Impact of the endothelial nitric oxide synthase gene G894T polymorphism on renal endothelial function in patients with type 2 diabetes.
OBJECTIVE
Endothelial dysfunction and increased oxidative stress contribute to the progression of diabetic nephropathy. To analyze the functional significance of the G894T polymorphism of NOS3, the gene encoding endothelial nitric oxide synthase (NOS), we assessed basal nitric oxide activity and the amount of oxidative stress in the renal circulation of patients with type 2 diabetes.


METHODS
Renal plasma flow (RPF) was assessed by steady-state input clearance technique with sodium para-aminohippurate in 84 patients with type 2 diabetes and 84 patients without diabetes. RPF was measured at baseline and after the infusion of the NOS inhibitor N-monomethyl-L-arginine (4.25 mg/kg); the substrate of NOS L-arginine (100 mg/kg); and coinfusion of vitamin C (3 g) with L-arginine (100 mg/kg).


RESULTS
The decrease of RPF to N-monomethyl-L-arginine was similar between carriers of the T allele and homozygous carriers of the G allele in patients with diabetes (-56+/-40 vs. -68.1+/-74 ml/min/1.73 m, P=0.342) and patients without diabetes (-66.7+/-81 vs. -58.3+/-63 ml/min/1.73 m, P=0.606). In patients with diabetes, however, carriers of the T allele revealed a more pronounced increase of RPF to coinfusion of vitamin C with L-arginine than homozygous carriers of the G allele (61.8+/-75 vs. 22.3+/-73 ml/min/1.73 m, P=0.021), whereas in patients without diabetes the response of RPF to coinfusion of vitamin C with L-arginine was similar between both groups (46.2+/-80 vs. 70.7+/-86 ml/min/1.73 m, P=0.217). Gene-environment interaction between disease (diabetes) and genotype (genotype GG vs. genotype GT/TT) was observed for increase of RPF to coinfusion of vitamin C with L-arginine (P=0.020).


CONCLUSIONS
G894T polymorphism of NOS3 has no impact on the basal nitric oxide activity of renal circulation. In contrast, the T allele is associated with increased oxidative stress in the renal circulation in patients with diabetes suggesting a specific role of the G894T polymorphism in the pathogenesis of diabetic nephropathy.
Ritt
Martin
M
Department of Nephrology and Hypertension, University of Erlangen-Nürnberg, Germany.
Ott
Christian
C
Delles
Christian
C
Schneider
Markus P
MP
Schmieder
Roland E
RE
D000483:Alleles; D000704:Analysis of Variance; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology; D015992:Body Mass Index; D008076:Cholesterol, HDL / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology* / Q000235:genetics* / Q000503:physiopathology; D004727:Endothelium / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology*; D005260:Female; D005838:Genotype; D006147:Guanine; D006439:Hemodynamics; D006720:Homozygote; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D052250:Nitric Oxide Synthase Type III / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D017595:Renal Plasma Flow / Q000187:drug effects; D013941:Thymine; D014280:Triglycerides / Q000097:blood; D019323:omega-N-Methylarginine / Q000008:administration & dosage / Q000494:pharmacology
D008076:Cholesterol, HDL; D014280:Triglycerides; D019323:omega-N-Methylarginine; D006147:Guanine; D001120:Arginine; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D001205:Ascorbic Acid; D013941:Thymine