Author Contributions. P.L. enrolled patients, performed clamps, analyzed data, and reviewed and edited the manuscript. F.P. enrolled patients, performed clamps, and reviewed and edited the manuscript. A.M.A., I.C., and P.Ci. performed clamps and reviewed and edited the manuscript. P.Ca. performed clamps and laboratory assays and reviewed and edited the manuscript. G.B.B. provided the study concept and design, supervised the protocol development and research, and wrote the manuscript. C.G.F. performed clamps, analyzed data, performed the statistical analysis, and reviewed and edited the manuscript. P.L. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Prior Presentation. Parts of this study were presented in poster form at the 74th Scientific Sessions of the American Diabetes Association, San Francisco, CA, 13–17 June 2014.