Vitamin D status and pathway genes in five European autoimmune Addison's disease cohorts

OBJECTIVE

While vitamin D regulates immune cells, little is known about it in autoimmune Addison's disease (AAD). We investigated the vitamin D status in AAD patients from five European populations to assess its deficiency. In addition, we studied two case-control cohorts for vitamin D metabolism and pathway genes.

DESIGN

Cross-sectional study.

METHODS

A total of 1028 patients with AAD from Germany (n = 239), Italy (n = 328), Norway (n = 378), UK (n = 44) and Poland (n = 39) and 679 controls from Germany (n = 301) and Norway (n = 378) were studied for 25(OH)D3 (primary objective). Secondary objectives (1,25(OH)2D3 and pathway genes) were examined in case-controls from Germany and Norway correlating 25(OH)D3 and single nucleotide polymorphisms within genes encoding the vitamin D receptor (VDR), 1-α-hydroxylase (CYP27B1), 25-hydroxylase (CYP2R1), 24-hydroxylase (CYP24A1) and vitamin D binding protein (GC/DBP).

RESULTS

Vitamin D deficiency (25(OH)D3 10-20 ng/mL) was highly prevalent in AAD patients (34-57%), 5-22% were severely deficient (<10 ng/mL), 28-38% insufficient (20-30 ng/mL) and only 7-14% sufficient (>30 ng/mL). Lower 25(OH)D3 and 1,25(OH)2D3 levels were observed both in Norwegian and German AAD (P = 0.03/0.003 and P = 1 × 10-5/< 1 × 10-7, respectively) the former was associated with CYP2R1 (rs1553006) genotype G. Whereas controls achieved sufficient median 25(OH)D3 in summers (21.4 to 21.9 ng/mL), AAD patients remained largely deficient (18.0 to 21.2 ng/mL) and synthesize less 1,25(OH)2D3.

CONCLUSION

Vitamin D deficiency and insufficiency are highly prevalent in AAD patients. The vitamin D status of AAD may be influenced by genetic factors and suggests individual vitamin D requirements throughout the year.

CTLA-4 as a genetic determinant in autoimmune Addison's disease

In common with several other autoimmune diseases, autoimmune Addison's disease (AAD) is thought to be caused by a combination of deleterious susceptibility polymorphisms in several genes, together with undefined environmental factors and stochastic events. To date, the strongest genomic association with AAD has been with alleles at the HLA locus, DR3-DQ2 and DR4. The contribution of other genetic variants has been inconsistent. We have studied the association of 16 single-nucleotide polymorphisms (SNPs) within the CD28-CTLA-4-ICOS genomic locus, in a cohort comprising 691 AAD patients of Norwegian and UK origin with matched controls. We have also performed a meta-analysis including 1002 patients from European countries. The G-allele of SNP rs231775 in CTLA-4 is associated with AAD in Norwegian patients (odds ratio (OR)=1.35 (confidence interval (CI) 1.10-1.66), P=0.004), but not in UK patients. The same allele is associated with AAD in the total European population (OR=1.37 (CI 1.13-1.66), P=0.002). A three-marker haplotype, comprising PROMOTER_1661, rs231726 and rs1896286 was found to be associated with AAD in the Norwegian cohort only (OR 2.43 (CI 1.68-3.51), P=0.00013). This study points to the CTLA-4 gene as a susceptibility locus for the development of AAD, and refines its mapping within the wider genomic locus.

Detection of a low-grade enteroviral infection in the islets of langerhans of living patients newly diagnosed with type 1 diabetes

The Diabetes Virus Detection study (DiViD) is the first to examine fresh pancreatic tissue at the diagnosis of type 1 diabetes for the presence of viruses. Minimal pancreatic tail resection was performed 3-9 weeks after onset of type 1 diabetes in six adult patients (age 24-35 years). The presence of enteroviral capsid protein 1 (VP1) and the expression of class I HLA were investigated by immunohistochemistry. Enterovirus RNA was analyzed from isolated pancreatic islets and from fresh-frozen whole pancreatic tissue using PCR and sequencing. Nondiabetic organ donors served as controls. VP1 was detected in the islets of all type 1 diabetic patients (two of nine controls). Hyperexpression of class I HLA molecules was found in the islets of all patients (one of nine controls). Enterovirus-specific RNA sequences were detected in four of six patients (zero of six controls). The results were confirmed in various laboratories. Only 1.7% of the islets contained VP1(+) cells, and the amount of enterovirus RNA was low. The results provide evidence for the presence of enterovirus in pancreatic islets of type 1 diabetic patients, which is consistent with the possibility that a low-grade enteroviral infection in the pancreatic islets contributes to disease progression in humans.

CYP21A2 polymorphisms in patients with autoimmune Addison's disease, and linkage disequilibrium to HLA risk alleles

OBJECTIVE

Steroid 21-hydroxylase, encoded by CYP21A2, is the major autoantigen in autoimmune Addison's disease (AAD). CYP21A2 is located in the region of the HLA complex on chromosome 6p21.3, which harbours several risk alleles for AAD. The objective was to investigate whether CYP21A2 gene variants confer risk of AAD independently of other risk alleles in the HLA loci.

DESIGN

DNA samples from 381 Norwegian patients with AAD and 340 healthy controls (HC) previously genotyped for the HLA-A, -B, -DRB1, and -DQB1 and MICA loci were used for genotyping of CYP21A2.

METHODS

Genotyping of CYP21A2 was carried out by direct sequencing. Linkage of CYP21A2 to the HLA loci was assessed using UNPHASED version 3.0.10 and PHASE version 2.1.

RESULTS

Heterozygotes of the single-nucleotide polymorphisms (SNPs) rs397515394, rs6467, rs6474, rs76565726 and rs6473 were detected significantly more frequently in AAD patients compared with HC (P<0.005), but all SNPs were in a linkage disequilibrium (LD) with high-risk HLA-DRB1 haplotypes. rs6472C protected against AAD (odds ratio=0.15, 95% CI (0.08-0.30), P=3.8×10(-10)). This SNP was not in an LD with HLA loci (P=0.02), but did not increase protection when considering the effect of HLA-DRB1 alleles. Mutations causing congenital adrenal hyperplasia were found in heterozygosity in <1.5% of the cases in both groups.

CONCLUSION

Genetic variants of CYP21A2 associated to AAD are in LD with the main AAD risk locus HLA-DRB1, and CYP21A2 does not constitute an independent susceptibility locus.

A common haplotype in NAPEPLD is associated with severe obesity in a Norwegian population-based cohort (the HUNT study)

Obesity has a strong genetic etiology involving numerous identified metabolic pathways and others not yet examined. We investigated the association between severe obesity and genetic variation in selected candidate genes, including three drug-related genes: cannabinoid receptor 1 (CNR1), N-acyl phosphatidylethanolamine phospholipase D (NAPEPLD), and gastric lipase (LIPF); and three genes related to inflammation: nicotinamide phosphoribosyltransferase, six-transmembrane epithelial antigen of the prostate 4 (STEAP4) and interleukin 18 (IL-18). Subjects were 1,632 individuals with severe obesity (BMI ≥ 35 kg/m²) and 3,379 controls (BMI 20-24.9 kg/m²) that took part in a Norwegian population based cohort study. Tagging single-nucleotide polymorphisms (SNPs) of the coding region of these genes were analyzed. SNP-haplotypes for each gene were constructed in order to analyze allelic, genotypic, and haplotypic association to obesity. A single SNPs rs17605251 in NAPEPLD was nominally associated with BMI ≥ 35 kg/m² (P = 0.035). A common haplotype in NAPEPLD was associated with BMI ≥ 35 kg/m² after correction for multiple testing. The allele frequency was 56.8% in cases and 60.3% in controls, giving an odds ratio (OR) of 0.87 (95% confidence interval (CI) 0.79, 0.95; P = 0.0016). Homozygosity for this haplotype was protective against obesity (OR 0.79 (CI 0.70-0.91); P = 0.00059). The SNP rs7913071 in LIPF was associated with obesity, but the association lost statistical significance after correction for multiple testing. The CNR1, IL-18, STEAP4, and nicotinamide phosphoribosyltransferase genes were not associated with obesity. In conclusion a common haplotype in NAPEPLD, an enzyme involved in endocannabinoid synthesis, was protective against obesity.

CD14 polymorphisms and serum CD14 levels through childhood: a role for gene methylation?

BACKGROUND

CD14 is a pattern-recognition receptor for environmental LPS, and engagement of the CD14-LPS complex activates innate host defense mechanisms. Single nucleotide polymorphisms (SNPs) in the CD14 gene have been associated with soluble CD14 (sCD14) levels, but inconsistencies between studies suggest the presence of regulatory mechanisms hitherto not well understood.

OBJECTIVE

We sought to investigate possible associations between CD14 SNPs and sCD14 levels at different time points in childhood (at birth [cord blood] and 2 and 10 years) and to explore whether these associations were related to CD14 gene methylation.

METHODS

Four SNPs, rs2569191 (-1145GA), rs5744455 (-550CT or -651CT), rs2569190 (-159CT or -260CT), and rs4914 in CD14 were genotyped in 762 children from the Environmental and Childhood Asthma study. Genotype frequencies were analyzed for association with sCD14 levels in 660 babies, 346 children at age 2 years, and 360 children at age 10 years. In a subgroup of 157 children with DNA available at both 2 and 10 years of age, CD14 methylation patterns were determined and analyzed against detected CD14 gene-sCD14 associations.

RESULTS

rs2569191, rs5744455, and rs2569190 were associated with sCD14 levels at birth and 2 years, but only rs5744455 was associated with sCD14 levels at 10 years. CD14 methylation increased significantly from age 2 to 10 years, and the level of methylation was inversely correlated with sCD14 levels at 10 years.

CONCLUSION

The reduced effect of CD14 polymorphisms on sCD14 levels from early to late childhood paralleled a small but significant increase in CD14 methylation during the same period.

FTO genotype and weight gain in obese and normal weight adults from a Norwegian population based cohort (the HUNT study)

The fat mass and obesity associated gene ( FTO) is associated with bodyweight and obesity. The aim of this study was to investigate if FTO genotype affects weight gain in adulthood. We investigated the weight development over a period of 11 years in a case-control study, consisting of 1,632 cases (BMI≥35 kg/m (2)) and 3,379 normal weight controls (BMI 20-24.9 kg/m (2)) from a Norwegian population based cohort, the HUNT study. Subjects were aged 20-80 at baseline, 25% men and 75% women. FTO genotype was assessed by genotyping of the SNP rs1421085. A strong association between FTO and obesity was found, consistent with an additive gene effect. Cases had an average weight gain of 11.1 kg, whereas controls had an average weight gain of 1.4 kg. Genotype was neither associated with weight gain in obese, nor controls. Cases had an average weight gain of 10.7 kg for individuals with zero risk alleles, 11.3 for one risk allele and 11.1 kg for two risk alleles. Controls had an average weight gain of 1.4 kg, 1.4 and 1.3 for the respective genotypes. In conclusion, FTO was associated with obesity, but not with weight gain in adults during 11 years of follow-up.

Programmed death ligand 1 (PD-L1) gene variants contribute to autoimmune Addison's disease and Graves' disease susceptibility

CONTEXT

Despite much investigation, a substantial amount of the genetic susceptibility to autoimmune diseases remains unaccounted for. Recently, a single-nucleotide polymorphism (SNP) in the programmed death ligand 1 (PD-L1) gene has been associated with Graves' disease (GD) in a Japanese patient cohort. Our aim was to determine whether variants in PD-L1 are also associated with autoimmune Addison's disease (AAD) and to replicate the previous association in patients with GD from the United Kingdom.

DESIGN AND PATIENTS

We analyzed eight SNPs within PD-L1 in a United Kingdom cohort of 315 AAD subjects and 316 healthy controls. We then replicated our experiment in a cohort of 342 Norwegian AAD cases and 379 controls and in 496 United Kingdom GD subjects.

RESULTS

Three of the eight SNPs studied, part of a haplotype block in the PD-L1 gene, showed modest association with both AAD and GD in the United Kingdom cohort, with maximum evidence at the marker RS1411262 [United Kingdom AAD odds ratio 1.33 (5-95% confidence interval 1.02-1.73), P(genotype) = 0.028; GD odds ratio 1.36 (5-95% confidence interval 1.07-1.72), P(genotype) = 0.033]. Association with genotypes at the same three markers was confirmed in the Norwegian AAD cohort [P(genotype) = 0.011-0.020]. A recessive effect at the most associated alleles was observed in both the AAD and GD cohorts.

CONCLUSIONS

We confirm the role of PD-L1 variants in GD susceptibility and extend these findings to demonstrate association in two Northern European patient cohorts with AAD. PD-L1 joins the growing number of known susceptibility loci exerting modest effects in these autoimmune disorders.

T cell-specific T-box transcription factor haplotype is associated with allergic asthma in children

BACKGROUND

T cell-specific T-box transcription factor (T-bet) is a member of the T-box family of transcription factors regulating lineage commitment of T(H) lymphocytes toward a predominant T(H)1 phenotype. Asthma and allergy are common complex diseases characterized by T(H)2-mediated inflammation.

OBJECTIVE

We aimed to assess possible relationships between the T-bet gene (TBX21) and asthma and allergy in children.

METHOD

Twelve single nucleotide polymorphisms (SNPs) in the TBX21 region were genotyped in 948 children from the Environment and Childhood Asthma study. Allele and haplotype frequencies were compared in children with and without asthma (by 10 years) and allergy (> or =1 positive skin prick test response), as well as for the quantitative traits bronchial hyperresponsiveness determined by means of methacholine bronchial challenge testing, lung function determined by means of forced flow volume loops, fractional exhaled nitric oxide measurement, eosinophil count, and serum total IgE level.

RESULTS

Allergic asthma was significantly associated with 2 of the tested SNPs (rs11650354 and rs16947078) and further associated with the particular haplotype including these SNPs, with homozygote status resulting in an odds ratio of 8.3 (95% CI, 2.5-26.9) for allergic asthma. Neither nonallergic asthma or "allergy alone" nor the remaining quantitative variables were associated with TBX21 SNPs or haplotypes.

CONCLUSION

An association between a specific TBX21 haplotype and allergic asthma in children is demonstrated for the first time and might explain previously detected associations between SNPs within TBX21 and asthma and bronchial hyperresponsiveness.

HLA Dr-Dq haplotypes and the TNFA-308 polymorphism: associations with asthma and allergy

BACKGROUND

The HLA (human leukocyte antigen) class II genes DQB1 and DRB1 and the Tumor Necrosis Factor alpha gene (TNFA) within the HLA complex (chromosome 6p21) have been associated with asthma and allergy. Due to the strong linkage disequilibrium characterizing this complex and the multiple asthma/allergy expressions, we aimed to determine which of these genes were primarily involved in specific asthma/allergy traits.

METHODS

The DRB1-DQB1 alleles and TNFA-308 polymorphism were genotyped in 959 children from the Environment and Childhood Asthma study and analyzed for possible associations with allergic and non-allergic asthma (with/without at least one positive skin prick test for allergens) and specific allergic sensitization, as well as bronchial hyperresponsiveness and total IgE, using both allele and extended haplotype analyses.

RESULTS

Different genes within the HLA complex were associated with separate asthma and allergy traits. Nonallergic asthma was associated with both the TNFA-308A allele [Odds ratio (OR) 1.7 (1.3-2.3)] and DRB1 03 allele [OR 1.6(1-2.6)], but extended DRB1 03-TNFA-308 haplotype analysis suggested that the DRB1-DQB1 association was secondary to linkage disequilibrium with the TNFA-308 polymorphism. Allergies were associated with HLA class II alleles only; birch sensitization with DQB1 0603-DRB1 13 [OR 2.3 (1.4-4.0)] and mugwort sensitization with DQB1 0609-DRB1 13 [OR 7.1 (1.9-27.0)] and DQB1 0501-DRB1 01 [OR 2.0 (1.0-4.0)].

CONCLUSIONS

Our data suggests that asthma is not associated with DRB1 or DQB1 but rather TNFA or a gene(s) in linkage disequilibrium, while sensitization to specific allergens is associated with particular alleles at the DQ and/or DR loci. A novel association between DQB1 0603-DRB1 13 and birch allergy is identified.

Eosinophil cationic protein (ECP) polymorphisms and association with asthma, s-ECP levels and related phenotypes

BACKGROUND

Eosinophil cationic protein (ECP) is a potent cytotoxic secretory protein with bactericidal and antiviral properties. ECP is released by activated eosinophils and regarded as a marker of eosinophilic inflammation. High levels of ECP have been reported in cases of active asthma and other allergic diseases. This study aimed to assess whether three single-nucleotide polymorphisms (SNPs) in the ECP gene (RNASE3) on chromosome 14 q24-q31 or their haplotypes are associated with asthma, allergy, or related phenotypes.

METHODS

The three SNPs -38CA, +371CG and +499CG in RNASE3 and their haplotypes were analyzed for associations with asthma, serum-ECP (s-ECP) levels, allergic sensitization (positive skin-prick test to common allergens), bronchial hyperresponsiveness (BHR) assessed by methacholine inhalation, and serum-IgE (s-IgE) levels in 177 families from Norway and the Netherlands identified through siblings with asthma.

RESULTS

Transmission disequilibrium test (TDT) demonstrated significant associations between the A-G-G haplotype and asthma as well as the specific phenotypes allergic asthma (but not non-allergic asthma), high s-ECP, high s-IgE and BHR, while the C-G-G haplotype was associated with reduced occurrence of these traits. In addition, the -38A allele was associated with high s-ECP levels and allergic asthma.

CONCLUSION

The present study suggests that the A-G-G haplotype in the RNASE3 gene influences the development of asthma, in particular, an allergic form of asthma. Furthermore, as the -38CA SNP lies in close vicinity of known intron-regulatory sites, results of SNP analysis suggest that the detected association is possibly linked to a genetic transcriptional control of s-ECP levels.

[Genetic causes of obesity]

BACKGROUND

Overweight and obesity represent an increasing health problem. Both genetic and environmental factors contribute to the development of obesity. This article summarises the genetic aspects of these conditions.

MATERIAL AND METHODS

A literature search was conducted using PubMed and OMIM. Both original and review articles were included.

RESULTS AND INTERPRETATION

The genetic influence on body weight is shown by twin and family studies. Environmental changes in recent decades have promoted the development of obesity in individuals at risk because of their genetic composition. Our understanding of the molecular pathways underlying common obesity is limited. During the last decade a handful of monogenic disorders leading to early, severe obesity in humans have been identified. All affect the central regulation of appetite. These conditions are rare, except for mutations in the melanocortin 4 receptor that account for about 5% of morbidly obese patients (BMI > 40 kg/m). The identification of monogenic forms of obesity has contributed valuable insight into the regulation of appetite and development of obesity, although causal treatment only exists for leptin deficiency. In addition, several well defined Mendelian syndromes are associated with overweight and obesity. The molecular genetic cause is known for some of these syndromes, but how appetite and energy balance are affected is still unclear.

Association of intercellular adhesion molecule-1 gene with type 1 diabetes

Intercellular adhesion molecule-1 (ICAM-1) functions via its ligands, the leucocyte integrins, in adhesion of immune cells to endothelial cells and in T cell activation. The third immunoglobulin-like extracellular domain binds integrin Mac-1 and contains a common non-conservative aminoacid polymorphism, G241R. Phenotypically, ICAM-1 has been associated with type 1 diabetes, a T-cell-mediated autoimmune disease. We assessed two independent datasets, and noted that R241 was associated with lower risk of type 1 diabetes than is G241 (3695 families, relative risk 0.91, p=0.03; 446 families, 0.60, p=0.006). Our data indicate an aetiological role for ICAM-1 in type 1 diabetes, which needs to be confirmed in future genetic and functional experiments.

Evidence by allelic association-dependent methods for a type 1 diabetes polygene (IDDM6) on chromosome 18q21

Type 1 diabetes is a common polygenic disease. Fine mapping of polygenes by affected sibpair linkage analysis is not practical and allelic association or linkage disequilibrium mapping will have to be employed to attempt to detect founder chromosomes. Given prior evidence of linkage of the Jk-D18S64 region of chromosome 18q12-q21 to type 1 diabetes, we evaluated the 12 informative microsatellite markers in the region for linkage with disease by the transmission disequilibrium test (TDT) in a UK data set of type 1 diabetic families (n = 195). Increased transmission of allele 4 of marker D18S487 to affected children was detected (P = 0.02). Support for this was extended in a total of 1067 families from four different countries by isolating, and evaluating by the TDT, two novel microsatellites within 70 kb of D18S487. Evidence for linkage and association was P = 5 x 10(-5) and 3 x 10(-4), respectively. There was no evidence for increased transmission of associated alleles to nonaffected siblings. Analysis of an additional 390 families by the TDT did not extend the evidence further, and reduced support in the total 1457 families to P = 0.001 for linkage and P = 0.003 for association. However, evidence for linkage by affected sibpair allele sharing was strong (P = 3.2 x 10(-5)) in the second data set. Heterogeneity in TDT results between data sets was, in part, accounted for by the presence of more than one common disease-associated haplotype (allelic heterogeneity) which confounds the analysis of individual alleles by the TDT. Guidelines for strategies for the mapping of polygenes are suggested with the emphasis on collections of large numbers of families from multiple populations that should be as genetically homogeneous as possible.

Evidence for a type 1 diabetes susceptibility locus (IDDM10) on human chromosome 10p11-q11

A region of linkage to type 1 diabetes has been defined on human chromosome 10p11-q11 (IDDM10; P = 0.0007) using 236 UK and 76 US affected sibpairs and a 1 cM resolution microsatellite marker map. Analysis by the transmission disequilibrium test (TDT) in 1159 families with at least one diabetic child, from the UK, the US, Norway, Sardinia and Italy provided additional support for linkage at D10S193 (P = 0.006, Pc = 0.17). Notably, 5.1 cM distal to D10S193, marker D10S588 also provided positive TDT results (P = 0.009, Pc = 0.25) but the allele under analysis was also preferentially transmitted to nonaffected siblings (P = 0.0008, Pc = 0.02). This allele was positively associated in an independent UK case control study and, importantly, was neutrally transmitted in control CEPH families. These results suggest a type 1 diabetes susceptibility locus on chromosome 10p11-q11 (provisionally designated IDDM10) and demonstrate the necessity of analysis of non affected siblings in disease families, as well as analysis of control families.