RELATIONSHIPS BETWEEN LIPID AVAILABILITY AND PROTEIN-UTILIZATION DURING PROLONGED FASTING
RELATIONSHIPS BETWEEN LIPID AVAILABILITY AND PROTEIN-UTILIZATION DURING PROLONGED FASTING
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DOI：
10.1007/bf00260757
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发表时间：
1992-06-01
影响因子：
2
通讯作者：
LEMAHO, Y
中科院分区：
文献类型：
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作者：
CHEREL, Y;ROBIN, JP;LEMAHO, Y
哺乳动物和鸟类通过调动脂肪储存和尽量减少蛋白质损失来适应长期禁食。该策略最终导致与促进食物觅食的行为变化相关的蛋白质利用率的增加。使用 Zucker 大鼠作为模型，我们研究了严重肥胖对长期禁食期间蛋白质损失模式的影响。发现了初始肥胖和蛋白质利用之间的两种相互作用。首先，蛋白质保存在肥胖大鼠中比在瘦大鼠中更有效：脂肪大鼠的每日氮排泄量和来自蛋白质的能量消耗比例低三倍，并且各种肌肉中每日蛋白质损失更低。而且，脂肪大鼠的这一蛋白质节约阶段要长九倍。其次，肥胖动物并没有表现出瘦同窝动物中氮排泄的后期增加。饥饿期间脂肪大鼠的全身蛋白质损失较多（57% vs 29%），相应地，其肌肉中的总蛋白质损失也较多。实验结束时，瘦老鼠和肥胖老鼠的初始脂质储备分别减少了 98% 和 82%，而肥胖老鼠的身体成分仍然肥胖。这些结果支持这样的假设：在严重肥胖的人类和动物中，早在脂肪储存耗尽之前就达到了致命的累积蛋白质损失，而蛋白质保存阶段仍在继续。相比之下，在瘦老鼠中，禁食后的存活似乎取决于脂质燃料的可用性。数据还表明，野生动物体内积累过多的脂肪不利于生存，因为它消除了氮排泄增加的后期阶段，而氮排泄增加与预期身体储备致命耗尽的食物觅食行为有关。
Mammals and birds adapt to prolonged fasting by mobilizing fat stores and minimizing protein loss. This strategy ends with an increase in protein utilization associated with behavioural changes promoting food foraging. Using the Zucker rat as a model, we have investigated the effect of severe obesity on this pattern of protein loss during long-term fasting. Two interactions between the initial adiposity and protein utilization were found. First, protein conservation was more effective in obese than in lean rats: fatty rats had a three times lower daily nitrogen excretion and proportion of energy expenditure deriving from proteins, and a lower daily protein loss in various muscles. This phase of protein sparing is moreover nine times longer in the fatty rats. Second, obese animals did not show the late increase in nitrogen excretion that occurred in their lean littermates. Total body protein loss during starvation was larger in fatty rats (57% versus 29%) and, accordingly, total protein loss was greater in their muscles. At the end of the experiment, lean and obese rats had lost 98% and 82%, respectively, of their initial lipid reserves, and fatty rats still had an obese body composition. These results support the hypothesis that in severely obese humans and animals a lethal cumulative protein loss is reached long before the exhaustion of fat stores, while the phase of protein conservation is still continuing. In contrast, in lean rats, survival of fasting seems to depend on the availability of lipid fuels. The data also suggest that accumulation of too much fat in wild animals is detrimental for survival, because it eliminates the late phase of increase in nitrogen excretion that is linked to a food foraging behaviour anticipating a lethal depletion of body reserves.