Category Archives: Neurology & Psychiatry

How complicated can neuropharmacology be?

A revolution is occurring in our thinking about the neurochemistry and treatment of depression.  Spectacular therapeutic results with ketamine imply that neurotransmission with glutamic acid is involved (see the older post below for the background)  In addition gamma amino butyric acid (GABA) may also be a player.  That’s why a recent review [ Neuron vol. 102 pp. 75 – 94 ’19 ] is worth a careful reading.

Like all new fields, early results are particularly confusing. In particular the statement was made that in addition to NMDA receptor blockers (such as ketamine) positive allosteric modifiers (PAMs) of the NMDAR also are therapeutic in depression (the latter in animal models only, a phase III trial in depression having failed).

So I wrote the lead author ”

Great review, but how do you reconcile the rapid antidepressant action of the NMDAR blocker ketamine and friends and an NMDAR PAM (positive allosteric modifier)”

I got the following back —

We have data indicating that ketamine blocks NMDA receptors on GABA neurons resulting in disinhibition and increased synaptic activity of principle neurons, whereas the PAM (rapastinel) acts directly on NMDA receptors on principle neurons to produce a similar downstream effect

It didn’t make sense that drugs having opposite effects on the same therapeutic target (the NMDAR) would have the same therapeutic effect.

So I wrote

If I understand you correctly, this implies that the subunit composition of the NMDARs at the two sites (GABA interneurons and principal neurons) is different.

I got the following back, which is positively Talmudic in its logical intricacy.

It could be the same receptor complex; because ketamine is an open channel blocker the GABA neurons, which are more active, would be more sensitive because activity is required to remove the Mg+2 block in the channel and thereby allow ketamine to enter and block the channel. The PAM does not require activity and could act at directly on principle neurons.

If this is correct, a lot of neuropharmacology on drug effects will require rethinking.  What does the readership think?

Stock tip — update

The FDA approved esketamine (Spravato) last week (see copy of original post at the end).  I had recommended buying Johnson and Johnson if the FDA approved it.  I think it’s a good long term buy, but there is no rush for the following reason — Esketamine is not a drug you can get a prescription for and take on you own. Because of the psychiatric side effects it must be administered in a SPRAVATO REMS.

Risk Evaluation and Mitigation Strategy (REMS): SPRAVATO™ is available only through a restricted program called the SPRAVATO™ REMS because of the risks of serious adverse outcomes from sedation, dissociation, and abuse and misuse.

Important requirements of the SPRAVATO™ REMS include the following:

  • Healthcare settings must be certified in the program and ensure that SPRAVATO™ is:
    • Only dispensed in healthcare settings and administered to patients who are enrolled in the program.
    • Administered by patients under the direct observation of a healthcare provider and that patients are monitored by a healthcare provider for at least 2 hours after administration of SPRAVATO™.
  • Pharmacies must be certified in the REMS and must only dispense SPRAVATO™ to healthcare settings that are certified in the program.

So you can’t go to some shady practitioner who’ll say you have treatment resistant depression and get some (e.g. the pill pushers for opiates, ‘medical’ marihuana  etc. etc.)

So there aren’t going to be hordes of users right away, although the stuff I’ve read implies that there will be eventually.

If you have a subscription to Cell have a look at vol. 101 pp. 774 – 778 ’19 by the guys at Yale who did some of the original work.  If not content yourself with this.

They are refreshingly honest.

Was the Discovery of Ketamine’s Antidepressant Serendipitous?Of course. However, its discovery emerged from the testing of a novel mechanistic hypothesis related to the pathophysiology of depression.”

Basically the authors rejected the regnant theory of depression, namely that the cause was to be found in monoamine neurotransmission (e.g. by dopamine, norepinephrine, serotonin).  There was some evidence that the cerebral cortex was involved in depression (not just the monamine nuclei of the brainstem), so they looked at the two major neurotransmitters in brain (glutamic acid, and GABA), and chose to see what would happen if they blocked one of the many receptors for glutamic acid, the NMDA receptor.  They chose ketamine to do this.
Here’s what they found,  A single dose of ketamine produced antidepressant effects that began within hours peaked in 24 – 72 hours and dissipated within 2 weeks (if ketamine wasn’t repeated).  This was in 50 – 75% people with treatment resistant depression.  Remarkable 1/3 of treated patients went into remission.    There simply has never been anything like this, which is why I thought the drug would be a blockbuster.
There is a lot of speculation about just which effect of esketamine is crucial (increase in glutamic acid release with AMPAR stimulation, brain derived neurotrophic factor (BDNF) release, TrkB receptor stimulation, mTORC1 activation, local protein synthesis, restoration of functional connectivity in functional MRI.   In animals one sees a rapid proliferation of dendritic spines.
As promised – here’s a copy of the first post

Stock tip

The past performance of stock recommendations is no guarantee that it will continue — which is fortunate as my first tip (ONTX) was a disaster.  I knew it was a 10 to one shot but with a 100 to 1 payoff.  People play the lottery with worse odds.  Anyway ONTX had a rationale — for the gory details see — https://luysii.wordpress.com/2016/06/01/in-a-gambling-mood/

For those brave souls who followed this recommendation (including yours truly) here’s another.

On 4 March 2019 if the FDA approves esketamine for depression, buy Johnson and Johnson.  Why?  Some people think that no drug for depression works that well, as big Pharma in the past only was reporting positive studies.  The following is from Nature 21 February 2019.

Depression drug A form of the hallucinogenic party drug ketamine has cleared one of the final hurdles towards clinical use as an antidepressant. During a 12 February meeting at the US Food and Drug Administration (FDA) in Silver Spring, Maryland,an independent advisory panel voted 14 to 2 in favour of recommending a compound known as esketamine for use in treating depression.

What’s so hot about esketamine?  First its mechanism of action is completely different than the SSRIs, Monoamine oxidase inhibitors, or tricyclic antidepressants.

As you likely know, antidepressants usually take a few weeks to work at least in endogenous depression.  My clinical experience as a neurologist is slightly different, as I only used it for patients with disease I couldn’t help (end stage MS etc. etc.) where the only normal response to the situation was depression.  They often helped patients within a week.

I was staggered when I read the following paper back in the day.  But there was no followup essentially.

archives of general psychiatry volume 63 pp. 856 – 864 2006
The paper is not from St. Fraudulosa Hospital in Plok Tic, but from the Mood Disorders Research Unit at the National Institute of Mental Health.
Here are the basics from the paper

Patients  Eighteen subjects with DSM-IV major depression (treatment resistant).

Interventions  After a 2-week drug-free period, subjects were given an intravenous infusion of either ketamine hydrochloride (0.5 mg/kg) or placebo on 2 test days, a week apart. Subjects were rated at baseline and at 40, 80, 110, and 230 minutes and 1, 2, 3, and 7 days postinfusion.

Main Outcome Measure  Changes in scores on the primary efficacy measure, the 21-item Hamilton Depression Rating Scale.

Results  Subjects receiving ketamine showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week. The effect size for the drug difference was very large (d = 1.46 [95% confidence interval, 0.91-2.01]) after 24 hours and moderate to large (d = 0.68 [95% confidence interval, 0.13-1.23]) after 1 week. Of the 17 subjects treated with ketamine, 71% met response and 29% met remission criteria the day following ketamine infusion. Thirty-five percent of subjects maintained response for at least 1 week.

Read this again: showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week.

This is absolutely unheard of.  Yet the paper essentially disappeared.

What is esketamine?  It’s related to ketamine (a veterinary anesthetic and drug of abuse) in exactly the same way that a glove for your left hand is related to a right handed glove.  The two drugs are optical isomers of each other.

What’s so important about the mirror image?  It means that esketamine may well act rather differently than ketamine (the fact that ketamine worked is against this).  The classic example is thalidomide, one optical isomer of which causes horrible malformations (phocomelia) while the other is a sedative used in the treatment of multiple myeloma and leprosy.

If toxic side effects can be avoided, the market is enormous.  It is estimated that 25% of women and 10% of men will have a major depression at some point in their lives.

Initially, Esketamine ( SPRAVATOTM)  will likely be limited to treatment resistant depression.  But depressed people will find a way to get it and  their docs will find a way to give it.  Who wants to wait three weeks.  Just think of the extremely sketchy ‘medical indications’ for marihuana.

 

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How to treat Alzheimer’s disease

Let’s say you’re an engineer whose wife has early Alzheimer’s disease.  Would you build the following noninvasive device to remove her plaques?  [ Cell vol. 177 pp. 256 – 271 ’19 ] showed that it worked in mice.

Addendum 18 April — A reader requested a better way to get to the paper — Here is the title — “Multisensory Gamma Stimulation Ameliorates Alzheimer’s Associated Pathology and Improves Cognition”.  It is from MIT — here is the person to correspond to  —Correspondence — lhtsai@mit.edu

The device emits sound and light 40 times a second.  Exposing mice  to this 1 hour a day for a week decreased the number of senile plaques all over the brain (not just in the auditory and visual cortex) and improved their cognition as well.

With apologies to Steinbeck, mice are not men (particularly these mice which carry 5 different mutations which cause Alzheimer’s disease in man).  Animal cognition is not human cognition.  How well do you think Einstein would have done running a maze looking for food?

I had written about the authors’ earlier work and a copy of that post will be found after the ****.

What makes this work exciting is that plaque reduction was seen not only  in the visual cortex (which is pretty much unaffected in Alzheimer’s) but in the hippocampus (which is devastated) and the frontal lobes (also severely affected).  Interestingly, to be effective, both sound and light had to be given simultaneously

Here are the details about the stimuli  —

“Animals were presented with 10 s stimulation blocks interleaved with 10 s baseline periods. Stimulation blocks rotated between auditory-only or auditory and visual stimulation at 20 Hz, 40 Hz, 80 Hz, or with random stimulation (pulses were delivered with randomized inter-pulse intervals determined from a uniform distribution with an average interval of 25 ms). Stimuli blocks were interleaved to ensure the results observed were not due to changes over time in the neuronal response. 10 s long stimulus blocks were used to reduce the influence of onset effects, and to examine neural responses to prolonged rhythmic stimulation. All auditory pulses were 1 ms-long 10 kHz tones. All visual pulses were 50% duty cycle of the stimulation frequency (25 ms, 12.5 ms, or 6.25 ms in length). For combined stimulation, auditory and visual pulses were aligned to the onset of each pulse.”

The device should not require approval by the FDA unless a therapeutic claim is made, and it’s about as noninvasive as it could be.

What could go wrong?  Well a flickering light could trigger seizures in people subject to photic epilepsy (under 1/1,000).

Certainly Claude Shannon who died of Alzheimer’s disease, would have had one built, as would Fields medal winner Daniel Quillen had he not passed away 8 years ago.

Here is the post of 12/16 which has more detail

 

*****

Will flickering light treat Alzheimer’s disease ?

Big pharma has spent zillions trying to rid the brain of senile plaques, to no avail. A recent paper shows that light flickering at 40 cycles/second (40 Hertz) can do it — this is not a misprint [ Nature vol. 540 pp. 207 – 208, 230 – 235 ’16 ]. As most know the main component of the senile plaque of Alzheimer’s disease is a fragment (called the aBeta peptide) of the amyloid precursor protein (APP).

The most interesting part of the paper showed that just an hour or so of light flickering at 40 Hertz temporarily reduced the amount of Abeta peptide in visual cortex of aged mice. Nothing invasive about that.

Should we try this in people? How harmful could it be? Unfortunately the visual cortex is relatively unaffected in Alzheimer’s disease — the disease starts deep inside the head in the medial temporal lobe, particularly the hippocampus — the link shows just how deep it is -https://en.wikipedia.org/wiki/Hippocampus#/media/File:MRI_Location_Hippocampus_up..png

You might be able to do this through the squamous portion of the temporal bone which is just in front of and above the ear. It’s very thin, and ultrasound probes placed here can ‘see’ blood flowing in arteries in this region. Another way to do it might be a light source placed in the mouth.

The technical aspects of the paper are fascinating and will be described later.

First, what could go wrong?

The work shows that the flickering light activates the scavenger cells of the brain (microglia) and then eat the extracellular plaques. However that may not be a good thing as microglia could attack normal cells. In particular they are important in the remodeling of the dendritic tree (notably dendritic spines) that occurs during experience and learning.

Second, why wouldn’t it work? So much has been spent on trying to remove abeta, that serious doubt exists as to whether excessive extracellular Abeta causes Alzheimer’s and even if it does, would removing it be helpful.

Now for some fascinating detail on the paper (for the cognoscenti)

They used a mouse model of Alzheimer’s disease (the 5XFAD mouse). This poor creature has 3 different mutations associated with Alzheimer’s disease in the amyloid precursor protein (APP) — these are the Swedish (K670B), Florida (I716V) and London (V717I). If that wasn’t enough there are two Alzheimer associated mutations in one of the enzymes that processes the APP into Abeta (M146L, L286V) — using the single letter amino acid code –http://www.biochem.ucl.ac.uk/bsm/dbbrowser/c32/aacode.html.hy1. Then the whole mess is put under control of a promoter particularly active in mice (the Thy1 promoter). This results in high expression of the two mutant proteins.

So the poor mice get lots of senile plaques (particularly in the hippocampus) at an early age.

The first experiment was even more complicated, as a way was found to put channelrhodopsin into a set of hippocampal interneurons (this is optogenetics and hardly simple). Exposing the channel to light causes it to open the membrane to depolarize and the neuron to fire. Then fiberoptics were used to stimulate these neurons at 40 Hertz and the effects on the plaques were noted. Clearly a lot of work and the authors (and grad students) deserve our thanks.

Light at 8 Hertz did nothing to the plaques. I couldn’t find what other stimulation frequencies were used (assuming they were tried).

It would be wonderful if something so simple could help these people.

For other ideas about Alzheimer’s using physics rather than chemistry please see — https://luysii.wordpress.com/2014/11/30/could-alzheimers-disease-be-a-problem-in-physics-rather-than-chemistry/

Apologies to Hamlet

Apologies to Shakespeare and Hamlet.  Serotonin does “more things in heaven and Earth, Horatio, than are dreamt of in your philosophy.”  How about chemically modifying histones?We all know about serotonin and depression (or at least we think we know).  Block serotonin reuptake by the releasing neuron and bingo you’ve  cured depression (sometimes).  Do not ask the lecturer which of the 15 known serotonin receptors in the brain the increased serotonin actually binds to and what effects the increased levels produce after binding (and which are important for the alleviation of depression).The two body organs producing the most serotonin are the brain and the gut.  Chemical modification of proteins by serotonin has been known for 10 years.  The enzyme responsible is transglutaminase2, it takes the NH2 group of serotonin and replaces the NH2 of glutamine with it — forming an isopeptide bond.

Interestingly, the serotonylation of histones is quite specific.  Only glutamine #5 on histone H3 is modified this way.  For the reaction to occur lysine #4 on histone H3 must be trimethylated (H3K4Me3) — now you can begin to see the combinatorial possibilities of the various histone modifications known.  Over 130 post-ranslational modifications of histones were known by 2013 [ Cell vol. 155 p. 42 ’13 ].

The H3K4Me3Q5Ser is enriched in euchromatin and correlates with permissive gene expression.  Changing glutamine #5 to something else so it can’t be serotonylated changes the transcription pattern, and deficits in cellular differentiation.  You can read more about it in Nature vol. 567 pp. 464 – 465, 535 – 539 ’19 ]

Babies are smarter than we thought

In a great study from France some 150 5 month old infants were shown to be able to associate an abstract 3 syllable pattern with an image and react when the pattern wasn’t consonant with images they’d been shown many times before [ Proc. Natl. Acad. Sci. vol. 116 pp.

Well, the kids weren’t geniuses and talking.  So how could the researchers make such a statement?  The babies were sitting in their parents laps with a high density (120 electrode) EEG cap on their heads.  They were exposed to monosyllable triplets in various patterns AAB, ABA, ABB, BBA etc. Following  each triplet presentation a picture of a fish or a lion was shown.

For example,  for most of the time they experienced AAB lion AAB lion AAB lion —but occasionally AAB fish was thrown in.  The EEG was quite different with the fish.

Even better, they exposed the child to the picture (lion) first followed by the trisyllable.  If the trisyllable was AAB there was no reaction, but it if was ABA there was a reaction implying that the babies had linked the picture and the sound pattern.

This is excellent evidence for the ability of 5 month old infants to associate an abstract (sound) pattern with an unrelated visual stimulus.

They did many more experiments but you get the idea.

You’d better. The infants did.

It would be fascinating to repeat the experiment with chimpanzees.

Measuring what the brain thinks it is perceiving rather than the stimulus itelf

It’s usually not hard to do neuropsychology experiments.  The hard part is being smart enough to think of a good one.  I found a recent one absolutely brilliant, as the authors were able to measure a signal which had to be coming from the conscious perception of motion in a particular direction [ Proc. Natl. Acad. Sci. vol. 116 pp. 5096 – 5101 ’19 ].

Throw any stimulus at a living human and you’ll get some sort of measurable electrical response or a measurable change in blood flow in a particular brain area (you can use functional MRI — fMRI to measure the latter).  But how do you know whether the response has anything to do with conscious perception.  You don’t.

Here’s where the cleverness of the authors comes in.  Probably most people reading this post know about Cartesian coordinates, but to not leave the nonMathematically inclined behind, I’ll use baseball to describe the experimental set up.

We talk about a baseball diamond, and that’s the way it looks to people sitting in the stands behind home plate.  But actually the 4 bases form a perfect square 90 feet on a side.

So turn the ‘diamond’ on its side so the path between home plate and first base is horizontal, as is the path between 2nd and third while the paths between first and second and between third base and home are vertical.

Now that you’re oriented, imagine this on a computer screen. What the authors did was to light up first and third for .15 seconds, turn things off for .067 seconds and then light up home plate and second base for .15 seconds.  So the dot pairs alternate about 4 times a second.

But what does this look like to a human being?  For about 10 seconds the dots actually appear to actually be moving horizontally, then they appear to be moving vertically.  Remember the dots themselves  aren’t moving at all, just blinking.

The brilliance of the setup is that with exactly the same stimulus (alternately lit pairs of dots) the same person will have two different perceptions of the way the dots are moving at different times.

What do you think they did next?

They put the same people in an MRI machine and then showed the dots actually moving across the screen horizontally and then vertically.  Different parts of the brain responded to vertical motion than responded to horizontal motion.  The response was increased blood flow to that area, which is what fMRI actually measures.

So then back to the original set up with alternate pairs of dots on and off about 4 times a second.  Then they asked people which way the dots appeared to be moving, and the area of the brain which lit up (showed increased flow) was the same one which lit up to actual motion in that direction.

So they were actually measuring conscious perception of motion, rather than some nonspecific response to the visual stimulus, because the stimulus didn’t change regardless of the way it was perceived.

One of things this means is that the brain is producing the same neural response when it perceives motion in one direction (even though none is present) that real motion produces.

I think this is just brilliant.  Bravo. Something for the philosophers among you to chew on.

Stock tip — update

The FDA approved esketamine (Spravato) last week (see copy of original post at the end).  I had recommended buying Johnson and Johnson if the FDA approved it.  I think it’s a good long term buy, but there is no rush for the following reason — Esketamine is not a drug you can get a prescription for and take on you own. Because of the psychiatric side effects it must be administered in a SPRAVATO REMS.

Risk Evaluation and Mitigation Strategy (REMS): SPRAVATO™ is available only through a restricted program called the SPRAVATO™ REMS because of the risks of serious adverse outcomes from sedation, dissociation, and abuse and misuse.

Important requirements of the SPRAVATO™ REMS include the following:

  • Healthcare settings must be certified in the program and ensure that SPRAVATO™ is:
    • Only dispensed in healthcare settings and administered to patients who are enrolled in the program.
    • Administered by patients under the direct observation of a healthcare provider and that patients are monitored by a healthcare provider for at least 2 hours after administration of SPRAVATO™.
  • Pharmacies must be certified in the REMS and must only dispense SPRAVATO™ to healthcare settings that are certified in the program.

So you can’t go to some shady practitioner who’ll say you have treatment resistant depression and get some (e.g. the pill pushers for opiates, ‘medical’ marihuana  etc. etc.)

So there aren’t going to be hordes of users right away, although the stuff I’ve read implies that there will be eventually.

If you have a subscription to Cell have a look at vol. 101 pp. 774 – 778 ’19 by the guys at Yale who did some of the original work.  If not content yourself with this.

They are refreshingly honest.

Was the Discovery of Ketamine’s Antidepressant Serendipitous?Of course. However, its discovery emerged from the testing of a novel mechanistic hypothesis related to the pathophysiology of depression.”

Basically the authors rejected the regnant theory of depression, namely that the cause was to be found in monoamine neurotransmission (e.g. by dopamine, norepinephrine, serotonin).  There was some evidence that the cerebral cortex was involved in depression (not just the monamine nuclei of the brainstem), so they looked at the two major neurotransmitters in brain (glutamic acid, and GABA), and chose to see what would happen if they blocked one of the many receptors for glutamic acid, the NMDA receptor.  They chose ketamine to do this.
Here’s what they found,  A single dose of ketamine produced antidepressant effects that began within hours peaked in 24 – 72 hours and dissipated within 2 weeks (if ketamine wasn’t repeated).  This was in 50 – 75% people with treatment resistant depression.  Remarkable 1/3 of treated patients went into remission.    There simply has never been anything like this, which is why I thought the drug would be a blockbuster.
There is a lot of speculation about just which effect of esketamine is crucial (increase in glutamic acid release with AMPAR stimulation, brain derived neurotrophic factor (BDNF) release, TrkB receptor stimulation, mTORC1 activation, local protein synthesis, restoration of functional connectivity in functional MRI.   In animals one sees a rapid proliferation of dendritic spines.
As promised – here’s a copy of the first post

Stock tip

The past performance of stock recommendations is no guarantee that it will continue — which is fortunate as my first tip (ONTX) was a disaster.  I knew it was a 10 to one shot but with a 100 to 1 payoff.  People play the lottery with worse odds.  Anyway ONTX had a rationale — for the gory details see — https://luysii.wordpress.com/2016/06/01/in-a-gambling-mood/

For those brave souls who followed this recommendation (including yours truly) here’s another.

On 4 March 2019 if the FDA approves esketamine for depression, buy Johnson and Johnson.  Why?  Some people think that no drug for depression works that well, as big Pharma in the past only was reporting positive studies.  The following is from Nature 21 February 2019.

Depression drug A form of the hallucinogenic party drug ketamine has cleared one of the final hurdles towards clinical use as an antidepressant. During a 12 February meeting at the US Food and Drug Administration (FDA) in Silver Spring, Maryland,an independent advisory panel voted 14 to 2 in favour of recommending a compound known as esketamine for use in treating depression.

What’s so hot about esketamine?  First its mechanism of action is completely different than the SSRIs, Monoamine oxidase inhibitors, or tricyclic antidepressants.

As you likely know, antidepressants usually take a few weeks to work at least in endogenous depression.  My clinical experience as a neurologist is slightly different, as I only used it for patients with disease I couldn’t help (end stage MS etc. etc.) where the only normal response to the situation was depression.  They often helped patients within a week.

I was staggered when I read the following paper back in the day.  But there was no followup essentially.

archives of general psychiatry volume 63 pp. 856 – 864 2006
The paper is not from St. Fraudulosa Hospital in Plok Tic, but from the Mood Disorders Research Unit at the National Institute of Mental Health.
Here are the basics from the paper

Patients  Eighteen subjects with DSM-IV major depression (treatment resistant).

Interventions  After a 2-week drug-free period, subjects were given an intravenous infusion of either ketamine hydrochloride (0.5 mg/kg) or placebo on 2 test days, a week apart. Subjects were rated at baseline and at 40, 80, 110, and 230 minutes and 1, 2, 3, and 7 days postinfusion.

Main Outcome Measure  Changes in scores on the primary efficacy measure, the 21-item Hamilton Depression Rating Scale.

Results  Subjects receiving ketamine showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week. The effect size for the drug difference was very large (d = 1.46 [95% confidence interval, 0.91-2.01]) after 24 hours and moderate to large (d = 0.68 [95% confidence interval, 0.13-1.23]) after 1 week. Of the 17 subjects treated with ketamine, 71% met response and 29% met remission criteria the day following ketamine infusion. Thirty-five percent of subjects maintained response for at least 1 week.

Read this again: showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week.

This is absolutely unheard of.  Yet the paper essentially disappeared.

What is esketamine?  It’s related to ketamine (a veterinary anesthetic and drug of abuse) in exactly the same way that a glove for your left hand is related to a right handed glove.  The two drugs are optical isomers of each other.

What’s so important about the mirror image?  It means that esketamine may well act rather differently than ketamine (the fact that ketamine worked is against this).  The classic example is thalidomide, one optical isomer of which causes horrible malformations (phocomelia) while the other is a sedative used in the treatment of multiple myeloma and leprosy.

If toxic side effects can be avoided, the market is enormous.  It is estimated that 25% of women and 10% of men will have a major depression at some point in their lives.

Initially, Esketamine ( SPRAVATOTM)  will likely be limited to treatment resistant depression.  But depressed people will find a way to get it and  their docs will find a way to give it.  Who wants to wait three weeks.  Just think of the extremely sketchy ‘medical indications’ for marihuana.

Does gamma-secretase have sex with its substrates?

This is a family blog (for the most part), so discretion is advised in reading further.   Billions have been spent trying to inhibit gamma-secretase.  Over 150 different mutations have been associated with familial Alzheimer’s disease.  The more we know about the way it works, the better.

A recent very impressive paper from China did just that [ Science vol. 363 pp. 690- 691, 701 eaaw0930 pp. 1 –> 8 ’19 ].

Gamma secretase is actually a combination of 4 proteins (presenilin1, nicastrin, APH1 (anterior pharynx defect) and PEN-2 (presenilin enhancer 2). It is embedded in membranes and has at least 19 transmembrane segments.  It cleaves a variety of proteins spanning membranes (e.g it hydrolyzes a peptide bond — which is just an amide).  The big deal is that cleavage occurs in the hydrophobic interior of the membrane rather than in the cytoplasm where there is plenty of water around.

Gamma secretase cleaves at least 20 different proteins this way, not just the amyloid precursor protein, one of whose cleavage products is the Abeta peptide making up a large component of the senile plaque of Alzheimer’s disease.

To get near gamma secretase, another enzyme must first cleave APP in another place so one extramembrane fragment is short.  Why so the rest of the protein can fit under a loop between two transmembrane helices of nicastrin.  This is elegance itself, so the gamma secretase doesn’t go around chopping up the myriad of extracellular proteins we have.

The 19 or so transmembrane helices of the 4 gamma secretase proteins form a horseshoe, into which migrates the transmembrane segment of the protein to be cleaved (once it can fit under the nicastrin loop).

So why is discretion advised before reading further?  Because the actual mechanism of cleavage involves intimate coupling of the proteins.    One of the transmembrane helices of presenilin1 unfolds to form two beta strands, and the transmembrane helix of the target protein unfolds to form one beta strand, the two strands pair up forming a beta sheet, and then the aspartic acid at the active site of gamma secretase cleaves the target (deflowers it if you will).  Is this sexual or what?

All in all another tribute to ingenuity (and possibly the prurience) of the blind watchmaker. What an elegant mechanism.

Have a look at the pictures in the Science article, but I think it is under a paywall.

Stock tip

The past performance of stock recommendations is no guarantee that it will continue — which is fortunate as my first tip (ONTX) was a disaster.  I knew it was a 10 to one shot but with a 100 to 1 payoff.  People play the lottery with worse odds.  Anyway ONTX had a rationale — for the gory details see — https://luysii.wordpress.com/2016/06/01/in-a-gambling-mood/

For those brave souls who followed this recommendation (including yours truly) here’s another.

On 4 March 2019 if the FDA approves esketamine for depression, buy Johnson and Johnson.  Why?  Some people think that no drug for depression works that well, as big Pharma in the past only was reporting positive studies.  The following is from Nature 21 February 2019.

Depression drug A form of the hallucinogenic party drug ketamine has cleared one of the final hurdles towards clinical use as an antidepressant. During a 12 February meeting at the US Food and Drug Administration (FDA) in Silver Spring, Maryland,an independent advisory panel voted 14 to 2 in favour of recommending a compound known as esketamine for use in treating depression.

What’s so hot about esketamine?  First its mechanism of action is completely different than the SSRIs, Monoamine oxidase inhibitors, or tricyclic antidepressants.

As you likely know, antidepressants usually take a few weeks to work at least in endogenous depression.  My clinical experience as a neurologist is slightly different, as I only used it for patients with disease I couldn’t help (end stage MS etc. etc.) where the only normal response to the situation was depression.  They often helped patients within a week.

I was staggered when I read the following paper back in the day.  But there was no followup essentially.

archives of general psychiatry volume 63 pp. 856 – 864 2006
The paper is not from St. Fraudulosa Hospital in Plok Tic, but from the Mood Disorders Research Unit at the National Institute of Mental Health.
Here are the basics from the paper

Patients  Eighteen subjects with DSM-IV major depression (treatment resistant).

Interventions  After a 2-week drug-free period, subjects were given an intravenous infusion of either ketamine hydrochloride (0.5 mg/kg) or placebo on 2 test days, a week apart. Subjects were rated at baseline and at 40, 80, 110, and 230 minutes and 1, 2, 3, and 7 days postinfusion.

Main Outcome Measure  Changes in scores on the primary efficacy measure, the 21-item Hamilton Depression Rating Scale.

Results  Subjects receiving ketamine showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week. The effect size for the drug difference was very large (d = 1.46 [95% confidence interval, 0.91-2.01]) after 24 hours and moderate to large (d = 0.68 [95% confidence interval, 0.13-1.23]) after 1 week. Of the 17 subjects treated with ketamine, 71% met response and 29% met remission criteria the day following ketamine infusion. Thirty-five percent of subjects maintained response for at least 1 week.

Read this again: showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week.

This is absolutely unheard of.  Yet the paper essentially disappeared.

What is esketamine?  It’s related to ketamine (a veterinary anesthetic and drug of abuse) in exactly the same way that a glove for your left hand is related to a right handed glove.  The two drugs are optical isomers of each other.

What’s so important about the mirror image?  It means that esketamine may well act rather differently than ketamine (the fact that ketamine worked is against this).  The classic example is thalidomide, one optical isomer of which causes horrible malformations (phocomelia) while the other is a sedative used in the treatment of multiple myeloma and leprosy.

If toxic side effects can be avoided, the market is enormous.  It is estimated that 25% of women and 10% of men will have a major depression at some point in their lives.

Initially, Esketamine ( SPRAVATOTM)  will likely be limited to treatment resistant depression.  But depressed people will find a way to get it and  their docs will find a way to give it.  Who wants to wait three weeks.  Just think of the extremely sketchy ‘medical indications’ for marihuana.

 

You might as well watch the Kardashians

You might as well watch the Kardashians.  Reading Shakespeare will not protect you against cognitive decline.  Although you can spindle and mutilate the intellectual cards you were dealt, you can’t play them.  That’s the rather depressing result of from  large (over 1,000 subjects) just in [ Proc. Natl. Acad. Sci. vol. 116 pp. 1832 – 1833, 2021 – 2026 ‘ 19 ].  You have doubtless heard that people who have higher educational attainment, who have had intellectually demanding occupations, who stay mentally and physically active have a lower incidence of Alzheimer’s disease.  This is true, but it’s because they were smarter to begin with.

Before describing the paper please do note that high intellectual attainment (due to high intellectual ability) is not absolutely  protective against Alzheimer’s.  Claude Shannon died of it (https://en.wikipedia.org/wiki/Claude_Shannon), as did a Fields medalist who entered college when I did, as did a classmate who wrote 43 papers testing new drugs.   It does lower the odds though.

There were intimations of this years ago [ J. Am. Med. Assoc. vol. 275 pp. 538 – 532 ’96 ] Catholic nuns ages 75 – 95 were studied. All had written an autobiographical essay at age 22 explaining why they wanted to enter the order.  14 died and some had Alzheimer’s.  The essays were read blind and scored for idea density, grammatical complexity etc. etc. Those with the lowest idea density etc. had Alzheimer’s, while those with the most intellectual complexity were free of Alzheimer neuropathology.  Of the 79 living nuns, the smart ones at age 22 remained smart for the most part at 75+ while the less gifted stayed the same.  This was a select and far from average group — all were college educated and were parochial school teachers for most of their lives.  So the group was controlled for education and occupation.

The PNAS study concerned military recruits (average age 20) entering the service between 1965 and 1975.  The people going in at age 20 were not Ivy League types, who had concocted all sorts of reasons they couldn’t serve.  The Ivy league types going in were JAG officers or Docs like myself, but we were educated and long past 20.  89% were white, 80% did not have combat exposure.

The group was part of the Vietnam Era Twin Study of Aging.  Subjects took the Armed Forces Qualification Test (AFQT) which measures cognitive ability.  Then some 1,237 were  retested at ages 51 – 59 and 1,009 were retested at an average age of 62.

Subjects filled out questionnaires concerning education, job complexity, physical and mental activity etc. etc.

So what was the best predictor of General Cognitive Ability (GCA) at 62?  It was not subsequent education, job complexity, intellectual engagement.  Each of them predicted under 1% of the variance of GCA at age 62.  The best predictor (and not that great) was GCA at 20, which accounted for over 10% of the variance.

Pretty depressing.  You can’t even play the hand you were dealt.

Somehow Princeton undergraduates have found this out and p. 15 of the 6 Feb ’19 issue of the Princeton Alumni Weekly describes the” Kardashian Lifestyle Klub, a registered student organization with about 150 members, meetings and University support“.

Proline rides again !

Proline is a kinky amino acid.  Kinky in the sense that it is only one of the twenty with a fixed configuration of its alpha carbon because of the ring (which may be why there is more of it in organisms living at high temperature) and kinky in the sense that when present in alpha helices it produces a kink.  The previous post shows how it is used to schlep the body weight’s worth of ATP we make each day out of our mitochondria — https://luysii.wordpress.com/2019/01/30/3939/.

Well here it is in one of the marijuana receptors (CB1).  Binding of delta9 THC in the 7 transmembrane alpha helix bundles of the G Protein Coupled Receptor (GPCR) causes an alteration in the kink allowing transmembrane helix 6 (TM6) to move outward toward the cytoplasm, creating a cavity on the intracellular side, where the G protein trimer can bind.

You can read much more about this in an exquisite paper [ Cell vol. 176 pp. 448 – 458 `19 ] describing the CB1 receptor bound to a synthetic ligand 20 times more potent that delta-9 tetrahydrocannabinol (delta9 THC).  It is a cryoEM study which used 177,000 projections to come up with a 3 Angstrom resolution structure of CB1 bound to MBDB-FUBINACA in complex with its G protein trimer.  They had to use a single chain variable fragment (scFv6) along with a positive allosteric modulator (PAM) called ZCZ-011 to stabilize the complex.

MBDB-FUBINACA is a story in itself.  It is presently the fentanyl of synthetic cannabinoids, which “has been linked to thousands of hospitalizations and numerous fatalities”  [ New England Journal of Medicine vol. 376 pp. 235 – 242 ’17 ].  I’m surprised I’ve never heard of it — have you? But then I’ve been retired from clinical practice for some time. Perhaps the mainstream press, pushing marihuana legalization as it has been, kept it quiet, or more likely there have been no further episodes of mass intoxication from the AMB-FUBINACA (aka the zombie drug) since 2017.

I’ve never knowingly used marihuana.  Frankly it scares me — for why please see — https://luysii.wordpress.com/2014/05/13/why-marihuana-scares-me/.

There are 4 molecular switches buried in GPCRs [ Current Med. Chem. vol. 19 pp. 1090 – 1109 ’12 ]

1. The ionic lock switch between the D/E R Y sequence at the cytoplasmic end of TM3 and E286 at the cytoplasmic end of TM6 (single letter amino acid code used) –http://130.88.97.239/bioactivity/aacodefrm.html

2. TM3 – TM7 lock switch.  In rhodopsin it is between the protonated Schiff base of lysine and a glutamic acid and it broken on light activation,.=

3. Toggle switch linked with the n P x x Y motif in TM7 (x stands for any amino acid) — much more about this later in the post.

4. Transmission switch — produced by agonist binding, the outward movement of TM6 to to ligand binding creating a hole fo the G protein to bind to the receptor on the cytoplasmic side.

So why did I call the Cell paper exquisite?  Because of the molecular detail it provides about just how MDMB FUBINACA activates CB1.  Here’s the structure of AB-FUBINACA — https://en.wikipedia.org/wiki/AB-FUBINACA.   Both look like drugs designed by a committee.  They both have a para-iodophenyl group, an amide, and a fused indole ring with an extra nitrogen (imidazole ring — I never could keep heterocyclic nomenclature straight).    MDMB has a methyl ester (in place of the amide) and a tertiary butyl group (in place of the isoPropyl group).

I don’t have time to look up how Pfizer came up with it.  The FUBINACAs do not resemble delta9 THC at all — https://en.wikipedia.org/wiki/Tetrahydrocannabinol.

The pictures in the paper show how the hydrophobic aromatic side chains of FIVE phenylalanines and 2 tryptophans create a nice oily space for delta9 THC and MBDB-FUBINACA to bind.

F200 (phenylAlanine 200) and W356 are the toggle twin switch which stabilize the inactive conformation of CB1.  The rotation of F200 to interact with the imidazole of FUBINACA, allows W356 to rotate outward, changing the kink produced the the proline #358  in TM6 allowing the helix to straighten and rotate outward toward the cytoplasm, creating a cavity for the G protein to bind to.

Definitely a tour de force for the blind watchman.