Hepatic Gene Expression and Metabolite Profiles of Androstenone and Skatole Relative to Plasma Estrone Sulfate Levels in Boars

Testicular steroids can alter the activity and expression of enzymes within the liver and may influence the metabolism of skatole and androstenone, which are responsible for boar taint. Plasma levels of estrone sulfate (E₁S) are indicative of the steroidogenic capacity of the boar and are variable between animals of similar live weights at slaughter. This study aimed to characterize the relationship between steroidogenic capacity and the metabolism of boar taint compounds by relating plasma E₁S levels at slaughter weight to the expression levels of genes regulating the metabolism of androstenone and skatole, along with their respective metabolite profiles. RT-qPCR was used to evaluate gene expression in the liver. Hepatocytes were also isolated and treated with androstenone or skatole, with metabolite levels in the incubation media quantified by high-performance liquid chromatography. Plasma E₁S levels ranged from 2.2–108.5 ng/mL and were positively correlated with overall skatole metabolism (<i>p</i> = 0.038), the production of metabolites 3-methyloxindole (<i>p</i> = 0.026) and 3-hydroxy-3-methyloxindole (<i>p</i> = 0.036), and expression levels of key genes involved in skatole metabolism, specifically <i>CYP2C33</i> (<i>p</i> = 0.0042), <i>CYP2C49</i> (<i>p</i> = 0.022), and <i>CYB5R1</i> (<i>p</i> = 0.017). There was no association between androstenone metabolism and plasma E₁S concentrations; however, there was evidence of possible co-regulation amongst genes involved in the metabolism of androstenone, skatole, and estrogens. These findings indicate that steroidogenic capacity is related to the rate of skatole, but not androstenone metabolism, in slaughter-weight boars.