NAD+ TECHNICAL APPENDIX

Pharmacology-Level Structured Reference Document

Machine-Facing Tertiary Page — v1.0 | Compiled 2026-03-04

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Document Classification: Technical Appendix — NOT marketing copy Intended Use: Structured evidence repository for internal reference, pipeline ingestion, and authority-layer content generation Evidence Provenance: Peer-reviewed literature through early 2025; all citations drawn from published record. Items marked [VERIFY] require live PubMed confirmation. Items marked [DATA ABSENT] indicate no known published data.

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TABLE OF CONTENTS

1. SECTION 1 — NAD+ SYSTEM ARCHITECTURE
2. SECTION 2 — PHARMACOKINETIC TABLES
3. SECTION 3 — EVIDENCE STRATIFICATION MATRIX
4. SECTION 4 — MECHANISTIC PATHWAY DIAGRAMS
5. SECTION 5 — SPECIES-SPECIFIC CONSTRAINTS
6. SECTION 6 — HIGH-AUTHORITY CITATION CORPUS

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SECTION 1 — NAD+ SYSTEM ARCHITECTURE

1A. Core NAD+ Biosynthesis Pathways

1A.1 Salvage Pathway (NAMPT-Dependent)

The salvage pathway is the dominant route for NAD+ regeneration in most mammalian tissues. It recycles nicotinamide (NAM), the byproduct of all NAD+-consuming enzymes.

NAM ──[NAMPT]──> NMN ──[NMNAT1/2/3]──> NAD+
 │ │
 │ Rate-limiting │ Compartment-specific
 │ Km ≈ 0.9 µM │ isoforms
 │ Homodimer │

Enzyme	Gene	Km (NAM)	Localization	Notes
NAMPT	NAMPT	~0.9 µM	Cytosol (iNAMPT); secreted (eNAMPT)	Rate-limiting; homodimer; expression declines with age
NMNAT1	NMNAT1	~22 µM (NMN)	Nucleus	Primary nuclear NAD+ synthase; critical for PARP1/sirtuin function
NMNAT2	NMNAT2	~45 µM (NMN)	Cytosol, Golgi, axons	Shortest-lived isoform (t½ ~2-4 h); loss triggers Wallerian degeneration
NMNAT3	NMNAT3	~130 µM (NMN)	Mitochondria	Mitochondrial NAD+ maintenance; expression varies by tissue

Key citations:

• Revollo JB, Grimm AA, Imai S. "The NAD biosynthesis pathway mediated by nicotinamide phosphoribosyltransferase regulates Sir2 activity in mammalian cells." J Biol Chem 2004; 279(49):50754-63. PMID: 15381699
• Berger F, Lau C, Dahlmann M, Ziegler M. "Subcellular compartmentation and differential catalytic properties of the three human nicotinamide mononucleotide adenylyltransferase isoforms." J Biol Chem 2005; 280(43):36334-41. PMID: 16118205

1A.2 Preiss-Handler Pathway

Converts dietary nicotinic acid (NA/niacin) to NAD+ in three enzymatic steps.

NA ──[NAPRT]──> NaMN ──[NMNAT1/2/3]──> NaAD ──[NADS]──> NAD+
 │ │
 │ First committed step │ Glutamine-dependent
 │ Epigenetically silenced │ amidation
 │ in some cancers │

Enzyme	Gene	Notes
NAPRT	NAPRT	Nicotinic acid phosphoribosyltransferase; widely expressed; silenced in IDH1-mutant gliomas and some other cancers
NMNAT1/2/3	(shared)	Same enzymes as salvage pathway; accept both NMN and NaMN
NADS	NADS	NAD synthetase; converts NaAD to NAD+ using glutamine as nitrogen donor

Clinical marker: NAAD (nicotinic acid adenine dinucleotide) is a sensitive biomarker of Preiss-Handler pathway flux. Elevated NAAD after NR supplementation paradoxically suggests NR-derived NAD+ is partially routed through this pathway (Trammell et al. 2016).

1A.3 De Novo Tryptophan Pathway (Kynurenine Pathway)

Eight enzymatic steps from L-tryptophan to NAD+. Quantitatively significant primarily in liver and kidney; immunomodulatory in extrahepatic tissues via IDO1.

L-Trp ──[TDO/IDO1/IDO2]──> N-formylkynurenine ──[AFMID]──> L-Kynurenine
 │
 ┌───────────────────────────────────────────────────┘
 │
 v
L-Kynurenine ──[KMO (FAD-dependent)]──> 3-Hydroxykynurenine
 │
 ──[KYNU (PLP-dependent)]──> 3-Hydroxyanthranilic acid
 │
 ──[HAAO]──> ACMS
 │
 ┌───────────────────────────┤
 │ │
 v v
 [spontaneous] [ACMSD/picolinic
 │ carboxylase]
 v │
 Quinolinic acid v
 │ Picolinic acid
 ──[QPRT]──> (exit pathway)
 │
 v
 NaMN ──> NaAD ──> NAD+

Enzyme	Gene	Cofactor	Tissue	Species Notes
TDO	TDO2	Heme	Liver (constitutive)	Conserved across mammals
IDO1	IDO1	Heme	Immune cells, placenta, gut (IFN-γ inducible)	Immunomodulatory; upregulated in inflammation
IDO2	IDO2	Heme	Liver, kidney	Lower activity than IDO1
KMO	KMO	FAD (Vitamin B2)	Liver, kidney	B2 deficiency impairs this step
KYNU	KYNU	PLP (Vitamin B6)	Liver, kidney	B6 deficiency impairs NAD+ synthesis from Trp
ACMSD	ACMSD	Zn²⁺	Liver, kidney	CRITICAL: Extremely high in cats — diverts ACMS → picolinic acid, blocking NAD+ synthesis
QPRT	QPRT	--	Liver, kidney, brain	Rate-limiting for de novo NAD+ from quinolinate

Species-critical note — CATS: Feline ACMSD activity is approximately 30-100× higher than in rats or humans (Ikeda et al. 1965). This effectively blocks the de novo pathway, making cats obligate dietary niacin requirers. All feline NAD+ must derive from preformed vitamin B3 (NA, NAM) or advanced precursors (NR, NMN).

1A.4 Cellular Compartmentalization of NAD+ Pools

NAD+ exists in three functionally distinct subcellular pools that are NOT freely interchangeable:

Compartment	[NAD+]	NAD+/NADH Ratio (free)	Key Consumers	Transport
Nuclear	~100-130 µM	High (~700:1 with cytosol)	SIRT1, SIRT6, SIRT7, PARP1, PARP2	Continuous with cytosol via nuclear pores
Cytosolic	~50-100 µM	~700:1 (free)	SIRT2, PARP-related	Free exchange with nucleus
Mitochondrial	~250-300 µM	~7-8:1 (free)	SIRT3, SIRT4, SIRT5, Complex I	SLC25A51 transporter (identified 2020)

Key compartmentalization discoveries:

• Mitochondria contain 40-70% of total cellular NAD+ at 3-10× higher concentration than cytosol
• SLC25A51 (also known as MCART1) identified as the mitochondrial NAD+ transporter in 2020:
  • Luongo TS, et al. Nature 2020; 588:174-179. PMID: 33177713
  • Kory N, et al. Nature 2020; 588:219-223. PMID: 33177712
• Nuclear and cytosolic NAD+ pools are freely exchangeable through nuclear pores
• Each compartment has its own NMNAT isoform for local NAD+ synthesis

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1B. NAD+ Consumers

1B.1 Sirtuins (SIRT1–SIRT7)

NAD+-dependent protein deacylases. Km values of 100-300 µM position them as sensitive sensors of NAD+ fluctuations.

Sirtuin	Localization	Primary Activity	Key Substrates	Km (NAD+)	Functions
SIRT1	Nucleus (cytosol)	Deacetylase	p53, FOXO1/3/4, PGC-1α, NF-κB, histones H3/H4	~100-150 µM	Metabolic regulation, stress response, inflammation suppression
SIRT2	Cytosol (nucleus)	Deacetylase	α-tubulin, FOXO3a, H4K16, PEPCK	~100-200 µM	Cell cycle regulation, myelination
SIRT3	Mitochondria	Deacetylase	SOD2, LCAD, IDH2, GDH, Complex I subunits	~150-250 µM	Mitochondrial protein acetylation homeostasis, ROS detox
SIRT4	Mitochondria	ADP-ribosyltransferase, lipoamidase	GDH, MCD	~200-300 µM	Glutamine/fatty acid metabolism
SIRT5	Mitochondria	Desuccinylase, demalonylase, deglutarylase	CPS1, SOD1, IDH2	~200-300 µM	Urea cycle, ROS homeostasis
SIRT6	Nucleus (chromatin)	Deacetylase, ADP-ribosyltransferase	H3K9ac, H3K56ac, PARP1	~800 µM (low affinity)	Telomere maintenance, DNA repair, glucose homeostasis
SIRT7	Nucleolus	Deacetylase	H3K18ac, PAF53, GABPβ1	Not well characterized	rDNA transcription, mitochondrial biogenesis

Key reference: Haigis MC, Sinclair DA. "Mammalian sirtuins: biological insights and disease relevance." Annu Rev Pathol 2010; 5:253-295. PMID: 20078221

1B.2 PARPs (Poly-ADP-Ribose Polymerases)

PARP	Localization	NAD+ Consumption	Function
PARP1	Nucleus	Largest single NAD+ consumer; can consume 80-90% of cellular NAD+ under DNA damage	DNA single/double-strand break repair; chromatin remodeling
PARP2	Nucleus	~5-10% of total PARP activity	Backup DNA repair; BER pathway
PARP3	Nucleus	Minor	DSB repair
Tankyrase 1/2	Cytosol/telomeres	Moderate	Telomere maintenance, Wnt signaling

Quantitative context: Under acute genotoxic stress, PARP1 can consume ~150 molecules of NAD+ per minute per PARP1 molecule. Chronic low-grade DNA damage (aging, inflammation) leads to sustained PARP activation, progressively depleting NAD+ pools.

Key reference: Bai P, Cantó C. "The role of PARP-1 and PARP-2 enzymes in metabolic regulation and disease." Cell Metab 2012; 16(3):290-295. PMID: 22921416

1B.3 CD38/CD157

Enzyme	Type	Localization	Products	NAD+ Consumption
CD38	Type II/III transmembrane glycoprotein, NADase	Ubiquitous; plasma membrane (ecto), ER, mitochondria	cADPR, ADPR, NAM	Dominant NADase driving age-related NAD+ decline
CD157 (BST-1)	GPI-anchored	Immune cells, gut	cADPR, ADPR	Minor contributor

CD38 and aging — critical pathway:

• CD38 expression increases 2-3 fold with aging in multiple tissues
• CD38 is upregulated by senescence-associated secretory phenotype (SASP) factors
• SASP-activated macrophages (M1-polarized) are major source of CD38
• CD38 knockout mice are protected from age-related NAD+ decline
• Quantitative: CD38 degrades ~100 molecules of NAD+ for every 1 molecule of cADPR produced (multifunctional NADase)

Key references:

• Camacho-Pereira J, et al. "CD38 dictates age-related NAD decline and mitochondrial dysfunction through an SIRT3-dependent mechanism." Cell Metab 2016; 23(6):1127-1139. PMID: 27304511. DOI: 10.1016/j.cmet.2016.05.006
• Tarragó MG, et al. "A potent and specific CD38 inhibitor ameliorates age-related metabolic dysfunction by reversing tissue NAD+ decline." Cell Metab 2018; 27(5):1081-1095. PMID: 29719225

1B.4 SARM1 (Sterile Alpha and TIR Motif Containing 1)

Parameter	Details
Function	Intrinsic NADase; executioner of axon degeneration (Wallerian degeneration)
Localization	Axons, neurons
Mechanism	Activated by NMN:NAD+ ratio increase (when NMNAT2 degrades); TIR domain has NADase activity
Products	NAM, ADPR, cADPR
Relevance	Neurodegenerative diseases; NR/NMN supplementation may counteract SARM1 by maintaining NAD+ levels

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1C. Age-Related NAD+ Decline Drivers

Quantitative Decline Estimates

Species	Measurement	Decline	Age Range	Citation
Human	Skin NAD+	~50% decline	20-77 years	Massudi et al. 2012, PLoS One 7:e42357
Human	Estimated whole-body	~1-2% per year after 40	Middle age onward	Composite estimate from multiple studies
Mouse	Liver NAD+	~30-40% decline	6 mo → 24 mo	Yoshino et al. 2011; Camacho-Pereira et al. 2016
Mouse	Muscle NAD+	~30-50% decline	Young → old	Multiple studies
Dog	Any tissue	[DATA ABSENT]	--	No published measurements
Cat	Any tissue	[DATA ABSENT]	--	No published measurements

Mechanistic Drivers (Rank-Ordered by Evidence Strength)

┌─────────────────────────────────────────────────────────────────────┐
│ AGE-RELATED NAD+ DECLINE │
│ │
│ ┌──────────────────┐ ┌──────────────────┐ ┌──────────────────┐ │
│ │ 1. CD38 │ │ 2. PARP │ │ 3. NAMPT │ │
│ │ Upregulation │ │ Hyperactivation │ │ Downregulation │ │
│ │ (2-3× increase) │ │ (DNA damage) │ │ (synthesis ↓) │ │
│ │ │ │ │ │ │ │
│ │ SASP → CD38↑ │ │ Accumulated DNA │ │ Circadian │ │
│ │ on macrophages │ │ lesions → chronic │ │ disruption; │ │
│ │ Inflammaging │ │ PARP1 activation │ │ eNAMPT↓ in │ │
│ │ │ │ │ │ adipose tissue │ │
│ └────────┬─────────┘ └────────┬─────────┘ └────────┬─────────┘ │
│ │ │ │ │
│ v v v │
│ ┌──────────────────────────────────────────────────────────────┐ │
│ │ TOTAL NAD+ POOL DEPLETION │ │
│ │ (~50% by age 50-60 in humans) │ │
│ └──────────────────────────────┬───────────────────────────────┘ │
│ │ │
│ v │
│ ┌──────────────────────────────────────────────────────────────┐ │
│ │ DOWNSTREAM CONSEQUENCES │ │
│ │ • Sirtuin activity ↓ (SIRT1/3 below Km) │ │
│ │ • Mitochondrial dysfunction (ETC impairment, ΔΨm loss) │ │
│ │ • DNA repair capacity ↓ (PARP cannot be fully activated) │ │
│ │ • Stem cell exhaustion │ │
│ │ • Chronic inflammation amplification (NF-κB derepression) │ │
│ └──────────────────────────────────────────────────────────────┘ │
│ │ │
│ v │
│ VICIOUS CYCLE / POSITIVE FEEDBACK │
│ (mitochondrial dysfunction → more ROS → │
│ more DNA damage → more PARP → less NAD+) │
└─────────────────────────────────────────────────────────────────────┘

Driver Detail Table

Driver	Mechanism	Evidence Level	Key Citation
CD38 upregulation	Senescent cell SASP → macrophage CD38 expression ↑ → NADase activity ↑	High (genetic + pharmacological confirmation)	Camacho-Pereira et al. 2016, Cell Metab
PARP hyperactivation	Accumulated DNA damage → chronic PARP1 engagement → NAD+ depletion	High (biochemical + in vivo)	Massudi et al. 2012; Bai & Cantó 2012
NAMPT decline	Circadian disruption, adipose dysfunction → reduced NAMPT expression and eNAMPT secretion	Moderate-High	Yoshino et al. 2011; Imai & Yoshino 2013
Inflammaging	Chronic low-grade inflammation → NF-κB → CD38↑, IDO1↑ (tryptophan diversion)	Moderate-High	Covarrubias et al. 2021
Mitochondrial dysfunction	ETC impairment → NADH recycling ↓ → functional NAD+ deficit; ROS↑ → DNA damage → PARP	Moderate (positive feedback evidence)	Gomes et al. 2013, Cell

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1D. NAD+ Precursors — Pathway Entry Points

Precursor	Molecular Weight	Pathway Entry	Key Enzyme	Distinguishing Feature
NR (Nicotinamide Riboside)	255.3 (free base); 290.7 (chloride salt)	Salvage (via NRK)	NRK1/NRK2 → NMN	Bypasses NAMPT (rate-limiting step); no flushing; no SIRT1 inhibition
NMN (Nicotinamide Mononucleotide)	334.2	Salvage (direct or via NR)	NMNAT1/2/3 (if enters cell); or CD73 → NR → NRK1	Absorption route debated (SLC12A8 controversy)
NAM (Nicotinamide)	122.1	Salvage (via NAMPT)	NAMPT (rate-limiting)	Endogenous recycling form; SIRT1 inhibitor at high dose; methyl sink
NA (Nicotinic Acid / Niacin)	123.1	Preiss-Handler	NAPRT	Flushing via GPR109A; potent lipid effects; cheapest form

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1E. Supporting Cofactors

Cofactor	Active Form	Role in NAD+ Metabolism	Deficiency Impact
Riboflavin (Vitamin B2)	FAD, FMN	KMO in de novo pathway requires FAD; Complex I (NADH → NAD+ recycling) requires FMN/FAD	Impaired tryptophan → NAD+ conversion; reduced NADH recycling capacity
Pyridoxine (Vitamin B6)	PLP	KYNU in de novo pathway requires PLP	Blocked kynurenine → 3-HAA step; impaired de novo NAD+ synthesis
Folate (Vitamin B9)	THF	One-carbon metabolism → methionine → SAM (methyl donor for NNMT-mediated NAM clearance)	Impaired NAM methylation/clearance
Cobalamin (Vitamin B12)	Methylcobalamin	Methionine synthase → SAM regeneration	SAM depletion; accumulation of unmethylated NAM
Zinc	Zn²⁺	ACMSD cofactor (de novo pathway branch point)	Altered tryptophan-to-NAD+ flux

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SECTION 2 — PHARMACOKINETIC TABLES

2.1 Nicotinamide Riboside (NR) — PK Profile

Markdown Table

Parameter	Value	Species	Study	Notes
Oral bioavailability (intact NR)	Low; extensive first-pass metabolism	Human	Trammell 2016, Ratajczak 2016	NR→NAM in gut/liver; NAD+ metabolome is PD surrogate
Tmax (blood NAD+)	~8 hours	Human (n=12)	Trammell et al. 2016	Single 1000 mg dose
Tmax (plasma NAM)	~1-2.7 hours	Human (n=12)	Trammell et al. 2016	Primary circulating metabolite
Tmax (plasma Me-NAM)	~3-4 hours	Human (n=12)	Trammell et al. 2016	Methylated metabolite
t½ (intact NR, plasma)	Minutes (very short)	Human	Inferred from Trammell 2016	No formal t½ reported; rapid first-pass
t½ (NAD+ elevation)	~12-16 hours (estimated from washout)	Human	Dellinger et al. 2017	Return to baseline kinetics
Steady-state NAD+	Reached by ~7-8 days	Human	Martens et al. 2018	300 mg/day chronic dosing
NAD+ elevation (blood)	40-90% (dose-dependent)	Human	Trammell 2016; Martens 2018	100-1000 mg dose range
NAD+ elevation (muscle)	~25%	Human (n=12)	Elhassan et al. 2019	First direct human muscle measurement
Liver NAD+ increase	50-80%	Mouse	Cantó et al. 2012	400 mg/kg/day
Muscle NAD+ increase	30-50%	Mouse	Cantó et al. 2012	400 mg/kg/day
Brain NAD+ increase	20-30%	Mouse	Multiple studies	Crosses BBB
NOAEL (rat, 90-day)	300 mg/kg/day	Rat	Conze et al. 2016	No adverse effects
LD50 (rat, acute)	>5000 mg/kg (not reached)	Rat	Conze et al. 2016	No mortality
Max studied dose (human)	2000 mg/day × 12 weeks	Human (n=40)	Dollerup et al. 2018	Well-tolerated
Typical rodent dose	300-500 mg/kg/day	Mouse/Rat	Multiple	~5-8× HED (BSA-adjusted)
Dog PK	[LIMITED]	Dog	ChromaDex GRN 635 (internal)	GRAS filing safety data not peer-reviewed
Cat PK	[DATA ABSENT]	Cat	--	No published data

Stability Profile

Factor	Sensitivity	Details
Heat	Moderate	NR-Cl degrades >40-50°C; 10-15% loss at 60°C over weeks
Moisture	High	Hygroscopic; glycosidic bond hydrolysis; store <60% RH
pH	Acid-sensitive	pH <3 → hydrolysis to NAM + ribose; most stable pH 5-7
Light	Moderate	UV degradation
Shelf life (NR-Cl, sealed)	24 months at 25°C/60% RH	Commercial NIAGEN specification

Formulation constraint for pet supplements: NR is NOT suitable for baked treats or extruded kibble. Soft chew formulations must control moisture. NR chloride salt is significantly more stable than free-base NR.

NR Safety Summary (Human)

Dose	Duration	n	AEs	Citation
100-1000 mg/day	8 weeks	140	Similar to placebo; mild GI	Conze et al. 2019, Sci Rep 9:9772
1000 mg/day	6 weeks	24	None significant	Martens et al. 2018
2000 mg/day	12 weeks	40	Mild flushing in some	Dollerup et al. 2018
No flushing	--	--	NR does not activate GPR109A	Pharmacological selectivity

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2.2 Nicotinamide Mononucleotide (NMN) — PK Profile

Absorption Route Controversy

Hypothesis	Evidence	Status (2025)
CD73 dephosphorylation → NR → NRK1 uptake	Ratajczak et al. 2016: CD73 cleaves NMN→NR extracellularly; blocking CD73 blocked uptake	Well-established as primary route for most tissues
SLC12A8 direct transport	Grozio et al. 2019 (Nat Metab 1:47-57): Identified SLC12A8 in small intestine; knockdown ↓ NMN uptake	Contested — no independent replication; questioned specificity
Both pathways coexist	--	Current working model

Practical implication: From a PK standpoint, oral NMN and oral NR likely converge on the same intracellular pathway (NMN → NAD+ via NMNAT), regardless of whether NMN enters cells directly or after conversion to NR.

Markdown Table

Parameter	Value	Species	Study	Notes
Oral bioavailability (intact NMN)	Low; detected transiently then rapidly cleared	Human	Igarashi 2022; Fukamizu 2022	Primary circulation as NAM metabolites
Tmax (intact NMN, plasma)	~60 minutes (brief appearance)	Human (n≈30)	Igarashi et al. 2022	Very rapid clearance
Tmax (blood NAD+)	~5-9 hours	Human (n≈30)	Igarashi et al. 2022	Single 250 mg dose
Tmax (plasma NAM)	~1-3 hours	Human (n≈30)	Fukamizu et al. 2022	Same metabolite profile as NR
t½ (intact NMN)	Minutes (extremely rapid)	Human	Multiple	Rapid dephosphorylation/uptake
NAD+ elevation (blood)	38-78% (dose-dependent)	Human (n=80)	Yi et al. 2023	300/600/900 mg/day × 60 days
Liver NAD+ increase	40-60%	Mouse	Mills et al. 2016	300 mg/kg/day × 12 months
Max studied dose (human, RCT)	900 mg/day × 60 days	Human (n=80)	Yi et al. 2023	All doses well-tolerated
Typical rodent dose	100-500 mg/kg/day	Mouse	Multiple	Oral or IP
Dog PK	[DATA ABSENT]	Dog	--	No published data
Cat PK	[DATA ABSENT]	Cat	--	No published data

NMN Stability Profile

Factor	Sensitivity	Details
Heat	Moderate	More heat-stable than NR; degrades >50-60°C
Moisture	High	Hygroscopic; phosphoester bond hydrolysis
pH	Stable pH 5-8	Hydrolyzes at pH <2 or >10
Gastric acid	Partially survives	Some dephosphorylation to NR by brush-border CD73
Storage	2-8°C recommended for bulk	Room temp acceptable short-term with desiccant

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2.3 Nicotinamide (NAM) — PK Profile

Parameter	Value	Species	Citation
Oral bioavailability	~100% (complete absorption)	Human	Knip et al. 2000
Tmax	0.5-1.0 hours	Human	Petley et al. 1995
t½	3-5 hours (dose-dependent; saturable methylation)	Human	Petley et al. 1995
Vd	~0.6-0.7 L/kg	Human	Standard pharmacology
Protein binding	Low (<20%)	Human	Standard reference
Primary metabolites	Me-NAM (NNMT), Me-2-Py, Me-4-Py (aldehyde oxidase)	Human	Shibata & Matsuo 1989
Renal excretion	~30-40% as metabolites	Human	Standard pharmacology
SIRT1 IC50	~50-150 µM (in vitro)	Cell-free	Bitterman et al. 2002
Flushing	None (does not activate GPR109A)	--	Pharmacological selectivity
Methyl sink concern	Yes — NNMT consumes SAM at high doses	>1 g/day	Bogan & Brenner 2008
Dog data	[LIMITED] — NRC dietary requirement only (~4-6 mg/kg BW/day)	Dog	NRC 2006
Cat data	[LIMITED] — NRC dietary requirement (~0.4 mg/kcal DM); cats CANNOT synthesize from Trp	Cat	NRC 2006

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2.4 Nicotinic Acid / Niacin (NA) — PK Profile

Parameter	Value	Species	Citation
Oral bioavailability	~100%	Human	Standard pharmacology
Tmax (IR)	0.5-1.0 hours	Human	Pieper 2003
Tmax (ER/Niaspan)	4-5 hours	Human	FDA label
t½ (parent, IR)	20-45 minutes	Human	Standard PK
Flushing	YES — GPR109A-mediated PGD2/PGE2 release	Human	Tunaru et al. 2003
Lipid effects	HDL↑ 15-35%; LDL↓ 5-25%; TG↓ 20-50%	Human	Knopp 1999
Hepatotoxicity	Dose-related; worse with SR formulations	Human	McKenney et al. 1994
Dog	[LIMITED] — NRC dietary requirement; dogs experience flushing (GPR109A conserved)	Dog	NRC 2006
Cat	[LIMITED] — obligate dietary requirement; no pharmacological PK data	Cat	NRC 2006

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2.5 Master PK Comparison Table

Parameter	NR (NIAGEN)	NMN	NAM	NA (IR)
Oral bioavailability (parent)	Low (first-pass)	Low (dephosphorylation)	~100%	~100%
Oral bioavailability (NAD+ effect)	High	High	Moderate (NAMPT-limited)	High
Tmax (parent)	<1h	~1h	0.5-1h	0.5-1h
Tmax (blood NAD+)	~8h	~5-9h	~2-4h (est.)	~4-8h (est.)
t½ (parent)	Minutes	Minutes	3-5h	20-45 min
NAD+ increase (blood)	40-90% @ 1000 mg/d	38-78% @ 300-900 mg/d	Modest-moderate	Significant @ 1-3 g/d
Flushing	No	No	No	YES
SIRT1 inhibition risk	Low	Low	YES at high dose	No
Methyl sink concern	Partial	Partial	YES	Moderate
Therapeutic range (human)	100-2000 mg/d	250-900 mg/d	100-3000 mg/d	1000-3000 mg/d
Dog PK	[LIMITED]	[ABSENT]	[LIMITED]	[LIMITED]
Cat PK	[ABSENT]	[ABSENT]	[LIMITED]	[LIMITED]

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2.6 Equimolar Dose Comparison

Precursor	MW (g/mol)	mg for 1 mmol	Mass Ratio vs NR-Cl
NR chloride	290.7	290.7	1.00×
NMN	334.2	334.2	1.15×
NAM	122.1	122.1	0.42×
NA	123.1	123.1	0.42×

Implication: 250 mg NMN = ~0.75 mmol; 250 mg NR-Cl = ~0.86 mmol. NR delivers ~15% more moles at equal mg dose. Must account for this in cross-study comparisons.

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2.7 PK Tables — JSON Format

{
 "pk_tables": {
 "generated": "2026-03-04",
 "provenance": "Peer-reviewed literature through early 2025; verify all values against primary sources",
 "precursors": [
 {
 "name": "Nicotinamide Riboside (NR)",
 "form": "NR chloride (NIAGEN)",
 "mw_gmol": 290.7,
 "pathway_entry": "Salvage via NRK1/NRK2",
 "pk_parameters": {
 "oral_bioavailability_parent": "Low (extensive first-pass metabolism to NAM)",
 "oral_bioavailability_nad_effect": "High",
 "tmax_blood_nad_hours": 8,
 "tmax_plasma_nam_hours": "1-2.7",
 "half_life_parent_plasma": "Minutes (not formally determined)",
 "half_life_nad_elevation_hours": "12-16 (estimated)",
 "steady_state_days": "7-8",
 "nad_elevation_blood_percent": "40-90 (dose-dependent, 100-1000 mg)",
 "nad_elevation_muscle_percent": "~25 (1000 mg/day × 21d, Elhassan 2019)",
 "noael_rat_mg_kg_day": 300,
 "ld50_rat_mg_kg": ">5000",
 "max_human_dose_studied_mg_day": 2000,
 "max_human_duration_weeks": 12,
 "flushing": false,
 "sirt1_inhibition": false
 },
 "species_data": {
 "human": {"status": "HIGH", "detail": "Multiple RCTs; PK well-characterized"},
 "mouse": {"status": "HIGH", "detail": "Extensive tissue distribution data"},
 "rat": {"status": "HIGH", "detail": "90-day tox study; GRAS"},
 "dog": {"status": "LIMITED", "detail": "ChromaDex GRAS filing internal data only; no peer-reviewed PK"},
 "cat": {"status": "ABSENT", "detail": "No published data; UGT1A6 deficiency concern"}
 },
 "stability": {
 "heat_sensitivity": "Moderate (degrades >40-50°C)",
 "moisture_sensitivity": "High (hygroscopic; store <60% RH)",
 "ph_stability": "Unstable pH <3; stable pH 5-7",
 "shelf_life_months": 24,
 "formulation_constraints": "Not suitable for baked/extruded products"
 }
 },
 {
 "name": "Nicotinamide Mononucleotide (NMN)",
 "mw_gmol": 334.2,
 "pathway_entry": "Salvage via NMNAT (direct) or CD73→NR→NRK1 (indirect)",
 "pk_parameters": {
 "oral_bioavailability_parent": "Low (rapid dephosphorylation/clearance)",
 "oral_bioavailability_nad_effect": "High",
 "tmax_blood_nad_hours": "5-9",
 "tmax_intact_nmn_plasma_hours": "~1 (transient)",
 "half_life_parent_plasma": "Minutes",
 "nad_elevation_blood_percent": "38-78 (dose-dependent, 300-900 mg/day)",
 "max_human_dose_studied_mg_day": 900,
 "max_human_duration_weeks": "8-12",
 "flushing": false,
 "sirt1_inhibition": false,
 "slc12a8_transporter": "Contested — single-lab finding (Grozio 2019); not independently replicated"
 },
 "species_data": {
 "human": {"status": "HIGH", "detail": "Multiple RCTs; safety established to 900 mg/day"},
 "mouse": {"status": "HIGH", "detail": "12-month long-term study (Mills 2016)"},
 "rat": {"status": "MODERATE", "detail": "Less tox data than NR"},
 "dog": {"status": "ABSENT", "detail": "No published data"},
 "cat": {"status": "ABSENT", "detail": "No published data"}
 },
 "stability": {
 "heat_sensitivity": "Moderate (degrades >50-60°C)",
 "moisture_sensitivity": "High (phosphoester hydrolysis)",
 "ph_stability": "Stable pH 5-8; hydrolyzes pH <2 or >10",
 "storage_recommendation": "2-8°C for bulk powder"
 }
 },
 {
 "name": "Nicotinamide (NAM)",
 "mw_gmol": 122.1,
 "pathway_entry": "Salvage via NAMPT (rate-limiting)",
 "pk_parameters": {
 "oral_bioavailability": "~100%",
 "tmax_hours": "0.5-1.0",
 "half_life_hours": "3-5 (saturable methylation)",
 "vd_L_kg": "0.6-0.7",
 "protein_binding_percent": "<20",
 "sirt1_ic50_uM": "50-150",
 "methyl_sink": true,
 "flushing": false,
 "max_human_dose_studied_mg_day": 3000,
 "hepatotoxicity_threshold_mg_day": ">3000"
 },
 "species_data": {
 "human": {"status": "HIGH", "detail": "Decades of clinical data"},
 "mouse": {"status": "HIGH", "detail": "Extensive"},
 "dog": {"status": "LIMITED", "detail": "NRC dietary requirement only; no pharmacological PK"},
 "cat": {"status": "LIMITED", "detail": "NRC dietary requirement; CANNOT synthesize from Trp"}
 }
 },
 {
 "name": "Nicotinic Acid (NA / Niacin)",
 "mw_gmol": 123.1,
 "pathway_entry": "Preiss-Handler via NAPRT",
 "pk_parameters": {
 "oral_bioavailability": "~100%",
 "tmax_IR_hours": "0.5-1.0",
 "tmax_ER_hours": "4-5",
 "half_life_parent_minutes": "20-45",
 "flushing": true,
 "flushing_receptor": "GPR109A (HCA2)",
 "hdl_increase_percent": "15-35",
 "ldl_decrease_percent": "5-25",
 "max_therapeutic_dose_mg_day": 3000
 },
 "species_data": {
 "human": {"status": "HIGH", "detail": "FDA-approved drug; extensive PK"},
 "mouse": {"status": "HIGH", "detail": "Extensive"},
 "dog": {"status": "LIMITED", "detail": "Dietary requirement; flushing observed"},
 "cat": {"status": "LIMITED", "detail": "Obligate dietary requirement; no pharmacological PK"}
 }
 }
 ]
 }
}

---

SECTION 3 — EVIDENCE STRATIFICATION MATRIX

3.1 Evidence Matrix by Precursor

Nicotinamide Riboside (NR)

Evidence Domain	Rating	Key Evidence
Mechanistic (cell/biochemical)	High	NRK1/NRK2 pathway fully elucidated (Bieganowski & Brenner 2004); crystal structures available; NAMPT bypass confirmed
Rodent healthspan/lifespan	High	HFD protection (Cantó 2012); muscle stem cell rejuvenation + 5% lifespan extension in aged mice (Zhang 2016); cardiac protection (Diguet 2018); neuroprotection (Gong 2013)
Large animal evidence	Limited	ChromaDex internal dog data (GRAS filing); not peer-reviewed; no published PK/PD
Human clinical trials	High	6+ RCTs (Trammell 2016, Martens 2018, Dollerup 2018, Elhassan 2019, Remie 2020, Conze 2019); doses 100-2000 mg; consistent NAD+ elevation
Veterinary clinical trials (dog/cat)	Absent	Zero published trials
Safety data	High (human/rodent); Absent (vet)	NOAEL 300 mg/kg/day rat; up to 2000 mg/day human × 12 weeks; GRAS status
PK robustness	High (human); Absent (vet)	Comprehensive metabolome PK in humans; no vet PK

Nicotinamide Mononucleotide (NMN)

Evidence Domain	Rating	Key Evidence
Mechanistic (cell/biochemical)	High	NMNAT pathway well-characterized; SLC12A8 transporter contested but mechanism understood; CD73-dependent route confirmed
Rodent healthspan/lifespan	High	12-month healthspan study (Mills 2016); insulin sensitivity (Yoshino 2011); mitochondrial rescue (Gomes 2013). No direct lifespan extension published
Large animal evidence	Absent	No published data
Human clinical trials	Moderate-High	5+ RCTs (Irie 2020, Yoshino 2021, Igarashi 2022, Yi 2023, Fukamizu 2022); doses 100-900 mg; consistent NAD+ elevation and safety
Veterinary clinical trials (dog/cat)	Absent	Zero published trials
Safety data	Moderate (human); Absent (vet)	Safe to 900 mg/day × 60 days; less extensive tox profile than NR
PK robustness	Moderate (human); Absent (vet)	Fewer PK studies than NR; SLC12A8 debate adds uncertainty

Nicotinamide (NAM)

Evidence Domain	Rating	Key Evidence
Mechanistic (cell/biochemical)	High	NAMPT pathway is the canonical salvage pathway; decades of enzymology
Rodent healthspan/lifespan	Moderate	Mitchell et al. 2018: healthspan improvement but NO lifespan extension with NAM
Large animal evidence	Limited	Dietary requirement data in dogs/cats; no pharmacological studies
Human clinical trials	High	Extensive clinical use (diabetes prevention ENDIT, dermatology ONTRAC); well-characterized PK
Veterinary clinical trials (dog/cat)	Absent (therapeutic doses)	NRC dietary data only
Safety data	High	Decades of safety data in humans; hepatotoxicity above 3 g/day
PK robustness	High	Fully characterized human PK

Nicotinic Acid (NA)

Evidence Domain	Rating	Key Evidence
Mechanistic (cell/biochemical)	High	Preiss-Handler pathway fully elucidated; GPR109A flushing mechanism characterized
Rodent healthspan/lifespan	Limited	Less studied as longevity intervention due to flushing
Large animal evidence	Limited	Dietary data in dogs/cats; flushing confirmed in dogs
Human clinical trials	High	FDA-approved lipid drug; massive clinical database
Veterinary clinical trials (dog/cat)	Absent (at pharmacological doses)	Dietary data only
Safety data	High	Extensive; flushing, hepatotoxicity, hyperglycemia well-characterized
PK robustness	High	Fully characterized; IR and ER formulations

---

3.2 Cross-Precursor Evidence Summary

EVIDENCE STRENGTH HEAT MAP

 Mechanistic Rodent Large Human Vet Safety PK
 Health Animal RCTs Trials Robust
NR ████████ ████████ ██░░░░ ████████ ░░░░░░ ████████ ████████
NMN ████████ ████████ ░░░░░░ ██████░░ ░░░░░░ ██████░░ ██████░░
NAM ████████ ██████░░ ██░░░░ ████████ ░░░░░░ ████████ ████████
NA ████████ ████░░░░ ██░░░░ ████████ ░░░░░░ ████████ ████████

████ = High ██ = Moderate ░░ = Limited (empty) = Absent

---

3.3 Interpretive Commentary

Where Evidence Is Strongest

1. Mechanistic biochemistry is robust for ALL four precursors. The NAD+ biosynthetic and salvage pathways are among the most thoroughly characterized metabolic networks.
2. Human safety is well-established for NR (up to 2000 mg/day × 12 weeks) and NAM/NA (decades of clinical use). NMN safety data is accumulating rapidly.
3. Rodent healthspan evidence is strong for NR and NMN, with multiple independent replications showing metabolic, cardiovascular, and neuroprotective benefits.

Where Extrapolation Is Occurring

1. ALL veterinary NAD+ supplementation claims are extrapolated from rodent and human data. Zero peer-reviewed veterinary clinical trials exist for any NAD+ precursor (NR, NMN, NAM, or NA) at supraphysiological doses in dogs or cats.
2. Canine dosing is derived from allometric scaling (BSA-adjusted) without species-specific PK validation.
3. Feline safety is extrapolated without accounting for UGT1A6 glucuronidation deficiency, obligate niacin dependency, or CKD prevalence.
4. Age-related NAD+ decline in companion animals is assumed but never measured.

Where Claims Should Be Bounded

1. No veterinary efficacy claims can be supported by direct evidence. All functional benefit statements (mobility, cognition, energy) for dogs/cats are translational hypotheses, not demonstrated outcomes.
2. Feline dosing should be approached with extreme caution given the complete absence of PK/safety data and known metabolic idiosyncrasies.
3. Lifespan extension claims should be limited: only Zhang et al. 2016 showed ~5% extension in aged mice (NR); NMN has not demonstrated lifespan extension. No companion animal lifespan data exists.
4. Head-to-head NR vs NMN comparison in humans has not been published. Claims of superiority of either precursor are not evidence-based.

---

SECTION 4 — MECHANISTIC PATHWAY DIAGRAMS

4.1 NR → NMN → NAD+ Salvage Pathway

 EXTRACELLULAR │ INTRACELLULAR
 │
 │
 NR (oral) │
 │ │
 │ ┌─── Gut/liver first-pass ───────┐ │
 │ │ PNP cleaves glycosidic bond │ │
 │ │ NR → NAM + Ribose │ │
 │ │ (major metabolic fate) │ │
 │ └────────────────────────────────┘ │
 │ │
 │ ┌─── Intact NR absorption ───────┐ │
 │ │ ENT1/ENT2 nucleoside │ │ NR
 │ │ transporters │ │ │
 │ └──────────────────────────┬─────┘ │ │
 │ │ │ │ ┌──────────────┐
 │ └───────────────│──────> │ NRK1/NRK2 │
 │ │ │ │ (kinases) │
 │ │ │ │ ATP→ADP │
 │ │ │ └──────┬───────┘
 │ │ │ │
 │ │ │ v
 │ │ │ NMN
 │ │ │ │
 │ │ │ ┌──────┴───────┐
 │ │ │ │ NMNAT1 │ ← Nucleus
 │ │ │ │ NMNAT2 │ ← Cytosol/axons
 │ │ │ │ NMNAT3 │ ← Mitochondria
 │ │ │ │ ATP→PPi │
 │ │ │ └──────┬───────┘
 │ │ │ │
 │ │ │ v
 │ │ │ NAD+
 │ │ │
 │ ADVANTAGE: Bypasses NAMPT │ │ (Directly enters pool
 │ (rate-limiting salvage step) │ │ without NAMPT bottleneck)

Species evidence: Human, mouse, rat (well-characterized). Dog, cat: NRK1/NRK2 genes conserved but activity not directly measured.

Key citations: Bieganowski & Brenner 2004, Cell; Ratajczak et al. 2016, Nat Commun; Trammell et al. 2016, Nat Commun

---

4.2 NMN Direct Contribution to NAD+ Pools

 NMN (oral)
 │
 ├──────────────────────────────────┐
 │ │
 v v
 ROUTE A: CD73-dependent ROUTE B: SLC12A8-dependent
 (well-established) (contested — Grozio 2019)
 │ │
 │ Ecto-5'-nucleotidase │ Direct NMN transporter
 │ (CD73) on cell surface │ (small intestine)
 │ NMN → NR + Pi │ Na+-dependent
 │ │ │ │
 │ v │ v
 │ NR enters cell │ NMN enters cell directly
 │ via ENT1/2 │ │
 │ │ │ │
 │ v │ │
 │ NRK1 → NMN │ │
 │ │ │ │
 └──────┼───────────────────────────┘ │
 │ │
 v v
 NMN (intracellular) NMN (intracellular)
 │ │
 └───────────┬───────────────────────┘
 │
 v
 NMNAT1/2/3
 (ATP → PPi)
 │
 v
 NAD+

 NET RESULT: Both routes converge on intracellular NMN → NAD+
 PRACTICAL IMPLICATION: Oral NMN and oral NR produce the same
 circulating metabolite profile (NAM, Me-NAM, Me-2-Py, Me-4-Py)

Species evidence: Route A confirmed in human, mouse. Route B: mouse intestine (single lab). No veterinary data.

---

4.3 NAD+ → SIRT1 Activation → Downstream Effects

 NAD+
 │
 ┌───────┴────────┐
 │ SIRT1 │
 │ (deacetylase) │
 │ Km ~100-150µM │
 └───────┬────────┘
 │
 │ Deacetylation + NAM release
 │
 ┌─────────────┼─────────────┐
 │ │ │
 v v v
 ┌──────────┐ ┌──────────┐ ┌──────────────┐
 │ PGC-1α │ │ FOXO1/3 │ │ NF-κB (p65) │
 │ (deAc) │ │ (deAc) │ │ (deAc) │
 └────┬─────┘ └────┬─────┘ └──────┬───────┘
 │ │ │
 v v v
 ┌────────────────┐ ┌──────────┐ ┌──────────────┐
 │ Mitochondrial │ │ Stress │ │ Inflammation │
 │ biogenesis ↑ │ │ resistance│ │ suppression │
 │ OXPHOS genes ↑ │ │ Autophagy│ │ NF-κB target │
 │ FAO genes ↑ │ │ SOD2 ↑ │ │ genes ↓ │
 │ TFAM ↑ │ │ Catalase↑│ │ TNF-α, IL-6 │
 └────────────────┘ │ DNA repair│ │ IL-1β ↓ │
 └──────────┘ └──────────────┘

 FEEDBACK LOOPS:
 • PGC-1α → NAMPT transcription ↑ → more NAD+ (positive feedback)
 • NF-κB suppression → less CD38 induction → less NAD+ degradation
 • FOXO → antioxidant defense → less DNA damage → less PARP consumption

Species evidence: SIRT1 mechanism conserved across all studied mammals (human, mouse, rat). Dog/cat SIRT1 ortholog exists but activity not directly studied in aging context.

---

4.4 NAD+ → PARP Consumption During DNA Repair

 DNA DAMAGE
 (SSB, DSB, oxidative lesions)
 │
 v
 ┌──────────────────────────────────────┐
 │ PARP1 ACTIVATION │
 │ │
 │ PARP1 binds DNA break │
 │ ↓ │
 │ Catalytic activation │
 │ ↓ │
 │ NAD+ → PAR chains + NAM │
 │ (up to 150 NAD+/min/PARP1) │
 │ ↓ │
 │ PAR chains recruit repair factors │
 │ (XRCC1, DNA Ligase III, Pol β) │
 │ │
 └──────────────┬───────────────────────┘
 │
 ┌─────────┴──────────┐
 │ │
 v v
 SUCCESSFUL REPAIR EXCESSIVE DAMAGE
 (NAD+ recovery) (chronic activation)
 │ │
 v v
 PAR degradation NAD+ depletion
 (PARG enzyme) (80-90% consumed)
 NAD+ recycled │
 v
 ┌──────────────┐
 │ CONSEQUENCES │
 │ │
 │ • Sirtuin │
 │ activity ↓ │
 │ • ATP crisis │
 │ (glycolysis│
 │ impaired) │
 │ • Parthanatos│
 │ (PAR→AIF→ │
 │ cell death)│
 └──────────────┘

 AGING CONTEXT:
 Accumulated DNA damage → chronic low-grade PARP activation
 → sustained NAD+ drain → "silent" NAD+ depletion over decades

Species evidence: PARP1 mechanism highly conserved. Quantified primarily in human and mouse cells.

---

4.5 CD38-Mediated NAD+ Degradation

 ┌─────────────────────────────────────────────────────────┐
 │ AGING │
 │ │
 │ Senescent cells accumulate │
 │ │ │
 │ v │
 │ SASP (Senescence-Associated Secretory Phenotype) │
 │ IL-6, TNF-α, MCP-1, etc. │
 │ │ │
 │ v │
 │ Macrophage polarization (M1/M2 shift) │
 │ │ │
 │ v │
 │ CD38 UPREGULATION (2-3× with age) │
 │ (on macrophages, endothelial cells, T cells) │
 └──────────────────────┬──────────────────────────────────┘
 │
 v
 ┌──────────────────────────────────────────────────┐
 │ CD38 NADase ACTIVITY │
 │ │
 │ LOCATION: Plasma membrane (ecto), ER, mito │
 │ │
 │ NAD+ ──[CD38]──> cADPR + NAM │
 │ NAD+ ──[CD38]──> ADPR + NAM │
 │ NMN ──[CD38]──> NR + Pi (also degrades NMN!) │
 │ │
 │ STOICHIOMETRY: ~100 NAD+ consumed per │
 │ 1 cADPR produced (extremely wasteful) │
 │ │
 │ CONSEQUENCE: CD38 is the dominant NADase │
 │ driving age-related NAD+ decline │
 └──────────────────────┬───────────────────────────┘
 │
 v
 ┌──────────────────────────────────────────────────┐
 │ TISSUE NAD+ DEPLETION │
 │ │
 │ CD38 KO mice: PROTECTED from age-related │
 │ NAD+ decline (Camacho-Pereira 2016) │
 │ │
 │ 78c (CD38 inhibitor): Restores NAD+ in aged │
 │ mice (Tarragó et al. 2018) │
 └──────────────────────────────────────────────────┘

Species evidence: CD38 mechanism demonstrated in mouse. Human CD38 upregulation with aging confirmed in tissue studies. Dog/cat: CD38 ortholog conserved, but age-related expression not studied.

---

4.6 NAD+ and Mitochondrial Function

 ┌─────────────────────────────────────────────────────┐
 │ MITOCHONDRIAL NAD+ POOL │
 │ [NAD+] ~250-300 µM │
 │ NAD+/NADH ratio ~7-8:1 (free) │
 │ │
 │ ENTRY: SLC25A51 transporter (Luongo 2020) │
 │ LOCAL SYNTHESIS: NMNAT3 │
 │ │
 │ ┌───────────────────────────────────────────┐ │
 │ │ ELECTRON TRANSPORT CHAIN │ │
 │ │ │ │
 │ │ NADH ──[Complex I]──> NAD+ + H⁺ + e⁻ │ │
 │ │ (FMN/FAD-dependent) │ │
 │ │ │ │
 │ │ NAD+/NADH ratio controls: │ │
 │ │ • TCA cycle flux │ │
 │ │ • β-oxidation rate │ │
 │ │ • ATP production │ │
 │ └───────────────────────────────────────────┘ │
 │ │
 │ ┌───────────────────────────────────────────┐ │
 │ │ SIRT3 ACTIVITY │ │
 │ │ │ │
 │ │ NAD+ ──[SIRT3]──> NAM + Ac-substrate │ │
 │ │ │ │
 │ │ Deacetylates: │ │
 │ │ • SOD2 → ↑ ROS detoxification │ │
 │ │ • LCAD → ↑ fatty acid oxidation │ │
 │ │ • IDH2 → ↑ NADPH → glutathione recycling │ │
 │ │ • Complex I subunits → ↑ ETC efficiency │ │
 │ └───────────────────────────────────────────┘ │
 │ │
 │ AGING VICIOUS CYCLE: │
 │ NAD+↓ → SIRT3↓ → SOD2 hyperacetylated → │
 │ ROS↑ → mtDNA damage → ETC dysfunction → │
 │ NADH recycling↓ → functional NAD+↓↓ │
 │ (positive feedback loop) │
 └─────────────────────────────────────────────────────┘

Species evidence: Mitochondrial NAD+ biology is highly conserved across mammals. SLC25A51 identified in human and mouse. Veterinary species: assumed conserved, not directly studied.

---

SECTION 5 — SPECIES-SPECIFIC CONSTRAINTS

5.1 DOG (Canis lupus familiaris)

Available Data

Domain	Status	Details
Baseline NAD+ levels	[DATA ABSENT]	Never measured in any canine tissue
Age-related NAD+ decline	[DATA ABSENT]	Assumed from rodent/human; never demonstrated in dogs
NR/NMN PK	[LIMITED]	ChromaDex GRAS filing (GRN 635) internal dog safety data; not peer-reviewed; no Cmax, Tmax, AUC, or t½ published
NR/NMN efficacy	[DATA ABSENT]	Zero published interventional studies
Niacin tolerance	[LIMITED]	Dogs experience flushing with NA (GPR109A conserved); dietary requirements established (NRC 2006)
Dietary niacin requirement	Established	NRC 2006: ~11.4 mg/kg DM; AAFCO: 11.4 mg/kg DM (maintenance)
Tryptophan→NAD+ conversion	Functional	Dogs can synthesize niacin from tryptophan (~60:1 ratio, similar to humans); QPRT functional
Historical significance	High	Canine "black tongue disease" was the animal model that led to niacin discovery (Elvehjem et al. 1938)

Allometric Dose Estimation

Parameter	Value	Basis
BSA Km factor (dog, 10 kg)	20	FDA Guidance 2005
Conversion from mouse dose	Mouse mg/kg × (3/20) = Dog mg/kg	BSA-adjusted
Estimated NR dose (from mouse 400 mg/kg)	~60 mg/kg/day	Allometric; NOT PK-validated
Estimated NR dose for 20 kg dog	~1200 mg/day	Theoretical; no dose-finding study exists
Conversion from human dose	Human mg/kg × 1.8 = Dog mg/kg	BSA-adjusted
Estimated NR dose (from human 15 mg/kg)	~27 mg/kg/day for dog	More conservative; still not validated

Known Safety Considerations

Concern	Assessment
Niacin toxicity	Dogs tolerate dietary niacin well; upper limit ~350 mg NA/kg BW (NRC); pharmacological NAM doses unstudied
Hepatotoxicity	No data for NR/NMN; NAM hepatotoxicity threshold unknown in dogs
Drug interactions	No data on NR/NMN interaction with common veterinary drugs (NSAIDs, antibiotics, chemotherapy)
GI tolerance	Unknown for NR/NMN; anecdotal reports suggest tolerability

Regulatory Status

• NR and NMN are NOT approved feed additives for dogs
• NOT listed in AAFCO Official Publication as recognized nutrients (beyond niacin)
• NASC quality seal available for compliant manufacturers
• FDA exercises enforcement discretion; low current risk but uncertain

---

5.2 CAT (Felis catus)

Critical Metabolic Differences

Feature	Impact	Evidence Level
ACMSD/picolinic acid carboxylase: ~30-100× higher than rat	Cannot synthesize NAD+ from tryptophan; ALL NAD+ must come from preformed B3	High (Ikeda et al. 1965; Da Silva et al. 1952; NRC 2006)
UGT1A6 deficiency (pseudogene)	Deficient glucuronidation → potentially altered NR/NMN metabolite clearance → higher systemic exposure per dose → greater reliance on methylation (NNMT) → increased SAM consumption	High for UGT1A6 deficiency (Court & Greenblatt 2000); ABSENT for NR/NMN-specific impact
Obligate carnivore metabolism	Higher protein catabolism; potentially higher NAD+ turnover	Moderate (inferred)
Slow N-acetylation	Unknown relevance to NAM metabolism	Limited (Trepanier 1999)
CKD prevalence: 30-40% of cats >10 years	Impaired renal clearance of NAD+ metabolites (Me-NAM, Me-2-Py, Me-4-Py) → potential accumulation	High for CKD prevalence (Marino et al. 2014); ABSENT for NAD+ metabolite accumulation

Available Data

Domain	Status	Details
NR/NMN PK	[DATA ABSENT]	Zero published data
NR/NMN safety	[DATA ABSENT]	Zero published data; UGT1A6 deficiency creates genuine safety concern
NR/NMN efficacy	[DATA ABSENT]	Zero published data
NAD+ levels	[DATA ABSENT]	Never measured in any feline tissue in aging context
Dietary niacin requirement	Established	NRC 2006: ~40 mg/kg DM (3.5-4× higher than dogs)

Safety Concerns Specific to Cats

┌─────────────────────────────────────────────────────────────┐
│ FELINE NAD+ PRECURSOR SAFETY MAP │
│ │
│ ┌──────────────────┐ ┌──────────────────────────────┐ │
│ │ UGT1A6 Deficiency│ │ ACMSD Activity (extreme) │ │
│ │ (glucuronidation │ │ → Cannot make NAD+ from Trp │ │
│ │ impaired) │ │ → Obligate B3 requirement │ │
│ └────────┬─────────┘ └──────────────┬───────────────┘ │
│ │ │ │
│ v v │
│ NAM/NR/NMN metabolite All NAD+ dependent on │
│ clearance potentially exogenous supply │
│ SLOWER than in dogs/humans (NA, NAM, NR, or NMN) │
│ │ │ │
│ v │ │
│ Greater reliance on NNMT │ │
│ (methylation clearance) │ │
│ │ │ │
│ v │ │
│ Increased SAM consumption ┌──────────┴──────────────┐ │
│ (methyl donor depletion?) │ CKD (30-40% cats >10y) │ │
│ │ Impaired renal clearance│ │
│ │ of methylated metabolites│ │
│ └──────────────────────────┘ │
│ │
│ BOTTOM LINE: Feline NR/NMN dosing is a genuine │
│ SAFETY UNKNOWN. Simple mg/kg scaling from dogs or │
│ humans is inappropriate. Species-specific PK study │
│ is needed before responsible dosing recommendations. │
└─────────────────────────────────────────────────────────────┘

---

5.3 HUMAN (Homo sapiens)

Clinical NAD+ Trial Overview

Trial	Precursor	Dose	Duration	n	Primary Outcome	NAD+ Change	Citation
Trammell 2016	NR	100-1000 mg single	Acute PK	12	PK profiling	2.7× at 1000 mg (8h)	Nat Commun 7:12948
Martens 2018	NR	1000 mg/day	6 weeks	24	Safety + NAD+	+60% PBMC NAD+	Nat Commun 9:1286
Dollerup 2018	NR	2000 mg/day	12 weeks	40	Insulin sensitivity	NAAD↑; no metabolic benefit	Am J Clin Nutr 108:343
Elhassan 2019	NR	1000 mg/day	21 days	12	Muscle NAD+ metabolome	+25% muscle NAD+	Cell Rep 28:1717
Remie 2020	NR	1000 mg/day	6 weeks	13	Metabolic function	NAD+↑; no functional benefit	Am J Clin Nutr 112:413
Yoshino 2021	NMN	250 mg/day	10 weeks	25	Muscle insulin sensitivity	+25% insulin-stim. glucose disposal	Science 372:1224
Igarashi 2022	NMN	250 mg/day	12 weeks	31	Gait speed, NAD+	+40% blood NAD+; improved gait	NPJ Aging 8:5
Yi 2023	NMN	300-900 mg/day	60 days	80	Dose-response NAD+	Dose-dependent (38-78%)	GeroScience 45:29

Safety/Tolerability Summary

• No serious adverse events in any published NR or NMN trial
• No hepatotoxicity, nephrotoxicity, or hematologic toxicity
• Mild GI symptoms (nausea, bloating) in minority; not significantly different from placebo
• NR does NOT cause flushing (unlike NA)
• Longest published human trial: 12 weeks (Dollerup 2018)

---

5.4 RODENT (Mus musculus / Rattus norvegicus)

Key Lifespan/Healthspan Intervention Data

Study	Precursor	Dose	Duration	Model	Key Finding
Cantó et al. 2012	NR	400 mg/kg/day	8-16 weeks	C57BL/6J HFD	Prevented obesity; improved mitochondrial function; enhanced exercise endurance
Zhang et al. 2016	NR	~400 mg/kg/day	Variable	Aged C57BL/6J (22-24 mo)	Rejuvenated muscle/intestinal stem cells; ~5% lifespan extension
Mills et al. 2016	NMN	100-300 mg/kg/day	12 months	C57BL/6N (5→17 mo)	Reversed age-related physiological decline; improved energy expenditure; no toxicity
Yoshino et al. 2011	NMN	500 mg/kg/day (IP)	Variable	HFD + aged mice	Restored NAD+; improved glucose tolerance
Gomes et al. 2013	NMN	500 mg/kg/day (IP)	1 week	Aged C57BL/6J	Reversed pseudohypoxic state; restored mitochondrial function
Mitchell et al. 2018	NAM	Various	Chronic	C57BL/6J	Healthspan improvement but NO lifespan extension
Diguet et al. 2018	NR	400 mg/kg/day	8 weeks	Heart failure model	Improved cardiac function

Tissue NAD+ Elevation (Rodent Summary)

Tissue	Precursor	Dose (mg/kg/day)	Elevation	Citation
Liver	NR	400	+50-80%	Cantó 2012
Skeletal muscle	NR	400	+30-50%	Cantó 2012
Liver	NMN	300	+40-60%	Mills 2016
Liver	NMN	500 (IP)	+50-100%	Yoshino 2011
Brain	NR	400	+20-30%	Multiple
Kidney	NR/NMN	300-400	Elevated	Multiple

---

5.5 Allometric Scaling Reference Table

Parameter	Mouse	Rat	Dog (10 kg)	Cat (5 kg, est.)	Human (60 kg)
BSA Km factor	3	6	20	~18 (estimated)	37
To convert FROM human dose (mg/kg)	×12.3	×6.2	×1.8	×2.1 (est.)	1.0
Example: Human 15 mg/kg NR	185 mg/kg	93 mg/kg	27 mg/kg	32 mg/kg (est.)	15 mg/kg
Mouse metabolic rate vs human	~7-12× per kg	~5-7× per kg	~2-3× per kg	~3-4× per kg (est.)	Reference

Note: Cat Km value (~18) is estimated from body weight and surface area calculations; not in FDA Guidance (which covers mouse, rat, rabbit, monkey, dog, human).

---

SECTION 6 — HIGH-AUTHORITY CITATION CORPUS

6A. Sectioned Bibliography

6A.1 NAD+ Biology — Landmark Reviews

1. Verdin E. "NAD+ in aging, metabolism, and neurodegeneration." Science 2015; 350(6265):1208-1213. PMID: 26785480. DOI: 10.1126/science.aac4854. Species: Review (multi-species). Evidence type: Review.
2. Cantó C, Menzies KJ, Auwerx J. "NAD+ Metabolism and the Control of Energy Homeostasis: A Balancing Act between Mitochondria and the Nucleus." Cell Metab 2015; 22(1):31-53. PMID: 26118927. DOI: 10.1016/j.cmet.2015.05.023. Evidence type: Review.
3. Yoshino J, Baur JA, Imai SI. "NAD+ Intermediates: The Biology and Therapeutic Potential of NMN and NR." Cell Metab 2018; 27(3):513-528. PMID: 29249689. DOI: 10.1016/j.cmet.2017.11.002. Evidence type: Review.
4. Rajman L, Chwalek K, Sinclair DA. "Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence." Cell Metab 2018; 27(3):529-547. PMID: 29514064. DOI: 10.1016/j.cmet.2018.02.011. Evidence type: Review.
5. Covarrubias AJ, Perrone R, Grozio A, Verdin E. "NAD+ metabolism and its roles in cellular processes during ageing." Nat Rev Mol Cell Biol 2021; 22(2):119-141. PMID: 33353981. DOI: 10.1038/s41580-020-00313-x. Evidence type: Review.
6. Katsyuba E, Romani M, Hober D, Auwerx J. "NAD+ homeostasis in health and disease." Nat Metab 2020; 2(1):9-31. PMID: 32694684. DOI: 10.1038/s42255-019-0161-5. Evidence type: Review.

6A.2 Hallmarks of Aging

7. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. "The Hallmarks of Aging." Cell 2013; 153(6):1194-1217. PMID: 23746838. DOI: 10.1016/j.cell.2013.05.039. Evidence type: Review.
8. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. "Hallmarks of aging: An expanding universe." Cell 2023; 186(2):243-278. PMID: 36599349. DOI: 10.1016/j.cell.2022.11.001. Evidence type: Review.

6A.3 CD38 and Aging

9. Camacho-Pereira J, Tarragó MG, Chini CCS, et al. "CD38 Dictates Age-Related NAD Decline and Mitochondrial Dysfunction through an SIRT3-Dependent Mechanism." Cell Metab 2016; 23(6):1127-1139. PMID: 27304511. DOI: 10.1016/j.cmet.2016.05.006. Species: Mouse. Evidence type: Mechanistic.
10. Tarragó MG, Chini CCS, Kanamori KS, et al. "A Potent and Specific CD38 Inhibitor Ameliorates Age-Related Metabolic Dysfunction by Reversing Tissue NAD+ Decline." Cell Metab 2018; 27(5):1081-1095. PMID: 29719225. DOI: 10.1016/j.cmet.2018.03.016. Species: Mouse. Evidence type: Mechanistic/Preclinical.

6A.4 NAMPT Research

11. Revollo JB, Grimm AA, Imai S. "The NAD biosynthesis pathway mediated by nicotinamide phosphoribosyltransferase regulates Sir2 activity in mammalian cells." J Biol Chem 2004; 279(49):50754-50763. PMID: 15381699. DOI: 10.1074/jbc.M408388200. Species: Human/mouse cells. Evidence type: Mechanistic.
12. Imai SI, Yoshino J. "NAD+ and sirtuins in aging and disease." Trends Cell Biol 2013; 24(8):464-471. PMID: 24786309. DOI: 10.1016/j.tcb.2014.04.002. Evidence type: Review.

6A.5 NR — Clinical and Preclinical

13. Bieganowski P, Brenner C. "Discoveries of nicotinamide riboside as a nutrient and conserved NRK genes establish a Preiss-Handler independent route to NAD+ in fungi and humans." Cell 2004; 117(4):495-502. PMID: 15137942. DOI: 10.1016/S0092-8674(04)00416-7. Species: Yeast/human cells. Evidence type: Mechanistic.
14. Trammell SAJ, Schmidt MS, Weidemann BJ, et al. "Nicotinamide riboside is uniquely and orally bioavailable in mice and humans." Nat Commun 2016; 7:12948. PMID: 27721479. DOI: 10.1038/ncomms12948. Species: Human (n=12), mouse. Evidence type: PK/Clinical.
15. Ratajczak J, Joffraud M, Trammell SAJ, et al. "NRK1 controls nicotinamide mononucleotide and nicotinamide riboside metabolism in mammalian cells." Nat Commun 2016; 7:13103. PMID: 27725675. DOI: 10.1038/ncomms13103. Species: Mouse. Evidence type: Mechanistic.
16. Martens CR, Denman BA, Mazzo MR, et al. "Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults." Nat Commun 2018; 9:1286. PMID: 29599443. DOI: 10.1038/s41467-018-03421-7. Species: Human (n=24). Evidence type: RCT.
17. Dollerup OL, Christensen B, Svart M, et al. "A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects." Am J Clin Nutr 2018; 108(2):343-353. PMID: 29992272. DOI: 10.1093/ajcn/nqy132. Species: Human (n=40). Evidence type: RCT.
18. Elhassan YS, Kluckova K, Fletcher RS, et al. "Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures." Cell Rep 2019; 28(7):1717-1728. PMID: 31412242. DOI: 10.1016/j.celrep.2019.07.043. Species: Human (n=12). Evidence type: Clinical (open-label).
19. Conze D, Brenner C, Kruger CL. "Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults." Sci Rep 2019; 9:9772. PMID: 31278280. DOI: 10.1038/s41598-019-46120-z. Species: Human (n=140). Evidence type: RCT (safety).
20. Cantó C, Houtkooper RH, Pirinen E, et al. "The NAD+ precursor nicotinamide riboside enhances oxidative metabolism and protects against high-fat diet-induced obesity." Cell Metab 2012; 15(6):838-847. PMID: 22682224. DOI: 10.1016/j.cmet.2012.04.022. Species: Mouse. Evidence type: Preclinical.
21. Conze DB, Crespo-Barreto J, Kruger CL. "Safety assessment of nicotinamide riboside, a form of vitamin B3." Hum Exp Toxicol 2016; 35(11):1149-1160. PMID: 26791540. DOI: 10.1177/0960327115626254. Species: Rat. Evidence type: Toxicology.
22. Zhang H, Ryu D, Wu Y, et al. "NAD+ repletion improves mitochondrial and stem cell function and enhances life span in mice." Science 2016; 352(6292):1436-1443. PMID: 27127236. DOI: 10.1126/science.aaf2693. Species: Mouse. Evidence type: Preclinical.
23. Remie CME, Roumans KHM, Moonen MPB, et al. "Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans." Am J Clin Nutr 2020; 112(2):413-426. PMID: 32320006. DOI: 10.1093/ajcn/nqaa072. Species: Human (n=13). Evidence type: RCT.

6A.6 NMN — Clinical and Preclinical

24. Mills KF, Yoshida S, Stein LR, et al. "Long-Term Administration of Nicotinamide Mononucleotide Mitigates Age-Associated Physiological Decline in Mice." Cell Metab 2016; 24(6):795-806. PMID: 28068222. DOI: 10.1016/j.cmet.2016.09.013. Species: Mouse. Evidence type: Preclinical.
25. Yoshino J, Mills KF, Yoon MJ, Imai S. "Nicotinamide mononucleotide, a key NAD+ intermediate, treats the pathophysiology of diet- and age-induced diabetes in mice." Cell Metab 2011; 14(4):528-536. PMID: 21982712. DOI: 10.1016/j.cmet.2011.08.014. Species: Mouse. Evidence type: Preclinical.
26. Grozio A, Mills KF, Yoshino J, et al. "Slc12a8 is a nicotinamide mononucleotide transporter." Nat Metab 2019; 1(1):47-57. PMID: 31131364. DOI: 10.1038/s42255-018-0009-4. Species: Mouse. Evidence type: Mechanistic.
27. Irie J, Inagaki E, Fujita M, et al. "Effect of oral administration of nicotinamide mononucleotide on clinical parameters and nicotinamide metabolite levels in healthy Japanese men." Endocr J 2020; 67(2):153-160. PMID: 31685720. DOI: 10.1507/endocrj.EJ19-0313. Species: Human (n=10). Evidence type: Phase 1 safety.
28. Yoshino M, Yoshino J, Kayser BD, et al. "Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women." Science 2021; 372(6547):1224-1229. PMID: 33888596. DOI: 10.1126/science.abe9985. Species: Human (n=25). Evidence type: RCT.
29. Igarashi M, Nakagawa-Nagahama Y, Miura M, et al. "Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men." NPJ Aging 2022; 8:5. PMID: 35927255 [VERIFY]. DOI: 10.1038/s41514-022-00084-z [VERIFY]. Species: Human (n=31). Evidence type: RCT.
30. Yi L, Maier AB, Tao R, et al. "The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial." GeroScience 2023; 45:29-43. PMID: 36482258 [VERIFY]. DOI: 10.1007/s11357-022-00705-1 [VERIFY]. Species: Human (n=80). Evidence type: RCT.

6A.7 Sirtuin Biology

31. Imai S, Armstrong CM, Kaeberlein M, Guarente L. "Transcriptional silencing and longevity protein Sir2 is an NAD-dependent histone deacetylase." Nature 2000; 403(6771):795-800. PMID: 10693811. DOI: 10.1038/35001622. Species: Yeast. Evidence type: Mechanistic (discovery).
32. Haigis MC, Sinclair DA. "Mammalian sirtuins: biological insights and disease relevance." Annu Rev Pathol 2010; 5:253-295. PMID: 20078221. DOI: 10.1146/annurev.pathol.4.110807.092250. Evidence type: Review.

6A.8 PARP Biology

33. Bai P, Cantó C. "The role of PARP-1 and PARP-2 enzymes in metabolic regulation and disease." Cell Metab 2012; 16(3):290-295. PMID: 22921416. DOI: 10.1016/j.cmet.2012.06.016. Evidence type: Review.
34. Massudi H, Grant R, Braidy N, et al. "Age-Associated Changes In Oxidative Stress and NAD+ Metabolism In Human Tissue." PLoS One 2012; 7(7):e42357. PMID: 22848760. DOI: 10.1371/journal.pone.0042357. Species: Human (tissue). Evidence type: Observational.

6A.9 Mitochondrial NAD+ Transport

35. Luongo TS, Eller JM, Lu MJ, et al. "SLC25A51 is a mammalian mitochondrial NAD+ transporter." Nature 2020; 588(7836):174-179. PMID: 33177713. DOI: 10.1038/s41586-020-2741-7. Species: Human/mouse cells. Evidence type: Mechanistic (discovery).
36. Kory N, Uit de Bos J, van der Rijt S, et al. "MCART1/SLC25A51 is required for mitochondrial NAD transport." Sci Adv 2020; 6(43):eabe5310. [Note: Some sources cite this in Nature — VERIFY exact journal]. PMID: 33177712 [VERIFY]. Species: Human cells. Evidence type: Mechanistic.

6A.10 Comparative/Veterinary Metabolism

37. NRC (National Research Council). Nutrient Requirements of Dogs and Cats. Washington, DC: The National Academies Press; 2006. Evidence type: Reference standard.
38. Ikeda M, Tsuji H, Nakamura S, Ichiyama A, Nishizuka Y, Hayaishi O. "Studies on the biosynthesis of nicotinamide adenine dinucleotide. II. A role of picolinic carboxylase in the biosynthesis of nicotinamide adenine dinucleotide from tryptophan in mammals." J Biol Chem 1965; 240:1395-1401. PMID: 14284754. Species: Cat, rat (comparative). Evidence type: Mechanistic.
39. Court MH, Greenblatt DJ. "Molecular genetic basis for deficient acetaminophen glucuronidation by cats: UGT1A6 is a pseudogene, and evidence for reduced diversity of expressed hepatic UGT1A isoforms." Pharmacogenetics 2000; 10(4):355-369. PMID: 10862526. Species: Cat. Evidence type: Mechanistic.
40. Elvehjem CA, Madden RJ, Strong FM, Woolley DW. "The isolation and identification of the anti-black tongue factor." J Biol Chem 1938; 123:137-149. Species: Dog. Evidence type: Mechanistic (historical landmark).
41. Marino CL, Lascelles BDX, Vaden SL, Gruen ME, Marks SL. "Prevalence and classification of chronic kidney disease in cats randomly selected from four age groups and in cats recruited for degenerative joint disease studies." J Feline Med Surg 2014; 16(6):465-472. PMID: 24217707. Species: Cat. Evidence type: Observational.
42. Gomes AP, Price NL, Ling AJ, et al. "Declining NAD+ induces a pseudohypoxic state disrupting nuclear-mitochondrial communication during aging." Cell 2013; 155(7):1624-1638. PMID: 24360282. DOI: 10.1016/j.cell.2013.11.037. Species: Mouse/human cells. Evidence type: Mechanistic.
43. Diguet N, Trammell SAJ, Tannous C, et al. "Nicotinamide Riboside Preserves Cardiac Function in a Mouse Model of Dilated Cardiomyopathy." Circulation 2018; 137(21):2256-2273. PMID: 29217642. DOI: 10.1161/CIRCULATIONAHA.116.026099. Species: Mouse. Evidence type: Preclinical.
44. Poyan Mehr A, Tran MT, Ralto KM, et al. "De novo NAD+ biosynthetic impairment in acute kidney injury in humans." Nat Med 2018; 24(9):1351-1359. PMID: 30127395. DOI: 10.1038/s41591-018-0138-z. Species: Human/mouse. Evidence type: Translational.
45. Creevy KE, Akey JM, Kaeberlein M, Promislow DEL, et al. "An open science study of ageing in companion dogs." Nature 2022; 602:51-57. PMID: 35110758. DOI: 10.1038/s41586-021-04282-9. Species: Dog. Evidence type: Observational (cohort design).

---

6B. Machine-Readable JSON Citation Corpus

{
 "citation_corpus": {
 "generated": "2026-03-04",
 "provenance": "Peer-reviewed literature through early 2025. PMIDs/DOIs marked [VERIFY] should be confirmed against PubMed.",
 "total_citations": 45,
 "nodes": [
 {
 "node": "NAD+ Biology — Core Reviews",
 "claim_supported": "NAD+ is a central metabolic regulator whose decline with age drives mitochondrial dysfunction, DNA repair impairment, and inflammatory activation across species",
 "citations": [
 {"authors": "Verdin E", "title": "NAD+ in aging, metabolism, and neurodegeneration", "journal": "Science", "year": 2015, "volume": "350(6265)", "pages": "1208-1213", "doi": "10.1126/science.aac4854", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/26785480/", "species": "Multi-species (review)", "evidence_type": "Review"},
 {"authors": "Yoshino J, Baur JA, Imai SI", "title": "NAD+ Intermediates: The Biology and Therapeutic Potential of NMN and NR", "journal": "Cell Metabolism", "year": 2018, "volume": "27(3)", "pages": "513-528", "doi": "10.1016/j.cmet.2017.11.002", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/29249689/", "species": "Multi-species (review)", "evidence_type": "Review"},
 {"authors": "Covarrubias AJ, Perrone R, Grozio A, Verdin E", "title": "NAD+ metabolism and its roles in cellular processes during ageing", "journal": "Nature Reviews Molecular Cell Biology", "year": 2021, "volume": "22(2)", "pages": "119-141", "doi": "10.1038/s41580-020-00313-x", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/33353981/", "species": "Multi-species (review)", "evidence_type": "Review"},
 {"authors": "Katsyuba E, Romani M, Hober D, Auwerx J", "title": "NAD+ homeostasis in health and disease", "journal": "Nature Metabolism", "year": 2020, "volume": "2(1)", "pages": "9-31", "doi": "10.1038/s42255-019-0161-5", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/32694684/", "species": "Multi-species (review)", "evidence_type": "Review"},
 {"authors": "Rajman L, Chwalek K, Sinclair DA", "title": "Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence", "journal": "Cell Metabolism", "year": 2018, "volume": "27(3)", "pages": "529-547", "doi": "10.1016/j.cmet.2018.02.011", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/29514064/", "species": "Multi-species (review)", "evidence_type": "Review"}
 ]
 },
 {
 "node": "CD38-Mediated Age-Related NAD+ Decline",
 "claim_supported": "CD38 is the dominant NADase driving age-related NAD+ decline; its expression increases 2-3× with aging via SASP-mediated macrophage activation",
 "citations": [
 {"authors": "Camacho-Pereira J, Tarragó MG, Chini CCS, et al.", "title": "CD38 Dictates Age-Related NAD Decline and Mitochondrial Dysfunction through an SIRT3-Dependent Mechanism", "journal": "Cell Metabolism", "year": 2016, "volume": "23(6)", "pages": "1127-1139", "doi": "10.1016/j.cmet.2016.05.006", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/27304511/", "species": "Mouse", "evidence_type": "Mechanistic"},
 {"authors": "Tarragó MG, Chini CCS, Kanamori KS, et al.", "title": "A Potent and Specific CD38 Inhibitor Ameliorates Age-Related Metabolic Dysfunction by Reversing Tissue NAD+ Decline", "journal": "Cell Metabolism", "year": 2018, "volume": "27(5)", "pages": "1081-1095", "doi": "10.1016/j.cmet.2018.03.016", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/29719225/", "species": "Mouse", "evidence_type": "Mechanistic/Preclinical"}
 ]
 },
 {
 "node": "NR Oral Bioavailability and Human PK",
 "claim_supported": "NR is orally bioavailable in humans, dose-dependently elevating blood NAD+ by 40-90% at doses of 100-1000 mg; intact NR undergoes extensive first-pass metabolism",
 "citations": [
 {"authors": "Trammell SAJ, Schmidt MS, Weidemann BJ, et al.", "title": "Nicotinamide riboside is uniquely and orally bioavailable in mice and humans", "journal": "Nature Communications", "year": 2016, "volume": "7", "pages": "12948", "doi": "10.1038/ncomms12948", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/27721479/", "species": "Human (n=12), Mouse", "evidence_type": "PK/Clinical"},
 {"authors": "Martens CR, Denman BA, Mazzo MR, et al.", "title": "Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults", "journal": "Nature Communications", "year": 2018, "volume": "9", "pages": "1286", "doi": "10.1038/s41467-018-03421-7", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/29599443/", "species": "Human (n=24)", "evidence_type": "RCT"}
 ]
 },
 {
 "node": "NR Safety Profile",
 "claim_supported": "NR is safe and well-tolerated in humans at doses up to 2000 mg/day for 12 weeks; GRAS status granted; NOAEL 300 mg/kg/day in rats",
 "citations": [
 {"authors": "Conze D, Brenner C, Kruger CL", "title": "Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride)", "journal": "Scientific Reports", "year": 2019, "volume": "9", "pages": "9772", "doi": "10.1038/s41598-019-46120-z", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/31278280/", "species": "Human (n=140)", "evidence_type": "RCT (safety)"},
 {"authors": "Conze DB, Crespo-Barreto J, Kruger CL", "title": "Safety assessment of nicotinamide riboside, a form of vitamin B3", "journal": "Human & Experimental Toxicology", "year": 2016, "volume": "35(11)", "pages": "1149-1160", "doi": "10.1177/0960327115626254", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/26791540/", "species": "Rat", "evidence_type": "Toxicology"}
 ]
 },
 {
 "node": "NMN Dose-Dependent NAD+ Elevation in Humans",
 "claim_supported": "NMN supplementation at 300-900 mg/day dose-dependently increases blood NAD+ levels (38-78%) in healthy adults with no serious adverse events",
 "citations": [
 {"authors": "Yi L, Maier AB, Tao R, et al.", "title": "The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults", "journal": "GeroScience", "year": 2023, "volume": "45", "pages": "29-43", "doi": "10.1007/s11357-022-00705-1", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/36482258/", "species": "Human (n=80)", "evidence_type": "RCT"},
 {"authors": "Yoshino M, Yoshino J, Kayser BD, et al.", "title": "Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women", "journal": "Science", "year": 2021, "volume": "372(6547)", "pages": "1224-1229", "doi": "10.1126/science.abe9985", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/33888596/", "species": "Human (n=25)", "evidence_type": "RCT"}
 ]
 },
 {
 "node": "NMN Long-Term Rodent Healthspan",
 "claim_supported": "12-month NMN supplementation mitigates age-associated physiological decline in mice including body weight, energy expenditure, insulin sensitivity, and eye function",
 "citations": [
 {"authors": "Mills KF, Yoshida S, Stein LR, et al.", "title": "Long-Term Administration of Nicotinamide Mononucleotide Mitigates Age-Associated Physiological Decline in Mice", "journal": "Cell Metabolism", "year": 2016, "volume": "24(6)", "pages": "795-806", "doi": "10.1016/j.cmet.2016.09.013", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/28068222/", "species": "Mouse", "evidence_type": "Preclinical"}
 ]
 },
 {
 "node": "Feline Obligate Niacin Requirement",
 "claim_supported": "Cats cannot synthesize NAD+ from tryptophan due to extremely high ACMSD activity that diverts the kynurenine pathway toward picolinic acid; all feline NAD+ must derive from preformed dietary niacin",
 "citations": [
 {"authors": "Ikeda M, Tsuji H, Nakamura S, Ichiyama A, Nishizuka Y, Hayaishi O", "title": "Studies on the biosynthesis of nicotinamide adenine dinucleotide. II. A role of picolinic carboxylase", "journal": "Journal of Biological Chemistry", "year": 1965, "volume": "240", "pages": "1395-1401", "doi": null, "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/14284754/", "species": "Cat, Rat (comparative)", "evidence_type": "Mechanistic"},
 {"authors": "NRC", "title": "Nutrient Requirements of Dogs and Cats", "journal": "National Academies Press", "year": 2006, "doi": null, "pubmed_url": null, "species": "Dog, Cat", "evidence_type": "Reference standard"}
 ]
 },
 {
 "node": "Feline UGT1A6 Deficiency",
 "claim_supported": "Cats are deficient in UGT1A6 glucuronidation, which may alter clearance kinetics of NAD+ precursor metabolites and increase reliance on methylation pathways",
 "citations": [
 {"authors": "Court MH, Greenblatt DJ", "title": "Molecular genetic basis for deficient acetaminophen glucuronidation by cats: UGT1A6 is a pseudogene", "journal": "Pharmacogenetics", "year": 2000, "volume": "10(4)", "pages": "355-369", "doi": null, "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/10862526/", "species": "Cat", "evidence_type": "Mechanistic"}
 ]
 },
 {
 "node": "Veterinary NAD+ Precursor Evidence",
 "claim_supported": "No published peer-reviewed studies exist for NR or NMN supplementation in dogs or cats as of early 2025; all veterinary dosing is extrapolated from rodent/human data via allometric scaling",
 "citations": [
 {"authors": "[DATA ABSENT]", "title": "No canine or feline NR/NMN clinical trials published", "journal": null, "year": null, "doi": null, "pubmed_url": null, "species": "Dog, Cat", "evidence_type": "DATA GAP"}
 ]
 },
 {
 "node": "Mitochondrial NAD+ Transport",
 "claim_supported": "SLC25A51 was identified in 2020 as the mammalian mitochondrial NAD+ transporter, resolving a decades-long question about how mitochondria maintain their NAD+ pool",
 "citations": [
 {"authors": "Luongo TS, Eller JM, Lu MJ, et al.", "title": "SLC25A51 is a mammalian mitochondrial NAD+ transporter", "journal": "Nature", "year": 2020, "volume": "588(7836)", "pages": "174-179", "doi": "10.1038/s41586-020-2741-7", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/33177713/", "species": "Human/Mouse cells", "evidence_type": "Mechanistic (discovery)"}
 ]
 },
 {
 "node": "Hallmarks of Aging Framework",
 "claim_supported": "NAD+ decline intersects with multiple hallmarks of aging including mitochondrial dysfunction, genomic instability, altered intercellular communication, and deregulated nutrient sensing",
 "citations": [
 {"authors": "López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G", "title": "The Hallmarks of Aging", "journal": "Cell", "year": 2013, "volume": "153(6)", "pages": "1194-1217", "doi": "10.1016/j.cell.2013.05.039", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/23746838/", "species": "Multi-species (review)", "evidence_type": "Review"},
 {"authors": "López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G", "title": "Hallmarks of aging: An expanding universe", "journal": "Cell", "year": 2023, "volume": "186(2)", "pages": "243-278", "doi": "10.1016/j.cell.2022.11.001", "pubmed_url": "https://pubmed.ncbi.nlm.nih.gov/36599349/", "species": "Multi-species (review)", "evidence_type": "Review"}
 ]
 }
 ]
 }
}

---

DATA GAP REGISTRY

Gap	Priority	Status	Impact on Claims
Formal NR oral bioavailability (IV comparator) in humans	High	No study published	Cannot quantify absolute bioavailability
NR or NMN PK in dogs	CRITICAL	ChromaDex internal only; no peer-reviewed data	Cannot validate canine dosing
NR or NMN PK in cats	CRITICAL	Completely absent	Feline dosing is a genuine safety unknown
Cat UGT1A6 impact on NR/NMN metabolite clearance	CRITICAL	Completely unstudied	Metabolite accumulation risk unquantified
Feline CKD + NAD+ precursor interaction	CRITICAL	Unstudied; CKD affects 30-40% cats >10y	Renal clearance impairment of NAD+ metabolites
Head-to-head NR vs NMN in humans	High	No published trial	Cannot claim superiority
SLC12A8 independent replication	Moderate	Only Imai lab published	NMN direct transport mechanism uncertain
Long-term (>1 year) human safety for NR or NMN	High	Only mouse long-term data (Mills 2016)	Long-term safety extrapolated
NAD+ tissue levels in humans after NR/NMN (beyond muscle)	High	Only Elhassan 2019 (muscle, NR)	Tissue-specific effects assumed
Canine age-related NAD+ decline	High	Never measured	Fundamental assumption unverified
NR/NMN interaction with veterinary drugs	Important	No data	Drug interaction risk unknown
Dose-response above 1000 mg NR or 900 mg NMN	Moderate	Very limited data	Ceiling effects unknown
NMN lifespan study in mice	Moderate	No direct lifespan study published	Only healthspan data exists for NMN

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DOCUMENT PROVENANCE & LIMITATIONS

Compilation date: 2026-03-04 Data sources: Peer-reviewed literature through early 2025 (training knowledge corpus); subagent-mediated PubMed verification for select DOIs/PMIDs Web search availability: Limited during compilation; some citations verified via PubMed fetch, others from training knowledge Recommended verification: All DOIs, PMIDs, exact page numbers, and volume numbers should be independently verified against PubMed before use in regulatory, commercial, or clinical documentation Post-2025 publications: Any publications from late 2025 or 2026 are NOT captured. Re-verification recommended for: canine/feline NR/NMN studies, new human RCTs, SLC12A8 replication attempts, Dog Aging Project NAD+ sub-studies

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END OF TECHNICAL APPENDIX