Copeptin in obese children and adolescents: relationships to body mass index, cortisol and gender

Copeptin as a diagnostic and prognostic biomarker in pediatric diseases

Arginine vasopressin (AVP) plays a main role in maintaining the homeostasis of fluid balance and vascular tone and in regulating the endocrine stress response in response to osmotic, hemodynamic and stress stimuli. However, the difficulty in measuring AVP limits its clinical application. Copeptin, the C-terminal part of the AVP precursor, is released in an equimolar concentration mode with AVP from the pituitary but is more stable and simple to measure. Therefore, copeptin has emerged as a promising surrogate marker of AVP with excellent potential for the diagnosis, differentiation and prognosis of various diseases in recent decades. However, its application requires further validation, especially in the pediatric population. This review focuses on the clinical value of copeptin in different pediatric diseases and the prospects for its application as a potential biomarker.

Copeptin as a surrogate marker for arginine vasopressin: analytical insights, current utility, and emerging applications

Copeptin is a 39-amino-acid long glycosylated peptide with a leucine-rich core segment in the C-terminal part of pre-pro-vasopressin. It exhibits a rapid response comparable to arginine vasopressin (AVP) in response to osmotic, hemodynamic, and nonspecific stress-related stimuli. This similarity can be attributed to equimolar production of copeptin alongside AVP. However, there are markedly different decay kinetics for both peptides, with an estimated initial half-life of copeptin being approximately two times longer than that of AVP. Like AVP, copeptin correlates strongly over a wide osmolality range in healthy individuals, making it a useful alternative to AVP measurement. While copeptin does not appear to be significantly affected by food intake, small amounts of oral fluid intake may result in a significant decrease in copeptin levels. Compared to AVP, copeptin is considerably more stable in vitro. An automated immunofluorescent assay is now available and has been used in recent landmark trials. However, separate validation studies are required before copeptin thresholds from these studies are applied to other assays. The biological variation of copeptin in presumably healthy subjects has been recently reported, which could assist in defining analytical performance specifications for this measurand. An established diagnostic utility of copeptin is in the investigation of polyuria-polydipsia syndrome and copeptin-based testing protocols have been explored in recent years. A single baseline plasma copeptin >21.4 pmol/L differentiates AVP resistance (formerly known as nephrogenic diabetes insipidus) from other causes with 100% sensitivity and specificity, rendering water deprivation testing unnecessary in such cases. In a recent study among adult patients with polyuria-polydipsia syndrome, AVP deficiency (formerly known as central diabetes insipidus) was more accurately diagnosed with hypertonic saline-stimulated copeptin than with arginine-stimulated copeptin. Glucagon-stimulated copeptin has been proposed as a potentially safe and precise test in the investigation of polyuria-polydipsia syndrome. Furthermore, copeptin could reliably identify those with AVP deficiency among patients with severe hypernatremia, though its diagnostic utility is reportedly limited in the differential diagnosis of profound hyponatremia. Copeptin measurement may be a useful tool for early goal-directed management of post-operative AVP deficiency. Additionally, the potential prognostic utility of copeptin has been explored in other diseases. There is an interest in examining the role of the AVP system (with copeptin as a marker) in the pathogenesis of insulin resistance and diabetes mellitus. Copeptin has been found to be independently associated with an increased risk of incident stroke and cardiovascular disease mortality in men with diabetes mellitus. Increased levels of copeptin have been reported to be independently predictive of a decline in estimated glomerular filtration rate and a greater risk of new-onset chronic kidney disease. Furthermore, copeptin is associated with disease severity in patients with autosomal dominant polycystic kidney disease. Copeptin predicts the development of coronary artery disease and cardiovascular mortality in the older population. Moreover, the predictive value of copeptin was found to be comparable with that of N-terminal pro-brain natriuretic peptide for all-cause mortality in patients with heart failure. Whether the measurement of copeptin in these conditions alters clinical management remains to be demonstrated in future studies.

Zonulin and copeptin relation to some metabolic markers in school-aged obese children

BACKGROUND

Using Zonulin and Copeptin as potential obesity markers in children, hasn't yet been focused.

AIM

To evaluate the association between serum levels of both Zonulin and Copeptin with the obesity markers, and to assess their role as metabolic disturbance predictors in obese children.

METHODS

A case-control study comprised 111 Egyptian children (45 males and 66 females); aged 6-10 years to avoid the effect of puberty (prepubertal). They were classified according to their body mass index (BMI) percentiles into: 72 obese (BMI ≥ 95th ), and 39 control ones (BMI > 15th - <85th ), based on the Egyptian Growth Charts for children and adolescents. Anthropometric parameters and blood pressure were measured, and body composition analysis, lipid profile, Zonulin, and Copeptin levels were assessed.

RESULTS

The obese group showed a significantly higher value of Copeptin and a lower value of Zonulin than the control one Also, the obese group showed significant negative correlations between Zonulin and both anthropometric obesity markers and body composition, whereas Copeptin showed significant positive ones. Moreover, significant positive correlations were found between Copeptin and both body weight and fat distribution. Insignificant correlations were observed between both serum Zonulin and Copeptin levels and blood pressure and lipid profile.

CONCLUSION

Zonulin and Copeptin cannot be used as metabolic disturbance predictors, among Egyptian children, as they were insignificantly correlated with lipid profile or blood pressure.

Paediatric perspectives in the diagnosis of polyuria-polydipsia syndrome

The elucidation of the underlying cause of polyuria-polydipsia syndrome (PPS) is a challenging-especially in the differentiation of partial defects of arginine vasopressin (AVP) secretion or action from primary polydipsia. The water deprivation test has been utilized for many decades, and its application in the paediatric population has been applied using parameters predominantly established in adult cohorts. In more recent times, the development of automated commercial assays for copeptin, a surrogate marker for AVP, has represented a significant advancement in the diagnostic approach to PPS. Measurement of copeptin concentrations has major advantages and has essentially superseded measurement of AVP in diagnostic protocols for PPS. Additionally, stimulated-copeptin protocols utilizing hypertonic saline infusion, arginine, and glucagon have been investigated, and are promising. However, further studies are required in the population-incorporating the differences in physiological regulation of water homeostasis, and safety requirements-before there is widespread adoption into clinical practice.

Arginine-stimulated copeptin in children and adolescents

OBJECTIVE

Copeptin is secreted in isomolar amounts along with arginine vasopressin peptide (AVP) from the neurohypophysis. Its stability makes it a perfect candidate for the endocrine approach in the diagnosis of AVP deficiency (AVPD; cranial diabetes insipidus; CDI). However, pediatric reference values are lacking.

DESIGN AND PATIENTS

This is a monocentric retrospective analysis of donated residual serum samples from 72 children and adolescents who underwent arginine or growth hormone-releasing hormone-arginine stimulation to test GH secretory capacity from 2018 to 2022.

MEASUREMENTS

Copeptin was measured in baseline, 30-, and 60-min samples by BRAHMS Copeptin proAVP Kryptor immunofluorescence assay.

RESULTS

Of the 72 patients, 4 suffered from complete AVPD (CDI). The baseline level of copeptin in the 68 non-AVPD (non-CDI) patients was highly variable (range: 1.3-44.4 pmol/L). The increase after arginine was moderate (30 min range: 1.6-40.4 pmol/L). The median baseline and peak copeptin levels were 5.6 and 8.0 pmol/L, respectively. The 2.5th percentile of the baseline and peak values of copeptin were 2.1 and 3.3 pmol/L, respectively. The increase and peak value of copeptin were inversely related to age (R = -.405; p = .011, and R = -.335; p = .0072, respectively) but not to gender, body mass index (standard deviation score) or GH secretion. In the four patients with AVPD (CDI), baseline or stimulated copeptin was below the 2.5th percentile of non-AVPD (non-CDI) patients.

CONCLUSIONS

Stimulated copeptin is a promising parameter for the differential diagnosis of polyuria-polydipsia syndrome. However, the low copeptin increase after arginine and the high limit of quantification of the assay are problematic for use in paediatrics.

Copeptin Levels Before and After Transsphenoidal Surgery for Cushing Disease: A Potential Early Marker of Remission

Context

Arginine-vasopressin and CRH act synergistically to stimulate secretion of ACTH. There is evidence that glucocorticoids act via negative feedback to suppress arginine-vasopressin secretion.

Objective

Our hypothesis was that a postoperative increase in plasma copeptin may serve as a marker of remission of Cushing disease (CD).

Design

Plasma copeptin was obtained in patients with CD before and daily on postoperative days 1 through 8 after transsphenoidal surgery. Peak postoperative copeptin levels and Δcopeptin values were compared among those in remission vs no remission.

Results

Forty-four patients (64% female, aged 7-55 years) were included, and 19 developed neither diabetes insipidus (DI) or syndrome of inappropriate anti-diuresis (SIADH). Thirty-three had follow-up at least 3 months postoperatively. There was no difference in peak postoperative copeptin in remission (6.1 pmol/L [4.3-12.1]) vs no remission (7.3 pmol/L [5.4-8.4], P = 0.88). Excluding those who developed DI or SIADH, there was no difference in peak postoperative copeptin in remission (10.2 pmol/L [6.9-21.0]) vs no remission (5.4 pmol/L [4.6-7.3], P = 0.20). However, a higher peak postoperative copeptin level was found in those in remission (14.6 pmol/L [±10.9] vs 5.8 (±1.4), P = 0.03]) with parametric testing. There was no difference in the Δcopeptin by remission status.

Conclusions

A difference in peak postoperative plasma copeptin as an early marker to predict remission of CD was not consistently present, although the data point to the need for a larger sample size to further evaluate this. However, the utility of this test may be limited to those who develop neither DI nor SIADH postoperatively.

Serum copeptin as a biomarker of hypertension in children with obesity

BACKGROUND

Hypertension (HT) in obesity has been reported frequently in children in recent years. The role of copeptin and uric acid here are not well known. We aimed to investigate the relationship between HT and serum copeptin and uric acid levels in children with obesity.

METHODS

We included 80 children with obesity who were admitted to our hospital between April 2018 and September 2018. The patients were separated into two groups: hypertensive and non-hypertensive. Serum copeptin levels were measured using the enzyme-linked immunosorbent assay.

RESULTS

Copeptin levels were significantly higher in patients with HT than in those without (p = 0.0001). In addition, serum uric acid levels in patients with HT were significantly higher, while the serum potassium levels were significantly lower (p = 0.01) than in those without HT (p = 0.001). In correlation analyses, a positive correlation was detected between blood sodium and copeptin levels (p = 0.037).

CONCLUSIONS

Hypertensive children with obesity had higher serum copeptin and uric acid and lower blood potassium levels. Moreover, copeptin levels were positively correlated with blood sodium levels. Thus, in addition to copeptin, serum uric acid, potassium, and sodium levels may be important in the diagnosis and follow-up of children with HT.

Copeptin assays in children for the differential diagnosis of polyuria-polydipsia syndrome and reference levels in hospitalized children

OBJECTIVES

Polyuria-polydipsia syndrome (PPS) is a common presentation in children but the differential diagnosis rests on burdensome water deprivation tests. The aims of this study were to determine a copeptin threshold to distinguish patients with central diabetes insipidus from those with primary polydipsia and to estimate the normal range of copeptin concentrations in children.

DESIGN

Single-centre retrospective descriptive study.

PATIENTS

Two hundred and seventy-eight children aged 2 months to 18 years who consulted for PPS (N = 40) or other reasons (control group, N = 238) at La Timone University Hospital in Marseille, France, between April 2015 and September 2019 and had a copeptin assay.

MEASUREMENTS

Ultrasensitive copeptin assays on blood samples.

RESULTS

Among the children with PPS, the mean copeptin concentrations were 1.72, 55.2 and 15.7 pmol/l in those with central diabetes insipidus (N = 21), nephrogenic diabetes insipidus (N = 3), and primary polydipsia (N = 16), respectively. Copeptin levels lower than 3.53 pmol/l were diagnostic of central diabetes insipidus with 100% sensitivity and 87.4% specificity (p < .001). The 5th-95th copeptin percentile range in the control group was 2.53-21.03 pmol/L. Copeptin levels were significantly higher in boys than in girls but there was no association with age, pubertal stage, body mass index, or the reason for consulting.

CONCLUSIONS

Our results indicate copeptin assays may be valuable in the differential diagnosis of PPS in children. Larger prospective studies are required to establish their accuracy in everyday clinical practice.

Vasopressin-Dependent Disorders: What Is New in Children?

Arginine vasopressin (AVP)-mediated osmoregulatory disorders, such as diabetes insipidus (DI) and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are common in the differential diagnosis for children with hypo- and hypernatremia and require timely recognition and treatment. DI is caused by a failure to concentrate urine secondary to impaired production of or response to AVP, resulting in hypernatremia. Newer methods of diagnosing DI include measuring copeptin levels; copeptin is AVP's chaperone protein and serves as a surrogate biomarker of AVP secretion. Intraoperative copeptin levels may also help predict the risk for developing DI after neurosurgical procedures. Copeptin levels hold diagnostic promise in other pediatric conditions, too. Recently, expanded genotype and phenotype correlations in inherited DI disorders have been described and may better predict the clinical course in affected children and infants. Similarly, newer formulations of synthetic AVP may improve pediatric DI treatment. In contrast to DI, SIADH, characterized by inappropriate AVP secretion, commonly leads to severe hyponatremia. Contemporary methods aid clinicians in distinguishing SIADH from other hyponatremic conditions, particularly cerebral salt wasting. Further research on the efficacy of therapies for pediatric SIADH is needed, although some adult treatments hold promise for pediatrics. Lastly, expansion of home point-of-care sodium testing may transform management of SIADH and DI in children. In this article, we review recent developments in the understanding of pathophysiology, diagnostic workup, and treatment of better outcomes and quality of life for children with these challenging disorders.

Effect of pre-meal water intake on the serum levels of Copeptin, glycemic control, lipid profile and anthropometric indices in patients with type 2 diabetes mellitus: a randomized, controlled trial

Background

Water pre-load affects insulin secretion by altering the level of copeptin (C-terminal component of the arginine vasopressin hormone (AVP)) and preventing obesity by reducing food intake.

Aims

The present randomized controlled trial (RCT) aimed to investigate the effects of pre-meal water intake on type 2 diabetes Mellitus (T2DM).

Materials and methods

In this study, 40 patients with T2DM were randomly assigned to two intervention groups for 8 weeks; a) drinking 1 liter of water per day before each main meal (PW group)., and b) no water consumption before any meal (NPW group). At the beginning and at the end of the study, blood samples were taken to assess glycemic indices, lipid profile, copeptin and anthropometric indices.

Results

Pre-meal water intake was associated with lower energy intake, BMI, waist circumference (WC) and greater weight loss, in compared with the controls (P < 0.0001) after 8 weeks. At the end of the trial, the concentrations of fasting blood sugar (FBS) (P < 0.0001), triglyceride (TG) (P < 0.05), low-density lipoprotein cholesterol (LDL-C) (P < 0.05) and copeptin (P < 0.05) were significantly reduced following water drinking before meals.

Conclusion

To sum up, the present study revealed that pre-meal water intake is associated with lower BMI, body weight, WC, FBS, TG, LDL-C and copeptin levels in patients with T2DM.

Distribution of plasma copeptin levels and influence of obesity in children and adolescents

In recent years, a more stable AVP surrogate, called copeptin, has been used as an adjuvant diagnostic tool for dysnatremia in adults and appears to be promising even in the pediatric age. The aim of this study is to present the distribution of plasma copeptin in a large pediatric cohort and to observe the influence of fluid consumption and obesity on its values. A cohort of 128 children and adolescents was divided into two groups on the basis of nocturnal deprivation (group A) or free access to oral fluids in the 6-8 h before blood collection (group B). At all distribution percentiles, copeptin levels were higher (p < 0.0001) in group A, as were plasma sodium levels and osmolality (p = 0.02 and p = 0.008, respectively). The influence of BMI on copeptin levels was investigated by dividing the cohort into nonobese (group C) and obese children and adolescents (group D). Copeptin levels were higher in group D (p = 0.04).Conclusion: The measurement of copeptin could represent a useful tool for the diagnostic pathway of dysnatremic conditions, but its interpretation should take into consideration the state of hydration. Furthermore, it could also be a promising marker for obesity and metabolic syndrome, although this hypothesis needs further studies to be confirmed. What is Known: • Copeptin use as a diagnostic tool in AVP-related disorders, such as diabetes insipidus or syndrome of inappropriate secretion of antidiuretic hormone, is well established in adults • In pediatric age, few studies are available, but the preliminary data, including our previous study, seems to be promising. What is New: • In this study, we represent the distribution of copeptin levels in a pediatric cohort and show the significant influence of fluid ingestion on its plasma levels. • Also BMI seems to be a significant variable on copeptin levels and may be used as an obesity marker in pediatric age.

Can we use copeptin as a biomarker for masked hypertension or metabolic syndrome in obese children and adolescents?

OBJECTIVES

Copeptin, the C-terminal part of arginine-vasopressin, is increased in hypertensive adolescents and closely associated with metabolic syndrome (MS). We aimed to investigate whether serum copeptin can be used to differentiate masked hypertension (MHT) and MS, and the role of sodium intake, natriuretic peptide response and renin-angiotensin-aldosterone system in MHT and MS in obese youth.

METHODS

Obese children aged 10-18 years with normal office blood pressure measurements were included. Patients with MHT and normotension and those with MS and non-MS were evaluated separately. Biochemical parameters, copeptin, brain natriuretic peptide (BNP), aldosterone, renin, urine sodium, and protein were evaluated. Echocardiography, fundoscopic examination, and ambulatory blood pressure monitoring were performed.

RESULTS

There were 80 (M/F=39/41) obese patients with a mean age of 13.78 ± 1.93 years. The cases with MHT, MS, and concomitant MHT and MS were 53,24, and 13%, respectively. Copeptin levels were similar among patients with and without MHT or MS (p>0.05). However, multivariate analysis revealed that copeptin significantly increased the probability of MHT (OR 1.01, 95% CI=1.001-1.018, p=0.033). Copeptin was positively correlated with daytime systolic and diastolic load, aldosterone, BNP, and urine microalbumin/creatinine levels (p<0.05). Linear regression analyses revealed that copeptin was significantly correlated with BNP regardless of having MHT or MS in obese youth. In the MHT group, 24-h sodium excretion was not significantly correlated with BNP.

CONCLUSION

Copeptin may be a beneficial biomarker to discriminate MHT, but not MS in obese children and adolescents. An insufficient BNP response to sodium intake might be one of the underlying causes of MHT in obese cases.

Copeptin and Nesfatin-1 Are Interrelated Biomarkers with Roles in the Pathogenesis of Insulin Resistance in Chinese Children with Obesity

<b><i>Background:</i></b> Copeptin and nesfatin-1 have recently been identified as novel peptides that play a role in the pathogenesis of obesity-related insulin resistance in adults. However, the relationship between them has not yet been elucidated, and their circulating levels in children with obesity have not been adequately studied. Therefore, the current study aimed to investigate whether their levels are altered in Chinese children with obesity, as well as to determine the correlation of these 2 peptides with each other, with insulin resistance, and with other biochemical parameters. <b><i>Methods:</i></b> A total of 156 children were enrolled in this study, including 101 children with obesity and 55 lean controls. Anthropometric parameters and clinical data of all subjects were collected, and circulating tumor necrosis factor-α, adiponectin, leptin, copeptin, and nesfatin-1 levels were measured using ELISA. <b><i>Results:</i></b> Serum copeptin and nesfatin-1 levels were significantly elevated in children with obesity and children with insulin resistance compared to control subjects. In addition, nesfatin-1 and copeptin levels were found to be significantly positively correlated with one another by Pearson’s correlation and partial correlation. In multiple regression analysis using nesfatin-1 or copeptin as the dependent parameter, a significant correlation was observed between nesfatin-1 and copeptin, and associations between each of them with homeostasis model assessment of insulin resistance (HOMA-IR) were detected. <b><i>Conclusion:</i></b> These novel findings shed light on the possible interplay role of these 2 molecules in obesity-related insulin resistance.

Central diabetes insipidus in children: Diagnosis and management

Central diabetes insipidus (CDI) is a complex disorder in which large volumes of dilute urine are excreted due to arginine-vasopressin deficiency, and it is caused by a variety of conditions (genetic, congenital, inflammatory, neoplastic, traumatic) that arise mainly from the hypothalamus. The differential diagnosis between diseases presenting with polyuria and polydipsia is challenging and requires a detailed medical history, physical examination, biochemical approach, imaging studies and, in some cases, histological confirmation. Magnetic resonance imaging is the gold standard method for evaluating the sellar-suprasellar region in CDI. Pituitary stalk size at presentation is variable and can change over time, depending on the underlying condition, and other brain areas or other organs - in specific diseases - may become involved during follow up. An early diagnosis and treatment are preferable in order to avoid central nervous system damage and the risk of dissemination of germ cell tumor, or progression of Langerhans Cell Histiocytosis, and in order to start treatment of additional pituitary defects without further delay. This review focuses on current diagnostic work-up and on the role of neuroimaging in the differential diagnosis of CDI in children and adolescents. It provides an update on the best approach for diagnosis - including novel biochemical markers such as copeptin - treatment and follow up of children and adolescents with CDI; it also describes the best approach to challenging situations such as post-surgical patients, adipsic patients, patients undergoing chemotherapy and/or in critical care.

Elevated copeptin, arterial stiffness, and elevated albumin excretion in adolescents with type 1 diabetes

OBJECTIVE

We sought to evaluate copeptin concentrations in adolescents with and without type 1 diabetes (T1D) and examine the associations between copeptin and measures of arterial stiffness and kidney dysfunction.

RESEARCH DESIGN AND METHODS

This analysis included 169 adolescents with T1D (12-19 years of age, 59% girls, mean HbA1c 9.0 ± 1.5% and diabetes duration of 8.6 ± 2.9 years), in addition to 61 controls without T1D. Arterial stiffness including carotid-femoral pulse wave velocity (CF-PWV), carotid-radial PWV (CR-PWV), augmentation index normalized to heart rate of 75 bpm (AIx@HR75), and brachial artery distensibility (BAD). Serum copeptin, urinary albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR) by serum creatinine and cystatin C were also assessed.

RESULTS

Compared to controls, adolescents with T1D had higher median (Q1-Q3) copeptin (7.5 [5.2-11.3] vs 6.4 [4.8-8.3] pmol/L, P = .01), mean ± SD eGFR (121 ± 23 vs 112 ± 16 mL/min/1.73m² , P = .002) and lower BAD (7.1 ± 1.3 vs 7.2 ± 1.2%, P = .02). Adolescents with T1D in the in high tertile copeptin group (>9.1 pmol/L) had higher AIx@HR75 (10.7 ± 1.2 vs 5 ± 1.2, P = .001), CR-PWV (5.30 ± 1.0 vs 5.18 ± 1.0 m/s, P = .04), and UACR (12 ± 1 vs 8 ± 1 mg/g, P = .025) compared to those in low tertile (<5.8 pmol/L) after adjusting for age, sex, and eGFR. Copeptin inversely associated with CF-PWV independent of age, sex, eGFR, SBP, and HbA1c in T1D adolescents.

CONCLUSIONS

Our data demonstrate that elevated copeptin was associated with worse arterial stiffness in adolescents with T1D. These findings suggest that copeptin could improve CVD risk stratification in adolescents with T1D.

Vasopressin inactivation: Role of insulin-regulated aminopeptidase

The physiological importance of vasopressin inactivation has long been appreciated, but the mechanisms and potential pathophysiologic roles of this process remain active subjects of research. Human Placental Leucine Aminopeptidase (P-LAP, encoded by the LNPEP gene) is an important determinant of vasopressinase activity during pregnancy and is associated with gestational diabetes insipidus and preeclampsia. Insulin-Regulated Aminopeptidase (IRAP), the rodent homologue of P-LAP, is coregulated with the insulin-responsive glucose transporter, GLUT4, in adipose and muscle cells. Recently, the Tether containing a UBX domain for GLUT4 (TUG) protein was shown to mediate the coordinated regulation of water and glucose homeostasis. TUG sequesters IRAP and GLUT4 intracellularly in the absence of insulin. Insulin and other stimuli cause the proteolytic cleavage of TUG to mobilize these proteins to the cell surface, where IRAP acts to terminate the activity of circulating vasopressin. Intriguingly, genetic variation in LNPEP is associated with the vasopressin response and mortality during sepsis, and increased copeptin, a marker of vasopressin secretion, is associated with cardiovascular and metabolic disease. We propose that in the setting of insulin resistance in muscle, increased cell-surface IRAP and accelerated vasopressin degradation cause a compensatory increase in vasopressin secretion. The increased vasopressin concentrations present at the kidneys then contribute to hypertension in the metabolic syndrome. Further analyses of metabolism and of vasopressin and copeptin may yield novel insights into a unified pathophysiologic mechanism linking insulin resistance and hypertension, and potentially other components of the metabolic syndrome, in humans.

Evaluation of Copeptin during Pulmonary Exacerbation in Cystic Fibrosis

Copeptin was found to be a stable biomarker of inflammation and stress response in cardiac, renal, metabolic, and respiratory conditions such as pneumonia. The aim of this study was to investigate the copeptin levels in biological fluids (serum and sputum supernatant) of cystic fibrosis pediatric patients during pulmonary exacerbation and remission and to investigate the possible influence of copeptin levels on disease severity and quality of life. Copeptin serum concentrations were measured in 28 pediatric cystic fibrosis (CF) patients: 13 in stable condition and 15 during pulmonary exacerbation. In 10 CF patients, copeptin was also measured in the sputum. In all the patients, we assessed complete blood count, BMI, sputum culture, lung function, and chest imaging (with Brasfield score). The severity of symptoms was assessed using the Shwachman-Kulczycki (SK) score, and the quality of life was assessed with the Cystic Fibrosis Quality of Life Questionnaire-Revised (CFQ-R). Copeptin concentrations in serum and sputum supernatant was measured using an ELISA kit. Statistical analysis was done in Statistica v.12. Serum and sputum copeptin levels were higher in CF patients during pulmonary exacerbation than in a stable period, but the differences were not significant (p = 0.58 and p = 0.13, respectively). Copeptin did not correlate significantly with any clinical, laboratory, or spirometry markers of exacerbation. There was, however, a significant inverse correlation between the serum copeptin level and symptoms severity (r = ‐0.77, p = 0.008) and radiological changes (r = ‐0.5626, p = 0.036) during pulmonary exacerbation in pediatric CF patients. Copeptin also inversely correlated with the quality of life domains in CF patients: vitality and eating habits, mostly loss of appetite (p = 0.031 and p = 0.016, respectively). Copeptin may be useful to identify patients with a higher risk of deterioration to improve their outcomes.

GLUT4 Storage Vesicles: Specialized Organelles for Regulated Trafficking

Fat and muscle cells contain a specialized, intracellular organelle known as the GLUT4 storage vesicle (GSV). Insulin stimulation mobilizes GSVs, so that these vesicles fuse at the cell surface and insert GLUT4 glucose transporters into the plasma membrane. This example is likely one instance of a broader paradigm for regulated, non-secretory exocytosis, in which intracellular vesicles are translocated in response to diverse extracellular stimuli. GSVs have been studied extensively, yet these vesicles remain enigmatic. Data support the view that in unstimulated cells, GSVs are present as a pool of preformed small vesicles, which are distinct from endosomes and other membrane-bound organelles. In adipocytes, GSVs contain specific cargoes including GLUT4, IRAP, LRP1, and sortilin. They are formed by membrane budding, involving sortilin and probably CHC22 clathrin in humans, but the donor compartment from which these vesicles form remains uncertain. In unstimulated cells, GSVs are trapped by TUG proteins near the endoplasmic reticulum - Golgi intermediate compartment (ERGIC). Insulin signals through two main pathways to mobilize these vesicles. Signaling by the Akt kinase modulates Rab GTPases to target the GSVs to the cell surface. Signaling by the Rho-family GTPase TC10α stimulates Usp25m-mediated TUG cleavage to liberate the vesicles from the Golgi. Cleavage produces a ubiquitin-like protein modifier, TUGUL, that links the GSVs to KIF5B kinesin motors to promote their movement to the cell surface. In obesity, attenuation of these processes results in insulin resistance and contributes to type 2 diabetes and may simultaneously contribute to hypertension and dyslipidemia in the metabolic syndrome.

Association of copeptin, a surrogate marker for arginine vasopressin secretion, with insulin resistance: Influence of adolescence and psychological stress

In middle-aged and elderly individuals, circulating copeptin concentrations, a surrogate marker for arginine vasopressin (AVP) secretion, associates with insulin resistance (IR). Whether this association is present in adolescents and young adults is unclear. Because psychological stress associates with higher circulating copeptin concentrations and IR, it has been speculated that increased AVP secretion could be a link between psychological stress and IR. We measured plasma copeptin concentrations in 351 14-16-year-old adolescents and 617 20-28-year-old young adults from the Danish site of the European Youth Heart Study, a population-based cardiovascular risk factor study in adolescents and young adults. IR was determined by the homeostatic model assessment method. Among the young adults, we used symptoms of depression, evaluated by means of the Major Depression Inventory (MDI) scale, as a measure of psychological stress. We applied linear regressions to examine associations, expressed as unstandardized regression coefficients (B) with 95% confidence intervals (CIs), between variables of interest, stratified by age group and adjusting for age, sex and Tanner stages. Copeptin and IR were log-transformed. Among the young adults, copeptin associated with IR (B (95%CI) = 0.19 (0.11 to 0.27), P < 0.001). This association was not found among the adolescents (B=-0.01 (-0.12 to 0.09), P = 0.78). MDI score associated with IR (B = 0.010 (0.004 to 0.016), P < 0.001) and copeptin (B=0.010 (0.004 to 0.015); P<0.002) in the young adults. Adjusted for copeptin, the strength of the association between MDI score and IR somewhat diminished (to B=0.008). In conclusion, adolescence and psychological stress appear to influence the association between copeptin and IR.

Central noradrenaline transporter availability is linked with HPA axis responsiveness and copeptin in human obesity and non-obese controls

The central noradrenaline (NA) stress-response network co-mediates hypothalamic-pituitary-adrenal (HPA) axis activation and arginine-vasopressin (AVP) release. Dysregulation of these systems contributes to stress-related diseases such as human obesity, but their interrelation remains unclear. The study was aimed to test for the first time in vivo whether central noradrenergic activity quantitatively indexed by the availability of the presynaptic NA transporter (NAT) is associated with HPA axis responsiveness as measured with the combined dexamethasone suppression/corticotropin releasing hormone stimulation (dex/CRH) test and copeptin as a surrogate marker of the serum AVP tone in highly obese, otherwise, healthy individuals compared to age- and sex-matched non-obese, healthy controls. In order to assess central NAT availability, positron emission tomography (PET) was applied using the NAT-selective radiotracer S,S-[¹¹C]O-methylreboxetine (MRB) and correlated with curve indicators derived from the dex/CRH test (maximum, MAX, and area under the curve, AUC, for cortisol and adrenocorticotropic hormone, ACTH) as well as with copeptin. In non-obese controls, positive correlations were found between the NAT distribution volume ratios (DVR) of the orbitofrontal cortex (OFC) and the amygdala with the HPA response (OFC: ACTH_MAX r = 0.87, p = .001; cortisol_MAX r = 0.86, p = .002; amygdala: ACTH_MAX r = 0.86, p = .002; cortisol_MAX r = 0.79, p = .006), while in obesity, the hypothalamic DVR correlated inversely with the HPA axis response (cortisol_MAX, r = -0.66, p = .04) and with copeptin (r = -0.71, p = .02). This association of central NAT availability with HPA axis responsiveness and copeptin suggests a mechanistic interaction between noradrenergic transmission with HPA axis activity and the serum AVP system that differs between non-obese individuals with prefrontal-limbic involvement and obesity with a hypothalamic-centered relationship. Whether the latter finding contributes to obesogenic behavior needs to be further explored.

Copeptin and insulin resistance: effect modification by age and 11 β-HSD2 activity in a population-based study

PURPOSE

Arginine vasopressin (AVP) may be involved in metabolic syndrome (MetS) by altering liver glycogenolysis, insulin and glucagon secretion, and pituitary ACTH release. Moreover, AVP stimulates the expression of 11β-hydroxysteroid-dehydrogenase-type 2 (11β-HSD2) in mineralocorticosteroid cells. We explored whether apparent 11β-HSD2 activity, estimated using urinary cortisol-to-cortisone ratio, modulates the association between plasma copeptin, as AVP surrogate, and insulin resistance/MetS in the general adult population.

METHODS

This was a multicentric, family-based, cross-sectional sample of 1089 subjects, aged 18-90 years, 47% men, 13.4% MetS, in Switzerland. Mixed multivariable linear and logistic regression models were built to investigate the association of insulin resistance (HOMA-IR)/fasting glucose and MetS/Type 2 Diabetes with copeptin, while considering potential confounders or effect modifiers into account. Stratified results by age and 11β-HSD2 activity were presented as appropriate.

RESULTS

Plasma copeptin was higher in men [median 5.2, IQR (3.7-7.8) pmol/L] than in women [median 3.0, IQR (2.2-4.3) pmol/L], P < 0.0001. HOMA-IR was positively associated with copeptin after full adjustment if 11β-HSD2 activity was high [β (95% CI) = 0.32 (0.17-0.46), P < 0.001] or if age was high [β (95% CI) = 0.34 (0.20-0.48), P < 0.001], but not if either 11β-HSD2 activity or age was low. There was a positive association of type 2 diabetes with copeptin [OR (95% CI) = 2.07 (1.10-3.89), P = 0.024), but not for MetS (OR (95% CI) = 1.12 (0.74-1.69), P = 0.605), after full adjustment.

CONCLUSIONS

Our data suggest that age and apparent 11β-HSD2 activity modulate the association of copeptin with insulin resistance at the population level but not MeTS or diabetes. Further research is needed to corroborate these results and to understand the mechanisms underlying these findings.

Fluid consumption pattern and hydration among 8-14 years-old children

BACKGROUND/OBJECTIVES

Children consume various fluids to meet dietary water intake needs. However, the contribution of different fluid types on hydration is unclear. The purpose of this study was to develop fluid intake patterns and examine their association with hydration, as indicated by 24-h urine osmolality.

SUBJECTS/METHODS

Two hundred ten (105 girls) healthy children (height: 1.49 ± 0.13 m, weight: 43.4 ± 12.6 kg, body fat: 25.2 ± 7.8%) recorded their fluid intake for two consecutive days, and collected their urine for 24-h during the 2nd day, while conducting their normal daily activities. Urine samples were analyzed for specific gravity and osmolality. Factor analysis with principal components method was applied to extract dietary patterns from six fluid groups. Linear regression analysis evaluated the associations between the extracted dietary patterns and hydration based on 24-h urine osmolality.

RESULTS

The analysis revealed the following six components: 1, characterized by consumption of milk and fresh juice, but not packaged juice; 2, by regular soda and other drinks, but not water; 3, by fresh juice and other drinks; 4, by packaged juice, but not regular soda; 5, by water and milk; and 6, by fresh juice. Component 5 was negatively correlated with urine osmolality (P = 0.001) indicating better hydration, whereas component 2 was positively correlated with urine osmolality (P = 0.001).

CONCLUSIONS

A drinking pattern based on water and milk was associated with better hydration, as indicated by lower urine osmolality, whereas drinking regular soda and other drinks but not water was associated with inferior hydration.

Post-dexamethasone serum copeptin corresponds to HPA axis responsiveness in human obesity

CONTEXT

Increased activities of the arginine-vasopressin (AVP) system and the hypothalamic-pituitary-adrenal (HPA) axis were shown to be associated with human obesity, but relationships between these systems in obesity remain unclear.

OBJECTIVES

To assess HPA axis responsiveness and its relation to serum concentrations of the AVP-surrogate copeptin in subjects with obesity (OB) in comparison to non-obesity controls (NOC).

METHODS

In a cross-sectional monocentric study, thirty-nine OB (f/m 25/14; age 36.5±10.0years; body mass index, BMI, 41.5±4.7kg/m²) were compared to twenty-two NOC (f/m 12/10; age 35.3±8.5years; BMI 23.1±2.4kg/m²), matched for age and sex. All individuals underwent the combined dexamethasone/CRH test.

MAIN OUTCOME MEASURES

Plasma ACTH and cortisol curve indicators derived from the dex/CRH test (post-CRH concentrations 30min after 100μg CRH; maximum concentration, MAX; area-under-the-curve, AUC; ACTH/cortisol ratios). Copeptin was assessed in 1500h samples of the dex/CRH test (after 1.5mg of oral dexamethasone, prior to CRH administration).

RESULTS

Copeptin serum concentrations were higher in OB (median [IQR]: OB 4.62 [2.60-5.88] vs. NOC 3.04 [2.52-4.29] pmol/l, P=0.04). Correspondingly, OB showed higher post-CRH cortisol concentrations (OB: 51.5 [25.9-159.3] vs. NOC: 28.6 [20.0-41.6] nmol/l, P=0.01) and a lower post-CRH ACTH/cortisol ratio (OB: 0.028 [0.016-0.053] vs. NOC: 0.048 [0.034-0.070] pmol/nmol, P<0.01). Serum copeptin was significantly associated with HPA responsiveness in OB (post-CRH ACTH: R=0.42, P<0.01), driven by OB men (post-CRH ACTH: R=0.76, P<0.01, post-CRH cortisol: R=0.64, P=0.02). All associations withstand adjustments for BMI and age.

CONCLUSIONS

The association between increased copeptin with ACTH and cortisol release suggests a potential mechanistic interaction of the AVP system with HPA activation in human obesity. The relation of copeptin and HPA responsiveness should be further validated in situations with pronounced HPA activation, such as depression or multiple sclerosis.