Genetic variation in thrombin-activatable fibrinolysis inhibitor is associated with the risk of diabetic nephropathy

Diabetic nephropathy is a kidney disease or damage that results as a complication of diabetes, especially Type 2 diabetes, while albuminuria is an early marker for diabetic nephropathy as it can predict cardiovascular events and mortality in diabetic patients. A potent inhibitor of fibrinolysis, the thrombin-activatable fibrinolysis inhibitor (TAFI) has been isolated and characterized from human plasma. We investigated the associations of the activity-related variants in the TAFI coding gene (505A/G,1040C/T) with the risk of diabetic nephropathy by examining 297samples including 140 health controls and 157 confirmed diabetic nephropathy patients. Diabetic nephropathy grades were further categorized by the urine albumin excretion (UAE)-to-creatinine ratios (ACR). We found little difference that was statistically significant in terms of 505A/G among patients and controls. While at 1040C/T, the detected frequency for the T allele in the group of diabetic nephropathy patients was significantly smaller than that of the control group (15.6% vs 25.7%, respectively; p<0.05). This was due to the relative decrease of T/T homozygotes in the patients (p<0.05, 95% odds ratio 0.28, confidence interval 0.11-0.70). Surprisingly, the difference was only observed with initial diabetic nephropathy stages. This study clearly indicates that, at 1040C/T, the frequency for the T allele is strongly associated with increased risk for diabetic nephropathy in a subset of the general population, implying that the T allele confers protection against the onset of diabetic nephropathy only in homozygosity and may function as a recessive trait.