Jinyi Zhao

Pharmacogenetic Variation and Metformin Response

Diabetes is a major health problem worldwide, and metformin, a traditional oral anti-hyperglycemic drug, is now believed to be the most widely prescribed antidiabetic drug. Metformin acts primarily by inhibiting hepatic glucose production and improving insulin sensitivity. Metformin is absorbed predominately by the small intestine and excreted in an unaltered form in the urine. The pharmacokinetics of metformin is primarily determined by membrane transporters, including the plasma membrane monoamine transporter (PMAT), the organic cation transporters (OCTs), the multidrug and toxin extrusion (MATE) transporters, and the critical protein kinase AMPactivated protein kinase (AMPK). PMAT may play a role in the uptake of metformin from the gastrointestinal tract, while OCTs mediate the intestinal absorption, hepatic uptake, and renal excretion of metformin. MATEs are believed to contribute to the hepatic and renal excretion of the drug. The pharmacologic effects of metformin are primarily exerted in the liver, at least partly via the activation of AMPK and the subsequent inhibition of gluconeogenesis. A considerable amount of pharmacogenetic research has demonstrated that genetic variation is one of the major factors affecting metformin response. Moreover, it has become increasingly clear that membrane transporters are important determinants of the pharmacokinetics of metformin. In this review, we will discuss the genetic variants of major transporters that purportedly determine the pharmacokinetics of metformin in terms of drug bioavailability, distribution, and excretion, such as PMAT, OCTs, and MATEs. Understanding how genetic variation affects metformin response will help promote more effective use of the drug for the treatment of type 2 diabetes (T2D).

miR-592/WSB1/HIF-1α axis inhibits glycolytic metabolism to decrease hepatocellular carcinoma growth

Hepatocellular carcinoma (HCC) cells rapidly switch their energy source from oxidative phosphorylation to glycolytic metabolism in order to efficiently proliferate. However, the molecular mechanisms responsible for this switch remain unclear. In this study, we found that miR-592 was frequently downregulated in human HCC tissues and cell lines, and its downregulation was closely correlated with aggressive clinicopathological features and poor prognosis of HCC patients. Overexpression of miR-592 inhibited aerobic glycolysis and proliferation in HCC cells in vitro. Conversely, knockdown of miR-592 promoted HCC growth in both subcutaneous injection and orthotopic liver tumor implantation models in vivo. Mechanistically, miR-592 downregulation in human HCCs was correlated with an upregulation of WD repeat and SOCS box containing 1 (WSB1). We further showed that miR-592 directly binds to the 3′-UTR of the WSB1 gene, thus disrupting hypoxia inducible factor-1α (HIF-1α) protein stabilization. In turn, overexpression of WSB1 in HCC cells rescued decreased HIF-1α expression, glucose uptake, and HCC growth induced by miR-592. Collectively, our clinical data and functional studies suggest that miR-592 is a new robust inhibitor of the Warburg effect and a promising therapeutic target for HCC treatment.

Brazilin exerts protective effects against renal ischemia-reperfusion injury by inhibiting the NF-κB signaling pathway

Renal ischemia-reperfusion (I/R) injury is associated with high morbidity and mortality as there is currently no available effective therapeutic strategy with which to treat this injury. Thus, the aim of this study was to investigate the potential protective effects of brazilin, a major active component of the Chinese medicine Caesalpinia sappan L., against renal I/R injury in vitro and in vivo. Rats were subjected to removal of the right kidney and I/R injury to the left kidney (ischemia for 45 min followed by reperfusion for 24 h). Treatment with brazilin (30 mg/kg, administered intravenously at 30 min prior to ischemia) led to the reversal of I/R-induced changes in serum creatinine (Scr) and blood urea nitrogen (BUN) levels, and also attenuated the histopathological damage induced by I/R. Furthermore, TUNEL assay revealed that brazilin reduced cell necrosis, and significantly decreased the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in renal tissue. Moreover, HK-2 cells were used in order to elucidate the mechanisms responsible for the protective effects of brazilin. The levels of phosphorylated IκBα and the nuclear translocation of nuclear factor-κB (NF-κB) were all evidently decreased by brazilin. These findings suggested that pre-treatment with brazilin protects against I/R-induced renal damage and suppresses the inflammatory response by inhibiting the activation of the NF-κB signaling pathway.

Synergistic efficacy of meropenem and rifampicin in a murine model of sepsis caused by multidrug-resistant Acinetobacter baumannii

Multidrug-resistant Acinetobacter baumannii becomes an increasing challenge due to the overuse of antibiotics. Combination therapies are considered as effective options to overcome this matter. The present study was to investigate the synergistic activity of meropenem combined with other antibiotics in vitro and in vivo. Checkerboard assay and time-kill assay were performed to study the combination effects in vitro. For the animal model, a murine sepsis model injected with inoculums intraperitoneally was used. Susceptibility test showed that all the twelve strains in this study were resistant to most of the antibiotics except rifampicin. In combination, meropenem plus rifampicin exhibited synergistic activity against six of twelve strains. In the sepsis model, meropenem monotherapy had no therapeutic effect in this model while it can enhance the activity of rifampicin in both survival rate and bacterial clearance from blood. Moreover, combination therapy significantly reduced plasma IL-6 levels compared with rifampicin monotherapy. Pharmacokinetic analysis of rifampicin was also performed in this study. These data above showed that there was synergistic activity between meropenem and rifampicin against multidrug-resistant Acinetobacter baumannii both in vitro and for experimental model of sepsis. It suggested that combining meropenem with rifampicin may be appropriate in treating multidrug-resistant Acinetobacter baumannii infections.

Application of a liquid chromatographic/tandem mass spectrometric method to a urinary excretion study of rabeprazole and two of its metabolites in healthy human urine

To study urinary excretion properties of rabeprazole and two of its metabolites, i.e. rabeprazole thioether and desmethyl rabeprazole thioether in human urine, a sensitive, selective, accurate and precise method for the quantification of rabeprazole and two of its metabolites using a liquid chromatographic/tandem mass spectrometric method has been developed and validated. Starting with a 200 μL urine aliquot, a general sample preparation was performed using protein precipitation with methanol. Analytes were separated on a Dikma Inspire™ C18 column (150 mm × 2.1mm, 5 μm) using a mixture of methanol and aqueous 10mM ammonium acetate buffer containing 0.05% formic acid (55:45, v/v) as mobile phase. Linearity was obtained over the concentration range of 0.1446-96.38 ng/mL, 0.3198-319.8 ng/mL and 0.05160-82.53 ng/mL for rabeprazole, rabeprazole thioether, desmethyl rabeprazole thioether in human urine, respectively. The fully validated method was applied to a urine excretion study of rabeprazole sodium administered as a 30 min intravenous infusion for the first time. The calculated cumulative urinary recovery just reached 0.04745‰, 1.272‰ and 0.1631‰ of dose within 24h post-dose for rabeprazole, rabeprazole thioether, and desmethyl rabeprazole thioether, respectively, after intravenous infusion administration, indicating that rabeprazole and its two main metabolites undergo substantial non-renal elimination in healthy Chinese volunteers.

High performance liquid chromatographic method for the determination of cinepazide maleate and its application to a pharmacokinetic study in rats.

A simple and reliable high performance liquid chromatographic (HPLC) method has been developed and validated to quantify cinepazide maleate, a calcium blocker, in rat plasma. Cinepazide maleate and Tinidazole (internal standard) have been extracted by a simple liquid-liquid extraction before injection into chromatographic system. Chromatographic separation was achieved on a reversed phase C18 column with a mobile phase consisted of a water mixture of 10mM potassium dihydrogen phosphate (pH=4.5):methanol (40:60, v/v), pumped at flow rate of 1.0mL/min, and detected at 303nm. The method exhibited a linear range of 0.12-120μg/mL in blank rat plasma, with the lower detection limit of 0.06μg/mL. The method was statistically validated for linearity, accuracy, precision, selectivity and stability following FDA guidelines. The intra- and inter-assay coefficients of variation did not exceed ±15% from the nominal concentration. The accuracy of cinepazide maleate was within ±15% of the theoretical value. The assay has been applied successfully in a pharmacokinetic study of cinepazide maleate after a single intravenous at three doses in rat. And cinepazide maleate injection can improve the bioavailability of cinepazide maleate greatly, and has a dose-dependence profile in rats.

Impact on L-carnitine Homeostasis of Short-term Treatment with the Pivalate Prodrug Tenofovir Dipivoxil

Pivalate‐generating prodrugs have been suggested to cause clinically significant hypocarnitinaemia. Tenofovir dipivoxil, a novel ester prodrug of tenofovir, can be used for treatment for hepatitis B and HIV infection and it was necessary to evaluate the effect of its treatment on carnitine homeostasis. We sought to investigate the effect of Class 1 drug tenofovir dipivoxil on endogenous L‐carnitine level during a 72‐hr test in healthy Chinese volunteers and to establish a suitable dose of L‐carnitine nutritional supplement for patients who were administered short‐term tenofovir dipivoxil tablets for treatment for hepatitis B and herpes simplex virus infection. Tenofovir dipivoxil was administered in one of eight dosing regimens (single dose 150, 300 and 600 mg, multiple dose 300, 450, and 600 mg, multiple dose 450 (600) mg tenofovir dipivoxil and 0.5 g L‐carnitine) to gender‐balanced groups of 84 healthy Chinese volunteers. Plasma concentrations of L‐carnitine were quantified before, during and after treatment. Plasma L‐carnitine concentrations fell during tenofovir dipivoxil dosing. The nadir in L‐carnitine concentration was dependent on the dose of tenofovir dipivoxil and it decreased from 6.1 ± 0.6 to 4.4 ± 0.8 μg/ml, 6.1 ± 1.8 to 3.3 ± 1.2 μg/ml, 6.2 ± 0.6 to 2.5 ± 0.5 μg/ml for single doses of 150, 300, 600 mg tenofovir dipivoxil tablets and from 6.0 ± 1.4 to 2.1 ± 1.5 μg/ml, 6.2 ± 0.4 to 0.9 ± 0.5 μg/ml for multiple doses of 450, 600 mg tenofovir dipivoxil tablets, respectively. Short‐term administration of tenofovir dipivoxil results in hypocarnitinaemia and increased losses of carnitine in resulting of minor adverse events of decreased food appetite, nausea, abdominal distention and muscle weakness.

Protective effect of hydroxysafflor yellow A against acute kidney injury via the TLR4/NF-κB signaling pathway

This study aimed to evaluate the protective effect of hydroxysafflor yellow A (HSYA) on ischemia/reperfusion (I/R)-induced acute kidney injury via the TLR4/NF-κB pathway, both in vitro and in vivo. Rats were subjected to removal of the right kidney and I/R injury to the left kidney. Rats subjected to renal I/R injury were treated with HSYA at 0.5 h prior to I/R injury. Renal function, histopathological analysis, and cells apoptosis were measured in vivo. In vitro, proximal renal tubular cells (HK-2) were subjected to hypoxia/reoxygenation (H/R). Apoptotic cell death and inflammatory cytokines, Toll-like receptor 4 (TLR4), and nuclear factor (NF)-κB expression were determined. Treatment of I/R rats with HSYA markedly reduced the levels of serum creatinine and blood urea nitrogen, attenuated renal cell apoptosis, alleviated changes in renal tissue morphology, and reduced IL-1β, TNF-α, and caspase-3 release. In vitro, HSYA effectively decreased NF-κB p65 and inflammatory cytokines, such as IL-1β, TNF-α, and IL-6. Thus, HSYA can protect renal function from I/R injury by ameliorating acute kidney injury and partly by promoting tubular cell survival via the TLR4/NF-κB pathway. These results suggest that HSYA can be used to prevent I/R-induced acute kidney injury.

Salvianolic acid A ameliorates renal ischemia/reperfusion injury by activating Akt/mTOR/4EBP1 signaling pathway

Salvianolic acid A (Sal A) has been shown to prevent and treat ischemic cardiovascular, as well as cerebral vascular diseases. However, little is known about Sal A in renal ischemia/reperfusion (I/R) injury. In this study, a renal I/R injury model in rats and a hypoxia/reoxygenation (H/R) model to damage proximal renal tubular cells (HK-2) were used to assess whether Sal A halts the development and progression of renal I/R injury. As compared with vehicle treatment, Sal A significantly attenuated kidney injury after renal I/R injury, accompanied by decreases in plasma creatinine, blood urea nitrogen levels, the number of apoptosis-positive tubular cells, and kidney oxidative stress. Sal A also activated phosphorylated protein kinase B (p-Akt) and phosphorylated-mammalian target of rapamycin (p-mTOR) compared with vehicle-treated I/R injury rats. In H/R-injured HK-2 cells, Sal A can reduce the levels of reactive oxygen species in a dose-related manner. Similar to the results from in vivo experiments, in vitro Sal A also increased the protein expression of phosphorylated-eukaryotic initiation factor 4E binding protein 1 (p-4EBP1) compared with vehicle. Furthermore, the cytoprotective activity of Sal A was inhibited by LY294002 and rapamycin. These findings indicate that Sal A can ameliorate renal I/R injury and promote tubular cell survival partly via the Akt/mTOR/4EBP1pathway. Sal A could be a candidate compound to prevent ischemic tissue damage.