GCG and type 1 diabetes mellitus: Subject 4 who had T1D 3 years at the time of the study, retained normal β-cell function with no significant change over time in fasting C-peptide levels from 1.05 ng/ml at baseline to 0.88 ng/ml at 40 weeks and in glucagon-stimulated C-peptide levels from 2.18 ng/ml at baseline to 2.01 ng/ml at 40 weeks (Fig. 6d).