Thyroid hormone reduces PCSK9 and stimulates bile acid synthesis in humans

Pathophysiological underpinnings of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is emerging as the leading cause of chronic liver disease worldwide, reflecting the global epidemics of obesity, metabolic syndrome, and type 2 diabetes. Beyond its strong association with excess adiposity, MASLD encompasses a heterogeneous population that includes individuals with normal body weight ("lean MASLD") highlighting the complexity of its pathogenesis. This disease results from a complex interplay between genetic susceptibility, epigenetic modifications, and environmental factors, which converge to disrupt metabolic homeostasis. Adipose tissue dysfunction and insulin resistance trigger an overflow of lipids to the liver, leading to mitochondrial dysfunction, oxidative stress, and hepatocellular injury. These processes promote hepatic inflammation and fibrogenesis, driven by cross talk among hepatocytes, immune cells, and hepatic stellate cells, with key contributions from gut-liver axis perturbations. Recent advances have unraveled pivotal molecular pathways, such as transforming growth factor-β signaling, Notch-induced osteopontin, and sphingosine kinase 1-mediated responses, that orchestrate fibrogenic activation. Understanding these interconnected mechanisms is crucial for developing targeted therapies. This review integrates current knowledge on the pathophysiology of MASLD, emphasizing emerging concepts such as lean metabolic dysfunction-associated steatohepatitis (MASH), epigenetic alterations, hepatic extracellular vesicles, and the relevance of extrahepatic signals. It also discusses novel therapeutic strategies under investigation, aiming to provide a comprehensive and structured overview of the evolving MASLD landscape for both basic scientists and clinicians.

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.

Exploring the Pleiotropy of PCSK9: A Wide Range of Influences from Lipid Regulation to Extrahepatic Function

In cardiovascular disease, the discovery of the proprotein convertase subtilisin/kexin type 9 (PCSK9) has undoubtedly opened a new chapter in regulating blood lipids. Since its first identification as a key regulator of low-density lipoprotein receptor (LDLR) degradation in 2003, the role of PCSK9 in cholesterol metabolism has been extensively studied. However, with further research, the pleiotropy of PCSK9 has gradually emerged, and its impact extends far beyond cholesterol metabolism in the liver. The purpose of this review is to systematically explore the pleiotropy of PCSK9, extending from its important role in lipid regulation to its extensive effects in extrahepatic tissues, and to reveal its potential role in cardiovascular health, nervous system function, and tumor biology. By integrating the latest research findings, this paper summarizes the complex mechanisms of action of PCSK9 in different biological processes and explores its potential and challenges as a therapeutic target.

Thyromimetics and MASLD: Unveiling the Novel Molecules Beyond Resmetirom

BACKGROUND

Resmetirom, the first FDA-approved drug for nonalcoholic steatohepatitis (NASH) with fibrosis in obese patients, when combined with lifestyle modifications, improves NASH resolution and reduces fibrosis by at least one stage. Low thyroid hormone (T3) levels are linked to a higher risk of developing metabolic dysfunction-associated steatotic liver disease (MASLD). Epidemiological studies have confirmed the positive correlation between hypothyroidism and MASLD. Unraveling the molecular mechanisms of T3 signaling pathways in MASLD will enhance the prospects of identifying effective and specific targets. Therefore, this review discusses the significant role of thyroid hormones in the homeostasis of fat metabolism and describes the possible molecular mechanisms of thyromimetics in the treatment of MASLD.

METHODS

A comprehensive search in PubMed and EMBASE was conducted using the keywords "thyromimetics and liver diseases," "thyroid hormone and liver diseases," "hypothyroidism and liver diseases," "T3, T4 and liver disease," and "resmetirom and liver disease." Relevant papers published before October 2024 were included.

RESULTS

T3 treatment enhances mitochondrial respiration, biogenesis, β-oxidation, and mitophagy, reducing liver lipid accumulation. However, T3 treatment causes cardiotoxicity through thyroid hormone receptor (THR)α agonistic activity. To address this, molecules with high THRβ agonistic but lower THRα activity have been developed. Besides resmetirom, other THRβ agonists like TG68, CS27109, MB07811, and KB-141 show promising results in experimental studies. These molecules upregulate THRβ target genes, activate genes for fatty acid β-oxidation in mitochondria and fatty acid breakdown in peroxisomes, downregulate the genes involved in de novo lipogenesis, reduce inflammation by downregulating NF-κB/JNK/STAT3 signaling pathways, and accelerate fibrosis resolution by downregulating the expressions of fibrosis marker genes in NASH liver tissue.

CONCLUSION

Future clinical studies should thoroughly investigate THRβ agonists, including TG68, CS27109, MB07811, and KB-141.

Association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio and serum thyroid function measures: Recent Findings from NHANES 2007-2012 and Mendelian randomization

Objective

There is limited epidemiological data regarding the association of blood lipids with thyroid hormones. Thus, the present article aims to explore whether there is an association between non-high-density to high-density lipoprotein cholesterol ratio (NHHR) and thyroid hormones.

Methods

We analyzed samples from 3,881 adults aged 20 years and above who took part in the National Health and Nutrition Examination Survey (NHANES) spanning 2007 to 2012. The study tested for thyroid hormones, including total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4), free thyroxine (FT4), as well as thyroid-stimulating hormone (TSH). Survey-weighted linear regression and restricted cubic spline (RCS) models were employed to investigate the relationship between NHHR and thyroid hormones. Subsequently, subgroup analyses were conducted. In Mendelian randomization (MR), the inverse variance weighting method (IVW) is used as the primary analytical approach.

Results

This study finally comprised 3,881 adults aged 20 years and older. After extensive adjustments for covariables, the regression analysis revealed significant negative associations between NHHR and FT4 (β: -0.11, 95% confidence interval [CI]: -0.18, -0.04), FT4/FT3 (β: -0.06, 95% CI: -0.08, -0.04), and TT4/TT3 (β: -0.001, 95% CI: -0.001, 0.000). Both observational and Mendelian randomization studies suggest that high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol may not significantly influence the risk of hyperthyroidism or hypothyroidism.

Conclusions

The study indicates negative associations between NHHR and FT4, as well as the ratios of FT4/FT3 and TT4/TT3. This suggests that NHHR may reflect changes in thyroid function, highlighting its potential clinical significance in assessing thyroid function and metabolic health.

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.

Analysis of thyroid function and structure and serum metabolomics in pregnant rats exposed to airborne contaminants: Combined perchlorate, thiocyanate, and nitrate exposure

OBJECTIVES

Perchlorates, nitrates, and thiocyanates constitute environmental endocrine disruptors; however, health damage caused by absorption through the respiratory tract remains poorly studied. We investigated the effects of inhalation of these pollutants on thyroid function and structure and serum metabolomics in pregnant rats.

METHODS

We established a Sprague-Dawley pregnant rat model exposed to perchlorate, nitrate, and thiocyanate at different gestational stages and compared maternal serum thyroid function levels, foetal development, thyroid morphology, and pathological changes between exposed and non-exposed groups at different concentrations. We used liquid chromatography-tandem mass spectrometry metabolomics methods to investigate corresponding changes in serum metabolites and metabolic biomarkers and identify metabolism-related pathways.

RESULTS

Free triiodothyronine levels in the medium-and high-concentration groups and free thyroxine levels in the low-, medium-, and high-concentration groups were significantly lower than those in the control group. Weight gain was significantly lower in the high-dose group than in the control group. Thyroid weight and organ coefficients were significantly higher in the medium-and high-dose groups at 15 and 19 days of pregnancy than in the control group. Thyroid epithelial cells demonstrated diffuse proliferation and lamination with increased atomisation concentrations, and thyroid cells tended to undergo apoptosis in the group with high thyroid epithelial cell concentration. Eight and 18 metabolic pathways were significantly affected in the GD15 and GD19 groups（GD15: The demise occurring 15 days into gestation,GD19: The demise occurring 15 days into gestation.）, respectively, post-exposure. The involved pathways included lipid, glucose, bile acid, choline, and gamma-aminobutyric acid metabolism and peroxisome proliferation-activated receptors.

CONCLUSIONS

Mixed thiocyanate, nitrate, and perchlorate exposure can result in subchronic toxicity in rats, affecting thyroid function and structure.

Low Serum Fibroblast Growth Factor 21 Level and Its Altered Regulation by Thyroid Hormones in Patients with Hashimoto's Thyroiditis on Levothyroxine Substitution

BACKGROUND/OBJECTIVES

Fibroblast growth factor 21 (FGF21) is a hormonal regulator of lipid and glucose metabolism exerting protection against atherosclerosis by multiple actions on the blood vessels, liver, and adipose tissues. We aimed to investigate serum FGF21 level and its relation to thyroid hormones and metabolic parameters among patients with Hashimoto's thyroiditis (HT).

METHODS

Eighty patients with HT on levothyroxine treatment and eighty-two age- and BMI-matched adults without thyroid disease serving as controls were enrolled. Serum FGF21 concentrations were determined with an enzyme-linked immunosorbent assay.

RESULTS

Median serum FGF21 level was significantly lower in HT patients compared with controls (74.2 (33.4-148.3) pg/mL vs. 131.9 (44.8-236.3) pg/mL; p = 0.03). We found a positive correlation between FGF21 and age, triglyceride, total cholesterol, and low-density lipoprotein cholesterol in both groups, while thyroid stimulating hormone and C-reactive protein showed a positive correlation, and thyroxine had an inverse correlation with FGF21 only in control subjects. According to multiple regression analyses, thyroid status is the main predictor of FGF21 in healthy controls, while it is not a significant predictor of FGF21 among HT patients on levothyroxine supplementation therapy.

CONCLUSIONS

Our results indicate that the physiological role of thyroid function in the regulation of FGF21 synthesis is impaired in HT patients, which may contribute to the metabolic alterations characteristic of HT patients.

Cross-Talk Between Thyroid Disorders and Nonalcoholic Fatty Liver Disease: From Pathophysiology to Therapeutics

The medical community acknowledges the presence of thyroid disorders and nonalcoholic fatty liver disease (NAFLD). Nevertheless, the interconnection between these two circumstances is complex. Thyroid hormones (THs), including triiodothyronine (T3) and thyroxine (T4), and thyroid-stimulating hormone (TSH), are essential for maintaining metabolic balance and controlling the metabolism of lipids and carbohydrates. The therapeutic potential of THs, especially those that target the TRβ receptor isoform, is generating increasing interest. The review explores the pathophysiology of these disorders, specifically examining the impact of THs on the metabolism of lipids in the liver. The purpose of this review is to offer a thorough analysis of the correlation between thyroid disorders and NAFLD, as well as suggest potential therapeutic approaches for the future.

A new mechanism of thyroid hormone receptor β agonists ameliorating nonalcoholic steatohepatitis by inhibiting intestinal lipid absorption via remodeling bile acid profiles

Excessive dietary calories lead to systemic metabolic disorders, disturb hepatic lipid metabolism, and aggravate nonalcoholic steatohepatitis (NASH). Bile acids (BAs) play key roles in regulating nutrition absorption and systemic energy homeostasis. Resmetirom is a selective thyroid hormone receptor β (THRβ) agonist and the first approved drug for NASH treatment. It is well known that the THRβ activation could promote intrahepatic lipid catabolism and improve mitochondrial function, however, its effects on intestinal lipid absorption and BA compositions remain unknown. In the present study, the choline-deficient, L-amino acid defined, high-fat diet (CDAHFD) and high-fat diet plus CCl4 (HFD+CCl4)-induced NASH mice were used to evaluate the effects of resmetirom on lipid and BA composition. We showed that resmetirom administration (10 mg·kg-1·d-1, i.g.) significantly altered hepatic lipid composition, especially reduced the C18:2 fatty acyl chain-containing triglyceride (TG) and phosphatidylcholine (PC) in the two NASH mouse models, suggesting that THRβ activation inhibited intestinal lipid absorption since C18:2 fatty acid could be obtained only from diet. Targeted analysis of BAs showed that resmetirom treatment markedly reduced the hepatic and intestinal 12-OH to non-12-OH BAs ratio by suppressing cytochrome P450 8B1 (CYP8B1) expression in both NASH mouse models. The direct inhibition by resmetirom on intestinal lipid absorption was further verified by the BODIPY gavage and the oral fat tolerance test. In addition, disturbance of the altered BA profiles by exogenous cholic acid (CA) supplementation abolished the inhibitory effects of resmetirom on intestinal lipid absorption in both normal and CDAHFD-fed mice, suggesting that resmetirom inhibited intestinal lipid absorption by reducing 12-OH BAs content. In conclusion, we discovered a novel mechanism of THRβ agonists on NASH treatment by inhibiting intestinal lipid absorption through remodeling BAs composition, which highlights the multiple regulation of THRβ activation on lipid metabolism and extends the current knowledge on the action mechanisms of THRβ agonists in NASH treatment.

Intrahepatic hypothyroidism in MASLD: Role of liver-specific thyromimetics including resmetirom

BACKGROUND AND AIMS

Thyroid hormones are important regulators of hepatic lipid homeostasis and whole-body energy expenditure. Recent evidence suggests that euthyroid individuals with metabolic dysfunction-associated steatohepatitis (MASH) develop intrahepatic hypothyroidism that promotes progression of MASH.

METHODS

A literature search was performed with Medline (PubMed), Scopus and Google Scholar electronic databases from inception till March 2024, using the following keywords: hypothyroidism and nonalcoholic fatty liver disease; MASLD and thyroid function; intrahepatic hypothyroidism; TRβ agonists; and resmetirom. Relevant studies were extracted that described pathogenesis of MASH in the context of thyroid functions.

RESULTS

In euthyroid individuals with MASH, there is decreased conversion of prohormone thyroxine (T4) to bioactive tri-iodothyronine (T3) and increased conversion of T4 to inactive metabolite reverse T3 (rT3). Consequently, reduced levels of T3 results in impaired intrahepatic TRβ signaling, a state of intrahepatic hypothyroidism, which promotes progression of MASH. Hepatic TRβ activation leads to metabolically beneficial effects in the liver including mitochondrial fatty acid uptake and β-oxidation, mitochondrial biogenesis, increasing surface low-density lipoprotein (LDL) receptor density and lowering of circulatory LDL-cholesterol. In recent years, selective thyroid hormone mimetics that exhibit TRβ-selective binding and liver-selective uptake have been designed. Resmetirom, a liver-specific thyromimetic, improves intrahepatic TRβ signaling and in clinical trials significantly improved liver inflammation, fibrosis and lipid profile in patients with MASH.

CONCLUSIONS

In euthyroid individuals with MASH, development of intrahepatic hypothyroidism results in further progression of the disease. In clinical trials, resmetirom treatment results in a significant improvement in steatosis, inflammation and fibrosis and is the first drug approved by the US Food and Drug Administration (FDA) for the treatment of noncirrhotic MASH with moderate to advanced fibrosis.

Metabolic Messengers: Thyroid Hormones

Thyroid hormones (THs) are key hormones that regulate development and metabolism in mammals. In man, the major target tissues for TH action are the brain, liver, muscle, heart, and adipose tissue. Defects in TH synthesis, transport, metabolism, and nuclear action have been associated with genetic and endocrine diseases in man. Over the past few years, there has been renewed interest in TH action and the therapeutic potential of THs and thyromimetics to treat several metabolic disorders such as hypercholesterolemia, dyslipidaemia, non-alcoholic fatty liver disease (NAFLD), and TH transporter defects. Recent advances in the development of tissue and TH receptor isoform-targeted thyromimetics have kindled new hope for translating our fundamental understanding of TH action into an effective therapy. This review provides a concise overview of the historical development of our understanding of TH action, its physiological and pathophysiological effects on metabolism, and future therapeutic applications to treat metabolic dysfunction.

Roles of fibroblast growth factors in the treatment of diabetes

Diabetes affects about 422 million people worldwide, causing 1.5 million deaths each year. However, the incidence of diabetes is increasing, including several types of diabetes. Type 1 diabetes (5%-10% of diabetic cases) and type 2 diabetes (90%-95% of diabetic cases) are the main types of diabetes in the clinic. Accumulating evidence shows that the fibroblast growth factor (FGF) family plays important roles in many metabolic disorders, including type 1 and type 2 diabetes. FGF consists of 23 family members (FGF-1-23) in humans. Here, we review current findings of FGFs in the treatment of diabetes and management of diabetic complications. Some FGFs (e.g., FGF-15, FGF-19, and FGF-21) have been broadly investigated in preclinical studies for the diagnosis and treatment of diabetes, and their therapeutic roles in diabetes are currently under investigation in clinical trials. Overall, the roles of FGFs in diabetes and diabetic complications are involved in numerous processes. First, FGF intervention can prevent high-fat diet-induced obesity and insulin resistance and reduce the levels of fasting blood glucose and triglycerides by regulating lipolysis in adipose tissues and hepatic glucose production. Second, modulation of FGF expression can inhibit renal and cardiac fibrosis by regulating the expression of extracellular matrix components, promote diabetic wound healing process and bone repair, and inhibit cancer cell proliferation and migration. Finally, FGFs can regulate the activation of glucose-excited neurons and the expression of thermogenic genes.

Inhibition of PCSK9 prevents and alleviates cholesterol gallstones through PPARα-mediated CYP7A1 activation

BACKGROUND & AIMS

Dysregulated cholesterol metabolism is the major factor responsible for cholesterol gallstones (CGS). Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a critical role in cholesterol homeostasis and its inhibitors secure approval for treating various cholesterol metabolic disorders such as hypercholesterolemia and cardiovascular diseases, but its role in CGS remains unclear. Our study aims to clarify mechanisms by which PCSK9 promotes CGS formation and explore the application of the PCSK9 inhibitor, alirocumab, in preventing and treating CGS.

APPROACH & RESULTS

The expressions of PCSK9 were notably increased in CGS patients' serum, bile, and liver tissues compared to those without gallstones. Moreover, among CGS patients, hepatic PCSK9 was positively correlated with hepatic cholesterol and negatively correlated with hepatic bile acids (BAs), suggesting PCSK9 was involved in disrupted hepatic cholesterol metabolism related to CGS. Mechanistically, in vitro experiments demonstrated that inhibition of PCSK9 enhanced nuclear expression of PPARα by diminishing its lysosomal degradation and subsequently activated CYP7A1 transcription. Finally, inhibition of PCSK9 prevented CGS formation and dissolved the existing stones in CGS mice by elevating the conversion of cholesterol into BAs through PPARα-mediated CYP7A1 activation. Additionally, serum PCSK9 level may function as a prognostic signature to evaluate the therapeutic efficacy of PCSK9 inhibitors.

CONCLUSIONS

Inhibition of PCSK9 exerts preventive and therapeutic effects on CGS by activating PPARα-mediated CYP7A1 expression and facilitating the conversion of cholesterol into BAs, which highlights the potential of PCSK9 inhibition as a promising candidate for preventing and treating CGS in clinical applications.

IMPACT AND IMPLICATIONS

PCSK9 plays a pivotal role in cholesterol metabolism and its inhibitors are approved for clinical use in cardiovascular diseases. Our study observes inhibition of PCSK9 prevents and dissolves CGS by activating PPARα-mediated CYP7A1 expression and facilitating the conversion of cholesterol into BAs. Mechanistically, PCSK9 inhibition enhanced the nuclear expression of PPARα by diminishing its lysosomal degradation and subsequently activated CYP7A1 transcription. Our study sheds light on the new function and mechanism of PCSK9 in CGS, providing a novel preventive and therapeutic target with potential clinical applications.

Can Lipid-Lowering Drugs Reduce the Risk of Cholelithiasis? A Mendelian Randomization Study

Background and Aims

Cholelithiasis etiology intricately involves lipid metabolism. We sought to investigate the plausible causal link between genetically proxied lipid-lowering medications-specifically HMGCR inhibitors, PCSK9 inhibitors, and NPC1L1 inhibitors-and cholelithiasis risk.

Methods

Our study utilized two genetic instruments for exposure to lipid-lowering drugs. These instruments encompassed genetic variants linked to low-density lipoprotein (LDL) cholesterol within or in proximity to drug target genes, along with loci governing gene expression traits of these targets. Effect estimates were derived through Inverse-variance-weighted MR (IVW-MR) and summary-data-based MR (SMR) methods.

Results

Higher HMGCR-mediated LDL cholesterol levels (IVW-MR, OR = 2.15, 95% CI = 1.58-2.94; P = 0.000) and increased HMGCR expression (SMR, OR = 1.19, 95% CI = 1.04-1.37; P = 0.014) are linked to elevated cholelithiasis risk, suggesting potential benefits of HMGCR inhibition. In contrast, higher PCSK9-mediated LDL cholesterol levels (IVW-MR, OR = 0.72, 95% CI = 0.56-0.94; P = 0.015) and increased PCSK9 expression (SMR, OR = 0.90, 95% CI = 0.82-0.99; P = 0.035) both correlate with lower cholelithiasis risk, indicating that PCSK9 inhibition may elevate this risk. Nevertheless, no substantial link emerged between NPC1L1-mediated LDL cholesterol or NPC1L1 expression and cholelithiasis in both IVW-MR and SMR analyses.

Conclusion

This MR investigation affirms the causal link between the utilization of HMGCR inhibitors and a diminished risk of cholelithiasis. Additionally, it indicates a causal link between PCSK9 inhibitors use and increased cholelithiasis risk. However, no significant correlation was found between NPC1L1 inhibitors use and cholelithiasis risk.

Conventional HDL Subclass Measurements Mask Thyroid Hormone-dependent Remodeling Activity Sites in Hypothyroid Individuals

Context

Earlier nuclear magnetic resonance spectroscopy (NMR) studies of plasma lipoproteins estimated by size as small, medium, and large particles, demonstrated hypothyroidism was associated with increases in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and intermediate-density lipoprotein (IDL) subclass particle number but variable changes in the high-density lipoprotein (HDL) subclasses. These disparate changes in HDL might be explained by reduced activity of the thyroid hormone-dependent remodeling proteins whose subclass specificity may be obscured when the 5 HDL subclasses identified by NMR are combined by size.

Objective

This work aimed to determine whether directional changes in particle number of individually measured HDL subclasses correlate with reduced activity of their thyroid hormone-dependent remodeling proteins in hypothyroid individuals.

Methods

VLDL, LDL, IDL, and HDL subclasses were measured by NMR in 13 thyroidectomized individuals 1 month following thyroid hormone withdrawal and 3 months after replacement. Changes in particle numbers in each subclass were compared when expressed individually and by size.

Results

Following thyroid hormone withdrawal, plasma lipids and VLDL, LDL, and IDL subclass particle number increased. HDL particle number nearly doubled in very small HDL-1 (P = .04), declined in small HDL-2 (P = .02), and increased 2-fold in HDL-5 (P = .0009).

Conclusion

The increment in HDL-1 and decline in HDL-2 subclasses is consistent with their precursor-product relationship and reduced lecithin cholesterol acyltransferase activity while the almost 2-fold increase in large HDL-5 is indicative of diminished action of hepatic lipase, phospholipid transfer protein, and endothelial lipase. These findings are inapparent when the 5 subclasses are expressed conventionally by size. This linking of specific HDL subclasses with HDL remodeling protein function provides new details about the specificity of their interactions.

The correlation between serum total bile acid and alanine aminotransferase of pregnant women and the disorders of neonatal hyperbilirubinemia-related amino acid metabolism

BACKGROUND

To explore the association between liver metabolism-related indicators in maternal serum and neonatal hyperbilirubinemia (NHB), and further investigate the predictive value of these indicators in NHB-related amino acid metabolism disorders.

METHODS

51 NHB and 182 No-NHB newborns and their mothers who treated in the Fourth Hospital of Shijiazhuang from 2018 to 2022 were participated in the study. The differences in clinical data were compared by the Mann-Whitney U test and Chi-square test. Multivariate logistic regression was used to analyze the relationship between maternal serum indicators and the occurrence of NHB. The correlation analysis and risk factor assessment of maternal serum indicators with NHB-related amino acid metabolic disorders were performed using Spearman correlation analysis and multivariate logistic regression.

RESULTS

Compared to the non NHB group, the NHB group had higher maternal serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), ALT/AST, and total bile acid (TBA), while lower levels of serum albumin (ALB), total cholesterol (TC) and high-density lipoprotein (HDL). The levels of alanine (ALA), valine (VAL), ornithine (ORN), and proline (PRO) in the newborns were reduced in NHB group, while arginine (ARG) showed a tendency to be elevated. Multiple logistic regression analysis showed that maternal ALT, AST, ALT/AST, and TBA levels were all at higher risk with the development of NHB, whereas ALB, TC, and HDL levels were negatively associated with NHB development. Increasing maternal TBA level was associated with lower ALA (r=-0.167, p = 0.011), VAL (r=-0.214, p = 0.001), ORN (r=-0.196, p = 0.003), and PRO in the newborns (r=-0.131, p = 0.045). Maternal ALT level was negatively associated with ALA (r=-0.135, p = 0.039), VAL (r=-0.177, p = 0.007), ORN (r=-0.257, p < 0.001), while ALT/AST was positively correlated with ARG (r = 0.133, p = 0.013). After adjustment for confounding factors, maternal serum TBA and ALT were the independent risk factor for neonatal ORN metabolic disorders [(adjusted odds ratio (AOR) = 0.379, 95%CI = 0.188-0.762, p = 0.006), (AOR = 0.441, 95%CI = 0.211-0.922, p = 0.030)]. Maternal ALT level was an independent risk factor for neonatal VAL metabolic disorders (AOR = 0.454, 95%CI = 0.218-0.949, p = 0.036).

CONCLUSIONS

The levels of high TBA, ALT, AST, and low HDL, TC of maternal were associated with the risk of NHB. Maternal TBA and ALT levels were independent risk factors for NHB-related amino acid disturbances which have value as predictive makers.

Understanding the Relationship between Nonalcoholic Fatty Liver Disease and Thyroid Disease

The prevalence of hypothyroidism in patients with nonalcoholic fatty liver disease (NAFLD) is high (22.4%). Thyroid hormones (THs) regulate many metabolic activities in the liver by promoting the export and oxidation of lipids, as well as de novo lipogenesis. They also control hepatic insulin sensitivity and suppress hepatic gluconeogenesis. Because of its importance in lipid and carbohydrate metabolism, the involvement of thyroid dysfunction in the pathogenesis of NAFLD seems plausible. The mechanisms implicated in this relationship include high thyroid-stimulating hormone (TSH) levels, low TH levels, and chronic inflammation. The activity of the TH receptor (THR)-β in response to THs is essential in the pathogenesis of hypothyroidism-induced NAFLD. Therefore, an orally active selective liver THR-β agonist, Resmetirom (MGL-3196), was developed, and has been shown to reduce liver fat content, and as a secondary end point, to improve nonalcoholic steatohepatitis. The treatment of NAFLD with THR-β agonists seems quite promising, and other agonists are currently under development and investigation. This review aims to shine a light on the pathophysiological and epidemiological evidence regarding this relationship and the effect that treatment with THs and selective liver THR-β agonists have on hepatic lipid metabolism.

Thyroid Hormones Regulate the Thermoregulatory Mechanisms of the Body: Review

Thyroid hormones (TH) play a critical role in metabolism, energy balance and thermogenesis. The mechanisms whereby thyroid hormone increases heat production have been analyzed with emphasis in more recent developments. Thyroid hormone increases obligatory thermogenesis as a result of the stimulation of numerous metabolic pathways involved in the development, remodeling and delivery of energy to the tissues. In this section, alterations in primary hyperthyroidism and hypothyroidism will be contrasted with the physiological characteristics of TH-dependent regulation in response to fasting and exposure to cold. The current review will discuss the situation with regard to regional thyroid hormones in the Central Nervous System (CNS) and more specifically, in peripheral cells. When caused by exposure to cold or fasting, local anomalies in the CNS are distinct from peripheral compartments, in contrast to hyperthyroidism and hypothyroidism, which differ when similar changes are observed. Lower hypothalamic TH concentrations are associated with cold exposure, although higher peripheral TH levels. The TH tendency is reversed by fasting. Primary hypothyroidism and hyperthyroidism impair them. The current study aims to trace the various mechanisms used by the thyroid gland to regulate the body's energy production process.

Metabolomic profile of patients on levothyroxine treatment for hypothyroidism

Background

Hypothyroidism is clinically characterized by a decrease in levels of the circulating thyroid hormones namely thyroxine and triiodothyronine. The main treatment for hypothyroidism is thyroid hormone replacement using levothyroxine to normalize serum thyroid hormone levels.

Objectives

In this study, we explored the metabolic changes in the plasma of patients with hypothyroidism after reaching a euthyroid state with levothyroxine treatment.

Methods

Plasma samples from 18 patients diagnosed as overt hypothyroidism were collected before and after levothyroxine treatment upon reaching a euthyroid state and were analyzed by high-resolution mass spectrometry-based metabolomics. Multivariate and univariate analyses evaluated data to highlight potential metabolic biomarkers.

Results

Liquid chromatography-mass spectrometry-based metabolomics revealed a significant decrease in the levels of ceramide, phosphatidylcholine, triglycerides, acylcarnitine, and peptides after levothyroxine treatment; this could indicate a change in the fatty acid transportation system and an enhanced β-oxidation, compared with a hypothyroid state. At the same time, the decrease in the peptides suggested a shift in protein synthesis. In addition, there was a considerable rise in glycocholic acid following therapy, suggesting the involvement of thyroid hormones in stimulating bile acid production and secretion.

Conclusions

A metabolomic analysis of patients with hypothyroidism revealed significant changes in several metabolites and lipids after treatment. This study showed the value of the metabolomics technique in providing a complementary understanding of the pathophysiology of hypothyroidism and as a crucial tool for examining the molecular impact of levothyroxine treatment on hypothyroidism. It was an important tool for investigating the therapeutic effects of levothyroxine on hypothyroidism at the molecular level.

Analysis of Risk Factors for Major Adverse Cardiovascular Events in Patients with Coronary Stent Restenosis after Revascularization

Background

To investigate the risk factors for myocardial infarction, recurrent in-stent restenosis (ISR) and target vessel revascularization (TVR) in patients with coronary ISR within 4 years after revascularization.

Methods

A total of 1884 patients who were hospitalized at Fuwai Hospital for ISR and successfully treated with coronary intervention between January 2017 and December 2018 were included to determine whether there were myocardial infarction, recurrent ISR, TVR and other major adverse cardiovascular events (MACEs) within 4 years after intervention. The patients were divided into the MACE group (215 patients) and the non-MACE group (1669 patients). The clinical data of patients in the two groups were compared, and the risk factors for postoperative MACEs in the ISR patients were obtained by multivariate logistic regression analysis. The receiver operating characteristic (ROC) curve was used to determine the optimal prediction threshold for postoperative MACEs in ISR patients. The difference in survival curves between the two groups was compared using Kaplan‒Meier survival analysis.

Results

The albumin (43.42 ± 4.77 vs. 44.17 ± 4.46, p = 0.021), direct bilirubin (2.5 (2, 3.5) vs. 2.8 (2.07, 3.73), p = 0.036) and free triiodothyronine (FT3) (2.85 ± 0.43 vs. 2.92 ± 0.42, p = 0.019) levels in the MACE group were significantly lower than those in the non-MACE group, and there was a significant negative correlation between albumin and FT3 and MACEs. The results of univariate and multivariate logistic regression analyses revealed that FT3 was an independent predictor of postoperative MACEs in ISR patients (Odds Ratio (OR) = 0.626, 95% CI: 0.429-0.913, p = 0.015). The ROC curve analysis determined that an FT3 value of 2.785 pmol/L was the optimal prediction threshold. According to the threshold, ISR patients were divided into the FT3 < 2.785 group and the FT3 ≥ 2.785 group. The Kaplan‒Meier analysis revealed that the postoperative recurrence rate of MACEs of the FT3 < 2.785 group was substantially greater than that of the FT3 ≥ 2.785 group (Hazard Ratio (HR) = 0.76, 95% CI: 0.58-0.994, p = 0.044).

Conclusions

FT3 can be used as an independent predictor of postoperative myocardial infarction, recurrent ISR and TVR in ISR patients. When FT3 is < 2.785 pmol/L, the incidence of postoperative myocardial infarction, recurrent ISR and TVR in ISR patients increases significantly.

Hepatic Energy Metabolism under the Local Control of the Thyroid Hormone System

The energy homeostasis of the organism is orchestrated by a complex interplay of energy substrate shuttling, breakdown, storage, and distribution. Many of these processes are interconnected via the liver. Thyroid hormones (TH) are well known to provide signals for the regulation of energy homeostasis through direct gene regulation via their nuclear receptors acting as transcription factors. In this comprehensive review, we summarize the effects of nutritional intervention like fasting and diets on the TH system. In parallel, we detail direct effects of TH in liver metabolic pathways with regards to glucose, lipid, and cholesterol metabolism. This overview on hepatic effects of TH provides the basis for understanding the complex regulatory network and its translational potential with regards to currently discussed treatment options of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) involving TH mimetics.

The role and molecular mechanism of gut microbiota in Graves' orbitopathy

PURPOSE

Graves' orbitopathy (GO) is an autoimmune orbital disorder. Gut microbiota dysfunction plays a vital role in autoimmune diseases, including Graves' disease (GD) and GO. In the present study, we aimed to investigate the change of gut microbiota in GD/GO using mouse model.

METHODS

The murine model of GD/GO was established by the challenge of adenovirus expressing thyroid-stimulating hormone (TSH) receptor (TSHR) (Ad-TSHR). The histological changes of orbital and thyroid tissues were analyzed by hematoxylin and eosin (H&E), Masson staining, and immunohistochemistry (IHC) staining. The fecal samples were collected for 16S rRNA gene sequencing and bioinformatics analysis.

RESULTS

The GD/GO model was established successfully, as manifested as the broadened eyelid, exophthalmia and conjunctive redness, severe inflammatory infiltration among thyroid glands and between extraocular muscle space, hypertrophic extraocular muscles, elevated thyroxine (T4) and decreased TSH, and positive CD34, CD40, collagen I, and α-SMA staining. A total of 222 operational taxonomic units (OUTs) were overlapped between mice in the Ad-NC and Ad-TSHR groups. The microbial composition of the samples in the two groups was mainly Bacteroidia and Clostridia, and the Ad-NC group had a significantly lower content of Bacteroidia and higher content of Clostridia. KEGG orthology analysis results revealed differences in dehydrogenase, aspartic acid, bile acid, chalcone synthase, acetyltransferase, glutamylcyclotransferase, glycogenin, and 1-phosphatidylinositol-4-phosphate 5-kinase between two groups; enzyme commission (EC) analysis results revealed differences in several dehydrogenase, oxidase, thioxy/reductase between two groups; MetaCyc pathways analysis results revealed differences in isoleucine degradation, oxidation of C1 compounds, tricarboxylic acid (TCA) cycle IV, taurine degradation, and biosynthesis of paromamine, heme, colonic acid building blocks, butanediol, lysine/threonine/methionine, and histidine/purine/pyrimidine between two groups.

CONCLUSION

This study induced a mouse model of GD/GO by Ad-TSHR challenge, and gut microbiota characteristics were identified in the GD/GO mice. The Bacteroidia and Clostridia abundance was changed in the GD/GO mice. These findings may lay a solid experimental foundation for developing personalized treatment regimens for GD patients according to the individual gut microbiota. Given the potential impact of regional differences on intestinal microbiota, this study in China may provide a reference for the global overview of the gut-thyroid axis hypothesis.

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.

Bile acid and receptors: biology and drug discovery for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), a series of liver metabolic disorders manifested by lipid accumulation within hepatocytes, has become the primary cause of chronic liver diseases worldwide. About 20%-30% of NAFLD patients advance to nonalcoholic steatohepatitis (NASH), along with cell death, inflammation response and fibrogenesis. The pathogenesis of NASH is complex and its development is strongly related to multiple metabolic disorders (e.g. obesity, type 2 diabetes and cardiovascular diseases). The clinical outcomes include liver failure and hepatocellular cancer. There is no FDA-approved NASH drug so far, and thus effective therapeutics are urgently needed. Bile acids are synthesized in hepatocytes, transported into the intestine, metabolized by gut bacteria and recirculated back to the liver by the enterohepatic system. They exert pleiotropic roles in the absorption of fats and regulation of metabolism. Studies on the relevance of bile acid disturbance with NASH render it as an etiological factor in NASH pathogenesis. Recent findings on the functional identification of bile acid receptors have led to a further understanding of the pathophysiology of NASH such as metabolic dysregulation and inflammation, and bile acid receptors are recognized as attractive targets for NASH treatment. In this review, we summarize the current knowledge on the role of bile acids and the receptors in the development of NAFLD and NASH, especially the functions of farnesoid X receptor (FXR) in different tissues including liver and intestine. The progress in the development of bile acid and its receptors-based drugs for the treatment of NASH including bile acid analogs and non-bile acid modulators on bile acid metabolism is also discussed.

Insight into the Evolving Role of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is the last discovered member of the family of proprotein convertases (PCs), mainly synthetized in hepatic cells. This serine protease plays a pivotal role in the reduction of the number of low-density lipoprotein receptors (LDLRs) on the surface of hepatocytes, which leads to an increase in the level of cholesterol in the blood. This mechanism and the fact that gain of function (GOF) mutations in PCSK9 are responsible for causing familial hypercholesterolemia whereas loss-of-function (LOF) mutations are associated with hypocholesterolemia, prompted the invention of drugs that block PCSK9 action. The high efficiency of PCSK9 inhibitors (e.g., alirocumab, evolocumab) in decreasing cardiovascular risk, pleiotropic effects of other lipid-lowering drugs (e.g., statins) and the multifunctional character of other proprotein convertases, were the cause for proceeding studies on functions of PCSK9 beyond cholesterol metabolism. In this article, we summarize the current knowledge on the roles that PCSK9 plays in different tissues and perspectives for its clinical use.

Update on dyslipidemia in hypothyroidism: the mechanism of dyslipidemia in hypothyroidism

Hypothyroidism is often associated with elevated serum levels of total cholesterol, LDL-C and triglycerides. Thyroid hormone (TH) affects the production, clearance and transformation of cholesterol, but current research shows that thyroid-stimulating hormone (TSH) also participates in lipid metabolism independently of TH. Therefore, the mechanism of hypothyroidism-related dyslipidemia is associated with the decrease of TH and the increase of TSH levels. Some newly identified regulatory factors, such as proprotein convertase subtilisin/kexin type 9, angiogenin-like proteins and fibroblast growth factors are the underlying causes of dyslipidemia in hypothyroidism. HDL serum concentration changes were not consistent, and its function was reportedly impaired. The current review focuses on the updated understanding of the mechanism of hypothyroidism-related dyslipidemia.

The impact of the gut microbiota on the reproductive and metabolic endocrine system

As the gut microbiota exerts various effects on the intestinal milieu which influences distant organs and pathways, it is considered to be a full-fledged endocrine organ. The microbiota plays a major role in the reproductive endocrine system throughout a woman's lifetime by interacting with estrogen, androgens, insulin, and other hormones. Imbalance of the gut microbiota composition can lead to several diseases and conditions, such as pregnancy complications, adverse pregnancy outcomes, polycystic ovary syndrome (PCOS), endometriosis, and cancer; however, research on the mechanisms is limited. More effort should be concentrated on exploring the potential causes and underlying the mechanisms of microbiota-hormone-mediated disease, and providing novel therapeutic and preventive strategies.As the gut microbiota exerts various effects on the intestinal milieu which influences distant organs and pathways, it is considered to be a full-fledged endocrine organ. The microbiota plays a major role in the reproductive endocrine system throughout a woman's lifetime by interacting with estrogen, androgens, insulin, and other hormones. Imbalance of the gut microbiota composition can lead to several diseases and conditions, such as pregnancy complications, adverse pregnancy outcomes, polycystic ovary syndrome (PCOS), endometriosis, and cancer; however, research on the mechanisms is limited. More effort should be concentrated on exploring the potential causes and underlying the mechanisms of microbiota-hormone-mediated disease, and providing novel therapeutic and preventive strategies.

Association of Maternal Thyroid Function with Gestational Hypercholanemia

Background: High bile acid concentration is associated with adverse perinatal outcomes (i.e., stillbirth and preterm birth) and experimental studies indicate that thyroid hormone regulates bile acid metabolism, but this has not yet been translated to clinical data in pregnant women. We aim to explore the association of thyroid function with bile acid concentrations and the risk of gestational hypercholanemia. Methods: This study comprised 68,016 singleton pregnancies without known thyroid or hepatobiliary diseases before pregnancy and thyroid medication based on a prospective cohort. Thyroid function and serum total bile acid (TBA) were routinely screened in both early (9-13 weeks) and late pregnancy (32-36 weeks). Hypercholanemia was defined as serum TBA concentration ≥10 μmol/L. Multiple linear regression models and multiple logistic regression models were performed. Results: A higher free thyroxine (fT4) during both early or late pregnancy was associated with a higher TBA concentration and a higher risk of hypercholanemia (all p < 0.01). A higher thyrotropin (TSH) in early pregnancy was associated with a higher TBA concentration in early pregnancy (p = 0.0155), but with a lower TBA concentration during later pregnancy (p < 0.0001), and there was no association of TSH with hypercholanemia. Overt hyperthyroidism in late pregnancy was associated with a 2.12-fold higher risk of hypercholanemia ([confidence interval; CI 1.12-4.03], p = 0.021) and subclinical hyperthyroidism during later pregnancy was associated with a 1.5-fold higher risk of hypercholanemia ([CI 1.14-1.97], p = 0.0034). Sensitivity analyses indicated that a high fT4 throughout pregnancy was associated with a higher risk of hypercholanemia rather than only in early or late pregnancy. Conclusions: A higher fT4 concentration during either early or late pregnancy, but not the TSH concentration, is associated with higher TBA and a higher risk of gestational hypercholanemia. Furthermore, hyperthyroidism during pregnancy could be a novel risk factor for hypercholanemia.

FGF21 Is Released During Increased Lipogenesis State Following Rapid-Onset Radioiodine-Induced Hypothyroidism

BACKGROUND

FGF21 pharmacological treatment reverses fatty liver and lowers serum triglyceride concentration but FGF21 serum level is increased in hepatic steatosis. FGF21 secretion is induced by thyroid hormones in vitro.

PURPOSE

To determine the influence of thyroid hormones and metabolic changes secondary to thyroid dysfunction on FGF21 secretion in humans.

MATERIALS AND METHODS

This was a case-control study. 82 hyperthyroid and 15 hypothyroid patients were recruited together with 25 healthy controls. Of those with hyperthyroidism, 56 received radioiodine treatment and 42 of them achieved hypothyroidism and then euthyroidism within one year following therapy. Radioiodine-induced hypothyroidism developed abruptly within a six week interval between clinic visits. FGF21 serum levels were determined with an ELISA method.

RESULTS

Serum FGF21 levels did not differ in hyper- and hypothyroid patients in comparison to controls [median 103.25 (interquartile range, 60.90-189.48) and 86.10 (54.05-251.02) vs 85.20 (58.00-116.80) pg/mL P=0.200 and 0.503, respectively]. In hyperthyroid patients treated with radioiodine, serum FGF21 levels increased significantly in rapid-onset hypothyroidism in comparison to the hyperthyroid and euthyroid phase [median 160.55 (interquartile range, 92.48 - 259.35) vs 119.55 (67.78-192.32) and 104.43 (55.93-231.93) pg/mL, P=0.034 and 0.033, respectively]. The rising serum FGF21 level correlated positively with serum triglycerides (Spearman coefficient rs=0.36, P=0.017) and inversely with serum SHBG (rs=-0.41, P=0.007), but did not correlate with thyroid hormone levels.

CONCLUSIONS

There was a transient increase in FGF21 serum level during rapid-onset hypothyroidism following radioiodine treatment. There was no association between FGF21 serum level and thyroid hormones. In radioiodine-induced hypothyroidism, the rising serum FGF21 concentration correlated positively with rising serum triglycerides and negatively with falling SHBG, reflecting increased hepatic lipogenesis.

Serum Fibroblast Growth Factor 21 Levels in Children and Adolescents with Hashimoto’s Thyroiditis before and after l-Thyroxin Medication: A Prospective Study

Backgrounds and Objectives: Fibroblast growth factor 21 (FGF-21) is a complex hormone, sharing common sites of action with thyroid hormones. We investigated the association among FGF-21 levels, resting metabolic rate (RMR), and l-thyroxin (LT4) treatment in children and adolescents with Hashimoto’s thyroiditis. Materials and Methods: A total of 60 youngsters with chronic autoimmune thyroiditis (AIT) (30 with subclinical hypothyroidism, 30 with euthyroidism) and 30 age and sex-matched healthy participants (5–18 years old) were enrolled in the study. Anthropometric, biochemical parameters, and RMR levels were assessed in all participants; serum FGF-21 levels were measured in the control group and the group with subclinical hypothyroidism before and six months after medication with LT4. Results: FGF-21 levels were lower in the treatment group compared with the healthy ones, but this difference was not statistically significant (p > 0.05); despite the increase in FGF-21 levels after six months of LT4 treatment, this difference was not statistically significant (p > 0.05). Free thyroxin (FT4) levels correlated well with FGF-21 levels (r = 0.399, p < 0.01), but further analysis revealed no interaction between these two variables. Both patient groups presented elevated triglyceride (TG) levels compared to controls (p < 0.05). LT4 treatment had no impact on RMR and lipid or liver or glycaemic parameters. An increase in fat mass and fat-free mass were reported, independently of FGF-21 levels. Conclusions: In youngsters with subclinical hypothyroidism due to Hashimoto’s thyroiditis, the serum FGF-21 levels are not significantly lower than in healthy individuals and increase after treatment with LT4 without a statistical significance. Further studies with a large number of young patients and severe hypothyroidism are recommended to confirm our results.

Microbiome Metabolites and Thyroid Dysfunction

Thyroid diseases are common conditions that have a negative impact on the health of all populations. The literature sheds light on the differences in the composition of the intestinal microbiota in patients suffering from thyroid diseases compared to healthy individuals. The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut–thyroid axis is discussed in the context of both thyroid diseases and intestinal dysbiosis. The purpose of this review is to describe associations between the microbiome and its metabolites and thyroid dysfunction. We try to explain the role of the microbiome in the metabolism of thyroid hormones and the impact of thyroid autoimmune diseases. In addition, we raise issues related to the influence of bacterial metabolites, such as short-chain fatty acids or secondary bile acids, in the functioning of the thyroid gland. Last but not least, we explored the interactions between the gut microbiota and therapeutics and supplements typically administered to patients with thyroid diseases.

A case of thyrotoxicosis-induced anemia in a patient with painless thyroiditis

Background

There have been several reports of secondary anemia associated with Graves’ disease. There are no reports of secondary anemia resulting from thyrotoxicosis due to painless thyroiditis (silent thyroiditis). We report the case of a patient with pancreatic diabetes who developed anemia caused by thyrotoxicosis due to painless thyroiditis.

Case presentation

The patient was a 37-year-old man who visited the hospital complaining of fatigue, palpitations, and dyspnea. His hemoglobin was 110 g/l (reference range, 135–176), and mean corpuscular volume was 81.5 fl (81.7–101.6). His free thyroxine (FT4) was high, at 100.4 pmol/l (11.6–21.9); the free triiodothyronine (FT3) was high, at 27.49 pmol/l (3.53–6.14); TSH was low, at < 0.01 mIU/l (0.50–5.00); and TSH receptor antibody was negative. Soluble IL-2 receptor (sIL-2R) was high, at 1340 U/ml (122–496); C-reactive protein (CRP) was high, at 6900 μg/l (< 3000); and reticulocytes was high, at 108 10⁹ /l (30–100). Serum iron (Fe) was 9.5 (9.1–35.5), ferritin was 389 μg/l (13–401), haptoglobin was 0.66 g/l (0.19–1.70. Propranolol was prescribed and followed up. Anemia completely disappeared by 12 weeks after disease onset. Thyroid hormones and sIL-2R had normalized by 16 weeks after onset. He developed mild hypothyroidism and was treated with L-thyroxine at 24 weeks.

Conclusions

This is the first case report of transient secondary anemia associated with thyrotoxicosis due to painless thyroiditis. The change in sIL-2R was also observed during the clinical course of thyrotoxicosis and anemia, suggesting the immune processes in thyroid gland and bone marrow.

Dyslipidemia, Insulin Resistance, Ectopic Lipid Accumulation, and Vascular Function in Resistance to Thyroid Hormone β

PURPOSE

In resistance to thyroid hormone due to mutations in thyroid hormone receptor β, peripheral tissues are variably refractory to the action of circulating thyroid hormones. We evaluated parameters contributing to atherosclerotic risk in this disorder.

METHODS

We measured low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), nonesterified fatty acids (NEFA), intrahepatic lipid (IHL) and intramyocellular lipid (IMCL), Homeostasis-model assessment of insulin resistance (HOMA-IR), augmentation index (AIx) and pulse wave velocity (PWV), flow-mediated dilatation, and carotid intima-media thickness (cIMT) in an unselected, genetically confirmed cohort of adult RTHβ patients (n = 27-77) and compared these with measurements in healthy subjects (up to n = 100) and thyrotoxic patients (n = 40).

RESULTS

Resistance to thyroid hormone beta (RTHβ) patients exhibited higher LDL-C (P = 0.008) and TG (P = 0.002) and lower HDL-C concentrations (P = 0.015 × 10-2) than control subjects, with LDL-C being higher than in thyrotoxic patients with comparable hyperthyroxinemia. Proprotein convertase subtilisin/kexin 9 (P = 0.002) and apolipoprotein B (P = 0.0009) levels were reduced in thyrotoxic patients but not lower in RTHβ patients or control subjects. Intrahepatic lipid (P = 0.02 × 10-4), IMCL (P = 0.002), HOMA-IR (P = 0.01 × 10-2), and NEFA (P = 0.04 × 10-6) were significantly higher in RTHβ patients than control subjects. Flow-mediated dilatation was increased (P = 0.04) but cIMT (P = 0.71), PWV P = 0.81), and AIx (P = 0.95) were unaltered in RTHβ patients.

CONCLUSIONS

We have documented mixed dyslipidemia with hepatic and IMCL accumulation in RTHβ, suggesting that surveillance for these metabolic abnormalities is warranted. How they combine with enhanced endothelial function and unaltered vessel wall thickness and compliance to determine overall cardiometabolic risk in this disorder remains to be defined.

Skeletal Muscle and Bone - Emerging Targets of Fibroblast Growth Factor-21

Fibroblast growth factor 21 (FGF21) is an atypical member of the FGF family, which functions as a powerful endocrine and paracrine regulator of glucose and lipid metabolism. In addition to liver and adipose tissue, recent studies have shown that FGF21 can also be produced in skeletal muscle. As the most abundant tissue in the human body, skeletal muscle has become increasingly recognized as a major site of metabolic activity and an important modulator of systemic metabolic homeostasis. The function and mechanism of action of muscle-derived FGF21 have recently gained attention due to the findings of considerably increased expression and secretion of FGF21 from skeletal muscle under certain pathological conditions. Recent reports regarding the ectopic expression of FGF21 from skeletal muscle and its potential effects on the musculoskeletal system unfolds a new chapter in the story of FGF21. In this review, we summarize the current knowledge base of muscle-derived FGF21 and the possible functions of FGF21 on homeostasis of the musculoskeletal system with a focus on skeletal muscle and bone.

Pulmonary Hypertension and Hypocholesterolemia Secondary to Thyrotoxicosis

Background

Thyroid disorders commonly affect the cardiovascular system. Thyrotoxicosis leading to pulmonary hypertension has been increasingly reported during recent years. Thyroid dysfunction affects the lipid metabolism, and thyrotoxicosis can be associated with low lipid levels. Thyrotoxicosis presenting with right ventricular dysfunction is rare, and only few cases had been reported. Case Presentation. A 53-year-old woman presented with progressive shortness of breath and swelling of body for four months. Examination showed generalized oedema and a systolic murmur over the left sternal border. Transthoracic echocardiography confirmed pulmonary hypertension with tricuspid regurgitation. Investigations revealed thyrotoxicosis and very low cholesterol levels. Diagnosis of Graves' disease was confirmed with detection of thyrotropin receptor antibodies. Pulmonary pressure was normalized six months after antithyroid therapy.

Conclusion

Thyrotoxicosis is a recognized cause of reversible pulmonary hypertension and acquired hypocholesterolemia. However, most clinicians are not aware of these associations. This case illustrates the importance of assessing thyroid function in patients presenting with pulmonary hypertension.

Treatment of Thyroid Dysfunction and Serum Lipids: A Systematic Review and Meta-analysis

CONTEXT

Hyperthyroidism is associated with low levels of cholesterol and triglycerides, and hypothyroidism is associated with hypercholesterolemia and hypertriglyceridemia.

OBJECTIVE

The aim of this systematic review was to investigate the impact of therapy for overt and subclinical hyper- and hypothyroidism on serum lipids.

DATA SOURCES

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Scopus from 1970 through April 5, 2018.

STUDY SELECTION

Pairs of independent reviewers selected randomized and observational studies evaluating lipid parameters in patients undergoing treatment for hyper- or hypothyroidism.

DATA EXTRACTION

Pairs of independent reviewers extracted data and appraised studies.

DATA SYNTHESIS

Treatment of overt hyperthyroidism showed a significant increase in total cholesterol (TC) by 44.50 mg/dL (95% confidence interval [CI]: 37.99, 51.02), low-density lipoprotein cholesterol (LDL-C) by 31.13 mg/dL (95% CI: 24.33, 37.93), high-density lipoprotein cholesterol (HDL-C) by 5.52 mg/dL (95% CI: 1.48, 9.56), apolipoprotein A (Apo A) by 15.6 mg/dL (95% CI: 10.38, 20.81), apolipoprotein B (apo B) by 26.12 mg/dL (95% CI: 22.67, 29.57), and lipoprotein (Lp[a]) by 4.18 mg/dL (95% CI: 1.65, 6.71). There was no significant change in triglyceride (TG) levels. Treatment of subclinical hyperthyroidism did not change any lipid parameters significantly. Levothyroxine therapy in overt hypothyroidism showed a statistically significant decrease in TC by -58.4 mg/dL (95% CI: -64.70, -52.09), LDL-C by -41.11 mg/dL (95% CI: -46.53, -35.69), HDL-C by -4.14 mg/dL (95% CI: -5.67, -2.61), TGs by -7.25 mg/dL (95% CI: -36.63, 17.87), apo A by -12.59 mg/dL (95% CI: -17.98, -7.19), apo B by -33.96 mg/dL (95% CI: 41.14, -26.77), and Lp(a) by -5.6 mg/dL (95% CI: -9.06, -2.14). Levothyroxine therapy in subclinical hypothyroidism showed similar changes but with a smaller magnitude. The studies contained varied population characteristics, severity of thyroid dysfunction, and follow-up duration.

CONCLUSIONS

Treatment of overt but not subclinical hyperthyroidism is associated with worsening of the lipid profile. Levothyroxine therapy in both overt and subclinical hypothyroidism leads to improvement in the lipid profile, with a smaller magnitude of improvement in subclinical hypothyroidism.

Thyroid Hormone Signaling and the Liver

Thyroid hormone (TH) plays a critical role in maintaining metabolic homeostasis throughout life. It is well known that the liver and thyroid are intimately linked, with TH playing important roles in de novo lipogenesis, beta-oxidation (fatty acid oxidation), cholesterol metabolism, and carbohydrate metabolism. Indeed, patients with hypothyroidism have abnormal lipid panels with higher levels of low-density lipoprotein levels, triglycerides (triacylglycerol; TAG), and apolipoprotein B levels. Even in euthyroid patients, lower serum-free thyroxine levels are associated with higher total cholesterol levels, LDL, and TAG levels. In addition to abnormal serum lipids, the risk of nonalcoholic fatty liver disease (NAFLD) increases with lower free thyroxine levels. As free thyroxine rises, the risk of NAFLD is reduced. This has led to numerous animal studies and clinical trials investigating TH analogs and TH receptor agonists as potential therapies for NAFLD and hyperlipidemia. Thus, TH plays an important role in maintaining hepatic homeostasis, and this continues to be an important area of study. A review of TH action and TH actions on the liver will be presented here.

Simultaneous Analysis of Fatty Alcohols, Fatty Aldehydes, and Sterols in Thyroid Tissues by Electrospray Ionization-Ion Mobility-Mass Spectrometry Based on Charge Derivatization

In this work, we developed a rapid and high-sensitivity method for simultaneous analyses of fatty alcohols, fatty aldehydes, and sterols by combining the optimized derivatization reaction with electrospray ionization-ion mobility-mass spectrometry (ESI-IM-MS). Pyridine and thionyl chloride were used as derivatization reagents as they were easily removed after the derivatization reaction and could generate permanently charged tags on different functional groups including hydroxyls and aldehydes. Through this one-step derivatization reaction, the sensitivity of detection for fatty alcohols, fatty aldehydes, and sterols was significantly increased. Moreover, the introduction of ion mobility spectrometry (IMS), offering an additional resolution power, ensured more sensitive and accurate detection of derivative products without increasing analytical time. Being connected with high-performance liquid chromatography, more than 15 kinds of compounds were analyzed within 4 min. Relative quantification using peak intensity ratios between d₀-/d₅-labeled ions were subsequently applied for analyzing these 15 kinds of compounds in human thyroid carcinoma and para-carcinoma tissues. The results showed significant differences in content of some analytes between these two kinds of tissues (p < 0.05). The correlations between most of the analytes in thyroid carcinoma tissues are better than the correlations in para-carcinoma tissues.

No Dataset Left Behind: Mechanistic Insights into Thyroid Receptor Signaling Through Transcriptomic Consensome Meta-Analysis

Background: Discovery-scale omics datasets relevant to thyroid receptors (TRs) and their physiological and synthetic bioactive small-molecule ligands allow for genome-wide interrogation of TR-regulated genes. These datasets have considerable collective value as a reference resource to allow researchers to routinely generate hypotheses addressing the mechanisms underlying the cell biology and physiology of TR signaling in normal and disease states. Methods: Here, we searched the Gene Expression Omnibus database to identify a population of publicly archived transcriptomic datasets involving genetic or pharmacological manipulation of either TR isoform in a mouse tissue or cell line. After initial quality control, samples were organized into contrasts (experiments), and transcript differential expression values and associated measures of significance were generated and committed to a consensome (for consensus omics) meta-analysis pipeline. To gain insight into tissue-selective functions of TRs, we generated liver- and central nervous system (CNS)-specific consensomes and identified evidence for genes that were selectively responsive to TR signaling in each organ. Results: The TR transcriptomic consensome ranks genes based on the frequency of their significant differential expression over the entire group of experiments. The TR consensome assigns elevated rankings both to known TR-regulated genes and to genes previously uncharacterized as TR-regulated, which shed mechanistic light on known cellular and physiological roles of TR signaling in different organs. We identify evidence for unreported genomic targets of TR signaling for which it exhibits strikingly distinct regulatory preferences in the liver and CNS. Moreover, the intersection of the TR consensome with consensomes for other cellular receptors sheds light on transcripts potentially mediating crosstalk between TRs and these other signaling paradigms. Conclusions: The mouse TR datasets and consensomes are freely available in the Signaling Pathways Project website for hypothesis generation, data validation, and modeling of novel mechanisms of TR regulation of gene expression. Our results demonstrate the insights into the mechanistic basis of thyroid hormone action that can arise from an ongoing commitment on the part of the research community to the deposition of discovery-scale datasets.

Hypothyroidism modifies differentially the content of lipids and glycogen, lipid receptors, and intraepithelial lymphocytes among oviductal regions of rabbits

Hypothyroidism affects the content of triacylglycerol (TAG), total cholesterol (TC), oxidized lipids, glycogen, and infiltration of immune cells into the ovary and uterus. This study aimed to analyze the impact of hypothyroidism on the lipid content of different regions of the oviduct. Control (n = 6) and hypothyroid (n = 6; 10 mg/kg/day of methimazole in the drinking water for 30 days) adult rabbits were used. In the fimbriae/infundibulum (FIM/INF), ampulla, (AMP), isthmus (IST), and utero-tubal junction (UTJ), the TAG and TC concentrations, presence of oxidized lipid, relative expressions of perilipin A (PLIN A), peroxisome proliferator-activated receptor γ (PPARγ), CAAT/enhancer-binding protein α (C/EBPα), and farnesoid X receptor (FXRα) were analyzed. The content of glycogen and glycans, as well as the infiltration of lymphocytes, were also quantified. In the FIM/INF, hypothyroidism reduced the content of TC, expression of C/EBPα, and presence of glycans while increased the number of intraepithelial lymphocytes. In the AMP and IST-UTJ regions, hypothyroidism increased the content of TAG, oxidized lipids, expression of PPARγ, and glycogen content but decreased the expression of PLIN-A. The FXRα expression in secretory cells of IST-UTJ was higher in the hypothyroid rabbits compared to controls. Additionally, hypothyroidism reduced the C/EBPα expression and the number of intraepithelial lymphocytes in the AMP and IST-UTJ regions, respectively. We demonstrated that the effect of hypothyroidism depends on the oviductal region, possibly associated with different physiological functions specific to each region. These alterations may be related to infertility, tubal disturbances, and ectopic pregnancy observed in hypothyroid women.

Subclinical Hyperthyroidism: Status of the Cholesterol Transfers to HDL and Other Parameters Related to Lipoprotein Metabolism in Patients Submitted to Thyroidectomy for Thyroid Cancer

Purpose: Lipid metabolism has been poorly explored in subclinical hyperthyroidism. The aim was to examine the effects of exogenous subclinical hyperthyroidism in women under levothyroxine treatment upon plasma lipids and aspects of HDL metabolism. Methodology: Ten women were studied in euthyroidism and again in exogenous subclinical hyperthyroidism. Thyroid function tests and plasma lipids were studied. Results: HDL-cholesterol (increased 21.6%, p = 0.0004), unesterified cholesterol (increased 12.3%, p = 0.04) and Lp(a) (increased 33,3%, P = 0.02) plasma concentrations were higher in subclinical hyperthyroidism compared to euthyroidism, but total cholesterol, LDL, non-HDL cholesterol, triglycerides, apo A-I, apo B were unchanged. PON1 activity (decreased 75%, p = 0.0006) was lower in subclinical hyperthyroidism. There were no changes in HDL particle size, CETP and LCAT concentrations. The in vitro assay that estimates the lipid transfers to HDL showed that esterified cholesterol (increased 7.1%, p = 0.03), unesterified cholesterol (increased 7.8%, p = 0.02) and triglycerides (increased 6.8%, p = 0.006) transfers were higher in subclinical hyperthyroidism. There were no changes in phospholipid transfers to HDL in subclinical hyperthyroidism. Conclusions: Several alterations in the plasma lipid metabolism were observed in the subclinical hyperthyroidism state that highlight the importance of this aspect in the follow-up of those patients. The increase in HDL-C and in the transfer of unesterified and esterified cholesterol to HDL, an important anti-atherogenic HDL function are consistently protective for cardiovascular health. The increase in Lp(a) and the decrease in PON-1 activity that are important risk factors were documented here in subclinical hyperthyroidism and these results should be confirmed in larger studies due to great data variation but should not be neglected in the follow-up of those patients.

Serum Fibroblast Growth Factor 21 Levels in Patients with Hyperthyroidism and its Association with Body Fat Percentage

BACKGROUND

Most of the actions of thyroid hormone (TH) on body metabolisms like maintenance of basal metabolic rate (BMR) and body fat are similar to that of fibroblast growth factor 21 (FGF21). We hypothesized that in patients with hyperthyroidism, the pathological changes in the BMR, body fat are mediated by TH through FGF21.

OBJECTIVES

To study the association of serum FGF21 levels with hyperthyroidism and correlate body fat percentage with serum FGF21 levels in hyperthyroid patients.

STUDY DESIGN

Case-control prospective follow-up study.

METHODOLOGY

A total of 68 hyperthyroid patients and age, sex-matched healthy controls who fulfilled the inclusion and exclusion criteria were studied. Among them, 45 cases were followed up at 3 to 6 months after the achievement of euthyroidism. Body fat percentage was calculated from Jackson and Pollock 3 site equation and Siri equation. BMR percentage was calculated by the Gale formula.

RESULTS

The mean age in years in the cases was similar to that of controls (36.14 ± 10.01 vs. 36.57 ± 10.53, P = 0.81). The serum FGF21 levels at baseline were significantly elevated in patients with hyperthyroidism compared to controls [median 406.6 pg/ml (interquartile range, 262.9-655.6) vs. 252.3 (125.1-341) P < 0.001] and declined dramatically following treatment with anti-thyroid drugs [405 (275.5-680.4) vs. 203.6 (154.6-230.6) P < 0.001]. Serum FGF21 levels negatively correlated with body fat percentage (r = -0.268, P = 0.002). After adjusting to various confounding factors, serum FGF21 was independently associated with hyperthyroidism and was significant. (OR [95%CI] 3.78 (1.046-13.666) P = 0.043).

CONCLUSION

Serum FGF21 levels were elevated in hyperthyroid patients and decreased following treatment with anti-thyroid drugs. It was independently associated with hyperthyroidism. There may be a future therapeutic role of FGF21 inhibition in the reversal of these changes in addition to anti-thyroid drugs in patients with hyperthyroidism.

Nonalcoholic Fatty Liver Disease and Hypercholesterolemia: Roles of Thyroid Hormones, Metabolites, and Agonists

Background: Thyroid hormones (THs) exert a strong influence on mammalian lipid metabolism at the systemic and hepatic levels by virtue of their roles in regulating circulating lipoprotein, triglyceride (TAG), and cholesterol levels, as well as hepatic TAG storage and metabolism. These effects are mediated by intricate sensing and feedback systems that function at the physiological, metabolic, molecular, and transcriptional levels in the liver. Dysfunction in the pathways involved in lipid metabolism disrupts hepatic lipid homeostasis and contributes to the pathogenesis of metabolic diseases, such as nonalcoholic fatty liver disease (NAFLD) and hypercholesterolemia. There has been strong interest in understanding and employing THs, TH metabolites, and TH mimetics as lipid-modifying drugs. Summary: THs regulate many processes involved in hepatic TAG and cholesterol metabolism to decrease serum cholesterol and intrahepatic lipid content. TH receptor β analogs designed to have less side effects than the natural hormone are currently being tested in phase II clinical studies for NAFLD and hypercholesterolemia. The TH metabolites, 3,5-diiodo-l-thyronine (T2) and T1AM (3-iodothyronamine), have different beneficial effects on lipid metabolism compared with triiodothyronine (T3), although their clinical application is still under investigation. Also, prodrugs and glucagon/T3 conjugates have been developed that direct TH to the liver. Conclusions: TH-based therapies show clinical promise for the treatment of NAFLD and hypercholesterolemia. Strategies for limiting side effects of TH are being developed and may enable TH metabolites and analogs to have specific effects in the liver for treatments of these conditions. These liver-specific effects and potential suppression of the hypothalamic/pituitary/thyroid axis raise the issue of monitoring liver-specific markers of TH action to assess clinical efficacy and dosing of these compounds.

Microbiota and Thyroid Interaction in Health and Disease

The microbiota has been identified as an important factor in health and in a variety of diseases. An altered microbiota composition increases the prevalence of Hashimoto's thyroiditis (HT) and Graves' disease (GD). Microbes influence thyroid hormone levels by regulating iodine uptake, degradation, and enterohepatic cycling. In addition, there is a pronounced influence of minerals on interactions between host and microbiota, particularly selenium, iron, and zinc. In manifest thyroid disorders, the microbiota may affect L-thyroxine uptake and influence the action of propylthiouracil (PTU). Although it is relatively well documented that thyroid disorders are linked to the composition of the microbiota, the role of specific genera and the potential use of therapies targeting the microbiota are less clear.

Changes in metabolic parameters and cardiovascular risk factors after therapeutic control of acromegaly vary with the treatment modality. Data from the Bicêtre cohort, and review of the literature

CONTEXT

Untreated acromegaly is associated with increased morbidity and mortality due to malignant, cardiovascular, and cerebrovascular disorders. Effective treatment of acromegaly reduces excess mortality, but its impact on cardiovascular risk factors and metabolic parameters are poorly documented.

AIM

We analyzed changes in cardiovascular risk factors and metabolic parameters in patients receiving various treatment modalities.

PATIENTS AND METHODS

We retrospectively studied 96 patients with acromegaly, both at diagnosis and after IGF-I normalization following surgery alone (n = 51) or medical therapy with first generation somatostatin analogues (SSA, n = 23), or pegvisomant (n = 22). Duration of follow-up was 77 (42-161) months, 75 (42-112) months, and 62 (31-93) months, in patients treated with surgery alone, SSA, and pegvisomant, respectively. In all the cases except four, patients treated medically had underwent previous unsuccessful surgery.

RESULTS

IGF-I normalization was associated with increased body weight, decreased systolic blood pressure (SBP) in hypertensive patients, decreased fasting plasma glucose (FPG) and HOMA-IR and HOMA-B levels, increased HDL cholesterol (HDLc); whereas, LDL cholesterol (LDLc) was not significantly different. Plasma PCSK9 levels were unchanged in patients with available values. Cardiovascular and metabolic changes varied with the treatment modality: surgery, but not pegvisomant, had a beneficial effect on SBP; FPG decreased after surgery but increased after SSA; the decline in HOMA-IR was only significant after surgery; pegvisomant significantly increased LDLc and total cholesterol; whereas SA increased HDLc and had no effect on LDLc levels.

CONCLUSION

Treatments used to normalize IGF-I levels in patients with acromegaly could have differential effects on cardiovascular risk factors and metabolic parameters.

Potential Role of Thyroid Receptor β Agonists in the Treatment of Hyperlipidemia

Thyroid hormones have important effects on cellular development, growth, and metabolism and are necessary for the healthy function of almost all tissues. Hyperthyroid patients with excess thyroid hormone levels experience tachycardia, fatigue, muscle wasting, and osteoporosis. However, although high thyroid hormone levels have adverse effects, efforts have been made to harness the beneficial effects, such as reduced serum low-density lipoprotein (LDL) cholesterol levels, elevated basal metabolic rate, and weight loss. Thyroid hormones interact with nuclear thyroid hormone receptors (TRs), and cholesterol levels are reduced through TRβ, whereas extrahepatic adverse actions are primarily connected to TRα. Thus, to develop a useful compound for clinical use, efforts have been focusing on developing compounds with isomer-specific functions based on the structure of thyroid hormones, i.e., thyromimetics that are liver and/or TRβ specific. In this short review, we discuss the development of the early thyromimetics that enabled, through modern molecular techniques, the progress towards improved design of TRβ-selective thyromimetics. We also address the early promise shown in human clinical trials and the current status of these drugs and other emerging compounds.

Cigarette Smoke Extract Modulates Functions of Peroxisome Proliferator-Activated Receptors

Cigarette smoke extract (CSE) contains many toxicants and may derange the physiological processes, such as cholesterol metabolism. We examined the impact of CSE on transcriptional regulation mediated peroxisome proliferator-activated receptors (PPARs) and its interaction with cofactors to elucidate differences in the molecular mechanism between CSE and other agonists of PPARs. We constructed several mutant PPARs (mPPARs) with amino acid substitution in the ligand-binding domain, which according to the molecular modeling, may affect the binding of agonists. In transient expression assays, each wild-type peroxisome proliferator-activated receptor (PPAR) mediated transcription stimulated by CSE was faintly yet significantly elevated compared to the control. The CSE-induced transcriptional activation was abolished in the H323A, H323Y, S342A, and H449A mPPARγs, although the activation elevated by pioglitazone was reserved. In the mPPARγ with Y473A and mPPARβ/δs with H286Y and Y436A, the pioglitazone-induced or L165041-activated transcriptional elevations were decreased and were lower than that of CSE-induced stimulation. These results suggested that CSE activated both mutant PPARs to be selectively different from those ligands. Mammalian two-hybrid assay illustrated that CSE could mildly recruit SRC1 or GRIP1 to the wild-type PPARγ. Representative ingredients, such as acrolein and crotonaldehyde present in CSE, could stimulate PPAR isoforms even at the toxicological concentrations and might possibly contribute to stimulatory effects. CSE mildly regulates the cholesterol metabolism-related genes, such as low density lipoprotein (LDL) receptor and Liver X receptor (LXR)β. In conclusion, these CSE effects the nuclear hormone receptors and their cofactors thereby disturbing metabolic phenomena. Therefore, CSE might be involved in cholesterol metabolism.