Why were we wrong for so long? The pancreas of type 1 diabetic patients commonly functions for decades.

The type 1 diabetes field has held firm to the dogma that the pancreas is no longer viable, and thus incapable of producing insulin, within 1 to 2 years of diagnosis for the majority of patients. A new study in this issue of Diabetologia (DOI: 10.1007/s00125-013-3067-x ), based on a hypersensitive assay, has found detectable C-peptide, a marker of insulin production, in individuals with long-standing type 1 diabetes. This new study confirms and expands a decades-long track record of research finding intact pancreatic islet cells in advanced disease. Because the evidence, stemming back to 1902, was largely histological in nature, it was dismissed as lacking functional corroboration. This new study in patients with long-term diabetes shows appropriate functioning of pancreatic islet cells after exposure to a mixed-meal stimulus. The weight of evidence now makes it clear that a large fraction of patients with long-standing diabetes have low level, but persistent functioning of pancreatic islet cells enduring more than a decade after disease onset.