Energy Balance
Energy Balance
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DOI：
10.1201/9781315380728-18
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Nasreen Begum
中科院分区：
文献类型：
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作者：
Nasreen Begum
身体在每天的禁食周期中保持能量平衡，在能量需求因体力消耗而增加的时期，以及能量供应因营养缺乏而耗尽的时期。在典型的一天中，消耗几餐，导致餐后几个小时的时间段，即进食状态，其中存在净能量增益。这种情况在睡眠期间和进餐间隙期间发生变化，此时净能量平衡，即卡路里摄入量减去卡路里摄入量，变为负值。这些都是导致重新进食的快速状态。身体维持能量平衡的能力是围绕一组消化，转换，运输和储存营养物质和能量的外周器官和组织，即胰腺肝脏脂肪组织肌肉胃肠道在进食状态下，营养物质-碳水化合物，脂肪和氨基酸-被吸收，转换和储存。作为对循环葡萄糖增加的响应，胰腺分泌胰岛素，其充当对其他外周组织的进食状态启动信号。肝脏吸收并储存葡萄糖作为糖原。甘油三酯被包装成大的、可运输的颗粒;这些被合成并储存在脂肪组织中，肌肉重建其蛋白质供应。在快速状态下，营养物质不再被吸收，而是驻留在外周组织中的能量源被动员和释放，以维持能量稳态。这种状态是由胰高血糖素从胰腺释放的信号。肝脏现在分解并释放储存的葡萄糖/糖原，启动糖原生成，启动脂肪酸氧化，并产生酮体作为减少的葡萄糖供应的替代/补充。脂肪组织降解其甘油三酯，从而向其他外周组织提供脂肪酸和甘油，肌肉利用脂肪酸氧化，酮体被运送到大脑。
The body maintains energy balance throughout the daily feed-fast cycles, across periods where energy demands increase due to physical exertion, and when energy supplies are depleted due to nutrient deprivation. During a typical day, several meals are consumed leading to periods of time several hours long after the meals, the fed state, where there is a net energy gain. This situation changes during sleep and during gaps in meal intake where the net energy balance, that is calories in minus calories out, becomes negative. These are the fast states that lead to refeeding. The ability of the body to maintain energy balance is centered about a set of peripheral organs and tissues that digest, convert, ship, and store nutrients and energy, namely, Pancreas Liver Adipose tissue Muscle Gastrointestinal tract In the fed state, nutrients – carbohydrates, fat, and amino acids – are taken in, converted, and stored. In response to the increase in circulating glucose, the pancreas secretes insulin that serves as a fed-state start signal to the other peripheral tissues. The liver takes up and stores the glucose as glycogen. Triglycerides are packaged into large, transportable particles; these are synthesized and stored in adipose (fat) tissue, and muscle rebuilds its supply of protein. In the fast state, nutrients are no longer taken in but instead energy sources residing in peripheral tissues are mobilized and released to maintain energy homeostasis. This state is signaled by glucagon release from the pancreas. The liver now breaks down and releases the stored glucose/glycogen, initiates gluconeogenesis, initiates fatty acid oxidation, and generates ketone bodies as an alternative/supplement to the dwindling glucose supply. Adipose tissue degrades their triglycerides thereby supplying fatty acids and glycerol to other peripheral tissues, muscle utilizes fatty acid oxidation, and ketone bodies are shipped to the brain.