Concentration-dependent effect of insulin on expression of SREBP-1, FAS and lipid droplet formation in HKC cells |
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| Authors: | HAO Jun LIU Qing-juan ZHENG Shu-shen LIU Shu-xia ZHAO Song WANG Hui WU Hai-jiang DUAN Hui-jun |
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| Institution: | Department of Pathology, Hebei Medical University, Shijiazhuang 050017, China. E-mail: duanhj@hebmu.edu.cn |
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| Abstract: | AIM: To investigate the effect of insulin at different concentrations on the expression of sterol regulatory element binding protein-1 (SREBP-1), fat acid synthase (FAS) and lipid droplet formation in human renal proximal tubular epithelial cell line (HKC). METHODS: HKC cells were treated with insulin at concentrations of 0 nmol/L, 1 nmol/L, 10 nmol/L, 100 nmol/L and 200 nmol/L respectively for 6 h. The analysis of SREBP-1 and FAS mRNA was performed by RT-PCR and the protein level of SREBP-1 was detected by Western blotting and immunocytochemistry. Oil red O staining was used to determine the cellular lipid droplet formation. RESULTS: Compared to HKC cells under the condition without insulin treatment (0 nmol/L group), the expression of SREBP-1 and FAS mRNA was significantly increased in HKC cells treated with insulin at concentrations of 10 nmol/L, 100 nmol/L or 200 nmol/L. Furthermore, the highest expression of SREBP-1 and FAS mRNA was observed in 100 nmol/L group. The SREBP-1 protein was located in the plasma of the HKC cells and was significantly upregulated in the cells treated with insulin at concentrations of 10 nmol/L, 100 nmol/L or 200 nmol/L. The results of Western blotting showed that the precursor and mature segments of SREBP-1 protein were increased in the cells of 10 nmol/L group, 100 nmol/L group and 200 nmol/L group, and those in 100 nmol/L group were the highest. The result of oil red O staining showed that the markedly deposited lipid droplet was only observed in 100 nmol/L group. CONCLUSION: The results suggest that insulin at high concentration up-regulates SREBP-1 and FAS, resulting in the formation and deposit of cellular lipid droplet in HKC cells, which may play an important role in the pathogenesis of renal lipid accumulation in metabolism syndrome. |
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