INS and type 2 diabetes mellitus: Numerous studies employing metabolite profiling in insulin-resistant humans or patients with type 2 diabetes (fasting plasma) have identified predominantly amino acids such as the BCAA and their degradation products (Newgard et al. 2009), glycine, citrulline and proline but also aminoadipic acid from lysine degradation as marker metabolites (Menni et al. 2013).