This is a working overview of Nuclear receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-08-15 and is reviewed periodically as new material appears.
Laboratory handling focuses on identity, purity, and stability. Reference standards are typically stored cold and dry, protected from light, because solutions can degrade over time. Analytical checks may use high-performance liquid chromatography with ultraviolet detection or mass spectrometry. Impurities and related substances can be separated chromatographically and compared with a known standard. Because cardarine is not an approved drug, compendial monographs are absent, and laboratories often rely on in-house methods. Reported purity varies among unregulated products and should not be assumed from a label.
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.
Safety discussions about cardarine frequently cite rodent carcinogenicity findings reported in the 2000s. In those studies, treated animals developed tumors at multiple sites, leading sponsors to discontinue clinical development. The relevance of these findings to humans has not been resolved, but they are a major reason the compound is not approved. Current literature emphasizes uncertainty about long-term effects and the risks of unregulated use. Regulators and health agencies have not established a safe human exposure level.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Typical form of reference material |
| Solubility | Low in water; soluble in DMSO | Used to prepare stock solutions |
| Typical storage | -20 °C, desiccated, protected from light | Common laboratory practice |
| Analytical method | LC-MS/MS | Detects parent compound and metabolites |
| Common test matrix | Urine or blood | Used in anti-doping analysis |
Sporting authorities added GW501516 to prohibited lists after it appeared in athlete samples and online markets. The World Anti-Doping Agency classifies it as a hormone and metabolic modulator, and its use can lead to an anti-doping rule violation. Some early laboratory work suggested effects on fatty acid oxidation and endurance-related metabolism in animals, but those findings do not establish safe or effective use in people. Reports of adverse events in humans are scarce and often anecdotal, which complicates risk assessment.
Legal status varies by country. In some places, cardarine is controlled under medicines or psychoactive substances laws; in others, it may be sold with minimal oversight as a research chemical. Customs agencies have intercepted shipments, and several national health agencies have issued warnings about products marketed for bodybuilding or performance enhancement. The lack of a standardized pharmaceutical supply means identity, purity, and contamination levels can differ widely between samples. These factors make cardarine a regulatory and public health concern rather than a conventional prescription drug.
Cardarine is a common name for GW501516, a synthetic compound first described in the 1990s as a selective agonist of the peroxisome proliferator-activated receptor delta. It was studied in preclinical models for metabolic and cardiovascular conditions, but it has not been approved as a medicine in the United States, Europe, or other major jurisdictions. Retail products labeled as cardarine are generally research chemicals or supplements, not pharmaceutical formulations. Because human safety and efficacy data remain limited, regulatory agencies treat it as an unapproved substance rather than a therapeutic product.
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.
=== Blood banking === Blood banking is a concentration within a clinical laboratory that analyzes specimens from potential transfusion recipients and provides compatible blood products to the healthcare team in charge of that patient's care. Several routine tests are performed including blood typing (determination of ABO/Rh status), antibody screening, serologic cross-matching, direct antiglobulin testing, and antibody identification. Beyond the presence of naturally occurring antibodies (isohemagglutinins) to the ABO and Rh(D) blood group antigens, additional immune-stimulated antibodies are considered unexpected alloantibodies. The identification of unexpected antibodies is a labor-intensive process, and sometimes requires the addition of special laboratory techniques to aid in the proper identification of the antibody. Among these techniques are elutions, adsorptions, and enzyme treatment. Some patients produce antibodies to high frequency antigens. That is, the red cell antigens are present in a significant portion of the human population. It may be questionable and very difficult to assess if the antibody is considered clinically significant or not. A clinically significant antibody is an antibody that is capable of causing in vitro hemolysis or a decreased survival of transfused donor red blood cells. Antibodies to high frequency antigens can be assessed for clinical significance using the monocyte monolayer assay.
== Total synthesis == Matinkhoo et al. devised strategies to surmount three synthetic hurdles to give α-amanitin in 2018. First, enantioselective synthesis of solid phase peptide synthesis-compatible (2S,3R,4R)-4,5-dihydroxyisoleucine was afforded in 11 steps from 2-(benzyloxy)acetaldehyde. Two key stereochemistry-defining steps include Brown crotylation at (3R,4R)-positions, and asymmetric Strecker amino acid synthesis at the (2S)-α carbon. Secondly, chemoselective inner ring closure by fluorocyclization between 6-hydroxytrytophan and cysteine was achieved by intra-annular Savige-Fontana reaction. This requires a solid phase peptide synthesis-compatible, and methyliminodiacetic acid (MIDA), a boron protecting group, orthogonal amino acid in 5 steps. As a final step, enantioselective oxidation at the tryptathionine linkage was achieved using a bulky organic oxidizing agent and an optimized solvent system to afford the desired bio-reactive (R)-enantiomer sulfoxide, completing the total synthesis.
These complications of advanced atherosclerosis are chronic, slowly progressive, and cumulative. Most commonly, soft plaque suddenly ruptures (see vulnerable plaque), causing the formation of a thrombus that will rapidly slow or stop blood flow, leading to the death of the tissues fed by the artery in approximately five minutes. This event is called an infarction.
Propranolol is a medication of the beta blocker class. It is used to treat high blood pressure, some types of irregular heart rate, thyrotoxicosis, capillary hemangiomas, akathisia, performance anxiety, and essential tremors, as well as to prevent migraine headaches, and to prevent further heart problems in those with angina or previous heart attacks. It can be taken orally, rectally, or by intravenous injection. The formulation that is taken orally comes in short-acting and long-acting versions. Propranolol appears in the blood after 30 minutes and has a maximum effect between 60 and 90 minutes when taken orally. Common side effects include nausea, abdominal pain, and constipation. It may worsen the symptoms of asthma. Propranolol may cause harmful effects for the fetus if taken during pregnancy; however, its use during breastfeeding is generally considered to be safe. It is a non-selective beta blocker which works by blocking β-adrenergic receptors. Propranolol was patented in 1962 and approved for medical use in 1964. It is on the World Health Organization's List of Essential Medicines. Propranolol is available as a generic medication. In 2023, it was the 69th most commonly prescribed medication in the United States, with more than 9 million prescriptions.
Side effects from therapeutic use can be much more varied depending on the location of injection and the dose of toxin injected. In general, side effects from therapeutic use can be more serious than those that arise during cosmetic use. These can arise from paralysis of critical muscle groups and can include arrhythmia, heart attack, and in some cases, seizures, respiratory arrest, and death. Additionally, side effects common in cosmetic use are also common in therapeutic use, including trouble swallowing, muscle weakness, allergic reactions, and flu-like syndromes. In response to the occurrence of these side effects, in 2008, the US Food and Drug Administration (FDA) notified the public of the potential dangers of the botulinum toxin as a therapeutic. Namely, the toxin can spread to areas distant from the site of injection and paralyze unintended muscle groups, especially when used for treating muscle spasticity in children treated for cerebral palsy. In 2009, the FDA announced that boxed warnings would be added to available botulinum toxin products, warning of their ability to spread from the injection site. However, the clinical use of botulinum toxin A in children with cerebral palsy has been proven to be safe with minimal side effects. Additionally, the FDA announced name changes to several botulinum toxin products, to emphasize that the products are not interchangeable and require different doses for proper use.
Sources: en.wikipedia.org
Since 1975, after the proposal by then Minister for Home Affairs Chua Sian Chin, the death penalty was mandated as the sole punishment for drug trafficking, should the amount of whichever drugs exceed the capital threshold. As a result of this legal reform, 28-year-old Penang-born Malaysian Teh Sin Tong became the first convicted drug trafficker to be hanged at Changi Prison on 28 April 1978, after the High Court found him guilty on 13 October 1976 (a year after the new laws took effect) for trafficking 254.7g of diamorphine across the Woodlands Checkpoint just six months prior to his sentencing. Under Schedule 2 of the Misuse of Drugs Act, any person importing or exporting more than the following quantities of drugs receives a mandatory death sentence:
=== India === Specialty training in India is overseen by the National Medical Commission (formerly Medical Council of India), responsible for recognition of post graduate training and by the National Board of Examinations. Education of Ayurveda in overseen by Central Council of Indian Medicine (CCIM), the council conducts UG and PG courses all over India, while Central Council of Homoeopathy does the same in the field of Homeopathy. Specialization and superspecialization in medicine and surgery are pursued after completing MBBS, for which higher medical (MD, DM) and surgical (MS, MCh) degrees are awarded. The following medical and surgical specialties and superspecialties are recognized by the National Medical Commission (formerly Medical Council of India) and National Board of Examinations in Medical Sciences:
== Early life and entry to science == Hofmann was born in Germany but when his father died, his mother returned with her one-year-old son to her family home in Switzerland. The family was business oriented but Klaus was determined to pursue a career in science. He studied steroid chemistry at the Federal Institute of Technology in Zürich (ETH) in the laboratories of Leopold Ružička. Here he developed a friendship with another faculty member, Tadeus Reichstein from whom he learned laboratory technique. For his postdoctoral experience he traveled to the United States to work with Max Bergmann on peptides, an entirely new field for him. From there he migrated across the street to the laboratory of Vincent du Vigneaud where he was introduced to a new vitamin, Biotin.
== Remodeling and growth == Soft tissues have the potential to grow and remodel reacting to chemical and mechanical long term changes. The rate the fibroblasts produce tropocollagen is proportional to these stimuli. Diseases, injuries and changes in the level of mechanical load may induce remodeling. An example of this phenomenon is the thickening of farmer's hands. The remodeling of connective tissues is well known in bones by the Wolff's law (bone remodeling). Mechanobiology is the science that study the relation between stress and growth at cellular level. Growth and remodeling have a major role in the cause of some common soft tissue diseases, like arterial stenosis and aneurisms and any soft tissue fibrosis. Other instance of tissue remodeling is the thickening of the cardiac muscle in response to the growth of blood pressure detected by the arterial wall.
Sources: en.wikipedia.org
Anti-doping and clinical laboratories commonly use liquid chromatography-tandem mass spectrometry. The method can identify GW501516 and its metabolites in urine or blood. Detection depends on sample timing and the amount present.
PPARδ is a nuclear receptor that regulates genes linked to fatty acid oxidation and energy metabolism. Activation can alter lipid handling and energy use in experimental models. The full range of effects in humans is still under study.
The solid compound is generally stable when kept cold, dry, and protected from light. Solutions may degrade faster, so laboratory protocols often specify fresh preparation or cold storage. Stability can depend on solvent, concentration, and container.
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.