Influence of estrogens on copper indicators: in vivo and in vitro studies

Classic copper indicators are not sensitive and specific for detecting excess copper exposure when this is higher than customary but not markedly elevated. Serum copper and ceruloplasmin (Cp) are the most commonly used indicators to assess nutritional status of copper. The objective of this paper was to study the influence of estrogens on these indicators and others used to assess early effects of excess copper exposure in humans and the expression of a set of copper related proteins in a hepatic cellular model. For the studies in humans, 107 healthy participants (18-50 years) were allocated as follows: group 1 (n = 39), women assessed on day 7 of their hormonal cycle; group 2 (n = 34), women assessed on day 21 of their hormonal cycle, and group 3 (n = 34, comparison group), healthy men. Participants received 8 mg Cu/day (as copper sulfate) during 6 months. Serum Cp and Cu, Cu-Zn-superoxide dismutase activity, liver function indicators [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma glutamyltransferase (GGT)], and serum Fe and Zn concentrations were measured monthly. In addition, the influence of estradiol on intracellular total copper content, hctr1, dmt1 and shbg mRNA abundance and hCTR1, and DMT1 expression was measured in HepG2 cells. Serum Cu, Fe, and Zn and liver aminotransferases but not Cu-Zn-superoxide dismutase varied depending on sex. Fe nutrition indicators, GGT, and ALT activities showed significant differences between the hormonal phases. Cellular experiments showed that estradiol increased cellular Cu concentration and hCTR1 and DMT1 mRNA expression and changed these proteins expression patterns. Estradiols significantly influence the responses to copper at the whole body and the cellular levels, suggesting that they help maintaining copper availability for metabolic needs.