High serum bilirubin is associated with lower prevalence of peripheral arterial disease among cardiac patients

The Metabolic Characteristics of Patients at the Risk for Diabetic Foot Ulcer: A Comparative Study of Diabetic Patients with and without Diabetic Foot

Backgrounds and Objective

Diabetic foot is a relatively severe complication in patients with type 2 diabetes (T2D), with peripheral neuropathy and angiopathy frequently serving as risk factors. However, it is unknown how the other major systemic metabolic factors impacted the profile of these patients, besides glucose management. Thus, we investigated the distinct characteristics of patients with diabetic foot ulcers and their relationships with angiopathy.

Materials and Methods

We obtained the laboratory data of 334 diabetic patients at Shanghai Pudong Hospital from 2020 to 2023. The comparisons were performed between the groups with or without diabetic foot, including glucose metabolism, lipids profile, liver and kidney function, thyroid function, and serum iron. The association between metabolic factors and lower extremity computed tomography angiography (CTA) was analyzed.

Results

We found significant disparities between groups in relation to age, serum protein content, liver transferase, serum creatinine, estimated glomerular filtration rate (eGFR), serum uric acid (UA), small dense low-density lipoprotein (sdLDL), lipoprotein A (LP(a)), apolipoprotein A1 (APOA1), thyroid function, serum iron, and hemoglobin (Hb) (p<0.05). The Spearman correlational analyses showed that the severity of CTA, categorized by the unilateral or bilateral plaque or occlusion, was positively significantly correlated with UA (r=0.499), triglyceride (TG) (r=0.751), whereas inversely correlated with serum albumin (r=-0.510), alanine aminotransferase (r=-0.523), direct bilirubin (DBil) (r=-0.494), total bilirubin (TBil) (r=-0.550), Hb (r=-0.646).

Conclusion

This cross-section investigation showed that compared to T2D only, the patients with diabetic foot ulcer (DFU) might display similar glucose metabolic control context but adverse metabolic profiles, and this profile is associated with macrovascular angiopathy characteristics and their severity.

Toward nanotechnology-enabled application of bilirubin in the treatment and diagnosis of various civilization diseases

Bilirubin, an open chain tetrapyrrole, has powerful antioxidant, anti-inflammatory, immuno-suppressive, metabolic-modulating and anti-proliferative activities. Bilirubin is a natural molecule that is produced and metabolized within the human body, making it highly biocompatible and well suited for clinical use. However, the use of bilirubin has been hampered by its poor water solubility and instability. With advanced construction strategies, bilirubin-derived nanoparticles (BRNPs) have not only overcome the disadvantages of bilirubin but also enhanced its therapeutic effects by targeting damaged tissues, passing through physiological barriers, and ensuring controlled sustained release. We review the mechanisms underlying the biological activities of bilirubin, BRNP preparation strategies and BRNP applications in various disease models. Based on their superior performance, BRNPs require further exploration of their efficacy, biodistribution and long-term biosafety in nonhuman primate models that recapitulate human disease to promote their clinical translation.

High-normal serum bilirubin decreased the risk of lower limb atherosclerosis in type 2 diabetes: a real-world study

BACKGROUND

Bilirubin has been found to protect against overt atherosclerotic diseases, but to date, few studies have investigated the effects of bilirubin especially within the normal range on lower limb atherosclerosis. Therefore, we aimed to assess the associations of bilirubin within normal limits including total bilirubin (TB), conjugated bilirubin (CB) and unconjugated bilirubin (UCB) with lower limb atherosclerosis in Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

7284 T2DM patients with normal levels of serum bilirubin were included in this cross-sectional, real-world study. Patients were divided into quintiles by TB levels (< 8.7, 8.7-10.19, 10.20-11.99, 12-13.99, > 13.99 µmol/L). Lower limb ultrasonography was conducted to detect lower limb plaque and stenosis. The association between serum bilirubin and lower limb atherosclerosis was explored by multiple logistic regression.

RESULTS

A remarkable decrease in the prevalence of lower limb plaque (77.5, 75.3, 70.7, 71.7 and 67.9%) and stenosis (21.1, 17.2, 13.3, 13.0 and 12.0%) was observed across the TB quintiles. Multivariable regression analysis showed that serum TB levels were negatively correlated with higher risks of lower limb plaque and stenosis, both as a continuous variable [OR (95%CI): 0.870 (0.784-0.964), p = 0.008 for plaque; and 0.835 (0.737-0.946), p = 0.005 for stenosis] and as categorized in quintiles (p = 0.015 and 0.016 for plaque and stenosis). Interestingly, serum CB levels were only negatively correlated with lower limb stenosis [OR (95%CI): 0.767 (0.685-0.858), p < 0.001], whereas serum UCB levels were only negatively associated with lower limb plaque [ OR (95%CI): 0.864 (0.784-0.952), p = 0.003] after a fully-adjusted analysis. Furthermore, serum CRP was significantly decreased across the TB quintiles and negatively associated with serum TB (r = -0.107, p < 0.001), CB (r = -0.054, p < 0.001), and UCB (r = -0.103, p < 0.001).

CONCLUSIONS

High-normal serum bilirubin levels were independently and significantly related to reduced risks of lower limb atherosclerosis in T2DM patients. Furthermore, serum bilirubin levels including TB, CB and UCB were inversely correlated with CRP. These results suggested that higher-normal serum bilirubin may exhibit an anti-inflammatory and protective effect against lower limb atherosclerotic progression in T2DM subjects.

Association Between Serum Bilirubin, Lipid Levels, and Prevalence of Femoral and Carotid Atherosclerosis: A Population-Based Cross-Sectional Study

BACKGROUND

Bilirubin may prevent lipid peroxidation and have important antiatherosclerotic effects. We determined associations of serum bilirubin and lipid with peripheral atherosclerosis.

METHODS

We included 4290 participants (35% men; median age, 60 years) from the southeast China who underwent B-mode ultrasound examination. Increased intima-media thickness or a focal structure encroaching into the arterial lumen by at least 0.5 mm or >50% of the surrounding intima-media thickness value was regarded as having atherosclerosis. Fasting serum bilirubin and lipid levels were measured. Cholesterol/(HDL [high-density lipoprotein] cholesterol+bilirubin), and LDL (low-density lipoprotein cholesterol)/(HDL+bilirubin) ratios were calculated. Unconditional and multinomial logistic regression models were used to examine associations of bilirubin or lipid with prevalence of peripheral atherosclerosis. Mediation analyses were performed to assess the effect of bilirubin on atherosclerosis risk mediated via lipid.

RESULTS

Compared with participants with the lowest levels of bilirubin, those with the highest tertile were less likely to have carotid or femoral atherosclerosis (odds ratios were 0.55-0.74). The highest levels of bilirubin significantly reduced the odds of concurrent carotid and femoral atherosclerosis by 35% to 45%. Participants with the highest levels of cholesterol, LDL, cholesterol/(HDL+bilirubin), and LDL/(HDL+bilirubin) ratios had 2.8- to 3.7-fold increased odds of concurrent carotid and femoral atherosclerosis. LDL accounted for 25.65% of the total bilirubin-atherosclerosis association. LDL and cholesterol mediated the associations between direct bilirubin and atherosclerosis (proportion: 20.40%, 9.67%, respectively).

CONCLUSIONS

Increased serum bilirubin levels are inversely associated with the prevalence of carotid or femoral atherosclerosis. LDL and cholesterol may mediate these associations.

Association between total bilirubin and bone mineral density level in adolescents

Background

Increasing bone mass accumulation in adolescence and obtaining greater peak bone mass is one of the effective methods to prevent osteoporosis in the future. We aimed to examine the association between total bilirubin and bone mineral density (BMD) level in adolescents.

Methods

We used the data from 2005–2010 and 2013–2014 cycles of National Health and Nutrition Examination Survey (NHANES). The BMD levels in the region of lumbar spine and femoral regions, including total femur, femoral neck, trochanter, and intertrochanter were measured. Univariable and multivariable linear regression model were used to assess the relationship between total bilirubin concentration and BMD.

Results

A total of 3741 participants aged 12–19 years were ultimately included in the study. There were 1997 (53.38%) males and 1744 (46.62%) females. Univariate analysis results showed that age, sex, race, education, income, body mass index, dietary calcium intake, and diabetes were correlated with BMD levels. Compared with the lowest quartile of total bilirubin concentration, the highest quartile of total bilirubin concentration was positively associated with BMD levels in the regions of total femur (β = 0.036, 95% CI = 0.021 to 0.050, P < 0.001), femur neck (β = 0.030, 95% CI = 0.016 to 0.044, P < 0.001), trochanter (β = 0.033, 95% CI = 0.019 to 0.046, P < 0.001), intertrochanter (β = 0.040, 95% CI = 0.023 to 0.056, P < 0.001), and lumbar spine (β = 0.032, 95% CI = 0.018 to 0.045, P < 0.001). We also observe the same trend in sensitivity analysis (P for trend < 0.001).

Conclusion

Our study demonstrated that total bilirubin concentration was positively associated with BMD levels in adolescents in United States. Total bilirubin concentration might be a protective marker against bone loss in adolescents.

Association of Plasma Bilirubin Levels With Peripheral Arterial Disease in Chinese Hypertensive Patients: New Insight on Sex Differences

Background and aims: Previous studies have indicated that Plasma total bilirubin (TBiL) might play an essential role in peripheral arterial disease (PAD). However, the effects of different levels of TBiL on PAD development remain uncertain. We aimed to examine the TBiL and the prevalence of PAD among Chinese adults with hypertension, with particular attention paid to sex differences.

Methods: A total of 10,900 hypertensive subjects were included in the current study. The mean age of our study participants was 63.86 ± 9.25 years, and there were 5,129 males and 5,771 females. The outcome was peripheral arterial disease (PAD), defined as present when the ankle-brachial index (ABI) of either side was ≤0.90. The association between TBiL and PAD was examined using multivariate logistic regression analysis and the restricted cubic spline.

Results: Of 10,900 hypertensive participants, 350 (3.21%) had PAD, and the mean plasma total bilirubin was 14.66 (6.86) μmol/L. The mean TBiL was 15.67 μmol/L in men and 13.76 μmol/L in women. The smoothing curve showed that a U-shaped curve association existed between TBiL and the prevalence of PAD in Chinese adults with hypertension. When stratified by sex, TBiL was significantly U-shaped associated with PAD among men but not women. Among males, the inflection point was 11.48 μmol/L; to the left inflection point, the effect size and 95% CI were 0.08, 0.01, 0.66, respectively; to the right inflection point, OR, 5.16; 95% CI,1.64, 16.25.

Conclusions: We found an independent U-shaped association between TBiL and the prevalence of PAD among hypertensive subjects and a differential association between men and women. We further revealed a turning point by threshold effect analysis.

The Nonlinear Relationship Between Total Bilirubin and Coronary Heart Disease: A Dose-Response Meta-Analysis

Background: Evidence suggests that the total bilirubin has a protective effect on coronary heart disease (CHD), but the dose-response relationship remains controversial, and there is no meta-analysis to assess the relationship.

Methods: As of October 1, 2021, relevant literature was selected from four databases (PubMed, Web of Science, Cochrane Library, and Embase) by using a retrieval strategy. The dose-response curve between the total bilirubin and CHD was fitted by a restricted cubic spline. Stata 12.0 was used for statistical analysis.

Results: A total of 170,209 (6,342 cases) participants from 7 prospective studies were analyzed in our meta-analysis. We calculated the pooled relative risks (RRs) and 95% CIs for the association between serum bilirubin level and risk of CHD using random-effects models. Compared with the first quantile, the bilirubin level in the third quantile had a protective effect on the risk of CHD (RR, 0.90; 95% CI, 0.82–0.99). The restricted cubic spline functions depicted a U-type curve relationship between bilirubin (3.42–49 μmol/L) and CHD (P_linear < 0.001). When the bilirubin level was in the range of 3.42–13μmol/L, the protective effect of bilirubin on CHD was enhanced with increasing bilirubin levels. When the bilirubin level exceeded 13μmol/L, the protective effect of bilirubin weakened, and a dangerous effect gradually appeared with further increases in bilirubin levels.

Conclusions: Compared with a low bilirubin level, a high bilirubin level has a protective effect on the risk of CHD, and there was a U-shaped dose-response relationship between them.

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.

Association of Mild Hyperbilirubinemia with Decreased ECG-Based Ventricular Repolarization Parameters in Young Men

OBJECTIVE

Hyperbilirubinemia is associated with protection against various oxidative stress-mediated diseases. We aimed to investigate the association between bilirubin and novel electrocardiography (ECG)-based ventricular repolarization parameters.

METHODS

We enrolled 201 healthy men with mild hyperbilirubinemia (group 1) and 219 healthy men with normal bilirubin levels (group 2). The Tpeak-Tend (Tp-e) interval (defined as the interval from the peak of the T wave to the end of the T wave), corrected (c) Tp-e interval, QT interval, cQT interval, and Tp-e interval/QT interval ratio were measured from leads V5 and V6 with 20 mm/mV amplitude and 50 mm/second rate.

RESULTS

The Tp-e interval, cTp-e interval, and Tp-e interval/QT interval ratio were significantly lower in group 1 compared with group 2. The cTp-e interval showed a significant negative correlation with total bilirubin, conjugated bilirubin, and unconjugated bilirubin. The cTp-e interval (odds ratio [OR], 0.900; P =.002) and Tp-e interval/QT interval ratio (OR, 0.922; P =.04) were significantly associated with mild hyperbilirubinemia.

CONCLUSION

We showed the association of mild hyperbilirubinemia with decreased novel ECG-based ventricular repolarization parameters.

The Relationship Between Serum Bilirubin Levels and Peripheral Arterial Disease and Gender Difference in Patients With Hypertension: BEST Study

We evaluated the relationship between serum bilirubin levels and ankle-brachial index (ABI) to determine whether gender affected the relationship between bilirubin levels and peripheral arterial disease (PAD) in patients with hypertension. A total of 543 patients were included in our studies (78 patients with PAD and 465 without PAD). Peripheral arterial disease was defined as ABI <0.90 for either and/or both sides. Serum bilirubin levels were measured with a vanadate oxidation method by using fasting venous blood samples. Serum total bilirubin (TBiL) and direct bilirubin (DBiL) levels were higher in males compared with females (both P < .05). Total bilirubin and DBiL were significantly lower in the PAD group. After adjustment for cardiovascular risk factors, PAD was independently negatively related to TBiL and DBiL, with odds ratios (OR) 0.914 (95% confidence interval [CI]: 0.845-0.990) and 0.748 (95% CI: 0.572-0.977). In addition, there was a relationship between PAD and bilirubin levels (TBiL-OR = 0.884, 95% CI: 0.792-0.985; DBiL-OR = 0.621; 95% CI: 0.424-0.909) only in males but not in females. Future studies should further evaluate whether interventions that increase serum bilirubin levels will have a particular role in PAD prevention in males.

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

INTRODUCTION

The effects of bilirubin on asymptomatic intracranial atherosclerosis (aICAS) remain uncertain.

OBJECTIVES

To investigate the association between bilirubin and aICAS in rural-dwelling Chinese people.

METHODS

This population-based study included 2013 participants from the Kongcun Town Study, which aimed to investigate the prevalence of aICAS in people aged ≥ 40 years who were free of stroke and hepatic and gall disease history. Baseline data were collected via interviews, clinical examinations, and laboratory tests. Total bilirubin (Tbil), direct bilirubin (Dbil), and indirect bilirubin (Ibil) levels were divided into high-concentration group and low-concentration group, respectively. We diagnosed aICAS and moderate-to-severe aICAS (m-saICAS) (≥ 50% stenosis) by integrating transcranial Doppler ultrasound with magnetic resonance angiography. The association between bilirubin and aICAS, as well as m-saICAS, was analyzed using logistic regression.

RESULTS

Of the 2013 participants, those in the high-concentration group of Tbil (odds ratio (OR), 0.50; 95% confidence interval (CI), 0.42-0.87), Dbil (OR 0.60, 95%CI 0.41-0.87), and Ibil (OR 0.67; 95%CI 0.47-0.97) had a lower risk of aICAS than those in the low-concentration group after adjusting all confounders. The high concentrations of Tbil, Dbil, and Ibil were also negatively associated with m-saICAS. After stratification according to age, Tbil, Dbil, and Ibil were significantly negatively associated with aICAS among participants aged ≥ 60 years.

CONCLUSION

Tbil, Dbil, and Ibil might be independent protective factors for aICAS and moderate-to-severe aICAS in rural-dwelling Chinese people, especially among older participants aged ≥ 60 years.

Bilirubin Safeguards Cardiorenal and Metabolic Diseases: a Protective Role in Health

PURPOSE OF REVIEW

To discuss recent advances indicating that bilirubin safeguards against cardiorenal and metabolic diseases.

RECENT FINDINGS

Several investigations from human patient populations and experimental animal models have shown that bilirubin improves cardiorenal and metabolic dysfunction. The latest studies found an entirely new function of bilirubin suggesting that it acts as a hormone signaling molecule capable of activating nuclear receptors for burning fat, which may explain several of its protective actions. This review highlights the current findings (within the last 3 years) regarding cardiorenal and metabolic protective effects of bilirubin and the latest mechanism(s) that may be mediating these effects.

Is serum total bilirubin a predictor of prognosis in arteriosclerotic cardiovascular disease? A meta-analysis

The protective role of serum total bilirubin, a widely recognized antioxidant, has been approved by numerous updating studies. However, regarding the effect of high serum total bilirubin level (STBL) in arteriosclerotic cardiovascular disease (ASCVD) are conflicting in different sources of data. We, therefore, performed this meta-analysis to evaluate the influence of STBL on risk of ASCVD.Four databases were used to identify the literature with a date of search of January, 2019. Finally, a total of 20 studies had been adopted. ASCVD was defined as acute coronary syndrome, stable angina, coronary revascularization, atherosclerotic stroke or transient ischemic attack, and peripheral arterial disease (PAD). All relevant data were collected from studies meeting the inclusion criteria.A total of 20 published studies (323,891 cases) met the inclusion criteria. The meta-analysis revealed that, in studies excluding heterogeneity, STBL was significantly positively related to in-hospital cardiovascular mortality (odds ratio [OR] 2.82, 95% confidence interval [CI] 1.83-4.36, Z = 4.69, P < .001) and major adverse cardiac events (OR 1.88, 95% CI 1.414-2.491, Z = 4.36, P < .001), also negatively associated with prognosis of acute myocardial infarction, pooled hazard ratio (HR) = 0.804 (95% CI 0.700-0.923, Z = 3.08, P = .002). The correlation similarity was also reflected in terms of patients with stroke (HR 0.78, 95% CI 0.70-0.88, Z = 4.24, P = .003). Combined analysis revealed that lower STBL was significantly associated with PAD, pooled OR = 0.91 (95% CI 0.85-0.98, Z = 2.39, P = .017). In general analysis, a conclusion can be drawn, that higher STBL was significantly negative correlated with cardiovascular disease, pooled HR = 0.83 (95% CI 0.73-0.94, Z = 3.02, P = .003).Higher STBL significantly improved the prognosis of ASCVD; furthermore, STBL was an important factor in the long-term prognosis of vascular-related disease prevention and can be used as a predictor in vascular-related disease risk prediction.

Serum Bilirubin and Coronary Artery Disease: Intricate Relationship, Pathophysiology, and Recent Evidence

Coronary artery disease (CAD) is a major cause of morbidity, mortality, and healthcare expenditure. A number of environmental and genetic risk factors have been known to contribute to CAD. More recently, a number of studies have supported as well as opposed a possible protective benefit of bilirubin in CAD, since it has anti-inflammatory, antioxidant, and antiaggregatory properties that may reduce atherogenesis. It also shares associations with different forms of CAD, namely stable CAD, unstable angina pectoris, stable angina pectoris, and acute myocardial infarction. Lack of sufficient evidence, however, has failed to elucidate a causal relationship between serum bilirubin level and risk of CAD. Therefore, in this update, we attempted to simplify this intricate relationship between bilirubin and CAD, revisit the pathophysiology of disease, how bilirubin may be protective, and to summarize the findings of the current literature.