Clinical significance of vitamin D deficiency and receptor gene polymorphism in systemic lupus erythematosus patients

Relationship between vitamin D receptor genotypes (FOK1rs2228570) and IL18 gene expression in sample of multiple sclerosis Iraqi patients

BACKGROUND

Multiple Sclerosis known as MS, this chronic inflammatory demyelinating condition affects the nervous system. It is a heterogenic and multifactorial disease. The goal of the current study was to investigate the relationship between MS patients' IL18 gene expression and the vitamin D receptor gene polymorphism (FOK1rs2228570).

OBJECTIVE

The aim of the study to investigate the association of vitamin D receptor (FOK1rs2228570) gene polymorphism and pro inflammatory cytokine (IL18) gene expression among multiple sclerosis Iraqi patients. Detection VDR polymorphism and determine whether this SNP is involved in susceptibility to multiple sclerosis and estimation IL18 gene expression and explore its relation with multiple sclerosis susceptibility.

METHODS

Blood samples were taken from 75 MS patients in Iraq (30 men and 45 women), as well as from 75 volunteers who seemed to be in a favorable state of health and fell within the age range of 20 to 50 years. Tetra-ARMS Polymerase Chain Reaction (Tetra-ARMS PCR) was used to find polymorphisms in the vitamin D receptor (VDR) gene, and Real-time Polymerase Chain Reaction (RT-PCR) was used to measure IL18 gene expression.

RESULTS

The findings from the analysis of VDR gene polymorphism in patients with MS indicated that the wild-type genotype T/T was present in 8 individuals, accounting for 10.6%, the heterogeneous genotype TC was 36 (48%), and the homogeneous genotype CC was 31 (41.3%), whilst T allele frequency was 52(34.6%) and C allele was 98(65.3%) with (P⩽ 0.01) significant difference and even as in control T/T genotype was 49(65.3%), TC genotype was 21(28%), CC genotype was 5(6.66%), T allele frequency was 119(79.3%) and C allele was 31(20.6%) with significant difference (P⩽ 0.001). While estimation of IL18 expression showed high elevation in patients' group (2.59 ± 0.51 fold) by significance difference (P⩽ 0.5) when compared to control group (1.35 ± 0.14 fold). The relationship between IL18 gene expression with VDR variant in MS patients demonstrated a significant rise (2.9 ± 0.51 fold) at CC genotype patients in IL18 folding gene expression, followed by (4.6 ± 0.17 fold) in TC genotype patients and finally (1.4 ± 0.08 fold) in TT genotype patients with highly significant (P⩽ 0.01).

CONCLUSION

The VDR(FOK1rs2228570) genotype was significantly correlated with IL18 expression in MS patients from Iraq.

Leveraging machine learning to evaluate factors influencing vitamin D insufficiency in SLE patients: A case study from southern Bangladesh

Vitamin D insufficiency appears to be prevalent in SLE patients. Multiple factors potentially contribute to lower vitamin D levels, including limited sun exposure, the use of sunscreen, darker skin complexion, aging, obesity, specific medical conditions, and certain medications. The study aims to assess the risk factors associated with low vitamin D levels in SLE patients in the southern part of Bangladesh, a region noted for a high prevalence of SLE. The research additionally investigates the possible correlation between vitamin D and the SLEDAI score, seeking to understand the potential benefits of vitamin D in enhancing disease outcomes for SLE patients. The study incorporates a dataset consisting of 50 patients from the southern part of Bangladesh and evaluates their clinical and demographic data. An initial exploratory data analysis is conducted to gain insights into the data, which includes calculating means and standard deviations, performing correlation analysis, and generating heat maps. Relevant inferential statistical tests, such as the Student's t-test, are also employed. In the machine learning part of the analysis, this study utilizes supervised learning algorithms, specifically Linear Regression (LR) and Random Forest (RF). To optimize the hyperparameters of the RF model and mitigate the risk of overfitting given the small dataset, a 3-Fold cross-validation strategy is implemented. The study also calculates bootstrapped confidence intervals to provide robust uncertainty estimates and further validate the approach. A comprehensive feature importance analysis is carried out using RF feature importance, permutation-based feature importance, and SHAP values. The LR model yields an RMSE of 4.83 (CI: 2.70, 6.76) and MAE of 3.86 (CI: 2.06, 5.86), whereas the RF model achieves better results, with an RMSE of 2.98 (CI: 2.16, 3.76) and MAE of 2.68 (CI: 1.83,3.52). Both models identify Hb, CRP, ESR, and age as significant contributors to vitamin D level predictions. Despite the lack of a significant association between SLEDAI and vitamin D in the statistical analysis, the machine learning models suggest a potential nonlinear dependency of vitamin D on SLEDAI. These findings highlight the importance of these factors in managing vitamin D levels in SLE patients. The study concludes that there is a high prevalence of vitamin D insufficiency in SLE patients. Although a direct linear correlation between the SLEDAI score and vitamin D levels is not observed, machine learning models suggest the possibility of a nonlinear relationship. Furthermore, factors such as Hb, CRP, ESR, and age are identified as more significant in predicting vitamin D levels. Thus, the study suggests that monitoring these factors may be advantageous in managing vitamin D levels in SLE patients. Given the immunological nature of SLE, the potential role of vitamin D in SLE disease activity could be substantial. Therefore, it underscores the need for further large-scale studies to corroborate this hypothesis.

A review of the critical role of vitamin D axis on the immune system

In recent years, the physiological and molecular functions of vitamin D (Vit-D) have been deeply investigated. At first, Vit-D was considered a regulator of mineral and skeletal homeostasis. However, due to the extensive-expression pattern of Vit-D receptor (VDR) in almost every non-skeletal cell, Vit-D is considered mainly a multifunctional agent with broad effects on various tissues, notably the immune system. The expression of VDR in immune cells such as dendritic cells, monocyte/macrophage, neutrophils, B cells and T cells has been well demonstrated. Besides, such immune cells are capable of metabolizing the active form of Vit-D which means that it can module the immune system in both paracrine and autocrine manners. Vit-D binding protein (DBP), that regulates the levels and homeostasis of Vit-D, is another key molecule capable of modulating the immune system. Recent studies indicate that dysregulation of Vit-D axis, variations in the DBP and VDR genes, and Vit-D levels might be risk factors for the development of autoimmune disease. Here, the current evidence regarding the role of Vit-D axis on the immune system, as well as its role in the development of autoimmune disease will be clarified. Further insight will be given to those studies that investigated the association between single nucleotide polymorphisms of DBP and VDR genes with autoimmune disease susceptibility.

Vitamin D Receptor (VDR) Genetic Variants: Relationship of FokI Genotypes with VDR Expression and Clinical Disease Activity in Systemic Lupus Erythematosus Patients

Vitamin D (VD) deficiency is more frequent in systemic lupus erythematosus (SLE) patients than in control subjects (CS); genetic variants in the VD receptor (VDR) could contribute to the clinical disease activity. This study was aimed to determine the association of the VDR variants FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) with susceptibility to the disease, VD status, VDR mRNA expression, and clinical disease activity in SLE patients. A cross-sectional study was conducted in 194 SLE and 196 CS Mexican women. Immunoassays quantified serum calcidiol and calcitriol. Genotyping was performed by allelic discrimination assays and mRNA VDR expression by qPCR. The FokI variant was not in linkage disequilibrium with BsmI, ApaI, and TaqI VDR variants. SLE patient carriers of the TT FokI genotype showed higher clinical disease activity scores. Notably, the mRNA VDR expression was higher in SLE patients vs. CS, in active vs. inactive SLE patients, and in participants of both study groups with vitamin D deficiency, higher calcitriol levels, and TT FokI genotype carriers. In conclusion, the TT FokI VDR genotype was related to high VDR expression and clinical disease activity in systemic lupus erythematosus patients.

Impact of Vitamin D Receptor Gene Polymorphism on Systemic Lupus Erythematosus Susceptibility: A Pooled Analysis

Background: This study was designed to evaluate the influence of vitamin D receptor (VDR) gene polymorphisms on systemic lupus erythematosus (SLE) susceptibility. Methods: All eligible investigations were identified, the number of the various genotypes in the case and control groups were reviewed. A pooled analysis was performed using the Stata software. The study was carried out according to the Ethics Review Committee of The Third Xiangya Hospital, Central South University. Results: This meta-analysis included 19 studies. In our analysis, the VDR Apal polymorphism was correlated with SLE susceptibility in the overall population (AA vs. aa: odds ratio [OR] = 1.374, 95% confidence interval [CI]: 1.115-1.692, p = 0.003; AA + Aa vs. aa: OR = 1.342, 95% CI: 1.139-1.583, p < 0.01). The VDR Bsml and Apal polymorphisms were correlated with SLE susceptibility in Caucasian subjects (BB vs. Bb + bb: OR = 0.734, 95% CI: 0.593-0.909, p = 0.005; B vs. b: OR = 0.865, 95% CI: 0.760-0.983, p = 0.026; AA vs. aa: OR = 1.329, 95% CI: 1.016-1.740, p = 0.038). The VDR BsmI and FokI polymorphisms were correlated with SLE in African subjects (B vs. b: OR = 1.898, 95% CI: 1.458-2.470, p＜0.01; BB + Bb vs. bb: OR = 2.935, 95% CI: 1.944-4.430, p < 0.01; FF vs. Ff + ff: OR = 2.424, 95% CI: 1.673-3.512, p < 0.01; F vs. f: OR = 1.720, 95% CI: 1.417-2.087, p < 0.01; FF vs. ff: OR = 3.154, 95% CI: 2.083-4.774, p < 0.01; FF + Ff vs. ff: OR = 1.803, 95% CI: 1.363-2.384, p < 0.01). In addition, the VDR Apal polymorphism was correlated with SLE in female subjects (AA vs. aa: OR = 1.392, 95% CI: 1.049-1.849, p = 0.022) when stratified by gender. But there was no association between the VDR TaqI polymorphism and SLE susceptibility in our analysis. Conclusions: The VDR Apal polymorphism was associated with SLE susceptibility in general populations; in addition, Apal polymorphism was associated with SLE in female subjects. The VDR Bsml gene polymorphism was correlated with SLE susceptibility in Caucasian and African populations, whereas the VDR FokI polymorphism was correlated with SLE in African populations. But there was no association between the VDR TaqI polymorphism and SLE susceptibility in our analysis.

VDR Polymorphisms in Autoimmune Connective Tissue Diseases: Focus on Italian Population

Vitamin D is an important hormone involved in various physiologic processes, and its activity is linked to binding with vitamin D receptor (VDR). Genetic polymorphisms in the VDR gene could modulate the expression or function of the receptor and, consequently, alter the effects of vitamin D. Variants in VDR gene have been associated with susceptibility to many illnesses sensitive to vitamin D administration and to autoimmune disorders, but no data are available regarding autoimmune connective tissue diseases in Italian population. We analyzed three VDR polymorphisms in 695 Italian patients with autoimmune connective tissue diseases (308 with systemic lupus erythematosus (SLE), 195 with primary Sjogren's syndrome (pSS), and 192 with rheumatoid arthritis (RA)) and in 246 healthy controls with the aim to evaluate a possible association of VDR SNPs with susceptibility to these diseases in the Italian population. Genotyping of rs2228570, rs7975232, and rs731236 in VDR gene was performed by an allelic discrimination assay. A case/control association study and a genotype/phenotype correlation analysis have been performed. We observed a higher risk to develop SLE for rs2228570 TT genotype (P = 0.029, OR = 1.79). No association was observed between susceptibility to pSS or RA and this SNP, although this variant is significantly less present in RA patients producing autoantibodies. For rs7975232 SNP, we observed a significant association of the variant homozygous genotype with SLE (P = 0.009, OR = 1.82), pSS (P = 0.046, OR = 1.66), and RA (P = 0.028, OR = 1.75) susceptibility. Moreover, we reported associations of this genotype with clinical phenotypes of SLE and pSS. Lastly, the GG genotype of rs731236 was associated with a lower RA susceptibility (P = 0.045, OR = 0.55). Our results show that the explored VDR polymorphisms are significantly associated with autoimmune connective tissue disorders and support the hypothesis that the genetic variability of VDR gene may be involved in susceptibility to these diseases in Italian population.

Vitamin D status in Hashimoto's thyroiditis and its association with vitamin D receptor genetic variants

BACKGROUND

Hashimoto's thyroiditis (HT) is considered the predominant cause of hypothyroidism in iodine sufficient countries. The deficiency of 25-OH-vitamin D3 serum level and the variation of vitamin D receptor (VDR) gene were implicated in a number of autoimmune disorders. This study aimed to test the hypothesis linking between VDR FokI and BsmI variants and HT, in addition to explain their impact on 25-OH-vitamin D3 serum level.

MATERIALS AND METHODS

Cross sectional study included 160 hypothyroid subjects, 112 patients with HT and 48 hypothyroid non-HT controls. They were diagnosed based on anti-TPO Ab and or anti-TG Ab results. All cases were subjected to full history taking, thyroid ultrasound examination and a panel of assays (TSH, f.T3, f.T4, anti-TPO Ab, anti-TG Ab, calcium, alkaline phosphatase and phosphate). Serum 25-OH-vitamin D3 was assayed using HPLC-UV method. VDR variants (FokI and BsmI) were genotyped using real-time PCR.

RESULTS

FokI AA genotype was statistically higher in HT patients than control group (P value = 0.02) with subsequently higher serum 25-OH-vitamin D3 level in comparison to all other genotypes (P value = 0.039). Serum 25-OH-vitamin D3 level was statistically indifferent between HT and control group (P value = 0.223). A statistically significant increase in total thyroid volume was observed in HT group (P value = 0.002).

CONCLUSION

FokI AA genotype is more associated with HT in Egyptian patients compared to hypothyroid non-HT controls. Moreover, patients with FokI AA genotype have statistically higher levels of 25-OH-vitamin D3 suggesting VDR dysfunction even in patients expressing normal level of vitamin D.

Association of Vitamin D Metabolism Gene Polymorphisms with Autoimmunity: Evidence in Population Genetic Studies

A high prevalence of vitamin D (calcidiol) serum deficiency has been described in several autoimmune diseases, including multiple sclerosis (MS), rheumatoid arthritis (AR), and systemic lupus erythematosus (SLE). Vitamin D is a potent immunonutrient that through its main metabolite calcitriol, regulates the immunomodulation of macrophages, dendritic cells, T and B lymphocytes, which express the vitamin D receptor (VDR), and they produce and respond to calcitriol. Genetic association studies have shown that up to 65% of vitamin D serum variance may be explained due to genetic background. The 90% of genetic variability takes place in the form of single nucleotide polymorphisms (SNPs), and SNPs in genes related to vitamin D metabolism have been linked to influence the calcidiol serum levels, such as in the vitamin D binding protein (VDBP; rs2282679 GC), 25-hydroxylase (rs10751657 CYP2R1), 1α-hydroxylase (rs10877012, CYP27B1) and the vitamin D receptor (FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) VDR). Therefore, the aim of this comprehensive literature review was to discuss the current findings of functional SNPs in GC, CYP2R1, CYP27B1, and VDR associated to genetic risk, and the most common clinical features of MS, RA, and SLE.

Vitamin D supplementation increases adipokine concentrations in overweight or obese adults

PURPOSE

Vitamin D regulates adipokine production in vitro; however, clinical trials have been inconclusive. We conducted secondary analyses of a randomized controlled trial to examine whether vitamin D supplementation improves adipokine concentrations in overweight/obese and vitamin D-deficient adults.

METHODS

Sixty-five individuals with a BMI ≥ 25 kg/m² and 25-hydroxyvitamin D (25(OH)D) ≤ 50 nmol/L were randomized to oral cholecalciferol (100,000 IU single bolus followed by 4,000 IU daily) or matching placebo for 16 weeks. We measured BMI, waist-to-hip ratio, % body fat (dual X-ray absorptiometry), serum 25(OH)D (chemiluminescent immunoassay) and total adiponectin, leptin, resistin, and adipsin concentrations (multiplex assay; flow cytometry). Sun exposure, physical activity, and diet were assessed using questionnaires.

RESULTS

Fifty-four participants completed the study (35M/19F; mean age = 31.9 ± 8.5 years; BMI = 30.9 ± 4.4 kg/m²). After 16 weeks, vitamin D supplementation increased 25(OH)D concentrations compared with placebo (57.0 ± 21.3 versus 1.9 ± 15.1 nmol/L, p < 0.001). There were no differences between groups for changes in adiponectin, leptin, resistin, or adipsin in unadjusted analyses (all p > 0.05). After adjustment for baseline values, season, sun exposure, and dietary vitamin D intake, there was a greater increase in adiponectin (β[95%CI] = 13.7[2.0, 25.5], p = 0.02) and leptin (β[95%CI] = 22.3[3.8, 40.9], p = 0.02) in the vitamin D group compared with placebo. Results remained significant after additional adjustment for age, sex, and % body fat (p < 0.02).

CONCLUSIONS

Vitamin D may increase adiponectin and leptin concentrations in overweight/obese and vitamin D-deficient adults. Further studies are needed to clarify the molecular interactions between vitamin D and adipokines and the clinical implications of these interactions in the context of obesity.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov: NCT02112721.

Vitamin D in SLE: a role in pathogenesis and fatigue? A review of the literature

Fatigue is a common, disabling problem that is highly prevalent in patients with systemic lupus erythematous (SLE). More recently, vitamin D status has been established as a potential contributor to SLE pathogenesis and manifestations, in particular fatigue. This review summarizes the literature regarding the role of vitamin D in SLE, and provides an overview of the recent literature examining the association between vitamin D and fatigue in patients with SLE. Finally, the role of vitamin D supplementation in the treatment of SLE-related fatigue is considered.

Vitamin D receptor FokI, TaqI, and ApaI polymorphisms and susceptibility to systemic lupus erythematosus: an updated meta-analysis

This study aimed to explore whether vitamin D receptor (VDR) polymorphisms are associated with susceptibility to systemic lupus erythematosus (SLE). Meta-analyses were conducted to determine the associations between the VDR FokI, TaqI, and ApaI polymorphisms and SLE in all subjects and each ethnic group. A total of 12 studies were considered in the meta-analysis, which involved 1974 patients and 2506 controls. Meta-analysis of the VDR FokI polymorphism showed no association between SLE and the FokI F allele in all study subjects (OR = 1.047, 95% CI = 0.781-1.403, p = 0.758). However, the meta-analysis showed a significant association between SLE and the VDR FokI F allele in the Arab population (OR = 1.721, 95% CI = 1.417-2.088, p < 0.001). Analysis using the recessive and dominant models and homozygote contrast showed the same pattern for the VDR FokI F allele in Europeans, Asians, and Arabs. This meta-analysis showed that polymorphisms in VDR FokI, TaqI, and ApaI are not associated with SLE susceptibility in overall, European and Asian populations. However, the VDR FokI polymorphism is associated with SLE susceptibility in the Arab population.

Vitamin D receptor gene FokI polymorphism in Egyptian children and adolescents with SLE: A case-control study

Background Childhood-onset systemic lupus erythematosus (cSLE) is a lifelong autoimmune disorder. The vitamin D receptor (VDR) gene is a potential candidate gene for cSLE susceptibility. In this study, we aimed to investigate the FokI polymorphism in the VDR gene in Egyptian children and adolescents with SLE, to determine whether this polymorphism could be a genetic marker for cSLE susceptibility or disease activity and we also measured the serum level of 25-hydroxyvitamin D [25(OH) D] to assess its relation to such polymorphism. Methods This was a case-control study, which included 300 patients with cSLE and 300 age, sex, and ethnicity-matched healthy controls. All participants were genotyped for the VDR gene FokI (rs2228570) polymorphism by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), while the serum [25(OH) D] levels were measured by enzyme-linked immunosorbent assay (ELISA). Results The VDR FokI FF genotype and F allele were overrepresented among cSLE patients compared with the controls, [odds ratio (OR) = 2.7; 95% confidence interval (CI): 1.6-4.4 for the FF genotype; p = 0.000; and OR = 1.6; 95% CI: 1.27-2.05 for the F allele; p = 0.000, respectively]. We found a significant association between VDR FokI FF genotype with lupus nephritis (OR: 4.8; 95% CI: 2.2-10.6; p = 0.002); and high disease activity index score ( p = 0.01). Conclusions The FokI polymorphism in the VDR gene may contribute to susceptibility to SLE in Egyptian children and adolescents. Moreover, the FF genotype constituted a risk factor for the development of lupus nephritis and was associated with low serum [25(OH) D] levels as well as higher disease activity index score among studied patients with cSLE.