Association between thyroid hormones, lipids and oxidative stress biomarkers in overt hypothyroidism

Hypothyroidism reduces the risk of lung cancer through oxidative stress response and the PI3K/Akt signaling pathway: An RNA-seq and Mendelian randomization study

Hypothyroidism has been suggested to play a role in tumor progression. However, the causal association between hypothyroidism and lung cancer remains unknow. To elucidate the potential association between hypothyroidism and lung cancer risk, we employ a Mendelian randomization (MR) approach. MR was performed to analyze pooled data from the International Lung Cancer Consortium (11,348 cases and 15,861 controls; European ancestry) to determine the causal relationship between hypothyroidism and lung cancer. We used 36, 83, and 14 single nucleotide polymorphisms as instrumental variables for hypothyroidism/myxoedema, hypothyroidism, and exercise, respectively. We further investigated the mechanisms involved in transcriptome analysis using data from The Cancer Genome Atlas and Genotype-Tissue Expression database. We conducted an initial validation of intermediary factor using a two-step MR analysis. Genetically predicted hypothyroidism was significantly related to the risk of overall lung cancer, specifically the risk of lung squamous cell cancer (LSCC) but not with the risk of lung adenocarcinoma (LUAD) as assessed using the inverse-variance weighted (IVM) method. A similar causal association was found between hypothyroidism/myxoedema and the risk of lung cancer, LSCC, and LUAD. Transcriptome analysis showed that genes associated with hypothyroidism, lung cancer, and LSCC were enriched in the PI3K/Akt signaling pathway and oxidative stress response. However, genes related to hypothyroidism and LUAD did not exhibit enrichment in these pathways. Hypothyroidism was significantly associated with strenuous sports or other exercises. Moreover, genetically predicted exercise was significantly related to the risk of overall lung cancer, and LSCC, but not LUAD. We detected no horizontal pleiotropy using the MR-PRESSO and MR Egger regression intercept. Hypothyroidism was causally associated with a lower risk of lung cancer, and these effects might be mediated by the oxidative stress response and the PI3K/Akt signaling pathway. Therefore, our study suggests that the potential factors and viable etiologies of hypothyroidism that contributed to lung cancer risk deserve further investigation.

Folic acid supplementation improved cognitive deficits associated with lithium administration during pregnancy in rat offspring

INTRODUCTION

The present study aimed to analyse both neurobehavioural and biochemical results of neonates born of mothers exposed to different doses of lithium along with the groups that received lithium at the highest dose with folic acid as a preventive treatment.

MATERIALS AND METHODS

Male and female rats were mated in separate cages, and pregnant rats were divided into eight first group as (1) vehicle; (2) propylthiouracil (PTU)-induced hypothyroidism; (3-4) received two different doses of lithium carbonate (15 and 30 mg/kg); (5-7) the highest doses of lithium (30 mg/kg) plus three different doses of folic acid (5, 10 and 15 mg/kg); and (8) received just folic acid (15 mg/kg). All treatments were dissolved in drinking water and continued until delivery, followed by returning to a regular diet without treatment.

RESULTS

Lithium (30 mg/kg) disrupts both behavioural and biochemical markers, including TSH, T3 and T4 as measuring indicators to assess thyroid function, IL-10 and TNF-α as anti-inflammatory and inflammatory agents, respectively, malondialdehyde as an oxidative stress marker, alongside SOD, and catalase activity as antioxidant indicators. Besides, folic acid, almost at the highest dose (15 mg/kg), attenuated memory impairement and anxiety-like behaviour caused by lithium. Moreover, the groups treated with folic acid alone in comparison with vehicles demonstrated higher levels of antioxidant and anti-inflammatory indicators.

CONCLUSION

According to the results, prenatal exposure to a high dose of lithium (30 mg/kg) leads to foetal neurodevelopmental disorder and growth restriction through various mechanisms more likely attributed to hypothyroidism, which means it should be either prohibited or prescribed cautiously during pregnancy.

The relationship between serum superoxide dismutase and thyroid function in obese patients after Laparoscopic sleeve gastrectomy

To investigate the cross-sectional and longitudinal correlation between serum superoxide dismutase (SOD) levels and thyroid function with obesity before and after laparoscopic sleeve gastrectomy (LSG). Patients with morbid obesity (n = 219, 112 males and 107 females) who underwent LSG were selected and they were subdivided into normal levels of SOD (NSOD, n = 112) and high levels of SOD (HSOD, n = 107) according to the median value of SOD levels (183 U/mL). SOD and thyroid hormones were measured and compared at baseline, 3, 6, and 12 months after LSG. The HSOD group had lower body mass index (BMI), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) than the NSOD group (p < 0.001, p = 0.031, p < 0.001, respectively). However, they had higher free triiodothyronine (FT3) and free thyroxine (FT4) (p = 0.019 and p = 0.017, respectively). SOD was significantly negatively associated with TSH and positively associated with FT4. Of all the patients, 22.31% (NSOD: 66.67%; HSOD: 33.33%) had subclinical hypothyroidism (SH), and there were lower SOD levels in the SH group. Preoperative SOD was a protective factor for SH. After LSG, SOD and FT4 levels were increased at 12 months after LSG, however, TSH, FT3, total triiodothyronine (TT3) and TT4 levels decreased compared to the preoperative levels at 3, 6, and 12 months in the SH group. Postoperative changes in FT4 and TT4 levels correlated with changes in SOD levels. SOD, which is correlated with thyroid hormones, protects against SH in patients with obesity. The improvement in thyroid function with SH after LSG may be related to increased SOD levels.

Dietary Supplementation of Chestnut Tannins in Prepartum Dairy Cows Improves Antioxidant Defense Mechanisms Interacting with Thyroid Status

Cows in the peripartal period undergo changes in thyroid hormones and are susceptible to lipomobilization and/or oxidative stress. The addition of chestnut tannins as polyphenolic compounds in the diet may improve feed efficiency and prevent oxidative stress-related health disorders in transition cows. However, the relationship between chestnut tannin supplementation and thyroid function, which plays an important role in metabolic regulation, has not been investigated in dairy cows. This study was conducted to investigate the effects of chestnut tannin supplementation during the close-up period on thyroid status and to evaluate the interaction between thyroid hormones and oxidative stress biomarkers in prepartum dairy cows. Forty multiparous Holstein cows were fed either a diet containing chestnut tannins (CNTs, n = 20, 1.96 g chestnut tannins/kg feed, dry matter) or a non-supplemented diet (CON, n = 20) during the last 25 ± 2 days of gestation. Blood samples were collected on the first day of study (before chestnut tannin supplementation) and d 5 before parturition to measure hormonal and oxidative stress indices. Serum concentrations of T3 (p = 0.04) and T4 (p = 0.05) were higher in CNT cows than in the CON group on day 5 before parturition. Thyroid status of CNT cows was associated with higher serum total antioxidant capacity (T-AOC, p < 0.01), activities of superoxide dismutase (SOD, p = 0.03) and glutathione peroxidase (GPx, p = 0.01), and reduced glutathione concentration (GSH, p = 0.05). Serum thiobarbituric acid reactive substances (TBARS) were lower (p = 0.04) which was associated with lower aspartate aminotransferase (AST, p = 0.02), and lactate dehydrogenase (LDH, p = 0.01) activities in the CNT than in the CON group. Estradiol and progesterone did not differ between CNT and CON cows. Chestnut tannin supplementation improves antioxidant protection, prevents oxidation-reduction processes, reduces the degree of liver cell membrane damage, and protects thyroid tissue from damage, allowing higher T3 and T4 synthesis. Considering the importance of the thyroid hormone status before parturition, mechanisms of thyroid hormone regulation in CNT-supplemented dairy cows require more detailed investigations.

Mendelian randomisation highlights hypothyroidism as a causal determinant of idiopathic pulmonary fibrosis

Background

Although the association between hypothyroidism and idiopathic pulmonary fibrosis (IPF) is found in observational studies, it remains uncertain whether hypothyroidism causally influences IPF.

Methods

Two-sample Mendelian randomisation (MR) was conducted with hypothyroidism genome-wide association study (GWAS) data in the UK Biobank from 289,307 individuals (18,740 cases and 270,567 controls) and the largest GWAS summary statistics of IPF from 11,259 individuals (2,668 cases and 8,591 controls). Findings were verified using an independent validation dataset, as well as through different MR methods with different model assumptions. A multivariable MR based on Bayesian model averaging was further performed to evaluate whether hypothyroidism, even given several other comorbidities of IPF, remained to be the true causal one of IPF.

Findings

A positive causal effect of hypothyroidism on IPF was revealed (MR inverse-variance weighted [MR-IVW], odds ratio [OR]=1.125, 95% confidence interval [CI] 1.028-1.231; P=0.011), which was further verified in an independent validation set (MR-IVW, OR=1.229, 95% CI 1.054-1.432; P=0.008). The results were consistent from a variety of MR methods. Bidirectional analyses also indicated no reverse causation. Multivariable MR analysis showed hypothyroidism had the strongest marginal evidence (marginal inclusion probability=0.397, false discovery rate=0.025) compared with other comorbidities of IPF.

Interpretation

Our results illustrate the significant causal effect of hypothyroidism on IPF, which holds even given several other comorbidities of IPF. These findings may have an important insight into pathogenesis and possible future therapies of IPF.

Funding

National Natural Science Foundation of China, the Natural Science Foundation of Shandong Province and the Young Scholars Program of Shandong University.

The Unity of Redox and Structural Remodeling of Brown Adipose Tissue in Hypothyroidism

Brown adipose tissue (BAT) is important for maintaining whole-body metabolic and energy homeostasis. However, the effects of hypothyroidism, one of the most common diseases worldwide, which increases the risk of several metabolic disorders, on BAT redox and metabolic homeostasis remain mostly unknown. We aimed to investigate the dynamics of protein expression, enzyme activity, and localization of antioxidant defense (AD) enzymes in rat interscapular BAT upon induction of hypothyroidism by antithyroid drug methimazole for 7, 15, and 21 days. Our results showed an increased protein expression of CuZn- and Mn-superoxide dismutase, catalase, glutamyl-cysteine ligase, thioredoxin, total glutathione content, and activity of catalase and thioredoxin reductase in hypothyroid rats, compared to euthyroid control. Concomitant with the increase in AD, newly established nuclear, mitochondrial, and peroxisomal localization of AD enzymes was found. Hypothyroidism also potentiated associations between mitochondria, peroxisomes, and lipid bodies, creating specific structural-functional units. Moreover, hypothyroidism induced protein expression and nuclear translocation of a master regulator of redox-metabolic homeostasis, nuclear factor erythroid 2-related factor 2 (Nrf2), and an increased amount of 4-hydroxynonenal (4-HNE) protein adducts. The results indicate that spatiotemporal overlap in the remodeling of AD is orchestrated by Nrf2, implicating the role of 4-HNE in this process and suggesting the potential mechanism of redox-structural remodeling during BAT adaptation in hypothyroidism.

The effects of powdered black cumin seeds on markers of oxidative stress, intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 in patients with Hashimoto's thyroiditis

OBJECTIVE

Oxidative stress plays an important role in the pathogenesis of Hashimoto's thyroiditis. Because of the major anti-oxidant properties of black cumin, the current study aimed to evaluate the effect of powdered Nigella sativa seeds on markers of oxidative stress, endothelial dysfunction and serum lipids in patients with Hashimoto's thyroiditis.

METHODS

Forty patients with Hashimoto's thyroiditis, aged between 22 and 50 years old, participated in the trial and were randomly allocated into two groups of intervention and control receiving powdered N. sativa or placebo daily for 8 weeks. Changes in markers of oxidative stress, including total anti-oxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and biomarkers of endothelial dysfunction including Intracellular Adhesion Molecule (ICAM)-1, Vascular Cell Adhesion Molecule (VCAM)-1 and serum lipids were also evaluated.

RESULTS

Treatment with N. sativa, significantly increased serum TAC, SOD and reduced MDA concentrations with no significant change in GPX (P < 0.05). A significant reduction in VCAM-1 (P = 0.0012), body mass index (P = 0.002), serum concentrations of low density lipoprotein cholesterol (P = 0.002) and triglyceride (P = 0.02) were also reported in N. sativa-treated group after 8 weeks; while serum high density lipoprotein cholesterol (HDL) also significantly increased (P < 0.05). No change in other parameters were reported.

CONCLUSIONS

Giving attention to the potent beneficial effects of powdered black cumin seeds in improving oxidative stress, endothelial dysfunction, serum lipids and anthropometric features in patients with Hashimoto's thyroiditis, this medicinal plant can be considered as a therapeutic agent in management of Hashimoto-related metabolic abnormalities.

TRIAL REGISTRATION NUMBER

Iranian registry of clinical trials (registration number IRCT2015021719082N4).

Thyroid hormones mediate metabolic rate and oxidative, anti-oxidative balance at different temperatures in Mongolian gerbils (Meriones unguiculatus)

Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T_a) in small mammals. Here, we hypothesized that T_a affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different T_as (5 °C, 23 °C and 37 °C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5 °C but decreased at 37 °C compared to the control (23 °C). Protein carbonyls increased in liver at 37 °C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T_a. After the effects of different T_as on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T_a induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T_a induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different T_as.

Does hypothyroidism augment sun-induced skin damage?

OBJECTIVES

We investigated the mutual effects of overt hypothyroidism and prolonged sunlight exposure on free radical accumulation and oxidative skin damage.

METHODS

Free radical accumulation was evaluated by monitoring the transformation of 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) into MTT-formazan. The pro-oxidant enzymes xanthine oxidase (XO) and NADPH-diaphorase were measured in the skin. XO activity was estimated based on the yield of uric acid, while NADPH-diaphorase reactivity was monitored histochemically as an indirect marker of nitric oxide synthase and nitric oxide activity. Cellular damage was determined by malondialdehyde formation, a marker for lipid peroxidation.

RESULTS

In the skin of both euthyroid and hypothyroid animals, solar simulated ultraviolet irradiance increased the activity of XO and the NADPHdiaphorase reactivity as a protective response to formation of free radicals, such as reactive oxygen or nitrogen species. These pro-oxidant enzymes diminished in hypothyroid rats. Accumulation of the same amount of free radicals led to similar peroxidation in both hypothyroid and irradiated euthyroid rats. Hypothyroid skin after UV-exposure showed even greater lipid peroxidation.

DISCUSSION

The hypothyroid state could be a risk factor for enhanced oxidative skin damage in chronic photo-exposed skin due to oxidative stress. The lipid peroxidation is one of the major pathways by which photo-oxidative stress promotes photocarcinogenesis and photo-aging.

Redox theory of aging: implications for health and disease

Genetics ultimately defines an individual, yet the phenotype of an adult is extensively determined by the sequence of lifelong exposures, termed the exposome. The redox theory of aging recognizes that animals evolved within an oxygen-rich environment, which created a critical redox interface between an organism and its environment. Advances in redox biology show that redox elements are present throughout metabolic and structural systems and operate as functional networks to support the genome in adaptation to environmental resources and challenges during lifespan. These principles emphasize that physical and functional phenotypes of an adult are determined by gene-environment interactions from early life onward. The principles highlight the critical nature of cumulative exposure memories in defining changes in resilience progressively during life. Both plasma glutathione and cysteine systems become oxidized with aging, and the recent finding that cystine to glutathione ratio in human plasma predicts death in coronary artery disease (CAD) patients suggests this could provide a way to measure resilience of redox networks in aging and disease. The emerging concepts of cumulative gene-environment interactions warrant focused efforts to elucidate central mechanisms by which exposure memory governs health and etiology, onset and progression of disease.

Role of levothyroxine and vitamin E supplementation in the treatment of oxidative stress-induced injury and apoptosis of myocardial cells in hypothyroid rats

OBJECTIVE

To explore the underlying mechanism and treatment of myocardial injury caused by hypothyroidism, we evaluated oxidative stress in serum and myocardial tissue of hypothyroid rats. The effect of levothyroxine (LT4) replacement therapy and vitamin E (VitE) supplementation on oxidative stress-induced injury and apoptosis of myocardial tissue is examined.

METHODS

Male Sprague-Dawley rats were divided into five groups: normal control group, propylthiouracil group (PTU group), LT4 treatment group (PTU + LT4 group), vitamin E treatment group (PTU + VitE group), and combined treatment group (PTU + LT4 + VitE group). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) expression in serum and myocardium were determined. Myocardial apoptosis index (AI) in each group was determined by TUNEL assay.

RESULTS

SOD levels in serum were significantly increased in PTU + VitE and PTU + LT4 + Vit E groups, as compared to that in PTU and PTU + LT4 groups (P < 0.05). MDA levels in serum and myocardial tissue were significantly lower in PTU + LT4, PTU + VitE, and PTU + LT4 + VitE groups, as compared to that in the PTU group (P < 0.05). Myocardial apoptosis was significantly increased in PTU and PTU + VitE groups as compared to that in the normal control group (P < 0.05), while it was significantly lower in PTU + LT4 and PTU + LT4 + VitE groups, as compared to that in the PTU group (P < 0.05).

CONCLUSION

In this study, levothyroxine replacement therapy and vitamin E supplementation appeared to ameliorate myocardial apoptosis in hypothyroid rats, the mechanism of which appears to be related to improved thyroid function and reduced oxidative stress.

Orthodontic treatment modifies the oxidant-antioxidant balance in saliva of clinically healthy subjects

PURPOSE

The aim of our study was to analyse salivary markers of oxidative stress and an antioxidant response in clinically healthy subjects with fixed orthodontic appliances.

MATERIAL/METHODS

37 volunteers were included in the study. Unstimulated (UWS) and stimulated (SWS) whole saliva were analysed for oxidative and antioxidant status and nickel levels immediately before the insertion of the appliances, an one week after and twenty four weeks after the insertion of fixed appliances.

RESULTS

A significant increase in tiobarbituric acid reactive substance (TBARS) and total oxidant status (TOS) one week, and total protein concentration twenty four weeks after the attachment of orthodontic appliances was found in the saliva. The markers of antioxidant status: superoxide dismutase (SOD), catalase (CAT), uric acid (UA), peroxidase (Px), and total antioxidant status (TAS) were not changed in all periods in UWS. In SWS a significant decrease in SOD1 and CAT was found whereas Px was increased one week after treatment and UA twenty four weeks following treatment. TAS was decreased in UWS and SWS twenty four weeks after orthodontic treatment. Oxidative status index (OSI) was elevated both in UWS and SWS one week after orthodontic treatment in comparison to the results obtained before and twenty four weeks. One week after treatment an increased concentration of nickel was also observed.

CONCLUSIONS

Orthodontic treatment modifies the oxidative-antioxidative balance in the saliva of clinically healthy subjects. Increased nickel concentration in saliva, released from orthodontic appliances, seems to be responsible for changes in the oxidative status of the saliva.

Perinatal hypothyroidism modulates antioxidant defence status in the developing rat liver and heart

In the present study, we investigated oxidative stress parameters and antioxidant defence status in perinatal hypothyroid rat liver and heart. We found that the proteincarbonyl content did not differ significantly between the three groups both in the pup liver and in the heart. The OH˙ level was significantly decreased in the hypothyroid heart but not in the liver compared with controls. A slight but not significant decrease in SOD activity was observed in both perinatal hypothyroid liver and heart. A significantly increased activity of CAT was observed in the liver but not in the heart of hypothyroid pups. The GPx activity was considerably increased compared with controls in the perinatal hypothyroid heart and was unaltered in the liver of hypothyroid pups. We also found that vitamin E levels in the liver decreased significantly in hypothyroidism and were unaltered in the heart of perinatal hypothyroid rats. The GSH content was elevated significantly in both hypothyroid liver and heart. The total antioxidant capacity was higher in the liver of the hypothyroid group but not in the hypothyroid heart. Thyroxine replacement could not repair the above changes to normal. In conclusion, perinatal hypothyroidism modulates the oxidative stress status of the perinatal liver and heart.

A meta-analysis of the association of serum ischaemia-modified albumin levels with human hypothyroidism and hyperthyroidism

Serum levels of ischaemia-modified albumin (IMA) have been studied as a novel and simple measure of oxidative stress (OXS) in different thyroid pathologies. However, results of available studies in the literature were not consistent. This meta-analysis was attempted to quantify the overall effect size for serum IMA levels in human hypothyroidism (HT) and hyperthyroidism (HYT) and to study its associations with the thyroid profile. Databases of PubMed/Medline, EMBASE, Google Scholar, Web of Science and Science Direct were searched for articles. Data on serum IMA levels in HT, HYT patients and euthyroid controls were extracted to compute standardized mean differences (SMD) by the random-effects model. The associations between IMA and thyroid profile were computed by the meta-analysis of correlation coefficients. IMA levels in HT patients (SMD=1.12; Z=2.76; P=0.006) and HYT patients (SMD=1.64; Z=2.57; P=0.01) were significantly higher than in euthyroid controls and the thyroid treatment showed a favourble effect on serum IMA levels. There were strong and significant correlations between IMA and hormonal status in HT and HYT groups. This meta-analysis showing increased IMA level in both HT and HYT patients and its association with thyroid profile suggests that serum IMA could be used as a simple measure of increased OXS in thyroid dysfunction.

The effect of L-thyroxine replacement therapy on ischemia-modified albümin and malondialdehyde levels in patients with overt and subclinical hypothyroidism

BACKGROUND AND OBJECTIVES

The main objective of this study was to evaluate the levels of ischemia-modified albumin (IMA) and malondialdehyde (MDA) in patients with subclinical (SHypo) and overt hypothyroidism (OHypo), and to assess the effects of levothyroxine (LT₄) therapy on the oxidative stress (OS) parameters. We also investigated the relationships among serum thyroid hormones, lipid parameters, and IMA and MDA in these patients.

DESIGN AND METHODS

Thirty untreated patients with OHypo, 25 untreated patients with Shypo, and 30 age- and sex-matched healthy controls were prospectively included in the study. Biochemical and hormonal parameters including IMA and MDA were evaluated in all patients just before and one month after the maintenance of euthyroidism.

RESULTS

Compared with the control subjects, the levels of MDA and triglycerides (TG) significantly increased in patients with SHypo (p < 0.001 and p < 0.05, respectively), whereas high density lipoprotein cholesterol (HDL-C) levels significantly decreased (p = 0.01). Patients with OHypo showed significantly high MDA, total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and TG levels (p = 0.001, p < 0.01, p = 0.01, and p < 0.01, respectively), and significantly low HDL-C levels compared with the controls (p < 0.05). MDA levels and lipid profile were not significantly different in the patients with OHypo when compared with the patients with SHypo. Serum IMA levels did not significantly change in patients with OHypo and SHypo compared with the controls. In the pre-treatment period, MDA levels were inversely correlated with HDL-C levels in patients with OHypo (r: -0.471, p = 0.009). Plasma MDA and LDL-C levels significantly decreased and HDL-C levels significantly increased in the groups of OHypo and SHypo after LT₄ treatment. Serum IMA levels did not significantly change with the therapy in all patient groups.

CONCLUSIONS

Increased MDA levels in both patient groups represent increased lipid peroxidation which might play an important role in the pathogenesis of the atherosclerosis seen in these patients. Increased OS in patients with SHypo and OHypo could be improved by LT₄ treatment. Also, MDA can be used as a reliable marker of OS and oxidative damage, while IMA is considered to be inappropriate.

The Effect of Experimental Thyroid Dysfunction on Markers of Oxidative Stress in Rat Pancreas

Preclinical Research The aim of the present study was to evaluate the effects of thyroid dysfunction on markers of oxidative stress in rat pancreas. Hypothyroidism and hyperthyroidism were, respectively, induced in rats via administration of propylthiouracil (PTU) and L-thyroxine sodium salt in drinking water for 45 days. The activities of superoxide dismutase (SOD), catalase (CAT), glutathioen peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), xanthine oxidase (XO), and nonenzymatic markers of oxidative stress including malondialdehyde (MDA), protein carbonyl (PC), reduced glutathione (GSH), and total thiols (T-SH) were determined in the rat pancreas. In hyperthyroid rats, pancreatic CAT, SOD, GPx, GR, XO, G6PD activities were increased compared with those in hypothyroid and control groups. There were no differences in activities of antioxidant enzymes between hypothyroid and control rats. Pancreatic MDA and PC in hyperthyroid rats increased compared with hypothyroid and the control animals. Whereas, hyperthyroid rats had decreased levels of tissue GSH and T-SH compared with hypothyroid and the control groups. The findings showed that only GSH level has decreased significantly in the hypothyroid group compared with control groups. In conclusion, our results showed that experimental hyperthyroidism induces oxidative stress in pancreas of rats, but hypothyroidism has no major impact on oxidative stress markers. Drug Dev Res 77 : 199-205, 2016.   © 2016 Wiley Periodicals, Inc.

Thyroid Hormones, Oxidative Stress, and Inflammation

Inflammation and oxidative stress (OS) are closely related processes, as well exemplified in obesity and cardiovascular diseases. OS is also related to hormonal derangement in a reciprocal way. Among the various hormonal influences that operate on the antioxidant balance, thyroid hormones play particularly important roles, since both hyperthyroidism and hypothyroidism have been shown to be associated with OS in animals and humans. In this context, the nonthyroidal illness syndrome (NTIS) that typically manifests as reduced conversion of thyroxine (T₄) to triiodothyronine (T₃) in different acute and chronic systemic conditions is still a debated topic. The pathophysiological mechanisms of this syndrome are reviewed, together with the roles of deiodinases, the enzymes responsible for the conversion of T₄ to T₃, in both physiological and pathological situations. The presence of OS indexes in NTIS supports the hypothesis that it represents a condition of hypothyroidism at the tissue level and not only an adaptive mechanism to diseases.

The relationship between oxidative stress and autoimmunity in Hashimoto's thyroiditis

OBJECTIVE

We have aimed to study the relation between Hashimoto's thyroiditis (HT) and thyroid autoantibodies and oxidative stress parameters in euthyroid, subclinical and overt hypothyroid stages.

DESIGN AND METHODS

A total of 124 patients were included in the study; 93 of whom were newly diagnosed with HT (31 patients in each of the euthyroid, subclinical hypothyroid and overt hypothyroid subgroups), aged over 18 and had not received any prior treatment and 31 of whom were healthy volunteers.

RESULTS

Total oxidant status (TOS) and oxidative stress index (OSI) levels were higher, and total antioxidant status (TAS) and total thiol and arylesterase levels were lower in the overt hypothyroid group compared to other groups. TOS and OSI levels increased, and TAS levels decreased significantly in each phase from euthyroid, subclinical hypothyroid, to overt hypothyroid subgroups among HT patients. There was a negative correlation between TAS, log (paraoxonase1) and paraoxonase1/HDL and anti-thyroid peroxidase and a negative correlation between anti-thyroglobulin and total thiol. It was also determined that overt hypothroidism was an individual predictor that effects all of the oxidative stress parameters, but not total thiol, levels.

CONCLUSION

Our results suggest that oxidative stress increases continuously during the development of subclinical hypothyroidism and overt hypothyroidism in patients with HT. To determine whether this is a cause or result, randomized, controlled trials that study the effect of antioxidant treatment on the development of overt hypothyroidism and its consequences, e.g., increase in total cholesterol levels, may be performed in euthyroid and/or subclinical hypothyroid patients with HT.

Ischemia-modified albumin levels in overt and subclinical hypothyroidism

BACKGROUND

Free radical-mediated oxidative stress (OS) has been implicated in the pathogenesis of thyroid disorders. The ischemia-modified albumin (IMA) has been proposed as a marker of protein oxidative damage, which has been found to reflect hypoxic stress.

AIM

Our aim was to evaluate IMA, malondialdehyde (MDA), and reduced glutathione (GSH) levels in patients with overt hypothyroidism (OHT) and subclinical hypothyroidism (SHT) in comparison to euthyroid controls.

SUBJECTS AND METHODS

Albumin, IMA, IMA/albumin ratio, MDA, GSH, total cholesterol (TC), triglycerides (TG), HDL-Cholesterol were assessed in 105 subjects grouped into OHT, SHT patients, and euthyroid controls with 35 subjects in each group.

RESULTS

MDA and IMA levels were significantly elevated while the GSH concentrations were significantly lower in OHT and SHT patients compared to controls (p < 0.01). When IMA values were normalized for albumin concentrations, the IMA/albumin ratio was also significantly elevated in both patient groups compared to controls (p < 0.01). These changes were more pronounced in the OHT group when compared to SHT group. In OHT group, thyroid-stimulating hormone (TSH) levels showed significant positive correlation with MDA (r = 0.470, p = 0.004), IMA (r = 0.530, p = 0.001), and IMA/albumin ratio (r = 0.525, p = 0.001). Both IMA (r = -0.342, p = 0.041), IMA/albumin ratio (r = -0.378, p = 0.023) showed significant negative correlation with GSH in OHT patients. No significant correlation between variables was, however, observed in SHT group.

CONCLUSIONS

Increase of MDA and IMA levels with decreased antioxidant status indicate the presence of OS in hypothyroid patients, which was more pronounced in OHT patients. Elevated levels of IMA can be a clinically useful marker of protein oxidative damage and OS in hypothyroidism.

Association Between Thyroid Hormones, Lipids and Oxidative Stress Markers in Subclinical Hypothyroidism

BACKGROUND

Oxidative stress plays a role in the pathogenesis of many chronic diseases. It is recognized in overt hypothyroidism while its existence in subclinical hypothyroidism (SCH) is not well established. The aim of this study was to determine whether there was increased oxidation of lipids and proteins in SCH, and examine their association with lipids and thyroid hormones.

METHODS

Male adults (35-59 years) with SCH (n=467) and euthyroid controls (n=190) were studied. Anthropometric measurements, plasma lipids, thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total antioxidant capacity (T-AOC), lipid peroxidation products, malondialdehyde (MDA), advanced oxidation protein products (AOPP) and dityrosine concentrations were measured.

RESULTS

Plasma concentrations of MDA were significantly higher (p<0.05) in SCH (8.11±1.39 nmol/mL) compared with euthyroid controls (7.34±1.31 nmol/mL) while AOPP, dityrosine and T-AOC levels were not different. MDA was not associated with TSH (β=-0.019, P=0.759), FT4 (β=-0.062, P=0.323) and FT3 (β=-0.018, P=0.780) in SCH while levels increased with elevated total cholesterol (β=0.229, P=0.001), LDL (β=0.203, P=0.009) and triglycerides (β=0.159, P=0.036) after adjustment for age and body mass index. T-AOC reduced (β=-0.327, P=0.030) with increased MDA in euthyroid controls and not in SCH (β=-0.068, P=0.349), while levels increased with elevated triglycerides in both groups.

CONCLUSIONS

Oxidative stress was increased in subclinical hypothyroidism as evidenced by the elevated lipid peroxidation product, malondialdehyde, while protein oxidation was absent. Thus, reduction of oxidative stress may be beneficial in patients with subclinical hypothyroidism.

Oxidized LDL Is Strictly Limited to Hyperthyroidism Irrespective of Fat Feeding in Female Sprague Dawley Rats

Metabolic dysfunctions might play a crucial role in the pathophysiology of thyroid dysfunctions. This study aimed to investigate the impact of a controlled diet (normal versus high fat feeding) on hypothyroid and hyperthyroid Sprague Dawley rats. Female Sprague Dawley rats (n = 66) were grouped into normal diet (n = 30) and high-fat diet (n = 36) groups and subdivided into controls, hypothyroid and hyperthyroid groups, induced through propylthiouracil or triiodothyronine (T3) treatment, respectively. After 12 weeks of treatment metabolic parameters, such as oxidized LDL (oxLDL), malondialdehyde (MDA), 4-hydroxynonenal (HNE), the lipid profile, body weight and food intake parameters were analyzed. Successfully induced thyroid dysfunctions were shown by T3 levels, both under normal and high fat diet. Thyroid dysfunctions were accompanied by changes in calorie intake and body weight as well as in the lipid profile. In detail, hypothyroid rats showed significantly decreased oxLDL levels, whereas hyperthyroid rats showed significantly increased oxLDL levels. These effects were seen under high fat diet and were less pronounced with normal feeding. Taken together, we showed for the first time in female SD rats that only hyper-, but not hypothyroidism, is associated with high atherogenic oxidized LDL irrespective of normal or high-fat diet in Sprague Dawley rats.

The relationships between thyroid hormones and thyroid-stimulating hormone with lipid profile in euthyroid men

BACKGROUND AND AIM

Alteration in lipid profile is a common observation in patients with thyroid dysfunction, but the current knowledge on the relationship between lipids and thyroid hormone levels in euthyroid state is insufficient. The current study aimed to determine the association between thyroid hormones and thyroid-stimulating hormone (TSH) with lipid profile in a euthyroid male population.

METHODS

A total of 708 Chinese and Malay men aged 20 years and above were recruited in this cross-sectional study. Their blood was collected for the determination of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), triglyceride (TG), free thyroxine (FT4), free triiodothyronine (FT3) and TSH levels. The association was analyzed using multiple regression and logistic regression models with adjustment for age, ethnicity, body mass index and FT4/FT3/TSH levels.

RESULTS

In multiple regression models, TSH was positively and significantly associated with TG (p<0.05). Free T4 was positively and significantly associated with TC, LDL-C and HDL-C (p<0.05). Free T3 was negatively and significantly associated with HDL-C (p<0.05). In binary logistic models, an increase in TSH was significantly associated with higher prevalence of elevated TG in the subjects (p<0.05), while an increase in FT4 was significantly associated with higher prevalence of elevated TC but a lower prevalence of subnormal HDL in the subjects (p<0.05). Free T3 was not associated with any lipid variables in the logistic regression (p>0.05).

CONCLUSIONS

In euthyroid Malaysian men, there are positive and significant relationships between TSH level and TG level, and between FT4 level and cholesterol levels.

Thyroid hormones and antioxidant systems: focus on oxidative stress in cardiovascular and pulmonary diseases

In previous works we demonstrated an inverse correlation between plasma Coenzyme Q₁₀ (CoQ₁₀) and thyroid hormones; in fact, CoQ₁₀ levels in hyperthyroid patients were found among the lowest detected in human diseases. On the contrary, CoQ₁₀ is elevated in hypothyroid subjects, also in subclinical conditions, suggesting the usefulness of this index in assessing metabolic status in thyroid disorders. A Low-T3 syndrome is a condition observed in several chronic diseases: it is considered an adaptation mechanism, where there is a reduction in pro-hormone T4 conversion. Low T3-Syndrome is not usually considered to be corrected with replacement therapy. We review the role of thyroid hormones in regulation of antioxidant systems, also presenting data on total antioxidant capacity and Coenzyme Q₁₀. Published studies suggest that oxidative stress could be involved in the clinical course of different heart diseases; our data could support the rationale of replacement therapy in low-T3 conditions.

The role of thyroid hormones as inductors of oxidative stress and neurodegeneration

Reactive oxygen species (ROS) are oxidizing agents amply implicated in tissue damage. ROS production is inevitably linked to ATP synthesis in most cells, and the rate of production is related to the rate of cell respiration. Multiple antioxidant mechanisms limit ROS dispersion and interaction with cell components, but, when the balance between ROS production and scavenging is lost, oxidative damage develops. Many traits of aging are related to oxidative damage by ROS, including neurodegenerative diseases. Thyroid hormones (THs) are a major factor controlling metabolic and respiratory rates in virtually all cell types in mammals. The general metabolic effect of THs is a relative acceleration of the basal metabolism that includes an increase of the rate of both catabolic and anabolic reactions. THs are related to oxidative stress not only by their stimulation of metabolism but also by their effects on antioxidant mechanisms. Thyroid dysfunction increases with age, so changes in THs levels in the elderly could be a factor affecting the development of neurodegenerative diseases. However, the relationship is not always clear. In this review, we analyze the participation of thyroid hormones on ROS production and oxidative stress, and the way the changes in thyroid status in aging are involved in neurodegenerative diseases.

Oxidative phosphorylation and ion transport in the mitochondria of two strains of rats varying in their resistance to stress and hypoxia

The role of mitochondria in the inherited or ontogenetically acquired reactions of organism to stress is not studied enough. In the present work, we examined the functional state of the coupled respiratory chain, potassium and calcium transport and rate of hydrogen peroxide production on two rat lines: August and Wistar-which possess different resistance to emotional stress and hypoxia. It was established that the respiration rate and efficiency of oxidative phosphorylation were higher in August rats than in Wistar ones. In August rats, the rate of potassium transport and ATP-dependent mitochondrial swelling as well as the concentration of the ion in the mitochondrial matrix were almost twice as higher comparatively to those parameters in Wistar rats. The rate of H2O2 production was found to be decreased in the mitochondria of August rats. It was also demonstrated that the two rat lines differed by their resistance to the opening of the palmitate/Ca(2+)-induced pore and by their ability to retain calcium within mitochondria. The paper discusses the involvement of the mitochondrial ATP-dependent potassium channel in the adaptation of animals to adverse effects.

Evaluation of protein oxidation and its association with lipid peroxidation and thyrotropin levels in overt and subclinical hypothyroidism

Both overt (OHT) and subclinical hypothyroid (SHT) disorders have been found to be associated with increased oxidative stress (OXS). Excess thyrotropin [thyroid stimulating hormone (TSH)] is known to directly produce OXS. Increased lipid peroxidation is known to facilitate protein carbonylation. However, the associations between lipid and protein oxidation and elevated TSH levels have not been studied. Thyroid profile, lipid peroxidation as malondialdehyde (MDA) levels and protein carbonylation as protein carbonyls (PCO) were estimated in OHT and SHT groups consisting of 36 patients each, in comparison to 39 euthyroid controls. We also determined the associations between TSH, MDA, and PCO levels in OHT and SHT groups. Increased oxidative damage was evidenced through significant elevations in the concentrations of MDA and PCO in OHT and SHT groups compared to controls (p < 0.01). Both TSH and MDA levels were positively associated with PCO in OHT group. Partial correlation analysis revealed that both excess TSH and increased MDA levels are mutually influencing elevated PCO. The results indicate that there is a simultaneous oxidative damage to lipids and proteins leading to increased MDA and PCO levels in both patient groups. Either of the excess TSH and increased MDA levels are combinably involved in the elevation of PCO in hypothyroidism.

Ischemia-modified albumin in patients with hyperthyroidism and hypothyroidism

BACKGROUND

The relationship between ischemia-modified albumin (IMA) and thyroid dysfunction remains uncertain. This study aimed to investigate the influence of overt hypothyroidism (Oho), overt hyperthyroidism (Ohe), and their treatments on serum IMA levels.

METHODS

A total of 35 untreated patients with Ohe, 35 untreated patients with Oho, and 35 control subjects were enrolled in the study. C-reactive protein (CRP), homocysteine (Hcy), IMA, and lipid profiles were measured and evaluated before and after treatment.

RESULTS

CRP, Hcy, and IMA levels and lipid profiles were higher in patients with Oho than in euthyroid or Ohe subjects (p<0.05). Basal IMA levels were reduced after treatments in all patients (p<0.05). In Ohe patients, serum IMA levels were positively correlated with free triiodothyronine (r=0.424, p=0.011) and free thyroxine (r=0.567, p<0.001) levels. In Oho patients, serum IMA levels were inversely correlated with free triiodothyronine (r=-0.555, p=0.001) and free thyroxine (r=-0.457, p=0.006) but positively correlated with anti-thyroid peroxidase antibody, C-reactive protein, and homocysteine levels (p<0.05). Linear regression analyses showed that free triiodothyronine was the most important factor affecting serum IMA levels in Ohe (β=0.694, p=0.019) and in Oho (β=-0.512, p=0.025).

CONCLUSIONS

IMA levels are increased in patients with thyroid dysfunction, particularly in overt hypothyroidism. Thyroid dysfunction has a significant impact on the oxidative stress status.

Are hsCRP Levels and LDL/HDL Ratio Better and Early Markers to Unmask Onset of Dyslipidemia and Inflammation in Asymptomatic Subclinical Hypothyroidism?

The implications of subclinical hypothyroidism (SCH) are many amongst which the most important is progression to overt hypothyroidism. Other debatable aspects are its association with cardiovascular risk, neuromuscular and psychiatric dysfunction, increased predisposition to developing metabolic syndrome and an underlying pro-inflammatory state. We aimed to study the lipid profile, lipoprotein(a) [Lp(a)] and hsCRP levels and insulin resistance in a group of patients with SCH in a referral hospital and see if any significant differences exist between them and euthyroids. This is a case-control study where the selection of controls and cases was based on the thyroid profile. Subjects were selected on their visit to clinical biochemistry lab for thyroid function tests. 33 euthyroids were taken as controls (Group I) and 38 patients comprising of subclinical hypothyroids were grouped as cases (Group II). Serum thyroid stimulating hormone (TSH) was in the range of 0.5-5.0 mIU/L for euthyroids and for subclinical hypothyroids the concentration of TSH was more than 5 mIU/L. The concentration of tri-iodothyronine (T3) and thyroxine (T4) were in normal reference range in both the groups. Individual lipid profile parameters failed to show a significant p value between cases and controls. The LDL/HDL ratio was highly significant (p value < 0.0001) and hsCRP was also statistically between the two groups (p value = 0.0054). Lp(a) and insulin resistance did not differ significantly. SCH is a common disorder that frequently progresses to overt hypothyroidism. This study underlines the importance of LDL/HDL ratio rather than measurement of individual lipid profile parameters in bringing to light the dyslipidemic state associated with SCH. Moreover the use of hsCRP to detect an underlying pro-inflammatory state in SCH can also be emphasized.

Association of lipids with oxidative stress biomarkers in subclinical hypothyroidism

Objective. The aim of the present study was to evaluate the oxidative stress biomarkers in patients with subclinical hypothyroidism (n = 20) and health controls (n = 20). Subjects and Methods. Total cholesterol (TC), triglycerides (TGs), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), thiobarbituric acid reactive substances (TBARSs), catalase (CAT), superoxide dismutase (SOD), and arylesterase (ARE) were analyzed. Results. TC, LDL-C, TBARS, and CAT were higher in subclinical hypothyroidism patients, whereas SOD did not change. Arylesterase activity was significantly lower in the SH group, compared with the control group. Correlation analyses revealed the association of lipids (TC and LDL-C) with both oxidative stress biomarkers and thyrotropin (TSH). Thyroid hormones were correlated only with triglyceride levels. In addition, TSH was significantly correlated with TBARS, CAT, and SOD. However, no significant correlations were observed after controlling TC levels. Conclusions. We found that SH patients are under increased oxidative stress manifested by reduced ARE activity and elevated lipoperoxidation and CAT activity. Secondary hypercholesterolemia to thyroid dysfunction and not hypothyroidism per se appears to be associated with oxidative stress in subclinical hypothyroidism.

Total oxidant/antioxidant status in sera of patients with thyroid cancers

Oxidative stress is considered to be involved in the pathophysiology of all cancers. In order to evaluate the total oxidant/antioxidant status in patients with thyroid cancer and to investigate the relationship between oxidative stress parameters and serum thyroid profiles among thyroid cancer patients and various controls, we determined oxidative status including total antioxidant status (TAS) and total oxidant status (TOS) and calculation of oxidative stress index (OSI) in sera in 82 thyroid cancer patients, 56 benign thyroid disease patients, and 50 healthy controls. It was found that serum TAS levels were significantly lower in patients with thyroid cancer than in controls (P<0.001), while serum TOS levels and OSI values were significantly higher (both P<0.001) in the cancer patients. No significant correlations were observed between various oxidative stress markers and thyroid profiles in either the thyroid cancer patients or the controls. Receiver operating characteristic curve analysis demonstrated that OSI was the best indicator for distinguishing cancer patients from benign thyroid diseased or healthy controls, followed by TOS and TAS. Risk estimate statistics also indicated that TOS and/or OSI were good risk factors to discriminate patients with thyroid cancer from two controls. These findings suggested that oxidants are increased and antioxidants are decreased in patients with thyroid cancer. OSI may be a more useful oxidative stress biomarker than TAS and TOS for monitoring the clinical status of thyroid cancer patients.

Lipid abnormalities and cardiometabolic risk in patients with overt and subclinical thyroid disease

Dyslipidemia is a common finding in patients with thyroid disease, explained by the adverse effects of thyroid hormones in almost all steps of lipid metabolism. Not only overt but also subclinical hypo- and hyperthyroidism, through different mechanisms, are associated with lipid alterations, mainly concerning total and LDL cholesterol and less often HDL cholesterol, triglycerides, lipoprotein (a), apolipoprotein A1, and apolipoprotein B. In addition to quantitative, qualitative alterations of lipids have been also reported, including atherogenic and oxidized LDL and HDL particles. In thyroid disease, dyslipidemia coexists with various metabolic abnormalities and induce insulin resistance and oxidative stress via a vice-vicious cycle. The above associations in combination with the thyroid hormone induced hemodynamic alterations, might explain the increased risk of coronary artery disease, cerebral ischemia risk, and angina pectoris in older, and possibly ischemic stroke in younger patients with overt or subclinical hyperthyroidism.

Thyroid hormone enhances the ability of serum to accept cellular cholesterol via the ABCA1 transporter

OBJECTIVE

The goal of this study was to examine the effects of thyroid hormone status on the ability of serum to accept cellular cholesterol.

METHODS AND RESULTS

Sera from hypophysectomized rats treated ± T(3) was used to evaluate the role of thyroid hormone on serum efflux capacity. 2D-DIGE analysis of serum proteins showed that T(3) treated rats had increased ApoA-I, ApoA-IV and fetuin A levels with decreased Apo E levels. Microarray and real-time RT-PCR analysis of rat liver revealed large increases in ApoA-I, ApoA-IV, ABCG5, and ABCG8 in response to T(3). J774 macrophages, BHK cells, and Fu5AH rat hepatoma cells were used to measure cholesterol efflux mediated by ABCA1, ABCG1 transporters or SR-BI. Sera from T(3)-treated rats stimulated efflux via ABCA1 but not by ABCG1 or SR-BI. Gel filtration chromatography revealed that T(3) treatment caused a decrease in HDL particle size accompanied by higher levels of lipid-poor ApoA-I.

CONCLUSIONS

Thyroid hormone enhances the ability of serum to accept cellular cholesterol via the ABCA1 transporter. This effect is most likely attributable to increases in small HDL and lipid poor ApoA-I in response to T(3).