Youn J H, Buchanan T A
Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.
Diabetes. 1993 May;42(5):757-63. doi: 10.2337/diab.42.5.757.
Effects of 24-h and 48-h fasting on maximal insulin-stimulated whole-body and muscle glucose uptake, glycogen synthesis, and glycolysis were studied in conscious rats by combining the glucose clamp technique with tracer methods. Fasting decreased body weight and basal plasma glucose, plasma insulin, hepatic glucose output, and glucose clearance (P < 0.05 for all). However, maximal insulin-stimulated whole-body glucose uptake, normalized to body weight, was almost identical in fed, 24-h fasted, and 48-h fasted rats (191 +/- 8, 185 +/- 14, and 182 +/- 5 mumol.kg-1.min-1, respectively; P > 0.7). Similarly, rates of insulin-stimulated glucose uptake by four different skeletal muscles, estimated by the 2-deoxyglucose injection technique, were not different among the three groups. In contrast to glucose uptake, insulin-stimulated whole-body glycolysis was decreased significantly after fasting (36% after 48 h fasting; P < 0.05), whereas insulin-stimulated whole-body glycogen synthesis was increased (44% after 48 h fasting; P < 0.05). In fed rats, glycolysis was the major pathway for glucose metabolism during hyperinsulinemia, accounting for 60 +/- 5% of glucose uptake. This fraction was decreased significantly by fasting (P < 0.01), so that after a 48-h fast, glycolysis accounted for only 40 +/- 3% of insulin-stimulated glucose uptake and glycogen synthesis became predominant pathway, accounting for 60 +/- 3% of whole-body glucose utilization. Whole-body patterns of glucose metabolism during hyperinsulinemia were paralleled by glucose metabolism in individual muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
通过将葡萄糖钳夹技术与示踪方法相结合，研究了24小时和48小时禁食对清醒大鼠最大胰岛素刺激的全身及肌肉葡萄糖摄取、糖原合成和糖酵解的影响。禁食使体重、基础血浆葡萄糖、血浆胰岛素、肝脏葡萄糖输出和葡萄糖清除率降低（所有指标P<0.05）。然而，以体重标准化后，喂食大鼠、禁食24小时大鼠和禁食48小时大鼠的最大胰岛素刺激的全身葡萄糖摄取几乎相同（分别为191±8、185±14和182±5μmol·kg-1·min-1；P>0.7）。同样，通过2-脱氧葡萄糖注射技术估算的胰岛素刺激的四种不同骨骼肌的葡萄糖摄取率在三组之间没有差异。与葡萄糖摄取相反，禁食后胰岛素刺激的全身糖酵解显著降低（禁食48小时后降低36%；P<0.05），而胰岛素刺激的全身糖原合成增加（禁食48小时后增加44%；P<0.05）。在喂食大鼠中，糖酵解是高胰岛素血症期间葡萄糖代谢的主要途径，占葡萄糖摄取的60±5%。该比例因禁食而显著降低（P<0.01），因此禁食48小时后，糖酵解仅占胰岛素刺激的葡萄糖摄取的40±3%，糖原合成成为主要途径，占全身葡萄糖利用的60±3%。高胰岛素血症期间全身葡萄糖代谢模式与单个肌肉中的葡萄糖代谢相似。（摘要截短于250字）
