Clinical Research On The Relationship Between DDAH Gene Polymorphisms Regulating ADMA And Chronic Kidney Disease

Background Asymmetrical dimethylarginine(ADMA),a kind of methylated arginine,can inhibit nitric oxide synthase(NOS) activity,thus impairing nitric oxide(NO) synthesis,being associated with endothelial dysfunction.ADMA is mainly degraded by dimethylarginine dimethylaminohydrolase(DDAH),being important for regulating the ADMA level.Decrease in DDAH and its activity could contribute to ADMA accumulation and inhibition of NOS activity.Whether DDAH/ADMA/NO systems are related to CKD by regulating vascular endothelial function remains unknown.Objective1.To compare plasma ADMA concentration in the control group and in the different stages of CKD and to elucidate the relationship between ADMA and CKD.2.To analyze the DDAH2(-449 G/C) and DDAH2(-1151 A/C) genotypes and the allelic frequency in the different stages of CKD in the control group.3.To study the relationships between the different genotypes of DDAH2(-449 G/C) and DDAH2(-1151 A/C) and the plasma ADMA level,and to discuss the effect of DDAH2(-449 G/C) and DDAH2(-1151 A/C) polymorphisms on plasma ADMA concentration.4.To analyze the contribution to GFR and ADMA made by the interaction function of DDAH2(-449 G/C) and DDAH2(-1151 A/C) polymorphisms.Methods1.A total of 186 patients(excluding the hypertensive renal disease, diabetic nephropathy,lupus nephropathy and renal replacement therapy) with CKD were selected as the CKD group.And 102 cases without previous medical diseases were as the control group.Blood and urine examinations of the control group show no abnormalities.The CKD group was divided into 5 stages according to the eGFR published by the Kidney Foundation of America.2.The plasma ADMA level was detected by HPLC.3.The polymorphisms of DDAH2(-449 G/C) was detected by PCR-RFLP.4.The polymorphisms of DDAH2(-1151 A/C) was detected by gene sequencing.Results1.ADMA is risk factor of CKD according to the analysis of the stepwise multiple regression on multifactors such as sex and age(OR＞1).2.The plasma ADMA concentration of CKD group was significantly higher than that of the control group.There was statistical significance between them(P＜0.05).The plasma ADMA concentration was increased with the development of CKD.3.The comparison of DDAH2(-449 C/G) genotypes and allelic frequency between the CKD group and the control group showed statistical significance(P＜0.05).It suggested there was a relationship between DDAH2(-449 C/G) polymorphisms and the onset of CKD.The allelic frequency of DDAH2(-449 C/G) G of CKD group was higher than that of the control group(P＜0.05).When the DDAH2(-449 C/G) was CC, CG and GG genotypes,not only the statistical significance showed among the overall plasma ADMA concentration,but also between any two of them(P＜0.05).4.The comparison of DDAH2(-1151 A/C) genotypes and allelic frequency between the CKD group and the control group showed statistcal significance(P＜0.05).It indicated that there was a relationship between DDAH2(-1151 A/C) polymorphisms and the onset of CKD.The allelic frequency of DDAH2(-1151 A/C) A of CKD group was higher than that of the control group(P＜0.05).When the DDAH2(-449 C / G) was AA, AC and CC genotype,not only the statistical significance showed among the overall plasma ADMA concentration,but also between ADMA concentrations when DDAH2(-1151 A/C) was CC and AA or AC genotype(P＜0.05).5.The interaction among GFR,DDAH2(-449 G/C) and DDAH2 (-1151 A/C) genotypes were as follows,the combination of DDAH2(-449 G/C) which were GC genotypes and DDAH2(-1151 A/C) which were CC genotypes induced the maximum GFR(123.758±32.413) ml/min/1.73m~2. The combination of DDAH2(-449 G/C) which were GG genotypes and DDAH2(-1151 A/C) which were AA genotypes induced the minimum GFR(46.297±50.492) ml/min/1.73m~2.The interaction among ADMA concentration,DDAH2(-449 G/C) and DDAH2(-1151 A/C) genotypes were as follows,the combination of DDAH2(-449 G/C) which were GG genotypes and DDAH2(-1151 A/C) which were AA genotypes induced the maximum ADMA(0.905±0.399)μmol/L.The combination of DDAH2(-449 G/C) which were GG genotypes and DDAH2(-1151 A/C) which were CC genotypes induced the minimum ADMA(0.452±0.252)μmol/L.Conclusion1.ADMA was one of the CKD risk factors,being related to the onset and developing of CKD.As the progress of renal function,the plasma ADMA concentration increases.2.DDAH2(-449 G/C) and DDAH2(-1151 C/A) polymorphism are related to the onset of CKD.The DDAH2(-449 C/G) G allele and DDAH2(-1151 A/C) A allele may be the susceptible factors of CKD.3.DDAH2(-449 G/C) and DDAH2(-1151 A/C) polymorphisms impact the serum ADMA concentration.4.The polymorphisms of DDAH2(-449 G/C) and DDAH2(-1151 A/C) can interact with plasma GFR and ADMA concentration.