Edmond J, Auestad N, Robbins R A, Bergstrom J D
Fed Proc. 1985 Apr;44(7):2359-64.
In the course of mammalian development milk has evolved with unique characteristics as has the capacity of the neonatal rat to process this nutrient source. The primary carbon source in milk is fat, which provides two readily utilized metabolites, acetoacetate and D(-)-3-hydroxybutyrate (ketone bodies), as well as free fatty acids and glycerol. Carbohydrate provides less than 12% of the caloric content of rat milk and glucose has to be produced by the suckling rat to maintain glucose homeostasis. One would predict that glucose would be used sparingly and in pathways that cannot be satisfied by other readily available metabolites. Studies of the uptake of metabolites and the development of key enzymes for the utilization of glucose and ketone bodies by developing brain support the concept that ketone bodies are preferred substrates for the supply of carbon to respiration and lipogenesis. Astrocytes, oligodendrocytes, and neurons from developing brain all have an excellent capacity to use ketone bodies for respiration. By contrast, glucose is utilized preferentially in the hexose monophosphate shunt by all three cell populations. We are examining the requirement for ketone bodies by developing brain with the application of a system to rear rat pups artificially on a milk substitute that promotes a hypoketonemia.
在哺乳动物的发育过程中，乳汁进化出了独特的特性，新生大鼠处理这种营养来源的能力也同样如此。乳汁中的主要碳源是脂肪，它提供了两种易于利用的代谢产物，乙酰乙酸和D(-)-3-羟基丁酸（酮体），以及游离脂肪酸和甘油。碳水化合物提供的热量不到大鼠乳汁热量的12%，哺乳的大鼠必须产生葡萄糖以维持葡萄糖稳态。可以预测，葡萄糖会被谨慎使用，且用于其他易于获得的代谢产物无法满足的途径。对发育中的大脑摄取代谢产物以及利用葡萄糖和酮体的关键酶的研究支持了这样一种观点，即酮体是呼吸和脂肪生成的碳供应的首选底物。发育中的大脑中的星形胶质细胞、少突胶质细胞和神经元都具有利用酮体进行呼吸的出色能力。相比之下，所有这三种细胞群体都优先在磷酸己糖途径中利用葡萄糖。我们正在通过应用一种系统来人工饲养大鼠幼崽，使其食用促进低酮血症的代乳品，以此来研究发育中的大脑对酮体的需求。
