Association of lipid peroxidation with endothelial dysfunction in patients with overt hypothyroidism

The Role of Oxidative Stress and Antioxidants in Cardiovascular Comorbidities in COPD

Oxidative stress driven by several environmental and local airway factors associated with chronic obstructive bronchiolitis, a hallmark feature of COPD, plays a crucial role in disease pathomechanisms. Unbalance between oxidants and antioxidant defense mechanisms amplifies the local inflammatory processes, worsens cardiovascular health, and contributes to COPD-related cardiovascular dysfunctions and mortality. The current review summarizes recent developments in our understanding of different mechanisms contributing to oxidative stress and its countermeasures, with special attention to those that link local and systemic processes. Major regulatory mechanisms orchestrating these pathways are also introduced, with some suggestions for further research in the field.

Recent Progress of Chronic Stress in the Development of Atherosclerosis

With the development of the times, cardiovascular diseases have become the biggest cause of death in the global aging society, causing a serious social burden. Atherosclerosis is a chronic inflammatory disease, which can occur in large and medium-sized blood vessels in the whole body. It takes atherosclerotic plaque as the typical pathological change and endothelial injury as the core pathophysiological mechanism. It is the pathological basis of coronary heart disease, peripheral artery disease, cerebrovascular disease, and other diseases. Recent studies have shown that chronic stress plays an important role in the occurrence and development of atherosclerosis, endothelial injury, lipid metabolism, and chronic inflammation. This process involves a large number of molecular targets. It is usually the cause of atherosclerotic cardiovascular and cerebrovascular diseases. If chronic stress factors exist for a long time, patients have genetic susceptibility, and the combination of environmental factors triggers the pathogenesis, which may eventually lead to complete blockage of the blood vessels, unstable rupture of plaques, and serious adverse cardiovascular events. This paper reviews the role of chronic stress in the occurrence and development of atherosclerosis, focusing on the pathophysiological mechanism.

Heavy Metal-Induced Cerebral Small Vessel Disease: Insights into Molecular Mechanisms and Possible Reversal Strategies

Heavy metals are considered a continuous threat to humanity, as they cannot be eradicated. Prolonged exposure to heavy metals/metalloids in humans has been associated with several health risks, including neurodegeneration, vascular dysfunction, metabolic disorders, cancer, etc. Small blood vessels are highly vulnerable to heavy metals as they are directly exposed to the blood circulatory system, which has comparatively higher concentration of heavy metals than other organs. Cerebral small vessel disease (CSVD) is an umbrella term used to describe various pathological processes that affect the cerebral small blood vessels and is accepted as a primary contributor in associated disorders, such as dementia, cognitive disabilities, mood disorder, and ischemic, as well as a hemorrhagic stroke. In this review, we discuss the possible implication of heavy metals/metalloid exposure in CSVD and its associated disorders based on in-vitro, preclinical, and clinical evidences. We briefly discuss the CSVD, prevalence, epidemiology, and risk factors for development such as genetic, traditional, and environmental factors. Toxic effects of specific heavy metal/metalloid intoxication (As, Cd, Pb, Hg, and Cu) in the small vessel associated endothelium and vascular dysfunction too have been reviewed. An attempt has been made to highlight the possible molecular mechanism involved in the pathophysiology, such as oxidative stress, inflammatory pathway, matrix metalloproteinases (MMPs) expression, and amyloid angiopathy in the CSVD and related disorders. Finally, we discussed the role of cellular antioxidant defense enzymes to neutralize the toxic effect, and also highlighted the potential reversal strategies to combat heavy metal-induced vascular changes. In conclusion, heavy metals in small vessels are strongly associated with the development as well as the progression of CSVD. Chelation therapy may be an effective strategy to reduce the toxic metal load and the associated complications.

COPD as an endothelial disorder: endothelial injury linking lesions in the lungs and other organs? (2017 Grover Conference Series)

Chronic obstructive pulmonary disease (COPD) is characterized by chronic expiratory airflow obstruction that is not fully reversible. COPD patients develop varying degrees of emphysema, small and large airway disease, and various co-morbidities. It has not been clear whether these co-morbidities share common underlying pathogenic processes with the pulmonary lesions. Early research into the pathogenesis of COPD focused on the contributions of injury to the extracellular matrix and pulmonary epithelial cells. More recently, cigarette smoke-induced endothelial dysfunction/injury have been linked to the pulmonary lesions in COPD (especially emphysema) and systemic co-morbidities including atherosclerosis, pulmonary hypertension, and chronic renal injury. Herein, we review the evidence linking endothelial injury to COPD, and the pathways underlying endothelial injury and the "vascular COPD phenotype" including: (1) direct toxic effects of cigarette smoke on endothelial cells; (2) generation of auto-antibodies directed against endothelial cells; (3) vascular inflammation; (4) increased oxidative stress levels in vessels inducing increases in lipid peroxidation and increased activation of the receptor for advanced glycation end-products (RAGE); (5) reduced activation of the anti-oxidant pathways in endothelial cells; (6) increased endothelial cell release of mediators with vasoconstrictor, pro-inflammatory, and remodeling activities (endothelin-1) and reduced endothelial cell expression of mediators that promote vasodilation and homeostasis of endothelial cells (nitric oxide synthase and prostacyclin); and (7) increased endoplasmic reticular stress and the unfolded protein response in endothelial cells. We also review the literature on studies of drugs that inhibit RAGE signaling in other diseases (angiotensin-converting enzyme inhibitors and angiotensin receptor blockers), or vasodilators developed for idiopathic pulmonary arterial hypertension that have been tested on cell culture systems, animal models of COPD, and/or smokers and COPD patients.

Lipid (per) oxidation in mitochondria: an emerging target in the ageing process?

Lipids are essential for physiological processes such as maintaining membrane integrity, providing a source of energy and acting as signalling molecules to control processes including cell proliferation, metabolism, inflammation and apoptosis. Disruption of lipid homeostasis can promote pathological changes that contribute towards biological ageing and age-related diseases. Several age-related diseases have been associated with altered lipid metabolism and an elevation in highly damaging lipid peroxidation products; the latter has been ascribed, at least in part, to mitochondrial dysfunction and elevated ROS formation. In addition, senescent cells, which are known to contribute significantly to age-related pathologies, are also associated with impaired mitochondrial function and changes in lipid metabolism. Therapeutic targeting of dysfunctional mitochondrial and pathological lipid metabolism is an emerging strategy for alleviating their negative impact during ageing and the progression to age-related diseases. Such therapies could include the use of drugs that prevent mitochondrial uncoupling, inhibit inflammatory lipid synthesis, modulate lipid transport or storage, reduce mitochondrial oxidative stress and eliminate senescent cells from tissues. In this review, we provide an overview of lipid structure and function, with emphasis on mitochondrial lipids and their potential for therapeutic targeting during ageing and age-related disease.

Levels of endothelial cell-specific molecule-1 (ESM-1) in overt hypothyroidisim

PURPOSE

Endothelial cell-specific molecule-1, endocan, is a proteoglycan that is expressed by the vascular endothelium. Endocan can be a biomarker of endothelial dysfunction caused by endothelial cell-dependent disorders. Endothelial dysfunction is an early step of atherosclerosis and is developed in hypothyroid patients, which indicates an association between hypothyroidism and atherosclerosis. Therefore, we aimed to investigate whether circulating endocan levels are associated with endothelial dysfunction in overt hypothyroid patients.

MATERIALS AND METHODS

Forty patients with hypothyroidism diagnosed in the last 5 years and 30 healthy subjects were recruited.

RESULTS

The mean endocan value in all patients was 0.63 ± 0.26 pg/ml, which was higher than that in controls (0.36 ± 0.10 pg/ml, p < 0.05). When we subgrouped the patients as hypothyroid and euthyroid, all groups demonstrated significantly different endocan levels, and hypothyroid patients had the highest endocan levels. A correlation analysis demonstrated that endocan levels were positively correlated with body mass index (BMI), thyroid-stimulating hormone (TSH), anti-thyroid peroxidase, and anti-thyroglobulin and negatively correlated with free thyroid hormone 4 (FT4) and vitamin D levels. In addition, in the patient group, endocan levels were correlated with FT4 levels independently in a covariance analysis.

CONCLUSIONS

The circulating endocan level increased in hypothyroid patients, suggesting that endocan levels may be an early biomarker of the development of endothelial dysfunction in patients with hypothyroidism. They may also prove useful in the prediction of cardiovascular diseases after further studies using cardiovascular disease biomarkers. In addition, targeting endocan levels to decrease cardiovascular risk may be a new treatment strategy in these patients.

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.

Levothyroxine but Not Selenium Increases Endothelial Progenitor Cell Counts in Patients with Hypothyroidism

BACKGROUND

Hypothyroidism is a common endocrine disease associated with increased oxidative stress, increased cardiovascular (CV) risk, CV events and endothelial dysfunction. Endothelial progenitor cells (EPCs) are a well-known marker of CV risk.

OBJECTIVE

The aim of this work was to ascertain whether hypothyroidism is associated with lower EPC counts and if treatment with levothyroxine (LT4) or selenium (Se) improves EPC counts compared to placebo.

METHODS

Hypothyrod patients (n = 100) were randomly divided into five groups to receive placebo (group A), LT4 (group B) or Se at doses of 83 µg (group C), 166 µg (group D) or 249 µg (group E) for 3 months. Each group comprised 20 patients: 10 with 'mild' hypothyroidism and 10 with 'severe' hypothyroidism. A healthy control group (group F) with 20 euthyroid subjects was also recruited. Subjects had to be free of CV disease, diabetes and drugs that interfere with EPCs. Anthropometric measurements (height, weight, BMI), blood pressure, fasting lipids and EPC analyses were performed at baseline and after 3 months.

RESULTS

EPC counts were significantly lower in hypothyroid patients compared to controls. EPCs increased after 3 months of treatment with LT4, but not with Se at any dosage. CD133+ and CD34+ EPC counts were negatively correlated with thyroid-stimulating hormone (TSH; r (2) = 0.523, p < 0.01 and r (2) = 0.517, p < 0.01, respectively) and positively correlated with FT4 (r (2) = 0.394, p < 0.01 and r (2) = 0.369, p < 0.01, respectively). TSH and FT4 were the only predictors of EPC counts.

CONCLUSIONS

Hypothyroidism is associated with low EPC counts. Treatment with LT4, but not Se, can improve EPC counts.

LDL biochemical modifications: a link between atherosclerosis and aging

Atherosclerosis is an aging disease in which increasing age is a risk factor. Modified low-density lipoprotein (LDL) is a well-known risk marker for cardiovascular disease. High-plasma LDL concentrations and modifications, such as oxidation, glycosylation, carbamylation and glycoxidation, have been shown to be proatherogenic experimentally in vitro and in vivo. Atherosclerosis results from alterations to LDL in the arterial wall by reactive oxygen species (ROS). Evidence suggests that common risk factors for atherosclerosis raise the likelihood that free ROS are produced from endothelial cells and other cells. Furthermore, oxidative stress is an important factor in the induction of endothelial senescence. Thus, endothelial damage and cellular senescence are well-established markers for atherosclerosis. This review examines LDL modifications and discusses the mechanisms of the pathology of atherosclerosis due to aging, including endothelial damage and oxidative stress, and the link between aging and atherosclerosis.

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.

Oxidative stress in patients with thyroidectomy and thyroparathyroidectomy under replacement therapy

Several studies have demonstrated an imbalance between free radicals and the antioxidative system in individuals with thyroid dysfunction. However, oxidative stress has not been evaluated in patients with thyroidectomy and thyroparathyroidectomy, who are under replacement therapy. The objective of this study was to evaluate the oxidative stress using malondialdehyde, nitric oxide, and catalase levels in patients with thyroidectomy and thyroparathyroidectomy. Nineteen patients with thyroidectomy, 20 patients with thyroparathyroidectomy, and 20 controls with no history of thyroid or parathyroid disease or surgery were included in the study. Serum malondialdehyde, nitric oxide, and catalase levels were examined. Levels of nitric oxide and malondialdehyde were elevated, and catalase levels decreased in patients with thyroidectomy and thyroparathyroidectomy compared with controls (p value for all the parameters: p<0.001). Free tetraiodothyronine was a potential predictor of malondialdehyde in the patient groups (p: 0.002). Catalase was negatively correlated with nitric oxide (p<0.01) and malondialdehyde (p<0.01). The results of the current study demonstrated that oxidative stress increased in patients with thyroidectomy and thyroparathyroidectomy despite the application of replacement therapies.

Effects of Salvia sclarea on chronic immobilization stress induced endothelial dysfunction in rats

Background

Although Salvia sclarea (clary sage) is widely used in aromatherapy and has antioxidant and antimicrobial properties, its mechanisms of action remain poorly understood. We therefore assessed whether clary sage is effective in treating endothelial dysfunction induced by chronic immobilization stress in rats.

Methods

Rats were intraperitoneally injected with almond oil, clary sage oil (5%, 10% or 20%), or nifedipine once daily, followed by immobilization stress (2 h/day) for 14 days. Systolic blood pressure (SBP) and heart rate (HR) were measured, as were serum concentrations of corticosterone (CORT); a biomarker of chronic stress, malondialdehyde (MDA); a biomarker of oxidative stress. Nitric oxide production was assessed by nitrite assays, and eNOS level, a biomarker of endothelial dysfunction, was measured by western blotting. Endothelial dysfunction was also assayed by measuring the effect of clary sage on the contraction of rat aortae.

Results

Treatment with 5% (p = 0.029), 10% (p = 0.008), and 20% (p = 0.008) clary sage significantly reduced SBP and treatment with 20% clary sage significantly reduced HR (p = 0.039) compared with the chronic immobilization stress group. Clary sage decreased CORT serum concentration (10%, p = 0.026; 20%, p = 0.012) and MDA (10%, p = 0.007; 20%, p = 0.027), findings similar to those observed with nifedipine. In addition, 20% clary sage significantly increased nitric oxide production (p <0.001) and eNOS expression level (p <0.001) and relaxed aortic rings in rats subjected to chronic immobilization stress.

Conclusions

Clary sage treatment of rats subjected to immobilization stress contributed to their recovery from endothelial dysfunction by increasing NO production and eNOS level as well as by decreasing oxidative stress. Appropriate concentration of clary sage may result in recovery from endothelial dysfunction. These findings indicate that clary sage oil may be effective in the prevention and treatment of stress-induced cardiovascular diseases.