The effects of estrogen on serum level and hepatocyte expression of PCSK9

We previously reported that serum PCSK9 levels are higher in postmenopausal women than in premenopausal women in a Han Chinese population. Whether this difference is related to estrogen has not been well-characterized. This study aims to examine if the alteration in estrogen level is responsible for the changes of serum PCSK9 concentration.

A sandwich ELISA assay was used to measure serum PCSK9 levels in 727 healthy women aged from 26 to 85 years old. Anthropometric and biochemical examination of parameters such as estrogen and serum lipids was also performed for these individuals. Next, we measured serum PCSK9 and estrogen levels of 30 healthy fertile women (24-26 years old) in their menstrual cycles and analyzed the correlation between serum PCSK9 level and estrogen concentration. Moreover, cell culture studies were carried out to examine if estrogen at physiological and non-physiological concentrations regulates hepatocyte PCSK9 expression.

Serum PCSK9 concentrations were significantly increased with aging. Aged group had higher serum PCSK9 levels than the middle aged group and the young group (60.29±28.47 vs 71.38±34.22 vs 83.81±33.50 ng/ml). Serum PCSK9 levels were positively correlated with age, BMI, serum total cholesterol and LDL-cholesterol (P<0.01), but not correlated with estrogen levels. There was no significantly difference of PCSK9 levels between the lower and the upper estradiol (E2) tertiles in the 727 women. There was either no significant difference in PCSK9 levels during the menstrual, ovulatory, luteal phases in the 30 healthy fertile women. Cell culture studies showed that 17β-estradiol at physiological concentrations did not significantly alter PCSK9 expression in human hepatocytes.

The serum PCSK9 levels were higher in postmenopausal women than those in pre-menopausal women. However, the difference in serum PCSK9 levels between postmenopausal and premenopausal woman appeared to be independent of estrogen status, and estrogen at physiological concentrations does not affect human hepatocyte PCSK9 expression.