title: Genetics, Diet, and Season Are Associated with Serum 25-Hydroxycholecalciferol Concentration in a Yup'ik Study Population from Southwestern Alaska.
abstract: BACKGROUND
  Low blood vitamin D concentration is a concern for people living in circumpolar regions, where sunlight is insufficient for vitamin D synthesis in winter months and the consumption of traditional dietary sources of vitamin D is decreasing.
  
  
  OBJECTIVE
  The objective was to characterize the effects of diet, genetic variation, and season on serum 25-hydroxycholecalciferol [25(OH)D3] concentrations in Yup'ik Alaska Native people living in rural southwest Alaska.
  
  
  METHODS
  This study was a cross-sectional design that assessed the associations of traditional diet (via a biomarker, the RBC δ(15)N value), age, gender, body mass index (BMI), community location, and genotype of select single nucleotide polymorphisms (SNPs) in cytochrome P450 family 2, subfamily R, peptide 1 (CYP2R1), 7-dehydrocholesterol reductase (DHCR7), and vitamin D binding protein (GC) with serum 25(OH)D3 concentrations in 743 Yup'ik male and female participants, aged 14-93 y, recruited between September 2009 and December 2013.
  
  
  RESULTS
  Yup'ik participants, on average, had adequate concentrations of serum 25(OH)D3 (31.1 ± 1.0 ng/mL). Variations in diet, BMI, age, gender, season of sample collection, and inland or coastal community geography were all significantly associated with serum 25(OH)D3 concentration. In models not adjusting for other covariates, age, diet, and seasonal effects explained 33.7%, 20.7%, and 9.8%, respectively, of variability in serum 25(OH)D3 concentrations. Of the 8 SNPs interrogated in CYP2R1 and DHCR7, only rs11023374 in CYP2R1 was significantly associated with serum 25(OH)D3, explaining 1.5% of variability. The GC haplotype explained an additional 2.8% of variability. Together, age, diet, gender, season of sample collection, BMI, geography of the community, and genotype at rs11023374 explained 52.5% of the variability in serum 25(OH)D3 concentrations.
  
  
  CONCLUSIONS
  Lower consumption of the traditional diet was associated with lower serum concentrations of 25(OH)D3. Younger adults and youth in this community may be at increased risk of adverse outcomes associated with vitamin D insufficiency compared with older members of the community, especially during seasons of low sunlight exposure, because of lower consumption of dietary sources of vitamin D.
authors.affiliation: Departments of Pharmaceutics.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Fohner
authors.affiliation: Departments of Pharmaceutics.
authors.forename: Zhican
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Departments of Pharmaceutics.
authors.forename: Joseph
authors.initials: J
authors.lastname: Yracheta
authors.affiliation: Center for Alaska Native Health Research, University of Alaska Fairbanks, Fairbanks, AK; and.
authors.forename: Diane M
authors.initials: DM
authors.lastname: O'Brien
authors.affiliation: Center for Alaska Native Health Research, University of Alaska Fairbanks, Fairbanks, AK; and.
authors.forename: Scarlett E
authors.initials: SE
authors.lastname: Hopkins
authors.affiliation: Center for Alaska Native Health Research, University of Alaska Fairbanks, Fairbanks, AK; and.
authors.forename: Jynene
authors.initials: J
authors.lastname: Black
authors.affiliation: Center for Alaska Native Health Research, University of Alaska Fairbanks, Fairbanks, AK; and.
authors.forename: Jacques
authors.initials: J
authors.lastname: Philip
authors.affiliation: School of Public Health, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Howard W
authors.initials: HW
authors.lastname: Wiener
authors.affiliation: School of Public Health, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Hemant K
authors.initials: HK
authors.lastname: Tiwari
authors.affiliation: Environmental Health Sciences, and.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Stapleton
authors.affiliation: Environmental Health Sciences, and.
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Tsai
authors.affiliation: Biostatistics, University of Washington, Seattle, WA;
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Thornton
authors.affiliation: Center for Alaska Native Health Research, University of Alaska Fairbanks, Fairbanks, AK; and.
authors.forename: Bert B
authors.initials: BB
authors.lastname: Boyer
authors.affiliation: Departments of Pharmaceutics, thummel@u.washington.edu.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Thummel
mesh_terms: D000293:Adolescent; D000328:Adult; D000413:Alaska / Q000453:epidemiology; D002112:Calcifediol / Q000097:blood*; D053493:Cholestanetriol 26-Monooxygenase / Q000235:genetics; D003430:Cross-Sectional Studies; D000072467:Cytochrome P450 Family 2; D004032:Diet; D004912:Erythrocytes; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007198:Indians, North American / Q000235:genetics; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D013472:Sunlight; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D014809:Vitamin D-Binding Protein / Q000235:genetics; D055815:Young Adult
chemical_list: D014809:Vitamin D-Binding Protein; D000072467:Cytochrome P450 Family 2; C506833:CYP2R1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; D002112:Calcifediol
keywords: Alaska Native; American Indian; cholecalciferol; polyunsaturated fatty acid; public health; vitamin D