Predictors of Serum Vitamin D Levels in African American and European American Men in Chicago

Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
American journal of men's health (Impact Factor: 1.15). 03/2012; 6(5):420-6. DOI: 10.1177/1557988312437240
Source: PubMed


Vitamin D deficiency is epidemiologically linked to prostate, breast, and colon cancer. When compared with European American (EA) men, African American (AA) men have increased risk of prostate cancer, but few studies evaluate vitamin D status in AA men. The authors evaluate the biological and environmental predictors of vitamin D deficiency in AA and EA men in Chicago, Illinois, a low ultraviolet radiation environment. Blood samples were collected from 492 men, aged between 40 and 79 years, from urology clinics at three hospitals in Chicago, along with demographic and medical information, body mass index, and skin melanin content using a portable narrow-band reflectometer. Vitamin D intake and ultraviolet radiation exposure were assessed using validated questionnaires. The results demonstrated that Black race, cold season of blood draw, elevated body mass index, and lack of vitamin D supplementation increase the risk of vitamin D deficiency. Supplementation is a high-impact, modifiable risk factor. Race and sunlight exposure should be taken into account for recommended daily allowances for vitamin D intake.

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Available from: Rick A Kittles, Oct 16, 2014
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    • "Circulating levels of 25(OH)D are strongly influenced by multiple factors. Various studies have demonstrated that dietary intake, dietary supplement use, season of blood draw, UVR exposure, smoking, sex, age, body mass index (BMI), and race/ethnicity are important predictors of serum 25(OH)D levels (Chan et al. 2010; Egan et al. 2008; Murphy et al. 2012; Shea et al. 2011). Of these predictors, many studies repeatedly demonstrated the strong associations of vitamin D intake and season of blood draw with serum 25(OH)D levels. "
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    ABSTRACT: Vitamin D deficiency is more common among African Americans (AAs) than among European Americans (EAs), and epidemiologic evidence links vitamin D status to many health outcomes. Two genome-wide association studies (GWAS) in European populations identified vitamin D pathway gene single-nucleotide polymorphisms (SNPs) associated with serum vitamin D [25(OH)D] levels, but a few of these SNPs have been replicated in AAs. Here, we investigated the associations of 39 SNPs in vitamin D pathway genes, including 19 GWAS-identified SNPs, with serum 25(OH)D concentrations in 652 AAs and 405 EAs. Linear and logistic regression analyses were performed adjusting for relevant environmental and biological factors. The pattern of SNP associations was distinct between AAs and EAs. In AAs, six GWAS-identified SNPs in GC, CYP2R1, and DHCR7/NADSYN1 were replicated, while nine GWAS SNPs in GC and CYP2R1 were replicated in EAs. A CYP2R1 SNP, rs12794714, exhibited the strongest signal of association in AAs. In EAs, however, a different CYP2R1 SNP, rs1993116, was the most strongly associated. Our models, which take into account genetic and environmental variables, accounted for 20 and 28 % of the variance in serum vitamin D levels in AAs and EAs, respectively. Electronic supplementary material The online version of this article (doi:10.1007/s00439-014-1472-y) contains supplementary material, which is available to authorized users.
    Full-text · Article · Aug 2014 · Human Genetics
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    • "Incidence and mortality rates for CRC in the US have declined since the late 1980s, but these trends have been less pronounced in African Americans (AAs), resulting in 20 % higher incidence and 44 % higher mortality rates in AAs compared to European Americans (EAs) [28]. AAs have lower serum vitamin D levels than other Americans [15, 29]. The lower vitamin D levels could be explained in part by skin color, which attenuates the production of vitamin D. Consequently, differences in serum vitamin D levels could contribute to the CRC health disparities between AAs and non-Hispanic whites. "
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    ABSTRACT: Disparities in both colorectal cancer (CRC) incidence and survival impact African Americans (AAs) more than other US ethnic groups. Because vitamin D is thought to protect against CRC and AAs have lower serum vitamin D levels, genetic variants that modulate the levels of active hormone in the tissues could explain some of the cancer health disparity. Consequently, we hypothesized that genetic variants in vitamin D-related genes are associated with CRC risk. To test this hypothesis, we studied 39 potentially functional single-nucleotide polymorphisms (SNPs) in eight genes (CYP2R1, CYP3A4, CYP24A1, CYP27A1, CYP27B1, GC, DHCR7, and VDR) in 961 AA CRC cases and 838 healthy AA controls from Chicago and North Carolina. We tested whether SNPs are associated with CRC incidence using logistic regression models to calculate p values, odds ratios, and 95 % confidence intervals. In the logistic regression, we used a log-additive genetic model and used age, gender, and percent West African ancestry, which we estimated with the program STRUCTURE, as covariates in the models. A nominally significant association was detected between CRC and the SNP rs12794714 in the vitamin D 25-hydroxylase gene CYP2R1 (p = 0.019), a SNP that has previously been associated with serum vitamin D levels. Two SNPs, rs16847024 in the GC gene and rs6022990 in the CYP24A1 gene, were nominally associated with left-sided CRC (p = 0.015 and p = 0.018, respectively). Our results strongly suggest that genetic variation in vitamin D-related genes could affect CRC susceptibility in AAs.
    Full-text · Article · Feb 2014 · Cancer Causes and Control
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    ABSTRACT: BACKGROUND: Prostate cancer is the most common type of cancer among men in the United States, and its incidence and mortality rates are disproportionate among ethnic groups. Although genome-wide association studies of European descents have identified candidate loci associated with prostate cancer risk, including a variant in IL16, replication studies in African Americans (AA) have been inconsistent. Here we explore single-nucleotide polymorphism (SNP) variation in IL16 in AAs and test for association with prostate cancer.METHODS: Association tests were conducted for 2,257 genotyped and imputed SNPs spanning IL16 in 605 AA prostate cancer cases and controls from Washington, D.C. Eleven of them were also genotyped in a replication population of 1,093 AAs from Chicago. We tested for allelic association adjusting for age, global and local West African ancestry.RESULTS: Analyses of genotyped and imputed SNPs revealed that a cluster of IL16 SNPs were significantly associated with prostate cancer risk. The strongest association was found at rs7175701 (P = 9.8 × 10(-8)). In the Chicago population, another SNP (rs11556218) was associated with prostate cancer risk (P = 0.01). In the pooled analysis, we identified three independent loci within IL16 that were associated with prostate cancer risk. SNP expression quantitative trait loci analyses revealed that rs7175701 is predicted to influence the expression of IL16 and other cancer-related genes.CONCLUSION: Our study provides evidence that IL16 polymorphisms play a role in prostate cancer susceptibility among AAs.Impact: Our findings are significant given that there has been limited focus on the role of IL16 genetic polymorphisms on prostate cancer risk in AAs. Cancer Epidemiol Biomarkers Prev; 21(11); 1-10. ©2012 AACR.
    Full-text · Article · Aug 2012 · Cancer Epidemiology Biomarkers & Prevention
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