Understanding the health promoting effects of mild hyperbilirubinemia: The effect of unconjugated bilirubin on lipid metabolism and anthropometric data

Autoren:Seyed Khoei, Nazlisadat; Wallner, Marlies; Mölzer, Christine; Wagner, Karl-Heinz
Abstrakt:Background Unconjugated Bilirubin (UCB), the end product of heme catabolism, is known as a powerful antioxidant. A mild elevation of circulating UCB, known as Gilbert`s Syndrome (GS), is a relatively common condition in the Caucasian population affecting 5-10% (depending on ethnicity and gender) of the adult population. Interestingly, individuals with endogenously elevated UCB are protected from chronic diseases, particularly cardiovascular disease (CVD), cancer and type 2 diabetes mellitus. Therefore, recent data on GS indicate that humans are protected from atherosclerosis by the anti-oxidative effect of UCB, however, this explains only part of the story. Objective The main purpose of this study is to compare results of lipid profile and anthropometric data in GS subjects with respective age- and gender matched controls, to discover if higher serum UCB is linked to improved lipid metabolism and anthropometric variables. Methods A total number of 248 subjects (124 age and gender matched-pairs) were included in this analysis. Group allocation in to GS or control group was based on serum UCB concentrations (</≥17.1 μM). All statistical tests were carried out using SPSS (IBM statistics, Version 23.0). For comparing differences between two independent groups, an independent sample T-Test (parametric data) or Mann-Whitney U-Test (non-parametric data) was used. To test for correlations, Pearson (parametric data) or Spearman (non-parametric data) was used. P-value <0.05 was considered significant and data are expressed as mean ± SD. Results The results show that serum UCB level was significantly higher in the Gilbert`s syndrome group compared to controls (30.66±11.45 vs. 8.75±3.63, p<0.001). However, the BMI, was significantly lower in subjects with GS (23.05±3.24 vs. 25.13±4.35, p<0.05). Total Cholesterol (TC), Triglycerides (TG), LDL-C, TC/HDL ratio and LDL/HDL ratio were significantly reduced in GS group compared to controls (all p<0.05). Furthermore, this analysis indicated that GS female-subjects had a significantly lower fat mass and abdominal circumference compared to their controls (p<0.05). Further analyses were conducted by dividing this dataset into two age subgroups (</≥35 years). There was no significant difference in lipid profile and anthropometric data (except BMI) between both groups in younger subjects (<35 years). However, older GS subjects (≥35 years), had significantly lower anthropometric variables (BMI, waist circumferences, hip circumference, WHR, abdominal circumference, fat mass) and also improved lipid profiles (reduced TC, TG, LDL-C, TC/HDL ratio and LDL/HDL ratio and higher HDL-C) when compared to their controls (all p<0.05). UCB was negatively correlated with BMI (r = −0.268, p ≤ 0.001) and fat mass (r = −0.22, p≤ 0.001) and all lipid variables (p < 0.05). Conclusion It was the main purpose of this paper to draw attention to the associations between elevated unconjugated bilirubin and the lipid profile as well as anthropometric data. Based on the data shown, it can be concluded that individuals with Gilbert`s syndrome show lower BMI and an improved lipid profile, especially at higher age.