The Type 2 Diabetes Mellitus Susceptibility GeneIGF2BP2Is Associated With Schizophrenia in a Han Chinese Population

Patients with schizophrenia have an increased prevalence of type 2 diabetes mellitus, and type 2 diabetes mellitus has shown an association with the rs4402960 gene polymorphism in the insulin-like growth factor II messenger RNA (mRNA)-binding protein 2 gene (IGF2BP2). We tested this polymorphism and mRNA expression levels of IGF2BP2 for an association in Han Chinese patients with schizophrenia compared to healthy controls.The rs4402960 polymorphism was genotyped in 790 chronic schizophrenic patients (diagnosed according to DSM-IV) and 1,083 unrelated healthy controls in a case-control design. The IGF2BP2 gene expression levels were assayed in 34 patients with chronic schizophrenia and 30 healthy controls by using real-time polymerase chain reaction (PCR). The study was conducted between 2005 and 2007.We found significant differences in the rs4402960 genotype (χ(2)2 = 7.316, P = .026) and allele (χ(2)1 = 7.056, P = .008) distributions between the patient and control groups. The rs4402960 T allelic frequency was significantly higher in male schizophrenic patients than male controls (28.9% vs 23.5%; P = .004) but not in female patients compared to female controls (27.1% vs 25.5%; P = .498). When real-time PCR was used, the IGF2BP2 gene's isoform B expression levels were significantly greater in schizophrenia than controls (P = .0008).These results suggest that the IGF2BP2 gene may play a role in susceptibility to schizophrenia, supporting the hypothesis that the co-occurrence of type 2 diabetes mellitus and schizophrenia may be explained by shared genetic risk variants. However, this finding remains preliminary since this association has yet to be replicated.