CI, 2.04-4.93; P<0.001) and 3.48 (95% CI, 1.77-7.03; P<0.001), respectively.

CONCLUSIONS

Using a post-hoc analysis our data show that elevated serum levels of copeptin are associated with type 2 diabetes and diabetic complications in Chinese population, suggesting a potential role of the AVP system (copeptin) in the pathophysiology of diabetes.

Genetic vasopressin 1b receptor variance in overweight and diabetes mellitus

OBJECTIVE

Recently, imbalance in the vasopressin (AVP) system, measured as elevated levels of copeptin (the C-terminal part of the AVP pro-hormone) in plasma, was linked to the development of abdominal obesity and diabetes mellitus (DM). Here, we aim to investigate if the genetic variation of the human AVP receptor 1b gene (AVPR1B) is associated with measures of obesity and DM.

DESIGN

Malmö Diet and Cancer study (MDC) is a population-based prospective cohort examined 1991-1996.

METHODS

Four tag single nucleotide polymorphisms (SNPs: rs35810727, rs28373064, rs35439639, rs35608965) of AVPR1B were genotyped in the cardiovascular cohort (n=6103) of MDC (MDC-CC) and associated with measures of obesity and DM. Significant SNPs were replicated in another 24 344 MDC individuals (MDC replication cohort).

RESULTS

In MDC-CC, the major allele of rs35810727 was associated with elevated BMI (β-coefficient ± s.e.m.; 0.30 ± 0.14, P=0.03) and waist (0.78 ± 0.36, P=0.03) after age and gender adjustment. The association with BMI was replicated in the MDC replication cohort (0.21 ± 0.07, P=0.003), whereas that with waist was not significant. In MDC-CC there was no association between the major allele of rs35810727 and DM, but in the complete MDC cohort (n=30 447) the major allele of rs35810727 was associated with DM (OR (95% CI); 1.10 (1.00-1.20), P=0.04).

CONCLUSIONS

Genetic variance of AVPR1B contributes to overweight. Furthermore, our data indicate a link between AVPR1B variance and DM development. Our data point at a relationship between the disturbance of the pharmacologically modifiable AVP system and the body weight regulation.

Divergent regulation of distinct glucocorticoid systems in alcohol dependence

Chronic alcohol consumption disrupts glucocorticoid signaling at multiple physiological levels to interact with several disease-related processes associated with neuroendocrine and psychiatric disorders. Excessive alcohol use produces stress-related neuroadaptations at the level of the hypothalamic-pituitary-adrenal (HPA) axis as well as within central (extra-hypothalamic) neural circuitry, including the central amygdala (CeA) and prefrontal cortex (PFC). Altered glucocorticoid receptor (GR) signaling in these areas following excessive alcohol exposure is postulated to mediate the transition from recreational drinking to dependence, as well as the manifestation of a host of cognitive and neurological deficits. Specifically, a bidirectional regulation of stress systems by glucocorticoids leads to the development of an HPA axis tolerance and a concomitant sensitization of cortical and subcortical circuitries. A greater understanding of how hypothalamic and extra-hypothalamic glucocorticoid systems interact to mediate excessive drinking and related pathologies will lead to more effective therapeutic strategies for alcohol use disorder (AUD) and closely related comorbidities.

Gender-specific co-activation of arginine vasopressin and the hypothalamic-pituitary-adrenal axis during stress

OBJECTIVE

To study the interaction between copeptin and hypothalamic-pituitary-adrenal (HPA) activation in men and women during hypoglycaemic stress.

DESIGN AND PATIENTS

A prospective study in 118 patients (mean age 47·7 ± 13·6 years, n = 52 women) undergoing insulin tolerance testing for suspected pituitary dysfunction.

MEASUREMENTS

Serum copeptin was measured in serially collected blood samples and assessed in relation to ACTH, cortisol and other endocrine parameters.

RESULTS

Symptomatic hypoglycaemia (mean glucose nadir, 1·6 ± 0·5 mmol/l) resulted in a rapid significant increase of serum copeptin. Individuals with impaired pituitary function had lower stress-induced copeptin levels (median, 6·26 pmol/l) than patients with intact pituitary (8·46 pmol/l, P < 0·001). A weak overall correlation between stress-induced copeptin and cortisol levels was observed (rs  = 0·31, P < 0·001). In female individuals, there was a positive correlation between stress-induced copeptin and ACTH (rs  = 0·47, P < 0·001) or cortisol levels (rs  = 0·42, P = 0·002), while in males, no correlation with ACTH levels (rs  = 0·03, P = 0·75) and poor correlation with cortisol levels (rs  = 0·24, P = 0·045) was observed. Patients with central diabetes insipidus showed lowest baseline (2·20 pmol/l) and stimulated copeptin levels (3·68 pmol/l).

CONCLUSIONS

The data from this study indicate that stress-induced release of AVP in women, but not in men, is linked to the co-activation of the hypothalamic-pituitary-adrenal system.

Copeptin, a surrogate marker for arginine vasopressin, is associated with cardiovascular and all-cause mortality in patients with type 2 diabetes (ZODIAC-31)

OBJECTIVE

Copeptin, a surrogate marker for arginine vasopressin, has been associated with cardiovascular (CV) events and mortality in patients with type 2 diabetes complicated by end-stage renal disease or acute myocardial infarction. For stable outpatients, these associations are unknown. Our aim was to investigate whether copeptin is associated with CV and all-cause mortality in patients with type 2 diabetes treated in primary care.

RESEARCH DESIGN AND METHODS

Patients with type 2 diabetes participating in the observational Zwolle Outpatient Diabetes Project Integrating Available Care (ZODIAC) study were included. Cox regression analyses with age as time scale were used to assess the relationship of baseline copeptin with CV and all-cause mortality.

RESULTS

We included 1,195 patients (age 67±12 years, 44% male). Median baseline copeptin concentration was 5.4 (interquartile range [IQR] 3.1-9.6) pmol/L. After a median follow-up of 5.9 (IQR 3.2-10.1) years, 345 patients died (29%), with 148 CV deaths (12%). Log2 copeptin was associated with CV (hazard ratio 1.17 [95% CI 0.99-1.39]; P=0.068) and all-cause mortality (1.22 [1.09-1.36]; P=0.001) after adjustment for age, sex, BMI, smoking, systolic blood pressure, total cholesterol to HDL ratio, duration of diabetes, HbA1c, treatment with ACE inhibitors and angiotensin receptor blockers, history of CV diseases, log serum creatinine, and log albumin to creatinine ratio; however, copeptin did not substantially improve risk prediction for CV (integrated discrimination improvement 0.14% [IQR -0.27 to 0.55%]) and all-cause mortality (0.77% [0.17-1.37%]) beyond currently used clinical markers.

CONCLUSIONS

We found copeptin to be associated with CV and all-cause mortality in patients with type 2 diabetes treated in primary care. Intervention studies should show whether the high CV risk in type 2 diabetes can be reduced by suppression of vasopressin, for example by reducing salt intake.

Stress responsiveness of the hypothalamic-pituitary-adrenal axis: age-related features of the vasopressinergic regulation

The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in adaptation to environmental stresses. Parvicellular neurons of the hypothalamic paraventricular nucleus secrete corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) into pituitary portal system; CRH and AVP stimulate adrenocorticotropic hormone (ACTH) release through specific G-protein-coupled membrane receptors on pituitary corticotrophs, CRHR1 for CRH and V1b for AVP; the adrenal gland cortex secretes glucocorticoids in response to ACTH. The glucocorticoids activate specific receptors in brain and peripheral tissues thereby triggering the necessary metabolic, immune, neuromodulatory, and behavioral changes to resist stress. While importance of CRH, as a key hypothalamic factor of HPA axis regulation in basal and stress conditions in most species, is generally recognized, role of AVP remains to be clarified. This review focuses on the role of AVP in the regulation of stress responsiveness of the HPA axis with emphasis on the effects of aging on vasopressinergic regulation of HPA axis stress responsiveness. Under most of the known stressors, AVP is necessary for acute ACTH secretion but in a context-specific manner. The current data on the AVP role in regulation of HPA responsiveness to chronic stress in adulthood are rather contradictory. The importance of the vasopressinergic regulation of the HPA stress responsiveness is greatest during fetal development, in neonatal period, and in the lactating adult. Aging associated with increased variability in several parameters of HPA function including basal state, responsiveness to stressors, and special testing. Reports on the possible role of the AVP/V1b receptor system in the increase of HPA axis hyperactivity with aging are contradictory and requires further research. Many contradictory results may be due to age and species differences in the HPA function of rodents and primates.

Copeptin, a marker of vasopressin, in abdominal obesity, diabetes and microalbuminuria: the prospective Malmö Diet and Cancer Study cardiovascular cohort

BACKGROUND

High plasma copeptin (copeptin), the C-terminal fragment of arginine vasopressin pro-hormone, has been associated with the metabolic syndrome (MetS), diabetes mellitus (DM) development and nephropathy. Here we tested whether elevated copeptin level is associated with later development of the MetS, its individual components and microalbuminuria.

METHODS

We analysed copeptin at baseline (1991-1994) in the population-based Malmö Diet and Cancer Study cardiovasular cohort and re-examined 2064 subjects 15.8 years later (mean age 72.8 years, 59% women) with oral glucose tolerance test and measurement of MetS and its individual components.

RESULTS

After age and sex adjustment, increasing quartiles of copeptin at baseline (the lowest quartile as reference) were associated with MetS (P for trend=0.008), incident abdominal obesity (P for trend=0.002), DM (P for trend=0.001) and microalbuminuria (P for trend=0.002). After additional adjustment for all the MetS components at baseline, increasing copeptin quartiles predicted incident abdominal obesity (odds ratios 1.55, 1.30 and 1.59; P for trend=0.04), DM (odds ratios 1.18, 1.32 and 1.46; P for trend=0.04) and microalbuminuria (odds ratios 1.05, 1.08 and 1.65; P for trend=0.02) but not MetS (P for trend=0.19) at the reexamination. Further, the relationship between copeptin and microalbuminuria was independent of baseline C-reactive protein, incident DM and incident hypertension.

CONCLUSION

Copeptin independently predicts DM and abdominal obesity but not the cluster of MetS. Apart from predicting DM and abdominal obesity, elevated copeptin signals increased risk of microalbuminuria. Interestingly, the association between copeptin and later microalbuminuria was independent of both prevalent and incident DM and hypertension. Our findings suggest a relationship between a dysregulated vasopressin system and cardiometabolic risk, which could have implications for risk assessment and novel preventive treatments.

Distinct receptor subtypes mediate arginine vasopressin-dependent ACTH release and intracellular calcium mobilization in rat pituitary cells

In the present study, adrenocorticotropic hormone (ACTH) release and intracellular calcium ([Ca(2+)](i)) increase induced by arginine vasopressin (AVP) were characterized in collagenase-dispersed and 3-day cultured rat anterior pituitary cells. AVP and the selective vasopressin V(1b) receptor agonist, [1-deamino-4-cyclohexylalanine]AVP (d[Cha(4)]AVP) induced ACTH release with nanomolar potencies in both cell preparations, and produced a maximal stimulation that was about 1.5 fold greater in the 3-day cultured cells, indicating that the vasopressin V(1b) receptor-ACTH release pathway is enhanced over time in culture. In dispersed cells, AVP, oxytocin and d[Cha(4)]AVP induced [Ca(2+)](i) increases with nanomolar potencies. The selective vasopressin V(1a) receptors antagonist, SR49059 (100 nM), together with the selective oxytocin receptors antagonist (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9)-vasotocin (100 nM), inhibited the maximal AVP response by ~70%, without affecting the response to d[Cha(4)]AVP, suggesting that the V(1b) receptor was only partially responsible for the AVP-induced [Ca(2+)](i) increase. In contrast, in 3-day cultures, AVP induced an increase in [Ca(2+)](i), while oxytocin and d[Cha(4)]AVP did not. The response to AVP was completely antagonized by SR49059, whereas the vasopressin V(1b) receptor antagonists, SSR149415 and (d(CH(2))(5)(1)Tyr(Me)(2),Thr(4),Orn(8),Tyr-NH(2)(9))-vasotocin had no effect, indicating that the [Ca(2+)](i) increase was mediated exclusively by vasopressin V(1a) receptors. In conclusion, the enhancement of vasopressin V(1b) receptor-mediated ACTH release and the lack of a detectable vasopressin V(1b) receptor coupling to [Ca(2+)](i) increase in cultured cells suggests the activation of a different/additional signaling pathway in the molecular mechanism of ACTH release.

Bench-to-bedside review: Vasopressin in the management of septic shock

This review of vasopressin in septic shock differs from previous reviews by providing more information on the physiology and pathophysiology of vasopressin and vasopressin receptors, particularly because of recent interest in more specific AVPR1a agonists and new information from the Vasopressin and Septic Shock Trial (VASST), a randomized trial of vasopressin versus norepinephrine in septic shock. Relevant literature regarding vasopressin and other AVPR1a agonists was reviewed and synthesized. Vasopressin, a key stress hormone in response to hypotension, stimulates a family of receptors: AVPR1a, AVPR1b, AVPR2, oxytocin receptors and purinergic receptors. Rationales for use of vasopressin in septic shock are as follows: first, a deficiency of vasopressin in septic shock; second, low-dose vasopressin infusion improves blood pressure, decreases requirements for norepinephrine and improves renal function; and third, a recent randomized, controlled, concealed trial of vasopressin versus norepinephrine (VASST) suggests low-dose vasopressin may decrease mortality of less severe septic shock. Previous clinical studies of vasopressin in septic shock were small or not controlled. There was no difference in 28-day mortality between vasopressin-treated versus norepinephrine-treated patients (35% versus 39%, respectively) in VASST. There was potential benefit in the prospectively defined stratum of patients with less severe septic shock (5 to 14 μg/minute norepinephrine at randomization): vasopressin may have lowered mortality compared with norepinephrine (26% versus 36%, respectively, P = 0.04 within stratum). The result was robust: vasopressin also decreased mortality (compared with norepinephrine) if less severe septic shock was defined by the lowest quartile of arterial lactate or by use of one (versus more than one) vasopressor at baseline. Other investigators found greater hemodynamic effects of higher dose of vasopressin (0.06 units/minute) but also unique adverse effects (elevated liver enzymes and serum bilirubin). Use of higher dose vasopressin requires further evaluation of efficacy and safety. There are very few studies of interactions of therapies in critical care - or septic shock - and effects on mortality. Therefore, the interaction of vasopressin infusion, corticosteroid treatment and mortality of septic shock was evaluated in VASST. Low-dose vasopressin infusion plus corticosteroids significantly decreased 28-day mortality compared with corticosteroids plus norepinephrine (44% versus 35%, respectively, P = 0.03; P = 0.008 interaction statistic). Prospective randomized controlled trials would be necessary to confirm this interesting interaction. In conclusion, low-dose vasopressin may be effective in patients who have less severe septic shock already receiving norepinephrine (such as patients with modest norepinephrine infusion (5 to 15 μg/minute) or low serum lactate levels). The interaction of vasopressin infusion and corticosteroid treatment in septic shock requires further study.

Unmasking of Partial Diabetes Insipidus during Stress but Not Maintenance Dosing of Glucocorticoids in an Infant with Septo-Optic Dysplasia

Background. It is well acknowledged that glucocorticoid (GC) replacement can unmask diabetes insipidus (DI) in subjects with hypopituitarism. Objective. To increase the awareness and monitoring for transient and symptomatic DI in children with partial hypopituitarism during periods in which increased GC needs are required. Methods/Case. A 2-month-old female infant with septo-optic dysplasia (SOD; on thyroid and maintenance GC replacement therapy at 8 mg/m(2)/day) developed transient DI during 2 separate episodes of stress (one hypothermia, one febrile) when stress dosing of GC (25 mg/m(2)/day) was instituted. Conclusion. Children not diagnosed with DI during initial evaluation for hypopituitarism may benefit from rescreening of serum sodium levels during acute periods of stress that demand "stress" GC dosing. This will permit treatment and/or increased vigilance for ensuing permanent DI.

Intranasal vasopressin affects pair bonding and peripheral gene expression in male Callicebus cupreus

Arginine vasopressin (AVP) is a neuropeptide hormone and neurotransmitter that has peripheral functions in water regulation, and central functions in the stress response and social bonding in male rodents. In this study, we investigated the role of AVP in partner preference behavior in a monogamous primate, the coppery titi monkey (Callicebus cupreus). Seven titi males each received three intranasal treatments: saline, low AVP (40 IU) and high AVP (80 IU) in random order, 1 week apart. They experienced a series of stimulus exposures to their female partner, a female stranger and an empty cage. Males were more likely to contact the stimulus and do so faster when either female stimulus was present. When pretreated with saline, males contacted the stranger more frequently than their partner; when pretreated with the high dosage of AVP, males contacted their partner more frequently than the stranger. We used microarray to measure peripheral changes in gene expression associated with intranasal AVP and found reduced expression of several genes coding for proinflammatory cytokines. The data presented here suggest that intranasally administered AVP has both central influences on social behavior and peripheral influences on inflammation in a nonhuman primate.

Plasma copeptin and the risk of diabetes mellitus

BACKGROUND

Animal studies suggest that the arginine vasopressin system may play a role in glucose metabolism, but data from humans are limited.

METHODS AND RESULTS

We analyzed plasma copeptin (copeptin), a stable C-terminal fragment of the arginine vasopressin prohormone. Using baseline and longitudinal data from a Swedish population-based sample (n=4742; mean age, 58 years; 60% women) and multivariable logistic regression, we examined the association of increasing quartiles of copeptin (lowest quartile as reference) with prevalent diabetes mellitus at baseline, insulin resistance (top quartile of fasting plasma insulin among nondiabetic subjects), and incident diabetes mellitus on long-term follow-up. New-onset diabetes mellitus was ascertained through 3 national and regional registers. All models were adjusted for clinical and anthropometric risk factors, cystatin C, and C-reactive protein. In cross-sectional analyses, increasing copeptin was associated with prevalent diabetes mellitus (P=0.04) and insulin resistance (P<0.001). During 12.6 years of follow-up, 174 subjects (4%) developed new-onset diabetes mellitus. The odds of developing diabetes mellitus increased across increasing quartiles of copeptin, even after additional adjustment for baseline fasting glucose and insulin (adjusted odds ratios, 1.0, 1.37, 1.79, and 2.09; P for trend=0.004). The association with incident diabetes mellitus remained significant in analyses restricted to subjects with fasting whole blood glucose <5.4 mmol/L at baseline (adjusted odds ratios, 1.0, 1.80, 1.92, and 3.48; P=0.001).

CONCLUSIONS

Elevated copeptin predicts increased risk for diabetes mellitus independently of established clinical risk factors, including fasting glucose and insulin. These findings could have implications for risk assessment, novel antidiabetic treatments, and metabolic side effects from arginine vasopressin system modulation.

Corticosterone- or metapyrone-induced alterations in adrenal function and expression of the arginine vasotocin receptor VT2 in the pituitary gland of domestic fowl, Gallus gallus

The avian neurohypophyseal hormone arginine vasotocin (AVT) is known to be involved in the regulation of adrenocorticotropin (ACTH) release by interacting with the VT2 receptor (VT2R), which is homologous to the mammalian vasopressin V1b receptor (V1bR). To study the role of glucocorticoid in the expression and regulation of the VT2R, corticosterone (1 or 5mg/bird/day) or metapyrone (10 or 50mg/kg body weight/day) were administered daily for 8 days to white leghorn chickens. While low doses were ineffective, a high dose of corticosterone upregulated, while metapyrone downregulated, pituitary VT2R mRNA expression and ir-VT2 in the cephalic lobe of the anterior pituitary. Further, although no change was observed in the expression of POMC mRNA, adrenal activity (as judged by the changes in total cholesterol, 3beta HSD, cortical cord width and cortico-medullary ratio) exhibited suppression or stimulation following treatment with corticosterone or metapyrone, respectively. In view of the classical negative feedback effect of glucocorticoids at the level of hypothalamic CRH neurons and pituitary corticotrophs, high corticosterone level-induced suppression of the CRH-ACTH axis may have been masked by VT2R-mediated stimulation of corticotrophs, and hence the POMC mRNA level did not change. The same argument could be used for metapyrone. It is concluded that expression of the VT2 receptor is regulated by glucocorticoids in chicken. These findings confirm a role for AVT, mediated by the VT2 receptor, in regulating ACTH secretion during stress and suggest that corticotroph VT2 receptor levels may be dynamically regulated depending on the HPA axis activity.

Interaction of vasopressin infusion, corticosteroid treatment, and mortality of septic shock

OBJECTIVE

Vasopressin and corticosteroids are often added to support cardiovascular dysfunction in patients who have septic shock that is nonresponsive to fluid resuscitation and norepinephrine infusion. However, it is unknown whether vasopressin treatment interacts with corticosteroid treatment.

DESIGN

Post hoc substudy of a multicenter randomized blinded controlled trial of vasopressin vs. norepinephrine in septic shock.

SETTING

Twenty-seven Intensive Care Units in Canada, Australia, and the United States.

PATIENTS

: Seven hundred and seventy-nine patients who had septic shock and were ongoing hypotension requiring at least 5 microg/min of norepinephrine infusion for 6 hours.

INTERVENTIONS

Patients were randomized to blinded vasopressin (0.01-0.03 units/min) or norepinephrine (5-15 microg/min) infusion added to open-label vasopressors. Corticosteroids were given according to clinical judgment at any time in the 28-day postrandomization period.

MEASUREMENTS

The primary end point was 28-day mortality. We tested for interaction between vasopressin treatment and corticosteroid treatment using logistic regression. Secondary end points were organ dysfunction, use of open-label vasopressors and vasopressin levels.

MAIN RESULTS

There was a statistically significant interaction between vasopressin infusion and corticosteroid treatment (p = 0.008). In patients who had septic shock and were also treated with corticosteroids, vasopressin, compared to norepinephrine, was associated with significantly decreased mortality (35.9% vs. 44.7%, respectively, p = 0.03). In contrast, in patients who did not receive corticosteroids, vasopressin was associated with increased mortality compared with norepinephrine (33.7% vs. 21.3%, respectively, p = 0.06). In patients who received vasopressin infusion, use of corticosteroids significantly increased plasma vasopressin levels by 33% at 6 hours (p = 0.006) to 67% at 24 hours (p = 0.025) compared with patients who did not receive corticosteroids.

CONCLUSIONS

There is a statistically significant interaction between vasopressin and corticosteroids. The combination of low-dose vasopressin and corticosteroids was associated with decreased mortality and organ dysfunction compared with norepinephrine and corticosteroids.

Cortisol infusion in late-gestation hypothalamo-pituitary disconnected sheep fetus restores pituitary cell responsiveness to arginine vasopressin

Corticotrophs in the fetal sheep become increasingly responsive to arginine vasopressin (AVP) in late gestation. We previously reported that this may be due in part to corresponding increases in signal transduction (inositol 1,4,5-trisphosphate, IP(3)). These ontogenic changes are prevented by hypothalamo-pituitary disconnection (HPD), which also prevents fetal plasma cortisol concentrations from increasing in late gestation. This led us to hypothesize that cortisol is involved in mediating the changes in pituitary responsiveness. HPD was performed on fetal sheep at 120 days gestational age (dGA). Half of the HPD fetuses were infused with cortisol for 3 days beginning at 135-137 dGA (HPD+C). The remaining HPD fetuses and a group of sham-operated control fetuses were infused with saline. Pituitary cells were isolated and cultured. After 48 h, a subset of cells was stimulated with 100 nM AVP for 2 h, and the medium was collected for ACTH analysis. Another subset of cells was stimulated with 100 nM AVP for 30 min, and the formation of IP(3) was determined. Plasma cortisol concentrations increased rapidly within the first 6 h after infusion (5.2 +/- 1.9 to 29.7 +/- 4.9 ng/ml) but did not increase thereafter. Cells from HPD+C and sham-operated fetuses secreted significantly more ACTH than those from HPD fetuses (% increase from control: 33.0 +/- 8.8%, 47.9 +/- 10.6%, and 11.9 +/- 2.4%, respectively). IP(3) formation was significantly increased in cells from HPD+C and sham-operated compared with HPD fetuses (% increase from control: 17.7 +/- 4.4%, 18.9 +/- 4.3%, and 4.6 +/- 1.5%, respectively). These findings support the idea that cortisol plays a role in mediating the increase in pituitary responsiveness to AVP in the late-gestation fetal sheep.

Ontogeny and effects of hypothalamic pituitary disconnection on formation of inositol trisphosphate in fetal sheep pituitary cells

In late gestation fetal sheep, the pituitary becomes increasingly responsive to stimulation by arginine vasopressin (AVP). This change appears to be one important factor mediating the plasma cortisol surge, a critical developmental event. It is not known precisely why pituitary corticotropes become more responsive at this time. In this study we examined the possibility that changes in second messenger generation [inositol trisphosphate (IP(3))] are responsible. Two studies were undertaken. The first was an ontogeny study, where pituitaries were isolated from 100-, 120-, and 140-d gestational age (dGA) fetal sheep. Cells were cultured, stimulated with AVP, and the formation of IP(3) assessed. The amount of IP(3) generated increased with gestational age (percent increases from unstimulated controls were 4.6, 11.5, and 21.5 for 100, 120, and 140 dGA, respectively), with significant differences between the 140-dGA group and both earlier groups apparent. The second study examined the impact of 120-dGA hypothalamo-pituitary disconnection (HPD), which prevents corticotrope maturation, on responsiveness of pituitary cells isolated from 140-dGA fetuses. Cells were stimulated with AVP, and the formation of IP(3) and secretion of ACTH were assessed. Significantly less IP(3) was formed, and ACTH secreted in cells from HPD compared with control fetuses (IP(3) and ACTH levels were 50% and 35% lower, respectively). Results from the HPD study demonstrate that the ontogenic changes in IP(3) after AVP require an intact hypothalamic-pituitary-adrenal axis. These findings suggest that heightened second messenger generation may be a key reason for increased ACTH secretory responsiveness to AVP in the late gestation sheep fetus.

Early response to venlafaxine antidepressant correlates with lower ACTH levels prior to pharmacological treatment

A link between stressful life events and development or exacerbation of depression has been established via a large body of evidence. An alteration in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis in depression has also been associated with an increase in cortisol secretion. As arginine-vasopressin (AVP) plays an important role in the activation of HPA axis during stress, the present study investigated ACTH and cortisol secretory response induced by an AVP-related peptide desmopressin (ddAVP) in patients with major depression. Prior to antidepressant treatment, endocrinological parameters were evaluated and correlated with the clinical response to venlafaxine treatment, which offers a dual antidepressant action. Depressive patients with no other psychiatric pathology were evaluated with 17-item Hamilton Depression Scale (HAM-D) in order to follow-up the response to venlafaxine. After 1 wk of treatment, 60% of patients reduced their initial HAM-D score to at least 25%; this group was classified as early responders. The other group (40%) started to reduce significantly their HAM-D score after 3 wk of treatment and was classified as late responders. After 6 wk of treatment both groups have reduced HAM-D score to at least 25% of the baseline score. Prior to the pharmacological treatment, both early and late responders showed salivary cortisol rhythm and urinary free cortisol (UFC) in 24-h similar to healthy subjects. However, we did observe differences in basal ACTH secretion, showing that the late responder group had higher basal ACTH than both early responders and controls. The ddAVP challenge promoted a robust secretion of ACTH only in late responders, suggesting a different sensitivity of pituitary vasopressin receptor. The differences in clinical response to venlafaxine among depressive patients seem to be related to endocrinological parameters.

Glucocorticoids differentially regulate expression of duodenal and renal calbindin-D9k through glucocorticoid receptor-mediated pathway in mouse model

Dexamethasone (Dex) is a member of the glucocorticoids (GCs), and is broadly used as an anti-inflammatory medication. Continuous administration with GCs induces adverse effects and suffering in humans (i.e., osteoporosis) due to negative calcium balance derived from low re- and absorption in the duodenum and kidney. A cytosolic calcium-binding protein, calbindin-D9k (CaBP-9k), is dominantly expressed in the renal and intestinal tissues involved in calcium re- and absorption and plays an active role in calcium transport. In the present study, we employed adrenalectomized (ADX) and sham-treated (Sham) male mice to examine the effect of Dex on CaBP-9k gene expression in the duodenum and kidney. Dex significantly reduced the levels of duodenal CaBP-9k mRNA and protein, and it restored ADX-induced decrease in renal CaBP-9k protein compared with the level of Sham control. Dex treatment increased calcium and phosphate levels in the sera of both Sham and ADX mice. In a time course experiment, Dex significantly decreased duodenal CaBP-9k at the transcriptional and translational levels at 3 days, whereas it temporarily increased CaBP-9k mRNA and protein levels at 12 and 24 h. Altered CaBP-9k expression by Dex was completely reversed by mifepristone, an antagonist for the GC receptor (GR). In addition, duodenal CaBP-9k and GR were colocalized on the enterocyte (duodenocyte), supporting a role for GR in regulating CaBP-9k. In ovariectomized (OVX) and ADX female mice daily treated with Dex for 3 days, duodenal CaBP-9k was expressed at the same level as in male mice. Also, no cross-activity of progesterone and Dex on their receptors was observed. Taken together, these results indicate that mouse CaBP-9k gene may be regulated by Dex in a tissue-specific manner, and reduced duodenal CaBP-9k via the GR pathway may take part in negative calcium absorption of GC-induced osteoporosis, whereas renal CaBP-9k may not be involved in the regulation of calcium homeostasis.

Male patients with paranoid schizophrenia have greater ACTH and cortisol secretion in response to metoclopramide-induced AVP release

Dynamic testing of the hypothalamic-pituitary-adrenal axis in schizophrenia has yielded conflicting results, which may be related to patient selection and previous exposure to psychotropic medication. The objective of this study was to determine the pattern of corticotropin (ACTH) and cortisol release in response to metoclopramide (a dopamine antagonist), which appears to be unique in its ability to release vasopressin (AVP), in drug naive patients with schizophrenia experiencing their first episode of psychosis. In this study, we examined AVP, ACTH and cortisol release in response to metoclopramide in 10 drug-naive, first-episode male patients with a DSM IV diagnosis of paranoid schizophrenia and compared them to healthy control subjects matched for age, sex and smoking status. Patients, as compared to controls had higher levels of baseline plasma cortisol (375.5+/-47.4/l vs. 273.8+/-42.2 nmol/l, respectively; t=2.48, df=9, p< 0.02) and plasma ACTH (14.9+/-0.85 vs. 11.3+/-0.57 pg/ml, respectively; t=4.29, df=9, p<0.001). AVP levels were lower in patients though this did not reach statistical significance (0.89+/-0.09 vs. 1.3+/-0.08 pmol/l, respectively; t=1.97, df=9, p<0.07). A repeated measures 2-way ANOVA to compare responses to metoclopramide over time between the two groups yielded a significant group by time interaction for cortisol (F=11.3, df=6, 108, p<0.001) and ACTH (F=15.65, df=6, 108, p<0.002). Post hoc Tukey's test revealed significant differences between the two groups at +30, +45, +60, +90 and +120 min for cortisol (p<0.01) and at +30, +45, +60 and +90 min for ACTH (p<0.01). The group by time interactions continued to remain significant when cortisol (F=10.9, df=6, 107, p<0.001) and ACTH (F=13.04, df=6, 108, p<0.002) were entered as co-variates. There was a significant positive correlation between AVP and cortisol responses in patients (r=0.65, df=8, p<0.01). Male patients with paranoid schizophrenia release greater amounts of ACTH and cortisol in responses to metoclopramide-induced AVP secretion than control subjects.

Reduced hypothalamic vasopressin secretion underlies attenuated adrenocorticotropin stress responses in pregnant rats

We sought to explain decreased ACTH secretory responses to stress in pregnant rats by investigating hypothalamic CRH and vasopressin secretion and actions on anterior pituitary corticotrophs. In late pregnancy median eminence, CRH content was reduced (by 12%). Anterior pituitary proopiomelanocortin mRNA expression, measured by in situ hybridization but not radioimmunoassayed ACTH content, was also reduced (by 45% on d 21); CRH receptor (CRHR)1 mRNA expression was unaltered in pregnancy, but V1b receptor mRNA expression was reduced (by 19%). ACTH secretory responses, measured in jugular blood, to CRH (200 ng/kg iv) or vasopressin (1.7 microg/kg, iv) were reduced on d 21 vs. virgins (49% and 44%), but the response to combined CRH and vasopressin injection was intact. Either antalarmin (CRHR1 antagonist; 20 mg/kg ip) or dP(Tyr(Me)2),Arg-NH2(9))AVP (V1a/b antagonist; 10 microg/kg, iv) pretreatment reduced the ACTH secretory response to forced swimming (90 sec) in virgin rats (by 57% and 40%), but only antalarmin was effective in pregnant rats (53% decrease). In vitro, measuring ACTH secretion from acutely dispersed anterior pituitary cells showed increased corticotroph sensitivity in pregnancy to CRH and to CRH augmentation by vasopressin, attributable to increased intracellular cAMP action. Hence, in late pregnancy, reduced anterior pituitary CRHR1 or V1b receptor expression did not impair corticotroph responses to CRH or vasopressin. Rather, diminished secretagogue secretion in vivo accounts for reduced action of stress levels of exogenous CRH or vasopressin alone; the late pregnancy attenuated ACTH secretory response to swim stress is deduced to be due to reduced vasopressin release by parvocellular paraventricular nuclei neurones.

Vasopressinergic regulation of the hypothalamic pituitary adrenal axis and stress adaptation

Vasopressin (VP) stimulates pituitary ACTH secretion through interaction with receptors of the V1b subtype (V1bR, V3R), located in the plasma membrane of the pituitary corticotroph, mainly by potentiating the stimulatory effects of corticotropin releasing hormone (CRH). Chronic stress paradigms associated with corticotroph hyperresponsiveness lead to preferential expression of hypothalamic VP over CRH and upregulation of pituitary V1bR, suggesting an important role for VP during adaptation of the hypothalamic-pituitary-adrenal (HPA) axis to stress. Vasopressinergic regulation of ACTH secretion depends on the number of V1bRs as well as coupling of the receptor to phospholipase C (PLC) in the pituitary. Regulation of V1bR gene transcription may involve a number of regulatory elements in the promoter region, of which a GAGA box was shown to be essential. Although V1bR gene transcription is necessary to maintain V1bR mRNA levels, the lack of correlation between VP binding and V1bR mRNA suggests that regulation of mRNA translation is a major regulatory step of the number of V1bRs. V1bR translation appears to be under tonic inhibition by upstream minicistrons and positive regulation through protein kinase C (PKC) activation of an internal ribosome entry site (IRES) in the 5' untranslated region (5'UTR) of the mRNA. The data provide mechanisms by which regulation of hypothalamic VP and pituitary V1bR content contribute to controlling HPA axis activity during chronic stress.

The role of hypothalamic input on corticotroph maturation in fetal sheep

Corticotropin-releasing hormone receptor type 1 (CRH-R1) expression and vasopressin type 1b (V1b) receptor protein decrease in late-gestation fetal sheep. Because hypothalamo-pituitary disconnection (HPD) has been demonstrated to prevent the morphological maturation of corticotrophs, we hypothesized that hypothalamic input is necessary for the maturational changes in CRH-R1 and V1b receptor levels. We measured CRH-R1 and V1b receptor expression in the anterior pituitaries of fetuses at 140 days gestational age (dGA) that underwent HPD or sham surgery at 120 dGA. CRH-R1 mRNA decreased similarly in HPD and sham-operated fetuses compared with 120 dGA naive fetuses. However, CRH-R1 protein levels were elevated in HPD fetuses compared with sham and were not different from 120 dGA values. V1b protein levels decreased similarly in HPD and sham-operated fetuses compared with 120 dGA naive fetuses. We conclude that hypothalamic input to the pituitary is necessary for the decrease in CRH-R1 receptor protein levels in late-gestation fetal sheep. However, hypothalamic input is not necessary for the decrease in V1b receptor expression seen in late gestation.

Ontogeny and effect of cortisol on vasopressin-1b receptor expression in anterior pituitaries of fetal sheep

Corticotroph responsiveness to arginine vasopressin (AVP) increases during late gestation in fetal sheep. The mechanism of this increase in AVP responsiveness is currently unknown but could be related to an increase in vasopressin type 1b (V1b) receptor expression in the pituitary during development. To determine if there are ontogenic changes in V1b receptor expression that may help explain the changes in ACTH responses to AVP, we studied pituitaries from three groups of fetal sheep [100, 120, or 140 days gestational age (dGA)]. V1b receptor mRNA and protein significantly decreased by 140 dGA. Peak V1b mRNA levels were detected at 100 dGA, while peak V1b protein levels were detected at 120 dGA. The reduction in V1b receptor expression in late gestation may be due to the naturally occurring peripartum increase in fetal plasma cortisol because cortisol infusion at 122-130 dGA decreased V1b receptor mRNA. Thus there is a marked decrease in the expression of the V1b receptor in the pituitary during fetal development, leaving the role of the V1b receptor in increasing AVP responsiveness uncertain.

Overexpression of the V3 vasopressin receptor in transgenic mice corticotropes leads to increased basal corticosterone

The vasopressin V3 receptor (V3) is specifically expressed in pituitary corticotropes and mediates the stimulatory effect of vasopressin on adrenocorticotropic hormone (ACTH) release. The V3 gene is overexpressed in corticotrope pituitary tumours compared to normal pituitaries. We hypothesized that V3 overexpression might induce changes in corticotrope function and alter the regulation of the hypothalamic-pituitary-adrenal axis. Thus, we generated transgenic mice (POMV3) expressing the human V3 receptor in the pituitary under the control of rat pro-opiomelanocortin (POMC) promoter sequences. The transgene was efficiently transcribed and vasopressin binding was increased in both corticotropes and melanotropes. In-vitro ACTH release and inositol phosphate formation were unchanged in POMV3 pituitaries, but the responses to vasopressin were significatively increased. In vivo, basal circulating concentrations of ACTH in POMV3 mice were similar to those of controls but corticosterone concentrations were moderately increased. In addition, the levels of POMC mRNA in the transgenic pituitaries were comparable to those of control mice. Finally, POMV3 mice responded with a similar maximal increase of ACTH and corticosterone to a 20-min acute restraint stress. Together, these results show that hypophyseal V3 overexpression led to increased basal concentrations of corticosterone and suggest that the negative glucocorticoid feedback may be altered at the pituitary level.

Attenuation of corticotropin-releasing hormone and arginine vasopressin responsiveness during late-gestation pregnancy in sheep

Responsiveness of the hypothalamo-pituitary-adrenal axis is decreased during pregnancy. Therefore, the objective of the present study was to determine if responsiveness at the level of individual corticotrophs to corticotropin-releasing hormone (CRH) or arginine vasopressin (AVP) is decreased during pregnancy in sheep. Anterior pituitaries (APs) were collected from pregnant and nonpregnant ewes. Half of the APs were dispersed, and cells were placed on immobilon and treated with vehicle, CRH (10 nM), or AVP (100 nM) for 2 h. Cells were then fixed and incubated with ACTH or pro-opiomelanocortin (POMC) antibodies. The percentage of cells staining positive for immunoreactive (ir) ACTH or POMC, the percentage of cells secreting irACTH or POMC, and the area of irACTH or POMC secretion were measured. RNA was extracted from the other half of the APs to quantify CRH type 1 (CRH-R1) and vasopressin type 1b (V1b) receptor mRNA by ribonuclease protection assay. CRH treatment increased the percentage of corticotrophs with relatively large areas of irACTH and POMC secretion in nonpregnant, but not in pregnant, ewes. AVP treatment significantly increased the percentage of irACTH- and POMC-secreting cells in nonpregnant, but not in pregnant, ewes. V1b receptor mRNA, but not CRH-R1 receptor mRNA, was significantly decreased during pregnancy. These results suggest that corticotroph responsiveness to CRH and AVP is decreased during pregnancy in sheep. Therefore, reduced corticotroph responsiveness may contribute to stress hyporesponsivity during pregnancy.

Acute and chronic regulation of pituitary receptors for vasopressin and corticotropin releasing hormone

At least two hypothalamic peptides, corticotropin releasing hormone (CRH) and vasopressin (VP), are important in regulating adrenocorticotropin (ACTH) release from the anterior pituitary. Both are secreted in a pulsatile manner and stimulate ACTH secretion by interacting with G protein-coupled receptors (GPCRs), namely the type 1 CRH receptor and V1b receptor, respectively. Repeated or prolonged stimulation with either peptide can cause reduced ACTH responsiveness or desensitisation, both in vivo and in vitro. Desensitisation of perifused sheep anterior pituitary cells to VP was found to be rapid and occurred following treatment with 5 nM VP for 5 min. This is within the range of concentrations and durations of VP pulses seen in sheep portal blood during acute stress. In contrast, significant desensitisation of the ACTH response to CRH required pre-treatment for longer than 25 min with a CRH concentration of 1 nM, suggesting that endogenous pulses may not elicit desensitisation. Although rapid GPCR desensitisation involves uncoupling of receptors from their G proteins, commonly mediated by receptor phosphorylation, and internalisation of receptors, desensitisation of neither the CRH nor VP receptor was mediated by PKA or PKC, respectively. Desensitisation of the response to VP was found to be dependent upon receptor internalisation, and resensitisation could be delayed by treatment with a protein phosphatase 2B inhibitor. The rapid kinetics of desensitisation of the ACTH response to VP suggest that this process is important in regulating the response to acute rather than chronic stress. If, as has been suggested, CRH acts in a permissive way to set corticotrope gain, desensitisation to CRH could also be important in long term regulation of ACTH secretion.

Mechanisms of regulation of G(11)alpha protein by dexamethasone in osteoblastic UMR 106-01 cells

We have previously demonstrated that glucocorticoids increased G(q/11)alpha protein expression and phospholipase C activity in the rat osteosarcoma cell line UMR 106-01. In this study, we demonstrated that G(11)alpha is the primary G(q)-subtype family member expressed in UMR cells. Dexamethasone treatment increased the expression of G(11)alpha protein in both a time- and a dose-dependent manner. Glucocorticoid treatment significantly increased the half-life of G(11)alpha protein from 20.3 to 63 h. Steady-state G(11)alpha mRNA level was also increased by glucocorticoid treatment by approximately 70%. This change was not the result of changes in RNA stability but rather the result of increased transcription, because the glucocorticoid-mediated upregulation of G(11)alpha mRNA was blocked by the transcription inhibitor actinomycin D. The dexamethasone induction of G(11)alpha mRNA occurred after a time lag of 12-24 h and was blocked by the protein synthesis inhibitor cycloheximide. These results suggest that the dexamethasone-induced rise in G(11)alpha protein results primarily from changes in the degradation rate of the protein, whereas changes in G(11)alpha mRNA play a smaller role and require de novo synthesis of regulatory protein(s).

Salt-loading increases vasopressin and vasopressin 1b receptor mRNA in the hypothalamus and choroid plexus

The choroid plexus plays a pivotal role in the production of cerebrospinal fluid (CSF). Messenger RNA (mRNA) transcripts encoding arginine vasopressin (AVP) and the vasopressin 1b receptor (V(1b)R) are found in various structures of the central nervous system, including the choroid plexus. The present study measured AVP and V(1b)R mRNA production in response to plasma hyperosmolality. Compared to rats maintained on water, 2% salt-drinking rats had increased levels of AVP and V(1b)R mRNAs in the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus and in the choroid plexus. The increase in V(1b)R mRNA in the SON and PVN as a result of plasma hyperosmolality may reflect changes in receptor production that, in turn, have a role in AVP autoregulation of hypothalamic magnocellular neurons. The increase of AVP and V(1b)R mRNAs in the choroid plexus further shows the involvement of AVP in the regulation of brain water content and cerebral edema.

Involvement of upstream open reading frames in regulation of rat V(1b) vasopressin receptor expression

The V(1b) vasopressin receptor, expressed mainly in the corticotroph of the anterior pituitary, mediates the stimulatory effect of vasopressin on ACTH release. To clarify the regulation of receptor expression, we cloned, sequenced (up to approximately 5 kb from the translation start site), and characterized the 5'-flanking region of the rat V(1b) receptor gene. We identified the transcription start site by amplification of cDNA ends and found a new intron within the 5'-untranslated region (5'-UTR) by comparing the sequence with that of cDNA. We then confirmed that the obtained promoter indeed has transcriptional activity by use of the luciferase reporter in AtT-20 mouse corticotroph cells. Interestingly, there were five short upstream open reading frames (uORFs) located within the 5'-UTR that were found to suppress V(1b) expression. Subsequent mutational analyses showed that the two downstream uORFs have an inhibitory effect on expression in both homologous and heterologous contexts. Furthermore, the inhibition did not accompany a parallel decrease in mRNA, suggesting that the suppressive effect occurs at a level downstream of transcription. Taken together, our data strongly suggest that the expression of the V(1b) receptor is regulated at the posttranscriptional as well as transcriptional level through uORFs within the 5'-UTR region of the mRNA. Whether the uORF-mediated regulation of V(1b) expression is functionally linked to any intracellular and/or extracellular factor(s) awaits further research.

Ectopic and abnormal hormone receptors in adrenal Cushing's syndrome

The mechanism by which cortisol is produced in adrenal Cushing's syndrome, when ACTH is suppressed, was previously unknown and was referred to as being "autonomous." More recently, several investigators have shown that some cortisol and other steroid-producing adrenal tumors or hyperplasias are under the control of ectopic (or aberrant, illicit, inappropriate) membrane hormone receptors. These include ectopic receptors for gastric inhibitory polypeptide (GIP), beta-adrenergic agonists, or LH/hCG; a similar outcome can result from altered activity of eutopic receptors, such as those for vasopressin (V1-AVPR), serotonin (5-HT4), or possibly leptin. The presence of aberrant receptors places adrenal cells under stimulation by a trophic factor not negatively regulated by glucocorticoids, leading to increased steroidogenesis and possibly to the proliferative phenotype. The molecular mechanisms responsible for the abnormal expression and function of membrane hormone receptors are still largely unknown. Identification of the presence of these illicit receptors can eventually lead to new pharmacological therapies as alternatives to adrenalectomy, now demonstrated by the long-term control of ectopic P-AR- and LH/hCGR-dependent Cushing's syndrome by propanolol and leuprolide acetate. Further studies will potentially identify a larger diversity of hormone receptors capable of coupling to G proteins, adenylyl cyclase, and steroidogenesis in functional adrenal tumors and probably in other endocrine and nonendocrine tumors.

Characterisation of vasopressin V(1A), angiotensin AT(1) and AT(2) receptor distribution and density in normotensive and hypertensive rat brain stem and kidney: effects of restraint stress

In the present study, we have examined neurochemical correlates that may be involved in the differential cardiovascular responses observed in normotensive and hypertensive rats during stress. Using a restraint stress paradigm, both normotensive Wistar Kyoto (WKY) and Spontaneously Hypertensive rats (SHR) underwent acute (1 h restraint in a perspex tube), chronic (1 h restraint for ten consecutive days) or no restraint (control) stress. Following cessation of restraint, rats were processed by incubating sections of brain stem and kidney with [125I]-HO-LVA (0.03 nM) or [125I]Sar(1)Ile(8)-AngiotensinII (0.5 nM), in the presence of PD123319 (10 microM) or losartan (10 microM), to determine the distribution and density of vasopressin V(1A), angiotensin AT(1) and AT(2) receptors, respectively. Analysis of autoradiograms indicated changes in the density of radioligand binding in acutely and chronically-stressed rats, as compared to controls. For example, V(1A) binding in the medial nucleus tractus solitarius (SolM) decreased in the WKY but increased in the SHR. AT(1) binding in SolM did not significantly change in the WKY but decreased in the SHR with repeated restraint. In kidney slices, AT(1) binding decreased with stress in the WKY (-17%) but increased in SHR (+10-15%). AT(2) binding in the kidney showed a pattern similar to that of AT(1) binding in SHR, but not WKY. Graded increases in V(1A) binding were measured in kidney medulla and cortex of both strains (+50-60% with chronic restraint). These results suggest that physiological adaptation to restraint is associated with specific changes in V(1A), AT(1) and AT(2) receptor density within brain nuclei and kidney.

Regulation of vasopressin V1b receptors in the anterior pituitary gland of the rat

Vasopressin secreted by parvocellular neurones of the hypothalamic paraventricular nucleus modulates pituitary adrenocorticotrophic hormone (ACTH) secretion by acting upon vasopressin V1b type receptors in the pituitary corticotroph coupled to phospholipase C. Regulation of V1b receptors contributes to the adaptation of the hypothalamic-pituitary-adrenal (HPA) axis to stress, as evidenced by the correlation between vasopressin receptor number and pituitary ACTH responsiveness. V1b receptor upregulation during chronic stress is associated with elevated circulating glucocorticoids and vasopressin expression in parvocellular neurones, suggesting that these factors control V1b receptor expression. Removal of circulating glucocorticoids by adrenalectomy causes sustained vasopressin receptor downregulation, but reduces V1b receptor mRNA only transiently. The latter effect is not mediated by increased corticotrophin-releasing hormone (CRH) and vasopressin release, since it is not prevented by lesions of the hypothalamic paraventricular nucleus. Adrenalectomy causes sustained V1b receptor loss in Brattleboro rats, which lack hypothalamic vasopressin, suggesting that vasopressin mediates V1b receptor mRNA recovery. Exogenous glucocorticoid administration downregulates pituitary vasopressin binding but increases V1b receptor mRNA and facilitates coupling of the receptor to phospholipase C, effects which may contribute to the refractoriness of vasopressin actions to glucocorticoid feedback. The lack of parallelism between changes in pituitary vasopressin binding and V1b receptor mRNA levels during manipulation of the HPA axis indicates that V1b receptor content depends on post-transcriptional mechanisms rather than steady-state V1b receptor mRNA levels. These studies suggest that interaction between glucocorticoids and vasopressin plays an important role in regulating V1b receptor mRNA expression during alterations of the HPA axis. In addition, the recent characterization of a major part of the V1b receptor gene provides a basis for studying the molecular mechanisms regulating the V1b receptor.

Altered pituitary sensitivity to corticotropin-releasing factor and arginine vasopressin participates in the stress hyporesponsiveness of lactation in the rat

The regulation of the activity of the hypothalamic-pituitary-adrenal (HPA) axis is modified during lactation, wherein a blunted stress-induced adrenocorticotropic hormone (ACTH) and glucocorticoid secretion is coupled with elevated basal secretion of these hormones. The involvement of pituitary modifications in lactation-induced stress hyporesponsiveness has yet to be established. In this study we tested the hypothesis that the pituitary sensitivity to corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) is altered in lactation in the rat. We examined the effect of exogenous CRF (0.1-5 microg/rat), AVP (0.01-0.5 microg/rat), and AVP (0.01-0.5 microg/rat)+CRF (0.1 microg/rat) on the ACTH response of virgin, mid-lactating (lactation day 10-12) females, as well as nursing females separated from their pups for 48 h. Additionally, to determine if changes in CRF- or AVP-receptor densities might mediate alterations in pituitary sensitivity, we compared pituitary CRF- and AVP-receptor binding by autoradiography in pregnant, mid-lactating, and virgin female rats. While both virgin and lactating female rats exhibited significant ACTH responses to CRF, the responses to the highest doses of CRF (2.0 and 5.0 microg/rat) were greater in virgin than in lactating females. Separation of the litter for 48 h partially restored pituitary responsiveness to 2.0 microg of CRF. Conversely, whereas lactating females displayed robust ACTH secretion following a high dose of AVP or following a combination of AVP+CRF, the response of virgin females was much smaller. These modifications in pituitary responsiveness were not accompanied by significant differences in pituitary CRF-and AVP-receptors levels between female groups. Our results demonstrate that a reduction in pituitary sensitivity to CRF, but not to AVP occur during lactation in the rat which mediates, at least in part, the stress hyporesponsiveness of lactation.

Steroidal regulation of portal arginine-vasopressin levels in aged Fischer 344 rats

Levels of hypophysial portal arginine-vasopressin (AVP), plasma ACTH and plasma corticosterone (B) were measured in four and 24 month old Fischer 344 rats. Portal levels of AVP were lower in older rats whereas plasma ACTH levels were elevated. Older rats given adrenalectomies with physiologic replacement doses of B exhibited levels of AVP, but not ACTH, which were comparable to that observable in younger rats. The findings suggest that altered AVP, but not ACTH, can be accounted for by higher B levels which are commonly demonstrable in aging rats.