Glycolysis plays a central role in organismal metabolism, but its quantitative inputs across mammalian tissues remain unclear. Here we use ¹³C-tracing in mice to quantify glycolytic intermediate sources: circulating glucose, intra-tissue glycogen, and circulating gluconeogenic precursors. Circulating glucose is the main source of circulating lactate, the primary end product of tissue glycolysis. Yet circulating glucose highly labels glycolytic intermediates in only a few tissues: blood, spleen, diaphragm, and soleus muscle. Most glycolytic intermediates in the bulk of body tissue, including liver and quadriceps muscle, come instead from glycogen. Gluconeogenesis contributes less but also broadly to glycolytic intermediates, and its flux persists with physiologic feeding (but not hyperinsulinemic clamp). Instead of suppressing gluconeogenesis, feeding activates oxidation of circulating glucose and lactate to maintain glucose homeostasis. Thus, the bulk of the body slowly breaks down internally stored glycogen while select tissues rapidly catabolize circulating glucose to lactate for oxidation throughout the body.

糖酵解在有机体代谢中起着核心作用，但其在哺乳动物组织中的定量输入仍不清楚。这里我们使用¹³在小鼠中进行 C 追踪以量化糖酵解中间体来源：循环葡萄糖、组织内糖原和循环糖异生前体。循环葡萄糖是循环乳酸的主要来源，乳酸是组织糖酵解的主要终产物。然而，循环葡萄糖仅在少数组织中高度标记糖酵解中间体：血液、脾脏、膈肌和比目鱼肌。大部分身体组织中的大多数糖酵解中间体，包括肝脏和股四头肌，都来自糖原。糖异生对糖酵解中间体的贡献较少但也很广泛，并且其通量持续存在于生理喂养（但不是高胰岛素钳夹）。喂养不是抑制糖异生，而是激活循环葡萄糖和乳酸的氧化以维持葡萄糖稳态。因此，