Screening of SNPs at 18 positional candidate genes, located within the GD-1 locus on chromosome 14q23-q32, for susceptibility to Graves' disease: a TDT study

The polymorphic inheritance of DIO2 rs225014 may predict body weight variation after Graves' disease treatment

OBJECTIVE

We aimed to investigate the role of DIO2 polymorphisms rs225014 and rs12885300 in Graves' disease patients, mainly for controlling body weight following treatment.

METHODS

We genotyped 280 GD patients by the time of diagnosis and 297 healthy control individuals using a TaqMan SNP Genotyping technique. We followed up 141 patients for 18.94 ± 6.59 months after treatment.

RESULTS

There was no relationship between the investigated polymorphisms with susceptibility to GD and gain or loss of weight after GD treatment. However, the polymorphic inheritance (CC+CT genotype) of DIO2 rs225014 was associated with a lower body weight variation after GD treatment (4.26 ± 6.25 kg) when compared to wild type TT genotype (6.34 ± 7.26 kg; p = 0.0456 adjusted for the follow-up time). This data was confirmed by a multivariate analysis (p = 0.0138) along with a longer follow-up period (p = 0.0228), older age (p = 0.0306), treatment with radioiodine (p-value = 0.0080) and polymorphic inheritance of DIO2 rs12885300 (p = 0.0306).

CONCLUSION

We suggest that DIO2 rs225014 genotyping may have an auxiliary role in predicting the post-treatment weight behavior of GD patients.

Association of PTPN22 polymorphism and its correlation with Graves' disease susceptibility in Polish adult population-A preliminary study

Background

Susceptibility to Graves' disease (GD) is determined by various genetic factors; the gene encoding protein tyrosine phosphatase (PTPN22) may be one of those associated with higher risk of GD. The aim was to estimate the association of the PTPN22 gene polymorphism rs2476601:c.C>T (c.1858C>T) with the predisposition to GD within the adult north‐eastern Polish population.

Methods

PTPN22 gene polymorphism was analyzed in individuals with clinical GD history (n = 166) and healthy subjects (n = 154). The presence of different variants of the investigated gene polymorphism was estimated using the DNA Sanger sequencing method.

Results

Patients with GD had a more frequent occurrence of the T gene allele of PTPN22 gene compared to the control group, however, it was not significant (p = 0.257). Analysis of genotype distribution showed significantly more frequent occurrence of TT homozygote in GD patients compared to control individuals (p = 0.016, OR = 9.28). Patients with ophthalmopathy had a less frequent occurrence of the T gene allele of PTPN22 gene compared to patients without ophthalmopathy, however, it was not significant (p = 0.12). Occurrence of the T gene allele of PTPN22 gene in GD manifestation in those under 40‐year old was more frequent compared to individuals over 40, but the obtained difference was also not significant (p = 0.75).

Conclusions

Our preliminary study suggest that PTPN22:c.1858C>T gene polymorphism may be associated with a predisposition to GD within the adult north‐eastern Polish population. The studied polymorphism of the PTPN22 gene did not significantly affect the risk of ophthalmopathy developing and disease manifestation before the age of 40.

CEP128 is a crucial risk locus for autoimmune thyroid diseases

Autoimmune thyroid disease (AITD) mainly includes Graves' disease (GD) and Hashimoto's thyroiditis (HT), and its pathogenesis is not clearly defined. This study was designed to explore risk loci for AITD. Genome-wide genetic data were analyzed to identify important risk loci for GD, and a case-control study with 845 AITD patients and 694 healthy controls was also conducted. The functional role of possible risk loci for GD was explored by analyzing the correlations of Centrosomal protein 128 (CEP128) expression level with intrathyroidal immune cells and key genes for candidate immune cells in GD thyroid tissues. CEP128 was identified as an important risk locus for GD in the genome-wide genetic analysis, and it was located near TSHR without obvious linkage disequilibrium with TSHR. Two tag single-nucleotide variants in CEP128 including a missense variant rs327463 were substantially related to genetic predisposition to GD and HT in the case-control study. CEP128 rs327463 was substantially related to GD under the allele model (OR = 1.31, 95%CI 1.08-1.59, P = 0.006) and the dominant model (OR = 1.37, 95%CI 1.09-1.72, P = 0.008), and it was related to HT under the recessive model (OR = 1.85, P = 0.031) and the homozygous model (OR = 1.91, P = 0.025). Moreover, CEP128 was substantially correlated with the frequencies of T-follicular helper (Tfh) cell and M1 macrophages in GD tissues. Gene set enrichment analysis suggested that CEP128 was related to several common immune pathways involved in GD pathogenesis, such as interferon-γ mediated signaling pathway and toll-like receptor signaling pathway. This study highlight the crucial role of CEP128 in the pathogenesis of GD, and polymorphisms in CEP128 contribute to genetic predisposition to both GD and HT.

Study of Deiodinase Type 2 Polymorphisms in Graves' Disease and Ophthalmopathy in a Swedish Population

BACKGROUND

Deiodinase type 2 (DIO2) is an enzyme that catalyzes the production of the active form of thyroid -hormone triiodothyronine (T3) from thyroxine (T4) and is important for maintaining intracellular T3 levels. Single nucleotide polymorphisms (SNPs) in DIO2 were associated with several diseases. The association of SNPs in DIO2 with Graves' disease (GD) was suggested in 2 Russian studies.

OBJECTIVES

The aim of the study was to examine whether SNPs in DIO2 are associated with GD or Graves' ophthalmopathy (GO).

METHODS

Seven SNPs in the DIO2 gene - rs225014 (Thr92Ala), rs12885300, rs2267872, rs225011, rs224995, rs225015, and rs2267873 - were studied to assess their association with GD and GO. In total, 712 patients with GD with (n = 311) or without (n = 399) ophthalmopathy and 1,183 sex-matched controls from Malmö, Sweden were analyzed. In GD patients with available data, the SNPs were examined for association with the levels of free T3, free T4, thyroid-stimulating hormone receptor antibodies (TRAb), and thyroid-peroxidase antibodies (TPOAb).

RESULTS

Rs225011 was nominally associated with GD (OR 1.18, CI 1.01-1.37, p = 0.036). None of the SNPs were associated with GO. In GD patients, none of the SNPs were associated with the free-T4 (fT4), TRAb, or TPOAb levels. A weak, nonsignificant association was observed between free-T3 (fT3) levels and rs225014 and rs12885300, separately.

CONCLUSIONS

Rs225011 in DIO2 was weakly associated with GD. The mechanism behind this association requires further study. None of the investigated common SNPs in DIO2 was significantly associated with GO, fT3, fT4, TRAb, or TPOAb in GD patients.

Association of Type II 5' Monodeiodinase Thr92Ala Single Nucleotide Gene Polymorphism and Circulating Thyroid Hormones Among Type 2 Diabetes Mellitus Patients

Diabetes mellitus and thyroid disorders are common endocrinopathies, which often occur parallel. Dyslipidemia is very common in both of these conditions. The development of hypothyroidism is well-known in type 1 diabetics, but it was not distinctly understood in type 2 diabetics. Thus we tried to examine the association between type II deiodinase (D2 or DIO2) Thr92Ala single nucleotide gene polymorphism and thyroid function among type 2 diabetes mellitus patients. A total of 130 type 2 diabetics were screened and genotyped for DIO2 Thr92Ala polymorphism. Fasting plasma glucose, Glycosylated haemoglobin, lipid and thyroid profiles, malondialdehyde (MDA) and paraoxonase were estimated according to standard procedures. A significant altered level of thyroid hormones (TH's) was found in Ala/Ala genotype when compared with Thr/Thr or Thr/Ala genotype. DIO2 and T3:T4 ratio significantly decreased, whereas total T4 and thyroid stimulating hormone levels significantly elevated among Ala/Ala genotype (131 ± 30 ng/ml; 0.12 ± 0.05; 7.17 ± 2.05 µg/dl; 4.77 ± 3.1 µIU/ml, respectively) when compared with Thr/Thr + Thr/Ala genotypes (176 ± 33 ng/ml; 0.21 ± 0.05; 5.21 ± 1.1 µg/dl; 2.59 ± 1.61 µIU/ml respectively). Moreover, D2 levels were significantly negatively correlated with TH's levels except total T4 among Ala/Ala genotypes. All the patients were having a poor glycemic control, and their glycemic status was positively correlating with MDA levels. On the other hand, serum paraoxonase activity decreased among Ala/Ala genotype (104 ± 21 vs. 118 ± 18 nmol/min/ml). In conclusion, DIO2 Ala92 homozygous variant found to be associated with altered levels of DIO2, Thyroid profile and paraoxonase. Hence, we recommend to do detail study of genetic factors related to thyroid function and prevent additional diabetic complications.

Genetics in endocrinology: genetic variation in deiodinases: a systematic review of potential clinical effects in humans

Iodothyronine deiodinases represent a family of selenoproteins involved in peripheral and local homeostasis of thyroid hormone action. Deiodinases are expressed in multiple organs and thyroid hormone affects numerous biological systems, thus genetic variation in deiodinases may affect multiple clinical endpoints. Interest in clinical effects of genetic variation in deiodinases has clearly increased. We aimed to provide an overview for the role of deiodinase polymorphisms in human physiology and morbidity. In this systematic review, studies evaluating the relationship between deiodinase polymorphisms and clinical parameters in humans were eligible. No restrictions on publication date were imposed. The following databases were searched up to August 2013: Pubmed, EMBASE (OVID-version), Web of Science, COCHRANE Library, CINAHL (EbscoHOST-version), Academic Search Premier (EbscoHOST-version), and ScienceDirect. Deiodinase physiology at molecular and tissue level is described, and finally the role of these polymorphisms in pathophysiological conditions is reviewed. Deiodinase type 1 (D1) polymorphisms particularly show moderate-to-strong relationships with thyroid hormone parameters, IGF1 production, and risk for depression. D2 variants correlate with thyroid hormone levels, insulin resistance, bipolar mood disorder, psychological well-being, mental retardation, hypertension, and risk for osteoarthritis. D3 polymorphisms showed no relationship with inter-individual variation in serum thyroid hormone parameters. One D3 polymorphism was associated with risk for osteoarthritis. Genetic deiodinase profiles only explain a small proportion of inter-individual variations in serum thyroid hormone levels. Evidence suggests a role of genetic deiodinase variants in certain pathophysiological conditions. The value for determination of deiodinase polymorphism in clinical practice needs further investigation.

Enhancement of soluble CD28 levels in the serum of Graves' disease

Graves' disease is an autoimmune disease of the thyroid gland mediated by T cells. CD28, a member of costimulatory molecules, plays a pivotal role in regulating T-cell responses. Plasma-soluble CD28 is one form of CD28 in peripheral blood. To investigate the concentrations of soluble CD28 in patients with Graves' disease, we used a sensitive dual monoclonal antibody sandwich enzyme-linked immunosorbent assay (ELISA) to detect the soluble form of CD28. Our results suggested that mean concentrations of soluble CD28 in plasma of patients with Graves' disease were 1.79 ±1.52 ng/ml, and levels of soluble CD28 in healthy subjects were only 0.83 ±1.35 ng/ml. Concentrations of soluble CD28 detected in patients with Graves' disease were significantly higher than those of healthy subjects (p < 0.01). Moreover, there was a significant positive correlation between the concentrations of soluble CD28 in plasma and levels of FT3 (r = 0.663), FT4 (r = 0.624) and TRAb (r = 0.728) in serum, but a negative correlation was found between sCD28 levels and TSH (r = -0.726). Through in vitro experiments we observed that engagement of soluble CD28 protein and B7-1/B7-2 molecules expressed on dendritic cells could exert the secretion of cytokine IL-6, which may promote the production of autoantibody and aggravate Graves' disease. Therefore, aberrant elevation of plasma-soluble CD28 in patients with Graves' disease may reflect the dysregulation of immune system, and may serve as a useful biomarker in Graves' disease diagnosis.

Type 2 deiodinase Thr92Ala polymorphism is associated with disrupted placental activity but not with dysglycemia or adverse gestational outcomes: a genetic association study

OBJECTIVE

To study whether the D2 Thr92Ala polymorphism-a genetic marker that is associated with reduced thyroid type 2 deiodinase (D2) activity, increased insulin resistance, and risk for type 2 diabetes-is associated with disrupted placental D2 activity and with glycemic control and gestational outcomes.

DESIGN

Cross-sectional study.

SETTING

Tertiary hospital in Brazil.

PATIENT(S)

Consecutive singleton-pregnancy patients, 18-45 years old.

INTERVENTION(S)

Clinical examination and genotyping of the D2 Thr92Ala polymorphism, with placental samples collected and assayed for D2 mRNA and activity.

MAIN OUTCOME MEASURE(S)

Glucose homeostasis and gestational outcomes.

RESULT(S)

A total of 294 patients were included in the study. The clinical and laboratory characteristics were similar among the D2 genotypes. No differences were observed in D2 placental mRNA levels, but D2 activity was decreased in patients with the Ala92Ala genotype (0.35 ± 0.15 vs. 1.96 ± 1.02 fmol/mg/min.). Newborn serum thyroid-stimulating hormone levels (TSHneo) did not differ according to maternal D2 Thr92Ala genotype. Also, maternal glucose control, insulin resistance evaluated by the homeostasis model assessment (HOMA-IR), and gestational outcomes did not differ across D2 genotypes.

CONCLUSION(S)

The D2 Ala92Ala genotype is associated with reduced placental D2 activity but is not associated with dysglycemia, increased insulin resistance, or worse gestational outcomes.

rs3827440, a nonsynonymous single nucleotide polymorphism within GPR174 gene in X chromosome, is associated with Graves' disease in Polish Caucasian population

Recently Chu et al. conducted a two-stage genome wide association study in Chinese that identified a novel X-linked Graves' disease (GD) susceptibility marker at rs3827440 - a nonsynonymous (P162S) nucleotide transition (519C<T) within G protein-coupled receptor 174 (GPR174) gene. We aimed to replicate this finding in Caucasians. Using the TaqMan approach we typed rs3827440 in 560 GD patients from Warsaw and 196 patients from Gliwice as well as ethically matched controls (N = 748, N = 198, respectively). We found an association of the rs3827440 T allele with GD using both an allelic and genotype comparison [odds ratio (OR) = 1.19, 95% confidence interval (CI): 1.03-1.38, P = 0.021; OR=1.32, 95% CI: 1.03-1.69, P = 0.03, respectively]. There was no difference in distribution of rs3827440 alleles/genotypes vs gender, tobacco smoking, ophthalmopathy or age at disease onset. Also, no statistically significant differences were observed after stratifying patients for DRB1*03- or GD-associated variants in CTLA4 or TSHR genes. Our study provides the first replication in a Caucasian population of the association between GD and rs3827440 originally reported among Chinese. Our results also validate statistical methodology used by Chu et al. to detect associations with X-linked markers.

The genetic basis of graves' disease

The presented comprehensive review of current knowledge about genetic factors predisposing to Graves’ disease (GD) put emphasis on functional significance of observed associations. In particular, we discuss recent efforts aimed at refining diseases associations found within the HLA complex and implicating HLA class I as well as HLA-DPB1 loci. We summarize data regarding non-HLA genes such as PTPN22, CTLA4, CD40, TSHR and TG which have been extensively studied in respect to their role in GD. We review recent findings implicating variants of FCRL3 (gene for FC receptor-like-3 protein), SCGB3A2 (gene for secretory uteroglobin-related protein 1- UGRP1) as well as other unverified possible candidate genes for GD selected through their documented association with type 1 diabetes mellitus: Tenr–IL2–IL21, CAPSL (encoding calcyphosine-like protein), IFIH1(gene for interferon-induced helicase C domain 1), AFF3, CD226 and PTPN2. We also review reports on association of skewed X chromosome inactivation and fetal microchimerism with GD. Finally we discuss issues of genotype-phenotype correlations in GD.

Immunogenetic mechanisms leading to thyroid autoimmunity: recent advances in identifying susceptibility genes and regions

The autoimmune thyroid diseases (AITD) include Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), which are characterised by a breakdown in immune tolerance to thyroid antigens. Unravelling the genetic architecture of AITD is vital to better understanding of AITD pathogenesis, required to advance therapeutic options in both disease management and prevention. The early whole-genome linkage and candidate gene association studies provided the first evidence that the HLA region and CTLA-4 represented AITD risk loci. Recent improvements in; high throughput genotyping technologies, collection of larger disease cohorts and cataloguing of genome-scale variation have facilitated genome-wide association studies and more thorough screening of candidate gene regions. This has allowed identification of many novel AITD risk genes and more detailed association mapping. The growing number of confirmed AITD susceptibility loci, implicates a number of putative disease mechanisms most of which are tightly linked with aspects of immune system function. The unprecedented advances in genetic study will allow future studies to identify further novel disease risk genes and to identify aetiological variants within specific gene regions, which will undoubtedly lead to a better understanding of AITD patho-physiology.

D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms interact in the modulation of insulin resistance in type 2 diabetic patients

Type 2 deiodinase (D2) converts T4 into its active metabolite T3, an essential step in thyroid metabolism. A Thr92Ala polymorphism in the gene encoding D2 has been inconsistently associated with insulin resistance (IR). Recently, it was reported that the D2 Thr92Ala (rs225014) and the peroxisome proliferator-activated receptor (PPAR) γ2 Pro12Ala (rs1801282) polymorphisms interact in the modulation of metabolic syndrome in nondiabetic subjects. Here, we investigated the effect of both polymorphisms, isolated or in combination, on IR in patients with type 2 diabetes mellitus (DM2). The D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms were genotyped in 721 DM2 patients. IR was evaluated using the homeostasis model assessment-IR (HOMA(IR)) index in a subgroup of 246 DM2 subjects. The frequencies of D2 Ala92 and PPARγ2 Ala12 variants were 0.390 and 0.074, respectively. Patients carrying D2 Ala/Ala genotype had a higher fasting plasma insulin and HOMA(IR) index as compared to patients carrying Thr/Ala or Thr/Thr genotypes (P = 0.022 and P = 0.001, respectively). A significant synergistic effect was observed between D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms on HOMA(IR) index, with carriers of both D2 Ala/Ala genotype and PPARγ2 Ala12 allele showing the highest HOMA(IR) values, after adjusting for age, gender, BMI, and use of medication for DM2 (P = 0.010). In conclusion, DM2 patients harboring both D2 Ala/Ala genotype and PPARγ2 Ala12 allele seem to present more severe IR than those with other D2/PPARγ2 genotype combinations. These findings suggest that these polymorphisms interact in the IR modulation, which may constitute a potential therapeutic target.

Association of the type 2 deiodinase Thr92Ala polymorphism with type 2 diabetes: case-control study and meta-analysis

OBJECTIVE

The type 2 deiodinase (D2) is a key enzyme for intracellular triiodothyronine (T(3)) generation. A single-nucleotide polymorphism in D2 (Thr92Ala) has been associated with increased insulin resistance in nondiabetic and type 2 diabetes (DM2) subjects. Our aim was to evaluate whether the D2 Thr92Ala polymorphism is associated with increased risk for DM2.

DESIGN AND METHODS

A case-control study with 1057 DM2 and 516 nondiabetic subjects was performed. All participants underwent genotyping of the D2 Thr92Ala polymorphism. Additionally, systematic review and meta-analysis of the literature for genetic association studies of D2 Thr92Ala polymorphism and DM2 were performed in Medline, Embase, LiLacs, and SciELO, and major meeting databases using the terms 'rs225014' odds ratio (OR) 'thr92ala' OR 'T92A' OR 'dio2 a/g'.

RESULTS

In the case-control study, the frequencies of D2 Ala92Ala homozygous were 16.4% (n=173) versus 12.0% (n=62) in DM2 versus controls respectively resulting in an adjusted OR of 1.41 (95% confidence intervals (CI) 1.03-1.94, P=0.03). The literature search identified three studies that analyzed the association of the D2 Thr92Ala polymorphism with DM2, with the following effect estimates: Mentuccia (OR 1.40 (95% CI 0.78-2.51)), Grarup (OR 1.09 (95% CI 0.92-1.29)), and Maia (OR 1.22 (95% CI 0.78-1.92)). The pooled effect of the four studies resulted in an OR 1.18 (95% CI 1.03-1.36, P=0.02).

CONCLUSIONS

Our results indicate that in a case-control study, the homozygosity for D2 Thr92Ala polymorphism is associated with increased risk for DM2. These results were confirmed by a meta-analysis including 11 033 individuals, and support a role for intracellular T(3) concentration in skeletal muscle on DM2 pathogenesis.

Tourette disorder spectrum maps to chromosome 14q31.1 in an Italian kindred

Tourette syndrome (TS) is a frequent neuropsychiatric disorder of unknown etiology. A number of chromosomal regions have been nominated as TS loci in linkage studies, but confirmation has met with limited success and causative mutations have not yet been definitely identified. Furthermore, TS, chronic tics, and obsessive–compulsive disorder (OCD) occur at increased frequencies among TS relatives, supporting the view that these phenotypes represent parts of the same genetically determined spectrum. We ascertained a four-generation Italian kindred segregating TS, chronic multiple motor tics (CMT), and OCD, and we performed a ten-centimorgan (cM) genome-wide linkage scan in order to map the underlying genetic defect. Suggestive linkage to chromosome 14q31.1 (multipoint LOD = 2.4) was detected by affected-only analysis under an autosomal dominant model and a narrower phenotype definition (only the subjects with TS and CMT were considered as affected). The linkage peak increased and it approached genome-wide significance (LOD = 3.29) when a broader phenotype definition was adopted (subjects with TS, CMT, and OCD considered as affected). Haplotype analysis defined a ∼2.3 cM critical region, shared by all the relatives with TS, CMT, or OCD. In conclusion, we provide strong evidence for linkage of TS spectrum to chromosome 14q31.1. Suggestive linkage to an overlapping region of chromosome 14q was reported in a recent scan of TS sibling pairs. This region might therefore contain an important gene for TS, and it should be prioritized for further study.

Cellular and molecular basis of deiodinase-regulated thyroid hormone signaling

The iodothyronine deiodinases initiate or terminate thyroid hormone action and therefore are critical for the biological effects mediated by thyroid hormone. Over the years, research has focused on their role in preserving serum levels of the biologically active molecule T(3) during iodine deficiency. More recently, a fascinating new role of these enzymes has been unveiled. The activating deiodinase (D2) and the inactivating deiodinase (D3) can locally increase or decrease thyroid hormone signaling in a tissue- and temporal-specific fashion, independent of changes in thyroid hormone serum concentrations. This mechanism is particularly relevant because deiodinase expression can be modulated by a wide variety of endogenous signaling molecules such as sonic hedgehog, nuclear factor-kappaB, growth factors, bile acids, hypoxia-inducible factor-1alpha, as well as a growing number of xenobiotic substances. In light of these findings, it seems clear that deiodinases play a much broader role than once thought, with great ramifications for the control of thyroid hormone signaling during vertebrate development and metamorphosis, as well as injury response, tissue repair, hypothalamic function, and energy homeostasis in adults.

Environmental factors and genetic background that interact to cause autoimmune thyroid disease

PURPOSE OF REVIEW

To provide an updated list of genetic and environmental causative factors of autoimmune thyroid disease, and report about the recent discoveries concerning their interaction in the pathogenesis of thyroid autoimmunity.

RECENT FINDINGS

Although significant discoveries have been made on genetic and environmental factors underlying the development of autoimmune thyroid disease, few data are available about the mechanisms by which they interact. The most interesting news in this field comes from research on molecular mimicry between microbial antigens and thyroid autoantigens. The molecular mimicry model postulates that, in predisposed subjects, a microbial antigen could trigger autoimmunity because of its structural similarity to an autoantigen of the host, and is a paradigmatic example of the multifactorial interaction of several genes and environmental factors to cause autoimmune diseases, including thyroid diseases.

SUMMARY

Recent findings help us to better understand the functional mechanisms of the immune system, which are still only partially known. Beyond the scientific interest, this knowledge has immediate repercussions on clinical practice because it can suggest possible therapeutic targets for new treatments, as well as better and more specific uses of currently available drugs and resources.

Susceptibility genes in Graves' ophthalmopathy: searching for a needle in a haystack?

The variety of clinical presentations of eye changes in patients with Graves' disease suggests that complex interactions between genetic, environmental, endogenous and local factors influence the development/severity of Graves' ophthalmopathy (GO). At present, the role of genetic factors in the development of GO remains unknown. Based on small case-control association studies with candidate genes, several susceptibility loci in GO have been proposed. These are human leucocyte antigen (HLA, 6p21.3), cytotoxic T-lymphocyte antigen-4 (CTLA-4, 2q33), tumour necrosis factor (TNF, 6p21.3), interferon-gamma (IFN-gamma, 12q14), intercellular adhesion molecule-1 (ICAM-1, 19p13), and thyroid stimulating hormone receptor gene (TSH-R, 14q31). Unfortunately, these results were either not confirmed or require replication in larger studies. There are many reasons for the lack of reproducibility of association studies in GO, including poor characterization of the studied groups and small sample sizes, which may result in both false positive and negative results. Thus, the genetic background of GO remains to be elucidated in future research. However, the possibility that GO may be a genetically heterogeneous disorder, or that the development of GO may be predominantly influenced by environmental factors such as cigarette smoking, can not be disregarded.

The Asp727Glu polymorphism in the TSH receptor is associated with insulin resistance in healthy elderly men

BACKGROUND

Variations in thyroid function within the normal range are associated with differences in metabolism and body composition. For instance, TSH is positively associated with body mass index (BMI). This could be due to alterations in thyroid hormone activity, or to direct effects of TSH, as the TSH receptor (TSHR) is also expressed in adipose tissue. The TSHR-Asp727Glu polymorphism is associated with lower serum TSH levels in vivo. In this study, we analysed whether serum thyroid parameters and the TSHR-Asp727Glu polymorphism were associated with glucose metabolism and insulin resistance. In addition, we analysed the Thr92Ala polymorphism in the type 2 deiodinase (D2), which was recently associated with insulin resistance.

METHODS

Genotypes were determined in a population of 349 elderly men (age 77.7 +/- 3.5 years), for whom serum thyroid parameters and data on insulin resistance, such as fasting blood glucose, serum insulin and homeostasis model assessment (HOMA) values, were available.

RESULTS

In nondiabetic, euthyroid subjects, TSH was positively associated with leptin levels, whereas FT4 and rT3 were significantly negatively correlated with insulin and HOMA. Carriers of the TSHR-Glu727 allele had a significantly higher glucose (P = 0.01), insulin (P = 0.001), glycated haemoglobin (HbA1c) (P = 0.002), HOMA (P = 0.001) and leptin (P = 0.008). The D2-Ala(92) allele showed a trend towards higher levels of insulin (P = 0.07) and a higher HOMA (P = 0.09).

CONCLUSION

In this population of nondiabetic elderly men, serum thyroid parameters and the TSHR-Asp727Glu polymorphism were associated with relative insulin resistance. Our study suggests that genetic variation in TSHR plays a role in insulin resistance and thereby influences glucose metabolism.

Genetic analysis and functional evaluation of the C/T(-318) and A/G(-1661) polymorphisms of the CTLA-4 gene in patients affected with Graves' disease

In this study, we evaluated the A/G(-1661), C/T(-318), A/G49 and A/G6230 single nucleotide polymorphisms (SNPs) of the cytotoxic T lymphocyte antigen 4 (CTLA-4) gene for association with Graves' disease (GD) in 126 Russian simplex families. The conditional TDT analysis revealed significant overtransmission of the A(-1661)G(-318) haplotype (P = 0.033) and undertransmission of the GT haplotype (P = 0.0043) from parents homozygous for both +49 and +6230 polymorphisms. Parents homozygous for both (-1661) and (-318) markers significantly overtransmitted the G49G6230 haplotype (P = 0.0013) and undertransmitted the AG haplotype (P = 0.035) to affected offspring. This suggests in favor of the independent genetic effects of the 3' and 5'ends of CTLA-4 in conferring the susceptibility to GD. Both SNPs located at the 5' untranslated region of CTLA-4 were functionally analyzed using the luciferase reporter assay. We observed differential activation of the C/T(-318) promoter variant when Jurkat T cells and HeLa cells were cotransfected with a plasmid expressing lymphoid enhancing factor 1 (LEF1) and various CTLA-4 promoter constructs. The (-318) SNP modifies a putative binding site for LEF1 so that it alters the stimulating effect of LEF1 on the expression ability of the CTLA-4 promoter. The (-1661) dimorphism modifies a potential binding site for myocyte enhancer factor 2 (MEF2). No significant correlation between the (-1661) SNP and MEF2 activity in cotransfection experiments was found. Observed data help for further understanding a functional role of CTLA-4 promoter polymorphisms in the pathogenic mechanism of GD.

Factors affecting statistical power in the detection of genetic association

The mapping of disease genes to specific loci has received a great deal of attention in the last decade, and many advances in therapeutics have resulted. Here we review family-based and population-based methods for association analysis. We define the factors that determine statistical power and show how study design and analysis should be designed to maximize the probability of localizing disease genes.