High-dose E2 supplementation protects against diet-induced obesity. Over 6 weeks, fish were overfed a brine shrimp diet (30 mg cysts per fish) supplemented with either untreated flakes, ethanol-treated flakes (vehicle), 50 mg E2/kg feed, or 250 mg E2/kg feed. Body weight (A) and length (B) gain. (C) Terminal blood glucose levels (mg/dL). Hepatic expression of (D) fasn, (E) hmgcr, and (F) esr1 normalized to β-actin. Error bars indicate mean ± SEM, n = 4–6. This was a mixed sex study. Data were not collected over week 5 of the study. Statistical tables are presented in Supplementary Figures S1–S5. Tables indicate statistically significant differences in body weight and length gain. *p < 0.05.

Six weeks of E2 supplementation mitigates diet-induced obesity in both sexes. Female weight (A) and length gain (B) over the feeding period. Male weight gain (D) and body length gain (E) over the feeding period. Terminal blood glucose was collected after an overnight fast (C, F). Error bars indicate mean ± SEM, n = 5–7 for female study and n = 4–7 for male study. Statistical tables for these data are provided in Supplementary Figures S6–S15. Tables indicate statistically significant differences in body weight and length gain. *p < 0.05, **p < 0.01.

E2 supplementation promotes sex-specific changes in liver lipid metabolism. Female (top) and male (bottom) hepatic qPCR analysis after an overnight fast. Hepatic expression of (A, D) fasn, (B, E) hmgcr, and (C, F) ldlr normalized to β-actin. Tissues were analyzed after 6 weeks of experimental diet. Error bars indicate mean ± SEM, n = 3–5 for females and n = 3–6 for males. Statistical tables for these data are provided in Supplementary Figures 10 and 15. *p < 0.05.

Four weeks of lard-enriched feeding promotes an alternative mechanism of obesity onset. Body weight (A) and length (B) gain. (C) Terminal blood glucose levels after an overnight fast. Hepatic expression of (D) fasn, (E) hmgcr, and (F) esr1 normalized to β-actin. (A–C) depict mixed sex data. (D–F) depict male data only. Error bars indicate mean ± SEM, (A–C) n = 6–7; (D–F) n = 3–4. *p < 0.05. ns, not statistically significant.

Proposed model of the role of E2 in obesity metabolism. (A) E2 supplementation independent of unsaturated fat intake increases esr1 expression with sex-specific effects on hmgcr expression, ultimately protecting both sexes from weight gain. Our data suggest that E2 levels regulate hepatic cholesterol synthesis through modulation of hmgcr expression. (B) Findings from Figure 4, with loss of E2-hmgcr regulation upon consumption of a high saturated fat diet.