Very sad

The failure of Lilly’s antibody against the aBeta protein is very sad on several levels. My year started out going to a memorial service for a college classmate, fellow doc and friend who died of Alzheimer’s disease. He had some 50 papers to his credit mostly involving clinical evaluation of drugs such as captopril. Even so it was an uplifting experience — here’s a link –https://luysii.wordpress.com/2016/01/05/an-uplifting-way-to-start-the-new-year/

There is a large body of theory that says it should have worked. Derek Lowe’s blog “In the Pipeline” has much more — and the 80 or so comments on his post will expose you to many different points of view on Abeta — here’s the link. http://blogs.sciencemag.org/pipeline/archives/2016/11/23/eli-lillys-alzheimers-antibody-does-not-work.

It’s time to ‘let 100 flowers bloom’ in Alzheimer’s research — https://en.wikipedia.org/wiki/Hundred_Flowers_Campaign. E. g. it’s time to look at some far out possibilities — we know that most will be wrong that they will be crushed, as Mao did to all the flowers. Even so it’s worth doing.

So to buck up your spirits, here’s an old post (not a link) raising the possibility that Alzheimer’s might be a problem in physics rather than chemistry. If that isn’t enough another post follows that one on Lopid (Gemfibrozil).

Could Alzheimer’s disease be a problem in physics rather than chemistry?

Two seemingly unrelated recent papers could turn our attention away from chemistry and toward physics as the basic problem in Alzheimer’s disease. God knows we could use better therapy for Alzheimer’s disease than we have now. Any new way of looking at Alzheimer’s, no matter how bizarre,should be welcome. The approaches via the aBeta peptide, and the enzymes producing it just haven’t worked, and they’ve really been tried — hard.

The first paper [ Proc. Natl. Acad. Sci. vol. 111 pp. 16124 – 16129 ’14 ] made surfaces with arbitrary degrees of roughness, using the microfabrication technology for making computer chips. We’re talking roughness that’s almost smooth — bumps ranging from 320 Angstroms to 800. Surfaces could be made quite regular (as in a diffraction grating) or irregular. Scanning electron microscopic pictures were given of the various degrees of roughness.

Then they plated cultured primitive neuronal cells (PC12 cells) on surfaces of varying degrees of roughness. The optimal roughness for PC12 to act more like neurons was an Rq of 320 Angstroms.. Interestingly, this degree of roughness is identical to that found on healthy astrocytes (assuming that culturing them or getting them out of the brain doesn’t radically change them). Hippocampal neurons in contact with astrocytes of this degree of roughness also began extending neurites. It’s important to note that the roughness was made with something neurons and astrocytes never see — silica colloids of varying sizes and shapes.

Now is when it gets interesting. The plaques of Alzheimer’s disease have surface roughness of around 800 Angstroms. Roughness of the artificial surface of this degree was toxic to hippocampal neurons (lower degrees of roughness were not). Normal brain has a roughness with a median at 340 Angstroms.

So in some way neurons and astrocytes can sense the amount of roughness in surfaces they are in contact with. How do they do this — chemically it comes down to Piezo1 ion channels, a story in themselves [ Science vol. 330 pp. 55 – 60 ’10 ] These are membrane proteins with between 24 and 36 transmembrane segments. Then they form tetramers with a huge molecular mass (1.2 megaDaltons) and 120 or more transmembrane segments. They are huge (2,100 – 4,700 amino acids). They can sense mechanical stress, and are used by endothelial cells to sense how fast blood is flowing (or not flowing) past them. Expression of these genes in mechanically insensitive cells makes them sensitive to mechanical stimuli.

The paper is somewhat ambiguous on whether expressing piezo1 is a function of neuronal health or sickness. The last paragraph appears to have it both ways.

So as we leave paper #1, we note that that neurons can sense the physical characteristics of their environment, even when it’s something as un-natural as a silica colloid. Inhibiting Piezo1 activity by a spider venom toxin (GsMTx4) destroys this ability. The right degree of roughness is healthy for neurons, the wrong degree kills them. Clearly the work should be repeated with other colloids of a different chemical composition.

The next paper [ Science vol. 342 pp. 301, 316 – 317, 373 – 377 ’13 ] Talks about the plumbing system of the brain, which is far more active than I’d ever imaged. The glymphatic system is a network of microscopic fluid filled channels. Cerebrospinal fluid (CSF) bathes the brain. It flows into the substance of the brain (the parenchyma) along arteries, and the fluid between the cellular elements (interstitial fluid) it exchanges with flows out of the brain along the draining veins.

This work was able to measure the amount of flow through the lymphatics by injected tracer into the CSF and/or the brain parenchyma. The important point about this is that during sleep these channels expand by 60%, and beta amyloid is cleared twice as quickly. Arousal of a sleeping mouse decreases the influx of tracer by 95%. So this amazing paper finally comes up with an explanation of why we spend 1/3 of our lives asleep — to flush toxins from the brain.

If you wish to read (a lot) more about this system — see an older post from when this paper first came out — https://luysii.wordpress.com/2013/10/21/is-sleep-deprivation-like-alzheimers-and-why-we-need-sleep-in-the-first-place/

So what is the implication of these two papers for Alzheimer’s disease?

First
The surface roughness of the plaques (800 Angstroms roughness) may physically hurt neurons. The plaques are much larger or Alzheimer would never have seen them with the light microscopy at his disposal.

Second
The size of the plaques themselves may gum up the brain’s plumbing system.

The tracer work should certainly be repeated with mouse models of Alzheimer’s, far removed from human pathology though they may be.

I find this extremely appealing because it gives us a new way of thinking about this terrible disorder. In addition it might explain why cognitive decline almost invariably accompanies aging, and why Alzheimer’s disease is a disorder of the elderly.

Next, assume this is true? What would be the therapy? Getting rid of the senile plaques in and of itself might be therapeutic. It is nearly impossible for me to imagine a way that this could be done without harming the surrounding brain.

Before we all get too excited it should be noted that the correlation between senile plaque burden and cognitive function is far from perfect. Some people have a lot of plaque (there are ways to detect them antemortem) and normal cognitive function. The work also leaves out the second pathologic change seen in Alzheimer’s disease, the neurofibrillary tangle which is intracellular, not extracellular. I suppose if it caused the parts of the cell containing them to swell, it too could gum up the plumbing.

As far as I can tell, putting the two papers together conceptually might even be original. Prasad Shastri, the author of the first paper, was very helpful discussing some points about his paper by Email, but had not heard of the second and is looking at it this weekend.

Also a trial of Lopid (Gemfibrozil) as something which might be beneficial is in progress — there is some interesting theory behind this. The trial has about another year to go. Here’s that post and happy hunting

Takes me right back to grad school

How many times in grad school did you or your friends come up with a good idea, only to see it appear in the literature a few months later by someone who’d been working on it for much longer. We’d console ourselves with the knowledge that at least we were thinking well and move on.

Exactly that happened to what I thought was an original idea in my last post — e.g. that Gemfibrozil (Lopid) might slow down (or even treat) Alzheimer’s disease. I considered the post the most significant one I’d ever written, and didn’t post anything else for a week or two, so anyone coming to the blog for any reason would see it first.

A commenter on the first post gave me a name to contact to try out the idea, but I’ve been unable to reach her. Derek Lowe was quite helpful in letting me link to the post, so presently the post has had over 200 hits. Today I wrote an Alzheimer’s researcher at Yale about it. He responded nearly immediately with a link to an ongoing clinical study in progress in Kentucky

On Aug 3, 2015, at 3:04 PM, Christopher van Dyck wrote:

Dear Dr. xxxxx

Thanks for your email. I agree that this is a promising mechanism.
My colleague Greg Jicha at U.Kentucky is already working on this:
https://www.nia.nih.gov/alzheimers/clinical-trials/gemfibrozil-predementia-alzheimers-disease

Our current efforts at Yale are on other mechanisms:
http://www.adcs.org/studies/Connect.aspx

We can’t all test every mechanism, but hopefully we can collectively test the important ones.

-best regards,
Christopher H. van Dyck, MD
Professor of Psychiatry, Neurology, and Neurobiology
Director, Alzheimers Disease Research Unit

Am I unhappy about losing fame and glory being the first to think of it? Not in the slightest. Alzheimer’s is a terrible disease and it’s great to see the idea being tested.

Even more interestingly, a look at the website for the study shows, that somehow they got to Gemfibrozil by a different mechanism — microRNAs rather than PPARalpha.

I plan to get in touch with Dr. Jicha to see how he found his way to Gemfibrozil. The study is only 1 year in duration, and hopefully is well enough powered to find an effect. These studies are incredibly expensive (and an excellent use of my taxes). I never been involved in anything like this, but data mining existing HMO data simply has to be cheaper. How much cheaper I don’t know.

Here’s the previous post —

Could Gemfibrozil (Lopid) be used to slow down (or even treat) Alzheimer’s disease?

Is a treatment of Alzheimer’s disease at hand with a drug in clinical use for nearly 40 years? A paper in this week’s PNAS implies that it might (vol. 112 pp. 8445 – 8450 ’15 7 July ’15). First a lot more background than I usually provide, because some family members of the afflicted read everything they can get their hands on, and few of them have medical or biochemical training. The cognoscenti can skip past this to the text marked ***

One of the two pathologic hallmarks of Alzheimer’s disease is the senile plaque (the other is the neurofibrillary tangle). The major component of the plaque is a fragment of a protein called APP (Amyloid Precursor Protein). Normally it sits in the cellular membrane of nerve cells (neurons) with part sticking outside the cell and another part sticking inside. The protein as made by the cell contains anywhere from 563 to 770 amino acids linked together in a long chain. The fragment destined to make up the senile plaque (called the Abeta peptide) is much smaller (39 to 42 amino acids) and is found in the parts of APP embedded in the membrane and sticking outside the cell.

No protein lives forever in the cell, and APP is no exception. There are a variety of ways to chop it up, so its amino acids can be used for other things. One such chopper is called ADAM10 (aka Kuzbanian). ADAM10breaks down APP in such a way that Abeta isn’t formed. The paper essentially found that Gemfibrozil (commercial name Lopid) increases the amount of ADAM10 around. If you take a mouse genetically modified so that it will get senile plaques and decrease ADAM10 you get a lot more plaques.

The authors didn’t artificially increase the amount of ADAM10 to see if the animals got fewer plaques (that’s probably their next paper).

So there you have it. Should your loved one get Gemfibrozil? It’s a very long shot and the drug has significant side effects. For just how long a shot and the chain of inferences why this is so look at the text marked @@@@

****

How does Gemfibrozil increase the amount of ADAM10 around? It binds to a protein called PPARalpha which is a type of nuclear hormone receptor. PPARalpha binds to another protein called RXR, and together they turn on the transcription of a variety of genes, most of which are related to lipid metabolism. One of the genes turned on is ADAM10, which really has never been mentioned in the context of lipid metabolism. In any event Gemfibrozil binds to PPARalpha which binds more effectively to RAR which binds more effectively to the promoter of the ADAM10 gene which makes more ADAM10 which chops of APP in such fashion that Abeta isn’t made.

How in the world the authors got to PPARalpha from ADAM10 is unknown — but I’ve written the following to the lead author just before writing this post.

Dr. Pahan;

Great paper. People have been focused on ADAM10 for years. It isn’t clear to me how you were led to PPARgamma from reading your paper. I’m not sure how many people are still on Gemfibrozil. Probably most of them have some form of vascular disease, which increases the risk of dementia of all sorts (including Alzheimer’s). Nonetheless large HMOs have prescription data which can be mined to see if the incidence of Alzheimer’s is less on Gemfibrozil than those taking other lipid lowering agents, or the population at large. One such example (involving another class of drugs) is JAMA Intern Med. 2015;175(3):401-407, where the prescriptions of 3,434 individuals 65 years or older in Group Health, an integrated health care delivery system in Seattle, Washington. I thought the conclusions were totally unwarranted, but it shows what can be done with data already out there. Did you look at other fibrates (such as Atromid)?

Update: 22 July ’15

I received the following back from the author

Dear Dr.

Wonderful suggestion. However, here, we have focused on the basic science part because the NIH supports basic science discovery. It is very difficult to compete for NIH R01 grants using data mining approach.

It is PPARα, but not PPARγ, that is involved in the regulation of ADAM10. We searched ADAM10 gene promoter and found a site where PPAR can bind. Then using knockout cells and ChIP assay, we confirmed the participation of PPARα, the protein that controls fatty acid metabolism in the liver, suggesting that plaque formation is controlled by a lipid-lowering protein. Therefore, many colleagues are sending kudos for this publication.

Thank you.

Kalipada Pahan, Ph.D.

The Floyd A. Davis, M.D., Endowed Chair of Neurology

Professor

Departments of Neurological Sciences, Biochemistry and Pharmacology

So there you have it. An idea worth pursuing according to Dr. Pahan, but one which he can’t (or won’t). So, dear reader, take it upon yourself (if you can) to mine the data on people given Gemfibrozil to see if their risk of Alzheimer’s is lower. I won’t stand in your way or compete with you as I’m a retired clinical neurologist with no academic affiliation. The data is certainly out there, just as it was for the JAMA Intern Med. 2015;175(3):401-407 study. Bon voyage.

@@@@

There are side effects, one of which is a severe muscle disease, and as a neurologist I saw someone so severely weakened by drugs of this class that they were on a respirator being too weak to breathe (they recovered). The use of Gemfibrozil rests on the assumption that the senile plaque and Abeta peptide are causative of Alzheimer’s. A huge amount of money has been spent and lost on drugs (antibodies mostly) trying to get rid of the plaques. None have helped clinically. It is possible that the plaque is the last gasp of a neuron dying of something else (e.g. a tombstone rather than a smoking gun). It is also possible that the plaque is actually a way the neuron was defending itself against what was trying to kill it (e.g. the plaque as a pile of spent bullets).

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Comments

  • YoYo  On November 29, 2016 at 5:13 am

    Do kids with progeria — rapid premature aging — develop Alzheimer’s or even just A-beta plaques? What about other neurodegenerative diseases of kids? We are in desperate need of smoking guns for this disease, and it seems like they would be a natural laboratory for studying the signaling cascade.

  • luysii  On November 29, 2016 at 11:52 am

    No dementia in progeria [ Cell vol. 156 pp. 400 – 407 ’14 ]

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