Background: A polymorphism (C825T) in exon 10 of the gene encoding the beta 3 subunit of heterotrimeric G proteins (GN beta 3) has recently been described, and the T allele was found to be associated with late-onset hypertension. Because hypertension is a known risk factor for the development of clinically manifest progressive renal disease, we examined the C825T polymorphism in older hemodialysis patients suffering from nondiabetic renal disease or type 2 diabetes with presumed diabetic nephropathy, respectively, and in older healthy controls.
Methods: Genotyping was performed by polymerase chain reaction, followed by restriction enzyme analysis.
Results: The study showed that the frequency of the T allele in the nondiabetic patients on dialysis (0.232) was significantly (P < 0.03) lower than in older healthy controls (0.293). In contrast, the frequency was significantly (P < 0.02) higher in older patients with type 2 diabetes on dialysis. No significant change in T-allele frequency was noted in older patients with type 2 diabetes without microangiopathy (0.286). The odds ratios for patients with type 2 diabetes on dialysis versus nondiabetic patients on dialysis were 3.24 (1.3 to 7.9, P < 0.00079) for TT/CC and 1.82 (1.07 to 3.09, P < 0.02) for CT/CC. The respective odds ratios for patients with type 2 diabetes on dialysis versus controls were 2.05 (1.07 to 3.9, P < 0.028) for CT/CC and 1.216 (0.79 to 1.87; P < 0.37) for CT/CC.
Conclusion: The data do not support a role of the hypertension-associated T allele in the genesis of dialysis-dependent end-stage renal failure in general, but are compatible with a specific role of the T allele in the development or progression of diabetic nephropathy.