Is β-Cell Dysfunction Present in Adult Autoantibody Negative Relatives of Individuals with Type 1 Diabetes Mellitus?

Abstract

Background/Objective: Individuals with a family history of type 1 diabetes mellitus (T1D) are at increased genetic risk for T1D. Previous studies identified the presence of β-cell dysfunction before clinical onset and diagnosis of T1D. However, it is unclear if β-cell dysfunction predates islet autoimmunity in individuals at high genetic risk. Our objective was to test β-cell function in islet antibody negative adults who have a first-degree relative with T1D. We hypothesized that individuals at genetic risk for T1D would exhibit β-cell dysfunction even without detectable islet autoimmunity.

Methods: We used ordinary one-way and Brown-Forsythe ANOVA to compare the repeated mixed meal tolerance test (MMTT) and hyperglycemic clamp glucose-stimulated β-cell response and function measures between three groups of individuals: normoglycemic adults without T1D family history age, sex, and BMI-matched islet antibody negative first-degree relatives of individuals with T1D, and islet antibody positive first-degree relatives of individuals with T1D.

Results: Neither the MMTT first-phase insulin secretion measures (c-peptide0-15 minutes, c-peptide0-30 minutes, insulin0-15 minutes, insulin0-30 minutes), nor second-phase measures (c-peptide0-120 minutes, insulin0-120 minutes, and glucose0-120 minutes) showed a statistically significant difference between groups. The clamp acute c-peptide response to glucose, insulin sensitivity, c-peptide steady state, first-phase β-cell function, and second-phase β-cell function were similar between subject groups in both visits. Fasting proinsulin:c-peptide ratios, a biomarker of β-cell stress, were also similar between participant groups.

Conclusion and Impact: Our data suggest that genetically at-risk autoantibody negative adult relatives of individuals with T1D do not demonstrate β-cell dysfunction compared to controls. Studies show that β-cell ER dysfunction preceding T1D onset is more striking in younger children. Thus, our findings may reflect the use of an adult study population. Alternatively, β-cell dysfunction in T1D may require initial autoimmune activation. This study will contribute to the growing understanding of risk factors contributing to T1D development.

This project was funded, in part, with support from the Research Training Program in Diabetes and Obesity funded, in part by grant 3T32DK064466 from the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Funding also provided by JDRF grant 2-SRA-2017-498-M-B.