Chiral resolution of plasma amino acids reveals enantiomer-selective associations with organ functions

Blood levels of d-amino acids reflect the clinical course of COVID-19

“…This study reveals the characteristic dynamics of d- amino acids during recovery. Although the blood d- alanine level shows a fluctuation with circadian rhythm [ 19 ] and the blood d -amino acid levels increase with the worsening of kidney function [ 10 , 11 , 14 , 20 ], the variations in the levels of d- amino acids observed in this study reflects pathological conditions of infectious diseases rather than the circadian rhythm or loss of kidney function, as we avoided the intra-day variation when harvesting the blood samples.…”

D-Asparagine is an Ideal Endogenous Molecule for Measuring the Glomerular Filtration Rate

“… 9 It has been reported as a biomarker of kidney function. 13 , 14 , 21 A trace amount of d -asparagine was detected in human blood, and the blood level of d -asparagine correlated with eGFR and predicted the worst prognosis of CKD. 13 Despite its low presence in the blood, d -asparagine is relatively abundant in urine.…”

Astrocytic d‐amino acid oxidase degrades d‐serine in the hindbrain

“…Indeed, germ-free mice show extremely low levels of urinary D-alanine [21] and inoculation of bacteria in germ-free animals restores urinary D-alanine to a high level [20]. Recently, we found that symbiotic microbes produce a variety of D-amino acids [22,37], and that DAO in the kidney or small intestine may degrade exogenous Damino acids to sustain L-amino acid dominance in the human body [39].…”

“…D-and L-Amino acids in tissues and body fluids were quantified using a two-dimensional HPLC system, as previously described [38,39] with modifications. Briefly, 25 lL of plasma was mixed with 25 lL of distilled or deionized water and 450 lL of methanol (Fujifilm-Wako Pure Chemical, Osaka, Japan) and vortexed for 2 min.…”