Tacrolimus decreases insulin sensitivity without reducing fasting insulin concentration: a 2-year follow-up study in kidney transplant recipients.

New Onset Diabetes after Transplantation (NODAT) is defined as sustained hyperglycemia developing in patients without diabetes history before transplantation. A cohort study was performed to access the effects of tacrolimus on insulin secretion and insulin sensitivity and consequently in the development of NODAT in kidney transplant recipients. Then, we further investigated the association between NODAT and single-nucleotide polymorphisms of IRS-1 and IRS-2 in renal allograft recipients. One hundred and fifty-eight kidney transplant patients, receiving tacrolimus as the base immunosuppressant, were divided into two groups: with or without NODAT. Plasma levels of fasting insulin concentration (FINS) and C-peptide were determined by enhanced chemiluminescence immunoassay and ADVIA Centaur C peptide assay, respectively. The genotypes of Gly1057Asp in IRS-2 and Gly972Arg in IRS-1 were detected through polymerase chain reaction fragment length polymorphism in NODAT and non-NODAT patients. It was found that the concentrations of fasting plasma insulin and C-peptide in NODAT and non-NODAT patients treated with tacrolimus were higher than that in healthy volunteers (p < 0.05). Fasting plasma insulin concentration in NODAT was significantly elevated compared with than that in non-NODAT group (p < 0.05). But there are no statistical differences in fasting plasma C-peptide concentrations between NODAT and non-NODAT groups. The allele and genotype frequencies of IRS-2 Gly1057Asp and IRS-1 Gly972Arg in NODAT patients were not significantly different from non-NODAT patients (p > 0.05). In conclusion, insulin resistance is the primary cause of tacrolimus-induced NODAT. The IRS-2 Gly1057Asp and IRS-1 Gly972Arg genotypes are not related to NODAT.