Spexin
A small appetite-related peptide whose blood level tracks body weight and blood sugar, studied in people only by measuring it
Spexin is a 14-residue peptide the body makes in fat, the gut, the pancreas and the brain. It was found by searching the genome rather than by isolating a hormone, and it turned up again when obese human fat was found to switch its gene down sharply. In rodents, injected spexin cuts food intake and body weight. In people it has only been measured: blood levels are lower in obesity and type 2 diabetes and rise after weight-loss surgery and exercise training. No one has yet given spexin to a person.
No established human dose Details ↓
Recommended Dosing
No established human dose
Spexin has never been given to a person in any study on this page. Human research has only measured it in blood and tissue, in people with obesity, diabetes or anorexia and before and after surgery or exercise.
What is it?
Spexin was first predicted from the human genome by computer, as a gene likely to code for a secreted peptide. Its mature form is 14 amino acids long with an amidated end, and the same sequence is found in mammals, birds and most fish. Gene-mapping work placed it in one family with galanin and kisspeptin, and lab tests showed that it switches on two of the three galanin receptors, GALR2 and GALR3, but not GALR1.
Interest in spexin as an obesity signal began in 2014, when a microarray screen found its gene was the most strongly reduced gene in fat from obese people, about 15-fold lower in both belly and under-the-skin fat. Blood levels fell in step and moved opposite to leptin. In the same study, giving spexin to rats and mice that had grown fat on a rich diet reduced how much they ate and how much they weighed, and it slowed the uptake of fatty acids into fat cells.
Since then most human studies have been simple comparisons of blood levels. Adults and children with obesity, people with type 1 or type 2 diabetes, and adults with metabolic syndrome tend to have less spexin in their blood than lean or healthy comparison groups. Two 2026 meta-analyses pooled the diabetes studies and found clearly lower levels, but the individual studies disagreed so much that the authors urged caution. Not every study agrees: in one group of adolescents, spexin did not differ between lean, obese and diabetic teenagers.
Spexin also moves with treatment. It rose within six months of gastric bypass in teenage girls, three months after sleeve gastrectomy in adults, and reached the level of lean controls six months after bariatric surgery. Twelve weeks of aerobic or resistance training raised it in men with type 2 diabetes, and a 2026 review of exercise studies found that training lasting three weeks or more raised it, while short bouts did not. These changes show association, not that spexin causes the benefits.
Animal work is broader than the human work and not uniformly positive. Thirty days of spexin improved insulin sensitivity and liver fat in obese and diabetic mice, and it sped bowel transit in mice. A 2025 mouse study found the opposite of protection in the kidney: repeated spexin worsened injury after a loss of blood supply and damaged healthy kidneys too. Spexin is not an approved drug anywhere, and no clinical trial has given it to people, so its effects in humans are unknown.
Mechanism of Action
Spexin acts through two of the receptors galanin uses. Most of what it does has been shown in rodents or cells; in people only its levels have been tracked.
Appetite, through GALR3
In mice, injected spexin reduced eating within hours, an effect a GALR3 blocker removed, with lower NPY activity in the hypothalamus (PMID 32831833).
Fat cells and fatty acids
Spexin slowed fatty-acid uptake into fat cells, and its gene is strongly switched down in obese human fat (PMID 24550067).
Gut movement, through GALR2
In mice it made intestinal muscle contract and sped transit, through GALR2 and L-type calcium channels (PMID 26160593).
Published Research
These studies were read from their PubMed abstracts on October 29, 2026. In people, spexin has only been measured in blood or tissue, before and after surgery, exercise or a glucose drink. Every study that gave spexin as a treatment was done in animals or cells and is labelled that way.
The gene most reduced in obese human fat
A microarray screen of human fat found the spexin gene was the most strongly reduced gene in obesity, about 15-fold lower in omental and subcutaneous fat, with blood spexin falling in parallel and moving opposite to leptin. Injected spexin cut calorie intake and body weight in diet-obese rats and mice without signs of taste aversion, and it reduced fatty-acid uptake into fat cells in the dish.
Where spexin is made, and a glucose drink
Spexin gene and protein were found in many human tissues, notably the adrenal gland, skin, stomach, small intestine, liver, pancreatic islets and fat, with little in muscle. Blood spexin was lower in type 2 diabetes and fell as fasting glucose, HbA1c and LDL cholesterol rose; it also moved opposite to blood glucose during a glucose tolerance test.
Lower in obese teenagers
In 69 adolescents, median spexin was lower in the 51 with obesity than in the 18 of normal weight (0.33 versus 0.42 ng/mL). It was not linked to leptin, adiponectin, insulin or glucose, but spexin level and BMI score together sorted the children into weight groups with high accuracy.
No difference in another teenage group
In 44 adolescents (22 normal weight, 10 obese, 12 obese with type 2 diabetes), fasting spexin was about the same in all three groups and did not change during a glucose tolerance test in 10 lean teenagers. It tracked none of the body-composition, fitness or blood measures, and the authors concluded the data did not support spexin as a metabolic marker in this age group.
Lower in type 1 and type 2 diabetes
In 29 people with type 1 diabetes, 30 with type 2 diabetes and 23 matched controls, fasting spexin was lower in both diabetes groups. Within groups it did not follow glucose, lipids, BMI or cortisol, which led the authors to suggest pancreatic production, rather than current blood-sugar control, may set the level in type 1 diabetes.
Modestly lower in metabolic syndrome
Among 260 adults, those with metabolic syndrome had lower median spexin (0.18 versus 0.26 ng/mL). The gap held under the WHO definition after adjusting for age and BMI; split by sex, the link was seen only in women and faded after adjustment, so the association was described as modest and sex-specific.
Low in anorexia nervosa too
In 30 adolescent inpatients with anorexia nervosa and 15 healthy girls, spexin was lower both while the patients were malnourished and after partial weight recovery, unlike phoenixin, which normalised with weight gain. Low spexin is therefore not specific to excess weight.
Rises after gastric bypass in teenagers
In 12 girls with severe obesity (mean BMI about 52) followed for a year after Roux-en-Y gastric bypass, spexin rose by six months and then held steady. Higher spexin went with lower insulin resistance and higher adiponectin, and its six-month rise tracked the fall in insulin resistance even after allowing for weight lost.
Rises after sleeve gastrectomy
In 30 adults followed for three months after laparoscopic sleeve gastrectomy, plasma spexin was higher at three months, kisspeptin rose by one month and galanin fell. Spexin moved with kisspeptin and opposite to galanin, and correlated with weight and glucose measures.
Back to the lean range six months after surgery
Before surgery, 53 patients with obesity (mean BMI 48.5) had lower spexin than 55 lean adults; three and six months after bariatric surgery their levels had risen to match the lean group. The size of the rise did not predict weight lost or track insulin resistance or CRP.
Exercise training raised it in diabetes
Thirty-six men with type 2 diabetes were randomised to resistance training, aerobic training or no exercise, three days a week for 12 weeks. Spexin rose by about 66% with resistance and 47% with aerobic training, alongside lower insulin resistance and visceral fat indices.
Meta-analysis: training, not single bouts
Six exercise studies in overweight or obese sedentary people and animals met the criteria. Spexin did not change after short bouts of aerobic exercise but rose after programmes of three weeks or longer, across aerobic, combined, interval and other training, alongside changes in metabolic markers.
Meta-analysis: lower in type 2 diabetes
Pooling 13 studies of 1,453 people with type 2 diabetes and 850 controls, spexin was clearly lower in diabetes and lower still in those with complications, while galanin was higher. Heterogeneity was extreme (I2 about 98%) and certainty very low; age was the only factor that explained part of it.
Systematic review of 24 studies
Twelve human and 12 animal or cell studies up to 2018 suggested spexin acts as an appetite-reducing factor with a favourable effect on metabolic status. The human studies were mostly cross-sectional, and the authors called for randomised trials.
A galanin-family peptide for GALR2 and GALR3
Gene-neighbourhood analysis placed spexin, galanin and kisspeptin in one ancient family. In receptor assays spexin activated human, frog and zebrafish GALR2 and GALR3 but not GALR1, and it was far more potent than galanin at GALR3.
Injected spexin reduced eating in mice
A single injection into the abdomen lowered food intake over the following hours in fasted and in freely feeding mice. A GALR3 blocker, but not a GALR2 blocker, cancelled the effect, and spexin lowered NPY gene activity in the hypothalamus.
Thirty days in obese and diabetic mice
Daily spexin for 30 days lowered body weight in healthy and diet-obese mice, improved insulin sensitivity in obese and diabetic mice, raised adiponectin, lowered leptin, and reduced liver fat and inflammatory cytokines.
Faster bowel transit through GALR2
Patients with functional constipation had lower blood spexin. In mice, spexin injections sped transit through the small intestine and colon and made gut muscle contract, an effect blocked by a GALR2 antagonist and by an L-type calcium-channel blocker.
A warning from the kidney
In 28 mice, repeated spexin made kidney injury after a temporary loss of blood supply worse and harmed healthy kidneys as well, with more inflammatory, cell-death and scarring signals through the Wnt/beta-catenin pathway. The authors say this raises concern about its therapeutic use.
Spexin across vertebrates
The review traces the conserved 14-residue sequence (with one substitution in many fish), the gene structure, a second spexin gene found only outside mammals, and the roles reported in insulin release, fat metabolism, feeding and reproduction.
Spexin in liver, fat, muscle and pancreas
This mini-review summarises animal and human work suggesting spexin lowers liver fat accumulation, shifts fat cells towards breaking down fat, raises glucose uptake in muscle and affects insulin secretion, and notes that its therapeutic potential still needs to be established.
No Established Human Dose
Spexin has never been given to a person in any study on this page. Human research has only measured it in blood and tissue, in people with obesity, diabetes or anorexia and before and after surgery or exercise. Every study that administered spexin used mice or rats, and one of them found it harmed the kidney, so there is no human dose and none can be inferred from the animal work.
What this rests on: PMID 24550067, PMID 42573161, PMID 41016963.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Spexin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Spexin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Spexin, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Spexin stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Spexin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
Unknown: no cited half-life and no label or trial duration on this page says how long Spexin lasts or how long it was given. Results reported in the studies are under Published Research.
Side effects, and when to stop or get help
From the Side Effects section: Worse kidney injury after loss of blood supply, and damage to healthy kidneys, with repeated dosing in mice (PMID 41016963); No taste aversion in the first rodent study, which looked for it (PMID 24550067); Faster gut transit in mice, which could matter for anyone with bowel problems (PMID 26160593). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Spexin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“No human safety data exist, because no study has given spexin to people”).
Interactions
Unknown: a PubMed search for human interaction studies of Spexin (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Spexin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder; it checks the measured mass against Spexin's expected mass, 1,619.9 Da, from this entry's molecular data. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not a medicine anywhere: no approval and no human treatment trial in the sources read). Sport: Prohibited (S0 catch-all).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
No human safety data exist, because no study has given spexin to people. From the animal work:
Contraindications & Cautions
Spexin is not a medicine, so there is no label or formal contraindication.
Legal Status
Spexin is a research peptide and a blood marker, not an approved drug.
Frequently Asked Questions
?What is spexin?
A 14-amino-acid peptide made in fat, the gut, the pancreas, the adrenal gland and the brain. It belongs to the galanin and kisspeptin family and acts on galanin receptors 2 and 3.
?Does spexin cause weight loss in people?
Nobody knows, because it has never been given to people. Injected spexin reduced eating and weight in obese rats and mice; in people, blood levels are simply lower in obesity and rise after weight-loss surgery.
?Is low spexin a sign of diabetes?
Two 2026 meta-analyses found lower spexin in type 2 diabetes, but the studies varied so much that the evidence was rated very low certainty. Spexin is not a validated diagnostic test.
?Does exercise raise spexin?
Training programmes of three weeks or more raised it in the studies pooled by a 2026 review, including a 12-week trial in men with type 2 diabetes; single short bouts of exercise did not.
?Is spexin safe to inject?
There are no human safety data at all. In one 2025 mouse study, repeated spexin worsened kidney injury and harmed healthy kidneys.
?How is spexin related to galanin?
The genes arose from a common ancestor, and spexin activates two of galanin's three receptors, GALR2 and GALR3. It does not activate GALR1.
References
- [clinical-trial] Walewski JL, et al. "Spexin is a novel human peptide that reduces adipocyte uptake of long chain fatty acids and causes weight loss in rodents with diet-induced obesity." Obesity (Silver Spring), 2014;22(7):1643-52. PMID: 24550067.
- [clinical-trial] Gu L, et al. "Spexin peptide is expressed in human endocrine and epithelial tissues and reduced after glucose load in type 2 diabetes." Peptides, 2015;71:232-9. PMID: 26211893.
- [clinical-trial] Kumar S, et al. "Decreased Circulating Levels of Spexin in Obese Children." J Clin Endocrinol Metab, 2016;101(7):2931-6. PMID: 27218269.
- [clinical-trial] Hodges SK, et al. "Effect of obesity and type 2 diabetes, and glucose ingestion on circulating spexin concentration in adolescents." Pediatr Diabetes, 2018;19(2):212-216. PMID: 28626942.
- [clinical-trial] Karaca A, et al. "Decreased Spexin Levels in Patients with Type 1 and Type 2 Diabetes." Med Princ Pract, 2018;27(6):549-554. PMID: 30184546.
- [clinical-trial] Al-Daghri NM, et al. "Spexin Levels Are Associated with Metabolic Syndrome Components." Dis Markers, 2018;2018:1679690. PMID: 30254709.
- [clinical-trial] Pałasz A, et al. "Longitudinal study on novel neuropeptides phoenixin, spexin and kisspeptin in adolescent inpatients with anorexia nervosa - association with psychiatric symptoms." Nutr Neurosci, 2021;24(11):896-906. PMID: 31736434.
- [clinical-trial] Kumar S, et al. "Roux-en-Y gastric bypass surgery in youth with severe obesity: 1-year longitudinal changes in spexin." Surg Obes Relat Dis, 2018;14(10):1537-1543. PMID: 30131311.
- [clinical-trial] Atabey M, et al. "Short-term changes and correlations of plasma spexin, kisspeptin, and galanin levels after laparoscopic sleeve gastrectomy." Surg Today, 2021;51(4):651-658. PMID: 33555434.
- [clinical-trial] Bufano A, et al. "Normalization of Spexin Levels in Patients with Obesity Submitted to Bariatric Surgery." Obes Surg, 2024;34(2):449-455. PMID: 38072893.
- [clinical-trial] Mohammadi A, et al. "Effect of Exercise Training on Spexin Level, Appetite, Lipid Accumulation Product, Visceral Adiposity Index, and Body Composition in Adults With Type 2 Diabetes." Biol Res Nurs, 2022;24(2):152-162. PMID: 34719994.
- [review] Aydemir İ, et al. "Exercise-Induced Regulation of Spexin: Implications for Metabolic Health: A Systematic Review and Meta-Analysis." Medicina (Kaunas), 2026;62(1). PMID: 41597393.
- [review] Mahat RK, et al. "Neuropeptide Alterations in Type 2 Diabetes Mellitus: A Meta-Analysis of Circulating Spexin and Galanin Levels." Endocrinol Diabetes Metab, 2026;9(5):e70303. PMID: 42573161.
- [review] Behrooz M, et al. "Spexin status in relation to obesity and its related comorbidities: a systematic review." J Diabetes Metab Disord, 2020;19(2):1943-1957. PMID: 33520870.
- [pubmed] Kim DK, et al. "Coevolution of the spexin/galanin/kisspeptin family: Spexin activates galanin receptor type II and III." Endocrinology, 2014;155(5):1864-73. PMID: 24517231.
- [pubmed] Lv S, et al. "Peripheral Spexin Inhibited Food Intake in Mice." Int J Endocrinol, 2020;2020:4913785. PMID: 32831833.
- [pubmed] Kolodziejski PA, et al. "30-Day spexin treatment of mice with diet-induced obesity (DIO) and type 2 diabetes (T2DM) increases insulin sensitivity, improves liver functions and metabolic status." Mol Cell Endocrinol, 2021;536:111420. PMID: 34384849.
- [pubmed] Lin CY, et al. "Spexin Enhances Bowel Movement through Activating L-type Voltage-dependent Calcium Channel via Galanin Receptor 2 in Mice." Sci Rep, 2015;5:12095. PMID: 26160593.
- [pubmed] Kulualp K, et al. "Exogenous spexin aggravates renal ischemia reperfusion injury and triggers toxicity in healthy kidneys." Front Med, 2025;19(5):842-854. PMID: 41016963.
- [review] Lim CH, et al. "Evolution of Structural and Functional Diversity of Spexin in Mammalian and Non-mammalian Vertebrate Species." Front Endocrinol (Lausanne), 2019;10:379. PMID: 31275244.
- [review] Harooni E, et al. "Spexin as a metabolic regulatory peptide in liver, adipose tissue, skeletal muscle, and pancreas: evidence from animal models and human studies." Horm Mol Biol Clin Investig, 2025;46(4):177-182. PMID: 41140072.
- [other] UniProt Q9BT56 (SPXN_HUMAN), peptide residues 36-49 with C-terminal glutamine amide, spexin-1; read October 28, 2026. https://www.uniprot.org/uniprotkb/Q9BT56/entry
- [other] PubChem CID 122705996, Spexin: formula C74H114N20O19S, molecular weight 1619.9. Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/122705996
Sources & Citations
Every study on this page was read from its PubMed record on October 29, 2026 (a PubMed search for spexin in titles and abstracts returned 262 records). Sequence from UniProt Q9BT56 and formula from PubChem, read October 28, 2026. Status from Drugs@FDA (openFDA) and the EMA medicines list. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.