brain
Case Study Unlocks Clues to Rare Resilience to Alzheimer’s Disease
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Biomedical breakthroughs most often involve slow and steady research in studies involving large numbers of people. But sometimes careful study of even just one truly remarkable person can lead the way to fascinating discoveries with far-reaching implications.
An NIH-funded case study published recently in the journal Nature Medicine falls into this far-reaching category [1]. The report highlights the world’s second person known to have an extreme resilience to a rare genetic form of early onset Alzheimer’s disease. These latest findings in a single man follow a 2019 report of a woman with similar resilience to developing symptoms of Alzheimer’s despite having the same strong genetic predisposition for the disease [2].
The new findings raise important new ideas about the series of steps that may lead to Alzheimer’s and its dementia. They’re also pointing the way to key parts of the brain for cognitive resilience—and potentially new treatment targets—that may one day help to delay or even stop progression of Alzheimer’s.
The man in question is a member of a well-studied extended family from the country of Colombia. This group of related individuals, or kindred, is the largest in the world with a genetic variant called the “Paisa” mutation (or Presenilin-1 E280A). This Paisa variant follows an autosomal dominant pattern of inheritance, meaning that those with a single altered copy of the rare variant passed down from one parent usually develop mild cognitive impairment around the age of 44. They typically advance to full-blown dementia around the age of 50 and rarely live past the age of 60. This contrasts with the most common form of Alzheimer’s, which usually begins after age 65.
The new findings come from a team led by Yakeel Quiroz, Massachusetts General Hospital, Boston; Joseph Arboleda-Velasquez, Massachusetts Eye and Ear, Boston; Diego Sepulveda-Falla, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; and Francisco Lopera, University of Antioquia, Medellín, Colombia. Lopera first identified this family more than 30 years ago and has been studying them ever since.
In the new case report, the researchers identified a Colombian man who’d been married with two children and retired from his job as a mechanic in his early 60s. Despite carrying the Paisa mutation, his first cognitive assessment at age 67 showed he was cognitively intact, having limited difficulties with verbal learning skills or language. It wasn’t until he turned 70 that he was diagnosed with mild cognitive impairment—more than 20 years later than the expected age for this family—showing some decline in short-term memory and verbal fluency.
At age 73, he enrolled in the Colombia-Boston biomarker research study (COLBOS). This study is a collaborative project between the University of Antioquia and Massachusetts General Hospital involving approximately 6,000 individuals from the Paisa kindred. About 1,500 of those in the study carry the mutation that sets them up for early Alzheimer’s. As a member of the COLBOS study, the man underwent thorough neuroimaging tests to look for amyloid plaques and tau tangles, both of which are hallmarks of Alzheimer’s.
While this man died at age 74 with Alzheimer’s, the big question is: how did he stave off dementia for so long despite his poor genetic odds? The COLBOS study earlier identified a woman with a similar resilience to Alzheimer’s, which they traced to two copies of a rare, protective genetic variant called Christchurch. This variant affects a gene called apolipoprotein E (APOE3), which is well known for its influence on Alzheimer’s risk. However, the man didn’t carry this same protective variant.
The researchers still thought they’d find an answer in his genome and kept looking. While they found several variants of possible interest, they zeroed in on a single gene variant that they’ve named Reelin-COLBOS. What helped them to narrow it down to this variant is the man also had a sister with the Paisa mutation who only progressed to advanced dementia at age 72. It turned out, in addition to the Paisa variant, the siblings also shared an altered copy of the newly discovered Reelin-COLBOS variant.
This Reelin-COLBOS gene is known to encode a protein that controls signals to chemically modify tau proteins, which form tangles that build up over time in the Alzheimer’s brain and have been linked to memory loss. Reelin is also functionally related to APOE, the gene that was altered in the woman with extreme Alzheimer’s protection. Reelin and APOE both interact with common protein receptors in neurons. Together, the findings add to evidence that signaling pathways influencing tau play an important role in Alzheimer’s pathology and protection.
The neuroimaging exams conducted when the man was age 73 have offered further intriguing clues. They showed that his brain had extensive amyloid plaques. He also had tau tangles in some parts of his brain. But one brain region, called the entorhinal cortex, was notable for having a very minimal amount of those hallmark tau tangles.
The entorhinal cortex is a hub for memory, navigation, and the perception of time. Its degeneration also leads to cognitive impairment and dementia. Studies of the newly identified Reelin-COLBOS variant in Alzheimer’s mouse models also help to confirm that the variant offers its protection by diminishing the pathological modifications of tau.
Overall, the findings in this one individual and his sister highlight the Reelin pathway and brain region as promising targets for future study and development of Alzheimer’s treatments. Quiroz and her colleagues report that they are actively exploring treatment approaches inspired by the Christchurch and Reelin-COLBOS discoveries.
Of course, there’s surely more to discover from continued study of these few individuals and others like them. Other as yet undescribed genetic and environmental factors are likely at play. But the current findings certainly offer some encouraging news for those at risk for Alzheimer’s disease—and a reminder of how much can be learned from careful study of remarkable individuals.
References:
[1] Resilience to autosomal dominant Alzheimer’s disease in a Reelin-COLBOS heterozygous man. Lopera F, Marino C, Chandrahas AS, O’Hare M, Reiman EM, Sepulveda-Falla D, Arboleda-Velasquez JF, Quiroz YT, et al. Nat Med. 2023 May;29(5):1243-1252.
[2] Resistance to autosomal dominant Alzheimer’s disease in an APOE3 Christchurch homozygote: a case report. Arboleda-Velasquez JF, Lopera F, O’Hare M, Delgado-Tirado S, Tariot PN, Johnson KA, Reiman EM, Quiroz YT et al. Nat Med. 2019 Nov;25(11):1680-1683.
Links:
Alzheimer’s Disease & Related Dementias (National Institute on Aging/NIH)
“NIH Support Spurs Alzheimer’s Research in Colombia,” Global Health Matters, January/February 2014, Fogarty International Center/NIS
“COLBOS Study Reveals Mysteries of Alzheimer’s Disease,” NIH Record, August 19, 2022.
Yakeel Quiroz (Massachusetts General Hospital, Harvard Medical School, Boston)
Joseph Arboleda-Velasquez (Massachusetts Eye and Ear, Harvard Medical School, Boston)
Diego Sepulveda-Falla Lab (University Medical Center Hamburg-Eppendorf, Hamburg, Germany)
Francisco Lopera (University of Antioquia, Medellín, Colombia)
NIH Support: National Institute on Aging; National Eye Institute; National Institute of Neurological Disorders and Stroke; Office of the Director
Changes in Normal Brain Connections Linked to Eating Disorders
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Anyone who has ever had a bad habit knows how vexingly difficult breaking it can be. The reason is the repeated action, initially linked to some type of real or perceived reward, over time changes the way our very brains are wired to work. The bad habit becomes automatic, even when the action does us harm or we no longer wish to do it.
Now an intriguing new study shows that the same bundled nerve fibers, or brain circuits, involved in habit formation also can go awry in people with eating disorders. The findings may help to explain why eating disorders are so often resistant to will power alone. They also may help to point the way to improved approaches to treating eating disorders, suggesting strategies that adjust the actual brain circuitry in helpful ways.
These latest findings, published in the journal Science Translational Medicine, come from the NIH-supported Casey Halpern, University of Pennsylvania’s Perelman School of Medicine, Philadelphia, and Cara Bohon, Stanford University School of Medicine, Stanford, CA [1].
Halpern, Bohon, and colleagues were interested in a growing body of evidence linking habitual behaviors to mental health conditions, most notably substance use disorders and addictions. But what especially intrigued them was recent evidence also suggesting a possible role for habitual behaviors in the emergence of eating disorders.
To look deeper into the complex circuitry underlying habit formation and any changes there that might be associated with eating disorders, they took advantage of a vast collection of data from the NIH-funded Human Connectome Project (HCP). It was completed several years ago and now serves as a valuable online resource for researchers.
The HCP offers a detailed wiring map of a normal human brain. It describes all the structural and functional neural connections based on careful analyses of hundreds of high-resolution brain scans. These connections are then layered with genetic, behavioral, and other types of data. This incredible map now allows researchers to explore and sometimes uncover the roots of neurological and mental health conditions within the brain’s many trillions of connections.
In the new study, Halpern, Bohon, and colleagues did just that. First, they used sophisticated mapping methods in 178 brain scans from the HCP data to locate key portions of a brain region called the striatum, which is thought to be involved in habit formation. What they really wanted to know was whether circuits operating within the striatum were altered in some way in people with binge eating disorder or bulimia nervosa.
To find out, the researchers recruited 34 women who have an eating disorder and, with their consent, imaged their brains using a variety of techniques. Twenty-one participants were diagnosed with binge eating disorder, and 13 had bulimia nervosa. For comparison purposes, the researchers looked at the same brain circuits in 19 healthy volunteers.
The two groups were otherwise similar in terms of their ages, weights, and other features. But the researchers suspected they might find differences between the healthy group and those with an eating disorder in brain circuits known to have links to habitual behaviors. And, indeed, they did.
In comparison to a “typical” brain, those from people with an eating disorder showed striking changes in the connectivity of a portion of the striatum known as the putamen. That’s especially notable because the putamen is known for its role in learning and movement control, including reward, thinking, and addiction. What’s more, those observed changes in the brain’s connections and circuitry in this key brain area were more evident in people whose eating disorder symptoms and emotional eating were more frequent and severe.
Using other brain imaging methods in 10 of the volunteers (eight with binge eating disorder and two healthy controls), the researchers also connected those changes in the habit-forming brain circuits to high levels of a protein receptor that responds to dopamine. Dopamine is an important chemical messenger in the brain involved in pleasure, motivation, and learning. They also observed in those with eating disorders structural changes in the architecture of the densely folded, outer layer of the brain known as grey matter.
While there’s much more to learn, the researchers note the findings may lead to future treatments aimed to modify the brain circuitry in beneficial ways. Indeed, Halpern already has encouraging early results from a small NIH-funded clinical trial testing the ability of deep brain stimulation (DBS) in people with binge eating disorder to disrupt signals that drive food cravings in another portion of the brain associated with reward and motivation, known as the nucleus accumbens, [2]. In DBS, doctors implant a pacemaker-like device capable of delivering harmless therapeutic electrical impulses deep into the brain, aiming for the spot where they can reset the abnormal circuitry that’s driving eating disorders or other troubling symptoms or behaviors.
But the latest findings published in Science Translational Medicine now suggest other mapped brain circuits as potentially beneficial DBS targets for tackling binge eating, bulimia nervosa, or other life-altering, hard-to-treat eating disorders. They also may ultimately have implications for treating other conditions involving various other forms of compulsive behavior.
These findings should come as a source of hope for the family and friends of the millions of Americans—many of them young people—who struggle with eating disorders. The findings also serve as an important reminder for the rest of us that, despite common misconceptions that disordered eating is a lifestyle choice, these conditions are in fact complex and serious mental health problems driven by fundamental changes in the brain’s underlying circuitry.
Finding new and more effective ways to treat serious eating disorders and other compulsive behaviors is a must. It will require equally serious ongoing efforts to unravel their underlying causes and find ways to alter their course—and this new study is an encouraging step in that direction.
References:
[1] Human habit neural circuitry may be perturbed in eating disorders. Wang AR, Kuijper FM, Barbosa DAN, Hagan KE, Lee E, Tong E, Choi EY, McNab JA, Bohon C, Halpern CH. Sci Transl Med. 2023 Mar 29;15(689):eabo4919.
[2] Pilot study of responsive nucleus accumbens deep brain stimulation for loss-of-control eating. Shivacharan RS, Rolle CE, Barbosa DAN, Cunningham TN, Feng A, Johnson ND, Safer DL, Bohon C, Keller C, Buch VP, Parker JJ, Azagury DE, Tass PA, Bhati MT, Malenka RC, Lock JD, Halpern CH. Nat Med. 2022 Sep;28(9):1791-1796.
Links:
Eating Disorders (National Institute of Mental Health/NIH)
Casey Halpern (Penn Medicine, Philadelphia)
Cara Bohon (Stanford University, Stanford, CA)
NIH Support: National Institute of Mental Health; National Institute of Neurological Disorders and Stroke
Childhood Cancer: Novel Nanoparticle Shows Early Promise for Brain Tumor
Posted on by Lawrence Tabak, D.D.S., Ph.D.
The human brain is profoundly complex, consisting of tens of billions of neurons that form trillions of interconnections. This complex neural wiring that allows us to think, feel, move, and act is surrounded by what’s called the blood-brain barrier (BBB), a dense sheet of cells and blood vessels. The BBB blocks dangerous toxins and infectious agents from entering the brain, while allowing nutrients and other essential small molecules to pass right through.
This gatekeeping function helps to keep the brain healthy, but not when the barrier prevents potentially life-saving drugs from reaching aggressive, inoperable brain tumors. Now, an NIH-funded team reporting in the journal Nature Materials describes a promising new way to ferry cancer drugs across the BBB and reach the sites of disease [1]. While the researchers have not yet tried this new approach in people, they have some encouraging evidence from studies in mouse models of medulloblastoma, an aggressive brain cancer that’s diagnosed in hundreds of children each year.
The team, including Daniel Heller, Memorial Sloan Kettering Cancer Center, New York, NY, and Praveen Raju, Icahn School of Medicine at Mount Sinai, New York, NY, wanted to target a protein called P-selectin. The protein is found on blood vessel cells at sites of infection, injury, or inflammation, including cancers. The immune system uses such proteins to direct immune cells to the places where they are needed, allowing them to exit the bloodstream and enter other tissues.
Heller’s team thought they could take advantage of P-selectin and its molecular homing properties as a potential way to deliver cancer drugs to patients. But first they needed to package the drugs in particles tiny enough to stick to P-selectin like an immune cell.
That’s when they turned to a drug-delivery construct called a nanoparticle, which can have diameters a thousand times smaller than that of a human hair. But what’s pretty unique here is the nanoparticles are made from chains of sugar molecules called fucoidan, which are readily extracted from a type of brown seaweed that grows in Japan. It turns out that this unlikely ingredient has a special ability to attract P-selectin.
In the new study, the researchers decided to put their novel fucoidan nanoparticles to the test in the brain, while building on their previous animal work in the lungs [2]. That work showed that when fucoidan nanoparticles bind to P-selectin, they trigger a process that shuttles them across blood vessel walls.
This natural mechanism should also allow nanoparticle-packaged substances in the bloodstream to pass through vessel walls in the BBB and into the surrounding brain tissue. The hope was it would do so without damaging the BBB, a critical step for improving the treatment of brain tumors.
In studies with mouse models of medulloblastoma, the team loaded the nanoparticles with a cancer drug called vismodegib. This drug is approved for certain skin cancers and has been tested for medulloblastoma. The trouble is that the drug on its own comes with significant side effects in children at doses needed to effectively treat this brain cancer.
The researchers found that the vismodegib-loaded nanoparticles circulating in the mice could indeed pass through the intact BBB and into the brain. They further found that the particles accumulated at the site of the medulloblastoma tumors, where P-selectin was most abundant, and not in other healthy parts of the brain. In the mice, the approach allowed the vismodegib treatment to work better against the cancer and at lower doses with fewer side effects.
This raised another possibility. Radiation is a standard therapy for children and adults with brain tumors. The researcher found that radiation boosts P-selectin levels specifically in tumors. The finding suggests that radiation targeting specific parts of the brain prior to nanoparticle treatment could make it even more effective. It also may help to further limit the amount of cancer-fighting drug that reaches healthy brain cells and other parts of the body.
The fucoidan nanoparticles could, in theory, deliver many different drugs to the brain. The researchers note their promise for treating brain tumors of all types, including those that spread to the brain from other parts of the body. While much more work is needed, these seaweed-based nanoparticles may also help in delivering drugs to a wide range of other brain conditions, such as multiple sclerosis, stroke, and focal epilepsy, in which seizures arise from a specific part of the brain. It’s a discovery that brings new meaning to the familiar adage that good things come in small packages.
References:
[1] P-selectin-targeted nanocarriers induce active crossing of the blood-brain barrier via caveolin-1-dependent transcytosis. Tylawsky DE, Kiguchi H, Vaynshteyn J, Gerwin J, Shah J, Islam T, Boyer JA, Boué DR, Snuderl M, Greenblatt MB, Shamay Y, Raju GP, Heller DA. Nat Mater. 2023 Mar;22(3):391-399.
[2] P-selectin is a nanotherapeutic delivery target in the tumor microenvironment. Shamay Y, Elkabets M, Li H, Shah J, Brook S, Wang F, Adler K, Baut E, Scaltriti M, Jena PV, Gardner EE, Poirier JT, Rudin CM, Baselga J, Haimovitz-Friedman A, Heller DA. Sci Transl Med. 2016 Jun 29;8(345):345ra87.
Links:
Medulloblastoma Diagnosis and Treatment (National Cancer Institute/NIH)
Brain Basics: Know Your Brain (National Institute of Neurological Disorders and Stroke/NIH)
The Daniel Heller Lab (Memorial Sloan Kettering Cancer Center, New York, NY)
Praveen Raju (Mount Sinai, New York, NY)
NIH Support: National Cancer Institute; National Institute of Neurological Disorders and Stroke
An Inflammatory View of Early Alzheimer’s Disease
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Detecting the earliest signs of Alzheimer’s disease (AD) in middle-aged people and tracking its progression over time in research studies continue to be challenging. But it is easier to do in shorter-lived mammalian models of AD, especially when paired with cutting-edge imaging tools that look across different regions of the brain. These tools can help basic researchers detect telltale early changes that might point the way to better prevention or treatment strategies in humans.
That’s the case in this technicolor snapshot showing early patterns of inflammation in the brain of a relatively young mouse bred to develop a condition similar to AD. You can see abnormally high levels of inflammation throughout the front part of the brain (orange, green) as well as in its middle part—the septum that divides the brain’s two sides. This level of inflammation suggests that the brain has been injured.
What’s striking is that no inflammation is detectable in parts of the brain rich in cholinergic neurons (pink), a distinct type of nerve cell that helps to control memory, movement, and attention. Though these neurons still remain healthy, researchers would like to know if the inflammation also will destroy them as AD progresses.
This colorful image comes from medical student Sakar Budhathoki, who earlier worked in the NIH labs of Lorna Role and David Talmage, National Institute of Neurological Disorders and Stroke (NINDS). Budhathoki, teaming with postdoctoral scientist Mala Ananth, used a specially designed wide-field scanner that sweeps across brain tissue to light up fluorescent markers and capture the image. It’s one of the scanning approaches pioneered in the Role and Talmage labs [1,2].
The two NIH labs are exploring possible links between abnormal inflammation and damage to the brain’s cholinergic signaling system. In fact, medications that target cholinergic function remain the first line of treatment for people with AD and other dementias. And yet, researchers still haven’t adequately determined when, why, and how the loss of these cholinergic neurons relates to AD.
It’s a rich area of basic research that offers hope for greater understanding of AD in the future. It’s also the source of some fascinating images like this one, which was part of the 2022 Show Us Your BRAIN! Photo and Video Contest, supported by NIH’s Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
References:
[1] NeuRegenerate: A framework for visualizing neurodegeneration. Boorboor S, Mathew S, Ananth M, Talmage D, Role LW, Kaufman AE. IEEE Trans Vis Comput Graph. 2021;Nov 10;PP.
[2] NeuroConstruct: 3D reconstruction and visualization of neurites in optical microscopy brain images. Ghahremani P, Boorboor S, Mirhosseini P, Gudisagar C, Ananth M, Talmage D, Role LW, Kaufman AE. IEEE Trans Vis Comput Graph. 2022 Dec;28(12):4951-4965.
Links:
Alzheimer’s Disease & Related Dementias (National Institute on Aging/NIH)
Role Lab (National Institute of Neurological Disorders and Stroke/NIH)
Talmage Lab (NINDS)
The Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Show Us Your BRAINs! Photo and Video Contest (BRAIN Initiative)
NIH Support: National Institute of Neurological Disorders and Stroke
Celebrating the Power of Connection This Holiday Season
Posted on by Lawrence Tabak, D.D.S., Ph.D.
Happy holidays to one and all! This short science video brings to mind all those twinkling lights now brightening the night, as we mark the beginning of winter and shortest day of the year. This video also helps to remind us about the power of connection this holiday season.
It shows a motor neuron in a mouse’s primary motor cortex. In this portion of the brain, which controls voluntary movement, heavily branched neural projections interconnect, sending and receiving signals to and from distant parts of the body. A single motor neuron can receive thousands of inputs at a time from other branching sensory cells, depicted in the video as an array of blinking lights. It’s only through these connections—through open communication and cooperation—that voluntary movements are possible to navigate and enjoy our world in all its wonder. One neuron, like one person, can’t do it all alone.
This power of connection, captured in this award-winning video from the 2022 Show Us Your Brains Photo and Video contest, comes from Forrest Collman, Allen Institute for Brain Science, Seattle. The contest is part of NIH’s Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
In the version above, we’ve taken some liberties with the original video to enhance the twinkling lights from the synaptic connections. But creating the original was quite a task. Collman sifted through reams of data from high-resolution electron microscopy imaging of the motor cortex to masterfully reconstruct this individual motor neuron and its connections.
Those data came from The Machine Intelligence from Cortical Networks (MICrONS) program, supported by the Intelligence Advanced Research Projects Activity (IARPA). It’s part of the Office of the Director of National Intelligence, one of NIH’s governmental collaborators in the BRAIN Initiative.
The MICrONS program aims to better understand the brain’s internal wiring. With this increased knowledge, researchers will develop more sophisticated machine learning algorithms for artificial intelligence applications, which will in turn advance fundamental basic science discoveries and the practice of life-saving medicine. For instance, these applications may help in the future to detect and evaluate a broad range of neural conditions, including those that affect the primary motor cortex.
Pretty cool stuff. So, as you spend this holiday season with friends and family, let this video and its twinkling lights remind you that there’s much more to the season than eating, drinking, and watching football games.
The holidays are very much about the power of connection for people of all faiths, beliefs, and traditions. It’s about taking time out from the everyday to join together to share memories of days gone by as we build new memories and stronger bonds of cooperation for the years to come. With this in mind, happy holidays to one and all.
Links:
“NIH BRAIN Initiative Unveils Detailed Atlas of the Mammalian Primary Motor Cortex,” NIH News Release, October 6, 2021
Forrest Collman (Allen Institute for Brain Science, Seattle)
Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Show Us Your Brains Photo and Video Contest (BRAIN Initiative)
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