Abstract
AimThe aim of the present study was to assess beta cell function based on an oral glucose tolerance test (OGTT) in participants with single islet autoantibody or an intravenous glucose tolerance test (IvGTT) in participants with multiple islet autoantibodies.Materials and methodsHealthy participants in Sweden and Finland, between 2 and 49.99 years of age previously identified as positive for a single (n = 30) autoantibody to either insulin, glutamic acid decarboxylase, islet antigen‐2, zinc transporter 8 or islet cell antibodies or multiple autoantibodies (n = 46), were included. Participants positive for a single autoantibody underwent a 6‐point OGTT while participants positive for multiple autoantibodies underwent an IvGTT. Glucose, insulin and C‐peptide were measured from OGTT and IvGTT samples.ResultsAll participants positive for a single autoantibody had a normal glucose tolerance test with 120 minutes glucose below 7.70 mmol/L and HbA1c values within the normal range (<42 mmol/mol). Insulin responses to the glucose challenge on OGTT ranged between 13.0 and 143 mIU/L after 120 minutes with C‐peptide values between 0.74 and 4.60 nmol/L. In Swedish participants, the first‐phase insulin response (FPIR) on IvGTT was lower in those positive for three or more autoantibodies (n = 13; median 83.0 mIU/L; range 20.0‐343) compared to those with two autoantibodies (n = 15; median 146 mIU/L; range 19.0‐545; P = .0330).ConclusionParticipants positive for a single autoantibody appeared to have a normal beta cell function. Participants positive for three or more autoantibodies had a lower FPIR as compared to participants with two autoantibodies, supporting the view that their beta cell function had deteriorated.
Highlights
Fasting insulin levels were higher in participants with multiple autoantibodies as compared with those positive only for a single autoantibody in the Swedish participants, but there was no difference between these two groups in the Finnish participants
The most important finding of this study was that all participants with only a single autoantibody had normal beta cell function based on glucose, C-peptide and insulin levels in the 6-point oral glucose tolerance test (OGTT) test
None of the participants with a single autoantibody was eligible to enter the randomized trial with either gluten free or regular diet. This finding is in line with a recent study reporting that single islet autoantibody at clinical diagnosis of type 1 diabetes is associated with older age in the patients as well as insulin resistance and higher body mass index (BMI).[8]
Summary
Participants eligible for the TEFA study were selected from a population of autoantibody-positive first-degree relatives of participants in The Environmental Determinants of Diabetes (TEDDY) study or those identified as autoantibody positive in one of the following studies: The Diabetes Prediction in Skåne (DiPiS) study, the Type 1 Diabetes Prediction and Prevention (DIPP) study in Finland or in TrialNet screening. Prior to inclusion into the randomized trial, potential participants were tested with either an OGTT in the case of positivity for a single autoantibody or an IvGTT if positive for multiple autoantibodies. Data from these two visits are presented in the current study. Participants positive for a single autoantibody underwent an OGTT (time-points −10, 0, 30, 60, 90 and 120 minutes) at their first study visit to assess the beta cell function before enrolment into the randomized trial. Serum insulin and serum C-peptide were all analysed using standard assays at local Departments of Clinical Chemistry at University Hospitals in Malmö, Oulu and Turku. The reference range for HbA1c analysed was as follows: Malmö 27-42 mmol/mol, Oulu 20-42 mmol/mol and Turku 20-42 mmol/mol
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