Rozance Paul J, Limesand Sean W, Barry James S, Brown Laura D, Thorn Stephanie R, LoTurco Dan, Regnault Timothy R H, Friedman Jacob E, Hay William W
Perinatal Research Center, Department of Pediatrics, University of Colorado Health Sciences Center, Aurora, CO 80045, USA.
Am J Physiol Endocrinol Metab. 2008 Feb;294(2):E365-70. doi: 10.1152/ajpendo.00639.2007. Epub 2007 Dec 4.
Hepatic glucose production is normally activated at birth but has been observed in response to experimental hypoglycemia in fetal sheep. The cellular basis for this process remains unknown. We determined the impact of 2 wk of fetal hypoglycemia during late gestation on enzymes responsible for hepatic gluconeogenesis, focusing on the insulin-signaling pathway, transcription factors, and coactivators that regulate gluconeogenesis. Hepatic phosphoenolpyruvate carboxykinase and glucose-6-phosphatase mRNA increased 12-fold and 7-fold, respectively, following chronic hypoglycemia with no change in hepatic glycogen. Chronic hypoglycemia decreased fetal plasma insulin with no change in glucagon but increased plasma cortisol 3.5-fold. Peroxisome proliferator-activated receptor-gamma coactivator-1alpha mRNA and phosphorylation of cAMP response element binding protein at Ser(133) were both increased, with no change in Akt, forkhead transcription factor FoxO1, hepatocyte nuclear factor-4alpha, or CCAAT enhancer binding protein-beta. These results demonstrate that chronic fetal hypoglycemia triggers signals that can activate gluconeogenesis in the fetal liver.
肝脏葡萄糖生成通常在出生时被激活,但在胎儿绵羊实验性低血糖反应中也已被观察到。这一过程的细胞基础仍然未知。我们确定了妊娠晚期2周的胎儿低血糖对负责肝脏糖异生的酶的影响,重点关注胰岛素信号通路、转录因子和调节糖异生的共激活因子。慢性低血糖后,肝脏磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶mRNA分别增加了12倍和7倍,而肝糖原没有变化。慢性低血糖降低了胎儿血浆胰岛素,胰高血糖素没有变化,但血浆皮质醇增加了3.5倍。过氧化物酶体增殖物激活受体γ共激活因子-1α mRNA和cAMP反应元件结合蛋白在Ser(133)处的磷酸化均增加,而Akt、叉头转录因子FoxO1、肝细胞核因子-4α或CCAAT增强子结合蛋白-β没有变化。这些结果表明,慢性胎儿低血糖触发的信号可激活胎儿肝脏中的糖异生。