CYP2R1-, CYP27B1- and CYP24-mRNA expression in German type 1 diabetes patients

Altered Expression of Vitamin D Metabolism Genes and Circulating MicroRNAs in PBMCs of Patients with Type 1 Diabetes: Their Association with Vitamin D Status and Ongoing Islet Autoimmunity

BACKGROUND

The immunomodulatory role of 1,25-Dihydroxy vitamin D3 (1,25(OH)2D3) is exerted through its interaction with the vitamin D receptor (VDR) present on pancreatic and immune cells. While a deficiency in vitamin D has been linked to Type 1 Diabetes Mellitus (T1DM), the exact molecular mechanism driving this down-regulation in T1DM is yet to be fully understood. This study aimed to decipher differences in the expression of genes associated with vitamin D metabolism in T1DM patients and to ascertain if there is a correlation between serum 1,25(OH)2D3 levels and the expression of these genes. We also sought to understand the influence of specific microRNAs (miRNAs) on the expression of vitamin D metabolism genes in peripheral blood mononuclear cells (PBMCs) of T1DM patients. Furthermore, the study delved into the potential implications of altered vitamin D metabolism genes and miRNAs on autoimmune processes.

METHODS

Utilizing real-time PCR, we assessed the expression profiles of genes encoding for 1-hydroxylases (CYP27B1) and 24-hydroxylases (CYP24A1), as well as related miRNAs, in PBMCs from 30 T1DM patients and 23 healthy controls. ELISA tests facilitated the measurement of 1,25(OH)2D3, GAD65, and IA-2 levels.

RESULTS

Our findings showcased downregulated CYP27B1 mRNA levels, while CYP24A1 expression remained stable compared to healthy subjects (CYP27B1, p = 0.0005; CYP24A1, p = 0.205, respectively). In T1DM patients, the levels of has-miR-216b-5p were found to be increased, while the levels of has-miR-21-5p were decreased in comparison to the control group. Notably, no correlation was identified between the expression of CYP27B1 in T1DM patients and the levels of has-miR-216b-5p, has-miR-21-5p, and 1,25(OH)2D3. A significant negative correlation was identified between CYP27B1 mRNA levels in PBMCs of T1DM and IA2, but not with GAD65.

CONCLUSIONS

The study highlights there were reduced levels of both CYP27B1 mRNA and has-miR-21-5p, along with elevated levels of has-miR-216b-5p in the PBMCs of T1DM. However, the absence of a correlation between the expression of CYP27B1, levels of has-miR-216b-5p, and the status of 1,25(OH)2D3 suggests the possible existence of other regulatory mechanisms. Additionally, the inverse relationship between IA2 autoantibodies and CYP27B1 expression in T1DM patients indicates a potential connection between this gene and the autoimmune processes inherent in T1DM.

Genetic variants in the vitamin D pathway and their association with vitamin D metabolite levels: Detailed studies of an inner-city pediatric population suggest a modest but significant effect in early childhood

OBJECTIVES

In a large cohort of healthy infants and toddlers 6-36 months of age (n = 776), we have been exploring the potential role of genetic variation in predisposition to vitamin D insufficiency. The genes encoding the key cytochrome P450 hydroxylases (CYP2R1, CYP24A1, and CYP27B1) harbour recurrent mutations of uncertain effect. This study was undertaken to look for biochemically relevant associations of these variants with inter-individual differences in vitamin D metabolism in an at-risk pediatric population.

METHODS

Genotyping for CYP2R1-CT (c.-1127 C>T, rs10741657), CYP24A1-AG (c.-686A>G, rs111622401), and CYP27B1-CA (c.-1261 C>A, rs10877012) mutations were performed using SNaPshot assay, followed by Sanger sequencing confirmation. Vitamin D metabolites and vitamin D binding protein (DBP) were measured by established methods.

RESULTS

In a multivariate regression model, with corrections for co-variates, subjects with the homozygous CYP2R1-TT variant had significantly higher concentrations of 25(OH)D, free 25(OH)D, and 24,25(OH)2D levels. In subjects with the CYP24A1-AG mutation, concentrations of 25(OH)D were significantly higher.

CONCLUSIONS

The CYP2R1-TT and CYP24A1-AG variants have measurable effects on the vitamin D pathway. It seems unlikely that they will be clinically relevant in isolation, but they may be members of the large pool of infrequent mutations contributing to different risks for the vitamin D deficiency phenotype.

Antifungal Drug Plasma Exposures: A Possible Contribution of Vitamin D-Related Gene Variants

Vitamin D (VD) seems to influence drug clearance and outcome. Antifungal drugs (AFU) are the most used azoles in clinical practice. In the literature, no data are available concerning VD’s impact on AFU therapy. The aim of this study was to analyze if VD pathway-related polymorphisms may influence voriconazole (VRC), itraconazole (ITC), and posaconazole (PSC) drug concentrations in order to identify patients with the highest probability of response and toxicity. Allelic discrimination was performed through real-time PCR, whereas drug concentrations were through liquid chromatography. A total of 636 samples of AFU-treated patients were included in the analysis. Concerning VRC, concentrations higher than the 1000 ng/mL efficacy cut-off value were predicted by Caucasian ethnicity, CYP24A1 3999, and CYP27B1 + 2838 polymorphisms, whereas levels higher than the 5000 ng/mL toxicity value by Caucasian, female sex, e.v. administration, and GC 1296. Considering PSC, concentrations higher than the 700 ng/mL efficacy cut-off value were predicted by VDR Cdx2, CYP27B1 − 1260, and GC 1296. Finally, for ITC, VDR BsmI was the only predictor of drug exposure higher than the 500 ng/mL efficacy cut-off value, whereas female sex, CYP27B1 − 1260, and VDR TaqI remained in the final regression model related to concentrations higher than the 1000 ng/mL toxicity-associated cut-off value. This is the first study reporting the influence of VD pathway-related gene SNPs on AFU exposures, efficacy, and toxicity.

Monocytic Cytokines in Autoimmune Polyglandular Syndrome Type 2 Are Modulated by Vitamin D and HLA-DQ

Context

Autoimmune polyglandular syndrome (APS-2: autoimmune Addison’s disease or type 1 diabetes) is conferred by predisposing HLA molecules, vitamin D deficiency, and heritable susceptibility. Organ destruction is accompanied by cytokine alterations. We addressed the monocytic cytokines of two distinct APS-2 cohorts, effects of vitamin D and HLA DQ risk.

Methods

APS-2 patients (n = 30) and healthy controls (n = 30) were genotyped for HLA DQA1/DQB1 and their CD14+ monocytes stimulated with IL1β and/or 1,25(OH)₂D₃ for 24 h. Immune regulatory molecules (IL-6, IL-10, IL-23A, IL-15, CCL-2, PD-L1), vitamin D pathway gene transcripts (CYP24A1, CYP27B1, VDR), and CD14 were analyzed by enzyme-linked immunosorbent assay and RTqPCR.

Results

Pro-inflammatory CCL-2 was higher in APS-2 patients than in controls (p = 0.001), whereas IL-6 showed a trend – (p = 0.1). In vitro treatment with 1,25(OH)₂D₃ reduced proinflammatory cytokines (IL-6, CCL-2, IL-23A, IL-15) whereas anti-inflammatory cytokines (IL-10 and PD-L1) rose both in APS-type 1 diabetes and APS-Addison´s disease. Patients with adrenal autoimmunity showed a stronger response to vitamin D. Expression of IL-23A and vitamin D pathway genes VDR and CYP27B1 varied by HLA genotype and was lower in healthy individuals with high-risk HLA (p = 0.0025; p = 0.04), while healthy controls with low-risk HLA showed a stronger IL-10 and CD14 expression (p = 0.01; p = 0.03).

Conclusion

1,25(OH)₂D₃ regulates the monocytic response in APS-2 disorders type 1 diabetes or Addison´s disease. The monocytic cytokine profile of individuals carrying HLA high-risk alleles is proinflammatory, enhances polyglandular autoimmunity and can be targeted by vitamin D.

Association of Vitamin D Pathway Gene CYP27B1 and CYP2R1 Polymorphisms with Autoimmune Endocrine Disorders: A Meta-Analysis

BACKGROUND

Studies on organ-specific autoimmune endocrine disorders showed correlations between disease risks and vitamin D pathways gene variants, such as CYP27B1 rs10877012 and rs4646536, or CYP2R1 rs10741657 single nucleotide polymorphisms. However, previous works presented inconsistent conclusions. Our study aimed at assessing the association of CYP27B1 and CYP2R1 polymorphisms with autoimmune endocrine disorder susceptibility using the meta-analysis method.

METHODS

Case-control studies of the subject of interest were identified from the databases Pubmed, Embase, Cochrane Library, and China National Knowledge Infrastructure. Studies that met inclusion and quality criteria were pooled. Observational outcomes were diagnosis of autoimmune Addison's disease, Graves disease, Hashimoto thyroiditis, or type 1 diabetes mellitus. Statistical analysis was performed using software STATA 16.0.

RESULTS

A total of 14 studies involving 12 929 patients (2243 autoimmune Addison disease, 1253 Graves disease, 612 Hashimoto thyroiditis, 8821 type 1 diabetes), and 12 907 healthy control subjects were pooled for meta-analysis. The rs10877012 minor allele A and its homozygote and heterozygote conferred low overall disease risk (OR [odds ratio] = 0.748, 95% CI [confidence interval] 0.620-0.902 in dominant model; OR = 0.709, 95% CI 0.571-0.879 in recessive model; OR = 0.777, 95% CI 0.674-0.895 in the allele model). The population carrying rs4646536 minor allele C and its homozygote and heterozygote showed decreased overall autoimmune endocrine disorders risk (OR = 0.849, 95% CI 0.748-0.963; OR = 0.868, 95% CI 0.790-0.955; OR = 0.915, 95% CI 0.875-0.957 in the dominant, recessive, and allele model, respectively). No significant genetic association was found for rs10741657.

CONCLUSION

Our study suggested CYP27B1 polymorphisms rs10877012 minor allele A and rs4646536 minor allele C were negatively related to susceptibilities of organ-specific autoimmune endocrine diseases.

Autoimmune thyroid disease and type 1 diabetes mellitus: same pathogenesis; new perspective?

Autoimmune thyroid disease (AITD) and type 1 diabetes mellitus (T1DM) are two common autoimmune diseases that can occur concomitantly. In general, patients with diabetes have a high risk of AITD. It has been proposed that a complex genetic basis together with multiple nongenetic factors make a variable contribution to the pathogenesis of T1DM and AITD. In this paper, we summarize current knowledge in the field regarding potential pathogenic factors of T1DM and AITD, including human leukocyte antigen, autoimmune regulator, lymphoid protein tyrosine phosphatase, forkhead box protein P3, cytotoxic T lymphocyte-associated antigen, infection, vitamin D deficiency, and chemokine (C-X-C motif) ligand. These findings offer an insight into future immunotherapy for autoimmune diseases.

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

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

Vitamin D level and gene polymorphisms in Korean children with type 1 diabetes

BACKGROUND

Vitamin D metabolism has been associated with type 1 diabetes.

OBJECTIVE

We aimed to clarify the association of 25-hydroxylase (CYP2R1) and 1α-hydroxylase (CYP27B1) with risk of developing type 1 diabetes in Korean children.

METHODS

In total, 252 children (96 type 1 diabetes and 156 healthy controls) under the age of 20 years were recruited. Serum 25-hydroxyvitamin D (25OHD) and 1α,25-dihydroxyvitamin D [1α,25(OH)₂ D] levels were determined. Allelic, genotypic, and haplotypic distribution of CYP2R1 (rs12794714, rs10766196, rs10741657, rs2060793, and rs10766197) and CYP27B1 (rs4646536, rs10877012, and rs3782130) polymorphisms were determined. Clinical and biochemical data were analyzed according to genotype.

RESULTS

Mean vitamin D level was considerably lower, and vitamin D deficiency was more prevalent in children with type 1 diabetes than in healthy controls. The GG genotype of CYP2R1 rs12794714 and AA genotype of CYP2R1 rs10766196 were significantly associated with risk of developing type 1 diabetes (odds ratio 2.00, 95% confidence interval 1.176-3.413 and odds ratio 1.88, 95% confidence interval 1.103-3.195, respectively). The GG+GA genotype of CYP2R1 rs12794714 and AA+AG genotype of CYP2R1 rs10766196 were associated with prevalent vitamin D deficiency in children with type 1 diabetes. These genotypes did not differ with respect to glycosylated hemoglobin and daily insulin requirement.

CONCLUSIONS

Serum 25OHD and 1α,25(OH)₂ D levels were lower in children with type 1 diabetes than in healthy controls. CYP2R1 rs12794714 and rs10766196 polymorphisms were associated with a higher risk of type 1 diabetes. Thus, polymorphisms in vitamin D metabolism may contribute to susceptibility to type 1 diabetes in Korean children.

Association of vitamin-D-related genetic variations and treatment response to pegylated interferon in patients with chronic hepatitis B

BACKGROUND

Vitamin D, a potent immune-modulator, has been linked to the pathogenesis of chronic hepatitis B (CHB). This study was aimed at investigating the association between single nucleotide polymorphisms (SNPs) in vitamin-D-related genes and treatment response to pegylated interferon (PEG-IFN) in patients with CHB.

METHODS

A total of 275 Thai patients (122 hepatitis B e antigen [HBeAg]-positive and 153 HBeAg-negative CHB) treated with 48-week PEG-IFN were recruited. Virological response (VR) at 48 weeks post-treatment was defined as HBeAg seroconversion plus HBV DNA <2,000 IU/ml for HBeAg-positive CHB and HBV DNA <2,000 IU/ml for HBeAg-negative CHB. The SNPs VDR (rs2228570), DBP (rs7041) and CYP27B1 (rs4646536) were analysed.

RESULTS

The distribution of TT, CT and CC genotypes of rs4646536 in this cohort was 21.8%, 46.2% and 32.0%, respectively. There was no difference in its distribution according to HBeAg status. In HBeAg-positive CHB, patients with TT genotype, compared with non-TT genotype, achieved higher VR (53.3% versus 31.5%; P=0.032) and hepatitis B surface antigen (HBsAg) clearance (20.0% versus 5.4%; P=0.016). In HBeAg-negative CHB, the corresponding figures were 60.0% versus 30.9% (P=0.003) and 16.7% versus 5.7% (P=0.045), respectively. Patients with TT genotype had more rapid HBsAg decline than those with non-TT genotype. However, SNPs rs2228570 and rs7041were not associated with VR and HBsAg clearance. Logistic regression analysis demonstrated that SNP rs4646536 and baseline HBsAg level were independent predictors of VR in both HBeAg-positive and HBeAg-negative CHB.

CONCLUSIONS

Our data suggest that SNP rs4646536 in the CYP27B1 gene is a predictive factor of response to PEG-IFN therapy in Thai patients with CHB.

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.

Vitamin D pathway genetic variants are able to influence sofosbuvir and its main metabolite pharmacokinetics in HCV mono-infected patients

Vitamin D levels and genetic variants were associated with drug outcome/toxicity and concentrations. The plasma exposure of GS-331007, the main sofosbuvir metabolite, has been related to SVR. We evaluated the impact of polymorphisms in genes (CYP27B1, CYP24A1, VDBP and VDR) related to vitamin D pathway on sofosbuvir and GS-331007 plasma levels in HCV mono-infected patients at one month of treatment. Polymorphisms were investigated through real-time PCR; drug plasma quantification was performed through a UHPLC-MS/MS method. GS-331007 levels were associated with CYP24A1rs2248359 and VDRCdx2 variants in all the analyzed patients and linear regression analysis showed that sex, body mass index, HCV genotype, baseline estimated glomerular filtration rate, VDRCdx2AG/GG and CYP27B1-1260TT genotypes significantly predict concentrations. We performed sub-analyses considering the HCV genotype and the concomitant drug, identifying polymorphisms associated with GS-331007 concentrations. This is the first study focusing on vitamin D pathway gene variants and DAAs concentrations, but further studies are required.

Are low sun exposure and/or vitamin D risk factors for type 1 diabetes?

Ultraviolet radiation and vitamin D, with their known immunosuppressive effects, have the potential to delay or inhibit type 1 diabetes.

Role of CYP27B1+2838 promoter polymorphism in the treatment of chronic hepatitis B HBeAg negative with PEG-interferon

In HBV-infected patients, the vitamin D deficiency has been related to chronic liver diseases, progression of hepatic fibrosis and poor response to the treatment. The CYP27B1 gene, which encodes the 1-α-hidroxylase and involved in the 1,25-dihydroxyvitamin D synthesis, was recently associated to type-1 diabetes, autoimmune disorders and treatment response in HCV. Then, we aimed to investigate the role of CYP27B1 polymorphisms in HBV treatment with PEG-IFN. We retrospectively enrolled 190 patients with chronic hepatitis B HBeAg negative treated for 48 weeks with PEG-IFN α-2a. We examined the role of rs4646536 CYP27B1 SNP (CYP27B1+2838) according to virological and serological response. Our results showed that the TT genotype of CYP27B1+2838 was significantly prevalent in patients with end-of-therapy virological response (37.6%) vs CT/CC (9.4%) (P < 0.001). Virological relapse was prevalent in patients with CT/CC genotype (12.6%) vs TT genotype (2.1%) (P < 0.001). TT genotype was also related to HBsAg loss (P = 0.004) and anti-HBs appearance (P = 0.002). In the multivariate analysis, the TT genotype resulted to be a good positive predictor of sustained virological response (OR = 5.632, IC = 1.938-16.368, P = 0.001) and serological response (OR = 6.161, IC = 1.856-20.457, P = 0.003). The CYP27B1+2838 polymorphism may be useful as pretreatment factor to selection of patients with higher probability of response to therapy.

Vitamin D status and gene transcription in immune cells

BACKGROUND

Vitamin D is a modulator of the immune system. Its insufficiency has been implicated in type 1 diabetes (T1D) and studies showed significant associations with polymorphisms of vitamin D genes. Aim of the study was to investigate whether gene expression in immune cells, vitamin D status and genetic variants are correlated in healthy controls (HC).

METHODS

From 23 HC monocytes (Mo), T-helper cells (Th) and natural killer cells (NK) were isolated. In all immune cells gene expression of vitamin D receptor (VDR), 25-vitamin-D-hydroxylase (CYP2R1) and 25-hydroxyvitamin-D3-1a-hydroxylase (CYP27B1) were measured by Taqman assay. Furthermore, CYP2R1 (rs10741657), CYP27B1 (rs10877012) and the VDR-FokI (rs10735810) polymorphisms in HC were genotyped. Finally, 25-hydroxyvitamin D3 (25(OH)D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plasma levels in HC were measured by radioimmunoassay.

RESULTS

All studied immune cells showed a significantly different gene expression of CYP2R1 and CYP27B1 (p=1×10(-6), respectively). When stratifying the HC according to vitamin D deficiency and vitamin D sufficiency, within the 25(OH)D3 deficient group significantly lower 1,25(OH)2D3 plasma levels (p=0.02) in HC and a significant down-regulation of the VDR expression only in Mo were observed (p=0.04). Furthermore, a significant correlation between CYP2R1 gene transcription and 1,25(OH)2D3 plasma levels in Th cells was found (p=0.04). No associations between the gene expression levels and the investigated polymorphism in all different immune cells were detected. However, vitamin D deficiency in combination with the "AC" CYP27B1 genotype appeared to inhibit the CYP27B1 expression in NK cells (p=0.03).

CONCLUSION

both 25(OH)D3 deficiency and low 1,25(OH)2D3 levels appear to interact with its system gene transcription illustrating the relevance for targeted vitamin D therapy. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Chronic kidney disease and diabetes mellitus predict resistance to vitamin D replacement therapy

BACKGROUND

25-Hydroxyvitamin D [25(OH)D] is a marker of nutritional status; however, chronic kidney disease (CKD) results in alterations in vitamin D metabolism, including the loss of vitamin D-binding proteins and alterations in CYP27B1 and CYP24 enzymes that metabolize 25(OH)D. This study was designed to determine the predictors of responsiveness to correction of vitamin D deficiency with oral vitamin D2 (ergocalciferol) in adults.

METHODS

A retrospective study of 183 veterans with 25(OH)D level <30 ng/mL, who were treated with 50,000 IU per week of vitamin D2, was performed. Logistic regression models were developed to determine the factors predicting the response to treatment, defined as either the change in serum 25(OH)D level/1000 IU of vitamin D2 or the number of vitamin D2 doses (50,000 IU per dose) administered.

RESULTS

The mean age of the patients was 63 ± 12 years. About 87% were men and 51% diabetic, and 29% had an estimated glomerular filtration rate of <60 mL/min/1.73 m. The average number of vitamin D2 doses was 10.91 ± 5.95; the average increase in 25(OH)D level was 18 ± 10.80 ng/mL. 25(OH)D levels remained <30 ng/mL in 61 patients after treatment. A low estimated glomerular filtration rate and the presence of diabetes mellitus were significant independent predictors for inadequate response to vitamin D2 treatment in logistic regression models. Patients with CKD required greater amounts of vitamin D2 to achieve similar increases in 25(OH)D levels, versus non-CKD patients.

CONCLUSIONS

The presence of CKD and diabetes mellitus is associated with resistance to correction of 25(OH)D deficiency with vitamin D2 therapy. The underlying mechanism needs to be evaluated in prospective studies.

Influence of the vitamin D plasma level and vitamin D-related genetic polymorphisms on the immune status of patients with type 1 diabetes: a pilot study

Vitamin D (VD) has been implicated in type 1 diabetes (T1D) by genetic and epidemiological studies. Individuals living in regions with low sunlight exposure have an increased T1D risk and VD supplementation reduced the risk in human individuals and mouse models. One possibility of how VD influences the pathogenesis of T1D is its immunomodulatory effect on dendritic cells (DC), which then preferentially activate regulatory T cells (T(regs) ). In the present pilot study, we collected blood samples from a small cohort of patients with T1D at baseline and months 6 and 12. VD-deficient patients were advised to supplement with 1000 IU/day VD. We found a considerable variation in the VD plasma level at baseline and follow-up. However, with higher VD plasma levels, a lower frequency of interleukin (IL)-4-producing CD8 T cells was observed. We further performed a comprehensive genotyping of 13 VD-related polymorphisms and found an association between VD plasma level and the genotype of the VD binding protein (DBP). The frequency of DC and T cell subsets was variable in patients of all subgroups and in individual patients over time. Nevertheless, we found some significant associations, including the 1,25-dihydroxyvitamin D(3) hydroxylase (CYP27B1) genotype with the frequency of DC subtypes. In summary, our preliminary results indicate only a limited influence of the VD plasma level on the immune balance in patients with T1D. Nevertheless, our pilot study provides a basis for a follow-up study with a larger cohort of patients.

Resequencing and fine-mapping of the chromosome 12q13-14 locus associated with multiple sclerosis refines the number of implicated genes

Multiple sclerosis (MS) is a common chronic inflammatory disease of the central nervous system. Susceptibility to the disease is affected by both environmental and genetic factors. Genetic factors include haplotypes in the histocompatibility complex (MHC) and over 50 non-MHC loci reported by genome-wide association studies. Amongst these, we previously reported polymorphisms in chromosome 12q13-14 with a protective effect in individuals of European descent. This locus spans 288 kb and contains 17 genes, including several candidate genes which have potentially significant pathogenic and therapeutic implications. In this study, we aimed to fine-map this locus. We have implemented a two-phase study: a variant discovery phase where we have used next-generation sequencing and two target-enrichment strategies [long-range polymerase chain reaction (PCR) and Nimblegen's solution phase hybridization capture] in pools of 25 samples; and a genotyping phase where we genotyped 712 variants in 3577 healthy controls and 3269 MS patients. This study confirmed the association (rs2069502, P = 9.9 × 10(-11), OR = 0.787) and narrowed down the locus of association to an 86.5 kb region. Although the study was unable to pinpoint the key-associated variant, we have identified a 42 (genotyped and imputed) single-nucleotide polymorphism haplotype block likely to harbour the causal variant. No evidence of association at previously reported low-frequency variants in CYP27B1 was observed. As part of the study we compared variant discovery performance using two target-enrichment strategies. We concluded that our pools enriched with Nimblegen's solution phase hybridization capture had better sensitivity to detect true variants than the pools enriched with long-range PCR, whilst specificity was better in the long-range PCR-enriched pools compared with solution phase hybridization capture enriched pools; this result has important implications for the design of future fine-mapping studies.

Synergism of CYP2R1 and CYP27B1 polymorphisms and susceptibility to type 1 diabetes in Egyptian children

CYP2R1 (25α-hydroxylase) catalyzes vitamin D(3) to 25-hydroxyvitamin D(3), while the CYP27B1 (1α-hydroxylase) catalyzes the 25(OH)D(3) to 1, 25(OH)(2)D(3). 1, 25(OH)(2)D(3) prevents the development of autoimmune diabetes. We aimed to investigate CYP2R1 and CYP27B1 genes polymorphisms and susceptibility to type 1 diabetes in children. One hundred and twenty type 1 diabetic patients and One hundred and twenty controls were genotyped for CYP2R1 (rs10741657) and CYP27B1 (rs10877012) polymorphism. GG genotype of CYP2R1 increased risk to develop type 1 diabetes, and CC genotype of CYP27B1 increased risk to develop type 1 diabetes. Our finding suggested that GG genotype of CYP2R1 polymorphism and/or CC genotype of CYP27B1 polymorphism increased the risk of developing of type 1 diabetes in Egyptian children. In addition there was a synergism between GG genotype of CYP2R1 and CC genotype of CYP27B1 regarding the risk of development of type 1 diabetes.

Single-nucleotide polymorphism at CYP27B1-1260, but not VDR Taq I, is possibly associated with persistent hepatitis B virus infection

BACKGROUND

Vitamin D, beyond its role in calcium and bone metabolism, exhibits immunomodulatory effects on innate and adaptive immune pathways and is suggestively related to liver diseases.

OBJECTIVE

This study investigated the association of single-nucleotide polymorphisms in genes involved in vitamin D functions with hepatitis B virus (HBV) infection.

METHODS

Five hundred Chinese Han subjects, including 274 chronic HBV patients, 68 HBV infection resolvers, and 158 healthy controls without HBV infection, were studied. The CYP27B1-1260 promoter and the VDR Taq I polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Although there was no difference between HBV patients and healthy controls, HBV patients and healthy controls had a higher frequency of the CYP27B1-1260 genotype CC (15.0% vs. 2.9%, p=0.004 and 13.3% vs. 2.9%, p=0.006, respectively) and allele C (38.3% vs. 25.7%, p=0.006 and 39.2% vs. 25.7%, p=0.006, respectively) compared with resolvers. The genotype and allele frequencies of the VDR Taq I polymorphism had no difference between patients, resolvers, and healthy controls.

CONCLUSION

These results suggest that the CYP27B1-1260 promoter polymorphism is possibly associated with the persistence, but not susceptibility to HBV infection in Chinese HBV patients, and that the VDR Taq I polymorphism is not suggested to be related to chronic HBV infection.

Contribution of a common variant in the promoter of the 1-α-hydroxylase gene (CYP27B1) to fracture risk in the elderly

CYP27B1 encodes mitochondrial 1α-hydroxylase, which converts 25-hydroxyvitamin D to its active 1,25-dihydroxylated metabolite. We tested the hypothesis that common variants in the CYP27B1 promoter are associated with fracture risk. The study was designed as a population-based genetic association study, which involved 153 men and 596 women aged 65-101 years, who had been followed for 2.2 years (range 0.1-5.5) between 1999 and 2006. During the follow-up period, the incidence of fragility fractures was ascertained. Bone ultrasound attenuation (BUA) was measured in all individuals, as were serum 25-hydroxyvitamin D and PTH concentrations; 86% subjects had vitamin D insufficiency. Genotypes were determined for the -1260C>A (rs10877012) and +2838T>C (rs4646536) CYP27B1 polymorphisms. A reporter gene assay was used to assess functional expression of the -1260C>A CYP27B1 variants. The association between genotypes and fracture risk was analyzed by Cox's proportional hazards model. We found that genotypic distribution of CYP27B1 -1260 and CYP27B1 +2838 polymorphisms was consistent with the Hardy-Weinberg equilibrium law. The two polymorphisms were in high linkage disequilibrium, with D' = 0.96 and r² = 0.94. Each C allele of the CYP27B1 -1260 polymorphism was associated with increased risk of fracture (hazard ratio = 1.34, 95% CI 1.03-1.73), after adjustment for age, sex, number of falls, and BUA. In transient transfection studies, a reporter gene downstream of the -1260(A)-containing promoter was more highly expressed than that containing the C allele. These data suggest that a common but functional variation within the CYP27B1 promoter gene is associated with fracture risk in the elderly.

Vitamin D and increasing incidence of type 1 diabetes-evidence for an association?

There has been an important shift in the views about the actions of vitamin D during the past decade. In addition to its well-established role in the regulation of calcium metabolism, vitamin D deficiency has been associated with the risk of several extra-skeletal diseases, including type 1 diabetes among other chronic conditions. It is notable that 1,25(OH)(2)D is known to regulate the expression of over 200 different genes, including the ones related to apoptosis and immune modulation. Increased vitamin D intake is currently considered as one of the most promising candidates for the prevention of type 1 diabetes, and it has been suggested that changes in vitamin D intake during the past decades have contributed to the recent trends in the incidence of the disease. This study reviews the evidence for the role of vitamin D in type 1 diabetes development, demonstrating that support has been obtained from various lines of investigation and that the possible biological mechanisms are plausible. However, much of the evidence has been obtained from animal experiments or observational studies in humans and there is an urgent need for well-designed, randomized, controlled trials to show whether the observed associations are indeed causal.

Confirmation of association between multiple sclerosis and CYP27B1

Multiple sclerosis, MS (OMIM No. 126200), is a complex inflammatory disease that is characterized by lesions in the central nervous system. Both genes and other environmental factors influence disease susceptibility. One of the environmental factors that has been implicated in MS and autoimmune disease, such as type 1 diabetes, is vitamin D deficiency, in which patients have lower levels of 25-hydroxyvitamin D3 (25-OHD(3)) in blood than do controls. Previtamin D(3) is produced in the skin, and turned into 25-OHD(3) in the liver. In the kidney, skin and immune cells, 25-OHD(3) is turned into bioactive 1,25(OH)(2)D(3) by the enzyme coded by CYP27B1 (cytochrome P450 family 27 subfamily B peptide 1) on chromosome 12q13.1-3. 1,25(OH)(2)D(3) binds to the vitamin D receptor, expressed in T cells and antigen-presenting cells. 1,25(OH)(2)D(3) has a suppressive role in the adaptive immune system, decreasing T-cell and dendritic cell maturation, proliferation and differentiation, shifting the balance between T-helper 1 (Th1) and Th2 cells in favor of Th2 cells and increasing the suppressive function of regulatory T cells. Rs703842 in the 12q13-14 region was associated with MS in a recent study by the Australian and New Zealand Multiple Sclerosis Genetics Consortium (ANZgene). We show associations with three SNPs in this region in our Swedish materials (2158 cases, 1759 controls) rs4646536, rs10877012 and rs10877015 (P=0.01, 0.01 and 3.5 × 10(-3), respectively). We imputed rs703842 SNP and performed a joint analysis with the ANZgene results, reaching a significant association for rs703842 (P=5.1 × 10(-11); odds ratio 0.83; 95% confidence interval 0.79-0.88). Owing to its close association with 25-OHD(3), our results lend further support to the role of vitamin D in MS pathology.

The role of cubilin gene polymorphisms and their influence on 25(OH)D3 and 1,25(OH)2D3 plasma levels in type 1 diabetes patients

BACKGROUND

Megalin and cubilin bind and internalize the 25(OH)D3-DBP complex in the kidney. Once the complex is internalized, 25(OH)D3 is released and activated to 1,25(OH)2D3 the ligand for the vitamin D receptor (VDR). Supporting the important role of cubilin in this process recent findings showed that cubilin deficiency results in decrease of 25(OH)D3 and 1,25(OH)2D3 plasma levels.

METHODS

Two hundred T1D patients and healthy controls (n=200) were genotyped for five polymorphisms (rs3740168, rs3740165, rs1801233, rs1801229 and rs2796835) within the cubilin gene. The polymorphisms were analyzed by RFLP or real time PCR. Statistic analyses were performed by using allele-wise and genotype-wise chi2 testing by using BiAS software. A p-value<0.05 was considered as significant.

RESULTS

We found that the genotype "AA" of the rs3740165 was more frequent in T1D patients compared to healthy controls (26.7% vs. 5.1%, p=4x10(-7)). Nevertheless no association between the rs3740165 polymorphism and the 25(OH)D3 or 1,25(OH)2D3 plasma levels was found. No association with the other studied polymorphisms was observed.

CONCLUSION

Thus our findings reveal a novel association of the cubilin rs3740165 polymorphism with type 1 diabetes. Nevertheless how exactly this polymorphism could increase the risk to develop type 1 diabetes is subject for further investigations.

Elevated plasma calcifediol is associated with aggressive periodontitis

BACKGROUND

Vitamin D is associated with a number of inflammatory diseases and plays a significant role in regulating bone metabolism. Serum calcifediol was demonstrated to be potentially associated with periodontal disease. The purpose of this study was to evaluate whether an association exists between plasma calcifediol concentrations and aggressive periodontitis (AgP) and whether plasma levels of bone-related biomarkers (osteocalcin, alkaline phosphatase, calcium, and phosphorus) regulated by vitamin D are related to AgP.

METHODS

Sixty-six patients with generalized AgP, 52 patients with chronic periodontitis, and 60 healthy controls were included in this study. Periodontal examination consisted of probing depth, attachment loss, and bleeding index measurements. Hematic calcifediol and bone-related biomarker levels were detected using radioimmunity assay kits or a biochemical analyzer.

RESULTS

Plasma calcifediol levels in patients with AgP were higher than those of healthy controls (29.28 versus 21.60 nmol/l; P <0.05) and were statistically significantly correlated with bleeding index (r = 0.321; P <0.05). Plasma osteocalcin concentrations in patients with AgP were higher than those of healthy controls (0.90 versus 0.70 ng/ml; P <0.05). Serum inorganic phosphorus values of both periodontitis groups were lower than those of healthy controls (1.06 +/- 0.18 mmol/l and 1.10 +/- 0.15 mmol/l versus 1.26 +/- 0.17 mmol/l; P <0.05).

CONCLUSION

Plasma calcifediol levels might be associated with periodontal inflammation.

A convergent model for placental dysfunction encompassing combined sub-optimal one-carbon donor and vitamin D bioavailability

We hypothesise that the risk of placental dysfunction/insufficiency rises cumulatively in response to several interdependent risk factors that convergently regulate 1,25-dihydroxyvitamin D (the biologically active form of vitamin D, [1,25-(OH)(2)D]) levels at the feto-maternal interface. These factors include; (i) disturbances in genetic or epigenetic regulation of one-carbon metabolism and/or vitamin D metabolism and (ii) insufficiency in maternal vitamin D or in dietary intake of micronutrients that are involved in one-carbon donation. We predict that the sub-optimal functioning of folate and vitamin D metabolic pathways, in concert, represents a potential novel risk pathway for adverse pregnancy outcomes. We base this prediction on five observations: In order to test this model, future epidemiological studies aimed at identifying risk factors for disorders linked to sub-optimal placental development and functioning, should: (a) measure circulating precursor molecules (including folate, vitamin B12, homocysteine, and vitamin D) in maternal and cord blood; (b) collect samples for examination of genotypic variation in both one-carbon and vitamin D regulatory genes and, (c) collect samples for examination of epigenetic status of genes regulating vitamin D homeostasis and action in the placenta.

Association of the vitamin D metabolism gene CYP27B1 with type 1 diabetes

OBJECTIVE

Epidemiological studies have linked vitamin D deficiency with the susceptibility to type 1 diabetes. Higher levels of the active metabolite 1 alpha,25-dihydroxyvitamin D (1 alpha,25(OH)(2)D) could protect from immune destruction of the pancreatic beta-cells. 1 alpha,25(OH)(2)D is derived from its precursor 25-hydroxyvitamin D by the enzyme 1 alpha-hydroxylase encoded by the CYP27B1 gene and is inactivated by 24-hydroxylase encoded by the CYP24A1 gene. Our aim was to study the association between the CYP27B1 and CYP24A1 gene polymorphisms and type 1 diabetes.

RESEARCH DESIGN AND METHODS

We studied 7,854 patients with type 1 diabetes, 8,758 control subjects from the U.K., and 2,774 affected families. We studied four CYP27B1 variants, including common polymorphisms -1260C>A (rs10877012) and +2838T>C (rs4646536) and 16 tag polymorphisms in the CYP24A1 gene.

RESULTS

We found evidence of association with type 1 diabetes for CYP27B1 -1260 and +2838 polymorphisms, which are in perfect linkage disequilibrium. The common C allele of CYP27B1 -1260 was associated with an increased disease risk in the case-control analysis (odds ratio for the C/C genotype 1.22, P = 9.6 x 10(-4)) and in the fully independent collection of families (relative risk for the C/C genotype 1.33, P = 3.9 x 10(-3)). The combined P value for an association with type 1 diabetes was 3.8 x 10(-6). For the CYP24A1 gene, we found no evidence of association with type 1 diabetes (multilocus test, P = 0.23).

CONCLUSIONS

The present data provide evidence that common inherited variation in the vitamin D metabolism affects susceptibility to type 1 diabetes.