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Vitamin D levels of XP-patients under stringent sun-protection

European Journal of Dermatology. Volume 20, Number 4, 457-60, July-August 2010, Investigative report

DOI : 10.1684/ejd.2010.0968

Summary

Author(s) : Mirka Hoesl, Klaus Dietz, Martin Röcken, Mark Berneburg , Department of Dermatology, Eberhard Karls University, Liebermeisterstraße 25, D-72076 Tübingen, Germany, Department of Medical Biometry, Eberhard Karls University, Liebermeisterstraße 25, D-72076 Tübingen, Germany.

Summary : Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by an increased skin cancer risk due to defective repair of ultraviolet (UV)-radiation induced DNA damage. Therefore patients with XP are required to apply stringent sun-protection. Since the skin needs UV-B irradiation for de novo vitamin D synthesis, it has been postulated that sun-protection may lead to a clinically relevant reduction of vitamin D levels. To investigate whether reduced vitamin D levels in XP-patients are caused by the stringent sun-protection measures employed, in this study we examined 15 patients with XP. The 25-hydroxyvitamin (25-OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D) serum levels were measured. Additionally, patients received a questionnaire about their sun-protection-behaviour. Serum levels for 25-OHD were decreased in 10 of 15 (67%) patients, however there was no statistically significant association between decreased 25-OHD serum levels and duration of sun-protection (p \= 0.84). Results for 1,25-(OH)2D levels showed a probability of <\; 0.16 and between 0.16 and 0.77 for sun-protection duration of <\; 20 and 20 to 40 years, respectively (p \= 0.0058). There was no statistically significant association between the duration of sun-protection with drometrizole trisiloxane and the probability of reduced 25-OHD and 1,25-(OH)2D levels. In conclusion, this investigation indicates that vitamin D serum levels in patients with XP may be normal, increased or decreased but this is not causally linked to the stringent photoprotective measures carried out in our group of investigated XP-patients.

Keywords : 1,25-(OH)2D, 1,25-dihydroxyvitamin D, 25-OHD, 25-hydroxyvitamin D, NER, nucleotide excision repair, UV, ultraviolet, XP, Xeroderma pigmentosum

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ARTICLE

Auteur(s) : Mirka Hoesl¹, Klaus Dietz², Martin Röcken¹, Mark Berneburg¹

¹Department of Dermatology, Eberhard Karls University, Liebermeisterstraße 25, D-72076 Tübingen, Germany
²Department of Medical Biometry, Eberhard Karls University, Liebermeisterstraße 25, D-72076 Tübingen, Germany

accepté le 19 F�vrier 2010

Xeroderma pigmentosum (XP) [1] is a rare autosomal recessive disorder with an incidence of 0.9 per 10⁶ live births in Europe and an estimated prevalence worldwide of 1:10⁶ [2]. Clinically, XP is characterized by xerotic skin, sun sensitivity, poikiloderma, telangiectasia and an approximately 2000-fold increased risk of developing skin cancer [3-6]. Skin tumors include basal cell carcinoma, squamous cell carcinoma as well as malignant melanoma [7]. This is explained by the fact that cells from XP patients are defective in the repair mechanism nucleotide excision repair [8]. Nucleotide excision repair is a tightly regulated multiprotein process whose main function is the removal of bulky helix distorting DNA damage inflicted by ultraviolet (UV) radiation. Genetic studies on cultured cells have revealed seven complementation groups (A-G) which are deficient in NER as well as a variant form, where cells are deficient in translesion synthesis. Due to these defects, cells of XP patients show a mutator phenotype, leading to mutations in genes such as p53, ultimately leading to the generation of UV-induced skin tumors. Therefore, patients with XP are required to apply stringent photoprotection to reduce the risk of developing skin cancer. This includes strict avoidance of direct sun-exposure, UV-protective screens on all windows, long sleeved protective clothing and application of sun-protection with very high protection levels in the UVA as well as the UVB range. The skin, besides other organs, is capable of de novo vitamin D synthesis. Keratinocytes, macrophages and fibroblasts synthesise active vitamin D from cholesterol precursors by photochemical activation (UVB) in the skin [9-12].

Recently vitamin D levels have been implicated in skin carcinogenesis and it has been postulated that photoprotection may lead to clinically relevant reduction of vitamin D levels [13-17]. To address this point we investigated in our cohort of patients suffering from XP whether the stringent photoprotective measures carried out by these patients are responsible for potentially reduced serum levels of vitamin D.

Methods

Patients

This retrospective study involved 15 patients with Xeroderma pigmentosum examined during their regular biannual check-up. All patients gave their informed consent to participate in the study and the investigation was approved by the local ethics committee. The group included 8 male and 7 female patients aged between 4 and 69 years (table 1). Six patients were younger than 18 years old. Eight of the 15 recruited patients were of German origin, while 3 originated from the Middle East, 3 from the mediterranean region and 1 patient from the Netherlands. The study included the complementation groups XP-A, XP-C, XP-D, XP-F and XP-V. One patient additionally suffered from trichothiodystrophy [18]. Measured serum calcium showed normal values and PTH was not measured. Exclusion criteria included substitution with Vitamin D or calcium other than normal food intake as well as renal failure or increased bone fractures.
Table 1 Age, gender, means of vitamin D levels and sun-protection (i) overall and (ii) with drometriazole trisiloxane of investigated XP-patients

Patient ID	Age	Vit 1.25-OH	Vit D 25-OH	Years of overall sunprotection	Years of sunprotection with drometriazole trisiloxane
1	7	154	8	3
3	23	89	32	23	6
4	11	86	19	9	9
5	4	89	42	3	4.5
7	38	81	66	8	0
9	62	26	15	61	0
10	35	25	18	32	2
11	26	25	11	23	12
12	11	99	24	10	12
13	16	187	54	12
14	24	92	7	20	0
15	21	56	24	18	6
16	11	87	23	3	5
17	23	54	10	10
18	69	160	50	35	4

Vitamin D assessment

Vitamin D levels 1,25-(OH)2D and 25-OHD were measured from patients’ serum samples with the range of normal values for 25-OHD set between 25-170 nmol/L. For 1,25-(OH)2D the range of normal values varies for infants, children and adults. For infants the range is 70-360 pmol/L, for children 70-220 pmol/L and for adults it is set between 45-135 pmol/L [19]. We did not differentiate between blood samples taken during summer or winter months. Laboratory and clinical evaluations were performed at the Department of Dermatology, Tübingen and at four other Dermatology clinics within Germany.

Sun-protection questionnaire

In addition to blood samples taken, patients received a questionnaire including 14 questions about their sun-protection-behaviour. The term “duration of sun protection” was defined as the time from when the patient remembered carrying out any measure aimed at avoiding deleterious ultraviolet radiation until the last time the patient carried out any form of this UV-avoidance. This sun protection could comprise any combination of protection by clothing, simply avoiding sunlight as well as using sun protection ointments containing (i) drometrizole trisiloxane or (ii) other commercially available sunscreens. Answers were either chosen from four given options (50%) or chosen from a scale ranging from 1-10.

Statistical analysis

All data were documented with Microsoft Excel and stored anonymously. Only patients who filled in the questionnaire and from whom data regarding vitamin D was available were included (table 1). Statistical analysis was performed using the statistical software JMP. The association between the duration of light protection and reduced vitamin D levels was assessed by logistic regression.

Results

Vitamin D values

Serum vitamin D levels of all investigated patients are given in table 1. Levels of 25-OHD were normal for 33% (5 of 15) of patients, increased for 0% and decreased for 67% (10 of 15) of investigated XP patients. Levels for active 1,25-(OH)2D are given in figure 1. They were normal for 73% (11 of 15), increased for 7% (1 of 15) and decreased for 20% (3 of 15) of patients, respectively.

Sun-protection

Duration of sun-protection was documented in all patients. Protective measures according to questionnaires included avoidance of ambient or artificial UV-radiation, textile UV-protection and application of sunscreen. Duration of sun-protection applied ranged from 3 to 61 years (table 1).

Association of decreased vitamin D values and duration of sun-protection

There was no statistically significant association (likelihood ratio test p = 0.8564) between 25-OHD serum levels and duration of sun-protection (figure 1, dashed line). Results for 1,25-(OH)2D levels in correlation with duration of sun-protection are given in figure 1 (solid line). Probabilities followed a sigmoidal shape of three phases. Approximately, within the first 20 years of sun-protection the probability of decreased 1,25-(OH)2D levels was not above 0.25. Within 20-40 years the probability ranged between 0.25 and 0.75. Above 40 years of sun-protection the probability of decreased 1,25-(OH)2D levels was above 0.75. Thus, for 30 years of sun-protection the probability of decreased vitamin D levels was under 50% (likelihood ratio test p = 0.0058).

Twelve of 15 patients used sunscreen with drometrizole trisiloxane (table 1). When looking at this particular subset of patients there was no statistically significant association between duration of sun-protection with drometrizole trisiloxane and probability of reduced serum levels of 25-OHD and 1,25-(OH)2D (p = 0.3852, p = 0.8540, respectively). All other parameters, like sunprotection by strict avoidance of any type of UV-exposure, clothing, UV-protective windowscreens, showed no statistically significant effect on the vitamin D values of our patients.

Discussion

Serum levels of 25-OHD were reduced in 67% of the investigated patients when a laboratory specific cut-off for normal values of 25-70 nmol/L was applied. Other authors even suggest a higher cut-off for normal 25-OHD values [20]. When applying this limit, 12 of 15 (80%) patients would be considered to have reduced vitamin D serum levels. In any case, these results indicate that levels of the important storage form [21] of vitamin D are decreased in patients suffering from xeroderma pigmentosum. Since de-novo synthesis of vitamin D requires ultraviolet radiation it has been hypothesised that this may be due to excessive photoprotection carried out by these patients in order to avoid carcinogenic UV-exposure [16, 22]. Interestingly, reduction of 25-OHD was not associated with any type or duration of sun-protection applied by these patients, thus indicating that, while 25-OHD may be reduced in XP patients, the underlying cause may not simply be due to lack of sun exposure or due to excessive sun-protection. It has been reported by others that XP-patients are at risk of having reduced vitamin D levels [22]. However, this study only investigated three patients, thus not allowing statistical analysis. Solitto et al. also investigated vitamin D levels in XP-patients for six years [21]. During this observation period XP-patients even showed normal serum levels for both metabolites 25-OHD and 1,25-(OH)2D. In addition to this finding, Solitto et al. could also not find a seasonal influence in these patients on vitamin D levels. The authors concluded that sun protection applied by XP patients does not vary during the year in order to achieve complete UV-avoidance.

In addition to XP, studies in patients suffering from lupus erythematosus, another skin disease requiring stringent sun-protection, revealed that patients also showed reduced vitamin D levels but in this study the authors found this to be more likely due to inflammation or therapeutic application of systemic glucocorticoids rather than sun-protection [23], thus supporting our finding that the application of stringent sun protection is not causally involved in reduced vitamin D serum levels.

De novo synthesis by UVB is known to be the most important source of vitamin D, but physiological serum levels can also be reached by oral uptake [14, 24]. It was not in the scope of this study to investigate the relationship between oral vitamin D substitution and subsequent serum levels. Furthermore, in our study we did not find reduced levels for serum calcium, osteoporosis or increased incidence of bone fractures.

Nevertheless, as a result of our study, we do recommend oral vitamin D substitution for XP-patients as well as other individuals who have to avoid any type of exposure to ultraviolet radiation.

As with 25-OHD, serum levels of 1,25-(OH)2D, also showed no association with type of sun protection but there was a positive association with the duration of all types of sun-protection taken together. However, this occurred only after decades of sun protection. Therefore, it appears prudent to say that with regards to this type of vitamin D, there may also be a potential risk of reduced levels of vitamin D serum levels but in order to observe this, the most rigid regimen to avoid any form of UV-exposure has to be applied for 30 years or longer.

Acknowledgements

Financial support: this study was in part supported by La Roche Posay. Conflict of interest: M.B. has received lecture honoraria from La Roche Posay.

References

1 Cleaver JE. Defective repair replication of DNA in xeroderma pigmentosum. Nature 1968; 218: 652-6.

2 Kleijer WJ, Laugel V, Berneburg M, et al. Incidence of DNA repair deficiency disorders in western Europe: Xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy. DNA Repair (Amst) 2008; 7: 744-50.

3 Berneburg M, Lehmann AR. Xeroderma pigmentosum and related disorders: defects in DNA repair and transcription. Adv Genet 2001; 43: 71-102.

4 Bootsma D, Kraemer KH, Cleaver JE, Hoeijmakers JHJ. Nucleotide excision repair syndromes: Xeroderma pigmentosum, Cockayne syndrome, and trichothyodystrophy. New York: McGraw Hill, 1998.

5 Kraemer KH, Lee MM, Scotto J. Xeroderma pigmentosum. Cutaneous, ocular, and neurologic abnormalities in 830 published cases. Arch Dermatol 1987; 123: 241-50.

6 Lehmann AR. DNA repair-deficient diseases, xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy. Biochimie 2003; 85: 1101-11.

7 Kraemer KH, Lee MM, Scotto J. DNA repair protects against cutaneous and internal neoplasia: evidence from xeroderma pigmentosum. Carcinogenesis 1984; 5: 511-4.

8 Friedberg EC, Walker G. C., and Siede, W. DNA Repair and Mutagenesis. Washington DC: ASM press, 1995.

9 Pillai S, Bikle DD, Elias PM. 1,25-Dihydroxyvitamin D production and receptor binding in human keratinocytes varies with differentiation. J Biol Chem 1988; 263: 5390-5.

10 Lehmann B, Sauter W, Knuschke P, et al. Demonstration of UVB-induced synthesis of 1 alpha,25-dihydroxyvitamin D3 (calcitriol) in human skin by microdialysis. Arch Dermatol Res 2003; 295: 24-8.

11 Lu J, Goldstein KM, Chen P, et al. Transcriptional profiling of keratinocytes reveals a vitamin D-regulated epidermal differentiation network. J Invest Dermatol 2005; 124: 778-85.

12 Hosl M, Berneburg M. Vitamin D and the skin. Hautarzt 2008; 59: 737-42.

13 Lehmann B, Meurer M. Extrarenal sites of calcitriol synthesis: the particular role of the skin. Recent Results Cancer Res 2003; 164: 135-45.

14 Holick MF. Evolution and function of vitamin D. Recent Results Cancer Res 2003; 164: 3-28.

15 Lehmann B, Genehr T, Knuschke P, et al. UVB-induced conversion of 7-dehydrocholesterol to 1alpha,25-dihydroxyvitamin D3 in an in vitro human skin equivalent model. J Invest Dermatol 2001; 117: 1179-85.

16 Querings K, Reichrath J. A plea for the analysis of Vitamin-D levels in patients under photoprotection, including patients with xeroderma pigmentosum (XP) and basal cell nevus syndrome (BCNS). Cancer Causes Control 2004; 15: 219.

17 Lautenschlager S, Wulf HC, Pittelkow MR. Photoprotection. Lancet 2007; 370: 528-37.

18 Broughton BC, Berneburg M, Fawcett H, et al. Two individuals with features of both xeroderma pigmentosum and trichothiodystrophy highlight the complexity of the clinical outcomes of mutations in the XPD gene. Hum Mol Genet 2001; 10: 2539-47.

19 Kruse K. Vitamin D and Parathyroid. Basel: Karger, 2003.

20 Holick MF. Vitamin D deficiency. N Engl J Med 2007; 357: 266-81.

21 Sollitto RB, Kraemer KH, DiGiovanna JJ. Normal vitamin D levels can be maintained despite rigorous photoprotection: six years' experience with xeroderma pigmentosum. J Am Acad Dermatol 1997; 37: 942-7.

22 Reichrath J. Sunlight, skin cancer and vitamin D: What are the conclusions of recent findings that protection against solar ultraviolet (UV) radiation causes 25-hydroxyvitamin D deficiency in solid organ-transplant recipients, xeroderma pigmentosum, and other risk groups? J Steroid Biochem Mol Biol 2007; 103: 664-7.

23 Renne J, Werfel T, Wittmann M. High frequency of vitamin D deficiency among patients with cutaneous lupus erythematosus. Br J Dermatol 2008; 159: 485-6; [corrected].

24 Mocanu V, Stitt PA, Costan AR, et al. Long-term effects of giving nursing home residents bread fortified with 125 microg (5000 IU) vitamin D(3) per daily serving. Am J Clin Nutr 2009; 89: 1132-7.