Distinct phenotypes and genotypes of debrisoquine hydroxylation among Europeans and Chinese

Controlled Ovarian Hyperstimulation Protocol in Infertile Patients During the COVID-19 Pandemic

Objectives: To explore the appropriate controlled ovarian hyperstimulation (COH) protocols in infertility patients who received the in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatments during the COVID-19 pandemic.

Materials and Methods: This retrospective cohort study evaluated the efficiency of the early follicular-phase long-acting GnRH-agonist long (EFLL) protocol (a new protocol developed by Chinese clinicians), prolonged pituitary down-regulation of EFLL protocol (Pro-EFLL), and the GnRH-ant protocol for couples meeting the study criteria between February 2020 and June 2020 who were treated by the First Affiliated Hospital of Zhengzhou University during the COVID-19 pandemic, and compared the pregnancy rates and miscarriage rates per fresh transfer cycle, number of retrieved oocytes, endometrial thickness on the day of hCG injection and the number of fertilized oocytes, mature oocytes, fertilized oocytes, and transferable embryos among the three protocols.

Results: We found that the prolonged pituitary down-regulation during the COVID-19 pandemic by utilizing a full-dose of GnRH-a administrated in infertility patients were no differences in clinical outcomes than other protocols, The prolonged pituitary down-regulation protocol and EFLL protocol were associated with a higher Endometrial thickness on the day of hCG injection (12.67 ± 2.21 vs. 12.09 ± 2.35 vs. 10.79 ± 2.38, P < 0.001), retrieved oocytes (14.49 ± 6.30 vs. 15.02 ± 7.93 vs. 10.06 ± 7.63, P < 0.001), mature oocytes (11.60 ± 5.71 vs. 11.96 ± 6.00 vs. 7.63 ± 6.50, P < 0.001), fertilized oocytes (9.14 ± 5.43 vs. 8.44 ± 5.34 vs. 5.42 ± 5.20, P < 0.001), and transferable embryos (4.87 ± 2.96 vs. 6.47 ± 5.12 vs. 3.00 ± 3.28 vs. P < 0.001) in the GnRH-antagonist protocol.

Conclusion: We recommend that patients start Gn injections 33–42 days after a pituitary downregulated full dose (3.75 mg) of gonadotropin-releasing hormone agonist during the COVID-19 pandemic, even a delay of 2–4 weeks does not affect the implantation rate. The study can provide a more detailed estimate and clinical management strategies for infertile couples during the COVID-19 pandemic.

Pharmacogenetics of cytochrome P450 and its applications in drug therapy: the past, present and future

The field of cytochrome P450 pharmacogenetics has progressed rapidly during the past 25 years. All the major human drug-metabolizing P450 enzymes have been identified and cloned, and the major gene variants that cause inter-individual variability in drug response and are related to adverse drug reactions have been identified. This information now provides the basis for the use of predictive pharmacogenetics to yield drug therapies that are more efficient and safer. Today, we understand which drugs warrant dosing based on pharmacogenetics to improve drug treatment. It is anticipated that, in the future, genotyping could be used to personalize drug treatment for vast numbers of subjects, decreasing the cost of drug treatment and increasing the efficacy of drugs and health in general. I estimate that such personalized P450 gene-based treatment would be relevant for 10-20% of all drug therapy.

Ethnic and genetic determinants of omeprazole disposition and effect

OBJECTIVES

To compare the pharmacokinetics and dynamics of omeprazole in white and Chinese subjects.

METHODS

This double-blind two-stage study, performed in the clinical research center of a university hospital, evaluated 15 healthy nonsmoking men (eight white subjects and seven Chinese extensive metabolizers of mephenytoin). Blood samples were obtained over 24 hours after the eighth omeprazole dose (40 mg/day). Omeprazole, omeprazole sulfone, and hydroxyomeprazole pharmacokinetics were calculated from the respective plasma concentration-time curves. Twelve- and 24-hour integrated plasma gastriun (AUCgas12 and AUCgas24) were calculated from the respective plasma gastrin concentrations. A week before the initiation of omeprazole the activities of CYP2D6, CYP2C19, and CYP3A4 were determined by previously established methods.

RESULTS

Omeprazole concentrations were significantly lower (mean area under the plasma concentration time curve extrapolated to infinity [AUCO-infinity] +/- SEM; 7.53 +/- 1.21 versus 12.80 +/- 2.13 mumol.hr.L-1, respectively; p < 0.05) and its oral clearance greater (319 +/- 60 versus 183 +/- 35 ml/min, respectively; p < 0.05) in the white subjects than in the Chinese subjects. Omeprazole and omeprazole sulfone AUCO-infinity values were well correlated with the S/R mephenytoin ratio (r = 0.82 and r = 0.84, respectively; p < 0.001) and with urinary 4'-hydroxymephenytoin (r = -0.58 [p < 0.03] and r = -0.52 [p < 0.02], respectively). Fasting gastrin, AUCgas12, and AUCgas24 were significantly greater in the Chinese subjects than in the white subjects (30.0 +/- 6.4 versus 14.4 +/- 1.2 pmol, respectively [p < 0.02]; 661 +/- 114 versus 334 +/- 38 pmol.hr.L-1, respectively [p < 0.002]; and 1414 +/- 228 versus 747 +/- 99 pmol.hr.L-1, respectively [p < 0.004]). In addition, the S/R mephenytoin ratio and omeprazole AUCO-infinity correlated with the extent of omeprazole induced hypergastrinemia.

CONCLUSION

The metabolism of omeprazole and the rise in gastrin concentration after its administration is genetically determined and ethnically dependent.

Determination of dextromethorphan metabolic phenotype by salivary analysis with a reference to genotype in Chinese patients receiving renal hemodialysis

BACKGROUND

The polymorphic metabolism of debrisoquin and sparteine by cytochrome P450IID6 (CYP2D6) is genetically determined. Determination of the CYP2D6 metabolic phenotype with conventional urine analytic methods is not feasible in anuric patients with renal failure. The possibility of using salivary analysis, with dextromethorphan as a probe drug, to determine the CYP2D6 metabolic phenotype in patients with renal failure was evaluated.

METHODS AND RESULTS

One hundred four Chinese patients with renal failure were recruited. All 104 patients were receiving hemodialysis. Saliva was collected before and at 3 hours after each patient took a capsule of dextromethorphan hydrobromide (30 mg). Four patients were excluded because of insufficient samples of saliva. The distribution of logarithms of the metabolic ratios (log[MR]) in the 100 patients appeared to be normal. Administration of quinidine sulfate (200 mg twice daily) to nine of the patients significantly and markedly increased the dextromethorphan metabolic ratios. The metabolic ratios of nine patients pretreated with quinidine were higher than any of the 100 patients with renal failure who did not receive quinidine pretreatment. A metabolic ratio of 33 separated these two groups. Genomic deoxyribonucleic acid was extracted from whole blood in a subset of patients. Polymerase chain reaction (PCR)-based methods were used to detect the CYP2D6 and B mutant genes. Mutant B alleles (which are common in white poor metabolizers) of CYP2D6 genes were not detected in any of the 47 subjects tested. A PCR-based test of cytosine (C188) to thymine (T188) polymorphism at 188 base pairs in exon 1 of CYP2D6 genes was performed in 61 patients. Subjects who were homozygous for C188 had significantly (p = 0.0067) lower log[MR] values than those who were homozygous for T188.

CONCLUSIONS

Determination of dextromethorphan metabolic ratios in saliva is feasible in patients with renal failure requiring hemodialysis. All subjects in this study appeared to be "extensive metabolizer" phenotype for CYP2D6, and no poor metabolizer was identified. From the results with quinidine pretreatment, a metabolic ratio of 33 is suggested to be a tentative antimode for identification of poor metabolizers in patients with renal failure.

Frequency of human CYP2D6 mutant alleles in a normal Chinese population

Substantial differences in the pharmacogenetics of debrisoquine hydroxylation exist between Caucasians and Chinese populations. Among Chinese, not only is the frequency of the poor metabolizer phenotype low, the contribution of the 29B mutation in the CYP2D6 gene is insignificant. By contrast the frequency of D6-J is very common (approximately 0.6) and is clearly related to the activity of debrisoquine hydroxylase. Its presence however, does not predict the poor metabolizer phenotype. The D6-C mutation was also not detectable in our population.

Molecular heterogeneity of the XbaI defined 44kb allele of the CYP2D locus within the Caucasian population

1. Cytochrome P450 debrisoquine (CYP2D6) activity is polymorphic and under genetic control. Most Caucasians are extensive metabolizers, but 5%-10% are poor metabolizers. 2. Restriction fragment length polymorphism analysis of the CYP2D6 locus identifies a 29kb XbaI fragment, either normal (D6-wt) or mutated, and three mutated XbaI alleles (44kb, 11.5kb and 16 + 9kb). The 44kb allele was initially considered as a poor metabolizer allele owing to a D6-B mutation, but cases of 44kb allele not carrying the D6-B, and therefore potentially functional, have been found. The degree of molecular heterogeneity of this allele was investigated by phenotype and genotype analysis of families. 3. Thirty-one French Caucasian families, representing 117 individuals, possessing at least one 44kb allele in each family were selected. Phenotypes were determined using dextromethorphan, and the XbaI, NcoI and BamH1 RFLPs of 42 independent chromosomes were analyzed. 4. 80% of the XbaI 44kb alleles carried the CYP2D6-B mutation and had an additional NcoI fragment (12.5kb or 4.8kb). The remaining 20% did not carry the CYP2D6-B or A mutations and had no extra NcoI fragment. 5. Information on three families demonstrated that 44kb alleles not carrying the CYP2D6-B mutation were associated with the extensive metabolizer phenotype. 6. We conclude that a substantial percentage of XbaI 44kb alleles is associated with a functional CYP2D gene, and therefore, that the XbaI 44kb allele is not consistently a poor metaboliser allele.