Environmental and genetic determinants of vitamin D status among older adults in London, UK

The Impact of Vitamin D and L-Cysteine Co-Supplementation on Upregulating Glutathione and Vitamin D-Metabolizing Genes and in the Treatment of Circulating 25-Hydroxy Vitamin D Deficiency

Vitamin D receptors are expressed in many organs and tissues, which suggests that vitamin D (VD) affects physiological functions beyond its role in maintaining bone health. Deficiency or inadequacy of 25(OH)VD is widespread globally. Population studies demonstrate that a positive association exists between a high incidence of VD deficiency and a high incidence of chronic diseases, including dementia, diabetes, and heart disease. However, many subjects have difficulty achieving the required circulating levels of 25(OH)VD even after high-dose VD supplementation, and randomized controlled clinical trials have reported limited therapeutic success post-VD supplementation. Thus, there is a discordance between the benefits of VD supplementation and the prevention of chronic diseases in those with VD deficiency. Why this dissociation exists is currently under debate and is of significant public interest. This review discusses the downregulation of VD-metabolizing genes needed to convert consumed VD into 25(OH)VD to enable its metabolic action exhibited by subjects with metabolic syndrome, obesity, and other chronic diseases. Research findings indicate a positive correlation between the levels of 25(OH)VD and glutathione (GSH) in both healthy and diabetic individuals. Cell culture and animal experiments reveal a novel mechanism through which the status of GSH can positively impact the expression of VD metabolism genes. This review highlights that for better success, VD deficiency needs to be corrected at multiple levels: (i) VD supplements and/or VD-rich foods need to be consumed to provide adequate VD, and (ii) the body needs to be able to upregulate VD-metabolizing genes to convert VD into 25(OH)VD and then to 1,25(OH)2VD to enhance its metabolic action. This review outlines the association between 25(OH)VD deficiency/inadequacy and decreased GSH levels, highlighting the positive impact of combined VD+LC supplementation on upregulating GSH, VD-metabolizing genes, and VDR. These effects have the potential to enhance 25(OH)VD levels and its therapeutic efficacy.

Serum Vitamin D Status in Older Adults: A Cohort Study

Background

Vitamin D is best known as a key regulator of bone metabolism and calcium and phosphate homeostasis. This study aimed to assess the effect of different factors on the five-year changes in serum vitamin D concentration among older adults.

Methods

This cohort study was conducted on adults aged ≥60 years living in Amirkola, in the North of Iran, from 2012 to 2017. Serum 25-hydroxyvitamin D (25-OH vitamin D) concentrations of <20, 20-29.99, and ≥30 ng/mL, respectively, were used to designate vitamin D deficiency, insufficiency, and sufficiency. Any variation between the second and baseline values of the 25-OH vitamin D concentration was reported as a five-year difference. Data were analyzed using SPSS version 17.0, and Chi square, t test, one-way ANOVA, and Tukey HSD post hoc tests were employed. P values less than 0.05 were considered statistically significant.

Results

The mean serum concentration of 25-OH vitamin D at baseline and follow-up examination in 1011 individuals was 34.68±33.18 and 23.88±14.91, respectively (P<0.001). Following a five-year follow-up, vitamin D deficiency, insufficiency, and sufficiency were found in 452 (44.7%), 334 (33.0%), and 225 (22.3%) cases, respectively. The reduction in serum 25-OH vitamin D concentration after five years was significantly influenced by the administration of vitamin D (P=0.013) and calcium (P=0.007) supplements, serum profile of parathyroid hormone (PTH) (P=0.010), calcium (P=0.021), and phosphorous (P=0.021). However, age, sex, body mass index, metabolic syndrome, and physical activity had no significant impact (P>0.05).

Conclusion

Regardless of age, sex, body mass index, metabolic syndrome, or physical activity, the mean serum concentration of vitamin D decreased over a five-year follow-up.

Differential effects of vitamin D on upper and lower body fat-free mass: potential mechanisms

Vitamin D insufficiency is a global health concern and low vitamin D status is regularly associated with reduced muscle mass and sarcopenia in observational research. Recent research using Mendelian randomization (MR) has highlighted the potentially causal positive effect of serum vitamin D (25(OH)D) on total, trunk and upper body appendicular fat-free mass (FFM). However, no such effect was found in lower body FFM, a result that mirrors the outcomes of some vitamin D intervention studies. Here we review the current literature on vitamin D, muscle mass and strength and discuss some potential mechanisms for the differing effects of vitamin D on upper and lower body FFM. In particular, differences in distribution of the vitamin D receptor as well as androgen receptors, in the upper and lower body musculature, will be discussed.

Vitamin D Related Gene Polymorphisms and Cholesterol Levels in a Mediterranean Population

In addition to its role in bone health, vitamin D (VitD) has been implicated in several pathological conditions. Specifically, VitD deficiency has been linked to an increased risk of dyslipidemia. Atherogenic dyslipidemia is characterized by increased low-density lipoprotein-cholesterol (LDL-C) and decreased high-density lipoprotein-cholesterol (HDL-C). In this study, we examined the association of six single nucleotide polymorphisms (SNPs) in VitD-related genes with VitD and lipid levels, in a cohort of 460 Lebanese participants free from chronic diseases. Our results showed no association of the examined SNPs with VitD concentrations. However, the presence of the minor allele in rs10741657G>A of CYP2R1 was associated with increased levels in LDL-C (β = 4.95, p = 0.04)] and decreased levels in HDL-C (β = −1.76, p = 0.007)]. Interestingly, rs10741657G>A interacted with gender to increase LDL-C levels in females (β = 6.73 and p = 0.03) and decrease HDL-C levels in males HDL-C (β = −1.09, p = 0.009). In conclusion, our results suggest that rs10741657 G>A in CYP2R1 is associated with circulating LDL-C and HDL-C levels in a Lebanese cohort. Although this association was gender-specific, where rs10741657G>A was associated with increased LDL in females and decreased HDL in males, the presence of the minor allele A was associated with increased cardiovascular risk in both genders. These findings need to be validated in a larger population. Further investigations are warranted to elucidate the molecular mechanism of VitD polymorphism and dyslipidemia.

Genetic, sociodemographic and lifestyle factors associated with serum 25-hydroxyvitamin D concentrations in Brazilian adults: the Pró-Saúde Study

This study aims to investigate factors associated with serum 25-hydroxyvitamin D [25(OH)D] concentration in Brazilian adults considering sociodemographic and lifestyle factors, as well as vitamin D-related single nucleotide polymorphisms (SNPs). This is a cross-sectional study (n = 491; 34-79y; 251 women), nested within a prospective cohort (Pró-Saúde Study). Associations between serum 25(OH)D and sociodemographic characteristics, diet, use of supplement, physical activity, season of blood collection, body fat, skin type, sun exposure index, and SNPs CYP2R1-rs10741657 and GC-rs2282679 were explored by multiple linear regression. The prevalence of serum 25(OH)D < 50nmol/L was 55%. Serum 25(OH)D was lower among women (β = -4.38; 95%CI: -8.02; -0.74), those with higher visceral fat (β = -4.02; 95%CI: -5.92; -2.12), and those with AC and CC genotypes for GC-rs2282679 (β = -6.84; 95%CI: -10.09; -3.59; β = -10.63; 95%CI: -17.52; -3.74, respectively). Factors directly associated with serum 25(OH)D included summer (β = 20.14; 95%CI: 14.38; 25.90), intermediate skin type (β = 6.16; 95%CI: 2.52; 9.80), higher sun exposure (β = 0.49; 95%CI: 0.22; 0.75), vitamin D intake (β = 0.48; 95%CI: 0.03; 0.93), and physical activity (β = 4.65; 95%CI: 1.54; 7.76). Besides physical activity, diet, and sun exposure, non-modifiable factors, such as GC genotypes must be considered when evaluating vitamin D insufficiency in mixed-race populations. Moreover, high visceral fat in association with poorer vitamin D status deserve attention given that both conditions are unfavorably related with chronic and acute health outcomes.

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.

Impact of vitamin D deficiency on COVID-19

Background & aims

COVID-19 has emerged as a global pandemic affecting millions of people. Vitamin D deficiency is one of the risk factors for increased susceptibility to COVID-19. This study aimed to examine the correlation between the prevalence of vitamin D deficiency and COVID-19 infection and mortality rates among the adult population in European and Asian continents.

Methods

Prevalence of vitamin D deficiency in each country was retrieved through literature searching on PubMed® database for the last ten years. As of December, 31^st 2020, COVID-19 infections and mortalities per million population were extracted from the ‘real time’ statistics of the Worldometer website. The association between both vitamin D deficiency and COVID-19 infections and mortalities were explored.

Results

Forty seven countries were included in the analysis. The prevalence of vitamin D deficiency ranged from 6.9 to 81.8% in European countries and 2.0–87.5% in Asian countries. Significantly positive correlations were observed for both COVID-19 infection (r = 0.76; p < 0.001) and mortality rates (r = 0.75; p < 0.001) in the Asian continent. The correlation values for the infections and mortality rates in the European continent were (r = 0.37; p = 0.08) and (r = 0.43; p = 0.04) respectively. When both the continents were combined, the correlation results for both infection (r = 0.42; p = 0.003) and mortality (r = 0.35; p = 0.016) rates with vitamin D deficiency values remained significant.

Conclusion

Prevalence of vitamin D deficiency was significantly associated with the mortality rate of COVID-19 in Europe and Asia. The association between the infection rate and prevalence of vitamin D deficiency was significant for Asia only. Both the associations were significant when the two continents were combined in the analysis. Therefore we suggest that vitamin D supplementation could play a key role in the prevention and/or treatment of the COVID-19 patients.

Vitamin D Receptor (VDR) Allelic Variants Correlating with Response to Vitamin D3 Supplementation in Breast Cancer Survivors

We investigated how vitamin D receptor (VDR) allelic variants affect breast cancer survivors' responses to vitamin D3 supplementation to increase circulating 25-hydroxy vitamin D (25(OH)D) levels. Two hundred and fourteen patients who were diagnosed with breast cancer at least 6 mo, prior to the study and had completed all treatment regimens were assigned to consume 4000 IU of vitamin D3 daily for 12 weeks. Linear and multinomial logistic regression analyses were used to analyze the association of VDR single nucleotide polymorphism (SNPs) with changes in circulating 25(OH)D. The TaqI and BsmI VDR sequence variants modified the effect of vitamin D3 treatment on the plasma 25(OH)D changes (P value = 0.008 for TaqI and P value = 0.0005 for BsmI). Patients with the bb [Q4 vs. Q1 odds ratio(OR) 8.04, 95% confidence interval (CI) 1.55-41.57] and tt [Q4 vs. Q1 OR 4.64 95%CI 1.02-21.02] genotype of BsmI and TaqI had larger increases in plasma 25(OH)D levels compared to those with BB and TT genotype respectively after adjustment for potential confounders. Haplotype analyses suggested the existence of specific combination of alleles that might be associated with circulating 25(OH)D changes. VDR allelic variants modulate vitamin D3 supplementation to increase plasma 25(OH) levels in breast cancer survivors.

Sarcopenia during COVID-19 lockdown restrictions: long-term health effects of short-term muscle loss

The COVID-19 pandemic is an extraordinary global emergency that has led to the implementation of unprecedented measures in order to stem the spread of the infection. Internationally, governments are enforcing measures such as travel bans, quarantine, isolation, and social distancing leading to an extended period of time at home. This has resulted in reductions in physical activity and changes in dietary intakes that have the potential to accelerate sarcopenia, a deterioration of muscle mass and function (more likely in older populations), as well as increases in body fat. These changes in body composition are associated with a number of chronic, lifestyle diseases including cardiovascular disease (CVD), diabetes, osteoporosis, frailty, cognitive decline, and depression. Furthermore, CVD, diabetes, and elevated body fat are associated with greater risk of COVID-19 infection and more severe symptomology, underscoring the importance of avoiding the development of such morbidities. Here we review mechanisms of sarcopenia and their relation to the current data on the effects of COVID-19 confinement on physical activity, dietary habits, sleep, and stress as well as extended bed rest due to COVID-19 hospitalization. The potential of these factors to lead to an increased likelihood of muscle loss and chronic disease will be discussed. By offering a number of home-based strategies including resistance exercise, higher protein intakes and supplementation, we can potentially guide public health authorities to avoid a lifestyle disease and rehabilitation crisis post-COVID-19. Such strategies may also serve as useful preventative measures for reducing the likelihood of sarcopenia in general and in the event of future periods of isolation.

Vitamin D Status in Russian Children and Adolescents: Contribution of Genetic and Exogenous Factors

Background: The problem of vitamin D deficiency is particularly relevant for the entire territory of Russia, since most parts of the country are located above the 42nd geographical latitude and the residents are therefore at risk of vitamin D deficiency. Despite the urgency of the problem, a comprehensive study of the molecular and genetic mechanisms and exogenous factors of vitamin D deficiency in children living in various geographical areas of the Russian Federation has not been conducted. Different variants in the loci of the genes responsible for the synthesis, hydroxylation, and transport of vitamin D (such as DHCR7, CYP2R1, CYP24A1, and GC), as well as VDR gene polymorphisms may also be associated with the risk of vitamin D deficiency. The aim of this study was to analyze the influence of exogenous factors on the blood levels of 25-hydroxyvitamin D (25(OH)D) in children of three regions of the Russian Federation, as well as the relationship of blood 25(OH)D levels with polymorphic variants of cytochrome P450 genes and VDR gene. Methods: We conducted blood 25(OH)D level analysis in 333 healthy children and adolescents in three regions located in different geographical zones of the Russian Federation. We studied the polymorphic variants c.1075A>C (I359L, rs1057910, CYP2C9 ^* 3) and c.430C>T (R144C, rs1799853, CYP2C9 ^* 2) in the CYP2C9 gene, c.1334T>C (M445T, rs4986910, CYP3A4 ^* 3), and CYP3A4 ^* 1B (c.-392C>T, rs2740574) in the CYP3A4 gene, 1846G>A, (rs3892097, CYP2D6 ^* 4) in the CYP2D6gene, TaqI (NM_000376.2: c.1056T>C; rs731236), FokI (NM_000376.2:c.2T>C; (rs2228570), and BsmI (NM_000376.2: c.1024+283G>A; rs1544410) in the VDR gene. We also analyzed the influence of exogenous factors on the level of 25(OH)D in children of the three study regions, as well as the relationship of the level of 25(OH)D with variants CYP2C9 ^* 2 (c.430C>T; R144C), CYP2C9 ^* 3 (c,1075A>C; I359L), CYP2D6 ^* 4 (1846G>A), CYP3A4 ^* 3 (c.1334T>C), and CYP3A4 ^* 1B (c.-392C>T) and rs731236, rs2228570 and rs1544410 in the VDR gene. Results: We found that the blood level of 25(OH)D depended on the geographical location and the number of sunny days per year. The average blood level of 25(OH)D in adolescent boys was statistically significantly lower than in girls of this age group. The level of 25(OH)D also significantly depended on the prophylactic dose of cholecalciferol administered to the subjects. In the study, it was shown that a dose of cholecalciferol ≥1,000 IU per day can achieve a normal level of 25(OH)D in healthy children. We found no statistically significant association between single-nucleotide polymorphic variants of cytochrome P450 genes (CYP2C9 ^* 3, CYP3A4 ^* 3, CYP2C9 ^* 2, CYP2D6 ^* 4, and CYP3A4 ^* 1B) and blood level of 25(OH)D in the subjects. We also did not find a relationship between the TaqI, FokI, and BsmI polymorphisms of the VDR gene and serum 25(OH)D concentration. Conclusion: Exogenous factors (time of year, place of residence, and prophylactic administration of cholecalciferol), as well as endogenous factors (age and sex), play a determining role in the development of vitamin D deficiency and insufficiency; in contrast to genetic factors-polymorphic variants of the genes of xenobiotic phase 1 enzymes (CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and the VDR gene-which do not play such role. This study shows the need to create a diagnostic algorithm for Vitamin D deficiency based on the age, season of the year, and prophylactic dose of cholecalciferol.

Effects of genetic polymorphisms in Vitamin D metabolic pathway on Vitamin D level and asthma control in South Indian patients with bronchial asthma

Objectives:

The study was designed to evaluate the single-nucleotide polymorphisms (SNPs) of genes involved in Vitamin D actions (rs2228570) and metabolic pathways (rs2248137 and rs10766197) and their associations with serum 25-hydroxy Vitamin D (25(OH)D) level and asthma control in South Indian patients with bronchial asthma.

Materials and Methods:

One hundred and two patients of South Indian origin with bronchial asthma either naive to inhaled corticosteroids (ICSs) or not receiving ICS for ≥1 month were included and were treated with ICS (beclomethasone 200 μg twice daily) for 8 weeks. One hundred and one unrelated healthy South Indians were used as controls. Pulmonary function test and fractional exhaled nitric oxide were used to assess asthma control. Serum 25(OH)D levels (chemiluminescence immunoassay) and SNPs in Vitamin D pathway (real-time polymerase chain reaction) were assessed. The associations of SNPs and serum 25(OH)D with asthma control was determined using linear regression. All analyses were performed using SPSS (version 19) and “SNPStats.” P < 0.05 was considered as statistically significant.

Results:

Vitamin D receptor (VDR) polymorphism (rs2228570) was found to be protective against asthma (P = 0.022), while there were no significant associations between the other two SNPs and asthma. Similarly, poor correlation and insignificant associations between the SNPs and serum 25(OH)D levels were observed in both cases and controls. There were also insignificant associations between the SNPs and asthma control.

Conclusion:

VDR polymorphism (rs2228570) was found to be protective against asthma in South Indians, while other genes involved in the metabolic pathway of Vitamin D did not show associations with asthma.

Glutathione Stimulates Vitamin D Regulatory and Glucose-Metabolism Genes, Lowers Oxidative Stress and Inflammation, and Increases 25-Hydroxy-Vitamin D Levels in Blood: A Novel Approach to Treat 25-Hydroxyvitamin D Deficiency

AIMS

25-Hydroxyvitamin D [25(OH)VD] deficiency/inadequacy is a major public health issue affecting more than 1 billion people worldwide. A convincing association exists between low levels of circulating 25(OH)VD and the poor health outcomes associated with chronic diseases. However, high supraphysiological doses of VD are needed to achieve the required 25(OH)VD levels in the blood, because many subjects respond poorly to supplementation.

RESULTS

This study reports a link between 25(OH)VD deficiency and a reduction in glutathione (GSH) in obese adolescents. The improvement in GSH status that results from cosupplementation with VD and l-cysteine (LC; a GSH precursor) significantly reduced oxidative stress in a mouse model of 25(OH)VD deficiency. It also positively upregulated VD regulatory genes (VDBP/VD-25-hydroxylase/VDR) in the liver and glucose metabolism genes (PGC-1α/VDR/GLUT-4) in muscle, boosted 25(OH)VD, and reduced inflammation and insulin resistance (IR) levels in the blood compared with supplementation with VD alone. In vitro GSH deficiency caused increased oxidative stress and downregulation of VDBP/VD-25-hydroxylase/VDR and upregulation of CYP24a1 in hepatocytes and downregulation of PGC-1α/VDR/GLUT-4 in myotubes. This study demonstrates that improvement in the GSH status exerts beneficial effects on the blood levels of 25(OH)VD, as well as on the inflammation and IR in a VD-deficient mouse model. Thus, the VD supplements widely consumed by the public are unlikely to be successful unless the GSH status is also corrected.

INNOVATION

These studies demonstrate a previously undiscovered mechanism by which GSH status positively upregulates the bioavailability of 25(OH)VD.

CONCLUSION

Supplementation with a combination of VD and LC or GSH precursor, rather than supplementation with VD alone, is beneficial and helps achieve more successful VD supplementation. Antioxid. Redox Signal. 00, 000-000.

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.

Effects of CYP2R1 gene variants on vitamin D levels and status: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

CYP2R1 is a key gene in the vitamin D metabolic pathway. It has been suggested that CYP2R1 gene variants in European populations are associated with concentrations of 25(OH)D, a biomarker of vitamin D levels and status in peripheral blood. However, a comprehensive meta-analysis of this effect including different ethnicities has never been conducted. The objective of this meta-analysis was to evaluate the association between CYP2R1 gene variants and 25(OH)D levels and vitamin D status.

METHODS

PubMed, EMBASE, Web of Science, CNKI and Wanfang databases were systematically searched up to May 2018. Reporting followed PRISMA guidelines. The quality of the evidence was assessed using the STREGA system. Random or fixed effects model combined estimates and sub-group tested for ethnic differences. The I² statistic quantified between-study variation due to heterogeneity.

RESULTS

Sixteen articles with a total of 52,417 participants met the inclusion criteria and were included in the meta-analysis. For rs10741657, GG genotype was associated with a clear descending trend of 25(OH)D levels when compared with the AA genotype [SMD = -2.32, 95% CI (-4.42, -0.20); SMD = -3.46, 95% CI (-6.60, -0.33) and SMD = -0.24, 95% CI (-0.51, -0.03) for total, Caucasian and Asian groups, respectively] with the following heterogeneities I² = 37.9%, 69.2% and 24.5%, respectively. However, under the AG/AA genetic model, significant changes in 25(OH)D levels [SMD and 95% CI: -1.27(-2.32, -0.23)] were only evident in the Caucasian population. The meta-analysis on vitamin D deficiency showed that the risk-allele G was associated with an increased risk of vitamin D deficiency (OR = 1.09; 95% CI = 1.03-1.15, P = 0.002). The association between rs10741657 and increased risk of vitamin D deficiency was significant (OR = 1.42; 95% CI = 1.11-1.83, P = 0.006) under the dominant model (GG + AG/AA), but not under the recessive model (GG/AG + AA), (OR = 1.28; 95% CI = 0.89-1.84, P = 0.181). There was no evidence of publication bias.

CONCLUSION

Published articles provide evidence supporting a major role for the rs10741657 polymorphism of the CYP2R1 gene in determining 25(OH)D levels and the presence of vitamin D deficiency.

The burgeoning role of cytochrome P450-mediated vitamin D metabolites against colorectal cancer

The metabolites of vitamin D₃ (VD3) mediated by different cytochrome P450 (CYP) enzymes, play fundamental roles in many physiological processes in relation to human health. These metabolites regulate a variety of cellular signal pathways through the direct binding of activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Thus, the polymorphisms of VDR and VD3 metabolizing enzymes lead to differentiated efficiency of VD3 and further affect serum VD3 levels. Moreover, VDR activation is demonstrated to inhibit the growth of various cancers, including colorectal cancer. However, excessive intake of vitamin D may lead to hypercalcemia, which limits the application of vitamin D tremendously. In this review, we have summarized the advances in VD3 research, especially the metabolism map of VD3 and the molecular mechanisms of inhibiting growth and inducing differentiation in colorectal cancer mediated by VDR-associated cellular signal pathways. The relationship between VDR polymorphism and the risk of colorectal cancer is also illustrated. In particular, novel pathways of the activation of VD3 started by CYP11A1 and CYP3A4 are highlighted, which produce several noncalcemic and antiproliferative metabolites. At last, the hypothesis is put forward that further research of CYP-mediated VD3 metabolites may develop therapeutic agents for colorectal cancer without resulting in hypercalcemia.

Methylation in 3' near region of GC gene and its association with the level of vitamin D binding protein and type 2 diabetes mellitus

As the major vitamin D binding protein (DBP), the group-specific component (GC) plays an important role in the bioactivity of vitamin D. Abnormal expression of GC gene may be associated with vitamin D related disease, type 2 diabetes mellitus (T2DM). DNA methylation is an important regulator of gene expression. It has been reported that methylation in 3' untranslated region played a role in regulation of protein expression via interaction with miRNA. This study hypothesized that DNA methylation of 3' near region of GC gene (3'GC) might be associated with T2DM. The methylation status of the 3'GC was assessed with high resolution melt method. Logistic regression was applied to assess the risk of T2DM at different levels of 3'GC methylation. The results showed that methylation level of the 3'GC was higher in T2DM patients than in non-T2DM individuals (P=.038). There was a significant association between 3'GC methylation level and T2DM (adjusted OR 1.282; 95% CI 1.062-1.548; P=.01). The association was independent upon serum glucose and insulin (adjusted OR 1.561; 95% CI 1.083-2.249; P=.017). Furthermore, there was a positive correlation between methylation level and the level of DBP in T2DM patients (r=0.126, P=.036). The association was also significant after adjusting the potential impact of rs705117 (P=.044). Besides, a positive correlation between methylation level and the level of fasting serum insulin was observed in non-T2DM (r=0.101, P<.001). These results suggest that methylation status of the 3'GC is most likely associated with DBP expression, insulin secretion, and T2DM.

Ancestry-Adjusted Vitamin D Metabolite Concentrations in Association With Cytochrome P450 3A Polymorphisms

We investigated the association between genetic polymorphisms in cytochrome P450 (CYP2R1, CYP24A1, and the CYP3A family) with nonsummer plasma concentrations of vitamin D metabolites (25-hydroxyvitamin D3 (25(OH)D3) and proportion 24,25-dihydroxyvitamin D3 (24,25(OH)2D3)) among healthy individuals of sub-Saharan African and European ancestry, matched on age (within 5 years; n = 188 in each ancestral group), in central suburban Pennsylvania (2006-2009). Vitamin D metabolites were measured using high-performance liquid chromatography with tandem mass spectrometry. Paired multiple regression and adjusted least-squares mean analyses were used to test for associations between genotype and log-transformed metabolite concentrations, adjusted for age, sex, proportion of West-African genetic ancestry, body mass index, oral contraceptive (OC) use, tanning bed use, vitamin D intake, days from summer solstice, time of day of blood draw, and isoforms of the vitamin D receptor (VDR) and vitamin D binding protein. Polymorphisms in CYP2R1, CYP3A43, vitamin D binding protein, and genetic ancestry proportion remained associated with plasma 25(OH)D3 after adjustment. Only CYP3A43 and VDR polymorphisms were associated with proportion 24,25(OH)2D3. Magnitudes of association with 25(OH)D3 were similar for CYP3A43, tanning bed use, and OC use. Significant least-squares mean interactions (CYP2R1/OC use (P = 0.030) and CYP3A43/VDR (P = 0.013)) were identified. A CYP3A43 genotype, previously implicated in cancer, is strongly associated with biomarkers of vitamin D metabolism. Interactive associations should be further investigated.

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.

Non-musculoskeletal benefits of vitamin D

The aim of this study is to determine and critically evaluate the plausible relationships of vitamin D with extra-skeletal tissues in humans. Severe vitamin D deficiency results in rickets in children and osteomalacia in adults; these beneficial effects in the musculoskeletal system and certain physiological functions are well understood. Nevertheless, mounting reports support additional beneficial effects of vitamin D, outside the musculoskeletal system. This review explores the recent advances in knowledge about the non-skeletal effects of vitamin D. Peer-reviewed papers were extracted from research databases using key words, to assess correlations between vitamin D and extra-skeletal diseases and conditions. As per the guidelines of the Preferred Reporting Items for Systematic Reviews (PRISMA); general interpretations of results are included; taking into consideration the broader evidence and implications. This review summarizes current knowledge of the effects of vitamin D status on extra-skeletal tissues with special attention given to relationships between vitamin D status and various diseases commonly affecting adults; the effects of intervention with vitamin D and exposure to sunlight. Evidence suggests that vitamin D facilitates the regulation of blood pressure; and cardiac; endothelial; and smooth muscle cell functions; playing an important role in cardiovascular protection. In addition; 1,25(OH)₂D improves immunity; subdues inflammation; and reduces the incidence and severity of common cancers; autoimmune diseases and infectious diseases. Almost all adequately powered; epidemiological and biological studies that use; adequate doses of vitamin D supplementation in D-deficient populations have reported favorable outcomes. These studies have concluded that optimizing 25(OH)D status improves the functionality of bodily systems; reduces comorbidities; improves the quality of life; and increases survival. Although accumulating evidence supports biological associations of vitamin D sufficiency with improved physical and mental functions; no definitive evidence exists from well-designed; statistically powered; randomized controlled clinical trials. Nevertheless, most studies point to significant protective effects of vitamin D in humans when the minimum 25(OH)D serum level exceeds 30ng/mL and is maintained throughout the year.

Association between serum 25-hidroxyvitamin D concentrations and ultraviolet index in Portuguese older adults: a cross-sectional study

Background

The older population is a risk group for hypovitaminosis D. The Ultraviolet Index (UVI) can be an indicator of potential for cutaneous synthesis of vitamin D but physiological and other environmental factors also influence vitamin D synthesis and status. Knowledge about vitamin D status in Portuguese older adults is limited. This study aims to explore the association between Ultraviolet Index and serum 25-hidroxyvitamin D3 [25(OH)D] levels accounting for other potential influential factors.

Methods

A cross-sectional study was conducted between December 2015 and June 2016, in 1497 Portuguese older adults (≥ 65 years) within Nutrition UP 65 project. For each participant, serum 25(OH)D was determined and the mean UVI (mUVI) in the respective residence district was calculated for the previous 30 days. Stepwise linear regression analyses were conducted for the following periods of blood collection: between December and June, December and March and April and June. Standardized regression coefficients (Sβ) and 95% confidence intervals were calculated.

Results

The median 25(OH)D concentration was 35.9 nmol/L. The UVI was independently and positively associated with 25(OH)D in the models for December–June (Sβ = 0.244, 95% CI: 0.198; 0.291, P < 0.001) and April–June (Sβ = 0.295, 95% CI: 0.299; 0.362, P < 0.001) and independently and negatively associated in December–March period (Sβ = −0.149, 95% CI: -0.211; −0.087, P < 0.001).

Conclusions

In this sample with high vitamin D deficiency frequency, the UVI was a predictor of 25(OH)D levels but the direction of the association varied according to the blood collection period. Our results suggest that accounting for the time of year in future research regarding vitamin status and related public health recommendations may be relevant.

Electronic supplementary material

The online version of this article (10.1186/s12877-017-0644-8) contains supplementary material, which is available to authorized users.

Nutritional modulation of age-related changes in the immune system and risk of infection

The immune system undergoes some adverse alterations during aging, many of which have been implicated in the increased morbidity and mortality associated with infection in the elderly. In addition to intrinsic changes to the immune system with aging, the elderly are more likely to have poor nutritional status, which further impacts the already impaired immune function. Although the elderly often have low zinc serum levels, several manifestations commonly observed during zinc deficiency are similar to the changes in immune function with aging. In the case of vitamin E, although its deficiency is rare, the intake above recommended levels is shown to enhance immune functions in the elderly and to reduce the risk of acquiring upper respiratory infections in nursing home residents. Vitamin D is a critical vitamin in bone metabolism, and its deficiency is far more common, which has been linked to increased risk of infection as demonstrated in a number of observational studies including those in the elderly. In this review, we focus on zinc, vitamin E, and vitamin D, the 3 nutrients which are relatively well documented for their roles in impacting immune function and infection in the elderly, to discuss the findings in this context reported in both the observational studies and interventional clinical trials. A perspective will be provided based on the analysis of information under review.

DHCR7: A vital enzyme switch between cholesterol and vitamin D production

The conversion of 7-dehydrocholesterol to cholesterol, the final step of cholesterol synthesis in the Kandutsch-Russell pathway, is catalyzed by the enzyme 7-dehydrocholesterol reductase (DHCR7). Homozygous or compound heterozygous mutations in DHCR7 lead to the developmental disease Smith-Lemli-Opitz syndrome, which can also result in fetal mortality, highlighting the importance of this enzyme in human development and survival. Besides serving as a substrate for DHCR7, 7-dehydrocholesterol is also a precursor of vitamin D via the action of ultraviolet light on the skin. Thus, DHCR7 exerts complex biological effects, involved in both cholesterol and vitamin D production. Indeed, we argue that DHCR7 can act as a switch between cholesterol and vitamin D synthesis. This review summarizes current knowledge about the critical enzyme DHCR7, highlighting recent findings regarding its structure, transcriptional and post-transcriptional regulation, and its links to vitamin D synthesis. Greater understanding about DHCR7 function, regulation and its place within cellular metabolism will provide important insights into its biological roles.