Résumé
Objective: To observe the impact of vascular calcification on kidney injury rats with the expressions of β-Klotho, fibroblast growth factor receptor 1 (FGFR1) in kidney tissue in order to find the predictor for early chronic kidney disease (CKD), to provide the prevention and investigation basis of vascular calcification and CKD. Methods: Vascular calcification model was induced by vitamin D3 and nicotine injection in experimental rats and the animals were divided into 2 groups: Normal control group and Calcification group. n=6 in each group. Serum levels of creatinine and urea nitrogen were examined by sarcosine oxidase method and UV-glutamate dehydrogenase method respectively; blood levels of calcium and phosphorus were detected by biochemistry method; kidney tissue alkaline phosphatases (ALP) activity was measured by ALP detection kit, protein expressions of β-Klotho and FGFR1 were assessed by ELISA.Results: Compared with Normal control group, Calcification group showed increased serum levels of creatinine (35.200±4.087) umol/L vs (26.000±5.0990) umol/L and urea nitrogen (6.900±0.623) mmol/L vs (5.400±0.803) mmol/L, both P<0.05; elevated kidney tissue ALP activity (60.510±31.090) U/g vs (26.590±8.664) U/g and β-Klotho protein expression (9.052±1.238) ng/mg vs (6.860±1.036) ng/mg, both P<0.05. Blood levels of calcium, phosphorus and kidney tissue FGFR1 protein content were similar between 2 groups. Conclusion: Large dose vitamin D3 and nicotine injection may induce vascular calcification and early CKD symptom in experimental rats; β-Klotho protein expression was significantly increased suggesting that β-Klotho had been involved in the early regulation of vascular calcification and it could be used for the early diagnosis of CKD at certain point.
Résumé
<p><b>OBJECTIVE</b>To observe the effect and mechanism of fibroblast growth factor 21 (FGF21) on rat vascular smooth muscle cells (VSMCs) calcification in vitro.</p><p><b>METHODS</b>VSMCs was treated with calcification medium containing calcium chloride and β-glycerophosphate to induce rat VSMCs calcification in vitro. VSMCs were divided into 5 groups: the control group (cultured in normal medium), the calcification group (incubated in calcified medium), the FGF21 group (cultured in calcified medium and FGF21), the PD166866 group (cultured in calcified medium and FGF21 and PD166866, inhibitor of fibroblast growth factor receptor-1 (FGFR1)), the GW9662 group (cultured in calcified medium and FGF21 and GW9662, inhibitor of peroxisome proliferators activated receptor-γ (PPAR-γ)). The calcification of VSMCs was detected by calcium content, alkaline phosphatase activity and alizarin red staining. The protein and mRNA expression of FGFR1, β-Klotho, osteocalcin and smooth muscle 22α (SM22α) were determined by western blot analysis and realtime-PCR, respectively.</p><p><b>RESULTS</b>(1) The mRNA (P < 0.01) and protein expressions of β-Klotho and FGFR1 were significantly downregulated in calcification group compared with control group (P < 0.05 or 0.01). (2) The protein levels and mRNA expression of calcium content, alkaline phosphatase activity and osteocalcin were significantly downregulated, while the protein levels and mRNA of SM22α were significantly increased in FGF21 group compared with calcification group (all P < 0.05). Moreover, alizarin red staining verified positive red nodules on calcified VSMCs was significantly reduced in FGF21 group than in calcification group. (3) Calcium content, alkaline phosphatase activity and alizarin red staining were similar between PD166866 group and calcification group (all P > 0.05). (4) Calcium content, alkaline phosphatase activity and alizarin red staining were similar between GW9662 group and calcification group (all P > 0.05).</p><p><b>CONCLUSION</b>The inhibition of VSMCs calcification by FGF21 is mediated by further downregulating FGFR1 and β-Klotho while activating PPAR-γ pathways.</p>