Braun Barry, Sharoff Carrie, Chipkin Stuart R, Beaudoin Francesca
Department of Exercise Science, University of Massachusetts, Amherst 01003, USA.
J Appl Physiol (1985). 2004 Sep;97(3):991-7. doi: 10.1152/japplphysiol.00231.2004. Epub 2004 May 7.
During exercise, obese individuals oxidize less glycogen and more fat than their lean counterparts, but the shift in substrate use may be mediated by insulin resistance rather than body fat per se. In addition, individuals with Type 2 diabetes are not resistant to contraction-mediated glucose uptake during exercise, but in vivo studies uncomplicated by hyperglycemia are lacking. The purpose of this study was to compare blood glucose uptake and the balance between carbohydrate and fat utilization during exercise in insulin-resistant (IR) and insulin-sensitive (IS) women of equivalent body fatness and maximal oxygen consumption (VO2 max). Twelve overweight sedentary women were divided into two groups with similar body mass index (IR = 28.5 +/- 1.6, IS = 27.5 +/- 1.9), lean mass (IR = 42.4 +/- 1.8 kg, IS = 41.5 +/- 1.9 kg), and VO2 max (IR = 29.7 +/- 3.5 ml.kg(-1).min(-1), IS = 30.7 +/- 3.9 ml.kg(-1).min(-1)) but a markedly different composite insulin sensitivity index (IR = 3.0 +/- 0.7, IS = 7.7 +/- 0.9). Blood glucose kinetics and substrate oxidation were assessed by stable isotope dilution and indirect calorimetry during 50 min of treadmill walking at 45% VO2 max. Total carbohydrate oxidation and estimated muscle glycogen use were significantly lower in the IR group. Blood glucose uptake was the same in the IR and IS groups. These data suggest that insulin resistance, independent of body fat, spares muscle glycogen and shifts substrate oxidation toward less carbohydrate use during exercise. Insulin-resistant individuals with normoglycemia appear to have no defect in blood glucose uptake during exercise.
在运动过程中，肥胖个体比瘦人氧化的糖原更少，脂肪更多，但底物利用的转变可能是由胰岛素抵抗介导的，而非身体脂肪本身。此外，2型糖尿病患者在运动期间对收缩介导的葡萄糖摄取并无抵抗，但缺乏无高血糖并发症的体内研究。本研究的目的是比较身体脂肪含量和最大耗氧量（VO2 max）相当的胰岛素抵抗（IR）和胰岛素敏感（IS）女性在运动期间的血糖摄取以及碳水化合物与脂肪利用之间的平衡。12名超重久坐的女性被分为两组，两组的体重指数相似（IR = 28.5 ± 1.6，IS = 27.5 ± 1.9）、去脂体重相似（IR = 42.4 ± 1.8 kg，IS = 41.5 ± 1.9 kg）、VO2 max相似（IR = 29.7 ± 3.5 ml·kg⁻¹·min⁻¹，IS = 30.7 ± 3.9 ml·kg⁻¹·min⁻¹），但综合胰岛素敏感性指数明显不同（IR = 3.0 ± 0.7，IS = 7.7 ± 0.9）。在以45% VO2 max进行50分钟跑步机行走期间，通过稳定同位素稀释和间接量热法评估血糖动力学和底物氧化。IR组的总碳水化合物氧化和估计的肌肉糖原利用显著更低。IR组和IS组的血糖摄取相同。这些数据表明，独立于身体脂肪的胰岛素抵抗可节省肌肉糖原，并在运动期间使底物氧化向减少碳水化合物利用的方向转变。血糖正常的胰岛素抵抗个体在运动期间的血糖摄取似乎并无缺陷。
