|Year : 2015 | Volume
| Issue : 3 | Page : 138-142
Protein Z serum levels as a risk factor for acute ischemic stroke in patients with systemic lupus erythematosus: a comparison with diabetic cases
Alyaa A El-Sherbeny MD 1, Emad A Abd El-Hadi1, Maram M Maher1, Hanan M EL-Saadny2, Doaa A El-Aidy3, Mona Gameel4, Magdy A Abd El-Aziz5
1 Department of Internal Medicine, Ain Shams University, Cairo, Egypt
2 Department of Rheumatology and Rehabilitation, Tanta University, Tanta, Egypt
3 Department of Neurology, Ain Shams University, Cairo, Egypt
4 Department of Rheumatology and Rehabilitation, Ain Shams University, Cairo, Egypt
5 Department of Biochemistry, Ain Shams University, Cairo, Egypt
|Date of Submission||28-Apr-2015|
|Date of Acceptance||15-May-2015|
|Date of Web Publication||8-Sep-2015|
Alyaa A El-Sherbeny
10 Ahmed Saman Street, Mostafa El-Nahas Street, Nasr City, 11762, Cairo
Source of Support: None, Conflict of Interest: None
Introduction A number of clinical studies that explored the role of protein Z in coronary heart disease, ischemic stroke, and deep vein thrombosis patients have been published. Particularly in ischemic stroke, patients or at least subgroups of patients with low levels (in the convalescent phase of stroke) or high levels (in the acute phase of stroke) of protein Z have been associated with increased risk of stroke.
Aim of the work This cross-sectional study aimed to investigate the role of protein Z in patients with systemic lupus erythematosus (SLE) and/or diabetes mellitus (DM) to determine the association between protein Z serum concentration and acute ischemic stroke in these patients.
Patients and methods The study was carried out on selected 40 stroke patients divided into 20 patients with SLE and 20 without SLE, who were further divided equally into diabetic and nondiabetic patients. Assessment included demographic data (age, height, weight, and BMI), clinical examination, laboratory investigations including complete blood count, erythrocyte sedimentation rate, HbA1c, lipid profile, protein Z level, MRI-brain, and extracranial carotid duplex ultrasound.
Results As regards protein Z levels, it was 4.4 ± 0.6 μg/ml in group I (DM+SLE), 3.0 ± 0.8 μg/ml in group II (SLE + no DM), 2.6 ± 0.8 μg/dl in group III (no SLE, no DM), and 1.1 ± 0.6 μg/dl in group IV (no SLE + DM), which demonstrated a significant difference between the four groups, with the highest protein Z serum level in group I.
Conclusion Our study demonstrated an independent association between increasing blood levels of protein Z in SLE rather than in DM patients and an increased risk for ischemic stroke. However, it remains unclear whether elevated protein Z concentrations are a cause or a consequence of ischemic stroke.
Keywords: diabetes mellitus, protein Z, systemic lupus erythematosus
|How to cite this article:|
El-Sherbeny AA, Abd El-Hadi EA, Maher MM, EL-Saadny HM, El-Aidy DA, Gameel M, Abd El-Aziz MA. Protein Z serum levels as a risk factor for acute ischemic stroke in patients with systemic lupus erythematosus: a comparison with diabetic cases. Egypt J Haematol 2015;40:138-42
|How to cite this URL:|
El-Sherbeny AA, Abd El-Hadi EA, Maher MM, EL-Saadny HM, El-Aidy DA, Gameel M, Abd El-Aziz MA. Protein Z serum levels as a risk factor for acute ischemic stroke in patients with systemic lupus erythematosus: a comparison with diabetic cases. Egypt J Haematol [serial online] 2015 [cited 2019 Dec 15];40:138-42. Available from: http://www.ehj.eg.net/text.asp?2015/40/3/138/164734
| Introduction|| |
Protein Z (Prot-Z) is a single chain vitamin K-dependent phospholipid-binding protein synthesized by the liver, showing wide homology with many coagulation factors such as VII, IX, X, and protein C  . Bovine form of Prot-Z promotes thrombus formation (with resultant bleeding upon its deficiency). In contrast, the human form of Prot-Z suppresses thrombus formation by inhibition of factor Xa through the Prot-Z-dependent protease inhibitor, which circulates in the human plasma in a complex with Prot-Z. Therefore, low human Prot-Z levels have been reported in patients with thromboembolic diseases (venous or arterial thrombosis), adverse obstetric history, in patients with antiphospholipid antibodies, and in peripheral arterial diseases (being associated with occurrence and severity of atherosclerotic peripheral arterial disease) , .
Moreover, when combined with factor V Leiden genotype, Prot-Z deficiency causes intrauterine and perinatal thrombosis and an apparent consumptive coagulopathy. Polymorphisms in the Prot-Z gene may affect Prot-Z levels and thus play a role in thrombosis  . In cases of venous thrombosis, a potential association with low Prot-Z levels was only demonstrated in subgroups of patients (men and individuals older than 55 years), but no effect of a concomitant factor V Leiden genotype was detected , .
A number of clinical studies that explored the role of Prot-Z in coronary heart disease, ischemic stroke, and deep vein thrombosis patients have been published. Particularly in ischemic stroke, patients or at least subgroups of patients with low levels (in the convalescent phase of stroke) or high levels (in the acute phase of stroke) of Prot-Z have been associated with increased risk of stroke. In contrast, there are studies that claim no association between Prot-Z levels and the risk for stroke , .
Actually, the reasons why Prot-Z levels are decreased in patients with clinical manifestations of thrombotic diseases are different and not yet determined. One possibility could be that the persistent activation of the coagulatory process is able to determine an increased consumption of such protein. Another possibility could be that Prot-Z is reduced in its synthesis by the liver and/or by other sources such as endothelial cells  .
A further option can be related to the presence of anti-Prot-Z antibodies, and another possibility could be the association between Prot-Z and some traditional risk factors. In addition, another explanation could reside on the association with the inflammatory state present in such kind of patients or the possible influence of the medical therapies  .
| Aim of the work|| |
Considering the fact that diabetes mellitus (DM) and systemic lupus erythematosus (SLE) are two independent risk factors for ischemic stroke, the aim of this study was to investigate the role of Prot-Z in stroke patients with SLE and/or DM to determine the association between Prot-Z and acute ischemic stroke and its postulated role as an additional risk factor for acute ischemic stroke.
| Patients and methods|| |
Selected 40 patients with an acute ischemic stroke diagnosed within first 7 days from onset, admitted in Ain Shams and Tanta University Hospitals, Neurology and Rheumatology Departments, between January and June 2014, were selected in the current study. All participants gave informed consent, and the study was approved by the local ethics committee. Ischemic stroke was defined as a clinical syndrome characterized by rapidly developing clinical symptoms and/or signs of focal, and at times global, loss of brain function, with symptoms lasting 24 h or greater or leading to earlier death and with no apparent cause other than that of vascular origin, with MRI-brain scan showing evidence of a recent infarct in the clinically relevant area of the brain (performed within 2 weeks of the event). They were divided into two groups: the first group included 20 patients with SLE fulfilling 1982 ACR criteria for the classification of SLE, and the second group included 20 age-matched and sex-matched patients without SLE. Each of the two groups was equally subdivided into diabetic and nondiabetic patients. Plasma Prot-Z levels were measured with a commercially available sandwich enzyme-linked immunosorbent assay within 7 days of the onset of the acute ischemic stroke. Prot-Z values were calculated from a standard curve provided by the kit and expressed in range between 1 and 4/ml. The interassay variation calculated from the values of normal plasma was satisfactory (coeffient variant (CV) = 4.6%). We considered Prot-Z deficiency at levels less than 1 μg/ml. Assessment also included demographic data (age, height, weight, and BMI), clinical examination, laboratory and radiologic investigations, including complete blood count, erythrocyte sedimentation rate, HbA1c, lipid profile, MRI-brain, and extracranial carotid duplex ultrasound.
Patients with antiphospholipid syndrome, a history of smoking, cardiac diseases, hypertension, peripheral vascular diseases or other thrombophilic disorder as a risk factor for ischemic strokes, and patients taking oral anticoagulants at the time of stroke, which can affect Prot-Z levels, were excluded from the study.
All data were analyzed using software (version 11; SPSS Inc., Chicago, Illinois, USA). Baseline characteristics were presented as mean ± SD for continuous variables and as frequency and percentage for the discrete ones. Comparisons between groups were carried out using analysis of variance. Correlation between variables was examined using Pearson's correlation coefficient. Multiple linear regression analysis was used to determine the independent predictors of serum Prot-Z levels. A P value less than 0.05 was considered statistically significant.
| Results|| |
Forty patients diagnosed clinically and radiologically as acute ischemic stroke patients within 7 days from onset were selected in a hospital-based study. They were divided into four groups: group I patients had SLE with DM, either with a history of diabetes or diagnosed during the presentation; group II patients had SLE without DM; group III patients had the diagnosis of neither SLE nor DM; and group IV patients did not have the diagnosis of SLE but had DM. [Table 1] shows demographic and baseline characteristics of the study patients. The mean age of groups I, II, III, and IV patients was 50.3 ± 6.8, 51.4 ± 6.7, 48.8 ± 7.6, and 48.7 ± 9.2, respectively. As regards sex distribution, there was no significant difference in male-to-female ratio between the four groups. It was 2: 8, 2: 8, 3: 7, and 2: 8, respectively. BMI was 41.6 ± 6.1 in group I, 41.5 ± 6.5 in group II, 40.9 ± 6.9 in group III, and 38.9 ± 8.6 in group IV, which showed no significant difference between the four groups.
Fasting glucose level was 159.7 ± 34.5 mg/dl in group I, 81.2 ± 14.8 mg/dl in group II, 84.9 ± 14.3 mg/dl in group III, and 163.9 ± 23.7 mg/dl in group IV. HbA1c level was 9.3 ± 1.3 g/dl in group I, 5.3 ± 0.5 g/dl in group II, 5.7 ± 0.4 g/dl in group III, and 9.5 ± 1.4 g/dl in group IV. Established normal range for Prot-Z antigen in healthy blood donor levels were found to have a wide variation, 2.9 ± 1.0 μg/ml, with a 95% confidence interval of 32-168%. There was no difference in Prot-Z levels with regard to age or sex ([Table 2]).
As regards Prot-Z levels, it was 4.4 ± 0.6 μg/ml in group I, 3.0 ± 0.8 μg/ml in group II, 2.6 ± 0.8 μg/dl in group III, and 1.1 ± 0.6 μg/dl in group IV. Prot-Z levels demonstrated a significant difference between the four groups, with the highest Prot-Z serum level in group I, followed by group II and group III, and the lowest was in group IV ([Figure 1]).
|Figure 1 Protein Z levels among the three groups. DM, diabetes mellitus; SLE, systemic lupus erythematosus.|
Click here to view
Carotid duplex findings among the studied groups were as follows ([Table 3]): in group I, seven patients had intimal thickening, two patients had atheromatous plaque, and one patient was normal; in group II, seven patients had intimal thickening and three patients had atheromatous plaques in carotid arteries; and in group III and group IV, four patients had intimal carotid thickening and six had normal carotid duplex study. Both intimal thickening and carotid atheromatous plaques were much evident in groups I and II.
Comparisons between carotid duplex lesions as regards serum Z protein levels are shown in [Table 4].
| Discussion|| |
Prot-Z is a vitamin K-dependent glycoprotein synthesized in the liver. The structure of Prot-Z is similar to other vitamin K-dependent coagulation factors, with highest homology to factors VII, IX, and X  . Prot-Z circulates in plasma in association with the recently characterized Prot-Z-dependent protease inhibitor  .
In the presence of Ca +2 and phospholipids, Prot-Z forms a complex with activated coagulation factor X and serves as a cofactor for the rapid inhibition of factor X. Although Prot-Z was characterized already in the 1980s, its role in normal and pathologic coagulation is still somewhat controversial. Other studies have suggested an association between Prot-Z deficiency and thrombosis. Prot-Z levels are antigenically determined by enzyme-linked immunosorbent assay. There is currently no established assay for the measurement of Prot-Z activity.
Miletich and Broze  established that, there was no difference in Prot-Z levels with regard to age or sex. Several polymorphisms were found in a healthy population and were correlated with Prot-Z levels, suggesting a partial explanation for the wide variation in its normal range  .
In our study, we found that in only two groups, groups I and II (stroke with SLE ± DM), the Prot-Z level was relatively higher compared with other groups and exceeds the normal level (4.4 μg/ml) in group I. This could be related to the possibility that Prot-Z could be considered as one of the acute phase reactants that increases during the acute phase of either the stroke or the SLE activity. This result was consistent with those of Kobelt et al.  and McQuillan et al.  , who found a significant, graded association between ischemic stroke and increasing concentrations of Prot-Z for all stroke patients, as well as stroke due to large-artery atherothrombosis. This association was independent of baseline differences between cases and controls, including age, sex, conventional vascular risk factors (hypertension, diabetes, hypercholesterolemia, and smoking), and past history of vascular events. They explained their results by the probability of considering Prot-Z one of the acute phase reactants. C-reactive protein (a well-recognized acute phase protein) is also markedly elevated during the first 7 days after acute ischemic stroke, although, unlike Prot-Z, it remains persistently elevated for at least 3-6 months, most likely as a result of persistent inflammation  .
However, in our subject selection we did not clearly specify whether the patients with SLE enrolled in the study are in activity or not. This issue needs to be clarified in further studies by performing other investigations such as C-reactive protein, C3, C4, and antibody titer to verify whether it is related to SLE activity or the event of acute stroke. Whether Prot-Z levels are elevated as a consequence of the acute stroke, as Prot-Z has been identified in atherosclerotic plaques and may be released into the blood during endothelial cell activation or after acute plaque rupture  ,or whether elevated levels cause stroke remains to be unclear.
It was found in our study that atheromatous plaques were found in group I (DM+SLE) (20%) and group II (30%). This could be explained in group I by the possible role of DM together with vasculitis in the pathogenesis of plaque formation, whereas intimal thickening was found among the four groups.
Our results were in contrast to those reported by Vasse et al.  and Heeb et al.  ,who stated that low Prot-Z levels were associated with an increased risk for ischemic stroke. We found in our study that the group with DM without SLE (group IV) had relatively less Prot-Z levels. This puts forth the question whether or not DM lowers the level of Protein Z. This was in disagreement with the findings of Heeb et al.  , who found that low plasma Prot-Z values were significantly associated with ischemic stroke, except in diabetic and female participants. This may need further studies with larger patient sample.
Lopaciuk et al.  and McQuillan et al.  found no correlation between Prot-Z levels and history of ischemic stroke. Lichy et al.  investigated polymorphisms in the Prot-Z gene in patients with a history of ischemic stroke. They found a significantly lower frequency of the A allele of intron F polymorphism in the group of patients compared with controls. This polymorphism was associated with decreased Prot-Z levels in the healthy controls. These results suggested that the presence of this polymorphism may have a protective effect against stroke and that high Prot-Z levels may represent a prothrombotic condition. A partial explanation could be the different populations that were studied. The patients in the series of Vasse et al.  were younger than those in the other studies, and patients with hyperlipidemia and hypertension were not included.
In contrast, 15-65% of patients in the other studies had at least one of these risk factors. Moreover, Kobelt et al.  suggested that Prot-Z levels are higher in hypertensive patients. Therefore, it is plausible that by excluding patients with hypertension the magnitude of Prot-Z effect will be higher.
There are several possible explanations for the divergent findings of previous studies. First, there were considerable differences in case mix and controls among the studies. Three of the previous studies included stroke patients with a mean age of less than 50 years ,, . Genetic factors may play a disproportionately greater role in the etiology and pathogenesis of stroke in selected younger patients and in certain ethnic populations and may also be an important determinant of Prot-Z levels , . Second, the time between the acute stroke event and measurement of Prot-Z levels varies among studies , and this may be an important cause of differences between studies.
Third, some studies have reported that patients with untreated hypertension, hyperlipidemia, or diabetes have higher Prot-Z levels compared with patients without these risk factors , .
Therefore, it is possible that by altering the level of these risk factors, differences in the use of antihypertensives, or lipid-lowering therapy after acute stroke may have given rise to variations in Prot-Z plasma concentrations between studies. However, the effects of these or other therapeutic interventions on Prot-Z concentrations have not been elucidated and require further study.
| Conclusion|| |
Our study has demonstrated an independent association between increasing blood levels of Prot-Z in SLE and DM and increased risk of ischemic stroke. Whether elevated Prot-Z concentrations are a cause or consequence of ischemic stroke remains unclear. Additional prospective studies with a larger patient sample should be performed to further elucidate the possible causal nature of this association.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]