Risk of developing diabetic nephropathy is not associated with synergism between the angiotensin II (type 1) receptor C1166 allele and poor glycaemic control

BACKGROUND: It has recently been reported that the risk of developing nephropathy in patients with insulin dependent (type 1) diabetes mellitus is strongly associated with synergism between poor glycaemic control and carriage of the hypertension associated angiotensin II (type 1) receptor C1166 allele. The same report also revealed an increase in risk of nephropathy in diabetic patients carrying a specific angiotensin II (type 1) receptor haplotype, i.e. C1166/140-bp microsatellite allele (major allele). METHODS: In order to replicate these findings we performed PCR-based genotyping for the A1166-->C DNA polymorphism and the CA repeat at the 3' end of the angiotensin II (type 1) receptor gene employing validated groups of type 1 diabetic patients with (cases, n = 95) and without (controls, n = 97) nephropathy. HbA1 values above the median (10.5) were used as an index of poor glycaemic control. RESULTS: The risk of nephropathy in carriers of the C1166 allele with HbA1 > 10.5 was 2.1 (95% CI 0.8-5.2) compared to 1.1 (95% CI 0.4-2.6) for non-carriers of the C1166 allele; however, these odds ratios were not significantly different. No difference in the frequency of the high-risk haplotype was found in cases compared to controls (12.4 vs 11.5%; chi2=0.0, P=0.938 with 1 df). CONCLUSIONS: The results of this study do not support previous findings that the risk of diabetic nephropathy is associated with synergism between poor glycaemic control and carriage of the C1166 allele or inheritance of the C1166/major microsatellite haplotype.