title: Ultraviolet B activated 1,25(OH)(2)D affects the level of fibroblast growth factor-23 in human.
abstract: Fibroblast growth factor 23 (FGF-23) is known as a phosphaturic factor regulating phosphate homeostasis.  Several studies suggest that dietary phosphate, serum phosphate and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] are candidate regulators of FGF-23.  While the human studies, which modulated the dietary or serum phosphate showed in rather controversial results, manipulation of the active vitamin D definitely affected FGF-23 in animals.  This study was conducted to elucidate the relationship between active vitamin D directly stimulated by ultraviolet B (UVB) exposure and FGF-23 level in human.  Ten healthy young adults were recruited to get the UVB exposure thrice a week at sub-minimal erythemal dose with gradual increment by 10% only for 4 weeks.  Serum calcium, phosphate, mineral-related hormones and bone turnover markers were analyzed before and after the UVB exposure every 4 week for 12 whole weeks.  Twenty five-hydroxyvitamin D [25(OH)D] increased by 115% (19.8 ng/mL to 40.5 ng/mL, p < 0.001) after 4 weeks of UVB exposure.  While 1,25(OH)(2)D increased by 75% (49.9 pg/mL to 64.4 pg/mL, p < 0.001) then both level decreased after 4 weeks of withdrawal.  C-telopeptide peaked at 2nd week then decreased, while osteocalcin increased gradually.  FGF-23 started to increase from the 4th week of UVB exposure then significantly at the 4th week after withdrawal of UVB (27.8 pg/mL to 41.4 pg/mL, p < 0.05).  UVB exposure effectively increased 1,25(OH)(2)D with delayed stimulatory effect on FGF-23.  This result could support the regulatory loop of 1,25(OH)(2)D and FGF-23 in human, FGF-23 regulation by 1,25(OH)(2)D.
authors.affiliation: Department of Dermatology, Yonsei University College of Medicine, Seoul 120-752, Korea. yumie@yuhs.ac
authors.forename: Ju Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Dong Yeob
authors.initials: DY
authors.lastname: Shin
authors.forename: Han Seok
authors.initials: HS
authors.lastname: Choi
authors.forename: Do Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Yoon Kee
authors.initials: YK
authors.lastname: Park
authors.forename: Sung-Kil
authors.initials: SK
authors.lastname: Lim
authors.forename: Yumie
authors.initials: Y
authors.lastname: Rhee
mesh_terms: D000328:Adult; D002118:Calcium / Q000097:blood; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D008297:Male; D010710:Phosphates / Q000097:blood; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: C000717427:FGF23 protein, human; D010710:Phosphates; D014807:Vitamin D; D005346:Fibroblast Growth Factors; C097949:1,25-dihydroxyvitamin D; D000089703:Fibroblast Growth Factor-23; D002118:Calcium