Clore J N, Helm S T, Nestler J E, Blackard W G
Department of Internal Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
J Clin Endocrinol Metab. 1990 Apr;70(4):865-8. doi: 10.1210/jcem-70-4-865.
We have previously reported a 25% fall in glucose utilization (Rd) and glucose production (Ra) in normal volunteers during an overnight fast, when glycogenolysis accounts for approximately 70% of hepatic glucose output (HGO). This reduction in Ra and Rd was positively correlated with reductions in glycerol and FFA. To determine if a similar fall in HGO occurs after a prolonged fast when HGO depends solely upon gluconeogenesis, seven normal male volunteers were fasted for 72 h. Glucose kinetics were then assessed overnight using a [3-3H]glucose infusion from 2200-0800 h. Plasma glucose (3.6 +/- 0.1 mM), immunoreactive insulin (2.7 +/- 0.4 mU/L), C-peptide (0.22 +/- 0.03 nmol/l), Rd (1.30 +/- 0.03 mg/kg.min), and Ra (1.28 +/- 0.03 mg/kg.min) were suppressed, and plasma glucagon (98.8 +/- 13.2 pmol/L) was elevated compared to values obtained during the overnight fast, but none of these parameters changed overnight after the 3-day fast. Plasma lactate (0.98 +/- 0.09 mmol/L) and alanine (0.18 +/- 0.03 mmol/L) levels were also unchanged throughout the night. Plasma glycerol (0.14 +/- 0.03 mmol/L) and FFA (0.98 +/- 0.07 mmol/L) were significantly elevated compared to values during the overnight fast, but failed to fall during the study as had been observed during a 14-h fast. We conclude that the modulation of HGO observed during an overnight fast does not occur during prolonged fasting. The lack of nocturnal modulation of HGO when plasma FFA and glycerol levels are fixed at elevated concentrations supports a role of FFA and/or glycerol in the modulation of HGO during an overnight fast.
我们之前曾报道，在正常志愿者过夜禁食期间，葡萄糖利用率（Rd）和葡萄糖生成率（Ra）下降了25%，此时糖原分解约占肝脏葡萄糖输出量（HGO）的70%。Ra和Rd的这种降低与甘油和游离脂肪酸（FFA）的减少呈正相关。为了确定在长时间禁食后，当HGO仅依赖糖异生时是否会出现类似的HGO下降，对7名正常男性志愿者进行了72小时的禁食。然后在22:00至08:00期间通过输注[3-3H]葡萄糖对葡萄糖动力学进行过夜评估。与过夜禁食期间获得的值相比，血浆葡萄糖（3.6±0.1 mM）、免疫反应性胰岛素（2.7±0.4 mU/L）、C肽（0.22±0.03 nmol/L）、Rd（1.30±0.03 mg/kg·min）和Ra（1.28±,03 mg/kg·min）受到抑制，血浆胰高血糖素（98.8±13.2 pmol/L）升高，但在3天禁食后的夜间这些参数均未改变。血浆乳酸（0.98±0.09 mmol/L）和丙氨酸（0.18±0.03 mmol/L）水平在整个夜间也未改变。与过夜禁食期间的值相比，血浆甘油（0.14±0.03 mmol/L）和FFA（0.98±0.07 mmol/L）显著升高，但在研究期间并未像在14小时禁食期间观察到的那样下降。我们得出结论，过夜禁食期间观察到的HGO调节在长时间禁食期间不会发生。当血浆FFA和甘油水平固定在升高浓度时HGO缺乏夜间调节，这支持了FFA和/或甘油在过夜禁食期间对HGO调节中的作用。
