The frequency of CYP2C19 genetic polymorphisms in Russian patients with peptic ulcers treated with proton pump inhibitors

Introduction

Cytochrome P450 is known to be a major enzyme responsible for the oxidative metabolism of drugs in the liver. Proton pump inhibitors, which are widely used as acid-inhibitory agents for the treatment of peptic ulcers, are mainly metabolized by CYP2C19, and by CYP3A4 to a lesser extent. CYP2C19 is the main isoenzyme which is related to the metabolism of omeprazole and esomeprazole, while both CYP2C19 and CYP3A4 undertake the metabolism of pantoprazole and lansoprazole. As for rabeprazole it undergoes non-enzymatic conversion and therefore has less reliance on CYP2C19. All the metabolites produced are inactive.^1,2

CYP2C19 has genetic polymorphisms that correlate with its activity. All the individuals may be classified as extensive metabolizers (EMs), poor metabolizers (PMs), intermediate metabolizers (IMs), and ultra-rapid metabolizers (UMs) according to their CYP2C19-based ability to metabolize proton pump inhibitors.^3,4

Individuals with CYP2C19*1/*1 genotype are EMs, they carry two wild-type alleles and have no mutation, whereas those who have CYP2C19*2 (681G>A) or CYP2C19*3 (636 G>A) mutation alleles are designated as IMs, if heterozygous, and PMs, if homozygous. IMs and especially PMs have superior acid suppression with conventional doses of proton pump inhibitors.^5–7 The CYP2C19*17 (−806 C>T) allele, a novel allele identified by Sim et al⁸ is associated with ultra-rapid phenotype and provides decreased acid suppression with standard recommended doses of proton pump inhibitors.^9–11 The areas under the concentration-time curve of proton pump inhibitors are higher in PMs than in EMs, whereas IMs are intermediate between the two; UMs have the lowest area under the concentration-time curve. Thus, proton pump inhibitors may not provide sufficient acid suppression in EMs and especially UMs.

Genotyping for CYP2C19 polymorphisms reveals considerable interethnic differences. Most PMs are to be found among Asian and African-American population (allele frequencies are 30% and 17% for CYP2C19*2; 5% and 0.4% for CYP2C19*3, respectively). CYP2C19*2 is also relatively common in Caucasians with an allele frequency of 15% compared to 0.04% for CYP2C19*3 allele.² Thus, genetic polymorphism of CYP2C19 could be of clinical concern in the treatment of peptic ulcers with proton pump inhibitors.

The aim of the study – to investigate the frequencies of CYP2C19*2, CYP2C19*3, and CYP2C19*17 alleles and genotypes in Russian patients with peptic ulcers.

Methods

We retrospectively reviewed the cases of 971 patients of Caucasian origin with Russian nationality from the Moscow region with endoscopically and histologically proven ulcers, 428 males (44%) and 543 females (56%). The mean age was 44.6±11.9 years (range: 15–88 years). We selected patients who were tested for CYP2C19 polymorphism. In all patients, CYP2C19 polymorphism testing and gastroduodenoscopy with biopsy were done after informed consent was obtained.

DNA was extracted from ethylenediaminetetraacetic acid whole blood samples (10 mL) and isolated from peripheral lymphocytes. The polymorphisms CYP2C19 681G>A (CYP2C19*2, rs4244285), CYP2C19 636 G>A (CYP2C19*3, rs4986893), and CYP2C19 −806 C>T (CYP2C19*17, rs12248560) were evaluated using real-time polymerase chain reaction. We used LightMix for CYP2C19*2 and CYP2C19*3 and LightSNiP for CYP2C19*17 (Roche^®; Hoffman-La Roche Ltd, Basel, Switzerland) in a LightCycler 2.0 system.¹²

Patients were referred to as EMs, PMs, IMs or UMs according to the Dutch Pharmacogenetics Working Group Guideline of the Royal Dutch Pharmacists Association (http://www.pharmgkb.org/guideline/PA166104957).

The correspondence of the distribution of the genotype frequencies to the Hardy-Weinberg equilibrium was assessed using a χ² test with Yates correction. A P-value <0.05 was considered statistically significant. The statistical analysis was performed using SPSS Statistic 20.

Results

Regarding CYP2C19 genotype, 317 patients out of 971 were CYP2C19*1/*1 carriers classified as EMs, 386 with CYP2C19*1/*17 or CYP2C19*17/*17 genotype were UMs, 251 were IMs, and 17 were PMs (Table 1).

Table 1 CYP2C19 genetic polymorphisms frequency in Russian patients with peptic ulcers

The allele frequencies were the following: CYP2C19*2 – 0.140, CYP2C19*3 – 0.006, CYP2C19*17 – 0.274 (Table 2). Genotype frequencies are summarized in Table 3.

Table 2 CYP2C19 allele frequency in Russian patients with peptic ulcers

Table 3 CYP2C19 genotype frequency in Russian patients with peptic ulcers

The observed genotype frequencies were in the Hardy-Weinberg equilibrium (P>0.05) for the majority of CYP2C19 polymorphisms. We did not calculate CYP2C19*3 deviation from the Hardy-Weinberg equilibrium because CYP2C19*3 mainly occurs in Asian populations and is rare in Caucasians.

Discussion

The incidence of peptic ulcer in different countries of the world varies from 5% to 15%. It has been reported that CYP2C19 polymorphism affects cure rates of peptic ulcers.^4–7 CYP2C19*2 and CYP2C19*3 alleles are associated with high eradication rates of Helicobacter pylori in patients with peptic ulcers, when triple therapy is administered.⁶ The data on CYP2C19*17 allele are very scarce. It is reported, that patients carrying ultra-rapid CYP2C19*17 allele have lower levels of proton pump inhibitors in plasma.⁷

Our study provides data on CYP2C19 genetic polymorphisms and is the first that has investigated CYP2C19*17 allele frequency in Russian patients with peptic ulcers.

We compared CYP2C19*2 allele and genotype frequency in our study and in Gaikovitch et al’s study on healthy volunteers from Voronezh area, Russia, and no statistically significant difference was found, P>0.05 (Tables 4 and 5).¹³

Table 4 CYP2C19*2 allele frequency in Russian patients with peptic ulcers compared to healthy Russian volunteers

Table 5 CYP2C19*2 genotype frequency in Russian patients with peptic ulcers compared to healthy Russian volunteers

The frequency of CYP2C19*2 allele in our study is also comparable with data described for healthy volunteers from Slovenia (15.9%), Italy (9.4%), Croatia (15%), the Netherlands (13.3%), Germany (15%), and Greece (13.1%).^14–19

CYP2C19*17 allele frequency in Russian patients tended to be higher than in Swedish (18%) and Chinese (4%) populations, thus a standard dose of proton pump inhibitors may not be effective in this group.⁸

Conclusion

There is a high frequency of CYP2C19 genotypes associated with modified response to proton pump inhibitors in Russian patients with peptic ulcers. Genotyping for CYP2C19 polymorphisms is suggested to be a useful tool for personalized dosing of proton pump inhibitors.

Disclosure

The authors declare no conflicts of interest.

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