The impact of human CES1 genetic variation on enzyme activity assessed by ritalinic acid/methylphenidate ratios

The present clinical trial investigated the impact of selected SNPs in CES1 on the metabolic activity of the enzyme. For this purpose, we used methylphenidate (MPH) as a pharmacological probe and the d-RA/d-MPH (metabolite/parent drug) ratios as a measure of enzymatic activity. This metabolic ratio (MR) was validated against the AUC ratios (AUC_{d -RA} /AUC_{d -MPH} ). CES1 SNPs from 120 volunteers were identified, and 12 SNPs fulfilling predefined inclusion criteria were analysed separately, comparing the effect of each genotype on the metabolic ratios. The SNP criteria were as follows: presence of Hardy-Weinberg equilibrium, a minor allele frequency ≥ 0.01 and a clearly interpretable sequencing result in at least 30% of the individuals. Each participant ingested 10 mg of racemic methylphenidate, and blood samples were drawn prior to and 3 hours after drug administration. The SNP analysis confirmed the considerable impact of rs71647871 (G143E) in exon 4 on drug metabolism. In addition, three volunteers with markedly lower median MR, indicating decreased CES1 activity, harboured the same combination of three SNPs in intron 5. The median MR for these SNPs was 8.2 for the minor allele compared to 16.4 for the major alleles (P = 0.04). Hence, one of these or the combination of these SNPs could be of clinical significance considering that the median MR of the G143E group was 5.4. The precise genetic relationship of this finding is currently unknown, as is the clinical significance.

Novel approach for CES1 genotyping: integrating single nucleotide variants and structural variation

Aim: Development of a specific procedure for genotyping of CES1A1 (CES1) and CES1A2, a hybrid of CES1A1  and the pseudogene CES1P1. Materials & methods: The number of CES1A1 and CES1A2  copies and that of CES1P1  were determined using real-time PCR. Long range PCRs followed by secondary PCRs allowed sequencing of single nucleotide variants in CES1A1 and CES1A2. Results & conclusion: A procedure consisting of two main steps was developed. Its first main step, the copy number determination, informed about presence of CES1A2 . This information enabled choice of PCR in the second main step, which selectively amplified CES1A1 and, if present, also CES1A2, for subsequent sequencing. Examination of 501 DNA samples suggested that our procedure is specific with potential for personalization of drug treatments.

Reappraisal of the genetic diversity and pharmacogenetic assessment of CES1

The CES1 gene encodes a hydrolase that metabolizes important drugs. Variants generated by exchange of segments with CES1P1 complicate genotyping of CES1. Using a highly specific procedure we examined DNA samples from 200 Caucasians and identified 46 single nucleotide variants (SNVs) in CES1 and 21 SNVs in CES1A2, a hybrid composed of CES1 and CES1P1. Several of these SNVs were novel. The frequencies of SNVs with a potential functional impact were below 0.02 suggesting limited pharmacogenetic potential for CES1 genotyping. In silico PCR revealed that the majority of the primer pairs for amplification of CES1 or CES1A2 in three previous studies lacked specificity, which partially explains a limited overlap with our findings.

The impact of CES1 genotypes on the pharmacokinetics of methylphenidate in healthy Danish subjects

AIMS

This study investigated the influence of CES1 variations, including the single nucleotide polymorphism (SNP) rs71647871 (G143E) and variation in copy number, on the pharmacokinetics of a single oral dose of 10 mg methylphenidate.

METHODS

CES1 genotype was obtained from 200 healthy Danish Caucasian volunteers. Based on the genotype, 44 (19 males and 25 females) were invited to participate in an open, prospective trial involving six predefined genotypes: three groups with two, three and four CES1 copies, respectively; a group of carriers of the CES1 143E allele; a group of individuals homozygous for CES1A1c (CES1VAR); and a group having three CES1 copies, in which the duplication, CES1A2, had increased transcriptional activity. Plasma concentrations of methylphenidate and its primary metabolites were determined at scheduled time points.

RESULTS

Median AUC of d-methylphenidate was significantly larger in the group carrying the 143E allele (53.3 ng ml^-1  h^-1 , range 38.6-93.9) than in the control group (21.4 ng ml^-1  h^-1 , range 15.7-34.9) (P < 0.0001). Median AUC of d-methylphenidate was significantly larger in the group with four CES1 copies (34.5 ng ml^-1  h^-1 , range 21.3-62.8) than in the control group (P = 0.01) and the group with three CES1 copies (23.8 ng ml^-1  h^-1 , range 15.3-32.0, P = 0.03). There was no difference between the groups with two and three copies of CES1.

CONCLUSIONS

The 143E allele resulted in an increased AUC, suggesting a significantly decreased CES1 enzyme activity. Surprisingly, this was also the case in subjects with homozygous duplication of CES1, perhaps reflecting an undiscovered mutation affecting the activity of the enzyme.

Population Pharmacokinetics of Methylphenidate in Healthy Adults Emphasizing Novel and Known Effects of Several Carboxylesterase 1 (CES1) Variants

The aim of this study was to identify demographic and genetic factors that significantly affect methylphenidate (MPH) pharmacokinetics (PK), and may help explain interindividual variability and further increase the safety of MPH. d‐MPH plasma concentrations, demographic covariates, and carboxylesterase 1 (CES1) genotypes were gathered from 122 healthy adults and analyzed using nonlinear mixed effects modeling. The structural model that best described the data was a two‐compartment disposition model with absorption transit compartments. Novel effects of rs115629050 and CES1 diplotypes, as well as previously reported effects of rs71647871 and body weight, were included in the final model. Assessment of the independent and combined effect of CES1 covariates identified several specific risk factors that may result in severely increased d‐MPH plasma exposure.

Distribution of HLA-G extended haplotypes and one HLA-E polymorphism in a large-scale study of mother-child dyads with and without severe preeclampsia and eclampsia

The etiological pathways and pathogenesis of preeclampsia have rendered difficult to disentangle. Accumulating evidence points toward a maladapted maternal immune system, which may involve aberrant placental expression of immunomodulatory human leukocyte antigen (HLA) class Ib molecules during pregnancy. Several studies have shown aberrant or reduced expression of HLA-G in the placenta and in maternal blood in cases of preeclampsia compared with controls. Unlike classical HLA class Ia loci, the nonclassical HLA-G has limited polymorphic variants. Most nucleotide variations are clustered in the 5'-upstream regulatory region (5'URR) and 3'-untranslated regulatory region (3'UTR) of HLA-G and reflect a stringent expressional control. Based on genotyping and full gene sequencing of HLA-G in a large number of cases and controls (n > 900), the present study, which to our knowledge is the largest and most comprehensive performed, investigated the association between the HLA-G 14-bp ins/del (rs66554220) and HLA-E polymorphisms in mother and newborn dyads from pregnancies complicated by severe preeclampsia/eclampsia and from uncomplicated pregnancies. Furthermore, results from extended HLA-G haplotyping in the newborns are presented in order to assess whether a combined contribution of nucleotide variations spanning the 5'URR, coding region, and 3'UTR of HLA-G describes the genetic association with severe preeclampsia more closely. In contrast to earlier findings, the HLA-G 14-bp ins/del polymorphism was not associated with severe preeclampsia. Furthermore, the polymorphism (rs1264457) defining the two nonsynonymous HLA-E alleles, HLA-E*01:01:xx:xx and HLA-E*01:03:xx:xx, were not associated with severe preeclampsia. Finally, no specific HLA-G haplotypes were significantly associated with increased risk of developing severe preeclampsia/eclampsia.

Pharmacodynamic Impact of Carboxylesterase 1 Gene Variants in Patients with Congestive Heart Failure Treated with Angiotensin-Converting Enzyme Inhibitors

BACKGROUND

Variation in the carboxylesterase 1 gene (CES1) may contribute to the efficacy of ACEIs. Accordingly, we examined the impact of CES1 variants on plasma angiotensin II (ATII)/angiotensin I (ATI) ratio in patients with congestive heart failure (CHF) that underwent ACEI dose titrations. Five of these variants have previously been associated with drug response or increased CES1 expression, i.e., CES1 copy number variation, the variant of the duplicated CES1 gene with high transcriptional activity, rs71647871, rs2244613, and rs3815583. Additionally, nine variants, representatives of CES1Var, and three other CES1 variants were examined.

METHODS

Patients with CHF, and clinical indication for ACEIs were categorized according to their CES1 genotype. Differences in mean plasma ATII/ATI ratios between genotype groups after ACEI dose titration, expressed as the least square mean (LSM) with 95% confidence intervals (CIs), were assessed by analysis of variance.

RESULTS

A total of 200 patients were recruited and 127 patients (63.5%) completed the study. The mean duration of the CHF drug dose titration was 6.2 (SD 3.6) months. After ACEI dose titration, there was no difference in mean plasma ATII/ATI ratios between subjects with the investigated CES1 variants, and only one previously unexplored variation (rs2302722) qualified for further assessment. In the fully adjusted analysis of effects of rs2302722 on plasma ATII/ATI ratios, the difference in mean ATII/ATI ratio between the GG genotype and the minor allele carriers (GT and TT) was not significant, with a relative difference in LSMs of 0.67 (95% CI 0.43-1.07; P = 0.10). Results of analyses that only included enalapril-treated patients remained non-significant after Bonferroni correction for multiple parallel comparisons (difference in LSM 0.60 [95% CI 0.37-0.98], P = 0.045).

CONCLUSION

These findings indicate that the included single variants of CES1 do not significantly influence plasma ATII/ATI ratios in CHF patients treated with ACEIs and are unlikely to be primary determinants of ACEI efficacy.

Individualization of treatments with drugs metabolized by CES1: combining genetics and metabolomics

CES1 is involved in the hydrolysis of ester group-containing xenobiotic and endobiotic compounds including several essential and commonly used drugs. The individual variation in the efficacy and tolerability of many drugs metabolized by CES1 is considerable. Hence, there is a large interest in individualizing the treatment with these drugs. The present review addresses the issue of individualized treatment with drugs metabolized by CES1. It describes the composition of the gene encoding CES1, reports variants of this gene with focus upon those with a potential effect on drug metabolism and provides an overview of the protein structure of this enzyme bringing notice to mechanisms involved in the regulation of enzyme activity. Subsequently, the review highlights drugs metabolized by CES1 and argues that individual differences in the pharmacokinetics of these drugs play an important role in determining drug response and tolerability suggesting prospects for individualized drug therapies. Our review also discusses endogenous substrates of CES1 and assesses the potential of using metabolomic profiling of blood to identify proxies for the hepatic activity of CES1 that predict the rate of drug metabolism. Finally, the combination of genetics and metabolomics to obtain an accurate prediction of the individual response to CES1-dependent drugs is discussed.

Potential role of the porcine superoxide dismutase 1 (SOD1) gene in pig reproduction

In a recent study we confirmed that QTL regions on pig chromosomes 11, 13, and 15 are associated with reproduction traits in the pig. Within these regions the genetic variation was largest on chromosome 13. The QTL region on this chromosome was therefore studied further to identify genes known to contribute to litter size. The superoxide dismutase (SOD1) gene localized at around 200 Mb in the pig (Sscrofa10) was the most obvious candidate gene. In the present study, we have cloned and sequenced the porcine SOD1 gene. The SOD1 amino acid sequence is highly conserved between human, mouse, rat, and pig. Expression studies by quantitative PCR showed differential levels of the SOD1 transcript in all tissues investigated. Sequence comparison between sows with high and low estimated breeding value (EBV) for litter size, revealed a total of eight single nucleotide polymorphisms (SNPs) in the noncoding sequence and no SNPs in the coding region. One of the intronic SNPs was genotyped in 248 sows with high and low EBV for litter size. Allele frequency differed significantly between the two group of sows indicating that polymorphism in the chromosome 13 locus has an impact on litter size. The sows homozygous for the A/A genotype conceive three piglets more compared to the A/T genotype, making this SNP a possible marker for litter size. However, this genotype was negatively correlated with other important traits under selection in the Danish pig production.

A study of the occurrence of monochorionic and monozygotic twinning in the pig

In humans as well as in most farm animals, monozygotic twins have been described. Nevertheless, only a few reports of twinning in the pig have been published. It has been suggested that monozygotic twins are formed during the first 14 days of pregnancy. This monozygotic twin study includes the investigation of porcine monochorionic embryos from 76 sows at days 26-29 post-insemination (p.i.), as well as an examination of 10 whole litters at days 21-22 p.i. In the former group, 29% of the sows carried monochorionic embryos. Based on DNA profiling using microsatellite markers, one monozygotic twin pair was found among these embryos. In the latter group, three monozygotic twin pairs were identified. Thus, it can be concluded that although the occurrence of monozygotic twins in pigs is a sporadic event, the fusion of extra-embryonic membranes is relatively common.

Porcine Parkin: Molecular cloning of PARK2 cDNA, expression analysis, and identification of a splicing variant

Parkin, encoded by the PARK2 gene, is an E3 ligase which functions as an integral component of the cytoplasmic ubiquitin/proteasomal protein degradation pathway. Mutations in the PARK2 gene, resulting in the loss of parkin function, leads to autosomal recessive juvenile Parkinsonism (AR-JP). This work reports the cloning and characterization of the porcine (Sus scrofa) PARK2 cDNA (SsPARK2) and splicing variants hereof. The PARK2 cDNA was amplified by the reverse transcriptase polymerase chain reaction (RT-PCR) using oligonucleotide primers derived from in silico sequences. The porcine PARK2 cDNA codes for a protein of 461 amino acids which shows a high similarity to orangutan (91%), human (86%), and to rat (82%) parkin. A splicing variant of the porcine PARK2 with a complete deletion of exon 9 was also identified. Expression analysis by quantitative real-time RT-PCR revealed presence of PARK2 transcript in all examined organs and tissues. Differential expression was observed, with very high levels of PARK2 mRNA in cerebellum, heart, and kidney. In addition, expression analysis showed that porcine PARK2 transcripts could be detected early in embryo development in different brain regions. The porcine PARK2 orthologue was mapped to chromosome 1p24-25. Single nucleotide polymorphism (SNP) analysis revealed seven SNPs in the porcine PARK2 gene, one missense and one silent mutation in exon 7 and five SNPs in intron 7.