Hyperbilirubinemia, augmentation of endothelial function, and decrease in oxidative stress in Gilbert syndrome

Vascular Function and Intima-media Thickness of a Leg Artery in Peripheral Artery Disease: A Comparison of Buerger Disease and Atherosclerotic Peripheral Artery Disease

Aim: Both vascular function and structure are independent predictors of cardiovascular events. The purpose of this study was to evaluate vascular function and structure of a leg artery in patients with peripheral artery disease (PAD).

Methods: We measured flow-mediated vasodilatation (FMD) and nitroglycerine-induced vasodilation (NID) as indices of vascular function and intima-media thickness (IMT) as an index of vascular structure of the popliteal artery in 100 subjects, including 20 patients with Buerger disease and 30 patients with atherosclerotic PAD, 20 age- and sex-matched subjects without Buerger disease (control group) and 30 age- and sex-matched patients without atherosclerotic PAD (control group).

Results: IMT was significantly larger in the Buerger group than in the control group (Buerger, 0.63 ± 0.20 mm; control, 0.50 ± 0.07 mm; P = 0.01), whereas there were no significant differences in FMD and NID between the two groups. IMT was significantly larger in the atherosclerotic PAD group than in the control group (atherosclerotic PAD, 0.80 ± 0.22 mm; control, 0.65 ± 0.14 mm; P < 0.01), and FMD and NID were significantly smaller in the atherosclerotic PAD group than in the control group (FMD: atherosclerotic PAD, 3.9% ± 1.1%; control, 5.0% ± 1.8%; P < 0.01; and NID: atherosclerotic PAD, 6.1% ± 2.0%; control, 8.4% ± 2.1%; P < 0.01).

Conclusion: These findings suggest that vascular function is preserved in patients with Buerger disease and that both vascular function and vascular structure are impaired in patients with atherosclerotic PAD.

Relationship between plasma bilirubin level and oxidative stress markers in HIV-infected patients on atazanavir- vs. efavirenz-based antiretroviral therapy

OBJECTIVES

Chronic oxidative stress (OS) may play a role in cardiovascular disease in HIV-infected patients, and increased bilirubin levels may have a beneficial role in counteracting OS. Atazanavir (ATV) inhibits UDP-glucuronosyl-transferase 1A1 (UGT1A1), thus increasing unconjugated bilirubin levels. We aimed to compare changes in OS markers in patients on ATV/ritonavir (ATV/r)- vs. efavirenz (EFV)-based first-line antiretroviral therapy (ART).

METHODS

A multicentre, prospective cohort study of HIV-infected patients who started first-line ART with either ATV/r or EFV was conducted. Lipoprotein-associated phospholipase A2 (Lp-PLA2), myeloperoxidase (MPO) and oxidized low-density lipoprotein (oxLDL) were measured for 145 patients in samples obtained at baseline and after at least 9 months of ART during which the initial regimen was maintained and the patient was virologically suppressed. The change in OS markers was modelled using multiple linear regressions adjusting for baseline values and confounders.

RESULTS

After adjustment for baseline variables, patients on ATV/r had a significantly greater decrease in Lp-PLA2 [estimated difference -16.3; 95% confidence interval (CI) -31.4, -1.25; P = 0.03] and a significantly smaller increase in OxLDL (estimated difference -21.8; 95% CI -38.0, -5.6; P < 0.01) relative to those on EFV, whereas changes in MPO were not significantly different (estimated difference 1.2; 95% CI -14.3, 16.7; P = 0.88). Adjusted changes in bilirubin were significantly greater for the ATV/r group than for the EFV group (estimated difference 1.33 mg/dL; 95% CI 1.03, 1.52 mg/dL; P < 0.01). Changes in bilirubin and changes in OS markers were significantly correlated.

CONCLUSIONS

When compared with EFV, ATV/r-based therapy was associated with lower levels of oxidative stress biomarkers, which was in part attributable to increased bilirubin levels.

Hyperbilirubinemia exaggerates endotoxin-induced hypothermia

Systemic inflammation is accompanied by an increased production of reactive oxygen species (ROS) and by either fever or hypothermia (or both). To study aseptic systemic inflammation, it is often induced in rats by the intravenous administration of bacterial lipopolysaccharide (LPS). Knowing that bilirubin is a potent ROS scavenger, we compared responses to LPS between normobilirubinemic Gunn rats (heterozygous, asymptomatic; J/+) and hyperbilirubinemic Gunn rats (homozygous, jaundiced; J/J) to establish whether ROS mediate fever and hypothermia in aseptic systemic inflammation. These two genotypes correspond to undisturbed versus drastically suppressed (by bilirubin) tissue accumulation of ROS, respectively. A low dose of LPS (10 μg/kg) caused a typical triphasic fever in both genotypes, without any intergenotype differences. A high dose of LPS (1,000 μg/kg) caused a complex response consisting of early hypothermia followed by late fever. The hypothermic response was markedly exaggerated, whereas the subsequent fever response was strongly attenuated in J/J rats, as compared to J/+ rats. J/J rats also tended to respond to 1,000 μg/kg with blunted surges in plasma levels of all hepatic enzymes studied (alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase), thus suggesting an attenuation of hepatic damage. We propose that the reported exaggeration of LPS-induced hypothermia in J/J rats occurs via direct inhibition of nonshivering thermogenesis by bilirubin and possibly via a direct vasodilatatory action of bilirubin in the skin. This hypothermia-exaggerating effect might be responsible, at least in part, for the observed tendency of J/J rats to be protected from LPS-induced hepatic damage. The attenuation of the fever response to 1,000 μg/kg could be due to either direct actions of bilirubin on thermoeffectors or the ROS-scavenging action of bilirubin. However, the experiments with 10 μg/kg strongly suggest that ROS signaling is not involved in the fever response to low doses of LPS.

Gender-related differences in susceptibility to oxidative stress in healthy middle-aged Serbian adults

Gender-related differences in the association between polymorphism of xenobiotic-metabolising enzymes or non-genetic biomarkers and susceptibility to oxidative stress was assessed in healthy middle-aged Serbian adults, by urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG/creatinine) and total antioxidant status in serum (TAOS). Females were more susceptible to oxidative stress. In both genders, positive predictor of the antioxidative protection was serum triglyceride, while BMI <25 kg/m(2) was associated with oxidative stress. Susceptibility to oxidative stress in males was associated with GSTT1*null allele and increased serum iron, but in females, it was decreased serum bilirubin. Early identification of the risk factors could be important in the prevention of oxidative stress-related diseases.

Heme oxygenase-1-derived bilirubin protects endothelial cells against high glucose-induced damage

Hyperglycemia and diabetes are associated with endothelial cell dysfunction arising from enhanced oxidative injury, leading to the progression of diabetic vascular pathologies. The redox-sensitive transcription factor nuclear factor-E2-related factor 2 (Nrf2) is a master regulator of antioxidant genes, such as heme oxygenase-1 (HO-1), involved in cellular defenses against oxidative stress. We have investigated the pathways involved in high glucose-induced activation of HO-1 in endothelial cells and examined the molecular mechanisms underlying cytoprotection. Elevated d-glucose increased intracellular generation of reactive oxygen species (ROS), leading to nuclear translocation of Nrf2 and HO-1 expression in bovine aortic endothelial cells, with no changes in cell viability. Superoxide scavenging and inhibition of endothelial nitric oxide synthase (eNOS) abrogated upregulation of HO-1 expression by elevated glucose. Inhibition of HO-1 increased the sensitivity of endothelial cells to high glucose-mediated damage, while addition of bilirubin restored cell viability. Our findings establish that exposure of endothelial cells to high glucose leads to activation of endogenous antioxidant defense genes via the Nrf2/ARE pathway. Upregulation of HO-1 provides cytoprotection against high glucose-induced oxidative stress through the antioxidant properties of bilirubin. Modulation of the Nrf2 pathway in the early stages of diabetes may thus protect against sustained damage by hyperglycemia during progression of the disease.

Serum bilirubin levels are inversely associated with PAI-1 and fibrinogen in Korean subjects

OBJECTIVES

Oxidative stress may contribute to atherosclerosis and increased activation of the coagulation pathway. Bilirubin may reduce activation of the hemostatic system to inhibit oxidative stress, which would explain its cardioprotective properties shown in many epidemiological studies. This study investigated the association of serum bilirubin with fibrinogen and plasminogen activator inhibitor-1 (PAI-1), respectively.

METHODS

A cross-sectional analysis was performed on 968 subjects (mean age, 56.0 ± 11.2 years; 61.1% men) undergoing a general health checkup. Serum biochemistry was analyzed including bilirubin subtypes, insulin resistance (using homeostasis model of assessment [HOMA]), C-reactive protein (CRP), fibrinogen, and PAI-1.

RESULTS

Compared with subjects with a total bilirubin (TB) concentration of <10.0 μmol/L, those with a TB concentration of >17.1 μmol/L had a smaller waist circumference, a lower triglyceride level, a lower prevalence of metabolic syndrome, and decreased HOMA-IR and CRP levels. Correlation analysis revealed linear relationships of fibrinogen with TB and direct bilirubin (DB), whereas PAI-1 was correlated with DB. After adjustment for confounding factors, bilirubin levels were inversely associated with fibrinogen and PAI-1 levels, respectively. Multivariate regression models showed a negative linear relationship between all types of bilirubin and fibrinogen, whereas there was a significant linear relationship between PAI-1 and DB.

CONCLUSIONS

High bilirubin concentrations were independently associated with low levels of fibrinogen and PAI-1, respectively. The association between TB and PAI-1 was confined to the highest TB concentration category whereas DB showed a linear association with PAI-1. Bilirubin may protect against the development of atherothrombosis by reducing the hemostatic response.

Telomere G-tail Length is a Promising Biomarker Related to White Matter Lesions and Endothelial Dysfunction in Patients With Cardiovascular Risk: A Cross-sectional Study

Background

The telomeric 3′-overhang (G-tail) length is essential for the biological effects of telomere dysfunction in vitro, but the association of length with aging and cardiovascular risk is unclear in humans. We investigated the association between the telomere G-tail length of leukocytes and cardiovascular risk, age-related white matter changes (ARWMCs), and endothelial function.

Methods

Patients with a history of cerebrovascular disease and comorbidity were enrolled (n = 102; 69 males and 33 females, 70.1 ± 9.2 years). Total telomere and telomere G-tail lengths were measured using a hybridization protection assay. Endothelial function was evaluated by ultrasound assessment of brachial flow-mediated dilation (FMD).

Findings

Shortened telomere G-tail length was associated with age and Framingham risk score (P = 0.018 and P = 0.012). In addition, telomere G-tail length was positively correlated with FMD values (P = 0.031) and negatively with the severity of ARWMCs (P = 0.002). On multivariate regression analysis, telomere G-tail length was independently associated with FMD values (P = 0.022) and the severity of ARWMCs (P = 0.033), whereas total telomere length was not associated with these indicators.

Interpretation

Telomere G-tail length is associated with age and vascular risk factors, and might be superior to total telomere length as a marker of endothelial dysfunction and ARWMC severity.

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Telomere G-tail length was measured using a hybridization protection assay in patients with vascular risk factors.

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Telomere G-tail length was independently related to endothelial function and age-related white matter changes.

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Telomere G-tail length might be a promising biomarker of vascular damage.

Bilirubin as a potential causal factor in type 2 diabetes risk: a Mendelian randomization study

Circulating bilirubin, a natural antioxidant, is associated with decreased risk of type 2 diabetes (T2D), but the nature of the relationship remains unknown. We performed Mendelian randomization in a prospective cohort of 3,381 participants free of diabetes at baseline (age 28-75 years; women 52.6%). We used rs6742078 located in the uridine diphosphate-glucuronosyltransferase locus as an instrumental variable (IV) to study a potential causal effect of serum total bilirubin level on T2D risk. T2D developed in a total of 210 participants (6.2%) during a median follow-up period of 7.8 years. In adjusted analyses, rs6742078, which explained 19.5% of bilirubin variation, was strongly associated with total bilirubin (a 0.68-SD increase in bilirubin levels per T allele; P < 1 × 10(-122)) and was also associated with T2D risk (odds ratio [OR] 0.69 [95% CI 0.54-0.90]; P = 0.006). Per 1-SD increase in log-transformed bilirubin levels, we observed a 25% (OR 0.75 [95% CI 0.62-0.92]; P = 0.004) lower risk of T2D. In Mendelian randomization analysis, the causal risk reduction for T2D was estimated to be 42% (causal OR for IV estimation per 1-SD increase in log-transformed bilirubin 0.58 [95% CI 0.39-0.84]; P = 0.005), which was comparable to the observational estimate (Durbin-Wu-Hausman χ(2) test, P for difference = 0.19). These novel results provide evidence that an elevated bilirubin level is causally associated with the risk of T2D and support its role as a protective determinant.

Assessment of endothelial function. History, methodological aspects, and clinical perspectives

In 1986, endothelial function was measured for the first time in patients with atherosclerotic coronary arteries. Since then, several methods for assessment of endothelial function, such as endothelium-dependent vasodilation induced by intra-arterial infusion of vasoactive agents using coronary angiography, Doppler flow guide wire, mercury-filled Silastic strain-gauge plethysmography, flow-mediated vasodilation, reactive hyperemia-peripheral arterial tonometry, and vascular response using an oscillometric method have been performed in humans. This review focuses on the assessment of endothelial function, including measurement history, methodological issues, and clinical perspectives.

Endothelial dysfunction is associated with the severity of cerebral small vessel disease

The pathogenesis of cerebral small vessel disease, a disease that involves white matter lesions (WMLs) and cerebral microbleeds (CMBs), is thought to be associated with endothelial dysfunction. Flow-mediated dilation (FMD) has been used to measure endothelium-dependent vasodilation. The aim of this study was to investigate the association between endothelial function (as measured by FMD) and cerebral small vessel disease. Patients with a history of cerebrovascular disease and comorbidities were enrolled in this study (n=102; 69 males, 70.1±9.2 years). The patients were divided into two groups according to the severity of WMLs, which were assessed by Fazekas classification; grades 0 to 1 as mild WMLs group and grades 2 to 3 as severe WMLs group. A gradient-echo MRI was performed in 96 patients (94.1%) to evaluate whether CMBs were present. The patients in the severe WMLs group (n=40) were older (P=0.001), more frequently exhibited hypertension (P=0.045) and diabetes mellitus (P=0.026) and possessed lower FMD values (P<0.001) than the patients in the mild WMLs group (n=62). CMBs were observed in 30 patients (31.3%). Using receiver operating characteristic curves, the optimal FMD cutoff values for predicting the presence of severe WMLs and CMBs were 3.9% and 3.7%, respectively. On multivariate logistic analysis, FMD <4.0% (odds ratio 9.50; 95% confidence interval 3.55-28.83) was independently associated with severe WMLs. Additionally, FMD <3.8% (5.82; 2.23-16.50) was also associated with the presence of CMBs. Endothelial dysfunction as evaluated by FMD may be predictive of the severity of cerebral small vessel disease.

Bilirubin provides perforator flap protection from ischaemia-reperfusion injury in a rat model: a preliminary result

The use of bilirubin, a well-known and powerful antioxidant, has gained popularity in recent years because of its role in the prevention of ischaemic heart disease in patients with Gilbert's syndrome. We investigate the effects of bilirubin on ischaemia-reperfusion (I/R) injury using a rat perforator flap model. Forty-eight rats were randomly divided into two groups: experimental (bilirubin) group (n = 24) and control group (n = 24). In each group, elevated bilateral deep inferior epigastric perforator (DIEP) flaps were created. The right (no ischaemia side) and left (ischaemia side) DIEP flaps were separated according to the presence of ischaemia induction. Ischaemia was induced in anaesthetised rats by perforator clamping for 15 or 30 minutes. After surgery, the flap survival was assessed daily on postoperative days 0 to 5, and overall histological changes of DIEP flaps above the perforator were analysed at postoperative day 5. The flap survival rate in the bilirubin group was significantly higher than that in the control group at the ischaemia side following perforator clamping for 15 or 30 minutes (93·42 ± 4·48% versus 89·63 ± 3·98%, P = 0·002; and 83·96 ± 4·23% versus 36·46 ± 6·38%, P < 0·001, respectively). The difference in flap survival between the two groups was the most prominent on the ischaemic side following 30 minutes of perforator clamping. From a morphologic perspective, pre-treatment with bilirubin was found to alleviate perforator flap necrosis caused by I/R injury in this experimental rat model.

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.

Bilirubin, platelet activation and heart disease: a missing link to cardiovascular protection in Gilbert's syndrome?

Gilbert's syndrome (GS) is a relatively common condition, inducing a benign, non-hemolytic, unconjugated hyperbilirubinemia. Gilbert's Syndrome is associated with mutation in the Uridine Glucuronosyl Transferase 1A1 (UGT1A1) gene promoter, reducing UGT1A1 activity, which normally conjugates bilirubin allowing its elimination from the blood. Individuals with GS demonstrate mildly elevated plasma antioxidant capacity caused by elevated levels of unconjugated bilirubin (UCB), reduced thiols and glutathione. Interestingly, the development of, and risk of mortality from, cardiovascular disease is remarkably reduced in GS individuals. An explanation for this protection may be explained by bilirubin's ability to inhibit multiple processes that induce platelet hyper-reactivity and thrombosis, thus far under-appreciated in the literature. Reactive oxygen species are produced continuously via metabolic processes and have the potential to oxidatively modify proteins and lipids within cell membranes, which may encourage the development of thrombosis and CVDs. Oxidative stress induced platelet hyper-reactivity significantly increases the risk of thrombosis, which can potentially lead to tissue infarction. Here, we discuss the possible mechanisms by which increased antioxidant status might influence platelet function and link this to cardiovascular protection in GS. In summary, this is the first article to discuss the possible role of bilirubin as an anti-thrombotic agent, which inhibits platelet activation and potentially, organ infarction, which could contribute to the reduced mortality rate in mildly hyperbilirbinemic individuals.

Bilirubin is an independent factor inversely associated with glycated hemoglobin level in pediatric patients with type 1 diabetes

OBJECTIVE

Bilirubin is a potent antioxidant, and serum total bilirubin (STB) concentrations correlate negatively with cardiovascular risk. In adult diabetic patients and in healthy adults, a negative correlation between STB and glycated hemoglobin (HbA1c) has been reported. We investigated whether there is such an association in children and adolescents with type 1 diabetes mellitus.

METHODS

The study group included 224 patients with type 1 diabetes duration of more than 12 months. Patients with suspected or confirmed hemolytic anemia or liver dysfunction were excluded.

RESULTS

A statistically significant negative correlation was found between STB and HbA1c (R = -0.15; p = 0.024), which retained its significance in multivariate analysis (β = -0.18, p = 0.005). Patients' age and daily insulin dose were positively correlated with HbA1c levels, whereas other variables included in the multivariate analysis [sex, diabetes duration, insulin regimen, C-peptide, hemoglobin, mean corpuscular hemoglobin concentration (MCHC), alanine transaminase (ALT), and aspartate transaminase (AST)] did not correlate with HbA1c. The mean HbA1c level in patients with STB >1.2 mg/dL (>21 µmol/L; the threshold for clinical diagnosis of Gilbert's syndrome) was lower than in patients with STB ≤1.2 mg/dL (≤21 µmol/L), and the mean difference was 0.63% (6.9 mmol/mol; 95% CI: 0.11-1.16%).

CONCLUSIONS

These results show that in young patients with type 1 diabetes, STB concentration is an independent factor inversely associated with HbA1c level. Further studies should investigate the background and long-term effects of this association.

Circulating bilirubin and defense against kidney disease and cardiovascular mortality: mechanisms contributing to protection in clinical investigations

Unconjugated bilirubin is an endogenous circulating antioxidant, bound to albumin, and therefore is retained in the vascular compartment. Bilirubin has well-documented neurotoxic effects in infants; however, current evidence indicates mildly elevated bilirubin is associated with protection from cardiovascular disease and all-cause mortality in adults. Recent clinical studies show mildly elevated bilirubin is associated with protection from kidney damage and dysfunction, in addition to cardiovascular events and all-cause mortality in patients undergoing hemodialysis. This is the first review to examine the clinical evidence and summarize the potential mechanisms of action that link bilirubin to protection from kidney damage, subsequent kidney failure, and dialysis-related mortality. With this understanding, it is hoped that new therapies will be developed to prevent renal dysfunction and mortality from cardiovascular disease in at-risk individuals.

Withholding parenteral nutrition during critical illness increases plasma bilirubin but lowers the incidence of biliary sludge

Cholestatic liver dysfunction (CLD) and biliary sludge often occur during critical illness and are allegedly aggravated by parenteral nutrition (PN). Delaying initiation of PN beyond day 7 in the intensive care unit (ICU) (late PN) accelerated recovery as compared with early initiation of PN (early PN). However, the impact of nutritional strategy on biliary sludge and CLD has not been fully characterized. This was a preplanned subanalysis of a large randomized controlled trial of early PN versus late PN (n = 4,640). In all patients plasma bilirubin (daily) and liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST], gamma-glutamyl transpeptidase [GGT], alkaline phosphatase [ALP], twice weekly; n = 3,216) were quantified. In a random predefined subset of patients, plasma bile acids (BAs) were also quantified at baseline and on days 3, 5, and last ICU-day (n = 280). Biliary sludge was ultrasonographically evaluated on ICU-day 5 (n = 776). From day 1 after randomization until the end of the 7-day intervention window, bilirubin was higher in the late PN than in the early PN group (P < 0.001). In the late PN group, as soon as PN was started on day 8 bilirubin fell and the two groups became comparable. Maximum levels of GGT, ALP, and ALT were lower in the late PN group (P < 0.01). Glycine/taurine-conjugated primary BAs increased over time in ICU (P < 0.01), similarly for the two groups. Fewer patients in the late PN than in the early PN group developed biliary sludge on day 5 (37% versus 45%; P = 0.04).

CONCLUSION

Tolerating substantial caloric deficit by withholding PN until day 8 of critical illness increased plasma bilirubin but reduced the occurrence of biliary sludge and lowered GGT, ALP, and ALT. These results suggest that hyperbilirubinemia during critical illness does not necessarily reflect cholestasis and instead may be an adaptive response that is suppressed by early PN.

Pregnancy with gilbert syndrome - a case report

A primigravida presented to us at 32 weeks of gestation with vomiting, myalgia and jaundice. On examination she had icterus, she was dehydrated, uterus was corresponding to dates and the fetal heart rate was good. On evaluation, all the investigations were normal except mild unconjugated hyperbilirubinaemia and hypoglycaemia. Based on the above findings we derived at a diagnosis of Gilbert syndrome. Dehydration due to vomiting aggravated her jaundice. On correcting her dehydration jaundice resolved, patient improved symptomatically and was discharged two days later. She was later admitted at term and underwent emergency caesarian section in view of fetal distress. Mother and baby were fine postoperatively and was discharged on the fifth postoperative day Gilbert syndrome is rare in obstetric practice. Virtually all patients have decreased activity of Uridine diphosphate glucuronosyl transferase (UDPGT). The case is reported due to its rarity.

Body fat percentage is a major determinant of total bilirubin independently of UGT1A1*28 polymorphism in young obese

Objectives

Bilirubin has potential antioxidant and anti-inflammatory properties. The UGT1A1*28 polymorphism (TA repeats in the promoter region) is a major determinant of bilirubin levels and recent evidence suggests that raised adiposity may also be a contributing factor. We aimed to study the interaction between UGT1A1 polymorphism, hematological and anthropometric variables with total bilirubin levels in young individuals.

Methods

350 obese (mean age of 11.6 years; 52% females) and 79 controls (mean age of 10.5 years; 59% females) were included. Total bilirubin and C-reactive protein (CRP) plasma levels, hemogram, anthropometric data and UGT1A1 polymorphism were determined. In a subgroup of 74 obese and 40 controls body composition was analyzed by dual-energy X-ray absorptiometry.

Results

The UGT1A1 genotype frequencies were 49.9%, 42.7% and 7.5% for 6/6, 6/7 and 7/7 genotypes, respectively. Patients with 7/7 genotype presented the highest total bilirubin levels, followed by 6/7 and 6/6 genotypes. Compared to controls, obese patients presented higher erythrocyte count, hematocrit, hemoglobin and CRP levels, but no differences in bilirubin or in UGT1A1 genotype distribution. Body fat percentage was inversely correlated with bilirubin in obese patients but not in controls. This inverse association was observed either in 6/7 or 6/6 genotype obese patients. UGT1A1 polymorphism and body fat percentage were the main factors affecting bilirubin levels within obese patients (linear regression analysis).

Conclusion

In obese children and adolescents, body fat composition and UGT1A1 polymorphism are independent determinants of total bilirubin levels. Obese individuals with 6/6 UGT1A1 genotype and higher body fat mass may benefit from a closer clinical follow-up.

Heme oxygenase-1: a metabolic nike

SIGNIFICANCE

Heme degradation, which was described more than 30 years ago, is still very actively explored with many novel discoveries on its role in various disease models every year.

RECENT ADVANCES

The heme oxygenases (HO) are metabolic enzymes that utilize NADPH and oxygen to break apart the heme moiety liberating biliverdin (BV), carbon monoxide (CO), and iron. Heme that is derived from hemoproteins can be toxic to the cells and if not removed immediately, it causes cell apoptosis and local inflammation. Elimination of heme from the milieu enables generation of three products that influences numerous metabolic changes in the cell.

CRITICAL ISSUES

CO has profound effects on mitochondria and cellular respiration and other hemoproteins to which it can bind and affect their function, while BV and bilirubin (BR), the substrate and product of BV, reductase, respectively, are potent antioxidants. Sequestration of iron into ferritin and its recycling in the tissues is a part of the homeodynamic processes that control oxidation-reduction in cellular metabolism. Further, heme is an important component of a number of metabolic enzymes, and, therefore, HO-1 plays an important role in the modulation of cellular bioenergetics.

FUTURE DIRECTIONS

In this review, we describe the cross-talk between heme oxygenase-1 (HO-1) and its products with other metabolic pathways. HO-1, which we have labeled Nike, the goddess who personified victory, dictates triumph over pathophysiologic conditions, including diabetes, ischemia, and cancer.

Association of bilirubin with coronary artery calcification and cardiovascular events in the general population without known liver disease: the Heinz Nixdorf Recall study

BACKGROUND

Bilirubin is a product of heme oxygenase and an antioxidant per se. In selected cohorts and patient studies, bilirubin was associated with decreased risk for cardiovascular events. We aimed to determine the association of serum bilirubin with coronary artery calcification (CAC) and incident cardiovascular disease in the unselected general population.

METHODS

Participants without prior coronary heart or liver disease were drawn from the population-based Heinz Nixdorf Recall study. CAC was measured from electron beam computed tomography and quantified using the Agatston method. Incident major cardiovascular events (coronary events, stroke, cardiovascular death) were assessed during follow-up. The association of bilirubin with CAC score and incident events was calculated using regression analysis.

RESULTS

A total of 3,553 subjects (mean age 59.4 years, 44 % male) were included. Bilirubin was inversely correlated with CAC in men [estimated % change in (CAC + 1) per each gender-specific standard deviation of bilirubin [95 % confidence interval (CI): -6.1 (-11.6; -1.7) %, p = 0.032] but less so in women [-3.6 (-7.7; 0.2) %, p = 0.065], when adjusting for age only. With adjustment for traditional cardiovascular risk factors, the association was less pronounced [men: -2.5 (-7.5; 2.6) %, p = 0.35, women: -0.2 (-4.1; 3.5) %, p = 0.9]. Likewise, higher bilirubin by one standard deviation was associated with 19 % lower frequency of incident cardiovascular events in age- and gender-adjusted Cox regression analysis [hazard ratio (95 % CI): 0.81 (0.68; 0.96), p = 0.014]; this effect was slightly attenuated after adjustment for traditional cardiovascular risk factors [0.87 (0.73; 1.04), p = 0.13].

CONCLUSION

Our data from a general population suggest that a potential protective role of bilirubin in the atherosclerosis process is largely secondary to a more beneficial risk factor profile.

Oxidative stress and endothelial dysfunction: clinical evidence and therapeutic implications

An imbalance of nitric oxide (NO) and reactive oxygen species (ROS), so-called "oxidative stress," may promote endothelial dysfunction, leading to cardiovascular complications. Activation of nicotinamide-adenine dinucleotide phosphate oxidase, xanthine oxidase, cyclooxygenase, and mitochondrial electron transport, inactivation of the antioxidant system, and uncoupling of endothelial NO synthase lead to oxidative stress along with an increase in ROS production and decrease in ROS degradation. Although experimental studies, both in vitro and in vivo, have shown a critical role of oxidative stress in endothelial dysfunction under the condition of excessive oxidative stress, there is little information on whether oxidative stress is really involved in endothelial function in humans. In a clinical setting, we showed an association between oxidative stress and endothelial function, especially in patients with renovascular hypertension as a model of increased oxidative stress and in patients with Gilbert syndrome as a model of decreased oxidative stress, through an increase in the antioxidant property of unconjugated bilirubin.

Serum bilirubin levels are lower in overweight asymptomatic middle-aged adults: an early indicator of metabolic syndrome?

OBJECTIVE

Low levels of bilirubin have recently been associated with obesity, diabetes mellitus, and metabolic syndrome. Here, we hypothesized that serum bilirubin levels might be already altered in overweight asymptomatic middle-aged individuals before full development of the metabolic syndrome.

METHODS

Healthy nonsmoking adults aged 25-49 (64 women and 32 men) participated in this cross-sectional study. All participants who reported stable weight within the last three months underwent standard anthropomorphological measurements of body composition, blood pressure measurements, aerobic and anaerobic capabilities assessment, dietary intake evaluation, and fasting serological measurements of total and direct bilirubin, glucose, insulin, triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and C-reactive protein. Participants were divided into normal-weight and overweight groups. Linear correlation and multiple regression analyses were used to examine the association of serum bilirubin levels with all metabolic syndrome risk factor changes.

RESULTS

Serum bilirubin levels were lower in overweight healthy individuals of both sexes, and were negatively associated with abdominal obesity, insulin resistance, fasting glucose, fasting insulin, fasting triglycerides, total cholesterol, low-density lipoprotein cholesterol, and C-reactive protein levels but positively associated with aerobic body capabilities.

CONCLUSION

Our findings suggest that serum bilirubin levels have the potential to be employed as an early biomarker for indicating asymptomatic individuals at increased risk of developing metabolic syndrome.

Nitroglycerine-Induced Vasodilation for Assessment of Vascular Function

Objective—

Nitroglycerine-induced vasodilation has been used as a control test for flow-mediated vasodilation (FMD) to differentiate endothelium-dependent from endothelium-independent response when evaluating endothelial function in humans. Recently, nitroglycerine-induced vasodilation has also been reported to be impaired in patients with atherosclerosis. The purpose of this study was to determine the relationships between nitroglycerine-induced vasodilation and cardiovascular risk factors.

Approach and Results—

We measured nitroglycerine-induced vasodilation and FMD in 436 subjects who underwent health examinations (mean age, 53±19 years; age range, 19–86 years), including patients with cardiovascular diseases. There was a significant relationship between nitroglycerine-induced vasodilation and FMD ( r =0.42; P <0.001). Univariate regression analysis revealed that nitroglycerine-induced vasodilation correlated with age ( r =−0.34; P <0.001), systolic blood pressure ( r =−0.32; P <0.001), diastolic blood pressure ( r =−0.24; P <0.001), heart rate ( r =−0.21; P <0.001), glucose ( r =−0.23; P <0.001), and smoking pack-year ( r =−0.12; P =0.01), as well as Framingham risk score ( r =−0.30; P <0.001). Nitroglycerine-induced vasodilation was significantly smaller in patients with cardiovascular disease than in both subjects with and without cardiovascular risk factors (10.5±5.6% versus 13.7±5.4% and 15.3±4.3%; P <0.001, respectively), whereas there was no significant difference in nitroglycerine-induced vasodilation between subjects with and without cardiovascular risk factors. Multivariate analysis revealed that male sex, body mass index, hypertension, diabetes mellitus, baseline brachial artery diameter, and FMD were independent predictors of nitroglycerine-induced vasodilation.

Conclusions—

These findings suggest that nitroglycerine-induced vasodilation may be a marker of the grade of atherosclerosis. FMD should be interpreted as an index of vascular function reflecting both endothelium-dependent vasodilation and endothelium-independent vasodilation in subjects with impaired nitroglycerine-induced vasodilation.

Total bilirubin is inversely associated with metabolic syndrome but not a risk factor for metabolic syndrome in Japanese men and women

Serum total bilirubin (TB) is a potent antioxidant and inversely associated with metabolic syndrome (MetS) in Asian populations. However, there has been no study which is aimed to investigate whether TB is a risk factor for MetS or not. We investigated cross-sectional and longitudinal associations between TB and MetS in 2,435 Japanese men and 1,436 Japanese women. The odds ratios [95 % confidence interval (CI)] of coexisting MetS for each 1 SD increase in log TB were 0.850 (0.754-0.958) (p = 0.008) in men and 0.809 (0.656-0.998) (p = 0.047) in women adjusted for sex, age, smoking, and other confounding covariates. Those for the third and fourth quartiles of TB compared with the lowest quartile were 0.720 (0.537-0.965) (p = 0.028) and 0.737 (0.530-1.052) (p = 0.095), respectively, in men and 0.822 (0.473-1.427) (p = 0.486) and 0.704 (0.362-1.369) (p = 0.301), respectively, in women. There was a tendency that TB and MetS changed inversely to each other. The similarly adjusted hazard ratios of developing MetS for each 1 SD increase in log TB and for the higher quartiles of TB compared with the lowest quartile were not significant either in men or in women. TB is inversely associated with MetS but not a risk factor for MetS in Japanese men and women.

Serum biomarkers and the prognosis of AMI patients

BACKGROUND

It has been proven that serum lactate dehydrogenase (LDH) and total bilirubin (TB) increase during acute myocardial infarction (AMI). However, how they influence the prognosis of AMI patients is still not completely known.

METHODS

A total of 239 patients diagnosed with AMI and admitted to the Fourth Clinical Hospital of Harbin Medical University, between 2007 and 2008, were enrolled in this study. All the patients had not undergone primary percutaneous coronary intervention (PCI) because the time window (24 h) was missed. They all underwent PCI 1 week after the onset of symptoms. Serum high-sensitivity C-reactive protein (hs-CRP), TB, LDH, and other biomarkers were determined between 24 and 48 h of symptom onset. All of the patients were followed up for an average of 3.2±0.4 years for occurrence of major adverse cardiac events (MACE).

RESULTS

Patients with MACE had significantly higher levels of hs-CRP, LDH, cystatin C, uric acid, a higher ratio of LDH and TB (LDH/TB), and a lower level of TB: 8.48±3.84 vs. 2.13±1.32 μmol/l, p<0.01; 1,355.8±654.3 vs. 1,151.7±415.4 U/l, p<0.01; 1.69±0.76 vs. 1.00±0.46 mg/l, p<0.01; 419.6±109.2 vs. 343.2±108.2 μmol/l, p<0.01 and 141.1±46.2 vs. 61.2±26.5, p<0.01; 18.3±6.7 vs. 14.8±6.6 mg/l, p<0.01, respectively. In the multivariate COX analysis, LDH, cystatin C, and LDH/TB were significantly associated with the prognosis of these patients.

CONCLUSIONS

Patients under higher oxidative stress tend to have more MACE. LDH, cystatin C, and LDH/TB are strongly related to the prognosis of AMI patients undergoing elective PCI.

Plasma total bilirubin levels predict amputation events in type 2 diabetes mellitus: the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study

AIMS/HYPOTHESIS

Bilirubin has antioxidant and anti-inflammatory activities. Previous studies demonstrated that higher bilirubin levels were associated with reduced prevalence of peripheral arterial disease (PAD). However, the relationship between bilirubin and lower-limb amputation, a consequence of PAD, is currently unknown. We hypothesised that, in patients with type 2 diabetes, bilirubin concentrations may inversely associate with lower-limb amputation.

METHODS

The relationship between baseline plasma total bilirubin levels and amputation events was analysed in 9,795 type 2 diabetic patients from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study. The analysis plan was pre-specified. Lower-limb amputation was adjudicated blinded to treatment allocation. Relevant clinical and biochemical data were available for analyses. Amputation was a pre-specified tertiary endpoint.

RESULTS

Bilirubin concentrations were significantly inversely associated with lower-limb amputation, with a greater than threefold risk gradient across levels. Individuals with lower bilirubin concentrations had a higher risk for first amputation (HR 1.38 per 5 μmol/l decrease in bilirubin concentration, 95% CI 1.07, 1.79, p = 0.013). The same association persisted after adjustment for baseline variables, including age, height, smoking status, γ-glutamyltransferase level, HbA1c, trial treatment allocation (placebo vs fenofibrate), as well as previous PAD, non-PAD cardiovascular disease, amputation or diabetic skin ulcer, neuropathy, nephropathy and diabetic retinopathy (HR 1.38 per 5 μmol/l decrease in bilirubin concentration, 95% CI 1.05, 1.81, p = 0.019).

CONCLUSIONS/INTERPRETATION

Our results identify a significant inverse relationship between bilirubin levels and total lower-limb amputation, driven by major amputation. Our data raise the hypothesis that bilirubin may protect against amputation in type 2 diabetes.

Bilirubin and beyond: a review of lipid status in Gilbert's syndrome and its relevance to cardiovascular disease protection

Gilbert's syndrome (GS) is characterized by a benign, mildly elevated bilirubin concentration in the blood. Recent reports show clear protection from cardiovascular disease in this population. Protection of lipids, proteins and other macromolecules from oxidation by bilirubin represents the most commonly accepted mechanism contributing to protection in this group. However, a recent meta-analysis estimated that bilirubin only accounts for ~34% of the cardioprotective effects within analysed studies. To reveal the additional contributing variables we have explored circulating cholesterol and triacylglycerol concentrations, which appear to be decreased in hyperbilirubinemic individuals/animals, and are accompanied by lower body mass index in highly powered studies. These results suggest that bilirubin could be responsible for the development of a lean and hypolipidemic state in GS. Here we also discuss the possible contributing mechanisms that might reduce circulating cholesterol and triacylglycerol concentrations in individuals with syndromes affecting bilirubin metabolism/excretion, which we hope will stimulate future research in the area. In summary, this article is the first review of lipid status in animal and human studies of hyperbilirubinemia and explores possible mechanisms that could contribute to lowering circulating lipid parameters and further explain cardiovascular protection in Gilbert's syndrome.