+Metformin: Metformin in combination; GKAs: Glucokinase Activator drugs; Y/N: YES/NO; mg·d^-1: mg·day^-1; QD: once a day; BID: twice a day. The included references: Meininger et al. 2011; Wilding et al.2013; Zhang et al.2013; Amin et al.2015; Zhi et al.2016; Zhu et al.2018; Vella et al.2019.