Hypothalamic-pituitary-thyroid Axis Research Articles

Adipocyte signaling affects thyroid-specific gene expression via down-regulation of TTF-2/FOXE1.

Obesity affects thyroid gland function. Hypothyroidism, thyroid nodules, goiter, and thyroid cancer are more frequent in patients with higher body mass index values. Although these data are supported by many clinical and epidemiological studies, very scarce is our knowledge at the molecular level. In this study, we present the first experimental evidence that adipocyte signaling down-regulates the expression of thyroid-specific transcription factor 2 (TTF-2/FOXE1). It plays a crucial role in thyroid development and thyroid homeostasis and it is strictly connected to thyroid cancer as well. We provide in vivo and in vitro evidence that inhibition of TTF-2/FOXE1 gene expression is mediated by adipocyte signaling.

Ramification of thyroid dysfunction in progression of jaundice in preterm infants among rural population of Prayagraj, India

In infants, overall growth is a continuous process and it depends upon the right care, nutrition, and metabolism. Metabolism is regulated by many factors and, the endocrine system is one of them. The thyroid gland is one of the important glands in the endocrine system and dysfunction of this gland may lead to many metabolic disorders. Prevalence of Jaundiceis the most common metabolic disorder in preterm infants (32-34 gestational weeks) and the root cause of many diseases. Keeping this fact, this study is designed to draw the relation between thyroid dysfunction in preterm infants and the prevalence of jaundice. A total of 200 preterm infants were randomly selected for the study as per consent given by their parents and their treating doctors. Out of these 116 infants were diagnosed with total bilirubin levels of more than 1mg/dl and selected as respondents for the research work. 3 ml venous blood samples were collected within 42-78 hrs after their birth from Infants having jaundice and estimated for triiodothyronine (T3), tetraidothyronine (T4), and thyroid stimulating hormones (TSH)and compared them with full term (34-36 gestational weeks)infants. The study reveals that 58% of preterm infants were high serum bilirubin and out of which 72% were suffering from congenital hypothyroidism as compared to fullterm infants. It may be because of the gestational period of 36 weeks have lower chances of thyroid dysfunction due to their completely matured hypothalamic pituitary thyroid axis (HPT). After statistical analysis of the data obtained, it is concluded that high serum total bilirubin is associated with thyroid gland dysfunction in newborn preterm infants and it is recommended that all newborn preterm infants must be screened early for thyroid dysfunction.

The role of supporting and disruptive mechanisms of FT3 homeostasis in regulating the hypothalamic-pituitary-thyroid axis.

Thyroid hormones are controlled by the hypothalamic-pituitary-thyroid (HPT) axis through a complex network of regulatory loops, involving the hormones TRH, TSH, FT4, and FT3. The relationship between TSH and FT4 is widely used for diagnosing thyroid diseases. However, mechanisms of FT3 homeostasis are not well understood. We used mathematical modelling to further examine mechanisms that exist in the HPT axis regulation for protecting circulating FT3 levels. A mathematical model consisting of a system of four coupled first-order parameterized non-linear ordinary differential equations (ODEs) was developed, accounting for the interdependencies between the hormones in the HPT axis regulation. While TRH and TSH feed forward to the pituitary and thyroid, respectively, FT4 and FT3 feed backward to both the pituitary and hypothalamus. Stable equilibrium solutions of the ODE system express homeostasis for a particular variable, such as FT3, if this variable stays in a narrow range while certain other parameter(s) and system variable(s) may vary substantially. The model predicts that (1) TSH-feedforward protects FT3 levels if the FT4 production rate declines and (2) combined negative feedback by FT4 and FT3 on both TSH and TRH production rates keeps FT3 levels insensitive to moderate changes in FT4 production rates and FT4 levels. The optimum FT4 and FT3 feedback and TRH and TSH-feedforward ranges that preserve FT3 homeostasis were found by numerical continuation analysis. Model predictions were in close agreement with clinical studies and individual patient examples of hypothyroidism and hyperthyroidism. These findings further extend the concept of HPT axis regulation beyond TSH and FT4 to integrate the more active sister hormone FT3 and mechanisms of FT3 homeostasis. Disruption of homeostatic mechanisms leads to disease. This provides a perspective for novel testable concepts in clinical studies to therapeutically target the disruptive mechanisms.

Lack of L-type amino acid transporter 2 in murine thyroid tissue induces autophagy

Proteolytic cleavage of thyroglobulin (Tg) for thyroid hormone (TH) liberation is followed by TH release from thyroid follicles into the circulation, enabled by TH transporters. The existence of a functional link between Tg-processing cathepsin proteases and TH transporters has been shown to be independent of the hypothalamus-pituitary-thyroid axis. Thus, lack of cathepsin K, combined with genetic defects in the TH transporters Mct8 and Mct10, that is the Ctsk-/-/Mct8-/y/Mct10-/- genotype, results in persistent Tg proteolysis due to autophagy induction. Because amino acid transport by L-type amino acid transporter 2 (Lat2) has been described to regulate autophagy, we asked whether Lat2 availability is affected in Ctsk-/-/Mct8-/y/Mct10-/- thyroid glands. Our data revealed that while mRNA amounts and subcellular localization of Lat2 remained unaltered in thyroid tissue of Ctsk-/-/Mct8-/y/Mct10-/- mice in comparison to WT controls, the Lat2 protein amounts were significantly reduced. These data suggest a direct link between Lat2 function and autophagy induction in Ctsk-/-/Mct8-/y/Mct10-/- mice. Indeed, thyroid tissue of Lat2-/- mice showed enhanced endo-lysosomal cathepsin activities, increased autophagosome formation, and enhanced autophagic flux. Collectively, these results suggest a mechanistic link between insufficient Lat2 protein function and autophagy induction in the thyroid gland of male mice.

ОСОБЕННОСТИ ЭКСПРЕССИИ ФАКТОРОВ ПРОЛИФЕРАЦИИТИРОЦИТОВ ПРИ ХРОНИЧЕСКОЙ ЭНДОГЕННОЙ ИНТОКСИКАЦИИ

Currently, thyroid diseases are one of the key problems of modern endocrinology, where the restoration of the thyroid parenchyma after exposure to negative factors and the direction of proliferative processes remain relevant. We conducted a study of the material obtained from deceased individuals as part of a standard pathoanatomical study, followed by animmunohistochemical staining of the expression of nonspecific markers of proliferative activity.It was found that the proliferative activity of thyrocytes increases from the upper to the lower part of the thyroid lobe. Also, in a comparative analysis of the central and peripheral zones, it was found that in normal conditions, the source of neoplasm of thyrocytes is located in the central zone, while when the tissue is involved in the pathological process, an increase in the expression of Ki-67 and PHH3 occursin the peripheral zone.The mitotic activity of cells can lead to the development of thyropathy and disruption of thyroid homeostasis,which serves as the basis for screening the thyroid gland in patients with chronic endogenous intoxication syndrome.

Acute exposure to microcystins affects hypothalamic-pituitary axes of male rats

Microcystins (MCs) produced by some cyanobacteria can cause toxicity in animals and humans. In recent years, growing evidence suggests that MCs can act as endocrine disruptors. This research systematically investigated effects of microcystin-LR (MC-LR) on endocrine organs, biosynthesis of hormones and positive/negative feedback of the endocrine system in rats. Male, Sprague-Dawley rats were acutely administrated MC-LR by a single intraperitoneal injection at doses of 45, 67.5 or 90 μg MC-LR/kg body mass (bm), and then euthanized 24 h after exposure. In exposed rats, histological damage of hypothalamus, pituitary, adrenal, testis and thyroid were observed. Serum concentrations of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and corticosterone (CORT), expressions of genes and proteins for biosynthesis of hormones were lesser, which indicated an overall suppression of the hypothalamus-pituitary-adrenal (HPA) axis. Along the hypothalamus-pituitary-gonadal (HPG) axis, lesser concentrations of gonadotropin-releasing hormone (GnRH) and testosterone (T), but greater concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E2) were observed. Except for greater transcription of cyp19a1 in testes, transcriptions of genes and proteins for T and E2 biosynthesis along the HPG axis were lesser. As for the hypothalamus-pituitary-thyroid (HPT) axis, after MCs treatment, greater concentrations of thyroid-stimulating hormone (TSH), but lesser concentrations of free tri-iodothyronine (fT3) were observed in serum. Concentrations of free tetra-iodothyronine (fT4) were greater in rats dosed with 45 μg MCs/kg, bm, but lesser in rats dosed with 67.5 or 90 μg MCs/kg, bm. Transcripts of genes for biosynthesis of hormones and receptors along the HPT axis and expressions of proteins for biosynthesis of tetra-iodothyronine (T4) and tri-iodothyronine (T3) in thyroid were significantly altered. Cross-talk among the HPA, HPG and HPT axes probably occurred. It was concluded that MCs caused an imbalance of positive and negative feedback of hormonal regulatory axes, blocked biosynthesis of key hormones and exhibited endocrine-disrupting effects.

Cadmium exposure promotes thyroid pyroptosis and endocrine dysfunction by inhibiting Nrf2/Keap1 signaling

Cadmium (Cd) is a ubiquitous toxic metal and environmental pollutant. Increasing studies have shown that Cd exposure increases the incidence of various endocrine system diseases, including thyrotoxicity reflected by thyroid structural damage and endocrine toxicity. However, the observed outcomes are complex and conflicting, leading to the mechanism of Cd-induced thyrotoxicity remaining obscure. In this study, 4-week-old male C57BL/6 mice were given 2 or 7 mg/kg Cadmium Chloride (CdCl2) intragastrically for 4 and 8 weeks, and the Cd-mediated thyrotoxicity was evaluated by determining alterations in thyroid structure and endocrine function, and alterations of oxidant stress, apoptosis, and pyroptosis. Our data showed that Cd exposure could reduce body weight and induce thyrotoxicity by impairing thyroid follicular morphology and endocrine function, accompanied by elevated oxidative stress and apoptosis, macrophage infiltration, and inflammatory cytokine secretion. Importantly, Cd significantly promoted thyroid follicular cell pyroptosis by increasing Nlrp3, Asc, Caspase-1, Gsdmd, IL-1β, and IL-18 expression. Mechanistical analysis suggested that Cd treatment could inhibit antioxidant pathway by downregulating antioxidant response protein, Nrf2, and upregulating its negative feedback regulator, Keap1. Collectively, our in vivo findings suggest that Cd exposure could facilitate thyroid follicular cell pyroptosis by inhibiting Nrf2/Keap1 signaling, thereby disrupting thyroid tissue structure and endocrine function, which offers novel insights into the Cd-mediated detrimental consequences on thyroid homeostasis.

Mathematical modeling and simulation of thyroid homeostasis: Implications for the Allan-Herndon-Dudley syndrome.

A mathematical model of the pituitary-thyroid feedback loop is extended to deepen the understanding of the Allan-Herndon-Dudley syndrome (AHDS). The AHDS is characterized by unusual thyroid hormone concentrations and a mutation in the SLC16A2 gene encoding for the monocarboxylate transporter 8 (MCT8). This mutation leads to a loss of thyroid hormone transport activity. One hypothesis to explain the unusual hormone concentrations of AHDS patients is that due to the loss of thyroid hormone transport activity, thyroxine (T 4) is partially retained in thyroid cells. This hypothesis is investigated by extending a mathematical model of the pituitary-thyroid feedback loop to include a model of the net effects of membrane transporters such that the thyroid hormone transport activity can be considered. A nonlinear modeling approach based on the Michaelis-Menten kinetics and its linear approximation are employed to consider the membrane transporters. The unknown parameters are estimated through a constrained parameter optimization. In dynamic simulations, damaged membrane transporters result in a retention of T 4 in thyroid cells and ultimately in the unusual hormone concentrations of AHDS patients. The Michaelis-Menten modeling approach and its linear approximation lead to similar results. The results support the hypothesis that a partial retention of T 4 in thyroid cells represents one mechanism responsible for the unusual hormone concentrations of AHDS patients. Moreover, our results suggest that the retention of T 4 in thyroid cells could be the main reason for the unusual hormone concentrations of AHDS patients.

Copper and Zinc Treatments Alter the Thyroid Endocrine System in Zebrafish Embryos/Larvae.

Copper (Cu2+) and zinc (Zn2+) are two kinds of heavy metals essential to living organisms. Cu2+ and Zn2+ at excessive concentrations can cause adverse effects on animals, but little is known about the thyroid-disrupting effects of these metals in fish, especially in the early developmental transition stage from embryos to larvae. Wild-type zebrafish embryos were used to expose to Cu2+ (0, 1.5, 15, and 150 μg/L) and Zn2+ (0, 20, 200, and 2000 μg/L) for 120 h. Thyroid hormone contents and transcriptional changes of the genes connected with the hypothalamic-pituitary-thyroid (HPT) axis were measured. Results showed that zebrafish embryos/larvae malformation rates were significantly increased in the Cu2+ and Zn2+ groups. Remarkably elevated thyroxine (T4) concentrations and reduced triiodothyronine (T3) concentrations were observed in Cu2+ and Zn2+ exposure fish. And the expression patterns of genes connected with the HPT axis were changed after Cu2+ and Zn2+ treatment. Based on principal component analysis (PCA) results, Zn2+ caused significant effects on the thyroid endocrine system at 200 μg/L, while Cu2+ resulted in thyroid disruption as low as 1.5 μg/L. In short, our study demonstrated that exposure to Cu2+ and Zn2+ induced developmental toxicity and thyroid disruption to zebrafish embryos/larvae.

Thyroid Hormone Transporters in Pregnancy and Fetal Development

Thyroid hormone is essential for fetal (brain) development. Plasma membrane transporters control the intracellular bioavailability of thyroid hormone. In the past few decades, 15 human thyroid hormone transporters have been identified, and among them, mutations in monocarboxylate transporter (MCT)8 and organic anion transporting peptide (OATP)1C1 are associated with clinical phenotypes. Different animal and human models have been employed to unravel the (patho)-physiological role of thyroid hormone transporters. However, most studies on thyroid hormone transporters focus on postnatal development. This review summarizes the research on the thyroid hormone transporters in pregnancy and fetal development, including their substrate preference, expression and tissue distribution, and physiological and pathophysiological role in thyroid homeostasis and clinical disorders. As the fetus depends on the maternal thyroid hormone supply, especially during the first half of pregnancy, the review also elaborates on thyroid hormone transport across the human placental barrier. Future studies may reveal how the different transporters contribute to thyroid hormone homeostasis in fetal tissues to properly facilitate development. Employing state-of-the-art human models will enable a better understanding of their roles in thyroid hormone homeostasis.

RELEVANCE OF DEIODINASE ENZYMES IN HEART TRANSPLANT – PRELIMINARY STUDY

<h3>Objective</h3> The hypothalamic-pituitary-thyroid (HPT) axis plays a critical role in the regulation of metabolism throughout the neuroendocrine system. The low triiodothyronine (T3) syndrome appears in several critical conditions that require intensive care, such as heart transplant (HTx) which is the gold standard therapeutic intervention for patients with end-stage chronic heart failure. Low T3 syndrome is hallmarked by reduced serum thyroid hormone (TH) levels; missing or reduced response of the HPT axis; and tissue-specific changes of the expression of deiodinase enzymes, catalyzing TH hormone metabolism. Current research aimed to study the interaction between cardiac deiodinase expression and adverse outcomes after HTx. <h3>Design and Method</h3> This prospective, single center study was approved by the IRB (65/2017). Patients who underwent heart transplant at the Heart and Vascular Centre of Semmelweis University between 2012 and 2020 were enrolled in current research. Demographic and perioperative laboratory parameters, thyroid disorders and adverse outcomes were recorded in our database. Expression of the TH activating Deiodinase 2 (DIO2) and TH inactivating Deiodinase 3 (DIO3) enzymes was measured with TaqMan qPCR in cardiac tissue samples and were normalized to hypoxanthine phosphoribosyl transferase (HPRT). cDNA content of samples was measured by Qubit, and 30 ng of cDNA was used in each qPCR reaction. Descriptive statistics, Spearman's correlation and Mann-Whitney U test were applied for the statistical analysis. <h3>Results</h3> The final analysis was performed on 294 patients, of whom 77 were female (26.2%) and 217 were male (73.8%). The median age of donors was 54 years (IQR 25-75: 45-59), while the median follow-up was 1223 days (IQR 25-75: 399-1990). Prior to surgery, 53 patients (18.0%) had subclinical serum TH levels, of whom 37 (12.6%) were on TH replacement. Patients required postoperative mechanical circulation support (n: 50; 17.0%), underwent rejection (n: 47; 16.0%), and reoperation (n: 34; 11.6%) had significantly lower DIO2 and DIO3 expression (respectively p: 0.016; 0.001; 0.044). However, cardiac DIO2 expression was significantly higher in patients with postoperative acute kidney injury (n: 75; 25.5%) (p: 0.033). <h3>Conclusions</h3> Our results emphasize the importance of cardiac TH metabolism during the perioperative period of heart transplant as DIO2 and DIO3 enzymes expressions may predict the occurrence of some complications after heart transplant. Unidirectional changes of the TH activating and inactivating deiodinases during the perioperative period of heart transplant do not suggest a coordinated cellular effort to shift TH signaling in the cardiac tissue except in patients with postoperative acute kidney injury.for observation.

Changes in pathophysiology of tumor growth and functional activity of the hypothalamic-pituitary-thyroid axis in rats of both sexes with the development of Guerin's carcinoma on the background of hypothyroidism

Purpose of the study. Was to analyze changes in pathophysiological parameters of transplantable tumor growth and functional activity of the hypothalamic-pituitary-thyroid axis (HPT) in rats of both sexes with Guerin's carcinoma in presence of induced hypothyroidism.Materials and methods. The dynamics of tumor growth and average life span were assessed in white alley rats of both sexes with Guerins carcinoma transplanted subcutaneously on the background of thyreostatic induced hypothyroidism. RIA (radioimmune assay) and ELISA (enzyme-linked immunosorbent assay) methods were used to determine levels of thyroid hormones in the blood and thyroid and tumor samples, and thyrotropin-releasing hormone (TRH) in the hypothalamus, as well as TSH in the pituitary gland. The experiment included 2 control groups: animals of both sexes with hypothyroidism (control group 1, number of rodents = 15) and animals with subcutaneously transplanted Guerin's carcinoma without hypothyroidism (control group 2, number of rodents = 15).Results. Hypothyroidism in female rats inhibited the tumor growth and improved median survival by 1.8 times (p &lt; 0.05). No such effect was observed in males of the main group. Levels of regulatory peptides of the hypothalamus and pituitary gland declined in females of the main group, while levels of TSH in the pituitary gland in males increased, despite a decrease in TRH by 3.5 times. TSH levels decreased in the thyroid and blood of animals of both sexes; however, a decrease in levels of total and free circulating thyroxine (T4 and FT4) by 1.6 times and by 2.8 times was found in the tumor, respectively; samples of Guerin's carcinoma in males of the main group remained saturated with T4 and FT4 as well as and in control group rodents without induced hypothyroidism.Conclusions. The gender differences in the pathophysiology of the tumor development in presence of hypothyroidism, as well as changes in the functional activity of the HPT axis in experimental animals revealed in this study can probably be associated with sex hormones, which requires further study of the hypothalamic-pituitary-gonadal (HPG) axis and steroid hormones in peripheral organs and tumor samples.

The Hypothalamic-Pituitary-Thyroid Axis Equivalent in Normal and Cancerous Oral Tissues: A Scoping Review.

The hypothalamic-pituitary-thyroid (HPT) axis is crucial in regulating thyroid hormone levels that contribute to the development and homeostasis of the human body. Current literature supports the presence of a local HPT axis equivalent within keratinocytes of the skin, with thyroid hormones playing a potential role in cancer progression. However, this remains to be seen within oral tissue cells. An electronic search of Scopus and PubMed/Medline databases was conducted to identify all original publications that reported data on the production or effects of HPT axis components in normal or malignant cells of the oral cavity. The search identified 221 studies, of which 14 were eligible. Eight studies were retrospective analyses of clinical samples, one study involved both in vivo and in vitro experiments, and the remaining five studies were conducted in vitro using cell lines. The search identified evidence of effects of HPT components on oral cancer cells. However, there were limited data for the production of HPT axis components by oral tissues. We conclude that a possible role of the local HPT axis equivalent in the oral mucosa may not be established at present. The gaps in knowledge identified in this scoping review, particularly regarding the production of HPT components by oral tissues, warrant further investigation.

Re-interpretation of the mechanism of type 2 diabetes mellitus based on a framework of psychosomatic medicine: a real-world study

ObjectiveUsing bipolar disorder (BD) as a control, we explored the possible developmental process of impaired glucose metabolism rhythm.MethodsIn total, 441 subjects (77, 162, 134, 54, and 14 in the pre-diabetes [pre-DM], DM, BD, BD + pre-DM, and BD + DM groups, respectively) and 160 controls were included. All subjects were assessed using the Neuroticism Extraversion Openness Five-Factor Inventory (NEO-FFI). The hypothalamic-pituitary-adrenal (HPA) and hypothalamic–pituitary–thyroid (HPT) axes were measured.ResultsCluster analysis showed that the BD, BD + DM, and DM groups were classified as the ‘disease group, the BD + pre-DM group as the ‘mixed period group’, and the pre-DM group as the ‘pre-disease group’. The conscientiousness factor scores of the NEO-FFI in the ‘disease group’ were higher than the norm but lower than the norm in the ‘pre-disease group’. The scores of neurotic factors in the ‘pre-disease’ and ‘mixed period’ groups were both significantly higher than that in the ‘disease group’ (corrected p < 0.001). The incidences of the abnormal HPA axis decreased gradually from the ‘pre-disease group’ to the ‘mixed period group’ then to the ‘disease group’, while those of the HPT axis slightly increased at first and then significantly decreased. The overall prediction rate of the multiple logistic regression model was 92.7%.ConclusionThis study suggests that progression of pre-diabetes to DM is a continuous process from local abnormalities to rhythm disorder of glucose metabolism. This understanding can be applied to the whole course management and early intervention of DM and to the future development of optimised treatment based on rhythm regulation.Trial registrationClinical trial registration number: ChiCTR1800019064. Name of trial registration: Identify and the optimization of treatment for non-infectious chronic diseases under the “stress-dysrhythmia” theory hypothesis (Registration date: 24/10/2018). The full trial protocol can be accessed at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/).

Higher central set point of thyroid homeostasis in drug-naïve patients affected by first episode schizophrenia

AimTo assess central set point of thyroid homeostasis in drug-naïve patients affected by first episode schizophrenia. MethodsThis cross-sectional study was conducted in Xinxiang city, Henan, China. Patients were drug-naïve patients affected by first episode schizophrenia, aged 14–50 years old and admitted to the “Second Affiliated Hospital of Xinxiang Medical University” from January 2018 to December 2018. Controls were healthy individuals who underwent annual health from Xinxiang city, a community population of the same age and time period. The parameters of “central set point of thyroid homeostasis” were measured by “thyroid-stimulating hormone (TSH) index” and “thyroid feedback quantile-based index”. The parameters were compared between schizophrenia patients and controls. Linear regression models adjusted by age and sex were used to assess the association of schizophrenia with the parameters. ResultsA total of 235 patients and 121 controls were included in this study. Patients affected by schizophrenia had significantly higher prevalence of hyperthyroxinemia and levels of free T4, “TSH index”, and “thyroid feedback quantile-based index” than controls. After adjusting age and sex, schizophrenia was independently associated with the higher level of “TSH index” (adjusted β 0.33, 95 % confidence interval 0.17, 0.49) and “thyroid feedback quantile-based index” (adjusted β 0.21, 95 % confidence interval 0.12, 0.30). The results with age and sex matched patients and controls were similar to those observed in the overall study population. ConclusionHigher central set point may be the underlying mechanism of thyroid allostatic load in drug-naïve patients affected first episode schizophrenia.

ODP297 Analysis of the responsible region of TRH in the hypothalamus-pituitary-thyroid axis using the Paraventricular nucleus-specific TRH deficient mice.

Abstract Objectives Thyrotropin-releasing hormone (TRH) was the first hypothalamic hormone isolated that stimulates pituitary thyroid-stimulating hormone (TSH) secretion. TRH was later found to be distributed throughout the brain, gastrointestinal tract and pancreaticβ-cells. We previously reported the TRH null mice (conventional TRHKO) which exhibit characteristic tertiary hypothyroidism, however the responsible regionfor the hypothalamic-pituitary-thyroid (HPT) axis remained obscure because of the broad expression of TRH in hypothalamus. Previous studies suggested that TRH in the hypothalamic paraventricular nucleus (PVN) was secreted through the median eminence (ME), however it was not directly demonstrated . To determine the region functionally responsible for the HPT axis, we established and analyzed PVN-specific TRH knock-out (PVN-TRHKO) mice. Methods For the targeting vector, a Neo-loxP cassette was inserted into the 3′-UTR of the Trh gene in ES cells. Another loxP site was placed at intron 1. After we obtained the Trh +/lox [neo+] founder mice, we crossed them with the CAG-FLPe transgenic mice to remove the Neo cassette. The offspring were backcrossed to wild-type mice, producing conditional knock-out mice without the Neo cassette, which were labeled as Trh +/lox . We crossed Trh +/lox with transgenic mice expressing Single-minded homolog (Sim)1-Cre recombinase and created PVN-TRHKO mice (Sim1-Cre; Trh lox/lox mice). We confirmed that most Sim1 was expressed in the PVN using Sim1-Cre/tdTomato mice. We performed the following experiments using PVN-TRHKO andTrh lox/lox mice as control (Ct). 1) immunostaining of TRH using antibody forproTRH in cerebrum, 2)qPCR analysis detecting the expression of preproTrh mRNA in hypothalamic PVN, 3) measurement of the level of serum free-T4 and TSH, 4)qPCR analysis detecting theexpression levels of Tshβ, Prl, Cga, Gh, Pomc and Lhβ gene mRNAin the anterior pituitary and 5)immunohistochemical analysis with antibodies for TSHβ and Prolactin in anterior pituitary. Results In the PVN-TRHKO mice, 1) ProTRH-immunopositive cells were lost in the area of PVN and ME, whereas proTRH detected in the medial preoptic area(MPA) and medial preoptic nucleus (MPO) in the hypothalamus.2)The expression level of proTRHmRNA was decreased to7.7% compared with Ct.3) Free-T4 levels decreased to 50% and the TSH levels increased to 170% of those in Ct. 4) TshβmRNA levels were decreased by 65% and thePrlmRNA levels were reduced to 55% of those in Ct. 5) The number of TSH-positive andProlactin-positive cells in the pituitary significantly decreased to 50% and 60% of those in Ct. Conclusions PVN-TRHKO mice exhibited tertiary hypothyroidism similar to conventional TRHKO. The pathway of TRH neuron from PVN to ME was lost in the PVN-TRHKO mice. These findings are conclusive evidence that the TRH neuron in the PVN is the center of the HPT axis. Presentation: No date and time listed

Comparison of developmental toxicity induced by PFOA, HFPO-DA, and HFPO-TA in zebrafish embryos

Hexafluoropropylene oxide dimer acids (HFPO-DA) and hexafluoropropylene oxide trimer acids (HFPO-TA) are alternatives to perfluorooctanoic acid (PFOA). However, little information on the comparison of their toxicities is available. Here, zebrafish embryos were exposed to PFOA, HFPO-DA, and HFPO-TA with exposure concentrations of 5 and 500 μg/L. Behavioral abnormal, enzyme activities and gene expression profiles in zebrafish embryos were determined. Results showed that exposure to PFOA and its alternatives increased heart rates and inhibited locomotor activity of zebrafish embryos. Further, their exposures changed the enzyme activities (acetylcholinesterase and oxidative stress-related enzymes), ATP content, and expressions of genes related to hypothalamic–pituitary–thyroid (HPT) axis, apoptosis, and lipid metabolism. Comparison analyses found that PFOA, HFPO-TA, and HFPO-DA exposures induced different effects on the embryonic development of zebrafish, which indicates the different modes of action. The HFPO-DA exposure induced specific effects on the disorder of lipid metabolism, HPT axis, and neurodevelopment. The HFPO-TA exposure also induced different effects from the PFOA exposure, which focused on lipid metabolism. The current data shows that the HFPO-DA and HFPO-TA might not be safe alternatives to PFOA. This study provides a new understanding of the biological hazards of PFOA alternatives in aquatic organisms, which can guide their usage.

Thyroid hormones: Metabolism and transportation in the fetoplacental unit.

The thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3), are of vital importance for fetal development. The concentration of THs in fetal circulation varies throughout gestation and differs from the concentration in the maternal serum, indicating the presence of maternal-fetal thyroid homeostasis regulatory mechanisms in the placenta. The passage of THs from maternal circulation to fetal circulation is modulated by plasma membrane transporters, enzymes, and carrier proteins. Monocarboxylate transporter 8, iodothyronine deiodinases (DIO2 and DIO3), and transthyretin are especially involved in this maternal-fetal thyroid modulation, shown by a greater expression in the placenta. THs also play a role in placental development and as expected, abnormal variations in TH levels are associated with pregnancy complications and can result in damage to the fetus. Although new evidence regarding TH regulation during pregnancy and its effects in the mother, placenta, and fetus has been published, many aspects of these interactions are still poorly understood. The objective of this review is to provide an evidence-based update, drawn from current data, on the metabolism and transport of THs in the placenta and their vital role in the maternal-fetal relationship.

Gluten-free diet attenuates the impact of exogenous vitamin D on thyroid autoimmunity in young women with autoimmune thyroiditis: a pilot study

Although both exogenous vitamin D and a gluten-free diet were found to reduce thyroid antibody titers, no study investigated interactions between gluten intake and vitamin D status in patients with autoimmune thyroid disorders. The aim of the present study was to assess whether the gluten-free diet determines the effect of vitamin D treatment on thyroid autoimmunity and thyroid function in young women with autoimmune (Hashimoto’s) thyroiditis. The study compared two groups of euthyroid premenopausal women with this disorder, matched for thyroid antibody titers: 31 women with non-celiac gluten sensitivity complying for at least 12 months with the gluten-free diet and 31 unaffected sisters of women with non-celiac gluten sensitivity remaining without any dietary intervention. Plasma titers of thyroid peroxidase and thyroglobulin antibodies, as well as plasma concentrations of thyrotropin, free thyroid hormones, prolactin, 25-hydroxyvitamin D and high-sensitive C-reactive protein were measured at entry and after a six-month follow-up. Moreover, at both time points, the structure parameters of thyroid homeostasis were assessed. Although exogenous vitamin D decreased titers of thyroid peroxidase and thyroglobulin antibodies and increased 25-hydroxyvitamin D levels in each treatment group, this effect was less pronounced in patients on the gluten-free diet than in patients not following any dietary recommendations. Only in the latter group of patients, vitamin D increased SPINA-GT. Treatment-induced changes in thyroid peroxidase and thyroglobulin antibodies correlated with the impact of treatment on 25-hydroxyvitamin D levels. The obtained results suggest that gluten-free diet may impair beneficial effects of exogenous vitamin D in individuals with Hashimoto’s thyroiditis.

Tsh Induces Agrp1 Neuron Proliferation in Oatp1c1-Deficient Zebrafish.

Thyroid hormones (THs), thyroxine (T4), and triiodothyronine (T3), regulate growth, metabolism, and neurodevelopment. THs secretion is controlled by the pituitary thyroid-stimulating hormone (TSH) and the hypothalamic-pituitary-thyroid (HPT) axis. The organic anion-transporting polypeptide 1C1 (OATP1C1/SLCO1C1) and the monocarboxylate transporter 8 (MCT8/SLC16A2) actively transport THs, which bind to their nuclear receptors and induce gene expression. A mutation in OATP1C1 is associated with brain hypometabolism, gradual neurodegeneration, and impaired cognitive and motor functioning in adolescent patients. To understand the role of Oatp1c1 and the mechanisms of the disease, we profiled the transcriptome of oatp1c1 mutant (oatp1c1 -/-) and mct8 -/- xoatp1c1 -/- adult male and female zebrafish brains. Among dozens of differentially expressed genes, agouti-related neuropeptide 1 (agrp1) expression increased in oatp1c1 -/- adult brains. Imaging in the hypothalamus revealed enhanced proliferation of Agrp1 neurons in oatp1c1 -/- larvae and adults, and increased food consumption in oatp1c1 -/- larvae. Similarly, feeding and the number of Agrp1 neurons increased in thyroid gland-ablated zebrafish. Pharmacological treatments showed that the T3 analog TRIAC (3,3',5-tri-iodothyroacetic acid), but not T4, normalized the number of Agrp1 neurons in oatp1c1 -/- zebrafish. Since the HPT axis is hyperactive in the oatp1c1 -/- brain, we used the CRISPR-Cas9 system to knockdown tsh in oatp1c1 -/- larvae, and inducibly enhanced the HPT axis in wild-type larvae. These manipulations showed that Tsh promotes proliferation of Agrp1 neurons and increases food consumption in zebrafish. The results revealed upregulation of both the HPT axis-Agrp1 circuitry and feeding in a zebrafish model for OATP1C1 deficiency.SIGNIFICANCE STATEMENT Mutation in the thyroid hormone (TH) transporter OATP1C1 is associated with cognitive and motor functioning disturbances in humans. Here, we used an oatp1c1 -/- zebrafish to understand the role of organic anion-transporting polypeptide 1C1 (Oatp1c1), and the characteristics of OATP1C1 deficiency. Transcriptome profiling identified upregulation of agrp1 expression in the oatp1c1 -/- brain. The oatp1c1 -/- larvae showed increased thyroid-stimulating hormone (tsh) levels, proliferation of Agrp1 neurons and food consumption. Genetic manipulations of the hypothalamic-pituitary-thyroid (HPT) axis showed that Tsh increases the number of Agrp1 neurons and food consumption. The T3 analog TRIAC (3,3',5-tri-iodothyroacetic acid) normalizes the number of Agrp1 neurons and may have potential for the treatment of Oatp1c1 deficiency. The findings demonstrate a functional interaction between the thyroid and feeding systems in the brain of zebrafish and suggest a neuroendocrinological mechanism for OATP1C1 deficiency.