Dipeptidyl peptidase-4 (DPP-4) inhibitors such as
vildagliptin and sitagliptin are generally well tolerated, and
are approved for use in patients with severe RI. Owing to their
glucose-dependent mechanism of action, they are generally
associated with a low risk of hypoglycaemia and are an attractive
treatment option for these difficult-to-treat patients [7].
All DPP-4 inhibitors improve glycaemic control by extending
the meal-induced increases in glucagon-like peptide-1 (GLP-
1) and glucose-dependent insulinotropic polypeptide (GIP)
for several hours by slowing the rate of inactivation of these
peptides. There are differences in the mechanisms of action of
DPP-4 inhibitors, in particular their catalytic binding kinetics
[8], which may translate into clinical differences. For example,
vildagliptin blocks DPP-4 through substrate-like binding
to the active site of the enzyme for an extended time [8]. By
contrast, sitagliptin exerts its effect through competitive enzyme
inhibition [8, 9]. Only vildagliptin has been shown to
block the inactivation of GLP-1 and GIP between meals and
overnight [8, 9]. However, there are limited data comparing
the various agents directly