In addition, studies performed in human beings also reported plasma ZAG levels to be negatively correlated with insulin levels and HOMA-IR (Ceperuelo-Mallafré et al., 2009; Yang et al., 2013), and circulating ZAG levels were lower in prediabetic and type 2 diabetes patients than in the corresponding controls (Yang et al., 2013). This evidence concerns the gene AZGP1 and type 2 diabetes mellitus.