Thyroid Hormone Analogues: An Update

Harnessing nuclear receptors to modulate hepatic stellate cell activation for liver fibrosis resolution

With the recent approval of Resmetirom as the first drug targeting nuclear receptors for metabolic dysfunction-associated steatohepatitis (MASH), there is promising way to treat MASH-associated liver fibrosis. However, liver fibrosis can arise from various pathogenic factors, and effective treatments for fibrosis due to other causes remain elusive. The activation of hepatic stellate cells (HSCs) represents a central link in the pathogenesis of hepatic fibrosis. Therefore, harnessing nuclear receptors to modulate HSC activation may be an effective approach to resolving the complex liver fibrosis caused by various factors. In this comprehensive review, we systematically explore the structure and physiological functions of nuclear receptors, shedding light on their multifaceted roles in HSC activation. Recent advancements in drug development targeting nuclear receptors are discussed, providing insights into their potential as rational and effective therapeutic targets for modulating HSC activation in the context of liver fibrosis. By elucidating the intricate interplay between nuclear receptors and HSC activation, this review contributes to the discovery of new nuclear receptor targets in HSCs for resolving hepatic fibrosis.

Drugs for dyslipidaemia: the legacy effect of the Scandinavian Simvastatin Survival Study (4S)

Since the discovery of statins and the Scandinavian Simvastatin Survival Study (4S) results three decades ago, remarkable advances have been made in the treatment of dyslipidaemia, a major risk factor for atherosclerotic cardiovascular disease. Safe and effective statins remain the cornerstone of therapeutic approach for this indication, including for children with genetic dyslipidaemia, and are one of the most widely prescribed drugs in the world. However, despite the affordability of generic statins, they remain underutilised worldwide. The use of ezetimibe to further decrease plasma LDL cholesterol and the targeting of other atherogenic lipoproteins, such as triglyceride-rich lipoproteins and lipoprotein(a), are likely to be required to further reduce atherosclerotic cardiovascular disease events. Drugs directed at these lipoproteins, including gene silencing and editing methods that durably suppress the production of proteins, such as PCSK9 and ANGPTL3, open novel therapeutic options to further reduce the development of atherosclerotic cardiovascular disease.

Hepatic thyroid hormone receptor-β signalling: Mechanisms and recent advancements in the treatment of metabolic dysfunction-associated steatohepatitis

The pharmacotherapy of metabolic dysfunction-associated steatotic liver disease (MASLD) and its progressive form, the metabolic dysfunction-associated steatohepatitis (MASH), remains a hot topic in research and a largely unmet need in clinical practice. As the first approval of a disease-specific drug, resmetirom, was regarded as a milestone for the management of this common liver disease, this comprehensive and updated review aimed to highlight the importance of the hepatic thyroid hormone (TH) receptor (THR)-β signalling for the treatment of MASH, with a special focus on resmetirom. First, the genomic and non-genomic actions of the liver-directed THR-β mediated mechanisms are summarized. THR-β has a key role in hepatic lipid and carbohydrate metabolism; disruption of THR-β signalling leads to dysmetabolism, thus promoting MASLD and possibly its progression to MASH and cirrhosis. In the clinical setting, this is translated into a significant association between primary hypothyroidism and MASLD, as confirmed by recent meta-analyses. An association between MASLD and subclinical intrahepatic hypothyroidism (i.e. a state of relatively low hepatic triiodothyronine concentrations, with circulating TH concentrations within the normal range) is also emerging and under investigation. In line with this, the favourable results of the phase 3 placebo-controlled MAESTRO trials led to the recent conditional approval of resmetirom by the US FDA for treating adults with MASH and moderate-to-advanced fibrosis. This conditional approval of resmetirom opened a new window to the management of this common and burdensome liver disease, thus bringing the global scientific community in front of new perspectives and challenges.

The Thyroid Hormone Analog GC-1 Mitigates Acute Lung Injury by Inhibiting M1 Macrophage Polarization

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life-threatening condition with a high mortality rate of ≈40%. Thyroid hormones (THs) play crucial roles in maintaining homeostasis of the cellular microenvironment under stress. The previous studies confirmed that the clinical-stage TH analog GC-1 significantly alleviates pulmonary fibrosis by improving the function of mitochondria in epithelial cells. However, the effects of GC-1 on macrophages in lung injury and the related mechanisms remain unclear. This study evaluated the therapeutic effects of GC-1 in two murine models of lipopolysaccharide (LPS)- or hydrochloric acid (HCl)-induced ALI. Additionally, mouse alveolar macrophages (AMs) and human THP-1-derived macrophages are utilized to investigate the impact of GC-1 on macrophage polarization. GC-1 effectively reduces the inflammatory response and lung injury in ALI mice, as evidenced by neutrophil infiltration, cytokine levels, alveolar fluid clearance, and pulmonary pathology. Notably, GC-1 selectively inhibits M1 macrophage polarization, which may be achieved by impeding NF-κB signaling activation through the DNMT3b-PPARγ-NF-κB pathway in a TH receptor β1 (TRβ1)-dependent manner, consequently suppressing the polarization of macrophages toward the M1 phenotype and overproduction of inflammatory cytokines. Overall, these findings highlight the immunomodulatory property of GC-1 as an anti-inflammatory strategy for ALI/ARDS and inflammation-related diseases.

Pharmaceutical Pollutants: Ecotoxicological Impacts and the Use of Agro-Industrial Waste for Their Removal from Aquatic Environments

Medicines are pharmaceutical substances used to treat, prevent, or relieve symptoms of different diseases in animals and humans. However, their large-scale production and use worldwide cause their release to the environment. Pharmaceutical molecules are currently considered emerging pollutants that enter water bodies due to inadequate management, affecting water quality and generating adverse effects on aquatic organisms. Hence, different alternatives for pharmaceuticals removal from water have been sought; among them, the use of agro-industrial wastes has been proposed, mainly because of its high availability and low cost. This review highlights the adverse ecotoxicological effects related to the presence of different pharmaceuticals on aquatic environments and analyzes 94 investigations, from 2012 to 2024, on the removal of 17 antibiotics, highlighting sulfamethoxazole as the most reported, as well as 6 non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac and ibuprofen, and 27 pharmaceutical drugs with different pharmacological activities. The removal of these drugs was evaluated using agro-industrial wastes such as wheat straw, mung bean husk, bagasse, bamboo, olive stones, rice straw, pinewood, rice husk, among others. On average, 60% of the agro-industrial wastes were transformed into biochar to be used as a biosorbents for pharmaceuticals removal. The diversity in experimental conditions among the removal studies makes it difficult to stablish which agro-industrial waste has the greatest removal capacity; therefore, in this review, the drug mass removal rate (DMRR) was calculated, a parameter used with comparative purposes. Almond shell-activated biochar showed the highest removal rate for antibiotics (1940 mg/g·h), while cork powder (CP) (10,420 mg/g·h) showed the highest for NSAIDs. Therefore, scientific evidence demonstrates that agro-industrial waste is a promising alternative for the removal of emerging pollutants such as pharmaceuticals substances.

Potential therapeutic strategies for MASH: from preclinical to clinical development

Current treatment paradigms for metabolic dysfunction-associated steatohepatitis (MASH) are based primarily on dietary restrictions and the use of existing drugs, including anti-diabetic and anti-obesity medications. Given the limited number of approved drugs specifically for MASH, recent efforts have focused on promising strategies that specifically target hepatic lipid metabolism, inflammation, fibrosis, or a combination of these processes. In this review, we examined the pathophysiology underlying the development of MASH in relation to recent advances in effective MASH therapy. Particularly, we analyzed the effects of lipogenesis inhibitors, nuclear receptor agonists, glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists, fibroblast growth factor mimetics, and combinatorial therapeutic approaches. We summarize these targets along with their preclinical and clinical candidates with the ultimate goal of optimizing the therapeutic prospects for MASH.

Evaluation of MELD Scores and Thyroid Hormones as Prognostic Factors of Liver Cirrhosis

Background and Objectives: Hepatic cirrhosis is a disease with an increasing frequency globally, but its mechanisms of disease development are not yet completely known. The aim of this study was to evaluate the relationship between thyroid hormone levels (T3, fT4, and TSH) and survival in patients with chronic liver disease. Materials and Methods: A total of 419 patients diagnosed with liver cirrhosis were included in the study. The MELD score was computed, and TSH, T3, and fT4 were collected from each patient using the ELISA procedure. Signs and symptoms of liver failure and portal hypertension confirmed the clinical diagnosis of liver cirrhosis, and biological tests and imaging methods confirmed the diagnosis. Results: The MELD score was positively associated with TSH on admission and TSH on discharge and negatively associated with T3 at discharge. TSH levels were higher in non-survivors than in survivors. The values of T3 and fT4 present no significant changes to be considered as prognostic factors. Conclusions: Although the differences between the median TSH values of the patients who died and those who survived are not very large, the statistical significance of the data obtained demonstrates that there are changes in metabolism of the thyroid hormones during the progression of liver cirrhosis. It is possible that TSH is the one which maintains the normal balance of thyroid activity for patients with liver cirrhosis, so it can be considered as an important marker of evolution of these patients.

Synthesis and preclinical testing of a selective beta-subtype agonist of thyroid hormone receptor ZTA-261

BACKGROUND

Thyroid hormones (TH) regulate the basal metabolic rate through their receptors THRα and THRβ. TH activates lipid metabolism via THRβ, however, an excess amount of TH can lead to tachycardia, bone loss, and muscle wasting through THRα. In recent years, TH analogs that selectively bind to THRβ have gained attention as new agents for treating dyslipidemia and obesity, which continue to pose major challenges to public health worldwide.

METHODS

We developed a TH analog, ZTA-261, by modifying the existing THRβ-selective agonists GC-1 and GC-24. To determine the THRβ-selectivity of ZTA-261, an in vitro radiolabeled TH displacement assay was conducted. ZTA-261 was intraperitoneally injected into a mouse model of high-fat diet-induced obesity, and its effectiveness in reducing body weight and visceral fat, and improving lipid metabolism was assessed. In addition, its toxicity in the liver, heart, and bone was evaluated.

RESULTS

ZTA-261 is more selective towards THRβ than GC-1. Although ZTA-261 is less effective in reducing body weight and visceral fat than GC-1, it is as effective as GC-1 in reducing the levels of serum and liver lipids. These effects are mediated by the same pathway as that of T3, a natural TH, as evidenced by similar changes in the expression of TH-induced and lipid metabolism-related genes. The bone, cardiac, and hepatotoxicity of ZTA-261 are significantly lower than those of GC-1.

CONCLUSIONS

ZTA-261, a highly selective and less toxic THRβ agonist, has the potential to be used as a drug for treating diseases related to lipid metabolism.

Effective TRIAC treatment of a THRβ-mutated patient with thyroid hormone resistance

Resistance to thyroid hormone (RTH) is a rare autosomal dominant disease characterized by an alteration of thyroid hormone negative feedback, usually as a consequence of a mutation in the thyroid hormone receptor-b gene (THRβ). It is characterized by high variability of clinical manifestations, ranging from isolated abnormal thyroid function tests without symptoms to severe and impaired clinical conditions. Here we report the case of a woman who was diagnosed with RTHβ when she was 35 years old and was treated with 3,5,3-triiodiothyroacetic acid (TRIAC) because of the onset of clinical symptoms of hyperthyroidism. This therapy has been effective in controlling thyrotoxicosis for 5 years. After this time the patient developed an autoimmune hyperthyroidism, with TSH receptor autoantibodies appearance, which caused a loss of efficacy of the drug in controlling the disease. The development of different pathophysiological mechanisms of thyrotoxicosis, as in this case, could be the reason for both variability of disease manifestations and of loss of response to drug therapy.

Exploring the potential of drug repurposing for liver diseases: A comprehensive study

Drug repurposing involves the investigation of existing drugs for new indications. It offers a great opportunity to quickly identify a new drug candidate at a lower cost than novel discovery and development. Despite the importance and potential role of drug repurposing, there is no specific definition that healthcare providers and the World Health Organization credit. Unfortunately, many similar and interchangeable concepts are being used in the literature, making it difficult to collect and analyze uniform data on repurposed drugs. This research was conducted based on understanding general criteria for drug repurposing, concentrating on liver diseases. Many drugs have been investigated for their effect on liver diseases even though they were originally approved (or on their way to being approved) for other diseases. Some of the hypotheses for drug repurposing were first captured from the literature and then processed further to test the hypothesis. Recently, with the revolution in bioinformatics techniques, scientists have started to use drug libraries and computer systems that can analyze hundreds of drugs to give a short list of candidates to be analyzed pharmacologically. However, this study revealed that drug repurposing is a potential aid that may help deal with liver diseases. It provides available or under-investigated drugs that could help treat hepatitis, liver cirrhosis, Wilson disease, liver cancer, and fatty liver. However, many further studies are needed to ensure the efficacy of these drugs on a large scale.

Circadian Gating of Thyroid Hormone Action in Hepatocytes

Thyroid hormones, thyroxin (T4) and the biologically active triiodothyronine (T3), play important roles in liver metabolic regulation, including fatty acid biosynthesis, beta-oxidation, and cholesterol homeostasis. These functions position TH signaling as a potential target for the treatment of metabolic dysfunction-associated steatotic liver disease (MASLD). Elevated T3 levels in the circulation are associated with increased hepatic lipid turnover, which is also under the control of the circadian clock system. In this study, we developed a cell system to study the impact of hepatocyte circadian rhythms on the metabolic response to T3 treatment under control and steatotic conditions. Synchronized AML-12 circadian reporter hepatocytes were treated with T3 at different circadian phases and metabolic conditions. T3 treatment increased metabolic activity in a dose-independent fashion and had no significant effect on circadian rhythms in AML-12 cells. T3 had marked time-of-treatment-dependent effects on metabolic transcript expression. Steatosis induction altered metabolic transcript expression in AML-12 cells. In this condition, the circadian rhythm period was lengthened, and this effect was independent of T3. Under steatotic conditions, T3 had marked time-of-treatment dependent effects on metabolic transcript expression, which differed from those observed under control conditions. These findings reveal a time-of-day-dependent response of hepatocytes to T3, which is further modulated by the metabolic state. Our data suggest that time has a strong influence on liver TH action, which might be considered when treating MASLD.

Effects of the Pituitary-targeted Gland Axes on Hepatic Lipid Homeostasis in Endocrine-associated Fatty Liver Disease-A Concept Worth Revisiting

Hepatic lipid homeostasis is not only essential for maintaining normal cellular and systemic metabolic function but is also closely related to the steatosis of the liver. The controversy over the nomenclature of non-alcoholic fatty liver disease (NAFLD) in the past three years has once again sparked in-depth discussions on the pathogenesis of this disease and its impact on systemic metabolism. Pituitary-targeted gland axes (PTGA), an important hormone-regulating system, are indispensable in lipid homeostasis. This review focuses on the roles of thyroid hormones, adrenal hormones, sex hormones, and their receptors in hepatic lipid homeostasis, and summarizes recent research on pituitary target gland axes-related drugs regulating hepatic lipid metabolism. It also calls on researchers and clinicians to recognize the concept of endocrine-associated fatty liver disease (EAFLD) and to re-examine human lipid metabolism from the macroscopic perspective of homeostatic balance.

Effect of Roxadustat on Thyroid Function in Patients With Renal Anemia

CONTEXT

Roxadustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, a recently developed class of drugs for treatment of anemia in chronic kidney disease (CKD), is reported to have a structure unlike that of other HIF-PH inhibitors but similar to that of triiodothyronine and bind to the thyroid hormone receptor in vitro. However, reports on the effects of roxadustat on thyroid function are limited and not detailed, and it remains unknown whether other HIF-PH inhibitors also affect thyroid function.

OBJECTIVE

To compare the effect of roxadustat with daprodustat, another HIF-PH inhibitor, on thyroid function in patients with renal anemia in CKD.

METHODS

This retrospective observational study included a total of 26 patients with anemia in CKD who were treated with roxadustat or daprodustat; thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured before and after treatment with the drugs.

RESULTS

After initiation of roxadustat, TSH showed a significant decrease (2.4732 [1.7858-4.9016] μIU/mL before treatment and 0.659 [0.112-2.005] μIU/mL after treatment, P < .05); FT4 showed a significant decrease (0.93 [0.84-1.05] ng/dL before treatment and 0.70 [0.53-0.85] ng/dL after treatment, P < .01). After daprodustat initiation, neither TSH nor FT4 showed a significant change (TSH: 3.044 [1.853-4.171] μIU/mL before treatment and 2.893 [1.866-4.894] μIU/mL after treatment, P = .635; FT4 was 0.93 [0.81-1.00] ng/dL before treatment and 0.97 [0.87-1.05] ng/dL after treatment, P = .328).

CONCLUSION

Roxadustat decreases TSH and FT4 levels while daprodustat does not.

Receptor modulators associated with the hypothalamus -pituitary-thyroid axis

The hypothalamus-pituitary-thyroid (HPT) axis maintains normal metabolic balance and homeostasis in the human body through positive and negative feedback regulation. Its main regulatory mode is the secretion of thyrotropin (TSH), thyroid hormones (TH), and thyrotropin-releasing hormone (TRH). By binding to their corresponding receptors, they are involved in the development and progression of several systemic diseases, including digestive, cardiovascular, and central nervous system diseases. The HPT axis-related receptors include thyrotropin receptor (TSHR), thyroid hormone receptor (TR), and thyrotropin-releasing hormone receptor (TRHR). Recently, research on regulators has become popular in the field of biology. Several HPT axis-related receptor modulators have been used for clinical treatment. This study reviews the developments and recent findings on HPT axis-related receptor modulators. This will provide a theoretical basis for the development and utilisation of new modulators of the HPT axis receptors.

Lack of thyroid hormone receptor beta is not detrimental for non-alcoholic steatohepatitis progression

Agonists for thyroid hormone receptor β (TRβ) show promise in preclinical studies and clinical trials to improve non-alcoholic fatty liver disease. A recent study on human livers, however, revealed reduced TRβ expression in non-alcoholic steatohepatitis (NASH), indicating a developing thyroid hormone resistance, which could constitute a major obstacle for those agonists. Using a rapid NASH paradigm combining choline-deficient high-fat diet and thermoneutrality, we confirm that TRβ declines during disease progression in mice similar to humans. Contrary to expectations, mice lacking TRβ showed less liver fibrosis, and NASH marker genes were not elevated. Conversely, increasing TRβ expression in wild-type NASH mice using liver-targeted gene therapy did not improve histology, gene expression, or metabolic parameters, indicating that TRβ receptor levels are of minor relevance for NASH development and progression in our model, and suggest that liver-rather than isoform-specificity might be more relevant for NASH treatment with thyroid hormone receptor agonists.

Thyroxine metabolite-derived 3-iodothyronamine (T1AM) and synthetic analogs as efficient suppressors of transthyretin amyloidosis

Aggregation and fibrillization of transthyretin (TTR) is a fatal pathogenic process that can cause cardiomyopathic and polyneuropathic diseases in humans. Although several therapeutic strategies have been designed to prevent and treat related pathological events, there is still an urgent need to develop better strategies to improve potency and wider applicability. Here, we present our study demonstrating that 3-iodothyronamine (T1AM) and selected thyronamine-like compounds can effectively prevent TTR aggregation. T1AM is one of the thyroid hormone (TH) metabolites, and T1AM and its analogs, such as SG2, SG6, and SG12, are notable molecules for their beneficial activities against metabolic disorders and neurodegeneration. Using nuclear magnetic resonance (NMR) spectroscopy and biochemical analysis, we confirmed that T1AM analogs could bind to and suppress acid-induced aggregation of TTR. In addition, we employed computational approaches to further understand the detailed mechanisms of the interaction between T1AM analogs and TTR. This study demonstrates that T1AM analogs, whose beneficial effects against several pathological processes have already been proven, may have additional benefits against TTR aggregation and fibrillization. Moreover, we believe that our work provides invaluable insights to enhance the pleiotropic activity of T1AM and structurally related analogs, relevant for their therapeutic potential, with particular reference to the ability to prevent TTR aggregation.

Intracellular spatiotemporal metabolism in connection to target engagement

The metabolism in eukaryotic cells is a highly ordered system involving various cellular compartments, which fluctuates based on physiological rhythms. Organelles, as the smallest independent sub-cell unit, are important contributors to cell metabolism and drug metabolism, collectively designated intracellular metabolism. However, disruption of intracellular spatiotemporal metabolism can lead to disease development and progression, as well as drug treatment interference. In this review, we systematically discuss spatiotemporal metabolism in cells and cell subpopulations. In particular, we focused on metabolism compartmentalization and physiological rhythms, including the variation and regulation of metabolic enzymes, metabolic pathways, and metabolites. Additionally, the intricate relationship among intracellular spatiotemporal metabolism, metabolism-related diseases, and drug therapy/toxicity has been discussed. Finally, approaches and strategies for intracellular spatiotemporal metabolism analysis and potential target identification are introduced, along with examples of potential new drug design based on this.

Synthetic Thyroid Hormone Receptor-β Agonists Promote Oligodendrocyte Precursor Cell Differentiation in the Presence of Inflammatory Challenges

Oligodendrocytes and their precursors are the cells responsible for developmental myelination and myelin repair during adulthood. Their differentiation and maturation processes are regulated by a complex molecular machinery driven mainly by triiodothyronine (T3), the genomic active form of thyroid hormone, which binds to thyroid hormone receptors (TRs), regulating the expression of target genes. Different molecular tools have been developed to mimic T3 action in an attempt to overcome the myelin repair deficit that underlies various central nervous system pathologies. In this study, we used a well-established in vitro model of neural stem cell-derived oligodendrocyte precursor cells (OPCs) to test the effects of two compounds: the TRβ1 ligand IS25 and its pro-drug TG68. We showed that treatment with TG68 induces OPC differentiation/maturation as well as both the natural ligand and the best-known TRβ1 synthetic ligand, GC-1. We then described that, unlike T3, TG68 can fully overcome the cytokine-mediated oligodendrocyte differentiation block. In conclusion, we showed the ability of a new synthetic compound to stimulate OPC differentiation and overcome inflammation-mediated pathological conditions. Further studies will clarify whether the compound acts as a pro-drug to produce the TRβ1 ligand IS25 or if its action is mediated by secondary mechanisms such as AMPK activation.

Endocrine disorders associated with obesity

Several endocrine disorders, including diabetes, insulinoma, Cushing syndrome, hypothyroidism, polycystic ovarian syndrome, and growth hormone deficiency, are associated with obesity. The mechanisms underlying the development of obesity vary according to the abnormalities of endocrine function. The primary actions of insulin, glucocorticoids (GCs), thyroid hormone, and growth hormone are associated with energy metabolism in the liver, muscle, adipose tissue, and other tissues. This chapter describes the pathogenesis of obesity and metabolic dysfunction associated with excess insulin or GCs and the deficiency of thyroid hormone or growth hormone.

Thyroid hormone Beta receptor agonists for treatment of kidney disease: A promising agent?

BACKGROUND

Chronic kidney disease is a common disorder affecting a significant portion of the adult population with high mortality and morbidity. Obesity and hyperlipidemia are prevalent in chronic kidney disease, and they may trigger fat accumulation in renal parenchyma and eventually fatty kidney. Chronic kidney disease and fatty kidney are also strongly associated with nonalcoholic fatty liver disease. Because they both lead to detrimental effects on organ function, they both need to be treated effectively to improve the outcome.

AIM

In this narrative review, we have hypothesized that thyroid hormone beta receptor agonists, a novel drug group, may potentially be beneficial in the management of chronic kidney disease due to its promising outcomes among patients with nonalcoholic fatty liver disease, a condition sharing multiple common underlying pathophysiological mechanisms.

RESULTS AND CONCLUSION

Thyroid hormone beta receptors are abundantly expressed in liver and kidney tissues, while both nonalcoholic fatty liver disease and chronic kidney disease share various similar pathophysiological mechanisms and triggers. Therefore, thyroid hormone beta receptor agonists may become a promising tool in the management of patients with chronic kidney disease.

Glucagon-modified Liposomes Delivering Thyroid Hormone for Anti-obesity Therapy

BACKGROUND

Thyroid hormones (active form T3) are naturally potent compounds that influence energy expenditure, cholesterol metabolism, and fat oxidation. T3 would be an effective anti-obesity drug if it would not be delivered to the heart and bones, which leads to serious side effects, such as cardiovascular and bone thyrotoxicity, muscle wasting, and so on.

METHODS

In this study, we designed a targeted drug delivery system that is a glucagon-modified liposome to deliver T3 to the liver and adipose tissues.

RESULTS

The liposomes exhibited excellent properties, including uniform nanoscale particle size, good physicochemical stability, and adequate drug release behavior. More importantly, the glucagon-modified liposomes were enriched in the liver, which minimized the undesired bone and cardiovascular thyrotoxicity of T3. Compared to the control group, T3-loading glucagon-modified liposomes could effectively decrease body weight, reverse hepatic steatosis, and correct hyperlipidemia and hyperglycemia in ob/ob mice, without the undesired cardiovascular and bone thyrotoxicity.

CONCLUSION

These findings indicate that delivery of thyroid hormone by glucagon-modified liposomes may provide an effective strategy for anti-obesity therapy.

Laboratory Thyroid Tests: A Historical Perspective

Background: This review presents a timeline showing how technical advances made over the last seven decades have impacted the development of laboratory thyroid tests. Summary: Thyroid tests have evolved from time-consuming manual procedures using isotopically labeled iodine as signals (¹³¹I and later ¹²⁵I) performed in nuclear medicine laboratories, to automated nonisotopic tests performed on multianalyte instruments in routine clinical chemistry laboratories. The development of isotopic radioimmunoassay techniques around 1960, followed by the advent of monoclonal antibody technology in the mid-1970s, led to the development of a nonisotopic immunometric assay methodology that forms the backbone of present-day thyroid testing. This review discusses the development of methods for measuring total thyroxine and triiodothyronine, direct and indirect free thyroid hormone measurements and estimates (free thyroxine and free triiodothyronine), thyrotropin (TSH), thyroid autoantibodies (thyroperoxidase, thyroglobulin [Tg] and TSH receptor autoantibodies), and Tg protein. Despite progressive improvements made in sensitivity and specificity, current thyroid tests remain limited by between-method differences in the numeric values they report, as well as nonspecific interferences with test reagents and interferences from analyte autoantibodies. Conclusions: Thyroid disease affects ∼10% of the U.S. population and is mostly managed on an outpatient basis, generating 60% of endocrine laboratory tests. In future, it is hoped that interferences will be eliminated, and the standardization/harmonization of tests will facilitate the establishment of universal test reference ranges.

Mitochondrial alterations in fatty liver diseases

Fatty liver diseases can result from common metabolic diseases, as well as from xenobiotic exposure and excessive alcohol use, all of which have been shown to exert toxic effects on hepatic mitochondrial functionality and dynamics. Invasive or complex methodology limits large-scale investigations of mitochondria in human livers. Nevertheless, abnormal mitochondrial function, such as impaired fatty acid oxidation and oxidative phosphorylation, drives oxidative stress and has been identified as an important feature of human steatohepatitis. On the other hand, hepatic mitochondria can be flexible and adapt to the ambient metabolic condition to prevent triglyceride and lipotoxin accumulation in obesity. Experience from studies on xenobiotics has provided important insights into the regulation of hepatic mitochondria. Increasing awareness of the joint presence of metabolic disease-related (lipotoxic) and alcohol-related liver diseases further highlights the need to better understand their mutual interaction and potentiation in disease progression. Recent clinical studies have assessed the effects of diets or bariatric surgery on hepatic mitochondria, which are also evolving as an interesting therapeutic target in non-alcoholic fatty liver disease. This review summarises the current knowledge on hepatic mitochondria with a focus on fatty liver diseases linked to obesity, type 2 diabetes and xenobiotics.

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 β-oxidation, which favors accumulation of triglycerides and lipotoxins, insulin resistance, and subsequently de novo lipogenesis. Recent studies indicate that liver-specific thyroid hormone receptor β 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.

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.

Thyroid Hormone Abuse in Elite Sports: The Regulatory Challenge

Abuse of androgens and erythropoietin has led to hormones being the most effective and frequent class of ergogenic substances prohibited in elite sports by the World Anti-Doping Agency (WADA). At present, thyroid hormone (TH) abuse is not prohibited, but its prevalence among elite athletes and nonprohibited status remains controversial. A corollary of prohibiting hormones for elite sports is that endocrinologists must be aware of a professional athlete's risk of disqualification for using prohibited hormones and/or to certify Therapeutic Use Exemptions, which allow individual athletes to use prohibited substances for valid medical indications. This narrative review considers the status of TH within the framework of the WADA Code criteria for prohibiting substances, which requires meeting 2 of 3 equally important criteria of potential performance enhancement, harmfulness to health, and violation of the spirit of sport. In considering the valid clinical uses of TH, the prevalence of TH use among young adults, the reason why some athletes seek to use TH, and the pathophysiology of sought-after and adverse effects of TH abuse, together with the challenges of detecting TH abuse, it can be concluded that, on the basis of present data, prohibition of TH in elite sport is neither justified nor feasible.

Effect of thyroid function on pre-β1 high-density lipoprotein levels in patients with Graves' disease undergoing radioiodine treatment

CONTEXT

The metabolism of HDL is altered in thyroid dysfunctions. Preβ-1 HDL is a very small discoidal precursor HDL and promotes cholesterol efflux via ABCA₁. The effects of thyroid dysfunctions on pre-β1 HDL are unknown. Thyroid hormone regulates ANGPTL3 expression, which may participate in HDL metabolism in thyroid dysfunctions.

OBJECTIVE

To determine the variation of HDL subfractions, especially preβ-1 HDL in thyroid dysfunctions, and whether ANGPTL3 mediates the effect of thyroid function on HDL metabolism.

METHODS

We recruited 26 patients with Graves' disease undergoing radioiodine treatment. They were evaluated at three time points: at baseline, when they were hypothyroid after radioiodine treatment, and when they were on stable levothyroxine replacement and euthyroid.

RESULTS

The concentrations of smaller HDL particles Preβ-1 HDL and HDL3 were highest at the hyperthyroid state, and lowest at the hypothyroid state. While the larger HDL particles HDL2 and HDL1 changed just the opposite. Preβ1-HDL and HDL3 were positively correlated to fT₃ and fT₄, while were negatively correlated to TSH. In contrast, HDL1 was negatively associated with fT₃ and fT₄, while was positively associated with TSH. The correlations between thyroid hormones and HDL subfractions remained significant after adjusting for ANGPTL3.

CONCLUSIONS

There is a shift form smaller HDL particles pre-β1 HDL and HDL3 to larger HDL particles HDL2 and HDL1 in hypothyroidism, while the change is just the opposite in hyperthyroidism. In future, cholesterol efflux capacity should be measured to determine if the function of HDL particles also changes with the shifting of HDL subfractions.

Non-genetic influences on lipoprotein(a) concentrations

An elevated level of lipoprotein(a) [Lp(a)] is a genetically regulated, independent, causal risk factor for cardiovascular disease. However, the extensive variability in Lp(a) levels between individuals and population groups cannot be fully explained by genetic factors, emphasizing a potential role for non-genetic factors. In this review, we provide an overview of current evidence on non-genetic factors influencing Lp(a) levels with a particular focus on diet, physical activity, hormones and certain pathological conditions. Findings from randomized controlled clinical trials show that diets lower in saturated fats modestly influence Lp(a) levels and often in the opposing direction to LDL cholesterol. Results from studies on physical activity/exercise have been inconsistent, ranging from no to minimal or moderate change in Lp(a) levels, potentially modulated by age and the type, intensity, and duration of exercise modality. Hormone replacement therapy (HRT) in postmenopausal women lowers Lp(a) levels with oral being more effective than transdermal estradiol; the type of HRT, dose of estrogen and addition of progestogen do not modify the Lp(a)-lowering effect of HRT. Kidney diseases result in marked elevations in Lp(a) levels, albeit dependent on disease stages, dialysis modalities and apolipoprotein(a) phenotypes. In contrast, Lp(a) levels are reduced in liver diseases in parallel with the disease progression, although population studies have yielded conflicting results on the associations between Lp(a) levels and nonalcoholic fatty liver disease. Overall, current evidence supports a role for diet, hormones and related conditions, and liver and kidney diseases in modifying Lp(a) levels.

The role of mitochondria in the pathophysiology and treatment of common metabolic diseases in humans

Common metabolic diseases such as obesity, type 2 diabetes mellitus and non-alcoholic fatty liver disease significantly contribute to morbidity and mortality worldwide. They frequently associate with insulin resistance and altered mitochondrial functionality. Insulin-responsive tissues can show changes in mitochondrial features such as oxidative capacity, mitochondrial content and turnover, which do not necessarily reflect abnormalities but rather adaption to a certain metabolic condition. Lifestyle modifications and classic or novel drugs can modify these alterations and help treating these metabolic diseases. This review addresses the role of mitochondria in human metabolic diseases and discusses potential future research directions.

Thyroid Hormone Receptor Agonist Promotes Hair Growth in Mice

Background

Thyroxine is important to maintain the normal operation of the body. Both clinical and experimental results show thyroxine is closely related to hair growth, the mechanism of which is not fully understood.

Purpose

Investigate the effect of thyroxine receptor agonist, TDM10842, for dorsal hair growth in C3H mice and explore its underlying mechanism.

Methods

Depilated mice were applied with the TDM10842, vehicle of this drug and without any materials on dorsal skin. RNA-sequencing (RNA-seq) was employed to identify the change in gene expression of skin tissues. Quantitative real-time PCR (rt-PCR) and immunoblotting were conducted to validate key differentially expressed genes (DEGs) between different groups.

Results

The TDM group showed early induction of anagen. 857, 782, and 276 differentially expressed genes were identified between 3 groups. As a critical DEG in group TDM, Pclaf was positively related to the motivation of Wnt/beta-catenin and Hedgehog signaling pathways, with a high expression of Ki67 and cyclinD1.

Conclusion

TDM10842 accelerates the anagen entrance and the potential mechanism might be the activation of Wnt/beta-catenin and Hedgehog pathways. Pclaf serves as a critical molecule involved in pathway activation, and cyclinD1 is an important effector protein downstream of the pathways.

Main Factors Involved in Thyroid Hormone Action

The thyroid hormone receptors are the mediators of a multitude of actions by the thyroid hormones in cells. Most thyroid hormone activities require interaction with nuclear receptors to bind DNA and regulate the expression of target genes. In addition to genomic regulation, thyroid hormones function via activation of specific cytosolic pathways, bypassing interaction with nuclear DNA. In the present work, we reviewed the most recent literature on the characteristics and roles of different factors involved in thyroid hormone function in particular, we discuss the genomic activity of thyroid hormone receptors in the nucleus and the functions of different thyroid hormone receptor isoforms in the cytosol. Furthermore, we describe the integrin αvβ3-mediated thyroid hormone signaling pathway and its rapid nongenomic action in the cell. We furthermore reviewed the thyroid hormone transporters enabling the uptake of thyroid hormones in the cell, and we also include a paragraph on the proteins that mediate thyroid receptors’ shuttling from the nucleus to the cytosol.

Hormone resistance in children: what primary care physicians need to know

Hormone resistance is defined as a reduced or absence of target tissues responsiveness to a hormone, where the presentation is related to either a relative lack or excess of hormones. Various disorders of hormone resistance were encountered including, Laron syndrome, nephrogenic diabetes insipidus, thyroid hormone resistance syndrome, pseudohypoparathyroidism, insulin resistance, familial glucocorticoid deficiency, pseudohypoaldosteronism, X linked hypophosphatemic rickets and androgen insensitivity syndrome. The article gives a summary that presents, in concentrated form, what the primary care physicians need to know about recognition, clinical presentation, diagnosis, and management of various hormone resistance in children.

Analysis of metabolomics profile in hypothyroid patients before and after thyroid hormone replacement

PURPOSE

The serum metabolic changes occurring during the transition from hypothyroidism to euthyroidism are not known. This study aimed to determine the metabolomic profile in hypothyroid patients before (HypoT₀) and after (HypoT₁) euthyroidism achieved through levothyroxine (L-T4) treatment.

METHODS

Eighteen patients with overt primary hypothyroidism were recruited for the study. All patients were treated with L-T4 to achieve euthyroidism. Thyrotropin (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and metabolomics profiles were measured before and after 3 months of treatment. The euthyroid control group consisted of 28 healthy volunteers. Metabolomics analysis was performed using Nuclear Magnetic Resonance (NMR) spectroscopy.

RESULTS

¹H NMR-based metabolomics profiling of patients with newly diagnosed hypothyroidism (HypoT₀) showed significantly higher levels of citrate, creatinine, glycerol, myo-inositol and serine, and lower levels of proline and taurine compared to controls. Interestingly, some metabolic changes were persistent three months after pharmacological treatments, despite normal serum TSH and thyroid hormone concentrations (HypoT₁). When an Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) model was built to evaluate possible differences in the metabolic profile between HypoT₀ and HypoT₁, the data obtained were not significantly different.

CONCLUSION

These results suggest that metabolic changes in the patients with hypothyroidism may persist after normalization of serum levels of FT3, FT4, and TSH, which currently represent the gold standard in laboratory testing for diagnosis and evaluation of thyroid pathology. So, the metabolomics approach may contribute to integrate classical hormone assays and to determine the euthyroid status achievement with greater efficacy.

Physiological Role and Use of Thyroid Hormone Metabolites - Potential Utility in COVID-19 Patients

Thyroxine and triiodothyronine (T3) are classical thyroid hormones and with relatively well-understood actions. In contrast, the physiological role of thyroid hormone metabolites, also circulating in the blood, is less well characterized. These molecules, namely, reverse triiodothyronine, 3,5-diiodothyronine, 3-iodothyronamine, tetraiodoacetic acid and triiodoacetic acid, mediate both agonistic (thyromimetic) and antagonistic actions additional to the effects of the classical thyroid hormones. Here, we provide an overview of the main factors influencing thyroid hormone action, and then go on to describe the main effects of the metabolites and their potential use in medicine. One section addresses thyroid hormone levels in corona virus disease 19 (COVID-19). It appears that i) the more potently-acting molecules T3 and triiodoacetic acid have shorter half-lives than the less potent antagonists 3-iodothyronamine and tetraiodoacetic acid; ii) reverse T3 and 3,5-diiodothyronine may serve as indicators for metabolic dysregulation and disease, and iii) Nanotetrac may be a promising candidate for treating cancer, and resmetirom and VK2809 for steatohepatitis. Further, the use of L-T3 in the treatment of severely ill COVID-19 patients is critically discussed.

Liver macrophages and inflammation in physiology and physiopathology of non-alcoholic fatty liver disease

Non‐alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome, being a common comorbidity of type 2 diabetes and with important links to inflammation and insulin resistance. NAFLD represents a spectrum of liver conditions ranging from steatosis in the form of ectopic lipid storage, to inflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Macrophages that populate the liver play important roles in maintaining liver homeostasis under normal physiology and in promoting inflammation and mediating fibrosis in the progression of NAFLD toward to NASH. Liver macrophages are a heterogenous group of innate immune cells, originating from the yolk sac or from circulating monocytes, that are required to maintain immune tolerance while being exposed portal and pancreatic blood flow rich in nutrients and hormones. Yet, liver macrophages retain a limited capacity to raise the alarm in response to danger signals. We now know that macrophages in the liver play both inflammatory and noninflammatory roles throughout the progression of NAFLD. Macrophage responses are mediated first at the level of cell surface receptors that integrate environmental stimuli, signals are transduced through multiple levels of regulation in the cell, and specific transcriptional programmes dictate effector functions. These effector functions play paramount roles in determining the course of disease in NAFLD and even more so in the progression towards NASH. The current review covers recent reports in the physiological and pathophysiological roles of liver macrophages in NAFLD. We emphasise the responses of liver macrophages to insulin resistance and the transcriptional machinery that dictates liver macrophage function.

Non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH)-related liver fibrosis: mechanisms, treatment and prevention

Liver fibrosis is the excessive expression and accumulation of extracellular matrix proteins in the liver. Fibrotic scarring occurs as the consequence of chronic injury and inflammation. While the successful treatment of hepatitis B and C reduced the burden of liver disease related to viral hepatitis, non-alcoholic fatty liver disease (NAFLD) or non-alcoholic steatohepatitis (NASH) are nowadays the leading causes of hepatic fibrosis worldwide. Although basic research activities have significantly advanced our understanding of the molecular disease pathogenesis, the present therapeutic options for fibrosis are still limited. In advanced disease stages, liver transplantation often remains the only curative treatment. This highlights the necessity of preventive strategies to avoid complications of fibrosis, particularly cirrhosis, portal hypertension and liver cancer. Lifestyle modifications (weight loss, exercise, healthy diet) are the basis for prevention and treatment of NAFLD-associated fibrosis. In the present review, we discuss recent advances in antifibrotic prevention and therapy. In particular, we review the current concepts for antifibrotic drug candidates in the treatment of NAFLD and NASH. While some compounds aim at reverting pathogenic liver metabolism, an alternative approach is to disconnect the injury (e.g., NAFLD) from inflammation and/or fibrosis. Investigational drugs typically target metabolic pathways, insulin resistance, hepatocyte death, inflammatory cell recruitment or activation, the gut-liver axis, matrix expression or matrix turnover. While several promising drug candidates failed in phase 2 or 3 clinical trials (including elafibranor, emricasan and selonsertib), promising results with the farnesoid X receptor agonist obeticholic acid, the pan-PPAR agonist lanifibranor and the chemokine receptor CCR2/CCR5 inhibitor cenicriviroc support the expectation of an effective pharmacological therapy for liver fibrosis in the near future. Tackling NAFLD-associated fibrosis from different directions by combinatorial drug treatment and effective lifestyle changes hold the greatest prospects.

Diphenyl-Methane Based Thyromimetic Inhibitors for Transthyretin Amyloidosis

Thyromimetics, whose physicochemical characteristics are analog to thyroid hormones (THs) and their derivatives, are promising candidates as novel therapeutics for neurodegenerative and metabolic pathologies. In particular, sobetirome (GC-1), one of the initial halogen-free thyromimetics, and newly synthesized IS25 and TG68, with optimized ADME-Tox profile, have recently attracted attention owing to their superior therapeutic benefits, selectivity, and enhanced permeability. Here, we further explored the functional capabilities of these thyromimetics to inhibit transthyretin (TTR) amyloidosis. TTR is a homotetrameric transporter protein for THs, yet it is also responsible for severe amyloid fibril formation, which is facilitated by tetramer dissociation into non-native monomers. By combining nuclear magnetic resonance (NMR) spectroscopy, computational simulation, and biochemical assays, we found that GC-1 and newly designed diphenyl-methane-based thyromimetics, namely IS25 and TG68, are TTR stabilizers and efficient suppressors of TTR aggregation. Based on these observations, we propose the novel potential of thyromimetics as a multi-functional therapeutic molecule for TTR-related pathologies, including neurodegenerative diseases.

Anti-fibrotic treatments for chronic liver diseases: The present and the future

Liver fibrosis reflects tissue scarring in the liver due to the accumulation of excessive extracellular matrix in response to chronically persistent liver injury. Hepatocyte cell death can trigger capillarization of liver sinusoidal endothelial cells, stimulation of immune cells including macrophages and Kupffer cells, and activation of hepatic stellate cells (HSCs), resulting in progression of liver fibrosis. Liver cirrhosis is the terminal state of liver fibrosis and is associated with severe complications, such as liver failure, portal hypertension, and liver cancer. Nevertheless, effective therapy for cirrhosis has not yet been established, and liver transplantation is the only radical treatment for severe cases. Studies investigating HSC activation and regulation of collagen production in the liver have made breakthroughs in recent decades that have advanced the knowledge regarding liver fibrosis pathophysiology. In this review, we summarize molecular mechanisms of liver fibrosis and discuss the development of novel anti-fibrotic therapies.

Hypothyroidism and Nonalcoholic Fatty Liver Disease: Pathophysiological Associations and Therapeutic Implications

Nonalcoholic fatty liver disease (NAFLD) is a complex clinical entity which can be secondary to many other diseases including hypothyroidism, characterized by lowering of thyroid hormones and increased thyroid stimulating hormone (TSH). A lot of emerging data published recently advocates the hypothesis that hypothyroid induced NAFLD could be a separate clinical entity, even suggesting possible treatment options for NAFLD involving substitution therapy for hypothyroidism along with lifestyle modifications. In addition, a whole new field of research is focused on thyromimetics in NAFLD/NASH treatment, currently in phase 3 clinical trials. In this critical review we summarized epidemiological and pathophysiological evidence linking these two clinical entities and described specific treatment options with the accent on promising new agents in NAFLD treatment, specifically thyroid hormone receptor (THR) agonist and its metabolites.

Selective Thyroid Hormone Receptor-Beta (TRβ) Agonists: New Perspectives for the Treatment of Metabolic and Neurodegenerative Disorders

Thyroid hormones (THs) elicit significant effects on numerous physiological processes, such as growth, development, and metabolism. A lack of thyroid hormones is not compatible with normal health. Most THs effects are mediated by two different thyroid hormone receptor (TR) isoforms, namely TRα and TRβ, with the TRβ isoform known to be responsible for the main beneficial effects of TH on liver. In brain, despite the crucial role of TRα isoform in neuronal development, TRβ has been proposed to play a role in the remyelination processes. Consequently, over the past two decades, much effort has been applied in developing thyroid hormone analogs capable of uncoupling beneficial actions on liver (triglyceride and cholesterol lowering) and central nervous system (CNS) (oligodendrocyte proliferation) from deleterious effects on the heart, muscle and bone. Sobetirome (GC-1) and subsequently Eprotirome (KB2115) were the first examples of TRβ selective thyromimetics, with Sobetirome differing from the structure of thyronines because of the absence of halogens, biaryl ether oxygen, and amino-acidic side chain. Even though both thyromimetics showed encouraging actions against hypercholesterolemia, non-alcoholic steatohepatitis (NASH) and in the stimulation of hepatocytes proliferation, they were stopped after Phase 1 and Phase 2–3 clinical trials, respectively. In recent years, advances in molecular and structural biology have facilitated the design of new selective thyroid hormone mimetics that exhibit TR isoform-selective binding, and/or liver- and tissue-selective uptake, with Resmetirom (MGL-3196) and Hep-Direct prodrug VK2809 (MB07811) probably representing two of the most promising lipid lowering agents, currently under phase 2–3 clinical trials. More recently the application of a comprehensive panel of ADME-Toxicity assays enabled the selection of novel thyromimetic IS25 and its prodrug TG68, as very powerful lipid lowering agents both in vitro and in vivo. In addition to dyslipidemia and other liver pathologies, THs analogs could also be of value for the treatment of neurodegenerative diseases, such as multiple sclerosis (MS). Sob-AM2, a CNS- selective prodrug of Sobetirome has been shown to promote significant myelin repair in the brain and spinal cord of mouse demyelinating models and it is rapidly moving into clinical trials in humans. Taken together all these findings support the great potential of selective thyromimetics in targeting a large variety of human pathologies characterized by altered metabolism and/or cellular differentiation.