S17. GLOBAL DNA METHYLATION IN CURRENT AND EMERGENT SUICIDAL IDEATION: ANALYSIS IN SCHIZOPHRENIA

BACKGROUND: Several lines of evidence have shown that epigenetic mechanisms influence suicidal behavior, but do not indicate specific susceptibility variants. In a recent study, analysis of global methylation levels found that psychiatric patients with a history of suicide attempt (SA) had significantly higher levels of 5-methyl cytosine (5mC), suggesting that patients with a history of SA have global hypermethylation of their genome. However, there is no study investigated the link between global DNA methylation and suicidal ideation (SI) in schizophrenia. In this study, we analyzed global DNA methylation in suicide ideators and non-ideators in a sample of schizophrenia patients to find if global DNA methylation can predict SI in schizophrenia. METHODS: There are several methods of detecting total 5-methylcytosine content in the genome. We used Cell Biolabs’ Global DNA Methylation ELISA Kit, which is a competitive enzyme immunoassay developed for rapid detection and quantitation of 5’-methyl-2’-deoxycytidine (5MedCyd) in DNA extracted from white blood cells (WBC). We digested the genomic DNA, extracted from WBC, into single nucleotides and the quantity of 5MedCyd was determined by comparing its absorbance with that of a known 5MedCyd standard curve. We measured global DNA methylation in predicting current and emergent suicidal ideation. RESULTS: In the analysis of current SI in our schizophrenia patients, the average quantity of 5MedCyd was 7.56 ± 0.77 ng 5mC/µg DNA for suicide ideators and 8.72 ± 1.97 ng 5mC/µg DNA for non-ideators. There was no evidence of a significant difference between these two groups in our analysis (p=0.176). Also, we did not find a significant difference between global DNA methylation change (global DNA methylation change between baseline and three-month follow-up visits) in patients with and without emergent SI (p=0.121). DISCUSSION: This preliminary analysis did not find a predictive role of global DNA methylation in SI in patients with schizophrenia. The small sample size, used in this pilot study, is probably responsible for the fact that the results found here did not support those of previous research, showing that methylation levels are higher in patients with a history of a suicide attempt.