Alzheimer's Might Actually Begin In Your Gut

There's a particular class of illnesses called the neurodegenerative diseases, which includes Parkinson's and Alzheimer's. These diseases have three things in common: the first is that they all seem to be caused by malfunctioning proteins in the brain; the second is that we had, until relatively recently, absolutely no idea where they came from. The third, unfortunately, is that at the moment, they're all incurable. While there can be a genetic component to stuff like Alzheimer's, that doesn't seem to be a good enough explanation for why the disease occurs in many cases (up to 90 percent of them, if some stats are to be believed). But a new bunch of science is alleging that the root of neurodegenerative diseases isn't in the brain at all, at least not originally; it's in the gut.

This isn't the first glimmer we've heard of this idea: in June this year, scientists from the Ecole polytechnique fédérale de Lausanne (say that five times fast) announced they were forming a task force with other scientists to expand on some previous research on the tie between Alzheimer's and the gut (the force, hilariously, will be called AD-gut). But a new study from the University of Louisiana provides more concrete evidence that what we're looking at here is a pretty definitive case of interconnected bodily systems gone awry.

Considering how many people struggle with Parkinson's, Alzheimer's and other neurodegenerative diseases (60,000 new cases of Parkinson's are diagnosed in the US every year), and what a wide societal impact the diseases have, this is important stuff. So how does the gut work on the brain?

Why Your Gut Might Be The Key To Parkinson's And Alzheimer's

The big thing that marks out Parkinson's et al from other diseases is what causes the symptoms. It's not just that the brains of the afflicted stop working. Rather, there's a problem in neurodegenerative diseases called "misfolding proteins;" basically, proteins are meant to fold a certain way when they're forming, and in people with these conditions, the process appears to go wrong at the very end; thus, the damaged proteins end up accumulating around certain regions of the brain. This is the stuff called "plaque" that causes the real degeneration of brain function; New Scientist describes it as "sticky, brain-clogging gunk that kills neurons and robs people of their memories and other mental faculties." There's a lot of variation in types of plaque and proteins, but obviously something must be causing the build-up.

And the University of Louisville researchers think they might have the answer, or at least part of it. They tested their hypothesis on old rats, by injecting them with E.coli, a bacteria that flourishes in the gut. They also had a control group injected with a different type of bacteria, one that was much more benign. Why E.coli? Because it produces a type of protein called curli, which are much less cute than they sound. Curli are a key part of the function of E.coli when it's taking over the gut, but they're also part of a bigger class of proteins called the amyloids, which have been linked to Parkinson's and similar diseases for ages.

Now, it seems, we know what the link actually is. In the rats who had E.coli, the levels of curli led to increases in the amount of plaque in the brain. A particular protein started to fold wrong all over the place, and "clump" around vulnerable areas of the brain: alpha-synuclein — which sounds like the name of a terrible sci-fi villain, but is actually one of the biggest protein culprits when it comes to Parkinson's plaque. The scientists also found that the gut bacteria had spawned more inflammation of the brain tissue in infected rats, and that the protein increase showed up in both their brains and their intestines.

This is amazing, and slightly gobsmacking, news. It turns out that taking care of your brain and protecting its faculties isn't just about doing your sudoku: it's about maintaining gut health, too. And if we can control the gut, maybe we can control the incidence of diseases, or eliminate them altogether.

What This Means For Your Brain

The implications of this are pretty massive. And they've already started to show up; just before the University of Louisiana study was published, a different study from the Human Microbiology Institute showed that neurodegenerative diseases might actually be indirectly contagious. Why? Because certain bacterial viruses can lead to illnesses in your gut flora, which can then influence Parkinson's and other diseases. It's an indirect effect, but it does show that when the gut is vulnerable, so is the brain.

But unfortunately, knowing about a link and actually being able to do anything about it are two very different things. The Michael J. Fox Foundation actually helped fund the University of Louisiana experiment, but hope for a cure for Fox himself — the most famous Parkinson's sufferer alive — remains currently a long way off. The information we have, though, could be useful when it comes to halting neurodegenerative diseases, slowing them down, or stopping them from turning up in the first place; the splendidly named AD-gut is trying to produce a "probiotic cocktail" that could alter gut flora and help stop proteins going wildly wrong. From there, we might be able to work out a kind of gut-management system that eradicates the whole problem entirely, but considering we've only just discovered what happens in rats, this is all decades away.

It is entirely possible that, within our lifetimes, we might swallow anti-Alzheimer's yogurt as part of our regular medical arsenal once we get above a certain age. Hopefully they might make it taste a bit less disgusting than current probiotic yogurts, but considering the emphasis on E.coli, I'm not hoping for much.