Environmental and genetic determinants of two vitamin D metabolites in healthy Australian children.
BACKGROUND
Vitamin D deficiency has been associated with adverse health outcomes. We examined genetic and environmental determinants of serum 25(OH)D3 and 1,25(OH)2D3 in childhood.


METHODS
The study sample consisted of 322 healthy Australian children (predominantly Caucasians) who provided a venous blood sample. A parental interview was conducted and skin phototype and anthropometry measures were assessed. Concentrations of 25(OH)D3 and 1,25(OH)2D3 were measured by selective solid-phase extraction-capillary liquid chromatography-tandem mass spectrometry. These concentrations were deseasonalised where relevant to remove the effect of month of sampling.


RESULTS
Deseasonalised log 25(OH)D3 and 1,25(OH)2D3 concentrations were only moderately correlated (r=0.42, p<0.001). The following predicted both 25(OH)D3 and 1,25(OH)2D3: UVR 6 weeks before the interview, natural skin and eye colour, height and vitamin D allelic metabolism score. The following predicted 25(OH)D3 only: lifetime sunburns and vitamin D allelic synthesis score. Overall, 43.5% and 25.6% of variation in 25(OH)D3 and 1,25(OH)2D3 could be explained. After accounting for 25(OH)D3 concentrations, higher UVR 6 weeks before the interview and vitamin D allelic metabolism score further predicted 1,25(OH)2D3 concentrations.


CONCLUSIONS
Environmental factors and genetic factors contributed to both vitamin D metabolite concentrations. The intriguing finding that the higher ambient UVR contributed to higher 1,25(OH)2D3 after accounting for 25(OH)D3 concentrations requires further evaluation.
Murdoch Childrens Research Institute, Melbourne, Victoria.
Abdulhadi
A
Bima
Murdoch Childrens Research Institute, Melbourne, Victoria.
Angela
A
Pezic
Murdoch Childrens Research Institute, Melbourne, Victoria.
Cong
C
Sun
Murdoch Childrens Research Institute, Melbourne, Victoria.
Fergus J
FJ
Cameron
Department of Endocrinology, Sunshine Hospital, University of Melbourne, Melbourne, Victoria.
Christine
C
Rodda
Menzies Research Institute, University of Tasmania, Hobart, Tasmania.
Ingrid
I
van der Mei
Murdoch Childrens Research Institute, Melbourne, Victoria.
Rachel
R
Chiaroni-Clarke
Menzies Research Institute, University of Tasmania, Hobart, Tasmania.
Terence
T
Dwyer
Murdoch Childrens Research Institute, Melbourne, Victoria.
Andrew
A
Kemp
Department of Pharmaceutical Sciences, University at Buffalo, State University of New York, Amherst, NY.
Jun
J
Qu
Murdoch Childrens Research Institute, Melbourne, Victoria.
John
J
Carlin
Murdoch Childrens Research Institute, Melbourne, Victoria.
Justine A
JA
Ellis
Department of Paediatrics, University of Melbourne, Melbourne, Victoria.
Anne-Louise
AL
Ponsonby
D001315:Australia / Q000453:epidemiology; D002112:Calcifediol / Q000378:metabolism*; D002117:Calcitriol / Q000378:metabolism*; D002648:Child; D004777:Environment; D005819:Genetic Markers; D006801:Humans; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D014808:Vitamin D Deficiency / Q000453:epidemiology* / Q000235:genetics / Q000378:metabolism; D014815:Vitamins / Q000378:metabolism*
D005819:Genetic Markers; D014815:Vitamins; D002117:Calcitriol; D002112:Calcifediol
1,25-dihydroxyvitamin D3; allelic score; determinants; ultraviolet radiation; vitamin D 25-hydroxyvitamin D3