College of Animal Science, Jilin University, Changchun, Jilin, 130062, P.R. China.
Institute of Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology (FBN), 18196, Dummerstorf, Germany.
Sci Rep. 2019 May 30;9(1):8056. doi: 10.1038/s41598-019-44509-4.
Retinol binding protein 4 (RBP4) facilitates the transport of retinol in the body but is also an adipokine and fatty acid transporter. Our study was aimed at investigating the associations between RBP4 abundance and fat deposition in cattle. Blood samples of 246 crossbred bulls were taken at 8 months of age and at slaughter at 18 months of age for the determination of RBP4, hormone levels, and fatty acid composition. Significant correlations between plasma RBP4 abundance at 8 months of age and carcass traits at 18 months of age were detected (e.g., r = 0.3; P < 0.001 to carcass fat). Furthermore, RBP4 abundances in the plasma and subcutaneous fat were higher (P < 0.05) in bulls with increased fat deposition, whereas the liver RBP4 expression was not (P > 0.05). Retinol binding protein 4 was immunohistochemically localized in or close to adipocytes within muscle and adipose tissue and in liver stellate cells but not in hepatocytes. Overall, our results indicate that increased RBP4 levels were associated with increased fat deposition and altered fatty acid composition, but not with altered glucose tolerance, in crossbred bulls. Moreover, our results suggest that adipose-tissue-derived RBP4 may contribute to the circulating RBP4 level.
视黄醇结合蛋白 4（RBP4）有助于视黄醇在体内的运输，但它也是一种脂肪因子和脂肪酸转运蛋白。我们的研究旨在探讨 RBP4 丰度与牛体脂肪沉积的关系。在 8 月龄和 18 月龄时，采集了 246 头杂交公牛的血液样本，用于测定 RBP4、激素水平和脂肪酸组成。在 8 月龄时，血浆 RBP4 丰度与 18 月龄时的胴体性状之间存在显著相关性（例如，r=0.3；P<0.001 与胴体脂肪）。此外，在脂肪沉积增加的公牛中，血浆和皮下脂肪中的 RBP4 丰度较高（P<0.05），而肝脏 RBP4 表达则没有（P>0.05）。免疫组织化学定位显示，RBP4 存在于肌肉和脂肪组织内的脂肪细胞或其附近，以及肝星状细胞内，但不存在于肝细胞内。总的来说，我们的结果表明，在杂交公牛中，RBP4 水平的升高与脂肪沉积的增加和脂肪酸组成的改变有关，但与葡萄糖耐量的改变无关。此外，我们的结果表明，脂肪组织来源的 RBP4 可能有助于循环 RBP4 水平的升高。
