| Chapter 1 The polymorphisms of drug transporters on the effect of telmisartan pharmacokineticsBackgroundTelmisartan is an angiotensinⅡreceptor antagonist,can high selectively and irreversibly antagonize AT1 receptor,but don't inhibit the angiotensin-converting enzyme or affect the effects of bradykinin.It also does not bind or block other hormone receptors or ion channels,therefore does not affect the other receptor systems including the cardiovascular condition system.In recent years,much evdences has shown that,,beside the effect on decrease the blood pressure,telmisartan also has the effects on other cardiovascular disease,endocrine diseases,nephropathy and diseases of the nervous system.The basis for the remarkable interindividual differences in the plasma concentration and response of telmisartan remains unknown.Several drug transporters are involved in the ADME process of telmisartan.Pharmacogenetics studies have shown that genes encoding drug transporters have a variety of single nucleotide polymorphisms(SNP).Genetic factors that affect the activity of drug transporters may be one of the reasons for the individual differences in telmisartan plasma concentration and drug response.There are three main drug transporters impact the process of telmisartan in vivo,MDR1(P-gp),MRP2 and OATP1B3.The polymorphisms of the genes can affect the pharmacokinetics of their own substrates.Therefore, in our researches,we investigated genetic polymorphisms of these three drug transporters on the effect of telmisartan pharmacokinetics in healthy volunteers and the steady-state concentration or treatment in hypertensive patients.MethodsGenotyping of the MDR1 C3435T,MRP2 G1249A,MRP2 C3972T, OATP1B3 T334G and OATP1B3 G699A polymorphism were performed by using method of polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP).Sixty unrelated male volunteers were enrolled and screened for their MDR1 C3435T genotypes,and were selected for participation in the further study.The subjects,whose genotype fit the requirements,received a single oral dose of 40 mg telmisartan.Venous blood samples of 5 mL were drawn from forearm vein into EDTA tubes before(0 h) and at 0.25,0.5,0.75,1,1.5,2,3,4, 6,8,10,12,24,and 48h,respectively,after telmisartan administration.Plasma was separated,and determined by high performance liquid chromatogrammass spectrometry(HPLC-MS).The pharmacokinetics of telmisartan was analyzed with DAS 2.0 software.Statistical analyses were performed by the SPSS 13.0 software for Windows. Essential hypertension patients were requested to measure the basis blood pressure before telmisartan therapy.All the patients were treated with telmisartan for 30 days,according to once a day,40 mg per time in every morning.Blood pressure was measured in the thirty-first days,and venous blood samples were collected before telmisartan administration.The plasma was used to determine the concentration of telmisartan and whole blood was used to analyze the genotypes of MDR1 C3435T,MRP2 C3972T,OATP1B3 T334G and OATP1B3 G699A,respectively.The plasma concentration of telmisartan was determined by high performance liquid chromatogram-fluorescence detector(HPLC-FLD).Statistical analyses were performed by the SPSS 13.0 software for Windows.ResultsThe allelic frequencies and genotype distribution of MDR1 C3435T, MRP2 G1249A,MRP2 C3972T,OATP1B3 T334G and OATP1B3 G699A were not different from those reported in Chinese.OATP1B3 T334G and OATP1B3 G699Apolymorphisms are in complete linkage disequilibrium.Mean±SD and variation of Tmax,Cmax,t1/2,AUC0-48 and AUC0-∞ of 40 mg orally administrated telmisartan were 1.4±0.7 h(0.5～3.0 h),312.7±279.7μg·L-1(26.4～871.7μg·L-1),13.9±8.1 h(2.5～38.9 h),1477.4±927.4μg·h·L-1 (184.8～3134.0μg·h·L-1) and 1662.3±1100.1μg·h·L-1(194.7～3816.2μg·h·L-1), respectively,in the overall 19 cases of subjects.There are significant individual differences in the pharmacokinetics of telmisartan.The blood pressure of 58 cases of essential hypertensive patients before and after telmisartan therapy were 164/94 mmHg(range:220～130 mmHg for SBP;128～70 mmHg for DBP) and 143/87 mmHg(range:194～110 mmHg for SBP;110～65 mmHg for DBP) respectively.There was also significant individual difference in the concentration of telmisartan.Statistical analysis showed that the polymorphism of MDR1 C3435T,MRP2 C3972T,OATP1B3 T334G/OATP1B3 G699A were not associated with plasma steady-state concentration of telmisartan.MRP2 C3972T polymorphism affected ASBP with telmisartan therapy,individuals with the 3972TT genotype showed significantly higher degree of decrease in SBP after telmisartan therapy.ConclusionWe found that the MDR1 C3435T,MRP2 G1249A,MRP2 C3972T,OATP1B3 T334G and OATP1B3 G699A polymorphism were not associated with the pharmacokinetics parameters of telmisartan in this study.The genetic polymorphisms of MDR1 C3435T,MRP2 C3972T,OATP1B3 T334G/OATP 1B3 G699A were not associated with telmisartan steady-state concentration, MRP2 C3972T polymorphism affectedΔSBP with telmisartan therapy. Chapter 2 Effect of genetic polymorphisms in SIRT1 and DDAH1 on antihypertensive efficacy of telmisartan in a Chinese populationBackgroundHypertension is an important disease which affecting human health and quality of life since the nearly half a century.Telmisartan is an angiotensinⅡreceptor antagonist;it is widely used in clinical treatment of hypertension. Evidence has shown that the response rate of telmisartan ranged from 52%to 56%in mild-to-moderate hypertension in patients with different ethnic backgrounds.A considerable percentage of patients also need dose titration during hypertension monotherapy.The basis for the remarkable interindividual difference in telmisartan response remains unknown.With the deep researches on the pharmacological effects of telmisartan, scientists found that telmisartan can increase the expression of PPAR-γ, reduce the expression of DDAH(Dimethylarginine dimethylaminohydrolase) and increase the concentration of the endogenous NO synthase inhibitor-ADMA (Asymmetric dimethylarginine).Therefore,telmisartan can not only decrease the BP,but also improve insulin resistance and glucose-lipid metabolism disorders,and have the antiatherogenic role.SIRT1 is one of silent information regulator 2(SIR2).Sirtuins require nicotinamide adenine dinucleotide(NAD+) as a cosubstrate for the deacetylation reaction,and they are highly preserved among numerous species and are associated with longevity,cell cycle regulation,apoptosis,DNA damage repair,and muscle differentiation.Deletion analysis of the AT1R gene promoter revealed that suppression of AT1R expression by resveratrol,a well known SIRT1 activator, is dependent on the most proximal promoter region(from -61 bp to -25 bp), which contains Sp1 binding site(GC box),the data suggested that resveratrol inhibits Sp1 binding to AT1R gene promoter and AT1R gene transcription, induced AT1R downregulation.We,therefore,hypothesized that the polymorphism of DDAH1 and SIRT1 maybe affect the treatment of telmisartan in the level of post-receptor.In this part of our researches,we focus on whether the DDAH1 and SIRT1 genetic polymorphisms may affect the antihypertensive efficacy of telmisartan,in order to find the SNPs which can impact the response of telmisartan,and provide guidance for the clinical application of telmisartan.MethodsEssential hypertension patients were requested to measure the basic blood pressure,and collected 5 mL blood samples.The plasma was used to detect the concentration of ADMA,and the blood cell was used to extract DNA. Patients were treated with telmisartan for 30 days,according to once a day,40 mg per time in the morning.Measure the blood pressure in the 31th days,and 7 mL blood samples were collected before telmisartan administration.The plasma was used to determine the concentration of ADMA. Genotype of the DDAH1 C143611G,DDAH1 C144563T and SIRT1 C-1138T polymorphism were performed by using method of polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP).The plasma concentration of ADMA was determined by high performance liquid chromatogram-mass spectrometry(HPLC-MS).Statistical analyses were performed by the SPSS 13.0 software for Windows.ResultsThe genotype and allele frequencies distribution characteristics of DDAH1 C143611G,DDAH1 C144563T and SIRT1 C-1138T were the same as the results reported in HapMap.58 cases of patients had finished the study.The mean concentration of ADMA was 0.355±0.014μmol·L-1(range from 0.632μmol·L-1 to 0.106μmol·L-1) before treatment,and 0.455±0.020μmol·L-1(range from 0.759μmol·L-1 to 0.140μmol·L-1) after 30-day therapy treatment.Fourteen EH cases showed decreased plasma concentration of ADMA after telmisartan treatment, while 44 EH cases showed increased plasma concentration of ADMA after telmisartan treatment.Significant differences in plasma concentration of before and after telmisartan treatment was observed(p＜0.001).Significant difference inΔSBP andΔDBP was observed among individuals with different genotypes of DDAH1 C144563T polymorphism. Significant difference inΔDBP was also observed among individuals with different genotypes of SIRT1 C-1138T polymorphism.No association was observed between DDAH1 C143611G polymorphism and the hypotensive effect of telmisartan.ConclusionDDAH1 C144563T and SIRT1 C-1138T polymorphism may affect the anti-hypertensive efficacy of telmisartan in Chinese population.
|
PDF Full Text Request