Targeting Thyroid Hormone/Thyroid Hormone Receptor Axis: An Attractive Therapy Strategy in Liver Diseases

Actions of thyroid hormones and thyromimetics on the liver

Thyroid hormones (triiodothyronine and thyroxine) are pivotal for metabolic balance in the liver and entire body. Dysregulation of the hypothalamus-pituitary-thyroid axis can contribute to hepatic metabolic disturbances, affecting lipid metabolism, glucose regulation and protein synthesis. In addition, reductions in circulating and intrahepatic thyroid hormone concentrations increase the risk of metabolic dysfunction-associated steatotic liver disease by inducing lipotoxicity, inflammation and fibrosis. Amelioration of hepatic metabolic disease by thyroid hormones in preclinical and clinical studies has spurred the development of thyromimetics that target THRB (the predominant thyroid hormone receptor isoform in the liver) and/or the liver itself to provide more selective activation of hepatic thyroid hormone-regulated metabolic pathways while reducing thyrotoxic side effects in tissues that predominantly express THRA such as the heart and bone. Resmetirom, a liver and THRB-selective thyromimetic, recently became the first FDA-approved drug for metabolic dysfunction-associated steatohepatitis (MASH). Thus, a better understanding of the metabolic actions of thyroid hormones and thyromimetics in the liver is timely and clinically relevant. Here, we describe the roles of thyroid hormones in normal liver function and pathogenesis of MASH, as well as some potential clinical issues that might arise when treating patients with MASH with thyroid hormone supplementation or thyromimetics.

Thyroid hormone T3 augments the cytotoxicity of sorafenib in Huh7 hepatocellular carcinoma cells by suppressing AKT expression

BACKGROUND AND OBJECTIVES

Hepatocellular carcinoma (HCC) is a primary cancer that poorly responds to treatment. Molecular cancer studies led to the development of kinase inhibitors, among which sorafenib stands out as a multi-kinase inhibitor approved by FDA for first line use in HCC patients. However, the efficiency of sorafenib was shown to be counteracted by numerous subcellular pathways involving the effector kinase AKT, causing resistance and limiting its survival benefit. On the way of breaking such resistance mechanisms and increase the efficiency of sorafenib, deeper understanding of hepatocellular physiology is essential. Thyroid hormones were shown to be metabolized in liver and inevitably affect the molecular behaviour of hepatocytes. Interestingly, thyroid hormone T3 was also demonstrated to be potentially influential in liver regeneration and treatment with this hormone reportedly led to a decrease in HCC tumor growths. In this study, we aimed to uncover the impact of T3 hormone on the cytotoxic response to sorafenib in HCC in vitro.

MATERIALS AND METHODS

We pre-treated the HCC cell line Huh-7 with T3 prior to sorafenib exposure both in 2D and 3D culture. We checked cell viability with MTT assay in 2D culture and measured the sizes of 3D spheroids with bright-field microscopy followed by a surface analysis with ImageJ. We also performed scratch assay to measure cell migration as well as western blot and qPCR to uncover affected pathways.

RESULTS

We observed an additive effect to sorafenib's cytotoxicity both in 2D and 3D culture. Cell migration assay also confirmed our finding and pointed out a benefit of T3 hormone in HCC cell migration. Western blot experiments showed that T3 exerts its additive effect by suppressing AKT expression upon sorafenib treatment both at protein and gene expression levels.

CONCLUSION

Our results open a promising new avenue in increasing sorafenib's cytotoxicity where thyroid hormone T3 is utilized to modulate AKT expression to combat resistance, and warrant further studies in the field.

An extended transcription factor regulatory network controls hepatocyte identity

Cell identity is specified by a core transcriptional regulatory circuitry (CoRC), typically limited to a small set of interconnected cell-specific transcription factors (TFs). By mining global hepatic TF regulons, we reveal a more complex organization of the transcriptional regulatory network controlling hepatocyte identity. We show that tight functional interconnections controlling hepatocyte identity extend to non-cell-specific TFs beyond the CoRC, which we call hepatocyte identity (Hep-ID)CONNECT TFs. Besides controlling identity effector genes, Hep-IDCONNECT TFs also engage in reciprocal transcriptional regulation with TFs of the CoRC. In homeostatic basal conditions, this translates into Hep-IDCONNECT TFs being involved in fine tuning CoRC TF expression including their rhythmic expression patterns. Moreover, a role for Hep-IDCONNECT TFs in the control of hepatocyte identity is revealed in dedifferentiated hepatocytes where Hep-IDCONNECT TFs are able to reset CoRC TF expression. This is observed upon activation of NR1H3 or THRB in hepatocarcinoma or in hepatocytes subjected to inflammation-induced loss of identity. Our study establishes that hepatocyte identity is controlled by an extended array of TFs beyond the CoRC.

CS27109, A Selective Thyroid Hormone Receptor-β Agonist Alleviates Metabolic-Associated Fatty Liver Disease in Murine Models

BACKGROUND/AIM

Thyroid hormone receptor-β (THR-β) agonists play crucial roles in dyslipidemia and metabolic associated fatty liver disease (MAFLD). We developed a novel oral and liver-targeted THR-β agonist, CS27109, and evaluated its efficacy in the treatment of metabolic disorders.

MATERIALS AND METHODS

We evaluated in vitro and in vivo efficacy and/or safety of CS27109 along with MGL3196 (a phase III THR-β agonist).

RESULTS

CS27109 showed pronounced activity and selectivity to THR-β and favorable PK properties, which was equivalent to MGL3196. In the hamster model, animals treated with a high dose of CS27109 showed equivalent reductions in serum TC and LDL-c with groups treated with MGL3196. In the rat model, CS27109 and MGL3196 reduced serum ALT, TC, TG, LDL-c, liver weight ratio, and liver steatosis. CS27109 simultaneously decreased liver TG and TC, and MGL3196 additionally reduced AST. In the mouse model, CS27109 dose-dependently reduced serum AST, ALT, liver inflammation, and NAS score, and also downregulated TC, LDL-c, liver steatosis, and fibrosis, but not in a dose-dependent manner. MGL3196 revealed an equivalent effect with CS27109 in that model. CS27109 also exhibited tolerable toxicity to the heart.

CONCLUSIONS

CS27109 shows comparative in vitro and in vivo efficacy with MGL3196, suggesting its potential therapeutic application in the treatment of MAFLD such as dyslipidemia and steatohepatitis.

Effect of Liraglutide on Serum TSH Levels in Patients with NAFLD and its Underlying Mechanisms

This study aimed to evaluate the effect of liraglutide on serum thyroid-stimulating hormone (TSH) levels in patients with type 2 diabetes mellitus (T2DM) and explore the underlying mechanisms via bioinformatics analysis. A total of 49 obese/overweight patients with T2DM received liraglutide during outpatient visits or hospitalization in the Department of Endocrinology. Meanwhile, the control group included 49 patients with T2DM but without nonalcoholic fatty liver disease (NAFLD) who were matched for age and sex (baseline from July 2016 to June 2021). Follow-up data on the last use of liraglutide were also retrieved. Age, sex, body mass index (BMI), and duration of diabetes were obtained from the participants' records. All patients were tested for biochemical markers hemoglobin A1c (HbA1c), alanine transaminase, aspartate transaminase, free triiodothyronine, free thyroxine (FT4), and TSH at baseline and follow-up. After adjusting for all factors with a p-value < 0.05, BMI, HbA1c, LDL, FT4, and TSH were identified as significant independent risk factors for NAFLD in the univariate analysis. Following liraglutide therapy (average time 16 months), these patients had significantly lower BMI, HbA1c, and TSH but higher high-density lipoprotein (HDL) levels than those in the baseline data (all p < 0.05), and further subgroup analysis stratified by duration of liraglutide use showed that the test for time trends had statistical differences in BMI and TSH but not in HbA1c and HDL. After the therapy, the NAFLD and NASH groups showed significantly decreased TSH levels after liraglutide therapy compared with the corresponding baseline data. Furthermore, the expression of THRB, which encodes TRβ, was significantly decreased in the NAFLD group, which may explain the thyroid hormone resistance-like manifestation in the clinical findings. In conclusion, liraglutide improves hepatic thyroid hormone resistance in T2DM with NAFLD, and restoration of impaired TRβ expression in NAFLD is a potential mechanism involved in the process of liraglutide therapy.

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

Aims

We conducted this study with two aims: (1) whether TRβ 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, TRβ 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-TRβ 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 TRβ) 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 TRβ reduced; (5) In vitro studies have shown SPP1 aggravated lipid deposition in hepatic cells dependent on down-regulating the expression of TRβ and TSH acts to promote secretion of SPP1 in M1 macrophage cells.

Conclusions

SPP1 secretion induced by M1 macrophage polarization, which may down-regulates TRβ 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.