Data_Sheet_1_Systemic Lactate Acts as a Metabolic Buffer in Humans and Prevents Nutrient Overflow in the Postprandial Phase.zip

On an organismal level, metabolism needs to react in a well-orchestrated manner to metabolic challenges such as nutrient uptake. Key metabolic hubs in human blood are pyruvate and lactate, both of which are constantly interconverted by very fast exchange fluxes. The quantitative contribution of different food sources to these metabolite pools remains unclear. Here, we applied in vivo stable isotope labeling to determine postprandial metabolic fluxes in response to two carbohydrate sources of different complexity. Depending on the ingested carbohydrate source, glucose or wheat flour, the net direction of the lactate dehydrogenase, and the alanine amino transferase fluxes were adjusted in a way to ensure sufficient availability, while, at the same time, preventing an overflow in the respective metabolite pools. The systemic lactate pool acts as a metabolic buffer which is fueled in the early- and depleted in the late-postprandial phase and thus plays a key role for systemic metabolic homeostasis.

从机体水平来看，新陈代谢需以精密协调的方式响应营养摄取等代谢应激。人体血液中的关键代谢枢纽为丙酮酸与乳酸，二者始终通过极快的交换通量实现相互转化。目前，不同食物来源对这些代谢物池（metabolite pools）的定量贡献仍不明确。本研究采用体内稳定同位素标记（in vivo stable isotope labeling）技术，针对两种复杂度不同的碳水化合物来源，测定其诱导的餐后代谢通量（postprandial metabolic fluxes）。根据摄入的碳水化合物来源（葡萄糖或小麦粉），乳酸脱氢酶（lactate dehydrogenase）与丙氨酸氨基转移酶（alanine amino transferase）的通量净方向会发生适应性调节，既保障代谢物的充足供应，同时又可避免对应代谢物池出现过载。全身乳酸池可作为代谢缓冲池：餐后早期被补充，餐后晚期被消耗，因此在维持全身代谢稳态（systemic metabolic homeostasis）中发挥关键作用。