Effect of low-protein diet on renal hypertrophy of diabetic glomerulus and its relationship with cyclin kinase inhibitor P27 level

Objective: To investigate the relationship between the cyclin kinase inhibitor P27 and the effect of low protein diet on the renal hypertrophy of diabetic glomerulus. Methods: STZ induced diabetic rats were given low protein diet or normal protein diet for 8 weeks. The P27 protein of glomerular lysate was detected with Western blotting analysis. The extracellular matrix (ECM) protein (type Ⅳ collagen and fibronectin) of glomerular lysate and 24 h urine albumin was examined with ELISA. Image analysis system was used to detect area of each glomerulus. Results: Glomerular P27 protein increased in diabetic rats no matter what kinds of diet they were given. Meanwhile, the 24 h urine albumin excretion, glomerular ECM, glomerular area elevated and so did the ratio of kidney mass over body mass in diabetic rats. Glomerular P27 level [(11.1± 3.6) vs (19.6±5.1), P 0.01],24 h urine albumin excretion [(18.13±3.23) vs (40.18±3.79) μg/24 h, P 0.01], glomerular area [(721±75) vs (815±97) μm 2, P 0.01] and the ratio of kidney mass over body mass [(12.03±1.85) vs (15.62±2.13), P 0.01] were lower in diabetic rats with low protein diet than diabetic rats with normal protein diet. Glomerular P27 level was linearly related with the ratio of kidney mass over body mass in diabetic rats. The blood glucose and serum albumin remained constant in diabetic rats no matter what kinds of diet they were given. Conclusion: Low protein diet can inhibit glomerular hypertrophy and may protect diabetic glomerulus through decreasing glomerular P27 level.