Tounian P, Schneiter P, Henry S, Tappy L
Institute of Physiology, Faculty of Medicine, University of Lausanne, Switzerland.
Clin Physiol. 1996 Jul;16(4):403-16. doi: 10.1111/j.1475-097x.1996.tb00729.x.
In order to determine whether or not hepatic glycogen breakdown contributes to systemic glucose flux during glucose infusion, net carbohydrate oxidation (indirect calorimetry) and the total rate of glucose appearance (6,6(-2)H-glucose) were measured in six healthy women during infusion of U-13 C labelled glucose (22 mumol/kg/min). Glucose infusion completely suppressed endogeneous glucose production and increased net carbohydrate oxidation from 10.9 +/- 1.6 to 18.9 +/- 1.0 mumol/kg/min. To differentiate between the oxidation of endogenous (i.e. glycogen) and of exogenous carbohydrates, the 13CO2 production was measured and the oxidation of exogenous 13C labelled carbohydrate was calculated. For this purpose, the specific recovery factor in breath of 13CO2 issued from oxidation of uniformly labelled glucose was determined during infusions of equimolar amounts of 13C bicarbonate, 1-13C acetate and 2-13C acetate. The average recovery was 53.9 +/- 1.5%. The oxidation of exogenous carbohydrate was 20.9 +/- 0.7 mumol/kg/min. This value was slightly higher than net carbohydrate oxidation, indicating that no oxidation of endogenous, unlabelled carbohydrate, and, hence, no utilization of hepatic glycogen took place. These results indicate that (i) estimation of glucose oxidation from indirect calorimetry and tracer technology give concordant results when an appropriate factor of 13CO2 recovery in breath is used, and (ii) utilization of previously formed glycogen is inhibited during hyperglycaemia and hyperinsulinaemia.
为了确定在输注葡萄糖期间肝糖原分解是否有助于全身葡萄糖通量，在6名健康女性输注U-13C标记的葡萄糖（22μmol/kg/分钟）期间，测量了净碳水化合物氧化（间接量热法）和葡萄糖出现的总速率（6,6(-2)H-葡萄糖）。葡萄糖输注完全抑制了内源性葡萄糖生成，并使净碳水化合物氧化从10.9±1.6增加到18.9±1.0μmol/kg/分钟。为了区分内源性（即糖原）和外源性碳水化合物的氧化，测量了13CO2的产生，并计算了外源性13C标记碳水化合物的氧化。为此，在输注等摩尔量的13C碳酸氢盐、1-13C乙酸盐和2-13C乙酸盐期间，测定了由均匀标记葡萄糖氧化产生的13CO2在呼出气体中的特定回收因子。平均回收率为53.9±1.5%。外源性碳水化合物的氧化为20.9±0.7μmol/kg/分钟。该值略高于净碳水化合物氧化，表明没有内源性未标记碳水化合物的氧化，因此没有肝糖原的利用。这些结果表明，（i）当使用适当的呼出气体中13CO2回收因子时，通过间接量热法和示踪技术估算葡萄糖氧化可得到一致的结果，并且（ii）在高血糖和高胰岛素血症期间，先前形成的糖原的利用受到抑制。
