Circulating total bilirubin and risk of non-alcoholic fatty liver disease in the PREVEND study: observational findings and a Mendelian randomization study

The Protective Effect of Bilirubin on MAFLD May Be Mediated by Improving Insulin Re-Sistance and Alleviating Chronic Inflammation

Background

Bilirubin, as a potent endogenous antioxidant, has demonstrated protective effects in various metabolic and inflammatory diseases. However, the precise role and underlying mechanisms of bilirubin in metabolic-associated fatty liver disease (MAFLD) remain unclear.

Methods

This study involved 3000 participants, categorized into non-MAFLD and MAFLD groups. Using weighted multiple linear regression and mediation effect analysis, this study examined the protective impact of total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL) on MAFLD risk. Additionally, potential mediators-inflammation and insulin resistance (IR) through which bilirubin exerts its protective effects were explored.

Results

TBIL and DBIL levels in the MAFLD group were significantly lower than those in the non-MAFLD group. Multiple linear regression analysis, adjusted for confounding variables, revealed that compared to the lowest tertile group (TBIL < 14.6), the odds ratios (ORs) for the middle tertile (TBIL 14.6-19.2) and the highest tertile (TBIL ≥ 19.3) groups were 0.735 and 0.615. Similarly, compared to the lowest tertile group (DBIL < 3.4), the ORs for the middle tertile (DBIL 3.4-4.4) and the highest tertile (DBIL ≥ 4.5) groups were 0.613 and 0.367. Mediation analysis revealed significant indirect effects of SIRI, PIV, TyG, TyGBMI, METS-IR, and AIP on the relationship between TBIL, DBIL, and MAFLD risk. Specifically, SIRI mediated 4.07% and 1.55% of the TBIL-MAFLD and DBIL-MAFLD associations, respectively; PIV mediated 9.56% and 4.22%; TyG mediated 69.27% and 81.91%; TyGBMI mediated 100% and 78.34%; METS-IR mediated 100% and 81.41%; and AIP mediated 100% for both TBIL-MAFLD and DBIL-MAFLD associations.

Conclusion

Our findings suggest that increased serum levels of TBIL and DBIL are significantly inversely correlated with MAFLD risk, with both serving as independent protective factors against MAFLD occurrence. Further mediation analysis indicates that this protective effect is likely mediated by improvements in IR and the alleviation of systemic chronic inflammation.

Further insights into influence factors of hypertension in older patients with obstructive sleep apnea syndrome: a model based on multiple centers

OBJECTIVE

To construct a novel model or a scoring system to predict hypertension comorbidity in older patients with obstructive sleep apnea syndrome (OSAS).

METHODS

A total of 1290 older patients with OSAS from six tertiary hospitals in China were enrolled. The sample was randomly divided into a modeling set (80%) and validation set (20%) using a bootstrap method. Binary logistic regression analysis was used to identify influencing factors. According to the regression coefficients, a vivid nomogram was drawn, and an intuitive score was determined. The model and score were evaluated for discrimination and calibration. The Z-test was utilized to compare the predictive ability between the model and scoring system.

RESULTS

In the multivariate analysis, age, body mass index (BMI), apnea-hypopnea index (AHI), total bilirubin (TB), high-density lipoprotein cholesterol (HDL-C), and fasting blood glucose (FBG) were significant predictors of hypertension. The area under the receiver operating characteristic curve of the model in the modeling and validation sets was 0.714 and 0.662, respectively. The scoring system had predictive ability equivalent to that of the model. Moreover, the calibration curve showed that the risk predicted by the model and the score was in good agreement with the actual hypertension risk.

CONCLUSIONS

This accessible and practical correlation model and diagram can reliably identify older patients with OSAS at high risk of developing hypertension and facilitate solutions on modifying this risk most effectively.

Circulating Bilirubin Levels, but Not Their Genetic Determinants, Are Inversely Associated with Steatotic Liver Disease in Adolescents

Epidemiologic studies suggest that elevated plasma unconjugated bilirubin confer protection against steatotic liver disease (SLD) in adults. However, evidence supporting this protective role in adolescents remains limited. We aimed to assess the association between serum bilirubin levels and their genetic determinants in protecting against SLD in Chilean adolescents. We conducted a cross-sectional study with 704 adolescents aged 15.4 ± 1 years (52% girls) of the Chilean Growth and Obesity Cohort Study. Ultrasonography echogenicity was used to diagnose SLD. We measured Z-scores of body mass index (z-BMI), total bilirubin (TB), and the genetic determinants of bilirubin (including rs887829 genotypes of UGT1A1 and bilirubin polygenic scores). Multiple logistic regression models evaluated the associations between standardized TB and its genetic determinants with SLD. We found that 1-SD of standardized plasma TB was significantly associated with a 30% reduction in the likelihood of SLD after adjustment by sex, age, z-BMI, and ethnicity (OR = 0.7; 95% CI = 0.50-0.96; p = 0.03). No significant associations were found among the rs887829 genotypes, bilirubin polygenic scores, and SLD in logistic regression models adjusted by covariates. Increased circulating bilirubin levels are unlikely causally associated with protection against SLD, and the cross-sectional association could be due to unmeasured confounding.

Urine cotinine versus self-reported smoking and the risk of chronic kidney disease

BACKGROUND AND HYPOTHESIS

Evidence on the role of smoking in the development of chronic kidney disease (CKD) has mostly relied on self-reported smoking status. We aimed to compare the associations of smoking status as assessed by self-reports and urine cotinine with CKD risk.

METHODS

Using the PREVEND prospective study, smoking status was assessed at baseline using self-reports and urine cotinine in 4333 participants (mean age, 52 years) without a history of CKD at baseline. Participants were classified as never, former, light current, and heavy current smokers according to self-reports and comparable cutoffs for urine cotinine. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated for CKD.

RESULTS

The percentages of self-reported and cotinine-assessed current smokers were 27.5% and 24.0%, respectively. During a median follow-up of 7.0 years, 593 cases of CKD were recorded. In analyses adjusted for established risk factors, the HRs (95% CI) of CKD for self-reported former, light current, and heavy current smokers compared with never smokers were 1.17 (0.95-1.44), 1.48 (1.10-2.00), and 1.48 (1.14-1.93), respectively. On further adjustment for urinary albumin excretion (UAE), the HRs (95% CI) were 1.07 (0.87-1.32), 1.26 (0.93-1.70), and 1.20 (0.93-1.57), respectively. For urine cotinine-assessed smoking status, the corresponding HRs (95% CI) were 0.81 (0.52-1.25), 1.17 (0.92-1.49), and 1.32 (1.02-1.71), respectively, in analyses adjusted for established risk factors plus UAE.

CONCLUSION

Self-reported current smoking is associated with increased CKD risk, but dependent on UAE. The association between urine cotinine-assessed current smoking and increased CKD risk is independent of UAE. Urine cotinine-assessed smoking status may be a more reliable risk indicator for CKD incidence than self-reported smoking status.

Self-reported smoking, urine cotinine, and risk of type 2 diabetes: Findings from the PREVEND prospective cohort study

BACKGROUND

Smoking is a major risk factor for type 2 diabetes (T2D), but the evidence has mostly relied on self-reports. We aimed to compare the associations of smoking exposure as assessed by self-reports and urine cotinine with T2D.

METHODS

Using the PREVEND prospective study, smoking status was assessed at baseline by self-reports and urine cotinine in 4708 participants (mean age, 53 years) without a history of diabetes. Participants were classified as never, former, light current and heavy current smokers according to self-reports and analogous cut-offs for urine cotinine. Hazard ratios (HRs) with 95% CIs were estimated for T2D.

RESULTS

During a median follow-up of 7.3 years, 259 participants developed T2D. Compared with self-reported never smokers, the multivariable adjusted HRs (95% CI) of T2D for former, light current, and heavy current smokers were 1.02 (0.75-1.4), 1.41 (0.89-2.22), and 1.30 (0.88-1.93), respectively. The corresponding adjusted HRs (95% CI) were 0.84 (0.43-1.67), 1.61 (1.12-2.31), and 1.58 (1.08-2.32), respectively, as assessed by urine cotinine. Urine cotinine-assessed but not self-reported smoking status improved T2D risk prediction beyond established risk factors.

CONCLUSION

Urine cotinine assessed smoking status may be a stronger risk indicator and predictor of T2D compared to self-reported smoking status.

Non-linear associations of circulating total bilirubin concentration with the risk of nonalcoholic fatty liver disease and all-cause mortality

INTRODUCTION AND OBJECTIVES

Accumulating evidence has supported that mild elevated total bilirubin exerts antioxidant and anti-inflammatory properties in multiple metabolic diseases. We aimed to explore the association of circulating total bilirubin concentration with non-alcoholic fatty liver disease (NAFLD) risk and all-cause mortality and examine the potential nonlinear relationships between them.

MATERIAL AND METHODS

We used nationally representative data from the National Health and Nutrition Examination Survey (NHANES). NAFLD was assessed using the fatty liver index (FLI) and United States fatty liver index (USFLI), respectively.

RESULTS

A total of 35 912 and 17 329 participants were included in FLI-NAFLD (case with NAFLD was diagnosed by FLI) and USFLI-NAFLD (case with NAFLD was diagnosed by USFLI) groups, respectively. The mean age of total population was 46.25 years, and 48.51% were male. Compared to participants with lowest quintile of total bilirubin concentration, those with highest quintile had lower risk of NAFLD in both FLI-NAFLD (OR: 0.48, 95% CI: 0.40, 0.59) and USFLI-NAFLD (OR: 0.55, 95% CI: 0.43, 0.70) groups. Compared to participants with lowest quintile of total bilirubin concentration, the association between total bilirubin concentration and all-cause mortality was not significant among those with highest quintile of total bilirubin concentration (HR: 0.89, 95% CI: 0.66, 1.20). The restricted spline curves showed the nonlinear U-shaped association of total bilirubin concentration with NAFLD risk and all-cause mortality. The segmented linear regression analysis showed negative associations between total bilirubin concentration and risk of NAFLD in both FLI-NAFLD (OR: 0.94, 95% CI: 0.93, 0.95) and USFLI-NAFLD (OR: 0.95, 95% CI: 0.93, 0.96) groups when total bilirubin concentration was below the turning point (FLI-NAFLD: 18.81 μmol/L; USFLI-NAFLD: 15.39 μmol/L) and these associations were not significant when total bilirubin concentration was higher than the turning point. Furthermore, all-cause mortality decreased (OR: 0.97, 95%CI: 0.95, 1.00) with increased total bilirubin concentration up to the turning point (11.97 μmol/L), and then all-cause mortality increased with increasing total bilirubin concentration (OR: 1.03, 95%CI: 1.02, 1.04).

CONCLUSIONS

We found that higher circulating total bilirubin concentration within the physiological range was associated with decreased risk of NAFLD and all-cause mortality among NAFLD patients.

Causal inference between serum bilirubin levels and juvenile idiopathic arthritis-associated uveitis: A bidirectional Mendelian randomization study

Background

Several observational studies have suggested an association between low serum bilirubin levels and Behçet's disease uveitis. However, the causal inference between bilirubin level and juvenile idiopathic arthritis-associated uveitis (JIAU) remains ambiguous. We investigated the potential causal relationship between serum bilirubin levels and JIAU using a bidirectional two-sample Mendelian randomization (MR) framework.

Methods

We systemically integrated summary-level data from published large-scale genome-wide association studies on bilirubin level and JIAU in a Caucasian British population. To determine the causal effect of bilirubin level on JIAU, we constructed strong instrumental variables using 47 and 80 single-nucleotide polymorphisms (SNPs) specific to direct bilirubin and total bilirubin levels, respectively. For reverse causal inference, seven SNPs associated with JIAU were included in our study. Multiple complementary methods were further performed to evaluate the robustness of MR estimates.

Results

The inverse-variance weighted estimate did not show any significant causal associations of genetically predicted serum direct or total bilirubin level with the risk of JIAU (odds ratio [OR]: 1.010, 95% confidence interval [CI]: 0.750-1.359, p = 0.947; OR: 0.867, 95% CI: 0.688-1.093; p = 0.227, respectively). MR-Egger and weighted median methods also obtained similar associations. Additionally, the results of reverse MR analyses using JIAU as exposure showed no associations of genetically predicted risk of JIAU with serum bilirubin levels (p > 0.05). In sensitivity analysis, the causal estimate between serum bilirubin levels and JIAU did not differ when SNPs associated with possible confounders were omitted.

Conclusion

Genetic evidence from our bidirectional analysis did not support a causal association between serum bilirubin levels and JIAU risk in the Caucasian British population. Future large-scale studies should be conducted to validate these findings and explore any causal effects on the disease process.

Ameliorative effects of bilirubin on cell culture model of non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is defined as the most prevalent hepatic disorder that affects a significant population worldwide. There are several genes/proteins, involving in the modulation of NAFLD pathogenesis; sirtuin1 (SIRT1), TP53-inducible regulator gene (TIGAR), and autophagy-related gene 5 (Atg5) are considered a chief group of these modulators that principally act by regulating the hepatic lipid metabolism, as well as preventing the lipid accumulation. Surprisingly, bilirubin, especially in its unconjugated form, might be able to alleviate NAFLD progression by decreasing lipid accumulation and regulating the expression levels of the above-stated genes.

METHODS AND RESULTS

Herein, the interactions between bilirubin and the corresponding genes' products were first analyzed by docking assessments. Afterwards, HepG2 cells were cultured under the optimum conditions, and then were incubated with high concentrations of glucose to induce NAFLD. After treating normal and fatty liver cells with particular bilirubin concentrations for 24- and 48-hour periods, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay, colorimetric method, and quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) were employed to assess cell viability status, intracellular triglycerides content, and mRNA expression levels of the genes, respectively. Intracellular lipid accumulation of HepG2 cells was significantly decreased after treating with bilirubin. Bilirubin also increased SIRT1 and Atg5 gene expression levels in fatty liver cells. TIGAR gene expression levels were variable upon the conditions and the cell type, suggesting a dual role for TIGAR during the NAFLD pathogenesis.

CONCLUSION

Our findings indicate the potential of bilirubin in the prevention from or amelioration of NAFLD through influencing SIRT1-related deacetylation and the process of lipophagy, as well as decreasing the intrahepatic lipid content. In vitro model of NAFLD was treated with unconjugated bilirubin under the optimal conditions.Desirably, bilirubin moderated the accumulation of triglycerides within the cells possibly through modulation of the expression of SIRT1, Atg5, and TIGAR genes. In the context, bilirubin was shown to increase the expression levels of SIRT1 and Atg5, while the expression of TIGAR was demonstrated to be either increased or decreased, depending on the treatment conditions. Created with BioRender.com.

Association between biological aging and lung cancer risk: Cohort study and Mendelian randomization analysis

Chronological age only represents the passage of time, whereas biological age reflects the physiology states and the susceptibility to morbidity and mortality. The association between biological age and lung cancer risk remains controversial. Hence, we conducted a prospective analysis in the UK Biobank study and two-sample Mendelian randomization analysis to investigate this association. Biological aging was evaluated by PhenoAgeAccel, derived from routine clinical biomarkers. Independent of chronological age, PhenoAgeAccel was positively associated with the risk of overall and histological subtypes of lung cancer. There was a joint effect of PhenoAgeAccel and genetics in lung cancer incidence. In Mendelian randomization analysis, the genetically predicted PhenoAgeAccel was associated with the increased risk of overall lung cancer, small cell, and squamous cell carcinoma. Our findings suggest PhenoAgeAccel is an independent risk factor for lung cancer, which could be incorporated with polygenic risk score to identify high-risk individuals for lung cancer.

Bilirubin Levels Are Negatively Correlated with Adiposity in Obese Men and Women, and Its Catabolized Product, Urobilin, Is Positively Associated with Insulin Resistance

Bilirubin levels in obese humans and rodents have been shown to be lower than in their lean counterparts. Some studies have proposed that the glucuronyl UGT1A1 enzyme that clears bilirubin from the blood increases in the liver with obesity. UGT1A1 clearance of bilirubin allows more conjugated bilirubin to enter the intestine, where it is catabolized into urobilin, which can be then absorbed via the hepatic portal vein. We hypothesized that when bilirubin levels are decreased, the urobilin increases in the plasma of obese humans, as compared to lean humans. To test this, we measured plasma levels of bilirubin and urobilin, body mass index (BMI), adiposity, blood glucose and insulin, and HOMA IR in a small cohort of obese and lean men and women. We found that bilirubin levels negatively correlated with BMI and adiposity in obese men and women, as compared to their lean counterparts. Contrarily, urobilin levels were positively associated with adiposity and BMI. Only obese women were found to be insulin resistant based on significantly higher HOMA IR, as compared to lean women. The urobilin levels were positively associated with HOMA IR in both groups, but women had a stronger linear correlation. These studies indicate that plasma urobilin levels are associated with obesity and its comorbidities, such as insulin resistance.

Associations between non-alcoholic fatty liver disease and cognitive impairment and the effect modification of inflammation

This study aimed to evaluate the association between non-alcoholic fatty liver disease (NAFLD) and cognitive impairment and explore the effect modification by the inflammatory status. A total of 4400 community-based participants aged 50–64 years from the Cardiovascular and Metabolic Disease Etiology Research Center were included in this cross-sectional study. NAFLD was identified as the Fatty Liver Index 30 or higher in the absence of excessive alcohol consumption. Cognitive impairment was defined as the total score of the Mini-Mental State Examination (cutoff 24). The inflammatory status was evaluated using white blood cell (WBC) and high-sensitivity C-reactive protein (hsCRP). Multivariate logistic regression analyses were performed. Stratified analyses by the WBC count (the highest quartile) and the hsCRP level (≥ 1.0 mg/dL vs. < 1.0 mg/dL) were conducted. Participants with NAFLD showed an increased prevalence of cognitive impairment (odds ratio [OR] = 1.26; 95% confidence interval [CI] = 1.04–1.52) compared with the non-NAFLD population. In women, this association was significantly stronger in the highest quartile WBC group than in lower WBC group (OR = 1.81; 95% CI = 1.19–2.74 vs. OR = 1.02; 95% CI = 0.78–1.33, p-interaction = 0.05). NAFLD was positively associated with a higher proportion of cognitive impairment, and this association was stronger in women with higher inflammatory status.

Molecular mechanisms of metabolic associated fatty liver disease (MAFLD): functional analysis of lipid metabolism pathways

The metabolic-associated fatty liver disease (MAFLD) is a condition of fat accumulation in the liver in combination with metabolic dysfunction in the form of overweight or obesity and insulin resistance. It is also associated with an increased cardiovascular disease risk, including hypertension and atherosclerosis. Hepatic lipid metabolism is regulated by a combination of the uptake and export of fatty acids, de novo lipogenesis, and fat utilization by β-oxidation. When the balance between these pathways is altered, hepatic lipid accumulation commences, and long-term activation of inflammatory and fibrotic pathways can progress to worsen the liver disease. This review discusses the details of the molecular mechanisms regulating hepatic lipids and the emerging therapies targeting these pathways as potential future treatments for MAFLD.

Association of Serum Bilirubin With Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Metabolic syndrome (MetS) and non-alcoholic fatty liver disease (NAFLD) are the leading chronic diseases worldwide. There are still many controversies about the association between serum bilirubin and MetS or NAFLD. This study aims to evaluate the association of serum total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL) with MetS and NAFLD.

METHODS

Multiple databases were searched for relevant studies until November 2021. Randomized controlled trials, cross-sectional and cohort studies evaluating the association between serum bilirubin levels and MetS or NAFLD were included.

RESULTS

Twenty-four cross-sectional and cohort studies with 101, 517 participants were finally analyzed. Fifteen studies and 6 studies evaluated the association between bilirubin and MetS or NAFLD in health screening population, respectively, while 3 studies evaluated the association between bilirubin and non-alcoholic steatohepatitis (NASH) in NAFLD patients. Random effect model analysis showed the inverse association between TBIL and MetS in male (95%CI=0.71-0.96) and gender-neutral (95%CI=0.61-0.91) group. However, no significant association was found in females. Notably, the inverse association between DBIL and MetS was noticed in male (95%CI=0.36-0.75), female (95%CI=0.16-0.58) and gender-neutral population (95%CI=0.67-0.92). IBIL level was inversely associated with MetS in females (95%CI=0.52-0.96), whereas no statistical correlation presented in males. TBIL was not statistically correlated with NAFLD in gender-neutral or male subgroup. Similarly, there were no association between DBIL or IBIL and NAFLD in gender-neutral subgroup. However, the negative correlation between DBIL and NAFLD existed in males (95%CI=0.76-0.96). In NAFLD patients, IBIL analysis showed an inverse association with NASH (95%CI=0.01-0.12).

CONCLUSION

Serum TBIL and DBIL levels, especially DBIL levels, assume an inverse correlation with MetS in healthy population. Serum IBIL is inversely associated with the onset and degree of NASH in NAFLD patients. Exogenous bilirubin supplement may be a potential strategy to assist in lowering the risk of developing MetS and NAFLD.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier CRD42021293349.

Identifying Potential Therapeutic Applications and Diagnostic Harms of Increased Bilirubin Concentrations: A Clinical and Genetic Approach

Bilirubin has antioxidant and anti-inflammatory properties in vitro and in animal studies and protects against inflammatory, cardiovascular, and other diseases in observational studies; therefore, bilirubin has potential as a therapeutic agent. However, observational studies could be confounded by many factors. We used a genetic (n = 61,281) and clinical (n = 234,670) approach to define the association between bilirubin and 19 conditions with a putative protective signal in observational studies. We also tested if individuals with genetically higher bilirubin levels underwent more diagnostic tests. We used a common variant in UGT1A1 (rs6742078) associated with an 26% increase in bilirubin levels in the genetic studies. Carriers of the variant had higher bilirubin levels (P = 2.2 × 10-16 ) but there was no significant association with any of the 19 conditions. In a phenome-wide association study (pheWAS) to seek undiscovered genetic associations, the only significant finding was increased risk of "jaundice-not of newborn." Carriers of the variant allele were more likely to undergo an abdominal ultrasound (odds ratio = 1.04, [1.00-1.08], P = 0.03). In contrast, clinically measured bilirubin levels were significantly associated with 15 of the 19 conditions (P < 0.003) and with 431 clinical diagnoses in the pheWAS (P < 1 × 10-5 adjusted for sex, age, and follow-up). With additional adjustment for smoking and body mass index, 7 of 19 conditions and 260 pheWAS diagnoses remained significantly associated with bilirubin levels. In conclusion, bilirubin does not protect against inflammatory or other diseases using a genetic approach; the many putative beneficial associations reported clinically are likely due to confounding.

Relationship of circulating total bilirubin, UDP-glucuronosyltransferases 1A1 and the development of non-alcoholic fatty liver disease: a cross-sectional study

Background

This study aimed to investigate the correlation of circulating total bilirubin (TB) and UGT1A1 with NAFLD in Chinese Han population.

Methods

172 adults were enrolled from the Qingdao Municipal Hospital from May 2019 to October 2020. All individuals were examined with MRI-PDFF and divided into no steatosis, mild steatosis, moderate steatosis, and severe steatosis groups according to the MRI-PDFF values. The biochemical indexes and UGT1A1 were measured.

Results

There was no significant difference of circulating TB and UGT1A1 levels between NAFLD group and controls. In the moderate steatosis and severe steatosis groups, the circulating TB levels were higher than that in control group (all P < 0.05). In addition, circulating TB levels were weak positively associated with liver fat fraction in NAFLD patients (ρ = 0.205, P = 0.001). There was no significant correlation between circulating UGT1A1 levels with liver fat fraction in patients with NAFLD (ρ = 0.080, P = 0.179), but positively correlation was found in patients with severe steatosis (ρ = 0.305, P = 0.026).

Conclusions

The circulating TB levels were significant high in patients with moderate and severe steatosis. Circulating TB levels were weakly associated with liver fat fraction in patients with NAFLD, and the circulating UGT1A1 levels were positively correlated with liver fat fraction in NAFLD patients with severe steatosis.

Trial registration: ChiCTR, ChiCTR1900022744. Registered 24 April 2019 – Retrospectively registered, http://www.chictr.org.cn/edit.aspx?pid=38304&htm=4.

Association of Serum Bilirubin and Functional Variants of Heme Oxygenase 1 and Bilirubin UDP-Glucuronosyl Transferase Genes in Czech Adult Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disorder worldwide. The aim of our study was to assess the role of bilirubin, and the heme oxygenase 1 (HMOX1) and bilirubin UDP-glucuronosyl transferase (UGT1A1) promoter gene variants, which are involved in bilirubin homeostasis, in the NAFLD development in adult patients. The study was performed on 84 patients with NAFLD and 103 age/sex-matched controls. Routine biochemistry, inflammatory markers, adipokines, and the fibrosis/steatohepatitis stage were determined in the NAFLD patients. The (GT)n/(TA)n dinucleotide variations in HMOX1/UGT1A1 gene promoters, respectively, were analyzed by fragment analysis. Compared to controls, serum bilirubin concentrations in NAFLD patients tended to be decreased, while the prevalence of phenotypic Gilbert syndrome was significantly low. Genetic variations in HMOX1 and UGT1A1 gene promoters did not differ between NAFLD patients and controls, and no relationship was found in the NAFLD patients between these gene variants and any of the laboratory or histological parameters. In conclusion, metabolism of bilirubin is dysregulated in NAFLD patients, most likely due to increased oxidative stress, since frequencies of the major functional variants in the HMOX1 or UGT1A1 gene promoters did not have any effect on development of NAFLD in adult patients.

Effects of iron-related compounds and bilirubin on redox homeostasis in endometriosis and its malignant transformations

OBJECTIVES

The balance between oxidative stress and antioxidant defense has been reported to differ between women with endometriosis and patients with its malignant transformation. The aim of this study is to investigate changes in redox balance in endometriosis and endometriosis-related ovarian cancer (EAOC) by simultaneously measuring iron-related compounds and bilirubin.

METHODS

This study included 235 patients with a histopathologically confirmed diagnosis of endometriosis (n=178) and EAOC (n=57). Cyst fluid samples were collected in Nara Medical University hospital from January 2013 to May 2019. The levels of iron-related compounds (total iron, heme iron, free iron, oxyhemoglobin [oxyHb], methemoglobin [metHb], and metHb/oxyHb ratio) and bilirubin were measured.

RESULTS

Total iron, heme iron, free iron, metHb/oxyHb ratio, and bilirubin were significantly elevated in endometriosis compared to EAOC. In both endometriosis and EAOC, iron-related compounds in the cyst were correlated with each other. There was no statistically significant difference in oxyHb and metHb levels between the two groups, but the metHb/oxyHb ratio was significantly higher in endometriosis than in EAOC. Bilirubin was positively correlated with total iron and free iron in EAOC, but there was no correlation between bilirubin and iron-related compounds in endometriosis.

CONCLUSIONS

Iron-induced oxidative stress in endometriosis may exceed bilirubin-dependent antioxidant capability, while redox homeostasis in EAOC can be maintained by at least bilirubin.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.

Higher Serum Bilirubin Levels in Response to Higher Carbohydrate Intake During Early Pregnancy and Lower Gestational Diabetes Mellitus Occurrence in Overweight and Obese Gravidae

Background and Aim: Serum bilirubin levels are recently shown to be a novel protector of gestational diabetes mellitus (GDM), yet whether they could be affected by carbohydrate quality is unclear. We aimed to examine the associations between dietary carbohydrate parameters and serum bilirubin levels during early pregnancy, with further exploration on a potential mediating role of serum bilirubin levels on carbohydrate parameters-GDM pathways. Methods: 260 healthy but overweight or obese gravidae (BMI ≥24 kg/m2) derived from a historical cohort in two hospitals in China were included. The associations between carbohydrate parameters (total carbohydrate intake, glycemic index GI, fiber intake, glycemic load GL) and serum bilirubin levels (total bilirubin, TB and direct bilirubin, DB) and GDM were evaluated by multivariable regression analysis. Generalized structural equation modeling was then applied to perform adjusted mediation analysis. Results: Increased serum bilirubin levels (mmol/L) and decreased GDM occurrence were observed following dietary carbohydrate intake (%E) and GL (g/1,000 kcal) in highest tertile compared to the lowest tertile [carbohydrate: TB: β = 0.926 (95%CI: 0.069, 1.782), DB: β = 0.554 (95%CI: 0.192, 0.916);GL:TB: β = 1.170 (95%CI: 0.339, 2.001); DB: β = 0.369 (95%CI: 0.016, 0.700); carbohydrate: adjusted OR = 0.43 (95%CI:0.19-0.99); GL: adjusted OR = 0.36 (95%CI:0.16, 0.84)]. The mediating effect of carbohydrate intake and GL on GDM through bilirubin levels was evaluated as modest (carbohydrate: 6.2% for TB, 1.3% for DB; GL: 8.7% for TB, 2.3% for DB). No association was observed regarding GI and fiber. Conclusions: Mildly elevated serum bilirubin levels appeared to be in response to higher energies consumed from carbohydrate during early pregnancy in healthy overweight or obese gravidae. However, the mediating effect of bilirubin levels on carbohydrate-GDM pathways is not evident. Larger investigation is further needed for solid evidence.

Insomnia affects the levels of plasma bilirubin and protein metabolism: an observational study and GWGEIS in UK Biobank cohort

STUDY OBJECTIVES

We aim to explore the mechanism of relationship between insomnia and liver metabolism by examining the gene × insomnia interactions.

METHODS

Individual level genotypic and phenotypic data were obtained from the UK Biobank cohort. Regression analysis was first conducted to test the association of insomnia with plasma total bilirubin (TBil; n = 186,793), direct bilirubin (DBil; n = 159,854) and total protein (TP; n = 171,574) in UK Biobank cohort. Second, genome-wide gene-environment interaction study (GWGEIS) was conducted by PLINK 2.0, and FUMA platform was used to identify enriched pathway terms.

RESULTS

In UK Biobank cohort, we found that TP (P < 2.00 × 10^-16), DBil (P = 1.72 × 10^-3) and TBil (P = 3.38 × 10^-5) were significantly associated with insomnia. GWGEIS of both DBil and TBil observed significant G × INSOMNIA effects between insomnia and UDP Glucuronosyltransferase Family 1 (rs6431558, P = 6.26 × 10^-11) gene. GWGEIS of TP also detected several significant genes interacting with insomnia, such as KLF15, (rs70940816, P = 6.77 × 10^-10) and DOK7, (rs2344205, P = 1.37 × 10^-9). Multiple gene ontology (GO) terms were identified for bilirubin, such as GO_URONIC_ACID_METABOLIC_PROCESS (adjusted P = 4.15 × 10^-26).

CONCLUSION

Our study results suggested negative associations between insomnia and DBil and TBil; and a positive association between insomnia and TP.

Association of Serum Bilirubin Level with Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease: A Cross-Sectional Study of 1672 Obese Children

As in adults, obesity also plays a central role in the development of metabolic syndrome (MS) in children. Non-alcoholic fatty liver disease (NAFLD) is considered a manifestation of MS. Not only MS but also NAFLD seem to be inversely associated with serum bilirubin concentrations, an important endogenous tissue protector when only mild elevated. The aim of the study was to evaluate the association between serum bilirubin levels and the prevalence of MS and NAFLD in Italian obese children and adolescents. A retrospective cross-sectional study was performed in 1672 patients aged from 5 to 18 years. Clinical and laboratory parameters were assessed. NAFLD was measured by liver ultrasonography. The study was approved by the Ethical Committee of the Istituto Auxologico Italiano (research project code 1C021_2020, acronym BILOB). MS was present in 24% and fatty liver (FL) in 38% of this population. Bilirubin was not associated with FL and MS as a whole, but it was inversely associated only with selected components of MS, i.e., large WC, high blood pressure and high triglycerides. Our data suggest that bilirubin is not protective against MS and NAFLD in the presence of severe obesity.

Causal effects of homocysteine levels on the changes of bone mineral density and risk for bone fracture: A two-sample mendelian randomization study

BACKGROUND & AIMS

Observational studies have demonstrated the relations of homocysteine (HCY) with bone mineral density (BMD) and bone fracture risk, but yielding contradictory results. The present study was conducted to evaluate whether the genetically predicted plasma HCY levels were causally associated with the change of BMD and the risk of bone fracture.

METHODS

Genetic summary statistics were extracted from genome-wide association study (GWAS) meta-analysis of plasma HCY levels (n = 44,147), GWAS meta-analyses of measured forearm (FA), femoral neck (FN) and lumbar spine (LS) BMD (n = up to 32,735), UK Biobank estimated heel BMD (eBMD) (n = 426,824) and fracture (n = 426,795) GWAS data. Two Sample Mendelian Randomization (TSMR) analysis was performed to assess the causal effects of genetically determined plasma HCY on the BMD and bone fractures.

RESULTS

The MR analysis indicated that, genetically decreased plasma HCY was associated with the increased FA-BMD based on the inverse variance weighting (IVW) method (standard deviation [SD] = 0.348, 95% CI: 0.146 to 0.550, P = 7 × 10^-4). However, there were no significant associations of genetically decreased plasma HCY with FN-BMD, LS-BMD, eBMD and the risk for bone fracture (SD = -0.041, 95% CI: -0.189 to 0.106, P = 0.582; SD = -0.053, 95% CI: -0.238 to 0.131, P = 0.572; SD = -0.030, 95% CI: -0.090 to 0.030, P = 0.328, odds ratio [OR]: 1.03, 95% CI: 0.94 to 1.13, P = 0.562, respectively). Moreover, the results also found that genetically determined HCY increase was not correlated with the changes of BMD and the risk for bone fracture.

CONCLUSION

Our study revealed that genetically decreased plasma HCY was associated with increase of FA-BMD.

Bilirubin as a metabolic hormone: the physiological relevance of low levels

Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.

Systematic Influence of Circulating Bilirubin Levels on Osteoporosis

Observational studies report some association between circulating bilirubin levels and osteoporosis, but it is unknown if this association is causal or confounded. In this two-sample Mendelian randomization (MR) study, we included a large genome-wide association study (GWAS) associated with total bilirubin levels among 317,639 people, a large meta-analysis to identify genetic variants associated with bone mineral density (BMD) estimated by heel quantitative ultrasound (eBMD) among 426,824 individuals and fracture among 1.2 million individuals. The results revealed that circulating bilirubin levels had no causal influence on eBMD (beta-estimate: 0.004, 95% confidence interval [CI]: -0.019 to 0.028, SE:0.012, P-value=0.705) or the risk of fracture (beta-estimate: -0.009, 95% CI: -0.035 to 0.017, SE:0.013, P-value=0.488), which were both confirmed by multiple sensitivity analyses. Our results confirm that circulating bilirubin levels have no causal role in eBMD or the incidence of fracture, indicating that circulating bilirubin levels is unlikely to be a causal risk factor for osteoporosis or fracture.

Serum Bilirubin Level Is Increased in Metabolically Healthy Obesity

OBJECTIVES

Bilirubin is a biochemical substance with metabolic benefits. The objective of this research was to elucidate the association between serum bilirubin levels and metabolic alterations in different obesity phenotypes.

METHODS

In total, 1,042 drug-naive participants were included in the study. Of them, 541 were obese patients and 501 were age-matched and sex-matched healthy control subjects. The obese patients were divided into metabolically healthy obesity (MHO) group and metabolically unhealthy obesity (MUHO) group according to the levels of fasting plasma glucose (FBG), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and blood pressure (BP). Clinical and biochemical parameters including total bilirubin (TBil), indirect bilirubin (IBil) and direct bilirubin (DBil) were measured. ANOVA or Kruskal-Wallis H test was used to test differences among the three groups. Pearson and Spearman correlations were used to analyze the relationships between two parameters. The relationships between bilirubin and other variables were analyzed using Multivariate regression analysis.

RESULTS

MHO group had favorable blood pressure, glucose and lipids profiles, along with increased TBil and DBil, and decreased high-sensitivity C-reactive protein (hsCRP) and homeostasis model assessment of insulin resistance (HOMA-IR) levels when compared to MUHO group (P < 0.05 for all). TBil and DBil were negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), fasting insulin (FINS), hsCRP and HOMA-IR, even after adjusted for age, gender and BMI (all P <0.01). Multivariate regression analysis demonstrated that HOMA-IR was independently correlated with TBil and DBIi levels (β = -0.400, P < 0.01).

CONCLUSION

MHO group harbors increased bilirubin level compared with MUHO group. HOMA-IR was independently correlated with TBil and DBIi levels.

Heme Oxygenase-1 in Gastrointestinal Tract Health and Disease

Heme oxygenase 1 (HO-1) is the rate-limiting enzyme of heme oxidative degradation, generating carbon monoxide (CO), free iron, and biliverdin. HO-1, a stress inducible enzyme, is considered as an anti-oxidative and cytoprotective agent. As many studies suggest, HO-1 is highly expressed in the gastrointestinal tract where it is involved in the response to inflammatory processes, which may lead to several diseases such as pancreatitis, diabetes, fatty liver disease, inflammatory bowel disease, and cancer. In this review, we highlight the pivotal role of HO-1 and its downstream effectors in the development of disorders and their beneficial effects on the maintenance of the gastrointestinal tract health. We also examine clinical trials involving the therapeutic targets derived from HO-1 system for the most common diseases of the digestive system.

A Nomogram Model Based on Noninvasive Bioindicators to Predict 3-Year Risk of Nonalcoholic Fatty Liver in Nonobese Mainland Chinese: A Prospective Cohort Study

The purpose of this study is to establish and validate an accurate and personalized nonalcoholic fatty liver disease (NAFLD) prediction model based on the nonobese population in China. This study is a secondary analysis of a prospective study. We included 6,155 nonobese adults without NAFLD at baseline, with a median follow-up of 2.3 years. Univariate and multivariate Cox regression analyses were used to determine independent predictors. The least absolute shrinkage and selection operator (LASSO) regression analysis was used to optimize the selection of variables. Based on the results of multivariate analysis, a prediction model was established. Harrell's consistency index (C-index) and area under the curve (AUC) were used to determine the discrimination of the proposed model. The goodness of fit of the calibration model was tested, and the clinical application value of the model was evaluated by decision curve analysis (DCA). The participants were randomly divided into a training cohort (n = 4,605) and a validation cohort (n = 1,550). Finally, seven of the variables (HDL-c, BMI, GGT, ALT, TB, DBIL, and TG) were included in the prediction model. In the training cohort, the C-index and AUC value of this prediction model were 0.832 (95% confidence interval (CI), 0.820-0.844) and 0.861 (95% CI, 0.849-0.873), respectively. In the validation cohort, the C-index and AUC values of this prediction model were 0.829 (95% CI, 0.806-0.852) and 0.859 (95% CI, 0.841-0.877), respectively. The calibration plots demonstrated good agreement between the estimated probability and the actual observation. DCA demonstrated a clinically effective predictive model. Our nomogram can be used as a simple, reasonable, economical, and widely used tool to predict the 3-year risk of NAFLD in nonobese populations in China, which is helpful for timely intervention and reducing the incidence of NAFLD.

Characteristics and risk factors of deep vein thrombosis in hemiplegic, healthy and bilateral limbs of hemiplegic patients: a 10-year retrospective study

Deep vein thrombosis (DVT) in hemiplegic patients mainly affects hemiplegic limbs, DVT can also occur only in healthy limbs, and some hemiplegic patients have DVT in both limbs. Characteristics and risk factors of DVT in hemiplegic, healthy, and bilateral limbs are unknown. To describe the proportion, risk factors, extent, and timing of DVT in hemiplegic, healthy and bilateral limbs. A 10-year retrospective review of consecutive patients was performed. DVT affected hemiplegic limbs in 34 (62%), healthy limbs in 11 (20%), and was bilateral in 10 (18%). DVT was more likely to develop in healthy limbs of hemiplegic patients without surgery (odds ratio (OR) 0.022; 95% confidence interval (CI) 0.001-0.922), and without diabetes (OR 0.023, 95% CI 0.001-0.853). Among the veins at the level of which DVT occurred, intermuscular veins represented 20 (45%) in hemiplegic, 5 (37%) in healthy, and 6 (74%) in bilateral limbs. The median time that DVT occurred after hemiplegia onset was 18 days (interquartile range [IQR] 9-79) in hemiplegic, 17 days (IQR 10-56) in healthy, and 21 days (IQR 8-27) in bilateral limbs. Early and effective prevention of DVT after surgery and optimal management of diabetes may reduce the risk of DVT in bilateral limbs. It's important to prevent proximal extension of calf vein DVT. DVT prophylaxis should be started early and continued for at least 3 weeks after hemiplegia onset.