Brain hunger-signaling peptide (Neuropeptide W-23)
A natural brain signaling molecule that stimulates appetite and may regulate body weight; discovered in 2002 and used only as a lab research tool.
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Endogenous peptide — produced naturally and routinely synthesized for research
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Endogenous peptide — receptor binding and activity established in published literature
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What this is
Neuropeptide W-23 (NPW-23) is a short signaling molecule made naturally in the brain. It belongs to a two-peptide family — NPW-23 and its slightly longer sibling NPW-30 — both produced from the same precursor gene (prepro-NPW) through proteolytic cleavage. The name "W" comes from the tryptophan residues (single-letter code W) that flank both the N- and C-termini of the mature peptide. NPW-23 was isolated from porcine hypothalamus in 2002 by Shimomura and colleagues at Takeda Chemical Industries (Shimomura 2002) and has no approved clinical use.
History
NPW-23 was discovered in 2002 through a reverse-pharmacology strategy: Shimomura and colleagues exposed Chinese Hamster Ovary (CHO) cells expressing two orphan G-protein-coupled receptors — GPR7 and GPR8 — to porcine hypothalamic extracts, monitoring inhibition of forskolin-induced cAMP production as a readout of receptor activation (Shimomura 2002). This screen identified NPW as the endogenous ligand for both receptors. The receptors were subsequently renamed NPBWR1 (GPR7) and NPBWR2 (GPR8) to reflect their shared ligand family with the related Neuropeptide B. A year later, Ishii, Fei, and Friedman at Rockefeller University showed that male mice with a targeted disruption of the GPR7 gene develop progressive adult-onset obesity, placing NPW-23 and its receptor into the expanding network of hypothalamic energy-balance regulators (Ishii 2003).
What it does
NPW-23 is a neuromodulator with effects on appetite, stress hormones, pain signaling, and cardiovascular tone — all principally studied through central (brain) administration in rodents. Intracerebroventricular (i.c.v.) infusion in rats elevates plasma corticosterone and activates the hypothalamic–pituitary–adrenal (HPA) axis via corticotropin-releasing factor (CRF) neurons in the paraventricular nucleus (Mondal 2003; Sakurai 2013). Central NPW administration also transiently increases food intake in fasted or light-phase rats, while sustained infusion suppresses feeding; conversely, immunoneutralisation of endogenous NPW with anti-NPW antibodies stimulates feeding, indicating that endogenous NPW tonically restrains appetite in certain contexts (Mondal 2003; Sakurai 2013). Intrathecal NPW-23 reduces inflammatory pain responses in rodent models without engaging opioid receptors, suggesting an independent spinal analgesic pathway (Dvorakova 2018). Centrally administered NPW also increases mean arterial blood pressure, heart rate, and plasma catecholamine concentrations in rats, while peripheral vascular studies show NPW-23 modulates the Cav1.2 L-type calcium channel current in vascular smooth muscle cells via NPBWR1 and the PLC/PKC pathway, contributing to arterial tone (Li Ji 2015).
Evidence
- Human: No human intervention trials for NPW-23 have been published. One registered trial (vagus nerve stimulation in systemic lupus erythematosus) measures circulating NPW as an exploratory biomarker but does not administer the peptide. No registered trials on ClinicalTrials.gov involve NPW-23 as a therapeutic agent.
- Animal: Male GPR7 (NPBWR1) knockout mice develop progressive adult-onset obesity with hyperphagia and decreased energy expenditure; female knockouts do not show the same phenotype, indicating sex-specific regulation (Ishii 2003). Exogenous NPW-23 administered i.c.v. elevates corticosterone and activates CRF neurons in rat PVN; CRF antagonist pretreatment blocks this effect (Mondal 2003; Sakurai 2013). Intrathecal NPW-23 suppresses Fos-like immunoreactivity in the spinal dorsal horn during inflammatory pain (Dvorakova 2018).
- In vitro: NPW-23 inhibits forskolin-stimulated cAMP production in CHO cells expressing NPBWR1 or NPBWR2, consistent with Gi-coupled signalling (Shimomura 2002). In rat vascular smooth muscle cells, NPW-23 stimulates PKC phosphorylation, elevates diacylglycerol, and modulates Cav1.2 current via GPR7 (Li Ji 2015).
Known effects
- Appetite modulation — Context-dependent (acute orexigenic; sustained or endogenous tone anorexigenic); Preclinical
- HPA axis activation — Elevates plasma corticosterone via CRF; Preclinical
- Inflammatory pain reduction — Intrathecal; opioid-independent; Preclinical
- Cardiovascular regulation — Increases blood pressure and heart rate (central); modulates vascular smooth muscle Cav1.2 current (peripheral); Preclinical
- Neuroendocrine effects — Stimulates prolactin; inhibits growth hormone; Preclinical
Safety signals
No human safety data exist for exogenous NPW-23 administration. All published evidence comes from rodent pharmacology. The obesity phenotype observed in male NPBWR1 knockout mice (Ishii 2003) suggests that chronic disruption of NPW signalling has metabolic consequences, though the direction of effect (loss vs. gain of NPW activity) remains a subject of investigation given the context-dependent feeding effects.
Regulatory status
- US: Not approved. No IND or clinical development programme identified.
- EU: Not approved.
- Research use: Investigational tool compound only; used in receptor pharmacology, neuroendocrinology, and pain research.
Mechanism
NPW-23 is the 23-residue N-terminal fragment of the 30-residue precursor NPW-30, generated by proteolytic cleavage at a pair of arginine residues at positions 24–25 of prepro-NPW; NPW-23 and NPW-30 are both biologically active, with NPW-23 showing slightly higher potency at NPBWR1 and NPBWR2 (Sakurai 2013). Both receptors couple to inhibitory Gi-class G-proteins, suppressing adenylyl cyclase (cAMP inhibition) and activating GIRK (Kir3) potassium channels; the Gβγ subunit additionally stimulates ERK (p42/p44) activity (Sakurai 2013). NPBWR2 (GPR8) is notably absent from the rodent genome, being expressed only in humans, rabbits, and certain other mammals, making rodents a model for NPBWR1 signalling only (Dvorakova 2018; Singh and Davenport 2006).
NPW-producing cell bodies in rodent brain are restricted to a few midbrain and brainstem nuclei — the Edinger–Westphal nucleus, ventral tegmental area, periaqueductal grey, and dorsal raphe — but their axons project broadly to the extended amygdala (central amygdala and bed nucleus of the stria terminalis), which express the highest levels of NPBWR1 mRNA (Sakurai 2013). The concentration of NPW inputs to limbic structures controlling stress and emotion, alongside the obesity and anxiety-related phenotypes of NPBWR1 knockout animals, positions NPW-23 as a hypothalamic–limbic integrator linking nutritional status, stress, and affect (Sakurai 2013; Dvorakova 2018).
In the periphery, NPW mRNA is expressed in gastric antral G cells, pancreatic islets, adrenal cortex and medulla, thyroid, testes, ovary, kidney, and lung; gastric NPW levels fall during fasting and rise after refeeding, consistent with a nutritional-state sensor role (Dvorakova 2018).
Open questions
- The opposing orexigenic and anorexigenic effects of acute versus sustained central NPW administration remain mechanistically unexplained
- NPBWR2's absence in rodents means that human NPW-23 pharmacology — where both receptors are expressed — may differ substantially from rodent predictions
- A human NPBWR1 polymorphism (rs33977775, 404A>T, Y135F within the conserved DRY motif) shows partially impaired cAMP inhibition and altered emotional responses to facial stimuli, but its metabolic phenotype in humans has not been characterised (Sakurai 2013)
- No selective NPBWR1 agonists or antagonists have advanced to clinical testing
- Whether circulating or CSF NPW levels are altered in human obesity, anxiety disorders, or chronic pain remains unstudied
Related peptides
- Neuropeptide B (NPB) — the closest structural relative; shares NPBWR1/NPBWR2 as ligands and overlapping CNS effects; NPB29 shows selective preference for NPBWR1 (EC50 ~0.23 nM) vs NPBWR2 (EC50 ~15.8 nM), distinguishing it from the less-selective NPW-23 (Sakurai 2013)
- NPW-30 — the longer isoform of the same gene; identical N-terminal sequence, slightly lower receptor potency than NPW-23
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Could steady, low-level activation of the NPW brain receptor prevent obesity even though a single large dose seems to make animals eat more?
If confirmed, this would mean that drugs designed to gently sustain NPW receptor signaling could fight obesity rather than worsen it, opening an entirely new class of weight-loss therapies based on restoring a naturally occurring brake on overeating.
If you shorten or redesign NPW-23, can you keep its ability to reduce overeating while losing the side effect of raising cortisol?
A peptide that activates only the 'helpful' side of this receptor could treat obesity without the metabolic and immune consequences of chronically elevated stress hormones, making it far safer for long-term use in patients with weight-related conditions.
Could an NPW-23-based drug reduce binge eating by calming the brain's stress response and appetite signals simultaneously through a single receptor?
Binge-eating disorder affects millions and has no drugs targeting its stress-eating root cause. If NPW-23 can address both stress hormones and appetite via one receptor, it could offer a new treatment option for people who eat compulsively in response to anxiety or trauma.
Is the very first amino acid of NPW-23 the single most essential contact point that switches on the hunger-regulating receptor?
If one amino acid does most of the work, chemists could build small drug-like molecules that mimic just that contact point. This could lead to oral pills for obesity or eating disorders that are far simpler and cheaper than peptide-based drugs.
Does the 23-amino-acid version of NPW preferentially switch on the GPR7 receptor while leaving the related GPR8 receptor largely untouched?
If true, NPW-23 could be used to study or treat hunger and stress disorders by activating only one of two closely related receptors, potentially reducing side effects that come from hitting both targets at once. This would matter to anyone developing appetite-suppressing drugs that need to avoid off-target cardiovascular effects.
Does the structurally disordered back half of NPW-23 snap into a rigid, receptor-specific shape upon binding, and does this explain why it does not accidentally activate other brain receptors?
Understanding this shape-shifting behavior could explain why NPW-23 is naturally selective, and could guide design of synthetic peptides or small molecules that inherit that selectivity, reducing the risk of off-target neurological effects in any future drug.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9381734728813171 | boltz-2 |
| ranking score | 0.8617234230041504 | boltz-2 |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep04486,
sequence = {WYKHVASPRYHTVGRAAGLLMGL},
target = {npbwr1},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}