Feeding dried chicory root to pigs decrease androstenone accumulation in fat by increasing hepatic 3β hydroxysteroid dehydrogenase expression

Influence of Sex and a High-Fiber Diet on the Gut Microbiome of Alentejano Pigs Raised to Heavy Weights

This study investigates the influence of sex and a dietary transition on the gut microbiota of a local Portuguese pig breed. Three groups of male Alentejano pigs (n = 10 each) were raised between ~40 and 160 kg LW. Group C included pigs that were surgically castrated, while the I group included intact ones; both were fed with commercial diets. The third group, IExp, included intact pigs that were fed commercial diets until ~130 kg, then replaced by an experimental diet based on legumes and agro-industrial by-products between ~130 and 160 kg. Fecal samples were collected two weeks before slaughter. The total DNA was extracted and used for 16S metabarcoding on a MiSeq® System. The dietary transition from a commercial diet to the experimental diet substantially increased and shifted the diversity observed. Complex carbohydrate fermenting bacteria, such as Ruminococcus spp. and Sphaerochaeta spp., were significantly more abundant in IExp (q < 0.05). On the other hand, castrated pigs presented a significantly lower abundance of the potential probiotic, Roseburia spp. and Lachnospiraceae NK4A136 group (q < 0.01), bacteria commonly associated with better gut health and lower body fat composition. Understanding the role of gut microbiota is paramount to ensure a low skatole deposition and consumers' acceptance of pork products from non-castrated male pigs.

Transcriptomic Profiling of Subcutaneous Backfat in Castrated and Intact Alentejano Pigs Finished Outdoors with Commercial and Fiber-Rich Diets

In this work, we studied the backfat transcriptome of surgically castrated (C), intact (I) and intact fed an experimental diet (IE) outdoor-reared male Alentejano (AL) pigs. The experimental diet was a high-fiber diet with locally produced legumes and by-products associated with a boar taint reduction effect. At slaughter (~160 kg), backfat samples were collected for total RNA sequencing. Intact pigs presented leaner carcasses, more total collagen, and more unsaturated intramuscular fat content than C animals. A total of 2726 differentially expressed genes (DEGs, |log2 FC|> 0.58, q < 0.05) were identified between C and I with overexpressed genes related to muscular activity (MYH1, ACTA1) or collagen metabolism (COL1A1, COL1A2) in I pigs. Between C and IE, 1639 DEGs of genes involved in lipidic metabolism (LEP, ME1, FABP4, ELOVL6) were overexpressed in C. Finally, only 28 DEGs were determined between I and IE. Clustering results indicated a drastic influence of the testis in the transcriptome of subcutaneous fat of AL pigs, while the diet had a marginal effect. Diet can reduce stress by increasing satiety in animals, and could have induced an increase of skatole degradation due to the higher expression of the CYP2A19 gene in the IE group.

Evaluation of Coated Biochar as an Intestinal Binding Agent for Skatole and Indole in Male Intact Finishing Pigs

The ban on piglet castration without anaesthesia poses a challenge for the meat industry since alternatives ensuring the production of flawless pork have to be established. The aim of this study was to evaluate the effects of biochar on skatole and indole concentration in faeces and plasma on a small scale in finishing boars to prove whether biochar was suitable for use in commercial pork production. Moreover, it was investigated whether biochar affects faecal properties or the performance. For a four-week trial period, 54 boars (bodyweight 97.2 ± 6.88 kg) were divided into three groups. The control (BC0) received no dietary biochar, one group received a diet containing 4% coated biochar (corresponding to 2% pure biochar) for the final two experimental weeks (BC2), and another group for the entire four weeks (BC4), respectively, prior to slaughter. Skatole and indole concentrations were measured in faeces and plasma at the beginning, in the middle and at the end of the trial. Mean skatole concentrations did not differ between groups, but in BC2 faecal skatole was significantly decreased at day 26, whereas in BC4 initial and final faecal skatole levels did not differ. At day 15 and 26, the faecal dry matter content was significantly higher in pigs fed the biochar diet (p < 0.05).

Porcine cytochrome P450 3A: current status on expression and regulation

The cytochrome P450s (CYPs) constitute a family of enzymes maintaining vital functions in the body and are mostly recognized for their significant role in detoxification. Of the CYP subfamilies, CYP3A, is one of the most active in the clearance of drugs and other xenobiotics. During the last decades, much focus has been on exploring different models for human CYP3A regulation, expression and activity. In that respect, the growing knowledge of the porcine CYP3As is of great interest. Although many aspects of porcine CYP3A regulation and activity are still unknown, the current literature provides a basic understanding of the porcine CYP3As that can be used e.g., when translating results from studies done in the porcine model into human settings. In this review, the current knowledge about porcine CYP3A expression, regulation, activity and metabolic significance are highlighted. Future research needs are also identified.

The synthesis of 16-androstene sulfoconjugates from primary porcine Leydig cell culture

Increased public interest in the welfare of pigs reared for pork production has led to an enhanced effort in finding alternatives to castration for controlling the unpleasant odour and flavour from heated pork products known as boar taint. The purpose of this study was to investigate the testicular metabolism of androstenone, one of the major components of boar taint. Leydig cells were isolated from mature boars and incubated with radiolabeled androstenone for 10 min, 1 h, 4 h, 8 h, and 12 h. Steroid profiles were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS/MS). Sulfoconjugated, but not glucuronidated steroids were produced by Leydig cells. Approximately 85% of androstenone was converted into sulfoconjugated metabolites in Leydig cell incubations after 8 h. This sulfoconjugate fraction included androstenol-3-sulfate and two major sulfated forms of androstenone. Following removal of the sulfate group, these two sulfated forms of androstenone returned the parent compound androstenone, and not a hydroxylated metabolite. These findings provided direct evidence for the testicular production of sulfoconjugated forms of androstenone and androstenol in the boar. The high proportion of sulfoconjugates produced by the Leydig cells emphasizes the importance of steroid conjugation, which serves to regulate the amount of unconjugated steroid hormones available for accumulation in adipose tissue.

On farm intervention studies on reduction of boar taint prevalence: Feeding strategies, presence of gilts and time in lairage

One of the challenges in the production of entire male pigs is the occurrence of boar taint. We separately tested the effect of 3 management strategies to reduce boar taint on respectively 2, 3, and 6 Flemish pig farms: 1) adapted feeding strategies, 2) presence of gilts in the compartment, and 3) varying lairage duration at the slaughterhouse. A commercialized feed concept resulted in a significant reduction of olfactory boar taint prevalence when fed for 2 weeks (T2W) compared to control (T-CON) (P = 0.030). For T2W and when fed for 3 weeks (T3W), androstenone (AND) (P = 0.002 for T2W, P = 0.029 for T3W) and skatole (SKA) (P < 0.001 for T2W and T3W) were significantly reduced compared to T-CON. Olfactory boar taint prevalence was significantly reduced when feeding 5% dried chicory roots (FI5%) (P = 0.032), but not for 3% dried chicory roots (FI3%) (P = 0.958). SKA concentration was significantly lower when feeding FI5% (P < 0.001) and when feeding FI3% (P = 0.034). Rearing entire male pigs separately from gilts and increasing lairage duration from <1 h to >3 h did not significantly affect boar taint.

Glucocorticoid receptor is involved in the differential expression of hepatic 3β-hydroxysteroid dehydrogenase between barrows and boars at finishing stage

The enzyme 3β-hydroxysteroid dehydrogenase (3β-HSD) plays an important role in androstenone metabolism in pig liver, and its defective expression is related to the development of boar taint. Early age castration is a common practice in many countries to avoid boar taint, yet whether and how castration affects porcine hepatic 3β-HSD expression are still poorly understood. In this study, we aimed to compare the expression of 3β-HSD between intact (boars) and castrated (barrows) male pigs, and to explore the potential factors regulating 3β-HSD transcription. Compared to barrows, boars showed worse carcass quality. Boars had significantly higher levels of serum androstenone (P < 0.01), testosterone (P < 0.01) and hepatic cortisol (P < 0.05), which were contrary to significantly lower expression of 3β-HSD messenger RNA (P < 0.01) and protein (P < 0.01) in the liver. Significant differences were detected for the hepatic expression of androgen receptor (AR) and CCAAT/enhancer binding protein β (C/EBPβ). Chromatin immunoprecipitation (ChIP) assay demonstrated reduced histone H3 acetylation (P < 0.05) but increased glucocorticoid receptor (GR) binding to 3β-HSD gene promoter in boars (P < 0.05). These results indicate that GR binding to 3β-HSD promoter is involved in the differential hepatic 3β-HSD expression between boars and barrows.

Modulation of Metabolic Detoxification Pathways Using Foods and Food-Derived Components: A Scientific Review with Clinical Application

Research into human biotransformation and elimination systems continues to evolve. Various clinical and in vivo studies have been undertaken to evaluate the effects of foods and food-derived components on the activity of detoxification pathways, including phase I cytochrome P450 enzymes, phase II conjugation enzymes, Nrf2 signaling, and metallothionein. This review summarizes the research in this area to date, highlighting the potential for foods and nutrients to support and/or modulate detoxification functions. Clinical applications to alter detoxification pathway activity and improve patient outcomes are considered, drawing on the growing understanding of the relationship between detoxification functions and different disease states, genetic polymorphisms, and drug-nutrient interactions. Some caution is recommended, however, due to the limitations of current research as well as indications that many nutrients exert biphasic, dose-dependent effects and that genetic polymorphisms may alter outcomes. A whole-foods approach may, therefore, be prudent.

Glucocorticoid receptor is involved in the breed-dependent transcriptional regulation of 3β-hydroxysteroid dehydrogenase in the liver of preweaning piglets

Background

Hepatic 3β-hydroxysteroid dehydrogenase (3β-HSD) plays an important role in steroid inactivation and catabolism. Serum concentrations of steroid hormones differ significantly between breeds in pigs, however the molecular mechanism regulating hepatic 3β-HSD expression in different breeds of pigs is poorly understood. In the present study, we used preweaning purebred male Large White (LW) and Erhualian (EHL) piglets as model to investigate the breed difference in the expression and regulation of 3β-HSD gene in porcine liver.

Results

The hepatic expression of 3β-HSD mRNA was significantly lower (P < 0.01) in EHL piglets compared to that in LW piglets. Significant breed differences were detected for the hepatic expression of transcription factors such as androgen receptor (AR), glucocorticoid receptor (GR), and CCAAT/enhancer binding protein β (C/EBPβ). The nucleoprotein contents of AR (P < 0.05), GR (P < 0.01) and phospho-Ser²¹¹GR (P < 0.01) were significantly higher in the liver of EHL piglets. Chromatin immunoprecipitation (ChIP) assay demonstrated significantly lower binding of GR, but not AR or C/EBPβ, to 3β-HSD gene promoter in EHL piglets (P < 0.05). GR was not detected to interact with C/EBPβ or AR in the co-immunoprecipitation analysis.

Conclusions

These results indicate that GR binding to 3β-HSD promoter is involved in the breed-dependent 3β-HSD expression in the liver of piglets.

Hydrolysable tannin fed to entire male pigs affects intestinal production, tissue deposition and hepatic clearance of skatole

The effect of adding hydrolysable tannins to the diet of fattening boars was studied. Performance, reproductive organ weights, salivary gland morphology, boar taint compounds and skatole metabolism were evaluated. At 123 days of age and 52 ± 6 kg liveweight, 24 Landrace × Large White boars were assigned within a litter to four treatment groups: control (T0 fed mixture with 13.2 MJ/kg, 17.5% crude proteins) and three experimental diets for which the T0 diet was supplemented with 1%, 2% and 3% of hydrolysable tannin-rich extract (T1, T2 and T3, respectively). Pigs were kept individually with ad libitum access to feed and water and slaughtered at 193 days of age and 122 ± 10 kg liveweight. Adding hydrolysable tannins to the diet had no negative effect on growth performance at 1% and 2%, whereas the 3% inclusion reduced feed intake and resulted in an adaptive response of the salivary glands (particularly parotid gland hypertrophy). Relative to T0, fat tissue skatole concentration was increased in the T1 group, but was similar in T2 and T3. Across treatments tissue skatole concentrations were proportional to the activity of hepatic CYP450. The results indicate the potential of tannin supplementation to reduce boar taint although further investigations are needed in order to establishing optimal dosage.

Regulation of cytochrome P450 mRNA expression in primary porcine hepatocytes by selected secondary plant metabolites from chicory (Cichorium intybus L.)

Chicory (Cichorium intybus) has been shown to induce enzymes of pharmacokinetic relevance (cytochrome P450; CYP). The aim of this study was to investigate the effects of selected secondary plant metabolites with a global extract of chicory root, on the expression of hepatic CYP mRNA (1A2, 2A19, 2C33, 2D25, 2E1 and 3A29), using primary porcine hepatocytes. Of the tested secondary plant metabolites, artemisinin, scoparone, lactucin and esculetin all induced increased expression of specific CYPs, while esculin showed no effect. In contrast, a global extract of chicory root decreased the expression of CYP1A2, 2C33, 2D25 and 3A29 at high concentrations. The results suggest that purified secondary metabolites from chicory affect CYP expression and thereby might affect detoxification in general, and that global extracts of plants can have effects different from individual components.

Regulation of 3β-hydroxysteroid dehydrogenase and sulphotransferase 2A1 gene expression in primary porcine hepatocytes by selected sex-steroids and plant secondary metabolites from chicory (Cichorium intybus L.) and wormwood (Artemisia sp.)

In pigs the endogenously produced compound androstenone is metabolised in the liver in two steps by 3β-hydroxysteroid dehydrogenase (3β-HSD) and sulphotransferase 2A1 (SULT2A1). The present study investigated the effect of selected sex-steroids (0.01-1 μM androstenone, testosterone and estradiol), skatole (1-100 μM) and secondary plant metabolites (1-100 μM) on the expression of 3β-HSD and SULT2A1 mRNA. Additionally the effect of a global methanolic extract of dried chicory root was investigated and compared to previous obtained in vivo effects. Primary hepatocytes were isolated from the livers of piglets (crossbreed: Landrace×Yorkshire and Duroc) and cultured for 24h before treatment for an additionally 24h. RNA was isolated from the hepatocytes and specific gene expression determined by RT-PCR using TaqMan probes. The investigated sex-steroids had no effect on the mRNA expression of 3β-HSD and SULT2A1, while skatole decreased the content of SULT2A1 30% compared to control. Of the investigated secondary plant metabolites artemisinin and scoparone (found in Artemisia sp.) lowered the content of SULT2A1 by 20 and 30% compared to control, respectively. Moreover, we tested three secondary plant metabolites (lactucin, esculetin and esculin) found in chicory root. Lactucin increased the mRNA content of both 3β-HSD and SULT2A1 by 200% compared to control. An extract of chicory root was shown to decrease the expression of both 3β-HSD and SULT2A1. It is concluded that the gene expression of enzymes with importance for androstenone metabolism is regulated by secondary plant metabolites in a complex manner.

Regulation of 3β-hydroxysteroid dehydrogenase/Δ⁵-Δ⁴ isomerase: a review

This review focuses on the expression and regulation of 3β-hydroxysteroid dehydrogenase/Δ⁵-Δ⁴ isomerase (3β-HSD), with emphasis on the porcine version. 3β-HSD is often associated with steroidogenesis, but its function in the metabolism of both steroids and xenobiotics is more obscure. Based on currently available literature covering humans, rodents and pigs, this review provides an overview of the present knowledge concerning the regulatory mechanisms for 3β-HSD at all omic levels. The HSD isoenzymes are essential in steroid hormone metabolism, both in the synthesis and degradation of steroids. They display tissue-specific expression and factors influencing their activity, which therefore indicates their tissue-specific responses. 3β-HSD is involved in the synthesis of a number of natural steroid hormones, including progesterone and testosterone, and the hepatic degradation of the pheromone androstenone. In general, a number of signaling and regulatory pathways have been demonstrated to influence 3β-HSD transcription and activity, e.g., JAK-STAT, LH/hCG, ERα, AR, SF-1 and PPARα. The expression and enzymic activity of 3β-HSD are also influenced by external factors, such as dietary composition. Much of the research conducted on porcine 3β-HSD is motivated by its importance for the occurrence of the boar taint phenomenon that results from high concentrations of steroids such as androstenone. This topic is also examined in this review.

Dried chicory root modifies the activity and expression of porcine hepatic CYP3A but not 2C--effect of in vitro and in vivo exposure

Hepatic cytochrome P450 expression and activity are dependent on many factors, including dietary ingredients. In the present study, we investigated the in vivo and in vitro effect of chicory root on hepatic CYP3A and 2C in male pigs. Chicory feeding increased the expression of CYP3A29 mRNA but not CYP2C33. Correspondingly, CYP3A activity was increased by chicory feeding, while CYP2C activity was not affected. Additionally, the in vitro effect of chicory extract on the CYP3A activity was investigated. It was shown that CYP3A activity in the microsomes from male pigs was inhibited, but this effect was eliminated by pre-incubation. In both male and female pigs the CYP3A activity was increased in the presence of chicory after pre-incubation. Furthermore, gender-related differences in mRNA expression and activity were observed. CYP3A mRNA expression was greater in female pigs; this was not reflected on activity. For CYP2C, no difference in mRNA expression was observed, while CYP2C activity was greater in female pigs. Surprisingly, the expression of the constitutive androstane receptor, pregnane X receptor and aryl hydrocarbon receptor did not differ with feed or gender. In conclusion, chicory root modifies the expression and activity of CYP3A in vivo and in vitro, while CYP2C is not affected.

Nutritional Influences on Skatole Formation and Skatole Metabolism in the Pig

Skatole is a tryptophan (TRP) metabolite with fecal odor. Together with the testicular steroid androstenone it is regarded as a main determinant of boar taint, even if elevated concentrations of skatole occur occasionally in gilts and barrows. Skatole concentrations in adipose tissue result from a complex process, which includes the availability of TRP and the presence of specialized bacteria in the gut in need of TRP for energy production, as well as absorption, transport and accumulation of skatole in adipose tissue. Several steps of this process are influenced by diet and specific feed compounds. In the present paper the current knowledge about physiological mechanisms of skatole dynamics is summarized. Additionally mechanisms are discussed, by which effective feeding strategies and feed additives exert their influence in the prevention of high skatole concentrations in adipose pig tissue. It was concluded that the most effective measures are those which influence several steps of skatole formation. Despite the numerous studies carried out in the field of skatole physiology, interesting aspects still need clarification, such as the effect of adipose tissue turnover. Reliable control of skatole accretion in fat of boars is one of the main prerequisites for pork production with entire males.