Objective To explore the expression and changes of serum irisin in adenine-induced chronic kidney disease (CKD) model, and the role of irisin and related pathway in CKD renal fibrosis. Methods Twenty male SD rats were randomly divided into a control group and a model group (CKD group) using a simple randomization method, with 10 rats in each group. At the end of the 2nd and 4th week, biochemical indicators, serum irisin and serum bone morphogenetic protein 7 (BMP7) levels, renal pathologic changes and interstitial fibrosis of renal tubules were measured in two groups of rats. The protein expression levels and messenger RNA (mRNA) expression levels of alpha-smooth muscle actin (α-SMA), collagen type I (Col-Ⅰ), BMP7, and Smad1 in rat kidney tissue were detected and compared. Results Compared with the control group at the end of the 2nd and 4th week, the CKD group showed that the serum creatinine (Scr), serum urea nitrogen (BUN), and 24-hour urinary protein level were increased (P<0.05), the protein expression levels and mRNA expression levels of α-SMA and Col-Ⅰ were increased (P<0.05), while the serum irisin and serum BMP7 were decreased (P<0.05), the protein expression levels and mRNA expression levels of BMP7 and Smad1 were reduced (P<0.05). Compared with the end of the 2nd week, the CKD group at the end of the 4th week showed that the serum Scr, serum BUN, and 24-hour urinary protein level were increased (P<0.05), the protein expression levels and mRNA expression levels of α-SMA and Col-Ⅰ were increased (P<0.05), while the serum irisin and serum BMP7 were decreased (P<0.05), the protein expression levels and mRNA expression levels of BMP7 and Smad1 were reduced (P<0.05). Compared to the control group, the renal tissue structure of the CKD group showed significant structural disorders and interstitial fibrosis of the renal tissue, which worsened over time. Serum irisin was negatively correlated with α- SMA and Col - Ⅰ (r=−0.917, −0.902, P<0.001) respectively, while serum irisin was positively correlated with serum BMP7 (r=0.842, P<0.001); Kidney tissue BMP7 was positively correlated with Smad1 (r=0.884, P<0.001). The cluster heat map showed that compared with the control group, BMP7 and recombinant fibronectin type Ⅲ domain containing were significantly decreased, α-SMA and Col-Ⅰ were significantly increased in CKD group; recombinant fibronectin type Ⅲ domain containing were positively correlated with BMP7, and negatively correlated with α-SMA and Col-Ⅰ. Conclusions irisin may be involved in the process of renal fibrosis in adenine-induced CKD via the BMP7/Smad1 axis. This will provide new ideas for the prevention and treatment of renal fibrosis.
Objective To observe the expression of hepcidin-ferroportin (FPN) pathway in adenine-induced chronic kidney disease (CKD) rat model and to explore the mechanism of its involvement in renal fibrosis in CKD. Methods A total of 20 6-week-old male SD rats without specific pathogen were selected. The rats were divided into control group and CKD group, with 10 rats in each group, using a simple random method. Rats were sacrificed at the end of the second and sixth weeks after modeling. The levels of serum creatinine (Scr), blood urea nitrogen (BUN) and 24 h urine protein quantification were measured. The pathological changes of rats were observed. The iron content of rat kidney tissue was detected by colorimetric method, and the level of serum hepcidin-25 was detected by enzyme linked immunosorbent assay method in both groups. Immunohistochemistry and reverse transcription-polymerase chain reaction were used to detect the renal protein and mRNA expression of α-smooth muscle actin (α-SMA), collagen type Ⅰ (Col-Ⅰ), FPN1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nuclear factor kappa-B (NF-κB) P65. Results Compared with the control group, the levels of Scr, BUN, and 24 h urine protein quantification were higher in the CKD group at the end of the second and sixth weeks of modeling (P<0.05). The results of renal tissue staining showed that the CKD group had obvious glomerular structural disorders, tubular dilation, and interstitial collagen fiber deposition. Compared with the control group, the serum hepcidin-25 level and the iron content of kidney tissues in the CKD group were significantly higher, and correlation analysis suggested that both were positively correlated with the renal function of rats (P<0.05). Compared with the control group, the protein and mRNA expression levels of α-SMA, Col-Ⅰ, HAMP, IL-6, TNF-α, NF-κB P65 were higher (P<0.05), while FPN1 expression was lower in CKD group at the end of the second and sixth weeks of modeling (P<0.05). Correlation analysis results showed that HAMP mRNA expression was positively correlated with α-SMA, Col-Ⅰ, IL-6, TNF-α, and NF-κB p65 (P<0.001), which was negatively correlated with FPN1 mRNA expression (P<0.001). FPN1 mRNA expression was significantly negatively correlated with α-SMA, Col-Ⅰ (P<0.001). Conclusions Ferroptosis may be present in the adenine-induced rat model of CKD, and it may be involved in the process of renal fibrosis through the interaction of HAMP-FPN signaling pathway with the inflammatory response. Serum hepcidin-25 is expected to be a serological marker for the early diagnosis of CKD.