D-Amino acids, long-term undetected enantiomers of L-amino acids, are now emerging as potential biomarkers, especially for kidney diseases. Management of chronic kidney disease (CKD), a global problem with its high prevalence and poor prognosis, is currently unsatisfactory due to the difficulty in estimating kidney function and in early detection of diseases. We now show that intra-body dynamics of D-serine reflect kidney function and diseases. The blood level of D-serine correlated well with the actual glomerular filtration ratio, a key kidney function. This correlation was compatible with those of conventional kidney markers, and blood level of D-serine was relatively unaffected by such clinical factors as body size. The balance between excretion and reabsorption of amino acids by the kidney was controlled with chiral selectivity, and the reabsorption of D-serine was sensitive to the presence of CKD. The combination of blood level and urinary dynamics of D-serine effectively distinguished CKD from non-CKD. These lines of evidence provide new insights into the enantioselective amino acid dynamics in the human body that reflect disease pathophysiology. D-Serine may serve as a vital biomarker that suppress CKD onset through the precise assessment of kidney function and the diagnosis of CKD.

We experienced a case of a 36-year-old female with rapidly progressive glomerulonephritis (RPGN) due to anti-neutrophil cytoplasmic antibody (ANCA)-associated nephritis and systemic lupus erythematosus (SLE) nephritis. Chiral amino acid metabolomics revealed a prominent profile of d-serine in this patient. At the fulminant period of RPGN, the level of plasma d-serine, a potential biomarker in CKD that reflects actual glomerular filtration ratio (GFR), was extremely high. On the other hand, urinary fractional excretion (FE) of d-serine, which was usually much higher than that of l-isoform, was 0% in this patient. These abnormal d-serine profiles normalized in response to the intensive treatment. Normalizations of blood d-serine levels were in parallel with those of blood creatinine levels and potentially reflect the recovery of GFR. FE of d-serine increased transiently before the normalization of d-serine profile, suggesting that kidney promotes urinary excretion of d-serine for the normalization of plasma d-serine level. These unexplored clinical features of d-serine well reflected the clinical course of this patient. Blood d-serine level can also serve as a biomarker in acute kidney injury (AKI) or RPGN, and, in combination with FE of d-serine, may render the clinical practitioners to judge the efficacy of intensive treatments.Electronic supplementary materialThe online version of this article (10.1007/s13730-019-00411-6) contains supplementary material, which is available to authorized users.

Orally disintegrating tablets (ODTs) containing propiverine hydrochloride (which is extremely bitter and leaves a feeling of numbness in the mouth) were prepared with a combined use of physical and organoleptic taste masking. Propiverine-loaded masking particles (PLMPs) were prepared with different amounts of gastric-soluble coatings as physical masking. ODTs without organoleptic masking were prepared by mixing each group of PLMPs with Ludiflash ® , crospovidone, and magnesium stearate. ODTs with organoleptic masking were also prepared by addition of L-menthol, aspartame, thaumatin, and cinnamon. Fifteen-minute dissolution of propiverine in solutions with pH 1.2 was ≥85% for all ODTs, whereas that in pH 6.8 solutions was ≤85% and increased with physical masking. A single blind randomized crossover trial was conducted. Ten healthy volunteers were asked to quantify the bitterness, numbness, and overall palatability using a 100-mm visual analog scale (VAS) at the period of disintegration as well as 1 and 5 min later. VAS scores of bitterness, numbness, and overall palatability improved along with increasing amounts of physical masking, and the effects persisted for 5 min. VAS scores for numbness increased over time regardless of the amount of physical masking. Bitterness, numbness, and overall palatability were significantly improved by organoleptic masking if the amount of physical masking was small. Combined use of physical and organoleptic masking is useful for improving palatability of ODTs containing propiverine.

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In vitro permeation of lidocaine (lidocaine base, LID) through excised rat skin was investigated using several LID-suspended oily formulations. The first skin permeation of LID from an LID-suspended oily solution such as liquid paraffin (LP), isopropyl myristate (IPM), polyoxyethylene (2) oleylether (BO-2), and diethyl sebacate (DES) was evaluated and compared with that from polyethylene glycol 400 (PEG400) solution, a hydrophilic base. The obtained permeation rate of LID, Japp, from PEG400, LP, IPM, BO-2, and DES was in the order of DES>BO-2=IPM>LP>PEG400, and increased with LID solubility in the oily solvents, although LID crystals were dispersed in all solvents. Subsequently, oily formulations that consisted of different ratios of the first oily solvent (IPM, BO-2, or DES) (each 0-20%), the second oily solvent (LP) and an oily mixture of microcrystalline wax/white petrolatum/paraffin (1/5/4) were evaluated. BO-2 groups at a concentration of 5% and 10% had the highest Japp among the oily formulations, although a higher BO-2 resulted in lower skin permeation. In addition, pretreatment with BO-2 increased the skin permeation of LID. These results suggest that the penetration enhancing effect by the system may be related to the skin penetration of BO-2 itself. Finally, mathematical analysis was done to evaluate the effect of BO-2, and it was shown that BO-2 improved the LID solubility in stratum corneum lipids to efficiently enhance the LID permeation through skin.