Pathways and genes involved in steroid hormone metabolism in male pigs: a review and update

Abstract

This paper reviews state-of-the-art knowledge on steroid biosynthesis pathways in the pig and provides an updated characterization of the porcine genes involved in these pathways with particular focus on androgens, estrogens, and 16-androstenes. At least 21 different enzymes appear to be involved in these pathways in porcine tissues together with at least five cofactors. Until now, data on several porcine genes were scarce or confusing. We characterized the complete genomic and transcript sequences of the single porcine CYP11B gene. We analyzed the porcine AKR1 gene cluster and identified four AKR1C, one AKR1C like genes and one AKR1E2 gene. We provide evidence that porcine AKR1C genes are not orthologous to human AKR1C. A new nomenclature is thus needed for this gene family in the pig. Thirty-two genes are now described: transcript (30+2 characterized in this study) and genomic (complete: 18+1 and partial: 12+1) sequences are identified. However, despite increasing knowledge on steroid metabolism in the pig, there is still no explanation of why porcine testes can produce androstenone and epiandrosterone, but not dihydrotestosterone (DHT), which is also a reduced steroid.

Keywords: 11-K-DHT; 11-K-Testo; 11-OH-DHT; 11-OH-Testo; 11-OH-Δ4-AD; 11-keto dihydrotestosterone; 11-ketotestosterone or 17-Hydroxyandrost-4-ene-3,11-dione; 11deoxycorticosterone or 21-hydroxyprogesterone (21-hydroxy-4-pregnene-3,20-dione); 11β hydroxy-androstenedione or 11β-hydroxyandrost-4-ene-3,17-dione; 11β-hydroxy dihydrotestosterone; 11β-hydroxy testosterone or 11β,17β-dihydroxy-4-androsten-3-one; 17-hydroxy pregnenolone; 17-hydroxy progesterone; 17OH- progesterone; 17OH-pregnenolone; 17β-estra-1,3,5(10)-triene-3,17-diol; 17β-hydroxy-5alpha-androst-1-en-3-one; 19-OH-Testo; 19-OH-Δ4-AD; 19-norTesto; 19-nortestosterone (or nandrolone) or 17β-hydroxyestra-4-en-3-one; 19β hydroxy-androstenedione or 19β hydroxyandrost-4-ene-3,17-dione; 19β-hydroxy testosterone or 17β,19-dihydroxyandrost-4-en-3-one; 20-OH-progesterone; 20αprogesterone or 4-pregnen-20-α-ol-3-one; 21 steroid hydroxylase enzyme encoded by porcine CYP21 gene; 3-hydroxyestra-1,3,5(10)-triene-17-one; 3α-hydroxy-5α-androstan-17-one; 4-pregnen-3,20-dione; 5-pregnen-3β-ol-20-one; 5-α reductase; 5α-R; 5α-Reduction; 5α-androstan-3,17-diol; AD; AKR1C; Adrenosterone; Androstadienol; Androstadienone; Androstanediol; Androstenone; Androsterone; Boar; CYP11; Cytb5; Cytb5-red; DHEA; DHT; DOC; EpiA; Estradiol; Estrone; HSD; Hormones; P450 aromatase encoded by one of the three porcine CYP19A genes; P450aro; P450c11; P450c17; P450c21; P450scc; Pregnenolone; Progesterone; S; StAR; Steroidogenesis; Testosterone; aa; amino acid; androst-4-ene-3,11,17-trione or 11-oxoandrostenedione; androstanedione or 5α-androstan-3,17-dione; androstenediol or 5-Androstene-3,17-diol; androstenedione or 4-Androstene-3,17-dione; cytochrome P450 side chain cleavage encoded by porcine CYP11A1 gene; cytochrome b5; cytochrome b5 reductase; dehydroepiandrosterone or 3β-hydroxyandrost-5-en-17-one; dihydrotestosterone or 17β-hydroxy-5α-androstan-3-one; enzyme encoded by porcine CYP11B gene; enzyme encoded by porcine CYP17A1 gene; epiandrosterone or 3β-hydroxy-5α-androstan-17-one; hydroxysteroid dehydrogenase; steroidogenic acute regulatory encoded by porcine STAR gene; sulphate; Δ 4,16-androstadien-3-ol; Δ 4,16-androstadien-3-one; Δ4-AD; Δ4-androstene -3-one; Δ5-ADiol.