Oxidative Stress and Related Biomarkers in Gilbert's Syndrome: A Secondary Analysis of Two Case-Control Studies

Neuroprotective Roles of the Biliverdin Reductase-A/Bilirubin Axis in the Brain

Biliverdin reductase-A (BVRA) is a multi-functional enzyme with a multitude of important roles in physiologic redox homeostasis. Classically, BVRA is well known for converting the heme metabolite biliverdin to bilirubin, which is a potent antioxidant in both the periphery and the brain. However, BVRA additionally participates in many neuroprotective signaling cascades in the brain that preserve cognition. Here, we review the neuroprotective roles of BVRA and bilirubin in the brain, which together constitute a BVRA/bilirubin axis that influences healthy aging and cognitive function.

Age-related influence on DNA damage, proteomic inflammatory markers and oxidative stress in hospitalized COVID-19 patients compared to healthy controls

COVID-19 infections are accompanied by adverse changes in inflammatory pathways that are also partly influenced by increased oxidative stress and might result in elevated DNA damage. The aim of this case-control study was to examine whether COVID-19 patients show differences in oxidative stress-related markers, unconjugated bilirubin (UCB), an inflammation panel and DNA damage compared to healthy, age-and sex-matched controls. The Comet assay with and without the treatment of formamidopyrimidine DNA glycosylase (FPG) and H2O2 challenge was used to detect DNA damage in whole blood. qPCR was applied for gene expression, UCB was analyzed via HPLC, targeted proteomics were applied using Olink® inflammation panel and various oxidative stress as well as clinical biochemistry markers were analyzed in plasma. Hospitalized COVID-19 patients (n = 48) demonstrated higher serum levels of 55 inflammatory proteins (p < 0.001), including hs-C-reactive protein levels (p < 0.05), compared to healthy controls (n = 48). Interestingly, significantly increased age-related DNA damage (%-DNA in tail) after formamidopyrimidine DNA glycosylase (FPG) treatment was measured in younger (n = 24, average age 55.7 years; p < 0.05) but not in older COVID-19 patients (n = 24, average age 83.5 years; p > 0.05). Although various oxidative stress markers were not altered (e.g., FRAP, malondialdehyde, p > 0.05), a significant increased ratio of oxidized to reduced glutathione was detected in COVID-19 patients compared to healthy controls (p < 0.05). UCB levels were significantly lower in individuals with COVID-19, especially in younger COVID-19 patients (p < 0.05). These results suggest that COVID-19 infections exert effects on DNA damage related to age in hospitalized COVID-19 patients that might be driven by changes in inflammatory pathways but are not altered by oxidative stress parameters.

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

Bilirubin and Redox Stress in Age-Related Brain Diseases

Cellular redox status has a crucial role in brain physiology, as well as in pathologic conditions. Physiologic senescence, by dysregulating cellular redox homeostasis and decreasing antioxidant defenses, enhances the central nervous system's susceptibility to diseases. The reduction of free radical accumulation through lifestyle changes, and the supplementation of antioxidants as a prophylactic and therapeutic approach to increase brain health, are strongly suggested. Bilirubin is a powerful endogenous antioxidant, with more and more recognized roles as a biomarker of disease resistance, a predictor of all-cause mortality, and a molecule that may promote health in adults. The alteration of the expression and activity of the enzymes involved in bilirubin production, as well as an altered blood bilirubin level, are often reported in neurologic conditions and neurodegenerative diseases (together denoted NCDs) in aging. These changes may predict or contribute both positively and negatively to the diseases. Understanding the role of bilirubin in the onset and progression of NCDs will be functional to consider the benefits vs. the drawbacks and to hypothesize the best strategies for its manipulation for therapeutic purposes.

Association of Low Serum Bilirubin Concentrations and Promoter Variations in the UGT1A1 and HMOX1 Genes with Type 2 Diabetes Mellitus in the Czech Population

Bilirubin has potent biological beneficial effects, protecting against atherosclerosis, obesity, and metabolic syndrome. The aim of this study was to assess serum bilirubin concentrations and (TA)n and (GT)n microsatellite variations in the promoter regions of the UGT1A1 and HMOX1 genes, respectively, in patients with type 2 diabetes mellitus (T2DM). The study was carried out in 220 patients with T2DM and 231 healthy control subjects, in whom standard biochemical tests were performed. The (TA)n and (GT)n dinucleotide variations were determined by means of fragment (size-based) analysis using an automated capillary DNA sequencer. Compared to controls, both male and female patients with T2DM had lower serum bilirubin concentrations (9.9 vs. 12.9 μmol/L, and 9.0 vs. 10.6 μmol/L, in men and women, respectively, p < 0.001). Phenotypic Gilbert syndrome was much less prevalent in T2DM patients, as was the frequency of the (TA)7/7UGT1A1 genotype in male T2DM patients. (GT)nHMOX1 genetic variations did not differ between diabetic patients and controls. Our results demonstrate that the manifestation of T2DM is associated with lower serum bilirubin concentrations. Consumption of bilirubin due to increased oxidative stress associated with T2DM seems to be the main explanation, although (TA)n repeat variations in UGT1A1 partially contribute to this phenomenon.

Serum bilirubin levels are negatively associated with atherogenic lipids in Saudi subjects with type 2 diabetes: A pilot study

<b>Background: </b>Recent research has demonstrated the possible relevance of bilirubin in metabolic and cardiovascular disorders. Lipid abnormalities are a major problem that is related with an increased risk of cardiovascular disease in diabetics. This study examined the relationship between serum bilirubin and direct bilirubin concentrations and atherogenic lipids in patients with type 2 diabetes (T2DM).<br /> <b>Methods</b>: This cross-sectional included 67 patients with type 2 diabetes and 39 matched healthy control. The lipid profile, including total cholesterol, HDL-C, and TG levels, fasting blood glucose, total bilirubin, direct bilirubin, ALT, AST, and ALP were measured using a dimension EXL clinical chemistry analyzer (Siemens Healthcare Diagnostics). Cholesterol in VLDL, LDL, and sdLDL were calculated from standard lipid assay results by the equations of Sampson et al.<br /> <b>Results</b>: Serum bilirubin was lower in non T2DM subjects nearly significant (p=0.0.51) whereas direct bilirubin concentrations were lower in T2DM (p=0.008). ALT, AST, and ALP levels were higher in T2DM groups. The mean values of LDL-C, sdLDL-C, non HDL-C and VLDL-C were significantly increased in T2DM group and lower HDL-C. An inverse relationship could be observed with increase in serum total bilirubin and serum levels of LDL-C (r²=0.139, p&lt;0.005), sdLDL-C (r²=0.137, p&lt;0.005), VLDL-C (r²=0.074, p&lt;0.044), and non HDL-C (r²=0.166, p&lt;0.002) in T2DM group. The same inverse relationship was observed with serum direct bilirubin and serum levels of LDL-C (r²=0.133, p&lt;0.006), sdLDL-C (r²=0.172, p&lt;0.001), VLDL-C (r²=0.118, p&lt;0.01), and non HDL-C (r²=0.182, p&lt;0.001) in T2DM group.<br /> <b>Conclusions</b>: A significant negative association was found between serum bilirubin levels and direct serum bilirubin with atherogenic lipids, suggesting that serum bilirubin may protect T2DM patients from development of cardiovascular disease. These findings indicate the need for additional research in a large cohort.

Bilirubin 2022: The Past, the Present and the Future

The present Special Issue (SI) addresses the double-faced Janus behavior of bilirubin [...]