Association of smoking and low serum bilirubin antioxidant concentrations

Differential effects of environmental exposures on clinically relevant endophenotypes between sexes

Sex and gender differences play a crucial role in health and disease outcomes. This study used data from the National Health and Nutrition Examination Survey to explore how environmental exposures affect health-related traits differently in males and females. We utilized a sex-stratified phenomic environment-wide association study (PheEWAS), which allowed the identification of associations across a wide range of phenotypes and environmental exposures. We examined associations between 272 environmental exposures, including smoking-related exposures such as cotinine levels and smoking habits, and 58 clinically relevant blood phenotypes, such as serum albumin and homocysteine levels. Our analysis identified 119 sex-specific associations. For example, smoking-related exposures had a stronger impact on increasing homocysteine, hemoglobin, and hematocrit levels in females while reducing serum albumin and bilirubin levels and increasing c-reactive protein levels more significantly in males. These findings suggest mechanisms by which smoking exposure may pose higher cardiovascular risks and greater induced hypoxia for women, and greater inflammatory and immune responses in men. The results highlight the importance of considering sex differences in biomedical research. Understanding these differences can help develop more personalized and effective health interventions and improve clinical outcomes for both men and women.

High-resolution metabolomics of exposure to tobacco smoke during pregnancy and adverse birth outcomes in the Atlanta African American maternal-child cohort

Exposure to tobacco smoke during pregnancy has been associated with a series of adverse reproductive outcomes; however, the underlying molecular mechanisms are not well-established. We conducted an untargeted metabolome-wide association study to identify the metabolic perturbations and molecular mechanisms underlying the association between cotinine, a widely used biomarker of tobacco exposure, and adverse birth outcomes. We collected early and late pregnancy urine samples for cotinine measurement and serum samples for high-resolution metabolomics (HRM) profiling from 105 pregnant women from the Atlanta African American Maternal-Child cohort (2014-2016). Maternal metabolome perturbations mediating prenatal tobacco smoke exposure and adverse birth outcomes were assessed by an untargeted HRM workflow using generalized linear models, followed by pathway enrichment analysis and chemical annotation, with a meet-in-the-middle approach. The median maternal urinary cotinine concentrations were 5.93 μg/g creatinine and 3.69 μg/g creatinine in early and late pregnancy, respectively. In total, 16,481 and 13,043 metabolic features were identified in serum samples at each visit from positive and negative electrospray ionization modes, respectively. Twelve metabolic pathways were found to be associated with both cotinine concentrations and adverse birth outcomes during early and late pregnancy, including tryptophan, histidine, urea cycle, arginine, and proline metabolism. We confirmed 47 metabolites associated with cotinine levels, preterm birth, and shorter gestational age, including glutamate, serine, choline, and taurine, which are closely involved in endogenous inflammation, vascular reactivity, and lipid peroxidation processes. The metabolic perturbations associated with cotinine levels were related to inflammation, oxidative stress, placental vascularization, and insulin action, which could contribute to shorter gestations. The findings will support the further understanding of potential internal responses in association with tobacco smoke exposures, especially among African American women who are disproportionately exposed to high tobacco smoke and experience higher rates of adverse birth outcomes.

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.

Patients with Gilbert syndrome and type 2 diabetes have lower prevalence of microvascular complications

Objective

Accumulating clinical evidence indicates an inverse relationship between oxidative stress and unconjugated hyperbilirubinemia. This study aimed to compare the prevalence of diabetes microvascular complications in patients with Gilbert syndrome and type 2 diabetes mellitus (T2D).

Methods

A total of 1200 electronic records with T2D were reviewed. From them, 50 patients with Gilbert syndrome (cases [indirect bilirubin ≥1.2 mg/dl without evidence of hemolysis or liver disease]) and 50 controls (T2D without hyperbilirubinemia) were included. Linear and logistic regression models were performed to evaluate the independent association between indirect hyperbilirubinemia with microvascular complications related with T2D.

Results

Both case and control group had the same proportion of gender (female = 20 [40 %]) and diabetes duration (14.0 ± 6.5 years) and similar mean of age (60 ± 9.6 and 60 ± 9.2 years, respectively, p = 0.91). The median of unconjugated bilirubin of case and control group was 1.4 (1.2–1.6) vs. 0.4 (0.2–0.6) mg/dl (p < 0.001), respectively. Patients with elevated unconjugated bilirubin had less urine albumin-creatinine ratio compared with control group (8.5 [4.3–23] vs. 80 [8–408] mg/g, p < 0.001), and lower rate of diabetes microvascular complications and metabolic syndrome. After adjustment for BMI, age, HbA1c, blood pressure, triglycerides, and the metabolic syndrome, the lineal regression analysis showed that unconjugated bilirubin protects against microalbuminuria in T2D patients (β = −414.11, 95 % CI [-747.9, −80.3], p = 0.006. Also, unconjugated hyperbilirubinemia was independently associated with a better glomerular filtration rate (GFR) (β = 9.87, 95 % CI [1.5, 18.3], P = 0.02).

Conclusions

Patients with Gilbert syndrome and T2D had a lower prevalence of diabetes microvascular complications.

Immediate effect of interscapular cupping on blood pressure, oxygen saturation, pulse rate and chest expansion in sedentary smoker students

Objectives

Increased sympathetic stimulation in smokers may be a risk factor for pulmonary and cardiovascular diseases. This study was conducted to assess the immediate effect of interscapular cupping on blood pressure (BP), oxygen (O2) saturation, chest expansion (CE), pulse rate (PR) in sedentary male smoker students.

Methods

Forty sedentary male smoker students– aged 18–25 years -were divided randomly into two equal numbered groups; wet cupping (WC) and dry cupping (DC) groups. Systolic and diastolic BP, upper and lower CE, O2 saturation and PR were measured immediately before and after a single cupping session in both groups.

Results

Both WC and DC types showed improvements in all measurements with a high statistically significant difference (p<0.05).

Conclusions

Interscapular cupping enhanced CE, O2 saturation, BP and PR in sedentary male smoker students.

Is there any relationship between serum levels of total bilirubin and the severity of erectile dysfunction?

OBJECTIVE

Recent studies have shown that atherosclerosis is associated with erectile dysfunction and the serum bilirubin level. In this study, the serum total bilirubin levels of patients with erectile dysfunction were measured to investigate the relationship between the levels of erectile dysfunction and total bilirubin.

METHODS

A total of 94 patients with erectile dysfunction were divided into three groups; severe erectile dysfunction (33 patients), moderate erectile dysfunction (31 patients), and mild erectile dysfunction (30 patients). In addition, a control group was formed with 31 healthy men. The International Index of Erectile Function-5 Questionnaire was used to measure the quality of erection in all the groups. The body mass index was calculated for all the participants. The serum glucose, low-density lipoprotein and high-density lipoprotein, cholesterol, triglyceride, total bilirubin, and total testosterone levels were also determined.

RESULTS

No statistically significant difference was observed between the groups in terms of the mean age, hypertension, smoking status, alcohol use, cardiovascular diseases, hepatobiliary disease, diabetes mellitus, and levels of total testosterone, low-density lipoprotein-cholesterol, and triglyceride. However, high-density lipoprotein, body mass index, and total bilirubin were significantly lower compared to the control group (p < 0.001). The serum total bilirubin level was found to be 0.41 ± 0.21 ng/dL in the severe erectile dysfunction, 0.43 ± 0.19 ng/dL in the moderate erectile dysfunction, and 0.48 ± 0.11 ng/dL in the mild erectile dysfunction groups (p < 0.001).

CONCLUSION

Considering the significant differences between the erectile dysfunction and control groups in terms of serum total bilirubin levels, a low level of bilirubin may have a role in the etiology of erectile dysfunction.

Association of serum bilirubin with longevity: Evidence from a retrospective longitudinal study and cross-sectional data

Bilirubin is a potent antioxidant and an important anti-inflammatory factor. Therefore, there has been an increasing focus on serum bilirubin as a negative risk factor of cardiovascular mortality in men and an indicator of improved survival in both sexes, but the direct mechanisms of these links and the causes of sex differences are not well understood. Moreover, the evidence from longitudinal studies on effects of bilirubin on longevity is limited. In this study, we retrospectively analyzed two groups of older adults to explore age-dependent changes in serum bilirubin levels and their associations with long-term survival in both sexes. Longitudinal data from 142 individuals (68 men and 74 women) aged 45 to 70 years were compared with cross-sectional data from 225 individuals (113 men and 112 women). The latter group was divided into four categories of survival, i.e. 53, 63, 68, and 76+ based on data on lifespan. ANOVA, t-test, and regression analysis were run. The analysis of the longitudinal data showed an increase in serum total bilirubin levels in men (0.3038e0.093x, R2 = 0.667) and women (0.1838e0.0187x, R2 = 0.950), while the analysis of cross-sectional data revealed a U-shaped pattern of age-related changes in men (0.001x2 - 0.1263x + 4.4524, R2 = 0.999) but an inverted U-shaped pattern in women (0.0006x2 + 0.072x - 1.6924, R2 = 0.195). On balance, these results suggest that elevated but normal bilirubin levels might confer a survival advantage in older men but not women. Alternatively, the positive relationship between serum total bilirubin and lifespan was not causal but coincidental. Further studies are needed to elucidate the direct mechanisms of the association between serum bilirubin levels and longevity in elderly people of both sexes.

Direct Bilirubin Levels and Risk of Metabolic Syndrome in Healthy Chinese Men

Background

Serum bilirubin is a potent endogenous antioxidant with anti-inflammatory properties. Several cross-sectional studies have reported that bilirubin was negatively associated with metabolic syndrome. However, in recent longitudinal studies, the relations between bilirubin and metabolic syndrome are inconsistent. Moreover, previous studies mainly focused on serum total bilirubin which is the sum of direct bilirubin and indirect bilirubin. For these reasons, the longitudinal effect of bilirubin subtypes on incident metabolic syndrome was evaluated in Chinese men.

Methods

The study cohort involved 1339 Chinese men without metabolic syndrome. Metabolic syndrome was defined by the American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI) criteria, using BMI for the replacement of waist circumference.

Results

There are 117 incident metabolic syndrome cases (8.7%) during 5 years of follow-up among 1339 metabolic syndrome-free participants at baseline. After adjusting for age, drinking, smoking, physical activity, TG, and LDL-C, the odd ratios (ORs) and 95% confidence intervals (CIs) for MetS incidence in the second, third, and fourth quartiles versus the first quartile of DBil concentration were 1.00 (0.61-1.63), 0.57 (0.32-1.02), and 0.51 (0.28-0.92) (P_trend = 0.031), respectively.

Conclusions

Our findings support the negative association between direct bilirubin and incident metabolic syndrome in healthy Chinese men over 5-year period.

Evaluation of genetic effect of NOS3 and G×E interaction on the variability of serum bilirubin in a Han Chinese population

Bilirubin was shown to be related to the generation and functional exertion of endothelial nitric oxide synthase (eNOS) whilst the genetic effect of NOS3 on bilirubin variability was rarely reported. Herein we assessed the associations of three single nucleotide polymorphisms (SNPs) of NOS3 (rs4496877, rs1808593, and rs3918186) with bilirubin elevation in 2077 adults. The results showed that rs1808593 was significantly associated with bilirubin elevation, and odds ratios (ORs) of dominant model for the elevation of total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IDBIL) were 0.837, 0.821 and 0.754, respectively (P < 0.05 for all). Stratification analysis indicated that rs3918186 was significantly associated with the elevation of TBIL and IDBIL in the males, and ORs of dominant model were 1.505 and 1.440 with P < 0.05 for all. In the smoking group, significant associations of rs4496877, rs1808593, and rs3918186 with TBIL elevation were observed, and ORs of dominant model were 1.739, 0.758 and 1.626 (P < 0.05 for all). rs4496877 and rs3918186 were both associated with TBIL elevation in the drinking group, and ORs were 1.557 and 1.769 with P < 0.05 for all. In the ≥55 year-old group, rs4496877 and rs1808593 were significantly associated with DBIL and IDBIL elevations, and ORs were 1.340 and 0.790 (P < 0.05). Meanwhile, rs4496877, rs1808593, rs3918186, smoking, and drinking were shown to have a notable interaction effects on the TBIL elevation. Our findings supported that NOS3 harbors the genetic susceptibility to the bilirubin elevation. Age, gender, smoking, and drinking could be involved in the genetic modification of NOS3 on the bilirubin variability.

Serum total bilirubin levels are negatively correlated with metabolic syndrome in aged Chinese women: a community-based study

We evaluated serum total bilirubin levels as a predictor for metabolic syndrome (MetS) and investigated the relationship between serum total bilirubin levels and MetS prevalence. This cross-sectional study included 1728 participants over 65 years of age from Eastern China. Anthropometric data, lifestyle information, and previous medical history were collected. We then measured serum levels of fasting blood-glucose, total cholesterol, triglycerides, and total bilirubin, as well as alanine aminotransferase activity. The prevalence of MetS and each of its individual component were calculated per quartile of total bilirubin level. Logistic regression was used to assess the correlation between serum total bilirubin levels and MetS. Total bilirubin level in the women who did not have MetS was significantly higher than in those who had MetS (P<0.001). Serum total bilirubin quartiles were linearly and negatively correlated with MetS prevalence and hypertriglyceridemia (HTG) in females (P<0.005). Logistic regression showed that serum total bilirubin was an independent predictor of MetS for females (OR: 0.910, 95%CI: 0.863-0.960; P=0.001). The present study suggests that physiological levels of serum total bilirubin might be an independent risk factor for aged Chinese women, and the prevalence of MetS and HTG are negatively correlated to serum total bilirubin levels.

Total bilirubin in athletes, determination of reference range

The purpose of this study was to determine a typical reference range for the population of athletes. Results of blood tests of 339 athletes (82 women and 257 men, aged 18-37 years) were retrospectively analysed. The subjects were representatives of different sports disciplines. The measurements of total bilirubin (BIT), iron (Fe), alkaline phosphatase (ALP), alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) were made using a Pentra 400 biochemical analyser (Horiba, France). Red blood cell count (RBC), reticulocyte count and haemoglobin concentration measurements were made using an Advia 120 haematology analyser (Siemens, Germany). In groups of women and men the percentage of elevated results were similar at 18%. Most results of total bilirubin in both sexes were in the range 7-14 μmol·L^-1 (49% of women and 42% of men). The highest results of elevated levels of BIT were in the range 21-28 μmol·L^-1 (12% of women and 11% of men). There was a significant correlation between serum iron and BIT concentration in female and male athletes whose serum total bilirubin concentration does not exceed the upper limit of the reference range. Elevated concentrations of total bilirubin appear to be due to changes caused by regular exercise. The obtained upper limit of the reference range for total bilirubin concentration in the group of athletes is 29.0 μmol·L^-1. It seems reasonable to use dedicated reference values for total bilirubin concentration in relation to the group of athletes.

Cigarette smoking behaviour and blood metabolomics

BACKGROUND

Identifying circulating metabolites related to cigarette smoking may provide insight into the biological mechanisms of smoking-related diseases and the nature of addiction. However, previous studies are limited, generally small, and have largely targeted a priori metabolites.

METHODS

We examined associations between cigarette smoking and metabolites using an untargeted metabolomics approach in 892 men and women from four studies including participants from Italy, USA, China and Finland. We examined associations between individual log-transformed metabolites and two key smoking phenotypes (current smoking status and cigarettes per day [cig/day]) using linear regression. Fixed-effect meta-analysis was used to combine results across studies. Strict Bonferroni thresholds were used as our significance criteria. We further examined associated metabolites with other metrics of smoking behaviuor (current versus former, former versus never, smoking duration and years since quitting) in the US study.

RESULTS

We identified a total of 25 metabolites associated with smoking behaviours; 24 were associated with current smoking status and eight with cig/day. In addition to three well-established nicotine metabolites (cotinine, hydroxycotinine, cotinine N-oxide), we found an additional 12 xenobiotic metabolites involved in benzoatic (e.g. 3-ethylphenylsulphate) or xanthine metabolism (e.g. 1-methylurate), three amino acids (o-cresol sulphate, serotonin, indolepropionate), two lipids (scyllo-inositol, pregnenolone sulphate), four vitamins or cofactors [e.g. bilirubin (Z,Z)], and one carbohydrate (oxalate).

CONCLUSIONS

We identified associations between cigarette smoking and a diverse range of metabolites. Our findings, with further validation in future studies, have implications regarding aetiology and study design of smoking-related diseases.

Association between serum bilirubin levels and decline in estimated glomerular filtration rate among patients with type 2 diabetes

AIMS

Studies indicate that elevated serum total bilirubin (TBil) levels are associated with lower risk of diabetic kidney disease (DKD). Few studies examined the associations of direct bilirubin (DBil) and indirect bilirubin (IBil) with the development of DKD.

METHODS

Type 2 diabetes patients (n=2,958) with estimated glomerular filtration (eGFR)≥60mlmin(-1) 1.73m(-2) from the Dongfeng-Tongji cohort were selected and followed up for 5years. Development of DKD was defined as decline in eGFR≥30% during follow-up. Generalize linear model was used to assess the associations of bilirubin levels with DKD development.

RESULTS

Compared with those in the first tertile of serum TBil, the relative risks (RRs) and 95% confidence intervals (CIs) of incident eGFR decline for tertile 2 to 3 were 0.83 (0.64-1.09) and 0.74 (0.56-0.98), Ptrend=0.04. The counterpart RRs (95% CIs) in IBil were 0.74 (0.57-0.97) and 0.75 (0.57-0.98), Ptrend=0.04. No significant associations were observed in DBil. Moreover, TBil and IBil interacted with smoking, the bilirubin-DKD associations were evident in ever smokers.

CONCLUSIONS

Our findings suggest that elevation of serum TBil or IBil levels are independent protective factors for development of DKD, particularly in smokers.

Fusing Data Mining, Machine Learning and Traditional Statistics to Detect Biomarkers Associated with Depression

BACKGROUND

Atheoretical large-scale data mining techniques using machine learning algorithms have promise in the analysis of large epidemiological datasets. This study illustrates the use of a hybrid methodology for variable selection that took account of missing data and complex survey design to identify key biomarkers associated with depression from a large epidemiological study.

METHODS

The study used a three-step methodology amalgamating multiple imputation, a machine learning boosted regression algorithm and logistic regression, to identify key biomarkers associated with depression in the National Health and Nutrition Examination Study (2009-2010). Depression was measured using the Patient Health Questionnaire-9 and 67 biomarkers were analysed. Covariates in this study included gender, age, race, smoking, food security, Poverty Income Ratio, Body Mass Index, physical activity, alcohol use, medical conditions and medications. The final imputed weighted multiple logistic regression model included possible confounders and moderators.

RESULTS

After the creation of 20 imputation data sets from multiple chained regression sequences, machine learning boosted regression initially identified 21 biomarkers associated with depression. Using traditional logistic regression methods, including controlling for possible confounders and moderators, a final set of three biomarkers were selected. The final three biomarkers from the novel hybrid variable selection methodology were red cell distribution width (OR 1.15; 95% CI 1.01, 1.30), serum glucose (OR 1.01; 95% CI 1.00, 1.01) and total bilirubin (OR 0.12; 95% CI 0.05, 0.28). Significant interactions were found between total bilirubin with Mexican American/Hispanic group (p = 0.016), and current smokers (p<0.001).

CONCLUSION

The systematic use of a hybrid methodology for variable selection, fusing data mining techniques using a machine learning algorithm with traditional statistical modelling, accounted for missing data and complex survey sampling methodology and was demonstrated to be a useful tool for detecting three biomarkers associated with depression for future hypothesis generation: red cell distribution width, serum glucose and total bilirubin.

The relationship between serum bilirubin concentration and coronary artery ectasia

Introduction

The pathophysiology of coronary artery ectasia (CAE) has not been clearly identified, although multiple abnormalities including arteritis, endothelial dysfunction, and atherothrombosis have been reported. Several studies have demonstrated that higher serum bilirubin inhibits the inflammation and proliferation of vascular smooth muscle cells; also there is a relationship between serum bilirubin and cardiovascular disease. However, the relationship between bilirubin and CAE is still unknown.

Aim

We compared serum bilirubin concentration between CAE patients and controls.

Material and methods

This study included 50 CAE patients (20 male, mean age: 60.26 ±10.6 years) and 30 control persons (10 male, mean age: 57.86 ±11.6 years). These participants underwent concurrent routine biochemical tests and leukocyte count, hemoglobin, hematocrit and platelet count in whole blood. These parameters were compared between groups.

Results

No statistically significant difference was found between the two groups in terms of basic characteristics. Total, direct and indirect serum bilirubin levels were significantly lower among persons with CAE patients than controls (0.37 ±0.4 vs. 0.71 ±0.6 and 0.13 ±0.1 vs. 0.27 ±0.2 and 0.24 ±0.2 vs. 0.43 ±0.4 mg/dl; all p<0.001, respectively).

Conclusions

Our study revealed a relationship between serum bilirubin and CAE.

Serum bilirubin concentration is modified by UGT1A1 haplotypes and influences risk of type-2 diabetes in the Norfolk Island genetic isolate

Background

Located in the Pacific Ocean between Australia and New Zealand, the unique population isolate of Norfolk Island has been shown to exhibit increased prevalence of metabolic disorders (type-2 diabetes, cardiovascular disease) compared to mainland Australia. We investigated this well-established genetic isolate, utilising its unique genomic structure to increase the ability to detect related genetic markers. A pedigree-based genome-wide association study of 16 routinely collected blood-based clinical traits in 382 Norfolk Island individuals was performed.

Results

A striking association peak was located at chromosome 2q37.1 for both total bilirubin and direct bilirubin, with 29 SNPs reaching statistical significance (P < 1.84 × 10⁻⁷). Strong linkage disequilibrium was observed across a 200 kb region spanning the UDP-glucuronosyltransferase family, including UGT1A1, an enzyme known to metabolise bilirubin. Given the epidemiological literature suggesting negative association between CVD-risk and serum bilirubin we further explored potential associations using stepwise multivariate regression, revealing significant association between direct bilirubin concentration and type-2 diabetes risk. In the Norfolk Island cohort increased direct bilirubin was associated with a 28 % reduction in type-2 diabetes risk (OR: 0.72, 95 % CI: 0.57-0.91, P = 0.005). When adjusted for genotypic effects the overall model was validated, with the adjusted model predicting a 30 % reduction in type-2 diabetes risk with increasing direct bilirubin concentrations (OR: 0.70, 95 % CI: 0.53-0.89, P = 0.0001).

Conclusions

In summary, a pedigree-based GWAS of blood-based clinical traits in the Norfolk Island population has identified variants within the UDPGT family directly associated with serum bilirubin levels, which is in turn implicated with reduced risk of developing type-2 diabetes within this population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0291-z) contains supplementary material, which is available to authorized users.

Active and Passive Smoking and Serum Total Bilirubin in a Rural Korean Population

INTRODUCTION

Serum bilirubin is an endogenous antioxidant biomarker and its low level is a potential risk factor for smoking related health disorders. This study investigated the association of cigarette smoke with serum total bilirubin among Koreans.

METHODS

Between 2006 and 2011, we examined 4899 Korean adults living in a rural community. After excluding 38 participants with serum bilirubin more than 2mg/dL, 75 participants who did not report their smoking status or who had liver or bile duct disorders, and 711 participants with liver enzymes exceeding the upper reference values, we performed a cross-sectional analysis on 4075 participants. Participants were classified into four groups: never-smokers without secondhand smoke exposure (SHSE), never-smokers with SHSE, former smokers, and active smokers. Serum total bilirubin concentration was measured using the enzyme method.

RESULTS

Compared to never-smokers without SHSE, never-smokers with SHSE (β = -0.025 mg/dL), former smokers (β = -0.049 mg/dL), and active smokers (β = -0.149 mg/dL) had significantly lower serum bilirubin even after adjusting for demographic factors, study year, alanine aminotransferase, gamma-glutamyl transferase, hemoglobin, lifestyle factors, and chronic diseases. A sex-stratified analysis indicated that for men, former smokers and active smokers were significantly associated with having lower bilirubin when compared to never-smokers without SHSE. However, for women, never-smokers with SHSE and active smokers were significantly associated with having lower bilirubin when compared to never-smokers without SHSE.

CONCLUSION

Our findings suggest that both active and passive cigarette smoking are associated with low serum bilirubin among Korean adults.

IMPLICATIONS

Our results suggest that not only active smoking but also passive smoking including SHSE can have an influence on decreasing serum bilirubin levels. With this different point of view, our study supports efforts to create smoke-free environments in order to foster more favorable serum bilirubin profiles, which may improve endothelial function and reduce the risk of cardiovascular disease.

Serum bilirubin levels predict future development of metabolic syndrome in healthy middle-aged nonsmoking men

BACKGROUND

Despite epidemiologic research demonstrating an inverse relationship between serum bilirubin levels and the prevalence of metabolic syndrome, prospective data on serum bilirubin as a predictor of incident metabolic syndrome are limited.

METHODS

Serum bilirubin was examined as a risk marker for incident metabolic syndrome in a prospective study of 468 Taiwanese middle-aged men who were free of metabolic syndrome and other systemic diseases at baseline. These subjects were followed up in annual health examinations between 2001 and 2009 for the development of metabolic syndrome, which was defined according to unified criteria set by several major organizations.

RESULTS

Among the study subjects, 377 were nonsmokers and 91 were current smokers. All individuals were then stratified into 3 groups according to their baseline serum bilirubin levels (low, normal, and high). During a mean follow-up period of 7.58 years, 66 subjects developed metabolic syndrome. The incidence of metabolic syndrome was significantly reduced in the high-bilirubin group compared with the low-bilirubin group (6.4% vs 22.4%, P < .001). Multivariate Cox regression analysis revealed that the hazard ratio for incident metabolic syndrome between the highest and lowest tertiles of serum bilirubin levels was 0.246 (95% confidence interval 0.120-0.503). However, although it remained clearly evident in nonsmokers, the inverse correlation was attenuated in current smokers.

CONCLUSIONS

Increased serum bilirubin was associated with a reduced future risk of metabolic syndrome in apparently healthy middle-aged, nonsmoking men. Our findings support the predictive role of serum total bilirubin for future development of metabolic syndrome.

Bilirubin treatment suppresses pulmonary inflammation in a rat model of smoke-induced emphysema

BACKGROUND

Cigarette smoking is a significant risk factor for emphysema, which is characterized by airway inflammation and oxidative damage.

OBJECTIVES

To assess the capacity of bilirubin to protect against smoke-induced emphysema.

METHODS

Smoking status and bilirubin levels were recorded in 58 patients with chronic obstructive pulmonary diseases (COPD) and 71 non-COPD participants. The impact of smoking on serum bilirubin levels and exogenous bilirubin (20 mg/kg/day) on pulmonary injury was assessed in a rat model of smoking-induced emphysema. At sacrifice lung histology, airway leukocyte accumulation and cytokine and chemokine levels in serum, bronchoalveolar lavage fluid (BALF) and lung were analyzed. Oxidative lipid damage and anti-oxidative components was assessed by measuring malondialdehyde, superoxide dismutase (SOD) activity and glutathione.

RESULTS

Total serum bilirubin levels were lower in smokers with or without COPD than non-smoking patients without COPD (P < 0.05). Indirect serum bilirubin levels were lower in COPD patients than patients without COPD (P < 0.05). In rats, cigarette smoke reduced serum total and indirect bilirubin levels. Administration of bilirubin reduced mean linear intercept and mean alveoli area, increased mean alveoli number, reduced macrophage, neutrophil and TNF-α content of BALF, and increased BALF and serum IL-10 level, but lowered local and systemic CCL2, CXCL2, CXCL8 and IL-17 levels. Bilirubin suppressed the smoke-induced systemic and regional oxidative lipid damage associated with increased SOD activity.

CONCLUSION

Bilirubin attenuated smoking-induced pulmonary injury by suppressing inflammatory cell recruitment and pro-inflammatory cytokine secretion, increasing anti-inflammatory cytokine levels, and anti-oxidant SOD activity in a rat model of smoke-induced emphysema.

Mildly elevated serum total bilirubin levels are negatively associated with carotid atherosclerosis among elderly persons with type 2 diabetes

Diabetes is strongly associated with several mechanisms of tissue damage such as oxidative stress. Serum bilirubin may have a beneficial role in preventing oxidative changes in cardiovascular disease (CVD). Limited information is available on whether serum bilirubin is an independent confounding factor for carotid atherosclerosis among elderly persons with type 2 diabetes. The study subjects were 169 men aged 79 ± 8 (mean ± SD) years and 205 women aged 81 ± 8 years that were enrolled consecutively from patients in the medical department. Carotid intima-media thickness (IMT) and plaque were derived via B-mode ultrasonography. Multiple linear regression analysis showed that serum total bilirubin (β = -0.160) was significantly associated with carotid IMT. Compared to subjects with a serum total bilirubin of tertile-1 (0.13-0.58 mg/dL), the multivariate-adjusted odds ratio (95% confidence interval) of carotid IMT ≥1.0 mm including plaque and carotid plaque was 0.46 (0.23-0.93) and 0.32 (0.17-0.60) in the Tertile-3 group (0.87-1.93 mg/dL), respectively. Next, data were further stratified by gender, age, smoking status, medication and prevalence of CVD. There were no significant differences in serum total bilirubin levels between selected subgroups. Our data demonstrated a negative association between serum total bilirubin and carotid atherosclerosis among elderly persons with type 2 diabetes.

The Milieu Intérieur study - an integrative approach for study of human immunological variance

The Milieu Intérieur Consortium has established a 1000-person healthy population-based study (stratified according to sex and age), creating an unparalleled opportunity for assessing the determinants of human immunologic variance. Herein, we define the criteria utilized for participant enrollment, and highlight the key data that were collected for correlative studies. In this report, we analyzed biological correlates of sex, age, smoking-habits, metabolic score and CMV infection. We characterized and identified unique risk factors among healthy donors, as compared to studies that have focused on the general population or disease cohorts. Finally, we highlight sex-bias in the thresholds used for metabolic score determination and recommend a deeper examination of current guidelines. In sum, our clinical design, standardized sample collection strategies, and epidemiological data analyses have established the foundation for defining variability within human immune responses.

The duration of diabetes is inversely associated with the physiological serum bilirubin levels in patients with type 2 diabetes

OBJECTIVE

The aim of this study was to assess the relationship between the duration of diabetes and the physiological serum bilirubin concentration in association with antioxidant properties in patients with type 2 diabetes.

METHODS

A total of 1,746 patients with type 2 diabetes were investigated in this cross-sectional study. An analysis of covariance was performed after adjusting for other covariates. Simple correlation analyses and a multivariate regression model were used to assess the association between the duration of diabetes and the serum bilirubin concentration.

RESULTS

The mean total bilirubin value differed significantly according to the tertile of diabetes duration (<5 years, 12.38 μmol/L, 95% confidence interval (CI) 12.02-12.76; 5-11.9 years, 12.33 μmol/L, 95% CI 11.97-12.69; ≥12 years, 11.73 μmol/L, 95% CI 11.35-12.11; p for trend =0.033), after adjustment for other covariates. In addition, an inverse correlation was found between the serum bilirubin concentration and diabetes duration (ρ=-0.211, p<0.001). According to a multivariate model, the association between the diabetes duration and serum bilirubin concentration remained significant, even after adjustment for confounding factors (β=-0.074, p=0.008).

CONCLUSION

The duration of diabetes is inversely associated with a serum bilirubin concentration within the physiologic range in patients with type 2 diabetes.

Cross-sectional and longitudinal associations between serum bilirubin and dyslipidemia in a health screening population

OBJECTIVE

To investigate cross-sectional and longitudinal associations between serum total bilirubin (TB) and dyslipidemia.

METHODS

Odds ratios (ORs) of prevalent dyslipidemia for TB were calculated in 2113 men and 1265 women. Correlation coefficients between baseline TB as well as the change in TB over 5 years and baseline log triglycerides, baseline HDL cholesterol and the changes in log triglycerides and HDL cholesterol over 5 years were calculated. Hazard ratios (HRs) of incident hypertriglyceridemia and hypo-HDL cholesterolemia for TB over 5 years were calculated in 1324 men and 915 women and 1583 men and 884 women, respectively.

RESULTS

The ORs of prevalent hypertriglyceridemia and hypo-HDL cholesterolemia for each one SD increase in TB were 0.83 (p < 0.001) in men and 0.71 (p = 0.074) in women and 0.64 (p < 0.001) in men and 0.78 (p = 0.089) in women, respectively adjusted for age, smoking, and other confounders. The baseline TB was significantly correlated with baseline log triglycerides and HDL cholesterol both in men and women while the change in TB was significantly correlated with the changes in log triglycerides and HDL cholesterol in men and the change in HDL cholesterol in women. The HRs of incident hypertriglyceridemia and hypo-HDL cholesterolemia for each one SD increase in TB were 0.99 (p = 0.848) in men and 0.74 (p = 0.033) in women and 1.08 (p = 0.345) in men and 0.85 (p = 0.220) in women, respectively adjusted for age, smoking, and other confounders.

CONCLUSION

Baseline TB was significantly associated with both prevalent hypertriglyceridemia and hypo-HDL cholesterolemia in men and with incident hypertriglyceridemia in women.

Association between serum bilirubin and estimated glomerular filtration rate among elderly persons

Chronic kidney disease (CKD) is a major public health problem. However, few studies have examined the significance of serum bilirubin as a risk factor for the development of CKD in the general Japanese population. The subjects comprised 413 men (mean age: 79±9 years; (range, 60-100 years) and 637 women (mean age: 81±8 years; range, 60-106 years) who visited the medical department of Seiyo Municipal Nomura Hospital. We examined the relationship between increased serum bilirubin and renal function that was evaluated by estimated glomerular filtration rate (eGFR) using CKD-EPI equations modified by a Japanese coefficient. Stepwise multiple regression analysis with eGFR as the objective variable, and adjusted risk factors as the explanatory variables, showed that serum bilirubin (β = 0.11, P<0.001) was significantly and independently associated with eGFR, in addition to gender, age, prevalence of antihypertensive medication, triglycerides, prevalence of antidiabetic medication, and serum uric acid. Compared with stages 1+2 (eGFR ≥60.0 ml/min/1.73 m2), mean multivariate-adjusted odds ratio {95% (confidence interval (CI)} for hypobilirubinemia (first quartile, <0.52 mg/dL) was 3.52 (range: 1.88-6.59). Next, to control potential confounding factors, data were further stratified by gender, age, medication (antihypertensive, antidyslipidemic, and antidiabetic agents), and prevalence of cardiovascular disease. The standardized coefficient for eGFR was significant in both groups, and there was no interaction between the groups. Our data demonstrated an independent positive association between serum bilirubin and eGFR in both genders. Low serum bilirubin level would be useful as a potential risk factor for renal function.

Mildly elevated serum bilirubin levels are negatively associated with carotid atherosclerosis among elderly persons

Serum bilirubin may have a beneficial role in preventing oxidative changes in atherosclerosis. Limited information is available on whether serum total bilirubin is an independent confounding factor for carotid atherosclerosis {for example, intima-media thickness (IMT), plaque} measured noninvasively by B-mode ultrasonography only among elderly persons. The study subjects were 325 men aged 79±8 (mean ± standard deviation) years and 509 women aged 81±8 years that were enrolled consecutively from patients aged ≥60 years in the medical department. Carotid IMT and plaque were derived via B-mode ultrasonography. Multiple linear regression analysis showed that in men age (β = 0.199, p = 0.002), smoking status (β = 0.154, p = 0.006), GGT (β = -0.139, p = 0.039), and GGT (β = -0.133, p = 0.022) were significantly and independently associated with carotid IMT, and in women age (β = 0.186, p<0.001), systolic blood pressure (β = 0.104, p = 0.046), diastolic blood pressure (β = -0.148, p = 0.004), prevalence of antihypertensive medication (β = 0.126, p = 0.004), fasting plasma glucose (β = 0.135, p = 0.003), GGT (β = -0.104, p = 0.032), estimated glomerular filtration rate, serum bilirubin (β = -0.119, p = 0.006), and prevalence of cardiovascular disease (CVD) (β = 0.103, p = 0.017) were also independently associated with carotid IMT. The odds ratios (ORs) {95% confidence interval (CI)} of increasing serum bilirubin category were negatively associated with carotid IMT ≥1.0 mm and plaque in both genders. Compared to subjects with a serum bilirubin of Quartile-1, the multivariate-OR (95% CI) of carotid plaque was 0.25 (0.11–0.57) in the Quartile-4 male group, and 0.41 (0.21–0.78) in the Quartile-2 female group, 0.51 (0.26–0.98) in the Quartile-3 female group, and 0.46 (0.24–0.89) in the Quartile-4 female group. Our data demonstrated an independently negative association between serum bilirubin and carotid atherosclerosis in both genders.

UGT1A1*28 polymorphism and acute lymphoblastic leukemia in children: a Danish case-control study

BACKGROUND

Oxidative stress is a possible risk factor in the development of acute lymphoblastic leukemia (ALL) in children. Bilirubin is a potent endogenous antioxidant, and the UGT1A1*28 polymorphism is the main genetic cause of variation in plasma bilirubin in Western Europe.

METHODS

In a case-control study of 665 incident cases of ALL in childhood in Denmark 1982-2010 and 1,379 controls, associations between UGT1A1*28 genotypes and ALL in childhood were estimated as odds ratios by logistic regression with adjustment for sex and birth decade. Subgroup analyses were carried out by age at onset in three groups, and on the ALL subtypes precursor B-cell, T-cell, and t(12;21) positive status. Cases were identified in The Danish Registry of Childhood Cancer, and genotypes were estimated from dried blood spots stored in The Danish Neonatal Screening Biobank. Controls were newborns with blood spots taken right before and after a case.

RESULTS

We found no association between ALL in childhood and UGT1A1*28 genotypes. The odds ratio was 1.01 (0.88-1.17) for heterozygotes and 1.03 (0.78-1.36) for homozygotes. Also, no associations were found in the subgroup analyses.

CONCLUSION

We found no association between the UGT1A1*28 genotypes and ALL in children.

Perfluorocarbons and Gilbert syndrome (phenotype) in the C8 Health Study Population

BACKGROUND

Gilbert syndrome (GS) is an inherited defect of bilirubin conjugation, most commonly caused by a gene mutation for the enzyme UGT1A. GS is known to affect the metabolism and excretion of drugs and xenobiotics. Perfluorocarbon compounds (PFCs) are bio-persistent environmental contaminants that affect metabolic regulation. In this study, we examined the associations of GS phenotype and serum PFCs in the C8 Health Study Population.

MATERIALS AND METHODS

Using 2005-2006 data from a large PFC-exposure population survey, we compared serum PFCs concentrations between GS and non GS clinical phenotypes, in a cross sectional design, adjusting for standard risk factors, including age, BMI, smoking status, socioeconomic status and gender.

RESULTS

Among 10 PFC compounds considered, only perfluorohexanoic acid (PFHxA) was seen at a significantly higher concentration in GS men and women.

CONCLUSION

PFHxA exposure may be associated with GS. Our findings do not support increased exposure in GS for other PFCs.

Protective Effects of Inducible HO-1 on Oxygen Toxicity in Rat Brain Endothelial Microvessel Cells

BACKGROUND

Reperfusion in ischemia is believed to generate cytotoxic oxidative stress, which mediates reperfusion injury. These stress conditions can initiate lipid peroxidation and damage to proteins, as well as promote DNA strand breaks. As biliverdin and bilirubin produced by heme oxygenase isoform 1 (HO-1) have antioxidant properties, the production of both antioxidants by HO-1 may help increase the resistance of the ischemic brain to oxidative stress. In the present study, the survival effect of HO-1 was confirmed using hemin.

METHODS

To confirm the roles of HO-1, carbon monoxide, and cyclic guanosine monophosphate further in the antioxidant effect of HO-1 and bilirubin, cells were treated with cycloheximide, desferoxamine, and zinc deuteroporphyrin IX 2,4 bis glycol, respectively.

RESULTS

HO-1 itself acted as an antioxidant. Furthermore, iron, rather than carbon monoxide, was involved in the HO-1-mediated survival effect. HO-1 activity was also important in providing bilirubin as an antioxidant.

CONCLUSION

Our results suggested that HO-1 helped to increase the resistance of the ischemic brain to oxidative stress.

Factor analysis of biochemical markers associated with bone mineral density in adults

[Purpose] The aim of this study was to find biochemical markers related to low bone mineral density in Korean adults. [Subjects and Methods] From August 1 to September 15, 2013, subjects receiving medical checkups were classified as lumbar spine bone normal, osteopenic, or osteoporotic using a bone mineral densitometer. Next, age, body mass index, and biochemical parameter differences were compared among the three groups. [Results] The results revealed that, the relevant factors were maximum blood pressure, minimum blood pressure, bone mineral density, total bilirubin, alkaline phosphatase (ALP), fasting blood glucose, iron, neutrophils, monocytes, and eosinophils. The bone mineral density of patients with osteoporosis was 0.763 times lower than that of normal subjects. The total bilirubin level of patients with osteoporosis was 0.45 times lower than that of normal subjects. The alkaline phosphatase level of patients with osteopenia was 1.059 times higher than that of normal subjects, and that in patients with osteoporosis was 1.088 times higher than that in normal subjects. The fasting blood glucose level of patients with osteoporosis was 0.963 times lower than that of normal subjects. The iron level of patients with osteoporosis was 0.986 times lower than that of normal subjects. [Conclusion] In conclusion, osteoporosis is a representative disease in elderly women due to aging and menopause, and more active interest should be taken for prevention and treatment.

Combined effects of smoking and bilirubin levels on the risk of lung cancer in Korea: the severance cohort study

BACKGROUND

Smoking is a major risk factor for lung cancer. Bilirubin, an antioxidant, is inversely associated with the risk of diseases related to oxidative stress. This study was conducted to determine the influence of smoking and bilirubin levels on the risk of lung cancer in the Severance cohort study.

METHODS

This study included 68,676 Korean who received a health examination at Severance Health Promotion Center from 1994 to 2004. Serum bilirubin measurements within normal range were divided into tertiles whereas smoking states were divided as never-smokers, former smokers and current smokers. A diagnosis of lung cancer was coded as occurring based on the report from the National Cancer Registry. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated using Cox proportional hazards model.

RESULTS

At the end of the study period, 240 patients (men: 181, women: 59) developed lung cancer. Compared to those with bilirubin levels ≥ 1.0 mg/dL, HRs (95% CI) for lung cancer were 2.8 (1.8-4.2) for subjects having bilirubin levels from 0.2 to 0.7 mg/dL in men. When we stratified our analysis by smoking status, bilirubin consistently showed a protective effect on the risk of lung cancer on both never- and current smokers. Current smokers having bilirubin levels from 0.2 to 0.7 mg/dL had a risk of lung cancer by 6.0-fold higher than never-smokers with bilirubin levels ≥ 1.0 mg/dL in men.

CONCLUSION

In this large prospective study, higher baseline bilirubin level in the normal range was associated with low risk of lung cancer. Smoking and low bilirubin levels were cumulatively associated with a higher risk of lung cancer.

Serum total bilirubin concentrations are inversely associated with total white blood cell counts in an adult population

BACKGROUND

Several studies have shown that serum bilirubin has a protective effect against cardiovascular disease and that inflammation plays an important role in its pathogenesis. This cross-sectional study investigated whether there was an association between blood total white blood cell count, a simple indicator of inflammation, and serum total bilirubin concentration in a cohort of an adult population in Taiwan.

METHODS

A total of 2458 apparently healthy adults (1246 men and 1212 women) who attended health examination at a medical centre in central Taiwan were enrolled. We collected anthropometric measurements, fasting blood test results, lifestyle habits and medical history.

RESULTS

Total white blood cell counts decreased progressively when the concentrations of total bilirubin increased as demonstrated in the total bilirubin quartiles. Both total bilirubin concentrations and total white blood cell counts showed significant correlations with the components of metabolic syndrome, including triglyceride and high-density lipoprotein cholesterol concentrations. Multivariate linear regression analysis revealed that, for both genders, total bilirubin showed an independent negative correlation with total white blood cell count after adjusting for conventional cardiovascular risk factors.

CONCLUSIONS

Higher serum total bilirubin concentrations within the reference range were associated with lower blood total white blood cell counts, regardless of other classical cardiovascular risk factors.

Smoking cessation is followed by increases in serum bilirubin, an endogenous antioxidant associated with lower risk of lung cancer and cardiovascular disease

INTRODUCTION

Lower concentrations of serum bilirubin, an endogenous antioxidant, have been associated with risk of many smoking-related diseases, including lung cancer and cardiovascular disease, and current smokers are reported to have lower bilirubin levels than nonsmokers and past smokers. This study evaluates the effects of smoking cessation on bilirubin levels.

METHODS

In a secondary analysis of a 6-week placebo-controlled trial of naltrexone for smoking cessation, indirect and total bilirubin concentrations were evaluated at baseline and following smoking cessation. Individuals who were continuously abstinent for 6 weeks (n = 155) were compared to those who were not (n = 193). Participants reported smoking ≥ 20 cigarettes daily at baseline and received smoking cessation counseling, 21 mg nicotine patch daily, and either placebo or 1 of 3 doses of naltrexone (25, 50, or 100mg) for 6 weeks. Change in indirect and total bilirubin following the quit date was measured at Weeks 1, 4, and 6 compared to baseline.

RESULTS

Individuals who were continuously abstinent from smoking, independent of naltrexone condition, showed a significantly greater mean increase in indirect (~unconjugated) bilirubin (0.06 mg/dl, SD = 0.165) compared to those who did not (mean = 0.02, SD = 0.148, p = .015). Similar results were obtained for total bilirubin (p = .037).

CONCLUSIONS

Smoking cessation is followed by increases in bilirubin concentration that have been associated with lower risk of lung cancer and cardiovascular disease.

Effects of serum bilirubin on atherosclerotic processes

This review highlights the protective roles of bilirubin against the atherosclerotic process. Bilirubin belongs to the superfamily of tetrapyrrolic compounds formed during heme catabolism. Although for decades bilirubin was considered to be a harmful waste product, recent epidemiologic studies have shown that serum bilirubin levels have consistently been inversely associated with cardiovascular disease (CVD), as well as cardiovascular risk factors such as metabolic syndrome and diabetes. These clinical studies are supported by in vitro and in vivo experimental data and have demonstrated that bilirubin not only has an ability to scavenge overproduced reactive oxygen species and inhibit vascular smooth muscle cell proliferation but, additionally, has anti-inflammatory effects. In this review, we will discuss the inverse association of serum bilirubin and CVD and cardiovascular risk factors established in various clinical studies. We also review detailed experimental studies about the effect of bilirubin on atherosclerotic processes. In vitro, animal and human studies have proved that bilirubin inhibits oxidation of cholesterol which is an important step of atherosclerosis. Bilirubin attenuates chemotactic activity of monocytes and strongly inhibits adhesion of leukocytes to venule and production of pro-inflammatory cytokines. Bilirubin has inhibited serum-driven smooth muscle cell cycle progression at the G1 phase. Lastly, we will discuss briefly the influence of bilirubin on lipoprotein composition and endothelial dysfunction.

Low serum bilirubin concentration is a predictor of chronic kidney disease

OBJECTIVE

Chronic kidney disease (CKD) is a worldwide public health problem. It is very important to identify the factors that affect CKD. Previous studies have reported that serum bilirubin concentration was positively correlated with renal function in a cross-sectional study. The aim of this study was to investigate the relationship between serum bilirubin concentration and the progression of CKD.

METHODS

A cohort study was performed on a consecutive series of 2784 subjects without CKD, defined as estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m(2), at baseline. We analyzed the relationship between serum total bilirubin concentration at baseline and new-onset CKD in the general population.

RESULTS

We followed the subjects for a median period of 7.7 years. There were 1157 females and 1627 males, and 231 females and 370 males developed CKD during this period. Multiple Cox regression analyses revealed that serum total bilirubin concentration (hazard ratio (HR) per 1.0 μmol/L increase 0.97 (95% CI 0.95-0.99), P = 0.0084) in addition to age, gamma-glutamyl transpeptidase (GGT), uric acid (UA), creatinine and medication for hypertension in men and serum total bilirubin concentration (HR per 1.0 μmol/L increase 0.96 (95% CI 0.93-1.00), P = 0.0309) in addition to age, GGT, alanine aminotransferase, UA, creatinine and medication for dyslipidemia in women were independent predictors of new-onset CKD, after adjusting for confounders.

CONCLUSION

Our study demonstrated that serum total bilirubin concentration could be a novel risk factor for the progression of CKD, defined as eGFR <60 ml/min/1.73 m(2), in the general population.

Serum bilirubin level and aortic intima-media thickness in patients without clinical manifestation of atherosclerotic cardiovascular disease

We investigated the association between serum bilirubin level and thoracic aortic intima-media thickness (IMT). The study population consisted of 417 patients without coronary artery disease, who underwent transesophageal echocardiography examination for various indications. The highest aortic IMT values were observed in the bilirubinlow group compared with the bilirubinhigh group (P < .001). Serum bilirubin level was associated with high-density lipoprotein cholesterol level (r = .162, P = .001), high-sensitivity C-reactive protein (hsCRP; r = -.265, P < .001), and aortic IMT (r = -.551, P < .001) in bivariate analysis. Multivariate linear regression analysis showed that serum bilirubin level was independently and negatively associated with hsCRP (β = -.095, P = .028) and aortic IMT (β = -.513, P < .001). Serum bilirubin level may be an independent predictor of the extent of subclinical aortic atherosclerosis assessed by thoracic aortic IMT.

The Relationship Between Serum Bilirubin Concentration and Atrial Fibrillation

Background

Several studies have demonstrated that higher serum bilirubin inhibits the inflammation and proliferation of vascular smooth muscle cells; also there is a relationship between serum bilirubin and cardiovascular disease. However, the relationship between bilirubin and atrial fibrillation (AF) is still unknown. In our study, we compared serum bilirubin, between nonvalvular AF patients and controls.

Materials and Method

One hundred and two patients with nonvalvular chronic AF without any other cardiovascular disease (mean age 62.51 ± 5.88) were included in our study. One hundred age-matched healthy people with sinus rhythm were accepted as control groups (mean age 61.35 ± 5.44). Routine biochemical parameters and serum bilirubin levels were performed.

Results

No statistically significant difference was found between two groups in terms of basic characteristics. Total, direct and indirect serum bilirubin levels were significantly lower among persons with AF compared to controls (0.82 ± 0.8 vs. 0.48 ± 0.5, 0.30 ± 0.2 vs. 0.19 ± 0.1 and 0.52 ± 0.5 vs. 0.29 ± 0.3 mg/dL; all P < 0.001, respectively).

Conclusion

As a result, our study revealed a relationship between serum bilirubin and nonvalvular AF.

Higher serum bilirubin level as a protective factor for the development of diabetes in healthy Korean men: a 4 year retrospective longitudinal study

OBJECTIVE

Bilirubin, a natural product of heme catabolism by heme oxygenase, one of key antioxidant enzymes, has been recognized as a substance with potent antioxidant and cytoprotective properties. Several studies have shown a significant negative relationship between serum bilirubin levels and the risk of metabolic disorders, including type 2 diabetes. However, longitudinal studies investigating the association of elevated serum bilirubin levels and type 2 diabetes are lacking. In the present study, we aimed to investigate the longitudinal effects of baseline serum bilirubin concentrations on the development of type 2 diabetes in healthy Korean men.

MATERIALS AND METHODS

This 4 year retrospective longitudinal observational study was conducted at the Asan Medical Center, Seoul, Republic of Korea. The study population consisted of 5960 men without type 2 diabetes who underwent routine health examinations in 2007 (baseline) and 2011 (follow-up). Baseline serum bilirubin concentrations were determined by the vanadate oxidation method.

RESULTS

During a 4 year period, 409 incident cases of diabetes (6.9 %) were identified. Incident type 2 diabetes decreased across the baseline bilirubin quartile categories (P for trend <0.001). In multivariable-adjusted model, the relative risk (RR) for the development of type 2 diabetes was significantly lower in the highest (i.e., 1.30-2.00 mg/dl) than in the lowest bilirubin quartile category (i.e., ≤ 0.90 mg/dl), even after adjustment for confounding variables (RR=0.69, 95% confidence interval 0.48-0.99, P for trend = 0.041).

CONCLUSIONS

The results indicate that serum total bilirubin level may provide additional information for predicting future development of type 2 diabetes in healthy subjects.

The relationship between serum bilirubin concentration and coronary slow flow

Background:

The pathophysiology of coronary slow flow (CSF) has not been clearly identified, although multiple abnormalities including arteritis, endothelial dysfunction, and atherothrombosis have been reported. Several studies have demonstrated that higher serum bilirubin inhibits the inflammation and proliferation of vascular smooth muscle cells; in addition, there is a relationship between serum bilirubin and cardiovascular disease. However, the relationship between bilirubin and CSF is still unknown. In our study, we compared serum bilirubin concentrations between CSF patients and controls.

Methods:

The study included 50 CSF patients (19 male, mean age 65.6 ± 13.7 years) and 30 controls (10 male, mean age 57.86 ± 11.6 years). Concurrent routine biochemical tests and leukocyte count, hemoglobin, hematocrit, and platelet count on whole blood count were performed in patients that underwent a coronary angiogram. These parameters were compared between groups.

Results:

No statistically significant difference was found between the two groups in terms of basic characteristics. Total, direct, and indirect serum bilirubin levels were significantly lower among CSF patients than controls (14.0 ± 12.0 versus 6.15 ± 6.8, 5.6 ± 3.4 versus 2.6 ± 1.7, and 8.4 ± 8.5 versus 3.6 ± 3.4 µmol/l; all p < 0.001, respectively).

Conclusions:

The study revealed a relationship between serum bilirubin and CSF.

Behavioral and clinical correlates of serum bilirubin concentrations in Japanese men and women

BACKGROUND

A considerable interest has been drawn to potential protective effects of bilirubin against oxidative stress-related diseases. Smoking is known to be associated with lower concentrations of serum bilirubin, but other behavioral correlates of serum bilirubin have not been well studied. In this cross-sectional study, we examined the associations of behavioral and clinical factors with serum total bilirubin in Japanese men and women.

METHOD

The study subjects comprised of 4802 men and 6414 women aged 49-76 years who participated in the baseline survey of an ongoing cohort study on lifestyle-related diseases in Fukuoka, Japan. With consideration to time of the day of blood sampling and fasting hours, the associations with smoking, alcohol intake, body mass index, physical activity, coffee, tea, blood pressure, glycated hemoglobin (HbA1c), HDL cholesterol and non-HDL cholesterol with serum bilirubin were evaluated by analysis of covariance and multiple linear regression analysis.

RESULTS

While smoking was negatively associated with serum bilirubin, alcohol consumption was positively associated with serum bilirubin in both men and women. Coffee consumption was associated with lower bilirubin concentrations in both sexes. In the multiple linear regression analysis, HDL cholesterol was positively and HbA1c was negatively associated with bilirubin in both men and women, and the associations were more evident in women.

CONCLUSION

Smoking, alcohol use and coffee consumption were important behavioral correlates of serum bilirubin in Japanese men and women. Serum HDL cholesterol was a measurable clinical correlate of bilirubin in women.

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

BACKGROUND

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality both in industrialized and developing countries. Atherosclerosis is a chronic inflammatory disease of the arterial wall, which also involves deposition and peroxidation of lipids. Bilirubin, an important endogenous antioxidant, may limit lipid peroxidation and retard the progression of atherosclerosis. Previous studies have reported an inverse relationship between serum bilirubin levels and the risk of coronary artery disease (CAD). Taking into account that atherosclerosis is a complex process that is initiated and accelerated by diverse risk factors, we aimed to test the antiatherosclerotic effects of bilirubin in a population with multiple risk factors for CAD.

METHODS

The study included 221 patients who underwent coronary angiography owing to symptoms suggestive of ischemia and/or positive noninvasive stress test results. Of the patients, 76 had normal coronary angiograms and served as the control group. The remaining 145 patients with documented CAD and two or more cardiovascular risk factors constituted the study group. The study group (n=145) was further classified according to the Gensini score as follows: group 1 if Gensini score was 1-19 (minimal CAD, n=82), and group 2 if Gensini score was 20 or higher (significant CAD, n=63). Biochemical assessments including total and direct serum bilirubin levels were carried out using standard methods in automated systems.

RESULTS

All of the cardiovascular risk factors were found significantly more frequently in the study group (groups 1 and 2) than in the control group. Total and direct serum bilirubin levels did not differ significantly between the control group, group 1, and group 2. There was a moderate and significant positive correlation between direct bilirubin levels and the Gensini score (r = 0.158, p = 0.019). There was no significant correlation between total bilirubin levels and the Gensini score.

CONCLUSION

In conclusion, our findings suggest that in the presence of multiple risk factors, similar concentrations of serum bilirubin may not confer the same level of protection against CAD as in an individual with a more favorable risk profile. The relationship between direct bilirubin levels and the Gensini score is unlikely to be causative, given the established antiatherosclerotic effects of bilirubin.

A genome-wide association study for serum bilirubin levels and gene-environment interaction in a Chinese population

Bilirubin is an effective antioxidant and is influenced by both genetic and environmental factors. Recent genome-wide association studies (GWAS) have identified multiple loci affecting serum total bilirubin levels. However, most of the studies were conducted in European populations and little attention has been devoted either to genetic variants associated with direct and indirect bilirubin levels or to the gene-environment interactions on bilirubin levels. In this study, a two-stage GWAS was performed to identify genetic variants associated with all types of bilirubin levels in 10,282 Han Chinese individuals. Gene-environment interactions were further examined. Briefly, two previously reported loci, UGT1A1 on 2q37 (rs6742078 and rs4148323, combined P = 1.44 × 10(-89) and P = 5.05 × 10(-69) , respectively) and SLCO1B3 on 12p12 (rs2417940, combined P = 6.93 × 10(-19) ) were successfully replicated. The two loci explained 9.2% and 0.9% of the total variations of total bilirubin levels, respectively. Ethnic genetic differences were observed between Chinese and European populations. More importantly, a significant interaction was found between rs2417940 in SLCO1B3 gene and smoking on total bilirubin levels (P = 1.99 × 10(-3) ). Single nucleotide polymorphism (SNP) rs2417940 had stronger effects on total bilirubin levels in nonsmokers than in smokers, suggesting that the effects of SLCO1B3 genotype on bilirubin levels were partly dependent on smoking status. Consistent associations and interactions were observed for serum direct and indirect bilirubin levels.

Genetically elevated bilirubin and risk of ischaemic heart disease: three Mendelian randomization studies and a meta-analysis

BACKGROUND

Elevated plasma levels of bilirubin, an endogenous antioxidant, have been associated with reduced risk of ischaemic heart disease (IHD) and myocardial infarction (MI). Whether this is a causal relationship remains unclear.

OBJECTIVE

We tested the hypothesis that elevated plasma bilirubin is causally related to decreased risk of IHD and MI.

DESIGN

We used a Mendelian randomization approach and three independent studies from Copenhagen, Denmark. We measured bilirubin in 43 708 white individuals from the general population, and genotyped rs6742078 G>T in the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene in 67 068 individuals, of whom 11 686 had IHD.

RESULTS

Third versus first tertile of baseline bilirubin levels was associated with 134% increased bilirubin levels, with sex- and age-adjusted hazard ratios (HRs) of 0.86 [95% confidence interval (CI), 0.76-0.98; P = 0.02] for IHD and 0.81 (95% CI, 0.66-0.99; P = 0.04) for MI, but with corresponding multifactorially adjusted HRs of 0.93 (95% CI, 0.82-1.06; P = 0.29) and 0.90 (95% CI, 0.73-1.12; P = 0.35). UGT1A1 rs6742078 TT versus GG genotype was associated with 95% increased bilirubin levels (P < 0.001); TT versus GG genotype was associated with odds ratios (ORs) of 1.03 (95% CI, 0.96-1.11; P = 0.73) for IHD and 1.01 (95% CI, 0.92-1.12; P = 0.68) for MI. Finally, in a meta-analysis of the present three studies and eight previous studies including a total of 14 711 cases and 60 324 controls, the random effects OR for ischaemic cardiovascular disease for genotypes with approximately 100% increased bilirubin levels versus reference genotypes was 1.01 (95% CI, 0.88-1.16).

CONCLUSION

These data suggest that plasma bilirubin is not causally associated with risk of IHD.

Heme oxygenase-1, oxidation, inflammation, and atherosclerosis

Atherosclerosis is an inflammatory process of the vascular wall characterized by the infiltration of lipids and inflammatory cells. Oxidative modifications of infiltrating low-density lipoproteins and induction of oxidative stress play a major role in lipid retention in the vascular wall, uptake by macrophages and generation of foam cells, a hallmark of this disorder. The vasculature has a plethora of protective resources against oxidation and inflammation, many of them regulated by the Nrf2 transcription factor. Heme oxygenase-1 (HO-1) is a Nrf2-regulated gene that plays a critical role in the prevention of vascular inflammation. It is the inducible isoform of HO, responsible for the oxidative cleavage of heme groups leading to the generation of biliverdin, carbon monoxide, and release of ferrous iron. HO-1 has important antioxidant, antiinflammatory, antiapoptotic, antiproliferative, and immunomodulatory effects in vascular cells, most of which play a significant role in the protection against atherogenesis. HO-1 may also be an important feature in macrophage differentiation and polarization to certain subtypes. The biological effects of HO-1 are largely attributable to its enzymatic activity, which can be conceived as a system with three arms of action, corresponding to its three enzymatic byproducts. HO-1 mediated vascular protection may be due to a combination of systemic and vascular local effects. It is usually expressed at low levels but can be highly upregulated in the presence of several proatherogenic stimuli. The HO-1 system is amenable for use in the development of new therapies, some of them currently under experimental and clinical trials. Interestingly, in contrast to the HO-1 antiatherogenic actions, the expression of its transcriptional regulator Nrf2 leads to proatherogenic effects instead. This suggests that a potential intervention on HO-1 or its byproducts may need to take into account any potential alteration in the status of Nrf2 activation. This article reviews the available evidence that supports the antiatherogenic role of HO-1 as well as the potential pathways and mechanisms mediating vascular protection.

Heme oxygenase-1, oxidation, inflammation, and atherosclerosis

Atherosclerosis is an inflammatory process of the vascular wall characterized by the infiltration of lipids and inflammatory cells. Oxidative modifications of infiltrating low-density lipoproteins and induction of oxidative stress play a major role in lipid retention in the vascular wall, uptake by macrophages and generation of foam cells, a hallmark of this disorder. The vasculature has a plethora of protective resources against oxidation and inflammation, many of them regulated by the Nrf2 transcription factor. Heme oxygenase-1 (HO-1) is a Nrf2-regulated gene that plays a critical role in the prevention of vascular inflammation. It is the inducible isoform of HO, responsible for the oxidative cleavage of heme groups leading to the generation of biliverdin, carbon monoxide, and release of ferrous iron. HO-1 has important antioxidant, antiinflammatory, antiapoptotic, antiproliferative, and immunomodulatory effects in vascular cells, most of which play a significant role in the protection against atherogenesis. HO-1 may also be an important feature in macrophage differentiation and polarization to certain subtypes. The biological effects of HO-1 are largely attributable to its enzymatic activity, which can be conceived as a system with three arms of action, corresponding to its three enzymatic byproducts. HO-1 mediated vascular protection may be due to a combination of systemic and vascular local effects. It is usually expressed at low levels but can be highly upregulated in the presence of several proatherogenic stimuli. The HO-1 system is amenable for use in the development of new therapies, some of them currently under experimental and clinical trials. Interestingly, in contrast to the HO-1 antiatherogenic actions, the expression of its transcriptional regulator Nrf2 leads to proatherogenic effects instead. This suggests that a potential intervention on HO-1 or its byproducts may need to take into account any potential alteration in the status of Nrf2 activation. This article reviews the available evidence that supports the antiatherogenic role of HO-1 as well as the potential pathways and mechanisms mediating vascular protection.

Cigarette smoking and serum bilirubin subtypes in healthy Korean men: the Korea Medical Institute study

OBJECTIVES

Cigarette smoking is a modifiable risk factor for cardiovascular disease. Bilirubin is a potent antioxidant and its concentration decreases in smokers. However, studies about the association between cigarette smoking and bilirubin are scarce and most are limited to total bilirubin. Additionally, bilirubin is highly related to hemoglobin. Therefore, this study evaluates the association between bilirubin subtypes and cigarette smoking in healthy Korean men independently of hemoglobin.

METHODS

This study included 48 040 Korean men aged 30 to 87 years who visited the Korea Medical Institute for routine health examinations from January to December, 2007. The association of smoking with total, direct, and indirect bilirubin was assessed by logistic regression analysis taking into consideration differences in subjects and smoking characteristics.

RESULTS

Current smokers had lower bilirubin concentrations than never-smokers and ex-smokers. Smoking amount and duration were inversely significantly associated with total, direct, and indirect bilirubin. In a multivariable adjusted model, compared to never-smokers, the odds ratios (ORs) and 95% confidence intervals (CIs) of current smokers with the highest number of pack-years were 1.7 (1.6 to 1.9) for total, 1.5 (1.4 to 1.6) for direct, and 1.7 (1.6 to 1.9) for indirect bilirubin. After further adjustment for hemoglobin, this association became stronger (OR [95% CI], 2.1 [1.9 to 2.2] for total; 1.9 [1.8 to 2.0] for direct; 2.0 [1.9 to 2.2] for indirect bilirubin).

CONCLUSIONS

In this study, bilirubin subtypes are inversely associated with smoking status, smoking amount, and smoking duration in healthy Korean men independently of hemoglobin. Further studies are needed to investigate this association in healthy Korean women.