A 50-bp Ins/Del polymorphism at the promoter region of the superoxide dismutase-1 and bipolar disorder type 1

Bipolar disorder type 1 (BPD) is a chronic psychiatric illness and is associated with oxidative stress. Superoxide dismutase-1 (SOD1; OMIM: 147450) metabolizes highly reactive and more dangerous superoxide radicals into less reactive molecules. A functional 50-bp insertion/deletion (Ins/Del) polymorphism in the promoter region of the gene has been reported. The primary aim of the current case-control study was to explore whether the SOD1 Ins/Del polymorphism associated with the risk of BPD. A secondary aim was to investigate the association between the study polymorphism and age of onset of BPD. The present case-control study was performed in Shiraz (southern Iran) on 228 BPD and 224 healthy blood donor controls. The genotypes of the SOD1 Ins/Del polymorphism were determined by polymerase chain reaction. There was no significant association between the genotypes of Ins/Del polymorphism and the risk of BPD. Using Cox proportional hazards regression model, after adjustment for family history of BPD, revealed a significant association between the SOD1 Ins/Del polymorphism and age of onset. The age of onset was significantly lower for the Del/Del genotype than the 'Ins/Ins + Ins/Del' genotypes (hazard ratio = 2.33, 95%CI: 1.08-5.02, p = .030). Our present findings revealed that although the SOD1 Ins/Del polymorphism was not associated with the risk of BPD, it was significantly associated with age of onset of BPD.