ORF30-02 - Estradiol Improves Lean Mass While Elevating Cardiac Oxidative Stress and Altering VLDL Triglycerides through Hepatic ERα in Androgen‑Deprived Male Mice

Estrogen co‑therapy was once paired with androgen‑deprivation therapy (ADT) for prostate cancer, but its use stopped in 2000 after a sharp rise in cardiovascular disease (CVD) morbidity among patients. The mechanisms linking estrogenic signaling to increased CVD risk in androgen-deprived biologically male patients remain unclear, so we examined estrogen‑driven changes in key CVD‑risk pathways using two transgenic mouse models. The first, a humanized CETP (huCETP) mouse expressing a minigene for human cholesterol‑ester transfer protein, allows for a humanized response to nutrient excess. Gonadectomized mice received a sub‑cutaneously implanted delayed‑release estradiol (E2) pellet or placebo, then were placed on a chronic Western diet and at thermoneutrality to induce dyslipidemia; body composition, cardiac oxidative markers, and metabolic parameters were measured. The second model used an albumin‑Cre‑mediated liver‑specific estrogen‑receptor α (ERα) knockout (ERα fl/fl) and was used to assess the role of liver ERα to very‑low‑density lipoprotein (VLDL) triglyceride (TG) content under the same experimental protocol.

Results: E2‑treated males retained more lean mass (60.4 ± 1.2 % vs 51.1 ± 0.97%; p = 0.0007, n=7) despite obesogenic diet and temperature conditions, indicating a favorable effect on body composition. However, cardiac malondialdehyde (MDA) concentrations, a marker of oxidative stress and inflammation, trended upward in E2 males versus placebo (9.32 ± 3.24 vs 2.99 ± 0.46 nmol/g; p = 0.058, n=3) and versus E2‑treated females (9.32 ± 3.23 vs 3.74 ± 0.61 nmol/g; p = 0.094, n=3), suggesting increased cardiac inflammation in males treated with E2. Consistently, pro‑NT‑BNP was significantly higher in E2-treated males than controls (268 ± 15 vs 172 ± 48 pg/mL; p = 0.026, n=3). Hepatic ERα protein content rose in E2 males relative to placebo males (4.69 ± 0.36 ng/ml vs 3.92 ± 0.18 ng/ml ; p = 0.032, n=5). Fast protein liquid chromatography showed a marked reduction in VLDL‑peak TG in E2-treated males versus placebo males (9.07 ± 0.69 vs 13.07 ± 0.87 mg/dL; p = 0.0001, n=3), yet TG was higher than in E2‑treated males versus females (9.07 ± 0.69 vs 5.44 ± 1.31 mg/dL; p = 0.0006, n=3). To determine the role of liver ERα in modifying VLDL composition in E2-treated males, FPLC was repeated in the LERKO model. Cre‑negative (ERα‑intact) E2-treated males displayed higher VLDL TG peaks than Cre‑positive liver ERα knockouts (5.76 ± 0.29 vs 4.47 ± 0.08 mg/dL; p < 0.0001, n=2), implicating hepatic ERα in increasing TG content of circulating VLDL. Overall, estradiol improves lean mass in hypogonadal males but may increase cardiac oxidative and lipotoxicity markers and alter triglyceride-rich lipoprotein composition via hepatic ERα, offering a pathway and possible mediator for the heightened CVD risk seen with estrogen therapy during ADT. Targeting liver ERα may help mitigate these cardiovascular effects.