Thyroid hormone inhibits ERK phosphorylation in pressure overload-induced hypertrophied mouse hearts through a receptor-mediated mechanism

Triiodothyronine (T3) suppresses hepatic tumorigenesis and development by inhibiting the phosphorylation of ERK

The effect of triiodothyronine (T3) on the phosphorylation of ERK and the occurrence and development of hepatocellular carcinoma (HCC) is controversial and remains to be clarified. In the present study, both in vitro (hepatoma cell lines) and in vivo (wild-type mice [WT] and mouse models of HCC [HrasG12Vand KrasG12Dtransgenic mice (Hras-Tg and Kras-Tg)]) systems were used to investigate the effect of T3 on p-ERK and hepatocarcinogenesis. The results showed that, in vitro, T3 treatment elevated the levels of p-ERK in hepatoma cells within 30 min. However, p-ERK levels returned to normal after 1 h with no significant effects on cellular proliferation or apoptosis. Interestingly, in vivo, T3 induced early rapid and transient activation of ERK and later persistent downregulation of p-ERK in liver tissues of WT. In Hras-Tg, liver weight, liver/body weight ratio, hepatic tumor numbers and sizes were significantly reduced withT3treatment compared with the untreated group. Furthermore, the levels of albumin, HrasG12V, and p-ERK in hepatic precancerous and tumor tissues were all significantly downregulated with T3 treatment; however, the levels of endogenous Hras were not affected. In WT, T3 also induced downregulation of Albumin in liver tissues, but without influence on the expression of endogenous Hras and p-MEK. Especially, the inhibitory effect of T3 on p-ERK and hepatic tumorigenesis and development without influence on the levels of KrasG12D and p-MEK was further confirmed in Kras-Tg. In conclusion, T3 suppresses hepatic tumorigenesis and development by independently and substantially inhibiting the phosphorylation of ERK in vivo.

Cardiac recovery from pressure overload is not altered by thyroid hormone status in old mice

Introduction

Thyroid hormones (THs) are known to have various effects on the cardiovascular system. However, the impact of TH levels on preexisting cardiac diseases is still unclear. Pressure overload due to arterial hypertension or aortic stenosis and aging are major risk factors for the development of structural and functional abnormalities and subsequent heart failure. Here, we assessed the sensitivity to altered TH levels in aged mice with maladaptive cardiac hypertrophy and cardiac dysfunction induced by transverse aortic constriction (TAC).

Methods

Mice at the age of 12 months underwent TAC and received T4 or anti-thyroid medication in drinking water over the course of 4 weeks after induction of left ventricular pressure overload.

Results

T4 excess or deprivation in older mice had no or only very little impact on cardiac function (fractional shortening), cardiac remodeling (cardiac wall thickness, heart weight, cardiomyocyte size, apoptosis, and interstitial fibrosis), and mortality. This is surprising because T4 excess or deprivation had significantly changed the outcome after TAC in young 8-week-old mice. Comparing the gene expression of deiodinases (Dio) 2 and 3 and TH receptor alpha (TRα) 1 and the dominant-negative acting isoform TRα2 between young and aged mice revealed that aged mice exhibited a higher expression of TRα2 and Dio3, while expression of Dio2 was reduced compared with young mice. These changes in Dio2 and 3 expressions might lead to reduced TH availability in the hearts of 12-month-old mice accompanied by reduced TRα action due to higher TRα2.

Discussion

In summary, our study shows that low and high TH availability have little impact on cardiac function and remodeling in older mice with preexisting pressure-induced cardiac damage. This observation seems to be the result of an altered expression of deiodinases and TRα isoforms, thus suggesting that even though cardiovascular risk is increasing with age, the response to TH stress may be dampened in certain conditions.

Stiffened fibre-like microenvironment based on patterned equidistant micropillars directs chondrocyte hypertrophy

Articular cartilage, composed of collagen type II as a major extracellular matrix and chondrocyte as a unique cell type, is a specialized connective tissue without blood vessels, lymphatic vessels and nerves. This distinctive characteristic of articular cartilage determines its very limited ability to repair when damaged. It is well known that physical microenvironmental signals regulate many cell behaviors such as cell morphology, adhesion, proliferation and cell communication even determine chondrocyte fate. Interestingly, with increasing age or progression of joint diseases such as osteoarthritis (OA), the major collagen fibrils in the extracellular matrix of articular cartilage become larger in diameter, leading to stiffening of articular tissue and reducing its resistance to external tension, which in turn aggravates joint damage or progression of joint diseases. Therefore, designing a physical microenvironment closer to the real tissue and thus obtaining data closer to the real cellular behaviour, and then revealing the biological mechanisms of chondrocytes in pathological states is of crucial importance for the treatment of OA disease. Here we fabricated micropillar substrates with the same topology but different stiffnesses to mimic the matrix stiffening that occurs in the transition from normal to diseased cartilage. It was first found that chondrocytes responded to stiffened micropillar substrates by showing a larger cell spreading area, a stronger enhancement of cytoskeleton rearrangement and more stability of focal adhesion plaques. The activation of Erk/MAPK signalling in chondrocytes was detected in response to the stiffened micropillar substrate. Interestingly, a larger nuclear spreading area of chondrocytes at the interface layer between the cells and top surfaces of micropillars was observed in response to the stiffened micropillar substrate. Finally, it was found that the stiffened micropillar substrate promoted chondrocyte hypertrophy. Taken together, these results revealed the cell responses of chondrocytes in terms of cell morphology, cytoskeleton, focal adhesion, nuclei and cell hypertrophy, and may be beneficial for understanding the cellular functional changes affected by the matrix stiffening that occurs during the transition from a normal state to a state of osteoarthritis.

High triiodothyronine levels induce myocardial hypertrophy via BAFF overexpression

Activated B cells contribute to heart diseases, and inhibition of B‐cell activating factor (BAFF) expression is an effective therapeutic target for heart diseases. Whether activated B cells participate in the development and progression of hyperthyroid heart disease, and what induces B cells activation in hyperthyroidism are unknown. The present study aimed to determine the roles of BAFF overexpression induced by high concentrations of triiodothyronine (T3) in the pathogenesis of hyperthyroid heart disease. Female C57BL/6J mice were subcutaneously injected with T3 for 6 weeks, and BAFF expression was inhibited using shRNA. Protein and mRNA expression of BAFF in mouse heart tissues evaluated via immunohistochemistry, western blotting and polymerase chain reaction (PCR). Proportions of B cells in mouse cardiac tissue lymphocytes were quantified via flow cytometry. Morphology and left ventricle function were assessed using pathological sections and echocardiography, respectively. Here, we demonstrate that compared with the control group, the proportion of myocardial B cells was larger in the T3 group; immunohistochemistry, western blotting and PCR analyses revealed increased protein and mRNA expression levels of TNF‐α and BAFF in heart tissues of the T3 group. Compared with the normal controls group, in the T3 group, the diameter of myocardial cells and some echocardiographic values significantly increased and hypertrophy and structural disorder were noticeable. Our results revealed that elevated levels of circulating T3 can promote the expression of BAFF in myocardial cells and can lead to B‐cell activation, an elevated inflammatory response and ventricular remodelling.

Biological mechanisms of aging predict age-related disease co-occurrence in patients

Genetic, environmental, and pharmacological interventions into the aging process can confer resistance to multiple age-related diseases in laboratory animals, including rhesus monkeys. These findings imply that individual mechanisms of aging might contribute to the co-occurrence of age-related diseases in humans and could be targeted to prevent these conditions simultaneously. To address this question, we text mined 917,645 literature abstracts followed by manual curation and found strong, non-random associations between age-related diseases and aging mechanisms in humans, confirmed by gene set enrichment analysis of GWAS data. Integration of these associations with clinical data from 3.01 million patients showed that age-related diseases associated with each of five aging mechanisms were more likely than chance to be present together in patients. Genetic evidence revealed that innate and adaptive immunity, the intrinsic apoptotic signaling pathway and activity of the ERK1/2 pathway were associated with multiple aging mechanisms and diverse age-related diseases. Mechanisms of aging hence contribute both together and individually to age-related disease co-occurrence in humans and could potentially be targeted accordingly to prevent multimorbidity.

Ezh2 promotes TRβ lysine methylation-mediated degradation in hepatocellular carcinoma

BACKGROUND

Post-translational modification (PTM) of proteins controls various cellular functions of transcriptional regulators and participates in diverse signal transduction pathways in cancer. The thyroid hormone (triiodothyronine, T3) plays a critical role in metabolic homeostasis via its direct interaction with the thyroid hormone receptor beta (TRβ). TRβ is involved in physiological processes, such as cell growth, differentiation, apoptosis, and maintenance of metabolic homeostasis through transcriptional regulation of target genes.

OBJECTIVE

This study was performed to characterize the specific PTM of TRβ is an active control mechanism for the proteasomal degradation of TRβ in transcriptional signaling pathways in hepatocellular carcinoma cells.

METHODS

Based on a previous study, we predicted that the lysine methyltransferase and methylation sites of TRβ by comparing the amino acid sequences of histone H3 and TRβ. Methyl-acceptor site of TRβ was confirmed by point mutation. TRβ protein stability was evaluated by ubiquitination assay with MG132. For glucose starvation, HepG2 cells were incubated in media without D-glucose. Proliferation-related proteins were detected by western blotting. MicroRNA level and autophagy marker were measured by real-time qPCR.

RESULTS

The presence of enhancer of zeste homolog 2 (Ezh2), a methyltransferase of H3 lysine 27, as a methyltransferase of TRβ also revealed that direct lysine methylation and consequent stimulated protein degradation of TRβ underlies the negative correlation between Ezh2 and TRβ. Notably, glucose starvation significantly increased lysine methylation, and methylated TRβ showed further protein instability leading to an increase in the proliferation and growth of hepatocellular carcinoma cells.

CONCLUSIONS

TRβ functions as a tumor suppressor in various cancers; therefore, we evaluated the effect of TRβ degradation on oncogenesis during glucose starvation. These data clearly define a functional model and provide a link between metabolism and cancer by regulating methyl-dependent protein levels of tumor suppressors. Taken together, maintaining TRβ against methyl-dependent degradation is considered a possible therapeutic target for cancer progression.

Targeting the DIO3 enzyme using first-in-class inhibitors effectively suppresses tumor growth: a new paradigm in ovarian cancer treatment

The enzyme iodothyronine deiodinase type 3 (DIO3) contributes to cancer proliferation by inactivating the tumor-suppressive actions of thyroid hormone (T3). We recently established DIO3 involvement in the progression of high-grade serous ovarian cancer (HGSOC). Here we provide a link between high DIO3 expression and lower survival in patients, similar to common disease markers such as Ki67, PAX8, CA-125, and CCNE1. These observations suggest that DIO3 is a logical target for inhibition. Using a DIO3 mimic, we developed original DIO3 inhibitors that contain a core of dibromomaleic anhydride (DBRMD) as scaffold. Two compounds, PBENZ-DBRMD and ITYR-DBRMD, demonstrated attenuated cell counts, induction in apoptosis, and a reduction in cell proliferation in DIO3-positive HGSOC cells (OVCAR3 and KURAMOCHI), but not in DIO3-negative normal ovary cells (CHOK1) and OVCAR3 depleted for DIO3 or its substrate, T3. Potent tumor inhibition with a high safety profile was further established in HGSOC xenograft model, with no effect in DIO3-depleted tumors. The antitumor effects are mediated by downregulation in an array of pro-cancerous proteins, the majority of which known to be repressed by T3. To conclude, using small molecules that specifically target the DIO3 enzyme we present a new treatment paradigm for ovarian cancer and potentially other DIO3-dependent malignancies.

Protective Effects of Thyroid Hormone Deprivation on Progression of Maladaptive Cardiac Hypertrophy and Heart Failure

Purpose: Thyroid hormones (TH) play a central role for cardiac function. TH influence heart rate and cardiac contractility, and altered thyroid function is associated with increased cardiovascular morbidity and mortality. The precise role of TH in onset and progression of heart failure still requires clarification. Methods: Chronic left ventricular pressure overload was induced in mouse hearts by transverse aortic constriction (TAC). One week after TAC, alteration of TH status was induced and the impact on cardiac disease progression was studied longitudinally over 4 weeks in mice with hypo- or hyperthyroidism and was compared to euthyroid TAC controls. Serial assessment was performed for heart function (2D M-mode echocardiography), heart morphology (weight, fibrosis, and cardiomyocyte cross-sectional area), and molecular changes in heart tissues (TH target gene expression, apoptosis, and mTOR activation) at 2 and 4 weeks. Results: In diseased heart, subsequent TH restriction stopped progression of maladaptive cardiac hypertrophy and improved cardiac function. In contrast and compared to euthyroid TAC controls, increased TH availability after TAC propelled maladaptive cardiac growth and development of heart failure. This was accompanied by a rise in cardiomyocyte apoptosis and mTOR pathway activation. Conclusion: This study shows, for the first time, a protective effect of TH deprivation against progression of pathological cardiac hypertrophy and development of congestive heart failure in mice with left ventricular pressure overload. Whether this also applies to the human situation needs to be determined in clinical studies and would infer a critical re-thinking of management of TH status in patients with hypertensive heart disease.

Sexual dimorphism in pre-clinical studies of depression

Although there is a sex bias in the pathological mechanisms exhibited by brain disorders, investigation of the female brain in biomedical science has long been neglected. Use of the male model has generally been the preferred option as the female animal model exhibits both biological variability and hormonal fluctuations. Existing studies that compare behavioral and/or molecular alterations in animal models of brain diseases are generally underrepresented, and most utilize the male model. Nevertheless, in recent years there has been a trend toward the increased inclusion of females in brain studies. However, current knowledge regarding sex-based differences in depression and stress-related disorders is limited. This can be improved by reviewing preclinical studies that highlight sex differences in depression. This paper therefore presents a review of sex-based preclinical studies of depression. These shed light on the discrepancies between males and females regarding the biological mechanisms that underpin mechanistic alterations in the diseased brain. This review also highlights the conclusions drawn by preclinical studies to advance our understanding of mood disorders, encouraging researchers to promote ways of investigating and managing sexually dimorphic disorders.

Left ventricular phosphorylation patterns of Akt and ERK1/2 after triiodothyronine intracoronary perfusion in isolated hearts and short-term in vivo treatment in Wistar rats

OBJECTIVES

To determine the effects of triiodothyronine (T3) intracoronary perfusion in isolated hearts and short-term administration in rats on the left ventricular (LV) phosphorylation patterns of Akt and ERK1/2.

MATERIALS AND METHODS

Cardiodynamic and hemodynamic parameters were evaluated in Langendorff-perfused hearts. Left ventricles were used for histomorphometric and Western blot analyses. Short-term hyperthyroidism was established by T3 (500 μg.kg^-1.d^-1; subcutaneous injection) for 1 (T3_1d), 3 (T3_3d), and 10 (T3_10d) days.

RESULTS

Isolated hearts receiving T3 perfusion did not modify LV developed pressure, +dP/dt_max, -dP/dt_min, heart rate, and coronary perfusion pressure compared with vehicle-perfused hearts. P-ERK1/2 and p-Akt levels in LV tissues after 5, 15, or 60 min of T3 or vehicle perfusion were similar. Compared with their time-matched controls, isolated hearts of T3_3d and T3_10d rats exhibited LV hypertrophy and increased absolute values of +dP/dt_max and -dP/dt_min (i.e., positive inotropic and lusitropic effects). P-ERK1/2 decreased in LV tissues of T3_1d and T3_10d but not in those of T3_3d rats, and p-Akt levels augmented in left ventricles of T3_3d and stayed unaltered in those of T3_1d and T3_10d rats.

CONCLUSION

T3 intracoronary perfusion did not alter cardiodynamics and hemodynamics nor influence the activation of Akt and ERK of normal hearts. Accordingly, the rapid non-genomic effects of T3 were not evident. Short-term T3 treatment provoked cardiac hypertrophy coincidental with increased LV function and associated with transient Akt activation and cyclic ERK1/2 inhibition; which implies activation of physiological hypertrophy signaling and deactivation of pathological hypertrophy signaling, respectively.

Local hyperthyroidism promotes pancreatic acinar cell proliferation during acute pancreatitis

Proliferation of pancreatic acinar cells is a critical process in the pathophysiology of pancreatic diseases, because limited or defective proliferation is associated with organ dysfunction and patient morbidity. In this context, elucidating the signalling pathways that trigger and sustain acinar proliferation is pivotal to develop therapeutic interventions promoting the regenerative process of the organ. In this study we used genetic and pharmacological approaches to manipulate both local and systemic levels of thyroid hormones to elucidate their role in acinar proliferation following caerulein-mediated acute pancreatitis in mice. In addition, molecular mechanisms mediating the effects of thyroid hormones were identified by genetic and pharmacological inactivation of selected signalling pathways.In this study we demonstrated that levels of the thyroid hormone 3,3',5-triiodo-l-thyronine (T3) transiently increased in the pancreas during acute pancreatitis. Moreover, by using genetic and pharmacological approaches to manipulate both local and systemic levels of thyroid hormones, we showed that T3 was required to promote proliferation of pancreatic acinar cells, without affecting the extent of tissue damage or inflammatory infiltration.Finally, upon genetic and pharmacological inactivation of selected signalling pathways, we demonstrated that T3 exerted its mitogenic effect on acinar cells via a tightly controlled action on different molecular effectors, including histone deacetylase, AKT, and TGFβ signalling.In conclusion, our data suggest that local availability of T3 in the pancreas is required to promote acinar cell proliferation and provide the rationale to exploit thyroid hormone signalling to enhance pancreatic regeneration. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Thyroid hormone receptors and resistance to thyroid hormone disorders

Thyroid hormone action is predominantly mediated by thyroid hormone receptors (THRs), which are encoded by the thyroid hormone receptor α (THRA) and thyroid hormone receptor β (THRB) genes. Patients with mutations in THRB present with resistance to thyroid hormone β (RTHβ), which is a disorder characterized by elevated levels of thyroid hormone, normal or elevated levels of TSH and goitre. Mechanistic insights about the contributions of THRβ to various processes, including colour vision, development of the cochlea and the cerebellum, and normal functioning of the adult liver and heart, have been obtained by either introducing human THRB mutations into mice or by deletion of the mouse Thrb gene. The introduction of the same mutations that mimic human THRβ alterations into the mouse Thra and Thrb genes resulted in distinct phenotypes, which suggests that THRA and THRB might have non-overlapping functions in human physiology. These studies also suggested that THRA mutations might not be lethal. Seven patients with mutations in THRα have since been described. These patients have RTHα and presented with major abnormalities in growth and gastrointestinal function. The hypothalamic-pituitary-thyroid axis in these individuals is minimally affected, which suggests that the central T3 feedback loop is not impaired in patients with RTHα, in stark contrast to patients with RTHβ.

In vivo selective expression of thyroid hormone receptor α1 in endothelial cells attenuates myocardial injury in experimental myocardial infarction in mice

Ischemic heart disease (IHD) is the single most common cause of death. New approaches to enhance myocardial perfusion are needed to improve outcomes for patients with IHD. Thyroid hormones (TH) are known to increase blood flow; however, their usefulness for increasing perfusion in IHD is limited because TH accelerates heart rate, which can be detrimental. Therefore, selective activation of TH effects is desirable. We hypothesized that cell-type-specific TH receptor (TR) expression can increase TH action in the heart, while avoiding the negative consequences of TH treatment. We generated a binary transgenic (BTG) mouse that selectively expresses TRα1 in endothelial cells in a tetracycline-inducible fashion. In BTG mice, endothelial TRα1 protein expression was increased by twofold, which, in turn, increased coronary blood flow by 77%, coronary conductance by 60%, and coronary reserve by 47% compared with wild-type mice. Systemic blood pressure was decreased by 20% in BTG mice after TRα1 expression. No effects on heart rate were observed. Endothelial TRα1 expression activated AKT/endothelial nitric oxide synthase pathway and increased A2AR adenosine receptor. Furthermore, hearts from BTG mice overexpressing TRα1 that were submitted to 20 min ischemia and 20 min reperfusion showed a 20% decline in left ventricular pressure (LVP) compared with control mice where LVP was decreased by 42%. Studies using an infarction mouse model demonstrated that endothelial overexpression of TRα1 decreased infarct size by 45%. In conclusion, selective expression of TRα1 in endothelial cells protects the heart against injury after an ischemic insult and does not result in adverse cardiac or systemic effects.

Small and large animal models in cardiac contraction research: advantages and disadvantages

The mammalian heart is responsible for not only pumping blood throughout the body but also adjusting this pumping activity quickly depending upon sudden changes in the metabolic demands of the body. For the most part, the human heart is capable of performing its duties without complications; however, throughout many decades of use, at some point this system encounters problems. Research into the heart's activities during healthy states and during adverse impacts that occur in disease states is necessary in order to strategize novel treatment options to ultimately prolong and improve patients' lives. Animal models are an important aspect of cardiac research where a variety of cardiac processes and therapeutic targets can be studied. However, there are differences between the heart of a human being and an animal and depending on the specific animal, these differences can become more pronounced and in certain cases limiting. There is no ideal animal model available for cardiac research, the use of each animal model is accompanied with its own set of advantages and disadvantages. In this review, we will discuss these advantages and disadvantages of commonly used laboratory animals including mouse, rat, rabbit, canine, swine, and sheep. Since the goal of cardiac research is to enhance our understanding of human health and disease and help improve clinical outcomes, we will also discuss the role of human cardiac tissue in cardiac research. This review will focus on the cardiac ventricular contractile and relaxation kinetics of humans and animal models in order to illustrate these differences.

American Thyroid Association Guide to investigating thyroid hormone economy and action in rodent and cell models

BACKGROUND

An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment approaches for patients with thyroid disease.

SUMMARY

Important clinical practices in use today for the treatment of patients with hypothyroidism, hyperthyroidism, or thyroid cancer are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a series of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings.

CONCLUSIONS

It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes.

Hyperthyroidism and cardiovascular complications: a narrative review on the basis of pathophysiology

Cardiovascular complications are important in hyperthyroidism because of their high frequency in clinical presentation and increased mortality and morbidity risk. The cause of hyperthyroidism, factors related to the patient, and the genetic basis for complications are associated with risk and the basic underlying mechanisms are important for treatment and management of the disease. Besides cellular effects, hyperthyroidism also causes hemodynamic changes, such as increased preload and contractility and decreased systemic vascular resistance causes increased cardiac output. Besides tachyarrythmias, impaired systolic ventricular dysfunction and diastolic dysfunction may cause thyrotoxic cardiomyopathy in a small percentage of the patients, as another high mortality complication. Although the medical literature has some conflicting data about benefits of treatment of subclinical hyperthyroidism, even high-normal thyroid function may cause cardiovascular problems and it should be treated. This review summarizes the cardiovascular consequences of hyperthyroidism with underlying mechanisms.

Ablation of ALCAT1 mitigates hypertrophic cardiomyopathy through effects on oxidative stress and mitophagy

Oxidative stress causes mitochondrial dysfunction and heart failure through unknown mechanisms. Cardiolipin (CL), a mitochondrial membrane phospholipid required for oxidative phosphorylation, plays a pivotal role in cardiac function. The onset of age-related heart diseases is characterized by aberrant CL acyl composition that is highly sensitive to oxidative damage, leading to CL peroxidation and mitochondrial dysfunction. Here we report a key role of ALCAT1, a lysocardiolipin acyltransferase that catalyzes the synthesis of CL with a high peroxidation index, in mitochondrial dysfunction associated with hypertrophic cardiomyopathy. We show that ALCAT1 expression was potently upregulated by the onset of hyperthyroid cardiomyopathy, leading to oxidative stress and mitochondrial dysfunction. Accordingly, overexpression of ALCAT1 in H9c2 cardiac cells caused severe oxidative stress, lipid peroxidation, and mitochondrial DNA (mtDNA) depletion. Conversely, ablation of ALCAT1 prevented the onset of T4-induced cardiomyopathy and cardiac dysfunction. ALCAT1 deficiency also mitigated oxidative stress, insulin resistance, and mitochondrial dysfunction by improving mitochondrial quality control through upregulation of PINK1, a mitochondrial GTPase required for mitochondrial autophagy. Together, these findings implicate a key role of ALCAT1 as the missing link between oxidative stress and mitochondrial dysfunction in the etiology of age-related heart diseases.

[Influence of thyroid function in CPK serum levels]

OBJECTIVE

To determine serum CPK variation based on TSH e free T4 (FT4), and to assess serum CPK in pathological states of the thyroid (hyperthyroidism and hypothyroidism), in relation to the euthyroidism.

MATERIAL AND METHODS

We evaluated retrospectively 6,230 laboratory results of TSH and CPK from 2007 to 2011. From these, 3,369 had free T4 results. We evaluated the correlation between CPK and TSH and the pathological states of the thyroid.

RESULTS

The correlation between TSH and CPK was positive (r = 0.065), while that between CPK and FT4 was negative (r = -0.091, p < 0.05). From the total of results analyzed, 586 (9.4%) were measures of hyperthyroidism, with a median (range) of CPK of 98 U/L (27 to 1,113), and 556 (8.9%) were of hypothyroidism, with CPK of 114 U/L (25-4,182).

CONCLUSION

A positive correlation was found between serum CPK and TSH, and a negative correlation between CPK and FT4. CPK was lower in the group with hyperthyroidism, and greater in that with hypothyroidism.

Impaired learning and memory performance in a subclinical hypothyroidism rat model induced by hemi-thyroid electrocauterisation

It is well known that clinical hypothyroidism (CH) can induce cognitive deficits, and the decision to start treatment for CH with thyroxine is usually straightforward. However, the relationship of cognition dysfunction with subclinical hypothyroidism (SCH) is inconsistent, and the decision concerning the need to treat SCH is controversial. In the present study, we induced a SCH rat model by hemi-thyroid electrocauterisation; then employed a serial of behavioural tests, including a beam balance, open field task and Morris water maze (MWM), to investigate the behaviour performance of SCH rats; and finally explored the protein expression of phosphorylated extracellular signal-regulated kinase (ERK)1/2 in the hippocampus by western blotting. The results demonstrated that hemi-thyroid electrocauterised rats had an elevated plasma thyrotrophin-stimulating hormone (TSH) level, with normal free thyroxine (fT4) and triiodothyronine (T3) concentrations, which defines SCH in humans. If rat SCH is diagnosed according to measurements of both plasma TSH higher than 97.5 percentile for the sham group and fT4 in the range 2.5-97.5 percentile for the sham group, the success rate of SCH modelling was 66.6%. SCH decreased exploratory behaviour but did not affect motor function in rats, showing a negative correlation of exploratory behaviour with plasma TSH concentration. Moreover, SCH rats displayed an impairment of learning and memory ability in the MWM task, with a longer escape latency in the acquisition phase and a shorter duration in the target quadrant in the test phase compared to that of sham rats. The mechanism for this might be related to the increased plasma TSH concentration, the decreased hippocampal T3 level and the enhanced expression of phosphorylated ERK1/2 in the hippocampus. The results of the present study, together with the results obtained in other studies, suggest that treatment is necessary for SCH.

Dose-dependent effects of thyroid hormone on post-ischemic cardiac performance: potential involvement of Akt and ERK signalings

The present study explored the effects of thyroid hormone (TH) treatment on post-ischemic cardiac function and potential implicated mechanisms. Acute myocardial infarction (AMI) was induced in mice by coronary artery ligation while sham-operated animals served as controls. This procedure resulted in a marked depression of cardiac function and significant reduction in TH levels in plasma. TH was given at a dose aiming to normalize T3 levels in plasma [AMI-TH (A)] and also at higher doses. The group of animals treated with the highest dose of TH, which displayed significantly increased mortality rate was included in the study [AMI-TH (B)]. In AMI-TH (A) mice, TH significantly improved left ventricular (LV) ejection fraction (EF%), [27.9% (1.4) in AMI versus 38.0 (3.1) in AMI-TH (A), P < 0.05], and favorably remodeled LV chamber while α-MHC was the dominant isoform expressed. In AMI-TH (B) mice, TH treatment resulted in increased mortality as compared to untreated mice (73% vs 47%, P < 0.05), while the favorable effect of TH was not evident in the survived animals. At the molecular level, TH, at the replacement dose, modestly increased p-Akt levels in the myocardium without any change in p-ERK levels. On the contrary, TH at the higher dose resulted in further increase in p-Akt along with an increase in p-ERK levels. In conclusion, TH appears to have a dose-dependent bimodal effect on post-ischemic cardiac performance and this effect may, at least in part, be mediated by a distinct pattern of activation of Akt and ERK signaling.

Src kinase integrates PI3K/Akt and MAPK/ERK1/2 pathways in T3-induced Na-K-ATPase activity in adult rat alveolar cells

We previously reported that the 3,5,3'-triiodo-L-thyronine (T3)-induced increase of Na-K-ATPase activity in rat alveolar epithelial cells (AECs) required activation of Src kinase, PI3K, and MAPK/ERK1/2. In the present study, we assessed the role of Akt in Na-K-ATPase activity and the interaction between the PI3K and MAPK in response to T3 by using MP48 cells, inhibitors, and constitutively active mutants in the MP48 (alveolar type II-like) cell line. The Akt inhibitor VIII blocked T3-induced increases in Na-K-ATPase activity and amount of plasma membrane Na-K-ATPase protein. The Akt inhibitor VIII also abolished the increase in Na-K-ATPase activity induced by constitutively active mutants of either Src kinase or PI3K. Moreover, constitutively active mutants of Akt increased Na-K-ATPase activity in the absence of T3. Thus activation of Akt was required for T3-induced Na-K-ATPase activity in AECs and is sufficient in the absence of T3. Inhibitors of Src kinase (PP1), PI3K (wortmannin), and ERK1/2 (U0126) all blocked the T3-induced Na-K-ATPase activity. PP1 blocked the activation of PI3K and also ERK1/2 by T3, whereas U0126 did not prevent T3 activation of Src kinase or PI3K activity. Wortmannin did not significantly alter T3-increased MAPK/ERK1/2 activity, suggesting that T3-activated PI3K/Akt and MAPK/ERK1/2 pathways acted downstream of the Src kinase. Furthermore, in the absence of T3, a constitutively active mutant of Src kinase increased activities of Na-K-ATPase, PI3K, and MAPK/ERK1/2. A constitutively active mutant of PI3K enhanced Na-K-ATPase activity but did not alter the MAPK/ERK1/2 activity significantly. In summary, in adult rat AECs T3-stimulated Src kinase activity can activate both PI3K/Akt and MAPK/ERK1/2, and activation of Akt is necessary for T3-induced Na-K-ATPase activity.