Abstract:

Objective: To study the effect of taurine on total cholesterol (TC), free cholesterol (FC) and cholesterol ester (EC)
levels as well as the protein expression of the rate-limiting enzyme CYP7A1 involved in cholesterol metabolism in HepG2
cells. Methods: The levels of intracellular TC, FC and EC were determined after the cells were cultured for 24 and 48 h in
DMEM supplemented with taurine at final concentrations of 0.1, 1, 10 and 20 mmol/L, respectively. The protein expression
of CYP7A1 was detected after the cells were cultured for 12, 24, 48 and 72 h in DMEM with 20 mmol/L taurine. Results:
The levels of intracellular TC and FC declined obviously after culture in the presence of 1,10 and 20 mmol/L taurine,
suggesting a positive dose-effect relationship, but EC levels did not continue to decrease when the taurine concentration
exceeded 1 mmol/L. A more pronounced decrease in intracellular TC and FC was observed when the culture time was
prolonged from 24 to 48 h. Intracellular FC was reduced to a greater extent by 20 mmol/L taurine than intracellular EC. The
highest protein expression of CYP7A1 was noted after 24 h culture. Conclusion: Taurine can enhance CYP7A1 expression
and promote intracellular cholesterol metabolism, and the decrease of cholesterol is associated with taurine concentration
and action duration, showing a superior effect at 48 h than at 24 h, and its main benefit is reducing intracellular FC.

Key words: taurine, cholesterol, cholesterol 7a-hydroxylase (CYP7A1), HepG2 cells