NEW YORK— A set of brain signals known to help memories form may also influence blood sugar levels, finds a new study in rats.
Researchers at NYU Grossman School of Medicine discovered that a peculiar signaling pattern in the brain region called the hippocampus, linked by past studies to memory formation, also influences metabolism, the process by which dietary nutrients are converted into blood sugar (glucose) and supplied to cells as an energy source.
The study revolves around brain cells called neurons that “fire” (generate electrical pulses) to pass on messages. Researchers in recent years discovered that populations of hippocampal neurons fire within milliseconds of each other in cycles, with the firing pattern is called a “sharp wave ripple” for the shape it takes when captured graphically by EEG, a technology that records brain activity with electrodes.
Published online in Nature on Aug. 11, a new study found that clusters of hippocampal sharp wave ripples were reliably followed within minutes by decreases in blood sugar levels in the bodies of rats. While the details need to be confirmed, the findings suggest that the ripples may regulate the timing of the release of hormones, possibly including insulin, by the pancreas and liver, as well of other hormones by the pituitary gland.
“Our study is the first to show how clusters of brain cell firing in the hippocampus may directly regulate metabolism,” says senior study author György Buzsáki, MD, PhD, the Biggs Professor in the Department of Neuroscience and Physiology at NYU Langone Health
“We are not saying that the hippocampus is the only player in this process, but that the brain may have a say in it through sharp wave ripples,” says Buzsáki, also a faculty member in the Neuroscience Institute at NYU Langone.
Known to keep blood sugar at normal levels, insulin is released by pancreatic cells, not continually, but periodically in bursts. As sharp wave ripples mostly occur during non-rapid eye movement (NREM) 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, say the study authors.
Previous work by Buzsaki’s team had suggested that the sharp wave ripples are involved in permanently storing each day’s memories the same night during NREM sleep, and his 2019 study found that rats learned faster to navigate a maze when ripples were experimentally prolonged.
“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,” says corresponding study author David Tingley, PhD, a post-doctoral scholar in Buzsaki’s lab.