Genetic and non-genetic correlates of vitamins K and D

Association of vitamin D-binding protein polymorphisms and serum 25(OH)D concentration varies among Chinese healthy infants of different VDR-FokI genotypes: A multi-centre cross-sectional study

Hypovitaminosis D during infancy is associated with the development of chronic diseases and poor health later in life. While the effect of environmental factors on vitamin D concentration has been extensively explored, this study aimed to explore the effect of genetic factors on vitamin D concentration among Chinese infants. We conducted a multi-centre cross-sectional study in Hong Kong from July 2019 to May 2021. A candidate genetic approach was adopted to study four selected genetic variants of the vitamin D-binding protein (DBP) and vitamin D receptor (VDR) (rs4588, rs7041, rs2282679 and rs2228570) to examine their associations with measured serum 25(OH)D concentration. A total of 378 Chinese infants aged 2-12 months were recruited in this study. Peripheral blood samples were collected from the infants to measure serum 25(OH)D concentration and extract DNA. Results showed that rs7041T and rs2282679C were significantly associated with lower serum 25(OH)D concentration. Further analysis of the DBP variants revealed that the GC1F allele was significantly associated with lower 25(OH)D concentration and identified as the risk DBP isoform in infants. While our results revealed that there is no direct association between VDR-FokI genotype and serum 25(OH)D concentration, a VDR-FokI genotype-specific pattern was observed in the association between DBP isoforms and serum 25(OH)D concentration. Specifically, significant associations were observed in the DBP genotypes GC1F/F, GC1F/2 and GC1S/2 among VDR-FokI TT/TC carriers, but not in VDR-FokI CC carriers. Our findings lay down the basis for the potential of genetic screening to identify high risk of hypovitaminosis D in Chinese infants.

Genetic determinants of Vitamin D deficiency in the Middle Eastern Qatari population: a genome-wide association study

Introduction

Epidemiological studies have consistently revealed that Vitamin D deficiency is most prevalent in Middle Eastern countries. However, research on the impact of genetic loci and polygenic models related to Vitamin D has primarily focused on European populations.

Methods

We conducted the first genome-wide association study to identify genetic determinants of Vitamin D levels in Middle Easterners using a whole genome sequencing approach in 6,047 subjects from the Qatar Biobank (QBB) project. We performed a GWAS meta-analysis, combining the QBB cohort with recent European GWAS data from the UK Biobank (involving 345,923 individuals). Additionally, we evaluated the performance of European-derived polygenic risk scores using UK Biobank data in the QBB cohort.

Results

Our study identified an association between a variant in a known locus for the group-specific component gene (GC), specifically rs2298850 (p-value = 1.71 × 10-08, Beta = -0.1285), and Vitamin D levels. Furthermore, our GWAS meta-analysis identified two novel variants at a known locus on chromosome 11, rs67609747 and rs1945603, that reached the GWAS significance threshold. Notably, we observed a moderately high heritability of Vitamin D, estimated at 18%, compared to Europeans. Despite the lower predictive performance of Vitamin D levels in Qataris compared to Europeans, the European-derived polygenic risk scores exhibited significant links to Vitamin D deficiency risk within the QBB cohort.

Conclusion

This novel study reveals the genetic architecture contributing to Vitamin D deficiency in the Qatari population, emphasizing the genetic heterogeneity across different populations.

Vitamin D: An Overview of Gene Regulation, Ranging from Metabolism to Genomic Effects

Vitamin D is a pro-hormone characterized by an intricate metabolism and regulation. It is well known for its role in calcium and phosphate metabolism, and in bone health. However, several studies have assessed a huge number of extra-skeletal functions, ranging from cell proliferation in some oncogenic pathways to antioxidant and immunomodulatory functions. Vitamin D exerts its role by binding to VDRs (vitamin D receptors), which are located in many different tissues. Moreover, VDRs are able to bind hundreds of genomic loci, modulating the expression of various primary target genes. Interestingly, plenty of gene polymorphisms regarding VDRs are described, each one carrying a potential influence against gene expression, with relapses in several chronic diseases and metabolic complications. In this review, we provide an overview of the genetic aspects of vitamin D and VDR, emphasizing the gene regulation of vitamin D, and the genetic modulation of VDR target genes. In addition, we briefly summarize the rare genetic disease linked to vitamin D metabolism.

Analysis of intronic SNP (rs4147358) and expression of SMAD3 gene in Atopic Dermatitis: A case-control study

BACKGROUND

Atopic Dermatitis (AD) is a multifactorial cutaneous disorder associated with chronic inflammation of the skin. Growing evidence points to TGF-β/SMAD signaling as a key player in mediating inflammation and the subsequent tissue remodeling, often resulting in fibrosis. This study investigates the role of a core transcription factor involved in TGF-β signaling i.e., SMAD3 genetic variants (rs4147358) in AD predisposition and its association with SMAD3 mRNA expression, serum IgE levels, and sensitization to various allergens in AD patients.

METHODS

A total of 246 subjects including 134 AD cases and 112 matched healthy controls were genotyped for SMAD3 intronic SNP by PCR-RFLP. mRNA expression of SMAD3 was determined by quantitative Real-Time PCR (qRT-PCR), Vitamin-D levels by chemiluminescence, and total serum IgE levels by ELISA. In-vivo allergy testing was performed for the evaluation of allergic reactions to house dust mites (HDM) and food allergens.

RESULTS

A significantly higher frequency of mutant genotype AA (cases: 19.4% vs controls: 8.9%) (OR = 2.8, CI = 1.2 - 6.7, p = 0.01) was observed in AD cases. The mutant allele 'A' also showed a 1.9-fold higher risk for AD compared to the wild allele 'C' indicating that the carriers of the A allele have a higher risk for AD predisposition (OR-1.9, CI = 1.3-2.8, p < 0.001). In addition, quantitative analysis of SMAD3 mRNA in peripheral blood showed 2.8-fold increased expression in AD cases as compared to healthy controls. Stratification analysis revealed the association of the mutant AA genotype with deficient serum Vitamin D levels (p = 0.02) and SMAD3 mRNA overexpression with HDM sensitization (p = 0.03). Furthermore, no significant association of genotypes with SMAD3 mRNA expression was observed.

CONCLUSION

Our study indicates that SMAD3 intronic SNP bears a significant risk of AD development. Moreover, overexpression of SMAD3 mRNA and its association with HDM sensitization highlights the possible role of this gene in AD pathogenesis.

Vitamin K and the Visual System-A Narrative Review

Vitamin K occupies a unique and often obscured place among its fellow fat-soluble vitamins. Evidence is mounting, however, that vitamin K (VK) may play an important role in the visual system apart from the hepatic carboxylation of hemostatic-related proteins. However, to our knowledge, no review covering the topic has appeared in the medical literature. Recent studies have confirmed that matrix Gla protein (MGP), a vitamin K-dependent protein (VKDP), is essential for the regulation of intraocular pressure in mice. The PREDIMED (Prevención con Dieta Mediterránea) study, a randomized trial involving 5860 adults at risk for cardiovascular disease, demonstrated a 29% reduction in the risk of cataract surgery in participants with the highest tertile of dietary vitamin K1 (PK) intake compared with those with the lowest tertile. However, the specific requirements of the eye and visual system (EVS) for VK, and what might constitute an optimized VK status, is currently unknown and largely unexplored. It is, therefore, the intention of this narrative review to provide an introduction concerning VK and the visual system, review ocular VK biology, and provide some historical context for recent discoveries. Potential opportunities and gaps in current research efforts will be touched upon in the hope of raising awareness and encouraging continued VK-related investigations in this important and highly specialized sensory system.

Association between Vitamin D Status and Health Status of Adults in Western Libya

Vitamin D (VitD) is essential for health and preventing diseases. This study aimed to investigate the possible association between VitD status and health status in 306 Libyan male and female young adults (18–25 Y) and adults (26–65 Y). There were 89.54% of subjects that had VitD levels below normal (<30 ng/mL), of which 45.42% were VitD deficient (<10 ng/mL) and 44.12% were VitD insufficient (10–29.9 ng/mL). VitD deficiency was associated with higher fasting blood sugar (FBS), low-density lipoprotein (LDL), and triacylglycerol (TAG) levels. Young adults had lower VitD levels than adults, which was associated with some health conditions. VitD insufficiency was associated with higher body mass index (BMI) values in adults, especially females, with higher FBS levels in adult males and higher hemoglobin A1c (HbA1c) levels in adult females. VitD deficiency in young adults was associated with higher TAG levels (more likely in adults) and lower high-density lipoprotein (HDL) values. Furthermore, VitD deficient adult females appeared to have a higher risk of sleeping problems, psychological disorders, headache, and osteoporosis, whereas their male counterparts appeared to be at a higher risk of developing obesity and diabetes mellitus (DM). Findings showed a serious prevalence of VitD inadequacy in the Libyan population, which appears to negatively affect health status and be associated with some disease conditions.

Prevalence and Risk Factors for Vitamin D Deficiency in Children and Adolescents in the Kingdom of Bahrain

BACKGROUND

Vitamin D deficiency has reached pandemic levels in the Middle East and North Africa (MENA) region, even though sunshine is abundant all year round for the cutaneous synthesis of vitamin D through the skin. This study aimed to determine the prevalence of vitamin D deficiency and risk factors associated with serum 25-hydroxy vitamin D (25(OH)D) in children and adolescents aged from 10 to 19 years, as well as the possible associations of vitamin D with calcium, magnesium and phosphate levels.

METHODS

A multi-center, cross-sectional study was conducted between May and August 2019 at the Ministry of Health in the Kingdom of Bahrain. A total of 383 boys and girls were selected from five health centers from five different regions in the Kingdom of Bahrain. Information about sex, age, education level, weight, height, degree of sunlight exposure, and physical activity levels was recorded. A blood sample was taken from each participant to test serum levels of 25(OH)D, calcium, magnesium and phosphate.

RESULTS

The results revealed that 92.1% of the participants were deficient in vitamin D. A significantly higher percentage of boys (96.2%) were vitamin D deficient (<20 ng/mL) than girls (88.3%) (p value = 0.004). Vitamin D deficiency were more prevalent among overweight (96.8%) and obese (96.2%) participants than normal body weight and wasted participants (p value < 0.001). Being male, overweight, or obese was significantly positively associated with a risk of vitamin D deficiency. Vitamin D deficiency was significantly associated with low serum levels of magnesium. No significant associations were detected between vitamin D deficiency and calcium and phosphate serum levels. However, vitamin D deficiency was significantly associated with low serum level of magnesium (p value = 0.017).

CONCLUSIONS

Our study revealed that vitamin D deficiency was more prevalent among overweight and obese adolescents and mostly boys rather than girls. Magnesium and phosphate were lower in adolescents and children with lower serum 25(OH)D, showing a clear association between these biomarkers and the 25(OH)D.

Genetic Determinants of 25-Hydroxyvitamin D Concentrations and Their Relevance to Public Health

Twin studies suggest a considerable genetic contribution to the variability in 25-hydroxyvitamin D (25(OH)D) concentrations, reporting heritability estimates up to 80% in some studies. While genome-wide association studies (GWAS) suggest notably lower rates (13−16%), they have identified many independent variants that associate with serum 25(OH)D concentrations. These discoveries have provided some novel insight into the metabolic pathway, and in this review we outline findings from GWAS studies to date with a particular focus on 35 variants which have provided replicating evidence for an association with 25(OH)D across independent large-scale analyses. Some of the 25(OH)D associating variants are linked directly to the vitamin D metabolic pathway, while others may reflect differences in storage capacity, lipid metabolism, and pathways reflecting skin properties. By constructing a genetic score including these 25(OH)D associated variants we show that genetic differences in 25(OH)D concentrations persist across the seasons, and the odds of having low concentrations (<50 nmol/L) are about halved for individuals in the highest 20% of vitamin D genetic score compared to the lowest quintile, an impact which may have notable influences on retaining adequate levels. We also discuss recent studies on personalized approaches to vitamin D supplementation and show how Mendelian randomization studies can help inform public health strategies to reduce adverse health impacts of vitamin D deficiency.

25-Hydroxyvitamin D Serum Levels Linked to Single Nucleotide Polymorphisms (SNPs) (rs2228570, rs2282679, rs10741657) in Skeletal Muscle Aging in Institutionalized Elderly Men Not Supplemented with Vitamin D

Sarcopenia (Sp) is the loss of skeletal muscle mass associated with aging that results in an involution of muscle function and strength. Vitamin D deficiency is a common health problem worldwide, especially among the elderly, and hypovitaminosis D leads to musculoskeletal disorders. The aim of this study was to evaluate the impact and presence of a possible linkage between Single Nucleotide Polymorphisms (SNPs) CYP2R1 (rs10741657), GC (rs2282679), and VDR (rs2228570), serum 25-OH/D concentrations and the link with the degree of sarcopenia in 19 institutionalized elderly men not supplemented with vitamin D. Levels of 25-OH vitamin D were quantified with a commercial enzyme-linked immunosorbent assay kit and 3 SNPs were genotyped with KASPar assays. Significant differences in 25-OH/D concentration were determined between the bi-allelic combinations of rs228679 and rs228570. We detected statistically significant weak positive correlations between the AA (rs10741657 and rs228570) and TT (rs228679) and alleles and 25-OH/D and the probability of having higher 25-OH/D concentrations was 2- to 3-fold higher. However, the GG alleles of the 3 SNPs showed that the probability of having optimal 25-0H/D concentrations decreases by 32% for rs10741657, 38% for rs228679, and 74% for rs228570, showing a strong negative correlation between the degree of sarcopenia and 25-OH/D levels. Allelic variations in CYP2R1 (rs10741657), GC (rs2282679), and VDR (rs10741657) affect vitamin D levels and decisively influence the degree of sarcopenia in institutionalized elderly people.

Haplotypes in the GC, CYP2R1 and CYP24A1 Genes and Biomarkers of Bone Mineral Metabolism in Older Adults

Candidate gene studies have analyzed the effect of specific vitamin D pathway genes on vitamin D availability; however, it is not clear whether genetic variants also affect overall bone metabolism. This study evaluated the association between genetic polymorphisms in GC, CYP2R1 and CYP24A1 and serum levels of total 25(OH)D, iPTH and other mineral metabolism biomarkers (albumin, total calcium and phosphorus) in a sample of 273 older Spanish adults. We observed a significant difference between CYP2R1 rs10741657 codominant model and total 25(OH)D levels after adjusting them by gender (p = 0.024). In addition, the two SNPs in the GC gene (rs4588 and rs2282679) were identified significantly associated with iPTH and creatinine serum levels. In the case of phosphorus, we observed an association with GC SNPs in dominant model. We found a relationship between haplotype 2 and 25(OH)D levels, haplotype 4 and iPTH serum levels and haplotype 7 and phosphorus levels. In conclusion, genetic variants in CYP2R1 and GC could be predictive of 25(OH)D and iPTH serum levels, respectively, in older Caucasian adults. The current study confirmed the role of iPTH as one of the most sensitive biomarkers of vitamin D activity in vivo.

Effects of vitamin D-related gene polymorphisms on attempted suicide

OBJECTIVE

Emerging evidence suggests that vitamin D might protect from attempted suicide. The study aimed to investigate the associations between single-nucleotide polymorphisms (SNPs) related to vitamin D levels identified in a large genome-wide association study and attempted suicide in rural China.

METHODS

This 1:1 matched case-control study included altogether 510 suicide attempters and 510 community controls. Genotypes of four target SNPs (DHCR7-rs12785878, CYP2R1-rs10741657, GC-rs2282679, and CYP24A1-rs6013897) were determined, and a genetic risk score (GRS) was constructed to evaluate the combined effect of them. Demographic and psychological information was acquired through face-to-face interviews.

RESULTS

The A allele of CYP24A1-rs6013897 was significantly associated with attempted suicide (OR = 1.27, 95% CI, 1.03-1.58, P = 0.029), even after adjusting for demographic and psychological confounders (adjusted OR = 1.53, 95% CI, 1.01-2.30, P = 0.043). The GRS analyses revealed a significantly higher risk of attempted suicide with a greater number of low vitamin D alleles (adjusted OR = 1.33, 95% CI, 1.13-1.58, P < 0.001). Subgroup analyses stratified by sex indicated that the genetic associations were only significant among males with adjusted ORs of 3.77 (95% CI, 1.56-9.10) for the A allele of rs6013897 and 2.04 (95% CI, 1.32-3.17) for GRS.

CONCLUSIONS

Our findings identity CYP24A1-rs6013897 as a potential biomarker for attempted suicide and indicate that a genetic predisposition to lower vitamin D levels may contribute to attempted suicide. It suggests the possibility that vitamin D may have the preventive potential for attempted suicide.

The Association between Vitamin D-Related Gene Polymorphisms and Serum 25-Hydroxyvitamin D Concentration: A Prospective Cohort Study in Pregnant Minangkabau Women, Indonesia

Several candidate genes in vitamin D synthesis and metabolism have been reported to have a significant association with 25-hydroxyvitamin D (25(OH)D) in Caucasians and African Americans. Few studies have indicated this relationship among Asians, especially in pregnant Minangkabau women, Indonesia. This study was conducted among 180 singleton pregnant women of West Sumatran Vitamin D Pregnant Mother (VDPM) cohort study. Serum 25(OH)D obtained in the third trimester (T3). Genetic risk scores (GRS) were created based on six vitamin D-related SNPs and their association with 25(OH)D levels were tested. Informations on demographics, lifestyle, pregnancy profile, and physical activity were collected using questionnaire. The average of 25(OH)D concentration was 21.21±10.41 ng/mL respectively. Vitamin D-GRS has significantly associated with serum 25(OH)D levels in the third trimester (p=0.006). However, the synthesis-GRS and metabolism-GRS group of vitamin D-related gene polymorphisms had no association with 25(OH)D concentration at T3 (p>0.05). A high prevalence of insufficient-deficient vitamin D status at T3 was common. We observed an association between vitamin D-GRS and 25(OH)D concentration. The results of this study provides additional support for possible role of genetic variants in vitamin D-related gene polymorphisms on 25(OH)D concentration during pregnancy. Further replication studies with larger sample sizes are needed to confirm thefindings.

Development and Validation of a Predictive Model of Hypovitaminosis D in General Adult Population: SCOPYD Study

The worldwide global increase in serum 25-hydroxyvitamin D (25(OH)D) measurements has led some countries to restrict reimbursement for certain clinical situations only. Another approach could consist in providing physicians with screening tools in order to better target blood test prescription. The objective of the SCOPYD study was to identify the best combination of predictors of serum VitD concentration among adults aged 18–70 years. Potential risk factors for VitD deficiency were collected using a comprehensive self-administered questionnaire. A multivariable linear regression was used to build a predictive model of serum 25(OH)D concentration. Among 2488 participants, 1080 (43.4%) had VitD deficiency (<50 nmol/L) and 195 (7.8%) had severe deficiency (<25 nmol/L). The final model included sunlight exposure in the preceding week and during the last holidays, month of blood sampling, age, sex, body mass index, skin phototype, employment, smoking, sport practice, latitude, and VitD supplementation in preceding year. The area under the curve was 0.82 (95% CI (0.78; 0.85)) for severe deficiency. The model predicted severe deficiency with a sensitivity of 77.9% (95% CI (69.1; 85.7)) and a specificity of 68.3% (95% CI (64.8; 71.9)). We identified a set of predictors of severe VitD deficiency that are easy to collect in routine that may help to better target patients for serum 25(OH)D concentration determination.

Recommendations on the measurement and the clinical use of vitamin D metabolites and vitamin D binding protein - A position paper from the IFCC Committee on bone metabolism

Vitamin D, an important hormone with a central role in calcium and phosphate homeostasis, is required for bone and muscle development as well as preservation of musculoskeletal function. The most abundant vitamin D metabolite is 25-hydroxyvitamin D [25(OH)D], which is currently considered the best marker to evaluate overall vitamin D status. 25(OH)D is therefore the most commonly measured metabolite in clinical practice. However, several other metabolites, although not broadly measured, are useful in certain clinical situations. Vitamin D and all its metabolites are circulating in blood bound to vitamin D binding protein, (VDBP). This highly polymorphic protein is not only the major transport protein which, along with albumin, binds over 99% of the circulating vitamin D metabolites, but also participates in the transport of the 25(OH)D into the cell via a megalin/cubilin complex. The accurate measurement of 25(OH)D has proved a difficult task. Although a reference method and standardization program are available for 25(OH)D, the other vitamin D metabolites still lack this. Interpretation of results, creation of clinical supplementation, and generation of therapeutic guidelines require not only accurate measurements of vitamin D metabolites, but also the accurate measurements of several other "molecules" related with bone metabolism. IFCC understood this priority and a committee has been established with the task to support and continue the standardization processes of vitamin D metabolites along with other bone-related biomarkers. In this review, we present the position of this IFCC Committee on Bone Metabolism on the latest developments concerning the measurement and standardization of vitamin D metabolites and its binding protein, as well as clinical indications for their measurement and interpretation of the results.

Genetic Risk Score for Serum 25-Hydroxyvitamin D Concentration Helps to Guide Personalized Vitamin D Supplementation in Healthy Finnish Adults

BACKGROUND

Genetic factors modify serum 25-hydroxyvitamin D [25(OH)D] concentration and can affect the optimal intake of vitamin D.

OBJECTIVES

We aimed to personalize vitamin D supplementation by applying knowledge of genetic factors affecting serum 25(OH)D concentration.

METHODS

We performed a genome-wide association study of serum 25(OH)D concentration in the Finnish Health 2011 cohort (n = 3339) using linear regression and applied the results to develop a population-matched genetic risk score (GRS) for serum 25(OH)D. This GRS was used to tailor vitamin D supplementation for 96 participants of a longitudinal Digital Health Revolution (DHR) Study. The GRS, serum 25(OH)D concentrations, and personalized supplementation and dietary advice were electronically returned to participants. Serum 25(OH)D concentrations were assessed using immunoassays and vitamin D intake using FFQs. In data analyses, cross-sectional and repeated-measures statistical tests and models were applied as described in detail elsewhere.

RESULTS

GC vitamin D-binding protein and cytochrome P450 family 2 subfamily R polypeptide 1 genes showed genome-wide significant associations with serum 25(OH)D concentration. One single nucleotide polymorphism from each locus (rs4588 and rs10741657) was used to develop the GRS. After returning data to the DHR Study participants, daily vitamin D supplement users increased from 32.6% to 60.2% (P = 6.5 × 10-6) and serum 25(OH)D concentration from 64.4 ± 20.9 nmol/L to 68.5 ± 19.2 nmol/L (P = 0.006) between August and November. Notably, the difference in serum 25(OH)D concentrations between participants with no risk alleles and those with 3 or 4 risk alleles decreased from 20.7 nmol/L to 8.0 nmol/L (P = 0.0063).

CONCLUSIONS

We developed and applied a population-matched GRS to identify individuals genetically predisposed to low serum 25(OH)D concentration. We show how the electronic return of individual genetic risk, serum 25(OH)D concentrations, and factors affecting vitamin D status can be used to tailor vitamin D supplementation. This model could be applied to other populations and countries.

Vitamin D Receptor (VDR) Gene Polymorphism in Patients Diagnosed with Colorectal Cancer

Colorectal cancer (CRC) is one of the most commonly occurring neoplasias in humans. The prevalence of CRC rates is still rising. Although the exact background of the disease still remains unknown, it is believed that CRC may not only be a result of environmental factors, but also genetic ones. One of the mechanisms underlying CRC might be the vitamin D pathway, as CRC is the most closely linked neoplasia to vitamin D deficiency. This study shows a possible association of the vitamin D receptor (VDR) polymorphisms FokI, BsmI, ApaI, and TaqI with CRC susceptibility. A total of 103 patients diagnosed with CRC (61 men and 42 women, aged 57-82 years) and 109 healthy people (50 men and 59 women, aged 47-68 years) were genotyped using PCR-RFLP for FokI, BsmI, ApaI, and TaqI. None of the single nucleotide polymorphisms (SNPs) individually increased or decreased the risk of CRC. The evaluation of haplotypes revealed two that might enhance the likelihood of CRC development: taB (OR = 30.22; 95% CI 2.81-325.31; p = 0.01) and tAb (OR = 3.84; 95% CI 1.29-11.38; p = 0.01). In conclusion, genotyping is an easy and robust procedure that needs to be performed only once in a lifetime. A creation of a relevant SNP's panel might contribute to the identification of the groups that are at the greatest risk of CRC.

Risk evaluation of vitamin D insufficiency or deficiency in children using simple scores: The Healthy Growth Study

Although identification of population groups at high risk for low vitamin D status is of public health importance,there are no risk prediction tools available for children in Southern Europe that can cover this need. The present study aimed to develop and validate 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children. A cross-sectional epidemiological study was conducted among 2280 schoolchildren (9--13-year-old) living in Greece. The total sample was randomly divided into 2 subsamples of 1524 and 756 children, used in the development and validation of the 2 scores, respectively. Multivariate logistic regression analyses were used to develop the 2 risk evaluation scores, while receiver operating characteristic curves were employed to identify the optimal "points of change" for each risk score, upon which vitamin D insufficiency and deficiency is diagnosed with the highest possible sensitivity and specificity. The components of the 2 risk evaluation scores included children's age, gender, region of residence, screen-time, body weight status, maternal education, and season. The increase in each score by 1 unit elevated the likelihood for vitamin D insufficiency and deficiency by 31% and 28%, respectively. The receiver operating characteristic curves showed that the optimal "points of change" for each risk score, upon which vitamin D insufficiency or deficiency is diagnosed with the highest possible sensitivity and specificity were 8.5 and 12.5, respectively. In conclusion, this study developed 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children living in Greece. However, more studies are required for these scores to be validated in other populations of children from different countries.

Effects of Vitamin D Supplementation on Lipid Profile in Adults with the Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Metabolic syndrome (MetS) increases the risk of cardiovascular disease, with atherogenic dyslipidemia being a major contributing factor.

METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to assess whether vitamin D supplementation (VDS) alleviates dyslipidemia in adults with MetS. Scientific databases (PUBMED, MEDLINE, CINAHL, EMBASE, Cochrane Library, ClinicalTrials.gov, International Clinical Trials Registry Platform) and the gray literature were searched for randomized controlled trials of VDS, reporting on blood lipids. A narrative review, meta-analyses, sensitivity analyses, and appraisal of the risk of bias and overall quality of evidence produced were conducted.

RESULTS

Seven studies were included, and four were meta-analyzed. The risk of bias was generally low, and the final quality of evidence was low or very low. VDS, whether in high or low dose, significantly increased endline vitamin D blood levels; did not affect total, low-density, high-density cholesterol levels, and novel lipid-related biomarkers; yet, significantly increased triglycerides (TG) levels compared with placebo (MD: 30.67 (95%CI: 4.89-56.45) mg/dL; p = 0.02 for low-dose VDS; and MD: 27.33 (95%CI: 2.06-52.59) mg/dL; p = 0.03 for high-dose VDS). Pertaining heterogeneity was high (I² = 86%; and I² = 51%, respectively), and some included studies had significantly higher baseline TG in the intervention arm. The sensitivity analyses revealed robust results.

CONCLUSION

VDS seems not to affect blood lipids in adults with MetS.

Cytokine Storm in COVID-19: "When You Come Out of the Storm, You Won't Be the Same Person Who Walked in"

In December 2019, a novel coronavirus, COVID-19, was discovered to be the causal agent of a severe respiratory infection named SARS-CoV-2, and it has since been recognized worldwide as a pandemic. There are still numerous doubts concerning its pathogenesis and particularly the underlying causes of the various clinical courses, ranging from severe manifestations to asymptomatic forms, including acute respiratory distress syndrome. The major factor responsible for acute respiratory distress syndrome is the so-called "cytokine storm," which is an aberrant response from the host immune system that induces an exaggerated release of proinflammatory cytokines/chemokines. In this review, we will discuss the role of cytokine storm in COVID-19 and potential treatments with which counteract this aberrant response, which may be valuable in the clinical translation.

Genetic gateways to COVID-19 infection: Implications for risk, severity, and outcomes

The dynamics, such as transmission, spatial epidemiology, and clinical course of Coronavirus Disease-2019 (COVID-19) have emerged as the most intriguing features and remain incompletely understood. The genetic landscape of an individual in particular, and a population in general seems to play a pivotal role in shaping the above COVID-19 dynamics. Considering the implications of host genes in the entry and replication of SARS-CoV-2 and in mounting the host immune response, it appears that multiple genes might be crucially involved in the above processes. Herein, we propose three potentially important genetic gateways to COVID-19 infection; these could explain at least in part the discrepancies of its spread, severity, and mortality. The variations within Angiotensin-converting enzyme 2 (ACE2) gene might constitute the first genetic gateway, influencing the spatial transmission dynamics of COVID-19. The Human Leukocyte Antigen locus, a master regulator of immunity against infection seems to be crucial in influencing susceptibility and severity of COVID-19 and can be the second genetic gateway. The genes regulating Toll-like receptor and complement pathways and subsequently cytokine storm induced exaggerated inflammatory pathways seem to underlie the severity of COVID-19, and such genes might represent the third genetic gateway. Host-pathogen interaction is a complex event and some additional genes might also contribute to the dynamics of COVID-19. Overall, these three genetic gateways proposed here might be the critical host determinants governing the risk, severity, and outcome of COVID-19. Genetic variations within these gateways could be key in influencing geographical discrepancies of COVID-19.

Personalized Nutrition for Management of Micronutrient Deficiency-Literature Review in Non-bariatric Populations and Possible Utility in Bariatric Cohort

Background

Bariatric surgery can effectively treat morbid obesity; however, micronutrient deficiencies are common despite recommendations for high-dose supplements. Genetic predisposition to deficiencies underscores necessary identification of high-risk candidates. Personalized nutrition (PN) can be a tool to manage these deficiencies.

Methods

Medline, PubMed, and Google Scholar were searched. Articles involving genetic testing, micronutrient metabolism, and bariatric surgery were included.

Results

Studies show associations between genetic variants and micronutrient metabolism. Research demonstrates genetic testing to be a predictor for outcomes among obesity and bariatric surgery populations. There is limited research in bariatric surgery and micronutrient genetic variants.

Conclusion

Genotype-based PN is becoming feasible to provide an effective treatment of micronutrient deficiencies associated with bariatric surgery. The role of genomic technology in micronutrient recommendations needs further investigation.

A genetic approach to study the relationship between maternal Vitamin D status and newborn anthropometry measurements: the Vitamin D pregnant mother (VDPM) cohort study

PURPOSE

Adverse effects of maternal vitamin D deficiency have been linked to adverse pregnancy outcomes. We investigated the relationship between maternal vitamin D status and newborn anthropometry measurements using a genetic approach and examined the interaction between genetic variations in involved in vitamin D synthesis and metabolism and maternal vitamin D concentrations on newborn anthropometry.

METHODS

The study was conducted in 183 pregnant Indonesian Minangkabau women. Genetic risk scores (GRSs) were created using six vitamin D-related single nucleotide polymorphisms and their association with 25-hydroxyvitamin D [25(OH)D] levels and newborn anthropometry (183 infants) were investigated.

RESULTS

There was no significant association between maternal 25(OH)D concentrations and newborn anthropometry measurements (P > 0.05, for all comparisons). After correction for multiple testing using Bonferroni correction, GRS was significantly associated with 25(OH)D in the third trimester (P = 0.004). There was no association between GRS and newborn anthropometric measurements; however, there was an interaction between GRS and 25(OH)D on head circumference (P = 0.030), where mothers of neonates with head circumference < 35 cm had significantly lower 25(OH)D if they carried ≥4 risk alleles compared to those who carried ≤3 risk alleles.

CONCLUSION

Our findings demonstrate the impact of vitamin D-related GRS on 25(OH)D and provides evidence for the effect of vitamin D-related GRS on newborn anthropometry through the influence of serum 25(OH)D levels among Indonesian pregnant women. Even though our study is a prospective cohort, before the implementation of vitamin D supplementation programs in Indonesia to prevent adverse pregnancy outcomes, further large studies are required to confirm our findings.

Genome-wide Association Study for Vitamin D Levels Reveals 69 Independent Loci

We aimed to increase our understanding of the genetic determinants of vitamin D levels by undertaking a large-scale genome-wide association study (GWAS) of serum 25 hydroxyvitamin D (25OHD). To do so, we used imputed genotypes from 401,460 white British UK Biobank participants with available 25OHD levels, retaining single-nucleotide polymorphisms (SNPs) with minor allele frequency (MAF) > 0.1% and imputation quality score > 0.3. We performed a linear mixed model GWAS on standardized log-transformed 25OHD, adjusting for age, sex, season of measurement, and vitamin D supplementation. These results were combined with those from a previous GWAS including 42,274 Europeans. In silico functional follow-up of the GWAS results was undertaken to identify enrichment in gene sets, pathways, and expression in tissues, and to investigate the partitioned heritability of 25OHD and its shared heritability with other traits. Using this approach, the SNP heritability of 25OHD was estimated to 16.1%. 138 conditionally independent SNPs were detected (p value < 6.6 × 10-9) among which 53 had MAF < 5%. Single variant association signals mapped to 69 distinct loci, among which 63 were previously unreported. We identified enrichment in hepatic and lipid metabolism gene pathways and enriched expression of the 25OHD genes in liver, skin, and gastrointestinal tissues. We observed partially shared heritability between 25OHD and socio-economic traits, a feature which may be mediated through time spent outdoors. Therefore, through a large 25OHD GWAS, we identified 63 loci that underline the contribution of genes outside the vitamin D canonical metabolic pathway to the genetic architecture of 25OHD.

Epigenome-wide association study reveals a molecular signature of response to phylloquinone (vitamin K1) supplementation

Evidence suggests there are roles for vitamin K in various chronic disease outcomes, but population-level diet and supplement recommendations are difficult to determine due to high levels of variability in measures of status and response to intake compared to other nutrients. In this preliminary investigation, a blood-based epigenome-wide association study (EWAS) comparing responders and non-responders to phylloquinone (vitamin K1) supplementation (NCT00183001) was undertaken in order to better understand the molecular underpinnings of this observed variability. Responders (n = 24) and non-responders (n = 24) were identified in a prior 3-year phylloquinone supplementation trial based on their changes in plasma phylloquinone concentrations. Differential DNA methylation was identified in multiple regions with previously unknown relationships to phylloquinone absorption and metabolism, such as at the TMEM263 locus. A hypothesis-driven analysis of lipid-related genes highlighted a site in the NPC1L1 gene, supplementing existing evidence for its role in phylloquinone absorption. Furthermore, an EWAS for baseline plasma phylloquinone concentrations revealed a strong correlation between the epigenomic signatures of phylloquinone baseline status and response to supplementation. This work can guide future epigenomic research on vitamin K and contributes to the development of more personalized dietary recommendations for vitamin K.

Multi-ethnic analysis shows genetic risk and environmental predictors interact to influence 25(OH)D concentration and optimal vitamin D intake

25-Hydroxyvitamin D (25(OH)D) concentration is a complex trait with genetic and environmental predictors that may determine how much vitamin D exposure is required to reach optimal concentration. Interactions between continuous measures of a polygenic score (PGS) and vitamin D intake (PGS*intake) or available ultraviolet (UV) radiation (PGS*UV) were evaluated in individuals of African (n = 1,099) or European (n = 8,569) ancestries. Interaction terms and joint effects (main and interaction terms) were tested using one-degree of freedom (1-DF) and 2-DF models, respectively. Models controlled for age, sex, body mass index, cohort, and dietary intake/available UV. In addition, in participants achieving Institute of Medicine (IOM) vitamin D intake recommendations, 25(OH)D was evaluated by level PGS. The 2-DF PGS*intake, 1-DF PGS*UV, and 2-DF PGS*UV results were statistically significant in participants of European ancestry (p = 3.3 × 10-18 , p =  2.1 × 10-2 , and p =  2.4 × 10-19 , respectively), but not in those of African ancestry. In European-ancestry participants reaching IOM vitamin D intake guidelines, the percent of participants achieving adequate 25(OH)D ( >20 ng/ml) increased as genetic risk decreased (72% vs. 89% in highest vs. lowest risk; p = .018). Available UV radiation and vitamin D intake interact with genetics to influence 25(OH)D. Individuals with higher genetic risk may require more vitamin D exposure to maintain optimal 25(OH)D concentrations.

Association between Body Fatness and Vitamin D3 Status in a Postmenopausal Population

Vitamin D is a micronutrient that plays a key role in phosphocalcic metabolism. The postmenopausal population presents a risk of deficiency in this vitamin due to hormonal alterations which, in the case of obesity, would be exacerbated. The objective was to assess the status of vitamin D in a postmenopausal population and determine the relationship of 25-hydroxivitamin D [25(OH)D] and its metabolites with anthropometric parameters. The study included 78 healthy postmenopausal women aged from 44 to 76. The nutrient intake assessment was carried out using the 24 h reminder (R24h). 25(OH)D was analyzed using ultra-high-performance liquid chromatography (UHPLC). A total of 80% and 68% of the women studied did not reach sufficient values of 25(OH)D and 25-hydroxivitamin D₃ [25(OH)D₃], respectively, which was inversely correlated with Body Mass Index (BMI) (r = −0.25, p = 0.04), hip perimeter (r = −0.26 and r = −0.24, all p < 0.05), arm circumference (r = −0.29, p = 0.01) and fat mass (r = −0.28 and r = −0.26, all p < 0.05). 25(OH)D₃ is the metabolite that contributed most to this association. In conclusion, 25(OH)D₃ levels are related to anthropometric parameters in the postmenopausal women in this study, confirming insufficient status in the majority of the population. Approach strategies are necessary to correct and avoid this risk in order to ensure future quality of life.

Genetic Components of 25-Hydroxyvitamin D Increase in Three Randomized Controlled Trials

The 25-Hydroxyvitamin D (25[OH)D) serum concentration depends on vitamin D intake, endogenous vitamin D production and genetic factors. The latter have been demonstrated in large genome-wide association studies indicating that single nucleotide polymorphisms (SNPs) in genes related to the vitamin D metabolism are as important for serum 25(OH)D levels as the influence of season. The mechanism on how these SNPs influence serum 25(OH)D levels are still unclear. The aim of the present study was to investigate the genetic effects of ten selected SNPs related to vitamin D metabolism on 25-hydroxyvitamin D increase (∆25(OH)D) after vitamin D supplementation in three randomized controlled trials. Genotypes of SNPs related to vitamin D metabolism were determined in 411 participants with 25(OH)D concentrations < 75 nmol/l receiving 20,000 IU cholecalciferol per week for 8 or 12 weeks after study inclusion. For the vitamin D receptor (VDR) rs10783219 polymorphism, the minor A-allele was associated with lower ∆25(OH)D values in the entire study population (p = 0.022), which was not consistent in all three cohorts when analysed separately. VDR rs10783219 might therefore be a genetic modulator of increasing 25-hydroxyvitamin D concentrations. Considering the wide-spread use of vitamin D supplementation, future large and well-designed randomized controlled trials (RCTs) should investigate the clinical impact of this polymorphism.

Effect of genetic factors on the response to vitamin D3 supplementation in the VIDARIS randomized controlled trial

OBJECTIVES

Supplementation provides the best means of improving vitamin D status; however, individual responses vary partly owing to genetics. The aim of this study was to determine whether 28 single nucleotide polymorphisms (SNPs) in six key vitamin D pathway genes (GC, DHCR7, CYP2 R1, CYP24 A1, CYP27 B1, VDR) were associated with differences in response to supplementation.

METHODS

Participants (N = 313; n = 160 vitamin D, n = 153 placebo) were part of VIDARIS (Vitamin D and Acute Respiratory Infections Study), a double-blind, randomized controlled trial involving oral monthly supplementation of either vitamin D₃ (200 000 IU each for the first 2 mo, thereafter 100 000 IU monthly) or placebo for 18 mo. Circulating 25-hydroxyvitamin D (25[OH]D) concentrations at baseline and 2, 6, 12, and 18 mo, and vitamin D binding protein (Gc-globulin) and calculated free 25(OH)D concentrations at baseline and 2 mo were obtained. Multiple regression was used to model associations between genetic variants and 25(OH)D, Gc-globulin, and free 25(OH)D concentrations.

RESULTS

SNPs within GC, CYP2 R1, and CYP27 B1 were associated with 25(OH)D concentrations following supplementation. However, only two GC gene SNPs (rs2282679, rs1155563) were significant after adjustment for multiple testing. This effect disappeared after more than 2 mo of supplementation. None of the SNPs were significantly associated with Gc-globulin concentrations; however, there was a significant interaction with one SNP in DHCR7 (rs12785878), which was associated with reduced free 25(OH)D concentrations in the supplemented arm.

CONCLUSION

Only variants of GC were associated with 25(OH)D concentrations after supplementation. This effect was modest and disappeared after >2 mo of supplementation, suggesting it may be time/dose-dependent and saturable.

The Contribution of Lipids to the Interindividual Response of Vitamin K Biomarkers to Vitamin K Supplementation

SCOPE

A better understanding of factors contributing to interindividual variability in biomarkers of vitamin K can enhance the understanding of the equivocal role of vitamin K in cardiovascular disease. Based on the known biology of phylloquinone, the major form of vitamin K, it is hypothesized that plasma lipids contribute to the variable response of biomarkers of vitamin K metabolism to phylloquinone supplementation.

METHODS AND RESULTS

The association of plasma lipids and 27 lipid-related genetic variants with the response of biomarkers of vitamin K metabolism is examined in a secondary analysis of data from a 3-year phylloquinone supplementation trial in men (n = 66) and women (n = 85). Year 3 plasma triglycerides (TG), but not total cholesterol, LDL-cholesterol, or HDL-cholesterol, are associated with the plasma phylloquinone response (men: β = 1.01, p < 0.001, R2  = 0.34; women: β = 0.61, p = 0.008, R2  = 0.11; sex interaction p = 0.077). Four variants and the TG-weighted genetic risk score are associated with the plasma phylloquinone response in men only. Plasma lipids are not associated with changes in biomarkers of vitamin K function (undercarboxylated osteocalcin and matrix gla protein) in either sex.

CONCLUSION

Plasma TG are an important determinant of the interindividual response of plasma phylloquinone to phylloquinone supplementation, but changes in biomarkers of vitamin K carboxylation are not influenced by lipids.

The genetics of vitamin D

Vitamin D plays an essential role in human health as it influences immune function, cell proliferation, differentiation and apoptosis. Vitamin D deficiency has been associated with numerous health outcomes, including bone disease, cancer, autoimmune disease, cardiovascular conditions and more. However, the causal role of vitamin D beyond its importance for bone health remains unclear and is under much debate. Twin and familial studies from past decades have demonstrated a nontrivial heritability of circulating vitamin D concentrations. Several large-scale genome-wide association studies (GWAS) have discovered associations of GC, NADSYN1/DHCR7, CYP2R1, CYP24A1, SEC23A, AMDHD1 with serum levels of vitamin D. A recent whole genome sequencing (WGS) study, combined with deep imputation of genome-wide genotyping, has identified a low-frequency synonymous coding variant at CYP2R1. Information on these genetic variants can be used as tools for downstream analysis such as Mendelian randomization. Here, we review the genetic determinants of circulating vitamin D levels by focusing on new findings from GWAS and WGS, as well as results from Mendelian randomization analyses conducted so far for vitamin D with various traits and diseases. The amount of variation in vitamin D explained by genetics is still small, and the putative causal relationship between vitamin D and other diseases remains to be demonstrated.

Influence of genetic variation in the vitamin D pathway on plasma 25-hydroxyvitamin D3 levels and survival among patients with metastatic colorectal cancer

PURPOSE

The relationships of genetic variation in the vitamin D pathway with circulating 25-hydroxyvitamin D3 [25(OH)D] levels and survival remain largely unknown for patients with metastatic colorectal cancer (mCRC).

METHODS

Among 535 patients participating in a randomized trial of chemotherapy for mCRC, we prospectively measured baseline plasma 25(OH)D and examined 124 tagging single-nucleotide polymorphisms (SNPs) within seven genes in the vitamin D pathway, including five SNPs associated with circulating 25(OH)D levels in previous genome-wide association studies (GWAS). We evaluated whether these SNPs were associated with plasma 25(OH)D levels and patient outcome (overall survival, time to progression, and tumor response), using linear, logistic, and Cox proportional hazards regression.

RESULTS

We observed a significant association between 25(OH)D levels and an additive genetic risk score determined by the five GWAS-identified SNPs (p = 0.0009). We did not observe any direct association between 25(OH)D-associated SNPs, individually or as a genetic risk score, and patient outcome. However, we found a significant interaction between 25(OH)D levels and rs12785878 genotype in DHCR7 on overall survival (pinteraction = 0.02).

CONCLUSION

Germline genetic variation in the vitamin D pathway informs baseline 25(OH)D levels among patients with mCRC. The association between 25(OH)D levels and overall survival may vary by DHCR7 genotype. ClinicalTrials.gov Identifier: NCT00003594 ( https://clinicaltrials.gov/ct2/show/NCT00003594 ).

Family-based Association between Allele T of rs4646536 in CYP27B1 and vitamin D deficiency

BACKGROUND

The circulating concentration of 25(OH)D is widely applied to indicate the vitamin D status, as the directly metabolic genes of 25(OH)D, CYP2R1, and CYP27B1 are associated with the concentration of 25(OH)D. However, the contributions of allelic transmission disequilibrium of single nucleotide polymorphisms (SNPs) in these genes to vitamin D deficiency remain unclear. We aimed at investigating the family-based association between SNPs of CYP2R1 and CYP27B1 and vitamin D deficiency.

METHOD

First, SNPs selected in family-based study were screened by a pilot case-control study. Second, allelic transmissions of the selected SNPs were investigated with family-based study (n = 880). Finally, associations between selected SNPs and the concentration of 25(OH)D were verified in siblings (n = 120).

RESULTS

The results of the pilot case-control study indicated that both CT and TT genotypes of rs4646536 in CYP27B1 could increase the susceptibility of vitamin D deficiency when compared with CC genotype. The adjusted ORs were 2.846 (95%CI 1.312-6.174, P = 0.008) and 2.609 (95%CI 1.197-5.687, P = 0.016), respectively. Furthermore, the results of family-based association test suggested that there was transmission disequilibrium for allele T of rs4646536 in vitamin D deficiency families. In addition, the concentration of 25(OH)D₃ for CC genotype was higher than CT genotype between siblings (P = 0.016).

CONCLUSIONS

Transmission disequilibrium of allele T of rs4646536 is associated with vitamin D deficiency.

Current vitamin D status in European and Middle East countries and strategies to prevent vitamin D deficiency: a position statement of the European Calcified Tissue Society

Vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) <50 nmol/L or 20 ng/mL) is common in Europe and the Middle East. It occurs in <20% of the population in Northern Europe, in 30-60% in Western, Southern and Eastern Europe and up to 80% in Middle East countries. Severe deficiency (serum 25(OH)D <30 nmol/L or 12 ng/mL) is found in >10% of Europeans. The European Calcified Tissue Society (ECTS) advises that the measurement of serum 25(OH)D be standardized, for example, by the Vitamin D Standardization Program. Risk groups include young children, adolescents, pregnant women, older people (especially the institutionalized) and non-Western immigrants. Consequences of vitamin D deficiency include mineralization defects and lower bone mineral density causing fractures. Extra-skeletal consequences may be muscle weakness, falls and acute respiratory infection, and are the subject of large ongoing clinical trials. The ECTS advises to improve vitamin D status by food fortification and the use of vitamin D supplements in risk groups. Fortification of foods by adding vitamin D to dairy products, bread and cereals can improve the vitamin D status of the whole population, but quality assurance monitoring is needed to prevent intoxication. Specific risk groups such as infants and children up to 3 years, pregnant women, older persons and non-Western immigrants should routinely receive vitamin D supplements. Future research should include genetic studies to better define individual vulnerability for vitamin D deficiency, and Mendelian randomization studies to address the effect of vitamin D deficiency on long-term non-skeletal outcomes such as cancer.

Association between Vitamin D Levels and Nonalcoholic Fatty Liver Disease: Potential Confounding Variables

Nonalcoholic fatty liver disease (NAFLD), historically considered to be the hepatic component of the metabolic syndrome, is a spectrum of fat-associated liver conditions, in the absence of secondary causes, that may progress to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Disease progression is closely associated with body weight or fatness, dyslipidemia, insulin resistance, oxidative stress, and inflammation. Recently, vitamin D deficiency has been linked to the pathogenesis and severity of NAFLD because of vitamin D "pleiotropic" functions, with roles in immune modulation, cell differentiation and proliferation, and regulation of inflammation. Indeed, several studies have reported an association between vitamin D and NAFLD/NASH. However, other studies have failed to find an association. Therefore, we sought to critically review the current evidence on the association between vitamin D deficiency and NAFLD/NASH, and to analyze and discuss some key variables that may interfere with this evaluation, such as host-, environment-, and heritability-related factors regulating vitamin D synthesis and metabolism; definitions of deficient or optimal vitamin D status with respect to skeletal and nonskeletal outcomes including NAFLD/NASH; methods of measuring 25(OH)D; and methods of diagnosing NAFLD as well as quantifying adiposity, the cardinal link between vitamin D deficiency and NAFLD.

A variant in CYP2R1 predicts circulating vitamin D levels after supplementation with high-dose of vitamin D in healthy adolescent girls

AIM

The determinants of serum vitamin D seems to be the environmental factors (dietary and supplementary intake and exposure to ultraviolet light) and genetic factors. We aimed to study the relationship between a vitamin D-associated genetic polymorphism and serum 25(OH)D concentrations in healthy adolescent girls in Iran, and its effects on a high-dose supplement of vitamin D.

MATERIAL AND METHOD

A total of 616 healthy adolescent girls with mean age 15 received 50,000 IU of vitamin D3 weekly over 9 weeks. Serum vitamin D levels and other metabolic factors were measured at baseline and after the intervention. The genotyping of the CYP2R1 variant (rs10741657) was performed by TaqMan genotyping assays.

RESULTS

Regardless of the genetic background, at baseline, 87% of adolescent girls were vitamin D deficient (serum 25(OH)D level < 50 nmol/l). High-dose supplementation with VitD reduced the proportion of girls who were deficient substantially to about 24%. The genetic analysis revealed that although at baseline there was not a gene-vitamin D association ( p trend = 0.1), the response to supplementation appeared to be modulated by this variant ( p trend < 0.001). However, other anthropometric and biochemical measures were not affected by this intervention, over this short period. Serum 25(OH)D was increased in all participants although the carriers of the minor A allele seemed to be better responders so that the percentages of the change serum vitamin D in the holder of AA and AG genotypes were 539.4 ± 443.1 and 443.7 ± 384.6, respectively, compared with those with common GG genotype (363.3 ± 354.0). Our regression analysis revealed that the probability of an increase in serum 25(OH)D in a participant with AA genotype was 2.5-fold greater than those with a GG genotype (OR = 2.5 (1.4-4.4); p value = 0.002).

CONCLUSION

Based on our findings, it appears that the rs10741657 variant of the CYP2R1 gene modulates the response to high-dose of vitamin D supplementation.

Impact of Vitamin D Status in Chronic Liver Disease

BACKGROUND

Vitamin D deficiency is extremely common in chronic liver disease (CLD) patients. Up to 93% of these patients have some degree of vitamin D insufficiency. Liver plays an important role in the metabolism and pleiotropic functions of vitamin D. Vitamin D deficiency has been associated with increased mortality, bacterial infections, portal hypertension complications, and fibrosis severity. We aimed to determine the impact of vitamin D level in CLD.

METHODS

One hundred fifty individuals consisting of 75 cirrhotic patients (cases) and 75 respective attendants (controls) were enrolled between July 2015 and July 2017. A detailed clinical and laboratory evaluation was done along with estimation of vitamin D level. Unpaired t-test and analysis of variance was used to compare difference in the level of continuous variables between different groups. Linear regression analysis was performed to analyze the correlation between vitamin D deficiency and severity of liver disease.

RESULTS

The age of patients ranged from 18 years to 69 years with mean of 48.85 ± 13.6 years in the case group and 46.57 ± 17.24 years in the control group. Out of 75 CLD patients, vitamin D deficiency (<20 ng/dl) was found in 31 (41.4%) patients, out of which 14(18.7%) suffered from severe vitamin D deficiency (<10 ng/ml). On applying analysis of variance test, there was significant difference in vitamin D level and serum albumin and serum bilirubin (P < 0.05). On linear regression, vitamin D level showed significant negative correlation with Child-Pugh score (r = -0.7379, P < 0.0001) and Model For End-Stage Liver Disease score (r = -0.6671, P < 0.0001).

CONCLUSION

Our study concluded that CLD is associated with a significantly low level of vitamin D, which was independent to patient's gender, body mass index, residence, and education level. The findings of our study suggest that awareness of serum vitamin D level in patients with CLD is important. Further studies are required to validate the importance of vitamin D levels and impact of vitamin D supplementation on CLD.

Genetic influence on serum 25-hydroxyvitamin D concentration in Korean men: a cross-sectional study

Background

Hypovitaminosis D is prevalent worldwide. It is more prevalent in Eastern Asia region, including Korea. In addition to various environmental factors that influence serum 25-hydroxyvitamin D (25(OH)D) concentration, genetic influence also plays a significant role based on studies estimating the heritability of 25(OH)D in non-Asian populations. The objective of this study was to determine the genetic influence on serum 25(OH)D concentration in Korean men using the twin and family data.

Methods

A total of 1126 Korean male adult twins and family members from the Healthy Twin Study with serum 25(OH)D measurement were included in this cross-sectional study. Intraclass correlation coefficients (ICCs) and heritability were calculated by mixed linear regression analysis and quantitative genetic analysis after adjusting for environmental and lifestyle factors.

Results

Mean (± standard deviation; SD) of serum 25(OH)D concentration was 15.34 ± 6.18 ng/ml. The prevalence of vitamin D insufficiency was 19.8% and that of vitamin D deficiency was 77.9%. After adjusting for age, the highest ICC (0.61) was observed for monozygotic twin pairs while the lowest ICC (0.31) was found for father-son pairs. Age-adjusted heritability was estimated to be 58%. When physical activity, multivitamin intake and season of blood sampling were further considered, the ICC and heritability did not materially change. In the sensitivity analysis after excluding known multivitamin users, age-adjusted heritability was reduced to 44%.

Conclusions

In our study of Korean male twins and family members, heritability of 25(OH)D was moderately high. This supports the finding that genetic factors have significant influence on vitamin D status.

Electronic supplementary material

The online version of this article (10.1186/s12263-018-0621-7) contains supplementary material, which is available to authorized users.

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.

The effect of age and gender on the genetic regulation of serum 25-hydroxyvitamin D - the FIN-D2D population-based study

In addition to sunlight and dietary sources, several genes in the metabolic pathway of vitamin D affect serum 25-hydroxyvitamin D (25OHD) concentration. It is not known whether this genetic regulation is influenced by host characteristics. We investigated the effect of age and gender on the genetic regulation of serum 25OHD concentration. In total, 2868 Finnish men and women aged 45-74 years participated in FIN-D2D population-based health survey in 2007. Of the 2822 participants that had serum 25OHD concentration available, 2757 were successfully genotyped. Age and gender-dependent association of SNPs with serum 25OHD concentration was studied in 10 SNPs with previously found association with vitamin D metabolites. Associations of 3 SNPs with serum 25OHD concentration were dependent on age with greater effects on younger (≤60 y) than older (>60 y) adults (rs10783219 in VDR, rs12512631 in GC and rs3794060 in NADSYN1/DHCR7; p_interaction = 0.03, 0.02 and 0.01, respectively). The results suggested a novel association between serum 25OHD concentration and rs8082391 in STAT5B gene in men but not in women (p_interaction = 0.01). After multiple testing correction with false discovery rate method, two age-dependent interactions (rs3794060 in NADSYN1/DHCR7 gene and rs12512631 in GC gene) remained statistically significant. This is the first study to suggest that genetic regulation of serum 25OHD concentration is age-dependent. Our results also indicated a novel association between serum 25OHD concentration and SNP in STAT5B gene in men. The results need to be confirmed in future studies preferably in a larger sample.

Genetic polymorphisms of vitamin D3 metabolizing CYP24A1 and CYP2R1 enzymes in Turkish patients with ischemic stroke

Objective Vitamin D deficiency is known as an important risk factor in pathogenesis of atherosclerosis, which contributes to stroke development. Genetic variations including single nucleotide polymorphisms (SNPs) in enzymes involved in vitamin D metabolism can affect susceptibility to the development of stroke. Therefore, the objective of this study was to investigate the association between polymorphisms of vitamin D metabolizing enzymes (rs927650 SNP in CYP24A1, and rs10741657 SNP in CYP2R1 genes,) and ischemic stroke risk in Turkish population. Materials and methods To test this hypothesis, we designed a case-control study which consisted of 256 ischemic stroke patients and 132 controls. Genotypes were determined by PCR-RFLP technique. Results No significant differences were found between patients and controls in terms of CYP24A1 rs927650 and CYP2R1 rs10741657 genotype frequencies. Polymorphic allele frequencies of CYP24A1 rs927650 and CYP2R1 rs10741657 were 0.414 and 0.660 in stroke patients, respectively. Conclusion This is the first study conducted regarding the association of CYP24A1 rs927650 and CYP2R1 rs10741657 genetic polymorphisms and ischemic stroke risk. The polymorphic genotypes of these polymorphisms, together with hypertension, diabetes, smoking, and obesity, were found as significant risk factors for ischemic stroke.

Genetic architecture: the shape of the genetic contribution to human traits and disease

Genetic architecture describes the characteristics of genetic variation that are responsible for heritable phenotypic variability. It depends on the number of genetic variants affecting a trait, their frequencies in the population, the magnitude of their effects and their interactions with each other and the environment. Defining the genetic architecture of a complex trait or disease is central to the scientific and clinical goals of human genetics, which are to understand disease aetiology and aid in disease screening, diagnosis, prognosis and therapy. Recent technological advances have enabled genome-wide association studies and emerging next-generation sequencing studies to begin to decipher the nature of the heritable contribution to traits and disease. Here, we describe the types of genetic architecture that have been observed, how architecture can be measured and why an improved understanding of genetic architecture is central to future advances in the field.

Polymorphic Human Sulfotransferase 2A1 Mediates the Formation of 25-Hydroxyvitamin D3-3-O-Sulfate, a Major Circulating Vitamin D Metabolite in Humans

Metabolism of 25-hydroxyvitamin D₃ (25OHD₃) plays a central role in regulating the biologic effects of vitamin D in the body. Although cytochrome P450-dependent hydroxylation of 25OHD₃ has been extensively investigated, limited information is available on the conjugation of 25OHD₃ In this study, we report that 25OHD₃ is selectively conjugated to 25OHD₃-3-O-sulfate by human sulfotransferase 2A1 (SULT2A1) and that the liver is a primary site of metabolite formation. At a low (50 nM) concentration of 25OHD₃, 25OHD₃-3-O-sulfate was the most abundant metabolite, with an intrinsic clearance approximately 8-fold higher than the next most efficient metabolic route. In addition, 25OHD₃ sulfonation was not inducible by the potent human pregnane X receptor agonist, rifampicin. The 25OHD₃ sulfonation rates in a bank of 258 different human liver cytosols were highly variable but correlated with the rates of dehydroepiandrosterone sulfonation. Further analysis revealed a significant association between a common single nucleotide variant within intron 1 of SULT2A1 (rs296361; minor allele frequency = 15% in whites) and liver cytosolic SULT2A1 content as well as 25OHD₃-3-O-sulfate formation rate, suggesting that variation in the SULT2A1 gene contributes importantly to interindividual differences in vitamin D homeostasis. Finally, 25OHD₃-3-O-sulfate exhibited high affinity for the vitamin D binding protein and was detectable in human plasma and bile but not in urine samples. Thus, circulating concentrations of 25OHD₃-3-O-sulfate appear to be protected from rapid renal elimination, raising the possibility that the sulfate metabolite may serve as a reservoir of 25OHD₃ in vivo, and contribute indirectly to the biologic effects of vitamin D.