Three items on this catalog are not peptides at all. NAD+ is a dinucleotide, AICAR a nucleoside from the purine biosynthesis pathway, 5-Amino-1MQ a small-molecule methylquinolinium. They are shelved together because they answer a similar research question, not because they share a chemical class — the subject of our piece on what counts as a peptide.
There is a more specific connection, and it is the reason for this roundup. NAD+ precursors and NNMT inhibitors sit at opposite ends of the same metabolic pipe. One adds material at the supply end; the other blocks a drain. And the most consequential 2026 findings are about the drain — the end nobody was writing marketing copy about.
The pipe, in one paragraph
Cells regenerate NAD+ mostly by salvage rather than synthesis from scratch: nicotinamide (NAM) is converted to nicotinamide mononucleotide (NMN) by NAMPT, and NMN is adenylylated to NAD+. Precursor strategies — nicotinamide riboside (NR), NMN — feed this loop.
NAM has two competing fates. It can re-enter salvage, or it can leave. Nicotinamide N-methyltransferase (NNMT) methylates NAM to 1-methylnicotinamide (1-MNA), consuming a methyl group from S-adenosylmethionine (SAM) in the process. That is the rationale for NNMT inhibition: block the methylation exit and you spare both the salvage substrate and the cell's methyl budget. Separately, 1-MNA is oxidised further to the terminal catabolites 2PY (N1-methyl-2-pyridone-5-carboxamide) and 4PY (N1-methyl-4-pyridone-3-carboxamide), which are excreted.
So: precursors push in at the top, NNMT diverts out the side, and 2PY/4PY are what comes out the bottom. Hold that shape — the 2026 literature runs along it.
What the 2026 systematic reviews actually concluded
Two evidence syntheses published this year are the best available summary of the human record.
Gallagher and Emmanuel, Ageing Research Reviews 2026;116:103057 is a PRISMA-guided systematic review covering January 2010 to October 2025, identifying 113 eligible intervention studies: 33 in humans (28 randomised) and 80 in rodents. The rodent literature was broadly favourable across metabolic, mitochondrial and inflammatory endpoints. In humans, oral NR and NMN consistently demonstrated biochemical target engagement — measurable rises in circulating or cellular NAD-related metabolites — and were generally well tolerated over weeks to months. Effects on functional, metabolic and vascular outcomes were "heterogeneous and often null or endpoint-specific."
The review's most useful finding is an absence. No eligible outcomes trial evaluated intravenous or intramuscular NAD+ itself for anti-ageing or wellness indications. One non-randomised intravenous NMN study contributed short-term safety and biomarker information; an intravenous NAD+ pharmacokinetic pilot was included only as contextual evidence. The parenteral route that dominates commercial framing has essentially no controlled outcome literature behind it.
Yang et al., Nutrients 2026;18(14):2251 (10 July 2026, PROSPERO CRD420261382497) is a meta-analysis of 15 randomised trials of oral NMN, 10 contributing to the safety analysis, durations two to 24 weeks. NMN did not increase adverse events, serious adverse events, withdrawals, or ALT/AST — and produced no significant effect on body weight, BMI, fasting glucose, HbA1c, lipid profile, or systolic blood pressure. Diastolic blood pressure fell slightly; HOMA-IR showed a non-significant downward trend. The authors' summary: tolerability looks favourable, "broad metabolic benefits were not evident."
Two 2026 trials that show the pattern precisely
Martens et al., Alzheimer's & Dementia 2026;22(7):e71605 is a 12-week double-blind placebo-controlled phase 2 pilot of NR in older adults with amnestic mild cognitive impairment (42 completers, 22 NR / 20 placebo). Blood NAD+ increased twofold in the NR group. There were no improvements in cognitive function, total cerebral blood flow, or blood pressure; exploratory analyses suggested regional CBF increases, particularly hippocampal.
That is a clean illustration of a distinction drawn in the evidence hierarchy piece: the compound unambiguously did the biochemical thing it was designed to do, and the prespecified clinical endpoints did not move. Target engagement is a necessary condition, not a result.
Lin et al., The Lancet Neurology 2026;25(5):469-481 is the more instructive design. A 12-week, single-centre, 2 × 2 factorial randomised trial in Friedreich's ataxia (66 randomised, ages 10-40, all completed) tested individualised exercise and NR, alone and combined, against attention control. Primary outcome was change in peak VO2.
The result rewards careful reading. Versus control, NR alone was 0.10 L/min (95% CI -0.05 to 0.26; adjusted p = 0.188) — null. Exercise alone was 0.16 (0.00 to 0.31; adjusted p = 0.103) — also not significant. The combination was 0.21 (0.05 to 0.36; adjusted p = 0.0299) — significant. But the combination was not statistically different from exercise alone (difference -0.05; p = 0.49).
The paper's own interpretation is careful: the combination was safe and increased cardiopulmonary fitness. A secondary account compressing that to "NR improved fitness in Friedreich's ataxia" is not lying — and is not supported by the factorial the investigators deliberately built to answer exactly that question. Read component by component, which is what a factorial is for, NR's contribution over exercise alone was not demonstrated.
The disposal end: 2PY and 4PY
Ferrell et al., Nature Medicine 2024;30:424-434 ("A terminal metabolite of niacin promotes vascular inflammation and contributes to cardiovascular disease risk") found serum 2PY and 4PY associated with increased three-year major adverse cardiovascular event risk across two validation cohorts — adjusted hazard ratios for 4PY of 1.89 (1.26-2.84) and 1.99 (1.26-3.14). A genetic variant linked to both metabolites also associated with soluble VCAM-1, and 4PY, but not its structural isomer 2PY, induced VCAM-1 expression and leukocyte adherence to vascular endothelium in mice. Association plus a candidate mechanism — not an established causal chain in humans.
Wang et al., Atherosclerosis 2025;404:119188 (Zurich, with Hazen and Auwerx among the authors) fed Apoe-knockout mice a high-cholesterol diet with three NR levels for 12 weeks. High-dose NR increased aortic sinus plaque lesions and raised plasma TNFα, IL-6 and LDL-cholesterol. Liver and plasma NAD+ were unchanged — but 4PY rose, hepatic SIRT1 fell and CD38 rose. The authors read this as NAD+ metabolism shifting away from sirtuins toward CD38 and PARP1, and conclude that "caution should be applied with presumed NAD+ boosters in patients with atherosclerosis." This is a rung-2 finding in a genetically modified mouse on a high-cholesterol diet, at the highest of three tested levels — not a human result, and the opposite direction from the hypothesis it was built to test.
Wakabayashi et al., Scientific Reports, 16 June 2026 (doi 10.1038/s41598-026-57552-9) is the newest piece and the most relevant to route claims. A randomised two-period crossover in 14 healthy adult men compared oral versus sublingual NMN over 60 minutes — the sublingual route being promoted on the premise that bypassing hepatic first-pass metabolism raises systemic availability. What it found: incremental AUC was significantly higher for 2PY and 4PY after sublingual dosing, with no significant difference in NMN, NAM, or NAD+ between routes. The authors could not distinguish the metabolic origin of the increase. Caveats are substantial — n = 14, single sex, a 60-minute window, all three authors employed by Meiji Holdings. Still: the measured difference between routes was in the catabolites, not in the molecule anyone is trying to raise.
None of this establishes that NAD+ precursors cause cardiovascular harm in humans. It does establish that the terminal end of the pathway is now an actively studied variable rather than inert exhaust — and that a strategy raising catabolites without raising NAD+ has not done what it set out to do.
The other end: NNMT inhibition, and an empty registry
If 2PY and 4PY come from methylated nicotinamide, NNMT starts them on their way. That is one framing of NNMT inhibition; the stronger framing is the SAM budget.
Li et al., BMC Medicine 2026;24 (12 June 2026) reviews NNMT as a cellular "methylation sink": by consuming SAM and generating S-adenosylhomocysteine, it couples metabolic state to epigenetic remodelling across DNA, RNA and protein. Note where the field's centre of gravity sits — the review is about cancer, covering NNMT upregulation in tumour cells and stromal lineages including cancer-associated fibroblasts. Most 2026 NNMT output is oncology, fibrosis and inflammatory bowel disease, not adipose tissue.
Puleo et al., Trends in Pharmacological Sciences 2026;47(6):638-654 is the year's medicinal-chemistry assessment, and it is blunt about the starting position: NNMT inhibitors have historically suffered "insufficient target engagement, reduced bioavailability, and unknown safety profiles," which have "led to limited preclinical success across diseases." Its optimism is directed at newer drug-like compounds with higher cellular affinity — scaffolds that came after the tool compounds.
Which is the point for this shelf. 5-Amino-1MQ is a 2018-vintage cell-permeable tool compound, characterised in the Neelakantan et al. work in Biochemical Pharmacology and used in the 2022 Scientific Reports diet-plus-inhibition mouse study. It is what a group reaches for to ask whether NNMT inhibition does anything in a model — not the compound the translational literature is now building around.
We checked the registry directly. A ClinicalTrials.gov v2 API search returns zero records for 5-Amino-1MQ, and no registered human trial of any NNMT inhibitor (the two hits for "NNMT" are a gene-expression endometrial study and a terminated hydroxychloroquine surgical study). Per the trial registry literacy piece, a registration is only an intention — here there is not even an intention on file.
AICAR had a quiet year
AICAR's 2026 appearances are almost entirely as a reagent, not a subject: papers on corneal hypoxia, retinal ganglion cells, hepatic steatosis and myocardial ischaemia use AICAR as the standard way to switch on AMPK in a model, then report on something else. A real laboratory role — but that is work about pathways, not about AICAR.
The registry is similarly quiet: two records total, both completed long ago. The prodrug/ZMP mechanism and the acadesine RED-CABG phase 3 futility stop are covered in the metabolic class primer and not re-argued here.
What this means for documentation
A test is meaningful only if it can detect a failure mode the molecule is capable of producing. Amino acid analysis, net peptide content, peptide mapping and counterion lines describe peptides; on a certificate of analysis for a dinucleotide, a nucleoside or a methylquinolinium salt they are template artifacts — evidence about the document, not the material. Look instead for a method matched to the chemistry, and for NAD+ specifically, whether the claim addresses its hygroscopicity and hydrolytic lability. More at /quality/.
FAQ
Does "NAD+ declines with age" establish a deficiency? No. A biomarker that falls with age may be a cause, a consequence, or a proxy for something else entirely — mitochondrial mass, turnover rate, or the load on consuming enzymes. And even if a decline is real, correlation with age does not establish that raising the value restores function. That is the same reasoning gap flagged for telomerase framing in the longevity class primer.
Precursors and NNMT inhibitors both aim to raise NAD+ — are they interchangeable research tools? No. A precursor adds substrate; an NNMT inhibitor spares substrate and alters the cell's methyl-donor economy, which is why the enzyme's most active 2026 literature is epigenetic and oncological rather than metabolic. Different variables, different off-target questions.
Why cover compounds that aren't peptides on a peptide site? Because they are stocked, and because they sort more honestly by mechanism than by chemical class — the metabolic class primer places them on the intracellular tier alongside MOTS-c for the same reason. Their documentation, stability behaviour and pharmacology all follow different rules from the rest of the library.
This article is educational and for the laboratory research community. Trulogic Labs products are sold for laboratory and research use only and are not for human consumption.