Vesna Boraska Perica

Association of established thyroid peroxidase autoantibody (TPOAb) genetic variants with Hashimoto’s thyroiditis

Abstract Hashimotos thyroiditis (HT) is the most common form of autoimmune thyroid diseases (AITD) characterized by progressive destruction of thyroid tissue that may lead to hypothyroidism. High thyroid autoantibodies against thyroid peroxidase (TPOAb) levels are present in 90% of patients with HT and serve as a clinical marker for the detection of early AITD/HT. The main aim of our study was to test whether recently identified genetic variants associated with TPOAb are also involved in HT development. A total of 504 unrelated individuals, including 200 patients with HT and 304 controls, were involved in this study. Diagnosis of HT cases was based on clinical examination, measurement of thyroid hormones (TSH and fT4) and antibodies (TgAb, TPOAb) and ultrasound examination. We selected and genotyped 14 known TPOAb-associated genetic variants. Case–control logistic regression model was used to test the association of selected genetic variants with HT. Additionally, we tested association of the same genetic variants with thyroid related quantitative traits (TPOAb levels, TgAb levels and thyroid gland volume) using linear regression. Three genetic variants showed nominal association with HT; rs10774625 in ATXN2 gene (p = 0.0149, OR = 0.73, CI = 0.56–0.94), rs7171171 near RASGRP1 gene (p = 0.0356, OR = 1.4, CI = 1.02–1.92) and rs11675434 in TPO gene (p = 0.041, OR = 1.31, CI = 1.01–1.69). Two of these SNPs (rs1077462, rs11675434) also showed association with TPOAb levels (p = 0.043, β = −0.39; p = 0.042, β = 0.40, respectively) and one (rs7171171) was associated with thyroid gland volume (p = 0.0226, β = −0.21). Our findings suggest that variants inside or near TPO, ATXN2 and RASGRP1 genes are associated with HT. Identified loci are novel to HT and represent good basis for further exploration of HT susceptibility.

Association of Established Thyroid-stimulating Hormone and Free Thyroxine Genetic Variants with Hashimoto’s Thyroiditis

ABSTRACT Hashimoto’s thyroiditis (HT), the most frequent autoimmune thyroid disease (AITD), is characterized by chronic inflammation of the thyroid gland that usually results in hypothyroidism. Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels are used as clinical determinants of thyroid function. The main aim of this study was to explore the association of established TSH and FT4 genetic variants with HT. We performed a case–control analysis using 23 genetic markers in 200 HT patients and 304 controls. Additionally, we tested the association of selected variants with several thyroid-related quantitative traits in HT cases only. Two genetic variants showed nominal association with HT: rs11935941 near NR3C2 gene (p = 0.0034, OR = 0.57, 95% CI = 0.39–0.83) and rs1537424 near MBIP gene (p = 0.0169, OR = 0.72, 95% CI = 0.55–0.94). Additionally, three SNPs showed nominal association with thyroglobulin antibody (TgAb) levels: rs4804416 in INSR gene (p = 0.0073, β = −0.51), rs6435953 near IGFBP5 gene (p = 0.0081, β = 0.75), and rs1537424 near MBIP gene (p = 0.0117, β = 0.49). GLIS3 genetic variant rs10974423 showed nominal association with thyroid peroxidase antibody (TPOAb) levels (p = 0.0465, β = −0.56) and NRG1 genetic variant rs7825175 was nominally associated with thyroid gland volume (p = 0.0272, β = −0.18). All detected loci were previously related to thyroid function or pathology. Findings from our study suggest biological relevance of NR3C2 and MBIP with HT, although these loci require additional confirmation in a larger replication study.

Whole-exome sequencing in an isolated population from the Dalmatian island of Vis.

We have whole-exome sequenced 176 individuals from the isolated population of the island of Vis in Croatia in order to describe exonic variation architecture. We found 290 577 single nucleotide variants (SNVs), 65% of which are singletons, low frequency or rare variants. A total of 25 430 (9%) SNVs are novel, previously not catalogued in NHLBI GO Exome Sequencing Project, UK10K-Generation Scotland, 1000Genomes Project, ExAC or NCBI Reference Assembly dbSNP. The majority of these variants (76%) are singletons. Comparable to data obtained from UK10K-Generation Scotland that were sequenced and analysed using the same protocols, we detected an enrichment of potentially damaging variants (non-synonymous and loss-of-function) in the low frequency and common variant categories. On average 115 (range 93–140) genotypes with loss-of-function variants, 23 (15–34) of which were homozygous, were identified per person. The landscape of loss-of-function variants across an exome revealed that variants mainly accumulated in genes on the xenobiotic-related pathways, of which majority coded for enzymes. The frequency of loss-of-function variants was additionally increased in Vis runs of homozygosity regions where variants mainly affected signalling pathways. This work confirms the isolate status of Vis population by means of whole-exome sequence and reveals the pattern of loss-of-function mutations, which resembles the trails of adaptive evolution that were found in other species. By cataloguing the exomic variants and describing the allelic structure of the Vis population, this study will serve as a valuable resource for future genetic studies of human diseases, population genetics and evolution in this population.

Dietary Factors Associated with Plasma Thyroid Peroxidase and Thyroglobulin Antibodies

The knowledge about dietary habits and their influence in the development of autoimmune thyroid disease is insufficient. The aim of this study was to analyse the association of dietary factors and plasma thyroid peroxidase antibodies (TPO-Ab) and/or thyroglobulin antibodies (Tg-Ab). The study enrolled 1887 participants originating from the South Croatia. Participants with elevated plasma TPO-Ab and/or Tg-Ab were defined as cases (n = 462) and those with TPO-Ab and/or Tg-Ab within referent values were defined as controls (n = 1425). Dietary intake was evaluated according to a food frequency questionnaire containing 58 food items. Principal component analysis was used to group food items into dietary groups. We used logistic regression analysis to examine dietary groups associated with positive plasma TPO-Ab and/or Tg-Ab. The results indicate that the dietary group with frequent consumption of animal fats and butter is associated with positive plasma TPO-Ab and/or Tg-Ab (p = 0.01). The dietary group with frequent consumption of vegetables as well as the dietary group with high consumption of dried fruit, nuts, and muesli are associated with negative findings of TPO-Ab and/or Tg-Ab (p = 0.048 and p = 0.02, respectively). We showed that the anti-inflammatory dietary groups are associated with the negative findings of plasma TPO-Ab and/or Tg-Ab.

Evaluation of Correlations Between Food-Specific Antibodies and Clinical Aspects of Hashimoto’s Thyroiditis

Abstract Objective: We have comprehensively evaluated an immunologic response to food antigens, mediated by immunoglobulin G (IgG) antibodies, on clinical aspects of Hashimoto’s thyroiditis (HT). Methods: IgG antibodies to 125 food antigens were measured in serum samples of 74 HT patients and 245 controls using microarray-based enzyme-linked immunosorbent assay (ELISA) test. We analyzed differences in IgG levels between two groups and evaluated correlations between food-specific IgG levels and HT-related clinical phenotypes (thyroid hormones/antibodies, symptoms of hypothyroidism, measures of body size and blood pressure) and food consumption in HT patients. Results: We observed increased IgG levels to 12 different food antigens in either HT cases or controls, of which plum-specific IgG antibodies were significantly higher (p = 1.70 × 10−8), and almond-specific IgG antibodies were significantly lower (p = 8.11 × 10−5) in HT patients in comparison to controls, suggesting their possible roles in HT etiology or symptomatology. There was no significant correlation between any of 12 increased food-specific IgG antibodies, along with gluten-specific IgG, with clinically important phenotypes, such as thyroid hormones/antibodies or symptoms. Among other tested correlations, the most interesting is the negative correlation between coffee and tea combined IgG levels and number of symptoms, suggesting possible beneficial effect of tea and coffee on disease symptoms. We also found that food consumption is not correlated with IgG levels. Conclusions: Distribution of food-specific IgG antibodies is comparable between HT patients and controls, with the exception of plum and almond. There is no evidence that increased food-specific IgG antibodies are associated with clinical aspects of HT. Clarification of biology behind formation of these antibodies is needed.

Thyroglobulin Antibodies are Associated with Symptom Burden in Patients with Hashimoto’s Thyroiditis: A Cross-Sectional Study

ABSTRACT Background: Hashimoto’s thyroiditis (HT) is the most common form of autoimmune thyroid disorders characterized by lower production of thyroid hormones and positivity to autoantibodies to thyroglobulin (TgAb) and/or thyroid peroxidase (TPOAb). We performed a comprehensive phenotypic characterization of patients with HT, with specific focus on thyroid autoimmunity, to get better understanding of disease manifestation. Methods: We collected information on thyroid-specific phenotypes (TSH, T3, T4, fT4, TgAb, TPOAb, thyroid volume) and other clinical phenotypes (age, body surface area, number of hypothyroidism symptoms, blood pressure) from 290 patients with HT without levothyroxine (LT4) therapy with the aim to test for correlations between thyroid-specific and clinical phenotypes. Results: Our key and novel finding is the existence of significant positive correlation between TgAb levels and the number of symptoms (r = 0.25, p = 0.0001) in HT patients without LT4 therapy that remained significant after adjustment for TPOAb, T3, TSH levels and thyroid volume (β = 0.66, SE = 0.3, p = 0.0299). Increased TgAb levels are significantly associated with fragile hair (p = 0.0043), face edema (p = 0.0061), edema of the eyes (p = 0.0293) and harsh voice (p = 0.0349). Conclusions: Elevated TgAb levels are associated with symptom burden in HT patients, suggesting a role of thyroid autoimmunity in clinical manifestations of HT. Based on these results, we recommend screening for TgAb antibodies in HT patients with symptom burden. We also suggest that further work on understandings of symptoms appearance due to their autoimmune or hypothyroid causation is needed.

Genome-wide meta-analysis identifies novel gender specific loci associated with thyroid antibodies level in croatians

Autoimmune thyroid diseases (AITD) are multifactorial endocrine diseases most frequently accompanied by Tg and TPO autoantibodies. Both antibodies have a higher prevalence in females and act under a strong genetic influence. To identify novel variants underlying thyroid antibody levels, we performed GWAS meta-analysis on the plasma levels of TgAb and TPOAb in three Croatian cohorts, as well as gender specific GWAS and a bivariate analysis. No significant association was detected with the level of TgAb and TPOAb in the meta-analysis of GWAS or bivariate results for all individuals. The bivariate analysis in females only revealed a genome-wide significant association for the locus near GRIN3A (rs4457391, P = 7.76 × 10-9). The same locus had borderline association with TPOAb levels in females (rs1935377, P = 8.58 × 10-8). In conclusion, we identified a novel gender specific locus associated with TgAb and TPOAb levels. Our findings provide a novel insight into genetic and gender differences associated with thyroid antibodies.