Pathophysiology of copeptin in kidney disease and hypertension

Water/fluid intake in Kıdney transplant recipients: An underrated topic

Although kidney transplantation (KT) is the best treatment option for end-stage kidney disease, long-term complications such as chronic kidney allograft dysfunction and cardiovascular disorders are observed. To decrease these complications, preventive measures must be applied in kidney transplant recipients (KTRs). One of these common measures is the increase of water/fluid intake although this is not evidence-based practice. Indeed, surprisingly very limited studies evaluated the impact of increased water/fluid intake on graft function, with small number of KTRs and short term follow-up. We suggest that the water/fluid intake should be personalized based on baseline graft function, time onset after KT (which water homeostasis changes), presence of hyponatremia and hypervolemia, concomitant medications, and patient willingness. Methods for estimating water/fluid intake (direct measurement, 24-h urine volume measurement, urine osmolarity) has both advantages and drawbacks and the best method has not been identified. Increase of water/fluid intake in specific conditions (in hot, and humid weather, before exercise, during Ramadan fasting) or in distinct KTRs (KTRs with de novo nephrolithiasis, frequent urinary tract infections) is not tested. Furthermore, the relationship between water/fluid intake and major cardiovascular adverse events are not known. There is no doubt that minimum amount of water/fluid intake is necessary for graft function (the amount is not known) but there is no evidence for a particular target level of water/fluid intake. In the current review, we summarize the studies assessing fluid/water intake in KTR, explained the pathophysiologic basis of water disorders in early period of KT and late after KT, elucidate conflicts and unknown issues of water intake in KTRs and suggest future research needs.

Urinary hyaluronidase activity is closely related to vasopressinergic system following an oral water load in men: a potential role in blood pressure regulation and early stages of hypertension development

Introduction

Blood pressure (BP) regulation is a complex process involving several factors, among which water-sodium balance holds a prominent place. Arginin-vasopressin (AVP), a key player in water metabolism, has been evoked in hypertension development since the 1980s, but, to date, the matter is still controversial. Hyaluronic acid metabolism has been reported to be involved in renal water management, and AVP appears to increase hyaluronidase activity resulting in decreased high-molecular-weight hyaluronan content in the renal interstitium, facilitating water reabsorption in collecting ducts. Hence, our aim was to evaluate urinary hyaluronidase activity in response to an oral water load in hypertensive patients (HT, n=21) compared to normotensive subjects with (NT+, n=36) and without (NT-, n=29) a family history of hypertension, and to study its association with BP and AVP system activation, expressed by serum copeptin levels and urine Aquaporin 2 (AQP2)/creatinine ratio.

Methods

Eighty-six Caucasian men were studied. Water load test consisted in oral administration of 15-20 ml of water/kg body weight over 40-45 min. BP, heart rate, serum copeptin, urine hyaluronidase activity and AQP2 were monitored for 4 hours.

Results

In response to water drinking, BP raised in all groups with a peak at 20-40 min. Baseline levels of serum copeptin, urinary hyaluronidase activity and AQP2/creatinine ratio were similar among groups and all decreased after water load, reaching their nadir at 120 min and then gradually recovering to baseline values. Significantly, a blunted reduction in serum copeptin, urinary hyaluronidase activity and AQP2/creatinine ratio was observed in NT+ compared to NT- subjects. A strong positive correlation was also found between urinary hyaluronidase activity and AQP2/creatinine ratio, and, although limited to the NT- group, both parameters were positively associated with systolic BP.

Discussion

Our results demonstrate for the first time the existence in men of a close association between urinary hyaluronidase activity and vasopressinergic system and suggest that NT+ subjects have a reduced ability to respond to water loading possibly contributing to the blood volume expansion involved in early-stage hypertension. Considering these data, AVP could play a central role in BP regulation by affecting water metabolism through both hyaluronidase activity and AQP2 channel expression.

Fibroblast growth factor 23 but not copeptin is independently associated with kidney failure and mortality in patients with chronic kidney disease

Background

Copeptin and intact fibroblast growth factor 23 (iFGF23) increase early during chronic kidney disease (CKD) and may be predictive of unfavourable outcomes. The aim of this study was to evaluate their respective associations with renal and vital outcomes in CKD patients.

Methods

We included CKD patients from the NephroTest cohort with concomitant measurements of plasma copeptin and iFGF23 concentrations and isotopic glomerular filtration rate measurement (mGFR). The primary endpoint was a composite outcome including kidney failure (KF) (dialysis initiation, pre-emptive transplantation or a 57% decrease of mGFR, corresponding to doubling of serum creatinine) or death before KF. Hazard ratios (HRs) of the primary endpoint associated with log-transformed copeptin and iFGF23 concentrations were estimated by Cox models. The slope of mGFR over time was analysed using a linear mixed model.

Results

A total of 329 CKD patients (243 men, mean age 60.3 ± 14.6 years) were included. Among them, 301 with an mGFR >15 ml/min/1.73 m2 were included in survival and mGFR slope analyses. During a median follow-up of 4.61 years (quartile 1-quartile 3: 3.72-6.07), 61 KFs and 32 deaths occurred. Baseline iFGF23 concentrations were associated with the composite outcome after multiple adjustments {HR 2.72 [95% confidence interval (CI) 1.85-3.99]}, whereas copeptin concentrations were not [HR 1.01 (95% CI 0.74-1.39)]. Neither copeptin nor iFGF23 were associated with mGFR slope over time.

Conclusion

Our study shows for the first time in population of CKD patients an independent association between iFGF23 and unfavourable renal and vital outcomes and shows no such association regarding copeptin, encouraging the integration of iFGF23 measurement into the follow-up of CKD.

Kidney collecting duct cells make vasopressin in response to NaCl-induced hypertonicity

Vasopressin has traditionally been thought to be produced by the neurohypophyseal system and then released into the circulation where it regulates water homeostasis. The questions of whether vasopressin could be produced outside of the brain and if the kidney could be a source of vasopressin are raised by the syndrome of inappropriate antidiuretic hormone secretion (vasopressin). We found that mouse and human kidneys expressed vasopressin mRNA. Using an antibody that detects preprovasopressin, we found that immunoreactive preprovasopressin protein was found in mouse and human kidneys. Moreover, we found that murine collecting duct cells made biologically active vasopressin, which increased in response to NaCl-mediated hypertonicity, and that water restriction increased the abundance of kidney-derived vasopressin mRNA and protein expression in mouse kidneys. Thus, we provide evidence of biologically active production of kidney-derived vasopressin in kidney tubular epithelial cells.

Cardiovascular Biomarkers: Lessons of the Past and Prospects for the Future

Cardiovascular diseases (CVDs) are a major healthcare burden on the population worldwide. Early detection of this disease is important in prevention and treatment to minimise morbidity and mortality. Biomarkers are a critical tool to either diagnose, screen, or provide prognostic information for pathological conditions. This review discusses the historical cardiac biomarkers used to detect these conditions, discussing their application and their limitations. Identification of new biomarkers have since replaced these and are now in use in routine clinical practice, but still do not detect all disease. Future cardiac biomarkers are showing promise in early studies, but further studies are required to show their value in improving detection of CVD above the current biomarkers. Additionally, the analytical platforms that would allow them to be adopted in healthcare are yet to be established. There is also the need to identify whether these biomarkers can be used for diagnostic, prognostic, or screening purposes, which will impact their implementation in routine clinical practice.

The Effects of Zinc Sulfate Supplementation on Serum Copeptin, C-Reactive Protein and Metabolic Markers in Zinc-Deficient Diabetic Patients on Hemodialysis: A Randomized, Double-Blind, Placebo-Controlled Trial

We aimed to investigate the association between zinc (Zn) supplementation and serum levels of copeptin, high-sensitive C-reactive protein (hs-CRP), glycemic control, anthropometric parameters and renal function in Zn -deficient diabetic hemodialysis patients (DHPs). This randomized, double-blind, placebo-controlled trial (RCT) was conducted on 46 DHPs with Zn-deficiency. The Zn supplement group (n = 21) received a 220-mg/day Zn sulfate capsule (containing 50 mg Zn), and the control group (n = 25) received a placebo capsule (220 mg corn starch), for 8 weeks. Fasting, predialysis blood samples were taken at baseline and after 8 weeks to assess fasting blood glucose (FBG), serum insulin, copeptin, high-sensitive C-reactive protein (hs-CRP), blood urea nitrogen (BUN), creatinine (Cr) concentrations, and homoeostatic model assessment (HOMA-IR) and quantitative insulin-sensitivity check index (QUICKI). Compared to controls, serum copeptin (P < 0.001), hs-CRP (P < 0.001), BUN (P < 0.001), Cr (P < 0.001), Zn (P < 0.001), FBG (P < 0.001) levels, BMI (P < 0.001), and body weight (P < 0.001) were significantly affected following ZnSO4 supplementation for 8 weeks. In contrast, QUICKI (P = 0.57), HOMA-IR (P = 0.60), and serum insulin (P = 0.55) were not affected following Zn supplementation in comparison with patients receiving placebo. Zn sulfate supplementation appears to have favorable effects on serum copeptin and hs-CRP, FBG, and renal function in Zn-deficient DHPs. Iranian Registry of Clinical Trials Identifier: IRCT20190806044461N1.

Improvement of outcome prediction of hospitalized patients with COVID-19 by a dual marker strategy using high-sensitive cardiac troponin I and copeptin

Background

COVID-19 has been associated with a high prevalence of myocardial injury and increased cardiovascular morbidity. Copeptin, a marker of vasopressin release, has been previously established as a risk marker in both infectious and cardiovascular disease.

Methods

This prospective, observational study of patients with laboratory-confirmed COVID-19 infection was conducted from June 6th to November 26th, 2020 in a tertiary care hospital. Copeptin and high-sensitive cardiac troponin I (hs-cTnI) levels on admission were collected and tested for their association with the primary composite endpoint of ICU admission or 28-day mortality.

Results

A total of 213 eligible patients with COVID-19 were included of whom 55 (25.8%) reached the primary endpoint. Median levels of copeptin and hs-cTnI at admission were significantly higher in patients with an adverse outcome (Copeptin 29.6 pmol/L, [IQR, 16.2–77.8] vs 17.2 pmol/L [IQR, 7.4–41.0] and hs-cTnI 22.8 ng/L [IQR, 11.5–97.5] vs 10.2 ng/L [5.5–23.1], P < 0.001 respectively). ROC analysis demonstrated an optimal cut-off of 19.3 pmol/L for copeptin and 16.8 ng/L for hs-cTnI and an increase of either biomarker was significantly associated with the primary endpoint. The combination of raised hs-cTnI and copeptin yielded a superior prognostic value to individual measurement of biomarkers and was a strong prognostic marker upon multivariable logistic regression analysis (OR 4.274 [95% CI, 1.995–9.154], P < 0.001). Addition of copeptin and hs-cTnI to established risk models improved C-statistics and net reclassification indices.

Conclusion

The combination of raised copeptin and hs-cTnI upon admission is an independent predictor of ICU admission or 28-day mortality in hospitalized patients with COVID-19.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01970-4.

Coexisting posterior reversible encephalopathy syndrome and ischemic hepatopathy: A case report

Posterior reversible encephalopathy syndrome (PRES) is acute neurologic symptoms with specific radiologic findings. This unique case shows coexisting PRES with acute liver injury, which could suggest common pathophysiologic process.

Higher Copeptin Levels are Associated with the Risk of Atrial Fibrillation in Patients with Rheumatic Mitral Stenosis

BACKGROUND

Correlations between increased copeptin levels and various cardiovascular diseases have been described. In this study, we aimed to investigate the correlation between increased copeptin levels and paroxysmal atrial fibrillation (PAF) in rheumatic mitral stenosis (MS).

METHODS

Patients with mild/moderate rheumatic MS and sinus rhythm were consecutively recruited from an echocardiography laboratory. Patients with a history of PAF and those with PAF on 24-48-hour ambulatory electrocardiography (ECG) monitoring constituted the study group, and those without PAF on ambulatory ECG monitoring constituted the control group. Clinical characteristics, echocardiographic parameters and levels of copeptin, plasma N-terminal proBNP (NT-proBNP) and high-sensitivity C-reactive protein (hs-CRP) were evaluated.

RESULTS

Twenty-nine patients with PAF and 124 control MS patients were studied. Patients in the PAF group were older, but the mitral valve areas and transmitral gradients were not different between the groups. In the PAF group, hs-CRP (1.2 vs. 0.8 mg/L, p < 0.001), NT-proBNP (335 vs. 115 pg/mL, p < 0.001) and copeptin (6.9 vs. 4.0 pmol/L, p < 0.001) levels were significantly higher than in the control group. Multivariable logistic regression analysis revealed that age [odds ratio (OR) 1.19, 95% confidence interval (CI) 1.04-1.38; p = 0.024], left atrial volume index (OR 1.23, 95% CI 1.06-1.41; p = 0.032), copeptin levels (OR 2.81, 95% CI 1.30-5.29; p < 0.001) and hs-CRP levels (OR 15.5, 95% CI 1.41-71.5; p = 0.012) were independent predictors of PAF.

CONCLUSIONS

In patients with mild/moderate rheumatic MS, higher copeptin and hs-CRP levels predicted a higher risk of developing atrial fibrillation.

The Emerging Role of Copeptin

Direct measurement of the nonapeptide vasopressin has been limited by analyte instability ex vivo and in vivo rapid degradation, low serum concentrations requiring a sensitive assay and inherent secretory pulsatility. Copeptin is a 39 amino acid glycopeptide cleavage product of vasopressin synthesis with high stability, providing a marker of vasopressin secretion. Copeptin measurement has applications in diagnosis of diabetes insipidus and other diseases with altered vasopressin secretion. This review summarises our current understanding of serum copeptin measurement in diabetes insipidus and possible future applications of copeptin assays. As vasopressin is a stress hormone, there is emerging evidence on the use of copeptin for diagnosis and prognostication of disorders such as syndrome of inappropriate anti-diuretic hormone secretion, diabetes mellitus, critical illness, stroke, cardiovascular disease, respiratory disease, renal disease and thermal stress. Copeptin concentration measurement is likely to improve the diagnostic reliability of diabetes insipidus and, as a marker of stress, may have diagnostic or prognostic utility in specific clinical circumstances. Further studies are needed to determine if goal-directed therapy using plasma copeptin concentrations may improve patient outcomes.

Pathophysiology and Individualized Management of Vasovagal Syncope and Postural Tachycardia Syndrome in Children and Adolescents: An Update

Vasovagal syncope (VVS) and postural tachycardia syndrome (POTS) are the main forms of orthostatic intolerance in pediatrics and both are underlying causes of neurally-mediated syncope. In recent years, increasing attention has been paid to the management of VVS and POTS in children and adolescents. A number of potential mechanisms are involved in their pathophysiology, but the leading cause of symptoms varies among patients. A few studies thus have focused on the individualized treatment of VVS or POTS based on selected hemodynamic parameters or biomarkers that can predict the therapeutic effect of certain therapies and improve their effectiveness. This review summarizes the latest developments in individualized treatment of VVS and POTS in children and indicates directions for further research in this field.

Association between serum copeptin levels and preeclampsia risk: A meta-analysis

The role of vasopressin in preeclampsia pathogenesis has been recently supported by experimental studies. This meta-analysis aims to accumulate literature evidence and evaluate whether serum copeptin levels differ among preeclamptic and healthy pregnant women. Medline, Scopus, CENTRAL, Web of Science and Google Scholar databases were systematically searched from inception. All observational studies reporting serum copeptin values among preeclamptic and healthy pregnant women were deemed eligible. Sixteen studies were included, comprising 2105 women. Preeclampsia was linked to significantly higher copeptin levels during the 1st (Standardized Mean Difference-SMD: 2.25, 95% Confidence Intervals-CI: 0.86-3.67), 2nd (SMD: 1.73, 95% CI: 0.31-3.14) and 3rd (SMD: 1.74, 95% CI: 0.96-2.53) trimester. This association was present for severe, non-severe, early and late-onset preeclampsia. Women with the severe form of the disease displayed significantly elevated copeptin levels (SMD: 1.47, 95% CI: 1.10-1.84) compared to those with the non-severe one, while no difference was evident between early and late-onset preeclampsia (SMD: -0.30, 95% CI: -0.91 to 0.31). In conclusion, the present meta-analysis suggests that preeclampsia is associated with significantly increased serum copeptin levels in all pregnancy trimesters, irrespective of disease severity and onset. Future large-scale cohort studies should confirm these findings and introduce cut-off values in order to clarify the exact accuracy of copeptin for the prediction of preeclampsia early in the course of pregnancy.

Copeptin Levels in Patients With Treatment-Resistant Hypertension Before and 6 Months After Renal Denervation

BACKGROUND

Copeptin, the C-terminal peptide of provasopressin, is released from the neurohypophysis and reflects the activity of the hormone arginine vasopressin in patients with hypertension. Elevated copeptin levels are associated with increased cardiovascular and all-cause mortality. The aim of this study is to compare copeptin levels in patients with treatment-resistant hypertension (TRH) before and 6 months after renal denervation (RDN).

METHODS

Copeptin was measured in 34 patients with TRH and 30 patients with primary hypertension stage 1 or 2 (HT). In addition, copeptin levels were measured in patients with TRH at 6-month follow-up visit after RDN. RDN was performed by an experienced interventionalist applying at least 4 ablations longitudinally and rotationally within the lengths of each renal artery to cover a full 4-quadrant ablation.

RESULTS

In patients with TRH 24-hour ambulatory blood pressure (BP) decreased from 154 ± 15/87 ± 12 mm Hg to 146 ± 13/83 ± 7.9 mm Hg after RDN (systolic: P = 0.001, diastolic: P = 0.034). There was no significant change in copeptin levels in these 34 patients with TRH before vs. 6 months after RDN (median 8.4 [interquartile range 3.6-14] vs. 8.5 [4.5-13] pmol/l, P = 0.334). Patients with TRH had higher copeptin levels (P = 0.024) than patients with HT (24-hour ambulatory BP: 142 ± 11/91 ± 8.3 mm Hg, copeptin: 4.2 [2.8-6.3] pmol/l).

CONCLUSION

Patients with TRH showed 2-fold higher copeptin levels than patients with HT. RDN did not lead to any change of copeptin levels in patients with TRH 6 months after procedure despite significant fall in BP.

CLINICAL TRIAL REGISTRATION

NCT01318395, NCT01687725.

Copeptin is independently associated with vascular calcification in chronic kidney disease stage 5

BACKGROUND

Vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD) present in 30-70% of patients with chronic kidney disease (CKD). Copeptin is a sensitive surrogate marker of arginine vasopressin (AVP), which is involved in many pathophysiologic processes in CKD. The aim of the present study was to explore the association of copeptin with VC in CKD stage 5.

METHODS

Copeptin was investigated in conjunction with living donor kidney transplantation in 149 clinically stable CKD stage 5 patients (CKD5), including 53 non-dialyzed (CKD5-ND) and 96 dialysis patients treated by peritoneal dialysis (PD) (n = 43) or hemodialysis (HD) (n = 53). We analyzed the association of copeptin with presence and extent of VC ascertained both histologically in biopsies from the inferior epigastric artery (n = 137) and by coronary artery calcification (CAC) score measured by computed tomography.

RESULTS

Patients with higher copeptin were older, had higher systolic blood pressure, higher prevalence of CVD and their preceding time on chronic dialysis was longer. In Spearman's rank correlations (Rho), copeptin concentrations were significantly associated with CAC score (Rho = 0.27; p = 0.003) and presence of medial VC (Rho = 0.21; p = 0.016). Multivariate logistic regression analysis showed that 1-SD higher age, male gender, diabetes and 1-SD higher copeptin were significantly associated with the presence of moderate-extensive VC.

CONCLUSIONS

High circulating levels of copeptin in CKD5 patients are independently associated with the degree of medial calcification ascertained by histology of arterial biopsies. Thus, plasma copeptin may serve as a marker of the uremic calcification process.

Antidiuretic Hormone and Serum Osmolarity Physiology and Related Outcomes: What Is Old, What Is New, and What Is Unknown?

CONTEXT

Although the physiology of sodium, water, and arginine vasopressin (AVP), also known as antidiuretic hormone, has long been known, accumulating data suggest that this system operates as a more complex network than previously thought.

EVIDENCE ACQUISITION

English-language basic science and clinical studies of AVP and osmolarity on the development of kidney and cardiovascular disease and overall outcomes.

EVIDENCE SYNTHESIS

Apart from osmoreceptors and hypovolemia, AVP secretion is modified by novel factors such as tongue acid-sensing taste receptor cells and brain median preoptic nucleus neurons. Moreover, pharyngeal, esophageal, and/or gastric sensors and gut microbiota modulate AVP secretion. Evidence is accumulating that increased osmolarity, AVP, copeptin, and dehydration are all associated with worse outcomes in chronic disease states such as chronic kidney disease (CKD), diabetes, and heart failure. On the basis of these pathophysiological relationships, an AVP receptor 2 blocker is now licensed for CKD related to polycystic kidney disease.

CONCLUSION

From a therapeutic perspective, fluid intake may be associated with increased AVP secretion if it is driven by loss of urine concentration capacity or with suppressed AVP if it is driven by voluntary fluid intake. In the current review, we summarize the literature on the relationship between elevated osmolarity, AVP, copeptin, and dehydration with renal and cardiovascular outcomes and underlying classical and novel pathophysiologic pathways. We also review recent unexpected and contrasting findings regarding AVP physiology in an attempt to explain and understand some of these relationships.

The Role of Volume Regulation and Thermoregulation in AKI during Marathon Running

BACKGROUND AND OBJECTIVES

Marathon runners develop transient AKI with urine sediments and injury biomarkers suggesting nephron damage.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To investigate the etiology, we examined volume and thermoregulatory responses as possible mechanisms in runners' AKI using a prospective cohort of runners in the 2017 Hartford Marathon. Vitals, blood, and urine samples were collected in 23 runners 1 day premarathon and immediately and 1 day postmarathon. We measured copeptin at each time point. Continuous core body temperature, sweat sodium, and volume were assessed during the race. The primary outcome of interest was AKI, defined by AKIN criteria.

RESULTS

Runners ranged from 22 to 63 years old; 43% were men. Runners lost a median (range) of 2.34 (0.50-7.21) g of sodium and 2.47 (0.36-6.81) L of volume via sweat. After accounting for intake, they had a net negative sodium and volume balance at the end of the race. The majority of runners had increases in core body temperature to 38.4 (35.8-41)°C during the race from their baseline. Fifty-five percent of runners developed AKI, yet 74% had positive urine microscopy for acute tubular injury. Runners with more running experience and increased participation in prior marathons developed a rise in creatinine as compared with those with lesser experience. Sweat sodium losses were higher in runners with AKI versus non-AKI (median, 3.41 [interquartile range (IQR), 1.7-4.8] versus median, 1.4 [IQR, 0.97-2.8] g; P=0.06, respectively). Sweat volume losses were higher in runners with AKI versus non-AKI (median, 3.89 [IQR, 1.49-5.09] versus median, 1.66 [IQR, 0.72-2.84] L; P=0.03, respectively). Copeptin was significantly higher in runners with AKI versus those without (median, 79.9 [IQR, 25.2-104.4] versus median, 11.3 [IQR, 6.6-43.7]; P=0.02, respectively). Estimated temperature was not significantly different.

CONCLUSIONS

All runners experienced a substantial rise in copeptin and body temperature along with salt and water loss due to sweating. Sodium and volume loss via sweat as well as plasma copeptin concentrations were associated with AKI in runners.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_08_13_CJASNPodcast_19_09_.mp3.

Osmoregulation Performance and Kidney Transplant Outcome

BACKGROUND

Kidney transplant recipients have an impaired ability to dilute urine but seldom develop baseline hyponatremia before ESRD. Although hyponatremia is a risk factor for adverse events in CKD and in kidney transplant recipients, it remains unclear whether subtler alterations in osmoregulation performance are associated with outcome.

METHODS

We studied a single-center prospective cohort of 1258 kidney transplant recipients who underwent a water-loading test 3 months after transplant to determine osmoregulation performance. Measured GFR (mGFR) was performed at the same visit. A group of 164 healthy candidates for kidney donation served as controls. We further evaluated the association of osmoregulation performance with transplantation outcomes and subsequent kidney function.

RESULTS

Unlike controls, most kidney transplant recipients failed to maintain plasma sodium during water loading (plasma sodium slope of -0.6±0.4 mmol/L per hour in transplant recipients versus -0.12±0.3 mmol/L per hour in controls; P<0.001). Steeper plasma sodium reduction during the test independently associated with the composite outcome of all-cause mortality and allograft loss (hazard ratio [HR], 1.73 per 1 mmol/L per hour decrease in plasma sodium; 95% confidence interval [95% CI], 1.23 to 2.45; P=0.002) and allograft loss alone (HR, 2.04 per 1 mmol/L per hour decrease in plasma sodium; 95% CI, 1.19 to 3.51; P=0.01). The association remained significant in a prespecified sensitivity analysis excluding patients with hyperglycemia. In addition, a steeper plasma sodium slope 3 months after transplantation independently correlated with lower mGFR at 12 months (β=1.93; 95% CI, 0.46 to 3.41; P=0.01).

CONCLUSIONS

Reduced osmoregulation performance occurs frequently in kidney transplant recipients and is an independent predictor of renal outcome.

Dialysate copeptin and peritoneal transport in incident peritoneal dialysis patients

Purpose

Systemic and intraperitoneal inflammation are characteristic features of patients with end-stage renal disease undergoing chronic peritoneal dialysis (PD). Arginine vasopressin (AVP) and its surrogate marker copeptin play important roles in many pathophysiological processes in chronic kidney disease. The aim of this study was to assess if copeptin concentrations in plasma and dialysate were related to peritoneal transport parameters and residual renal function (RRF) in incident PD patients.

Methods

In 37 clinically stable incident PD patients (mean age 50 years, 68% women, 32% diabetes), a 4 h peritoneal equilibration test (PET) was performed 4–6 weeks after the onset of PD. Plasma (at 2 h of PET) and dialysate (at 4 h) concentrations of copeptin, high-sensitivity C-reactive protein and interleukin-6 (IL-6) were determined.

Results

Plasma (80.7 ± 37.3 pg/mL) and dialysate (33.2 ± 18.0 pg/mL) concentrations of copeptin were correlated (Rs = 0.52, p = 0.001). Plasma and dialysate copeptin concentrations were negatively correlated with renal function as assessed by renal Kt/V (Rs = − 0.38; p = 0.021 and Rs = − 0.33; p = 0.047, respectively). At PET, dialysate copeptin negatively correlated with D/P creatinine (Rs = − 0.35, p = 0.033), and positively with D/D0 glucose (Rs = 0.33, p = 0.045) and ultrafiltration (Rs = 0.37, p = 0.024). Multivariate analysis showed that low dialysate copeptin (β = –0.30, p = 0.049) and high dialysate IL-6 (β = + 0.40, p = 0.012) were independent determinants of higher D/P creatinine.

Conclusions

Dialysate copeptin was negatively associated with D/P creatinine in incident PD patients suggesting a potential influence of copeptin or AVP on peritoneal solute transport rate that might involve vasoactive mechanisms.

A sensitive and rapid chemiluminescence immunoassay for point-of-care testing (POCT) of copeptin in serum based on high-affinity monoclonal antibodies via cytokine-assisted immunization

Purpose: Antibodies are key reagents in the development of immunoassay. We attempted to develop high-performance CPP immunoassays using high-affinity monoclonal antibodies prepared via cytokine-assisted immunization.

Methods: We used fetal liver tyrosine kinase 3 ligand (Flt3L), CC subtype chemokine ligand 20 (CCL20), and granulocyte-macrophage colony-stimulating factor (GM-CSF) to assist traditional subcutaneous immunization of preparing high-affinity monoclonal antibodies, and further to develop high-performance immunoassay methods for CPP.

Results: This novel immune strategy significantly enhanced immune response against CPP. Six anti-CPP monoclonal antibodies (mAbs) with high affinity were successfully screened and selected for application in a fully automated magnetic chemiluminescence immunoassay (CLIA). This robust and rapid assay can efficiently detect CPP in the range of 1.2–1250 pmol L^–1 with a detection limit of 6.25 pmol L^–1. Significantly, the whole incubation process can be completed in 30 min as compared to about 4.5 hr for the control ELISA kit. Furthermore, this assay exhibited high sensitivity and specificity, low intra-assay and inter-assay coefficients of variation (CVs < 15%). The developed assay was applied in the detection of CPP in 115 random serum samples and results showed a high correlation with data obtained using a commercially available ELISA kit (correlation coefficient, 0.9737).

Conclusion: Our assay could be applied in the point-of-care testing of CPP in the serum samples, and also the method developed in this study could be adopted to explore the detection and diagnosis of other biomarkers for various diseases.

Arginine Vasopressin and Posterior Reversible Encephalopathy Syndrome Pathophysiology: the Missing Link?

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological entity characterized by a typical brain edema. Its pathogenesis is still debated through hypoperfusion and hyperperfusion theories, which have many limitations. As PRES occurs almost exclusively in clinical situations with arginine vasopressin (AVP) hypersecretion, such as eclampsia and sepsis, we hypothesize that AVP plays a central pathophysiologic role. In this review, we discuss the genesis of PRES and its symptoms through this novel approach. We theorize that AVP axis stimulation precipitates PRES development through an increase in AVP secretion or AVP receptor density. Activation of vasopressin V_1a receptors leads to cerebral vasoconstriction, causing endothelial dysfunction and cerebral ischemia. This promotes cytotoxic edema through hydromineral transglial flux dysfunction and may increase endothelial permeability, leading to subsequent vasogenic brain edema. If our hypothesis is confirmed, it opens new perspectives for better patient monitoring and therapies targeting the AVP axis in PRES.

Prognostic utility of novel biomarkers in acute-on-chronic liver failure (ACLF) associated with hepatitis B: A multicenter prospective study

AIM

Flare-ups of chronic hepatitis B can sometimes be severe and even progress to acute-on-chronic liver failure (ACLF), with high short-term mortality. A timely estimation of the risk of death should be initiated early. The aim of the present study was to determine whether novel biomarkers add prognostic information beyond current clinical scoring systems.

METHODS

Patients with hepatitis B-associated ACLF were prospectively enrolled from five hospitals in China between August 2017 and March 2018. Their plasma was screened for soluble CD163 (sCD163), neutrophil gelatinase-associated lipocalin (NGAL), and copeptin. The association between these biomarkers and mortality was analyzed. The performance of the Model for End-stage Liver Disease, Asian-Pacific Association for the Study of the Liver-ACLF Research Consortium score, and the Chronic Liver Failure Consortium ACLF score, with or without biomarkers, were compared.

RESULTS

One hundred fifty one patients were enrolled. Advanced ACLF patients had significantly higher levels than early ACLF individuals of plasma biomarkers sCD163 (P = 0.001), NGAL (P = 0.006), and copeptin (P = 0.049). Thirty-four deaths occurred during the 28-day follow-up period (22.5%). Both sCD163 and NGAL showed a strong independent association with 28-day mortality, whereas copeptin did not. Scoring systems incorporating sCD163 and NGAL had better discrimination and calibration, as measured by area under the receiver operating characteristic curves, the Akaike information criteria, integrated discrimination improvement, and net reclassification improvement.

CONCLUSIONS

Soluble CD163 and NGAL are independently associated with short-term mortality in hepatitis B-associated ACLF. Use of a combination of sCD163 and NGAL improves prognostication.

Salt, water and nephron: Mechanisms of action and link to hypertension and chronic kidney disease

Our knowledge on sodium and water homeostasis and regulation continues to evolve. A considerable amount of new information in this area has emerged in recent years. This review summarizes existing and new literature and discusses complex multi-organ effects of high-salt and low-water intake and role of arginine vasopressin in this process, as well as the potential clinical significance of non-osmotic sodium storage pool and rhythmicity of urine sodium excretion. It has become clear that sodium and water dysregulation can exert profound effects on kidney and vascular health, far greater than previously recognized. Maladaptation to a combined high-salt and low-water intake can be linked to the growing epidemic of hypertension and chronic kidney disease.

Copeptin Blood Content as a Diagnostic Marker of Chronic Kidney Disease

Plasma content of copeptin increases with the advancement of chronic kidney disease (CKD). The purpose of this study was to evaluate copeptin content as a potential marker of CKD, as a single pathology or with coexisting heart failure. Seventy-six patients were divided into the following groups: Group 1 (control), without CKD and heart failure; Group 2, CKD stage 3a; Group 3, CKD stage 3b; Group 4, CKD stage 4; Group 5, CKD stage 5; and Group 6, CKD stage 3b and heart failure. For all patients, plasma concentrations of copeptin, creatinine, urea, cystatin C, sodium, C-reactive protein (CRP), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and blood pH were assessed. We found that plasma content of creatinine, urea, CRP, cystatin, NT-proBNP, and copeptin increased with CKD progression. Heart failure in CKD patients was not the cause of an appreciable increase of copeptin level. Copeptin/creatinine, copeptin/cystatin C ratios, and especially copeptin/eGFR ratio enhanced copeptin prognostic sensitivity concerning renal failure in CKD, compared with copeptin alone. The copeptin×NT-proBNP ratio decreased along CKD progression, reaching a nadir in the accompanying heart failure. In contradistinction, copeptin×NT-proBNP/creatinine ratio increased along CKD progression, reaching a peak in the accompanying heart failure. We conclude that copeptin is an important marker in CKD, but not so concerning heart failure in the disease. A decrease in copeptin×NT-proBNP and an increase in copeptin×NT-proBNP/creatinine ratio are useful markers of cardiac function decline in CKD.