Metabolic and hormonal effects of tacrolimus (FK506) or cyclosporin immunosuppression following renal transplantation

Twelve renal transplant recipients randomised to receive immunosuppression with either tacrolimus (FK506) or cyclosporin underwent oral glucose tolerance tests (OGTT) a median of 8 months (range 7-9) after transplantation. Six healthy subjects acted as controls. Compared with the controls, both transplant groups had significantly elevated fasting (p < 0.05 for both groups) and postprandial (p < 0.001 for tacrolimus and p < 0.05 for cyclosporin) blood glucose concentrations. Fasting hyperinsulinaemia was observed in both transplant groups (p < 0.05) relative to the control subjects. Glucose-stimulated plasma immunoreactive insulin concentrations in the tacrolimus-treatment group were significantly higher than in the cyclosporin group (p < 0.05) and the controls (p < 0.001). Postprandial blood alanine concentrations were also significantly elevated in the tacrolimus group compared with both the controls (p < 0.001) and cyclosporin-treated patients (p < 0.001). The raised insulin concentrations with normal or increased blood glucose concentrations after renal transplantation suggests that insulin resistance was more marked in patients receiving tacrolimus-based immunosuppression.