Nuclear receptor is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-02-02. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Primary target | PPARδ (NR1C2) | Nuclear receptor involved in lipid metabolism |
| Preclinical effect | Increased fatty acid oxidation | Observed in rodent studies |
| Key safety signal | Tumors in rodents after long-term exposure | Contributed to halted clinical development |
| Human trial status | No approved product; development stopped | Limited short-term metabolic data |
| Sport regulatory status | Prohibited at all times | WADA hormone and metabolic modulators class |
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.
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.
Stability of GW501516 depends on form, temperature, light exposure, and moisture. Solid reference material is typically stored frozen or refrigerated in a desiccator and protected from light. Solutions in organic solvents such as dimethyl sulfoxide are often kept frozen in aliquots to reduce freeze-thaw cycling. Aqueous solubility is low, so aqueous stock solutions can be difficult to prepare without cosolvents. Degradation may appear as changes in chromatographic purity or mass spectral signal. Stability studies are needed to establish shelf life for any specific preparation.
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.
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.
"The single most important synthetic application of alkyl hydroperoxides is without doubt the metal-catalysed epoxidation of alkenes." In the Halcon process tert-butyl hydroperoxide (TBHP) is employed for the production of propylene oxide. Of specialized interest, chiral epoxides are prepared using hydroperoxides as reagents in the Sharpless epoxidation. Hydroperoxides are intermediates in the production of many organic compounds in industry. For example, the cobalt catalyzed oxidation of cyclohexane to cyclohexanone: C6H12 + O2 → (CH2)5C=O + H2O Drying oils, as found in many paints and varnishes, function via the formation of hydroperoxides.
CooA is a homodimeric, heme-containing transcription factor of the CAP/CRP family, with each monomer comprising an N-terminal heme-binding regulatory domain and a C-terminal helix-turn-helix motif that acts as a DNA-binding domain. The N-terminal domain coordinates a b-type heme whose axial ligands differ between species (for example, His-Pro versus His-His), and carbon monoxide (CO) binding to this heme triggers conformational changes that activate DNA binding. The two subunits associate through a coiled-coil-like interface, positioning the paired helix–turn–helix motifs to recognize target palindromic sequences in promoter DNA and thereby regulate genes involved in CO oxidation. Several structures of CooA have been solved, including: RrCooA in the ferrous state (1FT9), ChCooA in the ferrous, imidazole-bound state (2FMY), ChCooA in the ferrous, CO-bound state (2HKX).
3. Int J Pharm Compd. 2026 Jul-Aug;30(4):329-336. Synthetic Peptides in Pharmacy Compounding: Analysis of PCAC Recommendations and Industry Safety Standards. Willis J(1), Vu N(2)(3). Author information: (1)University of Oklahoma College of Pharmacy. (2)ARL Bio Pharma, Oklahoma City, Oklahoma. Nvu@arlok.com. (3)University of Oklahoma College of Pharmacy, Oklahoma City, Oklahoma. Compounded peptides have quickly moved from a niche topic to a growing area of interest among patients and prescribers. These products are promoted for a wide range of uses, including tissue repair, inflammation, metabolic health, and healthy aging. This article examines the proposed uses of these peptides, the concerns raised during the review, and the practical implications for compounders. Copyright© by International Journal of Pharmaceutical Compounding, Inc.
== Types == As of 2011, 28 types of human collagen have been identified, described, and classified according to their structure. This diversity shows collagen's diverse functionality. All of the types contain at least one triple helix. Over 90% of the collagen in humans is Type I and Type III collagen.
Collagen is known to be a viscoelastic solid. When the collagen fiber is modeled as two Kelvin-Voigt models in series, each consisting of a spring and a dashpot in parallel, the strain in the fiber can be modeled according to the following equation:
Sources: en.wikipedia.org
=== Neutron source === The oxide of 241Am pressed with beryllium is an efficient neutron source. Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:
=== Lawsuits === According to analysts from UBS, 13,000 suits had been filed by March 2010. Included among those suing: Santa Clara County, California, which claims to have spent $2 million on rosiglitazone between 1999 and 2007 at its public hospital and is asking for "triple damages". In May 2010, GlaxoSmithKline (GSK) reached settlement agreements for some of the cases against the company, agreeing to pay $60 million to resolve 700 suits. In July 2010, GSK reached settlement agreements to close another 10,000 of the lawsuits against it, agreeing to pay about $460 million to settle these suits.
Proponents of such an exception have asserted that there is precedent in allowing psychiatrists to speak out when someone presents a clear and present danger. General John Kelly, Trump's second chief of staff, purchased a copy of The Dangerous Case of Donald Trump in an attempt to understand the president's psychoses and consulted it while he was running the White House, which he was known to refer to as "Crazytown." Kelly told others that the book was a helpful guide to a president he came to consider a pathological liar, and mentally ill. In September 2017, Jeanne Suk Gerson wrote in The New Yorker: "A strange consensus does appear to be forming around Trump's mental state", including Democrats and Republicans who doubt Trump's fitness for office. Also in September 2017, journalist Bill Moyers interviewed psychiatrist Robert Jay Lifton and said that Trump "makes increasingly bizarre statements that are contradicted by irrefutable evidence to the contrary". Lifton replied, "He doesn't have clear contact with reality, though I'm not sure it qualifies as a bona fide delusion." As an example, Lifton said, when Trump claimed that former president Barack Obama was born in Kenya, "he was manipulating that lie as well as undoubtedly believing it in part." In September 2017, psychiatrist Jeffrey Lieberman published an article commenting on Donald Trump's mental health. He said that, in accordance with the Goldwater rule, no diagnosis should be made of public figures, but also stated that assessing the president's fitness for government should not be left to politicians alone.
===== Morphology change ===== As shown by flow cytometry and electron microscopy, the most sensitive sign of activation, when exposed to platelets using ADP, are morphological changes. Mitochondrial hyperpolarization is a key event in initiating morphology changes. Intraplatelet calcium concentration increases, stimulating the interplay between the microtubule/actin filament complex. The continuous changes in shape from the unactivated to the fully activated platelet are best seen via scanning electron microscopy. The three steps along this path are named early dendritic, early spread, and spread. The surface of the unactivated platelet looks similar to the surface of the brain–a wrinkled appearance from numerous shallow folds that increase the surface area; early dendritic, an octopus with multiple arms and legs; early spread, an uncooked frying egg in a pan, the "yolk" is the central body; and the spread, a cooked fried egg with a denser central body. These changes are all brought about by the interaction of the microtubule/actin complex with the platelet cell membrane and open canalicular system (OCS), which is an extension and invagination of that membrane. This complex runs just beneath these membranes and is the chemical motor that pulls the invaginated OCS out of the interior of the platelet, like turning pants pockets inside out, creating the dendrites. This process is similar to the mechanism of contraction in a muscle cell. The entire OCS thus becomes indistinguishable from the initial platelet membrane as it forms the "fried egg".
Late historian Tony Judt likewise traced the trigger to Milošević's nationalist rise in Serbia from 1987 and to the failed hope for a "democratic and unified Yugoslavia" back to communism's collapse and the Cold War's end. Once Slovenia and Croatia seceded and the federal army moved on Slovenia's border, what followed were five distinct tragic wars that included a brief campaign against Slovenia ending in withdrawal, a bloodier Croatian-Serb war, the siege of Bosnia after its 1992 independence referendum, a separate Croat-Muslim conflict within Bosnia from 1993, and finally Kosovo, where Milošević—having lost everywhere else—turned back to the province he had first exploited in 1989, until NATO's 1999 military intervention stopped him.
Sources: en.wikipedia.org
==== Nuclear power ==== The Trump administration has sought to drastically expand the US's nuclear power generation, setting a goal to quadruple it by 2050. The administration seeks to revive production at decommissioned plants, such as the plant at Three Mile Island in Pennsylvania. It also seeks to promote the construction of new small modular reactors. The administration considers nuclear power generation a strategic priority because of its potential use in powering data centers needed to compete in the international AI development race. Experts are divided on the feasibility of Trump's nuclear power goals, with many expressing skepticism that they can be reached because of the high cost of nuclear power generation, while others say the conditions for financing nuclear power are relatively favorable. Despite efforts to increase nuclear power generation, data centers have led to steep increases in the cost of power in some communities, prompting local backlash.
=== Myopathies === Inflammatory myopathies are caused by the immune system inappropriately attacking components of muscle, leading to signs of muscle inflammation. They may occur in conjunction with other immune disorders, such as systemic sclerosis, and include dermatomyositis, polymyositis, and inclusion body myositis.
== Specificity == Retinal dehydrogenases are a subset of a larger family called aldehyde dehydrogenases. In particular, the three enzymes of the ALDH1A subfamily ALDH1A1 (aka RALDH1), ALDH1A2 (aka RALDH2), and ALDH1A3 (aka RALDH3) are known to preferentially act on retinal. While at least 19 different varieties of aldehyde dehydrogenases have been found in humans, many of them (like ALDH2) show little affinity for retinal. The size of the entrance tunnel to the enzyme active site appears to provide the specificity observed in ALDH1A1 for retinal as a substrate. The solvent-accessible diameter of the entrance tunnel is 150 Å3 in ALDH1A1, so the relatively large retinal can be accommodated while the solvent accessible diameter in ALDH2 is only 20 Å3 which limits accessibility to retinal but amply accommodates acetaldehyde.
== Advantages == An advantage of this method is that there can be real determination of protein partners quantitatively in vivo without prior knowledge of complex composition. It is also simple to execute and often provides high yield. One of the obstacles of studying protein protein interaction is the contamination of the target protein especially when we don’t have any prior knowledge of it. TAP offers an effective, and highly specific means to purify target protein. After 2 successive affinity purifications, the chance for contaminants to be retained in the eluate reduces significantly.
The hydrophobic effect represents the tendency of water to exclude non-polar molecules. The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect. However, a pure hydrocarbon molecule, for example hexane, cannot accept or donate hydrogen bonds to water. Introduction of hexane into water causes disruption of the hydrogen bonding network between water molecules. The hydrogen bonds are partially reconstructed by building a water "cage" around the hexane molecule, similar to that in clathrate hydrates formed at lower temperatures. The mobility of water molecules in the "cage" (or solvation shell) is strongly restricted. This leads to significant losses in translational and rotational entropy of water molecules and makes the process unfavorable in terms of free energy of the system. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. A positive free energy change of the surrounding solvent indicates hydrophobicity, whereas a negative free energy change implies hydrophilicity. In this way, the hydrophobic effect not only can be localized but also decomposed into enthalpic and entropic contributions.
Sources: en.wikipedia.org
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.
Small short-term human trials examined metabolic markers such as lipids and glucose. The trials did not continue after rodent cancer findings, so long-term human safety is unknown.
Controlled human trials have not established a performance benefit. Anecdotal reports exist, but they are not reliable evidence.
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.