Why Your Brain Consumes So Much Energy, Even At Rest
When compared under equal conditions, the brain spends much more energy than other organs. But the brain’s neurons consume a lot of fuel even when they’re not sending signals called neurotransmitters to each other. Now researchers at the Weill Cornell Institute of Medicine have discovered that the neurotransmitter packaging process may be responsible for this energy consumption.
In the study, published four days ago in Science Advances, researchers determined that tiny capsules called synaptic vesicles are an important source of energy consumption in dormant neurons. Neurons use these vesicles as containers for neurotransmitter molecules. These molecules are fired from communication ports called synaptic terminals to send signals to other neurons. Packing and packing neurotransmitters into vesicles is a chemical energy-consuming process. Scientists have also found that this process naturally leaks energy. This process leaks so much that it continues to consume a significant amount of energy even when the vesicles fill and the synaptic terminals become dormant.
D., who is professor of anesthesiology biochemistry and biochemistry at the Weill Cornell Institute of Medicine. “The findings will help us better understand why the human brain is so sensitive to cessation or reduction of refueling,” says Timothy Ryan.
The brain’s high energy consumption, even at rest, was first observed in studies conducted decades ago on the brain’s fuel consumption in coma and vegetative states. In those studies, it was discovered that even in these extremely dormant states, the brain’s glucose consumption drops by only half. This means that the brain still consumes a higher amount of energy compared to other organs. The sources of this resting energy loss have not been fully understood until now.
Dr. Ryan and his lab have shown in recent years that synaptic terminals, the bud-like structures of neurons from which neurotransmitter fires, consume significant energy in operation and exhibit a high degree of sensitivity to any disruption in refueling. In the new study, researchers examining fuel consumption when synaptic terminals are inactive, discovered that consumption is still high.
Scientists have discovered that this high energy consumption at rest is largely due to the pool of vesicles found at synaptic terminals. In a state of synaptic inactivity, each of the vesicles is completely filled with thousands of neurotransmitters, ready to send these signal-carrying loads across the synapses to the corresponding neurons.
Why does a synaptic vesicle consume energy even when it is full? In fact, an energy leak in the vesicle membrane; they discovered that a “flow of protein” occurs. A special “proton pump” enzyme in the vesicle needs to keep working, so even though the vesicle is already full of neurotransmitter molecules, it consumes fuel.
Experiments indicate that proteins called carriers are possible sources of this proton leak. The transporters normally take the neurotransmitters to the vesicles and change shape to transport the neurotransmitter. But in doing so, they also allow a proton to escape. Dr. Ryan speculates that the energy threshold in this shapeshifting process of transporters has been set low by evolution for faster reloading of neurotransmitters during synaptic activity. In this way, it is possible to think and act faster.
“Daha hızlı bir yükleme kapasitesinin olumsuz tarafı, rastgele meydana gelen ısıl dalgalanmaların bile taşıyıcıda şekil değişimini tetiklemesi ve hiç nörotransmiter sinyali yüklenmiyorken bile bu sürekli enerji kaybına sebep olmasıdır” diyor.
Kesecik başına düşen bu enerji sızıntısı ufak olsa da, insan beyninde yüzlerce trilyon sinaptik kesecik bulunduğu göz önüne alındığında bu enerji kaybının çok büyük olduğu görülüyor diyor Dr. Ryan.
Bulgu, beynin temel biyolojisini anlama bakımından önemli bir gelişme niteliğinde. Buna ilaveten beynin yakıt ikmalindeki bozulmaya karşı savunmasız olması, sinirbilimde büyük bir problem. Ayrıca, Alzheimer ve Parkinson hastalığının da içinde bulunduğu birçok yaygın beyin hastalığında metabolik yetersizlikler belirlenmiş. Bu araştırma hattı, nihayetinde önemli tıbbi bilmecelerin çözülmesine yardımcı olup yeni tedavilerin bulunmasını sağlayabilir.
“Eğer bu enerji kaybını güvenli biçimde düşürecek ve bu sayede beyin metabolizmasını yavaşlatacak bir yol olsaydı, klinik açıdan çok etkili olurdu” diyor Dr. Ryan.
Source: https://popsci.com.tr/beynin-dinlenenken-bile-neden-cok-enerji-tukettigi-bulundu/ Photograph: An animation showing nerves in the brain. Depiction: whitehoune/iStock and Webtecno