Association of single nucleotide polymorphisms in the gene encoding GLUT1 and diabetic nephropathy in Brazilian patients with type 1 diabetes mellitus.

Mesangial cells subject to high extracellular glucose concentrations, as occur in hyperglycaemic states, are unable to down regulate glucose influx, resulting in intracellular activation of deleterious biochemical pathways. A high expression of GLUT1 participates in the development of diabetic glomerulopathy. Variants in the gene encoding GLUT1 (SLC2A1) have been associated to this diabetic complication. The aim of this study was to test whether polymorphisms in SLC2A1 confer susceptibility to diabetic nephropathy (DN) in Brazilian type 1 diabetes patients. Four polymorphisms (rs3820589, rs1385129, rs841847 and rs841848) were genotyped in a Brazilian cohort comprised of 452 patients. A prospective analysis was performed in 155 patients. Mean duration of follow-up was 5.6 ± 2.4 years and the incidence of renal events was 18.0%. The rs3820589 presented an inverse association with the prevalence of incipient DN (OR: 0.36, 95% CI: 0.16 - 0.80, p=0.01) and with progression to renal events (HR: 0.20; 95% CI: 0.03 - 0.70; p=0.009). AGGT and AGAC haplotypes were associated with the prevalence of incipient DN and the AGAC haplotype was also associated with the prevalence of established/advanced DN. In conclusion, rs3820589 in the SLC2A1 gene modulates the risk to DN in Brazilian patients with inadequate type 1 diabetes control.

Sex-specific associations of variants in regulatory regions of NADPH oxidase-2 (CYBB) and glutathione peroxidase 4 (GPX4) genes with kidney disease in type 1 diabetes.

Oxidative stress is involved in the pathophysiology of diabetic nephropathy. The superoxide-generating nicotinamide adenine dinucleotide phosphate-oxidase 2 (NOX2, encoded by the CYBB gene) and the antioxidant enzyme glutathione peroxidase 4 (GPX4) play opposing roles in the balance of cellular redox status. In the present study, we investigated associations of single nucleotide polymorphisms (SNPs) in the regulatory regions of CYBB and GPX4 with kidney disease in patients with type 1 diabetes. Two functional SNPs, rs6610650 (CYBB promoter region, chromosome X) and rs713041 (GPX4 3'untranslated region, chromosome 19), were genotyped in 451 patients with type 1 diabetes from a Brazilian cohort (diabetic nephropathy: 44.6%) and in 945 French/Belgian patients with type 1 diabetes from Genesis and GENEDIAB cohorts (diabetic nephropathy: 62.3%). The minor A-allele of CYBB rs6610650 was associated with lower estimated glomerular filtration rate (eGFR) in Brazilian women, and with the prevalence of established/advanced nephropathy in French/Belgian women (odds ratio 1.75, 95% CI 1.11-2.78, p = 0.016). The minor T-allele of GPX4 rs713041 was inversely associated with the prevalence of established/advanced nephropathy in Brazilian men (odds ratio 0.30, 95% CI 0.13-0.68, p = 0.004), and associated with higher eGFR in French/Belgian men. In conclusion, these heterogeneous results suggest that neither CYBB nor GPX4 are major genetic determinants of diabetic nephropathy, but nevertheless, they could modulate in a gender-specific manner the risk for renal disease in patients with type 1 diabetes.