Glamour T S, McCullough A J, Sauer P J, Kalhan S C
Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
Am J Physiol. 1995 Apr;268(4 Pt 1):E789-96. doi: 10.1152/ajpendo.1995.268.4.E789.
Estimates of glucose oxidation measured by indirect respiratory calorimetry and by [U-13C]glucose tracer were compared as a function of respiratory exchange ratio (RER) in 14 studies performed on 9 healthy adult subjects. RER was varied between 0.7 and 1.04, either by fasting or by infusing glucose. 13C enrichment of plasma glucose and expired CO2 were measured by mass spectrometry. The two methods gave similar results when the nonprotein respiratory quotient (NPRQ) was between 0.76 and 0.90. Glucose oxidation by the tracer method was quantified to be higher than that by respiratory calorimetry when NPRQ was < 0.76; it was lower than the respiratory calorimetry estimate when NPRQ was > 0.90. The discrepancy between the two methods at low RER may represent the contribution of gluconeogenesis, whereas, at high RER, the discrepancy may be the consequence of lipogenesis. We conclude that respiratory calorimetry and [13C]glucose tracer give comparable results only in a narrow range of RER. These data are important when the disposal of glucose is compared using these techniques in different metabolic states with varying respiratory quotients.
在对9名健康成年受试者进行的14项研究中，比较了通过间接呼吸量热法和[U-13C]葡萄糖示踪剂测量的葡萄糖氧化估计值与呼吸交换率（RER）的关系。通过禁食或输注葡萄糖，使RER在0.7至1.04之间变化。通过质谱法测量血浆葡萄糖和呼出二氧化碳的13C富集情况。当非蛋白呼吸商（NPRQ）在0.76至0.90之间时，两种方法得出的结果相似。当NPRQ < 0.76时，示踪剂法测定的葡萄糖氧化量高于呼吸量热法；当NPRQ > 0.90时，示踪剂法测定的葡萄糖氧化量低于呼吸量热法的估计值。两种方法在低RER时的差异可能代表糖异生的贡献，而在高RER时，差异可能是脂肪生成的结果。我们得出结论，呼吸量热法和[13C]葡萄糖示踪剂仅在狭窄的RER范围内得出可比的结果。当在不同代谢状态下使用这些技术比较葡萄糖代谢情况且呼吸商不同时，这些数据很重要。
