Endothelial Functioning and Hemodynamic Parameters in Rats with Subclinical Hypothyroid and the Effects of Thyroxine Replacement

The Na+/K+-ATPase: A potential therapeutic target in cardiometabolic diseases

Cardiometabolic diseases (CMD) are a direct consequence of modern living and contribute to the development of multisystem diseases such as cardiovascular diseases and diabetes mellitus (DM). CMD has reached epidemic proportions worldwide. A sodium pump (Na⁺/K⁺-ATPase) is found in most eukaryotic cells' membrane and controls many essential cellular functions directly or indirectly. This ion transporter and its isoforms are important in the pathogenesis of some pathological processes, including CMD. The structure and function of Na⁺/K⁺-ATPase, its expression and distribution in tissues, and its interactions with known ligands such as cardiotonic steroids and other suspected endogenous regulators are discussed in this review. In addition, we reviewed recent literature data related to the involvement of Na⁺/K⁺-ATPase activity dysfunction in CMD, focusing on the Na⁺/K⁺-ATPase as a potential therapeutic target in CMD.

Hypothyroidism and Risk of Cardiovascular Disease

Thyroid hormones (TH) have a significant impact on cellular oxidative metabolism. Besides that, they maintain vascular homeostasis by positive effects on endothelial and vascular smooth muscle cells. Subclinical (SCH) and clinical (CH) hypothyroidism influences target organs by changing their morphology and function and impaired blood and oxygen supply induced by accelerated atherosclerosis. The increased risk of acceleration and extension of atherosclerosis in patients with SCH and CH could be explained by dyslipidemia, diastolic hypertension, increased arterial stiffness, endothelial dysfunction, and altered blood coagulation. Instability of atherosclerotic plaque in hypothyroidism could cause excessive activity of the elements of innate immunity, which are characterized by: the significant presence of macrophages in atherosclerotic plaques, increased nuclear factor kappa B (NFkB) expression, and elevated levels of tumor necrosis factor α (TNF-α) and matrix metalloproteinase (MMP) 9, with reduced interstitial collagen, which all together creates inflammation milieu resulted in plaque rupture. Optimal substitution by levothyroxine (LT4) restores biochemical euthyroidism. In postmenopausal women and elderly patients with hypothyroidism and associated vascular comorbidity, excessive LT4 substitution could lead to atrial rhythm disorders and osteoporosis. Therefore, it is of interest to maintain thyroid-stimulating hormone (TSH) levels in the reference range, thus eliminating the deleterious effects of lower or higher TSH levels on the cardiovascular system. This review summarizes the recent literature on subclinical and clinical hypothyroidism and atherosclerotic cardiovascular disease and discusses the effects of LT4 replacement therapy on restoring biochemical euthyroidism and atherosclerosis processes.

Cardiovascular Responses to 5-hydroxytryptamine in Methimazole-induced Hypothyroid Pithed Rats

BACKGROUND

Patients suffering from hypothyroidism tend to develop diastolic hypertension. 5-Hydroxytryptamine (5-HT) is an amine that contributes to the maintenance of the blood pressure through central and peripheral 5-HT receptors. Curiously, the hypothyroidism alters the density of the 5-HT receptors in rodent brains.

AIM OF THE STUDY

Analyze the effect of the methimazole-induced hypothyroidism on the peripheral cardiovascular responses elicited by 5-HT.

METHODS

The vasopressor and tachycardic responses to 5-HT (3-300 μg/kg), and the vasodepressor responses to 5-HT, 5-carboxamidotryptamine (5-CT, 0.001-0.1 μg/kg), isoprenaline (0.03-1 μg/kg) and acetylcholine (ACh, 0.03-3 μg/kg), during an infusion of methoxamine, were determined in pithed hypothyroid rats.

RESULTS

The tachycardic and vasopressor responses to 5-HT and the vasodepressor responses to 5-CT and ACh remained unaffected, the vasodepressor response to 5-HT reduced, and the vasodepressor response to isoprenaline enhanced and reduced at the lowest and highest dose, respectively.

CONCLUSION

These results suggest that hypothyroidism impairs the vasodepressor response to 5-HT, which could contribute to hypothyroidism-induced hypertension.

An investigation of thiol/disulfide homeostasis in patients with Behçet's disease

INTRODUCTION

Behçet's disease (BD) is a relapsing systemic inflammatory disorder. The diagnosis of BD is primarily based on clinical findings. Current biomarkers are not yet sufficient to diagnose and cannot anticipate the course of the disease and response to treatment. The aim of this study was to evaluate the relationship between the thiol-disulfide balance and disease activity and organ involvement in BD.

MATERIAL AND METHODS

A hundred fifty patients with BD and 100 age- and gender-matched healthy controls were included in the study. Disease activity was assessed with the BD Current Activity form score. Serum levels of native thiol (NT), total thiol (TT), and disulfide were measured and the disulfide/native thiol, disulfide/total thiol and native thiol/total thiol levels were calculated for the patient and control groups.

RESULTS

Native thiol, total thiol, native thiol/total thiol values of the BD patients were significantly lower than those of the control group. The disulfide/native thiol, disulfide/total thiol values of BD patients were higher compared to the control group and the disulfide value of the BD group was slightly higher compared to the control group. No correlation was determined between thiol levels and disease activity and organ involvement in BD.

CONCLUSIONS

In patients with Behcet's disease, the thiol-disulfide homeostasis balance shifted towards disulfide formation due to thiol oxidation. It may be used as a novel marker in BD because it is easy, practical, fully automated and relatively inexpensive.

Association between thyroid-stimulating hormone and maternal hemodynamics in hypertensive disorders of pregnancy: an observational study

Background

Hypertensive disorders of pregnancy (HDP) are characterized by hemodynamic disturbances. Altered thyroid function is a risk factor for poor outcomes of pregnancy. However, the associations between thyroid function biomarkers and maternal hemodynamics during pregnancy in HDP remain unclear.

Methods

From January 2016 to January 2018, pregnant women diagnosed with HDP admitted to the Nanjing Maternity and Child Health Care Hospital were prospectively enrolled in the third trimester. Normally distributed variables were expressed as mean ± standard deviation and skewed variables were expressed as median (25th percentile, 75th percentile). Correlations between thyroid-stimulating hormone (TSH) or free thyroxine (FT4) and maternal hemodynamic parameters were assessed by Pearson’s correlation coefficient and 95% confidence interval (95%CI). Bonferroni’s correction for multiple correlations was performed. Logistic regression models with odd ratio (OR) and 95%CI were applied to confirm the associations.

Results

A total of 163 third-trimester pregnant women with HDP with a mean gestational age of 35.62 ± 2.83 weeks were recruited. The infant birth weight of patients with elevated TSH levels was lower than that of patients with normal TSH levels (2635 ± 867 g vs. 3037 ± 673 g, p = 0.002). Reduced cardiac output (CO) was defined as CO < 3.5 L/min. The infant birth weight of patients with reduced CO was lower than that of patients with normal CO (2250 ± 510 g vs. 2890 ± 774 g, p = 0.002). TSH levels were significantly and negatively correlated with CO (r = − 0.260, 95%CI: − 0.392- -0.103, p < 0.001). FT4 levels were not significantly correlated with any of the maternal hemodynamic parameters (all p > 0.05). TSH level (OR = 1.371, 95%CI: 1.086–1.733, p = 0.008) was confirmed associated with reduced CO in the logistic regression analysis.

Conclusions

Elevated TSH levels are associated with reduced CO in HDP during the third trimester.

The effect of 131I-induced hypothyroidism on the levels of nitric oxide (NO), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), total nitric oxide synthase (NOS) activity, and expression of NOS isoforms in rats

Accumulating evidence has shown that hypothyroidism affects the cardiovascular system, significantly increasing the incidence of cardiovascular diseases. In the present study we investigated the effect of radioactive iodine (I-131)-induced hypothyroidism on several parameters of vascular function, such as nitric oxide (NO), total nitric oxide synthase (NOS) activity and expression of NOS isoforms, as well as on interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) as indicators of inflammation, in rats. A dose of 150 µCi of 131-I was determined as optimal for establishing the model of hypothyroidism in rats. After administration of 131-I, at the end of month 1, 2, and 4 (n = 3 for each time point), NO, IL-6, and TNF-α in the serum and total NOS activity in the aorta were determined in 150 µCi group, compared to controls. The mRNA and protein expression of endothelial, neuronal, and inducible NOS (eNOS, nNOS, and iNOS) in the rat aorta was also estimated, using quantitative reverse transcription polymerase chain reaction and Western blot, respectively. The levels of IL-6 and TNF-α increased in 150 µCi group; the results were significant at the end of month 2 and 4 for IL-6, and at all time points for TNF-α. The levels of NO decreased significantly at the end of month 2 and 4 in 150 µCi group. The total NOS activity increased significantly in 150 µCi group, at all three time points. Significant changes in the mRNA and protein expression of all three NOS isoforms were observed in 150 µCi group compared to controls. NO, IL-6, TNF-α levels and NOS activity and expression are altered in hypothyroid state, and the underlying mechanism should be further investigated.

Adipokine expression and endothelial function in subclinical hypothyroidism rats

The purpose of our study was to observe adipokine expression and endothelial function in subclinical hypothyroidism (sHT) rats and to determine whether levothyroxine (LT₄) treatment affects these changes. Sixty-five male Wistar rats were randomly divided into five groups: the control group; sHT A, B and C groups and the sHT + T₄ group. The sHT rats were induced by methimazole (MMI) and the sHT + T₄ rats were administered LT₄ treatment after 8 weeks of MMI administration. Thyroid function and lipid levels were measured using radioimmunoassays and enzymatic colorimetric methods, respectively. Serum adiponectin (APN), chemerin, TNF-α, endothelin (ET-1) and nitric oxide (NO) levels were measured using ELISA kits and a nitric-reductive assay. The expression of APN, chemerin and TNF-α in visceral adipose tissue (VAT) was measured in experimental rats using RT-PCR and Western blotting. Hematoxylin-eosin (HE) staining was used to observe changes in adipose tissue. The sHT rats had significantly higher levels of thyroid-stimulating hormone (TSH), TNF-α, chemerin, ET-1, total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) and lower levels of APN and NO than those in control and sHT + T₄ rats. Based on Pearson correlation analysis, the levels of chemerin, TNF-α, ET-1, LDL-C, TC and triglyceride (TG) were positively correlated with TSH, but APN and NO levels were negatively correlated with TSH. These findings demonstrated that high TSH levels contribute to the changes of adipokines and endothelial dysfunction in sHT, but LT₄ treatment ameliorates those changes.

The Change of Left Ventricular Function in Rats with Subclinical Hypothyroid and the Effects of Thyroxine Replacement

OBJECTIVE

The main purpose of this study was to explore the relationships between serca2a, Ryr2, adipokines, and the left ventricular function in the subclinical hypothyroidism with different TSH levels and to determine the impact of L-T4 treatment on these indexes.

METHODS

Sixty-five male Wistar rats were randomly divided into five groups: control group; sHT A, B, and C group; and sHT + T4 group. The sHT rats were induced by methimazole (MMI), and the sHT + T4 rats were administered with L-T4 treatment after 8 weeks of MMI administration. Serum TT4, TSH, APN, chemerin, and TNF-α were detected by radioimmunoassay kits and ELISA kits; left ventricular function was measured by PowerLab system via subclavian artery catheter. The expression of Serca2a, Ryr2, APN, chemerin, and TNF-α were detected by RT-PCR, Western blot, and immunohistochemistry.

RESULTS

The sHT groups had significantly higher TSH, chemerin, and TNF-α and lower Serca2a, Ryr2, and APN. The left ventricular pressure and heart rate in sHT groups were significantly lower in control and sHT + T4 group. Histopathological examination revealed the pathological changes in the sHT rats' heart. L-T4 administration reduced TSH level and improved left ventricular function.

CONCLUSIONS

TSH can impair left ventricular function by regulating several factors, and L-T4 treatment ameliorates it in sHT rats.

A comparison of the effects of Portulaca oleracea seeds hydro-alcoholic extract and Vitamin C on biochemical, hemodynamic and functional parameters in cardiac tissue of rats with subclinical hyperthyroidism

OBJECTIVE

The present study was performed to evaluate the effects of hydro-alcoholic extract of Portulaca oleracea (P. oleracea) seeds and Vitamin C on biochemical and hemodynamic parameters in cardiac tissue of rats with subclinical hyperthyroidism.

MATERIALS AND METHODS

Forty eight male rats were divided into six groups of 8 and treated for 4 weeks. T4 group received daily injection of levothyroxine sodium (20 μg/kg) and control group was given daily injection of saline. T4-Po groups were given T4 plus 100, 200, and 400 mg/kg of P. oleracea seeds extract in drinking water daily. T4-Vit C group received T4 plus daily injection of Vitamin C (100 mg/kg). At the end of the experiment, body weight, serum free T4 level, left ventricular developed pressure (LVDP), malondialdehyde (MDA) and total thiol levels were measured.

RESULTS

Free T4 levels were increased in all groups that were treated with T4. Weight gain was decreased in T4 and T4-Po100 groups compared to control group (p<0.001 and p<0.05). However, body weight was increased in T4-Po (200 and 400) and T4-Vit C groups compared to T4 group. LVDP was increased in T4 group compared to control group but, LVDP was decreased in T4-Po and T4-Vit C groups. Malondialdehyde was decreased in T4-Po groups and T4-Vit C group compared to T4 group. Total thiol groups were increased in T4-Po (200 and 400) and T4-Vit C groups compared to T4 group.

CONCLUSION

The results showed that P. oleracea extract has a protective effect on cardiac dysfunction due to subclinical hyperthyroidism induced by levothyroxine sodium in rats.

Thyrotropin Regulates eNOS Expression in the Endothelium by PGRN Through Akt Pathway

To investigate the expression of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) in the aorta of subclinical hypothyroidism (SCH) rat model. The mechanisms underlying thyrotropin (TSH) affecting eNOS and PGRN expression in human umbilical vein endothelial cells (HUVECs) cultured in vitro were investigated. In the current study, SCH rat models were established by the administration of L-T₄ injection after thyroidectomy in Wistar rats, as opposed to that in the normal and clinical hypothyroidism (CH) groups. The concentrations of NO (pmol/μL) in the SCH and CH groups were significantly lower than that in the normal group (40.8 ± 7.6 and 32.9 ± 10.8 vs. 51.2 ± 12.1, P < 0.05). However, the expression level of eNOS is increased significantly (P < 0.05) in both SCH and CH groups; a similar result was observed for the PGRN protein. In cultured HUVECs, TSH can also up-regulate the expression of eNOS; however, it is accompanied by a reduced concentration of NO and increased level of superoxide anion, thereby indicating uncoupled eNOS. As eNOS is increased, we found that Akt in HUVECs were upregulated by TSH, as well as PGRN expression. While inhibiting the expression of PGRN in HUVECs using siRNA, the expression of eNOS, as well as Akt were also inhibited. In conclusion, SCH can induce vascular endothelial dysfunction in rats, and PGRN participated in the process of TSH-induced expression of Akt/eNOS in the endothelium.

Effect of subclinical hypothyroidism on the skeletal system and improvement with short-term thyroxine therapy

The purpose of the study was to observe changes in the skeletal system of rats with subclinical hypothyroidism (SCH) and to determine whether L-thyroxine (L-T4) administration suppresses those changes. Sixty male Wistar rats were randomly divided into control, SCH, and SCH+T4 groups. SCH was induced in rats by administration of methimazole (MMI), and rats in the SCH+T4 group were treated with L-T4 after 45 days of MMI administration. The SCH group had higher thyroid-stimulating hormone (TSH) level than the control and SCH+T4 groups. There were no differences in serum thyroid hormone (FT4 and FT3) levels among the three groups. Bone mineral density; serum levels of BALP and TRACP-5b, two bone metabolic markers; and the biomechanical properties of the femurs were lower in the SCH group than in the control group. After L-T4 treatment, serum BALP and TRACP-5b levels and the femur biomechanical properties were higher in the SCH+T4 than the SCH group. Histopathological examination revealed damage to the structure of the femur trabecular bone network in rats with SCH, and L-T4 treatment improved this condition to some extent. These findings demonstrate that L-T4 treatment ameliorates the destructive effects of SCH on the skeletal system in rats.

Can the Thiol/Disulfide Imbalance Be a Predictor of Colchicine Resistance in Familial Mediterranean Fever?

Familial Mediterranean fever (FMF) is a chronic autoinflammatory condition characterized by fever attacks and recurrent polyserositis. Subclinical inflammation that persists during attack-free periods can result in oxidative stress (OS) damage. Thiol groups bind to reactive oxygen radicals and protect cells and tissues from OS damage. The aim of this study was to investigate the relationship between thiol-disulfide balance and colchicine resistance in FMF patients during an attack or attack-free period. A newly developed spectrophotometric method was used to measure native thiol (NT) and disulfide (DS) levels in FMF patients and an age-sex matched group of healthy controls. NT and DS levels were compared in FMF patients 1) with vs. without colchicine resistance; and 2) during an attack (FMF-AP) vs. attack-free period (FMF-AFP). A total of 118 FMF patients and 60 healthy controls were studied. NT (P < 0.001) and total thiol (TT) (P < 0.001) levels in FMF patients were significantly lower compared to healthy controls. NT (P = 0.030) and TT (P = 0.010) levels of FMF-AP patients were significantly lower than that of FMF-AFP patients. FMF-AP patients had significantly higher DS levels than FMF-AFP patients (P = 0.039). Compared to FMF patients without colchicine resistance, elevated levels of DS (P = 0.019) but not NT (P = 0.620) and TT (P = 0.718) were found in those with colchicine resistance. Thiol-disulfide homeostasis is altered in FMF patients during an attack period and this imbalance may be associated with colchicine resistance.