However, less attention has been paid to its role in day-to-day situations.

In a study published in Molecular Metabolism, University of Michigan researchers have shown that a specific population of neurons in the hypothalamus help the brain maintain blood glucose levels under routine circumstances.

Over the past five decades, researchers have shown that dysfunction of the nervous system can lead to fluctuations in blood glucose levels, especially in patients with diabetes.

Some of these neurons are in the ventromedial nucleus of the hypothalamus, a region of the brain that controls hunger, fear, temperature regulation and sexual activity.

"Most studies have shown that this region is involved in raising blood sugar during emergencies," said Alison Affinati, M.D., Ph.D., assistant professor of internal medicine and member of Caswell Diabetes Institute.

"We wanted to understand whether it is also important in controlling blood sugar during day-to-day activities because that's when diabetes develops."

The group focused on VMH^Cckbr neurons, which contain a protein called the cholecystokinin b receptor.

They used mouse models in which these neurons were inactivated.

By monitoring the blood glucose levels, the researchers found that VMH^Cckbr neurons play an important role in maintaining glucose during normal activities, including the early part of the fasting period between the last meal of the day and waking up in the morning.

"In the first four hours after you go to bed, these neurons ensure that you have enough glucose so that you don't become hypoglycemic overnight," Affinati said.

To do so, the neurons direct the body to burn fat through a process called lipolysis.

"In the first four hours after you go to bed, these neurons ensure that you have enough glucose so that you don't become hypoglycemic overnight."

-Alison Affinati, M.D., Ph.D.

The fats are broken down to produce glycerol, which is used to make sugar.

When the group activated the VMH^Cckbr neurons in mice, the animals had increased glycerol levels in their bodies.

These findings could explain what happens in patients with prediabetes, since they show an increase in lipolysis during the night.

The researchers believe that in these patients, the VMH^Cckbr neurons could be overactive, contributing to higher blood sugar.

These nerve cells, however, only controlled lipolysis, which raises the possibility that other cells might be controlling glucose levels through different mechanisms.

"Our studies show that the control of glucose is not an on-or-off switch as previously thought," Affinati said.

"Different populations of neurons work together, and everything gets turned on in an emergency. However, under routine conditions, it allows for subtle changes."

The team is working to understand how all the neurons in the ventromedial nucleus co-ordinate their functions to regulate sugar levels during different conditions, including fasting, feeding and stress.

They are also interested in understanding how the brain and nervous system together affect the body's control of sugar, especially in the liver and pancreas.

The work was carried out by a team of U-M researchers at the Caswell Diabetes Institute who focus on the neuronal control of metabolism -- the roles played by the brain and nervous system in metabolic control and disease.

Additional authors: Jiaao Su, Abdullah Hashsham, Nandan Kodur, Carla Burton, Amanda Mancuso, Anjan Singer, Jennifer Wloszek, Abigail J. Tomlinson, Warren T. Yacawych, Jonathan N. Flak, Kenneth T. Lewis, Lily R. Oles, Hiroyuki Mori, Nadejda Bozadjieva-Kramer, Adina F. Turcu, Ormond A. MacDougald and Martin G. Myers.

Funding/disclosures: Research support was provided by the Michigan Diabetes Research Center (NIH grant P30 DK020572), the Mouse Metabolic Phenotyping Center -- Live (U2CDK135066) Physiology Phenotyping Core, the Michigan Nutrition and Obesity Center Adipose Tissue Core (P30 DK089503); Department of Veterans Affairs (IK2BX005715); the Warren Alpert Foundation; Endocrine Fellows Foundation; Marilyn H. Vincent Foundation and Novo Nordisk. This work was also supported in part by NIH grant K08 DK1297226.

The research team found that even moderately irregular sleep doubles the risk of having another clinical event within six months, according to a study published on August 21 in the journal JACC Advances. A clinical event could be another visit to the emergency room, hospitalization or even death.

"Going to bed and waking up at consistent times is important for overall health," said lead author Brooke Shafer, Ph.D., a research assistant professor in the Sleep, Chronobiology and Health Laboratory in the OHSU School of Nursing. "Our study suggests that consistency in sleep timing may be especially important for adults with heart failure."

Researchers enrolled 32 patients who had been hospitalized for acutely decompensated heart failure at OHSU Hospital and Hillsboro Medical Center from September 2022 through October 2023. For one week following hospital discharge, participants used sleep diaries to record the time they fell asleep at night, woke up in the morning and the timing of naps they took during the day.

The participants were then categorized as regular sleepers or moderately irregular sleepers, based on their sleep patterns.

The study found:

• Following discharge from the hospital, 21 participants experienced a clinical event over the course of six months.
• Of that group, 13 were classified as moderately irregular sleepers compared with eight classified as having a regular sleep schedule.
• Statistically, the irregular sleepers had more than double the risk of an event across the six-month time span.

The increased risk of a clinical event for moderately irregular sleepers remained even when accounting for possible contributing factors like sleep disorders and other underlying medical conditions. The research team says the study is among the first to examine the impact of sleep regularity in the context of heart failure, and the findings add to a growing body of evidence suggesting the importance of maintaining a regular sleep schedule.

"Improving sleep regularity may be a low-cost therapeutic approach to mitigate adverse events in adults with heart failure," the authors conclude.

Shafer said the results strengthen the connection between sleep regularity and cardiovascular health.

"When we're asleep and in a resting state, our blood pressure and heart rate decrease compared with daytime levels," she said. "But variability in sleep timing may disrupt mechanisms involved in the regulation of the cardiovascular system. Irregular sleep may contribute to adverse outcomes, especially for people already affected by heart failure."

The next step would be to scale up the research to a larger cohort of participants and see whether improving sleep regularity lowers the risk of another clinical event, she said.

In addition to Shafer, co-authors include Shirin Hiatt, M.P.H., RN, Sophia Kogan, B.S.N., RN, Nathan Dieckmann, Ph.D., Christopher Chien, M.D., Quin Denfeld, Ph.D., RN, and Andrew McHill, Ph.D., all of OHSU; and Christopher Lee, Ph.D., RN, of Boston College.

The study was supported by the National Heart, Lung, and Blood Institute; the Eunice Kennedy Shriver National Institute of Child Health & Human Development; and the National Institute of Nursing Research, all of the National Institutes of Health, awards T32HL083808, K12AR084221 and R01NR019054, respectively; and the OHSU School of Nursing. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

The research, led by McGill University scientist Masha Prager-Khoutorsky in collaboration with an interdisciplinary team at McGill and the Research Institute of the McGill University Health Centre, suggests the brain may be a missing link in certain forms of high blood pressure - or hypertension - traditionally attributed to the kidneys.

"This is new evidence that high blood pressure can originate in the brain, opening the door for developing treatments that act on the brain," said Prager-Khoutorsky, associate professor in McGill's Department of Physiology.

Hypertension affects two-thirds of people over 60 and contributes to 10 million deaths worldwide each year. Often symptomless, the condition increases the risk of heart disease, stroke and other serious health problems.

About one-third of patients don't respond to standard medications, which primarily target the blood vessels and kidneys based on the long-standing view that hypertension begins there. The study, published in the journal Neuron, suggests the brain may also be a key driver of the condition, particularly in treatment-resistant cases.

How salt disrupts the brain

To mimic human eating patterns, rats were given water containing two per cent salt, comparable to a daily diet high in fast food and items like bacon, instant noodles and processed cheese.

The high-salt diet activated immune cells in a specific brain region, causing inflammation and a surge in the hormone vasopressin, which raises blood pressure. Researchers tracked these changes using cutting-edge brain imaging and lab techniques that only recently became available.

"The brain's role in hypertension has largely been overlooked, in part because it's harder to study," Prager-Khoutorsky said. "But with new techniques, we're able to see these changes in action."

The researchers used rats instead of the more commonly studied mice because rats regulate salt and water more like humans. That makes the findings more likely to apply to people, noted Prager-Khoutorsky.

Next, the scientists plan to study whether similar processes are involved in other forms of hypertension.

"Microglia regulate neuronal activity via structural remodeling of astrocytes" by Ning Gu et al., was published in Neuron and supported by the Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada and the Azrieli Foundation.