A practical reference on nuclear receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-04. Anything still debated is marked as such rather than presented as settled.
Cardarine is a synthetic compound also known as GW501516, GW-501516, and sometimes endurobol. It was developed as a selective agonist of peroxisome proliferator-activated receptor delta, a nuclear receptor involved in fatty acid oxidation and energy metabolism. The compound was studied in preclinical models for metabolic and cardiovascular conditions, but it did not become a marketed human medicine. In regulatory and anti-doping contexts, it is treated as a prohibited substance rather than a licensed medicine.
The pharmacological interest in cardarine centers on PPARδ activation and its downstream effects on lipid handling and mitochondrial function. In animal studies, PPARδ agonists have been associated with changes in exercise endurance and fatty acid utilization, though results vary by model and protocol. Human data remain sparse, and the absence of large controlled trials limits conclusions about efficacy. Researchers often describe the compound as a tool for probing PPARδ biology rather than a proven therapeutic agent.
GW501516 acts as an agonist at peroxisome proliferator-activated receptor delta, a nuclear receptor involved in transcription of genes related to lipid handling and energy use. Activation of PPARδ can shift skeletal muscle toward greater fatty acid oxidation in animal models, which is one reason it drew interest for metabolic disease and exercise research. The exact downstream effects depend on tissue, species, dose, and duration. Human data are sparse, so many proposed benefits remain hypotheses rather than established clinical outcomes.
Laboratory studies have examined GW501516 in cell cultures and rodents for conditions such as dyslipidemia, insulin resistance, and obesity. Some trials in humans were initiated, but development was discontinued after preclinical findings raised concerns about cancer in certain models. Those findings do not prove that the compound causes cancer in people, but they contributed to regulatory caution. Later reviews often describe the evidence as preliminary and insufficient for assessing long-term safety.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | GW501516, GW-501516, GW 501516, endurobol | Names vary in research and anti-doping documents. |
| Chemical class | Synthetic PPARδ agonist | Small-molecule nuclear receptor ligand. |
| CAS Registry Number | 317318-70-0 | Identifier commonly associated with GW501516. |
| Appearance | White to off-white powder | Typical for purified research material. |
| Solubility | Low in water; soluble in DMSO and ethanol | Organic solvents are common for laboratory stock solutions. |
GW501516 binds and activates PPARδ, a nuclear receptor that influences transcription of genes involved in fatty acid oxidation and energy use. Activation shifts some metabolic pathways in preclinical models, which is why the compound has been studied for lipid disorders and exercise-related endpoints. The exact downstream effects in humans are incompletely mapped. PPARδ is expressed in many tissues, including skeletal muscle, liver, and adipose tissue, so broad activation may have varied consequences. Researchers continue to examine how selective or partial activation might alter the balance between benefits and risks.
Published human data are sparse and mostly come from early-phase trials. Those studies examined short-term changes in lipids, glucose, and exercise capacity, but they were not large enough to establish efficacy or long-term safety. Some animal experiments reported increased running endurance, yet such findings do not prove a performance benefit in people. Anti-doping laboratories detect GW501516 and its metabolites in urine or blood using liquid chromatography-tandem mass spectrometry. Detection windows depend on dose, sample type, and individual metabolism. The method is sensitive enough to identify trace residues in tested samples.
Analytical laboratories typically identify cardarine and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is a common matrix in anti-doping testing, while blood and tissue may be used in research settings. Detection windows depend on the assay, the sample matrix, and the compound's metabolism. Because cardarine is extensively metabolized, laboratories often target specific metabolites to improve sensitivity and confirmation. Reference standards are required for reliable quantification. Method validation includes checks for selectivity, linearity, and carryover.
A persistent misconception is that cardarine is a fat-burning drug or a safe alternative to anabolic steroids. No approved therapeutic product exists, and human safety data are limited. The tumor findings in rodents remain a central concern in scientific reviews. Products sold online may contain inaccurate labels, impurities, or different compounds entirely, which complicates any assessment of effects. Independent testing of such products has reported frequent mislabeling. For these reasons, discussions in the literature emphasize risks and unknowns rather than benefits.
=== Circadian rhythm === There is evidence to suggest that adropin levels exhibit a circadian rhythm, meaning they follow a natural 24-hour cycle. Circadian rhythms play a vital role in regulating various physiological processes, including sleep-wake cycles, hormone secretion, and metabolism.
=== Acute gastroenteritis === A position paper from the ESPGHAN Working Group for Probiotics and Prebiotics, based on systematic reviews and randomized controlled trials, suggested that S. boulardii may be considered as an adjunct to rehydration therapy in the management of acute gastroenteritis in children. The recommendation was classified as strong despite the underlying evidence being rated as low quality.
== Bibliography == Escoffier, Auguste (1903). Le Guide culinaire. Aide mémoire de cuisine pratique. Paris, France: Flammarion. Escoffier, Auguste (1907). A Guide to Modern Cookery. Heinemann. OL 24167463M. Escoffier, A (1941). The Escoffier Cook Book. New York: Crown Publishers. Fannie Merritt Farmer (1896). The Boston Cooking-School Cook Book. Boston, Massachusetts: Little, Brown and Company. Beck, Simone; Louisette Bertholle; Julia Child (1961). Mastering the Art of French Cooking. New York: Alfred A. Knopf.
Sources: en.wikipedia.org
Phlebotomies are carried out by phlebotomists – people trained to draw blood mostly from veins for clinical or medical testing, transfusions, donations, or research. Blood is collected primarily by performing venipunctures, or by using capillary blood sampling with fingersticks or a heel stick in infants for the collection of minute quantities of blood. The duties of a phlebotomist may include interpreting the tests requested, drawing blood into the correct tubes with the proper additives, accurately explaining the procedure to the person and preparing them accordingly, practicing the required forms of asepsis, practicing standard and universal precautions, restoring hemostasis of the puncture site, giving instructions on post-puncture care, affixing tubes with electronically printed labels, and delivering specimens to a laboratory. Some countries, states, or districts require that phlebotomists be licensed or registered. A therapeutic phlebotomy may be carried out in the treatment of some blood disorders (examples: hemochromatosis, polycythemia vera, porphyria cutanea tarda), and chronic hives (in research).
Opioids can produce strong feelings of euphoria and are frequently used recreationally. Traditionally associated with illicit opioids such as heroin, prescription opioids are misused recreationally. Drug misuse and non-medical use include the use of drugs for reasons or at doses other than prescribed. Opioid misuse can also include providing medications to persons for whom it was not prescribed. Such diversion may be treated as crimes, punishable by imprisonment in many countries. In 2014, almost 2 million Americans abused or were dependent on prescription opioids.
== Mechanism and toxicity == κ-Bungarotoxin works as a postsynaptic neurotoxin. The postsynaptic neurotoxin is a prolonged, potentially irreversible, competitive antagonist of neuronal nicotinic acetylcholine receptors (nAChRs). Though α-bungarotoxin specifically binds to muscle nAChRs, κ-bungarotoxin targets the α3 and α4 - though α4 to a lesser extent - subunits of the nAChR in the central and autonomic nervous system, specifically in the avian ciliary ganglia because the α3 subunit of the nAChR is the main ganglionic type. One of Kappa-Bungarotoxin's target sites is the same as that of Alpha-Bungarotoxin, whereas the second target site of the nicotinic receptor is exclusively bound by κ-bungarotoxin. This, because neuronal nAChRs contain a broader variety of subunits than muscle nAChRs. By binding with a high affinity to the acetylcholine binding site of the neuronal nAChRs, Kappa-Bungarotoxin blocks these receptors for an eventual acetylcholine to bind. Normally, activation of the neuronal nAChRs by acetylcholine would release several neurotransmitters and generate inward ion influx, creating action potentials. However, when Kappa-Bungarotoxin is bound to the neuronal nAChRs, it inhibits depolarization at 75 nM and thus synaptic transmission. This blockade leads to the disruption of neuronal communication in the central nervous system and ganglia, causing neuromuscular paralysis and respiratory failure in prolonged κ-bungarotoxin exposure.
Sources: en.wikipedia.org
Cardarine is an investigational synthetic compound that acts as a PPARδ agonist. It is also known as GW501516 and has been studied mainly in preclinical research. It is not an approved medicine.
No. Cardarine is not a steroid hormone; it targets the nuclear receptor PPARδ. Its classification in anti-doping rules differs from anabolic steroids, though it remains prohibited in sport.
Early rodent studies reported tumor formation at multiple sites, which raised safety concerns. Sponsors stopped clinical development, and no approved human product exists.
It binds and activates PPARδ, a nuclear receptor that influences gene expression related to fatty acid metabolism and energy balance. This mechanism has been studied mainly in animals and cell models, not established as a safe human therapy.