Coexistence of aldose reductase gene and endothelial nitric oxide synthase polymorphisms associates with diabetic nephropathy

Zhengju FU; Changgui LI; Zhongchao WANG; Shengli YAN

ABSTRACT

BACKGROUND:

It has been demonstrated that the C-106T polymorphism at promotor region of aldose reductase gene and GLU298ASP (894G→T) polymorphism at exon 7 of endothelial nitric oxide synthase (eNOS) gene are associated with diabetic nephropathy, it should be further studied wnether the risk for diabetic nephropathy will increase when the above polymorphic sites coexist.

OBJECTIVE:

To investigate the association between the coexistence of the polymorphisms of both the C-106T at promotor region of aldose reductase gene and GLU298ASP (894G→T) at axon 7 of eNOS gene in chromosome 7q35 region and the genesis of diabetic nephropathy in northern Chinese Hah people.

DESIGN:

A case-controlled, comparative observation.

SETTING:

Department of Endocrinology, the Affiliated Hospital of Medical College, Qingdao University.PARTTCIPANTS; Totally 139 inpatients with type 2 diabetes mellitus were selected from the Department of Endocrinology, the Affiliated Hospital of Medical College, Qingdao University from November 2002 to April 2005,including 54 males and 85 females, (64±8) years of age. Inclusive criteria Accorded with the standards of diabetic diagnosis and classification by WHO in 1999. According to the 24-hour urinary albumin excretion rate (UAER), they were divided into diabetic nephropathy group (n =61) and non-diabetic nephropathy group (n =78). Meanwhile, 63 healthy controls were selected as the control group, including 24 males and 39 females, 50-78 years of age. All the enrolled subjects were Han people. Informed contents were obtained from all the subjects.

METHODS:

The genotypes and alleles of polymorphisms of GLU298ASP(894G→T) at exon 7 of eNOS gene and C-106T at promotor region of aldose reductase gene were detected by polymerase chain reaction restriction-fragment length polymorphism technique (PCR-RFLP), DNA sequencing technique and agarose gel electrophoresis separation technique.Then the frequency of genotypes and alleles were compared.MAIN OUTCOME

MEASURES:

① Polymorphisms of eNOS gene and aldose reductase gene; ② Results of the multivariant stepwise regression analysis of risk factors for diabetic nephropathy; ③ Polymorphisms of aldose reductase C-106T and eNOS 894G→T and the relative risk of diabetic nephropathy.

RESULTS:

All the 139 patients with type 2 diabetes mellitus and 63 healthy adults were involved in the analysis of results. ① The frequencies of the T allele and TG genotype at exon 7 894G→T polymorphic site of eNOS gene in the diabetic nephropathy group were significantly higher than those in the non-diabetic nephropathy group and control group (χ2=8.261, 19.629, P ＜ 0.05). ② The frequencies of the T allele and CT genotype at promotor region of aldose reductase gene in the diabetic nephropathy group were significantly higher than those in the non-diabetic nephropathy group and control group (χ2=6.343, 8.940, P ＜ 0.05, 0.01). ③ After associated analysis on the above gene polymorphisms, it was found that the frequency of TG/CT genotype in the diabetic nephropathy group were significantly higher than that in the non-diabetic nephropathy group and control group (χ2=6.972, P ＜ 0.01); whereas the frequency of GG/CC genotype was significantly lower than that in the non-diabetic nephropathy group and control group (χ2=13.304, P ＜ 0.05). ④Glycosylated hemoglobin (GHbA1c), systolic blood pressure, total cholesterol, polymorphisms of 894G→T at exon 7 of eNOS gene and C-106T at promotor region of aldose reductase gene were all the independent risk factors for diabetic nephropathy (Wald =5.627, 4.92, P ＜ 0.05). ⑤ GG/GC genotype might be the protective genotype for diabetic nephropathy (OR=0.25, P ＜ 0.01); The risk for diabetic nephropathy in the carrier of GG/CT or TG/CC genotype increased by 2.3 times and risk for diabetic nephropathy in the carrier of TG/CT genotype increased by 4.8 times.

CONCLUSION:

The coexistence of polymorphisms of 894G→T at exon 7 of eNOS gene and C-106T at promotor region of aldose reductase gene can increase the risk of diabetic nephropathy in patients with type 2 diabetes mellitus. And the TG/CT haplotype formed by the coexistence of polymorphism of these two genes is probably the predisposing genotype for diabetic nephropathy.