Beta cell dysfunction occurs independently of insulitis in type 1 diabetes pathogenesis

Area of Science:

• Endocrinology
• Immunology
• Cell Biology

Background:

• Type 1 diabetes (T1D) involves immune-mediated beta cell destruction, leading to insulin deficiency.
• However, significant beta cell mass often remains at T1D onset, with sporadic T cell infiltration of islets.

Purpose of the Study:

• To investigate the functional status of remaining beta cells in human pancreas tissue from recently diagnosed T1D donors.
• To determine if beta cell dysfunction is linked to T cell infiltration or is an intrinsic defect.

Main Methods:

• Utilized live human pancreas tissue slices from organ donors with recent-onset T1D.
• Assessed beta cell function via glucose-stimulated calcium (Ca2+) mobilization and insulin secretion.
• Performed fixed tissue staining and gene expression profiling of laser-capture microdissected islets.

Main Results:

• Beta cells from T1D donors exhibited significantly reduced Ca2+ mobilization and insulin secretion in response to glucose.
• Impaired beta cell function was observed in both T cell-infiltrated and non-infiltrated islets.
• Decreased expression of proteins and genes involved in glucose-stimulated insulin secretion pathway was identified.

Conclusions:

• Remaining beta cells in human T1D are largely dysfunctional, independent of T cell infiltration.
• Functional defects in the glucose stimulus-secretion coupling pathway contribute to beta cell impairment in T1D pathogenesis.