Food intake causes a major challenge for the human organism to keep all nutrients (e.g. sugars, amino acids, lipids, vitamins etc.) in a range that can be tolerated by the human body. This state after food consumption, i.e. the postprandial phase, is characterized by rapidly changing metabolite concentrations and metabolic flux adaptations. The quantification of metabolic fluxes in the highly dynamic postprandial phase represents a major experimental challenge.
Interdisciplinary approach – key for this investigation
An international team of researchers with different areas of expertise was needed to tackle this research question. Scientists from the Unilever Foods Innovation Centre designed the nutritional intervention study that involved twelve human subjects, in vivo stable isotope labeling and time-resolved blood collection. Two food products with different carbohydrate sources were investigated, a glucose solution and a wheat flour based porridge. The plasma samples were analyzed by scientists from the TU Braunschweig using a specialized analytical approach to obtain absolute concentrations of several central carbon metabolites. The generated data were used as input for a mathematical metabolic network model resembling the metabolic situation in the postprandial phase. This combined approach enabled the generation of quantitative metabolic fluxes in this highly dynamic metabolic state.
Plasma lactate pool enables metabolic flexibility
The researchers found that, depending on the consumed food product, the metabolic adaptations were vastly different. After intake of the nutritionally more complex wheat porridge, flux alterations were stronger as in the less complex glucose solution. The researchers showed that the net direction of several fluxes changed during the course of the postprandial phase and demonstrated that systemic lactate and to a lesser extent, pyruvate and alanine, serve as metabolic buffers in the postprandial phase: When excessive amounts of nutrients are available, the nutrients are converted into lactate and channeled into the systemic lactate pool, however, when nutrient availability is reduced, systemic lactate is mobilized to serve as substrate for other metabolic processes. Further investigations on metabolic flux alterations as accurate biomarkers in the context of metabolic diseases are warranted.
Schlicker L, Zhao G, Dudek C-A, Boers HM, Meyer-Hermann M, Jacobs DM and Hiller K (2022) Systemic Lactate Acts as a Metabolic Buffer in Humans and Prevents Nutrient Overflow in the Postprandial Phase. Front. Nutr. 9:785999. doi: 10.3389/fnut.2022.785999