Angiotensin-converting enzyme polymorphism in schizophrenia, bipolar disorders, and their first-degree relatives

Family, twin and adoption studies have provided major evidence for the role of genetics in numerous psychiatric disorders including schizophrenia (SZ) and bipolar disorders (BDs). As SZ and BD have some susceptibility genes in common and since unaffected first-degree relatives of these patients carry a high likelihood of these susceptibility genes, we aimed to elucidate the role of angiotensin-converting enzyme (ACE) genetic variants in patients with SZ, BD and their first-degree relatives.

The study sample comprised 239 patients with SZ, 184 patients with BD, 284 unaffected first-degree biological relatives of patients with SZ and 301 unaffected first-degree biological relatives of patients with BD and 210 healthy controls. The ACE genotypes were determined by polymerase chain reaction.

ACE insertion/deletion polymorphism was associated with SZ and BD. DD genotype and D allele distributions in bipolar patients and their first-degree relatives were significantly higher than those of SZ patients, their relatives, and controls. In contrast, II genotype and I allele were reduced in both the patient groups and their relatives as compared with controls.

In this study, the D allele might be responsible for clustering of psychotic symptoms and results in the psychotic manifestations of BD, whereas I allele seems to be protective against development of SZ and BD. SZ and BD characterized by similar or different gene variant in ACE could be a useful marker for these psychiatric disorders, if this polymorphism is replicated in the future studies.