Homoarginine test for evaluation of metabolic renal dysfunction

Low plasma L-homoarginine (hArg) concentration is an independent predictor of adverse cardiovascular outcomes and overall mortality, as well as the progression of chronic kidney disease (CKD). The enzyme L-arginine:glycinamidinotransferase (AGAT, EC 2.1.4.1) acts in the mitochondrial membrane of the renal tubular epithelium, forming the precursor of creatine, guanidinoacetic acid, and additionnaly by-product hArg. As it was shown recently, there is a decreased level of hArg in the late stages of CKD, however, the the level of hArg in the early stages of CKD remained unexplored. The aim of this study was to determine the diagnostic threshold levels of hArg in the blood of patients with stages 1 and 2 of CKD. In patients with the initial stages of CKD (n = 44) at the age of 58 (45-67) years, compared with the group of donors of 55 (42-58) years (n = 30), a significant decrease of hArg level was found. In the subgroup with stage CKD 2, the cut-off point of 1.59 μM threshold was characterized by greater sensitivity and specificity than in the subgroup with stage CKD 1 with 1.66 μM threshold level of hArg. For the full group, the hArg cut-off threshold was 1.60 μM, which is about to 0.2 μM lower than the lower limit of the reference interval for healthy individuals. It can be assumed that even before the formation of symptoms of proteinuria and albuminuria, a significant part of individuals from population cohort develops a state of decreased AGAT activity, since the expression of this enzyme is associated with a certain regulatory feedback inhibition at the body level. As a result of the study, it can be noted that in patients with early stages of CKD in the age group 45-67 years, there is a disturbance of the kidneys metabolic function. These metabolic changes can be detected by testing the level of hArg.