Characterization of Clofazimine as a Potential Substrate of Drug Transporter.

In this study, we explored clofazimine (CFZ) as a potential substrate of uptake and efflux transporters that might be involved in CFZ disposition, using transporter gene overexpressing cell lines in vitro. The intracellular concentrations of CFZ were significantly increased in the presence of selective inhibitors of P-gp and BCRP, which include verapamil, cyclosporine-A, PSC-833, quinidine, Ko143, and daunorubicin. In a bidirectional transport assay using transwell cultures of cell lines overexpressing P-gp and BCRP, the mean efflux ratios of CFZ were found to be 4.17 ± 0.63 and 3.37 ± 1.2, respectively. The Km and maximum rate of uptake (Vmax) were estimated to be 223.3 ± 14.73 µM and 548.8 ± 87.15 pmol/min/mg protein for P-gp and 381.9 ± 25.07 µM and 5.8 ± 1.22 pmol/min/mg protein for BCRP, respectively. Among the uptake transporters screened, the CFZ uptake rate was increased 1.93 and 3.09-fold in HEK293 cell lines overexpressing OAT1 and OAT3, respectively, compared to the control cell lines, but no significant uptake was observed in cell lines overexpressing OCT1, OCT2, OATP1B1, OATP1B3, OATP2B1, or NTCP. Both OAT1- and OAT3-mediated uptake was inhibited by the selective inhibitors diclofenac, probenecid, and butanesulfonic acid. The Km and Vmax values of CFZ were estimated to be 0.63 ± 0.15 µM and 8.23 ± 1.03 pmol/min/mg protein, respectively, for OAT1 and 0.47 ± 0.1 µM and 17.81 ± 2.19 pmol/min/mg protein, respectively, for OAT3. These findings suggest that CFZ is a novel substrate of BCRP, OAT1, and OAT3 and a known substrate of P-gp in vitro.

Long-term Comparison of Robotic and Laparoscopic Gastrectomy for Gastric Cancer: A Propensity Score-weighted Analysis of 2084 Consecutive Patients.

OBJECTIVE: To compare long-term outcomes between robotic and LG approaches using propensity score weighting based on a generalized boosted method to control for selection bias. SUMMARY OF BACKGROUND DATA: Minimally invasive surgical approaches for GC are increasing, yet limited evidence exists for long-term outcomes of robotic gastrectomy (RG). METHODS: Patients (n = 2084) with GC stages I-III who underwent LG or RG between 2009 and 2017 were analyzed. Generalized boosted method was used to estimate a propensity score derived from all available preoperative characteristics. Long-term outcomes were compared using the adjusted Kaplan-Meier method and the weighted Cox proportional hazards regression model. RESULTS: After propensity score weighting, the population was balanced. Patients who underwent RG showed reduced blood loss (16 mL less, P = 0.025), sufficient lymph node harvest from the initial period, and no changes in surgical outcomes over time. With 52-month median follow-up, no difference was noted in 5-year overall survival in unweighted [91.5% in LG vs 94% in RG; hazard ratio (HR), 0.71; 95% confidence interval (CI), 0.46-1.1; P = 0.126] and weighted populations (94.2% in LG vs 93.2% in RG; HR, 0.88; 95% CI, 0.52-1.48; P = 0.636). There were no differences in 5-year recurrence-free survival (RFS), with unweighted 5-year RFS of 95.4% for LG and 95.2% for RG (HR, 0.95; 95% CI, 0.55-1.64; P = 0.845) and weighted 5-year RFS of 96.3% for LG and 95.3% for RG (HR, 1.24; 95% CI, 0.66-2.33; P = 0.498). CONCLUSIONS: After balancing covariates, RG demonstrated reliable surgical outcomes from the beginning. Long-term survival after RG and LG for GC was similar.

Prediction of Survival Outcomes Based on Preoperative Clinical Parameters in Gastric Cancer.

BACKGROUND: Few current preoperative risk assessment tools provide essential, optimized treatment for gastric cancer. The purpose of this study was to develop and validate a nomogram that uses preoperative data to predict survival and risk assessments. METHODS: A survival prediction model was constructed using data from a developmental cohort of 1251 patients with stage I to III gastric cancer who underwent curative resection between January 2005 and December 2008 at Ajou University Hospital, Korea. The model was internally validated for discrimination and calibrated using bootstrap resampling. To externally validate the model, data from a validation cohort of 2012 patients with stage I to III gastric cancer who underwent surgery at multiple centers in Korea between January 2001 and June 2006 were analyzed. Analyses included the model's discrimination index (C-index), calibration plots, and decision curve that predict overall survival. RESULTS: Eight independent predictors, including age, sex, clinical tumor size, macroscopic features, body mass index, histology, clinical stages, and tumor location, were considered for developing the nomogram. The discrimination index was 0.816 (adjusted C-index) in the developmental cohort and 0.781 (adjusted C-index) in the external validation cohort. Additionally, in both the developmental and validation datasets, age and tumor size were significantly correlated with each other and were independent indicators for survival (P < 0.05). CONCLUSIONS: We developed a new nomogram by using the most common and significant preoperative parameters that can help to identify high-risk patients before treatment and help clinicians to make appropriate decisions for patients with stage I to III gastric cancer.

Comprehensive Substrate Characterization of 22 Antituberculosis Drugs for Multiple Solute Carrier (SLC) Uptake Transporters In Vitro.

The substrate potentials of antituberculosis drugs on solute carrier (SLC) transporters are not well characterized to date, despite a well-established understanding of their drug dispositions and pharmacokinetics. In this study, we investigated comprehensively the substrate potentials of the 22 currently available antituberculosis drugs for SLC family transporter-mediated uptake, using Xenopus laevis oocytes and stably transfected HEK-293 cells in vitro The result suggested that ethambutol, isoniazid, amoxicillin, and prothionamide act as novel substrates for the SLC transporters. In addition, in the presence of representative transporter inhibitors, the uptake of the antituberculosis drugs was markedly decreased compared with the uptake in the absence of inhibitor, suggesting involvement of the corresponding transporters. A cellular uptake study was performed, and the Km values of ethambutol were found to be 526.1 ± 15.6, 212.0 ± 20.1, 336.8 ± 20.1, and 455.0 ± 28 µM for organic cation transporter 1 (OCT1), OCT2, OCTN1, and OCTN2, respectively. Similarly, the Km of prothionamide was 805.8 ± 23.4 µM for OCT1, while the Km values of isoniazid and amoxicillin for organic anion transporter 3 (OAT3) were 233.7 ± 14.1 and 161.4 ± 10.6 µM, respectively. The estimated in vivo drug-drug interaction indexes from in vitro transporter inhibition kinetics for verapamil, probenecid, and ibuprofen against ethambutol, prothionamide, isoniazid, and amoxicillin were found to show potential for clinical drug interactions. In conclusion, this is the first study that demonstrated 22 antituberculosis drug interactions with transporters. This study will be helpful for mechanistic understanding of the disposition, drug-drug interactions, and pharmacokinetics of these antituberculosis drugs.

Inhibitory effects of Kampo medicines, Keishibukuryogan and Shakuyakukanzoto, on the substrate uptake activities of solute carrier organic anion transporters.

The aim of this study was to assess the effects of Keishibukuryogan (K-06) and Shakuyakukanzoto (TJ-68), commercial herbal medicines, on the substrate uptake activities of renal organic anion transporters. We performed transporter uptake and cell viability assays in Xenopus oocytes and HEK293 human kidney embryonic cells treated with K-06 or TJ-68. K-06 and TJ-68 markedly inhibited the substrate uptake activities of URAT1, OAT1, and OAT3, while they did not exhibit non-cytotoxic effects. Our findings demonstrated that K-06 and TJ-68 inhibited the substrate uptake activities of renal transporters, suggesting their mechanism of action as nephroprotective agents.

Evaluation of para-Aminosalicylic Acid as a Substrate of Multiple Solute Carrier Uptake Transporters and Possible Drug Interactions with Nonsteroidal Anti-inflammatory Drugs In Vitro.

para-Aminosalicylic acid (PAS) is a second-line antituberculosis drug that has been used to treat multidrug-resistant and extensively drug-resistant tuberculosis for more than 60 years. Renal secretion and glomerular filtration are the major pathways for the elimination of PAS. We comprehensively studied PAS transport by using cell lines that overexpressed various transporters and found that PAS acts as a novel substrate of an organic anionic polypeptide (OATP1B1), organic cationic transporters (OCT1 and OCT2), and organic anion transporters (OAT1 and OAT3) but is not a substrate of any ATP-binding cassette (ABC) transporters. Net PAS uptake was measured, and the transport affinities (Km values) for OATP1B1, OCT1, OCT2, OAT1, and OAT3 were found to be 50.0, 20.3, 28.7, 78.1, and 100.1 µM, respectively. The net uptake rates suggested that renal OAT1 and OAT3 play relatively major roles in PAS elimination. The representative inhibitors rifampin for OATP1B1, probenecid for OAT1 and OAT3, and verapamil for OCT1 and OCT2 greatly inhibited PAS uptake, suggesting that PAS is dependent on multiple transporters for uptake. We also evaluated nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), and metformin for the inhibition of PAS uptake via these transporters. Half-maximal (50%) inhibitory concentrations (IC50s) were kinetically determined and used to predict the drug-drug interactions (DDIs) affecting these transporters' activity toward PAS. We found that rifampin, probenecid, ibuprofen, naproxen, cimetidine, and quinidine each exhibited a significant potential for in vivo DDIs with PAS. In this study, PAS was found to be a novel substrate of several transporters, and drugs that inhibit these transporters can reduce PAS elimination.

Modified overlap method using knotless barbed sutures (MOBS) for intracorporeal esophagojejunostomy after totally laparoscopic gastrectomy.

BACKGROUND: Compared to end-to-side anastomosis with a circular stapler, the overlap method is favored for intracorporeal esophagojejunostomy because it facilitates handling of the stapler, even in narrow spaces, and wider anastomosis. However, it associates with technical difficulties during anastomosis, including difficult traction on the esophageal stump that necessitates stay sutures. Here, we introduce a new modified overlap method that employs knotless barbed sutures (MOBS) and report the outcomes of our case series. METHOD: All consecutive patients who underwent intracorporeal esophagojejunostomy in 2015-2016 were included. All patients underwent surgery as follows: After esophageal transection with a linear stapler, two V-loc 90 sutures (Covidien, Mansfield, MA, USA) were sutured in the center of the stapled line. The opening was made between the two threads, and the intraluminal space was identified. The jejunum was ascended toward the esophageal stump by inserting a 45-mm-long linear staple. The anastomosis was made at the space between the right and left crura. After firing the linear stapler, the entry hole was closed bidirectionally using the pre-sutured threads. RESULTS: Forty patients underwent MOBS (27 by laparoscopy; 13 by robot). Mean total operative and MOBS procedural times were 180.6 and 22.4 min, respectively. Mean hospital stay was 6.9 days. Two patients had major complications (5.0 %). There were no anastomosis-related complications. Laparoscopy and robot subgroups did not differ in mean MOBS procedural times (22.2 vs. 22.7 min, p = 0.787). CONCLUSION: MOBS is a safe and feasible method that is a good option for intracorporeal esophagojejunostomy after laparoscopic gastrectomy.

Pharmacogenetic analysis of advanced non-small-cell lung cancer patients treated with first-line paclitaxel and carboplatin chemotherapy.

BACKGROUND: Genetic polymorphisms contribute toward interindividual variations in drug response. We investigated the effects of genetic polymorphisms on the clinical outcome of advanced non-small-cell lung cancer patients with first-line paclitaxel and carboplatin. MATERIALS AND METHODS: A total of 194 non-small-cell lung cancer patients were prospectively enrolled from January 2010 to January 2013. We genotyped 11 polymorphisms in seven genes involved in the glycolysis pathway and the related pharmacokinetic/pharmacodynamic pathway. Genetic associations with PET-SUV, survival outcome, and toxicity were analyzed, and in-vitro drug transport activity was measured in the oocyte system. RESULTS: Patients with the c.334 T>G and c.699 G>A homozygous variant in SLCO1B3 showed a higher incidence of grade 3/4 anemia (P=0.002). Transport activities of oocyte that overexpress the SLCO1B3 c.699 G>A variant showed a significantly decreased uptake of paclitaxel compared with the wild-type expressing oocytes. In addition, patients with GG/GA/AA genotypes of ABCB1, c.2677 T>G/A locus showed inferior progression-free survival (hazard ratio=1.49, P=0.017) compared with other genotypes. The GA genotype of HIF1A, c.1834 G>A locus was associated with inferior progression-free survival compared with the GG genotype (hazard ratio=2.47, P=0.008). CONCLUSION: This study showed that the SLCO1B3 c.699 G>A polymorphism may predict anemia and ABCB1, HIF1A polymorphism are highly predictive for worse survival in advanced NSCLC with first-line paclitaxel and carboplatin.

Inhibitory Interaction Potential of 22 Antituberculosis Drugs on Organic Anion and Cation Transporters of the SLC22A Family.

Twenty-two currently marketed antituberculosis drugs were comprehensively evaluated for their inhibitory effect on organic anionic transporter (OAT)- and organic cation transporter (OCT)-mediated uptake using stably transfected HEK293 cells in vitro We observed moderate to strong inhibitory effects on OAT1- and OAT3-mediated para-aminohippurate (PAH) uptake and OCT1- and OCT2-mediated N-methyl-4-phenylpylidinium acetate (MPP+) uptake. Ciprofloxacin, linezolid, para-aminosalicylic acid (PAS), and rifampin were observed to have strong inhibitory effects, with the concentrations for a 50% inhibitory effect (IC50s) being 35.1, 31.1, 37.6, and 48.1 µM, respectively, for OAT1 and >100, 21.9, 24.6, and 30.2 µM, respectively, for OAT3. Similarly, pyrazinamide, rifabutin, and levofloxacin were observed to have inhibitory effects, with IC50 values being 36.5, 42.7, and 30.3 µM, respectively, for OCT1 and with the IC50 value for PAS being 94.2 µM for OCT2. In addition, we used zidovudine and metformin as clinically prescribed substrates of OATs and OCTs, respectively, and zidovudine and metformin uptake was also strongly inhibited by the antituberculosis drugs. Among the tested drugs, the highest drug-drug interaction (DDI) indexes were found for PAS, which were 9.3 to 13.9 for OAT1 and 12.0 to 17.7 for OAT3, and linezolid, which were 1.18 to 2.15 for OAT1 and 1.7 to 3.01 for OAT3. Similarly, the DDI indexes of pyrazinamide and levofloxacin were 0.57 and 0.30, respectively, for OCT1, and the DDI index of PAS was 3.8 for OCT2, suggesting a stronger possibility (DDI index value cutoff, >0.1) of in vivo DDIs. This is the first comprehensive report of the inhibitory potential of anti-TB drugs on OAT- and OCT-mediated uptake of prototype and clinically prescribed substrate drugs in vitro, providing an ability to predict DDIs between anti-TB drugs and other coprescribed drugs in clinical studies in vivo.

Characterization of 22 Antituberculosis Drugs for Inhibitory Interaction Potential on Organic Anionic Transporter Polypeptide (OATP)-Mediated Uptake.

We investigated the inhibitory interaction potential of 22 currently marketed antituberculosis (TB) drugs on organic anion-transporting polypeptide 1B1 (OATP1B1)-, OATP2B1-, and OATP1B3-mediated uptake using in vitro Xenopus oocytes and HEK cells. Rifabutin, ethambutol, amoxicillin, linezolid, p-amino salicylic acid, and rifapentine exhibited mild to moderate inhibitory effects on OATP-mediated uptake of estrone-3 sulfate, estradiol 17ß-d-glucuronide, and rosuvastatin. The 50% inhibitory concentration (IC50) values of rifabutin, amoxicillin, ethambutol, p-amino salicylic acid, and linezolid were 35.4, 36.2, 57.6, 72.6, and 65.9 µM, respectively, for uptake mediated by organic anionic transporter polypeptide 1B1 (OATP1B1) and 28.8, 28.9, 53.9, 31.5, and 61.0 µM, respectively, for uptake mediated by organic anionic transporter polypeptide 1B3 (OATP1B3). Streptomycin and linezolid showed greater inhibition of organic anionic transporter polypeptide 2B1 (OATP2B1)-mediated uptake, with IC50 values of 33.2 and 35.6 µM, respectively, along with mild inhibition of other drugs. Furthermore, rifabutin, amoxicillin, and rifapentine significantly inhibited OATP1B1-mediated rosuvastatin uptake, with IC50 values of 12.3, 13.0, and 11.0 µM, respectively, which showed a similar profile to estrone-3 sulfate uptake. The calculated R values ([I]u inlet,max/Ki, where [I]u inlet,max represents the maximum estimated inhibitor concentration inlet to the liver and Ki is the inhibition constant) as the drug-drug interaction (DDI) indexes of PAS, ethambutol, and amoxicillin were 26.1, 6.5, and 4.3 for OATP1B1 and 52.0, 8.0, and 4.6 for OATP1B3, and those for streptomycin, amikacin, and linezolid were 5.0, 4.2, and 4.4 for OATP2B1, respectively, suggesting a higher possibility of in vivo DDIs. This study is the first comprehensive report to show the novel inhibitory potential of 22 marketed anti-TB drugs on OATP-mediated uptake, providing evidence for future in vivo clinical DDI studies.

Increased serum bile acid concentration following low-dose chronic administration of thioacetamide in rats, as evidenced by metabolomic analysis.

A liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS)-based metabolomics approach was employed to identify endogenous metabolites as potential biomarkers for thioacetamide (TAA)-induced liver injury. TAA (10 and 30mg/kg), a well-known hepatotoxic agent, was administered daily to male Sprague-Dawley (SD) rats for 28days. We then conducted untargeted analyses of endogenous serum and liver metabolites. Partial least squares discriminant analysis (PLS-DA) was performed on serum and liver samples to evaluate metabolites associated with TAA-induced perturbation. TAA administration resulted in altered levels of bile acids, acyl carnitines, and phospholipids in serum and in the liver. We subsequently demonstrated and confirmed the occurrence of compromised bile acid homeostasis. TAA treatment significantly increased serum levels of conjugated bile acids in a dose-dependent manner, which correlated well with toxicity. However, hepatic levels of these metabolites were not substantially changed. Gene expression profiling showed that the hepatic mRNA levels of Ntcp, Bsep, and Oatp1b2 were significantly suppressed, whereas those of basolateral Mrp3 and Mrp4 were increased. Decreased levels of Ntcp, Oatp1b2, and Ostα proteins in the liver were confirmed by western blot analysis. These results suggest that serum bile acids might be increased due to the inhibition of bile acid enterohepatic circulation rather than increased endogenous bile acid synthesis. Moreover, serum bile acids are a good indicator of TAA-induced hepatotoxicity.

Glucuronidation of fimasartan, a new angiotensin receptor antagonist, is mainly mediated by UGT1A3.

1. Fimasartan is an angiotensin receptor II antagonist used to treat patients with hypertension. This drug is mainly excreted into bile as either the parent compound or a glucuronide conjugate. In this study, we examined the glucuronidation of fimasartan and characterized the UDP-glucuronosyltransferases (UGTs) responsible for the glucuronidation. 2. Only one type of fimasartan glucuronide was observed after incubation with pooled human liver microsomes (HLMs) and was identified as an N2-glucuronide based on comparison with an authentic standard. 3. Among the 12 UGT isoforms tested, UGT1A1, UGT1A3 and UGT2B7 showed catalytic activity toward fimasartan glucuronidation. The intrinsic clearance (CLint) of UGT1A3 was 68.5- and 21.4-fold higher than that of UGT1A1 and UGT2B7, respectively, and the estimated relative contribution of UGT1A3 in human liver was 94.1%. Both chemical inhibition and correlation studies demonstrated that fimasartan glucuronidation activity in HLMs was significantly related with UGT1A3 activity. Fimasartan glucuronide was identified as a substrate for P-glycoprotein (Pgp) and breast cancer response protein (BCRP). 4. These findings collectively indicate that UGT1A3 is the major UGT isoform responsible for the glucuronidation of fimasartan, and this glucuronide is excreted from hepatocytes via MDR1 and BCRP.

Prognostic impacts of participation in prospective surgical clinical trials on surgical outcomes in gastric cancer patients.

Various prospective surgical trials have been conducted on treating patients with gastric cancer. In clinical practice, patients and surgeons may hesitate to participate in prospective surgical trials due to trial-related complications. In this study, we evaluated the effects of participation in prospective surgical trials on surgical outcomes after radical gastrectomy for gastric cancer. This study included 1689 patients who underwent curative gastrectomy for gastric cancer between 2016 and 2020. The propensity score weighting (PSW) method was used to adjust for differences in baseline clinicopathological characteristics between patients who participated and those who did not participate in prospective surgical clinical trials. Perioperative outcomes and overall survival were compared between groups. Of the 1689 patients, 309 (18.3%) participated in surgical clinical trials (SCT group). Before PSW, the SCT group had a similar operation time, intraoperative blood loss, complications, major complications, and hospital stay as the non-SCT group but had superior overall survival. After PSW, overall survival and perioperative outcomes were not significantly different between the groups. The present study suggests that participation in prospective surgical trials was not associated with surgical outcomes. Patients and surgeons may participate in prospective surgical trials without fearing adverse effects on surgical outcomes.

Deep learning using computed tomography to identify high-risk patients for acute small bowel obstruction: development and validation of a prediction model : a retrospective cohort study.

OBJECTIVE: To build a novel classifier using an optimized 3D-convolutional neural network for predicting high-grade small bowel obstruction (HGSBO). SUMMARY BACKGROUND DATA: Acute SBO is one of the most common acute abdominal diseases requiring urgent surgery. While artificial intelligence and abdominal computed tomography (CT) have been used to determine surgical treatment, differentiating normal cases, HGSBO requiring emergency surgery, and low-grade SBO (LGSBO) or paralytic ileus is difficult. METHODS: A deep learning classifier was used to predict high-risk acute SBO patients using CT images at a tertiary hospital. Images from three groups of subjects (normal, nonsurgical, and surgical) were extracted; the dataset used in the study included 578 cases from 250 normal subjects, with 209 HGSBO and 119 LGSBO patients; over 38 000 CT images were used. Data were analyzed from 1 June 2022 to 5 February 2023. The classification performance was assessed based on accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve. RESULTS: After fivefold cross-validation, the WideResNet classifier using dual-branch architecture with depth retention pooling achieved an accuracy of 72.6%, an area under receiver operating characteristic of 0.90, a sensitivity of 72.6%, a specificity of 86.3%, a positive predictive value of 74.1%, and a negative predictive value of 86.6% on all the test sets. CONCLUSIONS: These results show the satisfactory performance of the deep learning classifier in predicting HGSBO compared to the previous machine learning model. The novel 3D classifier with dual-branch architecture and depth retention pooling based on artificial intelligence algorithms could be a reliable screening and decision-support tool for high-risk patients with SBO.

Prevention of Gallstones After Bariatric Surgery using Ursodeoxycholic Acid: A Narrative Review of Literatures.

Obesity by itself is a factor in the development of gallstone disease, and periods of weight loss after bariatric surgery further increase the risk of gallstone formation. In patients with obesity, hypersecretion of cholesterol may increase the risk of gallstone formation, which is approximately five-fold higher than that in the general population. The incidence of gallstone formation after bariatric surgery is 10-38% and often associated with a proportional increase in the risk of developing biliary complications. Routine postoperative administration of ursodeoxycholic acid (UDCA) is recommended to prevent gallstone formation. Several randomized trials have indicated that UDCA can effectively prevent gallstones and reduce the risk of cholecystectomy after bariatric procedures. The effective daily dose of UDCA in each study ranged from 500 to 1,200 mg, and it may be considered at least during the period of rapid weight loss (first 3-6 months postoperatively) to decrease the incidence of symptomatic gallstones.

Differential effect of genetic variants of Na(+)-taurocholate co-transporting polypeptide (NTCP) and organic anion-transporting polypeptide 1B1 (OATP1B1) on the uptake of HMG-CoA reductase inhibitors.

The purpose of this study was to investigate the effect of genetic variations in organic anion-transporting polypeptide 1B1 (OATP1B1) and Na(+)/taurocholate co-transporting polypeptide (NTCP) on the uptake of various statins having different affinities for these transporters. The functional activities and simultaneous expression of NTCP and OATP1B1 were confirmed by the uptake of taurocholate and estrone-3-sulphate as representative substrates for NTCP and OATP1B1, respectively, and by an immunofluorescence analysis. The substrate specificities of NTCP and OATP1B1 for statins and the effects of genetic variations on the uptake of rosuvastatin, pitavastatin, and atorvastatin were measured. Based on the K(m) values and intrinsic clearances of the three statins, pitavastatin was taken up more efficiently than rosuvastatin and atorvastatin by OATP1B1. Consequently, the cellular accumulation of pitavastatin was modulated according to the genetic variation of OATP1B1 (OATP1B1*15), rather than NTCP*2. In contrast, NTCP*2 displayed greater transport of atorvastatin and rosuvastatin, compared with NTCP wild type. Thus, the measurements of decreased rosuvastatin and atorvastatin transport by OATP1B1*15 were confounded by the presence of NTCP and its genetic variant, NTCP*2. In conclusion, the functional consequences of genetic variants of NTCP and OATP1B1 may be different for various statins, depending on the substrate specificity of the OATP1B1 and NTCP transporters.

Genetic polymorphisms in Na+-taurocholate co-transporting polypeptide (NTCP) and ileal apical sodium-dependent bile acid transporter (ASBT) and ethnic comparisons of functional variants of NTCP among Asian populations.

Genetic variants of Na(+)-taurocholate co-transporting polypeptide (NTCP; SLC10A1) and ileal apical sodium-dependent bile acid transporter (ASBT; SLC10A2), which greatly contribute to bile acid homeostasis, were extensively explored in the Korean population and functional variants of NTCP were compared among Asian populations. From direct DNA sequencing, six SNPs were identified in the SLC10A1 gene and 14 SNPs in the SLC10A2 gene. Three of seven coding variants were non-synonymous SNPs: two variants from SLC10A1 (A64T, S267F) and one from SLC10A2 (A171S). No linkage was analysed in the SLC10A1 gene because of low frequencies of genetic variants, and the SLC10A2 gene was composed of two separated linkage disequilibrium blocks contrary to the white population. The stably transfected NTCP-A64T variant showed significantly decreased uptakes of taurocholate and rosuvastatin compared with wild-type NTCP. The decreased taurocholate uptake and increased rosuvastatin uptake were shown in the NTCP-S267F variant. The allele frequencies of these functional variants were 1.0% and 3.1%, respectively, in a Korean population. However, NTCP-A64T was not found in Chinese and Vietnamese subjects. The frequency distribution of NTCP-S267F in Koreans was significantly lower than those in Chinese and Vietnamese populations. Our data suggest that NTCP-A64T and -S267F variants cause substrate-dependent functional change in vitro, and show ethnic difference in their allelic frequencies among Asian populations although the clinical relevance of these variants is remained to be evaluated.