title: Vitamin D in a northern Canadian first nation population: dietary intake, serum concentrations and functional gene polymorphisms.
abstract: The wide spectrum of vitamin D activity has focused attention on its potential role in the elevated burden of disease in a northern Canadian First Nations (Dené) cohort. Vitamin D insufficiency, and gene polymorphisms in the vitamin D receptor (VDR) and vitamin D binding protein (VDBP) have been implicated in susceptibility to infectious and chronic diseases. The objectives of this study were to determine the contribution of vitamin D from food, and measure the serum concentrations of 25-hydroxyvitamin D(3) (25-OHD(3)) and VDBP in Dené participants. Single nucleotide polymorphisms (SNPs) associated with the dysregulation of the innate immune response were typed and counted. Potential correlations between the SNPs and serum concentrations of 25-OHD(3) and VDBP were evaluated. Venous blood was collected in summer and winter over a one-year period and analyzed for 25-OHD(3) and VDBP concentrations (N = 46). A questionnaire was administered to determine the amount of dietary vitamin D consumed. Sixty-one percent and 30% of the participants had 25-OHD(3) serum concentrations <75 nmol/L in the winter and summer respectively. Mean vitamin D binding protein concentrations were within the normal range in the winter but below normal in the summer. VDBP and VDR gene polymorphisms affect the bioavailability and regulation of 25-OHD(3). The Dené had a high frequency of the VDBP D432E-G allele (71%) and the Gc1 genotype (90%), associated with high concentrations of VDBP and a high binding affinity to 25-OHD(3). The Dené had a high frequency of VDR Fok1-f allele (82%), which has been associated with a down-regulated Th1 immune response. VDBP and VDR polymorphisms, and low winter 25-OHD(3) serum concentrations may be risk factors for infectious diseases and chronic conditions related to the dysregulation of the vitamin D pathway.
authors.affiliation: Faculty of Medicine, Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. llarcombe@hsc.mb.ca
authors.forename: Linda
authors.initials: L
authors.lastname: Larcombe
authors.forename: Neeloffer
authors.initials: N
authors.lastname: Mookherjee
authors.forename: Joyce
authors.initials: J
authors.lastname: Slater
authors.forename: Caroline
authors.initials: C
authors.lastname: Slivinski
authors.forename: Matthew
authors.initials: M
authors.lastname: Singer
authors.forename: Chris
authors.initials: C
authors.lastname: Whaley
authors.forename: Lizette
authors.initials: L
authors.lastname: Denechezhe
authors.forename: Sara
authors.initials: S
authors.lastname: Matyas
authors.forename: Emily
authors.initials: E
authors.lastname: Turner-Brannen
authors.forename: Peter
authors.initials: P
authors.lastname: Nickerson
authors.forename: Pamela
authors.initials: P
authors.lastname: Orr
mesh_terms: D000328:Adult; D000483:Alleles; D002170:Canada; D002908:Chronic Disease; D004032:Diet; D005260:Female; D006801:Humans; D008297:Male; D053858:Metabolic Networks and Pathways; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011153:Population; D018167:Receptors, Calcitriol / Q000235:genetics*; D012307:Risk Factors; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood / Q000235:genetics / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000235:genetics / Q000378:metabolism; D014809:Vitamin D-Binding Protein / Q000235:genetics
chemical_list: D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C104450:25-hydroxyvitamin D