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 2025-08-11. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Regulatory status | Prohibited in sport | Listed by WADA as a metabolic modulator. |
| Approved medical use | None in major jurisdictions | Not a registered drug. |
| Common test matrix | Urine | Most anti-doping samples use urine. |
| Typical detection method | LC-MS/MS | Detects parent compound and metabolites. |
| Reference standard storage | -20 °C, desiccated | Typical for analytical standards. |
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.
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 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.
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 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.
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.
== Function == eNOS has a protective function in the cardiovascular system, which is attributed to NO production. Regulation of the vascular tone is one of the best known roles of NO in the cardiovascular system. Once produced in endothelial cells, NO diffuses across the vascular smooth muscle cell membranes and activates the enzyme soluble guanylate cyclase (sGC), which catalyzes the conversion of guanosine triphosphate into cyclic guanosine monophosphate (cGMP). cGMP, in turn, activates protein kinase G (PKG), which promotes multiple phosphorylation of cellular targets lowering cellular Ca2+ concentrations and promoting vascular relaxation. NO exerts antiproliferative effects by cGMP-dependent inhibiting Ca2+ influx or by directly inhibiting the activity of arginase and ornithine decarboxylase, decreasing the generation of polyamides required for DNA synthesis. NO also has antithrombotic effects that result of its diffusion across platelet membrane and sGC activation, resulting in inhibition of platelet aggregation. Moreover, NO affects leukocyte adhesion to the vascular endothelium by inhibiting the nuclear factor kappa B (NF-κB), which induces vascular endothelial expression of chemokines and adhesion molecules. In addition to these functions, NO produced by eNOS has antioxidant properties as it reduces superoxide anion formation as a result of NO-induced increases in the expression of superoxide dismutase, an antioxidant enzyme that catalyzes the conversion of superoxide anion to hydrogen peroxide.
The Life Sciences Institute (LSI) is a collaborative, multidisciplinary research institution located on the campus of the University of Michigan in Ann Arbor. It encompasses 27 faculty-led teams from 13 schools and departments throughout U-M. Of the university's $823 million in research expenditures, more than half is allocated for research in the life sciences, and the LSI is a cornerstone of this effort.
=== Adhesive organ === On the terminal region of the 5th tarsal segment, the C. vomitoria contain pulvilli, which are the cushion-like hairy feet on insects and many arthropods located at base of their two claws. The hair that project from the ventral surface is the key for the adhesion abilities of these flies. Additionally, they have large claws that help to hold on to irregular surfaces to prevent falling. Calliphora vomitoria, like other blowflies, also secrete non-volatile lipids through the hairs that are important for further adhesion. By a combination of the physical grip of the claws and hairs and the surface tension created by the lipid secretions, they are able to adhere to smooth surfaces with ease.
After his abdication on 14 December 1918, Ukrainian hetman Pavlo Skoropadskyi emigrated to Germany. From there he led the so-called Hetman movement (Ukrainian: Гетьманський рух), which consisted of a number of Ukrainian conservative monarchist organizations from different groups of Ukrainian diaspora. Most prominent of these organizations were the Ukrainian Union of Agrarians-Statists (Ukrainian: Український союз хліборобів-державників) founded in Vienna by Vyacheslav Lypynskyi and Serhiy Shemet, and the United Hetman Organization (Ukrainian: Союз гетьманців державників) active in Canada and the United States. In his "Letters to Brothers Agrarians", published in 1926, Lypynskyi elaborated the idea of an independent, classocratic, pan-Ukrainian "toilers' monarchy" without political parties, ruled by hetman and his dynasty with the help of an agrarian aristocracy and the co-operation of the productive classes. In Canada and the United States the Hetman movement emerged from the pre-WW1 Sich scouting societies and was implicitly supported by the Ukrainian Greek-Catholic Church. The movement supported the re-establishment of the Hetman state of Pavlo Skoropadskyi and devoted a lot of energy to military training of Ukrainian émigrés for the future liberation of their homeland, going as far as to acquire a number of airplanes. In 1940 the Canadian branch of the organization became one of the founders of the Ukrainian Canadian Congress.
With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina, all known cephalopods have an ink sac, which can be used to expel a cloud of dark ink to confuse predators. This sac is a muscular bag which originated as an extension of the hindgut. It lies beneath the gut and opens into the anus, into which its contents – almost pure melanin – can be squirted; its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion. The ejected cloud of melanin is usually mixed, upon expulsion, with mucus, produced elsewhere in the mantle, and therefore forms a thick cloud, resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen. However, a more sophisticated behavior has been observed, in which the cephalopod releases a cloud, with a greater mucus content, that approximately resembles the cephalopod that released it (this decoy is referred to as a pseudomorph). This strategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey. For more information, see Inking behaviors. The ink sac of cephalopods has led to a common name of "inkfish", formerly the pen-and-ink fish.
Sources: en.wikipedia.org
== In individuals without HIV/AIDS == Since the HIV/AIDS epidemic in the 1980s, IRIS is now mostly associated with the initiation of HIV treatment with highly active antiretroviral therapy (HAART), also referred to as antiretroviral therapy (ART). However, IRIS can still occur in the following conditions that do not involve HIV:
== Interactions == Actin beta has been shown to interact with SPTBN2. In addition, RNA-binding protein Sam68 was found to interact with the mRNA encoding actin beta, which regulates the synaptic formation of the dendritic spines with its cytoskeletal components. Actin beta has been shown to activate eNOS, thereby increasing NO production. An eight-amino acid motif (326-333) in eNOS has been shown to mediate the interaction between actin and eNOS.
=== Historical legality and modern-day usage in the United States === On October 24, 1968, possession of LSD was made illegal in the United States. The last FDA approved study of LSD in patients ended in 1980, while a study in healthy volunteers was made in the late 1980s. Legally approved and regulated psychiatric use of LSD continued in Switzerland until 1993. As of 2017, about 10% of people in the United States have used LSD at some point in their lives, while 0.7% have used it in the last year. The use of LSD among US adults increased by 56.4% from 2015 to 2018. In November 2020, Oregon became the first US state to decriminalize possession of small amounts of LSD after voters approved Ballot Measure 110.
===== Bio-Orthogonal/Quantitative Non-Canonical Amino acid Tagging ===== Bio-Orthogonal/Quantitative Non-Canonical Amino acid Tagging (BONCAT/QuaNCAT) uses azidohomoalanine (AHA) to tag proteins. This allows isolation of newly created proteins for MS. However, using AHA requires predepletion of intracellular methionine and introduction of AHA, stressing the cell and potentially altering translation dynamics within. Similar to pSILAC, AHA methods require longer pulses, thus limiting their efficacy in quantifying nascent peptides.
Sources: en.wikipedia.org
According to Circulation, "Beverages with added sugar are a prime candidate for taxation; they constitute >10% of caloric intake nationwide and provide little or no nutritional value." Weight gain is due to consumption of these sugary drinks along with other health issues such as diabetes, hypertension, and more. A penny-per-ounce tax on sugary drinks would raise the shelf price of these drinks by around 20%. Many studies have been done and it has shown that there has been a 14% to 20% reduction in the consumption of these taxed drinks. People's weight will determine if they choose healthier options or not to replace these sugary beverages. This interest of taxes on drinks has been gaining popularity across the U.S. According to Circulation, "They were considered as a measure at the federal level to fund healthcare reform in 2009 and were proposed in 11 states and 2 major cities in the 2009 to 2010 legislative cycle." There has been some resistance from the beverage industry. Policymakers are increasingly considering the beverage industry to promote public health. Non-profit organizations such as HealthCorps work to educate people on healthy eating and advocate for healthy food choices in an effort to combat obesity. Former American First Lady Michelle Obama led an initiative to combat childhood obesity entitled "Let's Move!". Obama said she aimed to wipe out obesity "in a generation". Let's Move! has partnered with other programs. Walking and bicycling to school helps children increase their physical activity.
== Interfaces == The interface between a liquid phase technique (HPLC) with a continuously flowing eluate, and a gas phase technique carried out in a vacuum was difficult for a long time. The advent of electrospray ionization changed this. Currently, the most common LC–MS interfaces are electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo-ionization (APPI). These are newer MS ion sources that facilitate the transition from a high pressure environment (HPLC) to high vacuum conditions needed at the MS analyzer. Although these interfaces are described individually, they can also be commercially available as dual ESI/APCI, ESI/APPI, or APCI/APPI ion sources. Various deposition and drying techniques, including moving belts, were used in the past, but the most common of these was the off-line MALDI deposition. A new approach still under development, called direct-EI LC–MS interface, couples a nano HPLC system and an electron ionization equipped mass spectrometer.
=== Evaluating similarity === Often the purpose of seeking a structural superposition is not so much the superposition itself, but an evaluation of the similarity of two structures or a confidence in a remote alignment. A subtle but important distinction from maximal structural superposition is the conversion of an alignment to a meaningful similarity score. Most methods output some sort of "score" indicating the quality of the superposition. However, what one actually wants is not merely an estimated "Z-score" or an estimated E-value of seeing the observed superposition by chance but instead one desires that the estimated E-value is tightly correlated to the true E-value. Critically, even if a method's estimated E-value is precisely correct on average, if it lacks a low standard deviation on its estimated value generation process, then the rank ordering of the relative similarities of a query protein to a comparison set will rarely agree with the "true" ordering. Different methods will superimpose different numbers of residues because they use different quality assurances and different definitions of "overlap"; some only include residues meeting multiple local and global superposition criteria and others are more greedy, flexible, and promiscuous. A greater number of atoms superposed can mean more similarity but it may not always produce the best E-value quantifying the unlikeliness of the superposition and thus not as useful for assessing similarity, especially in remote homologs.
Sources: en.wikipedia.org
Legal status varies by country, but cardarine is not approved as a medicine in major jurisdictions. It is often sold as a research chemical, a category that may not be lawful for human use. Buyers should check local laws and product labels carefully.
Anti-doping laboratories use LC-MS/MS to detect GW501516 and its metabolites, usually in urine. The method can identify the parent compound at low concentrations. Detection windows vary with dose and individual factors.
No, cardarine has no approved medical uses in major jurisdictions. Early research explored metabolic conditions, but those programs were discontinued. It is not a registered treatment for any disease.
No. Cardarine is a PPARδ agonist, while selective androgen receptor modulators act on androgen receptors. The two classes differ in receptor target and downstream effects.