GLP-1 receptor signaling may also support islet health by inhibiting β-cell apoptosis, promoting proliferation of β-cells, and reducing ER stress, with the net result of preserving or enhancing residual function; however, restoration of β-cell function has not been proven in human studies of islet transplantation or type 1 diabetes (145). Here, GLP1R is linked to type 1 diabetes mellitus.