Brain blood flow finding gives hope for Alzheimer’s therapy

You know that dizzy feeling you get when, after lying down for an extended period, you stand up a little too quickly?

That feeling is caused by a sudden reduction of blood flow to the brain, a reduction of around 30 percent. Now imagine living every minute of every day with that level of decreased blood flow.

People with Alzheimer’s disease don’t have to imagine it. The existence of cerebral blood flow reduction in Alzheimer’s patients has been known for decades, but the exact correlation to impaired cognitive function is less understood.

“People probably adapt to the decreased blood flow, so that they don’t feel dizzy all of the time, but there’s clear evidence that it impacts cognitive function,” said an associate professor.

A new study  offers an explanation for this dramatic blood flow decrease: white blood cells stuck to the inside of capillaries, the smallest blood vessels in the brain. And while only a small percentage of capillaries experience this blockage, each stalled vessel leads to decreased blood flow in multiple downstream vessels, magnifying the impact on overall brain blood flow.

The paper’s co-lead authors said, the study is the culmination of approximately a decade of study, data gathering and analysis. It began with a study in which one of the author was attempting to put clots into the vasculatures of Alzheimer’s mouse brains to see their effect.

“It turns out that … the blockages we were trying to induce were already in there,” she said. “It sort of turned the research around – this is a phenomenon that was already happening.”

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The researchers, determined that only about 2 percent of brain capillaries had “stalls” (blockages), but the cumulative effect of that small number of stalls was an approximately 20 percent overall decrease in brain blood flow, due to the slowing of downstream vessels by the capillaries that were stalled. Recent studies suggest that brain blood flow deficits are one of the earliest detectable symptoms of dementia.

To test the effect of the stalls on performance of memory tasks in Alzheimer’s mice, they were given an antibody that interfered with the adhesion of white blood cells to capillary walls, which caused the stalled capillaries to start flowing again and thus increased overall brain blood flow. Memory function was improved within a few hours, even in aged mice with more advanced stages of Alzheimer’s disease.

The authors are quick to point out, however, that the antibody is not something that can be used in humans. Also, of course, interfering with white blood cell adhesion would render an individual immunocompromised.

“What we’ve done is identify the cellular mechanism that causes reduced brain blood flow in Alzheimer’s disease models, which is neutrophils [white blood cells] sticking in capillaries,” the author said. “We’ve shown that when we block the cellular mechanism [that causes the stalls], we get an improved blood flow, and associated with that improved blood flow is immediate restoration of cognitive performance of spatial- and working-memory tasks.”

“Now that we know the cellular mechanism,” he said, “it’s a much narrower path to identify the drug or the therapeutic approach to treat it.”

The team has identified approximately 20 drugs, many of them already government approved for human use, that have potential in dementia therapy. Some of them, however, were designed to be taken in high doses for short periods of time to treat sepsis, or in the immediate aftermath of a heart attack or stroke. “They weren’t really intended to be something that you take for the rest of your life,” the author said. Nonetheless, the lab is screening these drugs in Alzheimer’s mice now. 

The author said he’s “super-optimistic” that, if the same capillary-blocking mechanism is at play in humans as it is in mice, this line of research “could be a complete game-changer for people with Alzheimer’s disease.”

Affordable new tech for measuring brain blood flow

A new technique for measuring blood flow in the human brain, based on conventional digital camera technology, could be significantly cheaper and more robust than prior methods, say scientists.
The method could be used in patients with stroke or traumatic brain injury, according to the researchers.

“Our setup is very promising, and the cost should be lower,” said study co-author.

The new method, called interferometric diffusing wave spectroscopy, or iDWS, could prove to be less expensive when compared to an experimental technique called diffuse correlation spectroscopy, or DCS.

If you shine a light into a cloudy solution, light particles, or photons, will be scattered in different directions and DCS uses essentially this approach to look inside someone’s skull.

Laser light is shined on the head and as photons from the laser pass through the skull and brain, they are scattered by blood and tissue.

A detector placed elsewhere on the head, where the photons make their way out again, picks up the light fluctuations due to blood motion. These fluctuations provide information about blood flow.

But the light signal is very weak, and the further it passes through the skull and brain tissue, the weaker it gets.

So DCS requires a number of very sensitive, expensive single photon counting detectors. Moreover, boosting the light going in risks burning the patient’s skin.

The researchers, therefore, took a different approach, based on the fact that overlapping light waves will reinforce or cancel each other out, like overlapping ripples on a pond.

They first split the light beam into “sample” and “reference” paths.

The sample beam goes into the patient’s head and another, stronger, reference beam is routed so that it reconnects with the sample beam before going to the detector.

This boosts the signal, meaning that instead of needing about 20 photon-counting detectors that cost a few thousand dollars each, the researchers could use a single complementary metal-oxide-semiconductor (CMOS)-based digital camera chip for a fraction of the price.

“The strong reference light enhances the weaker signal from the sample,” the researcher said.

An added advantage is that they do not need to turn off the room lights while making measurements with iDWS, he said.

Eventually, the researchers believe that may even be able to monitor brain blood flow outdoors, under bright sunlight.

THIS IS ONLY FOR INFORMATION, ALWAYS CONSULT YOU PHYSICIAN BEFORE HAVING ANY PARTICULAR FOOD/ MEDICATION/EXERCISE/OTHER REMEDIES.                                                                                                                                                                                                        PS- THOSE INTERESTED IN RECIPES ARE FREE TO  VIEW MY BLOG-                                                                                           https://gseasyrecipes.blogspot.com/  

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