Prolidase activity and its diagnostic performance in bipolar disorder

Objective: Proline has an important role in the brain. Prolidase, a proline splitting enzyme, which is also involved in oxidative stress is not investigated in bipolar disorder (BD). Methods: 66 BD type I patients and 66 healthy controls were enrolled. Serum prolidase activity was measured in both groups via venous sampling. We have compared patients and controls as well as 3 subgroups of patients (24 euthymic, 22 manic, and 20 depressive patients). Results: Prolidase activity was significantly higher in patients (p < 0.001, t = 14.517). There wasn't any significant difference among euthymic, manic and depressives (p = 0.305, f = 1.211). Positive predictive value was 98.5% and negative predictive value was 92.4% above the cutoff point 502.9375 U/L of prolidase activity. Conclusion: Prolidase activity is impaired in BD, which may be associated with oxidative stress. Prolidase activity may be a trait marker for diagnosing bipolar disorder. (C) 2010 Elsevier B.V. All rights reserved.