Comparative Phenotyping of Mice Reveals Canonical and Noncanonical Physiological Functions of TRα and TRß.

Thyroid hormone (TH) effects are mediated through TH receptors (TRs), TRα1, TRß1, and TRß2. The TRs bind to the DNA and regulate expression of TH target genes (canonical signaling). In addition, they mediate activation of signaling pathways (noncanonical signaling). Whether noncanonical TR action contributes to the spectrum of TH effects is largely unknown. The aim of this study was to attribute physiological effects to the TR isoforms and their canonical and noncanonical signaling. We conducted multiparameter phenotyping in male and female TR knockout mice (TRαKO, TRßKO), mice with disrupted canonical signaling due to mutations in the TR DNA binding domain (TRαGS, TRßGS), and their wild-type littermates. Perturbations in senses, especially hearing (mainly TRß with a lesser impact of TRα), visual acuity, retinal thickness (TRα and TRß), and in muscle metabolism (TRα) highlighted the role of canonical TR action. Strikingly, selective abrogation of canonical TR action often had little phenotypic consequence, suggesting that noncanonical TR action sufficed to maintain the wild-type phenotype for specific effects. For instance, macrocytic anemia, reduced retinal vascularization, or increased anxiety-related behavior were only observed in TRαKO but not TRαGS mice. Noncanonical TRα action improved energy utilization and prevented hyperphagia observed in female TRαKO mice. In summary, by examining the phenotypes of TRα and TRß knockout models alongside their DNA binding-deficient mutants and wild-type counterparts, we could establish that the noncanonical actions of TRα and TRß play a crucial role in modulating sensory, behavioral, and metabolic functions and, thus, contribute to the spectrum of physiological TH effects.

Effects of penthiopyrad on the hypothalamic-pituitary-thyroid (HPT) axis in zebrafish.

Exposure to specific pesticides has been demonstrated to alter normal thyroid function of aquatic vertebrates. This study aimed to investigate the impact of penthiopyrad (PO) on the thyroid function of zebrafish, further elucidating its toxic mechanisms on the early developmental stages of zebrafish. Exposure to sublethal doses of PO (0.3-1.2 mg/L) for 8 days from 2 h after fertilization resulted in a significant reduction in larval swim bladder size and body weight, accompanied by developmental abnormalities such as pigment deposition and abnormal abdominal development. Perturbations in the hypothalamic-pituitary-thyroid (HPT) axis in larvae manifested as a marked upregulation of crh, tg, ttr, and ugt1ab expression, alongside downregulation of trß expression, culminating in elevated thyroxine (T4) and triiodothyronine (T3) levels. Additionally, molecular docking results suggest that PO and its metabolites may disrupt the binding of thyroid hormones to thyroid hormone receptor beta (TRß), compromising the normal physiological function of TRß. These findings highlight the PO-induced adverse effects on the HPT axis of larvae under sublethal doses, eventually leading to abnormal development and growth inhibition.

Canonical and Noncanonical Contribution of Thyroid Hormone Receptor Isoforms Alpha and Beta to Cardiac Hypertrophy and Heart Rate in Male Mice.

Background: Stimulation of ventricular hypertrophy and heart rate are two major cardiac effects of thyroid hormone (TH). The aim of this study was to determine in vivo which TH receptor (TR)-α or ß-and which mode of TR action-canonical gene expression or DNA-binding independent noncanonical action-mediate these effects. Methods: We compared global TRα and TRß knockout mice (TRαKO; TRßKO) with wild-type (WT) mice to determine the TR isoform responsible for T3 effects. The relevance of TR DNA binding was studied in mice with a mutation in the DNA-binding domain that selectively abrogates DNA binding and canonical TR action (TRαGS; TRßGS). Hearts were studied with echocardiography at baseline and after 7 weeks of T3 treatment. Gene expression was measured with real-time polymerase chain reaction. Heart rate was recorded with radiotelemetry transmitters for 7 weeks in untreated, hypothyroid, and T3-treated mice. Results: T3 induced ventricular hypertrophy in WT and TRßKO mice, but not in TRαKO mice. Hypertrophy was also induced in TRαGS mice. Thus, hypertrophy is mostly mediated by noncanonical TRα action. Similarly, repression of Mhy7 occurred in WT and TRαGS mice. Basal heart rate was largely dependent on canonical TRα action. But responsiveness to hypothyroidism and T3 treatment as well as expression of pacemaker gene Hcn2 were still preserved in TRαKO mice, demonstrating that TRß could compensate for absence of TRα. Conclusions: T3-induced cardiac hypertrophy could be attributed to noncanonical TRα action, whereas heart rate regulation was mediated by canonical TRα action. TRß could substitute for canonical but not noncanonical TRα action.

Resmetirom: First Approval.

Resmetirom (Rezdiffra™) is an oral thyroid hormone receptor-ß (THR-ß) agonist being developed by Madrigal Pharmaceuticals, Inc., to target the key underlying causes of metabolic dysfunction associated steatohepatitis (MASH) [previously known as nonalcoholic steatohepatitis (NASH)]. In March 2024, resmetirom was approved for use (under accelerated approval) in conjunction with diet and exercise for the treatment of adults with noncirrhotic NASH with moderate to advanced liver fibrosis (consistent with stages F2 to F3 fibrosis) in the USA. Resmetirom is also under regulatory review in the EU for the treatment of MASH/NASH. This article summarizes the milestones in the development of resmetirom leading to this first approval for the treatment of adults with MASH/NASH.

Thyroid receptor ß: A promising target for developing novel anti-androgenetic alopecia drugs.

Androgenetic alopecia (AGA) significantly impacts the self-confidence and mental well-being of people. Recent research has revealed that thyroid receptor ß (TRß) agonists can activate hair follicles and effectively stimulate hair growth. This review aims to comprehensively elucidate the specific mechanism of action of TRß in treating AGA from various perspectives, highlighting its potential as a drug target for combating AGA. Moreover, this review provides a thorough summary of the research advances in TRß agonist candidates with anti-AGA efficacy and outlines the structure-activity relationships (SARs) of TRß agonists. We hope that this review will provide practical information for the development of effective anti-alopecia drugs.

The first MASH drug therapy on the horizon: Current perspectives of resmetirom.

The rising prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) poses a significant global health challenge, affecting over 30% of adults worldwide. MASLD is linked to increased mortality rates and substantial healthcare costs, primarily driven by its progression to metabolic dysfunction-associated steatohepatitis (MASH), which can lead to severe liver complications including cirrhosis and hepatocellular carcinoma. Despite its growing burden, effective pharmacotherapy for MASLD/MASH has been lacking until the recent conditional approval of resmetirom by the FDA. Resmetirom, a liver-targeted thyroid hormone receptor-ß selective drug, has shown promise in clinical trials for treating non-cirrhotic MASH with moderate to advanced fibrosis. It has demonstrated efficacy in reducing hepatic fat content, improving liver histology (both MASH resolution and fibrosis improvement), and ameliorating biomarkers of liver damage without significant effects on body weight or glucose metabolism. Notably, resmetirom also exhibits favourable effects on circulating lipids, potentially reducing cardiovascular risk in MASLD/MASH patients. The safety profile of resmetirom appears acceptable, with gastrointestinal adverse events being the most common, though generally mild or moderate. However, long-term surveillance is warranted to monitor for potential risks related to thyroid, gonadal, or bone diseases. Clinical implementation of resmetirom faces challenges in patient selection and monitoring treatment response, and will heavily rely on non-invasive tests for liver fibrosis assessment. Nonetheless, resmetirom represents a landmark breakthrough in MASLD/MASH treatment, paving the way for future therapeutic strategies aiming to mitigate the multifaceted risks associated with this complex metabolic liver disease.

Partial Resistance to Thyroid Hormone-Induced Tachycardia and Cardiac Hypertrophy in Mice Lacking Thyroid Hormone Receptor ß.

Background: Thyroid hormones regulate cardiac functions mainly through direct actions in the heart and by binding to the thyroid hormone receptor (TR) isoforms α1 and ß. While the role of the most abundantly expressed isoform, TRα1, is widely studied and well characterized, the role of TRß in regulating heart functions is still poorly understood, primarily due to the accompanying elevation of circulating thyroid hormone in TRß knockout mice (TRß-KO). However, their hyperthyroidism is ameliorated at thermoneutrality, which allows studying the role of TRß without this confounding factor. Methods: Here, we noninvasively monitored heart rate in TRß-KO mice over several days using radiotelemetry at different housing temperatures (22°C and 30°C) and upon 3,3',5-triiodothyronine (T3) administration in comparison to wild-type animals. Results: TRß-KO mice displayed normal average heart rate at both 22°C and 30°C with only minor changes in heart rate frequency distribution, which was confirmed by independent electrocardiogram recordings in freely-moving conscious mice. Parasympathetic nerve activity was, however, impaired in TRß-KO mice at 22°C, and only partly rescued at 30°C. As expected, oral treatment with pharmacological doses of T3 at 30°C led to tachycardia in wild-types, accompanied by broader heart rate frequency distribution and increased heart weight. The TRß-KO mice, in contrast, showed blunted tachycardia, as well as resistance to changes in heart rate frequency distribution and heart weight. At the molecular level, these observations were paralleled by a blunted cardiac mRNA induction of several important genes, including the pacemaker channels Hcn2 and Hcn4, as well as Kcna7. Conclusions: The phenotyping of TRß-KO mice conducted at thermoneutrality allows novel insights on the role of TRß in cardiac functions in the absence of the usual confounding hyperthyroidism. Even though TRß is expressed at lower levels than TRα1 in the heart, our findings demonstrate an important role for this isoform in the cardiac response to thyroid hormones.

Generation of THRB-GS(E125G_G126S) and THRB-KO human iPSC lines to study noncanonical thyroid hormone signalling.

THRB is a nuclear receptor, regulating gene expression dependent on thyroid hormone (TH) binding. The same receptor mediates signaling pathway activation in the cytosol. The challenge is to distinguish which of the two mechanisms is responsible for physiological effects of TH. We established an iPSC cell line with two mutations (E125G_G126S) in the THRB DNA-binding domain, which abrogates nuclear action and, thus, allows to study signaling pathway activation exclusively. We also generated a THRB knockout cell line to abolish all THRB effects. Comparison of WT and these two cell lines allows attribution of thyroid hormone effects to the underlying mechanism.

Thyroid hormone-regulated chromatin landscape and transcriptional sensitivity of the pituitary gland.

Thyroid hormone (3,5,3'-triiodothyronine, T3) is a key regulator of pituitary gland function. The response to T3 is thought to hinge crucially on interactions of nuclear T3 receptors with enhancers but these sites in pituitary chromatin remain surprisingly obscure. Here, we investigate genome-wide receptor binding in mice using tagged endogenous thyroid hormone receptor ß (TRß) and analyze T3-regulated open chromatin using an anterior pituitary-specific Cre driver (Thrbb2Cre). Strikingly, T3 regulates histone modifications and chromatin opening primarily at sites that maintain TRß binding regardless of T3 levels rather than at sites where T3 abolishes or induces de novo binding. These sites associate more frequently with T3-activated than T3-suppressed genes. TRß-deficiency blunts T3-regulated gene expression, indicating that TRß confers transcriptional sensitivity. We propose a model of gene activation in which poised receptor-enhancer complexes facilitate adjustable responses to T3 fluctuations, suggesting a genomic basis for T3-dependent pituitary function or pituitary dysfunction in thyroid disorders.

Thyroid hormone receptor Thra and Thrb knockout differentially affects osteoblast biology and thyroid hormone responsiveness in vitro.

Thyroid hormones (TH) are important modulators of bone remodeling and thus, thyroid diseases, in particular hyperthyroidism, are able to compromise bone quality and fracture resistance. TH actions on bone are mediated by the thyroid hormone receptors (TR) TRα1 and TRß1, encoded by Thra and Thrb, respectively. Skeletal phenotypes of mice lacking Thra (Thra0/0 ) and Thrb (Thrb-/- ) are well-described and suggest that TRα1 is the predominant mediator of TH actions in bone. Considering that bone cells might be affected by systemic TH changes seen in these mutant mice, here we investigated the effects of TR knockout on osteoblasts exclusively at the cellular level. Primary osteoblasts obtained from Thra0/0 , Thrb-/- , and respective wildtype (WT) mice were analyzed regarding their differentiation potential, activity and TH responsiveness in vitro. Thra, but not Thrb knockout promoted differentiation and activity of early, mature and late osteoblasts as compared to respective WT cells. Interestingly, while mineralization capacity and expression of osteoblast marker genes and TH target gene Klf9 was increased by TH in WT and Thra-deficient osteoblasts, Thrb knockout mitigated the responsiveness of osteoblasts to short (48 h) and long term (10 d) TH treatment. Further, we found a low ratio of Rankl, a potent osteoclast stimulator, over osteoprotegerin, an osteoclast inhibitor, in Thrb-deficient osteoblasts and in line, supernatants obtained from Thrb-/- osteoblasts reduced numbers of primary osteoclasts in vitro. In accordance to the increased Rankl/Opg ratio in TH-treated WT osteoblasts only, supernatants from these cells, but not from TH-treated Thrb-/- osteoblasts increased the expression of Trap and Ctsk in osteoclasts, suggesting that osteoclasts are indirectly stimulated by TH via TRß1 in osteoblasts. In conclusion, our study shows that both Thra and Thrb differentially affect activity, differentiation and TH response of osteoblasts in vitro and emphasizes the importance of TRß1 to mediate TH actions in bone.

Maternal thyroid hormone receptor ß activation in mice sparks brown fat thermogenesis in the offspring.

It is well established that maternal thyroid hormones play an important role for the developing fetus; however, the consequences of maternal hyperthyroidism for the offspring remain poorly understood. Here we show in mice that maternal 3,3',5-triiodothyronine (T3) treatment during pregnancy leads to improved glucose tolerance in the adult male offspring and hyperactivity of brown adipose tissue (BAT) thermogenesis in both sexes starting early after birth. The activated BAT provides advantages upon cold exposure, reducing the strain on other thermogenic organs like muscle. This maternal BAT programming requires intact maternal thyroid hormone receptor ß (TRß) signaling, as offspring of mothers lacking this receptor display the opposite phenotype. On the molecular level, we identify distinct T3 induced alterations in maternal serum metabolites, including choline, a key metabolite for healthy pregnancy. Taken together, our results connect maternal TRß activation to the fetal programming of a thermoregulatory phenotype in the offspring.

Zebrafish (Danio rerio) TRß- and TTR-based electrochemical biosensors: Construction and application for the evaluation of thyroid-disrupting activity of bisphenols.

Thyroid-disrupting chemicals (TDCs) have received increasing concerns because of their negative health impacts on both wildlife and humans. This study aimed to develop in vitro screening assays for TDCs based on thyroid hormone receptor ß (TRß) and transthyretin (TTR) proteins. Firstly, the recombinant ligand-binding domain of TRß (TRß-LBD) and TTR proteins of zebrafish were produced by eukaryotic expression system and then used as bio-recognition components to construct electrochemical biosensors. In the biosensors, the supported bilayer lipid membrane (s-BLM) was used as a matrix to immobilize proteins, and gold nanoflowers (AuNFs) were used to improve the sensitivity by increasing electroactive surface area. Under the optimizing conditions, the zfTRß-LBD/AuNFs/s-BLM/GCE biosensor had a detection range of 0.23 nM-1.92 µM and a detection limit of 0.07 nM for triiodothyronine (T3), while the zfTTR/AuNFs/s-BLM/GCE biosensor had a detection range of 0.46 nM-3.84 µM, with a detection limit of 0.13 nM. Based on the constructed biosensors, the order of T3 equivalent concentrations of bisphenols was BPA ≈ BPS > BPF > BPAF ≈ BPAP > BPZ, which was similar to the results of recombinant TRß two-hybrid yeast assay. Furthermore, the reliability of the biosensors was validated by molecular docking, in which BPA and BPS showed higher binding affinity to zfTRß-LBD. Therefore, this study provided a valuable tool for efficiently screening TDCs.

Reactivated thyroid hormone receptor ß attenuates anaplastic thyroid cancer (ATC) stem cell activity.

Anaplastic thyroid cancer (ATC) is one of the most aggressive solid cancers in humans, with limited treatment options. Recent studies suggest that cancer stem cell (CSC) activity contributes to therapeutic resistance and recurrence of ATC. We show that the expression of the endogenous thyroid hormone receptor ß gene (THRB) is silenced in ATC and demonstrate that the exogenously expressed TRß suppresses CSC activity. Decitabine is one of the demethylation agents to treat myelodysplastic syndrome and acute myeloid leukemia patients and is currently in clinical trials for hematopoietic malignancies and solid tumors. We aim to show that the re-expression of the endogenous THRB gene by decitabine can attenuate CSC activity to block ATC tumor growth. We treated ATC cell lines derived from human ATC tumors (11T and 16T cells) with decitabine and evaluated the effects of the reactivated endogenous TRß on CSC activity in vitro and in vivo xenograft models. We found that treatment of 11T and 16T cells with decitabine reactivated the expression of endogenous TRß, as evidenced by western blot and immunohistochemical analyses. The expressed TRß inhibited cell proliferation by arresting cells at the S phase, increased apoptotic cell death by upregulation of cleaved caspase-3, and markedly suppressed the expression of CSC regulators, including cMYC, ALDH, SOX2, CD44, and ß-catenin. Decitabine also inhibited xenograft tumor growth by suppressing CSC activity, inhibiting cancer cell proliferation, and increasing apoptosis. Our findings suggest that re-expression of the endogenous TRß is a novel therapeutic approach for ATC via suppression of CSC activity.

Adipocyte Thyroid Hormone ß Receptor-Mediated Hormone Action Fine-tunes Intracellular Glucose and Lipid Metabolism and Systemic Homeostasis.

Thyroid hormone (TH) has a profound effect on energy metabolism and systemic homeostasis. Adipose tissues are crucial for maintaining whole-body homeostasis; however, whether TH regulates systemic metabolic homeostasis through its action on adipose tissues is unclear. Here, we demonstrate that systemic administration of triiodothyronine (T3), the active form of TH, affects both inguinal white adipose tissue (iWAT) and whole-body metabolism. Taking advantage of the mouse model lacking adipocyte TH receptor (TR) α or TRß, we show that TRß is the major TR isoform that mediates T3 action on the expression of genes involved in multiple metabolic pathways in iWAT, including glucose uptake and use, de novo fatty acid synthesis, and both UCP1-dependent and -independent thermogenesis. Moreover, our results indicate that glucose-responsive lipogenic transcription factor in iWAT is regulated by T3, thereby being critically involved in T3-regulated glucose and lipid metabolism and energy dissipation. Mice with adipocyte TRß deficiency are susceptible to diet-induced obesity and metabolic dysregulation, suggesting that TRß in adipocytes may be a potential target for metabolic diseases. ARTICLE HIGHLIGHTS: How thyroid hormone (TH) achieves its diverse biological activities in the regulation of metabolism is not fully understood. Whether TH regulates systemic metabolic homeostasis via its action on white adipose tissue is unclear. Adipocyte TH receptor (TR) ß mediates the triiodothyronine effect on multiple metabolic pathways by targeting glucose-responsive lipogenic transcription factor in white adipose tissue; mice lacking adipocyte TRß are susceptible to high-fat diet-induced metabolic abnormalities. TRß in white adipocytes controls intracellular and systemic metabolism and may be a potential target for metabolic diseases.

Thyroid hormone activities of neutral and anionic hydroxylated polybrominated diphenyl ethers to thyroid receptor ß: A molecular dynamics study.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified as the strong endocrine disrupting chemicals to humans, which show structural similarity with endogenous thyroid hormones (THs) and thus disrupt the functioning of THs through competitive binding with TH receptors (TRs). Although previous studies have reported the hormone activities of some OH-PBDEs on TH receptor ß (TRß), the interaction mechanism remains unclear. Furthermore, hydroxyl dissociation of OH-PBDEs may alter their TR disrupting activities, which has not yet been investigated in depth. In this work, we selected 18 OH-PBDEs with neutral and anionic forms and performed molecular dynamics (MD) simulations to estimate their binding interactions with the ligand binding domain (LBD) of TRß. The results demonstrate that most of OH-PBDEs have stronger binding affinities to TRß-LBD than their anionic counterparts, and the hydroxyl dissociation of ligands differentiate the major driving force for their binding. More Br atoms in OH-PBDEs can result in stronger binding potential with TRß-LBD. Moreover, 5 hydrophobic residues, including Met313, Leu330, Ile276, Leu346, and Phe272, are identified to have important contributions to bind OH-PBDEs. These results clarify the binding mechanism of OH(O-)-PBDEs to TRß-LBD at the molecular level, which can provide a solid theoretical basis for accurate assessment of TH disrupting effects of these chemicals.

Alterations of DNA methylation and expression of genes related to thyroid hormone metabolism in colon epithelium of obese patients.

BACKGROUND: Colorectal cancer is common among obese individuals. The purpose of the current study was to determine changes in DNA methylation status and mRNA expression of thyroid hormone receptor beta (THRB), as a tumor suppressor, and thyroid hormone inactivating enzyme, type 3 deiodinase (DIO3) genes, in human epithelial colon tissues of healthy obese individuals. METHODS: Colon biopsies were analyzed by methylation sensitive-high resolution melting (MS-HRM) to investigate promoter methylation of DIO3 and THRB, and by quantitative real-time polymerase chain reaction to assay expression of DIO3 and THRB mRNA on eighteen obese and twenty-one normal-weight healthy men. RESULTS: There was no significant difference in mean methylation levels at the THRB promoter region between the two groups. Nevertheless, obesity decreased THRB expression levels, significantly (P < 0.05; fold change: 0.19). Furthermore, obesity attenuated DNA methylation (P < 0.001) and enhanced mRNA expression of DIO3 (P < 0.05; fold change: 3). CONCLUSIONS: Our findings suggest that obesity may alter expression of THRB and DIO3 genes through epigenetic mechanism. Alterations of THRB and DIO3 expressions may predispose colon epithelium of obese patients to neoplastic transformation.

Cell-Specific Transport and Thyroid Hormone Receptor Isoform Selectivity Account for Hepatocyte-Targeted Thyromimetic Action of MGL-3196.

Thyroid hormones (THs) and TH receptor-beta (TRß) reduce hepatic triglycerides, indicating a therapeutic potential for TH analogs in liver steatosis. To avoid adverse extrahepatic, especially TRα-mediated effects such as tachycardia and bone loss, TH analogs with combined TRß and hepatocyte specificity are desired. MGL-3196 is a new TH analog that supposedly meets these criteria. Here, we characterize the thyromimetic potential of MGL-3196 in cell-based assays and address its cellular uptake requirements. We studied the contribution of liver-specific organic anion transporters (OATP)1B1 and 1B3 to MGL-3196 action. The TR isoform-specific efficacy of MGL-3196 compared with 3,5,3'-triiodothyronine (T3) was determined with luciferase assays and gene expression analysis in OATP1B1 and OATP1B3 and TRα- or TRß-expressing cells and in primary murine hepatocytes (PMHs) from wild-type and TRß knockout mice. We measured the oxygen consumption rate to compare the effects of MGL-3196 and T3 on mitochondrial respiration. We identified OATP1B1 as the primary transporter for MGL-3196. MGL-3196 had a high efficacy (90% that of T3) in activating TRß, while the activation of TRα was only 25%. The treatment of PMHs with T3 and MGL-3196 at EC50 resulted in a similar induction of Dio1 and repression of Serpina7. In HEK293 cells stably expressing OATP1B1, MGL-3196 had comparable effects on mitochondrial respiration as T3. These data indicate that MGL-3196's hepatic thyromimetic action, the basis for its therapeutic use, results from a combination of hepatocyte-specific transport by OATP1B1 and the selective activation of TRß over TRα.

TSH-SPP1/TRß-TSH positive feedback loop mediates fat deposition of hepatocyte: Crosstalk between thyroid and liver.

Aims: We conducted this study with two aims: (1) whether TRß could be damaged by NAFLD, thereby represent thyroid hormone resistance-like manifestation and (2) to analyze the potential role of SPP1 in TH signaling pathway on the process of NAFLD. This study is expected to provide a new perspective on the therapeutic mechanism in the pathological course of NAFLD. Methods: A total of 166 patients diagnosed with type 2 diabetes mellitus (T2DM) were enrolled in this study. All patients had a BMI above 24 kg/m2 and were stratified into two groups: NAFLD and Non-NAFLD groups. Ages, gender, BMI, duration of diabetes and biochemical markers were obtained from participants' records. We downloaded the dataset GSE48452 from GEO. The Pathview library was used to make the thyroid hormone signaling pathway visualization. The CIBERSORT algorithm was applied to calculate the infiltrated immune cells in obese NAFLD patients. C57BL/6 mice were randomly selected to constitute the normal control (NC) group and were fed a normal chow diet; the rest of the mice were fed a high-fat diet (HFD). After 12 weeks HFD feeding, the mice were sacrificed by cervical dislocation, and blood samples were collected. Mouse livers were also collected; one part of each liver was fixed in 10% formalin for histological analysis, and the other part was snap-frozen for subsequent molecular analyses. To explore the relationship between SPP1, TRß and lipid deposition in hepatocytes, HepG2 cells were treated with 50 µ M concentration of PA and/or 20 ng/ml concentration of rh-SPP1 for 48h. In addition, the PC3.1-TRß plasmid was constructed for further validation in HepG2 cells. We used THP-1 cells to construct an M1 macrophage model in vitro. We then analyzed THP-1 cells treated with various concentrations of PA or TSH. Results: (1) After adjusting for all factors that appeared P value less than 0.1 in the univariate analysis, BMI, TSH, and FT3 were significant independent risk factors of NAFLD (ORs were 1.218, 1.694, and 2.259, respectively); (2) A further analysis with BMI stratification indiacted that both FT3 and TSH had a significant change between individuals with NAFLD and Non-NAFLD in obesity subgroup; however, there was no statistic difference in over-weight group; (3) Bioinformatics analysis of GSE48452 had shown that several key molecular (including TRß) of thyroid hormone pathway affected by NAFLD induced transcriptomic changes and the expression levels of SPP1, FABP4 and RPS4Y1 were significantly higher, while the expression levels of PZP and VIL1 were significantly decreased in NAFLD patients(adjusted p < 0.05, |logFC| > 1.0). The CIBERSORT algorithm showed increased M0 and M1, decreased M2 macrophage infiltration in NAFLD with comparison to healthy obese group; (4) After 12 weeks of HFD-feeding, the obesity mice had significantly higher serum TSH and In IHC-stained liver sections of obesity group, the intensity of SPP1 had a significantly increased, while TRß reduced; (5) In vitro studies have shown SPP1 aggravated lipid deposition in hepatic cells dependent on down-regulating the expression of TRß and TSH acts to promote secretion of SPP1 in M1 macrophage cells. Conclusions: SPP1 secretion induced by M1 macrophage polarization, which may down-regulates TRß in hepatocytes via paracrine manner, on the one hand, the lipid deposition aggravating in liver, on the other hand, a compensatory increase of TSH in serum. The increased TSH can further lead to the following SPP1 secretion of M1 macrophage. The positive feedback crosstalk between thyroid and liver, may be plays an important role in maintaining and amplifying pathological process of NAFLD.

NAFLD and thyroid function: pathophysiological and therapeutic considerations.

Nonalcoholic fatty liver disease (NAFLD) is a worldwide rising challenge because of hepatic, but also extrahepatic, complications. Thyroid hormones are master regulators of energy and lipid homeostasis, and the presence of abnormal thyroid function in NAFLD suggests pathogenic relationships. Specifically, persons with hypothyroidism feature dyslipidemia and lower hepatic ß-oxidation, which favors accumulation of triglycerides and lipotoxins, insulin resistance, and subsequently de novo lipogenesis. Recent studies indicate that liver-specific thyroid hormone receptor ß agonists are effective for the treatment of NAFLD, likely due to improved lipid homeostasis and mitochondrial respiration, which, in turn, may contribute to a reduced risk of NAFLD progression. Taken together, the possible coexistence of thyroid disease and NAFLD calls for increased awareness and optimized strategies for mutual screening and management.

Maternal cadmium exposure impairs placental angiogenesis in preeclampsia through disturbing thyroid hormone receptor signaling.

Cadmium is a ubiquitous environmental pollutant, which can increase the risk of preeclampsia. This study was designed to determine the mechanism of cadmium exposure during pregnancy impaired placental angiogenesis that was associated with the occurrence of preeclampsia. The effects of cadmium exposure on placental thyroid hormone receptor signaling were explored. JEG3 cells were treated with CdCl2 (20 µM) and the Dio2 inhibitor, IOP (100 µM). Cadmium levels in maternal blood and placentae were increased in preeclampsia group. Placental angiogenesis of preeclampsia was decreased with decreased expression of PLGF and VEGF and increased expression of sFlt1. Meanwhile, the expression and nuclear translocation of thyroid hormone receptor α were decreased in preeclampsia placenta, as well as the expression of Dio2, but not the expression and nuclear translocation of thyroid hormone receptor ß. Furthermore, we found that cadmium exposure downregulated the expression of thyroid hormone receptor α and Dio2, but not the expression of thyroid hormone receptor ß in JEG3 cells. Also, we found that cadmium exposure decreased the expression of PLGF and VEGF and increased the expression of sFlt1 in JEG3 cells. IOP pretreatment decreased the expression of PLGF and increased the expression of sFlt1. In conclusion, our results elucidated that cadmium exposure would impair placental angiogenesis in preeclampsia through disturbing thyroid hormone receptor signaling.