Administration of thyroid hormone increases reelin and brain-derived neurotrophic factor expression in rat hippocampus in vivo

The role of thyroid-stimulating hormone in regulating lipid metabolism: Implications for body-brain communication

Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates the thyroid gland to produce and release thyroid hormones, primarily thyroxine and triiodothyronine. These hormones are key players in body-brain communication, influencing various physiological processes, including the regulation of metabolism (both peripheral and central effects), feedback mechanisms, and lipid metabolism. Recently, the increasing incidence of abnormal lipid metabolism has highlighted the link between thyroid function and lipid metabolism. Evidence suggests that TSH can affect all bodily systems through body-brain communication, playing a crucial role in growth, development, and the regulation of various physiological systems. Lipids serve dual purposes: they are involved in energy storage and metabolism, and they act as vital signaling molecules in numerous cellular activities, maintaining overall human health or contributing to various diseases. This article reviews the role of TSH in regulating lipid metabolism via body-brain crosstalk, focusing on its implications for common lipid metabolism disorders such as obesity, atherosclerosis, nonalcoholic fatty liver disease, neuropsychiatric disorders (including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, and depression), and cerebrovascular disorders such as stroke.

Evidence for thyroid hormone regulation of amygdala-dependent fear-relevant memory and plasticity

The amygdala is an established site for fear memory formation, and clinical studies suggest involvement of hormone signaling cascades in development of trauma-related disorders. While an association of thyroid hormone (TH) status and mood disorders is established, the related brain-based mechanisms and the role of TH in anxiety disorders are unknown. Here we examine the role that TH receptor (TR, a nuclear transcriptional repressor when unbound and a transcriptional activator when bound to TH) may have in mediating the initial formation of fear memories in the amygdala. We identified mRNA levels of TR and other TH pathway regulatory genes, including thyrotropin-releasing hormone (Trh), transthyretin (Ttr), thyrotropin-releasing hormone receptor (Trhr), type 2 iodothyronine deiodinase (Dio2), mediator complex subunit 12 (Med12/Trap230) and retinoid X receptor gamma (Rxrg) to be altered in the amygdala following Pavlovian fear conditioning. Using TH agonist and antagonist infusion into the amygdala, we demonstrated that this pathway is both necessary and sufficient for fear memory consolidation. Inhibition of TH signaling with the TR antagonist 1-850 decreased fear memory consolidation; while activation of TR with T3 (triiodothyronine) resulted in increased memory formation. Using a systemic hypothyroid mouse model, we found that intra-amygdala infusions of T3 were sufficient to rescue deficits in fear memory. Finally, we demonstrated that T3 was sufficient to activate TR-specific gene pathways in the amygdala. These findings on the role of activity-dependent TR modulation support a model in which local TH is a critical regulator of fear memory-related plasticity in the amygdala.

Is the acquired hypothyroidism a risk factor for developing psychiatric disorders?

Hypothyroidism is a prevalent thyroid condition in which the thyroid gland fails to secrete an adequate amount of thyroid hormone into the bloodstream. This condition may develop due to genetic or acquired factors. The most frequent cause of acquired hypothyroidism is chronic autoimmune thyroiditis, also known as Hashimoto's disease. Acquired hypothyroidism is diagnosed when patients present with overt hypothyroidism (also known as clinical hypothyroidism), as they exhibit increased TSH and decreased T3 and T4 serum levels. This article examines the prevalence of psychiatric disorders among patients diagnosed with acquired hypothyroidism with or without Levothyroxine treatment. We discuss the available evidence indicating that acquired hypothyroidism may be a risk factor for psychiatric disorders, and the effectiveness of thyroid treatment in relieving psychiatric symptoms. Additionally, we provide critical details on thyroid hormone cutoff values reported in the literature, their potential clinical importance, and their correlation with psychiatric symptoms. Finally, we examined the various mechanisms by which acquired hypothyroidism can lead to depression. The high rate of comorbidity between hypothyroidism and psychiatric disorders deserves special attention, indicating the importance of consistent monitoring and timely identification of psychiatric symptoms to prevent disease exacerbation and facilitate therapeutic management. On the other hand, several mechanisms underlie the strong association between depression and acquired hypothyroidism. Deeper research into these mechanisms will allow knowledge of the pathophysiology of depression in patients with acquired hypothyroidism and will provide clues to design more precise therapeutic strategies for these patients.

Genetics of ischemic stroke functional outcome

Ischemic stroke, which accounts for 87% of cerebrovascular accidents, is responsible for massive global burden both in terms of economic cost and personal hardship. Many stroke survivors face long-term disability-a phenotype associated with an increasing number of genetic variants. While clinical variables such as stroke severity greatly impact recovery, genetic polymorphisms linked to functional outcome may offer physicians a unique opportunity to deliver personalized care based on their patient's genetic makeup, leading to improved outcomes. A comprehensive catalogue of the variants at play is required for such an approach. In this review, we compile and describe the polymorphisms associated with outcome scores such as modified Rankin Scale and Barthel Index. Our search identified 74 known genetic polymorphisms spread across 48 features associated with various poststroke disability metrics. The known variants span diverse biological systems and are related to inflammation, vascular homeostasis, growth factors, metabolism, the p53 regulatory pathway, and mitochondrial variation. Understanding how these variants influence functional outcome may be helpful in maximizing poststroke recovery.

Screening of liothyronine network pharmacology role in the treatment of ischemic stroke and molecular mechanism

OBJECTIVE

The present study aimed to elucidate mechanisms of liothyronine on the treatment of ischemic stroke (IS).

METHODS

Differential analysis based on R limma package was used to identify differentially expressed genes, which were then mapped into the connectivity map database for identification of liothyronine associated with IS. Tumor necrosis factor (TNF) signaling pathway was verified through pathway enrichment analysis via Enrichr online. Ischemia stroke mouse model was built up for further analysis. Infarct area and regional cerebral blood flow (rCBF) were measured by 2, 3, 5-triphenyltetrazolium chloride and laser Doppler flowmetry, respectively. Light microscope was used for the evaluation of body weight and dark neurons. Serum TXB2 , 6-Keto-PGF1a , TNF-α, and interleukin-6 (IL-6) levels in mice were measured using enzyme-linked immuno sorbent assay. In addition, relative protein expression levels of brain-derived neurotrophic factor, nestin, and Sox2 were detected by Western blot analysis.

RESULTS

Liothyronine with a negative connectivity was identified as one promising treatment for IS through TNF signaling pathway. The experimental results showed that liothyronine treatment significantly meliorated infarct area and the number of dark neurons in IS mice. Liothyronine greatly ameliorated the expression levels of TXB2 and 6-Keto-PGF1a . Besides, rCBF and body weight change of IS mice were increased gradually with increase of drug concentration. Based on pathway enrichment analysis, anti-inflammatory response (TNF-α and IL-6) relevant to TNF signaling pathway was identified, which was further validated in vitro. Furthermore, proteins as neural stem cell markers made a difference with liothyronine treatment.

CONCLUSION

Liothyronine may be a novel therapeutic component to exploit an effective medicine for the treatment of IS.

Bypassing the brain barriers: upregulation of serum miR-495 and miR-543-3p reflects thyroid-mediated developmental neurotoxicity in the rat

Evaluating the neurodevelopmental effects of thyroid-disrupting chemicals is challenging. Although some standardized developmental and reproductive toxicity studies recommend serum thyroxine (T4) measures in developing rats, extrapolating between a serum T4 reduction and neurodevelopmental outcomes is not straightforward. Previously, we showed that the blood-brain and blood-cerebrospinal fluid barriers may be affected by developmental hypothyroidism in newborn rats. Here, we hypothesized that if the brain barriers were functionally disturbed by abnormal thyroid action, then small molecules may escape from the brain tissue and into general circulation. These small molecules could then be identified in blood samples, serving as a direct readout of thyroid-mediated developmental neurotoxicity. To address these hypotheses, pregnant rats were exposed to propylthiouracil (PTU, 0 or 3 ppm) to induce thyroid hormone insufficiency, and dams were permitted to give birth. PTU significantly reduced serum T4 in postnatal offspring. Consistent with our hypothesis, we show that tight junctions of the brain barriers were abnormal in PTU-exposed pups, and the blood-brain barrier exhibited increased permeability. Next, we performed serum microRNA Sequencing (miRNA-Seq) to identify noncoding RNAs that may reflect these neurodevelopmental disturbances. Of the differentially expressed miRNAs identified, 7 were upregulated in PTU-exposed pups. Validation by qRT-PCR shows that miR-495 and miR-543-3p were similarly upregulated in males and females. Interestingly, these miRNAs have been linked to cell junction dysfunction in other models, paralleling the identified abnormalities in the rat brain. Taken together, these data show that miR-495 and miR-543-3p may be novel in vivo biomarkers of thyroid-mediated developmental neurotoxicity.

Hyperthyroidism leads learning and memory impairment possibly via GRIN2B expression alterations

The hippocampus as an important structure for learning and memory functions contains a high level of thyroid hormone receptors. Although there are numerous studies investigating the effects of thyroid hormones on cognitive dysfunction and psychiatric symptoms, the underlying molecular processes of these disorders have not yet been fully elucidated. In the present study, 24 male adult rats (4 months) were divided into 3 groups: control group, sham group and hyperthyroid group. Hyperthyroid group and sham group were treated with l-thyroxine or saline for 21 days. Each group was exposed to Morris water maze testing (MWMT), measuring their performance in a hidden-platform spatial task. After learning and memory tests, intracardiac blood was taken from the rats for serum thyroxine levels. Following blood collection, the rats were decapitated to isolate hippocampal tissue. GRIN2A, GRIN2B, BDNF, cFOS, Cdk5, cdk5r1 (p35), and cdk5r2 (p39) gene expression were evaluated using quantitative reverse transcriptase-PCR. Serum thyroxine level was found to be higher in hyperthyroid rats than in the control and sham groups. According to our MWMT findings, the memory performance of the hyperthyroid group was significantly impaired compared to the control and sham groups (p < 0.05). In the hippocampus, the GRIN2A gene expression level was decreased in the sham group, and the GRIN2B gene expression level was decreased in the sham and hyperthyroid groups compared to the control group (p < 0.05). There was no significant difference in other genes (p > 0.05). Hyperthyroidism impaired hippocampus-dependent spatial memory. Hyperthyroidism caused decreased level of GRIN2B gene expression in the hippocampus.

Thyroid hormones regulate reelin expression in neuropsychiatric disorders

The incidence and prevalence of hypothyroidism in pregnancy have increased over the past two decades, leading to the occurrence of neuropsychiatric disorders. However, the underlying mechanisms of thyroid hormone (TH)-regulated gene expression and neuropsychiatric development during the postnatal period remain unknown. Recent achievements have shown that reelin, a large extracellular glycoprotein, plays a crucial role in neuronal migration and localization during the development of neocortex and cerebellar cortex, thereby participating in the development of neuropsychiatric diseases. Reelin-induced neuronal migration requires triiodothyronine (T3) from the deiodination of thyroxine (T4) by fetal brain deiodinases. Previous studies have reported decreased reelin levels and abnormal gene expression, which are the same as the pathological alternations in reelin-induced neuropsychiatric disorders including schizophrenia and autism. Low T3 in the fetal brain due to hypothyroxinemia during pregnancy may be detrimental to neuronal migration, leading to neuropsychiatric disorders. In this review, we focus on the reelin expression between hypothyroidism and neuropsychiatric disorders.

Hypothyroidism and Diabetes-Related Dementia: Focused on Neuronal Dysfunction, Insulin Resistance, and Dyslipidemia

The incidence of dementia is steadily increasing worldwide. The risk factors for dementia are diverse, and include genetic background, environmental factors, sex differences, and vascular abnormalities. Among the subtypes of dementia, diabetes-related dementia is emerging as a complex type of dementia related to metabolic imbalance, due to the increase in the number of patients with metabolic syndrome and dementia worldwide. Thyroid hormones are considered metabolic regulatory hormones and affect various diseases, such as liver failure, obesity, and dementia. Thyroid dysregulation affects various cellular mechanisms and is linked to multiple disease pathologies. In particular, hypothyroidism is considered a critical cause for various neurological problems-such as metabolic disease, depressive symptoms, and dementia-in the central nervous system. Recent studies have demonstrated the relationship between hypothyroidism and brain insulin resistance and dyslipidemia, leading to diabetes-related dementia. Therefore, we reviewed the relationship between hypothyroidism and diabetes-related dementia, with a focus on major features of diabetes-related dementia such as insulin resistance, neuronal dysfunction, and dyslipidemia.

Thyroid-Related Hormone Levels in Clinical Patients With Moderately Severe-to-Profound Sudden Sensorineural Hearing Loss: A Prospective Study

Objectives: Sudden sensorineural hearing loss (SSNHL) is a common otological emergency, causing a measure of hearing loss and affecting the quality of life. This study aims to investigate the association of thyroid-related hormone levels with moderately severe-to-profound SSNHL.

Methods: The study included 70 patients with moderately severe-to-profound SSNHL and 100 age- and sex-matched healthy controls. Peripheral venous blood samples were taken from the participants, and their thyroid-related hormone levels were measured at admission and 1 week after treatment.

Results: In moderately severe-to-profound SSNaHL patients, the concentrations of total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH) (all P < 0.05) were significantly lower than in the control group. The TT3, TT4, FT3, and TSH levels were significantly higher in the effective group than in the ineffective group (all P < 0.05). Linear correlation analysis revealed that TSH level (R = 0.707, P < 0.05) elevation after treatment successfully predicted a favorable outcome of hearing recovery. Logistic regression analyses suggested low FT3 and TSH levels to be independent occurrence predictors, while the increase of TSH level may be an independent favorable outcome predictor.

Conclusions: The results suggest that low FT3 and TSH levels are risk factors for moderately severe-to-profound SSNHL. By discovering the positive association between TSH elevation and hearing recovery, along with the potential novel predictors of FT3 and TSH, our study may contribute valuable insights to the research and treatment of moderately severe-to-profound SSNHL.

Emerging role of free triiodothyronine in patients with anti-N-methyl-D-aspartate receptor encephalitis

We aimed to investigate the role of free triiodothyronine (FT3) in patients with anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis. 137 consecutive inpatients (2016–2019) were registered prospectively and followed up for 12 months. 96 eligible patients were included in the study. The modified Rankin scale (mRS) score was collected, and the score of 3–6 was defined as a poor outcome. The patients were equally classified into 3 subgroups based on their FT3 levels obtained within 24 h of admission, and the subgroup differences were analyzed by parametric or nonparametric tests as appropriate. Logistic regression analysis was performed. We found that there was no difference in the mRS scores upon admission among 3 subgroups, however, patients in the low-FT3 subgroup tended to have higher disease severity during hospitalization and worse outcome in follow-up visits, represented by higher chances of intense care unit (ICU) admission (P < 0.001), longer hospital stay (P < 0.001), greater maximum mRS scores during hospitalization (P = 0.011), lower rates of getting clinical improvement within 4 weeks of starting treatment (P = 0.006), and higher percentages of poor 1-year outcome (P = 0.002). The level of FT3 was an independent factor correlated with ICU admission (P = 0.002) and might be a potential predictor for 1-year outcome. Our preliminary results suggest that the FT3 may be a risk factor involved in the evolution and progression of anti-NMDAR encephalitis, whereas the underline mechanisms remain to be explored. Attention should be paid to these patients with relatively low FT3 upon admission, which might possibly aid clinical prediction and guide clinical decision-making.

T1AM-TAAR1 signalling protects against OGD-induced synaptic dysfunction in the entorhinal cortex

Abnormalities in thyroid hormones (TH) availability and/or metabolism have been hypothesized to contribute to Alzheimer's disease (AD) and to be a risk factor for stroke. Recently, 3-iodothyronamine (T₁AM), an endogenous amine putatively derived from TH metabolism, gained interest for its ability to promote learning and memory in the mouse. Moreover, T₁AM has been demonstrated to rescue the β-Amyloid dependent LTP impairment in the entorhinal cortex (EC), a brain area crucially involved in learning and memory and early affected during AD. In the present work, we have investigated the effect of T₁AM on ischemia-induced EC synaptic dysfunction. In EC brain slices exposed to oxygen-glucose deprivation (OGD), we demonstrated that the acute perfusion of T₁AM (5 μM) was capable of preventing ischemia-induced synaptic depression and that this protective effect was mediated by the trace amine-associated receptor 1 (TAAR1). Moreover, we demonstrated that activation of the BDNF-TrkB signalling is required for T₁AM action during ischemia. The protective effect of T₁AM was more evident when using EC slices from transgenic mutant human APP (mhAPP mice) that are more vulnerable to the effect of OGD. Our results confirm that the TH derivative T₁AM can rescue synaptic function after transient ischemia, an effect that was also observed in a Aβ-enriched environment.

Thyroid hormone, gene expression, and Central Nervous System: Where we are

Thyroid hormones (TH; T3 and T4) play a fundamental role in the fetal stage to the adult phase, controlling gene and protein expression in virtually all tissues. The endocrine and CNS systems have relevant interaction, and the TH are pivotal for the proper functioning of the CNS. A slight failure to regulate TH availability during pregnancy and/or childhood can lead to neurological disorders, for example, autism and cognitive impairment, or depression. In this review, we highlight how TH acts in controlling gene expression, its role in the CNS, and what substances widely found in the environment can cause in this tissue. We highlight the role of Endocrine Disruptors used on an everyday basis in the processing of mRNAs responsible for neurodevelopment. We conclude that TH, more precisely T3, acts mainly throughout its nuclear receptors, that the deficiency of this hormone, either due to the lack of its main substrate iodine, or by to incorrect organification of T4 and T3 in the gland, or by a mutation in transporters, receptors and deiodinases may cause mild (dysregulated mood in adulthood) to severe neurological impairment (Allan-Herndon-Dudley syndrome, presented as early as childhood); T3 is responsible for the expression of numerous CNS genes related to oxygen transport, growth factors, myelination, cell maturation. Substances present in the environment and widely used can interfere with the functioning of the thyroid gland, the action of TH, and the functioning of the CNS.

[Pathophysiological mechanisms of autism in children]

Based on the analysis of literature, the authors describe the neuropathophysiological mechanism of the formation of synapses, synaptic transmission and plasticity, which may underlie the pathogenesis of autism. The results of some studies confirm the involvement of aberrant expression of genes and proteins of synaptic contacts, cell adhesion molecules p120ctn, CNTN5, CNTN6, activation of NMDA glutamate, TrkB, p75 receptors, Ca²⁺-input, BDNF, serotonin and testosterone. This leads to an imbalance in the exciting, inhibitory synaptic transmission and forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD) at the level of individual neurons and their chains due to suppression of GABA synthesis, expression of its ionotropic and metabotropic receptors, G proteins, NGF, TrkA receptors, a reduction in the number of GABAergic neurons, their contacts and disruption of differentiation. The pathology of the nuclei of the thalamus, especially the reticular nucleus (RN), is associated with a disturbance of the expression of the subunits of metabotropic GABAβ receptors, Ca²⁺ channels, GABA excretion and the work of chlorine transmitters. These failures do not ensure the inhibitory effect of OC on the exciting associative and ventral nuclei of the thalamus, nor modify the incoming information to the cerebral cortex (CC) from these thalamus nuclei, the dentate gyrus of the hippocampus and the nuclei of the reticular formation. Information propagating into the somatosensory and associative regions of CC is not modified by mirror neurons (MN) when performing arbitrary actions, which prevents the formation of an adequate image in the neural networks of the associative cortex and promotes the development of hyperexcitability, irritability, increased visual and auditory sensitivity, anxiety, and the ability to form a holistic image based on the actions of other people.

Intra-day variations of blood reelin levels in healthy individuals

INTRODUCTION

Reelin (RELN) is an extracellular glycoprotein best known to be crucial for neuronal migration during the embryonic period and regulation of synaptic plasticity in the adult brain, with recent studies pointing to reelin playing an important part in the organization of peripheral organs as well. Abnormalities in RELN function are associated with a variety of medical conditions in human beings. These alterations partly also reflect in RELN's blood levels, which gives it a clinical relevance as a potential biomarker. Requirement for a possible clinical use is a profound understanding of RELN's physiology. We hypothesized blood RELN levels could underlie time-dependent variations and therefore examined individuals' serum reelin concentrations in the course of one day.

MATERIAL AND METHODS

We obtained blood samples from healthy individuals (n = 10) at several times of measurement over a time period of 24 h. We subsequently determined the respective serum RELN concentrations utilizing an enzyme-linked immunosorbent assay and tested for intra- and interindividual variations in serum RELN concentrations over time.

RESULTS

All tested individuals' serum RELN levels displayed significant intraindividual variations in the course of 24 h. Test subjects' reelin day profiles showed substantial divergence among each other.

CONCLUSIONS

Our findings point to short-term fluctuations in blood RELN levels being part of physiological RELN homeostasis. This is of special interest with regard to a potential clinical use of RELN as a biomarker.

Thyroid gland and brain: Enigma of Hashimoto's encephalopathy

The versatile clinical manifestations of the Hashimoto's chronic autoimmune thyroiditis often include psycho-neurological disorders. Although hypothyroidism disturbs significantly the ontogenesis and functions of central nervous system, causing in severe cases of myxedema profound impairment of cognitive abilities and even psychosis, the behavioral, motor and other psychoneurological disorders accompany euthyroid and slightly hypothyroid cases and periods of Hashimoto's disease as well, thus constituting the picture of so called "Hashimoto's encephalopathy". The entity, although discussed and explored for more than 50 years since its initial descriptions, remains an enigma of thyroidology and psychiatry, because its etiology and pathogenesis are obscure. The paper describes the development of current views on the role of thyroid in ontogeny and functions of brain, as well as classical and newest ideas on the etiology and pathogenesis of Hashimot's encephalopathy. The synopsis of the world case reports and research literature on this disorder is added with authors' own results obtained by study of 17 cases of Hashimoto's thyroiditis with schizophrenia-like clinical manifestations. The relation of the disease to adjuvant-like etiological factors is discussed. Three major mechanistic concepts of Hashimoto's encephalopathy are detailed, namely cerebral vasculitis theory, hormone dysregulation theory and concept, explaining the disease via direct action of the autoantibodies against various thyroid (thyroperoxidase, thyroglobulin, and TSH-receptor) and several extrathyroid antigens (alpha-enolase and other enzymes, gangliosides and MOG-protein, onconeuronal antigens) - all of them expressed in the brain. The article demonstrates that all above mentioned concepts intermingle and prone to unification, suggesting the unified scheme of pathogenesis for the Hashimoto's encephalopathy. The clinical manifestations, criteria, forms, course, treatment and prognosis of Hashimoto's encephalopathy and its comorbidity to other diseases - are also discussed in brief. The relation between Hashimoto's encephalopathy and non-vasculitis autoimmune encephalomyelitides of paraneoplastic and non-paraneoplastic origin is emphasized [1 figure, bibliography - 200 references].

Thyroid Hormones in the Brain and Their Impact in Recovery Mechanisms After Stroke

Thyroid hormones are of fundamental importance for brain development and essential factors to warrant brain functions throughout life. Their actions are mediated by binding to specific intracellular and membranous receptors regulating genomic and non-genomic mechanisms in neurons and populations of glial cells, respectively. Among others, mechanisms include the regulation of neuronal plasticity processes, stimulation of angiogenesis and neurogenesis as well modulating the dynamics of cytoskeletal elements and intracellular transport processes. These mechanisms overlap with those that have been identified to enhance recovery of lost neurological functions during the first weeks and months after ischemic stroke. Stimulation of thyroid hormone signaling in the postischemic brain might be a promising therapeutic strategy to foster endogenous mechanisms of repair. Several studies have pointed to a significant association between thyroid hormones and outcome after stroke. With this review, we will provide an overview on functions of thyroid hormones in the healthy brain and summarize their mechanisms of action in the developing and adult brain. Also, we compile the major thyroid-modulated molecular pathways in the pathophysiology of ischemic stroke that can enhance recovery, highlighting thyroid hormones as a potential target for therapeutic intervention.

Low-normal free triiodothyronine and high leukocyte levels in relation to stroke severity and poor outcome in acute ischemic stroke with intracranial atherosclerotic stenosis

BACKGROUND

It is uncertain that the effect of free triiodothyronine (FT3) within normal ranges on initial severity and early functional outcomes in acute ischemic stroke (AIS) patients with Intracranial Atherosclerotic Stenosis (ICAS). The predictive values of white blood cell (WBC) and FT3 are also unclear in symptomatic ICAS (sICAS) patients.

METHODS

We consecutively reviewed 848 ischemic stroke patients admitted into Xiangya Hospital within 72 h after symptom onset. sICAS was defined as AIS patient with degree of ICAS ≥50% proved by magnetic resonance angiography, computed tomography angiography or digital subtraction angiography. WBC and FT3 were assessed within 24 h after admission. Neurological severity was evaluated on admission using the National Institutes of Health Stroke Scale (NIHSS). Stroke outcomes were defined by the modified Rankin Scale (mRS) on the 14th day after admission.

RESULTS

Logistic regression analysis showed that hypertension, lower FT3 and higher WBC concentrations independently associated with severe stroke [FT3 (odds ratio(OR) = 0.543, 95% confidence interval(95% CI): 0.383-0.769); hypertension (OR = 0.436, 95% CI: 0.238-0.800); WBC (OR = 1.17; 95% CI:1.041-1.316]. Besides, lower FT3, higher FT4, higher WBC and higher plasma glucose concentrations independently associated with unfavorable outcomes [FT3 (OR = 0.460; 95% CI: 0.306-0.690); FT4 (OR = 1.151; 95% CI: 1.055-1.255); WBC (OR = 1.178; 95% CI: 1.039-1.334); Plasma glucose (OR = 1.160; 95% CI: 1.002-1.342)].

CONCLUSIONS

Lower FT3 levels within normal ranges and higher WBC count are independently associated with the severity and early poor prognosis of sICAS simultaneously, FT3 and WBC count might be important biomarkers for sICAS patients.

Prenatal thyroxine treatment promotes anxiolysis in male Swiss mice offspring

The proper functioning of the maternal thyroid plays a crucial role in fetal development. Thus, the aim of our study was to verify how maternal hyperthyroidism is able to change behavioral parameters in mice offspring during adulthood. For this purpose, pregnant Swiss mice (n = 24 and ~35 g) were randomly assigned into two groups: a control and a thyroxine (T4)-treatment group. The control was treated with 0.9% saline, while the treatment group received T4 (200 μg/kg, s.c.) once daily during the entire pregnancy period. After completing 70 days of life, a part of male offspring underwent a battery of tests, including open field, dark-light box, elevated plus maze, marble burying, rotarod and tail suspension tests. The other male pups were euthanized, being hippocampus and serum collected for RNA analysis and hormones measurement, respectively. Statistical analysis was performed using Student's t-test, and the means were considered significantly different when p < 0.05. In adult offspring, a significant decrease was observed for serum T3 in treated group. It was demonstrated that the T4 group had an increase in total distance traveled in an open field test. In the elevated plus maze test, we observed a higher time in opened arms as well as an increased in percentage of entries in these arms. In the hippocampus, T4 offspring had a higher expression of tryptophan hydroxylase 2 (TPH2), serotonin transporter (SERT) and glutamate decarboxylase 67 (GAD 67) in comparison to controls. These findings suggest that prenatal T4 treatment alters hippocampal serotonergic and GABAergic systems, promoting anxiolysis in male adult offspring.

The interplay between neuroendocrine and sleep alterations following traumatic brain injury

BACKGROUND

Sleep and endocrine disruptions are prevalent after traumatic brain injury (TBI) and are likely to contribute to morbidity.

OBJECTIVE

To describe the interaction between sleep and hormonal regulation following TBI and elucidate the impact that alterations of these systems have on cognitive responses during the posttraumatic chronic period.

METHODS

Review of preclinical and clinical literature describing long-lasting endocrine dysregulation and sleep alterations following TBI. The bidirectional relationship between sleep and hormones is described. Literature describing co-occurrence between sleep-wake disturbances and hormonal dysregulation will be presented. Review of literature describing cognitive effects of seep and hormones. The cognitive and functional impact of sleep disturbances and hormonal dysregulation is discussed within the context of TBI.

RESULTS/CONCLUSIONS

Sleep and hormonal alterations impact cognitive and functional outcome after TBI. Diagnosis and treatment of these disturbances will impact recovery following TBI and should be considered in the post-acute rehabilitative setting.

Low Tri-iodothyronine Syndrome Is Associated With Cognitive Impairment in Patients With Acute Ischemic Stroke: A Prospective Cohort Study

OBJECTIVE

Low tri-iodothyronine (T3) syndrome is a predictor of poor prognosis in patients with stroke. Poststroke cognitive impairment (PSCI) is a common and important complication after stroke. The association between low T3 syndrome and PSCI is unclear. We aimed to explore the potential relationship between low T3 syndrome and PSCI in the acute phase of ischemic stroke at a 1-month follow-up visit.

METHODS

In total, 314 ischemic stroke patients were consecutively enrolled in the study and followed up at 1 month. Thyroid hormones were measured within 24 hours after admission. Cognitive function was evaluated by the Mini-Mental State Exam (MMSE) 1 month after acute ischemic stroke. Cognitive impairment was defined as an MMSE score of less than 27. Cognitive impairment severity was categorized as severe, mild, or none (MMSE score <23, 23-26, or ≥27, respectively).

RESULTS

According to the MMSE score, 182 participants (58.0%) had cognitive impairment 1 month after stroke. Patients with low T3 syndrome were more prone to have cognitive impairment than patients with normal levels of T3 (p < 0.001). After adjusting for potential confounders in our logistic model, low T3 syndrome was independently associated with PSCI (odds ratio 4.319, 95% confidence interval 1.553-12.013, p = 0.005).

CONCLUSION

Low T3 syndrome in the acute phase of ischemic stroke was associated with a higher prevalence of 1-month PSCI, independently of established risk factors.

Hypothyroidism and Cognitive Disorders during Development and Adulthood: Implications in the Central Nervous System

Thyroid hormones (THs) play a critical function in fundamental signaling of the body regulating process such as metabolism of glucose and lipids, cell maturation and proliferation, and neurogenesis, to name just a few. THs trigger biological effects both by directly affecting gene expression through the interaction with nuclear receptors (genomic effects) and by activating protein kinases and/or ion channels (short-term effects). For years, a close relationship between the THs hormones and the central nervous system (CNS) has been described, not only for neuronal cells but also for glial development and differentiation. A deficit in thyroid hormones triiodothyronine (T₃) and thyroxine (T₄) is observed in the hypothyroid condition, generated by a iodine deficiency or an autoimmune response of the body. In the hypothyroid condition, several cellular deregulation and alterations have been described in dendrite spine morphology, cell migration and proliferation, and impaired synaptic transmission in the hippocampus, among others. The aim of this review is to describe the role of the thyroid hormones with focus in brain function and neurodegenerative disorders.

Low Free Triiodothyronine Predicts 3-Month Poor Outcome After Acute Stroke

BACKGROUND AND PURPOSE

The association between thyroid hormone levels and long-term clinical outcome in patients with acute stroke has not yet been thoroughly studied. The purpose of the present study was to test the hypothesis that thyroid hormone levels are associated with 3-month functional outcome and mortality after acute stroke.

METHODS

We retrospectively analyzed 702 consecutive patients with acute stroke (251 women; median age, 73 years) who were admitted to our department. General blood tests, including thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4), were performed on admission. Neurological severity was evaluated using National Institutes of Health Stroke Scale (NIHSS) scores on admission and modified Rankin Scale (mRS) scores at 3 months after stroke onset. Poor outcome was defined as an mRS score of 3-5 or death. The impact of thyroid function on 3-month outcome was evaluated using multiple logistic regression analysis.

RESULTS

Poor functional outcome was observed in 295 patients (42.0%). Age (P < .0001), female sex (P < .0001), admission NIHSS score (P < .0001), smoking (P = .0026), arterial fibrillation (P = .0002), preadmission mRS (P < .0001), estimated glomerular filtration rate (P = .0307), and ischemic heart disease (P = .0285) were significantly associated with poor functional outcome, but no relationship between FT4, TSH, and poor functional outcome was found. A multivariate logistic regression analysis showed that low FT3 values (<2.00 pg/mL) were independently associated with poor functional outcome (odds ratio [OR], 3.16; 95% confidence interval [CI], 1.60-6.24) and mortality (OR, 2.55; 95% CI, 1.33-4.91) at 3 months after stroke onset.

CONCLUSIONS

Our data suggest that a low FT3 value upon admission is associated with a poor 3-month functional outcome and mortality in patients with acute stroke.

Mild Maternal Hypothyroxinemia During Pregnancy Induces Persistent DNA Hypermethylation in the Hippocampal Brain-Derived Neurotrophic Factor Gene in Mouse Offspring

BACKGROUND

Thyroid hormones are essential for normal development of the central nervous system (CNS). Experimental rodents have shown that even a subtle thyroid hormone insufficiency in circulating maternal thyroid hormones during pregnancy may adversely affect neurodevelopment in offspring, resulting in irreversible cognitive deficits. This may be due to the persistent reduced expression of the hippocampal brain-derived neurotrophic factor gene Bdnf, which plays a crucial role in CNS development. However, the underlying molecular mechanisms remain unclear.

METHODS

Thiamazole (MMI; 0.025% [w/v]) was administered to dams from two weeks prior to conception until delivery, which succeeded in inducing mild maternal hypothyroxinemia during pregnancy. Serum thyroid hormone and thyrotropin levels of the offspring derived from dams with mild maternal hypothyroxinemia (M offspring) and the control offspring (C offspring) were measured. At 70 days after birth, several behavior tests were performed on the offspring. Gene expression and DNA methylation status were also evaluated in the promoter region of Bdnf exon IV, which is largely responsible for neural activity-dependent Bdnf gene expression, in the hippocampus of the offspring at day 28 and day 70.

RESULTS

No significant differences in serum thyroid hormone or thyrotropin levels were found between M and C offspring at day 28 and day 70. M offspring showed an impaired learning capacity in the behavior tests. Hippocampal steady-state Bdnf exon IV expression was significantly weaker in M offspring than it was in C offspring at day 28. At day 70, hippocampal Bdnf exon IV expression at the basal level was comparable between M and C offspring. However, it was significantly weaker in M offspring than in C offspring after the behavior tests. Persistent DNA hypermethylation was also found in the promoter region of Bdnf exon IV in the hippocampus of M offspring compared to that of C offspring, which may cause the attenuation of Bdnf exon IV expression in M offspring.

CONCLUSIONS

Mild maternal hypothyroxinemia induces persistent DNA hypermethylation in Bdnf exon IV in offspring as epigenetic memory, which may result in long-term cognitive disorders.

Immunity and inflammation predictors for short-term outcome of stroke in young adults

BACKGROUND

The current study was conducted to identify independent predictors of severity and short-term outcome of first-ever ischemic stroke in young adults.

METHODS

We retrospectively enrolled 325 consecutive patients aged 18-49 years with first-ever ischemic stroke admitted to our center between April 2013 and June 2015. Variables were systematically registered and compared between patients with different neurological severity (mild stroke: National Institutes of Health Stroke Scale [NIHSS] ≤ 8 and severe stroke: >8) and different stroke outcome (favorable: modified Rankin scale score 0-2 and unfavorable: 3-5 or death) at 14 days after stroke onset.

RESULTS

A total of 325 patients fulfilled the inclusion criteria. There were 242 patients with mild stroke. They exhibited lower white blood cell (WBC), globulin, plasma glucose, fibrinogen (Fib) levels and higher albumin, albumin/globulin (A/G), free triiodothyronine (FT3) levels. Logistic regression analysis showed that FT3 (≧3.18) and WBC (≧7.1) were independent predictors. There were 122 patients demonstrating an unfavorable outcome. Higher WBC, globulin, plasma glucose and Fib levels, lower albumin, FT3, A/G levels, higher NIHSS score and longer hospital stay were significantly associated with unfavorable outcome. In the logistic regression model, we found that A/G (≧1.56), FT3 (≧4.09) and WBC (≧7.1) were independent predictors for short-term outcome.

CONCLUSIONS

Our data suggested that higher A/G, FT3 levels served as independent predictors of favorable outcome, and a higher FT3 value may also predict mild stroke, while higher WBC may predict a poor functional outcome and severe stroke in patients with acute ischemia.

MECHANISMS IN ENDOCRINOLOGY: Maternal thyroid dysfunction during pregnancy and behavioural and psychiatric disorders of children: a systematic review

BACKGROUND

Maternal thyroid dysfunction during pregnancy may lead to persistent neurodevelopmental disorders in the offspring appearing in later life. This study aimed to review the available evidence concerning the relationship between maternal thyroid status during pregnancy and offspring behavioural and psychiatric disorders.

METHODS

Systematic electronic database searches were conducted using PubMed, Embase, PsycNET, Scopus, Google Scholar and Cochrane library. Studies including gestational thyroid dysfunction as the exposure and offspring behavioural and psychiatric disorders as the outcome were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed and, after thorough screening by two independent reviewers, 13 articles remained eligible for inclusion in this study.

RESULTS

Indicators of maternal thyroid dysfunction, including low and high thyroid hormone level and autoimmune thyroiditis, during early pregnancy, were found to be associated with several offspring behavioural and psychiatric disorders such as attention deficit hyperactivity disorder (ADHD), autism, pervasive developmental problems, externalising behaviour, in addition to epilepsy and seizure. The majority of associations were found with low maternal thyroid hormone level.

CONCLUSION

Maternal thyroid function during pregnancy, particularly hypothyroidism, is associated with behavioural and psychiatric disorders in children. Further studies are needed with a capacity to adjust for a fuller range of confounding factors.

Peripheral and central administration of T3 improved the histological changes, memory and the dentate gyrus electrophysiological activity in an animal model of Alzheimer's disease

The amyloid beta (Aβ) induced Alzheimer's disease (AD) is associated with formation the amyloid plaques, cognitive impairments and decline in spontaneous discharge of neurons. In the current study, we evaluated the effect of subcutaneous (S. C) and intrahippocampal (I. H) administrations of triiodothyronine (T3) on the histological changes, memory and the dentate gyrus (DG) electrophysiological activity in an animal model of AD. Eighty adult male Wistar rats (250-300 g) were divided randomly into five groups: Sham-Operated (Sh-O), AD + Vehicle (S. C), AD + Vehicle (I. H), AD+ T3 (S. C) and AD + T3 (I. H). In order to induce animal model of AD, Aβ (10 ng/μl, bilaterally) were injected intrahippocampally. Rats were treated with T3 and/or normal saline for 10 days. Passive avoidance and spatial memory were evaluated in shuttle box apparatus and Morris water maze, respectively. Neuronal single unit recording was assessed from hippocampal DG. The percent of total time that animals spent in target quarter, the mean latency time (sec), the step through latency and the average number of spikes/bin were decreased significantly in AD rats compared with the Sh-O group (p < 0.001) and were increased significantly in AD groups that have received T3 (S. C and I. H) in compared with AD group (p < 0.01, p < 0.001). Also, formation of amyloid plaques was decreased in AD rats treated with T3.The results showed that T3 injection (S. C and I. H), by reduction of neural damage and increment of neuronal spontaneous activity improved the memory deficits in Aβ-induced AD rats.

Improvement of memory and learning by intracerebroventricular microinjection of T3 in rat model of ischemic brain stroke mediated by upregulation of BDNF and GDNF in CA1 hippocampal region

Background

Ischemic stroke is a common leading cause of death and disability with lack of effective therapies. In this study, T3 was intra-ventricularly injected to evaluate gene expression and protein concentration of and brain-derived neurotrophic factor (BDNF) and Glial cell-derived neurotrophic factor (GDNF) in hippocampal CA1 region in rat model of brain ischemia/reperfusion (I/R).

Methods

In this study, transient middle cerebral artery occlusion (tMCAo) was used as model of ischemic brain stroke. Rats were randomly divided in four groups of Co, Sh, tMCAo and tMCAo + T3. Then, a single dose of intra-ventricular T3 was administered via a Hamilton syringe. Passive avoidance test was used as behavioral investigations. After 21 days, the animals were sacrificed and their brains were used for molecular and histopathological studies.

Results

T3 significantly improved the learning and memory compared with tMCAo group according to Morris water maze findings (P < 0.05). Step-through latency (STL) significantly decreased in tMCAo group (P < 0.05). There were significant increase in the STL of T3 group compared with tMCAo group (P < 0.05).A significant reduction in BDNF mRNAs and protein levels were observed in the tMCAo compared with Co and Sh group (P < 0.05). A significant increase of BDNF and GDNF mRNAs and proteins was recorded in tMCAo + T3 group compared with Co, Sh and tMCAO groups (P < 0.05).

Conclusions

The results of current study demonstrated that T3 had therapeutic effects on cerebral ischemic stroke by increasing the neurotrophic factors (BDNF, GDNF) in CA1 region of hippocampus.

Graphical abstract

The effects of intracerebroventricular microinjection of T3on memory and learning in rat model of ischemic brain stroke.

Retinoic acid-pretreated Wharton's jelly mesenchymal stem cells in combination with triiodothyronine improve expression of neurotrophic factors in the subventricular zone of the rat ischemic brain injury

Stroke is the consequence of limited blood flow to the brain with no established treatment to reduce the neurological deficits. Focusing on therapeutic protocols in targeting subventricular zone (SVZ) neurogenesis has been investigated recently. This study was designed to evaluate the effects of retinoic acid (RA)-pretreated Wharton's jelly mesenchymal stem cells (WJ-MSCs) in combination with triiodothyronine (T3) in the ischemia stroke model. Male Wistar rats were used to induce focal cerebral ischemia by middle cerebral artery occlusion (MCAO). There were seven groups of six animals: Sham, Ischemic, WJ-MSCs, RA-pretreated WJ-MSCs, T3, WJ-MSCs +T3, and RA-pretreated WJ-MSCs + T3. The treatment was performed at 24 h after ischemia, and animals were sacrificed one week later for assessments of retinoid X receptor β (RXRβ), brain-derived neurotrophic factor (BDNF), Sox2 and nestin in the SVZ. Pro-inflammatory cytokines in sera were measured at days four and seven after ischemia. RXRβ, BDNF, Sox2 and nestin had the significant expressions in gene and protein levels in the treatment groups, compared with the ischemic group, which were more vivid in the RA-pretreated WJ-MSCs + T3 (p ≤ 0.05). The same trend was also resulted for the levels of TNF-α and IL-6 at four days after ischemia (p ≤ 0.05). In conclusion, application of RA-pretreated WJ-MSCs + T3 could be beneficial in exerting better neurotrophic function probably via modulation of pro-inflammatory cytokines.

Stimulation of neurotrophic factors and inhibition of proinflammatory cytokines by exogenous application of triiodothyronine in the rat model of ischemic stroke

There is a positive relation between decreases of triiodothyronine (T3) amounts and severity of stroke. The aim of this study was to evaluate the effect of exogenous T3 application on levels of neurogenesis markers in the subventricular zone. Cerebral ischemia was induced by middle cerebral artery occlusion in male Wistar rats. There were 4 experimental groups: sham, ischemic, vehicle, and treatment. Rats were injected with T3 (25 μg/kg, IV injection) at 24 hours after ischemia. Animals were sacrificed at day 7 after ischemia. There were high levels of brain-derived neurotrophic factor, nestin, and Sox2 expressions in gene and protein levels in the T3 treatment group (P ≤ .05 vs ischemic group). Treatment group showed high levels of sera T3 and thyroxine (T4) but low levels of thyrotropin (TSH), tumor necrosis factor-α, and interleukin-6 (P ≤ .05 vs ischemic group) at day 4 after ischemia induction. Findings of this study revealed the effectiveness of exogenous T3 application in the improvement of neurogenesis possibly via regulation of proinflammatory cytokines.

Effects of forced swimming stress on thyroid function, pituitary thyroid-stimulating hormone and hypothalamus thyrotropin releasing hormone expression in adrenalectomy Wistar rats

In order to study the impact that is imposed on the hypothalamic-pituitary-thyroid (HPT) axis of adrenalectomy male Wistar rats by stress caused by swimming, the blood level of triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH), the expression of TSHβ mRNA at the pituitary and thyrotropin releasing hormone (TRH) expression at the paraventricular nucleus (PVN) were measured. A total of 50 male Wistar rats of 6-8 weeks of age and with an average weight of 190-210 grams were randomly divided into the following two groups: The surgical (without adrenal glands) and non-surgical (adrenalectomy) group. These two groups were then divided into the following five groups, according to the time delay of sacrifice following forced swim (10 min, 2 h, 12 h and 24 h) and control (not subjected to swimming) groups. A bilateral adrenalectomy animal model was established. Serum TSH in the blood was measurement by chemiluminescent immunoassay, and cerebrum tissue were excised for the measurement of TRH expression using an immunohistochemistry assay. In addition, pituitaries were excised for the extraction of total RNA. Finally, reverse transcription-quantitative polymerase chain reaction was performed for quantitation of TSHβ. Following swimming, the serum T3, T4 and TSH, the TSHβ mRNA expression levels in the pituitary and the TRH expression in the PVN of the surgical group were gradually increased. In the non-surgical group, no significant differences were observed in the serum T3, T4 and TSH levels compared with the control group. The TSHβ mRNA expression at the pituitary showed a similar result. Furthermore, the TRH expression at PVN was gradually increased and stress from swimming could increase the blood T4, T3 and TSH levels, TSHβ mRNA expression at the pituitary and TRH expression at the PVN in adrenalectomy Wistar rats. Moreover, the index in the surgical group changed significantly compared with the non-surgical group. In conclusion, the results suggest that there is a positive correlation between stress from forced swimming and the variation of the HPT axis.

Central and peripheral administrations of levothyroxine improved memory performance and amplified brain electrical activity in the rat model of Alzheimer's disease

Alzheimer's disease (AD) is associated with cognitive impairments and a decline in the spontaneous neuronal discharge. In the current study, we evaluated the effect of subcutaneous (S.C.) and intrahippocampal (I.H.) administrations of levothyroxine (LT-4) on the passive avoidance and spatial memory, as well as electrophysiological activity in an animal model of AD. One hundred-sixty male Wistar rats were divided into two main groups. The S.C. group included two Sham and four AD (vehicle or L-T4 25, 50 & 100μg/kg); and the I.H. had consisted of two Sham and two AD (vehicle or L-T4 10μg/kg) subgroups. To make an animal model of AD, amyloid beta (Aβ) plus ibotenic acid (Ibo) were injected I.H. Rats were treated with L-T4 and/or normal saline for ten days. Passive avoidance and spatial memory were evaluated in shuttle box and Morris water maze, respectively. Neuronal single unit recording was assessed from hippocampal dentate gyrus (DG). Results showed that the mean latency time (s) increased significantly (p<0.001) in AD animals and decreased significantly in both S.C. and I.H. L-T4 injected AD animals, compared with the AD group (p<0.001). The percentage of total time that animals spent in goal quarter and the step through latency decreased significantly in AD rats (p<0.001) and increased significantly in both S.C. and I.H. L-T4 injected AD animals in comparison with the AD group (p<0.01, p<0.001). Data showed that the average number of spikes/bin significantly decreased in the AD group (p<0.001). The S.C. and I.H. L-T4 injections in AD rats significantly increased the spike rate in comparison to the AD group (p<0.001). In conclusion, both S.C. and I.H. injections of L-T4 alleviated memory deficits and spontaneous neuronal activity in Aβ-induced AD rats. Also, I.H. microinjection of L-T4 had more beneficial effects on memory and neuronal electrophysiological activity in comparison to S.C. administration.

Age-Dependent Changes of Monocarboxylate Transporter 8 Availability in the Postnatal Murine Retina

The thyroid hormones (TH) triiodothyronine (T3) and its prohormone thyroxine (T4) are crucial for retinal development and function, and increasing evidence points at TH dysregulation as a cause for retinal degenerative diseases. Thus, precise regulation of retinal TH supply is required for proper retinal function, but knowledge on these mechanisms is still fragmentary. Several transmembrane transporters have been described as key regulators of TH availability in target tissues of which the monocarboxylate transporter 8 (MCT8), a high affinity transporter for T4 and T3, plays an essential role in the central nervous system. Moreover, in the embryonic chicken retina, MCT8 is highly expressed, but the postnatal availability of MCT8 in the mammalian retina was not reported to date. In the present study, spatiotemporal retinal MCT8 availability was examined in mice of different age. For this purpose, we quantified expression levels of Mct8 via Real-Time Reverse-Transcriptase PCR in mouse eyecups (C57BL/6) of juvenile and adult age groups. Additionally, age-dependent MCT8 protein levels were quantified via Western blotting and localized via immunofluorescence confocal microscopy. While no difference in Mct8 expression levels could be detected between age groups, MCT8 protein levels in juvenile animals were about two times higher than in adult animals based on Western blot analyses. Immunohistochemical analyses showed that MCT8 immunoreactivity in the eyecup was restricted to the retina and the retinal pigment epithelium. In juvenile mice, MCT8 was broadly observed along the apical membrane of the retinal pigment epithelium, tightly surrounding photoreceptor outer segments. Distinct immunopositive staining was also detected in the inner nuclear layer and the ganglion cell layer. However, in adult specimens, immunoreactivity visibly declined in all layers, which was in line with Western blot analyses. Since MCT8 was abundantly present in juvenile and about twofold lower in adult retinae, our findings suggest a pivotal role of MCT8 especially during postnatal maturation. The present study provides novel insights into age-dependent retinal TH supply, which might help to understand different aspects regarding retinal development, function, and disorders.

Thyroid hormone signaling: Contribution to neural function, cognition, and relationship to nicotine

Cigarette smoking is common despite its adverse effects on health, such as cardiovascular disease and stroke. Understanding the mechanisms that contribute to the addictive properties of nicotine makes it possible to target them to prevent the initiation of smoking behavior and/or increase the chance of successful quit attempts. While highly addictive, nicotine is not generally considered to be as reinforcing as other drugs of abuse. There are likely other mechanisms at work that contribute to the addictive liability of nicotine. Nicotine modulates aspects of the endocrine system, including the thyroid, which is critical for normal cognitive functioning. It is possible that nicotine's effects on thyroid function may alter learning and memory, and this may underlie some of its addictive potential. Here, we review the literature on thyroid function and cognition, with a focus on how nicotine alters thyroid hormone signaling and the potential impact on cognition. Changes in cognition are a major symptom of nicotine addiction. Current anti-smoking therapies have modest success at best. If some of the cognitive effects of nicotine are mediated through the thyroid hormone system, then thyroid hormone agonists may be novel treatments for smoking cessation therapies. The content of this review is important because it clarifies the relationship between smoking and thyroid function, which has been ill-defined in the past. This review is timely because the reduction in smoking rates we have seen in recent decades, due to public awareness campaigns and public smoking bans, has leveled off in recent years. Therefore, novel treatment approaches are needed to help reduce smoking rates further.

Thyroid hormones and functional outcomes after ischemic stroke

Background

Stroke is the fifth leading cause of death and the primary cause of long-term adult disability in the United States. Increasing evidence suggests that low T3 levels immediately following acute ischemic stroke are associated with greater stroke severity, higher mortality rates, and poorer functional outcomes. Prognosis is also poor in critically ill hospitalized patients who have non-thyroidal illness syndrome (NTIS), where T3 levels are low, but TSH is normal. However, data regarding the association between TSH levels and functional outcomes are contradictory. Thus, this study investigated the role of TSH on stroke outcomes, concomitantly with T3 and T4.

Findings

In this work, blood was collected from patients with radiologically confirmed acute ischemic stroke at 24±6 hours post-symptom onset and serum levels of TSH, free T3, and free T4 were measured. Stroke outcomes were measured at discharge, 3 and 12 months using the modified Rankin scale and modified Barthel Index as markers of disability. Though we found that lower levels of free T3 were associated with worse prognosis at hospital discharge, and at 3 and 12 months post-stroke, none of these outcomes held after multivariate analysis. Thus, it is likely that thyroid hormones are associated with other factors that impact stroke outcomes, such as sex, age and stroke etiology.

Conclusions

This study found that lower levels of free T3 were associated with poorer outcomes at hospital discharge, and at 3 and 12 months post stroke, however, these associations diminished after correction for other known predictors of stroke outcome. Thyroid hormones have a complex relationship with ischemic stroke and stroke recovery, which merits further larger investigations.

Thyroid receptor β involvement in the effects of acute nicotine on hippocampus-dependent memory

Cigarette smoking is common despite adverse health effects. Nicotine's effects on learning may contribute to addiction by enhancing drug-context associations. Effects of nicotine on learning could be direct or could occur by altering systems that modulate cognition. Because thyroid signaling can alter cognition and nicotine/smoking may change thyroid function, nicotine could affect learning through changes in thyroid signaling. These studies investigate the functional contributions of thyroid receptor (TR) subtypes β and α1 to nicotine-enhanced learning and characterize the effects of acute nicotine and learning on thyroid hormone levels. We conducted a high throughput screen of transcription factor activity to identify novel targets that may contribute to the effects of nicotine on learning. Based on these results, which showed that combined nicotine and learning uniquely acted to increase TR activation, we identified TRs as potential targets of nicotine. Further analyses were conducted to determine the individual and combined effects of nicotine and learning on thyroid hormone levels, but no changes were seen. Next, to determine the role of TRβ and TRα1 in the effects of nicotine on learning, mice lacking the TRβ or TRα1 gene and wildtype littermates were administered acute nicotine prior to fear conditioning. Nicotine enhanced contextual fear conditioning in TRα1 knockout mice and wildtypes from both lines but TRβ knockout mice did not show nicotine-enhanced learning. This finding supports involvement of TRβ signaling in the effect of acute nicotine on hippocampus-dependent memory. Acute nicotine enhances learning and these effects may involve processes regulated by the transcription factor TRβ.

Treatment with Iodine in Pregnant Rats with Marginal Iodine Deficiency Improves Cell Migration in the Developing Brain of the Progeny

Marginal iodine deficiency is a common health problem in pregnant women. Epidemiological and animal studies had shown that marginally maternal iodine deficiency could cause the mild changes of maternal thyroid function, eventually lead to a negative effect on neurodevelopment. But the underlying mechanisms responsible for the neurological impairment remain unclear. The aim of this study is to explore whether marginally maternal iodine deficiency could produce subtle changes in cell migration and cognitive function of offspring, and the optimal time of giving intervention to minimize the adverse effects. In the present study, we established a marginal iodine deficiency model, and iodine supplement was performed on pre-pregnancy (PP), G13 (gestation day 13), and postnatal day 0 (P0). Our data showed that there were changes in the cytoarchitecture and the percentage of bromodeoxyuridine (BrdU)-labeled cells in the cerebral cortex in marginal iodine deficiency rats. The Reelin expression was significantly lower, but Tenascin-C was higher in the cerebral cortex of marginal iodine deficiency group on P7 than the normal group, respectively. When iodine supplement, especially before G13 could reverse the abnormal expression of the two proteins involved in cell migration, which was consistent with the results of Morris Water Maze test. The three intervention groups had shorter escape latencies than the marginal iodine deficiency rats. The earlier that iodine is supplied, the better behavior performance would reach. Our findings suggested that iodine supplement in early stage of pregnancy could improve the cell migration of cerebral cortex and neurodevelopment of offspring.

Revisiting hippocampal sclerosis in mesial temporal lobe epilepsy according to the "two-hit" hypothesis

Hippocampal sclerosis (HS) is the most common neuropathological pattern observed in pharmacoresistant epilepsy and represents a critical feature in mesial temporal lobe epilepsy syndrome. However, its pathophysiological mechanisms and neuropathological consequences on seizures remain mostly unresolved. The new international classification of hippocampal sclerosis aims at standardizing its description to allow comparisons between different clinical studies. However, several aspects are not considered in this classification (granule cell dispersion, sprouting, glial modifications…). In this chapter, we discuss these different features associated with hippocampal sclerosis in perspective with the "two-hit" hypothesis and propose mechanisms that could be involved in the modulation of some specific neuropathological aspects like early life stress, hyperthermic seizures, brain lesions or hormonal modifications.

Resveratrol improved the spatial learning and memory in subclinical hypothyroidism rat induced by hemi-thyroid electrocauterization

The major purpose of this study was to investigate the effect of resveratrol (RES) on the spatial learning and memory ability in subclinical hypothyroidism (SCH) rat model and the potential mechanism. A SCH rat model was induced by hemi-thyroid electrocauterization and the activity of hypothalamus-pituitary-thyroid (HPT) axis was detected. The spatial learning and memory ability was tested using Morris water maze (MWM) and Y-maze. The protein expressions of synaptotagmin-1 (syt-1) and brain-derived neurotrophic factor (BDNF) in the hippocampus were measured via western blot. The results showed that SCH rat model was successfully duplicated. The SCH rats showed impaired learning and memory in the behavioral tests. However, these changes were reversed by the treatment of RES (15mg/kg) and levothyroxine (LT4). Moreover, RES treated rats exhibited reduced plasma TSH level and hypothalamic thyrotropin releasing hormone (TRH) mRNA expression, which suggested that the imbalance of HPT axis in the SCH rats could be reversed by RES treatment. Furthermore, RES treatment up-regulated the protein levels of syt-1 and BDNF in hippocampus. These findings indicated an amelioration effect of RES on the spatial learning and memory in the SCH rats, the mechanism of which might be involved with its ability of modifying the hyperactive HPT axis and up-regulating the hippocampal hypo-expression of syt-1 and BDNF.

Ischemic stroke functional outcomes are independently associated with C-reactive protein concentrations and cognitive outcomes with triiodothyronine concentrations: a pilot study

Elevated concentrations of C-reactive protein (CRP) and decreased concentrations of triiodothyronine (T3) were shown to predict poor outcomes in patients with stroke. However, the prognostic value of CRP and T3 has not been studied simultaneously in relation to stroke functional and cognitive outcomes despite of close interaction between inflammatory markers and thyroid function. We evaluated the association of thyroid hormone and CRP concentrations with immediate outcomes after ischemic stroke. Eighty-eight ischemic stroke patients on admission to the stroke unit were evaluated for clinical stroke severity (Scandinavian stroke scale or SSS) and concentrations of thyroid-stimulating hormone, free thyroxin, free T3, and CRP. Functional outcome (modified Rankin scale) and cognitive outcome (Mini mental state examination) were evaluated at discharge. Greater ln CRP concentrations (r = -0.35, p = 0.001), but not thyroid hormone concentrations, correlated with score on the SSS. In univariate analyses lower free T3 concentrations and higher CRP concentrations were associated with poor functional and poor cognitive outcomes. After adjustment for clinical stroke severity, higher CRP concentrations (β = 0.18, p = 0.04) remained associated with worse functional outcome and lower free T3 concentrations with worse cognitive outcome (β = 0.23, p = 0.03). In sum, clinical stroke severity is associated with elevated CRP concentration. Higher CRP concentration is independently associated with worse functional outcomes and lower free T3 concentration with worse cognitive outcomes at discharge. T3 and CRP can be important biomarkers in patients with acute ischemic stroke.

Individual differences in novelty seeking predict subsequent vulnerability to social defeat through a differential epigenetic regulation of brain-derived neurotrophic factor expression

Some personality traits, including novelty seeking, are good predictors of vulnerability to stress-related mood disorders in both humans and rodents. While high-novelty-seeking rats [high responders (HRs)] are vulnerable to the induction of depressive-like symptoms by social defeat stress, low-novelty-seeking rats [low responders (LRs)] are not. Here, we show that such individual differences are critically regulated by hippocampal BDNF. While LR animals exhibited an increase in BDNF levels following social defeat, HR individuals did not. This difference in hippocampal BDNF expression promoted the vulnerability of HR and the resilience of LR rats. Indeed, preventing activation of BDNF signaling by infusing the BDNF scavenger TrkB-Fc into the dentate gyrus of the hippocampus of LR rats led to social defeat-induced social avoidance, whereas its activation in HR rats by the TrkB agonist 7,8-dihydroxyflavone promoted social approach. Along with the changes in BDNF expression following defeat, we report in LR animals a downregulation of the inactive BDNF receptor TrkB.T1, associated with an activation of CREB through Akt-mediated signaling, but not MSK1-mediated signaling. In HR animals, none of these molecules were affected by social defeat. Importantly, the BDNF upregulation involved an epigenetically controlled transcription of bdnf exon VI, associated with a coherent regulation of relevant epigenetic factors. Altogether, our data support the importance of hippocampal BDNF regulation in response to stressful events. Moreover, we identify a specific and adaptive regulation of bdnf exon VI in the hippocampus as a critical regulator of stress resilience, and strengthen the importance of epigenetic factors in mediating stress-induced adaptive and maladaptive responses in different individuals.

Thyroid hormone-dependent development of early cortical networks: temporal specificity and the contribution of trkB and mTOR pathways

Early in neocortical network development, triiodothyronine (T3) promotes GABAergic neurons' population increase, their somatic growth and the formation of GABAergic synapses. In the presence of T3, GABAergic interneurons form longer axons and conspicuous axonal arborizations, with an increased number of putative synaptic boutons. Here we show that the increased GABAergic axonal growth is positively correlated with the proximity to non-GABAergic neurons (non-GABA). A differential innervation emerges from a T3-dependent decrease of axonal length in fields with low density of neuronal cell bodies, combined with an increased bouton formation in fields with high density of neuronal somata. T3 addition to deprived networks after the first 2 weeks of development did not rescue deficits in the GABAergic synaptic bouton distribution, or in the frequency and duration of spontaneous bursts. During the critical 2-week-period, GABAergic signaling is depolarizing as revealed by calcium imaging experiments. Interestingly, T3 enhanced the expression of the potassium-chloride cotransporter 2 (KCC2), and accelerated the developmental shift from depolarizing to hyperpolarizing GABAergic signaling in non-GABA. The T3-related increase of spontaneous network activity was remarkably reduced after blockade of either tropomyosin-receptor kinase B (trkB) or mammalian target of rapamycin (mTOR) pathways. T3-dependent increase in GABAergic neurons' soma size was mediated mainly by mTOR signaling. Conversely, the T3-dependent selective increase of GABAergic boutons near non-GABAergic cell bodies is mediated by trkB signaling only. Both trkB and mTOR signaling mediate T3-dependent reduction of the GABAergic axon extension. The circuitry context is relevant for the interaction between T3 and trkB signaling, but not for the interactions between T3 and mTOR signaling.