Promising Role of Growth Hormone-Boosting Peptide in Regulating the Expression of Muscle-Specific Genes and Related MicroRNAs in Broiler Chickens

SIMPLE SUMMARY: In chickens, breast muscle is a key contributor to meat yield. Skeletal muscle development is a complex process regulated by many genes, transcription factors, and miRNA through different muscle signaling pathways. The latter are activated by synthetic growth hormone-boosting peptides (GHBP) that mimic the effects of endogenous growth factors, mainly insulin-like growth factor-1 (IGF-1)/mammalian target of rapamycin (mTOR), and modulate myostatin gene expression. The molecular mechanisms underlying chicken breast muscle development in relation to GHBP are still unclear. In the current study, the role of GHBP in a chicken’s growth rate, skeletal muscle development-related genes and myomiRs, serum bio-chemical parameters, and myofiber characteristics post-hatching was evaluated. Using of GHBP at a level of 200 μg/kg positively regulated gene expression related to muscle growth and muscle-specific myomiRs. This was evidenced by upregulation of IGF-1, mTOR, myoD and myogenin genes, and miR-27b and miR-499 and downregulation of myostatin, Pax-3 and -7 genes and miR-1a, miR-133a, miR-133b, and miR-206 compared to the control group. Therefore, administration of GHBP at the level of 200 μg/kg to broiler chicks can accelerate their growth by enhancing skeletal muscle development via controlling the transcription of breast muscle-related genes and associated myomiRs. ABSTRACT: Appropriate skeletal muscle development in poultry is positively related to increasing its meat production. Synthetic peptides with growth hormone-boosting properties can intensify the effects of endogenous growth hormones. However, their effects on the mRNA and miRNA expression profiles that control muscle development post-hatching in broiler chicks is unclear. Thus, we evaluated the possible effects of synthetic growth hormone-boosting peptide (GHBP) inclusion on a chicken’s growth rate, skeletal muscle development-related genes and myomiRs, serum biochemical parameters, and myofiber characteristics. A total of 400 one-day-old broiler chicks were divided into four groups supplied with GHBP at the levels of 0, 100, 200 and 300 μg/kg for 7 days post-hatching. The results showed that the highest levels of serum IGF-1 and GH at d 20 and d 38 post-hatching were found in the 200 μg/kg GHBP group. Targeted gene expression analysis in skeletal muscle revealed that the GHBP effect was more prominent at d 20 post-hatching. The maximum muscle development in the 200 μg/kg GHBP group was fostered by the upregulation of IGF-1, mTOR, myoD, and myogenin and the downregulation of myostatin and the Pax-3 and -7 genes compared to the control group. In parallel, muscle-specific myomiR analysis described upregulation of miR-27b and miR-499 and down-regulation of miR-1a, miR-133a, miR-133b, and miR-206 in both the 200 and 300 μg/kg GHBP groups. This was reflected in the weight gain of birds, which was increased by 17.3 and 11.2% in the 200 and 300 μg/kg GHBP groups, respectively, when compared with the control group. Moreover, the maximum improvement in the feed conversion ratio was achieved in the 200 μg/kg GHBP group. The myogenic effects of GHBP were also confirmed via studying myofiber characteristics, wherein the largest myofiber sizes and areas were achieved in the 200 μg/kg GHBP group. Overall, our findings indicated that administration of 200 μg/kg GHBP for broiler chicks could accelerate their muscle development by positively regulating muscle-specific mRNA and myomiR expression and reinforcing myofiber growth.