Tag Archive for: model

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.

allopregnanolone molecule

Autism spectrum disorder risk linked to insufficient placental steroid

allopregnanolone molecule

A study led by Children’s National Hospital and presented during Neuroscience 2019 finds that loss of allopregnanolone, a key hormone supplied by the placenta, leads to long-term structural alterations of the cerebellum – a brain region essential for smooth motor coordination, balance and social cognition – and increases the risk of developing autism.

An experimental model study suggests that allopregnanolone, one of many hormones produced by the placenta during pregnancy, is so essential to normal fetal brain development that when provision of that hormone decreases – as occurs with premature birth – offspring are more likely to develop autism-like behaviors, a Children’s National Hospital research team reports at the Neuroscience 2019 annual meeting.

“To our knowledge, no other research team has studied how placental allopregnanolone (ALLO) contributes to brain development and long-term behaviors,” says Claire-Marie Vacher, Ph.D., lead author. “Our study finds that targeted loss of ALLO in the womb leads to long-term structural alterations of the cerebellum – a brain region that is essential for motor coordination, balance and social cognition ­– and increases the risk of developing autism,” Vacher says.

According to the Centers for Disease Control and Prevention, about 1 in 10 infants is born preterm, before 37 weeks gestation; and 1 in 59 children has autism spectrum disorder.

In addition to presenting the abstract, on Monday, Oct. 21, Anna Penn, M.D., Ph.D., the abstract’s senior author, will discuss the research with reporters during a Neuroscience 2019 news conference. This Children’s National abstract is among 14,000 abstracts submitted for the meeting, the world’s largest source of emerging news about brain science and health.

ALLO production by the placenta rises in the second trimester of pregnancy, and levels of the neurosteroid peak as fetuses approach full term.

To investigate what happens when ALLO supplies are disrupted, a research team led by Children’s National created a novel transgenic preclinical model in which they deleted a gene essential in ALLO synthesis. When production of ALLO in the placentas of these experimental models declines, offspring had permanent neurodevelopmental changes in a sex- and region-specific manner.

“From a structural perspective, the most pronounced cerebellar abnormalities appeared in the cerebellum’s white matter,” Vacher adds. “We found increased thickness of the myelin, a lipid-rich insulating layer that protects nerve fibers. From a behavioral perspective, male offspring whose ALLO supply was abruptly reduced exhibited increased repetitive behavior and sociability deficits – two hallmarks in humans of autism spectrum disorder.”

On a positive note, providing a single ALLO injection during pregnancy was enough to avert both the cerebellar abnormalities and the aberrant social behaviors.

The research team is now launching a new area of research focus they call “neuroplacentology” to better understand the role of placenta function on fetal and newborn brain development.

“Our team’s data provide exciting new evidence that underscores the importance of placental hormones on shaping and programming the developing fetal brain,” Vacher notes.

  • Neuroscience 2019 presentation
    Sunday, Oct. 20, 9:30 a.m. (CDT)
    “Preterm ASD risk linked to cerebellar white matter changes”
    Claire-Marie Vacher, lead author; Sonia Sebaoui, co-author; Helene Lacaille, co-author; Jackie Salzbank, co-author; Jiaqi O’Reilly, co-author; Diana Bakalar, co-author; Panagiotis Kratimenos, M.D., neonatologist and co-author; and Anna Penn, M.D., clinical neonatologist and developmental neuroscientist and senior author.
Beth Tarini

Getting to know SPR’s future President, Beth Tarini, M.D., MS

Beth Tarini

Quick. Name four pillar pediatric organizations on the vanguard of advancing pediatric research.

Most researchers and clinicians can rattle off the names of the Academic Pediatric Association, the American Academy of Pediatrics and the American Pediatric Society. But that fourth one, the Society for Pediatric Research (SPR), is a little trickier. While many know SPR, a lot of research-clinicians simply do not.

Over the next few years, Beth A. Tarini, M.D., MS, will make it her personal mission to ensure that more pediatric researchers get to know SPR and are so excited about the organization that they become active members. In May 2019 Dr. Tarini becomes Vice President of the society that aims to stitch together an international network of interdisciplinary researchers to improve kids’ health. Four-year SPR leadership terms begin with Vice President before transitioning to President-Elect, President and Past-President, each for one year.

Dr. Tarini says she looks forward to working with other SPR leaders to find ways to build more productive, collaborative professional networks among faculty, especially emerging junior faculty. “Facilitating ways to network for research and professional reasons across pediatric research is vital – albeit easier said than done. I have been told I’m a connector, so I hope to leverage that skill in this new role,” says Dr. Tarini, associate director for Children’s Center for Translational Research.

“I’m delighted that Dr. Tarini was elected to this leadership position, and I am impressed by her vision of improving SPR’s outreach efforts,” says Mark Batshaw, M.D., Executive Vice President, Chief Academic Officer and Physician-in-Chief at Children’s National. “Her goal of engaging potential members in networking through a variety of ways – face-to-face as well as leveraging digital platforms like Twitter, Facebook and LinkedIn – and her focus on engaging junior faculty will help strengthen SPR membership in the near term and long term.”

Dr. Tarini adds: “Success to me would be leaving after four years with more faculty – especially junior faculty – approaching membership in SPR with the knowledge and enthusiasm that they bring to membership in other pediatric societies.”

SPR requires that its members not simply conduct research, but move the needle in their chosen discipline. In her research, Dr. Tarini has focused on ensuring that population-based newborn screening programs function efficiently and effectively with fewer hiccups at any place along the process.

Thanks to a heel stick to draw blood, an oxygen measurement, and a hearing test, U.S. babies are screened for select inherited health conditions, expediting treatment for infants and reducing the chances they’ll experience long-term health consequences.

“The complexity of this program that is able to test nearly all 4 million babies in the U.S. each year is nothing short of astounding. You have to know the child is born – anywhere in the state – and then between 24 and 48 hours of birth you have to do testing onsite, obtain a specific type of blood sample, send the blood sample to an off-site lab quickly, test the sample, find the child if the test is out of range, get the child evaluated and tested for the condition, then send them for treatment. Given the time pressures as well as the coordination of numerous people and organizations, the fact that this happens routinely is amazing. And like any complex process, there is always room for improvement,” she says.

Dr. Tarini’s research efforts have focused on those process improvements.

As just one example, the Advisory Committee on Heritable Disorders in Newborns and Children, a federal advisory committee on which she serves, was discussing how to eliminate delays in specimen processing to provide speedier results to families. One possible solution floated was to open labs all seven days, rather than just five days a week. Dr. Tarini advocated for partnering with health care engineers who could help model ways to make the specimen transport process more efficient, just like airlines and mail delivery services. A more efficient and effective solution was to match the specimen pick-up and delivery times more closely with the lab’s operational times – which maximizes lab resources and shortens wait times for parents.

Conceptual modeling comes so easily for her that she often leaps out of her seat mid-sentence, underscoring a point by jotting thoughts on a white board, doing it so often that her pens have run dry.

“It’s like a bus schedule: You want to find a bus that not only takes you to your destination but gets you there on time,” she says.

Dr. Tarini’s current observational study looks for opportunities to improve how parents in Minnesota and Iowa are given out-of-range newborn screening test results – especially false positives – and how that experience might shake their confidence in their child’s health as well as heighten their own stress level.

“After a false positive test result, are there parents who walk away from newborn screening with lingering stress about their child’s health? Can we predict who those parents might be and help them?” she asks.

Among the challenges is the newborn screening occurs so quickly after delivery that some emotionally and physically exhausted parents may not remember it was done. Then they get a call from the state with ominous results. Another challenge is standardizing communication approaches across dozens of birthing centers and hospitals.

“We know parents are concerned after receiving a false positive result, and some worry their infant remains vulnerable,” she says. “Can we change how we communicate – not just what we say, but how we say it – to alleviate those concerns?”