The Shared Susceptibility Genes And Mechanism Of Schizophrenia And Type2Diabetes Mellitus In Han Chinese Population

Schizophrenia(SCZ) and type2diabetes mellitus (T2DM), both of which arepolygenetic heterogeneity disease, pose great public health challenges.40%of thepatients with schizophrenia have family histories of T2DM, and, not coincidently, theincidence rate of T2DM is obviously higher in schizophrenia patients than normalpopulations, suggesting the existence of shared susceptibility genes. Nowschizophrenia and T2DM through genome-wide association, transcriptomic andproteomic expression studies, having acquired many positive results, butschizophrenia and T2DM are both complex diseases, whose results produce poorreplication.ObjectiveThis present study chooses schizophrenia patients, T2DM patients, T2DM-combined schizophrenia patients and normal controls in Han Chinese populationas the objects of the study, and will take the susceptibility genes of T2DM identified by GWAS as the candidate genes. The association of the candidate genes with schizophrenia and T2DM will be explored respectively at gDNA andmRNA levels, in order to identify shared genes and possible mechanisms involved.MethodsA total of837indivduals with schizophrenia (SCZ group),166T2DM-combinedschizophrenia patients (SCZ+T2DM group),229T2DM patients (T2DM group)comparing with a control group with1109people from healthy control. All objectsare Han Chinese population from northern parts; patients with schizophrenia havebeen diagnosed according to ICD-10and Diabetes diagnosis in accordance with thediagnostic criteria of WHO1999.Peripheral blood samples are taken after getting the informed consent.of chosen patients. Genomic DNA was isolated from the whole blood5ml using a DNA extraction kit. Taking the susceptibility genes of T2DM identified byGWAS as the candidate genes，including IGF2BP2(rs4402960), SLC30A8(rs13266634), FTO (rs8050136), CDKN2A/B (rs10811661), CDKAL1(rs7754840), HHEX (rs1111875), KCNJ11(rs5219) and MTNR1B (rs1387153). Genotypeidentification database was established with PCR-RFLP and ABI PRISM7900HT sequence detection system.In addition, adopting Real-time PCR to test the mRNA expression levels ofIGF2BP2and its alternative splicing isoform a and isoform b. Relative levels of themwere calculated using2-ΔΔCt. GAPDH was used as an internal control. The data arecollected from three repeat experiments of each sample.The Hardy-Weinberg equilibrium (HWE) is that mating in the population mustbe random for genotypic distributions, the associations between all candidate SNPsand schizophrenia, the associations between all candidate SNPs and T2DM weretested using the online genetic SHEsis. The associations between IGF2BP2and itsalternative splicing isoform a/b with schizophrenia and control were performed withSPSS17.0.Results1Hardy-Weinberg equilibrium testThe goodness-of-fit χ2test showed that the genotypic distributions of IGF2BP2(rs4402960) and SLC30A8(rs13266634) did not deviate from Hardy-Weinbergequilibrium in both patient group and control group (P＞0.05). FTO (rs8050136),CDKN2A/B (rs10811661), CDKAL1(rs7754840), HHEX (rs1111875), KCNJ11(rs5219) and MTNR1B (rs1387153) were almost in HWE in healthy controls(P>0.05), SCZ (P>0.05), SCZ+T2DM (P>0.05) and T2DM(P>0.05). Thus, thissample pool was suitable for analysis. Except that the genotypic distributions of these1SNPs (rs1387153) were not in HWE in healthy controls (P<0.05). Then thegenotypic distributions of rs5219in SCZ and rs7754840in T2DM were not in HWE(both, P<0.05), and reveal that these SNPs could be the schizophrenic susceptibleSNPs or could be in close linkage to the schizophrenic susceptible SNPs.2Result of IGF2BP2(rs4402960) and SLC30A8(rs13266634) aboutassociation research of type2diabetes mellitus and schizophrenia in ChineseHan population Rs4402960presents in the IGF2BP2gene and rs13266634presents in theSLC30A8, was detected by adopting PCR-based restriction fragment lengthpolymorphism (PCR-RFLP) analysis among790Han Chinese patients withschizophrenia and1083ethnicity-matched healthy controls. The χ2test did not showallelic association and genotypic association for rs13266634(P＞0.05), the SLC30A8locus may not be associated with schizophrenia.Significant differnences in the rs4402960genotype and allele distributionsbetween the patient and control group (χ2=7.316,P=0.026; χ2=7.056,P=0.008,OR=1.221). A significant association between the rs4402960polymorphism andschizophrenia is discoverd from men patients, both at the genotypic and at the allele levels (χ2=8.39，P=0.015; χ2=8.08.P=0.004,OR=1.324),The results showed that the IGF2BP2in patients with T2DM was associated with the occurrenceof schizophrenia, possibly suggesting that it is responsible for both T2DM and schizophrenia.The result showed a trend of higher levels of IGF2BP2and isoform a,but therewas not a between-group significant difference. Yet, isoform b is obviously higher forpatients with schizophrenia than that for healthy controls(1.136±0.324vs0.885±0.227, t=3.54, P=0.0008or Z=-3.532.P=0.0004), suggesting the key role ofIGF2BP2in susceptibility to schizophrenia.Then isoform b is obviously higher forpatients with schizophrenia than that for levels of IGF2BP2(isoform a+isoform b) inhealthy controls(0.916±0.180，t=2.981，P=0.004或Z=-2.779，P=0.005).3Association Research of FTO、CDKN2A/B、CDKAL1、HHEX、KCNJ11and MTNR1B genes of type2diabetes mellitus and schizophrenia in HanChinese population(1) The analysis of SNP and SCZThe FTO（rs8050136）,CDKN2A/B（rs10811661）,CDKAL1（rs7754840）,HHEX（rs1111875）,KCNJ11（rs5219）and MTNR1B（rs1387153） were not associatedwith schizophrenia in Han Chinese population(all, P＞0.05). ThereCDKN2A/B(rs10811661）、CDKAL1(rs7754840)、HHEX(rs1111875) were associatedwith T2DM and schizophrenia-combined T2DM in Han Chinese population(rs10811661:χ2=10.09，P=0.002；OR=0.723; rs7754840: χ2=9.372，P=0.002， OR=1.364;rs1111875:χ2=4.853，P=0.028；OR=1.273).(2) The analysis of SNP and T2DMSignificant differnences in the CDKN2A/B (rs10811661) genotype and alleledistributions between the T2DM+patients and T2DM-patients (χ2=10.821,P=0.004;χ2=10.821,P=0.001,OR=0.744). Also Significant differnences in theCDKAL1(rs7754840)and HHEX(rs1111875) genotype and allele distributionsbetween the T2DM+patients and T2DM-patients(χ2=9.704,P=0.008;χ2=8.534,P=0.003,OR=1.296and χ2=11.769, P=0.003;χ2=12.018,P=0.001,OR=1.395).However, the FTO (rs8050136) and KCNJ11(rs5219) were not associated with T2DM(all, P＞0.05).Conclusion:1. The IGF2BP2gene in patients with T2DM was associated with the occurrenceof schizophrenia, which is possibly caused by both T2DM and schizophrenia.2. The IGF2BP2gene’s isoform b expression levels were significantly higher forpatients with schizophrenia than those for healthy controls, suggesting the key role ofIGF2BP2in susceptibility to schizophrenia.3. The SLC30A8locus may not be associated with schizophrenia.4. The CDKN2A/B (rs10811661), CDKAL1(rs7754840) and HHEX(rs1111875)were associated with schizophrenia-combined T2DM. Furthermore, they were notassociated with schizophrenia in Han Chinese population.5. The CDKN2A/B (rs10811661), CDKAL1(rs7754840) and HHEX(rs1111875)were associated with T2DM.