Age-related change of hepatic uridine diphosphate glucuronosyltransferase and sulfotransferase activities in male chickens and pigs

Ontogeny of CYP3A and UGT activity in preterm piglets: a translational model for drug metabolism in preterm newborns

Despite considerable progress in understanding drug metabolism in the human pediatric population, data remains scarce in preterm neonates. Improving our knowledge of the ADME properties in this vulnerable age group is of utmost importance to avoid suboptimal dosing, which may lead to adverse drug reactions. The juvenile (mini)pig is a representative model for hepatic drug metabolism in human neonates and infants, especially phase I reactions. However, the effect of prematurity on the onset of hepatic phase I and phase II enzyme activity has yet to be investigated in this animal model. Therefore, the aim of this study was to assess the ontogeny of CYP3A and UGT enzyme activity in the liver of preterm (gestational day 105-107) and term-born (gestational day 115-117) domestic piglets. In addition, the ontogeny pattern between the preterm and term group was compared to examine whether postconceptional or postnatal age affects the onset of enzyme activity. The following age groups were included: preterm postnatal day (PND) 0 (n = 10), PND 5 (n = 10), PND 11 (n = 8), PND 26 (n = 10) and term PND 0 (n = 10), PND 5 (n = 10), PND 11 (n = 8), PND 19 (n = 18) and PND 26 (n = 10). Liver microsomes were extracted, and the metabolism of CYP3A and UGT-specific substrates assessed enzyme activity. Preterm CYP3A activity was only detectable at PND 26, whereas term CYP3A activity showed a gradual postnatal increase from PND 11 onwards. UGT activity gradually increased between PND 0 and PND 26 in preterm and term-born piglets, albeit, being systematically lower in the preterm group. Thus, postconceptional age is suggested as the main driver affecting porcine CYP3A and UGT enzyme ontogeny. These data are a valuable step forward in the characterization of the preterm piglet as a translational model for hepatic drug metabolism in the preterm human neonate.

Pharmacokinetics of Levonorgestrel in Rat and Minipig and Pharmacokinetics of Etonogestrel in Rat Following Various Administration Routes

1. The objective of these studies was to determine the pharmacokinetics of levonorgestrel and etonogestrel in Sprague-Dawley rat or Göttingen minipig following various administration routes.2. Four sequential crossover studies were conducted: Study 1 administered levonorgestrel 30 µg intravenously and intradermally in four minipigs; Study 2 administered levonorgestrel 30 µg intravenously in 12 rats; Study 3 administered levonorgestrel 60 µg intravenously and subcutaneously in 12 rats; and Study 4 administered etonogestrel 30 µg intravenously in 12 rats. Samples were quantified using liquid chromatography-tandem mass spectrometry and pharmacokinetic parameters were estimated via noncompartmental analysis.3. C_max and AUC_inf for etonogestrel and levonorgestrel were similar following 30 µg intravenous bolus in rat, suggesting comparable pharmacokinetics. Levonorgestrel exposure was dose-proportional in rats, based on two-fold higher AUC_inf following levonorgestrel 60 versus 30 µg. Bioavailability of intradermal and subcutaneous levonorgestrel was 97.7% (Study 1) and 90.3% (Study 3), respectively. The minipig levonorgestrel clearance was 21.5 L/hr, which was about 10-fold higher than both the rat levonorgestrel (range: 0.985 to 1.45 L/hr) and etonogestrel clearance (range: 0.803 to 0.968 L/hr).4. These studies contribute to the gap in knowledge of nonclinical levonorgestrel and etonogestrel pharmacokinetics, which is necessary for ongoing development of long-acting reversible contraceptives.

Acute toxicity and metabolism of pesticides in birds

The median lethal dose of pesticide in acute oral toxicity, used as a conservative index in avian risk assessment, varies by the species with differences of less than one order of magnitude, depending on body size, feeding habit, and metabolic enzyme activity. The profiles of pesticide metabolism in birds with characteristic conjugations are basically common to those in mammals, but less information is available on their relevant enzymes. The higher toxicity of some pesticides in birds than in mammals is due to the lower activity of avian metabolic enzymes. The bioaccumulation in birds is limited for very hydrophobic pesticides resistant to metabolic degradation. Several in silico approaches using the descriptors of a pesticide molecule have recently been employed to estimate the profiles of acute oral toxicity and bioaccumulation.

The Neonatal and Juvenile Pig in Pediatric Drug Discovery and Development

Pharmacotherapy in pediatric patients is challenging in view of the maturation of organ systems and processes that affect pharmacokinetics and pharmacodynamics. Especially for the youngest age groups and for pediatric-only indications, neonatal and juvenile animal models can be useful to assess drug safety and to better understand the mechanisms of diseases or conditions. In this respect, the use of neonatal and juvenile pigs in the field of pediatric drug discovery and development is promising, although still limited at this point. This review summarizes the comparative postnatal development of pigs and humans and discusses the advantages of the juvenile pig in view of developmental pharmacology, pediatric diseases, drug discovery and drug safety testing. Furthermore, limitations and unexplored aspects of this large animal model are covered. At this point in time, the potential of the neonatal and juvenile pig as nonclinical safety models for pediatric drug development is underexplored.

Maternal Exposure Results in Long-Term Deoxynivalenol Persistence in Piglets' Plasma and Modulates the Immune System

Deoxynivalenol (DON)-contaminated feed represents a serious problem for pigs due to their high sensitivity to its toxicological effects. The aim of the present study was to evaluate the impact of intrauterine DON exposure on the immune system of piglets. Pure DON was intravenously administered to sows at the end of gestation (during the last 2–3 days of gestation, one dose of 300 µg per day). The plasma concentration of DON was analyzed using liquid chromatography combined with high-resolution Orbitrap-based mass spectrometry (LC–MS/MS (HR)) and selected immune parameters were monitored six times in piglets from birth to 18 weeks. DON was found in the plasma of 90% of newborn piglets at a mean concentration of 6.28 ng/mL and subsequently, at one, three, and seven weeks after birth with decreasing concentrations. Trace amounts were still present in the plasma 14 weeks after birth. Flow cytometry revealed a significant impact of DON on T lymphocyte subpopulations during the early postnatal period. Lower percentages of regulatory T cells, T helper lymphocytes, and their double positive CD4+CD8+ subset were followed by increased percentages of cytotoxic T lymphocytes and γδ T cells. The capacity to produce pro-inflammatory cytokines was also significantly lower after intrauterine DON exposure. In conclusion, this study revealed a long-term persistence of DON in the plasma of the piglets as a consequence of short-term intrauterine exposure, leading to altered immune parameters.

Age-associated changes of cytochrome P450 and related phase-2 gene/proteins in livers of rats

Cytochrome P450s (CYPs) are phase-I metabolic enzymes playing important roles in drug metabolism, dietary chemicals and endogenous molecules. Age is a key factor influencing P450s expression. Thus, age-related changes of CYP 1–4 families and bile acid homeostasis-related CYPs, the corresponding nuclear receptors and a few phase-II genes were examined. Livers from male Sprague-Dawley rats at fetus (−2 d), neonates (1, 7, and 14 d), weanling (21 d), puberty (28 and 35 d), adulthood (60 and 180 d), and aging (540 and 800 d) were collected and subjected to qPCR analysis. Liver proteins from 14, 28, 60, 180, 540 and 800 days of age were also extracted for selected protein analysis by western blot. In general, there were three patterns of their expression: Some of the drug-metabolizing enzymes and related nuclear receptors were low in fetal and neonatal stage, increased with liver maturation and decreased quickly at aging (AhR, Cyp1a1, Cyp2b1, Cyp2b2, Cyp3a1, Cyp3a2, Ugt1a2); the majority of P450s (Cyp1a2, Cyp2c6, Cyp2c11, Cyp2d2, Cyp2e1, CAR, PXR, FXR, Cyp7a1, Cyp7b1. Cyp8b1, Cyp27a1, Ugt1a1, Sult1a1, Sult1a2) maintained relatively high levels throughout the adulthood, and decreased at 800 days of age; and some had an early peak between 7 and 14 days (CAR, PXR, PPARα, Cyp4a1, Ugt1a2). The protein expression of CYP1A2, CYP2B1, CYP2E1, CYP3A1, CYP4A1, and CYP7A1 corresponded the trend of mRNA changes. In summary, this study characterized three expression patterns of 16 CYPs, five nuclear receptors, and four phase-II genes during development and aging in rat liver, adding to our understanding of age-related CYP expression changes and age-related disorders.

Comparative identification, nutritional, and physiological regulation of chicken liver-enriched genes

The liver performs a number of vital functions in the chicken. In order to identify unique gene expression patterns and link them to potential functions in the chicken liver, genes enriched in the liver of chickens needed to be investigated in a comparative manner. In this study, 41 liver-enriched genes were identified through chicken microarray, and many of them were validated through comparative analysis of mice and humans. Thirteen of them were unique in chickens, and their liver enhancement was confirmed by reverse transcription PCR. Furthermore, the expression of those 13 chicken liver-enriched genes was investigated, in response to nutritional and physiological challenges. Real-time PCR revealed that expression of PIT54 (P < 0.01), phosphoribosyl pyrophosphate synthetase 2 (PRPS2) (P < 0.05), sulfotransferase (SULT) (P < 0.05), and cytochrome P450 family 2 subfamily C, polypeptide 18 (CYP2C18) (P < 0.05) were significantly decreased in the liver during fasting compared to ad libitum control. During the post-laying stage, expression of GAL8 was significantly increased (P < 0.01), but CYP2C18 expression was significantly reduced (P < 0.05). Liver-enriched genes that were identified in this study and their expression patterns under fasting and the post-laying stage will serve as future targets to gain a better understanding of liver physiology, function and development in poultry.