Metabolomic studies of mice and humans have identified many plasma metabolite signatures in addition to HbA1C and insulin that are associated with the development and progression of T2D, such as high serum concentrations of FFAs, triglycerides, ketone bodies, leptin, and pro-inflammatory cytokines such as Mcp-1 and a low serum concentration of adiponectin [[101], [102], [103], [104], [105], [106], [107]]. Here, LEP is linked to type 2 diabetes mellitus.