The role of bilirubin and its protective function against coronary heart disease

Role of bilirubin in the prognosis of coronary artery disease and its relationship with cardiovascular risk factors: a meta-analysis

Background

Bilirubin is a heme catabolism product with antioxidant, anti-inflammatory, and anti-apoptotic properties and is implicated in the prognosis of several diseases. This study evaluates the prognostic role of bilirubin in coronary artery disease (CAD) patients.

Methods

After identifying studies from the literature, meta-analyses were performed to achieve a) overall estimates of serum total bilirubin levels in patients with myocardial infarction (MI), non-MI CAD and healthy individuals; b) odds ratios (OR) of adverse outcomes between higher and lower total bilirubin levels; c) standardized mean difference (SMD) in total bilirubin levels in patients with high vs low CAD severity; and d) correlation between disease severity and total bilirubin. Metaregression analyses were performed to examine the relationship between cardiovascular risk factors and increasing quantiles of total bilirubin levels.

Results

Forty-three studies were identified. Pooled serum total bilirubin levels were 0.72 mg/dl [95% confidence interval (CI): 0.60, 0.83] in MI patients; 0.65 mg/dl [95% CI: 0.60, 0.69] in non-MI CAD patients; and 0.66 mg/dl [95% CI: 0.56, 0.75] in healthy individuals. Higher total bilirubin levels were associated with greater odds of adverse outcomes in MI patients (OR: 1.08 [95% CI: 0.99, 1.18]) but lower odds in non-MI CAD patients (OR: 0.80 [95%CI: 0.73, 0.88]). Compared to non-severe cases, total bilirubin levels were higher in patients with severe MI (SMD 0.96 [95% CI: − 0.10, 2.01]; p = 0.074) but were lower in severe non-MI CAD patients (SMD − 0.30 [95%CI: − 0.56, − 0.03]; p = 0.02). Total bilirubin levels correlated positively with MI severity (r = 0.41 [95% CI: 0.24, 0.59]; p < 0.01) but correlated negatively with non-MI CAD severity (r =  − 0.17 [95% CI: − 0.48, 0.14]; p = 0.28). Female sex was inversely associated with increasing quantiles of bilirubin (meta-regression coefficient: − 8.164 [− 14.531, − 1.769]; p = 0.016) in MI patients.

Conclusion

Prognostic role of bilirubin for CAD appears complicated, as different odds are observed for MI and non-MI CAD patients which weakens the case of causal involvement of bilirubin in CAD etiology or prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02899-w.

Serum Bilirubin Level as a Potential Marker for the Hearing Outcome in Severe-Profound Bilateral Sudden Deafness

Supplemental Digital Content is available in the text

Objective:

To investigate the association of serum bilirubin level with hearing outcomes in bilateral sudden sensorineural hearing loss (BSSHL) patients.

Participants:

One hundred thirteen in-patient BSSHL patients were consecutively enrolled between July 2008 and December 2015 in a tertiary center.

Main Outcome Measures:

Multivariable linear regression, generalized estimating equations (GEE), and stratified analyses were applied to examine the association between serum bilirubin level and hearing outcome measures such as final hearing threshold and absolute and relative hearing gains in BSSHL.

Results:

After full adjustment for potential confounders, total bilirubin levels (TBIL) were observed to be positively and independently associated with hearing outcomes as measured by final hearing (β [95% confidence interval {CI}]: −1.5 [−2.7, −0.2] dB HL per 1 μmol/L increase in TBIL) and absolute and relative hearing gains (β [95% CI]: 1.4 [0.2, 2.7] dB and 1.6 [0.2, 3.1] dB, respectively) in the severe to profound hearing loss subpopulation.

Conclusions:

Higher TBIL levels, within the normal or mildly elevated ranges, were independently and significantly associated with better hearing outcome in BSSHL patients with severe to profound hearing loss. Given bilirubin elevation treatments exist, our finding suggests a novel pharmacological strategy for this specific subpopulation.

Predicting value of white cell count and total bilirubin on clinical outcomes in patients with ST-elevation myocardial infarction following percutaneous coronary intervention: a cohort study

OBJECTIVES

A combined equation based on white cell count (WCC) and total bilirubin (TB) was assessed for its ability to predict adverse clinical outcomes in patients with acute ST-segment elevation myocardial infarction (STEMI) with primary percutaneous coronary intervention (PCI).

DESIGN

A single-centre, prospective cohort study.

SETTING

The First Affiliated Hospital of Xinjiang Medical University.

METHOD

A total of 615 patients with STEMI postprimary PCI were enrolled. WCC and TB were collected at admission. Logistic regression was used to determine the combined equation. The primary endpoints were in-hospital mortality and major adverse cardiovascular events (MACE), which composed of cardiac death, cardiac shock, malignant arrhythmia (ventricular tachycardia, ventricular fibrillation), severe cardiac insufficiency, non-fatal myocardial infarction, angina pectoris readmission, severe cardiac insufficiency (cardiac III-IV level), stent restenosis and target vessels revascularisation during the hospitalisation and 36 months follow-up period.

RESULT

77 patients occurred in MACE during the hospitalisation (17 in-hospital mortality). WCC and TB were taken as an independent variables to make a category of logistic regression analysis of in-hospital MACE, the logistic regression model was: logit (P)=-8.00+0.265 WCC+0.077 TB, the combination of WCC and TB was more valuable on evaluating the in-hospital mortality (area under the curve 0.804, 95% CI 0.678 to 0.929, p<0.001). Multivariate logistic regression analysis showed that combined detection was an independent risk factor for in-hospital MACE (OR 5.85, 95% CI 3.425 to 9.990, p=0.032). During the follow-up period, 172 patients (29.5%) developed MACE. But the combined detection did not predict the long-term clinical outcome.

CONCLUSION

The combination of WCC and TB is an independent predictor for in-hospital outcomes in patients with STEMI than single detection.

Blood levels of heme oxygenase-1 versus bilirubin in patients with coronary artery disease

OBJECTIVE

Heme oxygenase-1 (HO-1) degrades heme to CO, iron, and biliverdin/bilirubin. Although serum bilirubin levels were often reported in patients with coronary artery disease (CAD), HO-1 levels in patients with CAD and the association between HO-1 and bilirubin levels have not been clarified.

METHODS

We measured plasma HO-1 and serum total bilirubin levels in 262 patients undergoing coronary angiography.

RESULTS

HO-1 levels were higher in patients with CAD than without CAD (median 0.46 vs. 0.35 ng/mL, P < 0.01), but bilirubin were lower in patients with CAD than without CAD (0.69 vs. 0.75 mg/dL, P < 0.02). Notably, HO-1 levels in CAD(-), 1-vessel, 2-vessel, and 3-vessel disease were 0.35, 0.51, 0.45, and 0.44 ng/mL, and were highest in 1-vessel disease (P < 0.05). Bilirubin levels in CAD(-), 1-vessel, 2-vessel, and 3-vessel disease were 0.75, 0.70, 0.68, and 0.66 mg/dL (P = NS). No correlation was found between HO-1 and bilirubin levels. In multivariate analysis, HO-1 levels were a significant factor for CAD independent of atherosclerotic risk factors and bilirulin levels. Odds ratio for CAD was 2.32 (95%CI = 1.29-4.17) for high HO-1 (>0.35 ng/mL).

CONCLUSIONS

Patients with CAD were found to have high HO-1 and low bilirubin levels in blood, but no correlation was found between HO-1 and bilirubin levels.

Serum Total Bilirubin Levels Provide Additive Risk Information over the Framingham Risk Score for Identifying Asymptomatic Diabetic Patients at Higher Risk for Coronary Artery Stenosis

BACKGROUND

The diagnosis of coronary artery disease (CAD) is often delayed in patients with type 2 diabetes. Serum total bilirubin levels are inversely associated with CAD. However, no studies have examined whether this can be used as a biochemical marker for identifying asymptomatic diabetic patients at higher risk for having obstructive CAD.

METHODS

We performed a cross-sectional study of 460 consecutive asymptomatic patients with type 2 diabetes. All patients underwent coronary computed tomographic angiography, and their serum total bilirubin levels were measured. Obstructive CAD was defined as ≥50% diameter stenosis in at least one coronary artery.

RESULTS

Serum total bilirubin tertiles showed an inverse association with the prevalence of obstructive CAD. In multivariate logistic regression analysis, the odds ratio for the highest versus the lowest tertile of total bilirubin was 0.227 (95% confidence interval [CI], 0.130 to 0.398), and an increment of 1 µmol/L in serum total bilirubin level was associated with a 14.6% decrease in obstructive CAD after adjustment for confounding variables. Receiver operating characteristic curve analysis showed that the area under the curve for the Framingham Risk Score (FRS) plus serum total bilirubin level was 0.712 (95% CI, 0.668 to 0.753), which is significantly greater than that of the FRS alone (P=0.0028).

CONCLUSION

Serum total bilirubin level is inversely associated with obstructive CAD and provides additive risk information over the FRS. Serum total bilirubin may be helpful for identifying asymptomatic patients with type 2 diabetes who are at higher risk for obstructive CAD.

A novel predictor of infarct-related artery patency before percutaneous intervention and in-hospital outcomes for ST-segment elevation myocardial infarction patients: serum bilirubin level

Introduction

Previous studies have reported a relationship between serum bilirubin levels and coronary artery disease (CAD). However, data are rare up to now regarding the relation of bilirubin levels with infarct-related artery (IRA) patency in the setting of ST-segment elevation myocardial infarction (STEMI). Moreover, previous studies reported that increased bilirubin was related to impaired post-intervention coronary flow. To our knowledge, the association between serum total bilirubin (TB) levels and pre-primary percutaneous coronary intervention (PCI) with patency of IRA flow in STEMI patients has not been investigated.

Aim

To evaluate the association of TB with pre-primary PCI, coronary flow and in-hospital major adverse cardiac events (MACE) in patients with STEMI.

Material and methods

A total of 360 consecutive patients with STEMI (mean age = 61.4 ±13.7 years) admitted within 12 h from the time of symptom onset were enrolled. Patients were divided into 2 groups based on the serum TB levels. We defined normal flow as pre-PCI TIMI 3 flow, while impaired flow was defined as pre-PCI TIMI ≤ 2 flow.

Results

Pre-PCI impaired flow was higher in the TB group than pre-PCI normal flow (p < 0.001). In-hospital mortality and MACE were significantly higher in the high TB group (p = 0.002, p < 0.001 respectively). In the receiver operating characteristic curve analysis, TB > 0.825 mg/dl predicted impaired IRA flow before p-PCI with a sensitivity of 79% and specificity of 71%.

Conclusions

The TB is an inexpensive and readily available marker for STEMI patients undergoing PCI. It can be used for risk stratification in this patient population.

Atherogenesis and iron: from epidemiology to cellular level

Iron accumulates in human atherosclerotic lesions but whether it is a cause or simply a downstream consequence of the atheroma formation has been an open question for decades. According to the so called "iron hypothesis," iron is believed to be detrimental for the cardiovascular system, thus promoting atherosclerosis development and progression. Iron, in its catalytically active form, can participate in the generation of reactive oxygen species and induce lipid-peroxidation, triggering endothelial activation, smooth muscle cell proliferation and macrophage activation; all of these processes are considered to be proatherogenic. On the other hand, the observation that hemochromatotic patients, affected by life-long iron overload, do not show any increased incidence of atherosclerosis is perceived as the most convincing evidence against the "iron hypothesis." Epidemiological studies and data from animal models provided conflicting evidences about the role of iron in atherogenesis. Therefore, more careful studies are needed in which issues like the source and the compartmentalization of iron will be addressed. This review article summarizes what we have learnt about iron and atherosclerosis from epidemiological studies, animal models and cellular systems and highlights the rather contributory than innocent role of iron in atherogenesis.

Bilirubin levels and their association with carotid intima media thickness and high-sensitivity C-reactive protein in patients with psoriasis vulgaris

BACKGROUND

Psoriasis vulgaris is associated with an increased risk of atherosclerosis. Carotid intima-media thickness (cIMT) may predict atherosclerosis.

AIMS

We assessed the correlation between bilirubin (a potent endogenous antioxidant) levels and cIMT in patients with psoriasis vulgaris. We also compared the levels of serum total bilirubin (TBil) and its fractions in control subjects and patients with psoriasis.

METHODS

We enrolled 115 participants (60 patients with psoriasis vulgaris and 55 control subjects). The levels of indirect bilirubin were calculated as the difference between TBil and direct bilirubin values. cIMT was measured in both common carotid arteries.

RESULTS

TBil levels were lower in patients with psoriasis than in the control group [median (range) 0.55 (0.30-1.23) vs. 0.59 (0.30-1.44) mg/dL] as were indirect bilirubin [0.43 (0.22-1.00) vs. 0.48 (0.25-1.12) mg/dL] and direct bilirubin [0.10 (0.01-0.23) vs. 0.13 (0.03-0.32) mg/dL]. Only direct bilirubin differed significantly (p=0.0002) but the number of patients with higher values of TBil and indirect bilirubin were significantly greater in the control group (p=0.0019 by the Fisher's test). The patients with psoriasis had a significantly greater cIMT compared with control subjects (0.54±0.08 vs. 0.50±0.07 mm, p=0.005). High-sensitivity C-reactive protein levels were higher in patients with psoriasis compared with controls (2.95±3.50 and 0.99±0.72 mg/L, p<0.001). There was a negative correlation between cIMT and TBil levels (r=-0.383, p<0.01). The results of the correlations were reinforced by multiple regression analysis.

CONCLUSION

To our knowledge, this is the first study to assess the association between TBil and cIMT in patients with psoriasis. Our results support the concept that psoriasis vulgaris is associated with an increased risk of atherosclerosis.