The adverse influence of pregnancy upon sulphation: a clue to the pathogenesis of intrahepatic cholestasis of pregnancy?

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.

Use of paracetamol, ibuprofen or aspirin in pregnancy and risk of cerebral palsy in the child

Background

It has been debated whether mild analgesics, mainly paracetamol, adversely affect aspects of neurodevelopment. We examined whether mother's use of paracetamol, aspirin or ibuprofen in pregnancy is associated with increased risk of cerebral palsy (CP) in the child.

Method

We included 185 617 mother-child pairs from the Danish National Birth Cohort and the Norwegian Mother and Child Cohort Study. We created harmonized definitions of analgesic use in pregnancy, as well as indications for analgesic use and other potential confounders. Children with CP were identified in nationwide registers. We estimated the average causal effect of analgesics on risk of CP using marginal structural models with stabilized inverse probability weights.

Results

Paracetamol use was reported in 49% of all pregnancies, aspirin in 3% and ibuprofen in 4%. Prenatal exposure to paracetamol ever in pregnancy was associated with increased risk of overall CP [adjusted odds ratio (aOR) 1.3, 95% confidence interval (CI): 1.0-1.7] and unilateral spastic CP (aOR 1.5, 95% CI: 1.0-2.2). The association appeared to be driven by an increased risk of unilateral spastic CP in children exposed in second trimester (aOR 1.6, 95% CI: 1.0-2.5). Children ever prenatally exposed to aspirin in pregnancy had an elevated risk of bilateral spastic CP (aOR 2.4, 95% CI: 1.1-5.3) compared with unexposed.

Conclusion

We observed an increased risk of spastic CP in children prenatally exposed to paracetamol and aspirin. Although we controlled for several important indications for analgesic use, we cannot exclude the possibility of confounding by underlying diseases.

Paracetamol pharmacokinetics and metabolism in young women

Background

There is relevant between individual variability in paracetamol clearance in young women. In this pooled study, we focused on the population pharmacokinetic profile of intravenous paracetamol metabolism and its covariates in young women.

Methods

Population PK parameters using non-linear mixed effect modelling were estimated in a pooled dataset of plasma and urine PK studies in 69 young women [47 at delivery, 8/47 again 10–15 weeks after delivery (early postpartum), and 7/8 again 1 year after delivery (late postpartum), 22 healthy female volunteers with or without oral contraceptives].

Results

Population PK parameters were estimated based on 815 plasma samples and 101 urine collections. Compared to healthy female volunteers (reference group) not on oral contraceptives, being at delivery was the most significant covariate for clearance to paracetamol glucuronide (Factor = 2.03), while women in early postpartum had decreased paracetamol glucuronidation clearance (Factor = 0.55). Women on contraceptives showed increased paracetamol glucuronidation clearance (Factor = 1.46). The oestradiol level did not further affect this model. Being at delivery did not prove significant for clearance to paracetamol sulphate, but was higher in pregnant women who delivered preterm (<37 weeks, Factor = 1.34) compared to term delivery and non-pregnant women. Finally, clearance of unchanged paracetamol was dependent on urine flow rate.

Conclusions

Compared to healthy female volunteers not on oral contraceptives, urine paracetamol glucuronidation elimination in young women is affected by pregnancy (higher), early postpartum (lower) or exposure to oral contraceptives (higher), resulting in at least a two fold variability in paracetamol clearance in young women.

Pharmacokinetics of paracetamol and its metabolites in women at delivery and post-partum

AIM

A recent report on intravenous (i.v.) paracetamol pharmacokinetics (PK) showed a higher total clearance in women at delivery compared with non-pregnant women. To describe the paracetamol metabolic and elimination routes involved in this increase in clearance, we performed a population PK analysis in women at delivery and post-partum in which the different pathways were considered.

METHODS

Population PK parameters using non-linear mixed effect modelling were estimated in a two-period PK study in women to whom i.v. paracetamol (2 g loading dose followed by 1 g every 6 h up to 24 h) was administered immediately following Caesarean delivery and in a subgroup of the same women to whom single 2 g i.v.loading dose was administered 10-15 weeks post-partum.

RESULTS

Population PK analysis was performed based on 255 plasma and 71 urine samples collected in 39 women at delivery and in eight of these 39 women 12 weeks post-partum. Total clearance was higher in women at delivery compared with 12th post-partum week (21.1 vs. 11.7 l h⁻¹) due to higher clearances to paracetamol glucuronide (11.6 vs. 4.76 l h⁻¹), to oxidative metabolites (4.95 vs. 2.77 l h⁻¹) and of unchanged paracetamol (1.15 vs. 0.75 l h⁻¹). In contrast, there was no difference in clearance to paracetamol sulphate.

CONCLUSION

The increased total paracetamol clearance at delivery is caused by a disproportional increase in glucuronidation clearance and a proportional increase in clearance of unchanged paracetamol and in oxidation clearance, of which the latter may potentially limit further dose increase in this patient group.

Prenatal and perinatal analgesic exposure and autism: an ecological link

BACKGROUND

Autism and Autism Spectrum Disorder (ASD) are complex neurodevelopmental disorders. Susceptibility is believed to be the interaction of genetic heritability and environmental factors. The synchronous rises in autism/ASD prevalence and paracetamol (acetaminophen) use, as well as biologic plausibility have led to the hypothesis that paracetamol exposure may increase autism/ASD risk.

METHODS

To explore the relationship of antenatal paracetamol exposure to ASD, population weighted average autism prevalence rates and paracetamol usage rates were compared. To explore the relationship of early neonatal paracetamol exposure to autism/ASD, population weighted average male autism prevalence rates for all available countries and U.S. states were compared to male circumcision rates - a procedure for which paracetamol has been widely prescribed since the mid-1990s. Prevalence studies were extracted from the U.S. Centers for Disease Control and Prevention Summary of Autism/ASD Prevalence Studies database. Maternal paracetamol usage and circumcision rates were identified by searches on Pub Med.

RESULTS

Using all available country-level data (n = 8) for the period 1984 to 2005, prenatal use of paracetamol was correlated with autism/ASD prevalence (r = 0.80). For studies including boys born after 1995, there was a strong correlation between country-level (n = 9) autism/ASD prevalence in males and a country's circumcision rate (r = 0.98). A very similar pattern was seen among U.S. states and when comparing the 3 main racial/ethnic groups in the U.S. The country-level correlation between autism/ASD prevalence in males and paracetamol was considerably weaker before 1995 when the drug became widely used during circumcision.

CONCLUSIONS

This ecological analysis identified country-level correlations between indicators of prenatal and perinatal paracetamol exposure and autism/ASD. State level correlation was also identified for the indicator of perinatal paracetamol exposure and autism/ASD. Like all ecological analyses, these data cannot provide strong evidence of causality. However, biologic plausibility is provided by a growing body of experimental and clinical evidence linking paracetamol metabolism to pathways shown to be important in autism and related developmental abnormalities. Taken together, these ecological findings and mechanistic evidence suggest the need for formal study of the role of paracetamol in autism.

Dexamethasone in the treatment of obstetric cholestasis: A case series

Twelve women with obstetric cholestasis were given dexamethasone after failure to respond to ursodeoxycholic acid. Clinical improvement was achieved in eight cases, without complete resolution of symptoms. Biochemical response was achieved in seven cases. All but two cases had good correlation between clinical and biochemical response. Women of Asian and South American origin were more likely to respond to dexamethasone than Caucasians. There were no reported maternal or fetal side-effects. However, the subsequent consequences of dexamethasone treatment for the mother and fetus have not been thoroughly evaluated. Therefore, even in Asian and South American women, larger studies of dexamethasone are required before this treatment can be recommended as a universally safe and effective treatment for obstetric cholestasis.

Ritodrine pharmacokinetics in twin pregnancy patients

OBJECTIVES

To establish a rational ritodrine therapy in relation to serum ritodrine concentration, we examined 14 twin pregnancy patients and determined their pharmacokinetic data.

METHODS

We measured serum concentrations of ritodrine in twin pregnancy patients using high-performance liquid chromatography (HPLC).

RESULTS

The twin pregnancy patients all exhibited linear ritodrine pharmacokinetic profiles. There was a statistically significant but slight negative correlation between gestation period and ritodrine clearance (y=-0.038x+2.75, r=0.349, p<0.001) among all patients. However, when analyzed on an individual basis, there was a high correlation found in three of the 14 patients.

CONCLUSION

Due to a decrease in total body clearance in three of the 14 patients, overall serum concentration of ritodrine increased at the end of the pregnancies. To further characterize ritodrine kinetics, additional studies are needed to determine an effective and safe therapy for ritodrine use in twin pregnancy patients.

Intrahepatic cholestasis of pregnancy: review of the literature and evaluation of current evidence

OBJECTIVE

To provide an overview of the epidemiology, etiology, pathogenesis, diagnosis, and management of intrahepatic cholestasis of pregnancy.

METHODS

We searched the Medline and PubMed database using the key words intrahepatic cholestasis of pregnancy, obstetric cholestasis, diagnosis, management, and complications.

RESULTS

Intrahepatic cholestasis of pregnancy, or obstetric cholestasis, is a liver condition that develops during pregnancy. It is associated with increased perinatal morbidity and mortality. Pruritus and risk of postpartum hemorrhage are the main causes of maternal morbidity. Intrahepatic cholestasis of pregnancy is a diagnosis of exclusion. The current management policies depend on regular fetal and maternal monitoring and delivery at fetal maturity. The analysis of the quality of previous studies provided in this review highlights the areas of deficiency in evidence-based knowledge of this subject.

CONCLUSIONS

More research is required into the etiology, pathogenesis, and monitoring modalities that can specifically predict fetal outcome in intrahepatic cholestasis of pregnancy. Clinical trials are required to identify the most suitable drugs for treatment.

Cholestasis of pregnancy: a review of the evidence

Intrahepatic cholestasis of pregnancy is a rare disorder, predominately occurring during the third trimester of pregnancy and characterized by pruritus, jaundice, and biochemical disturbances in liver enzymes. While intrahepatic cholestasis of pregnancy poses little maternal risk, there is significant risk to the fetus such as preterm delivery, non-reassuring fetal status, meconium staining, and perinatal mortality. Current evidence proposes susceptibility to derangements in the sulfation of steroid compounds, affecting the metabolism of progesterone and bile acids in the fetal/placental compartment. Treatment with ursodeoxycholic acid is suggested, coupled with close maternal-fetal surveillance and delivery as close to term as possible.

Intrahepatic cholestasis of pregnancy

Patients with ICP should be considered to have a high-risk pregnancy. Once the diagnosis of ICP is suspected, usually because of generalized pruritus, it should be confirmed by liver function tests, and other causes of cholestasis should be ruled out. Treatment with UDCA is effective in ameliorating the cholestasis and is especially useful in severe forms or when there is a history of sudden fetal death in a previous pregnancy. The understanding of the pathogenesis of ICP has recently progressed as the result of the discovery of several defects in the MDR3 gene in isolated affected patients. More studies of this and other genes that regulate bile flow, linked with careful clinical observations to rule out unsuspected chronic liver disease not related to pregnancy, should lead to the discovery of the pathogenesis of this enigmatic disorder.

Pregnancy and liver disease

Liver disease has an impact on women's health during pregnancy because of the complex interactions between the physiologic changes induced by pregnancy and the pathophysiologic changes of liver disease. In particular, liver diseases that predominantly afflict females, such as primary biliary cirrhosis and autoimmune hepatitis, pose a special problem for conception and management of pregnancy. Pregnancy, moreover, specifically is associated with several potentially life-threatening liver diseases. This article reviews comprehensively the impact of liver diseases on pregnancy and of pregnancy on liver function and liver disease.

Expression of an isoform of the testis-specific estrogen sulfotransferase in the murine placenta during the late gestational period

Cytosolic sulfotransferases play essential roles in regulating the activities and transfer of steroids. To evaluate their biological significance in the murine uterus and placenta during the course of gestation, we determined their activities with several steroids as substrates. Activated estrogen sulfotransferase (EST) was found in the placenta and uterus during the late gestational period. Reverse-transcribed cDNA of murine placental EST (mpEST) was isolated from mouse placenta at 18 days of gestation and its expression in the tissue coincided with a change in its enzyme activity. The open-reading frame of mpEST encodes a protein composed of 296 amino acids with a predicted molecular mass of 35.5 kDa and was revealed to be an isoform of the murine testis-specific EST gene (99.7%). Also, the amino acid sequence of mpEST showed 49.6 and 77.9% homology with human placental and endometrial EST, respectively, showing that it corresponds to human endometrial EST. COS-7 cells transfected with mpEST exhibited sulfotransferase activity with the phenolic hydroxy groups of steroids and artificial substrates. The best acceptor substrate was estrogen.

Intrahepatic cholestasis of pregnancy: a critical review

Intrahepatic cholestasis of pregnancy (ICP) is a disease predominantly of the third trimester of pregnancy, characterized primarily by pruritus, biochemical disturbances in liver enzymes, and less frequently jaundice. Although maternal pruritus can be severe, overall maternal morbidity and mortality associated with ICP is low. However, fetal morbidity and mortality are significant with associated risks for meconium-stained amniotic fluid, acute onset of fetal compromise, spontaneous preterm labor, and intrauterine fetal demise. Current literature recommends obstetric management that includes frequent fetal surveillance with delivery when fetal lung maturity has been established.

Bile acids and progesterone metabolites in intrahepatic cholestasis of pregnancy

The pathogenesis of intrahepatic cholestasis of pregnancy (ICP) can be related to abnormalities in the metabolism and disposition of sex hormones and/or bile acids, determined by a genetic predisposition interacting with environmental factors. The total amount of oestrogens and progesterone circulating in the blood or excreted in the urine of ICP patients is similar to normal pregnancies. Thus, the search for the cause has been focused on abnormal hormone metabolites. The cholestatic potential of some D-ring oestrogen metabolites is supported by experimental and clinical data. Similar observations with regard to bile acids and progesterone metabolites are still scarce. This article reviews current knowledge in this field, including our own data. Bile acid synthesis appears to be reduced in patients with ICP, in whom primary conjugated bile acids are retained in blood. The major bile acid in blood and urine of these patients is cholic acid instead of chenodeoxycholic acid present in normal pregnancies. Hydroxylation and sulfation of bile acids are enhanced, while glucuronidation appears to be of lesser importance. The synthesis of progesterone appears unimpaired, while the profiles of progesterone metabolites in plasma and urine are different from normal pregnancies, with a larger proportion of mono- and disulfated metabolites, mainly 3alpha,5alpha isomers. Glucuronidated metabolites, however, are unchanged. With the administration of ursodeoxycholic acid (UDCA) to patients with ICP, pruritus and serum liver values are improved, the concentration of bile acids in blood is diminished and the proportion of their conjugated metabolites returned to normal. Simultaneously, the concentration of sulfated progesterone metabolites in blood and their urinary excretion are reduced. The serum levels of bile acids and progesterone metabolites before UDCA administration and their decrease during treatment do not correlate with each other. We propose that patients with ICP have a selective defect in the secretion of sulfated progesterone metabolites into bile and speculate that this may be caused by genetic polymorphism of canalicular transporter(s) for steroid sulfates or their regulation. Interaction with oestrogen metabolites and/or some exogenous compounds may further enhance the process triggering ICP in genetically predisposed individuals.

Intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy is one of the primary disorders of the liver that adversely affects maternal well-being and fetal outcome. Early identification of this condition, careful interdisciplinary monitoring, and prompt delivery at fetal maturity can improve outcomes in the mother and child. Although the cause is unclear, IHCP probably arises from a genetic predisposition for increased sensitivity to estrogens and progestogens and altered membrane composition and expression of bile ducts, hepatocytes, and canalicular transport systems. As a result, the elevations in maternal levels of bile acids and their molar ratios seen in healthy pregnancy rise further in IHCP patients. Also, as the normal fetal-to-maternal transfer of bile acids across the trophoblast is impaired, the excess bile acids with abnormal profiles accumulate and are toxic to the fetus. The management of IHCP is dictated by the increased risks of fetal distress, spontaneous preterm delivery, and sudden death, as well as by alleviating pruritus in the mother. These risks to the fetus rise progressively to delivery, regardless of serum levels of bile acids and ALT. Close monitoring of these markers is essential but does not prevent sudden fetal distress and death. Provision should be made to induce labor as soon as fetal lung maturity has been established. Ursodeoxycholic acid is the only therapy that has proven effective, albeit in small studies, in alleviating pruritus and restoring towards normal the abnormal profiles of bile acids and sulfated steroids in serum and other body fluids. Ursodeoxycholic acid seems to have no obvious adverse effects on the fetus, but experience is insufficient to draw conclusions regarding teratogenicity and prevention of adverse outcomes.

Intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a disease of the third trimester of pregnancy involving pruritus and elevated bile acid levels. Its pathogenesis likely involves a genetic hypersensitivity to estrogen. Once thought to be benign for both mother and fetus, ICP has been associated with increased rates of fetal morbidity and mortality and an increased risk of maternal coagulopathy. Optimal obstetric management includes delivery after establishment of fetal lung maturity. Many treatments have been proposed for the maternal medical management of ICP, none of which is ideal.

Profiles of bile acids and progesterone metabolites in the urine and serum of women with intrahepatic cholestasis of pregnancy

BACKGROUND/AIMS AND METHODS

The etiology of intrahepatic cholestasis of pregnancy (JCP) is unknown. We have performed comprehensive chromatographic and mass spectrometric analyses of progesterone metabolites and bile acids in serum and urine of six patients in order to characterize changes that might be of importance for the development of the disease.

RESULTS

Conjugated bile acids were increased in serum and urine of patients with ICP while the levels of unconjugated bile acids were similar in healthy pregnancies and ICP. Unconjugated and conjugated 7 alpha, 12 alpha-dihydroxy-3-oxo-4-cholenoic acid was excreted in urine both in healthy pregnancies and in ICP, possibly indicating a rate limitation of 3-oxo-delta 4-steroid 5 beta-reductase in pregnancy. The serum levels and urinary excretion of total sulfated progesterone metabolites were increased in ICP while the glucuronides were unchanged or low. Confirming previous results, the fraction of metabolites with 3 alpha-hydroxy-5 alpha(H) configuration was increased. The urinary excretion of 5 alpha-pregnane-3 alpha, 20 alpha-diol 3-sulfate, 20-N-acetylglucosaminide was greatly increased in ICP, as was that of 3 alpha-hydroxy-5 alpha-androstane-17 beta-carboxylic acid, assumed to be a progesterone metabolite.

CONCLUSIONS

The combined results of this and previous studies are compatible with a primary change in the reductive metabolism of progesterone in ICP, resulting in increased formation of metabolites with a 3 alpha-hydroxy-5 alpha(H) configuration and a larger fraction of sulfates. There also seems to be a selective defect in the biliary secretion of sulfated metabolites, particularly disulfates.

Phenotypic variation in xenobiotic metabolism and adverse environmental response: focus on sulfur-dependent detoxification pathways

Proper bodily response to environmental toxicants presumably requires proper function of the xenobiotic (foreign chemical) detoxification pathways. Links between phenotypic variations in xenobiotic metabolism and adverse environmental response have long been sought. Metabolism of the drug S-carboxymethyl-L-cysteine (SCMC) is polymorphous in the population, having a bimodal distribution of metabolites, 2.5% of the general population are thought to be nonmetabolizers. The researchers developing this data feel this implies a polymorphism in sulfoxidation of the amino acid cysteine to sulfate. While this interpretation is somewhat controversial, these metabolic differences reflected may have significant effects. Additionally, a significant number of individuals with environmental intolerance or chronic disease have impaired sulfation of phenolic xenobiotics. This impairment is demonstrated with the probe drug acetaminophen and is presumably due to starvation of the sulfotransferases for sulfate substrate. Reduced metabolism of SCMC has been found with increased frequency in individuals with several degenerative neurological and immunological conditions and drug intolerances, including Alzheimer's disease, Parkinson's disease, motor neuron disease, rheumatoid arthritis, and delayed food sensitivity. Impaired sulfation has been found in many of these conditions, and preliminary data suggests that it may be important in multiple chemical sensitivities and diet responsive autism. In addition, impaired sulfation may be relevant to intolerance of phenol, tyramine, and phenylic food constituents, and it may be a factor in the success of the Feingold diet. These studies indicate the need for the development of genetic and functional tests of xenobiotic metabolism as tools for further research in epidemiology and risk assessment.