Synthesis Of Thyroxine Research Articles

Iodine: a scoping review for Nordic Nutrition Recommendations 2023.

Iodine is essential for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). As in many other parts of the world, insufficient iodine intake and consequently insufficient iodine status is a public health challenge in the Nordic and Baltic countries. The main dietary sources of iodine in the Nordic and Baltic countries include cow's milk, saltwater fish, eggs, products containing iodised salt, and iodised table salt. Only Denmark (DK), Finland (FI) and Sweden (SE) have implemented mandatory (DK) or voluntary (SE, FI) salt iodisation. New data, as well as recent studies from the Nordic and Baltic countries, strengthen the evidence that the main health challenges related to insufficient iodine intake remain thyroid function and thyroid disease, mental development, and cognitive function. Excessive intakes can also cause hyperthyroidism, autoimmune thyroid disease, and thyroid cancer.

Iodine Status of School Children Aged 6 to 12 Years in Rural and Urban Communities in Imo State, Southeast Nigeria

Background: Iodine is a trace element essential for the synthesis of thyroid hormones, thyroxine and triiodothyronine, which in turn play a crucial role in the growth and development of most organs, especially the brain. Iodine deficiency is therefore a serious medical condition fraught with dire consequences. Median urinary iodine concentrations of 100–199 mcg/L in children and adults, 150–249 mcg/L in pregnant women and >100 mcg/L in lactating women indicate iodine intakes are adequate. Objective: This study set to determine the Iodine status of children aged 6-12 years using MUIC in selected urban and rural communities of Imo state, South East Nigeria. Methods: It was cross sectional in nature and was carried out between July 2018 and January 2019. It involved 386 children aged 6-12 years who were selected from primary schools in both urban and rural local areas within the three educational zones of Imo State. Their urinary Iodine concentration was assayed using Ammonium persulphate technique of the Sandell- Koltkoff reaction method. Results: The median urine iodine concentration (MUIC) in the study participants ranged from 65 – 490 mcg/l with a median of 160mcg/l. While median urine iodine concentrations (MUIC) of 160 mcg/L and 156mcg/L, respectively, were observed in urban-dwelling and rural-dwelling school children respectively. Of the 386 participants, 30 had a MUIC of < 100\(\mu\)g/L therefore giving an iodine deficiency prevalence of 7.8%. They consisted of 14 participants from the urban areas and 16 from the rural areas. The difference between MUIC of children in rural and urban areas of Imo state was not statistically significant . (χ2 = 0.10: p = 0.75). Conclusion: While there was Iodine deficiency prevalence of 7.8%, there was no statistically significant difference between the Iodine status of pupils in urban and rural areas of Imo state.

SAT491 Development of Thyroidal Nodule in Congenital Hypothyroid Girl With Thyroid Peroxidase Gene Mutation

Abstract Disclosure: J. Lee: None. A. Oh: None. H. Han: None. Background: Reduced thyroxine synthesis in dyshormonogenesis induces increased thyrotropin (TSH) secretion through reduced negative feedback of thyroxine. Consequently, the affected patients are born with goiter or develop postnatal goiter, when L-thyroxine (LT4) supplementation is delayed. Cases of thyroid cancer have been reported in congenital hypothyroidism (CH) due to dyshormonogenesis, usually of follicular histology. Clinical Case: A 22-year lady has been taking LT4 since 8-years, under the diagnosis of goitrous CH. Her mother recalled neck swelling at newborn period. However, normal newborn screening test prevented neonatal goiter from further investigation. Initial test at 8-year of age revealed normal thyroid function without thyroid auto-antibodies, diffuse enlarged thyroid gland with increased uptake on 99mTc scan, and diffuse thyroid enlargement with heterogeneous echogenicity on ultrasonography (US). The goiter size waxed and waned according to the drug compliance. The highest TSH level (normal 0.17-4.05 μIU/mL) was 8.68 μIU/mL even without medication for 8 months by her own judgement. At 11.5-years, US found isoechoic solid nodule of 1.8 x 1.7 x 1.6 cm with peripheral halo in the inferior aspect of right thyroid, which was demonstrated to be benign follicular lesion favoring nodular hyperplasia on fine needle aspiration biopsy. With good drug compliance, the nodule size decreased to 1.1 x 0.9 cm at 18-years, and peripheral calcification appeared around the isoechoic solid nodule previously reported without change in size at 22-years. NGS panel for CH reported compound heterozygous variants in TPO gene. One pathogenic variant from asymptomatic father is c.2757del;p.(Met921Trpfs*53), the other likely pathogenic variant from asymptomatic mother is c.1580G>T;p.(Trp527Leu). Conclusion: This case is demonstrating development of thyroid nodule even with mild increased TSH level during LT4 medication in dyshormonogenic CH caused by TPO mutation. Regular follow-up and compliance to LT4 might be important to avoid thyroid tissue stimulation and possibly nodule formation by elevated TSH. Presentation Date: Saturday, June 17, 2023

Congenital Neck Mass: A Case Report

Congenital goiter is a very uncommon cause of neonatal neck mass. Administration of antithyroid drugs or radiation exposure during pregnancy may result in reduced synthesis of thyroxine and cause congenital goiter with or without thyroid dysfunction. We report a case of a full term, newborn male baby who had normal thyroid functions but was born with a neck swelling and no apparent abnormalities. Maternal investigations for thyroid function tests were found normal as well. Bangladesh J. Nuclear Med. 25(2): 121-124, 2022

Low-iodine diet before radioactive iodine therapy - to prescribe or not to prescribe

Iodine is the most important trace element in the human body. Its main function is to participate in the synthesis of thyroid hormones, thyroxine (T4) and triiodothyronine (T3). The main source of iodine for humans is food rich in this trace element. The iodine content in foods varies greatly. The main sources of iodine are seafood, iodized salt, seaweed, as well as dairy products and egg yolks. In addition, iodine is found in a number of drugs for external and internal use, dietary supplements, and in iodinated contrast agents.Low-iodine diet (less than 50 μg per day) is prescribed before radioactive iodine therapy (RAIT) for thyroid diseases, namely hyperthyroidism and differentiated thyroid cancer. Currently, there is no consensus on the clinical benefits of such a diet, especially in countries with iodine deficiency, such as Russia.The aim of this review is to assess the need for a low-iodine diet and its optimal duration, as well as to determine the clinical characteristics affecting the outcome of RAIT, based on data from recent studies.

Discovery of SYD5115, a novel orally active small molecule TSH-R antagonist

The thyrotropin receptor (TSH-R) regulates the thyroid gland and is normally activated by thyrotropin. In patients with Graves’ disease, TSH-R is also stimulated by stimulatory TSH-R autoantibodies leading to hyperthyroidism. In this paper, we describe the discovery of SYD5115 (67), a novel small molecule TSH-R antagonist with nanomolar potency. SYD5115 also blocks stimulating antibody induced synthesis of the thyroid hormone thyroxine (T4) in vivo, after a single oral dose. During optimization, several issues had to be addressed such as the low metabolic stability and the potential mutagenicity of our first series of compounds.

Genetic mutation profiles for children with congenital hypothyroidism in Fujian province

Objective: To explore the mutation characteristics of pathogenic genes in children with congenital hypothyroidism (CH) in Fujian. Methods: The clinical data of 116 unrelated CH children diagnosed in Fujian Provincial Maternal and Child Health Hospital from January 2019 to September 2020 were retrospectively analyzed, including 50 females and 66 males, with an average age of (20±10) days at diagnosis. Targeted exome sequencing technology was used to detect the mutation frequency, type and distribution characteristics of 29 genes related to thyroxine synthesis or thyroid development. Results: Three hundred and fifty-one potential functional mutations were detected in 105 of 116 CH patients, with a detection rate of 90.5% (105/116). DUOX2 (66.4%, 77/116) was the most frequent mutated gene, followed by TG (23.3%, 27/116), DUOXA1 (23.3%, 27/116), and TPO (12.1%, 14/116), which were all involved in thyroid hormone synthesis. Among the 105 children with CH, 70 cases carried double allele mutation. Except for 3 cases of thyroid dysplasia related genes (2 cases of TSHR and 1 case of GLIS3), the rest were also related to thyroid hormone synthesis. The gene with the highest carrier rate was DUOX2 (68.8%, 59/70), followed by TG (8.6%, 6/70), TPO (4.3%, 3/70), DUOXA2 (1.4%, 1/70) and DUOXA1 (1.4%, 1/70). Conclusion: The main mutated genes in CH children in Fujian are the key genes involved in thyroid hormone synthesis, such as DUOX2, TG and TPO.

Iodine status, impact of knowledge, and practice for adequate iodized salt utilization in house hold at North West Ethiopia.

Iodine is one of the crucial micronutrients required for the normal growth of humans from the fetal stage to adulthood through the synthesis of thyroxin (t3) and triiodothyronine (t4) hormones in the thyroid gland for regulation of metabolism, protein synthesis, and brain development. This study aimed to assess iodine status, the impact of knowledge and practice for adequate iodized salt utilization in household levels in North West Ethiopia. A population-based cross-sectional study was carried out using multistage sampling among 1398 residents from 28 December 2021 to 30 January 2022. A systematic random sampling technique was used to select the study participants. The collected data were entered into Epi-Data version 3.1 and then exported to STATA/R version 14 for further analysis. An adjusted odds ratio with 95% CI was used to declare statistical significance at p < 0.05. The overall mean (±SD) age of participants was 34.9 (±12.8) years. About 678 (48.5%) had 15-80 ppm, 23 (1.6%) had >80 ppm, 533 (38.13%) had 1.1 ppm to 14.9 ppm, and 147 (10.5) had no iodine in salt (0 ppm) after assessed by Rapid Test Kit. Only 48.5% of the sampled household had used adequate iodized salt with ≥15 ppm. The overall burden of goiter was estimated at 11.4/1000 population. Adequate iodized salt utilization was significantly associated with having formal education (adjusted odds ratio = 1.89: 95% confidence interval: 1.4, 2.6, p = 0.001), monthly income ≥5000 ETB/month (adjusted odds ratio = 1.99: 95% confidence interval: 1.5, 2.9, p = 0.001), and good knowledge score (adjusted odds ratio = 1.6: 95% confidence interval: 1.12, 2.6, p = 0.03) were predictors for proper iodized salt utilization. Coverage of adequately iodized salt was low and respondents' formal education, monthly income ≥5000 Ethiopian Birr/month, and good knowledge score were all significantly associated with proper iodized salt utilization. While the prevalence of goiter was not significantly identified as a public health problem as compared in the regions, however, in light of previous iodine deficiency in this region of Ethiopia, the salt iodization program should be done continually.

Dynamics of gut microbiota during pregnancy in women with TPOAb-positive subclinical hypothyroidism: a prospective cohort study

BackgroundAnti-thyroid peroxidase antibody (TPOAb) positivity can contribute to inhibit thyroxine synthesis. Gut microbiota can interact with metabolic or immune diseases. However, dynamics of gut microbiota from the second (T2) to the third trimester (T3) in women with TPOAb-positive/negative subclinical hypothyroidism (TPOAb+/TPOAb− SCH) have not been reported. Therefore, we aimed to evaluate whether gut microbiota can be potential therapeutic targets for managing TPOAb+ SCH.MethodsIn this single-center prospective cohort study, we observed gut microbiota dynamics by sequencing 16S rRNA from fecal samples collected in T2 (20–23+ 6 weeks) and T3 (28–33+ 6 weeks). TPOAb+/TPOAb− SCH were stratified depending on whether or not they used levothyroxine (LT4) during the pregnancy (LT4+/LT4−). Microbiome bioinformatics analyses were performed using QIIME2. The linear discriminant analysis effect size (LEfSe) was used for the quantitative analysis of biomarkers. Functional profiling was performed with PICRUSt2.ResultsDistinct gut microbiota dynamics from T2 to T3 were noted in the TPOAb− (n = 68) and TPOAb+ (n = 64) SCH groups. The TPOAb+ LT4− group was characterized by enriched bacterial amplicon sequence variants (ASVs) of Prevotella in T2 and Bacteria, Lachnospirales, Lachnospiraceae, Blautia, and Agathobacter in T3 and by depleted ASVs of Gammaproteobacteria, Enterobacterales, and Enterobacteriaceae in T2 and Actinobacteriota, Coriobacteriia, Actinobacteria, Coriobacteriales, Bifidobacteriales, Bifidobacteriaceae, Bifidobacterium, Dorea formicigenerans, and Bifidobacterium longum in T3. The TPOAb+ LT4+ group was characterized by enriched bacterial ASVs of Blautia, Streptococcus salivarius, and Bifidobacterium longum in T3 and by depleted ASVs of Bacteroidota, Bacteroidia, Bacteroidales, and Prevotella in T2 and Agathobacter in T3. Moreover, we identified 53 kinds of metabolic functions that were mainly involved in sugar, lipid, and amino acid metabolism.ConclusionsOur results indicated that low dynamics of gut microbiota composition and high dynamics of its metabolic function from T2 to T3 were associated with TPOAb+ SCH. We concluded that gut microbiota could be new targets for treatment of TPOAb+ SCH during pregnancy.Trial registrationThis study was retrospectively registered at the Chinese Clinical Trial Registry (registration number ChiCTR2100047175) on June 10, 2021.

Characteristics of the Intestinal Flora of TPOAb-Positive Women With Subclinical Hypothyroidism in the Second Trimester of Pregnancy: A Single-Center Prospective Cohort Study.

Pregnant women are at high risk of developing subclinical hypothyroidism (SCH), and anti-thyroid peroxidase antibody (TPOAb) positivity can further inhibit thyroxine synthesis. Emerging evidence indicates that intestinal flora can modulate metabolic and immune homeostasis. The characteristics of intestinal flora of TPOAb-positive women with SCH in their second trimester of pregnancy have not been reported. This single-center prospective observational cohort study investigated gut microbial composition and metabolic function using sequencing of the 16S rRNA gene in fecal samples from 75 TPOAb-positive women with SCH and 90 TPOAb-negative women with SCH during their second trimester of pregnancy. Women were treated with no levothyroxine (LT4), low-dose LT4 (≤50ug/d), or high-dose LT4 (>50ug/d). Taxonomic analysis showed Firmicutes and Bacteroidetes were the dominant phyla, followed by Actinobacteria and Proteobacteria. Faecalibacterium, Bacteroides, Prevotella 9, Bifidobacterium, Subdoligranulum, Lachnospira, and Megamonas were the predominant genera. The intestinal flora of TPOAb-positive women with SCH who received no LT4 was characterized by bacterial amplicon sequence variants (ASVs)/operational taxonomic units (OTUs) enriched in the genus Subdoligranulum. The intestinal flora of TPOAb-positive women with SCH who received low-dose or high-dose LT4 were characterized by bacterial ASVs/OTUs depleted of the species Ruminococcus sp._or Bacteroides massiliensis, respectively. A total of 19 metabolic functions of intestinal flora, mainly involving lipid and amino acid metabolism, discriminated TPOAb-positive and TPOAb-negative women with SCH. Our study suggests that there are differences in the composition and metabolic function of intestinal flora of TPOAb-positive and TPOAb-negative women with SCH treated with different doses of LT4 in the second trimester of pregnancy. The findings provide insight into intestinal flora as novel targets for the treatment of TPOAb-positive women with SCH during pregnancy.

The Study of Biological Activity of a New Thieno[2,3-D]-Pyrimidine-Based Neutral Antagonist of Thyrotropin Receptor.

The development of low-molecular-weight antagonists of thyroid-stimulating hormone (TSH) receptor is a promising trend in the treatment of autoimmune hyperthyroidism. We studied the effect of thieno[2,3-d]-pyrimidine derivative TPY1 on TSH-stimulated synthesis of thyroid hormones in the culture of FRTL-5 thyrocytes and on thyroliberin-stimulated production of thyroid hormones in rat blood. Preincubation of FRTL-5 cells with TPY1 suppressed the stimulatory effect of TSH on the synthesis of thyroxine and triiodothyronine. Intraperitoneal injection of TPY1 in a dose of 25 mg/kg reduced thyroliberin-stimulated levels of thyroid hormones in the blood and inhibited the expression of genes encoding thyroid peroxidase, thyroglobulin, and Na+/I- cotransporter responsible for thyroxine synthesis. In the absence of thyroliberin stimulation, TPY1 did not affect the levels of thyroid hormones and expression of thyroidogenesis genes. Thus, a new TPY1 antagonist of TSH receptor can be a prototype of a drug for the treatment of autoimmune hyperthyroidism.

Cryo-EM structure of native human thyroglobulin

The thyroglobulin (TG) protein is essential to thyroid hormone synthesis, plays a vital role in the regulation of metabolism, development and growth and serves as intraglandular iodine storage. Its architecture is conserved among vertebrates. Synthesis of triiodothyronine (T3) and thyroxine (T4) hormones depends on the conformation, iodination and post-translational modification of TG. Although structural information is available on recombinant and deglycosylated endogenous human thyroglobulin (hTG) from patients with goiters, the structure of native, fully glycosylated hTG remained unknown. Here, we present the cryo-electron microscopy structure of native and fully glycosylated hTG from healthy thyroid glands to 3.2 Å resolution. The structure provides detailed information on hormonogenic and glycosylation sites. We employ liquid chromatography–mass spectrometry (LC-MS) to validate these findings as well as other post-translational modifications and proteolytic cleavage sites. Our results offer insights into thyroid hormonogenesis of native hTG and provide a fundamental understanding of clinically relevant mutations.

ONTOGENETIC, BREED, AND SEASONAL FEATURES OF THE SYNTHESIS OF THYROXIN AND CORTISOL IN DOGS AND CATS

The article presents data on the breed and seasonal characteristics of the synthesis of thyroxine and cortisol in dogs of different breeds and cats that do not have a breed. It has been shown that the synthesis of thyroxine in dogs and cats depends on the breed, age and season. The functional activity of the thyroid gland in dogs decreases by 10-12, and in cats by 9-13 years of age. The highest level of thyroxine production throughout the entire research period belongs to the Griffon Petit-Brabancons. The synthesis of cortisol in dogs and cats is stable and does not undergo statistically significant changes. Seasonal dynamics of thyroxine is observed in dogs, but absent in cats. No sea-sonal dependence of cortisol synthesis has been reported in dogs and cats.

Influence of intranasally administered insulin on metabolic and hormonal parameters in adult male rats, impaired due to three-day fasting in the early postnatal period

Temporary cessation or restriction of breastfeeding can lead to metabolic disorders in adulthood. However, data on the effect of fasting in the early postnatal period on the functions of the endocrine system in adulthood are rare and contradictory. Approaches for the correction of metabolic and hormonal disorders caused by premature cessation of breastfeeding have not been developed yet. The aim of the work was to study the metabolic and hormonal parameters and changes in the hormonal status of the gonadal and thyroid systems in 10-month-old male rats with interruption of breastfeeding on days P19-P21, as well as to evaluate the restorative effect on them of four weeks of treatment with intranasal insulin (II) administered in the postnatal period (P28-P55) or in adulthood (P183-P210). Lactation interruption has been induced by treatment of lactating females with bromocriptine (10 mg/day/rat, P19-P21). Male rats with temporary cessation of breastfeeding developed characteristic signs of the metabolic syndrome (obesity, dyslipidemia, impaired glucose tolerance, hyperleptinemia), decreased levels of testosterone and thyroid hormones (fT4, tT3) and weakened the synthesis of testosterone and thyroxine, stimulated respectively by GnRH and thyroliberin. This was due to a decrease in the sensitivity of the testes to luteinizing hormone (LH) and the thyroid gland to thyroid-stimulating hormone (TSH). Treatment with II in early ontogenesis reduced body weight and fat, improved lipid profile, sensitivity to insulin, leptin, LH and TSH, restored the levels of testosterone and thyroid hormones and their stimulation by releasing factors. Treatment with II in adulthood normalized the levels of testosterone, thyroid hormones, their stimulation by releasing factors, but had a little effect on metabolic and hormonal parameters. The obtained data point to a wide range of metabolic and hormonal disorders in adult male rats with the "neonatal" model of metabolic syndrome and to the effectiveness of various strategies for their correction using long-term II treatment.

Proteomics and Organoid Culture Reveal the Underlying Pathogenesis of Hashimoto's Thyroiditis.

Hashimoto’s thyroiditis (HT) is an autoimmune disease, and its incidence continues to rise. Although scientists have studied this disease for many years and discovered the potential effects of various proteins in it, the specific pathogenesis is still not fully comprehended. To understand HT and translate this knowledge to clinical applications, we took the mass spectrometric analysis on thyroid tissue fine-needle puncture from HT patients and healthy people in an attempt to make a further understanding of the pathogenesis of HT. A total of 44 proteins with differential expression were identified in HT patients, and these proteins play vital roles in cell adhesion, cell metabolism, and thyroxine synthesis. Combining patient clinical trial sample information, we further compared the transient changes of gene expression regulation in HT and papillary thyroid carcinoma (PTC) samples. More importantly, we developed patient-derived HT and PTC organoids as a promising new preclinical model to verify these potential markers. Our data revealed a marked characteristic of HT organoid in upregulating chemokines that include C-C motif chemokine ligand (CCL) 2 and CCL3, which play a key role in the pathogenesis of HT. Overall, our research has enriched everyone’s understanding of the pathogenesis of HT and provides a certain reference for the treatment of the disease.

Aplasia cutis congenita in a newborn exposed to methimazole.

Untreated maternal hyperthyroidism during pregnancy can have severe consequences for both the mother and the fetus (5). The most commonly used drugs are synthetic antithyroid drugs such as methimazole (MT), carbimazole (CR), which is metabolized to MT, and propylthiouracil (PR). These drugs are practically equivalent in terms of activity, which consists in inhibiting the synthesis of thyroxine and 2,5,3 triiodothyronine by the thyroid. The choice of one drug over another basically depends on its side effects. Aplasia cutis is an embryogenetic defect that consists in the failure to close the skin and sometimes the underlying planes; it is in most cases an isolated defect but can be associated with other congenital malformations. Among the causal factors, which in most cases are not identifiable, drugs and genetic factors should be considered. Among the drugs benzodiazepines, low molecular weight heparins, leflunomide, and azathioprine were indicated; however, the drugs most frequently involved are CR and its metabolite MT (3). In a 2016 meta-analysis, the Authors (4) identified 61 cases of ACC induced by synthetic antithyroid drugs in the literature, of which 2 caused by PR and 59 by MT / CR administered in the first 10 weeks of pregnancy. This review showed that in 39.6% of cases ACC is associated with other malformations such as dysmorphism, anomalies of the fingers, persistence of urachus, choanal atresia, and encephalocele, giving rise to the concept of synthetic antithyroid drug embryopathy. The incidence of this embryopathy is less than 3% (4), much lower than other teratogens, for example retinoids. The responsibility of MT is supported by a study (2) that reported a higher incidence of ACC in pregnant women with normal functioning thyroid in a Spanish region where farm animals had been treated with MT to increase their body weight. The clear preponderance of cases induced by MT / CR would suggest preferring the PR in the first three months of pregnancy (6, 7), but there are still doubts about the choice of antithyroid drugs. In fact, although ACC and the malformations we have mentioned are more frequent with MT / CR, PR is also responsible for teratogenic effect, albeit of a different spectrum than MT / CR. Moeover, above all PR is sometimes responsible for liver disease so severe that it leads to liver transplantation (1). It is possible that genetic factors contribute to the pathogenesis of MT / CR embryopathy, as shown by the familiarity rate - 10% - (4), while in our series of 144 cases of ACC we found 8 family cases with an incidence of 5.5%, not unlike that of other Authors (3).

The structure of natively iodinated bovine thyroglobulin.

Thyroglobulin is a homodimeric glycoprotein that is essential for the generation of thyroid hormones in vertebrates. Upon secretion into the lumen of follicles in the thyroid gland, tyrosine residues within the protein become iodinated to produce monoiodotyrosine (MIT) and diiodotyrosine (DIT). A subset of evolutionarily conserved pairs of DIT (and MIT) residues can then engage in oxidative coupling reactions that yield either thyroxine (T4; produced from coupling of a DIT `acceptor' with a DIT `donor') or triiodothyronine (T3; produced from coupling of a DIT acceptor with an MIT donor). Although multiple iodotyrosine residues have been identified as potential donors and acceptors, the specificity and structural context of the pairings (i.e. which donor is paired with which acceptor) have remained unclear. Here, single-particle cryogenic electron microscopy (cryoEM) was used to generate a high-resolution reconstruction of bovine thyroglobulin (2.3 Å resolution in the core region and 2.6 Å overall), allowing the structural characterization of two post-reaction acceptor-donor pairs as well as tyrosine residues modified as MIT and DIT. A substantial spatial separation between donor Tyr149 and acceptor Tyr24 was observed, suggesting that for thyroxine synthesis significant peptide motion is required for coupling at the evolutionarily conserved thyroglobulin amino-terminus.

Characterization of Novel Human Immortalized Thyroid Follicular Epithelial Cell Lines.

Investigation of normal human thyroid function using in vitro culture systems is dependent on cells that recapitulate physiology of differentiated thyrocytes. Primary thyrocytes retain features of the native organ but have limited lifespan in culture. Immortalized thyrocytes offer an alternative if challenges maintaining phenotypic stability can be overcome to retain functional features of primary cells. CI-SCREEN immortalization technology was applied to normal human thyroid tissue to generate four cell line variants. The lines were characterized for transgene integration, biomarker expression, genomic stability, and proliferation rates. Thyroid Stimulating Hormone (TSH)-dependent morphology, thyroglobulin production, thyroxine hormone synthesis, and viability were assessed using conventional 2D monolayer and 3D microtissue culture formats in huThyrEC or h7H medium. Despite differential transgene profiles, the lines had similar biomarker expression patterns and proliferation rates. In 2D culture there was no thyroxine synthesis or changes in viability, but TSH-dependent thyroglobulin production was more significant for several lines in h7H than huThyrEC medium. Comparatively, in 3D microtissues, TSH-dependent thyroglobulin induction was greater for cell lines in h7H medium. Synthesis of thyroxine in one cell line was higher than background with TSH exposure, but not significantly different than control. Immortalization of primary human thyrocytes yielded transgenic lines of epithelial origin. When evaluated in 2D or 3D culture formats, h7H medium supported thyroglobulin production to a greater magnitude than huThyrEC medium. One cell line cultured in 3D microtissue format marginally recapitulated T4 synthesis under continuous TSH exposure. Select human thyroid cell lines exhibited morphological and functional features of primary thyrocytes and are a novel resource for in vitro disease modeling and toxicity testing that will enable reproducible culture models more representative of normal human thyroid function.

Thyroid hormone synthesis continues despite biallelic thyroglobulin mutation with cell death.

Complete absence of thyroid hormone is incompatible with life in vertebrates. Thyroxine is synthesized within thyroid follicles upon iodination of thyroglobulin conveyed from the endoplasmic reticulum (ER), via the Golgi complex, to the extracellular follicular lumen. In congenital hypothyroidism from biallelic thyroglobulin mutation, thyroglobulin is misfolded and cannot advance from the ER, eliminating its secretion and triggering ER stress. Nevertheless, untreated patients somehow continue to synthesize sufficient thyroxine to yield measurable serum levels that sustain life. Here, we demonstrate that TGW2346R/W2346R humans, TGcog/cog mice, and TGrdw/rdw rats exhibited no detectable ER export of thyroglobulin, accompanied by severe thyroidal ER stress and thyroid cell death. Nevertheless, thyroxine was synthesized, and brief treatment of TGrdw/rdw rats with antithyroid drug was lethal to the animals. When untreated, remarkably, thyroxine was synthesized on the mutant thyroglobulin protein, delivered via dead thyrocytes that decompose within the follicle lumen, where they were iodinated and cannibalized by surrounding live thyrocytes. As the animals continued to grow goiters, circulating thyroxine increased. However, when TGrdw/rdw rats age, they cannot sustain goiter growth that provided the dying cells needed for ongoing thyroxine synthesis, resulting in profound hypothyroidism. These results establish a disease mechanism wherein dead thyrocytes support organismal survival.

Growth performance, physiological parameters, and transcript levels of lipid metabolism-related genes in hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) fed diets containing Siberian ginseng.

In high-density aquaculture, fish health can suffer because of excessive feeding, which causes fatty liver disease. Siberian ginseng (Acanthopanax senticosus) has been used as a feed additive to promote animal growth, immunity, and lipid metabolism. In this study, we explored the effects of A. senticosus on the physiology of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂). A control group and five groups fed diets containing A. senticosus (0.5, 1, 2, 4, and 8 g A. senticosus/kg feed) were established and maintained for 8 weeks. Dietary supplementation with A. senticosus at 4 g/kg promoted growth of the hybrid yellow catfish. Serum total cholesterol (TC) and triacylglycerol (TG) levels at 2 g/kg A. senticosus (TC: 1.31 mmol/L; TG: 1.08 mmol/L) were significantly lower than in the control group (TC: 1.51 mmol/L; TG: 1.41 mmol/L), and 4 g/kg A. senticosus (17.20 μmol/g tissue) reduced the liver TG level compared with the control group (21.36 μmol/g tissue) (P <0.05). Comparative transcriptomic analysis of liver tissue between the control group and the group showing optimum growth (4 g/kg A. senticosus) revealed 820 differentially expressed genes and 44 significantly enriched pathways, especially lipid metabolism pathways such as unsaturated fatty acid and fatty acid metabolism. The transcript levels of five lipid metabolism-related genes were determined by quantitative real-time PCR. The results showed that 2-4 g/kg A. senticosus supplementation reduced the FADS2, ELOVL2, CYP24a, and PLPP3 transcript levels and 4 g/kg A. senticosus increased the DIO2 transcript level (P <0.05), leading to altered synthesis of TG and thyroxine and reduced fat deposition in the liver. Our results show that dietary A. senticosus affects the regulation of fat metabolism and promotes the growth of hybrid yellow catfish. A. senticosus is a healthy feed additive, and the appropriate dietary supplementation rate is 2-4 g/kg.