Sleep-Awake Profile Related Circadian D-Alanine Rhythm in Human Serum and Urine

Abstract

The circadian profiles of D-alanine (Ala) amounts in human serum and urine have been clarified using a two-dimensional HPLC system combining a microbore reversed-phase C18 column and a Pirkle-type enantioselective column. The two-dimensional HPLC system enables the determination of trace amounts of D-Ala in the clinical samples without severe interference from intrinsic substances in the human physiological fluids. In the volunteers having normal sleep-awake patterns, the amounts of D-Ala in the serum were high in the late evening and low in the morning. On the other hand, in the volunteers having the reversed sleep-awake patterns, the amounts of D-Ala in the serum were high in the morning and low in the nighttime. The similar circadian changes of D-Ala amounts were observed in the urine. These 24-h profiles of D-Ala are almost the same as those observed in rats and mice, suggesting that D-Ala has fundamental physiological functions related to rest-active conditions in mammals, and could also be useful as the biomarker for sleep-awake profiles.

Enantioselective and simultaneous determination of lactate and 3‐hydroxybutyrate in human plasma and urine using a narrow‐bore online two‐dimensional high‐performance liquid chromatography system

“…Therefore, in many studies, the sense of enantiomer discrimination is missing. Recently, the chiral separations of amino acids have been widely discussed because the minor D enantiomers were found in mammals, including humans, and clarified to have various functions and diagnostic values [13][14][15][16][17]. For instance, D-Ser mediates the neurotransmission [18,19] and D-Asp regulates the endocrine systems [20][21][22].…”

Multi-Dimensional High-Performance Liquid Chromatographic Determination of Chiral Amino Acids and Related Compounds in Real World Samples

“…10B). These circadian changes are also observed in mice [18] and humans [19], suggesting that D-Ala has some universal functions in mammals. In order to clarify the biological significance of D-Ala in the pituitary gland and in the pancreas, the cellular localization of D-Ala in these tissues has been examined.…”

Development of a Three-Dimensional HPLC System for the Simultaneous Determination of Lactate and 3-Hydroxybutyrate Enantiomers in Mammalian Urine

“…In the past 10-20 years, various researchers have developed 2D-HPLC systems for the chiral analyses of trace levels of intrinsic compounds in order to obtain high sensitivity and high selectivity. Actually, a large number of reports using 2D-HPLC was published for the trace analysis of enantiomers including amino acids [40][41][42][43][44], dipeptides [45] and hydroxy acids [32,34,35,38,39]. Concerning the hydroxy acids, 2D-HPLC methods for the LA and 3HB enantiomers have been reported including heart-cutting 2D-HPLC [32,34,35] and whole-fraction transfer 2D-HPLC [38,39].…”