If you have been reading about Nuclear receptor and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-03-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| 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 |
Regulatory bodies treat GW501516 as a prohibited substance in competitive sport. The World Anti-Doping Agency added it to the prohibited list, and it falls under classes covering metabolic modulators and hormone-related agents. It is not approved by drug regulators for human use, and it is not a lawful dietary supplement. Products sold under the cardarine name may contain unlisted ingredients or different compounds. Because no approved product exists, quality and identity are not guaranteed by pharmaceutical manufacturing standards.
Cardarine is a common name for the investigational chemical GW501516, also written GW-1516. It was developed as a peroxisome proliferator-activated receptor delta agonist for metabolic conditions such as dyslipidemia. Early research focused on lipid handling and energy use in skeletal muscle and other tissues. The compound was never approved as a medicine. In public discussion, it is often grouped with performance-enhancing substances, although its receptor target differs from that of anabolic steroids or selective androgen receptor modulators. Regulatory and health authorities have issued warnings about its use.
GW501516 acts on PPARδ, a nuclear receptor that helps regulate fatty acid oxidation and energy homeostasis. In animal studies, activation of this receptor was associated with increased endurance and changes in lipid metabolism. Human trials examined effects on blood lipids and other metabolic markers, but the compound did not advance to approval. Rodent studies later reported tumors in multiple tissues at doses used in those experiments. Whether those findings translate to human risk remains uncertain, and the clinical relevance of the animal data is still debated.
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.
In the fitness and bodybuilding literature, cardarine is frequently discussed as an endurance agent or fat-loss compound, although such claims are not supported by robust clinical evidence. Online descriptions often mix animal data, user anecdotes, and marketing language. Researchers who study PPARδ agonists distinguish between receptor activation in controlled experiments and unsupervised use of unverified products. The latter introduces unknown purity, dose, and interactions, making reported experiences difficult to interpret scientifically.
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.
== Mechanism == The creatine phosphate system is needed for the storage and transmission of phosphate-bound energy in the brain and muscle. The brain and muscle have particularly high metabolic demands, therefore, making creatine a necessary molecule in ATP homeostasis. In regard to the brain, in order for creatine to reach the brain, it must first pass through the blood–brain barrier (BBB). The BBB separates blood from brain interstitial fluid and is, therefore, able to regulate the transfer of nutrients to the brain from the blood. In order to pass through the BBB, creatine utilizes creatine transporter (CRT). When present at the BBB, CRT mediates the passage of creatine from the blood to the brain. When being transported from the blood to the brain, creatine has to constantly move against the creatine concentration gradient that is present at the border between the brain and circulating blood.
Most white Rhodesians felt that they were due independence following four decades of self-government, and that the British government was betraying them by withholding it. A stalemate developed between the British and Rhodesian prime ministers, Harold Wilson and Ian Smith respectively, between 1964 and 1965. The dispute largely surrounded the British condition that the terms for independence had to be acceptable "to the people of the country as a whole"; Smith contended that this was met, while the UK and African Nationalist Rhodesian leaders held that it was not. After Wilson proposed in late October 1965 that the UK might safeguard future black representation in the Rhodesian parliament by withdrawing some of the colonial government's devolved powers, then presented terms for an investigatory Royal Commission that the Rhodesians found unacceptable, Smith and his Cabinet declared independence. Calling this treasonous, the British colonial governor, Sir Humphrey Gibbs, formally dismissed Smith and his government, but they ignored him and appointed an "Officer Administering the Government" to take his place. While no country recognised the UDI, the Rhodesian High Court deemed the post-UDI government legal and de jure in 1968. The Smith administration initially professed continued loyalty to Queen Elizabeth II, but abandoned this in 1970 when it declared a republic in an unsuccessful attempt to win foreign recognition.
== Anatomy of the eyelids == Blepharoplasty involves modification of the anatomical structures of the upper and lower eyelids to improve both function and appearance. A detailed understanding of eyelid anatomy is essential for preserving eyelid support, maintaining normal closure and achieving natural, balanced results.
During maximum intensity exercise, muscle glycogen can supply 40 mmol glucose/kg wet weight/minute, whereas blood glucose can supply 4 – 5 mmol. Due to its high supply rate and quick ATP synthesis, during high-intensity aerobic activity (such as brisk walking, jogging, or running), the higher the exercise intensity, the more the muscle cell produces ATP from muscle glycogen. This reliance on muscle glycogen is not only to provide the muscle with enough ATP during high-intensity exercise, but also to maintain blood glucose homeostasis (that is, to not become hypoglycaemic by the muscles needing to extract far more glucose from the blood than the liver can provide). A deficit of muscle glycogen leads to muscle fatigue known as "hitting the wall" or "the bonk" (see below under glycogen depletion).
Sources: en.wikipedia.org
== Further reading == Ahnström, M. L.; Seyfert, M.; Hunt, M. C.; Johnson, D. E. (2006). "Dry aging of beef in a bag highly permeable to water vapor". Meat Science. 73 (4): 674–679. doi:10.1016/j.meatsci.2006.03.006. PMID 22062568. DeGeer, S. L.; Hunt, M. C.; Bratcher, C. L.; Crozier-Dodson, B. A.; Johnson, D. E.; Stika, J. F. (2009). "Effects of dry aging of bone-in and boneless strip loins using two aging processes for two aging times". Meat Science. 83 (4): 768–774. doi:10.1016/j.meatsci.2009.08.017. PMID 20416624.
SPECIAL obtains spatial localization from only a single dimension with pre-excitation inversion pulses (cycled on and off every other repetition time [TR]), making it a two-cycle sequence. The use of the preinversion pulse to remove one refocusing pulse (as compared with PRESS) is what allows SPECIAL to achieve a short TE, reaching a minimum of 2.2 msec on a preclinical scanner in rat brain while being able to recover the full signal and as low as 6 msec on a clinical 3T scanner. The largest drawback of SPECIAL and SPECIAL-sLASER is that they are two-cycle schemes, and systematic variations between cycles will manifest in their difference spectrum. Lipid contamination is a particularly large problem with SPECIAL and similar sequences. The state-of-the-art localization sequence is sLASER, which utilizes two pairs of adiabatic refocusing pulses. This has recently been recommended by consensus. The first is through OVS, which will reduce the contamination of lipid signals that originate from outside the voxel, although this comes at the cost of an increase in SAR. The second is not to set the amplitude of the pre-excitation inversion pulse to zero every other TR, but instead to shift the location of this ISIS plane such that the excited volume for the off condition is outside the object. This has been shown to greatly reduce lipid contamination, speculated to have arisen from the interaction between the RF pulse and lipid compartments due to incomplete relaxation, magnetization transfer, or the homonuclear Overhauser effect, although the exact mechanism remains unknown.
At midnight between 17 and 18 April 1980, the country was granted independence by Britain under the name of Zimbabwe. A new national flag was adopted, the draft for which had been handed to the Minister of Public Works Richard Hove by an unspecified designer. The initial design did not include the Zimbabwe Bird, which was added at the suggestion of Cederic Herbert, who pointed out its uniqueness and history. The final draft went through the approval of the Prime Minister-elect Robert Mugabe. The adoption of the new flag coincided with the swearing-in of Canaan Banana as the country's new president. The Zimbabwe Bird, used on every flag since 1968, is based on a statue discovered from the medieval ruined city of Great Zimbabwe in the country's south-east.
The global annual production of freshwater prawns (excluding crayfish and crabs) in 2007 was about 460,000 tonnes, exceeding 1.86 billion dollars. Additionally, China produced about 370,000 tonnes of Chinese river crab. In addition astaciculture is the freshwater farming of crayfish (mostly in the US, Australia, and Europe).
=== Post-operative complication === OSA can also occur as a serious post-operative complication that seems to be most frequently associated with pharyngeal flap surgery as compared to other procedures for the treatment of velopharyngeal inadequacy (VPI). In OSA, recurrent interruptions of respiration during sleep are associated with temporary airway obstruction. Following pharyngeal flap surgery, depending on size and position, the flap itself may have an "obturator" or obstructive effect within the pharynx during sleep, blocking ports of airflow and hindering effective respiration. There have been documented instances of severe airway obstruction, and reports of post-operative OSA continues to increase as healthcare professionals (i.e. physicians, speech language pathologists) become more educated about this possible dangerous condition. Subsequently, in clinical practice, concerns of OSA have matched or exceeded interest in speech outcomes following pharyngeal flap surgery. The surgical treatment for velopalatal insufficiency may cause obstructive sleep apnea syndrome. When velopalatal insufficiency is present, air leaks into the nasopharynx even when the soft palate should close off the nose. A simple test for this condition can be made by placing a tiny mirror on the nose and asking the subject to say "P". This p sound, a plosive, is normally produced with the nasal airway closed off – all air comes out of the pursed lips, none from the nose.
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.
Rodent studies reported increased endurance and fat oxidation after GW501516 exposure. Long-term studies also found higher rates of some tumors, which led to halted development.