Elizabeth Ramos-Lopez

Inherited Variation in Vitamin D Genes Is Associated With Predisposition to Autoimmune Disease Type 1 Diabetes

OBJECTIVE Vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] <50 nmol/L) is commonly reported in both children and adults worldwide, and growing evidence indicates that vitamin D deficiency is associated with many extraskeletal chronic disorders, including the autoimmune diseases type 1 diabetes and multiple sclerosis. RESEARCH DESIGN AND METHODS We measured 25(OH)D concentrations in 720 case and 2,610 control plasma samples and genotyped single nucleotide polymorphisms from seven vitamin D metabolism genes in 8,517 case, 10,438 control, and 1,933 family samples. We tested genetic variants influencing 25(OH)D metabolism for an association with both circulating 25(OH)D concentrations and disease status. RESULTS Type 1 diabetic patients have lower circulating levels of 25(OH)D than similarly aged subjects from the British population. Only 4.3 and 18.6% of type 1 diabetic patients reached optimal levels (≥75 nmol/L) of 25(OH)D for bone health in the winter and summer, respectively. We replicated the associations of four vitamin D metabolism genes (GC, DHCR7, CYP2R1, and CYP24A1) with 25(OH)D in control subjects. In addition to the previously reported association between type 1 diabetes and CYP27B1 (P = 1.4 × 10−4), we obtained consistent evidence of type 1 diabetes being associated with DHCR7 (P = 1.2 × 10−3) and CYP2R1 (P = 3.0 × 10−3). CONCLUSIONS Circulating levels of 25(OH)D in children and adolescents with type 1 diabetes vary seasonally and are under the same genetic control as in the general population but are much lower. Three key 25(OH)D metabolism genes show consistent evidence of association with type 1 diabetes risk, indicating a genetic etiological role for vitamin D deficiency in type 1 diabetes.

Vitamin D deficiency and a CYP27B1-1260 promoter polymorphism are associated with chronic hepatitis C and poor response to interferon-alfa based therapy

BACKGROUND & AIMS Vitamin D is an important immune modulator and preliminary data indicated an association between vitamin D deficiency and sustained virologic response (SVR) rates in hepatitis C virus (HCV) genotype 1 patients. We, therefore, performed a comprehensive analysis on the impact of vitamin D serum levels and of genetic polymorphisms with functional relevance within the vitamin D cascade on chronic hepatitis C and its treatment. METHODS Vitamin D serum levels, genetic polymorphisms within the vitamin D receptor and 1α-hydroxylase were determined in a cohort of 468 HCV genotype 1, 2, and 3 infected patients who were treated with interferon-alfa based regimens. RESULTS Chronic hepatitis C was associated with a high incidence of severe vitamin D deficiency compared to controls (25(OH)D(3)<10 ng/ml in 25% versus 12%, p<0.00001). 25(OH)D(3) deficiency correlated with SVR in HCV genotype 2 and 3 patients (50% and 81% SVR for patients with and without severe vitamin D deficiency, respectively, p<0.0001). In addition, the CYP27B1-1260 promoter polymorphism rs10877012 had substantial impact on 1,25-dihydroxyvitamin D serum levels (72, 61, and 60 pmol/ml for rs10877012 AA, AC, and CC, respectively, p=0.04) and on SVR rates in HCV genotype 1, 2, and 3 infected patients (77% and 65% versus 42% for rs10877012 AA, AC, and CC, respectively, p=0.02). CONCLUSIONS Chronic hepatitis C virus infection is associated with vitamin D deficiency. Reduced 25-hydroxyvitamin D levels and CYP27B1-1260 promoter polymorphism leading to reduced 1,25-dihydroxyvitamin D levels are associated with failure to achieve SVR in HCV genotype 1, 2, and 3 infected patients.

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

OBJECTIVE—Epidemiological studies have linked vitamin D deficiency with the susceptibility to type 1 diabetes. Higher levels of the active metabolite 1α,25-dihydroxyvitamin D (1α,25(OH)2D) could protect from immune destruction of the pancreatic β-cells. 1α,25(OH)2D is derived from its precursor 25-hydroxyvitamin D by the enzyme 1α-hydroxylase encoded by the CYP27B1 gene and is inactivated by 24-hydroxylase encoded by the CYP24A1 gene. Our aim was to study the association between the CYP27B1 and CYP24A1 gene polymorphisms and type 1 diabetes. RESEARCH DESIGN AND METHODS—We studied 7,854 patients with type 1 diabetes, 8,758 control subjects from the U.K., and 2,774 affected families. We studied four CYP27B1 variants, including common polymorphisms −1260C>A (rs10877012) and +2838T>C (rs4646536) and 16 tag polymorphisms in the CYP24A1 gene. RESULTS—We found evidence of association with type 1 diabetes for CYP27B1 −1260 and +2838 polymorphisms, which are in perfect linkage disequilibrium. The common C allele of CYP27B1 −1260 was associated with an increased disease risk in the case-control analysis (odds ratio for the C/C genotype 1.22, P = 9.6 × 10−4) and in the fully independent collection of families (relative risk for the C/C genotype 1.33, P = 3.9 × 10−3). The combined P value for an association with type 1 diabetes was 3.8 × 10−6. For the CYP24A1 gene, we found no evidence of association with type 1 diabetes (multilocus test, P = 0.23). CONCLUSIONS—The present data provide evidence that common inherited variation in the vitamin D metabolism affects susceptibility to type 1 diabetes.

The vitamin D receptor gene FokI polymorphism: Functional impact on the immune system

1α,25‐Dihydroxyvitamin D3 (1,25(OH)2D3) has important effects on the growth and function of multiple cell types. These pleiotropic effects of 1,25(OH)2D3 are mediated through binding to the vitamin D receptor (VDR). Several polymorphisms of the human VDR gene have been identified, with the FokI polymorphism resulting in VDR proteins with different structures, a long f‐VDR or a shorter F‐VDR. The aim of this study was to investigate the functional consequences of the FokI polymorphism in immune cells. In transfection experiments, the presence of the shorter F‐VDR resulted in higher NF‐κB‐ and NFAT‐driven transcription as well as higher IL‐12p40 promoter‐driven transcription. Marginal differences were observed for AP‐1‐driven transcription, and no differential effects were observed for transactivation of a classical vitamin D‐responsive element. Concordantly, in human monocytes and dendritic cells with a homozygous short FF VDR genotype, expression of IL‐12 (mRNA and protein) was higher than in cells with a long ff VDR genotype. Additionally, lymphocytes with a short FF VDR genotype proliferated more strongly in response to phytohemagglutinin. Together, these data provide the first evidence that the VDR FokI polymorphism affects immune cell behavior, with a more active immune system for the short F‐VDR, thus possibly playing a role in immune‐mediated diseases.

CYP2R1 (vitamin D 25‐hydroxylase) gene is associated with susceptibility to type 1 diabetes and vitamin D levels in Germans

The vitamin D system has been implicated in type 1 diabetes by epidemiological and immune intervention studies as well as by polymorphisms of the vitamin D binding protein (DBP) and CYP27B1 genes. CYP2R1, a cytochrome P450 enzyme, catalyzes the formation of vitamin D3 to 25‐hydroxyvitamin D3 (25(OH)D3), the main circulating vitamin D metabolite.

Protection From Type 1 Diabetes by Vitamin D Receptor Haplotypes

Abstract:  Vitamin D has been involved in the modulation of calcium and bone metabolism as well as in the immune system, where it suppresses the proliferation of activated T cells. These effects are exerted via the vitamin D receptor (VDR). Polymorphisms within this gene have been exhaustively studied in diverse autoimmune diseases but with inconsistent results. We previously reported a positive association of polymorphisms within the VDR gene (Apa I, Taq I, Bsm I, and Fok I). In the present article we extended our previous reports to seven additional polymorphisms (rs757343, rs9729, rs2853559, rs1989969, rs3847987, rs2238135, and rs4516035) in a larger set of German simplex type 1 diabetes families. Additionally we correlated serum levels of 25(OH)D3 and 1,25(OH)2D3 with VDR genotypes and haplotypes. The haplotypes “CG” (Taq I‐Apa I), “CGG” (Taq I‐Apa I‐Tru I), “CGC” (Taq I‐Apa I‐Fok I), “GCTG” (rs9729‐Taq I‐Apa I‐Tru I), and “CGGC”(Taq I‐Apa I, Tru I, Fok I) were less often transmitted, thus negatively associated with type 1 diabetes. Patients who carried the genotype “CC” of the rs3847987 polymorphism had higher median serum levels of 25(OH)D3. Furthermore, the majority of patients with this genotype possessed normal serum levels of 25(OH)D3. We conclude that variants of the VDR may confer a genetic protection from type 1 diabetes. Furthermore, normal serum levels of 25(OH)D3 appear to correlate with a VDR genotype. This supports a role of vitamin D in the immune pathogenesis of type 1 diabetes.

Vitamin D receptor polymorphisms in differentiated thyroid carcinoma.

BACKGROUND Vitamin D receptor (VDR) expression has been shown to be upregulated in several tumors and is supposed to represent an important endogenous response to tumor progression. To investigate the role of the VDR gene and its influence on 25(OH)D(3) and 1,25(OH)(2)D(3) plasma levels in thyroid carcinoma, we analyzed four VDR polymorphisms in patients and healthy controls (HC). METHODS Patients with thyroid carcinoma (n = 172) (n = 132 for papillary and n = 40 for follicular) and HC (n = 321) were genotyped for the ApaI (rs7975232), TaqI (rs731236), BsmI (rs1544410), and FokI (rs10735810) polymorphisms within the VDR gene and correlated with 25(OH)D(3) and 1,25(OH)(2)D(3) plasma levels. RESULTS The genotypes AA of the ApaI (rs7975232) and FF of the FokI (rs10735810) polymorphisms were significantly less frequent (12.5% vs. 35.2% and 25% vs. 42.1%, respectively, both corrected p [p(c)] = 0.04) in patients with follicular thyroid cancer (FTC) than in HC. Additionally, the haplotypes, Ta (57.5% vs. 41.4%; p(c) = 0.0207), af (24.6% vs. 14.3%; p(c) = 0.0116), Tab (51.1% vs. 36.8%; p(c) = 0.0495), and Tabf (18.7% vs. 13.6%; p(c) = 0.0240) were more frequent, whereas the haplotypes AF (17.1% vs. 37.2%; p(c) = 0.0008), BF (11.4% vs. 31.9%; p(c) = 0.012), tF (7.9% vs. 25.5%; p(c) = 0.0016), and tABF (7.6% vs. 23%; p(c) = 0.0115) were less frequent in the FTC patients compared to HC. Neither genotype nor haplotype frequencies differed between patients with papillary thyroid cancer (PTC) and HC. Further, individuals with PTC and FTC had a significantly lower level of circulating 1,25(OH)(2)D(3) compared to controls. In contrast, no differences of the 25(OH)D(3) concentration between patients and HC were observed. VDR polymorphisms were not associated with 25(OH)D(3) and 1,25(OH)(2)D(3) plasma levels. CONCLUSIONS Lower circulating levels of 1,25(OH)(2)D(3) are observed in patients with differentiated thyroid carcinoma. Further, while the alleles AA and FF of the ApaI (rs7975232) and FokI (rs10735810) VDR polymorphisms and the haplotype tABF confer to protection from follicular carcinoma, the haplotype Tabf appeared to be associated with an increased FTC risk. Since this is the first report associating VDR polymorphisms with thyroid carcinoma, these findings need to be confirmed in studies with larger numbers of patients.

Effect of a randomised controlled vitamin D trial on insulin resistance and glucose metabolism in patients with type 2 diabetes mellitus.

The aim of our study was to investigate the influence of a 6-month vitamin D supplementation in patients with noninsulin-requiring type 2 diabetes mellitus. We included 86 patients in a placebo-controlled, randomised, double-blind study. During 6 months patients received Vigantol oil once a week corresponding to a daily dose of 1904 IU or placebo oil, followed by 6 months of follow-up. At start and at 3-month intervals 25OHD, PTH, body mass index, HbA1c, insulin, C-peptide, and homeostasis model assessment-index were measured. The primary outcome was a change in fasting blood glucose and insulin levels. After 6 months of therapy, the verum groups 25OHD had increased to a median of 35 ng/ml in comparison to the placebo group (median 20 ng/ml, p<10-6). PTH tended to decrease in the verum group (25.5 pg/ml vs. 35.0 pg/ml, p=0.08). After 6 months of therapy, 31 patients (78%) achieved a 25OHD concentration of >20 ng/ml. Their HbA1c was significantly lower at baseline (p=0.008) and after therapy (p=0.009) than in patients with 25OHD below 20 ng/ml. C-Peptide, insulin, and HOMA-index did not change significantly in the verum group but fasting insulin was positively correlated with 25OHD concentrations after 6 months of therapy in both groups. There were no significant effects of vitamin D with a daily dose of 1904 IU on metabolic parameters in type 2 diabetes. However, the correlative findings of this study suggest a link of the 25OHD status and metabolic function in type 2 diabetes. Whether vitamin D therapy with higher doses can improve glucose metabolism needs to be investigated in follow-up trials.

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

1,25(OH)(2)D(3) and 25(OH)D(3) have been associated with type 1 diabetes. Diverse enzymes are involved in the synthesis of these metabolites: the 25-Vitamin-D-hydroxylase (CYP2R1), the 25-hydroxyvitamin-D(3)-1-alpha-hydroxylase (CYP27B1) and the 25(OH)D(3)-24-hydroxylase (CYP24) among others. Serum levels of 25(OH)D(3) and 1,25(OH)(2)D(3) were investigated in type 1 diabetes patients (n=173) and the mRNA expression of the CYP2R1, CYP27B1 and CYP24 genes in type 1 diabetes patients (n=33) and healthy controls (n=23). These parameters were correlated with the -1260 (C/A) polymorphism in the CYP27B1 gene. Lower expression of CYP27B1 mRNA in comparison with healthy controls (1.7165 versus 1.7815, P=0.0268) was found. Additionally, patients carrying the genotype CC possessed a reduced amount of CYP27B1 mRNA compared to healthy controls (1.6855 versus 1.8107, respectively, P=0.0220). The heterozygosity rate of the -1260 C/A polymorphism was more frequent in patients with normal levels of 1,25(OH)(2)D(3) (> or =19.9 pmol/ml) than in whose with a level of less than 19.9 pmol/ml (46.7% versus 22.2%, P=0.0134). No correlation with serum levels of 25(OH)D(3) was found. Thus, CYP27B1 gene could play a functional role in the pathogenesis of type 1 diabetes through modulation of its mRNA expression and influence serum levels of 1,25(OH)(2)D(3) via the -1260 C/A polymorphism.

TIM-3 polymorphisms in type 1 diabetes families

AbstractTIM-3 is a transmembrane protein preferentially expressed on differentiated Th1 cells, which play a role in Th1-mediated diseases including type 1 diabetes. We investigated the role of the rs10515746 (A/C), rs1036199 (A/C), and rs10053538 (A/C) single nucleotide polymorphisms (SNPs) within theTIM-3 gene in 186 German type 1 diabetes families (558 individuals) and its interaction with human leukocyte antigen (HLA) high-risk haplotypes DQ2(DQA*0501-DQB*0201)-DQ8 (DQA*0301-DQB*0302). Alleles A, C, and A of the rs10515746 (A/C), rs1036199 (A/C), and rs10053538 (A/C) SNPs were found in a frequency of 20.4%, 19.0%, and 4.2%, respectively. Transmission analysis of these polymorphisms did not show any significant difference. Although in patients with HLA DQx/x (neither HLA DQ2 nor DQ8) an undertransmission of allele A (14.3% vs. 85.7%) of the rs10053538 (A/C) SNP and an overtransmission of allele A (66.7% vs. 33.3%) of the rs10515746 (A/C) SNP was observed, these associations did not remain statistically significant after correction for multiple comparisons. Although we found no association of TIM-3 with type 1 diabetes in the German population, we cannot discard a possible association in a larger size.