Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, and Beijing Institute of Heart, Lung and Blood Vessel Diseases, Beijing 100029, China.
Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China; Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA.
Chin Med J (Engl). 2018 Mar 5;131(5):532-538. doi: 10.4103/0366-6999.226065.
Chronic kidney disease (CKD) is closely related to the cardiovascular events in vascular calcification (VC). However, little has known about the characteristics of kidney injury caused by VC. Fibroblast growth factor 21 (FGF21) is an endocrine factor, which takes part in various metabolic actions with the potential to alleviate metabolic disorder diseases. Even FGF21 has been regarded as a biomarker in CKD, the role of FGF21 in CKD remains unclear. Therefore, in this study, we evaluate the FGF21 on the kidney injury in VC rats.
The male Sprague-Dawley rats were divided into three groups: (1) control group, (2) Vitamin D3 plus nicotine (VDN)-induced VC group, (3) FGF21-treated VDN group. After 4 weeks, the rats were killed and the blood was collected for serum creatinine, urea nitrogen, calcium, and phosphate measurement. Moreover, the renal tissues were homogenized for alkaline phosphatases (ALPs) activity and calcium content. The levels of FGF21 protein were measured by radioimmunoassay. The levels of β-Klotho and FGF receptor 1 (FGFR1) protein were measured by enzyme-linked immunosorbent assay (ELISA). The structural damage and calcifications in aortas were stained by Alizarin-red S. Moreover, the structure of kidney was observed by hematoxylin and eosin staining.
The renal function impairment caused by VDN modeling was ameliorated by FGF21 treatment, inhibited the elevated serum creatinine and urea level by 20.5% (34.750 ± 4.334 μmol/L vs. 27.630 ± 2.387 μmol/L) and 4.0% (7.038 ± 0.590 mmol/L vs. 6.763 ± 0.374 mmol/L; P < 0.01), respectively, together with the structural damages of glomerular atrophy and renal interstitial fibrosis. FGF21 treatment downregulated the ALP activity, calcium content in the kidney of VC rats by 42.1% (P < 0.01) and 11.7% (P < 0.05) as well as ameliorated the aortic injury and calcification as compared with VDN treatment alone group, indicating an ameliorative effect on VC. ELISA assays showed that the expression of β-Klotho, a component of FGF21 receptor system, was increased in VDN-treated VC rats by 37.4% (6.588 ± 0.957 pg/mg vs. 9.054 ± 0.963 pg/mg; P < 0.01), indicating an FGF21-resistant state. Moreover, FGF21 treatment downregulated the level of β-Klotho in renal tissue by 16.7% (9.054 ± 0.963 pg/mg vs. 7.544 ± 1.362 pg/mg; P < 0.05). However, the level of FGFR1, the receptor of FGF21, kept unchanged under VDN and VDN plus FGF21 administration (0.191 ± 0.0376 ng/mg vs. 0.189 ± 0.032 ng/mg vs. 0.181 ± 0.034 ng/mg; P > 0.05).
In the present study, FGF21 was observed to ameliorate the kidney injury in VDN-induced VC rats. FGF21 might be a potential therapeutic factor in CKD by cutting off the vicious circle between VC and kidney injury.
慢性肾脏病（CKD）与血管钙化（VC）中的心血管事件密切相关。然而，人们对 VC 引起的肾脏损伤的特征知之甚少。成纤维细胞生长因子 21（FGF21）是一种内分泌因子，它参与各种代谢作用，具有缓解代谢紊乱疾病的潜力。即使 FGF21 已被视为 CKD 的生物标志物，但其在 CKD 中的作用仍不清楚。因此，在这项研究中，我们评估了 FGF21 在 VC 大鼠肾脏损伤中的作用。
雄性 Sprague-Dawley 大鼠分为三组：（1）对照组，（2）维生素 D3 加尼古丁（VDN）诱导的 VC 组，（3）FGF21 治疗的 VDN 组。4 周后，处死大鼠并采集血清肌酐、尿素氮、钙和磷进行测量。此外，还将肾组织匀浆用于碱性磷酸酶（ALPs）活性和钙含量的测定。采用放射免疫法测定 FGF21 蛋白水平。采用酶联免疫吸附试验（ELISA）测定β-Klotho 和 FGF 受体 1（FGFR1）蛋白水平。采用茜素红 S 染色主动脉的结构损伤和钙化。此外，通过苏木精和伊红染色观察肾脏的结构。
VDN 建模引起的肾功能损害通过 FGF21 治疗得到改善，抑制了血清肌酐和尿素水平的升高，分别降低了 20.5%（34.750±4.334 μmol/L 比 27.630±2.387 μmol/L）和 4.0%（7.038±0.590 mmol/L 比 6.763±0.374 mmol/L；P<0.01），同时改善了肾小球萎缩和肾间质纤维化的结构损伤。FGF21 治疗使 VC 大鼠的 ALP 活性和肾脏钙含量分别降低了 42.1%（P<0.01）和 11.7%（P<0.05），并改善了主动脉损伤和钙化，与 VDN 单独治疗组相比具有改善 VC 的作用。ELISA 检测显示，VDN 处理的 VC 大鼠中 FGF21 受体系统的组成部分β-Klotho 的表达增加了 37.4%（6.588±0.957 pg/mg 比 9.054±0.963 pg/mg；P<0.01），表明存在 FGF21 抵抗状态。此外，FGF21 治疗使肾组织中β-Klotho 水平降低了 16.7%（9.054±0.963 pg/mg 比 7.544±1.362 pg/mg；P<0.05）。然而，在 VDN 和 VDN 加 FGF21 给药下，FGFR1 的水平，即 FGF21 的受体，保持不变（0.191±0.0376 ng/mg 比 0.189±0.032 ng/mg 比 0.181±0.034 ng/mg；P>0.05）。
本研究观察到 FGF21 可改善 VDN 诱导的 VC 大鼠的肾脏损伤。FGF21 可能通过阻断 VC 与肾脏损伤之间的恶性循环，成为 CKD 的潜在治疗因子。
