Challet E, le Maho Y, Robin J P, Malan A, Cherel Y
Centre d'Ecologie et Physiologie Energétiques, Centre National de la Recherche Scientifique, Strasbourg, France.
Pharmacol Biochem Behav. 1995 Mar;50(3):405-12. doi: 10.1016/0091-3057(94)00287-s.
During fasting, most of the energy is derived from lipids whereas proteins are efficiently spared. However, there is a late rise in net protein utilization. Fasting is also associated with an increase in locomotor activity. Because the plasma corticosterone level increases concomitantly with these metabolic and behavioral changes, the involvement of corticosterone has been hypothesized. To test this, the net protein utilization and locomotor activity were investigated in fasted adrenalectomized (Adx) rats, with or without replacement with corticosterone, and in fasted intact rats treated with RU486, an antagonist of type II glucocorticoid receptors. During the phase of fasting characterized by protein sparing, urine nitrogen loss was further reduced in Adx rats and in RU486-treated controls compared with intact rats and with Adx rats with corticosterone replacement: this indicates a catabolic effect of corticosterone through type II receptors. In the last phase of fasting, the rise in net protein breakdown was suppressed in Adx rats and restored by corticosterone replacement. The increase in locomotor activity induced by fasting in controls was suppressed in Adx and restored by corticosterone replacement. This rise in running activity was still present in RU486-treated rats. In conclusion, this study shows that corticosterone plays a critical role in the changes of both protein catabolism and locomotor activity during prolonged fasting.
在禁食期间，大部分能量来自脂质，而蛋白质则得到有效节省。然而，净蛋白质利用率后期会上升。禁食还与运动活动增加有关。由于血浆皮质酮水平与这些代谢和行为变化同时升高，因此有人推测皮质酮参与其中。为了验证这一点，对禁食的肾上腺切除（Adx）大鼠（有无皮质酮替代）以及用II型糖皮质激素受体拮抗剂RU486处理的禁食完整大鼠的净蛋白质利用率和运动活动进行了研究。在以蛋白质节省为特征的禁食阶段，与完整大鼠以及接受皮质酮替代的Adx大鼠相比，Adx大鼠和接受RU486处理的对照组的尿氮损失进一步减少：这表明皮质酮通过II型受体具有分解代谢作用。在禁食的最后阶段，Adx大鼠净蛋白质分解的上升受到抑制，皮质酮替代可使其恢复。对照组中由禁食诱导的运动活动增加在Adx大鼠中受到抑制，皮质酮替代可使其恢复。在接受RU486处理的大鼠中，这种跑步活动的增加仍然存在。总之，这项研究表明皮质酮在长期禁食期间蛋白质分解代谢和运动活动的变化中起关键作用。
