Department of Basic Pharmaceutical Sciences, College of Pharmacy, The University Louisiana at Monroe, Monroe, LA 71209, USA.
J Neurosci Res. 2012 Jul;90(7):1347-58. doi: 10.1002/jnr.23032. Epub 2012 Mar 19.
CNS neurons exhibit sustained activation by recurring hypoglycemia in the presence of estrogen. We investigated the impact of estradiol on fuel uptake and detection of energy imbalance by hindbrain A2 metabolosensory neurons during acute vs. chronic hypoglycemia. A2 neurons were laser dissected from estradiol benzoate (EB)- and oil (O)-implanted ovariectomized rats after single or serial injection of neutral protamine Hagedorn (NPH) insulin for single-cell qPCR or high-sensitivity Western blotting. Acute NPH increased A2 GLUT3 mRNA but not protein in EB, but decreased both profiles in O rats. Single insulin dosing did not alter monocarboxylate transporter-2 (MCT2) mRNAs in EB or O, but increased MCT2 protein in EB. Preceding hypoglycemia augmented baseline transporter mRNA and protein in O, but decreased GLUT4 and increased MCT2 proteins in EB. Chronic NPH increased A2 MCT2 and GLUT3 proteins in EB, but elevated GLUT4 protein in O. A2 phospho-AMPK (pAMPK) protein was progressively diminished by acute and chronic hypoglycemia in EB, but elevated in O after serial NPH. Dopamine-β-hydroxylase (DβH) transcripts were decreased in EB during acute and chronic hypoglycemia, but unaltered by serial NPH dosing in O. These results suggest that estrogen enhances A2 lactate utilization during acute hypoglycemia, thereby lessening AMPK activation relative to euglycemic controls. Cellular adaptation to chronic hypoglycemia may involve estrogen-dependent augmentation of lactate and GLUT3-mediated glucose uptake and hormone-independent increases in GLUT4 expression, coincident with diminished pAMPK-mediated signaling of energy deficiency. The data also imply that increased lactate and glucose uptake during recurring hypoglycemia may be required for sustained DβH transcriptional reactivity to this metabolic stress.
CNS 神经元在雌激素存在的情况下会因反复发生的低血糖而持续激活。我们研究了雌二醇对急性和慢性低血糖期间后脑 A2 代谢感觉神经元对燃料摄取和能量失衡检测的影响。A2 神经元是从苯甲酸雌二醇（EB）和油（O）植入的卵巢切除大鼠中激光分离出来的，这些大鼠在单次或连续注射中性鱼精蛋白 Hagedorn（NPH）胰岛素后，进行单细胞 qPCR 或高灵敏度 Western blot 分析。急性 NPH 增加了 EB 中的 A2 GLUT3 mRNA，但不增加 O 中的 GLUT3 蛋白；而在 O 大鼠中，两种情况的 GLUT3 蛋白都减少了。单次胰岛素给药不会改变 EB 或 O 中的单羧酸转运蛋白 2（MCT2）mRNA，但会增加 EB 中的 MCT2 蛋白。先前的低血糖会增加 O 中的基线转运体 mRNA 和蛋白，但会降低 EB 中的 GLUT4 蛋白并增加 MCT2 蛋白。慢性 NPH 增加了 EB 中的 A2 MCT2 和 GLUT3 蛋白，但增加了 O 中的 GLUT4 蛋白。急性和慢性低血糖会逐渐降低 EB 中的 A2 磷酸 AMPK（pAMPK）蛋白，但在连续 NPH 后会在 O 中升高。急性和慢性低血糖期间，EB 中的多巴胺-β-羟化酶（DβH）转录物减少，但 O 中的连续 NPH 给药不会改变。这些结果表明，雌激素增强了 A2 在急性低血糖期间对乳酸的利用，从而相对于正常血糖对照，减少了 AMPK 的激活。细胞对慢性低血糖的适应可能涉及雌激素依赖性增加乳酸和 GLUT3 介导的葡萄糖摄取，以及激素独立增加 GLUT4 表达，同时减少能量缺乏的 pAMPK 介导的信号传导。数据还表明，在反复发生的低血糖期间增加乳酸和葡萄糖摄取可能是维持 DβH 对这种代谢应激的转录反应所必需的。
