Vitamins and Antioxidants: Topical and Systemic
The therapeutic approach with antioxidants originated from the description of the occurrence of the oxidative stress and possible vitamin deficiency in vitiligo patients, involving melanocytes and other epidermal as well as nonepidermal cells [4 , 14 ], a
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3.4
Mauro Picardo and Maria Lucia Dell’Anna
Contents
3.4.1 Introduction
3.4.1
Introduction ............................................................ 369
3.4.2
Vitamin B 12 and folic acid, para-aminobenzoic acid......................................... 369
3.4.3
L-Phenylalanine ..................................................... 370
3.4.4
Antioxidants............................................................ Backround ................................................................ Studies ...................................................................... Safety concerns ........................................................
370 370 370 372
References ........................................................................... 373
The therapeutic approach with antioxidants originated from the description of the occurrence of the oxidative stress and possible vitamin deficiency in vitiligo patients, involving melanocytes and other epidermal as well as nonepidermal cells [4, 14], and, besides possible nutritional aspects, of the mostly neurogenic view of vitiligo for vitamin B12 and folic acid (Chap 2.2.3). Increased production of H2O2, biopterins and catecholamines, defective expression and/or activity of the antioxidant enzymes catalase and glutathione peroxidise in addition to lipid peroxidation are the metabolic alterations reported by the literature [4, 14] (Chap. 2.2.6). In the last decade, several studies looking at the efficacy of vitamins and antioxidants in vitiligo have been performed. However, published studies are frequenly of poor quality, involving a small number of patients, or are lacking control groups, follow-up, or relevant clinical data.
3.4.2 Vitamin B 12 and folic acid, para-aminobenzoic acid
M. Picardo () Istituto Dermatologico San Gallicano, via Elio Chianesi, 00144 Roma, Italy e-mail: [email protected]
Vitamin B12 and folic acid have been found to be decreased in sera of vitiligo patients, even in the absence of specific clinical manifestations [7, 9], but the initial mechanism accounting for the reduction has been poorly evaluated. Folic acid and vitamin B12 derivatives interact in the one-carbon cycle, and the folate form N-N-methylene tetrahydrofolate gives the methyl group to homocysteine producing, in a vitamin B12-dependent manner, methionine. This enzymatic reaction determines the level of homocysteine, and the depigmentation may be due to the deficient methionine
M. Picardo and A. Taïeb (eds.), Vitiligo, DOI 10.1007/978-3-540-69361-1_3.4, © Springer-Verlag Berlin Heidelberg 2010
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synthesis and homocysteine build-up. Taking into account that homocystinuria can cause the syndrome described as “pigmentary dilution,” characterized by fair skin and hair, [14] and that the alteration of the homocysteine metabolism may be related to the catalase polymorphism, it is interesting to point out that in vitiligo patients, the serum level of homocysteine has been found increased and positively correlated with the activity of the disease [14]. The pteridine in
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