Study Of SST And GHRH With Hypertension And Stroke,and Gene-gene Interaction Analysis In IGF1 Signaling Pathway

Part 1 Study of SST and GHRH with Hypertension and StrokeObjective: Hypertension is the leading risk factor for cardiovascular diseases and contributes to an increasing burden worldwide.This study aimed to explore the relationship between somatostatin(SST)and growth hormone releasing hormone(GHRH)polymorphisms with hypertension and stroke in a Chinese Han population.Methods: A population-based epidemiological survey was carried out in Yixing City,Jiangsu Province,using the method of cluster epidemiological sampling.A total of 4222 participations including 2012 hypertensive cases and 2210 healthy controls matched by age(5 years)and sex were recruited in a case-control study.After the baseline survey,the participations were prospectively follow-uped for a median of 5.01 years.Haploview software(version 4.2)was used to screen the tagging single-nucleotide polymorphisms(tag SNPs)with r2>0.8 and minimum allele frequency > 0.05.Finally,GHRH rs6032470,SST rs3755792 and rs7624906 were genotyped.A binary logistical regression model was used to compare the genetic association between genes variation and hypertension in case-control study.Cox regression model was used to analyze the association between gene variation and hypertension as well as stroke incidence in follow-up study.Results: There was no significant association between the three SNPs and hypertension in the case-control study.No association between genes and hypertension was found in further subgroup analyses based on age,sex,smoking and drinking.There were 613 new cases of hypertension and 171 new cases of ischemic stroke in the follow-up study,and the incidence rates were 65.68 / 1000 person-years and 8.05 / 1000 person-years,respectively.Cox regression analyses showed no association between SST and GHRH gene variation with hypertension as well as ischemic stroke.In the drinking population,the SST rs3755792(G>A)variation was associated with decreased hypertension incidence,the incidence densities of GG,GA,AA genotype carriers were 8.49,5.76 and 3.97(/ 100 person-years),respectively,and the HR(95%CI)was 0.580(0.385-0.874),P value was 0.09 and after bonferroni correction,the correlation was still statistically significant with P=0.027.In the smoking group,the variants at SST presented significant association with incident hypertension,the HR of rs3755792(GA+AA vs.GG)was 0.634(P=0.037),and the HR of rs7624906(CT+TT vs.CC)was 1.803(P=0.005,Boferroni corrected P=0.015).Moreover,in smoking population,GHRH rs6032470 had a statistically association with incident ischemic stroke,whereas the association were not significant after Boferroni correction.Conclusions: Our findings suggested that SST harbors genetic susceptible loci with incident hypertension,smoking and drinking might modify the genetic effect.In smoking population,the variation of GHRH rs6032470 was associated with the risk of ischemic stroke.Whereas,the result needs to be further verified in other populations.Part 2 Gene-Gene Interaction Analysis in IGF1 Signaling Pathway with strokeObject: Insulin-like growth factor(IGF)-1 signaling pathway and its relevant genes were involved in the pathogenesis of atherosclerosis and vascular disease.Here we conducted a gene-based analyses to identify the association of IGF1 signaling pathway with susceptibility to stroke.Method: A total of 2070 stroke inpatients and 2243 controls from Chinese Han population were recruited into the study.Haploview software(version 4.2)was used to screen the tagging single-nucleotide polymorphisms(tag SNPs)with r2>0.8 and minimum allele frequency > 0.05,and 26 tag SNPs of IGF1 pathway were genotyped.Logistic regression model was used to evaluate the association between SNPs with stroke,and the odds ratio(OR)and 95% confidence interval(CI)were calculated.Relative excess risk due to interaction(RERI),attributable proportion due to interaction(AP),synergistic index(S)and 95%CIs were used to evaluate the additive interaction between genes.A model based multivariate dimensionality reduction method(MB-MDR)and logarithmic likelihood ratio test(LRT)were used to evaluate the effect of gene multiplication interaction on genetic susceptibility to stroke.A weighted genetic risk score(GRS)of 26 variants was constructed,and the association of GRS with stroke was estimated.Gene expression was determined by real-time Polymerase chain reaction(q RT-PCR),and nonparametric Kruskal-Wallis tests were used to assessed the differences in m RNA expression levels.Result: Our results indicated that variants of rs6032470 at GHRH was significantly associated with hemorrhagic stroke and intracerebral hemorrhage,and OR(95%CI)of rs6032470(TT vs.CC)was 1.368(1.136-1.647)and 1.387(1.145-1.680),After FDR correction,the P values both were 0.026.The additive interaction between GHRH rs6032470 and IGFBP1 rs1874479 in regard to HS were examined.The ORs(95%CIs)of RERI,AP and S were 1.274(0.011-2.536),0.445(0.259-0.631)and 3.169(1.720-5.841),P values were 0.287,0.019 and 0.001.The GRS was significantly associated with stroke and its subtypes.Participants in the high quartile of genetic risk score were estimated to have 1.375 times increased risk of ischemic stroke compared with those in the low quartile(P trend=0.002),and 1.564 times increased hemorrhagic stroke(P trend=0.002).The results exhibited that the relative expression of IGF1 m RNA was significantly higher in IS cases than controls,with a P value of 0.001.Conversely,relative m RNA expression of IGFBP3 common variant,IGFBP3 transcript 1 and IGFBP3 transcript 2 were significantly lower in stroke cases,and P values were less than 0.05 for all.Spearman correlation analysis showed that the m RNA expression of IGFBP3 transcripts 2 was negatively correlated with GRS(r = 0.285,P=0.005).Conclusion: Our findings indicated that GHRH potentiated the risk of stroke via both main effects and gene-gene interaction with IGFBP1.The genetic risk score of multigene locus may regulated expression levels of genes which were involved in the pathogenesis of stroke.