Pharmacogenetics of human cytosolic sulfotransferases

Cholesterol Sulfate: Pathophysiological Implications and Potential Therapeutics

Cholesterol sulfate (CS) is a naturally occurring cholesterol derivative that is widely distributed across various tissues and body fluids. In humans, its biosynthesis is primarily mediated by the sulfotransferase (SULT) 2B1b (SULT2B1b). Over the years, CS has been found to play critical roles in various physiological processes, including epidermal cell adhesion, sperm capacitation, platelet adhesion, coagulation, glucolipid metabolism, bone metabolism, gut microbiota metabolism, neurosteroid biosynthesis, T-cell receptor signaling, and immune cell migration. In this review, we first introduce the endogenous regulation of CS biosynthesis and metabolism. We then highlight current advances in the understanding of the physiological roles of CS. Finally, we delve into the implications of CS in various diseases, with a particular focus on its mechanism of action and potential therapeutic applications. A comprehensive understanding of CS's physiological function, biosynthesis regulation, and role as a disease modifier offers novel insights that could pave the way for innovative therapeutic strategies targeting a wide range of conditions.

Complex roles for sulfation in the toxicities of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent organic toxicants derived from legacy pollution sources and their formation as inadvertent byproducts of some current manufacturing processes. Metabolism of PCBs is often a critical component in their toxicity, and relevant metabolic pathways usually include their initial oxidation to form hydroxylated polychlorinated biphenyls (OH-PCBs). Subsequent sulfation of OH-PCBs was originally thought to be primarily a means of detoxication; however, there is strong evidence that it may also contribute to toxicities associated with PCBs and OH-PCBs. These contributions include either the direct interaction of PCB sulfates with receptors or their serving as a localized precursor for OH-PCBs. The formation of PCB sulfates is catalyzed by cytosolic sulfotransferases, and, when transported into the serum, these metabolites may be retained, taken up by other tissues, and subjected to hydrolysis catalyzed by intracellular sulfatase(s) to regenerate OH-PCBs. Dynamic cycling between PCB sulfates and OH-PCBs may lead to further metabolic activation of the resulting OH-PCBs. Ultimate toxic endpoints of such processes may include endocrine disruption, neurotoxicities, and many others that are associated with exposures to PCBs and OH-PCBs. This review highlights the current understanding of the complex roles that PCB sulfates can have in the toxicities of PCBs and OH-PCBs and research on the varied mechanisms that control these roles.

A comprehensive review on structural and therapeutical insight of Cerebroside sulfotransferase (CST) - An important target for development of substrate reduction therapy against metachromatic leukodystrophy

This review is an effort towards the development of substrate reduction therapy using cerebroside sulfotransferase (CST) as a target protein for the development of inhibitors intended to treat pathophysiological condition resulting from the accumulation of sulfatide, a product from the catalytic action of CST. Accumulation of sulfatides leads to progressive impairment and destruction of the myelin structure, disruption of normal physiological transmission of electrical impulse between nerve cells, axonal loss in the central and peripheral nervous system and cumulatively gives a clinical manifestation of metachromatic leukodystrophy. Thus, there is a need to develop specific and potent CST inhibitors to positively control sulfatide accumulation. Structural similarity and computational studies revealed that LYS85, SER172 and HIS141 are key catalytic residues that determine the catalytic action of CST through the transfer of sulfuryl group from the donor PAPS to the acceptor galactosylceramide. Computational studies revealed catalytic site of CST consists two binding site pocket including PAPS binding pocket and substrate binding pocket. Specific substrate site residues in CST can be targeted to develop specific CST inhibitors. This review also explores the challenges of CST-directed substrate reduction therapy as well as the opportunities available in natural products for inhibitor development.

Transcriptomics and Metabolomics Reveal Tomato Consumption Alters Hepatic Xenobiotic Metabolism and Induces Steroidal Alkaloid Metabolite Accumulation in Mice

SCOPE

Tomato consumption is associated with many health benefits including lowered risk for developing certain cancers. It is hypothesized that tomato phytochemicals are transported to the liver and other tissues where they alter gene expression in ways that lead to favorable health outcomes. However, the effects of tomato consumption on mammalian liver gene expression and chemical profile are not well defined.

METHODS AND RESULTS

The study hypothesizes that tomato consumption would alter mouse liver transcriptomes and metabolomes compared to a control diet. C57BL/6J mice (n = 11-12/group) are fed a macronutrient matched diet containing either 10% red tomato, 10% tangerine tomato, or no tomato powder for 6 weeks after weaning. RNA-Seq followed by gene set enrichment analyses indicates that tomato type and consumption, in general, altered expression of phase I and II xenobiotic metabolism genes. Untargeted metabolomics experiments reveal distinct clustering between control and tomato fed animals. Nineteen molecular formulas (representing 75 chemical features) are identified or tentatively identified as steroidal alkaloids and isomers of their phase I and II metabolites; many of which are reported for the first time in mammals.

CONCLUSION

These data together suggest tomato consumption may impart benefits partly through enhancing detoxification potential.

Analysis of evolutionary and functional features of the bullfrog SULT1 family

We identified the bullfrog Rana catesbeiana sulfotransferase 1 (SULT1) family from the BLAST search tool of the public databases based on the SULT1 families of Nanorana parkeri, Xenopus laevis, and Xenopus tropicalis as queries, revealing the characteristics of the anuran SULT1 family. The results showed that the anuran SULT1 family comprises six subfamilies, four of which were related to the mammalian SULT1 subfamily. Additionally, the bullfrog has two SULT1Cc subfamily members that are consistent with the characteristics of the expanded Xenopus SULT1C subfamily. Several members of the bullfrog SULT1 family were suggested to play important roles in sulfation during metamorphosis. Among these, cDNAs encoding SULT1Cc1 and SULT1Y1 were cloned, and the sulfation activity was analyzed using recombinant proteins. The affinity for 2-naphthol and 3'-phosphoadenosine 5'-phosphosulfate (PAPS) and the enzymatic reaction rate were higher in SULT1Cc1 than in SULT1Y1. Both the enzymes showed inhibitory effect of many thyroid hormones (THs) analogs on the sulfation of 2-naphthol. The potency of sulfation activities of SULT1Cc1 and SULT1Y1 against T4 indicated their possible role in the intracellular T4 clearance during metamorphosis.

Interactions of Betel Quid Constituents with Drug Disposition Pathways: An Overview

Global estimates indicate that over 600 million individuals worldwide consume the areca (betel) nut in some form. Nonetheless, its consumption is associated with a myriad of oral and systemic ailments, such as precancerous oral lesions, oropharyngeal cancers, liver toxicity and hepatic carcinoma, cardiovascular distress, and addiction. Users commonly chew slivers of areca nut in a complex consumable preparation called betel quid (BQ). Consequently, the user is exposed to a wide array of chemicals with diverse pharmacokinetic behavior in the body. However, a comprehensive understanding of the metabolic pathways significant to BQ chemicals is lacking. Henceforth, we performed a literature search to identify prominent BQ constituents and examine each chemical's interplay with drug disposition proteins. In total, we uncovered over 20 major chemicals (e.g., arecoline, nicotine, menthol, quercetin, tannic acid) present in the BQ mixture that were substrates, inhibitors, and/or inducers of various phase I (e.g., CYP, FMO, hydrolases) and phase II (e.g., GST, UGT, SULT) drug metabolizing enzymes, along with several transporters (e.g., P-gp, BCRP, MRP). Altogether, over 80 potential interactivities were found. Utilizing this new information, we generated theoretical predictions of drug interactions precipitated by BQ consumption. Data suggests that BQ consumers are at risk for drug interactions (and possible adverse effects) when co-ingesting other substances (multiple therapeutic classes) with overlapping elimination mechanisms. Until now, prediction about interactions is not widely known among BQ consumers and their clinicians. Further research is necessary based on our speculations to elucidate the biological ramifications of specific BQ-induced interactions and to take measures that improve the health of BQ consumers.

Unravelling sex-specific BPA toxicokinetics in children using a pediatric PBPK model

Bisphenol A (BPA) is a widely known endocrine disruptor (ED) found in many children's products such as toys, feeding utensils, and teething rings. Recent epidemiology association studies have shown postnatal BPA exposure resulted in developing various diseases such as diabetes, obesity, and neurodegeneration, etc., later in their lives. However, little is known about its sex-specific metabolism and consequently internal exposure. The aim of this study was to develop a sex-specific pediatric physiologically based pharmacokinetic model (PBPK) for BPA to compare their toxicokinetic differences. First, the published adult PBPK model was re-validated, and then this model was extended by interpolation to incorporate pediatric sex specific physiological and biochemical parameters. We used both the classical body weight and ontogeny-based scaling approach to interpolate the metabolic process. Then, the pharmacokinetic attributes of the models using the two-scaling approach mentioned above were compared with adult model. Further, a sex-specific PBPK model with an ontogeny scaling approach was preferred to evaluate the pharmacokinetic differences. Moreover, this model was used to reconstruct the BPA exposure from two cohorts (Helix and PBAT Cohort) from 7 EU countries. The half-life of BPA was found to be almost the same in boys and girls at the same exposure levels. Our model estimated BPA children's exposure to be about 1500 times higher than the tolerable daily intake (TDI) recently set by European Food Safety Authority (EFSA) i.e., 0.04 ng/kg BW/day. The model demonstrated feasibility of extending the adult PBPK to sex-specific pediatric, thus investigate a gender-specific health risk assessment.

Pharmacogenetics of human sulfotransferases and impact of amino acid exchange on Phase II drug metabolism

Sulfotransferases (SULTs) are Phase II drug-metabolizing enzymes (DMEs) catalyzing the sulfation of a variety of endogenous compounds, natural products, and drugs. Various drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDS) can inhibit SULTs, affecting drug-drug interactions. Several polymorphisms have been identified for SULTs that might be crucial for interindividual variability in drug response and toxicity or for increased disease risk. Here, we review current knowledge on non-synonymous single nucleotide polymorphisms (nsSNPs) of human SULTs, focusing on the coded SULT allozymes and molecular mechanisms explaining their variable activity, which is essential for personalized medicine. We discuss the structural and dynamic bases of key amino acid (AA) variants implicated in the impacts on drug metabolism in the case of SULT1A1, as revealed by molecular modeling approaches.

Detectability of oxandrolone, metandienone, clostebol and dehydrochloromethyltestosterone in urine after transdermal application

Situations of both, intentional as well as inadvertent or accidental doping, necessitate consideration in today's doping controls, especially in the light of the substantial consequences that athletes are facing in case of so-called adverse analytical findings. The aim of this study was to investigate, whether a transdermal uptake of doping substances would be possible. In addition to the period of detectability of the particular substances or respective characteristic metabolites, the possibility of deducing the route of administration by metabolite patterns was also assessed. Twelve male subjects were included in the study. Four common anabolic androgenic steroids (AAS) were dissolved in dimethylsulfoxide (DMSO) to facilitate transdermal administration on different skin regions. One half of the test persons received only oxandrolone (17α-methyl-2-oxa-4,5α-dihydrotestosterone), the other half was applied a mixture of oxandrolone, metandienone (17β-hydroxy-17-methylandrosta-1,4-dien-3-one), clostebol (4-chlorotestosterone-17β-acetate) and dehydrochloromethyltestosterone (DHCMT). Urine samples were collected 1 hour, 6 hours and one sample per day for the next 14 consecutive days. Measurements were conducted on a GC-MS/MS or LC-MS/MS system. Substance findings were obtained at least 1 day after application on nearly all skin locations. The results indicated inter-individual variability in detection windows, also varying between the different analytes and possible impact of skin location and skin thickness, respectively. Nevertheless, a rapid and rather long detectability of all substances (or respective metabolites) was given, in some cases within hours after administration and for up to 10-14 days. Hence, the transdermal application or exposure to the investigated AAS is a plausible scenario that warrants consideration in anti-doping.

Pharmacogenetics of Drugs Used in the Treatment of Cancers

Pharmacogenomics is based on the understanding of the individual differences in drug use, the response to drug therapy (efficacy and toxicity), and the mechanisms underlying variable drug responses. The identification of DNA variants which markedly contribute to inter-individual variations in drug responses would improve the efficacy of treatments and decrease the rate of the adverse side effects of drugs. This review focuses only on the impact of polymorphisms within drug-metabolizing enzymes on drug responses. Anticancer drugs usually have a very narrow therapeutic index; therefore, it is very important to use appropriate doses in order to achieve the maximum benefits without putting the patient at risk of life-threatening toxicities. However, the adjustment of the appropriate dose is not so easy, due to the inheritance of specific polymorphisms in the genes encoding the target proteins and drug-metabolizing enzymes. This review presents just a few examples of such polymorphisms and their impact on the response to therapy.

Genetic Polymorphisms of Very Important Pharmacogene Variants in the Blang Population from Yunnan Province in China

Background

We aimed to enrich the pharmacogenomic information of a Blang population (BP) from Yunnan Province in China.

Methods

We genotyped 55 very important pharmacogene (VIP) variants from the PharmGKB database and compared their genotype distribution (GD) in a BP with that of 26 populations by the χ² test. The minor allele frequency (MAF) distribution of seven significantly different single-nucleotide polymorphisms (SNPs) was conducted to compare the difference between the BP and 26 other populations.

Results

Compared with the GD of 55 loci in the BP, among 26 studied populations, GWD, YRI, GIH, ESN, MSL, TSI, PJL, ACB, FIN and IBS were the top-10 populations, which showed a significantly different GD >35 loci. CHB, JPT, CDX, CHS, and KHV populations had a significantly different GD <20 loci. A GD difference of 27–34 loci was found between the BP and 11 populations (LWK, CEU, ITU, STU, PUR, CLM, GBR, ASW, BEB, MXL and PEL). The GD of five loci (rs750155 (SULT1A1), rs4291 (ACE), rs1051298 (SLC19A1), rs1131596 (SLC19A1) and rs1051296 (SLC19A1)) were the most significantly different in the BP as compared with that of the other 26 populations. The genotype frequency of rs1800764 (ACE) and rs1065852 (CYP2D6) was different in all populations except for PEL and LWK, respectively. MAFs of rs1065852 (CYP2D6) and rs750155 (SULT1A1) showed the largest fluctuation between the BP and SAS, EUR, AFR and AMR populations.

Conclusion

Our data can provide theoretical guidance for safe and efficacious personalized drug use in the Blang population.

Multi-omics integration analysis identifies novel genes for alcoholism with potential overlap with neurodegenerative diseases

Identification of causal variants and genes underlying genome-wide association study (GWAS) loci is essential to understand the biology of alcohol use disorder (AUD) and drinks per week (DPW). Multi-omics integration approaches have shown potential for fine mapping complex loci to obtain biological insights to disease mechanisms. In this study, we use multi-omics approaches, to fine-map AUD and DPW associations at single SNP resolution to demonstrate that rs56030824 on chromosome 11 significantly reduces SPI1 mRNA expression in myeloid cells and lowers risk for AUD and DPW. Our analysis also identifies MAPT as a candidate causal gene specifically associated with DPW. Genes prioritized in this study show overlap with causal genes associated with neurodegenerative disorders. Multi-omics integration analyses highlight, genetic similarities and differences between alcohol intake and disordered drinking, suggesting molecular heterogeneity that might inform future targeted functional and cross-species studies.

SULT genetic polymorphisms: physiological, pharmacological and clinical implications

INTRODUCTION

Cytosolic sulfotransferases (SULTs)-mediated sulfation is critically involved in the metabolism of key endogenous compounds, such as catecholamines and thyroid/steroid hormones, as well as a variety of drugs and other xenobiotics. Studies performed in the past three decades have yielded a good understanding about the enzymology of the SULTs and their structural biology, phylogenetic relationships, tissue/organ-specific/developmental expression, as well as the regulation of the SULT gene expression. An emerging area is related to the functional impact of the SULT genetic polymorphisms.

AREAS COVERED

The current review aims to summarize our current knowledge about the above-mentioned aspects of the SULT research. An emphasis is on the information concerning the effects of the polymorphisms of the SULT genes on the functional activity of the SULT allozymes and the associated physiological, pharmacological, and clinical implications.

EXPERT OPINION

Elucidation of how SULT SNPs may influence the drug-sulfating activity of SULT allozymes will help understand the differential drug metabolism and eventually aid in formulating personalized drug regimens. Moreover, the information concerning the differential sulfating activities of SULT allozymes toward endogenous compounds may allow for the development of strategies for mitigating anomalies in the metabolism of these endogenous compounds in individuals with certain SULT genotypes.

A simple method to measure sulfonation in man using paracetamol as probe drug

Sulfotransferase enzymes (SULT) catalyse sulfoconjugation of drugs, as well as endogenous mediators, gut microbiota metabolites and environmental xenobiotics. To address the limited evidence on sulfonation activity from clinical research, we developed a clinical metabolic phenotyping method using paracetamol as a probe substrate. Our aim was to estimate sulfonation capability of phenolic compounds and study its intraindividual variability in man. A total of 36 healthy adult volunteers (12 men, 12 women and 12 women on oral contraceptives) received paracetamol in a 1 g-tablet formulation on three separate occasions. Paracetamol and its metabolites were measured in plasma and spot urine samples using liquid chromatography-high resolution mass spectrometry. A metabolic ratio (Paracetamol Sulfonation Index—PSI) was used to estimate phenol SULT activity. PSI showed low intraindividual variability, with a good correlation between values in plasma and spot urine samples. Urinary PSI was independent of factors not related to SULT activity, such as urine pH or eGFR. Gender and oral contraceptive intake had no impact on PSI. Our SULT phenotyping method is a simple non-invasive procedure requiring urine spot samples, using the safe and convenient drug paracetamol as a probe substrate, and with low intraindividual coefficient of variation. Although it will not give us mechanistic information, it will provide us an empirical measure of an individual’s sulfonator status. To the best of our knowledge, our method provides the first standardised in vivo empirical measure of an individual’s phenol sulfonation capability and of its intraindividual variability. EUDRA-CT 2016-001395-29, NCT03182595 June 9, 2017.

Generating a Precision Endoxifen Prediction Algorithm to Advance Personalized Tamoxifen Treatment in Patients with Breast Cancer

Tamoxifen is an endocrine treatment for hormone receptor positive breast cancer. The effectiveness of tamoxifen may be compromised in patients with metabolic resistance, who have insufficient metabolic generation of the active metabolites endoxifen and 4-hydroxy-tamoxifen. This has been challenging to validate due to the lack of measured metabolite concentrations in tamoxifen clinical trials. CYP2D6 activity is the primary determinant of endoxifen concentration. Inconclusive results from studies investigating whether CYP2D6 genotype is associated with tamoxifen efficacy may be due to the imprecision in using CYP2D6 genotype as a surrogate of endoxifen concentration without incorporating the influence of other genetic and clinical variables. This review summarizes the evidence that active metabolite concentrations determine tamoxifen efficacy. We then introduce a novel approach to validate this relationship by generating a precision endoxifen prediction algorithm and comprehensively review the factors that must be incorporated into the algorithm, including genetics of CYP2D6 and other pharmacogenes. A precision endoxifen algorithm could be used to validate metabolic resistance in existing tamoxifen clinical trial cohorts and could then be used to select personalized tamoxifen doses to ensure all patients achieve adequate endoxifen concentrations and maximum benefit from tamoxifen treatment.

Small-molecule control of neurotransmitter sulfonation

Controlling unmodified serotonin levels in brain synapses is a primary objective when treating major depressive disorder-a disease that afflicts ∼20% of the world's population. Roughly 60% of patients respond poorly to first-line treatments and thus new therapeutic strategies are sought. To this end, we have constructed isoform-specific inhibitors of the human cytosolic sulfotransferase 1A3 (SULT1A3)-the isoform responsible for sulfonating ∼80% of the serotonin in the extracellular brain fluid. The inhibitor design includes a core ring structure, which anchors the inhibitor into a SULT1A3-specific binding pocket located outside the active site, and a side chain crafted to act as a latch to inhibit turnover by fastening down the SULT1A3 active-site cap. The inhibitors are allosteric, they bind with nanomolar affinity and are highly specific for the 1A3 isoform. The cap-stabilizing effects of the latch can be accurately calculated and are predicted to extend throughout the cap and into the surrounding protein. A free-energy correlation demonstrates that the percent inhibition at saturating inhibitor varies linearly with cap stabilization - the correlation is linear because the rate-limiting step of the catalytic cycle, nucleotide release, scales linearly with the fraction of enzyme in the cap-open form. Inhibitor efficacy in cultured cells was studied using a human mammary epithelial cell line that expresses SULT1A3 at levels comparable with those found in neurons. The inhibitors perform similarly in ex vivo and in vitro studies; consequently, SULT1A3 turnover can now be potently suppressed in an isoform-specific manner in human cells.

Recent advances in the personalized treatment of estrogen receptor-positive breast cancer with tamoxifen: a focus on pharmacogenomics

Introduction: Tamoxifen is still an important drug in hormone-dependent breast cancer therapy. Personalization of its clinical use beyond hormone receptor positivity could improve the substantial variability of the treatment response.Areas covered: The overview of the current evidence for the treatment personalization using therapeutic drug monitoring, or using genetic biomarkers including CYP2D6 is provided. Although many studies focused on the PK aspects or the impact of CYP2D6 variability the translation into clinical routine is not clearly defined due to the inconsistent clinical outcome data.Expert opinion: We believe that at least the main candidate factors, i.e. CYP2D6 polymorphism, CYP2D6 inhibition, endoxifen serum levels may become important predictors of clinical relevance for tamoxifen treatment personalization in the future. To achieve this aim, however, further research should take into consideration more precise characterization of the disease, epigenetic factors and also utilize an appropriately powered multifactorial approach instead of a single gene evaluating studies.

Detection of clostebol in sports: Accidental doping?

The detection of clostebol misuse in sports has been growing recently, especially in Italy, due to the ample availability of pharmaceutical formulations containing clostebol acetate (Trofodermin®) and the use of more sensitive instrumentation by the antidoping laboratories. Most of these cases have been claimed to be related to a nonconscious use of the drug or through contact with relatives or teammates using it. We have investigated, through the application of the well-known and currently used gas chromatographic mass spectrometric procedures, the likelihood of these allegations and have demonstrated that after a single transdermal administration of 5 mg of clostebol acetate and a transient contact with the application area, it is possible to generate adverse analytical findings in antidoping controls. We have reviewed the Phase I and Phase II clostebol metabolism in order to generate evidences that may help the sport authorities reviewing these cases. The main clostebol metabolite (4-chloro-androst-4-en-3α-ol-17-one, M1) generally used at the screening level as well as other three metabolites (M2-M4) are mainly excreted as glucuronides, whereas M5 (4ζ-chloro-5ζ-androstan-3β-ol-17-one) is predominantly excreted as sulfate. Neither the 5α-reductases activity (impaired by the presence of the chlorine in C4) nor specific sulfotransferases present in the skin allowed a clear distinction of the administration route. Studies with a larger number of volunteers and probably investigating another physiological fluid allowed in antidoping such as blood are needed for a deeper investigation. It is not unreasonable to establish a reporting level for M1, maybe creating some false negatives but excluding nonintentional doping scenarios.

Cholesterol and oxysterol sulfates: Pathophysiological roles and analytical challenges

Cholesterol and oxysterol sulfates are important regulators of lipid metabolism, inflammation, cell apoptosis, and cell survival. Among the sulfate-based lipids, cholesterol sulfate (CS) is the most studied lipid both quantitatively and functionally. Despite the importance, very few studies have analysed and linked the actions of oxysterol sulfates to their physiological and pathophysiological roles. Overexpression of sulfotransferases confirmed the formation of a range of oxysterol sulfates and their antagonistic effects on liver X receptors (LXRs) prompting further investigations how are the changes to oxysterol/oxysterol sulfate homeostasis can contribute to LXR activity in the physiological milieu. Here, we aim to bring together for novel roles of oxysterol sulfates, the available techniques and the challenges associated with their analysis. Understanding the oxysterol/oxysterol sulfate levels and their pathophysiological mechanisms could lead to new therapeutic targets for metabolic diseases. LINKED ARTICLES: This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.

Effect of Environmental Exposure and Pharmacogenomics on Drug Metabolism

BACKGROUND

Pesticides are major xenobiotic compounds and environmental pollutants, which are able to alter drug-metabolizing enzyme as well as pharmacokinetics of drugs. Subsequent to the release of the human genome project, genetic variations (polymorphism) become an integral part of drug development due to their influence on disease susceptibility/ progression of the disease and their impact on drug absorption, distribution, metabolism of active metabolites and finally excretion of the drug. Genetic polymorphisms crucially regulate pharmacokinetics and pharmacodynamics of drugs under the influence of physiological condition, lifestyle, as well as pathological conditions collectively.

OBJECTIVE

To review all the evidence concerning the effect of environmental exposure on drug metabolism with reference to pharmacogenomics.

METHODS

Scientific data search and review of basic, epidemiological, pharmacogenomics and pharmacokinetics studies were undertaken to evaluate the influence of environmental contaminants on drug metabolism.

RESULTS

Various environmental contaminants like pesticides effectively alter drug metabolism at various levels under the influence of pharmacogenomics, which interferes with pharmacokinetics of drug metabolism. Genetic polymorphism of phase I and phase II xenobiotic-metabolizing enzymes remarkably alters disease susceptibility as well as the progression of disease under the influence of various environmental contaminants at various levels.

CONCLUSION

Individual specific drug response may be attributed to a large variety of factors alone or in combination ranging from genetic variations (SNP, insertion, deletion, duplication etc.) to physiological setting (gender, age, body size, and ethnicity), environmental or lifestyle factors (radiation exposure, smoking, alcohol, nutrition, exposure to toxins, etc.); and pathological conditions (obesity, diabetes, liver and renal function).

Ontogeny of Hepatic Sulfotransferases and Prediction of Age-Dependent Fractional Contribution of Sulfation in Acetaminophen Metabolism

Cytosolic sulfotransferases (SULTs), including SULT1A, SULT1B, SULT1E, and SULT2A isoforms, play noteworthy roles in xenobiotic and endobiotic metabolism. We quantified the protein abundances of SULT1A1, SULT1A3, SULT1B1, and SULT2A1 in human liver cytosol samples (n = 194) by liquid chromatography-tandem mass spectrometry proteomics. The data were analyzed for their associations by age, sex, genotype, and ethnicity of the donors. SULT1A1, SULT1B1, and SULT2A1 showed significant age-dependent protein abundance, whereas SULT1A3 was invariable across 0-70 years. The respective mean abundances of SULT1A1, SULT1B1, and SULT2A1 in neonatal samples was 24%, 19%, and 38% of the adult levels. Interestingly, unlike UDP-glucuronosyltransferases and cytochrome P450 enzymes, SULT1A1 and SULT2A1 showed the highest abundance during early childhood (1 to <6 years), which gradually decreased by approx. 40% in adolescents and adults. SULT1A3 and SULT1B1 abundances were significantly lower in African Americans compared with Caucasians. Multiple linear regression analysis further confirmed the association of SULT abundances by age, ethnicity, and genotype. To demonstrate clinical application of the characteristic SULT ontogeny profiles, we developed and validated a proteomics-informed physiologically based pharmacokinetic model of acetaminophen. The latter confirmed the higher fractional contribution of sulfation over glucuronidation in the metabolism of acetaminophen in children. The study thus highlights that the ontogeny-based age-dependent fractional contribution (fm) of individual drug-metabolizing enzymes has better potential in prediction of drug-drug interactions and the effect of genetic polymorphisms in the pediatric population.

Identification of equol-7-glucuronide-4'-sulfate, monoglucuronides and monosulfates in human plasma of 2 equol producers after administration of kinako by LC-ESI-MS

Equol is a product formed during the biotransformation of the naturally occurring isoflavone daidzein by intestinal bacteria. The role of equol in the prevention of several hormone-dependent diseases such as prostate cancer and osteoporosis as well as vasomotor symptoms has been extensively investigated. Equol primarily occurs in the form of major metabolites such as glucuronides and sulfates, while intact equol has been detected at only ca. 1% in human plasma. However, to date, conjugated metabolites have been evaluated by measuring the free equol obtained after selective enzymatic hydrolysis. Thus, the precise types of conjugates circulating in vivo and the position(s) of the conjugation sites on the equol skeleton have yet to be clarified. Our study describes the identification of polar equol metabolites in the plasma of 2 equol-producers obtained at 8 hours after consuming 50 g of kinako (approximately 37 mg of daidzein). The structural identification of these conjugated metabolites in plasma was performed by comparison to the LC-ESI-MS n and 1H-NMR spectral data of the corresponding chemically synthesized compounds. The results of the LC-ESI-MS/MS analysis indicated that the main conjugated metabolite in plasma was (S)-equol-7-glucuronide-4'-sulfate along with lower amounts of 7- and 4'-monoglucuronides as well as 7- and 4'-monosulfates.

Isoform-specific therapeutic control of sulfonation in humans

The activities of hundreds, perhaps thousands, of metabolites are regulated by human cytosolic sulfotransferases (SULTs) - a 13-member family of disease relevant enzymes that catalyze transfer of the sulfuryl moiety (-SO₃) from PAPS (3'-phosphoadenosine 5'-phosphosulfonate) to the hydroxyls and amines of acceptors. SULTs harbor two independent allosteric sites, one of which, the focus of this work, binds non-steroidal anti-inflammatory drugs (NSAIDs). The structure of the first NSAID-binding site - that of SULT1A1 - was elucidated recently and homology modeling suggest that variants of the site are present in all SULT isoforms. The objective of the current study was to assess whether the NSAID-binding site can be used to regulate sulfuryl transfer in humans in an isoform specific manner. Mefenamic acid (Mef) is a potent (K_i 27 nM) NSAID-inhibitor of SULT1A1 - the predominant SULT isoform in small intestine and liver. Acetaminophen (APAP), a SULT1A1 specific substrate, is extensively sulfonated in humans. Dehydroepiandrosterone (DHEA) is specific for SULT2A1, which we show here is insensitive to Mef inhibition. APAP and DHEA sulfonates are readily quantified in urine and thus the effects of Mef on APAP and DHEA sulfonation could be studied non-invasively. Compounds were given orally in a single therapeutic dose to a healthy, adult male human with a typical APAP-metabolite profile. Mef profoundly decreased APAP sulfonation during first pass metabolism and substantially decreased systemic APAP sulfonation without influencing DHEA sulfonation; thus, it appears the NSAID site can be used to control sulfonation in humans in a SULT-isoform specific manner.

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view

BACKGROUND

Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

AIMS

To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

METHODS

A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

RESULTS

Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

CONCLUSIONS

The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.

Cardiovascular Pharmacogenomics: Does It Matter If You're Black or White?

Race and ancestry have long been associated with differential risk and outcomes to disease as well as responses to medications. These differences in drug response are multifactorial with some portion associated with genomic variation. The field of pharmacogenomics aims to predict drug response in patients prior to medication administration and to uncover the biological underpinnings of drug response. The field of human genetics has long recognized that genetic variation differs in frequency between ancestral populations, with some single nucleotide polymorphisms found solely in one population. Thus far, most pharmacogenomic studies have focused on individuals of European and East Asian ancestry, resulting in a substantial disparity in the clinical utility of genetic prediction for drug response in US minority populations. In this review, we discuss the genetic factors that underlie variability to drug response and known pharmacogenomic associations and how these differ between populations, with an emphasis on the current knowledge in cardiovascular pharmacogenomics.

Genetic polymorphisms of 3'-untranslated region of SULT1A1 and their impact on tamoxifen metabolism and efficacy

Purpose

Tamoxifen has a wide inter-variability. Recently, two SNPs in the 3′-untranslated region (UTR) of the SULT1A1 gene, rs6839 and rs1042157, have been associated with decreased SULT1A1 activity. The aim of this study is to investigate the role of the rs6839 and rs1042157 on tamoxifen metabolism and relapse-free survival (RFS) in women diagnosed with early-breast cancer receiving tamoxifen.

Methods

Samples from 667 patients collected in the CYPTAM study (NTR1509) were used for genotyping (CYP2D6, SULT1A1 rs6839 and rs1042157) and measurements of tamoxifen and metabolites. Patients were categorized in three groups depending on the decreased SULT1A1 activity due to rs6839 and rs1042157: low activity group (rs6839 (GG) and rs1042157 (TT)); high activity group (rs6839 (AA) and rs1042157 (CC)); and medium activity group (all the other combinations of rs6839 and rs1042157). Associations between SULT1A1 phenotypes and clinical outcome (RFS) were explored.

Results

In the low SULT1A1 activity group, higher endoxifen and 4-hydroxy-tamoxifen concentrations were found, compared to the medium and high activity group (endoxifen: 31.23 vs. 30.51 vs. 27.00, p value: 0.016; 4-hydroxy-tamoxifen: 5.55 vs. 5.27 vs. 4.94, p value:0.05). In terms of relapse, the low activity group had a borderline better outcome compared to the medium and high SULT1A1 activity group (adjusted Hazard ratio: 0.297; 95% CI 0.088–1.000; p value: 0.05).

Conclusion

Our results suggested that rs6839 and rs1042157 SNPs have a minor effect on the concentrations and metabolic ratios of tamoxifen and its metabolites, and RFS in women receiving adjuvant tamoxifen.

Electronic supplementary material

The online version of this article (10.1007/s10549-018-4923-7) contains supplementary material, which is available to authorized users.

Effects of genetic polymorphisms on the sulfation of dehydroepiandrosterone and pregnenolone by human cytosolic sulfotransferase SULT2A1

The cytosolic sulfotransferase (SULT) SULT2A1 is known to mediate the sulfation of DHEA as well as some other hydroxysteroids such as pregnenolone. The present study was designed to investigate how genetic polymorphisms of the human SULT2A1 gene may affect the sulfation of DHEA and pregnenolone. Online databases were systematically searched to identify human SULT2A1 single nucleotide polymorphisms (SNPs). Of the 98 SULT2A1 non-synonymous coding SNPs identified, seven were selected for further investigation. Site-directed mutagenesis was used to generate cDNAs encoding these seven SULT2A1 allozymes, which were expressed in BL21 Escherichia coli cells and purified by glutathione-Sepharose affinity chromatography. Enzymatic assays revealed that purified SULT2A1 allozymes displayed differential sulfating activity toward both DHEA and pregnenolone. Kinetic analyses showed further differential catalytic efficiency and substrate affinity of the SULT2A1 allozymes, in comparison with wild-type SULT2A1. These findings provided useful information concerning the effects of genetic polymorphisms on the sulfating activity of SULT2A1 allozymes.

Sulfonation, an underexploited area: from skeletal development to infectious diseases and cancer

Sulfonation is one of the most abundant cellular reactions modifying a wide range of xenobiotics as well as endogenous molecules which regulate important biological processes including blood clotting, formation of connective tissues, and functionality of secreted proteins, hormones, and signaling molecules. Sulfonation is ubiquitous in all tissues and widespread in nature (plants, animals, and microorganisms). Although sulfoconjugates were discovered over a century ago when, in 1875, Baumann isolated phenyl sulfate in the urine of a patient given phenol as an antiseptic, the significance of sulfonation and its roles in human diseases have been underappreciated until recent years. Here, we provide a current overview of the significance of sulfonation reactions in a variety of biological functions and medical conditions (with emphasis on cancer). We also discuss research areas that warrant further attention if we are to fully understand how deficiencies in sulfonation could impact human health which, in turn, could help define treatments to effect improvements in health.

Controlling Sulfuryl-Transfer Biology

In humans, the cytosolic sulfotransferases (SULTs) catalyze regiospecific transfer of the sulfuryl moiety (-SO3) from 3'-phosphoadenosine 5'-phosphosulfate to thousands of metabolites, including numerous signaling small molecules, and thus regulates their activities and half-lives. Imbalances in the in vivo set points of these reactions leads to disease. Here, with the goal of controlling sulfonation in vivo, molecular ligand-recognition principles in the SULT and nuclear receptor families are integrated in creating a strategy that can prevent sulfonation of a compound without significantly altering its receptor affinity, or inhibiting SULTS. The strategy is validated by using it to control the sulfonation and estrogen receptor (ER) activating activity of raloxifene (a US Food and Drug Administration-approved selective estrogen receptor modulator) and its derivatives. Preventing sulfonation is shown to enhance ER-activation efficacy 10(4)-fold in studies using Ishikawa cells. The strategy offers the opportunity to control sulfuryl transfer on a compound-by-compound basis, to enhance the efficacy of sulfonated drugs, and to explore the biology of sulfuryl transfer with unprecedented precision.

Relationship of SULT1A1 copy number variation with estrogen metabolism and human health

Human cytosolic sulfotransferase 1A1 (SULT1A1) is considered to be one of the most important SULT isoforms for metabolism, detoxification, and carcinogenesis. This theory is driven by observations that SULT1A1 is widely expressed in multiple tissues and acts on a wide range of phenolic substrates. SULT1A1 is subject to functional common copy number variation (CNV) including deletions or duplications. However, it is less clear how SULT1A1 CNV impacts health and disease. To better understand the biological role of SULT1A1 in human health, we genotyped CNV in 14,275 Marshfield Clinic patients linked to an extensive electronic health record. Since SULT1A1 is linked to steroid metabolism, select serum steroid hormones were measured in 100 individuals with a wide spectrum of SULT1A1 CNV genotypes. Furthermore, comprehensive phenome-wide association studies (PheWAS) were conducted using diagnostic codes and clinical text data. For the first time, individuals homozygous null for SULT1A1 were identified in a human population. Thirty-six percent of the population carried >2 copies of SULT1A1 whereas 4% had ≤1 copy. Results indicate SULT1A1 CNV was negatively correlated with estrone-sulfate to estrone ratio predominantly in males (E1S/E1; p=0.03, r=-0.21) and may be associated with increased risk for common allergies. The effect of SULT1A1 CNV on circulating estrogen metabolites was opposite to the predicted CNV-metabolite trend based on enzymatic function. This finding, and the potential association with common allergies reported herein, warrants future studies.

SULT1A1 copy number variation: ethnic distribution analysis in an Indian population

Cytosolic sulfotransferases (SULTs) are phase II detoxification enzymes involved in metabolism of numerous xenobiotics, drugs and endogenous compounds. Interindividual variation in sulfonation capacity is important for determining an individual's response to xenobiotics. SNPs in SULTs, mainly SULT1A1 have been associated with cancer risk and also with response to therapeutic agents. Copy number variation (CNVs) in SULT1A1 is found to be correlated with altered enzyme activity. This short report primarily focuses on CNV in SULT1A1 and its distribution among different ethnic populations around the globe. Frequency distribution of SULT1A1 copy number (CN) in 157 healthy Indian individuals was assessed using florescent-based quantitative PCR assay. A range of 1 to >4 copies, with a frequency of SULT1A1 CN =2 (64.9%) the highest, was observed in our (Indian) population. Upon comparative analysis of frequency distribution of SULT1A1 CN among diverse population groups, a statistically significant difference was observed between Indians (our data) and African-American (AA) (p = 0.0001) and South African (Tswana) (p < 0.0001) populations. Distribution of CNV in the Indian population was found to be similar to that in European-derived populations of American and Japanese. CNV of SULT1A1 varies significantly among world populations and may be one of the determinants of health and diseases.

Tetrahydrobiopterin regulates monoamine neurotransmitter sulfonation

Monoamine neurotransmitters are among the hundreds of signaling small molecules whose target interactions are switched "on" and "off" via transfer of the sulfuryl-moiety (-SO3) from PAPS (3'-phosphoadenosine 5'-phosphosulfate) to the hydroxyls and amines of their scaffolds. These transfer reactions are catalyzed by a small family of broad-specificity enzymes-the human cytosolic sulfotransferases (SULTs). The first structure of a SULT allosteric-binding site (that of SULT1A1) has recently come to light. The site is conserved among SULT1 family members and is promiscuous-it binds catechins, a naturally occurring family of flavanols. Here, the catechin-binding site of SULT1A3, which sulfonates monoamine neurotransmitters, is modeled on that of 1A1 and used to screen in silico for endogenous metabolite 1A3 allosteres. Screening predicted a single high-affinity allostere, tetrahydrobiopterin (THB), an essential cofactor in monoamine neurotransmitter biosynthesis. THB is shown to bind and inhibit SULT1A3 with high affinity, 23 (±2) nM, and to bind weakly, if at all, to the four other major SULTs found in brain and liver. The structure of the THB-bound binding site is determined and confirms that THB binds the catechin site. A structural comparison of SULT1A3 with SULT1A1 (its immediate evolutionary progenitor) reveals how SULT1A3 acquired high affinity for THB and that the majority of residue changes needed to transform 1A1 into 1A3 are clustered at the allosteric and active sites. Finally, sequence records reveal that the coevolution of these sites played an essential role in the evolution of simian neurotransmitter metabolism.

Implications of sulfotransferase activity in interindividual variability in drug response: clinical perspective on current knowledge

The interindividual variability in drug response is a major issue in clinical practice and in drug development. Sulfoconjugation is an important Phase II reaction catalyzed by cytosolic sulfotransferases (SULTs), playing a major role in homeostatic functions, xenobiotic detoxification, and carcinogen bioactivation. SULT display wide interindividual variability, explained only partially by genetic variation, suggesting that other non-genetic, epigenetic, and environmental influences could be major determinants of variability in SULT activity. This review focuses on the factors known to influence SULT variability in expression and activity and the available evidence regarding the impact of SULT variability on drug response.

New PCOS-like phenotype in older infertile women of likely autoimmune adrenal etiology with high AMH but low androgens

How anti-Müllerian hormone (AMH) and testosterone (T) interrelate in infertile women is currently largely unknown. We, therefore, in a retrospective cohort study investigated how infertile women with high-AMH (AMH ≥75th quantile; n=144) and with normal-AMH (25th-75th quantile; n=313), stratified for low-T (total testosterone ≤19.0ng/dL), normal-T (19.0-29.0ng/dL) and high-T (>29.0ng/dL) phenotypically behaved. Patient age, follicle stimulating hormone (FSH), dehyroepiandrosterone (DHEA), DHEA sulphate (DHEAS), cortisol (C), adrenocorticotrophic hormone (ACTH), IVF outcomes, as well as inflammatory and immune panels were then compared between groups, with AMH and T as variables. We identified a previously unknown infertile PCOS-like phenotype, characterized by high-AMH but, atypically, low-T, with predisposition toward autoimmunity. It presents with incompatible high-AMH and low-T (<19.0ng/dL), is restricted to lean PCOS-like patients, presenting delayed for tertiary fertility services. Since also characterized by low DHEAS, low-T is likely of adrenal origina, and consequence of autoimmune adrenal insufficiency since also accompanied by low-C and evidence of autoimmunity. DHEA supplementation in such patients equalizes low- to normal-T and normalizes IVF cycle outcomes. Once recognized, this high-AMH/low-T phenotype is surprisingly common in tertiary fertility centers but, currently, goes unrecognized. Its likely adrenal autoimmune etiology offers interesting new directions for investigations of adrenals control over ovarian function via adrenal androgen production.

A high frequency missense SULT1B1 allelic variant (L145V) selectively expressed in African descendants exhibits altered kinetic properties

1. Human cytosolic sulfotransferase 1B1 (SULT1B1) sulfates small phenolic compounds and bioactivates polycyclic aromatic hydrocarbons. To date, no SULT1B1 allelic variants have been well-characterized. 2. While cloning SULT1B1 from human endometrial specimens, an allelic variant resulting in valine instead of leucine at the 145th amino acid position (L145V) was detected. NCBI reported this alteration as the highest frequency SULT1B1 allelic variant. 3. L145V frequency comprised 9% of 37 mixed-population human patients and was specific to African Americans with an allelic frequency of 25%. Structurally, replacement of leucine with valine potentially destabilizes a conserved helix (α8) that forms the "floor" of both the substrate and PAPS binding domains. This destabilization results in altered kinetic properties including a four-fold decrease in affinity for PAP (3', 5'-diphosphoadenosine). K_ms for 3'-phosphoadenosine- 5'-phosphosulfate (PAPS) are similar; however, maximal turnover rate of the variant isoform (0.86 pmol/(min*μg)) is slower than wild-type (WT) SULT1B1 (1.26 pmol/(min*μg)). The L145V variant also displays altered kinetics toward small phenolic substrates, including a diminished p-nitrophenol K_m and increased susceptibility to 1-naphthol substrate inhibition. 4. No significant correlation between genotype and prostate or colorectal cancer was observed in patients; however, the variant isoform could underlie specific pathologies in sub-Saharan African carriers.

The role of metabolism (and the microbiome) in defining the clinical efficacy of dietary flavonoids

At a population level, there is growing evidence of the beneficial effects of dietary flavonoids on health. However, there is extensive heterogeneity in the response to increased intake, which is likely mediated via wide interindividual variability in flavonoid absorption and metabolism. Flavonoids are extensively metabolized by phase I and phase II metabolism (which occur predominantly in the gastrointestinal tract and liver) and colonic microbial metabolism. A number of factors, including age, sex, and genotype, may affect these metabolic processes. In addition, food composition and flavonoid source are likely to affect bioavailability, and emerging data suggest a critical role for the microbiome. This review will focus on the current knowledge for the main subclasses of flavonoids, including anthocyanins, flavonols, flavan-3-ols, and flavanones, for which there is growing evidence from prospective studies of beneficial effects on health. The identification of key factors that govern metabolism and an understanding of how the differential capacity to metabolize these bioactive compounds affect health outcomes will help establish how to optimize intakes of flavonoids for health benefits and in specific subgroups. We identify research areas that need to be addressed to further understand important determinants of flavonoid bioavailability and metabolism and to advance the knowledge base that is required to move toward the development of dietary guidelines and recommendations for flavonoids and flavonoid-rich foods.

The structure of the catechin-binding site of human sulfotransferase 1A1

We are just beginning to understand the allosteric regulation of the human cytosolic sulfotransferase (SULTs) family-13 disease-relevant enzymes that regulate the activities of hundreds, if not thousands, of signaling small molecules. SULT1A1, the predominant isoform in adult liver, harbors two noninteracting allosteric sites, each of which binds a different molecular family: the catechins (naturally occurring flavonols) and nonsteroidal antiinflammatory drugs (NSAIDs). Here, we present the structure of an SULT allosteric binding site-the catechin-binding site of SULT1A1 bound to epigallocatechin gallate (EGCG). The allosteric pocket resides in a dynamic region of the protein that enables EGCG to control opening and closure of the enzyme's active-site cap. Furthermore, the structure offers a molecular explanation for the isozyme specificity of EGCG, which is corroborated experimentally. The binding-site structure was obtained without X-ray crystallography or multidimensional NMR. Instead, a SULT1A1 apoprotein structure was used to guide positioning of a small number of spin-labeled single-Cys mutants that coat the entire enzyme surface with a paramagnetic field of sufficient strength to determine its contribution to the bound ligand's transverse (T₂) relaxation from its 1D solution spectrum. EGCG protons were mapped to the protein surface by triangulation using the T₂ values to calculate their distances to a trio of spin-labeled Cys mutants. The final structure was obtained using distance-constrained molecular dynamics docking. This approach, which is readily extensible to other systems, is applicable over a wide range of ligand affinities, requires little protein, avoids the need for isotopically labeled protein, and has no protein molecular weight limitations.

Isozyme Specific Allosteric Regulation of Human Sulfotransferase 1A1

The human cytosolic sulfotransferases (SULTs) comprise a 13-member enzyme family that regulates the activities of hundreds, perhaps thousands, of signaling small molecules via regiospecific transfer of the sulfuryl moiety (-SO3) from PAPS (3'-phosphoadenosine 5'-phosphosulfate) to the hydroxyls and amines of acceptors. Signaling molecules regulated by sulfonation include numerous steroid and thyroid hormones, epinephrine, serotonin, and dopamine. SULT1A1, a major phase II metabolism SULT isoform, is found at a high concentration in liver and has recently been show to harbor two allosteric binding sites, each of which binds a separate and complex class of compounds: the catechins (naturally occurring polyphenols) and nonsteroidal anti-inflammatory drugs. Among catechins, epigallocatechin gallate (EGCG) displays high affinity and specificity for SULT1A1. The allosteric network associated with either site has yet to be defined. Here, using equilibrium binding and pre-steady state studies, the network is shown to involve 14 distinct complexes. ECGG binds both the allosteric site and, relatively weakly, the active site of SULT1A1. It is not a SULT1A1 substrate but is sulfonated by SULT2A1. EGCG binds 17-fold more tightly when the active-site cap of the enzyme is closed by the binding of the nucleotide. When nucleotide is saturating, EGCG binds in two phases. In the first, it binds to the cap-open conformer; in the second, it traps the cap in the closed configuration. Cap closure encapsulates the nucleotide, preventing its release; hence, the EGCG-induced cap stabilization slows nucleotide release, inhibiting turnover. Finally, a comprehensive quantitative model of the network is presented.

The importance of adrenal hypoandrogenism in infertile women with low functional ovarian reserve: a case study of associated adrenal insufficiency

BACKGROUND

Low testosterone (T), whether due to ovarian and/or adrenal insufficiency, usually results in poor follicle maturation at small growing follicle stages. The consequence is a phenotype of low functional ovarian reserve (LFOR), characterized by poor granulosa cell mass, low anti-Müllerian hormone and estradiol but rising follicle stimulating hormone. Such hypoandrogenism can be of ovarian and/or adrenal origin. Dehydroepiandrosterone sulfate (DHEAS) is exclusively produced by adrenals and, therefore, reflects adrenal androgen production in the zona reticularis. We here determined in a case study of infertile women with LFOR the presence of adrenal hypoandrogenism, its effects on ovarian function, and the possibility of presence of concomitant adrenal insufficiency (AI), thus reflecting insufficiency of all three adrenal cortical zonae.

METHODS

We searched our center's anonymized electronic research database for women with LFOR, who were also characterized by peripheral adrenal hypoandrogenemia (total testosterone < 16.9 ng/dL) and low DHEAS (<76.0 μg/dL). Among 225 women with LFOR, we identified 29 (12.9 %). The adrenal function of so identified women were further investigated with morning cortisol and ACTH levels and/or standard ACTH stimulation tests. We also determined the prevalence of classical AI (insufficiency glucocorticoid production by zona fasciculata) in hypoandrogenic women with LFOR, and impact of adrenal hypoandrogenism on ovaries.

RESULTS

Among 14/28 women with adrenal hypoandrogenism due to insufficiency of the zona reticularis available for follow up, 4 (28.6 %) also demonstrated previously unrecognized classical primary, secondary or tertiary AI due to insufficiency of the zona fasciculata. An additional patient with presenting diagnosis of seemingly primary ovarian insufficiency (POI), demonstrated extremely low T and DHEAS levels, a diagnosis of Addison's disease, and was on glucocorticoid but not androgen supplementation. As her dramatic improvement in ovarian function criteria after androgen supplementation confirmed, her correct diagnosis, therefore, was actually secondary ovarian insufficiency (SOI) due to adrenal hypoandrogenism.

CONCLUSIONS

Women with LFOR, characterized by low T and DHEAS, are also at risk for AI, while women with AI may be at risk for adrenal induced hypoandrogenism and, therefore, SOI. A currently undetermined percentage of POI patients actually are, likely, affected by SOI, a for prognostic reasons highly significant difference in diagnosis.

Design and Interpretation of Human Sulfotransferase 1A1 Assays

The human sulfotransferases (SULTs) regulate the activities of hundreds, if not thousands, of small molecule metabolites via transfer of the sulfuryl-moiety (-SO3) from the nucleotide donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the hydroxyls and amines of the recipients. Our understanding of the molecular basis of SULT catalysis has expanded considerably in recent years. The basic kinetic mechanism of these enzymes, previously thought to be ordered, has been redefined as random for SULT2A1, a representative member of the superfamily. An active-site cap whose structure and dynamics are highly responsive to nucleotides was discovered and shown to be critical in determining SULT selectivity, a topic of longstanding interest to the field. We now realize that a given SULT can operate in two specificity modes-broad and narrow-depending on the disposition of the cap. More recent work has revealed that the caps of the SULT1A1 are controlled by homotropic allosteric interactions between PAPS molecules bound at the dimer's active sites. These interactions cause the catalytic efficiency of SULT1A1 to vary in a substrate-dependent fashion by as much as two orders of magnitude over a range of PAPS concentrations that spans those found in human tissues. SULT catalysis is further complicated by the fact that these enzymes are frequently inhibited by their substrates. This review provides an overview of the mechanistic features of SULT1A1 that are important for the design and interpretation of SULT1A1 assays.

Associations between peripheral androgens and cortisol in infertile women

Testosterone has in recent years been proven essential for normal growth and maturation of small growing follicles. Concomitantly, low functional ovarian reserve (LFOR), characterized by a small growing follicle pool, has been associated with low testosterone levels, which can be of ovarian and/or adrenal origin. In this study we, therefore, investigated whether peripheral sex steroid precursors and testosterone levels potentially reflect on adrenal function. In a retrospective cohort study of 355 consecutive infertile women, who presented to an academically affiliated fertility center in New York City, we investigated in a series of statistical models whether low peripheral sex steroid precursors and testosterone are associated with peripheral cortisol (C) levels, reflecting adrenal function. To determine potential correlations, we investigated the dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), androstenedione (AD), total testosterone (TT), free testosterone (FT); sex hormone binding globulin (SHBG), anti-Müllerian hormone (AMH), thyroid stimulating hormone (TSH) and C in a series of multivariate and logistic regression analyses, utilizing C either as a continuous variable or with cut off <5.0μg/dL, and TT only as a continuous variable. Practically all models demonstrated significant predictability of peripheral sex hormone precursors for C levels, with DHEA demonstrating the strongest and most consistent predictability as an individual parameter and as part of the DHEAS/DHEA ratio. We conclude that in infertile women peripheral sex hormone precursors, especially DHEA, reflect C levels and, therefore, adrenal function. In infertile women, at all ages low levels of sex hormone precursors, therefore, should be considered indications for further adrenal assessments.

Genetics of androgen metabolism in women with infertility and hypoandrogenism

Hypoandrogenism in women with low functional ovarian reserve (LFOR, defined as an abnormally low number of small growing follicles) adversely affects fertility. The androgen precursor dehydroepiandrosterone (DHEA) is increasingly used to supplement treatment protocols in women with LFOR undergoing in vitro fertilization. Due to differences in androgen metabolism, however, responses to DHEA supplementation vary between patients. In addition to overall declines in steroidogenic capacity with advancing age, genetic factors, which result in altered expression or enzymatic function of key steroidogenic proteins or their upstream regulators, might further exacerbate variations in the conversion of DHEA to testosterone. In this Review, we discuss in vitro studies and animal models of polymorphisms and gene mutations that affect the conversion of DHEA to testosterone and attempt to elucidate how these variations affect female hormone profiles. We also discuss treatment options that modulate levels of testosterone by targeting the expression of steroidogenic genes. Common variants in genes encoding DHEA sulphotransferase, aromatase, steroid 5α-reductase, androgen receptor, sex-hormone binding globulin, fragile X mental retardation protein and breast cancer type 1 susceptibility protein have been implicated in androgen metabolism and, therefore, can affect levels of androgens in women. Short of screening for all potential genetic variants, hormonal assessments of patients with low testosterone levels after DHEA supplementation facilitate identification of underlying genetic defects. The genetic predisposition of patients can then be used to design individualized fertility treatments.

The allosteric binding sites of sulfotransferase 1A1

Human sulfotransferases (SULTs) comprise a small, 13-member enzyme family that regulates the activities of thousands of compounds-endogenous metabolites, drugs, and other xenobiotics. SULTs transfer the sulfuryl-moiety (-SO3) from a nucleotide donor, PAPS (3'-phosphoadenosine 5'-phosphosulfate), to the hydroxyls and primary amines of acceptors. SULT1A1, a progenitor of the family, has evolved to sulfonate compounds that are remarkably structurally diverse. SULT1A1, which is found in many tissues, is the predominant SULT in liver, where it is a major component of phase II metabolism. Early work demonstrated that catechins and nonsteroidal anti-inflammatory drugs inhibit SULT1A1 and suggested that the inhibition was not competitive versus substrates. Here, the mechanism of inhibition of a single, high affinity representative from each class [epigallocatechin gallate (EGCG) and mefenamic acid] is determined using initial-rate and equilibrium-binding studies. The findings reveal that the inhibitors bind at sites separate from those of substrates, and at saturation turnover of the enzyme is reduced to a nonzero value. Further, the EGCG inhibition patterns suggest a molecular explanation for its isozyme specificity. Remarkably, the inhibitors bind at sites that are separate from one another, and binding at one site does not affect affinity at the other. For the first time, it is clear that SULT1A1 is allosterically regulated, and that it contains at least two, functionally distinct allosteric sites, each of which responds to a different class of compounds.

3'-Phosphoadenosine 5'-phosphosulfate allosterically regulates sulfotransferase turnover

Human cytosolic sulfotransferases (SULTs) regulate the activities of thousands of small molecules—metabolites, drugs, and other xenobiotics—via the transfer of the sulfuryl moiety (-SO₃) from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to the hydroxyls and primary amines of acceptors. SULT1A1 is the most abundant SULT in liver and has the broadest substrate spectrum of any SULT. Here we present the discovery of a new form of SULT1A1 allosteric regulation that modulates the catalytic efficiency of the enzyme over a 130-fold dynamic range. The molecular basis of the regulation is explored in detail and is shown to be rooted in an energetic coupling between the active-site caps of adjacent subunits in the SULT1A1 dimer. The first nucleotide to bind causes closure of the cap to which it is bound and at the same time stabilizes the cap in the adjacent subunit in the open position. Binding of the second nucleotide causes both caps to open. Cap closure sterically controls active-site access of the nucleotide and acceptor; consequently, the structural changes in the cap that occur as a function of nucleotide occupancy lead to changes in the substrate affinities and turnover of the enzyme. PAPS levels in tissues from a variety of organs suggest that the catalytic efficiency of the enzyme varies across tissues over the full 130-fold range and that efficiency is greatest in those tissues that experience the greatest xenobiotic “load”.

Adrenal androgens and androgen precursors-definition, synthesis, regulation and physiologic actions

The human adrenal produces more 19 carbon (C19) steroids, by mass, than either glucocorticoids or mineralocorticoids. However, the mechanisms regulating adrenal C19 steroid biosynthesis continue to represent one of the most intriguing mysteries of endocrine physiology. This review will discuss the C19 steroids synthesized by the human adrenal and the features within the adrenal that allow production of these steroids. Finally, we consider the effects of these steroids in normal physiology and disorders of adrenal C19 steroid excess.