Metabolic aspects of tacrolimus in renal transplantation. Consequences for the choice of an immunosuppressive regimen and for the management of post-transplant diabetes mellitus.

The occurrence of post-transplant diabetes mellitus (PTDM) is an important complication after renal transplantation associated with an increased risk of chronic transplant dysfunction and of cardiovascular morbidity and mortality. Both tacrolimus and cyclosporine have been associated with PTDM. In the initial studies, PTDM seemed to occur more often in tacrolimus treated patients than in cyclosporine treated patients. The mechanism by which tacrolimus could cause PTDM was unknown and the relative roles of tacrolimus and corticosteroids, which are often prescribed concomitantly with tacrolimus, were unknown. In several studies we used fasting glucose and insulin levels to assess (peripheral) insulin resistance, and intravenous glucose tolerance tests to assess insulin secretion by the pancreatic b-cells in response to a stimulus (glucose load). Thus, we evaluated the mechanism by which tacrolimus causes glucose metabolic disorders, risk factors for glucose metabolic disorders during tacrolimus treatment, the relative roles of corticosteroids and tacrolimus trough levels in glucose metabolic disorders, and also differences in glucose metabolism between patients using tacrolimus versus patients using cyclosporine. Based on the results of these studies and the available literature, the consequences for the choice of a primary immunosuppressive agent and guidelines for the treatment of PTDM during tacrolimus-based immunosuppression are discussed.