Protective Role of Bilirubin Against Increase in hsCRP in Different Stages of Hypothyroidism

Serum Bilirubin and Markers of Oxidative Stress and Inflammation in a Healthy Population and in Patients with Various Forms of Atherosclerosis

Oxidative stress and inflammation contribute significantly to atherogenesis. We and others have demonstrated that mildly elevated serum bilirubin levels protect against coronary and peripheral atherosclerosis, most likely due to the antioxidant and anti-inflammatory activities of bilirubin. The aim of the present study was to assess serum bilirubin and the markers of oxidative stress and inflammation in both healthy subjects and patients with various forms of atherosclerosis. The study was performed in patients with premature myocardial infarction (n = 129), chronic ischemic heart disease (n = 43), peripheral artery disease (PAD, n = 69), and healthy subjects (n = 225). In all subjects, standard serum biochemistry, UGT1A1 genotypes, total antioxidant status (TAS), and concentrations of various pro- and anti-inflammatory chemokines were determined. Compared to controls, all atherosclerotic groups had significantly lower serum bilirubin and TAS, while having much higher serum high-sensitivity C-reactive protein (hsCRP) and most of the analyzed proinflammatory cytokines (p < 0.05 for all comparisons). Surprisingly, the highest inflammation, and the lowest antioxidant status, together with the lowest serum bilirubin, was observed in PAD patients, and not in premature atherosclerosis. In conclusion, elevated serum bilirubin is positively correlated with TAS, and negatively related to inflammatory markers. Compared to healthy subjects, patients with atherosclerosis have a much higher degree of oxidative stress and inflammation.

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.