Schenk Simon, Cook Jill N, Kaufman Amy E, Horowitz Jeffrey F
Substrate Metabolism Laboratory, Division of Kinesiology, The Univ. of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109-2214, USA.
Am J Physiol Endocrinol Metab. 2005 Mar;288(3):E519-25. doi: 10.1152/ajpendo.00401.2004. Epub 2004 Nov 2.
High plasma fatty acid availability and a positive energy balance in sedentary individuals reduce insulin sensitivity. This study's purpose was to determine whether high plasma fatty acid availability and systemic caloric excess after exercise also impair insulin sensitivity. On two separate occasions, seven nonobese women performed 90 min of exercise at approximately 65% peak oxygen uptake. In one trial, a lipid + heparin emulsion (Lipid) was infused overnight to increase plasma fatty acid availability. In the other trial, saline was infused as control. The next morning, a muscle biopsy was taken to measure muscle glycogen and intramuscular triglyceride (IMTG) concentrations. Three hours after the overnight infusion was stopped, insulin sensitivity was assessed with an intravenous glucose tolerance test, using minimal model analysis (Si). During the overnight infusions, plasma fatty acid concentration was approximately fourfold higher [means (SD): 0.84 (0.36) vs. 0.22 (0.09) mmol/l; P = 0.003], and the next morning IMTG concentration was approximately 30% greater [49.2 (6.6) vs. 38.3 (7.7) mmol/kg dry wt; P = 0.036] in Lipid compared with saline. However, muscle glycogen concentration was not different between trials (P = 0.82). Lipid caused a 24-h surplus of approximately 1100 kcal above energy balance (P = 0.00001), whereas energy balance was maintained in saline. Despite these differences in fatty acid and energy availability, Si the morning after exercise was not different between trials (P = 0.72). Thus insulin sensitivity the morning after a single exercise session was not reduced despite overnight exposure to a fourfold increase in plasma fatty acid concentration, elevated IMTG concentration, and systemic delivery of approximately 1,100-kcal excess.
久坐不动的个体血浆脂肪酸利用率高和能量平衡为正会降低胰岛素敏感性。本研究的目的是确定运动后血浆脂肪酸利用率高和全身热量过剩是否也会损害胰岛素敏感性。在两个不同的时间段，七名非肥胖女性以约65%的峰值摄氧量进行了90分钟的运动。在一次试验中，过夜输注脂质+肝素乳剂（脂质）以提高血浆脂肪酸利用率。在另一次试验中，输注生理盐水作为对照。第二天早晨，进行肌肉活检以测量肌肉糖原和肌内甘油三酯（IMTG）浓度。在过夜输注停止三小时后，使用最小模型分析（Si）通过静脉葡萄糖耐量试验评估胰岛素敏感性。在过夜输注期间，脂质组的血浆脂肪酸浓度大约高出四倍[均值（标准差）：0.84（0.36）与0.22（0.09）mmol/L；P = 0.003]，且第二天早晨，脂质组的IMTG浓度比生理盐水组大约高30%[49.2（6.6）与38.3（7.7）mmol/kg干重；P = 0.036]。然而，两次试验之间的肌肉糖原浓度没有差异（P = 0.82）。脂质组导致能量平衡出现约1100千卡的24小时盈余（P = 0.00001），而生理盐水组维持能量平衡。尽管脂肪酸和能量供应存在这些差异，但运动后第二天早晨的Si在两次试验之间没有差异（P = 0.72）。因此，尽管过夜暴露于血浆脂肪酸浓度增加四倍、IMTG浓度升高以及全身输送约1100千卡多余热量的情况，单次运动后第二天早晨的胰岛素敏感性并未降低。
