Weltan S M, Bosch A N, Dennis S C, Noakes T D
Department of Physiology, University of Cape Town Medical School, Observatory, South Africa.
Am J Physiol. 1998 Jan;274(1):E72-82. doi: 10.1152/ajpendo.1998.274.1.E72.
Euglycemia was maintained in 13 subjects with low muscle glycogen [low glycogen, euglycemic (LGE), n = 8; low glycogen, euglycemic, hyperinsulinemic (LGEI), n = 5] and 6 subjects with normal muscle glycogen (NGE), whereas hyperglycemia was maintained in 8 low muscle glycogen subjects (LGH). All subjects cycled for 145 min at 70% of maximal oxygen uptake during the infusions. Insulin was infused in LGEI at 0.2 mU.kg-1.min-1. During exercise, respiratory exchange ratio (RER) was lower and norepinephrine higher in LGE than in NGE. In LGEI and LGH, RER at the start of exercise was the same as in LGE but did not decrease as in LGE. Free fatty acids (FFA) were higher and plasma insulin concentrations lower in LGE than NGE, LGEI, or LGH over the first 45 min of exercise. Rate of glucose infusion (Ri) and rate of glucose oxidation (Rox) were higher in LGH and LGEI than in NGE or LGE, and Ri matched Rox in all groups except LGH, in which Ri was greater than Rox. Muscle glycogen disappearance was greater in NGE than LGE, LGEI, or LGH, but the latter three groups did not differ. In conclusion, this study showed that low muscle glycogen content results in a decrease in RER, an increase in FFA, fat oxidation, and norepinephrine both at rest and during exercise, and does not affect Rox when euglycemia is maintained by infusion of glucose alone. Rox was increased only during insulin and hyperglycemia.
13名肌肉糖原含量低的受试者（低糖原、血糖正常组，即LGE组，n = 8；低糖原、血糖正常、高胰岛素组，即LGEI组，n = 5）和6名肌肉糖原含量正常的受试者（NGE组）维持了血糖正常，而8名肌肉糖原含量低的受试者（LGH组）维持了高血糖。在输注期间，所有受试者均以最大摄氧量的70%进行了145分钟的骑行。LGEI组以0.2 mU·kg-1·min-1的速率输注胰岛素。运动期间，LGE组的呼吸交换率（RER）低于NGE组，去甲肾上腺素高于NGE组。在LGEI组和LGH组中，运动开始时的RER与LGE组相同，但不像LGE组那样下降。在运动的前45分钟内，LGE组的游离脂肪酸（FFA）高于NGE组、LGEI组或LGH组，血浆胰岛素浓度低于NGE组、LGEI组或LGH组。LGH组和LGEI组的葡萄糖输注速率（Ri）和葡萄糖氧化速率（Rox）高于NGE组或LGE组，除LGH组Ri大于Rox外，所有组的Ri均与Rox匹配。NGE组的肌肉糖原消失量大于LGE组、LGEI组或LGH组，但后三组之间无差异。总之，本研究表明，低肌肉糖原含量导致静息和运动时RER降低、FFA增加、脂肪氧化增加以及去甲肾上腺素增加，并且在仅通过输注葡萄糖维持血糖正常时不影响Rox。仅在胰岛素和高血糖期间Rox增加。
