Analysis of Incretin Hormones After Orthotopic Liver Transplantation

Several well-known risk factors play an important role in the development of new-onset diabetes mellitus after orthotopic liver transplantation (OLT). Immunosuppressant drugs and hepatitis C virus (HCV) infection have a direct effect on pancreatic beta cells resulting insulin hyposecretion. Steroids mainly cause peripheral insulin resistance. Although in type 2 diabetes mellitus the incretin-insulin axis is impaired and incretin hormones are advantageous targets of many antidiabetic drugs, the endocrinologic background of new-onset diabetes mellitus after transplantation (NODAT) is still not completely understood.

During the first postoperative year the oral glucose tolerance test (OGTT) was performed on 21 patients after OLT. Patients' glycemic metabolic status was determined according to the results of OGTT. The level of incretin hormones, namely glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), were measured with competitive enzyme-linked immunoassay reaction.

Six patients had normal glucose tolerance (NGT), 9 had impaired glucose tolerance (IGT, serum glucose 7.8-11.0 mmol/L), and 6 were diagnosed with NODAT (serum glucose >11.1 mmol/L). Fasting insulin and c-peptide levels were higher if IGT/NODAT was found. Insulin secretion was not further stimulated after OGTT. GIP and GLP-1 levels did not differ significantly, not even after glucose load. HCV infection had not influenced the levels of incretin hormones [GLP-1 (0 min): 1.21 ± 0.27 vs 1.38 ± 0.65; P = ns; GLP-1 (120 min): 1.46 ± 0.61 vs 1.07 ± 0.58; P = ns; GIP (0 min): 2.55 ± 0.95 vs 1.99 ± 0.63; P = ns, GIP (120 min): 2.62 ± 0.6 vs 2.33 ± 0.77; P = ns].

The stimulation of insulin secretion in NODAT is limited. Incretin hormones are present independently from the current glycemic status. The use of dipeptidyl peptidase-4 inhibitors through their positive effect on the incretin-insulin axis can be beneficial in the therapy of NODAT after liver transplantation.