Effect of prolonged exercise on oxidative damage and susceptibility to oxidants of rat tissues in severe hyperthyroidism

Deneysel hipertiroidide fiziksel ve vital bulguların ve karnozinin etkisinin değerlendirilmesi

Purpose: This study aims to investigate the effects of experimental hyperthyroidism and carnosine which is known to have antioxidant properties on physical and vital findings in rats, and to determine the relationship between these parameters and free T3 (FT3) levels. Materials and Methods: Rats were analyzed in 7 groups (each containing 12 animals); control (CONT), hyperthyroidism-1 (T:10-day L-thyroxine (L-T4) administration), hyperthyroidism-2 (T-T: 20-day L-T4 administration), Carnosine (10 day carnosine administration), Hyperthyroidism-1 + Carnosine (T-C), Hyperthyroidism-2 + Carnosine (T-TC), and Carnosine + Hyperthyroidism-1 (C-T). In order to create a hyperthyroidism model, L-thyroxine (L-T4) doses of 300 µg/kg rat weight/day and carnosine doses of 300 µg/kg rat weight/ day were intraperitoneally (ip) administered to the rats. Results: After 10 and 20 days of thyroxine administration, FT3 levels (T:3.640.51pg/mL, T-T: 4.060.91pg/mL) and body temperature (T:37.10.3oC, T-T: 37.60.3oC), significantly increased while body weight decreased (T:240.722.0g, T-T:263.028.7g). Carnosine administration only prevented the increase of FT3 levels, but had no effect on other parameters. Conclusion: The increased FT3 levels observed with L-T4 administration were consistent with the physical and vital findings, but carnosine administration did not reflect the expected effects on the physical findings observed in the hyperthyroid condition.

An Investigation of Oxidative Stress and Thiol/Disulphide Homeostasis in Graves' Disease

Background and objectives: The aim of this study was to research oxidative stress and thiol/disulphide homeostasis in Graves’ patients. Materials and Methods: The study included 33 Graves’ patients (research group) and 35 healthy subjects (control group). Serum oxidative stress and thiol/disulphide homeostasis (a new and automated spectrophotometric method developed by Erel and Neselioglu) parameters were studied and compared between the groups. Results: The native and total thiol levels and the native thiol/total thiol ratio were lower in patients with Graves’ disease compared to the control group (p < 0.001, p < 0.001, and p = 0.006, respectively). TOS (total antioxidant status), PC (protein carbonyl), OSI (Oxidative stress index), and disulphide/native thiol and disulphide/total thiol ratios were determined to be higher in the Graves’ disease group than in the control group (p < 0.001, p = 0.001, p = 0.001, p = 0.004, and p = 0.006, respectively). In the Graves’ disease group, the free triiodothyronine (FT3) and free thyroxine (FT4) levels were significantly positively correlated with impaired thiol/disulphide homeostasis and oxidative stress parameters (p < 0.05). Conclusion: The results of the current study demonstrated that oxidative stress and thiol/disulphide homeostasis increased towards disulphide formation due to thiol oxidation in Graves’ disease. In addition, a positive correlation of FT3 and FT4 was observed with oxidative stress parameters and impaired thiol/disulphide homeostasis.

Cardiac ischemia/reperfusion injury is inversely affected by thyroid hormones excess or deficiency in male Wistar rats

AIM

Thyroid dysfunctions can increase the risk of myocardial ischemia and infarction. However, the repercussions on cardiac ischemia/reperfusion (IR) injury remain unclear so far. We report here the effects of hypothyroidism and thyrotoxicosis in the susceptibility to IR injury in isolated rat hearts compared to euthyroid condition and the potential role of antioxidant enzymes.

METHODS

Hypothyroidism and thyrotoxicosis were induced by administration of methimazole (MMZ, 300 mg/L) and thyroxine (T4, 12 mg/L), respectively in drinking water for 35 days. Isolated hearts were submitted to IR and evaluated for mechanical dysfunctions and infarct size. Superoxide dismutase types 1 and 2 (SOD1 and SOD2), glutathione peroxidase types 1 and 3 (GPX 1 and GPX3) and catalase mRNA levels were assessed by quantitative RT-PCR to investigate the potential role of antioxidant enzymes.

RESULTS

Thyrotoxicosis elicited cardiac hypertrophy and increased baseline mechanical performance, including increased left ventricle (LV) systolic pressure, LV developed pressure and derivatives of pressure (dP/dt), whereas in hypothyroid hearts exhibited decreased dP/dt. Post-ischemic recovery of LV end-diastolic pressure (LVEDP), LVDP and dP/dt was impaired in thyrotoxic rat hearts, whereas hypothyroid hearts exhibited improved LVEDP and decreased infarct size. Catalase expression was decreased by thyrotoxicosis.

CONCLUSION

Thyrotoxicosis was correlated, at least in part, to cardiac remodeling and increased susceptibility to IR injury possibly due to down-regulation of antioxidant enzymes, whereas hypothyroid hearts were less vulnerable to IR injury.

Dietary supplementation with the microalga Galdieria sulphuraria (Rhodophyta) reduces prolonged exercise-induced oxidative stress in rat tissues

We studied the effects of ten-day 1% Galdieria sulphuraria dietary supplementation on oxidative damage and metabolic changes elicited by acute exercise (6-hour swimming) determining oxygen consumption, lipid hydroperoxides, protein bound carbonyls in rat tissue (liver, heart, and muscle) homogenates and mitochondria, tissue glutathione peroxidase and glutathione reductase activities, glutathione content, and rates of H₂O₂ mitochondrial release. Exercise increased oxidative damage in tissues and mitochondria and decreased tissue content of reduced glutathione. Moreover, it increased State 4 and decreased State 3 respiration in tissues and mitochondria. G. sulphuraria supplementation reduced the above exercise-induced variations. Conversely, alga supplementation was not able to modify the exercise-induced increase in mitochondrial release rate of hydrogen peroxide and in liver and heart antioxidant enzyme activities. The alga capacity to reduce lipid oxidative damage without reducing mitochondrial H₂O₂ release can be due to its high content of C-phycocyanin and glutathione, which are able to scavenge peroxyl radicals and contribute to phospholipid hydroperoxide metabolism, respectively. In conclusion, G. sulphuraria ability to reduce exercise-linked oxidative damage and mitochondrial dysfunction makes it potentially useful even in other conditions leading to oxidative stress, including hyperthyroidism, chronic inflammation, and ischemia/reperfusion.

Modulation of hepatic redox status and mitochondrial metabolism by exercise: therapeutic strategy for liver diseases

Liver steatosis (non-alcoholic fatty liver disease, NAFLD) is deemed as the hepatic face of the metabolic syndrome, with both physical inactivity and hypercaloric/unbalanced diet, together with increasing age playing a role as predisposing factors. Consequently, one of the most effective strategies used to counteract this scenario is physical exercise. Given the importance of redox signaling in cellular remodeling, in which mitochondria are closely implicated along with important roles on substrate oxidation, here we briefly review the effects of both acute and chronic forms of physical exercise on the modulation of hepatic redox state, highlighting the relevance of mitochondrial metabolism and function in the induction of liver phenotypes that antagonize metabolic alterations associated with liver metabolic diseases.

Vitamin E management of oxidative damage-linked dysfunctions of hyperthyroid tissues

INTRODUCTION

Thyroid hormones affect growth, development, and metabolism of vertebrates, and are considered the major regulators of their homeostasis. On the other hand, elevated circulating levels of thyroid hormones are associated with modifications in the whole organism (weight loss and increased metabolism and temperature) and in several body regions. Indeed, tachycardia, atrial arrhythmias, heart failure, muscle weakness and wasting, bone mass loss, and hepatobiliary complications are commonly found in hyperthyroid animals and humans.

RESULTS

Most thyroid hormone actions result from influences on transcription of T3-responsive genes, which are mediated through nuclear receptors. However, there is significant evidence that tissue oxidative stress underlies some dysfunctions produced by hyperthyroidism.

DISCUSSION

During the last decades, increasing interest has been turned to the use of antioxidants as therapeutic agents in various diseases and pathophysiological disorders believed to be mediated by oxidative stress. In particular, because elevated circulating levels of thyroid hormones are associated with tissue oxidative injury, more attention has been paid to explore the application of antioxidants as therapeutic agents in thyroid related disorders.

CONCLUSIONS

At present, vitamin E is among the most commonly consumed dietary supplements due to the belief that it, as an antioxidant, may attenuate morbidity and mortality. This is due to the results of numerous scientific studies, which demonstrate that vitamin E has a primary function to destroy peroxyl radicals, thus protecting polyunsaturated fatty acids biological membranes from oxidative damage. However, results are also available indicating that protective vitamin E effects against oxidative damage can be obtained even through different mechanisms.

Activation of NF-kappaB in lymphocytes and increase in serum immunoglobulin in hyperthyroidism: possible role of oxidative stress

This study evaluated oxidative stress, serum IgM and IgG, and nuclear factor (NF)-kappaB signaling in lymphocytes of hyperthyroidism patients. GSH content in lymphocytes was significantly lower and serum malondialdehyde, IgM and IgG levels were significantly higher in hyperthyroidism as compared to controls. In lymphocytes, the NF-kappaB signaling pathway was studied by western blot analysis of p65 and p-IkappaBalpha. Density of p-IkappaBalpha and p65 (in nuclear fraction) was significantly higher in hyperthyroidism as compared to controls. The density of p-IkappaBalpha and p65 had significant positive correlation with serum malondialdehyde level and negative correlation with lymphocyte GSH level in hyperthyroid cases. The serum IgG and IgM levels were correlated significantly with density of p-IkappaBalpha and p65. As immunoglobulin production is regulated by the NF-kappaB pathway, we conclude that the oxidative stress-induced activation of the NF-kappaB pathway might play a role in the rise of serum immunoglobulin level in hyperthyroidism.

Effect of T3 treatment on the response to ischemia–reperfusion of heart preparations from sedentary and trained rats

We investigated whether swim training modifies the effect of T(3) treatment on rat heart response to ischemia-reperfusion. Homogenates of Langendorff preparations perfused for 25 min after 20-min ischemia were used for biochemical determinations and isolation of mitochondrial fractions. Oxidative damage and antioxidant levels of homogenates, O(2) consumption and H(2)O(2) release rates, oxidative damage, and susceptibility to Ca(2+)-induced swelling of mitochondria were determined. During reperfusion, hyperthyroid hearts displayed significant tachycardia and low inotropic recovery. This pattern was improved by training, which also attenuated tissue oxidative damage and glutathione depletion. Similar training effects were shown in euthyroid preparations. Moreover, training reduced mitochondrial H(2)O(2) production and oxidative damage in hyperthyroid and euthyroid hearts and susceptibility to Ca(2+)-induced swelling only in the hyperthyroid ones. Rates of mitochondrial O(2) consumption were not different in sedentary and trained hyperthyroid rats. However, determination of the oxidative capacity suggested that, in the sedentary rats, O(2) consumption was conditioned by oxidative damage mitochondria have suffered, whereas in trained rats, it was due to changes in mitochondrial characteristics. The above results suggest that moderate training is able to reduce hyperthyroid heart susceptibility to oxidative damage and dysfunction modifying mitochondrial population.

Role of mitochondria in exercise-induced oxidative stress in skeletal muscle from hyperthyroid rats

Previous study showed that exercise induces higher oxidative damage and respiratory capacity reduction in hyperthyroid than in euthyroid skeletal muscle. Because impaired cell function can result from mitochondrial dysfunction, we evaluated the changes induced by exercise in oxygen consumption of skeletal muscle mitochondria from euthyroid and hyperthyroid rats. The mitochondrial function was related with indices of oxidative damage and nitric oxide production, scavenger levels and mitochondrial ROS production rates. Our results show that exercise increased state 4 and decreased state 3 respiration, and the highest changes happened in hyperthyroid preparations. This was consistent with the observation that oxidative damage and NO(*) derivative content were increased by T(3) administration and exercise, reaching the highest levels in hyperthyroid exercised rats. Our results also indicate that the high mitochondrial oxidative damage induced by T(3) and exercise is due to enhanced ROS production, which is dependent on increases in mitochondrial content and reduction degree, respectively, of autoxidizable electron carriers.