The Next Frontier in Alzheimer’s Research
Exploring eye scans, gene editing and sound training
En español | For all the bad news about Alzheimer's disease — the failed drug trials, the elusive target of amyloid plaques, the massive toll it's taking on our aging population and their caregivers — research into the brain disease has been given an unprecedented financial boost in recent years. Federal funding has soared to 2.4 billion dollars in 2019, as the National Institutes of Health has made this area of research a funding priority unmatched in scale since the agency's war on cancer in the 1970s.
The increased funding has spearheaded an “explosion of new possibilities that are exciting and optimistic for the future,” and allowed the scientific community to “think outside the box to get effective treatments faster,” says Keith Fargo, director of scientific programs and outreach at the Alzheimer's Association.
New research approaches include everything from studying herpes simplex as a possible cause of Alzheimer's disease to using antidepressant or antiviral drugs as viable treatment options. Researchers are even studying whether the microbiome plays a role in the disease. Here is a look at other cutting-edge areas of research that could one day lead to a cure — or, more likely, a cocktail of effective treatments for the disease.
Getting past the brain's blood barrier
Serving as the brain's security system, this nearly impermeable barrier is a complex membrane of tightly woven cells that prevent harmful substances such as bacteria and toxins from entering the brain.
Now, Vibhor Krishna, assistant professor of neurosurgery at the Ohio State University, in Columbus, hopes to gain entrance past the barrier to help treat patients with Alzheimer's.
He has begun enrolling patients with mild to moderate cognitive impairment in a trial that will use new ultrasound technology to open five sections of the blood-brain barrier with ultrasound waves. By causing microscopic particles in the brain to oscillate, ultrasound briefly opens the brain's entrance. He believes that will stimulate the patient's own immune system to clear some of the plaque from the brain.
"We're very excited about this research,” says Krishna, who notes that the goal is one day to deliver medication through the barrier for Alzheimer's patients.
Other investigators are also studying whether electromagnetic waves can break down the blood-brain barrier and scatter the plaque of patients with Alzheimer's.
Training brain cells with light and sound
Li-Huei Tsai, director of the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology, in Cambridge, is using light and sound to prompt brain cells to reduce amyloid and tau tangles, which are the hallmarks of Alzheimer's.
"This treatment keeps brain cells from dying, and it also improves learning and memory,” Tsai says. In her study, patients sit 3 to 5 feet in front of a device with flashing lights and sound for one hour daily for several weeks. The lights and sounds induce brain waves known as gamma oscillation, which have been shown to reduce the levels of amyloid plaques in mice. Tsai's approach has so far been used in a small trial of patients with Alzheimer's. The benefits faded when patients stopped using the device, but Tsai says this isn't any different than what happens when patients need to stay on cholesterol drug therapy or hypertensive medications for life.
The device has been licensed to Cognito Therapeutics, and larger clinical trials will begin soon.
Diagnosing Alzheimer's through eye scans
“The eyes have long been known to be the windows into our health. I think more recently it is also being seen as a window into our brain health,” notes Sharon Fekrat, professor of ophthalmology and codirector of the Duke Neurodegenerative Disease Retinal Imaging Repository, in Durham, North Carolina.
Ophthalmologists are used to looking into the eyes of patients to see if they have signs of hypertension, diabetic retinopathy and a host of other conditions. Fekrat is evaluating retinal imaging for the diagnosis of Alzheimer's disease in a large-scale clinical trial.
"We're imaging as many people as we can enroll in the trial and hope to calculate a person's risk of Alzheimer's disease by looking at their retina and optic nerve. It is the ultimate ideal. It's plausible, and I think we are on the cusp of something potentially very promising,” she says.
In other eye-related research, investigators at the University of California, San Diego, School of Medicine are studying pupil response during cognitive tests as an early measure of presymptomatic, or very early-stage, Alzheimer's.
Evaluating “synaptic” health
Researchers have long thought that high levels of amyloid and tau tangles play a role in the development of Alzheimer's, but they have only recently begun looking at synapses, or junctions between nerve cells where messages pass through, as another major piece of the puzzle.
Christopher van Dyck, director of the Alzheimer's disease research unit at Yale University School of Medicine, in New Haven, Connecticut, and his team have begun using positron-emission tomography (PET) imaging to measure what he calls “synaptic health.” This is done by scanning for a protein called synaptic vesicle glycoprotein 2A (SV2A), which changes as synapses degenerate. This, he explains, “lets us measure the loss of brain cells across synapses.”
Expanding PET imaging beyond amyloid and tau tangles to include a look at brain structure and function across synapses could provide a much more complete picture of how Alzheimer's affects the brain or how it spreads.
Discovering new genes
You may have heard of the APOE gene, which made big news with the finding that it makes the protein APOE4, linked to late-onset Alzheimer's and the development of amyloid deposits in the brain of those with the disease. Now, researchers have found more genes, MS4A and TREM2, that have been implicated in potentially causing or protecting against the disease.
Carlos Cruchaga of Washington University School of Medicine in St. Louis, Missouri, says that just a few years ago, researchers didn't understand the biology of these genes. Today, they have found that a variant of MS4A regulates TREM2 levels, which are what protect against the disease. “If we can regulate TREM2 levels, we can also modify the risk of getting Alzheimer's disease,” he says.
"I think this opens up a whole new approach,” Cruchaga adds. “We need combination therapies similar to what is being used in HIV treatment. We are still very far away, but we need to try new approaches."
Exploring links to glucose and insulin
Suzanne Craft at Wake Forest Baptist Medical Center, in Winston-Salem, North Carolina, is studying whether intranasal insulin can be used to treat Alzheimer's, because many patients with the disease have insulin resistance. “We've seen a two-year delay in symptoms with use of the drug and our delivery device,” says Craft, who is moving to a phase 3 trial of the device next fall.
Craft is also studying whether people at risk for Alzheimer's would benefit from following a ketogenic diet, because it reduces blood glucose and body weight as well as increases blood ketone levels, which play a role in glucose metabolism.
Timing the test
As researchers such as Douglas Scharre, professor of clinical neurology and psychology at the Ohio State University, tell it, finding a biomarker — some measurable flag in the body — that would signal problems with cognition early on is one of the “holy grails” of Alzheimer's research.
Scharre's hypothesis is that such early detection could also happen through a novel way of measuring cognitive skills: specifically, the time it takes to respond to a question on a memory skills test or to perform a standard task such as drawing a clockface. Scharre and his team are digitizing cognitive screening tools, like the SAGE test (self-administered gerocognitive exam) for mild cognitive impairment (MCI), and then studying the timing of the responses. “Time mode is going to make Alzheimer's disease testing more accurate and predictable than what it is now,” he says.
Many of the drugs that target amyloid in patients with Alzheimer's failed because they were given too late, says Randall Bateman, a neurologist at the Washington University School of Medicine.
"You need to treat plaques when they're growing and starting,” he says.
Bateman and his colleagues are preparing to launch three trials of an entirely new class of drugs that will target tau proteins, which aggregate and grow when dementia first becomes symptomatic.
These new drugs are designed with CRISPR technology — a genetic editing tool. They will try to silence the growth of tau genes by changing the DNA and RNA of an affected persons’ cells.
"I think in general, you need to throw a lot of drugs at this disease. You just don't want to be too myopic,” he says. “This is a very powerful approach that is very different.”
Cheryl Platzman Weinstock is an award–winning journalist who reports about health and science research and its impact on society for national media outlets including National Public Radio and The New York Times.