Asymmetric dimethylarginine(ADMA)and its enantiomer,symmetric dimethylarginine(SDMA),are naturally-occurring methylated metabolites of the L-arginine amino acid moiety of proteins followed by proteolysis(Grosse et al.,2020).These metabolites were first identified in human urine in 1970.At present,several other L-arginine metabolic products are known to occur naturally and invoke their distinct biological effects in health and disease.