A Narrow-Band Ultraviolet B Course Improves Vitamin D Balance and Alters Cutaneous CYP27A1 and CYP27B1 mRNA Expression Levels in Haemodialysis Patients Supplemented with Oral Vitamin D

Background/Aims: Chronic kidney disease (CKD) patients on dialysis
areprone to vitamin D insufficiency despite oral vitamin D
supplementation.Here, we studied whether narrow-band ultraviolet B
(NB-UVB) exposuresimprove vitamin D balance. Methods: 14
haemodialysis patients and 15healthy subjects receiving oral
cholecalciferol 20 mu g daily got nineNB-UVB exposures on the
entire body. Serum 25-hydroxyvitamin D (25(OH)D)was measured by
radioimmunoassay. Cutaneous mRNA expression levels ofCYP27A1 and
CYP27B1, two enzymes required for hydroxylation of vitamin Dinto
its active metabolite, were also measured. Results: The
baselineserum 25(OH)D concentration was 57.6 +/- 18.2 nmol/l in the
CKD patientsand 74.3 +/- 14.8 nmol/l in the healthy subjects. The
NB-UVB courseincreased serum 25(OH)D by 14.0 nmol/l (95% CI
8.7-19.5) and 17.0nmol/l (CI 13.7-20.2), respectively. At baseline
the CKD patients showedsignificantly increased CYP27B1 levels
compared to the healthy subjects.Conclusions: A short NB-UVB course
is an efficient way to improvevitamin D balance in CKD patients on
dialysis who are receiving oralvitamin D supplementation. The
increased cutaneous CYP27B1 levels in theCKD patients suggest that
the loss of renal activity of this enzyme isat least partially
compensated for by the skin.