Delayed short-term secretory regulation of ghrelin in obese animals: Evidenced by a specific RIA for the active form of ghrelin
Delayed short-term secretory regulation of ghrelin in obese animals: Evidenced by a specific RIA for the active form of ghrelin
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DOI：
10.1210/en.2002-220225
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发表时间：
2002-09-01
期刊：
影响因子：
4.8
通讯作者：
Nakao, K
中科院分区：
文献类型：
--
作者：
Ariyasu, H;Takaya, K;Nakao, K
Ghrelin 是一种酰化肽，其脂质修饰对其生物活性至关重要。先前的研究表明，它能强烈刺激 GH 释放，并具有有效的促食欲作用。同时，有足够的证据表明进食状态会影响血浆生长素释放肽水平。禁食会刺激生长素释放肽的分泌，进食会降低血浆生长素释放肽的水平。在这项研究中，我们考虑了其分子形式，研究了遗传性肥胖动物禁食对血浆生长素释放肽的调节作用。与对照小鼠相比，ob/ob 和 db/db 小鼠中活性形式的生长素释放肽以及总生长素释放肽的血浆水平降低。 Zucker 脂肪 (fa/fa) 大鼠在禁食后也表现出比对照大鼠更低的血浆生长素释放肽水平。然而，胰岛素引起的低血糖会刺激禁食的脂肪大鼠分泌生长素释放肽。此外，注射葡萄糖可降低大鼠血浆生长素释放肽水平。还研究了肥胖严重程度对生长素释放肽分泌调节的影响。即使在禁食 48 小时后，老年肥胖大鼠的血浆生长素释放肽水平也较低。这些数据表明，肥胖动物中总生长素释放肽和活性形式生长素释放肽的短期分泌调节被延迟，并且血糖水平可能参与了延迟调节。
Ghrelin is an acylated peptide, whose lipid modification is essential for its biological activities. Previous studies demonstrated that it strongly stimulates GH release and has a potent orexigenic action. Meanwhile, there is enough evidence showing that feeding states influence plasma ghrelin levels. Fasting stimulates ghrelin secretion, and feeding reduces plasma ghrelin levels. In this study we examined the regulation of plasma ghrelin by fasting in genetically obese animals considering its molecular forms. Plasma levels of active form of ghrelin as well as those of total ghrelin were reduced in ob/ob and db/db mice compared with those in their control mice. Zucker fatty (fa/fa) rats also showed lower plasma ghrelin levels by fasting than the control rats. Insulin-induced hypoglycemia, however, stimulated ghrelin secretion in the fasted fatty rats. Moreover, glucose injection was revealed to reduce plasma ghrelin levels in rats. The effect of the severity of obesity on secretory regulation of ghrelin was also studied. Older fatty rats showed low plasma ghrelin levels even after 48-h fasting. These data suggest that the short-term secretory regulation of total ghrelin and the active form of ghrelin is delayed in obese animals and that blood glucose levels may be involved in the delayed regulation.