Spexin

What is Spexin?

Spexin, also called neuropeptide Q (NPQ) or SPX, is a 14-amino-acid peptide hormone encoded by the C12ORF39 gene. It was identified in 2007 through a bioinformatic screen for unannotated secreted peptides and has since been characterized as a selective agonist of galanin receptor 2 (GalR2) and galanin receptor 3 (GalR3) — notably not galanin receptor 1 (GalR1). Spexin is expressed in the brain, pancreas, adipose tissue, gut, gonads, and kidney, and circulates at low picomolar concentrations. Circulating spexin is consistently reduced in humans with obesity, type 2 diabetes, and metabolic-dysfunction-associated fatty liver disease (MAFLD), and preclinical studies show exogenous spexin reduces food intake, body weight, and long-chain fatty acid uptake into adipocytes. Spexin is currently a research molecule — there is no approved spexin drug, no registered clinical trial of exogenous spexin for any indication, and no established therapeutic dose.

What Spexin Is Investigated For

Spexin is most often discussed in the context of obesity and metabolic health, both as a biomarker (levels drop in obesity, T2D, and MAFLD, and rise with weight loss and bariatric surgery) and as a proposed therapeutic. Preclinical evidence is suggestive but early: in rodents and non-human primates, exogenous spexin reduces food intake, body weight, and adipocyte fatty acid uptake via GalR2 activation, and improves glucose tolerance in diet-induced obesity models. What spexin is not: a validated human therapeutic. There is no approved spexin product, no registered clinical trial of exogenous administration, no established dose, no human pharmacokinetic data, and no head-to-head comparison with approved obesity drugs (semaglutide, tirzepatide). The "spexin for weight loss" framing that appears in research-chemical marketing extrapolates from preclinical data and biomarker correlations — real signals, but several development steps short of a proven therapy.

History & Discovery

Spexin was identified in 2007 by Mirabeau and colleagues using a bioinformatic screen of the human genome for secreted peptide hormones that had escaped annotation. Initial functional characterization described effects on cardiovascular function and gastrointestinal motility. The connection to metabolism emerged through work by Walewski and colleagues in 2014, who found that spexin mRNA was the single most down-regulated transcript in obese human adipose tissue — a finding that reframed spexin as a candidate metabolic hormone. Subsequent work from Kim and colleagues established the GalR2/GalR3 receptor selectivity in 2014–2015, which pharmacologically grounded the observed metabolic effects. Since then, the field has accumulated a growing biomarker literature in humans (obesity, T2D, MAFLD, PCOS, cardiovascular disease) and a parallel preclinical therapeutic literature in rodents and non-human primates, but translation to human clinical trials has not yet occurred.

How It Works

Spexin is a small hormone your body makes in the brain, pancreas, gut, and fat tissue. It acts on two of the three galanin receptors (GalR2 and GalR3), telling the body to eat less and store less fat. People with obesity and diabetes tend to have low spexin levels, and in animal studies giving spexin causes weight loss. But it has never been tested as a drug in humans — there is no approved spexin product, and "spexin" sold online is a research chemical, not a validated therapy.

Spexin is a 14-amino-acid amidated peptide (NWTPQAMLYDLKGAQ) derived from a 116-aa preproprotein encoded by the C12ORF39 gene on chromosome 12. It is highly conserved across vertebrates and is expressed in brain (especially hypothalamus and brainstem), pancreas, adipose tissue, gastrointestinal tract, gonads, kidney, and heart. Spexin binds to galanin receptor 2 (GalR2) and galanin receptor 3 (GalR3) — both Gi/Go-coupled GPCRs — with low nanomolar affinity, but does not activate GalR1. This receptor selectivity is unusual among galanin-family peptides and is what gives spexin its distinctive pharmacology. Central administration of spexin in rodents reduces food intake, body weight, and orexigenic neuropeptide expression in the arcuate nucleus. Peripheral administration reduces long-chain fatty acid uptake into adipocytes (via GalR2 on adipose tissue), improves glucose tolerance, and reduces plasma lipids in diet-induced obesity models. Additional effects described in preclinical work include modulation of cardiovascular function (reduced heart rate and blood pressure in some models), anxiolytic behavior (via GalR2 in the amygdala), antinociception, modulation of reproductive hormone secretion, and effects on gastrointestinal motility. A 2026 rat study (Saltık et al., Pflügers Arch) extended the GI mechanism specifically: spexin disrupted the fasting migrating myoelectric complex in jejunal and ileal segments, and the effect was blocked by the GalR2 antagonist M871 and partially by the muscarinic antagonist atropine — implicating GalR2 with an indirect muscarinic contribution as the receptor route for spexin's gut-motility effects. Circulating spexin in humans is reduced ~50% or more in obesity, type 2 diabetes, MAFLD, polycystic ovary syndrome, and several other metabolic states, and rises with weight loss. A growing 2025–2026 literature also identifies exercise as a non-pharmacological lever for endogenous spexin — multiple systematic reviews and meta-analyses now report that aerobic and combined-modality exercise programs raise circulating spexin in adults with obesity and type 2 diabetes, paralleling the metabolic improvements they produce.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Spexin:

• 01No published human clinical trial of exogenous spexin for any indication.
• 02No human pharmacokinetic data — half-life, bioavailability, and effective plasma concentration in humans are unknown.
• 03Whether selective GalR2/GalR3 activation is sufficient for clinically meaningful weight loss in humans, or whether additional receptor engagement is required.
• 04Long-term effects of chronic GalR2/GalR3 activation on mood, anxiety, reproduction, pain perception, and cardiovascular function.
• 05Whether spexin's antifibrotic and cardiometabolic effects in preclinical models reflect direct receptor pharmacology or secondary effects of improved metabolic state.
• 06Whether a small-molecule GalR2/GalR3 agonist is a more viable drug-development path than the peptide itself.

Forms & Administration

Spexin is not available as an approved therapy. In preclinical studies, synthetic spexin is administered subcutaneously, intraperitoneally, or by intracerebroventricular injection depending on the research question. The peptide is small but likely has limited oral bioavailability without reformulation. No human clinical pharmacokinetic or dosing data exist. The practical clinical path to elevating endogenous spexin today is through weight loss — diet, exercise, or bariatric surgery — all of which tend to normalize circulating levels.

Common Questions

Who Spexin Is NOT For

Drug & Supplement Interactions

No characterized drug interactions exist because spexin has no human pharmacokinetic or clinical dataset. Theoretical interactions include additive appetite suppression with GLP-1 agonists or amylin analogs, potential interference with galaninergic psychiatric research tools, and uncharacterized effects in patients on cardiovascular or endocrine therapy given spexin's broad receptor distribution. None of this has been clinically studied.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions