Altered activity of xenobiotic detoxifying enzymes at menopause – A cross-sectional study
Introduction
Natural menopause, resulting from the loss of ovarian function and the progressive decline in circulating estrogen levels, does not occur at a discrete point in time, but is rather a process that begins around mid-40s and, despite the considerable inter-individual variation, the average age of onset is estimated at 51 years (McKinlay et al., 2008). The transition to menopause instigates multiple metabolic changes independent of chronological aging. Indeed, menopause has been associated with important disease risks including alterations in lipid metabolism favoring an atherogenic lipoprotein profile (Auro et al., 2014; Wang et al., 2018), altered glucose metabolism (Slopien et al., 2018), increased cardiovascular disease (Appelman et al., 2015; Colpani et al., 2018) and osteoporosis (Karlamangla et al., 2018). Despite the wealth of information on the metabolic changes emanating from the decline of estrogens at menopause, there is a striking paucity of data concerning the possible consequences of menopause on xenobiotic metabolism, although numerous studies have shown that the activity of xenobiotic-metabolizing enzymes may be modulated by female reproductive hormones. Thus, CYP1A2 activity is inhibited by estrogen-containing oral contraceptives (OCs) (Rasmussen and Brøsen, 1996; Granfors et al., 2005), by hormonal replacement therapy (HRT) in pre- and postmenopausal women (Pollock et al., 1999; O'Connell et al., 2006), during pregnancy (Vistisen et al., 1992; Tsutsumi et al., 2001; Tracy et al., 2005) and at the late follicular phase (LFP) of the menstrual cycle (Nagata et al., 1997; Kamimori et al., 1999; Asprodini et al., 2019). CYP2A6 activity is enhanced at LFP (Asprodini et al., 2019), during pregnancy (Dempsey et al., 2002), or following the use of OCs (Benowitz et al., 2006). Conversely, the activity of XO and NAT2 enzymes remain unaltered during pregnancy (Tsutsumi et al., 2001), following estrogen therapy (O'Connell et al., 2006), or after the use of OCs (Rasmussen and Brøsen, 1996).
The cytochrome P450 (CYP) superfamily is one of the major metabolizing enzyme systems in humans. Within the CYP superfamily, isoenzymes belonging to enzyme families 1–3 are responsible for 70–80% of all phase I dependent oxidative metabolism of clinically used drugs and they participate in the metabolism of a wide range of structurally diverse substrates such as endogenous compounds and xenobiotic chemicals (Evans and Relling, 1999). CYP1A2 is almost exclusively expressed in the liver accounting for approximately 13% of its total content (Shimada et al., 1994; Faber et al., 2005). It has the highest catalytic activity for the 2- and 4-hydroxylations of estradiol and estrone (Yamazaki et al., 1998), and it is involved in the biotransformation of several pharmaceutical drugs, such as theophylline, clozapine and olanzapine (Faber et al., 2005; Pelkonen et al., 2008). CYP2A6 is a highly polymorphic enzyme, it is expressed in the liver. It is responsible for the biotransformation of nicotine and its metabolite cotinine, several drugs such as valproic acid and pilocarpine and compounds of toxicological significance such as nitrosamines and aflatoxin B1 (Pelkonen et al., 2008; Di et al., 2009; Tanner and Tyndale, 2017). Although cytochrome P450 mediates primarily detoxification reactions, certain substrates are metabolically activated following P450 metabolism, resulting in the generation of reaction products with increased toxicity or mutagenicity, thus, leading to increased cancer risk. For example, CYP1A2 interacts with many environmental chemicals (Pasanen et al., 1995; Lagueux et al., 1999; Kim et al., 2004; Mizukawa et al., 2015; Docea et al., 2017; Vaughan et al., 2019). Correspondingly, CYP2A6 is responsible for the mutagenic activation of essentially all tobacco-related N-nitrosamines examined (Kamataki et al., 2002); as a consequence, allelic variation leading to reduction of CYP2A6 activity has been associated with reduced risk for lung cancer (Kamataki et al., 2005). It is of note that members of the CYP1 subfamily have been suggested to be responsible for the metabolic activation of several flavonoids leading to the suppression of cancer cell proliferation (Tsatsakis et al., 2011; Wilsher et al., 2017; Surichan et al., 2018a, 2018b; Surichan et al., 2018a, 2018b). Xanthine oxidase (XO) is the rate-limiting enzyme in purine catabolism and can oxidize a variety of endogenous substrates (aldehydes, purines, pyrimidines and pteridines). It contributes to liver detoxification through the catabolism of aminopurines (such as 2-aminopurine), heterocyclic compounds (such as 4-hydroxypyrimidine and retinol) (Battelli et al., 2014) and xenobiotics (such as antiviral and anticancer agents) (Pritsos, 2000; Battelli et al., 2014). N-acetyltransferase-2 (NAT2) is a polymorphic enzyme involved in the acetylation of several drugs, such as procainamide, nitrazepam, clonazepam, and isoniazid (Evans, 1989), and in the metabolism of environmental carcinogens including aromatic and heterocyclic amines (Dupret and Rodrigues-Lima, 2005).
Caffeine has been widely accepted as a metabolic probe for the simultaneous assessment of CYP1A2, CYP2A6, XO and NAT2 phenotypes by the use of caffeine metabolite ratios (Relling et al., 1992; Cascorbi et al., 1995; Asprodini et al., 1998; Begas et al., 2007; Hakooz, 2009; Nehlig, 2018). In humans, most of caffeine is 3N-demethylated by CYP1A2 to paraxanthine (1,7-dimethylxanthine, 17X) (Butler et al., 1989) which is bio-transformed to 1,7-dimethyluric acid (17U) by CYP2A6 and to 1-methylxanthine (1X) by CYP1A2. 1X is eventually converted to 1-methyluric acid (1U) by XO, whereas, a small portion of paraxanthine is metabolized to 5-acetylamino- 6-formylamino-3-methyluracil (AFMU) by NAT2 (Gu et al., 1992; Kot and Daniel, 2008) (Fig. 1). The safety, availability and ease of administration of caffeine have made it possible to conduct large population studies in which CYP1A2, CYP2A6, XO and NAT2 enzyme activities can be assessed and compared between different subgroups of subjects (Hakooz, 2009; Nehlig, 2018).
Τo our knowledge, no study has thus far addressed the issue of the influence of menopause on the above-mentioned xenobiotic-metabolizing enzyme activities with the exception of previous reports presenting incidental evidence on the effect of menopause on CYP1A2 (Hong et al., 2004) and CYP2A6 (Benowitz et al., 2006) enzyme activity. Therefore, the present study was designed to examine the hypothesis that the activity of xenobiotic metabolizing enzymes is modulated at menopause, independent of chronological age. To this end, we used caffeine as a metabolic probe to assess CYP1A2, CYP2A6, XO and NAT2 enzyme CMRs in a cohort of postmenopausal healthy women and to compare these CMRs to premenopausal women and to age-matched men.
Section snippets
Subjects and study design
Data were obtained from 152 (women n = 84, men n = 68) non-smoking volunteers aged between 19 and 80 yrs. All volunteers were healthy according to medical history, physical examination and recent blood tests. Female volunteers were grouped according to menopausal status into pre- (n = 37) and postmenopausal (n = 47) groups. Menopause was specified, retrospectively, as the lack of spontaneous menstruation for at least 12 consecutive months prior to the recruitment to the study (McKinlay et al.,
Results
All enrolled volunteers (n = 152) completed the study. No subject reported adverse effects following caffeine intake. The mean (±SD) age of women (n = 84) was 52.29 ± 14.54 yrs (median 54.4, range 19–80) and that of men (n = 68) 50.01 ± 17.04 yrs (median 48.0, range 22–79). There was no statistically significant difference in terms of age between premenopausal women (38.65 ± 8.26 yrs) and men<50 (35.94 ± 7.95 yrs, p > 0.05) and between postmenopausal women (63.02 ± 7.81 yrs) and men>50
Discussion
The effect of menopause on xenobiotic metabolism is an important yet under-investigated topic, albeit the effect of several other female-specific conditions such as menstruation, pregnancy, or the use of OCs and HRT (Harris et al., 1995; Schwartz, 2007; Marazziti et al., 2013) has been adequately studied. The present study is the first to demonstrate lower CYP1A2 and higher CYP2A6 CMRs in postmenopausal compared to premenopausal women and age-matched men. These changes could be attributed to
Acknowledgments
We thank all volunteers who participated in the study. The study was financially supported by the Research Committee of the University of Thessaly [Grant 4822].
References (114)
- et al.
Sex differences in cardiovascular risk factors and disease prevention
Atherosclerosis
(2015) - et al.
Pathophysiology of circulating xanthine oxidoreductase: new emerging roles for a multi-tasking enzyme
Biochim. Biophys. Acta
(2014) - et al.
Effects of short-term saffron (Crocus sativus L.) intake on the in vivo activities of xenobiotic metabolizing enzymes in healthy volunteers
Food Chem. Toxicol.
(2019) - et al.
Effects of peppermint tea consumption on the activities of CYP1A2, CYP2A6, Xanthine Oxidase, N-acetyltranferase-2 and UDP-glucuronosyltransferases-1A1/1A6 in healthy volunteers
Food Chem. Toxicol.
(2017) - et al.
CYP polymorphisms and pathological conditions related to chronic exposure to organochlorine pesticides
Toxicology Reports
(2017) - et al.
Genetic polymorphism of CYP2A6 as one of the potential determinants of tobacco-related cancer risk
Biochem. Biophys. Res. Commun.
(2005) - et al.
Bone health during the menopause transition and beyond
Obstet. Gynecol. Clin. N. Am.
(2018) - et al.
Identification of cytochrome P450 isoforms involved in 1-hydroxylation of pyrene
Environ. Res.
(2004) - et al.
The relative contribution of human cytochrome P450 isoforms to the four caffeine oxidation pathways: an in vitro comparative study with cDNA-expressed P450s including CYP2C isoforms
Biochem. Pharmacol.
(2008) - et al.
Cytochrome P450 CYP1A1 enzyme activity and DNA adducts in placenta of women environmentally exposed to organochlorines
Environ. Res.
(1999)
The normal menopause transition
Maturitas
Organohalogens and their hydroxylated metabolites in the blood of pigs from an open waste dumping site in south India: association with hepatic cytochrome P450
Environ. Res.
Influence of some anti-inflammatory drugs on the activity of aryl hydrocarbon hydroxylase and the cytochrome P450 content
Environ. Res.
Increased theophylline metabolism in the menstrual phase of healthy women
J. Allergy Clin. Immunol.
Induction of hepatic CYP1A in male F344/NCr rats by dietary exposure to Aroclor 1254: examination of immunochemical, RNA, catalytic, and pharmacokinetic endpoints
Environ. Res.
The effects of gender, age, ethnicity, and liver cirrhosis on cytochrome P450 enzyme activity in human liver microsomes and inducibility in cultured human hepatocytes
Toxicol. Appl. Pharmacol.
Effects of simulated nuclear fuel particles on the histopathology and CYP enzymes in the rat lung and liver
Environ. Res.
Cellular distribution, metabolism and regulation of the xanthine oxidoreductase enzyme system
Chem. Biol. Interact.
Menopause and diabetes: EMAS clinical guide
Maturitas
Nobiletin bioactivation in MDA-MB-468 breast cancer cells by cytochrome P450 CYP1 enzymes
Food Chem. Toxicol.
Tangeretin inhibits the proliferation of human breast cancer cells via CYP1A1/CYP1B1 enzyme induction and CYP1A1/CYP1B1–mediated metabolism to the product 4′ hydroxy tangeretin
Toxicol. In Vitro
Xanthine oxidase activity is influenced by environmental factors in Ethiopians
Eur. J. Clin. Pharmacol.
Age-related increase in xanthine oxidase activity in human plasma and rat tissues
Free Radic. Res.
Pharmacokinetics and metabolism of natural methylxanthines in animal and man
Handb. Exp. Pharmacol.
Alterations in xenobiotic-metabolizing enzyme activities across menstrual cycle in healthy volunteers
J. Pharmacol. Exp. Ther.
Determination of N-acetylation phenotyping in a Greek population using caffeine as a metabolic probe
Eur. J. Drug Metab. Pharmacokinet.
A metabolic view on menopause and ageing
Nat. Commun.
Bioequivalence revisited: influence of age and sex on CYP enzymes
Clin. Pharmacol. Ther.
In vivo evaluation of CYP1A2, CYP2A6, NAT-2 and xanthine oxidase activities in a Greek population sample by the RP-HPLC monitoring of caffeine metabolic ratios
Biomed. Chromatogr.
Female sex and oral contraceptive use accelerate nicotine metabolism
Clin. Pharmacol. Ther.
Sex, race, and smoking impact olanzapine exposure
J. Clin. Pharmacol.
Human cytochrome P-450PA (P-450IA2), the phenacetin O-deethylase, is primarily responsible for the hepatic 3-demethylation of caffeine and N-oxidation of carcinogenic arylamines
Proc. Natl. Acad. Sci. U.S.A.
A urinary metabolite ratio that reflects systemic caffeine clearance
Clin. Pharmacol. Ther.
CYP1A2 activity, gender and smoking, as variables influencing the toxicity of caffeine
Br. J. Clin. Pharmacol.
Arylamine N-acetyltransferase (NAT2) mutations and their allelic linkage in unrelated Caucasian individuals: correlation with phenotypic activity
Am. J. Hum. Genet.
A population and family study of CYP1A2 using caffeine urinary metabolites
Eur. J. Clin. Pharmacol.
Growth hormone treatment increases cytochrome P450-mediated antipyrine clearance in man
J. Clin. Endocrinol. Metab.
Effect of age and smoking on in vivo CYP1A2, flavin-containing monooxygenase, and xanthine oxidase activities in Koreans: determination by caffeine metabolism
Clin. Pharmacol. Ther.
Lifestyle factors, cardiovascular disease and all-cause mortality in middle-aged and elderly women: a systematic review and meta-analysis
Eur. J. Epidemiol.
A longitudinal study of weight and the menopause transition: results from the Massachusetts Women's Health Study
Menopause
Immune aging, dysmetabolism, and inflammation in neurological diseases
Front. Neurosci.
Accelerated metabolism of nicotine and cotinine in pregnant smokers
J. Pharmacol. Exp. Ther.
Sexually dimorphic regulation of hepatic isoforms of human cytochrome p450 by growth hormone
J. Pharmacol. Exp. Ther.
Structure, function, regulation and polymorphism of human cytochrome P450 2A6
Curr. Drug Metabol.
In vivo evaluation of CYP2A6 and xanthine oxidase enzyme activities in the Serbian population
Eur. J. Clin. Pharmacol.
Comparison of N-acetyltransferase-2 enzyme genotype-phenotype and xanthine oxidase enzyme activity between Swedes and Koreans
J. Clin. Pharmacol.
Structure and regulation of the drug-metabolizing enzymes arylamine N-acetyltransferases
Curr. Med. Chem.
N-acetyltransferase
Pharmacol. Ther.
Pharmacogenomics: translating functional genomics into rational therapeutics
Science
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