Nature: The brain signals that help memory form may affect blood sugar!

Researchers at New York University’s Grossman School of Medicine have discovered that there is a special signal pattern in the area of ​​the brain called the hippocampus.
Past studies have shown that the hippocampus is involved in memory formation.
It also affects metabolism, the process by which dietary nutrients are converted into blood sugar (glucose) and supplied to cells as an energy source
.

This research revolves around a type of brain cell called a neuron, which "burns" (produces electrical impulses) to transmit information
.

In recent years, researchers have discovered that neurons in the hippocampus fire each other in a period of several milliseconds.

A new study published on the website of "Nature" on August 11 found that the sharp waves of the hippocampus do cause the blood sugar levels in mice to drop within a few minutes
.

Although the details have yet to be confirmed, the results of the study indicate that these ripples may regulate the time when the pancreas and liver release hormones, which may include insulin and the time when the pituitary gland releases other hormones

"Our research shows for the first time how activated brain cell clusters in the hippocampus directly regulate metabolism," said senior research author Gy?rgy Buzsáki, MD, Biggs Professor of Neuroscience and Physiology, New York University Langone School of Health

"We are not saying that the hippocampus is the only participant in this process, but the brain may have a say in it through sharp waves," said Buzsáki, who is also a faculty member at New York University's Langone Institute of Neuroscience
.

Insulin is released by pancreatic cells, but not continuously, but periodic bursts
.

The authors of the study said that since sharp wave ripples mainly occur during non-rapid eye movement (NREM) sleep, the impact of sleep disorders on sharp wave ripples may provide a difference between poor sleep quality and high blood sugar levels in patients with type 2 diabetes.

The previous work of Buzsaki's team showed that during non-REM sleep, sharp wave ripples are involved in the permanent storage of daily memories on the same night.
His 2019 study found that when the ripples are extended by the experiment, mice learn faster To navigate the maze
.

"There is evidence that for efficiency reasons, the brain has evolved to use the same signal to achieve two distinct functions, namely memory and hormonal regulation," said corresponding author Dr.
David Tingley, a postdoctoral scholar in the Buzsaki laboratory.

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Dual role

Researchers say that the hippocampus is a good candidate brain area for multiple functions because it is connected to other brain areas, and hippocampal neurons have many surface proteins (receptors) that are sensitive to hormone levels, so they can Adjust your activities as part of the feedback loop
.

The new findings indicate that hippocampal ripples reduce blood sugar levels as part of this cycle

Tinley added: "Animals may first develop a system to control the release of hormones in a rhythmic cycle, but when they later develop more complex brains, they will apply the same mechanism to memory
.

"

Research data also shows that the hippocampal sharp wave signal is transmitted to the hypothalamus, which is thought to dominate and affect the pancreas and liver, but this is through an intermediate brain structure called the lateral septum
.

The researchers found that ripples may only affect the lateral septum through amplitude (the degree to which hippocampal neurons emit signals at the same time), rather than the order of ripple combinations, which may encode memory when the signal reaches the cortex

Consistent with this theory, short-term ripples of more than 30 times per minute in non-rapid eye movement sleep can cause a decrease in peripheral glucose levels, which is several times larger than a single ripple
.

Importantly, closing the lateral septum can eliminate the impact of hippocampal sharp wave ripples on surrounding blood sugar

In order to confirm that the hippocampus discharge pattern causes the glucose level to drop, the research team used a technique called optogenetics to artificially induce ripples by redesigning the hippocampus cells, including light-sensitive channels
.

Illuminating these cells through glass fibers produces ripples that have nothing to do with the behavior of the mouse or the state of the brain (such as resting or awake)

Next, the research team will seek to expand its theory that several hormones may be affected by dramatic fluctuations at night, including through studies on human patients
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Buzsaki said that future research may also reveal devices or treatments that can regulate blood sugar fluctuations and improve memory
.

In addition to Tinley and Bouzsaki, the authors of the study are Ekin Kaya, Catherine McLean, and Jordan Carpenter of the New York University Langone Health Center
.
This research was funded by the National Institutes of Health MH122391, U19 NS104590 and U19NS107616
.

Journal Reference :

1. David Tingley, Kathryn McClain, Ekin Kaya, Jordan Carpenter, György Buzsáki.
   A metabolic function of the hippocampal sharp wave-ripple .
   Nature , 2021; DOI: 10.
   1038/s41586-021-03811-w