Regulation of Porcine Hepatic Cytochrome P450 by Chicory Root – Implication for Boar Taint

.............................................................................................................................................. 5 Resumé ................................................................................................................................................ 6 List of included publications ............................................................................................................. 7 Contributions ............................................................................................................................................... 8 List of supporting publications ......................................................................................................... 9 Abbreviations ................................................................................................................................... 10 1.0 Introduction ................................................................................................................................ 11 1.1 The liver ................................................................................................................................................ 11 1.2 Hepatic detoxification ......................................................................................................................... 12 1.2.1 Phase I metabolism ......................................................................................................................... 13 1.2.2 Phase II metabolism........................................................................................................................ 14 1.3 Boar taint .............................................................................................................................................. 15 1.3.1 Skatole metabolising enzymes ........................................................................................................ 15 1.3.2 Androstenone metabolising enzymes ............................................................................................. 17 1.3.3 Solutions to the boar taint problem ................................................................................................. 19 1.3.4 Feeding strategies to prevent boar taint .......................................................................................... 21 1.4 Methods for studying liver metabolism ............................................................................................. 23 2.0 Objective ..................................................................................................................................... 25 2.1 Hypothesis ............................................................................................................................................ 25 3.0 Materials and methods .............................................................................................................. 26 3.1 Animals, feeding and sampling........................................................................................................... 26 3.1.1 In vivo experiment .......................................................................................................................... 26 3.1.2 In vitro experiment ......................................................................................................................... 27 3.2 Preparation of hepatic microsomes .................................................................................................... 29 3.3 mRNA expression ................................................................................................................................ 29 3.4 Protein expression ............................................................................................................................... 31 3.5 Cytochrome P450 dependent activities .............................................................................................. 31 3.6 Analysis of boar taint compounds and hormones ............................................................................. 33 3.7 Statistics ................................................................................................................................................ 33 4.0 Results ......................................................................................................................................... 34 4.1 Microsomes – comparison of preparation methods ......................................................................... 34 4.2 In vivo effects of chicory root .............................................................................................................. 35 4.2.1 mRNA expression of hepatic XRs and Phase I and II enzymes ..................................................... 35 4.2.2 Protein expression of hepatic Phase I and II enzymes .................................................................... 36 4.2.3 Activity of hepatic Phase I enzymes ............................................................................................... 37 4.2.4 Boar taint compounds and hormones ............................................................................................. 38 4.3 In vitro effect of chicory root on CYP mRNA expression ................................................................ 39 4.3.1 Effect of standard CYP inducers .................................................................................................... 39 4.3.2 Effect of secondary plant metabolites............................................................................................. 41 4.3.3 Effect of chicory root extract .......................................................................................................... 41 4.4 Gender-related differences in hepatic Phase I enzymes ................................................................... 43 5.0 Discussion .................................................................................................................................... 45 5.1 Microsomes – comparison of two different preparation methods .................................................. 45 5.2 In vivo effects of chicory root on Phase I and II enzymes ................................................................ 46 5.3 In vitro effect of chicory root on Phase I enzymes ............................................................................ 48 5.4 Gender-related differences in Phase I enzymes ................................................................................ 50 5.5 Implication for boar taint ................................................................................................................... 52 6.0 Conclusions ................................................................................................................................. 54 7.0 Perspectives for future research ............................................................................................... 56 8.0 Reference List ............................................................................................................................. 57