Effects of testis testosterone deficiency on gene expression in the adrenal gland and skeletal muscle of ducks.

Testosterone has an anabolic effect on skeletal muscle. The testes produce most of the testosterone in vivo , while the adrenal glands contribute smaller amounts. When testis testosterone is deficient the adrenal gland increases steroid hormone synthesis, which is referred to as compensatory testicular adaptation (CTA).To reveal the effects of testis testosterone deficiency on adrenal steroid hormones synthesis and skeletal muscle development, gene expression related to adrenal steroid hormones synthesis and skeletal muscle development were determined by RNA-seq. The results showed that castrating male ducks had significant effects on their body weight but no significant impact on cross-sectional area (CSA) or density of pectoral muscle fibres. In skeletal muscle protein metabolism, expression levels of the catabolic gene atrogin1/MAFbx and the anabolic gene eEF2 were significantly higher, with concomitant increases after castration. The adrenal glands' alteration of the steroid hormone 11β-hydroxylase (CYP11B1) was significantly lower following castration. Expression pattern analysis showed that the adrenal glands' glucocorticoid receptor (NR3C1/GR) had a potential regulatory relationship with the skeletal muscle-related genes (Pax7, mTOR, FBXO32, FOXO3, and FOXO4). The data showed that castration affected muscle protein metabolism, adrenal steroid and testosterone synthesis. In addition, it was speculated that, after castration, steroid hormones produced by the adrenal gland could have a compensatory effect, which might mediate the changes in skeletal muscle protein metabolism and development.