SERUM BILIRUBIN CORRELATES WITH SERUM ADIPOKINES IN NORMAL WEIGHT AND OVERWEIGHT ASYMPTOMATIC ADULTS

Association between bilirubin and biomarkers of metabolic health and oxidative stress in the MARK-AGE cohort

Recent studies have shown that elevated concentrations of unconjugated bilirubin (UCB) may be a protective host factor against the development of noncommunicable diseases (NCDs), whereas low levels of UCB are associated with the opposite effect. The results of this European study, in which 2,489 samples were tested for their UCB concentration using high-performance liquid chromatography (HPLC) and additional data from the MARK-AGE database were used for analysis, provide further evidence that elevated UCB concentrations are linked to a lower risk of developing NCDs and may act as a predictive marker of biological aging as individuals with elevated UCB concentrations showed favorable outcomes in metabolic health and oxidative-stress-related biomarkers. These findings underline the significance of studying individuals with moderate hyperbilirubinemia and investigate UCB routinely, also in the setting of aging, since this condition affects millions of people worldwide but has been underrepresented in clinical research and practice until now.

The role of bilirubin as a biomarker of rheumatic diseases: a systematic review and meta-analysis

The identification of novel, yet easily measurable biomarkers of inflammation and oxidative stress might assist in the diagnosis and management of patients with rheumatic diseases (RDs). We conducted a systematic review and meta-analysis of studies investigating the circulating concentrations of bilirubin, the end product of heme metabolism and a potent endogenous antioxidant with anti-inflammatory properties, in patients with RDs and healthy controls. The electronic databases PubMed, Scopus, and Web of Science were searched from inception to 31 December 2023 for relevant articles. We evaluated the risk of bias and the certainty of evidence using the Joanna Briggs Checklist and the Grades of Recommendation, Assessment, Development, and Evaluation Working Group system, respectively. In 17 eligible studies, all with low risk of bias, compared to controls, patients with RDs had significantly lower concentrations of total bilirubin (standard mean difference, SMD=-0.68, 95% CI -0.91 to -0.44, p<0.001; I2 = 92.5%, p<0.001; low certainty of evidence), direct (conjugated) bilirubin (SMD=-0.67, 95% CI -0.92 to -0.41, p<0.001; I2 = 81.7%, p<0.001; very low certainty of evidence), and the active antioxidant and anti-inflammatory indirect (unconjugated) form of bilirubin (SMD=-0.71, 95% CI -1.18 to -0.24, p=0.003; I2 = 95.1%, p<0.001; very low certainty of evidence). The results of the meta-analysis were stable in sensitivity analysis. In meta-regression, there were no significant associations between the SMD of total bilirubin and several clinical and demographic characteristics, including age, male to female ratio, number of participants, liver enzymes and erythrocyte sedimentation rate. In subgroup analysis, the SMD of total bilirubin was significant across a range of RDs, including rheumatoid arthritis, systemic lupus erythematosus, primary Sjögren syndrome, and myositis. Therefore, the results of our systematic review and meta-analysis suggests that the reductions in bilirubin concentrations observed in patients with RDs reflect a state of impaired antioxidant and anti-inflammatory defence due to bilirubin consumption and highlight the promising role of this endogenous product as a biomarker of RDs.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023500649.

Adipokines as Regulators of Autophagy in Obesity-Linked Cancer

Excess body weight and obesity have become significant risk factors for cancer development. During obesity, adipose tissue alters its biological function, deregulating the secretion of bioactive factors such as hormones, cytokines, and adipokines that promote an inflammatory microenvironment conducive to carcinogenesis and tumor progression. Adipokines regulate tumor processes such as apoptosis, proliferation, migration, angiogenesis, and invasion. Additionally, it has been found that they can modulate autophagy, a process implicated in tumor suppression in healthy tissue and cancer progression in established tumors. Since the tumor-promoting role of autophagy has been well described, the process has been suggested as a therapeutic target in cancer. However, the effects of targeting autophagy might depend on the tumor type and microenvironmental conditions, where circulating adipokines could influence the role of autophagy in cancer. Here, we review recent evidence related to the role of adipokines in cancer cell autophagy in an effort to understand the tumor response in the context of obesity under the assumption of an autophagy-targeting treatment.

Serum Bilirubin Levels in Overweight and Obese Individuals: The Importance of Anti-Inflammatory and Antioxidant Responses

Obesity is a chronic condition involving low-grade inflammation and increased oxidative stress; thus, obese and overweight people have lower values of serum bilirubin. Essentially, bilirubin is a potent endogenous antioxidant molecule with anti-inflammatory, immunomodulatory, antithrombotic, and endocrine properties. This review paper presents the interplay between obesity-related pathological processes and bilirubin, with a focus on adipose tissue and adipokines. We discuss potential strategies to mildly increase serum bilirubin levels in obese patients as an adjunctive therapeutic approach.

Association Between Gamma-Glutamyl Transferase, Total Bilirubin and Systemic Lupus Erythematosus in Chinese Women

Background

Systemic lupus erythematosus (SLE) affects many organs and systems of the human organism, at present, its specific pathogenesis is not completely clear, but inflammation is considered to be an important factor involved in the pathogenesis and progression of SLE. Gamma-glutamyl transpeptidase (GGT) and total bilirubin (TBIL) have different effects on inflammation: GGT has pro-inflammatory effects, on the contrary, TBIL has anti-inflammatory effects. Study has found that GGT and TBIL play opposite roles in metabolic diseases. However, the roles of them in SLE are unknown. Meanwhile, the relationship between GGT and SLE also remains unexplored.

Method

We recruited 341 SLE patients and 332 healthy individuals in Liaocheng People’s Hospital from August 2018 to May 2019. We diagnosed SLE using 2019 revised American College of Rheumatology (ACR) SLE criteria, and modeled the study outcomes using logistic regression to explore the respective relationship between GGT, TBIL and SLE. We also analyzed the interaction of GGT and TBIL in the progression of SLE.

Results

We found that the levels of CRP, IL-6 and TNF-α in the aggravated group were significantly higher than those in the unaggravated group, the levels of C3 and C4 in the aggravated group were significantly lower than those in the unaggravated group. According to Spearman correlation analysis, GGT is proportional to CRP (r_s=0.417) and IL-6 (r_s=0.412), inversely proportional to C3 (r_s=-0.177) and C4 (r_s=0.-132). TBIL was inversely proportional to CRP (r_s=-0.328) and TNF(r_s=-0.360), and positively proportional to C3 (r_s=0.174) and C4 (r_s=0.172). In the fully adjusted model, compared to the lowest quartile, the highest quartile of GGT exhibited a positive association with the risk of SLE aggravation (OR=2.99, 95% CI: 1.42–6.31, P<0.001). At the same time, compared to the highest quartile, the quartile lowest of TBIL exhibited a positive association with the risk of SLE aggravation (OR=2.66, 95% CI: 1.27–5.59, P<0.001) in the fully adjusted model. Through interaction analysis, we found that women with high GGT levels had an increased risk of SLE aggravation when they had a low level of TBIL (OR=3.68, 95% CI: 1.51–9.01, for women with Q1 TBIL and Q4 GGT compared to women with Q2-Q4 TBIL and Q1-Q3 GGT, P for interaction <0.001), the combined AUC value (AUC_COMBINED=0.711) of high GGT level and TBIL were higher than their respective values (AUC_GGT=0.612, AUC_TBIL=0.614).

Conclusion

We found that the effects of GGT and TBIL in the progression of SLE are opposite. High GGT level might be a risk factor for SLE aggravation, as GGT levels increased, so did the risk of SLE aggravation. At the same time, we found that low TBIL level might be a risk factor for SLE aggravation. Moreover, high GGT level and low TBIL level had a subadditive effect on the increased risk of SLE aggravation.

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.

Bilirubin Nanoparticles Reduce Diet-Induced Hepatic Steatosis, Improve Fat Utilization, and Increase Plasma β-Hydroxybutyrate

The inverse relationship of plasma bilirubin levels with liver fat accumulation has prompted the possibility of bilirubin as a therapeutic for non-alcoholic fatty liver disease. Here, we used diet-induced obese mice with non-alcoholic fatty liver disease treated with pegylated bilirubin (bilirubin nanoparticles) or vehicle control to determine the impact on hepatic lipid accumulation. The bilirubin nanoparticles significantly reduced hepatic fat, triglyceride accumulation, de novo lipogenesis, and serum levels of liver dysfunction marker aspartate transaminase and ApoB100 containing very-low-density lipoprotein. The bilirubin nanoparticles improved liver function and activated the hepatic β-oxidation pathway by increasing PPARα and acyl-coenzyme A oxidase 1. The bilirubin nanoparticles also significantly elevated plasma levels of the ketone β-hydroxybutyrate and lowered liver fat accumulation. This study demonstrates that bilirubin nanoparticles induce hepatic fat utilization, raise plasma ketones, and reduce hepatic steatosis, opening new therapeutic avenues for NAFLD.