Effect of serum albumin and bilirubin on the risk of myocardial infarction (the Framingham Offspring Study)

Association between C-Reactive Protein to Albumin Ratio and Multi-Vessel Coronary Artery Disease in Patients with Stable Coronary Artery Disease

Multivessel coronary artery disease (MV-CAD) remains a prevalent and serious health concern despite advances in treatment. Early identification and risk stratification are crucial for optimizing treatment. The CRP-to-albumin ratio (CAR) has emerged as a promising biomarker in various inflammatory diseases. This study investigated the potential of CAR as a marker for MV-CAD. We retrospectively analyzed 1360 patients with suspected CAD. Patients were divided into three groups based on CAR tertiles. Logistic regression analyses were carried out to estimate the association between MHR and MV-CAD. Elevated CAR levels were significantly associated with an increased prevalence of CAD (p < 0.001), severe CAD (p < 0.001), and MV-CAD (p < 0.001). Patients with the highest CAR tertile had five times higher odds of MV-CAD compared to the lowest tertile (p < 0.001). CAR demonstrated moderate accuracy in predicting MV-CAD (AUC: 0.644, 95% CI: 0.615-0.674, p < 0.001). CAR holds promise as a tool for the early identification and risk stratification of multivessel CAD. Further research is warranted to validate its clinical utility and explore its potential to guide treatment decisions and improve outcomes in patients with this high-risk condition.

Sex-Specific Risk Factors Associated With First Acute Myocardial Infarction in Young Adults

IMPORTANCE

An increasing proportion of people in the US hospitalized for acute myocardial infarction (AMI) are younger than 55 years, with the largest increase in young women. Effective prevention requires an understanding of risk factors associated with risk of AMI in young women compared with men.

OBJECTIVES

To assess the sex-specific associations of demographic, clinical, and psychosocial risk factors with first AMI among adults younger than 55 years, overall, and by AMI subtype.

DESIGN, SETTING, AND PARTICIPANTS

This study used a case-control design with 2264 patients with AMI, aged 18 to 55 years, from the VIRGO (Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients) study and 2264 population-based controls matched for age, sex, and race and ethnicity from the National Health and Nutrition Examination Survey from 2008 to 2012. Data were analyzed from April 2020 to November 2021.

EXPOSURES

A wide range of demographic, clinical, and psychosocial risk factors.

MAIN OUTCOMES AND MEASURES

Odds ratios (ORs) and population attributable fractions (PAF) for first AMI associated with demographic, clinical, and psychosocial risk factors.

RESULTS

Of the 4528 case patients and matched controls, 3122 (68.9%) were women, and the median (IQR) age was 48 (44-52) years. Seven risk factors (diabetes [OR, 3.59 (95% CI, 2.72-4.74) in women vs 1.76 (1.19-2.60) in men], depression [OR, 3.09 (95% CI, 2.37-4.04) in women vs 1.77 (1.15-2.73) in men], hypertension [OR, 2.87 (95% CI, 2.31-3.57) in women vs 2.19 (1.65-2.90) in men], current smoking [OR, 3.28 (95% CI, 2.65-4.07) in women vs 3.28 (2.65-4.07) in men], family history of premature myocardial infarction [OR, 1.48 (95% CI, 1.17-1.88) in women vs 2.42 (1.71-3.41) in men], low household income [OR, 1.79 (95% CI, 1.28-2.50) in women vs 1.35 (0.82-2.23) in men], hypercholesterolemia [OR, 1.02 (95% CI, 0.81-1.29) in women vs 2.16 (1.49-3.15) in men]) collectively accounted for the majority of the total risk of AMI in women (83.9%) and men (85.1%). There were significant sex differences in risk factor associations: hypertension, depression, diabetes, current smoking, and family history of diabetes had stronger associations with AMI in young women, whereas hypercholesterolemia had a stronger association in young men. Risk factor profiles varied by AMI subtype, and traditional cardiovascular risk factors had higher prevalence and stronger ORs for type 1 AMI compared with other AMI subtypes.

CONCLUSIONS AND RELEVANCE

In this case-control study, 7 risk factors, many potentially modifiable, accounted for 85% of the risk of first AMI in young women and men. Significant differences in risk factor profiles and risk factor associations existed by sex and by AMI subtype. These findings suggest the need for sex-specific strategies in risk factor modification and prevention of AMI in young adults. Further research is needed to improve risk assessment of AMI subtypes.

Prognostic value of the C-reactive protein to albumin ratio in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

Background/aim

This study investigated whether baseline serum level of C-reactive protein (CRP)/albumin ratio is associated with infarct localization, number of vascular lesions, and in-hospital mortality in patients undergoing primary percutaneous coronary intervention (PCI) for acute ST elevation myocardial infarction (STEMI).

Methods

The study population consisted of 116 patients diagnosed with STEMI. The CRP/albumin ratio at first admission, cardiac troponin-I (cTnI), PCI results, and clinical outcomes were recorded.

Results

The mean CRP/albumin ratio, cTnI level, and mean number of vascular lesions were significantly higher in non-survivors than in survivors (p = 0.006, p = 0.004, and p = 0.007, respectively). Multivariate logistic regression analysis demonstrated that the CRP/ albumin ratio and number of coronary artery lesions were independent predictors of mortality in STEMI patients. According to these analyses, the presence of ≥ 2 vessel lesions was the most important predictor of mortality, with an odds ratio of 2.009 (95% confidence interval: 1.191–3.387, p = 0.009).

Conclusion

This study demonstrates the potential utility of the CRP/albumin ratio for predicting the clinical outcome of patients with STEMI. In addition, the presence of ≥ 2 vascular lesions contributed to a 2-fold increase in mortality rate in STEMI patients.

Brief Report: Hyperbilirubinemia Is Associated With a Decreased Risk of Carotid Atherosclerosis in HIV-Infected Patients on Virological Suppression

OBJECTIVE

To investigate the association between total, direct, and indirect bilirubin and the presence of carotid lesions in a large sample of HIV-1-infected patients on virological suppression.

DESIGN

Retrospective study on adult HIV-1-infected patients, with a carotid ultrasound (CUS) examination performed between January 2008 and August 2016, with HIV-RNA <50 copies per milliliter at CUS and without previous cardiovascular events.

METHODS

Intima media thickness was measured in 4 segments: carotid common artery and bifurcation on the left and right sides. Carotid lesion was defined as an intima media thickness ≥1.5 mm in ≥1 region at CUS. Patients were classified as: normal if all bilirubin values before CUS were below the upper normal limit and with hyperbilirubinemia if ≥1 bilirubin value above upper normal limit before CUS was recorded. Multivariate logistic regression was used to determine whether hyperbilirubinemia showed association with the presence of ≥1 carotid lesion, after adjusting for confounding factors.

RESULTS

Overall, 903 patients were evaluated, 511 with ≥1 and 392 without carotid lesions. At multivariate analysis, total [adjusted odds ratio (95% confidence interval) 0.57 (0.36 to 0.90), P = 0.016] and indirect hyperbilirubinemia before CUS [adjusted odds ratio (95% confidence interval) 0.62 (0.40 to 0.97), P = 0.036] were associated with a lower risk of carotid lesions in addition to younger age, negative hepatitis C virus antibodies, higher nadir CD4, lower low-density lipoprotein cholesterol, higher high-density lipoprotein cholesterol, lower triglycerides, and no use of statin; no effect of atazanavir treatment on carotid lesions was detected.

CONCLUSIONS

In HIV-1-treated patients, total or indirect hyperbilirubinemia was likely associated with the absence of carotid lesions.

Bilirubin Is Inversely Associated With Cardiovascular Disease Among HIV-Positive and HIV-Negative Individuals in VACS (Veterans Aging Cohort Study)

Background

Bilirubin may protect against cardiovascular disease (CVD) by reducing oxidative stress. Whether elevated bilirubin reduces the risk of CVD events among HIV⁺ individuals and if this differs from uninfected individuals remain unclear. We assessed whether bilirubin independently predicted the risk of CVD events among HIV⁺ and uninfected participants in VACS (Veterans Aging Cohort Study).

Methods and Results

We conducted a prospective cohort study using VACS participants free of baseline CVD. Total bilirubin was categorized by quartiles. CVD as well as acute myocardial infarction, heart failure, and ischemic stroke events were assessed. Cox regression was used to evaluate hazard ratios of outcomes associated with quartiles of total bilirubin in HIV⁺ and uninfected people after adjusting for multiple risk factors. There were 96 381 participants (30 427 HIV⁺); mean age was 48 years, 48% were black, and 97% were men. There were 6603 total incident CVD events over a mean of 5.7 years. In adjusted models, increasing quartiles of baseline total bilirubin were associated with decreased hazards of all outcomes (hazard ratio, 0.86; 95% confidence interval, 0.80–0.91). Among HIV⁺ participants, results persisted for heart failure, ischemic stroke, and total CVD, but nonsignificant associations were observed for acute myocardial infarction.

Conclusions

VACS participants (regardless of HIV status) with elevated bilirubin levels had a lower risk of incident total CVD, acute myocardial infarction, heart failure, and ischemic stroke events after adjusting for known risk factors. Future studies should investigate how this apparently protective effect of elevated bilirubin could be harnessed to reduce CVD risk or improve risk estimation among HIV⁺ individuals.

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

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

Hyperbilirubinemia, Hypertension, and CKD: the Links

PURPOSE OF REVIEW

This review aims to highlight recent advances on the role of hyperbilirubinemia in hypertension and chronic kidney disease, with a focus on the pathophysiological mechanisms explaining the protective effects of bilirubin. An overview of pharmacologic induction of hyperbilirubinemia will also be discussed.

RECENT FINDINGS

The findings depict a protective role of bilirubin in the development of hypertension and cardiovascular diseases. Hyperbilirubinemia is also negatively correlated with the development and progression of chronic kidney disease. Commonly used drugs play a role in pharmacologic induction of hyperbilirubinemia. Bilirubin is therefore an exciting target for new therapeutic interventions for its antioxidant properties can be pivotal in the management of hypertension and in preventing and halting the progression of chronic kidney disease. Longitudinal studies are warranted to evaluate the prospective association between bilirubin levels and incident hypertension and chronic kidney disease in the general population. Interventions to induce hyperbilirubinemia need to be explored as a novel therapeutic approach in fighting disease burden.

Direct, indirect and total bilirubin and risk of incident coronary heart disease in the Dongfeng-Tongji cohort

BACKGROUND

Total bilirubin (TBIL) is known to be inversely associated with coronary heart disease (CHD) risk, however, whether this association is dose-response remains inconsistent and it is unclear which subtype of bilirubin is responsible for the potential protective effect.

METHODS

We included 12,097 participants who were free of CHD, stroke, cancer and potential liver, biliary and renal diseases at baseline from September 2008 to June 2010 and were followed-up until October 2013. Cox proportional hazards models were used to assess the hazard ratios (HR) and 95% confidence interval (95% CI) of bilirubin with incident CHD risk.

RESULTS

The adjusted HRs for incident CHD increased with increasing direct bilirubin (DBIL) (p for trend = .013). Participants within the highest quintile of DBIL had 30% higher risk of incident CHD compared to those in the lowest quintile (95% CI: 1.07, 1.58). In contrast, compared with subjects in the lowest quintile of TBIL, those in the third quintile had the lowest of 24% risk for CHD incidence (95% CI: 0.63, 0.92), which showed a U-shaped association (p for quadratic trend = .040).

CONCLUSIONS

DBIL was associated with a dose-response increased risk for CHD incidence. However, a U-shaped association existed between TBIL, indirect bilirubin and incident CHD risk. Key messages Direct bilirubin is independently associated with incident coronary heart disease (CHD) in a dose-response manner. A similarly consistent U-shaped association was found between total bilirubin, indirect bilirubin and incident CHD. The potential protective effect of total bilirubin within the normal range on incident CHD should be mainly attributed to mild-to moderate elevated levels of indirect bilirubin.

Bilirubin Prevents Atherosclerotic Lesion Formation in Low-Density Lipoprotein Receptor-Deficient Mice by Inhibiting Endothelial VCAM-1 and ICAM-1 Signaling

Background

Numerous epidemiological studies support an inverse association between serum bilirubin levels and the incidence of cardiovascular disease; however, the mechanism(s) by which bilirubin may protect against atherosclerosis is undefined. The goals of the present investigations were to assess the ability of bilirubin to prevent atherosclerotic plaque formation in low‐density lipoprotein receptor‐deficient (Ldlr^−/−) mice and elucidate the molecular processes underlying this effect.

Methods and Results

Bilirubin, at physiological concentrations (≤20 μmol/L), dose‐dependently inhibits THP‐1 monocyte migration across tumor necrosis factor α–activated human umbilical vein endothelial cell monolayers without altering leukocyte binding or cytokine production. A potent antioxidant, bilirubin effectively blocks the generation of cellular reactive oxygen species induced by the cross‐linking of endothelial vascular cell adhesion molecule 1 (VCAM‐1) or intercellular adhesion molecule 1 (ICAM‐1). These findings were validated by treating cells with blocking antibodies or with specific inhibitors of VCAM‐1 and ICAM‐1 signaling. When administered to Ldlr^−/− mice on a Western diet, bilirubin (30 mg/kg intraperitoneally) prevents atherosclerotic plaque formation, but does not alter circulating cholesterol or chemokine levels. Aortic roots from bilirubin‐treated animals exhibit reduced lipid and collagen deposition, decreased infiltration of monocytes and lymphocytes, fewer smooth muscle cells, and diminished levels of chlorotyrosine and nitrotyrosine, without changes in VCAM‐1 or ICAM‐1 expression.

Conclusions

Bilirubin suppresses atherosclerotic plaque formation in Ldlr^−/− mice by disrupting endothelial VCAM‐1‐ and ICAM‐1‐mediated leukocyte migration through the scavenging of reactive oxygen species signaling intermediaries. These findings suggest a potential mechanism for the apparent cardioprotective effects of bilirubin.

Decreased admission serum albumin level is an independent predictor of long-term mortality in hospital survivors of acute myocardial infarction. Soroka Acute Myocardial Infarction II (SAMI-II) project

BACKGROUND

Decreased serum albumin level (SAL) was reported to be associated with increased risk of cardiovascular events and short term-mortality in patients with acute myocardial infarction (AMI).

OBJECTIVES

To evaluate the association between SAL and long-term mortality in AMI hospital survivors.

METHODS

Retrospective analysis of patients admitted in a tertiary medical center for AMI 2002-2012 and discharged alive.

EXCLUSION CRITERIA

active infections, inflammatory diseases, significant liver or kidney failure, malignancy, ejection-fraction <20%, severe heart valvular-disease and missing SAL. SAL was categorized as following: <3.4, 3.4-3.7, 3.7-3.9, 3.9-4.1 and >4.1g/dL. The primary outcome was all-cause mortality for up-to 10-years post-AMI.

RESULTS

Out of 12,535 patients, 8750 were included. Patients with reduced SAL were older, higher rate of women, increased prevalence of severe left ventricular dysfunction, chronic renal failure, diabetes mellitus and ST-elevation AMI, 3-vessel coronary artery disease, and in-hospital complications. While the prevalence of chronic ischemic coronary disease, dyslipidemia, smokers and obesity, was lower. Mortality rates throughout the follow-up period increased as SAL decreased with 17.6%, 24%, 28.5%, 38.6%, and 57.5% for SAL of >4.1, 3.9-4.1, 3.7-3.9, 3.4-3.7 and <3.4g/dL respectively (p-for-trend <0.001). Using the SAL category of >4.1g/dL as the reference group, Adjusted Hazard Ratio values were 1.14 (p=0.107), 1.23 (p=0.007), 1.39 (p<0.001) and 1.70 (p<0.001) for the SAL categories of 3.9-4.1, 3.7-3.9, 3.4-3.7 and <3.4g/dL respectively.

CONCLUSIONS

Decreased SAL on admission, including levels within "normal" clinical range, is significantly associated with long-term all-cause mortality in hospital survivors of AMI with a "dose-response" type association.

Inflammatory bowel diseases, chronic liver diseases and the lung

This review is devoted to the distinct associations of inflammatory bowel diseases (IBD) and chronic liver disorders with chronic airway diseases, namely chronic obstructive pulmonary disease and bronchial asthma, and other chronic respiratory disorders in the adult population. While there is strong evidence for the association of chronic airway diseases with IBD, the data are much weaker for the interplay between lung and liver multimorbidities. The association of IBD, encompassing Crohn's disease and ulcerative colitis, with pulmonary disorders is underlined by their heterogeneous respiratory manifestations and impact on chronic airway diseases. The potential relationship between the two most prevalent liver-induced pulmonary vascular entities, i.e. portopulmonary hypertension and hepatopulmonary syndrome, and also between liver disease and other chronic respiratory diseases is also approached. Abnormal lung function tests in liver diseases are described and the role of increased serum bilirubin levels on chronic respiratory problems are considered.

Serum bilirubin and the risk of hypertension

BACKGROUND

Experimental studies suggest oxidative stress could lead to the development of hypertension. Serum bilirubin is a major contributor to the antioxidant capacity in blood plasma and has been identified as an independent cardiovascular risk factor in cohort studies. However, data on the relationship between bilirubin and blood pressure are scarce and inconclusive.

METHODS

We analysed data from the National Health and Nutrition Examination Surveys (NHANES) 1999-2012 (N=31069). Fifty multiple imputed data sets were generated and analysed to avoid selection/confounding bias due to excluding individuals/variables with missing values. A minimal sufficient adjustment set of variables (MSAS) needed to estimate the unconfounded effect of bilirubin on blood pressure and hypertension (systolic/diastolic blood pressure ≥ 140/90 mmHg or using antihypertensive medication) was identified using the back-door criterion and included in all regression models.

RESULTS

After adjustment for the MSAS variables, systolic blood pressure decreased progressively up to -2.5 mmHg (p<0.001) and the prevalence of hypertension was up to 25% lower (P<0.001) in those with bilirubin ≥ 1.0 mg/dl-the highest two deciles-compared with those with 0.1-0.4 mg/dl-the lowest decile. Sensitivity analyses showed these results were unlikely to be explained by residual confounding or selection bias.

CONCLUSIONS

High serum bilirubin may decrease the risk of hypertension by inactivating and inhibiting the synthesis of reactive oxygen species in vascular cells. Strategies to boost the bioavailability of circulating and tissue bilirubin or to mimic bilirubin's antioxidant properties could have a significant impact on prevention and control of hypertension as well as coronary heart disease.

Liver function parameters in hip fracture patients: relations to age, adipokines, comorbidities and outcomes

AIM

To asses liver markers in older patients with hip fracture (HF) in relation to age, comorbidities, metabolic characteristics and short-term outcomes.

METHODS

In 294 patients with HF (mean age 82.0±7.9 years, 72.1% women) serum alanine aminotransferase (ALT), gammaglutamyltransferase (GGT), alkaline phosphatase (ALP), albumin, bilirubin, 25(OH)vitaminD, PTH, calcium, phosphate, magnesium, adiponectin, leptin, resistin, thyroid function and cardiac troponin I were measured.

RESULTS

Elevated ALT, GGT, ALP or bilirubin levels on admission were observed in 1.7%-9.9% of patients. With age GGT, ALT and leptin decrease, while PTH and adiponectin concentrations increase. Higher GGT (>30 U/L, median level) was associated with coronary artery disease (CAD), diabetes mellitus (DM), and alcohol overuse; lower ALT (≤20 U/L, median level) with dementia; total bilirubin>20 μmol/L with CAD and alcohol overuse; and albumin>33 g/L with CAD. Multivariate adjusted regression analyses revealed ALT, ALP, adiponectin, alcohol overuse and DM as independent and significant determinants of GGT (as continuous or categorical variable); GGT for each other liver marker; and PTH for adiponectin. The risk of prolonged hospital stay (>20 days) was about two times higher in patients with GGT>30 U/L or adiponectin>17.14 ng/L (median level) and 4.7 times higher if both conditions coexisted. The risk of in-hospital death was 3 times higher if albumin was <33 g/L.

CONCLUSIONS

In older HF patients liver markers even within the normal range are associated with age-related disorders and outcomes. Adiponectin (but not 25(OH)vitaminD, PTH, leptin or resistin) is an independent contributor to higher GGT. Serum GGT and albumin predict prolonged hospital stay and in-hospital death, respectively. A unifying hypothesis of the findings presented.

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.

Effect of low serum total bilirubin levels (≤0.32 mg/dl) on risk of coronary artery disease in patients with metabolic syndrome

The objective of this study was to investigate the effects of low serum bilirubin levels on the risk for future coronary artery disease (CAD) in a prospective cohort. CAD events were examined according to baseline serum bilirubin levels in a prospective large-scale, community-based Korean cohort in 2 subsequent prospective biennial surveys. A total of 8,593 subjects were included, 0.9% of whom reported newly developed CAD events during the 4 years of follow-up. Cox regression analyses showed that the lowest serum total bilirubin level category (bilirubin ≤0.32 mg/dl) was an independent risk factor for future CAD events (adjusted hazard ratio [HR] 1.890, 95% confidence interval [CI] 1.088 to 3.284; p = 0.024). Subjects with metabolic syndrome had a higher risk for future CAD events than those without metabolic syndrome (HR 3.366, 95% CI 2.079 to 5.448, p <0.001). Low bilirubin levels increased the CAD risk in subjects with metabolic syndrome further (HR 2.016, 95% CI 1.069 to 3.800; p = 0.030), with these subjects showing a >6 times higher risk for CAD than subjects with bilirubin levels >0.32 mg/dl and no metabolic syndrome (HR 6.228, 95% CI 3.118 to 12.437; p <0.001). In conclusion, the addition of low serum bilirubin levels to the traditional risk factors for CAD, such as metabolic syndrome, may yield an improvement of risk prediction.

Heme oxygenase in neuroprotection: from mechanisms to therapeutic implications

Heme oxygenase (HO) was regarded as an enzyme to degrade heme in aging red blood cells; recent studies suggested HO might have other functions such as neuroprotection. HO degrades heme to produce carbon monoxide (CO), iron (Fe²⁺) and biliverdin, which is rapidly converted to bilirubin (BR). Three isoforms of HO were identified in the brain: inducible form (HO-1) and constitutive forms (HO-2 and HO-3). HO-1 and HO-2 may have different mechanisms to protect neurons from oxidative stress. HO-1 is normally barely detectable in the brain. HO-1 can be induced mainly in microglia and astrocytes by oxidative stimulus rapidly. HO-1 might function as an emerging molecule to protect neurons against acute insults mediated by facilitating iron efflux from cells under stress conditions. Up-regulation of HO-1 was also found in brain glial cells in the aging and neurodegenerative diseases. This may lead to iron deposition and oxidative mitochondrial injury. HO-1 may confer neuroprotection or neurotoxic effect because of the balance between beneficial and toxic effects of heme and heme products. Pharmacological modulation of HO-1 induction represents a therapeutic strategy for several nervous system disorders. HO-2 predominantly expressed in neurons. Bilirubin has been demonstrated to protect neurons from oxidative stress in vivo and in vitro. Bilirubin can be oxidized to biliverdin by scavenging peroxyl radicals. HO-2 could protect neurons through bilirubin pathway. HO-2 might also promote neuronal survival through the CO-cGMP-MAPK pathway. Biliverdin/bilirubin may be possible therapeutic candidates to treat nervous system disease related with oxidative damage.

Higher serum direct bilirubin levels were associated with a lower risk of incident chronic kidney disease in middle aged Korean men

Background

The association between serum bilirubin levels and incident chronic kidney disease (CKD) in the general population is unknown. We aimed to examine the association between serum bilirubin concentration (total, direct, and indirect) and the risk of incident CKD.

Methods and Findings

Longitudinal cohort study of 12,823 Korean male workers 30 to 59 years old without CKD or proteinuria at baseline participating in medical health checkup program in a large worksite. Study participants were followed for incident CKD from 2002 through 2011. Estimated glomerular filtration rate (eGFR) was estimated by using the CKD-EPI equation. CKD was defined as eGFR <60 mL/min per 1.73 m². Parametric Cox models and pooled logistic regression models were used to estimate adjusted hazard ratios for incident CKD. We observed 238 incident cases of CKD during 70,515.8 person-years of follow-up. In age-adjusted models, the hazard ratios for CKD comparing quartiles 2–4 vs. quartile 1 of serum direct bilirubin were 0.93 (95% CI 0.67–1.28), 0.88 (0.60–1.27) and 0.60 (0.42–0.88), respectively. In multivariable models, the adjusted hazard ratio for CKD comparing the highest to the lowest quartile of serum direct bilirubin levels was 0.60 (95% CI 0.41–0.87; P trend = 0.01). Neither serum total nor indirect bilirubin levels were significantly associated with the incidence of CKD.

Conclusions

Higher serum direct bilirubin levels were significantly associated with a lower risk of developing CKD, even adjusting for a variety of cardiometabolic parameters. Further research is needed to elucidate the mechanisms underlying this association and to establish the role of serum direct bilirubin as a marker for CKD risk.

Physiological antioxidative network of the bilirubin system in aging and age-related diseases

Oxidative stress is detrimental to life process and is particularly responsible for aging and age-related diseases. Thus, most organisms are well equipped with a spectrum of biological defense mechanisms against oxidative stress. The major efficient antioxidative mechanism is the glutathione system, operating a redox cycling mechanism for glutathione utilization, which consists of glutathione and its peroxidase and reductase. However, this system is mainly effective for hydrophilic oxidants, while lipophilic oxidants require another scavenging system. Since many age-related pathological conditions are related to lipid peroxidation, especially in association with the aging process, the physiological role of the scavenging system for lipophilic oxidants should be considered. In this regard, the biliverdin to bilirubin conversion pathway, via biliverdin reductase (BVR), is suggested to be another major protective mechanism that scavenges lipophilic oxidants because of the lipophilic nature of bilirubin. The efficiency of this bilirubin system might be potentiated by operation of the intertwined bicyclic systems of the suggested redox metabolic cycle of biliverdin and bilirubin and the interactive control cycle of BVR and heme oxygenase. In order to combat oxidative stress, both antioxidative systems against hydrophilic and lipophilic oxidants are required to work cooperatively. In this regard, the roles of the bilirubin system in aging and age-related diseases are reassessed in this review, and their interacting networks are evaluated.

Bile pigments in pulmonary and vascular disease

The bile pigments, biliverdin, and bilirubin, are endogenously derived substances generated during enzymatic heme degradation. These compounds have been shown to act as chemical antioxidants in vitro. Bilirubin formed in tissues circulates in the serum, prior to undergoing hepatic conjugation and biliary excretion. The excess production of bilirubin has been associated with neurotoxicity, in particular to the newborn. Nevertheless, clinical evidence suggests that mild states of hyperbilirubinemia may be beneficial in protecting against cardiovascular disease in adults. Pharmacological application of either bilirubin and/or its biological precursor biliverdin, can provide therapeutic benefit in several animal models of cardiovascular and pulmonary disease. Furthermore, biliverdin and bilirubin can confer protection against ischemia/reperfusion injury and graft rejection secondary to organ transplantation in animal models. Several possible mechanisms for these effects have been proposed, including direct antioxidant and scavenging effects, and modulation of signaling pathways regulating inflammation, apoptosis, cell proliferation, and immune responses. The practicality and therapeutic-effectiveness of bile pigment application to humans remains unclear.

Association of Serum Total Bilirubin with Serum High Sensitivity C-reactive Protein in Middle-aged Men

Background

It has been suggested that bilirubin has an inverse association with cardiovascular disease (CVD) due to its antioxidant properties. However, there are few data regarding the relationship between serum total bilirubin (sTB) and risk factors for CVD in Koreans. This study aimed to evaluate the relationship between sTB and high sensitivity C-reactive protein (hsCRP), which is an independent risk factor for CVD.

Methods

We performed a cross sectional study in 6,800 men who were examined at a health promotion center at a university hospital in Korea between May 2005 and June 2006. We grouped the subjects according to values of serum hsCRP (above or below 1.0 mg/L) and compared the characteristics of the two groups. To evaluate the relationship between sTB and hsCRP, we classified the subjects according to quartile values of sTB. Multivariate logistic regression analyses were used to analyze the relationship of levels of sTB and hsCRP after adjusting for known risk factors for CVD.

Results

Serum hsCRP was significantly associated with body mass index (BMI), smoking, diabetes, hypertension, fasting plasma glucose, systolic blood pressure, alanine aminotransferase, and total cholesterol/high density lipoprotein (TC/HDL-C) ratio, but not with age or alcohol use. As levels of sTB increased, there was a decrease in age, numbers of smokers, BMI, and TC/HDL ratio. Compared to the lowest quartile of sTB, levels of hsCRP decreased with odds ratios of 0.82 (95% CI, 0.71 to 0.96), 0.75 (95% CI, 0.65 to 0.88), and 0.63 (95% CI, 0.54 to 0.74) in the 2nd, 3rd, and 4th quartiles of bilirubin, respectively.

Conclusion

Bilirubin may be inversely associated with hsCRP

Low serum total bilirubin concentrations are associated with increased prevalence of metabolic syndrome in Chinese

BACKGROUND

To investigate the association between serum concentrations of total bilirubin (TBil) in the physiological range and metabolic syndrome (MS) in middle-aged and elderly Chinese, as well as any associations between serum TBil concentrations and insulin resistance, hyperinsulinemia, and systemic inflammation.

METHODS

A cross-sectional study was conducted on 1423 individuals recruited from an urban community of Shanghai (average age 62.3 years) to investigate the relationship between bilirubin and cardiovascular diseases. Metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria for Asian Americans.

RESULTS

Total bilirubin concentrations were significantly lower in individuals with MS compared with those without (0.65 ± 0.21 vs 0.69 ± 0.22 mg/dL, respectively; P=0.002). The adjusted mean concentration of TBil decreased gradually with an increase in the number of components of MS (P(trend) < 0.0001). After adjustment for a range of potential confounders (e.g. age, sex, body mass index, smoking, alcohol intake, homeostasis model assessment of insulin resistance etc.), each 1 SD increase in TBil was found to be associated with a 17% reduction in the risk of MS (odds ratio 0.83; 95% confidence interval 0.73-0.95; P=0.006). Furthermore, after adjustment for all covariables, each 1 SD increase in TBil was found to be associated with lower odds of central obesity, hypertriglyceridemia, low high-density lipoprotein-cholesterol, and hyperglycemia. Serum TBil concentrations were inversely associated with hyperinsulinemia, insulin resistance, and systemic inflammation.

CONCLUSIONS

Serum TBil concentrations within the physiological range were inversely associated with MS and insulin resistance, hyperinsulinemia, and systemic inflammation in middle-aged and elderly Chinese.

High serum bilirubin levels and diabetic retinopathy: the Hisayama Study

PURPOSE

To assess the association between serum total bilirubin levels and diabetic retinopathy prevalence in participants of the Hisayama Study who had diabetes and impaired glucose metabolism.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Of 3119 participants of the Hisayama Study Eye Examinations in 2007, Japan, 1672 aged ≥40 years with either diabetes or impaired glucose metabolism (defined by a 75-g oral glucose tolerance test) were enrolled in the present study.

METHODS

Diabetic retinopathy was assessed via ophthalmic examination after pupil dilatation. The presence and the severity of diabetic retinopathy were determined by grading of color fundus photographs using the modified Airlie House classification system. Association of diabetic retinopathy with serum bilirubin quartiles was assessed using logistic regression model adjusting for age and known risk factors for diabetic retinopathy.

MAIN OUTCOME MEASURES

Prevalent diabetic retinopathy.

RESULTS

Diabetic retinopathy was present in 70 of 1672 (4.2%) participants. The prevalence of diabetic retinopathy in persons with the highest bilirubin quartile (≥0.9 mg/dL) was 2.7%, compared with the prevalence of 3.4%, 5.1%, and 5.1% in those with the first (<0.6 mg/dL), second (0.6-0.69 mg/dL), and third quartiles (0.7-0.89 mg/dL). After adjusting for factors known to be associated with diabetic retinopathy, the prevalence was significantly lower among persons with the highest bilirubin quartile compared with those with the lowest quartile (odds ratio [OR], 0.25; 95% confidence interval [CI], 0.09-0.72) or compared with those in the 3 lower quartiles (OR, 0.25; 95% CI, 0.11-0.58).

CONCLUSIONS

Elevated serum bilirubin levels may be protective against diabetic retinopathy among persons with either diabetes or impaired glucose metabolism, independent of known risk factors for diabetic retinopathy.

Heme oxygenase-1: a novel therapeutic target for gastrointestinal diseases

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in the catabolism of heme, followed by production of biliverdin, free iron and carbon monoxide (CO). HO-1 is a stress-responsive protein induced by various oxidative agents. Recent studies demonstrate that the expression of HO-1 in response to different inflammatory mediators may contribute to the resolution of inflammation and has protective effects in several organs against oxidative injury. Although the mechanism underlying the anti-inflammatory actions of HO-1 remains poorly defined, both CO and biliverdin/bilirubin have been implicated in this response. In the gastrointestinal tract, HO-1 is shown to be transcriptionally induced in response to oxidative stress, preconditioning and acute inflammation. Recent studies suggest that the induction of HO-1 expression plays a critical protective role in intestinal damage models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid, and dextran sulfate sodium, indicating that activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in the gastrointestinal tract. In addition, CO derived from HO-1 is shown to be involved in the regulation in gastro-intestinal motility. These in vitro and in vivo data suggest that HO-1 may be a novel therapeutic target in patients with gastrointestinal diseases.

Constituents of bile, bilirubin and TUDCA, protect against oxidative stress-induced retinal degeneration

Two constituents of bile, bilirubin and tauroursodeoxycholic acid (TUDCA), have antioxidant activity. However, bilirubin can also cause damage to some neurons and glial cells, particularly immature neurons. In this study, we tested the effects of bilirubin and TUDCA in two models in which oxidative stress contributes to photoreceptor cell death, prolonged light exposure and rd10+/+ mice. In albino BALB/c mice, intraperitoneal injection of 5 mg/kg of bilirubin or 500 mg/kg of TUDCA prior to exposure to 5000 lux of white light for 8 h significantly reduced loss of rod and cone function assessed by electroretinograms. Both treatments also reduced light-induced accumulation of superoxide radicals in the outer retina, rod cell death assessed by outer nuclear layer thickness, and disruption of cone inner and outer segments. In rd10+/+ mice, intraperitoneal injections of 5 or 50 mg/kg of bilirubin or 500 mg/kg of TUDCA every 3 days starting at postnatal day (P) 6, caused significant preservation of cone cell number and cone function at P50. Rods were not protected at P50, but both bilirubin and TUDCA provided modest preservation of outer nuclear layer thickness and rod function at P30. These data suggest that correlation of serum bilirubin levels with rate of vision loss in patients with retinitis pigmentosa could provide a useful strategy to test the hypothesis that cones die from oxidative damage in patients with retinitis pigmentosa. If proof-of-concept is established, manipulation of bilirubin levels and administration of TUDCA could be tested in interventional trials.

Exogenous biliverdin improves the function of lung grafts from brain dead donors in rats

BACKGROUND

Biliverdin, a product of heme oxygenase-1 (HO-1), ameliorates the posttransplant functions of heart, kidney, and liver. In this study, we investigated the effects of biliverdin on lung grafts from brain dead (BD) rat donors.

METHODS

Male Wistar rats were randomly divided into 3 groups. The sham group (n = 7), did not undergo BD. Both donor and recipient rats in the BD biliverdin group (n = 8) were injected with biliverdin (35 mg/kg in 1 mL) intraperitoneally after confirmed BD and transplantation. In the BD group (n = 8), both donor and recipient rats received the same volume of saline (35 mg/kg in 1 mL) as the BD biliverdin group. All donor rats were observed for 1.5 hours before undergoing lung transplantation. Two hours after transplantation, we obtained blood and lung graft samples.

RESULTS

Biliverdin reversed the aggravation of Pa(O(2)) in recipients, reduced the grafts wet/dry ratio, decreased the severity of lung injury measured by histologic examination, reduced serum tumor necrosis factor-alpha and interleukin-8 levels and inhibited myeloperoxidase activity (MPO) in the grafts. Furthermore, it significantly decreased malonaldehyde levels and increased superoxide dismutase levels. Biliverdin reduced cell apoptosis, activated protein expression of biliverdin reductase, and inhibited expression of HO-1 and nuclear factor (NF)-kappaB in lung grafts.

CONCLUSION

Biliverdin exerts protective effects on lung grafts from BD donors through anti-inflammatory, antioxidant, and anti-apoptotic mechanisms.

Plasma bilirubin and UGT1A1*28 are not protective factors against first-time myocardial infarction in a prospective, nested case-referent setting

BACKGROUND

Bilirubin, an effective antioxidant, shows a large variation in levels between individuals and has been positively associated with reduced cardiovascular disease risk. A major reason for the variability is a common promoter polymorphism, UGT1A1*28, which reduces the transcription of the enzyme that conjugates bilirubin, UDP-glucuronosyltransferase 1A1. The aim of the study was to evaluate a possible protective effect of plasma bilirubin and the UGT1A1*28 polymorphism against myocardial infarction in a prospective case-referent setting.

METHODS AND RESULTS

Subjects (n=618) with a first-ever myocardial infarction (median event age, 60.5 years; median lag time, 3.5 years) and 1184 matched referents were studied. Plasma bilirubin was lower in cases versus referents. Despite a strong gene-dosage effect on bilirubin levels in both cases and referents, the UGT1A1*28 polymorphism did not influence the risk of myocardial infarction. Among multiple other variables, serum iron showed one of the strongest associations with bilirubin levels.

CONCLUSIONS

We found no evidence for a protective effect of the UGT1A1*28 polymorphism against myocardial infarction and consequently neither for bilirubin. The lower bilirubin levels in cases might be caused by decreased production, increased degradation, or increased elimination.

Variants in the UGT1A1 gene and the risk of pediatric nonalcoholic fatty liver disease

OBJECTIVE

Oxidative stress is increased in nonalcoholic fatty liver disease (NAFLD). Variants in the UGT1A1 gene contribute to increased bilirubin levels, and bilirubin can act as an antioxidant. We hypothesize that variant UGT1A1 genotypes reduce the risk for NAFLD development.

METHODS

Two hundred thirty-four obese children 6 to 13 years of age were recruited. NAFLD was determined through liver ultrasonography. The UGT1A1 genotypes UGT1A1*6 and UGT1A1*28 were detected. We assessed the effects of UGT1A1 genotypes on pediatric NAFLD.

RESULTS

In total, 12% of the obese children had NAFLD. The subjects with NAFLD had lower serum total bilirubin levels (0.25 +/- 0.30 mg/dL) than did those without NAFLD (0.36 +/- 0.38 mg/dL; P = .021). With conditioning on the effects of age- and gender-adjusted BMI, waist/hip ratio, and adiponectin levels, variant UGT1A1*6 genotypes were a protecting factor for NAFLD, with an estimated adjusted odds ratio of 0.31 (95% confidence interval: 0.11-0.91; P = .033), but variant UGT1A1*28 genotypes were not significantly associated with the occurrence of NAFLD.

CONCLUSIONS

Variant UGT1A1*6 genotypes are associated with a lower risk of NAFLD in obese Taiwanese children. The UGT1A1 genotype is a new risk factor for pediatric NAFLD.

Bench-to-bedside review: Carbon monoxide--from mitochondrial poisoning to therapeutic use

Carbon monoxide (CO) is generated during incomplete combustion of carbon-containing compounds and leads to acute and chronic toxicity in animals and humans depending on the concentration and exposure time. In addition to exogenous sources, CO is also produced endogenously by the activity of heme oxygenases (HOs) and the physiological significance of HO-derived CO has only recently emerged. CO exerts vasoactive, anti-proliferative, anti-oxidant, anti-inflammatory and anti-apoptotic effects and contributes substantially to the important role of the inducible isoform HO-1 as a mediator of tissue protection and host defense. Exogenous application of low doses of gaseous CO might provide a powerful tool to protect organs and tissues under various stress conditions. Experimental evidence strongly suggests a beneficial effect under pathophysiological conditions such as organ transplantation, ischemia/reperfusion, inflammation, sepsis, or shock states. The cellular and molecular mechanisms mediating CO effects are only partially characterized. So far, only a few studies in humans are available, which, however, do not support the promising results observed in experimental studies. The protective effects of exogenous CO may strongly depend on the pathological condition, the mode, time point and duration of application, the administered concentration, and on the target tissue and cell. Differences in bioavailability of endogenous CO production and exogenous CO supplementation might also provide an explanation for the lack of protective effects observed in some experimental and clinical studies. Further randomized, controlled clinical studies are needed to clarify whether exogenous application of CO may turn into a safe and effective preventive and therapeutic strategy to treat pathophysiological conditions associated with inflammatory or oxidative stress.

Bilirubin and glutathione have complementary antioxidant and cytoprotective roles

Glutathione (GSH) and bilirubin are prominent endogenous antioxidant cytoprotectants. Despite tissue levels that are thousands of times lower than GSH, bilirubin is effective because of the biosynthetic cycle wherein it is generated from biliverdin by biliverdin reductase (BVR). When bilirubin acts as an antioxidant, it is oxidized to biliverdin, which is immediately reduced by BVR to bilirubin. Why does the body employ both of these 2 distinct antioxidant systems? We show that the water-soluble GSH primarily protects water soluble proteins, whereas the lipophilic bilirubin protects lipids from oxidation. Mice with deletion of heme oxygenase-2, which generates biliverdin, display greater lipid than protein oxidation, while the reverse holds for GSH depletion. RNA interference depletion of BVR increases oxidation of lipids more than protein. Depletion of BVR or GSH augments cell death in an oxidant-specific fashion.

Heme Oxygenase-1 is an Essential Cytoprotective Component in Oxidative Tissue Injury Induced by Hemorrhagic Shock

Hemorrhagic shock causes oxidative stress that leads to tissue injuries in various organs including the lung, liver, kidney and intestine. Excess amounts of free heme released from destabilized hemoproteins under oxidative conditions might constitute a major threat because it can catalyze the formation of reactive oxygen species. Cells counteract this by rapidly inducing the rate-limiting enzyme in heme breakdown, heme oxygenase-1 (HO-1), which is a low-molecular-weight stress protein. The enzymatic HO-1 reaction removes heme. As such, endogenous HO-1 induction by hemorrhagic shock protects tissues from further degeneration by oxidant stimuli. In addition, prior pharmacological induction of HO-1 ameliorates oxidative tissue injuries induced by hemorrhagic shock. In contrast, the deletion of HO-1 expression, or the chemical inhibition of increased HO activity ablated the beneficial effect of HO-1 induction, and exacerbates tissue damage. Thus, HO-1 constitutes an essential cytoprotective component in hemorrhagic shock-induced oxidative tissue injures. This article reviews recent advances in understanding of the essential role of HO-1 in experimental models of hemorrhagic shock-induced oxidative tissue injuries with emphasis on the role of its induction in tissue defense.

Serum bilirubin levels, UGT1A1 polymorphisms and risk for coronary artery disease

Low levels of the antioxidative serum bilirubin are associated with vascular aging and an increased risk for coronary artery disease (CAD). UGT1A1 is the major gene influencing bilirubin concentrations. Therefore, we investigated an association of bilirubin levels and two polymorphisms in the promoter of UGT1A1 (-53(TA-repeat) polymorphism and T-3279G) in 477 patients with premature, familial CAD and 619 age- and sex-matched controls. Bilirubin concentrations were significantly lower in cases than in controls (0.62+/-0.36 vs. 0.76+/-0.41 mg/dl for men, p=1.2 x 10(-10); and 0.42+/-0.29 vs. 0.55+/-0.23 mg/dl, p=1.9 x 10(-9) for women). Both polymorphisms showed a strong association with bilirubin levels with higher levels for homozygote carriers of the minor allele. These associations were most pronounced in male controls and patients (p=5.9 x 10(-26) and p=3.4 x 10(-16), respectively, for the -53(TA-repeat) polymorphism). Logistic regression analysis revealed low bilirubin levels but not the UGT1A1 polymorphisms to be significantly associated with CAD: OR (95% CI) 0.90 (0.86-0.94), p=2.6 x 10(-6) for men and 0.77 (0.68-0.87), p=3.2 x 10(-5) for women, respectively for each 0.1mg/dl increase of bilirubin. These results indicate that it is rather decreased bilirubin levels in general than the changes in the genetic variation of this gene that increase the risk for CAD.

Delayed adverse vascular events after splenectomy in hereditary spherocytosis

BACKGROUND

It is probable that the variety and frequency of delayed adverse vascular events after splenectomy are underappreciated. Splenectomy is performed for a wide variety of conditions, and delayed postsplenectomy hazards are not often studied.

OBJECTIVE

To estimate the relative risk of adverse vascular events in members of hereditary spherocytosis families who have or have not had a splenectomy.

METHODS

Members of families in which hereditary spherocytosis exists were systematically questioned about adverse vascular events.

RESULTS

The cumulative incidence of arterial and venous events at age 70 years was greater in persons who had undergone a splenectomy for spherocytosis (arterial, 22% females, 32% males; venous, 20% females, 19% males) than in affected persons who did not undergo splenectomy (arterial, 3% females, 2% males; venous, 6% females, 4% males) or non-affected family members (arterial, 10% females, 17% males; venous, 4% females, 12% males). Affected subjects who undergo splenectomy are at greatly increased risk of arterial events as compared to affected subjects who do not undergo splenectomy [arterial, hazard ratio (HR) 7.2, 95% confidence interval (CI) 2.8-17.2; venous, HR 3.3, 95% CI 1.1-9.8].

CONCLUSION

There is a significant, long-lasting, increased risk of adverse arterial and venous thromboembolic events after splenectomy performed for hereditary spherocytosis. A review of the literature indicates that this is also true when splenectomy is performed for several other indications.

Gilbert syndrome, UGT1A1*28 allele, and cardiovascular disease risk: possible protective effects and therapeutic applications of bilirubin

Serum bilirubin has been shown to be inversely related to cardiovascular disease (CVD) in both retrospective and prospective studies. Meta-analysis of existing studies has also confirmed that serum bilirubin concentrations are inversely related to CVD. Less information is known about the protective effects of slightly elevated serum bilirubin concentrations. In this review, we will focus primarily on the association of serum bilirubin and CVD and the possible protective roles of bilirubin, heme oxygenase (HO), and bilirubin UDP-glucuronosyltransferase (UGT1A1). HO and biliverdin reductase control the formation of bilirubin, whereas UGT1A1 controls bilirubin conjugation and clearance. Because of the health and therapeutic implications of slightly elevated serum bilirubin concentrations, we will discuss the recent prospective studies on cardiovascular risk in individuals with Gilbert syndrome (GS) as well as those with the UGT1A1*28 allele. Such individuals have decreased hepatic bilirubin UDP-glucuronosyltransferase activity, decreased bilirubin clearance, and increased serum bilirubin concentrations. Lastly, we will discuss some of the therapeutic approaches that could be used to increase serum bilirubin concentrations to prevent CVD and other oxidative and inflammatory diseases.

Laboratory markers of thrombosis risk in children with hereditary spherocytosis

BACKGROUND

Recent data suggest that adults with hereditary spherocytosis (HS) may be protected from atherothrombosis before splenectomy but have increased risk of thrombosis following splenectomy. In order to aid in making informed decisions regarding splenectomy in children with HS, we conducted a retrospective study of several surrogate laboratory markers of thrombosis risk in children with HS.

METHODS

A retrospective record review was performed on 246 children with HS. Platelet count and hemoglobin concentration were recorded prior to and following splenectomy in each patient. Serum cholesterol levels were collected from the record when available.

RESULTS

Prior to splenectomy, hypocholesterolemia was common. Mean platelet counts in 31 evaluable patients pre- and post-splenectomy were 334 and 608 x 10(9)/L, respectively (P < 0.001). Twenty-nine patients (94%) exhibited persistent thrombocytosis following splenectomy. Hemoglobin values following splenectomy often rose to higher than age and gender-matched norms, with 30% of measurements greater than the 90th percentile and 17% greater than the 97th percentile.

CONCLUSIONS

The findings of hypocholesterolemia before splenectomy and thrombocytosis and mild polycythemia afterwards support the hypothesis that patients with HS might be protected from thrombosis before splenectomy and/or more susceptible afterwards. Prospective studies of additional prothrombotic biomarkers and thrombotic events in HS patients are warranted.

Statins and sepsis: multiple modifications at multiple levels

Sepsis, an infection-induced inflammatory syndrome, is a leading and increasing cause of mortality worldwide. Animal and human observational studies suggest statins may prevent the morbidity and mortality associated with the sepsis syndrome. In this Review, we describe the demonstrated mechanisms through which statins modulate the inflammatory response associated with sepsis. These mechanisms include effects on cell signalling with consequent changes at the transcriptional level, the induction of haem oxygenase, the direct alteration of leucocyte-endothelial cell interaction, and the reduced expression of MHC II. Since statins do not target individual inflammatory mediators, but possibly reduce the overall magnitude of the systemic response, this effect could prove an important distinguishing feature modulating the host response to septic insults. This work establishes the biological plausibility needed for future trials of statins in critical illness.

The Heme Catabolic Pathway and its Protective Effects on Oxidative Stress‐Mediated Diseases

Bilirubin, the principal bile pigment, is the end product of heme catabolism. For many years, bilirubin was thought to have no physiological function other than that of a waste product of heme catabolism--useless at best and toxic at worst. Although hyperbilirubinemia in neonates has been shown to be neurotoxic, studies performed during the past decade have found that bilirubin has a number of new and interesting biochemical and biological properties. In addition, there is now a strong body of evidence suggesting that bilirubin may have a beneficial role in preventing oxidative changes in a number of diseases including atherosclerosis and cancer, as well as a number of inflammatory, autoimmune, and degenerative diseases. The results also suggest that activation of the heme oxygenase and heme catabolic pathway may have beneficiary effects on disease prevention either through the action of bilirubin or in conjunction with bilirubin. If so, it may be possible to therapeutically induce heme oxygenase, increase bilirubin concentrations, and lower the risk of oxidative stress-related diseases.

Lowered levels of serum albumin and HDL-cholesterol in children with a recent mild infection

BACKGROUND

Infections are associated with atherogenic changes in serum.AIM. To elucidate effects of recent infections on risk factors for coronary heart disease in children.

SUBJECTS AND METHODS

In 1983 and again 3 years later, 2458 individuals aged 9, 12, 15, 18 and 21 years were investigated. In 1986, 106 subjects had symptoms of infection during the past 2 weeks before their follow-up visit. Their serum albumin and lipid concentrations were compared to those in 1983 when these individuals probably were healthy. An age- and sex-matched healthy control group from the cohort 1986 was chosen for comparison. For cholesterol age, sex and body mass index specific Z-scores in addition to actual values were used in statistical comparisons.

RESULTS

Serum albumin was 42 g/L in subjects with positive history of infection and 46 g/L in healthy controls (P<0.0001). HDL-cholesterol and the ratio of HDL- to total cholesterol were lower with increasing evidence of infection. Elevated serum C-reactive protein (CRP) or orosomucoid grouped the subjects with high and low serum HDL-cholesterol concentrations better than history of infection alone.

CONCLUSION

A mild infection lowers serum HDL-cholesterol and serum albumin concentrations, which both favour atherogenesis.

Heme oxygenase-1: from bench to bedside

As aspects of basic science come to play an increasingly prominent role in clinical medicine, heme oxygenase-1 is one of several molecules emerging as a central player in diseases of the lung and intensive care unit. Although the apparent raison d'être of this enzyme is to dispose of heme, its activity results in cytoprotection against oxidative injury and cellular stresses. As the lung interfaces directly with an oxidizing environment, it is expected that heme oxygenase-1 would be involved in many aspects of lung health and disease. The protective effects of heme oxygenase-1 and products of its enzymatic activity, including carbon monoxide, biliverdin and bilirubin, and ferritin, have opened the door to potential therapeutic and disease-monitoring possibilities that one day may be applicable to pulmonary medicine. This article introduces readers to the history of heme oxygenase research, the role of this enzyme in the lung, and related new developments to look forward to in the fields of pulmonary and critical care medicine.

A covalently linked recombinant albumin dimer is more rapidly cleared in vivo than are wild-type and mutant C34A albumin

Mammalian albumins are abundant plasma proteins that exhibit a relatively slow terminal clearance. For this reason they have been fused to potentially therapeutic proteins with rapid terminal clearance to produce fusion proteins with more desirable clearance profiles. A disulfide-linked albumin dimer has been described, but its abundance and stability in plasma are uncertain. To determine whether an obligatory albumin dimer incapable of dissociation would clear less rapidly than monomeric albumin, we expressed 3 recombinant rabbit serum albumin (RSA) polypeptides: H6RSA, RSA modified by the addition of an N-terminal hexahistidinyl tag; H6RSA(C34A), H6RSA with a single cysteine (Cys) 34-to-alanine (Ala) substitution (C34A); and DiRSA, H6RSA(C34A) joined by way of its C-terminus to RSA(C34A) through an intervening hexaglycine spacer. The C34A mutation was introduced to eliminate the possibility of disulfide bond-mediated dimerization. We expressed the proteins with the use of the yeast Pichia pastoris and purified them using nickel-chelate, ion exchange, and gel-filtration chromatography. After radioiodination and injection into rabbits, H6RSA and H6RSA(C34A) exhibited indistinguishable terminal catabolic half-lives (4.9 +/- 0.7 and 4.8 +/- 0.5 days, mean +/- SD), whereas that of DiRSA was reduced to 3.0 +/- 0.3 days (p<.05). The three proteins circulated in intact form, and their distributions in liver, lung, kidney, heart, and spleen did not differ 24 hours after injection. Although more DiRSA than H6RSA(C34A) was present in urine, in both cases it was in acid-soluble form. Ethyl palmitate treatment reduced the relative acceleration of DiRSA clearance compared with that of H6RSA(C34A), suggesting a role for the reticuloendothelial system in the differential clearance of the larger protein. Our results suggest that an albumin fusion protein should include only a single copy of albumin; that if the fusion protein exceeds a certain size, it may not acquire the slow clearance profile of native albumin; and that albumin dimerization through Cys34 probably does not contribute substantially to albumin metabolism in vivo.