Although GLP-1-based drugs were shown to ameliorate T2D (Wang and Brubaker, 2002; Buteau et al., 2003), they showed very marginal therapeutic effects for T1D subjects in both humans and rodent models, possibly due to their restricted immune regulatory effects (Hadjiyanni et al., 2008; Pettus et al., 2013; Wan et al., 2015). Here, GCG is linked to type 1 diabetes mellitus.