|Year : 2017 | Volume
| Issue : 1 | Page : 15-22
The role of apolipoprotein E gene polymorphism in psoriatic patients and its relation to disease severity
Shawky M El-Farargy1, Ayman K Abd El-Hamid2, Ghada H. A. Neanaa MBBCh 1
1 Department of Dermatology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Biochemistry, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||06-Dec-2014|
|Date of Acceptance||18-Feb-2015|
|Date of Web Publication||25-Jul-2017|
Ghada H. A. Neanaa
Borg Al-Yocer, Shebin El-Kom, Menoufia, 32511
Source of Support: None, Conflict of Interest: None
The aim of the study was to investigate the relationship between apolipoprotein E (APO-E) gene polymorphism and psoriasis and its relation to disease severity.
APO-E is a plasma glycoprotein with known functions in plasma lipoprotein metabolism and in lipid transport within tissues. The association between APO-E alleles E2/E3/E4 and psoriasis has been reported by some authors, but others have not confirmed this.
Patients and methods
This is a comparative cross-sectional case–control study that was carried out on 55 individuals who were divided into two groups: the patient group, consisting of 40 patients who were subdivided into those with early-onset and those with late-onset disease, and the control group, consisting of 15 normal individuals. Both patients and controls underwent history taking, clinical examinations, and laboratory investigations for assessment of APO-E polymorphism by means of PCR, restriction enzymes, and gel electrophoresis, and lipid profile assessment by the colorimetric method.
APO-E genotypes E2/E3 and E3/E4 and allele E4 were significantly higher among psoriatic patients. There was no significant relation between APO-E genotypes and severity, age at onset, duration, sex, types, and sites involved. There was a highly significant increase in total cholesterol, triglycerides, and low-density lipoprotein and a highly significant decrease in high-density lipoprotein in psoriatic patients. There was a nonsignificant relation between lipid profile of the patients and severity of the disease with a significant increase in the lipid profile with allele E4.
The apolipoprotein polymorphism is significantly associated with the pathogenesis of psoriasis, with no relation to disease severity, age at onset, duration, sex, types, and sites involved. The lipid profile is significantly different in psoriatic patients compared with normal subjects but with no relation to severity of the disease and with a relation to the gene allele E4.
Keywords: apolipoprotein E, gene polymorphism, lipid profile, psoriasis, psoriasis severity
|How to cite this article:|
El-Farargy SM, Abd El-Hamid AK, Neanaa GH. The role of apolipoprotein E gene polymorphism in psoriatic patients and its relation to disease severity. Menoufia Med J 2017;30:15-22
|How to cite this URL:|
El-Farargy SM, Abd El-Hamid AK, Neanaa GH. The role of apolipoprotein E gene polymorphism in psoriatic patients and its relation to disease severity. Menoufia Med J [serial online] 2017 [cited 2019 Apr 18];30:15-22. Available from: http://www.mmj.eg.net/text.asp?2017/30/1/15/211527
| Introduction|| |
Psoriasis is a chronic skin disease affecting 1–3% of the population worldwide. Chronic plaque psoriasis, the most common clinical variety, has an important genetic component .
Apolipoprotein E (APO-E) is a plasma glycoprotein with known functions in plasma lipoprotein metabolism and lipid transport within tissues. It is synthesized by the liver, macrophages, and the central nervous system . It is implicated in psoriasis by providing protection against some infections, and by modulating mitogen-activated T-lymphocyte proliferation surrounding CD83+ mature dermis dendritic cells, eventually producing chemokines that activate T lymphocytes .
The APO-E gene is located on the chromosomal locus 19q13, and polymorphism at the APO-E locus results in three common alleles, designated E2, E3, and E4, corresponding to three isoforms (E2, E3, E4, respectively) of the APO-E protein, which can be isolated by isoelectric focusing . The association between APO-E E2/E3/E4 and psoriasis has been reported by some authors, but others have not confirmed this association . The aim of this study was to investigate the relationship between APO-E gene polymorphism and psoriasis and its relation with disease severity.
| Patients and Methods|| |
This is a comparative cross-sectional case–control study that was carried out on 55 individuals recruited from the Dermatology Outpatient Clinic, Faculty of Medicine, Menoufia University, spanning the period from March 2011 to July 2014. The participants of the study were divided into two groups:
- Patient group: This included 40 patients (cases) with three clinical varieties of psoriasis: 20 patients with psoriasis vulgaris, 10 with guttate psoriasis, and 10 with pustular psoriasis. They were divided into two subgroups:
- Subgroup 1: 18 patients with early-onset psoriasis (onset <30 years).
- Subgroup 2: 22 patients with late-onset psoriasis (onset >30 years).
- Control group: This included 15 age and sex-matched normal individuals who were selected as healthy volunteers.
Psoriatic patients and controls with accompanying diseases in which the APO-E polymorphism has been reported as a risk factor – for example, Alzheimer's disease, Parkinson's disease, traumatic brain injury, multiple sclerosis, atherosclerosis, coronary artery disease, Down's syndrome, diabetic nephropathy, diabetic retinopathy, and hyperlipoproteinemia type III – were excluded from the study. Every individual signed an informed consent form for participation in the study.
Patients were subjected to full history taking, including personal history (name, age, and sex), present history (duration, site, age at onset, previous medications, associated dermatological or systemic disease), and family history of psoriasis.
Complete clinical examination was performed on every participant, including general examination and dermatological examination to assess the distribution, morphology, and severity of psoriasis using the Psoriasis Area and Severity Index (PASI) score:
PASI = 0.1(Eh+ Ih+Dh)Ah + 0.2(Eu + Iu +Du)Au + 0.3(Et+ It+ Dt)At+ 0.4(E1+ I1+ D1)A1.
- In the PASI score, four main body areas are assessed: the head (h), accounting for 10% of the body surface area (BSA), the upper limbs (u), accounting for 20% of BSA, the trunk (t), accounting for 30% of BSA, and the lower limbs (l), accounting for 40% of BSA.
- Erythema (E), induration (I), and desquamation (D) are classified into five grades: grade 0, none; grade 1, mild; grade 2, moderate; grade 3, severe; and grade 4, very severe.
- The area (A) affected is classified into six grades based on the extent of the lesions: grade 1, more than 10%; grade 2, 10–29%; grade 3, 30–49%; grade 4, 50–69%; grade 5, 70–89%; and grade 6, 90–100%.
- Patients were classified on the basis of their PASI score, as in the study by Schmitt and Wozel , as follows: patients with mild psoriasis, PASI less than 7; those with moderate psoriasis, PASI 7–12; and those with severe psoriasis, PASI more than 12.
Venous blood of 5–10 ml was drawn from the cubital vein of every participant (the patients had been fasting for 12 h). Five milliliters were transferred slowly into a vacuumed EDTA tube for isolation of white blood cells for genotyping. The remaining was transferred slowly into a plain tube for determination of serum lipid profile.
- Assessment of APO-E polymorphism by PCR and restriction enzymes:
- Isolation of peripheral blood mononuclear cells: Lymphoflot (BTL Industries, Inc USA) solution has a higher density than platelets, lymphocytes, and monocytes, but a lower density than erythrocytes and granulocytes. Diluted blood is layered onto the density gradient. During the centrifugation procedure that follows, erythrocytes and granulocytes pass through the density gradient medium because of their higher density, whereas platelets, lymphocytes, and monocytes settle above the density gradient because of their lower density.
- DNA extraction using QIAamp DNA Blood Mini Kits: QIAamp DNA Blood Mini Kits (Qiagen, Germany) provide fast and easy methods for purification of total DNA from whole blood, plasma, serum, or buffy coat for reliable PCR. The simple QIAamp spin procedure is ideal for simultaneous processing of multiple samples, and yields pure DNA ready for direct amplification.
- Detection of APO-E gene by means of the following:
- PCR: 10′ Qiagen PCR buffer, dNTP mix, and primer solutions were thawed at room temperature before use. Taq DNA polymerase was kept at −20°C until use. A master mix was prepared. The amount was multiplied by the number of samples in each run forming the master mix of the run. The master mix was mixed thoroughly, and appropriate volumes were dispensed into PCR tubes. Template DNA was added (10 μl) to the individual tubes containing the master mix to reach a final volume of 25 μl. PCR amplification was performed using Perkin Elmer Thermal Cycler 2400.
- Gel electrophoresis: 2% agarose was boiled in a microwave oven and the gel was then poured into a mold to solidify. In the microwell plate, 10 μl of PCR product with 2 μl of loading dye (mixed well with frequent pipetting) was added. A volume of 5 μl of 100-bp ladder was used. A run for 30 min at 125 V was performed. The agarose gel was visualized under UV light.
- APO-E gene typing by means of the following:
- Two restriction enzymes (restriction fragment length polymorphism technique): Hae II (New England Biolabs, Hitchin, UK) and Afl III (New England Biolabs) [Table 1] and [Figure 1]
- Gel electrophoresis: 4% agarose gel was prepared as follows: 2 g agarose powder was dissolved in 50 ml of 0.5× TBE buffer and boiled in a microwave oven; the gel was then poured into a mold to solidify. In the microwell plate, 25 μl of PCR product with 2 μl of loading dye (mixed well with frequent pipetting) was added. A volume of 5 μl of ladder of ØX174 RF DNA was used. A run for 60 min at 125 V was performed. The agarose gel was visualized under UV light.
Assessment of lipid profile: It included assessment of serum total cholesterol, serum triglycerides, high-density lipoprotein (HDL)-cholesterol, and low-density lipoprotein (LDL)-cholesterol by the colorimetric method, using human kits supplied by Spinreact.
|Table 1 Apolipoprotein E gene typing using two restriction enzymes (restriction fragment length polymorphism technique)|
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|Figure 1: Apolipoprotein E gene typing using two restriction enzymes (restriction fragment length polymorphism technique). |
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Primary outcome measures
They included variation of APO-E genotypes and alleles between patients and controls and their relation with severity, age at onset, duration, sex, types, and sites of psoriasis.
Secondary outcome measures
They included assessment of the lipid profile of patients and controls and their relation with severity of the disease and different APO-E genotypes.
Data were statistically described in terms of range, mean, SD, median, frequencies (number of cases), and percentages when appropriate. Comparison of quantitative variables between the study groups was made using the t-test. The Kruskal–Wallis test was used when there was one nominal variable and one ranked variable. For comparing categorical data, the c 2-test was conducted. The exact test was used when the expected frequency was less than 5. A P value less than 0.05 was considered statistically significant. Odds ratios were calculated when needed.
| Results|| |
The current study included 55 participants who were distributed as 40 patients (17 male and 23 female patients), with a mean age of 42.42 ± 11.72 years, and 15 individuals who acted as normal controls (seven male and eight female individuals), with a mean age of 39.0 ± 4.10 years. There was no statistically significant difference between the two groups regarding age and sex (P = 0.12 and 0.78, respectively). There was significant family history among psoriasis patients (P = 0.02) [Table 2].
The proportion of individuals with genotype E3/E3 was higher among controls than among psoriatic patients (73.3 vs. 30%, respectively) and it was considered as a reference genotype, whereas the prevalence of E2/E3 and E3/E4 genotypes was significantly higher among psoriatic patients than among controls (P = 0.04 and 0.05, respectively). E2/E3, E2/E4, and E3/E4 genotypes increase the risk of occurrence of psoriasis, with odds ratios 5.5, 5.5, and 7.33, respectively. Thus, the E3 allele was more prevalent among controls than among patients (88.3 vs. 55%, respectively), whereas E2 and E4 alleles were more prevalent among patients (22.5 vs. 10% and 22.5 vs. 6.7%, respectively) with statistical significance for E4 (P = 0.02) [Table 3].
There was no significant relation between APO-E genotypes and severity of the disease in patients (P > 0.05 for all genotypes) [Table 4]. There was no significant relation between APO-E genotypes in patients and age at onset of the disease (P > 0.05 for all genotypes) [Figure 2]. There was no relation between different genotypes and age, duration, sex, types, and sites involved (P>0.05 for all parameters) [Table 5].
|Table 4 Distribution of apolipoprotein E genotypes in patients and their relation to severity of psoriasis|
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|Figure 2: A bar graph representing the relation between apolipoprotein E (APO-E) genotypes and age at onset of psoriasis (P > 0.05 for all genotypes).|
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|Table 5 Sociodemographic and clinical criteria in relation to apolipoprotein E genotypes among cases|
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There was a very highly significant increase in total cholesterol, triglycerides, and LDL, and a very highly significant decrease in HDL in psoriatic patients compared with controls (P < 0.001 for all measures) [Figure 3]. There was a nonsignificant relation between lipid profile of the patients and severity of the disease [Figure 4]. By observation of the relationship between the different genotypes and lipid profile, there was a statistically significant increase in levels of total cholesterol, triglycerides, and LDl. However, HDL showed no significant difference between the different genotypes (P = 0.79) [Table 6].
|Figure 3: A bar graph showing the comparison between patient and control groups regarding different measurements of lipid profile (P < 0.001 for all measurements). HDL, high-density lipoprotein; LDL, low-density lipoprotein.|
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|Figure 4: A bar graph showing the relation between the lipid profile of patients and severity of the disease (P > 0.05 for all measurements). HDL, high-density lipoprotein; LDL, low-density lipoprotein; PASI, Psoriasis Area and Severity Index.|
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|Table 6 Lipid profile in relation to apolipoprotein E genotypes among cases|
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| Discussion|| |
Psoriasis is a chronic and recurrent inflammatory skin disease characterized by infiltration of inflammatory cells into the epidermis and by altered keratinocyte differentiation . It affects ∼2% of the population and exerts a lifelong burden on those affected . Psoriasis affects both sexes equally and can appear at any age .
Although many theories have been put forth in the pathogenesis of psoriasis, it is yet to be fully understood. It had been suggested that psoriasis is a T-cell-mediated autoimmune disorder, in which activated T cells produce cytokines. The cytokines stimulate keratinocyte proliferation as well as production of antigenic adhesion molecules in the dermal blood vessels .
The inheritance pattern of psoriasis is still unclear, but there is strong evidence of a genetic predisposition of the disease . The risk of developing psoriasis in first-degree relatives of affected subjects is about 10 times greater than that in the general population . The present study was carried out to investigate the relationship between APO-E gene polymorphism and psoriasis and its relation to the severity of the disease.
The current study showed no significant difference between case and control groups regarding age and sex, revealing homogeneity of the study groups and nullifying the possible effect of age and sex on the disease process.
In the present study, there was a significant positive family history of psoriasis among patients. This is in agreement with the results of Ko et al. , who reported that in about one-third of cases psoriasis is inherited. Epidemiologic studies showed that between 4.4 and 41% of psoriasis patients report a positive family history of the disease.
In the current study, the genotypes E3/E3 and allele E3 were significantly higher in the control group and were considered as references. Genotypes E2/E3 and E3/E4 were significantly higher among psoriatic patients than among controls. APO-E alleles E2 and E4 were higher among patients, with statistical significance for E4. These findings are consistent with the results of Han et al. , who collected the APO-E allele and genotype distribution data published and then pooled the genetic data according to Asian and European populations. They showed that APO-E polymorphisms were associated with psoriasis. Allele E2 was associated with increased susceptibility for psoriasis; however, allele E3 may decrease psoriasis risk. In addition, allele E4 may be a risk factor for psoriasis in European populations . Also, Karpouzis et al.  reported a higher frequency of the E2 allele and predominance of the E2/E3 genotype in the entire psoriasis vulgaris group, as well as in the late-onset psoriasis vulgaris subgroup when compared with matched controls. Zhang and Wu  reported that APO-E E4 was associated with psorasis, and may act as a therapeutic target in the future. In contrast, Coto-Segura et al.  found a nonsignificantly higher frequency of APO-E E4 carriers (E3/E4, E4/E4, and E2/E4 genotypes) among patients (0.20 in patients vs. 0.15 in controls). But they suggested that APO-E E4 could be a risk factor for developing a severe form of psoriasis . The difference with Coto-Segura et al. can be explained by population differences and different sample sizes.
In the current study, there was no significant relation between APO-E genotypes and severity, age at onset, duration, sex, types, and sites involved. However, these findings are against the findings reported by Coto-Segura et al. , who found that APO-E E4 carriers were significantly more frequent in patients with severe psorasis compared with controls (P = 0.003) and with patients with nonsevere psoriasis (P = 0.017). They stated that the APO-E E4 allele could be a risk factor for developing a severe form of psoriasis . Also, Karpouzis et al.  found that allele E2 is significantly more frequent in late-onset psoriasis vulgaris (P = 0.029). Imamura et al.  found a tendency for higher frequencies of E3/E2 and E2 in patients with early onset than in those with late onset, in those with severe type than mild or moderate type, and in patients with a universal form of plaque-type eruption and guttate form than in those with localized form of plaque-type eruption. These differences fell short of statistical significance. The difference between the current study and all of these studies is attributed to the different ethnic and population characteristics of the different study groups and the small sample size in the current study.
In the present study there was a highly significant increase in total cholesterol, triglyceride, and LDL and a highly significant decrease in HDL in psoriatic patients compared with controls. This is in agreement with the results of Akhyani et al. , who reported that high serum lipid level was significantly more common in psoriasis. This fact may be responsible for the higher prevalence of cardiovascular accidents in psoriatic patients. It may be beneficial to perform early screening and treatment of hyperlipidemia in psoriatic patients to prevent atherosclerosis and its complications .
Pietrzak et al.  reported that in most of the studies a statistically significantly elevated level of total cholesterol, LDL-cholesterol, and/or triglycerides was demonstrated in psoriatic patients compared with healthy controls. Moreover, there was a decrease in HDL-cholesterol in the serum of psoriatic patients . In another study by Mallbris et al. , it was found that serum very low-density lipoprotein (VLDL)-cholesterol levels were significantly higher in psoriatic patients. Unchanged LDL-cholesterol and increased HDL-cholesterol levels were found in serum samples obtained from psoriatic patients compared with controls . Only a few studies showed no differences in lipid serum levels between psoriatic patients and healthy controls. Toker et al.  reported that there was no significant difference between psoriatic patients and healthy controls with respect to HDL-cholesterol, LDL-cholesterol, and VLDL-cholesterol.
In our study there was a nonsignificant relation between the lipid profile of patients and severity of the disease. This coincides with the results of Toker et al. , who reported that there was no significant correlation between lesion percentage and the lipid profile parameters studied. In the current study, there was a statistically highly significant increase in the levels of total cholesterol, triglycerides, and LDL regarding the following Apolipoprotein E genotypes and alleles; E3/E3, E2/E3, E2/E4, E3/E4 and E4/ E4.
| Conclusion|| |
Apolipoprotein polymorphism is significantly associated with the pathogenesis of psoriasis, with no relation to disease severity, age at onset, duration, sex, types, and sites involved. The lipid profile is significantly different in psoriatic patients compared with normal subjects but there is no relation to severity of the disease and is related to the gene allele E4.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]