Objective: To explore the effect of high fat diet on the expression of sterol regulatory element binding protein-1 (SREBP-1), transforming growth factor-beta1 (TGF-beta1) and alpha-smooth muscle actin (alpha-SMA) in renal tubular cells and extracellular matrix accumulation in Wistar rats.
Methods: The Wistar rats were treated with high fat diet for 12 weeks and renal lipid deposit was detected by the method of Oil Red O staining. The immunohistochemistry and Western blot were used to investigate the expression of SREBP-1, TGF-beta1, alpha-SMA and fibronectin (FN) protein. The expression of SREBP-1 mRNA was determined with in situ hybridization. Masson staining was for the detection of extracellular matrix (ECM) accumulation.
Results: The weight of rats raised by high fat diet increased, in company with the high serum glucose, serum triglyceride and serum insulin. The Oil Red O staining revealed that the renal proximal tubular epithelial cells showed significant lipid droplet in high fat diet rats. SREBP-1 protein and mRNA were located in the renal tubular cells and the expressions of high fat diet rats were higher than those of normal control rats. They were respectively 1.88 times and 1.85 times than those of normal control group. TGF-beta1 and alpha-SMA protein were also located in renal tubular cells and high fat diet up-regulated the expression of them. ECM accumulation was detected with Masson staining and the result showed that high fat diet treatment increased interstitial ECM product and FN protein was found high expression.
Conclusion: High fat diet may induce lipid droplet deposit in renal tubular cells by up-regulation of the expression of SREBP-1, which causes ECM accumulation by increasing the expression of TGF-beta1 and alpha-SMA.