RESUMO
To explore the effects and underlying mechanism of vitamin A on beef marbling fat development, angus steers were injected vitamin A at birth and 1 month of age and in vitro experiments were performed to investigate the effects of retinoic acid (RA) on angiogenesis and adipogenesis of intramuscular stromal vascular (SVF) cells. Results showed that vitamin A administration increased the intramuscular PDGFRα+ adipose progenitors, improved adipogenic potential of intramuscular SVF cells and dramatically upregulated VEGFA. At slaughter, vitamin A increased intramuscular triacylglycerols by 45% without affecting overall fatness. In a 3D culture system, RA promoted capillary sprout development and promoted the subsequent adipogenesis of intramuscular SVF cells by activating VEGFA/VEGFR2 signaling. However, during terminal adipogenesis, RA downregulated PPARγ, C/EBPα and inhibited lipid accumulation. In conclusion, vitamin A/RA upregulate VEGFA and stimulate intramuscular vascular capillary development, which increases intramuscular adipose progenitors and contributes to adipocyte formation. When administrated at neonatal stage, vitamin A promotes beef marbling development without affecting overall fatness.