Figure 1.

β cell secretory capacity data from an individual with adult-onset T1D, initially diagnosed with T2D and at the time of glucose-potentiated arginine testing before initiating insulin therapy. Under fasting conditions, the acute insulin (A) or C-peptide (B) response to arginine appear “normal” (although not when considering the fasting glucose was elevated at 162.5 mg/dL (not shown)), and further elevation of the glucose cannot further potentiate insulin release as the entire reserve capacity for secretion (~15% of normal) is already engaged under the fasting condition. The normal data are 95% CI based on 28 nondiabetic individuals.