Serum bilirubin as a predictor of lipid oxidation in post-covid-19 patients and its association with disease severity
Jumana Saleh, Maha Al-Riyami, Zubaida Saif Al-Shukailiyah
كلية الطب والعلوم الصحية-جامعة السلطان قابوس · عمان
COVID-19, caused by SARS-CoV-2, has been associated with significant inflammatory, metabolic, and oxidative stress disturbances that may persist beyond the acute phase and contribute to cardiovascular complications. An imbalance between oxidant and antioxidant systems is thought to play a key role in disease progression. Although bilirubin is recognized for its antioxidant properties, its role in post-COVID-19 metabolic manifestations remains inadequately investigated. This study aimed to assess the association between serum bilirubin levels and oxidative stress markers in post-COVID-19 patients stratified by disease severity. In vitro antioxidant effects of bilirubin were evaluated using copper-induced oxidation assays on human serum. In vivo, serum bilirubin concentrations were measured alongside key redox parameters, including reduced glutathione, glutathione peroxidase, malondialdehyde (MDA), oxidized lipoproteins, and antioxidant capacity as indicated by the lag phase in copper-induced oxidation curves. Results revealed a significant inverse correlation between serum bilirubin levels and disease severity (p = 0.039). Bilirubin concentrations were significantly lower in severe and mild/moderate cases (7.08 ± 0.89 µmol/L and 8.41 ± 0.6 µmol/L, respectively) compared to controls (10.3 ± 0.86 µmol/L). Lower bilirubin levels were associated with elevated MDA levels (R = 0.319, p = 0.003), indicating increased lipid peroxidation and oxidative stress. No significant correlations were observed between bilirubin and glutathione or glutathione peroxidase activities. Oxidized low-density lipoprotein (LDL) emerged as the strongest predictor of MDA levels, explaining approximately 7% of its variance (R² = 0.07, p = 0.01), suggesting a specific link between bilirubin and LDL lipid peroxidation. These findings suggest that bilirubin’s antioxidant capacity may play a vital role in attenuating oxidative stress and lipid peroxidation in post-COVID-19 patients. This study underscores bilirubin’s potential as a therapeutic target for managing oxidative stress-related complications in COVID-19. Further research is warranted to explore the therapeutic potential of bilirubin and its analogs in reducing disease severity and improving clinical outcomes in this patient population.