Fetal programming and molecular characterization of the skeletal muscle development in ruminants
Authors:   , Costa Thaís Correia 
Published: December 2022

The intrauterine conditions modulate the skeletal muscle development and establish, at least partially, the postnatal body composition, influencing the final meat quality. Therefore, it is important that the maternal plane of nutrition meets the requirements or maternal body reserves may be mobilized in order to allow an adequate fetal growth. Although, many studies have reported the effects of maternal nutrition on fetal skeletal muscle development, the insight into the molecular pathway’s regulation needs further investigation. Thus, the current study was developed based on three experiments. The aim of the first study was to investigate the impact of maternal protein restriction during mid-gestation on the skeletal muscle composition of the offspring. From day 100 to 200 of gestation, the cows were exposed to a diet containing a protein supplement (CON, n = 9) or not (RES, n = 9). Samples from calves’ Longissimus thoracis were taken at two time point postnatally, at 30d and 450d of age. RES diet triggered a decrease (P < 0.01) in muscle fiber number in both stages of evaluation, while collagen content was higher at 30d of age (P < 0.05). Although, no difference (P > 0.05) was observed in the expression of MHC2X at 450d, calves at 30d of age had greater expression of this gene. These results clearly shows that maternal protein restriction during a critical period of gestation permanently impact muscle fiber formation, alter the initial fiber metabolism and collagen accumulation. However, an adequate postnatal environment may contribute to muscle fiber type switching. The second and third studies were developed considering the same treatments and experimental units aiming to elucidate the effects of maternal feed restriction during different stages (first or last half) of gestation on the transcriptome and proteome profile in the skeletal muscle of the newborn goat. Fourteen pregnant goats, gestating males were assigned into one of the experimental treatments: animals fed at 50% maintenance requirements from 8-84d of gestation and then fed at 100% of maintenance requirement from day 85 of gestation to parturition (RM, n = 6), or fed at 100% of maintenance requirement from 8–84 d of gestation and then fed at 50% of maintenance requirement from day 85 of gestation to parturition (MR, n = 8). The offspring (n = 14) were slaughter at birth, the Longissimus thoracis muscle was sampled and the transcriptome and proteome profiles were evaluated. Transcriptome analysis showed a total of 20,359 transcripts, where 766 and 1146 were found as exclusively expressed in treatments RM and MR, respectively. From the 66 differentially expressed (DE) genes (FDR < 0.05), 6 and 60 genes were up and downregulated in treatment RM compared to MR, respectively. The upregulation of genes in treatment RM are involved with the maintenance of satellite cells, possibly due to the impairment in myoblast differentiation during the prenatal period. Moreover, the upregulation of genes related to low marbled carcasses, may conduct the reduction in the deposition of intramuscular fat in the offspring. Maternal feeding restriction during the last half of gestation (MR) provided an upregulation of genes related with the balance between glucose anabolism and catabolism, in addition to an activation of protective mechanisms against the excessive cell oxidative stress. Proteomic analysis identified a total of 415 sarcoplasmic proteins, and after filtering, 181 and 46 proteins were found exclusively in treatments RM and MR, respectively. From the 159 proteins present in both treatments, only 13 were deemed differentially abundant proteins (DAPs) considering FDR < 0.05. Through the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, it was identified enriched biological processes (BP) and signaling pathways (SP) related with the energy-investment phase of glycolysis, in addition to the increase in the usage of glycogen and fatty acids storages in RM compared to MR. While the proteins found in MR treatment showed enriched BP and SP associated with the energy-generation phase of glycolysis, and an enhancement in the biosynthesis of glutamine. Altogether the results generated by transcriptome and proteome analyses suggest that maternal feed restriction alter the abundance of this molecules, mainly altering the skeletal muscle composition and the overall energy metabolism of the newborns’ skeletal muscle. Keywords: Beef cattle. Caprine. Developmental programming. Proteome. Skeletal Muscle. Transcriptome.