Vitamin D receptor gene BsmI, FokI, ApaI, TaqI polymorphisms and bone mineral density in a group of Turkish type 1 diabetic patients

Immunogenetic Prediction of VDR Gene SNPs: Lack of Association with Susceptibility to Type 1 Diabetes in Jordanian Patients

PURPOSE

The interaction of Vitamin D and its receptor plays a crucial role in immune modulation. Therefore, the relationship between the pathogenesis of type 1 diabetes and the genetic variants of Vitamin D receptor, which is involved in the activity of Vitamin D, was studied extensively in different populations. The association of Vitamin D receptor gene polymorphisms with predisposition to type 1 diabetes revealed controversial and inconclusive results. The aim of this study was to examine the association of four Vitamin D receptor polymorphisms with type 1 diabetes in Jordanian patients.

PATIENTS AND METHODS

Analysis of the single nucleotide polymorphisms FokI (rs2228570), ApaI (rs7975232), TaqI (rs731236) and BsmI (rs1544410) in 100 Jordanian volunteers (50 control and 50 Type 1 diabetes patients) was performed using the highly specific New Generation Sequencing technology.

RESULTS

The distribution of allele, genotype as well as haplotype frequencies exhibited no significant (P > 0.05) differences between type 1 diabetes patients and controls. Furthermore, no differences (P > 0.05) in the frequency of the genotypes of the Vitamin D receptor genetic variants were found in relation to the age of disease onset.

CONCLUSION

These findings suggest these four single nucleotide polymorphisms of the Vitamin D receptor gene seem not to be associated with type 1 diabetes predisposition in Jordanian patients. Further wide genome studies are recommended to detect other genetic variant associations with type 1 diabetes among Jordanians.

Vitamin D receptor gene polymorphisms and the risk of the type 1 diabetes: a meta-regression and updated meta-analysis

BACKGROUND

The association between the polymorphisms in the vitamin D receptor (VDR) gene and the risk of type 1 diabetes mellitus (T1DM) has been evaluated in several studies. However, the findings were inconclusive. Thus, we conducted a meta-analysis to comprehensively evaluate the effect of VDR gene polymorphisms on the risk of T1DM.

METHODS

All relevant studies reporting the association between VDR gene polymorphisms and susceptibility to T1DM published up to May 2020 were identified by comprehensive systematic database search in ISI Web of Science, Scopus, and PubMed/MEDLINE. Strength of association were assessed by calculating of pooled odds ratios (ORs) and 95% confidence intervals (CIs). The methodological quality of each study was assessed according to the Newcastle-Ottawa Scale. To find the potential sources of heterogeneity, meta-regression and subgroup analysis were also performed.

RESULTS

A total of 39 case-control studies were included in this meta-analysis. The results of overall population rejected any significant association between VDR gene polymorphisms and T1DM risk. However, the pooled results of subgroup analysis revealed significant negative and positive associations between FokI and BsmI polymorphisms and T1DM in Africans and Americans, respectively.

CONCLUSIONS

This meta-analysis suggested a significant association between VDR gene polymorphism and T1DM susceptibility in ethnic-specific analysis.

Effects of vitamin D and estrogen receptor polymorphisms on bone mineral density in adolescents with anorexia nervosa

Background Anorexia nervosa (AN) is a serious eating disorder that is associated with decreased bone mineral density (BMD) and greater lifetime risk for fractures. The aim of this study was to determine the correlation between BMD and genetic polymorphisms in AN. Methods This case-control study analyzed vitamin D receptor (VDR) (VDRBsml, VDRFokl) and estrogen receptor (ESR) (ESR1Xbal, ESR1Pvull) polymorphisms in 45 adolescents diagnosed with AN and 46 age-matched healthy controls. BMD values of the AN group were classified as low or normal, and polymorphisms were compared between cases and controls. The effects of body mass index (BMI), duration of disease and amenorrhea on BMD were also evaluated. Results In girls with AN, a positive effect of the bb genotype of VDRBsmI polymorphism on femur Z-scores (p = 0.103) and of the Ff genotype of VDRFokI polymorphism on vertebra Z-scores (p = 0.097) was observed. In boys with AN, a positive effect of the Ff genotype of VDRFokI polymorphism on vertebra BMD (g/cm2) was detected (p = 0.061). No association was detected between ESR polymorphisms. An inverse relationship was observed between BMD and duration of illness and amenorrhea. A direct relationship was detected between BMD and BMI. Conclusions Specific VDR gene polymorphism genotypes may have positive effects on BMD in patients with AN. Additionally, the lack of association between ESR gene polymorphisms on BMD could be attributed to the low estrogen status of the patient.

Vitamin D status of Turkish type 1 diabetic patients

INTRODUCTION

Vitamin D was associated with the pathogenesis, treatment and prognosis of type 1 and type 2 diabetes mellitus. The aim of this study is to assess vitamin D status of Turkish adult type 1 DM patients and compare them with health controls and also to assess the relationship of vitamin D and glycemic control.

METHOD

Study was designed as cross-sectional and conducted in a tertiary Hospital diabetes unit. 296 type diabetic patients and 151 healthy controls was included to the study. Venous samples were collected into plain tubes after overnight fasting. Serum 25-hydroxyvitamin D level was measured by radioimmunoassay technique. Statistical analysis was performed with SPSS 15.0.

RESULTS

25-Hydroxyvitamin D levels were similar between patients with type 1 diabetes (22, 9 ± 17, 4 ng/ml) and controls (24, 5 ± 19, 3 ng/ml) (p = 0,382). Most of the participants have 25-Hydroxyvitamin D deficiency. As shown in Table 2 serum 25-Hydroxyvitamin D level was not associated with most of the biochemical or anthropometric parameters.

CONCLUSION

As a result there were no difference between type 1 diabetics and healthy controls according to their vitamin D levels. Further studies with a larger sample of patients will improve our understanding of the relation of vitamin D and diabetes.

Relationship of four vitamin D receptor gene polymorphisms with type 1 diabetes mellitus susceptibility in Kuwaiti children

Background

The incidence of type 1 diabetes mellitus (T1DM) in Kuwait is amongst the highest in the world. Vitamin D is considered to be involved in immune modulation and its deficiency contribute to autoimmune destruction of insulin producing beta cells in T1DM patients. Vitamin D has been shown to exert its effects via a nuclear vitamin D receptor (VDR) and therefore, VDR gene may be considered a candidate for T1DM susceptibility.

Methods

The genotypes of four VDR gene polymorphisms were determined in 253 Kuwaiti Arab T1DM patients and 214 healthy controls by PCR-RFLP analysis. Serum concentrations of three autoantibodies i.e. ICA (Islet cell autoantibody), GADA (Glutamic acid decarboxylase) and INS (Insulin autoantibody) were determined by radio-immunoassays.

Results

Statistically significant differences were detected between the genotypes of two VDR gene polymorphisms (FokI, C > T, rs10735810 and TaqI, C > T, rs731236) between T1DM patients and controls (P < 0.0001). In both, the frequency of variant alleles was considerably high in T1DM than in the controls. In contrast, the VDR gene ApaI (G > T, rs7975232) and BsmI (A > G, rs1544410) polymorphisms did not show association with T1DM. The homozygous variant genotypes of FokI, ApaI and TaqI polymorphisms show significant differences between various age-of-onset subgroups while no such association was detected in the case of BsmI polymorphism. Significant differences were also noted between heterozygous genotypes of all four polymorphisms especially between 4-6y and > 6y age-of-onset subgroups of T1DM patients. Three autoantibodies, ICA (Islet cell), GADA (glutamate decarboxylase) and INS (insulin) were positively associated to, varying degrees, with T1DM in Kuwaiti Arabs harboring different VDR gene polymorphism genotypes.

Conclusions

Our results demonstrate a significant effect of two VDR gene polymorphisms (FokI and TaqI) and three autoantibodies on genetic susceptibility of T1DM in Kuwaiti Arabs along with other factors.

Assessment of bone quality in patients with diabetes mellitus

Substantial evidence exists that diabetes mellitus is associated with an increased risk of osteoporotic fractures. Low bone strength as well as bone extrinsic factors are probably contributing to the increased bone fragility in diabetes. Bone density and quality are important determinants of bone strength. Although bone mineral density (BMD) and the fracture risk assessment tool (FRAX) are very useful clinical tools in assessing bone strength, they may underestimate the fracture risk in diabetes mellitus. Through advances in new technologies such as trabecular bone score (TBS) and peripheral quantitative computed tomography (pQCT), we can better assess the bone quality and fracture risk of patients with diabetes mellitus. Invasive assessments such as microindentation and histomorphometry have been great complement to the existing bone analysis techniques. Bone turnover markers have been found to be altered in diabetes mellitus patients and may be associated with fractures. This review will give a brief summary of the current development and clinical uses of these assessments.

Evaluation of vitamin D receptor gene polymorphisms (Fok-I and Bsm-I) in T1DM Saudi children

BACKGROUND

Vitamin D deficiency conferred strongest susceptibility to pathogenesis of type 1 diabetes mellitus (T1DM). Altered gene expression and function have strong effect on VDR gene polymorphism.

OBJECTIVES

We aimed to check for the association of two single nucleotide polymorphisms (SNPs) in VDR gene (Fok-I and Bsm-I) with T1DM in Saudi children.

SUBJECTS AND METHODS

Cross-sectional study included 100 T1DM Saudi children, plus 102 unrelated healthy subjects. PCR technique was used for detection of Fok-I and Bsm-I SNPs in VDR gene.

RESULTS

Regarding the Fok-I polymorphisms, T1DM cases showed a significant increased frequency of the heterozygous genotype (Ff) than controls (33% vs 21%, OR = 1.9, 95% CI = 1.006-3.587, P = .04). In the meantime, they showed significantly lower frequency of the homozygous (ff) genotype (64% vs 79%, OR = 0.51, 95% CI = 0.28-0.96, P = .03). Cases showed also a significantly lower frequency of the (f) allele than controls (80.5% vs 87.7%, OR = 0.57, 95% CI = 0.33-0.995, P = .04). On the other hand, cases showed significantly higher frequency of the Bsm-I homozygous (bb) and heterozygous (Bb) genotypes (25% vs 11.8%, P = .01, OR = 2.5, 95% CI = 1.18-5.31) & (45% vs 27.5%, P = .0, OR = 2.1, 95 % CI = 1.20-3.89, respectively). Cases showed also significantly higher frequency of (b) allele compared to control (47.5% vs 25.5%, P = .0, OR = 2.6, 95% CI = 1.74-4.02). Haplotype analysis showed an increased risk with the fB and fb haplotypes.

CONCLUSION

This study emphasizes a positive association between SNPs (Fok-I and Bsm-I) and T1DM among Saudi children with increased risk with the Fok-I F and Bsm-I b alleles.

Osteocalcin Serum Levels in Gestational Diabetes Mellitus and Their Intrinsic and Extrinsic Determinants: Systematic Review and Meta-Analysis

BACKGROUND

Undercarboxylated osteocalcin (ucOC) increases insulin release and insulin resistance in mice. In humans, evidence is scarce but a correlation of ucOC and total osteocalcin (tOC) with glycemic status markers has been demonstrated. The relationship of ucOC and tOC with gestational diabetes mellitus (GDM) has been even less characterized.

OBJECTIVE

To assess the mean difference of tOC and ucOC serum concentrations among nondiabetic pregnant women and women diagnosed as GDM in the second trimester of pregnancy and to determine the possible intrinsic and extrinsic contributors to this difference.

METHODS

A systematic search was performed to identify relevant studies published in English and Spanish using PubMed, SCOPUS, ISI Web of Knowledge, and PROSPERO database for meta-analysis. Observational studies measuring mean serum levels of osteocalcin among GDM, with at least 10 subjects analyzed in each group were selected. Mean difference (MD) by random effects model was used. Heterogeneity between studies was assessed using Cochran's Q, H, and I ² statistics.

RESULTS

From 38 selected studies, 5 were retained for analysis for a total of 1119 pregnant women. Serum concentrations of tOC were not significantly different among women with GDM and nondiabetic pregnant controls (MD: 1.56; 95% CI: -0.70 to 3.82; p = 0.175). Meanwhile, ucOC serum levels were significantly higher among women with GDM (MD: 1.17; 95% CI: 0.24 to 2.11; p = 0.013). The only factor influencing tOC was the UV index, showing a reduction in mean difference between GDM and controls when exposed to higher concentrations of UV rays.

CONCLUSIONS

This meta-analysis provides evidence to support the use of ucOC as a potential marker for GDM rather than tOC, yielding very little variability among studies and no difference among methods or brands used for its analysis.

Inherited Variation in Vitamin D Genes and Type 1 Diabetes Predisposition

The etiology and pathophysiology of type 1 diabetes remain largely elusive with no established concepts for a causal therapy. Efforts to clarify genetic susceptibility and screening for environmental factors have identified the vitamin D system as a contributory pathway that is potentially correctable. This review aims at compiling all genetic studies addressing the vitamin D system in type 1 diabetes. Herein, association studies with case control cohorts are presented as well as family investigations with transmission tests, meta-analyses and intervention trials. Additionally, rare examples of inborn errors of vitamin D metabolism manifesting with type 1 diabetes and their immune status are discussed. We find a majority of association studies confirming a predisposing role for vitamin D receptor (VDR) polymorphisms and those of the vitamin D metabolism, particularly the CYP27B1 gene encoding the main enzyme for vitamin D activation. Associations, however, are tenuous in relation to the ethnic background of the studied populations. Intervention trials identify the specific requirements of adequate vitamin D doses to achieve vitamin D sufficiency. Preliminary evidence suggests that doses may need to be individualized in order to achieve target effects due to pharmacogenomic variation.

Role of Vitamin D in Intima Media Thickness in Patients with Type 1 Diabetes Mellitus

Increased carotid intima media thickness indicates subclinical atherosclerosis. We evaluated the relation between vitamin D level and intima media thickness in patients with type 1 DM. 93 patients (female/male: 48/45, aged 31.5 ± 11.9 years, A1c 9.48 ± 2.43, vitamin D [15.9 (12.1-19.2)]) with type 1 DM were included into the study. Common carotid artery IMT was measured by real time B mode ultrasonography (MyLab 70 XVG, Esaote SpA, Genoa, Italy). Vitamin D was measured using radioimmunassay. Male and female patients (n = 14, 15%) had similar rates of plaque presence (p = 0.377). IMT was similar according to gender. IMT [0.45 (0.40-0.50)] was positively correlated with age, duration of diabetes, creatinine, LDL/HDL ratio, and ALP. Median IMT was higher in current smokers, patients with retinopathy, and nephropathy, and overweight/obese patients. IMT was not different according to vitamin D status. However calcium level corrected for albumin was in positive correlation with mean IMT (r = 0.221, p = 0.033). We detected high frequency of vitamin D deficiency (78%) defined as less than 20 ng/ml. Vitamin D and diabetes control defined as A1c have no effect on intima media thickness in type 1 DM. Traditional cardiovascular risk factors including age, duration of DM, smoking, and BMI adversely affect intima media thickness.

TaqI, FokI, and ApaI Polymorphisms in the Vitamin D Receptor in Behçet's Disease in Turkish Population

Objectives. In our study we aimed to determine VDR gene polymorphisms in patients with Behçet's disease (BD) and neuro-Behçet's disease (NBD) in Turkish population. Methods. PBL obtained from 37 patients with BD, 21 patients with NB, and 30 healthy controls were investigated. Genomic DNA was extracted from whole blood using the QIAamp Blood Kit. VDR ApaI (rs7975232), VDR FokI (rs2228570), and VDR TaqI (rs731236) genotyping was performed by real-time polymerase chain reaction with SimpleProbe melting-curve analysis. Results. The allelic and genotype distributions of FokI and TaqI polymorphisms were not different among Behçet's disease, neuro-Behçet's disease, and control subjects in Turkish population (p > 0.05). Only the frequency of ApaI A allele in control is higher than that in BD (60% versus 38.5%), and the p value is 0.014, but the power is not enough to conclude that ApaI A allele is protective in BD in our study. Taken together, we found no significant differences between the BD, NBD, and control groups regarding the distribution of ApaI, TaqI, and FokI genotype and alleles frequencies. Conclusions. Future studies with larger patients' numbers may show differences between VDR polymorphisms and Behçet's disease.

Vitamin D receptor gene TaqI and Apal polymorphisms and steroid responsiveness in childhood idiopathic nephrotic syndrome

Background

Vitamin D activity is controlled by vitamin D receptors (VDRs), which are affected by different genetic polymorphisms, including TaqI and Apal restriction fragment length polymorphisms (RFLPs), which have been reported to be associated with several diseases. The aim of this study was to determine the frequency and the association of VDR gene polymorphisms with idiopathic nephrotic syndrome (INS) and steroid responsiveness in Kuwaiti children.

Subjects and methods

Genotypes of the VDR TaqI gene polymorphism and the Apal gene polymorphism were analyzed using polymerase chain reaction-RFLP in 78 INS patients and 56 matched controls.

Results

A total of 78 INS (62 steroid sensitive [SS] and 16 steroid resistant [SR]) patients with a mean age of 6.5±3.1 years were studied. Male:female ratio was 2:1. The TT genotype of VDR–TaqI polymorphism was detected in 41% of the INS patients compared to 42% of the controls (P=0.816). The heterozygous TC genotype was detected in 33% of INS patients compared to 46% of the controls (P=0.462). The CC genotype was detected in 25.6% of INS patients and 21% of the controls (P=0.719). The C-allele frequency, in its homozygous and heterozygous forms, was 71% in INS patients compared to 63% in the controls (P=0.342). Similarly, no significant difference was detected in terms of VDR–Apal polymorphism in INS patients compared to the controls for all the three genotypes (P=0.76, P=0.207, and P=0.364, respectively, for GG, GT, and TT genotypes). The T-allele frequency, in its homozygous and heterozygous forms, was 89% in INS patients compared to 93% in the controls (P=0.076). No significant difference was found in any of the allele frequencies between SS and SR subgroups when compared with each other or when compared to the controls.

Conclusion

Our data do not support the use of VDR–TaqI or –Apal gene polymorphisms as genetic markers of INS nor do they predict steroid responsiveness in children with the disease.

Vitamin D receptor biochemical and genetic profiling and HLA-class II genotyping among Lebanese with multiple sclerosis - A pilot study

BACKGROUND

Multiple sclerosis (MS) is an autoimmune demyelinating disease affecting mostly young adult females with multifactorial etiology. Recent studies suggested that adequate vitamin D levels may lower the risk of developing MS.

OBJECTIVES

Our aim was to explore the relationship between vitamin D receptor (VDR) polymorphism, HLA-DR locus genotype, and serum vitamins D and A levels in the Lebanese population.

METHODS

Fifty MS patients were recruited for this study. The control group consisted of 48 healthy and 51 patients with other neurological disorders (non-MS). Biochemical analysis included serum 25 hydroxyvitamin D (25OHD) and vitamin A. Molecular analysis targeted VDR genotypes (ApaI, TaqI and BsmI) and low resolution HLA typing for DRB1 locus.

RESULTS

Healthy and non-MS groups had comparable parameters and were combined into one control group. No significant differences were found between MS and control groups for VDR genotypes. The frequency of HLA-DRB1*15 was significantly higher in MS patients (22%) compared to controls (8%) (p=0.018). Odds ratio for MS in the presence of DRB1*15 allele was 3.21 (p=0.018). Cosegregation with A (ApaI) and b (BsmI) alleles did not influence the risk for MS. 25OHD levels were significantly higher in MS patients compared to controls (p=0.002), due to more frequent oral supplementation (p=0.005). Vitamin A levels were comparable between the two groups. When all parameters were included in a logistic regression model adjusted for supplementation, only HLA-DRB1*15 (OR=3.42; p=0.027) contributed significantly to MS risk.

CONCLUSION

There was no association between serum vitamin D or A or VDR genotypes and MS. HLA-DRB1*15 was the major factor imposing more than 3 folds greater risk for developing MS among Lebanese.

Pre-treatment VD levels and VDR receptors as potential predictors of occurrence and overall survival in paediatric patients with solid tumours-a single institution pilot study

Recently, vitamin D has been recognized as an important player in the immune system, and multiple studies suggested its involvement in cancer, too. The aims of this study were to investigate selected single nucleotide polymorphisms (SNPs) in the VDR gene, BsmI (rs1544410; A > G), FokI (rs 2228570; C > T), TaqI (rs731236; T > C), ApaI (rs 7975232; C > T) and Cdx-2 (rs11568820; A > G), and to evaluate their possible predictive role for outcomes in patients with paediatric solid tumours. A total of 111 children with paediatric solid tumours were enrolled at the Department of Paediatric Oncology, University Hospital Brno (Brno, Czech Republic) along with a control population of 787 adults; all study subjects were available for genotyping of selected SNPs, and the prediagnostic levels of 25-hydroxycholecalciferol (25(OH)D3) and 1,25-dihydroxycholecalciferol (1,25(OH)2D3) were measured in the cases, too. In FokI, the heterozygote CT genotype was weakly associated with a decreased risk of paediatric solid cancer occurrence 0.82 (0.53-1.28), while the CC genotype was associated with a decreased risk of 0.58 (0.30-1.09), p = 0.09. The 1,25(OH)2D3 prediagnostic levels were indicative of the overall survival in the cases (β = -0.012, HR 0.988, 95 % CI (0.978-0.998), while higher prediagnostic levels of 1,25(OH)2D3 were associated with a statistically significant increase in overall mortality. We observed multiple effects of the alleles of the investigated polymorphisms and of 1,25(OH)2D3 on overall survival, regardless of the underlying disease.

Lower serum 25 (OH) D concentrations in type 1 diabetes: A meta-analysis

OBJECTIVE

Vitamin D may have protective effects against type 1 diabetes (T1D). However, the results of current cross-sectional studies have been inconsistent. We aimed to examine the association of serum vitamin D and T1D by conducting a meta-analysis.

METHODS

Multiple databases were searched until April 2014 to identify relevant studies. The search term was "serum vitamin D" and "type 1 diabetes". Random effects model was used to calculate the pooled risk estimate. The data were accessed by software Review manager 5.2.

RESULTS

We included a total of 23 studies (11 studies with 1900 participants of children or adolescents and 13 studies with 3494 participants of adults) in our meta-analysis. In children or adolescents, serum 25(OH) D in T1D was 5.69 ng/ml [95% confidence interval (CI) (2.82-8.55, P<0.0001) lower than in healthy controls. In adults, serum 25(OH) D in T1D was 2.61 ng/ml [95% confidence interval (CI) (1.13-4.09, P=0.0005) lower than in healthy controls. We did not find evidence of publication bias.

CONCLUSION

Serum 25OHD is significantly lower in patients with T1D than in healthy controls.

[The role of vitamin D3 in the regulation of the mineral metabolism in experimental type 1 diabetes]

Diabetes was shown to be associated with a considerable lowering of 25(OH)D3 in blood serum of mice. Vitamin D3 deficiency was correlated with impaired mineral metabolism in bone tissue, indicating the development of secondary osteoporosis. A decrease in weight, length and diameter (diaphysis, proximal metaepiphysis) of tibia in diabetic animals was observed as compared with control. Diabetes caused hypocalcemia, hypophosphatemia and increased enzymatic activity of alkaline phosphatase (ALP) and its isoenzymes in serum. This changes were accompanied by the impairments of vitamin D3 25-hydroxylase isoforms (CYP27A1 and CYP2R1) expression, which are the main enzymes of cholecalciferol biotransformation to 25(OH)D3 - precursor of hormonally active form of vitamin D3. A decrease in bone resorption processes was established after vitamin D3 administration as it is evident from normalization of bone morphometrical parameters and mineral metabolism in diabetic mice. Vitamin D3 ability to counter diabetes-induced alterations in bone tissue can be ascribed, at least in part, to its positive effects on the formation of vitamin D3 hormonally active forms.

Association between bone mineral density and type 1 diabetes mellitus: a meta-analysis of cross-sectional studies

A few studies have investigated the relationship between type 1 diabetes mellitus (T1DM) and bone mineral density (BMD) values. This meta-analysis was performed to explore differences between T1DM and healthy individuals in BMD values measured at five bone sites.We searched the database of PubMed for cross-sectional studies about the association of T1DM and BMD, and a meta-analysis was conducted.The results suggested significant association between T1DM and decreased BMD values of total body. The pooled mean differences (MDs) were -0.06 [95% confidence interval (CI): -0.11, -0.01] for all people. As for the association between T1DM and spine BMD values, the pooled MDs were -0.04 (95% CI: -0.07, -0.01) for males and -0.03 (95% CI: -0.06, 0.00) for females <20 years old. As for femur BMD values, the pooled MDs were -0.06 (95% CI: -0.13, 0.00) for all people, -0.03 (95% CI: -0.06, -0.01) for females and -0.04(95% CI: -0.05, -0.02) for males. As for hip BMD values, the pooled MDs were -0.06 (95% CI: -0.08, -0.04) for females. As for forearm BMD values, the pooled MDs were -0.01 (95% CI: -0.02, 0.00) for females.The results of this meta-analysis suggest the overall association between T1DM and reduced BMD values. Notably, the influence of T1DM on BMD seems to depend on gender or patient's age. Reduced BMD values may occur early after T1DM diagnosis. Future clinical and basic research studies are needed to further understand the mechanisms of decreased BMD values in T1DM patients.

The implication of vitamin D and autoimmunity: a comprehensive review

Historically, vitamin D has been associated with the regulation of bone metabolism. However, increasing evidence demonstrates a strong association between vitamin D signaling and many biological processes that regulate immune responses. The discovery of the vitamin D receptor in multiple immune cell lineages, such as monocytes, dendritic cells, and activated T cells credits vitamin D with a novel role in modulating immunological functions and its subsequent role in the development or prevention of autoimmune diseases. In this review we, discuss five major areas in vitamin D biology of high immunological significance: (1) the metabolism of vitamin D; (2) the significance of vitamin D receptor polymorphisms in autoimmune diseases, such as multiple sclerosis, type 1 diabetes mellitus, and systemic lupus erythematosus; (3) vitamin D receptor transcriptional regulation of immune cell lineages, including Th1, Th17, Th2, regulatory T, and natural killer T cells; (4) the prevalence of vitamin D insufficiency/deficiency in patients with multiple sclerosis, type 1 diabetes mellitus, and systemic lupus erythematosus; and finally, (5) the therapeutic effects of vitamin D supplementation on disease severity and progression.

A meta-analysis of association of vitamin D receptor BsmI gene polymorphism with the risk of type 1 diabetes mellitus

Association between vitamin D receptor (VDR) BsmI (rs1544410) gene polymorphism and the risk of type 1 diabetes mellitus (T1DM) from the published reports are still conflicting. This study was conducted to evaluate the relationship between VDR BsmI gene polymorphism and the risk of T1DM using meta-analysis method. The association studies were identified from PubMed, and Cochrane Library on 1 December 2013, and eligible investigations were included and synthesized using meta-analysis method. Twenty-three reports were recruited into this meta-analysis for the association of VDR BsmI gene polymorphism with T1DM susceptibility. In overall populations, bb genotype was associated with T1DM, but the B allele and BB genotype were not. In Asians and Latino population, B allele and bb genotype were associated with TIDM risk, but BB genotype was not. In Caucasians, VDR BsmI gene polymorphism was not associated with the T1DM risk. In Africans, B allele and BB genotype were associated with T1DM risk, but the bb genotype was not. However, the sample size for Latino population and Africans was small. In conclusion, VDR BsmI B allele, bb genotype was associated with T1DM risk in Asians, and bb genotype was associated with T1DM risk in overall populations. However, more studies should be conducted to confirm it.

Associations between two polymorphisms (FokI and BsmI) of vitamin D receptor gene and type 1 diabetes mellitus in Asian population: a meta-analysis

Background

Vitamin D receptor (VDR) gene polymorphisms are possibly involved in the development of type 1 diabetes mellitus (T1DM). However, the results to date have been inconclusive. We performed a meta-analysis to examine the association between 2 polymorphisms (FokI and BsmI) of the VDR gene and T1DM in the Asian population.

Methods

Literature was retrieved from PubMed, Web of Science, CBM, Embase and Chinese databases. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a random or fixed effect model.

Results

In total, 20 papers (BsmI: 13 studies; FokI: 13 studies) were included. In contrast to the FokI polymorphism, the BsmI polymorphism was associated with an increased risk of T1DM in the Asian population (OR = 1.47, 95% CI = 1.13–1.91, P = 0.004 for B vs. b). Upon stratification by regional geography, an increased risk of T1DM in association with the BsmI polymorphism was observed in the East Asian population (OR = 1.97, 95% CI = 1.38–2.83, P<0.001 for B vs. b), whereas the FokI polymorphism was associated with an increased risk of T1DM in the West Asian population (OR = 1.45, 95% CI = 1.12–1.88, P = 0.004 for F vs. f).

Conclusions

Our meta-analysis suggests that the BsmI polymorphism may be a risk factor for susceptibility to T1DM in the East Asian population, and the FokI polymorphism is associated with an increased risk of T1DM in the West Asian population. However, because the study size was limited, further studies are essential to confirm our results.

The role of vitamin d deficiency in the incidence, progression, and complications of type 1 diabetes mellitus

The "nonclassic" role of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been recently widely recognized. In type 1 diabetes mellitus (T1D), it plays an immunomodulatory role through the vitamin D receptor (VDR) present on pancreatic and immune cells. Specific VDR allelic variants have been associated with T1D in many countries. Furthermore, vitamin D deficiency has been prevalent in T1D, and the seasonal and latitude variability in the incidence of T1D can be partly explained by the related variability in vitamin D level. In fact, retrospective studies of vitamin D supplementation during pregnancy or infancy showed a lower incidence of T1D. We will review the different mechanisms of the vitamin D protective effect against insulitis and present the available data on the role of vitamin D deficiency in the control, progression, and complications of T1D.

Polymorphisms in the vitamin D receptor gene and type 1 diabetes mellitus risk: an update by meta-analysis

Four well known polymorphisms (BsmI, FokI, ApaI, TaqI) in the VDR gene have been implicated in susceptibility to type 1 diabetes mellitus (T1DM), but the results to date have been inconclusive. The aim of this study was to investigate the association between polymorphisms in the VDR gene and T1DM risk by meta-analysis. A total of 57 case-control studies in 26 published studies were included. The results indicated that the BsmI polymorphism is associated with increased risk of T1DM (BB+Bb vs. bb: OR=1.30, 95% CI=1.03-1.63), while the FokI, ApaI and TaqI polymorphisms were not. In the subgroup analysis by ethnicity, the increased risk of T1DM remained in the Asian subgroup for the BsmI polymorphism; whereas no significant association was found in other populations for other polymorphisms. Results from the current study suggest that the BsmI polymorphism is associated with increased risk of T1DM, especially in Asians. Further studies are needed to confirm our results.