Molecular estimation of alteration in intestinal microbial composition in Hashimoto’s thyroiditis patients

Abstract

The gut microbiota has a crucial effect on human health and physiology. Hypothyroid Hashimoto’s thyroiditis (HT) is an autoimmune disorder manifested with environmental and genetic factors. However, it is hypothesized that intestinal microbes might play a vital role in the pathogenesis of HT. The aim of current was to investigate and characterize the gut microbial composition of HT patients both quantitatively and qualitatively. The fecal samples from 29 HT patients and 12 healthy individuals were collected. The PCR-DGGE targeted V3 site of 16S rRNA gene and real time PCR for Bifidobacterium Lactobacillus, Bacteroides vulgatus and Clostridium leptum were performed. Pyrosequencing of 16S rRNA gene with V4 location was performed on 20 randomly selected samples. The comparative analysis of diversity and richness indices revealed diversification of gut microbiota in HT as compared to control. The statistical data elucidate the alterations in phyla of HT patients which was also affirmed at the family level. We observed the declined abundance of Prevotella_9 and Dialister, while elevated genera of the diseased group included Escherichia-Shigella and Parasutterella. The alteration in gut microbial configuration was also monitored at the species level, which showed an increased abundance of E. coli in HT. Therefore, the current study is in agreement with the hypothesis that HT patients have intestinal microbial dysbiosis. The taxa statistics at species-level along with each gut microbial community were modified in HT. Thus, the current study may offer the new insights into the treatment of HT patients, disease pathway, and mechanism.

Introduction

The human gut microbiota is a major factor for host health status, and its contribution is crucial for normal body mechanism, thus considered as vital aspect for influencing the health grading of an individual [1]. The complexion of the human gut microbiota is quite diverse with approximately 100 trillion microbes in the body serve as a metabolic, nutrition, absorption and immune function against pathogens [2]. The abnormality in the body homeostasis can, in turn, affect the composition pattern of gut microbiota, therefore resulting in diseases implications [3].

HT is specifically organ linked autoimmune disease characterized by thyroid gland chronic inflammation. The disease was first reported in 1912 by Hakaru Hashimoto and was referred as autoimmune thyroid deficient disease (AITD). The exact pathogenicity of the disease still needs to be unraveled under the intense phase of most probable mechanisms [4]. The disease is now believed to be the autoimmune [5] endocrine disorder [6] considered as the contributing factor of hypothyroidism [7].

This autoimmune disorder manifested with no unusual clinical symptoms but with the gradual deterioration of thyroid gland, characterized by goiter, hypothyroidism, weight gain, constipation, and depression [8].

The epidemiological data depicted the prevalence of disease frequency eight times higher in females as compared to males [9]. The most common cause of hypothyroidism is iodine deficiency [10], [11], [12]. The body’s innate immune mechanism permits the binding of specific receptors thus identifying the molecules related to gut bacteria. The specificity of bound receptors activate the immune response of the host and release the defensive cytokines, white blood cells and peptides [13].

The recent molecular studies performed on 250 Chinese HT patients identified that single nucleotide polymorphism (SNP) in STAT3 gene has an association with HT [14]. The bacteriocins production by intestinal bacteria competing for nutrients and clinging of gut lining thus averting any colonization by pathogens [15].

The modulation in gut floral configuration has been linked to numerous disease disorders, including colitis, Crohn’s disease, viral diarrhea, metabolic diseases like obesity, and diabetes type II [16]. Mori K et al. described the possible relationship between thyroid autoimmunity and gut with weak evidence having very few studies consolidating such link. Furthermore, the review emphasizes to validate the hypothesis of gut microbial dysbiosis in HT with further research [17].

The current study aim was to estimate the alteration, similarity, and diversity of gut microbiota quantitatively and qualitatively in HT patients in comparison to healthy controls. By using PCR-DGGE and sensitive metagenomic pyrosequencing, we have monitored the gut microbial similarity and diversity in patients suffering from HT disease. The investigations demonstrated the variation in bacterial taxa richness in contrast to controls, with some distinct gut microbes depicting significantly higher or lower abundance against the control. The significance of these alterations in the gut microbiota of HT was notably high-pitched as never reported before regarding gut microbial characterization in HT. Current findings thus help to illustrate the overall composition of gut microbiota in HT patients.