This is a working overview of nuclear receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Handling and quality assessment of cardarine reference material follow general laboratory practices for poorly characterized compounds. It typically appears as a white to off-white powder and is sparingly soluble in water but soluble in organic solvents such as dimethyl sulfoxide and ethanol. Storage recommendations usually specify a cool, dry, dark place, with long-term storage at low temperature and desiccation. Purity may be checked by high-performance liquid chromatography with ultraviolet detection, while identity is confirmed by mass spectrometry and nuclear magnetic resonance. No pharmacopeial monograph exists, so reported purity and stability depend on the supplier’s methods.
GW501516 acts as a selective agonist at PPARδ, a nuclear receptor that regulates transcription of genes involved in lipid handling and energy metabolism. Activation of PPARδ in preclinical models increases fatty acid oxidation, mitochondrial biogenesis, and exercise endurance in rodents. These effects have made the compound a subject of metabolic research and also a target for sport anti-doping rules. In humans, however, controlled studies are limited, and whether similar endurance or metabolic changes occur at tolerated exposures remains an open question. The receptor’s broad tissue distribution also means downstream effects may vary by organ and condition.
PPARδ is a nuclear receptor that influences transcription of genes involved in fatty acid oxidation, lipid transport, and energy homeostasis. GW501516 binds and activates this receptor with high selectivity relative to PPARα and PPARγ in laboratory assays. Activation alters expression of target genes in skeletal muscle, liver, and adipose tissue in animal models. The exact clinical consequences of these changes in humans remain incompletely characterized, and observed effects in animals do not establish therapeutic benefit or safety.
Published studies have examined GW501516 in animal models of obesity, insulin resistance, and exercise endurance. Early human trials reportedly ended, and development was discontinued after preclinical findings raised concerns about cancer in some rodent studies. Regulatory agencies have not approved cardarine for any medical use. Its availability through non-pharmaceutical channels raises questions about identity, purity, and legal status that are separate from its laboratory pharmacology. Those questions are often addressed through analytical testing rather than assumptions about product labels.
Cardarine is a common name for GW501516, also GW-1516, a synthetic compound developed as a peroxisome proliferator-activated receptor delta (PPARδ) agonist. It belongs to a class of agents that modulate gene transcription related to lipid and energy metabolism. The compound was studied in preclinical and early clinical research for metabolic and cardiovascular conditions, but it did not progress to approved therapeutic use. Its name appears in fitness and sports contexts despite not being approved as a drug.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Visual description for typical solid reference material. |
| Solubility | Poorly soluble in water; soluble in DMSO | Solubility depends on solvent, purity, and form. |
| Storage | Cool, dry, protected from light | Long-term storage often uses low temperature and desiccant. |
| Common analytical method | LC-MS/MS | Used for detection and quantification in biological matrices. |
| Common synonyms | GW-501516; GW501516; endurobol | Naming varies among literature, vendors, and databases. |
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.
Anti-doping laboratories identify GW501516 and related metabolites using liquid chromatography coupled with tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be analyzed. The method targets the parent compound and phase I and phase II metabolites, which extend the detection window. Because the substance is prohibited at all times, athletes can be tested outside competition. Detection limits and windows depend on the assay, sample type, and individual metabolism.
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.
Anti-doping laboratories identify GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the usual matrix, and detection can occur after the parent compound has cleared from blood. The exact detection window depends on dose, formulation, individual metabolism, and assay sensitivity. Because the compound is prohibited at all times, athletes are subject to testing in and out of competition. Analytical methods continue to improve as new metabolites and designer analogs are characterized.
GW501516 acts as a ligand for PPAR delta, a nuclear receptor that regulates transcription of genes involved in fatty acid oxidation and energy use. Activation of this receptor in skeletal muscle shifts metabolism toward fat burning in animal models. The compound does not burn fat directly; it changes gene expression over hours to days. Researchers study it to understand metabolic flexibility and exercise adaptation. Effects observed in rodents are not automatically expected in humans.
The first long-acting analogue, insulin glargine, was approved in 2000. Insulin aspart, insulin glulisine, and insulin detemir were all approved by 2005. The second wave of insulin analogues, which include insulin degludec and insulin icodec, started in the 2010s. Insulin analogues are on the World Health Organization's List of Essential Medicines.
== Definition == Per United States legislation, the Dietary Supplement Health and Education Act of 1994 provided the following definition of dietary supplements: "The Dietary Supplement Health and Education Act of 1994 (DSHEA) defines the term "dietary supplement" to mean a product ... intended to supplement the diet that bears or contains one or more of the following dietary ingredients: a vitamin, a mineral, an herb or other botanical, an amino acid, a dietary substance for use by man to supplement the diet by increasing the total dietary intake, or a concentrate, metabolite, constituent, extract, or combination of any of the aforementioned ingredients. Furthermore, a dietary supplement must be labeled as a dietary supplement and be intended for ingestion and must not be represented for use as conventional food or as a sole item of a meal or of the diet. In addition, a dietary supplement cannot be approved or authorized for investigation as a new drug, antibiotic, or biologic, unless it was marketed as a food or a dietary supplement before such approval or authorization. Under DSHEA, dietary supplements are deemed to be food, except for purposes of the drug definition." Per DSHEA, dietary supplements are consumed orally, and are mainly defined by what they are not: conventional foods (including meal replacements), medical foods, preservatives, or pharmaceutical drugs. Products intended for use as a nasal spray or topical application, such as a lotion applied to the skin, do not qualify. FDA-approved drugs cannot be ingredients in dietary supplements.
== Etymology == The English name for the element potassium comes from the word potash, which refers to an early method of extracting various potassium salts: placing in a pot the ash of burnt wood or tree leaves, adding water, heating, and evaporating the solution. Humphry Davy named the element potassium after isolating the metal itself. The symbol K stems from kali, itself from the root word alkali, which in turn comes from Arabic: القَلْيَه al-qalyah 'plant ashes'. In 1797, the German chemist Martin Klaproth discovered "potash" in the minerals leucite and lepidolite, and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed calling kali. In 1807, Humphry Davy produced the element via electrolysis: in 1809, Ludwig Wilhelm Gilbert proposed the name Kalium for Davy's "potassium". In 1814, the Swedish chemist Berzelius advocated the name kalium for potassium, with the chemical symbol K. The English and French-speaking countries adopted the name Potassium, which was favored by Davy and French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard, whereas the other Germanic countries adopted Gilbert and Klaproth's name Kalium. The "Gold Book" of the International Union of Pure and Applied Chemistry has designated the official chemical symbol as K.
=== Neurotransmitter release is calcium-dependent === Neurotransmitter release is dependent on an external supply of Ca2+ ions which enter axon terminals via voltage-gated calcium channels. Vesicular fusion with the terminal membrane and release of the neurotransmitter is caused by the generation of Ca2+ gradients induced by incoming action potentials. The Ca2+ ions cause the mobilization of newly synthesized vesicles from a reserve pool to undergo this membrane fusion. This mechanism of action was discovered in squid giant axons. Lowering intracellular Ca2+ ions provides a direct inhibitory effect on neurotransmitter release. After release of the neurotransmitter occurs, vesicular membranes are recycled to their origins of production. Calcium ion channels can vary depending on the location of incidence. For example, the channels at an axon terminal differ from the typical calcium channels of a cell body (whether neural or not). Even at axon terminals, calcium ion channel types can vary, as is the case with P-type calcium channels located at the neuromuscular junction.
Sources: en.wikipedia.org
In July 2023, the Biden administration secured voluntary commitments from seven companies – Amazon, Anthropic, Google, Inflection, Meta, Microsoft, and OpenAI – to manage the risks associated with AI. The companies committed to ensure AI products undergo both internal and external security testing before public release; to share information on the management of AI risks with the industry, governments, civil society, and academia; to prioritize cybersecurity and protect proprietary AI system components; to develop mechanisms to inform users when content is AI-generated, such as watermarking; to publicly report on their AI systems' capabilities, limitations, and areas of use; to prioritize research on societal risks posed by AI, including bias, discrimination, and privacy concerns; and to develop AI systems to address societal challenges, ranging from cancer prevention to climate change mitigation. In September 2023, eight additional companies – Adobe, Cohere, IBM, Nvidia, Palantir, Salesforce, Scale AI, and Stability AI – subscribed to these voluntary commitments. In January 2023, the NIST released the Artificial Intelligence Risk Management Framework (AI RMF 1.0), providing voluntary guidance for organizations to identify, assess, and manage risks associated with AI systems. The Biden administration, in October 2023 signaled that they would release an executive order leveraging the federal government's purchasing power to shape AI regulations, hinting at a proactive governmental stance in regulating AI technologies.
=== Media preparation and washing units === The washing unit provides cleaning services for laboratory glassware and plasticware. It handles laundering of work clothing and decontamination of genetically modified organism (GMO) waste and hazardous laboratory waste. The media preparation unit prepares cultivation media and solutions for tissue culture. It produces bacteriological media and agar plates.
=== More complex general models === When developing more detailed models for in-depth analysis, models are mostly generated for specific outbreak scenarios of specific diseases, including compartments for targeted research questions like hospitalization compartments or detection dynamics. Even though those models are often tailored for specific situations, there are complex models, still usable for a broad variety of different diseases. One of those attempts to create a general model includes twelve compartments, extending the well-known SEIR model by a second stage of infection, detection compartments, and two doses of vaccination. Additionally smear infections are incorporated via an external Pathogen
18 October — The Primary Principals Collective Bargaining Union accepts a 2.5% pay rise offer following four months of negotiations with the Ministry of Education. This will be followed by another 2.1% pay rise in 2026. 20 October: The New Zealand Government introduces two new requirements for job seeker beneficiaries who have failed a welfare obligation: engaging in three job search activities weekly and attending at least one employment-training course per month. A measles case linked to international travel is reported in Auckland. 21 October: Strong winds cause power outages, fallen trees and disrupt road and rail travel across the Wairarapa region. Lines company Powerco reports that 10,000 houses in the area have lost electricity due to fallen power lines. Strong winds and heavy rains disrupt road, rail and air travel in the Wellington Region. One person is killed by a fallen tree branch in Mount Victoria during a storm that hits Wellington. Strong winds cause four vegetation fires in the Hawke's Bay Pōrangahau area, leading to the evacuation of vie homes. Strong winds and dry conditions cause six fires in the Kaikōura District, leading to the destruction of 14 buildings and local evacuations. Three new measles cases are reported in Manawatū and Nelson. 22 October: Fire and Emergency New Zealand deploys numerous firefighters and helicopters to combat fires in the Kaikōura District and Pōrangahau. Strong winds and fires cause power outages and flight disruptions through the lower North Island and upper South Island.
== Anaerobic == The most well-studied anaerobic FGE is the bacterial AtsB, an iron-sulfur cluster containing enzyme present in Klebsiella pneumoniae, that is able to convert either cysteine or serine to fGly with a distinctly different mechanism than the aerobic form. While AtsB can convert either, its activity increases four fold when in the presence of cysteine over serine. AtsB is 48% similar to an enzyme present in Clostridium perfringens. Both enzymes possess the Cx3Cx2C motif unique to the radical S-adenosyl methionine superfamily and are able to use a reduction reaction to cleave S-adenosyl methionine. These two enzymes fall into a larger group called the anaerobic Sulfatase Maturing Enzymes, which are able to convert cysteine into fGly without the use of oxygen.
Sources: en.wikipedia.org
Cardarine targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not bind the androgen receptor in the way SARMs do.
Most methods use liquid chromatography with tandem mass spectrometry. Urine is common in anti-doping testing, and blood or plasma may be used in research.
Typical guidance is cool, dry, dark storage, often at low temperature and with desiccant. Stability data are limited, so storage conditions should be verified for each batch or supplier.
Cardarine is commonly known as GW501516 or GW-1516. These names refer to the same synthetic compound. It is not a brand-name approved medicine.