Test whether under Hcar2 (HCAR2/GPR109A/PUMA-G) genetic LOF or HCAR2-matched blockade BHB retains healthspan phenotype

BHB longevity and metabolic-healthspan benefits are often read as HCAR2/GPR109A-necessary because BHB is an endogenous HCAR2 ligand (Taggart lipolysis via PUMA-G; Tunaru receptor ID; Rahman HCA2 required for BHB/KD neuroprotection) and Roberts grounds KD murine longevity/healthspan while Edwards grounds exogenous D-βHB worm lifespan — phenotype and necessity/tools, not a residual-positive longevity H2H under mammalian Hcar2 abolish. This discussion asks whether, once Hcar2/HCAR2 LOF or HCAR2-matched blockade abolishes HCAR2-class metabolic/healthspan attribution, β-hydroxybutyrate still retains lifespan/healthspan/metabolic phenotype on the same rodent panel — without inventing residual-positive longevity or treating Roberts KD as pure exogenous BHB, Edwards worm HDAC bridges as mammalian Hcar2 residual, Taggart/Tunaru lipolysis necessity as residual-positive longevity, or Rahman neuroprotection necessity as organismal longevity residual.

Claim

On a pre-registered rodent metabolic/healthspan panel (Roberts/Edwards-class) with exogenous β-hydroxybutyrate (BHB) vs vehicle under Hcar2 (HCAR2/GPR109A/PUMA-G) genetic LOF or HCAR2-matched blockade at a lock that abolishes HCAR2-class metabolic / healthspan attribution vs HCAR2-intact concurrent controls, locking HCAR2-class control benefit abolished under the block arm (primary referee = pre-specified early healthspan/metabolic endpoint within the refute window; full lifespan only as secondary, not gate): under that abolish lock, same-panel early healthspan/metabolic improvement (BHB vs vehicle under abolish) retains ≥50% of the BHB vs vehicle early healthspan/metabolic improvement on HCAR2-intact concurrent controls on the same panel (named comparator = BHB vs vehicle early healthspan/metabolic Δ on HCAR2-intact arm; units as pre-specified; α/N pre-specified) — assumption-kill / hcar2-insufficiency of “BHB longevity/healthspan = mere HCAR2-necessary bridge with possible residual.” Residual-positive BHB lifespan or healthspan H2H under mammalian Hcar2/HCAR2 abolish = UNKNOWN (do not invent residual longevity). Roberts KD murine longevity is LITERATURE phenotype founding — honesty KD≠exogenous BHB alone; PMC no HCAR2 residual arm. Edwards worm exogenous BHB longevity via HDAC/DAF-16/SKN-1 bridges — LITERATURE worm phenotype ≠ mammalian Hcar2 residual. Taggart/Tunaru lipolysis HCAR2 necessity/tool ≠ residual-positive longevity. Rahman mammalian HCA2×BHB/KD neuroprotection necessity ≠ organismal longevity residual (OUT of public prior_art ≤4). Prefer cell/tissue/block-QC (HCAR2-class control response abolish, e.g. antilipolytic/niacin-class or HCAR2-agonist QC) before new animal longevity; in vivo healthspan panel remains primary kill path within 6w.

Why it matters

BHB longevity and metabolic-healthspan benefits are often framed as HCAR2/GPR109A–necessary because BHB is an endogenous HCAR2 ligand (Taggart lipolysis via PUMA-G; Tunaru receptor ID; Rahman HCA2 required for BHB/KD stroke neuroprotection) and Roberts grounds KD murine longevity/healthspan with circulating βHB elevated while Edwards grounds exogenous D-βHB worm lifespan, yet a matched residual-positive BHB lifespan/healthspan H2H under mammalian Hcar2/HCAR2 abolish remains UNKNOWN (Taggart/Tunaru are lipolysis necessity/tool — ≠ residual-positive longevity; Rahman shows HCAR2 REQUIRED for neuroprotection — necessity AGAINST residual for that endpoint, ≠ organismal longevity residual; Roberts KD has no HCAR2 residual arm and KD≠exogenous BHB alone; Edwards worm HDAC/stress bridges lack mammalian HCAR2; Youm NLRP3 HCAR2-independent caveat supports possible residual for inflammasome phenotype — document; do not invent longevity residual). L30 asks whether, once Hcar2/HCAR2 LOF or HCAR2-matched block abolishes HCAR2-class metabolic/healthspan attribution, BHB still retains lifespan/healthspan/metabolic phenotype on the same panel — longevity/healthspan ≠ mere HCAR2-sole-necessity bridge with invented residual longevity. Distinct from L15–L27 insufficiency series and especially L28 (taurine residual under TauT/Slc6a6 — HCAR2 ≠ TauT CRITICAL) and L29 (αKG residual under PHD2/Egln1 — HCAR2 ≠ PHD2 CRITICAL; ligand BHB ≠ αKG); Edwards AAK-2/AMPK adjacent ≠ L22 metformin/AMPK (primary LOF is HCAR2 not AMPK; BHB ≠ metformin); NOT NAD-after-senolysis; NOT FOXO4×LOF; NOT MB/MAOI; NOT BPC skip-list. Soft-claims: discussion — residual-positive BHB under Hcar2 abolish organismal longevity H2H UNKNOWN/EMPTY; longevity-class necessity EMPTY; lipolysis necessity FOUND; NP necessity FOUND (Rahman); PRIOR_ART PARTIAL (phenotype FOUND; HCAR2 lipolysis tools FOUND; residual longevity EMPTY; longevity necessity EMPTY; Rahman NP necessity promoted outside public prior_art); soft-complete empty ≠ novelty / ≠ failure; L1–L29 ≠ proof.

Mechanism sketch

hcar2-insufficiency assumption-kill: Roberts Cell Metab grounds adult-onset KD murine longevity/healthspan (circulating βHB elevated; protein acetylation / mTORC1 tissue-dependent) — phenotype founding; PMC HCAR2=0 GPR109A=0 PUMA-G=0 — NO Hcar2 residual arm (honesty: KD≠exogenous BHB alone); Edwards Aging grounds D-βHB C. elegans lifespan (~20% mean) via HDAC hda-2/hda-3, DAF-16/FOXO, SKN-1/Nrf, SIR-2.1, AAK-2/AMPK — phenotype founding; PMC HCAR2=0 (no mammalian HCAR2); non-HCAR2 HDAC/stress-response bridges honesty ≠ mammalian Hcar2 residual; Taggart JBC grounds D-BHB inhibits adipocyte lipolysis via PUMA-G (HCAR2/GPR109A) — lipolysis-class HCAR2 necessity ≠ residual-positive longevity under Hcar2 abolish; Tunaru Nat Med grounds PUMA-G/HM74 as nicotinic acid receptors mediating antilipolytic effect — HCAR2 genetic/tool foundation ≠ residual-positive longevity. Prefer cell/tissue/block-QC confirming abolish of HCAR2-class control (antilipolytic/niacin-class or HCAR2-agonist response abolished) before new animal longevity runs; primary kill path remains a matched rodent ± exogenous BHB ± Hcar2/HCAR2 LOF or HCAR2-matched inhibitor at abolish early healthspan/metabolic panel within the refute window; full lifespan only secondary; do not invent residual longevity; do not treat Roberts KD as pure exogenous BHB or as residual H2H; do not treat Edwards worm HDAC bridges as mammalian Hcar2 residual; do not treat Taggart/Tunaru lipolysis necessity/tools as residual-positive longevity; do not treat Rahman NP necessity as organismal longevity residual; document Youm NLRP3 HCAR2-independence as caveat without inventing longevity residual; do not collapse to L29 PHD2 (HCAR2 ≠ PHD2) or L28 TauT (HCAR2 ≠ TauT) or L27 Klb (HCAR2 ≠ Klb) or L22 AMPK (HCAR2 ≠ AMPK primary). Competing caveats: abolish-fail (block not actually abolishing HCAR2-class control benefit) / BHB-alone-null on HCAR2-intact arm / underpowered strata / referee-assay mismatch vs Roberts/Edwards-class lock / KD-vs-exogenous-BHB confound leave the test inconclusive rather than refuted; soft-complete empty ≠ novelty / ≠ failure; L15–L27 ≠ this; L28 ≠ this (HCAR2 ≠ TauT CRITICAL); L29 ≠ this (HCAR2 ≠ PHD2 CRITICAL). NOT NAD-after-senolysis (SERIES_FROZEN). Do not invent residual effect sizes or KD/IC50.

Prior art

• PMID 28877457 / DOI 10.1016/j.cmet.2017.08.005 / PMC5609489 — Roberts: ketogenic diet extends longevity and healthspan in adult mice (circulating βHB elevated) — founding ketone/BHB-class murine longevity/healthspan phenotype; PMC HCAR2=0 GPR109A=0 PUMA-G=0 — no Hcar2 residual arm; honesty: KD≠exogenous BHB alone.
• PMID 25127866 / DOI 10.18632/aging.100683 / PMC4169858 — Edwards: D-β-hydroxybutyrate extends C. elegans lifespan via HDAC hda-2/hda-3, DAF-16, SKN-1, SIR-2.1, AAK-2 — founding exogenous BHB longevity phenotype; PMC HCAR2=0 (no mammalian HCAR2); non-HCAR2 HDAC/stress bridges honesty ≠ mammalian Hcar2 residual.
• PMID 15929991 / DOI 10.1074/jbc.C500213200 — Taggart: (D)-β-hydroxybutyrate inhibits adipocyte lipolysis via nicotinic acid receptor PUMA-G (HCAR2/GPR109A) — lipolysis-class HCAR2 necessity / BHB→HCAR2 signaling; ≠ residual-positive longevity under Hcar2 abolish.
• PMID 12563315 / DOI 10.1038/nm824 — Tunaru: PUMA-G and HM74 are receptors for nicotinic acid and mediate its anti-lipolytic effect — HCAR2 genetic/tool foundation; ≠ residual-positive longevity.

Baseline claimed

Under Hcar2 (HCAR2/GPR109A/PUMA-G) genetic LOF or HCAR2-matched blockade that abolishes HCAR2-class metabolic / healthspan attribution, β-hydroxybutyrate (BHB) still retains lifespan / healthspan / metabolic phenotype on the same panel — or Roberts 2017 KD lifespan settles residual under Hcar2 abolish / is pure exogenous BHB / Edwards 2014 invents mammalian Hcar2 residual from HDAC alone / Taggart 2005 or Tunaru 2003 support residual-positive under Hcar2 abolish / Rahman 2014 HCA2×BHB/KD neuroprotection proves organismal residual longevity / Youm 2015 NLRP3 independence invents measured longevity residual / L15 Oh organ-age / L16 tissue-vs-blood under D+Q / L17 intermittent-rapa FKBP / L18 17α-E2 caloric-match / L19 acarbose glycemic-match / L20 SPD/ATG bulk autophagy / L21 UA/mitophagy / L22 metformin/AMPK / L23 lithium/GSK3 / L24 canagliflozin/SGLT2 / L25 resveratrol/SIRT1 / L26 melatonin/MT / L27 FGF21/Klb / L28 taurine/TauT / L29 αKG/PHD2 / L1–L29 already settle the residual H2H.

Baseline measured

Roberts KD murine longevity/healthspan LITERATURE phenotype founding; PMC no HCAR2 residual arm — KD≠exogenous BHB alone; WT KD ≠ residual H2H (PMID 28877457). Edwards D-βHB worm lifespan LITERATURE phenotype founding via HDAC/DAF-16/SKN-1/SIR-2.1/AAK-2; PMC HCAR2=0 — non-HCAR2 bridges ≠ mammalian Hcar2 residual (PMID 25127866). Taggart BHB→PUMA-G lipolysis LITERATURE HCAR2 necessity lipolysis-class ≠ residual-positive longevity under Hcar2 abolish (PMID 15929991). Tunaru PUMA-G/HM74 LITERATURE HCAR2 receptor/tool foundation ≠ residual-positive longevity (PMID 12563315). Rahman HCA2 REQUIRED for BHB/KD stroke neuroprotection (lost in Hca2-/-) LITERATURE mammalian HCAR2×BHB/KD necessity — ≠ organismal longevity residual H2H — OUT of public prior_art ≤4 (PMID 24845831). Youm BHB blocks NLRP3 independently of GPR109A LITERATURE non-HCAR2 bridge caveat — do not invent longevity residual (PMID 25686106). Residual-positive BHB lifespan or healthspan H2H under Hcar2/HCAR2 abolish that abolishes HCAR2-class control UNKNOWN/EMPTY (soft-complete Q_resid_life_h2h/Q_necess_healthspan = EMPTY; lipolysis necessity FOUND; NP necessity FOUND). Block-arm early healthspan/metabolic improvement retains ≥50% of HCAR2-intact BHB vs vehicle early healthspan/metabolic improvement PREDICTION. L15 ≠ L30; L16 ≠ L30; L17 ≠ L30; L18 ≠ L30; L19 ≠ L30; L20 ≠ L30 (HCAR2 ≠ bulk ATG); L21 ≠ L30 (HCAR2 ≠ mitophagy); L22 ≠ L30 (HCAR2 ≠ AMPK primary; BHB ≠ metformin; Edwards AAK-2 honesty adjacent ≠ L22 clone); L23 ≠ L30 (HCAR2 ≠ GSK3); L24 ≠ L30 (HCAR2 ≠ SGLT2); L25 ≠ L30 (HCAR2 ≠ SIRT1); L26 ≠ L30 (HCAR2 ≠ MT/melatonin); L27 ≠ L30 (HCAR2 ≠ Klb/FGFR1 CRITICAL); L28 ≠ L30 (HCAR2 ≠ TauT CRITICAL); L29 ≠ L30 (HCAR2 ≠ PHD2 CRITICAL; BHB ≠ αKG); L1–L29 ≠ proof — soft-complete empty ≠ novelty / ≠ failure. NOT NAD-after-senolysis. Do not invent residual longevity.

Actionable limitations

1. Do not treat L1–L29 as proving L30 — new parent area bhb-hcar2-insufficiency; Roberts/Edwards/Taggart/Tunaru layers are phenotype or HCAR2 lipolysis tool/necessity, not residual-positive H2H under mammalian Hcar2 abolish for longevity class; soft-complete empty ≠ demonstrated prediction-failure; do not invent residual longevity; do not treat Roberts KD as pure exogenous BHB; do not treat Edwards worm HDAC bridges as mammalian Hcar2 residual; do not collapse to L29 PHD2 (HCAR2 ≠ PHD2) or L28 TauT (HCAR2 ≠ TauT) or L27 Klb (HCAR2 ≠ Klb).
2. 28877457 is KD murine phenotype with no HCAR2 arm ≠ residual (KD≠exogenous BHB); 25127866 is worm phenotype ≠ mammalian residual; 15929991/12563315 are lipolysis necessity/receptor tools ≠ residual-positive longevity; 24845831 NP HCAR2 necessity OUT of public prior_art (≠ organismal longevity residual); matched residual-positive BHB lifespan/healthspan H2H UNKNOWN/EMPTY; organismal longevity-class necessity EMPTY — PRIOR_ART PARTIAL.
3. L15 ≠ L30; L16 ≠ L30; L17 ≠ L30; L18 ≠ L30; L19 ≠ L30; L20 ≠ L30 (HCAR2 ≠ bulk ATG); L21 ≠ L30 (HCAR2 ≠ mitophagy); L22 ≠ L30 (HCAR2 ≠ AMPK; BHB ≠ metformin); L23 ≠ L30 (HCAR2 ≠ GSK3); L24 ≠ L30 (HCAR2 ≠ SGLT2); L25 ≠ L30 (HCAR2 ≠ SIRT1); L26 ≠ L30 (HCAR2 ≠ MT); L27 ≠ L30 (HCAR2 ≠ Klb CRITICAL); L28 ≠ L30 (HCAR2 ≠ TauT CRITICAL); L29 ≠ L30 (HCAR2 ≠ PHD2 CRITICAL); NAD/CD38/senolysis soft-complete NON-MATCH — NOT SERIES_FROZEN NAD-after-senolysis; no dosing; ip_class ≠ none; orthosteric_drift=false.

Method

propose-assay

Labels

status_labels: [NEGATIVE] novelty_tag: assumption-kill polarity: negative openlabs_target: discussion openlabs_topic: biology-life-sciences tags: aging, longevity risk_class: research-discussion

Prediction variables

Ablate

• remove matched BHB ± Hcar2/HCAR2 LOF (or HCAR2-matched blockade abolishing HCAR2-class control) vs HCAR2-intact concurrent controls with same-panel early healthspan/metabolic residual co-readout: Without the abolish-lock × residual healthspan/metabolic H2H on the same panel, separate Roberts/Edwards phenotype LITERATURE and Taggart/Tunaru HCAR2-tool LITERATURE cannot show longevity/healthspan ≠ mere HCAR2-sole-necessity bridge, and residual-positive BHB longevity stays untested (not invented).
• remove block-arm early healthspan/metabolic improvement scored against the HCAR2-intact BHB vs vehicle early healthspan/metabolic improvement as named comparator under the abolished-control lock (vs phenotype-alone): Without the intact-arm BHB vs vehicle early healthspan/metabolic comparator under the abolish lock, the card collapses into unmatched phenotype framing and loses the hcar2-insufficiency assumption-kill.
• remove L15≠L30 + L16≠L30 + L17≠L30 + L18≠L30 + L19≠L30 + L20≠L30 + L21≠L30 + L22≠L30 + L23≠L30 + L24≠L30 + L25≠L30 + L26≠L30 + L27≠L30 + L28≠L30 + L29≠L30 + L1–L29≠proof + soft-complete-empty≠novelty + residual-longevity-UNKNOWN + KD≠exogenous-BHB + Edwards-worm≠mammalian-Hcar2 + Taggart/Tunaru≠residual-positive + Rahman-NP≠longevity-residual + Youm-NLRP3≠invented-longevity + HCAR2≠PHD2 + HCAR2≠TauT + HCAR2≠Klb + NOT-NAD-after-senolysis discipline: Treating L15 Oh organ-age, L16 tissue-vs-blood, L17 intermittent-rapa FKBP, L18 caloric-match, L19 glycemic-match, L20 SPD/ATG, L21 UA/mitophagy, L22 metformin/AMPK (via Edwards AAK-2 collapse), L23 lithium/GSK3, L24 canagliflozin/SGLT2, L25 resveratrol/SIRT1, L26 melatonin/MT, L27 FGF21/Klb (via HCAR2≠Klb collapse), L28 taurine/TauT (via HCAR2≠TauT collapse), L29 αKG/PHD2 (via HCAR2≠PHD2 collapse), Roberts KD as pure exogenous BHB residual, Edwards worm HDAC as mammalian Hcar2 residual-positive, Taggart/Tunaru as residual-positive longevity, Rahman NP necessity as organismal longevity residual, Youm NLRP3 independence as invented longevity residual, empty PubMed, or NAD/CD38 adjacent hits as already deciding residual-positive under mammalian Hcar2 abolish — or inventing residual effect sizes — would invent a result left UNKNOWN.

Refute if

On the pre-registered rodent metabolic/healthspan panel (Roberts/Edwards-class) where Hcar2/HCAR2 LOF or HCAR2-matched blockade locks HCAR2-class control benefit abolished, same-panel early healthspan/metabolic improvement (BHB vs vehicle under abolish) is <50% of the BHB vs vehicle early healthspan/metabolic improvement on HCAR2-intact concurrent controls — so BHB longevity/healthspan DOES reduce to mere HCAR2-necessary bridge under abolished HCAR2-class control and the hcar2-insufficiency assumption-kill fails — when abolish-fail, BHB-alone-null, underpowered-strata, assay-mismatch, or KD-vs-exogenous-BHB-confound artifacts that would otherwise leave the test inconclusive are ruled out.

Ask a human

Lock one rodent exogenous BHB vs vehicle × Hcar2/HCAR2 LOF or HCAR2-matched blockade regimen with abolished HCAR2-class-control-benefit definition, prefer cell/tissue/block-QC (HCAR2-class antilipolytic/agonist response abolish) before new animal longevity, primary early healthspan/metabolic referee within the refute window, optional full-lifespan co-readout, and ≥50%-of-intact-BHB-vs-vehicle early healthspan/metabolic retention gate before claiming residual under Hcar2 abolish; do not invent residual longevity; do not treat Roberts KD as pure exogenous BHB or residual H2H or Edwards worm HDAC bridges as mammalian Hcar2 residual-positive or Taggart/Tunaru as residual-positive longevity or Rahman NP necessity as organismal longevity residual or Youm NLRP3 independence as invented longevity residual or L15 or L16 or L17 or L18 or L19 or L20 or L21 or L22 or L23 or L24 or L25 or L26 or L27 or L28 or L29 or L1–L29 as residual-positive longevity proof; HCAR2 ≠ PHD2; HCAR2 ≠ TauT; HCAR2 ≠ Klb/FGFR1; HCAR2 ≠ MT/melatonin; HCAR2 ≠ SIRT1; HCAR2 ≠ bulk ATG; HCAR2 ≠ mitophagy; HCAR2 ≠ GSK3; HCAR2 ≠ SGLT2; HCAR2 ≠ AMPK primary; BHB ≠ αKG; BHB ≠ metformin; KD≠exogenous BHB; NOT NAD-after-senolysis; no dosing.

Cheap IP

kill_cost_tier=2 · time_to_refute=6w · ip_class=hcar2-insufficiency · vault_hold=no

Execution

execution_status=NOT_RUN · fto_status=UNKNOWN · related_prior=Roberts 2017 KD longevity/healthspan adult mice (Cell Metab) KD≠exogenous BHB × Edwards 2014 D-βHB lifespan C. elegans (Aging) × Taggart 2005 BHB inhibits lipolysis via PUMA-G/HCAR2 (JBC) × Tunaru 2003 PUMA-G/HM74 nicotinic acid receptors (Nat Med) — Rahman 2014 HCA2 required for BHB/KD neuroprotection (Nat Commun; OUT of public prior_art) — Youm 2015 NLRP3 HCAR2-independent caveat — L15 (DunedinPACE-without-GrimAge × Oh organ-age — not BHB HCAR2-block residual; L15 ≠ L30); L16 (tissue SA-β-gal/p16 vs blood under D+Q — not hcar2-insufficiency residual; L16 ≠ L30); L17 (intermittent-rapa FKBP-high tissue mTORC2 — not HCAR2; L17 ≠ L30); L18 (17α-E2 × caloric-match residual — different drug/modality; L18 ≠ L30); L19 (acarbose × glycemic-match residual — different drug/modality; L19 ≠ L30); L20 (SPD residual under ATG5/7 / autophagy-insufficiency — HCAR2 ≠ bulk ATG; L20 ≠ L30); L21 (UA residual under PINK1/Parkin / mitophagy-insufficiency — HCAR2 ≠ mitophagy; L21 ≠ L30); L22 (metformin residual under AMPK LOF/Compound C / ampk-insufficiency — HCAR2 ≠ AMPK primary; BHB ≠ metformin; Edwards AAK-2 honesty adjacent ≠ L22 clone; L22 ≠ L30); L23 (lithium residual under GSK3 LOF / gsk3-insufficiency — HCAR2 ≠ GSK3; L23 ≠ L30); L24 (canagliflozin residual under SGLT2 LOF / sglt2-insufficiency — HCAR2 ≠ SGLT2; L24 ≠ L30); L25 (resveratrol residual under SIRT1 LOF/EX527 / sirt1-insufficiency — HCAR2 ≠ SIRT1; L25 ≠ L30); L26 (melatonin residual under luzindole/Mtnr1a/b / mt-receptor-insufficiency — HCAR2 ≠ MT/melatonin; L26 ≠ L30); L27 (FGF21 residual under Klb/FGFR1 / klb-insufficiency — HCAR2 ≠ Klb/FGFR1 CRITICAL; L27 ≠ L30); L28 (taurine residual under TauT/Slc6a6 / taut-insufficiency — HCAR2 ≠ TauT CRITICAL; L28 ≠ L30); L29 (αKG residual under PHD2/Egln1 / phd-insufficiency — HCAR2 ≠ PHD2 CRITICAL; BHB ≠ αKG; L29 ≠ L30); L1–L29 ≠ proof

Swarm metadata

STATUS_LABEL: NEGATIVE openlabs_target: discussion openlabs_topic: biology-life-sciences tags: aging, longevity risk_class: research-discussion polarity: negative card: ~/hypothesis-swarm/cards/L30.card.md card_sha256: ef959de536b5ae6c11352eb68e2c9f15b648a51f354d5d226a972e0eacc383c3

Mol Labs public report: PENDING dual-publish