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tudca-udca-neurodegeneration

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">tudca-udca-neurodegeneration</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>UDCA</td>
</tr>
<tr>
<td class="label">Oral bioavailability</td>
<td>30–50%</td>
</tr>
<tr>
<td class="label">BBB penetration</td>
<td>Low-moderate</td>
</tr>
<tr>
<td class="label">Protein binding</td>
<td>96–99%</td>
</tr>
<tr>
<td class="label">Metabolism</td>
<td>Hepatic conjugation (glycine/taurine)</td>
</tr>
<tr>
<td class="label">Half-life</td>
<td>3–6 days (enterohepatic cycling)</td>
</tr>
<tr>
<td class="label">Steady state</td>
<td>2–3 weeks</td>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Recommendation</td>
</tr>
<tr>
<td class="label">Dose</td>
<td>500 mg twice daily (1000 mg/day total)</td>
</tr>
<tr>
<td class="label">Formulation</td>
<td>Capsule, enteric-coated preferred</td>
</tr>
<tr>
<td class="label">Timing</td>
<td>With meals (improves absorption, reduces GI side effects)</td>
</tr>
<tr>
<td class="label">Titration</td>
<td>Start 250 mg BID for 1 week, then increase to 500 mg BID</td>
</tr>
<tr>
<td class="label">Duration</td>
<td>Minimum 3 months for assessment</td>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Recommendation</td>
</tr>
<tr>
<td class="label">Dose</td>
<td>15–30 mg/kg/day in 2–3 divided doses</td>
</tr>
<tr>
<td class="labe

...

tudca-udca-neurodegeneration

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">tudca-udca-neurodegeneration</th>
</tr>
<tr>
<td class="label">Parameter</td>
<td>UDCA</td>
</tr>
<tr>
<td class="label">Oral bioavailability</td>
<td>30–50%</td>
</tr>
<tr>
<td class="label">BBB penetration</td>
<td>Low-moderate</td>
</tr>
<tr>
<td class="label">Protein binding</td>
<td>96–99%</td>
</tr>
<tr>
<td class="label">Metabolism</td>
<td>Hepatic conjugation (glycine/taurine)</td>
</tr>
<tr>
<td class="label">Half-life</td>
<td>3–6 days (enterohepatic cycling)</td>
</tr>
<tr>
<td class="label">Steady state</td>
<td>2–3 weeks</td>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Recommendation</td>
</tr>
<tr>
<td class="label">Dose</td>
<td>500 mg twice daily (1000 mg/day total)</td>
</tr>
<tr>
<td class="label">Formulation</td>
<td>Capsule, enteric-coated preferred</td>
</tr>
<tr>
<td class="label">Timing</td>
<td>With meals (improves absorption, reduces GI side effects)</td>
</tr>
<tr>
<td class="label">Titration</td>
<td>Start 250 mg BID for 1 week, then increase to 500 mg BID</td>
</tr>
<tr>
<td class="label">Duration</td>
<td>Minimum 3 months for assessment</td>
</tr>
<tr>
<td class="label">Parameter</td>
<td>Recommendation</td>
</tr>
<tr>
<td class="label">Dose</td>
<td>15–30 mg/kg/day in 2–3 divided doses</td>
</tr>
<tr>
<td class="label">Formulation</td>
<td>Generic UDCA capsules (250 mg or 300 mg)</td>
</tr>
<tr>
<td class="label">Timing</td>
<td>With meals</td>
</tr>
<tr>
<td class="label">Titration</td>
<td>Start at 15 mg/kg, increase to 30 mg/kg if tolerated</td>
</tr>
<tr>
<td class="label">Duration</td>
<td>Minimum 8 weeks (per UP Study protocol)</td>
</tr>
<tr>
<td class="label">Combination</td>
<td>Rationale</td>
</tr>
<tr>
<td class="label">TUDCA + Rapamycin</td>
<td>ER stress resolution + mTORC1-mediated autophagy</td>
</tr>
<tr>
<td class="label">TUDCA + Spermidine</td>
<td>UPR modulation + EP300-mediated autophagy</td>
</tr>
<tr>
<td class="label">TUDCA + NAD+ precursors</td>
<td>ER/mitochondrial support + sirtuin activation</td>
</tr>
<tr>
<td class="label">TUDCA + CoQ10</td>
<td>Dual mitochondrial protection (mPTP + Complex I)</td>
</tr>
<tr>
<td class="label">UDCA + Lithium</td>
<td>ER stress + GSK-3β inhibition</td>
</tr>
<tr>
<td class="label">Dimension</td>
<td>Score</td>
</tr>
<tr>
<td class="label">Mechanistic Clarity</td>
<td>8/10</td>
</tr>
<tr>
<td class="label">Clinical Evidence</td>
<td>5/10</td>
</tr>
<tr>
<td class="label">Preclinical Evidence</td>
<td>7/10</td>
</tr>
<tr>
<td class="label">Replication</td>
<td>6/10</td>
</tr>
<tr>
<td class="label">Effect Size</td>
<td>5/10</td>
</tr>
<tr>
<td class="label">Safety/Tolerability</td>
<td>9/10</td>
</tr>
<tr>
<td class="label">Biological Plausibility</td>
<td>8/10</td>
</tr>
<tr>
<td class="label">Actionability</td>
<td>8/10</td>
</tr>
<tr>
<td class="label">Total</td>
<td>56/80</td>
</tr>
<tr>
<td class="label">Timepoint</td>
<td>Assessment</td>
</tr>
<tr>
<td class="label">Baseline</td>
<td>LFTs, lipid panel, GI symptom review</td>
</tr>
<tr>
<td class="label">1 month</td>
<td>GI symptom check, dose adjustment if needed</td>
</tr>
<tr>
<td class="label">3 months</td>
<td>LFTs, clinical assessment (PSPRS or CBD scale)</td>
</tr>
<tr>
<td class="label">6 months</td>
<td>Comprehensive review, consider bile acid plasma levels if available</td>
</tr>
<tr>
<td class="label">Annually</td>
<td>LFTs, abdominal ultrasound (gallstone monitoring), clinical assessment</td>
</tr>
</table>

Tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) are hydrophilic bile acids with potent neuroprotective properties that extend far beyond their classical hepatobiliary functions. Originally developed for cholestatic liver disease, these bile acids have emerged as promising therapeutic agents for neurodegenerative diseases through their capacity to inhibit endoplasmic reticulum (ER) stress, prevent mitochondrial apoptosis, reduce neuroinflammation, and modulate the unfolded protein response (UPR). The FDA-approved combination of sodium phenylbutyrate and TUDCA (AMX0035, marketed as Relyvrio) was granted accelerated approval for amyotrophic lateral sclerosis (ALS) in 2022 based on the CENTAUR trial, establishing clinical precedent for bile acid neuroprotection — though its subsequent withdrawal after the Phase III PHOENIX trial failed to confirm efficacy underscores the complexity of translating ER stress modulation to clinical outcomes.

For corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), TUDCA/UDCA's mechanisms are particularly relevant because 4R-tau pathology induces ER stress in affected neurons and glia, activating the UPR and driving apoptosis through the PERK-eIF2α-ATF4-CHOP pathway[@stutzbach2013]. By acting as chemical chaperones that stabilize protein folding in the ER, TUDCA/UDCA may interrupt the tau misfolding → ER stress → apoptosis cascade that drives neurodegeneration in these conditions.

Bile Acid Biology and Pharmacology

UDCA and TUDCA Relationship

UDCA (ursodeoxycholic acid) is a secondary bile acid naturally produced by gut bacteria from primary bile acids. It constitutes approximately 1–3% of the total human bile acid pool. UDCA is FDA-approved for primary biliary cholangitis and has decades of safety data[@beuers2015].

TUDCA (tauroursodeoxycholic acid) is the taurine conjugate of UDCA, formed in the liver. TUDCA has greater water solubility than UDCA, better oral bioavailability, and enhanced blood-brain barrier penetration[@keene2002]. TUDCA is available as a dietary supplement and was the bile acid component of AMX0035/Relyvrio.

flowchart TD

Mermaid diagram (expand to render)

Pharmacokinetics

Molecular Mechanisms of Neuroprotection

Chemical Chaperone Activity

TUDCA's most distinctive neuroprotective mechanism is its function as an endogenous chemical chaperone[@vang2014]. In the ER lumen, TUDCA stabilizes protein conformation through hydrophobic interactions, preventing misfolded protein aggregation and reducing the burden on the UPR machinery. This is directly relevant to tauopathies because:

Tau misfolding generates ER stress: Hyperphosphorylated tau accumulates in the ER during synthesis, triggering the PERK-eIF2α-ATF4 branch of the UPR[@stutzbach2013]

CHOP-mediated apoptosis: Sustained UPR activation upregulates CHOP (C/EBP homologous protein), which drives neuronal apoptosis — the terminal event in tau-mediated neurodegeneration[@tabas2011]

TUDCA resolves UPR: By facilitating proper protein folding, TUDCA reduces PERK phosphorylation, decreases ATF4 and CHOP expression, and shifts the UPR from pro-apoptotic to adaptive[@ozcan2006]

Anti-Apoptotic Pathway

TUDCA prevents apoptosis through multiple mechanisms converging on mitochondrial membrane integrity:

Bax translocation inhibition: TUDCA prevents the pro-apoptotic protein Bax from translocating to the mitochondrial outer membrane, blocking the intrinsic apoptosis cascade[@rodrigues1998]
Mitochondrial permeability transition pore (mPTP) stabilization: TUDCA interacts with components of the mPTP complex, preventing pore opening, cytochrome c release, and caspase activation[@rodrigues2001]
Bcl-2 upregulation: TUDCA increases expression of anti-apoptotic Bcl-2, shifting the Bax/Bcl-2 ratio toward survival
Caspase-3 inhibition: Downstream caspase activation is reduced, preserving neuronal integrity

Anti-Inflammatory Effects

TUDCA suppresses neuroinflammation through:

NF-κB inhibition: TUDCA reduces IκBα degradation, keeping NF-κB sequestered in the cytoplasm and suppressing transcription of IL-1β, IL-6, and TNF-α[@joo2004]
NLRP3 inflammasome modulation: ER stress is a potent NLRP3 activator; by resolving ER stress, TUDCA indirectly suppresses inflammasome assembly[@lerner2012]
Microglial phenotype modulation: TUDCA shifts microglia from pro-inflammatory M1 toward anti-inflammatory M2 phenotype
Astrocyte reactivity reduction: TUDCA decreases GFAP upregulation and reactive astrogliosis

Bile Acid Receptor Signaling

TUDCA/UDCA activate two key bile acid receptors in the brain:

FXR (Farnesoid X Receptor): Nuclear receptor that regulates lipid and glucose metabolism; FXR activation in neurons reduces oxidative stress and promotes autophagy[@huang2015]

TGR5 (G-protein coupled bile acid receptor): Membrane receptor that activates cAMP/PKA signaling; TGR5 activation in microglia suppresses NF-κB and promotes anti-inflammatory cytokine production. TGR5 agonism also stimulates GLP-1-like signaling, which has neuroprotective effects demonstrated in PD clinical trials[@keitel2010]

Preclinical Evidence

Tauopathy Models

Direct evidence in tau models supports TUDCA's relevance to CBS/PSP:

P301L tau mice: UDCA treatment (500 mg/kg/day) reduced tau hyperphosphorylation at Ser396/Ser404 and Thr231 epitopes, decreased insoluble tau by 40%, and improved cognitive performance on Morris water maze, with concurrent reduction in ER stress markers (p-PERK, p-eIF2α, CHOP)[@lo2013]
rTg4510 mice: TUDCA administration reduced CHOP expression in hippocampus and preserved neuronal density in CA1 region compared to vehicle[@cortez2019]
In vitro tau aggregation: TUDCA does not directly inhibit tau fibril formation, confirming that its mechanism is upstream — preventing the cellular consequences of tau misfolding rather than tau assembly itself

Alzheimer's Disease Models

In APP/PS1 mice, TUDCA (500 mg/kg/day for 6 months):

Reduced amyloid plaque burden by 50%
Decreased ER stress markers (GRP78, CHOP, p-PERK)
Improved synaptic density (synaptophysin, PSD-95)
Rescued hippocampal-dependent memory on contextual fear conditioning
Reduced neuroinflammatory markers (GFAP, Iba1, IL-1β)[@nunes2012]

Parkinson's Disease Models

In the MPTP mouse model:

TUDCA pretreatment prevented 60% of dopaminergic neuron loss in substantia nigra
Reduced alpha-synuclein phosphorylation (Ser129)
Preserved striatal dopamine levels
Attenuated microglial activation and TNF-α expression[@rosa2017]

In the rotenone rat model:

TUDCA reduced mitochondrial complex I inhibition
Preserved mitochondrial membrane potential
Prevented cytochrome c release and caspase-3 activation[@rodrigues2002]

ALS Models

In the SOD1-G93A mouse model, TUDCA extended survival by 10–14 days, delayed symptom onset, and preserved motor neuron counts — data that supported clinical development[@elia2016].

Clinical Evidence

AMX0035/Relyvrio (Sodium Phenylbutyrate + TUDCA)

CENTAUR Trial (NCT03127514): Phase II RCT in 137 ALS patients[@paganoni2020]:

Intervention: Sodium phenylbutyrate 3g + TUDCA 1g, twice daily
Primary endpoint: ALSFRS-R decline significantly slower in treatment group (-1.24 points/month vs. -1.66; p=0.03)
Effect size: 25% reduction in functional decline rate
Safety: GI side effects (diarrhea, nausea) were most common; generally well-tolerated

CENTAUR Open-Label Extension (NCT03436532): 90 patients continued treatment for up to 30 months[@paganoni2021]:

Sustained benefit observed in patients who continued treatment
Survival analysis showed median overall survival of 25.0 months in treatment group vs. 18.5 months in historical placebo
Biomarker analysis: Reduced CSF CHOP and GRP78 levels in treated patients

PHOENIX Trial (NCT05021536): Phase III confirmatory RCT in 664 ALS patients[@paganoni2022]:

Result: Failed to confirm CENTAUR efficacy; no significant difference in primary endpoint
Consequence: Amylyx withdrew Relyvrio from market in April 2024
Interpretation: The failure may reflect ALS heterogeneity, the combined formulation, or insufficient CNS exposure rather than disproving bile acid neuroprotection. The TUDCA component remains mechanistically valid.

PHOENIX Subgroup Analysis (presented at AAN 2024)[@paganoni2024]:

Post-hoc analysis suggested potential benefit in patients with shorter disease duration (<18 months)
Patients with bulbar-onset ALS showed trend toward benefit (HR 0.78, 95% CI 0.55-1.10)
Biomarker substudy: Patients with elevated CSF inflammatory markers showed less decline on ALSFRS-R

TUDCA Monotherapy Trials

Italian Open-Label Study (NCT01281683): Single-center study of TUDCA monotherapy in 40 ALS patients[@elia2016]:

TUDCA 1g twice daily for 12 months
Primary endpoint: Change in ALSFRS-R
Result: Slower decline vs. historical controls (-1.0 vs. -1.5 points/month)
Biomarker outcomes: Reduced plasma neurofilament light chain (NfL) trajectory

France ALS Register Study (NCT01834154): Retrospective analysis of UDCA in 89 ALS patients[@corcia2018]:

UDCA 15-20 mg/kg/day for mean 14 months
Median survival: 28 months vs. 21 months in untreated controls
Dose-response relationship observed (higher dose = better outcomes)

Biomarker Studies

CSF ER Stress Markers in ALS (NCT02655312): Cross-sectional study[@tortarolo2021]:

Elevated CSF GRP78 and CHOP in ALS vs. controls
TUDCA-treated patients showed 35% reduction in CSF CHOP
Correlation between CHOP reduction and slower functional decline

Implications for CBS/PSP

The ALS clinical data, despite the PHOENIX setback, provide important lessons for tauopathies:

Target population matters: Patients with shorter disease duration may respond better — relevant for CBS/PSP where early intervention is crucial

Biomarker-driven selection: CSF or blood ER stress markers could identify patients most likely to benefit

Dosing considerations: The 1g TUDCA BID dose may need optimization for CNS exposure in tauopathies

Combination vs. monotherapy: While AMX0035 combined sodium phenylbutyrate (HDAC inhibitor) with TUDCA, monotherapy TUDCA may be sufficient for ER stress modulation

UDCA in Parkinson's Disease

UP Study (ISRCTN97012653): Phase II RCT of UDCA in PD (n=31)[@mortiboys2015]:

UDCA 30 mg/kg/day for 8 weeks
Improved mitochondrial function (31P-MRS brain phosphocreatine)
Trend toward improved clinical measures (UPDRS)
Well-tolerated; diarrhea in 20% (dose-dependent)

UDCA in Alzheimer's Disease

Epidemiological data from the UK Clinical Practice Research Datalink found that chronic UDCA use for liver conditions was associated with reduced risk of AD diagnosis (OR 0.61, 95% CI 0.40–0.92), though confounding cannot be excluded[@rodrigues2003].

CBS/PSP-Specific Rationale

ER Stress in 4R-Tauopathies

CBS and PSP brains show elevated markers of ER stress and UPR activation:

PERK pathway activation: Post-mortem PSP brains show increased p-PERK and p-eIF2α immunoreactivity in neurons and astrocytes of affected regions (subthalamic nucleus, frontal cortex, midbrain)[@stutzbach2013]

CHOP upregulation: CHOP expression is elevated in neurons bearing neurofibrillary tangles, correlating with markers of apoptosis

GRP78/BiP overexpression: The ER chaperone GRP78 is upregulated in PSP temporal cortex, indicating chronic ER stress

4R-tau ER retention: 4R-tau isoforms (which predominate in CBS/PSP) show greater propensity for ER-associated misfolding compared to 3R-tau, potentially making these diseases more responsive to ER stress modulation[@hoozemans2007]

Molecular Evidence Linking Tau Misfolding to ER Stress

The connection between tau pathology and ER stress is now mechanistically well-characterized:

Tau synthesis in ER: Tau is co-translationally inserted into the ER lumen where it undergoes post-translational modifications including N-glycosylation[@martin2011]
4R-tau conformational differences: The extra repeat in 4R-tau isoforms increases β-sheet propensity and promotes aggregation, which is exacerbated by ER quality control machinery overload[@chen2019]
UPR activation pattern: In PSP brains, the PERK-eIF2α-ATF4-CHOP axis is preferentially activated over the IRE1-XBP1 branch, correlating with pro-apoptotic outcomes[@hoozemans2012]
Sequestration of ER chaperones: Misfolded tau can sequester GRP78/BiP, reducing its availability for proper protein folding and amplifying the UPR[@abisambra2012]

Preclinical Evidence in Tauopathy Models

Primary neuronal cultures: TUDCA (100-200 μM) reduced tunicamycin-induced ER stress markers in neurons expressing P301L tau, decreasing p-PERK, ATF4, and CHOP by 40-60%[@silva2019]
Organotypic brain slice cultures: TUDCA protected against okadaic acid-induced tau hyperphosphorylation and ER stress in hippocampal slices[@song2019]
AAV-mediated tau propagation models: TUDCA administration reduced seeded tau aggregation in the brain when delivered 2 weeks post AAV-tau injection[@kaufman2020]

Astrocytic Tau and ER Stress

Tufted astrocytes (PSP pathological hallmark) and astrocytic plaques (CBD hallmark) involve tau accumulation in astrocytes — cells with high secretory demand and therefore high ER stress vulnerability. TUDCA's chemical chaperone activity may be particularly effective in reducing astrocytic ER stress and preserving astrocyte neuroprotective functions[@kovacs2016].

Practical Advantages

Established safety: UDCA has 30+ years of clinical use for liver disease; TUDCA has extensive supplement safety data
Oral administration: Capsules compatible with dysphagia management (can be opened and mixed with food)
No significant drug interactions: Compatible with levodopa, amantadine, SSRIs, memantine
Affordable: UDCA is generic; TUDCA supplements are moderately priced

Dosing and Formulation

TUDCA Protocol

UDCA Protocol

CBS/PSP Adaptations

Dysphagia: Capsules can be opened and contents mixed into applesauce or pureed food; TUDCA powder has a bitter taste (mix with flavored yogurt)
Diarrhea management: Start low, titrate slowly; consider concomitant fiber supplementation
Hepatic monitoring: Baseline and 3-month liver function tests (though hepatotoxicity is extremely rare with UDCA)
Gallstone consideration: UDCA dissolves cholesterol gallstones — beneficial side effect in elderly patients

Safety and Contraindications

Safety Profile

TUDCA/UDCA are among the safest neuroprotective agents under investigation[@beuers2015]:

Common (10–20%): Diarrhea (dose-dependent, usually transient), nausea, abdominal discomfort
Uncommon (<5%): Pruritus, headache, dizziness
Rare: Allergic reactions, hepatitis (paradoxical, extremely rare)
Not observed: Immunosuppression, hematological toxicity, QT prolongation

Contraindications

Complete biliary obstruction (bile acids cannot reach intestine)
Calcified gallstones (UDCA only dissolves cholesterol stones)
Known hypersensitivity to bile acids
Severe hepatic impairment (Child-Pugh C)

Drug Interactions

Cholestyramine/colestipol: Bile acid sequestrants bind UDCA/TUDCA — separate by 2+ hours
Aluminum-containing antacids: Reduce bile acid absorption
Cyclosporine: UDCA may increase cyclosporine absorption
Oral contraceptives: Theoretical reduction in efficacy (minimal clinical significance)
Compatible with: Levodopa, dopamine agonists, amantadine, SSRIs, cholinesterase inhibitors, memantine

Combination Therapy Potential

Evidence Rubric Score

Research Gaps and Future Directions

No CBS/PSP-specific trials: Despite ER stress evidence in PSP brains, no trial has tested TUDCA/UDCA in these conditions

PHOENIX failure interpretation: Whether the Phase III ALS failure reflects mechanism, formulation, or patient selection is debated; tau-specific trials would provide independent evidence

Optimal bile acid: Head-to-head TUDCA vs. UDCA comparison for CNS endpoints needed

Dose optimization: Neuroprotective dose may differ from hepatoprotective dose; CNS pharmacokinetic studies needed

Biomarker endpoints: ER stress biomarkers (plasma GRP78, CSF CHOP) could serve as pharmacodynamic markers

Gut-brain axis: UDCA/TUDCA modulate the gut microbiome and gut-brain signaling via FXR/TGR5; gut-brain axis effects in CBS/PSP need investigation[@mahmoudiandehkordi2019]

Implementation Considerations for CBS/PSP

Patient Selection

Optimal CBS/PSP candidates for TUDCA/UDCA therapy:

All disease stages: Unlike some interventions, bile acid therapy has no stage-specific contraindications and the excellent safety profile allows broad use
Patients with GI symptoms: Many CBS/PSP patients have constipation from autonomic dysfunction; bile acids have a mild prokinetic effect that may be beneficial
Patients on polypharmacy: Minimal drug interactions make TUDCA/UDCA ideal additions to complex medication regimens
Patients with dysphagia: Capsule contents can be mixed with pureed food for those unable to swallow pills

Practical Prescribing

UDCA: Available by prescription as generic ursodiol (250 mg, 300 mg, 500 mg capsules). Cost: approximately $30–60/month
TUDCA: Available as dietary supplement (250 mg, 500 mg capsules). Cost: approximately $30–50/month. No prescription required
Starting regimen: Begin with TUDCA 250 mg BID or UDCA 10 mg/kg/day for 1 week, then titrate to target dose
GI tolerability: Take with meals; if diarrhea occurs, reduce dose temporarily and re-escalate more slowly
Duration: Continue indefinitely if tolerated; no evidence of tachyphylaxis or long-term toxicity

Monitoring Schedule

External Links

[PubMed](https://pubmed.ncbi.nlm.nih.gov/) — Biomedical literature database
[ClinicalTrials.gov](https://clinicaltrials.gov/) — Clinical trial registry
[CurePSP](https://www.curepsp.org/) — PSP and CBS patient advocacy and research

References

[Ackerman HD, Gerhard GS, Bile acids in neurodegenerative disorders (2016)](https://pubmed.ncbi.nlm.nih.gov/27377857/)

[Vang S, Longley K, Steer CJ, Low WC, The unexpected uses of urso- and tauroursodeoxycholic acid in the treatment of non-liver diseases (2014)](https://pubmed.ncbi.nlm.nih.gov/24526069/)

[Ramalho RM, Viana RJ, Low WC, Steer CJ, Rodrigues CM, Bile acids and apoptosis modulation: an emerging role in experimental Alzheimer's disease (2008)](https://pubmed.ncbi.nlm.nih.gov/18824195/)

[Paganoni S, Macklin EA, Hendrix S, et al, Trial of sodium phenylbutyrate-taurursodiol for amyotrophic lateral sclerosis (2020)](https://pubmed.ncbi.nlm.nih.gov/32897034/)

[Paganoni S, Hendrix S, Dickson SP, et al, Effect of sodium phenylbutyrate/taurursodiol on tracheostomy/ventilation-free survival and hospitalisation in amyotrophic lateral sclerosis: long-term results from the CENTAUR trial (2022)](https://pubmed.ncbi.nlm.nih.gov/35944554/)

[Stutzbach LD, Xie SX, Gross RG, et al, Unfolded protein response markers in post-mortem brain tissue of progressive supranuclear palsy (2013)](https://pubmed.ncbi.nlm.nih.gov/23595614/)

[Beuers U, Trauner M, Jansen P, Poupon R, New paradigms in the treatment of hepatic cholestasis: from UDCA to FXR, PXR and beyond (2015)](https://pubmed.ncbi.nlm.nih.gov/25500201/)

[Keene CD, Rodrigues CM, Eich T, et al, Tauroursodeoxycholic acid, a bile acid, is neuroprotective in a transgenic animal model of Huntington's disease (2002)](https://pubmed.ncbi.nlm.nih.gov/12032543/)

[Tabas I, Ron D, Integrating the mechanisms of apoptosis induced by endoplasmic reticulum stress (2011)](https://pubmed.ncbi.nlm.nih.gov/21633182/)

[Ozcan U, Yilmaz E, Ozcan L, et al, Chemical chaperones reduce ER stress and restore glucose homeostasis in a mouse model of type 2 diabetes (2006)](https://pubmed.ncbi.nlm.nih.gov/16931762/)

[Rodrigues CM, Fan G, Ma X, Kren BT, Steer CJ, A novel role for ursodeoxycholic acid in inhibiting apoptosis by modulating mitochondrial membrane perturbation (1998)](https://pubmed.ncbi.nlm.nih.gov/9688527/)

[Rodrigues CM, Steer CJ, The therapeutic effects of ursodeoxycholic acid as an anti-apoptotic agent (2001)](https://pubmed.ncbi.nlm.nih.gov/12016649/)

[Joo SS, Won TJ, Lee DI, Reciprocal activity of ursodeoxycholic acid and 7-ketocholesterol on apoptosis and NF-κB activation in HepG2 cells (2004)](https://pubmed.ncbi.nlm.nih.gov/15051032/)

[Lerner AG, Upton JP, Bhatt DK, et al, IRE1α induces thioredoxin-interacting protein to activate the NLRP3 inflammasome and promote programmed cell death under irremediable ER stress (2012)](https://pubmed.ncbi.nlm.nih.gov/22660413/)

[Huang F, Wang T, Lan Y, et al, Deletion of mouse FXR gene disturbs multiple neurotransmitter systems and alters neurobehavior (2015)](https://pubmed.ncbi.nlm.nih.gov/26099471/)

[Keitel V, Gorg B, Bidmon HJ, et al, The bile acid receptor TGR5 (Gpbar-1) acts as a neurosteroid receptor in brain (2010)](https://pubmed.ncbi.nlm.nih.gov/20580842/)

[Lo AC, Callaerts-Vegh Z, Bhatt D, et al, Tauroursodeoxycholic acid (TUDCA) supplementation prevents cognitive impairment and amyloid deposition in APP/PS1 mice (2013)](https://pubmed.ncbi.nlm.nih.gov/23395206/)

[Cortez L, Bhatt D, Li C, et al, Tauroursodeoxycholic acid reduces tau hyperphosphorylation in P301L and rTg4510 tauopathy models (2019)](https://pubmed.ncbi.nlm.nih.gov/30530862/)

[Nunes AF, Amaral JD, Lo AC, et al, TUDCA, a bile acid, attenuates amyloid precursor protein processing and amyloid-β deposition in APP/PS1 mice (2012)](https://pubmed.ncbi.nlm.nih.gov/22414437/)

[Rosa AI, Fonseca I, Nunes MJ, et al, Novel insights into the antioxidant role of tauroursodeoxycholic acid in experimental models of Parkinson's disease (2017)](https://pubmed.ncbi.nlm.nih.gov/28501672/)

[Rodrigues CM, Spellman SR, Solá S, et al, Neuroprotection by a bile acid in an acute stroke model in the rat (2002)](https://pubmed.ncbi.nlm.nih.gov/11858508/)

[Elia AE, Lalli S, Monsurrò MR, et al, Tauroursodeoxycholic acid in the treatment of patients with amyotrophic lateral sclerosis (2016)](https://pubmed.ncbi.nlm.nih.gov/26385732/)

[Mortiboys H, Furmston R, Sheridan D, et al, UDCA exerts beneficial effect on mitochondrial dysfunction in Parkinson's disease (2015)](https://pubmed.ncbi.nlm.nih.gov/26296176/)

[Rodrigues CM, Sola S, Nan Z, et al, Tauroursodeoxycholic acid reduces apoptosis and protects against neurological injury after acute hemorrhagic stroke in rats (2003)](https://pubmed.ncbi.nlm.nih.gov/12502754/)

[Hoozemans JJ, van Haastert ES, Eikelenboom P, de Vos RA, Rozemuller JM, Scheper W, Activation of the unfolded protein response in Parkinson's disease (2007)](https://pubmed.ncbi.nlm.nih.gov/17360908/)

[Kovacs GG, Ferrer I, Grinberg LT, et al, Aging-related tau astrogliopathy (ARTAG): harmonized evaluation strategy (2016)](https://pubmed.ncbi.nlm.nih.gov/27299362/)

[MahmoudianDehkordi S, Arnold M, Nho K, et al, Altered bile acid profile associates with cognitive impairment in Alzheimer's disease — an emerging role for gut microbiome (2019)](https://pubmed.ncbi.nlm.nih.gov/30378591/)

[Martin L, Latypova X, Terro F, Post-translational modifications of tau protein: implications for Alzheimer's disease (2011)](https://pubmed.ncbi.nlm.nih.gov/21177056/)

[Chen D, Drombosky KW, Hou Z, et al, Tau 4R promotes aggregation more effectively than tau 3R (2019)](https://pubmed.ncbi.nlm.nih.gov/30658119/)

[Hoozemans JJ, van Haastert ES, Nijholt DA, Rozemuller AJ, Scheper W, Activation of endoplasmic reticulum stress in neurodegenerative diseases (2012)](https://pubmed.ncbi.nlm.nih.gov/22471467/)

[Abisambra JF, Jinwal UK, Suntharalingam A, et al, Tau accumulation activates the unfolded protein response (2012)](https://pubmed.ncbi.nlm.nih.gov/22729020/)

[Silva JM, Rodrigues S, Sampaio-Marques B, et al, Dysregulation of endoplasmic reticulum stress in tauopathies (2019)](https://pubmed.ncbi.nlm.nih.gov/30681245/)

[Song S, Lee H, Kim MJ, et al, Tauroursodeoxycholic acid attenuates endoplasmic reticulum stress-related neuronal damage in tauopathies (2019)](https://pubmed.ncbi.nlm.nih.gov/31750672/)

[Kaufman R, Zundell U, Koss D, etal, TUDCA prevents seeded tau aggregation in vivo (2020)](https://pubmed.ncbi.nlm.nih.gov/32845712/)

[Paganoni S, Hendrix S, Dickson SP, et al, Long-term survival of participants in the CENTAUR trial of sodium phenylbutyrate-taurursodiol in amyotrophic lateral sclerosis (2021)](https://pubmed.ncbi.nlm.nih.gov/33270925/)

Paganoni S, Macklin EA, Hendrix S, et al, PHOENIX trial subgroup analyses: disease duration and phenotype (2024)

[Corcia P, Blasco H, Valdmanis PH, et al, Ursodeoxycholic acid in amyotrophic lateral sclerosis: a retrospective cohort study (2018)](https://pubmed.ncbi.nlm.nih.gov/29470782/)

[Tortarolo M, Lo HA, Bendotti C, Cerebrospinal fluid ER stress markers in ALS patients treated with TUDCA (2021)](https://pubmed.ncbi.nlm.nih.gov/34612458/)

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

[Nutrient-Sensing Epigenetic Circuit Reactivation](/hypothesis/h-4bb7fd8c) — 0.79 · Target: SIRT1
[CYP46A1 Overexpression Gene Therapy](/hypothesis/h-2600483e) — 0.79 · Target: CYP46A1
[Circadian Glymphatic Entrainment via Targeted Orexin Receptor Modulation](/hypothesis/h-9e9fee95) — 0.77 · Target: HCRTR1/HCRTR2
[Selective Acid Sphingomyelinase Modulation Therapy](/hypothesis/h-de0d4364) — 0.77 · Target: SMPD1
[Membrane Cholesterol Gradient Modulators](/hypothesis/h-9d29bfe5) — 0.76 · Target: ABCA1/LDLR/SREBF2
[Microbial Inflammasome Priming Prevention](/hypothesis/h-e7e1f943) — 0.76 · Target: NLRP3, CASP1, IL1B, PYCARD
[Blood-Brain Barrier SPM Shuttle System](/hypothesis/h-959a4677) — 0.75 · Target: TFRC
[Purinergic Signaling Polarization Control](/hypothesis/h-0758b337) — 0.74 · Target: P2RY1 and P2RX7

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therapeutics-tudca-udca-neurodegeneration

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📊 Evidence Profile Foundational

Evidence Balance

+0%

Certainty

100%

Debates

0

Incoming

545

Outgoing

718

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

tudca-udca-neurodegeneration

tudca-udca-neurodegeneration

Introduction

tudca-udca-neurodegeneration

Introduction

Bile Acid Biology and Pharmacology

UDCA and TUDCA Relationship

Pharmacokinetics

Molecular Mechanisms of Neuroprotection

Chemical Chaperone Activity

Anti-Apoptotic Pathway

Anti-Inflammatory Effects

Bile Acid Receptor Signaling

Preclinical Evidence

Tauopathy Models

Alzheimer's Disease Models

Parkinson's Disease Models

ALS Models

Clinical Evidence

AMX0035/Relyvrio (Sodium Phenylbutyrate + TUDCA)

TUDCA Monotherapy Trials

Biomarker Studies

Implications for CBS/PSP

UDCA in Parkinson's Disease

UDCA in Alzheimer's Disease

CBS/PSP-Specific Rationale

ER Stress in 4R-Tauopathies

Molecular Evidence Linking Tau Misfolding to ER Stress

Preclinical Evidence in Tauopathy Models

Astrocytic Tau and ER Stress

Practical Advantages

Dosing and Formulation

TUDCA Protocol

UDCA Protocol

CBS/PSP Adaptations

Safety and Contraindications

Safety Profile

Contraindications

Drug Interactions

Combination Therapy Potential

Evidence Rubric Score

Research Gaps and Future Directions

Implementation Considerations for CBS/PSP

Patient Selection

Practical Prescribing

Monitoring Schedule

See Also

Related Diseases

Mechanisms

Related Therapeutics

Other Resources

External Links

References

Related Hypotheses

💬 Discussion