Bilirubin is an Endogenous Antioxidant in Human Vascular Endothelial Cells

Bilirubin: Photophysical and photochemical properties, phototherapy, analytical methods of measurement. A short review

Bilirubin, a yellow bile pigment, plays an important role in the body, being a potent antioxidant and having anti-inflammatory, immunomodulatory, cytoprotective, and neuroprotective functions. This makes bilirubin promising as a therapeutic and diagnostic agent in biomedicine. However, excess bilirubin is toxic and should be removed from the body. Bilirubin exhibits photochemical activity, which has been the subject of numerous studies up to now. Such studies are relevant because the bilirubin photochemistry provides the basis for bilirubin removing in phototherapy of neonatal jaundice (neonatal hyperbilirubinemia) and for some therapeutic applications. Furthermore, it can model several elementary processes of molecular photonics. In particular, the bilirubin molecule is capable of ultrafast Z-E photoisomerization and contains two almost identical dipyrromethenone chromophores capable of exciton coupling. The present review considers the data on the photophysical and photochemical properties of bilirubin and ultrafast routes of its phototransformations, as well as its photochemical reactions in phototherapy of neonatal hyperbilirubinemia and the ways to decrease the possible adverse effects of the phototherapy. The main analytical methods of bilirubin measurement in biological systems are also viewed.

The Multifaceted Role of Bilirubin in Liver Disease: A Literature Review

Bilirubin, the primary breakdown product of hemoproteins, particularly hemoglobin, plays a key role in the diagnosis, prognosis, and monitoring of liver diseases. In acute liver diseases, such as acute liver failure, drug-induced liver injury, and viral hepatitis, bilirubin serves as a biomarker reflecting the extent of hepatocyte loss and liver damage. Chronic liver diseases, including alcohol-related liver disease, chronic hepatitis C virus infection, metabolic dysfunction-associated fatty liver disease, and autoimmune liver diseases, are marked by persistent liver injury and inflammation. Bilirubin levels in chronic liver diseases provide insight into liver function, disease severity, and prognosis. As a versatile biomarker, bilirubin offers valuable information on the pathophysiology of liver diseases and aids in guiding clinical decision-making regarding the treatment of liver diseases and their complications. This review aimed to explore the multifunctional role of bilirubin in liver diseases by analyzing its biological functions beyond its role as a biomarker of liver damage.

cRGD-Conjugated Bilirubin Nanoparticles Alleviate Dry Eye Disease Via Activating the PINK1-Mediated Mitophagy

Purpose

The purpose of this study was to evaluate the cytoprotective effect and the mechanism of cRGD-conjugated bilirubin nanoparticles (cNPs@BR) in dry eye disease (DED).

Methods

The binding capacity and cellular uptake of cNPs@BR in human corneal epithelial cells (HCECs) were assessed by immunofluorescence. The anti-inflammation and anti-oxidative stress effects of cNPs@BR were determined by flow cytometry, immunofluorescence, Western blot, chromatin immunoprecipitation (ChIP), and ELISA assay in LPS-stimulated RAW264.7 cells and hypertonic HCECs. The function of ocular surface barrier, tear production, and the number of goblet cells after cNPs@BR treatment were further assessed by fluorescein sodium staining, phenol red cotton threads, quantitative PCR (qPCR), hematoxylin and eosin (H&E) staining, and Periodic Acid-Schiff (PAS) staining in a 0.2% BAC-induced DED mouse model. Furthermore, the mechanism of cNPs@BR in treating DED was explored by RNA sequencing and RNA interference.

Results

The cRGD peptide prolonged the retention time of nanoparticles on HCECs and enhanced the cellular uptake efficiency. In both cell models, 20 µM cNPs@BR pretreatment ameliorated oxidative stress by decreasing the intracellular reactive oxygen species (ROS) levels and the expression of NOX4 and 4-HNE, while promoting HO-1 and nuclear Nrf2 levels. Moreover, cNPs@BR alleviated the inflammatory response by inhibiting NF-κB p65 nuclear translocation and decreasing the expression of iNOS and the secretion of IL-1β, IL-6, and TNF-α. In addition, cNPs@BR protected ocular surface epithelium against oxidative stress and inflammation and restored conjunctival goblet cells in the mouse model of DED by activating PINK1-mediated mitophagy.

Conclusions

The cNPs@BR suppressed oxidative stress and inflammatory response in the ocular surface epithelium and restored goblet cells by activating PINK1-mediated mitophagy.

Oxidative stress: fundamentals and advances in quantification techniques

Oxidative species, generated endogenously via metabolism or from exogenous sources, play crucial roles in the body. At low levels, these species support immune functions by participating in phagocytosis. They also aid in cellular signaling and contribute to vasomodulation. However, when the levels of oxidative species exceed the body's antioxidant capacity to neutralize them, oxidative stress occurs. This stress can damage cellular macromolecules such as lipids, DNA, RNA, and proteins, driving the pathogenesis of diseases and aging through the progressive deterioration of physiological functions and cellular structures. Therefore, the body's ability to manage oxidative stress and maintain it at optimal levels is essential for overall health. Understanding the fundamentals of oxidative stress, along with its reliable quantification, can enable consistency and comparability in clinical practice across various diseases. While direct quantification of oxidant species in the body would be ideal for assessing oxidative stress, it is not feasible due to their high reactivity, short half-life, and the challenges of quantification using conventional techniques. Alternatively, quantifying lipid peroxidation, damage products of nucleic acids and proteins, as well as endogenous and exogenous antioxidants, serves as appropriate markers for indicating the degree of oxidative stress in the body. Along with the conventional oxidative stress markers, this review also discusses the role of novel markers, focusing on their biological samples and detection techniques. Effective quantification of oxidative stress may enhance the understanding of this phenomenon, aiding in the maintenance of cellular integrity, prevention of age-associated diseases, and promotion of longevity.

Association between serum total bilirubin with Parkinson's disease among American adults (NHANES 1999 to 2018)

Background

Currently, the existing evidence on the correlation between serum total bilirubin (STB) and Parkinson's disease (PD) is insufficient. The objective of this study was to clarify the relationship between STB levels and PD within the US (United States) population.

Methods

A cross-sectional analysis was conducted using data from 25,637 participants in the National Health and Nutrition Examination Survey (NHANES) 1999-2018. Weighted logistic regression, smooth curve fitting, subgroup analysis, and sensitivity analyses were employed to validate the research objectives.

Results

Among all eligible subjects, the mean age was 57.11 ± 11.78 years. The prevalence of PD was 1.18 % overall, with 47.86 % in males. After adjusting for multiple variables, the odds ratio [OR] (95 % confidence interval [CI]) for PD associated with STB levels in T2 and T3 were 0.59 (95 % CI = 0.40-0.85, p = 0.006) and 0.67 (95 % CI = 0.45-0.99, p = 0.045), respectively, when compared to STB levels in T1. The analysis using restricted cubic splines (RCS) indicated an L-shaped relationship between STB levels and the prevalence of PD (p for nonlinearity = 0.004), with the lowest risk observed at 10.84 μmol/L. Comparable patterns of association were noted in subgroup analyses. Furthermore, consistent findings were derived from additional sensitivity analyses.

Conclusions

Our study findings indicated that the level of STB is significantly negatively correlated with the prevalence of PD. Therefore, more prospective studies need to be designed to prove the causal relationship between them.

Association of total bilirubin and prognosis in disorders of consciousness

Accurate prediction of the recovery of Disorders of Consciousness (DoC) is of paramount significance for clinicians and families. Serum total bilirubin (TBIL) formed by activation of heme oxygenase 2, is associated with incidence and prognosis of cardiovascular and cerebrovascular diseases. However, studies that based TBIL and DoC are limited. The study attempted to examine the association between serum TBIL levels and prognosis in patients with DoC. One hundred and sixty-eight patients with DoC in the Second hospital of Shandong University from June 2021 to June 2023 were recruited. The clinical characteristics and venous blood samples were collected within 24 h after admission. The diagnosis of DoC was determined by two skilled investigators employing various behavioral evaluations along the coma recovery scale-revised (CRS-R) and the investigators conducted follow-up assessments of diagnosis at 1, 3, and 6 months after admission. For statistical analysis, we categorized patients with an improvement in clinical diagnosis from study entry as having a "good outcome". In total, 139 individuals enrolled in the study. The median TBIL level was 8.2 μmol/L. Good recovery of DoC at 1, 3, and 6 months occurred in 25 (18.0%), 41 (29.5%), and 56 (40.3%) patients, respectively. After full adjustment, a significant association was found between TBIL levels and the prognosis of DoC at 1, 3, and 6 months. When TBIL levels were analyzed as categorical variables, an increasing trend in the tertiles of TBIL levels demonstrated a significant positive association with the recovery of DoC at 1, 3, and 6 months. Stratified analysis revealed that the association between serum TBIL levels and the recovery of DoC remained consistent across different sub-populations. A high serum TBIL level is associated with an improved likelihood of recovery of DoC. Additional research is required to elucidate the underlying pathophysiological causal association between TBIL levels and DoC.

Bile Acids and Bilirubin Role in Oxidative Stress and Inflammation in Cardiovascular Diseases

Bile acids (BAs) and bilirubin, primarily known for their role in lipid metabolism and as heme catabolite, respectively, have been found to have diverse effects on various physiological processes, including oxidative stress and inflammation. Indeed, accumulating evidence showed that the interplay between BAs and bilirubin in these processes involves intricate regulatory mechanisms mediated by specific receptors and signaling pathways under certain conditions and in specific contexts. Oxidative stress plays a significant role in the development and progression of cardiovascular diseases (CVDs) due to its role in inflammation, endothelial dysfunction, hypertension, and other risk factors. In the cardiovascular (CV) system, recent studies have suggested that BAs and bilirubin have some opposite effects related to oxidative and inflammatory mechanisms, but this area of research is still under investigation. This review aims to introduce BAs and bilirubin from a biochemical and physiological point of view, emphasizing their potential protective or detrimental effects on CVDs. Moreover, clinical studies that have assessed the association between BAs/bilirubin and CVD were examined in depth to better interpret the possible link between them.

Bilirubin Exerts Protective Effects on Alveolar Type II Pneumocytes in an In Vitro Model of Oxidative Stress

Newborn infants face a rapid surge of oxygen and a more protracted rise of unconjugated bilirubin after birth. Bilirubin has a strong antioxidant capacity by scavenging free radicals, but it also exerts direct toxicity. This study investigates whether cultured rat alveolar epithelial cells type II (AEC II) react differently to bilirubin under different oxygen concentrations. The toxic threshold concentration of bilirubin was narrowed down by means of a cell viability test. Subsequent analyses of bilirubin effects under 5% oxygen and 80% oxygen compared to 21% oxygen, as well as pretreatment with bilirubin after 4 h and 24 h of incubation, were performed to determine the induction of apoptosis and the gene expression of associated transcripts of cell death, proliferation, and redox-sensitive transcription factors. Oxidative stress led to an increased rate of cell death and induced transcripts of redox-sensitive signaling pathways. At a non-cytotoxic concentration of 400 nm, bilirubin attenuated oxidative stress-induced responses and possibly mediated cellular antioxidant defense by influencing Nrf2/Hif1α- and NFκB-mediated signaling pathways. In conclusion, the study demonstrates that rat AEC II cells are protected from oxidative stress-induced impairment by low-dose bilirubin.

Bioproduction of porphyrins, phycobilins, and their proteins using microbial cell factories: engineering, metabolic regulations, challenges, and perspectives

Porphyrins, phycobilins, and their proteins have abundant π-electrons and strongly absorb visible light, some of which bind a metal ion in the center. Because of the structural and optical properties, they not only play critical roles as an essential component in natural systems but also have attracted much attention as a high value specialty chemical in various fields, including renewable energy, cosmetics, medicines, and foods. However, their commercial application seems to be still limited because the market price of porphyrins and phycobilins is generally expensive to apply them easily. Furthermore, their petroleum-based chemical synthesis is energy-intensive and emits a pollutant. Recently, to replace petroleum-based production, many studies on the bioproduction of metalloporphyrins, including Zn-porphyrin, Co-porphyrin, and heme, porphyrin derivatives including chlorophyll, biliverdin, and phycobilins, and their proteins including hemoproteins, phycobiliproteins, and phytochromes from renewable carbon sources using microbial cell factories have been reported. This review outlines recent advances in the bioproduction of porphyrins, phycobilins, and their proteins using microbial cell factories developed by various microbial biotechnology techniques, provides well-organized information on metabolic regulations of the porphyrin metabolism, and then critically discusses challenges and future perspectives. Through these, it is expected to be able to achieve possible solutions and insights and to develop an outstanding platform to be applied to the industry in future research.

Antioxidant Activity of Bilirubin in Micellar and Liposomal Systems Is pH-Dependent

Bilirubin (BR), a product of heme catabolism, plays a critical role in biological systems. Although increased levels of BR result in hyperbilirubinemia or jaundice, there is increasing evidence that lower concentrations substantially decrease the risk of oxidative stress-mediated diseases due to antioxidant functions of BR. We studied the radical-trapping ability of BR in two model systems, micellar and liposomal, at a broad pH range. At pH < 6.0, BR behaves as a retardant; however, at pH ≥ 6.0, BR becomes strong radical trapping antioxidant, with rate constants for reaction with lipidperoxyl radicals (kinh) within the range from 1.2 × 104 M-1 s-1 to 3.5 × 104 M-1 s-1, and in liposomal system, the activity of BR is comparable to α-tocopherol. This transition is likely facilitated by the ionization of carboxyl groups, leading to a conformational shift in BR and improved solubility/localization at the water/lipid interface. This is the first experimental evidence of the role of pH on the antioxidant activity of bilirubin, and the observed pH-dependent radical-trapping ability of BR holds practical significance, particularly in jaundice treatment where light therapy targets the skin's weakly acidic surface. Minor adjustments toward neutral or alkaline pH can enhance radical-trapping action of BR, thereby mitigating oxidative stress induced with blue or violet light exposure.

Sex differences in the relationship between serum total bilirubin and risk of incident metabolic syndrome in community-dwelling adults: Propensity score analysis using longitudinal cohort data over 16 years

BACKGROUND

Research on identifiable risks for metabolic syndrome (MetS) is ongoing, and growing evidence suggests that bilirubin is a potent antioxidant and cytoprotective agent against MetS. However, there have been conflicting results on the association between bilirubin and MetS. Our study aimed to validate the association by separately stratifying data for men and women in a longitudinal prospective study.

METHODS

Data were derived from the Korean Genome Epidemiology Study provided by the Korea Centers for Disease Control and Prevention. Data from 5,185 adults aged 40-69 years (3,089 men and 2,096 women) without MetS were analyzed. The participants were divided according to sex-specific quartiles of serum total bilirubin levels and followed up biennially for 16 years (until 2018). The log-rank test was used for obtaining the Kaplan-Meier curves of cumulative incidence of MetS according to sex-specific serum total bilirubin quartiles, and the hazard ratios (HRs) with 95% confidence intervals (CIs) for incident metabolic syndrome were analyzed with a multiple Cox proportional hazard regression analysis model, after propensity score matching for removing differences at baseline.

RESULTS

With increasing serum total bilirubin quartiles, the incidence rate per 1000 person-years proportionally decreased in both men and women. After propensity score matching and adjusting for confounding variables, the HRs (95% CIs) for MetS of the highest quartile in reference to the lowest quartile were 1.00 (0.80-1.24) for men and 0.80 (0.65-0.99) for women. Higher quartiles of serum total bilirubin showed significantly lower cumulative incidence of MetS in women (log-rank test p = 0.009), but not in men (log-rank test p = 0.285).

CONCLUSION

Serum total bilirubin levels were significantly inversely associated with MetS in women, but there was no significant association observed in men. Sex differences in the effects of serum total bilirubin should be noted when predicting incident MetS by sex in clinical settings.

Bilirubin Down-Regulates Oxidative Stress and Fibroblast Growth Factor 23 Expression in UMR106 Osteoblast-Like Cells

INTRODUCTION

Fibroblast growth factor 23 (FGF23) is a major regulator of phosphate and vitamin D metabolism in the kidney, and its higher levels in plasma are associated with poorer outcomes in kidney and cardiovascular diseases. It is produced by bone cells upon enhanced oxidative stress and inhibits renal phosphate reabsorption and calcitriol (active form of vitamin D) production. Bilirubin, the final product of the heme catabolic pathway in the vascular bed, has versatile biological functions, including antioxidant and anti-inflammatory effects. This study explored whether bilirubin alters FGF23 production.

METHODS

Experiments were performed using UMR106 osteoblast-like cells. Fgf23 transcript levels were determined by quantitative real-time polymerase chain reaction, C-terminal and intact FGF23 protein levels were determined by enzyme-linked immunosorbent assay, and cellular oxidative stress was assessed by CellROX assay.

RESULTS

Unconjugated bilirubin down-regulated Fgf23 gene transcription and FGF23 protein abundance; these effects were paralleled by lower cellular oxidative stress levels. Also, conjugated bilirubin reduced Fgf23 mRNA abundance.

CONCLUSION

Bilirubin down-regulates FGF23 production in UMR106 cells, an effect likely to be dependent on the reduction of cellular oxidative stress.

Association between serum total bilirubin and diabetic kidney disease in US diabetic patients

Background

Bilirubin has been widely reported to be a protective factor against diabetic kidney disease (DKD) in Asian populations. However, few large-sample analyses have been conducted in American populations. This study aimed to investigate the association between serum total bilirubin (STB) level and DKD in a US diabetic cohort.

Methods

This cross-sectional study enrolled participants from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. Univariate and multivariate logistic regression analyses were performed to assess the association between STB level and DKD. Three models were conducted to control the potential confounding factors. Subgroup analysis was carried out for further validation.

Results

Among the 5,355 participants, the median age [interquartile range (IQR)] was 62 [52-71] years; 2,836 (52.96%) were male, and 1,576 (29.43%) were diagnosed with DKD. In the entire cohort, no significant association between STB level and DKD was observed in any logistic regression models (p > 0.05). Subgroup analysis revealed that, in U.S. diabetic males, STB levels > 11.98 µmol/L were associated with a nearly 30% lower risk of DKD than STB levels ≤ 8.55 µmol/L. Additionally, a moderate STB level (8.56-11.98 μmol/L) was found associated with a nearly 25% lower risk of DKD in U.S. diabetic patients over 65 years old.

Conclusion

The association of STB level with DKD may depict differences across diverse populations, among which the impact of race, sex, and age requires thorough consideration and relevant inferences should be interpreted cautiously.

Activation of the Nrf-2/HO-1 signalling axis can alleviate metabolic syndrome in cardiovascular disease

Background: Cardiovascular disease (CVD) is widely observed in modern society. CVDs are responsible for the majority of fatalities, with heart attacks and strokes accounting for approximately 80% of these cases. Furthermore, a significant proportion of these deaths, precisely one-third, occurs in individuals under 70. Metabolic syndrome encompasses a range of diseases characterized by various physiological dysfunctions. These include increased inflammation in adipose tissue, enhanced cholesterol synthesis in the liver, impaired insulin secretion, insulin resistance, compromised vascular tone and integrity, endothelial dysfunction, and atheroma formation. These factors contribute to the development of metabolic disorders and significantly increase the likelihood of experiencing cardiovascular complications.Method: We selected studies that proposed hypotheses regarding metabolic disease syndrome and cardiovascular disease (CVD) and the role of Nrf2/HO-1 and factor regulation in CVD research investigations based on our searches of Medline and PubMed.Results: A total of 118 articles were included in the review, 16 of which exclusively addressed hypotheses about the role of Nrf2 on Glucose regulation, while 16 involved Cholesterol regulation. Likewise, 14 references were used to prove the importance of mitochondria on Nrf2. Multiple studies have provided evidence suggesting the involvement of Nrf2/HO-1 in various physiological processes, including metabolism and immune response. A total of 48 research articles and reviews have been used to highlight the role of metabolic syndrome and CVD.Conclusion: This review provides an overview of the literature on Nrf2/HO-1 and its role in metabolic disease syndrome and CVD.

Relationship between bilirubin and systemic lupus erythematosus: A systematic review and meta-analysis

AIMS

Systemic lupus erythematosus (SLE) is an autoimmune disease with a high prevalence worldwide. This study aimed to examine the correlation between serum bilirubin levels and SLE.

METHODS

The Cochrane library, Embase, PubMed, and China National Knowledge Infrastructure (CNKI) databases were examined and assessed until March 2023. RevMan 5.3 software was utilized for the analysis of clinical trails.

RESULTS

Five case-control studies were chosen and incorporated, examining the levels of serum bilirubin in patients with SLE compared to healthy individuals, as well as in active SLE patients versus inactive ones, in different sexes and in SLE patients with or without lupus nephritis (LN). The results of this meta-analysis demonstrated that serum bilirubin in healthy individuals were obviously increased compared to SLE patients (MD = 4.76; 95% CI, 3.15-6.38, p < .00001). Additionally, inactive SLE patients had higher levels of bilirubin than active SLE patients (MD = 3.15; 95% CI, 0.46-5.84, p = .02), and SLE patients without lupus nephritis had higher levels of serum bilirubin than those with lupus nephritis (MD = 4.91;95% CI, 2.87-6.95, p < .00001). Nevertheless, there were no disparities observed among SLE patients of varying sexes (MD = 0.34; 95% CI, -0.01 to 0.69, p = .06).

CONCLUSION

The concentration of serum bilirubin may potentially be used as an indicator for estimating the advancement of SLE and reflecting the presence of kidney complications in individuals with SLE. Furthermore, more high quality studies were needed to identify these findings.

Heme Oxygenase-1 and Its Role in Colorectal Cancer

Heme oxygenase-1 (HO-1) is an enzyme located at the endoplasmic reticulum, which is responsible for the degradation of cellular heme into ferrous iron, carbon monoxide and biliverdin-IXa. In addition to this main function, the enzyme is involved in many other homeostatic, toxic and cancer-related mechanisms. In this review, we first summarize the importance of HO-1 in physiology and pathophysiology with a focus on the digestive system. We then detail its structure and function, followed by a section on the regulatory mechanisms that control HO-1 expression and activity. Moreover, HO-2 as important further HO isoform is discussed, highlighting the similarities and differences with regard to HO-1. Subsequently, we describe the direct and indirect cytoprotective functions of HO-1 and its breakdown products carbon monoxide and biliverdin-IXa, but also highlight possible pro-inflammatory effects. Finally, we address the role of HO-1 in cancer with a particular focus on colorectal cancer. Here, relevant pathways and mechanisms are presented, through which HO-1 impacts tumor induction and tumor progression. These include oxidative stress and DNA damage, ferroptosis, cell cycle progression and apoptosis as well as migration, proliferation, and epithelial-mesenchymal transition.

Retinopathy of Prematurity and Glucose-6-Phosphate Dehydrogenase Activity: A Case-Control Study

OBJECTIVE

To determine whether red blood cell glucose-6-phosphate dehydrogenase (G6PD) activity is associated with retinopathy of prematurity (ROP).

METHODS

This case-control study was conducted in a Level-3 neonatal unit. Subjects were inborn boys with birth weight <2000 g. "Cases" were consecutive subjects with ROP of any severity. "Controls" were consecutive unrelated subjects without ROP. Recipients of blood or exchange transfusions were excluded. Sixty cases (out of 98 screened) and 60 controls (out of 93 screened) were enrolled. G6PD activity (quantitative assay) as the candidate risk factor was evaluated.

RESULTS

Sixty cases with 60 controls [mean (SD) gestation 28.80 (2.2) and 30.60 (2.2) wk respectively] were compared. "Cases" had a higher median (1st, 3rd quartile) G6PD activity compared to "controls" [7.39 (4.7, 11.5) vs. 6.28 (4.2, 8.8) U/g Hb, p = 0.084]. G6PD activity was highest among ROP requiring treatment [8.68 (4.7, 12.3)] followed by ROP not requiring treatment [6.91 (4.4, 11.0)], followed by controls (plinear trend = 0.06). Gestation, birth weight, duration of oxygen, breastmilk feeding, and clinical sepsis were other variables associated with ROP on univariable analysis. On multivariable logistic regression, G6PD activity [Adjusted OR 1.14 (1.03, 1.25), p = 0.01] and gestation [Adjusted OR 0.74 (0.56, 0.97), p = 0.03] independently predicted ROP. C-statistic of the model was 0.76 (95% CI 0.67, 0.85).

CONCLUSIONS

Higher G6PD activity was independently associated with ROP after adjusting for confounders. Each 1 U/g Hb increase in G6PD increased the odds of ROP by 14%. Severer forms of ROP were associated with higher levels of G6PD activity.

Targeting endothelial vascular cell adhesion molecule-1 in atherosclerosis: drug discovery and development of vascular cell adhesion molecule-1-directed novel therapeutics

Vascular cell adhesion molecule-1 (VCAM-1) has been well established as a critical contributor to atherosclerosis and consequently as an attractive therapeutic target for anti-atherosclerotic drug candidates. Many publications have demonstrated that disrupting the VCAM-1 function blocks monocyte infiltration into the sub-endothelial space, which effectively prevents macrophage maturation and foam cell transformation necessary for atherosclerotic lesion formation. Currently, most VCAM-1-inhibiting drug candidates in pre-clinical and clinical testing do not directly target VCAM-1 itself but rather down-regulate its expression by inhibiting upstream cytokines and transcriptional regulators. However, the pleiotropic nature of these regulators within innate immunity means that optimizing dosage to a level that suppresses pathological activity while preserving normal physiological function is extremely challenging and oftentimes infeasible. In recent years, highly specific pharmacological strategies that selectively inhibit VCAM-1 function have emerged, particularly peptide- and antibody-based novel therapeutics. Studies in such VCAM-1-directed therapies so far remain scarce and are limited by the constraints of current experimental atherosclerosis models in accurately representing the complex pathophysiology of the disease. This has prompted the need for a comprehensive review that recounts the evolution of VCAM-1-directed pharmaceuticals and addresses the current challenges in novel anti-atherosclerotic drug development.

Oxidative status alteration during aerobic-dominant mixed and anaerobic-dominant mixed effort in judokas

This study aimed to depict the oxidative status variation in judokas during aerobic-dominant mixed effort (AeDME) and anaerobic-dominant mixed effort (AnDME). It is to be expected that the sporting commitment of Judo is a stimulus of oxidative stress leading to the recruitment of antioxidant responses. Blood samples were collected from 17 athletes at rest, immediately after a training session (AeDME) and after a 5-min bout (AnDME). AeDME and AnDME caused significant increases in malondialdehyde (MDA) (p < 0.01 and p < 0.001 respectively) and glutathione (GSH) (p = 0.018 and p < 0.001 respectively). Blood thiol concentrations decreased following AeDME and AnDME (p < 0.001) whilst catalase decreased significantly after AnDME (p = 0.026) only. Uric acid increased significantly after AnDME than after AeDME (p = 0.047) while, conversely, total bilirubin was higher after AnDME than after AeDME (p = 0.02). We may ultimately summarize that AeDME and AnDME caused oxidative stress, higher in AnDME, and some antioxidant response slightly higher in AnDME compared to AeDME. In sports, monitoring of oxidative stress status is recommended as part of the training regimen.

High-normal unconjugated bilirubin is associated with decreased risk of chronic kidney disease in type 2 diabetes: A real-world study

OBJECTIVE

To investigate the association between serum unconjugated bilirubin (UCB) within normal limits and chronic kidney disease (CKD) in T2DM patients.

METHOD

This cross-sectional, real-world study was performed in 8661 hospitalised T2DM patients. The subjects were stratified into quintiles based on serum UCB levels. The clinical characteristics and CKD prevalence were compared among the UCB quantile groups. The associations of serum UCB levels and quintiles with CKD were also analysed by binary logistic regression.

RESULTS

After controlling for age, sex, and diabetes duration (DD), the CKD prevalence (20.4%, 12.2%, 10.6%, 8.3%, and 6.4% for the first, second, third, fourth, and fifth quintiles, respectively, p < 0.001 for trend) was significantly decreased across the serum UCB quintiles. The fully adjusted regression model showed negative associations of serum UCB levels (OR: 0.660, 95% CI: 0.585-0.744; p < 0.001 for trend) and quintiles (p < 0.001) with the presence of CKD. Compared with the subjects in the lowest UCB quintile, the risk of CKD decreased by 36.2%, 54.3%, 53.8%, and 62.1%, respectively, in those from the second to the highest UCB quintile. Additionally, C-reactive protein (CRP) levels were significantly higher in the subjects with CKD than in those without CKD (p < 0.001), and significantly decreased across the UCB quintiles (p < 0.001 for trend).

CONCLUSIONS

Serum UCB levels within the normal range were significantly and negatively linked to CKD in T2DM patients. High-normal UCB may be an independent protective factor for CKD by its antioxidant and the following anti-inflammatory activities through its signalling activity, which was indicated by clearly decreased CRP levels across the UCB quintiles.

Endogenous and Exogenous Antioxidants as Agents Preventing the Negative Effects of Contrast Media (Contrast-Induced Nephropathy)

The use of conventional contrast media for diagnostic purposes (in particular, Gd-containing and iodinated agents) causes a large number of complications, the most common of which is contrast-induced nephropathy. It has been shown that after exposure to contrast agents, oxidative stress often occurs in patients, especially in people suffering from various diseases. Antioxidants in the human body can diminish the pathological consequences of the use of contrast media by suppressing oxidative stress. This review considers the research studies on the role of antioxidants in preventing the negative consequences of the use of contrast agents in diagnostics (mainly contrast-induced nephropathy) and the clinical trials of different antioxidant drugs against contrast-induced nephropathy. Composite antioxidant/contrast systems as theranostic agents are also considered.

Prognostic value of liver damage assessed through direct bilirubin levels and skeletal muscle weakness in patients with heart failure

BACKGROUND

Patients with heart failure (HF) often exhibit signs of liver dysfunction such as high bilirubin concentrations, leading to physical dysfunction and poor prognosis. Nevertheless, the relationship between direct bilirubin (DB), a fractionated form of total bilirubin, and dynapenia remains unclear, as does their effect on prognosis.

OBJECTIVES

This study investigated the association between DB concentrations and dynapenia in patients with HF.

METHODS

This retrospective study included patients with HF who underwent assessments for DB concentration, and handgrip and leg strengths to evaluate dynapenia and muscle weakness, respectively. Multiple logistic regression analyses examined the associations of DB with muscle strength and dynapenia. Additionally, we examined the prognostic value of comorbid high DB concentrations (≥0.5 mg/dL) and dynapenia. The endpoint was all-cause mortality.

RESULTS

Of 853 inpatients, high DB was identified in 147 and dynapenia in 377 (44.2%). Multiple regression analysis revealed that high DB was independently associated with decreased muscle strength (handgrip strength, P = 0.027; leg strength, P = 0.002). After adjusting for covariates, the high DB group (odds ratio: 1.800, 95% confidence interval [CI]: 1.203-2.695, P = 0.004) had a significantly higher risk of dynapenia than the low DB group. During the follow-up period, 189 patients died (median, 1.77 years; interquartile range, 0.64-3.81 years). The risk of death was significantly higher in the high DB and dynapenia group, even after adjusting for HF severity (hazard ratio: 2.610, 95% CI: 1.680-4.051, P<0.001).

CONCLUSIONS

High DB is associated with muscle weakness, and when combined with dynapenia, DB predicts a poorer prognosis in patients with HF.

Electrochemical approaches based on micro- and nanomaterials for diagnosing oxidative stress

This review article comprehensively discusses the various electrochemical approaches for measuring and detecting oxidative stress biomarkers and enzymes, particularly reactive oxygen/nitrogen species, highly reactive chemical molecules, which are the byproducts of normal aerobic metabolism and can oxidize cellular components such as DNA, lipids, and proteins. First, we address the latest research on the electrochemical determination of reactive oxygen species generating enzymes, followed by detection of oxidative stress biomarkers, and final determination of total antioxidant activity (endogenous and exogenous). Most electrochemical sensing platforms exploited the unique properties of micro- and nanomaterials such as carbon nanomaterials, metal or metal oxide nanoparticles (NPs), conductive polymers and metal-nano compounds, which have been mainly used for enhancing the electrocatalytic response of sensors/biosensors. The performance of the electroanalytical devices commonly measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in terms of detection limit, sensitivity, and linear range of detection is also discussed. This article provides a comprehensive review of electrode fabrication, characterization and evaluation of their performances, which are assisting to design and manufacture an appropriate electrochemical (bio)sensor for medical and clinical applications. The key points such as accessibility, affordability, rapidity, low cost, and high sensitivity of the electrochemical sensing devices are also highlighted for the diagnosis of oxidative stress. Overall, this review brings a timely discussion on past and current approaches for developing electrochemical sensors and biosensors mainly based on micro and nanomaterials for the diagnosis of oxidative stress.

Association of serum total bilirubin and potential predictors with mortality in acute respiratory failure: A retrospective cohort study

BACKGROUND

Total serum bilirubin (TBIL) levels are a risk factor in critically ill patients. However, the relationship between the dynamics of TBIL and the prognosis of acute respiratory failure (ARF) patients is unclear.

OBJECTIVES

This study aimed to investigate the impact of different levels of TBIL during hospitalization on mortality in ARF patients.

METHODS

This study used a retrospective cohort study. We extracted information on ARF patients from the Medical Information Bank for Intensive Care (MIMIC)-III (version 1.4). We used propensity score matching (PSM) to adjust for the level of potential baseline-level differences between groups. Cox regression was used to analyze mortality risk factors in patients with ARF. Subgroup analysis was used to explore special populations.

RESULTS

2673 patients were included in the study, and 19.7% developed hyperbilirubinemia (TBIL ≥ 2 mg/dL) during their hospitalization. After PSM, multivariate Cox regression showed a 50% and 135% increased risk of death for a maximum value of TBIL ≥ 5 mg/dL and minimum value of TBIL ≥ 2 mg/dL during hospitalization, respectively, compared to the control population. In addition, age ≥ 65 years, previous comorbid malignancies, respiratory rate ≥ 22 beats/min, SpO2 ≥ 95, BUN ≥ 20 mg/dL, lactate ≥ 5 mmol/L, platelet < 100 * 10 ^ 9/L were independent risk factors for 1-year mortality in ARF patients. Subgroup analysis showed that high bilirubin had a greater effect on patients aged less than 65 years (P for interaction < 0.05).

CONCLUSIONS

Hyper TBIL (TBIL max ≥ 5 mg/dL or TBIL min ≥ 2 mg/dL) was an independent risk factor for 1-year mortality in patients with ARF. This study suggests that clinicians should be aware of TBIL levels and intervene early in these patients.

Assessment of the general condition and quality of life of women of post-reproductive age after asymptomatic COVID-19 and 12 months after moderate COVID-19

   The aim. To assess the general condition, laboratory parameters, quality of life of women of post-reproductive age after asymptomatic COVID-19 and 12 months after moderate COVID-19.   Material and methods. We examined 47 women (45–69 years old), divided into 3 groups: those who did not have COVID-19, not vaccinated (group 1 – control; n = 15); women 12 months after moderate COVID-19, accompanied by pneumonia (group 2; n = 19); women with IgG in their blood who deny any symptoms of COVID-19 (group 3; n = 13).   Results and discussion. An assessment of the general condition of women in post-reproductive age was carried out. In women 12 months after COVID-19 we found a lower level of total bilirubin compared to the group with asymptomatic COVID-19 (p = 0.004). An increase in thrombin time was determined in the groups of patients with symptomatic (p = 0.014) and asymptomatic (p = 0.025) COVID-19 course compared with the control group. Patients with asymptomatic COVID-19 course had a higher level of high-density lipoprotein cholesterol compared with the control group (p = 0.016) and the group 2 (p = 0.006). Compared with the control group, the group 2 had lower scores for general health (p = 0.006), vital activity (p = 0.013), general physical well-being (p = 0.039), physical functioning (p = 0.046); and the group 3 had higher scores in role functioning due to physical condition (p = 0.049). When comparing groups 2 and 3, lower scores in the group of women who recovered from the moderate COVID-19 were found in physical functioning (p = 0.002), pain intensity (p = 0.034), role functioning due to physical condition (p = 0.049), general health (p = 0.003), vital activity (p = 0.018), general physical well-being (p = 0.001).   Conclusion. 12 months after moderate COVID-19, there is a pronounced deterioration in physical and emotional health; and in asymptomatic patients, better protective functions of an organism can be assumed.

Pharmaceutical strategies for preventing toxicity and promoting antioxidant and anti-inflammatory actions of bilirubin

Bilirubin (BR) is the final product of haem catabolism. Disruptions along BR metabolic/transport pathways resulting from inherited disorders can increase plasma BR concentration (hyperbilirubinaemia). Unconjugated hyperbilirubinemia may induce BR accumulation in brain, potentially causing irreversible neurological damage, a condition known as BR encephalopathy or kernicterus, to which newborns are especially vulnerable. Numerous pharmaceutical strategies, mostly based on hemoperfusion, have been proposed over the last decades to identify new valid, low-risk alternatives for BR removal from plasma. On the other hand, accumulating evidence indicates that BR produces health benefits due to its potent antioxidant, anti-inflammatory and immunomodulatory action with a significant potential for the treatment of a multitude of diseases. The present manuscript reviews both such aspects of BR pharmacology, gathering literature data on applied pharmaceutical strategies adopted to: (i) reduce the plasma BR concentration for preventing neurotoxicity; (ii) produce a therapeutic effect based on BR efficacy in the treatment of many disorders.

Protective activity of purpurin against d-galactosamine and lipopolysaccharide-induced hepatorenal injury by upregulation of heme oxygenase-1 in the RBC degradation cycle

Acute liver failure, associated with oxidative stress and sustained inflammation is the major clinical manifestation of liver diseases with a high mortality rate due to limited therapeutic options. Purpurin is a bioactive compound of Rubia cordifolia that has been used in textile staining, as a food additive, and as a treatment of multiple chronic and metabolic diseases associated with inflammation and oxidative stress. The present work aimed to investigate the protective efficacy of purpurin against hepatorenal damage. Thirty-six female albino rats were equally assigned into six groups. Purpurin was administered orally once a day for 6 days at doses of 05, 10, and 20 mg/kg, respectively. Intraperitoneal injection of lipopolysaccharide (50 μg/kg) was administered to the animals on 6th day evening, 1 h after d-galactosamine (300 mg/kg) administration to induce hepatorenal injury. The results revealed that purpurin alleviated alterations in serological and hematological parameters as well as restored histoarchitectural and cellular integrity of the liver and kidney. Purpurin restored superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and glutathione content in hepatorenal tissues. Accompanied by the diminution of increased bilirubin and biliverdin, purpurin also diminished total cholesterol, triglyceride, and lipid peroxidation in hepatorenal tissues. Purpurin markedly attenuated the elevation of CYP2E1, restored glutathione-S-transferase, and prevented DNA damage in hepatorenal tissues. Purpurin reduced iron overload by reducing heme depletion and recycling of ferritin and hemosiderin. It also reinforced biliverdin reductase, heme oxygenase-1 to employ hepatorenal protection by regulating antioxidant enzymes and other pathways that produced NADPH. Thus, it may be concluded that purpurin has protective potential against acute hepatorenal injury.

Association between non-alcoholic fatty liver disease and metabolically healthy deterioration across different body shape phenotypes at baseline and change patterns

Non-alcoholic fatty liver disease (NAFLD) is a hepatic manifestation of metabolic syndrome (MetS), and the relationship between NAFLD and metabolic deterioration remains unclear. This study aimed to investigate dynamic changes in metabolically healthy phenotypes and to assess the impact of non-alcoholic fatty liver disease (NAFLD) on the conversion from metabolically healthy (MH) to metabolically unhealthy (MU) phenotypes across body shape phenotypes and phenotypic change patterns. We defined body shape phenotypes using both the body mass index (BMI) and waist circumference (WC) and defined metabolic health as individuals scoring ≤ 1 on the NCEP-ATP III criteria, excluding WC. A total of 12,910 Chinese participants who were MH at baseline were enrolled in 2013 and followed-up in 2019 or 2020. During a median follow-up of 6.9 years, 27.0% (n = 3,486) of the MH individuals developed an MU phenotype. According to the multivariate Cox analyses, NAFLD was a significant predictor of conversion from the MH to MU phenotype, independent of potential confounders (HR: 1.12; 95% confidence interval: 1.02–1.22). For the MH-normal weight group, the relative risk of NAFLD in phenotypic conversion was 1.21 (95% CI 1.03–1.41, P = 0.017), which was relatively higher than that of MH-overweight/obesity group (HR: 1.14, 95% CI 1.02–1.26, P = 0.013). Interestingly, the effect of NAFLD at baseline on MH deterioration was stronger in the “lean” phenotype group than in the “non-lean” phenotype group at baseline and in the “fluctuating non-lean” phenotype change pattern group than in the “stable non-lean” phenotype change pattern group during follow-up. In conclusion, lean NAFLD is not as benign as currently considered and requires more attention during metabolic status screening.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Efficacy of oral and topical antioxidants in the prevention and management of oral mucositis in head and neck cancer patients: a systematic review and meta-analyses

PURPOSE

To evaluate the effectiveness of antioxidants in the prevention and management of oral mucositis in adults undergoing radiotherapy and/or chemotherapy with diagnosed head and neck cancer (HNC) compared to placebo intervention.

METHODS

Cochrane, EMBASE, PubMed, and Web of Science databases were used to search for randomized controlled trials (RCTs) comparing oral or topical antioxidants with placebo in clinically diagnosed HNC adult patients receiving radiotherapy with/without chemotherapy. The primary outcome was to assess the efficacy of the antioxidant to prevent and decrease the incidence/prevalence and severity of oral/oropharyngeal mucositis. The risk of bias was assessed following Cochrane's guidelines.

RESULTS

The database search resulted in 203 records up to February 19, 2021. Thirteen RCTs were included with 650 HNC-diagnosed patients. Included studies showed a statistically significant improvement in mucositis severity score for all antioxidants except melatonin. However, further studies are needed as only one study reported outcomes for zinc, propolis, curcumin, and silymarin. Patients receiving vitamin E were 60% less likely to develop severe mucositis grade 2 or higher than those receiving placebo in one study (P = 0.040). Patients receiving zinc were 95% less likely to develop severe mucositis (grades 3-4) in one study compared to placebo (P = 0.031). One meta-analysis showed no statistical difference in the risk of having severe mucositis (grades 3-4) with 199 patients compared to placebo for honey (n = 2 studies, P = 0.403). Meta-analyses could not be conducted for zinc, propolis, curcumin, melatonin, silymarin, and selenium due to the lack of studies reporting similar outcomes for the same intervention.

CONCLUSION

Though oral and topical antioxidants significantly improved mucositis severity scores in HNC patients receiving radiotherapy with/without chemotherapy in individual studies, the quality of the evidence was low due to the small number of studies and unclear/high-risk bias. Additionally, large RCTs are needed to confirm these results.

Y, Wang X, He X, Wu X, Xu C, Tang Y, Liu WT, Kong X, Hu L. Bilirubin Improves Gap Junction to Alleviate Doxorubicin-Induced Cardiotoxicity by Regulating AMPK-Axl-SOCS3-Cx43 Axis

Doxorubicin induces severe cardiotoxicity, accompanied by the high level of bilirubin in the blood. The conventional wisdom is that bilirubin is considered as a marker of liver damage. By contrast, here we aim to explore the potential protective effect of bilirubin on doxorubicin-induced cardiotoxicity, and investigate the mechanism for drug development. Doxorubicin was used to establish cardiotoxicity model in vitro and in vivo. The electrocardiogram (ECG), echocardiography and molecular biological methods were used to detect the effects of bilirubin on doxorubicin-induced cardiotoxicity. Consecutive intraperitoneal injection of bilirubin for 7 days significantly attenuated doxorubicin-induced arrhythmia, prolonged survival time and reduced the levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase MB (CK-MB) and α-hydroxybutyrate dehydrogenase (α-HBDH) in mice. Bilirubin also markedly inhibited doxorubicin-induced phosphorylation of c-Jun N-terminal kinase (JNK) and connexin 43 (Cx43), and improved gap junction function in vitro and in vivo. In addition, bilirubin activated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and induced suppressor of cytokine signaling 3 (SOCS3) expression, which was abolished by Axl inhibition. Moreover, pretreatment with AMPK agonist or AMPK inhibitor could mimic or abolish the cardioprotective effect of bilirubin on H9C2 cells in vitro, respectively. Altogether, bilirubin upregulates gap junctions' function to protect against doxorubicin-induced cardiotoxicity by activating AMPK-Axl-SOCS3 signaling axis. We enrich the physiological function of bilirubin, and provide theoretical support for drug development.

Nitrogen-Doped Carbon Dots as a Fluorescent Probe for the Highly Sensitive Detection of Bilirubin and Cell Imaging

Nitrogen-doped carbon dots (NCDs) with bright blue fluorescence were constructed by a hydrothermal method using sucrose and L-proline as raw materials. The NCDs were characterized by transmitted electron microscopy, X-ray diffractometry, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and ultraviolet-visible absorption (UV-vis) and fluorescence spectroscopy to investigate the morphology, elemental composition, and optical properties. The NCDs had good water solubility, high dispersibility with an average diameter of only 1.7 nm, and satisfactory optical properties with a fluorescence quantum yield of 23.4%. The NCDs were employed for the detection of bilirubin. A good linear response of the NCDs in the range 0.35-9.78 μM was obtained for bilirubin with a detection limit of 33 nM. The NCDs were also applied to the analysis of real samples, serum and urine, with a recovery of 95.34%-104.66%. The low cytotoxicity and good biocompatibility of the NCDs were indicated by an MTT assay and cell imaging of HeLa cells. Compared with other detection systems, using NCDs for bilirubin detection was a facile and efficient method with good selectivity and sensitivity.

Biomarkers associated with rhythm status after cardioversion in patients with atrial fibrillation

Biomarkers may help to improve our knowledge about the complex pathophysiology of atrial fibrillation (AF). In this study we sought to identify significant changes in biomarkers and clinical measures in patients with and without AF recurrence after electrical cardioversion. We measured 21 conventional and new biomarkers before and 30 days after electrical cardioversion and assessed the associations of changes in biomarker levels with rhythm status at follow-up. Significant between-group changes were observed for bone morphogenetic protein 10 (BMP10), N-terminal pro-B-type natriuretic peptide (NT-proBNP) and total bilirubin. Their respective changes were - 10.4%, - 62.0% and - 25.6% in patients with sinus rhythm, and 3.1%, 1.1% and - 9.4% in patients with recurrent AF, for a between-group difference of - 13.5% (95% confidence interval [CI] - 19.3% to - 7.6%; P < 0.001), - 63.1% (95% CI - 76.6% to - 49.6%; P < 0.001) and - 16.3% (95% CI - 27.9% to - 4.7%; P = 0.007). In multivariable models, the reductions of BMP10 and NT-proBNP were significantly associated with follow-up rhythm status (β coefficient per 1 - SD decrease, - 3.85; 95% CI - 6.34 to - 1.35; P = 0.003 for BMP10 and - 5.84; 95% CI - 10.22 to - 1.47; P = 0.009 for NT-proBNP. In conclusion, changes in BMP10 und NT-proBNP levels were independently associated with rhythm status after cardioversion, suggesting that these markers may be dependent on the actual heart rhythm.

Reactive Oxygen Species (ROS) and Antioxidants as Immunomodulators in Exercise: Implications for Heme Oxygenase and Bilirubin

Exercise is commonly prescribed as a lifestyle treatment for chronic metabolic diseases as it functions as an insulin sensitizer, cardio-protectant, and essential lifestyle tool for effective weight maintenance. Exercise boosts the production of reactive oxygen species (ROS) and subsequent transient oxidative damage, which also upregulates counterbalancing endogenous antioxidants to protect from ROS-induced damage and inflammation. Exercise elevates heme oxygenase-1 (HO-1) and biliverdin reductase A (BVRA) expression as built-in protective mechanisms, which produce the most potent antioxidant, bilirubin. Together, these mitigate inflammation and adiposity. Moderately raising plasma bilirubin protects in two ways: (1) via its antioxidant capacity to reduce ROS and inflammation, and (2) its newly defined function as a hormone that activates the nuclear receptor transcription factor PPARα. It is now understood that increasing plasma bilirubin can also drive metabolic adaptions, which improve deleterious outcomes of weight gain and obesity, such as inflammation, type II diabetes, and cardiovascular diseases. The main objective of this review is to describe the function of bilirubin as an antioxidant and metabolic hormone and how the HO-1-BVRA-bilirubin-PPARα axis influences inflammation, metabolic function and interacts with exercise to improve outcomes of weight management.

Bilirubin ameliorates murine atherosclerosis through inhibiting cholesterol synthesis and reshaping the immune system

Atherosclerosis is a chronic inflammatory disease caused mainly by lipid accumulation and excessive inflammatory immune response. Although the lipid-lowering and cardioprotective properties of bilirubin, as well as the negative relationship between bilirubin and atherosclerosis, were well documented, it is not yet clear whether bilirubin can attenuate atherosclerosis in vivo. In this study, we investigated the role of bilirubin in improving atherosclerosis. We found that mildly elevated bilirubin significantly reduced the risk factors of atherosclerosis, such as plasma glucose, total cholesterol, and low-density lipoprotein cholesterol, and the formation of atherosclerotic plaques, liver total cholesterol, and cholesterol ester concentration in apolipoprotein E-deficient (ApoE^-/-) mice fed a western-type (high fat) diet. It was further found that bilirubin could promote the degradation of 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR), a rate-limiting enzyme for endogenous cholesterol synthesis. Using mass cytometry-based high dimensional single cell analysis, we observed a decrease of natural killer cells and an increase of dendritic cells and myeloid-derived suppressor cells, which all are closely associated with atherosclerosis risk factors and contribute to the improvement of atherosclerosis, in ApoE^-/- mice treated with bilirubin. By in-depth analysis, modulation of multiple spleen or peripheral blood T cell clusters exhibiting either positive or negative correlations with total cholesterol or low-density lipoprotein cholesterol was detected after bilirubin treatment. In this study, we demonstrate that bilirubin serves as a negative regulator of atherosclerosis and reduces atherosclerosis by inhibiting cholesterol synthesis and modulating the immune system.

Biochemical and Endocrine Parameters for the Discrimination and Calibration of Bipolar Disorder or Major Depressive Disorder

OBJECTIVES

Conventional biochemical indexes may have predictive values in clinical identification between bipolar disorder (BD) and major depressive disorder (MDD).

METHODS

This study included 2,470 (BD/MDD = 1,333/1,137) hospitalized patients in Shanghai as training sets and 2,143 (BD/MDD = 955/1,188) in Hangzhou as test sets. A total of 35 clinical biochemical indexes were tested, including blood cells, immuno-inflammatory factors, liver enzymes, glycemic and lipid parameters, and thyroid and gonadal hormones. A stepwise analysis of a multivariable logistic regression was performed to build a predictive model to identify BD and MDD.

RESULTS

Most of these biochemical indexes showed significant differences between BD and MDD groups, such as white blood cell (WBC) in the hematopoietic system, uric acid (UA) in immuno-inflammatory factors, direct bilirubin (DBIL) in liver function, lactic dehydrogenase (LDH) in enzymes, and fasting blood glucose (FBG) and low-density lipoprotein (LDL) in glucolipid metabolism (p-values < 0.05). With these predictors for discrimination, we observed the area under the curve (AUC) of the predictive model to distinguish between BD and MDD to be 0.772 among men and 0.793 among women, with the largest AUC of 0.848 in the luteal phase of women. The χ² values of internal and external validation for male and female datasets were 2.651/10.264 and 10.873/6.822 (p-values < 0.05), respectively. The AUCs of the test sets were 0.696 for males and 0.707 for females.

CONCLUSION

Discrimination and calibration were satisfactory, with fair-to-good diagnostic accuracy and external calibration capability in the final prediction models. Female patients may have a higher differentiability with a conventional biochemical index than male patients.

TRIAL REGISTRATION

ICTRP NCT03949218. Registered on 20 November 2018. Retrospectively registered. https://www.clinicaltrials.gov/ct2/show/NCT03949218?id=NCT03949218&rank=1.

Association of Serum Bilirubin With Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Metabolic syndrome (MetS) and non-alcoholic fatty liver disease (NAFLD) are the leading chronic diseases worldwide. There are still many controversies about the association between serum bilirubin and MetS or NAFLD. This study aims to evaluate the association of serum total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL) with MetS and NAFLD.

METHODS

Multiple databases were searched for relevant studies until November 2021. Randomized controlled trials, cross-sectional and cohort studies evaluating the association between serum bilirubin levels and MetS or NAFLD were included.

RESULTS

Twenty-four cross-sectional and cohort studies with 101, 517 participants were finally analyzed. Fifteen studies and 6 studies evaluated the association between bilirubin and MetS or NAFLD in health screening population, respectively, while 3 studies evaluated the association between bilirubin and non-alcoholic steatohepatitis (NASH) in NAFLD patients. Random effect model analysis showed the inverse association between TBIL and MetS in male (95%CI=0.71-0.96) and gender-neutral (95%CI=0.61-0.91) group. However, no significant association was found in females. Notably, the inverse association between DBIL and MetS was noticed in male (95%CI=0.36-0.75), female (95%CI=0.16-0.58) and gender-neutral population (95%CI=0.67-0.92). IBIL level was inversely associated with MetS in females (95%CI=0.52-0.96), whereas no statistical correlation presented in males. TBIL was not statistically correlated with NAFLD in gender-neutral or male subgroup. Similarly, there were no association between DBIL or IBIL and NAFLD in gender-neutral subgroup. However, the negative correlation between DBIL and NAFLD existed in males (95%CI=0.76-0.96). In NAFLD patients, IBIL analysis showed an inverse association with NASH (95%CI=0.01-0.12).

CONCLUSION

Serum TBIL and DBIL levels, especially DBIL levels, assume an inverse correlation with MetS in healthy population. Serum IBIL is inversely associated with the onset and degree of NASH in NAFLD patients. Exogenous bilirubin supplement may be a potential strategy to assist in lowering the risk of developing MetS and NAFLD.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier CRD42021293349.

Protective effect of aqueous leaf extracts of Chromolaena odorata and Tridax procumbens on doxorubicin-induced hepatotoxicity in Wistar rats

Background:

The liver is one of the organs affected by doxorubicin toxicity. Therefore, in this study, the potential protective role of aqueous leaf extracts of Chromolaena odorata and Tridax procumbens against doxorubicin-induced hepatotoxicity was investigated.

Methods:

In order to achieve this, their impact on hepatic biomarkers of oxidative stress, lipid and electrolytes’ profile, and plasma biomarkers of liver functions/integrity were monitored in doxorubicin treated rats. The animals were treated with either metformin (250 mg/kg body weight orally for 14 days) or the extracts (50, 75, and 100 mg/kg orally for 14 days) and/or doxorubicin (15 mg/kg, intraperitoneal, 48 h before sacrifice).

Results:

The hepatic malondialdehyde, cholesterol, calcium, and sodium concentrations, and plasma activities of alanine and aspartate transaminases and alkaline phosphatase, as well as plasma albumin to globulin ratio of test control were significantly (P < .05) higher than those of all the other groups. However, the plasma albumin, total protein, globulin, and total bilirubin concentrations; hepatic concentrations of ascorbic acid, chloride, magnesium, and potassium; and hepatic activities of catalase, glutathione peroxidase, and superoxide dismutase of test control were significantly (P < .05) lower than those of all the other groups.

Conclusions:

Pretreatment with the extracts and metformin prevented to varying degrees, doxorubicin-induced hepatic damage, as indicated by the attenuation of doxorubicin-induced adverse alterations in hepatic biomarkers of oxidative stress, lipid and electrolyte profiles, and plasma biomarkers of hepatic function/integrity, and keeping them at near-normal values.

Hepatoprotective effect and metabonomics studies of radix gentianae in rats with acute liver injury

CONTEXT

As a well-known traditional Chinese medicine for protecting the liver, the mechanism of Radix Gentianae (RG) remains unclear.

OBJECTIVE

The hepatoprotective effect and metabonomics of RG were studied to explore the molecular and metabolic mechanisms of RG protecting the liver.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into control and model group (n = 10, orally given distilled water), intervention group (4 subgroups, n = 10, prophylactically and orally given 0.63, 2.5 and 5.6 g/kg RG and 0.2 g/kg bifendatatum for 7 d). On day 7 of the intervention, all rats except the control were injected intraperitoneally with 2.5% carbon tetrachloride vegetable oil solution (1.5 mL/kg) to induce liver injury. After 24 h of carbon tetrachloride injection, rat serum and liver tissue were collected for determining AST, ALT, TNF-α, MCP-1, IL-6, SOD, MDA, GSH, and GSH-PX. Rat serum was used for analysing endogenous metabolism by UPLC-Q-TOF-MS.

RESULTS

Different doses of RG can significantly decrease the levels of AST, ALT, TNF-α, MCP-1, IL-6 and MDA, and increase the levels of SOD, GSH, and GSH-PX in rats with liver injury (p < 0.05; TNF-α, and IL-6, p < 0.05 only at 5.6 g/kg dose). Eight biomarkers of liver injury were obtained in serum metabonomics, involving five significant metabolic pathways. RG can improve steroid biosynthesis, linoleic acid metabolism, porphyrin and chlorophyll metabolism, and fatty acid biosynthesis.

CONCLUSION

RG demonstrated a good ability to protect the liver and improving endogenous metabolism in rats with liver injury. This can help us understand the mechanism of RG and more clinical verifications were inspired.

Serum Total Bilirubin Level Is Associated With Hospital Mortality Rate in Adult Critically Ill Patients: A Retrospective Study

Background: Serum bilirubin level has been suggested to be associated with mortality for patients with severe sepsis. This study aimed to investigate the association of serum total bilirubin level with hospital mortality rate in adult critically ill patients.

Method: Data were extracted from the Medical Information Mart for Intensive Care-III (MIMIC-III) database. Patients with measured serum total bilirubin levels that recorded within 24 h after admission were involved in this study. Association of serum total bilirubin level and hospital mortality rate was assessed using logistic regression analysis. Propensity score-matching (PSM) was used to minimize differences between different groups.

Results: A total of 12,035 critically ill patients were herein involved. In patients with serum total bilirubin level ≥ 2 mg/dL, the hospital mortality rate was 31.9% compared with 17.0% for patients with serum total bilirubin level < 2 mg/dL (546/1714 vs. 1750/10321, P < 0.001). The results of multivariable logistic regression analysis showed that the odds ratio of mortality in patients with serum total bilirubin level ≥ 2 mg/dL was 1.654 [95% confidence interval (CI): 1.307, 2.093, P < 0.001]. After propensity score matching, in patients with serum total bilirubin level ≥ 2 mg/dL, the weighted hospital mortality rate was 32.2% compared with 24.8% for patients with serum total bilirubin level < 2 mg/dL, P = 0.001).

Conclusions: Serum total bilirubin concentration was found to be independently associated with hospital mortality rate in adult critically ill patients.

Serum Bilirubin Levels in Overweight and Obese Individuals: The Importance of Anti-Inflammatory and Antioxidant Responses

Obesity is a chronic condition involving low-grade inflammation and increased oxidative stress; thus, obese and overweight people have lower values of serum bilirubin. Essentially, bilirubin is a potent endogenous antioxidant molecule with anti-inflammatory, immunomodulatory, antithrombotic, and endocrine properties. This review paper presents the interplay between obesity-related pathological processes and bilirubin, with a focus on adipose tissue and adipokines. We discuss potential strategies to mildly increase serum bilirubin levels in obese patients as an adjunctive therapeutic approach.

Association of Serum Bilirubin with the Severity and Outcomes of Intracerebral Hemorrhages

Intracerebral hemorrhage (ICH) is the second most common subtype of stroke, and it is often associated with a high mortality rate and significant morbidity among survivors. Recent studies have shown that bilirubin, a product of heme metabolism, can exhibit cytoprotective, antioxidant and, anti-inflammatory properties. However, little is known about the role of bilirubin in combating several pathophysiological pathways caused by intracerebral bleeding in patients with ICH. In this study, data were collected retrospectively on 276 patients with ICH who were admitted to a university hospital between 5 January 2014 and 31 December 2017. We assessed the relationship between levels of total, direct, and indirect serum bilirubin and assessments of initial stroke severity and clinical outcomes by using Spearman’s rank correlation and Kruskal-Wallis H tests. A secondary examination of the carrier protein albumin was also undertaken. Our study found that higher levels of direct bilirubin were correlated with worse admission Glasgow Coma Scales (GCS) (r_s = −0.17, p = 0.011), worse admission ICH Scores (r_s = 0.19, p = 0.008), and worse discharge modified Rankin Scales (mRS) (r_s = 0.15, p = 0.045). Direct bilirubin was still significantly correlated with discharge mRS after adjusting for temperature at admission (r_s = 0.16, p = 0.047), oxygen saturation at admission (r_s = 0.15, p = 0.048), white blood cell count (r_s = 0.18, p = 0.023), or Troponin T (r_s = 0.25, p = 0.001) using partial Spearman’s correlation. No statistical significance was found between levels of total or indirect bilirubin and assessments of stroke severity and outcomes. In contrast, higher levels of albumin were correlated with better admission GCS (r_s = 0.13, p = 0.027), discharge GCS (r_s = 0.15, p = 0.013), and discharge mRS (r_s = −0.16, p = 0.023). We found that levels of total bilirubin, direct bilirubin, and albumin were all significantly related to discharge outcomes classified by discharge destinations (p = 0.036, p = 0.014, p = 0.016, respectively; Kruskal-Wallis H tests). In conclusion, higher direct bilirubin levels were associated with greater stroke severity at presentation and worse outcomes at discharge among patients with ICH. Higher levels of albumin were associated with lower stroke severity and better clinical outcomes. Future prospective studies on the free bioactive bilirubin are needed to better understand the intricate relationships between bilirubin and ICH.

Highly Emissive Biological Bilirubin Molecules: Shedding New Light on the Phototherapy Scheme

Bilirubin (BR) is the main end-product of the hemoglobin catabolism. For decades, its photophysics has been mainly discussed in terms of ultrafast deactivation of the excited state in solution, where, indeed, BR shows a very low green emission quantum yield (EQY), 0.03%, resulting from an efficient nonradiative isomerization process. Herein, we present, for the first time, unique and exceptional photophysical properties of solid-state BR, which amend by changing the type of crystal, from a closely packed α crystal to an amorphous loosely packed β crystal. BR α crystals show a very bright red emission with an EQY of ca. 24%, whereas β crystals present, in addition, a low green EQY of ca. 0.5%. By combining density functional theory (DFT) calculations and time-resolved emission spectroscopy, we trace back this dual emission to the presence of two types of BR molecules in the crystal: a "stiff" monomer, M1, distorted by particularly strong internal H-bonds and a "floppy" monomer, M2, having a structure close to that of BR in solution. We assign the red strong emission of BR crystals to M1 present in both the α and β crystals, while the low green emission, only present in the amorphous (β) crystal, is interpreted as M2 emission. Efficient energy-transfer processes from M2 to M1 in the closely packed α crystal are invoked to explain the absence of the green component in its emission spectrum. Interestingly, these unique photophysical properties of BR remain in polar solvents such as water. Based on these unprecedented findings, we propose a new model for the phototherapy scheme of BR inside the human body and highlight the usefulness of BR as a strong biological fluorescent probe.

A UGT1A1 variant is associated with serum total bilirubin levels, which are causal for hypertension in African-ancestry individuals

Serum bilirubin is associated with several clinical outcomes, including hypertension, type 2 diabetes (T2D), and drug metabolism. Here, we describe findings from our genome-wide association studies (GWAS) of serum (TBIL) using a generalized linear mixed model in West Africans (n = 1127), with adjustment for age, sex, body mass index, T2D, significant principal components of population structure, and cryptic relatedness. Genome-wide conditional analysis and CAVIARBF were used to fine map significant loci. The causal effect of TBIL on hypertension was assessed by Mendelian randomization (MR) using the GWAS findings as instrumental variables (IVs) in African Americans (n = 3,067). The SNP rs887829 (UGT1A1) was significantly associated with TBIL levels (effect allele (T) frequency = 0.49, β (SE) = 0.59 (0.04), p = 9.13 × 10^-54). Genome-wide conditional analysis and regional fine mapping pointed to rs887829 as a possible causal variant with a posterior inclusion probability of 0.99. The T allele of rs887829 is associated with lower hepatic expression of UGT1A1. Using rs887829 as an IV, two-stage least-squares MR showed a causal effect of bilirubin on hypertension (β = -0.76, 95% CI [-1.52, -0.01], p = 0.0459). Our finding confirms that UGT1A1 influences bilirubin levels. Notably, lower TBIL is causally associated with the increased risk of hypertension.

Evaluation of nutritional composition of Citrullus lanatus Linn. (watermelon) seed and biochemical assessment of the seed oil in rats

The present study investigated the nutritional composition of watermelon seeds and the effect of extracted oil on the biochemical parameters in rats after 28 days of oral administration. The watermelon seeds showed considerable proximate values but with less moisture, crude fiber, ash, and phytochemical components. The maximal dose of 50 ml/kg of watermelon seed oil (WMSO) showed no sign of toxicity in rats. WMSO significantly decreased serum cholesterol, triglyceride, LDL, ALT, and MDA but enhanced the level of HDL, VLDL, SOD, and CAT without compromising the liver integrity. For glucose tolerance, a positive oral glucose-lowering was observed. The fatty acid analysis showed the presence of three major fatty acids; 9,12-octadecadienoic acid (52.32%), n-hexadecenoic acid (21.23%), and oleic acid (10.11%) with good oxidative stability and fatty acid ratio. The outcome of this study suggests that the seeds and oil from watermelon could have a beneficial effect on man. PRACTICAL APPLICATIONS: Plant-based oils have gained significant interest globally as a source of food, cosmetics, and compounds with therapeutic potential against certain human diseases. The watermelon seed oil is a rich source of oleic acid, linoleic, and palmitic acid. These prominent biologically active fatty acid components have contributed to the robust biochemical effects observed in this study. Based on the data obtained in this work on the nutritional analysis of the watermelon seed and potent antioxidative capacity, improved liver biomarkers, good oxidative stability, and the fatty acid ratio of WMSO, we proposed that consumption of the seed and its oil could offer a cheap and affordable nutraceutical for human benefits. However, we recommend further studies on the biological activity and safety aspect of watermelon seed oil for its long-term usage.

Inverse association between serum bilirubin level and testosterone deficiency in middle-aged and older men

Low serum bilirubin levels have been associated with increased risk of cardiovascular disease (CVD) and metabolic syndrome. Testosterone deficiency could also contribute to increased risk of CVD and metabolic syndrome. Therefore, this study aimed to examine the relationship between serum bilirubin level and testosterone deficiency in 1284 Korean men aged 45 to 70 years. Serum bilirubin level was categorized into quartiles: Q1 ≤ 0.7, Q2 0.8-0.9, Q3 1.0-1.1, and Q4 ≥ 1.2 mg/dL. Testosterone deficiency was defined as level less than 8.0 nmol/L, as suggested by the position statement of International Society of Andrology. The overall prevalence of testosterone deficiency was 5.8% and significantly decreased with the quartiles from Q1 to Q4. Compared with the referent fourth quartile (serum bilirubin ≥ 1.2 mg/dL), the ORs (95% CIs) for testosterone deficiency was 2.29 (1.04-4.94) for the first quartile after adjusting for age, fasting glucose, triglyceride, HDL-cholesterol, leukocyte count, hemoglobin, smoking status, and alcohol intake. We found inversely graded associations of serum bilirubin level with testosterone deficiency. These findings suggest that low bilirubin level may be interpreted as a state of testosterone deficiency in middle-aged and older men.

Can bilirubin nanomedicine become a hope for the management of COVID-19?

Bilirubin has been proven to possess significant anti-inflammatory, antioxidant and antiviral activities. Recently, it has been postulated as a metabolic hormone. Further, moderately higher levels of bilirubin are positively associated with reduced risk of cardiovascular diseases, diabetes, metabolic syndrome and obesity. However, due to poor solubility the therapeutic delivery of bilirubin remains a challenge. Nanotechnology offers unique advantages which may be exploited for improved delivery of bilirubin to the target organ with reduced risk of systemic toxicity. Herein, we postulate the use of intravenous administration or inhalational delivery of bilirubin nanomedicine (BNM) to combat systemic dysfunctions associated with COVID-19, owing to the remarkable preclinical efficacy and optimistic results of various clinical studies of bilirubin in non-communicable disorders. BNM may be used to harness the proven preclinical pharmacological efficacy of bilirubin against COVID-19 related systemic complications.

Neutrophil extracellular traps enhance procoagulant activity and thrombotic tendency in patients with obstructive jaundice

BACKGROUND & AIMS

Patients with obstructive jaundice (OJ) are considered to be prothrombotic with increased risk of thromboembolism complications. The role of neutrophil extracellular traps (NETs) in procoagulant activity (PCA) and thrombosis risk in patients with OJ is unclear. In this study, we investigated NETs formation in OJ patients and the role of elevated unconjugated bilirubin (UCB) in inducing NETs, resulting in enhanced PCA and endothelial injury.

METHODS

NETs of OJ patients and healthy controls were measured. NETs PCA was assessed via coagulation time (CT), fibrin formation and purified coagulation complex production assays. Visualization of NETs and mitochondrial reactive oxygen species (MitoROS) were performed with a fluorescence microscope. We further used confocal microscopy to quantify the exposure of phosphatidylserine (PS), fibrin strands and FVa/Xa on Human umbilical vein endothelial cells (HUVECs).

RESULTS

Assessment of NETs components levels revealed greater NETs production in OJ patients than in healthy controls. Importantly, OJ-NETs were responsible for enhanced PCA. UCB induced NETs formation via MitoROS accumulation and mitochondrial mobilization. HUVECs cocultured with OJ NETs lost their cell-cell junctions and consequently converted to a procoagulant phenotype. The PCA was attenuated by using DNase I alone or in combination with lactadherin.

CONCLUSIONS

Our results suggest that UCB-induced NETs play a prominent role in promoting the hypercoagulable and prothrombotic state in OJ patients. The increased MitoROS accumulation in neutrophils initiated NETosis. NETs are promising targets for indicating or improving coagulation disorders in OJ patients.