98-OR: ß-Cell Dysfunction and Mitochondrial Loss Occur Independently of Insulitis in Type 1 Diabetes Pathogenesis

Introduction: Type 1 diabetes (T1D) is characterized by a period of β cell dysfunction prior to β cell death. During this time, β cells lack a first-phase insulin response and exhibit an intolerance to glucose. However, the underlying mechanisms of this dysfunction remain unclear. Here, we use live human pancreas tissue slices (LPTS) to investigate the possible mechanisms underlying β cell dysfunction in T1D.

Methods: LPTS from organ donors without diabetes (ND, n=13), donors without T1D and positive for one (sAAb⁺, n=6) or multiple T1D-relavent autoantibodies (mAAb⁺, n=2), and individuals with short-duration T1D (T1D⁺, n=9) were studied. Simultaneous time-lapse Ca²⁺ imaging and CD3⁺ T-cell tracking were conducted to assess alterations in β-cell function. Additionally, fixed pancreas sections (ND, n=8; sAAb⁺, n=7; mAAb⁺, n=7; T1D⁺, n=6) were probed with a panel of 22 antibodies to investigate mechanisms underlying β-cell dysfunction including insulin, CD3, ATP5B (a mitochondrial ATP synthase subunit), and ATPIF1 (ATP synthase inhibitor).

Results: Islets within LPTS from ND and AAb⁺ donors exhibited typical Ca²⁺ mobilization in response to high glucose (HG) and potassium chloride (KCl) stimulations. Islets from T1D⁺ donors had significantly diminished Ca²⁺ responses to HG compared to ND donors (p<0.05, one-way ANOVA). Low glucose and KCl stimulations between ND, AAb⁺, and T1D⁺donors were similar, indicating that the dysfunction occurs in the glucose metabolism pathway. Additionally, there were no significant differences in HG responses in insulitic and non-insulitic islets from T1D⁺ LPTS with both being dysfunctional. Fixed tissue staining revealed a significant (p<0.0001, two-way ANOVA) decrease in mitochondria in β cells from T1D⁺ donors.

Conclusion: The loss of HG responses in T1D⁺ β cells independent of the local T cell infiltration, coupled with the decrease in mitochondria, indicates that the dysfunction likely originates in the β cell and contributes to T1D pathogenesis.