Introduction: New-onset diabetes after transplantation (NODAT) is strongly associated with postoperative hyperglycemia, and reduced patient as well as graft survival. In our recent proof-of-concept clinical trial (TIP), we have shown that immediate post-transplant basal insulin therapy decreases hyperglycemia and reduces the prevalence of NODAT by improving pancreatic β-cell function. In consequence, a collaborative multicenter study on NODAT prevention using basal insulin has been approved by the National Institutes of Health (NIH), and will start recruiting 380 patients at 6 international transplant centers, including the Medical University of Vienna and the University of Michigan in 2012. In addition to the NIH-sponsored trial, the Vienna SAPT-NODAT study will test the hypotheses that intensive subcutaneous insulin treatment with short acting insulin, applied continuously through an insulin pump in combination with a glucose sensor (SAPT), (i) improves glycemic control, (ii) reduces the prevalence of NODAT and prediabetes, and (iii) offers further β-cell protection, in comparison to the standard of care control group, and the basal insulin treatment group.

Methods: Combining the NIH-sponsored basal insulin study and the SAPT-NODAT study will yield three study arms, with 28 patients in each arm, namely: \[1\] the control arm, treated by standard-of-care; \[2\] the basal insulin arm, treated predominantly with intermediate acting NPH insulin (human insulin isophane, Humulin N, Eli Lilly); \[3\] the SAPT arm, treated with short acting insulin (Insulin lispro, Humalog, Eli Lilly), applied continuously by SAPT technology. Adult patients with absence of diabetes will be randomized prior to renal transplantation and stratified by deceased donor or living donor, if they are capable of understanding the study and are willing to give informed written consent for all three study arms. Patients will receive standard triple immunosuppressive medications (twice-daily tacrolimus, mycophenolate mofetil or mycophenolic sodium and steroids) with predefined tacrolimus targets and steroid doses. The algorithm for insulin administration is designed to account for the prominent evening peak of hyperglycemia observed in our previous TIP-study. The primary endpoint is HbA1c (in rel.%), at 3 months, and superiority will be assumed if a statistically significant difference between the SAPT-treatment group versus the standard-of-care control group can be determined, by two-sided Student's t-test. Secondary endpoints will be compared between all three groups and will include hypoglycemic events, glycemic variability, 2h glucose ≥200 mg/dL (by oral glucose tolerance test \[OGTT\] to determine prevalence of diabetes, prediabetes and normal glucose tolerance), beta cell function and insulin sensitivity derived from OGTT, serum creatinine, quality of life measures, patient and graft survival. All secondary endpoint comparisons relying on OGTTs will be made at 6, 12 and 24 months after kidney transplantation, respectively. The result of the 6-months OGTT will be blinded to patients and investigators to prevent subsequent treatment bias.

Discussion: Basal insulin treatment in our previous proof-of-concept study could not prevent a high number of transplant patients exhibiting overt prediabetes (impaired glucose tolerance) at 3, 6 and 12 months, probably on the basis that hyperglycemia was improved, but far from being aggressively treated in patients receiving basal insulin. Prediabetes however is an independent predictor of all-cause mortality in patients after renal transplantation, and therefore not only a harbinger of overt diabetes mellitus but rather a high-risk condition per se. The use of HbA1c as primary endpoint at three months is debatable, but necessary to determine whether SAPT technology may lead to a clinically meaningful improvement of overall glucose control. Specifically, in our previous study (TIP), we observed an intra-individual rise in HbA1c (0.5±0.7 rel.%) from baseline to 3 months, despite basal insulin treatment. If the intra-individual rise in the SAPT arm will remain below that value, SAPT technology could be considered to be a clinically meaningful improvement. The SAPT-NODAT study, besides holding promise to further improve glycemic control, thereby reducing diabetes, prediabetes and possibly cardiovascular events after transplantation, may ensure that the present team of investigators continues to take the lead in post-transplant insulin administration, which is emerging as a central focus in NODAT-prevention and may soon reach broader clinical application.

(Study approval: EK-Nr. 10/2012)