Lipid dynamics in goldfish (Carassius auratus) during a period of gonadal recrudescence: Effects of β-sitosterol and 17β-estradiol exposure

The potential for contaminants to alter lipid or cholesterol dynamics in fish is rarely investigated and may include critical physiological endpoints that are impacted by exposure to endocrine-active substances. The current study investigated plasma and tissue lipid dynamics over a period of recrudescence in goldfish, while also examining the potential for β-sitosterol (β-sit), a phytosterol and 17β-estradiol (E2), an endogenous estrogen, to alter lipid homeostasis. Goldfish were exposed to 0 μg/g (no chemical; control), 200 μg/g β-sit (72.3% sitosterol mixture) or 10 μg/g 17β-estradiol (E2) via Silastic® implants for a period of five months. Plasma lipids peaked in control fish coincident with maximum liver size, while gonadal cholesterol concentration was highest concomitant with maximum gonad size. Plasma lipid concentrations were highly affected by E2 but not β-sit exposure; E2 elevated total cholesterol (p < 0.001) and triglyceride (TG; p < 0.001) and decreased high-density lipoprotein (HDL) concentration (p < 0.001) in male fish. Tissue cholesterol concentrations were minimally affected by β-sit exposure, while hepatic cholesterol concentrations were increased in E2 exposed females (p = 0.041), indicating elevated liver lipogenesis in response to E2, but not β-sit, exposure. The present study demonstrates differential effects by β-sit and E2 on plasma lipoprotein profile and TG concentration and indicates estrogen-specific effects on hepatic lipid metabolism during gonadal development.