Fasting parameters for estimation of stimulated β cell function in islet transplant recipients with or without basal insulin treatment

• Published in: American journal of transplantation Vol. 21; no. 1; pp. 297 - 306
• Main Authors: Uitbeijerse, Bas S., Nijhoff, Michiel F., Sont, Jacob K., Koning, Eelco J. P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Limited 01.01.2021; John Wiley and Sons Inc
• Subjects: Beta cells; Blood Glucose; C-Peptide; clinical research/practice; Diabetes; Diabetes Mellitus, Type 1; endocrinology/diabetology; Fasting; Glucose; Humans; Insulin; insulin/C‐peptide; Islet cells; islet transplantation; Islets of Langerhans; Islets of Langerhans Transplantation; Laboratory testing; Original; ORIGINAL ARTICLES; Pancreatic islet transplantation; Peptides; Transplants & implants; islet transplantation; endocrinology/diabetology; diabetes; clinical research/practice; islets of Langerhans; insulin/C-peptide
• ISSN: 1600-6135; 1600-6143
• DOI: 10.1111/ajt.16135

In order to assess β cell secretory capacity after islet transplantation, standardized mixed meal stimulation tests are often used. But these tests are cumbersome and the effect of exogenous insulin on the test results is unclear. The aim of our study was to determine to what extent fasting glycemic indices can estimate stimulated β cell function in islet transplant recipients with and without basal insulin. In total 100 mixed meal stimulation tests, including 31 with concurrent basal insulin treatment, were performed in 36 islet transplant recipients. In a multivariate model, fasting C‐peptide and fasting glucose together estimated peak C‐peptide with R2 = .87 and area under the curve (AUC) C‐peptide with a R2 = .93. There was a larger increase of glucose during tests in which exogenous insulin was used (+7.9 vs +5.3 mmol/L, P < .001) and exogenous insulin use was associated with a slightly lower estimated peak C‐peptide (relative change: −15%, P = .02). In islet transplant recipients the combination of fasting C‐peptide and glucose can be used to accurately estimate stimulated β cell function after a mixed meal stimulation test, whether exogenous basal insulin is present or not. These data indicate that graft function can be reliably determined during exogenous insulin treatment and that regular islet graft stimulation tests can be minimized. Fasting C‐peptide and glucose can accurately estimate stimulated β cell function during a mixed meal tolerance test in islet transplant recipients, irrespective of concurrent basal insulin use.