Identification and characterization of endogenous biomarkers for hepatic vectorial transport (OATP1B3-P-gp) function using metabolomics with serum pharmacology.

The organic anion-transporting polypeptide 1B3 and P-glycoprotein (P-gp) provide efficient directional transport (OATP1B3-P-gp) from the blood to the bile that serves as a key determinant of hepatic disposition of the drug. Unfortunately, there is still a lack of effective means to evaluate the disposal ability mediated by transporters. The present study was designed to identify a suitable endogenous biomarker for the assessment of OATP1B3-P-gp function in the liver. We established stably transfected HEK293T-OATP1B3 and HEK293T-P-gp cell lines. Results showed that azelaic acid (AzA) was an endogenous substrate for OATP1B3 and P-gp using serum pharmacology combined with metabolomics. There is a good correlation between the serum concentration of AzA and probe drugs of rOATP1B3 and rP-gp when rats were treated with their inhibitors. Importantly, after 5-fluorouracil-induced rat liver injury, the relative mRNA level and expression of rOATP1B3 and rP-gp were markedly down-regulated in the liver, and the serum concentration of AzA was significantly increased. These observations suggest that AzA is an endogenous substrate of both OATP1B3 and P-gp, and may serve as a potential endogenous biomarker for the assessment of the function of OATP1B3-P-gp for the prediction of changes in the pharmacokinetics of drugs transported by OATP1B3-P-gp in liver disease states.

Preventive effect of LCZ696 on hypoxic pulmonary hypertension in rats via regulating the PI3K/AKT signaling pathway.

Hypoxic pulmonary hypertension (HPH) is a devastating disease worldwide; however, effective therapeutic drugs are lacking. This study investigated the effects and underlying mechanisms of LCZ696 treatment on hypoxia-induced pulmonary hypertension. Male Sprague-Dawley (SD) rats were kept in a hypobaric chamber with an oxygen concentration of 5% for 4 weeks. Rats were treated with either LCZ696 (18 mg/kg, 36 mg/kg, and 72 mg/kg) or sildenafil. The mean pulmonary artery pressure (mPAP), right ventricle hypertrophy index (RVHI), and lung system index were measured. Hematoxylin-eosin (HE) staining, Masson staining, and immunofluorescence staining were used for histological analysis. Enzyme linked immunosorbent assay (ELISA) kits were used to determine the concentrations of inflammatory and hypoxia-related factors. Western blotting was used to examine the expression of apoptotic and PI3K/AKT signaling pathway proteins in rat lung tissue. Hypoxia increased mPAP, RVHI, and lung system index and induced pulmonary vascular remodeling, pulmonary arteriomyosis, and pulmonary artery fibrosis. LCZ696 treatment reduced the increase in mPAP, RVHI, and the lung system index and ameliorated the induced pathological changes. Hypoxia upregulated expression of NF-kB, TNF-α, IL-6, HIF-1α, and Vascular endothelial growth factor (VEGF), decreased the ratio of Bax/Bcl-2, and activated the PI3K/AKT signaling pathway in lung tissue, and these effects were partially reversed by treatment with LCZ696. These results demonstrated that LCZ696 can ameliorate hypoxia-induced HPH by suppressing apoptosis, inhibiting the inflammatory response, and inhibiting the PI3K/AKT signaling pathway. It provides a reference for clinical rational drug use and lays a foundation for the study of HPH therapeutic drugs.

Erythropoietin promotes energy metabolism to improve LPS-induced injury in HK-2 cells via SIRT1/PGC1-α pathway.

Acute kidney injury (AKI) is one of frequent complications of sepsis with high mortality. Mitochondria is the center of energy metabolism participating in the pathogenesis of sepsis-associated AKI, and SIRT1/PGC1-α signaling pathway plays a crucial role in the modulation of energy metabolism. Erythropoietin (EPO) exerts protective functions on chronic kidney disease. We aimed to assess the effects of EPO on cell damage and energy metabolism in a cell model of septic AKI. Renal tubular epithelial cells HK-2 were treated with LPS and human recombinant erythropoietin (rhEPO). Cell viability was detected by CCK-8 and mitochondrial membrane potential was determined using JC-1 fluorescent probe. Then the content of ATP, ADP and NADPH, as well as lactic acid, were measured for the assessment of energy metabolism. Oxidative stress was evaluated by detecting the levels of ROS, MDA, SOD and GSH. Pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1ß, were measured with ELISA. Moreover, qRT-PCR and western blot were performed to detect mRNA and protein expressions. shSIRT1 was used to knockdown SIRT1, while EX527 and SR-18292 were applied to inhibit SIRT1 and PGC1-α, respectively, to investigate the regulatory mechanism of rhEPO on inflammatory injury and energy metabolism. In LPS-exposed HK-2 cells, rhEPO attenuated cell damage, inflammation and abnormal energy metabolism, as indicated by the elevated cell viability, the inhibited oxidative stress, cell apoptosis and inflammation, as well as the increased mitochondrial membrane potential and energy metabolism. However, these protective effects induced by rhEPO were reversed after SIRT1 or PGC1-α inhibition. EPO activated SIRT1/PGC1-α pathway to alleviate LPS-induced abnormal energy metabolism and cell damage in HK-2 cells. Our study suggested that rhEPO played a renoprotective role through SIRT1/PGC1-α pathway, which supported its therapeutic potential in septic AKI.

Enalapril increases the urinary excretion of metformin in rats by inducing multidrug and toxin excretion protein 1 in the kidney.

Two-thirds of patients with type 2 diabetes mellitus have hypertension, and thus the combination of two or more drugs to treat these diseases is common. It has been shown that the combination of metformin and enalapril has beneficial effects, but few studies have evaluated the interactions between these two drugs. This study investigated the effects of enalapril on the pharmacokinetics and urinary excretion of metformin in rats, with a focus on transporter-mediated drug interactions. Rats were dosed orally with metformin alone (100 mg/kg) or in combination with enalapril (4 mg/kg). The concentration of metformin was measured by high performance liquid chromatography and the level of organic cation transporters (rOCTs) and multidrug and toxin excretion protein 1 (rMATE1), which mediate the uptake and efflux of metformin, respectively, were evaluated by immunoblotting. After single and 7-day dosing, the plasma concentration of metformin in the co-administration group was significantly lower than that in the metformin-only group, and the CL/F and urinary excretion were increased in the co-administration group. Enalapril did not affect the Kp of metformin but reduced renal slice-uptake of metformin. The expression of rMATE1 was increased, whereas rOCT2 expression was decreased in rat kidney. Importantly, long-term co-administration of metformin and enalapril markedly decreased the level of lactic acid and uric acid in the blood. Enalapril increases the urinary excretion of metformin through the up-regulation of rMATE1. This reveals a new mechanism of drug interactions and provides a basis for drug dosage adjustment when these drugs are co-administered.

An LC-MS/MS analytical method for the determination of uremic toxins in patients with end-stage renal disease.

End-stage renal disease (ESRD) is the last stage of chronic kidney disease, characterized by the progressive accumulation of uremic toxins (UTs). Hemodialysis is the standard approach to remove UTs from the body. Creatinine and urea levels are important indices of hemodialysis effectiveness, but the utility of those markers to estimate the removal of UTs, especially protein-binding UTs is limited. We developed an LC-MS/MS method for the quantification of UTs and to provide markers for evaluating hemodialysis effectiveness. These substances were extracted from serum samples after acetonitrile precipitation of protein and then separated on a HILIC column. The flow rate was 0.6 mL/min with a run time of 8.0 min for the negative ion mode and positive ion mode each. In this study 26 UTs were determined in normal subjects and in patients with ESRD before and after hemodialysis; serum levels were significantly higher in patients with ESRD than in subjects with normal renal function. A significant decrease in a variety of serum UTs were observed in patients after dialysis treatment, but no change in the levels of orotic acid, CMPF, kynurenic acid, p-cresol sulfate, phenyl-ß-d-glucuronide, 4-ethylphenyl sulfate and 3-indolyl-ß-d-glucopyranoside was found. These results show that some UTs could not be completely removed by hemodialysis. In addition, some biomarkers of different types of UTs are proposed for evaluating hemodialysis effectiveness.

rhEPO inhibited cell apoptosis to alleviate acute kidney injury in sepsis by AMPK/SIRT1 activated autophagy.

BACKGROUND: Nowadays, people diagnosed sepsis may develop acute kidney injury (AKI), resulting heavy burden of health care. Recombinant human erythroprotein (rhEPO) has been suggested to have multifunction and may be used in the prevention or treatment of AKI, and its underlying mechanism remains largely unknown. METHODS: In our study, cell model induced by LPS-activated cell apoptosis in vitro and AKI animal model caused by lipopolysaccharide (LPS) injection in vivo. MTT assay and Flow Cytometry were conducted to analyze cell viability and apoptosis, respectively. Western bot was used to analyze expressions of apoptosis and autophagy associated proteins, and effects on AMPK/SIRT1 pathway. RESULTS: Our results suggested that rhEPO inhibited LPS-induced cell apoptosis in HK-2 and HEK-293. Moreover, we found that rhEPO activated autophagy to prevented cell apoptosis, changing the expression level of autophagy associated proteins such as LC3-I/LC3-II and P62, and AMPK/SIRT1 pathway was involved in its regulation. Additionally, both EX527 (SIRT1 inhibitor) and Compound C (AMPK inhibitor) blocked the autophagy effects caused by rhEPO and thus reversed the anti-apoptotic effects of rhEPO. Furthermore, our data demonstrated that rhEPO inhibited LPS-induced kidney tubular injury and decreased the expression level of apoptotic proteins by altering the expression level of autophagy related proteins and AMPK/SIRT1 pathway related proteins in vitro. CONCLUSION: Collectively, rhEPO suppressed LPS-induced cell apoptosis via AMPK/SIRT1 pathway mediated autophagy, and modulating their levels may serve as potential way in preventing AKI.

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.

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

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.

Multicomponent determination of traditional Chinese medicine preparation yin-zhi-huang injection by LC-MS/MS for screening of its potential bioactive candidates using HepaRG cells.

Yin-zhi-huang (YZH) injection is an injectable multiherbal prescription derived from the ancient Chinese medicine formula of Yin-chen-hao-tang, which is widely used in the clinic for the treatment of jaundice and chronic liver diseases. To date, the systematic study of the components in this multiherbal prescription still lacks suitable analytical methods that are able to simultaneously detect a broad array of components at low concentrations. In this study, a new liquid chromatography-tandem mass spectrometry method using dynamic multiple reaction monitoring mode was developed to determine multiple peaks in traditional Chinese medicine preparation YZH injection. This simple, selective and sensitive method enabled the quantification of 22 components with standard materials with a lower limit of quantification of 1.46-12.5 ng/mL in cell lysates. This method was successfully applied to celluar uptake and binding investigation of components in YZH injection. The results indicated that this strategy might be a useful approach for rapidly screening of the potential bioactive candidates from YZH injection, and the discovered candidates could be used to investigate the pharmacodynamics in further studies.

[Effects of metoprolol or/and pravastatin on the pharmacokinetics of metformin in rats].

This study investigates the effects of metoprolol (METO) or/and pravastatin (PRAV) on the pharmacokinetics of metformin (METF) in rats. Twenty-eight male SD rats were divided into METF group, METF+METO group, METF+PRAV group and METF+METO+PRAV group. Blood samples were collected at 10, 20, 40, 60, 90, 120, 180, 240, 360, 480 and 600 min after oral administration of metformin, and concentration of metformin in plasma was determined by HPLC. Compared to the METF group, Cmax of metformin was significantly decreased (P < 0.01) and MRT0−t , t1/2 and V were significantly increased in the METF+METO group; t1/2 was significantly decreased in the METF+PRAV group; Cmax was significantly decreased and MRT0−t was significantly increased in the METF+METO+PRAV group. Compared to the METF+METO group, MRT0−t of metformin was significantly decreased in the METF+METO+PRAV group. Compared to the METF+PRAV group, Cmax of metformin was significantly decreased (P < 0.01), and MRT0−t , t1/2 and V were significantly increased in the METF+METO+PRAV group. There exist multiple drug interactions of metformin, metoprolol and pravastatin in rats.

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 © 2016 John Wiley & Sons, Ltd.

Gender-Related Differences in the Expression of Organic Cation Transporter 2 and its Role in Urinary Excretion of Metformin in Rats.

Organic cation transporter 2 (rOCT2) and multidrug and toxin extrusion protein 1 (rMATE1) are mainly expressed in rat renal proximal tubules and mediate urinary excretion of cationic drugs, such as metformin. Accumulated evidence indicated that renal rOCT2 expression in male rats is much higher than that of female rats. However, it is unclear whether the gender-related differences in rOCT2 expression between male and female rats can affect the urinary excretion of metformin. The aim of this study was to investigate the effect of gender on the pharmacokinetics of metformin and to clarify the effect of gender-related differences on renal rOCT2 expression and its role in urinary excretion of metformin. Renal rOCT2 levels, but not rOCT1 and rMATE1, were significantly lowered in female rats when compared to that of male rats (P < 0.01), while the pharmacokinetic parameters, i.e., AUC0→t, t 1/2, CL/F, and cumulative urinary excretion of metformin, did not show any significant differences between female and male rats following oral administration of metformin at l00 mg/kg (P > 0.05). However, when metformin was orally administered at the dose of 500 mg/kg, the cumulative urinary excretion and renal tissue-to-plasma concentration ratio of metformin in female rats (26,689 ± 1266 µg and 2.96 ± 0.47 mL/g, respectively) were markedly lowered compared to that of male rats (32,949 ± 1384 µg and 4.20 ± 0.31 mL/g, respectively), and the plasma concentration of metformin in female rats (55.9 ± 4.5 µg/mL) was significantly increased compared to that of male rats (43.5 ± 3.1 µg/mL) at 2 h after oral administration. These results indicated that effect of gender-related differences on renal rOCT2 expression indeed contributes to the decreased urinary excretion of metformin in female rats when metformin was administered at relatively high doses.

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.

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).

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.

[Study of pharmacokinetics of digoxin in ovariectomized rats model].

This study aims to investigate the change of plasma concentration of digoxin (DIG) in rats with ovariectomy. Twelve female SD rats were randomly assigned into ovariectomized group and sham group (n = 6). All rats plasma was collected after a single dose of 2 mg x kg(-1) DIG administrated orally, serum DIG concentration was determined by LC-MS/MS. The level of P-gp in the intestinal was analyzed by Western blotting. Pharmacokinetic calculations were performed on each individual using DAS 2.0 practical pharmacokinetic software. Compared with the sham group, C(max) of ovariectomized group decreased significantly (P < 0.01). There was no significant difference of AUC(0-t), and the level of P-gp was elevated in ovariectomized group. It was found that C(max) of DIG was significantly reduced after ovariectomy, and the change was associated with the decreased level of estrogen, which contributes to the increased level of P-gp.

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 ß1 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.

[Simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-ms/MS and its application on pharmacokinetic interactions study].

The study aims to establish a method for simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-MS/MS and to study its pharmacokinetic interactions. Eighteen male SD rats were divided into repaglinide group, pravastatin sodium group and co-administration group. Blood samples were collected at different times after oral administration. Repaglinide and pravastatin sodium in rat plasma were separated by Agilent HC-C18 with the mobile phase consisting of methanol-0.1% formic acid (80 : 20). Detection and quantification were performed by using ESI-MS. The detector was operated in selected Reaction-monitoring mode at m/z 453.3-->230.1 for repaglinide, m/z 447.2-->327.4 for pravastatin sodium and m/z 285.1-->192.9 for diazepam as the internal standard. The calibration curve obtained was linear (R2>0.99) over the concentration range of 9.77-10,000 ng.mL-1 for repaglinide and 4.88-625 ng.mL-1 for pravastatin sodium. Compared with the single administration group, Cmax and AUC0-6h of repaglinide increased significantly (P<0.05) and tmax of pravastatin sodium prolonged (P<0.05) in co-administration group. The method is found to be simple, sensitive and accurate for determining the concentration of repaglinide and pravastatin sodium in rat plasma. There exists pharmacokinetic interactions in the co-administration of repaglinide and pravastatin sodium.

[Improvement in blood glucose fluctuations of insulin-treated type 1 diabetic patients with additional use of acarbose and assessed by continuous blood glucose monitoring program].

OBJECTIVE: To investigate the effect of combined use of insulin and acarbose on glucose excursion in type 1 diabetic patients. METHODS: 120 cases were randomly divided into control group and observation group. The control group received preprandial ultra-short effect insulin and long-acting insulin before bedtime while the observation group received acarbose 50 mg added to the medicine taken by the control group. Continuous Glucose Monitoring System (CGMS) was used to watch the blood glucose fluctuations. Data related to blood glucose level, glucose excursions after meals and hypoglycemia at night were compared between patients in the two groups. RESULTS: The average blood glucose (9.37 ± 1.70) mmol/L, the largest amplitude of glycemic excursions (LAGE) (11.42 ± 2.73) mmol/L, hyperglycemia-area under curve 0.89 ± 0.54, mean amplitude of glycemic excursions (MAGE) (5.13 ± 2.23) mmol/L, M-value (18.93 ± 11.43) mmol/L and insulin dosage (42.11 ± 14.42) U/day of observation group were significantly lower than in the control group (P < 0.05). Glucose excursions after meals and the times (0.33 ± 0.50)/day, the maintenance time (43.75 ± 43.50)/min and low glycemic index (LBGI) (0.005 ± 0.002) mmol/L of hypoglycemia at night were also significantly lower than in the control group, with statistically significant (P < 0.05) differences. CONCLUSION: The blood glucose fluctuation was significantly improved, with the decrease of insulin dosage while both glucose excursions and hypoglycemia at night reduced in patients with type1 diabetes mellitus after the acarbose treatment.We suggested that this program deserve further observation.

[Secretion and action of insulin among Han and Uygur subjects with impaired fasting glucose and impaired glucose tolerance from Xinjiang].

OBJECTIVE: To compare insulin secretion and action with impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and combined glucose intolerance (CGI, IFG and IGT) between Han and Uygur populations living in Xinjiang. METHODS: A multicenter cross-section survey (The Third Diabetes Epidemiological Survey in China) was conducted in Xinjiang from 2007 to 2008 including 2203 subjects (Han 1118, Uygur 1085) underwent an oral glucose test (OGTT). Homeostasis model assessment on insulin resistance (HOMA-IR) and ß cell function (HOMA-ß) were calculated. The ratio of incremental insulin (ΔI30) and glucose (ΔG30) response was used to evaluate the early insulin secretion. ΔI30/ΔG30/HOMA-IR was used to evaluate the glucose disposition index (DI). RESULTS: There were differences noticed regarding the waist circumstances (WC), body mass index (BMI), lipids, 0 and 120 min insulin levels in different glucose tolerance status between the Hans and Uygurs. Data related to NGT, IFG, CGI, WC from the Uygurs was significantly different from that of the Hans (P < 0.01), while the NGT, IFG, IGT and 120-minute plasma insulin levels of the Hans were significantly different from that of the Uygurs (P < 0.01). HOMA-IR and HOMA-ß in Hans were significantly different from those of the Uygurs (P < 0.01). There were significant differences noticed on data related to ΔI30/ΔG30, and DI among the two populations with different ethnicities. CONCLUSION: Regarding the regulation of impaired glucose, the insulin resistance among the Hans was significantly different from that of the Uygurs, while there seemed to be a compensatory secretion of pancreatic ß cells which played the role of maintaining blood glucose homeostasis.