The Influence of Bovine Milk High or Low in Isoflavones on Hepatic Gene Expression in Mice

Isoflavones have generated much attention due to their potential positive effects in various diseases. Phytoestrogens especially equol can be found in bovine milk, as feed ration for dairy cows is comprised of plants containing phytoestrogens. The aim of this study was to analyze the changes in hepatic gene expression after dietary intake of milk high and low in isoflavones. In addition to pelleted feed female NMRI mice were offered water, water added either 17β-estradiol, equol, Tween 80, and milk high and low in isoflavone content for a week. Gene expression was analyzed using an array qPCR kit. It was revealed that Tween 80 and 17β-estradiol upregulated both phase I and phase II genes to the same extent whereas equol alone, high and low isoflavone milk did not alter the expression of phase I genes but decreased the expression of phase II genes. This study shows that dietary isoflavones can regulate the transcription of especially phase II liver enzymes which potentially could give rise to an increase in reactive oxygen metabolites that may contribute to the development of cancer

Porcine foetal and neonatal CYP3A liver expression

Human cytochrome P450 3A7 (CYP3A7) and cytochrome P450 3A4 (CYP3A4) are hepatic metabolising enzymes which participates in the biotransformation of endo- and exogenous substances in foetuses and neonates respectively. These CYP3A enzymes display an inverse relationship: CYP3A7 is the dominant enzyme in the foetal liver, whereas the expression of CYP3A4 is low. After parturition there is a shift in the expression, thus CYP3A7 is down regulated, while the level of CYP3A4 gradually increases and becomes the dominant metabolising CYP3A enzyme in the adult. The minipig is increasingly being used as a model for humans in biomedical studies, because of its many similarities with the human physiology and anatomy. The aim of this study was to examine whether, as in humans, a shift is seen in the hepatic expression of a CYP3A7- like enzyme to cytochrome P450 3A29 (CYP3A29) (an orthologue to the human CYP3A4) in minipigs. This was elucidated by examining the hepatic mRNA expression of CYP3A7 and CYP3A29 in 39 foetuses and newborn Göttingen minipigs using quantitative real time polymerase chain reaction (qPCR). Furthermore the immunochemical level of CYP3A7-LE and CYP3A29 was measured in liver microsomes using western blotting. The expression of CYP3A29 was approximately 9- fold greater in neonates compared to foetuses, and a similar difference was reflected on the immunochemical level. It was not possible to detect a significant level of foetal CYP3A7 mRNA, but immunoblotting showed a visible difference depending on age. This study demonstrates an increase in the expression of CYP3A29, the CYP3A4 orthologue in perinatal minipigs as in humans, which suggests that the minipig could be a good model when testing for human foetal toxicity towards CYP3A4 substrates

In Vitro Cytochrome P450 Formation of a Mono-Hydroxylated Metabolite of Zearalenone Exhibiting Estrogenic Activities: Possible Occurrence of This Metabolite in Vivo

The mycoestrogen zearalenone (ZEN), as well as its reduced metabolites, which belong to the endocrine disruptor bio-molecule family, are substrates for various enzymes involved in steroid metabolism. In addition to its reduction by the steroid dehydrogenase pathway, ZEN also interacts with hepatic detoxification enzymes, which convert it into hydroxylated metabolites (OH-ZEN). Due to their structures to that of estradiol, ZEN and its derived metabolites bind to the estrogen receptors and are involved in endocrinal perturbations and are possibly associated with estrogen-dependent cancers. The primary aim of this present study was to identify the enzymatic cytochrome P450 isoforms responsible for the formation of the most abundant OH-ZEN. We thus studied its in vitro formation using hepatic microsomes in a range of animal model systems including man. OH-ZEN was also recovered in liver and urine of rats treated orally with ZEN. Finally we compared the activity of ZEN and its active metabolites (α-ZAL and OH-ZEN) on estrogen receptors using HeLa ER-α and ER-β reporter cell lines as reporters. OH-ZEN estrogenic activities were revealed to be limited and not as significant as those of ZEN or α-ZAL

In vitro inhibition of porcine cytochrome P450 by 17β -estradiol and 17α-estradiol

Sexually mature pigs are known to possess high concentrations of testicular steroids, which have been shown to change the activities of cytochrome P450 in vitro. The aim of the present study was to evaluate the regulation of CYP1A and CYP2E1 activity by the steroids dihydrotestosterone (DHT), 3β-androstenol, 17β-estradiol and 17α-estradiol. Catalytic activities of 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD) were used as markers of CYP1A activities, while p-nitrophenol hydroxylase (PNPH) was used as a marker of CYP2E1 activities. Of the steroids tested, only 17β-estradiol and 17α-estradiol inhibited EROD and MROD activities. This inhibition was observed when a steroid concentration of 100 µM was used, while lower concentrations showed no inhibitory effect. PNPH activities were inhibited only by 100 µM of 17β-estradiol. The significance of these results in vivo is unknown because inhibition was only found when concentrations of estrogens higher than physiological levels were used. Nevertheless, the results provided further evidence on the important role of estrogens in regulation of porcine cytochrome P450 activities

Profiling the Impact of Medium Formulation on Morphology and Functionality of Primary Hepatocytes in vitro

The characterization of fully-defined in vitro hepatic culture systems requires testing of functional and morphological variables to obtain the optimal trophic support, particularly for cell therapeutics including bioartificial liver systems (BALs). Using serum-free fully-defined culture medium formulations, we measured synthetic, detoxification and metabolic variables of primary porcine hepatocytes (PPHs) - integrated these datasets using a defined scoring system and correlated this hepatocyte biological activity index (HBAI) with morphological parameters. Hepatic-specific functions exceeded those of both primary human hepatocytes (PHHs) and HepaRG cells, whilst retaining biotransformation potential and in vivo-like ultrastructural morphology, suggesting PPHs as a potential surrogate for PHHs in various biotech applications. The HBAI permits assessment of global functional capacity allowing the rational choice of optimal trophic support for a defined operational task (including BALs, hepatocellular transplantation, and cytochrome P450 (CYP450) drug metabolism studies), mitigates risk associated with sub-optimal culture systems, and reduces time and cost of research and therapeutic applications