Harshi Peiris, Ph.D. Profile picture
Jun 23 8 tweets 4 min read Read on X
Yesterday: Faecalibacterium prausnitzii depleted in Parkinson's disease.

Today: the same bacterium, a different brain disease ... Alzheimer's.

In Alzheimer's, its depletion triggers a completely different chain — one that targets the blood-brain barrier and drives neuroinflammation from the inside.

Here's the science 👇

#Alzheimers #GutBrainAxis
F. prausnitzii has been identified as depleted in Alzheimer's patients across multiple human cohort studies.

Ueda et al. 2021 (Cell Reports Medicine) identified specific F. prausnitzii strains as candidate targets for gut microbiome-based intervention in Alzheimer's-type dementia.

Depletion correlates with worse MMSE cognitive scores — the standard clinical test for dementia severity.
The AD mechanism is different from Parkinson's.

↓ F. prausnitzii
→ ↓ butyrate
→ HDAC inhibition lost
→ NF-kB pathway hyperactivated in microglia
→ TNF-alpha, IL-1beta, IL-6 elevation
→ accelerated amyloid-beta deposition
→ tau hyperphosphorylation

Butyrate also maintains claudin-5, the blood-brain barrier tight junction protein. When F. prausnitzii falls, the BBB becomes permeable to peripheral inflammation.Image
A 2025 study (Molecular Brain) examined butyrate's role in the BBB transport of Alzheimer's amyloid-beta peptides directly.

In germ-free mice colonized with butyrate-deficient microbiomes, key BBB proteins were altered — consistent with increased amyloid accumulation.

Butyrate production is significantly reduced in AD patients and correlates with cognitive decline.Image
Worth noting for your own research lens.

Emerging evidence suggests gut microbiome differences — including F. prausnitzii abundance — may partly explain sex differences in Alzheimer's risk.

Women carry approximately two-thirds of the global Alzheimer's burden. The gut-brain axis is increasingly implicated as one contributing pathway.

This is early-stage but scientifically credible. [EMERGING]Image
Image
Same dietary levers as in PD — because the same bacterium responds to the same inputs:

✓ High dietary fiber (inulin, FOS, resistant starch)
✓ Jerusalem artichoke, chicory root, leeks, asparagus
✓ Mediterranean diet pattern
✓ Polyphenol-rich foods

No approved F. prausnitzii supplement exists. Clinical trials in development.

NOTE: Probiotics carry real risks for immunocompromised individuals, the elderly, and children. Always consult your doctorImage
Tomorrow: this same bacterium in a completely different context.

Not a brain disease. Aging itself.

Centenarian studies are revealing that people who live past 100 have something in common — and F. prausnitzii is part of the story.

Follow @Neuroscope_mp for Part 3.

#Alzheimers #Dementia #GutBrainAxis #Neuroscience #MicrobiomeImage
If you missed yesterday’s thread on Parkinson’s, here it is 👇
Today, we’re covering how the exact same bacteria affect Alzheimer’s through a totally different pathway.

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More from @Neuroscope_mp

Jun 23
🚨 BREAKING
A new drug just hit Phase 3 trials with weight loss numbers that rival bariatric SURGERY.

28.7% of body weight gone.
~71 lbs average.
In 68 weeks.

No scalpel. Once-a-week injection.
It's called Retatrutide — the triple agonist changing obesity treatment.

Let’s explore the good and the bad about it.
Thread 🧵👇
What makes Retatrutide different from Ozempic or Mounjaro?

It hits THREE hormone receptors at once:
→ GLP-1: Kills appetite, slows digestion
→ GIP: Boosts insulin, improves fat metabolism
→ Glucagon: Burns MORE energy, melts liver fat

Ozempic hits 1.
Mounjaro hits 2.
This hits all 3.

That 3rd pathway is the game changer. 👇Image
Before Phase 3, Phase 2 was already jaw-dropping.
Published in the New England Journal of Medicine (2023):
338 adults. 48 weeks.

→ 12mg dose: 24.2% average weight loss
→ 100% of patients lost at least 5%
→ 83% lost at least 15%

And the weight was STILL dropping at week 48.
No plateau. (This matters enormously.) 👇Image
Image
Read 12 tweets
Jun 22
BREAKING 🧵
A major network meta-analysis (550 Parkinson’s patients + 456 controls) ...
Found that one gut bacterium is consistently missing in PD.
And lower levels correlate with worse balance and walking problems.

That bacterium is Faecalibacterium prausnitzii.

Here's what the science says 👇

#Parkinsons #GutBrainAxis
F. prausnitzii is one of the most abundant bacteria in a healthy gut, making up to 5% of your total microbiome.

It’s a butyrate producer (a key short-chain fatty acid).

Think of it as your gut’s natural anti-inflammatory firefighter.

It feeds colon cells, reduces inflammation, and sends signals to the brain.
In Parkinson’s, F. prausnitzii is consistently depleted.

Li et al. (2023) reviewed 26 human studies.

It was one of only 5 genera with repeated depletion across studies. A

A separate network meta-analysis (550 PD vs 456 controls) confirmed the same pattern across continents. Image
Read 7 tweets
Jun 18
Parkinson’s isn’t one disease anymore.

Meet Henry, 64 — newly diagnosed.

His neurologist used skin biopsy, gut markers, and inflammation testing to map his specific drivers.

Now they’re building a precision plan using today’s tools + tomorrow’s clinical trials: replace lost neurons, repair the gut, calm inflammation, and monitor closely.

This is what the future of Parkinson’s care is starting to look like.

Thread 🧠👇
Meet Henry, 64 — just diagnosed after months of a tremor in his right hand.

His neurologist didn’t stop at the clinical exam.

She ordered a skin biopsy for misfolded alpha-synuclein (positive) + a DaTscan.
It came back positive. Diagnosis confirmed.

This matters: up to 25% of Parkinson’s diagnoses based on symptoms alone are wrong.

Confirm the pathology first. These tests are available now.

Don’t skip this step.
Henry’s neurologist went deeper.

She had him track symptoms in detail and ran bloodwork + gut markers.

Two major clues emerged:
• Constipation and GI issues for nearly 10 years
• Elevated chronic low-grade inflammation markers

This pattern suggests “gut-first” Parkinson’s — a distinct Parkinson’s subtype.

Researchers are now using biomarkers like fecal calprotectin, short-chain fatty acids, and inflammatory panels to separate gut-driven PD from brain-first PD for better-targeted trials.
More biomarkers to define these two underlying root causes are In clinical research right now.
Read 19 tweets
Jun 16
BREAKING: A blood-based protein test can reveal how fast your brain's support cells are aging.

If they’re aging too fast, your Alzheimer’s risk jumps 12.59x.
60,542 people.
7,000+ proteins.
40+ cell types.

This is one of the biggest aging papers of 2026.
Here's what it means for your brain. 🧠👇
Your body doesn't age as one unit.

Your liver cells, immune cells, neurons, gut cells — they all have their own biological clocks.

And they don't tick at the same speed.

This study used 7,000 proteins in blood to build aging clocks for 40+ different cell types.

20–25% of people showed accelerated aging in at least one cell type.
1–3% were aging fast in 10 or more cell types simultaneously.

Your chronological age? It barely predicts disease.
Your cellular age? That's a different story.Image
Image
Image
Image
So what are astrocytes, and why do they keep showing up in Alzheimer's research?

Think of astrocytes as the brain's maintenance crew.

They:
→ Feed neurons
→ Clear metabolic waste
→ Maintain the blood-brain barrier
→ Regulate synapses
→ Control brain inflammation

When astrocytes age and malfunction, everything downstream starts to fail.

A 2025 NYU review (Gildea & Liddelow, Mol Neurodegeneration) confirmed:
Glial cells are the most transcriptionally altered cells in the aging brain.
Astrocyte aging is now a primary target for neurodegeneration prevention.

The neurons weren't first to fail. The support crew was.Image
Read 10 tweets
Jun 12
BREAKING:
Researchers are shining near-infrared light through people's skulls — and it's showing real signals in Alzheimer's brain scans.
Not a gadget.
Not wellness.

Peer-reviewed trials at NYU, Harvard, and a major French multicenter study are now enrolling.

Here's what science actually says — and what it doesn't. 🧵
Photobiomodulation (PBM) = non-thermal red to near-infrared light (typically 600–1100 nm) delivered via LED or laser devices.
It's not heat.
It's not UV.
It's invisible light at specific wavelengths that penetrates tissue.

The key finding: near-infrared light is absorbed by a mitochondrial enzyme called cytochrome c oxidase — the same enzyme that is measurably reduced in Alzheimer's brain tissue.
That overlap is why neuroscientists are paying attention.
#Mitochondria #RedLightTherapy #PBMImage
I'm a neuroscientist. I study neurodegeneration.
Most PBM content online is device company marketing or fringe wellness claims.
So let me give you the actual evidence pyramid:
✅ Animal models: strong, consistent signals
✅ Small human RCTs: promising but limited by sample size
✅ Mechanism: biologically coherent and measurable

⏳ Large definitive trial: still running
This is not a cure.
But it is a legitimate research direction — and the trials are serious.Image
Read 11 tweets
Jun 11
BREAKING: 19 hours after a single high-dose psilocybin session, an 80-year-old woman with advanced Alzheimer’s who hadn’t spoken fluidly in 5 years started talking about her life for 4 straight hours.

She hadn't spoken a fluid sentence in 5 years.
This just-published case report is extraordinary — and heavily caveated.

Here's what actually happened. Hype vs the real science.🧵
#Alzheimers #Neuroscience #Psilocybin #Neuroplasticity
Here's the full picture:
• 10-year Alzheimer's history. 5 years of near-silence.
• Given 5g of high-potency "Enigma" strain psilocybin mushrooms under supervision in Brazil.
• Acute phase: suspected hyperthermia, profuse sweating, 19-hour sleep-like state.
• Then: spontaneous speech. Autobiographical memories. Four hours of conversation.
• Over the following weeks, bladder continence returned (lost for 5 years), she dressed herself, smiled, and made jokes.
• Second session one month later: recalled family by name, described surfing with her son.Image
🔬 MY TAKE

I'm a Scientist.
I've spent 20+ years researching neurodegeneration, aging and cancer.
This is one case report — N=1, no imaging, no biomarkers, no control group.
The authors themselves say causality cannot be established.
And yet I couldn't stop reading it.

Here's why it's scientifically plausible — and why it's not a cure. 👇Image
Read 10 tweets

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