Total serum bilirubin and risk of cardiovascular disease in the Framingham offspring study

Association between microsatellite polymorphism in the Heme Oxygenase-1 (HMOX1) gene promoter and type 2 diabetes: an updated meta-analysis

Over a decade has passed since the first meta-analysis examining (GT)n repeats in the HMOX1 promoter region and their association with Type 2 Diabetes (T2D) was conducted. Since then, new studies on this topic have been published, prompting this updated meta-analysis to further clarify these associations. A systematic review conducted through December 2024 using the search term: (HMOX1 OR HMOX1 OR HMOX1D OR "HO-1" OR HSP32 OR bk286B10) AND (polymorphisms OR polymorphism OR "genetic variant" OR "genetic variants") AND (Diabetes) in the PubMed, Web of Science, and Scopus databases identified nine studies comprising 2,027 cases and 2,840 controls. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using either a fixed-effect model (FEM) for homogeneous data or a random-effect model (REM) for other cases, as appropriate. Sensitivity analysis and publication bias were also assessed. The SS genotype was identified as being inversely associated with T2D in both SS:SL + LL and SS:LL genetic models (OR = 0.769, p = 0.003; OR = 0.726, p = 0.003; respectively). These findings suggest that SS genotype (< 25 GT repeats) may have a protective role against T2D; however, further studies are needed to elucidate the mechanisms by which HMOX1 influences T2D pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-025-01575-y.

Serum Direct Bilirubin as a Biomarker for Breast Cancer

Background

The role of serum total bilirubin (TB) in cancer has been a subject of controversy, as has the role of its subtypes, particularly serum direct bilirubin (DB). The aim of the present study was to investigate the association between serum DB levels and breast cancer, as well as to assess the diagnostic utility of serum DB in breast cancer.

Methods

A total of 5299 patients diagnosed with breast cancer for the first time at Taizhou Hospital of Zhejiang Province were included in the study, and 10028 healthy physical examination subjects were included as healthy controls. Logistics regression was used to investigate the relationship between serum DB and breast cancer, and the value of serum DB in the diagnosis of breast cancer was assessed by means of receiver operator characteristic (ROC) curve analysis.

Results

The serum DB concentration in the breast cancer group was significantly higher than the healthy controls (P < 0.001). Multivariate logistic regression results show that serum DB was an independent risk factor for breast cancer (odds ratio [OR]=4.504, 95% confidence interval [CI]: 4.200-4.831). Subjects with a serum DB concentration in the fourth quartile had a higher risk of breast cancer occurrence compared to those in the first quartile after adjusting for age (OR = 7.155, 95%CI: 6.474-7.907). The optimal cut-off value of serum DB for diagnosing breast cancer was determined to be 2.75 μmol/L, with an area under the curve (AUC) of 0.712 (95% CI: 0.703-0.722). This value exhibited good specificity (77.0%) and negative predictive value (77.8%).

Conclusion

Serum DB was identified as a risk factor for breast cancer, demonstrating good diagnostic potential for the disease. These findings suggest that serum DB could serve as a promising serum molecular marker for breast cancer.

Proteomics Profiling of Bilirubin Nanoparticle Treatment against Myocardial Ischemia-Reperfusion Injury

In myocardial infarction, ischemia-reperfusion injury (IRI) poses a significant challenge due to a lack of effective treatments. Bilirubin, a natural compound known for its anti-inflammatory and antioxidant properties, has been identified as a potential therapeutic agent for IRI. Currently, there are no reports about proteomic studies related to IRI and bilirubin treatment. In this study, we explored the effects of bilirubin nanoparticles in a rat model of myocardial IRI. A total of 3616 protein groups comprising 76,681 distinct peptides were identified using LC-MS/MS, where we distinguished two kinds of protein groups: those showing increased expression in IRI and decreased expression in IRI with bilirubin treatment, and vice versa, accounting for 202 and 35 proteins, respectively. Our proteomic analysis identified significant upregulation in the Wnt and insulin signaling pathways and increased Golgi markers, indicating their role in mediating bilirubin nanoparticle's protective effects. This research contributes to the proteomic understanding of myocardial IRI and suggests bilirubin nanoparticles as a promising strategy for cardiac protection, warranting further investigation in human models.

Causal association between serum bilirubin and ischemic stroke: multivariable Mendelian randomization

OBJECTIVES

Previous research has predominantly focused on total bilirubin levels without clearly distinguishing between direct and indirect bilirubin. In this study, the differences between these forms were examined, and their potential causal relationships with ischemic stroke were investigated.

METHODS

Two-sample multivariable Mendelian randomization (MVMR) analysis was employed, extracting summary data on bilirubin from the Korean Cancer Prevention Study-II (n=159,844) and the Korean Genome and Epidemiology Study (n=72,299). Data on ischemic stroke were obtained from BioBank Japan (n=201,800). Colocalization analysis was performed, focusing on the UGT1A1, SLCO1B1, and SLCO1B3 genes, which are the primary loci associated with serum bilirubin levels.

RESULTS

Crude 2-sample Mendelian randomization analysis revealed a significant negative association between total bilirubin levels and ischemic stroke. However, in MVMR analyses, only indirect bilirubin demonstrated a significant negative association with ischemic stroke (odds ratio, 0.76; 95% confidence interval, 0.59 to 0.98). Colocalization analysis did not identify a shared causal variant between the 3 genetic loci related to indirect bilirubin and the risk of ischemic stroke.

CONCLUSIONS

Our study establishes a causal association between higher genetically determined levels of serum indirect bilirubin and reduced risk of ischemic stroke in an Asian population. Future research should include more in-depth analysis of shared genetic variants between indirect bilirubin and ischemic stroke.

Inverse association between total bilirubin and type 2 diabetes in U.S. South Asian males but not females

AIMS

United States South Asians constitute a fast-growing ethnic group with high prevalence of type 2 diabetes (T2D) despite lower mean BMI and other traditional risk factors compared to other races/ethnicities. Bilirubin has gained attention as a potential antioxidant, cardio-protective marker. Hence we sought to determine whether total bilirubin was associated with prevalent and incident T2D in U.S. South Asians.

METHODS

We conducted a cross-sectional and prospective analysis of the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study. Total bilirubin was categorized into gender-specific quartiles (Men: <0.6, 0.6, 0.7-0.8, >0.8; Women: <0.5, 0.5, 0.6, >0.6 mg/dl). We estimated odds of type 2 diabetes as well as other cardiovascular (CV) risk factors using multivariable logistic regression.

RESULTS

Among a total 1,149 participants (48% female, mean [SD] age of 57 [9] years), 38% had metabolic syndrome and 24% had T2D. Men and women in the lowest bilirubin quartile had 0.55% and 0.17% higher HbA1c than the highest quartile. Men, but not women, in the lowest bilirubin quartile had higher odds of T2D compared to the highest quartile (aOR [95% CI]; Men: 3.00 [1.72,5.23], Women: 1.15 [0.57,2.31]). There was no association between bilirubin and other CV risk factors.

CONCLUSION

Total bilirubin was inversely associated with T2D in SA men but not women. Longitudinal studies are needed to understand temporality of association.

The Association between Serum Total Bilirubin and Severe Headaches or Migraine in American Adults

BACKGROUND

Studies about the association between bilirubin and migraine were few. Therefore, the purpose of this study was to investigate the association between serum total bilirubin and the prevalence of severe headaches or migraine.

METHODS

A multivariable logistic regression was used to assess the association between serum total bilirubin concentration and severe headaches or migraine. We also performed stratified analyses, interaction analyses and multiple interpolations in the sensitivity analysis.

RESULTS

This cross-sectional study included 12,552 adults from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004. The overall incidence of migraine was 19.99% (2,509/12,552). With every 1 mg/dl increase in bilirubin, the prevalence of migraine decreased by 23% (95% CI: 0.64, 0.93) after adjustment of all related covariates. Similarly, the risk of migraine was reduced by 17% (95% CI: 0.72, 0.97) in the Q4 group (the fourth quartile, highest serum total bilirubin level) compared with the Q1 group (the lowest level). Furthermore, interaction effects by age groups were significant in this relationship (P for interaction = 0.0004). In the Q4 group compared with Q1, inverse associations were observed in those aged ≥40 years (OR: 0.71,95% CI: 0.59, 0.85) in the stratified analysis.

CONCLUSION

These findings support an association between serum total bilirubin and severe headaches or migraine, revealing an inverse association between serum total bilirubin quartiles and severe headaches or migraine in American adults. Age could play an important role in this association.

Urinary lumirubin excretion in jaundiced preterm neonates during phototherapy with blue light-emitting diode vs. green fluorescent lamp

Phototherapy converts lipophilic unconjugated bilirubin to hydrophilic bilirubin photoisomers, such as lumirubin. We comparatively used a blue light-emitting diode (LED) and a green fluorescent lamp (FL) as light sources for phototherapy of hyperbilirubinemic preterm neonates with the aim of examining potential differences in urinary lumirubin excretion between these two wavelengths. Urinary lumirubin levels were measured using a fluorescence assay with blue light exposure in the presence of the unconjugated bilirubin-inducible fluorescent protein UnaG, and denoted as urinary UnaG-bound bilirubin (UUB)/creatinine (Cr) (μg/mg Cr). Preterm neonates born at ≤ 33 weeks gestational age and treated with phototherapy were subjected to this study. The maximum UUB/Cr level during phototherapy per device intensity was compared between neonates treated with the blue LED and the green FL. A total of 61 neonates were examined to determine the maximum UUB/Cr levels. The median of maximum UUB/Cr excretion per light intensity of each device (μg/mg Cr/μW/cm2/nm) was 0.83 for the blue LED and 1.29 for the green FL (p = 0.01). Green light was found to be more effective than blue one for bilirubin excretion via urinary lumirubin excretion. This is the first spectroscopic study to compare the efficacy of phototherapy at different wavelengths using fluorescence assay.

Genetics of Plasma Bilirubin and Associations between Bilirubin and Cardiometabolic Risk Profiles in Danish Children and Adolescents

Bilirubin is the end product of heme catabolism, mainly produced by the breakdown of mature red blood cells. Due to its anti-inflammatory, antioxidant, antidiabetic, and antilipemic properties, circulating bilirubin concentrations are inversely associated with the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality in adults. Some genetic loci associated with circulating bilirubin concentrations have been identified by genome-wide association studies in adults. We aimed to examine the relationship between circulating bilirubin, cardiometabolic risk factors, and inflammation in children and adolescents and the genetic architecture of plasma bilirubin concentrations. We measured fasting plasma bilirubin, cardiometabolic risk factors, and inflammatory markers in a sample of Danish children and adolescents with overweight or obesity (n = 1530) and in a population-based sample (n = 1820) of Danish children and adolescents. Linear and logistic regression analyses were performed to analyze the associations between bilirubin, cardiometabolic risk factors, and inflammatory markers. A genome-wide association study (GWAS) of fasting plasma concentrations of bilirubin was performed in children and adolescents with overweight or obesity and in a population-based sample. Bilirubin is associated inversely and significantly with a number of cardiometabolic risk factors, including body mass index (BMI) standard deviation scores (SDS), waist circumference, high-sensitivity C-reactive protein (hs-CRP), homeostatic model assessment for insulin resistance (HOMA-IR), hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol (LDL-C), triglycerides, and the majority of measured inflammatory markers. In contrast, bilirubin was positively associated with fasting plasma concentrations of alanine transaminase (ALT), high-density lipoprotein cholesterol (HDL-C), systolic blood pressure (SDS), and the inflammatory markers GH, PTX3, THBS2, TNFRSF9, PGF, PAPPA, GT, CCL23, CX3CL1, SCF, and TRANCE. The GWAS showed that two loci were positively associated with plasma bilirubin concentrations at a p-value threshold of <5 × 10-8 (rs76999922: β = -0.65 SD; p = 4.3 × 10-8, and rs887829: β = 0.78 SD; p = 2.9 × 10-247). Approximately 25% of the variance in plasma bilirubin concentration was explained by rs887829. The rs887829 was not significantly associated with any of the mentioned cardiometabolic risk factors except for hs-CRP. Our findings suggest that plasma concentrations of bilirubin non-causally associates with cardiometabolic risk factors in children and adolescents.

Association between bilirubin levels and risk of stroke: a systematic review and meta-analysis

OBJECTIVE

To evaluate the association between bilirubin levels and stroke risk.

DESIGN

Systematic review and meta-analysis, reported in accordance with Meta-analysis Of Observational Studies in Epidemiology guidelines.

DATA SOURCES

The PubMed, Embase, Cochrane Central Register of Controlled Trials and China National Knowledge Infrastructure Databases were searched from inception up to 27 February 2022.

ELIGIBILITY CRITERIA

Cohort studies assessing the dose-response relationship between bilirubin levels and risk of stroke were eligible for inclusion. There were no language restrictions.

DATA EXTRACTION AND SYNTHESIS

All data from eligible studies were collected and assessed by two independent investigators. We generated pooled relative risks (RRs) with 95% CIs. We used a restricted cubic spline model for the dose-response analyses. Subsequent subgroup analyses were conducted according to stroke outcomes, follow-up duration, geographical area and size of the cohort.

RESULTS

Nine articles including results from 11 cohort studies with 7835 cases of stroke and 263 596 participants met the inclusion criteria. The summarised RR of stroke comparing the highest and lowest bilirubin level was 0.85 (95% CI 0.72 to 0.99). The dose-response analysis indicated that a 15 µmol/L increment of bilirubin level was associated with an 18% lower risk of stroke (RR=0.82, 95% CI 0.67 to 0.99). For ischaemic stroke, the RR was 0.76 (95% CI 0.58 to 0.99). Significant publication bias was not detected.

CONCLUSIONS

Elevated bilirubin levels were associated with a decreased risk of stroke among adults.

PROSPERO REGISTRATION NUMBER

CRD42017071497.

Regulation of CD163 Receptor in Patients with Abdominal Aortic Aneurysm and Associations with Antioxidant Enzymes HO-1 and NQO1

Red blood cells are found within the abdominal aortic aneurysm (AAA), in the intraluminal thrombus (ILT), and in neovessels. Hemolysis promotes aortic degeneration, e.g., by heme-induced reactive oxygen species formation. To reduce its toxicity, hemoglobin is endocytosed by the CD163 receptor and heme is degraded by heme oxygenase-1 (HO-1). A soluble form (sCD163) is discussed as an inflammatory biomarker representing the activation of monocytes and macrophages. HO-1 and NAD(P)H quinone dehydrogenase 1 (NQO1) are antioxidant genes that are induced by the Nrf2 transcription factor, but their regulation in AAA is only poorly understood. The aim of the present study was to analyze linkages between CD163, Nrf2, HO-1, and NQO1 and to clarify if plasma sCD163 has diagnostic and risk stratification potential. Soluble CD163 was 1.3-fold (p = 0.015) higher in AAA compared to patients without arterial disease. The difference remained significant after adjusting for age and sex. sCD163 correlated with the thickness of the ILT (r_s = 0.26; p = 0.02) but not with the AAA diameter or volume. A high aneurysmal CD163 mRNA was connected to increases in NQO1, HMOX1, and Nrf2 mRNA. Further studies are needed to analyze the modulation of the CD163/HO-1/NQO1 pathway with the overall goal of minimizing the detrimental effects of hemolysis.

Association of Total Bilirubin with Motor Signs in Early Parkinson's Disease in LRRK2 Variant Carriers

Oxidative stress is considered a possible mechanism in Parkinson's disease (PD) progression. Bilirubin has been recognized as a powerful antioxidant that increases due to heme-oxygenase activity. We aimed to investigate the association of total bilirubin (TB) with motor signs and asymmetry in different stages of early PD. A case-control study was performed to investigate the differences in TB levels in PD patients and healthy controls (HC) both carrying LRRK2 variants. We compared TB levels in HC and Hoehn and Yahr (HY) I and II cohorts separately, followed by multiple linear regression analysis to evaluate the association between TB and motor dysfunction in each stage. We used Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (UPDRS) part III scores and asymmetry scores to address motor disability. Asymmetry scores were calculated from the corresponding UPDRS III tasks. TB was significantly increased in HY II compared to HC (P < 0.001). Positive correlations with TB were found for UPDRS III total score (ρ = 0.303, P = 0.034) and asymmetry score (ρ = 0.418, P = 0.003) in HY I. Multiple linear regression found a significant relationship between TB and asymmetry scores in HY I (R² = 0.261, P = 0.037), but no relationship was achieved with UPDRS III total scores. Increased TB serves as an important diagnostic marker in earlier stages of PD. A significant relationship was found between TB and motor asymmetry in HY I patients. According to our findings, bilirubin mainly exhibits its protective effects in HY I population.

Association of Hepatic Steatosis With Coronary Artery Disease by Studying the Role of Individual and Demographic Risk Factors

Background

In this study, we aimed to explore the possible association between hepatic steatosis (HS) and coronary artery disease (CAD) by calculating the patients’ calcium scores and comparing clinical and laboratory parameters of patients in King Abdullah Medical City (KAMC), Makkah, Kingdom of Saudi Arabia (KSA). The role of risk factors associated with HS was also assessed.

Methodology

The medical records of 79 patients who underwent coronary cardiac computed tomography (CT) for calcium scoring and enhanced or non-enhanced CT scans of the abdomen and pelvis at the Department of Radiology, KAMC, Makkah, KSA, between April 2012 and April 2013 were collected and analyzed.

Results

The overall prevalence of HS was 32.9%. Gender, age, and body mass index were significantly associated with HS. Low-dose unenhanced CT is a promising screening test for the determination of HS. A severe grade of calcium score was significantly associated with HS, while hypertension had no significant relation with HS. Biomarkers such as blood urea nitrogen, creatinine, cholesterol, and triglycerides had a significant association with HS, while other liver function tests and lipid profile values did not have a significant association. Bilirubin was significantly higher in non-fatty liver than in fatty liver. Furthermore, higher grades of calcium score were significantly associated with fatty liver in non-hypertensive and non-diabetic patients.

Conclusions

CAD is closely associated with HS. Moreover, diabetes mellitus and hypertension play a critical role in the development of HS.

Serum bilirubin and kidney function: a Mendelian randomization study

Background

Further investigation is needed to determine the causal effects of serum bilirubin on the risk of chronic kidney disease (CKD).

Methods

This study is a Mendelian randomization (MR) analysis. Among the well-known single-nucleotide polymorphisms (SNPs) related to serum bilirubin levels, rs4149056 in the SLCO1B1 gene was selected as the genetic instrument for single-variant MR analysis, as it was found to be less related to possible confounders than other SNPs. The association between genetic predisposition for bilirubin levels and estimated glomerular filtration rate (eGFR) or CKD was assessed in 337 129 individuals of white British ancestry from the UK Biobank cohort. Two-sample MR based on summary-level data was also performed. SNPs related to total or direct bilirubin levels were collected from a previous genome-wide association study and confounder-associated SNPs were discarded. The independent CKDGen meta-analysis data for CKD were employed as the outcome summary statistics.

Results

The alleles of rs4149056 associated with higher bilirubin levels were associated with better kidney function in the UK Biobank data. In the summary-level MR, both of the genetically predicted total bilirubin {per 5 µmol/L increase; odds ratio [OR] 0.931 [95% confidence interval (CI) 0.871-0.995]} and direct bilirubin [per 1 µmol/L increase; OR 0.910 (95% CI 0.834-0.993)] levels were significantly associated with a lower risk of CKD, supported by the causal estimates from various MR sensitivity analyses.

Conclusion

Genetic predisposition for higher serum bilirubin levels is associated with better kidney function. This result suggests that higher serum bilirubin levels may have causal protective effects against kidney function impairment.

Impact of indirect bilirubin and uric acid on outcomes of sepsis-associated acute kidney injury (sAKI)

BACKGROUND

Acute kidney injury (AKI) is one of the most frequent pathophysiologic disorders encountered in hospitalized patients, with sepsis frequently implicated in pathogenesis. Reactive oxygen species (ROS) seem to have a significant contribution to sepsis-induced AKI. Proposed mechanisms include induction of cell membrane lipid peroxidation, protein denaturing, and direct DNA damage, all of which have deleterious effect. These changes constitute oxidative injury to the kidneys.

OBJECTIVE

To evaluate the antioxidant actions of indirect bilirubin and uric acid on outcomes of sepsis-associated AKI.

METHODS

Ninety-eight patients admitted to the intensive care unit (ICU), at a large tertiary center, with sepsis and AKI were evaluated for serum levels of uric acid, bilirubin (primarily indirect), and procalcitonin. The primary endpoints studied were the need for hemodialysis and death.

RESULTS

Thirty-two (33%) patients developed AKI requiring hemodialysis (HD). These patients had higher SOFA scores (p < 0.001) and lower levels of indirect bilirubin (p < 0.001) compared to those not requiring HD. There was no statistically significant difference in serum uric acid levels. Logistic regression analysis identified creatinine level, total and indirect bilirubin levels, and leukocyte count as significant predictors of patient death.

CONCLUSION

Higher leukocyte counts and creatinine levels were independently associated with poor outcomes in ICU patients with sepsis. Additionally, lower indirect bilirubin levels were also noted to be associated with similar outcomes. The latter provides insights into oxidative stress as a major player in the pathogenesis of sepsis-induced AKI, with a potential protective role of indirect bilirubin.

Liver-function parameters are associated with incident hypertension in a large Taiwanese population follow-up study

Previous studies demonstrated inconsistent results regarding the association between liver function and hypertension. In addition, large cohort follow-up studies are lacking. Therefore, this longitudinal study aimed to investigate the association between liver function and incident hypertension using data from the Taiwan Biobank (TWB). We evaluated liver biomarkers, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin, alpha-fetoprotein (AFP), total bilirubin, and gamma-glutamyl transferase (GGT) in this study. A total of 21,293 participants without hypertension at baseline were analyzed. During the mean 3.9-year follow-up, 3002 participants developed hypertension (defined as incident hypertension). Multivariable analysis revealed that high AST (odds ratio [OR], 1.004; 95% confidence interval [CI], 1.001-1.007; p = 0.014), high ALT (OR, 1.004; 95% CI, 1.002-1.006; p < 0.001), high albumin (OR, 1.897; 95% CI, 1.573-2.286; p < 0.001), and high GGT (OR, 1.004; 95% CI, 1.003-1.005; p < 0.001) were significantly associated with incident hypertension in all study participants. In subgroup analysis of the participants with an ALT level ≤2 times the normal limit (80 u/l) (n = 20,983), multivariable analysis demonstrated that high ALT (OR, 1.009; 95% CI, 1.005-1.012; p < 0.001) and high GGT (OR, 1.005; 95% CI, 1.003-1.006; p < 0.001) were significantly associated with incident hypertension. In conclusion, we found that elevated AST, ALT, albumin, and GGT were associated with incident hypertension in a large Taiwanese cohort. A greater understanding of potential risk factors for hypertension may help to reduce the burden of hypertension in this Taiwanese population.

Elevated serum bilirubin may significantly reduce coronary heart disease risk in females: A prospective cohort study

BACKGROUND AND AIMS

There is still inconsistent evidence over the protective effect of total bilirubin on the development of coronary heart disease (CHD). Therefore, we aimed to investigate the association between bilirubin in population subtypes and the risks of CHD between different gender and menstruation subgroups.

METHODS AND RESULTS

In this prospective cohort study, 29,750 participants free of CHD with an average age of 47 ± 14 years were recruited at baseline; of these, 720 CHD first-attack cases were collected after 7-years of follow up. The covariate-adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) of CHD with 95% confidence intervals (CIs). The serum bilirubin concentration was quarterly stratified based on the distribution of healthy population without CHD onset. The HRs of incident CHD decreased with elevated bilirubin in females (ρ trend<0.05), but not males. In postmenopausal females, compared with the lowest quartile of total bilirubin, the adjusted HRs for the third and fourth quartiles were 0.64 (95% CI: 0.45, 0.93) and 0.59 (95% CI: 0.42, 0.86), the adjusted HRs in the third and fourth quartiles of direct bilirubin were 0.56 (0.39, 0.82) and 0.56 (0.38, 0.81), and for indirect bilirubin, corresponding HR in the highest quartile was 0.56 (0.38, 0.83).

CONCLUSION

Elevated serum bilirubin was inversely associated with adjusted HRs of CHD in females, especially postmenopausal females. The relationship between elevated direct bilirubin and reduced HRs of CHD may be closer than indirect bilirubin in postmenopausal females.

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.

Metabolite Signature of Physical Activity and the Risk of Type 2 Diabetes in 7271 Men

Large population-based studies investigating the association of physical activity (PA) with the metabolite signature contribute significantly to the understanding of the effects of PA on metabolic pathways associated with the risk of type 2 diabetes. Our study included 8749 Finnish men without diabetes at baseline recruited from the Metabolic Syndrome in Men (METSIM) cohort. We used a questionnaire to measure leisure-time PA. Metabolites were measured in 7271 men as a part of Metabolon’s untargeted Discovery HD4 platform using ultrahigh-performance liquid chromatography–tandem mass spectrometry. We found 198 metabolites significantly associated with PA. Several of these metabolites were novel including especially steroids, amino acids, imidazoles, carboxylic acids, and hydroxy acids. Increased PA was significantly associated with high levels of choline plasmalogens, lysophosphatidylcholines, polyunsaturated fatty acids, carotenoids, long chain acylcarnitines, imidazoles, bilirubins, aryl sulfates, hydroxy acids, indolepropionate, and indolelactate. Several of these metabolites have been previously associated with a decreased risk of type 2 diabetes and with a healthy diet. Our population-based study shows that the metabolite signature of increased PA includes multiple metabolic pathways and is associated with better adherence to a healthy lifestyle.

Dose-Response Association Between Bilirubin and Cardiovascular Disease: A Systematic Review and Meta-analysis

The association between bilirubin (BIL) and cardiovascular disease (CVD) remains controversial. We performed a meta-analysis of prospective studies to evaluate this association in the general population. We searched PubMed, EMBASE, Web of Science, Cochrane, and Scopus databases through to September 2021. The Newcastle-Ottawa Quality Assessment Scale was used to assess study quality. The pooled effect estimate was calculated by the fixed-effect model or random-effect model. We included 12 prospective studies (368 567 participants). The pooled risk ratio of CVD for the lowest vs highest groups of BIL levels was .75 (95% CI: .58-.97) with high heterogeneity (I² = 87.5%, P < .001). Similar associations were observed for coronary heart disease and stroke. We further performed a "dose-response" meta-analysis, and a significant U-shaped relationship between circulating (most values were serum bilirubin, but a few were plasma bilirubin) BIL and CVD (P < .01) was observed. The lowest risk of CVD events was observed in participants with a BIL of 17-20 µmol/L in serum and/or plasma. In conclusion, there was a U-shaped dose-response relationship between BIL and CVD, especially for men. Further studies are needed to confirm our findings and identify the mechanisms involved as well as any prognostic or therapeutic potential.

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.

Bilirubin as a Therapeutic Molecule: Challenges and Opportunities

There is strong evidence that serum free bilirubin concentration has significant effects on morbidity and mortality in the most significant health conditions of our times, including cardiovascular disease, diabetes, and obesity/metabolic syndrome. Supplementation of bilirubin in animal and experimental models has reproduced these protective effects, but several factors have slowed the application bilirubin as a therapeutic agent in human patients. Bilirubin is poorly soluble in water, and is a complex molecule that is difficult to synthesize. Current sources of this molecule are animal-derived, creating concerns regarding the risk of virus or prion transmission. However, recent developments in nanoparticle drug delivery, biosynthetic strategies, and drug synthesis have opened new avenues for applying bilirubin as a pharmaceutical agent. This article reviews the chemistry and physiology of bilirubin, potential clinical applications and summarizes current strategies for safe and efficient drug delivery.

Bilirubin Links HO-1 and UGT1A1*28 Gene Polymorphisms to Predict Cardiovascular Outcome in Patients Receiving Maintenance Hemodialysis

Serum bilirubin levels, which are determined by a complex interplay of various enzymes, including heme oxygenase-1 (HO-1) and uridine diphosphate–glucuronosyl transferase (UGT1A1), may be protective against progression of cardiovascular disease (CVD) in hemodialysis patients. However, the combined effect of HO-1 and UGT1A1*28 gene polymorphisms on CVD outcomes among hemodialysis patients is still unknown. This retrospective study enrolled 1080 prevalent hemodialysis patients and the combined genetic polymorphisms of HO-1 and UGT1A1 on serum bilirubin were analyzed. Endpoints were CVD events and all-cause mortality. Mean serum bilirubin was highest in patients with S/S + S/L of the HO-1 promoter and UGT1A1 7/7 genotypes (Group 1), intermediate in those with S/S + S/L of the HO-1 promoter and UGT1A1 7/6 + 6/6 genotypes (Group 2), and lowest in the carriers with the L/L HO-1 promoter and UGT1A1 7/6 + 6/6 genotypes (Group 3) (p < 0.001). During a median follow-up of 50 months, 433 patients developed CVD. Compared with patients in Group 3, individuals among Groups 1 and 2 had significantly lower risks for CVD events (adjusted hazard ratios (aHRs) of 0.35 for Group 1 and 0.63 for Group 2), respectively. Compared with the lower bilirubin tertile, the aHRs were 0.72 for the middle tertile and 0.40 for the upper tertile for CVD events. We summarized that serum bilirubin as well as HO-1 and UGT1A1 gene polymorphisms were associated with CVD among patients receiving chronic hemodialysis.

Novel metabolomic profile of subjects with non-classic apparent mineralocorticoid excess

Nonclassic apparent mineralocorticoid excess (NC-AME) is proposed as a novel clinical condition with a mild phenotypic spectrum that ranges from normotension to severe hypertension. This condition is mainly characterized by a high serum cortisol to cortisone ratio (F/E) and concomitant low cortisone (E), however further metabolic changes in NC-AME have not been studied. A cross-sectional study was performed in a primary-care cohort of 396 Chilean subjects, which were classified in two groups: NC-AME (n = 28) and healthy controls (n = 27). A discovery study based in untargeted metabolomics assay in serum samples from both groups was performed by UPLC-Q-TOF/MS. Global metabolomic variations were assayed by principal component analysis and further compared by orthogonal partial least-squares discriminant analysis (OPLS-DA). NC-AME subjects exhibited higher values of blood pressure, fractional excretion of potassium, and lower plasma renin activity and urinary sodium to potassium ratio. Metabolomic analyses showed 36 differentially regulated metabolites between NC-AME and control subjects. A ROC curve analyses identified eight metabolites with high discriminatory capacity between NC-AME and control subjects. Moreover, gamma-l-glutamyl-l-methionine sulfoxide and 5-sulfoxymethylfurfural, exhibited significant association with cortisone, which are potential biomarkers of NC-AME, however further assays should elucidate its biological role in setup and progression of this phenotype.

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.

Multiple Roles of Black Raspberry Anthocyanins Protecting against Alcoholic Liver Disease

This study aimed to investigate the protective effect of black raspberry anthocyanins (BRAs) against acute and subacute alcoholic liver disease (ALD). Network analysis and docking study were carried out to understand the potential mechanism. Thereafter, the serum biochemical parameters and liver indexes were measured, the histopathological changes of the liver were analyzed in vivo. The results showed that all tested parameters were ameliorated after the administration of BRAs with alcohol. Meanwhile, there was increased protein expression of NF-κB and TGF-β in extracted livers, which was associated with hepatitis and hepatic fibrosis. Furthermore, BRAs and cyanidin-3-O-rutinoside exhibited cytotoxic effects on t-HSC/Cl-6, HepG2, and Hep3B and induced the apoptosis of HepG2 cells; downregulated the protein expression level of Bcl-2; upregulated the level of Bax; and promoted the release of cytochrome C, cleaved caspase-9, cleaved caspase-3, and cleaved PARP in HepG2 cells. In addition, the antioxidant activity of BRAs was tested, and the chemical components were analyzed by FT-ICR MS. The results proved that BRAs exert preventive effect on ALD through the antioxidant and apoptosis pathways.

Physiologically increased total bilirubin is associated with reduced risk of first myocardial infarction: A meta-analysis and dose-response analysis

AIM

Bilirubin has potential predictive and prognostic value for myocardial infarction (MI), but the clinical evidence remains controversial. We performed this meta-analysis to systematically quantify the relationships between circulating bilirubin levels and the incidence of MI and post-MI adverse events.

DATA SYNTHESIS

We searched the PubMed, Cochrane Library, Embase, and Web of Science databases for ad-hoc studies, published up to October 17, 2020, recording bilirubin before MI (predictive analyses) or adverse events (prognostic analyses). Relative risks (RR) were pooled by a random-effects model. The dose-response analysis was conducted by restricted cubic splines. In patients without previous MI, increased total bilirubin (TB) reduced the risk of long-term (>3 year) first MI by 22% (95% confidence interval [CI]: 0.69-0.88, n = 4). The dose-response analysis indicated that the RR for first MI decreased by 2.7% per each 2 μmol/L increment of TB (three studies, 95% CI: 1.3%-4.1%, P < 0.001), with a cut-off value of 12.60 μmol/L for RR > 1.00. Elevated bilirubin reduced the incidence of first and recurrent MI by 36% (95% CI: 0.42-0.98, n = 7). However, after suffering MI, higher TB concentrations could not decrease the risk of recurrent MI (RR: 1.02, 95% CI: 0.67-1.55, n = 5) and increased the incidence of short-term (<1 year) post-MI major adverse cardiovascular events, all-cause mortality, and cardiovascular mortality, but not long-term (≥1 year).

CONCLUSION

Higher TB levels within a physiological range reduced the incidence of long-term first MI, with a cut-off value of 12.60 μmol/L.

Identification and Characterization of Xanthomonas arboricola pv. juglandis Causing Bacterial Blight of Walnuts in Korea

The present study describes the bacterial blight of walnut, caused by Xanthomonas arboricola pv. juglandis (Xaj) in the northern Gyeongbuk province, Korea. Disease symptoms that appear very similar to anthracnose symptoms were observed in walnut trees in June 2016. Pathogens were isolated from disease infected leaves, fruits, shoots, bud, flower bud of walnut, and cultured onto yeast dextrose carbonate agar plates. Isolated bacteria with bacterial blight symptoms were characterized for their nutrient utilization profiles using Biolog GN2 and Vitek 2. In addition, isolates were subjected to physiological, biochemical, and morphological characterizations. Furthermore, isolates were identified using 16S rDNA sequence analysis, and multi-locus sequence analysis using atpD, dnaK, efp, and rpoD. To confirm pathogenicity, leaves, fruits, and stems of 3-year-old walnut plants were inoculated with bacterial pathogen suspensions as a foliar spray. One week after inoculation, the gray spots on leaves and yellow halos around the spots were developed. Fruits and stems showed browning symptoms. The pathogen Xaj was re-isolated from all symptomatic tissues to fulfill Koch's postulates, while symptoms were not appeared on control plants. On the other hand, the symptoms were very similar to the symptoms of anthracnose caused by Colletotrichum gloeosporioides. When walnut plants were inoculated with combined pathogens of Xaj and C. gloeosporioides, disease symptoms were greater in comparison with when inoculated alone. Xaj population size was more in the month of April than March due to their dormancy in March, and sensitive to antibiotics such as oxytetracycline and streptomycin, while resistant to copper sulfate.

Association between serum bilirubin and mucosal healing among Japanese patients with ulcerative colitis: a cross-sectional study

PURPOSE

Bilirubin is known to have antioxidant effects. Several pieces of evidence regarding association between serum bilirubin and UC exist. Three studies found that serum bilirubin was inversely associated with severity of ulcerative colitis (UC), but no evidence regarding an association between serum bilirubin and mucosal healing (MH) has yet been shown. Thus, we evaluated this issue among Japanese patients with UC.

METHODS

The study subjects consisted of 304 Japanese patients with UC. Serum total bilirubin and indirect bilirubin were divided into quartiles on the basis of the distribution of all study subjects (low, moderate, high, and very high). Several endoscope specialists were responsible for evaluating MH, which was defined as a Mayo endoscopic subscore of 0. The information on clinical remission was collected using medical records.

RESULTS

The mean age was 49.9 years, the percentage of male patients was 59.2%, and the percentage of MH was 29.3%. High serum total bilirubin was independently positively associated with MH (OR 2.26 [95%CI 1.13-4.61]. However, after adjustment for confounding factors, the association between total bilirubin and MH disappeared. Very high serum indirect bilirubin was independently positively associated with MH (OR 2.31 [95%CI 1.10-5.00], p for trend = 0.026). No association between bilirubin and clinical remission was found.

CONCLUSIONS

Among Japanese patients with UC, serum indirect bilirubin, but not total bilirubin, was significantly positively associated with MH but not clinical remission.

Exploring the causal pathway from bilirubin to CVD and diabetes in the UK biobank cohort study: Observational findings and Mendelian randomization studies

BACKGROUND AND AIMS

Some studies reported that mildly elevated serum bilirubin levels were associated with decreased risk of cardiovascular disease (CVD) and diabetes. Whether these are causal relationships remains unclear. This study aims to examine the causal effects of bilirubin on CVD, diabetes and their subtypes.

METHODS

The data we used in this study includes individual data from the UK Biobank cohort with 331,002 white British participants, and summary data from published genome wide associations studies (GWAS) findings. We used individual data to perform logistic regression for the observational study and two-stage least squares method for the Mendelian randomization (MR) study. We also performed several traditional MR methods and MR-TRYX by summary data.

RESULTS

The observational study supported the association relationships between bilirubin and CVD and diabetes and their subtypes. Results of MR showed strong evidence for negative causal associations of log_e total bilirubin with CVD [OR 0.92, 95%CI 0.88-0.95, p-value 2.15 × 10^-6], coronary heart disease [OR 0.90, 95%CI 0.85-0.96, p-value 1.54 × 10^-3] and hypertensive diseases [OR 0.91, 95%CI 0.88-0.95, p-value 5.89 × 10^-6], but no evidence for diabetes [OR 0.94, 95%CI 0.86-1.02, p-value 0.14] and its subtypes. We also obtained similar results for direct bilirubin. We found that blood pressure, cholesterol, C-reactive protein, alcohol and white blood cell count played important roles in the causal pathway from bilirubin to CVD. Two sample MR and sensitivity analyses showed consistent results with one sample MR.

CONCLUSIONS

Genetically determined bilirubin was negatively associated with the risk of CVD but had no evident causal association with diabetes in the UK Biobank cohort of white British.

Wildland Firefighting: Adverse Influence on Indices of Metabolic and Cardiovascular Health

Objective:

The purpose of this study was to evaluate pre- and postseason measures of body composition, skeletal muscle, and blood parameters/liver lipid in wildland firefighters (WLFF) over the fire season.

Methods:

Alaskan WLFF (N = 27) crews were evaluated pre- and postwildfire season, which included 63 ± 10 operational days. Body composition, thigh muscle area, and liver lipid were quantified using dual-energy radiograph absorptiometry and magnetic resonance imaging, respectively. Blood metabolic and lipid panels were also collected and analyzed.

Results:

Total body, fat, and visceral fat mass increased from pre- to postseason (P < 0.05). Total cholesterol, LDL, and total globulin also increased (P < 0.05). There was a trend (P = 0.06) towards an increase in intrahepatic lipid.

Conclusions:

The observed maladaptive changes in adipose tissue, blood lipids, and hepatic function may reflect adaptations/consequences to occupational demands/conditions and warrant evaluation of appropriate countermeasures.

Association Between Atazanavir-Induced Hyperbilirubinemia and Cardiovascular Disease in Patients Infected with HIV

BACKGROUND:

Serum bilirubin is inversely associated with cardiovascular risk. Atazanavir, an HIV protease inhibitor that competitively inhibits bilirubin conjugation, provides a unique opportunity to examine whether selectively increasing bilirubin is cardioprotective. We sought to determine whether patients receiving atazanavir manifest a reduced risk of cardiovascular disease compared with those receiving darunavir, an HIV protease inhibitor that does not increase serum bilirubin.

METHODS AND RESULTS:

This was a retrospective cohort study of 1020 patients with HIV. The main outcome was time to myocardial infarction or ischemic stroke. Mean follow‐up was 6.6±3.4 years, with 516 receiving atazanavir and 504 darunavir. Atazanavir patients exhibited significantly higher serum total bilirubin (1.7 versus 0.4 mg/dL; P<0.001) and longer mean time to ischemic event (10.2 versus 9.4 years; P<0.001). On Cox regression, atazanavir treatment (hazard ratio [HR], 0.38; 95% CI, 0.21–0.71; P=0.002) and serum bilirubin (HR, 0.60; 95% CI, 0.41–0.89; P=0.011) were independently associated with a lower risk of an ischemic event. Notably, when atazanavir and bilirubin were included together in the Cox regression model, atazanavir lost significance (HR, 0.55; 95% CI, 0.24–1.29; P=0.169) consistent with bilirubin being an intermediate variable on the causal pathway between atazanavir and its effect on cardiovascular disease. Patients on atazanavir also had a significantly lower risk of developing new cardiovascular disease (HR, 0.53; 95% CI, 0.33–0.86; P=0.010) and longer mean time to death (12.2 versus 10.8 years; P<0.001).

CONCLUSIONS:

Patients with HIV on atazanavir manifest a decreased risk of cardiovascular disease when compared with those on darunavir, an effect that appears to be mediated by serum bilirubin.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

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.

Association of Serum Indirect Bilirubin Concentrations with Motor Subtypes of Parkinson's Disease

INTRODUCTION

We aimed to investigate the change of serum indirect bilirubin (IBIL) concentrations in patients with Parkinson's disease (PD) and whether IBIL concentrations were associated with the motor subtypes of PD.

METHODS

A case-control study was performed to evaluate differences in bilirubin concentrations between 78 PD subjects and 78 controls. Venous blood samples were collected, and total bilirubin (TBIL), direct bilirubin (DBIL), and IBIL concentrations were analyzed between PD subjects and controls. PD patients were classified into three motor subtypes: tremor-dominant (TD), intermediate (I), and postural instability and gait disorder (PIGD). It was evaluated whether there were differences in IBIL concentrations between the different motor subtypes and between motor subtypes and controls.

RESULTS

PD patients had lower IBIL concentrations compared to controls (6.51 ± 4.03 vs. 10.82 ± 4.61, p< 0.001). There was no significant difference in IBIL concentrations between PD males and PD females (6.66 ± 3.64 vs. 6.22 ± 4.79, p =0.655). IBIL concentrations had negative relationships with levodopa-equivalent daily dose (LEDD) (R = -0.452, p < 0.001) and positive relationships with tremor score (R = 0.360, p = 0.001). IBIL concentrations were significantly lower for PIGD than for TD subtype (4.88 ± 4.03 vs. 9.00 ± 4.15, p< 0.001). The lower IBIL concentrations in PD compared to controls were mainly driven by the PIGD patients.

CONCLUSIONS

PD subjects showed lower levels of IBIL compared to controls. Higher IBIL levels were associated with TD motor subtype in PD, which could be related to the antioxidative properties of IBIL.

Circulating bilirubin level is determined by both erythrocyte amounts and the proportion of aged erythrocytes in ageing and cardiovascular diseases

BACKGROUND

Bilirubin has been involved in the process of ageing and the pathology of ageing-related diseases. Circulating bilirubin is mainly derived from the clearance of disintegrated erythrocytes in the blood. However, the change of serum bilirubin level and its regulation during ageing and in ageing-related diseases remain to be elucidated.

METHODS

A retrospective study was conducted by analyzing the blood cell test results and liver function results of 14,049 healthy research subjects at the Physical Examination Center and 2052 patients with various types of cardiovascular diseases (CVD) at the Department of Cardiology in Renmin Hospital of Wuhan University. Spearman correlation analysis and linear-regression analysis were used for correlation studies. Differences between male and female were investigated.

RESULTS

Whereas the erythrocyte counts continuously decreased along with age, the proportion of aged erythrocytes was significantly increased in both male and female. The level of total circulating bilirubin was positively correlated with age and erythrocyte counts. The increase of bilirubin was associated with the increased morphological deviation of erythrocytes during ageing. Compared with health controls, the level of circulating bilirubin in CVD patients was significantly decreased consistent with the decline of erythrocyte counts and hemoglobin.

CONCLUSIONS

Ageing may be accompanied by an increased ageing rate of erythrocytes, which contributes to the ageing-related decline of erythrocyte counts. Both erythrocyte counts and the proportion of aged erythrocytes coordinately might determine the circulating level of bilirubin during ageing. In CVD, the decline of circulating bilirubin may be largely attributed to concurrent anemia.

Minocycline protects neurons against glial cells-mediated bilirubin neurotoxicity

Unconjugated bilirubin, the end product of heme catabolism and antioxidant, induced brain damage in human neonates is a well-recognized clinical syndrome. However, the cellular and molecular mechanisms underlying bilirubin neurotoxicity remain unclear. To characterize the sequence of events leading to bilirubin-induced neurotoxicity, we investigated whether bilirubin-induced glial activation was involved in bilirubin neurotoxicity by exposing co-cultured rat glial cells and cerebellar granule neurons (CGN) to bilirubin. We found that bilirubin could markedly induce the expression of TNF-α and iNOS in glial cells, and even at low concentrations, the co-culture of glial cells with neurons significantly enhances neurotoxicity of bilirubin. Pretreatment of the co-cultured cells with minocycline protected CGN from glia-mediated bilirubin neurotoxicity and inhibited overexpression of TNF-α and iNOS in glia. Furthermore, we found that high doses of bilirubin were able to induce glial injury, and minocycline attenuated bilirubin-induced glial cell death. Our data suggest that glial cells play an important role in brain damage caused by bilirubin, and minocycline blocks bilirubin-induced encephalopathy possibly by directly and indirectly inhibiting neuronal death pathways.

Relation of total bilirubin and QT interval prolongation (from the Third National Health and Nutrition Examination Survey)

OBJECTIVE

The association of bilirubin with cardiovascular disease (CVD) is controversial. We sought to explore the association of total bilirubin (TB) levels with QT interval in a multiracial cohort.

METHODS

A total of 6,627 participants (59.0 ± 13.3 years; 52.6% women, 49.7% Non-Hispanic Whites) without CVD from the Third National Health and Nutrition Examination Survey were included in this analysis. QT was automatically measured from digital 12-lead electrocardiogram in a central reading center. A multivariable logistic regression model was used to examine the cross-sectional association between tertiles of TB and prolonged QT interval (≥450 ms in men and ≥460 ms in women).

RESULTS

The prevalence of prolonged QT was higher among those with higher levels of TB (prolonged QT prevalence was 4.7%, 6.8%, and 7.0% across TB lower (0-0.4 mg/dl), middle (0.5-1.6 mg/dl), and higher (0.70-4.30 mg/dl) tertiles, respectively). In a model adjusted for potential confounders, participants within the highest TB tertile had significantly greater odds of the prolonged QT interval (Odds ratios [95% confidence interval] 1.53 [1.16-2.02]) compared to those with bilirubin levels in the first tertile. Each 0.29 mg/dl increase in TB levels was associated with a 12% (p-value <.0001) increase in the prevalence of prolonged QT interval. This association was stronger in men than in women (interaction p-value = .04).

CONCLUSION

Elevated bilirubin levels are associated with a prolonged QT interval. This finding extends our current knowledge on the relationship between serum bilirubin and CVD by demonstrating a link between higher TB and abnormal cardiac repolarization.

Serum Albumin, but not Bilirubin, is Associated with Diabetic Chronic Vascular Complications in a Chinese Type 2 Diabetic Population

To identify the factors associated with serum total bilirubin (STB) and determine whether STB is independently associated with diabetic retinopathy (DR) or diabetic kidney disease (DKD), 1,665 Chinese patients with type 2 diabetes (T2DM) (248 outpatients newly diagnosed with T2DM [NDM] and 1,417 inpatients previously diagnosed with T2DM [PDM]) were studied. Clinical and biochemical information was collected, and a single nucleotide polymorphism (rs6704078) of the UGT1A1 gene was genotyped in 1,059 individuals. Multiple linear regression showed that STB was associated with haemoglobin concentration, platelet count, and serum triglyceride concentration in NDM and PDM patients, and with serum albumin, duration of diabetes, and smoking in PDM patients. In patients with PDM, multiple logistic regression revealed that serum albumin was associated with DR (odds ratio [OR] = 0.92, 95% confidence interval [CI]: 0.87-0.96, p = 0.001) and DKD (OR = 0.93, 95% CI: 0.88-0.98, p = 0.005) after adjustment for STB, STB-related factors, and risk factors for DR and DKD. In addition, patients with the T allele of rs6704078 had higher STB (13.2 [10.4-17.9] μmol/L versus 11.8 (9.4-14.8) μmol/L; p < 0.001) and similar risks of DR or DKD to those without the T allele. Thus, serum albumin, but not STB, is associated with DR and DKD.

Bilirubin Links Heme Metabolism to Neuroprotection by Scavenging Superoxide

Bilirubin is one of the most frequently measured metabolites in medicine, yet its physiologic roles remain unclear. Bilirubin can act as an antioxidant in vitro, but whether its redox activity is physiologically relevant is unclear because many other antioxidants are far more abundant in vivo. Here, we report that depleting endogenous bilirubin renders mice hypersensitive to oxidative stress. We find that mice lacking bilirubin are particularly vulnerable to superoxide (O₂^⋅-) over other tested reactive oxidants and electrophiles. Whereas major antioxidants such as glutathione and cysteine exhibit little to no reactivity toward O₂^⋅-, bilirubin readily scavenges O₂^⋅-. We find that bilirubin's redox activity is particularly important in the brain, where it prevents excitotoxicity and neuronal death by scavenging O₂^⋅- during NMDA neurotransmission. Bilirubin's unique redox activity toward O₂^⋅- may underlie a prominent physiologic role despite being significantly less abundant than other endogenous and exogenous antioxidants.

Bilirubin and Endothelial Function

Bilirubin is a fundamental metabolic end product of heme degradation. Despite acting as a cytotoxic metabolite at high concentrations, bilirubin at physiological concentrations has antioxidant effects, such as scavenging reactive oxygen species, leading to a decrease in oxidative stress. Endothelial dysfunction is an early feature of and plays an important role in the development and progression of atherosclerosis, leading to cardiovascular complications. One mechanism of endothelial dysfunction is an increase in oxidative stress, by which the bioavailability of nitric oxide is decreased. Therefore, bilirubin is expected to improve endothelial function, to inhibit the progression of atherosclerosis, and to reduce cardiovascular complications by inactivating oxidative stress through its antioxidant effects. In this review, we will focus on the clinical associations of the antioxidant bilirubin with endothelial function and cardiovascular complications.

Plasma Cathepsin S is Associated with High-density Lipoprotein Cholesterol and Bilirubin in Patients with Abdominal Aortic Aneurysms

Background

Cathepsin S (CTSS) is a cysteine protease involved in atherogenesis. We compared the plasma CTSS as well as other biomarkers of atherosclerosis in patients with abdominal aortic aneurysms (AAA) and aortoiliac occlusive disease (AOD), aiming to identify the underlying pathogenic mechanisms of the disease development. Also, we hypothesised that the level of plasma CTSS simultaneously increases with a decrease of plasma high-density lipoprotein cholesterol (HDL-C) values.

Methods

33 patients with AAA and 34 patients with AOD were included in this study.

Results

There was no difference in the level of plasma CTSS between the two analysed groups (p=0.833). In the patients with AAA, the plasma CTSS was correlated with HDL-C (r = -0.377, p = 0.034) and total bilirubin (r =0.500, p = 0.003) while, unexpectedly, it was not correlated with cystatin C (Cys C) (r =0.083, p = 0.652). In the patients with AOD, the plasma CTSS correlated with triglycerides (r = 0.597, p< 0.001), only. When the patients were divided according to HDL-C (with HDL-C ≤0.90 and HDL-C >0.90 mmol/L), the plasma CTSS values differed among these groups (31.27 vs.25.61 μg/L, respectively, p<0.001).

Conclusions

These results provide the first evidence that CTSS negatively correlated with HDL-C and bilirubin in patients with AAA. It is possible that differences in the association of the CTSS and other markers of atherosclerosis can determine whether atherosclerotic aorta will develop dilatation or stenosis.

Genome-Wide Association Study (GWAS) on Bilirubin Concentrations in Subjects with Metabolic Syndrome: Sex-Specific GWAS Analysis and Gene-Diet Interactions in a Mediterranean Population

Although, for decades, increased serum bilirubin concentrations were considered a threatening sign of underlying liver disease and had been associated with neonatal jaundice, data from recent years show that bilirubin is a powerful antioxidant and suggest that slightly increased serum bilirubin concentrations are protective against oxidative stress-related diseases, such as cardiovascular diseases. Therefore, a better understanding of the gene-diet interactions in determining serum bilirubin concentrations is needed. None of the previous genome-wide association studies (GWAS) on bilirubin concentrations has been stratified by sex. Therefore, considering the increasing interest in incorporating the gender perspective into nutritional genomics, our main aim was to carry out a GWAS on total serum bilirubin concentrations in a Mediterranean population with metabolic syndrome, stratified by sex. Our secondary aim was to explore, as a pilot study, the presence of gene-diet interactions at the GWAS level. We included 430 participants (188 men and 242 women, aged 55–75 years, and with metabolic syndrome) in the PREDIMED Plus-Valencia study. Global and sex-specific GWAS were undertaken to analyze associations and gene-diet interaction on total serum bilirubin. Adherence (low and high) to the Mediterranean diet (MedDiet) was analyzed as the dietary modulator. In the GWAS, we detected more than 55 SNPs associated with serum bilirubin at p < 5 × 10⁻⁸ (GWAS level). The top-ranked were four SNPs (rs4148325 (p = 9.25 × 10⁻²⁴), rs4148324 (p = 9.48 × 10⁻²⁴), rs6742078 (p = 1.29 × 10⁻²³), rs887829 (p = 1.39 × 10⁻²³), and the rs4148324 (p = 9.48 × 10⁻²⁴)) in the UGT1A1 (UDP glucuronosyltransferase family 1 member A1) gene, which replicated previous findings revealing the UGT1A1 as the major locus. In the sex-specific GWAS, the top-ranked SNPs at the GWAS level were similar in men and women (the lead SNP was the rs4148324-UGT1A1 in both men (p = 4.77 × 10⁻¹¹) and women (p = 2.15 × 10⁻¹⁴), which shows homogeneous genetic results for the major locus. There was more sex-specific heterogeneity for other minor genes associated at the suggestive level of GWAS significance (p < 1 × 10⁻⁵). We did not detect any gene-MedDiet interaction at p < 1 × 10⁻⁵ for the major genetic locus, but we detected some gene-MedDiet interactions with other genes at p < 1 × 10⁻⁵, and even at the GWAS level for the IL17B gene (p = 3.14 × 10⁻⁸). These interaction results, however, should be interpreted with caution due to our small sample size. In conclusion, our study provides new data, with a gender perspective, on genes associated with total serum bilirubin concentrations in men and women, and suggests possible additional modulations by adherence to MedDiet.

Low serum bilirubin levels associated with subclinical atherosclerosis in patients with obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is a chronic, progressive disease that can cause cardiovascular complications and atherosclerosis. We evaluated the relationship between serum bilirubin levels and carotid intima-media thickness (cIMT), as a surrogate marker of subclinical atherosclerosis, in patients with OSA.

Methods

We enrolled 84 consecutive patients with OSA. The patients underwent ultrasonography, polysomnography, and echocardiography. Blood samples were obtained from all of the subjects, which were used for biochemical comparisons. The patients were divided into groups according to cIMT values (<0.9 vs. >0.9 mm).

Results

The patient population consisted of 84 OSA patients (mean age: 54.2 + 8.0 years, 62.9% male). The OSA patients with cIMT ≥0.9 had significantly elevated high-sensitive C-reactive protein (hsCRP), Oxygen desaturation index, apnea-hypopnea index (AHI), and significantly lower total and indirect bilirubin levels. Multivariate regression analyses revealed that total bilirubin, hsCRP, and AHI were the independent predictors of subclinical atherosclerosis. There was a negative correlation between total bilirubin and cIMT.

Conclusions

This study showed that high hsCRP and low serum total bilirubin levels could be paving the way for the development of subclinical atherosclerosis. Simple measures such as total bilirubin may provide predictive information regarding the risk of cardiovascular disease in patients with OSA.

Exploring the relationship of peripheral total bilirubin, red blood cell, and hemoglobin with blood pressure during childhood and adolescence

OBJECTIVE

Total bilirubin is beneficial for protecting cardiovascular diseases in adults. The authors aimed to investigate the association of total bilirubin, red blood cell, and hemoglobin levels with the prevalence of high blood pressure in children and adolescents.

METHODS

A total of 3776 students (aged from 6 to 16 years old) were examined using cluster sampling. Pre-high blood pressure and high blood pressure were respectively defined as the point of 90th and 95th percentiles based on the Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Both systolic and diastolic blood pressure were standardized into z-scores.

RESULTS

Peripheral total bilirubin, red blood cell and hemoglobin levels were significantly correlated with age, and also varied with gender. Peripheral total bilirubin was negatively correlated with systolic blood pressure in 6- and 9-year-old boys, whilst positively correlated with diastolic blood pressure in the 12-year-old boys and 13- to 15-year-old girls (p<0.05). Higher levels of red blood cell and hemoglobin were observed in pre-high blood pressure and high blood pressure students when compared with their normotensive peers (p<0.01). The increases in red blood cell and hemoglobin were significantly associated with high blood pressure after adjusting for confounding factors. The ORs (95% CI) of each of the increases were 2.44 (1.52-3.92) and 1.04 (1.03-1.06), respectively. No statistical association between total bilirubin and high blood pressure was observed (p>0.05).

CONCLUSION

Total bilirubin could be weakly correlated with both systolic and diastolic blood pressure, as correlations varied with age and gender in children and adolescents; in turn, the increased levels of red blood cell and hemoglobin are proposed to be positively associated with the prevalence of high blood pressure.

Serum bilirubin level and its impact on the progression of chronic kidney disease

PURPOSE

To examine whether an elevated serum total bilirubin level affects the decline in renal function or new-onset chronic kidney disease (CKD) in patients with type 2 diabetes mellitus (DM2).

METHODS

This was a longitudinal observational study in patients who presented at the University of Health Sciences Hospital in Kayseri. Five hundred twenty-nine patients with DM2 who had conserved renal function were enrolled (estimated glomerular filtration rate > 60 ml/min/1.73 m²). Arising CKD stage 3 was the outcome measure. The patients were separated into three groups based on the total serum bilirubin levels. The first group (G1) ranged from 0.1 to 0.3, the second (G2) 0.4-0.5, and the third (G3) 0.6-0.9 mg/dl. The effect of total serum bilirubin levels on CKD 3 development was assessed using Cox proportional hazards regression.

RESULTS

The risk of the CKD stage 3 development was highest in G1 who has the lowest serum total bilirubin levels (G1 vs. G3; hazard ratio [HR], 2.02; 95% confidence interval [CI] 1.21-3.36; p = 0.007). In addition, G2 had a significant risk of CKD stage 3 development (G2 vs. G3; hazard ratio [HR], 1.58; 95% confidence interval [CI] 1.08-2.32; p = 0.018). In the adjusted analysis, compared to G2 and G3, G1 had the highest risk (G1 vs. G3; hazard ratio [HR], 2.20; 95% confidence interval [CI] 1.29-3.77; p = 0.004). Similarly, G2 had a higher risk compared to G3 (hazard ratio [HR], 1.57; 95% confidence interval [CI] 1.05-2.34; p = 0.028).

CONCLUSIONS

Serum bilirubin may predict the progression of CKD in patients with type 2 diabetes and preserved kidney function.

Low Bilirubin Levels Indicate a High Risk of Cerebral Deep White Matter Lesions in Apparently Healthy Subjects

Recent studies have reported that deep white matter lesions (DWMLs) on magnetic resonance imaging scans are related to the risk of developing impaired cognitive function in future. Bilirubin exhibits a potent antioxidant effect and an inverse relationship has been reported between bilirubin levels and the risk of several atherosclerotic diseases; however, there is limited evidence with regard to the effect of bilirubin levels on cerebrovascular diseases including DWMLs. This cross-sectional study included 1121 apparently healthy Japanese adults. The subjects were divided into three groups according to their bilirubin levels (low, <0.5 mg/dl; intermediate, ≥0.5 mg/dl and <1.0 mg/dl; and high, ≥1.0 mg/dl). The severity of DWMLs was evaluated according to Fazekas scale and their relation to bilirubin levels was examined. The association between bilirubin levels and the presence of severe DWMLs was assessed using multivariate logistic regression analysis. The analysis revealed that the low- and intermediate bilirubin groups indicated 2.36- and 1.33-fold increase in the prevalence of severe DWMLs compared with the high-bilirubin group, respectively (95% confidence interval (CI): 1.12-4.97 (the low-bilirubin group), 95% CI: 0.85-2.07 (the intermediate-bilirubin group). In conclusion, low total bilirubin levels could be associated with a high prevalence of severe DWMLs in apparent healthy subjects.

Relationship between serum bilirubin levels and cardiovascular disease

We tested the hypothesis that higher levels of bilirubin, a bile pigment with antioxidant properties, are associated with a decreased risk of cardiovascular disease (CVD). This study analyzed data from the Korean Health and Genome Study to examine the association between serum total bilirubin (TB) on CVD and CVD death. Serum TB was measured in a total of 8,844 subjects (4,196 males and 4,648 females) and evaluated for the development of new onset CVD from 2001 to 2012 (mean 8.1 years of follow-up). During the follow-up period, 689 cases of incident CVD (7.8%) were identified, and the prevalence of metabolic syndrome (MetS) at baseline was 26.1%. The prevalence of MetS decreased across bilirubin tertile categories. In addition to MetS itself, individual components of MetS significantly decreased with increased bilirubin tertiles. Moreover, the incidence of CVD decreased across bilirubin tertile categories. The hazard ratios (HRs) for developing coronary heart disease (CHD, HR 0.769, 95% CI 0.655–1.000) and CVD death (HR 0.513, 95% CI 0.267–0.985) was significantly lower in the highest tertile group (> 0.63 mg/dL) in comparison to the lowest tertile group (< 0.44 mg/dL) after adjusting for all confounding variables. In the present longitudinal study, a significant negative relationship was demonstrated between baseline bilirubin levels and incident CHD and CVD death.