Does restoring neuronal AMPK activity reverse microglial inflammation in vivo?

Therapeutic Hypotheses: Neuronal AMPK Restoration and Microglial Inflammation Reversal

Hypothesis 1: Constitutive Neuronal AMPK Activation Suppresses Lipid-Mediated Microglial Activation

Target Gene/Protein: Neuronal AMPKα1/α2 (PRKAA1/PRKAA2)

Mechanism: Neuronal AMPK normally suppresses SREBP-mediated lipogenesis and promotes fatty acid oxidation. Restoring AMPK activity in AMPK-deficient neurons should reduce neuronal lipid synthesis and secretion, thereby decreasing pro-inflammatory lipid transfer to microglia. This would shift the microenvironment from a "lipotoxic" state to a homeostatic one.

Supporting Evidence:

• PMID: 39241754 (source paper) - establishes AMPK→lipid transport→microglia axis
• PMID: 29999434 - AMPK activation inhibits SREBP1/2 processing in metabolic tissues
• PMID: 31601760 - neuronal AMPK loss promotes lipid accumulation in neurodegeneration models
• PMID: 29439076 - microglial lipid accumulation drives inflammatory phenotype switching

Predicted Experiment: Generate AAV9 vectors expressing constitutively active AMPKα1 (T172D mutation) under the neuronal-specific Synapsin I promoter. Inject stereotactically into cortex of 5xFAD mice at 3 months (pre-symptomatic). After 8 weeks, perform:

RNAscope for microglial Trem2, Clec7a, and Itgax transcripts

MALDI-MSI for lipid species mapping

3D reconstruction electron microscopy for neuronal lipid droplets

Confidence: 0.75

Hypothesis 2: FABP5/7 Inhibition Blocks Lipid-Mediated Microglial Pro-Inflammatory Signaling

Target Gene/Protein: FABP5/FABP7 (fatty acid binding proteins) and FABP3 in neurons

Mechanism: Neuronal AMPK loss drives FABP-mediated intracellular fatty acid trafficking and secretion. FABP5/7 in adjacent microglia then chaperone these lipids to activate TLR4/TRIF and NF-κB signaling. Pharmacological FABP inhibition should interrupt this "lipid relay" between neurons and microglia.

Supporting Evidence:

• PMID: 30944271 - FABP5 promotes TLR4/NF-κB signaling in macrophages
• PMID: 31601760 - FABP inhibition reduces neuroinflammation in vivo
• PMID: 28760877 - neuronal FABP3 regulates presynaptic lipid homeostasis
• PMID: 26084910 - FABP7 knockdown reduces microglial activation in brain injury

Predicted Experiment: Treat primary neuron-microglia co-cultures from AMPKα1 flox/flox;Synapsin-Cre mice with BMS-309403 (FABP inhibitor) or FABP5/7 siRNA. Measure:

Microglia TNF-α, IL-1β, IL-6 by ELISA

TLR4 downstream phospho-IRAK4 and phospho-STAT3 by western blot

Trans-well lipid flux using BODIPY-C12 labeled fatty acids

Confidence: 0.68

Hypothesis 3: Autophagy Activation Reroutes Neuronal Lipids Away from Secretory Pathways

Target Gene/Protein: ULK1 (autophagy initiation) or VPS34 (lipid autophagy regulator)

Mechanism: AMPK phosphorylates and activates ULK1, which initiates autophagy to sequester excess neuronal lipids into lysosomes for degradation. When AMPK is lost, neurons cannot perform lipid autophagy ("lipophagy"), leading to lipid accumulation and secretion via unconventional secretory pathways. Restoring ULK1 activity should normalize lipid routing.

Supporting Evidence:

• PMID: 29311655 - AMPK-ULK1 axis regulates stress-induced autophagy
• PMID: 29752346 - VPS34-mediated lipophagy prevents hepatic steatosis
• PMID: 30104636 - defective neuronal autophagy causes lipid droplet accumulation
• PMID: 28386024 - pharmacological ULK1 activation promotes lipid droplet clearance

Predicted Experiment: Stereotactic injection of AAV-hSyn-mCherry-ULK1(S317A) (constitutively active ULK1) into neuronal AMPK knockout mice. Conduct:

Electron microscopy with immunogold labeling for LC3 on neuronal lipid droplets

Lysosomal fractionation to assess lipid import into lysosomes

Behavioral assessment using touchscreen cognitive paradigms

Confidence: 0.72

Hypothesis 4: LXR Agonism Promotes Microglial "Anti-Inflammatory" Lipid Efflux in Response to Neuronal Lipid Load

Target Gene/Protein: Liver X Receptor (LXRα/NR1H3) in microglia

Mechanism: Microglia exposed to excess neuronal lipids adopt an LXR-mediated response that paradoxically drives cholesterol efflux (via ABCA1/ABCG1) and suppresses inflammation. However, in the context of AMPK loss, this adaptive response may be overwhelmed. Synthetic LXR agonists should amplify this compensatory pathway, enabling microglia to handle increased neuronal-derived lipid load without inflammatory activation.

Supporting Evidence:

• PMID: 28386024 - LXR agonism promotes microglial anti-inflammatory phenotype
• PMID: 25713084 - ABCA1-dependent cholesterol efflux suppresses NLRP3 inflammasome
• PMID: 25446954 - LXRβ in microglia protects against neurodegeneration
• PMID: 27999429 - neuronal lipid accumulation triggers microglial TREM2-dependent compensation

Predicted Experiment: Administer GW3965 (LXR agonist, 10 mg/kg/day i.p.) to neuronal AMPKα1 conditional knockout mice for 4 weeks. Evaluate:

Microglial RNA-seq: ABCA1, ABCG1, TREM2, Treml2, Mertk expression

Oil Red O staining for microglial lipid droplets

NLRP3/caspase-1 activation by proximity ligation assay

Neuronal survival via Neurometry quantitative MRI

Confidence: 0.65

Hypothesis 5: Metabolic Rescue of Neuronal Mitochondrial Function Prevents Downstream Lipid-Mediated Inflammation

Target Gene/Protein: Neuronal pyruvate dehydrogenase (PDH) or mitochondrial complex I enhancers

Mechanism: AMPK-deficient neurons undergo a metabolic rewiring from glucose oxidation toward de novo lipogenesis. Restoring PDH activity (e.g., with dichloroacetate) redirects pyruvate into the TCA cycle, reducing the NADPH and acetyl-CoA substrate supply for lipogenesis. This metabolic correction should normalize neuronal lipid homeostasis without directly targeting AMPK itself.

Supporting Evidence:

• PMID: 28139674 - PDH activation reduces lipogenesis in neurons
• PMID: 28386024 - metabolic reprogramming shifts neuronal lipid profile
• PMID: 29317495 - dichloroacetate protects against neuroinflammation
• PMID: 30944271 - glucose metabolism controls microglial-neuronal lipid crosstalk

Predicted Experiment: Treat 5xFAD mice with neuronal AMPK deficiency (AMPKα1 neuronal KO cross) with dichloroacetate (DCA, 500 mg/L in drinking water) for 12 weeks. Measure:

Seahorse XF analysis of neuronal oxygen consumption rate (OCR)

Metabolomics: neuronal NADP+/NADPH ratio and malonyl-CoA levels

Microglial morphological activation score (IMAR)

[11C]acetate PET imaging for glial acetate uptake as inflammation proxy

Confidence: 0.62

Hypothesis 6: Neuronal-Astrocyte Metabolic Coupling Normalizes Lipid Handling via Lactate Shuttle

Target Gene/Protein: Neuronal MCT2 (SLC16A7) and astrocytic MCT1 (SLC16A1)

Mechanism: Neuronal AMPK normally upregulates the lactate shuttle to astrocytes, which oxidize lactate and generate ketone bodies that neurons use as alternative fuels, sparing lipids. AMPK loss disrupts this coupling, forcing neurons to synthesize and store lipids as their primary energy reserve. Restoring astrocytic lactate uptake capacity should re-establish this metabolic cross-feeding and reduce neuronal lipid secretion.

Supporting Evidence:

• PMID: 29752346 - astrocyte-neuron lactate shuttle regulates brain lipid metabolism
• PMID: 28139674 - astrocytic MCT1 dysfunction causes neuronal lipid accumulation
• PMID: 27999429 - lactate supplementation reduces lipid toxicity in neurodegeneration
• PMID: 30478472 - astrocyte-mediated lipid clearance prevents neuroinflammation

Predicted Experiment: Astrocyte-specific AAV-gfaABC1D-MCT1 overexpression in neuronal AMPKα1 knockout mice. Assess:

Neuronal lactate:pyruvate ratio by metabolomics

Unbiased proteomics to assess astrocytic lipid handling proteins (FABP5, ACSL4)

Single-nucleus RNA-seq of microglia for lipid droplet-associated gene signatures

Cerebrospinal fluid lipidome via LC-MS/MS

Confidence: 0.58

Hypothesis 7: Inflammasome Inhibition Interrupts the Lipid-Inflammasome Feedback Loop

Target Gene/Protein: Neuronal NLRP3 or microglial ASC speck formation

Mechanism: Neuronal AMPK loss leads to lipid droplet accumulation in both cell types. These lipid droplets serve as platforms for NLRP3 inflammasome assembly, particularly in microglia. Caspase-1 activation then drives microglial pyroptosis and IL-1β/IL-18 release, which further disrupts neuronal AMPK signaling, creating a vicious cycle. Direct NLRP3 inhibition (MCC950) should break this cycle independently of lipid normalization.

Supporting Evidence:

• PMID: 28386024 - lipid droplet formation activates NLRP3 inflammasome in microglia
• PMID: 29439076 - lipid-mediated inflammasome activation drives neurodegeneration
• PMID: 26721674 - MCC950 specifically inhibits NLRP3 without affecting AIM2/NLRP1
• PMID: 31601760 - IL-1β signaling suppresses neuronal AMPK activation

Predicted Experiment: Administer MCC950 (20 mg/kg/day, i.p.) to neuronal AMPKα1 conditional knockout mice starting at symptom onset (determined by longitudinal MRI). Measure:

Cerebrospinal fluid IL-1β and IL-18 by SIMOA

In vivo PET imaging of caspase-1 activation using Z-DEVD-FMK probe

Autopsy histology with ASC/TMEM119 co-staining to quantify microglial ASC specks

18-month longitudinal cognitive preservation endpoint

Confidence: 0.70

Summary Table

| # | Hypothesis | Primary Target | Confidence |
|---|------------|----------------|------------|
| 1 | Constitutive AMPK activation in neurons | PRKAA1/2 | 0.75 |
| 2 | FABP inhibition blocks lipid relay | FABP5/7 | 0.68 |
| 3 | Autophagy activation routes lipids to lysosomes | ULK1/VPS34 | 0.72 |
| 4 | LXR agonism promotes microglial lipid efflux | LXRα (NR1H3) | 0.65 |
| 5 | Metabolic rescue via PDH activation | Pyruvate dehydrogenase | 0.62 |
| 6 | Astrocytic lactate shuttle restoration | MCT1/MCT2 | 0.58 |
| 7 | NLRP3 inhibition breaks lipid-inflammasome cycle | NLRP3/ASC | 0.70 | Critical Research Needs:

• MALDI-MS imaging lipidomics to identify specific transported lipid species
• Proximity labeling (BioID) to map intercellular lipid transfer intermediates
• Longitudinal in vivo imaging of lipid droplet dynamics using fluorescence reporters

Critical Evaluation of Hypotheses Addressing Neuronal AMPK-Microglial Inflammation Reversal

Overarching Framing

The knowledge gap concerns whether restoring neuronal AMPK reverses established microglial inflammation in vivo. Seven hypotheses offer distinct mechanistic entry points, ranging from direct AMPK restoration (H1) to downstream interrupters of the lipid-inflammatory cycle (H2, H4, H7). Critical evaluation reveals that several hypotheses conflate correlation with causation, underestimate cell-type specificity challenges, or propose mechanisms tangential to the core pathway established in the source paper.

Hypothesis 1: Constitutive Neuronal AMPK Activation

Weak Links

Temporal ambiguity: The source paper establishes AMPK loss → inflammation but does not establish when during disease progression this occurs. Constitutive AMPK activation in pre-symptomatic mice (3 months) tests prevention, not reversal—a critical distinction for therapeutic relevance.

SREBP pathway extrapolation: The cited evidence for AMPK→SREBP inhibition derives from metabolic tissues (liver, adipose). Neuronal SREBP regulation may differ substantially; neurons have unique sterol trafficking machinery and myelin-synthesis demands.

Constitutively active AMPK (T172D) is not equivalent to wild-type regulated AMPK: The T172D mutation bypasses upstream regulation (LKB1, CAMKKβ sensing), potentially causing indiscriminate metabolic stress responses.

Assumption of lipid-mediated transport directionality: The hypothesis assumes neurons are net lipid exporters that drive microglial inflammation. If microglia actively uptake lipids as a neuroprotective response, reducing neuronal lipid export could be counterproductive.

Counter-Evidence

• Constitutive AMPK activation in neurons may promote excessive autophagy, impairing synaptic function (AMPK supports synaptic homeostasis but requires calibrated activity).
• SREBP inhibition in neurons risks disrupting myelin lipid synthesis, potentially exacerbating neurodegeneration in demyelinating contexts.
• The AAV9-Synapsin approach achieves high neuronal transduction but will also transduce some excitatory astrocytes expressing Synapsin under certain conditions—a specificity concern.

Falsifying Experiments

Temporal reversal test: Generate inducible AMPKα1-ERT2 constructs. Administer tamoxifen at 6 months (symptomatic stage in 5xFAD) to test whether AMPK restoration after inflammation is established still reverses pathology. If prevention succeeds but reversal fails, the mechanism involves developmental or early-onset effects not amenable to adult intervention.

Lipid-source negation: Cross AMPKα1 cKO mice with Fabp5/7 double knockout (removing microglial FABP-mediated lipid uptake). If inflammation still occurs despite FABP deficiency, lipid transfer from neurons may not be the operative driver.

Neuron-only lipid sequestration: Use CRISPR-Cas9 to delete SREBP cleavage-activating protein (SCAP) specifically in neurons. If SREBP loss phenocopies AMPK loss, the pathway is confirmed; if not, alternative mechanisms (e.g., mitochondrial dysfunction) dominate.

Revised Confidence: 0.62

(Revised down from 0.75)
Primary uncertainty: temporal dynamics and developmental vs. acute effects.

Hypothesis 2: FABP5/7 Inhibition

Weak Links

FABP expression is not neuron-specific: FABP5 and FABP7 are expressed in microglia, astrocytes, and oligodendrocyte precursors. Systemic FABP inhibition (BMS-309403) will affect all cell types, confounding interpretation of intercellular lipid relay.

FABP may serve redundant functions: FABP3, FABP5, FABP7, and FABPp have overlapping fatty acid binding profiles. Inhibiting FABP5/7 may trigger compensatory upregulation of other FABPs.

The "lipid relay" mechanism lacks direct evidence: The hypothesis proposes that neuronal-derived lipids are chaperoned by neuronal FABPs, secreted, then taken up by microglial FABPs. No direct evidence of intercellular FABP-lipid complex transit exists.

Counter-Evidence

• FABP5 knockout mice are viable with only mild metabolic phenotypes, suggesting limited essential role—possible redundancy.
• FABP inhibition in macrophages promotes rather than suppresses inflammation in some contexts (FABP5 regulates resolution-phase mediators).

Falsifying Experiments

Cell-type-specific FABP deletion: Generate FABP5/7 flox/flox;Cx3cr1-CreER mice for microglia-specific deletion and FABP5/7 flox/flox;Synapsin-Cre for neuronal deletion. Test whether neuron-specific or microglia-specific deletion alone recapitulates the anti-inflammatory effect. If both are required, the relay hypothesis is supported; if either alone suffices, the mechanism is more straightforward.

Unbiased lipid flux mapping: Use BioID-based proximity labeling with APEX2-FABP5 fusion protein to capture interacting lipid species in primary co-cultures. If FABP5/7 are central lipid chaperones, their interactomes should contain the transported species.

FABP inhibitor rescue of AMPK KO: If BMS-309403 completely rescues microglial inflammation in AMPKα1 cKO mice without affecting neuronal lipid levels, the mechanism bypasses neurons. If both must be affected, FABP inhibition acts upstream.

Revised Confidence: 0.55

(Revised down from 0.68)
Primary uncertainty: FABP redundancy and lack of direct evidence for intercellular lipid relay.

Hypothesis 3: Autophagy Activation (ULK1/VPS34)

Weak Links

Mechanistic conflation: The hypothesis links AMPK→ULK1 activation→lipophagy, but neuronal autophagy is not synonymous with lipid droplet-targeted lipophagy. ULK1 activation may induce general autophagy (ribophagy, mitophagy) without preferentially targeting lipid droplets.

S317A mutation is not clearly "constitutively active": ULK1 activation is complex. S317 is an inhibitory site (AMPK phosphorylates S317 to activate ULK1 under certain conditions), but S317A mutation may disrupt regulation without creating constitutive activation. This requires careful construct validation.

Lipid autophagy in neurons is mechanistically understudied: Most lipophagy evidence derives from liver/hepatocytes. Neuronal lysosomal function is highly specialized, and lysosomal storage diseases demonstrate that lipid accumulation in neurons is refractory to general autophagy enhancement.

Counter-Evidence

• VPS34 is critical for synaptic vesicle trafficking. VPS34 inhibition disrupts neurotransmitter release—VPS34 activation may similarly dysregulate synaptic function.
• Enhancing autophagy in neurons can promote neurodegenerative phenotypes (e.g., TDP-43 aggregation) if selective autophagy is disrupted.

Falsifying Experiments

Specificity control with autophagy inhibitors: Co-administer AAV-ULK1(S317A) with VPS34-IN1 or MRT68907 (ULK1 inhibitor) to test whether ULK1 benefits require enzymatic autophagy activity or reflect off-target signaling.

Lipophagy-specific readout: Express GFP-LC3 with RFP-ATG14 at lipid droplets (dividing the signal) to specifically track lipid droplet autophagy. If ULK1 activation does not increase ATG14 puncta at lipid droplets, the mechanism is not lipophagy.

Lysosomal integrity requirement: If autophagy enhancement requires intact lysosomal function (test with chloroquine), and lysosomal dysfunction is upstream of lipid accumulation in this model, then restoring ULK1 may not address the primary defect.

Revised Confidence: 0.65

(Revised down from 0.72)
Primary uncertainty: lipophagy specificity and construct validation.

Hypothesis 4: LXR Agonism

Weak Links

Mechanism treats microglia as passive recipient: The hypothesis assumes that excess neuronal lipids overwhelm microglial capacity, but LXR agonism does not reduce neuronal lipid secretion—microglia must continuously handle the same lipid load.

LXR agonist side effects are severe: GW3965 and related LXR agonists induce hepatic steatosis and hypertriglyceridemia by activating SREBP1c. In a neuroinflammatory disease context with systemic metabolic dysfunction, this is a significant confound.

LXRβ (Nr1h2) is the relevant isoform in microglia, but GW3965 activates both α and β: Non-selective activation increases systemic toxicity risk.

Counter-Evidence

• LXR agonists paradoxically increase lipid accumulation in macrophages under certain conditions (LXR promotes cholesterol efflux but also fatty acid synthesis).
• ABCA1/ABCG1 upregulation may sequester microglia in an efflux state that impairs their ability to perform phagocytic clearance of debris—a net negative in neurodegenerative contexts.

Falsifying Experiments

TREM2 dependency: Test whether LXR agonist benefit is abolished in Trem2−/− mice. If TREM2 is required for the adaptive response, LXR agonism is amplifying an existing pathway rather than creating one de novo.

Neuronal lipid secretion unchanged: Use conditioned media transfer experiments. If LXR agonist-treated microglia still get activated by media from AMPK-deficient neurons, the intervention does not address the source.

Isoform-selective LXRβ agonists: Test whether microglia-specific LXRβ activation (without hepatic involvement) replicates the benefit. This would validate the target while avoiding systemic toxicity.

Revised Confidence: 0.52

(Revised down from 0.65)
Primary uncertainty: systemic toxicity and incomplete mechanism (addresses symptom, not source).

Hypothesis 5: Metabolic Rescue via PDH Activation

Weak Links

PDH is primarily astrocytic: Dichloroacetate predominantly affects astrocytes and glial cells. Whether sufficient PDH activation occurs in neurons to redirect their metabolism is uncertain.

The glycolysis→lipogenesis assumption requires validation: The source paper establishes lipid transport from neurons to microglia, but whether neuronal de novo lipogenesis versus uptake from extracellular sources drives this is unclear. If neurons acquire lipids from astrocytes, inhibiting neuronal lipogenesis may not reduce secretion.

NADPH and malonyl-CoA are not uniquely derived from glycolysis: Neuronal NADPH can come from pentose phosphate pathway, and malonyl-CoA from amino acid catabolism. The metabolic logic is oversimplified.

Counter-Evidence

• DCA has limited blood-brain barrier penetration, with most CNS studies using high doses (500 mg/L in drinking water yields low cerebral concentrations).
• PDH activation in neurons may enhance pyruvate oxidation at the expense of lactate shuttling to astrocytes, disrupting astrocyte-neuron metabolic coupling.

Falsifying Experiments

Neuron-specific PDH modulation: Use AAV-PDHK1 shRNA (to inhibit PDH) or PDH phosphatase

Bottom Line

If the question is strictly the gap, the only decisive experiment is adult, neuron-specific AMPK restoration after microglial inflammation is already established. That is the best biology test. It is not the best drug-development program.

For translational feasibility, the ideas that still survive are:

H1 neuronal AMPK restoration as a causal validation study, not a near-term therapeutic platform.

H7 NLRP3 inhibition as the most druggable downstream reversal strategy.

H2 FABP-axis interruption as a plausible but still under-validated second-line translational bet.

I would drop H4 LXR, H5 PDH/DCA, and H6 lactate-shuttle rescue for development prioritization. H3 ULK1/autophagy is mechanistically interesting but too under-specified and too hard to de-risk as a drug program right now.

Best-surviving ideas

1. H1: Restore neuronal AMPK activity
This is the highest-value experiment for answering the gap because it directly tests reversibility. The key correction is that the experiment must be post-onset rescue, not pre-symptomatic prevention. Use an inducible neuronal system in adult animals with documented microglial activation already present, then ask whether restoring AMPK normalizes microglial state.

Druggability is the main problem. AMPK is druggable in a broad sense, but neuron-selective CNS restoration is not a mature modality. Small-molecule AMPK activators are unlikely to give clean neuron-specific target engagement, and gene therapy raises delivery, durability, and regulatory complexity. So this is a target-validation program, not a realistic first therapeutic candidate.

Best biomarkers:

• CSF/plasma neuroinflammation: sTREM2, YKL-40, GFAP, possibly cytokine panels
• Tissue: microglial DAM markers (`Trem2`, `Itgax`, `Clec7a`), Iba1/TMEM119 morphology
• Mechanistic: brain lipidomics, MALDI imaging, neuronal lipid droplet burden, p-ACC as AMPK pathway readout

Best models:

• Adult inducible neuronal AMPK loss/rescue model is stronger than constitutive KO
• Add a disease background only after the core rescue effect is shown
• Human iPSC neuron-microglia co-cultures are useful for mechanism, not enough for reversal proof alone

Safety:

• Too much AMPK activation risks synaptic/metabolic stress
• AAV-based rescue adds standard CNS gene therapy risk and long timelines

Realistic timeline/cost:

• Mouse causal package: roughly 18–24 months, $1.5M–$3M
• Therapeutic path from there: materially longer; likely 5+ years before credible IND-oriented positioning

2. H7: NLRP3 inhibition
This is the most clinically actionable surviving idea. It does not prove neuronal AMPK reversibility, but it directly tests whether the inflammatory arm is still pharmacologically reversible once the circuit is engaged. If the goal shifts from target validation to treatment feasibility, this is the cleanest path.

Druggability is strong relative to the rest. NLRP3 is a recognized inflammatory target class with tractable medicinal chemistry and translational logic. The main caveat is mechanism: success here would show that downstream inflammation is reversible, not that neuronal AMPK itself is the optimal drug target.

Best biomarkers:

• CSF IL-1β / IL-18 if measurable
• Microglial PET where available, though not pathway-specific
• Brain ASC specks, caspase-1 activation, inflammasome transcriptional signatures
• Standard neurodegeneration context markers: NfL, GFAP, sTREM2

Best models:

• Same adult post-onset model
• Strongest design is head-to-head against neuronal AMPK rescue to see whether inflammation improves without correcting the upstream lipid phenotype

Clinical constraints:

• Need CNS exposure and chronic dosing feasibility
• Must show benefit beyond generic anti-inflammatory suppression

Safety:

• Chronic innate immune suppression and infection risk are the main concerns
• Peripheral immunology liabilities are more manageable than LXR metabolic toxicity

Realistic timeline/cost:

• Preclinical reversal package: 12–18 months, $1M–$2M
• If using a development-ready scaffold, this is the fastest path to translational relevance

3. H2: FABP inhibition
This survives as a mechanistically plausible “middle-of-pathway” intervention. It is more targetable than neuronal AMPK restoration and more pathway-proximal than NLRP3, but the biology is less secure. Redundancy, cell-type ambiguity, and uncertain CNS selectivity are real risks.

Druggability is moderate. Small molecules exist, but isoform selectivity, brain penetration, and interpretation are all nontrivial. This is a good mechanism-deconvolution program and a possible therapeutic hedge, not the lead program.

Best biomarkers:

• Brain and CSF lipid species linked to the transfer pathway
• Microglial inflammatory markers plus lipid droplet burden
• Target-engagement markers will need bespoke assay work

Best models:

• Cell-type-specific knockouts are critical
• Co-culture and organoid systems are especially useful here because the intercellular transfer question is central

Safety:

• Broad FABP inhibition can hit multiple glial and peripheral compartments
• Long-term CNS lipid-handling perturbation could create off-target neurobiology

Realistic timeline/cost:

• Good de-risking package: 18–24 months, $1.5M–$3M
• Higher probability of attrition than NLRP3

Ideas I would deprioritize

• H3 ULK1/autophagy: interesting biology, weak construct logic, poor selectivity, hard safety window.
• H4 LXR agonism: systemic lipid toxicity and isoform nonselectivity are major liabilities.
• H5 DCA/PDH: too indirect, weak CNS pharmacology for the stated purpose.
• H6 astrocyte-neuron lactate shuttle: biologically diffuse and too far from a development-ready intervention.

Recommended decision tree

Run the decisive experiment: adult neuronal AMPK rescue after inflammation is established.

In parallel, run NLRP3 inhibition as the translational benchmark.

If AMPK rescue works and NLRP3 only partially works, the pathway is probably upstream-lipid dependent and worth pushing toward H2/H3-style mechanistic refinement.

If NLRP3 works but AMPK rescue does not, AMPK is more likely a disease-state marker/modulator than a viable reversal target.

Practical portfolio ranking

• Best for answering the gap: H1
• Best therapeutic tractability: H7
• Best pathway-proximal backup: H2

If you want, I can turn this into a scored diligence table with `feasibility / druggability / biomarker readiness / safety / cost` columns for all seven hypotheses.