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Vitamin D deficiency is a candidate risk factor for a range of adverse health outcomes. In a genome-wide association study of 25 hydroxyvitamin D (25OHD) concentration in 417,580 Europeans we identify 143 independent loci in 112 1-Mb regions, providing insights into the physiology of vitamin D and implicating genes involved in lipid and lipoprotein metabolism, dermal tissue properties, and the sulphonation and glucuronidation of 25OHD. Mendelian randomization models find no robust evidence that 25OHD concentration has causal effects on candidate phenotypes (e.g. BMI, psychiatric disorders), but many phenotypes have (direct or indirect) causal effects on 25OHD concentration, clarifying the epidemiological relationship between 25OHD status and the health outcomes examined in this study. Vitamin D is a precursor of the steroid hormone 1,25-dihydroxyvitamin D3, and its deficiency is associated with many adverse health outcomes. Here, Revez et al. perform a genome-wide association study for circulating 25-hydroxyvitamin D in 417,580 individuals and test for potential causal relationships with other traits using Mendelian randomization.

Little is known about how genetic and nongenetic factors modify responses of vitamin D supplementation in nonwhite populations. To investigate factors modifying 25-hydroxyvitamin D [25(OH)D] and bioavailable 25(OH)D [25(OH)DBio] responses after vitamin D3 supplementation. In this 20-week, randomized, double-blinded, placebo-controlled trial, 448 Chinese with vitamin D deficiency received 2000 IU/d vitamin D3 or placebo. Serum 25(OH)D, vitamin D-binding protein (VDBP), parathyroid hormone (PTH) and calcium were measured, and 25(OH)DBio was calculated based on VDBP levels. Six common polymorphisms in vitamin D metabolism genes were genotyped. Between-arm net changes were +30.6 ± 1.7 nmol/L for 25(OH)D, +2.7 ± 0.2 nmol/L for 25(OH)DBio, and -5.2 ± 1.2 pg/mL for PTH, corresponding to 70% [95% confidence interval (CI), 62.8% to 77.2%] net reversion rate for vitamin D deficiency at week 20 (P < 0.001). Only 25(OH)DBio change was positively associated with calcium change (P < 0.001). Genetic factors (GC-rs4588/GC-rs7041, VDR-rs2228570, and CYP2R1-rs10741657; P ≤ 0.04) showed stronger influences on 25(OH)D or 25(OH)DBio responses than nongenetic factors, including baseline value, body mass index, and sex. An inverse association of PTH-25(OH)D was demonstrated only at 25(OH)D of <50.8 (95% CI, 43.6 to 59.0) nmol/L. Supplemented 2000 IU/d vitamin D3 raised 25(OH)D and 25(OH)DBio but was unable to correct deficiency in 25% of Chinese participants, which might be partially attributed to the effect of genetic modification. More studies are needed to elucidate appropriate vitamin D recommendations for Asians and the potential clinical implications of 25(OH)DBio.

Vitamin D deficiency has been associated with type 1 diabetes in observational studies, but evidence from randomized controlled trials (RCTs) is lacking. The aim of this study was to test whether genetically decreased vitamin D levels are causally associated with type 1 diabetes using Mendelian randomization (MR). For our two-sample MR study, we selected as instruments single nucleotide polymorphisms (SNPs) that are strongly associated with 25-hydroxyvitamin D (25OHD) levels in a large vitamin D genome-wide association study (GWAS) on 443,734 Europeans and obtained their corresponding effect estimates on type 1 diabetes risk from a large meta-analysis of 12 type 1 diabetes GWAS studies (Ntot = 24,063, 9,358 cases, and 15,705 controls). In addition to the main analysis using inverse variance weighted MR, we applied 3 additional methods to control for pleiotropy (MR-Egger, weighted median, and mode-based estimate) and compared the respective MR estimates. We also undertook sensitivity analyses excluding SNPs with potential pleiotropic effects. We identified 69 lead independent common SNPs to be genome-wide significant for 25OHD, explaining 3.1% of the variance in 25OHD levels. MR analyses suggested that a 1 standard deviation (SD) decrease in standardized natural log-transformed 25OHD (corresponding to a 29-nmol/l change in 25OHD levels in vitamin D-insufficient individuals) was not associated with an increase in type 1 diabetes risk (inverse-variance weighted (IVW) MR odds ratio (OR) = 1.09, 95% CI: 0.86 to 1.40, p = 0.48). We obtained similar results using the 3 pleiotropy robust MR methods and in sensitivity analyses excluding SNPs associated with serum lipid levels, body composition, blood traits, and type 2 diabetes. Our findings indicate that decreased vitamin D levels did not have a substantial impact on risk of type 1 diabetes in the populations studied. Study limitations include an inability to exclude the existence of smaller associations and a lack of evidence from non-European populations. Our findings suggest that 25OHD levels are unlikely to have a large effect on risk of type 1 diabetes, but larger MR studies or RCTs are needed to investigate small effects.

Although there have been numerous observations of vitamin D deficiency and its links to chronic diseases, no studies have reported on how vitamin D status and vitamin D3 supplementation affects broad gene expression in humans. The objective of this study was to determine the effect of vitamin D status and subsequent vitamin D supplementation on broad gene expression in healthy adults. (Trial registration: ClinicalTrials.gov NCT01696409). A randomized, double-blind, single center pilot trial was conducted for comparing vitamin D supplementation with either 400 IUs (n = 3) or 2000 IUs (n = 5) vitamin D3 daily for 2 months on broad gene expression in the white blood cells collected from 8 healthy adults in the winter. Microarrays of the 16 buffy coats from eight subjects passed the quality control filters and normalized with the RMA method. Vitamin D3 supplementation that improved serum 25-hydroxyvitamin D concentrations was associated with at least a 1.5 fold alteration in the expression of 291 genes. There was a significant difference in the expression of 66 genes between subjects at baseline with vitamin D deficiency (25(OH)D<20 ng/ml) and subjects with a 25(OH)D>20 ng/ml. After vitamin D3 supplementation gene expression of these 66 genes was similar for both groups. Seventeen vitamin D-regulated genes with new candidate vitamin D response elements including TRIM27, CD83, COPB2, YRNA and CETN3 which have been shown to be important for transcriptional regulation, immune function, response to stress and DNA repair were identified. Our data suggest that any improvement in vitamin D status will significantly affect expression of genes that have a wide variety of biologic functions of more than 160 pathways linked to cancer, autoimmune disorders and cardiovascular disease with have been associated with vitamin D deficiency. This study reveals for the first time molecular finger prints that help explain the nonskeletal health benefits of vitamin D. ClinicalTrials.gov NCT01696409.

Background Vitamin D deficiency in women diagnosed with polycystic ovary syndrome (PCOS) remarkably decreases the chance of pregnancy, which might be related to its impact on metabolic abnormalities in these patients. It is hypothesized that vitamin D supplementation influences metabolic profile of these patients and indirectly might affect fertility and the outcomes. Therefore, this study was conducted to determine the effects of vitamin D supplementation on the levels of anti-Müllerian hormone (AMH), metabolic profiles, and gene expression of insulin and lipid metabolism in infertile women with PCOS who were candidate for in vitro fertilization (IVF). Methods This study was a randomized, double-blinded, placebo-controlled trial conducted among 40 infertile women, aged 18–40 years, diagnosed with PCOS and was candidate for IVF. Participants were randomly assigned into two intervention groups for receiving either 50,000 IU vitamin D or placebo ( n  = 20 each group) every other week for 8 weeks. Gene expression for insulin and lipid metabolism was conducted using peripheral blood mononuclear cells (PBMCs) of women with PCOS, via RT-PCR method. Results Vitamin D supplementation led to a significant reduction in serum AMH (− 0.7 ± 1.2 vs. − 0.1 ± 0.5 ng/mL, P  = 0.02), insulin levels (− 1.4 ± 1.6 vs. -0.3 ± 0.9 μIU/mL, P  = 0.007), homeostatic model of assessment for insulin resistance (− 0.3 ± 0.3 vs. -0.1 ± 0.2, P  = 0.008), and a significant increase in quantitative insulin sensitivity check index (+ 0.009 ± 0.01 vs. + 0.001 ± 0.004, P  = 0.04), compared with the placebo. Moreover, following vitamin D supplementation there was a significant decrease in serum total- (− 5.1 ± 12.6 vs. + 2.9 ± 10.9 mg/dL, P  = 0.03) and LDL-cholesterol levels (− 4.5 ± 10.3 vs. + 2.5 ± 10.6 mg/dL, P = 0.04) compared with the placebo. Conclusion Overall, the findings of this trial supported that 50,000 IU vitamin D supplementation every other week for 8 weeks had beneficial effects on insulin metabolism, and lipid profile of infertile women with PCOS who are candidate for IVF. These benefits might not be evident upon having sufficient vitamin D levels. Trial registration This study was retrospectively registered in the Iranian website ( www.irct.ir ) for clinical trials registration ( http://www.irct.ir : IRCT20170513033941N27).

This study examined the associations of 25-hydroxyvitamin D and specific host genetic variants that affect vitamin D levels or its effects on immune function, with the risk of TB or mortality in children. A case-cohort sample of 466 South African infants enrolled in P1041 trial (NCT00080119) underwent 25-hydroxyvitamin D testing by chemiluminescent immunoassay. Single nucleotide polymorphisms (SNPs) that alter the effect of vitamin D [e.g. vitamin D receptor (VDR)], vitamin D levels [e.g. vitamin D binding protein (VDBP)], or toll like receptor (TLR) expression (SIGIRR including adjacent genes PKP3 and TMEM16J) were identified by real-time PCR. Outcomes were time to TB, and to the composite of TB or death by 192 weeks of follow-up. Effect modification between vitamin D status and SNPs for outcomes was assessed. Median age at 25-hydroxyvitamin D determination was 8 months; 11% were breastfed, 51% were HIV-infected and 26% had low 25-hydroxyvitamin D (<32ng/mL). By 192 weeks, 138 incident TB cases (43 definite/probable, and 95 possible) and 26 deaths occurred. Adjusting for HIV status and potential confounders, low 25-hydroxyvitamin D was associated with any TB (adjusted hazard ratio [aHR] 1.76, 95% CI 1.01-3.05; p = 0.046) and any TB or death (aHR 1.76, 95% CI 1.03-3.00; p = 0.038). Children with low 25-hydroxyvitamin D and TMEM 16J rs7111432-AA or PKP3 rs10902158-GG were at increased risk for probable/definite TB or death (aHR 8.12 and 4.83, p<0.05) and any TB or death (aHR 4.78 and 3.26, p<0.005) respectively; SNPs in VDBP, VDR, and vitamin D precursor or hydroxylation genes were not. There was significant interaction between low 25-hydroxyvitamin D and, TMEM 16J rs7111432-AA (p = 0.04) and PKP3 rs10902158-GG (p = 0.02) SNPs. Two novel SNPs, thought to be associated with innate immunity, in combination with low vitamin D levels were identified as increasing a young child's risk of developing TB disease or death. Identifying high-risk children and providing targeted interventions such as vitamin D supplementation may be beneficial. ClinicalTrials.gov NCT00080119.

SummaryWe studied the association between CYP2R1 genetic polymorphisms and circulating 25-hydroxyvitamin D [25(OH)D] before and after supplementation with vitamin D3 in 218 elderly. We found differences between 3 and 8 ng/ml in circulating levels at baseline in women but not in the response after 1 year of supplementation.IntroductionThis study evaluated the association between polymorphisms in four single nucleotide polymorphisms (SNPs) of the CYP2R1 gene and 25(OH)D levels before and 1 year after supplementation with two different doses of vitamin D3 (600 IU daily or a dose equivalent to 3750 IU daily), in a cohort of 218 (96 men and 122 women) Lebanese elderly overweight subjects.MethodsGenotyping was performed for rs12794714, rs10741657, rs1562902, and rs10766197 SNPs using real-time PCR. The 25(OH)D levels were measured by liquid chromatography tandem mass spectrometry.ResultsAt baseline, the mean ± SD age was 71.0 ± 4.7 years, BMI 30.3 ± 4.6 kg/m2, and 25(OH)D level was 20.5 ± 7.6 ng/ml. There were significant differences in mean 25(OH)D levels between genotypes in women, but not in men. After adjustment for age, season, and BMI, the homozygous for the low frequency gene variant (HLV) of rs1562902 and rs10741657 SNPs had the highest mean 25(OH)D levels with difference of 7.6 ng/ml for rs1562902 SNP (p < 0.01) and of 5.9 ng/ml for rs10741657 (p = 0.05) compared to the homozygous for the major polymorphisms (HMPs). Conversely, for rs10766197 and rs12794714 SNPs, HMP had the highest mean 25(OH)D levels with difference of 6 ng/ml for rs10766197 (p = 0.003) and of 4.8 ng/ml (p = 0.02) for rs12794714, compared to the HLV. CYP2R1 genetic polymorphisms explained 4.8 to 9.8 % of variability in 25(OH)D in women. After 1 year, there was no difference in the response to vitamin D3 supplementation between genotypes in either gender.ConclusionThis study showed a difference in 25(OH)D levels between CYP2R1 genotypes that equates a daily supplementation of 400–800 IU vitamin D, depending on genotype. It underscores possible important genetic contributions for the high prevalence of hypovitaminosis D in the Middle East.

•This study analyzed the relationship between serum 25-hydroxyvitamin D (25[OH]D) level and muscle mass and function, and investigated whether this relationship was modified by vitamin D receptor gene polymorphisms.•With serum 25(OH)D levels <10.0 ng/mL, the risk of low handgrip strength was 3.04 times higher than that with serum 25(OH)D levels >20.0 ng/mL.•T allele of Fok1 and bb genotype of Bsm1 were significantly associated with more handgrip strength and a significant interaction exists between 25(OH)D and vitamin D receptor genotypes. The aim of this cross-sectional study was to investigate the association of serum 25-hydroxyvitamin D (25[OH]D) levels and vitamin D receptor (VDR) genotypes with skeletal muscle mass and function in elderly subjects in northern China. A total of 275 men and 510 women, ages 63.1 to 72.5 y, in two randomly selected communities in Beijing were investigated. The investigation included a questionnaire, physical measurements, muscle mass and function measurements, serum 25(OH)D levels, and VDR gene polymorphisms analysis. In the group with 25(OH)D levels <10.0 ng/mL, the proportion with low handgrip strength was 3.04 times higher than that in the group with 25(OH)D levels >20.0 ng/mL for men (odds ratio: 3.04; 95% confidence interval, 1.13-8.20) but not for women. The general linear model showed that higher 25(OH)D levels and having T allele of Fok1 and the bb genotype of Bsm1 were significantly associated with more handgrip strength. The regression coefficients (β) were 1.80 (P < 0.01), 1.26 (P < 0.01), and 2.90 (P < 0.01), respectively. There was a significant interaction between 25(OH)D and VDR gene polymorphisms for handgrip strength for both Fok1 (β = 2.86; P < 0.01) and Bsm1 (β = 3.14; P = 0.02) after adjustment for potential confounders (sex, age, body mass index, fat mass, physical activity, sun exposure, energy, and protein intake). 25(OH)D levels are associated with handgrip strength for men and this relationship could be modified with the interaction between 25(OH)D and VDR gene polymorphisms (Fok1 and Bsm1).

In a longitudinal study including 642 healthy 8–11-year-old Danish children, we investigated associations between vitamin D dependent SNP and serum 25-hydroxyvitamin D (25(OH)D) concentrations across a school year (August–June). Serum 25(OH)D was measured three times for every child, which approximated measurements in three seasons (autumn, winter, spring). Dietary and supplement intake, physical activity, BMI and parathyroid hormone were likewise measured at each time point. In all, eleven SNP in four vitamin D-related genes: Cytochrome P450 subfamily IIR1 (CYP2R1); 7-dehydrocholesterol reductase/nicotinamide adenine dinucleotide synthetase-1(DHCR7/NADSYN1); group-specific complement (GC); and vitamin D receptor were genotyped. We found minor alleles of CYP2R1 rs10500804, and of GC rs4588 and rs7041 to be associated with lower serum 25(OH)D concentrations across the three seasons (all P<0·01), with estimated 25(OH)D differences of −5·8 to −10·6 nmol/l from major to minor alleles homozygosity. In contrast, minor alleles homozygosity of rs10741657 and rs1562902 in CYP2R1 was associated with higher serum 25(OH)D concentrations compared with major alleles homozygosity (all P<0·001). Interestingly, the association between season and serum 25(OH)D concentrations was modified by GC rs7041 (P interaction=0·044), observed as absence of increase in serum 25(OH)D from winter to spring among children with minor alleles homozygous genotypes compared with the two other genotypes of rs7041 (P<0·001). Our results suggest that common genetic variants are associated with lower serum 25(OH)D concentrations across a school year. Potentially due to modified serum 25(OH)D response to UVB sunlight exposure. Further confirmation and paediatric studies investigating vitamin D-related health outcomes of these genotypic differences are needed.

Self-reported tiredness or low energy, often referred to as fatigue, has been linked to low levels of circulating 25-hydroxyvitamin D (25OHD), a biomarker of vitamin D status. Although it is uncertain if the association is causal, fatigue is a common indication for testing, and correcting, low 25OHD-levels. We used two-sample Mendelian randomization to test for genetic evidence of a causal association between low 25OHD-levels and fatigue. Genetic-25OHD associations were estimated from the largest genome-wide association study of vitamin D to date, and genetic-fatigue associations were estimated in 327,478 individuals of European descent in UK Biobank, of whom 19,526 (5.96%) reported fatigue (tiredness or low energy nearly every day over the past two weeks). Using seven genome-wide significant 25OHD-reducing genetic variants, there was little evidence for a causal effect of 25OHD on fatigue [odds ratio for fatigue was 1.05 with 95% confidence interval (CI) of 0.87–1.27 per unit decrease in log-transformed 25OHD (1.02 with 95% CI of 0.99-1.06 per 1-SD decrease in log-transformed 25OHD)]. There was also little evidence of association between any individual 25OHD-reducing variant and fatigue. Our results suggest that a clinically relevant protective effect of 25OHD-levels on fatigue is unlikely. Therefore, vitamin D supplementation of the general population to raise 25OHD-levels is not likely to be useful in preventing fatigue.