1921-2021: From insulin discovery to islet transplantation in type 1 diabetes.

One century after the discovery of insulin, the French Health regulations have just authorized the reimbursement for islet transplantation. Intraportal islet allotransplantation from a pancreatic donor is indicated in patients with type 1 diabetes (T1D) complicated with lability or hypoglycemia unawareness, or in case of a functioning kidney graft; islet auto-transplantation may be indicated after pancreatic surgery.Compared with insulin even administered in closed-loop pumps, the specificity of islet allotransplantation is the restoration of C-peptide secretion. Long-term insulin-independence is observed when the engrafted islet mass is sufficient, at the cost of immunosuppression. Fewer low-glucose events and less glucose variability, are observed even with minimal functional islet graft, after islet transplantation as at onset of T1D, when a residual C-peptide secretion is maintained, an objective currently approached with less aggressive immuno-modulating therapies than in the past. Therefore, restoration or preservation of endogen insulin secretion is an important goal, allowing to maintain a long-term glucose balance with more than 70% of time in range 3.9-10mmol/L and less than 3% of time <3.9mmol/L, thus reducing the occurrence of diabetic complications. In the clinical setting, - the preservation of C-peptide at early stage of T1D, - the use of technological ressources (multi-injections, sensors, insulin pump, closed-loop systems) at later stages, - and islet transplantation when hypoglycemia awareness becomes impaired are complementary for a personalized care all along the life of T1D patients.