Association of FSHR gene polymorphisms with poor ovarian response in patients undergoing IVF: A systematic review and meta-analysis

BACKGROUND

The results of studies on the association between polymorphisms in the FSHR gene and the risk of POR undergoing IVF have been inconsistent with each other, so we conducted a meta-analysis of all the available studies to explore the association between polymorphisms in the FSHR gene and the risk of POR.

METHODS

Literature that met the inclusion criteria was collected by searching six electronic databases and basic data from included studies were extracted. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of association between follicle-stimulating hormone receptor (FSHR) gene polymorphism and poor ovarian response (POR) risk. Begg's and Egger's tests were used to determine whether there was publication bias, and sensitivity analysis and TSA analysis were used to verify the stability and reliability of the results.

RESULTS

We included 24 articles, 22 of which explored rs6166, including 2,206 cases and 3,897 controls. 6 articles explored rs6165, including 444 cases and 875 controls. Under additive, heterozygote, and dominant models, rs6166 was significantly associated with POR (S vs. N: OR = 1.29, 95 % CI = 1.05-1.59, P = 0.017; NS vs. NN: OR = 1.33, 95 % CI = 1.02-1.74, P = 0.038; NS + SS vs. NN: OR = 1.38, 95 % CI = 1.04-1.84, P = 0.025). In ethnicity-based subgroup analyses, the additive, homozygote, heterozygote, and dominant models increased Asian POR risk. Among the five genetic models, rs6165 was significantly associated with POR (T vs. C: OR = 1.64, 95 % CI = 1.25-2.16, P = 0.000; TT vs. CC: OR = 2.76, 95 % CI = 1.43-5.32, P = 0.003; CT vs. CC: OR = 1.58, 95 % CI = 1.19-2.10, P = 0.001; TT vs. CC + CT: OR = 2.32, 95 % CI = 1.67-3.23, P = 0.000; CT + TT vs. CC: OR = 1.80, 95 % CI = 1.22-2.65, P = 0.003). In ethnicity-based subgroup analyses, all five genetic models increased the risk of POR in Caucasians.

CONCLUSION

According to the current meta-analysis, the rs6166 S allele was significantly associated with an increased risk of POR, especially in Asian populations. The rs6165 T allele was significantly associated with an increased risk of POR, especially in Caucasian populations.

The Pendulum Movement of Orbital Fat and Retro-Orbicularis Oculi Fat: A New Strategy for Correction of Sunken Eyelid Deformity in Revision Upper Blepharoplasty for Asian Patients

BACKGROUND

With an increasing number of East Asians undergoing blepharoplasty, the number of patients with secondary upper eyelid deformities is increasing. The sunken eyelid deformity is a common deformity after upper blepharoplasty in Asians due to over-resection, retraction, or atrophy of the nasal and central orbital fat pads. Herein, we present a novel procedure, the pendulum movement of orbital fat and retro-orbicularis oculi fat ("POR" technique), for correction of sunken eyelid deformity in secondary Asian blepharoplasty.

METHODS

Patients who underwent secondary upper blepharoplasty with the POR technique by the senior author between January 2020 and October 2021 were identified retrospectively. Those with fewer than 6 months of follow-up were excluded. Patient charts and images were reviewed for demographic data, comorbidities, concomitant eyelid deformities, and postoperative complications. Pre- and postoperative aesthetics, including degree of sunken eyelid deformity, were assessed by two independent raters and by self-reported patient satisfaction.

RESULTS

Forty-nine consecutive patients were identified, all of whom were female and had grade I or II sunken eyelid deformity. Median follow-up was 8 months. Concomitant deformities included high tarsal crease (N = 31 patients, 63.3%), ptosis (N = 13, 26.5%), and upper eyelid retraction (N = 5, 10.2%). Almost patients had improvement in their eyelid volume, and 95.9% had improvement in their aesthetic rating. Approximately 93.9% of patients were satisfied with the outcome.

CONCLUSIONS

The POR technique is an effective technique for correction of sunken eyelid deformity and can be utilized in conjunction with other techniques during secondary blepharoplasty.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Exploring Novel Variants of the Cytochrome P450 Reductase Gene (POR) from the Genome Aggregation Database by Integrating Bioinformatic Tools and Functional Assays

Cytochrome P450 oxidoreductase (POR) is an essential redox partner for steroid and drug-metabolizing cytochromes P450 located in the endoplasmic reticulum. Mutations in POR lead to metabolic disorders, including congenital adrenal hyperplasia, and affect the metabolism of steroids, drugs, and xenobiotics. In this study, we examined approximately 450 missense variants of the POR gene listed in the Genome Aggregation Database (gnomAD) using eleven different in silico prediction tools. We found that 64 novel variants were consistently predicted to be disease-causing by most tools. To validate our findings, we conducted a population analysis and selected two variations in POR for further investigation. The human POR wild type and the R268W and L577P variants were expressed in bacteria and subjected to enzyme kinetic assays using a model substrate. We also examined the activities of several cytochrome P450 proteins in the presence of POR (WT or variants) by combining P450 and reductase proteins in liposomes. We observed a decrease in enzymatic activities (ranging from 35% to 85%) of key drug-metabolizing enzymes, supported by POR variants R288W and L577P compared to WT-POR. These results validate our approach of curating a vast amount of data from genome projects and provide an updated and reliable reference for diagnosing POR deficiency.

SNPs in cytochrome P450 genes decide on the fate of individuals with genetic predisposition to Parkinson's disease

Parkinson's disease (PD) is one of the most frequent neurological diseases affecting millions of people worldwide. While the majority of PD cases are of unknown origin (idiopathic), about 5%-10% are familial and linked to mutations in different known genes. However, there are also people with a genetic predisposition to PD who do not develop the disease. To elucidate factors leading to the manifestation of PD we compared the occurrence of single nucleotide polymorphisms (SNPs) in various cytochrome P450 (P450) genes in people with a genetic predisposition and suffering from PD (GPD) to that of people, who are genetically predisposed, but show no symptoms of the disease (GUN). We used the PPMI (Parkinson's Progression Markers Initiative) database and the gene sequences of all 57 P450s as well as their three redox partners. Corresponding odds ratios (OR) and confidence intervals (CI) were calculated to assess the incidence of the various SNPs in the two groups of individuals and consequently their relation to PD. We identified for the first time SNPs that are significantly (up to 10fold!) over- or under-represented in GPD patients compared to GUN. SNPs with OR > 5 were found in 10 P450s being involved in eicosanoid, vitamin A and D metabolism as well as cholesterol degradation pointing to an important role of endogenous factors for the manifestation of PD clinical symptoms. Moreover, 12 P450s belonging to all P450 substrate classes as well as POR have SNPs that are significantly under-represented (OR < 0.2) in GPD compared to GUN, indicating a protective role of those SNPs and the corresponding P450s regarding disease advancement. To the best of our knowledge our data for the first time demonstrate an association between known PD predisposition genes and SNPs in other genes, shown here for different P450 genes and for their redox partner POR, which promote the manifestation of the disease in familial PD. Our results thus shed light onto the pathogenesis of PD, especially the switch from GUN to GPD and might further help to advance novel strategies for preventing the development or progression of the disease.

A CYPome-wide study reveals new potential players in the pathogenesis of Parkinson's disease

Genetic and environmental factors lead to the manifestation of Parkinson's disease (PD) but related mechanisms are only rudimentarily understood. Cytochromes P450 (P450s) are involved in the biotransformation of toxic compounds and in many physiological processes and thus predestinated to be involved in PD. However, so far only SNPs (single nucleotide polymorphisms) in CYP2D6 and CYP2E1 have been associated with the susceptibility of PD. Our aim was to evaluate the role of all 57 human P450s and their redox partners for the etiology and pathophysiology of PD and to identify novel potential players which may lead to the identification of new biomarkers and to a causative treatment of PD. The PPMI (Parkinson's Progression Markers Initiative) database was used to extract the gene sequences of all 57 P450s and their three redox partners to analyze the association of SNPs with the occurrence of PD. Applying statistical analyses of the data, corresponding odds ratios (OR) and confidence intervals (CI) were calculated. We identified SNPs significantly over-represented in patients with a genetic predisposition for PD (GPD patients) or in idiopathic PD (IPD patients) compared to HC (healthy controls). Xenobiotic-metabolizing P450s show a significant accumulation of SNPs in PD patients compared with HC supporting the role of toxic compounds in the pathogenesis of PD. Moreover, SNPs with high OR values (>5) in P450s catalyzing the degradation of cholesterol (CYP46A1, CY7B1, CYP39A1) indicate a prominent role of cholesterol metabolism in the brain for PD risk. Finally, P450s participating in the metabolism of eicosanoids show a strong over-representation of SNPs in PD patients underlining the effect of inflammation on the pathogenesis of PD. Also, the redox partners of P450 show SNPs with OR > 5 in PD patients. Taken together, we demonstrate that SNPs in 26 out of 57 P450s are at least 5-fold over-represented in PD patients suggesting these P450s as new potential players in the pathogenesis of PD. For the first time exceptionally high OR values (up to 12.9) were found. This will lead to deeper insight into the origin and development of PD and may be applied to develop novel strategies for a causative treatment of this disease.

Hepatic nuclear factor 4 alpha promotes the ferroptosis of lung adenocarcinoma via transcriptional activation of cytochrome P450 oxidoreductase

Background

Lung adenocarcinoma is one of the most prevalent cancers while ferroptosis is crucial for cancer therapies. This study aims to investigate the function and mechanism of hepatic nuclear factor 4 alpha (HNF4A) in lung adenocarcinomas' ferroptosis.

Materials and Methods

HNF4A expression in ferroptotic A549 cells was detected. Then HNF4A was knocked down in A549 cells while overexpressed in H23 cells. Cells with changed HNF4A expression were tested for cytotoxicity and the level of cellular lipid peroxidation. The expression of cytochrome P450 oxidoreductase (POR) expression was examined after HNF4A was knocked down or overexpressed. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and dual-luciferase assays were performed to validate the regulation of HNF4A on POR. Finally, POR was restored in HNF4A-altered cells to check whether it restores the effect of HNF4A on ferroptosis.

Results

We found that HNF4A expression significantly decreased in the ferroptosis of A549 cells, and this change can be blocked by deferoxamine, an inhibitor of ferroptosis. Knockdown of HNF4A inhibited ferroptosis in A549 cells while overexpression of HNF4A promoted ferroptosis in H23 cells. We identified a key ferroptosis-related gene, POR serves as a potential target gene of HNF4A, whose expression was significantly changed in lung adenocarcinoma cells knocking down or overexpressing HNF4A. We demonstrated that HNF4A was bound to the POR's promoter to enhance POR expression, and identified the binding sites via ChIP-qPCR and luciferase assays. Restoration of POR expression blocked the promoting effect of HNF4A on ferroptosis in lung adenocarcinoma.

Conclusion

HNF4A promotes POR expression through binding to the POR's promoter, and subsequently promotes the ferroptosis of lung adenocarcinoma.

Congenital adrenal hyperplasia, disorders of sex development, and infertility in patients with POR gene pathogenic variants: a systematic review of the literature

BACKGROUND

P450 oxidoreductase (POR) deficiency (PORD) is characterized by congenital adrenal hyperplasia (CAH) and disorders of sex development (DSD) in both sexes. PORD can also associate with skeletal defects. However, the prevalence of these phenotypes is unknown.

AIM

To evaluate the prevalence of CAH, DSD, and infertility of patients with POR gene pathogenic variants by a systematic review of the literature.

METHODS

The literature search was performed through PubMed, MEDLINE, Cochrane, Academic One Files, Google Scholar, and Scopus databases. All studies reporting information on CAH, DSD, testicular adrenal rest tumor (TARTs), and fertility in patients with POR gene pathogenic variants were included. Finally, the prevalence of abnormal phenotypes was calculated.

RESULTS

Of the 246 articles initially retrieved, only 48 were included for a total of 119 (46 males and 73 females) patients with PORD. We also included the case of a male patient who consulted us for CAH and TARTs but without DSD. This patient, found to be a carrier of combined heterozygous POR mutation, reached fatherhood spontaneously. All the patients found had CAH. The presence of DSD was found in 65.2%, 82.1%, and 82.1% of patients with compound heterozygosity, homozygosity, or monoallelic heterozygous variants, respectively. The prevalence was significantly higher in females than in males. The prevalence of TARTs in patients with PORD is 2.7%. Only 5 women with PORD became pregnant after assisted reproductive techniques and delivered a healthy baby. Except for the recently reported proband, no other studies focused on male infertility in patients with POR gene variants.

CONCLUSION

This systematic review of the literature reports the prevalence of CAH, DSD, and TARTs in patients with PORD. The unknown prevalence of POR gene pathogenetic variants and the paucity of studies investigating fertility do not allow us to establish whether PORD is associated with infertility. Further studies on both women and men are needed to clarify this relationship.

The impact of the embryo banking on the cumulative live birth rate in women with poor ovarian response according to the Bologna criteria

Purpose

To evaluate the impact of embryo banking on the cumulative live birth rate (CLBR) and the time to live birth (TTLB) in poor ovarian responders (POR) according to the Bologna criteria.

Methods

A total of 276 infertile women undergoing IVF with POR were included in this retrospective study. They were divided into two groups with (n = 121) or without (n = 155) embryo banking at the discretion of the attending physicians. A total of 656 and 405 stimulation cycles were started in the two groups respectively during the 24 month follow-up.

Results

The biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth rate per transfer were comparable between two groups (p > 0.05). The CLBR was significantly lower in the banking group than in the non-banking group (31.4% (38/121) and 43.2% (67/151), p < 0.05). TTLB was significantly longer in the banking group (20.5 months vs. 16.0 months, p < 0.001). In the Kaplan-Meier analysis, the cumulative incidence of live birth was significantly lower in the banking group compared with the non-banking group (Log rank test, chi-square = 21.958, p < 0.001).

Conclusions

Embryo banking in women undergoing IVF with POR based on the Bologna criteria reduces CLBR and lengthens TTLB when compared with no embryo banking.

Mechanism of Guilu Erxian ointment based on targeted metabolomics in intervening in vitro fertilization and embryo transfer outcome in older patients with poor ovarian response of kidney-qi deficiency type

OBJECTIVE

To study the effect of Guilu Erxian ointment on the outcome of IVF-ET in older patients with poor ovarian response infertility of kidney-qi deficiency type, and to verify and analyze the mechanism of action of traditional Chinese medicine on improving older patients with poor ovarian response infertility of kidney-qi deficiency type from the perspective of metabolomics using targeted metabolomics technology, identify the related metabolic pathways, and provide metabolic biomarker basis and clinical treatment ideas for improving older patients with poor ovarian response infertility.

METHODS

This study was a double-blind, randomized, placebo-controlled trial, and a total of 119 infertile patients who underwent IVF-ET at Shandong Center for Reproduction and Genetics of Integrated Traditional Chinese and Western Medicine were selected. Eighty older patients with infertility undergoing IVF were randomly divided into older treatment group and older placebo group, and another 39 young healthy women who underwent IVF-ET or ICSI due to male factors were selected as the normal control group. Flexible GnRH antagonist protocol was used for ovulation induction in all three groups, and Guilu Erxian ointment and placebo groups started taking Guilu Erxian ointment and placebo from the third day of menstruation until IVF surgery. And ultra-high performance liquid chromatography-triple quadrupole mass spectrometer (UHPLC-QTRAP MS) was used to detect metabolites in the three groups of samples.

RESULTS

Compared with the placebo group, the number of oocytes retrieved, 2PN fertilization, high-quality embryos, total number of available embryos and estrogen on HCG day were increased in the treatment group, and the differences were statistically significant (P > 0.05), but the clinical pregnancy rate of fresh embryos and frozen embryos were not statistically significant (P > 0.05). The results of targeted metabolomics analysis showed that follicular fluid in the treatment group clustered with the normal young group and deviated from the placebo group. A total of 55 significant differential metabolites were found in the follicular fluid of older patients with poor ovarian response of kidney-qi deficiency type and patients in the normal young group, after Guilu Erxian ointment intervention, Metabolites such as L-Aspartic acid, Glycine, L-Serine, Palmitoleic Acid, Palmitelaidic acid, L-Alanine, Gamma-Linolenic acid, Alpha-Linolenic Acid, and N-acetyltryptophan were down-regulated, mainly involving amino acid metabolism and fatty acid metabolism.

CONCLUSION

Guilu Erxian ointment can effectively improve the clinical symptoms and IVF outcomes of older patients with poor ovarian response of kidney-qi deficiency type. There were differences in follicular fluid metabolites between older patients with poor ovarian response of kidney-qi deficiency type and normal women. L-Aspartic acid, L-Alanine, Aminoadipic acid, L-Asparagine, L-Arginine, L-Serine, Gamma- Linolenic acid, Pentadecanoic acid and Alpha-Linolenic Acid are closely related to older patients with poor ovarian response due to deficiency of kidney-qi and may be inferred as biomarkers. The mechanism of Guilu Erxian ointment intervention may be mainly through amino acid metabolism and fatty acid metabolism regulation.

Loss of Protein Stability and Function Caused by P228L Variation in NADPH-Cytochrome P450 Reductase Linked to Lower Testosterone Levels

Cytochrome P450 oxidoreductase (POR) is the redox partner of steroid and drug-metabolising cytochromes P450 located in the endoplasmic reticulum. Mutations in POR cause a broad range of metabolic disorders. The POR variant rs17853284 (P228L), identified by genome sequencing, has been linked to lower testosterone levels and reduced P450 activities. We expressed the POR wild type and the P228L variant in bacteria, purified the proteins, and performed protein stability and catalytic functional studies. Variant P228L affected the stability of the protein as evidenced by lower unfolding temperatures and higher sensitivity to urea denaturation. A significant decline in the rate of electron transfer to cytochrome c and thiazolyl blue tetrazolium (MTT) was observed with POR P228L, while activities of CYP3A4 were reduced by 25% and activities of CYP3A5 and CYP2C9 were reduced by more than 40% compared with WT POR. The 17,20 lyase activity of CYP17A1, responsible for the production of the main androgen precursor dehydroepiandrosterone, was reduced to 27% of WT in the presence of the P228L variant of POR. Based on in silico and in vitro studies, we predict that the change of proline to leucine may change the rigidity of the protein, causing conformational changes in POR, leading to altered electron transfer to redox partners. A single amino acid change can affect protein stability and cause a severe reduction in POR activity. Molecular characterisation of individual POR mutations is crucial for a better understanding of the impact on different redox partners of POR.

Characterization of POR haplotype distribution in African populations and comparison with other global populations

Background & aim: POR is an enzyme that mediates electron transfer to enable the drug-metabolizing activity of CYP450 proteins. However, POR has been understudied in pharmacogenomics despite this vital role. This study aimed to characterize the genetic variation in POR across African populations and to compare the star allele (haplotype) distribution with that in other global populations. Materials & methods: POR star alleles were called from whole-genome sequencing data using the StellarPGx pipeline. Results: In addition to the common POR*1 and *28 (defined by rs1057868), five novel rare haplotypes were computationally inferred. No significant frequency differences were observed among the majority of African populations. However, POR*28 was observed at a higher frequency in individuals of non-African ancestry. Conclusion: This study highlights the distribution of POR alleles in Africa and across global populations with a view toward informing future precision medicine implementation.

Two chloroplast-localized MORF proteins act as chaperones to maintain tetrapyrrole biosynthesis

Tetrapyrroles have essential functions as pigments and cofactors during plant growth and development, and the tetrapyrrole biosynthesis pathway is tightly controlled. Multiple organellar RNA editing factors (MORFs) are required for editing of a wide variety of RNA sites in chloroplasts and mitochondria, but their biochemical properties remain elusive. Here, we uncovered the roles of chloroplast-localized MORF2 and MORF9 in modulating tetrapyrrole biosynthesis and embryogenesis in Arabidopsis thaliana. The lack or reduced transcripts of MORF2 or MORF9 significantly affected biosynthesis of the tetrapyrrole precursor 5-aminolevulinic acid and accumulation of Chl and other tetrapyrrole intermediates. MORF2 directly interacts with multiple tetrapyrrole biosynthesis enzymes and regulators, including NADPH:PROTOCHLOROPHYLLIDE OXIDOREDUCTASE B (PORB) and GENOMES UNCOUPLED4 (GUN4). Strikingly, MORF2 and MORF9 display holdase chaperone activity, alleviate the aggregation of PORB in vitro, and are essential for POR accumulation in vivo. Moreover, both MORF2 and MORF9 significantly stimulate magnesium chelatase activity. Our findings reveal a previously unknown biochemical property of MORF proteins as chaperones and point to a new layer of post-translational control of the tightly regulated tetrapyrrole biosynthesis in plants.

P450 oxidoreductase regulates barrier maturation by mediating retinoic acid metabolism in a model of the human BBB

The blood-brain barrier (BBB) selectively regulates the entry of molecules into the central nervous system (CNS). A crosstalk between brain microvascular endothelial cells (BMECs) and resident CNS cells promotes the acquisition of functional tight junctions (TJs). Retinoic acid (RA), a key signaling molecule during embryonic development, is used to enhance in vitro BBB models’ functional barrier properties. However, its physiological relevance and affected pathways are not fully understood. P450 oxidoreductase (POR) regulates the enzymatic activity of microsomal cytochromes. POR-deficient (PORD) patients display impaired steroid homeostasis and cognitive disabilities. Here, we used both patient-specific POR-deficient and CRISPR-Cas9-mediated POR-depleted induced pluripotent stem cell (iPSC)-derived BMECs (iBMECs) to study the role of POR in the acquisition of functional barrier properties. We demonstrate that POR regulates cellular RA homeostasis and that POR deficiency leads to the accumulation of RA within iBMECs, resulting in the impaired acquisition of TJs and, consequently, to dysfunctional development of barrier properties.

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Retinoic acid (RA) promotes functional barrier properties

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POR-deficient iPS-brain endothelial-like cells display impaired barrier development

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POR mediates CYP26-dependent cellular RA catabolism

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RA accumulation induces a pro-inflammatory response

A disease-associated missense mutation in CYP4F3 affects the metabolism of leukotriene B4 via disruption of electron transfer

BACKGROUND

Cytochrome P450 4F3 (CYP4F3) is an ω-hydroxylase that oxidizes leukotriene B4 (LTB4), prostaglandins, and fatty acid epoxides. LTB4 is synthesized by leukocytes and acts as a chemoattractant for neutrophils, making it an essential component of the innate immune system. Recently, involvement of the LTB4 pathway was reported in various immunological disorders such as asthma, arthritis, and inflammatory bowel disease. We report a 26-year-old female with a complex immune phenotype, mainly marked by exhaustion, muscle weakness, and inflammation-related conditions. The molecular cause is unknown, and symptoms have been aggravating over the years.

METHODS

Whole exome sequencing was performed and validated; flow cytometry and enzyme-linked immunosorbent assay were used to describe patient's phenotype. Function and impact of the mutation were investigated using molecular analysis: co-immunoprecipitation, western blot, and enzyme-linked immunosorbent assay. Capillary electrophoresis with ultraviolet detection was used to detect LTB4 and its metabolite and in silico modelling provided structural information.

RESULTS

We present the first report of a patient with a heterozygous de novo missense mutation c.C1123 > G;p.L375V in CYP4F3 that severely impairs its activity by 50% (P < 0.0001), leading to reduced metabolization of the pro-inflammatory LTB4. Systemic LTB4 levels (1034.0 ± 75.9 pg/mL) are significantly increased compared with healthy subjects (305.6 ± 57.0 pg/mL, P < 0.001), and immune phenotyping shows increased total CD19+ CD27- naive B cells (25%) and decreased total CD19+ CD27+ IgD- switched memory B cells (19%). The mutant CYP4F3 protein is stable and binding with its electron donors POR and Cytb5 is unaffected (P > 0.9 for both co-immunoprecipitation with POR and Cytb5). In silico modelling of CYP4F3 in complex with POR and Cytb5 suggests that the loss of catalytic activity of the mutant CYP4F3 is explained by a disruption of an α-helix that is crucial for the electron shuffling between the electron carriers and CYP4F3. Interestingly, zileuton still inhibits ex vivo LTB4 production in patient's whole blood to 2% of control (P < 0.0001), while montelukast and fluticasone do not (99% and 114% of control, respectively).

CONCLUSIONS

A point mutation in the catalytic domain of CYP4F3 is associated with high leukotriene B4 plasma levels and features of a more naive adaptive immune response. Our data provide evidence for the pathogenicity of the CYP4F3 variant as a cause for the observed clinical features in the patient. Inhibitors of the LTB4 pathway such as zileuton show promising effects in blocking LTB4 production and might be used as a future treatment strategy.

Impact of POR*28 Variant on Tacrolimus Pharmacokinetics in Kidney Transplant Patients with Different CYP3A5 Genotypes

BACKGROUND

The introduction of tacrolimus (TAC) in clinical practice was essential to the establishment of transplantation as therapy for patients with chronic renal disease. However, the higher interindividual variation of TAC metabolism has been an important limiting factor for its clinical use. Although the relationship between CYP3A5 polymorphisms and TAC pharmacokinetics (PK) is well established, the effects of other genetic variants on TAC metabolism, such as POR*28, still remain uncertain.

OBJECTIVE

To evaluate the impact of POR variants on TAC PK in renal transplant patients with different CYP3A5 genotypes (expressers and non-expressers).

METHODS

A total of 115 patients were included in this study. Genomic DNA was isolated from peripheral blood, and the real-time PCR technique was used to analyze the polymorphism POR rs1057868; C>T.

RESULTS

During the initial post-transplant period, variant allele carriers (*1/*28 and *28/*28) showed a lower TAC dose requirement than POR wild homozygotes (*1/*1). Regarding the influence of the different polymorphisms of POR within the CYP3A5 expresser and non-expresser groups, no differences were observed in any of the PK parameters analyzed during 12 months after transplantation.

CONCLUSION

In the studied population, the variant allelic POR*28 was significantly associated with lower TAC dose requirements and higher Co/D ratio in the first-month post-transplant. However, the effects of this polymorphism on the CYP3A5 enzyme activity were not observed.

Generation of Caco-2 cells stably expressing CYP3A4·POR·UGT1A1 and CYP3A4·POR·UGT1A1*6 using a PITCh system

The small intestine plays a critical role in the absorption and metabolism of orally administered drugs. Therefore, a model capable of evaluating drug absorption and metabolism in the small intestine would be useful for drug discovery. Patients with genotype UGT1A1*6 (exon 1, 211G > A) treated with the antineoplastic drug SN-38 have been reported to exhibit decreased glucuronide conjugation and increased incidence of intestinal toxicity and its severe side effects, including severe diarrhea. To ensure the safety of drugs, we must develop a drug metabolism and toxicity evaluation model which considers UGT1A1*6. In this study, we generated CYP3A4·POR·UGT1A1 KI- and CYP3A4·POR·UGT1A1*6 KI-Caco-2 cells for pharmaceutical research using a PITCh system. The CYP3A4·POR·UGT1A1 KI-Caco-2 cells were shown to express functional CYP3A4 and UGT1A1. The CYP3A4·POR·UGT1A1*6 KI-Caco-2 cells were sensitive to SN-38-induced intestinal toxicity. We thus succeeded in generating CYP3A4·POR·UGT1A1 KI- and CYP3A4·POR·UGT1A1*6 KI-Caco-2 cells, which can be used in pharmaceutical research. We also developed an intestinal epithelial cell model of patients with UGT1A1*6 and showed that it was useful as a tool for drug discovery.

POR polymorphisms are associated with 21 hydroxylase deficiency

PURPOSE

Genotype-phenotype correlation in congenital 21 hydroxylase deficiency is strong but by no means absolute. Indeed, clinical and hormonal features may vary among patients carrying similar CYP21A2 mutations, suggesting that modifier genes may contribute to the phenotype. Aim of the present study was to evaluate whether polymorphisms in the p450  oxidoreductase (POR) gene may affect clinical features in patients with 21 hydroxylase deficiency METHODS: Sequencing of the POR gene was performed in 96 patients with 21 hydroxylase deficiency (49 classic, 47 non-classic) and 43 control subjects.

RESULTS

Prevalence of POR polymorphisms in patients with 21 hydroxylase was comparable to controls and known databases. The rs2228104 polymorphism was more frequently associated with non-classic vs classic 21 hydroxylase deficiency (allelic risk 7.09; 95% C.I. 1.4-29.5, p < 0.05). Classic 21 hydroxylase-deficient carriers of the minor allele in the rs2286822/rs2286823 haplotype presented more frequently the salt-wasting form (allelic risk 1.375; 95% C.I. 1.138-1.137), more severe Prader stage at birth (allelic risk 3.85; 95% C.I. 3.78-3.92), higher ACTH levels, and younger age at diagnosis.

CONCLUSIONS

Polymorphisms in the POR gene are associated with clinical features of 21 hydroxylase deficiency both as regards predisposition to classic vs non-classic forms and severity of classic adrenal hyperplasia.

Inhibition of phase-1 biotransformation and cytostatic effects of diphenyleneiodonium on hepatoblastoma cell line HepG2 and a CYP3A4-overexpressing HepG2 cell clone

Cell-based in vitro liver models are an important tool in the development and evaluation of new drugs in pharmacological and toxicological drug assessment. Hepatic microsomal enzyme complexes, consisting of cytochrome P450 oxidoreductase (CPR) and cytochrome P450 monooxygenases (CYPs), play a decisive role in catalysing phase-1 biotransformation of pharmaceuticals and xenobiotics. For a comprehensive understanding of the phase-1 biotransformation of drugs, the availability of well-characterized substances for the targeted modulation of in vitro liver models is essential. In this study, we investigated diphenyleneiodonium (DPI) for its ability to inhibit phase-1 enzyme activity and further its toxicological profile in an in vitro HepG2 cell model with and without recombinant expression of the most important drug metabolization enzyme CYP3A4.

Aim of the study was to identify effective DPI concentrations for CPR/CYP activity modulation and potentially associated dose and time dependent hepatotoxic effects. The cells were treated with DPI doses up to 5,000nM (versus vehicle control) for a maximum of 48 h and subsequently examined for CYP3A4 activity as well as various toxicological relevant parameters such as cell morphology, integrity and viability, intracellular ATP level, and proliferation. Concluding, the experiments revealed a time- and concentration-dependent DPI mediated partial and complete inhibition of CYP3A4 activity in CYP3A4 overexpressing HepG2-cells (HepG2-CYP3A4). Other cell functions, including ATP synthesis and consequently the proliferation were negatively affected in both in vitro cell models. Since neither cell integrity nor cell viability were reduced, the effect of DPI in HepG2 can be assessed as cytostatic rather than cytotoxic.

G6PD inhibits ferroptosis in hepatocellular carcinoma by targeting cytochrome P450 oxidoreductase

Ferroptosis is an important cell necrosis and has been a focus in cancer related research.Increcsing studies have focused on the phenotype and function of ferroptosis in tumorigenesis, but the underlying mechanism remains poorly understood. Here, we used bioinformatics approaches to identify differentially expressed genes associated with HCC and ferroptosis. We found that G6PD (glucose-6-phosphate dehydrogenase) was highly expressed in HCC and was associated with poor prognosis. G6PD promoted the proliferation, migration and invasion, as well as inhibited ferroptosis in HCC cells. Pathway and functional enrichment analyses revealed that G6PD was related to the P450 metabolic pathway. POR (cytochrome P450 oxidoreductase) was downregulated in HCC and was significantly correlated with the prognosis. G6PD inhibited ferroptosis inin HCC cells through POR. Knockdown of G6PD reduced the tumor volume and tumor weight in vivo. Our study demonstrated that G6PD deficiency suppresses cell growth, metastasis, and tumorigenesis via upregulating POR, suggesting that G6PD may be used as a biomarker for the treatment of HCC in the future.

19-hydroxy Steroids in the Aromatase Reaction: Review on Expression and Potential Functions

Scientific evidence related to the aromatase reaction in various biological processes spanning from mid-1960 to today is abundant; however, as our analytical sensitivity increases, a new look at the old chemical reaction is necessary. Here, we review an irreversible aromatase reaction from the substrate androstenedione. It proceeds in 3 consecutive steps. In the first 2 steps, 19-hydroxy steroids are produced. In the third step, estrone is produced. They can dissociate from the enzyme complex and either accumulate in tissues or enter the blood.

In this review, we want to highlight the potential importance of these 19-hydroxy steroids in various physiological and pathological conditions. We focus primarily on 19-hydroxy steroids, and in particular on the 19-hydroxyandrostenedione produced by the incomplete aromatase reaction. Using a PubMed database and the search term “aromatase reaction,” 19-hydroxylation of androgens and steroid measurements, we detail the chemistry of the aromatase reaction and list previous and current methods used to measure 19-hydroxy steroids.

We present evidence of the existence of 19-hydroxy steroids in brain tissue, ovaries, testes, adrenal glands, prostate cancer, as well as during pregnancy and parturition and in Cushing’s disease. Based on the available literature, a potential involvement of 19-hydroxy steroids in the brain differentiation process, sperm motility, ovarian function, and hypertension is suggested and warrants future research.

We hope that with the advancement of highly specific and sensitive analytical methods, future research into 19-hydroxy steroids will be encouraged, as much remains to be learned and discovered.

Amphipol-facilitated elucidation of the functional tetrameric complex of full-length cytochrome P450 CYP2B4 and NADPH-cytochrome P450 oxidoreductase

Interactions of membrane-bound mammalian cytochromes P450 (CYPs) with NADPH-cytochrome P450 oxidoreductase (POR), which are required for metabolism of xenobiotics, are facilitated by membrane lipids. A variety of membrane mimetics, such as phospholipid liposomes and nanodiscs, have been used to simulate the membrane to form catalytically active CYP:POR complexes. However, the exact mechanism(s) of these interactions are unclear because of the absence of structural information of full-length mammalian CYP:POR complexes in membranes. Herein, we report the use of amphipols (APols) to form a fully functional, soluble, homogeneous preparation of full-length CYP:POR complexes amenable to biochemical and structural study. Incorporation of CYP2B4 and POR into APols resulted in a CYP2B4:POR complex with a stoichiometry of 1:1, which was fully functional in demethylating benzphetamine at a turnover rate of 37.7 ± 2.2 min^-1, with a coupling efficiency of 40%. Interestingly, the stable complex had a molecular weight (M_w) of 338 ± 22 kDa determined by multiangle light scattering, suggestive of a tetrameric complex of 2CYP2B4:2POR embedded in one APol nanoparticle. Moreover, negative stain electron microscopy (EM) validated the homogeneity of the complex and allowed us to generate a three-dimensional EM map and model consistent with the tetramer observed in solution. This first report of the full-length mammalian CYP:POR complex by transmission EM not only reveals the architecture that facilitates electron transfer but also highlights a potential use of APols in biochemical and structural studies of functional CYP complexes with redox partners.

Vascular biotransformation of organic nitrates is independent of cytochrome P450 monooxygenases

BACKGROUND AND PURPOSE

Organic nitrates such as nitroglycerin (NTG) or pentaerythritol tetranitrate (PETN) have been used for over a century in the treatment of angina or ischaemic heart disease. These compounds are prodrugs which release their nitrovasodilators upon enzymic bioactivation by aldehyde dehydrogenase (ALDH2) or cytochromes P450 (CYP). Whereas ALDH2 is known to directly activate organic nitrates in vessels, the contribution of vascular CYPs is unknown and was studied here.

EXPERIMENTAL APPROACH

As all CYPs depend on cytochrome P450 reductase (POR) as electron donor, we generated a smooth muscle cell-specific, inducible knockout mouse of POR (smcPOR^-/- ) to investigate the contribution of POR/CYP to vascular biotransformation of organic nitrates.

KEY RESULTS

Microsomes containing recombinant CYPs expressed in human vascular tissues released nitrite from NTG and PETN with CYP2C9 and CYP2C8 being most efficient. SFK525, a CYP suicide inhibitor, blocked this effect. smcPOR^-/- mice exhibited no obvious cardiovascular phenotype (normal cardiac weight and endothelium-dependent relaxation) and plasma and vascular nitrite production was similar to control (CTL) animals. NTG- and PETN-induced relaxation of isolated endothelium-intact or endothelium-denuded vessels were identical between CTL and smcPOR^-/- . Likewise, nitrite release from organic nitrates in aortic rings was not affected by deletion of POR in smooth muscle cells (SMCs). In contrast, inhibition of ALDH2 by benomyl (10 μM) inhibited NTG-induced nitrite production and relaxation. Deletion of POR did not modulate this response.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that metabolism by vascular CYPs does not contribute to the pharmacological function of organic nitrates.

The oxidoreductases POR and CYB5R1 catalyze lipid peroxidation to execute ferroptosis

Our recent study showed that two oxidoreductases - NADPH-cytochrome P450 reductase (POR) and NADH-cytochrome b5 reductase (CYB5R1) - transfer electrons to oxygen to generate hydrogen peroxide (H₂O₂). H₂O₂ then reacts with ferrous iron, generating hydroxyl radicals that cause peroxidation of polyunsaturated-fatty-acid chains of membrane phospholipids, resulting in plasma membrane rupture and ferroptosis.

TCF7L2 rs7903146 C>T gene polymorphism is not associated with hypoglycemia in sulfonylurea-treated type 2 diabetic patients

OBJECTIVES

Hypoglycemia is the most common adverse effect of sulfonylureas (SUs) and a major concern when using these drugs. Transcription factor 7-like 2 (TCF7L2) rs7903146 C>T polymorphism is an established and well characterized genetic marker of type 2 diabetes (T2DM) risk. The aim of the present study was to analyze the potential association of TCF7L2 rs7903146 C>T polymorphism with SU-induced hypoglycemia in a well characterized cohort of SU-treated patients previously genotyped for cytochrome P450 2C9 (CYP2C9) and P450 oxidoreductase (POR).

METHODS

The study group consisted of 176 SU-treated T2DM patients of whom 92 had experienced at least one drug-associated hypoglycemic event. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for TCF7L2 rs7903146 genotyping.

RESULTS

TCF7L2 rs7903146 C>T genotype and allele frequency did not differ between cases and controls (p=0.745 and 0.671, respectively). In logistic regression analysis adjusted for other factors affecting hypoglycemia, including CYP2C9 and POR genotypes, TCF7L2 rs7903146 C>T polymorphism did not increase the risk of hypoglycemia (OR=1.238, 95% C.I.=0.750-2.044, p=0.405).

CONCLUSIONS

TCF7L2 rs7903146 C>T polymorphism is not associated with SU-induced hypoglycemia. Identifying additional gene polymorphisms associated with SU-induced hypoglycemia is crucial for improving T2DM patient therapy with SUs.

Next-Generation Sequencing Revealed Disease-Causing Variants in Two Genes in a Patient With Combined Features of Spherocytosis and Antley-Bixler Syndrome With Genital Anomalies and Disordered Steroidogenesis

Conventionally, patients with combined rare diseases are often difficult to diagnose. This is because some clinicians tend to consider the multiple disease symptoms as the presentation of a complicated “syndrome.” This pattern of thinking also confines their way of filtering pathogenic mutations. Some real pathogenic mutations might be ignored due to not covering all disease presentations. Here we report the case of a girl who was suffering from spherocytosis and Antley-Bixler syndrome with genital anomalies and disordered steroidogenesis. She remained undiagnosed even after targeted gene detection before. However, after performing next-generation sequencing and analyzing the sequencing data, we identified two mutations: c.2978T > A in ANK1 and c.1370G > A in POR. Our findings and experiences in diagnosing these mutations could contribute to the existing knowledge on the clinical and genetic diagnosis of patients with disease presentations in multiple systems.

Clinical, endocrinological, and molecular features of four Korean cases of cytochrome P450 oxidoreductase deficiency

PURPOSE

Cytochrome P450 oxidoreductase (POR) deficiency is a rare autosomal recessive disorder caused by mutations in the POR gene encoding an electron donor for all microsomal P450 enzymes. It is characterized by adrenal insufficiency, ambiguous genitalia, maternal virilization during pregnancy, and skeletal dysplasia. In this study, we investigated the clinical, hormonal, and molecular characteristics of patients with POR deficiency in Korea.

METHODS

This study included four patients with POR deficiency confirmed by biochemical and molecular analysis of POR. Clinical and biochemical findings were reviewed retrospectively. Mutation analysis of POR was performed by Sanger sequencing after polymerase chain reaction amplification of all coding exons and the exon-intron boundaries.

RESULTS

All patients presented with adrenal insufficiency and ambiguous genitalia regardless of their genetic sex. Two patients harbored homozygous p.R457H mutations in POR and presented with adrenal insufficiency and genital ambiguity without skeletal phenotypes. The other two patients with compound heterozygous mutations of c.[1329_1330insC];[1370G&gt;A] (p.[I444Hfs*6];[R457H]) manifested skeletal abnormalities, such as craniosynostosis and radiohumeral synostosis, suggesting Antley-Bixler syndrome. They also had multiple congenital anomalies involving heart, kidney, and hearing ability. All patients were treated with physiologic doses of oral hydrocortisone.

CONCLUSION

We report the cases of 4 patients with POR deficiency identified by mutation analysis of POR. Although the study involved a small number of patients, the POR p.R457H mutation was the most common, suggesting founder effect in Korea. POR deficiency is rare and can be misdiagnosed as 21-hydroxylase or 17α-hydroxylase/17,20-lyase deficiency. Therefore, molecular analysis is critical for confirmatory diagnosis.

Identification of pharmacogenetic biomarkers for efficacy of cytoreductive surgery plus hyperthermic intraperitoneal mitomycin C in patients with colorectal peritoneal metastases

INTRODUCTION

Mitomycin C (MMC) is commonly used in patients with colorectal peritoneal metastases (CPM) treated with cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS + HIPEC). MMC requires metabolic activation prior to exert its cytotoxic effect of which the main activating enzymes are NQO1 and POR. However, not all patients are able to activate MMC for example due to polymorphisms in the genes encoding these enzymes. The aim of this study was to investigate the association of NQO1∗2, NQO1∗3, and POR∗28 with the efficacy of CRS + HIPEC with MMC in patients with CPM.

METHOD

A retrospective follow-up design was used to study genetic association in patients with histologically proven CPM treated with CRS + HIPEC with MMC with respect to peritoneal recurrence rate after 3 months (primary endpoint), after 6 months, disease-free survival and overall survival. Genetic polymorphisms NQO1∗2, NQO1∗3, and POR∗28 were tested for association.

RESULTS

A total of 253 patients were included. In NQO1∗3 carriers the peritoneal recurrence rate 3 and 6 months after HIPEC was significantly higher than in wild type patients, respectively 30.0% vs 3.8% (p = 0.009) and 40.0% vs 12.1% (p = 0.031). In line with these results, NQO1∗3 was associated with a shorter disease-free survival (HR 2.04, 95% CI [1.03-4.03]). There was no significant association with overall survival (HR 1.42, 95% CI [0.66-3.07]).

CONCLUSION

Carriership of the NQO1∗3 allele is associated with worse peritoneal recurrence rate and disease-free survival. These results suggest that individualization of patients treated with CRS + HIPEC based upon pharmacogenetics may be beneficial.

Molecular Basis of CYP19A1 Deficiency in a 46,XX Patient With R550W Mutation in POR: Expanding the PORD Phenotype

CONTEXT

Mutations in cytochrome P450 oxidoreductase (POR) cause a form of congenital adrenal hyperplasia (CAH). We report a novel R550W mutation in POR identified in a 46,XX patient with signs of aromatase deficiency.

OBJECTIVE

Analysis of aromatase deficiency from the R550W mutation in POR.

DESIGN, SETTING, AND PATIENT

Both the child and the mother had signs of virilization. Ultrasound revealed the presence of uterus and ovaries. No defects in CYP19A1 were found, but further analysis with a targeted Disorders of Sexual Development NGS panel (DSDSeq.V1, 111 genes) on a NextSeq (Illumina) platform in Madrid and Barcelona, Spain, revealed compound heterozygous mutations c.73_74delCT/p.L25FfsTer93 and c.1648C > T/p.R550W in POR. Wild-type and R550W POR were produced as recombinant proteins and tested with multiple cytochrome P450 enzymes at University Children's Hospital, Bern, Switzerland.

MAIN OUTCOME MEASURE AND RESULTS

POR-R550W showed 41% of the WT activity in cytochrome c and 7.7% activity for reduction of MTT. Assays of CYP19A1 showed a severe loss of activity, and CYP17A1 as well as CYP21A2 activities were also lost by more than 95%. Loss of CYP2C9, CYP2C19, and CYP3A4 activities was observed for the R550W-POR. Predicted adverse effect on aromatase activity as well as a reduction in binding of NADPH was confirmed.

CONCLUSIONS

Pathological effects due to POR-R550W were identified, expanding the knowledge of molecular pathways associated with aromatase deficiency. Screening of the POR gene may provide a diagnosis in CAH without defects in genes for steroid metabolizing enzymes.

NADPH-cytochrome P450 reductase expression and enzymatic activity in primary-like human hepatocytes and HepG2 cells for in vitro biotransformation studies

BACKGROUND:

Human hepatocyte in vitro cell culture systems are important models for drug development and toxicology studies in the context of liver xenobiotic metabolism. Often, such culture systems are used to elucidate the biotransformation of xenobiotics or drugs and further investigate drug and drug metabolite effects on biological systems in terms of potential therapeutic benefit or toxicity. Human hepatocytes currently used for such in vitro studies are mostly primary cells or cell lines derived from liver cancers. Both approaches have limitations such as low proliferation capacity and progressive dedifferentiation found in primary cells or lack of liver functions in cell lines, which makes it difficult to reliably predict biotransformation of xenobiotics in patients. In order to overcome these limitations, HepaFH3 cells and Upcyte^® hepatocytes representing primary-like hepatocytes of the first and second generation are increasingly used. Based on primary human hepatocyte cells transduced for stable expression of Upcyte^® proliferation genes, they are mitotically active and exhibit liver functions over an extended period, making them comparable to primary human hepatocytes. These hepatocyte models show active liver metabolism such as urea and glycogen formation as well as biotransformation of xenobiotics. The latter is based on the expression, activity and inducibility of cytochrome P450 enzymes (CYP) as essential phase I reaction components. However, for further characterisation in terms of performance and existing limitations, additional studies are needed to elucidate the mechanisms involved in phase I reactions. One prerequisite is sufficient activity of microsomal NADPH-cytochrome P450 reductase (POR) functionally connected as electron donor to those CYP enzymes.

OBJECTIVE:

For Upcyte^® hepatocytes and HepaFH3 cells, it is so far unknown to what extent POR is expressed, active, and may exert CYP-modulating effects. Here we studied POR expression and corresponding enzyme activity in human hepatoblastoma cell line HepG2 and compared this with HepaFH3 and Upcyte^® hepatocytes representing proliferating primary-like hepatocytes.

METHODS:

POR expression of those hepatocyte models was determined at mRNA and protein level using qRT-PCR, Western Blot and immunofluorescence staining. Kinetic studies on POR activity in isolated microsomes were performed by a colorimetric method.

RESULTS:

The investigated hepatocyte models showed remarkable differences at the level of POR expression. Compared to primary-like hepatocytes, POR expression of HepG2 cells was 4-fold higher at mRNA and 2-fold higher at protein level. However, this higher expression did not correlate with corresponding enzyme activity levels in isolated microsomes, which were comparable between all cell systems tested. A tendency of higher POR activity in HepG2 cells compared to HepaFH3

(p = 0.0829) might be present. Compared to primary human hepatocyte microsomes, POR activity was considerably lower in all hepatocyte models.

CONCLUSION:

In summary, our study revealed that POR expression and activity were clearly detectable in all in vitro hepatocyte models with the highest POR expression in cancer cell line HepG2. However, POR activity was lower in tested hepatocyte models when compared to human primary hepatocyte microsomes. Whether this was caused by e.g. polymorphisms or metabolic differences of investigated hepatocyte models will be target for future studies.

Differential effects of variations in human P450 oxidoreductase on the aromatase activity of CYP19A1 polymorphisms R264C and R264H

Aromatase (CYP19A1) converts androgens into estrogens and is required for female sexual development and growth and development in both sexes. CYP19A1 is a member of cytochrome P450 family of heme-thiolate monooxygenases located in the endoplasmic reticulum and depends on reducing equivalents from the reduced nicotinamide adenine dinucleotide phosphate via the cytochrome P450 oxidoreductase coded by POR. Both the CYP19A1 and POR genes are highly polymorphic, and mutations in both these genes are linked to disorders of steroid biosynthesis. We have previously shown that R264C and R264H mutations in CYP19A1, as well as mutations in POR, reduce CYP19A1 activity. The R264C is a common polymorphic variant of CYP19A1, with high frequency in Asian and African populations. Polymorphic alleles of POR are found in all populations studied so far and, therefore, may influence activities of CYP19A1 allelic variants. So far, the effects of variations in POR on enzymatic activities of allelic variants of CYP19A1 or any other steroid metabolizing cytochrome P450 proteins have not been studied. Here we are reporting the effects of three POR variants on the aromatase activities of two CYP19A1 variants, R264C, and R264H. We used bacterially expressed and purified preparations of WT and variant forms of CYP19A1 and POR and constructed liposomes with embedded CYP19A1 and POR proteins and assayed the CYP19A1 activities using radiolabeled androstenedione as a substrate. With the WT-POR as a redox partner, the R264C-CYP19A1 showed only 15% of aromatase activity, but the R264H had 87% of aromatase activity compared to WT-CYP19A1. With P284L-POR as a redox partner, R264C-CYP19A1 lost all activity but retained 6.7% of activity when P284T-POR was used as a redox partner. The R264H-CYP19A1 showed low activities with both the POR-P284 L as well as the POR-P284 T. When the POR-Y607C was used as a redox partner, the R264C-CYP19A1 retained approximately 5% of CYP19A1 activity. Remarkably, The R264H-CYP19A1 had more than three-fold higher activity compared to WT-CYP19A1 when the POR-Y607C was used as the redox partner, pointing toward a beneficial effect. The slight increase in activity of R264C-CYP19A1 with the P284T-POR and the three-fold increase in activity of the R264H-CYP19A1 with the Y607C-POR point toward a conformational effect and role of protein-protein interaction governed by the R264C and R264H substitutions in the CYP19A1 as well as P284 L, P284 T and Y607C variants of POR. These studies demonstrate that the allelic variants of P450 when present with a variant form of POR may show different activities, and combined effects of variations in the P450 enzymes as well as in the POR should be considered when genetic data are available. Recent trends in the whole-exome and whole-genome sequencing as diagnostic tools will permit combined evaluation of variations in multiple genes that are interdependent and may guide treatment options by adjusting therapeutic interventions based on laboratory analysis.

Variability of voriconazole concentrations in patients with hematopoietic stem cell transplantation and hematological malignancies: influence of loading dose, procalcitonin, and pregnane X receptor polymorphisms

AIMS

Voriconazole (VCZ) displays highly variable pharmacokinetics affecting treatment efficacy and safety. We aimed to identify the factors affecting VCZ steady-state trough concentration (Cssmin) to provide evidence for optimizing VCZ treatment regimens.

METHODS

A total of 510 Cssmin of 172 patients with hematopoietic stem cell transplantation and hematologic malignancies and their clinical characteristics and genotypes of FMO, POR, and PXR were included in this study.

RESULTS

In univariate analysis, the standard loading dose of VCZ significantly increased the Cssmin of VCZ (P < 0.001). The Cssmin of VCZ was significantly correlated with patients' total bilirubin (TB) (P < 0.001) and procalcitonin (PCT) (P < 0.001). FMO3 rs2266780 (P = 0.025), POR rs10954732 (P = 0.015), PXR rs2461817 (P = 0.010), PXR rs7643645 (P = 0.003), PXR rs3732359 (P = 0.014), PXR rs3814057 (P = 0.005), and PXR rs6785049 (P = 0.013) have a significant effect on Cssmin of VCZ. Loading dose, TB, PCT level, and PXRrs3814057 polymorphism were independent influencing factors of VCZ Cssmin in the analysis of multivariate linear regression. And loading dose, PCT, and PXR rs3814057 had significant effects on the probability of the therapeutic window of VCZ.

CONCLUSION

The high variability of VCZ Cssmin may be partially explained by loading dose, liver function, inflammation, and PXR polymorphisms. This study suggests the VCZ standard loading dose regimen significantly increased Cssmin and probability of the therapeutic window providing treatment benefits. Patients in the high PCT group may be more likely to exceed 5.5 μg/mL, thus suffering from VCZ toxicity.

Variability in Loss of Multiple Enzyme Activities Due to the Human Genetic Variation P284T Located in the Flexible Hinge Region of NADPH Cytochrome P450 Oxidoreductase

Cytochromes P450 located in the endoplasmic reticulum require NADPH cytochrome P450 oxidoreductase (POR) for their catalytic activities. Mutations in POR cause multiple disorders in humans related to the biosynthesis of steroid hormones and also affect drug-metabolizing cytochrome P450 activities. Electron transfer in POR occurs from NADH to FAD to FMN, and the flexible hinge region in POR is essential for domain movements to bring the FAD and FMN close together for electron transfer. We tested the effect of variations in the hinge region of POR to check if the effects would be similar across all redox partners or there will be differences in activities. Here we are reporting the effects of a POR genetic variant P284T located in the hinge region of POR that is necessary for the domain movements and internal electron transfer between co-factors. Human wild-type and P284T mutant of POR and cytochrome P450 proteins were expressed in bacteria, purified, and reconstituted for enzyme assays. We found that for the P284T variant of POR, the cytochrome c reduction activity was reduced to 47% of the WT and MTT reduction was reduced to only 15% of the WT. No impact on ferricyanide reduction activity was observed, indicating intact direct electron transfer from FAD to ferricyanide, but a severe loss of CYP19A1 (aromatase) activity was observed (9% of WT). In the assays of drug-metabolizing cytochrome P450 enzymes, the P284T variant of POR showed 26% activity for CYP2C9, 44% activity for CYP2C19, 23% activity for CYP3A4, and 44% activity in CYP3A5 assays compared to the WT POR. These results indicate a severe effect on several cytochrome P450 activities due to the P284T variation in POR, which suggests a negative impact on both the steroid as well as drug metabolism in the individuals carrying this variation. The negative impact of P284T mutation in the hinge region of POR seems to be due to disruption of FAD to FMN electron transfer. These results further emphasize the importance of hinge region in POR for protein flexibility and electron transfer within POR as well as the interaction of POR with different redox partners.

Androgens and ovarian function: translation from basic discovery research to clinical impact

In the last decade, it has been revealed that androgens play a direct and important role in regulating female reproductive function. Androgens mediate their actions via the androgen receptor (AR), and global and cell-specific Ar-knockout mouse models have confirmed that AR-mediated androgen actions play a role in regulating female fertility and follicle health, development and ovulation. This knowledge, along with the clinical data reporting a beneficial effect of androgens or androgen-modulating agents in augmenting in vitro fertilization (IVF) stimulation in women termed poor responders, has supported the adoption of this concept in many IVF clinics worldwide. On the other hand, substantial evidence from human and animal studies now supports the hypothesis that androgens in excess, acting via the AR, play a key role in the origins of polycystic ovary syndrome (PCOS). The identification of the target sites of these AR actions and the molecular mechanisms involved in underpinning the development of PCOS is essential to provide the knowledge required for the future development of novel, mechanism-based therapies for the treatment of PCOS. This review will summarize the basic scientific discoveries that have enhanced our knowledge of the roles of androgens in female reproductive function, discuss the impact these findings have had in the clinic and how a greater understanding of the role androgens play in female physiology may shape the future development of effective strategies to improve IVF outcomes in poor responders and the amelioration of symptoms in patients with PCOS.

Impact of Tumour Hypoxia on Evofosfamide Sensitivity in Head and Neck Squamous Cell Carcinoma Patient-Derived Xenograft Models

Tumour hypoxia is a marker of poor prognosis and failure of chemoradiotherapy in head and neck squamous cell carcinoma (HNSCC), providing a strategy for therapeutic intervention in this setting. To evaluate the utility of the hypoxia-activated prodrug evofosfamide (TH-302) in HNSCC, we established ten early passage patient-derived xenograft (PDX) models of HNSCC that were characterised by their histopathology, hypoxia status, gene expression, and sensitivity to evofosfamide. All PDX models closely resembled the histology of the patient tumours they were derived from. Pimonidazole-positive tumour hypoxic fractions ranged from 1.7-7.9% in line with reported HNSCC clinical values, while mRNA expression of the Toustrup hypoxia gene signature showed close correlations between PDX and matched patient tumours, together suggesting the PDX models may accurately model clinical tumour hypoxia. Evofosfamide as a single agent (50 mg/kg IP, qd × 5 for three weeks) demonstrated antitumour efficacy that was variable across the PDX models, ranging from complete regressions in one p16-positive PDX model to lack of significant activity in the three most resistant models. Despite all PDX models showing evidence of tumour hypoxia, and hypoxia being essential for activation of evofosfamide, the antitumour activity of evofosfamide only weakly correlated with tumour hypoxia status determined by pimonidazole immunohistochemistry. Other candidate evofosfamide sensitivity genes-MKI67, POR, and SLFN11-did not strongly influence evofosfamide sensitivity in univariate analyses, although a weak significant relationship with MKI67 was observed, while SLFN11 expression was lost in PDX tumours. Overall, these data confirm that evofosfamide has antitumour activity in clinically-relevant PDX tumour models of HNSCC and support further clinical evaluation of this drug in HNSCC patients. Further research is required to identify those factors that, alongside hypoxia, can influence sensitivity to evofosfamide and could act as predictive biomarkers to support its use in precision medicine therapy of HNSCC.

Impact of CYP3A5, POR, and CYP2C19 Polymorphisms on Trough Concentration to Dose Ratio of Tacrolimus in Allogeneic Hematopoietic Stem Cell Transplantation

Single nucleotide polymorphisms in drug-metabolizing genes may affect tacrolimus pharmacokinetics. Here, we investigated the influence of genotypes of CYP3A5, CYP2C19, and POR on the concentration/dose (C/D) ratio of tacrolimus and episodes of acute graft-versus-host disease (GVHD) in Japanese recipients of allogeneic hematopoietic stem cell transplantation (HSCT). Thirty-six patients receiving the first HSCT using tacrolimus-based GVHD prophylaxis were enrolled with written informed consent. During continuous intravenous infusion, HSCT recipients carrying the CYP3A5*1 allele, particularly those with at least one POR*28 allele, had a significantly lower tacrolimus C/D ratio throughout all three post-HSCT weeks compared to that in recipients with POR*1/*1 (p < 0.05). The CYP3A5*3/*3 genotype and the concomitant use of voriconazole were independent predictors of an increased tacrolimus C/D ratio during the switch from continuous intravenous infusion to oral administration (p < 0.05). In recipients receiving concomitant administration of voriconazole, our results suggest an impact of not only CYP3A5 and CYP2C19 genotypes, but also plasma voriconazole concentration. Although switching from intravenous to oral administration at a ratio of 1:5 was seemingly appropriate in recipients with CYP3A5*1, a lower conversion ratio (1:2-3) was appropriate in recipients with CYP3A5*3/*3. Our results suggest that CYP3A5, POR, and CYP2C19 polymorphisms are useful biomarkers for individualized dosage adjustment of tacrolimus in HSCT recipients.

Impact of CYP3A5 phenotype on tacrolimus concentrations after sublingual and oral administration in lung transplant

Aim: This study evaluated the impact of CYP3A5 genotype and other patient characteristics on sublingual (SL) tacrolimus exposure and compared the relationship with oral administration. Patients & methods: Tacrolimus concentrations were retrospectively collected for adult lung transplant recipients, who were genotyped for CYP3A5*3, CYP3A4*22, CYP3A7*1C, and POR*28. Regression analyses were performed to determine covariates that impacted the SL and oral tacrolimus concentration/dose ratios. Results: An interaction of CYP3A5 genotype and CYP3A inhibitor increased the SL concentration/dose, while cystic fibrosis decreased the SL concentration/dose. The oral concentration/dose was independently associated with these covariates and was increased by serum creatinine and number of tacrolimus doses. Conclusion: This study suggests personalized dosing strategies for tacrolimus likely need to consider characteristics beyond CYP3A5 genotype.

Risk factors for inadequate response to ovarian stimulation in assisted reproduction cycles: systematic review

PURPOSE

Controlled ovarian stimulation is a fundamental part of a successful assisted reproduction treatment, and recognizing patients at risk of a poor response allows the development of targeted research to propose new treatment strategies for this specific group. The objective of this systematic review was to determine risk factors for poor ovarian response (POR) to controlled stimulation in assisted reproduction cycles described in the literature.

METHODS

The primary databases MEDLINE, Cochrane, LILACS, and SciELO were consulted, using specific terms with a restriction for articles in English or Portuguese published in the last 10 years.

RESULTS AND CONCLUSION

Our data suggest that environmental endocrine disruptors, tobacco, genetic mutations, endometriomas, ovarian surgery, chemotherapy, and short menstrual cycles are factors that influence stimulation in assisted reproduction cycles. Further studies are necessary for characterizing patients with prior risk factors.

Characterization of Ferredoxin-Dependent Biliverdin Reductase PCYA1 Reveals the Dual Function in Retrograde Bilin Biosynthesis and Interaction With Light-Dependent Protochlorophyllide Oxidoreductase LPOR in Chlamydomonas reinhardtii

Bilins are linear tetrapyrroles commonly used as chromophores of phycobiliproteins and phytochromes for light-harvesting or light-sensing in photosynthetic organisms. Many eukaryotic algae lack both phycobiliproteins and phytochromes, but retain the bilin biosynthetic enzymes including heme oxygenase (HO/HMOX) and ferredoxin-dependent biliverdin reductase (FDBR). Previous studies on Chlamydomonas reinhardtii heme oxygenase mutant (hmox1) have shown that bilins are not only essential retrograde signals to mitigate oxidative stress during diurnal dark-to-light transitions, they are also required for chlorophyll accumulation and maintenance of a functional photosynthetic apparatus in the light. However, the underlying mechanism of bilin-mediated regulation of chlorophyll biosynthesis is unclear. In this study, Chlamydomonas phycocyanobilin:ferredoxin oxidoreductase PCYA1 FDBR domain was found to specifically interact with the rate-limiting chlorophyll biosynthetic enzyme LPOR (light-dependent protochlorophyllide oxidoreductase). PCYA1 is partially associated with chloroplast envelope membrane, consistent with the observed export of bilin from chloroplast to cytosol by cytosolic expression of a bilin-binding reporter protein in Chlamydomonas. Both the pcya1-1 mutant with the carboxyl-terminal extension of PCYA1 eliminated and efficient knockdown of PCYA1 expression by artificial microRNA exhibited no significant impact on algal phototrophic growth and photosynthetic proteins accumulation, indicating that the conserved FDBR domain is sufficient and minimally required for bilin biosynthesis and functioning. Taken together, these studies provide novel insights into the regulatory role of PCYA1 in chlorophyll biosynthesis via interaction with key Chl biosynthetic enzyme.

Differentiation-associated urothelial cytochrome P450 oxidoreductase predicates the xenobiotic-metabolizing activity of "luminal" muscle-invasive bladder cancers

Extra-hepatic metabolism of xenobiotics by epithelial tissues has evolved as a self-defence mechanism but has potential to contribute to the local activation of carcinogens. Bladder epithelium (urothelium) is bathed in excreted urinary toxicants and pro-carcinogens. This study reveals how differentiation affects cytochrome P450 (CYP) activity and the role of NADPH:P450 oxidoreductase (POR). CYP1A1 and CYP1B1 transcripts were inducible in normal human urothelial (NHU) cells maintained in both undifferentiated and functional barrier-forming differentiated states in vitro. However, ethoxyresorufin O-deethylation (EROD) activity, the generation of reactive BaP metabolites and BaP-DNA adducts, were predominantly detected in differentiated NHU cell cultures. This gain-of-function was attributable to the expression of POR, an essential electron donor for all CYPs, which was significantly upregulated as part of urothelial differentiation. Immunohistology of muscle-invasive bladder cancer (MIBC) revealed significant overall suppression of POR expression. Stratification of MIBC biopsies into "luminal" and "basal" groups, based on GATA3 and cytokeratin 5/6 labeling, showed POR over-expression by a subgroup of the differentiated luminal tumors. In bladder cancer cell lines, CYP1-activity was undetectable/low in basal PORlo T24 and SCaBER cells and higher in the luminal POR over-expressing RT4 and RT112 cells than in differentiated NHU cells, indicating that CYP-function is related to differentiation status in bladder cancers. This study establishes POR as a predictive biomarker of metabolic potential. This has implications in bladder carcinogenesis for the hepatic versus local activation of carcinogens and as a functional predictor of the potential for MIBC to respond to prodrug therapies.

Efficacy and safety of follitropin alfa/lutropin alfa in ART: a randomized controlled trial in poor ovarian responders

STUDY QUESTION

How does the efficacy and safety of a fixed-ratio combination of recombinant human FSH plus recombinant human LH (follitropin alfa plus lutropin alfa; r-hFSH/r-hLH) compare with that of r-hFSH monotherapy for controlled ovarian stimulation (COS) in patients with poor ovarian response (POR)?

SUMMARY ANSWER

The primary and secondary efficacy endpoints were comparable between treatment groups and the safety profile of both treatment regimens was favourable.

WHAT IS KNOWN ALREADY

Although meta-analyses of clinical trials have suggested some beneficial effect on reproductive outcomes with r-hLH supplementation in patients with POR, the definitions of POR were heterogeneous and limit the comparability across studies.

STUDY DESIGN, SIZE, DURATION

Phase III, single-blind, active-comparator, randomized, parallel-group clinical trial. Patients were followed for a single ART cycle. A total of 939 women were randomized (1:1) to receive either r-hFSH/r-hLH or r-hFSH. Randomization, stratified by study site and participant age, was conducted via an interactive voice response system.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women classified as having POR, based on criteria incorporating the ESHRE Bologna criteria, were down-regulated with a long GnRH agonist protocol and following successful down-regulation were randomized (1:1) to COS with r-hFSH/r-hLH or r-hFSH alone. The primary efficacy endpoint was the number of oocytes retrieved following COS. Safety endpoints included the incidence of adverse events, including ovarian hyperstimulation syndrome (OHSS). Post hoc analyses investigated safety outcomes and correlations between live birth and baseline characteristics (age and number of oocytes retrieved in previous ART treatment cycles or serum anti-Müllerian hormone (AMH)). The significance of the treatment effect was tested by generalized linear models (Poisson regression for counts and logistic regression for binary endpoints) adjusting for age and country.

MAIN RESULTS AND THE ROLE OF CHANCE

Of 949 subjects achieving down-regulation, 939 were randomized to r-hFSH/r-hLH (n = 477) or r-hFSH (n = 462) and received treatment.

Efficacy assessment: In the intention-to-treat (ITT) population, the mean (SD) number of oocytes retrieved (primary endpoint) was 3.3 (2.71) in the r-hFSH/r-hLH group compared with 3.6 (2.82) in the r-hFSH group (between-group difference not statistically significant). The observed difference between treatment groups (r-hFSH/r-hLH and r-hFSH, respectively) for efficacy outcomes decreased over the course of pregnancy (biochemical pregnancy rate: 17.3% versus 23.9%; clinical pregnancy rate: 14.1% versus 16.8%; ongoing pregnancy rate: 11.0% versus 12.4%; and live birth rate: 10.6% versus 11.7%). An interaction (identified post hoc) between baseline characteristics related to POR and treatment effect was noted for live birth, with r-hFSH/r-hLH associated with a higher live birth rate for patients with moderate or severe POR, whereas r-hFSH was associated with a higher live birth rate for those with mild POR. A post hoc logistic regression analysis indicated that the incidence of total pregnancy outcome failure was lower in the r-hFSH/r-hLH group (6.7%) compared with the r-hFSH group (12.4%) with an odds ratio of 0.52 (95% CI 0.33, 0.82; P = 0.005).

Safety assessment: The overall proportion of patients with treatment-emergent adverse events (TEAEs) occurring during or after r-hFSH/r-hLH or r-hFSH use (stimulation or post-stimulation phase) was 19.9% and 26.8%, respectively. There was no consistent pattern of TEAEs associated with either treatment.

LIMITATIONS, REASONS FOR CAUTION

Despite using inclusion criteria for POR incorporating the ESHRE Bologna criteria, further investigation is needed to determine the impact of the heterogeneity of POR in the Bologna patient population. The observed correlation between baseline clinical characteristics related to POR and live birth rate, as well as the observed differences between groups regarding total pregnancy outcome failure were from post hoc analyses, and the study was not powered for these endpoints. In addition, the attrition rate for pregnancy outcomes in this trial may not reflect general medical practice. Furthermore, as the patient population was predominantly White these results might not be applicable to other ethnicities.

WIDER IMPLICATIONS OF THE FINDINGS

In the population of women with POR investigated in this study, although the number of oocytes retrieved was similar following stimulation with either a fixed-ratio combination of r-hFSH/r-hLH or r-hFSH monotherapy, post hoc analyses showed that there was a lower rate of total pregnancy outcome failure in patients receiving r-hFSH/r-hLH, in addition to a higher live birth rate in patients with moderate and severe POR. These findings are clinically relevant and require additional investigation. The benefit:risk balance of treatment with either r-hFSH/r-hLH or r-hFSH remains positive.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Merck KGaA, Darmstadt, Germany. P.H. has received honoraria for lectures and unrestricted research grants from Ferring, Merck KGaA and MSD. D.R. is a former employee of EMD Serono, a business of Merck KGaA, Darmstadt, Germany. J.S., J.H. and W.C. are employees of EMD Serono Research and Development Institute, a business of Merck KGaA, Darmstadt, Germany. T.D.’H. and S.L. are employees of Merck KGaA, Darmstadt, Germany.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT02047227; EudraCT Number: 2013-003817-16.

TRIAL REGISTRATION DATE

ClinicalTrials.gov: 24 January 2014; EudraCT: 19 December 2013.

DATE OF FIRST PATIENT'S ENROLMENT

30 January 2014.

Application of methyl-TROSY to a large paramagnetic membrane protein without perdeuteration: 13C-MMTS-labeled NADPH-cytochrome P450 oxidoreductase

NMR spectroscopy of membrane proteins involved in electron transport is difficult due to the presence of both the lipids and paramagnetic centers. Here we report the solution NMR study of the NADPH-cytochrome P450 oxidoreductase (POR) in its reduced and oxidized states. We interrogate POR, first, in its truncated soluble form (70 kDa), which is followed by experiments with the full-length protein incorporated in a lipid nanodisc (240 kDa). To overcome paramagnetic relaxation in the reduced state of POR as well as the signal broadening due to its high molecular weight, we utilized the methyl-TROSY approach. Extrinsic 13C-methyl groups were introduced by modifying the engineered surface-exposed cysteines with methyl-methanethiosulfonate. Chemical shift dispersion of the resonances from different sites in POR was sufficient to monitor differential effects of the reduction-oxidation process and conformation changes in the POR structure related to its function. Despite the high molecular weight of the POR-nanodisc complex, the surface-localized 13C-methyl probes were sufficiently mobile to allow for signal detection at 600 MHz without perdeuteration. This work demonstrates a potential of the solution methyl-TROSY in analysis of structure, dynamics, and function of POR, which may also be applicable to similar paramagnetic and flexible membrane proteins.

Altered CYP19A1 and CYP3A4 Activities Due to Mutations A115V, T142A, Q153R and P284L in the Human P450 Oxidoreductase

All cytochromes P450s in the endoplasmic reticulum rely on P450 oxidoreductase (POR) for their catalytic activities. Mutations in POR cause metabolic disorders of steroid hormone biosynthesis and affect certain drug metabolizing P450 activities. We studied mutations A115V, T142A, Q153R identified in the flavin mononucleotide (FMN) binding domain of POR that interacts with partner proteins and P284L located in the hinge region that is required for flexibility and domain movements in POR. Human wild-type (WT) and mutant POR as well as CYP3A4 and CYP19A1 proteins in recombinant form were expressed in bacteria, and purified proteins were reconstituted in liposomes for enzyme kinetic assays. Quality of POR protein was checked by cytochrome c reduction assay as well as flavin content measurements. We found that proteins carrying mutations A115V, T142A located close to the FMN binding site had reduced flavin content compared to WT POR and lost almost all activity to metabolize androstenedione via CYP19A1 and showed reduced CYP3A4 activity. The variant P284L identified from apparently normal subjects also had severe loss of both CYP19A1 and CYP3A4 activities, indicating this to be a potentially disease causing mutation. The mutation Q153R initially identified in a patient with disordered steroidogenesis showed remarkably increased activities of both CYP19A1 and CYP3A4 without any significant change in flavin content, indicating improved protein–protein interactions between POR Q153R and some P450 proteins. These results indicate that effects of mutations on activities of individual cytochromes P450 can be variable and a detailed analysis of each variant with different partner proteins is necessary to accurately determine the genotype-phenotype correlations of POR variants.

Evaluation of Selected CYP51A1 Polymorphisms in View of Interactions with Substrate and Redox Partner

Cholesterol is essential for development, growth, and maintenance of organisms. Mutations in cholesterol biosynthetic genes are embryonic lethal and few polymorphisms have been so far associated with pathologies in humans. Previous analyses show that lanosterol 14α-demethylase (CYP51A1) from the late part of cholesterol biosynthesis has only a few missense mutations with low minor allele frequencies and low association with pathologies in humans. The aim of this study is to evaluate the role of amino acid changes in the natural missense mutations of the hCYP51A1 protein. We searched SNP databases for existing polymorphisms of CYP51A1 and evaluated their effect on protein function. We found rare variants causing detrimental missense mutations of CYP51A1. Some missense variants were also associated with a phenotype in humans. Two missense variants have been prepared for testing enzymatic activity in vitro but failed to produce a P450 spectrum. We performed molecular modeling of three selected missense variants to evaluate the effect of the amino acid substitution on potential interaction with its substrate and the obligatory redox partner POR. We show that two of the variants, R277L and especially D152G, have possibly lower binding potential toward obligatory redox partner POR. D152G and R431H have also potentially lower affinity toward the substrate lanosterol. We evaluated the potential effect of damaging variants also using data from other in vitro CYP51A1 mutants. In conclusion, we propose to include damaging CYP51A1 variants into personalized diagnostics to improve genetic counseling for certain rare disease phenotypes.

Influence of two variants of CYP450 oxidoreductase on the stable dose of acenocoumarol in a Spanish population

AIM

To evaluate the influence of two variants of P450 oxidoreductase (POR), rs2868177 and POR*28, on the stable dosage of acenocoumarol.

PATIENTS & METHODS

For this observational, cross-sectional study, patients were undergone stable anticoagulant treatment with acenocoumarol. Univariate and multiple regression analyses were performed to assess the influence of POR polymorphisms.

RESULTS

About 340 patients were enrolled. Multiple regression had a coefficient of determination (R²) of 51.5% and an Akaike information criterion of 234.22. The inclusion of POR*28 polymorphisms increased the R² to 52.0% and reduced the Akaike information criteria to 230.58. The POR*28 heterozygote showed statistical significance in the algorithm.

CONCLUSION

The POR*28 heterozygote appears to be associated with the stable dose of acenocoumarol, but its clinical contribution to the prediction of the dosing of this drug is minimal.

Impact on CYP19A1 activity by mutations in NADPH cytochrome P450 oxidoreductase

Cytochrome P450 aromatase (CYP19A1), in human placenta metabolizes androgens to estrogens and uses reduced nicotinamide adenine dinucleotide phosphate through cytochrome P450 oxidoreductase (POR) for the energy requirements of its metabolic activities. Mutations in the human POR lead to congenital adrenal hyperplasia due to loss of activities of several steroid metabolizing enzymatic reactions conducted by the cytochrome P450 proteins located in the endoplasmic reticulum. Effect of POR mutations on different P450 activities depend on individual partner proteins. In this report we have studied the impact of mutations found in the POR on the enzymatic activity of CYP19A1. We expressed wild type as well mutant human POR proteins in bacteria and purified the recombinant proteins, which were then used in an in vitro reconstitution system in combination with CYP19A1 and lipids for enzymatic analysis. We found that several mutations as well as polymorphisms in human POR can cause reduction of CYP19A1 activity. This would affect metabolism of estrogens in people with variations of POR allele. The POR mutants Y181D and R616X were found to have no activity in supporting CYP19A1 reactions. The POR mutations Y607C and delF646 showed a loss of 60-90% activity and two polymorphic forms of POR, R316W and G413S showed similar to WT activity. One POR variant, Q153R had almost double the activity of WT. Loss of CYP19A1 activity may contribute to disordered steroidogenesis in female patients with POR mutations as well as in mothers with POR variants carrying a male child.

Impact of genetic and nongenetic factors on interindividual variability in 4β-hydroxycholesterol concentration

PURPOSE

Individual variability in the endogenous CYP3A metabolite 4β-hydroxycholesterol (4βOHC) is substantial, but to which extent this is determined by genetic and nongenetic factors remains unclear. The aim of the study was to evaluate the explanatory power of candidate genetic variants and key nongenetic factors on individual variability in 4βOHC levels in a large naturalistic patient population.

METHODS

We measured 4βOHC concentration in serum samples from 655 patients and used multiple linear regression analysis to estimate the quantitative effects of CYP3A4*22, CYP3A5*3, and POR*28 variant alleles, comedication with CYP3A inducers, inhibitors and substrates, sex, and age on individual 4βOHC levels.

RESULTS

4βOHC concentration ranged >100-fold in the population, and the multiple linear regression model explained about one fourth of the variability (R ² = 0.23). Only comedication with inducers or inhibitors, sex, and POR genotype were significantly associated with individual variability in 4βOHC level. The estimated quantitative effects on 4βOHC levels were greatest for inducer comedication (+>313%, P < 0.001), inhibitor comedication (-34%, P = 0.021), and female sex (+30%, P < 0.001), while only a modestly elevated 4βOHC level was observed in carriers vs. noncarriers of POR*28 (+11%, P = 0.023).

CONCLUSIONS

These findings suggest that the CYP3A4*22, CYP3A5*3, and POR*28 variant alleles are of limited importance for overall individual variability in 4βOHC levels compared to nongenetic factors.