Metabolic adaptations in pregnancy and their implications for the availability of substrates to the fetus
Metabolic adaptations in pregnancy and their implications for the availability of substrates to the fetus
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DOI：
10.1038/sj.ejcn.1600984
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发表时间：
2000-03-01
影响因子：
4.7
通讯作者：
Herrera, E
中科院分区：
文献类型：
--
作者：
Herrera, E
在怀孕的前三分之二，母亲处于合成代谢状态，由于饮食过多和脂肪生成增加，她的脂肪库增加。在妊娠的最后三分之一，母亲切换到分解代谢状态。葡萄糖是穿过胎盘的最丰富的营养素，尽管在胚胎发育活动中增加，但其引起母体低血糖。脂肪组织脂解活性增强，增加到达肝脏的FFA和甘油的血浆水平;因此，甘油三酯的产生增加，以极低密度脂蛋白（VLDL）的形式返回循环。甘油也被用作一种优先的促胚胎发生的底物，从而为胎儿节省了其他更必需的底物，如氨基酸。在禁食条件下，脂肪酸通过β-氧化途径转化为酮体，这些化合物很容易穿过胎盘屏障并被胎儿代谢。增强的肝脏产生的VLDL-甘油三酯与脂肪组织脂蛋白脂肪酶（LPL）的减少和胆固醇酯转移蛋白的血浆活性的增加一起导致这些脂蛋白的强烈增加和甘油三酯在低密度和高密度脂蛋白中的成比例富集。母体甘油三酯不会穿过胎盘，但LPL和其他脂肪酶的存在允许它们水解，向胎儿释放脂肪酸。在禁食条件下，母体肝脏使用循环中的甘油三酯作为生酮底物。在分娩前后，乳腺中的LPL活性被诱导，将循环的甘油三酯驱动到该器官用于乳汁合成，从而使来自母亲饮食的必需脂肪酸可供哺乳新生儿使用。
During the first two-thirds of gestation, the mother is in an anabolic condition, increasing her fat depots thanks to both hyperphagia and enhanced lipogenesis. During the last third of gestation, the mother switches to a catabolic condition. Glucose is the mast abundant nutrient crossing the placenta, which causes maternal hypoglycemia despite an increase in the gluconeogenetic activity. Adipose tissue lipolytic activity becomes enhanced, increasing plasma levels of FFA and glycerol that reach the liver; consequently there is an enhanced production of triglycerides that return to the circulation in the form of very low density lipoproteins (VLDL). Glycerol is also used as a preferential gluconeogenetic substrate, saving other more essential substrates, like amino acids, far the fetus.Under fasting conditions, fatty acids are converted into ketone bodies throughout the beta-oxidation pathway, and these compounds easily cross the placental barrier and are metabolized by the fetus. An enhanced liver production of VLDL-triglycerides together with a decrease in adipose tissue lipoprotein lipase (LPL) and an increase in plasma activity of cholesterol ester transfer protein causes both an intense increment in these lipoproteins and a proportional enrichment of triglycerides in both low and high density lipoproteins. Maternal triglycerides do not cross the placenta, but the presence of LPL and other lipases allows their hydrolysis, releasing fatty acids to the fetus. Under fasting conditions, the maternal liver uses circulating triglycerides as ketogenic substrates. Around parturition there is an induction of LPL activity in the mammary glands, driving circulating triglycerides to this organ for milk synthesis, allowing essential fatty acids derived from the mother's diet to become available to the suckling newborn.