Estradiol regulates insulin dependent stimulation of LDL-receptor expression in HepG(2) cells.

The low density lipoprotein, one of the major vehicle for extraneous cholesterol, internalizes into the cells through the process of LDL-receptor mediated endocytosis. The expression of LDL-receptor on the cell surface is a function of various hormone regulated transcription of the receptor gene. The present study elucidates the differential expression pattern of LDL-receptor protein in human hepatoma HepG(2) cells by the influence of two hormones, insulin and estrogen (β-estradiol), as compared to the basal level expression of the receptor protein. The combined effect of insulin and β-estradiol reveals that β-estradiol is the ultimate regulator between these two hormones and supershades the message of insulin on LDL-receptor expression. The receptor protein level immunobloted by anti LDL-receptor antibody after treating cells with insulin, β-estradiol and mixture of both also reflects the same phenomena. This comparative study makes it consistent that cell saturation with sterol (β-estradiol) is the prime regulator of LDL-receptor expression between the two hormones, insulin and estrogen.