Association between serum bilirubin and asymptomatic intracranial atherosclerosis: results from a population-based study

Exploring the adverse effects of 1,3,6,8-tetrabromo-9H-carbazole in atherosclerotic model mice by metabolomic profiling integrated with mechanism studies in vitro

Given its wide distribution in the environment and latent toxic effects, 1,3,6,8-tetrabromo-9H-carbazole (1368-BCZ) is an emerging concern that has gained increasing attention globally. 1368-BCZ exposure is reported to have potential cardiovascular toxicity. Although atherosclerosis is a cardiovascular disease and remains a primary cause of mortality worldwide, no evidence has been found regarding the impact of 1368-BCZ on atherosclerosis. Therefore, we aimed to explore the deleterious effects of 1368-BCZ on atherosclerosis and the underlying mechanisms. Serum samples from 1368-BCZ-treated atherosclerotic model mice were subjected to metabolomic profiling to investigate the adverse influence of the pollutant. Subsequently, the molecular mechanism associated with the metabolic pathway of atherosclerotic mice that was identified following 1368-BCZ exposure was validated in vitro. Serum metabolomics analysis revealed that 1368-BCZ significantly altered the tricarboxylic acid cycle, causing a disturbance in energy metabolism. In vitro, we further validated general markers of energy metabolism based on metabolome data: 1368-BCZ dampened adenosine triphosphate (ATP) synthesis and increased reactive oxygen species (ROS) production. Furthermore, blocking the aryl hydrocarbon receptor (AhR) reversed the high production of ROS induced by 1368-BCZ. It is concluded that 1368-BCZ decreased the ATP synthesis by disturbing the energy metabolism, thereby stimulating the AhR-mediated ROS production and presumably causing aggravated atherosclerosis. This is the first comprehensive study on the cardiovascular toxicity and mechanism of 1368-BCZ based on rodent models of atherosclerosis and integrated with in vitro models.

Inflammation, Dopaminergic Brain and Bilirubin

Dopamine is a well-known neurotransmitter due to its involvement in Parkinson's disease (PD). Dopamine is not only involved in PD but also controls multiple mental and physical activities, such as the pleasure of food, friends and loved ones, music, art, mood, cognition, motivation, fear, affective disorders, addiction, attention deficit disorder, depression, and schizophrenia. Dopaminergic neurons (DOPAn) are susceptible to stressors, and inflammation is a recognized risk for neuronal malfunctioning and cell death in major neurodegenerative diseases. Less is known for non-neurodegenerative conditions. Among the endogenous defenses, bilirubin, a heme metabolite, has been shown to possess important anti-inflammatory activity and, most importantly, to prevent DOPAn demise in an ex vivo model of PD by acting on the tumor necrosis factor-alpha (TNFα). This review summarizes the evidence linking DOPAn, inflammation (when possible, specifically TNFα), and bilirubin as an anti-inflammatory in order to understand what is known, the gaps that need filling, and the hypotheses of anti-inflammatory strategies to preserve dopamine homeostasis with bilirubin included.

Associations of hematological and biochemical markers with intracranial atherosclerotic stenosis in stroke-free populations: A systematic review and meta-analysis of observational studies

BACKGROUND AND AIMS

Intracranial atherosclerotic stenosis (ICAS) is an important cause of ischemic stroke and transient ischemic attack. We aimed to synthesize relevant evidence on the associations of hematological and biochemical markers with ICAS in stroke-free populations.

METHODS AND RESULTS

We searched MEDLINE and EMBASE for articles reporting associations of hematological and biochemical markers with ICAS presence in stroke-free populations. Weighted mean difference (WMD) and 95% confidence interval (CI) for each biomarker were pooled using fixed- or random-effects models. Among 32 studies included in the systematic review, 23 studies (48,326 subjects) with 22 biomarkers were meta-analyzed. Compared with subjects without ICAS, those with ICAS had significantly higher white blood cell (4118 subjects, WMD 0.28 per 10⁹/L, 95% CI 0.01-0.56), neutrophil (4326 subjects, WMD 0.24 per 10⁹/L, 0.10-0.38), neutrophil/lymphocyte ratio (4326 subjects, WMD 0.16, 0.07-0.26), low-density lipoprotein (28,606 subjects, WMD 0.12 mmol/L, 0.05-0.19), non-high-density lipoprotein (3671 subjects, WMD 0.17 mmol/L, 0.08-0.25), C-reactive protein (CRP; 5355 subjects, WMD 0.06 mg/dL, 0.04-0.07), high-sensitivity CRP (9383 subjects, WMD 0.07 mg/dL, 0.01-0.13), uric acid (5966 subjects, WMD 17.91 μmol/L, 11.16-24.66), creatinine (5731 subjects, WMD 4.03 μmol/L, 0.77-7.29), and homocysteine (7053 subjects, WMD 2.25 μmol/L, 1.02-3.48), but lower lymphocyte (4326 subjects, WMD -0.12 per 10⁹/L, -0.19--0.04). Sensitivity analyses showed similar results.

CONCLUSIONS

Several hematological and biochemical markers easily accessible were associated with ICAS presence in stroke-free populations. This can facilitate early identification of subjects at a high risk of ICAS, who may benefit from ICAS screening and prevention.

PROSPERO REGISTRATION NUMBER

CRD42021247990.

Longitudinal Associations Between Serum Bilirubin Level and Carotid Atherosclerosis Plaque in a Health Screening Population

This study aimed to determine the relationship between bilirubin levels and carotid atherosclerosis (CAS) in the health screening population. After propensity score matching, this retrospective cohort study included 4360 subjects who underwent health examinations regularly in Hebei General Hospital between January 2010 and December 2019 and had no carotid plaque at baseline. After an average follow-up of 26.76 months, the main endpoint Cox regression analysis of carotid plaques was performed. After adjusting the confounding factors, Cox regression analysis showed that when serum total bilirubin (TBIL) and unconjugated bilirubin (UCB) increased by 1 standard deviation (SD), the risk of carotid plaque decreased by 7.30% (95% confidence interval (CI): 2.80-11.60%) and 15.70% (95% CI: 11.40-19.80%), respectively. When conjugated bilirubin (CB) increased by 1 SD, the risk of carotid plaques increased by 24.3% (95% CI: 19.7-29.0%). TBIL and UCB levels were negatively associated with CAS, and CB levels were positively associated with CAS.

Endothelial Dysfunction and Endocan Levels in Patients with Gilbert Syndrome and Moderate Hyperbilirubinemia

In this study, we aim to evaluate the presence of endothelial dysfunction in Gilbert syndrome patients with left ventricular mass index (LVMI) and endocan levels. The study included 60 patients who diagnosed with Gilbert syndrome and 60 healthy controls who did not have any known diseases. Human endocan levels were measured using a sandwich ELISA method. The endocan and LVMI levels were lower in the Gilbert syndrome group than in the healthy controls. In the Gilbert syndrome group, total bilirubin level was negatively correlated with LVMI (r = -0246; P = .007) and endocan levels (r = -.270; P = .046). In the Gilbert syndrome group, increasing age (β ± SE = 20.78 ± 7.47; P = .006), was a positive independent predictor of LVMI, and increasing high-density lipoprotein cholesterol (HDL-C) (β ± SE = -.27 ± .09; P = .007), and total bilirubin levels (β ± SE = -6.09 ± 3.02; P = .046) were found to be a negative independent predictor. These results support that endothelial dysfunction is decreased in Gilbert Syndrome patients with mild hyperbilirubinemia compared with the healthy control group.

Serum Bilirubin Levels and Extent of Symptomatic Intracranial Atherosclerotic Stenosis in Acute Ischemic Stroke: A Cross-Sectional Study

Background: Bilirubin plays a paradoxical role in the pathological mechanism of stroke. To date, few clinical studies have investigated the effect of serum bilirubin on symptomatic intracranial atherosclerotic stenosis (sICAS). This study aims to evaluate the connection between serum bilirubin and sICAS.

Methods: From September 2015 to May 2020, 1,156 sICAS patients without hepatobiliary diseases admitted to our hospital were included. Patients were distributed into none-mild (0–49%), moderate (50–69%) and severe-occlusion sICAS groups (70–100%) by the degree of artery stenosis. Moderate and severe-occlusion sICAS patients were classified into three groups by the number of stenotic arteries (single-, two- and multiple-vessel stenosis). The relationship between serum bilirubin levels and sICAS was analyzed by logistic regression analysis.

Results: In univariable analyses, sICAS patients with severe and multiple atherosclerotic stenoses had lower levels of total bilirubin (Tbil), direct bilirubin (Dbil), and indirect bilirubin (Ibil). In multinomial logistic regression analyses, when compared with the highest tertile of bilirubin, lower levels of Tbil, Dbil, and Ibil showed higher risks of severe-occlusion sICAS (95% CI: 2.018–6.075 in tertile 1 for Tbil; 2.380–7.410 in tertile 1 for Dbil; 1.758–5.641 in tertile 1 for Ibil). Moreover, the logistic regression analyses showed that lower levels of Tbil, Dbil, and Ibil were related to multiple (≥3) atherosclerotic stenoses (95% CI: 2.365–5.298 in tertile 1 and 2.312–5.208 in tertile 2 for Tbil; 1.743–3.835 in tertile 1 and 1.416–3.144 in tertile 2 for Dbil; 2.361–5.345 in tertile 1 and 1.604–3.545 in tertile 2 for Ibil) when compared with tertile 3.

Conclusions: Our findings suggest that lower bilirubin levels may indicate severe and multiple intracranial atherosclerotic stenoses.

Decreased Serum Total Bilirubin Level Predicts Early Neurological Deterioration in Patients with Acute Ischemic Stroke

OBJECTIVE

This study aimed to investigate the relationship between serum total bilirubin (TBil) level and early neurological deterioration (END) in patients with acute ischemic stroke of large artery atherosclerosis.

PATIENTS AND METHODS

In this retrospective study, a total of 291 patients with acute ischemic stroke were enrolled. The demographic and laboratory dates were collected. Stroke severity had been assessed using the National Institutes of Health Stroke Scale (NIHSS). Multivariable logistic regression was used to examine the independent association between TBil and END.

RESULTS

Approximately 63 (21.6%) of the patients were diagnosed with END within the first seven days. The proportion of hypertension, diabetes mellitus (DM) and previous stroke/transient ischemic attack (TIA) was significant greater in the lowest quartile (<9.8 μmol/l) of TBil. The proportion of patients with an elevated TBil levels was significantly lower in the END group than in the non-END group. After controlling for covariates, the first quartiles (<9.8 μmol/l) of TBil were still associated with END. In addition, an increased level of CRP and age were also associated with an increased risk of END.

CONCLUSION

The TBil levels in patients with acute cerebral infarction may be a useful biomarker for the prediction of END.

The Role of Bilirubin and the Other "Yellow Players" in Neurodegenerative Diseases

Bilirubin is a yellow endogenous derivate of the heme catabolism. Since the 1980s, it has been recognized as one of the most potent antioxidants in nature, able to counteract 10,000× higher intracellular concentrations of H2O2. In the recent years, not only bilirubin, but also its precursor biliverdin, and the enzymes involved in their productions (namely heme oxygenase and biliverdin reductase; altogether the "yellow players"-YPs) have been recognized playing a protective role in diseases characterized by a chronic prooxidant status. Based on that, there is an ongoing effort in inducing their activity as a therapeutic option. Nevertheless, the understanding of their specific contributions to pathological conditions of the central nervous system (CNS) and their role in these diseases are limited. In this review, we will focus on the most recent evidence linking the role of the YPs specifically to neurodegenerative and neurological conditions. Both the protective, as well as potentially worsening effects of the YP's activity will be discussed.