diseases, osteoporosis, sarcopenia, and diabetes. Vitamin-D receptor (VDR) plays a crucial role in the gene network that modulates vitamin-D signaling. In this study, we evaluated the role of VDR gene variability in human longevity by selecting five polymorphisms of the VDR gene that capture variability at the 50, coding, and 30 regions. We obtained genotype data from 104 octogenarians ([85 years) and 114 controls (1740 years). Although differences in genotype and allele distribution did not reach statistical significance, haplotype distribution was distinctive, mainly for 30 region haplotypes and particularly in males. Our results suggest a role for VDR gene variability in aging and longevity.

Longevity is a multifactorial trait based on biological and non-biological factors. Recent socioeconomic improvements and advances in prevention and treatment of diseases have increased life expectancy in humans without affecting maximum lifespan potential. Vitamin-D deficiency is considered a risk factor for life-limiting illnesses such as cardiovascular and immune-related diseases and cancer. Vitamin-D acts through VDR, which regulates the expression of vitamin-D-response genes. VDR variants have been associated with susceptibility to various diseases.

Several VDR polymorphisms with functional effects have been described in the promoter, coding, and 30 untranslated region (UTR). Two common polymorphisms, Cdx (rs1568820) and A1012G (rs4516035), have been located in the regulatory region that affects binding to transcription factors. The rs1568820 polymorphism alters the site for the intestinal-specific transcription caudal-related homeodomain protein-2 (Cdx), affecting vitamin-D-VDR-mediated intestinal calcium absorption. The rs4516035 modifies the GATA-3 transcription factor recognition sequence, involved in the polarization of Th2 cells. In addition, a common FokI (rs10735810) polymorphism has been described in the VDR coding region that alters the first ATG start site to an alternate ACG giving rise to a VDR protein that is three amino acids shorter. Functional differences among rs10735810 show that the VDR protein coded by the allele (short 424 aas) interacted more efficiently with TFIIB and showed greater transcriptional activity than the full-length VDR protein coded by the allele. Finally, a common fragment length polymorphism (RFLP), as BsmI (rs1544410), and a microsatellite designated as PolyA (rs17878969), has been described in the 30-UTR region. Functional effects of 30-UTR have been related to alterations in VDR mRNA.

LD blocks range from 5 to 50 kb and are characterized by a reduced diversity of allelic combinations (haplotypes). Studies of the VDR genomic region in Caucasians have revealed a scattered LD pattern with rs1568820 and rs4516035 polymorphisms included in a single block of the VDR promoter and rs1544410 and rs17878969 polymorphisms included in a 30UTR block. Blocks are separated by a hotspot recombination region that includes the rs10735810 polymorphism. In this study, we obtained genotype information from five polymorphic variants located in the VDR gene at: 50 promoter region, rs11568820 and rs4516035; coding region, rs10735810; and 30UTR, rs1544410 and rs17878969.

In conclusion, VDR gene variability may play a role in aging and longevity. Vitamin-D deficiency is considered a risk factor for life-limiting illnesses, and VDR variants have been associated with susceptibility to various diseases. The study of LD patterns is essential for designing association studies of complex phenotypes.Diseases and immune system disturbances (Uitterlinden et al. 2004b) are factors that we propose make VDR a candidate gene involved in human longevity, due to its ability to protect against age-related diseases and modulate the immune response. We conducted an association study for longevity using the known haplotype block structure of the VDR genomic region, considering both single genotypes and haplotypes. 

Statistical analysis was performed by comparing genotype and allele distribution between controls and octogenarians using contingency table analysis via the OpenEpi web resource (Sullivan et al. 2009). Fisher exact test P values were considered for each comparison, and correction for multiple testing was done using the SNP spectral decomposition approach, which takes into account the linkage disequilibrium between markers (Nyholt 2004). The significance threshold required to maintain a Type I error rate of 5% was P = 0.036 for two-marker haplotypes and P = 0.011 for five-marker haplotypes. Pairwise linkage disequilibrium was measured by the normalized D0 coefficient (Lewontin 1988), which was estimated using Haploview 4.2 software (Barrett et al. 2005). Absolute D0 values range from 0 (no disequilibrium) to 1 (complete disequilibrium), indicating a nonrandom distribution of alleles with fewer observed haplotypes than expected.

Subjects included 214 Caucasian individuals from the city of Lleida in northeast Spain between January and June 2004: 104 octogenarians ([85 years), consisting of 72 women (mean age 89.4 ± 3.6; range 85-100) and 32 men (mean age 89.4 ± 3.2; range 85-97), and 110 sex-matched healthy young individuals, 75 women (mean age 28 ± 5.8; range 17-39) and 35 men (mean age 29 ± 8.6; range 17-40), were selected as cases and controls, respectively. A comprehensive medical history was obtained from each octogenarian, focusing on the absence of vitamin-D-related illnesses such as osteoporosis, autoimmune diseases, immunodeficiency, and cancer. Written informed consent was obtained from all subjects in accordance with Spanish laws, and the Ethics Committee for our institution approved the study.