Effects of Genetic and Nongenetic Factors on Total and Bioavailable 25(OH)D Responses to Vitamin D Supplementation

Prevalence of low vitamin D levels among older US Asian and Pacific Islander adults

While US Asian and Pacific Islander adults have lower 25-hydroxyvitamin D (25(OH)D) levels than White adults, ethnic subgroup data remain limited. In a large California population, the adjusted prevalence of 25(OH)D < 20 ng/mL (50 nmol/L) was 1.5- to 2.7-fold higher for Asian/Pacific Islander compared to White adults, with substantial variation by ethnicity.

PURPOSE

US Asian and Pacific Islander (PI) adults generally have lower 25-hydroxyvitamin D [25(OH)D] levels than non-Hispanic White (NHW) adults, but subgroup data remain limited. We compared sex- and ethnicity-specific prevalence of low 25(OH)D among older Asian/PI and NHW adults.

METHODS

Data from 102,556 Asian/PI and 381,724 NHW adults aged 50-89 years with measured 25(OH)D in 2012-2019 and body mass index (BMI, within ± 1 year) were examined in a California healthcare system. Low 25(OH)D < 20 ng/mL (50 nmol/L) was examined by race and ethnicity. Covariates included age, smoking, BMI, and season of measurement. Modified Poisson regression was used to estimate prevalence ratios (aPR), adjusting for covariates.

RESULTS

Among 31,287 Asian/PI men and 71,269 Asian/PI women, the prevalence of low 25(OH)D was 22.6% and 14.7%, respectively, significantly higher than observed for 122,162 NHW men (12.3%) and 259,562 NHW women (9.9%). Within Asian/PI subgroups, low 25(OH)D prevalence ranged from 17 to 18% (Korean, Japanese, Filipino), 22 to 24% (Chinese, Vietnamese), 28% (South Asian), and 35% (Native Hawaiian/PI) among men and 11 to 14% (Japanese, Filipina, Chinese, Korean), 17 to 18% (South Asian, Vietnamese), and 26% (Native Hawaiian/PI) among women. The corresponding aPRs (NHW reference) for men and women were as follows: Native Hawaiian/PI, 2.70 and 2.34; South Asian, 2.56 and 2.07; Vietnamese, 2.17 and 2.31; Chinese, 2.04 and 1.89; Korean, 1.60 and 1.85; Filipino, 1.58 and 1.52; and Japanese, 1.58 and 1.49 (p < 0.001).

CONCLUSION

In a large US healthcare population of older Asian/PI adults, low 25(OH)D prevalence was 1.5- to 2.7-fold higher for Asian/PI compared to NHW adults, with substantial variation by sex and ethnicity.

Association of rs4588 polymorphism in vitamin D binding protein gene with polycystic ovarian syndrome in Iranian women: a case-control study

OBJECTIVE

Vitamin D deficiency and variations in the vitamin D binding protein (VDBP) gene may play a role in the development of Polycystic ovary syndrome (PCOS). This study aims to investigate the association of the rs4588 polymorphism with PCOS in Iranian women, as well as its association with infertility and recurrent pregnancy loss (RPL) in these patients.

RESULTS

The analysis revealed statistically significant differences in the distributions of genotypes and alleles of the rs4588 polymorphism among the three groups (p < 0.0001). The AC genotype and A allele showed an association with an elevated risk of PCOS and infertility. In this study, no association was found between genotypes and alleles of the rs4588 polymorphism and the risk of RPL in women with PCOS. Subjects with the AA or AC genotype exhibited significantly higher levels of LDL compared to those with the CC genotype.

Relationship between Vitamin D3 Deficiency, Metabolic Syndrome and VDR, GC, and CYP2R1 Gene Polymorphisms

The presence of vitamin D3 deficiency associated with the presence of metabolic syndrome (MS) has important public health effects. This study aims to investigate the relationship between vitamin D3 deficiency, MS and vitamin D3 receptor (VDR), GC Vitamin D binding protein (GC), and cytochrome P450 family 2 subfamily R member 1 (CYP2R1) gene polymorphisms, and genes whose encoded proteins are responsible for vitamin D3 metabolism and transport. A total of 58 participants were included in this study (age 39 ± 12 years) and were selected over a 12-month period. They were divided into four groups, depending on the presence of polymorphisms in VDR, GC, and CYP2R1 genes and their weight status. At baseline, in months 3, 6, and 12, biochemical parameters including 25(OH)D3, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, and homeostatic model assessment (HOMA index), the insulin resistance indicator were measured. Our results show that all subjects in the polymorphism group supplemented with vitamin D3 reached an optimal level of vitamin D3 associated with high concentrations of 25(OH)D3. Weight loss was most significant in patients in the POW group (overweight patients).

Associations of vitamin D receptor polymorphisms with risk of Alzheimer's disease, Parkinson's disease, and mild cognitive impairment: a systematic review and meta-analysis

Vitamin D is a lipid soluble steroid hormone, which plays a critical role in the calcium homeostasis, neuronal development, cellular differentiation, and growth by binding to vitamin D receptor (VDR). Associations between VDR gene polymorphism and Alzheimer's disease (AD), Parkinson's disease (PD), and mild cognitive impairment (MCI) risk has been investigated extensively, but the results remain ambiguous. The aim of this study was to comprehensively assess the correlations between four VDR polymorphisms (FokI, BsmI, TaqI, and ApaI) and susceptibility to AD, PD, and MCI. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the relationship of interest. Pooled analyses suggested that the ApaI polymorphism decreased the overall AD risk, and the TaqI increased the overall PD susceptibility. In addition, the BsmI and ApaI polymorphisms were significantly correlated with the overall MCI risk. Stratified analysis by ethnicity further showed that the TaqI and ApaI genotypes reduced the AD predisposition among Caucasians, while the TaqI polymorphism enhanced the PD risk among Asians. Intriguingly, carriers with the BB genotype significantly decreased the MCI risk in Asian descents, and the ApaI variant elevated the predisposition to MCI in Caucasians and Asians. Further studies are need to identify the role of VDR polymorphisms in AD, PD, and MCI susceptibility.

Genetic variations of vitamin D receptor and vitamin D supplementation interaction in relation to serum vitamin D and metabolic traits: a systematic review and meta-analysis

Background: It is now becoming increasingly recognized that the effects of vitamin D supplementation may vary by several factors including vitamin D deficiency status, ethnicity, and/or the presence of genetic variants, which affect individual responses to supplementation. This study investigates the interaction between metabolic traits and circulating 25-hydroxyvitamin-D (25OHD) concentration with 4 polymorphisms of vitamin D receptor (VDR) including BsmI, ApaI, TaqI, FokI, and vitamin D supplementation. Methods: A systematic review and meta-analysis of papers until August 2021 on PubMed, The Cochrane Library, Scopus, Web of Science, Google Scholar, ProQuest, Science Direct, and Embase about the association between functionally relevant VDR variants and vitamin D supplementation on circulating 25OHD and metabolic traits. Results: A total of 2994 cases from 16 randomized controlled trial (RCT) studies were included in meta-analyses. There were no significant changes in the serum concentrations of 25OHD and metabolic traits after vitamin D supplementation in different variants of BsmI, ApaI, TaqI, and FokI polymorphism in the VDR gene in the overall analysis (p>0.05). However, the results showed there is significant interaction between these above VDR polymorphisms and vitamin D supplement on serum 25OHD level after subgroup analyses based on the study duration, gender, age, BMI, health status, Hardy-Weinberg Equilibrium, PCR, and race (p<0.05). Conclusions: The present meta-analysis demonstrates that the effect of vitamin D supplementation on serum 25OHD and metabolic traits is independent of genetic variants of the VDR gene (BsmI, ApaI, TaqI, and FokI). However, future trials should consider inter-individual differences and, in particular, should aim to clarify whether certain subgroups of individuals may benefit from vitamin D supplementation in the context of metabolic health.

Association of Vitamin D Genetic Risk Score with Noncommunicable Diseases: A Systematic Review

Background and Aims: The genetic risk score (GRS) is an important tool for estimating the total genetic contribution or susceptibility to a certain outcome of interest in an individual, taking into account their genetic risk alleles. This study aims to systematically review the association between the GRS of low vitamin D with different noncommunicable diseases/markers. Methods: The article was first registered in PROSPERO CRD42023406929. PubMed and Embase were searched from the time of inception until March 2023 to capture all the literature related to the vitamin D genetic risk score (vD-GRS) in association with noncommunicable diseases. This was performed using comprehensive search terms including "Genetic Risk Score" OR "Genetics risk assessment" OR "Genome-wide risk score" AND "Vitamin D" OR 25(HO)D OR "25-hydroxyvitamin D". Results: Eleven eligible studies were included in this study. Three studies reported a significant association between vD-GRS and metabolic parameters, including body fat percentage, body mass index, glycated hemoglobin, and fasting blood glucose. Moreover, colorectal cancer overall mortality and the risk of developing arterial fibrillation were also found to be associated with genetically deprived vitamin D levels. Conclusions: This systematic review highlights the genetic contribution of low-vitamin-D-risk single nucleotides polymorphisms (SNPs) as an accumulative factor associated with different non-communicable diseases/markers, including cancer mortality and the risk of developing obesity, type 2 diabetes, and cardiovascular diseases such as arterial fibrillation.

Free and bioavailable 25-hydroxyvitamin D thresholds for bone metabolism and their associations with metabolic syndrome in Chinese women of childbearing age

Objective

The free hormone hypothesis suggests that free and bioavailable 25-hydroxyvitamin D [25(OH)D] may better reflect vitamin D bioactivity. This study aimed to determine the free and bioavailable 25(OH)D characteristics, estimate their thresholds based on parathyroid hormone (PTH) and bone turnover markers (BTMs), assess their associations with the risk of metabolic syndrome (MetS), and evaluate their potential advantages.

Methods

A cross-sectional study was conducted using a nationally representative database (n = 1,505, female, 18-45 years). Serum total 25(OH)D, vitamin D-binding protein, albumin, PTH, and BTMs [osteocalcin, β-CrossLaps of type 1 collagen containing cross-linked C-telopeptide (β-CTX), and procollagen type 1 N-terminal propeptide (P1NP)] were measured. Free 25(OH)D and bioavailable 25(OH)D were calculated. The threshold associations of 25(OH)D with PTH and BTMs were analyzed. The relationship between 25(OH)D and MetS risk was examined. An intervention study was then performed in 39 women (18-47 years) to assess the associations of increasing 25(OH)D with PTH and BTMs after vitamin D supplementation.

Results

In the cross-sectional study, the three forms of 25(OH)D were found to have similar distribution characteristics. Free and bioavailable 25(OH)D correlated well with total 25(OH)D. Significant total 25(OH)D cutoffs were observed for PTH (14.19 ng/mL and 18.03 ng/mL), osteocalcin (15.14 ng/mL), β-CTX (14.79 ng/mL), and P1NP (15.08 ng/mL). Free and bioavailable 25(OH)D cutoffs were only found for P1NP (3.47 pg/mL and 1.66 ng/mL, respectively). A total 25(OH)D of <15.14 ng/mL was marginally associated with a higher risk of reduced high-density lipoprotein cholesterol (HDL-C) [odd ratios (OR) = 1.371 (0.991-1.899)]. The ORs of higher versus lower free and bioavailable 25(OH)D levels for reduced HDL-C were 0.770 (0.621-0.956) and 0.772 (0.622-0.958), respectively. The results of the intervention study indicated that PTH and BTMs responded more sensitively to total 25(OH)D than to free or bioavailable 25(OH)D.

Conclusion

Free and bioavailable 25(OH)D only had a threshold effect on P1NP. The active 25(OH)D thresholds could be used for risk assessment of reduced HDL-C. However, no superiority of free or bioavailable 25(OH)D was found based on the response of PTH and BTMs to changes in 25(OH)D in Chinese women of childbearing age following vitamin D supplementation.

Clinical trial registration

http://www.chictr.org.cn, ChiCTR2200058290.

Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate

Following two requests from the European Commission (EC), the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin D and to propose a conversion factor (CF) for calcidiol monohydrate into vitamin D3 for labelling purposes. Vitamin D refers to ergocalciferol (vitamin D2), cholecalciferol (vitamin D3), and calcidiol monohydrate. Systematic reviews of the literature were conducted to assess the relative bioavailability of calcidiol monohydrate versus vitamin D3 on serum 25(OH)D concentrations, and for priority adverse health effects of excess vitamin D intake, namely persistent hypercalcaemia/hypercalciuria and endpoints related to musculoskeletal health (i.e. falls, bone fractures, bone mass/density and indices thereof). Based on the available evidence, the Panel proposes a CF for calcidiol monohydrates of 2.5 for labelling purposes. Persistent hypercalciuria, which may be an earlier sign of excess vitamin D than persistent hypercalcaemia, is selected as the critical endpoint on which to base the UL for vitamin D. A lowest-observed-adverse-effect-level (LOAEL) of 250 μg/day is identified from two randomised controlled trials in humans, to which an uncertainty factor of 2.5 is applied to account for the absence of a no-observed-adverse-effect-level (NOAEL). A UL of 100 μg vitamin D equivalents (VDE)/day is established for adults (including pregnant and lactating women) and for adolescents aged 11-17 years, as there is no reason to believe that adolescents in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults. For children aged 1-10 years, a UL of 50 μg VDE/day is established by considering their smaller body size. Based on available intake data, European populations are unlikely to exceed the UL, except for regular users of food supplements containing high doses of vitamin D.

Impact of Intravenous Iron Substitution on Serum Phosphate Levels and Bone Turnover Markers-An Open-Label Pilot Study

The association between intravenous iron substitution therapy and hypophosphatemia was previously reported in patients with iron deficiency anemia. However, the extent of hypophosphatemia is thought to depend on the type of iron supplementation. We hypothesized that the intravenous application of ferric carboxymaltose and iron sucrose leads to a different longitudinal adaptation in serum phosphate levels. In this open-label pilot study, a total of 20 patients with inflammatory bowel diseases or iron deficiency anemia were randomly assigned to one of two study groups (group 1: ferric carboxymaltose, n = 10; group 2: iron sucrose, n = 10). Serum values were controlled before iron substitution therapy, as well as 2, 4, and 12 weeks after the last drug administration. The primary objective of the study was the longitudinal evaluation of serum phosphate levels after iron substitution therapy with ferric carboxymaltose and iron sucrose. The secondary objective was the longitudinal investigation of calcium, 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone, procollagen type 1 amino-terminal propeptide (P1NP), beta-CrossLaps (CTX), hemoglobin (Hb), iron, ferritin, and transferrin saturation levels. Two weeks after drug administration, phosphate levels were significantly lower (p < 0.001) in group 1 and ferritin levels were significantly higher (p < 0.001) in group 1. Phosphate levels (0.8-1.45 mmol/L) were below the therapeutic threshold and ferritin levels (10-200 ng/mL for women and 30-300 ng/mL for men) were above the therapeutic threshold in group 1. P1NP (15-59 µg/L) and CTX (<0.57 ng/mL) levels were above the therapeutic threshold in group 2. Four weeks after drug administration, significant differences were still observed between both study groups for phosphate (p = 0.043) and ferritin (p = 0.0009). All serum values except for Hb were within the therapeutic thresholds. Twelve weeks after drug administration, no differences were observed in all serum values between both study groups. Hb values were within the therapeutic threshold in both study groups. Serum 25(OH)D levels did not differ between both study groups throughout the whole study period and remained within the therapeutic threshold.

Vitamin D binding protein gene polymorphisms are associated with lower plasma 25-hydroxy-cholecalciferol concentrations in Ethiopian lactating women

Ethiopian women have been reported to have low plasma 25-hydroxy-cholecalciferol (25(OH)D) concentrations despite an abundance of sunshine. Low dietary vitamin D intake, limited skin exposure to sun, and genetics are among factors suggested to affect vitamin D status in this population. In this study (Clinical Trial NCT02210884), we hypothesized that polymorphisms in the vitamin D binding protein (VDBP) gene (rs7041, rs4588) are associated with reduced plasma 25(OH)D concentrations in Ethiopian women. Lactating Ethiopian women (n = 110) were randomly assigned to weekly administration of vitamin D3 (15,000 IU) or a placebo. Plasma 25(OH)D was measured at baseline (within 2 weeks of delivery, before supplementation) and at 3, 6, and 12 months after delivery. Associations between VDBP polymorphism status for rs7041 and rs4588 and plasma 25(OH)D were determined by analysis of variance and multiple linear and logistic regressions. Multiple linear regression with maternal age as a covariate revealed that rs7041 is associated with reduced plasma 25(OH)D (P = .021) and more risk alleles at rs7041 and rs4588 are associated with reduced plasma 25(OH)D (P = .017). Logistic regression models for vitamin D insufficiency showed that additional risk alleles for rs7041 and rs4588 are associated with increased odds ratios (OR = 1.66; 95% CI, 1.10-2.62; P = .019) for plasma 25(OH)D below 40 nmol/L. Supplementation increased plasma 25(OH)D at 3 months in women with fewer risk alleles and across all genotypes at 6 and 12 months. VDBP polymorphisms may contribute to vitamin D insufficiency in Ethiopian lactating women. Furthermore, VDBP polymorphisms may blunt short-term responses to vitamin D supplementation and require longer periods of intervention.

Variability in response to vitamin D supplementation according to vitamin D metabolism related gene polymorphisms in healthy adults

OBJECTIVE

The aim of this study was to determine the influence of polymorphisms in some key gene actors of the vitamin D (vitD) metabolic pathway on supplementation efficacy.

METHODS

In total, 245 healthy participants were recruited from occupational medicine service in Sahloul University Hospital with vitD deficiency [25(OH)D ≤ 30 ng/ml]. After giving an informed consent, all participants were asked to complete a generalized questionnaire and to follow a detailed personalized supplementation protocol. Genetic study was performed by PCR-RFLP for 15 single nucleotide polymorphisms (SNPs) belonging to DBP, CYP2R1, CYP27B14, CYP24A1 and VDR genes. Statistical study was carried out with SPSS23.0.

RESULTS

Among the studied SNPs, non-response was significantly associated with variant alleles of rs4588 (OR* = 11.51; p < 0.001), rs10766197 (OR* = 6.92; p = 0.008) and rs12794714 (OR* = 5.09; p = 0.004). These three SNPs contributed in 18.8% in response variability with rs4588 being the most influential (10.3%). There was a significant linear negative correlation between baseline 25(OH)D and post supplementation 25(OH)D concentration (r = -0.437; p < 0.001) as well as a linear negative association between the increase in 25(OH)D concentration and GRS (GRS: genetic risk score = the sum of risk alleles) (r = -0.149; p = 0.033).

CONCLUSIONS

DBP-rs4588, CYP2R1-rs10766197 and rs12794714 variants are associated with variations in serum 25(OH)D concentrations and efficacy of response to vitD supplementation in Tunisian adults. Taking into account these variations can help to better adapt vitD intake to ensure a higher response to supplementation.

Personalized nutrition: A review of genotype-based nutritional supplementation

Nutritional disorders have become a major public health issue, requiring increased targeted approaches. Personalized nutrition adapted to individual needs has garnered dramatic attention as an effective way to improve nutritional balance and maintain health. With the rapidly evolving fields of genomics and nutrigenetics, accumulation of genetic variants has been indicated to alter the effects of nutritional supplementation, suggesting its indispensable role in the genotype-based personalized nutrition. Additionally, the metabolism of nutrients, such as lipids, especially omega-3 polyunsaturated fatty acids, glucose, vitamin A, folic acid, vitamin D, iron, and calcium could be effectively improved with related genetic variants. This review focuses on existing literatures linking critical genetic variants to the nutrient and the ways in which these variants influence the outcomes of certain nutritional supplementations. Although further studies are required in this direction, such evidence provides valuable insights for the guidance of appropriate interventions using genetic information, thus paving the way for the smooth transition of conventional generic approach to genotype-based personalized nutrition.

Association of Serum 25(OH)D with Metabolic Syndrome in Chinese Women of Childbearing Age

Objective: To analyze the associations between serum 25(OH)D levels and the risk of metabolic syndrome (MetS) and its components, and the related genetic and non-genetic factors in non-diabetic women of childbearing age in China. Methods: Subjects were randomly selected from the 2015 Chinese Adult Chronic Disease and Nutrition Surveillance. The data of sociodemographic characteristics and lifestyle factors were obtained through questionnaire survey. Anthropometry was measured by trained interviewers, and fasting blood was collected to test 25-hydroxyvitamin D [25(OH)D], total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), and other related parameters. Generalized linear mode and multivariate logistic analysis were performed to analyze the associations between serum 25(OH)D and MetS and its components, adjusting for the possible confounders. Results: Body mass index (BMI), serum alanine aminotransferase (ALT), hypersensitive C-reactive protein (hs-CRP), 25(OH)D, phosphorus (P), and parathyroid hormone (PTH) levels were associated with the number of MetS’s components. G allele carriers of GC rs2282679 had higher diastolic blood pressure (DBP) and FBG levels compared with the TT genotypes, while higher genetic risk score (GRS) seemed to be associated with reduced HDL-C level. The odds ratio (OR) for MetS in lowest group of 25(OH)D was 1.533 (0.980−2.399) after adjusting for season, district, area type, latitude, age, BMI, PTH, P, ALT, CRE, interleukin-6 (IL-6), and hs-CRP, compared with the median group, but the association was not significant. An insufficient 25(OH)D concentration (<14.22 ng/mL) was significantly related to the risk of elevated waist circumference (WC) (OR = 1.612 (1.014−2.561)) and TG (OR = 2.210 (1.318−3.706)), and reduced HDL-C (OR = 1.639 (1.206−2.229)) after adjusting for the confounders among these women. Moreover, these relationships were not affected by vitamin D metabolism-related gene polymorphisms. Conclusion: After comprehensively considering various influencing factors, significant associations between insufficient serum 25(OH)D and MetS‘s components, including elevated WC, TG, and reduced HDL-C, were observed. However, MetS, hypertension, and hyperglycemia were not found independently associated with 25(OH)D levels.

Daily v. weekly oral vitamin D3 therapy for nutritional rickets in Indian children: a randomised controlled open-label trial

The aim of the study was to compare the efficacy of daily v. weekly oral vitamin D3 therapy in radiological healing of nutritional rickets. Children 6 months to 12 years (n 132) diagnosed with nutritional rickets were randomised into three groups (n 44): group A - 2000 IU daily vitamin D3 for 12 weeks, B - 60 000 IU weekly for 3 weeks, C - 60 000 IU weekly for 6 weeks. Serum calcium, phosphorus, 25-hydroxyvitamin D (25(OH)D), parathyroid hormone and X-ray score were estimated at baseline and 12 weeks (endline). The proportion of children who achieved complete radiological healing at endline was compared between three groups by χ2 and delta change in laboratory parameters by ANOVA (parametric data) or Kruskal Wallis test (non-parametric data), respectively. Baseline 25(OH)D ≤ 20 ng/ml was seen in 119 (90·2 %), hyperparathyroidism in 90 (68·8 %) and hypocalcaemia in 96 (72·7 %). A total of 120/132 children completed the study. Complete radiological healing seen in 30 (75 %) in group A, 23 (60·5 %) in group B and 26 (61·9 %) in group C; P = 0·15, with comparable endline X-ray scores; P = 0·31. The median (interquartile range (IQR)) delta X-ray score (baseline-endline) was 7 (4,9), 5 (2·25, 6) and 6 (4,7) in groups A, B and C, respectively; P = 0·019. Median (IQR) 25(OH)D endline levels in groups A, B and C were 50·0 (26·5, 66·5), 42·1 (28·4, 54·4) and 53·5 (33·7, 71·2) ng/ml, respectively; P = 0·045. Radiological scores were comparable at endline among daily and weekly vitamin D groups with greater change from baseline in daily supplemented group.

Vitamin D biomarkers for Dietary Reference Intake development in children: a systematic review and meta-analysis

BACKGROUND

Circulating 25-hydroxyvitamin D [25(OH)D] has been the accepted vitamin D exposure/intake biomarker of choice within recent DRI exercises, but use of other vitamin D-related biomarkers as well as functional markers has been suggested. These may be of value in future vitamin D DRI exercises, such as the FAO/WHO's one for young children.

OBJECTIVES

To systematically review the usefulness of circulating 25(OH)D, parathyroid hormone (PTH), free and bioavailable 25(OH)D, C3-epimer of 25(OH)D, vitamin D3, 24,25-dihydroxyvitamin D [24,25(OH)2D], and bone turnover markers and calcium absorption as vitamin D biomarkers for DRI development in children.

METHODS

Methods included structured searches of published articles, full-text reviews, data extraction, quality assessment, meta-analysis, and random-effects meta-regression.

RESULTS

Fifty-nine vitamin D supplementation randomized controlled trials (RCTs) were included (39 in infants/children as the priority group and the remainder in adults since pediatric studies were absent/limited). Vitamin D supplementation significantly raised circulating 25(OH)D in infants and children, but the response was highly heterogeneous [weighted mean difference (WMD): 27.7 nmol/L; 95% CI: 22.9, 32.5; 27 RCTs; I2 = 93%]. Meta-regression suggested an increase by 1.7 nmol/L (95% CI: 0.7, 2.6) in serum 25(OH)D per each 100-IU increment in vitamin D intake (P = 0.0005). Vitamin D supplementation had a significant effect on circulating 24,25(OH)2D (WMD: 3.4 nmol/L; 95% CI: 2.4, 4.5; 13 RCTs; I2 = 95%), with a dose-response relation (+0.15 nmol/L per 100 IU; 95% CI: -0.01, 0.29). With circulating PTH, although there was a significant effect of vitamin D on WMD (P = 0.05), there was no significant dose-response relation (P = 0.32). Pediatric data were too limited in relation to the usefulness of the other biomarkers.

CONCLUSIONS

Circulating 25(OH)D may be a useful biomarker of vitamin D exposure/intake for DRI development in infants and children. Circulating 24,25(OH)2D also showed some promise, but further data are needed, especially in infants and children.

Threshold for Relationship between Vitamin D and Parathyroid Hormone in Chinese Women of Childbearing Age

Background: The aim of this study was to assess the relationship between serum 25-hydroxyvitamin D [25(OH)D] and serum intact parathyroid hormone (PTH) in Chinese childbearing women, and to estimate the optimum threshold of 25(OH)D that maximally inhibits the PTH, which is considered to be the optimal status for vitamin D sufficiency. Methods: Serum samples were selected from the biological samples' bank of the Chinese Chronic Diseases and Nutrition Survey (CCDNS) 2015. The serum 25(OH)D concentration was determined by liquid chromatography tandem mass spectrometry and the serum PTH was determined by electronic chemiluminescence. Simple linear and partial correlation analysis, locally weighted regression smooth scatterplot (LOESS), nonlinear least squares estimation (NLS), and segmented regression (SR) were utilized to estimate the relationship of 25(OH)D and PTH, and to determine the threshold of 25(OH)D. Results: A total of 1568 serum samples of 25(OH)D concentration and PTH concentration were analyzed. A significant inverse relationship between 25(OH)D and PTH concentration was observed below 15.25 (14.22-16.28) ng/mL, and PTH decreased slowly with the increase of 25(OH)D above 16.75 (15.43-18.06) ng/mL after adjusting by age, latitude, city type, season, corrected calcium, and phosphorus. A very short plateau of PTH was found at 15.25 ng/mL and 16.75 ng/mL in terms of 25(OH)D according to LOESS, NLS, and SR. Conclusions: The serum 25(OH)D was negatively correlated with the serum PTH. The threshold of VitD sufficiency was found in the range of 14.22-18.06 ng/mL in terms of serum 25(OH)D concentration for Chinese childbearing women aged 18-44 years old.

Unveiling Genetic Variants Underlying Vitamin D Deficiency in Multiple Korean Cohorts by a Genome-Wide Association Study

BACKGROUND

Epidemiological data have shown that vitamin D deficiency is highly prevalent in Korea. Genetic factors influencing vitamin D deficiency in humans have been studied in Europe but are less known in East Asian countries, including Korea. We aimed to investigate the genetic factors related to vitamin D levels in Korean people using a genome-wide association study (GWAS).

METHODS

We included 12,642 subjects from three different genetic cohorts consisting of Korean participants. The GWAS was performed on 7,590 individuals using linear or logistic regression meta- and mega-analyses. After identifying significant single nucleotide polymorphisms (SNPs), we calculated heritability and performed replication and rare variant analyses. In addition, expression quantitative trait locus (eQTL) analysis for significant SNPs was performed.

RESULTS

rs12803256, in the actin epsilon 1, pseudogene (ACTE1P) gene, was identified as a novel polymorphism associated with vitamin D deficiency. SNPs, such as rs11723621 and rs7041, in the group-specific component gene (GC) and rs11023332 in the phosphodiesterase 3B (PDE3B) gene were significantly associated with vitamin D deficiency in both meta- and mega-analyses. The SNP heritability of the vitamin D concentration was estimated to be 7.23%. eQTL analysis for rs12803256 for the genes related to vitamin D metabolism, including glutamine-dependent NAD(+) synthetase (NADSYN1) and 7-dehydrocholesterol reductase (DHCR7), showed significantly different expression according to alleles.

CONCLUSION

The genetic factors underlying vitamin D deficiency in Korea included polymorphisms in the GC, PDE3B, NADSYN1, and ACTE1P genes. The biological mechanism of a non-coding SNP (rs12803256) for DHCR7/NADSYN1 on vitamin D concentrations is unclear, warranting further investigations.

Is Bioavailable Vitamin D Better Than Total Vitamin D to Evaluate Vitamin D Status in Obese Children?

INTRODUCTION

Free hormones are biologically more active in target tissues. Thus, measurement of vitamin D taking into account bioavailability and free vitamin D may be preferable, especially when evidence is contradictory, as in obese children. In order to assess bioavailablity and free vitamin D, using a previously reported formula, vitamin D-binding protein (VDBP) level was measured and VDBP polymorphisms were also evaluated because of variations in binding affinity.

METHODS

Eighty-four obese and 78 healthy children were included. Anthropometry, calcium, phosphorus, alkaline-phosphatase, parathyroid hormone (PTH), 25 hydroxyvitamin D [25(OH)D], bioavailable-free vitamin D, and VDBP concentration and polymorphism were evaluated in the whole group.

RESULTS

Obese girls had significantly higher PTH than normal weight girls (p=0.001). Regardless of gender, obese children had significantly higher concentrations of VDBP (p=0.008) and PTH (p=0.002). When samples taken in winter were analyzed, PTH and VDBP were found to be higher and bioavailable and free vitamin D lower in the obese group. There was no difference in terms of total vitamin D between groups during the winter season.

CONCLUSION

While total, free, and bioavailable vitamin D in the obese group was similar to the control group in autumn, free and bioavailable vitamin D in the winter was lower in the obese than the control group. In addition, PTH was higher in the obese group in both autumn and winter. Therefore, more research is needed to evaluate the variability of free and bioavailable vitamin D according to body habitus, season and the effect any differences may have.

Vitamin D-related polymorphisms and vitamin D levels as risk biomarkers of COVID-19 disease severity

Vitamin D is a fundamental regulator of host defences by activating genes related to innate and adaptive immunity. Previous research shows a correlation between the levels of vitamin D in patients infected with SARS-CoV-2 and the degree of disease severity. This work investigates the impact of the genetic background related to vitamin D pathways on COVID-19 severity. For the first time, the Portuguese population was characterized regarding the prevalence of high impact variants in genes associated with the vitamin D pathways. This study enrolled 517 patients admitted to two tertiary Portuguese hospitals. The serum concentration of 25 (OH)D, was measured in the hospital at the time of patient admission. Genetic variants, 18 variants, in the genes AMDHD1, CYP2R1, CYP24A1, DHCR7, GC, SEC23A, and VDR were analysed. The results show that polymorphisms in the vitamin D binding protein encoded by the GC gene are related to the infection severity (p = 0.005). There is an association between vitamin D polygenic risk score and the serum concentration of 25 (OH)D (p = 0.04). There is an association between 25 (OH)D levels and the survival and fatal outcomes (p = 1.5e−4). The Portuguese population has a higher prevalence of the DHCR7 RS12785878 variant when compared with its prevalence in the European population (19% versus 10%). This study shows a genetic susceptibility for vitamin D deficiency that might explain higher severity degrees in COVID-19 patients. These results reinforce the relevance of personalized strategies in the context of viral diseases.

Trial registration: NCT04370808.

Association Between Serum 25-hydroxyvitamin D Concentrations and Mortality Among Adults With Prediabetes

OBJECTIVES

To investigate the association of circulating 25-hydroxyvitamin D [25(OH)D] levels with mortality among adults with prediabetes.

METHODS

This retrospective cohort study included 15,195 adults with prediabetes (aged ≥20 years) from the National Health and Nutrition Examination Survey (NHANES) III and NHANES 2001-2014. Mortality from all causes, cardiovascular disease (CVD), and cancer was linked to National Death Index mortality data.

RESULTS

The median (interquartile range) concentration of serum 25(OH)D was 60.5 (45.3, 77.4) nmol/L, and only 23.1% had sufficient vitamin D (≥75 nmol/L). Elevated serum 25(OH)D concentrations were significantly associated with lower levels of insulin, homeostasis model assessment of insulin resistance, triglyceride, and C-reactive protein, and higher levels of high-density lipoprotein at baseline (all Ptrend < 0.05). During a median follow up of 10.7 years, 3765 deaths (including 1080 CVD deaths and 863 cancer deaths) were identified. Compared with participants with 25(OH)D <30 nmol/L, the multivariate-adjusted hazard ratios and 95% confidence intervals for participants with 25(OH)D ≥ 75 nmol/L were 0.66 (0.53, 0.82) for all-cause mortality (Ptrend < 0.001), 0.66 (0.48, 0.89) for CVD mortality (Ptrend = 0.001), and 0.82 (0.49, 1.35) for cancer mortality (Ptrend = 0.32). For per-unit increment in ln-transformed 25(OH)D, there was a 27% lower risk of all-cause mortality and a 34% lower risk of CVD mortality (both P < 0.01).

CONCLUSIONS

These findings suggested that higher serum 25(OH)D concentrations were associated with lower all-cause and CVD mortality among individuals with prediabetes.

Association between Polymorphisms in Vitamin D Pathway-Related Genes, Vitamin D Status, Muscle Mass and Function: A Systematic Review

An association between vitamin D level and muscle-related traits has been frequently reported. Vitamin D level is dependent on various factors such as sunlight exposure and nutrition. But also on genetic factors. We, therefore, hypothesize that single nucleotide polymorphisms (SNPs) within the vitamin D pathway-related genes could contribute to muscle mass and function via an impact on vitamin D level. However, the integration of studies investigating these issues is still missing. Therefore, this review aimed to systematically identify and summarize the available evidence on the association between SNPs within vitamin D pathway-related genes and vitamin D status as well as various muscle traits in healthy adults. The review has been registered on PROSPERO and was conducted following PRISMA guidelines. In total, 77 studies investigating 497 SNPs in 13 different genes were included, with significant associations being reported for 59 different SNPs. Variations in GC, CYP2R1, VDR, and CYP24A1 genes were reported most frequently, whereby especially SNPs in the GC (rs2282679, rs4588, rs1155563, rs7041) and CYP2R1 genes (rs10741657, rs10766197, rs2060793) were confirmed to be associated with vitamin D level in more than 50% of the respective studies. Various muscle traits have been investigated only in relation to four different vitamin D receptor (VDR) polymorphisms (rs7975232, rs2228570, rs1544410, and rs731236). Interestingly, all of them showed only very low confirmation rates (6-17% of the studies). In conclusion, this systematic review presents one of the most comprehensive updates of the association of SNPs in vitamin D pathway-related genes with vitamin D status and muscle traits in healthy adults. It might be used for selecting candidate SNPs for further studies, but also for personalized strategies in identifying individuals at risk for vitamin D deficiency and eventually for determining a potential response to vitamin D supplementation.

Development and analytical validation of a novel bioavailable 25-hydroxyvitamin D assay

BACKGROUND

Bioavailable 25-hydroxyvitamin D (25OHD) may be a better indicator of vitamin D sufficiency than total 25OHD. This report describes a novel assay for measuring serum bioavailable 25OHD.

METHODS

We developed an assay for 25OHD % bioavailability based on competitive binding of 25OHD tracer between vitamin D-binding protein (DBP)-coated affinity chromatography beads and serum DBP. Bioavailable 25OHD, total 25OHD, albumin, and DBP protein concentrations were measured in 89 samples from hospitalized patients and 42 healthy controls to determine how the DBP binding assay responds to differences in concentrations of DBP and compares to calculated bioavailable 25OHD values.

RESULTS

DBP binding assay showed a linear relationship between DBP-bound 25OHD tracer recovered from bead supernatant and DBP calibrator concentrations (y = 0.0017x +0.731, R2 = 0.9961, p<0.001). Inversion of this relationship allowed interpolation of DBP binding equivalents based upon 25OHD tracer recovered. The relationship between DBP binding equivalents and % bioavailability fits a non-linear curve, allowing calculation of % bioavailable 25OHD from DBP binding equivalents (y = 10.625x-0.817, R2 = 0.9961, p<0.001). In hospitalized patient samples, there were linear relationships between DBP protein concentrations and DBP binding equivalents (y = 0.7905x + 59.82, R2 = 0.8597, p<0.001), between measured vs. calculated % bioavailability (y = 0.9528 + 0.0357, R2 = 0.7200, p<0.001), and between absolute concentrations of measured vs. calculated bioavailable 25OHD (y = 1.2403 + 0.1221, R2 = 0.8913, p<0.001).

CONCLUSIONS

The DBP-binding assay for bioavailable 25OHD shows expected changes in 25OHD % bioavailability in response to changes in DBP concentrations and concordance with calculated bioavailable 25OHD concentrations.

25-OHD response to vitamin D supplementation in children: effect of dose but not GC haplotype

OBJECTIVE

GC/DBP effects on response to vitamin D supplementation have not been well-studied. Thus we assessed free and total 25-OHD after vitamin D treatment across the six common GC haplotypes.

DESIGN

This double-blind, randomized study compared two vitamin D3 doses in healthy, urban-dwelling 6-month to 10-year-old children at-risk for vitamin D deficiency. Randomization was stratified by GC haplotype.

METHODS

Children were randomized to receive 2800 or 7000 International Units of vitamin D3 weekly. 25-OHD and 1,25(OH)2D were sampled at baseline and after 1-6 months of supplementation.

RESULTS AND CONCLUSIONS

One hundred ninety-two of 225 enrolled subjects completed the study. After one month, total 25-OHD increased with both doses and were higher with 7000 IU/week (85.5 ± 22.8 nmol/L) compared to 2800 IU/week (76.8 ± 18.0 nmol/L), despite equivalent baseline levels. No further significant increase occurred at 6 months (89.8 ± 35.5 and 74.3 ± 18.3 nmol/L, respectively). Free 25-OHD similarly changed. 25-OHD differed among GC groups at baseline. Although no significant effects of individual GC haplotypes on incremental changes were evident, a trend toward an effect of combined 'at risk' GC alleles on response was evident (P = 0.06). Total 1,25(OH)2D showed modest increases, moreso with the larger dose. In urban-dwelling children at-risk for vitamin D deficiency, 1 month of vitamin D3 2800 IU/week increased 25-OHD across all GC haplotype groups, and somewhat enhanced with 7000 IU/week with no further significant increases after 6 months of supplementation. Free 25-OHD measures offer no monitoring advantage over total 25-OHD.

Immunomodulatory Effects of Vitamin D Supplementation in a Deficient Population

In addition to its canonical functions, vitamin D has been proposed to be an important mediator of the immune system. Despite ample sunshine, vitamin D deficiency is prevalent (>80%) in the Middle East, resulting in a high rate of supplementation. However, the underlying molecular mechanisms of the specific regimen prescribed and the potential factors affecting an individual's response to vitamin D supplementation are not well characterized. Our objective is to describe the changes in the blood transcriptome and explore the potential mechanisms associated with vitamin D3 supplementation in one hundred vitamin D-deficient women who were given a weekly oral dose (50,000 IU) of vitamin D3 for three months. A high-throughput targeted PCR, composed of 264 genes representing the important blood transcriptomic fingerprints of health and disease states, was performed on pre and post-supplementation blood samples to profile the molecular response to vitamin D3. We identified 54 differentially expressed genes that were strongly modulated by vitamin D3 supplementation. Network analyses showed significant changes in the immune-related pathways such as TLR4/CD14 and IFN receptors, and catabolic processes related to NF-kB, which were subsequently confirmed by gene ontology enrichment analyses. We proposed a model for vitamin D3 response based on the expression changes of molecules involved in the receptor-mediated intra-cellular signaling pathways and the ensuing predicted effects on cytokine production. Overall, vitamin D3 has a strong effect on the immune system, G-coupled protein receptor signaling, and the ubiquitin system. We highlighted the major molecular changes and biological processes induced by vitamin D3, which will help to further investigate the effectiveness of vitamin D3 supplementation among individuals in the Middle East as well as other regions.

Whole Genome Interpretation for a Family of Five

Although best practices have emerged on how to analyse and interpret personal genomes, the utility of whole genome screening remains underdeveloped. A large amount of information can be gathered from various types of analyses via whole genome sequencing including pathogenicity screening, genetic risk scoring, fitness, nutrition, and pharmacogenomic analysis. We recognize different levels of confidence when assessing the validity of genetic markers and apply rigorous standards for evaluation of phenotype associations. We illustrate the application of this approach on a family of five. By applying analyses of whole genomes from different methodological perspectives, we are able to build a more comprehensive picture to assist decision making in preventative healthcare and well-being management. Our interpretation and reporting outputs provide input for a clinician to develop a healthcare plan for the individual, based on genetic and other healthcare data.

Association of Serum 25-Hydroxyvitamin D Concentrations With All-Cause and Cause-Specific Mortality Among Individuals With Diabetes

OBJECTIVE

The evidence regarding vitamin D status and mortality among people with diabetes is scarce. This study aimed to examine the association of serum 25-hydroxyvitamin D [25(OH)D] concentrations with all-cause and cause-specific mortality among adults with diabetes.

RESEARCH DESIGN AND METHODS

This study included 6,329 adults with diabetes from the Third National Health and Nutrition Examination Survey (NHANES III) and NHANES 2001-2014. Death outcomes were ascertained by linkage to National Death Index records through 31 December 2015. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% CIs for mortality from all causes, cardiovascular disease (CVD), and cancer.

RESULTS

The weighted mean (95% CI) level of serum 25(OH)D was 57.7 (56.6, 58.8) nmol/L, and 46.6% had deficient vitamin D (<50 nmol/L [20 ng/mL]). Higher serum 25(OH)D levels were significantly associated with lower levels of glucose, insulin, HOMA of insulin resistance, HbA_1c, blood lipids, and C-reactive protein at baseline (all P _trend < 0.05). During 55,126 person-years of follow-up, 2,056 deaths were documented, including 605 CVD deaths and 309 cancer deaths. After multivariate adjustment, higher serum 25(OH)D levels were significantly and linearly associated with lower all-cause and CVD mortality: there was a 31% reduced risk of all-cause mortality and a 38% reduced risk of CVD mortality per one-unit increment in natural log-transformed 25(OH)D (both P < 0.001). Compared with participants with 25(OH)D <25 nmol/L, the multivariate-adjusted HRs and 95% CI for participants with 25(OH)D >75 nmol/L were 0.59 (0.43, 0.83) for all-cause mortality (P _trend = 0.003), 0.50 (0.29, 0.86) for CVD mortality (P _trend = 0.02), and 0.49 (0.23, 1.04) for cancer mortality (P _trend = 0.12).

CONCLUSIONS

Higher serum 25(OH)D levels were significantly associated with lower all-cause and CVD mortality. These findings suggest that maintaining adequate vitamin D status may lower mortality risk in individuals with diabetes.

Total, Bioavailable, and Free 25(OH)D Relationship with Indices of Bone Health in Elderly: A Randomized Controlled Trial

CONTEXT

Questions regarding the superiority of free and bioavailable 25-hydroxyvitamin D [25(OH)D] in predicting health outcomes remain unresolved.

OBJECTIVE

This study investigates the impact of vitamin D variables-total, bioavailable, or free 25(OH)D-on indices of bone and mineral metabolism, at baseline and in response to 2 vitamin D doses.

DESIGN

Our objectives are implemented as exploratory analyses on data collected in a 1-year, double-blind, randomized controlled trial completed in July 2014.

SETTING

Participants were recruited from 3 major hospitals in an ambulatory setting.

PARTICIPANTS

Participants were >65 years of age, overweight, and had a baseline serum 25(OH)D between 10 and 30 ng/mL. A total of 221 participants completed the study.

INTERVENTION

Subjects were randomized to receive calcium and oral vitamin D3 (600 IU/day or 3750 IU/day) supplementation.

RESULTS

Participants who received the higher vitamin D dose had levels that were 1.3- to 1.4-fold higher than those taking the lower dose, for all variables (P value < 0.001). Serum values of bioavailable and free 25(OH)D were associated with total 25(OH)D, with r values of 0.942 and 0.943, respectively (P value < 0.001). Parathyroid hormone (PTH) was negatively associated with all vitamin D variables, with correlation coefficients ranging from -0.22 to -0.25, while calcium and bone turnover markers (carboxy-terminal collagen crosslinks and osteocalcin) did not. Only total 25(OH)D had a positive relationship with % change bone mineral density (BMD) at the femoral neck at 12 months, while only free and bioavailable 25(OH) had a positive relationship with % change total body BMD at 12 months.

CONCLUSION

Calculated free and bioavailable 25(OH)D do not appear to be superior to total 25(OH)D in predicting indices of bone health in an elderly population.

Vitamin D supplementation prior to in vitro fertilisation in women with polycystic ovary syndrome: a protocol of a multicentre randomised, double-blind, placebo-controlled clinical trial

INTRODUCTION

Polycystic ovary syndrome (PCOS) is one of the leading causes of female infertility, affecting around 5% of women of childbearing age in China. Vitamin D insufficiency is common in women with PCOS and is associated with lower live birth rates. However, evidence regarding the effectiveness of vitamin D supplementation in women with PCOS is inconclusive. This multicentre randomised, double-blinded, placebo-controlled trial aims to evaluate the effectiveness of vitamin D supplementation prior to in vitro fertilisation (IVF) on the live birth rate in women with PCOS.

METHODS AND ANALYSIS

We plan to enrol women with PCOS scheduled for IVF. After informed consent, eligible participants will be randomised in a 1:1 ratio to receive oral capsules of 4000 IU vitamin D per day or placebo for around 12 weeks until the day of triggering. All IVF procedures will be carried out routinely in each centre. The primary outcome is live birth after the first embryo transfer. The primary analysis will be by intention-to-treat analysis. To demonstrate or refute that treatment with vitamin D results in a 10% higher live birth rate than treatment with placebo, we need to recruit 860 women (48% vs 38% difference, anticipating 10% loss to follow-up and non-compliance, significance level 0.05 and power 80%).

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee in Women's Hospital of Zhejiang University on 2 March 2020 (reference number: IRB-20200035-R). All participants will provide written informed consent before randomisation. The results of the study will be submitted to scientific conferences and a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04082650.

Serum Bioavailable, Rather Than Total, 25-hydroxyvitamin D Levels Are Associated With Hepatocellular Carcinoma Survival

BACKGROUND AND AIMS

Free and bioavailable 25-hydroxyvitamin D (25OHD) are emerging measurements of vitamin D status. It remains unclear whether circulating free or bioavailable 25OHD are relevant to hepatocellular carcinoma (HCC) prognosis. Our aim was to test the hypothesis that bioavailable 25OHD may be a better serum biomarker of vitamin D status than total 25OHD on the association with HCC survival.

APPROACH AND RESULTS

We included 1,031 newly diagnosed, previously untreated patients with HCC from the Guangdong Liver Cancer Cohort enrolled between September 2013 and April 2017. Serum total 25OHD levels were measured using an electrochemiluminescence immunoassay. Serum-free 25OHD levels were measured using a two-step enzyme-linked immunosorbent assay. Bioavailable 25OHD levels were calculated from measured free 25OHD and albumin using a previously validated equation. Primary outcomes were liver cancer-specific (LCSS) and overall survival (OS). Cox proportional hazards models were performed to calculate the multivariable hazard ratios (HRs) and 95% confidence intervals (CIs). During a median follow-up of 726 days, 430 patients had deceased, including 393 deaths from HCC. In multivariable analyses, higher bioavailable 25OHD levels were significantly associated with better survival, independent of nonclinical and clinical prognostic factors including serum C-reactive protein, Barcelona Clinic Liver Cancer stage, and cancer treatment. The multivariable-adjusted HRs in the highest versus lowest quartile of bioavailable 25OHD levels were 0.69 (95% CI: 0.51, 0.93; P for trend = 0.014) for LCSS and 0.71 (95% CI: 0.53, 0.94; P for trend = 0.013) for OS. In contrast, neither total nor free 25OHD levels were associated with LCSS or OS.

CONCLUSIONS

Higher bioavailable, rather than total, 25OHD levels were independently associated with improved survival in a population-based HCC cohort, suggesting a potential utility of bioavailable 25OHD in HCC prognosis.

Vitamin D in Type 2 Diabetes: Genetic Susceptibility and the Response to Supplementation

Variants of vitamin D metabolism-genes may predispose to type 2 diabetes (T2D). This study investigated the impact of these variants on disease susceptibility, Vitamin D, parathyroid hormone, C-peptide and HbA1c levels before and after cholecalciferol supplementation in patients with T2D.Twelve polymorphisms within CYP2R1, CYP27B1, DBP, VDR and CYP24A1 were genotyped in 553 T2D patients and 916 controls. In addition 65 patients receiving either cholecalciferol or placebo were analyzed during 6 months intervention and 6 months follow-up.T2D risk alleles are VDR rs7975232 "G" (p_c=0.031), rs1544410 "G" (p_c=0.027) and CYP2R1 rs10741657 "A" (p_c=0.016). Patients with genotypes CYP27B1 rs10877012 "CC" (p_c=4x10^-5), DBP rs7041 "GG" (p_c=0.003), rs4588 "CC" (p_c = 3x10^-4), CYP24A1 rs2585426 "CG" (p_c=0.006) and rs2248137 "CG" (p_c=0.001) showed lower 25(OH)D3 and DBP rs4588 "CC" lower 1,25(OH)2D3 levels (p_c=0.005). Whereas DBP rs4588 "CC" (p_c=0.009), CYP27B1 rs10877012 "AC" (p_c=0.059), VDR rs7975323 "AG" (p_c=0.033) and rs1544410 "GG" (p_c=0.013) are associated with higher 25(OH)D3 levels at 6 months' follow-up. Significant PTH suppression was detected for CYP2R1 "AG" (p_c=0.002), DBP rs4588 "CC" (p_c<0.001), VDR rs110735810 "CT" (p_c<0.001) and CYP24A1 rs2248137 "GG" (p_c=0.021).Genetic variants of the vitamin D system predispose to type 2 diabetes and regulate - partially - vitamin D metabolism, concentrations and the vitamin D status. Vitamin D insufficiency is a T2D risk factor. The response to cholecalciferol supplementation can be measured as 25(OH)D3 increment and PTH suppression. This process is regulated by genes of the vitamin D system conferring modest T2D risk.

Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis

Importance

Vitamin D and calcium supplements are recommended for the prevention of fracture, but previous randomized clinical trials (RCTs) have reported conflicting results, with uncertainty about optimal doses and regimens for supplementation and their overall effectiveness.

Objective

To assess the risks of fracture associated with differences in concentrations of 25-hydroxyvitamin D (25[OH]D) in observational studies and the risks of fracture associated with supplementation with vitamin D alone or in combination with calcium in RCTs.

Data Sources

PubMed, EMBASE, Cochrane Library, and other RCT databases were searched from database inception until December 31, 2018. Searches were performed between July 2018 and December 2018.

Study Selection

Observational studies involving at least 200 fracture cases and RCTs enrolling at least 500 participants and reporting at least 10 incident fractures were included. Randomized clinical trials compared vitamin D or vitamin D and calcium with control.

Data Extraction and Synthesis

Two researchers independently extracted data according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and assessed possible bias. Rate ratios (RRs) were estimated using fixed-effects meta-analysis. Data extraction and synthesis took place between July 2018 and June 2019.

Main Outcomes and Measures

Any fracture and hip fracture.

Results

In a meta-analysis of 11 observational studies (39 141 participants, 6278 fractures, 2367 hip fractures), each increase of 10.0 ng/mL (ie, 25 nmol/L) in 25 (OH)D concentration was associated with an adjusted RR for any fracture of 0.93 (95% CI, 0.89-0.96) and an adjusted RR for hip fracture of 0.80 (95% CI, 0.75-0.86). A meta-analysis of 11 RCTs (34 243 participants, 2843 fractures, 740 hip fractures) of vitamin D supplementation alone (daily or intermittent dose of 400-30 000 IU, yielding a median difference in 25[OH]D concentration of 8.4 ng/mL) did not find a reduced risk of any fracture (RR, 1.06; 95% CI, 0.98-1.14) or hip fracture (RR, 1.14; 95% CI, 0.98-1.32), but these trials were constrained by infrequent intermittent dosing, low daily doses of vitamin D, or an inadequate number of participants. In contrast, a meta-analysis of 6 RCTs (49 282 participants, 5449 fractures, 730 hip fractures) of combined supplementation with vitamin D (daily doses of 400-800 IU, yielding a median difference in 25[OH]D concentration of 9.2 ng/mL) and calcium (daily doses of 1000-1200 mg) found a 6% reduced risk of any fracture (RR, 0.94; 95% CI, 0.89-0.99) and a 16% reduced risk of hip fracture (RR, 0.84; 95% CI, 0.72-0.97).

Conclusions and Relevance

In this systematic review and meta-analysis, neither intermittent nor daily dosing with standard doses of vitamin D alone was associated with reduced risk of fracture, but daily supplementation with both vitamin D and calcium was a more promising strategy.

Genetic Variation of the Vitamin D Binding Protein Affects Vitamin D Status and Response to Supplementation in Infants

CONTEXT

Single nucleotide polymorphisms (SNPs) of the vitamin D binding protein encoding the GC (group component) gene affect 25-hydroxyvitamin D (25OHD) concentrations, but their influence on vitamin D status and response to vitamin D supplementation in infants is unknown.

OBJECTIVE

To study GC genotype-related differences in 25OHD concentrations and the response to supplementation during a vitamin D intervention study in infants.

DESIGN

In this randomized controlled trial, healthy term infants received vitamin D3 (10 or 30 μg/d) from 2 weeks to 24 months of age. GC SNPs rs2282679, rs4588, rs7041, and rs1155563 were genotyped. rs4588/7041 diplotype and haplotypes of rs2282679, rs4588, and rs7041 (Haplo3SNP) and of all four SNPs (Haplo4SNP) were determined.

MAIN OUTCOME MEASURES

25OHD measured in cord blood at birth and at 12 and 24 months during intervention.

RESULTS

A total of 913 infants were included. Minor allele homozygosity of all studied GC SNPs, their combined haplotypes, and rs4588/rs7041 diplotype 2/2 were associated with lower 25OHD concentrations at all time points in one or both intervention groups [analysis of covariance (ANCOVA) P < 0.043], with the exception of rs7041, which did not affect 25OHD at birth. In the high-dose supplementation group receiving 30 μg/d vitamin D3, but not in those receiving 10 µg/d, genotype of rs2282679, rs4588, and rs7041; diplotype; and Haplo3SNP significantly affected intervention response (repeated measurement ANCOVA Pinteraction < 0.019). Minor allele homozygotes had lower 25OHD concentrations and smaller increases in 25OHD throughout the intervention.

CONCLUSIONS

In infants, vitamin D binding protein genotype affects 25OHD concentration and efficiency of high-dose vitamin D3 supplementation.

Vitamin D pathway related polymorphisms and vitamin D receptor expression in breast cancer

Vitamin D deficiency is an emerging risk factor for breast cancer suggesting its role in breast cancer pathogenesis. Recent evidence suggests vitamin D receptor (VDR) expression is a prognosis predictor in breast cancer. We set out to determine the status of VDR expression in histologically characterized breast cancers, and whether common genetic variants modify VDR expression in breast cancer. One-hundred and twenty Kuwaiti female breast cancer fixed tissues were assessed for VDR expression to identify the level and location of its expression by immunohistochemistry. VDR variants (rs731236, rs2228570), and vitamin D binding protein (VDBP) variants (rs4588, rs7041) genotypes were ascertained in breast cancer specimens using Taqman genotyping assays. VDR nuclear expression correlated with low grade tumors (p = 0.01), whereas cytoplasmic expression correlated with lymph node positive tumors (p = 0.03). Absence of VDR expression was a marker for high-grade dedifferentiated tumors (p = 0.01). VDBP rs7041 associated with breast cancer risk (OR 1.92, 95% CI: 1.34 - 2.73; p = 0.0004), and VDR rs2228570 correlated with increased VDR cytoplasmic expression (p < 0.0001). In conclusion, VDR expression is altered in breast cancer confirming its involvement in breast cancer progression. Genetic factors appear to play a role in breast cancer risk, and may modify tumor sensitization to vitamin D.

Hypercalcemia Without Hypervitaminosis D During Cholecalciferol Supplementation in Critically Ill Patients

BACKGROUND

Vitamin D deficiency during critical illness has been associated with worsened outcomes. Because most critically ill patients with severe traumatic injuries are vitamin D deficient, we investigated the efficacy and safety of cholecalciferol therapy for these patients.

METHODS

Fifty-three patients (>17 years of age) admitted to the trauma intensive care unit who had a serum 25-hydroxy vitamin D (25-OH vit D) concentration <20 ng/mL were given 10,000 IU of cholecalciferol daily. Efficacy was defined as achievement of a 25-OH vit D of 30-79.9 ng/mL. Safety was evaluated by the presence of hypercalcemia (serum ionized calcium [iCa] >1.32 mmol/L) or hypervitaminosis D (25-OH vit D >79.9 nmol/L). Patients were monitored for 2 weeks during cholecalciferol therapy.

RESULTS

Twenty-four patients (45%) achieved target 25-OH vit D. No patients experienced hypervitaminosis D. Hypercalcemia occurred in 40% (n = 21) of patients; 2 patients experienced an iCa >1.49 nmol/L. 25-OH vit D was significantly greater for those who developed hypercalcemia (37.2 + 11.2 vs 28.4 + 5.6 ng/mL, respectively, P < 0.001) by the second week of cholecalciferol. Of 24 patients who achieved target 25-OH vit D, 14 (58%) experienced hypercalcemia in contrast to 24% of patients (7 out of 29) who did not achieve target 25-OH vit D (P = 0.024).

CONCLUSIONS

Cholecalciferol normalized serum 25-OH vit D concentrations in less than half of patients yet was associated with a substantial proportion of patients with hypercalcemia without hypervitaminosis D.

Determinants of the magnitude of response to vitamin D supplementation in adolescent girls identified using a decision tree algorithm

Vitamin D (VitD) supplementation is an inexpensive and effective approach for improving VitD insufficiency/deficiency. However, the response to supplementation, with respect to the increase in serum 25(OH)D level varies between individuals. In this study, we have assessed the factors associated with the response to VitD supplementation using a decision-tree algorithm. Serum VitD levels, pre- and post-VitD supplementation was used as the determinant of responsiveness. The model was validated by constructing a receiver operating characteristic curve. Serum VitD at baseline levels was at the apex of the tree in our model, followed by serum low-density lipoprotein cholesterol and triglyceride, age, waist-hip ratio, and high-density lipoprotein cholesterol. Our model suggests that these determinants of responsiveness to VitD supplementation had sensitivity, specificity, and accuracy, 59.4, 75.8 and 69.3%, respectively. The decision tree model appears to be a relatively accurate, specific, and sensitive approach for identifying the factors associated with response to VitD supplementation.

Bioavailability of Fat-Soluble Vitamins and Phytochemicals in Humans: Effects of Genetic Variation

Recent data have shown that interindividual variability in the bioavailability of vitamins A (β-carotene), D, and E, and carotenoids (lutein and lycopene), as well as that of phytosterols, is modulated by single nucleotide polymorphisms (SNPs). The identified SNPs are in or near genes involved in intestinal uptake or efflux of these compounds, as well as in genes involved in their metabolism and transport. The phenotypic effect of each SNP is usually low, but combinations of SNPs can explain a significant part of the variability. Nevertheless, results from these studies should be considered preliminary since they have not been validated in other cohorts. Guidelines for future studies are provided to ensure that sound associations are elucidated that can be used to build consolidated genetic scores that may allow recommended dietary allowances to be tailored to individuals or groups by taking into account the multiloci genotypic signature of people of different ethnic origin or even of individuals.

A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe

BACKGROUND/OBJECTIVES

Optimal doses of vitamin D (VitD) supplement in different populations are unclear. We aim to evaluate the relationship between VitD supplementation and post-intervention serum 25-hydroxyvitamin D [25(OH)D] concentration, to provide a recommended dosage of VitD for achieving an optimal 25(OH)D concentration for different populations.

SUBJECTS/METHODS

Literature search was conducted in Embase, etc. Randomized controlled trials about VitD supplemental intakes and their effect on 25(OH)D concentration were enrolled. The effect on 25(OH)D concentration between different supplementation doses in each population group was compared by meta-analysis. Multivariate meta-regression model is utilized to establish reference intake dosage of VitD.

RESULTS

A total of 136 articles were included about children (3-17 years), adults (18-64 years), postmenopausal women, the elderly ( >64 years), pregnant, or lactating women. Overall, intervention groups obtained higher 25(OH)D concentration than controls and there was obvious dose-response effect between intake dose and 25(OH)D concentration. Baseline 25(OH)D concentration and age were significant indicators for 25(OH)D concentration. To reach sufficient 25(OH)D concentration (75 nmol/L), the recommended VitD supplemental intakes was 1340 and 2250 IU/day for children and pregnant women, 2519 and 797 IU/day for European adults aged 18-64 and 65-85 years, 729, 2026, and 1229 IU/day for adults in North America, Asia and Middle East and Africa, respectively.

CONCLUSIONS

Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested.

Vitamin D and cardiometabolic disorders: a review of current evidence, genetic determinants and pathomechanisms

Vitamin D deficiency has been implicated in the pathophysiology of cardiometabolic disorders including obesity, type 2 diabetes mellitus, cardiovascular diseases and polycystic ovary syndrome. Despite a large number of experimental and observational studies supporting a role for vitamin D in these pathologies, randomized controlled trials have reported little to no effect of vitamin D supplementation in the prevention or treatment of these disorders, although some results remain ambiguous. Polymorphisms in genes related to vitamin D metabolism, particularly in the vitamin D receptor and binding protein and the metabolizing enzyme 1-α-hydroxylase, have emerged as potential contributors to these divergent results. It is now becoming increasingly recognized that the effects and potential benefits of vitamin D supplementation may vary by several factors including vitamin D deficiency status, ethnicity and/or the presence of genetic variants, which affect individual responses to supplementation. However, these factors have seldom been explored in the available literature. Future trials should consider inter-individual differences and, in particular, should aim to clarify whether certain subgroups of individuals may benefit from vitamin D supplementation in the context of cardiometabolic health.

The GC2 haplotype of the vitamin D binding protein is a risk factor for a low plasma 25-hydroxyvitamin D concentration in a Han Chinese population

Background

The GC haplotype of the vitamin D binding protein (encoded by the GC gene) might be a risk factor to the vitamin D (VD) nutritional status for many populations, while evidences from the Chinese Han population are sparse. We test the association between vitamin D binding protein genotypes and VD status as well as the metabolic parameters of glucose and lipids in a Han Chinese population.

Methods

In a cross-sectional study conducted at a health examination centre (registered in ClinicalTrials.gov as QLS2013), 2641 adults were included and grouped according to their plasma 25-hydroxyvitamin D (25OHD) concentrations as VD deficient (VDD), insufficient (VDI), or sufficient (VDS). The rs7041 and rs4588 genotypes were analysed with a molecular beacon-based qPCR method using blood samples.

Results

Plasma 25OHD concentrations were lower in the GC2/2, rs7041T/T, and rs4588A/A genotypes than the GC1f/1s, rs7041G/T, and rs4588C/C genotypes (P <  0.05). After adjusting for confounders, the GC2 haplotype increased the risk of low VD status (P <  0.05) in both genders. More genotypic models revealed the negative contributions of rs4588A than rs7041T to low VD status (P <  0.05). The combined rates of VDD and VDI were 80.2% in males and 86.1% in females. Compared with VDI, VDS, or both, VDD showed higher plasma concentrations of fasting blood glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides in males (P <  0.05); however, no significant differences were found with regard to these parameters between the subgroups defined by the GC genotypes (P > 0.05).

Conclusions

In a Han Chinese population, the GC2 haplotype or more exactly rs4588A is a risk factor for low VD status but is not associated with glucose and lipid metabolic disorders, which are inversely correlated with the circulating 25OHD concentration in males.

Trial registration

The study was retrospectively registered in January 2018 as NCT03406234 in the ClinicalTrials.gov online system.

Electronic supplementary material

The online version of this article (10.1186/s12986-019-0332-0) contains supplementary material, which is available to authorized users.

Effect of vitamin D supplementation on free and total vitamin D: A comparison of Asians and Caucasians

OBJECTIVES

It is well established that UK Asians typically have lower vitamin D levels than Caucasians. It is also known that vitamin D binding protein (DBP) is lower in some races than Caucasians. To investigate how ethnicity, skin colour and genetic variation affect the response to vitamin D (15000 IU) administered to young Asian and Caucasian men.

DESIGN

Prospective, single-centre clinical trial.

PARTICIPANTS

Sixty young men (18-25 year) of Asian (n = 30) and Caucasian (n = 30) origin.

MEASUREMENTS

We measured serum calcium, phosphate, magnesium, alkaline phosphatase, albumin, parathyroid hormone; total 25 hydroxyvitamin D (25OHD); calculated and directly measured free 25OHD; DBP at baseline and 4 weeks; DBP genotype, skin colour (Fitzpatrick scale), dietary vitamin D and calcium intake at baseline; and urine calcium:creatinine ratio at baseline, 1 and 4 weeks.

RESULTS

At baseline, Asians had lower serum total 25OHD (26.4 [13.7] vs 34.1 [12.3] nmol/L P = 0.0272) and DBP (6.7 [3.4] vs 9.6 [4.4] nmol/L; P = 0.0065) but similar free 25OHD (16.7 [10.4] vs 17.8 [7.5] pmol/L P = 0.6530). After dosing, total 25OHD rose similarly in each group (≈56 nmol/L), but measured free 25OHD rose more in Asians (18.1 [9.4] vs 12.2 [13.3] pmol/L P = 0.0464). Lower DBP at baseline, possibly reflecting genotype differences, was associated with a greater change in measured free 25OHD in Caucasians, but not in Asians.

CONCLUSIONS

Asian compared with Caucasian males had a larger increment in measured free 25OHD following 150 000 units vitamin D3, possibly reflecting differences in DBP affinity for 25OHD. Ethnicity should be considered when devising guidelines for the treatment of vitamin D deficiency.

Personalized Nutrition in Disrupting Cancer - Proceedings From the 2017 American College of Nutrition Annual Meeting

Cancer is a major public health problem and is the second leading cause of death in the United States and worldwide; nearly one in six deaths are attributable to cancer. Approximately 20% of all cancers diagnosed in the United States are attributable to unhealthy diet, excessive alcohol consumption, physical inactivity, and body fatness. Individual cancers are distinct disease states that are multifactorial in their causation, making them exceedingly cumbersome to study from a nutrition standpoint. Genetic influences are a major piece of the puzzle and personalized nutrition is likely to be most effective in disrupting cancer during all stages. Increasing evidence shows that after a cancer diagnosis, continuing standard dietary recommendations may not be appropriate. This is because powerful dietary interventions such as short-term fasting and carbohydrate restriction can disrupt tumor metabolism, synergizing with standard therapies such as radiation and drug therapy to improve efficacy and ultimately, cancer survival. The importance of identifying dietary interventions cannot be overstated, and the American College of Nutrition's commitment to advancing knowledge and research is evidenced by dedication of the 2017 ACN Annual Meeting to "Disrupting Cancer: The Role of Personalized Nutrition" and this resulting proceedings manuscript, which summarizes the meeting's findings.

Impact of genetic influence on serum total- and free 25-hydroxyvitamin-D in humans

Serum 25-hydroxyvitamin D /25OHD/ levels in humans are determined primarily by environmental factors such as UV-B radiation and diet, including vitamin D intake. Although some genetic determinants of 25OHD levels have been shown, the magnitude of this association has not yet been clarified. The present study evaluates the genetic contribution to total- /t-25OHD/ and free-25OHD /f-25OHD/ in a representative sample of the Hungarian population (n = 462). The study was performed at the end of winter to minimize the effect of sunlight, which is a major determinant of serum vitamin D levels. Single nucleotide polymorphisms (SNPs) of five genes playing major roles in vitamin D metabolism were investigated (NADSYN1, DHCR7, GC, CYP2R1 and CYP24A1). The selected SNPs account for 13.1% of the variance of t-25OHD levels. More than half of the genetic effect on t-25OHD levels was explained by two polymorphisms (rs7935125 in NADSYN1 and rs2762941 in CYP24A1), which had not previously been investigated with respect to vitamin D metabolism. No SNPs exhibited association with f-25OHD levels. Unexpectedly, SNPs that showed univariate associations with vitamin D binding protein (DBP) levels were not associated with f-25OHD levels questioning the biological significance of these polymorphisms. The present study shows that t-25OHD levels are significantly influenced by genetic factors, however, the clinical significance of this observation remains to be defined, as variation in f-25OHD levels are marginally explained by genetic effects.

Why should we measure free 25(OH) vitamin D?

Vitamin D, either in its D₂ or D₃ form, is essential for normal human development during intrauterine life, kidney function and bone health. Vitamin D deficiency has also been linked to cancer development and some autoimmune diseases. Given this huge impact of vitamin D on human health, it is important for daily clinical practice and clinical research to have reliable tools to judge on the vitamin D status. The major circulating form of vitamin D is 25-hydroxyvitamin D (25(OH)D), although it is not the most active metabolite, the concentrations of total 25-hydroxyvitamin D in the serum are currently routinely used in clinical practice to assess vitamin D status. In the circulation, vitamin D - like other steroid hormones - is bound tightly to a special carrier - vitamin D-binding protein (DBP). Smaller amounts are bound to blood proteins - albumin and lipoproteins. Only very tiny amounts of the total vitamin D are free and potentially biologically active. Currently used vitamin D assays do not distinguish between the three forms of vitamin D - DBP-bound vitamin D, albumin-bound vitamin D and free, biologically active vitamin D. Diseases or conditions that affect the synthesis of DBP or albumin thus have a huge impact on the amount of circulating total vitamin D. DBP and albumin are synthesized in the liver, hence all patients with an impairment of liver function have alterations in their total vitamin D blood concentrations, while free vitamin D levels remain mostly constant. Sex steroids, in particular estrogens, stimulate the synthesis of DBP. This explains why total vitamin D concentrations are higher during pregnancy as compared to non-pregnant women, while the concentrations of free vitamin D remain similar in both groups of women. The vitamin D-DBP as well as vitamin D-albumin complexes are filtered through the glomeruli and re-uptaken by megalin in the proximal tubule. Therefore, all acute and chronic kidney diseases that are characterized by a tubular damage, are associated with a loss of vitamin D-DBP complexes in the urine. Finally, the gene encoding DBP protein is highly polymorphic in different human racial groups. In the current review, we will discuss how liver function, estrogens, kidney function and the genetic background might influence total circulating vitamin D levels and will discuss what vitamin D metabolite is more appropriate to measure under these conditions: free vitamin D or total vitamin D.

Genomic Response to Vitamin D Supplementation in the Setting of a Randomized, Placebo-Controlled Trial

BACKGROUND

Vitamin D deficiency has been associated with multiple diseases, but the causal relevance and underlying processes are not fully understood. Elucidating the mechanisms of action of drug treatments in humans is challenging, but application of functional genomic approaches in randomized trials may afford an opportunity to systematically assess molecular responses.

METHODS

In the Biochemical Efficacy and Safety Trial of Vitamin D (BEST-D), a double-blind, placebo-controlled, dose-finding, randomized clinical trial, 305 community-dwelling individuals aged over 65 years were randomly allocated to treatment with vitamin D3 4000 IU, 2000 IU or placebo daily for 12 months. Genome-wide genotypes at baseline, and transcriptome and plasma levels of cytokines (IFN-γ, IL-10, IL-8, IL-6 and TNF-α) at baseline and after 12 months, were measured. The trial had >90% power to detect 1.2-fold changes in gene expression.

FINDINGS

Allocation to vitamin D for 12-months was associated with 2-fold higher plasma levels of 25-hydroxy-vitamin D (25[OH]D, 4000 IU regimen), but had no significant effect on whole-blood gene expression (FDR < 5%) or on plasma levels of cytokines compared with placebo. In pre-specified analysis, rs7041 (intron variant, GC) had a significant effect on circulating levels of 25(OH)D in the low dose, but not in the placebo or high dose vitamin D regimen. A gene expression quantitative trait locus analysis (eQTL) demonstrated evidence of 31,568 cis-eQTLs (unique SNP-probe pairs) among individuals at baseline and 34,254 after supplementation for 12 months (any dose). No significant associations involving vitamin D supplementation response eQTLs were found.

INTERPRETATION

We performed a comprehensive functional genomics and molecular analysis of vitamin D supplementation in a randomized, placebo-controlled trial. Although this study was limited to mostly Caucasian individuals aged over 65 years, the results differ from many previous studies and do not support a strong effect of vitamin D on long-term transcriptomic changes in blood or on plasma cytokine levels. The trial demonstrates the feasibility of applying functional genomic and genetic approaches in randomized trials to assess molecular and individual level responses.

KEY RESULT

Supplementation with high-dose vitamin D in older people for 12 months in a randomized, placebo-controlled trial had no significant effect on gene expression or on plasma concentrations of selected cytokines.

TRIAL REGISTRATION

SRCTN registry (Number 07034656) and the European Clinical Trials Database (EudraCT Number 2011-005763-24).

Cholecalciferol Supplementation Promotes Bone Turnover in Chinese Adults with Vitamin D Deficiency

BACKGROUND

Bone turnover markers (BTMs) are proposed as alternative indicators for bone mineral density in diagnosis and management of osteoporosis. However, little is known about the effects of vitamin D supplementation on BTMs in nonwhite populations.

OBJECTIVE

We aimed to investigate the responses in BTMs after vitamin D supplementation in Asians.

METHODS

In this secondary data analysis of a randomized, double-blind, placebo-controlled trial, 448 Chinese adults [mean ± SD age: 31.9 ± 8.0 y; mean ± SD body mass index (kg/m2): 22.1 ± 2.6; 69% were women] with vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] <50 nmol/L) received 2000 IU/d cholecalciferol or placebo for 20 wk. Serum concentrations of 25(OH)D, parathyroid hormone (PTH), calcium, and markers of bone formation and resorption were measured at weeks 0 and 20. Intention-to-treat analysis was applied, and between-group differences were compared by general linear models with adjustments.

RESULTS

Cholecalciferol supplementation increased the serum bone alkaline phosphatase (BALP) concentration (+1.7 ± 1.9 µg/L) significantly more than placebo (+1.1 ± 1.7 µg/L; P = 0.004), but not circulating concentrations of procollagen type I N-terminal propeptide (PINP), β-isomerized C-terminal telopeptide of type I collagen (β-CTX), or tartrate-resistant acid phosphatase 5b (TRAP5b) (P ≥ 0.53). Notably, a pooled analysis indicated that changes in serum 25(OH)D were positively associated with changes in serum BALP, PINP, and TRAP5b (r = 0.07-0.16, P ≤ 0.02), but inversely with changes in PTH (r = -0.15, P < 0.001). Among cholecalciferol-treated participants, individuals who achieved serum 25(OH)D ≥75 nmol/L had greater increases in serum β-CTX (224% compared with 146%; P = 0.02) and TRAP5b (22.2% compared with 9.1%; P = 0.007), but smaller decreases in serum calcium (-1.3% compared with -1.9%; P = 0.005) and calcium-phosphorus product (-2.6% compared with -3.3%; P = 0.02) compared with those with serum 25(OH)D <75 nmol/L.

CONCLUSIONS

Daily supplementation with 2000 IU cholecalciferol for 20 wk may promote bone formation in Chinese adults with vitamin D deficiency. More studies are needed to elucidate the potential clinical implications of BTMs.This trial was registered at clinicaltrials.gov as NCT01998763.

Association Between Vitamin D Metabolism Gene Polymorphisms and Risk of Tunisian Adults' Asthma

INTRODUCTION

Several studies have shown a strong correlation between the serum vitamin D level and asthma severity and deficits in lung function.

OBJECTIVE

Study the relationship between vitamin D and the severity of asthma by targeting five SNPs of vitamin D metabolism gene pathway in a Tunisian adult asthmatics population.

METHODS

Our case-control study includes 154 adult asthmatic patients and 154 healthy Tunisian subjects. We genotyped many variants in three human genes encoding key components of the vitamin D metabolism, CYP2R1, CYP27B1, GC. The GC gene rs4588 and rs7041 polymorphisms were analysed using the PCR-RFLP method, while rs10741657 and rs12794714 for CYP2R1 gene and rs10877012 of CYP27B1 gene were investigated using TaqMan PCR genotyping techniques.

RESULTS

We found that the presence of at least one copy of the rs12794714 A, allele was associated with lower risk of developing asthma (OR 0.61). Further, the rs12794714 is a protector factor against asthma severity (OR 0.5). However, the presence of rs10877012 TG genotype is a risk factor related to asthma severity (OR 1.89). When we classified the population according to sex, our results showed that rs10877012 TT genotype was a risk factor for women subjects (OR 6.7). Moreover, the expression of TT genotype was associated with a higher risk of asthma in non-smoker patients (OR 7.13). We found a significant lower VD serum levels in asthmatics than controls but no impact of the polymorphisms on VD levels.

CONCLUSIONS

We found that rs12794714 and rs10877012 SNPs were associated with asthma risk.

The effect of vitamin D and calcium supplementation in pediatric steroid-sensitive nephrotic syndrome

BACKGROUND

Low serum levels of total 25-hydroxycholecalciferol (25(OH)D) occur in nephrotic syndrome (NS). We aimed to assess the effects of vitamin D3 and calcium supplementation on 25(OH)D levels, bone mineralization, and NS relapse rate in children with steroid-sensitive NS.

METHODS

A randomized controlled trial (RCT) was performed in children with steroid-sensitive NS. The treatment group received vitamin D3 (60,000 IU orally, weekly for 4 weeks) and calcium supplements (500 to 1,000 mg/day for 3 months) after achieving NS remission. Blood samples for bone biochemistry were taken during relapse (T0), after 6 weeks (T1) and 6 months (T2) of randomization, whereas a lumbar DXA scan was performed at T0 and T2. Renal ultrasound was performed after study completion in the treatment group and in all patients with hypercalciuria.

RESULTS

Of the 48 initial recruits, 43 patients completed the study. Post-intervention, 25(OH)D levels showed significant improvements in the treatment group compared with controls at T1 (p < 0.001) and T2 (p < 0.001). However, this was not associated with differences in bone mineral content (BMC) (p = 0.44) or bone mineral density (BMD) (p = 0.64) between the groups. Additionally, there was no reduction in relapse number in treated patients (p = 0.54). Documented hypercalciuria occurred in 52% of patients in the treatment group, but was not associated with nephrocalcinosis.

CONCLUSIONS

Although supplementation with calcium and vitamin D improved 25(OH)D levels significantly, there was no effect on BMC, BMD or relapse rate over a 6-month follow-up. Occurrence of hypercalciuria mandates caution and appropriate monitoring if using such therapy. Appropriate dosage of vitamin D3 remains uncertain and studies examining biologically active vitamin D may provide answers.

Vitamin D in Asthma: Mechanisms of Action and Considerations for Clinical Trials

There is increasing interest in the therapeutic utility of vitamin D in asthma, which is supported by a significant body of evidence on epidemiologic associations between vitamin D insufficiency and worse asthma control. In support of a causal relationship, vitamin D beneficially modulates diverse immunologic pathways in heterogeneous asthma endotypes, regulating the actions of lymphocytes, mast cells, antigen-presenting cells, and structural cells to dampen excessive inflammatory responses. Allergic asthma is characterized by a failure of immune tolerance and the development of pathologic responses to inhaled aeroallergens, and vitamin D has been extensively shown to support immune regulation. Alarmin cytokines are increasingly implicated in nonallergic eosinophilic inflammation, which vitamin D also regulates. Steroid resistance and pathologic interleukin (IL)-17 responses are features of severe asthma, and vitamin D beneficially enhances the response to steroids in these individuals. Additionally, vitamin D enhances antimicrobial pathways, which is of relevance to infection-precipitated asthma exacerbations. These mechanisms support a role for vitamin D as secondary prevention to reduce exacerbations and inflammation in asthma. Similar mechanisms, and effects on fetal lung development, likely underlie a primary prevention therapeutic role in pregnancy for vitamin D to reduce the development of asthma in children. However, randomized controlled trials of variable design show inconsistent positive outcomes for vitamin D interventions in asthma. Increased understanding of the biological characteristics of vitamin D reveals methodological issues that might explain certain negative outcomes. Importantly, on systematic review of the trials to date, vitamin D is shown to be beneficial in asthma. The evidence discussed in this review supports the importance of optimizing vitamin D in holistic asthma care.

Vitamin D Supplementation and Non-Alcoholic Fatty Liver Disease: Present and Future

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic hepatic disease throughout the Western world and is recognized as the main cause of cryptogenic cirrhosis; however, the identification of an effective therapy for NAFLD is still a major challenge. Vitamin D deficiency is a wide-spread condition which reaches epidemic proportions in industrialized countries, mainly in relation to current lifestyle and limited dietary sources. Epidemiological studies point towards an association between hypovitaminosis D and the presence of NAFLD and steatohepatitis (NASH), independently of confounders such as obesity and insulin resistance. Furthermore, several pieces of experimental data have shown the anti-fibrotic, anti-inflammatory and insulin-sensitizing properties exerted by vitamin D on hepatic cells. However, results from trials evaluating the effects of oral vitamin D supplementation on liver damage in NAFLD and NASH are controversial. The aim of this review is to give an overview of the evidence currently available from clinical trials and to discuss possible shortcomings and new strategies to be considered in future investigations.