In particular, the branched-chain amino acids (BCAAs) leucine, isoleucine and valine are essential amino acids synthesized by gut bacteria (Amorim Franco and Blanchard, 2017) and are associated with insulin resistance (Newgard et al., 2009) and increased risk of type 2 diabetes (Lotta et al., 2016). Here, INS is linked to type 2 diabetes mellitus.