R. Nolsoe

Variations of the interleukin-6 promoter are associated with features of the metabolic syndrome in Caucasian Danes.

Aims/hypothesisThe cytokine interleukin 6 (IL-6) is an essential regulator of the acute phase response associated with insulin-resistant states including type 2 diabetes and obesity. Three polymorphisms at positions −597, −572, and −174 of the IL6 promoter have been reported to influence IL6 transcription. The aim of this study was to investigate whether the IL6 promoter polymorphisms were associated with features of the WHO-defined metabolic syndrome and related quantitative traits in 7,553 Caucasian Danes.MethodsUsing analysis of PCR-generated primer extension products by mass spectrometry we examined −597 G/A, −572 G/C, and −174 G/C IL6 variants in the population-based Inter99 study cohort of middle-aged people (n=6,164) and in a group of type 2 diabetic patients (n=1,389).ResultsThe −174 G/C and −597 G/A polymorphisms were in strong linkage disequilibrium (R2=0.95). In the Inter99 cohort the −174 G-allele was associated with insulin resistance (p<0.02) and dyslipidaemia (p<0.007) whereas the C-allele of the −572 polymorphism was associated with increased serum insulin release during an OGTT (p<0.0005). Composite genotype or haplotype analyses of all 3 IL6 promoter variants showed associations with type 2 diabetes (p<0.002), obesity (p<0.02), and the metabolic syndrome (p<0.01).ConclusionsThe present studies suggest that single-nucleotide polymorphisms and composite genotypes or haplotypes of the IL6 promoter may be associated with several features of the metabolic syndrome in Caucasians.

Mutation analysis of suppressor of cytokine signalling 3, a candidate gene in Type 1 diabetes and insulin sensitivity

Aims/hypothesisBeta cell loss in Type 1 and Type 2 diabetes mellitus may result from apoptosis and necrosis induced by inflammatory mediators. The suppressor of cytokine signalling (SOCS)-3 is a natural inhibitor of cytokine signalling and also influences insulin signalling. SOCS3 could therefore be a candidate gene in the development of Type 1 and Type 2 diabetes mellitus.MethodsMutation analysis of the SOCS3 gene was performed in 21 patients with Type 1 diabetes mellitus and in seven healthy subjects. An identified promoter variant was examined in (i) 250 families with Type 1 diabetic family members (1097 individuals); (ii) 212 glucose-tolerant first-degree relatives of Type 2 diabetic patients; and (iii) 370 population-based young, healthy subjects who were unrelated.ResultsThree mutations were identified in the promoter region, but none in the coding region or the 3′UTR. Two of the three mutations had allele frequencies below 1% whereas the C −920→A substitution had a minor allele frequency of 8%. In the group of young healthy subjects the insulin sensitivity index was higher among homozygous carriers of the A-allele than among heterozygous and wild-type subjects (p=0.027, uncorrected). The same trend was found in the group of first-degree relatives of Type 2 diabetic patients. No association or linkage was found to Type 1 diabetes mellitus.Conclusions/interpretationHomozygosity for the A-allele of the C −920→A promoter polymorphism of the SOCS3 gene may be associated with increased whole-body insulin sensitivity, but deserves further investigation.

The intercellular adhesion molecule-1 K469E polymorphism in type 1 diabetes.

Abstract. Type 1 (insulin-dependent) diabetes is a complex trait. The region harboring the ICAM1 gene on 19p13 links to type 1 diabetes, and a growing body of evidence indicates that intercellular adhesion molecule-1 (ICAM-1) could play a role in type 1 diabetes development. Recently, association studies of an ICAM-1 K469E polymorphism in type 1 diabetes populations have reported conflicting results. Hence, we performed a transmission disequilibrium test analysis of the ICAM-1 K469E variations in 253 Danish type 1 diabetes families. Linkage and association was not found between the ICAM-1 K469E variation and type 1 diabetes in Danish patients (Ptdt≥0.48), and our data did not indicate an interaction between ICAM1 and IDDM1 in predisposition to type 1 diabetes in Danes (P=0.78). We did not observe significant association with late-onset type 1 diabetes (Ptdt≥0.12) or differences in transmission patterns between groups of affected offspring stratified for age at onset (P≥0.19), as suggested in Japanese patients. Combined analysis of the present and previously reported transmission data comprising 728 affected offspring of Romanian, Finnish, and Danish ancestry suggested association between the ICAM-1 E469 allele and type 1 diabetes (Ptdt=0.013), but association was not found in the combined Scandinavian material. In conclusion, we found no association of the ICAM-1 K469E polymorphism with type 1 diabetes or its subsets stratified for age at onset and HLA risk in Danish patients. Analysis of ICAM-1 K469E transmissions reported in three populations suggested association to type 1 diabetes, but also demonstrated heterogeneity between populations.

Functional promoter haplotypes of the human FAS gene are associated with the phenotype of SLE characterized by thrombocytopenia

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by production of autoantibodies against intracellular antigens and tissue injury. Defective apoptosis of activated immune cells leads to the development of autoantibodies in SLE. FasL initiated apoptosis is central for peripheral tolerance. Fas deficiencies in humans and mice predispose toward systemic autoimmunity. SLE is conferred by many genes. The genetic effects may be concentrated by familial clustering or by stratifying of subphenotypes. We have tested polymorphisms and haplotypes in FAS and FASL for association to SLE or subphenotypes in 126 multiplex American SLE pedigrees and found association of the FAS codon214 ACC/T as well as the FAS−670G>A′-codon214 ACC/T′ haplotype to thrombocytopenia in SLE. Furthermore we have functionally characterized the FAS/FASL promoter polymorphisms associated with SLE in other populations and demonstrate that the activity depends on the allelic variants as well as on the haplotype. The presence of FAS−670G, which affects STAT1 binding, leads to the highest activity. FASL−844C activity is modified by the cis acting −478A and, hence, the haplotype and not the individual variant, determines the promoter activity. We conclude that the FAS/FASL promoter haplotypes are functional and that polymorphisms in FAS may contribute to thrombocytopenia in SLE.

Functional SOCS1 polymorphisms are associated with variation in obesity in whites

Aims/hypothesis:  The suppressor of cytokine signalling 1 (SOCS1) is a natural inhibitor of cytokine and insulin signalling pathways and may also play a role in obesity. In addition, SOCS1 is considered a candidate gene in the pathogenesis of both type 1 diabetes (T1D) and type 2 diabetes (T2D). The objective was to perform mutation analysis of SOCS1 and to test the identified variations for association to T2D‐related quantitative traits, T2D or T1D.

Complete molecular scanning of the human Fas gene: mutational analysis and linkage studies in families with Type I diabetes mellitus

Aims/hypothesis. The human Fas gene (FAS) on chromosome 10q24.1 encoding a cell surface receptor involved in apoptosis was evaluated as a candidate susceptibility gene for Type I (insulin-dependent) diabetes mellitus. Apoptosis mediated by Fas is important in maintaining peripheral self-tolerance and in down-regulating the immune response and could have a role in immune-mediated beta-cell destruction.¶Methods. We did a molecular scan of the entire human FAS (promoter, exons 1–9 including exon-intron boundaries and the 3 ′UTR) using single strand conformational polymorphism-heteroduplex analysis.¶Results. We identified 15 mutations, of which 11 are new. Of these a g-1194A→T and a g-295Ains give rise to alterations of transcription-factor-binding consensus sequences for c-Myb, SP-1 and NF-kB, respectively. A total of 1068 people from a Danish family collection comprising 138 Type I diabetic sib-pair families (289 affected and 121 unaffected offspring) and 103 Type I diabetic parent-offspring multiplex families (103 affected and 112 unaffected offspring) were typed for the three most frequent polymorphisms with high heterozygosity indices and for a FAS microsatellite. Haplotypes were established and data analysed using the extended transmission disequilibrium test, ETDT.¶Conclusion/interpretation. We found no overall evidence for linkage of the FAS polymorphisms to Type I diabetes. We conclude that it is unlikely that the Fas gene does contribute to genetic susceptibility for Type I diabetes. [Diabetologia (2000) 43: 800–808]

Association of a microsatellite in FASL to type II diabetes and of the FAS-670G>A genotype to insulin resistance.

Type II diabetes is caused by a failure of the pancreatic β-cells to compensate for insulin resistance leading to hyperglycaemia. There is evidence for an essential role of an increased β-cell apoptosis in type II diabetes. High glucose concentrations induce IL-1β production in human β-cells, Fas expression and concomitant apoptosis owing to a constitutive expression of FasL. FASL and FAS map to loci linked to type II diabetes and estimates of insulin resistance, respectively. We have tested two functional promoter polymorphisms, FAS-670 G>A and FASL-844C>T as well as a microsatellite in the 3′ UTR of FASL for association to type II diabetes in 549 type II diabetic patients and 525 normal-glucose-tolerant (NGT) control subjects. Furthermore, we have tested these polymorphisms for association to estimates of β-cell function and insulin resistance in NGT subjects. We found significant association to type II diabetes for the allele distribution of the FASL microsatellite (P-value 0.02, Bonferroni corrected). The FAS-670G>A was associated with homeostasis model assessment insulin resistance index and body mass index (P-values 0.02 and 0.02). We conclude that polymorphisms of FASL and FAS associate with type II diabetes and estimates of insulin resistance in Danish white subjects.

Association of interferon-γ and interleukin 10 genotypes and serum levels with partial clinical remission in type 1 diabetes

We studied whether serum interferon (IFN)‐γ or interleukin (IL)‐10 levels and their corresponding functional polymorphic genotypes are associated with partial remission of type 1 diabetes (T1D). A multi‐centre study was undertaken in patients with newly diagnosed T1D and matched controls. T1D patients were followed for 3 months and characterized for remission status. Partial clinical remission was defined as a daily insulin dose ≤ 0·38 units/kg/24 h with an HbA1c ≤ 7·5%. Thirty‐three patients and 32 controls were phenotyped for serum concentrations of IFN‐γ and IL‐10 and genotyped for functional polymorphisms of the IFN‐γ and IL‐10 genes. Sixteen of 25 informative patients (63%) remitted. Serum IFN‐γ concentrations were significantly decreased in remitters but increased in non‐remitters compared to controls, and did not change over time in any group. IFN‐γ genotypes corresponded with serum levels in controls and non‐remitters, but not in remitters who displayed the lowest serum IFN‐γ levels despite more often carrying high‐producing IFN‐γ genotypes. Neither the frequency of IL‐10 genotypes nor serum IL‐10 concentration differed between patients and controls. The combination of high‐producing IFN‐γ genotype together with low serum IFN‐γ concentration at the time of diagnosis provided a strong positive predictive value for remission. Serum IFN‐γ concentrations predicted by genotype and observed serum levels were discordant in remitters, suggestive of regulation overruling genetic predisposition. Although high‐producing genotypes were less frequent in remitters, they were predictive of remission in combination with low serum IFN‐γ levels. These data imply that remission is partially immune‐mediated and involves regulation of IFN‐γ transcription.

Mutation Scan of a Type 1 Diabetes Candidate Gene

Abstract: Type 1 (insulin‐dependent) diabetes, T1DM, is the result of an immune‐mediated destruction of the pancreatic β cells dependent mainly on T helper cells and macrophages. Interleukin‐18 (IL‐18) is a proinflammatory cytokine produced mainly by macrophages. IL‐18 is capable of inducing T lymphocyte synthesis of IFNγ, thereby skewing the T helper response toward a T helper type 1 (Th1) profile. IL‐18 binding protein (IL18BP) neutralizes IL‐18 and leads to a reduced Th1 response. Polymorphisms in IL18BP may affect the activity of IL‐18 and the magnitude of the Th1 response and may play a role in the pathogenesis of T1DM. The aim of the study was therefore to identify polymorphisms in IL18BP and to test these for association with T1DM. We evaluated the human IL18BP gene on chromosome 11q13 as a candidate susceptibility gene for T1DM and scanned the entire IL18BP (promoter, exons 1‐6, and 3′UTR) for polymorphisms using single‐strand conformational polymorphism analysis and direct sequencing. We identified a total of 11 polymorphisms, all having allele frequencies ranging between 0.05 and 0.10. Four were in the 5′UTR: −257G→T, −78C→T, −65G→A, and −59A→G. Three were in intron 3: IVS3+140A→C, IVS4−147G→T, and IVS4−59G→T. The last four, 38*A→T, 48*T→A, 388*C→G, and 440*_441*insG, were in the 3′UTR of IL18BP. However, none of these were frequent enough to permit association studies in T1DM and we conclude that IL18BP does not contribute to the overall genetic susceptibility to type 1 diabetes.