GCG and diabetes mellitus: Increased post-prandial GLP-1 levels have been implicated as the causal factor for improved glucose homeostasis and remission of diabetes following RYGB (Lindqvist et al., 2013), but it is notable that the beneficial effects of surgery persist in mice lacking GLP-1 and its receptor (Mokadem et al., 2014, Ye et al., 2014).