Leaky ATP from either Mitochondria or Neurons in Fragile X and Autism

 

 

For leaky ATP, Popeye might want to try Dexpramipexole and

Suramin, or even the already approved Mirapex

If you are old enough to be a parent, you will have encountered problems with some kind of leak.  A leaky roof, a leaky pipe, a leaky washing machine, an air-conditioning unit... The list goes on, the older you get.

I have been preoccupied by fixing a leak recently.  We have a large roof terrace and, in the winter, water started leaking from the ceiling in the floor below.  I improvised a system to catch all the water, but still I had to find the source of the leak.

I did finally find the source of the problem and most importantly without digging up 95% of the terrace.  Now I have to put the 5% back together again.

Leaks are often extremely difficult to locate, because water always finds the easiest path and the dripping you see might have originated from a leak far away.  Nobody wants to fix leaks, because it can be a pretty thankless task and you can cause plenty of damage in the process, without solving the problem.  So, as with fixing autism, I ended up doing much of the fixing myself.  The damage had actually been there since the house was built, hidden under ceramic tiles.

I recently read about leaky ATP in Fragile-X, where ATP leaks from the mitochondria into the cell.

This fits neatly into Professor Naviaux’s belief that ATP is leaking from the cell into the extracellular space, as the basis for his concept of the cell danger response, as a unifying and treatable feature of most autism.

Sounds complicated?

Just think of it as bunch of leaks you need to fix.

 

 What is ATP? 

ATP has many functions:- 

·        It is the fuel your cells need to function.

·        It is a signalling molecule within a cell and importantly between different cells.

·        It is used to make your DNA

  

Mitochondria

Each cell in your brain contains many mitochondria and these are where ATP is produced. Mitochondria die and are replaced, whereas if the host brain cell dies, it is lost forever. Cell death in the brain is bad news.

The ATP – ADP Cycle 

You can think of ATP as a fully charged battery.  Once the energy has been used up the flat battery is called ADP and it goes back for recharging in the mitochondria.  It is a continuous cycle.

ADP is powered back to ATP through the process of releasing the chemical energy available in food; this is constantly performed via aerobic respiration in the mitochondria. This process is also called OXPHOS and has been covered in previous posts.  In most mitochondrial disease the problem is that one of the four mitochondrial enzyme complexes is insufficient; this means that the ATP-ADP cycle is restricted.  There is then insufficient energy to power the brain in times of peak energy requirement.  This can cause loss of myelination and ultimately cell death.

 

  

ATP in Fragile X

It looks like in Fragile X the mitochondria in the brain do not work properly. ATP is leaking from the mitochondria and this stops synapses from maturing. 

A synapse is just the junction between one neuron and its neighbour.

The immature synapse manifests as autistic behavior.  When you plug the leak with Dexpramipexole, a drug trialed for ALS and now asthma, dendritic spines mature and autistic behavior is reduced.

To what extent this leakage occurs in idiopathic autism is unknown, but we know that impaired dendritic spine formation/morphology is a key feature of most autism and that it can be modified, although the sooner you start the better the result will be.

It looks to me that some people diagnosed with mitochondrial disease based on blood tests may actually have leaking ATP which then affects metabolic pathways and shows up with odd blood test results, that is then misdiagnosed as mitochondrial disease.  Note that many people diagnosed with mitochondrial disease show no response to therapy.

In Professor Naviaux’s theory, the ATP leak is from the cell membrane, like the outer wall of the cell.  He thinks that ATP is leaking and this then sends a false danger signal to the rest of your brain.  This is his Cell Danger Response (CDR).  Because the brain thinks it is under attack it is set in a permanent pro-inflammatory state, this gets in the way of basic functions the developing brain needs to complete.  This might explain why the microglia (the brain’s immune cells) are found to be permanently activated in autism; this then means that they do not carry out their regular brain housekeeping activities very well, like pruning synapses.

Naviaux wants to plug the leaks in the cell wall using Suramin, which is an old anti-parasite drug made by Bayer, the giant German company.

The link between the Fragile X research from Yale and Naviaux’s work at UCSD is that ATP needs to be kept in the right place for the brain to function correctly.

Leaky ATP will cause you big problems.

 

 

Now for the supporting research

 

Leaky ATP in Fragile X

 

Fragile X syndrome traits may stem from leaky mitochondria

The persistent leak influences which metabolic pathway the cell uses to generate energy, the team discovered by using a technique called mass spectrometry. For example, fragile X neurons produce more enzymes associated with glycolysis — a pathway commonly used by immature cells — than do typical neurons. Previous studies have shown altered mitochondrial metabolism in people with other forms of autism2.

Adding dexpramipexole to the cells of fragile X mice decreased production of lactate dehydrogenase and other enzymes linked to glycolysis, suggesting that closing the leak causes the neurons to start to use different, more mature metabolic pathways.

Giving injections of dexpramipexole to fragile X model mice lessened their hyperactivity, repetitive behaviors and excessive grooming — traits that are reminiscent of those seen in people with autism and in those with fragile X syndrome. Mice that received the dexpramipexole injections also had neurons with more mature dendritic spines and decreased levels of protein synthesis.

Dexpramipexole has been tested in people with the neurological disease amyotrophic lateral sclerosis and found safe, but it is unclear how it would affect young people if taken over sustained periods of time.

 

ATP Synthase c-Subunit Leak Causes Aberrant Cellular Metabolism in Fragile X Syndrome

Loss of the gene (Fmr1) encoding Fragile X mental retardation protein (FMRP) causes increased mRNA translation and aberrant synaptic development. We find neurons of the Fmr1^-/y mouse have a mitochondrial inner membrane leak contributing to a "leak metabolism." In human Fragile X syndrome (FXS) fibroblasts and in Fmr1^-/y mouse neurons, closure of the ATP synthase leak channel by mild depletion of its c-subunit or pharmacological inhibition normalizes stimulus-induced and constitutive mRNA translation rate, decreases lactate and key glycolytic and tricarboxylic acid (TCA) cycle enzyme levels, and triggers synapse maturation. FMRP regulates leak closure in wild-type (WT), but not FX synapses, by stimulus-dependent ATP synthase β subunit translation; this increases the ratio of ATP synthase enzyme to its c-subunit, enhancing ATP production efficiency and synaptic growth. In contrast, in FXS, inability to close developmental c-subunit leak prevents stimulus-dependent synaptic maturation. Therefore, ATP synthase c-subunit leak closure encourages development and attenuates autistic behaviors.

 

Highlights 

·        ATP synthase c-subunit leak in Fragile X causes aberrant metabolism

·        Changes in ATP synthase component stoichiometry regulate protein synthesis rate

·        Inhibition of the leak normalizes synaptic spine morphology and Fragile X behavior

 

In Brief

Lack of FMRP in Fragile X neurons is associated with a leak in the ATP synthase, the blockade of which normalizes cellular and behavioral disease phenotypes.

 

Now they fix the leak using Dexpramipexole (Dex) and cyclosporine A (CsA)

 

 

We have found that the mitochondrial inner membrane leak of FX neurons and cells is caused by abnormal levels of ATP synthase c-subunit. The c-subunit leak causes persistence of a mitochondrial leak metabolic phenotype characterized by high glycolytic flux, high lactate levels, and increased levels of glycolytic and TCA enzymes. The leak also aberrantly elevates overall and specific protein synthesis; a decrease in c-subunit level or pharmacological inhibition of the ATP synthase leak reduces protein synthesis rates and decreases the levels of leak metabolism enzymes. In Fmr1/y synapses, stimulation-dependent protein synthesis is absent. This is correlated with a lack of stimulus induced EF2 phosphorylation and a lack of synthesis of the ATP synthase b-subunit. These abnormalities are readily reversed by ATP synthase leak inhibitors, suggesting that leak closure is required for the ATP-dependent phosphorylation of EF2 adjacent to mitochondria. EF2 phosphorylation may regulate the change in subsets of proteins synthesized and may be correlated with- the overabundant synthesis of enzymes supporting a high flux glycolytic/TCA cycle ‘‘leak’’ metabolism indicative of metabolic immaturity. Consistent with the hypothesis that the c-subunit leak is also a major cause of synapse immaturity, we find that inhibition of the ATP synthase leak allows the maturation of synapses and normalizes autistic behaviors.

 

 

 

Closing Leaky Mitochondria Halts Behavioral Problems in Fragile X, Study Suggests

“In Fragile X neurons, the synapses fail to mature during development. The synapses remain in an immature state and this seems to be related to their immature metabolism,” she said.

The investigators tested whether closing the leak to boost the efficiency of ATP production would lessen behavioral abnormalities.

They first saw that nerve cells treated with an ATP synthase inhibitor named dexpramipexole (Dex) — a form of the common Parkinson’s therapy Mirapex ER (pramipexole) and previously tested as a treatment for amyotrophic lateral sclerosis — increased the levels of ATP.

Two-day treatment with Dex also reversed autistic-like behaviors, namely excessive time spent grooming and compulsive shredding of the animals’ nests. The treatment also reduced hyperactivate behaviors.

“We find that inhibition of the ATP synthase leak allows for the maturation of synapses and normalizes autistic behaviors in a mouse model of [fragile X],” the team wrote.

Jonas and her team now intend to further test the effectiveness of this and other leak-closing therapies for improving learning.

The lab is conducting a study assessing the role of leaky membranes in memory formation. Findings could pave the way for novel therapeutics for fragile X and autism, as well as for Alzheimer’s disease.

 

 

 

Dr Naviaux and Suramin for Autism

 

I have covered Suramin in previous posts.  There is a presentation below by Prof Naviaux that is for lay people, it is good to hear directly from the man himself.

 

Autism Treatment, the cell danger response and the SAT1 trial

https://youtu.be/pqd_BoCeRUw

In essence he says that when cells are stressed, they leak ATP and this creates the cell danger response.  If you have suramin in your bloodstream, it plugs the ATP channels and stops it leaking out of the cell and so blocks the cell danger response.

It is the cell danger response that is causing the symptoms we see as autism.

  

Conclusion

Who to call to fix an ATP leak?

If it is a case of Fragile X, there looks to be potential solution, but you will definitely not find it at your local doctor’s office.

For a mouse with Fragile X, you might choose Dexpramipexole.  Dexpramipexole was developed as a therapy for ALS (motor neuron disease), but failed in phase 3 trials and is now being developed for asthma.

For a human, the logical place to start would be the already approved Mirapex, which is currently used to treat Parkinson's disease and restless legs syndrome.

Mirapex - a miracle for Fragile X?

Clearly somebody should make a clinical trial of the existing drug.

I expect what will happen is that the Yale researchers will come up will a new drug that can be patented as a novel therapy for Fragile X.  This way they get to make some money, but a decade is wasted.

Is leaky ATP from mitochondria an issue in broader autism, beyond Fragile X? That is still unknown, but the Yale researchers seem to think their work has potential application in both autism and Alzheimer’s.

In the case of broader autism, Dr Naviaux and his partner Kuzani have some competition from Paxmedica.  Both groups seek to monetize Dr Naviaux’s published research.

It looks like the German giant Bayer does not want to help either group.  Instead of just tapping into Bayer’s existing production of Suramin, Kuzani and Paxmedica will have to figure out how to produce Suramin.

This all helps us to understand why there still are no approved therapies for core Autism or indeed Fragile X and yet there is a mountain of research.  Too many barriers and interests to overcome.

If you want to fix leaky ATP any time soon, you will be doing it mainly by yourself.  This has been my experience with most other kinds of leak!