A practical reference on Nuclear receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-11-22. Anything still debated is marked as such rather than presented as settled.
Quality assessment for cardarine samples usually combines identity, purity, and impurity testing. Nuclear magnetic resonance spectroscopy and mass spectrometry can confirm molecular structure, while high-performance liquid chromatography estimates purity. Certificates of analysis from testing laboratories may list these results, but they do not establish safety or legality. In the absence of approved manufacturing, products sold online may contain the wrong compound, variable amounts, or unlisted contaminants. Independent verification is therefore central to analytical work and to interpreting any reported biological activity.
Laboratory detection of GW501516 commonly uses liquid chromatography coupled with tandem mass spectrometry. The method can identify the parent compound or its metabolites in urine and blood after sample cleanup. Protein precipitation, solid-phase extraction, or enzymatic hydrolysis may precede analysis, depending on the matrix. Reference standards are required for accurate quantification and confirmation. Because the compound is not approved, testing often occurs in anti-doping, forensic, or research settings rather than routine clinical care. Results are reported with limits of detection and quantification.
Cardarine is frequently described as a fat-burning or endurance-enhancing supplement, but these claims exceed the available evidence. The compound is not a hormone, steroid, or selective androgen receptor modulator. Research articles discuss it as a tool compound for studying PPARδ biology, while anti-doping literature focuses on its abuse and detection. Quality of unapproved products is uncertain, and independent analyses have found impurities or incorrect labeling. Open questions include whether human cancer risk resembles that seen in rodents and how often non-athletes use the substance.
Cardarine has no approved therapeutic indication and is not marketed as a medicine. The World Anti-Doping Agency lists GW501516 as a prohibited substance at all times, covering both in-competition and out-of-competition periods. National laws vary: some countries treat it as an unapproved drug subject to import controls, while others have specific restrictions on sale for human consumption. It is often sold as a research chemical, a label that does not imply safety or legality. Enforcement actions have targeted online vendors and shipments.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Common for reference-grade material. |
| Solubility | Low in water | Dissolves in DMSO and some organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture. |
| Analytical method | LC-MS/MS | Used for trace detection in biological matrices. |
| Purity assessment | HPLC with UV detection | Often combined with NMR and mass spectrometry. |
The compound is typically described as a laboratory compound rather than a therapeutic product. Published reports have explored its role in lipid disorders, insulin sensitivity, and exercise metabolism, yet no major drug regulator has approved it for medical use. Commercial samples sold under the cardarine name may vary in purity and identity. Analytical confirmation is therefore necessary when the material is discussed in scientific or regulatory contexts. Its classification as a prohibited substance in sport further shapes how it is studied and reported.
Cardarine is a common name for GW501516, a synthetic compound studied for its effects on lipid and glucose metabolism. It functions as an agonist at peroxisome proliferator-activated receptor delta, or PPARδ, a nuclear receptor that influences gene expression. The molecule is not a steroid, nor is it a selective androgen receptor modulator. It is also known in research and sports literature as GW-501516 and endurobol. Early laboratory work examined its metabolic activity in cell cultures and animal models.
Activation of PPARδ changes transcription of genes involved in fatty acid transport, mitochondrial function, and skeletal muscle fuel preference. In rodent studies, pharmacological PPARδ activation was associated with increased endurance and altered body composition. These findings generated interest in performance enhancement, but species differences and study designs limit direct extrapolation to humans. Small human trials were conducted in the 2000s and later discontinued. The extent to which cardarine produces similar metabolic or performance effects in people remains an open question.
In laboratory settings, cardarine is studied as a tool compound for probing PPARδ biology. Published experiments often use cell cultures, rodent models, or isolated tissues. Some investigations focus on metabolic effects, while others assess potential risks such as carcinogenicity observed in long-term animal studies. Because human trials are sparse, most knowledge comes from preclinical work and adverse event reports. Scientific literature frequently notes the gap between animal findings and human outcomes. The compound is not a dietary supplement and is not intended for human consumption.
Cardarine is a common name for GW501516, a synthetic compound developed in the 1990s through research collaborations involving GlaxoSmithKline. It belongs to a class of molecules known as peroxisome proliferator-activated receptor delta agonists. Early studies explored its effects on lipid metabolism and energy expenditure in animal models. The compound was never approved as a human medicine, and clinical development was discontinued. In the years since, it has appeared in fitness and bodybuilding communities as a performance-enhancing substance. Regulatory agencies classify it as an unapproved drug.
PPARδ is a nuclear receptor that regulates gene expression related to fatty acid oxidation, glucose homeostasis, and mitochondrial function. GW501516 binds to this receptor with high affinity and activates downstream signaling in skeletal muscle and other tissues. Animal studies reported increased endurance and altered fuel preference, but human data remain limited and inconsistent. The precise relationship between receptor activation and observed physiological changes is still an area of active investigation. Researchers have also examined whether the compound affects inflammation or cell proliferation. No approved therapeutic indication exists for cardarine.
Human trials of GW501516 were small and short in duration. They examined lipid levels, glucose handling, and other metabolic markers, but the programs were halted after the animal cancer findings. No approved therapeutic product exists, and published human data are insufficient for establishing long-term safety. Reports of use for athletic performance come mainly from non-clinical settings and cannot be verified through controlled trials. Independent testing of products sold as cardarine has found inconsistent purity and labeling.
Laboratory studies indicate that GW501516 activates PPARδ, a nuclear receptor involved in fatty acid oxidation and energy metabolism. In rodent experiments, treated animals often showed increased endurance and reduced fat mass. These effects were observed under controlled conditions and do not establish safe or effective use in humans. The exact dose-response relationship in humans remains poorly characterized. Species differences in metabolism can affect how results translate across animals and people.
Safety concerns emerged from long-term animal studies. In rodents given the compound for extended periods, researchers found an increased incidence of certain cancers, including liver and bladder tumors. These findings contributed to the discontinuation of clinical development. Whether similar risks apply to short-term or low-level exposure in humans is not established, and controlled human safety data are limited. The relevance of high-dose rodent carcinogenicity findings to human use remains a subject of debate.
Products sold as cardarine have been found to contain incorrect compounds, variable amounts, or no active ingredient at all. Independent testing is required to verify identity and purity. Common analytical approaches include high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance for structural confirmation. These methods can distinguish GW501516 from related PPAR agonists and from unrelated steroids. For regulators and researchers, such verification is central to interpreting both biological results and adverse event reports.
Cardarine is prohibited in competitive sport under the World Anti-Doping Agency code, where it is classified as a metabolic modulator. It is not approved as a prescription medicine in the United States, European Union, or other major markets. Regulatory action has focused on its presence in sports and in products marketed as research chemicals. Because it has no accepted medical indication, supply is often unregulated. This status creates legal and safety uncertainties for anyone who encounters the substance.
Anti-doping laboratories detect GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be used in some programs. Detection depends on factors such as dose, timing, metabolism, and the sensitivity of the assay. Published methods describe limits of detection in the low nanogram per milliliter range for related compounds. Exact detection windows are not fixed for all situations and remain an area of ongoing study.
Clot-dissolving agents (tissue plasminogen activator) Maggot larval debridement Correction of the underlying plasma calcium and phosphorus abnormalities (lowering the Ca x P product below 55 mg2/dL2) Avoiding further local tissue trauma (including avoiding all subcutaneous injections, and all not-absolutely-necessary infusions and transfusions) Patients who have received kidney transplants also receive immunosuppression. Considering lowering the dose of or discontinuing the use of immunosuppressive drugs in people who have received kidney transplants and continue to have persistent or progressive calciphylactic skin lesions can contribute to an acceptable treatment of calciphylaxis. A group in 2013 reported plasma exchange effective and proposed a serum marker and perhaps a mechanistic mediator (calciprotein)
== Structural studies == As of late 2007, 29 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1A27, PDB: 1BHS, PDB: 1DHT, PDB: 1EQU, PDB: 1FDS, PDB: 1FDT, PDB: 1FDU, PDB: 1FDV, PDB: 1FDW, PDB: 1GZ6, PDB: 1I5R, PDB: 1IKT, PDB: 1IOL, PDB: 1JTV, PDB: 1QYV, PDB: 1QYW, PDB: 1QYX, PDB: 1S1P, PDB: 1S1R, PDB: 1S2A, PDB: 1S2C, PDB: 1XF0, PDB: 1YB1, PDB: 1ZQ5, PDB: 2F38, PDB: 2FGB, PDB: 2HQ1, PDB: 2PD6, and PDB: 3DHE.
Chickenpox was commonly confused with smallpox in the immediate post-eradication era. Chickenpox and smallpox could be distinguished by several methods. Unlike smallpox, chickenpox does not usually affect the palms and soles. Additionally, chickenpox pustules are of varying size due to variations in the timing of pustule eruption: smallpox pustules are all very nearly the same size since the viral effect progresses more uniformly. A variety of laboratory methods were available for detecting chickenpox in the evaluation of suspected smallpox cases.
== In culture == The jalapeño is a Mexican chili but was designated by the Texas Legislature as the official "State Pepper of Texas" in 1995. In Mexico, jalapeños are used in many forms such as in salsa, pico de gallo, or grilled jalapeños. Jalapeños were included as food on the Space Shuttle as early as 1982. Guinness World Records recognizes Alfredo Hernandes for the most jalapeños eaten in a minute: 16, on 17 September 2006 at the La Costeña Feel the Heat Challenge in Chicago, Illinois. Patrick Bertoletti holds the Major League Eating jalapeño records at 275 pickled jalapeños in 8 minutes on 1 May 2011, and 191 pickled jalapeños in 6.5 minutes on 16 September 2007 in the 'Short-Form'. Joaquín Guzmán, also known as "El Chapo", the leader of the Sinaloa Cartel, operated a cannery in Guadalajara producing "Comadre Jalapeños" in order to ship cocaine to the US. The official mascot of the 1986 FIFA World Cup was Pique, a jalapeño pepper, characteristic of Mexican cuisine, with a moustache, a Colimote sombrero, and Mexican football team colors. Its name comes from picante, a Spanish word meaning "spicy", and was also a pun on the "PK" abbreviation of the football term penalty kick. Pique is also a common Spanish name. September 5th is recognized as National Jalapeno Day.
==== Local application to the breasts ==== Transdermal application of progesterone with the intention of systemic therapy should not be equated with local treatment. The site of application of transdermal progesterone has been found to significantly influence its absorption. When transdermal progesterone is applied to the breasts, high concentrations within breast tissue have been observed. In one study, a 3- to 5-fold increase in local progesterone levels in the breast was observed with 50 mg transdermal progesterone in an alcohol/water-based gel applied to each breast in premenopausal women. In another study, a 70- to 110-fold increase in local concentrations of progesterone in the breasts was measured with application of a hydroalcoholic gel to the breasts in premenopausal women. A study observed a significant increase in circulating levels of progesterone when it was applied as a topical ointment to the breasts but not when it was applied to other areas like the thigh or abdomen. However, two other studies observed no apparent increase in circulating levels of progesterone with transdermal application of progesterone to the breasts. On the basis of its 10% transdermal bioavailability when applied to the breasts, a 50 mg dose of progesterone applied transdermally may result in a local concentration of progesterone in the breasts equivalent to 5 mg.
Sources: en.wikipedia.org
In healthy individuals, this minor pathway – which involves the conversion of L-leucine to α-KIC and then HMB – is the predominant route of HMB synthesis. A small fraction of L-leucine metabolism – less than 5% in all tissues except the testes, where it accounts for about 33% – is initially catalyzed by leucine aminomutase, producing β-leucine, which is subsequently metabolized into β-ketoisocaproate (β-KIC), β-ketoisocaproyl-CoA, and then acetyl-CoA by a series of uncharacterized enzymes. The metabolism of HMB is catalyzed by an uncharacterized enzyme which converts it to β-hydroxy β-methylbutyryl-CoA (HMB-CoA). HMB-CoA is metabolized by either enoyl-CoA hydratase or another uncharacterized enzyme, producing β-methylcrotonyl-CoA (MC-CoA) or hydroxymethylglutaryl-CoA (HMG-CoA) respectively. MC-CoA is then converted by the enzyme methylcrotonyl-CoA carboxylase to methylglutaconyl-CoA (MG-CoA), which is subsequently converted to HMG-CoA by methylglutaconyl-CoA hydratase. HMG-CoA is then cleaved into acetyl-CoA and acetoacetate by HMG-CoA lyase or used in the production of cholesterol via the mevalonate pathway.
==== Administering the department ==== The permanent under-secretary at the Environment Department, Sir John Garlick, described Heseltine's arrival as a change from "a very conservative Labour secretary of state, Peter Shore, to a very radical Conservative Secretary of State". On his first day Heseltine took him out to lunch at the Connaught and drew up a list of what he wanted to accomplish in office (the list appears in Heseltine's book Where There's A Will, and was returned to him at the end of his time at the Environment). Only a quarter of Heseltine's agenda consisted of manifesto commitments and other political goals; the rest of it consisted of administrative and organisational changes. Peter Hennessy observed that Heseltine was more interested in the nuts and bolts of Whitehall reform than any minister since David Lloyd George. Heseltine was quite ruthless about moving civil servants with whom he was dissatisfied, but nonetheless staff thought he had mellowed somewhat since the early 1970s, and was more relaxed and fun to work with. His permanent secretaries Sir John Garlick and Sir George Moseley thought highly of him. He preferred to reach decisions through informal discussion rather than wading through paperwork. He instituted Peter Walker's custom of morning "prayer" meetings (ministers and PPSs with no civil servants present), now common in Whitehall but an innovation at the time. The department had a budget of £14 billion a year and employed 52,000 people. The Conservatives were pledged to cut 100,000 off the 730,000 strong civil service.
American biochemist at the NIH, who isolated the first cell receptor. William Astbury FRS (1898–1961). British physicist and molecular biologist at the Royal Institution, University of Leeds, a pioneer in applying X-ray crystallography to biological molecules such as proteins Daniel Atkinson (1921–2024). American biochemist at UCLA known for the concept of energy charge
It has one boxed warning by the US FDA, namely severe hepatotoxicity including fatalities. The most common side effects of pazopanib are nausea, vomiting, diarrhoea (occurs in about half of patients), changes in hair colour, hypertension (which usually occurs during the first few weeks of treatment), appetite loss, hyperglycaemia, hypoglycaemia, electrolyte abnormalities (including hypocalcaemia, hypomagnesemia, hypophosphatemia), laboratory anomalies (including increased AST, ALT and protein in the urine), oedema, hair loss or discolouration, taste changes, abdominal pain, rash, fatigue and bone marrow suppression (including leucopenia, neutropenia, thrombocytopenia and lymphopenia). It has been associated with a low, but real risk of potentially fatal liver damage.
This competition could alter the post-transcriptional gene regulation (PTGR) of ADME-related genes, leading to indirect modulation of the expression of drug-metabolizing enzymes or transporters and causing DDIs with co-administered drugs. Short hairpin RNAs (shRNAs) may additionally compete with pre-miRNAs for the nuclear export protein Exportin-5 (XPO5) and the cytoplasmic ribonuclease Dicer, disrupting global miRNA biogenesis and posing further DDI risk. The U.S. Food and Drug Administration has issued guidance specific to oligonucleotide therapeutics, recommending assessment of QTc interval prolongation, immunogenicity, organ-impairment effects on PD endpoints, and the potential for RNAi machinery competition as part of the DDI risk framework for this drug class.
Sources: en.wikipedia.org
== Clinical significance == Increasing evidence links aberrant CL metabolism and content to human disease. Human conditions include neurological disorders, cancer, and cardiovascular and metabolic disorders (a full list can be found at). As the number of human diseases with CL profile abnormalities has exponentially grown, the use of qualitative and quantitative diagnostics has emerged as a necessity.
The head is as large as an ordinary flour barrel, and has the shape of a sea lion head. The neck, if the creature may be said to have a neck, is of the same diameter as the body. The mouth is on the underside of the head and is protected by two tentacle tubes about eight inches in diameter and about 30 feet long. These tubes resemble an elephant's trunk and obviously were used to clutch in a sucker like fashion any object within their reach. Another tube or tentacle of the same dimensions stands out on the top of the head. Two others, one on each side, protrude from beyond the monster's neck, and extend fully 15 feet along the body and beyond the tail. The tail, which is separated and jagged with cutting points for several feet, is flanked with two more tentacles of the same dimensions as the others and 30 feet long. The eyes are under the back of the mouth instead of over it. This specimen is so badly cut up by sharks and sawfish that only the stumps of the tentacles remain, but pieces of them were found strewn for some distance on the beach, showing that the animal had a fierce battle with its foes before it was disabled and beached by the surf. Grant describes the animal as having seven "tentacles" and a "tail". If the "tail" is interpreted as another tentacle, giving a total of eight, this would suggest an octopus as opposed to a decapod, such as the squid or cuttlefish. Furthermore, nothing in the description indicates the presence of the long feeding tentacles found in squid, as the "tentacles" are said to be of the same dimensions.
International Chemical Safety Card 1262 (2-methylpentane) Material Safety Data Sheet for Hexane National Pollutant Inventory – n-hexane fact sheet Phytochemica l database entry Center for Disease Control and Prevention Warning from National Safety Council "COMMON CHEMICAL AFFECTS AUTO MECHANICS" Australian National Pollutant Inventory (NPI) page "EPA does not consider n-hexane classifiable as a human carcinogen." Federal Register / Vol. 66, No. 71 / Thursday, 12 April 2001 / Rules and Regulations
== Synthesis == In the female, relaxin is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua. In the male, it is produced in the prostate and is present in human semen.
In the United States in 1999, there were 14,420 non-fatal traumatic amputations according to the American Statistical Association. Of these, 4,435 occurred as a result of traffic and transportation accidents and 9,985 were due to labor accidents. Of all traumatic amputations, the distribution percentage is 30.75% for traffic accidents and 69.24% for labor accidents. The United States Bureau of Labor Statistics reported 6,200 cases of work-related amputations in 2018. The most common causes of amputations were machinery (58% cases), crush injuries from parts or material (15%), and other tools/instruments/equipment such hand tools (7%). A study found that in 2010, 22.8% of patients undergoing amputation of a lower extremity in the United States were readmitted to the hospital within 30 days. In 2017, an estimated 57.7 million people globally were living with existing traumatic limb injuries. Of these 57.7 million, the leading causes of amputation "were falls (36.2%), road injuries (15.7%), other transportation injuries (11.2%), and mechanical forces (10.4%)." On 2 August 2023, an investigation by The Wall Street Journal found that Ukrainian medical amputations in the war came to between 20,000 and 50,000 including both military and civilians. In comparison, during World War One 41,000 British and 67,000 Germans needed amputations. In 2025, Israel's attacks on the Gaza Strip during the Gaza war caused Gaza to have the highest number of child amputees per capita in the world.
Sources: en.wikipedia.org
LC-MS/MS is common, often after sample cleanup. The assay targets GW501516 or its metabolites.
Reference material is usually kept cold, dry, and protected from light. Frozen aliquots reduce repeated freeze-thaw cycles.
No approved pharmaceutical product exists, so manufacturing and quality controls are not standardized. Products may contain different compounds or impurities.
Legal status varies by country. It is not approved as a medicine, and it is prohibited in sport. Some jurisdictions restrict import, sale, or possession.