Team of scientists at the University of Zurich conducted a research providing support for a theory that nerve cells glucose and lactate to satisfy their energy demand. Although this idea has been known for a while, these scientists demonstrated for the first time in the intact mouse brain that lactate is being exchanged between different brain cells. This study finally confirms a 20-year old hypothesis.
Unsurprisingly, human brain demands for a lot of energy. However, despite an extensive number of researches performed on the subject, it remained unclear, how this energy is supplied to the brain cells. Scientists knew that lactic acid plays a role in this process, but there was only a hypothesis explaining what this role exactly is. It says that brain energy metabolism relies on cooperation between astrocytes and neurons. Astrocytes in this equation are the ones that produce lactate, which then covers energy demands of neurons. However, this remained a hypothesis only for 20 years, because of lack of experimental techniques, but now scientists managed to confirm the hypothesis.
The lactate flow is mediated by a specific transporter in this process. Professor Bruno Weber, leader of the research team, explained that these transporters “can be imagined as revolving doors in a shopping mall, which begin to turn faster when more people enter or exit”. During the experiments scientists accelerated these “revolving doors”. Interestingly, lactate levels changes in astrocytes only. However, based on the research and several control experiments, clear lactate gradient between astrocytes and neurons was confirmed.
It is also interesting how scientists managed to measure lactate levels in separate cells. They used fluorescent protein that binds lactate and changes the amount of light that fluorescent molecule releases. Using this protein scientists then investigated brain of anesthetized mice, measuring fluorescence changes with a special two-photon microscope.
The results of the research are extremely important not only because they almost give final confirmation to the 20 year old hypothesis. The brain metabolism problems are associated with a variety of diseases. This means that by bettering our understanding about how energy demands in our brain are met, we can in the future expect novel treatments for these diseases.