Oxidative stress and protein glycation in primary hypothyroidism. Male/female difference

Changes in biomarkers of redox status in serum and saliva of dogs with hypothyroidism

BACKGROUND

Hypothyroidism is the most common endocrine disorder diagnosed in dogs, leading to deleterious effects on a dog's life quality. This study aims to evaluate changes in the redox status in canine hypothyroidism. For this purpose, a comprehensive panel of antioxidants and oxidants biomarkers were measured in serum and saliva of 23 dogs with hypothyroidism, 21 dogs with non-thyroidal illness, and 16 healthy dogs. Among the antioxidants, cupric reducing antioxidant capacity (CUPRAC), ferric reducing ability of plasma (FRAP), Trolox equivalent antioxidant capacity (TEAC), thiol, paraoxonase type 1 (PON-1) and glutathione peroxidase (GPx) were determined in serum and CUPRAC, ferric reducing ability of saliva (FRAS) and TEAC in saliva. The oxidant biomarkers included were total oxidant status (TOS), peroxide-activity (POX-Act), reactive oxygen-derived compounds (d-ROMs), advanced oxidation protein products (AOPP), and thiobarbituric acid reactive substances (TBARS) in serum and AOPP and TBARS in saliva.

RESULTS

Results showed a significantly higher TEAC, PON-1, GPx, TOS, POX-Act, and d-ROMs, and a significantly lower AOPP in serum of dogs with hypothyroidism. Meanwhile, significantly lower FRAS and AOPP were observed in saliva of dogs with hypothyroidism. Once salivary concentrations were corrected based on their total protein concentrations, the only analyte showing significant changes was TBARS which was significantly higher in dogs with hypothyroidism.

CONCLUSIONS

Our results show that dogs with hypothyroidism present alterations in the redox status in both serum and saliva. This study should be considered a preliminary study and further research addressing these changes should be made using larger populations.

Emerging roles of Keap1/Nrf2 signaling in the thyroid gland and perspectives for bench-to-bedside translation

The signaling pathway centered on the transcription factor nuclear erythroid factor 2-like 2 (Nrf2) has emerged during the last 15 years as a target for the prevention and treatment of diseases broadly related with oxidative stress such as cancer, neurodegenerative and metabolic diseases. The roles of Nrf2 are expanding beyond general cytoprotection, and they encompass its crosstalk with other pathways as well as tissue-specific functions. The thyroid gland relies on reactive oxygen species for its main physiological function, the synthesis and secretion of thyroid hormones. A few years ago, Nrf2 was characterized as a central regulator of the antioxidant response in the thyroid, as well as of the transcription and processing of thyroglobulin, the major thyroidal protein that serves as the substrate for thyroid hormone synthesis. Herein, we summarize the current knowledge about the roles of Nrf2 in thyroid physiology, pathophysiology and disease. We focus specifically on the most recent publications in the field, and we discuss the implications for the preclinical and clinical use of Nrf2 modulators.

Are Nutritional Patterns among Polish Hashimoto Thyroiditis Patients Differentiated Internally and Related to Ailments and Other Diseases?

There is not any diet recommended for Hashimoto's disease, despite that those patients are often undernourished. Because of the high heterogeneity of Hashimoto's patients, insight into dietary patterns might shed some light on the patient-tailored dietary approach, thus improving their treatment and helping to identify patients with the highest probability of particular nutritional deficiencies. The aim of this study was to identify Hashimoto's patients' dietary patterns and their characterization based on both socio-demographic variables and dietary self-assessment. We collected data online from patients with Hashimoto's disease. The questionnaire formula used in the study was developed based on a validated food frequency questionnaire KomPAN®. K-means pattern analyses were used to characterize patients into patterns based on the frequency of particular types of foods consumption and socio-demographic factors. Four patterns were identified. We labeled them as 'Convenient', 'Non-meat', 'Pro-healthy', and 'Carnivores' with participants proportions at approximately one-fourth per each pattern. The patients were mainly of the female gender (94.08%), with a female: male ratio of 15.9. Hashimoto's patients differed in their food product choices, food choice motives, dieting experience, nutritional knowledge, smoking habits, food allergies and intolerances, and lipid disorders, and thus represent different eating patterns. However, these patterns were not determined by comorbidities or the majority of ailments.

The Level of Zinc, Copper and Antioxidant Status in the Blood Serum of Women with Hashimoto's Thyroiditis

The aim of this study was to analyze selected indicators of oxidative stress. The study subjects consisted of 42 women with Hashimoto’s disease and a control group of 30 healthy women. The concentration of zinc (Zn) and copper (Cu) in the serum was determined by Atomic Absorption Spectrometry (AAS) and the total antioxidative potential by the Ferric Reducing Ability of Plasma (FRAP) method. In addition, an assessment of concentrations of thiobarbituric acid reactive substances (TBARS) and total phenolics was carried out. Our research showed a significant difference in TBARS concentration (p < 0.0001 (ES: 0.92)) without significant differences in Zn, Cu, FRAP and total phenolics concentrations. Analysis of the correlation of the obtained results of biochemical tests for both groups showed a highly significant dependence of FRAP and total phenolics concentration in the blood of the examined women (r = 0.5283, p = 0.0003). The obtained results indicate no differences in Cu, Zn, and FRAP concentrations in the blood between two analyzed groups and a significantly higher concentration of TBARS in Hashimoto’s thyroiditis women. The concentration of total phenolics significantly influences the value of the FRAP.

Interdependence of oxidative/antioxidant system indicators and thyroid status under conditions of prolonged exposure to small doses of radiation

We have studied the interdependence of the intensity of oxidative processes/antioxidant level and the thyroid status parameters in a group of students aged 18–24 who lived for a long time in the territory of enhanced radioecological control (density of soil contamination by isotopes (137Cs 3.7 ∙ 104 – 18.5 ∙ 104 Bq/m2). We examined 50 people from relatively environmentally friendly areas (control group) and 50 people from IV radiation zone (experimental group). In the experimental group, there were no individuals with clinical manifestations of thyroid pathology. However, subgroups with signs of hyperthyroidism and hypothyroidism were identified. We evaluated the level of cortisol, thyrotrophic hormone (TSH), triiodothyronine (T3), thyroxine (T4), malonic dialdehyde (MDA), ceruloplasmin (CP), transferrin (Tf), sulfhydryl groups (SH); we calculated the oxidative stress index (OSI). The research was conducted one month before the examination time and also during the exams as a factor in increased emotional stress. A lowered CP level was found in the subgroup with signs of hypothyroidism; SH groups – in all subgroups, separated by thyroid status. The oxidative stress index was higher in all students examined of the experimental group, compared with the control. The growth of MDA level is marked in the experimental group – it is the most strongly pronounced in conditions of additional emotional load in people with signs of hyperthyroidism and hypothyroidism. CP level significantly decreased in the subgroup of hyperthyroidism on the background of T3 decrease. OSI increased in all students examined from the experimental group. In the subgroup of hypothyroidism it became significantly higher than in the subgroup of euthyroidism. A positive correlation between the levels of CP and T3 was found. The highest values of the correlation coefficients were noted for subgroups with signs of hyperthyroidism and hypothyroidism, with the coefficient significance increasing under conditions of emotional stress. The index of oxidative stress in the experimental group positively correlated with the level of TSH – in terms of emotional stress, the statistical significance of the coefficients disappeared. In the subgroups divided by thyroid status, variability of interactions between OSI and T3 was observed but it was not statistically significant. It was found that the participation of thyroid status in supporting redox homeostasis in people aged 18–24 who suffered from chronic small-doze radiation exposure was realized mainly by the influence on the antioxidant system. The ability of thyroid hormones to maintain a proper antioxidant state was suppressed in this group. The unbalanced relationship between thyroid hormones and oxidative stress indicators is strongly manifested under conditions of additional emotional stress.

Vitamin E improved redox homeostasis in heart and aorta of hypothyroid rats

OBJECTIVES

The objective of this study was to evaluate the effect of vitamin E on the oxidative stress parameters and antioxidant defense enzymes in the heart and aorta of 6-n-propylthiouracil (PTU)-induced hypothyroid rats.

METHODS

The animals were divided into 4 experimental groups: Group 1 (Euthyroid) received tap water, Group 2 (Hypothyroid) received 0.05 % of PTU in dissolved in their drinking water, Group 3 (PTU+Vit E) hypothyroid rats treated with vitamin E, and Group 4 (Euthyroid+Vit E). Vitamin E was injected daily (20 mg/kg) to groups 3 and 4 via daily gavage for 6 weeks. Malondialdehyde (MDA) levels, total thiol levels, and the activities of Cu, Zn-superoxide dismutase (SOD) and catalase (CAT) were evaluated in the aortic and cardiac tissues.

RESULTS

A significant decrease of thyroxine (T4) serum levels confirmed hypothyroidism in rats, which received PTU. The MDA level increased and total thiol level decreased in the hypothyroid group compared to control group (p<0.001). Th e activities of SOD and CAT significantly decreased in the hypothyroid rats in comparison to the control. Vitamin E treatment resulted in increased levels of total thiol, SOD, and CAT within aortic and cardiac tissues and decreased levels of MDA in comparison with the hypothyroid group (p<0.01-p<0.001).

CONCLUSIONS

PTU-induced hypothyroidism resulted in oxidative stress. Chronic administration of vitamin E to hypothyroid rats decreased the oxidative stress markers in the aortic and cardiac tissues.

Muscle fatigue: general understanding and treatment

Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.

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.

Oxidative stress in hypothyroid patients and the role of antioxidant supplementation

CONTEXT

The available data concerning oxidant stress and antioxidant capacity in hypothyroidism are scanty and inconclusive. While some authors suggest that tissues may be protected from oxidant damage because of a hypometabolic state in hypothyroidism, others report increased oxidative stress in hypothyroidism. Selenium acts as a cofactor for the thyroid hormone (TH) deiodinases that activate and then deactivate various THs and their metabolites. Selenium may inhibit thyroid autoimmunity.

AIMS

The study was designed, first, to study the impact of oxidative stress in patients of primary hypothyroidism due to autoimmune thyroiditis, by estimation of serum malondialdehyde (MDA) as a biomarker of oxidative stress. Second, to study the change in MDA level pre- and post-L-thyroxine treatment. Finally, to look into the possible role of selenium supplementation on oxidative stress in autoimmune hypothyroidism.

SUBJECTS AND METHODS

Patients attending endocrine outpatient department (OPD) services of IPGMER and SSKM hospital were considered for the study. Sixty treatment-naive adult patients (age > 18 years) with hypothyroidism were included in the study. The patients were divided into two groups, each comprised thirty patients. One group was treated with L-thyroxine and placebo (Group A). The other group received L-thyroxine replacement along with selenium (100 mcg twice a day) as antioxidant supplementation (Group B). The patients were blinded about selenium and placebo. The study duration for both groups was 6 months. The starting dose of L-thyroxine was 1.6 mcg/kg body weight free thyroxine (FT4), and thyroid-stimulating hormone (TSH) was repeated after 12 weeks. L-thyroxine dose adjustments were done if needed. MDA was assessed at the beginning and at the end of the study, i.e., after 6 months of treatment. The control cohort was composed of thirty healthy adults. Only overt hypothyroidism (OH) cases were included in the study.

STATISTICAL ANALYSIS USED

Normality of data was determined using Anderson-Darling test, Shapiro-Wilk test, and QQ plot. P values were calculated using ANOVA and post hoc Bonferroni tests for normally distributed data. Correlation analysis was carried out using Pearson correlation test. P < 0.05 considered to be statistically significant.

RESULTS

After treatment in Group A patients, FT4 showed a significant increment while TSH value decreased. MDA level reduced after treatment, (P < 0.001). After treatment in Group B patients, FT4 showed increment while TSH value decreased (P < 0.05). After treatment, there was a drop in estimated MDA level (P < 0.001). MDA level shows a significant drop in both groups after treatment. In Group B, there is more decline in the MDA percentage but did not reach statistical significance. By performing repeated measure MANOVA, no significant difference was found in the MDA levels between the two groups. MDA reduction when expressed as percentage showed reduction of 39.5% in patients of Group A. Similarly, Group B patients showed a percentage reduction of 45.4%.

CONCLUSIONS

Oxidative stress compounds hypothyroidism. Hypothyroidism is a state of increased oxidative stress. In this study, biomarker, MDA level is high in treatment-naive primary hypothyroid patients. After treatment with L-thyroxine, the stress marker is reduced to a significant extent. MDA can be used as a useful biomarker to measure and monitor oxidative stress. The role of the addition of antioxidant in the form of selenium remained inconclusive.

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.

Supplementation of T3 recovers hypothyroid rat liver cells from oxidatively damaged inner mitochondrial membrane leading to apoptosis

Hypothyroidism is a growing medical concern. There are conflicting reports regarding the mechanism of oxidative stress in hypothyroidism. Mitochondrial oxidative stress is pivotal to thyroid dysfunction. The present study aimed to delineate the effects of hepatic inner mitochondrial membrane dysfunction as a consequence of 6-n-propyl-2-thiouracil-induced hypothyroidism in rats. Increased oxidative stress predominance in the submitochondrial particles (SMP) and altered antioxidant defenses in the mitochondrial matrix fraction correlated with hepatocyte apoptosis. In order to check whether the effects caused by hypothyroidism are reversed by T₃, the above parameters were evaluated in a subset of T₃-treated hypothyroid rats. Complex I activity was inhibited in hypothyroid SMP, whereas T₃ supplementation upregulated electron transport chain complexes. Higher mitochondrial H₂O₂ levels in hypothyroidism due to reduced matrix GPx activity culminated in severe oxidative damage to membrane lipids. SMP and matrix proteins were stabilised in hypothyroidism but exhibited increased carbonylation after T₃ administration. Glutathione content was higher in both. Hepatocyte apoptosis was evident in hypothyroid liver sections; T₃ administration, on the other hand, exerted antiapoptotic and proproliferative effects. Hence, thyroid hormone level critically regulates functional integrity of hepatic mitochondria; hypothyroidism injures mitochondrial membrane lipids leading to hepatocyte apoptosis, which is substantially recovered upon T₃ supplementation.

The hidden phenomenon of oxidative stress during treatment of subclinical-mild hypothyroidism: a protective nutraceutical intervention

Recent studies suggest that subjects with hypothyroidism under therapy with levothyroxine (L-T4) might develop oxidative stress. The aim of this study was to test a redox-balance modulator, fermented papaya-based nutraceutical (FPP), together with subclinical (SH) or mild hypothyroidism (MH) treatment in view of biochemical changes. A total of 60 females treated for SH-MH were divided into two matched groups and received either FPP 3 grams 1 sachet three times a day (t.i.d.) or placebo for 3 months. A significant baseline increase of all oxidative markers was observed in SH-MH (p<0.05 vs. control) and even more under T4 treatment (p<0.05). FPP caused a normalization of redox markers (p<0.01 vs. placebo). Thyroid supplementation accelerates mitochondrial oxygen consumption and oxidative stress, whereas a redox-modulator therapy is advisable, given the long-lasting treatment in such cases.

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.

Association of sympathovagal imbalance with cardiovascular risks in overt hypothyroidism

Background:

Cardiovascular morbidities have been reported in hypothyroidism.

Aims:

The objective of this study is to investigate the link of sympathovagal imbalance (SVI) to cardiovascular risks (CVRs) and the plausible mechanisms of CVR in hypothyroidism.

Materials and Methods:

Age-matched 104 females (50 controls, 54 hypothyroids) were recruited and their body mass index (BMI), cardiovascular parameters, autonomic function tests by spectral analysis of heart rate variability (HRV), heart rate response to standing, deep breathing and blood pressure response to isometric handgrip were studied. Thyroid profile, lipid profile, immunological and inflammatory markers were estimated and their association with low-frequency to the high-frequency ratio (LF-HF) of HRV, the marker of SVI was assessed by multivariate regression.

Results:

Increased diastolic pressure, decreased HRV, increased LF-HF, dyslipidemia and increased high-sensitive C-reactive protein (hsCRP) were observed in hypothyroid patients and all these parameters had significant correlation with LF-HF. BMI had no significant association with LF-HF. Atherogenic index (β 1.144, P = 0.001) and hsCRP (b 0.578, P = 0.009) had independent contribution to LF-HF. LF-HF could significantly predict hypertension status (odds ratio 2.05, confidence interval 1.110-5.352, P = 0.008) in hypothyroid subjects.

Conclusions:

SVI due to sympathetic activation and vagal withdrawal occurs in hypothyroidism. Dyslipidemia and low-grade inflammation, but not obesity contribute to SVI and SVI contributes to cardiovascular risks.

Levothyroxine and lung cancer in females: the importance of oxidative stress

BACKGROUND

Levothyroxine (LT4) treatment can lead to iatrogenic hyperthyroidism and oxidative stress that can cause patient discomfort. Oxidative stress is also recognized as one of the causes of chronic diseases and cancer.

METHODS

The prevalence of breast, colorectal, gastric and lung cancer in 18 Italian Regions during 2010 was correlated with the sales of LT4 in 2009. The cancer prevalence was analyzed in women aged 30-84. This age range corresponds to more than 80% of the consumers of the drug and to about 99% of all malignant cancers. The correlation between sales of LT4 and cancers was determined with the technique of Density Ellipses. The age and smoking contribution for lung cancer was determined with the Sequential test.

RESULTS

No significant correlation was seen between LT4 sales and breast, colorectal and gastric cancers. A significant correlation was instead found for lung cancer (p<0.05) corrected for smoking and age.

CONCLUSIONS

LT4 consumption in Italy is about 0.7 boxes/women/year. There is a correlation between lung cancer and LT4 treatment and oxidative stress caused by LT4 supplementation can be one of the causes. Although we cannot exclude that dysthyroidism needing LT4 supplementation might be the ground for lung cancer itself and measuring oxidative stress could be helpful in avoiding excessive use of the drug.

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.

Altered fructosamine and lipid fractions in subclinical hypothyroidism

BACKGROUND

Thyroid function disorders lead to changes in the lipoprotein metabolism.

OBJECTIVES

To study the lipid and the glycaemic abnormalities in the subclinical hypothyroidism cases and to compare the same with the euthyroid, overt hypothyroid and the hyperthyroid subjects.

METHODOLOGY

Four groups, euthyroid (Group-I), hypothyroid (Group-II), subclinical hypothyroid (Group-III) and hyperthyroid (Group-IV), which consisted of 30 subjects each, of either sex, who were aged 25-55 years, underwent Fasting Plasma Glucose (FPG), fructosamine, lipid profile and total T3, T4 and TSH estimations. The subjects who were on lipid lowering or thyroid disorder drugs and known diabetics were excluded from the study.

RESULTS

In Group-III, all the lipid fractions were comparable to those of Group-II and they were significantly deranged, as compared to those of Group-I. The fructosamine levels were significantly higher in Group-II and Group-III (p<0.05), but the subclinical hypothyroid pool had statistically lower levels than the hypothyroid pool (376.63±54.73, 587.80±65.10). In the Group-IV patients, the LDL-C levels were significantly higher as compared to those in the euthyroid pool. The fructosamine levels were significantly lower in comparison with both the euthyroid and the hypothyroid pools (both in Groups-II and III). The FPG levels were higher in all the classes of the thyroid abnormalities (subclinical hypothyroidnot significant) but within the reference range of 70-100mg/dl.

CONCLUSION

Since the lipid derangement in subclinical hypothyroidism is on par with that in overt hypothyrodism, the subclinical hypothyroid cases also need to be treated similarly. The fructosamine values which are largely in excess of the FPG values, indicate a higher propensity to glycation and a decreased turnover of the proteins in the hypothyroid and the subclinical hypothyroid pools. Vice versa is true of the hyperthyroid pool. Fructosamine can be included in the thyroid work up of the patients to assess the metabolic function and the subsequent response after the initiation of the therapy.

Biomarkers of peripheral muscle fatigue during exercise

BACKGROUND

Biomarkers of peripheral muscle fatigue (BPMFs) are used to offer insights into mechanisms of exhaustion during exercise in order to detect abnormal fatigue or to detect defective metabolic pathways. This review aims at describing recent advances and future perspectives concerning the most important biomarkers of muscle fatigue during exercise.

RESULTS

BPMFs are classified according to the mechanism of fatigue related to adenosine-triphosphate-metabolism, acidosis, or oxidative-metabolism. Muscle fatigue is also related to an immunological response. impaired calcium handling, disturbances in bioenergetic pathways, and genetic responses. The immunological and genetic response may make the muscle susceptible to fatigue but may not directly cause muscle fatigue. Production of BPMFs is predominantly dependent on the type of exercise. BPMFs need to change as a function of the process being monitored, be stable without appreciable diurnal variations, correlate well with exercise intensity, and be present in detectable amounts in easily accessible biological fluids. The most well-known BPMFs are serum lactate and interleukin-6. The most widely applied clinical application is screening for defective oxidative metabolism in mitochondrial disorders by means of the lactate stress test. The clinical relevance of most other BPMFs, however, is under debate, since they often depend on age, gender, physical fitness, the energy supply during exercise, the type of exercise needed to produce the BPMF, and whether healthy or diseased subjects are investigated.

CONCLUSIONS

Though the role of BPMFs during fatigue is poorly understood, measuring BPMFs under specific, standardised conditions appears to be helpful for assessing biological states or processes during exercise and fatigue.

Thyroid disorders

All forms of thyroid diseases are much more frequently observed in women than men, although the reasons are still not completely elucidated.Hyperthyroidism is defined by elevated circulating free thyroid hormones. The prevalence is about 2 % in women and 0.2 % in men. The most frequent causes are various forms of thyroid autonomy in elderly women and Graves' disease, which occurs mostly in younger women.Hypothyroidism is defined by a lack of thyroid hormones. It is a common endocrine disorder caused by autoimmune thyroiditis (Hashimoto thyroiditis), iodine deficiency or following surgery or radioiodine therapy. Thyroxine requirements depend on fat-free mass and are, therefore, somewhat higher in males who are more often undersubstituted. In pregnancy lower TSH-reference ranges have to be considered and thyroid function should be monitored throughout pregnancy to avoid harm to the foetus caused by maternal thyroid dysfunctions. If overtreated women more often feature fractures, whereas males more often develop atrial fibrillation.

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.

Evaluating the extent of pregravid risk factors of gestational diabetes mellitus in women in tehran

BACKGROUND

Gestational diabetes mellitus (GDM) is associated with maternal and fetal complications. Specific outcomes in previous pregnancies are considered as risk factors for GDM in the consecutive pregnancies. The aim of this study was to evaluate the pregravid risk factors of GDM in multigravid women.

METHODS

We conducted a retrospective cross sectional study on 114 multigravid women with GDM without previous history of diabetes and compared them with non-diabetic controls. We used modified criteria of Carpenter and Coustan for screening. Risk factors were obtained from medical records of individuals.

RESULTS

We found that women of 26 years and older who had previous neonates with birth weight more than 3800 gram and those affected with hypothyroidism or chronic hypertension were at risk for GDM. The difference of the number of preterm birth in GDM women and healthy controls was statistically significant (p=0.05). There was no significant difference between the numbers of pregnancies, parity, previous fetal and neonatal death and abortion number between patients and the control group.

CONCLUSION

Our results show that maternal age over 26 years, birth weight of previous neonate more than 3800 g, hypothyroidism, chronic hypertension and probably history of preterm birth are significant risk factors for GDM.

Modest inhibition of the growth hormone axis does not affect mitochondrial reactive oxygen species generation or redox state, unlike calorie restriction

AIM

Modest inhibition of the growth hormone (GH) axis by overexpression of the antisense GH gene in male Wistar rats reduced food intake and body weight, and lengthened the lifespan, even if fed ad libitum (AL). These findings were comparable with those induced by 30% calorie restriction (CR) in wild-type (WT) rats, suggesting importance of the GH signal pathway in the effect of CR. The present study evaluated the effects of GH inhibition and CR on mitochondrial oxidative stress and redox state in the liver.

METHODS

Transgenic and WT rats were fed AL or 30% CR diets from 6weeks of age. Liver tissues were collected at 6 and 24months of age. The mitochondria fraction was prepared from liver tissue homogenates. The total reactive oxygen species (ROS) generation, the protein levels of glutathione (GSH) and oxidized GSH (GSSG), and the superoxide dismutase 2 activity were measured.

RESULTS

The results revealed that CR, but not modest inhibition of GH, decreased mitochondrial ROS generation and increased the mitochondrial GSH redox potential.

CONCLUSION

The present study suggests that CR affects mitochondrial function and redox state through a pathway distinct from GH signaling.

Gender-specific differences in the urinary expression of aldosterone, IL-1α and IL-1β

Aims: This pilot investigation examined the possibility of using urine specimens to explore the difference between the expression of several biomarkers based on gender. These biomarkers include several associated with cardiac damage, oxidative stress and inflammation. Materials & methods: Urine specimens were assayed for total protein, aldosterone, high-sensitivity C-reactive protein, myeloperoxidase and IL-1α and -1β using ELISA. Results: We observed significant differences between the sexes for aldosterone and IL-1α and -1β. Conclusion: The presence of gender-based differences in the urinary expression of these biomarkers may be important for establishing normal baseline values in males and females, and may prove to be of value in the development of rapid noninvasive ways to assess inflammatory and oxidative injury during routine urinalysis.

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

BACKGROUND

The aim of this study was to investigate the effect of hypothyroidism on lipid peroxidation and the antioxidant profile, as well as to evaluate the interaction between thyroid hormones and biomarkers of oxidative stress in patients with overt hypothyroidism. We also evaluated the influence of cholesterol concentrations on biomarkers of oxidative stress in these same patients.

METHODS

Total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and vitamin E were measured in 20 subjects with overt hypothyroidism (OH) and 20 controls.

RESULTS

TC, LDL cholesterol, triglycerides, TBARS, SOD, CAT, and vitamin E were significantly higher in the OH group. Significant correlation was observed for TSH and SOD, CAT, vitamin E and TBARS. Correlation was observed for triiodothyronine (T3) and SOD, CAT, vitamin E and TBARS. Significant correlation was also observed for free thyroxine and vitamin E and TBARS. However, correlation between T3 and CAT remained significant after controlling for TC concentrations.

CONCLUSIONS

Overt hypothyroidism is associated with an increase in oxidative stress, and hypercholesterolemia has a stronger influence on development of oxidative stress in hypothyroid conditions compared with thyroid hormones.