| Effects of Low Protein Diet Supplemented Withα-ketoacid on Renal Interstitial Fibrosis and EMT in Adenine-induced Chronic Renal Failure RatsBACKGROUND & OBJECTIVE Dietary protein restriction and supplemented with EAA-α-ketoacid have been considered as a strategy to slow renal disease progression. The renal interstitial fibrosis is closely related to the progressive lose of renal function. Epithelia- mesenchymal transition (EMT) is a major pathway leading to generation of the renal interstitial fibrosis. EMT is regulated by numerous growth factors and cytokines. Overexpression of transforming growth factor-β1(TGF-β1) plays an important role in the initiation and progression of tubulointersitial fibrosis. Vascular endothelial growth factor (VEGF) is a survival factor for tubular epithelial cells, and it is proven that VEGF is beneficial to inhibit EMT of renal tubular epithelia cells induced by TGFβ1. Up-regulated expression of thrombospondin- 1 (TSP- 1) activates latent TGFβ1, which is strongly associated with progression of renal disease. It is not clear whether the favorable effect of LPD+αKA on CRF is due to the inhibitory action of this diet on EMT. The present study aimed to evaluate the effects on the renal interstitial fibrosis and EMT of LPD supplemented with ketoacids in comparison with a conventional LPD in adenine induced CRF rat model.METHODS Forty-six male Wistar rats were divided into two parts: normal control rats (n= 10 ) and adenine-CRF rats(n=36), which were treated with 150mg/kg/day adenine intragastrically. After six weeks, adenine induced CRF rats were divided into three groups: a. NPD (contain 20% casein diet) group, n=12; b. LPD ( 6% casein diet) group, n=12; c.LPD+αKA(casein 5%+αKA 1%)group, n=12. All the rats were sacrificed at week 10, 14. Body weight, 24 hour urine protein excretion, hemoglobin, serum creatinine, BUN, calcium and phosphorus were measured. Masson stain of renal tissue was performed to grade the extent of renal interstitial fibrosis. Immunohistochemistry, RT-PCR and Westem blot methods were used to evaluate the extent of expressions of alpha smooth muscle actin (α-SMA), E-cadherin, TGFβ1, MCP-1, VEGF and TSP-1.RESULTS The BUN levels of LPD and LPD+αKA group were significantly lower than that in NPD group at week 10. The levels of serum creatinine, hemoglobin and body weight were not different between the three groups over time. Proteinuria in both LPD and LPD+αKA groups were lower significantly than in NPD group. Serum calcium levels of LPD and LPD+αKA groups were significantly higher than that in NPD group at week 14. The extent of renal fibrosis in LPD and LPD+αKA groups was reduced than in NPD group, LPD+αKA group was significant lower than LPD group(p＜0.05). Expressions ofα-SMA in LPD and LPD+αKA group were lower than that in NPD group. On the other hand, E-cadherin expression in LPD and LPD+αKA rats were significantly stronger than that in NPD rats, and that in LPD+αKA was more effective than LPD(LPD vs LPD+αKA p＜0.05). The expression of VEGF was reduced in NPD group compared with normal control, meanwhile the TSP-1 expression level was clearly increased at 10 week. The expression of VEGF in LPD+αKA group augmented than that in NPD or LPD groups, and the TSP-1 expression in the LPD+αKA group was lower than that in NPD or LPD groups at 10 week. Expression of TGF-β1 was markedly lower in LPD+αKA treated adenine-induced CRF rats than in NPD or LPD treated groups at the end of the 10th week. No difference was found in MCP-1 expressions between NPD, LPD or LPD+αKA groups.CONCLUSION LPD and LPD+αKA ameliorate proteinuria, EMT and the renal fibrosis in adenine-induced CRF rat model, and these effects of LPD+αKA is more better than LPD. The mechanism of the therapeutic effects of LPD+αKA on adenine-induced CRF is related to suppressing the overexpression of TGFβ1 and TSP-1 or the downregulation of VEGF. The exact mechanism needs to be studied further. |
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