6. Clinical applications


6. Immune system and vitamin D: Vitamin D is a potent immunomodulator. 1,25 (OH)2D decreases the maturation of dendritic cells (DCs) decreasing their ability to present antigen and to activate T cells [23]. Furthermore, it suppresses production of IL-12 (important for Th1 development), IL-23, and IL-6 (important for Th17 development) [24]. But, there is no any approved vitamin D drug for immune modulation [1]. Studies have suggested an association of vitamin D with autoimmune diseases like multiple sclerosis [25] and asthma [26].

8. SLE

Figure 2.

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Vitamin D deficiency is quite prevalent in SLE patients which may be attributable to various reasons. Avoidance of sunshine, photoprotection, renal insufficiency, and the use of medications which alter the metabolism of vitamin D or downregulate the functions of the vitamin D receptor like glucocorticoids, anticonvulsants, antimalarials, and the calcineurin inhibitors are some of the causes of VDD as shown in Figure 2 [37]. In a study by Toloza, vitamin D insufficiency was found in 66.7% and deficiency in 17.9% of SLE patients [38]. The frequency varied in different studies: Saudi Arabia (89.7%) [39], Norway (82%) [40], Poland (71%) [41], Hong Kong (27%) [42], and the United States (20%) [43]. Low serum vitamin D levels were related to cumulative glucocorticoid dose [38]. Corticosteroids accelerate the catabolism of 25(OH)D and 1,25(OH)2D and have a significant role in secondary osteoporosis [44]. Patients taking corticosteroids often require higher daily doses of vitamin D to maintain adequate levels [45]. Similarly, a commonly used antimalarial, hydroxychloroquine (HCQ), inhibits conversion of 25(OH)D to

A review by Sakthiswary demonstrated a substantial evidence in support of the association between vitamin D levels and SLE disease activity. However, vitamin D level is not associated with organ damage [47]. A study by Suzan showed a significant negative correlation that existed between 25(OH)D and anti-dsDNA and a positive correlation between 25(OH)D levels and C4 [48]. Another similar study showed a significant negative correlation between the serum concentration of vitamin D and the standardized values of disease activity scores as measured by the SLEDAI-2K and ECLAM scales [49]. An Australian study showed that low vitamin D

The two-sided relation between vitamin D and SLE showing that low levels of vitamin D resulted from SLE and

SLE complications that come from vitamin D deficiency [37].

1,25(OH)2D leading to low levels of vitamin D [46].

Vitamin D in Rheumatic Diseases: Interpretation and Significance

DOI: http://dx.doi.org/10.5772/intechopen.88677

