Change of renin-angiotensin system in cultured mesangial cells by serum from nephrectomized rats feeding with low protein diet and α-keto acid supplement / 中华肾脏病杂志

ABSTRACT

Objective To observe the changes of renin-angiotensin system (RAS) in cultured mesangial cells by serum from 3/4 nephrectomized rats feeding with low protein diet and α-keto acid. Methods Thirty male SD rats received 3/4 nephrectomy (Nx) were placed on 18%normal protein diet (NPD,n=10),6% low protein diet(LPD,n=10) or 5% low protein plus 1%α-keto acid diet (LK,n=10) flor 12 weeks.Ten male SD sham-operated rats fed with 18% normal protein diet were used as control (sham group).In addition,mesangial cells were cultured in sera (10%) collected from above animals treated with or without losartan (0.02 mmol/L)for 48 hours.ELISA was applied to detect the level of Ang II,TGF-β1 and fibronectin (FN) in cell medium.Westem blotting was used to determine the protein level of ATI receptor (AT1R)and real-time PCR was used to detect the mRNA level of AT1R,TGF-β1 and FN. Results (1) Nutritional indices including body weight,total protein and albumin had no significant difference in each group. (2) Serum creatinine and 24 h pruteinuria were significantly inceased in nephrectomized groups compared to sham group(P<0.05,respectively).24 h proteinuria was greatly lower in LK group than that in NPD and LPD groups(P<0.05,respectively).(3)LK greatly decteased the level of Ang II[NPD(12.70±0.12)mg/g protein;sham(8.04±0.62)mg/g protein]in supernatant as well as the protein and mRNA expression of AT1R in cultured mesangial cells (P<0.05).(4)NPD serum directly induced higher secretion[FNsham(20.58±0.46)g/g protein,NPD (39.84±0.06)g/g protein;TGF-β1sham(10.12±O.56)mg/g protein,NPD(83.85±3.58)mg/g protein] and mRNA expression of FN and TGF-β1 compared with sham group (P<0.05).LPD decreased these increment (P<0.05) and LK showed stronger inhibitory effect (P<0.05). (5)Losartan application sharply reduced FN and TGF-β1 production both in supematant and in mRNA expression in NPD serum treated cells (P<0.05,respectively). Conclusion Low protein diet with α-keto acids supplement directly inhibits the RAS in mesangial cells which may contribute to its beneficial effect on the kidney.