Yan-rong Ma

Simultaneous Determination of Metformin, Metoprolol and its Metabolites in Rat Plasma by LC–MS-MS: Application to Pharmacokinetic Interaction Study

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for the simultaneous quantitation of metformin (MTF), metoprolol (MET), α-hydroxymetoprolol (HMT) and O-desmethylmetoprolol (DMT) in rat plasma using paracetamol as an internal standard (IS), respectively. The sample preparation involved a protein-precipitation method with methanol after the addition of IS. The separation was performed on an Agilent HC-C18 column (4.6 × 250 mm, 5 µm) at a flow rate of 1.0 mL/min, using methanol-water containing 0.1% formic acid (39:61, v/v) as mobile phase, and total run time was 8.5 min. MS-MS detection was accomplished in multiple reaction monitoring mode with positive electrospray ionization. The monitored transitions were m/z 130.1 → 60.2 for MTF, m/z 268.2 → 116.1 for MET, m/z 284.2 → 116.1 for HMT, m/z 254.2 → 116.1 for DMT and m/z 152.3 → 110.1 for IS. The method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, matrix effect and recovery over a concentration range of 19.53-40,000 ng/mL for MTF, 3.42-7,000 ng/mL for MET, 2.05-4,200 ng/mL for HMT and 1.95-4,000 ng/mL for DMT, respectively. The analytical method was successfully applied to drug interaction study of MTF and MET after oral administration of MTF and MET. Results suggested that the coadministration of MTF and MET results in a significant drug interaction in rat.

Inhibitory effect of atenolol on urinary excretion of metformin via down-regulating multidrug and toxin extrusion protein 1 (rMate1) expression in the kidney of rats.

Renal tubular secretion is an important pathway for the elimination of many clinically used drugs. Metformin, a commonly prescribed first-line antidiabetic drug, is secreted primarily by the renal tubule. Many patients with type 2 diabetes mellitus (T2DM) receiving metformin may together be given selective β1 blockers (e.g., atenolol). Therefore, it is of great use to evaluate the effect of atenolol on metformin urinary excretion for exploring drug interactions and predicting the adverse effect of drugs. The aim of this study was to investigate the effect of atenolol on the pharmacokinetic of metformin and plasma lactate (LCA) level in rats, for high LCA is a serious adverse reaction of metformin after long-term metformin treatment. In this study, rats were treated with metformin alone or in combination with atenolol. Plasma, urine and tissue concentration of metformin was determined by HPLC method, while Western blotting and immunohistochemical analysis were used to evaluate the renal expression of rat organic cation transporter 2 (rOct2) and multidrug and toxin extrusion protein 1 (rMate1). The results showed that, after 7 days drug treatment, the AUC0 → t of metformin in atenolol and metformin co-administration group was significantly increased by 19.5% compared to that in metformin group, while the 24h cumulative urinary excretion of metformin was significantly decreased by 57.3%. In addition, atenolol treatment significantly decreased the renal expression of rMate1, but had no effect on rOct2 expression, renal blood perfusion and glomerular filtration. Moreover, plasma LCA level in atenolol and metformin co-administration group was significantly increased by 83.3% compared to that in metformin group after 60 days drug treatment. These results indicated that atenolol can inhibit urinary excretion of metformin via decreasing renal rMate1 expression, and long-term atenolol and metformin co-administration may induce potential lactic acidosis. Our results, for the first time, provided an important experimental evidence that rMate1 is the target of transporter-mediated drug interactions concerning metformin and atenolol.

Effect of hesperidin on the pharmacokinetics of CPT-11 and its active metabolite SN-38 by regulating hepatic Mrp2 in rats.

The usage of irinotecan hydrochloride (CPT‐11) chemotherapy is hindered by its dose‐limiting diarrhea which appears to be associated with the intestinal exposure to SN‐38, the active metabolite of CPT‐11. Hesperidin, a safe and natural food ingredient flavonoid, exhibits various biological properties. Accumulated evidence showed that the regulatory effect of hesperidin on the expression of Mrp2 in the liver may be one of the critical factors controlling the biliary excretion of SN‐38. This study examined the effect of hesperidin on the pharmacokinetics of CPT‐11 and SN‐38 as well as the regulatory effect on the hepatic expression of Mrp2. Compared with the control group, the AUC5‐t was increased to 115% of CPT‐11 and 122% of SN‐38; the CL was decreased to 87% for CPT‐11; the tissue concentration was increased in the liver, kidney and colon; and the accumulated biliary excretion was significantly decreased to 77% for CPT‐11 and 76% for SN‐38 in hesperidin‐treated rats. Furthermore, the expression of Mrp2 in the liver was significantly decreased to 37% in the hesperidin‐treated rats compared with that of the control group. These results indicate that oral administration of hesperidin significantly increased the AUC5‐t and reduced the clearance of CPT‐11 and SN‐38, possibly by decreasing the hepatic expression of Mrp2, and thus inhibiting the biliary excretion of CPT‐11 and SN‐38. The results from this present study suggest that hesperidin may reduce the exposure of CPT‐11 and SN‐38 in the intestine by reducing the amount of biliary excretion of CPT‐11 and SN‐38. Copyright

Development of a LC-MS/MS method for simultaneous determination of metoprolol and its metabolites, α-hydroxymetoprolol and O-desmethylmetoprolol, in rat plasma: application to the herb–drug interaction study of metoprolol and breviscapine

A simple, specific and sensitive LC-MS/MS method was developed and validated for the simultaneous determination of metoprolol (MET), α-hydroxymetoprolol (HMT) and O-desmethylmetoprolol (DMT) in rat plasma. The plasma samples were prepared by protein precipitation, then the separation of the analytes was performed on an Agilent HC-C18 column (4.6 × 250 mm, 5 µm) at a flow rate of 1.0 mL/min, and post-column splitting (1:4) was used to give optimal interface flow rates (0.2 mL/min) for MS detection; the total run time was 8.5 min. Mass spectrometric detection was achieved using a triple-quadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. The method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, matrix effect and recovery over a concentration range of 3.42-7000 ng/mL for MET, 2.05-4200 ng/mL for HMT and 1.95-4000 ng/mL for DMT. The analytical method was successfully applied to herb-drug interaction study of MET and breviscapine after administration of breviscapine (12.5 mg/kg) and MET (40 mg/kg). The results suggested that breviscapine have negligible effect on pharmacokinetics of MET in rats; the information may be beneficial for the application of breviscapine in combination with MET in clinical therapy.

Hesperidin Alleviates Oxidative Stress and Upregulates the Multidrug Resistance Protein 2 in Isoniazid and Rifampicin-Induced Liver Injury in Rats

Isoniazid (INH) and rifampicin (RFP), two front‐line drugs used in tuberculosis therapy, may lead to seriously hepatotoxicity. The current study was carried out to investigate the hepatoprotective effects of hesperidin against INH‐ and RFP‐induced oxidative damage. The liver injury animal model of rats was induced by INH (75 mg/kg) and RFP (150 mg/kg) coadministration for 7 days, and hesperidin, at the dose of 50, 100, and 200 mg/kg, was orally administered to rats 2 h before INH and RFP administration. The biochemical and pathologic examinations were performed after rats were sacrificed. Moreover, the serum and liver glutathione (GSH), glutathione disulfide (GSSG), malondialdehyde (MDA), GSH peroxidase, and GSSG reductase were determined by test kits, and the expression of multidrug resistance proteins 2 (Mrp2) was determined by Western blotting and immunohistochemistry. The results showed that hesperidin significantly alleviated liver injury as indicated by the decreased levels of ALT, AST, bilirubin, total bile acid, and glutathione peroxidase and the increased levels of the GSH/GSSG ratio and the expression of Mrp2. Moreover, hesperidin could effectively reduce the pathological tissue damage. These results indicate that hesperidin can attenuate INH‐ and RFP‐induced oxidative damage, and the underlying mechanism may have correlation with its effect on the upregulation of Mrp2.

Effect of cholecystectomy on bile acids as well as relevant enzymes and transporters in mice: Implication for pharmacokinetic changes of rifampicin

Background and purpose: Long‐term medical consequences of cholecystectomy are believed to be uncommon. It has been reported that bile acids (BAs) changed after cholecystectomy. As important signaling molecules, the alternations of BAs might favour the regulatory effect on enzymes and transporters involved in BAs physiological homeostasis at the transcriptional level, which could lead to pharmacokinetic changes of drugs. Here, we determined the effect of cholecystectomy on BAs, relevant enzymes and transporters and pharmacokinetic parameters of rifampicin, and explored the potential mechanisms at the transcriptional regulatory level via nuclear receptors. Methods: Parameters of BAs in different specimens, mRNA and protein expression of enzymes, transporters and nuclear receptors that relate to BAs homeostasis in liver and ileum, and the pharmacokinetic character of rifampicin were measured in sham‐operated and cholecystectomized mice. Key results: Cholecystectomy associated with considerable decreased BAs pool size that could attribute to increased fecal excretion. Most notably, as the Fxr and Pxr ligands, the alternations of hepatic and ileal individual BAs affected expression of enzymes Cyp3a11 and transporters Ntcp and Bsep in liver and Asbt in ileum significantly following cholecystectomy. Eventually, the rifampicin bioavailability was improved with depressed clearance in mice without gallbladders. Conclusion: As natural ligands for Fxr and Pxr, the alternations of individual BAs lead to the regulation of hepatic and ileal relevant enzymes and transporters after cholecystectomy. Especially, the down‐regulation of hepatic Cyp3a11 suggests that undesirable pharmacokinetic alternations of drugs especially Cyp3a11 substrates like rifampicin might occur in phase with cholecystectomy. Graphical abstract Figure. No caption available.

Metoprolol decreases the plasma exposure of metformin via the induction of liver, kidney and muscle uptake in rats

Drug interactions are one of the commonest causes of side effects, particularly in long‐term therapy. The aim of the current study was to investigate the possible effects of metoprolol on the pharmacokinetics of metformin in rats and to clarify the mechanism of drug interaction. In this study, rats were treated with metformin alone or in combination with metoprolol. Plasma, urine and tissue concentrations of metformin were determined by HPLC. Western blotting and real‐time qPCR were used to evaluate the expression of rOCTs and rMATE1. The results showed that, after single or 7‐day repeated administration, the plasma concentrations of metformin in the co‐administration group were significantly decreased compared with that in the metformin group. However, the parameter V/F of metformin in the co‐administration group was markedly increased compared with that in the metformin group. The hepatic, renal and muscular Kp of metformin were markedly elevated after co‐administration with metoprolol. Consistently, metformin uptake in rat kidney slices was significantly induced by metoprolol. In addition, multiple administrations of metoprolol significantly reduced the expression of rMATE1 in rat kidney as well as the urinary excretion of metformin. Importantly, after long‐term administration, lactic acid and uric acid levels in the co‐administration group were increased by 25% and 26%, respectively, compared with that in the metformin group. These results indicate that metoprolol can decrease the plasma concentration of metformin via the induction of hepatic, renal and muscular uptake, and long‐term co‐administration of metformin and metoprolol can cause elevated lactic acid and uric acid levels. Copyright

Serum serotonin reduced the expression of hepatic transporter Mrp2 and P-gp via regulating nuclear receptor CAR in PI-IBS rats

Hepatic transporters and drug metabolizing enzymes (DMEs) play important roles in the pharmacological effects and (or) side-effects of many drugs, and are regulated by several mediators, including neurotransmitters. This work aimed to investigate whether serum levels of 5-hydroxytryptamine (5-HT) affected the expression of hepatic transporters or DMEs. The expression of hepatic transporters was assessed using the Western-blot technique in a 2,4,6-trinitrobenzenesulfonic-acid-induced rat model of post-infectious irritable bowel syndrome (PI-IBS), in which serum levels of 5-HT were significantly elevated. To further clarify the underlying mechanism, the 5-HT precursor 5-hydroxytryptophan (5-HTP) and the 5-HT depleting agent parachlorophenylalanine (pCPA) were applied to adjust serum levels of 5-HT. Serum levels of 5-HT were measured using LC-MS/MS; the expression of hepatic transporters, DMEs, and nuclear receptors were examined by Western-blot technique. Our results showed that in PI-IBS rats the expression of multidrug resistance protein 2 (Mrp2) was significantly decreased, while colonic enterochromaffin cell density and serum levels of 5-HT were all significantly increased. Moreover, 5-HTP treatment significantly increased serum levels of 5-HT and decreased the expression of Mrp2 and glycoprotein P (P-gp), whereas treatment with pCPA markedly decreased serum levels of 5-HT and increased the expression of Mrp2 and P-gp. Our results indicated that serum 5-HT regulates the expression of Mrp2 and P-gp, and the underlying mechanism may be related to the altered expression of the nuclear receptor constitutive androstane receptor (CAR).

The urinary excretion of metformin, ceftizoxime and ofloxacin in high serum creatinine rats: Can creatinine predict renal tubular elimination?

ABSTRACT The renal excretion of creatinine and most drugs are the net result of glomerular filtration and tubular secretion, and their tubular secretions are mediated by individual transporters. Thus, we hypothesized that the increase of serum creatinine (SCr) levels attributing to inhibiting tubular transporters but not glomerular filtration rate (GFR) could be used to evaluate the tubular excretion of drugs mediated by identical or partial overlap transporter with creatinine. In this work, we firstly developed the creatinine excretion inhibition model with normal GFR by competitively inhibiting tubular transporters, and investigated the renal excretion of metformin, ceftizoxime and ofloxacin in vivo and in vitro. The results showed that the 24‐hour urinary excretion of metformin and ceftizoxime in model rats were decreased by 25% and 17% compared to that in control rats, respectively. The uptake amount and urinary excretion of metformin and ceftizoxime could be inhibited by creatinine in renal cortical slices and isolated kidney perfusion. However, the urinary excretion of ofloxacin was not affected by high SCr. These results showed that the inhibition of tubular creatinine transporters by high SCr resulted to the decrease of urinary excretion of metformin and ceftizoxime, but not ofloxacin, which implied that the increase of SCr could also be used to evaluate the tubular excretion of drugs mediated by identical or partial overlap transporter with creatinine in normal GFR rats. Graphical abstract Figure. No Caption available.

Alteration of renal excretion pathways in gentamicin-induced renal injury in rats

The kidney plays a major part in the elimination of many drugs and their metabolites, and drug‐induced kidney injury commonly alters either glomerular filtration or tubular transport, or both. However, the renal excretion pathway of drugs has not been fully elucidated at different stages of renal injury. This study aimed to evaluate the alteration of renal excretion pathways in gentamicin (GEN)‐induced renal injury in rats. Results showed that serum cystatin C, creatinine and urea nitrogen levels were greatly increased by the exposure of GEN (100 mg kg–1), and creatinine concentration was increased by 39.7% by GEN (50 mg kg–1). GEN dose‐dependently upregulated the protein expression of rOCT1, downregulated rOCT2 and rOAT1, but not affected rOAT2. Efflux transporters, rMRP2, rMRP4 and rBCRP expressions were significantly increased by GEN(100), and the rMATE1 level was markedly increased by GEN(50) but decreased by GEN(100). GEN(50) did not alter the urinary excretion of inulin, but increased metformin and furosemide excretion. However, GEN(100) resulted in a significant decrease of the urinary excretion of inulin, metformin and p‐aminohippurate. In addition, urinary metformin excretions in vivo were significantly decreased by GEN(100), but slightly increased by GEN(50). These results suggested that GEN(50) resulted in the induction of rOCTs‐rMATE1 and rOAT3‐rMRPs pathway, but not changed the glomerular filtration rate, and GEN(100)‐induced acute kidney injury caused the downregulated function of glomerular filtration ‐rOCTs‐rMATE1 and ‐rOAT1‐rMRPs pathway.