The Association Of An (AC-)_n Dinucleotide Repeat Polymorphic Marker At 5' End Of The Aldose Reductase Gene With Diabetic Retinopathy In NIDDM

Aims: To study the association of an (AC)n dinucleotide repeat sequence polymorphic which is in 2.1 Kb upstream of the transcription start site at the 5' end of the aldose reductase gene with diabetic retinopathy in NIDDM.Methods: 30 normal person as healthy control group; 22 NIDDM patients who had evidence of proliferative retinopathy or significant nonproliferative retinopathy within 5 years of diagnosis of NBDDM, and youger than 60 years as retinopathy group;22 NEDDM patients who had no evidence of clinical retinopathy more than 10 years of diagnosis of NIDDM as control group were recruited.And they all came from Northen China.At first , DNA were isolated from 74 person's white blood cells, and the region containing the dinucleotide repeat was amplified by PCR with a pair of amplification primers which Ko designed. Then , the PCR products of the DNA samples whose alleles were homozygotes were selected, purifed, and sequenced directly in order to find out the types of alleles. Finally, using the purifed PCR products that was sequenced as marker , the samples' genotypes were detected by 8% formamide-urea acrilamide gel electrophoresis together with silver-staining. The PCR products whose alleles were homozygotes and different from marker were sequencede too. The results of sequencing is agreement with the detecting, that clarified the methods were accurate.Results:All samples exhibted 14 different genotypes and 7 different alleles. 7 alleles were Z-6, Z-4, Z-2, Z, Z+2, Z+4, Z+6, AC dinucleotide repeats21, 22, 23, 24, 25, 26, 27, the length of PCR products were 132, 134, 136, 138, 140, 142, 144bp. The most prevalent allele was Z((AC)24 repeats) allele, the frequence of Z allele was 0.3 in healthy group , 0.307 in NIDDM group. The distribution of the different alleles of the (AC)n dinucleotide repeat sequence inthe healthy group and NIDDM group has no significant difference ( x 2=0.930, P=0.988). The distribution of the different alleles of the (AC)n dinucleotide repeat sequence in the retinopathy group and control group has significant difference ( x2=13.412, P=0.037) . Fisher's exact test was applied to compare the frequency of each allele between patients with and without retinopathy . The frenquency of the Z-2 allele was found to be significantly greater in the retinopathy group(P=0. 006). And the frenquency of the Z+2 allele was less in the retinopathy group(P=0.033).There was a homozygote Z-2 allele in the retinopathy group . When the homozygote was only scored once, the Z-2 allele differences between the two group was significant too (P=0. 014) .Conclusion: an (AC)n dinucleotide repeat sequence polymorphic which is in 2.1 Kb upstream of the transcription start site at the 5' end of the aldose reductase gene was associated with diabetic retinopathy in NIDDM, but had no assciation with the NIDDM. The alleles(Z-2) was found to be associated with proliferative retinopathy in patients with non-insulin-dependent diabetes,and may be a risk factor; whereas Z+2 alleles was a protective factor for DR of NIDDM patients.