Copeptin: a biomarker of cardiovascular and renal function

Arginine vasopressin (AVP or antidiuretic hormone) is one of the key hormones in the human body responsible for a variety of cardiovascular and renal functions. It has so far escaped introduction into the routine clinical laboratory due to technical difficulties and preanalytical errors. Copeptin, the C-terminal part of the AVP precursor peptide, was found to be a stable and sensitive surrogate marker for AVP release. Copeptin behaves in a similar manner to mature AVP in the circulation, with respect to osmotic stimuli and hypotension. During the past years, copeptin measurement has been shown to be of interest in a variety of clinical indications, including cardiovascular diseases such as heart failure, myocardial infarction, and stroke. This review summarizes the recent progress on the diagnostic use of copeptin in cardiovascular and renal diseases and discusses the potential use of copeptin measurement in the context of therapeutic interventions with vasopressin receptor antagonists.

Circulating Dickkopf-1 in acute ischemic stroke and clinically stable cerebrovascular disease

OBJECTIVES

Previous data suggest that Dickkopf-1 (Dkk-1), an inhibitor of the canonical/β-catenin cascade of the Wnt pathway, is upregulated in carotid atherosclerosis and acute myocardial ischemia. It is currently unclear if such upregulation also occurs in cerebral ischemia.

METHODS

We measured plasma levels of Dkk-1 in patients with acute ischemic stroke (n=57) within 24h from symptom onset, in patients with clinically stable cerebrovascular disease (n=29) and in healthy controls (n=29). Stroke severity on admission was determined by the National Institutes of Stroke Scale (NIHSS). The modified Rankin Scale (mRS) served to define outcome at day 90. Ischemic stroke subtype and cause was determined by the Oxfordshire Community Stroke Project (OCSP) criteria and the Causative Classification of Stroke System (CCS).

RESULTS

Dkk-1 plasma levels were significantly higher in acute stroke patients (median 727.1 pg/ml) as compared to patients with stable cerebrovascular disease (median 534.2 pg/ml; p=0.017) or healthy controls (median 371.3 pg/ml; p<0.001). The difference of Dkk-1 levels between patients with stable cerebrovascular disease and healthy controls was also significant (p=0.005). No significant differences in Dkk-1 plasma levels were found between different causes or subtypes of ischemic stroke. No correlation of Dkk-1 levels was found with stroke severity on admission and outcome at day 90.

CONCLUSION

Our study provides for the first time evidence for a release of Dkk-1 into the circulation in patients with acute ischemic stroke and also in patients with clinically stable cerebrovascular disease.

Anterior pituitary axis hormones and outcome in acute ischaemic stroke

BACKGROUND

Early and accurate prediction of outcome in acute stroke is important and influences risk-optimized therapeutic strategies. Endocrine alterations of the hypothalamic-pituitary axis are amongst the first measurable alterations after cerebral ischaemia. We therefore evaluated the prognostic value of cortisol, triiodothyronine (T3), free thyroxine (fT4), thyroid-stimulating hormone (TSH) and growth hormone (GH) in patients with an acute ischaemic stroke.

METHODS

In an observational study including 281 patients with ischaemic stroke, anterior pituitary axis hormones (i.e. cortisol, T3, fT4, TSH and GH) were simultaneously assessed to determine their value to predict functional outcome and mortality within 90 days and 1 year.

RESULTS

In receiver operating characteristic curve analysis, the prognostic accuracy of cortisol was higher compared to all measured hormones and was in the range of the National Institutes of Health Stroke Scale (NIHSS). Cortisol was an independent prognostic marker of functional outcome and death [odds ratio (OR) 1.0 (1.0-1.01) and 1.62 (1.37-1.92), respectively, P<0.0002 for both, adjusted for age and the NIHSS] in patients with ischaemic stroke, but added no significant additional predictive value to the clinical NIHSS score.

CONCLUSION

Cortisol is an independent prognostic marker for death and functional outcome within 90 days and 1 year in patients with ischaemic stroke. By contrast, other anterior pituitary axis hormones such as peripheral thyroid hormones and GH are only of minor value to predict outcome in stroke.

Correlation of plasma copeptin and vasopressin concentrations in hypo-, iso-, and hyperosmolar States

BACKGROUND

Copeptin, the C-terminal moiety of provasopressin, is cosecreted with vasopressin. Copeptin may be a useful parameter to characterize disorders of water homeostasis and can be readily measured in plasma or serum. However, it is unknown to date how circulating copeptin and vasopressin levels correlate at different plasma osmolalites.

OBJECTIVE

To correlate plasma copeptin with plasma osmolality and vasopressin concentrations in healthy subjects during iso-, hypo-, and hyperosmolar states.

METHODS

Plasma osmolalities, copeptin, and vasopressin levels were measured in 20 volunteers at baseline, after an oral water load, and during and after iv infusion of 3% saline. Correlation coefficients were determined between plasma osmolalites and copeptin and vasopressin concentrations, as well as between vasopressin and copeptin concentrations.

RESULTS

Median plasma osmolalities decreased from 290 mOsm/kg (range, 284-302) at baseline to 281 (273-288) mOsm/kg after water load and rose to 301 (298-307) mOsm/kg after hypertonic saline. Median plasma copeptin concentrations decreased from 3.3 (1.1-36.4) pm at baseline to 2.0 (0.9-10.4) pm after water load and increased to 13.6 (3.7-43.3) pm after hypertonic saline. Vasopressin and copeptin concentrations correlated with plasma osmolality (Spearman's rank correlation coefficient 0.49 and 0.77, respectively). There was a close correlation of vasopressin and copeptin concentrations (Spearman's rank correlation coefficient 0.8).

CONCLUSION

Plasma vasopressin and copeptin correlate strongly over a wide range of osmolalities in healthy individuals. Therefore, the measurement of copeptin, which remains stable for several days, is a useful alternative to vasopressin measurements and will likely facilitate the differential diagnosis of disorders of water metabolism.

Copeptin levels associate with cardiovascular events in patients with ESRD and type 2 diabetes mellitus

In ESRD, the neurohormone arginine vasopressin (AVP) may act primarily through V1a and V1b receptors, which promote vasoconstriction, myocardial hypertrophy, and release of adrenocorticotropic hormone. The preanalytical instability of AVP limits the investigation of whether this hormone associates with cardiovascular events, but the stable glycopeptide copeptin may serve as a surrogate because it is co-secreted with AVP from the posterior pituitary. Here, we studied whether copeptin predicts cardiovascular risk and mortality in ESRD. We measured copeptin at baseline in 1241 hemodialysis patients with type 2 diabetes participating in the German Diabetes and Dialysis Study. The median copeptin level was 81 pmol/L (interquartile range, 81 to 122 pmol/L). In Cox regression analyses, compared with patients with copeptin levels in the lowest quartile (≤51 pmol/L), patients with copeptin levels in the highest quartile (>122 pmol/L) had a 3.5-fold increased risk for stroke (HR, 3.48; 95% CI: 1.71 to 7.09), a 73% higher risk for sudden death (HR, 1.73; 95% CI: 1.01 to 2.95), a 42% higher risk for combined cardiovascular events (HR, 1.42; 95% CI: 1.06 to 1.90), and a 48% higher risk for all-cause mortality (HR, 1.48; 95% CI: 1.15 to 1.90). In contrast, we did not detect significant associations between copeptin levels and risks for myocardial infarction or death caused by congestive heart failure. In conclusion, copeptin levels strongly associate with stroke, sudden death, combined cardiovascular events, and mortality in hemodialysis patients with type 2 diabetes. Whether vasopressin receptor antagonists will improve these outcomes requires further studies.

Change in plasma copeptin level after acute spontaneous basal ganglia hemorrhage

High plasma copeptin levels are associated with mortality after intracerebral hemorrhage (ICH). However, there is a paucity of data available on whether copeptin is an independent prognostic marker of mortality. Thus, we sought to furthermore evaluate this relation. Thirty healthy controls and 86 patients with acute ICH were included. Plasma samples were obtained on admission and at days 1, 2, 3, 5, and 7 after ICH. Its concentration was measured by enzyme-linked immunosorbent assay. After ICH, plasma copeptin level in patients increased during the 6-h period immediately, peaked in 24h, decreased gradually thereafter, and was substantially higher than that in healthy controls during the 7-day period. A multivariate analysis showed plasma copeptin level was an independent predictor for 1-week mortality (odds ratio, 1.013; 95% confidence interval (CI), 1.003-1.023; P=0.009) and positively associated with hematoma volume (t=6.616, P<0.001). A receiver operating characteristic curve identified that a baseline plasma copeptin level >577.5pg/mL predicted 1-week mortality with 87.5% sensitivity and 72.2% specificity (area under curve (AUC), 0.873; 95% CI, 0.784-0.935). The AUC of the copeptin concentration was similar to those of Glasgow Coma Scale (GCS) scores and hematoma volumes (P=0.136 and 0.280). However, copeptin did not statistically significantly improve the AUCs of GCS scores and hematoma volumes (P=0.206 and 0.333). Hence, increased plasma copeptin level is associated with hematoma volume and an independent prognostic marker of mortality after ICH.

Prognostic Value of Copeptin

Background and Purpose— An accurate long-term outcome prediction may improve management of stroke patients. We investigated the ability of copeptin to predict 1-year outcome in stroke patients.

Methods— In this preplanned post hoc analysis, the National Institutes of Health Stroke Scale score and copeptin levels were measured on admission in a cohort of patients with ischemic stroke. The primary end point was functional outcome (modified Rankin Scale score <3 or 3–6) after 1 year. The secondary end point was all-cause mortality.

Results— Of 362 patients, 341 (94.2%) completed the 1-year follow-up, 146 (43%) patients had an unfavorable functional outcome, and 66 (20%) died. Multivariate logistic-regression analysis adjusted for age and National Institutes of Health Stroke Scale score showed that copeptin was an independent predictor of functional outcome (odds ratio=4.00; 95% CI, 1.94–8.19) and death (odds ratio=2.68; 95% CI, 1.24–5.82). The area under the receiver operating characteristic curve of copeptin was 0.72 (95% CI, 0.67–0.77) for functional outcome and 0.74 (95% CI, 0.69–0.78) for mortality. Copeptin improved the area under the receiver operating characteristic curve of the National Institutes of Health Stroke Scale score for functional outcome from 0.70 (95% CI, 0.64–0.74) to 0.76 (95% CI, 0.71–0.82; P =0.002) and for mortality from 0.74 (95% CI, 0.69–0.78) to 0.78 (95% CI, 0.71–0.85; P =0.04).

Conclusions— Copeptin levels are a useful, complementary tool to predict functional outcome and mortality 1 year after stroke.

Clinical Trial Registration— ISCTRN 00390962; clinicaltrials.gov No. NCT00390962.

Copeptin is associated with mortality and outcome in patients with acute intracerebral hemorrhage

Background

Spontaneous intracerebral hemorrhage (ICH) accounts for a high mortality and morbidity. Early prediction of outcome is crucial for optimized care and treatment decision. Copeptin, the C-terminal part of provasopressin, has emerged as a new prognostic marker in a variety of diseases, but its prognostic value in ICH is unknown.

Methods

In 40 consecutive patients who were admitted to the hospital within 72 hours after a spontaneous ICH, the plasma copeptin level was measured with a sandwich immunoassay upon admission. The prognostic value of copeptin to predict 30 day mortality and functional outcome after 90 days was assessed. A favorable outcome was defined as a Barthel score above 85 and a score below 3 on the Modified Rankin Scale.

Results

Copeptin correlated positively with hematoma volume (r = 0.32, p < 0.05) and negatively with the Glasgow Coma Scale (GCS) on admission (r = -0.35, p < 0.05). Copeptin levels were higher in patients who died within 30 days than in 30-day survivors (179.0 pmol/l (IQR 33.7- 566.0) vs. 12.9 pmol/l (IQR 5.2 - 42.8), p = 0.003). Copeptin levels were also higher in patients with an unfavorable functional outcome at 90 days compared to patients with a favorable outcome (32.4 pmol/l (IQR 9.5-97.8) vs. 11.9 pmol/l (IQR 3.2-19.8), p = 0.04). For the prediction of death, receiver-operating-characteristics analysis revealed an area under the curve (AUC) for copeptin of 0.88 (95%CI 0.75-1.00). The predictive value of the copeptin concentration was thus similar to that of GCS (AUC 0.82 (95%CI 0.59-1.00) p = 0.53), of the ICH Score (AUC 0.89, (95%CI 0.76-1.00), p = 0.94) and the ICH Grading Scale (AUC 0.86 (95%CI 0.69-1.00), p = 0.81).

Conclusions

Copeptin is a new prognostic marker in patients with an ICH. If this finding can be confirmed in larger studies, copeptin might be an additional valuable tool for risk stratification and decision-making in the acute phase of ICH.

Trial Registration

(Clinical Trial Registration: ISCTRN00390962)