Quantitative assessment of the associations between four polymorphisms (FokI, ApaI, BsmI, TaqI) of vitamin D receptor gene and risk of diabetes mellitus

Association between vitamin D receptor polymorphisms and diabetic retinopathy in Uygur Chinese with type 2 diabetes

PURPOSE

This study was to investigate the potential association between vitamin D receptor(VDR) gene polymorphisms and the risk of diabetic retinopathy(DR) in the Uygur population in China, focusing on four specific VDR gene single nucleotide polymorphisms(SNPs) as candidate SNPs.

METHODS

The study genotyped a total of 151 DR patients and 130 healthy controls from the Uygur population using the single-base terminal extension (SNaPshot) method for four VDR gene SNPs: rs1544410, rs7975232, rs2228570, and rs731236. Hardy-Weinberg equilibrium was assessed using the χ2 test. Genotype frequencies were determined by directly counting the genotypes and correlating them with population data. The χ2 test was utilized to compare allele and genotype frequencies between patients and controls.

RESULTS

Compared to the healthy control group, the study observed a significantly higher frequency of the "TT" genotype at rs1544410 in the DR group. Additionally, within the non-proliferative diabetic retinopathy (NPDR) group, a significantly higher frequency of the "AA" genotype at rs7975232 was noted. No significant differences were found in the comparison of all haplotypes between patients and controls.

CONCLUSIONS

The study concluded that the rs1544410 polymorphism is associated with DR, and the rs7975232 polymorphism is associated with susceptibility to NPDR in the Uygur population in China.

Association Among Vitamin D Receptor Gene Polymorphisms, Metabolic Control, and Inflammatory Markers in Type 2 Diabetes: A Systematic Review and Meta-Analysis

CONTEXT

Single-nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) contribute to inadequate metabolic profiles in individuals with type 2 diabetes mellitus (T2DM).

OBJECTIVE

We sought to elucidate the relationship among SNPs in the VDR and markers for glycemic control, lipid profile, and inflammation in individuals with T2DM.

DATA SOURCES

We performed a systematic search in the MEDLINE (via PubMed), EMBASE, and SCOPUS databases in July 2021 and updated the search in October 2023.

DATA EXTRACTION

6 observational studies were selected from the databases, and 1 study was included after checking the reference list. Two authors independently completed the selection and data extraction of studies and population characteristics, the prevalence of SNPs in the VDR, genotyping methods, and laboratory findings, and performed summary statistics of the results.

DATA ANALYSIS

The meta-analyses were performed on 5 studies including 1198 adults with T2DM. The duration of the diabetes diagnosis ranged from 5.0 to 14.7 years. A random-effects model was used to pool the results using a 2-tailed (P < .05). Effect sizes were reported as standardized mean differences (SMDs) and 95% confidence intervals (CIs). Four SNPs in the VDR were identified (Fokl, BsmI, Taql, and Apal) by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The Fokl SNP was identified in 5 studies and associated with a higher percentage of glycated hemoglobin (HbA1c%) (SMD,  0.41 [95% CI, 0.15-0.67]). The Bsml in 4 studies was associated with higher triacylglycerol (SMD, 0.21 [95% CI, 0.03-0.38]). The Taql SNP was identified in 2 studies and did not show any associations, and the Apal SNP was identified in only 1 study and was not analysed in the meta-analysis.

CONCLUSIONS

Although the studies identified 4 SNPs in the VDR, the results of the meta-analysis allowed us to infer only the association of the SNPs Fokl and Bsml with increased %HbA1c and triacylglycerol levels, respectively, in individuals with T2DM.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42021268152.

Investigating the association between FOK1 polymorphism in the vitamin D receptor (VDR) gene and type 2 diabetes prevalence: A comprehensive analysis

There is mounting evidence that suggests vitamin D insufficiency may have a role in the emergence of type 2 diabetes. Additionally, as VDR mediates the actions of vitamin D, variants in its sequence could have implications in this disease. One of these polymorphisms, Fok1 (rs2228570), has been demonstrated to generate changes in the receptor's structure, causing a shorter protein. The purpose of this research is to establish a potential association between the Fok1 polymorphism and DM2. To achieve such goal, a comprehensive study of this SNP was conducted using functional in-silico analysis and a systematic review with meta-analysis. Additionally, an examination of VDR gene expression in patients with diabetes compared to controls was performed in order to investigate possible differences in expression levels. Our expression analysis showed that VDR has no differential expression between these two groups. To study its functional consequences and stability, different tools were combined, without consistent results. Finally, our systematic review and meta-analysis showed that theFok1 variant was not significantly associated with the DM2 prevalence. This extensive analysis did not provide support for an association between the presence of Fok1 polymorphism and DM2. This result aligns with some previous studies but contrasts others that have reported both protective and risk factors.

Tru9I Variant as a Novel Genetic Marker for Vitamin D Deficiency in Alopecia Areata

Introduction

Alopecia areata (AA), is a common autoimmune nonscarring alopecia. Vitamin D is involved in various biological processes such as immune regulation, cellular growth, and specialization, as well as the maintenance of the hair cycle. We aimed to explore the impact of different Tru9I variant genotypes on serum vitamin D levels and vitamin D receptor (VDR) gene expression.

Methods

Case-control study that included 72 individuals diagnosed with AA, along with age and sex matched healthy controls of 72 individuals. Blood samples were obtained to measure Vitamin D level and VDR gene expression focusing on Tru9I variant genotypes.

Results

Our findings indicate, for the first time, a possible association between the "U" allele and low vitamin D levels, along with altered activity of the VDR gene as observed in patients with AA.

Conclusion

This suggests a complex causal relationship between genetic factors and vitamin D in AA. Interestingly, "u" allele was found to be significantly more prevalent in the healthy control group than in the patients group, raising the possibility of its protective mechanism against the development of this disease in healthy individuals.

La osteocalcina se asocia con la densidad mineral ósea y los polimorfismos del gen VDR en la diabetes tipo 1 y 2

Objetivos

El metabolismo óseo se encuentra alterado en la diabetes mellitus (DM). El objetivo de este estudio es evaluar la relación entre los marcadores de remodelado óseo (MRO), los polimorfismos en el gen receptor de la vitamina D (VDR) y la densidad mineral ósea (DMO) en la DM tipo 1 (T1D) y tipo 2 (T2D).

Métodos

Se incluyó a 165 pacientes (53 T1D y 112 T2D). La DMO se midió mediante absorciometría de rayos X de energía dual (DEXA). Se realizó un análisis de la osteocalcina (OC) en plasma, beta-CrossLaps (β-CTX), propéptido aminoterminal del procolágeno tipo 1 (P1NP) y los polimorfismos en el gen VDR.

Resultados

Se incluyó a 53 pacientes con T1D (41 años (31–48)) y 112 con T2D (60 años [51–66]). No se observaron diferencias estadísticamente significativas en relación a la DMO. Los pacientes con T1D presentaron niveles superiores de OC (p<0,001) y P1NP (p<0,001). Las áreas bajo la curva para la predicción de patología ósea para la OC fueron 0,732 (p=0,038) en T1D y 0,697 (p=0,007) en T2D. Se observó una relación estadísticamente significativa entre el alelo A de BsmI (p=0,03), el alelo A de ApaI (p=0,04) y el alelo C de Taql (p=0,046) y una menor DMO. Así mismo, se encontró una correlación significativa entre los niveles elevados de OC y el alelo G de BsmI (p=0,044), el alelo C de ApaI (p=0,011), el alelo T de Taql (p=0,006) y el alelo C de FokI (p=0,004).

Conclusiones

El elevado valor predictivo negativo del punto de corte de la OC indica que la OC podría ser útil a la hora de descartar el riesgo de pérdida ósea, lo que permitiría diseñar un tratamiento personalizado para prevenir dicha patología.

Osteocalcin associates with bone mineral density and VDR gene polymorphisms in type 1 and type 2 diabetes

Objectives

Bone metabolism is impaired in diabetes mellitus (DM). Our objective is to evaluate the association of bone turnover markers (BTM) and vitamin D receptor (VDR) gene polymorphisms with bone mineral density (BMD) in DM type 1 (T1D) and DM type 2 (T2D).

Methods

A total of 165 patients (53 T1D and 112 T2D) were enrolled. BMD was measured by dual-energy X-ray absorptiometry (DEXA). Plasma osteocalcin (OC), beta-CrossLaps (β-CTX) and N-amino terminal propeptide of type I collagen (P1NP) and VDR gene polymorphisms were evaluated.

Results

Participants were 53 T1D (41 years [31-48]) and 112 T2D (60 years [51-66]). BMD were not statistically different between the groups. OC (p<0.001) and P1NP levels (p<0.001) were higher in patients with T1D. The areas under the curve for the prediction of bone pathology were 0.732 (p=0.038) for OC in T1D and 0.697 (p=0.007) in T2D. A significant association was found between lower lumbar BMD and the A allele of BsmI (p=0.03), the A allele of ApaI (p=0.04) and the allele C of the Taql (p=0.046). Also, a significant correlation was found with higher OC levels and the G allele of BsmI (p=0.044), C allele of ApaI (p=0.011), T allele of Taql (p=0.006) and with C allele of FokI (p=0.004).

Conclusions

The high negative predictive value of the cut-off point for OC suggests that could be useful in excluding the risk suffering bone loss, allowing offering a personalized clinical approach to prevent this pathology.

The effect of BsmI (rs1544410) single nucleotide polymorphism of vitamin D receptor (VDR) on insulin resistance in healthy children and adolescents: a cross-sectional study

The increasing prevalence of metabolic syndrome, type 2 diabetes, and insulin resistance are driven by complex interactions between genetic and environmental factors. One of the single nucleotide polymorphisms (SNPs) in the VDR gene associated with vitamin D levels is the rs1544410 SNP. This study examined the association of the rs1544410 polymorphism with insulin resistance to predict and screen for possible association with type 2 diabetes and target these individuals for appropriate treatment. This cross-sectional study examined 270 children and adolescents aged 9 to 18 years. Anthropometric and biochemical parameters were determined. Insulin resistance/sensitivity was determined using Quicki, HOMA-IR, MacAuley, Revised MacAuley, Bennetts, FIRI and insulin-to-glucose ratio. The BsmI single nucleotide polymorphism (rs1544410) was determined using the PCR-RFLP method after extracting DNA from peripheral blood collected from fasted subjects, and the resulting data were analyzed using SPSS software and statistical tests.According to linear regression analysis, a significant difference was found in Insulin to glucose ratio, FIRI and HOMA-IR indices between Bb / bb and BB genotypes and it was observed that individuals with BB genotype polymorphism of BsmI vitamin D receptor gene, after Adjustment of age, sex, BMI are at greater risk for insulin resistance and type 2 diabetes.This study demonstrated that those with the BB genotype of VDR BsmI polymorphism were at higher risk for insulin resistance and developing type 2 DM.

Level of biochemical parameters in patients with type 2 diabetes mellitus depending on the genotype of the FokI polymorphism in the vitamin D3 receptor (VDR gene)

OBJECTIVES

Diabetes mellitus type 2 (T2DM) is a multifactorial and polygenic disorder characterised by chronic hyperglycaemia accompanied by impaired lipid, carbohydrate, and protein metabolism. The disease is associated with several genetic polymorphisms, including the FokI polymorphism in the vitamin D receptor (VDR) gene.

METHODS

We conducted a study of 327 probands (191 T2DM patients, 136 controls), with a mean age 65.06 (SD ± 10.88) years of patients with T2DM and 58.89 (SD ± 6.59) years in the healthy probands. We investigated the association between FokI polymorphism and biochemical parameters in T2DM patients in the Slovak population. Anthropometric measurements, biochemical, and genetic analysis were statistically evaluated by Statistica ver.13 software using t-tests.

RESULTS

Biochemical analysis confirmed significantly higher mean values of total cholesterol (TC), triglyceride (TG), glucose (GLU), and uric acid (UA) (p < 0.001) in T2DM probands and statistically significantly lower values of high-density lipoprotein (HDL), cholesterol and vitamin D (p < 0.001). Allele frequencies and genotype distributions of the FokI (rs2228570) polymorphism were not significantly different between T2DM patients and controls (p = 0.909). Patients with T2DM and TT genotype had the highest glucose level of 11.39 (SD ± 2.32) uU/ml (p < 0.001).

CONCLUSION

Our study did not provide evidence for an association of the investigated FokI polymorphism of the VDR gene with T2DM in the Slovak population. Further research is needed to evaluate the impact of single nucleotide polymorphisms (SNPs) in the VDR gene, focusing on related genetic analyses in a larger T2DM cohort.

Role of FokI rs2228570 and Tru9I rs757343 Polymorphisms in the Mortality of Patients Infected with Different Variants of SARS-CoV-2

BACKGROUND AND AIM

Low vitamin D levels are associated with the severity of coronavirus disease 19 (COVID-19). Vitamin D receptor gene polymorphisms, such as Tru9I rs757343 and FokI rs2228570, have been suggested to be potential risk factors for severe COVID-19 outcomes. This study investigated how Tru9I rs757343 and FokI rs2228570 polymorphisms influenced the mortality rate of COVID-19 in relation to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants.

METHODS

The polymerase chain reaction-restriction fragment length polymorphism assay was used to genotype Tru9I rs757343 and FokI rs2228570 genotypes in 1,734 recovered and 1,450 deceased patients.

RESULTS

Our results demonstrated that the high mortality rate was correlated with FokI rs2228570 TT genotype in all three variants but was much higher in the Omicron BA.5 variant than in the Alpha and Delta variants. Furthermore, in patients infected with the Delta variant, FokI rs2228570 CT genotype was more highly correlated with the mortality rate compared to other variants. Thus, a high mortality rate was correlated with the Tru9I rs757343 AA genotype in the Omicron BA.5 variant, whereas this relationship was not observed in the other two variants. The T-A haplotype was related to COVID-19 mortality in all three variants, but its effect was more pronounced in the Alpha variant. Moreover, the T-G haplotype was significantly associated with all three variants.

CONCLUSION

Our findings showed that the effects of Tru9I rs757343 and FokI rs2228570 polymorphisms were related to SARS-CoV-2 variants. However, further studies are still required to validate our findings.

Vitamin D deficiency and vitamin D receptor FokI polymorphism as risk factors for COVID-19

BACKGROUND

Given the sparse data on vitamin D status in pediatric COVID-19, we investigated whether vitamin D deficiency could be a risk factor for susceptibility to COVID-19 in Egyptian children and adolescents. We also investigated whether vitamin D receptor (VDR) FokI polymorphism could be a genetic marker for COVID-19 susceptibility.

METHODS

One hundred and eighty patients diagnosed to have COVID-19 and 200 matched control children and adolescents were recruited. Patients were laboratory confirmed as SARS-CoV-2 positive by real-time RT-PCR. All participants were genotyped for VDR Fok1 polymorphism by RT-PCR. Vitamin D status was defined as sufficient for serum 25(OH) D at least 30 ng/mL, insufficient at 21-29 ng/mL, deficient at <20 ng/mL.

RESULTS

Ninety-four patients (52%) had low vitamin D levels with 74 (41%) being deficient and 20 (11%) had vitamin D insufficiency. Vitamin D deficiency was associated with 2.6-fold increased risk for COVID-19 (OR = 2.6; [95% CI 1.96-4.9]; P = 0.002. The FokI FF genotype was significantly more represented in patients compared to control group (OR = 4.05; [95% CI: 1.95-8.55]; P < 0.001).

CONCLUSIONS

Vitamin D deficiency and VDR Fok I polymorphism may constitute independent risk factors for susceptibility to COVID-19 in Egyptian children and adolescents.

IMPACT

Vitamin D deficiency could be a modifiable risk factor for COVID-19 in children and adolescents because of its immune-modulatory action. To our knowledge, ours is the first such study to investigate the VDR Fok I polymorphism in Caucasian children and adolescents with COVID-19. Vitamin D deficiency and the VDR Fok I polymorphism may constitute independent risk factors for susceptibility to COVID-19 in Egyptian children and adolescents. Clinical trials should be urgently conducted to test for causality and to evaluate the efficacy of vitamin D supplementation for prophylaxis and treatment of COVID-19 taking into account the VDR polymorphisms.

A meta-analysis suggests the association of reduced serum level of vitamin D and T-allele of Fok1 (rs2228570) polymorphism in the vitamin D receptor gene with celiac disease

Purpose

As an immune-modulator, vitamin D is known to regulate immune response and is implicated in disease pathogenesis. Celiac disease (CD) is a systemic autoimmune disease and susceptibility conferred by vitamin D metabolism is under investigation. Studies on the association of vitamin D metabolism and genetic polymorphisms are expected to explain CD pathogenesis. We performed a systematic review-based meta-analysis to investigate the 25(OH)D serum levels and susceptibility conferred by the genetic variants of VDR in CD.

Methods

Systematic review was conducted through a web-based literature search following stringent study inclusion-exclusion criteria. The Newcastle-Ottawa Scale and GRADE tools were used to assess the quality of evidence in studies and the study outcome. Cohen's κ value was estimated to access the reviewer's agreement. RevMan 5.4.1 was used to perform the meta-analyses. Weighted mean difference and Meta p-value was assessed for 25(OH)D serum levels. Meta-odds ratio and Z-test p-value were evaluated to estimate the allelic susceptibility of VDR variants.

Results

A total of 8 out of 12 studies were evaluated for "25(OH)D" serum level, while four studies were found eligible for SNPs (Bsm1, Apa1, Fok1, and Taq1) of VDR. Significantly higher levels [WMD = 5.49, p < 0.00001] of 25(OH)D were observed in healthy controls than in patients with CD. rs2228570-T (Fok1) [Meta-OR = 1.52, p = 0.02] was confirmed to be predisposing allele for CD.

Conclusion

Reduced serum level of 25(OH)D and association of Fok1 T-allele of VDR confirmed in this study plays a critical role in immunomodulation and maintaining barrier integrity, which is majorly implicated in CD.

The vitamin D receptor gene variants, ApaI, TaqI, BsmI, and FokI in diabetic foot ulcer and their association with oxidative stress

INTRODUCTION

To date, numerous disorders have been linked to vitamin D deficiency. Several lines of evidence indicate a relationship between vitamin D deficiency and the risk of developing type 2 diabetes. It has been postulated that vitamin D may influence insulin activity, which can predispose individuals to develop type 2 diabetes.

MATERIALS AND METHODS

In this case-control study, 262 patients with definite type 2 diabetes were enrolled, considering whether they were being affected by diabetic foot ulcers or not. The plasma levels of vitamin D and homocysteine were measured using ELISA, and the PCR-RFLP technique was utilized to determine allele and genotype frequencies. The antioxidant capacity of plasma samples of diabetic patients was analyzed using the thiobarbituric acid reactive substance (TBARS) and ferric reducing ability of plasma (FRAP) assays.

RESULTS

The obtained results demonstrated no significant difference in the frequency of TaqI and BsmI polymorphisms between the case and control groups. However, the frequency of genotypes and alleles of the ApaI polymorphism in the VDR gene significantly differed between the case and control groups. A significant correlation was found between ApaI polymorphism and oxidative stress, as patients with the GG genotype had lower levels of TBARS than those with other genotypes. Furthermore, in the case group, patients with the CC genotype of BsmI showed a significant decrease in TBARS levels.

DISCUSSION

It seems that the plasma levels of vitamin D do not differ between patients with or without diabetic foot ulcers; however, the presence of some VDR gene polymorphisms is thought to be involved in the development of diabetic foot ulcers via increasing oxidative stress.

The relationship between vitamin D receptor gene polymorphisms and periodontitis in turkish individuals with type 2 diabetes mellitus

Background and Aim

Vitamin D receptor (VDR) gene polymorphisms have been implicated in the pathogenesis of many diseases, such as periodontitis and diabetes mellitus (DM). The present study aimed to evaluate the distributions of VDR polymorphisms in diabetic individuals with healthy periodontium (DMH), diabetic individuals with periodontitis (DMP), nondiabetic individuals with healthy periodontium (H), and nondiabetic individuals with periodontitis (P).

Material and Methods

A total of 200 individuals (DMH = 40, DMP = 60, H = 40, and P = 60) were recruited. All clinical periodontal parameters, demographical, and biochemical variables were recorded. Blood samples were collected, and genomic DNA was isolated by Purelink® Genomic DNA Mini Kit. Genotyping of VDR polymorphisms ApaI, BsmI, FokI, and TaqI were determined by real-time polymerase chain reaction (PCR) using allele-specific probes.

Results

The distribution of the BsmI variant showed differences between DMH and H groups (P = 0.034). In addition, carrying the GG genotype (OR = 0.317; 95% CI = 0.126-0.797; P = 0.013) and the G allele (OR = 2.373; 95% CI = 1.203-4.681; P = 0.012) increased the risk of type 2 DM. Moreover, it was determined that the frequency of CC genotype of FokI variant was higher in DMP compared to DMH (P = 0.046). It was determined that having the CC genotype (OR = 2.706; 95% CI = 1.185-6.176; P = 0.017) and the C allele (OR = 1.917; 95% CI = 0.995-3.694; P = 0.049) increased the risk of periodontitis among diabetic individuals. No differences were detected among groups in the genotype and allele distributions of ApaI and TaqI variants (P > 0.05).

Conclusions

The present study showed that the BsmI variant was a risk factor for DM among periodontally healthy individuals and the FokI variant for periodontitis among diabetic individuals.

Evaluation of association studies and a systematic review and meta-analysis of VDR polymorphisms in type 2 diabetes mellitus risk

ABSTRACT

Numerous original studies and 4 published meta-analyses have reported the association between the Vitamin D receptor (VDR) BsmI, FokI, ApaI, and TaqI polymorphisms and type 2 diabetes mellitus (T2DM) risk. However, the results were inconsistent. Therefore, an updated meta-analysis was performed to further explore these issues.To further explore the association between the VDR BsmI, FokI, ApaI, and TaqI polymorphisms and T2DM risk.PubMed, EMBASE, Scopus, and Wanfang databases were searched. The following search strategy were used: (VDR OR vitamin D receptor) AND (polymorphism OR variant OR mutation) AND (diabetes OR mellitus OR diabetes mellitus). Pooled crude odds ratios with 95% confidence intervals were applied to evaluate the strength of association in 5 genetic models. Statistical heterogeneity, the test of publication bias, and sensitivity analysis were carried out using the STATA software (Version 12.0). To evaluate the credibility of statistically significant associations, we applied the false-positive report probabilities (FPRP) and Bayesian false discovery probability (BFDP) test.Overall, the VDR BsmI polymorphism was associated with a significantly decreased T2DM risk in Asians; the VDR FokI polymorphism was associated with a significantly decreased T2DM risk in Asians, African countries, and Asian countries; the VDR ApaI polymorphism was associated with a significantly decreased T2DM risk in Caucasians and North American countries.On the VDR ApaI polymorphism, a significantly increased T2DM risk was found in a mixed population. However, when we further performed a sensitivity analysis, FPRP, and BFDP test, less-credible positive results were identified (all FPRP > 0.2 and BFDP > 0.8) in any significant association.In summary, this study strongly indicates that all significant associations were less credible positive results, rather than from true associations.

Vitamin D receptor gene polymorphisms in Sudanese children with type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a T cell mediated autoimmune disease. Vitamin D was found to suppress the incidence of diabetes when bind to its receptor (VDR), probably by suppressing T cell activations. Thus the VDR gene polymorphism may have an impact on pathophysiology of this disease. Since there was no consistent association between VDR polymorphisms and the risk of T1DM, this study aimed to investigate a VDR gene polymorphism in Sudanese children with T1DM. We examined the VDR gene Bsm1 (rs1544410), Apa1 (rs7975232), and Taq1 (rs731236) single nucleotide polymorphisms in 174 children with T1DM, and 56 children as control, and the association of these polymorphisms with the diabetic control. Among study patients, the majority (85.63%) of diabetic patients reported metabolically poor controlled (HbA1c > 8%). As compared with the control, patients with T1DM presented more commonly with Bsm1 B allele (p = 0.001; OR 0.283; 95% CI 0.131–0.609) and Taq1 T allele (p = 0.05; OR 2.429; 95% CI 1.073–5.496). Apa1 A allele was less common in patients with T1DM without statistical difference (p = 0.862; OR 1.085; 95% CI 0.546–2.156). Our study suggests that, Bsm1 and Taq1 polymorphisms of the VDR gene associated with the prevalence of T1DM.

The Role of Apa-I Vitamin D Receptor Gene Polymorphism in Type 2 Diabetes Mellitus

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a chronic metabolic syndrome caused by insulin secretion abnormalities, insulin action, or both. Gene polymorphism is a risk factor of T2DM. AIM: This study aims to see the role of Apa-I Vitamin D receptor gene polymorphism on T2DM. METHODS: This study was an analytic observational with a case–control approach, consisting of 70 T2DM patients and 70 healthy subjects as a control. Genotyping of the Apa-I Vitamin D receptor gene polymorphism was performed using the polymerase chain reactions-restriction fragment length polymorphisms method. The role of the Apa-I Vitamin D receptor gene polymorphism and the risk of T2DM were analyzed using the Chi-square test. RESULTS: The results showed that there was a significant association between codominant (TT genotype); dominant; recessive models of the Apa-I Vitamin D receptor gene polymorphism with the risk of T2DM (p < 0.05; odds ratio [OR] = 0.204, 95% confidence interval [CI] = 0.063–0.662; OR = 0.337, 95% CI = 0.113–1.004; OR = 0.367, 95% CI = 0.180–0.747, respectively), but not in codominant (GT genotype) and over-dominant models (p > 0.05). CONCLUSION: This study shows a role of the codominant (TT genotype); dominant; recessive models of the Apa-I Vitamin D receptor gene polymorphism on T2DM, but not in codominant (GT genotype) and over-dominant models.

Vitamin D pathway-related gene polymorphisms and their association with metabolic diseases: A literature review

PURPOSE

Given that the relationship between vitamin D status and metabolic diseases such as obesity and type 2 diabetes (T2D) remains unclear, this review will focus on the genetic associations, which are less prone to confounding, between vitamin D-related single nucleotide polymorphisms (SNPs) and metabolic diseases.

METHODS

A literature search of relevant articles was performed on PubMed up to December 2019. Those articles that had examined the association of vitamin D-related SNPs with obesity and/or T2D were included. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data. In total, 73 articles were included in this review.

RESULTS

There is a lack of research focusing on the association of vitamin D synthesis-related genes with obesity and T2D; however, the limited available research, although inconsistent, is suggestive of a protective effect on T2D risk. While there are several studies that investigated the vitamin D metabolism-related SNPs, the research focusing on vitamin D activation, catabolism and transport genes is limited. Studies on CYP27B1, CYP24A1 and GC genes demonstrated a lack of association with obesity and T2D in Europeans; however, significant associations with T2D were found in South Asians. VDR gene SNPs have been extensively researched; in particular, the focus has been mainly on BsmI (rs1544410), TaqI (rs731236), ApaI (rs7975232) and FokI (rs2228570) SNPs. Even though the association between VDR SNPs and metabolic diseases remain inconsistent, some positive associations showing potential effects on obesity and T2D in specific ethnic groups were identified.

CONCLUSIONS

Overall, this literature review suggests that ethnic-specific genetic associations are involved. Further research utilizing large studies is necessary to better understand these ethnic-specific genetic associations between vitamin D deficiency and metabolic diseases.

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.

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.

The Role of Vitamin D Receptor Gene Polymorphisms in Colorectal Cancer Risk

Vitamin D deficiency has been associated with increased colorectal cancer (CRC) incidence risk and mortality. Vitamin D mediates its action through the binding of the vitamin D receptor (VDR), and polymorphisms of the VDR might explain these inverse associations. The aim of the study was the investigation of the relevance of rs731236; Thermus aquaticus I (TaqI), rs7975232; Acetobacter pasteurianus sub. pasteurianus I (ApaI), rs2228570; Flavobacterium okeanokoites I (FokI) and rs1544410, Bacillus stearothermophilus I (BsmI) polymorphisms of the VDR gene to colorectal carcinogenesis (CRC) and progression. Peripheral blood was obtained from 397 patients with early operable stage II/III (n = 202) and stage IV (n = 195) CRC. Moreover, samples from 100 healthy donors and 40 patients with adenomatous polyps were also included as control groups. Genotyping in the samples from patients and controls was performed using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP). A significant association was revealed between all four polymorphisms and cancer. Individuals with homozygous mutant (tt, aa, ff or bb) genotypes were more susceptible to the disease (p < 0.001). All of the mutant genotypes detected were also significantly associated with stage IV (p < 0.001), leading to significantly decreased survival (p < 0.001). Moreover, all four polymorphisms were significantly associated with KRAS (Kirsten ras oncogene) mutations and Toll-like receptor (TLR2, TLR4 and TLR9) genetic variants. In multivariate analysis, tt, aa and ff genotypes emerged as independent factors associated with decreased overall survival (OS) (p = 0.001, p < 0.001 and p = 0.001, respectively). The detection of higher frequencies of the VDR polymorphisms in CRC patients highlights the role of these polymorphisms in cancer development and progression.

Vitamin D Receptor Overexpression in β-Cells Ameliorates Diabetes in Mice

Vitamin D deficiency has been associated with increased incidence of diabetes, both in humans and in animal models. In addition, an association between vitamin D receptor (VDR) gene polymorphisms and diabetes has also been described. However, the involvement of VDR in the development of diabetes, specifically in pancreatic β-cells, has not been elucidated yet. Here, we aimed to study the role of VDR in β-cells in the pathophysiology of diabetes. Our results indicate that Vdr expression was modulated by glucose in healthy islets and decreased in islets from both type 1 diabetes and type 2 diabetes mouse models. In addition, transgenic mice overexpressing VDR in β-cells were protected against streptozotocin-induced diabetes and presented a preserved β-cell mass and a reduction in islet inflammation. Altogether, these results suggest that sustained VDR levels in β-cells may preserve β-cell mass and β-cell function and protect against diabetes.

Variants rs1544410 and rs2228570 of the vitamin D receptor gene and glycemic levels in adolescents from Northeast Brazil

Introduction

Objective: to verify the association of serum concentrations of 25-hydroxyvitamin D and glycemic levels with the genetic variants rs1544410 and rs2228570 of the VDR gene in adolescents from the Northeast region of Brazil. Materials and methods: a cross-sectional epidemiological study with 208 adolescents from public schools in the city of João Pessoa (Paraíba, Brazil) between 15 and 19 years of age. Blood samples were collected for DNA extraction and analysis of polymorphisms rs1544410 and rs2228570, as well as biochemical analyses (25-hydroxyvitamin D, parathyroid hormone, calcium and glycemia). Results: the mean age was 17.7 (± 1.14) years. Half of adolescents had sufficient serum levels of 25-hydroxyvitamin D and the other half had insufficient/deficient vitamin. The most frequent genotypic distribution was bb and Ff and of lesser frequency BB and ff. There was a significant relationship between the genotypes of rs1544410 and glycemia values (p = 0.049) in the relationships between the genotypes BBxbb (p = 0.012) and Bbxbb (p = 0.037); (p = 0.036, OR = 2.15, 95% CI = 1.05-4.41), and in the BB+Bb group analysis when compared to the bb (p = 0.025, OR = 1.89, 95% CI = 1.08-3.29) presented higher risk of glycemia above the median. On the other hand, when Bb+bb was analyzed in relation to BB, adolescents had a greater chance of blood glucose below the median (p = 0.025, OR = 0.66, CI = 0.47-0.95). Conclusion: this study showed a significant relation of glycemia with the distribution of rs1544410 polymorphism genotypes.

Diminished 25-OH vitamin D3 levels and vitamin D receptor variants are associated with susceptibility to type 2 diabetes with coronary artery diseases

Background

Role of plasma vitamin D and genetic variants of its receptor (VDR) in susceptibility to different diseases has been documented. Various studies in different populations have been highlighted strong associations with diabetes and cardiovascular diseases. Vitamin D deficiency has been linked with the development of type 2 diabetes (T2D) and the onset of coronary artery diseases (CAD). However, the role of vitamin D in predisposition to CAD in patients with T2D is ill‐defined.

Materials and Methods

We enrolled 674 Chinese T2D patients, and based on clinical phenotype, patients were further categorized into patients with (n = 138) or without coronary artery disease (n = 536). Five hundred twenty‐one healthy subjects from similar geographical areas, free from diabetic or coronary disorders, were enrolled as controls. Serum levels of 25‐OH vitamin D were quantified by ELISA. Common VDR (FokI, TaqI, BsmI, and ApaI) polymorphisms were genotyped by polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP).

Results

Patients with T2D displayed lower levels of 25‐OH vitamin D compared with healthy controls. Furthermore, T2D patients with CAD clinical phenotype had the lowest levels of vitamin D. Prevalence of FokI and TaqI mutants was significantly higher in diabetic patients when compared to controls. Interestingly, Tt genotype was more frequent in the artery disease group in comparison with T2D patients without heart involvement. Combined analysis of VDR polymorphisms and serum levels of vitamin D revealed a significant role in predisposition to T2D with or without CAD.

Conclusions

Lower vitamin D levels and variants of VDR polymorphisms (FokI and TaqI) are associated with susceptibility to T2D and clinical manifestation.

Association of Vitamin D receptor gene BsmI polymorphism with type 2 diabetes mellitus in Pakistani population

Background

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder with strong genetic components. The reported association of vitamin D receptor (VDR) gene polymorphisms varies among ethnic groups.

Objectives

The present study was conducted to determine association of vitamin D receptor gene BsmI (rs1544410 A>G) polymorphism with type 2 diabetes mellitus in Pakistani population.

Methods

Blood samples were collected from 150 T2DM patients and 100 non-diabetic engaged by convenient sampling method. After collection of demographic data, assessment of fasting glucose (FG), vitamin D, HbA1c, renal function tests, liver function tests and lipid profile was done. Candidate gene polymorphism was analyzed by DNA amplification with polymerase chain reaction and endonuclease digestion.

Results

Biochemical parameters were significantly different among case and control groups. Associations of BsmI genotype with T2DM, related complications and biochemical variables were not significant.

Conclusion

The current study did not provide evidence for the association of VDR gene BsmI polymorphism with T2DM in Pakistani population.

Lower Vitamin D Levels, but Not VDR Polymorphisms, Influence Type 2 Diabetes Mellitus in Brazilian Population Independently of Obesity

Background and Objectives: Vitamin D levels have been associated with a diversity of diseases, including obesity. Vitamin D presents a pleiotropic action, and can regulate insulin secretion and inflammatory responses. Vitamin D receptor (VDR) gene polymorphisms are involved in the gene expression regulation and have been associated with type 2 diabetes mellitus (T2DM). This study aimed to evaluate the association between the polymorphisms ApaI (rs7975232), BsmI (rs1544410), FokI (rs10735810), and TaqI (rs731236) in the VDR gene in people diagnosed with T2DM, and plasma 25-hydroxivitamin D levels [25(OH)D]. Materials and Methods: A total of 101 T2DM patients and 62 gender, age, and body mass index (BMI) matched non-diabetic controls were included in this study. Molecular analyzes were performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The plasma 25(OH)D levels were measured by high performance liquid chromatography. Results: The plasma 25(OH)D levels were lower in T2DM patients (17.2 (16.6) ng/mL) when compared with the control subjects (30.8 (16.2) ng/mL, p < 0.0001), independently of obesity status. We found no difference between genotypic and allelic frequencies of the VDR polymorphisms when comparing the T2DM group and control group (p > 0.05 for all), and did not show any association with plasma 25(OH)D levels. Conclusions: These results suggest that T2DM is associated with lower plasma 25(OH)D levels, which are not related to BMI and VDR gene polymorphisms.

Vitamin D receptor rs7975232, rs731236 and rs1544410 single nucleotide polymorphisms, and 25-hydroxyvitamin D levels in Egyptian children with type 1 diabetes mellitus: effect of vitamin D co-therapy

Purpose: We aimed to examine the possible association role of vitamin D and vitamin D receptor (VDR) single nucleotide polymorphisms (SNPs) in type 1 diabetes mellitus (T1DM) development, glycemic control and complications among a cohort of Egyptian children. Subjects and methods: A prospective case-control study has been conducted on 50 Egyptian children with T1DM who were comparable with 50 controls. Vitamin D and HbA1c were measured. VDR-SNPs [ApaI (rs7975232), TaqI (rs731236) and BsmI (rs1544410)] detection was done by polymerase chain reaction through restriction fragment length polymorphism (PCR-RFLP) technique. Vitamin D supplements were given to the included T1DM children with low vitamin D and reassessments of both HbA1c% and 25(OH)D serum levels were performed in those children three months later. Results: Eighty percent of the included diabetic patients have poor glycemic control. Vitamin D was deficient in 68% and insufficient in 16% of diabetic patients. Significant improvements in both vitamin D and glycemic status among T1DM children, who have low vitamin D and received vitamin D supplementations. There were significantly negative correlations between serum levels of vitamin D with both HbA1c % (r= -0.358, P˂0.05) and daily insulin dose (r=-0.473, P˂0.05). Compared with controls, T1DM children presented more commonly with ApaI a allele (OR: 2.87; 95%CI: 1.39-5.91, P˂0.05) and BsmI b allele (OR: 4.38; 95%CI: 2.30-8.33, P˂0.05). TaqI t allele wasn't significantly differing among patients and controls (P˃0.05). Aa+aa and Bb+bb genotypes were significantly higher among T1DM vs the controls (OR: 3.08;, 95%CI: 1.33-7.15, P˂0.05 and OR: 9.33; 95%CI: 3.61-24.17, P˂0.05respectively). Conclusion: ApaI and BsmI were associated with risk of T1DM development among Egyptian children. Low vitamin D status was frequently occurring among T1DM with significant improvement in the glycemic control of such children when adding vitamin D supplements to the standard insulin therapy.

Vitamin D and Type I Diabetes

Vitamin D is a fat-soluble vitamin that plays an important role in bone metabolism but is also endowed with the capability of modulating inflammatory and immune function. Recent studies reported a relationship between low vitamin D levels and several autoimmune diseases such as Type 1 Diabetes. Vitamin D regulates the expression of over 200 genes, also related to immune modulation, suggesting a putative role in these diseases pathogenesis. This review overviews the most recent advances on the association between vitamin D and increased risk of Type 1 Diabetes as well as between vitamin D and either glucose homeostasis or insulin sensitivity. The effects of vitamin D in modulating the immune response and balancing anti-inflammatory cytokines, suggest that vitamin D system may represent an unforeseen target for the design of novel strategies for the treatment of patients with autoimmune diseases and in particular Type 1 Diabetes.

Vitamin D in pediatric age: consensus of the Italian Pediatric Society and the Italian Society of Preventive and Social Pediatrics, jointly with the Italian Federation of Pediatricians

Vitamin D plays a pivotal role in the regulation of calcium-phosphorus metabolism, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur.Besides its historical skeletal functions, in the last years it has been demonstrated that vitamin D directly or indirectly regulates up to 1250 genes, playing so-called extraskeletal actions. Indeed, recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious, allergic and autoimmune diseases. Thus, vitamin D deficiency may affect not only musculoskeletal health but also a potentially wide range of acute and chronic conditions. At present, the prevalence of vitamin D deficiency is high in Italian children and adolescents, and national recommendations on vitamin D supplementation during pediatric age are lacking. An expert panel of the Italian Society of Preventive and Social Pediatrics reviewed available literature focusing on randomized controlled trials of vitamin D supplementation to provide a practical approach to vitamin D supplementation for infants, children and adolescents.

Expression of JAZF1, ABCC8, KCNJ11and Notch2 genes and vitamin D receptor polymorphisms in type 2 diabetes, and their association with microvascular complications

BACKGROUND

We studied JAZF1, ABCC8, KCNJ11and Notch2 gene expression and vitamin D receptor (VDR) polymorphisms (Fok1 and Bsm1) in patients with type 2 diabetes mellitus (T2DM) and tried to find out their association with microvascular complications in these patients.

METHODS

The study was conducted on 180 patients (93 complicated and 87 noncomplicated) and 150 healthy subjects. Reverse-transcriptase polymerase chain reaction (RT-PCR) was used to assess gene expression and real-time PCR was used to detect VDR genotypes. Serum vitamin D was assessed using Elisa technique.

RESULTS

After adjustment for age, sex, body mass index and glycated hemoglobin, altered Notch2 gene expression was found between patients and controls and between complicated and noncomplicated cases (p = 0.001 and 0.001, respectively) and ABCC8 gene expression showed significant difference between patients and controls only (p = 0.003), while JAZF1and KCNJ11 expression showed no significant difference between the studied groups (p = 0.3 and 0.4, respectively). Serum vitamin D level was decreased in patients compared with controls (p = 0.001), while no difference was detected between complicated and noncomplicated cases (p = 0.1). Our results revealed no significant difference in VDR Fok1 and Bsm1 genotype distributions (p = 0.7 and 0.1, respectively) and allele frequencies (p = 0.4 and 0.1, respectively) between patients and controls. Patients with complications showed increased frequencies of Fok1GG genotype and G allele, while patients without complications showed increased frequencies of AA, then AG Fok1 genotype and A allele (p = 0.001 and 0.001, respectively). In addition, the frequencies of CC Bsm1 genotype and C allele were significantly higher among patients with complications, while frequencies of TT Bsm1 genotype and T allele were significantly higher among patients without complications (p = 0.02 and 0.003, respectively).

CONCLUSION

Altered expression of Notch2 and ABCC8 genes may play a role in the pathogenesis of T2DM. Altered expression of Notch2 and VDR polymorphisms may play a role in the development of microvascular complications in diabetic patients. These results may assist in early identification and management of diabetic complications.

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.

Association of vitamin D receptor polymorphisms and type 1 diabetes susceptibility in children: a meta-analysis

BACKGROUND

There have been studies focused on FokI, BsmI, ApaI and TaqI polymorphisms of the vitamin D receptor (VDR) gene and susceptibility to type 1 diabetes mellitus with controversial results.

METHODS

This present study is a meta-analysis investigating the association between FokI, ApaI, TaqI and BsmI polymorphisms of VDR gene and type 1 DM in children. A literature search was performed using Medline, EMBASE, Cochrane and PubMed. Any study was considered eligible for inclusion if at least one of FokI, ApaI, TaqI and BsmI polymorphisms was determined, and outcome was type 1 DM at pediatric age.

RESULTS

A total of 9 studies comprising 1053 patients and 1017 controls met the study inclusion criteria. The pooled odds ratios (ORs) of the FokI, ApaI, TaqI and BsmI polymorphisms were combined and calculated. Forest plots and funnel plots of the OR value distributions were drawn. Our meta-analysis has demonstrated statistically significant associations between DM1 and VDR genotypes, BsmIBB (P < 0.05), BsmIBb, (P < 0.05), BsmIbb (P < 0.05), TaqITT (P < 0.05) and TaqItt (P < 0.05) in children.

CONCLUSION

The results indicated that BsmIBB, BsmIBb and TaqItt polymorphisms were associated with an increased risk of type 1 DM, whereas BsmIbb and TaqITT had protective effect for type 1 DM in children.

Study and evaluation the impact of vitamin D receptor variants on the risk of type 2 diabetes mellitus in Han Chinese

BACKGROUND

Vitamin D and the vitamin D receptor (VDR) are associated with susceptibility to type 2 diabetes mellitus (T2DM). The purpose of the present study was to screen more single nucleotide polymorphisms (SNPs) of VDR and assess their effects on the risk of T2DM in Han Chinese.

METHOD

Four SNPs were genotyped in 1191 individuals (397 cases, 794 controls). Allele frequencies and genotype distributions were analyzed. Effects were investigated by evaluating genotype distribution with regard to phenotypes, insulin resistance, and β-cell function. Haplotype analysis and gene risk score (GRS) were used to evaluate the combined and additive roles of VDR SNPs on T2DM pathogenesis.

RESULTS

There was a significant association between rs739837 and T2DM in two models and allele frequency distribution. The novel locus rs2239179 differed significantly between cases and controls, especially in males and those aged >55 years, in three models and allele frequency distribution. The TT genotype of rs739837 was associated with higher triglyceride than GG and TG genotypes, and higher total cholesterol levels than the GG genotype. Compared with the GTGA haplotype, the GCGG haplotype reduced the risk of T2DM. Trend Chi-squared tests showed that there was significant association between the weighted GRS and the risk of T2DM (P_trend  = 0.034).

CONCLUSION

This study provides novel evidence that rs739837 is associated with lipid metabolism in T2DM patients. The rs739837 and rs2239179 SNPs were associated with the risk of T2DM in Han Chinese. The VDR SNPs had combined and additive effects on the risk of T2DM.

Vitamin D receptor gene FokI variant in diabetic foot ulcer and its relation with oxidative stress

PURPOSE

The patient's suffering and financial costs affiliated with Diabetic Foot Ulcer (DFU), as one of the most important complications of diabetes, are highly undesirable and this highlights the importance of preventive medicine about this disorder. Furthermore hyperglycemia causes generation of free radicals which leads to oxidative stress (OS). Hence, this study aims to examine the association between vitamin D receptor (VDR) gene FokI polymorphism and DFU in Iranian population and also its correlation with OS biomarkers.

MATERIALS AND METHODS

In a case-control study, a total of 212 patients with type 2 diabetes with and without diabetic foot ulcer were included. Genotyping was conducted by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. Samples were analyzed for thiobarbituric reactive substances (TBARS) and ferric reducing ability of plasma (FRAP) as markers of OS.

RESULTS

The results indicated a significant difference in genotype frequencies of VDR gene FokI polymorphism in patients with diabetic foot ulcer in comparison to those without diabetic foot ulcer (TT+TC vs. CC p=0.04; OR=1.76; 95% CI=1.02-3.05). Moreover, the patients carrying the T allele had a significantly higher level of TBARS (p=0.01).

CONCLUSIONS

We found a significant association between FokI functional variant of VDR gene and diabetic foot ulcer in an Iranian population. Increased levels of TBARS in patients carrying the T allele of FokI polymorphism indicate an association between this variant and OS in patients with diabetes.

The association between vitamin D receptor gene polymorphisms (TaqI and FokI), Type 2 diabetes, and micro-/macrovascular complications in postmenopausal women

Introduction

Since there is evidence of the action of vitamin D as a modulator of insulin release and atherosclerosis, it may well be that the vitamin D receptor polymorphisms are associated with diabetes and its chronic complications.

Aims

To examine the associations between vitamin D receptor polymorphisms (FokI and TaqI) and Type 2 diabetes (T2DM) and its associated chronic complications in postmenopausal women.

Methods

This cross-sectional study analyzed 100 postmenopausal women with T2DM (mean age 65.7±7.18 years) and 100 postmenopausal women without diabetes in the control group (mean age 65.1±9.18 years; P=0.1608). We evaluated clinical and metabolic parameters and analyzed TaqI and FokI polymorphisms.

Results

There were no significant differences in genotype and allele frequencies between patients and controls in either of the polymorphisms studied. In the group of patients with diabetes, there were no significant differences in either polymorphism in relation to stroke, retinopathy, nephropathy, or neuropathy. However, in patients with T2DM and coronary artery disease, f genotype (P=0.0361) and the combination of Ff + ff genotypes were observed less frequently (P=0.0462).

Conclusion

This study suggests the potential protective factor of FokI polymorphism for coronary artery disease in postmenopausal women with T2DM in the recessive model.

Lack of association between FokI polymorphism in vitamin D receptor gene (VDR) & type 2 diabetes mellitus in the Tunisian population

BACKGROUND & OBJECTIVES

The impact of several environmental and genetic factors on diabetes is well documented. Though the association between the vitamin D receptor (VDR) gene polymorphisms and type 2 diabetes mellitus (T2DM) has been analyzed in different ethnic groups, the results have been inconsistent. The aim of this study was to evaluate the possible association between VDR FokI polymorphism and genetic susceptibility to T2DM in Tunisian population.

METHODS

A total of 439 unrelated patients with T2DM and 302 healthy controls were included in the study. Genomic DNA was extracted from blood and genotyped for the single nucleotide polymorphism (SNP) of FokI (T/C: (rs2228570) by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The genotype distribution and the relative allelic frequencies for the FokI polymorphism were not significantly different between T2DM and controls: in T2DM patients the frequencies of the CC, CT, and TT genotypes were 52.6, 41.0, and 6.1 per cent, respectively, and in controls the genotype frequencies were 55.6, 38.7, and 5.6 per cent, respectively. In our study, the TT genotype of the FokI polymorphism was not associated with T2DM (OR =1.19, 95% CI 0.63 - 2.25, P=0.577).

INTERPRETATION & CONCLUSIONS

Our study showed no significant association of the FokI polymorphism in the vitamin D receptor gene with type 2 diabetes mellitus in Tunisian population.

T-cell cytokine gene polymorphisms and vitamin D pathway gene polymorphisms in end-stage renal disease due to type 2 diabetes mellitus nephropathy: comparisons with health status and other main causes of end-stage renal disease

BACKGROUND

T-cell cytokine gene polymorphisms and vitamin D pathway gene polymorphisms were evaluated as possibly associated with end-stage renal disease (ESRD) resulting from type 2 diabetes mellitus (DM) nephropathy.

METHODS

Studies were conducted among hemodialysis (HD) patients with ESRD due to type 2 DM nephropathy, chronic glomerulonephritis, chronic infective tubulointerstitial nephritis, and hypertensive nephropathy as well as in healthy subjects. A frequency distribution of T-cell-related interleukin (IL) genes (IL18 rs360719, IL12A rs568408, IL12B rs3212227, IL4R rs1805015, IL13 rs20541, IL28B rs8099917, IL28B, and rs12979860) and vitamin D pathway genes (GC genes: rs2298849, rs7041, and rs1155563; VDR genes: rs2228570, rs1544410; and RXRA genes: rs10776909, rs10881578, and rs749759) was compared between groups.

RESULTS

No significant differences in a frequency distribution of tested polymorphisms were shown between type 2 DM nephropathy patients and controls. A difference was found in IL18 rs360719 polymorphic distribution between the former group and chronic infective tubulointerstitial nephritic patients (P trend = 0.033), which also differed in this polymorphism from controls (P trend = 0.005).

CONCLUSION

T-cell cytokine and vitamin D pathway gene polymorphisms are not associated with ESRD due to type 2 DM nephropathy in Polish HD patients. IL18 rs360719 is probably associated with the pathogenesis of chronic infective tubulointerstitial nephritis.

Associations study of vitamin D receptor gene polymorphisms with diabetic microvascular complications: a meta-analysis

BACKGROUND

Emerging evidence from preclinical and clinical studies has shown that vitamin D plays an important role in the pathogenesis of diabetic microvascular complications (DMI). Several potentially functional polymorphisms (ApaI, BsmI, FokI and TaqI) of vitamin D receptor (VDR) gene have been implicated in DMI risk, but individually published studies showed inconclusive results. The aim of this study was to quantitatively summarize the association between VDR polymorphisms and DMI risk.

METHODS

We searched all the publications about the associations mentioned as above from PubMed and ISI database updated in December 2013. Meta-analysis of the overall odds ratios (ORs) with 95% confidence intervals (CIs) was calculated with the fixed or random effect model.

RESULTS

Eight studies involving 2734 subjects were included. Allelic and genotypic comparisons between cases and controls were evaluated. Overall analysis suggests that no significant association was observed among the ApaI, BsmI, FokI and TaqI variants and DMI risk in diabetic patients (all P values >0.05). In the stratified analysis, significant association was observed with diabetic nephropathy (DN) for VDR gene FokI polymorphism under a dominant model (OR 1.35, 95% CI 1.05-1.74, P=0.02) in Caucasians.

CONCLUSIONS

This meta-analysis indicated that the FokI polymorphism in VDR gene might affect individual susceptibility to DN in Caucasians. Further investigations are needed to confirm our results.

Relationship between vitamin D receptor gene polymorphisms and migraine without aura in an Iranian population

BACKGROUND

Inflammation has a key role in migraine pathophysiology. Vitamin D is an effective anti-inflammatory agent. The aim of this study was to investigate the association between migraine and two vitamin D receptor (VDR) polymorphisms (TaqI and FokI) and also the relationship between VDR polymorphisms and headache severity.

METHODS

In this case-control study we assessed 103 patients with newly diagnosed migraine without aura and 100 healthy subjects. Patients filled headache impact test-6 (HIT-6) as a tool to assess headache severity.

RESULTS

Genotype frequencies of VDR were significantly different between control and migraine patients. Heterozygote genotypes (Ff and Tt) were statistically more frequent in the migraine patients than the control subjects both for TaqI gene (P = 0.018; OR = 1.81, 95% CI = 1.03-3.18) and FokI gene polymorphisms (P = 0.001; OR = 2.91, 95% CI = 1.47-5.77). Also f and t alleles were more frequent in the migraine patients. Total HIT-6 score was significantly different between FokI heterozygote and homozygote patients (60.32 ± 1.87 versus 49.87 ± 2.69, resp., P = 0.004).

CONCLUSIONS

In conclusion our results showed that TaqI and FokI gene polymorphisms are associated with migraine without aura in Iranians patients. Also headache severity in FokI heterozygote patients was significantly greater than in the homozygote patients.

Vitamin D Receptor Fok-I polymorphism modulates diabetic host response to vitamin D intake: need for a nutrigenetic approach

OBJECTIVE

Interpopulation as well as interindividual variations in response to vitamin D intake commonly observed in subjects with type 2 diabetes may be related to genetic makeup. One of the candidate genes potentially responsible for this diversity is vitamin D receptor (VDR). This study aimed to investigate the interactive effect of VDR Fok-I polymorphism and vitamin D intake on diverse aspects of diabetic host response.

RESEARCH DESIGN AND METHODS

Glycemic status, lipid profiles, inflammatory biomarkers, and VDR Fok-I genotypes were determined in diabetic subjects (n = 140) who participated in a randomized controlled trial. Participants consumed two 250-mL bottles per day of yogurt drink (doogh) fortified with 500 IU vitamin D/250 mL for 12 weeks.

RESULTS

Mean serum 25(OH)D increased by ~30 nmol/L (P < 0.001). The time × intervention effect was significant for 25(OH)D (P = 0.030), HDL (P = 0.011), high-sensitivity C-reactive protein (hsCRP) (P < 0.001), interleukin (IL)-4 (P = 0.008), and IL-6 (P = 0.017) among the genotypic groups. The alleles were defined as ''F'' or ''f'' depending on the absence or presence of the restriction site, respectively. The least increment in 25(OH)D was in ff (23.0 ± 3.8 nmol/L) compared with Ff (31.2 ± 3.4 nmol/L) and FF (35.6 ± 2.7 nmol/L) (P for trend = 0.009), but only the difference between ff and FF was significant (P = 0.023). FF group had the largest decrement of both hsCRP and IL-6 compared with Ff (P < 0.001 and P = 0.038) and ff (P = 0.010 and P = 0.048), respectively.

CONCLUSIONS

We concluded that those of VDR ff genotype may be regarded as "low responders" to vitamin D intake in terms of response of circulating 25(OH)D and certain inflammatory biomarkers. A nutrigenetic approach may, therefore, be needed to protect diabetic patients from vitamin D deficiency.

Lack of an association between vitamin D receptor BsmI gene polymorphism and the risk of end-stage renal disease: a meta-analysis

OBJECTIVE

To evaluate the association between vitamin D receptor (VDR) BsmI gene polymorphism and the risk of end-stage renal disease (ESRD).

METHODS

All eligible studies were included in our meta-analysis of a search of the PubMed, Embase, Cochrane and China National Knowledge Infrastructure (CNKI) databases according to predefined criteria. The fixed-effects or, in the presence of heterogeneity, random-effects models were used to calculate the pooled odds ratio (OR) and corresponding 95% confidence interval (CI).

MATERIALS

Six studies including 863 patients and 1,063 controls were recruited for the analysis of the association between the VDR BsmI gene polymorphism and the risk of ESRD.

RESULTS

The B allele/BB genotype was not associated with the ESRD risk in the overall population, Caucasians or Asians (overall population: p=0.492 and 0.382, Caucasians: p=0.765 and 0.522, Asians: p=0.607 and 0.481). The Bb/bb genotype was also not associated with the risk of ESRD in the overall population, Caucasians or Asians (overall population: p=0.556 and 0.166, Caucasians: p=0.770 and 0.965, Asians: p=0.411 and 0.098). The exclusion of any single study had little impact on the p value in the overall population. No evidence of publication bias was observed.

CONCLUSION

VDR BsmI gene polymorphism appears to not be associated with the risk of ESRD in the overall population, Caucasians or Asians. However, more studies should be performed in the future.