Pro12Ala polymorphism in the PPARG gene contributes to the development of diabetic nephropathy in Chinese type 2 diabetes

Abstract

Objective— Oxidative stress is a major contributing factor in the development of diabetic nephropathy. Peroxisome proliferator-activated receptor gamma (PPAR-γ) heterozygous mice and Pro12Ala polymorphism in PPARG exhibited increased resistance to oxidative stress. Smoking increases the production of reactive oxygen species, which accelerates oxidative stress under hyperglycemia. To determine whether the Pro12Ala polymorphism, alone or in combination with smoking, contributes to the development of diabetic nephropathy, a case-control study was performed in 760 Chinese patients with type 2 diabetes.

Research design and methods— Among patients, 532 had diabetic nephropathy with micro-albuminuria (n=245) or overt-albuminuria (n=287), and 228 did not show either of these symptoms but had been suffering from diabetes for ≥ 10 years and were not undergoing antihypertensive treatment.

Results— After adjusting for confounders, the Pro/Pro genotype significantly associated with diabetic nephropathy, odds ratio (OR) 2.30 (95% CI 1.18-4.45), p=0.014; smoking was also an independent risk factor for diabetic nephropathy with OR 1.99 (1.08-3.68), p=0.029. In addition, we identified possible synergistic effects, i.e., the high-risk group (smokers with the Pro/Pro genotype) showed 4.52 times higher risk (95% CI, 1.78-11.48; p=0.002) of diabetic nephropathy than the low-risk group (nonsmokers with Pro/Ala genotype) in a multiple-logistic-regression analysis controlled for the confounders.

Conclusions— Our results indicated that the Pro/Pro genotype and smoking were significant independent risk factors for diabetic nephropathy. The possible synergistic effects of genotype and smoking may aggravate oxidative stress and contribute to the development of diabetic nephropathy.