Publications by authors named "Mladen Tzvetkov"

76 Publications

TIM-3 Genetic Variants Are Associated with Altered Clinical Outcome and Susceptibility to Gram-Positive Infections in Patients with Sepsis.

Int J Mol Sci 2020 Nov 6;21(21). Epub 2020 Nov 6.

Department of Anesthesiology, University Medical Center, Georg August University, D-37075 Goettingen, Germany.

: Previous studies have reported the fundamental role of immunoregulatory proteins in the clinical phenotype and outcome of sepsis. This study investigated two functional single nucleotide polymorphisms (SNPs) of T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), which has a negative stimulatory function in the T cell immune response. : Patients with sepsis ( = 712) were prospectively enrolled from three intensive care units (ICUs) at the University Medical Center Goettingen since 2012. All patients were genotyped for the TIM-3 SNPs rs1036199 and rs10515746. The primary outcome was 28-day mortality. Disease severity and microbiological findings were secondary endpoints. : Kaplan-Meier survival analysis demonstrated a significantly lower 28-day mortality for TIM-3 rs1036199 AA homozygous patients compared to C-allele carriers (18% vs. 27%, = 0.0099) and TIM-3 rs10515746 CC homozygous patients compared to A-allele carriers (18% vs. 26%, = 0.0202). The TIM-3 rs1036199 AA genotype and rs10515746 CC genotype remained significant predictors for 28-day mortality in the multivariate Cox regression analysis after adjustment for relevant confounders (adjusted hazard ratios: 0.67 and 0.70). Additionally, patients carrying the rs1036199 AA genotype presented more Gram-positive and infections, and rs10515746 CC homozygotes presented more infections. : The studied TIM-3 genetic variants are associated with altered 28-day mortality and susceptibility to Gram-positive infections in sepsis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21218318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664272PMC
November 2020

Differences in Metformin and Thiamine Uptake between Human and Mouse Organic Cation Transporter 1: Structural Determinants and Potential Consequences for Intrahepatic Concentrations.

Drug Metab Dispos 2020 12 9;48(12):1380-1392. Epub 2020 Oct 9.

Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Greifswald, Germany (M.J.M., S.R., C.W., S.O., M.V.T.); Department of Pharmaceutical Chemistry, Division of Drug Design and Medicinal Chemistry, University of Vienna, Vienna, Austria (A.T., B.Z.); and Department of General, Visceral, and Pediatric Surgery (J.G.) and Institute of Clinical Pharmacology (T.S., J.B.), University Medical Center Göttingen, Göttingen, Germany

The most commonly used oral antidiabetic drug, metformin, is a substrate of the hepatic uptake transporter OCT1 (gene name ). However, OCT1 deficiency leads to more pronounced reductions of metformin concentrations in mouse than in human liver. Similarly, the effects of OCT1 deficiency on the pharmacokinetics of thiamine were reported to differ between human and mouse. Here, we compared the uptake characteristics of metformin and thiamine between human and mouse OCT1 using stably transfected human embryonic kidney 293 cells. The affinity for metformin was 4.9-fold lower in human than in mouse OCT1, resulting in a 6.5-fold lower intrinsic clearance. Therefore, the estimated liver-to-blood partition coefficient is only 3.34 in human compared with 14.4 in mouse and may contribute to higher intrahepatic concentrations in mice. Similarly, the affinity for thiamine was 9.5-fold lower in human than in mouse OCT1. Using human-mouse chimeric OCT1, we showed that simultaneous substitution of transmembrane helices TMH2 and TMH3 resulted in the reversal of affinity for metformin. Using homology modeling, we suggest several explanations, of which a different interaction of Leu155 (human TMH2) compared with Val156 (mouse TMH2) with residues in TMH3 had the strongest experimental support. In conclusion, the contribution of human OCT1 to the cellular uptake of thiamine and especially of metformin may be much lower than that of mouse OCT1. This may lead to an overestimation of the effects of OCT1 on hepatic concentrations in humans when using mouse as a model. In addition, comparative analyses of human and mouse orthologs may help reveal mechanisms of OCT1 transport. SIGNIFICANCE STATEMENT: OCT1 is a major hepatic uptake transporter of metformin and thiamine, but this study reports strong differences in the affinity for both compounds between human and mouse OCT1. Consequently, intrahepatic metformin concentrations could be much higher in mice than in humans, impacting metformin actions and representing a strong limitation of using rodent animal models for predictions of OCT1-related pharmacokinetics and efficacy in humans. Furthermore, OCT1 transmembrane helices TMH2 and TMH3 were identified to confer the observed species-specific differences in metformin affinity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/dmd.120.000170DOI Listing
December 2020

Inherited and Acquired Determinants of Hepatic CYP3A Activity in Humans.

Front Genet 2020 21;11:944. Epub 2020 Aug 21.

Institute for Clinical Pharmacology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany.

Human CYP3A enzymes (including CYP3A4 and CYP4A5) metabolize about 40% of all drugs and numerous other environmental and endogenous substances. CYP3A activity is highly variable within and between humans. As a consequence, therapy with standard doses often results in too low or too high blood and tissue concentrations resulting in therapeutic failure or dose-related adverse reactions. It is an unanswered question how much of the big interindividual variation in CYP3A activity is caused by genetic or by environmental factors. This question can be answered by the twin study approach. Using midazolam as CYP3A probe drug, we studied 43 monozygotic and 14 dizygotic twins and measured midazolam and its metabolite 1-OH-midazolam. In addition, endogenous biomarkers of CYP3A activity, 4ß-OH-cholesterol and 6ß-OH-cortisol, were analyzed. Additive genetic effects accounted for only 15% of the variation in midazolam AUC, whereas 48% was attributed to common environmental factors. In contrast, 73, 56, and 31% of 1-OH-midazolam, 4ß-OH-cholesterol and 6ß-OH-cortisol variation was due to genetic effects. There was a low phenotypic correlation between the four CYP3A biomarkers. Only between midazolam and its 1-OH-metabolite, and between midazolam and 6ß-OH-cortisol we found significant bivariate genetic correlations. Midazolam AUC differed depending on the variant ( = 0.001) whereas plasma 4ß-OH-cholesterol was significantly lower in homozygous carriers of ( = 0.02). Apparently, non-genomic factors played a dominant role in the inter-individual variation of the CYP3A probe drug midazolam. A small intra-individual pharmacokinetic variation after repeated administration of midazolam was rated earlier as indication of high heritability of CYP3A activity, but according to present data that could also largely be due to constant environmental factors and/or heritability of liver blood flow. The higher heritabilities of 4ß-OH-cholesterol and of 1-OH-midazolam may deserve further research on the underlying factors beyond CYP3A genes. ClinicalTrials.gov: NCT01845194 and EUDRA-CT: 2008-006223-31.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fgene.2020.00944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7472781PMC
August 2020

A double-Flp-in method for stable overexpression of two genes.

Sci Rep 2020 08 20;10(1):14018. Epub 2020 Aug 20.

Institute of Clinical Pharmacology, University Medical Center Göttingen, Georg-August University, Robert-Koch-Str. 40, 37075, Göttingen, Germany.

Overexpression of single genes in mammalian cells is widely used to investigate protein function in basic and applied biosciences and in drug research. A better understanding of interactions of two proteins is an important next step in the advancement of our understanding of complex biological systems. However, simultaneous and robust overexpression of two or more genes is challenging. The Flp-In system integrates a vector into cell lines at a specific genomic locus, but has not been used for integration of more than one gene. Here we present a modification of the Flp-In system that enables the simultaneous targeted integration of two genes. We describe the modification and generation of the vectors required and give the complete protocol for transfection and validation of correct genomic integration and expression. We also provide results on the stability and reproducibility, and we functionally validated this approach with a pharmacologically relevant combination of a membrane transporter facilitating drug uptake and an enzyme mediating drug metabolism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-71051-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441062PMC
August 2020

An Innovative Therapeutic Option for the Treatment of Skeletal Sarcomas: Elimination of Osteo- and Ewing's Sarcoma Cells Using Physical Gas Plasma.

Int J Mol Sci 2020 Jun 23;21(12). Epub 2020 Jun 23.

Department of Gynecology and Gynecological Oncology, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany.

Osteosarcoma and Ewing's sarcoma are the most common malignant bone tumors. Conventional therapies such as polychemotherapy, local surgery, and radiotherapy improve the clinical outcome for patients. However, they are accompanied by acute and chronic side effects that affect the quality of life of patients, motivating novel research lines on therapeutic options for the treatment of sarcomas. Previous experimental work with physical plasma operated at body temperature (cold atmospheric plasma, CAP) demonstrated anti-oncogenic effects on different cancer cell types. This study investigated the anti-cancer effect of CAP on two bone sarcoma entities, osteosarcoma and Ewing's sarcoma, which were represented by four cell lines (U2-OS, MNNG/HOS, A673, and RD-ES). A time-dependent anti-proliferative effect of CAP on all cell lines was observed. CAP-induced alterations in cell membrane functionality were detected by performing a fluorescein diacetate (FDA) release assay and an ATP release assay. Additionally, modifications of the cell membrane and modifications in the actin cytoskeleton composition were examined using fluorescence microscopy monitoring dextran-uptake assay and G-/F-actin distribution. Furthermore, the CAP-induced induction of apoptosis was determined by TUNEL and active caspases assays. The observations suggest that a single CAP treatment of bone sarcoma cells may have significant anti-oncogenic effects and thus may be a promising extension to existing applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21124460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7352911PMC
June 2020

Oral Yohimbine as a New Probe Drug to Predict CYP2D6 Activity: Results of a Fixed-Sequence Phase I Trial.

Clin Pharmacokinet 2020 07;59(7):927-939

Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany.

Objective: Yohimbine pharmacokinetics were determined after oral administration of a single oral dose of yohimbine 5 mg and a microdose of yohimbine 50 µg in relation to different cytochrome P450 (CYP) 2D6 genotypes. The CYP2D6 inhibitor paroxetine was used to investigate the influence on yohimbine pharmacokinetics. Microdosed midazolam was applied to evaluate a possible impact of yohimbine on CYP3A activity and the possibility of combining microdosed yohimbine and midazolam to simultaneously determine CYP2D6 and CYP3A activity.

Methods: In a fixed-sequence clinical trial, 16 healthy volunteers with a known CYP2D6 genotype [extensive (10), intermediate (2) and poor (4) metaboliser] received an oral dose of yohimbine 50 µg, yohimbine 5 mg at baseline and during paroxetine as a CYP2D6 inhibitor. Midazolam (30 µg) was co-administered to determine CYP3A activity at each occasion. Plasma concentrations of yohimbine, its main metabolite 11-OH-yohimbine, midazolam and paroxetine were quantified using validated liquid chromatography-tandem mass spectrometry assays.

Results: Pharmacokinetics of yohimbine were highly variable and a CYP2D6 genotype dependent clearance was observed. After yohimbine 5 mg, the clearance ranged from 25.3 to 15,864 mL/min and after yohimbine 50 µg, the clearance ranged from 39.6 to 38,822 mL/min. A more than fivefold reduction in clearance was caused by paroxetine in CYP2D6 extensive metabolisers, while the clearance in poor metabolisers was not affected. Yohimbine did not alter CYP3A activity as measured by microdosed midazolam.

Conclusions: The pharmacokinetics of yohimbine were highly correlated with CYP2D6, which was further supported by the clearance inhibition caused by the CYP2D6 inhibitor paroxetine. With these data, yohimbine is proposed to be a suitable probe drug to predict CYP2D6 activity. In addition, the microdose can be used in combination with microdosed midazolam to simultaneously evaluate CYP2D6 and CYP3A activity without any interaction between the probe drugs and because the microdoses exert no pharmacological effects.

Clinical Trial Registration: EudraCT2017-001801-34.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s40262-020-00862-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7329762PMC
July 2020

Comparison of In Vitro and In Vivo Results Using the GastroDuo and the Salivary Tracer Technique: Immediate Release Dosage Forms under Fasting Conditions.

Pharmaceutics 2019 Dec 7;11(12). Epub 2019 Dec 7.

Department of Biopharmaceutics and Pharmaceutical Technology, Institute of Pharmacy, University of Greifswald, 17489 Greifswald, Germany.

The fasted state administration of immediate release (IR) dosage forms is often regarded as uncritical since physiological aspects seem to play a minor role for disintegration and drug release. However, recent in vivo studies in humans have highlighted that fasted state conditions are in fact highly dynamic. It was therefore the aim of this study to investigate the disintegration and drug release behavior of four different IR formulations of the probe drug caffeine under physiologically relevant conditions with the aid of the GastroDuo. One film-coated tablet and three different capsule formulations based on capsule shells either made from hard gelatin or hydroxypropylmethyl cellulose (HPMC) were tested in six different test programs. To evaluate the relevance of the data generated, the four IR formulations were also studied in a four-way cross-over study in 14 healthy volunteers by using the salivary tracer technique (STT). It could be shown that the IR formulations behaved differently in the in vitro test programs. Thereby, the simulated parameters affected the disintegration and dissolution behavior of the four IR formulations in different ways. Whereas drug release from the tablet started early and was barely affected by temperature, pH or motility, the different capsule formulations showed a longer lag time and were sensitive to specific parameters. However, once drug release was initiated, it typically progressed with a higher rate for the capsules compared to the tablet. Interestingly, the results obtained with the STT were not always in line with the in vitro data. This observation was due to the fact that the probability of the different test programs was not equal and that certain scenarios were rather unlikely to occur under the controlled and standardized conditions of clinical studies. Nonetheless, the in vitro data are still valuable as they allowed to discriminate between different formulations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/pharmaceutics11120659DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956200PMC
December 2019

Stereoselective cell uptake of adrenergic agonists and antagonists by organic cation transporters.

Biochem Pharmacol 2020 01 27;171:113731. Epub 2019 Nov 27.

Institute of Clinical Pharmacology, University Medical Center Göttingen, Georg-August University, D-37075 Göttingen, Germany.

Stereoselectivity is well described for receptor binding and enzyme catalysis, but so far has only been scarcely investigated in carrier-mediated membrane transport. We thus studied transport kinetics of racemic (anti)adrenergic drugs by the organic cation transporters OCT1 (wild-type and allelic variants), OCT2, OCT3, MATE1, and MATE2-K with a focus on stereospecificity. OCT1 showed stereoselective uptake with up to 2-fold higher v over their corresponding counterpart enantiomers for (R,R)-fenoterol, (R,R)-formoterol, (S)-salbutamol, (S)-acebutolol, and (S)-atenolol. Orciprenaline and etilefrine were also transported stereoselectively. The K was 2.1-fold and 1.5-fold lower for the (S,S)-enantiomers of fenoterol and formoterol, while no significant difference in K was seen for the other aforementioned drugs. Common OCT1 variants showed similar enantiopreference to wild-type OCT1, with a few notable exceptions (e.g. a switch in enantiospecificity for fenoterol in OCT1*2 compared to the wild-type). Other cation transporters showed strong differences to OCT1 in stereoselectivity and transport activity: The closely related OCT2 displayed a 20-fold higher v for (S,S)-fenoterol compared to (R,R)-fenoterol and OCT2 and OCT3 showed 3.5-fold and 4.6-fold higher v for the pharmacologically active (R)-salbutamol over (S)-salbutamol. MATE1 and MATE2-K generally mediated transport with a higher capacity but lower affinity compared to OCT1, with moderate stereoselectivity. Our kinetic studies showed that significant stereoselectivity exists in solute carrier-mediated membrane transport of racemic beta-adrenergic drugs with surprising, and in some instances even opposing, preferences between closely related organic cation transporters. This may be relevant for drug therapy, given the strong involvement of these transporters in hepatic and renal drug elimination.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bcp.2019.113731DOI Listing
January 2020

Highly Variable Pharmacokinetics of Tyramine in Humans and Polymorphisms in OCT1, CYP2D6, and MAO-A.

Front Pharmacol 2019 30;10:1297. Epub 2019 Oct 30.

Institute of Clinical Pharmacology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany.

Tyramine, formed by the decarboxylation of tyrosine, is a natural constituent of numerous food products. As an indirect sympathomimetic, it can have potentially dangerous hypertensive effects. data indicated that the pharmacokinetics of tyramine possibly depend on the organic cation transporter OCT1 genotype and on the CYP2D6 genotype. Since tyramine is a prototypic substrate of monoamine oxidase A (MAO-A), genetic polymorphisms in MAO-A may also be relevant. The aims of this study were to identify to what extent the interindividual variation in pharmacokinetics and pharmacodynamics of tyramine is determined by genetic polymorphisms in OCT1, CYP2D6, and MAO-A. Beyond that, we wanted to evaluate tyramine as probe drug for the activity of MAO-A and OCT1. Therefore, the pharmacokinetics, pharmacodynamics, and pharmacogenetics of tyramine were studied in 88 healthy volunteers after oral administration of a 400 mg dose. We observed a strong interindividual variation in systemic tyramine exposure, with a mean AUC of 3.74 min*µg/ml and a high mean CL/F ratio of 107 l/min. On average, as much as 76.8% of the dose was recovered in urine in form of the MAO-catalysed metabolite 4-hydroxyphenylacetic acid (4-HPAA), confirming that oxidative deamination by MAO-A is the quantitatively most relevant metabolic pathway. Systemic exposure of 4-HPAA varied only up to 3-fold, indicating no strong heritable variation in peripheral MAO-A activity. Systolic blood pressure increased by more than 10 mmHg in 71% of the volunteers and correlated strongly with systemic tyramine concentration. In less than 10% of participants, individually variable blood pressure peaks by >40 mmHg above baseline were observed at tyramine concentrations of >60 µg/l. Unexpectedly, the functionally relevant polymorphisms in OCT1 and CYP2D6, including the CYP2D6 poor and ultra-rapid metaboliser genotypes, did not significantly affect tyramine pharmacokinetics or pharmacodynamics. Also, the MOA-A genotypes, which had been associated in several earlier studies with neuropsychiatric phenotypes, had no significant effects on tyramine pharmacokinetics or its metabolism to 4-HPAA. Thus, variation in tyramine pharmacokinetics and pharmacodynamics is not explained by obvious genomic variation, and human tyramine metabolism did not indicate the existence of ultra-low or -high MAO-A activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fphar.2019.01297DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6831736PMC
October 2019

In vivo characterization of enTRinsic™ drug delivery technology capsule after intake in fed state: A cross-validation approach using salivary tracer technique in comparison to MRI.

J Control Release 2019 11 15;313:24-32. Epub 2019 Oct 15.

Department of Biopharmaceutics and Pharmaceutical Technology, Institute of Pharmacy, University of Greifswald, Felix-Hausdorff-Straße 3, D-17487, Greifswald, Germany. Electronic address:

The instability of various small molecules, vaccines and peptides in the human stomach is a complex challenge for oral drug delivery. Recently, a novel gastro-resistant capsule - the enTRinsic™ Drug Delivery Technology capsule - has been developed. In this work, the salivary tracer technique based on caffeine has been applied to study the in vivo disintegration of enTRinsic™ capsules in 16 healthy volunteers. In addition, magnetic resonance imaging (MRI) was used to visualize GI transit and to verify the disintegration times determined by using the salivary tracer technique. The enTRinsic™ capsules filled with 50mg of caffeine and 5mg of black iron oxide were administered in the fed state, i.e. 30min after a light meal (500kcal). In the first hour after capsule intake, the subjects were placed in supine position in the MRI scanner and scans were performed in short time intervals. After 1h, the subjects could leave the MRI scanner in between the MRI measurements, which were performed every 15min until disintegration of the capsule was confirmed (maximum observation time: 8h). Saliva samples were obtained simultaneously with MR imaging. Caffeine concentrations in saliva were determined by LC/MS-MS. The starting point of capsule disintegration was determined visually by inspection of the MR images as well as by the onset of salivary caffeine concentrations. In 14 out of 16 subjects, the capsule disintegrated in the small intestine. In one subject, the enTRinsic™ capsule was not emptied from the stomach within the observation time. In another subject, disintegration occurred during gastric emptying in the antropyloric region. In this study, we demonstrated that the enTRinsic™ capsules are also gastro resistant when taken under fed state conditions. Furthermore, we demonstrated the feasibility of using low dose caffeine as a salivary tracer for the determination of the disintegration of an enteric formulation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jconrel.2019.10.023DOI Listing
November 2019

Opioids as Substrates and Inhibitors of the Genetically Highly Variable Organic Cation Transporter OCT1.

J Med Chem 2019 11 4;62(21):9890-9905. Epub 2019 Nov 4.

Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT) , University Medicine Greifswald , 17487 Greifswald , Germany.

Genetic variants in the hepatic uptake transporter OCT1, observed in 9% of Europeans and white Americans, are known to affect pharmacokinetics and efficacy of tramadol, morphine, and codeine. Here, we report further opioids to be substrates and inhibitors of OCT1. Methylnaltrexone, hydromorphone, oxymorphone, and meptazinol were identified as OCT1 substrates. Methylnaltrexone is the strongest OCT1 substrate currently reported. It showed 86-fold higher accumulation in OCT1-overexpressing cells compared to control cells. We observed substantial differences in the inhibitory potency among structurally highly similar morphinan opioids (IC ranged from 6.4 μM for dextrorphan to 2 mM for oxycodone). The ether linkage of C4-C5 in the morphinan ring leads to a strong reduction of inhibitory potency. In conclusion, although polyspecific, OCT1 possesses a strong selectivity for its ligands. In contrast to methylnaltrexone and hydromorphone, oxycodone and hydrocodone do not interact with OCT1 and may be safer for use in individuals with genetic OCT1 deficiency.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.9b01301DOI Listing
November 2019

Variability and Heritability of Thiamine Pharmacokinetics With Focus on OCT1 Effects on Membrane Transport and Pharmacokinetics in Humans.

Clin Pharmacol Ther 2020 03 23;107(3):628-638. Epub 2019 Nov 23.

Department of Clinical Pharmacology, University Medical Center, Georg August University, Goettingen, Germany.

Thiamine is substrate of the hepatic uptake transporter organic cation transporter 1 (OCT1), and pathological lipid metabolism was associated with OCT1-dependent thiamine transport. However, it is unknown whether clinical pharmacokinetics of thiamine is modulated by OCT1 genotype. We analyzed thiamine transport in vitro, thiamine blood concentrations after high-dose and low-dose (nutritional) intake, and heritability of thiamine and thiamine-phosphate blood concentrations. The variant OCT1*2 had reduced and OCT1*3 to OCT1*6 had deficient thiamine uptake activity. However, pharmacokinetics of thiamine did not differ depending on OCT1 genotype. Further studies in primary human hepatocytes indicated that several cation transporters, including OCT1, OCT3, and THTR-2, contribute to hepatic uptake of thiamine. As much as 54% of the variation in thiamine and 75% in variation of thiamine monophosphate plasma concentrations was determined by heritable factors. Apparently, thiamine is not useful as a probe drug for OCT1 activity, but the high heritability, particularly of thiamine monophosphate, may stimulate further genomic research.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cpt.1666DOI Listing
March 2020

Effects of Single Nucleotide Polymorphism Ala270Ser (rs316019) on the Function and Regulation of hOCT2.

Biomolecules 2019 10 7;9(10). Epub 2019 Oct 7.

Medizinische Klinik D, Experimentelle Nephrologie, Universitätsklinikum Münster, 48149 Münster, Germany.

The human organic cation transporter 2 (hOCT2) is highly expressed in proximal tubules of the kidneys, where it plays an important role in the secretion of organic cations. Since many drugs are organic cations, hOCT2 has relevant pharmacological implications. The hOCT2 gene is polymorphic, and the nonsynonymous single nucleotide polymorphism (SNP) causing the substitution of alanine at position 270 of the protein sequence with serine (Ala270Ser) is present with high frequency in the human population. Therefore, Ala270Ser has potentially important pharmacologic consequences. Here, we analyzed the transport properties and rapid regulation of hOCT2 wildtype and hOCT2 Ala270Ser expressed in human embryonic kidney cells using real-time uptake measurements. Moreover, we compared the expression of hOCT2 in the plasma membrane determined by biotinylation experiments and the cellular transport and toxicity of cisplatin measured by inductively coupled plasma mass spectrometry and a viability test, respectively. The transport characteristics and regulation of the wildtype and mutated hOCT2 were very similar. Interestingly, a higher affinity of hOCT2 Ala270Ser for creatinine was observed. Compared with hOCT2 wildtype, the plasma membrane expression, cisplatin transport, and cisplatin-associated toxicity of hOCT2 Ala270Ser were significantly lower. In conclusion, these findings suggest that Ala270Ser has subtle but important effects on hOCT2 function, which are probably difficult to detect in studies with patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/biom9100578DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6843571PMC
October 2019

Pharmacokinetic Drug-Drug Interactions Between Trospium Chloride and Ranitidine Substrates of Organic Cation Transporters in Healthy Human Subjects.

J Clin Pharmacol 2020 03 22;60(3):312-323. Epub 2019 Sep 22.

Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany.

Trospium chloride, a muscarinic receptor blocker, is poorly absorbed with different rates from areas in the jejunum and the cecum/ascending colon. To evaluate whether organic cation transporter (OCT) 1, OCT2 and multidrug and toxin extrusion (MATE) 1 and MATE2-K are involved in pharmacokinetics, competitions with ranitidine, a probe inhibitor of the cation transporters, were evaluated in transfected HEK293 cells. Furthermore, a drug interaction study with trospium chloride after intravenous (2 mg) and oral dosing (30 mg) plus ranitidine (300 mg) was performed in 12 healthy subjects and evaluated by noncompartmental analysis and population pharmacokinetic modeling. Ranitidine inhibited OCT1, OCT2, MATE1, and MATE2-K with half maximal inhibitory concentration values of 186 ± 25 µM, 482 ± 105 µM, 134 ± 37 µM, and 35 ± 11 µM, respectively. In contrast to our hypothesis, coadministration of ranitidine did not significantly decrease oral absorption of trospium. Instead, renal clearance was lowered by ∼15% (530 ± 99 vs 460 ± 120 mL/min; P < .05). It is possible that ranitidine was not available in competitive concentrations at the major colonic absorption site, as the inhibitor is absorbed in the small intestine and undergoes degradation by microbiota. The renal effects apparently result from inhibition of MATE1 and/or MATE2-K by ranitidine as predicted by in vitro to in vivo extrapolation. However, all pharmacokinetic changes were not of clinical relevance for the drug with highly variable pharmacokinetics. Intravenous trospium significantly lowered mean absorption time and relative bioavailability of ranitidine, which was most likely caused by muscarinic receptor blocking effects on intestinal motility and water turnover.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jcph.1523DOI Listing
March 2020

An in vitro study on interaction of anisodine and monocrotaline with organic cation transporters of the SLC22 and SLC47 families.

Chin J Nat Med 2019 Jul;17(7):490-497

Clinical Pharmacokinetics Lab, China Pharmaceutical University, Nanjing 211198, China. Electronic address:

Current study systematically investigated the interaction of two alkaloids, anisodine and monocrotaline, with organic cation transporter OCT1, 2, 3, MATE1 and MATE2-K by using in vitro stably transfected HEK293 cells. Both anisodine and monocrotaline inhibited the OCTs and MATE transporters. The lowest IC was 12.9 µmol·L of anisodine on OCT1 and the highest was 1.8 mmol·L of monocrotaline on OCT2. Anisodine was a substrate of OCT2 (K = 13.3 ± 2.6 µmol·L and V = 286.8 ± 53.6 pmol/mg protein/min). Monocrotaline was determined to be a substrate of both OCT1 (K = 109.1 ± 17.8 µmol·L, V = 576.5 ± 87.5 pmol/mg protein/min) and OCT2 (K = 64.7 ± 14.8 µmol·L, V = 180.7 ± 22.0 pmol/mg protein/min), other than OCT3 and MATE transporters. The results indicated that OCT2 may be important for renal elimination of anisodine and OCT1 was responsible for monocrotaline uptake into liver. However neither MATE1 nor MATE2-K could facilitate transcellular transport of anisodine and monocrotaline. Accumulation of these drugs in the organs with high OCT1 expression (liver) and OCT2 expression (kidney) may be expected.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/S1875-5364(19)30070-6DOI Listing
July 2019

Lack of an Association between the Functional Polymorphism TREM-1 rs2234237 and the Clinical Course of Sepsis among Critically Ill Caucasian Patients-A Monocentric Prospective Genetic Association Study.

J Clin Med 2019 Mar 3;8(3). Epub 2019 Mar 3.

Department of Anesthesiology, University Medical Center, Georg August University, D-37075 Goettingen, Germany.

Sepsis is a life-threatening condition and a significant challenge for those working in intensive care, where it remains one of the leading causes of mortality. According to the sepsis-3 definition, sepsis is characterized by dysregulation of the host response to infection. The TREM-1 gene codes for the triggering receptor expressed on myeloid cells 1, which is part of the pro-inflammatory response of the immune system. This study aimed to determine whether the functional TREM-1 rs2234237 single nucleotide polymorphism was associated with mortality in a cohort of 649 Caucasian patients with sepsis. The 90-day mortality rate was the primary outcome, and disease severity and microbiological findings were analyzed as secondary endpoints. TREM-1 rs2234237 TT homozygous patients were compared to A-allele carriers for this purpose. Kaplan⁻Meier survival analysis revealed no association between the clinically relevant TREM-1 rs2234237 single nucleotide polymorphism and the 90-day or 28-day survival rate in this group of septic patients. In addition, the performed analyses of disease severity and the microbiological findings did not show significant differences between the TREM-1 rs2234237 genotypes. The TREM-1 rs2234237 genotype was not significantly associated with sepsis mortality and sepsis disease severity. Therefore, it was not a valuable prognostic marker for the survival of septic patients in the studied cohort.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/jcm8030301DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6463065PMC
March 2019

Combined Application of MRI and the Salivary Tracer Technique to Determine the in Vivo Disintegration Time of Immediate Release Formulation Administered to Healthy, Fasted Subjects.

Mol Pharm 2019 04 8;16(4):1782-1786. Epub 2019 Mar 8.

Department of Biopharmaceutics and Pharmaceutical Technology, Institute of Pharmacy , University of Greifswald , Felix-Hausdorff-Straße 3 , 17489 Greifswald , Germany.

The process of disintegration is a crucial step in oral drug delivery with immediate release dosage forms. In this work, the salivary tracer technique was applied as a simple and inexpensive method for the investigation of the in vivo disintegration time of hard gelatin capsules filled with caffeine. The disintegration times observed with the salivary tracer technique were verified by magnetic resonance imaging (MRI). After an overnight fast of at least 10 h and caffeine abstinence of minimum 72 h, conventional hard gelatin capsules containing 50 mg caffeine and 5 mg iron oxide were administered to 8 healthy volunteers. For the period of 1 h after capsule intake, subjects were placed in supine position in the MRI scanner, and scans were performed in short time intervals. Each MRI measurement was directly followed by saliva sampling by drooling. Salivary caffeine concentrations were determined by high performance liquid chromatography followed by mass spectrometric detection (LC/MS-MS). The time point of capsule disintegration was determined by visual inspection of the MR images as well as by an increase in the salivary caffeine concentration. The results indicated that the difference in mean disintegration times of the capsules as determined by the two in vivo methods was around 4 min (8.8 min for MRI vs 12.5 min for saliva). All disintegration times determined by the salivary tracer technique were slightly higher. This delay could be explained by the fact that the appearance of caffeine in saliva required drug absorption in the small intestine. Because capsule disintegration happened mainly in the stomach, the exact site of disintegration as well as the processes of gastric mixing and gastric emptying contributed to the delay between the two methods. This work demonstrated the feasibility of the salivary tracer technique to investigate the in vivo disintegration of immediate release dosage forms in a simple and reliable manner.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.molpharmaceut.8b01320DOI Listing
April 2019

CTLA-4 Genetic Variants Predict Survival in Patients with Sepsis.

J Clin Med 2019 Jan 10;8(1). Epub 2019 Jan 10.

Department of Anesthesiology, University Medical Center, Georg August University, D-37075 Goettingen, Germany.

Cytotoxic T lymphocyte-associated protein 4 (CTLA-4) is a coinhibitory checkpoint protein expressed on the surface of T cells. A recent study by our working group revealed that the rs231775 single nucleotide polymorphism (SNP) in the CTLA-4 gene was associated with the survival of patients with sepsis and served as an independent prognostic variable. To further investigate the impact of CTLA-4 genetic variants on sepsis survival, we examined the effect of two functional SNPs, CTLA-4 rs733618 and CTLA-4 rs3087243, and inferred haplotypes, on the survival of 644 prospectively enrolled septic patients. Kaplan⁻Meier survival analysis revealed significantly lower 90-day mortality for rs3087243 G allele carriers ( = 502) than for AA-homozygous ( = 142) patients (27.3% vs. 40.8%, = 0.0024). Likewise, lower 90-day mortality was observed for TAA haplotype-negative patients ( = 197; compound rs733618 T/rs231775 A/rs3087243 A) than for patients carrying the TAA haplotype ( = 447; 24.4% vs. 32.9%, = 0.0265). Carrying the rs3087243 G allele hazard ratio (HR): 0.667; 95% confidence interval (CI): 0.489⁻0.909; = 0.0103) or not carrying the TAA haplotype (HR: 0.685; 95% CI: 0.491⁻0.956; = 0.0262) remained significant covariates for 90-day survival in the multivariate Cox regression analysis and thus served as independent prognostic variables. In conclusion, our findings underscore the significance of CTLA-4 genetic variants as predictors of survival of patients with sepsis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/jcm8010070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352177PMC
January 2019

Impact of Promoter Polymorphisms on the Transcriptional Regulation of the Organic Cation Transporter OCT1 (SLC22A1).

J Pers Med 2018 Dec 11;8(4). Epub 2018 Dec 11.

Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, 17487 Greifswald, Germany.

The organic cation transporter 1 (OCT1, SLC22A1) is strongly expressed in the human liver and facilitates the hepatic uptake of drugs such as morphine, metformin, tropisetron, sumatriptan and fenoterol and of endogenous substances such as thiamine. OCT1 expression is inter-individually highly variable. Here, we analyzed SNPs in the promoter concerning their potential contribution to the variability in OCT1 expression. Using electrophoretic mobility shift and luciferase reporter gene assays in HepG2, Hep3B, and Huh7 cell lines, we identified the SNPs -1795G>A (rs6935207) and -201C>G (rs58812592) as having effects on transcription factor binding and/or promoter activity. The A-allele of the -1795G>A SNP showed allele-specific binding of the transcription factor NF-Y leading to 2.5-fold increased enhancer activity of the artificial SV40 promoter. However, the -1795G>A SNP showed no significant effects on the native promoter activity. Furthermore, the -1795G>A SNP was not associated with the pharmacokinetics of metformin, fenoterol, sumatriptan and proguanil in healthy individuals or tropisetron efficacy in patients undergoing chemotherapy. Allele-dependent differences in USF1/2 binding and nearly total loss in promoter activity were detected for the G-allele of -201C>G, but the SNP is apparently very rare. In conclusion, common promoter SNPs have only minor effects on OCT1 expression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/jpm8040042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6313513PMC
December 2018

The CTLA-4 rs231775 GG genotype is associated with favorable 90-day survival in Caucasian patients with sepsis.

Sci Rep 2018 10 11;8(1):15140. Epub 2018 Oct 11.

Department of Anesthesiology, University Medical Center, Georg August University, Robert-Koch-Str. 40, D-37075, Goettingen, Germany.

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a surface protein on T cells, that has an inhibitory effect on the host immune reaction and prevents overreaction of the immune system. Because the functional single-nucleotide polymorphism (SNP) rs231775 of the CTLA-4 gene is associated with autoimmune diseases and because of the critical role of the immune reaction in sepsis, we intended to examine the effect of this polymorphism on survival in patients with sepsis. 644 septic adult Caucasian patients were prospectively enrolled in this study. Patients were followed up for 90 days. Mortality risk within this period was defined as primary outcome parameter. Kaplan-Meier survival analysis revealed a significantly lower 90-day mortality risk among GG homozygous patients (n = 101) than among A allele carriers (n = 543; 22% and 32%, respectively; p = 0.03565). Furthermore, the CTLA-4 rs231775 GG genotype remained a significant covariate for 90-day mortality risk after controlling for confounders in the multivariate Cox regression analysis (hazard ratio: 0.624; 95% CI: 0.399-0.975; p = 0.03858). In conclusion, our study provides the first evidence for CTLA-4 rs231775 as a prognostic variable for the survival of patients with sepsis and emphasizes the need for further research to reveal potential functional associations between CTLA-4 and the immune pathophysiology of sepsis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-33246-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181961PMC
October 2018

OCT1 Deficiency Affects Hepatocellular Concentrations and Pharmacokinetics of Cycloguanil, the Active Metabolite of the Antimalarial Drug Proguanil.

Clin Pharmacol Ther 2019 01 1;105(1):190-200. Epub 2018 Aug 1.

Institute for Clinical Pharmacology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany.

Cycloguanil, the active metabolite of proguanil, acts on malaria schizonts in erythrocytes and hepatocytes. We analyzed the impact of the organic cation transporter OCT1 on hepatocellular uptake and pharmacokinetics of proguanil and cycloguanil. OCT1 transported both proguanil and cycloguanil. Common variants OCT1*3 and OCT1*4 caused a substantial decrease and OCT1*5 and OCT1*6 complete abolishment of proguanil uptake. In 39 healthy subjects, low-activity variants OCT1*3 and OCT1*4 had only minor effects on proguanil pharmacokinetics. However, both, cycloguanil area under the time-concentration curve and the cycloguanil-to-proguanil ratio were significantly dependent on number of these low-functional alleles (P = 0.02 for both). Together, CYP2C19, CYP3A5, OCT1 polymorphisms, and sex accounted for 61% of the variation in the cycloguanil-to-proguanil ratio. Most importantly, in vitro OCT1 inhibition caused a fivefold decrease of intracellular cycloguanil concentrations in primary human hepatocytes. In conclusion, OCT1-mediated uptake is a limiting step in bioactivation of proguanil, and OCT1 polymorphisms may affect proguanil efficacy against hepatic malaria schizonts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cpt.1128DOI Listing
January 2019

Assay Conditions Influence Affinities of Rat Organic Cation Transporter 1: Analysis of Mutagenesis in the Modeled Outward-Facing Cleft by Measuring Effects of Substrates and Inhibitors on Initial Uptake.

Mol Pharmacol 2018 04 16;93(4):402-415. Epub 2018 Jan 16.

Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany (V.G.,S.R. C.M.A., U.R. H.K.); Institute of Clinical Pharmacology, University Medical Center, Georg-August University, Göttingen, Germany (M.J.M., M.V.T.); Institute of Pharmacology, Center of Drug Absorption and Transport, University Medical Center Greifswald, Greifswald, Germany (M.V.T.); and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany (T.D.M., H.K.)

The effects of mutations in the modeled outward-open cleft of rat organic cation transporter 1 (rOCT1) on affinities of substrates and inhibitors were investigated. Human embryonic kidney 293 cells were stably transfected with rOCT1 or rOCT1 mutants, and uptake of the substrates 1-methyl-4-phenylpyridinium (MPP) and tetraethylammonium (TEA) or inhibition of MPP uptake by the nontransported inhibitors tetrabutylammonium (TBuA), tetrapentylammonium (TPeA), and corticosterone was measured. Uptake measurements were performed on confluent cell layers using a 2-minute incubation or in dissociated cells using incubation times of 1, 5, or 10 seconds. With both methods, different apparent Michaelis-Menten constant () values, different IC values, and varying effects of mutations were determined. In addition, varying IC values for the inhibition of MPP uptake and varying effects of mutations were obtained when different MPP concentrations far below the apparent value were used for uptake measurements. Eleven mutations were investigated by measuring initial uptake in dissociated cells and employing 0.1 M MPP for uptake during inhibition experiments. Altered affinities for substrates and/or inhibitors were observed when Phe160, Trp218, Arg440, Leu447, and Asp475 were mutated. The mutations resulted in changes of apparent values for TEA and/or MPP Mutation of Trp218 and Asp475 led to altered IC values for TBuA, TPeA, and corticosterone, whereas the mutation of Phe160 and Leu447 changed the IC values for two inhibitors. Thereby amino acids in the outward-facing conformation of rOCT1 could be identified that interact with structurally different inhibitors and probably also with different substrates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/mol.117.110767DOI Listing
April 2018

Effects of genetic polymorphisms on the OCT1 and OCT2-mediated uptake of ranitidine.

PLoS One 2017 13;12(12):e0189521. Epub 2017 Dec 13.

Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen, Germany.

Background: Ranitidine (Zantac®) is a H2-receptor antagonist commonly used for the treatment of acid-related gastrointestinal diseases. Ranitidine was reported to be a substrate of the organic cation transporters OCT1 and OCT2. The hepatic transporter OCT1 is highly genetically variable. Twelve major alleles confer partial or complete loss of OCT1 activity. The effects of these polymorphisms are highly substrate-specific and therefore difficult to predict. The renal transporter OCT2 has a common polymorphism, Ala270Ser, which was reported to affect OCT2 activity.

Aim: In this study we analyzed the effects of genetic polymorphisms in OCT1 and OCT2 on the uptake of ranitidine and on its potency to inhibit uptake of other drugs.

Methods And Results: We characterized ranitidine uptake using HEK293 and CHO cells stably transfected to overexpress wild type OCT1, OCT2, or their naturally occurring allelic variants. Ranitidine was transported by wild-type OCT1 with a Km of 62.9 μM and a vmax of 1125 pmol/min/mg protein. Alleles OCT1*5, *6, *12, and *13 completely lacked ranitidine uptake. Alleles OCT1*2, *3, *4, and *10 had vmax values decreased by more than 50%. In contrast, OCT1*8 showed an increase of vmax by 25%. The effects of OCT1 alleles on ranitidine uptake strongly correlated with the effects on morphine uptake suggesting common interaction mechanisms of both drugs with OCT1. Ranitidine inhibited the OCT1-mediated uptake of metformin and morphine at clinically relevant concentrations. The inhibitory potency for morphine uptake was affected by the OCT1*2 allele. OCT2 showed only a limited uptake of ranitidine that was not significantly affected by the Ala270Ser polymorphism.

Conclusions: We confirmed ranitidine as an OCT1 substrate and demonstrated that common genetic polymorphisms in OCT1 strongly affect ranitidine uptake and modulate ranitidine's potential to cause drug-drug interactions. The effects of the frequent OCT1 polymorphisms on ranitidine pharmacokinetics in humans remain to be analyzed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189521PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5728534PMC
January 2018

OCT1 pharmacogenetics in pain management: is a clinical application within reach?

Pharmacogenomics 2017 Nov 24;18(16):1515-1523. Epub 2017 Oct 24.

Department of Clinical Pharmacology, University Medical Center Göttingen, Göttingen, Germany.

Beside drug metabolizing enzymes alsogenetically variable membrane transporters may substantially contribute to the interindividual variability in pharmacokinetics and efficacy of opioids and other analgesics. The organic cation transporter OCT1 is strongly expressed in the sinusoidal membrane of the human liver. It may affect hepatic uptake and thus limit metabolic rates. OCT1 is highly genetically variable. Genetic polymorphisms lead to substantially reduced OCT1 activity in up to 9% of the Europeans and the white Americans. This review summarize the data on the effect of OCT1 polymorphisms on pharmacokinetics and efficacy of opioids like morphine, codeine, and tramadol and of anti-migraine drugs. It discuss currently possible applications and perspectives for establishing OCT1 pharmacogenetics as a useful tool in personalized pain management.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2217/pgs-2017-0095DOI Listing
November 2017

The FER rs4957796 TT genotype is associated with unfavorable 90-day survival in Caucasian patients with severe ARDS due to pneumonia.

Sci Rep 2017 08 29;7(1):9887. Epub 2017 Aug 29.

Department of Anaesthesiology, University Medical Centre, Georg August University, Robert-Koch-Str.40, D-37075, Goettingen, Germany.

A recent genome-wide association study showed that a genetic variant within the FER gene is associated with survival in patients with sepsis due to pneumonia. Because severe pneumonia is the main cause of acute respiratory distress syndrome (ARDS), we aimed to investigate the effect of the FER polymorphism rs4957796 on the 90-day survival in patients with ARDS due to pneumonia. An assessment of a prospectively collected cohort of 441 patients with ARDS admitted to three intensive care units at the University Medical Centre identified 274 patients with ARDS due to pneumonia. The 90-day mortality risk was recorded as the primary outcome parameter. Sepsis-related organ failure assessment (SOFA) scores and organ support-free days were used as the secondary variables. FER rs4957796 TT-homozygous patients were compared with C-allele carriers. The survival analysis revealed a higher 90-day mortality risk among T homozygotes than among C-allele carriers (p = 0.0144) exclusively in patients with severe ARDS due to pneumonia. The FER rs4957796 TT genotype remained a significant covariate for the 90-day mortality risk in the multivariate analysis (hazard ratio, 4.62; 95% CI, 1.58-13.50; p = 0.0050). In conclusion, FER rs4957796 might act as a prognostic variable for survival in patients with severe ARDS due to pneumonia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-017-08540-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5575093PMC
August 2017

Increased Systemic Exposure and Stronger Cardiovascular and Metabolic Adverse Reactions to Fenoterol in Individuals with Heritable OCT1 Deficiency.

Clin Pharmacol Ther 2018 05 8;103(5):868-878. Epub 2017 Dec 8.

Institute for Clinical Pharmacology, University Medical Center Göttingen, Göttingen, Germany.

Fenoterol is a widely used anti-asthmatic and tocolytic agent, but high plasma concentrations of fenoterol may lead to severe and even fatal adverse reactions. We studied whether heritable deficiency of the liver organic cation transporter 1 (OCT1), a trait observed in 3% of Europeans and white Americans, affects fenoterol plasma concentrations and toxicity. OCT1 transported fenoterol with high affinity, and OCT1 inhibition in human hepatocytes reduced fenoterol uptake threefold. After administration of 180 µg of fenoterol to 39 healthy individuals, the OCT1-deficient individuals (zero active OCT1 alleles; n = 5) showed 1.9-fold greater systemic fenoterol exposure (P = 4.0 × 10 ) and 1.7-fold lower volume of distribution (P = 8.0 × 10 ). Correspondingly, the OCT1-deficient individuals had a 1.5-fold stronger increase in heart rate (P = 0.002), a 3.4-fold greater increase in blood glucose (P = 3.0 × 10 ), and significantly lower serum potassium levels. In conclusion, heritable OCT1 deficiency significantly increases plasma concentrations of fenoterol and may be an important factor underlying the excess mortality associated with fenoterol.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cpt.812DOI Listing
May 2018

Low heritability in pharmacokinetics of talinolol: a pharmacogenetic twin study on the heritability of the pharmacokinetics of talinolol, a putative probe drug of MDR1 and other membrane transporters.

Genome Med 2016 11 8;8(1):119. Epub 2016 Nov 8.

Institute for Clinical Pharmacology, University Medical Center, Georg-August University, Robert-Koch-Straße 40, 37075, Göttingen, Germany.

Background: Efflux transporters like MDR1 and MRP2 may modulate the pharmacokinetics of about 50 % of all drugs. It is currently unknown how much of the variation in the activities of important drug membrane transporters like MDR1 or MRP2 is determined by genetic or by environmental factors. In this study we assessed the heritability of the pharmacokinetics of talinolol as a putative probe drug for MDR1 and possibly other membrane transporters.

Methods: Talinolol pharmacokinetics were investigated in a repeated dose study in 42 monozygotic and 13 same-sex dizygotic twin pairs. The oral clearance of talinolol was predefined as the primary parameter. Heritability was analyzed by structural equation modeling and by within- and between-subject variance and talinolol clearance was correlated with polymorphisms in MDR1, MRP2, BCRP, MDR5, OATP1B1, and OCT1.

Results: Talinolol clearance varied approximately ninefold in the studied sample of healthy volunteers. The correlation of clearances between siblings was not significantly different for the monozygotic and dizygotic pairs. All data analyses consistently showed that variation of talinolol pharmacokinetics was mainly determined by environmental effects. Structural equation modeling attributed 53.5 % of the variation of oral clearance to common environmental effects influencing both siblings to the same extent and 46.5 % to unique environmental effects randomly affecting individual subjects. Talinolol pharmacokinetics were significantly dependent on sex, body mass index, total protein consumption, and vegetable consumption.

Conclusions: The twin study revealed that environmental factors explained much more of the variation in pharmacokinetics of talinolol than genetic factors.

Trial Registration: European clinical trials database number: EUDRA-CT 2008-006223-31. Registered 26 September 2008. ClinicalTrials.gov number: NCT01845194 .
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13073-016-0372-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5101708PMC
November 2016

Loss-of-function polymorphisms in the organic cation transporter OCT1 are associated with reduced postoperative tramadol consumption.

Pain 2016 11;157(11):2467-2475

Institute of Clinical Pharmacology, University Medical Center, Göttingen, Germany.

The organic cation transporter OCT1 (SLC22A1) mediates uptake and metabolism of the active tramadol metabolite (+)O-desmethyltramadol in the liver. In this study, the influence of OCT1 genetic polymorphisms on pharmacokinetics and analgesic efficacy of tramadol in patients recovering from surgery was analyzed in addition to the CYP2D6 genotype. Postoperative patients who received tramadol through patient-controlled analgesia were enrolled. Genotypes resulting in 0, 1, or 2 active OCT1 alleles were determined as well as CYP2D6 genotypes. The primary endpoint was the 24-hour postoperative tramadol consumption in patients with 0 vs at least 1 active OCT1 allele. Secondary endpoint was the OCT1-dependent plasma concentration (areas under the concentration-time curves) of the active tramadol metabolite (+)O-desmethyltramadol. Of 205 patients, 19, 82, and 104 carried 0, 1, and 2 active OCT1 alleles, respectively. Cumulative tramadol consumption through patient-controlled analgesia was lowest in patients with 0 active OCT1 allele compared with the group of patients with 1 or 2 active alleles (343 ± 235 vs 484 ± 276 mg; P = 0.03). Multiple regression revealed that the number of active OCT1 alleles (P = 0.014), CYP2D6 (P = 0.001), pain scores (P < 0.001), and the extent of surgery (0.034) had a significant influence on tramadol consumption. Plasma areas under the concentration-time curves of (+)O-desmethyltramadol were 111.8 (95% confidence interval: 63.4-160.1), 80.2 (65.1-95.3), and 64.5 (51.9-77.2) h·ng·mL in carriers of 0, 1, or 2 active OCT1 alleles (P = 0.03). Loss of OCT1 function resulted in reduced tramadol consumption and increased plasma concentrations of (+)O-desmethyltramadol in patients recovering from surgery. Therefore, analyzing OCT1 next to CYP2D6 genotype might further improve future genotype-dependent dose recommendations for tramadol.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/j.pain.0000000000000662DOI Listing
November 2016

[Severe hypoglycemia following tramadol intake in a 79 year old non-diabetic patient].

Dtsch Med Wochenschr 2016 Sep 4;141(20):1480-1482. Epub 2016 Oct 4.

We report about a 79 year old non-diabetic patient who was admitted to the emergency room with severe hypoglycemia (blood glucose level: 36 mg / dl and Glasgow Coma Scale Score: 3). After the infusion of G40 % her blood glucose level stabilised. The patient reported to have taken 50 mg of Tramadol during the night to treat her headache. No other differential diagnosis for hypoglycemia (i.e. diabetes, insulinoma, severe liver or kidney disease) could be established. Therefore, we suspected a tramadol induced hypoglycemia. The mechanisms and the risk factors for this potential side effect remain unclear. The patient showed no abnormality in metabolism (CYP2D6) or membrane transport (OCT1) of tramadol. No further treatment for hypoglycemic episodes was needed. The patient was discharged after the differential diagnosis and pharmacogenetic testing was completed. Hypoglycemia is a little known adverse effect after tramadol intake, which has only been published in few cases. Tramadol, a weak opioid analgesic classified as step 2 of the WHO cancer pain ladder, is used in moderate pain. Given the continuous rise in tramadol prescription due to better management of chronic pain, further investigation of this issue seems needed as well as an increased awareness amongst physicians.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1055/s-0042-114217DOI Listing
September 2016