Contributions of gluconeogenesis to glucose production in the fasted state
Contributions of gluconeogenesis to glucose production in the fasted state
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DOI：
10.1172/jci118803
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发表时间：
1996-07-15
影响因子：
15.9
通讯作者：
Kalhan, SC
中科院分区：
文献类型：
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作者：
Landau, BR;Wahren, J;Kalhan, SC
健康受试者摄入 (H2O)-H-2，禁食 14、22 和 42 小时后，测定与血糖中的 2、5 和 6 碳结合的氢以及体内水中的氘富集度。在甲醛中分离与碳结合的氢，将其转化为六亚甲基四胺用于分析。与葡萄糖的碳 5 结合的氘富集到水中或碳 2 上的氘直接等于通过糖异生形成的葡萄糖的分数。禁食14小时后，糖异生对葡萄糖产生的贡献为47+/-4%，22小时后为67+/-4%，42小时后为93+/-2%。甘油向葡萄糖的转化包括在使用碳 5 处富集的估计中，但不包括碳 6 处的富集。根据富集估计，与丙酮酸碳 3 结合的氢（变成与葡萄糖碳 6 结合的氢）和通过糖原分解产生的葡萄糖碳 2 处的氢与水的平衡接近完成 80%。因此，无需其他示踪方法中所需的校正即可确定糖异生速率。在健康受试者中，过夜快速糖异生约占 50%，禁食 42 小时后几乎所有葡萄糖生成。
Healthy subjects ingested (H2O)-H-2 and after 14, 22, and 42 h of fasting the enrichments of deuterium in the hydrogens bound to carbons 2, 5, and 6 of blood glucose and in body water were determined. The hydrogens bound to the carbons were isolated in formaldehyde which was converted to hexamethylenetetramine for assay. Enrichment of the deuterium bound to carbon 5 of glucose to that in water or to carbon 2 directly equals the fraction of glucose formed by gluconeogenesis. The contribution of gluconeogenesis to glucose production was 47+/-4% after 14 h, 67+/-4% after 22 h, and 93+/-2% after 42 h of fasting. Glycerol's conversion to glucose is included in estimates using the enrichment at carbon 5, but not carbon 6. Equilibrations with water of the hydrogens bound to carbon 3 of pyruvate that become those bound to carbon 6 of glucose and of the hydrogen at carbon 2 of glucose produced via glycogenolysis are estimated from the enrichments to be similar to 80% complete. Thus, rates of gluconeogenesis can be determined without corrections required in other tracer methodologies. After an overnight fast gluconeogenesis accounts for similar to 50% and after 42 h of fasting for almost all of glucose production in healthy subjects.