Journal of Photochemistry and Photobiology B: Biology
Pilot study of folate status in healthy volunteers and in patients with psoriasis before and after UV exposure
Introduction
In 1978 Branda and Eaton [1] demonstrated a significant destruction of folate by UVA in plasma samples ex vivo from healthy volunteers and in serum from psoriasis patients treated with methoxsalen. Together with the fact that folate deficiency in pregnancy may lead to serious complications, Branda and Eaton, and some years later Jablonski, proposed a new hypothesis for human skin darkening: Dark skin may have been developed to protect folates against the strong equatorial solar radiation. This hypothesis has neither been finally verified nor rejected. The effects, if any, of UV radiation on the folate status in humans have not yet been carefully studied. Some studies have suggested that solar or artificial UV radiation can deplete folates in humans [1], [2], [3], while other studies have claimed that UV radiation has no effect on folate levels [2], [4], [5], [6]. Discrepancies in the different works may be due partly to differences in UV sources (UVA or UVB), used fluences, skin conditions (healthy, psoriasis, vitiligo, etc.), and methods for measurements of folates in blood (Table 1).
Thus, there is no consensus on whether folate is degraded during UV exposure of humans. There is a strong need for further studies of the folate photobiology and pathophysiology. This may be of high relevance for patients with psoriasis, which affects 1–3% of many populations [9], because UV radiation therapy, alone or in combination with other therapies, is commonly used to treat such patients [10]. Different UV radiation sources are being used in the treatment of psoriasis. Narrowband UVB (nUVB) and broadband UVB sources are most often applied in clinical settings for psoriasis patients. UV radiation from sun (heliotherapy) or sunbeds (“home” photoherapy) is also beneficial for psoriasis patients [9], [11]. The beneficial effects of such UVB therapy may partly be related to the cutaneous synthesis of vitamin D [2], [4], [12], [13]. If another vitamin, folate, is degraded in vivo by UV radiation, this may affect the outcome of psoriasis treatments negatively, and even lead to initiation of serious disease in these patients. Folate deficiency has been linked to cardiovascular diseases, male infertility, pregnancy complications, and some types of cancer [14], [15], [16]. Recently, we [4] and Rose et al. [8] concluded that nUVB phototherapy does not influence serum and erythrocyte folate levels in these patients. However, the influence of broadband UVB phototherapy, sunbeds and solar radiation on folate levels has not been thoroughly studied. The aim of the present pilot study was to investigate the serum and erythrocyte folate status in patients with psoriasis before and after exposure to sunlight or broadband UVB, and in healthy volunteers before and after use of sunbeds. In some cases plasma homocysteine and serum 25-hydoxyvitamin D (25(OH)D) were also measured.
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Patients and volunteers
These studies were approved by the regional ethical committee. All psoriasis patients and volunteers gave informed consent. All were over 18 years old and living in Oslo region (59°N). Volunteers were excluded from the study if they were pregnant, lactating or planning pregnancy, or had hypersensitivity to sunlight. The participants were Caucasians and had Fitzpatrick skin types II or III. Folate intake through diet, folic acid intake through fortified foods or supplements were not estimated.
The influence of solar radiation on folate levels in patients with psoriasis and in healthy volunteers (study 1)
Serum and erythrocytes folate concentrations were measured in May or June and approximately three months later in four patients with psoriasis (Fig. 1, Fig. 2) and in 13 healthy volunteers (Fig. 1, Fig. 3). UV radiation doses were not controlled or directly measured. To control that these patients received more UV radiation during these months than before, serum concentrations of 25(OH)D were measured, because UVB radiation initiates the synthesis of vitamin D [18]. Serum levels of 25(OH)D were
Discussion
Folate levels were measured in psoriasis patients and healthy volunteers before and after exposure to UV radiation (Fig. 1). Baseline serum folate levels were in the normal range, but statistically significantly lower (34%, P = 0.01) in psoriasis patients than in healthy volunteers (Fig. 1A). Baseline erythrocyte folate concentrations were lower 13%, although statistically insignificantly (P = 0.27), in psoriasis patients (Fig. 1). Reduced folates levels in psoriasis patients after phototherapy
Acknowledgements
The present work was financed by the Norwegian Cancer Society (DNK). We appreciate the help of Dr. Gunnar Volden in taking blood sample in studies 1, 2, and 4. We also appreciate the help of the personnel at Fürst Medical Laboratory and at the Department of Medical Biochemistry (Rikshospitalet).
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