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Prognostic value of leptin: 6-Month outcome in patients with intracerebral hemorrhage
Peptides 43 (2013) 133–136
Contents lists available at SciVerse ScienceDirect
Peptides journal homepage: www.elsevier.com/locate/peptides
Prognostic value of leptin: 6-Month outcome in patients with intracerebral hemorrhage夽 Xin Zhang a,∗ , Xiao-Min Lu b , Li-Fa Huang a , Xu Li a a b
Department of Neurosurgery, Traditional Chinese Medical Hospital of Zhejiang Province, 54 Youdian Road, Hangzhou 310006, China Department of Surgery, Wushan Branch, The First Hangzhou Municipal People’s Hospital, 34 Yanguan Lane, Hangzhou 310002, China
a r t i c l e
i n f o
Article history: Received 27 February 2013 Received in revised form 11 March 2013 Accepted 11 March 2013 Available online 18 March 2013 Keywords: Leptin Intracerebral hemorrhage 6-Month clinical outcome
a b s t r a c t Leptin has recently been discussed as a novel biomarker for the clinical outcome of critical illness. This study aims to investigate the prognostic value of leptin with regard to long-term clinical outcomes in patients with intracerebral hemorrhage. In 50 healthy controls and 92 patients with acute spontaneous basal ganglia hemorrhage presenting to the emergency department of a large primary care hospital, we measured plasma leptin levels using an enzyme-linked immunosorbent assay in a blinded fashion. Plasma leptin levels on admission were considerably higher in patients than healthy controls. A significant correlation emerged between plasma leptin level and National Institutes of Health Stroke Scale score. A multivariate analysis identified plasma leptin level as an independent predictor for 6-month clinical outcomes including 6-month mortality and unfavorable outcome (Modified Rankin Scale score > 2). Using receiver operating characteristic curves, we calculated areas under the curve for 6-month clinical outcomes. The predictive performance of leptin was similar to, but did not obviously improve that of National Institutes of Health Stroke Scale scores. Thus, leptin may help in the prediction of 6-month mortality and unfavorable outcome after intracerebral hemorrhage. © 2013 Elsevier Inc. All rights reserved.
1. Introduction
2. Materials and methods
Leptin, the 16,000 Da protein product of the obesity gene (ob), is principally derived from white adipose tissue, and not only acts on the central nervous system to reduce appetite and increase energy expenditure, but also plays crucial roles in regulating inflammation and immune [1,4,8,9,13–15]. Present investigations on animals have found that brain cortex leptin mRNA expression and serum leptin level are up-regulated in mouse with ischemic brain injury and in rat with traumatic brain injury [2,6,18]. Moreover, leptin levels in peripheral blood are highly associated with cerebral hemorrhagic or ischemic stroke [16,17], and independently predict in-hospital and 1-week mortality of patients with intracerebral hemorrhage (ICH) and 6-month clinical outcome of pediatric traumatic brain injury [7,11,19]. This follow-up study further evaluated leptin as a marker to predict long-term functional outcome and mortality at 6 months after admission in acute ICH patients.
2.1. Study population
夽 Institution at which the work was performed: Traditional Chinese Medical Hospital of Zhejiang Province. ∗ Corresponding author. Tel.: +86 0571 87068001. E-mail address: [email protected] (X. Zhang). 0196-9781/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.peptides.2013.03.010
This prospective study was conducted during the period of January 2010–March 2012 by the Department of Neurosurgery, Traditional Chinese Medical Hospital of Zhejiang Province. The consecutive patients with acute spontaneous basal ganglia hemorrhage were evaluated within 6 h from symptoms onset at the emergency room. Exclusion criteria included existing previous neurological disease, head trauma, use of antiplatelet or anticoagulant medication, presence of other prior systemic diseases including uremia, liver cirrhosis, malignancy, and chronic heart or lung disease, with the exceptions of diabetes mellitus and hypertension. The patients who underwent a surgical procedure and had missing of follow-up or unavailable leptin measurements were also excluded. Healthy individuals were evaluated as controls if they presented to our hospital and had blood collected as part of medical examination on March 2012. The study was conducted in accordance with the guidelines approved by the Human Research Ethics Committee at Traditional Chinese Medical Hospital of Zhejiang Province. Written informed consent was obtained from the study subjects or their relatives.
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2.2. Clinical and radiological assessment The level of neurological status on admission was assessed by National Institutes of Health Stroke Scale (NIHSS) scores. Early neurological deterioration was defined as the increase of ≥4 points in the NIHSS score at 24 h from symptoms onset. At 6 months after ICH, the patients that scored >2 on the modified Rankin Scale were considered as having an unfavorable outcome. All computerized tomography scans were performed according to the neuroradiology department protocol. Investigators who read them were blinded to clinical information. Patients underwent an initial CT scan on admission and a follow-up CT scan at 24 h from symptoms onset. Hematoma volume was measured according to the previously reported formula A × B × C × 0.5 [10]. Hematoma growth was defined as an increase of >33% in the volume of intraparenchymal hemorrhage as measure by CT compared with the initial scan [5]. Fig. 1. Graph showing receiver operating characteristic curve analysis of plasma leptin level for 6-month mortality.
2.3. Immunoassay methods The informed consents were obtained from study population or family members in all cases before the blood were collected. Venous blood in the healthy individuals or the ICH patients was drawn at study entry or on admission. The blood samples were immediately placed into sterile EDTA test tubes and centrifuged at 3000g for 30 min at 4 ◦ C to collect plasma. Plasma was stored at −70 ◦ C until assayed. The concentration of leptin in plasma was analyzed by enzyme-linked immunosorbent assay using commercial kits (R&D Systems, Minneapolis, MN, USA) in accordance with the manufactures’ instructions. The person carrying out the assays was completely blinded to the clinical information. 2.4. Statistical analysis Statistical analysis was done using the SPSS 12.0 statistical package (SPSS Inc., Chicago, IL, USA) and MedCalc 9.6.4.0. (MedCalc Software, Mariakerke, Belgium). All values are expressed as mean ± standard deviation or counts (percentage) unless otherwise specified. Significance for intergroup differences was assessed by chi-square test or Fisher exact test for categorical variables and Mann–Whitney U test for continuous variables. Receiver operating characteristics (ROC) curves were configured to establish the cut-off points of leptin with the optimal sensitivity and specificity predicting 6-month clinical outcomes. Finally, 2 logistic regression analyses were performed to determine the factors that could be considered as independent predictors of 6-month clinical outcomes, using the forward stepwise method. Variables showing a P < 0.1 in univariate analysis were included in the multivariate model. In a combined logistic-regression model, we estimated the additive benefit of leptin to NIHSS score. A P value < 0.05 was considered significant.
3. Results
P < 0.001) as well as between plasma leptin level and plasma Creactive protein level (r = 0.542, P < 0.001). 3.2. Impact of leptin on 6-month mortality Thirty-four patients (37.0%) died from ICH at 6 months. Higher baseline plasma leptin level was associated with 6-month mortality, as well as other variables shown in Table 1. A multivariate analyses selected NIHSS score (odds ratio (OR), 1.221; 95% confidence interval (CI), 1.129–1.804; P < 0.001) and baseline plasma leptin level (OR, 1.216; 95% CI, 1.124–2.501; P < 0.001) as the independent predictors for 6-month mortality. A ROC curve showed that the plasma leptin level predicted 6-month mortality of patients with high area under curve (AUC) (Fig. 1). The predictive value of the leptin concentration was thus similar to that of NIHSS score (AUC, 0.850; 95% CI, 0.761–0.916) (P = 0.586). In a combined logistic-regression model, leptin improved the AUC of NIHSS score to 0.880 (95% CI, 0.796–0.939) but the difference was not significant (P = 0.228). 3.3. Impact of leptin on 6-month unfavorable outcome Fifty-one patients (55.4%) suffered from unfavorable outcome at 6 months. Higher baseline plasma leptin level was associated with 6-month unfavorable outcome, as well as other variables shown in Table 1. A multivariate analyses selected NIHSS score (OR, 1.304; 95% CI, 1.142–1.917; P < 0.001) and baseline plasma leptin level (OR, 1.284; 95% CI, 1.141–2.760; P < 0.001) as the independent predictors for 6-month unfavorable outcome. A ROC curve showed that the plasma leptin level predicted 6-month unfavorable outcome of patients with high AUC (Fig. 2). The predictive value of the leptin concentration was thus similar to that of NIHSS score (AUC, 0.882; 95% CI, 0.798–0.940) (P = 0.329). In a combined logistic-regression model, leptin improved the AUC of NIHSS score to 0.920 (95% CI, 0.845–0.966) but the difference was not significant (P = 0.067).
3.1. Study population’s characteristics 4. Discussion Finally, 92 ICH patients and 50 healthy controls were enrolled in this study. The intergroup differences in age, gender and body mass index were not statistically significant (all P > 0.05). The demographic, clinical and laboratory data of patients were provided in Table 1. The admission leptin levels were significantly increased in all patients (19.1 ± 7.7 ng/mL) compared with healthy control individuals (7.9 ± 3.3 ng/mL, P < 0.001). A significant correlation emerged between plasma leptin level and NIHSS score (r = 0.561,
Recent two studies have demonstrated that leptin levels in peripheral blood independently predict in-hospital and 1-week mortality of the patients with ICH [7,19]. To the best of our knowledge, this study is among few studies that analyzed the association of plasma leptin level with long-term clinical outcomes in ICH. This study demonstrated that the plasma leptin levels on admission is considerably increased and markedly predicts 6-month
X. Zhang et al. / Peptides 43 (2013) 133–136
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Table 1 Patients’ characteristics and the factors associated with 6-month clinical outcomes. Characteristics
Gender (male/female) Age (years) Body mass index (kg/m2 ) Hypertension Diabetes mellitus NIHSS score Hematoma volume (mL) Presence of intraventricular hemorrhage Hemorrhage growth Early neurological deterioration Admission time (h) Plasma-sampling time (h) Systolic arterial pressure (mm Hg) Diastolic arterial pressure (mm Hg) Blood glucose level (mmol/L) Plasma C-reactive protein level (mg/L) Plasma D-dimer level (mg/L) Plasma leptin level (ng/mL)
Overall (n = 92)
54/38 64.6 ± 10.7 25.5 ± 2.2 81 (88.0%) 22 (23.9%) 19.0 ± 5.3 31.6 ± 18.4 38 (41.3%) 15 (16.3%) 22 (23.9%) 2.2 ± 1.3 4.6 ± 2.4 171.9 ± 26.2 92.5 ± 12.5 12.4 ± 4.5 8.8 ± 3.4 2.4 ± 1.0 19.1 ± 7.7
6-Month mortality
6-Month functional outcome
Survival group (n = 58)
Non-survival group (n = 34)
Univariate analysis P values
Favorable outcome (n = 41)
Unfavorable outcome (n = 51)
Univariate analysis P values
34/24 62.5 ± 10.9 25.3 ± 2.3 49 (84.5%) 9 (15.5%) 16.7 ± 5.0 23.8 ± 15.2 16 (27.6%) 6 (10.3%) 8 (13.8%) 2.2 ± 1.3 4.9 ± 2.6 170.1 ± 27.4 91.9 ± 13.7 11.3 ± 3.3 8.0 ± 3.0 2.2 ± 1.0 16.1 ± 7.4
20/14 68.4 ± 9.6 25.9 ± 1.9 32 (94.1%) 13 (38.2%) 22.9 ± 3.3 44.9 ± 15.7 22 (64.7%) 9 (26.5%) 14 (41.2%) 2.1 ± 1.2 4.1 ± 2.2 174.9 ± 24.1 93.6 ± 10.0 14.4 ± 5.5 10.2 ± 3.8 2.7 ± 0.9 24.3 ± 5.1
0.985 0.010 0.225 0.169 0.014 <0.001 <0.001 <0.001 0.043 0.003 0.584 0.144 0.396 0.481 0.004 0.004 0.014 <0.001
25/16 62.0 ± 10.3 25.1 ± 2.4 35 (85.4%) 5 (12.2%) 15.2 ± 4.7 22.4 ± 15.0 8 (19.5%) 3(7.3%) 5 (12.2%) 2.4 ± 1.4 5.0 ± 2.7 175.2 ± 26.8 93.7 ± 14.2 11.0 ± 3.4 7.6 ± 2.6 2.0 ± 0.9 14.1 ± 6.8
29/22 66.7 ± 10.9 25.9 ± 2.0 46 (90.2%) 17 (33.3%) 22.0 ± 3.5 39.0 ± 17.6 30 (58.8%) 12 (23.5%) 17 (33.3%) 2.0 ± 1.2 4.3 ± 2.2 169.2 ± 25.7 91.6 ± 10.9 13.6 ± 5.0 9.8 ± 3.7 2.7 ± 1.0 23.2 ± 5.7
0.690 0.036 0.107 0.478 0.018 <0.001 <0.001 <0.001 0.036 0.018 0.158 0.162 0.281 0.427 0.004 0.002 0.001 <0.001
Numerical variables were presented as mean ± standard deviation. Categorical variables were expressed as counts (percentage). Numerical variables were analyzed by Mann–Whitney U-test. Categorical variables were analyzed by chi-square test or Fisher exact test.
clinical outcomes. Importantly, the prognostic value of leptin is similar to that of the NIHSS score, substantiating its potential as a new prognostic biomarker. Leptin is a 146 amino acid protein with a molecular weight of 16 kDa encoded by the ob gene and primarily, but not exclusively, is expressed by the white adipose tissue and is implicated in obesity, food intake, and energy homeostasis [1,9]. Several activating effects toward T cells, monocytes, endothelium cells and cytokine production have been reported and might suggest a pro-inflammatory role for leptin in the setting of acute systemic inflammation [4,8,13–15]. Leptin enters the brain via saturable transport across the blood–brain barrier [3]. Leptin mRNA is selectively transcribed in specific areas of the brain and pituitary in rat, pig, sheep and human [12]. Brain cortex leptin mRNA expression and serum leptin level are up-regulated in mouse with ischemic brain injury and in rat with traumatic brain injury [2,6,18]. These observations imply that the enhancement of leptin level in the peripheral blood of patients with ischemic or hemorrhagic stroke and pediatric traumatic brain injury could be a general response in the pathology of brain damage [7,11,16,17,19]. In agreement with
recent report [7], this study also found that plasma leptin level is related to plasma C-reactive protein level in ICH. Theses findings suggest leptin may contribute to the inflammatory process of hemorrhagic brain injury. In addition, our data suggested that plasma leptin level might reflect the severity of ICH (as demonstrated by the close relation between leptin and the NIHSS score). Leptin independently predicted 6-month mortality and unfavorable outcome in this group of ICH patients and its discriminative power (reflected by AUC) was in the range of the NIHSS score which is known to be a strong individual outcome predictor. However, leptin did not statistically significantly improve the AUC of the NIHSS score. Therefore, the detection of plasma leptin concentration can be useful for the clinical management of ICH. 5. Conclusions This study suggests that higher plasma leptin level correlates with disease severity and markers of system inflammation and represents a novel biomarker for predicting 6-month clinical outcomes in patients with ICH. Competing interests The authors declare that they have no competing interests. References
Fig. 2. Graph showing receiver operating characteristic curve analysis of plasma leptin level for 6-month unfavorable outcome.
[1] Ahima RS, Qi Y, Singhal NS. Adipokines that link obesity and diabetes to the hypothalamus. Prog Brain Res 2006;153:155–74. [2] alerio A, Dossena M, Bertolotti P, Boroni F, Sarnico I, Faraco G, et al. Leptin is induced in the ischemic cerebral cortex and exerts neuroprotection through NF-kappaB/c-Rel-dependent transcription. Stroke 2009;40:610–7. [3] Banks WA, Kastin AJ, Huang W, Jaspan JB, Maness LM. Leptin enters the brain by a saturable system independent of insulin. Peptides 1996;17:305–11. [4] Biesiada G, Czepiel J, Ptak-Belowska A, Targosz A, Krzysiek-Maczka G, Strzalka M, et al. Expression and release of leptin and proinflammatory cytokines in patients with ulcerative colitis and infectious diarrhea. J Physiol Pharmacol 2012;63:471–81. [5] Brott T, Broderick J, Kothari R, Barsan W, Tomsick T, Sauerbeck L, et al. Early hemorrhage growth in patients with intracerebral hemorrhage. Stroke 1997;28:1–5. [6] Brown R, Thompson HJ, Imran SA, Ur E, Wilkinson M. Traumatic brain injury induces adipokine gene expression in rat brain. Neurosci Lett 2008;432:73–8.
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[7] Dong XQ, Huang M, Hu YY, Yu WH, Zhang ZY. Time course of plasma leptin concentrations after acute spontaneous basal ganglia hemorrhage. World Neurosurg 2010;74:286–93. [8] Fantuzzi G. Adipose tissue, adipokines, and inflammation. J Allergy Clin Immunol 2005;115:911–9. [9] Friedman JM, Halaas JL. Leptin and the regulation of body weight in mammals. Nature 1998;395:763–70. [10] Kothari RU, Brott T, Broderick JP, Barsan WG, Sauerbeck LR, Zuccarello M, et al. The ABCs of measuring intracerebral hemorrhage volumes. Stroke 1996;27:1304–5. [11] Lin C, Huang SJ, Wang N, Shen ZP. Relationship between plasma leptin levels and clinical outcomes of pediatric traumatic brain injury. Peptides 2012;35:166–71. [12] Morash B, Li A, Murphy PR, Wilkinson M, Ur E. Leptin gene expression in the brain and pituitary gland. Endocrinology 1999;140:5995–8. [13] Otero M, Lago R, Gomez R, Dieguez C, Lago F, Gomez-Reino J, et al. Towards a pro-inflammatory and immunomodulatory emerging role of leptin. Rheumatology (Oxford) 2006;45:944–50.
[14] Paz-Filho G, Mastronardi C, Franco CB, Wang KB, Wong ML, Licinio J. Leptin: molecular mechanisms, systemic pro-inflammatory effects, and clinical implications. Arq Bras Endocrinol Metabol 2012;56:597–607. [15] Rajendran K, Devarajan N, Ganesan M, Obesity Ragunathan M, Inflammation. Acute myocardial infarction – expression of leptin, IL-6 and high sensitivity-CRP in Chennai based population. Thromb J 2012;10:13. [16] Söderberg S, Ahrén B, Stegmayr B, Johnson O, Wiklund PG, Weinehall L, et al. Leptin is a risk marker for first-ever hemorrhagic stroke in a population-based cohort. Stroke 1999;30:328–37. [17] Söderberg S, Stegmayr B, Ahlbeck-Glader C, Slunga-Birgander L, Ahrén B, Olsson T. High leptin levels are associated with stroke. Cerebrovasc Dis 2003;15:63–9. [18] Wei Y, Wang L, Clark JC, Dass CR, Choong PF. Elevated leptin expression in a rat model of fracture and traumatic brain injury. J Pharm Pharmacol 2008;60:667–72. [19] Zhao QJ, Sun M, Zhang XG, Wang LX. Relationship between serum leptin levels and clinical outcomes of hypertensive intracerebral hemorrhage. Clin Exp Hypertens 2012;34:161–4.
Contents lists available at SciVerse ScienceDirect
Peptides journal homepage: www.elsevier.com/locate/peptides
Prognostic value of leptin: 6-Month outcome in patients with intracerebral hemorrhage夽 Xin Zhang a,∗ , Xiao-Min Lu b , Li-Fa Huang a , Xu Li a a b
Department of Neurosurgery, Traditional Chinese Medical Hospital of Zhejiang Province, 54 Youdian Road, Hangzhou 310006, China Department of Surgery, Wushan Branch, The First Hangzhou Municipal People’s Hospital, 34 Yanguan Lane, Hangzhou 310002, China
a r t i c l e
i n f o
Article history: Received 27 February 2013 Received in revised form 11 March 2013 Accepted 11 March 2013 Available online 18 March 2013 Keywords: Leptin Intracerebral hemorrhage 6-Month clinical outcome
a b s t r a c t Leptin has recently been discussed as a novel biomarker for the clinical outcome of critical illness. This study aims to investigate the prognostic value of leptin with regard to long-term clinical outcomes in patients with intracerebral hemorrhage. In 50 healthy controls and 92 patients with acute spontaneous basal ganglia hemorrhage presenting to the emergency department of a large primary care hospital, we measured plasma leptin levels using an enzyme-linked immunosorbent assay in a blinded fashion. Plasma leptin levels on admission were considerably higher in patients than healthy controls. A significant correlation emerged between plasma leptin level and National Institutes of Health Stroke Scale score. A multivariate analysis identified plasma leptin level as an independent predictor for 6-month clinical outcomes including 6-month mortality and unfavorable outcome (Modified Rankin Scale score > 2). Using receiver operating characteristic curves, we calculated areas under the curve for 6-month clinical outcomes. The predictive performance of leptin was similar to, but did not obviously improve that of National Institutes of Health Stroke Scale scores. Thus, leptin may help in the prediction of 6-month mortality and unfavorable outcome after intracerebral hemorrhage. © 2013 Elsevier Inc. All rights reserved.
1. Introduction
2. Materials and methods
Leptin, the 16,000 Da protein product of the obesity gene (ob), is principally derived from white adipose tissue, and not only acts on the central nervous system to reduce appetite and increase energy expenditure, but also plays crucial roles in regulating inflammation and immune [1,4,8,9,13–15]. Present investigations on animals have found that brain cortex leptin mRNA expression and serum leptin level are up-regulated in mouse with ischemic brain injury and in rat with traumatic brain injury [2,6,18]. Moreover, leptin levels in peripheral blood are highly associated with cerebral hemorrhagic or ischemic stroke [16,17], and independently predict in-hospital and 1-week mortality of patients with intracerebral hemorrhage (ICH) and 6-month clinical outcome of pediatric traumatic brain injury [7,11,19]. This follow-up study further evaluated leptin as a marker to predict long-term functional outcome and mortality at 6 months after admission in acute ICH patients.
2.1. Study population
夽 Institution at which the work was performed: Traditional Chinese Medical Hospital of Zhejiang Province. ∗ Corresponding author. Tel.: +86 0571 87068001. E-mail address: [email protected] (X. Zhang). 0196-9781/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.peptides.2013.03.010
This prospective study was conducted during the period of January 2010–March 2012 by the Department of Neurosurgery, Traditional Chinese Medical Hospital of Zhejiang Province. The consecutive patients with acute spontaneous basal ganglia hemorrhage were evaluated within 6 h from symptoms onset at the emergency room. Exclusion criteria included existing previous neurological disease, head trauma, use of antiplatelet or anticoagulant medication, presence of other prior systemic diseases including uremia, liver cirrhosis, malignancy, and chronic heart or lung disease, with the exceptions of diabetes mellitus and hypertension. The patients who underwent a surgical procedure and had missing of follow-up or unavailable leptin measurements were also excluded. Healthy individuals were evaluated as controls if they presented to our hospital and had blood collected as part of medical examination on March 2012. The study was conducted in accordance with the guidelines approved by the Human Research Ethics Committee at Traditional Chinese Medical Hospital of Zhejiang Province. Written informed consent was obtained from the study subjects or their relatives.
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X. Zhang et al. / Peptides 43 (2013) 133–136
2.2. Clinical and radiological assessment The level of neurological status on admission was assessed by National Institutes of Health Stroke Scale (NIHSS) scores. Early neurological deterioration was defined as the increase of ≥4 points in the NIHSS score at 24 h from symptoms onset. At 6 months after ICH, the patients that scored >2 on the modified Rankin Scale were considered as having an unfavorable outcome. All computerized tomography scans were performed according to the neuroradiology department protocol. Investigators who read them were blinded to clinical information. Patients underwent an initial CT scan on admission and a follow-up CT scan at 24 h from symptoms onset. Hematoma volume was measured according to the previously reported formula A × B × C × 0.5 [10]. Hematoma growth was defined as an increase of >33% in the volume of intraparenchymal hemorrhage as measure by CT compared with the initial scan [5]. Fig. 1. Graph showing receiver operating characteristic curve analysis of plasma leptin level for 6-month mortality.
2.3. Immunoassay methods The informed consents were obtained from study population or family members in all cases before the blood were collected. Venous blood in the healthy individuals or the ICH patients was drawn at study entry or on admission. The blood samples were immediately placed into sterile EDTA test tubes and centrifuged at 3000g for 30 min at 4 ◦ C to collect plasma. Plasma was stored at −70 ◦ C until assayed. The concentration of leptin in plasma was analyzed by enzyme-linked immunosorbent assay using commercial kits (R&D Systems, Minneapolis, MN, USA) in accordance with the manufactures’ instructions. The person carrying out the assays was completely blinded to the clinical information. 2.4. Statistical analysis Statistical analysis was done using the SPSS 12.0 statistical package (SPSS Inc., Chicago, IL, USA) and MedCalc 9.6.4.0. (MedCalc Software, Mariakerke, Belgium). All values are expressed as mean ± standard deviation or counts (percentage) unless otherwise specified. Significance for intergroup differences was assessed by chi-square test or Fisher exact test for categorical variables and Mann–Whitney U test for continuous variables. Receiver operating characteristics (ROC) curves were configured to establish the cut-off points of leptin with the optimal sensitivity and specificity predicting 6-month clinical outcomes. Finally, 2 logistic regression analyses were performed to determine the factors that could be considered as independent predictors of 6-month clinical outcomes, using the forward stepwise method. Variables showing a P < 0.1 in univariate analysis were included in the multivariate model. In a combined logistic-regression model, we estimated the additive benefit of leptin to NIHSS score. A P value < 0.05 was considered significant.
3. Results
P < 0.001) as well as between plasma leptin level and plasma Creactive protein level (r = 0.542, P < 0.001). 3.2. Impact of leptin on 6-month mortality Thirty-four patients (37.0%) died from ICH at 6 months. Higher baseline plasma leptin level was associated with 6-month mortality, as well as other variables shown in Table 1. A multivariate analyses selected NIHSS score (odds ratio (OR), 1.221; 95% confidence interval (CI), 1.129–1.804; P < 0.001) and baseline plasma leptin level (OR, 1.216; 95% CI, 1.124–2.501; P < 0.001) as the independent predictors for 6-month mortality. A ROC curve showed that the plasma leptin level predicted 6-month mortality of patients with high area under curve (AUC) (Fig. 1). The predictive value of the leptin concentration was thus similar to that of NIHSS score (AUC, 0.850; 95% CI, 0.761–0.916) (P = 0.586). In a combined logistic-regression model, leptin improved the AUC of NIHSS score to 0.880 (95% CI, 0.796–0.939) but the difference was not significant (P = 0.228). 3.3. Impact of leptin on 6-month unfavorable outcome Fifty-one patients (55.4%) suffered from unfavorable outcome at 6 months. Higher baseline plasma leptin level was associated with 6-month unfavorable outcome, as well as other variables shown in Table 1. A multivariate analyses selected NIHSS score (OR, 1.304; 95% CI, 1.142–1.917; P < 0.001) and baseline plasma leptin level (OR, 1.284; 95% CI, 1.141–2.760; P < 0.001) as the independent predictors for 6-month unfavorable outcome. A ROC curve showed that the plasma leptin level predicted 6-month unfavorable outcome of patients with high AUC (Fig. 2). The predictive value of the leptin concentration was thus similar to that of NIHSS score (AUC, 0.882; 95% CI, 0.798–0.940) (P = 0.329). In a combined logistic-regression model, leptin improved the AUC of NIHSS score to 0.920 (95% CI, 0.845–0.966) but the difference was not significant (P = 0.067).
3.1. Study population’s characteristics 4. Discussion Finally, 92 ICH patients and 50 healthy controls were enrolled in this study. The intergroup differences in age, gender and body mass index were not statistically significant (all P > 0.05). The demographic, clinical and laboratory data of patients were provided in Table 1. The admission leptin levels were significantly increased in all patients (19.1 ± 7.7 ng/mL) compared with healthy control individuals (7.9 ± 3.3 ng/mL, P < 0.001). A significant correlation emerged between plasma leptin level and NIHSS score (r = 0.561,
Recent two studies have demonstrated that leptin levels in peripheral blood independently predict in-hospital and 1-week mortality of the patients with ICH [7,19]. To the best of our knowledge, this study is among few studies that analyzed the association of plasma leptin level with long-term clinical outcomes in ICH. This study demonstrated that the plasma leptin levels on admission is considerably increased and markedly predicts 6-month
X. Zhang et al. / Peptides 43 (2013) 133–136
135
Table 1 Patients’ characteristics and the factors associated with 6-month clinical outcomes. Characteristics
Gender (male/female) Age (years) Body mass index (kg/m2 ) Hypertension Diabetes mellitus NIHSS score Hematoma volume (mL) Presence of intraventricular hemorrhage Hemorrhage growth Early neurological deterioration Admission time (h) Plasma-sampling time (h) Systolic arterial pressure (mm Hg) Diastolic arterial pressure (mm Hg) Blood glucose level (mmol/L) Plasma C-reactive protein level (mg/L) Plasma D-dimer level (mg/L) Plasma leptin level (ng/mL)
Overall (n = 92)
54/38 64.6 ± 10.7 25.5 ± 2.2 81 (88.0%) 22 (23.9%) 19.0 ± 5.3 31.6 ± 18.4 38 (41.3%) 15 (16.3%) 22 (23.9%) 2.2 ± 1.3 4.6 ± 2.4 171.9 ± 26.2 92.5 ± 12.5 12.4 ± 4.5 8.8 ± 3.4 2.4 ± 1.0 19.1 ± 7.7
6-Month mortality
6-Month functional outcome
Survival group (n = 58)
Non-survival group (n = 34)
Univariate analysis P values
Favorable outcome (n = 41)
Unfavorable outcome (n = 51)
Univariate analysis P values
34/24 62.5 ± 10.9 25.3 ± 2.3 49 (84.5%) 9 (15.5%) 16.7 ± 5.0 23.8 ± 15.2 16 (27.6%) 6 (10.3%) 8 (13.8%) 2.2 ± 1.3 4.9 ± 2.6 170.1 ± 27.4 91.9 ± 13.7 11.3 ± 3.3 8.0 ± 3.0 2.2 ± 1.0 16.1 ± 7.4
20/14 68.4 ± 9.6 25.9 ± 1.9 32 (94.1%) 13 (38.2%) 22.9 ± 3.3 44.9 ± 15.7 22 (64.7%) 9 (26.5%) 14 (41.2%) 2.1 ± 1.2 4.1 ± 2.2 174.9 ± 24.1 93.6 ± 10.0 14.4 ± 5.5 10.2 ± 3.8 2.7 ± 0.9 24.3 ± 5.1
0.985 0.010 0.225 0.169 0.014 <0.001 <0.001 <0.001 0.043 0.003 0.584 0.144 0.396 0.481 0.004 0.004 0.014 <0.001
25/16 62.0 ± 10.3 25.1 ± 2.4 35 (85.4%) 5 (12.2%) 15.2 ± 4.7 22.4 ± 15.0 8 (19.5%) 3(7.3%) 5 (12.2%) 2.4 ± 1.4 5.0 ± 2.7 175.2 ± 26.8 93.7 ± 14.2 11.0 ± 3.4 7.6 ± 2.6 2.0 ± 0.9 14.1 ± 6.8
29/22 66.7 ± 10.9 25.9 ± 2.0 46 (90.2%) 17 (33.3%) 22.0 ± 3.5 39.0 ± 17.6 30 (58.8%) 12 (23.5%) 17 (33.3%) 2.0 ± 1.2 4.3 ± 2.2 169.2 ± 25.7 91.6 ± 10.9 13.6 ± 5.0 9.8 ± 3.7 2.7 ± 1.0 23.2 ± 5.7
0.690 0.036 0.107 0.478 0.018 <0.001 <0.001 <0.001 0.036 0.018 0.158 0.162 0.281 0.427 0.004 0.002 0.001 <0.001
Numerical variables were presented as mean ± standard deviation. Categorical variables were expressed as counts (percentage). Numerical variables were analyzed by Mann–Whitney U-test. Categorical variables were analyzed by chi-square test or Fisher exact test.
clinical outcomes. Importantly, the prognostic value of leptin is similar to that of the NIHSS score, substantiating its potential as a new prognostic biomarker. Leptin is a 146 amino acid protein with a molecular weight of 16 kDa encoded by the ob gene and primarily, but not exclusively, is expressed by the white adipose tissue and is implicated in obesity, food intake, and energy homeostasis [1,9]. Several activating effects toward T cells, monocytes, endothelium cells and cytokine production have been reported and might suggest a pro-inflammatory role for leptin in the setting of acute systemic inflammation [4,8,13–15]. Leptin enters the brain via saturable transport across the blood–brain barrier [3]. Leptin mRNA is selectively transcribed in specific areas of the brain and pituitary in rat, pig, sheep and human [12]. Brain cortex leptin mRNA expression and serum leptin level are up-regulated in mouse with ischemic brain injury and in rat with traumatic brain injury [2,6,18]. These observations imply that the enhancement of leptin level in the peripheral blood of patients with ischemic or hemorrhagic stroke and pediatric traumatic brain injury could be a general response in the pathology of brain damage [7,11,16,17,19]. In agreement with
recent report [7], this study also found that plasma leptin level is related to plasma C-reactive protein level in ICH. Theses findings suggest leptin may contribute to the inflammatory process of hemorrhagic brain injury. In addition, our data suggested that plasma leptin level might reflect the severity of ICH (as demonstrated by the close relation between leptin and the NIHSS score). Leptin independently predicted 6-month mortality and unfavorable outcome in this group of ICH patients and its discriminative power (reflected by AUC) was in the range of the NIHSS score which is known to be a strong individual outcome predictor. However, leptin did not statistically significantly improve the AUC of the NIHSS score. Therefore, the detection of plasma leptin concentration can be useful for the clinical management of ICH. 5. Conclusions This study suggests that higher plasma leptin level correlates with disease severity and markers of system inflammation and represents a novel biomarker for predicting 6-month clinical outcomes in patients with ICH. Competing interests The authors declare that they have no competing interests. References
Fig. 2. Graph showing receiver operating characteristic curve analysis of plasma leptin level for 6-month unfavorable outcome.
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