Decreased testosterone levels after caponization leads to abdominal fat deposition in chickens

- Decreased testosterone levels after caponization leads to abdominal fat deposition in chickens.
- 0.05) and serum and AF testosterone levels decreased significantly ( P <.
- 0.01) after caponization.
- In AF tissue, 90 differentially expressed genes related to lipid metabolism were screened by gene expression profiling in caponized and sham-treated chickens.
- In vitro, Fat content was significantly lower in cells treated with testosterone compared with control cells ( P <.
- Conclusions: The results of this study indicate that testosterone reduction likely regulates gene expression through PPAR and cell junction pathways resulting in increased fat accumulation.
- Caponization has been shown to cause a significant reduction in testosterone levels in roosters.
- Until now, the molecular mechanisms of how androgen levels affect lipogenesis in the avian species were not known.
- Using the Beijing-You (BJY) chicken, a typical local breed in China, an investigation on global gene expression profiles related to lipid metabolism in abdominal fat following caponization was performed using gene expression profiling.
- issues) of the Institute of Animal Sciences, Chinese Academy of Agricultural Sciences (Beijing, China).
- Ten birds from each of the two groups were euthanized under carbon dioxide anesthesia by severing the carotid artery at 10, 14, and 19 w after caponization or sham oper- ations.
- After slaughter, AF was dissected in the same area for all chickens.
- The abdominal fat weight (AFW) was recorded, and the AF percentage (AFP.
- Determination of serum and AF testosterone levels Serum testosterone and estradiol concentrations were determined using a radioimmunoassay kit (Huaying, Beijing, China) as previously described method [12]..
- Testosterone levels in AF were also measured using a chicken-specific testosterone ELISA kit (Fangcheng Bio- logical Technology Co., Ltd., Beijing, China).
- Gene expression profiling.
- Illumina, San Diego, CA, USA), gene expression profiling was undertaken by Berry Genomics (Beijing, China) using total RNA from AF samples in three each of capon and control chickens (taken 14 w after caponi- zations or sham operations).
- Gene expression levels were calculated using the RPKM (Reads Per Kb per Million mapped reads) method as described by Mortazavi et al.
- After the primary preadipocytes were obtained from the AF of chickens (2–4 weeks old.
- Using the same RNA samples as used for gene expres- sion profiling, qRT-PCR was performed to confirm the results of gene expression profiling, and 11 representa- tive genes related to lipid metabolism were selected.
- The results are expressed as the mean fold-change in gene expression from triplicate analyses, using control group samples as the calibrators (arbitrarily assigned an expression level of 1 for each gene).
- Correlations between relative abundances from qRT-PCR and gene expression profiling data were also calculated..
- Values are reported as the mean ± standard error of the mean (SEM).
- Caponization accelerates AF deposition.
- after caponization (Fig.
- These results suggest that the caponization enhanced AF deposition.
- Differential AF gene expression 14 weeks after caponization.
- To understand the changes in AF deposition in capons compared with controls, AF samples were obtained 14 w after caponization to screen for potential candidate genes that affect AF accumulation.
- 0.05) between capons and control group chickens were screened: 463 were up-regulated and 409 were down-regulated in capons compared with controls (Additional File 1)..
- Based on known DEGs, a cluster analysis of all six samples was performed to validate data from the gene expression profiling using Cluster 3.0 software, and it revealed that three samples each from the same group were clustered together (Fig.
- To validate the data obtained from gene expression profiling, 11 represen- tative DEGs were selected to examine the relative expression using qRT-PCR.
- GO analysis was performed based on known DEGs and identified particular GO terms in the main biological processes category, included the following processes: lipid metabolism, regulation of cell differentiation, cell cycle, pro- tein metabolism, hormone metabolism, transmembrane transport, oxidation-reduction, muscle system, regulation of the immune system, blood circulation, regulation of apoptosis, and ATP biosynthesis (Additional File 2)..
- 1 AFW and AFP increase in the abdominal fat of male chickens after caponization.
- The AFWs of Chickens after caponization (capons) or not (sham-operated chickens), were recorded at wks, respectively.
- The results show that AFW significantly increases in capons compared with control chickens at 14 wk.
- after caponization.
- is expressed as a percentage of AFW/live weight and significantly increased in capons compared with sham-operated control chickens at 14 wk.
- AF gene expression is enriched for pathways involved in lipid metabolism after caponization.
- 4a), including well-known pathways related to lipid metabolism (PPAR signaling, arachidonic acid metabolism, and fatty acid.
- As for the PPAR pathway, 11 genes related to lipid metabolism, including 6 representative genes (apolipo- protein A1, APOA1.
- fatty acid desatur- ase 2, FADS2), were specifically associated with the PPAR signaling pathway (Additional File 5: Figure S1), and the mRNA levels of these genes changed signifi- cantly (P <.
- 0.01) in the capons compared with controls (Fig.
- 4b), suggesting that caponization induces gene expression changes that regulate AF deposition..
- Decreased testosterone levels influence AF deposition after Caponization.
- Given that the role of sex hormones in lipid metabolism was previously reported [4], the relationship between testosterone and estradiol and AF deposition was also explored here.
- 5a, serum testosterone levels significantly decreased (P <.
- after caponization in the capon group compared with those of the control group.
- after caponization or sham operations (Fig.
- a Cluster analysis heat-map data using the gene expression profiling.
- Using Cluster 3.0 software and based on the 872 known DEGs in the AF tissue of capons vs.
- 3 Data verification from Gene Expression Profiling analysis by Q-PCR.
- b The correlation analysis examined the fold-changes of 11 DEGs measured by gene expression profiling and Q-PCR to validate the gene expression profiling results.
- 0.01), indicating that the results from the gene expression profiling were accurate ( n = 11).
- 4 Enrichment of candidate pathways related to lipid metabolism and verification of related genes a The nine enriched pathways were screened based on 872 known DEGs.
- b The changes in expression of six representative genes involved in the PPAR signaling pathway.
- The mRNA levels of RXRG , FADS2 , FABP7, and SCD , which promote lipid deposition, were significantly up-regulated in AF tissues of capons compared with sham-operated control chickens 14 wk.
- a and (c) Serum and AF testosterone levels were significantly reduced in capons compared with sham-operated control chickens.
- after caponization, testosterone levels were measured with an ELISA kit.
- b Serum estradiol levels were not different between the capons and the control chickens.
- 5c, the results showed that capon AF had lower testosterone levels (P <.
- 0.05) compared with control AF, suggesting that the reduction in serum and AF testoster- one levels might correlate with greater AF deposition..
- An additional in vitro experiment (with 0 or 30 ng/mL testosterone) was performed to confirm the effect of tes- tosterone on AF deposition.
- Similarly, the expressions of RXRG, FABP3, and FABP7 (the important factor involved in the PPAR signaling.
- 0.01) in cells treated with testosterone for 4 d compared with untreated cells (Fig.
- It has been reported that caponization accelerates AF de- position in male chickens, which is accompanied by de- creased testosterone levels [4, 5].
- b RXRG and FABP7 mRNA expression were significantly down-regulated in cells treated with 30 ng/mL testosterone compared with untreated cells.
- Therefore, it was speculated that caponization would induce fat accumulation by re- ducing testosterone levels in male chickens, although the molecular mechanisms behind this hypothesis have remained incompletely understood.
- Using capons, the findings of this study showed that serum testosterone levels were significantly reduced with greater AF accumulation in caponized chickens com- pared with controls, which is consistent with previous observations [4, 25].
- The findings indicate that re- duced serum and AF testosterone levels might be related to AF deposition after caponization in male chickens..
- Remark- ably, both in vitro and in vivo studies reached the same conclusions, which show that caponization accelerates AF deposition because of reduced testosterone levels..
- Based on the results of AF deposition and reduced serum testosterone levels after caponization, the AF.
- tissue samples from capons and sham-operated controls were subjected to gene expression profiling to screen for DEGs and the enriched pathways after caponization in capons versus control chickens.
- The results of cluster analysis and qRT-PCR supported the accuracy of the gene expression profiling..
- GO and KEGG analyses based on 872 known DEGs were performed, and 90 DEGs related to lipid metabol- ism were further screened, including RXRG, FABP3, and FABP7 [26–29].
- Among the nine enriched pathways, classical pathways related to lipid metabolism (PPAR and fatty acid metabolism) were screened, and six representative DEGs related to lipid metabolism (APOA1, SCD, FABP3, FABP7, RXRG, and FADS2) were enriched and identified in the PPAR pathway.
- Consider- ing the importance of the PPAR pathway and the genes related to lipid metabolism it was shown that caponization-accelerated AF deposition might be associ- ated with the changed expression of related genes through the PPAR pathway in the AF of chicken.
- In addition, pathways related to cell junctions (ECM – receptor interactions, CAMs, cytokine-cytokine.
- 7 The regulatory network regarding the influence of reduced testosterone levels on lipid deposition in caponized chickens, which is based on significantly enriched KEGG pathwaysThis network is involved in the cellular functions of lipid metabolism (PPAR signaling pathway) and cell junctions..
- receptor interactions, and focal adhesions) were enriched in this study, which showed that these pathways pro- moted activation of the PPAR pathway to induce AF de- position in chickens, consistent to what was shown in the study by Cui et al.
- In the present study, these findings support the assertion that pathways related to cell junctions are also involved in testosterone the regu- lation of AF deposition..
- 0.01) in cells treated with testos- terone for 4 d compared with those in untreated cells..
- Together, these analyses demonstrate that pathways re- lated to cell junctions (focal adhesion, ECM – receptor interaction, cytokine-cytokine receptor interaction, and CAMs), and PPAR might form networks with pathways related to lipid metabolism to influence the AF deposition in male chickens after caponization (Fig.
- In conclusion, our study hypothesized that reduced testos- terone levels after caponization accelerates AF deposition by changing the expression of related genes through cell junctions and PPAR pathways in the AF of male chickens..
- These findings provide a useful foundation for deciphering the molecular mechanisms underlying AF deposition in capons.
- Additional file 1: 872 DEGs between the capon and the control chicken groups.
- Additional file 2: The enriched the GO-terms in the BP category based on 872 DEGs.
- Additional file 3: The 86 DEGs related to lipid metabolism using GO- terms analysis based on a total of 872 DEGs 45 up-regulated and 41 down-regulated.
- AF: Abdominal fat.
- The data sets supporting the conclusions of this article are included in the article and its additional files..
- JW and GZ contributed to the design of the study.
- The control of the false discovery rate in multiple testing under dependency.
- Analysis of relative gene expression data using real-time quantitative PCR and the 2 −ΔΔ C T method.
- Effects of caponization and ovariectomy on objective indices related to meat quality in chickens.
- Association of the ADRB3, FABP3, LIPE, and LPL gene polymorphisms with pig intramuscular fat content and fatty acid composition.
- A high fat diet enhances the sensitivity of chick adipose tissue to the effects of centrally injected neuropeptide Y on gene expression of adipogenesis-associated factors.
- Adipocyte fatty acid-binding protein: an important gene related to lipid metabolism in chickenadipocytes.
- Identifying genes involved in the variability of genetic fatness in the growing chicken.
- Zinc mediates the SREBP-SCD axis to regulate lipid metabolism in Caenorhabditis elegans.
- Fatty acid composition of chicken breast meat is dependent on genotype-related variation of FADS1 and FADS2 gene expression and desaturating activity..
- Effects of caponization on growth, carcass, and meat characteristics and the mRNA expression of genes related to lipid metabolism in roosters of a Chinese indigenous breed

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