The functional polymorphisms of VDR, GC and CYP2R1 are involved in the pathogenesis of autoimmune thyroid diseases

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.

How Does Vitamin D Affect Immune Cells Crosstalk in Autoimmune Diseases?

Vitamin D is a secosteroid hormone that is highly involved in bone health. Mounting evidence revealed that, in addition to the regulation of mineral metabolism, vitamin D is implicated in cell proliferation and differentiation, vascular and muscular functions, and metabolic health. Since the discovery of vitamin D receptors in T cells, local production of active vitamin D was demonstrated in most immune cells, addressing the interest in the clinical implications of vitamin D status in immune surveillance against infections and autoimmune/inflammatory diseases. T cells, together with B cells, are seen as the main immune cells involved in autoimmune diseases; however, growing interest is currently focused on immune cells of the innate compartment, such as monocytes, macrophages, dendritic cells, and natural killer cells in the initiation phases of autoimmunity. Here we reviewed recent advances in the onset and regulation of Graves' and Hashimoto's thyroiditis, vitiligo, and multiple sclerosis in relation to the role of innate immune cells and their crosstalk with vitamin D and acquired immune cells.

Vitamin D and the Thyroid: A Critical Review of the Current Evidence

Vitamin D is necessary for the normal functioning of many organs, including the thyroid gland. It is, therefore, not surprising that vitamin D deficiency is considered a risk factor for the development of many thyroid disorders, including autoimmune thyroid diseases and thyroid cancer. However, the interaction between vitamin D and thyroid function is still not fully understood. This review discusses studies involving human subjects that (1) compared vitamin D status (primarily determined by serum calcidiol (25-hydroxyvitamin D [25(OH)D]) levels) with thyroid function assessed by thyroid stimulating hormone (TSH), thyroid hormones, and anti-thyroid antibody levels; and (2) evaluated the effect of vitamin D supplementation on thyroid function. Due to the many inconsistencies in the results between the studies, it is still difficult to draw a definite conclusion on how vitamin D status affects thyroid function. Studies in healthy participants observed either a negative correlation or no association between TSH and 25(OH)D levels, while the results for thyroid hormones showed high variability. Many studies have observed a negative association between anti-thyroid antibodies and 25(OH)D levels, but equally many studies have failed to observe such an association. Regarding the studies that examined the effect of vitamin D supplementation on thyroid function, almost all observed a decrease in anti-thyroid antibody levels after vitamin D supplementation. Factors that could contribute to the high variability between the studies are the use of different assays for the measurement of serum 25(OH)D levels and the confounding effects of sex, age, body-mass index, dietary habits, smoking, and the time of year when the samples were collected. In conclusion, additional studies with larger numbers of participants are needed to fully understand the effect of vitamin D on thyroid function.

Vitamin D receptor gene polymorphisms are associated with the risk and features of myasthenia gravis in the Han Chinese population

Vitamin D receptor gene (VDR) polymorphisms are candidate genetic variants for susceptibility to autoimmune diseases. Here, we explored the association between VDR polymorphisms and myasthenia gravis (MG) susceptibility and disease features in a Han Chinese population. A total of 151 patients with MG and 146 healthy controls were genotyped for VDR rs1544410, rs2228570, rs731236, and rs7975232 polymorphisms using the improved multiple ligase detection reaction. Information regarding age at onset, acetylcholine receptor (AChR-Ab) and muscle-specific kinase (MuSK-Ab) antibody status, thymus status, involved muscles at onset, and Osserman type at maximum worsening during 2-year follow-up was obtained and used for subclassification grouping. Intergroup comparisons of allele and genotype frequencies and haplotype distributions were performed between the MG and control groups and between each pair of MG subgroups. The VDR rs7975232 polymorphism was associated with the risk of MG in allele, codominant (CC vs. CA), and dominant models (p = 0.040, p = 0.018, and p = 0.018, respectively). Moreover, subjects with the ACC haplotype (order of rs731236, rs7975232, rs1544410) were more likely to develop MG than those with other haplotypes (OR = 1.486, 95% CI: 1.017-2.171, p = 0.040). In a dominant model, the rs7975232 CC genotype frequency was significantly higher in the ocular MG group than in the generalized MG group (p = 0.019). The study findings suggest that the VDR rs7975232 C allele and the ACC haplotype can be associated to an increased susceptibility to the development of MG. Trial registration: NCT05380128.

Association Between Vitamin D Deficiency and Autoimmune Thyroid Disorder: A Systematic Review

Despite recent evidence that low serum 25-hydroxyvitamin D (25(OH)D) levels and deflects may influence the emergence of autoimmune thyroid disorders (AITD), the relationship between vitamin D deficiency and Graves’ disease (GD) and Hashimoto's thyroiditis (HT), which comprise AITD, remains unclear. We retrieved studies that described vitamin D association with HT and GD from PubMed/Medline, Google Scholar, and the Cochrane Library. We included research studies that compared vitamin D levels and deficiency or sufficiency between AITD cases such as HT and GD cases and control subjects. The final assessment comprised 11 studies that recruited 1952 AITD cases (HT and GD) that were published between 2011 and 2021; these were included in the final review. All the included studies were observational, and more precisely, case-control studies that recruited healthy subjects as well as controls. The majority of the studies reviewed indicated that HT and GD patients have a greater prevalence of vitamin D deficiency or low serum 25 (OH)-D levels. Two studies failed to establish an association between vitamin D deficiency and HT and GD disease. In conclusion, vitamin D deficiency or insufficiency can increase the rate of autoimmune diseases such as HT and GD. Randomized controlled trials with a longer follow-up period are needed to confirm the causal relationship between autoimmune thyroid disorder and vitamin D and to provide more reliable insights into the relevance of treatment effects of vitamin D therapy or supplementation.

Genetics, Epigenetics, Cellular Immunology, and Gut Microbiota: Emerging Links With Graves' Disease

Graves’ disease (GD) is a well-known organ-specific autoimmune disease characterized by hyperthyroidism, goiter, and exophthalmos. The incidence of GD is approximately 2.0–3.0% in China and 0.5–2.0% in Western countries. Due to the complex pathogenesis and etiology of GD, current treatment methods have great side effects that seriously endanger human health. Therefore, it is particularly important to understand the pathogenesis of GD. Various studies have shown that genetics, epigenetics, cellular immunology, and gut microbiota are all involved in the development of GD. Genetically, CD25 gene and VDR gene polymorphisms are involved in the development of GD by increasing the ratio of Th17/Treg cells. Epigenetically, miR-23a-3p and lncRNA-MEG3 lead to Th17/Treg imbalance and participate in the progression of GD. Moreover, commensal microbe deletion can disrupt Th17/Treg balance and participate in the occurrence of GD. The imbalance of Th17/Treg cells induced by genetics, epigenetics, and gut microbiota plays a vital role in the pathogenesis of GD. Therefore, this article reviews the role of genetics, epigenetics, cellular immunology, and gut microbiota in the pathogenic mechanism of GD. This may lead to the development of novel therapeutic strategies and providing promising therapeutic targets.

The VDR gene confers a genetic predisposition to Graves' disease and Graves' ophthalmopathy in the Southwest Chinese Han population

OBJECTIVE

Graves' disease (GD) is a common autoimmune disease manifesting with diffuse symmetric thyroid gland enlargement, pretibial myxedema, and Graves' ophthalmopathy (GO). Recently, the vitamin D receptor (VDR) gene has been linked to various autoimmune diseases. This study aimed to investigate the association of VDR gene polymorphisms with susceptibility to GD and GO in the Southwest Chinese Han population.

METHODS

A two-stage association study was performed in 1,209 controls and 650 GD patients by PCR-RFLP assay. Real-time PCR and ELISA were carried out to quantify gene expression and cytokine production.

RESULTS

The first-stage study showed that the frequency of VDR/Apa I AA genotype was significantly increased in GD (Pc = 1.67 × 10^-2, OR = 1.98). The second-stage and combined studies confirmed the association of VDR/Apa I with GD (AA genotype: Pc = 3.45 × 10^-4, OR = 1.87; A allele: Pc = 2.62 × 10^-2, OR = 1.20). The stratification analysis showed that GO patients had a higher frequency of the VDR/Apa I AA genotype (Pc = 8.69 × 10^-5, OR = 2.84). Functional experiments showed a decreased VDR expression and TGF-β1 production as well as an increased IL-17 production in VDR/Apa I AA genotype carriers.

CONCLUSION

The VDR/Apa I polymorphism is significantly associated with GD and GO, and it may be involved in the development of GD and GO by influencing VDR mRNA expression levels and the secretion levels of cytokines.

Impact of Vitamin D and Vitamin D Receptor on Risk of Cardiovascular Diseases in Children and Adolescents with Obesity in Sichuan, China: A Cross-Sectional Study

BACKGROUND

Previous studies have demonstrated the close relationship between vitamin D, vitamin D receptor (VDR), and obesity. Nevertheless, few studies have reported wherther the relationship among these is associated with the risk of cardiovascular diseases (CVDs) in Chinese children and adolescents.

OBJECTIVE

The present study aimed to reveal the effects of obesity, serum vitamin D levels, and VDR FokI genotype on the risk of CVDs in children and adolescents in Sichuan, China.

METHODS

Children and adolescents were recruited into a cross-sectional study. Serum vitamin D levels, serum lipid levels, and VDR FokI gene polymorphisms were measured in the laboratory. The selected lipid factors were used as biomarkers of CVD risk. The impact of obesity, vitamin D levels and VDR FokI genotype on CVD risk factors were investigated.

RESULTS

Higher lipid levels were observed in children and adolescents in the obese group, when compared to the nonobese group. In the obese group, the C allele carriers had significantly lower concentrations of lipids, when compared to the TT genotype. C allele carriers who were vitamin D deficient had lower levels of total cholesterol (TC), triglycerides (TG), apolipoprotein B (Apo-B), total cholesterol/high-density lipoprotein cholesterol (TC/HDL-C), low-density lipoprotein cholesterol/high-density lipoprotein cholesterol (LDL-C/HDL-C), and triglycerides/high-density lipoprotein cholesterol (TG/HDL-C), when compared to those with the TT genotype in obese children and adolescents. For vitamin D-insufficient obese children and adolescents, the TC, Apo-B, and TC/HDL-C in the C allele carriers were significantly lower, when compared to those in the TT genotype in obese children and adolescents.

CONCLUSION

Obese children with low vitamin D levels, who are carriers of the C allele of the FokI gene, have lower levels of several biochemical markers of CVD risk, when compared to those who were TT homozygous. Obese children and adolescents may benefit from vitamin D supplementation, terms of lowering their CVD risk, particularly when they are carriers of the C allele of the FokI gene.

Relationship between vitamin D receptor gene polymorphisms (BsmI, TaqI, ApaI, and FokI) and calcium intake on bone mass in young Japanese women

Background

The high prevalence of low bone mass in young women in Japan has emerged as a serious health issue in recent years. Therefore, the aim of the present study was to reevaluate the relationship between genetic and dietary factors, as well as its influence on bone mass in young Japanese women, with particular emphasis on vitamin D receptor (VDR) gene polymorphisms and calcium intake.

Methods

A total of 499 Japanese women aged 20–24 years were enrolled in the study. The bone mass of the calcaneus was assessed using the quantitative ultrasound method and expressed as the osteo sono-assessment index (OSI). VDR gene polymorphisms (BsmI, TaqI, ApaI, and FokI) were analyzed using DNA extracted from saliva. Calcium intake was assessed using the Food Frequency Questionnaire based on food groups (FFQg) and adjusted with the energy intake. Participants were divided into two groups based on the median calcium intake (250 mg/1000 kcal).

Results

Consequently, bone mass was significantly different among the BsmI and TaqI genotypes after adjusting for body mass index (BMI) (p = 0.030 and 0.019, respectively). In addition, the BsmI AA and ApaI GT genotypes showed significant differences in bone mass between the calcium-intake groups, with low OSI in the low-calcium intake group and high OSI in the high-calcium intake group, respectively, even after adjusting for BMI (p = 0.020 and 0.038, respectively).

Conclusions

These findings may prove instrumental in developing a logical approach towards preventing bone loss in young Japanese women.

Assessment of vitamin D-binding protein (DBP) gene polymorphisms and their correlation with multiple sclerosis: a case-control study in a sample of the Syrian population

Background

Vitamin D deficiency is a major health concern as it increases the risk of developing many serious diseases. Recently, the correlation between vitamin D deficiency and multiple sclerosis (MS) is a matter of serious debate. In this case-control study, we aimed to assess the correlation between genetic changes in the vitamin D-binding protein (DBP) gene and their consequence on MS patients. Our sample study consisted of 110 individuals; 40 patients with MS as cases and 70 healthy controls. Vitamin D levels were determined by immunofluorescence assay, and polymorphisms at rs7041 (c.1296 T > G p.Asp416Glu) and rs4588 (c.1307C > A p.Thr420Lys) of the DBP gene were genotyped using PCR/RFLP method for all cases and controls.

Results

Our results showed that genotype frequencies were consistent with Hardy-Weinberg equilibrium. A significant association was found in rs7041 (c.1296TT) homozygous wild-type, and the odds ratio was < 1 suggesting a protective role against developing MS (OR; 0.03, p = 0.0002) whereas the c.1296GG genotype was significantly correlated with an increased risk for MS by 6 folds (OR: 6.0000, p < 0.0001). No significant association was noted at rs4588 and MS occurrence. In addition, our compound genotyping results revealed that haplotypes 1S-1S are 6 times more likely to develop MS, whereas haplotypes 1F-1F had a more protective role in MS patients (OR: 0.063, p = 0.06.), respectively. The risk of vitamin D insufficiency in patients was greater by 14 folds compared to controls (OR: 14.05, p = 0.0128). Furthermore, the c.1296GG genotype was associated significantly by more than 4 times with insufficient levels of vitamin D and by 7 folds with vitamin deficiency.

Conclusions

We conclude that polymorphisms in the DBP gene could have independent effects on the risk of developing multiple sclerosis. The homozygous recessive genotype at rs7041 was associated with insufficient levels of vitamin D and with the risk of MS emergence.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Vitamin D and Autoimmune Thyroid Disease-Cause, Consequence, or a Vicious Cycle?

Vitamin D is a steroid hormone traditionally connected to phosphocalcium metabolism. The discovery of pleiotropic expression of its receptor and of the enzymes involved in its metabolism has led to the exploration of the other roles of this vitamin. The influence of vitamin D on autoimmune disease—namely, on autoimmune thyroid disease—has been widely studied. Most of the existing data support a relationship between vitamin D deficiency and a greater tendency for development and/or higher titers of antibodies linked to Hashimoto’s thyroiditis, Graves’ disease, and/or postpartum thyroiditis. However, there have also been some reports contradicting such relationships, thus making it difficult to establish a unanimous conclusion. Even if the existence of an association between vitamin D and autoimmune thyroid disease is assumed, it is still unclear whether it reflects a pathological mechanism, a causal relationship, or a consequence of the autoimmune process. The relationship between vitamin D’s polymorphisms and this group of diseases has also been the subject of study, often with divergent results. This text presents a review of the recent literature on the relationship between vitamin D and autoimmune thyroid disease, providing an analysis of the likely involved mechanisms. Our thesis is that, due to its immunoregulatory role, vitamin D plays a minor role in conjunction with myriad other factors. In some cases, a vicious cycle is generated, thus contributing to the deficiency and aggravating the autoimmune process.

Immunomodulatory Effects of Vitamin D in Thyroid Diseases

Vitamin D is a secosteroid with a pleiotropic role in multiple physiological processes. Besides the well-known activity on bone homeostasis, recent studies suggested a peculiar role of vitamin D in different non-skeletal pathways, including a key role in the modulation of immune responses. Recent evidences demonstrated that vitamin D acts on innate and adaptative immunity and seems to exert an immunomodulating action on autoimmune diseases and cancers. Several studies demonstrated a relationship between vitamin D deficiency, autoimmune thyroid disorders, and thyroid cancer. This review aims to summarize the evidences on the immunomodulatory effect of vitamin D on thyroid diseases.

Immunomodulatory effect of vitamin D and its potential role in the prevention and treatment of thyroid autoimmunity: a narrative review

The main role of vitamin D is to control mineral homeostasis. However, recent studies suggested the existence of a number of extraskeletal effects. Among the latter, preclinical studies provided consistent data on the involvement of vitamin D in innate and adaptive immunity and autoimmunity. Molecular biology studies showed that both vitamin D receptor and vitamin D enzymatic complexes are expressed in a large number of cells and tissues unrelated to mineral homeostasis. In contrast, only a few randomized clinical trials in humans investigated the possible role of vitamin D in the prevention or treatment of immunological disorders. In this regard, low serum vitamin D levels have been reported in observational trials in human autoimmune disorders. The aim of the present paper was to review the potential implications of vitamin D in immune modulation, with special focus on thyroid autoimmune disorders.

Impact of CYP2R1, CYP27A1 and CYP27B1 genetic polymorphisms controlling vitamin D metabolism on susceptibility to hepatitis C virus infection in a high-risk Chinese population

CYP27A1, CYP2R1 and CYP27B1 hydroxylases are involved in the synthesis of 1, 25-hydroxyvitamin D₃, which plays a role in the immune regulation and pathogenesis of hepatitis C virus (HCV) infection. The aim of the present study was to investigate the relationships between polymorphisms in vitamin D pathway genes and HCV infection outcomes in a Chinese population. Nine single-nucleotide polymorphisms (SNPs) of CYP27A1, CYP2R1 and CYP27B1 were genotyped in a high-risk Chinese population. The distributions of these SNPs were compared among groups with different outcomes of HCV infection, including 863 cases of persistent HCV infection, 524 cases of spontaneous clearance, and 1079 uninfected controls. The results showed that the CYP2R1 rs12794714-G, rs10741657-A, rs1562902-C, and rs10766197-G alleles were significantly associated with increased susceptibility to HCV infection (all P_FDR < 0.05, in additive/dominant models), and the combined effect of the four unfavorable alleles was related to an elevated risk of HCV infection in a locus-dosage manner (P_trend = 0.008). Moreover, haplotype analysis suggested that, compared with the most frequent haplotype (A_rs12794714G_rs10741657T_rs1562902A_rs10766197), the haplotype containing four unfavorable alleles, GACG, was associated with a higher risk of HCV infection. The results of our study suggest that genetic variants in CYP2R1 may be biomarkers for predicting the susceptibility to HCV infection in the Chinese population.

Vitamin D Receptor Gene Polymorphisms and Autoimmune Thyroiditis: Are They Associated with Disease Occurrence and Its Features?

Purpose

Vitamin D, besides its role in calcium-phosphorus metabolism, turned out to play a significant immunomodulating function. Until now four single nucleotide polymorphisms of vitamin D receptor gene (VDR), rs2228570 (FokI), rs1544410 (BsmI), rs7975232 (ApaI), and rs731236 (TaqI), have been studied in autoimmune thyroid disorders, with conflicting results. Another functional polymorphism of the VDR gene, rs11568820 (Cdx2), has been shown to influence the immune system, although it has not been studied for its association with autoimmune thyroiditis to date. Therefore, the study aimed to evaluate the association of these five VDR gene polymorphisms with susceptibility to autoimmune thyroiditis among Caucasian Polish population. A relationship between the studied polymorphisms and selected clinical features of the disease was additionally assessed.

Methods

223 patients with autoimmune thyroiditis and 130 control subjects were enrolled in the study. VDR polymorphisms were studied by PCR-RFLP or TaqMan real-time PCR.

Results

Allele and genotype distributions of any of the studied polymorphisms did not differ significantly between patients and controls. Similarly, frequencies of haplotypes derived from rs1544410-rs7975232-rs731236 (BsmI-ApaI-TaqI) polymorphisms were not significantly different in the two studied groups. However, a weak association between rs1544410 (BsmI) or rs7975232 (ApaI) VDR polymorphisms and thyroid volume was found (p = 0.03 and p = 0.04, resp.).

Conclusions

Our results suggest that VDR gene is not a major susceptibility factor for autoimmune thyroiditis development, at least in Caucasian Polish population.

Association between vitamin D receptor gene polymorphisms and Graves' disease: a systematic review and meta-analysis

PURPOSE

The pathogenesis of Graves' disease (GD) and orbitopathy (GO) is not completely elucidated. On the other hand, vitamin D receptor (VDR) gene polymorphisms have been associated with vulnerability to a plethora of chronic autoimmune diseases. The primary aim of this study was to synthesize evidence on the association between VDR gene polymorphisms and GD. Secondary aim was to investigate their association with GO.

METHODS

A comprehensive search was conducted in PubMed, CENTRAL and Scopus, up to December 8, 2018. Data were expressed as odds ratio (OR) with 95% confidence intervals (CI). Heterogeneity was quantified with I² index.

RESULTS

Ten studies were included in the qualitative and quantitative analysis. TT subtype of TaqI polymorphism was associated with an increased risk of GD compared with Tt and tt polymorphisms (OR: 1.42; 95% CI, 1.05-1.94, p = 0.025), whereas tt was associated with a lower risk of GD, compared with TT and Tt polymorphisms (OR: 0.79; 95% CI, 0.62-0.99, p = 0.043). No association was found for ApaI, BsmI, and FokI polymorphisms. The bb subtype of BsmI polymorphism was associated with a lower risk in Asian, but with a higher GD risk in Caucasian populations, compared with BB/Bb subtypes. No eligible study was found regarding the association between VDR gene polymorphisms and the risk of GO.

CONCLUSIONS

The TT subtype of the TaqI polymorphism was associated with a higher susceptibility for GD compared with Tt and tt. Regarding BsmI, the bb subtype was associated with increased GD risk in Caucasians, whereas it is protective in Asians.

Role of cytochrome P450 polymorphisms and functions in development of ulcerative colitis

Cytochromes P450s (CYPs) are terminal enzymes in CYP dependent monooxygenases, which constitute a superfamily of enzymes catalysing the metabolism of both endogenous and exogenous substances. One of their main tasks is to facilitate the excretion of these substances and eliminate their toxicities in most phase 1 reactions. Endogenous substrates of CYPs include steroids, bile acids, eicosanoids, cholesterol, vitamin D and neurotransmitters. About 80% of currently used drugs and environmental chemicals comprise exogenous substrates for CYPs. Genetic polymorphisms of CYPs may affect the enzyme functions and have been reported to be associated with various diseases and adverse drug reactions among different populations. In this review, we discuss the role of some critical CYP isoforms (CYP1A1, CYP2D6, CYP2J2, CYP2R1, CYP3A5, CYP3A7, CYP4F3, CYP24A1, CYP26B1 and CYP27B1) in the pathogenesis or aetiology of ulcerative colitis concerning gene polymorphisms. In addition, their significance in metabolism concerning ulcerative colitis in patients is also discussed showing a clear underestimation in genetic studies performed so far.

Functional Abnormalities and Thyroid Nodules in Patients with End-stage Renal Disease

BACKGROUND/AIM

Clinical and subclinical hypothyroidism is more common in patients with end-stage renal disease (ESRD) than in the general population. Patients with ESRD with hypothyroidism are more susceptible to cardiovascular disease, with an increased risk of mortality than those with normal thyroid function. Moreover, these patients have higher incidence of benign and malignant nodules.

PATIENTS AND METHODS

This was a retrospective study on 2,147 patients with ESRD on the renal transplant waiting list between 2000 and 2015 aimed at identifying the presence of hypothyroidism and associated variables.

RESULTS

Hypothyroidism was detected in 437/2,147 (20.3%) patients, 289 of them having the subclinical form. Cardiovascular disease and older age were significantly associated with hypothyroidism, and autosomal polycystic kidney disease was correlated to goiter (p<0.001).

CONCLUSION

Thyroid abnormalities, particularly hypothyroidism with nodules, should be investigated in patients with ESRD on a waiting list for renal transplant to control cardiovascular complications and cancer risk.

PTPN22 and CTLA-4 Polymorphisms Are Associated With Polyglandular Autoimmunity

CONTEXT

Single nucleotide polymorphisms (SNPs) of various genes increase susceptibility to monoglandular autoimmunity. Data on autoimmune polyglandular syndromes (APSs) are scarce.

OBJECTIVE

Evaluate potential associations of eight SNPs with APSs.

SETTING

Academic referral endocrine clinic.

PATIENTS

A total of 543 patients with APS and monoglandular autoimmunity and controls.

INTERVENTION

The SNP protein tyrosine phosphatase nonreceptor type 22 (PTPN22) rs2476601 (+1858); cytotoxic T-lymphocyte‒associated antigen 4 (CTLA-4) rs3087243 (CT60) and rs231775 (AG49); vitamin D receptor (VDR) rs1544410 (Bsm I), rs7975232 (Apa I), rs731236 (Taq I); tumor necrosis factor α rs1800630 (-863); and interleukin-2 receptor alpha rs10795791 were tested by single-base extension in all subjects.

RESULTS

The PTPN22 +1858 allele and genotype distribution were markedly different between APS, type 1 diabetes [T1D; odds ratio (OR): 2.67; 95% confidence interval (CI): 1.52 to 4.68; P = 0.001], Graves disease (GD; OR: 1.94; 95% CI: 1.16 to 3.25; P = 0.011), and controls (OR: 3.31, 95% CI: 1.82 to 6.02; P < 0.001). T-allele carriers' risk for APS was increased (OR: 3.76; 95% CI: 1.97 to 7.14; P < 0.001). T-allele frequency was higher among APS than controls (OR: 3.25; 95% CI: 1.82 to 5.82; P < 0.001), T1D (OR: 2.54; 95% CI: 1.48 to 4.36; P = 0.001), or GD (OR: 1.89; 95% CI: 1.15 to 3.11; P = 0.012). The SNP CTLA-4 CT60 G-allele carriers were more frequent in APS (85%) than controls (78%) (OR: 1.55; 95% CI: 0.81 to 2.99). Combined analysis of CTLA-4 AG49 and CT60 revealed OR 4.89; 95% CI: 1.86 to13.59; P = 0.00018 of the genotype combination AG/GG for APS vs controls. VDR polymorphisms Bsm I, Apa I, and Taq I did not, but the haplotypes differed between APS and controls (P = 0.0011).

CONCLUSIONS

PTPN22 and CTLA-4 polymorphisms are associated with APS and differentiate between polyglandular and monoglandular autoimmunity.

The association of FokI and ApaI polymorphisms in vitamin D receptor gene with autoimmune thyroid diseases in the northwest of Iran

Background: Some genetic factors are involved in the etiology of Hashimoto thyroiditis and Graves’ disease as autoimmune thyroid diseases (AITDs). Effects of vitamin D receptor gene polymorphisms in AITDs development have already been investigated in some previous studies. However, no study has been done on the association between VDR FokI and ApaI polymorphisms and AITDs in an Iranian population. In this study, the possible effects of FokI and ApaI polymorphisms on AITDs were investigated in the population of northwest of Iran.

Methods: A total of 121 AITDs adult patients and 117 healthy controls matched by age and sex in the same population were included in this study. FokI and ApaI polymorphisms were genotyped by polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP). Chi-square test and odds ratio (OR) with 95% CI were used to analyze the data.

Results: FokI and ApaI genotypes frequencies were not significantly different between the 2 groups (p= 0.06, p= 0.73, respectively). However, FokI "CC" and "CT" genotypes were related to AITDs risk (p= 0.03; OR= 3.75; 95% CI, 1.16-12.17 and p= 0.04; OR= 3.41; 95% CI, 1.03-11.28, respectively).

Conclusion: These data suggest that FokI polymorphisms are involved in AITDs susceptibility in the population of northwest of Iran.

Vitamin D in Graves Disease: Levels, Correlation with Laboratory and Clinical Parameters, and Genetics

OBJECTIVE

The aim was to compare the vitamin D levels in patients with Graves disease (GD) with the general population and to correlate the vitamin D levels with laboratory and clinical parameters in GD. Moreover, we examined the genetic variation in genes involved in the vitamin D metabolism and their association with GD.

METHODS

The levels of vitamin D were compared in 292 patients with newly diagnosed GD and 2,305 controls. Single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR), vitamin D binding protein (DBP), and 1-α-hydroxylase (CYP27B1) were examined for association with GD and/or Graves ophthalmopathy (GO) in 708 patients and 1,178 controls.

RESULTS

Patients with GD had significantly lower vitamin D levels compared to controls (55.0 ± 23.2 vs. 87.2 ± 27.6 nmol/L, p < 0.001). In patients with GD (n = 219), there was no association between the levels of vitamin D at diagnosis and free thyroxine (fT₄), free triiodothyronine (fT₃), thyrotropin receptor antibodies (TRAb), GO at diagnosis, or relapse after terminating treatment with antithyroid drugs. Two SNPs in VDR were associated with GD: rs10735810 (OR = 1.36, 95% CI: 1.02-1.36, p = 0.02) and rs1544410 (OR = 1.47, 95% CI: 1.03-1.47, p = 0.02). There was no difference in the mean vitamin D level between genotypes in either rs10735810 or rs154410.

CONCLUSIONS

Patients with GD had lower vitamin D levels compared to the general population; however, the vitamin D levels did not affect the laboratory or clinical parameters of GD. SNPs in the VDR influenced the risk of GD through mechanisms other than reducing the vitamin D levels.

Meta-Analysis of the Association between Vitamin D Receptor Polymorphisms and the Risk of Autoimmune Thyroid Disease

The association between vitamin D receptor (VDR) polymorphisms (rs731236, rs1544410, rs2228570, and rs7975232) and the risk of autoimmune thyroid disease (AITD) had been investigated in previous studies. However, the results of these studies remained controversial. Thus, a meta-analysis was performed to derive a more precise conclusion. All related articles were systematically searched by PubMed, Embase, Google Scholar, and Chinese National Knowledge Infrastructure (CNKI). The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the strength of association. The overall results indicated that VDR rs731236 and rs2228570 polymorphisms were significantly associated with a reduced risk of AITD. However, a stratification analysis based on clinical types showed that VDR rs731236 and rs2228570 polymorphisms were associated only with a reduced risk of HT. A stratification analysis by ethnicity showed that VDR rs731236 polymorphism was significantly associated with a reduced risk of AITD in Asian and African populations. VDR rs2228570 polymorphism was associated with a reduced risk of AITD in Asian populations. VDR rs1544410 polymorphism was associated with a reduced risk of AITD in European and African populations, but with an increased risk of AITD in Asian populations. VDR rs7975232 polymorphism was significantly associated with an increased risk of AITD in African populations. In conclusion, the present study suggested that VDR rs731236, rs1544410, rs2228570, and rs7975232 polymorphisms were significantly associated with AITD risk. However, more well-designed studies should be performed to verify the current results.

Increased Risk of Thyroid Dysfunction Among Patients With Rheumatoid Arthritis

Background: Thyroid dysfunction seems to be common among rheumatoid arthritis (RA) patients, but the risk of thyroid dysfunction in RA has not been well-defined. Methods: We performed a case-control study of 65 RA patients and 550 matched non-RA subjects to assess the risk of thyroid dysfunction among Chinese RA patients. A systematic review and meta-analysis was also conducted to comprehensively define the relationship between RA and thyroid dysfunction. Results: The case-control study indicated that the prevalence of thyroid dysfunction was significantly higher in RA patients than controls (OR = 2.89, P < 0.001). Further subgroup analyses revealed positive correlations of RA with hypothyroidism (OR = 2.28, P = 0.006) and hyperthyroidism (OR = 8.95, P < 0.001). Multivariate logistic regression analysis revealed an independent association between RA and thyroid dysfunction (Adjusted OR = 2.89, 95%CI 1.63-5.12, P < 0.001). Meta-analysis of 15 independent studies also showed an obviously increased risk of thyroid dysfunction among RA patients (RR = 2.86, 95%CI 1.78-4.58, P < 0.001). Further subgroup analysis showed RA could obviously increase risk of hyperthyroidism (RR = 2.73, 95%CI 1.29-5.77, P = 0.043) and hypothyroidism (RR = 2.02, 95%CI 1.49-2.74, P < 0.001). Conclusion: Our study provides strong evidence for the increased risk of thyroid dysfunction among RA patients. Screening of thyroid dysfunction may be recommended for RA patients.

The Role of Vitamin D in Thyroid Diseases

The main role of vitamin D is regulating bone metabolism and calcium and phosphorus homeostasis. Over the past few decades, the importance of vitamin D in non-skeletal actions has been studied, including the role of vitamin D in autoimmune diseases, metabolic syndromes, cardiovascular disease, cancers, and all-cause mortality. Recent evidence has demonstrated an association between low vitamin D status and autoimmune thyroid diseases such as Hashimoto’s thyroiditis and Graves’ disease, and impaired vitamin D signaling has been reported in thyroid cancers. This review will focus on recent data on the possible role of vitamin D in thyroid diseases, including autoimmune thyroid diseases and thyroid cancers.

Does vitamin D play a role in autoimmune endocrine disorders? A proof of concept

In the last few years, more attention has been given to the "non-calcemic" effect of vitamin D. Several observational studies and meta-analyses demonstrated an association between circulating levels of vitamin D and outcome of many common diseases, including endocrine diseases, chronic diseases, cancer progression, and autoimmune diseases. In particular, cells of the immune system (B cells, T cells, and antigen presenting cells), due to the expression of 1α-hydroxylase (CYP27B1), are able to synthesize the active metabolite of vitamin D, which shows immunomodulatory properties. Moreover, the expression of the vitamin D receptor (VDR) in these cells suggests a local action of vitamin D in the immune response. These findings are supported by the correlation between the polymorphisms of the VDR or the CYP27B1 gene and the pathogenesis of several autoimmune diseases. Currently, the optimal plasma 25-hydroxyvitamin D concentration that is necessary to prevent or treat autoimmune diseases is still under debate. However, experimental studies in humans have suggested beneficial effects of vitamin D supplementation in reducing the severity of disease activity. In this review, we summarize the evidence regarding the role of vitamin D in the pathogenesis of autoimmune endocrine diseases, including type 1 diabetes mellitus, Addison's disease, Hashimoto's thyroiditis, Graves' disease and autoimmune polyendocrine syndromes. Furthermore, we discuss the supplementation with vitamin D to prevent or treat autoimmune diseases.

Sunshine vitamin and thyroid

Vitamin D exerts its canonical roles on the musculoskeletal system and in the calcium/phosphorus homeostasis. In the last years, increasing evidences suggested several extra-skeletal actions of this hormone, indicating that vitamin D may produce effects in almost all the body tissues. These are mediated by the presence of vitamin D receptor (VDR) and thanks to the presence of the 1-α-hydroxylase, the protein that converts the 25-hydroxyvitamin (calcidiol) to the active form 1,25-dihydroxyvitamin (calcitriol). Several studies evaluated the possible role of vitamin D in the pathogenesis of thyroid diseases, and this review will focus on the available data of the literature evaluating the association between vitamin D and thyroid function, vitamin D and autoimmune thyroid diseases, including Hashimoto's thyroiditis, Graves' disease and post-partum thyroiditis, and vitamin D and thyroid cancer.

Vitamin D receptor polymorphisms in immune thrombocytopenic purpura

BACKGROUND

Vitamin D receptor (VDR) polymorphisms have been studied in immune-mediated disorders, but not yet in immune thrombocytopenic purpura (ITP). We investigated whether VDR variants were associated with ITP in children.

METHODS

The study included 44 children with a diagnosis of ITP and 100 healthy controls. Five VDR polymorphisms (Cdx-2, FokI, BsmI, ApaI and TaqI) were genotyped and used to evaluate the association of VDR variants with ITP.

RESULTS

The distribution of the three Cdx-2 genotype groups (GG, GA, and AA) was significantly different between ITP patients and controls (P = 0.025); the homozygous GG genotype of Cdx-2 was overrepresented in ITP patients. The frequency of the A allele of Cdx-2 was significantly different between patients and controls (P = 0.01). The A allele of Cdx-2 was associated with a decreased risk of ITP (OR, 0.343; 95% CI: 0.150-0.782). No statistically significant difference was found between the ITP group and control group for Fok1, Bsm1, Apa1, and Taq1 polymorphisms (P > 0.5).

CONCLUSION

There appears to be an interaction between the Cdx-2 variant of VDR and childhood immune thrombocytopenia.

Environmental Basis of Autoimmunity

The three common themes that underlie the induction and perpetuation of autoimmunity are genetic predisposition, environmental factors, and immune regulation. Environmental factors have gained much attention for their role in triggering autoimmunity, with increasing evidence of their influence as demonstrated by epidemiological studies, laboratory research, and animal studies. Environmental factors known to trigger and perpetuate autoimmunity include infections, gut microbiota, as well as physical and environmental agents. To address these issues, we will review major potential mechanisms that underlie autoimmunity including molecular mimicry, epitope spreading, bystander activation, polyclonal activation of B and T cells, infections, and autoinflammatory activation of innate immunity. The association of the gut microbiota on autoimmunity will be particularly highlighted by their interaction with pharmaceutical agents that may lead to organ-specific autoimmunity. Nonetheless, and we will emphasize this point, the precise mechanism of environmental influence on disease pathogenesis remains elusive.

Vitamin D receptor gene FokI but not TaqI, ApaI, BsmI polymorphism is associated with Hashimoto's thyroiditis: a meta-analysis

Four VD receptor (VDR) gene polymorphisms (TaqI, ApaI, FokI and BsmI) have been reported to influence Hashimoto’s thyroiditis (HT) risk. However, individual studies have produced inconsistent results. We conducted a comprehensive meta-analysis of eleven case-control studies to better understand roles of the four polymorphisms in HT development. The results showed only FokI polymorphism was significantly associated with the risk of HT (F vs f: OR = 1.44, 95% CI = 1.09–1.91, P = 0.010; FF vs Ff + ff: OR = 1.72, 95% CI = 1.09–2.70, P = 0.019). Subgroup analyses demonstrated the significant effect was only present in Asian population (F vs f: OR = 1.45, 95% CI = 1.07–1.95, P = 0.016; FF vs ff: OR = 1.64, 95% CI = 1.03–2.59, P = 0.036; FF + Ff vs ff: OR = 1.34, 95% CI = 1.00–1.80, P = 0.047; FF vs Ff + ff: OR = 1.64, 95% CI = 1.03–2.64, P = 0.039), but not in Caucasian. For TaqI, ApaI and BsmI polymorphisms, no significant association was found in any model comparison. Based on the current literature, it appears that only VDR FokI polymorphism is associated with HT risk in Asian population, but not in Caucasians; and the TaqI, ApaI and BsmI polymorphisms have not positive association neither in the overall population, nor when stratified by ethnicity. Further well-designed studies with larger sample sizes and different ethnic population are needed to clarify the present findings.

Association of Vitamin D Deficiency and Thyroid Function in Postmenopausal Women

Pupose: Although there are reports of vitamin D (VitD) insufficiency in immune-mediated hypothyroidism, an association between VitD and thyroid-stimulating hormone (TSH) levels has yet to be shown. We aim to examine VitD and TSH levels among postmenopausal women, as both conditions are more prevalent in elderly women. Methods: The clinic records of postmenopausal women during their routine maintenance visits were reviewed. All patients were examined for the symptoms related to thyroid function and osteoporosis. Participants were divided into three subgroups according to their TSH levels (below <0.5 mIU/L, 0.51-4.0 mIU/L and >4.0 mIU/L). Patient characteristics and VitD levels were compared between these subgroups. Multivariate linear regression model was constructed using serum VitD and serum TSH as the dependent variables to identify factors independently associated with these laboratory values. Results: Two-hundred and nighty nine postmenopausal women were included. Average age was 62.2±7.5 years old. VitD was insufficient (10-30 ng/mL) in 12.0% and deficient (<10 ng/mL) in 60.9% of the participants. In 11.3%, TSH was low and in 7.6% of women, TSH was high, while the remaining 80.1%, had normal TSH levels. Subjects with low TSH had significantly higher VitD concentrations (34.2±29.1 ng/mL) compared to the other two groups (P-value: 0.039). In multivariate regression analysis, TSH was not a contributing factor, as age was the only significant predictor of VitD levels. Meanwhile, no predictor (including age and VitD) was identified for TSH levels in linear regression analysis. Conclusion: Age was the only independent predictor of serum VitD in this study population. Though suppressed TSH was associated with higher VitD levels, the association was not linear between TSH and VitD in postmenopausal women.

Skin Involvement and Pulmonary Hypertension Are Associated with Vitamin D Insufficiency in Scleroderma

Vitamin D status has been linked to immune system and autoimmune disorders; in fact, low levels of vitamin D are common in many autoimmune disorders. The aims of our study were to assess the prevalence of vitamin D insufficiency and the possible correlation with clinical parameters in systemic sclerosis (SSc). We recruited 40 patients (38 female and two male) with scleroderma and 40 healthy controls matched for age and gender. Demographic and clinical parameters were recorded and the 25-hydroxivitamin D3 serum levels were measured. Serum 25-hydroxivitamin D3 levels were significantly lower in patients with systemic sclerosis than in the control group. The prevalence of 25-hydroxivitamin D3 insufficiency was 50% in the patients and 22.5% in the control group. A statistically significant association was observed between the insufficiency of 25-hydroxivitamin D3 and skin involvement (p = 0.02) and echocardiography systolic pulmonary artery pressure >35 mmHg (p = 0.02). Our data show that the systemic sclerosis group has significantly lower serum 25-hydroxivitamin D3 concentrations compared to the control group; skin involvement and pulmonary hypertension are associated with vitamin D3 insufficiency.

Is vitamin D a player or not in the pathophysiology of autoimmune thyroid diseases?

1,25-Dihydroxyvitamin D is a steroid hormone derived from vitamin D, playing an important role in maintaining an adequate serum level of calcium and phosphorus. It is now clear that vitamin D exerts an endocrine action on the cells of the immune system, generating anti-inflammatory and immunoregulatory effects. The mechanisms underlying the role of vitamin D in autoimmunity are not completely understood. Lower vitamin D levels have been found in several autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, type 1 diabetes mellitus, multiple sclerosis, inflammatory bowel diseases, autoimmune thyroid diseases (i.e. Hashimoto's thyroiditis and Graves' disease) and autoimmune gastritis. Several genetic studies have demonstrated an association between thyroid autoimmunity susceptibility and gene polymorphisms of vitamin D receptor, vitamin D binding protein, 1-alpha-hydroxylase and 25-hydroxylase. Of note, some papers do not confirm this connection. With regard to the role of vitamin D in autoimmune thyroid diseases, available data remain controversial. Only few reports have analyzed the supposed association between autoimmune thyroid diseases and vitamin D concentration with inconclusive results. In our experience, low serum levels of vitamin D do not correlate either with Hashimoto's thyroiditis or with Graves' disease. The inability to achieve an unambiguous conclusion is in part due to the limitations in study design. In fact, most of the studies are cross-sectional surveys with a small number of subjects. In addition, the heterogeneity of the study population, seasonal variation of blood sampling, inter-method analytical variability of vitamin D assays and different definitions of vitamin D deficiency/insufficiency contribute to contradicting results. Therefore, further randomized, controlled, prospective trials are needed in order to demonstrate the causality of vitD in AITD and consequently the role of vitamin D supplementation in prevention or improvement of AITD, providing also information on the best formulation, dose and timing of supplementation.