Differentiation of glucose transport in human brain gray and white matter
Differentiation of glucose transport in human brain gray and white matter
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DOI：
10.1097/00004647-200105000-00002
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发表时间：
2001-05-01
影响因子：
6.3
通讯作者：
Rothman, DL
中科院分区：
文献类型：
--
作者：
de Graaf, RA;Pan, JW;Rothman, DL
应用H-1定位核磁共振波谱技术，通过测定正常血糖和两种高血糖状态下的稳态葡萄糖浓度，研究了人脑灰质和白色质葡萄糖转运动力学。同时对三个12 mL体积进行核磁共振光谱测量。主要含有灰色或白色物质。从定量T-1弛豫磁共振图像确定确切的体积组成。根据标准（不可逆）或可逆Michaelis-Menten动力学，用两种动力学转运模型拟合作为血糖水平函数的绝对脑葡萄糖浓度。脑灰质和白色物质的稳态脑葡萄糖水平相似，尽管白色物质水平始终高出15%至20%。最大葡萄糖转运速率Vmax与大脑葡萄糖代谢利用率CMRGlc的比值，使用标准转运模型时，灰质和白色物质分别为3.2 +/- 0.10和3.9 +/- 0.15，使用可逆转运模型时，灰质和白色物质分别为1.8 +/- 0.10和2.2 +/- 0.12。在标准模型中，灰质酸性白色物质的Michaelis-Menten常数Km为6.2 +/- 0.85和7.3 +/- 1.1 mmol/L，在可逆模型中为1.1 +/- 0.66和1.7 +/- 0.88 mmol/L。考虑到白色物质中CMRGlc的速率低三倍，这一发现表明血脑屏障葡萄糖转运活性在白色物质中低类似的量。血脑屏障上葡萄糖转运活性的调节可能是维持整个大脑皮层葡萄糖稳态的重要机制。
Localized H-1 nuclear magnetic resonance spectroscopy has been applied to determine human brain gray matter and white matter glucose transport kinetics by measuring the steady-stare glucose concentration under normoglycemia and two levels of hyperglycemia. Nuclear magnetic resonance spectroscopic measurements were simultaneously performed on three 12-mL volumes. containing predominantly gray or white matter. The exact volume compositions were determined from quantitative T-1 relaxation magnetic resonance images. The absolute brain glucose concentration as a function of the plasma glucose level was fitted with two kinetic transport models, based on standard (irreversible) or reversible Michaelis-Menten kinetics. The steady-state brain glucose levels were similar for cerebral gray and white matter, although the white matter levels were consistently 15% to 20% higher. The ratio of the maximum glucose transport rate, V-max, to the cerebral metabolic utilization rate of glucose, CMRGlc, was 3.2 +/- 0.10 and 3.9 +/- 0.15 for gray matter and white matter using the standard transport model and 1.8 +/- 0.10 and 2.2 +/- 0.12 for gray matter and white matter using the reversible transport model. The Michaelis-Menten constant K-m was 6.2 +/- 0.85 and 7.3 +/- 1.1 mmol/L for gray matter acid white matter in the standard model and 1.1 +/- 0.66 and 1.7 +/- 0.88 mmol/L in the reversible model. Taking into account the threefold lower rate of CMRGlc in white matter, this finding suggests that blood-brain barrier glucose transport activity is lower by a similar amount in white matter. The regulation of glucose transport activity at the blood-brain barrier may be an important mechanism for maintaining glucose homeostasis: throughout the cerebral cortex.