Serum B-cell Lymphoma-2 (Bcl-2) Levels in Patients with Bipolar Mania: A Cross-Sectional Study Exploring the Neuroinflammatory Hypothesis of Bipolar Disorder

Introduction: The B-cell lymphoma-2 (Bcl-2) protein plays an essential role in the regulation of cell survival. Bcl-2 has neuroprotective and anti-apoptotic functions that have been linked to the neuroinflammatory hypothesis of bipolar disorder (BD). Mood stabilizer treatment for BD has been found to upregulate the Bcl-2 gene, suggesting a mechanism for their therapeutic effects. Certain single-nucleotide polymorphisms in Bcl-2 mRNA have also been linked to BD, highlighting the importance of Bcl-2 abnormalities in BD neurobiology. Aim: The aim of the current study was to determine if serum Bcl-2 levels could be used as a biomarker for BD. Methodology: In this cross-sectional study, serum Bcl-2 was measured in patients with bipolar mania, unaffected first-degree relatives (FDR), and healthy controls (HCs) (21 in each group). Furthermore, a correlation between serum Bcl-2 levels and Young Mania Rating Scale (YMRS) scores was performed to assess potential associations with manic symptoms. Results: Serum Bcl-2 concentrations were elevated in individuals with BD and their FDR when compared with HCs; however, these differences did not reach statistical significance. Additionally, serum Bcl-2 levels did not show significant correlations with age, number of mood episodes, or YMRS scores. Conclusion: Although the difference in serum Bcl-2 levels was not statistically significant among the groups, higher serum Bcl-2 levels were observed in patients and their unaffected FDRs compared to HCs. Further research using a longitudinal approach that considers the various phases of mania is needed to explore this possibility more comprehensively.