PRESERVED PROINSULIN SECRETION IN LONG-STANDING TYPE 1 DIABETES

Area of Science:

• Endocrinology
• Immunology
• Metabolic Diseases

Background:

• Type 1 Diabetes (T1D) is characterized by autoimmune destruction of pancreatic beta cells.
• Residual beta-cell function, indicated by C-peptide microsecretion, is observed in some individuals with long-standing T1D.
• Proinsulin, a precursor to insulin, is typically measurable only in the early stages of T1D.

Purpose of the Study:

• To measure proinsulin levels in a diverse group of individuals with long-standing T1D.
• To investigate whether proinsulin secretion occurs in individuals with T1D who have undetectable C-peptide levels.

Main Methods:

• Serum proinsulin concentrations were measured in 97 participants with T1D (disease duration >3 years).
• Participants were recruited from the T1D Exchange Clinic Network as part of the Residual C-peptide Study.
• Measurements were taken from random postmeal blood samples.

Main Results:

• All 48 participants with detectable C-peptide (C-peptide [+]) had measurable serum proinsulin.
• Eight out of 49 participants with undetectable C-peptide (C-peptide [-]) also had detectable serum proinsulin (16%).

Conclusions:

• Proinsulin secretion can persist in a subset of individuals with long-standing T1D, irrespective of measurable C-peptide levels.
• The reasons for sustained proinsulin secretion in some T1D patients years after diagnosis remain unclear.