title: Vitamin D insufficiency in Arabs and South Asians positively associates with polymorphisms in GC and CYP2R1 genes.
abstract: BACKGROUND
  A number of genetic studies have reported an association between vitamin D related genes such as group-specific component gene (GC), Cytochrome P450, family 2, subfamily R, polypeptide 1 (CYP2R1) and 7-dehydrocholesterol reductase/nicotinamide-adenine dinucleotide synthetase 1 (DHCR7/NADSYN1) and serum levels of the active form of Vitamin D, 25 (OH) D among African Americans, Caucasians, and Chinese. Little is known about how genetic variations associate with, or contribute to, 25(OH)D levels in Arabs populations.
  
  
  METHODS
  Allele frequencies of 18 SNPs derived from CYP2R1, GC, and DHCR7/NADSYN1 genes in 1549 individuals (Arabs, South Asians, and Southeast Asians living in Kuwait) were determined using real time genotyping assays. Serum levels of 25(OH)D were measured using chemiluminescence immunoassay.
  
  
  RESULTS
  GC gene polymorphisms (rs17467825, rs3755967, rs2282679, rs7041 and rs2298850) were found to be associated with 25(OH)D serum levels in Arabs and South Asians. Two of the CYP2R1 SNPs (rs10500804 and rs12794714) and one of GC SNPs (rs1155563) were found to be significantly associated with 25(OH)D serum levels only in people of Arab origin. Across all three ethnicities none of the SNPs of DHCR7/NADSYN1 were associated with serum 25(OH)D levels and none of the 18 SNPs were significantly associated with serum 25(OH)D levels in people from South East Asia.
  
  
  CONCLUSIONS
  Our data show for the first time significant association between the GC (rs2282679 and rs7041), CYP2R1 (rs10741657) SNPs and 25(OH)D levels. This supports their roles in vitamin D Insufficiency in Arab and South Asian populations respectively. Interestingly, two of the CYP2R1 SNPs (rs10500804 and rs12794714) and one GC SNP (rs1155563) were found to correlate with vitamin D in Arab population exclusively signifying their importance in this population.
authors.affiliation: Department of Biostatistics & Epidemiology, Dasman Diabetes Institute, Kuwait City, Kuwait; Clinical Epidemiology, Sidra Medical and Research Centre, Doha, Qatar.
authors.forename: Naser
authors.initials: N
authors.lastname: Elkum
authors.affiliation: Genetics & Genomics Unit, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Fadi
authors.initials: F
authors.lastname: Alkayal
authors.affiliation: Department of Biostatistics & Epidemiology, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Fiona
authors.initials: F
authors.lastname: Noronha
authors.affiliation: Genetics & Genomics Unit, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Maisa M
authors.initials: MM
authors.lastname: Ali
authors.affiliation: Genetics & Genomics Unit, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Motasem
authors.initials: M
authors.lastname: Melhem
authors.affiliation: Clinical Services, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Monira
authors.initials: M
authors.lastname: Al-Arouj
authors.affiliation: Clinical Services, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Bennakhi
authors.affiliation: Department of Biostatistics & Epidemiology, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Kazem
authors.initials: K
authors.lastname: Behbehani
authors.affiliation: Genetics & Genomics Unit, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Osama
authors.initials: O
authors.lastname: Alsmadi
authors.affiliation: Biochemistry & Molecular Biology Unit, Dasman Diabetes Institute, Kuwait City, Kuwait.
authors.forename: Jehad
authors.initials: J
authors.lastname: Abubaker
mesh_terms: D000704:Analysis of Variance; D018912:Arabs / Q000235:genetics*; D044466:Asian People / Q000235:genetics*; D053493:Cholestanetriol 26-Monooxygenase / Q000235:genetics*; D000072467:Cytochrome P450 Family 2; D005787:Gene Frequency; D006801:Humans; D007118:Immunoassay; D007730:Kuwait; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D014808:Vitamin D Deficiency / Q000097:blood / Q000235:genetics*; D014809:Vitamin D-Binding Protein / Q000235:genetics*
chemical_list: D014809:Vitamin D-Binding Protein; D000072467:Cytochrome P450 Family 2; C506833:CYP2R1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase