Thorn Stephanie R, Regnault Timothy R H, Brown Laura D, Rozance Paul J, Keng Jane, Roper Michael, Wilkening Randall B, Hay William W, Friedman Jacob E
Department of Pediatrics, University of Colorado Denver, Aurora, Colorado 80045, USA.
Endocrinology. 2009 Jul;150(7):3021-30. doi: 10.1210/en.2008-1789. Epub 2009 Apr 2.
Expression of key metabolic genes and proteins involved in mRNA translation, energy sensing, and glucose metabolism in liver and skeletal muscle were investigated in a late-gestation fetal sheep model of placental insufficiency intrauterine growth restriction (PI-IUGR). PI-IUGR fetuses weighed 55% less; had reduced oxygen, glucose, isoleucine, insulin, and IGF-I levels; and had 40% reduction in net branched chain amino acid uptake. In PI-IUGR skeletal muscle, levels of insulin receptor were increased 80%, whereas phosphoinositide-3 kinase (p85) and protein kinase B (AKT2) were reduced by 40%. Expression of eukaryotic initiation factor-4e was reduced 45% in liver, suggesting a unique mechanism limiting translation initiation in PI-IUGR liver. There was either no change (AMP activated kinase, mammalian target of rapamycin) or a paradoxical decrease (protein phosphatase 2A, eukaryotic initiation factor-2 alpha) in activation of major energy and cell stress sensors in PI-IUGR liver and skeletal muscle. A 13- to 20-fold increase in phosphoenolpyruvate carboxykinase and glucose 6 phosphatase mRNA expression in the PI-IUGR liver was-associated with a 3-fold increase in peroxisome proliferator-activated receptor-gamma coactivator-1 alpha mRNA and increased phosphorylation of cAMP response element binding protein. Thus PI-IUGR is-associated with reduced branched chain amino acid uptake and growth factors, yet up-regulation of proximal insulin signaling and a marked increase in the gluconeogenic pathway. Lack of activation of several energy and stress sensors in fetal liver and skeletal muscle, despite hypoxia and low energy status, suggests a novel strategy for survival in the PI-IUGR fetus but with potential maladaptive consequences for reduced nutrient sensing and insulin sensitivity in postnatal life.
在胎盘功能不全导致的宫内生长受限(PI-IUGR)的妊娠晚期胎羊模型中,研究了肝脏和骨骼肌中参与mRNA翻译、能量感应和葡萄糖代谢的关键代谢基因和蛋白质的表达。PI-IUGR胎儿体重减轻55%;氧气、葡萄糖、异亮氨酸、胰岛素和IGF-I水平降低;净支链氨基酸摄取减少40%。在PI-IUGR骨骼肌中,胰岛素受体水平增加80%,而磷脂酰肌醇-3激酶(p85)和蛋白激酶B(AKT2)减少40%。肝脏中真核起始因子-4e的表达减少45%,表明在PI-IUGR肝脏中存在一种限制翻译起始的独特机制。PI-IUGR肝脏和骨骼肌中主要能量和细胞应激传感器的激活要么没有变化(AMP激活激酶、雷帕霉素哺乳动物靶标),要么出现矛盾的降低(蛋白磷酸酶2A、真核起始因子-2α)。PI-IUGR肝脏中磷酸烯醇丙酮酸羧激酶和葡萄糖6磷酸酶mRNA表达增加13至20倍,与过氧化物酶体增殖物激活受体-γ共激活因子-1αmRNA增加3倍以及cAMP反应元件结合蛋白磷酸化增加有关。因此,PI-IUGR与支链氨基酸摄取和生长因子减少有关,但近端胰岛素信号上调,糖异生途径显著增加。尽管存在缺氧和低能量状态,但胎儿肝脏和骨骼肌中几种能量和应激传感器未被激活,这表明PI-IUGR胎儿有一种新的生存策略,但可能对出生后营养感应和胰岛素敏感性降低产生适应不良后果。