The aldose reductase inhibitor epalrestat exerts nephritic protection on diabetic nephropathy in db/db mice through metabolic modulation.

Epalrestat is an inhibitor of aldose reductase in the polyol pathway and is used for the management of diabetic neuropathy clinically. Our pilot experiments and accumulated evidences showed that epalrestat inhibited polyol pathway and reduced sorbitol production, and suggested the potential renal protection effects of epalrestat on diabetic nephropathy (DN). To evaluate the protective effect of epalrestat, the db/db mice were used and exposed to epalrestat for 8 weeks, both the physiopathological condition and function of kidney were examined. For the first time, we showed that epalrestat markedly reduced albuminuria and alleviated the podocyte foot process fusion and interstitial fibrosis of db/db mice. Metabolomics was employed, and metabolites in the plasma, renal cortex, and urine were profiled using a gas chromatography-mass spectrometry (GC/MS)-based metabolomic platform. We observed an elevation of sorbitol and fructose, and a decrease of myo-inositol in the renal cortex of db/db mice. Epalrestat reversed the renal accumulation of the polyol pathway metabolites of sorbitol and fructose, and increased myo-inositol level. Moreover, the upregulation of aldose reductase, fibronectin, collagen III, and TGF-ß1 in renal cortex of db/db mice was downregulated by epalrestat. The data suggested that epalrestat has protective effects on DN, and the inhibition of aldose reductase and the modulation of polyol pathway in nephritic cells be a potentially therapeutic strategy for DN.

Application of liquid chromatography-tandem mass spectrometry to study the effect of docetaxel on pharmacokinetics and tissue distribution of apatinib in mice.

Apatinib, a highly selective small-molecule inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2), has attracted many attentions due to its anticancer activity in various malignancies containing non-small-cell lung cancer (NSCLC). Our previous preclinical study confirmed the enhanced anti-tumor efficacy of combined treatment between apatinib and docetaxel for NSCLC. However, the effects of docetaxel on pharmacokinetics and tissue distribution of apatinib are not clear. In present study, a reliable HPLC-MS/MS method was established for determination of apatinib. This method had a good linearity in the range of 1-5000 ng/mL, and the recovery and matrix effect were 100.1-103.5%, 77.6-83.5%, respectively. Plasma exposure level of apatinib and the values of Cmax, AUC0-12h, T1/2, and MRT were not affected by multi-dose of docetaxel. The tissue distributions (kidney, heart, lung, spleen) of apatinib in combined treatment group were lower at 0.25 h but higher at 2 h, and that in intestine and liver were not significantly changed compared with control group. However, pre-treatment with docetaxel had no significant effect on AUC0-4h of apatinib in tissues in mice. In conclusion, plasma and tissues exposure levels of apatinib were not affected by long-termed treatment with docetaxel, indicating that docetaxel is less likely to increase the side effect of apatinib such as hypertension, hand-foot syndrome and so on.

Quantitative GC-MS assay of citric acid from humans and db/db mice blood serum to assist the diagnosis of diabetic nephropathy.

The early diagnosis of diabetic nephropathy (DN) is rather challenging. Our previous study suggested that citric acid is a potential marker for the early diagnosis of diabetic nephropathy in db/db mice. For the first time, in this study, a surrogate analyte of 13C6-citric acid was employed to generate calibration curves for the quantitative measurement of the endogenous citric acid in the sera of db/db mice and diabetic nephropathy patients by GC/MS after the analytes were extracted, methoximated and trimethylsilylated. The constant response factor of 13C6-citric acid versus citric acid over the linear range indicated the identical ionization efficiency of these two compounds. The full validation assessments suggested that the method is sensitive, specific, reliable, reproducible and has acceptable parameters. Statistical analysis revealed cut-off citric acid concentrations of 29.24 µg/mL with a 95% confidence interval between 32.75 and 39.16 µg/mL in the diabetic nephropathy patients and 16.74 and 22.57 µg/mL in the normal controls. The areas under the receiver operating characteristic curves indicated accuracies of over 90% for the diagnoses of early diabetic nephropathy in both humans and db/db mice, which suggests that the serum citric acid level is potentially a biomarker that could assist in the diagnosis of diabetic nephropathy.

Sensitive analysis and pharmacokinetic study of epalrestat in C57BL/6J mice.

Epalrestat is clinically applied for the management of diabetic peripheral neuropathy, yet its pharmacokinetic properties are not well understood. In this study, a rapid and sensitive LC-MS/MS method was established for assaying epalrestat in bio-samples of mice. The method was validated and it showed a good linearity over the range of 2-5000ng/mL, a precision of less than 12.3%, and recovery and matrix effects of 112.5-123.6% and 87.9-89.5%, respectively. After administration of a single dose of epalrestat administered, the exposure level of AUC0-∞ was positively dose-dependent and the mean Cmax, AUC0-12h, T1/2, and MRT were 36.23±7.39µg/mL, 29,086.5µg/Lh, 1.2h and 1.8h, respectively. Epalrestat was highly exposed in stomach, intestine, liver and kidney, and only a small amount was detected in brain, urine and feces. Multi-dose of epalrestat significantly increased MRT and apparent volume of distribution (Vd) relative to those of a single-dose.