School of Kinesiology, Univ. of Michigan, Ann Arbor, MI 48109-2214, USA.
Am J Physiol Endocrinol Metab. 2012 Nov 15;303(10):E1264-72. doi: 10.1152/ajpendo.00320.2012. Epub 2012 Sep 25.
Previously, we reported that overeating for only a few days markedly suppressed the secretion of growth hormone (GH). The purpose of the present study was to determine the role of this reduction in GH concentration on key metabolic adaptations that occur during 2 wk of overeating. Nine nonobese, healthy adults were admitted to the hospital for 2 wk, during which time they ate ∼4,000 kcal/day (70 kcal·kg fat-free mass(-1)·day(-1); 50% carbohydrate, 35% fat, and 15% protein), and their plasma GH concentration was allowed to decline naturally (control). An additional eight subjects underwent the same overeating intervention and received exogenous GH treatment (GHT) administered in four daily injections to mimic physiological GH secretion throughout the 2-wk overeating period. We measured plasma insulin and glucose concentrations in the fasting and postprandial state as well as fasting lipolytic rate, proteolytic rate, and fractional synthetic rate (FSR) using stable-isotope tracer methods. GHT prevented the fall in plasma GH concentration, maintaining plasma GH concentration at baseline levels (1.2 ± 0.2 ng/ml), which increased fasting and postprandial assessments of insulin resistance (P < 0.05) and increased fasting lipidemia (all P < 0.05 vs. control). In addition, preventing the suppression in GH with overeating also blunted the increase in systemic proteolysis (P < 0.05 GHT vs. control). However, GHT did not alter lipolysis or FSR in response to overeating. In conclusion, our main findings suggest that the suppression in GH secretion that naturally occurs during the early stages of overeating may help attenuate the insulin resistance and hyperlipidemia that typically accompany overeating.
此前，我们曾报道过仅几天的过度进食就会显著抑制生长激素（GH）的分泌。本研究的目的是确定这种 GH 浓度降低对过度进食 2 周期间发生的关键代谢适应的作用。9 名非肥胖、健康的成年人被收入医院 2 周，在此期间他们每天摄入约 4000 千卡（70 千卡·kg 去脂体重-1·天-1；50%碳水化合物，35%脂肪，15%蛋白质），并且允许他们的血浆 GH 浓度自然下降（对照）。另外 8 名受试者接受了相同的过度进食干预，并接受了外源性 GH 治疗（GHT），每天注射 4 次，以模拟生理 GH 分泌在整个 2 周过度进食期间。我们使用稳定同位素示踪剂方法测量了空腹和餐后状态下的血浆胰岛素和葡萄糖浓度，以及空腹脂肪分解率、蛋白分解率和分数合成率（FSR）。GHT 防止了血浆 GH 浓度的下降，将血浆 GH 浓度维持在基线水平（1.2±0.2ng/ml），这增加了空腹和餐后胰岛素抵抗的评估（P<0.05），并增加了空腹血脂异常（所有 P<0.05 与对照）。此外，防止 GH 被过度进食抑制也减弱了全身蛋白分解的增加（P<0.05 GHT 与对照）。然而，GHT 并没有改变脂肪分解或 FSR 对过度进食的反应。总之，我们的主要发现表明，过度进食早期自然发生的 GH 分泌抑制可能有助于减轻过度进食通常伴随的胰岛素抵抗和高脂血症。
