Urinary biopyrrins levels are elevated in relation to severity of heart failure

The Association Between Oxidative Stress and the Progression of Heart Failure: A Systematic Review

Chronic heart failure (CHF) is a progressive multifactorial condition where the role of oxidative stress may have implications in the pathogenesis of the disease. Despite growing interest among researchers and clinicians, the limited, unorganized, and divergent findings regarding the association between oxidative stress and the progression of heart failure (HF) have prompted us to conduct this study. Drawing upon the evolving nature of this research domain, this study is one of the first of its kind to present a systematic and comprehensive overview of the existing evidence regarding the role of oxidative stress production in the progression of HF. This study systematically reviews peer-reviewed empirical studies published in English, particularly focusing on the association between oxidative stress and the progression of HF. Parameters, such as publication year, study design, population demographics (size, age, and gender), types of HF, and characterization of markers in the existing studies, were reviewed. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) procedure, a thorough search was conducted on PubMed, Cochrane, Embase, and Sage databases, without any restrictions on the publication dates of articles, which yielded a total of 1,808 records on the association of oxidative stress production with clinical outcomes in HF patients. The analysis of the content of 17 articles offered a robust observation of this phenomenon, providing insights into the levels of oxidative stress, antioxidant markers, and the enzymes involved in the production of reactive oxygen species (ROS), and their association with the progression and severity of HF. The findings highlighted various knowledge gaps and future research priorities are recommended in the areas of interest and unexplored areas.

Dupilumab therapy reduces urinary biopyrrin levels in atopic patients: a new possible biomarker of oxidative status in atopic dermatitis

BACKGROUND

Accumulating evidence suggests that oxidative stress is involved in the inflammatory process of atopic dermatitis (AD). Biopyrrins are the end products of the oxidative reaction of bilirubin with reactive oxygen species. The aim of our study was to explore the correlation between urinary biopyrrin levels and AD severity as well as to assess the possible modification of them in AD patients during biologic therapy with human monoclonal antibody dupilumab.

METHODS

For this purpose, 25 adult patients with moderate-severe AD who were candidates for dupilumab therapy independently from the study, and 15 healthy control subjects, matched by sex and age, were enrolled. Morning urine samples were collected from all study participants. For AD patients, a collection was planned before starting therapy with dupilumab (WO), after 8, 16, 52 weeks (W8, W16, W52, respectively), and two years (Y2) of treatment. The analysis of urinary levels of biopyrrins was performed by ELISA assay.

RESULTS

Our results demonstrated that urinary biopyrrin levels were significantly augmented in AD patients, and interestingly they correlated with disease severity. Furthermore, dupilumab therapy decreased levels of urinary biopyrrins in AD patients after eight and 16 weeks, maintaining the result after 52 weeks as well as after two years of treatment. The correlation analysis showed a statistically significant positive correlation between the urinary concentration of biopyrrins and EASI Index, circulating total IgE as well as plasma C reactive protein levels.

CONCLUSIONS

Dupilumab therapy was able to ameliorate oxidative state in AD patients.

A Platform for the Synthesis of Oxidation Products of Bilirubin

Bilirubin is the principal product of heme catabolism. High concentrations of the pigment are neurotoxic, yet slightly elevated levels are beneficial. Being a potent antioxidant, oxidative transformations of bilirubin occur in vivo and lead to various oxidized fragments. The mechanisms of their formation, intrinsic biological activities, and potential roles in human pathophysiology are poorly understood. Degradation methods have been used to obtain samples of bilirubin oxidation products for research. Here, we report a complementary, fully synthetic method of preparation. Our strategy leverages repeating substitution patterns in the parent tetracyclic pigment. Functionalized ready-to-couple γ-lactone, γ-lactam, and pyrrole monocyclic building blocks were designed and efficiently synthesized. Subsequent modular combinations, supported by metal-catalyzed borylation and cross-coupling chemistries, translated into the concise assembly of the structurally diverse bilirubin oxidation products (BOXes, propentdyopents, and biopyrrins). The discovery of a new photoisomer of biopyrrin A named lumipyrrin is reported. Synthetic bilirubin oxidation products made available in sufficient purity and quantity will support future in vitro and in vivo investigations.

Novel Oxidative Stress Biomarkers with Risk Prognosis Values in Heart Failure

Oxidative stress (OS) is mediated by reactive oxygen species (ROS), which in cardiovascular and other disease states, damage DNA, lipids, proteins, other cellular and extra-cellular components. OS is both initiated by, and triggers inflammation, cardiomyocyte apoptosis, matrix remodeling, myocardial fibrosis, and neurohumoral activation. These have been linked to the development of heart failure (HF). Circulating biomarkers generated by OS offer potential utility in patient management and therapeutic targeting. Novel OS-related biomarkers such as NADPH oxidases (sNox2-dp, Nrf2), advanced glycation end-products (AGE), and myeloperoxidase (MPO), are signaling molecules reflecting pathobiological changes in HF. This review aims to evaluate current OS-related biomarkers and their associations with clinical outcomes and to highlight those with greatest promise in diagnosis, risk stratification and therapeutic targeting in HF.

Studying the Association Between Occupational Stress and Urinary Levels of Oxidative Stress Biomarkers (8-OHdG and Biopyrrins) in Brickfield Workers

OBJECTIVES

The aims of the study are to measure the prevalence and level of occupational stress (OS) and to explore its association with oxidative stress among some brickfield workers.

METHODS

Eighty-six brickfield workers and 90 administrative controls were assessed using the Arabic validated version of the Occupational Stress Index. The urinary levels of oxidative biomarkers; 8-hydroxy-2'-deoxyguanosine and biopyrrins were also measured.

RESULTS

The prevalence of moderate and severe OS in addition to the urinary levels of both oxidative biomarkers was significantly higher among the brickfield workers compared with their controls. Both biomarkers levels were significantly and positively correlated with scores of Occupational Stress Index, duration of employment, and with each other. The receiver operating characteristic analysis showed significant specificity and sensitivity of both biomarkers for determining the level of OS.

CONCLUSIONS

A significant association between occupational and oxidative stresses was detected in brickfield workers.

Advances in congestive heart failure biomarkers

Congestive heart failure (CHF) is the leading cause of morbidity and mortality in the elderly worldwide. Although many biomarkers associated with in heart failure, these are generally prognostic and identify patients with moderate and severe disease. Unfortunately, the role of biomarkers in decision making for early and advanced heart failure remains largely unexplored. Previous studies suggest the natriuretic peptides have the potential to improve the diagnosis of heart failure, but they still have significant limitations related to cut-off values. Although some promising cardiac biomarkers have emerged, comprehensive data from large cohort studies is lacking. The utility of multiple biomarkers that reflect various pathophysiologic pathways are increasingly being explored in heart failure risk stratification and to diagnose disease conditions promptly and accurately. MicroRNAs serve as mediators and/or regulators of renin-angiotensin-induced cardiac remodeling by directly targeting enzymes, receptors and signaling molecules. The role of miRNA in HF diagnosis is a promising area of research and further exploration may offer both diagnostic and prognostic applications and phenotype-specific targets. In this review, we provide insight into the classification of different biochemical and molecular markers associated with CHF, examine clinical usefulness in CHF and highlight the most clinically relevant.

Naltrexone-Induced Cardiac Function Improvement is Associated With an Attenuated Inflammatory Response and Lipid Perioxidation in Volume Overloaded Rats

In previous studies, upregulation of myocardial opioid receptors as well as the precursors of their endogenous ligands were detected in the failing heart due to chronic volume overload. Moreover, opioid receptor blockade by naltrexone improved left ventricular function. In parallel, inflammatory processes through cytokines have been confirmed to play an important role in the pathogenesis of different forms of heart failure. Thus, the present study examined the systemic and myocardial inflammatory response to chronic volume overload and its modulation by chronic naltrexone therapy. Chronic volume overload was induced in male Wistar rats by applying an infrarenal aortocaval fistula (ACF) for 28 days during which the selective opioid receptor antagonist naltrexone (n = 6) or vehicle (n = 6) were administered via a subcutaneously implanted Alzet minipump. The ultrastructural, morphometric and hemodynamic characterization of ACF animals were performed using an intraventricular conductance catheter in vivo and electron microscopy in vitro. Co-localization of mu-, delta- and kappa-opioid receptor subtypes (MOR, DOR, and KOR respectively) with the voltage gated L-type Ca2+ channel (Cav1.2), the ryanodine receptor (RyR), and mitochondria in cardiomyocytes as well as IL-6, IL-12, TNF-alpha, and Malondialdehyde (MDA) were determined using double immunofluorescence confocal microscopy, RT-PCR and ELISA, respectively. In rat left ventricular myocardium, three opioid receptor subtypes MOR, DOR, and KOR colocalized with Cav1.2, RyR and mitochondria suggesting a modulatory role of the excitation-contraction coupling. In rats with ACF-induced volume overload, signs of heart failure and myocardial ultrastructural damage, chronic naltrexone therapy improved cardiac function and reversed the systemic and myocardial inflammatory cytokine expression as well as lipid peroxidation. In conclusion, antagonism of the cardiodepressive effects of the myocardial opioid system does not only improve left ventricular function but also blunts the inflammatory response and lipid peroxidation.

Relationship between serum bilirubin levels, urinary biopyrrin levels, and retinopathy in patients with diabetes

Objective

Previous reports have indicated that serum bilirubin levels may be associated with diabetic retinopathy. However, the detailed mechanism is not fully understood. In this study, we evaluated the relationship between the severity of diabetic retinopathy and various factors including bilirubin levels and factors influencing bilirubin metabolism.

Methods

The study participants consisted of 94 consecutive patients with diabetes mellitus admitted to Kyushu University Hospital from April 2011 to July 2012. The patients were classified into three groups: no retinopathy (NDR), simple retinopathy (SDR), and pre-proliferative or proliferative retinopathy (PDR). The relationship between the severity of retinopathy and various factors was evaluated using univariate and logistic regression analyses. In addition, multivariate regression analysis was performed to evaluate the significant determinants for bilirubin levels.

Results

In univariate analysis, a significant difference was found among NDR, SDR and PDR in bilirubin levels, duration of diabetes, systolic blood pressure, and macroalbuminuria. Logistic regression analysis showed that PDR was significantly associated with bilirubin levels, duration of diabetes, and systolic blood pressure (OR 0.737, 95% CI 0.570–0.952, P = 0.012; OR 1.085, 95% CI 1.024–1.149, P = 0.006; OR 1.036, 95% CI 1.011–1.062, P = 0.005, respectively). In turn, multivariate regression analysis showed that bilirubin levels were negatively associated with high-sensitivity C-reactive protein levels and PDR, but positively correlated with urinary biopyrrin levels, oxidized metabolites of bilirubin.

Conclusion

PDR was negatively associated with bilirubin levels. This negative association may be due to a decreased production of bilirubin rather than its increased consumption considering the positive association between bilirubin and biopyrrin levels.

Clinical significance of reactive oxidative metabolites in patients with heart failure with reduced left ventricular ejection fraction

BACKGROUND

We investigated the clinical significance of the derivative of reactive oxygen metabolites (DROM), a new marker of reactive oxygen species (ROS), in patients with heart failure (HF) with reduced left ventricular ejection fraction (LVEF) (HFrEF).

METHODS AND RESULTS

Serum DROM concentrations were measured in 201 consecutive patients with HFrEF (EF < 50%) in stable condition. DROM values were significantly higher in patients with HFrEF than in risk-matched patients without HF (P < 0.01). They also correlated significantly with high-sensitivity C-reactive protein and B-type natriuretic peptide. Kaplan-Meier analysis demonstrated significantly higher probabilities of HF-related events in the high-DROM group than in the low-DROM group (log-rank test, P < 0.01). Multivariable Cox hazard analysis revealed that DROM were independent and significant predictors of cardiovascular events. In a subgroup analysis, DROM levels were also measured at the aortic root and coronary sinus in 49 patients. The transcardiac gradient of DROM values was significantly higher in patients with HFrEF than in patients without HF (P = 0.04), indicating an association between DROM production in the coronary circulation and HFrEF development. Changes in DROM following optimal therapy were significantly associated with LVEF improvement (r = 0.34, P = 0.04).

CONCLUSIONS

The higher levels of DROM and their association with cardiovascular events suggest the clinical benefit of DROM measurements in the risk stratification of patients with HFrEF.

Biomarkers in heart failure: the past, current and future

Despite the enhanced knowledge of the pathophysiology of heart failure (HF), it still remains a serious syndrome with substantial morbidity, mortality, and frequent hospitalizations. These are due to the current improvements in other cardiovascular diseases (like myocardial infarction), the aging population, and growing prevalence of comorbidities. Biomarker-guided management has brought a new dimension in prognostication, diagnosis, and therapy options. Following the recommendation of natriuretic peptides (B-type natriuretic peptide and N-terminal-proBNP), many other biomarkers have been thoroughly studied to reflect different pathophysiological processes (such as fibrosis, inflammation, myocardial injury, and remodeling) in HF and some of them (like cardiac troponins, soluble suppression of tumorigenesis-2, and galectin 3) have subsequently been recommended to aid in the diagnosis and prognostication in HF. Consequently, multi-marker approach has also been approved owing to the varied nature of HF syndrome. In this review, we discussed the guidelines available for HF biomarkers, procedures for evaluating novel markers, and the utilities of both emerging and established biomarkers for risk stratification, diagnosis, and management of HF in the clinics. We later looked at how the rapidly emerging field-OMICs, can help transform HF biomarkers discoveries and establishment.

Malondialdehyde and Uric Acid as Predictors of Adverse Outcome in Patients with Chronic Heart Failure

In chronic heart failure (HF), some parameters of oxidative stress are correlated with disease severity. The aim of this study was to evaluate the importance of oxidative stress biomarkers in prognostic risk stratification (death and combined endpoint: heart transplantation or death). In 774 patients, aged 48-59 years, with chronic HF with reduced ejection fraction (median: 24.0 (20-29)%), parameters such as total antioxidant capacity, total oxidant status, oxidative stress index, and concentration of uric acid (UA), bilirubin, protein sulfhydryl groups (PSH), and malondialdehyde (MDA) were measured. The parameters were assessed as predictive biomarkers of mortality and combined endpoint in a 1-year follow-up. The multivariate Cox regression analysis was adjusted for other important clinical and laboratory prognostic markers. Among all the oxidative stress markers examined in multivariate analysis, only MDA and UA were found to be independent predictors of death and combined endpoint. Higher serum MDA concentration increased the risk of death by 103.0% (HR = 2.103; 95% CI (1.330-3.325)) and of combined endpoint occurrence by 100% (HR = 2.000; 95% CI (1.366-2.928)) per μmol/L. Baseline levels of MDA in the 4^th quartile were associated with an increased risk of death with a relative risk (RR) of 3.64 (95% CI (1.917 to 6.926), p < 0.001) and RR of 2.71 (95% CI (1.551 to 4.739), p < 0.001) for the occurrence of combined endpoint as compared to levels of MDA in the 1^st quartile. Higher serum UA concentration increased the risk of death by 2.1% (HR = 1.021; 95% CI (1.005-1.038), p < 0.001) and increased combined endpoint occurrence by 1.4% (HR = 1.014; 95% CI (1.005-1.028), p < 0.001), for every 10 μmol/L. Baseline levels of UA in the 4^th quartile were associated with an increased risk for death with a RR of 3.21 (95% CI (1.734 to 5.931)) and RR of 2.73 (95% CI (1.560 to 4.766)) for the occurrence of combined endpoint as compared to the levels of UA in the 1^st quartile. In patients with chronic HF, increased MDA and UA concentrations were independently related to poor prognosis in a 1-year follow-up.

Progress in the development of selective heme oxygenase-1 inhibitors and their potential therapeutic application

Heme oxygenases (HOs) are a family of enzymes involved in the selective catabolism of free circulating heme. While HO-2 is constitutively expressed, HO-1 is strongly overexpressed under stressful stimuli (e.g., oxidative stress). Under these conditions, HO-1 exerts its strong cytoprotective activities and plays a crucial role in stimulating cell survival by removing the pro-oxidant heme and by producing carbon monoxide and biliverdin (promptly reduced to bilirubin). Unfortunately, the broad spectrum of HO-1 cytoprotective effects has been well experimentally documented both in normal and tumor cells, where the enzyme can be overexpressed, making it an exciting target in the management of some type of tumors. Development of non-competitive HO-1 inhibitors dates back in 2002 with the discovery of Azalanstat. Since then, many efforts have been devoted to the identification of selective HO-1 and HO-2 inhibitors and to unravel the molecular determinants responsible for selectivity. Molecular modeling studies supported the identification of chemical features involved in the recognition and inhibition of these enzymes. Herein, medicinal chemistry aspects and in silico studies related to the development of HO inhibitors will be discussed. The purpose of this review is to highlight recent advances in the development of new selective HO-1 and HO-2 inhibitors and covers the last six years (2013-2018).

Immunity, Inflammation, and Oxidative Stress in Heart Failure: Emerging Molecular Targets

PURPOSE

Heart failure (HF) remains a major cause of morbidity and mortality worldwide. Although various therapies developed over the last two decades have shown improved long term outcomes in patients with established HF, there has been little progress in preventing the adverse cardiac remodeling that initiates HF. To fill the gap in treatment, current research efforts are focused on understanding novel mechanisms and signaling pathways. Immune activation, inflammation, oxidative stress, alterations in mitochondrial bioenergetics, and autophagy have been postulated as important pathophysiological events in this process. An improved understanding of these complex processes could facilitate a therapeutic shift toward molecular targets that can potentially alter the course of HF.

METHODS

In this review, we address the role of immunity, inflammation, and oxidative stress as well as other novel emerging concepts in the pathophysiology of HF that may have therapeutic implications.

CONCLUSION

Based on the experimental and clinical studies presented here, we anticipate that a better understanding of the pathophysiology of HF will open the door for new therapeutic targets. A one-size-fits-all approach may not be appropriate for all patients with HF, and further clinical trials utilizing molecular targeting in HF may result in improved outcomes.

Bilirubin oxidation derived from oxidative stress is associated with disease severity of atopic dermatitis in adults

BACKGROUND

Bilirubin is an essential antioxidant. Its oxidative metabolites, biopyrrins, are sensitive urinary markers of oxidative stress. Multiple studies suggest that oxidative stress affects the pathogenesis of skin diseases such as atopic dermatitis (AD).

AIM

To examine oxidative stress-induced bilirubin oxidation and its association with AD pathogenesis in adults.

METHODS

In total, 11 patients with AD and 7 healthy controls (HCs) were enrolled. Bilirubin oxidation profiles in the combined urine of the patients and that of the HCs were examined using high-performance liquid chromatography (HPLC) and fast atom bombardment mass spectrometry. The concentrations of urinary biopyrrins and serum biomarkers for AD disease severity, such as IgE and thymus and activation-regulated chemokine (TARC)/CCL17, were measured by ELISA to determine correlations between urinary biopyrrins and serum biomarkers. Local bilirubin oxidation in AD skin lesions was assessed by immunohistochemical analyses using two antibodies against bilirubin.

RESULTS

Levels of dipyrrole-monopyrrole-aldehyde, a novel urinary biopyrrin, were higher in patients with AD than in HCs, and increased with disease severity based on the SCORing Atopic Dermatitis (SCORAD) objective scoring system. Additionally, urinary biopyrrin levels correlated significantly with serum IgE and TARC/CCL17 levels. Furthermore, immunohistochemical analyses revealed that biopyrrins were strongly expressed in both infiltrating and resident cells in AD lesions. However, bilirubin was expressed at low levels in the lesions, suggesting that bilirubin oxidation is augmented in AD lesions.

CONCLUSIONS

Bilirubin oxidation derived from oxidative stress in the skin lesions can be associated with disease severity of AD.

Study of respiratory chain dysfunction in heart disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. A part from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the aging heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practicing clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

Serum paraoxonase activity in patients with ischaemic and nonischaemic dilated cardiomyopathy

BACKGROUND

This study examined whether the serum PON1 activity is different in patients with ischaemic dilated cardiomyopathy (IDCM) and nonischaemic dilated cardiomyopathy (NDCM) and the relation between the serum PON1 activity and serum pro-BNP levels.

METHODS AND RESULTS

In this study, we enrolled 60 patients with left ventricular systolic failure (New York Heart Association [NYHA] class III-IV) and a left ventricular ejection fraction (EF) < 40% as determined by echocardiography and 30 healthy subjects. The patients with systolic heart failure were divided into two groups: patients with IDCM and patients with NDCM. Blood samples were obtained to measure the serum PON1 activity and the serum pro-BNP levels. The median serum PON1 activities were lower among the patients with IDCM or with NDCM compared with the control subjects (p < .001, p = .043, respectively). Compared with the control subjects, the patients with IDCM or with NDCM had higher serum pro-BNP levels (p < .001, p < .001, respectively). The serum PON1 activity was negatively correlated with the serum pro-BNP levels in patients with IDCM (r = -0.548, p < .001). The area under the ROC curve of the serum PON1 activity was 0.798. Using a serum PON1 activity of 201.3 U/L as a cut-off value, the sensitivity was 86.84% and specificity was 66.67% for the diagnosis of IDCM.

CONCLUSIONS

In this study, the serum PON1 activity was significantly reduced in the patients with IDCM or with NDCM compared with the control subjects. The serum PON1 activity of the patients with IDCM was negatively correlated with the serum pro-BNP levels.

Bilirubin and atherosclerotic diseases

Bilirubin is the final product of heme catabolism in the systemic circulation. For decades, increased serum/plasma bilirubin levels were considered an ominous sign of an underlying liver disease. However, data from recent years convincingly suggest that mildly elevated bilirubin concentrations are associated with protection against various oxidative stress-mediated diseases, atherosclerotic conditions being the most clinically relevant. Although scarce data on beneficial effects of bilirubin had been published also in the past, it took until 1994 when the first clinical study demonstrated an increased risk of coronary heart disease in subjects with low serum bilirubin levels, and bilirubin was found to be a risk factor for atherosclerotic diseases independent of standard risk factors. Consistent with these results, we proved in our own studies, that subjects with mild elevation of serum levels of unconjugated bilirubin (benign hyperbilirubinemia, Gilbert syndrome) have much lower prevalence/incidence of coronary heart as well as peripheral vascular disease. We have also demonstrated that this association is even more general, with serum bilirubin being a biomarker of numerous other diseases, often associated with increased risk of atherosclerosis. In addition, very recent data have demonstrated biological pathways modulated by bilirubin, which are responsible for observed strong clinical associations.

Urinary Biopyrrins: A New Marker of Oxidative Stress in Psoriasis

Background:

Psoriasis is a common chronic, relapsing, immune-mediated disease involving skin and joints of genetically predisposed individuals. Oxidative stress has been found to play many important roles in cellular damage and loss of function in a number of tissues and organs and is believed to contribute to the pathogenesis of a variety of diseases. Urinary biopyrrin levels have gained attention as an indicator of oxidative stress.

Aim and Objective:

To measure urinary biopyrrins excretion as a marker of oxidative stress in psoriasis.

Patients and Methods:

This case–control study was carried out on 85 subjects; 55 cases with chronic plaque psoriasis and 30 age, gender and body mass index-matched normal subjects as a control group. Urinary biopyrrin levels were measured using enzyme immunoassay.

Results:

There was a highly significant difference between cases and controls regarding urinary biopyrrins level (P < 0.001). There was significant positive correlation between biopyrrins level and both the age of cases (r = 0.28, P = 0.01) and psoriasis area and severity index score (r = 0.99, P < 0.001).

Conclusion:

Urinary biopyrrins are increased in patients with psoriasis, and the level is correlated with disease severity. Further large-scale studies involving different ages and different clinical varieties of the disease are needed to expand and validate current findings. The clinical usefulness of antioxidants in psoriasis treatment needs to be evaluated in future research. Furthermore, the value of biopyrrins as biomarkers for monitoring response to therapy needs to be evaluated.

Current perspectives on hydralazine and nitrate therapies in heart failure

The origins of the hydralazine/isosorbide dinitrate (H+ISDN) combination therapy are rooted in the first large-scale clinical trial in heart failure: V-HeFT I. Initially utilized for the balanced vasodilatory properties of each drug, we now know there is "more to the story." In fact, the maintenance of the nitroso-redox balance may be the true mechanism of benefit. Since the publication of V-HeFT I 30 years ago, H+ISDN has been the subject of much discussion and debate. Regardless of the many controversies surrounding H+ISDN, one thing is clear: therapy is underutilized and many patients who could benefit never receive the drugs. Ongoing physician and patient education are mandatory to improve the rates of H+ISDN use.

The breathing heart - mitochondrial respiratory chain dysfunction in cardiac disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. Apart from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the ageing heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practising clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

Coronary microvascular dysfunction and diastolic load correlate with cardiac troponin T release measured by a highly sensitive assay in patients with nonischemic heart failure

OBJECTIVES

This study investigated factors associated with cardiac troponin T (cTnT) release from failing myocardium.

BACKGROUND

Persistent and modest elevation of serum cTnT is frequently observed in heart failure (HF) patients free of coronary artery disease, although the mechanisms underlying this finding remain unclear.

METHODS

We evaluated serum cTnT levels in the aortic root (Ao) and coronary sinus (CS) using a highly sensitive assay in 90 nonischemic HF patients and 47 non-HF patients. Transcardiac cTnT and plasma B-type natriuretic peptide (BNP) release were described as the differences between CS and Ao cTnT levels [ΔcTnT (CS-Ao)] and BNP levels [ΔBNP (CS-Ao)], respectively. Coronary flow reserve (CFR) was measured in 68 HF patients using an intracoronary Doppler guidewire.

RESULTS

ΔcTnT (CS-Ao) levels were available in 76 HF patients and 28 non-HF patients (84% vs. 60%; p = 0.001), and higher in HF patients than non-HF patients (p < 0.001). Among HF patients, log[ΔcTnT (CS-Ao)] correlated with log[ΔBNP (CS-Ao)] (r = 0.368, p = 0.001), pulmonary capillary wedge pressure (r = 0.253, p = 0.03) and left ventricular end-diastolic pressure (LVEDP) (r = 0.321, p = 0.005). Multivariate regression analysis identified LVEDP as an independent parameter that correlated with ΔcTnT (CS-Ao). ΔcTnT (CS-Ao) levels were available in 58 HF patients who were evaluated for CFR. Coronary microvascular dysfunction, diagnosed by CFR <2.0, was observed in 18 HF patients. ΔcTnT (CS-Ao) was higher in patients with coronary microvascular dysfunction (4.8 [2.0 to 8.1] ng/l) than those without (2.0 [1.2 to 4.6] ng/l; p = 0.04).

CONCLUSIONS

cTnT release from failing myocardium correlated with diastolic load and coronary microvascular dysfunction in nonischemic HF patients.

Reactive oxygen species in cardiovascular disease

Based on the "free radical theory" of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that reactive oxygen species and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding of reactive oxygen species has evolved to the point at which we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review addresses our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology.

Increased serum levels of oxidative stress are associated with hospital readmissions due to acute heart failure

OBJECTIVES

Inflammation and serum oxidative stress (OS) are important components in heart failure (HF) deterioration. In this study we tested the hypothesis that an increase in patients' sera OS levels is associated with acute HF (AHF) readmissions.

METHODS

Thirty consecutive patients (mean age 71 ± 10 years) admitted with AHF were included in the study. Serum OS in these patients was measured in-hospital and repeatedly after discharge over a period of 8 weeks of follow-up in which we reordered patients' HF readmissions. Of the 30 patients, 13 (43%) were readmitted (RAD group) and 17 (57%) did not require readmission (NRAD group).

RESULTS

OS levels before discharge from the first hospital admission in the 2 groups were similar (p = 0.84 and p = 0.56, respectively). However, using repeated measures ANOVA, we found that the interaction between the time points and the 2 groups of patients (RAD and NRAD) was statistically significant (p = 0.037). It is important to note that OS serum levels were more predictive of HF readmissions than were repeated simultaneous serum measurements of NT-proBNP (p = 0.97).

CONCLUSIONS

Increased OS levels in AHF patients, after they have been discharged from the hospital, are associated with higher HF readmission rates. In AHF, OS is a dynamic parameter associated with HF deterioration.

Diminished antioxidant activity of high-density lipoprotein-associated proteins in systolic heart failure

BACKGROUND

Diminished serum arylesterase activity, catalyzed by the high-density lipoprotein-associated paraoxonase-1, is associated with heightened systemic oxidative stress and atherosclerosis risk. In the present study, we sought to determine the prognostic role of serum arylesterase activity in subjects with systolic heart failure, particularly in relation to established cardiac biomarkers.

METHODS AND RESULTS

We measured serum arylesterase activity in 760 subjects with impaired left ventricular systolic function (left ventricular ejection fraction <50%), and prospectively followed major adverse cardiac events (including death, nonfatal myocardial infarction, and stroke) for 3 years. In our study cohort (mean age, 64±11 years; 74% men; median left ventricular ejection fraction, 35%; median creatinine clearance, 96 mg/dL), mean serum arylesterase activity (98±25 μmol/L/min/mL) was lower compared with that in healthy control subjects (mean, 115±26 μmol/L/min/mL, P<0.01) but higher compared with advanced decompensated heart failure subjects (mean, 69±22 μmol/L/min/mL, P<0.01). Within our cohort, there was modest correlation between serum arylesterase activity and high-density lipoprotein cholesterol (r=0.33, P<0.01) as well as B-type natriuretic peptide (r=-0.23, P<0.01). Lower serum arylesterase activity was a strong predictor of poorer outcomes (hazard ratio, 2.94; 95% confidence interval, 1.54, 5.62; P<0.001). After adjusting for traditional risk factors, medication use, B-type natriuretic peptide, and creatinine clearance, lower serum arylesterase still conferred an increased risk of major adverse cardiac events at 3 years (hazard ratio, 2.69; 95% confidence interval, 1.37 to 5.28; P=0.004).

CONCLUSIONS

In patients with systolic heart failure, decreased serum arylesterase activity, a measure of diminished antioxidant properties of high-density lipoprotein, predicts higher risk of incident long-term adverse cardiac event independent of established clinical and biochemical risk factors.

Oxidative stress associated with rapid weight reduction decreases circulating adiponectin concentrations

The effect of stress associated with acute weight reduction on adipocytokine production is incompletely understood. In the present study, we have investigated the changes in circulating adipocytokine concentrations and urinary concentrations of stress markers in male collegiate wrestlers during acute weight reduction for a competition. Twenty healthy Japanese male wrestlers (18-22 years of age) who participated in the national collegiate wrestling tournament were studied. Body weight, body fat amount, serum testosterone, serum leptin, serum adiponectin, urinary 8-hydroxy-2'- deoxyguanosine (8-OHdG) and urinary biopyrrins were analyzed during acute weight reduction for the competition. Body weight, body fat amount and the serum concentrations of testosterone, leptin and adiponectin significantly decreased on the day of weigh-in compared with the levels 12 days before weigh-in. In contrast, urinary concentrations of 8-OHdG and biopyrrins significantly increased on the day of weigh-in compared with the concentrations 12 days before weigh-in. A positive correlation was observed between the serum concentrations of adiponectin and testosterone, and a negative correlation was observed between the concentrations of serum adiponectin and urinary biopyrrins. The present results suggest that rapid weight reduction increases the urinary concentrations of stress markers, which is associated with a decrease in serum concentrations of adiponectin.

Biomarkers of oxidative stress in heart failure

Oxidative stress is the relative excess of reactive oxygen species (ROS) versus endogenous defense mechanisms. Abundant evidence has demonstrated the role of ROS, along with reactive nitrogen species (RNS), in the pathophysiology of cardiovascular disease, including heart failure. Many biomarkers of oxidative stress have been studied as surrogates of oxidative damage. Recently, markers of impaired nitric oxide signaling have also been identified. Many biomarkers have been associated with prognosis and mortality, and some may even be modified by therapy. However, the clinical utility is limited by less than optimal standardization techniques and the lack of sufficient large-sized, multimarker prospective trials.

Serum oxidative stress level correlates with clinical parameters in chronic systolic heart failure patients

BACKGROUND

Serum oxidative stress (OS) level has an important role in the inflammatory process of heart failure.

HYPOTHESIS

The study was designed to analyze serum OS levels in chronic heart failure (HF) patients and to examine the relation between OS levels and other clinical and prognostic parameters of HF.

METHODS

We studied 82 consecutive chronic symptomatic HF patients with systolic LV dysfunction (ejection fraction <45%). The serum OS level was determined using thermochemiluminescence assay. We compared the serum OS levels with patients' clinical and prognostic parameters.

RESULTS

Higher serum OS levels were associated with higher New York Heart Association class (P = .01), worse renal function (serum urea, creatinine, and creatinine clearance) (P<.001) and higher serum levels of hs-C-reactive protein and N-terminal pro brain natriuretic peptide (P = .001, P<.001, respectively).

CONCLUSIONS

In chronic systolic HF patients, high serum OS levels correlate with advanced disease and known markers of poor prognosis.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Inhibitors of the heme oxygenase - carbon monoxide system: on the doorstep of the clinic?

The past decade has seen substantial developments in our understanding of the physiology, pathology, and pharmacology of heme oxygenases (HO), to the point that investigators in the field are beginning to contemplate therapies based on administration of HO agonists or HO inhibitors. A significant amount of our current knowledge is based on the judicious application of metalloporphyrin inhibitors of HO, despite their limitations of selectivity. Recently, imidazole-based compounds have been identified as potent and more selective HO inhibitors. This 'next generation' of HO inhibitors offers a number of desirable characteristics, including isozyme selectivity, negligible effects on HO protein expression, and physicochemical properties favourable for in vivo distribution. Some of the applications of HO inhibitors that have been suggested are treatment of hyperbilirubinemia, neurodegenerative disorders, certain types of cancer, and bacterial and fungal infections. In this review, we address various approaches to altering HO activity with a focus on the potential applications of second-generation inhibitors of HO.

Biphasic elevation of bilirubin oxidation during myocardial ischemia reperfusion

BACKGROUND

The time course of oxidative stress involving nitric oxide (NO) after myocardial ischemia reperfusion (MIR) has not been elucidated in detail, so the present study was designed to assess the dynamics of oxidative stress after MIR, urinary excretion of oxidized bilirubin metabolites (ie, biopyrrins) and their generation in various organs.

METHODS AND RESULTS

Rat models of MIR were created by occluding the left coronary artery for 30 min followed by 48 h of reperfusion. Levels of urinary biopyrrins increased biphasically at 8 h and 24 h after MIR. Biopyrrins were upregulated in the lungs at 8 h after MIR, according to immunohistochemistry and ELISA, and at 24 h biopyrrin expression was increased in the heart and lungs. The NO synthase inhibitor, NG-monomethyl-L-arginine, significantly diminished biopyrrin synthesis in the heart and lungs at 24 h, but not in the lungs at 8 h after MIR. Hemodynamic assessment revealed increased left ventricle end-diastolic pressure, suggesting that lung congestion influences pulmonary biopyrrin formation.

CONCLUSIONS

The dynamics of urinary biopyrrins might reflect earlier biopyrrin generation in the lungs and delayed formation in both the lungs and heart when NO is involved. Therefore, urinary biopyrrins can serve as a useful marker of systemic oxidative stress after MIR.

Bilirubin oxidation provoked by nitric oxide radicals predicts the progression of acute cardiac allograft rejection

Bilirubin, a strong intrinsic antioxidant, quenches free radicals produced under inflammatory conditions. The oxidized bilirubin metabolites, i.e. biopyrrins, are immediately excreted into urine and can indicate the intensity of oxidation in vivo. Our preliminary studies suggested the involvement of reactive nitrogen species (RNS) in generation of biopyrrins. However, little is known about biological significance of bilirubin oxidation by RNS. Here, we analyzed the correlation between bilirubin oxidation and nitric oxide (NO) radicals during rat acute cardiac allograft rejection. In allograft recipients, urinary biopyrrins steeply increased on day 3 prior to the increase in myocardial tissue damage marker, serum troponin-T. In contrast, no significant changes in urinary biopyrrins were evident in recipients of isografts or cyclosporine-A treated allografts. Urinary nitrotyrosine, a marker of oxidation by NO radicals also increased on day 3, while administration of a NO synthase inhibitor, N(G)-monomethyl-L-arginine apparently diminished the elevation of urinary biopyrrins as well as nitrotyrosine. Immunohistochemistry revealed enhanced local expression of heme oxygenase-1, biopyrrins and nitrotyrosine in allografts in accordance with the cellular infiltrates, suggesting that changes in urinary biopyrrins reflect the bilirubin oxidation in grafts undergoing rejection. These results indicate that locally evoked bilirubin oxidation by NO radicals can predict the progression of rejection.

Urinary excretion of oxidative metabolites of bilirubin in subjects with Gilbert syndrome

BACKGROUND AND AIM

Bilirubin is a potent endogenous antioxidant substance. Recent data suggest a direct relationship exists between urinary excretion of biopyrrins, a novel group of bilirubin oxidative metabolites, and severity of oxidative stress. The aim of this study was to evaluate urinary excretion of biopyrrins in subjects with Gilbert syndrome.

METHODS

The study included patients with Gilbert syndrome (n = 33) and healthy blood donors (n = 25). In all subjects complete biochemical tests were conducted along with analysis of urinary excretion of biopyrrins. Linear and logistic regression analyses were used for multiple adjustments of possible confounders/modifiers.

RESULTS

As expected, high serum bilirubin levels were found in the Gilbert syndrome group as compared to controls (27.8 +/- 9.7 vs 9.9 +/- 3.0 micromol/L, P < 0.001). In contrast, urinary levels of biopyrrins were substantially lower in the Gilbert syndrome group as compared to normobilirubinemic control subjects (19.9 +/- 26.0 vs 90.2 +/- 139.1 U/g urinary creatinine, P < 0.001). The Gilbert syndrome group also had very low prevalence odds ratios for urinary biopyrrins above the median of the control values even after adjustment for possibly confounding factors (odds ratio 0.18, 95% confidence interval 0.33-0.94; P = 0.042).

CONCLUSIONS

An inverse relationship was demonstrated between serum bilirubin level and urinary excretion of biopyrrins, which is presumably due to antioxidative effects of elevated serum bilirubin levels in Gilbert syndrome.

Diurnal variation of biopyrrin excretion in random urine specimens is not corrected by creatinine

Circulating bilirubin is thought to function as a physiological antioxidant. One of the decomposition products of this process is the biopyrrins, which include two regioisomers: biotripyrrin-a (1,14,15,17-tetrahydro-2,7,13-trimethyl-1,14-deoxy-3-vinyl-16H-tripyrrin-8,12-dipropionic acid) and biotripyrrin-b (1,14,15,17-tetrahydro-3,7,13-trimethyl-1,14-deoxy-3-vinyl-16H-tripyrrin-8,12-dipropionic acid). We measured biopyrrins in random urine specimens and investigated whether the biopyrrin values obtained were valid when expressed as a ratio of the creatinine (Cr) concentrations. All of the random urine specimens collected over 48 hr were from presumably healthy adults. We measured the biopyrrins by means of an enzyme-linked immunosorbent assay (ELISA) using an anti-bilirubin monoclonal antibody. When the values were expressed in terms of the ratio to Cr, the within-day coefficient of variation (%CV) of the excretion of biopyrrins was reduced to 27%+/-10% (P<0.05) from 59%+/-27%. However, assay values on random or spot urine specimens were unreliable because of the large %CV. The biopyrrin concentrations only in the first-morning-urine specimens in terms of both absolute amounts and ratios to Cr significantly reflected those in a 24-hr urine specimen (P<0.001). Concentrations in a random urine specimen voided at the second collection or later did not correlate with the concentration in a 24-hr urine specimen (P>0.05), even if their values were corrected by Cr. The amounts of biopyrrins excreted in 24-hr urine specimens were significantly correlated with the 24-hr cortisol excretion (P<0.001) but not to uropepsin (P>0.05).

Diagnostic accuracy of serum B-type natriuretic peptide for myocardial ischemia detection during exercise testing with Spect perfusion imaging

OBJECTIVE

To determine whether serum B-type natriuretic peptide measured at rest and peak exercise and DeltaBNP contribute to the predictive value and diagnostic accuracy of exercise test in the diagnosis of myocardial ischemia.

BACKGROUND

Ventricular myocytes release BNP in response to increased wall stress that occurs in acute ischemia. During exercise testing, transient myocardial ischemia could also cause acute myocardial stress and changes in circulating BNP.

METHODS

BNP was measured before and immediately after exercise testing with radionuclide imaging in 203 consecutive subjects referred for chest pain evaluation. Tested subjects were classified as ischemic and non-ischemic based on exercise results, and no ischemia, mild-moderate, and severe ischemia according to perfusion scan results. A logistic regression model, constructed of an ROC and an AUC (area under the curve), was used.

RESULTS

Ischemic ECG changes (> or =1 mm, horizontal S-T shift) were detected in the treadmill exercise test in 127 subjects (62.6%), and 76 (37.4%) had neither ST segment shift nor chest pain. Baseline BNP was higher in the ischemic group compared to the non-ischemic group (p=0.044); peak BNP was also higher in the ischemic group (p=0.025), as was DeltaBNP (p=0.0126). Of these 127 subjects, 106 (52% of all) had abnormal perfusion scan results. In the ischemic group, the median baseline, peak exercise BNP, and DeltaBNP values from baseline to peak were higher than in the non-ischemic group. In the severe ischemic group these variables were approximately three-fold higher than in the mild-moderate ischemic group (p<0.0001 for baseline; p<0.0001 for peak; and p<0.0001 for DeltaBNP). Rest, peak exercise, and DeltaBNP values were significantly higher in patients with previous myocardial infarction (p<0.001) and in patients treated with beta blockers; peak exercise BNP was higher in hypertensives and diabetics (p<0.05). The ROC convergence model showed that the AUC for peak-exercise BNP was best able to discriminate and predict severe ischemia and no ischemia, while DeltaBNP from rest to peak exercise discriminated best between mild-moderate and severe ischemia.

CONCLUSIONS

Peak exercise BNP and DeltaBNP improved the sensitivity, specificity, positive likelihood ratio, predictive value, and diagnostic accuracy of severe ischemia detection during an exercise test. The contribution of BNP determination during exercise was, however, less impressive than previously reported by others.

The Heme Catabolic Pathway and its Protective Effects on Oxidative Stress‐Mediated Diseases

Bilirubin, the principal bile pigment, is the end product of heme catabolism. For many years, bilirubin was thought to have no physiological function other than that of a waste product of heme catabolism--useless at best and toxic at worst. Although hyperbilirubinemia in neonates has been shown to be neurotoxic, studies performed during the past decade have found that bilirubin has a number of new and interesting biochemical and biological properties. In addition, there is now a strong body of evidence suggesting that bilirubin may have a beneficial role in preventing oxidative changes in a number of diseases including atherosclerosis and cancer, as well as a number of inflammatory, autoimmune, and degenerative diseases. The results also suggest that activation of the heme oxygenase and heme catabolic pathway may have beneficiary effects on disease prevention either through the action of bilirubin or in conjunction with bilirubin. If so, it may be possible to therapeutically induce heme oxygenase, increase bilirubin concentrations, and lower the risk of oxidative stress-related diseases.

Novel and potential future biomarkers for assessment of the severity and prognosis of chronic heart failure

Over the last two decades, the pathophysiology and biomolecular basis of heart failure syndrome has reached sound and more comprehensive understanding. This knowledge has allowed expert researchers and clinicians to explore an entirely new spectrum of potential biochemical markers derived from different cellular and signaling pathways that lead to myocardial hypertrophy, chronic damage of the myocyte, apoptosis, and, ultimately, myocardial remodeling. Indeed, the link between myocardial remodeling and adverse outcomes, as well as the recognition of the myocardial interstitium as a multifunctional dynamic entity strongly influenced by systemic neurohormonal and inflammatory activation, has provided a solid ground for research of biomarkers that might correlate with severity and prognostication in chronic heart failure. This paper reviews and summarize recent literature on some of the most interesting circulating biomarkers with potential use for the stratification of patients with chronic heart failure.

Bilirubin and the risk of common non-hepatic diseases

Bilirubin is a potent antioxidant but can be toxic at high concentrations. This article critically reviews the reported relationships of plasma bilirubin levels to the severity and/or incidence of various common non-hepatic diseases. Plasma bilirubin levels are reportedly negatively related to the risk of atherosclerotic diseases, cancers, demyelinating neuropathies and seasonal affective disorder. By contrast, the incidence and severity of schizophrenia are increased by elevated bilirubin levels. The data strongly suggest that the level of plasma bilirubin should be considered as a risk factor for several common non-hepatic diseases. Additional studies are needed to clarify the mechanisms of this influence, which are thought to be related to unconjugated bilirubin counteracting the oxidative stress underlying these disorders.