The higher diabetogenic risk of tacrolimus depends on pre-existing insulin resistance. A study in obese and lean Zucker rats.

Insulin resistance may interact with calcineurin inhibitors, enhancing the diabetogenic effect of tacrolimus compared with cyclosporine-A. We studied both drugs in insulin-resistant animals: obese Zucker rats (n = 45), and insulin-sensitive animals: lean Zucker rats (n = 21). During 11 days, animals received saline-buffer, cyclosporine-A (2.5 mg/kg/day) or tacrolimus (0.3 mg/kg/day). At Days 0 and 12 animals underwent intraperitoneal glucose tolerance test (0-30-60-120 min). Islet morphometry, beta-cell proliferation, apoptosis and Ins2 gene expression were analyzed. By Day 12, no lean animal had developed diabetes, while all obese animals on tacrolimus and 40% on cyclosporine-A had. In obese animals, tacrolimus reduced beta-cell proliferation and Ins2 gene expression compared with cyclosporine-A. Five days after treatment discontinuation, partial recovery was observed, with only 10% and 60% of the animals on cyclosporine and tacrolimus remaining diabetic respectively. Beta-cell proliferation increased in animals on tacrolimus while Ins2 gene expression remained unaltered. In conclusion, insulin resistance exacerbated the diabetogenic effect of tacrolimus compared with cyclosporine-A. This may be explained by greater inhibition of Ins2 gene and beta-cell proliferation by tacrolimus in the insulin resistant state. Discontinuation of the drugs may allow the recovery of the metabolic alterations. © Copyright 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.