INTRODUCTION

 

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) that starts in most patients with a relapsing-remitting disease course. The etiology of MS is multifactorial. Both genetic susceptibility and environmental exposure contribute to the pathogenesis.¹ One of the environmental factors associated with the development of MS is vitamin D.²

Vitamin D is produced in the skin by ultraviolet radiation (UVR), is found in certain foods, and may be taken as a supplement.³ The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25-OH-D), is critical for bone metabolism, but also has important immunomodulatory properties⁴, effecting a reduction in proinflammatory immune pathways.^5,6 The major circulating form, and that used to measure vitamin D, is 25-hydroxyvitamin D (25-OH-D).⁷

There is substantial epidemiological evidence, including prospective cohort studies, indicating that higher levels of serum 25 (OH) D are associated with a lower risk of MS onset.⁸ However, the effect of vitamin D on clinical course is less clear. Here we examine whether decreasing levels of serum 25 (OH) D are associated with a higher risk of relapse of MS.

 

Aim of The Work

               The present study aims to evaluate the association between levels of serum 25 (OH) D, and the risk of relapse of MS.

PATIENTS AND METHODS

 

The present study included 22 patients, aged 18-32 years with clinically definite MS using 2005 McDonald criteria⁹, and relapsing remitting disease course, presented to neurology clinic at National Hospital and Al-Mousa Hospital KSA from January 2011 to September 2012. Patients were excluded from participation if they suffered from other serious diseases. Verbal informed consent was obtained from all patients.

Exacerbation was defined as a worsening of existing symptoms or the appearance of new symptoms lasting for more than 24 hours, after a period of more than 30 days of improvement or stability, confirmed by neurologic examination¹⁰, in the absence of fever, known infection, concurrent steroid withdrawal, or externally derived increases in body temperature.¹¹

All patients visited the outpatient clinic of the Hospital regularly every 2 months for one year. On every visit, disability was measured using the Kurtzke Expanded Disability Status Scale (EDSS).¹² Blood samples for 25 (OH) D measurements were taken, and MRI brain and/or cervical with contrast were done at the first visit and at the end of one year, as well as at the time of relapse if present. Furthermore, patients were instructed to contact the hospital when they experienced symptoms of neurologic impairment.

Serum 25(OH) D was extracted using acetonitrile and concentrations measured with a commercially available radioimmunoassay (DiaSorin Inc., Stillwater, MN; detection range: 12.5–250 nmol/L; interbatch reproducibility: 4.6% at 32 nmol/L, 6.4% at 125 nmol/L). All samples were stored at -20 °C, shielded from light. Serum 25 (OH) D levels were referred to the internationally accepted norms.¹³ The official international standard for serum 25-hydroxyvitamin D levels has been established, with norms fall between 75 and 200 nmol/l, insufficiency existing below 75 nmol/l and deficiency below 25 nmol/l.(14-21)

The MRIs were performed according to a standardized protocol comprising T2 weighted and T1 weighted gadolinium-enhancing (Gd+) scans using a standard head coil with a 1.5 Tesla MRI unit.  Radiologist evaluated scans to determine gadolinium-enhancing (GE) lesions, and total volume of T2 lesions (baseline and follow up).

 

Statistical Analysis

All data were entered into a database for later analysis using the Statistical Package for the Social Sciences (SPSS version 11.0 for Windows). Statistical significance was established at p < 0.05. For group comparisons, a non-paired two-tailed t -test was performed. For correlations, a bivariate Pearson correlation coefficients was performed.

 

RESULTS

 

The present study included 22 patients with RRMS followed for one year (Table 1). 10 (45%) patients were males, and 12 (55%) were females. Mean (±SD) age in year was 24.5 (±3.9). The mean (±SD) serum 25(OH) D at the time of inclusion to the study was 41.6 nmol/L (±17.3). The mean (±SD) baseline Expanded Disability Status Scale (EDSS) was 2.6 (±0.9). At the end of one year follow up, the mean (±SD) serum 25(OH) D was 43.4 nmol/L (±18.1), and that of EDSS was 2.7 (±0.8). Baseline and follow up serum 25 (OH) D were not significantly higher (P=0.655, and 0.862 respectively) in males (43.7±24.9, and 44.3±24.6) than females (39.9±7.5, and 42.8±11.5). Disability status scales at time of inclusion, and at the end of follow up period were higher in males (2.7±1.1, and 2.9±1.1) than females (2.5±0.6, and 2.5±0.6) but the differences were not significant (P=0.694, and P=0.429). A total of nine confirmed relapses occurred in nine participants (6 males, and 3 females) during one-year follow up.

In general patients with MS had vitamin D insufficiency (baseline serum 25 (OH) D 41.6±17.3, and follow up serum 25 (OH) D  43.4±18.1) according to the international standard for serum 25 (OH) D.^14-21 Moreover patients with confirmed relapses (Figures 1 and 2) had significantly (P=0.001, and P<0.001) lower baseline serum 25(OH) D (28.9±5.4) and follow up serum 25(OH) D (28.4±7.6) compared to patients without relapses (50.5±17.2, and 53.8±15.9 respectively). Inverse correlations were observed between baseline serum 25 (OH) D (Figure 3) and baseline EDSS (P=0.000), and follow up EDSS (P=0.001) as well as between follow up serum 25 (OH) D (Figure 4) and baseline EDSS (P=0.000), and follow up EDSS (P=0.000).

 

Table 1. Characteristics of patients.

 

Variable (n = 22)	Mean  or %	SD
Age, in year	24.5	3.9
Baseline EDSS	2.6	0.9
Follow up EDSS	2.7	0.8
Baseline serum vitamin D	41.6	17.3
Follow up serum vitamin D	43.4	18.1
Gender, female/male	55/45
Disease activity, relapse/no relapse	41/59

EDSS  Expanded Disability Status Scale

 

Table 2. Clinical and laboratory characteristics of patients with and without relapses.

 

Variable	Relapses		No relapses		P-value
	Mean	SD	Mean	SD
Age, in year	22.8	3.6	25.6	3.9	0.094
Baseline EDSS	3.1	0.9	2.3	0.7	0.031*
Follow up EDSS	3.2	0.9	2.3	0.6	0.034*
Baseline serum vitamin D	28.9	5.4	50.5	17.2	0.001**
Follow up serum vitamin D	28.4	7.6	53.8	15.9	0.000**

EDSS  Expanded Disability Status Scale, * Significant at P<0.05, ** Significant at P<0.01

 

 

Figure 1. Baseline serum 25 (OH) D level in patients with and without relapses.

 

 

 

Figure 2. Follow up serum 25 (OH) D level in patients with and without relapses.

 

 

 

Figure 3. Correlation between baseline serum 25 (OH) D level and Expanded Disability Status Scale.

 

 

 

Figure 4. Correlation between follow up serum 25 (OH) D level and Expanded Disability Status Scale

 

 

DISCUSSION

 

In this study, we found that patients with MS had lower serum levels of 25- hydroxyvitamin D than the official international standard for serum 25-hydroxyvitamin D levels. This was in accordance with the study of Soilu-Hannine and colleagues (2005) who found low serum levels of vitamin D in MS patients at the onset of the disease.²² Also,  Munger and colleagues (2006), reported a decreased  risk of MS with increasing serum levels of 25 (OH) D.³⁸ At the same time, Kargt and colleagues (2009),  found  that,  higher levels of 25 (OH) D  inversely associated with MS in women.²³ 

Our results converge with a growing body of evidence supporting a protective role for vitamin D in MS development as we found that patients with MS had vitamin D insufficiency. Vitamin D is a potent immunomodulator²⁴, and several studies have shown that administration of the biologically active hormone 1,25- dihydroxy vitamin D prevents experimental autoimmune encephalomyelitis (EAE) onset and progression in mice. ^25,26. The exact mechanisms of this protection are unknown, but evidence suggests an indirect effect, possibly mediated by regulatory T cells.^24,27 Of interest, regulatory T cells have been shown to be suppressed in individuals with MS.²⁸ An inhibitory effect of levels of 25-hydroxyvitamin D in autoimmune reactions is consistent with the accelerated onset of EAE²⁶, and experimental type 1 diabetes in vitamin D–deficient mice.²⁹ This effect could be mediated by local synthesis of 1,25-dihydroxyvitamin D from 25-hydroxyvitamin D by activated macrophages expressing 1-α- hydroxylase. If sufficient 1,25- dihydroxyvitamin D is produced, it may exert paracrine effects on surrounding T lymphocytes, thereby regulating the tissue-specific immune responses.²⁴

In the present study, we show that lower 25-OH-D levels were significantly associated with a higher relapse risk in patients with relapsing-remitting MS. This was in accordance with the study of Soilu-Hanninen and colleagues (2005) where the relative risk of remaining relapse-free within the previous 2 years before diagnosis increased by 51% for each 10 nmol/L increase of 25(OH) vitamin D level.(22) Similarly, in a large prospective longitudinal study in relapse-remitting MS an increase in serum 25(OH) vitamin D levels with 10 nmol/L was associated with a 9% to 12% risk reduction for relapses.³⁰

Furthermore, results reproduced within a pediatric population study exhibit a 14% decrease in relapsing risk for each 10 nmol/L increase in vitamin D status.³¹ More recently Runia and colleagues (2012) reported a similar relation between lower 25-OH-D levels and the higher exacerbation risk in patients with relapsing-remitting MS³². There is biological plausibility for vitamin D as a protective factor against relapses. 1,25-OH-D shifts the immune response away from a proinflammatory profile and enhances anti-inflammatory pathways in multiple settings^5,6,33; furthermore, a correlation between serum 25-OH-D concentrations and a more anti-inflammatory Th1/Th2 ratio has been found.³⁴

In addition, we observed a negative correlation between 25(OH) D serum levels and EDSS. This was in agreement with the recent study of  Kragt and colleagues (2009), who found the same tendency.²³ Also, the effect of vitamin D levels and disability status in MS was evaluated in cross-sectional studies reporting a negative correlation between vitamin D levels and the Expanded Disability Status Scale (EDSS), the most widely accepted disability scale in MS studies.^35,36 This correlation may be mediated through a genetic regulation of vitamin D metabolism in patients with MS^37,38, in particular in the HLA system^39,40, and the influence of a vitamin D receptor gene polymorphism on disability.^39,41

 

Conclusion

               The result of this study concludes that low vitamin D level is a risk for MS onset, more over low vitamin D level increased the incidence of relapses and associated with more severe disease.

 

[Disclosure: Authors report no conflict of interest]

 

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