Unraveling the functional role of the orphan solute carrier, SLC22A24 in the transport of steroid conjugates through metabolomic and genome-wide association studies.

Variation in steroid hormone levels has wide implications for health and disease. The genes encoding the proteins involved in steroid disposition represent key determinants of interindividual variation in steroid levels and ultimately, their effects. Beginning with metabolomic data from genome-wide association studies (GWAS), we observed that genetic variants in the orphan transporter, SLC22A24 were significantly associated with levels of androsterone glucuronide and etiocholanolone glucuronide (sentinel SNPs p-value <1x10-30). In cells over-expressing human or various mammalian orthologs of SLC22A24, we showed that steroid conjugates and bile acids were substrates of the transporter. Phylogenetic, genomic, and transcriptomic analyses suggested that SLC22A24 has a specialized role in the kidney and appears to function in the reabsorption of organic anions, and in particular, anionic steroids. Phenome-wide analysis showed that functional variants of SLC22A24 are associated with human disease such as cardiovascular diseases and acne, which have been linked to dysregulated steroid metabolism. Collectively, these functional genomic studies reveal a previously uncharacterized protein involved in steroid homeostasis, opening up new possibilities for SLC22A24 as a pharmacological target for regulating steroid levels.

Individual variability of human olfactory sensitivity to volatile steroids: Environmental and genetic factors.

The sensitivity to androstenone and possible factors, determining the sensitivity were investigated for the large sample of inhabitants of central Russia (n = 860). Specific anosmia was detected in 48.8% of subjects. Women were more sensitive to androstenone than men. The proportion of men, but not women perceiving the smell of androstenone as a strong one in the concentration used decreased with age. Smoking, blood group, or ethnicity had no significant effect on the expression of specific anosmia and the perception of androstenone odor intensity.

Blood and adipose tissue steroid metabolomics and mRNA expression of steroidogenic enzymes in periparturient dairy cows differing in body condition.

In high-yielding dairy cows, the rapidly increasing milk production after parturition can result in a negative nutrient balance, since feed intake is insufficient to cover the needs for lactation. Mobilizing body reserves, mainly adipose tissue (AT), might affect steroid metabolism. We hypothesized, that cows differing in the extent of periparturient lipomobilization, will have divergent steroid profiles measured in serum and subcutaneous (sc)AT by a targeted metabolomics approach and steroidogenic enzyme profiles in scAT and liver. Fifteen weeks antepartum, 38 multiparous Holstein cows were allocated to a high (HBCS) or normal body condition (NBCS) group fed differently until week 7 antepartum to either increase (HBCS BCS: 3.8 ± 0.1 and BFT: 2.0 ± 0.1 cm; mean ± SEM) or maintain BCS (NBCS BCS: 3.0 ± 0.1 and BFT: 0.9 ± 0.1 cm). Blood samples, liver, and scAT biopsies were collected at week -7, 1, 3, and 12 relative to parturition. Greater serum concentrations of progesterone, androsterone, and aldosterone in HBCS compared to NBCS cows after parturition, might be attributed to the increased mobilization of AT. Greater glucocorticoid concentrations in scAT after parturition in NBCS cows might either influence local lipogenesis by differentiation of preadipocytes into mature adipocytes and/or inflammatory response.

DSRIG: Incorporating graphical structure in the regularized modeling of SNP data.

Genetic selection of farm animals plays an important role in genetic improvement programs. Regularized regression methods on single nucleotide polymorphism (SNP) data from a set of candidate genes can help to identify genes that are associated with the trait of interest. This complex task must also consider the relative effect sizes on the desired trait and account for the relationships among the candidate SNPs so that selection of a SNP does not promote other undesirable traits through breeding. We present the Doubly Sparse Regression Incorporating Graphical structure (DSRIG), a novel regularized method for genetic selection that exploits the relationships among candidate SNPs to improve prediction. DSRIG was applied in the prediction of skatole and androstenone levels, two compounds known to be associated with boar taint. DSRIG was shown to provide a predictive benefit when compared to ordinary least squares (OLS) and the least absolute shrinkage and selection operator (LASSO) in a cross-validation procedure. The relative sizes of the coefficient estimates over the cross-validation procedure were compared to determine which SNPs may have the greatest impact on expression of the boar taint compounds and a consensus graph was used to infer the relationships among SNPs.

An omics investigation into chronic widespread musculoskeletal pain reveals epiandrosterone sulfate as a potential biomarker.

Chronic widespread musculoskeletal pain (CWP) is common, having a population prevalence of 10%. This study aimed to define the biological basis of the CWP/body mass association by using a systems biology approach. Adult female twins (n = 2444) from the TwinsUK registry who had extensive clinical, anthropometric, and "omic" data were included. Nontargeted metabolomics screening including 324 metabolites was carried out for CWP and body composition using dual-energy X-ray absorptiometry. The biological basis of these associations was explored through a genome-wide association study and replicated in an independent population sample (Cooperative Health Research in the Region of Augsburg [KORA] study, n = 2483). A causal role for the genetic variants identified was sought in CWP using a Mendelian randomisation study design. Fat mass/height2 was the body composition variable most strongly associated with CWP (TwinsUK: P = 2.4 × 10(-15) and KORA: P = 1.59 × 10(-10)). Of 324 metabolites examined, epiandrosterone sulfate (EAS) was highly associated with both CWP (P = 1.05 × 10(-09) in TwinsUK and P = 3.70 × 10(-06) in KORA) and fat mass/height2. Genome-wide association study of EAS identified imputed single nucleotide polymorphism rs1581492 at 7q22.1 to be strikingly associated with EAS levels (P ≤ 2.49 × 10(-78)), and this result was replicated in KORA (P = 2.12 × 10(-9)). Mendelian randomization by rs1581492 genotype showed that EAS is unlikely to be causally related to CWP. Using an agnostic omics approach to focus on the association of CWP with body mass index, we have confirmed a steroid hormone association and identified a genetic variant upstream of the CYP genes, which likely controls this response. This study suggests that steroid hormone abnormalities result from pain rather than causing it, and EAS may provide a biomarker that identifies subgroups at risk of CWP.

A genome-wide linkage scan for steroids and SHBG levels in black and white families: the HERITAGE Family Study.

To identify loci-harboring genes affecting steroid hormone and SHBG plasma levels, a genomic-wide scan was performed in the HERITAGE Family Study at baseline. The following steroid hormones were assayed: androstane-3 alpha, 17 beta-diol glucuronide, androsterone glucuronide, cortisol, dihydrotestosterone, estradiol, 17-hydroxyprogesterone (OH-PROG), progesterone (PROG), pregnenolone ester, and testosterone. A total of 509 markers on the 22 autosomes were genotyped, and a maximum of 357 pairs of siblings from white families and 103 from black families were available for the study. Significant linkages with LOD scores over 3.6 (P < 2.2 x 10(-5)) for SHBG were observed in blacks on 1q44 (D1S321), 5p13.3 (D5S1986), 10q24.1 (D10S1239), and 12q12 (D12S1653) in both singlepoint and multipoint analyses. Promising evidence of linkage (1.75 < LOD < 3.6; 2.2 x 10(-5) < P < 0.0023) for SHBG was observed on 1q44 in singlepoint analysis in whites. In addition, several other loci in blacks exhibited promising evidence of linkage, suggesting that many genes can potentially regulate SHBG levels. In the case of C21 steroids, promising linkages were found on 1q43 (D1S517) for PROG, 2p25.1 (D2S1400) for pregnenolone ester, and 18q21.32 (D18S38) for OH-PROG in whites and on 3q25.33 (D3S1763) for OH-PROG in blacks, both singlepoint and multipoint analyses (P < 0.0023). The strongest signals for C19 steroids were found on 22q12.3 for testosterone in whites (P = 0.0024 in multipoint) and on 8q22.1 for dihydrotestosterone in blacks. In blacks, the strongest evidence of linkage for estradiol (C18 steroid) was provided by marker D1S1588 on 1p21.3 and in whites by markers D2S2374 and D2S2347 on 2p21, and D6S465 on 6p12.3. Several genes encoding enzymes of the steroid biosynthesis pathways but also other potential candidate genes were located in the vicinity of the genomic regions showing evidence of linkage in this genomic scan.

Familial resemblance for free androgens and androgen glucuronides in sedentary black and white individuals: the HERITAGE Family Study. Health, Risk Factors, Exercise Training and Genetics.

Familial correlation analyses were used to evaluate the familial aggregation of plasma androgens and androgen glucuronides (testosterone (TESTO), dihydrotestosterone (DHT), androstane-3 alpha,17 beta-diol glucuronide (3 alpha-DIOL-G), and androsterone glucuronide (ADT-G)) in 505 members of 99 white families and 296 members of 111 black families participating in the Health, Risk Factors, Exercise Training and Genetics (HERITAGE) Family Study. Each of these four measures was determined by RIA after separation of conjugated and unconjugated steroid using C18 column chromatography. All participants were sedentary prior to being including in this study. Significant spouse correlations, as well as parent-offspring and sibling correlations, were found for TESTO, DHT, 3 alpha-DIOL-G, and ADT-G in the white sample, suggesting that common familial environments and genes contribute to the familial resemblance. In the black sample, significant sibling and parent-offspring correlations were found for all four phenotypes, while the spouse correlation was marginally significant for 3 alpha-DIOL-G and not significant for TESTO, DHT, and ADT-G. The non-significance of spouse correlations in the black individuals may be due to the small number of spouse pairs. The maximal heritability estimates of TESTO, DHT, 3 alpha-DIOL-G, and ADT-G were 69%, 87%, 74%, and 56% for white individuals and 70%, 73%, 62%, and 48% for black individuals respectively. Sex differences in heritability estimates were found in the white individuals, but they were less dramatic in the black individuals. In conclusion, plasma levels of androgens and androgen glucuronides are highly heritable in both white individuals and black individuals. There are notable sex differences in the white individuals.

Detection of quantitative trait loci for fat androstenone levels in pigs.

A QTL analysis of fat androstenone levels from a three-generation experimental cross between Large White and Meishan pig breeds was carried out. A total of 485 F2 males grouped in 24 full-sib families, their 29 parents and 12 grandparents were typed for 137 markers distributed over the entire porcine genome. The F2 male population was measured for fat androstenone levels at 100, 120, 140, and 160 d of age and at slaughter around 80 kg liveweight. Statistical analyses were performed using two interval mapping methods: a line-cross (LC) regression method, which assumes alternative alleles are fixed in founder lines, and a half- full-sib (HFS) maximum likelihood method, where allele substitution effects were estimated within each half- and full-sib family. Both methods revealed genomewide significant gene effects on chromosomes 3, 7, and 14. The QTL explained, respectively, 7 to 11%, 11 to 15%, and 6 to 8% of phenotypic variance. Three additional significant QTL explaining 4 to 7% of variance were detected on chromosomes 4 and 9 using LC method and on chromosome 6 using HFS method. Suggestive QTL were also obtained on chromosomes 2, 10, 11, 13, and 18. Meishan alleles were associated with higher androstenone levels, except on chromosomes 7, 10, and 13, although 10 and 13 additive effects were near zero. The QTL had essentially additive effects, except on chromosomes 4, 10, and 13. No evidence of linked QTL or imprinting effects on androstenone concentration could be found across the entire porcine genome. The steroid chromosome P450 21-hydroxylase (CYP21) and cytochrome P450 cholesterol side chain cleavage subfamily XIA (CYP11A) loci were investigated as possible candidate genes for the chromosome 7 QTL. No mutation of coding sequence has been found for CYP21. Involvement of a candidate regulatory mutation of CYP11A gene proposed by others can be excluded in our animals.

Boar taint in entire male pigs: a genomewide association study for direct and indirect genetic effects on androstenone.

Androstenone is one of the compounds causing boar taint of pork and is highly heritable (approximately 0.6). Recently, indirect genetic effects (IGE; also known as associative effects or social genetic effects) were found for androstenone, meaning that pen mates (boars) affect each other's androstenone level genetically. Similar to estimating variance components with a direct-indirect animal model, direct and indirect genetic SNP effects can be estimated for androstenone. This study aims to detect SNP with significant direct genetic effects and IGE on androstenone. The dataset consisted of 1,282 noncastrated boars (993 boars genotyped) from 184 groups of pen members. After quality control, 46,421 SNP were included in the analysis. One model for single-SNP regression was fitted, where both the direct SNP effect of the individual itself and the indirect SNP effects of its pen mates were included. None of the SNP (direct or indirect) were found genomewide significant. One QTL on SSC6 was chromosome-wide significant for the direct effect. A single SNP on SSC9 and 2 regions and a single SNP on SSC14 were found for the indirect effect. A backwards elimination method and haplotype analysis were used to quantify the variance explained by the SNP. The backwards elimination method identified 4 independent regions affecting androstenone. The QTL on SSC6 explained 2.1 and 2.6% of the phenotypic variance using the backwards elimination method or the haplotype analysis. The QTL on SSC14 explained 3.4 and 2.7% of the phenotypic variance using the backwards elimination method or the haplotype analysis. The single association on SSC9 explained 2.2% of the phenotypic variance. All significant QTL together explained 7 to 8% of phenotypic variance and 40 to 44% of the total genetic variance available for response to selection. Besides the newly discovered QTL and the confirmation of known QTL, this study also presents a methodology to model SNP for IGE.

Efficiency of different selection strategies against boar taint in pigs.

The breeding scheme of a Swiss sire line was modeled to compare different target traits and information sources for selection against boar taint. The impact of selection against boar taint on production traits was assessed for different economic weights of boar taint compounds. Genetic gain and breeding costs were evaluated using ZPlan+, a software based on selection index theory, gene flow method and economic modeling. Scenario I reflected the currently practiced breeding strategy as a reference scenario without selection against boar taint. Scenario II incorporated selection against the chemical compounds of boar taint, androstenone (AND), skatole (SKA) and indole (IND) with economic weights of -2.74, -1.69 and -0.99 Euro per unit of the log transformed trait, respectively. As information sources, biopsy-based performance testing of live boars (BPT) was compared with genomic selection (GS) and a combination of both. Scenario III included selection against the subjectively assessed human nose score (HNS) of boar taint. Information sources were either station testing of full and half sibs of the selection candidate or GS against HNS of boar taint compounds. In scenario I, annual genetic gain of log-transformed AND (SKA; IND) was 0.06 (0.09; 0.02) Euro, which was because of favorable genetic correlations with lean meat percentage and meat surface. In scenario II, genetic gain increased to 0.28 (0.20; 0.09) Euro per year when conducting BPT. Compared with BPT, genetic gain was smaller with GS. A combination of BPT and GS only marginally increased annual genetic gain, whereas variable costs per selection candidate augmented from 230 Euro (BPT) to 330 Euro (GS) or 380 Euro (both). The potential of GS was found to be higher when selecting against HNS, which has a low heritability. Annual genetic gain from GS was higher than from station testing of 4 full sibs and 76 half sibs with one or two measurements. The most effective strategy to reduce HNS was selecting against chemical compounds by conducting BPT. Because of heritabilities higher than 0.45 for AND, SKA and IND and high genetic correlations to HNS, the (correlated) response in units of the trait could be increased by 62% compared with scenario III with GS and even by 79% compared with scenario III, with station testing of siblings with two measurements. Increasing the economic weights of boar taint compounds amplified negative effects on average daily gain, drip loss and intramuscular fat percentage.

Direct and associative effects for androstenone and genetic correlations with backfat and growth in entire male pigs.

In the pig industry, male piglets are surgically castrated early in life to prevent boar taint. Boar taint is mainly caused by androstenone and skatole. Androstenone is a pheromone that can be released from the salivary glands when the boar is sexually aroused. Boars are housed in groups and as a consequence boars can influence and be influenced by the phenotype of other boars by (non-)heritable social interactions. The influence of these social interactions on androstenone is not well understood. The objective of this study is to investigate whether androstenone concentrations are affected by (non-)heritable social interactions and estimate their genetic correlation with growth rate and backfat. The dataset contained 6,245 boars, of which 4,455 had androstenone observations (68%). The average number of animals per pen was 7 and boars were housed in 899 unique pen-groups (boars within a single pen) and 344 unique compartment-groups (boars within a unique 'room' within a barn during time). Four models including different random effects, were compared for androstenone. Direct genetic, associative (also known as social genetic or indirect genetic effects), group, compartment, common environment and residual effects were included as random effects in the full model (M3). Including random pen and compartment effects (non-heritable social effects) significantly improved the model (M2) compared with including only direct, common environment and residual as random effects (M1, P < 0.001), and including associative effects even more (M3, P < 0.001). The sum of the direct and associative variance components determines the total genetic variance of the trait. The associative effect explained 11.7% of the total genetic variance. Backfat thickness was analysed using M2 and growth using M3. The genetic correlation between backfat (direct genetic variance) and total genetic variance for androstenone was close to 0. Backfat and the direct and associative effects for androstenone had genetic correlations of 0.14 ± 0.08 and -0.25 ± 0.18, respectively. The genetic correlation between total genetic variances for growth rate and androstenone was 0.33 ± 0.18. The genetic correlation between direct effects was 0.11 ± 0.09 and between associative effects was 0.42 ± 0.31. The genetic correlations and current selection towards lower backfat and greater growth rate suggest that no major change in androstenone is expected when breeding goals are not changed. For selection against boar taint and therefore also against androstenone , results recommend that at least the social environment of the boars should be considered.

Genetic and metabolic aspects of androstenone and skatole deposition in pig adipose tissue: a review.

High levels of androstenone and skatole in fat tissues are considered the primary causes of boar taint, an unpleasant odour and flavour of the meat from non-castrated male pigs. The aim of this article is to review our current knowledge of the biology and genetic control of the accumulation of androstenone and skatole in fat tissue. Two QTL mapping studies have shown the complexity of the genetic control of these traits. During the last ten years, several authors have taken a more physiological approach to investigate the involvement of genes controlling the metabolism of androstenone and skatole. Although some authors have claimed the identification of candidate genes, it is more appropriate to talk about target genes. This suggests that genes affecting androstenone and skatole levels will have to be sought for among specific or non-specific transcription factors interacting with these target genes.

Detection of quantitative trait loci for androstenone, skatole and boar taint in a cross between Large White and Meishan pigs.

'Boar taint' is a strong perspiration-like, urine-like unpleasant odour given off upon heating or cooking of meat from some intact (uncastrated) male pigs. Data from the F(2) generation of a Large White (LW) x Meishan (MS) crossbred population were analysed to detect quantitative trait loci (QTL) for traits associated with boar taint. Fat samples from 178 intact male pigs slaughtered at 85 +/- 5 kg were analysed for the major contributors to boar taint (androstenone, indole and skatole). Fat and lean samples from cooked meat were scored for boar, abnormal and pork flavour and odour by a trained sensory panel (SP). A scan with 117 markers covering the whole genome was performed in the F(2) individuals, together with their F(1) parents and purebred grandparents. At the 5% chromosomal significance threshold (approximately equal to the genome-wide suggestive significance threshold), QTL were detected for the laboratory estimate of androstenone on chromosomes 2, 4, 6, 7 and 9. However, only on chromosome 6 were there QTL for boar flavour (BF) traits in the same or adjacent marker intervals as a QTL for the laboratory estimate of androstenone. On chromosome 14, QTL were detected for the laboratory estimates of indole and skatole, the SP score for skatole and the scores for BF in lean and BF in fat. In all five cases, the MS allele generally increased the estimate or score, compared with the LW allele, but it appeared that desirable and undesirable alleles were present in both breeds. This locus on chromosome 14 has considerable potential for use to reduce the incidence of boar taint, especially if further research can identify the causative polymorphism or strongly associated markers.