The GLUT-1 XbaI gene polymorphism is associated with vascular calcifications in nondiabetic uremic patients

Background: Glucose transporters mediate the facilitative uptake of glucose into cells, with GLUT-1 being the predominant isoform in vascular smooth muscle cell (VSMC). Clones of human cells overexpressing the GLUT-1 transporter showed a high increase in intracellular glucose concentrations, mimicking the diabetic milieu. It is possible that high intracellular glucose together with uremic factors may play an important role in vascular calcification by transforming VSMC into osteoblast-like cells. The XbaI polymorphism in the GLUT-1 gene has been linked to variations in GLUT-1 expression, with consequent changes in intracellular glucose concentration.

Methods: To assess the association between the GLUT-1 XbaI gene polymorphism and the presence of VC in nondiabetic uremic patients, a total of 105 nondiabetic patients on hemodialysis were studied. VC were evaluated by conventional simple X-ray. Mean values of serum calcium, phosphorous, cholesterol, triglycerides, HbA1c, PTH and insulin were measured. Height, weight, BMI and waist circumference were also determined. The GLUT-1 XbaI polymorphism in the second intron of the gene was ascertained by means of the polymerase chain reaction and restriction fragment length polymorphism analysis on DNA isolated from peripheral blood DNA. In the absence of an XbaI site, a fragment of 305 bp was seen (so-called x allele), whereas fragments of 232 and 73 bp were generated if the XbaI site was present (X allele).

Results: Genotype distribution in all patients was similar to the Caucasian population. However, when the patients were grouped according to the presence or absence of VC, there were marked differences in the frequency of the GLUT1 genotypes: the xx GLUT-1 genotype was more prevalent in the group with VC (30.7 vs. 4.5%, p = 0.001). Stepwise logistic regression demonstrated that the xx GLUT-1 genotype was independently associated with the presence of VC after adjusting for other variables such as age, calcium x phosphrus product, BMI and time on dialysis (OR 7.68; 95% CI 1.28-45.7).

Conclusions: GLUT-1 XbaI gene polymorphism is associated with vascular calcifications in nondiabetic uremic patients.