Brain Memory Signals Appear to Regulate Metabolism

Megan Brooks

August 13, 2021

Rhythmic brain signals that help encode memories also appear to influence blood sugar levels and may regulate the timing of the release of hormones, early, pre-clinical research shows.

"Our study is the first to show how clusters of brain cell firing in the hippocampus may directly regulate metabolism," senior author György Buzsáki, MD, PhD, professor, Department of Neuroscience and Physiology, NYU Grossman School of Medicine and NYU Langone Health in New York City, said in a news release.

"Evidence suggests that the brain evolved, for reasons of efficiency, to use the same signals to achieve two very different functions in terms of memory and hormonal regulation," added corresponding author David Tingley, PhD, a post-doctoral scholar in Buzsáki's lab.

Additional research may also reveal devices or therapies that can adjust the brain signals to lower blood sugar and improve memory, the researchers say.

The study was published online August 11 in Nature.

It's recently been discovered that populations of hippocampal neurons fire within milliseconds of each other in cycles. This firing pattern is called a "sharp wave ripple" for the shape it takes when captured graphically by electroencephalogram.

In their study, Buzsáki, Tingley, and colleagues observed that clusters of sharp wave ripples recorded from the hippocampus of rats were "reliably" and rapidly, followed by decreases in blood sugar concentrations in the animals.

"This correlation was not dependent on circadian, ultradian, or meal-triggered fluctuations, it could be mimicked with optogenetically induced ripples in the hippocampus, but not in the parietal cortex, and was attenuated to chance levels by pharmacogenetically suppressing activity of the lateral septum (LS), the major conduit between the hippocampus and hypothalamus," the researchers report.

These observations suggest that hippocampal sharp wave ripples may regulate the timing of the release of hormones, possibly including insulin, by the pancreas and liver, as well as other hormones by the pituitary gland, the researchers note.

As sharp wave ripples mostly occur during non-rapid eye movement sleep, the impact of sleep disturbance on sharp wave ripples may provide a mechanistic link between poor sleep and high blood sugar levels seen in type 2 diabetes, they suggest.

"There are a couple of experimental studies showing that if you deprive a young healthy person for 48 hours from sleep, their glucose tolerance resembles that of a diabetic person, Buzsáki noted in an interview with Medscape Medical News.

Moving forward, the researchers will seek to extend their theory that several hormones could be affected by nightly sharp wave ripples.

The research was funded by National Institutes of Health. The authors have disclosed no relevant financial relationships.

Nature. Published online August 11, 2021. Abstract

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