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Urinary d-lactate is highly correlated to diabetic nephropathy - a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d-lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N-acetyl-β-d-glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d-lactate was analyzed using column-switching high-performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N-acetyl-β-d-glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d-lactate to creatinine in the urine of aristolochic acid-treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d-lactate reflects renal injury conditions in aristolochic acid-treated mice and may be a marker for the assessment of nephropathy.

Methylglyoxal (MG) can cause protein glycation, resulting in cell damage and dysfunction. Accumulation of MG and its downstream metabolite Nε-(carboxyethyl)lysine (CEL) has been identified in several variations of nephropathy, including diabetic, hypertensive, and gentamicin-induced nephropathies. In this study, we investigated the effects of low-molecular-weight chitosan (lmw-chitosan) on MG-induced carbonyl stress in aristolochic acid-induced nephropathy. We used a buffer to investigate whether MG could be scavenged by lmw-chitosan in vitro. In addition, we also used a mouse model of aristolochic acid-induced nephropathy, which exhibits 12-fold greater accumulation of MG in the kidneys than that found in control animals, to examine whether lmw-chitosan could decrease MG levels in vivo. Examination of the binding of lmw-chitosan with MG in vitro demonstrated that the concentration of lmw-chitosan necessary to achieve 50% inhibition was 4.60 µg mL−1. Treatment with lmw-chitosan (500 mg kg−1 day−1 orally) for 14 days significantly decreased renal MG accumulation from 212.86 ± 24.34 to 86.15 ± 33.79 µg g−1 protein (p < 0.05) and CEL levels from 4.60 ± 0.27 to 2.84 ± 0.28 µmol µg−1 protein (p < 0.05) in the aristolochic acid-induced nephropathy model. These data suggest that lmw-chitosan might represent a novel treatment modality for MG-related diseases such as nephropathy.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-1106-4) contains supplementary material, which is available to authorized users.

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