Diabetic microvascular complications are not associated with two polymorphisms in the GLUT-1 and PC-1 genes regulating glucose metabolism in Caucasian type 1 diabetic patients.

An XbaI polymorphism in the gene encoding the glucose transporter, GLUT-1, is associated with development of diabetic nephropathy in Chinese type 2 diabetic patients. In addition, an amino acid variant (K121Q) in the gene encoding the glycoprotein plasma cell differentiating antigen (PC-1), a specific inhibitor of insulin receptor signalling, has been reported to predict a faster progression of nephropathy in Italian and British type 1 diabetic patients. The XbaI and K121Q polymorphisms were determined by PCR-RFLP in Danish type 1 diabetic patients with nephropathy (122 men/77 women, age 40.9+/-9.6 years, diabetes duration 27+/-8 years) and type 1 diabetic patients with persistent normoalbuminuria (118 men/74 women, age 42.7+/-10.2 years, diabetes duration 26+/-9 years). Proliferative retinopathy was present in 156 patients (40%), while 67 patients (17%) had no diabetic retinopathy. There were no differences in the frequency of GLUT-1 XbaI genotypes between type 1 diabetic patients with diabetic nephropathy and type 1 diabetic patients with normoalbuminuria: 72 (41%)/87 (50%)/16 (9%) vs 94 (49%)/74 (39%)/24 (13%) had GLUT-1 XbaI +/+, +/- or -/- genotype respectively (NS). The frequency of PC-1 KK, KQ and QQ genotypes were 141 (71%)/52 (26%)/6 (3%) vs 138 (73%)/45 (24%)/7 (4%) in patients respectively with and without nephropathy (NS). Neither were associations between the investigated polymorphisms and simplex or proliferative retinopathy revealed. Neither the PC-1 K121Q nor the GLUT-1 XbaI polymorphism contribute to the genetic susceptibility of diabetic microvascular complications in Danish type 1 diabetic patients.