Starvation in the rat. II. Effect of age and obesity on protein sparing and fuel metabolism.
Starvation in the rat. II. Effect of age and obesity on protein sparing and fuel metabolism.
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大鼠饥饿。
DOI：
10.1152/ajpendo.1980.239.4.e277
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Ruderman,NB
中科院分区：
文献类型：
--
作者：
Goodman,MN;Larsen,PR;Kaplan,MM;Aoki,TT;Young,VR;Ruderman,NB
16 周大的对照和肥胖大鼠比 8 周大的对照大鼠存活时间更长。此外，与 8 周龄组不同，它们保留组织 RNA 和蛋白质。为了评估其基础，比较了三组中饥饿对循环燃料和激素以及氮和 3-甲基组氨酸 (3MH) 尿排泄的影响。 16 周龄肥胖大鼠和对照大鼠的尿氮和 3MH 在长期饥饿期间减少，表明两组都能够保存蛋白质并减少肌肉蛋白水解。相比之下，8 周龄对照大鼠的尿氮和 3MH 并未减少。老年大鼠的蛋白质保存与血液中丙氨酸水平的降低以及脂质燃料、酮体和游离脂肪酸水平的增加有关。尽管 8 周龄大鼠在饥饿的最初几天内酮体和游离脂肪酸也有所增加，但没有证据表明蛋白质会减少。在所有组中，随着脂肪储存最终耗尽，血脂水平下降，蛋白质分解代谢增加。饥饿导致所有大鼠的胰岛素水平下降至相当水平；然而，老年组较晚才达到最低水平。两个对照组的甲状腺素和三碘甲状腺原氨酸（T3）在禁食期间均下降；然而，肥胖大鼠的 T3 并没有降低。这些发现支持这样的论点：长期饥饿期间蛋白质的保存需要持续提供脂质燃料。胰岛素和甲状腺激素在调节这些适应中的作用尚不清楚。
Sixteen-week-old control and obese rats survive longer than 8-wk-old control rats. In addition, unlike the 8-wk-old group, they conserve tissue RNA and protein. To evaluate the basis for this, the effects of starvation on circulating fuels and hormones and the urinary excretion of nitrogen and 3-methylhistidine (3MH) were compared in the three groups. Urinary nitrogen and 3MH diminished during prolonged starvation in 16-wk-old obese and control rats, suggesting that both groups are able to conserve protein and curtail muscle proteolysis. In contrast, urine nitrogen and 3MH did not decrease in 8-wk-old control rats. Protein conservation in the older rats was associated with diminished blood levels of alanine and increased levels of lipid fuels, ketone bodies, and free fatty acids. Although ketone bodies and free fatty acids were also increased during the first few days of starvation in 8-wk-old rats, there was no evidence of protein sparing. In all groups, as fat stores became exhausted terminally, blood lipid levels decreased and protein catabolism increased. Starvation caused insulin to decrease to comparable levels in all rats; however, minimal levels were reached later in the older groups. Thyroxine and triiodothyronine (T3) decreased during the fast in both control groups; however, T3 did not decrease in the obese rats. These findings support the contention that the conservation of protein during prolonged starvation requires the continued availability of lipid fuels. The role of insulin and thyroid hormone in modulating these adaptations is unclear.