The Transcriptomic Response of the Murine Thyroid Gland to Iodide Overload and the Role of the Nrf2 Antioxidant System

Transcriptomic landscape of hyperthyroidism in mice overexpressing thyroid-Stimulating hormone

Activation of thyroid-stimulating hormone receptor (TSHR) fundamentally leads to hyperthyroidism. To elucidate TSHR signaling, we conducted transcriptome analyses for hyperthyroid mice that we generated by overexpressing TSH. TSH overexpression drastically changed their thyroid transcriptome. In particular, enrichment analyses identified the cell cycle, phosphatidylinositol 3-kinase/Akt pathway, and Ras-related protein 1 pathway as possibly associated with goiter development. Regarding hyperthyroidism, Slc26a4 was exclusively upregulated with TSH overexpression among genes crucial to thyroid hormone secretion. To verify its significance, we overexpressed TSH in Slc26a4 knockout mice. TSH overexpression caused hyperthyroidism in Slc26a4 knockout mice, equivalent to that in control mice. Thus, we did not observe significant changes in known genes and pathways involved in thyroid hormone secretion with TSH overexpression. Our datasets might include candidate genes that have not yet been identified as regulators of thyroid function. Our transcriptome datasets regarding hyperthyroidism can contribute to future research on TSHR signaling.

The Oxidoreductase Retinol Saturase in Thyroid Gland Is Regulated by Hypothyroidism and Iodide Overload and Its Deletion Impairs Metabolic Homeostasis in Mice

Aims: Thyroid hormones (TH) are major regulators of cell differentiation, growth, and metabolic rate. TH synthesis in the thyroid gland requires high amounts of H2O2 to oxidize iodide for the iodination of thyroglobulin (TG). Retinol Saturase (RetSat) is an oxidoreductase implicated in dihydroretinol formation and cellular sensitivity toward peroxides and ferroptosis. RetSat is highly expressed in metabolically active organs where it regulates lipid metabolism and the production of reactive oxygen species. Due to the high expression of RetSat in the thyroid gland and its role in peroxide sensitivity, we investigated the regulation and function of RetSat in the thyroid gland in appropriate mouse models. Results: RetSat is strongly expressed in thyrocytes, induced by hypothyroidism, and decreased by iodide overload in mice. Thyrocyte-specific deletion of RetSat increased circulating thyroid-stimulating hormone levels, altered thyroid morphology, and disturbed metabolic homeostasis in a diet- and sex-dependent manner without major effects on the concentrations of circulating TH. Moreover, deletion of RetSat increased TG protein levels but lowered TG iodination upon iodide overload. In cultured thyrocytes, acute RetSat depletion altered the expression of genes involved in TH biosynthesis and the response to endoplasmic reticulum stress. Innovation: This is the first report that specifically dissects the regulation and function of the oxidoreductase RetSat in the thyroid gland. Conclusion: Deletion of RetSat in thyrocytes induces compensatory feedback mechanisms to maintain TH homeostasis in mice. We conclude that RetSat in the thyroid gland is required for TH biosynthesis and secretion and metabolic homeostasis in mice. Antioxid. Redox Signal. 00, 000-000.

Nrf2, gp91phox and IL-17 are associated with severity and clinical outcomes of patients with subclinical hypothyroidism: a comparative study

The mechanisms underlying subclinical hypothyroidism (SCH) remain unclear, making timely and accurate differentiation between hypothyroidism and SCH, as well as severity assessment, challenging. This study aimed to investigate the role of NFE2 like bZIP transcription factor 2 (Nrf2), gp91phox, and interleukin-17 (IL-17) in the pathogenesis of SCH. In this prospective comparative study, 105 SCH patients, 105 hypothyroidism patients, and 105 healthy individuals were enrolled from January 2022 to August 2023. SCH patients were categorized into mild-moderate and severe groups based on thyroid-stimulating hormone (TSH) levels. Levels of TSH, free T4 (FT4), free T3 (FT3), thyroglobulin antibodies (TG-Ab), thyroid peroxidase antibodies (TPO-Ab), cholesterol (TC), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-ch), and low-density lipoprotein-cholesterol (LDL-ch) were measured. Nrf2, IL-1β, IL-6, IL-17, and gp91phox levels were tested using ELISA. Nrf2, IL-17 and gp91phox were significantly higher in SCH and hypothyroidism patients compared to the healthy controls, with hypothyroidism patients showing the highest levels. Nrf2 levels were negatively correlated with TSH, TG-Ab and IL-17, but not gp91phox. Nrf2, IL-17 and gp91phox could be used for diagnosis of SCH and severe SCH. Only TG-Ab, IL-17 and gp91phox were independent risk factors for severe SCH. This study demonstrates a negative correlation between serum Nrf2 levels and SCH severity. TG-Ab, IL-17, and gp91phox are independent risk factors, and their associations with SCH pathology suggest their potential roles in the disease mechanism. These findings provide insights into SCH pathogenesis and highlight the need for further research to elucidate their diagnostic or prognostic significance.

Transcriptomic profiling of the response to excess iodide in Keap1 hypomorphic mice reveals new gene-environment interactions in thyroid homeostasis

Iodide plays a pivotal role in thyroid homeostasis due to its crucial involvement in thyroid hormone biosynthesis. Exposure to pharmacological doses of iodide elicits in the thyroid an autoregulatory response to preserve thyroid function, as well as an antioxidant response that is mediated by the Keap1/Nrf2 signaling pathway. The objective of the present study was to investigate the transcriptional response of the thyroid to excess iodide in a background of enhanced Nrf2 signaling. Keap1 knockdown (Keap1KD) mice that have activated Nrf2 signaling were exposed or not to excess iodide in their drinking water for seven days and compared to respective wild-type mice. RNA-sequencing of individual mouse thyroids identified distinct transcriptomic patterns in response to iodide, with Keap1KD mice showing an attenuated inflammatory response, altered thyroidal autoregulation, and enhanced cell growth/proliferative signaling, as confirmed also by Western blotting for key proteins involved in antioxidant, autoregulatory and proliferative responses. These findings underscore novel gene-environment interactions between the activation status of the Keap1/Nrf2 antioxidant response system and the dietary iodide intake, which may have implications not only for the goiter phenotype of Keap1KD mice but also for humans harboring genetic variations in KEAP1 or NFE2L2 or treated with Nrf2-modulating drugs.

Recent Advances in Transcription Factors Biomarkers and Targeted Therapies Focusing on Epithelial-Mesenchymal Transition

Transcription factors involve many proteins in the process of transactivating or transcribing (none-) encoded DNA to initiate and regulate downstream signals, such as RNA polymerase. Their unique characteristic is that they possess specific domains that bind to specific DNA element sequences called enhancer or promoter sequences. Epithelial-mesenchymal transition (EMT) is involved in cancer progression. Many dysregulated transcription factors-such as Myc, SNAIs, Twists, and ZEBs-are key drivers of tumor metastasis through EMT regulation. This review summarizes currently available evidence related to the oncogenic role of classified transcription factors in EMT editing and epigenetic regulation, clarifying the roles of the classified conserved transcription factor family involved in the EMT and how these factors could be used as therapeutic targets in future investigations.

Associations between urinary iodine concentration and the prevalence of metabolic disorders: a cross-sectional study

Background

Few studies have examined the role of iodine in extrathyroidal function. Recent research has shown an association between iodine and metabolic syndromes (MetS) in Chinese and Korean populations, but the link in the American participants remains unknown.

Purpose

This study aimed to examine the relationship between iodine status and metabolic disorders, including components associated with metabolic syndrome, hypertension, hyperglycemia, central obesity, triglyceride abnormalities, and low HDL.

Methods

The study included 11,545 adults aged ≥ 18 years from the US National Health and Nutrition Examination Survey (2007-2018). Participants were divided into four groups based on their iodine nutritional status(ug/L), as recommended by the World Health Organization: low UIC, < 100; normal UIC, 100-299; high UIC, 300-399; and very high, ≥ 400. The Odds ratio (OR) for MetS basing the UIC group was estimated using logistic regression models for our overall population and subgroups.

Results

Iodine status was positively associated with the prevalence of MetS in US adults. The risk of MetS was significantly higher in those with high UIC than in those with normal UIC [OR: 1.25; 95% confidence intervals (CI),1.016-1.539; p = 0.035). The risk of MetS was lower in the low UIC group (OR,0.82; 95% CI: 0.708-0.946; p = 0.007). There was a significant nonlinear trend between UIC and the risk of MetS, diabetes, and obesity in overall participants. Participants with high UIC had significantly increased TG elevation (OR, 1.24; 95% CI: 1.002-1.533; P = 0.048) and participants with very high UIC had significantly decreased risk of diabetes (OR, 0.83; 95% CI: 0.731-0.945, p = 0.005). Moreover, subgroup analysis revealed an interaction between UIC and MetS in participants aged < 60 years and ≥ 60 years, and no association between UIC and MetS in older participants aged ≥ 60 years.

Conclusion

Our study validated the relationship between UIC and MetS and their components in US adults. This association may provide further dietary control strategies for the management of patients with metabolic disorders.

Application of oral inorganic iodine in the treatment of Graves' disease

Iodine is a crucial trace element for the human body and the basic raw material for the synthesis of thyroid hormones. Oral inorganic iodine includes dietary iodine and therapeutic iodine, both of which are closely associated with thyroid immunity and metabolism. Graves' disease (GD), also known as diffuse toxic goiter, is characterized by hyperthyroidism and high iodine metabolism. Clinically, patients diagnosed with GD are often asked to limit iodine intake or even avoid iodine in their diet. The latest research has demonstrated that the interference of dietary iodine with antithyroid drugs (ATDs) treatment may be overestimated. In addition, as a medication for GD treatment, the administration of inorganic iodine has shown positive results in patients with mild hyperthyroidism, a low thyroid autoantibody concentration, a small thyroid volume, a high iodine diet and so on. Inorganic iodine may also be used as an alternative when patients experience side effects with traditional ATDs and for those who still prefer conservative treatment. Due to its low teratogenicity, blood toxicity and bone marrow toxicity, inorganic iodine plays a unique role in special populations, such as pregnant or lactating patients and patients receiving tumor radiotherapy or chemotherapy. In this review, the research progress, biological function, doses and effects, applicable populations and specific applications of dietary iodine and therapeutic iodine are summarized to provide references for the diagnosis and treatment of GD, thus improving the quality of life of GD patients.

Emerging roles of Keap1/Nrf2 signaling in the thyroid gland and perspectives for bench-to-bedside translation

The signaling pathway centered on the transcription factor nuclear erythroid factor 2-like 2 (Nrf2) has emerged during the last 15 years as a target for the prevention and treatment of diseases broadly related with oxidative stress such as cancer, neurodegenerative and metabolic diseases. The roles of Nrf2 are expanding beyond general cytoprotection, and they encompass its crosstalk with other pathways as well as tissue-specific functions. The thyroid gland relies on reactive oxygen species for its main physiological function, the synthesis and secretion of thyroid hormones. A few years ago, Nrf2 was characterized as a central regulator of the antioxidant response in the thyroid, as well as of the transcription and processing of thyroglobulin, the major thyroidal protein that serves as the substrate for thyroid hormone synthesis. Herein, we summarize the current knowledge about the roles of Nrf2 in thyroid physiology, pathophysiology and disease. We focus specifically on the most recent publications in the field, and we discuss the implications for the preclinical and clinical use of Nrf2 modulators.

Patent Review (2017-2020) of the Keap1/Nrf2 Pathway Using PatSeer Pro: Focus on Autoimmune Diseases

Research on the antioxidant pathway comprising the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and its cytoplasmic inhibitor Kelch-like ECH-associated protein 1 (Keap1) is ever increasing. As modulators of this pathway have started to be used in clinical trials and clinical practice, Nrf2 has become the subject of several patents. To assess the patent landscape of the last three years on Nrf2 and evaluate the main fields they refer to, we used the web-based tool PatSeer Pro to identify patents mentioning the Nrf2 pathway between January 2017 and May 2020. This search resulted in 509 unique patents that focus on topics such as autoimmune, neurodegenerative, liver, kidney, and lung diseases and refer to modulators (mainly activators) of the Nrf2 pathway as potential treatments. Autoimmunity emerged as the main theme among the topics of Nrf2 patents, including a broad range of diseases, such as systemic sclerosis, systemic lupus erythematosus, multiple sclerosis, inflammatory bowel diseases, Hashimoto's thyroiditis, etc.; however, there was a dearth of experimental support for the respective patents' claims. Given that chronic inflammation is the main element of the pathophysiology of most autoimmune diseases, the majority of patents referring to activation of Nrf2 as a method to treat autoimmune diseases base their claims on the well-established anti-inflammatory role of Nrf2. In conclusion, there is strong interest in securing intellectual property rights relating to the potential use of Nrf2 pathway activators in a variety of diseases, and this trend parallels the rise in related research publications. However, in the case of autoimmunity, more research is warranted to support the potential beneficial effects of Nrf2 modulation in each disease.

The Keap1/Nrf2 Signaling Pathway in the Thyroid-2020 Update

The thyroid gland has a special relationship with oxidative stress. On the one hand, like all other tissues, it must defend itself against reactive oxygen species (ROS). On the other hand, unlike most other tissues, it must also produce reactive oxygen species in order to synthesize its hormones that contribute to the homeostasis of other tissues. The thyroid must therefore also rely on antioxidant defense systems to maintain its own homeostasis in the face of continuous self-exposure to ROS. One of the main endogenous antioxidant systems is the pathway centered on the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) and its cytoplasmic inhibitor Kelch-like ECH-associated protein 1 (Keap1). Over the last few years, multiple links have emerged between the Keap1/Nrf2 pathway and thyroid physiology, as well as various thyroid pathologies, including autoimmunity, goiter, hypothyroidism, hyperthyroidism, and cancer. In the present mini-review, we summarize recent studies shedding new light into the roles of Keap1/Nrf2 signaling in the thyroid.