GCG and diabetes mellitus: These suggestions came from few preclinical studies [212–214], which are basically inconclusive because the histological changes are not reproduced in all studies and vary between different GLP-1-based therapies and from very limited clinical data [215, 216], namely, observational studies [217–221], and from pancreases from organ donors with and without diabetes [222], which have limited value to conclude the issue, as commented by Ryder (2013) [223].