GATM and diabetes mellitus: Among these, homo-L-arginine, a naturally occurring, non-proteinogenic, cationic amino acid catalyzed by the liver via glycine amidinotransferase (AGAT); an enzyme from the creatine biosynthesis pathway (60) is known to exert protective roles on the endothelial function and energy metabolic processes in different organs. However, its low levels have been attributed to diabetes, kidney diseases, and to cardiovascular diseases with high mortality rates (60–62).