Abstract
Simple SummaryIn the U.S., approximately 90% of all cattle on feed receive an anabolic implant at some point during production. Despite the widespread use, how they operate to increase growth of cattle remains unknown. Polyamines are amino acid derivatives, which are potent growth stimulants, produced through the polyamine biosynthetic pathway. Emerging research suggests that the hormones in anabolic implants interact with the polyamine biosynthetic pathway. The purpose of this research was to investigate the effects of steroidal hormones, polyamine precursors, and polyamines on mRNA abundance of bovine satellite cells, muscle precursor cells. The results from this study suggest that polyamine precursors and polyamines alter transcription factors involved in induction of differentiation of bovine satellite cells and the polyamine biosynthetic pathway, while the hormones in anabolic implants alter genes involved in the polyamine biosynthetic pathway. These results mean that polyamines may impact differentiation of bovine satellite cells, ultimately affecting growth of cattle.Emerging research suggests that hormones found in anabolic implants interact with polyamine biosynthesis. The objective of this study was to determine the effects of steroidal hormones, polyamines and polyamine precursors on bovine satellite cell (BSC) differentiation and polyamine biosynthesis temporally. Primary BSCs were induced to differentiate in 3% horse serum (CON) and treated with 10 nM trenbolone acetate (TBA), 10 nM estradiol (E2), 10 nM TBA and 10 nM E2, 10 mM methionine, 8 mM ornithine, 2 mM putrescine, 1.5 mM spermidine, or 0.5 mM spermine. Total mRNA was isolated 0, 2, 4, 8, 12, 24, and 48 h post-treatment. Abundance of mRNA for genes associated with induction of BSC differentiation: paired box transcription factor 7, myogenic factor 5, and myogenic differentiation factor 1 and genes in the polyamine biosynthesis pathway: ornithine decarboxylase and S-adenosylmethionine—were analyzed. Overall, steroidal hormones did not impact (p > 0.05) mRNA abundance of genes involved in BSC differentiation, but did alter (p = 0.04) abundance of genes involved in polyamine biosynthesis. Polyamine precursors influenced (p < 0.05) mRNA of genes involved in BSC differentiation. These results indicate that polyamine precursors and polyamines impact BSC differentiation and abundance of mRNA involved in polyamine biosynthesis, while steroidal hormones altered the mRNA involved in polyamine biosynthesis.
Highlights
For the livestock industry, skeletal muscle growth is extremely important as, through a series of changes, it becomes meat [1,2]
No effects (p > 0.05) of steroidal hormone or steroidal hormone*time were observed relative to abundance of PAX7, MYF5, or MYOD mRNA at 2, 4, 8, 12, 24, or 48 h posttreatment (Figure 2)
Myogenin was not expressed by any of the cultures at any time point assessed. These data demonstrate that the steroidal hormones found in anabolic implants increase abundance of MYF5 at 4 and 8 h, respectively, post-induction to differentiate
Summary
Skeletal muscle growth is extremely important as, through a series of changes, it becomes meat [1,2]. There is a positive correlation between environmental sustainability and improved productivity [3]. Understanding mechanisms that improve skeletal muscle growth is necessary to produce cattle that are more environmentally sustainable, while decreasing costs to producers. Mammalian muscle fiber number is primarily fixed at birth, making hypertrophy of existing fibers the primary mechanism for postnatal growth [4,5,6]. Hypertrophy eventually requires additional nuclei from satellite cells for muscle growth [4,5,6,7]. Satellite cells are muscle precursor cells that proliferate, differentiate and fuse into myotubes or with existing muscle fibers to support hypertrophy [5]. Differentiation and phenotypic maturation are necessary for satellite cells to fuse [8]. Markers of differentiation in skeletal muscle include increased expression of myogenic differentiation factor 1 (MyoD), myogenic factor 5 (Myf5), and myogenin, and decreased expression of paired box transcription factor 7 (Pax7) [6,9,10]
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