Numerous studies have shown that gut microbes and SCFAs could indirectly regulate energy homeostasis and insulin signaling, as well as low-grade inflammation, which may further influence the pathogenesis of type 2 diabetes (T2D) (Kimura et al., 2013; Qin et al., 2012; Tai, Wong & Wen, 2015). Here, INS is linked to type 2 diabetes mellitus.