Ayuso M, Fernández A, Isabel B, Rey A, Benítez R, Daza A, López-Bote C J, Óvilo C
J Anim Sci. 2015 Jun;93(6):2730-44. doi: 10.2527/jas.2014-8573.
Vitamin A is a key regulator of gene expression, influencing adipogenesis and lipid metabolism in animal tissues. This experiment was conducted to assess the effect of dietary vitamin A level and administration time on productive traits, intramuscular fat (IMF) content in ham muscles, tissue fatty acid composition, and expression of a panel of adipogenic and lipogenic candidate genes in Iberian pigs. Sixty piglets of 16.3 kg (SD = 2.5 kg) live weight (LW) were either fed a vitamin A-enriched diet (10,000 IU vitamin A/kg; CONTROL, n = 20) or a diet without supplemented vitamin A, applied from 16.3 kg (SD = 2.5 kg; early restriction group, ER, n = 20) or from an average weight of 35.8 kg (SD = 3.1 kg; late restriction group, LR, n = 20). Two slaughters were performed when pigs reached the averaged weights of 101.4 (SD = 4.1 kg) and 157.9 kg LW (SD = 7 kg) and samples from liver, heart, and backfat were obtained in both sacrifice times. In addition, ham subcutaneous fat and Semimembranosus (SM) and Biceps Femoris (BF) muscles were sampled at the last sacrifice. Dietary vitamin A level produced no effect on carcass traits in any of the harvests, while a small effect was observed on fatty acid composition in backfat at 101.4 kg LW. However, at 157.9 kg LW, the ER and LR groups showed higher MUFA content and lower SFA content in backfat, ham fat, and IMF (P < 0.01). In IMF, a decrease in n-6/n-3 PUFA ratio was observed in the restricted groups (P < 0.005). Intramuscular fat content in SM muscle was greater (P < 0.05) in the ER group than in the CONTROL and LR groups, while no difference was detected in BF muscle. Little effect of dietary vitamin A was observed in liver. Regarding changes in gene expression, ACSL4, CEBPB, and IGF1 genes were upregulated (P < 0.0001, P < 0.0001, and P < 0.05, respectively) in the ER group in hepatic tissue, whereas CRABPII and SCD genes were upregulated (P < 0.05) in the same group in adipose tissue. On the other hand, was downregulated ( < 0.05) in the ER group in adipose tissue. Results found in this experiment show that long-term restriction of dietary vitamin A has a positive effect on nutritional and sensorial parameters of ham meat. Moreover, gene expression results were consistent with the vitamin A transcriptional regulation of adipogenesis and lipogenesis and with the changes observed in meat and fat composition.
维生素A是基因表达的关键调节因子，影响动物组织中的脂肪生成和脂质代谢。本实验旨在评估日粮维生素A水平和添加时间对伊比利亚猪生产性能、火腿肌肉中肌内脂肪（IMF）含量、组织脂肪酸组成以及一组脂肪生成和脂质生成候选基因表达的影响。选取60头体重16.3 kg（标准差 = 2.5 kg）的仔猪，分别饲喂富含维生素A的日粮（10,000 IU维生素A/kg；对照组，n = 20）或不添加维生素A的日粮，从16.3 kg（标准差 = 2.5 kg；早期限制组，ER，n = 20）或平均体重35.8 kg（标准差 = 3.1 kg；晚期限制组，LR，n = 20）开始饲喂。当猪达到平均体重101.4（标准差 = 4.1 kg）和157.9 kg体重（标准差 = 7 kg）时进行两次屠宰，在两个屠宰时间均采集肝脏、心脏和背膘样本。此外，在最后一次屠宰时采集火腿皮下脂肪以及半膜肌（SM）和股二头肌（BF）肌肉样本。日粮维生素A水平对任何一次屠宰时的胴体性状均无影响，而在体重101.4 kg时，观察到对背膘脂肪酸组成有轻微影响。然而，在体重157.9 kg时，ER组和LR组的背膘、火腿脂肪和IMF中MUFA含量较高，SFA含量较低（P < 0.01）。在IMF中，限制组的n-6/n-3多不饱和脂肪酸（PUFA）比值降低（P < 0.005）。ER组SM肌肉中的肌内脂肪含量高于对照组和LR组（P < 0.05），而BF肌肉中未检测到差异。日粮维生素A对肝脏的影响较小。关于基因表达的变化，ER组肝脏组织中ACSL4、CEBPB和IGF1基因上调（分别为P < 0.0001、P < 0.0001和P < 0.05），而同一组脂肪组织中CRABPII和SCD基因上调（P < 0.05）。另一方面，ER组脂肪组织中的 下调（< 0.05）。本实验结果表明，长期限制日粮维生素A对火腿肉的营养和感官参数有积极影响。此外，基因表达结果与维生素A对脂肪生成和脂质生成的转录调控以及肉和脂肪组成的变化一致。
