Posts

brain network illustration

$2.5M to protect the brain from metabolic insult

brain network illustration

The brain comprises only 2% of the body’s volume, but it uses more than 20% of its energy, which makes this organ particularly vulnerable to changes in metabolism.

More than 30 million Americans have diabetes, with the vast majority having Type 2 disease. Characterized by insulin resistance and persistently high blood sugar levels, poorly controlled Type 2 diabetes has a host of well-recognized complications: compared with the general population, a greatly increased risk of kidney disease, vision loss, heart attacks and strokes and lower limb amputations.

But more recently, says Nathan A. Smith, MS, Ph.D., a principal investigator in Children’s National Research Institute’s Center for Neuroscience Research, another consequence has become increasingly apparent. With increasing insulin resistance comes cognitive damage, a factor that contributes significantly to dementia diagnoses as patients age.

The brain comprises only 2% of the body’s volume, but it uses more than 20% of its energy, Smith explains – which makes this organ particularly vulnerable to changes in metabolism. Type 2 diabetes and even prediabetic changes in glucose metabolism inflict damage upon this organ in mechanisms with dangerous synergy, he adds. Insulin resistance itself stresses brain cells, slowly depriving them of fuel. As blood sugar rises, it also increases inflammation and blocks nitric oxide, which together narrow the brain’s blood vessels while also increasing blood viscosity.

When the brain’s neurons slowly starve, they become increasingly inefficient at doing their job, eventually succumbing to this deprivation. These hits don’t just affect individual cells, Smith adds. They also affect connectivity that spans across the brain, neural networks that are a major focus of his research.

While it’s well established that Type 2 diabetes significantly boosts the risk of cognitive decline, Smith says, it’s been unclear whether this process might be halted or even reversed. It’s this question that forms the basis of a collaborative Frontiers grant, $2.5 million from the National Science Foundation split between his laboratory; the lead institution, Stony Brook University; and Massachusetts General Hospital/Harvard Medical School.

Smith and colleagues at the three institutions are testing whether changing the brain’s fuel source from glucose to ketones – byproducts from fat metabolism – could potentially save neurons and neural networks over time. Ketones already have shown promise for decades in treating some types of epilepsy, a disease that sometimes stems from an imbalance in neuronal excitation and inhibition. When some patients start on a ketogenic diet – an extreme version of a popular fat-based diet – many can significantly decrease or even stop their seizures, bringing their misfiring brain cells back to health.

Principal Investigator Smith and his laboratory at the Children’s National Research Institute are using experimental models to test whether ketones could protect the brain against the ravages of insulin resistance. They’re looking specifically at interneurons, the inhibitory cells of the brain and the most energy demanding. The team is using a technique known as patch clamping to determine how either insulin resistance or insulin resistance in the presence of ketones affect these cells’ ability to fire.

They’re also looking at how calcium ions migrate in and out of the cells’ membranes, a necessary prerequisite for neurons’ electrical activity. Finally, they’re evaluating whether these potential changes to the cells’ electrophysiological properties in turn change how different parts of the brain communicate with each other, potentially restructuring the networks that are vital to every action this organ performs.

Colleagues at Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital and Harvard Medical School, led by Principal Investigator Eva-Maria Ratai, Ph.D.,  will perform parallel work in human subjects. They will use imaging to determine how these two fuel types, glucose or ketones, affect how the brain uses energy and produces the communication molecules known as neurotransmitters. They’re also investigating how these factors might affect the stability of neural networks using techniques that investigate the performance of these networks both while study subjects are at rest and performing a task.

Finally, colleagues at the Laufer Center for Physical and Quantitative Biology at Stony Brook University, led by Principal Investigator Lilianne R. Mujica-Parodi, Ph.D., will use results generated at the other two institutions to construct computational models that can accurately predict how the brain will behave under metabolic stress: how it copes when deprived of fuel and whether it might be able to retain healthy function when its cells receive ketones instead of glucose.

Collectively, Smith says, these results could help retain brain function even under glucose restraints. (For this, the research team owes a special thanks to Mujica-Parodi, who assembled the group to answer this important question, thus underscoring the importance of team science, he adds.)

“By supplying an alternate fuel source, we may eventually be able to preserve the brain even in the face of insulin resistance,” Smith says.

Suvankar Majumdar

Spotlight on Suvankar Majumdar, M.D.

Suvankar Majumdar

As a provider with international experience, Suvankar Majumdar, M.D., joined Children’s National in August 2017 as chief of Children’s Division of Hematology within the Center for Cancer and Blood Disorders. Dr. Majumdar is excited to be at Children’s National because of the opportunities for growth, cutting-edge research and continuing education that our diverse population of patients can provide clinicians.

Born in Zambia, in southern Africa, and educated in the United Kingdom, Dr. Majumdar moved to Zimbabwe to study medicine, which he considers the turning point of his career. While in medical school, Dr. Majumdar oversaw and managed the treatment of patients with HIV and other chronic illnesses and determined that blood disorders, particularly sickle cell, was where he wanted to place his focus. Since then, he has served as the Director of the Comprehensive Pediatric Sickle Cell Program as well as Director of the Hemophilia Treatment Center at the University of Mississippi and is a recognized leader in hematology and sickle cell disease. It is this expertise, as well as his dedication to research studies, that have already made him an asset to Children’s National.

Within the Division of Hematology, Children’s providers focus on treating patients with blood disorders, bleeding and clotting disorders, red blood cell disorders (such as sickle cell) and more. Since coming to Children’s National, Dr. Majumdar has experienced a tremendous amount of dedication and enthusiasm from his colleagues. “I’m excited to build on what our faculty has accomplished so far. We’re already well poised to become a national leader in hematology,” he says. “I have no doubt that we will continue to accomplish our goals through collaboration and working toward a common life-saving cause.”

One of his immediate goals for the division is to focus on bringing improved patient care and accessibility in the surrounding Washington area. Additionally, Dr. Majumdar is currently conducting two research studies for sickle cell disease. As one of his studies enters the second phase, he’s focused on seeing the impact of an intravenous citrulline, a nitric oxide booster, on patients with sickle cell disease. Another study has begun to determine if specific genetic mutations that cause prolonged QT, or irregular heartbeats in patients, cause mortality, as sickle cell patients are predisposed to cardiac episodes.

It is Dr. Majumdar’s hope that the hematology team at Children’s National will also continue training the next generation of providers to advance research, education and clinical aspects of the field. To those looking to join the specialty, Dr. Majumdar suggests keeping an open mind when it comes to collaborating with colleagues. “My dad always said to my siblings and I that ‘to break one stick is easy, but to break three sticks is harder’ and really impressed upon us that we’re stronger together,” he says. “By working together, we’re more likely to produce the results that we’re looking for.”

Being located in the nation’s capital, providers at Children’s National are accustomed to seeing a diverse array of patients. For Dr. Majumdar, this presents a unique opportunity. “Meeting and interacting with different patients and families was really appealing when I decided to come to Children’s National. The variety of cases we see in the Division of Hematology can definitely present new challenges, but it’s also more rewarding,” he says.

Working with the pediatric population is also a passion of his. “Children are resilient and tend to bounce back quickly,” Dr. Majumdar says. “As a parent, I try to empathize with treatment concerns and always treat every child as if they were my own. I’m always going to make sure it’s the best level of care possible.”