Increased plasma levels of D-amino were shown in a study to predict the risk of disease progression in chronic kidney disease (CKD) patients. The data from the Japanese study, which enrolled 108 CKD patients who were followed up for about four years, was published in the journal Scientific Reports.
Most amino acids, the building units of proteins, may occur in two structural forms: L-amino acids and D-amino acids. Although in life systems there is a preference for L-forms, trace amounts of several D-amino acids have been detected in human tissues and fluids.
Previous studies had already pointed to the potential relationship between the amounts of D-amino acids and kidney function.
In the study “Chiral amino acid metabolomics for novel biomarker screening in the prognosis of chronic kidney disease,” led by Japan’s Osaka University researchers, D-amino acids were investigated as possible biomarkers for chronic kidney disease, a disease that has been estimated to affect about 10 percent of the Japanese population.
Researchers used two-dimensional high-performance liquid chromatography (2D-HPLC) to separate and identify 16 D-amino acids in the plasma of a cohort of advanced CKD patients. They found that higher levels of D-Asparagine and D-Serine were associated with increased risk of disease progression and kidney failure, from two to four times.
“With accurate 2D-HPLC-based analytical platform and the longitudinal information, we demonstrated that the increased levels of D-amino acids were associated with worse prognoses of CKD patients,” the authors wrote in their study. “The present 2D-HPLC-based analytical platform will provide the strong technical basis for further chiral amino acid metabolomics.”
Normal kidney function may play an essential role to maintain low levels of D-amino acids in the blood, which could explain the higher levels observed in chronic kidney disease patients. In addition, D-Serine increases in the spinal fluid of patients with neurological diseases, suggesting that in CKD patients it may be associated with cognitive disability.
Researchers believe that D-amino acids levels, measured in the plasma by 2D-HPLC, may work as possible disease biomarkers, improving the prognosis and treatment of CKD patients.