Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506, USA.
J Anim Sci. 2010 Jan;88(1):124-30. doi: 10.2527/jas.2009-2258. Epub 2009 Sep 25.
Angiopoietin-like protein 4 (ANGPTL4; also known as fasting-induced adipose factor) is a plasma protein that stimulates oxidation of fatty acids and inhibits fat accumulation. The gastrointestinal tract appears to play an important role in regulating plasma ANGPTL4 concentration in some situations and may be influenced by microbes within the gastrointestinal tract. Our aim was to determine which tissues express ANGPTL4 in the bovine. Rumen, omasum, abomasum, duodenum, jejunum, ileum, colon, pancreas, liver, and subcutaneous adipose tissue samples were collected postmortem from 2 steers. Abundance of ANGPTL4 messenger RNA was quantified by quantitative real-time PCR, and was most abundant in liver and adipose tissue (P < 0.05). We also detected ANGPTL4 messenger RNA throughout the gastrointestinal tract, although its abundance was approximately 10% of that found in liver and adipose tissue. Western blot analysis revealed that ANGPTL4 protein was most abundant in liver and adipose tissue (P < 0.05), but omasal, abomasal, and ileal samples contained at least 60% as much ANGPTL4 protein as the liver and adipose tissue samples, and the protein was detected in all tissues. Finally, cross-sections of the liver, pancreas, and rumen wall were used for indirect immunofluorescent detection of ANGPTL4. Despite the low abundance of ANGPTL4 measured by quantitative real-time PCR and Western blot in ruminal tissue, immunofluorescence demonstrated that expression of ANGPTL4 in ruminal epithelial cells was equivalent to or greater than that in liver hepatocytes. These findings indicate that, as in other species studied, liver and adipose tissue are key sources of ANGPTL4 in cattle. However, the protein was also highly abundant in ruminal epithelium, making it possible that commensal microbes may influence ANGPTL4 synthesis and secretion in the ruminant gastrointestinal tract.
血管生成素样蛋白 4（ANGPTL4；也称为禁食诱导脂肪因子）是一种血浆蛋白，可刺激脂肪酸的氧化并抑制脂肪堆积。在某些情况下，胃肠道似乎在调节血浆 ANGPTL4 浓度方面发挥着重要作用，并且可能受到胃肠道内微生物的影响。我们的目的是确定牛中哪些组织表达 ANGPTL4。从 2 头公牛死后采集瘤胃、网胃、瓣胃、十二指肠、空肠、回肠、结肠、胰腺、肝脏和皮下脂肪组织样本。通过定量实时 PCR 定量 ANGPTL4 信使 RNA 的丰度，其在肝脏和脂肪组织中最丰富（P <0.05）。我们还在整个胃肠道中检测到 ANGPTL4 信使 RNA，尽管其丰度约为肝脏和脂肪组织的 10%。Western blot 分析显示 ANGPTL4 蛋白在肝脏和脂肪组织中最丰富（P <0.05），但网胃、瓣胃和回肠样本中的 ANGPTL4 蛋白含量至少为肝脏和脂肪组织样本的 60%，并且在所有组织中都检测到该蛋白。最后，使用肝、胰腺和瘤胃壁的横截面进行 ANGPTL4 的间接免疫荧光检测。尽管瘤胃组织中通过定量实时 PCR 和 Western blot 测量的 ANGPTL4 丰度较低，但免疫荧光显示 ANGPTL4 在瘤胃上皮细胞中的表达与肝脏肝细胞中的表达相当或更高。这些发现表明，与在其他研究物种中一样，肝脏和脂肪组织是牛中 ANGPTL4 的主要来源。然而，该蛋白在瘤胃上皮细胞中也高度丰富，这使得共生微生物可能影响反刍动物胃肠道中 ANGPTL4 的合成和分泌。
