Abstract effects. The level of significance was set

Abstract

Background and Objective:
Systemic lupus erythematosus (SLE) is an autoimmune disease with various organs
being involved. Vitamin D is an essential ingredient in regulating the immune
system. This study aimed to investigate the relationship between vitamin D and
the severity of lupus activity.

Materials
and Method: This case-control study was
carried out on 38 patients with lupus on the basis of the ACR criteria and 44
healthy subjects with no history of rheumatology disease. To
measure the level of 25-hydroxy vitamin D, venous blood samples (5 cc) were
taken from each participant. The activity of the lupus disease was measured by
SLEDAI scale. Chi-square, independent sample t-test, one-way ANOVA and multiple
linear regression analysis were used to measure multivariate effects. The level
of significance was set to be P <0.05. Results: Thirty-five lupus patients and 40 healthy subjects were female (P = 0.847). The vitamin D deficiency was observed in the case group (42.1%) and control group (11.4%). The mean value of serum vitamin D3 level was 35.3 ng/ml in the control group, 24.6 ng/ml and 21.3 ng/ml in patients with mild and  severe SLE, respectively(P = 0.024). Conclusion: In this study, high levels of 25-hydroxy vitamin D were observed among the healthy subjects, compared to the patients with SLE. Also, the level of vitamin D significantly decreased with increasing severity of SLE activity. Key words: Systemic lupus erythematosus, Vitamin D, 25-hydroxy vitamin D, SLE activity   Introduction Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with various organs being involved. It has different clinical manifestations from a skin and simple dermatologic and joint signs to life-threatening disorders such as renal, cardiovascular and neurological complications. The most important manifestation of this disease is renal involvement or lupus nephritis, reported in many patients (40-50%). The disease occurs throughout the world; however, its prevalence and severity varies in different societies. Over the past 50 years, the incidence of SLE has increased up to 10 times(1, 2). There is no definite cure for the disease and it is generally inhibited by corticosteroids and immunosuppressive drugs(2). Various factors including genetic background, environmental factors, gender, hormonal factors and viral infections contribute to the incidence and exacerbation of the disease. Recent studies have indicated the role of vitamin D deficiency in the development of autoimmune and malignant diseases(2). It should be noted that the individual with SLE are recommended to avoid sunlight in order for skin rash and disease exacerbation to be prevented, which reduces the serum concentration of vitamin D in these persons(3). Cholecalciferol is made from 7-dehydrocholesterol by UV rays in skin. Some foods like egg yolk and fish oil are sources of vitamin D3(4). The level of vitamin D in the body is associated with the season, with its lowest levels observed in winter and its highest levels reported at the end of the summer(5). Vitamin D is effective in regulating calcium absorption through endocrine mechanisms and in expressing gens through autocrine mechanisms(6). Vitamin D deficiency is also associated with high risk of rickets in children and osteomalacia in adults as well as bone fracture, cancer, autoimmune diseases, Infectious diseases, diabetes type I and II, hypertension, heart disease and multiple sclerosis(7). Some studies have shown that the increased vitamin D3 concentration enhances telomere length in leukocytes, resulting in longer lifespan of leukocytes and preventing inflammatory disease(8). Vitamin D metabolites and vitamin D receptors exist in a variety of cells, including immune system cells containing antigen-presenting cells, T lymphocyte cells, B lymphocyte cells and monocytes. Recent studies have shown the direct effects of calcitriol on the homeostasis of B cells, such as the inhibition of memory and plasma cells production and an increase in the apoptosis of antibody-producing B cells. Such a cellular immune control is of paramount importance in autoimmune diseases(5). Various studies have reported low levels of vitamin D in SLE patients compared to non-SLE patients(9, 10). A study also claimed a reduction in vitamin D as a risk factor for SLE patients and found that its enhanced reception prevents SLE and rheumatoid arthritis(11, 12). In some studies, there was a reverse relationship between serum vitamin D3 levels and SLE activity (11, 13, 14). On the other hand in some studies, the vitamin D deficiency was not associated with the duration of the disease and its severity(2, 3). Because of limited studies and inconsistent findings on the relationship between serum vitamin D levels and the SLE activity and since this disease causes a lot of complications for the patient, the current study was to determine the relationship between vitamin D level and SLE activity. If such a relationship is proved, treatment with vitamin D is much easier than treatment with immunosuppressive drugs.   Materials and Method Design: This case-control study was carried out on 38 patients with SLE on the basis of the ACR criteria and 44 healthy subjects with no history of rheumatologic diseases. The participants in the control group were referring from the Internal Medicine Clinics, had no diagnosed rheumatologic and autoimmune diseases, receive no vitamin D supplementation and were at the pre-menopausal age. Data collection method: All participants were included in the study after being evaluated clinically and laboratory and receiving sufficient description by the physician and having informed consent, Venous blood samples (5 cc) were taken and sent to a laboratory in order for their 25-hydroxy vitamin D level and serum creatinine to be measured. 25-hydroxy vitamin D was measured by Corgeh Mix kit (made in Germany) through using ELISA method. D3 levels above 30 ng/ml, 30-16 ng/ml and below 15 ng/ml were considered as normal, insufficiency  and deficiency(15, 16). The creatinine level was measured with Pars Azmoon kit (made in Iran) through using biochemical method. The activity of SLE was calculated using the standard SLEDAI instrument, based on clinical and laboratory findings. Regarding this scale, the scores below 6, 6-12 and above 12 were also considered as inactive, mild and severe diseases, respectively. Data analysis: First, Kolmogorov-Smirnov test was employed to test the normality of vitamin D3 and blood creatinine data. Then, the mean and standard deviation of these indices were calculated and independent t- test was run. Chi-square and Fisher's exact tests were used to examine the relationship between qualitative variables. Multiple linear regression analysis were used to measure multivariate effects   Results  This study was performed on 38 patients with SLE as the case group and 44 healthy subjects as the control group. Three subjects (9.1%) in the control group and 3 cases (7.9%) in the SLE group were male (P = 0.847). The mean ages of the participants in the control and case group were 34.9 ± 15.9 and 35.7 ± 11.9 years, respectively (p=0.787). The mean serum creatinine level was 0.93 in the case group and 0.85 in the control group (P = 0.013). The subjects in the case group had vitamin D3 deficiency (42.1%) and vitamin D3 insufficiency (28.9%). The corresponding values in the control group were 11.4% and 47.7%, respectively (P = 0.006) (Table 1). The most common clinical signs were as follows: Arthralgia (36.8%), arthritis (31.6%), photosensitivity (31.6%), anemia (71.1%) and edema (23.7%). Moreover, the most common paraclinical findings were AntidsDNA (84.3%), ANA (81.4%), complement deficiency, positive antiphospholipid and high ESR (18.4%) (Figure 1). In patients with severe and mild SLE, vitamin D3 deficiency was observed in 46.7% and 39.1% of patients, respectively. There was a statistically significant relationship between the severity of the disease and the vitamin D3 level (P = 0.026). The mean serum vitamin D3 level was 35.3 ng/ml in the control group, 24.6 and 21.3 ng/ml in patients with mild and severe SLE respectively. Also, there was a significant difference between these groups regarding the vitamin D3 level (P = 0.024) (Table 2). Additionally, multiple linear regression analysis was used for multivariate analysis. The results of this model reflected the significant effects of the disease on the vitamin D level, indicating that the severity of the disease enhances as the vitamin D level decreases (B = -7.019). This model had a relatively high explanatory power (Adjusted R Square= 0.64) (Table 3).   Discussion In this study, serum vitamin D3 level and the disease activity were compared in 38 patients with SLE and 44 healthy individuals. The vitamin D3 deficiency was diagnosed in 42.1% of patients and 11.4% of healthy subjects (P = 0.006). The mean serum vitamin D3 level was 23.3 ng/ml for the patients and 35.3 ng/ml for the healthy group. Although these values were 24.6 ng/ml and 21.3 ng/ml in patients with mild and severe SLE. Significant difference was observed between the groups regarding the vitamin D3 level (P = 0.024), showing a significant relationship between vitamin D3 level and SLE activity. In addition, there was no relationship between vitamin D deficiency and the levels of albumin, Creatinin, hemoglobin, AntidsDNA titer  and complements level (C3, C4, CH50) (P >0.05),
Photosensitivity was also reported in 31.6% of patients.

Some studies supported the relationship between vitamin D3
deficiency and SLE. Toloza et al. (2010) conducted a study on patients with SLE
and found a correlation between vitamin D deficiency and clinical
manifestations and SLE disease activity(3). In the present study, the high prevalence of vitamin D deficiency
in patients (42.1%) and its low prevalence in healthy subjects (11.4%) can
highlight the role of vitamin D3 in the pathogenesis and severity of SLE
disease.

In Toloza’s et al. study, vitamin D3 deficiency and insufficiency were
reported in 17.9% and 66.7% of patients(3). In Anna Abou-raya’s (2013) study, the mean vitamin D level was
19.8 ng/ml among the patients and 28.7 ng/ml in the control group(12). Ruiz -Irastorza et al. (2008) examined 92 SLE patients, of whom
75% had vitamin D3 deficiency and 15% had vitamin D3 insufficiency.
Photosensitivity was also observed in 68% of the patients(17).

The prevalence of vitamin D3 deficiency in the Ruiz–Irastorza’s et
al. study was greater than that in this study. This can be due to the high
photosensitivity reported in the present study. Reduced photosensitivity can
provide more exposure to sunlight and reduce the likelihood of vitamin D3
deficiency(2).

Szodoray et al. (2011) conducted their study on 177 patients with SLE and
found that the mean vitamin D3 level was 13.2±6.28 ng/ml. The prevalence
of vitamin D3 insufficiency and deficiency was observed in 44.6% and 37.3% of
the patients(18). These findings are consistent with the findings of the present
study. In a systematic review (2013), the relationship between vitamin D3
deficiency and SLE was highlighted and sufficient evidence was presented to
support the correlation between vitamin D3 and SLE; however, the relationship
between vitamin D3 deficiency and other clinical features of the disease should
be concerned in future studies(19).

There are some inconsistencies regarding the findings of some
studies conducted to determine the relationship between vitamin D3 level and
the SLE activity. For example, Bonakdar et al. (2011) observed a significant
relationship between vitamin D3 deficiency and SLE activity at the onset of the
disease and a more severe vitamin D3 deficiency with low albumin and hemoglobin
levels and a higher Antids DNA titer(20). In Kim’s et al. (2010) study, there was no association between
serum vitamin D3 level and disease activity with respect to the SLE Disease
Activity Index and Antids DNA level, even though, a positive correlation was
found between the vitamin D3 level and hemoglobin and complement(21). Ruiz-Irastorza et al. (2008) noticed no significant relationship
between the vitamin D3 level and the severity of SLE but a significant
correlation between vitamin D3 deficiency and fatigue(17).
Furthermore, the present study examined the effects of disease severity on
vitamin D3 level by eliminating the effect of confounder factors using multiple
linear regression models. The only factor affecting the vitamin D3 level in
this model was the severity of SLE activity. In other words, it can be
concluded that decrease in vitamin D3 level leads to an increase in the disease
severity. Differences in the vitamin D3 level for the SLE and healthy groups
can be the result of the high prevalence of photosensitivity in SLE patients,
high use of sunscreen and the consumption of steroid for the treatment and
control of the disease. In Iran and other Islamic countries, women’s veils also
reduce the skin exposure to sunlight, leading to higher prevalence of vitamin D3
deficiency. In order to reveal the true association between vitamin D3
deficiency and SLE disease, studies with a larger sample size and sample
homogeneity in terms of age and gender are recommended.

Of subjects, 11.4% experienced vitamin D3 deficiency and 47.7% had
vitamin D3 insufficiency however, these values were 39.1% and 34.8% in patients
with mild activity and 46.7% and 20% in patients with severe activity,
respectively. The findings implied an increased percentage of vitamin D3
deficiency as the disease activity enhances (p = 0.026). In CCMOK’s (2017)
study on 376 SLE patients, the 25-hydroxy vitamin D level was below 15 ng/ml
in 26%, 15-30 ng/ml in 54% and above 30 ng/ml in 20% of the
patients and the vitamin D3 deficiency was associated with disease severity and
its tendency to relapse(22). Cutolo (2009) measured serum vitamin D3 levels in 21 patients
with SLE activity were also assessed using ECLAM and SLEDAI. The results showed
that serum vitamin D3 level in SLE patients was lower than that in the healthy
group and the severity of SLE was inversely correlated with serum vitamin D3
level(11). In a cohort study by Amital (2010), 378 patients with SLE were
selected and the disease activity was measured using ECLAM and SLEDAI and serum
25-hydroxy vitamin D concentration was also measured in these patients. The
findings revealed a reverse relationship between serum vitamin D3 concentration
and SLE activity(13).

Conclusion

In this study, high levels of 25-hydroxy vitamin D were observed in
healthy subjects compared to patients with SLE and the vitamin D3 level
significantly decreased with a significant increase in the SLE activity.

Acknowledgements

This research was based on the results of a research project (No.
90101) approved at Kashan University of Medical Sciences. The authors would
like to express their gratitude to all patients who participated in this study.

 

Tables and Figures

Table 1: Frequency, mean and standard deviation of demographic and
clinical characteristics of the two study groups

variables

groups

P.value

case

control

(f/m) sex

35/3

40/4

N.S

Age

35.7±11.9

34.9±15.9

0.787

Creatinin

0.93±0.16

0.85±0.13

0.013

VitD3

Deficiency

16(42.1)

5(11.4)

0.006

Insufficiency

11(28.9)

21(47.7)

normal

11(28.9)

18(40.9)

mean±SD

23.3±15.8

35.3±22.4

0.007

 Severity of SLE

Mild

23(60.5)

moderate

15(39.5)

mean±SD

1.39±0.49

Disease duration

4.08±4.7

 

 

 

 

Table 2: Distribution
table of vitamin D serum level with severity of lupus

Vit D3 level

Severity of disease

mean±SD

total

sufficient

insufficient

deficiency

35.3±22.4

44

18(40.9)

21(47.7)

5(11.4)

Healthy group(control)

24.6±16.4

23

6(26.1)

8(34.8)

9(39.1)

mild

Severity of SLE

21.3±15.1

15

5(33.3)

3(20)

7(46.7)

severe

23.3±15.8

38

11(28.9)

11(28.9)

16(42.1)

case

P2=0.024

P1=0.026

P.value

 

 

Figure
1: Clinical sign and symptoms of lupus patients

 

 

 

Table
3) Regression parameters in estimation of Vit D level based on predictors

 

variables
 
 
 
 

Unstandardized
Coefficients

t
 

Sig.
 

Adjusted
R Square

B

Std.
Error

(Constant)

49.757

14.608

3.406

.001

0.64

Gender

-6.037

7.818

-.772

.442

AGE

.042

.156

.267

.790

Creatinin  level

-18.519

15.274

-1.213

.229

SLE Activity

-7.019

2.891

-2.428

.018