Stumvoll M, Meyer C, Perriello G, Kreider M, Welle S, Gerich J
Medizinische Klinik, Eberhard-Karls-Universität, Tübingen, Germany.
Am J Physiol. 1998 May;274(5):E817-26. doi: 10.1152/ajpendo.1998.274.5.E817.
To assess the contribution of the human kidney to gluconeogenesis (GN) and its role in conversion of glutamine and alanine to glucose, we used a combination of isotopic and organ balance techniques in nine normal postabsorptive volunteers and measured both overall and renal incorporation of these precursors into glucose before and after infusion of epinephrine. In the postabsorptive basal state, renal incorporation of glutamine (27 +/- 2 mumol/min) and alanine (2.1 +/- 0.5 mumol/min) into glucose accounted for 72.8 +/- 3.3 and 3.9 +/- 0.5% of their overall incorporation into glucose (37 +/- 2 and 51 +/- 6 mumol/min, respectively) and 19.0 +/- 3.5 and 1.4 +/- 0.2%, respectively, of overall renal glucose release. Infusion of epinephrine, which increased systemic and renal glucose release more than twofold (P < 0.001), increased overall glutamine and alanine incorporation into glucose (both P < 0.001) and increased renal GN from glutamine (P < 0.001) but not from alanine (P = 0.15). Renal glutamine GN now accounted for 90.3 +/- 4.0% of overall glutamine GN (P = 0.01 vs. basal), whereas renal alanine GN still accounted for only 4.8 +/- 1.7% of overall alanine GN (P = 0.36 vs. basal). With the assumption that kidney and liver are the only gluconeogenic organs in humans, these results indicate that glutamine GN occurs primarily in kidney, whereas alanine GN occurs almost exclusively in liver. Isotopic studies of glutamine and alanine incorporation into plasma glucose may provide a selective, noninvasive method to assess hepatic and renal GN.
为评估人肾脏对糖异生（GN）的贡献及其在谷氨酰胺和丙氨酸转化为葡萄糖过程中的作用，我们对9名正常空腹志愿者采用了同位素和器官平衡技术相结合的方法，并在输注肾上腺素前后测量了这些前体物质整体和肾脏掺入葡萄糖的情况。在空腹基础状态下，肾脏将谷氨酰胺（27±2 μmol/分钟）和丙氨酸（2.1±0.5 μmol/分钟）掺入葡萄糖分别占其整体掺入葡萄糖量（分别为37±2和51±6 μmol/分钟）的72.8±3.3%和3.9±0.5%，分别占肾脏整体葡萄糖释放量的19.0±3.5%和1.4±0.2%。输注肾上腺素使全身和肾脏的葡萄糖释放增加了两倍多（P<0.001），增加了整体谷氨酰胺和丙氨酸掺入葡萄糖的量（均P<0.001），增加了肾脏由谷氨酰胺生成的糖异生（P<0.001），但未增加由丙氨酸生成的糖异生（P = 0.15）。此时肾脏谷氨酰胺糖异生占整体谷氨酰胺糖异生的90.3±4.0%（与基础状态相比P = 0.01），而肾脏丙氨酸糖异生仍仅占整体丙氨酸糖异生的4.8±1.7%（与基础状态相比P = 0.36）。假设肾脏和肝脏是人类仅有的糖异生器官，这些结果表明谷氨酰胺糖异生主要发生在肾脏，而丙氨酸糖异生几乎完全发生在肝脏。对谷氨酰胺和丙氨酸掺入血浆葡萄糖的同位素研究可能提供一种评估肝脏和肾脏糖异生的选择性、非侵入性方法。
