Laboratório de Endocrinologia Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS, Bloco G, Rio de Janeiro 21941-902, Brazil.
J Nutr Biochem. 2010 Oct;21(10):935-40. doi: 10.1016/j.jnutbio.2009.07.008. Epub 2009 Sep 29.
n-3 polyunsaturated fatty acids (PUFAs) present in fish oil (FO) potently decrease serum lipids, which is also an effect of thyroid hormones. Both PUFAs and thyroid hormones affect hepatic lipid metabolism, and here we hypothesized that a long-term diet rich in n-3 PUFAs would enhance thyroid hormone action in the liver. Female rats received isocaloric and normolipid diets containing either soybean oil (SO) or FO during lactation. Male offspring received the same diet as their dams since weaning until sacrifice when they were 11 weeks old. FO group, as compared to SO group, exhibited lower body weight since 5 weeks of age until sacrifice, with no alterations in food ingestion, lower retroperitoneal white fat mass and elevated inguinal fat mass relative to body weight, with unchanged water and lipid but reduced protein percentage in their carcasses. FO diet resulted in lower serum triglycerides and cholesterol. Serum total triiodothyronine, total thyroxine and thyrotropin were similar between groups. However, liver thyroid hormone receptor (TR) β1 protein expression was higher in the FO group and correlated negatively with serum lipids. Liver 5'-deiodinase activity, which converts thyroxine into triiodothyronine, was similar between groups. However, the activity of hepatic mitochondrial glycerophosphate dehydrogenase, the enzyme involved in thermogenesis and a well-characterized target stimulated by T3 via TRβ1, was higher in the FO group, suggesting enhancement of thyroid hormone action. These findings suggest that the increase in thyroid hormone signaling pathways in the liver may be one of the mechanisms by which n-3 PUFAs exert part of their effects on lipid metabolism.
n-3 多不饱和脂肪酸（PUFAs）存在于鱼油（FO）中，能强有力地降低血清脂质，这也是甲状腺激素的作用。PUFAs 和甲状腺激素都影响肝脏的脂质代谢，我们假设长期富含 n-3 PUFAs 的饮食会增强甲状腺激素在肝脏中的作用。雌性大鼠在哺乳期接受含大豆油（SO）或 FO 的等热量和正常脂质饮食。雄性后代从断奶开始到 11 周大时接受与母鼠相同的饮食。与 SO 组相比，FO 组从 5 周龄到处死时的体重较低，摄食量无变化，腹膜后白色脂肪质量较低，腹股沟脂肪质量相对于体重较高，其尸体中的水分和脂质不变，但蛋白质百分比降低。FO 饮食可降低血清甘油三酯和胆固醇。血清总三碘甲状腺原氨酸、总甲状腺素和促甲状腺激素在两组之间相似。然而，FO 组肝脏甲状腺激素受体（TR）β1 蛋白表达较高，与血清脂质呈负相关。肝脏 5'-脱碘酶活性，将甲状腺素转化为三碘甲状腺原氨酸，在两组之间相似。然而，参与产热的肝线粒体甘油磷酸脱氢酶的活性，以及 T3 通过 TRβ1 刺激的特征明确的靶酶，在 FO 组中较高，提示甲状腺激素作用增强。这些发现表明，肝脏中甲状腺激素信号通路的增加可能是 n-3 PUFAs 发挥其部分脂质代谢作用的机制之一。
