Search

Transducin β-like 1 X-linked receptor 1 (mouse Tbl1xr1) or TBL1X/Y related 1 (human TBL1XR1), part of the NCoR/SMRT corepressor complex, is involved in nuclear receptor signaling. Variants in TBL1XR1 cause a variety of neurodevelopmental disorders including Pierpont syndrome caused by the p.Tyr446Cys variant. We recently reported a mouse model carrying the Tbl1xr1 Y446C/Y446C variant as a model for Pierpont syndrome. To obtain insight into mechanisms involved in altered brain development we studied gene expression patterns in the cortex of mutant and wild type (WT) mice, using RNA-sequencing, differentially expressed gene (DEG) analysis, gene set enrichment analysis (GSEA), weighted gene correlation network analysis (WGCNA) and hub gene analysis. We validated results in mutated mouse cortex, as well as in BV2 and SK-N-AS cell lines, in both of which Tbl1xr1 was knocked down by siRNA. Two DEGs (adj.P. Val < 0.05) were found in the cortex, Mpeg1 (downregulated in mutant mice) and 2900052N01Rik (upregulated in mutant mice). GSEA, WGCNA and hub gene analysis demonstrated changes in genes involved in ion channel function and neuroinflammation in the cortex of the Tbl1xr1 Y446C/Y446C mice. The lowered expression of ion channel genes Kcnh3 and Kcnj4 mRNA was validated in the mutant mouse cortex, and increased expression of TRIM9, associated with neuroinflammation, was confirmed in the SK-N-AS cell line. Conclusively, our results show altered expression of genes involved in ion channel function and neuroinflammation in the cortex of the Tbl1xr1 Y446C/Y446C mice. These may partly explain the impaired neurodevelopment observed in individuals with Pierpont syndrome and related TBL1XR1-related disorders., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Recurrence is a key outcome to evaluate the treatment effect of differentiated thyroid carcinoma (DTC). However, no consistent definition of recurrence is available in current literature or international guidelines. Therefore, the primary aim of this systematic review was to delineate the definitions of recurrence of DTC, categorized by total thyroidectomy with radioactive iodine ablation (RAI), total thyroidectomy without RAI and lobectomy, to assess if there is a generally accepted definition among these categories. Methods: This study adhered to the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. In December 2023, a systematic literature search in MEDLINE and EMBASE was performed for studies reporting on the recurrence of DTC, from January 2018 to December 2023. Studies that did not provide a definition were excluded. Primary outcome was the definition of recurrence of DTC. Secondary outcome was whether studies differentiated between recurrence and persistent disease. Two independent investigators screened the titles and abstracts, followed by full-text assessment and data extraction. The study protocol was registered in PROSPERO, CRD42021291753. Results: In total, 1450 studies were identified. Seventy studies met the inclusion criteria, including 69 retrospective studies and 1 randomised controlled trial (RCT). Median number of patients in the included studies was 438 (range 25-2297). In total, 17 studies (24.3%) reported on lobectomy, 4 studies (5.7%) on total thyroidectomy without RAI, and 49 studies (70.0%) with RAI. All studies defined recurrence using one or a combination of four diagnostic modalities cytology/pathology, imaging studies, thyroglobulin (-antibodies), and a predetermined minimum tumor-free time span. The most common definition of recurrence following lobectomy was cytology/pathology-proven recurrence (47.1% of this subgroup), following total thyroidectomy with RAI was cytology/pathology-proven recurrence and/or anomalies detected on imaging studies (22.4% of this subgroup). No consistent definition was found following total thyroidectomy without RAI. Nine studies (12.9%) differentiated between recurrence and persistent disease. Conclusion: Our main finding is that there is no universally accepted definition for recurrence of DTC in the current studies across any of the treatment categories. The findings of this study will provide the basis for a future, international Delphi-based proposal to establish a universally accepted definition of recurrence of DTC. A uniform definition could facilitate global discussion and enhance the assessment of treatment outcomes regarding recurrence of DTC.

Background: Thyroid-stimulating hormone (TSH) and subsequent free thyroxine (FT4) concentrations outside the reference interval (RI) are used to diagnose thyroid diseases. Most laboratories do not provide age-specific RIs for TSH and FT4 beyond childhood, although TSH concentrations vary with age. Therefore, we aimed to establish TSH and FT4 age-specific RIs throughout life and aimed to determine whether using these RIs would result in reclassification of thyroid disease diagnoses in adults. Methods: This multicenter retrospective cross-sectional study used big data to determine indirect RIs for TSH and FT4. These RIs were determined by TMC and refineR-analysis, respectively, using four different immunoassay platforms (Roche, Abbott, Siemens, and Beckman Coulter). Retrospective data (2008-2022) from 13 Dutch laboratories for general practitioners and local hospitals were used. RIs were evaluated per manufacturer. Age groups were established from 2 to 20 years by 2-year categories and decade categories between 20 and 100 years. Results: We included totally 7.6 million TSH and 2.2 million FT4 requests. TSH upper reference limits (URLs) and FT4 lower reference limits were higher in early childhood and decreased toward adulthood. In adulthood, TSH URLs increased from 60 years in men, and from 50 years in women, while FT4 URLs increased from 70 years onward. Using adult age-specific RIs resulted in a decrease in diagnoses of subclinical and overt hypothyroidism in women above 50 and men above 60 years in our Roche dataset. Conclusion: This study stressed the known importance of using age-specific RIs for TSH and FT4 in children. This study also showed the clinical relevance of using age-specific RIs for TSH in adulthood to reduce diagnoses of subclinical hypothyroidism in older persons. Therefore, implementation of adult TSH age-specific RIs should be strongly considered. Data are less uniform regarding FT4 age-specific RIs and more research should be performed before implementing these in clinical practice.

The association between suboptimal thyroid function ((sub)clinical hypothyroidism or low normal thyroid function) and the metabolic syndrome and metabolic dysfunction-associated steatotic liver disease (MASLD) is clearly established. Furthermore, in MASLD, thyroid hormones have low intracellular concentrations and the activation of the thyroid hormone receptor (THR) is reduced. Administration of thyroid hormone has been shown to reduce liver triglycerides by stimulating fatty acid disposal through lipophagy and beta-oxidation, and to lower LDL-cholesterol. As thyroid hormone exerts it's effects in many different organs, including heart and bone, several drug candidates have been developed acting as selective thyromimetics for the THR-β nuclear receptor with potent and targeted liver actions. Importantly, these compounds have reduced affinity for the THR-α nuclear receptor and tissue distribution profiles that differ from endogenous thyroid hormones thereby reducing unwanted cardiovascular side effects. The most advanced compound, resmetirom, is an oral drug that demonstrated, in a large phase 3 trial in MASH patients, the ability to remove liver fat, reduce aminotransferase levels and improve atherogenic dyslipidemia with a good tolerability profile. This translated into histological improvement that led to accelerated approval of this drug for active fibrotic steatohepatitis, a milestone achievement as a first MASH drug., Competing Interests: Declaration of Competing Interest VR: Consulting for Boehringer-Ingelheim, Madrigal, Novo-Nordisk, 89Bio, Akero, LG Chem Sciences, Sagimet, Astra Zeneca. Grant to Institution: MSD; TSS. is a founder and senior advisor to Autobahn Therapeutics., EB: Received consultancy and speaker fees from Madrigal, on thyroid function monitoring board Aligos., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

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., (© 2024. Springer Nature Limited.)

Background: Mutations in TBL1X, part of the NCOR1/SMRT corepressor complex, were identified in patients with hereditary X-linked central congenital hypothyroidism and associated hearing loss. The role of TBL1X in thyroid hormone (TH) action, however, is incompletely understood. The aim of the present study was to investigate the role of TBL1X on T3-regulated gene expression in two human liver cell models., Methods: A human hepatoma cell line (HepG2) wherein TBL1X was downregulated using siRNAs, and human-induced pluripotent stem cell-derived hepatocytes (iHeps) generated from individuals with a TBL1X N365Y mutation. Both cell types were treated with increasing concentrations of T3. The expression of T3-regulated genes was measured by qPCR., Results: KLF9, CPT1A, and PCK1 mRNA expression were higher upon T3 stimulation in the HepG2 cells with decreased TBL1X expression compared to controls, while DIO1 mRNA expression was lower. Hemizygous TBL1X N365Y iHeps exhibited decreased expression of CPT1A, G6PC1, PCK1, FBP1, and ELOVL2 compared to cells with the heterozygous TBL1X N365Y allele, but KLF9 and HMGCS2 expression was unaltered., Conclusion: Downregulation of TBL1X in HepG2 cells and the TBL1X N365Y variant in iHeps have differential effects on T3-regulated gene expression. This suggests that TBL1X may play a gene context role in TH action.

Background: Subclinical thyroid diseases are often the subject of debate concerning their clinical significance, the appropriateness of diagnostic testing, and possible treatment. This systematic review addresses the variation in international guidelines for subclinical hyperthyroidism, focusing on diagnostic workup, treatment, and follow-up recommendations., Methods: Following the PRISMA guidelines, we searched PubMed, Embase, and guideline-specific databases and included clinical practice guidelines with recommendations on subclinical hyperthyroidism. Guideline recommendations were extracted, and quality assessment was performed using selected questions of the Appraisal of Guidelines for Research & Evaluation (AGREE) II instrument., Results: Of the 2624 records screened, 22 guidelines were included, which were published between 2007 and 2021. Guideline quality was generally intermediate to low. Diagnostic approaches differed substantially, particularly in the extent of recommended testing. Treatment initiation depended on TSH levels, age, and comorbidities, but the level of detail regarding defining precise comorbidities varied. Recommendations for monitoring intervals for follow-up ranged from 3 to 12 months., Conclusion: This review underscores the existing variability in (inter)national guidelines concerning subclinical hyperthyroidism. There isa need for clear recommendations in guidelines considering diagnostic workup, treatment, and follow-up of subclinical hyperthyroidism. In order to establish this, future research should focus on determining clear and evidence-based intervention thresholds.

Purpose: Pituitary surgery can lead to post-surgical adrenal insufficiency with the need for glucocorticoid replacement and significant disease related burden. In patients who do not receive hydrocortisone replacement before surgery, at our center, an early morning plasma cortisol concentration using a cut-off value of 450 nmol/L 3 days after surgery (POD3) is used to guide the need for hydrocortisone replacement until dynamic confirmatory testing using metyrapone. The aim of this study was to critically assess the currently used diagnostic and treatment algorithm in patients undergoing pituitary surgery in our pituitary reference center., Methods: Retrospective analysis of all patients with a POD3 plasma cortisol concentration < 450 nmol/L who received hydrocortisone replacement and a metyrapone test after 3 months. Plasma cortisol concentration was measured using an electrochemiluminescence immunoassay (Roche). All patients who underwent postoperative testing using metyrapone at Amsterdam UMC between January 2018 and February 2022 were included. Patients with Cushing's disease or those with hydrocortisone replacement prior to surgery were excluded., Results: Ninety-five patients were included in the analysis. The postoperative cortisol concentration above which no patient had adrenal insufficiency (i.e. 11-deoxycortisol > 200 nmol/L) was 357 nmol/L (Sensitivity 100%, Specificity 31%, PPV:32%, NPV:100%). This translates into a 28% reduction in the need for hydrocortisone replacement compared with the presently used cortisol cut-off value of 450 nmol/L., Conclusion: Early morning plasma cortisol cut-off values lower than 450 nmol/L can safely be used to guide the need for hydrocortisone replacement after pituitary surgery., (© 2024. The Author(s).)

Individuals with nonalcoholic fatty liver disease (NAFLD) have an altered gut microbiota composition. Moreover, hepatic DNA methylation may be altered in the state of NAFLD. Using a fecal microbiota transplantation (FMT) intervention, we aimed to investigate whether a change in gut microbiota composition relates to altered liver DNA methylation in NAFLD. Moreover, we assessed whether plasma metabolite profiles altered by FMT relate to changes in liver DNA methylation. Twenty-one individuals with NAFLD underwent three 8-weekly vegan allogenic donor ( n  = 10) or autologous ( n  = 11) FMTs. We obtained hepatic DNA methylation profiles from paired liver biopsies of study participants before and after FMTs. We applied a multi-omics machine learning approach to identify changes in the gut microbiome, peripheral blood metabolome and liver DNA methylome, and analyzed cross-omics correlations. Vegan allogenic donor FMT compared to autologous FMT induced distinct differential changes in I) gut microbiota profiles, including increased abundance of Eubacterium siraeum and potential probiotic Blautia wexlerae ; II) plasma metabolites, including altered levels of phenylacetylcarnitine (PAC) and phenylacetylglutamine (PAG) both from gut-derived phenylacetic acid, and of several choline-derived long-chain acylcholines; and III) hepatic DNA methylation profiles, most importantly in Threonyl-TRNA Synthetase 1 ( TARS) and Zinc finger protein 57 ( ZFP57) . Multi-omics analysis showed that Gemmiger formicillis and Firmicutes bacterium &#95; CAG &#95;170 positively correlated with both PAC and PAG. E siraeum negatively correlated with DNA methylation of cg16885113 in ZFP57 . Alterations in gut microbiota composition by FMT caused widespread changes in plasma metabolites (e.g. PAC, PAG, and choline-derived metabolites) and liver DNA methylation profiles in individuals with NAFLD. These results indicate that FMTs might induce metaorganismal pathway changes, from the gut bacteria to the liver.

Context: Liver fat content and visceral fat volume are associated with insulin resistance and cardiovascular disease and are higher in men than in women., Objective: To determine the effect of estradiol and testosterone treatment on liver fat and visceral fat in transgender persons., Design: Open-label intervention study (SHAMVA) with a 1-year follow-up., Setting: Gender clinic in a hospital., Patients: 8 trans women and 18 trans men receiving hormone treatment., Interventions: Trans women received an antiandrogen and after 6 weeks estradiol was added. Trans men were randomized to receive triptorelin, testosterone, and anastrozole for 12 weeks or triptorelin and testosterone for 12 weeks, followed by only testosterone until week 52., Main Outcome Measures: Liver fat content, visceral and abdominal subcutaneous fat volume, measured by magnetic resonance spectrometry or imaging at baseline, 6, 8, 18, and 58 weeks in transwomen or at baseline; at 6 and 12 weeks in trans men with anastrozole; and at 52 weeks in trans men without anastrozole., Results: In trans women, liver fat content decreased by 1.55% (-2.99 to -0.12) after 58 weeks, compared to week 6. Visceral fat did not change. In trans men with anastrozole, the liver fat content and visceral fat volume did not change. In trans men without anastrozole, after 52 weeks, liver fat content increased by 0.83% (0.14 to 1.52) and visceral fat volume increased by 34% (16 to 51)., Conclusions: Sex hormones regulate liver fat content and visceral fat in men and women., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Endocrine Society.)

Objective: Congenital hypothyroidism (CH) is an inborn thyroid hormone (TH) deficiency mostly caused by thyroidal (primary CH) or hypothalamic/pituitary (central CH) disturbances. Most CH newborn screening (NBS) programs are thyroid-stimulating-hormone (TSH) based, thereby only detecting primary CH. The Dutch NBS is based on measuring total thyroxine (T4) from dried blood spots, aiming to detect primary and central CH at the cost of more false-positive referrals (FPRs) (positive predictive value (PPV) of 21% in 2007-2017). An artificial PPV of 26% was yielded when using a machine learning-based model on the adjusted dataset described based on the Dutch CH NBS. Recently, amino acids (AAs) and acylcarnitines (ACs) have been shown to be associated with TH concentration. We therefore aimed to investigate whether AAs and ACs measured during NBS can contribute to better performance of the CH screening in the Netherlands by using a revised machine learning-based model., Methods: Dutch NBS data between 2007 and 2017 (CH screening results, AAs and ACs) from 1079 FPRs, 515 newborns with primary (431) and central CH (84) and data from 1842 healthy controls were used. A random forest model including these data was developed., Results: The random forest model with an artificial sensitivity of 100% yielded a PPV of 48% and AUROC of 0.99. Besides T4 and TSH, tyrosine, and succinylacetone were the main parameters contributing to the model's performance., Conclusions: The PPV improved significantly (26-48%) by adding several AAs and ACs to our machine learning-based model, suggesting that adding these parameters benefits the current algorithm.

Transducin β-like 1 X-linked receptor 1 (TBL1XR1) is a WD40 repeat-containing protein and part of the corepressor complex SMRT/NCoR that binds to the thyroid hormone receptor (TR). We recently described a mutation in TBL1XR1 in patients with Pierpont syndrome. A mouse model bearing this Tbl1xr1 mutation (Tbl1xr1Y446C/Y446C ) displays several aspects of the Pierpont phenotype. Although serum thyroid hormone (TH) concentrations were unremarkable in these mice, tissue TH action might be affected due to the role of TBL1XR1 in the SMRT/NCoR corepressor complex. The aim of the present study was to evaluate tissue TH metabolism and action in a variety of tissues of Tbl1xr1Y446C/Y446C mice. We studied the expression of genes involved in TH metabolism and action in tissues of naïve Tbl1xr1Y446C/Y446C mice and wild type (WT) mice. In addition, we measured deiodinase activity in liver (Dio1 and Dio3), kidney (Dio1 and Dio3) and BAT (Dio2). No striking differences were observed in the liver, hypothalamus, muscle and BAT between Tbl1xr1Y446C/Y446C and WT mice. Pituitary TRα1 mRNA expression was lower in Tbl1xr1Y446C/Y446C mice compared to WT, while the mRNA expression of Tshβ and the positively T3-regulated gene Nmb were significantly increased in mutant mice. Interestingly, Mct8 expression was markedly higher in WAT and kidney of mutants, resulting in (subtle) changes in T3-regulated gene expression in both WAT and kidney. In conclusion, mice harboring a mutation in TBL1XR1 display minor changes in cellular TH metabolism and action. TH transport via MCT8 might be affected as the expression is increased in WAT and kidney. The mechanisms involved need to be clarified.

WD40 repeat-containing proteins play a key role in many cellular functions including signal transduction, protein degradation, and apoptosis. The WD40 domain is highly conserved, and its typical structure is a β-propeller consisting of 4-8 blades which probably serves as a scaffold for protein-protein interaction. Some WD40 repeat-containing proteins form part of the corepressor complex of nuclear hormone receptors, a family of ligand-dependent transcription factors that play a central role in the regulation of gene transcription. This explains their involvement in endocrine physiology and pathology. In the present review, we first touch upon the structure of WD40 repeat-containing proteins. Next, we describe our current understanding of the role of WD40 domain-containing proteins in nuclear receptor signaling, e.g., as corepressor or coactivator. In the final part of this review, we focus on WD40 domain-containing proteins that are associated with endocrine pathologies. These pathologies vary from isolated dysfunction of one endocrine axis, e.g., congenital isolated central hypothyroidism, to more complex congenital syndromes comprising endocrine phenotypes, such as the Triple-A syndrome.

Thyroid hormones play an essential role in regulating whole-body homeostasis. Deiodinases are known to convert thyroid hormone from the prohormone thyroxine (T4) to the bioactive hormone tri-iodothyronine (T3) and convert both T4 and T3 toward their inactive metabolites 3,3',5'-tri-iodothyronine (rT3) and 3,3'-di-iodothyronine (3,3'-T2). Deiodinases are thus important for the regulation of intracellular thyroid hormone concentrations. This is known to be crucial both during development and adult life in regulating thyroid hormone-related gene transcription. This review discusses the importance of liver deiodinases in determining serum and liver thyroid hormone concentrations, liver metabolism and liver disease.

Common symptoms of overt hypothyroidism are non-specific and include fatigue, lethargy, and dry skin. Although the diagnosis is considered to be straightforward, no single symptom can be used to identify patients with overt hypothyroidism, while many patients with subclinical hypothyroidism are asymptomatic. A large population-based study on the spectrum of symptoms in subclinical hypothyroidism showed similar rates of thyroid disease-related symptoms compared with euthyroid subjects, while the TSH concentration had no impact on symptom score. Together, these findings make it challenging to attribute symptoms to their underlying cause. This is also true in the case of unexplained persistent symptoms in levothyroxine-treated patients. Although generally considered a life-long replacement therapy, successful thyroid hormone discontinuation resulting in euthyroidism has been reported in approximately one third of patients. Thus, we overtreat patients with (subclinical) hypothyroidism, highlighting the importance of reliable diagnostic criteria. The diagnostic process, including the implementation of robust TSH and FT4 reference intervals, is especially challenging in specific situations including aging, pregnancy, non-thyroidal illness, and central hypothyroidism. There is a clear need for improved adherence to current guidelines from scientific societies and for willingness to manage symptoms without a clear pathological correlate, especially in the case of mild TSH elevations. This review will highlight recent literature on this topic and offers some practice points., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jansen, Boelen, Heijboer, Bruinstroop and Fliers.)

Background: The gut is a target organ of thyroid hormone (TH) that exerts its action via the nuclear thyroid hormone receptor α1 (TRα1) expressed in intestinal epithelial cells. THs are partially metabolized via hepatic sulfation and glucuronidation, resulting in the production of conjugated iodothyronines. Gut microbiota play an important role in peripheral TH metabolism as they produce and secrete enzymes with deconjugation activity (β-glucuronidase and sulfatase), via which TH can re-enter the enterohepatic circulation. Summary: Intestinal epithelium homeostasis (the finely tuned balance between cell proliferation and differentiation) is controlled by the crosstalk between triiodothyronine and TRα1 and the presence of specific TH transporters and TH-activating and -inactivating enzymes. Patients and experimental murine models with a dominant-negative mutation in the TRα exhibit gross abnormalities in the morphology of the intestinal epithelium and suffer from severe symptoms of a dysfunctional gastrointestinal tract. Over the past decade, gut microbiota has been identified as an essential factor in health and disease, depending on its compositional and functional profile. This has led to a renewed interest in the so-called gut-thyroid axis. Disruption of gut microbial homeostasis (dysbiosis) is associated with autoimmune thyroid disease (AITD), including Hashimoto's thyroiditis, Graves' disease, and Graves' orbitopathy. These studies reviewed here provide new insights into the gut microbiota roles in thyroid disease pathogenesis and may be an initial step toward microbiota-based therapies in AITD. However, it should be noted that cause-effect mechanisms remain to be proven, for which prospective cohort studies, randomized clinical trials, and experimental studies are needed. Conclusion: This review aims at providing a comprehensive insight into the interplay between TH metabolism and gut homeostasis.

Currently, thyroid hormone status is predominantly determined by the measurement of serum thyroid-stimulating hormone and free thyroxine. Although it is assumed that serum thyroid hormone (TH) concentrations within the reference range represent euthyroidism, it is unknown whether this reflects euthyroidism in all tissues (e.g. brain, muscle, bone and liver). To date, no serum marker has been established for clinical use that represents TH status within tissues accurately. However, several biomarkers have been investigated and innovative techniques have been used to unravel new biomarkers. This review provides an overview of proposed serum biomarkers that reflect tissue TH status in humans. Furthermore, we discuss the feasibility of these serum markers in clinical practice.

Hepatic macroautophagy/autophagy and fatty acid metabolism are transcriptionally regulated by nuclear receptors (NRs); however, it is not known whether their transcriptional co-activators are involved in autophagy. We thus examined MED1 (mediator complex subunit 1), a key component of the Mediator Complex that directly interacts with NRs, on these processes. We found that MED1 knockdown (KD) in cultured hepatic cells decreased autophagy and mitochondrial activity that was accompanied by decreased transcription of genes involved in these processes. Lipophagy and fatty acid β-oxidation also were impaired. These effects also occurred after thyroid hormone stimulation, nutrient-replete or -deplete conditions, and in liver-specific Med1 KD ( Med1 LKD) mice under fed and fasting conditions. Together, these findings showed that Med1 played a key role in hepatic autophagy, mitochondria function, and lipid metabolism under these conditions. Additionally, we identified downregulated hepatic genes in Med1 LKD mice, and subjected them to ChIP Enrichment Analysis. Our findings showed that the transcriptional activity of several NRs and transcription factors (TFs), including PPARA and FOXO1, likely were affected by Med1 LKD. Finally, Med1 expression and autophagy also were decreased in two mouse models of nonalcoholic fatty liver disease (NAFLD) suggesting that decreased Med1 may contribute to hepatosteatosis. In summary, MED1 plays an essential role in regulating hepatic autophagy and lipid oxidation during different hormonal and nutrient conditions. Thus, MED1 may serve as an integrator of multiple transcriptional pathways involved in these metabolic processes. Abbreviations: BAF: bafilomycin A 1 ; db/db mice; Lepr db/db mice; ECAR: extracellular acidification rate; KD: knockdown; MED1: mediator complex subunit 1; NAFLD: nonalcoholic fatty liver disease; OCR: oxygen consumption rate; PPARA/PPARα: peroxisomal proliferator activated receptor alpha; TF: transcription factor; TFEB: transcription factor EB; tf-LC3: tandem fluorescence RFP-GFP-LC3; TG: triglyceride; TH: Thyroid hormone; TR: thyroid hormone receptors; V-ATPase: vacuolar-type H + -ATPase; WDF: Western diet with 15% fructose in drinking water.

Objective: Nonalcoholic fatty liver disease (NAFLD) comprises a spectrum ranging from hepatosteatosis to progressive nonalcoholic steatohepatitis that can lead to cirrhosis. Humans with low levels of prohormone thyroxine (T 4 ) have a higher incidence of NAFLD, and thyroid hormone treatment is very promising in all patients with NAFLD. Deiodinase type 1 (Dio1) is a hepatic enzyme that converts T 4 to the bioactive T 3 and therefore regulates thyroid hormone availability within hepatocytes. We investigated the role of this intrahepatic regulation during the progression of NAFLD., Methods: We investigated hepatic thyroid hormone metabolism in two NAFLD models: wild-type mice fed a Western diet with fructose and Lepr db mice fed a methionine- and choline-deficient diet. AAV8-mediated liver-specific Dio1 knockdown was employed to investigate the role of Dio1 during the progression of NAFLD. Intrahepatic thyroid hormone levels, deiodinase activity, and metabolic parameters were measured., Results: Dio1 expression and activity were increased in the early stages of NAFLD and were associated with an increased T 3 /T 4 ratio. Prevention of this increase by AAV8-mediated liver-specific Dio1 knockdown increased hepatic triglycerides and cholesterol and decreased the pACC/ACC ratio and acylcarnitine levels, suggesting there was lower β-oxidation. Dio1 siRNA KD in hepatic cells treated with fatty acids showed increased lipid accumulation and decreased oxidative phosphorylation., Conclusion: Hepatic Dio1 gene expression was modulated by dietary conditions, was increased during hepatosteatosis and early NASH, and regulated hepatic triglyceride content. These early adaptations likely represent compensatory mechanisms that reduce hepatosteatosis and prevent NASH progression., (Copyright © 2021 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Background: Thyroid hormone (TH) has important functions in controlling hepatic lipid metabolism. Individuals with resistance to thyroid hormone beta (RTHβ) who harbor mutations in the THRB gene experience loss-of-function of thyroid hormone receptor beta (TRβ), which is the predominant TR isoform expressed in the liver. We hypothesized that individuals with RTHβ may have increased hepatic steatosis. Methods: Controlled attenuation parameter (CAP) was assessed in individuals harboring the R243Q mutation of the THRB gene ( n  = 21) and in their wild-type (WT) first-degree relatives ( n  = 22) using the ultrasound-based transient elastography (TE) device (FibroScan). All participants belonged to the same family, lived on the same small island, and were therefore exposed to similar environmental conditions. CAP measurements and blood samples were obtained after an overnight fast. The observers were blinded to the status of the patients. Results: The hepatic fat content was increased in RTHβ individuals compared with their WT relatives (CAP values of 263 ± 21 and 218.7 ± 43 dB/m, respectively, p  = 0.007). The CAP values correlated with age and body mass index (BMI) (age: r  = 0.55, p  = 0.011; BMI: r  = 0.51, p  = 0.022) in the WT first-degree relatives but not in RTHβ individuals, suggesting that the defect in TRβ signaling was predominant over the effects of age and obesity. Circulating free fatty acid levels were significantly higher in RTHβ individuals (0.29 ± 0.033 vs. 0.17 ± 0.025 mmol/L, p  = 0.02). There was no evidence of insulin resistance evaluated by the homeostatic model assessment of insulin resistance in both groups studied. Conclusions: Our findings provide evidence that impairments in intrahepatic TRβ signaling due to mutations of the THRB gene can lead to hepatic steatosis, which emphasizes the influence of TH in the liver metabolism of lipids and provides a rationale for the development TRβ-selective thyromimetics. Consequently, new molecules with a very high TRβ affinity and hepatic selectivity have been developed for the treatment of lipid-associated hepatic disorders, particularly nonalcoholic fatty liver disease.

Background & Aims: We studied the role of interleukin 11 (IL11) signaling in the pathogenesis of nonalcoholic steatohepatitis (NASH) using hepatic stellate cells (HSCs), hepatocytes, and mouse models of NASH., Methods: We stimulated mouse and human fibroblasts, HSCs, or hepatocytes with IL11 and other cytokines and analyzed them by imaging, immunoblot, and functional assays and enzyme-linked immunosorbent assays. Mice were given injections of IL11. Mice with disruption of the interleukin 11 receptor subunit alpha1 gene (Il11ra1 -/- ) mice and Il11ra1 +/+ mice were fed a high-fat methionine- and choline-deficient diet (HFMCD) or a Western diet with liquid fructose (WDF) to induce steatohepatitis; control mice were fed normal chow. db/db mice were fed with methionine- and choline-deficient diet for 12 weeks and C57BL/6 NTac were fed with HFMCD for 10 weeks or WDF for 16 weeks. Some mice were given intraperitoneal injections of anti-IL11 (X203), anti-IL11RA (X209), or a control antibody at different timepoints on the diets. Livers and blood were collected; blood samples were analyzed by biochemistry and liver tissues were analyzed by histology, RNA sequencing, immunoblots, immunohistochemistry, hydroxyproline, and mass cytometry time of flight assays., Results: HSCs incubated with cytokines produced IL11, resulting in activation (phosphorylation) of ERK and expression of markers of fibrosis. Livers of mice given injections of IL11 became damaged, with increased markers of fibrosis, hepatocyte cell death and inflammation. Following the HFMCD or WDF, livers from Il11ra1 -/- mice had reduced steatosis, fibrosis, expression of markers of inflammation and steatohepatitis, compared to and Il11ra1 +/+ mice on the same diets. Depending on the time of administration of anti-IL11 or anti-IL11RA antibodies to wild-type mice on the HFMCD or WDF, or to db/db mice on the methionine and choline-deficient diet, the antibodies prevented, stopped, or reversed development of fibrosis and steatosis. Blood samples from Il11ra1 +/+ mice fed the WDF and given injections of anti-IL11 or anti-IL11RA, as well as from Il11ra1 -/- mice fed WDF, had lower serum levels of lipids and glucose than mice not injected with antibody or with disruption of Il11ra1., Conclusions: Neutralizing antibodies that block IL11 signaling reduce fibrosis, steatosis, hepatocyte death, inflammation and hyperglycemia in mice with diet-induced steatohepatitis. These antibodies also improve the cardiometabolic profile of mice and might be developed for the treatment of NASH., (Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.)

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.

Context: Nonalcoholic fatty liver disease (NAFLD) is highly prevalent in patients with type 2 diabetes mellitus (T2DM) and associated with significant morbidity and mortality. Thyroid hormone (TH) increases β-oxidation of fatty acids and decreases intrahepatic lipid content (IHLC) in rodents with NAFLD., Objective: We investigated the possibility of low intrahepatic TH concentration in NAFLD and studied the effect of TH treatment in humans., Design/setting: This was a phase 2b single-arm study in six hospitals in Singapore. Intrahepatic thyroid hormone concentrations were measured in rats with induced NAFLD., Patients: Euthyroid patients with T2DM and steatosis measured by ultrasonography., Intervention: Levothyroxine was titrated to reach a thyroid-stimulating hormone level of 0.34 to 1.70 mIU/L before a 16-week maintenance phase., Main Outcome Measures: The primary outcome measure was change in IHLC measured by proton magnetic resonance spectroscopy after treatment., Results: Twenty male patients were included in the per-protocol analysis [mean ± SD: age, 47.8 ± 7.8 years; body mass index (BMI), 30.9 ± 4.4 kg/m2; baseline IHLC, 13% ± 4%]. After treatment, IHLC was decreased 12% (±SEM, 26%) relative to baseline (absolute change, -2%; 95% CI, -3 to 0; P = 0.046). Small decreases in BMI (P = 0.044), visceral adipose tissue volume (P = 0.047), and subcutaneous adipose tissue volume (P = 0.045) were observed. No significant changes in glucose regulation or lipid profile occurred., Conclusion: This study demonstrated the efficacy and safety of low-dose TH therapy for NAFLD in men. TH or TH analogs may be beneficial for this condition.

Introduction: Insulin and the GLP-1 receptor agonist liraglutide are both effective in reaching glycemic targets. The efficacy of an insulin-to-liraglutide switch in an obese population with concurrent use of sulfonylurea and metformin is unknown. We assessed the efficacy and determinants of success of an insulin-to-liraglutide switch in these patients., Methods: In a retrospective study we analyzed all patients that underwent an insulin-to-liraglutide switch during routine medical care (January 2009-February 2015). It was assessed if patients still continued liraglutide 12 months after the switch or discontinued because of poor glycemic control or side effects. Baseline characteristics were compared between the groups to establish determinants of success., Results: A total of 104 patients made an insulin-to-liraglutide switch (43% male; mean age 57.2 ± 9.9 years; mean BMI 39.8 ± 5.4 kg/m 2 ). Sixty patients still continued liraglutide after 12 months (58%) whereas 37 patients discontinued treatment because of poor glycemic control within 12 months (36%) and seven patients discontinued liraglutide because of intolerable side effects (7%). Insulin dose and insulin frequency at baseline were significantly lower in patients that continued liraglutide. Patients reaching HbA1c ≤ 7% (53 mmol/mol) showed lower baseline HbA1c levels, shorter duration of diabetes, and shorter duration of insulin therapy., Conclusion: The majority of patients continued liraglutide after a switch from insulin therapy with on average no change in glycemic control and decrease of body weight. HbA1c levels at baseline, duration of insulin therapy, and duration of diabetes were predictive of reaching glycemic control on liraglutide alone. In current practice this also indicates which patients on insulin can reduce their insulin dose after adding a GLP-1 receptor agonist. Plain language summary available for this article.

Objective: Elevated very low-density lipoprotein (VLDL)-triglyceride (TG) secretion from the liver contributes to an atherogenic dyslipidemia that is associated with obesity, diabetes and the metabolic syndrome. Numerous models of obesity and diabetes are characterized by increased central nervous system (CNS) neuropeptide Y (NPY); in fact, a single intracerebroventricular (icv) administration of NPY in lean fasted rats elevates hepatic VLDL-TG secretion and does so, in large part, via signaling through the CNS NPY Y1 receptor. Thus, our overarching hypothesis is that elevated CNS NPY action contributes to dyslipidemia by activating central circuits that modulate liver lipid metabolism., Methods: Chow-fed Zucker fatty (ZF) rats were pair-fed by matching their caloric intake to that of lean controls and effects on body weight, plasma TG, and liver content of TG and phospholipid (PL) were compared to ad-libitum (ad-lib) fed ZF rats. Additionally, lean 4-h fasted rats with intact or disrupted hepatic sympathetic innervation were treated with icv NPY or NPY Y1 receptor agonist to identify novel hepatic mechanisms by which NPY promotes VLDL particle maturation and secretion., Results: Manipulation of plasma TG levels in obese ZF rats, through pair-feeding had no effect on liver TG content; however, hepatic PL content was substantially reduced and was tightly correlated with plasma TG levels. Treatment with icv NPY or a selective NPY Y1 receptor agonist in lean fasted rats robustly activated key hepatic regulatory proteins, stearoyl-CoA desaturase-1 (SCD-1), ADP-ribosylation factor-1 (ARF-1), and lipin-1, known to be involved in remodeling liver PL into TG for VLDL maturation and secretion. Lastly, we show that the effects of CNS NPY on key liporegulatory proteins are attenuated by hepatic sympathetic denervation., Conclusions: These data support a model in which CNS NPY modulates mediators of hepatic PL remodeling and VLDL maturation to stimulate VLDL-TG secretion that is dependent on the Y1 receptor and sympathetic signaling to the liver.

Our body is well designed to store energy in times of nutrient excess, and release energy in times of food deprivation. This adaptation to the external environment is achieved by humoral factors and the autonomic nervous system. Claude Bernard, in the 19th century, showed the importance of the autonomic nervous system in the control of glucose metabolism. In the 20th century, the discovery of insulin and the development of techniques to measure hormone concentrations shifted the focus from the neural control of metabolism to the secretion of hormones, thus functionally "decapitating" the body. Just before the end of the 20th century, starting with the discovery of leptin in 1994, the control of energy metabolism went back to our heads. Since the start of 21st century, numerous studies have reported the involvement of hypothalamic pathways in the control of hepatic insulin sensitivity and glucose production. The autonomic nervous system is, therefore, acknowledged to be one of the important determinants of liver metabolism and a possible treatment target. In this chapter, we review research to date on the hypothalamic control of hepatic lipid metabolism., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The hypothalamus has long been appreciated to be fundamental in the control and coordination of homeostatic activity. Historically, this has been viewed in terms of the extensive neuroendocrine control system resulting from processing of hypothalamic signals relayed to the pituitary. Through these actions, endocrine signals are integrated throughout the body, modulating a vast array of physiological processes. Our understanding of the responses to endocrine signals is crucial for the diagnosis and management of many pathological conditions. More recently, the control emanating from the hypothalamus over the autonomic nervous system has been increasingly recognized as a powerful additional modulator of peripheral tissues. However, the neuroendocrine and autonomic control pathways emanating from the hypothalamus are not separate processes. They appear to act as a single integrated regulatory system, far more subtle and complex than when each is viewed in isolation. Consequently, hypothalamic regulation should be viewed as a summation of both neuroendocrine and autonomic influences. The neural regulation is believed to be fine and rapid, whereas the hormonal regulation is more stable and widespread. In this chapter, we will focus on the hypothalamic control of hepatic glucose and lipid metabolism., (© 2014 S. Karger AG, Basel.)

The liver is a key organ in controlling glucose and lipid metabolism during feeding and fasting. In addition to hormones and nutrients, inputs from the autonomic nervous system are also involved in fine-tuning hepatic metabolic regulation. Previously, we have shown in rats that during fasting an intact sympathetic innervation of the liver is essential to maintain the secretion of triglycerides by the liver. In the current study, we hypothesized that in the postprandial condition the parasympathetic input to the liver inhibits hepatic VLDL-TG secretion. To test our hypothesis, we determined the effect of selective surgical hepatic denervations on triglyceride metabolism after a meal in male Wistar rats. We report that postprandial plasma triglyceride concentrations were significantly elevated in parasympathetically denervated rats compared with control rats (P = 0.008), and VLDL-TG production tended to be increased (P = 0.066). Sympathetically denervated rats also showed a small rise in postprandial triglyceride concentrations (P = 0.045). On the other hand, in rats fed on a six-meals-a-day schedule for several weeks, a parasympathetic denervation resulted in >70% higher plasma triglycerides during the day (P = 0.001), whereas a sympathetic denervation had no effect. Our results show that abolishing the parasympathetic input to the liver results in increased plasma triglyceride levels during postprandial conditions.

The pontine noradrenergic cell groups, A5, A6 (locus coeruleus), and A7, provide the only noradrenergic innervation of the spinal cord, but the individual contribution of each of these populations to the regional innervation of the spinal cord remains controversial. We used an adeno-associated viral (AAV) vector encoding green fluorescent protein under an artificial dopamine beta-hydroxylase (PRSx8) promoter to trace the spinal projections from the A5, A6, and A7 groups. Projections from all three groups travel through the spinal cord in both the lateral and ventral funiculi and in the dorsal surface of the dorsal horn, but A6 axons take predominantly the dorsal and ventral routes, whereas A5 axons take mainly a lateral and A7 axons a ventral route. The A6 group provides the densest innervation at all levels, and includes all parts of the spinal gray matter, but it is particularly dense in the dorsal horn. The A7 group provides the next most dense innervation, again including all parts of the spinal cord, but is it denser in the ventral horn. The A5 group supplies only sparse innervation to the dorsal and ventral horns and to the cervical and lumbosacral levels, but provides the densest innervation to the thoracic intermediolateral cell column, and in particular to the sympathetic preganglionic neurons. Thus, the pontine noradrenergic cell groups project in a roughly topographic and complementary fashion onto the spinal cord. The pattern of spinal projections observed suggests that the locus coeruleus might have the greatest effect on somatosensory transmission, the A7 group on motor function, and the A5 group on sympathetic function., (Copyright © 2011 Wiley Periodicals, Inc.)

Excessive secretion of triglyceride-rich very low-density lipoproteins (VLDL-TG) contributes to diabetic dyslipidemia. Earlier studies have indicated a possible role for the hypothalamus and autonomic nervous system in the regulation of VLDL-TG. In the current study, we investigated whether the autonomic nervous system and hypothalamic neuropeptide Y (NPY) release during fasting regulates hepatic VLDL-TG secretion. We report that, in fasted rats, an intact hypothalamic arcuate nucleus and hepatic sympathetic innervation are necessary to maintain VLDL-TG secretion. Furthermore, the hepatic sympathetic innervation is necessary to mediate the stimulatory effect of intracerebroventricular administration of NPY on VLDL-TG secretion. Since the intracerebroventricular administration of NPY increases VLDL-TG secretion by the liver without affecting lipolysis, its effect on lipid metabolism appears to be selective to the liver. Together, our findings indicate that the increased release of NPY during fasting stimulates the sympathetic nervous system to maintain VLDL-TG secretion at a postprandial level.