Peng Dong Qiao, Smith Stephen B, Lee Hong Gu
Department of Animal Science and Technology, Sanghuh College of Life Sciences, Konkuk University, Seoul, 05029, South Korea.
Department of Animal Science, Texas A&M University, College Station, TX, 77843, USA.
J Anim Sci Biotechnol. 2021 Mar 5;12(1):34. doi: 10.1186/s40104-021-00558-2.
During growth in cattle, the development of intramuscular adipose tissue and muscle is dependent upon cell hyperplasia (increased number of adipocytes) and hypertrophy (increased size of adipocytes). Based on the results of previous studies, other adipose tissue depots (e.g., perirenal and subcutaneous) develop from the fetal stage primarily as brown adipose tissue. The hyperplastic stage of intramuscular adipose is considered to develop from late pregnancy, but there is no evidence indicating that intramuscular adipose tissue develops initially as brown adipose tissue. Hyperplastic growth of intramuscular adipose continues well into postweaning and is dependent on the timing of the transition to grain-based diets; thereafter, the late-stage development of intramuscular adipose tissue is dominated by hypertrophy. For muscle development, hyperplasia of myoblasts lasts from early (following development of somites in the embryo) to middle pregnancy, after which growth of muscle is the result of hypertrophy of myofibers. Vitamin A is a fat-soluble compound that is required for the normal immunologic function, vision, cellular proliferation, and differentiation. Here we review the roles of vitamin A in intramuscular adipose tissue and muscle development in cattle. Vitamin A regulates both hyperplasia and hypertrophy in in vitro experiments. Vitamin A supplementation at the early stage and restriction at fattening stage generate opposite effects in the beef cattle. Appropriate vitamin A supplementation and restriction strategy increase intramuscular adipose tissue development (i.e., marbling or intramuscular fat) in some in vivo trials. Besides, hyperplasia and hypertrophy of myoblasts/myotubes were affected by vitamin A treatment in in vitro trials. Additionally, some studies reported an interaction between the alcohol dehydrogenase-1C (ADH1C) genotype and vitamin A feed restriction for the development of marbling and/or intramuscular adipose tissue, which was dependent on the timing and level of vitamin A restriction. Therefore, the feed strategy of vitamin A has the visible impact on the marbling and muscle development in the cattle, which will be helpful to promote the quality of the beef.
在牛的生长过程中，肌内脂肪组织和肌肉的发育取决于细胞增生（脂肪细胞数量增加）和肥大（脂肪细胞大小增加）。根据先前的研究结果，其他脂肪组织库（如肾周和皮下脂肪组织）从胎儿期开始主要发育为棕色脂肪组织。肌内脂肪的增生阶段被认为从妊娠后期开始，但没有证据表明肌内脂肪组织最初是作为棕色脂肪组织发育的。肌内脂肪的增生性生长在断奶后仍会持续很长时间，并且取决于向谷物型日粮过渡的时间；此后，肌内脂肪组织的后期发育以肥大为主。对于肌肉发育，成肌细胞的增生从胚胎期体节发育后的早期持续到妊娠中期，之后肌肉的生长是肌纤维肥大的结果。维生素A是一种脂溶性化合物，对正常免疫功能、视力、细胞增殖和分化是必需的。在此，我们综述维生素A在牛肌内脂肪组织和肌肉发育中的作用。在体外实验中，维生素A调节增生和肥大。在肉牛中，早期补充维生素A和育肥期限制维生素A会产生相反的效果。在一些体内试验中，适当的维生素A补充和限制策略可增加肌内脂肪组织的发育（即大理石花纹或肌内脂肪）。此外，在体外试验中，维生素A处理会影响成肌细胞/肌管的增生和肥大。另外，一些研究报道了乙醇脱氢酶-1C（ADH1C）基因型与维生素A饲料限制对大理石花纹和/或肌内脂肪组织发育的相互作用，这取决于维生素A限制的时间和水平。因此，维生素A的饲料策略对牛的大理石花纹和肌肉发育有明显影响，这将有助于提高牛肉品质。
