#144

Never say never… Published this month:

Short-term Sirolimus Treatment Restores Hippocampus and Caudate Volumes and Global Cerebral Blood Flow in Asymptomatic APOE4 Carriers Compared with Non-carriers 2025

:thinking:

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#145

yabut…

  1. 1mg/day is not the usual dose for dementia or longevity…

  2. I have not seen a human study showing Evro is better at crossing the BBB than siro in humans. One would have to dose such that serum levels were similar between the two drugs and then measure CSF levels. That would tell me their relative efficiency of crossing the BBB.

  3. In my opinion neuroprotection in a seziure disorder does not = crossing the BBB or engaging with brain MTOR

  4. The FDA is using the same data we are. I think it has been biased by only studying Evro and not comparing the two head to head (explaining Evro approval for some brain cancers).

#146
  1. Yes.
  2. Yes. I hope one of the ongoing trials will look at that (I didn’t check).
  3. How could everolimus protect from seizure and reduce neuroinflammation without crossing the BBB? And why would sirolimus fail to do both?
  4. It’s not only the FDA but also the clinical practice: offlabel use for brain tumors seems to prefer everolimus. Could be herd mentality though.
#147

By improving mitochondria more generally and those mitochondria being spread around.

#148

But why sirolimus does not at the same dose?

#149

I dont have the time to read up on this at the moment so i dont have an answer, sorry.

#150

No worries. The sources are there: Everolimus instead of Sirolimus / Rapamycin? Anyone else trying? - #136 by adssx

For me, they invalidate your hypothesis.

#151

You may be right. I need to spend some time looking at this and don’t have the time at the moment.

#152

I have had a short look now.

I think you probably need to directly compare the drugs in individual tests. The difficulty with people with MSA is that it is quite possible to consider that their cells are not in a position to adequately respond to the inhibition of mTOR. Hence whether drug gets to the cells or not and what quantity gets there does not really matter.

SIrolimus could have made glucose metabolism worse in the rat brain experiment by increasing the peaks of glucose.

However, Table 3 in the paper; Sirolimus, but not the structurally related RAD (everolimus), enhances the negative effects of cyclosporine on mitochondrial metabolism in the rat brain 2001
Indicates quite a high concentration of Rapamyin in the brain. That at least should confirm that it passes the BBB. I am not sure we need Rapamycin to get into the mitochondria. AIUI mTOR is found in the nucleus, the cytosol and sometimes in the mitochondria. Whether it is the copies of the complex in the mitochondria that are essential for mitophagy or not I don’t know.

However, I think one should assume that if Rapamycin can get into brain cells through the BBB then its ability to get into the mitochondria is much the same as other cells.

In terms of comparing the drugs there is a question as to the maximum dosage that is known to be safe. I am personally concerned that there may be an edema risk from rapamycin below the normal maximum dose of 40mg per day (which equates to a one off dose of 160mg).

Having spent a little more time looking at this I am still inclined to continue with Rapamycin and not spend any material amount of time looking at other mTOR inhibitors (other than Urolithin A).

I think Rapamycin does what I want it to do which is to get cells to destroy the less efficient mitochondria.

I have now implanted my CGM to try out a reasonably high dose of UA to see if it moves the needle in an obvious way on glucose (which then gives a way of comparing it to Rapamycin),

#153

Rapamycin (RAPA) is found to have neuro-protective properties in various neuroinflammatory pathologies, including brain aging. With magnetic resonance imaging (MRI) techniques, we investigated the effect of RAPA in a lipopolysaccharide (LPS)-induced inflammaging model in rat brains. Rats were exposed to saline (control), or LPS alone or LPS combined with RAPA treatment (via food over 6 weeks). Arterial spin labeling (ASL) perfusion imaging was used to measure relative cerebral blood flow (rCBF). MR spectroscopy (MRS) was used to measure brain metabolite levels. Contrast-enhanced MRI (CE-MRI) was used to assess blood-brain barrier (BBB) permeability. Immunohistochemistry (IHC) was used to confirm neuroinflammation. RAPA restored NF-κB and HIF-1α to normal levels. RAPA was able to significantly restore rCBF in the cerebral cortex post-LPS exposure (p < 0.05), but not in the hippocampus. In the hippocampus, RAPA was able to restore total creatine (Cr) acutely, and N-acetyl aspartate (NAA) at 6 weeks, post-LPS. Myo-inositol (Myo-Ins) levels were found to decrease with RAPA treatment acutely post-LPS. RAPA was also able to significantly restore the BBB acutely post-LPS in both the cortex and hippocampus (p < 0.05 for both). RAPA was found to increase the percent change in BOLD signal in the cortex at 3 weeks, and in the hippocampus at 6 weeks post-LPS, compared to LPS alone. RAPA treatment also restored the neuronal and macro-vascular marker, EphB2, back to normal levels. These results indicate that RAPA may play an important therapeutic role in inhibiting neuroinflammation by normalizing brain vascularity, BBB, and some brain metabolites, and has a high translational capability.

Rapamycin (RAPA) is found to have neuro-protective properties in various neuroinflammatory pathologies, including brain aging. With magnetic resonance imaging (MRI) techniques, we investigated the effect of RAPA in a lipopolysaccharide (LPS)-induced inflammaging model in rat brains. Rats were exposed to saline (control), or LPS alone or LPS combined with RAPA treatment (via food over 6 weeks). Arterial spin labeling (ASL) perfusion imaging was used to measure relative cerebral blood flow (rCBF). MR spectroscopy (MRS) was used to measure brain metabolite levels. Contrast-enhanced MRI (CE-MRI) was used to assess blood-brain barrier (BBB) permeability. Immunohistochemistry (IHC) was used to confirm neuroinflammation. RAPA restored NF-κB and HIF-1α to normal levels. RAPA was able to significantly restore rCBF in the cerebral cortex post-LPS exposure (p < 0.05), but not in the hippocampus. In the hippocampus, RAPA was able to restore total creatine (Cr) acutely, and N-acetyl aspartate (NAA) at 6 weeks, post-LPS. Myo-inositol (Myo-Ins) levels were found to decrease with RAPA treatment acutely post-LPS. RAPA was also able to significantly restore the BBB acutely post-LPS in both the cortex and hippocampus (p < 0.05 for both). RAPA was found to increase the percent change in BOLD signal in the cortex at 3 weeks, and in the hippocampus at 6 weeks post-LPS, compared to LPS alone. RAPA treatment also restored the neuronal and macro-vascular marker, EphB2, back to normal levels. These results indicate that RAPA may play an important therapeutic role in inhibiting neuroinflammation by normalizing brain vascularity, BBB, and some brain metabolites, and has a high translational capability.

https://www.researchgate.net/figure/Rapamycin-Crosses-the-Blood-Brain-Barrier-and-Blocks-mTOR-in-Tumor-Tissue-A-Rapamycin_fig2_5636832

Rapamycin Crosses the Blood–Brain Barrier and Blocks mTOR in Tumor Tissue (A) Rapamycin concentrations in tumor tissue (filled squares) and peripheral blood (empty circles) grouped by rapamycin dose cohorts (2 mg, 5 mg, or 10 mg per os daily). Intratumoral rapamycin concentration for patient 11 could not be determined due to insufficient frozen tumor material. The last preoperative dose of rapamycin was given on the day of craniotomy and peripheral blood was collected within 24 h of surgery. (B) Quantification of mTOR activity in tumor tissue by immunohistochemistry. The cartoon to the left depicts the S6 kinase 1 branch of the mTOR signaling pathway resulting in phosphorylation of S6 ribosomal protein at serine 235/236 and serine 240/244. The panel to the right shows a comparison between immunoblotting (top) and IHC (bottom) for the determination of S6 phosphorylation in tumor tissue from rapamycin patients 1, 2, and 3. The fold change in serine 235/236 phosphorylation between S2 and S1 for patients 1, 2, and 3 were 0.45, 1.01, and 0.45, respectively (see Figure S2A). (C) Changes in S6 phosphorylation between S2 and S1 ( y -axis: ratio of S6 phosphorylation in S2 sample to S6 phosphorylation in S1 sample) for all patients for whom matched S1 and S2 samples were available (14/15 rapamycin patients and 9/9 patients who did not receive rapamycin). S6 phosphorylation was determined by IHC using phosphosite-specific antibodies against serine 235/236 (left) and serine 240/244 (right). Please see Figures S1 and S2 for details regarding IHC scoring method and results for individual tumors. p -values for the difference in mean S2/S1 ratios for each group were determined using the Kruskal Wallace test. doi:10.1371/journal.pmed.0050008.g002

Rapamycin (RAPA) is found to have neuro-protective properties in various neuroinflammatory pathologies, including brain aging. With magnetic resonance imaging (MRI) techniques, we investigated the effect of RAPA in a lipopolysaccharide (LPS)-induced inflammaging model in rat brains. Rats were exposed to saline (control), or LPS alone or LPS combined with RAPA treatment (via food over 6 weeks). Arterial spin labeling (ASL) perfusion imaging was used to measure relative cerebral blood flow (rCBF). MR spectroscopy (MRS) was used to measure brain metabolite levels. Contrast-enhanced MRI (CE-MRI) was used to assess blood-brain barrier (BBB) permeability. Immunohistochemistry (IHC) was used to confirm neuroinflammation. RAPA restored NF-κB and HIF-1α to normal levels. RAPA was able to significantly restore rCBF in the cerebral cortex post-LPS exposure (p < 0.05), but not in the hippocampus. In the hippocampus, RAPA was able to restore total creatine (Cr) acutely, and N-acetyl aspartate (NAA) at 6 weeks, post-LPS. Myo-inositol (Myo-Ins) levels were found to decrease with RAPA treatment acutely post-LPS. RAPA was also able to significantly restore the BBB acutely post-LPS in both the cortex and hippocampus (p < 0.05 for both). RAPA was found to increase the percent change in BOLD signal in the cortex at 3 weeks, and in the hippocampus at 6 weeks post-LPS, compared to LPS alone. RAPA treatment also restored the neuronal and macro-vascular marker, EphB2, back to normal levels. These results indicate that RAPA may play an important therapeutic role in inhibiting neuroinflammation by normalizing brain vascularity, BBB, and some brain metabolites, and has a high translational capability.

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#154

Many molecules influence brain health without crossing the BBB. Klotho, GLP-1s, to name a couple.

#155

Of course but that’s not the point: why does everolimus but not sirolimus reduce seizures in humans and neuroinflammation in animal models of seizures? That’s the question.

#156

I was simply responding to your comment here. I’m not sure what the reason is, but perhaps it’s due to the different tissue distribution or perhaps that an equivalent dose of everolimus causes a higher peak mtor inhibition due to the enhanced pharmacokinetics. This may imply that higher doses of rapamycin (eg 14d dosing schemes) would be better.

#157

Given that Everolimus is a more recent drug than Sirolimus perhaps the availability of IP protection has affected the funding available for testing.

#158

@John_Hemming No it was tested in both everolimus and sirolimus and failed in sirolimus:

#159

Reading the second paper i see in vitro tests of rapamycin and everolimus, but it appears that only everolimus was tested in vivo. (The KpK group vs KeK) I am, however, using my phone whilst taking my son to a climbing lesson. Hence i am not sure i am right.

The first paper does not appear to test rapamycin.

#160

The first paper says:

mTORC1 inhibitors are approved for adjunctive treatment of TSC-refractory seizures [Citation16,Citation17]. Everolimus, which had previously been approved for treating TSC-associated SEGA and renal angiomyolipoma, was shown to reduce seizures in phase 3 EXIST-3 study and was subsequently approved for the treatment of refractory partial seizures in patients with TSC [Citation15–Citation17]. Sirolimus is another mTORC1 inhibitor that has been evaluated to treat multiple manifestations of TSC, similarly to everolimus [Citation3]. However, in an open-label crossover study evaluating sirolimus as add-on therapy in intractable TSC seizures (patients randomly assigned to treatment with of sirolimus either during the first or second period of 6 months over a 12-month study), sirolimus did not significantly reduce seizure frequency [Citation43] (Table 2). Because of the strong phase 3 data now available for everolimus for seizure reduction in TSC, and the lack of large-scale clinical data (and regulatory approval) for sirolimus, the authors currently recommend using the mTOR inhibitor that has the approved indication, particularly if the indication has made the drug easier to obtain due to insurance issues or cost. Pharmacologically, these drugs have the same effect of inhibiting mTORC1; however, they differ in terms of lipid solubility, half-life, and metabolism [Citation3]. In clinical practice we have found that some patients can be switched from one mTOR inhibitor to the other if necessary due to adverse effects or lack of efficacy; in some cases, this may also lead to improvement.

I didn’t notice the last bit when I first read the paper. The individual variability is very interesting :thinking:

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#161

That is in another paper. When i am back home i need to revert to working on my main company’s accounts and dont have time to spend chasing down references.

I agree it is sensible over time to see what can be done to improve on rapamycin. But it is not on my priority list at the moment.

Everolimus may be better than rapamycin for some purposes. OTOH I now have my CGM running and intend first trying a chunky dose of UA. Then depending on the situation i want to take another dose of rapamycin ideally with still a relatively high level of mk7.

#162

I think you make good points but I think it is important not to overstate them.

The answer to your first point could be as simple as dose. Everolimus is apparently more bioavailable so its serum levels may be higher in studies comparing effect on seizures and neuroinflamation on a mg for mg basis. It’s also often dosed differently due to its shorter T 1/2.

The answer could also be similar to the debate on why canagliflozin might increase longevity and empagliflozin might not. We don’t really know because we don’t know the precise mechanism and we don’t know what is important for the longevity component. I was simply stating that it is not clear that everolimus’ mechanism of action in seizure treatment proceeds through MTOR inhibition. It might even be through systemic changes that do permeate the BBB.

Your final point about the FDA and clinical practice I think comes from the fact that Everolimus has been pushed in studies because of a profit motive. Papers are published and data spun to suggest that it is a vast improvement over Rapa but as I said they usually don’t include Rapa as a control but rather site historical data about Rapa’s side effects and claim that the same effects were not seen in their study. Nobody is doing this for Rapa because the patent has long run out and it is cheap and easy to produce. I appreciate the studies you sited that actually do make direct rapa comparisons.

Everolimus also has an IV protocol so it is easy to dose for these studies without worrying about bio-availability from the gut.

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#163

The other point that doesn’t make sense to me is that the molecular modifications to rapa to produce everolimus make it more water soluble and more polar… This would seem to reduce it’s ability to cross the BBB and engage brain MTOR.

To produce everolimus, a modification is made to the C40 position of the rapamycin molecule by adding a hydroxyethyl group, essentially creating a hydroxyethyl ether derivative of rapamycin, which significantly improves its pharmacokinetic properties compared to the original rapamycin molecule; this change allows for better oral bioavailability and absorption in the body

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