This study investigated whether vitamin A (VA) administration during the neonatal stage could increase the number of intramuscular adipocytes in Hu sheep by promoting vascularity. A total of 56 newborn male Hu sheep were divided into four groups and received intramuscular injections of either 0, 7500 IU retinoic acid (RA), 7500 IU VA, or a combination of 7500 IU VA and 5 mg SU5416 (an angiogenic inhibitor), at 1, 7, 14, and 21 days of age. At 15 days of age, 6 sheep from each group were randomly selected and sacrificed for intramuscular adipogenic capacity analysis. The remaining 8 sheep in each group were raised until they were 8 months old. VA-treated sheep exhibited an increase in preadipocytes, elevated expression of adipogenic genes (CCAAT enhancer binding protein alpha [CEBPA] and CCAAT enhancer binding protein beta [CEBPB]) and angiogenic genes (vascular endothelial growth factor A [VEGFA]), and stromal vascular fraction cells in the longissimus dorsi (LD) muscle with enhanced adipogenic capacity (P ＜ 0.05). These effects were entirely negated by SU5416. Upon slaughter, VA increased final weight, carcass weight, and average daily gain (P ＜ 0.05) but did not affect feed intake at 21 to 32 weeks (P = 0.824). VA increased the number of intramuscular adipocytes in the LD and semitendinosus (ST) muscle (P ＜ 0.05) without changing the adipocyte number of the omentum, perirenal and subcutaneous fats (P ＞ 0.05). VA injections also increased intramuscular triglyceride (TG) content (P = 0.016) without changing the omentum fat weight or subcutaneous fat thickness (P ＞ 0.05), but it did increase the perirenal fat weight (P = 0.011). Consistently, SU5416 mitigated the effects of VA on intramuscular TG content and adipocyte count, correlating with a decrease in vascularity. In contrast, RA injections didn't affect the intramuscular fat (P = 0.744) but reduced the TG content of the omentum and perirenal fat (P ＜ 0.05). In conclusion, intramuscular injections of VA but not RA at the neonatal stage improved the growth performance of Hu sheep, increasing the number of intramuscular adipocytes and marbling by promoting angiogenesis.

中文翻译：

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新生儿维生素 A 但不给予视黄酸通过促进血管形成增加绵羊肌内脂肪细胞的数量


本研究调查了新生儿期维生素 A （VA） 给药是否可以通过促进血管分布来增加胡羊肌内脂肪细胞的数量。将 56 只新生雄性胡羊分为 4 组，在 1、7、14 和 21 日龄时接受 0， 7500 IU 视黄酸 （RA）、7500 IU VA 或 7500 IU VA 和 5 mg SU5416 （血管生成抑制剂） 的组合肌肉注射。在 15 日龄时，从每组中随机选择 6 只绵羊并处死用于肌内成脂能力分析。每组其余 8 只羊被饲养到 8 个月大。VA 处理的绵羊表现出前脂肪细胞增加，成脂基因（CCAAT 增强子结合蛋白 α [CEBPA] 和 CCAAT 增强子结合蛋白 β [CEBPB]）和血管生成基因（血管内皮生长因子 A [VEGFA]）和基质血管部分细胞的表达升高，背最长肌 （LD） 肌肉中的基质血管部分细胞具有增强的成脂能力 （P < 0.05）。这些影响被 SU5416 完全抵消了。屠宰后，VA 增加了最终体重、胴体重量和平均日增重 （P < 0.05），但不影响 21 至 32 周的采食量 （P = 0.824）。VA 增加了 LD 和半腱肌 （ST） 肌肉中肌内脂肪细胞的数量 （P < 0.05），而没有改变网膜、肾周和皮下脂肪的脂肪细胞数量 （P > 0.05）。VA 注射还增加了肌内甘油三酯 （TG） 含量 （P = 0.016），而没有改变网膜脂肪重量或皮下脂肪厚度 （P > 0.05），但它确实增加了肾周脂肪重量 （P = 0.011）。一致地，SU5416 减轻了 VA 对肌内 TG 含量和脂肪细胞计数的影响，与血管分布的减少相关。 相比之下，RA 注射不影响肌内脂肪 （P = 0.744），但降低了网膜和肾周脂肪的 TG 含量 （P < 0.05）。总之，新生儿期肌内注射 VA 而不注射 RA 改善了胡羊的生长性能，通过促进血管生成增加肌内脂肪细胞和大理石花纹的数量。